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Aims: Cerebral hypometabolism occurs years prior to a diagnosis of neurodegenerative diseases and coincides with reduced cerebral perfusion and declining noradrenergic transmission from the locus coeruleus. In pre‐clinical models, β‐adrenoceptor (β‐AR) agonists increase cerebrocortical glucose metabolism, and may have therapeutic potential for neurodegenerative diseases. This study investigated the safety and effects on regional cerebral blood flow (rCBF) of the oral, brain‐penetrant β2‐AR agonist, clenbuterol, in healthy volunteers (HV) and patients with mild cognitive impairment (MCI) or Parkinson's disease (PD). Methods: This study evaluated the safety and effects on cerebral activity of the oral, brain‐penetrant, β2‐AR agonist clenbuterol (20–160 μg) in healthy volunteers and patients with MCI or PD. Regional CBF, which is tightly coupled to glucose metabolism, was measured by arterial spin labelling MRI in 32 subjects (25 HV and 8 MCI or PD) across five cohorts. In some cohorts, low doses of nadolol (1–5 mg), a β‐AR antagonist with minimal brain penetration, were administered with clenbuterol to control peripheral β2‐AR responses. Results: Significant, dose‐dependent increases in rCBF were seen in multiple brain regions, including hippocampus, amygdala and thalamus, following the administration of clenbuterol to HVs (mean changes from baseline in hippocampal rCBF of −1.7%, 7.3%, 22.9%, 28.4% 3 h after 20, 40, 80 and 160 μg clenbuterol, respectively). In patients with MCI or PD, increases in rCBF following 80 μg clenbuterol were observed both without and with 5 mg nadolol (in hippocampus, 18.6%/13.7% without/with nadolol). Clenbuterol was safe and well‐tolerated in all subjects; known side effects of β2‐agonists, including increased heart rate and tremor, were mild in intensity and were blocked by low‐dose nadolol. Conclusions: The effects of clenbuterol on rCBF were evident both in the absence and presence of low‐dose nadolol, suggesting central nervous system (CNS) involvement. Concomitant inhibition of the peripheral effects of clenbuterol by nadolol confirms that meaningful β2‐AR antagonism in the periphery was achieved without interrupting the central effects of clenbuterol on rCBF. [ABSTRACT FROM AUTHOR]

Cardiovascular complications are the major cause of diabetes mellitus-related morbidity and mortality. Increased renin–angiotensin–aldosterone system activity and decreased β-adrenergic receptor (β-AR) responsiveness contribute to diabetic cardiac dysfunction. We evaluated the effect of sacubitril/valsartan (neprilysin inhibitor plus angiotensin receptor antagonist combination) and valsartan treatments on the diabetic cardiac function through β-AR responsiveness and on protein expression of diastolic components. Six-week-old male Sprague Dawley rats were divided into control, diabetic, sacubitril/valsartan (68 mg/kg)-, and valsartan-treated (31 mg/kg) diabetic groups. Diabetes was induced by a high-fat diet plus low-dose streptozotocin (30 mg/kg, intraperitoneal). After 10 weeks of diabetes, rats were treated for 4 weeks. Systolic/diastolic function was assessed by in vivo echocardiography and pressure–volume loop analysis. β-AR-mediated responsiveness was assessed by in vitro papillary muscle and Langendorff heart experiments. Protein expression of sarcoplasmic reticulum calcium ATPase2a, phospholamban, and phosphorylated phospholamban was determined by Western blot. Sacubitril/valsartan improved ejection fraction and fractional shortening to a similar extent as valsartan alone. None of the treatments affected in vivo diastolic parameters or the expression of related proteins. β1-/β2-AR-mediated responsiveness was partially restored in treated animals. β3-AR-mediated cardiac relaxation (an indicator of diastolic function) responses were comparable among groups. The beneficial effect of sacubitril/valsartan on systolic function may be attributed to improved β1-/β2-AR responsiveness. [ABSTRACT FROM AUTHOR]

Background: Partial bladder outlet obstruction (pBOO) causes deposition of extracellular matrix (ECM), promotes bladder fibrosis, and decreases bladder compliance. Methods: To investigate the effect of β-adrenoceptor (ADRB) on the ECM deposition of pBOO rat model and explore its underlying mechanism, human bladder smooth muscle cells (hBSMCs) were exposed to the pathological hydrostatic pressure (100 cm H2O) for 6 h, reverse transcription-polymerase chain reaction (RT-PCR) and western blotting were employed. Then the rats of sham operation and pBOO model were treated with vehicle or ADRB agonists for 3 weeks, and the alterations of the bladder were observed via Masson staining and immunohistochemical analysis. Results: 100 cm H2O hydrostatic pressure significantly upregulated the expression of collagen I (COL1), collagen III (COL3) and fibronectin (FN), and downregulated the expression of ADRB2 and ADRB3 of hBSMCs at 6 h. The agonists of ADRB2 and ADRB3, Formoterol and BRL 37344, decreased COL1 and FN expression of hBSMCs under 100 cm H2O for 6 h compared with the cells exposed to hydrostatic pressure only. As the classic downstream pathways of ADRB, the EPAC pathway inhibited COL1 and FN expression of hBSMCs via regulating SMAD3 and SMAD2 activities, respectively. In pBOO rats, Procaterol (ADRB2 agonist), and Mirabegron (ADRB3 agonist) inhibited the formation of collagen and decreased the expression of FN and COL1 in the bladders of pBOO rats. Conclusions: The bladder fibrosis of pBOO and deposition of hBSMCs ECM under hydrostatic pressure were regulated by ADRB2, and ADRB3 via EPAC/SMAD2/FN and EPAC/SMAD3/COL1 pathways, these findings pave an avenue for effective treatment of pBOO.

ABSTRACT: The response of basilar arteries to noradrenaline varies among many animal species, but remains little studied in poultry. Accordingly, we aimed to characterize the adrenergic receptor (AR) subtypes that modulate vascular response in basilar arteries in the chicken, with isometric recording of arterial ring tension using an organ bath. We demonstrated the presence of both alpha and beta (α and β) receptor subtypes through evaluating the response to noradrenaline, with and without a range of β-AR and α-AR antagonists. The concentration-dependent relaxations then induced by a range of β-AR agonists indicated a potency ranking of isoproterenol > noradrenaline > adrenaline > procaterol. We then investigated the effects of β-AR antagonists that attenuate the effect of isoproterenol (propranolol for β1,2,3-ARs, atenolol for β1-ARs, butoxamine for β2-ARs, and SR 59230A for β3-ARs), with Schild regression analysis, ascertaining multiple β-AR subtypes, with neither the β1-AR nor the β2-AR as the dominant subtype. SR 59230A was the only antagonist to yield a pA2 value (7.52) close to the reported equivalent for the relevant receptor subtype. Furthermore, treatment with SR 58611 (a β3-AR agonist) induced relaxation, which was inhibited (P < 0.01) by L-NNA and SR 59230A. Additionally, treating basilar arterial strips (containing endothelium) with SR 58611 induced nitric oxide (NO) production, which was inhibited (P < 0.01) by L-NNA and SR 59230A. Based on this first characterization of AR subtypes in chicken basilar arteries (to our knowledge), we suggest that α- and β-ARs are involved in contraction and relaxation, and that β3-ARs, especially those on the endothelium, may play an important role in vasodilation via NO release.

Objective: Age-related decline within the noradrenergic system is associated with reduced cognition. The β-adrenoceptors are widely expressed in the brain as well as in the peripheral. Medications targeting β-adrenoceptor activity have been widely used in older adults. The aim of this study was to explore the associations between β-adrenoceptor acting drugs and the risk of dementia in the older population. Methods: The subjects' information was collected fromthe electronicmedical record (EMR) database. A propensity score matching strategy was conducted to select control participants for users of β2-agonists or β-antagonists. Logistic regression analysis was performed to estimate the risk of dementia with the use of β2-agonists or β-antagonists. Results: A total of 1,429 participants in the EMR database were included in the study. The use of β2-agonists was strongly associated with a decreased risk of dementia [OR = 0.324, 95% confidence interval (CI): 0.149-0.707, P = 0.005]. This decreased risk showed a statistically significant inverse time-dependent pattern (Ptrend = 0.014). However, the use of non-selective β-antagonists significantly correlated with an increased dementia risk (OR = 1.961, 95% CI: 1.144-3.359, P = 0.014), although no time-dependent manner was found (Ptrend = 0.220). There was no association between selective β1-antagonists usage and dementia risk (OR = 1.114, P = 0.625). Conclusion: The use of β-adrenoceptor acting drugs seems to be associated with the risk of dementia. Pharmacological interventions modulating β2-adrenoceptor activity might be a potential target in therapeutics for dementia. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to address the status, role, and mechanism of sympathetic nerve infiltration in the progression of stomach adenocarcinoma (STAD). Methods: Sympathetic nerve and its neurotransmitter NE, β-ARs, and associated signaling molecules in the STAD tissues and the adjacent tissues from 46 STAD patients were examined using immunostaining, HPLC, and western blotting. The effects and mechanisms of β2-AR activation on the proliferation, migration and invasion of AGS and SGC-7901 gastric cancer (GC) cell lines were examined using CCK-8, transwell, and western blotting assays. Correlations between genes and STAD survival were analyzed using bioinformatics. Results: Striking sympathetic nerve infiltration, elevations of NGF, TrkA, GAP43, TH, S100, NE, β2-AR, YKL-40, syndecan-1, MMP9, CD206, and CD31 were observed in the STAD tissues compared to the adjacent tissues. Activation of β2-AR in the two GC cell lines significantly amplified the expressions of NGF, YKL-40, MMP9, syndecan-1, p-STAT3 and p-ERK, and increased GC cell proliferation, migration and invasion. Bioinformatic analyses revealed positive correlations of NGF, β2-AR, syndecan-1, and macrophage infiltration, respectively, with low survival of STAD, of β2-AR respectively with STAT3, ERK1/2 (MAPK1/3), YKL-40, MMP9, and syndecan-1, and of YKL-40 with MMP9. Conclusion: Sympathetic nerves significantly infiltrated into human STAD tissues as a result of high NGF and TrkA expressions; elevated NE led to overactivation of β2-AR-STAT3/ERK-YKL-40 signaling pathway, and finally caused cancer cell growth and invasion, M2 macrophage infiltration, angiogenesis, matrix degradation and STAD metastasis and progression.

Abstract Background and objective Sympathetic activity plays an important role in the proliferation and differentiation of stem cells, and it changes over time, thereby exerting differential effects on various stem cell types. Aging causes sympathetic hyperactivity in aged tissues and blunts sympathetic nerves regulation, and sympathetic abnormalities play a role in aging-related diseases. Currently, the effect of sympathetic activity on skeletal muscle stem cells, namely satellite cells (SCs), is unclear. This study aimed to investigate the effects of skeletal muscle sympathetic activity on SC aging and skeletal muscle repair. Materials and methods To evaluate skeletal muscle and fibrotic areas, numbers of SCs and myonuclei per muscle fiber, β2-adrenoceptor (β2-ADR) expression, muscle repair, and sympathetic innervation in skeletal muscle, aged mice, young mice that underwent chemical sympathectomy (CS) were utilized. Mice with a tibialis anterior muscle injury were treated by barium chloride (BaCl2) and clenbuterol (CLB) in vivo. SCs or C2C12 cells were differentiated into myotubes and treated with or without CLB. Immunofluorescence, western blot, sirius red, and hematoxylin–eosin were used to evaluate SCs, myogenic repair and differentiation. Results The number of SCs, sympathetic activity, and reparability of muscle injury in aged mice were significantly decreased, compared with those in young mice. The above characteristics of young mice that underwent CS were similar to those of aged mice. While CLB promoted the repair of muscle injury in aged and CS mice and ameliorated the reduction in the SC number and sympathetic activity, the effects of CLB on the SCs and sympathetic nerves in young mice were not significant. CLB inhibited the myogenic differentiation of C2C12 cells in vitro. We further found that NF-κB and ERK1/2 signaling pathways were activated during myogenic differentiation, and this process could be inhibited by CLB. Conclusion Normal sympathetic activity promoted the stemness of SCs to thereby maintain a steady state. It also could maintain total and self-renewing number of SCs and maintain a quiescent state, which was correlated with skeletal SCs via β2-ADR. Normal sympathetic activity was also beneficial for the myogenic repair of injured skeletal muscle.

Nicotinic acid adenine dinucleotide phosphate (NAADP) and cyclic ADP-ribose (cADPR) are Ca2+-mobilizing messengers important for modulating cardiac excitation-contraction coupling and pathophysiology. CD38, which belongs to the ADP-ribosyl cyclase family, catalyzes synthesis of both NAADP and cADPR in vitro However, it remains unclear whether this is the main enzyme for their production under physiological conditions. Here we show that membrane fractions from WT but not CD38-/- mouse hearts supported NAADP and cADPR synthesis. Membrane permeabilization of cardiac myocytes with saponin and/or Triton X-100 increased NAADP synthesis, indicating that intracellular CD38 contributes to NAADP production. The permeabilization also permitted immunostaining of CD38, with a striated pattern in WT myocytes, whereas CD38-/- myocytes and nonpermeabilized WT myocytes showed little or no staining, without striation. A component of β-adrenoreceptor signaling in the heart involves NAADP and lysosomes. Accordingly, in the presence of isoproterenol, Ca2+ transients and contraction amplitudes were smaller in CD38-/- myocytes than in the WT. In addition, suppressing lysosomal function with bafilomycin A1 reduced the isoproterenol-induced increase in Ca2+ transients in cardiac myocytes from WT but not CD38-/- mice. Whole hearts isolated from CD38-/- mice and exposed to isoproterenol showed reduced arrhythmias. SAN4825, an ADP-ribosyl cyclase inhibitor that reduces cADPR and NAADP synthesis in mouse membrane fractions, was shown to bind to CD38 in docking simulations and reduced the isoproterenol-induced arrhythmias in WT hearts. These observations support generation of NAADP and cADPR by intracellular CD38, which contributes to effects of β-adrenoreceptor stimulation to increase both Ca2+ transients and the tendency to disturb heart rhythm.

A2A and A2B adenosine receptors produce regionally selective regulation of vascular tone and elicit differing effects on mean arterial pressure (MAP), whilst inducing tachycardia. The tachycardia induced by the stimulation of A2A or A2B receptors has been suggested to be mediated by a reflex increase in sympathetic activity. Here, we have investigated the role of β1- and β2-adrenoceptors in mediating the different cardiovascular responses to selective A2A and A2B receptor stimulation. Hemodynamic variables were measured in conscious male Sprague-Dawley rats (350–450 g) via pulsed Doppler flowmetry. The effect of intravenous infusion (3 min per dose) of the A2A-selective agonist CGS 21680 (0.1, 0.3, 1.0 µg.kg−1.min−1) or the A2B-selective agonist BAY 60–6583 (4.0, 13.3, 40.0 µg.kg−1.min−1) in the absence or following pre-treatment with the non-selective β-antagonist propranolol (1.0 mg.kg−1), the selective β1-antagonist CGP 20712A (200 µg.kg−1), or the selective β2-antagonist ICI 118,551 (2.0 mg.kg−1) was investigated (maintenance doses also administered). CGP 20712A and propranolol significantly reduced the tachycardic response to CGS 21680, with no change in the effect on MAP. ICI 118,551 increased BAY 60–6583-mediated renal and mesenteric flows, but did not affect the heart rate response. CGP 20712A attenuated the BAY 60–6583-induced tachycardia. These data imply a direct stimulation of the sympathetic activity via cardiac β1-adrenoceptors as a mechanism for the A2A- and A2B-induced tachycardia. However, the regionally selective effects of A2B agonists on vascular conductance were independent of sympathetic activity and may be exploitable for the treatment of acute kidney injury and mesenteric ischemia. [ABSTRACT FROM AUTHOR]

The mechanism of severe hypoglycemia (SH)-induced cardiovascular disease in diabetes remains unknown. Our previous study found that SH inhibits cardiac function and lipid metabolism in diabetic mice. Conversely, in nondiabetic mice, SH does not induce cardiac dysfunction but promotes cardiac lipid metabolism. This study aims to clarify the effect of increased fatty acid metabolism on the resistance of cardiomyocytes to β-adrenoceptor activation during hypoglycemia in diabetes. Results revealed that cardiomyocytes with enhanced lipid metabolism were more vulnerable to damage due to β-adrenoceptor activation, which presented as decreased cell viability, disorder of mitochondrial structure, dissipation of mitochondrial membrane potential, dysfunction of mitochondrial oxidative phosphorylation, nonapoptotic damage, and accumulation of ROS and calcium from mitochondria to cytoplasm, all of which were partially reversed by mitochondrial antioxidant Mito-TEMPO. The SH-induced cardiac dysfunction, and reduction of myocardial energy metabolism in diabetic mice were rescued by Mito-TEMPO. Our findings indicate that high fatty acid metabolism crippled cardiac resistance to β-adrenoceptor hyperactivation, with mitochondrial ROS playing a pivotal role in this process. Reducing mitochondrial ROS in diabetes could disrupt this synergistic effect and prevent poor cardiac outcomes caused by SH.

Survival in pancreatic cancer (pancreatic ductal adenocarcinoma, PDAC) at just 5 months is the worst of all cancers. It is predicted to become the second highest cause of cancer deaths worldwide this decade and unlike most cancers, there has been little progress in improving survival in PDAC. Numerous studies including molecular and mechanistic studies, cancer biology studies and retrospective human epidemiological studies suggest that two well-known, approved drug classes - β-blockers and H1-antihistamines - may be beneficial and thus may potentially prolong life in patients with PDAC. In our opinion, the body of evidence has reached a point where the potential gains outweigh the very low risks involved in a clinical study in PDAC. We thus believe that it is now time for a clinical trial involving these two agents in PDAC patients. As a repurposing of generic drugs, this is not likely to be appealing to pharmaceutical companies and therefore is likely to require governmental, philanthropic and /or charitable organisational input. In this article, we opine and propose that an urgent clinical trial is needed to determine if repurposing these two orally administered, inexpensive, largely safe drug classes, either alone or in combination, could prolong survival in PDAC and thus improve the outcome for the 10,000 people worldwide who die from PDAC each week., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Physiological Society.)

Different from skeletal muscle, the heart autonomously generates rhythmic contraction independently from neuronal inputs. However, speed and strength of the heartbeats are continuously modulated by environmental, physical or emotional inputs, delivered by cardiac innervating sympathetic neurons, which tune cardiomyocyte (CM) function, through activation of β-adrenoceptors (β-ARs). Given the centrality of such mechanism in heart regulation, β-AR signaling has been subject of intense research, which has reconciled the molecular details of the transduction pathway and the fine architecture of cAMP signaling in subcellular nanodomains, with its final effects on CM function. The importance of mechanisms keeping the elements of β-AR/cAMP signaling in good order emerges in pathology, when the loss of proper organization of the transduction pathway leads to detuned β-AR/cAMP signaling, with detrimental consequences on CM function. Despite the compelling advancements in decoding cardiac β-AR/cAMP signaling, most discoveries on the subject were obtained in isolated cells, somehow neglecting that complexity may encompass the means in which receptors are activated in the intact heart. Here, we outline a set of data indicating that, in the context of the whole myocardium, the heart orchestra (CMs) is directed by a closely interacting and continuously attentive conductor, represented by SNs. After a roundup of literature on CM cAMP regulation, we focus on the unexpected complexity and roles of cardiac sympathetic innervation, and present the recently discovered Neuro-Cardiac Junction, as the election site of “SN-CM” interaction. We further discuss how neuro-cardiac communication is based on the combination of extra- and intra-cellular signaling micro/nano-domains, implicating neuronal neurotransmitter exocytosis, β-ARs and elements of cAMP homeostasis in CMs, and speculate on how their dysregulation may reflect on dysfunctional neurogenic control of the heart in pathology.

Different from skeletal muscle, the heart autonomously generates rhythmic contraction independently from neuronal inputs. However, speed and strength of the heartbeats are continuously modulated by environmental, physical or emotional inputs, delivered by cardiac innervating sympathetic neurons, which tune cardiomyocyte (CM) function, through activation of β-adrenoceptors (β-ARs). Given the centrality of such mechanism in heart regulation, β-AR signaling has been subject of intense research, which has reconciled the molecular details of the transduction pathway and the fine architecture of cAMP signaling in subcellular nanodomains, with its final effects on CM function. The importance of mechanisms keeping the elements of β-AR/cAMP signaling in good order emerges in pathology, when the loss of proper organization of the transduction pathway leads to detuned β-AR/cAMP signaling, with detrimental consequences on CM function. Despite the compelling advancements in decoding cardiac β-AR/cAMP signaling, most discoveries on the subject were obtained in isolated cells, somehow neglecting that complexity may encompass the means in which receptors are activated in the intact heart. Here, we outline a set of data indicating that, in the context of the whole myocardium, the heart orchestra (CMs) is directed by a closely interacting and continuously attentive conductor, represented by SNs. After a roundup of literature on CM cAMP regulation, we focus on the unexpected complexity and roles of cardiac sympathetic innervation, and present the recently discovered Neuro-Cardiac Junction, as the election site of "SN-CM" interaction. We further discuss how neuro-cardiac communication is based on the combination of extra- and intra-cellular signaling micro/nano-domains, implicating neuronal neurotransmitter exocytosis, β-ARs and elements of cAMP homeostasis in CMs, and speculate on how their dysregulation may reflect on dysfunctional neurogenic control of the heart in pathology. [ABSTRACT FROM AUTHOR]

Background and objective: Sympathetic activity plays an important role in the proliferation and differentiation of stem cells, and it changes over time, thereby exerting differential effects on various stem cell types. Aging causes sympathetic hyperactivity in aged tissues and blunts sympathetic nerves regulation, and sympathetic abnormalities play a role in aging-related diseases. Currently, the effect of sympathetic activity on skeletal muscle stem cells, namely satellite cells (SCs), is unclear. This study aimed to investigate the effects of skeletal muscle sympathetic activity on SC aging and skeletal muscle repair. Materials and methods: To evaluate skeletal muscle and fibrotic areas, numbers of SCs and myonuclei per muscle fiber, β2-adrenoceptor (β2-ADR) expression, muscle repair, and sympathetic innervation in skeletal muscle, aged mice, young mice that underwent chemical sympathectomy (CS) were utilized. Mice with a tibialis anterior muscle injury were treated by barium chloride (BaCl2) and clenbuterol (CLB) in vivo. SCs or C2C12 cells were differentiated into myotubes and treated with or without CLB. Immunofluorescence, western blot, sirius red, and hematoxylin–eosin were used to evaluate SCs, myogenic repair and differentiation. Results: The number of SCs, sympathetic activity, and reparability of muscle injury in aged mice were significantly decreased, compared with those in young mice. The above characteristics of young mice that underwent CS were similar to those of aged mice. While CLB promoted the repair of muscle injury in aged and CS mice and ameliorated the reduction in the SC number and sympathetic activity, the effects of CLB on the SCs and sympathetic nerves in young mice were not significant. CLB inhibited the myogenic differentiation of C2C12 cells in vitro. We further found that NF-κB and ERK1/2 signaling pathways were activated during myogenic differentiation, and this process could be inhibited by CLB. Conclusion: Normal sympathetic activity promoted the stemness of SCs to thereby maintain a steady state. It also could maintain total and self-renewing number of SCs and maintain a quiescent state, which was correlated with skeletal SCs via β2-ADR. Normal sympathetic activity was also beneficial for the myogenic repair of injured skeletal muscle. [ABSTRACT FROM AUTHOR]

Background and Purpose: The physiological role of vascular β3 -adrenoceptors is not fully understood. Recent evidence suggests cardiac β3 -adrenoceptors are functionally effective after down-regulation of β1 /β2 -adrenoceptors. The functional interaction between the β3 -adrenoceptor and other β-adrenoceptor subtypes in rat striated muscle arteries was investigated.Experimental Approach: Studies were performed in cremaster muscle arteries isolated from male Sprague-Dawley rats. β-adrenoceptor expression was assessed through RT-PCR and immunofluorescence. Functional effects of β3 -adrenoceptor agonists and antagonists and other β-adrenoceptor ligands were measured using pressure myography.Key Results: All three β-adrenoceptor subtypes were present in the endothelium of the cremaster muscle artery. The β3 -adrenoceptor agonists mirabegron and CL 316,243 had no effect on the diameter of pressurized (70 mmHg) cremaster muscle arterioles with myogenic tone, while the β3 -adrenoceptor agonist SR 58611A and the nonselective β-adrenoceptor agonist isoprenaline caused concentration-dependent dilation. In the presence of β1/2 -adrenoceptor antagonists nadolol (10 μM), atenolol (1 μM) and ICI 118,551 (0.1 μM) both mirabegron and CL 316,243 were effective in causing vasodilation and the potency of SR 58611A was enhanced, while responses to isoprenaline were inhibited. The β3 -adrenoceptor antagonist L 748,337 (1 μM) inhibited vasodilation caused by β3 -adrenoceptor agonists (in the presence of β1/2 -adrenoceptor blockade), but L 748,337 had no effect on isoprenaline-induced vasodilation.Conclusion and Implications: All three β-adrenoceptor subtypes were present in the endothelium of the rat cremaster muscle artery, but β3 -adrenoceptor mediated vasodilation was only evident after blockade of β1/2 -adrenoceptors. This suggests constitutive β1/2 -adrenoceptor activity inhibits β3 -adrenoceptor function in the endothelium of skeletal muscle resistance arteries. [ABSTRACT FROM AUTHOR]

New Findings: What is the central question of this study?The acute hypoxic compensatory reaction is based on haemodynamic changes, and β‐adrenoceptors are involved in haemodynamic regulation. What is the role of β‐adrenoceptors in haemodynamics during hypoxic exposure?What is the main finding and its importance?Activation of β2‐adrenoceptors attenuates the increase in pulmonary artery pressure during hypoxic exposure. This compensatory reaction activated by β2‐adrenoceptors during hypoxic stress is very important to maintain the activities of normal life. The acute hypoxic compensatory reaction is accompanied by haemodynamic changes. We monitored the haemodynamic changes in rats undergoing acute hypoxic stress and applied antagonists of β‐adrenoceptor (β‐ARs) subtypes to reveal the regulatory role of β‐ARs on haemodynamics. Sprague–Dawley rats were randomly divided into control, atenolol (β1‐AR antagonist), ICI 118,551 (β2‐AR antagonist) and propranolol (non‐selective β‐AR antagonist) groups. Rats were continuously recorded for changes in haemodynamic indexes for 10 min after administration. Then, a hypoxic ventilation experiment [15% O2, 2200 m a.sl., 582 mmHg (0.765 Pa), PO2 87.3 mmHg; Xining, China] was conducted, and the indexes were monitored for 5 min after induction of hypoxia. Plasma catecholamine concentrations were also measured. We found that, during normoxia, the mean arterial pressure, heart rate, ascending aortic blood flow and pulmonary artery pressure were reduced in the propranolol and atenolol groups. Catecholamine concentrations were increased significantly in the atenolol group compared with the control group. During hypoxia, mean arterial pressure and total peripheral resistance were decreased in the control, propranolol and ICI 118,551 groups. Pulmonary arterial pressure and pulmonary vascular resistance were increased in the propranolol and ICI 118,551 groups. During hypoxia, catecholamine concentrations were increased significantly in the control group, but decreased in β‐AR antagonist groups. In conclusion, the β2‐AR is involved in regulation of pulmonary haemodynamics in the acute hypoxic compensatory reaction, and the activation of β2‐ARs attenuates the increase in pulmonary arterial pressure during hypoxic stress. This compensatory reaction activated by β2‐ARs during hypoxic stress is very important to maintain activities of normal life. [ABSTRACT FROM AUTHOR]

Sympathetic dysfunction is suggested to contribute to development of multiple sclerosis and experimental autoimmune encephalomyelitis (EAE) alike. Considering important role of microglia in development/resolution of neuroinflammation, contribution of noradrenaline, the key sympathetic end-point mediator, in modulation of microglial phenotypic and functional properties in rat EAE model was examined. The study showed that noradrenaline acting in neurocrine and autocrine/paracrine way might influence microglia during EAE. Propranolol treatment over the effector phase moderated EAE course. This was associated with the increased proportion of microglia expressing CX3CR1, the key molecule in their immunomodulatory/neuroprotective action, and upregulation of CX3CR1 downstream Nrf2 gene. This correlated with the increased heme oxygenase-1 (HO-1) expression and phagocytic capacity of microglia, and their phenotypic changes mirrored in increased proportion of CD163- and CD83-expressing cells. The enhanced HO-1 expression was linked with the decreased proportion of microglial cells expressing IL-1β and IL-23, and possibly IL-6, followed by increased proportion of IL-10–expressing microglia, and downregulated MCP-1/CCL2 expression. Consistently, spinal cord infiltration with blood-borne myeloid and CD4+ T cells, as well as CD4+ T-cell reactivation/proliferation and differentiation into highly pathogenic IL-17+ cells co-producing IFN-γ and GM-CSF were decreased in propranolol-treated rats compared with saline-injected controls. The in vitro investigations of the effects of noradrenaline on microglia showed that noradrenaline through β-adrenoceptor may influence Nrf2 expression also via CX3CR1-independent route. The study suggests β-adrenoceptor–mediated neuroinflammation-promoting role of noradrenaline in EAE via modulation of microglial Nrf2 expression, and thereby forms the basis for further translational pharmacological research to improve multiple sclerosis therapy.

The role of stress effector systems in the initiation and progression of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), the most commonly used experimental model of MS, has strongly been suggested. To corroborate this notion, alterations in activity of the sympathoadrenal and sympathoneural axes of sympathoadrenal system (a major communication pathway between the central nervous system and the immune system), mirrored in altered release of their end-point mediators (adrenaline and noradrenaline, respectively), are shown to precede (in MS) and/or occur during development of MS and EAE in response to immune cell activation (in early phase of disease) and disease-related damage of sympathoadrenal system neurons and their projections (in late phase of disease). To add to the complexity, innate immunity cells and T-lymphocytes synthesize noradrenaline that may be implicated in a local autocrine/paracrine self-amplifying feed-forward loop to enhance myeloid-cell synthesis of proinflammatory cytokines and inflammatory injury. Furthermore, experimental manipulations targeting noradrenaline/adrenaline action are shown to influence clinical outcome of EAE, in a disease phase-specific manner. This is partly related to the fact that virtually all types of cells involved in the instigation and progression of autoimmune inflammation and target tissue damage in EAE/MS express functional adrenoceptors. Although catecholamines exert majority of immunomodulatory effects through β2-adrenoceptor, a role for α-adrenoceptors in EAE pathogenesis has also been indicated. In this review, we summarize all aforementioned aspects of immunopathogenetic action of catecholamines in EAE/MS as possibly important for designing new strategies targeting their action to prevent/mitigate autoimmune neuroinflammation and tissue damage.

Cardio-stimulatory actions of aciclovir have been considered to primarily depend on the sympathetically-mediated reflex resulting from its hypotensive effect. To further clarify onset mechanisms of the cardio-stimulatory actions, we initially studied them using isoflurane-anesthetized dogs under thorough β 1 -adrenoceptor blockade with atenolol (1 mg/kg, i.v.) (n = 4). Aciclovir (20 mg/kg/10 min, i.v.) decreased mean arterial blood pressure by 10 mmHg, whereas it increased heart rate by 10 bpm and maximum upstroke velocity of ventricular pressure by 928 mmHg/s, and shortened AH interval by 2 ms, indicating that cardio-stimulatory actions were not totally abolished by β 1 -adrenoceptor blockade. Then, unknown mechanisms of cardio-stimulatory action were explored. Since aciclovir has a similar chemical structure to theophylline, in silico molecular docking simulation was performed, indicating aciclovir as well as theophylline possesses strong likelihood of interactions with phosphodiesterase 1A, 1C and 3A. Indeed, aciclovir inhibited phosphodiesterase 1A derived from the bovine heart (n = 4), moreover it exerted positive chronotropic action on the atrial tissue preparation of rats along with an increase of tissue cyclic AMP concentration (n = 4). These results indicate that cardio-stimulatory actions of aciclovir could result from not only hypotension-induced, reflex-mediated increase of sympathetic tone but also its inhibitory effects on phosphodiesterase in the heart., Competing Interests: Declaration of competing interest The authors indicated no potential conflict of interest., (Copyright © 2024 The Authors. Production and hosting by Elsevier B.V. All rights reserved.)

The role of stress effector systems in the initiation and progression of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), the most commonly used experimental model of MS, has strongly been suggested. To corroborate this notion, alterations in activity of the sympathoadrenal and sympathoneural axes of sympathoadrenal system (a major communication pathway between the central nervous system and the immune system), mirrored in altered release of their end-point mediators (adrenaline and noradrenaline, respectively), are shown to precede (in MS) and/or occur during development of MS and EAE in response to immune cell activation (in early phase of disease) and disease-related damage of sympathoadrenal system neurons and their projections (in late phase of disease). To add to the complexity, innate immunity cells and T-lymphocytes synthesize noradrenaline that may be implicated in a local autocrine/paracrine self-amplifying feed-forward loop to enhance myeloid-cell synthesis of proinflammatory cytokines and inflammatory injury. Furthermore, experimental manipulations targeting noradrenaline/adrenaline action are shown to influence clinical outcome of EAE, in a disease phase-specific manner. This is partly related to the fact that virtually all types of cells involved in the instigation and progression of autoimmune inflammation and target tissue damage in EAE/MS express functional adrenoceptors. Although catecholamines exert majority of immunomodulatory effects through β2-adrenoceptor, a role for α-adrenoceptors in EAE pathogenesis has also been indicated. In this review, we summarize all aforementioned aspects of immunopathogenetic action of catecholamines in EAE/MS as possibly important for designing new strategies targeting their action to prevent/mitigate autoimmune neuroinflammation and tissue damage. [ABSTRACT FROM AUTHOR]

β-Blockers (BB) are one of the most commonly prescribed pharmaceuticals used for treating cardiovascular and acute anxiety-related disorders. This class of drugs inhibit β-adrenoceptor signalling and given their growing, widespread use, BB are routinely detected in surface waters at nM concentrations. This is concerning as trace levels of BB impart developmental and reproductive dysfunction in non-target aquatic organisms, with potential for ecological risks. To date, environmental pharmaceutical risks to non-target animals are not part of the monitoring framework due to the lack of bioassays for assessing their biological effects. Behavioral endpoints have the advantage of a systems-level integration of multiple sensory signals and motor responses for toxicity screening; however, they are not currently used for risk assessment of environmental contaminants. The zebrafish (Danio rerio) embryo photomotor response (zfPMR) has been used in high-throughput behavioral screenings for neuroactive drug effects at high, therapeutic concentrations. Our objective here was to examine if we could utilize the zfPMR for screening environmental levels of BB. Embryos were placed into 96-well plates, exposed to chemicals and/or municipal wastewater effluent (MWWE), and their zfPMRs were measured with video-analysis. To specifically target BB, embryos were co-treated with isoproterenol, a β-adrenergic agonist that stimulates the zfPMR, and the inhibition of isoproterenol-induced response was used as a biomarker of BB exposure. Our results reveal that the inhibition of isoproterenol-stimulated zfPMRs can be used as a biosensor capable of detecting BB in the parts-per-billion to parts-per-trillion in water samples, including diluted MWWE. The method developed detects BB in spite of the presence of other neuroactive compounds in water samples. This systems level approach of rapid screening for BB effects provides the most promising evidence to date that behavioral neuromodulation can be potentially applied for environmental effects monitoring of pharmaceuticals. Image 1 • zfPMR is a rapid drug screening assay with potential for environmental application. • Isoproterenol stimulates zfPMR, and β-blockers (BB) inhibit this response. • Environmental levels of propranolol inhibit the isoproterenol-stimulated zfPMR. • Municipal wastewater effluent inhibits the isoproterenol-stimulated zfPMR. • Isoproterenol-stimulated zfPMR can be used as a biosensor for environmental BB. [ABSTRACT FROM AUTHOR]

In conventional meat-type (British United Turkey (B.U.T.) Big 6) turkey hearts, it has been shown that all cardiac chambers exhibit down-regulation of the β1-adrenoceptors (β1-AR) and concomitantly cAMP accumulation with increasing age regardless of sex. In this study we proved the hypothesis that breed differences exist in age-dependent alterations in the β1-AR system. Right (RA) and left (LA) atrial as well as right (RV) and left (LV) ventricular tissues were collected from male and female Cröllwitzer "wild-type" turkey poults of increasing age (6 wk, 12 wk, 16 wk, 21 wk). The β1-AR density and function were quantified by (-)-[125I]-iodocyanopindolol (ICYP) radioligand binding analysis in cell membranes from 4 cardiac chambers. Basal and stimulated cAMP production was determined as indicator of the receptor function. Wild-type turkeys showed significantly higher heart to body weight ratio than the meat-type B.U.T. Big 6 turkeys. In both sexes of Cröllwitzer turkey hearts, the β1-AR density decreased with age but significance was reached in male cardiac chambers. The receptor affinity (KD) and subtype distribution were not altered. Sex had no effect on agerelated decrease in receptor density but had an effect on adenylate cyclase (AC) activity and subsequently cAMP production. In male Cröllwitzer turkey hearts of all ages, cAMP remained at same level, whereas this was even increased in female cardiac chambers. Thus, breed affected age-related receptor-, G-protein and AC-stimulated cAMP formation in normal ventricles and atria, with females exhibiting pronounced increase with age. This suggests that the receptor signaling in wild-type turkey hearts is not as blunted as in hearts of meat-type turkey poults in which stressful farming conditions and fast growing lead to receptor down-regulation. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: One hallmark symptom of post‐traumatic stress disorder (PTSD) is an inability to restrict fear responses to the appropriate predictor. An infusion of glucocorticoids (GCs) after a high‐intensity shock has been shown to induce PTSD‐like memory impairments. In addition to GCs, noradrenergic signalling is also recognized as a key biomarker underlying PTSD symptomatology. Methods: To explore the role of the noradrenergic system in PTSD‐like memory impairments, in this study, various doses of the β‐adrenoceptor antagonist propranolol were systemically or bilaterally injected into the dorsal hippocampus immediately after unpaired cue‐shock contextual fear conditioning, and then the rats were tested 24 h later. Results: Interestingly, we found that only low‐dose propranolol could induce PTSD‐like memory impairments, as rats showed reduced freezing to the correct predictor and generalized fear responses to the safe cues, accompanied by increased NE levels in the hippocampus and altered neural activity within the frontal‐subcortical circuit. Conclusion: These findings demonstrate that the noradrenergic system is involved in regulating the consolidation of contextual fear memory and that propranolol can dose‐dependently induce PTSD‐like memory impairments. [ABSTRACT FROM AUTHOR]

Suo Quan Wan (SQW) has been used to treat lower urinary tract symptoms (LUTS) in elderly patients for hundreds of years in China. β-adrenoceptors (β-ARs), particularly β3-adrenoceptor (β3-AR), was reported to be important in the bladder dysfunction of the elderly. The present study was conducted to explore the effect of β-AR, and particularly the β3-adrenoceptor, in aging rat bladder function in vitro and to test the therapeutic effect of SQW on LUTS in an aging rat model based on the β3-adrenoceptor. Briefly, the bladder detrusor muscles of young (age, 3 months) and aging (age, 15 months) female rats were separated. A β-AR non-selective agonist, isoprenaline (ISO), subtype β3-AR agonist (BRL37344A) and β3-AR antagonist (SR59230A) were used to define the tension change of detrusor muscles between young and aging rats in vitro. For blank controls, 12 young rats were marked, and 48 aging female rats were randomly divided into four groups as follows: Model, SQW high, SQW middle and SQW low. Following oral administration of SQW for 6 weeks in aging rats, urodynamic and bladder detrusor tests were used to evaluate the therapeutic effect of SQW. The expression of β3-AR mRNA was investigated using reverse transcription-quantitative polymerase chain reaction. Using ISO and BRL37344A in vitro, maximum relaxation (Emax), intrinsic activity (IA), and log (50% effective concentration) (PD2) were significantly decreased in aging rats compared with that in young rats (P<0.05). Significant changes were also observed in the β3-AR antagonist experiment, which blocked ISO-induced relaxation, with significant decreases observed in Emax, IA and PD2, and a significant increase observed in PA2 for the aging rats compared with the young controls (P<0.05). SQW was demonstrated to enhance bladder control, storage and contraction ability. Furthermore, SQW was able to increase the sensitivity and expression of β3-AR in an aging rat. In conclusion, the decrease in β3-AR sensitivity in aging rats and the expression resulted in bladder detrusor dysfunction. In addition, the therapeutic effect of SQW against LUTS relies on the former's effect on the urethral sphincter, bladder detrusor and β3-AR. [ABSTRACT FROM AUTHOR]

Background & Purpose: Hydrogen (H2) has been shown to have a strong antioxidant effect on preventing oxidative stress-related diseases. The goal of the present study is to determine the pharmacodynamics of H2 in a model of isoproterenol (ISO)-induced cardiac hypertrophy.Methods: Mice (C57BL/6J; 8-10 weeks of age) were randomly assigned to four groups: Control group (n=10), ISO group (n=12), ISO plus H2 group (n=12), H2 group (n=12). Mice received H2 (1ml/100g/day, intraperitoneal injection) for 7 days before ISO (0.5mg/100g/day, subcutaneous injection) infusion, and then administered ISO with or without H2 for another 7 days. Then, cardiac function was evaluated by echocardiography. Cardiac hypertrophy was reflected by heart weight/body weight, gross hearts and heart sections stained with H&E, and relative ANP and BNP mRNA levels. Cardiac reactive oxygen species (ROS), 3-nitrotyrosine and p67 (phox) levels were analyzed by Dihydroethidium staining, immunohistochemistry and western blotting, respectively. For in vitro study, H9c2 cardiomyocytes were pretreated with hydrogen rich medium for 30 minutes, and then administrated with ISO (10 μM) for the indicated time. The medium and ISO were re-changed every 24 hours. Cardiomyocyte surface areas, relative ANP and BNP mRNA levels, the expression of 3-nitrotyrosine, and the dissipation of mitochondrial membrane potential (MMP) were examined. Moreover, the expression of ERK1/2, p-ERK1/2, p38, p-p38, JNK, p-JNK were measured by western blotting both in vivo and in vitro.Results: Intraperitoneal injection of hydrogen prevents cardiac hypertrophy and improves cardiac function in ISO-infused mice. Hydrogen rich medium blocks ISO-mediated cardiomyocytes hypertrophy in vitro. Hydrogen blocked the excessive expression of NADPH oxidase and the accumulation of ROS, attenuated the decrease of MMP, and inhibited ROS-sensitive ERK1/2, p38, JNK1/2 signaling pathways.Conclusions: H2 inhibited ISO-induced cardiac/cardiomyocytes hypertrophy both in vivo and in vitro, and improved the impaired left ventricular function. H2 exerts its protective effects partially through blocking ROS-sensitive ERK1/2, p38, JNK1/2 signaling pathways.

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) provide a unique opportunity to study human heart physiology and pharmacology and repair injured hearts. The suitability of hiPSC-CM critically depends on how closely they share physiological properties of human adult cardiomyocytes (CM). Here we investigated whether a 3D engineered heart tissue (EHT) culture format favors maturation and addressed the L-type Ca2+-current (ICa,L) as a readout. The results were compared with hiPSC-CM cultured in conventional monolayer (ML) and to our previous data from human adult atrial and ventricular CM obtained when identical patch-clamp protocols were used. HiPSC-CM were 2-3 fold smaller than adult CM, independently of culture format (capacitance ML 45±1 pF (n=289), EHT 45±1 pF (n=460), atrial CM 87±3 pF (n=196), ventricular CM 126±8 pF (n=50)). Only 88% of ML cells showed ICa, but all EHT. Basal ICa density was 10±1 pA/pF (n=207) for ML and 12±1 pA/pF (n=361) for EHT and was larger than in adult CM (7±1 pA/pF (p

BackgroundPropofol may decrease myocardial contractility via actions on the β-adrenoceptor-mediated signal transduction. The aim of this study was to evaluate the effect of propofol via β-adrenoceptor-mediated signal transduction by measuring the tissue levels of cAMP (cyclic adenosine monophosphate).MethodsThe effects of propofol on β-adrenoceptor mediated cascades were measured with cAMP concentrations, which were stimulated by agonists (l-isoproterenol, GTPγS, and forskolin) of each step of β-adrenoceptor-mediated cascades.ResultsWhile the production of cAMP stimulated by isoproterenol, GTPγS, or forskolin are increased (P < 0.05), application of each concentration of propofol (0.1, 1, 10, 100 µM) did not alter the levels of cAMP.ConclusionsConsidering that propofol did not alter the tissue cAMP levels when stimulated by isoproterenol, GTPγS, and forskolin, propofol appears to have no effect on the β-adrenoceptor signaling pathway in guinea pig ventricular myocardium.

Early odor preference learning in rodents occurs within a sensitive period (≤postnatal day (P)10-12), during which pups show a heightened ability to form an odor preference when a novel odor is paired with a tactile stimulation (e.g. stroking). Norepinephrine (NE) release from the locus coeruleus during stroking mediates this learning. However, in older pups, stroking loses its ability to induce learning. The cellular and circuitry mechanisms underpinning the sensitive period for odor preference learning is not well understood. We first established the sensitive period learning model in mice - odor paired with stroking induced odor preference in P8 but not P14 mice. This learning was dependent on NE-β-adrenoceptors as it was prevented by propranolol injection prior to training. We then tested whether there are developmental changes in pyramidal cell excitability and NE responsiveness in the anterior piriform cortex (aPC) in mouse pups. Although significant differences of pyramidal cell intrinsic properties were found in two age groups (P8-11 and P14+), NE at two concentrations (0.1 and 10 μM) did not alter intrinsic properties in either group. In contrast, in P8-11 pups, NE at 0.1 μM presynaptically decreased miniature IPSC and increased miniature EPSC frequencies. These effects were reversed with a higher dose of NE (10 μM), suggesting involvement of different adrenoceptor subtypes. In P14+ pups, NE at higher doses (1 and 10 μM) acted both pre- and postsynaptically to promote inhibition. These results suggest that enhanced synaptic excitation and reduced inhibition by NE in the aPC network may underlie the sensitive period.

Key points β-Adrenergic receptor agonists such as isoproterenol induce cutaneous vasodilatation and sweating in humans, but the mechanisms underpinning this response remain unresolved., Using intradermal microdialysis, we evaluated the roles of nitric oxide synthase (NOS) and cyclooxygenase (COX) in β-adrenergic cutaneous vasodilatation and sweating elicited by administration of isoproterenol., We show that while NOS contributes to β-adrenergic cutaneous vasodilatation, COX restricts cutaneous vasodilatation., We also show that combined inhibition of NOS and COX augments β-adrenergic sweating, These new findings advance our basic knowledge regarding the physiological control of cutaneous blood flow and sweating, and provide important and new information to better understand the physiological significance of β-adrenergic receptors in the skin., Abstract β-Adrenergic receptor agonists such as isoproterenol can induce cutaneous vasodilatation and sweating in humans, but the mechanisms underpinning this response remain unresolved. We evaluated the hypotheses that (1) nitric oxide synthase (NOS) contributes to β-adrenergic cutaneous vasodilatation, whereas cyclooxygenase (COX) limits the vasodilatation, and (2) COX contributes to β-adrenergic sweating. In 10 young males (25 ± 5 years), cutaneous vascular conductance (CVC) and sweat rate were evaluated at four intradermal forearm skin sites infused with (1) lactated Ringer solution (control), (2) 10 m m Nω-nitro- l-arginine ( l-NNA), a non-specific NOS inhibitor, (3) 10 m m ketorolac, a non-specific COX inhibitor, or (4) a combination of l-NNA and ketorolac. All sites were co-administered with a high dose of isoproterenol (100 μ m) for 3 min to maximally induce β-adrenergic sweating (β-adrenergic sweating is significantly blunted by subsequent activations). Approximately 60 min after the washout period, three incremental doses of isoproterenol were co-administered (1, 10 and 100 μ m each for 25 min). Increases in CVC induced by the first and second 100 μ m isoproterenol were attenuated by l-NNA alone, and those in response to all doses of isoproterenol were reduced by l-NNA with co-infusion of ketorolac (all P ≤ 0.05). Ketorolac alone augmented increases in CVC induced by 10 μ m and by the second 100 μ m isoproterenol (both P ≤ 0.05). While isoproterenol-induced sweating was not affected by the separate administration of l-NNA or ketorolac (all P > 0.05), their combined administration augmented sweating elicited by the first 3 min of 100 μ m isoproterenol ( P = 0.05). We show that while NOS contributes to β-adrenergic cutaneous vasodilatation, COX restrains the vasodilatation. Finally, combined inhibition of NOS and COX augments β-adrenergic sweating. [ABSTRACT FROM AUTHOR]

Summary Spike timing-dependent synaptic plasticity (STDP) serves as a key cellular correlate of associative learning, which is facilitated by elevated attentional and emotional states involving activation of adrenergic signaling. At cellular levels, adrenergic signaling increases dendrite excitability, but the underlying mechanisms remain elusive. Here we show that activation of β2-adrenoceptors promoted STD long-term synaptic potentiation at mouse hippocampal excitatory synapses by inactivating dendritic Kv1.1-containing potassium channels, which increased dendrite excitability and facilitated dendritic propagation of postsynaptic depolarization, potentially improving coincidental activation of pre- and postsynaptic terminals. We further demonstrate that adrenergic modulation of Kv1.1 was mediated by the signaling scaffold SAP97, which, through direct protein-protein interactions, escorts β2 signaling to remove Kv1.1 from the dendrite surface. These results reveal a mechanism through which the postsynaptic signaling scaffolds bridge the aroused brain state to promote induction of synaptic plasticity and potentially to enhance spike timing and memory encoding. [ABSTRACT FROM AUTHOR]

Context:Folium Eriobotryae(FE), the dry leaf ofEriobotrya japonica(Thunb.) Lindl. (Rosaceae), has been widely used to treat respiratory disorders. Objective:To examine the bronchodilatory activity of FE and the potential mechanisms involved. Materials and methods:The effects of ethyl acetate fraction of FE (EFE) (0.05–0.3 mg/mL) on the isolated tracheal strips, and ursolic acid (UA) (5–30 μg/mL) that was the main constituent of EFE, were testedin vitro. Meanwhile, acetylcholine (Ach) and histamine (His)-induced bronchospasm were conductedin vivoin guinea pig. Furthermore, mechanisms of relaxant effects of EFE and UA were evaluated in the absence and presence of specific inhibitors. Results:Within vitrostudies, the contractile response evoked by Ach or His (EC50 = 0.21 and 0.16 mg/mL) was decreased by EFE, and UA caused a concentration-dependent relaxation precontracted by His (EC50 = 23.2 μg/mL). Within vivostudies, EFE strongly prolonged preconvulsive time similar to isoprenalin. The bronchodilator effects of EFE could be blocked by propranolol (1 μM),NG-nitro-l-arginine methyl ester (l-NAME) (100 μM) and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ) (1 μM). EFE also inhibited the contraction in Ca2+-free medium and produced rightward parallel displacement of CaCl2curves. In addition, the relaxant effects of UA could only be blocked byl-NAME and ODQ. Discussion and conclusion:These results suggest that bronchodilator activities of EFE were related to activation of β-adrenoceptor and NO/cGMP pathway. Blockage of Ca2+ channels and inhibition of IP3R-mediated internal Ca2+ release were also involved. Additionally, UA produced relaxant effects by the NO/cGMP pathway. [ABSTRACT FROM AUTHOR]

Background and Purpose: Hydrogen (H2) has been shown to have a strong antioxidant effect on preventing oxidative stress-related diseases. The goal of the present study is to determine the pharmacodynamics of H2 in a model of isoproterenol (ISO)-induced cardiac hypertrophy. Methods: Mice (C57BL/6J; 8-10 weeks of age) were randomly assigned to four groups: Control group (n = 10), ISO group (n = 12), ISO plus H2 group (n = 12), and H2 group (n = 12). Mice received H2 (1 ml/100g/day, intraperitoneal injection) for 7 days before ISO (0.5 mg/100g/day, subcutaneous injection) infusion, and then received ISO with or without H2 for another 7 days. Then, cardiac function was evaluated by echocardiography. Cardiac hypertrophy was reflected by heart weight/body weight, gross morphology of hearts, and heart sections stained with hematoxylin and eosin, and relative atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) mRNA levels. Cardiac reactive oxygen species (ROS), 3-nitrotyrosine and p67 (phox) levels were analyzed by dihydroethidium staining, immunohistochemistry and Western blotting, respectively. For in vitro study, H9c2 cardiomyocytes were pretreated with H2-rich medium for 30 min, and then treated with ISO (10 µM) for the indicated time. The medium and ISO were re-changed every 24 h. Cardiomyocyte surface areas, relative ANP and BNP mRNA levels, the expression of 3-nitrotyrosine, and the dissipation of mitochondrial membrane potential (MMP) were examined. Moreover, the expression of extracellular signal-regulated kinase1/2 (ERK1/2), p-ERK1/2, p38, p-p38, c-Jun NH2- terminal kinase (JNK), and p-JNK were measured by Western blotting both in vivo and in vitro. Results: Intraperitoneal injection of H2 prevented cardiac hypertrophy and improved cardiac function in ISO-infused mice. H2-rich medium blocked ISO-mediated cardiomyocytes hypertrophy in vitro. H2 blocked the excessive expression of NADPH oxidase and the accumulation of ROS, attenuated the decrease of MMP, and inhibited ROS-sensitive ERK1/2, p38, and JNK signaling pathways. Conclusion: H2 inhibits ISO-induced cardiac/cardiomyocytes hypertrophy both in vivo and in vitro, and improves the impaired left ventricular function. H2 exerts its protective effects partially through blocking ROS-sensitive ERK1/2, p38, and JNK signaling pathways. [ABSTRACT FROM AUTHOR]

Thestimulatory effect of the extract of Portulaca oleracea (P. olerace) on β-adrenoceptor of tracheal smooth muscle was examined. To examine β-adrenoceptor stimulatory effect, concentration response curve to isoprenaline was obtained in pre-contracted tracheal smooth muscle in the presence of three concentrations of aqueous-ethanolic extract, propranolol, and saline. Values of EC50 (the effective concentration of isoprenaline, causing 50% of maximum response) and dose ratio-1(CR-1) were measured. This effect was tested innon-incubated tracheal smooth muscle (group 1) and incubated tissues with chlorpheniramine (group 2). Concentration-response curves to isoprenaline in the presence of two higher concentrations of the extract in group 1 and all three concentrations in group 2 showed leftward shifts compared to isoprenaline curves produced in the presence of saline in both groups. EC50 obtained in the presence of propranolol was significantly higher than that of saline in both groups of experiments (p<0.05 for both cases). However, the EC50 obtained in the presence of two higher concentrations of the extract in group 1 and lower concentration in group 2 were nonsignificantly but those obtained of medium and high extract concentrations in the group 2 were significantly (p<0.05 for both cases)lower than those of saline. The values of (CR-1) obtained in the presence of all concentrations of the extract in groups1 and 2 were significantly lower than that of propranolol (p<0.05 to p<0.001).The results indicated a stimulatory effect of the P. olerace extract on ß2-adrenoceptors of tracheal smooth muscle. [ABSTRACT FROM AUTHOR]

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) provide a unique opportunity to study human heart physiology and pharmacology and repair injured hearts. The suitability of hiPSC-CM critically depends on how closely they share physiological properties of human adult cardiomyocytes (CM). Here we investigated whether a 3D engineered heart tissue (EHT) culture format favors maturation and addressed the L-type Ca2+-current (ICa,L) as a readout. The results were compared with hiPSC-CM cultured in conventional monolayer (ML) and to our previous data from human adult atrial and ventricular CM obtained when identical patch-clamp protocols were used. HiPSC-CM were two- to three-fold smaller than adult CM, independently of culture format [capacitance ML 45 ± 1 pF (n = 289), EHT 45 ± 1 pF (n = 460), atrial CM 87 ± 3 pF (n = 196), ventricular CM 126 ± 8 pF (n = 50)]. Only 88% of ML cells showed ICa, but all EHT. Basal ICa density was 10 ± 1 pA/pF (n = 207) for ML and 12 ± 1 pA/pF (n = 361) for EHT and was larger than in adult CM [7 ± 1 pA/pF (p < 0.05, n = 196) for atrial CM and 6 ± 1 pA/pF (p < 0.05, n = 47) for ventricular CM]. However, ML and EHT showed robust T-type Ca2+-currents (ICa,T). While (-)-Bay K 8644, that activates ICa,L directly, increased ICa,Lto the same extent in ML and EHT, β1- and β2-adrenoceptor effects were marginal in ML, but of same size as (-)-Bay K 8644 in EHT. The opposite was true for serotonin receptors. Sensitivity to β1 and β2-adrenoceptor stimulation was the same in EHT as in adult CM (-logEC50: 5.9 and 6.1 for norepinephrine (NE) and epinephrine (Epi), respectively), but very low concentrations of Rp-8-Br-cAMPS were sufficient to suppress effects (-logEC50: 5.3 and 5.3 respectively for NE and Epi). Taken together, hiPSC-CM express ICa,L at the same density as human adult CM, but, in contrast, possess robust ICa,T. Increased effects of catecholamines in EHT suggest more efficient maturation. [ABSTRACT FROM AUTHOR]

Takotsubo syndrome (TTS) is characterized by short-term contractile dysfunction with its mechanism undefined. We showed that activation of cardiac Hippo pathway mediates mitochondrial dysfunction and that stimulation of β-adrenoceptors (βAR) activates Hippo pathway. Here, we investigated the role of βAR-Hippo signaling in mediating mitochondrial dysfunction in isoproterenol (Iso)-induced TTS-like mouse model. Elderly postmenopausal female mice were administered with Iso (1.25 mg/kg/h for 23 h). Cardiac function was determined by serially echocardiography. At days 1 and 7 post-Iso exposure, mitochondrial ultrastructure and function were examined by electron microscopy and various assays. Alterations in cardiac Hippo pathway and effects of genetic inactivation of Hippo kinase (Mst1) on mitochondrial damage and dysfunction in the acute phase of TTS were investigated. Isoproterenol exposure induced acute increase in biomarkers of cardiac damage and ventricular contractile dysfunction and dilation. At day 1 post-Iso, we observed extensive abnormalities in mitochondrial ultrastructure, downregulation of mitochondrial marker proteins, and mitochondrial dysfunction evidenced by lower ATP content, increased lipid droplets, higher contents of lactate, and augmented reactive oxygen species (ROS). All changes were reversed by day 7 . βAR stimulation led to activation of cardiac Hippo pathway with enhanced expression of Hippo kinase Mst1 and inhibitory YAP phosphorylation, as well as reduced nuclear YAP-TEAD1 interaction. In mice with cardiac expression of inactive mutant Mst1 gene, acute mitochondrial damage and dysfunction were mitigated. Stimulation of cardiac βAR activates Hippo pathway that mediates mitochondrial dysfunction with energy insufficiency and enhanced ROS, promoting acute but short-term ventricular dysfunction. NEW & NOTEWORTHY Takotsubo syndrome (TTS) is featured by activation of sympatho-β-adrenoceptor (βAR) system leading to acute loss of ventricular contractile performance. However, the molecular mechanism remains undefined. We demonstrated, in an isoproterenol-induced murine TTS-like model, extensive mitochondrial damage, metabolic dysfunction, and downregulated mitochondrial marker proteins, changes temporarily associated with cardiac dysfunction. Mechanistically, stimulation of βAR activated Hippo signaling pathway and genetic inactivation of Mst1 kinase ameliorated mitochondrial damage and metabolic dysfunction at the acute phase of TTS.

GTP binding proteins are classified into two families: heterotrimeric large G proteins which are composed of three subunits, and one subunit of small G proteins. Roles of small G proteins in the intracellular trafficking of G protein-coupled receptors (GPCRs) were studied. Among various small G proteins tested, GTP-bound form (G23V) of RalA inhibited the internalization of dopamine D 2 receptor independently of the previously reported downstream effectors of RalA, such as Ral-binding protein 1 and PLD. With high affinity for GRK2, active RalA inhibited the GPCR endocytosis by sequestering the GRK2 from receptors. When it was tested for several GPCRs including an endogenous GPCR, lysophosphatidic acid receptor 1, agonist-induced conversion of GTP-bound to GDP-bound RalA, which presumably releases the sequestered GRK2, was observed selectively with the GPCRs which have tendency to undergo endocytosis. Conversion of RalA from active to inactive state occurred by translocation of RGL, a guanine nucleotide exchange factor, from the plasma membrane to cytosol as a complex with Gβγ. These results suggest that agonist-induced Gβγ-mediated conversion of RalA from the GTP-bound form to the GDP-bound form could be a mechanism to facilitate agonist-induced internalization of GPCRs. [ABSTRACT FROM AUTHOR]

Early odor preference learning in rodents occurs within a sensitive period [≤postnatal day (P)10-12], during which pups show a heightened ability toform an odor preference when a novel odor is paired with a tactile stimulation (e.g., stroking). Norepinephrine (NE) release from the locus coeruleus during stroking mediates this learning. However, in older pups, stroking loses its ability to induce learning. The cellular and circuitry mechanisms underpinning the sensitive period for odor preference learning is not well understood. We first established the sensitive period learning model in mice - odor paired with stroking induced odor preference in P8 but not P14 mice. This learning was dependent on NE-β-adrenoceptors as it was prevented by propranolol injection prior to training. We then tested whether there are developmental changes in pyramidal cell excitability and NE responsiveness in the anterior piriform cortex (aPC) in mouse pups. Although significant differences of pyramidal cell intrinsic properties were found in two age groups (P8-11 and P14+), NE at two concentrations (0.1 and 10 μM) did not alter intrinsic properties in either group. In contrast, in P8-11 pups, NE at 0.1 μM presynaptically decreased miniature IPSC and increased miniature EPSC frequencies. These effects were reversed with a higher dose of NE (10 μM), suggesting involvement of different adrenoceptor subtypes. In P14+ pups, NE at higher doses (1 and 10 μM) acted both pre- and postsynaptically to promote inhibition. These results suggest that enhanced synaptic excitation and reduced inhibition by NE in the aPC network may underlie the sensitive period. [ABSTRACT FROM AUTHOR]

The circulatory system is one of the first systems that develops during embryogenesis. Angiogenesis describes the formation of blood vessels as a part of the circulatory system and is essential for organ growth in embryogenesis as well as repair in adulthood. A dysregulation of vessel growth contributes to the pathogenesis of many disorders. Thus, an imbalance between pro- and antiangiogenic factors could be observed in infantile hemangioma (IH). Infantile hemangioma is the most common benign tumor during infancy, which appears during the first month of life. These vascular tumors are characterized by rapid proliferation and subsequently slower involution. Most IHs regress spontaneously, but in some cases they cause disfigurement and systemic complications, which requires immediate treatment. Recently, a therapeutic effect of propranolol on IH has been demonstrated. Hence, this nonselective β- blocker became the first-line therapy for IH. Over the last years, our understanding of the underlying mechanisms of IH has been improved and possible mechanisms of action of propranolol in IH have postulated. Previous studies revealed that gap junction proteins, the connexins (Cx), might also play a role in the pathogenesis of IH. Therefore, affecting gap junctional intercellular communication is suggested as a novel therapeutic target of propranolol in IH. In this review we summarize the current knowledge of the molecular processes leading to IH and provide new insights of how connexins might be involved in the development of these vascular tumors.

Acetlycholine is involved in the control of airway smooth muscle constriction and in recruitment of inflammatory cells via neuronal and paracrine effects on muscarinic type 3 receptors. Long acting muscarinic antagonists ( LAMA) are well established in guidelines for COPD but are not currently licensed for use in asthma. There are emerging data from key clinical trials to show that LAMA may confer bronchodilator effects and improved control when used in addition to inhaled corticosteroid ( ICS) alone or in conjunction with long acting β-adrenoceptor agonists ( LABA). Further studies in persistent asthmatic patients are required to evaluate ICS sparing effects of LAMA looking particularly at airway hyper-responsiveness and surrogate inflammatory markers, in addition to evaluation of possible synergy between LAMA and LABA when given together. Future possible development of combination inhalers comprising ICS/ LAMA or ICS/ LAMA/ LABA will require long term studies looking at asthma control and exacerbations in both adult and paediatric patients. [ABSTRACT FROM AUTHOR]

Different pharmacological effects of Achillea millefolium including its relaxant effect on smooth muscle have been shown previously. In the present study the stimulatory effect of the plant extract on (β-adrenoceptor of tracheal muscle was examined in order to investigate one possible mechanism for its observed relaxant effect. Effect of three concentrations of hydroethanol extract, 10 nM propranolol, and saline on (β-adrenoceptor was tested in two experimental groups including; nonincubated tracheal smooth muscles (group 1) and incubated tracheal smooth muscle with chlorpheniramine (group 2). Concentration response curves to isoprenaline were performed in precontracted tracheal smooth muscle in the presence of the extract, propranolol and saline. Values of EC50 and CR-1 were measured. Leftward shifts in isoprenaline curves were observed in the presence of medium and high concentrations of the extract compared with saline in both groups. The values of EC50 obtained in the presence of medium and high concentrations of the extract only in group 1 were nonsignificantly lower than that of saline. The values of CR-1 obtained in the presence of all concentrations of the extract in both groups were negative and significantly different with that of propranolol. The results indicated a small stimulatory effect of the extract on β2-adrenoceptors. [ABSTRACT FROM AUTHOR]

Background and Purpose In small arteries, small conductance Ca2+-activated K+ channels ( SKCa) and intermediate conductance Ca2+-activated K+ channels ( IKCa) restricted to the vascular endothelium generate hyperpolarization that underpins the NO- and PGI2-independent, endothelium-derived hyperpolarizing factor response that is the predominate endothelial mechanism for vasodilatation. As neuronal IKCa channels can be negatively regulated by PKA, we investigated whether β-adrenoceptor stimulation, which signals through cAMP/ PKA, might influence endothelial cell hyperpolarization and as a result modify the associated vasodilatation. Experimental Approach Rat isolated small mesenteric arteries were pressurized to measure vasodilatation and endothelial cell [ Ca2+]i, mounted in a wire myograph to measure smooth muscle membrane potential or dispersed into endothelial cell sheets for membrane potential recording. Key Results Intraluminal perfusion of β-adrenoceptor agonists inhibited endothelium-dependent dilatation to ACh (1 nM-10 μM) without modifying the associated changes in endothelial cell [ Ca2+]i. The inhibitory effect of β-adrenoceptor agonists was mimicked by direct activation of adenylyl cyclase with forskolin, blocked by the β-adrenoceptor antagonists propranolol (non-selective), atenolol ( β1) or the PKA inhibitor KT-5720, but remained unaffected by ICI 118 551 ( β2) or glibenclamide ( ATP-sensitive K+ channels channel blocker). Endothelium-dependent hyperpolarization to ACh was also inhibited by β-adrenoceptor stimulation in both intact arteries and in endothelial cells sheets. Blocking IKCa {with 1 μM 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole ( TRAM-34)}, but not SKCa (50 nM apamin) channels prevented β-adrenoceptor agonists from suppressing either hyperpolarization or vasodilatation to ACh. Conclusions and Implications In resistance arteries, endothelial cell β1-adrenoceptors link to inhibit endothelium-dependent hyperpolarization and the resulting vasodilatation to ACh. This effect appears to reflect inhibition of endothelial IKCa channels and may be one consequence of raised circulating catecholamines. [ABSTRACT FROM AUTHOR]

Background: The possible mechanism(s) of inotropic and chronotropic effects of the extract from Rosa damascena (R. damascena) on heart was examined. Methods: Inotropic and chronotropic effects of four concentrations of the extract from R. damascena and isoprenaline were examined in isolated guinea-pig hearts perfused through aorta in a Langendorff model. All measurements were performed in three different groups: 1) In the presence and absence of propranolol, 2) In the presence and absence of methacholine and 3) In the presence of diltiazem (n = 12 for each group). Results: In all groups both isoprenaline and the extract caused an increase in heart rate and contractility (p < 0.05 to p < 0.001). Only in group 1, the final concentration of isoprenaline in the absence of propranolol caused significant greater increase in heart rate compared to the extract (207.6 ± 11.0 compared to 162.6 ± 11.8, p < 0.01). The percent increase in heart contractility due to the final concentration of the extract in the absence (362.4 ± 36.9 compared to 227.7 ± 31.6, p < 0.01) and presence of propranolol (577.1 ± 62.9 compared to 357.5 ± 45.6, p < 0.001) in group 1 and absence (403.7 ± 42.1 compared to 244.8 ± 18.9, p < 0.005) and presence of methcholine (499.88 ± 64.64 compared to 323.90 ± 44.49, p < 0.05) in groups 2 was significantly greater than the increase caused by isoprenaline. Conclusions: The results of this study suggest that inotropic and chornotropic effect of R. damascena is possibly due to the stimulatory effect of this plant on beta-adrenoceptors. [ABSTRACT FROM AUTHOR]

Clinically observed differences in airway reactivity and asthma exacerbations in women at different life stages suggest a role for sex steroids in modulating airway function although their targets and mechanisms of action are still being explored. We have previously shown that clinically relevant concentrations of exogenous estrogen acutely decrease intracellular calcium ([Ca2+]i) in human airway smooth muscle (ASM), thereby facilitating bronchodilation. In this study, we hypothesized that estrogens modulate cyclic nucleotide regulation, resulting in decreased [Ca2+]i in human ASM. In Fura-2-loaded human ASM cells, 1 nM 17β-estradiol (E2) potentiated the inhibitory effect of the β-adrenoceptor (β-AR) agonist isoproterenol (ISO; 100 nM) on histamine-mediated Ca2+ entry. Inhibition of protein kinase A (PKA) activity (KT5720; 100 nM) attenuated E2 effects on [Ca2+]i. Acute treatment with E2 increased cAMP levels in ASM cells comparable to that of ISO (100 pM). In acetylcholine-contracted airways from female guinea pigs or female humans, E2 potentiated ISO-induced relaxation. These novel data suggest that, in human ASM, physiologically relevant concentrations of estrogens act via estrogen receptors (ERs) and the cAMP pathway to nongenomically reduce [Ca2+]i, thus promoting bronchodilation. Activation of ERs may be a novel adjunct therapeutic avenue in reactive airway diseases in combination with established cAMPactivating therapies such as β2-agonists. [ABSTRACT FROM AUTHOR]

BACKGROUND AND PURPOSE Muscarinic acetylcholine receptors (mAChRs) and β-adrenoceptors in the airways and lungs are clinically important in chronic obstructive pulmonary disease (COPD) and asthma. However, the quantitative and qualitative estimation of these receptors by radioligand binding approaches in human airways has not yet been reported because of tissue limitations. EXPERIMENTAL APPROACH The regional distribution and relative proportion of mAChR and β-adrenoceptor subtypes were evaluated in human bronchus and lung parenchyma by a tissue segment binding method with [3H]-N-methylscopolamine ([3H]-NMS) for mAChRs and [3H]-CGP-12,177 for β-adrenoceptors. Functional responses to carbachol and isoprenaline were also analysed in the bronchus. KEY RESULTS The M3 subtype predominantly occurred in the bronchus, but the density decreased from the segmental to subsegmental bronchus, and was absent in lung parenchyma. On the other hand, the M1 subtype occurred in the lung only, and the M2 subtype was distributed ubiquitously in the bronchus and lungs. β2-adrenoceptors were increased along the airways, and their densities in the subsegmental bronchus and lung parenchyma were approximately twofold higher than those of mAChRs in the same region. β1-adrenoceptors were also detected in lung parenchyma but not in the bronchus. The muscarinic contractions and adrenoceptor relaxations in both bronchial regions were mediated through M3-mAChRs and β2-adrenoceptors, respectively. CONCLUSIONS AND IMPLICATIONS From the present radioligand binding approach with intact tissue segments, we constructed a distribution map of mAChRs and β-adrenoceptors in human bronchus and lung parenchyma for the first time, providing important evidence for future pharmacotherapy and new drug development for respiratory disorders. [ABSTRACT FROM AUTHOR]

The article examines the hypothesis that KCNQ4-enoced voltage-dependent potassium (Kv7.4) contribute to ß-adrenoceptor-mediated vasodilation in the renal vasculature. It mentions that the application of the Kv7 blocker linopirdine attenuated isoproterenol-induced relaxation and current. The article concludes that Kv7.4 responses are abolished in the renal vasculature which resulted in impaired responsiveness to vasodilators and enhanced vasopasm in hypertension.

Aims Membrane potential is a key determinant of vascular tone and many vasodilators act through the modulation of ion channel currents [e.g. the ATP-sensitive potassium channel (KATP)] involved in setting the membrane potential. Adenylyl cyclase (AC) isoenzymes are potentially important intermediaries in such vasodilator signalling pathways. Vascular smooth muscle cells (VSMCs) express multiple AC isoenzymes, but the reason for such redundancy is unknown. We investigated which of these isoenzymes are involved in vasodilator signalling and regulation of vascular ion channels important in modulating membrane potential. Methods and results AC isoenzymes were selectively depleted (by >75%) by transfection of cultured VSMCs with selective short interfering RNA sequences. AC6 was the predominant isoenzyme involved in vasodilator-mediated cAMP accumulation in VSMCs, accounting for ∼60% of the total response to β-adrenoceptor (β-AR) stimulation. AC3 played a minor role in β-AR signalling, whereas AC5 made no significant contribution. AC6 was also the principal isoenzyme involved in β-AR-mediated protein kinase A (PKA) signalling (determined using the fluorescent biosensor for PKA activity, AKAR3) and the substantial β-AR/PKA-dependent enhancement of KATP current. KATP current was shown to play a vital role in setting the resting membrane potential and in mediating the hyperpolarization observed upon β-AR stimulation. Conclusion AC6, but not the closely related AC5, plays a principal role in vasodilator signalling and regulation of the membrane potential in VSMCs. These findings identify AC6 as a vital component in the vasodilatory apparatus central to the control of blood pressure. [ABSTRACT FROM AUTHOR]

Abstract: Local movements of receptors in the plasma membrane have been extensively studied, as it is generally believed that the dynamics of membrane distribution of receptors regulate their functions. However, the properties of large-scale (>5μm) receptor movements in the membrane are relatively obscure. In the present study, we addressed the question as to whether the large-scale movement of receptor in the plasma membrane at the whole cell level can be explained quantitatively by its local diffusive properties. We used HEK 293 cells transfected with human β2-adrenoceptor fused to photoconvertible fluorescent protein dendra2 as a model system; and found that 1) functional integrity of the dendra2-tagged receptor remains apparently intact; 2) in a mesoscopic scale (~4μm), ~90% of the receptors are mobile on average, and receptor influx to, and out-flux from a membrane area can be symmetrically explained by a diffusion-like process with an effective diffusion coefficient of ~0.1μm2/s; 3) these mobility parameters are not affected by the activity state of the receptor (assessed by using constitutively active receptor mutants); 4) in the macroscopic scale (4–40μm), although a slowly diffusing fraction of receptors (with D<0.01μm2/s) is identifiable in some cases, the movement of the predominant fraction is perfectly explained by the same effective diffusion process observed in the mesoscopic scale, suggesting that the large scale structure of the cell membrane as felt by the receptor is apparently homogeneous in terms of its mesoscopic properties. We also showed that intracellular compartments and plasma membrane are kinetically connected even at steady-state. [Copyright &y& Elsevier]

Heart disease is associated with increased sympathetic nerve activity and elevated levels of circulating catecholamines, resulting in chronic stimulation of the β-adrenergic receptors (β-AR) and consequent pathological cardiac remodeling. Experimentally, chronic administration of the β-AR agonist isoproterenol (ISO) has been most commonly used to model β-AR-induced cardiac remodeling. However, it remains unclear whether β-AR-mediated cardiac remodeling and dysfunction differs between sustained versus pulsatile (intermittent) exposure to a β-agonist. Here, we compare the effects of intermittent versus sustained administration of ISO on cardiac remodeling and function in mice. Animals were administered 5 mg (kg d) ISO for 2 weeks either by daily subcutaneous injection, or continuous infusion via an implanted osmotic minipump. Cardiac function and remodeling were determined by echocardiography, micromanometry and histology. Moreover, Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) were utilized to define the proteins and genes involved. Both sustained and intermittent administration of ISO resulted in a similar degree of cardiac hypertrophy (16% and 19%, respectively). However, mice receiving ISO by daily injection developed more severe ventricular systolic and diastolic dysfunction and myocardial fibrosis compared with mice receiving ISO via the osmotic minipump. The disparity in results between the delivery methods is suggested to be due, at least in part, to increased expression of fibrogenic factors, including connective tissue growth factor (CTGF) and NADPH oxidase (NOX4), in mice receiving intermittent application of ISO. In summary, compared with sustained exposure to a β-AR agonist, intermittent β-AR stimulation leads to more severe cardiac dysfunction and fibrosis. These findings not only further our understanding of β-AR function in the setting of cardiac pathophysiology, but also highlight that significant differences can result dependent upon the mode of experimental β-AR stimulation in inducing cardiomyopathy. [ABSTRACT FROM AUTHOR]