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Protein kinase G (PKG) is activated by nitric oxide (NO)-induced cGMP binding or alternatively by oxidant-induced interprotein disulfide formation. We found preactivation with cGMP attenuated PKG oxidation. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) blockade of cGMP production increased disulfide PKG to 13 ± 2% and 29±4% of total in aorta and mesenteries, respectively. This was potentially anomalous, because we observed 2.7-fold higher NO levels in aorta than mesenteries; consequently, we had anticipated that ODQ would induce more disulfide in the conduit vessel. ODQ also constricted aorta, whereas it had no effect on mesenteries. Thus, mesenteries, but not aorta, can compensate for loss of NO-cGMP by recruiting disulfide activation of PKG. Mechanistically, this is explained by loss of cGMP allowing disulfide formation in response to basal oxidant production. Why aorta treated with ODQ generated less PKG disulfide that is insufficient to induce vasoconstriction was unclear. One potential explanation, especially because aorta were much less sensitive than mesenteries to exogenous H(2)O(2)-induced relaxation (EC(50)=205 ± 24 and 33 ± 2 µmol/L, respectively) was that conduit vessels may have higher peroxidase capacity. Indeed, we found that aorta express 49 ± 22% and 80 ± 25% more peroxiredoxin and thioredoxin, respectively, than mesenteries, and their 2-Cys peroxiredoxin peroxidatic cysteines were also less sensitive to hyperoxidation. The higher peroxidase capacity of aortas would explain their constriction during cGMP removal and their insensitivity to H(2)O(2)-induced relaxation compared with mesenteries. In summary, cGMP binding to PKG induces a state that is resistant to disulfide formation. Consequently, cGMP depletion sensitizes PKG to oxidation; this happens to a lesser extent in aortas than in mesenteries, because the conduit vessels generate more NO and express more peroxiredoxin. [ABSTRACT FROM AUTHOR]

Background: Pulmonary hypertension (PH) is a chronic vascular disease characterized, among other abnormalities, by hyperproliferative smooth muscle cells and a perturbed cellular redox and metabolic balance. Oxidants induce cell cycle arrest to halt proliferation; however, little is known about the redox-regulated effector proteins that mediate these processes. Here, we report a novel kinase-inhibitory disulfide bond in cyclin D-CDK4 (cyclin-dependent kinase 4) and investigate its role in cell proliferation and PH., Methods: Oxidative modifications of cyclin D-CDK4 were detected in human pulmonary arterial smooth muscle cells and human pulmonary arterial endothelial cells. Site-directed mutagenesis, tandem mass-spectrometry, cell-based experiments, in vitro kinase activity assays, in silico structural modeling, and a novel redox-dead constitutive knock-in mouse were utilized to investigate the nature and definitively establish the importance of CDK4 cysteine modification in pulmonary vascular cell proliferation. Furthermore, the cyclin D-CDK4 oxidation was assessed in vivo in the pulmonary arteries and isolated human pulmonary arterial smooth muscle cells of patients with pulmonary arterial hypertension and in 3 preclinical models of PH., Results: Cyclin D-CDK4 forms a reversible oxidant-induced heterodimeric disulfide dimer between C7/8 and C135, respectively, in cells in vitro and in pulmonary arteries in vivo to inhibit cyclin D-CDK4 kinase activity, decrease Rb (retinoblastoma) protein phosphorylation, and induce cell cycle arrest. Mutation of CDK4 C135 causes a kinase-impaired phenotype, which decreases cell proliferation rate and alleviates disease phenotype in an experimental mouse PH model, suggesting this cysteine is indispensable for cyclin D-CDK4 kinase activity. Pulmonary arteries and human pulmonary arterial smooth muscle cells from patients with pulmonary arterial hypertension display a decreased level of CDK4 disulfide, consistent with CDK4 being hyperactive in human pulmonary arterial hypertension. Furthermore, auranofin treatment, which induces the cyclin D-CDK4 disulfide, attenuates disease severity in experimental PH models by mitigating pulmonary vascular remodeling., Conclusions: A novel disulfide bond in cyclin D-CDK4 acts as a rapid switch to inhibit kinase activity and halt cell proliferation. This oxidative modification forms at a critical cysteine residue, which is unique to CDK4, offering the potential for the design of a selective covalent inhibitor predicted to be beneficial in PH., Competing Interests: Disclosures None.

Background: Although it has long been recognized that smooth muscle Na/K ATPase modulates vascular tone and blood pressure (BP), the role of its accessory protein phospholemman has not been characterized. The aim of this study was to test the hypothesis that phospholemman phosphorylation regulates vascular tone in vitro and that this mechanism plays an important role in modulation of vascular function and BP in experimental models in vivo and in humans., Methods: In mouse studies, phospholemman knock-in mice (PLM 3SA ; phospholemman [FXYD1] in which the 3 phosphorylation sites on serines 63, 68, and 69 are mutated to alanines), in which phospholemman is rendered unphosphorylatable, were used to assess the role of phospholemman phosphorylation in vitro in aortic and mesenteric vessels using wire myography and membrane potential measurements. In vivo BP and regional blood flow were assessed using Doppler flow and telemetry in young (14-16 weeks) and old (57-60 weeks) wild-type and transgenic mice. In human studies, we searched human genomic databases for mutations in phospholemman in the region of the phosphorylation sites and performed analyses within 2 human data cohorts (UK Biobank and GoDARTS [Genetics of Diabetes Audit and Research in Tayside]) to assess the impact of an identified single nucleotide polymorphism on BP. This single nucleotide polymorphism was expressed in human embryonic kidney cells, and its effect on phospholemman phosphorylation was determined using Western blotting., Results: Phospholemman phosphorylation at Ser63 and Ser68 limited vascular constriction in response to phenylephrine. This effect was blocked by ouabain. Prevention of phospholemman phosphorylation in the PLM 3SA mouse profoundly enhanced vascular responses to phenylephrine both in vitro and in vivo. In aging wild-type mice, phospholemman was hypophosphorylated, and this correlated with the development of aging-induced essential hypertension. In humans, we identified a nonsynonymous coding variant, single nucleotide polymorphism rs61753924, which causes the substitution R70C in phospholemman. In human embryonic kidney cells, the R70C mutation prevented phospholemman phosphorylation at Ser68. This variant's rare allele is significantly associated with increased BP in middle-aged men., Conclusions: These studies demonstrate the importance of phospholemman phosphorylation in the regulation of vascular tone and BP and suggest a novel mechanism, and therapeutic target, for aging-induced essential hypertension in humans.

Group 3 pulmonary hypertension (PH), which occurs secondary to hypoxia lung diseases, is one of the most common causes of PH worldwide and has a high unmet clinical need. A deeper understanding of the integrative pathological and adaptive molecular mechanisms within this group is required to inform the development of novel drug targets and effective treatments. The production of oxidants is increased in PH Group 3, and their pleiotropic roles include contributing to disease progression by promoting prolonged hypoxic pulmonary vasoconstriction and pathological pulmonary vascular remodeling, but also stimulating adaptation to pathological stress that limits the severity of this disease. Inflammation, which is increasingly being viewed as a key pathological feature of Group 3 PH, is subject to complex regulation by redox mechanisms and is exacerbated by, but also augments oxidative stress. In this review, we investigate aspects of this complex crosstalk between inflammation and oxidative stress in Group 3 PH, focusing on the redox-regulated transcription factor NF-κB and its upstream regulators toll-like receptor 4 and high mobility group box protein 1. Ultimately, we propose that the development of specific therapeutic interventions targeting redox-regulated signaling pathways related to inflammation could be explored as novel treatments for Group 3 PH.

Nitro-oleate (10-nitro-octadec-9-enoic acid), which inhibits soluble epoxide hydrolase (sEH) by covalently adducting to C521, increases the abundance of epoxyeicosatrienoic acids (EETs) that can be health promoting, for example by lowering blood pressure or their anti-inflammatory actions. However, perhaps consistent with their impact on angiogenesis, increases in EETs may exacerbate progression of some cancers. To assess this, Lewis lung carcinoma (LLc1) cells were exposed to oleate or nitro-oleate, with the latter inhibiting the hydrolase and increasing their proliferation and migration in vitro. The enhanced proliferation induced by nitro-oleate was EET-dependent, being attenuated by the ETT-receptor antagonist 14,15-EE-5(Z)-E. LLc1 cells were engineered to stably overexpress wild-type or C521S sEH, with the latter exhibiting resistance to nitro-oleate-dependent hydrolase inhibition and the associated stimulation of tumor growth in vitro or in vivo. Nitro-oleate also increased migration in endothelial cells isolated from wild-type (WT) mice, but not those from C521S sEH knock-in (KI) transgenic mice genetically modified to render the hydrolase electrophile-resistant. These observations were consistent with nitro-oleate promoting cancer progression, and so the impact of this electrophile was examined in vivo again, but this time comparing growth of LLc1 cells expressing constitutive levels of wild-type hydrolase when implanted into WT or KI mice. Nitro-oleate inhibited tumor sEH (P < 0.05), with a trend for elevated plasma 11(12)-EET/DHET and 8(9)EET/DHET (dihydroxyeicosatrienoic acid) ratios when administered to WT, but not KI, mice. Although in vitro studies with LLc1 cells supported a role for nitro-oleate in cancer cell proliferation, it failed to significantly stimulate tumor growth in WT mice implanted with the same LLc1 cells in vivo, perhaps due to its well-established anti-inflammatory actions. Indeed, pro-inflammatory cytokines were significantly down-regulated in nitro-oleate treated WT mice, potentially countering any impact of the concomitant inhibition of sEH., (Copyright © 2019. Published by Elsevier B.V.)

Chronic hypoxia causes pulmonary hypertension (PH), vascular remodeling, right ventricular (RV) hypertrophy, and cardiac failure. Protein kinase G Iα (PKGIα) is susceptible to oxidation, forming an interprotein disulfide homodimer associated with kinase targeting involved in vasodilation. Here we report increased disulfide PKGIα in pulmonary arteries from mice with hypoxic PH or lungs from patients with pulmonary arterial hypertension. This oxidation is likely caused by oxidants derived from NADPH oxidase-4, superoxide dismutase 3, and cystathionine γ-lyase, enzymes that were concomitantly increased in these samples. Indeed, products that may arise from these enzymes, including hydrogen peroxide, glutathione disulfide, and protein-bound persulfides, were increased in the plasma of hypoxic mice. Furthermore, low-molecular-weight hydropersulfides, which can serve as "superreductants" were attenuated in hypoxic tissues, consistent with systemic oxidative stress and the oxidation of PKGIα observed. Inhibiting cystathionine γ-lyase resulted in decreased hypoxia-induced disulfide PKGIα and more severe PH phenotype in wild-type mice, but not in Cys42Ser PKGIα knock-in (KI) mice that are resistant to oxidation. In addition, KI mice also developed potentiated PH during hypoxia alone. Thus, oxidation of PKGIα is an adaptive mechanism that limits PH, a concept further supported by polysulfide treatment abrogating hypoxia-induced RV hypertrophy in wild-type, but not in the KI, mice. Unbiased transcriptomic analysis of hypoxic lungs before structural remodeling identified up-regulation of endothelial-to-mesenchymal transition pathways in the KI compared with wild-type mice. Thus, disulfide PKGIα is an intrinsic adaptive mechanism that attenuates PH progression not only by promoting vasodilation but also by limiting maladaptive growth and fibrosis signaling., Competing Interests: The authors declare no conflict of interest., (Copyright © 2019 the Author(s). Published by PNAS.)

The kinase p38α MAPK (p38α) plays a pivotal role in many biological processes. p38α is activated by canonical upstream kinases that phosphorylate the activation region. The purpose of our study was to determine whether such activation may depend on redox-sensing cysteines within p38α. p38α was activated and formed a disulfide-bound heterodimer with MAP2K3 (MKK3) in rat cardiomyocytes and isolated hearts exposed to H 2 O 2 This disulfide heterodimer was sensitive to reduction by mercaptoethanol and was enhanced by the thioredoxin-reductase inhibitor auranofin. We predicted that Cys-119 or Cys-162 of p38α, close to the known MKK3 docking domain, were relevant for these redox characteristics. The C119S mutation decreased whereas the C162S mutation increased the dimer formation, suggesting that these two Cys residues act as vicinal thiols, consistent with C119S/C162S being incapable of sensing H 2 O 2 Similarly, disulfide heterodimer formation was abolished in H9C2 cells expressing both MKK3 and p38α C119S/C162S and subjected to simulated ischemia and reperfusion. However, the p38α C119S/C162S mutants did not exhibit appreciable alteration in activating dual phosphorylation. In contrast, the anti-inflammatory agent 10-nitro-oleic acid (NO 2 -OA), a component of the Mediterranean diet, reduced p38α activation and covalently modified Cys-119/Cys-162, probably obstructing MKK3 access. Moreover, NO 2 -OA reduced the dephosphorylation of p38α by hematopoietic tyrosine phosphatase (HePTP). Furthermore, steric obstruction of Cys-119/Cys-162 by NO 2 -OA pretreatment in Langendorff-perfused murine hearts prevented the p38-MKK3 disulfide dimer formation and attenuated H 2 O 2 -induced contractile dysfunction. Our findings suggest that cysteine residues within p38α act as redox sensors that can dynamically regulate the association between p38 and MKK3., (© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.)

Background: Protein kinase G (PKG) Iα is the end-effector kinase that mediates nitric oxide (NO)-dependent and oxidant-dependent vasorelaxation to maintain blood pressure during health. A hallmark of cardiovascular disease is attenuated NO production, which in part is caused by NO Synthase (NOS) uncoupling, which in turn increases oxidative stress because of superoxide generation. NOS uncoupling promotes PKG Iα oxidation to the interprotein disulfide state, likely mediated by superoxide-derived hydrogen peroxide, and because the NO-cyclic guanosine monophosphate (cGMP) pathway otherwise negatively regulates oxidation of the kinase to its active disulfide dimeric state. Diet-induced obesity is associated with NOS uncoupling, which may in part contribute to the associated cardiovascular dysfunction due to exacerbated PKG Iα disulfide oxidation to the disulfide state. This is a rational hypothesis because PKG Iα oxidation is known to significantly contribute to heart failure that arises from chronic myocardial oxidative stress., Methods and Results: Bovine arterial endothelial cells (BAECs) or smooth muscle cells (SMCs) were exposed to drugs that uncouple NOS. These included 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) which promotes its S-glutathiolation, 4-diamino-6-hydroxy-pyrimidine (DAHP) which inhibits guanosine-5'-triphosphate-cyclohydrolase 2 to prevent BH 4 synthesis or methotrexate (MTX) which inhibits the regeneration of BH 4 from BH 2 by dihydrofolate reductase. While all the drugs mentioned above induced robust PKG Iα disulfide dimerization in cells, exposure of BAECs to NOS inhibitor L-NMMA did not. Increased PKG Iα disulfide formation occurred in hearts and aortae from mice treated in vivo with DAHP (10mM in a drinking water for 3 weeks). Redox-dead C42S PKG Iα knock-in (KI) mice developed less pronounced cardiac posterior wall hypertrophy and did not develop cardiac dysfunction, assessed by echocardiography, compared to the wild-type (WT) mice after chronic DAHP treatment. WT or KI mice were then subjected to a diet-induced obesity protocol by feeding them with a high fat Western-type diet (RM 60% AFE) for 27 weeks, which increased body mass, adiposity, plasma leptin, resistin and glucagon levels comparably in each genotype. Obesity-induced hypertension, assessed by radiotelemetry, was mild and transient in the WT, while the basally hypertensive KI mice were resistant to further increases in blood pressure following high fat feeding. Although the obesogenic diet caused mild cardiac dysfunction in the WT but not the KI mice, gross changes in myocardial structure monitored by echocardiography were not apparent in either genotype. The level of cyclic guanosine monophosphate (cGMP) was decreased in the aortae of WT and KI mice following high fat feeding. PKG Iα oxidation was not evident in the hearts of WT mice fed a high fat diet., Conclusions: Despite robust evidence for PKG Iα oxidation during NOS uncoupling in cell models, it is unlikely that PKG Iα oxidation occurs to a significant extent in vivo during diet-induced obesity and so is unlikely to mediate the associated cardiovascular dysfunction., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

The Frank-Starling mechanism allows the amount of blood entering the heart from the veins to be precisely matched with the amount pumped out to the arterial circulation. As the heart fills with blood during diastole, the myocardium is stretched and oxidants are produced. Here we show that protein kinase G Iα (PKGIα) is oxidant-activated during stretch and this form of the kinase selectively phosphorylates cardiac phospholamban Ser16-a site important for diastolic relaxation. We find that hearts of Cys42Ser PKGIα knock-in (KI) mice, which are resistant to PKGIα oxidation, have diastolic dysfunction and a diminished ability to couple ventricular filling with cardiac output on a beat-to-beat basis. Intracellular calcium dynamics of ventricular myocytes isolated from KI hearts are altered in a manner consistent with impaired relaxation and contractile function. We conclude that oxidation of PKGIα during myocardial stretch is crucial for diastolic relaxation and fine-tunes the Frank-Starling response.

Angiogenesis is essential for tissue development, wound healing and tissue perfusion, with its dysregulation linked to tumorigenesis, rheumatoid arthritis and heart disease. Here we show that pro-angiogenic stimuli couple to NADPH oxidase-dependent generation of oxidants that catalyse an activating intermolecular-disulphide between regulatory-RIα subunits of protein kinase A (PKA), which stimulates PKA-dependent ERK signalling. This is crucial to blood vessel growth as 'redox-dead' Cys17Ser RIα knock-in mice fully resistant to PKA disulphide-activation have deficient angiogenesis in models of hind limb ischaemia and tumour-implant growth. Disulphide-activation of PKA represents a new therapeutic target in diseases with aberrant angiogenesis.

Sepsis and sepsis-associated multiorgan failure represent the major cause of mortality in intensive care units worldwide. Cardiovascular dysfunction, a key component of sepsis pathogenesis, has received much research interest, although research translatability remains severely limited. There is a critical need for more comprehensive preclinical sepsis models, with more clinically relevant end points, such as microvascular perfusion. The purpose of this study was to compare microcirculatory blood flow measurements, using a novel application of laser speckle contrast imaging technology, with more traditional hemodynamic end points, as part of a multiparameter monitoring system in preclinical models of sepsis. Our aim, in measuring mesenteric blood flow, was to increase the prognostic sensitivity of preclinical studies. In two commonly used sepsis models (cecal ligation and puncture, and lipopolysaccharide), we demonstrate that blood pressure and cardiac output are compromised postsepsis, but subsequently stabilize over the 24-h recording period. In contrast, mesenteric blood flow continuously declines in a time-dependent manner and in parallel with the development of metabolic acidosis and organ dysfunction. Importantly, these microcirculatory perturbations are reversed by fluid resuscitation, a mainstay intervention associated with improved outcome in patients. These data suggest that global hemodynamics are maintained at the expense of the microcirculation and are, therefore, not sufficiently predictive of outcome. We demonstrate that microcirculatory blood flow is a more sensitive biomarker of sepsis syndrome progression and believe that incorporation of this biomarker into preclinical models will facilitate sophisticated proof-of-concept studies for novel sepsis interventions, providing more robust data on which to base future clinical trials., (Copyright © 2015 the American Physiological Society.)

Dysregulated blood pressure control leading to hypertension is prevalent and is a risk factor for several common diseases. Fully understanding blood pressure regulation offers the possibility of developing rationale therapies to alleviate hypertension and associated disease risks. Although hydrogen sulfide (H2S) is a well-established endogenous vasodilator, the molecular basis of its blood-pressure lowering action is incompletely understood. H2S-dependent vasodilation and blood pressure lowering in vivo was mediated by it catalyzing formation of an activating interprotein disulfide within protein kinase G (PKG) Iα. However, this oxidative activation of PKG Iα is counterintuitive because H2S is a thiol-reducing molecule that breaks disulfides, and so it is not generally anticipated to induce their formation. This apparent paradox was explained by H2S in the presence of molecular oxygen or hydrogen peroxide rapidly converting to polysulfides, which have oxidant properties that in turn activate PKG by inducing the disulfide. These observations are relevant in vivo because transgenic knockin mice in which the cysteine 42 redox sensor within PKG has been systemically replaced with a redox-dead serine residue are resistant to H2S-induced blood pressure lowering. Thus, a primary mechanism by which the reductant molecule H2S lowers blood pressure is mediated somewhat paradoxically by the oxidative activation of PKG., (© 2014 American Heart Association, Inc.)

Oxidative post-translational modifications of proteins resulting from events that increase cellular oxidant levels play important roles in physiological and pathophysiological processes. Evaluation of alterations to protein redox states is increasingly common place because of methodological advances that have enabled detection, quantification and identification of such changes in cells and tissues. This mini-review provides a synopsis of biochemical methods that can be utilized to monitor the array of different oxidative and electrophilic modifications that can occur to protein thiols and can be important in the regulatory or maladaptive impact oxidants can have on biological systems. Several of the methods discussed are valuable for monitoring the redox state of established redox sensing proteins such as Keap1.

Soluble epoxide hydrolase (sEH) is inhibited by electrophilic lipids by their adduction to Cys521 proximal to its catalytic center. This inhibition prevents hydrolysis of the enzymes' epoxyeicosatrienoic acid (EET) substrates, so they accumulate inducing vasodilation to lower blood pressure (BP). We generated a Cys521Ser sEH redox-dead knockin (KI) mouse model that was resistant to this mode of inhibition. The electrophilic lipid 10-nitro-oleic acid (NO2-OA) inhibited hydrolase activity and also lowered BP in an angiotensin II-induced hypertension model in wild-type (WT) but not KI mice. Furthermore, EET/dihydroxy-epoxyeicosatrienoic acid isomer ratios were elevated in plasma from WT but not KI mice following NO2-OA treatment, consistent with the redox-dead mutant being resistant to inhibition by lipid electrophiles. sEH was inhibited in WT mice fed linoleic acid and nitrite, key constituents of the Mediterranean diet that elevates electrophilic nitro fatty acid levels, whereas KIs were unaffected. These observations reveal that lipid electrophiles such as NO2-OA mediate antihypertensive signaling actions by inhibiting sEH and suggest a mechanism accounting for protection from hypertension afforded by the Mediterranean diet.

The prevalence of obesity among pregnant women is increasing. Evidence from human cohort studies and experimental animals suggests that offspring cardiovascular and metabolic function is compromised through early life exposure to maternal obesity. Previously, we reported that juvenile offspring of obese rats develop sympathetically mediated hypertension associated with neonatal hyperleptinemia. We have now addressed the hypothesis that neonatal exposure to raised leptin in the immediate postnatal period plays a causal role. Pups from lean Sprague-Dawley rats were treated either with leptin (3 mg/kg IP) or with saline twice daily from postnatal day 9 to 15 to mimic the exaggerated postnatal leptin surge observed in offspring of obese dams. Cardiovascular function was assessed by radiotelemetry at 30 days, and 2 and 12 months. In juvenile (30 days) leptin-treated rats, hearts were heavier and night-time (active period) systolic blood pressure was raised (mm Hg; mean ± SEM: male leptin-treated, 132 ± 1 versus saline-treated, 119 ± 1, n=6, P<0.05; female leptin-treated, 132 ± 2 versus saline-treated, 119 ± 1, n=6, P<0.01), and the pressor response to restraint stress and leptin challenge increased compared with saline-treated rats. Heart rate variability demonstrated an increased low:high frequency ratio in 30-day leptin-treated animals, indicative of heightened sympathetic efferent tone. Echocardiography showed altered left ventricular structure and systolic function in 30-day female leptin versus saline-treated rats. These disorders persisted to adulthood. In isolated hearts, contractile function was impaired at 5 months in male leptin-treated rats. Exogenously imposed hyperleptinemia in neonatal rats permanently influences blood pressure and cardiac structure and function.

Aberrant proliferation of mesangial cells (MCs) is a key finding in progressive glomerular disease. TH1177 is a small molecule that has been shown to inhibit low-voltage activated T-type Ca(2+) channels (TCCs). The current study investigates the effect of TH1177 on MC proliferation in vitro and in vivo. The effect of Ca(2+) channel inhibition on primary rat MC proliferation in vitro was studied using the microculture tetrazolium assay and by measuring bromodeoxyuridine incorporation. In vivo, rats with Thy1 nephritis were treated with TH1177 or vehicle. Glomerular injury and average glomerular cell number were determined in a blinded fashion. Immunostaining for Ki-67 and phosphorylated ERK were also performed. The expression of TCC isoforms in healthy and diseased tissue was investigated using quantitative real-time PCR. TCC blockade caused a significant reduction in rat MC proliferation in vitro, whereas L-type inhibition had no effect. Treatment of Thy1 nephritis with TH1177 significantly reduced glomerular injury (P < 0.005) and caused a 49% reduction in glomerular cell number (P < 0.005) compared to the placebo. TH1177 also reduced Ki-67-positive and pERK-positive cells per glomerulus by 52% (P < 0.01 and P < 0.005, respectively). These results demonstrate that TH1177 inhibits MC proliferation in vitro and in vivo, supporting the hypothesis that TCC inhibition may be a useful strategy for studying and modifying MC proliferative responses to injury., (Copyright © 2013 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Sepsis is a common life-threatening clinical syndrome involving complications as a result of severe infection. A cardinal feature of sepsis is inflammation that results in oxidative stress. Sepsis in wild-type mice induced oxidative activation of cGMP-dependent protein kinase 1 alpha (PKG Iα), which increased blood vessel dilation and permeability, and also lowered cardiac output. These responses are typical features of sepsis and their combined effect is a lowering of blood pressure. This hypotension, a hallmark of sepsis, resulted in underperfusion of end organs, resulting in their damage. A central role for PKG Iα oxidative activation in injury is supported by oxidation-resistant Cys42Ser PKG Iα knock-in mice being markedly protected from these clinical indices of injury during sepsis. We conclude that oxidative activation of PKG Iα is a key mediator of hypotension and consequential organ injury during sepsis.

Background: Although nitroglycerin has remained in clinical use since 1879, the mechanism by which it relaxes blood vessels to lower blood pressure remains incompletely understood. Nitroglycerin undergoes metabolism that generates several reaction products, including oxidants, and this bioactivation process is essential for vasodilation. Protein kinase G (PKG) mediates classic nitric oxide-dependent vasorelaxation, but the 1α isoform is also independently activated by oxidation that involves interprotein disulfide formation within this homodimeric protein complex. We hypothesized that nitroglycerin-induced vasodilation is mediated by disulfide activation of PKG1α., Methods and Results: Treating smooth muscle cells or isolated blood vessels with nitroglycerin caused PKG1α disulfide dimerization. PKG1α disulfide formation was increased in wild-type mouse aortas by in vivo nitroglycerin treatment, but this oxidation was lost as tolerance developed. To establish whether kinase oxidation underlies nitroglycerin-induced vasodilation in vivo, we used a Cys42Ser PKG1α knock-in mouse that cannot transduce oxidant signals because it does not contain the vital redox-sensing thiol. This redox-dead knock-in mouse was substantively deficient in hypotensive response to nitroglycerin compared with wild-type littermates as measured in vivo by radiotelemetry. Resistance blood vessels from knock-ins were markedly less sensitive to nitroglycerin-induced vasodilation (EC(50)=39.2 ± 10.7 μmol/L) than wild-types (EC(50)=12.1 ± 2.9 μmol/L). Furthermore, after ≈24 hours of treatment, wild-type controls stopped vasodilating to nitroglycerin, and the vascular sensitivity to nitroglycerin was decreased, whereas this tolerance phenomenon, which routinely hampers the management of hypertensive patients, was absent in knock-ins., Conclusions: PKG1α disulfide formation is a significant mediator of nitroglycerin-induced vasodilation, and tolerance to nitroglycerin is associated with loss of kinase oxidation.

Blood pressure regulation is crucial for the maintenance of health, and hypertension is a risk factor for myocardial infarction, heart failure, stroke and renal disease. Nitric oxide (NO) and prostacyclin trigger well-defined vasodilator pathways; however, substantial vasorelaxation in response to agents such as acetylcholine persists when the synthesis of these molecules is prevented. This remaining vasorelaxation activity, termed endothelium-derived hyperpolarizing factor (EDHF), is more prevalent in resistance than in conduit blood vessels and is considered a major mechanism for blood pressure control. Hydrogen peroxide (H2O2) has been shown to be a major component of EDHF in several vascular beds in multiple species, including in humans. H2O2 causes the formation of a disulfide bond between the two α subunits of protein kinase G I-α (PKGI-α), which activates the kinase independently of the NO-cyclic guanosine monophosphate (cGMP) pathway and is coupled to vasodilation. To test the importance of PKGI-α oxidation in the EDHF mechanism and blood pressure control in vivo, we generated a knock-in mouse expressing only a C42S 'redox-dead' version of PKGI-α. This amino acid substitution, a single-atom change (an oxygen atom replacing a sulfur atom), blocked the vasodilatory action of H2O2 on resistance vessels and resulted in hypertension in vivo.

Formation of nitric oxide and its derivative reactive nitrogen species during endotoxemia has been implicated in the pathogenesis of the associated cardiovascular dysfunction. This stress can promote nitrosative post-translational modifications of proteins that may alter their activity and contribute to dysregulation. We utilized the ascorbate-dependent biotin-switch method to assay protein S-nitrosylation and immunoblotted for tyrosine nitration to monitor changes in nitrosative protein oxidation during endotoxemia. Hearts from lipopolysaccharide (LPS)-treated rats showed no apparent variation in global protein S-nitrosylation, but this may be due to the poor sensitivity of the biotin-switch method. To sensitize our monitoring of protein S-nitrosylation we exposed isolated hearts to the efficient trans-nitrosylating agent nitrosocysteine (which generated a robust biotin-switch signal) and then identified a number of target proteins using mass spectrometry. We were then able to probe for these target proteins in affinity-capture preparations of S-nitrosylated proteins prepared from vehicle- or LPS-treated animals. Unexpectedly this showed a time-dependent loss in S-nitrosylation during sepsis, which we hypothesized, may be due to concomitant superoxide formation that may lower nitric oxide but simultaneously generate the tyrosine-nitrating agent peroxynitrite. Indeed, this was confirmed by immunoblotting for global tyrosine nitration, which increased time-dependently and temporally correlated with a decrease in mean arterial pressure. We assessed if tyrosine nitration was causative in lowering blood pressure using the putative peroxynitrite scavenger FeTPPS. However, FeTPPS was ineffective in reducing global protein nitration and actually exacerbated LPS-induced hypotension., (Copyright © 2010 Elsevier Inc. All rights reserved.)

The ischemic preconditioning (IPC) limits myocardial injury provoked by a subsequent prolonged ischemia-reperfusion (I/ R). The underlying mechanisms of enhanced resistance of heart are actively studied, but for sure it was established that mitochondria play a major role in IPC-stimulated adaptation to ischemia. In this article we present and discuss evidences that cardioprotective effect of IPC is mediated by inhibition of mitochondria permeability transition pore (MPTP) opening. It was shown that IPC effectively prevents the excessive production of ROS by mitochondria during I/R and promotes a more complete restoration of function of isolated rat hearts. It was revealed that MPTP formation due to I/R was inhibited in IPC heart. Mitochondrial factor, the marker of MPTP opening found in outflow probes, was released in much lesser amounts in IPC hearts that in non-IPC. Furthermore, mitochondria isolated from IPC hearts showed a decreased sensitivity to calcium ions, a MPTP inductor, and, thus, massive MPTP-depended swelling of mitochondria was abrogated in IPC hearts. In our experiments we observed slight increase in inducible NOS activity right after short ischemic stimuli. We suppose that increased NO production by iNOS is involved in inhibition of MPTP and this may be one of the possible mechanisms of decreased sensitivity of mitochondria to calcium ions. It is concluded that among the processes involved in formation of cardioprotective effect of IPC, a reduction of membrane permeability due to the inhibition of MPTP opening plays a crucial role.

Diet-induced obesity in rat pregnancy has been shown previously to be associated with consistently raised blood pressure in the offspring, attributed to sympathetic over-activation, but the relative contributions to this phenotype of maternal obesity versus raised dietary fat is unknown. Sprague-Dawley female rats were fed either a control (4.3% fat, n = 11) or lard-enriched (23.6% fat, n = 16) chow 10 days prior to mating, throughout pregnancy and lactation. In conscious adult (9-month-old) offspring cardiovascular parameters were measured (radiotelemetry). The short period of fat-feeding did not increase maternal weight versus controls and the baseline blood pressure was similar in offspring of fat fed dams (OF) and controls (OC). However, adult male OF showed heightened cardiovascular reactivity to acute restraint stress (p<0.01; Δ systolic blood pressure (SBP) and Δheart rate (HR)) with a prolonged recovery time compared to male OC. α1/β-adrenergic receptor blockade normalised the response. Also, after dietary salt-loading (8%-NaCl ad libitum for 1 week) male OF demonstrated higher SBP (p<0.05) in the awake phase (night-time) and increased low/high frequency ratio of power spectral density of HR variability versus OC. Baroreflex gain and basal power spectral density components of the heart rate or blood pressure were similar in male OF and OC. Minor abnormalities were evident in female OF. Fat feeding in the absence of maternal obesity in pregnant rats leads to altered sympathetic control of cardiovascular function in adult male offspring, and hypertension in response to stressor stimuli.

We studied the sensitivity of mitochondrial permeability transition pore (MPTP) opening to natural inductors--Ca2+ ions in the rat heart mitochondria with chronic deficiency of nigrostriatal dopamine caused by an injection of selective neurotoxin 6-hydroxidofamine in an ascending lateral bundle of the forebrain. MPTP-opening was determined specrophotometrically (lamda=520 nm) by a decrease in an optical density resulting from mitochondrial swelling. It has been shown that the rat heart mitochondria with chronic deficiency of nigrostriatal dopamine are more sensitive to Ca2+ in its physiological concentration (10(-7) mol/l) and overload (10(-6) - 10(-4) mol/l) in comparison to control animals. Thus, obtained results lead to a conclusion that an increased sensitivity of the mitochondrial permeability transition pore to calcium and mitochondrial membrane permeability may be one of the causes previously reported of disturbance in contractile function of the rat heart with chronic deficiency of nigrostriatal dopamine.

Nitric oxide reacts rapidly with superoxide to produce the potent oxidant peroxynitrite. In vivo mitochondria produce superoxide as well as NO. In heart mitochondria of aging rats the amount of NO and O2(-) are increased thus the levels of peroxynitrite produced may be increased too, in this reason mitochondria may be a major site of peroxynitrite formation. Oxidative stress induces cyclosporine A-sensitive mitochondrial efflux of calcium and proapoptotic factors through MPTP (mitochondrial permeability transition pore) opening in heart mitochondria which may contribute to tissue damage and mitochondrial dysfunction in aging rats. We tested the levels of NO and superoxide generation in mitochondria simultaneously with cyclosporine A-sensitive MPTP opening by Ca2+ and phenylarsine oxide (PAO) to determine whether downregulation of both NO and O2(-) generation in heart mitochondria by potent steroid antioxidant and free radical scavenger ecdysterone may protect heart mitochondria of aging rats again tissue damage. C27-phytosteroid hormone ecdysterone (10 mkg/100g, per os, 2 weeks) mimics action of its structural analog C27- steroid hormone calcitriol (1alpha,25-dihydroxyvitamin D3) and exert its cardio protection in aging heart mitochondria by inhibition of MPTP opening with effectivity of action of hormone melatonine (150 mkg/100g, 2 weeks [ V.F. Sagach et al. Fyziol. J (Ukr), 2006, 52(2), 3-15]). MPTP inhibition is dependent on paradoxycally high activation by ecdusterone of oxidative degradation of L-arginine by mtcNOS in mitochondria, by downregulation of superoxide generation and L-arginine degradation by arginase II and NO generation by mtiNOS in de novo and by NADP-dependent mtNR (nitrate reductase) in salvage pathways. These results suggest that MPTP opening may be directly influenced by ecdysterone signaling in mitochondria. The signaling pathway by which ecdysterone may coregulate the O2(-) and NO generation in heart mitochondria of aging rats may involve an outer mitochondrial membrane estrogen receptor coupled to mitochondrial PI3K/Akt/PKB activation results in superactivation and constitutive NO synthesis by mtcNOS.

This study evaluated generation of O2*- and NO in heart mitochondria isolated from 9-week old streptozotocin (STZ)-induced diabetic rats and the effect of ecdysterone treatment on these parameters. Mitochondria isolated from 9-week old placebo-treated rats were used as control. Several parameters were evaluated: O2*- production, the levels of stable NO metabolites nitrate, nitrite and total nitrosothiols, the level of bilirubine (as marker of CO generation), inducible (iNOS) and constitutive (nNOS) mtNOS, NADH- dependent nitrate reductase (NR) and inducible arginase II (AII) activity. We observed that diabetes was accompanied by a significant decrease in nNOS activity, nitrite, total nitrosothiols and bilirubine content while iNOS, NR and AII activity, as well as O2*- generation was increased in heart mitochondria. Ecdysterone treatment normalized the levels of stable NO metabolites, ability to generate superoxide, iNOS and nNOS activity, but not bilirubine level, NR and AII activity. These results suggest that ecdysterone treatment attenuates diabetes-induced mitochondrial alterations protecting against oxidative and nitrosative stresses. Thus, ecdysterone therapy, besides its well known importance in the maintenance of glycemic control, may help to protect against mitochondrial dysfunction associated to several age-related disorders.

Protective properties of coenzyme Q10 (CoQ10) on the: (i) Langendorff isolated guinea pig heart's function under ischemia and reperfusion (I/R) and on the isolated mitochondria (ii) the mitochondrial permeability transition pore (MPTP) opening under exposure to calcium as natural MPTP inductor and phenylarsine oxide as oxidant--were studied. Physiological characteristic of contractile function, myocardial oxygen consumption and mitochondrial factor release as index of MPTP opening were compared before and after ischemia of isolated heart in control animals and animals with preliminary administration of CoQ10 per os. It have been shown that I/R disturbances of heart function were decreased and oxygen metabolism was normalised in animals treated with CoQ10 in compare to non-treated control. It was accompanied with substantial stabilization of mitochondrial membrane. Decreased I/R disturbances of isolated heart from CoQ10-treated animals were correlated to amount of mitochondrial factor released to coronary flow. Moreover, preliminary incubation of mitochondria, isolated from rat heart, with CoQ10 (10(-5) mol/l) substantially prevented calcium and phenylarsine-induced, cyclosporine A-sensitive mitochondrial swelling. This protective effect was increased in experiments with deenergizing mitochondria. Results of physiological and biochemical study reveal that one of the mechanisms of CoQ10's cardioprotective effect could be direct inhibition of mitochondrial permeability transition pore opening during ischemia and reperfusion of the heart.

The effect of the hormone of pineal gland melatonin on the ischemic tolerance and the sensitivity of mitochondrial permeability transition pore opening in old rat heart were studied. It has been shown in the Langendorf's isolated rat heart that heart contractile functional changes under ischemia and reperfusion were more pronounced in old (24-27 months) rat hearts in comparison with the adult (5-6 months) animals. A two-week's in vivo course of intraperitoneal injection of melatonin (1,5 mg/kg weight) to old rats contributed to the rehabilitation of the functional changes of isolated heart after ischemia during reperfusion and decreased the sensitivity of mitochondrial permeability transition pore opening to Ca2+ and phenilarsinoxide in comparison with old animals which did not received melatonin. It was accompanied by the significant decreasing in mRNA bax expression in old rat heart, lessening in content of the superoxide radicals and dien conjugates and twice increasing in the activity of constitutive NO-synthase in heart mitochondria of old rat after a course of melatonin injection. The protective feffect of melatonin on the mitochondrial permeability transition pore opening could be used for correction of the cardiac dysfunction with aging.

On the mitochondria isolated from the heart tissue of adult rats we studied the sensitivity of mitochondrial permeability transition pore (MPTP) opening to its inductor--phenylarsine oxide (PAO) after mitochondrial swelling, registered by spectrophotometric technique at n = 520 nm. In adult rat under influence of two modes of normobaric intermittent hypoxic training (IHT): i) softer but prolonged one induced by breathing in normobaric chamber with 11% O2 gas mixture, 15 minuets sessions with 15 minuets rest intervals, 5 times daily (first mode) and ii) more severe but shorter one induced by breathing with 8% O2 gas mixture (second mode) were used. The intensity of lipid peroxidation and antioxidant defense mechanisms in rat organism were estimated before and after IHT by measuring malon dialdehyde (MDA) content and enzymatic activity of superoxide dismutase (SOD) and catalase (CAT) in the blood and the liver. It has been shown that IHT in the first mode didn't essentially influence both on PAO induced, cyclosporin A--sensitive mitochondrial swelling and indexes of lipid peroxidation as well as the SOD and CAT enzymatic activity. It was established that IHT in the second mode caused pronounced increase in MDA content both in the blood and the liver by 67% and 32% respectively; considerable augmentation of SOD activity in this tissues (by 49% and 32% respectively) and CAT activity (by 18% and 43% respectively). Moreover, in forty five days the activity of SOD exceeded its initial level in three times in both the blood and the liver. It has been established that IHT in the second mode provoke to twice decrease in PAO-induced mitochondrial swelling as compared with mitochondria of the control group, and even in forty five days after IHT stopping the protective effect on mitochondrial PTP opening was well-preserved. These effects were completely abolished in the presence of an inhibitor--cyclosporin A (10(-5) mol/l) that demonstrated mitochondrial swelling to be due to the mitochondrial PTP opening. Our experiments showed that the influence of IHT in more severe mode decreased the sensitivity of mitochondria to the PAO in rat heart mitochondria. Thus resistance of the mitochondrial membrane to an inductor of PTP opening--PAO increase under the influence of IHT in the second mode.

We studied the sensitivity of mitochondrial permeability transition pore (MPTP) opening to its inductor-phenylarsineoxide (PAO) in adult (6 months), old rat heart (24 months) and in old rat heart under conditions of intermittent hypoxic training (IHT). We defined the sensitivity of MPTP opening on two parameters: the alterations in mitochondrial swelling and the release ofmitochondrial substances (mitochondrial factor). It was shown that mitochondria of old rat heart are more sensitive to PAO which caused opening of cyclosporin-sensitive MPTP and MPTP-dependent factor release, in comparison with those of adult rat heart mitochondria. One of the causes of increased sensitivity of MPTP opening to PAO is development of an oxidative stress with age that was accompanied by increase of an active metabolite of oxygen IHT on PAO-induced MPTP-opening and MPTP-dependent factor release from old rat heart mitochondria. IHT also reduced the content of H2O2 and *OH in old rat hearts. IHT can be used as protective procedure preventing MPTP opening in aging and, probably, in a numerous chronic pathological states of organism under oxidative stress.

An age-related increase in the sensitivity of the mitochondrial permeability transition pore (MPTP) to inductors of it's opening, Ca2+ ions and phenylarsineoxide (PAO) was studied in experiments in vitro on isolated heart mitochondria of adult and old rats. Two indices were measured spectrophotometrically (lambda = 520 nm) by a decrease in an optical density (OD), resulting from mitochondrial swelling and a release of mitochondrial unidentified substances (mitochondrial factor, MF) registered also spectrophotometrically in a range of waves lambda = 230-260 nm. Dose-dependent effect of Ca2+ (10(-7)-10(-4) mol/l) and PAO (10(-8)-10(-4) mol/l) on swelling of the mitochondria were observed in samples from both adult and old rats. Swelling of the mitochondria from the heart of old rats induced by application of the above inductors was more intensive than the respective effect in samples from adult rats. In samples from the heart of both adult and old rats Ca2+ ions within the tested concentration range (10(-7)-10(-4) mol/l) evoked the release of MF in a dose-dependent manner. Mitochondria from the heart of old rats were found to be capable of releasing some amounts of MF in the absence of the MPTP inductors PAO. When this inductor was applied in a 10(-9) to 10(-4) mol/l concentration range, isolated mitochondria from the heart of old rats released unidentified substances with the absorption peaks at two wavelength, lambda = 230 nm and lambda = 240-245 nm. The former peak was found to be Cyclosporin A-insensitive, while the latter peak could be practically completely inhibited by this antibiotic. The concentrations of tested solutions (10(-7) mol/l CaCl2 and 10(-9) mol/l PAO), at which the release of the factor from the mitochondria of the old rat heart was observed, were significantly lower than those in adult rats. Our experimental data show that mitochondria isolated from the heart tissue of old rats demonstrate significantly higher sensitivity to inductors of MPTP-opening, Ca(2+)-overload and PAO as compared to that typical of adult animals. A higher sensitivity of MPTP-opening in the heart of old rats was accompanied by a higher basal level of expression of mRNA of the bax gene, as compared to that found in adult animals. The expression of the bcl-2 gene showed no age group-related differences. It can be supposed that a proapoptotic agent, the Bax protein, is related to an increase in the sensitivity of the MPTP (in particular to that manifested in the processes of pore formation) in the course of aging. Antioxidants, melathonin and trolox, when applied in 10(-5) mol/l concentration, presented to a certain extent opening of the MPTP-induced by 10(-5) mol/l PAO in samples from adult and old rats. These findings can be used for correction of increased sensitivity of the MPTP to different inductors, which is typical of old rats. We conclude that physiological aging is accompanied by the mitochondrial dysfunction. The MF-released capability of the mitochondria from heart tissue of old rats observed both in the presence and absence of MPTP-opening inductors (probably related to a higher sensitivity of MPTP-opening) is one of the manifestation of such dysfunction.

In experiments in vitro on isolated heart mitochondria of rats, an activation of mitochondrial permeability transition pore (PTP) was induced by either modelling an oxidative stress with PTP-inductor phenylarsine oxide (PAO) or by calcium overload (CaCl2). PTP-opening was determined spectrophotometrically (lambda = 520 nm) by a decrease in an optical density (OD), resulting from mitochondrial swelling. We also observed a release of mitochondrial unidentified substances (mitochondrial factor, MF) registered spectrophotometrically in a range of waves lambda = 230-260 nm. Both correlation between mitochondrial swelling and a release of the mitochondrial factor have been found in experiments with PAO at concentrations 10(-7)-10(-4) mol/l, and in those with CaCl2 at concentrations 10(-6)-10(-4) mol/l. The classical inhibitor of mitochondrial PTP cyclosporin A (Cs A, 10(-5) mol/l) inhibited mitochondrial swelling and a release of that factor completely. Our experimental data give evidence for mitochondrial origin of the factor and its release following PTP-opening by PTP-inductors--PAO and CaCl2. Mitochondrial swelling that accompanied the factor's release might contribute to PTP-opening and be useful in defining the mitochondrial sensitivity either with inductors or inhibitors of mitochondrial PTP in different tissues under normal and pathological states of organism.