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Aims H2S is known to confer cardioprotection; however, the pathways mediating its effects in vivo remain incompletely understood. The purpose of the present study is to evaluate the contribution of cGMP-regulated pathways in the infarct-limiting effect of H2S in vivo. Methods and results Anaesthetized rabbits were subjected to myocardial ischaemia (I)/reperfusion (R), and infarct size was determined in control or H2S-exposed groups. The H2S donor sodium hydrosulfide (NaHS, an agent that generates H2S) increased cardiac cGMP and reduced the infarct size. The cGMP-dependent protein kinase (PKG)-I inhibitor DT2 abrogated the protective effect of NaHS, whereas the control peptide TAT or L-nitroarginine methyl ester (L-NAME) did not alter the effect of NaHS. Moreover, the KATP channel inhibitor, glibenclamide, partially reversed the effects of NaHS, whereas inhibition of mitochondrial KATP did not modify the NaHS response. NaHS enhanced phosphorylation of phospholamban (PLN), in a PKG-dependent manner. To further investigate the role of PLN in H2S-mediated cardioprotection, wild-type and PLN KOmice underwent I/R. NaHS did not exert cardioprotection in PLN KOmice. Unlike whatwas observed in rabbits, genetic or pharmacological inhibition of eNOS abolished the infarct-limiting effect of NaHS in mice. Conclusions Our findings demonstrate (i) that administration of NaHS induces cardioprotection via a cGMP/PKG/PLN pathway and (ii) contribution of nitric oxide to the H2S response is species-specific. [ABSTRACT FROM AUTHOR]

The risk for cardiovascular morbidity and mortality is increased in chronic kidney disease; in this process micro-inflammation plays an essential role. Responsible mechanisms remain to a large extent unidentified. In this pilot study transcriptome analysis of peripheral blood monocytes was used to identify in an unprejudiced manner which factors could be discriminative for cardiovascular disease in patients with chronic kidney disease on hemodialysis. Forty gender- and age-matched, non-diabetic, non-smoking subjects with CRP < 20 mg/L were recruited: 9 healthy controls, 11 patients with eGFR > 60 mL/min/1.73m2 and a history of cardiovascular event (CVE), 10 patients with chronic kidney disease stage 5 on hemodialysis without previous cardiovascular event (CKD5HD) and 10 with a previous cardiovascular event (CKD5HD/CVE). Monocytes were isolated and their mRNA was submitted to focused transcriptome analysis using a macroarray platform containing ca. 700 genes associated with macrophage functional capacity. The macroarray data indicated 9 genes (8 upregulated and 1 downregulated) with a significant differential expression in CKD5HD/CVE vs. CVE alone, after excluding genes differentially expressed in CKD5HD vs. control. For FCGR3A (CD16) and CX3CR1 (chemokine receptor) the upregulation vs. control and vs. CVE could be confirmed by quantitative RT-PCR for all CKD5HD patients. Furthermore, CX3CR1 relative expression on monocytes correlated with CRP. Flow cytometric analysis of purified monocytes confirmed a significant increase in the percentage of CD16 positive monocytes in all CKD5HD patients vs. control and CVE. The present study indicates the importance of a specific pro-inflammatory monocyte subpopulation, positive for CD16 and the co-expressed chemokine receptor, CX3CR1, discriminative for CKD5HD patients. [ABSTRACT FROM AUTHOR]

Background: Volatile anesthetics increase levels of the neurotransmitter nitric oxide (NO) and the secondary messenger molecule cyclic guanosine monophosphate (cGMP) in the brain. NO activates the enzyme guanylyl cyclase (GC) to produce cGMP. We hypothesized that the NO-GC-cGMP pathway contributes to anesthesia-induced unconsciousness. Methods: Sevoflurane-induced loss and return of righting reflex (LORR and RORR, respectively) were studied in wild-type mice (WT) and in mice congenitally deficient in the GC-1α subunit (GC-1−/− mice). Spatial distributions of GC-1α and the GC-2α subunit in the brain were visualized by in situ hybridization. Brain cGMP levels were measured in WT and GC-1−/− mice after inhaling oxygen with or without 1.2% sevoflurane for 20 min. Results: Higher concentrations of sevoflurane were required to induce LORR in GC-1−/− mice than in WT mice (1.5 ± 0.1 vs. 1.1 ± 0.2%, respectively, n = 14 and 14, P < 0.0001). Similarly, RORR occurred at higher concentrations of sevoflurane in GC-1−/− mice than in WT mice (1.0 ± 0.1 vs. 0.8 ± 0.1%, respectively, n = 14 and 14, P < 0.0001). Abundant GC-1α and GC-2α mRNA expression was detected in the cerebral cortex, medial habenula, hippocampus, and cerebellum. Inhaling 1.2% sevoflurane for 20 min increased cGMP levels in the brains of WT mice from 2.6 ± 2.0 to 5.5 ± 3.7 pmol/mg protein (n = 13 and 10, respectively, P = 0.0355) but not in GC-1−/− mice. Conclusion: Congenital deficiency of GC-1α abolished the ability of sevoflurane anesthesia to increase cGMP levels in the whole brain, and increased the concentration of sevoflurane required to induce LORR. Impaired NO-cGMP signaling raises the threshold for producing sevoflurane-induced unconsciousness in mice.

The goal of this study was to identify the cellular mechanisms responsible for cardiac dysfunction in endotoxemic mice. We aimed to differentiate the roles of cGMP [produced by soluble guanylyl cyclase (sGC)] versus oxidative posttranslational modifications of Ca2+ transporters. C57BL/6 mice [wild-type (WT) mice] were administered lipopolysaccharide (LPS; 25 μg/g ip) and euthanized 12 h later. Cardiomyocyte sarcomere shortening and Ca2+ transients (ΔCai) were depressed in LPSchallenged mice versus baseline. The time constant of Ca2+ decay (τCa) was prolonged, and sarcoplasmic reticulum Ca2+ load (CaSR) was depressed in LPS-challenged mice (vs. baseline), indicating decreased activity of sarco(endo)plasmic Ca2+-ATPase (SERCA). L-type Ca2+ channel current (ICa,L) was also decreased after LPS challenge, whereas Na+/Ca2+ exchange activity, ryanodine receptors leak flux, or myofilament sensitivity for Ca2+ were unchanged. All Ca2+-handling abnormalities induced by LPS (the decrease in sarcomere shortening, ΔCai, CaSR, ICa,L, and τCa prolongation) were more pronounced in mice deficient in the sGC main isoform (sGCα1 -/- mice) versus WT mice. LPS did not alter the protein expression of SERCA and phospholamban in either genotype. After LPS, phospholamban phosphorylation at Ser16 and Thr17 was unchanged in WT mice and was increased in sGCα1 -/- mice. LPS caused sulphonylation of SERCA Cys674 (as measured immunohistochemically and supported by iodoacetamide labeling), which was greater in sGCα1 -/- versus WT mice. Taken together, these results suggest that cardiac Ca2+ dysregulation in endotoxemic mice is mediated by a decrease in L-type Ca2+ channel function and oxidative posttranslational modifications of SERCA Cys674, with the latter (at least) being opposed by sGC-released cGMP. [ABSTRACT FROM AUTHOR]

In the heart, nitric oxide (NO) modulates contractile function; however, the mechanisms responsible for this effect are incompletely understood. NO can elicit effects via a variety of mechanisms including S-nitrosylation and stimulation of cGMP synthesis by soluble guanylate cyclase (sGC). sGC is a heterodimer comprised of a β1- and an α1- or α2-subunit. sGCα1β1 is the predominant isoform in the heart. To characterize the role of sGC in the regulation of cardiac contractile function by NO, we compared left ventricular cardiac myocytes (CM) isolated from adult mice deficient in the sGC α1-subunit (sGCα1-/-) and from wild-type (WT) mice. Sarcomere shortening under basal conditions was less in sGCα1-/- CM than in WT CM. To activate endogenous NO synthesis from NO synthase 3, CM were incubated with the β3-adrenergic receptor (β3-AR) agonist BRL 37344. BRL 37344 decreased cardiac contractility in WT CM but not in sGCα1-/- myocytes. Administration of spermine NONOate, an NO donor compound, did not affect sarcomeric shortening in CM of either genotype; however, in the presence of isoproterenol, addition of spermine NONOate reduced sarcomere shortening in WT but not in sGCα1-/- CM. Neither BRL 37344 nor spermine NONOate altered calcium handling in CM of either genotype. These findings suggest that sGCα1 exerts a positive inotropic effect under basal conditions, as well as mediates the negative inotropic effect of β3-AR signaling. Additionally, our work demonstrates that sGCα1β1 is required for NO to depress β1/β2-AR-stimulated cardiac contractility and that this modulation is independent of changes in calcium handling. [ABSTRACT FROM AUTHOR]

Reperfusion injury limits the benefits of revascularization in the treatment of myocardial infarction (MI). Breathing nitric oxide (NO) reduces cardiac ischemia-reperfusion injury in animal models; however, the signaling pathways by which inhaled NO confers cardioprotection remain uncertain. The objective of this study was to learn whether inhaled NO reduces cardiac ischemia-reperfusion injury by activating the cGMP-generating enzyme, soluble guanylate cyclase (sGC), and to investigate whether bone marrow (BM)-derived cells participate in the sGC-mediated cardioprotective effects of inhaled NO. Wild-type (WT) mice and mice deficient in the sGC α1-subunit (sGCα1-/- mice) were subjected to cardiac ischemia for 1 h, followed by 24 h of reperfusion. During ischemia and for the first 10 min of reperfusion, mice were ventilated with oxygen or with oxygen supplemented with NO (80 parts per million). The ratio of MI size to area at risk (MI/AAR) did not differ in WT and sGCα1-/- mice that did not breathe NO. Breathing NO decreased MI/AAR in WT mice (41%, P = 0.002) but not in sGCα1-/- mice (7%, P = not significant). BM transplantation was performed to restore WT BM-derived cells to sGCα1-/- mice. Breathing NO decreased MI/AAR in sGCα1-/- mice carrying WT BM (39%, P = 0.031). In conclusion, these results demonstrate that a global deficiency of sGCα1 does not alter the degree of cardiac ischemia-reperfusion injury in mice. The cardioprotective effects of inhaled NO require the presence of sGCα1. Moreover, our studies suggest that BM-derived cells are key mediators of the ability of NO to reduce cardiac ischemia-reperfusion injury. [ABSTRACT FROM AUTHOR]

Septic shock is associated with life-threatening vasodilation and hypotension. To cause vasodilation, vascular endothelium may release nitric oxide (NO), prostacyclin (PGI2), and the elusive endothelium-derived hyperpolarizing factor (EDHF). Although NO is critical in controlling vascular tone, inhibiting NO in septic shock does not improve outcome, on the contrary, precipitating the search for alternative therapeutic targets. Using a hyperacute tumor necrosis factor (TNF)-induced shock model in mice, we found that shock can develop independently of the known vasodilators NO, cGMP, PGI2, or epoxyeicosatrienoic acids. However, the antioxidant tempol efficiently prevented hypotension, bradycardia, hypothermia, and mortality, indicating the decisive involvement of reactive oxygen species (ROS) in these phenomena. Also, in classical TNF or lipopolysaccharide-induced shock models, tempol protected significantly. Experiments with (cell-permeable) superoxide dismutase or catalase, N-acetylcysteine and apocynin suggest that the ROS-dependent shock depends on intracellular $$ ^\bullet {\hbox{OH}} $$ radicals. Potassium channels activated by ATP (KATP) or calcium (KCa) are important mediators of vascular relaxation. While NO and PGI2-induced vasodilation involves KATP and large-conductance BKCa channels, small-conductance SKCa channels mediate vasodilation induced by EDHF. Interestingly, also SKCa inhibition completely prevented the ROS-dependent shock. Our data thus indicate that intracellular $$ ^\bullet {\hbox{OH}} $$ and SKCa channels represent interesting new therapeutic targets for inflammatory shock. Moreover, they may also explain why antioxidants other than tempol fail to provide survival benefit during shock. [ABSTRACT FROM AUTHOR]

Background. Acute peritonitis is the most frequent complication of peritoneal dialysis (PD). Increased nitric oxide (NO) release by NO synthase (NOS) isoforms has been implicated in acute peritonitis, but the role played by the NOS isoforms expressed in the peritoneum is unknown. [ABSTRACT FROM PUBLISHER]

Altered cGMP signaling has been implicated in myocardial depression, morbidity, and mortality associated with sepsis. Previous studies, using inhibitors of soluble guanylate cyclase (sGC), suggested that cGMP generated by sGC contributed to the cardiac dysfunction and mortality associated with sepsis. We used sGCα1-deficient (sGCα1-/-) mice to unequivocally determine the role of sGCα1β1 in the development of cardiac dysfunction and death associated with two models of inflammatory shock: endotoxinand TNF-induced shock. At baseline, echocardiographic assessment and invasive hemodynamic measurements of left ventricular (LV) dimensions and function did not differ between wild-type (WT) mice and sGCα1-/- mice on the C57BL/6 background (sGCα1-/-B6 mice). At 14 h after endotoxin challenge, cardiac dysfunction was more pronounced in sGCα1-/-B6 than WT mice, as assessed using echocardiographic and hemodynamic indexes of LV function. Similarly, Ca2+ handling and cell shortening were impaired to a greater extent in cardiomyocytes isolated from sGCα1-/-B6 than WT mice after endotoxin challenge. Importantly, morbidity and mortality associated with inflammatory shock induced by endotoxin or TNF were increased in sGCα1-/-B6 compared with WT mice. Together, these findings suggest that cGMP generated by sGCα1β1 protects against cardiac dysfunction and mortality in murine inflammatory shock models. [ABSTRACT FROM AUTHOR]

In this publication, we review the activities of the European Uremic Toxin Work Group (EUTox) in the field of uremic toxin research. Founded in 1999 under the umbrella of the European Society of Artificial Organs (ESAO), and active since 2000, this group focuses essentially on questions related to solute retention and removal during chronic kidney disease, and on the deleterious impact of those solutes on biological/biochemical systems. As of January 1, 2009, the group had met 28 times; it organized the third meeting, “Uremic Toxins in Cardiovascular Disease,” which took place in October 2008 in Amiens, France. The current group is composed of 25 members belonging to 23 European research institutions. As of November 1, 2008, in total 69 papers had been published to which at least two different research groups belonging to EUTox have contributed in a collaborative effort. Of these, 40 papers were on original research and eight were specific EUTox reviews or position statements. A website ( ) summarizes all relevant information concerning the work group. EUTox also developed an interactive uremic toxin database, where concentrations of known toxins are displayed, to be used by researchers in the field. In the future, EUTox intends to continue its focus on bench to bedside research with specific consideration of proteomics, metabonomics, secretomics, and genomics. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) activates soluble guanylate cyclase (sGC) to produce guanosine-3′,5′-cyclic-monophosphate (cGMP). The aim of this study was to investigate the nitrergic regulation of jejunal motility in sGCα1 knockout (KO) mice. Functional responses to nitrergic stimuli and cGMP levels in response to nitrergic stimuli were determined in circular muscle strips. Intestinal transit was determined. Nitrergic relaxations induced by electrical field stimulation and exogenous NO were almost abolished in male KO strips, but only minimally reduced and sensitive to ODQ in female KO strips. Basal cGMP levels were decreased in KO strips, but NO still induced an increase in cGMP levels. Transit was not attenuated in male nor female KO mice. In vitro, sGCα1β1 is the most important isoform in nitrergic relaxation of jejunum, but nitrergic relaxation can also occur via sGCα2β1 activation. The latter mechanism is more pronounced in female than in male KO mice. In vivo, no important implications on intestinal motility were observed in male and female KO mice. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) has been shown to cause enteric smooth muscle relaxation by activating soluble guanylyl cyclase (sGC). In gastric fundus, the sGCα1β1 heterodimer is believed to be the most important isoform. The aim of our study was to investigate the role of the sGCα1/α2 subunits in the relaxant effect of CO and CORM-2 in murine gastric fundus using wild-type (WT) and sGCα1 knock-out (KO) mice. In WT mice, CO (bolus)-induced relaxations were abolished by the sGC inhibitor 1H-[1,2,4]oxadiazolo-[4,3- a]quinoxalin-1-one (ODQ), while CORM-2- and CO (infusion)-induced relaxations were only partially inhibited by ODQ. In sGCα1 KO mice, relaxant responses to CO and CORM-2 were significantly reduced when compared with WT mice, but ODQ still had an inhibitory effect. The sGC sensitizer 1-benzyl-3-(5′-hydroxymethyl-2′-furyl-)-indazol (YC-1) was able to potentiate CO- and CORM-2-induced relaxations in WT mice but lost this potentiating effect in sGCα1 KO mice. Both in WT and sGCα1 KO mice, CO-evoked relaxations were associated with a significant cGMP increase; however, basal and CO-elicited cGMP levels were markedly lower in sGCα1 KO mice. These data indicate that besides the predominant sGCα1β1 isoform, also the less abundantly expressed sGCα2β1 isoform plays an important role in the relaxant effect of CO in murine gastric fundus; however, the sGC stimulator YC-1 loses its potentiating effect towards CO in sGCα1 KO mice. Prolonged administration of CO—either by the addition of CORM-2 or by continuous infusion of CO—mediates gastric fundus relaxation in both a sGC-dependent and sGC-independent manner. [ABSTRACT FROM AUTHOR]

Aim: The effects of nitric oxide (NO) in the cardiovascular system are attributed in part to cGMP synthesis by the α1β1 isoform of soluble guanylate cyclase (sGC). Because available sGC inhibitors are neither enzyme- nor isoform-specific, we generated knockout mice for the α1 subunit (sGCα1−/− mice) in order to investigate the function of sGCα1β1 in the regulation of blood pressure and cardiac function. [ABSTRACT FROM PUBLISHER]

The principal target of the relaxant neurotransmitter nitric oxide (NO) is soluble guanylate cyclase (sGC). As the α1β1-isoform of sGC is the predominant one in the gastrointestinal tract, the aim of this study was to investigate the role of sGC in nitrergic regulation of gastric motility in male and female sGCα1 knock-out (KO) mice. In circular gastric fundus muscle strips, functional responses and cGMP levels were determined in response to nitrergic and non-nitrergic stimuli. sGC subunit mRNA expression in fundus was measured by real-time RT-PCR; in vivo gastric emptying of a phenol red meal was determined. No changes were observed in sGC subunit mRNA levels between wild-type (WT) and KO tissues. Nitrergic relaxations induced by short trains of electrical field stimulation (EFS) were abolished, while those by long trains of EFS were reduced in KO strips; the latter responses were abolished by 1 H[1,2,4,]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). The relaxations evoked by exogenous NO and the NO-independent sGC activator BAY 41-2272 were reduced in KO strips but still sensitive to ODQ. Relaxations induced by vasoactive intestinal peptide (VIP) and 8-bromo-cGMP were not influenced. Basal cGMP levels were decreased in KO strips but NO, long train EFS and BAY 41-2272 still induced a moderate ODQ-sensitive increase in cGMP levels. Gastric emptying, measured at 15 and 60 min, was increased at 15 min in male KO mice. sGCα1β1 plays an important role in gastric nitrergic relaxation in vitro, but some degree of nitrergic relaxation can occur via sGCα2β1 activation in sGCα1 KO mice, which contributes to the moderate in vivo consequence on gastric emptying. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Soluble guanylyl cyclase (sGC), the predominant receptor for nitric oxide (NO), exists in 2 active isoforms (α2β1 and α1β1). In vascular tissue sGCα1β1 is believed to be the most important. The aim of our study was to investigate the functional importance of the sGCα1-subunit in vasorelaxation. Methods: Aortic and femoral artery segments from male and/or female sGCα1 −/− mice and wild-type littermates were mounted in a small-vessel myograph for isometric tension recording. This was supplemented with biochemical measurements of the cGMP concentration and sGC enzyme activity. Results: The functional importance of sGCα1β1 was demonstrated by the significantly decreased relaxing effects of acetylcholine (ACh), sodium nitroprusside (SNP), S-nitroso-N-acetylpenicillamine (SNAP), NO gas, YC-1, BAY 41-2272 and T-1032 in the sGCα1 −/− mice of both genders. Moreover, the basal and SNP-stimulated cGMP levels and basal sGC activity were significantly lower in the sGCα1 −/− mice. However, the relaxing effects of NO, BAY 41-2272 and YC-1 seen in blood vessels from sGCα1 −/− mice indicate a role for an sGCα1β1-independent mechanism. The increase in sGC activity after addition of BAY 41-2272 and the inhibition of the ACh-, SNP-, SNAP- and NO gas-induced response by the sGC inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) in the sGCα1 −/− mice are observations suggesting that the sGCα2β1 isoform is also functionally active. However, the insignificant increase in cGMP in response to SNP and the non-upregulated sGCα2 expression level in the sGCα1 −/− mice suggest rather the involvement of (an) sGC-independent mechanism(s). Conclusions: We conclude that sGCα1β1 is involved in the vasorelaxation induced by NO-dependent and NO-independent sGC activators in both genders. However, the remaining relaxation seen in the sGCα1 −/− mice suggests that besides sGCα1β1 also the minor isoform sGCα2β1 and/or (an) sGC-independent mechanism(s) play(s) a substantial role. [Copyright &y& Elsevier]

Abstract: Sepsis is a systemic inflammatory response syndrome resulting from an inappropriate innate immune response to infection. TNF and interleukin (IL)-6 are critically involved in this syndrome and although conclusive in vivo evidence is missing, innate immune cells are believed to be the principal producers of these cytokines. We investigated this assumption by performing bone marrow transplantations (BMT) between LPS-sensitive (C3H/HeN) and LPS-hyporesponsive (C3H/HeJ) mice. For adequate LPS-induced systemic TNF production, the hematopoietic cell population was absolutely required. In contrast, IL-6 could be detected in the circulation of LPS-treated chimeric mice, of which either the hematopoietic or the parenchymal cell population was hyporesponsive to LPS. So, whereas hematopoietic cells are the sole source of systemic TNF in an LPS-induced model of sepsis, both hematopoietic and parenchymal cells are required for systemic IL-6 production. Moreover, LPS-induced IL-6 production in parenchymal cells may be partially mediated by the TNF/TNF-R1 pathway as evidenced by the systemic IL-6 levels in LPS-treated wild type (WT), TNF-R1-deficient and chimeric mice. [Copyright &y& Elsevier]