[Show abstract][Hide abstract] ABSTRACT: The physiological and pathological roles of hydrogen sulfide (H2S) in the regulation of cardiovascular functions have been recognized. H2S protects against the hypoxia/reoxygenation (H/R)-induced injury and apoptosis of cardiomyocytes, and ischemic post-conditioning (PC) plays an important role in cardioprotection from H/R injury in neonatal cardiomyocytes but not in aging cardiomyocytes. Whether H2S is involved in the recovery of PC-induced cardioprotection in aging cardiomyocytes is unclear. In the present study, we found that both H/R and PC decreased cystathionine-γ-lyase (CSE) expression and the production rate of H2S. Supplementation of NaHS protected against H/R-induced apoptosis, the expression of cleaved caspase-3 and cleaved caspase-9, the release of cytochrome c (Cyt c), and mPTP opening. The addition of NaHS also counteracted the reduction of cell viability caused by H/R and increased the phosphorylation of ERK1/2, PI3K, Akt, GSK-3β and mitochondrial membrane potential. Additionally, NaHS increased Bcl-2 expression, promoted PKC-ε translocation to the cell membrane, and activated mitochondrial ATP-sensitive K channels (mitoKATP). PC alone did not provide cardioprotection in H/R-treated aging cardiomyocytes, which was significantly restored by the supplementation of NaHS. In conclusion, our results suggest that exogenous H2S restores PC-induced cardioprotection via the inhibition of mPTP opening by the activation of the ERK1/2-GSK-3β, PI3K-Akt-GSK-3β and PKC-ε-mitoKATP pathways in aging cardiomyocytes. These findings provide a novel target for the treatment of aging ischemic cardiomyopathy.
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Preview · Article · Aug 2015 · Cell and Bioscience
[Show abstract][Hide abstract] ABSTRACT: This study explored the mechanisms underlying the recovery of myocardial protection from ischemic post-conditioning (PC) by exogenous hydrogen sulfide (H2 S) in aged rat hearts. We observed that ischemia/reperfusion (I/R) inhibited the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and promoted phosphorylation of p38 MAPK and c-Jun N-terminal kinase (JNK) in both young hearts and aged hearts. PC up-regulated ERK1/2 phosphorylations and down-regulated p38 MAPK and JNK phosphorylations. Exogenous H2 S further enhanced the role of PC in the young hearts. In the aged hearts, PC failed to affect all these 3 MAPK members, while co-treatment with exogenous H2 S induced ERK1/2 and reduced p38 MAPK and JNK phosphorylations. These results suggest that exogenous H2 S recovers PC-induced cardioprotection via MAPK pathway in the aged hearts.
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No preview · Article · Jun 2015 · Cell Biology International
[Show abstract][Hide abstract] ABSTRACT: Hydrogen sulfide (H2S) plays an important role during rat myocardial injury. However, little is known about the role of H2S in hyperhomocysteinemia (HHcy)-induced cardiac dysfunction as well as the underlying mechanisms. In this study, we investigated whether sodium hydrosulfide (NaHS, a H2S donor) influences methionine-induced HHcy rat myocardial injury in intact rat hearts and primary neonatal rat cardiomyocytes. HHcy rats were induced by methionine (2.0 g/kg) and the daily administration of 80 μmol/L NaHS in the HHcy + NaHS treatment group. At the end of 4, 8, and 12 weeks, the ultrastructural alterations and functions of the hearts were observed using transmission electron microscopy and echocardiography system. The percentage of apoptotic cardiomyocytes, the mitochondrial membrane potential, and the production of reactive oxygen species (ROS) were measured. The expressions of cystathionine-γ-lyase (CSE), Bax and Bcl-2, caspase-3, phospho-endothelial nitric oxide synthase and the mitochondrial NOX4 and cytochrome c were analyzed by Western blotting. The results showed the cardiac dysfunction, the ultrastructural changes, and the apoptotic rate increase in the HHcy rat hearts. In the primary neonatal rat cardiomyocytes of HHcy group, ROS production was increased markedly, whereas the expression of CSE was decreased. However, treatment with NaHS significantly improved the HHcy rat hearts function, the ultrastructural changes, and decreased the levels of ROS in the primary neonatal rat cardiomyocytes administrated with HHcy group. Furthermore, NaHS down-regulated the expression of mitochondrial NOX4 and caspase-3 and Bax and inhibited the release of cytochrome c from mitochondria. In conclusion, H2S is involved in the attenuation of HHcy myocardial injury through the protection of cardiac mitochondria.
No preview · Article · Nov 2014 · Molecular and Cellular Biochemistry
[Show abstract][Hide abstract] ABSTRACT: We tested the hypothesis that removing endocardial endothelium (EE) negatively impacts the force-frequency relationship (FFR) of ventricular myocardium and dissected the signaling that underlies this phenomenon. EE of rat trabeculae was selectively damaged by brief (<1 s) exposure to 0.1% Triton X-100. Force, intracellular Ca(2+) transient (iCa(2+)), and activity of protein kinase A (PKA) and protein kinase C (PKC) were determined. In control muscles, force and iCa(2+) increased as the stimulation frequency increased in steps of 0.5 Hz up to 3.0 Hz. However, EE-denuded (EED) muscles exhibited a markedly blunted FFR. Neither isoproterenol (ISO; 0.1-5 nmol/L) nor endothelin-1 (ET-1; 10-100 nmol/L) alone restored the slope of FFR in EED muscles. Intriguingly, however, a positive FFR was restored in EED preparations by combining low concentrations of ISO (0.1 nmol/L) and ET-1 (20 nmol/L). In intact muscles, PKA and PKC activity increased proportionally with the increase in frequency. This effect was completely lost in EED muscles. Again, combining ISO and ET-1 fully restored the frequency-dependent rise in PKA and PKC activity in EED muscles. In conclusion, selective damage of EE leads to significantly blunted FFR. A combination of low concentrations of ISO and ET-1 successfully restores FFR in EED muscles. The interdependence of ISO and ET-1 in this process indicates cross-talk between the β1-PKA and ET-1-PKC pathways for a normal (positive) FFR. The results also imply that dysfunction of EE and/or EE-myocyte coupling may contribute to flat (or even negative) FFR in heart failure.
Full-text · Article · May 2013 · Journal of Applied Physiology
[Show abstract][Hide abstract] ABSTRACT: Aims: Alterations in calcium homeostasis in the intracellular endo/sarcoplasmic reticulum (ER/SR) and mitochondria of cardiomyocytes cause cell death via the SR and mitochondrial apoptotic pathway, contributing to ventricular dysfunction. However, the role of the calcium-sensing receptor (CaR) in cardiac hypertrophy and heart failure has not been studied. This study examined the possible involvement of CaR in the SR and mitochondrial apoptotic pathway in an experimental model of heart failure. Methods and Results: In Wistar rats, cardiac hypertrophy and heart failure were induced by subcutaneous injection of isoproterenol (Iso). Calindol, an activator of CaR, and calhex231, an inhibitor of CaR, were administered by caudal vein injection. Cardiac remodeling and left ventricular function were then analyzed in these rats. After 2, 4, 6 and 8 weeks after the administration of Iso, the rats developed cardiac hypertrophy and failure. The cardiac expression of ER chaperones and related apoptotic proteins was significantly increased in the failing hearts. Furthermore, the expression of ER chaperones and the apoptotic rate were also increased with the administration of calindol, whereas the expression of these proteins was reduced with the treatment of calhex231. We also induced cardiac hypertrophy and failure via thoracic aorta constriction (TAC) in mice. After 2 and 4 weeks of TAC, the expression of ER chaperones and apoptotic proteins were increased in the mouse hearts. Furthermore, Iso induced ER stress and apoptosis in cultured cardiomyocytes, while pretreatment with calhex231 prevented ER stress and protected the myocytes against apoptosis. To further investigate the effect of CaR on the concentration of intracellular calcium, the calcium concentration in the SR and mitochondria was determined with Fluo-5N and x-rhod-1 and the mitochondrial membrane potential was examined with JC-1 using laser confocal microscopy. After treatment with Iso for 48 hours, activation of CaR reduced [Ca(2+)]SR, increased [Ca(2+)]m, decreased the mitochondrial membrane potential, increased the expression of ER stress chaperones and related apoptotic proteins, and induced the release of cytochrome c from the mitochondria. Conclusions: Our results demonstrated that CaR activation caused Ca(2+) release from the SR into the mitochondria and induced cardiomyocyte apoptosis through the SR and mitochondrial apoptotic pathway in failing hearts.
No preview · Article · May 2013 · Cellular Physiology and Biochemistry
[Show abstract][Hide abstract] ABSTRACT: In the study, we investigated how exogenous H2S (hydrogen sulfide) influenced streptozotocin (STZ)-induced diabetic myocardial injury through cardiac mitochondrial protection and nitric oxide (NO) synthesis in intact rat hearts and primary neonatal rat cardiomyocytes. Diabetes was induced by STZ (50 mg/kg) and the daily administration of 100 μM NaHS (sodium hydrosulfide, an H2S donor) in the diabetes + NaHS treatment group. At the end of 4, 8, and 12 weeks, the morphological alterations and functions of the hearts were observed using transmission electron microscopy and echocardiography system. The percentage of apoptotic cardiomyocytes, the mitochondrial membrane potential, the production of reactive oxygen species (ROS) and the level of NO were measured. The expressions of cystathionine-γ-lyase (CSE), caspase-3 and -9, the mitochondrial NOX4 and cytochrome c were analyzed by western blotting. The results showed the cardiac function injured, morphological changes and the apoptotic rate increased in the diabetic rat hearts. In the primary neonatal rat cardiomyocytes of high glucose group, ROS production was increased markedly, whereas the expression of CSE and the level of NO was decreased. However, treatment with NaHS significantly reversed the diabetic rat hearts function, the morphological changes and decreased the levels of ROS and NO in the primary neonatal rat cardiomyocytes administrated with high glucose group. Furthermore, NaHS down-regulated the expression of mitochondrial NOX4 and caspase-3 and -9 and inhibited the release of cytochrome c from mitochondria in the primary neonatal rat cardiomyocytes. In conclusion, H2S is involved in the attenuation of diabetic myocardial injury through the protection of cardiac mitochondria.
No preview · Article · Sep 2012 · Molecular and Cellular Biochemistry
[Show abstract][Hide abstract] ABSTRACT: Rationale:
In the myocardium, redox/cysteine modification of proteins regulating Ca(2+) cycling can affect contraction and may have therapeutic value. Nitroxyl (HNO), the one-electron-reduced form of nitric oxide, enhances cardiac function in a manner that suggests reversible cysteine modifications of the contractile machinery.
To determine the effects of HNO modification in cardiac myofilament proteins.
Methods and results:
The HNO-donor, 1-nitrosocyclohexyl acetate, was found to act directly on the myofilament proteins, increasing maximum force (F(max)) and reducing the concentration of Ca(2+) for 50% activation (Ca(50)) in intact and skinned cardiac muscles. The effects of 1-nitrosocyclohexyl acetate are reversible by reducing agents and distinct from those of another HNO donor, Angeli salt, which was previously reported to increase F(max) without affecting Ca50. Using a new mass spectrometry capture technique based on the biotin switch assay, we identified and characterized the formation by HNO of a disulfide-linked actin-tropomyosin and myosin heavy chain-myosin light chain 1. Comparison of the 1-nitrosocyclohexyl acetate and Angeli salt effects with the modifications induced by each donor indicated the actin-tropomyosin and myosin heavy chain-myosin light chain 1 interactions independently correlated with increased Ca(2+) sensitivity and force generation, respectively.
HNO exerts a direct effect on cardiac myofilament proteins increasing myofilament Ca(2+) responsiveness by promoting disulfide bond formation between critical cysteine residues. These findings indicate a novel, redox-based modulation of the contractile apparatus, which positively impacts myocardial function, providing further mechanistic insight for HNO as a therapeutic agent.
Full-text · Article · Jul 2012 · Circulation Research
[Show abstract][Hide abstract] ABSTRACT: Nuclear Ca(2+) plays a pivotal role in the regulation of gene expression. IP3 (inositol-1,4,5-trisphosphate) is an important regulator of nuclear Ca(2+). We hypothesized that the CaR (calcium sensing receptor) stimulates nuclear Ca(2+) release through IICR (IP3-induced calcium release) from perinuclear stores. Spontaneous Ca(2+) oscillations and the spark frequency of nuclear Ca(2+) were measured simultaneously in NRVMs (neonatal rat ventricular myocytes) using confocal imaging. CaR-induced nuclear Ca(2+) release through IICR was abolished by inhibition of CaR and IP3Rs (IP3 receptors). However, no effect on the inhibition of RyRs (ryanodine receptors) was detected. The results suggest that CaR specifically modulates nuclear Ca(2+) signalling through the IP(3)R pathway. Interestingly, nuclear Ca(2+) was released from perinuclear stores by CaR activator-induced cardiomyocyte hypertrophy through the Ca(2+)-dependent phosphatase CaN (calcineurin)/NFAT (nuclear factor of activated T-cells) pathway. We have also demonstrated that the activation of the CaR increased the NRVM protein content, enlarged cell size and stimulated CaN expression and NFAT nuclear translocation in NRVMs. Thus, CaR enhances the nuclear Ca(2+) transient in NRVMs by increasing fractional Ca(2+) release from perinuclear stores, which is involved in cardiac hypertrophy through the CaN/NFAT pathway.
No preview · Article · Jun 2012 · Cell Biology International
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: The purpose was to develop a rabbit model of intimal hyperplasia with controllable lesion. METHODS: Following 1 week of a 2% cholesterol diet, 32 New Zealand White male rabbits underwent right femoral arteries surgical perfusion with distilled water for 1, 3, 5, or 7 min (n=8/group). After a further 4 weeks of the same diet, serum total cholesterol, triglyceride, low-density lipoprotein, and high-density lipoprotein were measured in all rabbits. Intimal hyperplasia in histological sections of arteries were assessed by intimal proliferation ratio. Macrophage numbers and levels of proteins matrix metalloproteinase 9, tissue inhibitor of metalloproteinase 2, and alpha smooth muscle actin in lesions were analyzed by immunohistochemistry. RESULTS: Serum lipids levels showed no statistical difference between experimental groups. Intimal proliferation ratio increased gradually with perfusion time, and a positive linear correlation was calculated between intimal proliferation ratio and duration of distilled water perfusion. Similarly, number of macrophages and levels of matrix metalloproteinase 9, tissue inhibitor of metalloproteinase 2, and alpha smooth muscle actin in lesions increased with perfusion time. CONCLUSIONS: A novel model of intimal hyperplasia was established by intravascular distilled water perfusion in high-cholesterol-fed rabbits. Importantly, this model exhibits time-dependent neointimal proliferation lesions that can be readily controlled in terms of extent, thus providing an avenue for further studies.
No preview · Article · Mar 2012 · Cardiovascular pathology: the official journal of the Society for Cardiovascular Pathology
[Show abstract][Hide abstract] ABSTRACT: Our previous studies demonstrated that caclium-sensing receptor (CaR) stimulation elicited phospholipase C (PLC)-mediated inositol triphosphate (IP3) formation, leading to an elevation in [Ca2+]i
released from the endo(sarco)plasmic reticulum (ER) to induce ER stress and perturbations of ER function, which cause cardiomyocyte apoptosis during ischemia/reperfusion (I/R). The aim of this study was to determine whether the protection of post-conditioning (PC) from I/R heart injury involved relieving calcium-sensing receptor (CaR)-induced ER stress. Male Wistar rats were subjected to 30 min of ischemia followed by 2 h of reperfusion. The rats were post-conditioned after the 30 min of ischemia by three cycles of 10 s of reperfusion followed by 10 s of ischemia at the onset of reperfusion. Meanwhile, GdCl3, an activator of CaR, and NPS-2390, a specific inhibitor, were administered. We found that the PC and PC with NPS-2390 groups improved the recovery of cardiac function during reperfusion compared to the IR and PC groups with GdCl3, respectively. [Ca2+]i
and [Ca2+]ER were determined using Fluo-4 AM and Fluo-5N AM, respectively, using laser confocal microscopy. [Ca2+]i
was significantly increased, whereas [Ca2+]ER was significantly decreased in the I/R and PC groups with GdCl3. The rate of apoptotic cells was significantly decreased as shown by TUNEL (Terminal deoxy-nucleotidyl transferase-mediated dUTP nick end labeling) assay in PC and PC with NPS-2390 groups compared to the I/R and PC groups with GdCl3. In the I/R and PC groups with GdCl3, the activated fragments of caspase-12, the cleavage products of activating transcription factor 6 (ATF6) and phospho-JNK (c-Jun NH2-terminal kinase) were increased compared to the PC and PC with GdCl3 groups. These results demonstrated that PC could protect the myocardium from I/R injury by inhibiting CaR-induced sarcoplasmic reticulum stress.
No preview · Article · Feb 2012 · Molecular and Cellular Biochemistry
[Show abstract][Hide abstract] ABSTRACT: The calcium-sensing receptor (CaSR) is a G protein-coupled receptor (GPCR) that activates intracellular effectors; for example, it causes inositol phosphate (IP) and 1,2 diacylglycerol (DAG) accumulation, stimulating the release of intracellular calcium and the activation of the protein kinase Cs (PKCs). The activation of CaSR by ischemia/reperfusion (I/R) induces cardiomyocyte apoptosis through the mitochondrial apoptotic pathway; however, the underlying mechanisms remain unclear. In this study, rat hearts were subjected to 30 min of ischemia followed by 2 h of reperfusion in the presence of a CaSR activator, GdCl(3). Our results revealed that, under these conditions, the expression of CaSR was increased, the number of apoptotic cardiomyocytes was significantly increased (as shown by terminal deoxy-nucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay) and the cells with a typical apoptotic morphology were observed using transmission electron microscopy. Our data further showed that mitochondria isolated from hearts that had undergone I/R combined with GdCl(3) exhibited a significant increase in the translocation of phosphorylated PKCδ to the mitochondria, an increase in cytochrome c (cyt c) release from the mitochondria and a marked decrease in mitochondrial potential. The administration of rottlerin, an inhibitor of PKCδ, significantly reduced reperfusion-induced apoptosis, phospho-PKCδ translocation to the mitochondria and the release of cyt c from the mitochondria. Thus, the involvement of CaSR in cardiac apoptosis through the mitochondrial pathway during I/R with GdCl(3) is related to phospho-PKCδ translocation to the mitochondria.
No preview · Article · Jul 2011 · Molecular and Cellular Biochemistry
[Show abstract][Hide abstract] ABSTRACT: Previously, we showed that oral allopurinol increased survival in mice with post-ischemic cardiomyopathy and attributed this outcome to an improvement of excitation-contraction coupling that boosted contractility. In this study, we tested the sustainability of this enhanced contraction associated with decreased oxidative damage over an extended time. Mice were divided into three groups: sham-operated control, myocardial infarction-heart failure (MI-HF), and oxypurinol-treated heart failure (Oxy-HF). After 9-11 months, echocardiography showed that mice treated with oxypurinol (1mM in drinking water) had significantly higher left ventricle fractional contraction and fractional wall thickening during systole than did mice in the MI-HF group (left ventricle fractional contraction: 28.4+/-2.2% vs. 19.9+/-2.3%, P<0.05; left ventricle fractional wall thickening: 45.0+/-4.0% vs. 23.5+/-2.0%, P<0.05). Left ventricular diastolic dimension, however, remained enlarged (0.50+/-0.04 vs. 0.54+/-0.05 cm, not significant). Twitch force was significantly higher at any given external Ca(2+) concentration in the Oxy-HF group than in the MI-HF group (P<0.01); amplitudes of intracellular Ca(2+) transients were also higher in the Oxy-HF group but were not statistically different from those of the MI-HF group. Force-frequency relation was improved in the Oxy-HF group. Muscle in the Oxy-HF group exhibited increases in myofilament Ca(2+) responsiveness, as evidenced by significantly higher maximal Ca(2+)-activated force (77.8+/-12.7 vs. 36.4+/-4.4 mN/mm(2), P<0.01). Finally, lipid peroxidation and myofilament oxidation were suppressed in the Oxy-HF group. These results indicate that the beneficial effects of antioxidation can be sustained by long-term treatment with oxypurinol after ischemic heart failure, with significantly improved cardiac contractility.
No preview · Article · Sep 2009 · European journal of pharmacology
[Show abstract][Hide abstract] ABSTRACT: In addition to O-phosphorylation, O-linked modifications of serine and threonine by beta-N-acetyl-D-glucosamine (GlcNAc) may regulate muscle contractile function. This study assessed the potential role of O-GlcNAcylation in cardiac muscle contractile activation. To identify specific sites of O-GlcNAcylation in cardiac myofilament proteins, a recently developed methodology based on GalNAz-biotin labeling followed by dithiothreitol replacement and light chromatography/tandem mass spectrometry site mapping was adopted. Thirty-two O-GlcNAcylated peptides from cardiac myofilaments were identified on cardiac myosin heavy chain, actin, myosin light chains, and troponin I. To assess the potential physiological role of the GlcNAc, force-[Ca(2+)] relationships were studied in skinned rat trabeculae. Exposure to GlcNAc significantly decreased calcium sensitivity (pCa50), whereas maximal force (F(max)) and Hill coefficient (n) were not modified. Using a pan-specific O-GlcNAc antibody, it was determined that acute exposure of myofilaments to GlcNAc induced a significant increase in actin O-GlcNAcylation. This study provides the first identification of O-GlcNAcylation sites in cardiac myofilament proteins and demonstrates their potential role in regulating myocardial contractile function.
Full-text · Article · Dec 2008 · Circulation Research