Xinxue Liao

Hydrogen Sulfide Protects against Chemical Hypoxia-Induced Injury by Inhibiting ROS-Activated ERK1/2 and p38MAPK Signaling Pathways in PC12 Cells

Hydrogen sulfide (H2S) has been proposed as a novel neuromodulator and neuroprotective agent. Cobalt chloride (CoCl2) is a well-known hypoxia mimetic agent. We have demonstrated that H2S protects against CoCl2-induced injuries in PC12 cells. However, whether the members of mitogen-activated protein kinases (MAPK), in particular, extracellular signal-regulated kinase1/2(ERK1/2) and p38MAPK are involved in the neuroprotection of H2S against chemical hypoxia-induced injuries of PC12 cells is not understood. We observed that CoCl2 induced expression of transcriptional factor hypoxia-inducible factor-1 alpha (HIF-1α), decreased cystathionine-β synthase (CBS, a synthase of H2S) expression, and increased generation of reactive oxygen species (ROS), leading to injuries of the cells, evidenced by decrease in cell viability, dissipation of mitochondrial membrane potential (MMP) , caspase-3 activation and apoptosis, which were attenuated by pretreatment with NaHS (a donor of H2S) or N-acetyl-L cystein (NAC), a ROS scavenger. CoCl2 rapidly activated ERK1/2, p38MAPK and C-Jun N-terminal kinase (JNK). Inhibition of ERK1/2 or p38MAPK or JNK with kinase inhibitors (U0126 or SB203580 or SP600125, respectively) or genetic silencing of ERK1/2 or p38MAPK by RNAi (Si-ERK1/2 or Si-p38MAPK) significantly prevented CoCl2-induced injuries. Pretreatment with NaHS or NAC inhibited not only CoCl2-induced ROS production, but also phosphorylation of ERK1/2 and p38MAPK. Thus, we demonstrated that a concurrent activation of ERK1/2, p38MAPK and JNK participates in CoCl2-induced injuries and that H2S protects PC12 cells against chemical hypoxia-induced injuries by inhibition of ROS-activated ERK1/2 and p38MAPK pathways. Our results suggest that inhibitors of ERK1/2, p38MAPK and JNK or antioxidants may be useful for preventing and treating hypoxia-induced neuronal injury.

The Role of Macrolide Antibiotics in Increasing Cardiovascular Risk

BACKGROUND Large cohort studies provide conflicting evidence regarding the potential for oral macrolide antibiotics to increase the risk of serious cardiac events. OBJECTIVES This study performed a meta-analysis to examine the link between macrolides and risk of sudden cardiac death (SCD) or ventricular tachyarrhythmias (VTA), cardiovascular death, and death from any cause. METHODS We performed a search of published reports by using MEDLINE (January 1, 1966, to April 30, 2015) and EMBASE (January 1, 1980, to April 30, 2015) with no restrictions. Studies that reported relative risk (RR) estimates with 95% confidence intervals (CIs) for the associations of interest were included. RESULTS Thirty-three studies involving 20,779,963 participants were identified. Patients taking macrolides, compared with those who took no macrolides, experienced an increased risk of developing SCD or VTA (RR: 2.42; 95% CI: 1.61 to 3.63), SCD (RR: 2.52; 95% CI: 1.91 to 3.31), and cardiovascular death (RR: 1.31; 95% CI: 1.06 to 1.62). No association was found between macrolides use and all-cause death or any cardiovascular events. The RRs associated with SCD or VTA were 3.40 for azithromycin, 2.16 for clarithromycin, and 3.61 for erythromycin, respectively. RRs for cardiovascular death were 1.54 for azithromycin and 1.48 for clarithromycin. No association was noted between roxithromycin and adverse cardiac outcomes. Treatment with macrolides is associated with an absolute risk increase of 118.1 additional SCDs or VTA, and 38.2 additional cardiovascular deaths per 1 million treatment courses. CONCLUSIONS Administration of macrolide antibiotics is associated with increased risk for SCD or VTA and cardiovascular death but not increased all-cause mortality.

Hydrogen sulfide protects H9c2 cells against doxorubicin-induced cardiotoxicity through inhibition of endoplasmic reticulum stress

The roles of hydrogen sulfide (H2S) and endoplasmic reticulum (ER) stress in doxorubicin (DOX)-induced cardiotoxicity are still unclear. This study aimed to dissect the hypothesis that H2S could protect H9c2 cells against DOX-induced cardiotoxicity by inhibiting ER stress. Our results showed that exposure of H9c2 cells to DOX significantly inhibited the expression and activity of cystathionine-γ-lyase (CSE), a synthetase of H2S, accompanied by the decreased cell viability and the increased reactive oxygen species (ROS) accumulation. In addition, exposure of cells to H2O2 (an exogenous ROS) mimicked the inhibitory effect of DOX on the expression and activity of CSE. Pretreatment with N-acetyl-l-cysteine (NAC) (a ROS scavenger) attenuated intracellular ROS accumulation, cytotoxicity, and the inhibition of expression and activity of CSE induced by DOX. Notably, the ER stress-related proteins, including glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) were obviously upregulated in DOX-treated H9c2 cells. Pretreatment with sodium hydrosulfide (NaHS, a H2S donor) before DOX exposure markedly suppressed DOX-induced overexpressions of GRP78 and CHOP, cytotoxicity and oxidative stress. In conclusion, we have demonstrated that ROS-mediated inhibition of CSE is involved in DOX-induced cytotoxicity in H9c2 cells, and that exogenous H2S can confer protection against DOX-induced cardiotoxicity partly through inhibition of ER stress.

Inhibition of ROS-activated ERK1/2 pathway contributes to the protection of H2S against chemical hypoxia-induced injury in H9c2 cells.

Hydrogen sulfide (H2S) has been shown to exert cardioprotective effects. However, the roles of extracellular signal-regulated protein kinases 1/2 (ERK1/2) in H2S-induced cardioprotection have not been completely elucidated. In this study, cobalt chloride (CoCl2), a chemical hypoxia mimetic agent, was applied to treat H9c2 cells to establish a chemical hypoxia-induced cardiomyocyte injury model. The results showed that pretreatment with NaHS (a donor of H2S) before exposure to CoCl2 attenuated the decreased cell viability, the increased apoptosis rate, the loss of mitochondrial membrane potential (ΔΨm), and the intracellular accumulation of reactive oxygen species (ROS) in H9c2 cells. Exposure of H9c2 cells to CoCl2 or hydrogen peroxide (H2O2) upregulated expression of phosphorylated (p) ERK1/2, which was reduced by pretreatment with NaHS or N-acetyl-l-cysteine, a ROS scavenger. More importantly, U0126, a selective inhibitor of ERK1/2, mimicked the above cytoprotection of H2S against CoCl2-induced injury in H9c2 cells. In conclusion, these results indicate that H2S protects H9c2 cells against chemical hypoxia-induced injury partially by inhibiting ROS-mediated activation of ERK1/2.

Novel insights into the role of HSP90 in cytoprotection of H2S against chemical hypoxia-induced injury in H9c2 cardiac myocytes

The present study evaluated potential mechanisms of hydrogen sulfide (H2S)-mediated cardioprotection using an in vitro chemical hypoxia-induced injury model. We have demonstrated that H2S protects H9c2 cardiomyoblasts (H9c2) against chemical hypoxia-induced injuries by suppressing oxidative stress and preserving mitochondrial function. The aim of this study was to investigate the role of heat shock protein 90 (HSP90) in cardioprotection of H2S in H9c2 cells. The findings of the present study showed that cobalt chloride (CoCl2), a chemical hypoxia agent, significantly enhanced the expression of HSP90 and that 17-allylamino-17-demethoxy geldanamycin (17-AAG), a selective inhibitor of HSP90, aggravated concentration-dependent cytotoxicity induced by CoCl2. Exogenous administration of NaHS (a donor of H2S) augmented not only HSP90 expression under normal conditions, but also CoCl2-induced overexpression of HSP90. Pre-treatment with 17-AAG significantly blocked the cardioprotection of H2S against CoCl2-induced injuries, leading to increases in cytotoxicity and apoptotic cells. Furthermore, pre-treatment with 17-AAG also antagonized the inhibitory effects of NaHS on overproduction of reactive oxygen species (ROS), a loss of mitochondrial membrane potential (MMP) and ATP depletion induced by CoCl2. In conclusion, these results demonstrate that the increased expression of HSP90 may be one of the endogenous defensive mechanisms for resisting chemical hypoxia-induced injury in H9c2 cells. We also provide novel evidence that HSP90 mediates the cardioprotection of H2S against CoCl2-induced injuries by its antioxidant effect and preservation of mitochondrial function in H9c2 cells.

Effectiveness and Safety of Warfarin in Dialysis Patients With Atrial Fibrillation: A Meta-Analysis of Observational Studies

AbstractIn routine practice, warfarin is widely used in dialysis patients with atrial fibrillation (AF) for stroke prevention though the ratio of risks to benefits remains unclear. Recent cohort studies investigating the association between warfarin use and the risks of stroke and bleeding in dialysis patients with AF present conflicting results.The objective of this study was to assess the effectiveness and safety of warfarin use in patients with AF undergoing dialysis.Three databases PubMed, EMBASE, and OVID were searched from their inception to August 2015.Observational studies which assessed the ischemic stroke or bleeding risk of warfarin use in dialysis patients with AF were included. Two reviewers independently extracted data and assessed methodological quality based on the Newcastle–Ottawa Scale score. Combined hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using the random-effects model and heterogeneity was assessed based on the Cochrane Q-statistic test and the I2 statistic. Metaregression analyses were performed to explore the source of heterogeneity.A total of 11 eligible studies with 25,407 patients were included in the analysis. Warfarin use, in comparison with no-warfarin use, was not associated with a lower risk for ischemic stroke (HR 0.95, 95% CI 0.66–1.35). Sensitivity analyses found results to be robust. Metaregression analysis showed that demographic feature, clinical characteristics, or study-level variable had no impact of warfarin use on stroke risk. In addition, warfarin use was associated with a 27% higher risk for bleeding (95% CI 1.04–1.54). Overall, warfarin use did not have a significant association with reduced mortality (95% CI 0.96–1.11).It appears that warfarin use is not beneficial in reducing stroke risk, but with a high risk for bleeding in dialysis patients with AF. Randomized trials are needed to determine the risk-benefit ratio of warfarin in dialysis patients with AF.

PDE5 inhibitor sildenafil in the treatment of heart failure: A meta-analysis of randomized controlled trials

BACKGROUND Clinical trials have evaluated the use of phosphodiesterase (PDE) 5 inhibitors sildenafil as a potential adjunct in the treatment of heart failure (HF) with mixed results. Thus, we undertook a meta-analysis to evaluate the clinical viability of sildenafil in HF. METHODS Relevant studies were searched and identified in the MEDLINE and EMBASE databases. Randomized clinical trials (RCT) comparing sildenafil to placebo, in heart failure patients, reporting at least one outcome of interest were included. Data were extracted regarding the characteristics and clinical outcomes. RESULTS We identified 9 RCTs enrolling 612 HF patients. There were no significant differences in adverse events between sildenafil group and placebo group (RR=1.10, 95% CI=0.74 to 1.65, P=0.41), whereas sildenafil therapy was associated with a marked improvement in hemodynamic parameter peak VO2 (MD=3.25, 95% CI=2.07 to 4.42, P<0.00001) in HF with reduced ejection fraction (HFrEF) patients but not in HF with preserved ejection fraction (HFpEF) patients. Also, sildenafil therapy improved VO2 at anaerobic threshold (AT) (MD=3.47, 95% CI=1.68 to 5.27, P=0.0002), VE/VCO2 slope (MD=-7.06, 95% CI=-8.93 to -5.19, P<0.00001) and LV ejection fraction (MD=5.43, 95% CI=3.66 to 7.20, P<0.00001) compared to placebo in HF patients, which had no impact on blood pressure and heart rate. For quality of life (emotional function, fatigue and breathlessness), there was no significant difference between the two groups. CONCLUSIONS Sildenafil improved hemodynamic parameters particularly in HFrEF patients when compared to placebo, with no increase in adverse events. Sildenafil treatment was well tolerated and had no impact on quality of life.

Spinal MCP-1 Contributes to the Development of Morphine Antinociceptive Tolerance in Rats

Background:The chemokine monocyte chemoattractant protein-1 (MCP-1) has been shown to contribute to neuropathic pain. However, whether MCP-1 is involved in the development of morphine antinociceptive tolerance is incompletely understood. Methods:Morphine antinociceptive tolerance was induced by intrathecal administration of 15 &mgr;g of morphine daily for 7 days. Immunohistochemistry was used to test the changes in the morphology of spinal MCP-1 immunoreactivity and OX-42-IR. The role of MCP-1 in morphine antinociceptive tolerance is explored by hot-water tail-flick test. Results:Our findings showed that intrathecal chronic morphine exposure obviously increased MCP-1 immunoreactivity in the spinal cord. Moreover, the increased MCP-1 immunoreactivity was observed mainly in the spinal neurons. Intrathecal injections of MCP-1-neutralizing antibody significantly reduced the development of morphine antinociceptive tolerance, suggesting that spinal neuronal MCP-1 contributes to tolerance to morphine antinociception. Treatment with MCP-1-neutralizing antibody also reduced the spinal microglial activation induced by chronic morphine treatment. Conclusions:This study revealed for the first time that spinal neuronal MCP-1 is a key mediator of the spinal microglial activation and that spinal MCP-1 is involved in morphine antinociceptive tolerance. Inhibition of MCP-1 may provide a new therapy for morphine tolerance management.

Cyclooxygenase mediates cardioprotection of angiotensin-(1-7) against ischemia/reperfusion-induced injury through the inhibition of oxidative stress

Angiotensin (Ang)-(1-7) exhibits cardioprotective effects in myocardial ischemia reperfusion (I/‌R)-induced injury. However, the roles of oxidation and cyclooxygenase (COX) in the cardioprotection of Ang-(1-7) remain unclear. This study was conducted to investigate whether oxidation and COX were involved in the cardioprotection of Ang-(1-7) against I/‌R-induced injury in isolated rat hearts. The hearts were subjected to 15 min regional ischemia followed by 30 min reperfusion. Myocardial I/‌R treatment induced significant cardiac dysfunction, including ventricular arrhythmia (VA) and a reduction of left ventricular systolic pressure (LVSP), cardiomyocyte apoptosis and oxidative stress, manifesting as an increase in malondialdehyde (MDA) production and a decrease in superoxide dismutase (SOD) activity. Pretreatment of the hearts with 1.0 nmol/‌l Ang-(1-7) for 30 min prior to ischemia considerably attenuated I/‌R-induced VA, apoptosis and MDA production, and enhanced LVSP and SOD activity. These cardioprotective effects of Ang-(1-7) were antagonized by the intraperitoneal injection of 5 mg/‌kg body weight indomethacin (IDM, a COX inhibitor), presenting as an enhancement of VA, apoptosis and MDA production as well as a reduction of LVSP and SOD activity. In conclusion, COX mediated Ang-(1-7)-induced cardioprotection via its antioxidative mechanism.

Exogenous Hydrogen Sulfide Attenuates High Glucose-Induced Cardiotoxicity by Inhibiting NLRP3 Inflammasome Activation by Suppressing TLR4/NF-κB Pathway in H9c2 Cells

Background/Aims: This study aimed to investigate whether exogenous hydrogen sulfide (H2S) confered cardiac protection against high glucose (HG)-induced injury by inhibiting NLRP3 inflammasome activation via a specific TLR4/NF-κB pathway. Methods: H9c2 cardiac cells were exposed to 33 mM glucose for 24 h to induce HG-induced cytotoxicity. The cells were pretreated with NaHS (a donor of H2S) before exposure to HG. Cell viability, cell apoptosis, intracellular reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and TLR4, NF-κB, NLRP3 inflammasome, IL-1β, IL-18 and caspase-3 expression were measured by standard methods. Results: H2S attenuated HG-induced cell apoptosis, ROS expression and loss of MMP and reduced the expression of NLRP3, ASC, pro-caspase-1, caspase-1, IL-1β, IL-18 and caspase-3. In addition, H2S inhibited the HG-induced activation of TLR4 and NF-κB. Furthermore, NLRP3 inflammasome activation was regulated by the TLR4 and NF-κB pathway. Conclusion: The present study demonstrated for the first time that H2S appears to suppress HG-induced cardiomyocyte inflammation and apoptosis by inhibiting the TLR4/NF-κB pathway and its downstream NLRP3 inflammasome activation. Thus H2S might possess potential in the treatment of diabetic cardiomyopathy.