Cardioprotective Actions of Hydrogen Sulfide

描述(申请人提供)：硫化氢(H_2S)最近被鉴定为一种生理上重要的内源性气体信号分子，具有多种生物学活性。硫化氢是由两种内源性酶--胱硫醚3裂解酶(CGL)和胱硫醚2合成酶(CBS)以微摩尔量产生的，对维持心血管内环境的稳定至关重要。硫化氢可减轻白细胞黏附，调节线粒体呼吸，抑制细胞凋亡和氧化应激。这些生理作用是治疗心肌缺血再灌注损伤的理想方法。初步数据清楚地表明，生理水平的硫化氢显著改善了MI-R损伤并保护了左心功能。初步数据还表明，硫化氢治疗可触发“早期”和“晚期”心肌预适应。我们还证明，心脏限制性CGL过表达的小鼠表现出显著增加的心肌硫化氢生物利用度和对心肌I-R损伤的保护作用。建议研究的中心假设是，硫化氢触发心脏保护信号级联，在MI-R损伤的背景下提供强大的心脏保护。这项拟议的研究将评估在“急性”和“慢性”药物预适应期间以及在再灌流时的急性硫化氢治疗期间，硫化氢治疗所诱导的各种心脏保护信号。具体目的1：探讨三磷酸腺苷敏感钾通道(KATP通道)在硫化氢介导的抗心肌缺血再灌注损伤中的作用。体外研究将评估硫化氢对KATP通道激活和线粒体功能的影响。体内研究将使用心肌细胞KATP(SuR 1，KIR 6.1和KIR 6.2亚基)缺失的基因靶向小鼠，经硫化氢处理和MI-R处理后进行。具体目的2：探讨抗氧化剂在硫化氢介导的心脏保护中的作用。研究将评估在MI-R期间硫化氢对NRF-2激活和氧化应激的急性和慢性影响。研究还将探讨硫化氢对MI-R前心肌中抗氧化剂信号通路的诱导作用。具体目的3：探讨风险通路在硫化氢介导的心脏保护中的作用。研究将探讨硫化氢对MI-R后风险通路(PI3K、Akt、PKC5和ERK1/2)激活、下游抗凋亡信号、MPTP开放和心肌细胞死亡的影响。这些研究将极大地扩展我们目前对MI-R损伤的分子和细胞病理生理学的认识，并为发展硫化氢治疗急性心肌梗死提供基础。公共卫生相关性：尽管在医疗保健方面取得了许多进展，但心血管疾病仍然是美国的头号杀手，急性心肌梗死(即心脏病发作)每年影响近110万人，在美国每年造成约22万人死亡。这项拟议的研究将评估一种新的治疗剂(即硫化氢)在具有临床相关性和高度平移的急性心肌梗死实验模型系统中的疗效。实验将确定硫化氢保护心脏免受急性心肌梗死的精确细胞机制。其他研究将检验一种关键的硫化氢生成酶基因过度表达对急性心肌梗死严重程度的影响。这项拟议的研究将极大地促进我们目前对心脏病发作期间心肌细胞死亡机制的理解。从这些研究中获得的信息将有助于开发治疗急性心肌梗死患者的新疗法。

DESCRIPTION (provided by applicant): Hydrogen sulfide (H2S) has recently been identified as a physiologically important endogenous gaseous signaling molecule with a diverse array of biological activities. H2S is produced in micromolar quantities by two endogenous enzymes, cystathionine 3lyase (CGL) and cystathionine 2 synthase (CBS) and is critical for the maintenance of cardiovascular homeostasis. H2S attenuates leukocyte adhesion, modulates mitochondrial respiration, and inhibits both apoptosis, and oxidative stress. These physiological actions are ideal for the treatment of myocardial ischemia-reperfusion (MI-R) injury. Preliminary data clearly demonstrate that physiological levels of H2S significantly ameliorate MI-R injury and preserve left ventricular function. Preliminary data also indicate that H2S therapy triggers both "early" and "late" myocardial preconditioning. We also demonstrate that mice with cardiac-restricted CGL overexpression exhibit significantly increased myocardial H2S bioavailability and protection against myocardial I-R injury. The central hypothesis for the proposed studies is that H2S triggers a cardioprotective signaling cascade that confers robust cardioprotection in the setting of MI-R injury. The proposed studies will evaluate the various cardioprotective signals induced by H2S therapy during both "acute" and "chronic" pharmacological preconditioning as well as the during acute H2S therapy at the time of reperfusion. Specific Aim 1: To investigate the contribution of ATP sensitive K+ channels (KATP channels) in H2S- mediated cardioprotection against myocardial ischemia-reperfusion injury. In vitro studies will evaluate the effects of H2S on KATP channel activation and mitochondrial function. In vivo Studies will be performed using gene-targeted mice with cardiac myocyte deletion of KATP (Sur 1, Kir 6.1, and Kir 6.2 subunits) treated with H2S and subjected to MI-R. Specific Aim 2: To investigate the role of antioxidants in H2S-mediated cardioprotection. Studies will evaluate the acute and chronic effects of H2S on Nrf-2 activation and oxidative stress during MI-R. Studies will also investigate the effects of H2S on the induction of antioxidant signaling pathways in the myocardium prior to MI-R. Specific Aim 3: To investigate the role of the RISK pathway in H2S-mediated cardioprotection. Studies will investigate the effects of H2S on RISK pathway (PI3K, Akt, PKC5, and Erk 1/2) activation, downstream anti-apoptotic signaling, MPTP opening, and myocardial cell death following MI-R. The proposed studies will significantly extend our current understanding of the molecular and cellular pathophysiology of MI-R injury and provide the foundation for the development of H2S therapy for the treatment of acute myocardial infarction. PUBLIC HEALTH RELEVANCE: Despite numerous advances in health care, cardiovascular disease remains the number one killer in the United States and acute myocardial infarction (i.e., heart attack) affects nearly 1.1 million people every year and is responsible for approximately 220,000 deaths per year in the United States. The proposed studies will evaluate the efficacy of a novel therapeutic agent (i.e., hydrogen sulfide) in a clinically relevant and highly translational experimental model system of acute myocardial infarction. Experiments will determine the precise cellular mechanisms by which hydrogen sulfide protects the heart against acute myocardial infarction. Additional studies will examine the effects of genetic overexpression of a critical hydrogen sulfide generating enzyme on the severity of acute myocardial infarction. The proposed studies will significantly advance our current understanding of the mechanisms responsible for myocardial cell death during a heart attack. Information gained from these studies will help with the development of novel therapies for the treatment of patients suffering from acute myocardial infarction.