Regulation of cellular bioenergetics by hydrogen sulfide

描述(申请人提供)：我们最近发现了气态生物介体硫化氢(H2S)的基本生物调节机制。首先，我们发现线粒体内由3-巯基丙酮酸硫转移酶(3-MST)驱动的硫化氢生成过程产生了生理数量的硫化氢，从长远来看，这一过程驱动和平衡了氧化磷酸化，维持了细胞的生物能量学。其次，我们还发现，硫化氢介导的生物能量功能遵循钟形剂量反应，其中低(内源)水平的硫化氢支持细胞能量学，而高水平的硫化氢变得抑制和有害。此外，我们最近证明，硫化氢在调节血管张力中起着关键作用，至少部分是通过 作为血管磷酸二酯酶5(PDE5)的生理性(内源性)抑制物。血流量和氧气向组织输送的调节是细胞代谢的关键决定因素；因此，在体内，硫化氢的生物能量作用是其对局部血流的影响和对细胞能量过程(氧化磷酸化、糖酵解)直接调节作用的结果。目前项目的第一个总体目标是表征硫化氢在体外和体内的生物能量作用。这些过程很可能会发挥作用 在正常生理中起着重要的调节作用。此外，该项目的第二个目标是在选定的危重疾病(各种病因的循环系统)模型中表征硫化氢的生物能量作用。第二个总体目标是指导临床对循环系统休克的实验性治疗的新方法的需要，以及初步数据表明在危重疾病中有明显的硫化氢稳态改变。我们的研究将描述(A)产生硫化氢的酶表达的变化；(B)氧化还原状态和活性氧/氮物种的变化；以及(C)组织缺氧/酸中毒程度的变化在循环系统休克中硫化氢生物功能的变化。我们的项目将最终形成一个统一的概念，将解决当前该领域的争议，并将定义关键的分子决定因素，使硫化氢的代谢和血管效应在循环系统休克中有利与有害。在目标1中，我们将在体外静息条件下以及在体外模拟循环休克的各种相关代谢方面的条件下，确定硫化氢对线粒体功能和细胞生物能量学的调节。在目标2中，我们将确定硫化氢失衡在循环休克时血管张力调节中的作用。在目标3中，我们将定义 在循环系统休克小鼠模型中，硫化氢失衡导致多器官衰竭的分子机制。最后，在目标4中，我们将研究硫化氢在体外循环休克患者白细胞细胞生物能量学变化中的作用。这些研究既与生物能量学领域有关，也与危重疾病的发病机制有关。

DESCRIPTION (provided by applicant): We have recently discovered fundamental biological regulatory mechanisms of the gaseous biological mediator hydrogen sulfide (H2S). First and foremost, we have discovered that an intramitochondrial H2S generating process, driven by the enzyme 3-mercaptopyruvate sulfurtransferase (3-MST) produces H2S in physiological amounts, which, in term, drives and balances oxidative phosphorylation and maintains cellular bioenergetics. Next, we have also discovered that H2S-mediated bioenergetic functions follow a bell-shaped dose-response, where low (endogenous) levels of H2S support cellular energetics, while high levels of H2S become inhibitory and deleterious. In addition, we have recently demonstrated that H2S plays a critical role in the regulation of vascular tone, at least in part by acting as a physiological (endogenous) inhibitor of vascular phosphodiesterase 5 (PDE5). Regulation of blood flow and oxygen delivery to tissues is a critical determinant of cellular metabolism; hence, the in vivo bioenergetic role of H2S is the consequence of a combination of its effects on regional blood flow and its direct regulatory actions on cellular energetic processe (oxidative phosphorylation, glycolysis). The first overall goal of the current project is to characterize the bioenergetic roles of H2S in vitro and in vivo. These processes are likely to play important regulatory roles in normal physiology. In addition, the second goal of the project is to characterize the bioenergetic roles of H2S in selected models of critical illness (circulatory shoc of various etiologies). This second overall goal is guided by the clinical need for novel approaches for the experimental therapy of circulatory shock, as well as by preliminary data demonstrating that there are marked alterations in H2S homeostasis in critical illness. Our investigations will delineate the role of (a) changes in the expression of H2S-producing enzymes; (b) changes in redox status and reactive oxygen/nitrogen species and (c) changes in the degree of tissue hypoxia/acidosis in the biological functions of H2S in circulatory shock. Our project will culminate in the formulation of a unifying concept that will resolve current controversies in the field, and will define the key molecular determinants, which render the metabolic and vascular effects of H2S beneficial vs. detrimental in circulatory shock. In Aim 1, we will determine the regulation of mitochondrial function and cellular bioenergetics by H2S under resting in vitro conditions, as well as during conditions, when various relevant metabolic aspects of circulatory shock are modeled in vitro. In Aim 2, we will determine the role of H2S imbalance in the regulation of vascular tone during circulatory shock. In Aim 3, we will define the molecular mechanisms by which H2S imbalance contributes to the development of multiple organ failure in murine models of circulatory shock. Finally, in Aim 4, we will investigate the rol of H2S in changes in cellular bioenergetics in leukocytes from patients with circulatory shock ex vivo. These studies are fundamentally relevant for both the field of bioenergetics, as well as for the pathogenesis of critical illness.