Regulation of Hepatic Stellate Cells by Extracellular Nucleotides

描述(申请人提供)：纤维化，或疤痕的形成，发生在几乎所有器官的损伤反应。尽管慢性肝病的治疗取得了进展，但在美国和世界各地，肝纤维化和随后的肝硬变仍然是一个严重的健康问题。肝星状细胞(HSC)是肝脏的主要纤维化细胞。尽管近年来对HSC功能的认识取得了重要进展，但调节HSC活性的关键信号机制尚未完全清楚。P2Y受体是G蛋白偶联的细胞外ATP和其他核苷酸的受体。P2Y受体通过三磷酸肌醇(IP3)介导的钙信号诱导下游细胞效应。最近，我们报道了HSC表达P2Y受体，这些受体的激活诱导了HSC的纤维化。我们现在已经观察到HSC在HSC内的不同区域表达IP3受体(IP3R)：细胞核和细胞延伸。这种独特的IP3R表达模式允许通过这两个细胞区段介导的P2Y受体激活的不同效果。我们还观察到，在整个动物体内阻断P2Y受体可能会阻止肝纤维化的发展，这表明通过P2Y受体的信号转导是疾病状态下肝纤维化的重要介质。因此，我们认为，P2Y受体的激活通过在HSC内不同的亚细胞室中的多个下游效应来诱导肝纤维化。我们将通过以下三个具体目标来验证这一假说：1.确定P2Y受体激活对细胞核内HSC功能的影响。2.确定P2Y受体激活对细胞延伸中HSC功能的影响。3.确定阻断P2Y受体是否能抑制肝纤维化。我们相信，拟议的实验结果将导致对HSC功能的新理解，并最终可能导致开发治疗肝纤维化的新的药理学方法。 公共卫生相关性：晚期肝纤维化导致肝硬变，是导致肝功能衰竭的最重要原因，在没有肝移植的情况下会导致死亡。已经提出了多种治疗方法来预防或逆转肝纤维化；然而，由于对肝纤维化的基本机制了解不完全，这些方法一直受到阻碍。在拟议的工作中，我们将确定在肝纤维化发病机制中重要的新途径，这反过来应该导致新的方法来预防或治疗患者的肝纤维化。

DESCRIPTION (provided by applicant): Fibrogenesis, or scar formation, occurs as a response to injury in almost all organs. Liver fibrosis and subsequent cirrhosis remains a critical health problem in the United States and worldwide despite advances in therapy of chronic liver disease. Hepatic stellate cells (HSC) are the primary fibrogenic cells of the liver. Although there have been important advances in the understanding of HSC function in recent years, critical signaling mechanisms regulating HSC activity have not been completely understood. P2Y receptors are G protein coupled receptors for extracellular ATP and other nucleotides. P2Y receptors induce downstream cellular effects through inositol triphosphate (IP3)-mediated calcium signals. Recently, we reported that HSC express P2Y receptors, and that activation of these receptors induces fibrogenesis in HSC. We have now observed that HSC express IP3 receptors (IP3R) at distinct regions within HSC: the nucleus and cell extensions. This unique pattern of IP3R expression allows for distinct effects of P2Y receptor activation mediated by these two cellular compartments. We have also observed that blockade of P2Y receptors in the whole animal may prevent development of liver fibrosis, suggesting that signaling via P2Y receptors is an important mediator of liver fibrosis in disease states. Thus we propose that P2Y receptor activation induces liver fibrosis via multiple downstream effects in distinct subcellular compartments within HSC. We will test this hypothesis through the following three Specific Aims: 1. Determine the effects of P2Y receptor activation on the function of HSC in the nucleus. 2. Determine the effects of P2Y receptor activation on the function of HSC in cell extensions. 3. Identify whether blockade of P2Y receptors inhibits liver fibrosis. We believe that the results of the proposed experiments will lead to novel understanding of HSC function and may ultimately lead to the development of new pharmacologic approaches to the treatment of liver fibrosis. Public Health Relevance: Advanced liver fibrosis, leading to cirrhosis, is the most important cause of liver failure, leading to death in the absence of liver transplantation. Multiple therapeutic approaches have been proposed to prevent or reverse liver fibrosis; however, these have been stymied due to incomplete understanding of the basic mechanisms of liver fibrosis. In the proposed work, we will identify novel pathways that are important in the pathogenesis of liver fibrosis, which should in turn lead to new approaches to prevent or liver fibrosis in patients.