Regulation of hepatic repair responses by metabolites of the uric acid pathway

描述（由申请人提供）：肝细胞凋亡导致修复反应，包括肝星状细胞（HSC）趋化、收缩和基质重塑。从凋亡的肝细胞调节这些反应的信号是不确定的。尿酸途径（UAP）介导嘌呤分解为尿酸。通过这一途径的通量在组织中大大增加。通过坏死或凋亡导致细胞死亡，UAP代谢产物调节许多器官对损伤的细胞反应。我们发现，在原代小鼠HSC中，腺苷i)抑制PDGF诱导的HSC中Ca++的动员和趋化ii)通过A2a受体诱导肌动蛋白重组和HSC的收缩iii)上调TGF β和胶原1 mRNA。包括尿酸在内的许多其他UAP代谢物也可诱导HSC收缩，并上调TGF β和胶原1 mRNA。在两种肝损伤模型中，远端抑制UAP导致更大的纤维化。该提议的假设是，UAP的代谢物调节HSC分化，以应对肝脏组织损伤。特异性目的1:a)确定腺苷介导的肌动蛋白重组和HSC收缩的细胞内信号通路b)确定cAMP、PKA通路在腺苷介导的PDGF诱导的胞质ca2 ++升高的抑制中的作用。具体目的2:a)确定腺苷下游的UAP代谢物是否抑制ATP和PDGF介导的Ca++动员和原代HSC的趋化性；b)确定除尿酸外，UAP代谢物在腺苷下游的作用中对腺苷受体的要求；c)确定尿酸诱导HSC分化的细胞内信号通路。特异性目的3:a)确定免疫系统在腺苷介导的肝纤维化体内调节中的作用。b)测定腺苷调节肝硬化肝内血管阻力的能力。我们已经确定了UAP在HSC分化和调节中的新作用。该研究发现了一组在肝修复中起作用的新分子，并对肝纤维化的新疗法具有指导意义。

DESCRIPTION (provided by applicant): Hepatocyte apoptosis results in repair responses including hepatic stellate cell (HSC) chemotaxis, contraction and matrix remodeling. The signals from apoptotic hepatocytes which modulate these responses are poorly identified. The uric acid pathway (UAP) mediates the breakdown of purines to uric acid. Flux through this pathway is greatly increased in tissues .undergoing cellular death by necrosis or apoptosis, and UAP metabolites regulate cellular responses to injury in many organs. We show that in primary mouse HSC adenosine i) results in inhibition of PDGF induced Ca++ mobilization and chemotaxis in HSC ii) induces actin reorganization and contraction of HSC via the A2a receptor iii) upregulates TGF beta and collagen 1 mRNA. A number of other UAP metabolites including uric acid also induce HSC contraction, and in addition upregulate TGF beta and collagen 1 mRNA. Distal inhibition of the UAP results in greater fibrosis in two models of liver injury. The hypothesis for this proposal is that metabolites of the UAP regulate HSC differentiation in response to tissue injury in the liver. Specific Aim 1: a) Determine the intracellular signaling pathways responsible for adenosine mediated actin reorganization and HSC contraction b) Determine the role of the cAMP, PKA pathway in adenosine mediated inhibition of PDGF induced cytosolic Ca++ increase. Specific Aim 2: a) Determine if UAP metabolites downstream of adenosine inhibit ATP and PDGF mediated Ca++ mobilization and chemotaxis of primary HSC b) Establish the requirement for adenosine receptors in the effect of UAP metabolites downstream of adenosine with the exception of uric acid c) Determine the intracellular signaling pathways responsible for uric acid induced HSC differentiation. Specific Aim 3: a) Determine the role of the immune system in adenosine mediated regulation of liver fibrosis in-vivo. b) Determine the ability of adenosine to regulate intrahepatic vascular resistance in cirrhotic livers. We have identified a new role for the UAP in HSC differentiation and regulation. This identifies a new set of molecules with a role in hepatic repair, and has implications for new therapies in liver fibrosis.