HSPG Interactions in Liver Disease

摘要 R01提案的中心目标是了解肝素的分子和细胞相互作用 硫酸盐蛋白多糖(HSPGs)在对乙酰氨基酚(APAP)肝损伤中的作用 (艾力)。意外或故意误用APAP是西方世界急性肝功能衰竭的主要原因。 虽然触发AILI的机制众所周知，但那些促进肝脏恢复的机制却鲜为人知。 HSPG通过其硫酸乙酰肝素(HS)链结合和调节各种组织损伤因子，但 HSPGs在体内组织损伤和修复中的意义和机制尚不清楚。我们 检测肝细胞主要细胞表面HSPG Syndecan-1(Sdc1)在AILI中的作用。删除Sdc1 导致APAP肝病小鼠肝损伤无对抗进展。然而，APAP的直接肝毒性 APAP后早期过量用药不受Sdc1缺失的影响，提示Sdc1在以后进行调节 影响APAP肝病进展和转归的机制。富于活力的艾力表型 Sdc1缺失(Sdc1-/-)小鼠被追溯到肝脏中夸大的先天性免疫反应和缺陷 在促生存中Akt信号在肝细胞和肝细胞的增殖，从而导致肝脏的放大 损坏。含有2-O-硫酸盐基序的纯化Sdc1或肝素化合物的投药拯救Sdc1-/- 艾力通过抑制先天免疫反应，促进肝细胞增殖和肝脏 修理。此外，与N-乙酰半胱氨酸相比，HS显示出显著延长的治疗效果 (NAC)，APAP过量的临床解毒剂。这些发现表明Sdc1和Hs，无论是单独还是在 与NAC结合，可提供一种新的治疗策略来对抗AILI，特别是在治疗患者方面 入院后NAC治疗不再有效。基于这些初步数据，我们认为Sdc1是 一个关键的内源性因素，阻止肝损伤的永久存在，并促进肝修复在艾力。这 假设将在三个具体目标中得到检验。目标1将定义Sdc1是如何从肝细胞中释放的 并建立了Sdc1HS中的离散结构基序提供了对AILI的保护。目标2将 阐明Sdc1阻止AILI进展的生物学机制。目标3将决定Sdc1如何 促进肝细胞增殖，促进肝修复。这些研究预计将建立一个 肝损伤与修复的新整合途径。

ABSTRACT The central goal of this R01 proposal is to understand how molecular and cellular interactions of heparan sulfate proteoglycans (HSPGs) modulate the pathogenesis of acetaminophen (APAP)-induced liver injury (AILI). Accidental or intentional misuse of APAP is the leading cause of acute liver failure in the Western world. While mechanisms that trigger AILI are well known, those that facilitate liver recovery are less understood. HSPGs bind and regulate various tissue injury factors through their heparan sulfate (HS) chains, but the significance and mechanisms of HSPGs in tissue injury and repair in vivo remain largely unknown. We examined the role of syndecan-1 (Sdc1), the major cell surface HSPG of hepatocytes, in AILI. Deletion of Sdc1 in mice led to unopposed progression of liver injury in APAP liver disease. However, direct APAP hepatoxicity at early times after APAP overdose was unaffected by Sdc1 deletion, suggesting that Sdc1 regulates later mechanisms that affect the progression and outcome of APAP liver disease. The exuberant AILI phenotypes of Sdc1 null (Sdc1-/-) mice were traced to an exaggerated innate immune response in the liver and a deficiency in pro-survival Akt signaling in hepatocytes and hepatocyte proliferation, which led to amplification of liver damage. Administration of purified Sdc1 or heparan compounds containing 2-O-sulfate motifs rescued Sdc1-/- mice from AILI by inhibiting innate immune responses, and by potentiating hepatocyte proliferation and liver repair. Furthermore, HS showed a significantly prolonged therapeutic efficacy as compared to N-acetylcysteine (NAC), the clinical antidote for APAP overdose. These findings suggest that Sdc1 and HS, either alone or in combination with NAC, could provide a new therapeutic strategy to combat AILI, especially in treating patients admitted after NAC treatment is no longer effective. Based on these preliminary data, we propose that Sdc1 is a critical endogenous factor that halts the perpetuation of liver injury and facilitates liver repair in AILI. This hypothesis will be tested in 3 specific aims. Aim 1 will define how Sdc1 is released from hepatocytes during AILI and establish that discrete structural motifs in Sdc1 HS provide protection against AILI. Aim 2 will elucidate the biological mechanisms of how Sdc1 halts the progression of AILI. Aim 3 will determine how Sdc1 enhances hepatocyte proliferation and facilitates liver repair in AILI. These studies are expected to establish a new integrated pathway in liver injury and repair.