Role of Lysosome Damage in ALD Pathogenesis

摘要： 尽管最近的进展已经澄清了酒精相关性肝病（ALD）的病因，但细胞凋亡和肝细胞凋亡仍然是一个重要的因素。 而导致进行性肝损伤的分子改变仅被部分理解。而且 目前还没有FDA批准的治疗方法可以阻止或逆转ALD的进展。因此，我们迫切需要 确定导致进行性肝损伤的细胞和分子机制，以改善疾病 预后，并确定新的治疗目标和程序，减轻甚至预防ALD。 大量饮酒会影响所有组织，但对肝脏的损害最大。这是因为 酒精（乙醇或EtOH）主要在肝脏中代谢产生毒性产物（乙醛， 超氧化物和羟基自由基），持续饮酒会破坏和损害结构和功能 膜结合细胞器，包括ER，细胞外基质和溶酶体。后一种细胞器 降解真核细胞中几乎所有的大分子。我们的目标是确定特定的改变诱导 通过EtOH代谢物，导致肝细胞和枯否细胞（驻留肝脏）中的溶酶体损伤 巨噬细胞），并且其分别导致实质细胞死亡和炎性信号传导。 溶酶体在细胞质量控制中起着至关重要的作用，因为它们回收废弃的蛋白质和功能失调的蛋白质。 包括受损的溶酶体。如果细胞不修复/清除受损的溶酶体，它们将继续 泄露它们的蛋白水解酶以触发细胞死亡并引起枯否细胞的炎症信号。 我们和其他人以前报道过慢性乙醇（EtOH）消耗导致错误的溶酶体生物合成 和溶酶体膜不稳定性。在这里，我们展示了令人兴奋的新的试点数据，表明慢性乙醇 人类和啮齿类动物的消耗导致溶酶体膜损伤和随后的细胞渗漏。 溶酶体组织蛋白酶（和其它水解酶），其导致肝细胞损伤。此外，这种损害 释放溶酶体膜成分进入循环，这可能是肝损伤的预后标志。 我们的试验数据，在此提出，表明初级和/或次级EtOH代谢物损害溶酶体 在肝细胞和枯否细胞中，诱导组织蛋白酶渗漏，导致细胞死亡和炎症。 这些新的观察结果支持了我们的假设，即慢性EtOH氧化损伤溶酶体， 细胞毒性溶酶体水解酶的泄漏，从而导致肝损伤和炎症。测试 根据我们的假设，我们提出以下具体目标： 在目标1中，我们将确定乙醇诱导的溶酶体损伤，引发肝细胞损伤的机制。 在目标2中，我们将研究EtOH诱导的溶酶体损伤的机制， Kupffer细胞中的信号。 我们预计，这项研究的结果将揭示新的机制，乙醇氧化促进 通过破坏溶酶体导致肝脏病理学的进展。

Abstract: Despite recent advances that have clarified the etiologies of alcohol-associated liver disease (ALD), the cellular and molecular alterations that lead to progressive liver damage are only partially understood. Furthermore, there are currently no FDA-approved therapies that block, or reverse ALD progression. Thus, it is urgent that we identify cellular and molecular mechanisms that contribute to progressive liver damage, to improve disease prognosis, and identify new treatment targets and procedures that alleviate or even prevent ALD. Heavy alcohol consumption affects all tissues, but it causes the greatest damage to the liver. This is because alcohol (ethanol or EtOH) is primarily metabolized in the liver to generate toxic products (acetaldehyde, superoxide, and hydroxyl radicals) that, with continued drinking, damage and impair the structure and function of membrane-bound organelles, including the ER, mitochondrion, and the lysosome. The latter organelle degrades nearly all macromolecules in eukaryotic cells. Our objective is to identify specific alterations induced by EtOH metabolite(s) that cause lysosome damage in hepatocytes and Kupffer cells (resident liver macrophages), and which leads to parenchymal cell death and inflammatory signaling, respectively. Lysosomes have a crucial role in cellular quality control, as they recycle obsolete proteins and dysfunctional organelles, including damaged lysosomes. If cells do not repair/remove damaged lysosomes, they will continue to leak their proteolytic enzymes to trigger cell death and provoke inflammatory signaling by Kupffer cells. We and others previously reported that chronic ethanol (EtOH) consumption causes faulty lysosome biogenesis and lysosomal membrane instability. Here, we show exciting new pilot data indicating that chronic EtOH consumption by both humans and rodents causes lysosomal membrane damage and subsequent leakage of lysosomal cathepsin(s) (and other hydrolases) that contribute to liver cell injury. Furthermore, such damage releases lysosomal membrane components into the circulation, which may be prognostic markers of liver injury. Our pilot data, presented herein, suggest that primary and/or secondary EtOH metabolites damage lysosomes in hepatocytes and Kupffer cells, inducing cathepsin leakage which contribute to cell death and inflammation. These novel observations support our hypothesis that chronic EtOH oxidation damages lysosomes, causing leakage of cytotoxic lysosomal hydrolases, thereby, contributing to liver injury and inflammation. To test our hypothesis, we propose the following Specific Aims: In Aim 1 we will define the mechanisms of EtOH-induced lysosome damage that incite hepatocyte injury. In Aim 2 we will investigate the mechanisms of EtOH-induced lysosome damage that incite inflammatory signaling in Kupffer cells. We anticipate that the outcome of this research will reveal novel mechanisms by which EtOH oxidation promotes the progression of liver pathology by damaging lysosomes.