ALCOHOL AND LIVER ENDOTHELIAL CELLS IN IMMUNE RESPONSES

肝内皮细胞(LECs)的主要功能是通过其所谓的清道夫功能来识别、内化和降解各种细胞外基质成分和修饰蛋白，从而实现宿主防御和动态平衡。来自实验室外的报道表明，对照组大鼠的晶状体上皮细胞能够与最近表征的丙二醛-乙醛(MAA)加合物结合并降解。长期饮用乙醇可使乙醇喂养或对照组大鼠晶状体上皮细胞的降解减少50%-60%。也有研究表明，可溶性MSS加合物可使LECs上调黏附分子(ICAM-1、VCAM-1)的表达，并增加多种细胞因子/趋化因子(TNF-α、MCP-1和MIP-2)的分泌。因此，这些数据强烈地表明，存在一个受体家族，即清道夫受体，它们似乎介导了晶状体上皮细胞对MAA修饰蛋白的许多生物学功能。在正常情况下，MAA修饰的蛋白质似乎与晶状体上皮细胞上的清道夫受体结合，并被降解。然而，在长期摄入乙醇之后，这些加合物的降解率有所下降。这可能会导致MAA加合物与另一种受体(S)结合，从而在晶状体上皮细胞中启动信号级联反应，从而可能导致炎症和/或纤维化反应的刺激。因此，这些研究导致了一种假设，即随着慢性乙醇的消耗，肝细胞MAA修饰的蛋白(S)被释放到周围组织中。然而，慢性酒精暴露改变了MAA修饰的蛋白质与其受体(S)的结合，从而减少了蛋白质的降解，增加了促炎和促纤维化介质的释放。因此，本研究项目的主要目标是定义和表征晶状体上皮细胞上负责MAA修饰蛋白结合的受体(S)。最初，MAA修饰的蛋白质与LECs结合的功能后果将通过检测MAA加合物对黏附分子表达、趋化因子/细胞因子的分泌和纤维连接蛋白的释放的影响来解决。然后将使用清道夫受体的各种配体、抗体和化学抑制剂来研究这个/这些受体(S)的特异性。此外，两个调节炎性反应基因表达的因子(AP-1)将作为MAA加合物诱导效应的中介进行研究。最后，我们将评估MAA加合物在肝脏毒性中的作用，在已知的动物模型中，MAA加合物的形成是通过长期摄入乙醇和给予诱导脂质过氧化的药物来实现的。

The major function of liver endothelial cells (LECs) is in host defense and homeostasis via their so-called "scavenger" function whereby they recognize, internalize an degrade a variety of extracellular matrix components and modified proteins. Reports from out laboratory have shown that LECs from control rats are capable of binding to and degrading the recently characterized malondialdyhyde-acetaldehyde (MAA) adduct, chronic ethanol consumption results in a 50-60 percent decrease in degradation of this ligand to LECs frm either ethanol-fed or control rates were observed. It has also been shown that soluble MSS-adducts cause LECs to upregulate the expression of adhesion molecules (ICAM-1, VCAM-1), and increase the secretion of various cytokines/chemokines (TNF-alpha, MCP-1 and MIP-2). Thus these data stronglyu suggest that there are a family of receptors, designated scavenger receptors, which appear to mediate many of the biological functions of LECs in response to MAA-modified proteins. Under normal conditions, MAA-modified proteins appear to bind to scavenger receptors on LECs and are degraded. However, following chronic ethanol consumption, there is a decrease in the degradation of these adducts. This may cause th MAA-adducts to bind to another receptor(s), thereby initiating a signal cascade in LECs that may result in the stimulation of inflammatory and/or fibrotic responses. Therefore, these studies have led to the hypothesis that following chroni ethanl consumption, hepatocyte MAA- modified protein(s) are released into the surrounding tissues. However, chronic alochol exposure alters the binding of MAA-modified proteins to its receptor(s) such that there is a decrease in protein degradation and an increased in the release of pro-inflammatory and pro-fibrotic mediators. Therefore, the principal objective of this research project is to define and characterize the receptor(s) on LECs responsible for the binding of MAA- modified proteins. Initially, the functional consequences of binding of MAA-modified proteins to LECs will be addressed by examining the effects of MAA-adducts on the expression of adhesion molecules, the secretion of the chemokines/cytokines and the release of fibronectin. The specificity of this/these receptor(s) will then be investigated using various ligands, antibodies and chemical inhibitors for scavenger receptor. Additionally, two factors regulating the expression of genes in inflammatory (AP-1) will be examined as mediators of MAA-adduct induced effects. Finally, we will evaluate the role of MAA-adducts in hepatotoxicity in animal models known to perpetuate MAA- adducts formation by way of chronic ethanol ingestion and administration of agents that induce lipid peroxidation.