Ethanol Effects on Antigen Presentation in Liver Cells

描述(申请人提供)：建议的R21研究的主要目标是研究乙醇和乙醇代谢对乙醇代谢肝细胞系中主要组织相容性复合体(MHC)L限制的抗原肽递呈的影响。在干扰素γ(IFNy)激活后，这些多肽被主要的抗原修剪酶、蛋白酶体和亮氨酸氨基肽酶切割。我们以前的研究表明，乙醇抑制乙醇代谢的HepG2细胞中的蛋白酶体活性，并且这些经乙醇处理的细胞不能正确地转导IFNy信号。我们假设，在肝细胞中，乙醇代谢阻断了IFNy介导的信号转导。这会损害IFNy调节的免疫蛋白酶体和亮氨酸氨基肽酶的诱导，损害它们产生抗原呈递的多肽的能力，并可能改变免疫反应。因此，我们提出以下特异性目标：特异性目的1：研究乙醇或其代谢是否影响干扰素诱导小鼠重组肝癌细胞和表达酒精脱氢酶和细胞色素P4502E1的人重组肝癌细胞中MHC类L限制性抗原呈递的多肽的裂解。特异性目的2：通过检测乙醇对小鼠重组HepB6细胞和人重组HepG2细胞中JAK-STAT1信号转导通路特定成分的影响，确定乙醇暴露是否影响IFNy介导的信号转导。特异性目的3：利用小鼠重组肝癌细胞内卵清蛋白裂解和卵清蛋白多肽SIINFEKL-H-2kb复合体递呈的模型，确定乙醇或其代谢是否影响肝细胞呈递MHC类L限制性抗原。这项研究的结果将阐明酒精对肝细胞抗原提呈的影响、免疫反应的改变以及与酒精相关的病毒性肝炎进展的可能机制之间的联系。

DESCRIPTION (provided by applicant): The major objective of the proposed R21 investigation is to examine the influence of ethanol and ethanol metabolism on major histocompatibility complex (MHC) class l-restricted presentation of antigenic peptides in ethanol-metabolizing liver cell lines. After activation with interferon gamma (IFNy), these peptides are cleaved by major antigen-trimming enzymes, the proteasome and leucine amino peptidase. Our previous investigations have indicated that ethanol suppresses proteasome activity in ethanol-metabolizing HepG2 cells, and that these ethanol-treated cells do not properly transduce the IFNy signal. We hypothesize that in liver cells, ethanol metabolism blocks IFNy-mediated signal transduction. This impairs IFNy-regulated induction of the immunoproteasome and of leucine amino peptidase, compromising their ability to generate peptides for antigen presentation and may alter immune response. We therefore propose the following Specific Aims: SPECIFIC AIM 1: To investigate whether ethanol or its metabolism affects the IFNy-induced cleavage of peptides for MHC class l-restricted antigen presentation in mouse recombinant HepB6 cells and in human recombinant HepG2 cells that express alcohol dehydrogenase and cytochrome P4502E1. SPECIFIC AIM 2: To determine whether ethanol exposure affects IFNy-mediated signal transduction by examining ethanol-elicited alterations in specific components of the JAK-STAT1 signal transduction pathway in mouse recombinant HepB6 cells and in human recombinant HepG2 cells. SPECIFIC AIM 3: To determine whether ethanol or its metabolism affects MHC class l-restricted antigen presentation by liver cells, using a model of the intracellular cleavage of ovalbumin (OVA) and the presentation of OVA peptide SIINFEKL-H-2Kb complex on the surface of mouse recombinant HepB6 cells. The results derived from this study will clarify the link between the effects of ethanol on antigen presentation by liver cells, altered immune response and the possible mechanisms of alcohol-related progression of viral hepatitis.