This proposal is based on the overall hypothesis that alcohol modulates the hepatic immune system at the plasma membrane and molecular levels by altering cell surface receptor expression (binding sites for HIV-1) and production of soluble mediators (chemokines) in hepatic non-parenchymal cells [NPC], i.e., Kupffer cells and sinusoidal endothelial cells. Specifically, acute or chronic alcohol regulates the expression of CD4, chemokine receptors and mannose-specific receptors on hepatic NPC as a result of ethanol-induced alteration in plasma membranes on hepatic NPC. This event could also lead to enhanced intracellular production of H2O2 which in turn activates NF-kappaB. The nuclear translocation and activation of NF-kappaB, a transcription factor, enhances the expression of m-RNA and synthesis of alpha and beta-chemokines. These chemokines could potentially block the binding of HIV-1 or exacerbate its replication in CD4 lymphocytes. The HIV-1 gp120-induced production of beta-chemokines by hepatic NPC may also be modulated by alcohol. The liver is the major organ for microbial clearance and ethanol metabolism. Thus, hepatic cells become susceptible to these agents that could have an impact on the liver itself as well as on the overall homeostasis of the host. For example increased production of pro-inflammatory mediators by hepatic NPC which are the largest contributors of these agents, may also regulate functions of immunocompetent cells in other organs. Thus, based on these considerations, the following specific aims are proposed.
Specific aim 1 : To determine the effect of acute or chronic alcohol intoxication of hiv-1 GP120 binding, expression of mannose-specific receptors and CD4 on hepatic NPC. The internalization and degradation of HIV-1 gp120 by hepatic NPC will be examined.
Specific aim 2 : To determine the effect of acute or chronic alcohol intoxication on the intracellular production of H2O2, activation of NF-kappaB, m-RNA expression and secretion of alpha (CINC or IL-8) and beta (Rantes, MIP-1 alpha, MIP-1beta, MCP-1) chemokines in hepatic NPC. The biological activity of HIV-1 gp120 on beta-chemokine production will be assessed, as well as the role of endogenous and exogenous endotoxin on the above parameters (specific aims 1&2). The latter objective will test the hypothesis that chronic alcohol-mediated influx of LPS from the gut to the circulation is responsible, at least in part, for the regulation of hepatic NPC functions at the plasma membrane and molecular levels.
Specific aim 3 : To determine the effect of chronic alcohol intoxication on hepatic NPC functions, i.e., superoxide anion production, phagocytosis, chemokine and cytokine production, chemokine receptor (CXCR4 & CCR5) expression and SIV gp120 binding. This study will also examine chemokine-mediated SIV-1 replication in a simian model of SIV-1/AIDS. The overall regulation of the above processes by alcohol may further comprise susceptible individuals to HIV-1 infections and opportunistic pathogens associated with this viral infection.
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