Among injection drug users (IDUs), human immunodeficiency virus (HIV) and hepatitis C virus (HCV) are the two blood-borne pathogens most commonly transmitted. About 25% of HIV infected persons in the United States are also infected with Hepatitis C virus (HCV) while the incidence of HCV infection among persons who acquired HIV from injection drug use approaches 90%. Although the role of HCV in progression of HIV disease remains unclear, co-infection with HIV infection has been associated with accelerated progression of chronic hepatitis C towards cirrhosis and end stage liver disease. The mechanisms responsible for more rapid progression of hepatic disease and increased HCV viremia in individuals co-infected with HIV-1 are not fully understood. Viral infection rapidly triggers intracellular signaling events, leading to an innate cellular antiviral state, and damage to the innate immunity may generate a favorable microenvironment for persistent viral infection. Most liver damage associated with HCV infection is mediated by innate and acquired immune responses. Morphine, the major metabolite of heroin, is the most common opiate drug and preferentially activates <-opioid receptors (MOR). Chronic morphine use and abuse has been shown to impair host innate immune responses, including the production of chemokines and pro-inflammatory cytokines, phagocytosis, and neutrophil migration, which can lead to increased susceptibility to bacterial and viral infections. Morphine, through down- regulation of IFN-1 mediated innate immunity, favors HCV replication in hepatic cells. Chemokines and pro- inflammatory cytokines are important mediators of the immune response and the inflammatory process. More specifically, the pro-inflammatory cytokine, tumor necrosis factor-1 (TNF-1) plays an integral role in hepatocyte injury and cell death in a number of pathophysiological states such as liver injury from toxins, ischemia/ reperfusion, and hepatitis virus. In addition, morphine-induced oxidative damage has been hypothesized to contribute too many of the systemic manifestations of liver disease and hepatotoxicity experimentally shown in mice and in heroin abusers. Activation of MOR can trigger increased production of reactive oxygen species (ROS) and apoptosis. Using a recently established in vitro HCV infection system, we will test the hypothesis that opioids contributes to HCV disease progression by disrupting the response of hepatocytes to HCV and HIV through 1) increase production of cytokines and chemokines and 2) induction of reactive oxidative species(ROS) and nitric oxide (NO).
Studies in this proposal will focus on assaying the extent by which opioids and HIV enhances the susceptibility of HCV infection in human hepatocytes in particular, to proinflammatory cytokine tumor necrosis factor-alpha (TNF-1) and we will investigate the mechanisms by which opiates and HIV affect viral replication and toxicity in HCV infected hepatocytes.
