The mechanisms by which alcohol and HIV render the lung susceptible to injury


Principal Investigator: DAVID MARSHALL GUIDOT
Abstract: DESCRIPTION (provided by applicant): Project Abstract Chronic infection with human immunodeficiency virus type 1 (HIV-1) has emerged in the past 25 years as one of the greatest health challenges our society has ever faced. Despite the development of effective anti-retroviral regimens, the infection is at present incurable and infected individuals must battle a chronic disease that increases their risk of lung disease, heart disease, kidney failure and malignancies. Notably, pneumonia and other pulmonary complications are the most common causes of death in HIV-1-infected individuals. In parallel, alcohol abuse is a common chronic illness that likewise renders individuals susceptible to diverse complications including pneumonia and acute lung injury. Unfortunately, alcohol abuse often complicates HIV-1 infection, and this combination has devastating health consequences that are particularly damaging to vulnerable populations such as our nation's veterans. Experimental and clinical evidence reveals a potential common mechanism by which HIV-1 and alcohol damage the lung. Specifically, each causes oxidative stress and depletion of the anti-oxidant glutathione within the airways. The body's defenses against oxidative stress depend in part on the ability of cells to activate the anti-oxidant response element (ARE). Activation of the ARE is mediated by the nuclear transcription factor Nrf2, a zinc-finger protein that turns on a genetic program that stimulates the production of multiple anti-oxidants including glutathione. In experimental models, chronic alcohol ingestion inhibits Nrf2 expression and nuclear binding, decreases glutathione levels within the alveolar space by >80%, and impairs alveolar epithelial function. In parallel, chronic HIV-1 transgene expression in experimental models also decreases glutathione levels and impairs alveolar epithelial function, and treatment of lung epithelial cells with the HIV-1-related protein gp120 inhibits Nrf2 expression. These findings suggest that HIV-1 and alcohol independently block activation of the ARE by inhibiting the expression and/or actions of Nrf2. More recent experimental evidence reveals that chronic alcohol ingestion superimposed on HIV-1 transgene expression causes greater alveolar epithelial dysfunction than either stress alone. Remarkably, this common mechanism may involve zinc bioavailability within the alveolar space. Both alcohol abuse and HIV-1 infection are associated with zinc deficiency in humans, and zinc levels are significantly decreased in both the alcohol and HIV-1 experimental models. Most intriguingly, dietary zinc supplementation improves alveolar epithelial function in both alcohol-fed and HIV-1 transgenic animals, and these salutary effects are associated with increased Nrf2 nuclear binding. Taken together, these clinical and experimental findings suggest that alcohol abuse and HIV-1 infection both interfere with zinc homeostasis and activation of anti-oxidant defenses within the airway and thereby render the lung susceptible to injury. This project is designed to test the hypothesis that Nrf2 expression mediates the alcoholic and HIV-1 lung phenotypes, and that Nrf2 expression in this context is modulated by zinc bioavailability within the alveolar space. This hypothesis will be tested in model systems that employ primary rat alveolar epithelial cells and an established rat lung epithelial cell line in vitro, as well as HIV-1 transgenic rats with and without chronic alcohol ingestion in vivo. This project has important implications for our understanding of the basic mechanisms by which alcohol abuse and HIV-1 infection interact to increase the risk of serious lung injury. In parallel, this project may help us improve the health of these vulnerable individuals with relatively simple dietary supplements such as zinc, either alone or in combination with thiol anti-oxidants such as S- adenosylmethionine that can also improve glutathione homeostasis and protect against oxidative injury. Most importantly, the ultimate goal of this project is to improve the health of veterans as well as individuals in the general population who are suffering from HIV-1 infection and/or alcohol abuse. PUBLIC HEALTH RELEVANCE: Project Narrative Chronic infection with the human immunodeficiency virus type 1 (HIV-1) and alcohol abuse each take an enormous toll on the well-being of the veteran population, and in combination produce devastating health consequences for these vulnerable individuals. Although the development of effective anti-retroviral therapies has improved the prognosis for HIV-1-infected individuals, it remains an incurable chronic illness that causes great morbidity and mortality. Unfortunately, HIV-1 infection is often complicated by alcohol abuse and this is a major challenge in our goal of helping veterans live healthy lives. The lung is a common target in these veterans, and acute and chronic forms of respiratory failure are a major cause of disability and early death. At present, we know very little about how HIV-1 and alcohol damage the lung and there are no specific therapies. This research project is designed to determine how alcohol and HIV-1 interact to make the lung susceptible to injury, and to develop effective treatments that can improve the health of these vulnerable individuals.
Funding Period: 2010-10-01 - 2014-09-30
more information: NIH RePORT