Effects of chronic alcohol feeding and murine AIDS virus infection on liver antioxidant defense systems in mice

Alcohol and HIV: Experimental and Clinical Evidence of Combined Impact on the Lung

Despite antiretroviral therapy, lung disease is a leading cause of death in individuals infected with human immunodeficiency virus type 1 (HIV). Individuals infected with HIV are susceptible to serious bacterial and viral infections, such as pneumococcus and influenza, which are particularly problematic for lung health, resulting in lung injury. Additionally, HIV-infected individuals are susceptible to a number of pulmonary diseases for unknown reasons. Alcohol, the most commonly abused drug in the world, continues to exact an enormous toll on morbidity and mortality in individuals living with HIV. Chronic alcohol abuse has been shown to affect lung immunity, resulting in significant lung injury. There is a paucity of literature on the additive effects of HIV and alcohol, two diseases of immune senescence, in the lung. This chapter begins by discussing the latest literature evaluating the epidemiology of HIV, alcohol use, and lung health focusing on two prevalent infections, tuberculosis and pneumococcal pneumonia. In parallel, we discuss the interactions of alcohol and HIV on the risk for acute lung injury and subsequent morbidity and mortality. We then discuss the pathophysiology of how these two diseases of immune dysfunction affect the lung, with a focus on the oxidative stress, alveolar macrophage host immune capacity, and immunomodulatory role of zinc in the airway. Finally, we review the latest literature on how HIV and alcohol affect other pulmonary disorders including chronic obstructive pulmonary disease, pulmonary hypertension, and lung cancer.

Chronic alcohol ingestion exacerbates skeletal muscle myopathy in HIV-1 transgenic rats

Background

Separately, chronic alcohol ingestion and HIV-1 infection are associated with severe skeletal muscle derangements, including atrophy and wasting, weakness, and fatigue. One prospective cohort study reported that 41% of HIV-infected patients met the criteria for alcoholism, however; few reports exist on the co-morbid effects of these two disease processes on skeletal muscle homeostasis. Thus, we analyzed the atrophic effects of chronic alcohol ingestion in HIV-1 transgenic rats and identified alterations to several catabolic and anabolic factors.

Findings

Relative plantaris mass, total protein content, and fiber cross-sectional area were reduced in each experimental group compared to healthy, control-fed rats. Alcohol abuse further reduced plantaris fiber area in HIV-1 transgenic rats. Consistent with previous reports, gene levels of myostatin and its receptor activin IIB were not increased in HIV-1 transgenic rat muscle. However, myostatin and activin IIB were induced in healthy and HIV-1 transgenic rats fed alcohol for 12 weeks. Catabolic signaling factors such as TGFβ₁, TNFα, and phospho-p38/total-p38 were increased in all groups compared to controls. There was no effect on IL-6, leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), or ciliary neurotrophic factor (CNTF) in control-fed, transgenic rats. However, the co-morbidity of chronic alcohol abuse and HIV-1-related protein expression decreased expression of the two anabolic factors, CT-1 and CNTF.

Conclusions

Consistent with previous reports, alcohol abuse accentuated skeletal muscle atrophy in an animal model of HIV/AIDS. While some catabolic pathways known to drive alcoholic or HIV-1-associated myopathies were also elevated in this co-morbid model (e.g., TGFβ₁), consistent expression patterns were not apparent. Thus, specific alterations to signaling mechanisms such as the induction of the myostatin/activin IIB system or reductions in growth factor signaling via CT-1- and CNTF-dependent mechanisms may play larger roles in the regulation of muscle mass in alcoholic, HIV-1 models.

Ethanol blocks leukocyte recruitment and endothelial cell activation in vivo and in vitro

Immune system impairment and increased susceptibility to infection among alcohol abusers is a significant but not well-understood problem. We hypothesized that acute ethanol administration would inhibit leukocyte recruitment and endothelial cell activation during inflammation and infection. Using LPS and carrageenan air pouch models in mice, we found that physiological concentrations of ethanol (1-5 g/kg) significantly blocked leukocyte recruitment (50-90%). Because endothelial cell activation and immune cell-endothelial cell interactions are critical regulators of leukocyte recruitment, we analyzed the effect of acute ethanol exposure on endothelial cell activation in vivo using the localized Shwartzman reaction model. In this model, ethanol markedly suppressed leukocyte accumulation and endothelial cell adhesion molecule expression in a dose-dependent manner. Finally, we examined the direct effects of ethanol on endothelial cell activation and leukocyte-endothelial cell interactions in vitro. Ethanol, at concentrations within the range found in human blood after acute exposure and below the levels that induce cytotoxicity (0.1-0.5%), did not induce endothelial cell activation, but significantly inhibited TNF-mediated endothelial cell activation, as measured by adhesion molecule (E-selectin, ICAM-1, VCAM-1) expression and chemokine (IL-8, MCP-1, RANTES) production and leukocyte adhesion in vitro. Studies exploring the potential mechanism by which ethanol suppresses endothelial cell activation revealed that ethanol blocked NF-kappaB nuclear entry in an IkappaBalpha-dependent manner. These findings support the hypothesis that acute ethanol overexposure may increase the risk of infection and inhibit the host inflammatory response, in part, by blocking endothelial cell activation and subsequent immune cell-endothelial cell interactions required for efficient immune cell recruitment.

The keys of oxidative stress in acquired immune deficiency syndrome apoptosis

Apoptosis is the main cause of CD4+ T-lymphocyte depletion in acquired immune deficiency syndrome (AIDS). Various agents appear to be able to trigger apoptosis in CD4+ T cells, including viral proteins (i.e. gp120, Tat), inappropriate secretion of inflammatory cytokines by activated macrophages (i.e. tumor necrosis factor alpha) and toxins produced by opportunistic micro-organisms. Since oxidative stress can also induce apoptosis, it can be hypothesized that such a mechanism could participate in CD4+ T-cell apoptosis observed in AIDS. This correlates strongly with the observation that AIDS patients present low levels of antioxidants (i.e. superoxide dismutase-Mn, vitamin E, selenium and glutathion) most likely due to inappropriate nutrition (i.e. diets poor in antioxidants), alcohol and drug consumption, and digestive problems associated with the disease. Furthermore, the coadministration of the antiviral drug zidovudine with antioxidants increases its therapeutic potential. Finally, the following additional observations support the hypothesis that oxidative stress is involved in cell apoptosis in AIDS: (1) The depletion of the anti-apoptotic/antioxidant protein Bcl-2 in human immunodeficiency virus (HIV)-infected CD4+ cells; (2) a decrease of apoptosis in HIV-infected cells treated with antioxidants and; (3) the presence of the pro-apoptotic/pro-oxidant cytokines secreted by activated macrophages in AIDS patients. Therefore, anti-apoptotic/antioxidant strategies should be considered, alongside antiviral strategies, in order to design a more efficient therapy for AIDS in the near future.

Liver antioxidant defenses in mice fed ethanol and the AIN-76A diet

The effects of chronic alcohol (EtOH) ingestion on antioxidant defenses in mice fed AIN-76A liquid diets were investigated. C57Bl/6 female mice were divided into three groups and fed the AIN-76A liquid EtOH diet containing EtOH to provide 31% of total caloric intake (TCI), the same basic diet containing EtOH to provide 35% of TCI, or an isocaloric AIN-76A liquid control diet. After 3 weeks, the mice were killed and livers were excised for biochemical analysis. Liver reduced glutathione (GSH) levels, and activities of both Mn-superoxide dismutase (SOD) and Cu/Zn-SOD were significantly decreased by both levels of EtOH. Activities of catalase and glutathione transferase (GT) were significantly increased, whereas glutathione peroxidase (GP) activity was not affected by either level of EtOH. Our previous study using the Lieber-DeCarli liquid EtOH diet caused a decline of total SOD and GP activities. The results suggest that chronic EtOH administration decreases liver antioxidant defenses; however, the mice fed the AIN-76A EtOH liquid diet can maintain a higher antioxidant defense capability than those fed Lieber-DeCarli EtOH liquid diet.

Ethanol as a possible cofactor in the development of murine AIDS

Chronic ethanol (EtOH) abuse in humans leads to a variety of immunomodulatory events that can alter resistance to a number of infectious agents. Whether alcohol abuse affects the susceptibility to human immunodeficiency virus infection or the subsequent development of acquired immune deficiency syndrome (AIDS) is a matter of extreme importance; however, available information in humans or animal models is limited. The goal of this study was to evaluate the effect of chronic EtOH feeding in mice on the development of immunodeficiency in the murine model of AIDS (MAIDS). C57BI/6 mice were placed on the Lieber-DeCarli liquid EtOH diet (25% or 31% total caloric intake) or a nutrient-matched isocaloric liquid control diet. Seven days later, mice were infected with the LP-BM5 murine leukemia virus mixture, and groups of infected and noninfected mice were assayed at defined time points postinfection for antigen-specific and nonspecific immune responses. In the absence of retroviral infection, chronic EtOH feeding (5-8 weeks) led to reductions in spleen weights, compared with isocaloric controls. In spite of reduced spleen size, mitogenic responses of spleen cells to concanavalin A (ConA) and lipopolysaccharide (LPS) were elevated in EtOH-fed mice, as compared with mice fed the control diet. Chronic EtOH feeding also enhanced the allogeneic mixed lymphocyte response and increased antigen-specific priming of both B-cells and CD4+ T-cells to the antigen, sheep red blood cells. In MAIDS-infected mice, chronic EtOH feeding delayed but did not prevent the onset of virus-induced immunodeficiency and MAIDS-induced autoantibody synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)