Imbalance between oxidants and antioxidants in the lungs of HIV-seropositive individuals.

Following the initial infection with HIV, there is evidence of immune dysfunction despite an apparent normal clinical state. In the context that the lung is a major site affected by opportunistic infection, and that some components of the immune system are activated during early HIV infection, we hypothesized that there may be activation of alveolar macrophages (AM), a key component of the pulmonary host defense system. Compared to cells from normal individuals, AM of asymptomatic HIV-seropositive (HIV+) individuals (CDC-stage II) spontaneously released significantly more superoxide anion (O2-.) (P < 0.002). The O2-. release by AM of HIV-infected individuals was comparable to the spontaneous O2-.-release by AM of cigarette smokers (P > 0.6), a condition often associated with chronic damage of respiratory tissues. The destructive effects of oxidants are normally suppressed by antioxidant defense systems. Evaluation of the concentrations of glutathione, a major component of the pulmonary antioxidant protective screen, demonstrated that the HIV+ state is also characterized by a significant glutathione deficiency in lung epithelial lining fluid (P < 0.001) and in venous plasma (P < 0.001). This suggests that the alveolar structures of HIV+ individuals are continuously exposed to increased amounts of toxic oxygen radicals without adequate protection, i.e. the reactive oxygen metabolites may cause sufficient tissue damage culminating in interstitial lung disease. Further, since many immune functions are susceptible to injury by extracellular oxidants, the consequences of an unsuppressed oxidant burden in the lung may amplify the extent of local immunocompromise. In addition, since glutathione plays an important role in modulating lymphocyte activation and effector functions independent of its antioxidant activity, the systemic glutathione deficiency may contribute to the progressive global immune dysfunction that characterizes HIV infection.