Lung diseases are major causes of morbidity and mortality in patients infected with the Human Immunodeficiency Virus (HIV). Currently antiretroviral therapy (ART) has changed HIV into a chronic disease. In the pre-ART era, pulmonary infections were very common. In patients with ART, however, pulmonary infections are less frequent and noninfectious lung disorders, such as COPD, pulmonary hypertension, lung cancer, and pulmonary fibrosis are emerging as important causes of illness. These are important cause of morbidity and mortality, yet the mechanisms responsible for these disorders in HIV patients are unknown. All pulmonary disorders mentioned above are associated with, among other things, lung inflammation and tissue remodeling characterized by alterations in matrix expression, deposition, and degradation. Interestingly, HIV infection is also associated with oxidant stress caused by oxidation of the thiol disulfide couple cysteine (Cys)/cysteine (CySS) redox potential (Eh);also termed Eh Cys/CySS. This is important because in vitro studies show that an oxidized Eh Cys/CySS stimulates lung cells to produce more fibronectin (a matrix glycoprotein implicated in tissue injury and repair), transforming growth factor b (a pro-fibrotic growth factor), and pro-inflammatory cytokines like interleukin-1b. It also stimulates the proliferation and epithelial- mesenchymal transformation of lung fibroblasts, processes implicated in tissue remodeling. These data suggest that HIV-related oxidation of Eh Cys/CySS may promote lung tissue remodeling. We have shown that one mechanism by which oxidation of Eh Cys/CySS stimulates tissue remodeling is through the activation of nicotinic acetylcholine receptors (nAChRs). This is intriguing considering that HIV-1 proteins like gp120 bind and increase the expression and signaling of nAChRs expressed in brain, and this mechanism has been implicated in HIV-related dementia. We hypothesize that patients with HIV infection have oxidation of the Eh Cys/CySS which, together with gp120, activates nAChR-mediated signaling in lung cells and leads to their expression of cellular products with pro-inflammatory and pro-fibrotic effects such as cytokines and growth factors, matrix glycoproteins, and tissue proteases. The persistent and exaggerated production of these factors activates lung tissue remodeling thereby promoting HIV-related lung disease. The type of disease developed (e.g., COPD versus pulmonary hypertension), however, is dependent on both the genetic makeup of the subject and external factors such as smoking and infection. It is important that this hypothesis be tested considering that diet and other interventions have been shown to influence Eh Cys/CySS (9). If found to be causal, Eh Cys/CySS and nAChRs can be targeted for intervention in the hope of reducing the incidence and/or severity of HIV-related non-infectious lung disease.
Lung diseases are major causes of death in patients with HIV infection. We are investigating what damages the lung in HIV infected patients compared to patients without HIV. Our ultimate goal is develop treatments to prevent lung diseases in these patients.