Cultured AIDS‐related kaposi's sarcoma (AIDS‐KS) cells demonstrate impaired bioenergetic adaptation to oxidant challenge: Implication for oxidant stress in AIDS‐KS pathogenesis

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Abstract
Despite its recognition as the most prevalent HIV associated cancer, speculation still abounds regarding the pathogenesis of AIDS-related Kaposi's sarcoma (AIDS-KS). However, it has been established that both cytokines, e.g. IL-6, and HIV-associated products, e.g., Tat, are integral in AIDS-KS cellular proliferation. Further, both experimental and clinical evidence is accumulating to link reactive oxygen intermediates (ROI) with both cytokine induction (primarily via nuclear factor-κB [NF-κB] dependent routes) as well as the subsequent cytokine, tumor necrosis factor α (TNFα) stimulation of HIV replication. Features of AIDS-KS patients, such as retention of phagocytes, presence of sustained immunostimulation, and a frequent history of KS lesions arising at traumatized sites, make oxidant stress a viable clinical factor in AIDS-KS development. Time course nucleotide profile analyses show that AIDS-KS cells have an inherent, statistically significant, biochemical deficit, even prior to oxidant stress, due to (1) a more glycolytic bioenergetic profile, resulting in lower levels of high energy phosphates (impairing capacity for glutathione [GSH] synthesis and DNA repair); (2) lower levels of NADPH (compromising the activities of GSSG reductase and peroxidase function of catalase); and (3) reduced levels of GSH (impeding both GSH peroxidase and GSH-S-transferases). Following exposure to physiologically relevant levels of H2O2 only the human microvascular endothelial cells (a putative AIDS-KS progenitor cell) responded with bioenergetic adaptations that reflected co-ordination of energy generating and cytoprotective pathways, e.g., retention of the cellular energy charge, increased NAD+, and an accentuation of the ATP, NADPH, and total adenine nucleotide differences relative to AIDS-KS cells. Also, some of the AIDS-KS strains retained intracellular GSSG subsequent to oxidant challenge, inviting the formation of deleterious protein mixed disulfides. While the results of our study address some AIDS-KS issues, they also raise an etiological question, i.e., Does the inability to tolerate oxidant stress arise in conjunction with AIDS-KS neoplastic development, or is it pre-existing in the population at risk? Regardless, use of antioxidant therapy (low risk/potentially high benefit) in both the “at risk” population as well as in those individuals with active disease may prove a useful preventative and/or treatment modality.