THIOL REDOX MODULATION OF TUMOR-NECROSIS-FACTOR-ALPHA RESPONSIVENESS IN CULTURED AIDS-RELATED KAPOSIS-SARCOMA CELLS

Both clinical and experimental evidence indicates that AIDS-related Ka posi's sarcoma (AIDS-KS) has a multifactorial pathogenesis with factor s such as HIV viral load, latent virus induction, and opportunistic in fections contributing to disease progression. However, a consistent fe ature that unites these apparently diverse putative etiologic agents i s sustained serum elevations of pro-inflammatory cytokines such as tum or necrosis factor-alpha (TNF-alpha). While virtually every cell respo nds to TNF-alpha with gene activation, the extent of TNF-alpha-mediate d cellular signaling is regulated by a delicate balance between signal activation and signal arresting events. Reactive oxygen intermediates (ROI), which are generated as a consequence of TNF-alpha membrane int eraction, are part of this TNF-alpha-initiated cellular activation cas cade. Previous studies in our laboratory have shown that AIDS-KS cells possess impaired oxygen intermediate scavenging capacities, thereby e stablishing conditions permissive for the intracellular retention of R OI. In this study, we used cellular capacity to upregulate the cytopro tective enzyme superoxide dismutase (SOD) to address the extent of cel lular response to TNF-alpha. Concurrent with the SOD analyses, nucleot ide profiles were obtained to assess cellular bioenergetic responses d uring TNF-alpha challenge. Proliferative growth levels of mitochondria l (Mn)SOD activities showed an activity spectrum ranging from lowest a ctivity in AIDS-KS cells, to intermediate levels in matched,nonlesiona l cells from the AIDS-KS donors, to highest activities in HIV-normal f ibroblasts. In contrast, following TNF-alpha challenge, the AIDS-KS an d KS donor nonlesional cells showed a 11.89-and 5.86-fold respective i ncrease in MnSOD activity, while the normal fibroblasts demonstrated a 1.35-fold decrease. Subsequent thiol redox modulation studies showed that only the normal fibroblast cultures showed a potentiation of TNF- alpha-mediated MnSOD upregulation following GSH depletion. In addition , provision of the GSH precursor, N-acetylcysteine during TNF-alpha ch allenge only diminished MnSOD activity and mitochondrial compartmental ization in the AIDS-KS cells, a finding that likely reflects the lower levels of reduced thiols in this cellular population. Our data, which show that a perturbation in their cellular thiol redox status accentu ates AIDS-KS cellular responsiveness to TNF-alpha, suggest a biochemic al rationale for the recognized TNF-alpha AIDS-KS clinical correlation . (C) 1998 Wiley-Liss Inc.