9-NITROCAMPTOTHECIN INHIBITS TUMOR NECROSIS FACTOR-MEDIATED ACTIVATION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 AND ENHANCES APOPTOSIS IN A LATENTLY INFECTED T-CELL CLONE

Transition from latency to active replication is a crucial stage for t he process of human immunodeficiency virus type 1 (HIV-1) infection an d life cycle, HIV-1 replication in latently infected cells can be stro ngly induced by the cytokine tumor necrosis factor alpha (TNF-alpha) a nd the proliferation-arresting chemical sodium butyrate (NaB). We have investigated the ability of the drug 9-nitrocamptothecin (9NC), a pot ent cellular topoisomerase (topo I) inhibitor currently in clinical tr ials in cancer patients, to regulate HIV-1 replication in latently inf ected lymphocytic ACH-2 cells on reactivation with either TNF-alpha or NaB, Treatment of ACH-2 cells with 9NC alone resulted in increased le vels of viral transcripts, while there was a slight reduction or no ch ange in the levels of host cell transcripts. However, pretreatment of ACH-2 cells with 9NC inhibited TNF-alpha-induced extracellular HIV-1 p 24 levels up to similar to 95% and nearly 80% of the cell-associated v iral RNAs, The quantitative decrease in viral products was concomitant with a decrease in cellular gene expression and induction of apoptosi s in the host cells, 9NC blocked the infected cells at the boundary of the S and G2 phases, resulting in an accelerated apoptosis that was f urther enhanced with TNF-alpha treatment, Similar results were observe d following concurrent exposure Ito TNF-alpha and 9NC, but 9NC failed to inhibit upregulation of HIV-1 mRNA in ACH-2 cells exposed to TNF-al pha before 9NC treatment, Further, 9NC had no inhibitory effect on NaB -induced apoptosis and upregulation, of HIV-1 mRNA expression regardle ss of whether 9NC and NaB were used concurrently or in various treatme nt sequences, In uninfected lymphocytic CEM cells derived from a commo n parental cell line, a slight downregulation of cellular gene express ion was detected along with low-level apoptosis, These results demonst rate that 9NC impairs TNF-alpha-induced, but not NaB-induced, HIV-1 ac tivation, and suggest a means of inhibiting active HIV-1 viremia arisi ng as a result of elevated TNF-alpha levels.