Death of cultured human neuroblastoma cells induced by HIV-1 gp120 is prevented by NMDA receptor antagonists and inhibitors of nitric oxide and cyclooxygenase

The cytotoxic effects of the human immunodeficiency virus type 1 (HIV-1) coat protein gp120 were studied in human CHP100 neuroblastoma cell cultures. Incubation of neuroblastoma cultures with gp120 (1 pM-10 nM) induces cell death which is not concentration-related. The significant cell death evoked by 10 pM gp120 was prevented by neutralization of the viral protein with a monoclonal anti-gp120 (IgG) antibody. In addition, gp120-induced cytotoxicity was inhibited by [DL-(E)-2-amino-4-methyl-5-phosphono-3-pentenoic acid] (CGP37849; 100 μM), [(±)-3R∗, 4as∗, 6R∗, 8aR∗-6-(phosphonomethyl) decahydro-isoquinoline-3-carboxylic acid] (LY274614; 100 μM), MK801 (dizocilpine; 200 nM) and 7-chloro kynurenic acid (100 μM), selective antagonists of the NMDA receptor complex; by contrast, (6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 100 μM), a non-NMDA antagonist, was ineffective. Prevention of the lethality elicited by the HIV-1 coat protein was also obtained by incubating neuroblastoma cells with gp120 in Ca²⁺-free medium. The lethal effects induced by gp120 involve activation of L-arginine-nitric oxide (NO) pathway since these were prevented by haemoglobin (10 μM), a NO-trapping agent, and by D-arginine (1 mM), the less active enantiomer of the endogenous precursor of NO synthesis. Cytoprotection was also afforded by N^ω-nitro-L-arginine methyl ester (L-NAME; 200 μM), an inhibitor of NO synthase, and this was reversed by L-arginine (1 mM). Interestingly, indomethacin and flufenamic acid (10 μM), two inhibitors of cyclooxygenase, protected neuroblastoma cells from death induced by gp120. Furthermore, indomethacin prevented the neuroblastoma cell death evoked by exposure of cultures to sodium nitroprusside (SNP; 0.2–1.6 mM), a NO donor. Finally significant cytotoxic effects were observed after incubation of neuroblastoma cells with prostaglandin E₂ (0.1–10 μM). In conclusion, the present data suggest that death of human CHP100 neuroblastoma cells in culture produced by gp120 involves NO and PGE₂ production.