THE NITRIC-OXIDE DONOR SIN-1 PROTECTS ENDOTHELIAL-CELLS FROM TUMOR-NECROSIS-FACTOR-ALPHA MEDIATED CYTOTOXICITY - POSSIBLE ROLE FOR CYCLIC-GMP AND HEME OXYGENASE

In cultured endothelial cells, incubation with TNF-alpha (50 ng/ml) fo r 72 h markedly reduced viability of endothelial cells. A 6-h pre-incu bation with the nitric oxide (NO) donor linsidomine (SIN-1, 10-150 mu M) protected endothelial cells in a concentration-dependent manner and increased viability by up to 59% of control. The unmetabolized parent compound molsidomine and the NO-free metabolite of SIN-1 3-morpholino iminoacetonitrile (SIN-1C) were without cytoprotective effect. Cytopro tection by SIN-1 was completely abolished by the NO scavenger nyl-4,4, 5,5,-tetramethylimidazoline-1-oxyl-3-oxide (PTIO, 30 mu M) A cytoprote ctive effect comparable to SIN-1 was observed when preincubating the c ells with dibutyryl cyclic GMP (10-100 mu M). Moreover, no protection by SIN-1 occurred in the presence of cycloheximide (1 mu M) or 1H-[1,2 ,4] oxadiazole[4,3-a]quinoxalin-1-one (ODQ, 0.1 mu M), a selective inh ibitor of soluble guanylyl cyclase. Tin protoporphyrin-IX (SnPP, 25 mu M), an inhibitor of heme oxygenase, was found to attenuate SIN-1-indu ced cytoprotection, Our results demonstrate that SIN-1 produces a long -term endothelial protection against cellular injury by TNF-alpha, pre sumably via a cyclic GMP-dependent pathway leading to up-regulation of protective proteins such as heme oxygenase. (C) 1997 Academic Press L imited.