NITRIC-OXIDE INHIBITS STRESS-INDUCED ENDOTHELIAL-CELL APOPTOSIS

Objectives: To determine a mechanism by which nitric oxide alters indu ction of stress-induced endothelial cell apoptosis in vitro. Apoptosis is a form of cellular suicide that has been implicated in the pathoge nesis of multiple organ dysfunction syndrome. Design: Prospective, con trolled trial, Setting: Research laboratory of a large, academic medic al center. Subjects: Cultured primary porcine aortic endothelial cells . Interventions: Cells were treated with a range of doses of agents th at either spontaneously generate nitric oxide (S-nitroso-N-acetyl-D,L- penicillamine [SNAP] or )-N-(2-ammonioethyl)amino]diazen-1-lum-1,2-dio late [DETA-NO]) or block nitric oxide production (Nm-methyl-L-arginine [L-NMA]), The ability of these agents to alter the rate of cell death by apoptosis (induced by the sequence stimuli lipopolysaccharide [LPS ] followed by sodium arsenite) was measured. Mechanistic studies inclu ded examining the ability of: a) nitric oxide ''donors'' to alter nucl ear factor kappa B (NF-kappa B) DNA binding activity and the level of I kappa B alpha accumulation; and b) B stable cyclic guanosine monopho sphate (cGMP) analog (8-bromo-cGMP) to mimic the effect of nitric oxid e donors. Measurements and Main Results: The sequence LPS/sodium arsen ite increased the rate of endothelial cell apoptosis (47,4%, p<.05 vs, control), as measured by fluorescent-activated cell scanning using an nexin V/propidium iodide staining, DETA-NO generated nitric oxide las indicated by an increase in the concentration of the stable end-produc ts of nitric oxide metabolism) and decreased the rate of endothelial c ell apoptosis (20.6% at a dose of 2 mM, p=.0001 vs, control), DETA-NO also decreased NF-kappa B DNA binding activity and the apparent accumu lation of its endogenous inhibitor, I kappa B alpha. The 8-bromo-cGMP did not mimic the effects of nitric oxide donors (DETA-NO) on apoptosi s, Conclusions: These data suggest that exogenous nitric oxide can blo ck stress-induced endothelial cell apoptosis in vitro. The mechanistic studies are consistent with our hypothesis that inhibitors of NF-kapp a B DNA binding activity are associated with protection against apopto sis-inducing stimuli, The results do not support a role for cGMP in me diating the protective effect of DETA-NO in our model, (Crit Care Med 1998; 26:1500-1509).