Effect of the nitric oxide inhibitor, L-N-G-monomethylarginine, on accumulation of interleukin-6 and interleukin-8, and nuclear factor-kappa B activity in a human endothelial cell line

Objective: To determine the effect of the nitric oxide synthase inhibitor, L-N-G-monomethylarginine, on interleukin-6 and interleukin-8 accumulation, and nuclear factor-kappa B expression in an endothelial cell model of sepsi s. Design: Controlled cell culture experiments examining the immunomodulatory effects of nitric oxide synthase inhibition. Subjects: A human endothelial cell line (EA.hy926). Measurements and Results: Cells were incubated with tumor necrosis factor-a lpha and interleukin (IL)-1 beta in the presence of L-N-G-monomethylarginin e (L-NMMA). IL-6 and IL-8 were measured in culture supernatants using enzym e immunoassay. Nuclear factor-kappa B was measured using electrophoretic mo bility shift assay and was quantified using phosphorimaging. IL-6 accumulat ion was decreased (p < .05) and IL-8 accumulation increased (p < .01) with L-NMMA. Increased nuclear factor-kappa B expression in stimulated cells was unaltered on exposure to L-NMMA. Cell viability was unaffected. Conclusions: Excessive production of nitric oxide has been implicated in se ptic shock, and the use of nitric oxide synthase inhibitors has been sugges ted. The immunoregulatory actions of nitric oxide synthase inhibitors affec ts the profile of cytokine release. This effect is not mediated through mod ulation of nuclear factor-kappa B. These findings have implications for the use of nitric oxide synthase inhibiting agents in septic shock.