Decrease in IL-10 and increase in TNF-α levels in renal tissues during systemic inhibition of nitric oxide in anesthetized mice

Earlier, we demonstrated that the inhibition of nitric oxide synthase (NOS) by nitro-L-arginine methyl ester (L-NAME) infusion increases the endogenous production of proinflammatory cytokine, tumor necrosis factor (TNF-alpha). In the present study, we examined the hypothesis that inhibition of nitric oxide (NO) production leads to the suppression of interleukin (IL)-10 (anti-inflammatory cytokine) generation which facilitates the enhancement of TNF-alpha production endogenously. Using appropriate enzyme-linked immunosorbent assay kits and immunohistochemical staining, the levels of IL-10 and TNF-alpha in plasma (P) and in renal tissues (R) were measured in anesthetized mice (C57BL/6; similar to 10 weeks age; n = 6/group) infused with or without L-NAME (200 mu g/min/kg; i.v. for 2 h). Compared to vehicle-treated control mice, L-NAME-treated mice had a lower level of IL-10 ( P, 0.3 +/- 0.1 vs. 2.6 +/- 0.6 ng/mL; R, 0.5 +/- 0.1 vs. 3 +/- 0.1 ng/mg protein) and a higher level of TNF-alpha ( P, 432 +/- 82 vs. undetected pg/mL; R, 58 +/- 7 vs. 6 +/- 5 pg/mg protein). IL-10 protein expression, present mostly in the distal nephron segments in control mice, was markedly downregulated in L-NAME-treated mice. Compared to control mice, TNF-alpha expression increased 2.5-fold in renal cortical sections (mostly in the distal nephron segments) in L-NAME-treated mice. Coinfusion of a NO donor, S-nitroso-N-acetyl-penicillamine (SNAP; 25 mu g/min/kg) with L-NAME in a separate group of mice prevented these changes in IL-10 and TNF-alpha induced by L-NAME. IL-10 infusion (0.075 ng/min/g) in L-NAME-treated mice markedly attenuated L-NAME-induced increments in TNF-alpha. Thus, these results demonstrate that NOS inhibition decreases endogenous IL-10 generation and thus, minimizes its immune downregulating action on the TNF-alpha production in the kidney.