Inhibition of LPS-induced NO production by taurine chloramine in macrophages is mediated though Ras-ERK-NF-kappaB.

Taurine is an abundant free amino acid in inflammatory cells that protects cells from inflammatory damages. Although the protection mechanism remains unclear, taurine chloramine (Tau-Cl) produced by the reaction between taurine and hypochlorous acid in neutrophils plays an important role. In this study, we investigated the mechanism(s) by which Tau-Cl inhibits LPS-induced NO production in macrophages. Tau-Cl inhibited LPS-induced iNOS expression and NO production in RAW 264.7 cells. LPS treatment elevated the level of active Ras-GTP, and Tau-Cl inhibited LPS-induced Ras activation. Tau-Cl also inhibited ERK1/2 activation in a dose-dependent manner in both RAW 264.7 cells and murine peritoneal macrophages, whereas it did not exert any effect on p38 MAPK activation. Furthermore, Tau-Cl inhibited NF-kappaB activation without affecting AP-1 activity. These results suggest that Tau-Cl suppresses LPS-induced NO production by inhibiting specific signaling pathways. Thus, Tau-Cl protects cells from inflammatory injury resulting from overproduction of NO in a signaling pathway-specific manner.