Role of mitogen-activated protein kinases in the iNOS production and cytokine secretion by Salmonella enterica serovar Typhimurium porins.

The expression of inducible nitric oxide synthase (iNOS) is a critical factor in both physiological and pathological functions. The present study examined the role of mitogen-activated protein kinases (MAPKs) in the regulation of iNOS and proinflammatory cytokine production in RAW 264.7 cells in response to Salmonella enterica serovar Typhimurium porins. By use of Western blotting for iNOS detection and enzyme-linked immunosorbent assay (ELISA) for quantization of cytokine secretion, selective pharmacological inhibitors of MAPK pathways were tested for dissecting the molecular mechanisms underlying the mediation of these signaling in porins-stimulated murine macrophages. S. enterica serovar Typhimurium porins activated iNOS expression, NO production and interleukin (IL)-6, IL-8 and tumor necrosis factor-alpha (TNF-alpha) release. Treatment of cells with SB203580 and SP600125 (inhibitors of p38 and JNK, respectively) significantly affected porin-stimulated iNOS and NO production. Concomitant decrease in the proinflammatory cytokine secretion was detected. These data confirm the importance of the MAPKs cascade in macrophage activation by bacterial product opening up new strategies for therapy of septic shock.