Effect of N-nitrosodimethylamine on inducible nitric oxide synthase expression and production of nitric oxide by neutrophils and mononuclear cells: the role of JNK signalling pathway.

In neutrophils (PMN) and mononuclear cells (PBMC), one of the enzymes responsible for nitric oxide (NO) synthesis is inducible nitric oxide synthase (iNOS). Changes in iNOS expression result from various signalling pathways including the mitogen-activated protein kinase (MAPK) pathway activated by endogenic and exogenic factors. N-nitrosodimethylamine (NDMA) is a xenobiotic with widespread occurrence in human environment and has an effect on cells of the immune system. The aim of this study was to determine the effect of NDMA on iNOS expression and NO production by human PMN and PBMC cells in the light of superoxide anion production by PMN cells. Moreover, the role of JNK and p38 pathways in NO production with involvement of iNOS was studied. Additionally, the function of JNK pathway in generation of superoxide anion was determined. Moreover, nitrotyrosine expression was studied in PMN and PBMC cells in the presence of NDMA. This work shows that NDMA increases iNOS expression and NO production by PMN and PBMC cells. In addition, elevated expression of phospho-JNK and phospho-p38, which are markers of JNK and p38 MAPK pathways activation, were observed. Lower iNOS expression and NO production by neutrophils exposed to extended action of NDMA were observed after application of inhibitor of JNK and p38 pathways. Lower phospho-p38 expression in PMN stimulated by NDMA was found as a result of arresting JNK pathway, whereas, application of inhibitor of p38 pathway resulted in enhanced phospho-JNK expression in PMN and PBMC cells. Increased ability to release superoxide anion by NDMA-stimulated PMN cells was observed. This ability was reduced after the application of inhibitor of JNK pathway. In PMN and PBMC cells exposed to NDMA, an increased expression of nitrotyrosine, which is dependant on JNK and p38 pathways that are activated by this particular xenobiotic, was observed. Generally, increased induction of iNOS related to elevated production of NO by PMN and PBMC cells exposed to NDMA may result in dysfunction of regulation of immunity responses controlled by this molecule in various conditions. Increased expression of nitrotyrosine in PMN and PBMC cells exposed to NDMA may affect their functions in an auto- and/or a paracrine way. Mutual interactions of JNK and p38 MAPK during the induction of iNOS expression in cells exposed to NDMA indicate complex mechanism of induction of iNOS synthase.