Glutamine inhibits interleukin-1beta induced nitric oxide production and inducible nitric oxide synthase expression: experiment with cultured rat hepatocytes

Abstract

To investigate the influences of glutamine (Gln) on nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression in hepatocytes activated by interleukin (IL)-1beta, a pro-inflammatory cytokine. Primary hepatocytes were isolated from SD rats by in situ collagenase perfusion, and cultured with normal saline (NS), IL-1beta (1 nmol/L) alone, IL-1beta (1 nmol/L) with Gln of 2, 5, or 10 mmol/L for 24 hours. The concentration of NO in the supernatant was detected by biochemical method. Western blotting and real-time quantitative reverse transcription PCR (RT-PCR) were used to detect the protein and mRNA expression of iNOS in the hepatocytes. The binding activity nuclear factor kappa B (NF-kappaB) in hepatocytes cellular localization of nuclear factor kappa B (NF-kappaB) in the nuclei of hepatocytes was investigated using electrophoretic mobility shift assay (EMSA). The average NO concentration of the IL-1beta group was 72.7 micromol/L, significantly higher than that of the NS group [(41.7) micromol/L, P < 0.01]. The NO concentrations in the supernatant of the IL-1beta + Gln 5 and 10 mmol/L groups were 52.9 and 44.4 micromol/L respectively, both significantly higher than that of the NS group (both P < 0.05). The iNOS mRNA and protein expression levels of the IL-1beta group were 11 and 2.5 times as those of the NS group (both P < 0.05). Gln dose-dependently decreased the iNOS mRNA and protein expression levels in the hepatocytes. The NO concentration and levels of iNOS mRNA and protein expression in the hepatocytes of the Gln 10 mmol/L group were not significantly different from those of the NS group. The NF-kappaB levels in the nuclei of hepatocytes of the IL-1beta group, 3 IL-1beta + Gln group, and only Gln group were all higher than that of the NS group. Glutamine down-regulates the iNOS gene over-expression mediated by IL-1betain hepatocytes through an NF-kappaB independent pathway.