IL-8 and p53 are inversely regulated through JNK, p38 and NF-κB p65 in HepG2 cells during an inflammatory response

Abstract

It is reported that Nuclear factor-kappaB (NF-kappaB) activation is dysregulated in chronic inflammatory diseases like psoriasis, rheumatoid arthritis and cancer, resulting in an over expression of pro-inflammatory cytokines and an inhibition of apoptosis. We studied NF-kappaB activation and the induction of interleukin 8 (IL-8) and p53 gene expression in an interleukin 1beta (IL-1beta) stimulated HepG2 cell line. NF-kappaB induced IL-8 and p53 protein production was studied using specific siRNA, an IkappaB kinase 2 inhibitor, and mitogen activated protein kinase (MAPK) inhibitors. Results were analyzed by different techniques including Western blotting and ELISA. IL-1beta induced both the IL-8 and p53 mRNA expression and protein production of IL-8, but not p53. Knockdown of NF-kappaB p65 expression with siRNA strongly reduced IL-8 production and significantly induced protein levels of p53. An IkappaB kinase 2 inhibitor, sc514, also strongly reduced IL-8 and significantly induced p53 protein levels. Using three MAPK inhibitors we showed that p38 MAPK and JNK dependent mechanisms are involved in the regulation of the IL-8 and p53 protein expression. Our results indicate that IL-8 and p53 protein expression is regulated through inverse activation of the p38 MAPK and the JNK pathways and the NF-kappaB p65 expression.