Effect of EGCG on Expression of Neurogenin 3 via the MAP Kinase Signaling Pathway in AR42J Cells, a Rat Pancreatic Tumor Cell Line

Epigallocatechin gallate (EGCG), or epigallocatechin 3-gallate, is the ester of epigallocatechin and gallic acid, and is a type of catechin. EGCG may be therapeutic for many disorders including diabetics and some types of cancer. However it is unknown whether EGCG can induce transdifferentiation of pancreatic cells in pancreatitis. The aim of this study was to investigate the effects of EGCG on the expression of pancreatic regenerating related markers in pancreatic AR42J cells, a model of pancreatic progenitor cells. AR42J cells, differentiated with betacellulin and activin A, were cultured with/without EGCG in a time-dependent manner. Cell growth rate, levels of mRNA, and protein expression were examined with the MTT assay, quantitative PCR, and Western blots, respectively. The results showed that AR42J cell growth rates were inhibited by EGCG in a dose-dependent manner. mRNA and protein expression of amylase, insulin and neurogenin 3 (ngn 3) increased in AR42J cells treated with EGCG. Additionally, we demonstrated that the signal transduction pathway of mitogen-activated protein (MAP) kinase is active in EGCG-treated AR42J cells. ERK and JNK phosphorylation decreased in cells treated with EGCG but not p38 phosphorylation. Activation of the p38 MAP kinase pathway was confirmed by specific MAP kinase pathways inhibitors: U0126 for ERK, SP600126 for JNK, and SB203580 for p38. Activated p38 phosphorylation was inhibited by the specific p38 inhibitor SB203580 but p38 phosphorylation was inhibited with increased EGCG treatment. The ERK and JNK MAP kinase pathways were not affected by EGCG treatment. Although further studies are needed, these results suggest that EGCG affects the induction of pancreatic cell regeneration by increasing the ngn 3 protein and mRNA expression and activating the p38 MAP kinase pathway.

Activation of MAPK/ERK and MAPK/P38 is Essential for Proinflammatory Response by Chlamydia trachomatis / 生物化学与生物物理进展

Chlamydial infection in human urogenital tract induces inflammation and causes tissue damage and scarring. It is thought that cytokine production by the Chlamydia-infected cells plays a key role in chlamydial disease processes. Although many cytokines have been detected during chlamydial infection, little is known about the molecular mechanisms on how Chlamydia triggers and sustains the inflammatory cytokine cascades. In the current study, chlamydial infection of the human cervical epithelial cell line HeLa cells can induce the production of IL-8, IL-1α, IL-1β and IL-6. Using inhibitors for probing intracellular kinase signaling pathways required for the Chlamydia-induced cytokines, it was found that the Chlamydia-activated MAPK / P38 pathway is required for the chlamydial induction of IL-1α and IL-6 while both the Chlamydia-activated MAPK/ERK and MAPK/P38 pathways contribute to the production of IL-8.