ABSTRACT
Objective:To investigate the protective effect of glycyrrhizic acid (GA) from tumor necrosis factor-α+actinomycetes ketone （TNF-α+CHX） induced apoptosis in rat small intestine crypt epithelial cell line (IEC-6) via AU rich element mRNA binding protein HuR mediated posttranscription of p21 and the potential mechanism. Method:The cultured IEC-6 cells were observed. The experiment was divided into blank group, GA (60 μmol·L-1) group, TNF-α+CHX group and GA+TNF-α+CHX group. Cytoplasmic and nuclear HuR were measured by Western blot. The interaction of HuR and p21 mRNA was detected by biotin pull down and RNA IP. Luciferase activity was measured after transfection with construct with p21 3'-UTR cloned into downstream of luciferase reporter. Cell apoptosis was detected by real-time dynamic cell analyzer, p21 and cysteine proteinas-3 precursor protein（proCaspase-3） association was analysised by CO-IP. Result:After GA treatment for 48 h, cytoplasmic HuR protein expression increased（P<0.05）,the binding between HuR and p21 mRNA expression up regulated(P<0.05), luciferase activity increased(P<0.01), and p21 mRNA and protein expression also increased(P<0.05), while these results were abolished by HuR silencing with siRNA. GA enhanced p21 and procaspase3 interaction(P<0.05), and attenuated TNF-α+CHX induced apoptosis in IEC-6 cells. Conclusion:GA protected IEC-6 cells from TNF-α/CHX induced apoptosis via HuR mediated p21 posttranscription, which due to GA enhanced HuR binding to endogenous and recombinant p21 mRNA and increased p21 interaction with proCaspase3.