ABSTRACT
<p><b>BACKGROUND</b>Green tea is an important source of flavonoids in human diets and epidemiological data correlate green tea consumption with a reduced cancer risk. Given its complicated properties at effective concentrations, we put epigallocatechin-3-gallate (EGCG) that previously reported on its anti-proliferative activities against several cancer cell lines on our research agenda to further examine the mechanism of its chemopreventive potential.</p><p><b>METHODS</b>RNA interference (RNAi) expression vector pSilencer 3.1-H1 was used to construct recombinant nuclear factor erythroid 2 related factor 2 (Nrf2)-targeting RNAi plasmids. EGCG (5 microg/ml) was added into the culture fluid of cells before and after transfection. RT-PCR and Western blotting were used to detect the expression of uridine 5'-diphosphate-glucuronosyltransferase (UGT) 1A in cells. Forty male BALB/c mice were assigned to four groups: a normal unexposed control and three groups treated with varying doses of EGCG. Four weeks later, the mice were sacrificed, and their colon tissues were subjected to mRNA and protein expression of Nrf2 and UGT1A via RT-PCR and Western blotting analysis.</p><p><b>RESULTS</b>EGCG up-regulated the expression of Nrf2 and increased the level of UGT1A in cells. The blockade of Nrf2 activity via RNA intervention largely attenuated the induction of UGT1A expression by EGCG. In mice, the mRNA and protein levels of Nrf2 and UGT1A detected by RT-PCR and Western blotting increased (both P < 0.05 compared with the control). This increase in Nrf2 expression also had a positive correlation with an increased UGT1A expression.</p><p><b>CONCLUSIONS</b>EGCG mediated its effect in part by inducing the NRF2 signaling pathway and increasing UGT1A expression. Both in vitro and in vivo studies demonstrated the role of NRF2 and UGT1A expression in the potential use of EGCG as a possible chemopreventive agent and supported further study of EGCG for cancer treatment.</p>
Subject(s)
Animals , Humans , Male , Mice , Anticarcinogenic Agents , Pharmacology , Therapeutic Uses , Blotting, Western , Caco-2 Cells , Catechin , Pharmacology , Therapeutic Uses , Colonic Neoplasms , Drug Therapy , Metabolism , Gene Expression Regulation , Gene Expression Regulation, Neoplastic , Glucuronosyltransferase , Genetics , Metabolism , Mice, Inbred BALB C , NF-E2-Related Factor 2 , Genetics , Metabolism , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
<p><b>BACKGROUND</b>Hepatic fibrosis is the key stage of the pathological progress from hepatic injury to cirrhosis. Ursodeoxycholic acid (UDCA) has been known as having significant clinical therapeutic effects on chronic liver diseases. Our research aimed to study the effect of UDCA on the signaling pathway of transforming growth factor beta1 (TGFbeta1)/Smad and discuss its possible molecular mechanisms of inhibiting hepatic fibrosis.</p><p><b>METHODS</b>Rat hepatic stellate cells were cultured in vitro and randomly assigned to 4 groups. Group A was control group, with only DMEM culture medium applied, and groups B, C, D were experimental groups, with different doses of UDCA (1.0 mmol/L, 0.5 mmol/L and 0.25 mmol/L respectively) added into their DMEM culture medium for further culture of 24 hours and 48 hours. The protein expressions of TGFbeta1, TGF type I receptor, Smad3, Smad4 and Smad7 were measured by Western blotting, as well as the expressions of TGFbeta1, Smad3, Smad7 and cAMP response element (CREB) binding protein (CBP) mRNA by real-time PCR. SPSS 11.5 statistical package was adopted for data analyses.</p><p><b>RESULTS</b>Compared with control group, the mRNA expressions of TGFbeta1 in the high and middle UDCA dose groups for 24 hours and 48 hours significantly decreased (P < 0.05), the protein expressions of TGFbeta1 in the two above groups for 48 hours and in the high dose group for 24 hours significantly decreased (P < 0.05). The protein and mRNA expressions of Smad3 in each UDCA dose group for 24 hours and 48 hours significantly decreased, with significant difference among different UDCA dose groups and between that of 24 hours and 48 hours observed (P < 0.05). The protein and mRNA expressions of Smad7 in the high and middle UDCA dose groups for 24 hours and 48 hours significantly increased. The CBP mRNA expression in each UDCA dose group for 24 hours and 48 hours significantly decreased (P < 0.05), with significant difference among different UDCA dose groups observed (P < 0.05).</p><p><b>CONCLUSION</b>UDCA could curb the development of hepatic fibrosis through affecting the signaling pathway of TGFbeta1/Smad by inhibiting the expressions of TGFbeta1, Smad3 and CBP and increasing the expression of Smad7.</p>