Inhibitory Effects of 2,3,4',5-tetrahydroxystilbene-2-O-β-D-glucoside on Angiotensin Ⅱ-Induced Proliferation of Vascular Smooth Muscle Cells

Objective：To investigate the effect of 2,3,4’,5-tetrahydroxystilbene-2-0- p-D-glucoside（TSG）,an active component extracted from the root of Polygonum multiflorum,on angiotensin Ⅱ（Ang Ⅱ）-induced proliferation of cultured rat vascular smooth muscle cells（VSMCs） and to identify the potential mechanism.Methods：Cell proliferation and cell cycle were determined by cell counting,5-bromo-2’-deoxyuridine incorporation assay,proliferating cell nuclear antigen protein expression and flow cytometry.Levels of phosphorylated extracellular signal-regulated kinase 1/2（ERK1/2）,mitogenic extracellular kinase 1/2（MEK1/2） and Src in VSMCs were measured by Western blot.The expression of c-fos,c-jun and c-myc mRNA were measured by reverse transcription polymerase chain reaction（RT-PCR）.Intracellular reactive oxygen species（ROS） was measured by fluorescence assay.Results：TSG significantly inhibited Ang Ⅱ-induced VSMCs proliferation and arrested cells in the G1/S checkpoint（P〈0.05 or P〈0.01）.TSG decreased the levels of phosphorylated ERK1/2,MEK1/2 and Src in VSMCs（P〈0.05 or P〈0.01）.TSG also suppressed c-fos,c-jun and c-myc mRNA expression（P〈0.05 or P〈0.01）.In addition,the intracellular ROS was reduced by TSG（P〈0.01）.Conclusions：TSG inhibited Ang Ⅱ-induced VSMCs proliferation.Its antiproliferative effect might be associated with down-regulation of intracellular ROS,followed by the suppression of the Src-MEK1/2-ERK1/2 signal pathway,and hence,blocking cell cycle progression.

Enhanced absorption and inhibited metabolism of emodin by 2,3,5,4＇-tetrahydroxystilbene-2-O-β-D-glucopyranoside： Possible mechanisms for Polygoni Multiflori Radix-induced liver injury

Polygoni Multiflori Radix(PMR) has been commonly used as a tonic in China for centuries. However, PMR-associated hepatotoxicity is becoming a safety issue. In our previous in vivo study, an interaction between stilbenes and anthraquinones has been discovered and a hypothesis is proposed that the interaction between stilbene glucoside-enriching fraction and emodin may contribute to the side effects of PMR. To further support our previous in vivo results in rats, the present in vitro study was designed to evaluate the effects of 2, 3, 5, 4'-tetrahydroxystilbene-2-O-β-D-glucopyranoside(TSG) on the cellular absorption and human liver microsome metabolism of emodin. The obtained results indicated that the absorption of emodin in Caco-2 cells was enhanced and the metabolism of emodin in human liver microsomes was inhibited after TSG treatment. The effects of the transport inhibitors on the cellular emodin accumulation were also examined. Western blot assay suggested that the depressed metabolism of emodin could be attributed to the down-regulation of UDP-glucuronosyltransferases(UGTs) 1A8, 1A10, and 2B7. These findings definitively demonstrated the existence of interaction between TSG and emodin, which provide a basis for a better understanding of the underlying mechanism for PMR-induced liver injury.

Screening and Identifying Hepatotoxic Components in Polygoni multiflori Radix and Polygoni multiflori Radix Praeparata

Objective: In this study, the hepatotoxic components of Polygoni multiflori Radix and Polygoni multiflori Radix Praeparata(known as Heshouwu [HSW] and Zhiheshouwu [ZHSW] in China, respectively) were screened, isolated, and identified. Materials and Methods: The ethanol extracts of HSW and ZHSW were separated into 80 fractions according to their polarity in the preparation liquid phase. Chang liver cell line was used to screen the toxic components of HSW and ZHSW in vitro. The obtained toxic mixture was further collected, isolated, and identified to confirm the hepatotoxic compounds of HSW and ZHSW. Results: The identifid hepatotoxic compounds include 2,3,5,4’-tetrah ydroxystilbene-2-O-β-D-glucoside, emodin, physcion-8-O-β-d-glucoside, physcion, and citreorosein, the fist two among them were the main components of HSW and ZHSW. After processing of HSW, the contents of 2,3,5,4’-tetrahydroxystilbene-2-O-β-D-glucoside and emodin in ZHSW were signifiantly decreased. Conclusions: The traditional processing with herb has signifiant effects on the components, especially the toxic components, in the extract of HSW and is an effective method to reduce its toxicity.