Published online Nov 21, 2017. doi: 10.3748/wjg.v23.i43.7678
Peer-review started: June 30, 2017
First decision: July 25, 2017
Revised: August 15, 2017
Accepted: September 5, 2017
Article in press: September 5, 2017
Published online: November 21, 2017
To investigate the effect of resveratrol on biliary secretion of cholephilic compounds in healthy and bile duct-obstructed rats.
Resveratrol (RSV) or saline were administered to rats by daily oral gavage for 28 d after sham operation or reversible bile duct obstruction (BDO). Bile was collected 24 h after the last gavage during an intravenous bolus dose of the Mdr1/Mrp2 substrate azithromycin. Bile acids, glutathione and azithromycin were measured in bile to quantify their level of biliary secretion. Liver expression of enzymes and transporters relevant for bile production and biliary secretion of major bile constituents and drugs were analyzed at the mRNA and protein levels using qRT-PCR and Western blot analysis, respectively. The TR-FRET PXR Competitive Binding Assay kit was used to determine the agonism of RSV at the pregnane X receptor.
RSV increased bile flow in sham-operated rats due to increased biliary secretion of bile acids (BA) and glutathione. This effect was accompanied by the induction of the hepatic rate-limiting transporters for bile acids and glutathione, Bsep and Mrp2, respectively. RSV also induced Cyp7a1, an enzyme that is crucial for bile acid synthesis; Mrp4, a transporter important for BA secretion from hepatocytes to blood; and Mdr1, the major apical transporter for xenobiotics. The findings were supported by increased biliary secretion of azithromycin. The TR-FRET PXR competitive binding assay confirmed RSV as a weak agonist of the human nuclear receptor PXR, which is a transcriptional regulator of Mdr1/Mrp2. RSV demonstrated significant hepatoprotective properties against BDO-induced cirrhosis. RSV also reduced bile flow in BDO rats without any corresponding change in the levels of the transporters and enzymes involved in RSV-mediated hepatoprotection.
Resveratrol administration for 28 d has a distinct effect on bile flow and biliary secretion of cholephilic compounds in healthy and bile duct-obstructed rats.
Core tip: For the first time, our results provide information about the ability of resveratrol to increase bile flow in healthy rats by increasing the biliary excretion of bile acids and glutathione via posttranscriptional induction of their rate-limiting transporters, Bsep and Mrp2, respectively, and via the up-regulation of Cyp7a1, an enzyme that is crucial for bile acid synthesis. Resveratrol simultaneously induced hepatic expression of Mdr1, which was verified by increased biliary excretion of its substrate, azithromycin. Our findings were consistent with an agonistic effect of resveratrol on PXR. Our data therefore imply that oral administration of resveratrol may modify the kinetics of endo- and xenobiotics.