An antioxidant Trolox restores decreased oral absorption of cyclosporine A after liver ischemia-reperfusion through distinct mechanisms between CYP3A and P-glycoprotein in the small intestine.

Oxidative stress is a critical mediator of various injuries following ischemia-reperfusion (I/R) associated with organ transplantation. Although oral bioavailability of cyclosporine A (CsA) was decreased by increased first-pass metabolism through CYP3A and P-glycoprotein (P-gp) specifically in the upper small intestine after liver I/R, the mechanism responsible for them remained to be clarified. In the present study, the effect of Trolox (an α-tocopherol analogue) on the decreased oral absorption of CsA through elevated intestinal CYP3A and P-gp after liver I/R and their regulations were investigated. Rats were subjected to 60 min of liver ischemia followed by 12h of reperfusion. Trolox was administered intravenously 5 min before reperfusion. Trolox diminished the increased malondialdehyde and total glutathione levels in plasma by liver I/R and concomitantly prevented the decreased area under the blood concentration-time curve of orally administered CsA as well as initial absorption rate of CsA from upper small intestine. The elevated CYP3A mRNA and activity in the upper small intestine as well as expression levels of P-gp in upper, middle, and lower small intestines after liver I/R were attenuated by Trolox administration. The elevations of CYP3A levels specifically in the upper small intestine of I/R rats were correlated with the lithocholic acid levels in the bile. These results demonstrate that Trolox ameliorates the decreased oral absorption of CsA through elevated intestinal CYP3A and P-gp by preventing oxidative stress, where the biliary lithocholic acid may be responsible for the elevated transcription of CYP3A specifically in the upper small intestine after liver I/R.