Anticholestatic Effect of Bardoxolone Methyl on Hepatic Ischemia-reperfusion Injury in Rats.

Cholestasis is a sign of hepatic ischemia-reperfusion injury (IRI), which is caused by the dysfunction of hepatocyte membrane transporters (HMTs). As transcriptional regulation of HMTs during oxidative stress is mediated by nuclear factor erythroid 2-related factor 2, we hypothesized that bardoxolone methyl (BARD), a nuclear factor erythroid 2-related factor 2 activator, can mitigate cholestasis associated with hepatic IRI. BARD (2 mg/kg) or the vehicle was intravenously administered into rats immediately before sham surgery, 60 min of ischemia (IR60), or 90 min of ischemia (IR90); tissue and blood samples were collected after 24 h to determine the effect on key surrogate markers of bile metabolism and expression of HMT genes (Mrp (multidrug resistance-associated protein) 2, bile salt export pump, Mrp3, sodium-taurocholate cotransporter, and organic anion-transporting polypeptide 1). Significantly decreased serum bile acids were detected upon BARD administration in the IR60 group but not in the IR90 group. Hepatic tissue analyses revealed that BARD administration increased mRNA levels of Mrp2 and Mrp3 in the IR60 group, and it decreased those of bile salt export pump in the IR90 group. Protein levels of multidrug resistance-associated protein 2, multidrug resistance-associated protein 3, and sodium-taurocholate cotransporter were higher in the IR90 group relative to those in the sham or IR60 groups, wherein the difference was notable only when BARD was administered. Immunohistochemical and morphometric analyses showed that the area of expression for multidrug resistance-associated protein 2 and for sodium-taurocholate cotransporter was larger in the viable tissues than in the necrotic area, and the area for multidrug resistance-associated protein 3 was smaller; these differences were notable upon BARD administration. BARD may have the potential to change HMT regulation to mitigate cholestasis in hepatic IRI.