Transfecting the multidrug resistance protein 2 gene improves transcellular organic anion transport

Eisai hyperbilirubinuria rats (EHBRs) lack functionally active multidrug resistance protein 2 (Mrp2), which causes impaired biliary excretion of numerous organic anions. We previously reported that Mrp3 expression is enhanced while organic anion transporting polypeptide 1 (Oatp1) or Oatp2 expression is reduced in the liver of EHBRs. Mrp3 mediates basolateral efflux of organic anions but not canalicular export. In this study, we transfected the human MRP2 gene into the liver of EHBRs and evaluated whether its transfection improves transcellular transport of organic anions in hepatocytes of EHBRs. The protein expression vector (pDEST26) including the full-length human MRP2 cDNA was developed. This vector was mixed with the hemagglutinating virus of Japan (HJV) envelope protein and transfected into the liver of EHBRs via the portal vein. Expression of Mrp3, Oatp1 and Oatp2 was evaluated by reverse transcription-polymerase chain reaction and Western blot analysis. mRNA and protein expression of MRP2 were detected in hepatocytes from transfected EHBRs. The serum-conjugated bilirubin level in EHBRs decreased to a normal level (35.7 to 6.4 µmol/l) with the expression of human MRP2. The change in expression of Mrp3, Oatp1 and Oatp2 in the liver of EHBRs was normalized by transfecting MRP2. Transfection of human MRP2 was performed using the HJV envelope protein. Transfection of MRP2 is useful for improving the transcellular transport of organic anions in the livers of EHBRs.