Use of cassette dosing in sandwich-cultured rat and human hepatocytes to identify drugs that inhibit bile acid transport

Hepatocellular accumulation of bile acids due to inhibition of the canalicular bile salt export pump (BSEP/ ABCB11) is one proposed mechanism of drug-induced liver injury (DILI). Some hepatotoxic compounds also are potent inhibitors of bile acid uptake by Na +-dependent taurocholate cotransporting polypeptide (NTCP/ SLC10A1). This study used a cassette dosing approach in rat and human sandwich-cultured hepatocytes (SCH) to determine whether known or suspected hepatotoxic drugs inhibit bile acid transport individually or in combination. [ 3H]-Taurocholate served as the NTCP/BSEP probe substrate. Individually, cyclosporin A and rifampin decreased taurocholate in vitro biliary clearance (Cl biliary) and biliary excretion index (BEI) by more than 20% in rat SCH, suggesting that these drugs primarily inhibited canalicular efflux. In contrast, ampicillin, carbenicillin, cloxacillin, nafcillin, oxacillin, carbamazepine, pioglitazone, and troglitazone decreased the in vitro Cl biliary by more than 20% with no notable change in BEI, suggesting that these drugs primarily inhibited taurocholate uptake. Cassette dosing ( n = 2–4 compounds per cassette) in rat SCH yielded similar findings, and results in human SCH were consistent with rat SCH. In summary, cassette dosing in SCH is a useful in vitro approach to identify compounds that inhibit the hepatic uptake and/or excretion of bile acids, which may cause DILI.