Certain drugs impair bile acid export, which can lead to intrahepatic accumulation and cause drug-induced cholestasis. Bile acid transport and metabolism are key components in maintaining bile acid homeostasis. BSEP (bile salt export pump) and MRP2 (multidrug resistance associated protein 2) are thought to play a role in bile acid transport from hepatocytes into bile ducts.
In an effort to create a model that is more translational to human clinical results, we have developed two human microtissue (MT) models to investigate pro-cholestatic compound detection. These 3D models, HepaRG and primary human liver MTs (hLiMTs), create a cellular environment more similar to tissue than standard 2D monolayer cultures, including bile canaliculi formation as well as functional BSEP and MRP2.
Inhibition of the BSEP transporter and/or the MRP2 transporter has been reported to be a mechanism in the manifestation of cholestasis. The fluorescent indicator dyes, CMFDA and CLF, are effluxed by MRP2 and BSEP, respectively, into the bile canaliculi. Using these dyes in conjunction with confocal high content screening, it is possible to monitor the effects of drugs on MRP2 and BSEP-mediated transporter activity in the liver.
Known MRP2 and BSEP inhibitors were assessed using this approach. The MRP2 inhibitor benzbromarone and the BSEP inhibitor troglitazone are both known to cause cholestatic hepatotoxicity in vivo, and effectively inhibited the transport of CMFDA and CLF respectively in this study. This research indicates that single organotypic liver MTs combined with automated confocal HCS can provide an early screen for drug-induced cholestasis, however, Cyprotex will be evaluating a larger test set of compounds to confirm the utility of the model
This research was present at 2016 SOT and ToxExpo.