Pharmacotoxicology of clinically-relevant concentrations of obeticholic acid in an organotypic human hepatocyte system

Nonalcoholic steatohepatitis (NASH) is an emerging health crisis with no approved therapies. Obeticholic acid (OCA), a farnesoid X receptor (FXR) agonist, shows promise in NASH trials. However, the precise mechanisms mediating OCA effects and impact on cholesterol metabolism are not fully understood. We explored the pharmaco-toxicological effects of OCA on patho-physiological pathways in hepatocytes using a previously described perfused organotypic liver system that allows culture in near-physiolbgical insulin/glucose milieus, and exhibits drug responses at clinically-relevant concentrations. Primary hepatbcytes experienced 48-hour exposure to OCA at concentrations approximating therapeutic (0.5 mu M) and supratherapeutic (10 mu M) levels. Global transcriptomics by RNAseq was complimented by cellular viability (MTT), CYP activity assays, and secreted FGF19 levels in the media. Dose-dependent, transcriptional effects suggested suppression of bile acid synthesis (4,down arrow CYP7A1, down arrow CYP27A1) and increased bile efflux (up arrow ABCB4,up arrow ABCB11, up arrow OSTA, up arrow OSTB). Pleiotropic effects included suppression of TGF beta and IL-6 signaling pathways, and signatures suggestive of HDL suppression (up arrow SCARB1, down arrow ApoAl, down arrow LCAT) and LDL elevation (up arrow ApoB, down arrow CYP7A1). OCA exhibited direct FXR-mediated effects with increased FGF19 secretion. Transcriptomics revealed regulation of metabolic, anti-inflammatory, and anti-fibrotic pathways beneficial in NASH, and predicted cholesterol profiles consistent with clinical findings. Follow-up studies under lipotoxic/inflammatory conditions would corroborate these effects in a disease-relevant environment. (C) 2016 Elsevier Ltd. All rights reserved.