Influence of drugs on bile acid excretion

Determination of liver specific toxicities in rat hepatocytes by high content imaging during 2-week multiple treatment

DILI is a major safety issue during drug development and one of the leading causes for market withdrawal. Despite many efforts made in the past, the prediction of DILI using in vitro models remains very unreliable. In the present study, the well-established hepatocyte Collagen I-Matrigel™ sandwich culture was used, mimicking chronic drug treatment after multiple incubations for 14 days. Ten drugs associated with different types of specific preclinical and clinical liver injury were evaluated at non-cytotoxic concentrations. Mrp2-mediated transport, intracellular accumulation of neutral lipids and phospholipids were selected as functional endpoints by using Cellomics™ Arrayscan® technology and assessed at five timepoints (day 1, 3, 7, 10, 14). Liver specific functional impairments after drug treatment were enhanced over time and could be monitored by HCI already after few days and before cytotoxicity. Phospholipidosis-inducing drugs Chlorpromazine and Amiodarone displayed the same response as in vivo. Cyclosporin A, Chlorpromazine, and Troglitazone inhibited Mrp2-mediated biliary transport, correlating with in vivo findings. Steatosis remained difficult to be reproduced under the current in vitro testing conditions, resulting into false negative and positive responses. The present results suggest that the repeated long-term treatment of rat hepatocytes in the Collagen I-Matrigel™ sandwich configuration might be a suitable tool for safety profiling of the potential to induce phospholipidosis and impair Mrp2-mediated transport processes, but not to predict steatosis.

Oral contraceptives raise the cholesterol saturation of bile by increasing biliary cholesterol secretion

To discover the mechanism by which oral contraceptives increase the level of cholesterol saturation of human bile, we measured biliary lipid secretion rates, gallbladder and hepatic bile lipid composition, bile acid pool size, bile acid composition, and plasma lipoprotein levels in five healthy women during routine oral contraceptive treatment and again during normal menstrual cycles on no medication. The molar percent cholesterol in both gallbladder and hepatic bile was higher in every subject while taking oral contraceptives (p less than .02). Oral contraceptive usage was accompanied by a significant enhancement of biliary cholesterol secretion (65 versus 46 mg/hr, p less than .01), but there was no significant change in bile acid or phospholipid secretion, total bile acid pool size, or bile acid composition. These findings indicate that oral contraceptive usage increases biliary cholesterol secretion, thereby raising the level of cholesterol saturation of bile and predisposing to cholesterol precipitation and gallstone formation.