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Abstract
The farnesoid X receptor (FXR) is a nuclear receptor that regulates genes involved in bile acid homeostasis. FXR agonists, obeticholic acid (OCA) and chenodeoxycholic acid (CDCA), increase mRNA expression of efflux transporters in sandwich-cultured human hepatocytes (SCHH). This study evaluated the effects of OCA and CDCA treatment on the uptake, basolateral efflux, and biliary excretion of a model bile acid, taurocholate (TCA), in SCHH. In addition, changes in the protein expression of TCA uptake and efflux transporters were investigated. SCHH were treated with 1 µM OCA, 100 µM CDCA, or vehicle control for 72 hours followed by quantification of deuterated TCA uptake and efflux over time in Ca2+-containing and Ca2+-free conditions (n = 3 donors). A mechanistic pharmacokinetic model was fit to the TCA mass-time data to obtain estimates for total uptake clearance (CLUptake), total intrinsic basolateral efflux clearance (CLint,BL), and total intrinsic biliary clearance (CLint,Bile). Modeling results revealed that FXR agonists significantly increased CLint,BL by >6-fold and significantly increased CLint,Bile by 2-fold, with minimal effect on CLUptake. Immunoblotting showed that protein levels of the basolateral transporter subunits organic solute transporter α and β (OSTα and OSTβ) in FXR agonist-treated SCHH were significantly induced by >2.5- and 10-fold, respectively. FXR agonist-mediated changes in the expression of other TCA transporters in SCHH were modest. In conclusion, this is the first report demonstrating that OCA and CDCA increased TCA efflux in SCHH, which contributed to reduced intracellular TCA concentrations. Increased basolateral efflux of TCA was consistent with increased OSTα/β protein expression in OCA- and CDCA-treated SCHH.
Footnotes
- Received December 8, 2017.
- Accepted February 20, 2018.
This work was supported by Intercept Pharmaceuticals and the National Institutes of Health National Institute of General Medical Sciences [Grants R01-GM041935 and R35-GM122576]. C.G. is supported, in part, by the University of North Carolina Royster Society of Fellows. K.L.R.B. is a coinventor of the sandwich-cultured hepatocyte technology for quantification of biliary excretion (B-CLEAR) and related technologies, which have been licensed exclusively to Qualyst Transporter Solutions LLC. B-CLEAR is covered by U.S. patent 6,780,580 and other U.S. and international patents both issued and pending.
This work was presented, in part, as a poster at the following conferences: Guo C, LaCerte C, Edwards J, Brouwer KR, Brouwer KLR. Mechanistic pharmacokinetic modeling revealed functional increase in bile acid efflux by the FXR agonists obeticholic acid and chenodeoxycholic acid. Eighth American Conference on Pharmacometrics (Fort Lauderdale, FL, Oct. 16-18, 2017); Guo C, Brouwer KLR. Impact of hepatic efflux transporter modulation on bile acid disposition: prediction and evaluation using mechanistic pharmacokinetic modeling. American Association of Pharmaceutical Scientists Annual Meeting (San Diego, CA, Nov. 13-15, 2017); and Guo C, Edwards J, LaCerte C, Freeman KM, Brouwer KR, Brouwer KLR. Functional increase in bile acid efflux after treatment of sandwich-cultured human hepatocytes with the FXR agonists chenodeoxycholic acid and obeticholic acid. Third Workshop of the International Transporter Consortium in 2017 (Washington D.C., Mar. 13-14, 2017).
- Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics
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