Differential regulation of drug transporter expression by all-trans retinoic acid in hepatoma HepaRG cells and human hepatocytes

Abstract

All-trans retinoic acid (atRA) is the active form of vitamin A, known to activate retinoid receptors, especially the heterodimer retinoid X receptor (RXR):retinoic acid receptor (RAR) that otherwise may play a role in regulation of some drug transporters. The present study was designed to characterize the nature of human hepatic transporters that may be targeted by atRA and the heterodimer RXR:RAR. Exposure of human hepatoma HepaRG cells and primary human hepatocytes to 5 M atRA down-regulated mRNA levels of various sinusoidal solute carrier (SLC) influx transporters, including organic anion transporting polypeptide (OATP) 2B1, OATP1B1, organic cation transporter (OCT) 1 and organic anion transporter (OAT) 2, and induced those of the canalicular breast cancer resistance protein (BCRP). The retinoid concomitantly reduced protein expression of OATP2B1 and OATP1B1 and activity of OATPs and OCT1 and induced BCRP protein expression in HepaRG cells. Some transporters such as OATP1B3 and the bile salt export pump (BSEP) were however down-regulated by atRA in primary human hepatocytes, but induced in HepaRG cells, thus pointing out discrepancies between these two liver cell models in terms of detoxifying protein regulation. atRA-mediated repressions of OATP2B1, OATP1B1, OAT2 and OCT1 mRNA expression were finally shown to be counteracted by knocking-down expression of RAR and RXR through siRNA transfection in HepaRG cells. atRA thus differentially regulated human hepatic drug transporters, mainly in a RXR:RAR-dependent manner, therefore establishing retinoids and retinoid receptors as modulators of liver drug transporter expression.

Loss of organic cation transporter 3 (Oct3) leads to enhanced proliferation and hepatocarcinogenesis

“…We did not use tumor cell lines to examine endogenous OCT expression and functionality because there is a strong downregulation in all cancer cell lines, which makes these models highly artificial and defective [ 21 ]. Furthermore, cancer cell lines have been extensively studied, showing very different results compared to primary hepatocytes [ 30 ]. In primary WT and Oct3 −/− hepatocytes Slc22A1 mRNA expression was significantly upregulated after 24 hours of quinine treatment in vivo (p<0.05).…”

Trafficking and other regulatory mechanisms for organic anion transporting polypeptides and organic anion transporters that modulate cellular drug and xenobiotic influx and that are dysregulated in disease

“…Increased OATP1A2 expression could contribute to breast cancer pathogenesis because increased influx of the substrate oestrone 3‐sulfate could drive tumour cell proliferation (Meyer zu Schwabedissen et al, ). In contrast, the CAR ligand phenobarbital down‐regulated OATP1B3 and OAT2 in human liver slices (Jigorel et al, ), and the retinoic acid receptor ligand all‐ trans ‐retinoic acid down‐regulated OATP1B1 and OATP2B1 mRNAs and immunoreactive proteins in primary human hepatocytes (Le Vee et al, ). Exposure of human liver‐derived cells to AhR ligands repressed OATP1B1, OATP1B3 and OAT2 mRNAs (Jigorel et al, ; Le Vee et al, ).…”

Mechanisms of Triptolide-Induced Hepatotoxicity and Protective Effect of Combined Use of Isoliquiritigenin: Possible Roles of Nrf2 and Hepatic Transporters

“…Our data showed that TP treatment induced hepatic damage both in vitro and in vivo , indicating successful modeling and relieving effect of ISL combined treatment, which is consistent with our previous studies ( Cao et al, 2016a , b ). The present study for the first time used human normal L02 hepatocytes rather than hepatoma cells or rodent hepatocytes, which is as close to clinical practice as possible, since there are differences in physiological conditions as well as distributions and expression levels of transporters between human normal hepatocytes and hepatoma cells or rodent hepatocytes ( Nicolaou et al, 2012 ; Le Vee et al, 2013 ).…”