Down-Regulation of Organic Anion Transporter Expression in Human Hepatocytes Exposed to the Proinflammatory Cytokine Interleukin 1β

Abstract

ABSTRACT:Interleukin (IL) 1␤ is a proinflammatory cytokine known to markedly alter expression of major organic anion transporters in rodent hepatocytes. However, its effects toward human hepatic transporters remain poorly characterized. Therefore, the present study was aimed at determining IL-1␤ effects on expression of organic anion transporters in primary human hepatocytes and highly differentiated human hepatoma HepaRG cells. Exposure to 1 ng/ml IL-1␤ was first shown to markedly repress mRNA expression of sodium-taurocholate cotransporting polypeptide (NTCP), a major sinusoidal transporter handling bile acids, in both human hepatocytes and HepaRG cells. Interleukin (IL) 1␤, a major proinflammatory cytokine contributing to endotoxin-or sepsis-induced cholestasis in liver, impairs hepatic detoxification pathways (Prandota, 2005;Aitken et al., 2006). Thus, IL-1␤ decreases expression of various drug-metabolizing enzymes, including cytochromes P450 and glutathione S-transferases, in human and rat hepatocytes (Abdel-Razzak et al., 1993;Maheo et al., 1997). In addition, it interferes with drug-related regulation of detoxifying proteins (Assenat et al., 2004).Organic anion transporters handling bile acids or drugs also constitute important targets of IL-1␤ in rodents (Geier et al., 2007;Petrovic et al., 2007). Indeed, IL-1␤-treated mice display reduced expression of various hepatic transporters, including solute carrier (SLC) proteins like sinusoidal sodium-dependent taurocholate transporter Ntcp (Slc10a1) and organic anion transporting polypeptides (Oatp) 1 (Slco1a1) and Oatp2 (Slco1a2), and ATP binding cassette (ABC) transporters like bile salt export pump (Bsep) (Abcb11) and multidrug resistance-associated protein (Mrp) 2 (Abcc2) (Hartmann et al., 2002;Geier et al., 2005). In addition, Ntcp and Mrp2 are also down-regulated in primary rat hepatocytes exposed to IL-1␤ (Denson et al., 2002;Li et al., 2002). However, IL-1␤-mediated regulation of hepatic organic anion transporters remains much less characterized in human hepatocytes than in their rodent counterparts, even if MRP2 (ABCC2) and MRP3 (ABCC3) have been shown to constitute targets of IL-1␤ in certain human hepatoma cell lines (Lee and Piquette-Miller, 2003;Hisaeda et al., 2004). In this context, it is noteworthy that an inverse correlation between sodium-taurocholate cotransporting polypeptide (NTCP) (SLC10A1) mRNA levels and IL-1␤ secretion has been recently reported in human liver slices exposed to lipopolysaccharide (LPS) (Elferink et al., 2004), suggesting that at least some human organic anion transporters, especially NTCP, may be downregulated by IL-1␤, as their rodent counterparts. The present study was designed to investigate this hypothesis. Using human primary hepatocytes and human highly differentiated hepatoma HepaRG cells, well recognized as convenient models for studying regulation of transporters Le Vee et al., 2006), we report that IL-1␤ treatment markedly reduced functional expression of NTCP in human hepatocytes; mRNA levels of other major ...

Diminished Expression of Apical Sodium-Dependent Bile Acid Transporter in Gallstone Disease Is Independent of Ileal Inflammation

“…This finding was complemented by Xia et al [30 ]who detected in cholangiocytes an IL-1β-induced downregulation of ASBT by the ubiquitin-proteasome pathway. In addition, it has been found that some cytokines contribute to the downregulation of hepatobiliary bile acid transporters [31]. Nevertheless, our findings argue against a major role of ileal cytokines in gallstone disease.…”

Regulation of hepatic ABCC transporters by xenobiotics and in disease states

“…Treatment of HepaRG cells with phenobarbital upregulates MRP2 mRNA levels (Le Vee et al, 2006; Lambert et al, 2009). Treatment of primary human hepatocytes and HepaRG cells with IL-1β results in significant downregulation of MRP2 mRNA in a time-dependent manner (Le Vee et al, 2008). …”

“…Treatment of primary human hepatocytes with IL-1β downregulates MRP3 mRNA expression (Le Vee et al, 2008). Treatment of human hepatocytes with TNF-α or IL-6 for 48 hours does not change MRP3 mRNA levels or protein localization, but it induces MRP3 protein expression levels (Vee et al, 2009).…”

“…In proliferating, confluent, and 1.5% dimethyl-sulfoxide (DMSO)-treated HepaRG cells, a human hepatoma cell line, MRP3 mRNA expression is higher than in primary hepatocytes (Le Vee et al, 2006) and treatment of HepaRG cells with IL-1β downregulates MRP3 mRNA (Le Vee et al, 2008). …”

“…In contrast, exposure of human hepatocytes to IL-6 for 8 or 24 hours reduces MRP4 mRNA levels (Vee et al, 2009). Treatment of primary human hepatocytes with the proinflammatory cytokine, IL-1β, results in slight upregulation of MRP4 at 8 hours and reduction at 24 hours after treatment (Le Vee et al, 2008). …”