Cytokine-dependent regulation of hepatic organic anion transporter gene transactivators in mouse liver

Abstract

Proinflammatory cytokines such as TNF-alpha and IL-1beta lead to downregulation of hepatic organic anion transporters in cholestasis. This adapted response is transcriptionally mediated by nuclear hormone receptors and liver-specific transcription factors. Because little is known in vivo about cytokine-dependent regulatory events, mice were treated with either TNF-alpha or IL-1beta for up to 16 h. Transporter mRNA expression was determined by Northern blot analysis, nuclear activity, and protein-expression of transactivators by EMSA and Western blotting. TNF-alpha induces a sustained decrease in Ntcp, Oatp1/Oatp1a1, and Bsep mRNA expression but exerts only transient [multidrug resistance-associated protein 2 (Mrp2)] or no effects (Mrp3) on Mrps. In addition to Ntcp and Oatp1/Oatp1a1, IL-1beta also downregulates Bsep, Mrp2, and Mrp3 mRNAs to some extent. To study transcriptional regulation, Ntcp and Bsep promoters were first cloned from mice revealing a new distal Ntcp hepatocyte nuclear factor 1 (HNF-1) element but otherwise show a conserved localization to known rat regulatory elements. Changes in transporter-expression are preceeded by a reduction in binding activities at IR-1, ER-8, DR-5, and HNF-1alpha sites after 4 h by either cytokine, which remained more sustained by TNF-alpha in the case of nuclear receptors. Nuclear protein levels of retinoid X receptor (RXR)-alpha are significantly decreased by TNF-alpha but only transiently affected by IL-1beta. Minor reductions of retinoic acid receptor, farnesoid X receptor, pregnane X receptor, and constitutive androstane receptor nuclear proteins are restricted to 4 h after cytokine application and paralleled by a decrease in mRNA levels. Basolateral and canalicular transporter systems are downregulated by both cytokines, TNF-alpha and IL-1beta. Activity of HNF-1alpha as regulator of mNtcp is suppressed by both cytokines. Decreased binding activities of nuclear receptor heterodimers may be explained by a reduction of the ubiquitous heterodimerization partner RXR-alpha.

Adenosine Triphosphate–Binding Cassette Subfamily C Member 2 Is the Major Transporter of the Hepatobiliary Imaging Agent 99mTc-Mebrofenin

“…Here, we found that multiple cytokines were activated by inflammatory perturbations, including significant and prolonged activation of TNF-a. In agreement with our findings, inflammatory cytokines downregulated the expression of bile canalicular transporters in the short term, including Abcc2, Abcb11, and other genes (16)(17)(18), although not Slco1b1 (19). Here, we found that downregulation of canalicular transporters can continue in the long term during ongoing activation of inflammatory cells and local release of relevant cytokines.…”

Differential Regulation of Hepatic Transporters in the Absence of Tumor Necrosis Factor-α, Interleukin-1β, Interleukin-6, and Nuclear Factor-κB in Two Models of Cholestasis

“…These include Ntcp, Bsep, Oatp1, Oatp11, Mrp1, and Mrp9. The ability of LPS to down-regulate Ntcp, Oatp1, and Bsep mRNA expression has been demonstrated previously in vivo in rats and mice (Trauner et al, 1998;Hartmann et al, 2002;Geier et al, 2003;Cherrington et al, 2004;Siewert et al, 2004;Geier et al, 2005). The current results in IL-6(Ϫ/Ϫ) mice also confirm a previous report in which LPS administration resulted in transcriptional down-regulation of Ntcp, Bsep, and Oatp1 that was equally robust in WT and IL-6(Ϫ/Ϫ) mice (Siewert et al, 2004).…”

“…Ntcp, Bsep, Oatp1, Oatp2, and Mrp2 mRNA expression in mice (Hartmann et al, 2002;Siewert et al, 2004;Geier et al, 2005). Given that both TNF-␣ and IL-1␤ have the ability to signal activation of NF-B-mediated transcription, each is likely to constitute at least one facet of compensatory signaling in the acute-phase response to LPS in TNFR1(Ϫ/Ϫ) and IL-1RI(Ϫ/Ϫ) mice.…”

“…Previous studies have supported the notion that these three cytokines are essential in the regulation of transporter expression in models of intrahepatic cholestasis (Whiting et al, 1995;Green et al, 1996;Geier et al, 2003;Siewert et al, 2004). However, data regarding the activation and/or influence of cytokines in hepatic transporter regulation during obstructive cholestasis are not entirely clear (Bohan et al, 2003;Geier et al, 2005). In vivo studies have shown that bile acids are capable of inducing Kupffer cells to release proinflammatory cytokines and subsequently effect transcriptional alterations in the neighboring parenchymal cells (Miyake et al, 2000).…”

Inflammatory Bowel Disease Alters Intestinal Bile Acid Transporter Expression

“…Sundaram et al (1998) have shown in a rabbit model that in the chronically inflamed ileum, Na + -BA cotransport is inhibited by decreases in both cotransporter affinity for BA and cotransporter numbers; specific but undetected immune-inflammatory mediators were invoked. A large body of evidence exists for cytokine-dependent deregulation of hepatobiliary BA transporters during inflammation (Geier et al, 2005). Therefore, we paid attention to biopsy in activedisease-inflamed regions.…”