Cytokine-dependent regulation of hepatic organic anion transporter gene transactivators in mouse liver.
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.
Geier
Andreas
A
Dept. of Internal Medicine III, Division of Gastroenterology and Hepatology, Aachen Univ., Pauwelsstrasse 30, D-52074 Aachen, Germany. ageier@ukaachen.de
Dietrich
Christoph G
CG
Voigt
Sebastian
S
Ananthanarayanan
Meenakshisundaram
M
Lammert
Frank
F
Schmitz
Anne
A
Trauner
Michael
M
Wasmuth
Hermann E
HE
Boraschi
Diana
D
Balasubramaniyan
Natarajan
N
Suchy
Frederick J
FJ
Matern
Siegfried
S
Gartung
Carsten
C
D020121:5' Untranslated Regions / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D005786:Gene Expression Regulation / Q000187:drug effects*; D007375:Interleukin-1 / Q000494:pharmacology* / Q000502:physiology; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D027361:Organic Anion Transporters / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D015534:Trans-Activators / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology* / Q000502:physiology
D020121:5' Untranslated Regions; D007375:Interleukin-1; D027361:Organic Anion Transporters; D012333:RNA, Messenger; D015534:Trans-Activators; D014409:Tumor Necrosis Factor-alpha