Role of liver-enriched transcription factors in the down-regulation of organic anion transporting polypeptide 4 (oatp4; oatplb2; slc21a10) by lipopolysaccharide.
Lipopolysaccharide (LPS) administration is a model of cholestasis. Organic anion transporting polypeptide 4 (Oatp4; Slc21a10) is almost exclusively expressed in liver. Therefore, it was hypothesized that LPS would down-regulate mouse Oatp4 and that this action is due to a decrease in nuclear binding activity of one or more liver-enriched transcription factors to mouse Oatp4 promoter. The present study indicates a time-dependent decrease in mouse Oatp4 mRNA levels by LPS. Moreover, LPS produced a rapid and profound decrease in nuclear binding activity to the mouse Oatp4 putative response elements for hepatocyte nuclear factor (HNF) 1, CAAT/enhancer binding protein (C/EBP), HNF3, and heterodimers of retinoid X receptor (RXR) and retinoic acid receptor (RAR). Maximal decrease in nuclear binding activity to these response elements preceded a significant reduction of Oatp4 mRNA levels. HNF1alpha bound to the Oatp4 HNF1 response element as a homodimer. Multiple copies of the Oatp4 HNF1alpha response element, inserted upstream of a minimal promoter, were sufficient to mediate reporter activity and responded to the coexpression of HNF1alpha in mouse hepatoma cells. Moreover, HNF1alpha dose dependently activated the Oatp4 promoter (-4.8 kilo-bases to +30 bp). Therefore, HNF1alpha is a potent trans-activator of the mouse Oatp4 promoter. In addition, Oatp4 mRNA levels were markedly decreased (95%) in HNF1alpha-null mice as compared with wild-type mice, suggesting that HNF1alpha levels are critical for the constitutive expression of the Oatp4 gene. Taken together, these findings suggest that the LPS-induced down-regulation of Oatp4 is likely due to reduction in the binding of HNF1alpha, C/EBP, HNF3, and RXR:RAR to the Oatp4 promoter.
Li
Ning
N
Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA.
Klaassen
Curtis D
CD
D000818:Animals; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008110:Liver Extracts; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000502:physiology*; D027361:Organic Anion Transporters / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000187:drug effects* / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000502:physiology*; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology
D004268:DNA-Binding Proteins; D051538:Hepatocyte Nuclear Factor 1-alpha; C496488:Hnf1a protein, mouse; C496496:Hnf1b protein, mouse; D008070:Lipopolysaccharides; D008110:Liver Extracts; D009687:Nuclear Proteins; D027361:Organic Anion Transporters; D012333:RNA, Messenger; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta