Hepatobiliary organic anion transporters are differentially regulated in acute toxic liver injury induced by carbon tetrachloride.
OBJECTIVE
Hepatobiliary transporters are down-regulated in cholestasis, but their expression in acute, non-cholestatic, cytokine-mediated liver injury is unknown. Thus we studied the molecular mechanisms, by which sodium taurocholate cotransporting polypeptide (Ntcp), organic anion transporting polypeptide 1 (Oatp1), Oatp2, Oatp4, multidrug-resistance protein 2 (Mrp2) and bile salt export pump (Bsep) are regulated in liver injury induced by carbon tetrachloride (CCl(4)).


METHODS
mRNA and protein levels were determined in rats 24 and 72h after CCl(4) injection. Transporter gene transcription and binding activities of Ntcp and Mrp2 transactivators were assessed by nuclear runoff and electrophoretic mobility shift assays.


RESULTS
mRNA levels significantly declined to 41+/-44% for Ntcp, 65+/-41% for Oatp1 and 64+/-28% for Oatp2, but remained unchanged for Oatp4, canalicular Mrp2 and Bsep. Protein levels declined only for Oatp4 (-50+/-17%) and Ntcp (-23+/-13%) at 24h. Reduced mRNA levels (Ntcp, Oatp1, Oatp2) were associated with decreased transcriptional activities. Binding activity of Ntcp transactivators (hepatocyte nuclear factor 1 alpha (HNF1alpha) and CAAT enhancer binding protein alpha (C/EBPalpha) were reduced by 24h, whereas retinoid X receptor alpha (RXRalpha):retinoid acid receptor alpha (RARalpha) as transactivator of both Ntcp and Mrp2 remained unaltered. Recovery of acute hepatitis and changes in gene expression occurred after 72h.


CONCLUSIONS
Acute liver injury results in down-regulation of basolateral organic anion transporters similar to liver regeneration after partial hepatectomy, but in contrast to endotoxin-induced cholestasis. Maintained binding activity of RXRalpha:RARalpha may explain differences in Mrp2 expression.
Department of Internal Medicine III, University of Technology, Pauwelsstrasse 30, 52074 Aachen, Germany.
Andreas
A
Geier
Suk Kyum
SK
Kim
Thomas
T
Gerloff
Christoph G
CG
Dietrich
Frank
F
Lammert
Saul J
SJ
Karpen
Bruno
B
Stieger
Peter J
PJ
Meier
Siegfried
S
Matern
Carsten
C
Gartung
D000208:Acute Disease; D000818:Animals; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D002251:Carbon Tetrachloride; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D056486:Chemical and Drug Induced Liver Injury; D016207:Cytokines / Q000235:genetics; D004268:DNA-Binding Proteins; D015870:Gene Expression / Q000187:drug effects; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D008107:Liver Diseases / Q000378:metabolism* / Q000503:physiopathology*; D008297:Male; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins; D027361:Organic Anion Transporters; D029363:Organic Anion Transporters, Sodium-Dependent; D029362:Organic Anion Transporters, Sodium-Independent / Q000235:genetics* / Q000378:metabolism*; D027701:Organic Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D000074542:Solute Carrier Organic Anion Transporter Family Member 1B3; D027981:Symporters; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
D022762:CCAAT-Enhancer-Binding Proteins; D002251:Carbon Tetrachloride; D002352:Carrier Proteins; D016207:Cytokines; D004268:DNA-Binding Proteins; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009687:Nuclear Proteins; D027361:Organic Anion Transporters; D029363:Organic Anion Transporters, Sodium-Dependent; D029362:Organic Anion Transporters, Sodium-Independent; D027701:Organic Cation Transport Proteins; D012333:RNA, Messenger; D000074542:Solute Carrier Organic Anion Transporter Family Member 1B3; D027981:Symporters; D014157:Transcription Factors; C496489:Hnf1a protein, rat; C421102:Slco1a1 protein, rat; C503597:Slco1a4 protein, rat; C421207:Slco1b2 protein, rat; C451262:Slco1c1 protein, rat; C071908:sodium-bile acid cotransporter; C421109:multidrug resistance-associated protein 1