Combination of ursodeoxycholic acid and glucocorticoids upregulates the AE2 alternate promoter in human liver cells.
Primary biliary cirrhosis (PBC) is a cholestatic disease associated with autoimmune phenomena and alterations in both biliary bicarbonate excretion and expression of the bicarbonate carrier AE2. The bile acid ursodeoxycholic acid (UCDA) is currently used in treatment of cholestatic liver diseases and is the treatment of choice in PBC; however, a subset of PBC patients respond poorly to UDCA monotherapy. In these patients, a combination of UDCA and glucocorticoid therapy appears to be beneficial. To address the mechanism of this benefit, we analyzed the effects of UDCA and dexamethasone on AE2 gene expression in human liver cells from hepatocyte and cholangiocyte lineages. The combination of UDCA and dexamethasone, but not UDCA or dexamethasone alone, increased the expression of liver-enriched alternative mRNA isoforms AE2b1 and AE2b2 and enhanced AE2 activity. Similar effects were obtained after replacing UDCA with UDCA conjugates. In in vitro and in vivo reporter assays, we found that a UDCA/dexamethasone combination upregulated human AE2 alternate overlapping promoter sequences from which AE2b1 and AE2b2 are expressed. In chromatin immunoprecipitation assays, we demonstrated that combination UCDA/dexamethasone treatment induced p300-related interactions between HNF1 and glucocorticoid receptor on the AE2 alternate promoter. Our data provide a potential molecular explanation for the beneficial effects of the combination of UDCA and glucocorticoids in PBC patients with inadequate response to UDCA monotherapy.
Arenas
Fabián
F
Division of Gene Therapy and Hepatology, Center for Applied Medical Research, Clínica Universitaria, University of Navarra School of Medicine, CIBERehd, Pamplona, Spain.
Hervias
Isabel
I
Uriz
Miriam
M
Joplin
Ruth
R
Prieto
Jesús
J
Medina
Juan F
JF
D000818:Animals; D027321:Anion Transport Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D017920:Antiporters / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D002756:Cholagogues and Choleretics / Q000494:pharmacology* / Q000627:therapeutic use; D047369:Chromatin Immunoprecipitation; D003907:Dexamethasone / Q000494:pharmacology* / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D005786:Gene Expression Regulation; D005938:Glucocorticoids / Q000494:pharmacology* / Q000627:therapeutic use; D051538:Hepatocyte Nuclear Factor 1-alpha / Q000235:genetics / Q000378:metabolism; D051539:Hepatocyte Nuclear Factor 1-beta / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008105:Liver Cirrhosis, Biliary / Q000188:drug therapy; D051379:Mice; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D064606:SLC4A Proteins; D014158:Transcription, Genetic / Q000187:drug effects*; D015854:Up-Regulation; D014580:Ursodeoxycholic Acid / Q000494:pharmacology* / Q000627:therapeutic use; D050880:p300-CBP Transcription Factors / Q000378:metabolism
D027321:Anion Transport Proteins; D017920:Antiporters; D002756:Cholagogues and Choleretics; D005938:Glucocorticoids; C496487:HNF1A protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; D064606:SLC4A Proteins; D051539:Hepatocyte Nuclear Factor 1-beta; D014580:Ursodeoxycholic Acid; D003907:Dexamethasone; D050880:p300-CBP Transcription Factors