H3 histamine receptor agonist inhibits biliary growth of BDL rats by downregulation of the cAMP-dependent PKA/ERK1/2/ELK-1 pathway.
Histamine regulates many functions by binding to four histamine G-coupled receptor proteins (H1R, H2R, H3R and H4R). As H3R exerts their effects by coupling to Galpha(i/o) proteins reducing adenosine 3', 5'-monophosphate (cAMP) levels (a key player in the modulation of cholangiocyte hyperplasia/damage), we evaluated the role of H3R in the regulation of biliary growth. We posed the following questions: (1) Do cholangiocytes express H3R? (2) Does in vivo administration of (R)-(alpha)-(-)-methylhistamine dihydrobromide (RAMH) (H3R agonist), thioperamide maleate (H3R antagonist) or histamine, in the absence/presence of thioperamide maleate, to bile duct ligated (BDL) rats regulate cholangiocyte proliferation? and (3) Does RAMH inhibit cholangiocyte proliferation by downregulation of cAMP-dependent phosphorylation of protein kinase A (PKA)/extracellular signal-regulated kinase 1/2 (ERK1/2)/ets-like gene-1 (Elk-1)? The expression of H3R was evaluated in liver sections by immunohistochemistry and immunofluorescence, and by real-time PCR in cholangiocyte RNA from normal and BDL rats. BDL rats (immediately after BDL) were treated daily with RAMH, thioperamide maleate or histamine in the absence/presence of thioperamide maleate for 1 week. Following in vivo treatment of BDL rats with RAMH for 1 week, and in vitro stimulation of BDL cholangiocytes with RAMH, we evaluated cholangiocyte proliferation, cAMP levels and PKA, ERK1/2 and Elk-1 phosphorylation. Cholangiocytes from normal and BDL rats express H3R. The expression of H3R mRNA increased in BDL compared to normal cholangiocytes. Histamine decreased cholangiocyte growth of BDL rats to a lower extent than that observed in BDL RAMH-treated rats; histamine-induced inhibition of cholangiocyte growth was partly blocked by thioperamide maleate. In BDL rats treated with thioperamide maleate, cholangiocyte hyperplasia was slightly higher than that of BDL rats. In vitro, RAMH inhibited the proliferation of BDL cholangiocytes. RAMH inhibition of cholangiocyte growth was associated with decreased cAMP levels and PKA/ERK1/2/Elk-1 phosphorylation. Downregulation of cAMP-dependent PKA/ERK1/2/Elk-1 phosphorylation (by activation of H3R) is important in the inhibition of cholangiocyte growth in liver diseases.
Francis
Heather
H
Department of Research and Education, College of Medicine, Scott & White Hospital and The Texas A & M University System Health Science Center, Temple, TX 76504, USA.
Franchitto
Antonio
A
Ueno
Yoshiyuki
Y
Glaser
Shannon
S
DeMorrow
Sharon
S
Venter
Julie
J
Gaudio
Eugenio
E
Alvaro
Domenico
D
Fava
Giammarco
G
Marzioni
Marco
M
Vaculin
Bradley
B
Alpini
Gianfranco
G
D000818:Animals; D001652:Bile Ducts / Q000601:surgery; D001653:Bile Ducts, Intrahepatic / Q000187:drug effects* / Q000254:growth & development / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000187:drug effects*; D004359:Drug Therapy, Combination; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006632:Histamine / Q000494:pharmacology; D017442:Histamine Agonists / Q000494:pharmacology*; D006965:Hyperplasia / Q000139:chemically induced / Q000473:pathology; D008026:Ligation; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D020935:MAP Kinase Signaling System; D008297:Male; D008761:Methylhistamines / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D010880:Piperidines / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D036143:Receptor, EphA8 / Q000378:metabolism; D018100:Receptors, Histamine H3 / Q000235:genetics / Q000378:metabolism*
D017442:Histamine Agonists; D008761:Methylhistamines; D010880:Piperidines; D018100:Receptors, Histamine H3; C069357:alpha-methylhistamine; D006632:Histamine; D000242:Cyclic AMP; D036143:Receptor, EphA8; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C052075:thioperamide