title: After damage of large bile ducts by gamma-aminobutyric acid, small ducts replenish the biliary tree by amplification of calcium-dependent signaling and de novo acquisition of large cholangiocyte phenotypes.
abstract: Large cholangiocytes secrete bicarbonate in response to secretin and proliferate after bile duct ligation by activation of cyclic adenosine 3', 5'-monophosphate signaling. The Ca(2+)-dependent adenylyl cyclase 8 (AC8, expressed by large cholangiocytes) regulates secretin-induced choleresis. Ca(2+)-dependent protein kinase C (PKC) regulates small cholangiocyte function. Because gamma-aminobutyric acid (GABA) affects cell functions by activation of both Ca(2+) signaling and inhibition of AC, we sought to develop an in vivo model characterized by large cholangiocyte damage and proliferation of small ducts. Bile duct ligation rats were treated with GABA for one week, and we evaluated: GABA(A), GABA(B), and GABA(C) receptor expression; intrahepatic bile duct mass (IBDM) and the percentage of apoptotic cholangiocytes; secretin-stimulated choleresis; and extracellular signal-regulated kinase1/2 (ERK1/2) phosphorylation and activation of Ca(2+-)dependent PKC isoforms and AC8 expression. We found that both small and large cholangiocytes expressed GABA receptors. GABA: (i) induced apoptosis of large cholangiocytes and reduced large IBDM; (ii) decreased secretin-stimulated choleresis; and (iii) reduced ERK1/2 phosphorylation and AC8 expression in large cholangiocytes. Small cholangiocytes: (i) proliferated leading to increased IBDM; (ii) displayed activation of PKCbetaII; and (iii) de novo expressed secretin receptor, cystic fibrosis transmembrane regulator, Cl(-)/HCO(3)(-) anion exchanger 2 and AC8, and responded to secretin. Therefore, in pathologies of large ducts, small ducts replenish the biliary epithelium by amplification of Ca(2+)-dependent signaling and acquisition of large cholangiocyte phenotypes.
authors.affiliation: Texas A & M Health Science Center, Medical Research Building, Temple, TX 76504, USA.
authors.forename: Romina
authors.initials: R
authors.lastname: Mancinelli
authors.forename: Antonio
authors.initials: A
authors.lastname: Franchitto
authors.forename: Eugenio
authors.initials: E
authors.lastname: Gaudio
authors.forename: Paolo
authors.initials: P
authors.lastname: Onori
authors.forename: Shannon
authors.initials: S
authors.lastname: Glaser
authors.forename: Heather
authors.initials: H
authors.lastname: Francis
authors.forename: Julie
authors.initials: J
authors.lastname: Venter
authors.forename: Sharon
authors.initials: S
authors.lastname: Demorrow
authors.forename: Guido
authors.initials: G
authors.lastname: Carpino
authors.forename: Shelley
authors.initials: S
authors.lastname: Kopriva
authors.forename: Mellanie
authors.initials: M
authors.lastname: White
authors.forename: Giammarco
authors.initials: G
authors.lastname: Fava
authors.forename: Domenico
authors.initials: D
authors.lastname: Alvaro
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Alpini
mesh_terms: D000818:Animals; D001652:Bile Ducts / Q000473:pathology*; D001659:Biliary Tract / Q000378:metabolism / Q000473:pathology*; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D008297:Male; D010641:Phenotype; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D018079:Receptors, GABA / Q000378:metabolism; D015398:Signal Transduction; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D018079:Receptors, GABA; D005680:gamma-Aminobutyric Acid; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D002118:Calcium