title: Knockout of histidine decarboxylase decreases bile duct ligation-induced biliary hyperplasia via downregulation of the histidine decarboxylase/VEGF axis through PKA-ERK1/2 signaling.
abstract: Histidine is converted to histamine by histidine decarboxylase (HDC). We have shown that cholangiocytes 1) express HDC, 2) secrete histamine, and 3) proliferate after histamine treatment via ERK1/2 signaling. In bile duct-ligated (BDL) rodents, there is enhanced biliary hyperplasia, HDC expression, and histamine secretion. This studied aimed to demonstrate that knockdown of HDC inhibits biliary proliferation via downregulation of PKA/ERK1/2 signaling. HDC(-/-) mice and matching wild-type (WT) were subjected to sham or BDL. After 1 wk, serum, liver blocks, and cholangiocytes were collected. Immunohistochemistry was performed for 1) hematoxylin and eosin, 2) intrahepatic bile duct mass (IBDM) by cytokeratin-19, and 3) HDC biliary expression. We measured serum and cholangiocyte histamine levels by enzyme immunoassay. In total liver or cholangiocytes, we studied: 1) HDC and VEGF/HIF-1α expression and 2) PCNA and PKA/ERK1/2 protein expression. In vitro, cholangiocytes were stably transfected with shRNA-HDC plasmids (or control). After transfection we evaluated pPKA, pERK1/2, and cholangiocyte proliferation by immunoblots and MTT assay. In BDL HDC(-/-) mice, there was decreased IBDM, PCNA, VEGF, and HDC expression compared with BDL WT mice. Histamine levels were decreased in BDL HDC(-/-). BDL HDC(-/-) livers were void of necrosis and inflammation compared with BDL WT. PKA/ERK1/2 protein expression (increased in WT BDL) was lower in BDL HDC(-/-) cholangiocytes. In vitro, knockdown of HDC decreased proliferation and protein expression of PKA/ERK1/2 compared with control. In conclusion, loss of HDC decreases BDL-induced biliary mass and VEGF/HIF-1α expression via PKA/ERK1/2 signaling. Our data suggest that HDC is a key regulator of biliary proliferation.
authors.affiliation: Scott & White Healthcare, Temple, Texas;
authors.forename: Allyson
authors.initials: A
authors.lastname: Graf
authors.affiliation: Central Texas Veterans Health Care System, Temple, Texas; Scott & White Healthcare, Temple, Texas; Texas A&M Health Science Center, Temple, Texas;
authors.forename: Fanyin
authors.initials: F
authors.lastname: Meng
authors.affiliation: Scott & White Healthcare, Temple, Texas;
authors.forename: Laura
authors.initials: L
authors.lastname: Hargrove
authors.affiliation: Scott & White Healthcare, Temple, Texas;
authors.forename: Lindsey
authors.initials: L
authors.lastname: Kennedy
authors.affiliation: Texas A&M Health Science Center, Temple, Texas;
authors.forename: Yuyan
authors.initials: Y
authors.lastname: Han
authors.affiliation: Scott & White Healthcare, Temple, Texas; hfrancis@sw.org hfrancis@medicine.tamhsc.edu.
authors.forename: Taylor
authors.initials: T
authors.lastname: Francis
authors.affiliation: Scott & White Healthcare, Temple, Texas;
authors.forename: Kyle
authors.initials: K
authors.lastname: Hodges
authors.affiliation: Yamagata University, Department of Gastroenterology, Yamagata, Japan; and CREST, Japan Science and Technology Corporation, Tokyo, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Ueno
authors.affiliation: Scott & White Healthcare, Temple, Texas;
authors.forename: Quy
authors.initials: Q
authors.lastname: Nguyen
authors.affiliation: Scott & White Healthcare, Temple, Texas;
authors.forename: John F
authors.initials: JF
authors.lastname: Greene
authors.affiliation: Central Texas Veterans Health Care System, Temple, Texas; Scott & White Healthcare, Temple, Texas; Texas A&M Health Science Center, Temple, Texas;
authors.forename: Heather
authors.initials: H
authors.lastname: Francis
mesh_terms: D000818:Animals; D001652:Bile Ducts / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D049109:Cell Proliferation; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D015536:Down-Regulation; D004847:Epithelial Cells / Q000378:metabolism / Q000502:physiology; D017353:Gene Deletion; D006632:Histamine / Q000097:blood / Q000378:metabolism; D006640:Histidine Decarboxylase / Q000235:genetics / Q000378:metabolism*; D006965:Hyperplasia / Q000201:enzymology / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D020935:MAP Kinase Signaling System; D051379:Mice; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
chemical_list: D042461:Vascular Endothelial Growth Factor A; D006632:Histamine; D017868:Cyclic AMP-Dependent Protein Kinases; D006640:Histidine Decarboxylase
keywords: BDL; HDC knockout; cholangiocyte; histamine; proliferation