title: P2Y2 purinergic receptor activation is essential for efficient hepatocyte proliferation in response to partial hepatectomy.
abstract: Extracellular nucleotides via activation of P2 purinergic receptors influence hepatocyte proliferation and liver regeneration in response to 70% partial hepatectomy (PH). Adult hepatocytes express multiple P2Y (G protein-coupled) and P2X (ligand-gated ion channels) purinergic receptor subtypes. However, the identity of key receptor subtype(s) important for efficient hepatocyte proliferation in regenerating livers remains unknown. To evaluate the impact of P2Y2 purinergic receptor-mediated signaling on hepatocyte proliferation in regenerating livers, wild-type (WT) and P2Y2 purinergic receptor knockout (P2Y2-/-) mice were subjected to 70% PH. Liver tissues were analyzed for activation of early events critical for hepatocyte priming and subsequent cell cycle progression. Our findings suggest that early activation of p42/44 ERK MAPK (5 min), early growth response-1 (Egr-1) and activator protein-1 (AP-1) DNA-binding activity (30 min), and subsequent hepatocyte proliferation (24-72 h) in response to 70% PH were impaired in P2Y2-/- mice. Interestingly, early induction of cytokines (TNF-α, IL-6) and cytokine-mediated signaling (NF-κB, STAT-3) were intact in P2Y2-/- remnant livers, uncovering the importance of cytokine-independent and nucleotide-dependent early priming events critical for subsequent hepatocyte proliferation in regenerating livers. Hepatocytes isolated from the WT and P2Y2-/- mice were treated with ATP or ATPγS for 5-120 min and 12-24 h. Extracellular ATP alone, via activation of P2Y2 purinergic receptors, was sufficient to induce ERK phosphorylation, Egr-1 protein expression, and key cyclins and cell cycle progression of hepatocytes in vitro. Collectively, these findings highlight the functional significance of P2Y2 purinergic receptor activation for efficient hepatocyte priming and proliferation in response to PH.
authors.affiliation: Department of Pediatrics, Division of Gastroenterology, Hepatology and Nutrition, Texas Children's Liver Center, Houston, Texas; Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, Texas;
authors.forename: Bryan C
authors.initials: BC
authors.lastname: Tackett
authors.affiliation: Department of Pediatrics, Division of Gastroenterology, Hepatology and Nutrition, Texas Children's Liver Center, Houston, Texas;
authors.forename: Hongdan
authors.initials: H
authors.lastname: Sun
authors.affiliation: Department of Pediatrics, Division of Gastroenterology, Hepatology and Nutrition, Texas Children's Liver Center, Houston, Texas;
authors.forename: Yu
authors.initials: Y
authors.lastname: Mei
authors.affiliation: Department of Pediatrics, Division of Gastroenterology, Hepatology and Nutrition, Texas Children's Liver Center, Houston, Texas; Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, Texas;
authors.forename: Janielle P
authors.initials: JP
authors.lastname: Maynard
authors.affiliation: Department of Pediatrics, Division of Gastroenterology, Hepatology and Nutrition, Texas Children's Liver Center, Houston, Texas;
authors.forename: Sayuri
authors.initials: S
authors.lastname: Cheruvu
authors.affiliation: Department of Pediatrics, Division of Gastroenterology, Hepatology and Nutrition, Texas Children's Liver Center, Houston, Texas;
authors.forename: Arunmani
authors.initials: A
authors.lastname: Mani
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas; and.
authors.forename: Andres
authors.initials: A
authors.lastname: Hernandez-Garcia
authors.affiliation: Department of Diagnostic Sciences, University of Texas Dental Branch in Houston, Houston, Texas.
authors.forename: Nadarajah
authors.initials: N
authors.lastname: Vigneswaran
authors.affiliation: Department of Pediatrics, Division of Gastroenterology, Hepatology and Nutrition, Texas Children's Liver Center, Houston, Texas; Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, Texas;
authors.forename: Saul J
authors.initials: SJ
authors.lastname: Karpen
authors.affiliation: Department of Pediatrics, Division of Gastroenterology, Hepatology and Nutrition, Texas Children's Liver Center, Houston, Texas; Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, Texas; sundarat@bcm.edu.
authors.forename: Sundararajah
authors.initials: S
authors.lastname: Thevananther
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D016213:Cyclins / Q000494:pharmacology; D051766:Early Growth Response Protein 1 / Q000096:biosynthesis / Q000235:genetics; D006498:Hepatectomy; D022781:Hepatocytes / Q000187:drug effects*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D058912:Purinergic P2Y Receptor Agonists / Q000494:pharmacology*; D058473:Receptors, Purinergic P2Y2 / Q000187:drug effects* / Q000235:genetics
chemical_list: D016213:Cyclins; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D058912:Purinergic P2Y Receptor Agonists; D058473:Receptors, Purinergic P2Y2; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate
keywords: P2Y2 purinergic receptors; extracellular ATP; hepatocyte proliferation; liver regeneration; partial hepatectomy