title: FGL2/fibroleukin mediates hepatic reperfusion injury by induction of sinusoidal endothelial cell and hepatocyte apoptosis in mice.
abstract: OBJECTIVE
  Sinusoidal endothelial cell (SEC) and hepatocyte death are early, TNF-α mediated events in ischemia and reperfusion of the liver (I/Rp). We previously reported that TNF-α induced liver injury is dependent on Fibrinogen like protein 2 (FGL2/Fibroleukin) and showed that FGL2 binding to its receptor, FcγRIIB, results in lymphocyte apoptosis. In this study we examine whether I/Rp is induced by specific binding of FGL2 to FcγRIIB expressed on SEC.
  
  
  METHODS
  Hepatic ischemia and reperfusion was induced in wild type (WT) mice and in mice with deletion or inhibition of FGL2 and FcRIIB. Liver injury was determined by AST release, necrosis and animal death. Apoptosis was evaluated with caspase 3 and TUNEL staining.
  
  
  RESULTS
  FGL2 deletion or inhibition resulted in decreased liver injury as determined by a marked reduction in both levels of AST and ALT and hepatocyte necrosis. Caspase 3 staining of SEC (12% vs. 75%) and hepatocytes (12% vs. 45%) as well as TUNEL staining of SEC (13% vs. 60%, p=0.02) and hepatocytes (18% vs. 70%, p=0.03), markers of apoptosis, were lower in Fgl2(-/-) compared to WT mice. In vitro incubation of SEC with FGL2 induced apoptosis of SEC from WT mice, but not FcγRIIB(-/-) mice. Deletion of FcγRIIB fully protected mice against SEC and hepatocyte death in vivo. Survival of mice deficient in either Fgl2(-/-) (80%) or FcγRIIB(-/-) (100%) was markedly increased compared to WT mice (10%) which were subjected to 75min of total hepatic ischemia (p=0.001).
  
  
  CONCLUSIONS
  FGL2 binding to the FcγRIIB receptor expressed on SEC is a critical event in the initiation of the hepatic reperfusion injury cascade through induction of SEC and hepatocyte death.
authors.affiliation: Multi Organ Transplant Program, Department of Surgery, University of Toronto, Toronto General Hospital, Toronto, Canada.
authors.forename: Nazia
authors.initials: N
authors.lastname: Selzner
authors.forename: Hao
authors.initials: H
authors.lastname: Liu
authors.forename: Markus U
authors.initials: MU
authors.lastname: Boehnert
authors.forename: Oyedele A
authors.initials: OA
authors.lastname: Adeyi
authors.forename: Itay
authors.initials: I
authors.lastname: Shalev
authors.forename: Agata M
authors.initials: AM
authors.lastname: Bartczak
authors.forename: Max
authors.initials: M
authors.lastname: Xue-Zhong
authors.forename: Justin
authors.initials: J
authors.lastname: Manuel
authors.forename: Ori D
authors.initials: OD
authors.lastname: Rotstein
authors.forename: Ian D
authors.initials: ID
authors.lastname: McGilvray
authors.forename: David R
authors.initials: DR
authors.lastname: Grant
authors.forename: Melville J
authors.initials: MJ
authors.lastname: Phillips
authors.forename: Gary A
authors.initials: GA
authors.lastname: Levy
authors.forename: Markus
authors.initials: M
authors.lastname: Selzner
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D042783:Endothelial Cells / Q000473:pathology / Q000502:physiology; D005340:Fibrinogen / Q000235:genetics / Q000502:physiology*; D022781:Hepatocytes / Q000473:pathology; D008099:Liver / Q000293:injuries* / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017452:Receptors, IgG / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D015427:Reperfusion Injury / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology
chemical_list: C490637:Fgl2 protein, mouse; D017452:Receptors, IgG; D005340:Fibrinogen