title: Loss of interleukin-21 receptor activation in hypoxic endothelial cells impairs perfusion recovery after hindlimb ischemia.
abstract: OBJECTIVE
  Surgical hindlimb ischemia (HLI) in mice has become a valuable preclinical model to study peripheral arterial disease. We previously identified that the different phenotypic outcomes after HLI across inbred mouse strains is related to a region on the short arm of mouse chromosome 7. The gene coding the interleukin-21 receptor (IL-21R) lies at the peak of association in this region.
  
  
  RESULTS
  With quantitative real-time polymerase chain reaction, we found that a mouse strain with a greater ability to upregulate IL-21R after HLI had better perfusion recovery than a strain with no upregulation after HLI. Immunofluorescent staining of ischemic hindlimb tissue showed IL-21R expression on endothelial cells (ECs) from C57BL/6 mice. An EC-enriched fraction isolated from ischemic hindlimb muscle showed higher Il-21R levels than an EC-enriched fraction from nonischemic limbs. In vitro, human umbilical vein ECs showed elevated IL-21R expression after hypoxia and serum starvation. Under these conditions, IL-21 treatment increased cell viability, decreased cell apoptosis, and augmented tube formation. In vivo, either knockout Il21r or blocking IL-21 signaling by treating with IL-21R-Fc (fusion protein that blocks IL-21 binding to its receptor) in C57BL/6 mice resulted in less perfusion recovery after HLI. Both in vitro and in vivo modulation of the IL-21/IL-21R axis under hypoxic conditions resulted in increased signal transducer and activator of transcription 3 phosphorylation and a subsequent increase in the B-cell lymphoma leukemia-2/BCL-2-associated X protein ratio.
  
  
  CONCLUSIONS
  Our data indicate that IL-21R upregulation and ligand activation in hypoxic ECs may help perfusion recovery by limiting/preventing apoptosis and favoring cell survival and angiogenesis through the signal transducer and activator of transcription 3 pathway.
authors.affiliation: From the Robert M. Berne Cardiovascular Research Center (T.W., A.C., A.O.D., S.H., K.H., L.C., R.J.L., B.H.A.) and Division of Cardiovascular Medicine, Department of Medicine (S.H., B.H.A.), University of Virginia, Charlottesville; and Laboratory of Molecular Immunology and the Immunology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD (R.S., W.J.L.).
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.affiliation: From the Robert M. Berne Cardiovascular Research Center (T.W., A.C., A.O.D., S.H., K.H., L.C., R.J.L., B.H.A.) and Division of Cardiovascular Medicine, Department of Medicine (S.H., B.H.A.), University of Virginia, Charlottesville; and Laboratory of Molecular Immunology and the Immunology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD (R.S., W.J.L.).
authors.forename: Alexis
authors.initials: A
authors.lastname: Cunningham
authors.affiliation: From the Robert M. Berne Cardiovascular Research Center (T.W., A.C., A.O.D., S.H., K.H., L.C., R.J.L., B.H.A.) and Division of Cardiovascular Medicine, Department of Medicine (S.H., B.H.A.), University of Virginia, Charlottesville; and Laboratory of Molecular Immunology and the Immunology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD (R.S., W.J.L.).
authors.forename: Ayotunde O
authors.initials: AO
authors.lastname: Dokun
authors.affiliation: From the Robert M. Berne Cardiovascular Research Center (T.W., A.C., A.O.D., S.H., K.H., L.C., R.J.L., B.H.A.) and Division of Cardiovascular Medicine, Department of Medicine (S.H., B.H.A.), University of Virginia, Charlottesville; and Laboratory of Molecular Immunology and the Immunology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD (R.S., W.J.L.).
authors.forename: Surovi
authors.initials: S
authors.lastname: Hazarika
authors.affiliation: From the Robert M. Berne Cardiovascular Research Center (T.W., A.C., A.O.D., S.H., K.H., L.C., R.J.L., B.H.A.) and Division of Cardiovascular Medicine, Department of Medicine (S.H., B.H.A.), University of Virginia, Charlottesville; and Laboratory of Molecular Immunology and the Immunology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD (R.S., W.J.L.).
authors.forename: Kevin
authors.initials: K
authors.lastname: Houston
authors.affiliation: From the Robert M. Berne Cardiovascular Research Center (T.W., A.C., A.O.D., S.H., K.H., L.C., R.J.L., B.H.A.) and Division of Cardiovascular Medicine, Department of Medicine (S.H., B.H.A.), University of Virginia, Charlottesville; and Laboratory of Molecular Immunology and the Immunology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD (R.S., W.J.L.).
authors.forename: Lingdan
authors.initials: L
authors.lastname: Chen
authors.affiliation: From the Robert M. Berne Cardiovascular Research Center (T.W., A.C., A.O.D., S.H., K.H., L.C., R.J.L., B.H.A.) and Division of Cardiovascular Medicine, Department of Medicine (S.H., B.H.A.), University of Virginia, Charlottesville; and Laboratory of Molecular Immunology and the Immunology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD (R.S., W.J.L.).
authors.forename: R John
authors.initials: RJ
authors.lastname: Lye
authors.affiliation: From the Robert M. Berne Cardiovascular Research Center (T.W., A.C., A.O.D., S.H., K.H., L.C., R.J.L., B.H.A.) and Division of Cardiovascular Medicine, Department of Medicine (S.H., B.H.A.), University of Virginia, Charlottesville; and Laboratory of Molecular Immunology and the Immunology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD (R.S., W.J.L.).
authors.forename: Rosanne
authors.initials: R
authors.lastname: Spolski
authors.affiliation: From the Robert M. Berne Cardiovascular Research Center (T.W., A.C., A.O.D., S.H., K.H., L.C., R.J.L., B.H.A.) and Division of Cardiovascular Medicine, Department of Medicine (S.H., B.H.A.), University of Virginia, Charlottesville; and Laboratory of Molecular Immunology and the Immunology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD (R.S., W.J.L.).
authors.forename: Warren J
authors.initials: WJ
authors.lastname: Leonard
authors.affiliation: From the Robert M. Berne Cardiovascular Research Center (T.W., A.C., A.O.D., S.H., K.H., L.C., R.J.L., B.H.A.) and Division of Cardiovascular Medicine, Department of Medicine (S.H., B.H.A.), University of Virginia, Charlottesville; and Laboratory of Molecular Immunology and the Immunology Center, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD (R.S., W.J.L.). annex@virginia.edu.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Annex
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics; D015687:Cell Hypoxia / Q000502:physiology; D002470:Cell Survival / Q000235:genetics; D002478:Cells, Cultured; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D005786:Gene Expression Regulation; D006614:Hindlimb / Q000098:blood supply*; D007511:Ischemia / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000032:analysis; D011897:Random Allocation; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D053655:Receptors, Interleukin-21 / Q000235:genetics*; D020127:Recovery of Function; D015424:Reperfusion; D015398:Signal Transduction; D015854:Up-Regulation
chemical_list: D012333:RNA, Messenger; D053655:Receptors, Interleukin-21
keywords: peripheral arterial diseases; receptors, interleukin 21
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