title: Toll-like receptor 2-blocking antibodies promote angiogenesis and induce ERK1/2 and AKT signaling via CXCR4 in endothelial cells.
abstract: OBJECTIVE
  Toll-like receptor 2 (TLR2) inhibition by function blocking antibodies (ABs) is associated with enhanced preservation of endothelial cell function during vascular disease. In the present study, we investigated the capacity of TLR2-blocking ABs to modulate the angiogenic response of endothelial cells in vitro and in vivo.
  
  
  RESULTS
  Incubation of endothelial cells with mono- or polyclonal anti-TLR2 ABs resulted in increased tube formation, sprouting, and migration of endothelial cells compared with controls. In a mouse model of hindlimb ischemia, using TLR2-deficient or anti-TLR2 AB-treated wild-type mice resulted in increased new capillary formation and enhanced reperfusion. The effects of anti-TLR2 ABs were similar to those exerted by stromal cell-derived factor-1, and we show that anti-TLR2 ABs yet not TLR2 ligands lead to comparable activation of extracellular signal-regulated kinase1/2 and AKT but not p38 mitogen-activated protein kinase as activation of the CXCR4 canonical signal transduction pathways by stromal cell-derived factor-1. Immunoprecipitation of TLR2 revealed that anti-TLR2 ABs initiate an association of TLR2 with CXCR4 and mitogen-activated protein kinase activation. The proangiogenic properties of anti-TLR2 ABs were abolished by both G-protein inhibition and CXCR4 knockdown in endothelial cells.
  
  
  CONCLUSIONS
  Our results provide evidence for a proangiogenic effect of TLR2-blocking ABs on endothelial cells in vitro and in vivo. They identify a novel molecular mechanism linking TLR2 to angiogenic processes that is independent from the activation of inflammatory cascades and further support the concept of a beneficial effect of TLR2 inhibition for endothelial cell function in vascular disease.
authors.affiliation: Clinic for Anesthesiology and Critical Care Medicine, University Hospital Rostock, Rostock, Germany. nana-maria.wagner@med.uni-rostock.de
authors.forename: Nana-Maria
authors.initials: NM
authors.lastname: Wagner
authors.forename: Laura
authors.initials: L
authors.lastname: Bierhansl
authors.forename: Gabriele
authors.initials: G
authors.lastname: Nöldge-Schomburg
authors.forename: Brigitte
authors.initials: B
authors.lastname: Vollmar
authors.forename: Jan Patrick
authors.initials: JP
authors.lastname: Roesner
mesh_terms: D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology*; D002478:Cells, Cultured; D054377:Chemokine CXCL12 / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D006614:Hindlimb / Q000098:blood supply; D007511:Ischemia / Q000276:immunology / Q000378:metabolism / Q000503:physiopathology; D020935:MAP Kinase Signaling System / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D018482:Muscle, Skeletal / Q000098:blood supply; D018919:Neovascularization, Physiologic / Q000276:immunology*; D058729:Peripheral Arterial Disease / Q000276:immunology* / Q000378:metabolism / Q000503:physiopathology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D019718:Receptors, CXCR4 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D019138:Antibodies, Blocking; C514936:CXCR4 protein, mouse; D054377:Chemokine CXCL12; D034741:RNA, Small Interfering; D019718:Receptors, CXCR4; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; C514862:Akt1 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases
keywords: CXCR4 receptor; Toll-like receptor 2; angiogenesis inducing agents; inflammation; physiological neovascularization