title: Wound healing is impaired in MyD88-deficient mice: a role for MyD88 in the regulation of wound healing by adenosine A2A receptors.
abstract: Synergy between Toll-like receptor (TLR) and adenosine A2A receptor (A2AR) signaling switches macrophages from production of inflammatory cytokines such as tumor necrosis factor-alpha to production of the angiogenic growth factor vascular endothelial growth factor (VEGF). We show in this study that this switch critically requires signaling through MyD88, IRAK4, and TRAF6. Macrophages from mice lacking MyD88 (MyD88(-/-)) or IRAK4 (IRAK4(-/-)) lacked responsiveness to TLR agonists and did not respond to A2AR agonists by expressing VEGF. Suppression of TRAF6 expression with siRNA in RAW264.7 macrophages also blocked their response to TLR and A2AR agonists. Excisional skin wounds in MyD88(-/-) mice healed at a markedly slower rate than wounds in wild-type MyD88(+/+) mice, showing delayed contraction, decreased and delayed granulation tissue formation, and reduced new blood vessel density. Although macrophages accumulated to higher levels in MyD88(-/-) wounds than in controls, expression of VEGF and HIF1-alpha mRNAs was elevated in MyD88(+/+) wounds. CGS21680, an A2AR agonist, promoted repair in MyD88(+/+) wounds and stimulated angiogenesis but had no significant effect on healing of MyD88(-/-) wounds. These results suggest that the synergistic interaction between TLR and A(2A)R signaling observed in vitro that switches macrophages from an inflammatory to an angiogenic phenotype also plays a role in wound healing in vivo.
authors.affiliation: Department of Cell Biology and Molecular Medicine, The Cardiovascular Research Institute, New Jersey Medical School, UMDNJ, 185 South Orange Ave., Newark, NJ 07103, USA.
authors.forename: Lisa
authors.initials: L
authors.lastname: Macedo
authors.forename: Grace
authors.initials: G
authors.lastname: Pinhal-Enfield
authors.forename: Vera
authors.initials: V
authors.lastname: Alshits
authors.forename: Genie
authors.initials: G
authors.lastname: Elson
authors.forename: Bruce Neil
authors.initials: BN
authors.lastname: Cronstein
authors.forename: Samuel Joseph
authors.initials: SJ
authors.lastname: Leibovich
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D058908:Adenosine A2 Receptor Agonists; D000818:Animals; D002460:Cell Line; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics; D008264:Macrophages / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000502:physiology*; D018919:Neovascularization, Physiologic / Q000235:genetics / Q000276:immunology*; D010627:Phenethylamines / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D043705:Receptor, Adenosine A2A / Q000378:metabolism*; D048029:TNF Receptor-Associated Factor 6 / Q000037:antagonists & inhibitors / Q000235:genetics; D051193:Toll-Like Receptors / Q000378:metabolism; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism; D014945:Wound Healing / Q000235:genetics / Q000276:immunology*
chemical_list: D058908:Adenosine A2 Receptor Agonists; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D053594:Myeloid Differentiation Factor 88; D010627:Phenethylamines; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D043705:Receptor, Adenosine A2A; D048029:TNF Receptor-Associated Factor 6; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D042461:Vascular Endothelial Growth Factor A; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D053592:Interleukin-1 Receptor-Associated Kinases; C507774:Irak4 protein, mouse; D000241:Adenosine