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.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.