PKCθ‐JunB axis via upregulation of VEGFR3 expression mediates VEGFR2‐induced pathological retinal neovascularization

Abstract

Pathological retinal neovascularization is the most common cause of vision loss. PKCθ has been shown to play a role in type 2 diabetes, that is linked to retinal neovascularization. Based on these findings, in this study, we have determined the role of PKCθ in retinal neovascularization using human retinal microvascular endothelial cells (HRMVECs) and oxygen‐induced retinopathy (OIR) as models. VEGFA induced PKCθ phosphorylation in a time dependent manner in HRMVECs and down regulation of its levels attenuated VEGFA‐induced HRMVECs migration, sprouting and tube formation but not DNA synthesis. Furthermore, genetic deletion of PKCθ in C57BL/6 mice inhibited hypoxia‐induced retinal endothelial cell proliferation, tip cell formation, sprouting and neovascularization. We also observed that VEGFA induces VEGFR3 expression via PKCθ‐dependent JunB induction in the regulation of HRMVEC migration, sprouting, and tube formation in vitro and OIR‐induced retinal endothelial cell proliferation, tip cell formation, sprouting and neovascularization in vivo. In addition, PKCθ‐JunB axis modulates VEGFA‐induced VEGFR3 promoter activity and its expression downstream to VEGFR2 activation both in vitro and in vivo. Depletion of VEGFR2 or 3 levels attenuated VEGFA‐induced HRMVEC migration, sprouting and tube formation in vitro and retinal angiogenesis in vivo and it appears that these events were dependent on STAT3 activation. In addition, VEGFR3 appears to be mediating retinal neovascularization in a ligand dependent and independent manner downstream to VEGFR2 activation. Together, these observations infer that PKCθ‐dependent JunB‐mediated VEGFR3 expression targeting STAT3 activation is required for VEGFA‐VEGFR2 induced pathological retinal neovascularization.Support or Funding InformationThis work was supported by a grant EY04856 from NIH to GNR.