Both Kdr and Flt1 play a vital role in hypoxia‐induced Src‐PLD1‐PKCγ‐cPLA2 activation and retinal neovascularization

Abstract

Previously we have reported that Src‐PLD1‐PKCγ‐cPLA2 signaling plays a role in hypoxia induced retinal neovascularization. In the present study we explored the upstream mechanisms of Src‐PLD1‐PKCγ‐cPLA2 activation and retinal neovascularization. VEGFA, while having no effect on Flt1 phosphorylation, induced Kdr phosphorylation in human retinal microvascular endothelial cells (HRMVECs). Depletion of either Kdr or Flt1 attenuated VEGFA‐induced Src‐PLD1‐PKCγ‐cPLA2 activation, DNA synthesis, migration, and tube formation, albeit more robustly with Kdr downregulation. Hypoxia induced tyrosine phosphorylation of Kdr and Flt1 in mouse retina and depletion of Kdr or Flt1 blocked hypoxia‐induced Src‐PLD1‐PKCγ‐cPLA2 activation and retinal neovascularization. Hypoxia induced VEGFA and VEGFB expression in retina, and inhibition of their expression blocked hypoxia‐induced Kdr and Flt1 phosphorylation, respectively. Furthermore, depletion of VEGFA or VEGFB attenuated hypoxia‐induced Src‐PLD1‐PKCγ‐cPLA2 activation and retinal neovascularization. These findings suggest that both VEGFA and VEGFB mediate hypoxia‐induced Src‐PLD1‐PKCγ‐cPLA2 activation and retinal neovascularization via activation of Kdr and Flt1, respectively. Suported by EY014856, National Eye Institute/NIH