Mechanisms of retinal angiogenesis

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Previously we have demonstrated that Src-PLD1-PKCγ-cPLA2 signaling is involved in the modulation of retinal neovascularization. Our studies have also demonstrated that activation of Pak1-cofilin signaling axis is required for retinal neovascularization. Furthermore, we have shown that besides VEGFA, VEGFC via CREB- mediated activation of DLL4-NOTCH1 signaling plays an important role in the enhancement of HRMVEC migration, proliferation, sprouting and tube formation in vitro in a cell culture model and retinal neovascularization in vivo in an OIR model. During the course of these studies, we found that both VEGFA and hypoxia stimulate PKCθ very robustly and depletion of its levels completely blocks the migrating and sprouting capacity of HRMVECs in response to VEGFA. We have also observed that both VEGFA and hypoxia induce Flt4 expression profoundly and this response requires PKCθ-mediated JunB induction. Furthermore, both VEGFA and hypoxia triggered the induction of expression of CDC6, a regulatory component of pre-replication complex (pre-RC) and involved in loading the mini chromosome maintenance proteins (MCM2-7) onto the DNA, which plays a rate-limiting step in replication. In addition, down regulation of CDC6 levels completely abolished VEGFA-induced DNA synthesis. Based on these novel discoveries, we propose that PKCθ via enhancing EC migration and sprouting and CDC6 via enhancing EC proliferation play an integral role in the modulation retinal neovascularization. To test this central hypothesis, we will address the following four specific aims. Aim 1. To test the hypothesis that PKCθ mediates hypoxia-induced retinal neovascularization. Aim 2. To test the hypothesis that JunB mediates hypoxia-induced retinal neovascularization. Aim 3. To test the hypothesis that PKCθ-JunB signaling axis targets Flt4 induction in mediating retinal neovascularization. Aim 4. To test the hypothesis that CDC6 plays an essential role in retinal neovascularization. The results of the proposed experiments may provide novel information in regard to the molecular mechanisms underling pathological retinal neovascularization, which could lead to the development of new therapeutic compounds against this ocular disease.