NSC23766 effectively inhibited retinal neovascularization by disrupting the positive feedback loop between Rac1 and VEGFR2.

Retinal neovascularization (RNV) is a leading cause of blindness. Although anti-VEGF therapy remains the first-line treatment for RNV, a subset of patients exhibits poor or no response to anti-VEGF agents. Therefore, exploring alternative therapeutic strategies is imperative. Rac1, a small GTPase, has been reported to regulate angiogenesis through multiple signaling pathways. Nevertheless, the precise role of Rac1 in RNV progression remains unclear. Our study demonstrates that NSC23766, a Rac1 activation inhibitor, effectively attenuates VEGF-induced angiogenic responses in human retinal microvascular endothelial cells (HRMECs), including proliferation, migration, invasion, and tube formation. Furthermore, phalloidin staining revealed that NSC23766 significantly inhibits VEGF-induced cytoskeleton rearrangement in HRMECs while modulating phosphorylation levels of LIMK and cofilin. Western blot analysis reveals that VEGF-induced VEGFR2 phosphorylation activates Rac1 in a time-dependent manner. Further investigation demonstrates that NSC23766 suppresses VEGFR2 phosphorylation by blocking Rac1 activation. Based on these findings, we propose the existence of a positive feedback loop between Rac1 and VEGFR2. Notably, in an oxygen-induced retinopathy (OIR) mouse model, intravitreal injection of NSC23766 significantly attenuated RNV progression. Therefore, our findings suggest that NSC23766 is a potential therapeutic strategy for RNV by disrupting the positive feedback loop between Rac1 and VEGFR2.