Divergent mechanisms, unified therapy: saracatinib targets Src/HIF signaling in endothelial and microglial cells to treat retinopathy

Retinal neovascularization (RNV) causes severe visual impairment in neovascular ocular disorders. This study investigated the therapeutic potential and mechanism of saracatinib, a Src kinase inhibitor, in suppressing RNV. Intravitreal saracatinib was administered to oxygen-induced retinopathy (OIR) mice. Retinal tissues were evaluated via immunofluorescence, Real-time quantitative polymerase chain reaction, and Western blotting. In vitro, hypoxic models of human retinal microvascular endothelial cells (HRMECs) and BV2 microglial cells were established to mimic the hypoxic microenvironment of retinopathy. Cell functions were assessed by migration, tube formation, and inflammatory cytokine assays, with molecular analyses of Src-HIF signaling. In the OIR model, saracatinib markedly suppressed subretinal neovascular growth and enhanced retinal perfusion. In endothelial cells (ECs), saracatinib attenuated migration and tube formation, accompanied by downregulation of pro-angiogenic and chemotactic mediators such as VEGFA and MCP-1. In microglial cells, hypoxia-induced inflammatory cytokine expression, including TNF-α and IL-1β, was reduced by saracatinib. Mechanistic analyses further indicated that these protective actions were tightly linked to regulation of the Src-hypoxia-inducible factor (HIF) signaling cascade: in ECs, saracatinib decreased Src phosphorylation, thereby restraining nuclear translocation and protein expression of HIF-1α, along with suppression of HIF-2α. Similarly, in microglia, saracatinib inhibited Src activation and diminished both nuclear translocation and expression of HIF-1α and HIF-2α. Saracatinib mitigates RNV via cell-specific regulation of the Src-HIF axis: targeting HIF-1α in ECs to inhibit angiogenesis and HIF-1α/HIF-2α in microglia to alleviate inflammation. It addresses inflammation-angiogenesis crosstalk, offering a promising alternative or adjunct to anti-VEGF therapies.