[Tetramethylpyrazine inhibits neovascularization in oxygen-induced retinopathy based on microglial polarization]

Neovascular eye diseases are a major cause of blindness, primarily proliferative diabetic retinopathy and retinopathy of prematurity, and the latter is the leading cause of blindness due to neovascular eye diseases in children. Laser ablation and intravitreal anti-vascular endothelial growth factor(VEGF) injections are currently effective treatments for retinal neovascularization, but they have certain limitations. In some patients, escape from VEGF signaling may occur, presenting as secondary drug resistance or non-response to therapy, so searching for new therapeutic strategies is necessary. This study aimed to investigate the effects of tetramethylpyrazine(TMP) on retinal neovascularization based on microglial polarization and to explore its mechanism of action. In this experiment, a mouse model of oxygen-induced retinopathy(OIR) was used. From postnatal day 12 to postnatal day 16, TMP was administered via intraperitoneal injection for intervention and treatment. The model was verified through methods such as fundus fluorescein angiography and retinal flat-mount staining. The research showed that intraperitoneal injection of TMP in the OIR model reduced pathological angiogenesis and improved the area of avascular zones. TMP modulated the polarization of proinflammatory microglia to anti-inflammatory microglia. Additionally, TMP decreased the expression of the inflammatory cytokine tumor necrosis factor-α(TNF-α) in OIR retinas and reversed the expression levels of the anti-inflammatory cytokine interleukin-10(IL-10). Mechanistically, TMP downregulated the phosphorylation levels of the phosphatidylinositol 3-kinase(PI3K)/protein kinase B(AKT)/mammalian target of rapamycin(mTOR) signaling pathway, and changes in the phosphorylation level of this pathway can affect the expression of related proteins, thereby regulating the functional state of microglia and facilitating the recovery of resident microglia, accompanied by a reduction in macrophage infiltration. The results suggest that TMP has anti-angiogenic and anti-inflammatory effects in OIR mice by inhibiting the PI3K/AKT/mTOR pathway and promoting the polarization of microglia toward an anti-inflammatory phenotype. These findings suggest its therapeutic potential in treating neovascular retinal diseases.