Homoplantaginin alleviates high glucose-induced vascular endothelial senescence by inhibiting mtDNA-cGAS-STING pathway via blunting DRP1-mitochondrial fission-VDAC1 axis

Vascular endothelial senescence is a major risk factor for diabetic vascular complications. Abnormal mitochondrial fission by dynamically related protein 1 (DRP1) accelerates vascular endothelial cell senescence. Homoplantaginin (Hom) is a flavonoid in Salvia plebeia R. Br. with protecting mitochondrial and repairing vascular properties. However, the relevant mechanism of Hom against diabetic vascular endothelial cell senescence remains unclear. Here, we used db/db mice and high glucose (HG)-treated human umbilical vein endothelial cells (HUVECs) to assess the anti-vascular endothelial cell senescence of Hom. We found that Hom inhibited senescence-associated beta-galactosidase activity, decreased the levels of senescence markers, and senescence-associated secretory phenotype factors. Additionally, Hom inhibited the expression of cGAS-STING pathway and downstream inflammatory factors. STING inhibitor H-151 delayed endothelial senescence, whereas STING overexpression attenuated the anti-endothelial senescence effect of Hom. Furthermore, we observed that Hom reduced mitochondrial fragmentation and inhibited abnormal mitochondrial fission using transmission electron microscopy. Importantly, Hom has a stronger effect on mitochondrial fission protein than mitochondrial fusion protein, especially downregulated the expression of DRP1. DRP1 inhibitor Mdivi-1 suppressed cGAS-STING pathway and vascular endothelial senescence, yet DRP1 agonist FCCP attenuated the effect of Hom. Surprisingly, Hom blunted abnormal mitochondrial fission mediated by DRP1 mitochondrial localization, suppressed interaction of DRP1 with VDAC1 and prevented VDAC1 oligomerization, which was necessary for mtDNA escape and subsequent cGAS-STING pathway activation. These results revealed a previously unrecognized mechanism that Hom alleviated vascular endothelial senescence by inhibited mtDNA-cGAS-STING signaling pathway via blunting DRP1-mitochondrial fission-VDAC1 axis.