Empagliflozin attenuates cardiac microvascular ischemia/reperfusion injury through improving mitochondrial homeostasis

Abstract Background Empagliflozin has been reported to protect endothelial cell function, regardless of diabetes status. However, the role of empagliflozin in microvascular protection during myocardial ischemia reperfusion injury (I/R) has not been fully understood. Methods Electron microscopy, western blots, immunofluorescence, qPCR, mutant plasmid transfection, co-immunoprecipitation were employed to explore whether empagliflozin could alleviate microvascular damage and endothelial injury during cardiac I/R injury. Results In mice, empagliflozin attenuated I/R injury-induced microvascular occlusion and microthrombus formation. In human coronary artery endothelial cells, I/R injury led to adhesive factor upregulation, endothelial nitric oxide synthase inactivation, focal adhesion kinase downregulation, barrier dysfunction, cytoskeletal degradation and cellular apoptosis; however, empagliflozin treatment diminished these effects. Empagliflozin improved mitochondrial oxidative stress, mitochondrial respiration and adenosine triphosphate metabolism in I/R-treated human coronary artery endothelial cells by preventing the phosphorylation of dynamin-related protein 1 (Drp1) and mitochondrial fission 1 protein (Fis1), thus repressing mitochondrial fission. The protective effects of empagliflozin on mitochondrial homeostasis and endothelial function were abrogated by the re-introduction of phosphorylated Fis1, but not phosphorylated Drp1, suggesting that Fis1 dephosphorylation is the predominant mechanism whereby empagliflozin inhibits mitochondrial fission during I/R injury. Besides, I/R injury induced Fis1 phosphorylation primarily by activating the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) pathway, while empagliflozin inactivated this pathway by exerting anti-oxidative effects. Conclusions These results demonstrated that empagliflozin can protect the microvasculature by inhibiting the DNA-PKcs/Fis1/mitochondrial fission pathway during myocardial I/R injury.