Empagliflozin Ameliorates Ouabain-Induced Na+ and Ca2+ Dysregulations in Ventricular Myocytes in an Na+-Dependent Manner

Purpose Sodium-glucose cotransporter 2 (SGLT2) inhibitors are a novel class of glucose-lowering agents that have improved clinical outcomes in patients with heart failure; however, their therapeutic mechanisms remain elusive. Although contradictory results have been reported, it has been proposed that improving Na + homeostasis may be the underlying mechanism of action of SGLT2 inhibitors in heart failure treatment. This study explored whether empagliflozin ameliorates Na + and Ca 2+ handling disorders induced by ouabain in an Na + -dependent manner. Methods Isolated ventricular myocytes of mice were incubated with ouabain to establish a cellular model of Na + overload. Effects of empagliflozin on Na + and Ca 2+ handling were evaluated using an ionOptix system and a confocal microscope. Distinct cytosolic Na + levels were established by incubating different ouabain concentrations (10, 50, and 100 μmol/L). Results In the absence of ouabain, 1 μmol/L empagliflozin had a negligible impact on Na + and Ca 2+ handling in ventricular myocytes. Ouabain (50 μmol/L) significantly enhanced cytosolic Na + levels and dysregulated Ca 2+ handling, including an increased Ca 2+ transient amplitude, elevated Ca 2+ content in the sarcoplasmic reticulum, and enhanced spontaneous Ca 2+ release normalized by treatment with 1 μmol/L empagliflozin within 10 min. All Na + and Ca 2+ handling abnormalities induced by ouabain were reversed by 1 μmol/L empagliflozin. The efficacy of empagliflozin was more potent at higher cytosolic Na + levels. Pretreatment with the Na + /H + exchanger (NHE) inhibitor (1 μmol/L cariporide) abolished the effects of empagliflozin. Conclusion Empagliflozin ameliorates ouabain-induced Na + and Ca 2+ handling disorders in a cytosolic Na + -dependent manner, potentially by inhibiting the NHE.