Figure.

Late I_Na inhibition by empagliflozin requires CaMKII. A, Original recordings and mean data of empagliflozin- or AiP-mediated inhibition of late I_Na in human ventricular cardiomyocytes from patients with AS (n=patients). B, Original recordings and mean data of late sodium current (late I_Na) in murine cardiomyocytes from wild-type (WT) or CaMKIIδ^-/- mice (n=cells per mice). The ATX-dependent enhancement of late I_Na could not be blocked by empagliflozin. C, In contrast, the H₂O₂-dependent stimulation of late I_Na was blocked by CaMKII inhibition (AiP, CaMKII^−/−), by transgenic inhibition of CaMKII-dependent Na_V1.5 phosphorylation (S571A), or in the presence of empagliflozin. D, In contrast with local anesthetic lidocaine, neither empagliflozin nor AiP could block enhanced late I_Na in mice with phosphomimetic substitution of glutamic acid for serine at 571 (S571E). E and F, Western blots of cardiomyocytes on empagliflozin show reduced CaMKII-autophosphorylation (T287) and reduced CaMKII-dependent Na_V1.5 phosphorylation. For comparison of multiple groups, mixed-effects analysis plus Holm-Sidak (A) or linear mixed model plus Sidak were performed. For comparison of 2 groups, paired t test was done (F). A indicates ampere; AIP, autocamtide-2-related inhibitory peptide; AS, aortic stenosis; ATX II or ATX, Anemonia viridis toxin 2; CaMKII, Ca/calmodulin-dependent kinase II; CaMKIIdelta-/-, CaMKII delta knock out δ; E, Empa; Empa, empagliflozin; F, farad; GAPDH, Glyceraldehyde 3-phosphate dehydrogenase; HF, heart failure; kDa= kilo Dalton; ms, miliseconds; p, phosphorylated; pA, picoampere; S571A and S571E: Nav1.5 with a phosphomimetic mutation at Ser571 (S571E), or Nav1.5 with the phosphorylation site ablated (S571A); V, vehicle; and WT, wildtype.