Empagliflozin inhibits increased Na influx in HFpEF cardiomyocytes and reduces arrhythmic activity in human atrial trabeculae

Abstract

Background Heart failure with preserved ejection fraction (HFpEF) is a major health problem associated with substantial morbidity and mortality. However, the underlying pathophysiological mechanisms are poorly understood, and effective treatment strategies are scarce. Importantly, SGLT2i, which have been suggested to improve cellular Na and Ca homeostasis in HFrEF, have recently been shown to also improve clinical outcomes in patients with HFpEF. Interestingly, post-hoc analyses of clinical data suggest an involvement of anti-arrhythmic effects of SGLT2i. Purpose We tested, if isolated human atrial cardiomyocytes from patients with HFpEF exhibit an increased Na influx that is responsive to treatment with the SGLT2i empagliflozin (Empa) and if Empa has anti-arrhythmic properties in human atrial trabeculae. Methods Atrial biopsies were obtained from 101 patients undergoing elective cardiac surgery. Na influx was measured as increase in [Na]i during Na/K-ATPase inhibition in isolated cardiomyocytes loaded with the Na-sensitive fluorescence dye Asante Natrium Green–2 AM (ANG-2). Western Blot and HDAC4 pulldown assay were used to investigate NaV1.5 expression/phosphorylation as well as CaMKII expression/autophosphorylation and activity. Anti-arrhythmic effects of Empa were evaluated as the reduction in premature atrial complexes (PACs), which were induced in electrically field-stimulated (1Hz) human atrial trabeculae by superfusion with isoproterenol (100 nM) and high Ca (3.5 mM). Results Compared to patients without heart failure (NF), Na influx was almost doubled in HFpEF patients (NF vs HFpEF: 0.21±0.02 vs 0.38±0.04 mmol/L/min (N=7 vs 18); p=0.005) (Fig. 1D, E). CaMKII expression, CaMKII autophosphorylation, CaMKII activity, and CaMKII-dependent NaV1.5 phosphorylation were significantly increased in atrial biopsies of HFpEF patients, whereas NaV1.5 protein abundance remained unchanged (Fig. 1A–C). Consistent with these results, the increased Na influx was significantly reduced by treatment with the specific CaMKII inhibitor autocamtide-2 related inhibitory peptide (AIP) and the late INa inhibitor tetrodotoxin (TTX) (Fig. 1D, E). Importantly, Empa also abolished the increased Na influx in HFpEF cardiomyocytes (Fig. 1D, E). Multivariate linear regression analysis, adjusting for clinical co-variates, revealed HFpEF to be an independent predictor of cardiomyocyte Na handling. In line with Empa-mediated inhibition of Na influx, the frequency of PACs in human atrial trabeculae was significantly reduced by Empa (Fig. 1F, G). Conclusion This is the first study to demonstrate increased Na influx in human cardiomyocytes from HFpEF patients potentially by an increased CaMKII-dependent NaV1.5 phosphorylation. Excitingly, treatment with Empa decreases this Na influx in HFpEF cardiomyocytes and reduces isoproterenol-induced arrhythmic activity in human atrial trabeculae, which could contribute to the cardioprotective effects of this drug in patients with HFpEF. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Else Kröner-Fresenius-Stiftung,Deutsche Forschungsgemeinschaft

CaMKIIδ-dependent dysregulation of atrial Na+ homeostasis promotes pro-arrhythmic activity in an obstructive sleep apnea mouse model

“…Recently, we showed for the first time that intracellular Na + entry and Na + concentration are higher in the atrial myocytes of patients with HFpEF, a condition in which SDB is very common, which could contribute to atrial contractile dysfunction and arrhythmias (Trum et al, 2024). Interestingly, we also showed that patients with SDB have increased late Na + current in their remodeled atria, which could contribute to intracellular Na + overload (Lebek et al, 2022).…”

“…Indeed, direct oxidation of the ryanodine type-2 receptors (RyR2) can promote increased diastolic sarcoplasmic reticulum Ca 2+ release and subsequent arrhythmias (Huang et al, 2021). On the other hand, CaMKIIδ is a kinase central to myocardial Na + and Ca 2+ homeostasis that can also be directly oxidized at methionine-281 and -282, thereby releasing the catalytic domain leading to increased enzyme activation (Erickson et al, 2008;Lebek et al, 2023b;Lebek et al, 2024).…”

“…It is also unclear whether myocardial Na + concentration is actually affected by the altered Na + currents in SDB. Recently, we demonstrated for the first time that intracellular Na + entry and Na + concentration were higher in the atrial myocytes of patients with heart failure and preserved ejection fraction-conditions in which SDB is very common (Trum et al, 2024).…”