Cardiac Late Sodium Channel Current Is a Molecular Target for the Sodium/Glucose Cotransporter 2 Inhibitor Empagliflozin

Abstract

Background: Sodium/glucose co-transporter 2 (SGLT2) inhibitors exert robust cardioprotective effects against heart failure in diabetes patients and there is intense interest to identify the underlying molecular mechanisms that afford this protection. As the induction of the late component of the cardiac sodium channel current (late-I Na ) is involved in the etiology of heart failure, we investigated whether these drugs inhibit late-I Na . Methods: Electrophysiological, in silico molecular docking, molecular, calcium imaging and whole heart perfusion techniques were employed to address this question. Results: The SGLT2 inhibitor empagliflozin reduced late-I Na in cardiomyocytes from mice with heart failure and in cardiac Nav1.5 sodium channels containing the LQT3 mutations R1623Q or ∆KPQ. Empagliflozin, dapagliflozin and canagliflozin are all potent and selective inhibitors of H 2 O 2 -induced late-I Na (IC 50s = 0.79, 0.58 and 1.26 µM respectively) with little effect on peak-I Na . In mouse cardiomyocytes, empagliflozin reduced the incidence of spontaneous calcium transients induced by the late-I Na activator veratridine in a similar manner to tetrodotoxin, ranolazine and lidocaine. The putative binding sites for empagliflozin within Nav1.5 were investigated by simulations of empagliflozin docking to a 3D homology model of human Nav1.5 and point mutagenic approaches. Our results indicate that empagliflozin binds to Nav1.5 in the same region as local anaesthetics and ranolazine. In an acute model of myocardial injury, perfusion of isolated mouse hearts with empagliflozin or tetrodotoxin prevented activation of the cardiac NLRP3 inflammasome and improved functional recovery after ischemia. Conclusions: Our results provide evidence that late-I Na may be an important molecular target in the heart for the SGLT2 inhibitors, contributing to their unexpected cardioprotective effects.

Cardioprotection by SGLT2 Inhibitors—Does It All Come Down to Na+?

“…Since late I Na is a major contributor to Na + overload in heart failure and inhibition of this current has proven to be cardioprotective in many models of cardiac disease [ 19 , 94 , 95 ], the idea of SGLT2i-mediated inhibition of this current seems appealing. Indeed, a recent study using mice with TAC (transverse aortic constriction)-induced heart failure as well as HEK293T cells transfected with Na v 1.5 channels harboring LQT3 mutations (causing increased late I Na ) showed that empagliflozin was able to significantly reduce late I Na without affecting peak I Na under the chosen experimental conditions (holding potential −120 mV, pacing frequency 1 Hz) [ 17 ]. This desirable preference for late I Na over peak I Na is shared by class Ib anti-arrhythmic drugs as well as ranolazine, but might—as for these drugs—become less pronounced under more physiological membrane potentials and at higher heart rates [ 96 , 97 ].…”

“…Applying a homology-modeling approach based on the structure of human Na v 1.4 Philippaert and colleagues developed a transmembrane model of human Na v 1.5. Molecular docking simulations and introduction of targeted mutations revealed the amino acids F1760 and W1345 in the fDIII-DIV site as putative interaction partners with SGLT2i [ 17 ]. Intriguingly, F1760 was also reported to be elementary in the binding of local anesthetics (e.g., lidocaine) [ 97 , 98 ] as well as ranolazine [ 99 ].…”

“…However, the reasons for decreased oxidative stress remain elusive as the observed downregulation of inflammatory pathways could also be secondary [ 113 ]. Of note, reduced [Na + ] i (e.g., due to decreased late I Na ) as well as inhibition of CaMKII can contribute to both reduced oxidative stress and inhibition of inflammatory pathways (e.g., by inhibition of the NLRP3 inflammasome) [ 17 ] and might thus be centrally involved in SGLT2i-mediated amelioration of diastolic dysfunction ( Figure 3 ).…”

“…Against this background it is tempting to speculate that SGLT2i, which were shown to reduce [Na + ] i as well as oxidative stress and inhibit CaMKII, also possess anti-arrhythmic effects ( Figure 3 ). Apart from its potential effects on arrhythmic triggers SGLT2i have repeatedly been shown to also positively affect the arrhythmic substrate, especially by reduction of fibrosis, which can be explained by anti-inflammatory and anti-fibrotic effects that might also be mediated by restoration of intracellular Ca 2+ and Na + homeostasis [ 17 , 142 ]. In this regard it is important to mention that CaMKII activity in the diseased heart also regulates inflammation e.g., by stimulation of NFκB with consequent expression of complement factor B within cardiomyocytes [ 143 , 144 , 145 ].…”

“…Therefore, many (pre-) clinical trials were performed to gain further mechanistic insights. Consequently, a myriad of potential mechanisms was proposed including direct cardiac effects such as inhibition of cardiac Na + /H + exchanger 1 (NHE1) [ 13 , 14 , 15 ], Ca 2+ /calmodulin-dependent protein kinase II (CaMKII) [ 10 , 16 ], and late Na + current (late I Na ) [ 17 ]. Intriguingly, these proteins are centrally involved in cardiac Na + homeostasis, which is fundamentally disrupted in heart failure [ 18 , 19 , 20 ], making it an interesting target for heart failure treatment.…”