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Fibroblast growth factor homologous factors serve as a molecular rheostat in tuning arrhythmogenic cardiac late sodium current.

ABSTRACT: Voltage-gated sodium (Nav1.5) channels support the genesis and brisk spatial propagation of action potentials in the heart. Disruption of Na_V1.5 inactivation results in a small persistent Na influx known as late Na current (I _Na,L), which has emerged as a common pathogenic mechanism in both congenital and acquired cardiac arrhythmogenic syndromes. Here, using low-noise multi-channel recordings in heterologous systems, LQTS3 patient-derived iPSCs cardiomyocytes, and mouse ventricular myocytes, we demonstrate that the intracellular fibroblast growth factor homologous factors (FHF1-4) tune pathogenic I _Na,L in an isoform-specific manner. This scheme suggests a complex orchestration of I _Na,L in cardiomyocytes that may contribute to variable disease expressivity of Na_V1.5 channelopathies. We further leverage these observations to engineer a peptide-inhibitor of I _Na,L with a higher efficacy as compared to a well-established small-molecule inhibitor. Overall, these findings lend insights into molecular mechanisms underlying FHF regulation of I _Na,L in pathophysiology and outline potential therapeutic avenues.

SUBMITTER: Chakouri N

PROVIDER: S-EPMC9161660 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Fibroblast growth factor homologous factors serve as a molecular rheostat in tuning arrhythmogenic cardiac late sodium current.

Chakouri Nourdine N Rivas Sharen S Roybal Daniel D Yang Lin L Diaz Johanna J Hsu Allen A Mahling Ryan R Chen Bi-Xing BX Owoyemi Josiah O JO DiSilvestre Deborah D Sirabella Dario D Corneo Barbara B Tomaselli Gordon F GF Dick Ivy E IE Marx Steven O SO Ben-Johny Manu M

Nature cardiovascular research 20220516 5

Voltage-gated sodium (Nav1.5) channels support the genesis and brisk spatial propagation of action potentials in the heart. Disruption of NaV1.5 inactivation results in a small persistent Na influx known as late Na current (I Na,L), which has emerged as a common pathogenic mechanism in both congenital and acquired cardiac arrhythmogenic syndromes. Here, using low-noise multi-channel recordings in heterologous systems, LQTS3 patient-derived iPSCs cardiomyocytes, and m ...[more]

PMID: 35662881

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Project description:Heart failure constitutes a major public health problem worldwide. The electrophysiological remodeling of failing hearts sets the stage for malignant arrhythmias, in which the role of the late Na(+) current (I(NaL)) is relevant and is currently under investigation. In this study we examined the role of I(NaL) in the electrophysiological phenotype of ventricular myocytes, and its proarrhythmic effects in the failing heart. A model for cellular heart failure was proposed using a modified version of Grandi et al. model for human ventricular action potential that incorporates the formulation of I(NaL). A sensitivity analysis of the model was performed and simulations of the pathological electrical activity of the cell were conducted. The proposed model for the human I(NaL) and the electrophysiological remodeling of myocytes from failing hearts accurately reproduce experimental observations. The sensitivity analysis of the modulation of electrophysiological parameters of myocytes from failing hearts due to ion channels remodeling, revealed a role for I(NaL) in the prolongation of action potential duration (APD), triangulation of the shape of the AP, and changes in Ca(2+) transient. A mechanistic investigation of intracellular Na(+) accumulation and APD shortening with increasing frequency of stimulation of failing myocytes revealed a role for the Na(+)/K(+) pump, the Na(+)/Ca(2+) exchanger and I(NaL). The results of the simulations also showed that in failing myocytes, the enhancement of I(NaL) increased the reverse rate-dependent APD prolongation and the probability of initiating early afterdepolarizations. The electrophysiological remodeling of failing hearts and especially the enhancement of the I(NaL) prolong APD and alter Ca(2+) transient facilitating the development of early afterdepolarizations. An enhanced I(NaL) appears to be an important contributor to the electrophysiological phenotype and to the dysregulation of [Ca(2+)](i) homeostasis of failing myocytes.

Project description:BackgroundSGLT2 (sodium/glucose cotransporter 2) inhibitors exert robust cardioprotective effects against heart failure in patients with diabetes, and there is intense interest to identify the underlying molecular mechanisms that afford this protection. Because the induction of the late component of the cardiac sodium channel current (late-INa) is involved in the etiology of heart failure, we investigated whether these drugs inhibit late-INa.MethodsElectrophysiological, in silico molecular docking, molecular, calcium imaging, and whole heart perfusion techniques were used to address this question.ResultsThe SGLT2 inhibitor empagliflozin reduced late-INa in cardiomyocytes from mice with heart failure and in cardiac Nav1.5 sodium channels containing the long QT syndrome 3 mutations R1623Q or ΔKPQ. Empagliflozin, dapagliflozin, and canagliflozin are all potent and selective inhibitors of H2O2-induced late-INa (half maximal inhibitory concentration = 0.79, 0.58, and 1.26 µM, respectively) with little effect on peak sodium current. In mouse cardiomyocytes, empagliflozin reduced the incidence of spontaneous calcium transients induced by the late-INa 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 three-dimensional 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 anesthetics and ranolazine. In an acute model of myocardial injury, perfusion of isolated mouse hearts with empagliflozin or tetrodotoxin prevented activation of the cardiac NLRP3 (nuclear-binding domain-like receptor 3) inflammasome and improved functional recovery after ischemia.ConclusionsOur results provide evidence that late-INa may be an important molecular target in the heart for the SGLT2 inhibitors, contributing to their unexpected cardioprotective effects.

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Fibroblast growth factor homologous factors serve as a molecular rheostat in tuning arrhythmogenic cardiac late sodium current.

Publications

Fibroblast growth factor homologous factors serve as a molecular rheostat in tuning arrhythmogenic cardiac late sodium current.

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