Sex‐Specific Arrhythmias Caused by Cardiac Sodium Channel Nav1.5 Mutation Alters Cardiomyocyte Metabolism
Authors: Lee Tim Y. , Hogarth Kaley , Szabo Elod , Maynes Jason T. 
Published: May 2022

IntroductionThe activation of cardiac Nav1.5 sodium channels initiates the action potential in the heart to facilitate coordinated contraction. Mutations in Nav1.5 disrupts the action potential leading to arrhythmic diseases which increases the risk of sudden cardiac arrest. The gain of function Arg222Gln mutation in Nav1.5 disrupts structural interactions during channel activation, creating an aberrant pore leading to excessive cations entering the cardiomyocyte (CM). The chronic arrhythmia resulting from Arg222Gln places prolonged stress on the heart which can trigger adverse metabolic reprogramming. We have generated a mouse model possessing the human Arg222Gln mutation where the males illustrate a significant arrhythmia burden, whereas females appear to be protected. We hypothesize that sex‐specifc metabolic reprogramming could provide an explanation for the observed difference in phenotype.MethodsThe human exon containing the Arg222Gln mutation was knocked into the equivalent mouse locus under the endogenous promoter. Shot‐gun proteomics of total heart lysate was performed using LC‐LC mass spectrometry. Significant proteins were identified with at least two unique peptides and a 5% false discovery rate. Clustering and differentially expressed proteins were analyzed using Metaboanalyst and pathway gene ontological analysis was performed with Cytoscape. Cellular metabolism (oxygen consumption) was measured using isolated adult primary CMs with the Seahorse XFe Analyzer.ResultsAfter filtering, mass spectrometry yielded 1654 identified protein across all four analyzed groups (wild‐type and Arg222Gln of both sexes). Unsupervised clustering of the data using principal component analysis and hierarchical clustering revealed complete segregation of the four groups. Sex status contributed most significantly to data segregation, with secondary (but clear) segregation based on Arg222Gln mutation. Comparing Arg222Gln male versus females, there were 157 upregulated proteins and 231 down regulated proteins (P<0.05, ±2‐fold change). Pathway analysis of the differentially expressed proteins reveal multiple changes in metabolic pathways including fatty acid metabolism, pyruvate metabolism, and lactate metabolism. Basal respiration of the isolated CMs in all four groups were unchanged, however maximal respiratory capacity of Arg222Gln males were significantly lower (116.9±13.5pmol O2/min, P<0.05) compared to the wild‐type males (407.3±16.4pmol O2/min). There were no differences between wild‐type females (451.4±22.4pmol O2/min) and Arg222Gln females (463.2±33.7pmol O2/min).ConclusionWe demonstrate sex‐specific proteomic changes in a mouse model of arrhythmia caused by a gain‐of‐function Nav1.5 mutation. While there were many perturbed pathways in our analysis, metabolic changes featured prominently. Our data suggests that metabolic reprogramming could play a role in the cardioprotection in females or a compensatory detrimental mechanism in males harboring the Arg222Gln mutation. Future experiments will aim to understand how sex affects cardiac metabolism in the context of Arg222Gln, specifically targeting the specific roles of sex hormones.