AUTHOR=Wegener Jörg W. , Wagdi Ahmed , Wagner Eva , Katschinski Dörthe M. , Hasenfuss Gerd , Bruegmann Tobias , Lehnart Stephan E. 

TITLE=The RyR2-R2474S Mutation Sensitizes Cardiomyocytes and Hearts to Catecholaminergic Stress-Induced Oxidation of the Mitochondrial Glutathione Pool

JOURNAL=Frontiers in Physiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.777770

DOI=10.3389/fphys.2021.777770

ISSN=1664-042X

ABSTRACT=<p>Missense mutations in the cardiac ryanodine receptor type 2 (RyR2) characteristically cause catecholaminergic arrhythmias. Reminiscent of the phenotype in patients, RyR2-R2474S knockin mice develop exercise-induced ventricular tachyarrhythmias. In cardiomyocytes, increased mitochondrial matrix Ca<sup>2+</sup> uptake was recently linked to non-linearly enhanced ATP synthesis with important implications for cardiac redox metabolism. We hypothesize that catecholaminergic stimulation and contractile activity amplify mitochondrial oxidation pathologically in RyR2-R2474S cardiomyocytes. To investigate this question, we generated double transgenic RyR2-R2474S mice expressing a mitochondria-restricted fluorescent biosensor to monitor the glutathione redox potential (<italic>E</italic><sub>GSH</sub>). Electrical field pacing-evoked RyR2-WT and RyR2-R2474S cardiomyocyte contractions resulted in a small but significant baseline <italic>E</italic><sub>GSH</sub> increase. Importantly, β-adrenergic stimulation resulted in excessive <italic>E</italic><sub>GSH</sub> oxidization of the mitochondrial matrix in RyR2-R2474S cardiomyocytes compared to baseline and RyR2-WT control. Physiologically β-adrenergic stimulation significantly increased mitochondrial <italic>E</italic><sub>GSH</sub> further in intact beating RyR2-R2474S but not in RyR2-WT control Langendorff perfused hearts. Finally, this catecholaminergic <italic>E</italic><sub>GSH</sub> increase was significantly attenuated following treatment with the RyR2 channel blocker dantrolene. Together, catecholaminergic stimulation and increased diastolic Ca<sup>2+</sup> leak induce a strong, but dantrolene-inhibited mitochondrial <italic>E</italic><sub>GSH</sub> oxidization in RyR2-R2474S cardiomyocytes.</p>