The inotropic and arrhythmogenic effects of acutely increased late INa are associated with elevated ROS but not oxidation of PKARIα

• Published in: Frontiers in cardiovascular medicine 2024-07, Vol.11, p.1379930
• Main Authors: Gissibl, Theresa, Stengel, Laura, Tarnowski, Daniel, Maier, Lars S., Wagner, Stefan, Feder, Anna-Lena, Sag, Can Martin
• Format: Article
• Language: English
• Subjects: CaMKII; Cardiovascular Medicine; excitation contraction coupling (ECC); L-type Ca2+ current (ICa); oxidative stress; PKARIα
• ISSN: 2297-055X; 2297-055X
• DOI: 10.3389/fcvm.2024.1379930

Acute stimulation of the late sodium current (INaL) as pharmacologically induced by Anemonia toxin II (ATX-II) results in Na+-dependent Ca2+ overload and enhanced formation of reactive oxygen species (ROS). This is accompanied by an acute increase in the amplitude of the systolic Ca2+ transient. Ca2+ transient amplitude is determined by L-type Ca2+-mediated transsarcolemmal Ca2+ influx (ICa) into the cytosol and by systolic Ca2+ release from the sarcoplasmic reticulum (SR). Type-1 protein kinase A (PKARIα) becomes activated upon increased ROS and is capable of stimulating ICa, thereby sustaining the amplitude of the systolic Ca2+ transient upon oxidative stress.BackgroundAcute stimulation of the late sodium current (INaL) as pharmacologically induced by Anemonia toxin II (ATX-II) results in Na+-dependent Ca2+ overload and enhanced formation of reactive oxygen species (ROS). This is accompanied by an acute increase in the amplitude of the systolic Ca2+ transient. Ca2+ transient amplitude is determined by L-type Ca2+-mediated transsarcolemmal Ca2+ influx (ICa) into the cytosol and by systolic Ca2+ release from the sarcoplasmic reticulum (SR). Type-1 protein kinase A (PKARIα) becomes activated upon increased ROS and is capable of stimulating ICa, thereby sustaining the amplitude of the systolic Ca2+ transient upon oxidative stress.We aimed to investigate whether the increase of the systolic Ca2+ transient as acutely induced by INaL (by ATX-II) may involve stimulation of ICa through oxidized PKARIα.ObjectivesWe aimed to investigate whether the increase of the systolic Ca2+ transient as acutely induced by INaL (by ATX-II) may involve stimulation of ICa through oxidized PKARIα.We used a transgenic mouse model in which PKARIα was made resistant to oxidative activation by homozygous knock-in replacement of redox-sensitive Cysteine 17 with Serine within the regulatory subunits of PKARIα (KI). ATX-II (at 1 nmol/L) was used to acutely enhance INaL in freshly isolated ventricular myocytes from KI and wild-type (WT) control mice. Epifluorescence and confocal imaging were used to assess intracellular Ca2+ handling and ROS formation. A ruptured-patch whole-cell voltage-clamp was used to measure INaL and ICa. The impact of acutely enhanced INaL on RIα dimer formation and PKA target structures was studied using Western blot analysis.MethodsWe used a transgenic mouse model in which PKARIα was made resistant to oxidative activation by homozygous knock-in replacement of redox