Gissibl, Theresa and Stengel, Laura and Tarnowski, Daniel and Maier, Lars S. and Wagner, Stefan and Feder, Anna-Lena and Sag, Can Martin (2024) The inotropic and arrhythmogenic effects of acutely increased late INa are associated with elevated ROS but not oxidation of PKARIα. FRONTIERS IN CARDIOVASCULAR MEDICINE, 11: 1379930. ISSN 2297-055X,
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Background: Acute stimulation of the late sodium current (I-NaL) 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 (I-Ca) into the cytosol and by systolic Ca2+ release from the sarcoplasmic reticulum (SR). Type-1 protein kinase A (PKARI alpha) becomes activated upon increased ROS and is capable of stimulating I-Ca, thereby sustaining the amplitude of the systolic Ca2+ transient upon oxidative stress. Objectives: We aimed to investigate whether the increase of the systolic Ca2+ transient as acutely induced by I-NaL (by ATX-II) may involve stimulation of I-Ca through oxidized PKARI alpha. Methods: We used a transgenic mouse model in which PKARI alpha was made resistant to oxidative activation by homozygous knock-in replacement of redox-sensitive Cysteine 17 with Serine within the regulatory subunits of PKARI alpha (KI). ATX-II (at 1 nmol/L) was used to acutely enhance I-NaL 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 I-NaL and I-Ca. The impact of acutely enhanced I-NaL on RI alpha dimer formation and PKA target structures was studied using Western blot analysis. Results: ATX-II increased I-NaL to a similar extent in KI and WT cells, which was associated with significant cytosolic and mitochondrial ROS formation in both genotypes. Acutely activated Ca2+ handling in terms of increased Ca2+ transient amplitudes and elevated SR Ca2+ load was equally present in KI and WT cells. Likewise, cellular arrhythmias as approximated by non-triggered Ca2+ elevations during Ca2+ transient decay and by diastolic SR Ca2+-spark frequency occurred in a comparable manner in both genotypes. Most importantly and in contrast to our initial hypothesis, ATX-II did not alter the magnitude or inactivation kinetics of I-Ca in neither WT nor KI cells and did not result in PKARI alpha dimerization (i.e., oxidation) despite a clear prooxidant intracellular environment. Conclusions: The inotropic and arrhythmogenic effects of acutely increased I-NaL are associated with elevated ROS, but do not involve oxidation of PKARI alpha.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | LATE SODIUM CURRENT; DEPENDENT PROTEIN-KINASE; CALCIUM; CHANNEL; CAMKII; MODULATION; ACTIVATION; OVERLOAD; MYOCYTES; CONSEQUENCES; PKARI alpha; excitation contraction coupling (ECC); CaMKII; oxidative stress; L-type Ca2+ current (I-Ca) |
| Subjects: | 600 Technology > 610 Medical sciences Medicine |
| Divisions: | Medicine > Lehrstuhl für Innere Medizin II |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 24 Jul 2025 12:56 |
| Last Modified: | 24 Jul 2025 12:56 |
| URI: | https://pred.uni-regensburg.de/id/eprint/63707 |
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