CaMKII and reactive oxygen species contribute to early reperfusion arrhythmias, but oxidation of CaMKIIδ at methionines 281/282 is not a determining factor

J Mol Cell Cardiol. 2023 Feb:175:49-61. doi: 10.1016/j.yjmcc.2022.12.002. Epub 2022 Dec 14.


Background: Available evidence suggest that Ca2+/calmodulin-dependent protein kinase type IIδ (CaMKIIδ) and reactive oxygen species (ROS) are important in early ischemia-reperfusion arrhythmias (IRA). Since ROS can activate CaMKIIδ by oxidation of two methionines at positions 281/282, oxidized-CaMKIIδ (Ox-CaMKIIδ) has been proposed to be important for IRA. However, direct evidence for this is missing.

Methods: We exposed Langendorff-perfused hearts and ventricular cardiomyocytes from C57BL/6 mice to global and simulated ischemia, respectively, and recorded arrhythmic events during early reperfusion. Hearts were collected for immunoblotting of key phosphoproteins. We evaluated the effects of beta-adrenoceptor stimulation, inhibition of CaMKII, and reduced ROS levels with isoprenaline, KN93/AIP and N-acetylcysteine (NAC), respectively. We further tested the importance of Ox-CaMKIIδ by using hearts and cardiomyocytes from mice with CaMKIIδ resistant to oxidation of methionines 281 and 282 (MMVV).

Results: Hearts treated with KN93, AIP or NAC had lower incidence of early IRA, and NAC-treated cardiomyocytes had lower incidence of arrhythmogenic events. However, hearts from MMVV mice had a similar incidence of early IRA to wild type mice (WT), and MMVV and WT cardiomyocytes had a similar frequency of Ca2+ waves and Ca2+ sparks. Immunoblotting confirmed high levels of oxidation in early reperfusion, but revealed no significant differences in the phosphorylation levels of Ca2+-handling proteins in MMVV and WT hearts.

Conclusions: Although CaMKII and ROS both contribute to early IRA, hearts from mice with CaMKII resistant to oxidation at methionines 281/282 were not protected from such arrhythmias, suggesting that oxidation at these sites is not a determining factor.

Keywords: Arrhythmias; CaMKII; Calcium; Electrophysiology; Ischemia; Ischemic heart disease; Myocardial infarction; Reactive oxygen species; Reperfusion; Ventricular arrhythmias.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arrhythmias, Cardiac / metabolism
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2* / metabolism
  • Methionine* / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Myocytes, Cardiac / metabolism
  • Phosphorylation
  • Racemethionine / metabolism
  • Reactive Oxygen Species / metabolism
  • Reperfusion / adverse effects


  • Reactive Oxygen Species
  • KN 93
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • Methionine
  • Racemethionine