While systolic cardiomyocyte function is preserved, diastolic myocyte function and recovery from acidosis are impaired in CaMKIIδ-KO mice

Stefan Neef, Can M. Sag, Maria Daut, Henrik Bäumer, Clemens Grefe, Ali El-Armouche, Jaime DeSantiago, Laetitia Pereira, Donald M Bers, Johannes Backs, Lars S. Maier

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

Objective: CaMKII contributes to impaired contractility in heart failure by inducing SR Ca2+-leak. CaMKII-inhibition in the heart was suggested to be a novel therapeutic principle. Different CaMKII isoforms exist. Specifically targeting CaMKIIδ, the dominant isoform in the heart, could be of therapeutic potential without impairing other CaMKII isoforms. Rationale: We investigated whether cardiomyocyte function is affected by isoform-specific knockout (KO) of CaMKIIδ under basal conditions and upon stress, i.e. upon ß-adrenergic stimulation and during acidosis. Results: Systolic cardiac function was largely preserved in the KO in vivo (echocardiography) corresponding to unchanged Ca2+-transient amplitudes and isolated myocyte contractility in vitro. CaMKII activity was dramatically reduced while phosphatase-1 inhibitor-1 was significantly increased. Surprisingly, while diastolic Ca2+-elimination was slower in KO most likely due to decreased phospholamban Thr-17 phosphorylation, frequency-dependent acceleration of relaxation was still present. Despite decreased SR Ca2+-reuptake at lower frequencies, SR Ca2+-content was not diminished, which might be due to reduced diastolic SR Ca2+-loss in the KO as a consequence of lower RyR Ser-2815 phosphorylation. Challenging KO myocytes with isoproterenol showed intact inotropic and lusitropic responses. During acidosis, SR Ca2+-reuptake and SR Ca2+-loading were significantly impaired in KO, resulting in an inability to maintain systolic Ca2+-transients during acidosis and impaired recovery. Conclusions: Inhibition of CaMKIIδ appears to be safe under basal physiologic conditions. Specific conditions exist (e.g. during acidosis) under which CaMKII-inhibition might not be helpful or even detrimental. These conditions will have to be more clearly defined before CaMKII inhibition is used therapeutically.

Original languageEnglish (US)
Pages (from-to)107-116
Number of pages10
JournalJournal of Molecular and Cellular Cardiology
Volume59
DOIs
StateAccepted/In press - Jun 2013
Externally publishedYes

Keywords

  • Acidosis
  • Calcium handling
  • CaMKII
  • Excitation contraction coupling
  • SERCA function
  • SR Ca-leak

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Molecular Biology

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    Neef, S., Sag, C. M., Daut, M., Bäumer, H., Grefe, C., El-Armouche, A., DeSantiago, J., Pereira, L., Bers, D. M., Backs, J., & Maier, L. S. (Accepted/In press). While systolic cardiomyocyte function is preserved, diastolic myocyte function and recovery from acidosis are impaired in CaMKIIδ-KO mice. Journal of Molecular and Cellular Cardiology, 59, 107-116. https://doi.org/10.1016/j.yjmcc.2013.02.014