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Assessment of Sarcoplasmic Reticulum Calcium Reserve and Intracellular Diastolic Calcium Removal in Isolated Ventricular Cardiomyocytes
Published on: September 18, 2017
Calcium/Calmodulin Protein Kinase II-Dependent Ryanodine Receptor Phosphorylation Mediates Cardiac Contractile
Marisa Sepúlveda1, Luis A Gonano, Manuel Viotti
11Centro de Investigaciones Cardiovasculares, Conicet La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina.2Servicio de Cardiología, Conicet La Plata, Facultad de Veterinaria, Universidad Nacional de La Plata, La Plata, Argentina.3Laboratório de Cardiologia Celular e Molecular - IBCCF - Centro de Ciencias da Saúde, Universidade Federal do Rio de Janeiro, Instituto de Biofísica Carlos Chagas Filho, Rio de Janeiro, Brazil.4Centro Nacional de Biologia Estrutural e Bioimagem - CENABIO-UFRJ, Rio de Janeiro, Brazil.
Objectives:
Sepsis is associated with cardiac contractile dysfunction attributed to alterations in Ca handling. We examined the subcellular mechanisms involved in sarcoplasmic reticulum Ca loss that mediate altered Ca handling and contractile dysfunction associated with sepsis.
Design:
Randomized controlled trial.
Setting:
Research laboratorySUBJECTS:: Male wild type and transgenic miceINTERVENTIONS:: We induced sepsis in mice using the colon ascendens stent peritonitis model.
Measurements And Main Results:
Twenty-four hours after colon ascendens stent peritonitis surgery, we observed that wild type mice had significantly elevated proinflammatory cytokine levels, reduced ejection fraction, and fractional shortening (ejection fraction %, 54.76 ± 0.67; fractional shortening %, 27.53 ± 0.50) compared with sham controls (ejection fraction %, 73.57 ± 0.20; fractional shortening %, 46.75 ± 0.38). At the cardiac myocyte level, colon ascendens stent peritonitis cells showed reduced cell shortening, Ca transient amplitude and sarcoplasmic reticulum Ca content compared with sham cardiomyocytes. Colon ascendens stent peritonitis hearts showed a significant increase in oxidation-dependent calcium and calmodulin-dependent protein kinase II activity, which could be prevented by pretreating animals with the antioxidant tempol. Pharmacologic inhibition of calcium and calmodulin-dependent protein kinase II with 2.5 µM of KN93 prevented the decrease in cell shortening, Ca transient amplitude, and sarcoplasmic reticulum Ca content in colon ascendens stent peritonitis myocytes. Contractile function was also preserved in colon ascendens stent peritonitis myocytes isolated from transgenic mice expressing a calcium and calmodulin-dependent protein kinase II inhibitory peptide (AC3-I) and in colon ascendens stent peritonitis myocytes isolated from mutant mice that have the ryanodine receptor 2 calcium and calmodulin-dependent protein kinase II-dependent phosphorylation site (serine 2814) mutated to alanine (S2814A). Furthermore, colon ascendens stent peritonitis S2814A mice showed preserved ejection fraction and fractional shortening (ejection fraction %, 73.06 ± 6.31; fractional shortening %, 42.33 ± 5.70) compared with sham S2814A mice (ejection fraction %, 71.60 ± 4.02; fractional shortening %, 39.63 ± 3.23).
Conclusions:
Results indicate that oxidation and subsequent activation of calcium and calmodulin-dependent protein kinase II has a causal role in the contractile dysfunction associated with sepsis. Calcium and calmodulin-dependent protein kinase II, through phosphorylation of the ryanodine receptor would lead to Ca leak from the sarcoplasmic reticulum, reducing sarcoplasmic reticulum Ca content, Ca transient amplitude and contractility. Development of organ-specific calcium and calmodulin-dependent protein kinase II inhibitors may result in a beneficial therapeutic strategy to ameliorate contractile dysfunction associated with sepsis.
Insights
Sepsis causes heart dysfunction by increasing calcium and calmodulin-dependent protein kinase II (CaMKII) activity, leading to calcium leakage from the sarcoplasmic reticulum. Inhibiting CaMKII may treat sepsis-induced cardiac dysfunction.
Area of Science:
- Cardiology
- Molecular Biology
- Physiology
Background:
- Sepsis is linked to cardiac contractile dysfunction due to impaired calcium (Ca) handling.
- Alterations in sarcoplasmic reticulum Ca handling are implicated in sepsis-induced cardiac dysfunction.
Purpose of the Study:
- To investigate the subcellular mechanisms of sarcoplasmic reticulum Ca loss in sepsis-induced cardiac contractile dysfunction.
- To determine the role of calcium and calmodulin-dependent protein kinase II (CaMKII) in sepsis-related cardiac dysfunction.
Main Methods:
- Male wild type and transgenic mice underwent sepsis induction via the colon ascendens stent peritonitis model.
- Cardiac function, myocyte shortening, Ca transient amplitude, and sarcoplasmic reticulum Ca content were assessed.
- CaMKII activity and its role in ryanodine receptor phosphorylation were examined using pharmacologic inhibitors and transgenic models.
Main Results:
- Sepsis induced cardiac dysfunction, characterized by reduced ejection fraction and fractional shortening in wild type mice.
- Sepsis led to decreased myocyte shortening, Ca transient amplitude, and sarcoplasmic reticulum Ca content.
- Oxidation-dependent CaMKII activation was observed, which was preventable by antioxidant treatment (tempol) and CaMKII inhibition (KN93, AC3-I peptide).
- Mutating the CaMKII phosphorylation site on the ryanodine receptor (S2814A) preserved cardiac function in septic mice.
Conclusions:
- Oxidation and subsequent CaMKII activation play a causal role in sepsis-induced cardiac contractile dysfunction.
- CaMKII-mediated phosphorylation of the ryanodine receptor contributes to Ca leak from the sarcoplasmic reticulum, impairing contractility.
- Targeting CaMKII with organ-specific inhibitors presents a potential therapeutic strategy for sepsis-related cardiac dysfunction.
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