Altered Calcium Handling in Reperfusion Injury

Sarcoplasmic reticulum (SR) calcium handling is central not only in the control of heart function during excitation-contraction coupling but also in mitochondrial energetics and apoptosis. Recent studies have identified the anti-apoptotic protein, HS-1 associated protein X-1 (HAX-1) as a novel regulator of SR calcium cycling. Although HAX-1 has been shown to localize to mitochondria in various tissues, we found out that it also localizes to SR through its interaction with phospholamban (PLN) in cardiac muscle. Acute or chronic overexpression of HAX-1 in cardiomyocytes promoted PLN inhibition on the calcium ATPase (SERCA) and decreased cardiomyocyte calcium kinetics and contractile parameters. Accordingly, ablation of HAX-1 significantly enhanced SERCA activity and calcium kinetics. Furthermore, the HAX-1/PLN interaction appeared to also regulate cardiomyocyte survival. Indeed, overexpression of HAX-1 and the associated depressed SR Ca-load attenuated endoplasmic reticulum stress induced apoptosis, as evidenced by reduction of both caspase-12 activation and pro-apoptotic transcription factor C/EBP homologous protein induction during ischemia/reperfusion injury. In addition, the depressed SR Ca-cycling by HAX-1 overexpression was associated with reduced mitochondrial Ca-load as reflected by: a) hyper-phosphorylation of pyruvate dehydrogenase (PDH) and decreases in its activity, to diminish ATP production consistent with the attenuated energetic demand in these hearts; and b) reduced levels of reactive oxygen species, indicating protection from oxidative damage and preserved mitochondrial integrity. These findings suggest that HAX-1 is a key regulator of Ca-cycling, apoptosis and energetics in the heart. Thus, decreases in HAX-1 levels, observed during ischemia/reperfusion injury, may contribute to the deteriorated function and progression to heart failure development.

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The Role of Calcium Handling Mechanisms in Reperfusion Injury

Current Pharmaceutical Design ◽

10.2174/1381612825666181120155953 ◽

2019 ◽

Vol 24 (34) ◽

pp. 4077-4089 ◽

Cited By ~ 3

Author(s):

Konstantinos Pittas ◽

Dimitrios A. Vrachatis ◽

Christos Angelidis ◽

Styliani Tsoucala ◽

Georgios Giannopoulos ◽

...

Keyword(s):

Reperfusion Injury ◽

Cell Injury ◽

Ischemia Reperfusion Injury ◽

Beta Blockers ◽

Ischemia Reperfusion ◽

Ryanodine Receptors ◽

Coronary Intervention ◽

Calcium Handling ◽

Converting Enzyme Inhibitors ◽

Ca2 Channels

Cardiovascular diseases, such as stroke and myocardial infarction (MI) remain the major cause of death and disability worldwide. However, the mortality of MI has declined dramatically over the past several decades because of advances in medicines (thrombolytic agents, antiplatelet drugs, beta blockers, and angiotensin converting enzyme inhibitors) and approaches to restore tissue perfusion (percutaneous coronary intervention and cardiopulmonary bypass). Animal studies have been shown that these treatments have been effective in reducing acute myocardial ischemic injury and limiting MI size. The paradox is that the process of reperfusion can itself amplify cell injury and death, known as myocardial ischemia-reperfusion injury (I/R). Intensive research has uncovered several complex mechanisms of cardiomyocyte damage after reperfusion,and potential therapeutic targets for preventing I/R. Importantly, it is now recognized that excessive elevation of intracellular and mitochondrial Ca2+during reperfusion predisposes the cells to hypercontracture, proteolysis and mitochondrial failure and eventually to necrotic or apoptotic death. These enormous alterations in cytosolic Ca2+ levels are induced by the Ca2+ channels of the sarcolemma(L-Type Ca2+channels, sodium/calcium exchanger), the endoplasmic/ sarcoplasmic reticulum (SERCA ATPase) and ryanodine receptors, SOCE(store-operated calcium entry), lysosomes and others, which are modified by I/R injury. The overall goal of this review is to describe the different pathways that lead to I/R injury via Ca2+ overload, focus on recent discoveries and highlight prospects for therapeutic strategies for clinical benefit.

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Endothelial extracellular vesicles contain protective proteins and rescue ischemia-reperfusion injury in a human heart-on-chip

Science Translational Medicine ◽

10.1126/scitranslmed.aax8005 ◽

2020 ◽

Vol 12 (565) ◽

pp. eaax8005 ◽

Cited By ~ 1

Author(s):

Moran Yadid ◽

Johan U. Lind ◽

Herdeline Ann M. Ardoña ◽

Sean P. Sheehy ◽

Lauren E. Dickinson ◽

...

Keyword(s):

Stem Cell ◽

Reperfusion Injury ◽

Extracellular Vesicles ◽

Human Heart ◽

Ischemia Reperfusion Injury ◽

Ischemia Reperfusion ◽

Calcium Handling ◽

Dependent Manner ◽

Cardiac Tissues ◽

Human Cardiomyocytes

Extracellular vesicles (EVs) derived from various stem cell sources induce cardioprotective effects during ischemia-reperfusion injury (IRI). These have been attributed mainly to the antiapoptotic, proangiogenic, microRNA (miRNA) cargo within the stem cell–derived EVs. However, the mechanisms of EV-mediated endothelial signaling to cardiomyocytes, as well as their therapeutic potential toward ischemic myocardial injury, are not clear. EV content beyond miRNA that may contribute to cardioprotection has not been fully illuminated. This study characterized the protein cargo of human vascular endothelial EVs (EEVs) to identify lead cardioactive proteins and assessed the effect of EEVs on human laminar cardiac tissues (hlCTs) exposed to IRI. We mapped the protein content of human vascular EEVs and identified proteins that were previously associated with cellular metabolism, redox state, and calcium handling, among other processes. Analysis of the protein landscape of human cardiomyocytes revealed corresponding modifications induced by EEV treatment. To assess their human-specific cardioprotection in vitro, we developed a human heart-on-a-chip IRI assay using human stem cell–derived, engineered cardiac tissues. We found that EEVs alleviated cardiac cell death as well as the loss in contractile capacity during and after simulated IRI in an uptake- and dose-dependent manner. Moreover, we found that EEVs increased the respiratory capacity of normoxic cardiomyocytes. These results suggest that vascular EEVs rescue hlCTs exposed to IRI possibly by supplementing injured myocytes with cargo that supports multiple metabolic and salvage pathways and therefore may serve as a multitargeted therapy for IRI.

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