How does mitochondrial Ca2+ change during ischemia and reperfusion? Implications for activation of the permeability transition pore

Mitochondrial oxidative stress, calcium and dynamics in cardiac ischaemia-reperfusion injury

Ischaemia-reperfusion injury (IRI) is a major cause of cardiomyocyte damage and death from myocardial infarction. Oxidative stress, dysregulated calcium (Ca2+) handling and disrupted mitochondrial dynamics are all key factors in IRI and can play a role in cell death. Mitochondria are a primary source of oxidative stress, which is generated by electron leak from the respiratory chain complexes and the oxidation of accumulated succinate upon reperfusion. The mitochondrial permeability transition pore (mPTP), a high conductance channel that forms following reperfusion of ischaemic mitochondria, has been implicated in reperfusion-induced cell death. Although factors including mitochondrial Ca2+ overload and oxidative stress that regulate mPTP opening have been well characterized, the composition of the mPTP is still actively investigated. Clinically, mPTP opening and IRI complicate treatment of myocardial infarction. Therefore, many possible therapeutics to reduce the damaging effects of reperfusion are under investigation. Antioxidants, pharmaceutical approaches, postconditioning and synthetic polymers have all been investigated for use in IRI. Still, many of these therapeutics of interest have shown mixed evidence underlying their use in preclinical and clinical research. In this review we discuss our current understanding of the contributions of mitochondrial oxidative stress, mitochondrial Ca2+ and mitochondrial dynamics to cardiomyocyte damage and death in IRI, and where further clarification of these mechanisms is needed to identify potential therapeutic targets.

Involvement of Oxidative Stress in Mitochondrial Abnormalities During the Development of Heart Disease

Background: Several mitochondrial abnormalities such as defective energy production, depletion of energy stores, Ca2+ accumulation, generation of reactive oxygen species, and impaired intracellular signaling are associated with cardiac dysfunction during the development of different heart diseases. Methods: A narrative review was compiled by a search for applicable literature in MEDLINE via PubMed. Results: Mitochondria generate ATP through the processes of electron transport and oxidative phosphorylation, which is used as energy for cardiac contractile function. Mitochondria, in fact, are the key subcellular organelle for the regulation of intracellular Ca2+ concentration and are considered to serve as a buffer to maintain Ca2+ homeostasis in cardiomyocytes. However, during the development of heart disease, the excessive accumulation of intracellular Ca2+ results in mitochondria Ca2+-overload, which, in turn, impairs mitochondrial energy production and induces cardiac dysfunction. Mitochondria also generate reactive oxygen species (ROS), including superoxide anion radicals and hydroxyl radicals as well as non-radical oxidants such as hydrogen peroxide, which promote lipid peroxidation and the subsequent disturbance of Ca2+ homeostasis, cellular damage, and death. Conclusion: These observations support the view that both oxidative stress and intracellular Ca2+-overload play a critical role in mitochondrial disruption during the pathogenesis of different cardiac pathologies.