Integrative simulation analysis of myocardial ischaemia–reperfusion injury

Cardiac ischaemia, reduced coronary blood flow, causes significant damages to the heart, and paradoxically reperfusion, restored flow after ischaemia, often results in more severe injury. Although the mechanisms underlying cardiac ischaemia–reperfusion injury have been intensively investigated, effective therapeutic strategies applicable during reperfusion to mitigate this damage have not been established yet. To obtain more insights into the mechanisms underlying ischaemia–reperfusion injury, and to explore effective methods to relieve reperfusion injury, we developed a comprehensive mathematical model of ventricular myocyte, implementing excitation–contraction (E–C) coupling, cytosolic and mitochondrial pH regulation, pH dependence of major components of E–C coupling and cellular energy metabolism, including mitochondrial oxidative phosphorylation. The mathematical model successfully reproduced experimentally observed findings on cardiac ischaemia–reperfusion injury, such as intracellular and extracellular acidosis, cytosolic Na+ overload, cytosolic Ca2+ overload, mitochondrial dysfunction, action potential shortening and contraction failure. It was found that the reperfusion-induced exacerbation of Na+i, Ca2+i overloads was mainly caused by insufficient production of NADH, which is used in mitochondrial oxidative phosphorylation to synthesize ATP for Na+/K+ pump and sarcoplasmic/endoplasmic reticulum Ca2+ pump (SERCA) to expel accumulated cytosolic Na+ and Ca2+, respectively. It was suggested that the preservation of mitochondrial NADH production, attenuation of ATP consumption via SERCA or contraction for a short period or activation of the Na+/K+ pump during reperfusion mitigates reperfusion injury.