Bursts of reperfusion arrhythmias occur independently of area at risk size and are the first marker of reperfusion injury

Cellular mechanisms and pathways in myocardial reperfusion injury

Despite the progress of cardiovascular medicine, ischemia-reperfusion injury can contribute to increased mortality and prolonged hospitalization after myocardial infarction. Ischemia-reperfusion injury pathophysiology encompasses many cells including cardiomyocytes, fibroblasts, mesenchymal stromal cells, vascular endothelial and smooth muscle cells, platelets, polymorphonuclear cells, macrophages, and T lymphocytes. However, specific mechanisms for all contributing cells and molecular pathways are still under investigation. What is definitely known is that endothelial dysfunction, immunity activation and inflammatory response are crucial events during ischemia-reperfusion injury while toll-like receptors, inflammasomes, reactive oxygen species, intracellular calcium overload and mitochondrial permeability transition pore opening consist of key molecular mediators. Indicatively, cardiac fibroblasts through inflammasome activation mediate the initial inflammatory response. Cardiac mesenchymal stromal cells can respond to myocardial injury by pro-inflammatory activation. Endothelial cell activation contributes to the impaired vasomotion, inflammation and thrombotic events and together with platelet activation leads to microcirculation dysfunction and polymorphonuclear cells recruitment promoting inflammation. Polymorphonuclear cells and monocytes/macrophages subsets are critically involved in the inflammation process by producing toxic proteolytic enzymes and reactive oxygen species. T cells subsets are also involved in several stages of ischemia-reperfusion injury. In this review, we summarize the specific contribution of each of the above cells and the related molecular pathways in the pathophysiology of ischemia-reperfusion injury.

Angiotensin receptor-neprilysin inhibitior (thiorphan/irbesartan) decreased ischemia-reperfusion induced ventricular arrhythmias in rat; in vivo study

Ventricular arrhythmias are considered as a major risk of sudden cardiac death. This study was designed to investigate the potential effects of angiotensin receptor neprilysin inhibitor; thiorphan/irbesartan (TH/IRB) combination therapy on myocardial ischemic-reperfusion (I/R)-induced arrhythmia. Fifty male Wistar rats were divided into 5 groups; (I, II): Sham, I/R both received DMSO intraperitoneally before the procedure. (III, IV, V): TH/IRB + IR (0.1/5 mg/kg, 0.1/10 mg/kg and 0.1/15 mg/kg). The drugs were injected intraperitoneally 15 min before I/R induction. Electrocardiograms changes, mean arterial blood pressure, incidence of ventricular tachycardia (VT), incidence of ventricular fibrillation (VF) and arrhythmia score were assessed. Cardiac levels of creatinine kinase-MB (CK-MB), Malondialdehyde (MDA), superoxide dismutase (SOD), endothelin-1 (ET-1), ATP content, and Na⁺/K⁺-ATPase pump activity were measured. TH (0.1 mg/kg) in combination with IRB (5, 10 and 15 mg/kg) produced significant decrease in QTc interval duration, ST height, incidence of VT and VF, duration of VT + VF, and arrhythmia score compared to I/R group. All treated groups showed significant decrease in the cardiac levels of: CK-MB, MDA and ET-1 and significant increase in SOD, ATP content, and Na⁺/K⁺-ATPase pump activity compared to I/R. TH/IRB + IR (0.1/10 mg/kg) group produced significant decrease in CK-MB, MDA and ET-1 and a significant increase in SOD, ATP content, and Na⁺/K⁺-ATPase pump activity compared to other treated groups. In conclusion, angiotensin receptor neprilysin inhibitor (thiorphan/irbesartan) decreased arrhythmia score and decreased cardiac damage. These could be explained in part by its ability to decrease oxidative stress and ET-1, increase ATP, and Na⁺/K⁺-ATPase pump activity in this rat model of I/R-induced arrhythmia.