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Prolonged activation of cardiomyocytes calpain 2 in sudden cardiac death caused by early myocardial ischemia and acute myocardial infarction contributes to activation of myocytes apoptosis in the area of myocardial ischemia and infarction

Objectives The aim of the study was to analyze the expression of calpain 2 and the degree of apoptosis of the cardiomyocytes and to compare them between the examined groups of people who died of sudden cardiac death (SCD) caused by early myocardial ischemia (EMI)/acute myocardial infarction (AMI) and control groups. Patients and Methods Respondents were divided into three groups. Group 1 consisted of 50 persons who died of SCD caused by EMI in the period from January 2013 to August 2019. The tissue samples were taken from the zone of ischemia/infarction and the opposite left ventricular wall during the forensic autopsy at the Department of Forensic Medicine and Criminalistics, Faculty of Medicine, University of Rijeka. Group 2 consisted of 51 persons who died of SCD caused by AMI. The control group included myocardial samples obtained from 50 persons who died of instant death by head gunshot. The expression of calpain 2 in the studied heart cells was analyzed immunohistochemically, while the degree of apoptosis was determined by the TUNEL method. Statistical data processing was performed using the computer program MedCalcStatistical Software version 20.011. Results Calpain 2 in myocytes showed greater expression in the zone of EMI (and even greater in AMI zone) compared to the opposite wall and control group (P<0.0001). Apoptotic activity of myocytes positive¬ly correlated with the age of the person in the area of EMI/AMI, also on the opposite wall of the myocardium (P=0.0004) and was higher in AMI than EMI. Since apoptotic activity positively correlated with the expression of calpain 2 in myocytes (P=0.048), calpain 2 positive myocytes from the area of EMI/ AMI increased the risk of apoptosis 106.72-fold. The risk of AMI in persons with a high degree of apoptot¬ic activity in myocytes was 2.15-fold higher. Conclusion The influence of ischemia as well as its length is reflected in the intensity of activation of calpain 2 myocytes. Expression level of myocyte calpain 2 is associated with apoptotic activity of these cells suggesting that prolonged activation of calpain 2 by ischemia contributes to more significant activation of myocyte apoptosis in the area of myocardial ischemia/infarction.

apoptosis ; immunohistochemistry ; ischemia ; calpain ; myocardium

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