Objectives Calpains belong to a family of calcium-dependent intracellular cysteine proteases. Previous studies demonstrated that calpain activation contributes substantially to ischaemia/reperfusion (I/R) injury. However, it remains unclear whether administration of calpain inhibitor ameliorates I/R-caused heart injury in vivo.
AIM The objective of this study was to investigate the role of calpain inhibitor PD150606 (PD) in I/R-induced cardiomyocyte apoptosis.
Methods Male C57BL/6 mice, 2–4 months of age, were randomly divided into sham, I/R, and PD+I/R group (1 mg/kg by IV injection 30 min before ischaemia). Mice were subjected to ischaemia by ligation of the left anterior descending coronary artery for 45 min, then reperfusion for 3 h. The risk and necrotic areas were assessed by Evans blue dye and triphyenyltertrazolium chloride (TTC) staining, respectively. Myocardial apoptosis was assessed by using TUNEL staining, ELISAs for cytochrome c level, and fluorescence assays for the activity of calpain and caspase-3 activities.
Results Compared to I/R group, the ratio of infarct to risk size was significantly decreased in PD+I/R group (38.26±1.91% vs 29.53±1.64%). Compared to control, myocardial caspase-3 activity was significantly increased in I/R group, however, it was significantly decreased in PD+I/R group (2.47±0.37, 5.13±0.50 and 3.40±0.39 AMC cleaved pmol/mg protein, respectively). Calpain activity (1.15±0.16, 2.07±0.15 and 1.55±0.10 arbitrary units/mg protein, respectively), cytochrome c concentration (5.66±0.54, 8.38±0.64 and 7.57±0.56 ng/mg protein, respectively), and TUNEL-positive nuclei (0.56±0.05%, 10.16±1.20% and 4.60±0.50%, respectively) were significantly increased in I/R mouse compared with control, but were decreased by PD treatment.
Conclusions Calpain inhibitor PD treatment is an effective strategy to prevent I/R induced myocardial apoptosis in vivo.