Hydroxytyrosol protects against myocardial ischemia reperfusion injury by inhibiting mitochondrial permeability transition pore opening

Hydroxytyrosol (HT), a phenolic compound extracted from olive oil, is reported to protect against myocardial ischemia reperfusion injury (MIRI), but its mechanism has not been fully elucidated. The mitochondria permeability transition pore (MPTP) is an important therapeutic target for MIRI. The present study aimed to investigate the role of MPTP in the cardioprotection of HT. Isolated rat hearts were mounted on a Langendorff apparatus and subjected to 30 min of ischemia followed by 120 min of reperfusion to mimic a MIRI model. Isolated hearts were pretreated with different doses of HT (10, 100 and 1,000 µM) for 10 min prior to ischemia. Myocardial infarct size was detected using TTC staining. Changes in myocardial cell structure were observed using hematoxylin and eosin staining. MPTP opening was detected spectrophotometrically. Myocardial cell apoptosis was observed with terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling assays. The expression of apoptosis-associated proteins was measured by western blot analysis. The data revealed that HT (100 and 1,000 µM) treatment significantly alleviated pathological damage in ischemic myocardium and reduced myocardial infarct size compared with the untreated control. However, no significant difference was observed in the 10 µM HT treatment group compared with the untreated control. It was further revealed that HT decreased the B cell lymphoma-2 (Bcl-2)-like protein 4 (Bax)/Bcl-2 ratio, suppressed MPTP opening and subsequently decreased the expression of cytochrome c, cleaved caspase-9 and −3, thereby inhibiting apoptosis. Additionally, the beneficial effects of HT on MIRI were reversed by atractyloside, which induces MPTP opening. In conclusion, the present study demonstrated that HT inhibited MPTP opening, partially via modulation of Bax and Bcl-2, thereby protecting against MIRI and thereby providing a pharmacological basis for future research and treatment of MIRI.