Tongxinluo Ameliorates Myocardial Ischemia-Reperfusion Injury Mainly via Activating Parkin-Mediated Mitophagy and Downregulating Ubiquitin-Proteasome System

Abstract

Objective: To investigate the protective effects and mechanism of Chinese herbal compound Tongxinluo Capsule (, TXL) on the Parkin-mediated mitophagy and the ubiquitin-proteasome system in a rat model of myocardial ischemia-reperfusion injury (MIRI).

Methods: Seventy adult male Sprague-Dawley rats were randomly divided into 7 groups: sham group, MIRI group, low- and high-dose TXL (0.5 and 1 g·kg^-1·d^-1, respectively) groups, atorvastatin (ATV) group (7.2 g·kg^-1·d^-1), chloroquine (CQ) group (10 g·kg^-1·d^-1), and highdose TXL + CQ group. After pharmacological administration for 7 days, rats underwent left anterior descending artery ligation surgery to establish the MIRI models with 50 min ischemia followed by 4 h reperfusion. Blood was taken for cardiac troponin I (cTnI) detection and hearts were harvested for infarct staining and apoptosis detection. The autophagy or mitophagy proteins and ubiquitinated proteins were detected by Western blotting.

Results: Compared with the sham group, the MIRI group exhibited a larger infarcted area (27.13%±0.01%, P<0.01), a higher apoptotic index (34.33%±2.03% vs.1.81%±0.03%, P<0.01), and higher cTnI expression (14.18±1.01 vs. 7.96±0.32, P<0.01). The mitochondrial integrity was damaged in the MIRI group, while TXL and ATV alleviated the damage of MIRI. More autophagosomes were observed in the high-dose TXL group than in the MIRI group (7.00±0.58 vs. 4.33±1.15, P<0.05). More amounts of PTEN-induced putative kinase protein 1 (PINK1) and Parkin translocated onto the mitochondria were detected in the high-dose TXL group than in the MIRI group (P<0.05). The ubiquitin response was signifificantly downregulated in the high-dose TXL group relative to the MIRI group (P<0.05). CQ administration abolished the activation of autophagy flux and the PINK1/ Parkin pathway induced by high-dose of TXL.

Conclusions: TXL ameliorates MIRI via activating Parkin-mediated mitophagy in rats. The downregulation of the ubiquitin-proteasome system is also involved.

Keywords: Chinese medicine; Parkin; ischemia-reperfusion injury; mitophagy; ubiquitin.