Abstract
Background
Ischaemic heart disease is the most common cause of death globally. Although reperfusion therapy is essential to restore myocardial blood flow, it can also damage heart tissues, this process is known as ischaemia/reperfusion (I/R) injury. Cardiac autonomic imbalance including sympathetic overactivity and diminished parasympathetic activity plays an important role in cardiac I/R injury, resulting in left ventricular (LV) dysfunction. Increased vagus nerve activity by an electrical stimulation from an implantable medical device has been shown to be cardioprotective in cardiac I/R injury. However, the role of pharmacological intervention that increases parasympathetic activity on the heart during I/R is not clear.
Purpose
We investigated the effects of a parasympathomimetic drug, donepezil, on the heart with I/R injury. We hypothesized that donepezil exerts cardioprotective effects in rats with cardiac I/R injury by attenuating the impairment of cardiac mitochondrial function, mitochondrial dynamics and mitophagy, resulting in improved LV function.
Methods
Forty male Wistar rats were randomly divided into sham and I/R groups. In I/R group, rats were subjected to acute cardiac I/R injury by ligating left anterior descending coronary artery (LAD) for 30 mins followed by reperfusion for 120 mins, while sham group had similar operation but did not have LAD ligation. Moreover, rats in the I/R group were randomly assigned to be treated with either saline (vehicle group) or donepezil 3 mg/kg by intravenous injection. In donepezil-treated rats, they were divided into 3 subgroups to receive the drug at one of the following time-points; before ischaemia, or during ischaemia, or at the onset of reperfusion. During I/R protocol, LV function was recorded. At the end of protocol, the heart was removed to determine infarct size, cardiac mitochondrial function, mitochondrial dynamics, and mitophagy.
Results
Rats with cardiac I/R injury showed increased infarct size when compared to sham group (Fig. 1A). Rats in all donepezil-treated groups showed reduction of infarct size compared to the vehicle group. This accounts for ∼63%, ∼47%, and ∼44% reduction for the treatment before ischaemia, during ischaemia and onset of reperfusion, respectively. In addition, all donepezil-treated rats had improved LV function by attenuating the reduction of LV ejection fraction (Fig. 1B). The reduction in cardiac mitochondrial ROS production (Fig. 1C), increased mitophagy as indicated by increased PINK-1 expression (Fig. 1D), and rebalancing mitochondrial dynamics were also found in all donepezil-treated rats.
Conclusion
Donepezil protects against cardiac I/R injury by reducing mitochondrial ROS production, enhancing mitophagy, and improving mitochondrial dynamics, leading to decreased infarct size and improved cardiac function.
Figure 1. The effects of donepezil in cardiac I/R
Funding Acknowledgement
Type of funding source: Public Institution(s). Main funding source(s): Thailand Research Fund grants TRF-Royal Golden Jubilee Program (TK and NC), RTA6180003 (SCC), RSA6180056 (SP); The NSTDA Research Chair grant from the National Science and Technology Development Agency Thailand (NC)
Pre-ischaemic mitochondrial substrate constraint by inhibition of malate-aspartate shuttle preserves mitochondrial function after ischaemia-reperfusion