Vagus nerve stimulation by focused ultrasound attenuates acute myocardial ischemia/reperfusion injury predominantly through cholinergic anti-inflammatory pathway

Abstract

BackgroundThe invasive method using electrically stimulating vagus nerve has been demonstrated to inhibit the inflammatory response against acute myocardial ischemia/reperfusion(I/R) injury. This neuro-regulatory technique used is invasive implantation of electrical stimulators which have the risk of infection and other complications. A non-invasive method of vagus nerve stimulation applying on acute myocardial I/R injury is particularly important and desirable. ObjectivesThis study aimed to test the hypothesis that focused ultrasound stimulation(FUS) of vagus nerve attenuates acute myocardial I/R injury through cholinergic anti-inflammatory pathway. MethodsThis study was completed with two parts. In the first part, ischemia was induced by left anterior descending coronary artery (LAD) occlusion for 30 minutes (min), followed by 2 hours (h) of reperfusion, FUS lasted for 50 min after reperfusion for 10 min. Infammatory markers, arrhythmia score, histopathology, infammatory markers 7 nicotinic acetylcholine receptor (7nAchR) protein were determined. In the second part, ischemia was induced by LAD occlusion for 30 min, followed by 24h of reperfusion, FUS lasted for 50 min after reperfusion for 10 min. Myocardial fibrosis, infarct size, echocardiographic measurements, biomarkers of pro-oxidative stress, antioxidant and myocardial apoptosis were determined. ResultsFUS of vagus nerve significantly decreased the level of infammatory markers in I/R+FUS group compared with the I/R group, I/R+vagotomy group and I/R+vagotomy+FUS group. FUS decreased the incidence of ventricular tachycardia (VT) and ventricular fibrillation (VF), while also reduced arrhythmia score in I/R+FUS group compared with the I/R group. These improvements were associated with the inhibition of acute inflammatory reaction through cholinergic anti-inflammatory pathway. FUS limited myocardial fibrosis and infarct size, preserved left ventricular function. This cardioprotective effect was associated with alleviation of apoptosis and oxidative stress. ConclusionsThe noninvasive method of ultrasonic neuromodulation using FUS of vagus nerve exerted protective effects on acute myocardial I/R injury. Its potential mechanisms involved the suppression of acute inflammatory reaction through cholinergic anti-inflammatory pathway.