Pulsed Ultrasound Attenuates the Hyperglycemic Exacerbation of Myocardial Ischemia-Reperfusion Injury

Objective: Acute hyperglycemia during myocardial infarction worsens outcomes in part by inflammatory mechanisms. Pulsed ultrasound has anti-inflammatory potential in bone healing and neuromodulation. We hypothesized that pulsed ultrasound would attenuate the hyperglycemic exacerbation of myocardial ischemia-reperfusion injury via the cholinergic anti-inflammatory pathway. Methods: Acute hyperglycemia was induced in wild-type C(57)BL6 or acetylcholine-receptor knockout (alpha 7nAChR(-/-)) mice by intraperitoneal injection of glucose. Pulsed ultrasound (frequency 7 MHz, bursting mechanical index 1.2, duration 1 second, repeated every 6 seconds for 2 minutes, 20-second total exposure) was performed at the spleen or neck after glucose injection. Separate mice underwent vagotomy before treatment. The left coronary artery was occluded for 20 minutes, followed by 60 minutes of reperfusion. The primary end point was infarct size in explanted hearts. Results: Splenic pulsed ultrasound significantly decreased infarct size in wild-type C57BL6 mice exposed to acute hyperglycemia and myocardial ischemia-reperfusion injury (5.2% +/- 4.4% vs 16.9% +/- 12.5% of risk region, P = .013). Knockout of alpha 7nAChR abrogated the beneficial effect of splenic pulsed ultrasound (22.2% +/- 12.1%, P = .79 vs control). Neck pulsed ultrasound attenuated the hyperglycemic exacerbation of myocardial infarct size (3.5% +/- 4.8%, P = .004 vs control); however, the cardioprotective effect disappeared in mice that underwent vagotomy. Plasma acetylcholine, beta(2) adrenergic receptor, and phosphorylated Akt levels were increased after splenic pulsed ultrasound treatment. Conclusions: Pulsed ultrasound treatment of the spleen or neck attenuated the hyperglycemic exacerbation of myocardial ischemia-reperfusion injury leading to a 3-fold decrease in infarct size. Pulsed ultrasound may provide cardioprotection via the cholinergic anti-inflammatory pathway and could be a promising new nonpharmacologic, noninvasive therapy to reduce infarct size during acute myocardial infarction and improve patient outcomes.