Abstract
Little is known whether topical analgesic creams, whose natural products enter the blood stream after application, affect myocardial infarct size. Here we tested whether topical analgesic creams can trigger remote cardioprotection and the mechanism involved. Male Sprague Dawley rats were used for an in vivo rodent model consisting of 30 minutes left anterior descending coronary artery ischemia and 2 hours of reperfusion followed by infarct size assessment. The topical analgesic IcyHot, applied to the abdomen prior to ischemia, reduced myocardial infarct size versus control (41 ± 3* vs 62 ± 1, n= 6/group, *P < 0.001). In contrast, the topical analgesic creams Preparation H, Aspercreme Heat, or Tiger Balm did not alter infarct size. IcyHot, unlike Preparation H, increased circulating methyl salicylate levels during reperfusion (3.0 ± 0.6 vs 0.4 ± 0.2 mg/dL, n = 6, *P < 0.001, measured at the internal jugular vein). Methyl salicylate (10 μM) applied to isolated adult cardiac myocytes during reoxygenation reduced cell death when compared to vehicle (21% ± 2%* vs 30% ± 2% of trypan blue positive cells, n = 9/group, *P < 0.01). Further, treatment with the TRP ankyrin 1 (TRPA1) inhibitors TCS-5861528 (1 μM) or AP-18 (1 μM) blocked the methyl salicylate-induced protective effect in isolated adult cardiomyocytes. In intact rodents, either of the TRPA1 inhibitors (1 mg/kg, intravenous) given prior to IcyHot topical application blocked IcyHot-induced infarct size reduction. IcyHot also reduced infarct size when applied 24 hours prior to myocardial ischemia or during myocardial ischemia versus control. Together, these findings support IcyHot analgesic cream can trigger remote cardioprotection through releasing methyl salicylate into the bloodstream with cardioprotection occurring by a TRPA1-dependent mechanism.