Introduction: Myocardial ischemia-reperfusion (I/R) results in the generation of oxygen-derived free radicals, the accumulation of lipid peroxidation-derived unsaturated aldehydes, variable angina (ischemic pain) and infarction. Pain receptors known as transient receptor potential ankyrin-1 (TRPA1) are activated by endogenous aldehydes, including acrolein and 4-hydroxynonenal, yet the contribution of TRPA1 (a calcium permeable channel) to I/R-induced myocardial injury has not been assessed.
Hypothesis: We tested the hypothesis that the absence of TRPA1 would affect I/R injury.
Methods and Results: Adult male C57BL/6 mice hearts and isolated cardiomyocytes were positively stained with an immunofluorescent antibody to TRPA1 with intense localization at intercalated disks. Presence of mRNA for human TRPA1 and mTrpa1 was confirmed by qRT-PCR in cardiomyocytes from human induced pluripotent stem cells or from hearts of wild type (WT) mice, respectively. Genetic deficiency of TRPA1 did not alter basal cardiac function measured by echocardiography. Disruption of the TRPA1 gene decreased infarct size (WT, 34.1±9.3% of risk region; TRPA1-null, 14.3±9.9%, n=8,7, respectively, p<0.05) after I/R (30 min I, 24h R) in situ, indicating that TRPA1-null mice were significantly protected against myocardial I/R injury than were WT mice. The I/R-induced area at risk, however, was similar (AAR: WT, 40.3±8.4%; TRPA1-null, 42.2±11.3% of the left ventricle). A plausible mechanism of protection was observed when acrolein-induced cardiomyocyte hypercontraction was delayed in the presence of the TRPA1 inhibitor, HC-030031, indicating that TRPA1 contributes to calcium overload during I/R. TRPA1 inhibitor-induced protection was similar to that provided by SN-6, a Na+/Ca++ exchange inhibitor, further supporting the role of calcium overload in acrolein-induced cardiomyocyte toxicity.
Conclusions: TRPA1 contributes to I/R injury by mediating the cytotoxicity of endogenously-generated aldehydes. For example, acrolein stimulates a TRPA1-dependent calcium overload and hypercontraction in cardiomyocytes. TRPA1 inhibitors may be used to decrease both angina and myocardial ischemia-reperfusion injury.