Protective effects of Red/Near Infrared Radiation on Murine Cardiac Ischemia/Reperfusion Injury

Red/Near infrared radiation (R/NIR) has been reported to reduce myocardial infarct (MI) size in rabbits after ischemia/reperfusion (I/R) injury (Lohr N.L, JMCC 2009). The precise mechanisms responsible for the cardioprotective effects of R/NIR are incompletely understood. We sought to identify the most beneficial wavelengths in the R/NIR light spectrum for limiting murine cardiac I/R injury. Anesthetized and ventilated mice underwent left coronary artery ligation for 60 min followed by reperfusion. R/NIR was applied for three min at the beginning of reperfusion. Area at risk (AAR) and MI size were measured at 24h of reperfusion. We investigated several wavelengths at varying levels of irradiance. A 19% decrease of MI/AAR was observed in wild mice when hearts were irradiated with red light (690 nm) at 0.06 W/cm2 of irradiance for 3 min at the time of reperfusion (59 ± 9% control group, n=7, vs 47 ± 7% irradiated group, n=6, P<0.05). The cardioprotective effect of light appears related to both the specific wavelength and the level of irradiance across the broad spectrum of R/NIR radiation. By defining the specific wavelengths that provide maximal cardioprotection, genetically altered mice will further provide the precise mechanisms underling the cardioprotective effect of R/NIR. This work was supported by NIH grant R01AI050875 and laboratory royalties from licensed patents.