Blue laser-induced selective vasorelaxation by the activation of NOSs

Phototherapy has been tried for treating cardiovascular diseases. In particular, ultraviolet and blue visible lights were suggested to be useful due to their nitric oxide (NO)-production ability in the skin. However, the effects of blue light on the arterial contractility are controversial. Here, we hypothesized that appropriate protocol of blue laser can induce selective vasorelaxation by activating vasodilating signaling molecules in arteries. Using organ chamber arterial mechanics, NO assay, Matrigel assay, and microarray, we showed that a 200-Hz, 300-μs, 445-nm pulsed-laser (total energy of 600 mJ; spot size 4 mm) induced selective vasorelaxation, without vasocontraction in rat mesenteric arteries. The laser stimulation increased NO production in the cord blood-endothelial progenitor cells (CB-EPCs). Both the laser-induced vasorelaxation and NO production were inhibited by a non-selective, pan-NO synthase inhibitor, L-N^G-Nitro arginine methyl ester. Microarray study in CB-EPCs suggested up-regulation of cryptochrome (CRY)2 as well as NO synthase (NOS)1 and NOSTRIN (NOS trafficking) by the laser. In conclusion, this study suggests that the 445-nm blue puled-laser can induce vasorelaxation possibly via the CRY photoreceptors and NOSs activation. The blue laser-therapy would be useful for treating systemic hypertension as well as improving local blood flow depending on the area of irradiation.