Influence of Low-energy Laser Irradiation on Nitric Oxide Expression in Vascular Endothelial Cells

Anti-inflammatory action of low-energy laser has been reported and widely applied for clinical dental treatment. However, its action mechanism is unclear. In this study, focusing on the dynamics of nitric oxide (NO) , we investigated the anti-inflammatory effect of low-energy laser on vascular endothelial cells. Vascular endothelial cells were cultured and irradiated with low-energy laser. Cells were divided into those cultured in media containing (LPS additive group) and not containing LPS (control group) , and each group was irradiated with laser. The amount of synthesized NO was quantitated 24 hours later using a nitrate/nitrite measurement kit, and expression of NO synthases (NOSs) was observed using immunostaining. The NO quantitation, indicated that the synthesized amount decreased in the irradiated LPS additive group. On immunostaining, inducible NOS (i-NOS) expression reduced in the LPS additive group. These findings suggested that i-NOSs were involved in the low-energy laser-induced decrease in NO synthesis. It was suggested that the anti-inflammatory effect of low-energy laser irradiation might arise from decreased NO synthesis in the infiammation.