In Vitro Effects of Low-Level Laser Therapy on the Viability and Secretory Activity of Resting Macrophages

Background/Objectives: Low-level laser therapy (LLLT) covers a wide range of parameters in terms of laser properties and dosage, which is important for its effects. It is important to select safe, optimal irradiation conditions to obtain the desired therapeutic effect of LLLT on cells. This article is focused on the selection of favourable (biostimulating) exposure conditions for LLLT, which are the beam application method (continuous [C] or pulsed [P] laser beam), radiation power and LLLT dose, on the viability and secretory activity regarding resting macrophages of the RAW 264.7 cell line. Methods: RAW 264.7 macrophages were seeded on 24-well tissue culture. ASTAR PhysioGo 400C apparatus with a spot applicator generating electromagnetic radiation in the infrared light range of 808 nm and power of 100 mW and 200 mW was used for laser irradiation of macrophages. Cells were treated with different doses of constant radiation 5 J/cm²/well or 10 J/cm²/well. Results: It was shown that the most beneficial radiation parameters for cells were obtained with a pulsed laser beam of 200 mW power and a dose of 5 J/cm², which caused an increase in macrophage adhesion and viability, as well as an increase in NO secretion by macrophages and their TOS, with a simultaneous decrease in the secretion of TNF-α, MCP-1 and MMP-9 by cells. Conclusions: The research results presented above indicate that the effect of LLLT on resting macrophages modulates their biological activity, and the intensity of photobiostimulation depends on the irradiation parameters, including wavelength, power, dose and method of laser beam application.