Evaluation of laser-photobiomodulation different irradiation parameters on macrophages (RAW 264.7) inflammatory mediators' production.

PURPOSE

Macrophages are pivotal cells in the inflammatory process, and their functions can be modulated by laser irradiation. However, there is no consensus in the literature about Laser-photobiomodulation (L-PBM) parameters that are more suited to stimulate or inhibit them. The goal of this research is to contribute to the understanding of the effects of different L-PBM protocols on inflammatory mediators' production/inhibition and cell viability of macrophage cells in vitro.

MATERIALS AND METHODS

The macrophages cells (RAW 264.7) were divided into two groups: LPS-stimulated (Lipopolysaccharide from Escherichia coli) and non-LPS-stimulated. Each group was subdivided into non-irradiated and irradiated groups. The irradiated group was further divided into: 660 nm, 1 J, 10s; 660 nm, 2 J, 20s; 660, 3 J, 30s; 808 nm 1 J, 10s; 808 nm, 2 J, 20s; 808, 3 J, 30s groups. To all groups and subgroups, a negative (non-irradiated) group was added. All groups and subgroups were evaluated for cell viability, Nitric oxide (NO), interleukin-6 (IL-6) and Tumor Necrosis Factor- α (TNF-α) production.

RESULTS

The results indicated that macrophages irradiated at 660 nm and 808 nm, operating in 1 J, 10s; 2 J, 20s and 3 J, 30s did not change NO, TNF-α and IL-6 production nor cell Viability in non-LPS groups. However, in LPS-stimulated macrophages, a significant stimulatory effect on NO production was observed after laser-irradiation with 660 nm for 2 J, 20s. This NO-stimulatory effect was not observed in the 880 nm irradiated group. LPS-activated macrophages and L-PBM irradiation at 660 nm and 808 nm also resulted in significant inhibitory effects on TNF-α and IL-6 production after 2 J, 20s irradiation. However, TNF-α and IL-6 inhibition using 1 J, 10s was achieved only in 660 nm group.

CONCLUSION

Our findings suggested that, if other parameters are fixed, time and related fluence/energy delivery are important dimensions to consider in L-PBM-production/inhibition on the inflammatory mediators tested. The NO synthesis was more prone to be modulated by a specific wavelength (660 nm) and a broader time-range inhibition of TNF-α and IL-6 was observed in 660 nm groups. Cell viability was not changed in any parameter tested.