Effects of Visible Light on Release of IL-10 from Lymphocytes

Introduction: In recent years the medical and dental professions have become aware of the ever increasing array of clinical applications offered by low level laser therapy (LLLT). However, the effects of non-coherent visible light sources on the regulation of inflammatory responses at the cellular and cytokine levels have not been established. Anti-inflammatory interleukin 10 (IL-10) is an important regulatory cytokine that affects the entire inflammatory process. Objective: Our study aim was to investigate the effect of visible light sources at wavelengths of 400-500nm, on the release of IL-10 by stimulated lymphocytes. Materials and Methods: Lymphocytes from mouse spleens were isolated, plated on 96-well-microplates containing RPMI media and stimulated with heat-killed Porphyromonas gingivalis for periopathogenic challenge. Prior to the challenge, the cells were exposed to a plasma arc curing (PAC) light, halogen lamp or light emitting diode (LED) light, with fluences of 0.6 - 93.6 J/cm2 for up to 2 min. The plates were incubated for 24h and 48h, and the levels of IL-10 were determined by ELISA. Results: Light exposure of lymphocytes to PAC at 7.8 and 93.6 J/cm2 for 10 sec and 2 min respectively, induced the release of IL-10 after 24h of incubation. Exposure to only 1.6 J/cm2 for 2 sec induced the release of IL-10 after 48h of incubation. IL-10 was not released following exposure to a halogen light at 286mW/cm2 after 24h of incubation, but release of the cytokine was detected after 48 h of incubation, following exposure to a 2.9 and 34.3 J/cm2 for 10 sec and 2 min, respectively. LED light did not influence the release of IL-10. Conclusions: Blue light sources used in dental practice, like halogen lamp and PAC, induce the release of IL-10. This phenomenon suggests that these light sources may exert biological effects, such as down regulation of the inflammatory response.