Photobiomodulatory Effect of Blue Light on Oral Fibroblasts

Objectives: Photobiomodulation (PBM) is a non-invasive therapy that utilises light to promote tissue healing. PBM has been used to treat an array of systemic and oral diseases. Classically red light has been used in practice, however recently blue light has been reported to induce beneficial effects. This project aims to investigate the potential therapeutic effects of blue light irradiation on human gingival fibroblasts (HGFs), key cells involved in periodontal diseases.
Methods: Pooled HGFs from healthy donors (n=3, ethics code: RG_12-020) were seeded at 7000 cells/well in black-walled 96 well plates in media supplemented with foetal bovine serum (FBS) or FBS and Escherichia coli Lipopolysaccharide (E.coli LPS 1µg/ml) to induce a pro-inflammatory response, incubated overnight (37oC, 5% CO2) and subsequently irradiated using a bespoke LED array (400-450nm, 24mW/cm2, 5.76J/cm2). Effects of PBM on mitochondrial activity (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT), total reactive oxygen species production (ROS assay), adenosine triphosphate production (ATP assay) and the pro-inflammatory/cytokine response (interleukin-8 (IL-8), enzyme-linked immunosorbent assay (ELISA)) were assessed 24hrs post-irradiation. Data were analysed using one-way ANOVA followed by Tukey test (Sigma plot).
Results: Irradiation of untreated (no LPS) cultures at 400nm induced 13%, 27%, 13% and 13% increases in MTT, ROS, ATP and IL-8 levels, respectively (p<0.05). Irradiation at 450nm induced 15% and 8% increase in ROS and IL-8 levels, respectively (p<0.05). Irradiation of LPS-treated cultures at 400nm induced 41% decreases in IL-8 secretion (p<0.05) and 18% increases in ATP production compared with LPS control (p<0.05). Light at 450nm resulted in 19% and 39% decreases in ROS and IL-8 levels, respectively (p<0.05) relative to LPS control.
Conclusions: Data indicate a differential response to PBM dependent on the presence or absence of disease mediators. Notably post-application of inflammatory challenge, blue light induced decreases in the inflammatory response. This could be important in treatment of periodontal disease.