Simultaneous irradiation of 660 and 808 nm on gingival epithelial cells and fibroblasts induces different patterns of oxidative/antioxidative activities: What is the role of the cell type and irradiation parameters?

The aim of this study was to investigate whether simultaneous irradiation at 660 and 808 nm generates different patterns of oxidative/antioxidative activities compared to consecutive irradiation. Primary cultures of gingival keratinocytes and fibroblasts were exposed to a diose laser (660 ± 2 nm and 808 ± 2 nm, 100 mW, 0.09 cm2 spot area) using double irradiation with the two wavelengths (consecutive or simultaneous) for 6, 10, and 20 s. The two irradiation regimens did not increase cell viability in any of the experimental conditions. Lipid peroxidation was increased after consecutive irradiation in epithelial cells, which was not detected after simultaneous irradiation. After 20s of the simultaneous mode, ROS levels increased, but antioxidative balance decreased. In the fibroblasts, the two double irradiations induced ROS reduction, increase in lipid peroxidation, and improvement of antioxidative balance, mainly after the 20 s irradiation time. In conclusion, simultaneous and consecutive irradiation induced distinct oxidative stress modulation in oral epithelial cells and fibroblasts. The imbalance in the oxidative system observed after longer exposures, allied with the absence of a significant increase in the viability of the two cell types, suggests a contraindication for longer simultaneous irradiation in clinical situations that demand cellular stimulation.

Photobiomodulation Therapy Minimizes the DNA Damage in 5FU-Treated Gingival Fibroblasts.

5-Fluoroufacil (5FU) is a chemotherapeutic agent indicated for solid tumors but causes oral mucositis, which can be prevented and treated using photobiomodulation therapy (PBMT). It is unknown whether PBMT modifies DNA damage induced by 5FU in oral cells. The aim of this study was to investigate the effect of PBMT on DNA damage and repair and on oxidative stress in gingival fibroblasts exposed to 5FU. Primary gingival fibroblasts were exposed to 5FU and then treated with a laser (660 nm, 100 mW, 1 W cm-2 , 0.09 cm2 spot area) for three different irradiation times (6, 10 or 20 s). Six-second irradiation decreased DNA damage and lipidic peroxidation. All irradiated groups showed low H2AX levels and increased p53 expression. Ten-second irradiation showed a trend to induce high lipidic peroxidation levels and DNA damage than other irradiation groups. In conclusion, the PBMT effect on DNA damage and repair was dependent on the time irradiation: 6 s-time irradiation (6.6 J cm-2 ) protect gingival fibroblasts from 5FU-related genotoxicity and oxidative stress, whereas 10s- and 20s-time irradiations (11.1 J cm-2 and 22.2 J cm-2 , respectively) increased the risk of DNA damage after the 5FU exposure.