Induction of Oxidative Stress by Blue Light-irradiation Against Rat Gingiva

Objectives: We investigated the induction and the protection of oxidative stress by blue light irradiation (BLI) against rat palate gingiva.
Methods: Reactive oxygen species (ROS) were produced by BLI to excite flavin-adenine dinucleotide (FAD) which were measured by electron paramagnetic resonance spectroscopy. Under anesthesia, Wister rat (male, n=5) palate gingiva was irradiated (15 minutes a day) or non-irradiated the blue light for 4 consecutive days. On the last day, the rat palate gingiva was collected after sacrifice. N-acetyl-L-cysteine (NAC, 100 mg/kg) as an antioxidant was administered through the study from the previous day. To assessment the oxidative stress, the lipid peroxidation and glutathione quantitation levels were analyzed. This study was compliant with the guidelines for experimental procedures found in the Declaration of Helsinki of the World Medical Association and was approved by Institutional Animal Care Committees. All experiments were performed in minimum 3 times. Dunnett’s multiple comparison tests were performed with the statistical analysis software (GraphPad Prism 6). A P-value of less than 0.05 was considered statistically significant.
Results: BLI excited FAD and generated singlet oxygen (¹O₂) which is one of the major ROS. ¹O₂ was scavenged by applying NAC. BLI was enhanced the lipid peroxidation and the glutathione disulfide (GSSG) levels. The intracellular GSSG concentration increased by BLI was controlled by NAC.
Conclusions: These results suggested that BLI on rat palate gingiva may cause oxidative stress by generating ¹O₂ from FAD present in mitochondria and enhancing intracellular GSSG concentration. In conclusions, since these phenomena were significantly inhibited by the pre-administration of NAC before BLI, antioxidants pre-administration might contribute the oral tissue protection from BLI in dental treatment.
This study was supported by JSPS KAKENHI Grant Number JP18K09894 and Major Course Field Integrated Fundamental Research 1, Graduate School of Dentistry, Kanagawa Dental University.