Efeito do LED vermelho e infravermelho na produção de radicais livres por células pulpares após estímulo com lipopolissacarídeo

Abstract

Studies have showed positive effects related to the pulp tissue repair, after the use of light sources such as laser or Light Emitting Diodes (LED). However, the specific irradiation parameter that may be beneficial or harmful to the inflammatory modulation of this tissue remains unknown. The aim of the study was to evaluate the effect of different parameters of the red and infrared LED on the oxidative stress modulation and on the viability of pulp cells of primary teeth. Pulp cells were obtained from 5 healthy exfoliated teeth and cultured in 24-compartment acrylic plates (105 cells/compartment) using DMEM supplemented with 10% fetal bovine serum (FBS). After 24 hours, the production of inflammatory mediators was induced by the application of lipopolysaccharide (LPS) at a concentration of 10µg/mL in culture medium. Right after the application of LPS, the cells were irradiated only once (630nm and 850nm, 40mW/cm2 and 80 mW/cm2) in the energy exposures of 4J/cm2, 15J/cm2 and 30J/cm2. To assess cell viability, number of viable cells and cell morphology, MTT, Trypan Blue and Scanning Electron Microscopy (SEM) tests were performed respectively. In addition, quantification of nitric oxide (NO) was performed using Griess reagent, and the quantification of reactive oxygen species (ROS) using a fluorescence probe (DCFH-DA). All evaluations were performed 24 hours after irradiation. The Kruskal-Wallis and Mann-Whitney statistical tests were used (p<0.05). For the red LED, an increase on viability was observed in cells exposed to LPS and irradiated with 15J/cm2 and 30J/cm2 at 40mW/cm2 and 4J/cm2 and 15J /cm2 at 80 mW/cm2 compared to the control group (p<0.05). The doses of 4J/cm2 to 40mW/cm2 and 15J/cm2 and 30J/cm2 at 80mW/cm2 modulated oxidative stress when compared to the group treated only with LPS (p<0.05). For the infrared LED, all irradiation parameters were able to decrease the concentrations of ROS after LPS application when compared to the non-irradiated group (p<0.05). The SEM images indicated cells with normal morphology and adhered to the substrate. It was concluded that the red LED using 15J/cm² and 30J/cm2 at 40mW/cm2 and 15J/cm2 at 80mW/cm² and the infrared LED using 15J/cm2 at 40mW/cm2 were the most effective parameters for stimulating viability and modulating the oxidative stress of pulp cells from primary teeth.