Avaliação da indução de lesões no DNA por lasers terapêuticos de baixa potência

Abstract

In regenerative medicine there is an increasing use of low level lasers in therapeutic protocols for treatment of diseases in soft tissues and the bone tissue. Lasers emit light beams with special properties, in which the wavelength, frequency, power and emission mode are properties which determine ther photophysical, photochemical and photobiological responses. However, it is suggested that low level lasers induced the generation of free radicals which could react with important biomolecules, such as DNA. These reactions can result in damage and induce DNA repair mechanisms preserving the genetic code integrity and cell homeostasis. Therefore, the purpose of this study was to evaluate DNA damage in peripheral blood cells from Wistar rats and expression of ERCC1 and ERCC2 genes in biological tissues exposed to low level lasers at wavelengths, fluences, powers and emission modes used in therapeutic protocols. In order to achieve the aims, peripheral blood samples were exposed to red laser (660 nm) and infrared (808 nm) at different fluences, power and emission modes, and the induction of DNA damage was evaluated by comet assay. In other experiments, DNA damage was assessed by a modified comet assay utilizing the repair enzymes: formamidopyrimidine DNA glycosylase (FPG) and endonuclease III. Skin and muscle from Wistar rats were exposed to lasers and samples from tissues were collected to RNA extraction, cDNA synthesis and gene expression evaluation by real-time PCR. Data from this study showed that exposure to lasers induces DNA damage depending on the fluence, power and emission mode, and that these damages are targeted by FPG and endonuclease III. ERCC1 and ERCC2 RNAm relative expression in exposed tissues was changed depending on the wavelength and fluences used. Results suggest that oxidative DNA damage could be considered for patient safety and therapeutic efficacy, as well as changes in the expression of DNA repair genes participate in effects of biostimulation justifying the therapeutic applications of low level lasers.