Efeito do laser de baixa potência sobre a modulação de mediadores inflamatórios, marcadores de estresse oxidativo, expressão de fatores miogênicos e na determinação dos fenótipos de fibras musculares durante o reparo do músculo esquelético de ratos

Abstract

Muscle injuries are a major clinical conditions found in the rehabilitation center. The Low-Level Laser Therapy (LLLT) has demonstrated positive effects on muscle repair process. However, there is no description in the literature as could influence the determination of the phenotype of newly formed fibers and the type of myosin heavy chain (MHC) expressed and little is known about its effects in modulating oxidative stress. This study analyzed the effect of LLLT on the modulation of inflammatory mediators, markers of oxidative stress, expression of myogenic factor and determining the MHC isoforms during the repair process of skeletal muscle in rats. Wistar rats were divided into three groups: 1) control group; 2) non-treated injury group and 3) Injury treated with LLLT. Cryoinjury was induced by two applications of a metal probe cooled in liquid nitrogen directly onto the belly of the tibialis anterior (TA) muscle. The study periods were 12 and 24 hours for analysis of inflammatory markers (elastase-neutrophilic, CD-68, NO, IL-1β and IL-6) by immunohistochemistry and oxidative stress (lipid peroxidation, protein oxidation, SOD, CAT, GPx and TRAP) and 1, 3, 7 and 14 days for gene expression analysis of MHC isoforms (I, IIA, IIB and IIX), MyoD, myogenin, IL-6, calcineurin and myostatin by qRT-PCR. The results showed that LLLT was able to modulate oxidative stress and inflammatory mediators decreasing the lipid peroxidation, protein oxidation, number of neutrophils, IL-1β and IL-6 as well as an increase in the enzymatic activity of SOD, NO synthesis and the number of macrophages after 12 and 24 hours. LLLT was able to modulate the myogenic factors and MHC isoforms increasing the mRNA expression of MyoD and decreasing IL-6, calcineurin and MHC mRNA expression after 3 and 7 days, as well as, to increase the myogenin, IL- 6, MHC IIA, MHC IIB and myostatin mRNA expression and decrease the calcineurina mRNA expression after 14 days. In conclusion, LLLT administered following muscle injury has a positive effect on the inflammatory mediators and oxidative damage, myogenic factors and in the determining of MyHC isoforms. Moreover, the results suggest that LLLT can be considered an effective therapeutic tool for treatment of muscle injuries.