Estudo do papel do laser de baixa intensidade na modulação do estresse oxidativo muscular induzido pelo exercício resistido em ratas

Abstract

Oxidative stress comprises the circumstance in which there is imbalance between the generation of oxidizing agents and the antioxidant defense systems, which results in injury and cellular dysfunction. In this context, there is enough data to consider physical exercise as an inducing condition for increased production of free radicals. It follows that, oxidative stress induced by exercise increases the risk of muscle damage resulting in cellular dysfunction and delay the recovery process. The high incidence of muscle injuries mainly during intense periods of training has directly affected the growing number of studies that seek a way to minimize oxidative damage and, consequently, to accelerate the tissue repair. In this context, low-level laser therapy (LLLT) has emerged as an option to minimize oxidative damage and modulate tissue repair. Different studies have showed positive effects of LLLT when applied before and after resistance exercise in the reduction of biochemical markers of muscle damage and modulation of the inflammatory process. The objective of the present study was to evaluate the effects of previous application of LLLT on oxidative stress markers in experimental model of resistance exercise in rats. Sixty Wistar rats were randomly divided into five experimental groups: (1) Sham (n = 12); (2) Control (n = 12); (3) LLLT 4 J (n = 12); (4) LLLT 8 J (n = 12) and (5) LLLT 12 J (n = 12). The animals were submitted to only one exercise session, which consisted of four climbs on the ladder carrying the maximum load. For LLLT, infrared laser (830 nm, output power 100 mW, beam area 0.0028 cm2, total energies of 4, 8 and 12 J and irradiation times 40, 80 and 120 seconds, respectively) were used. Irradiation was performed in 3 points (proximal, medial and distal) in the gastrocnemius muscle of both lower limbs. After irradiation, the animals were submitted to a resistance exercise session. Afterwards, the animals were euthanized and the right gastrocnemius muscle collected for analysis of oxidative stress markers (malondialdehyde [MDA], 4-hydroxynonenal [4-HNE], protein oxidation, superoxide dismutase [SOD] and, catalase [CAT]). The results showed that LLLT in its different doses was able to modulate the oxidative stress reducing the immunoblot of 4- HNE and reduction of the oxidized proteins of the groups irradiated with 8 and 12 J, when compared to the non-irradiated resistance exercise group. In relation to SOD enzyme, it was possible to observe the increase of its activity in the different energy doses (4, 8 and 12 J) in relation to the non-irradiated resistance exercise group. In conclusion, LLLT treatment at different irradiation doses (4, 8 and 12 J) modulated the

oxidative stress in the gastrocnemius muscle of rats submitted to a high-intensity resistance exercise session, preventing an increase in lipoperoxidation, improvement in defense antioxidant activity linked to the enzymatic activity of SOD and higher doses resulted in normalization of protein oxidation levels.