Efeito anti-inflamatório do laser de baixa potência na artrite induzida por zymosan

Abstract

Arthritis is a muscle skeletal disorder characterized by inflammation of the joints, which has a significant socioeconomic impact, as observed in various rheumatic disorders such as rheumatoid arthritis (RA), chronic autoimmune disease associated with patients motor incapacity. Current strategies for the treatment of RA aim to relieve symptoms and modifying the degenerative course of the disease, but may have serious side effects and not always result in clinical improvement. In this context, the use of low-power laser therapy appears as non-invasive alternative for the arthritis treatment due to their anti-inflammatory and tissue regeneration properties. However, the anti-inflammatory mechanisms of the laser in biological tissues are not completely understood. Thus, this study aims to evaluate the anti-inflammatory effects of therapeutic low-power lasers in an induced inflammatory process, which resembles RA. An inflammatory process was induced in the talocrural and subtalar joints of the two rear paws of C57BL/6 using a zymosan injection in the periarticular region. The animals were divided into 8 groups (n = 6): (I) control, (II) zymosan, (III) euthanized 5 hours after induction with zymosan (IV) zymosan + dexamesona, (V) laser 3J/cm2 (VI ) laser 30J/cm2 (VII) + zymosan laser 3J/cm2 (VIII) laser zymosan + 30J/cm2. The low power laser conditions were: λ = 830 nm (infrared), 10mW power and fluences of 3 J/cm2 and 30J/cm2 at continuous mode of light emission. Irradiation was carried out for 4 consecutive days, starting 5 hours after inflammation-induced by zymosan. Twenty four hours after the last application of the laser, the animals were euthanized, their joints dissected and distributed: (a) morphological analysis, (b) DNA fragmentation analysis by TUNEL and (c) expression analysis of genes encoding proteins related to apoptotic pathways by real time PCR. Morphological analysis revealed the presence of inflammatory cell infiltrate in the adjacent connective tissue of periarticular region for all groups that received zymosan. This infiltration decreased significantly after laser irradiation using 30J/cm2 fluence. Both groups irradiated demonstrated DNA fragmentation rate incresed and only observed in inflammatory cells. DNA fragmentation is usually observed to cell death by apoptosis. This result is corroborated by expression increase of genes that encode proteins associated with both intrinsic and extrinsic pathways of apoptosis. The inflammatory process resolution for Zy+3J/cm2 group was slower than Zy+30J/cm2, since it was observed high cell density and DNA fragmentation rate in inflammatory cells. Thus, the low-power laser, particularly in 30J/cm2 fluence, could reduce the inflammatory infiltration in periarticular area, accelerating the inflammatory cells apoptosis. The use of low power infrared laser can be a good alternative for inflammatory joint disorders treatment, since it is a noninvasive method. Additionally, this type of treatment did not show side effects on other healthy surrounding tissues, acting especially in inflammatory cells.