Laser de baixa potência como tratamento da inflamação articular induzida por zymosan

Abstract

Arthrosis and rheumatoid arthritis (RA) are joint diseases characterized by different pathophysiological mechanisms. However, they may present remarkably similar clinical symptoms, including pain and function loss of joint and structural damage, characterized by osteophytes in arthrosis and bone erosion in RA. The main treatments for RA include drugs which cause several side effects such as osteoporosis, susceptibility to infections, metabolic effects, and high toxicity. In general terms, such treatments can represent high cost to governments. Therewith, the low-level laser therapy (LLLT) appears as therapeutic option which may be helpful in inflammatory process resolution, reducing medication use time, costs and quality of life improving. Therefore, the aim was to evaluate LLLT inflammatory process resolution zymosan induced. Infrared laser parameters were: 830nm, 10mW, continuous light emission mode, purchased two energy densities (3J/cm2 and 30J/cm2 ) and treatment times (24h, 48h and 72h). C57BL/6 mice were distributed into groups: ZY- arthritis induced; ZY + Dexa – arthritis induced and treated with dexamethasone; ZY + 3 J/cm2 – arthritis induced and treated with LLLT at 3 J/cm2 ; and ZY + 30 J/cm2 - arthritis induced and treated with LLLT at 30 J/cm2 . For each group described, 3 treatment times were used: 24h, 48h and 72h (1, 2 or 3 LLLT sessions or dexamethasone, respectively). The number of animals per subgroup was 5, totalling 60 animals. The zymosan was injected in crural and subtalar regions, both mice hind limbs. The results demonstrated inflammatory cells influx, predominantly polymorphonuclear in connective tissue adjacent after 24 hours, persisting after two treatment sessions both LLLT and dexamethasone groups (48 hours). Decrease of inflammatory infiltrate was observed in groups treated for 3 consecutive days (72h), especially with LLLT at 30 J/cm2 and dexamethasone. It was observed that dexamethasone and LLLT at 30J/cm2 treatments showed tendency to reduce inflammation at all times tested (24h, 48h and 72h) when compared with untreated group (ZY), although no statistical differences were observed (p>0.05). On the other hand, LLLT at 3J/cm2 showed slight reduction in inflammatory area, only from 48h and it did also not present statistical differences when compared with untreated group (ZY) (p>0.05). Additionally, after 48 hours, ZY group increased its inflammation area. This finding may indicate the inflammatory process peak for this experimental model. Our results demonstrate that LLLT tends to reduce the inflammatory process after 48 hours at the highest energy density (30 J/cm2 ), while at the lowest energy density (3 J/cm2 ) the anti-inflammatory effect was slower. LLLT at 30J/cm2 presents anti-inflammatory behaviour similar to drugs used in inflammatory pathologies, such as dexamethasone.