Efeito laser de baixa intensidade sobre a nocicepção e inflamação aguda em ratas idosas submetidas a protocolo experimental para tendinopatia por meio de colagenase

Abstract

This study was aimed at determining if low level laser therapy (LLLT) can decrease pain, hyperalgesia, and expression of inflammatory mediators, such as tumor necrosis factor alpha (TNF-α), interleukin (IL)6 and IL-10, in an acute collagenase-induced tendinopathy rat model. Forty female Wistar rats (10 adult and 30 aged rats) were assigned to three groups G1 (control adult rats), G2 (aged rats with tendinopathy) and G3 (LLLT-treated, aged rats with tendinopathy), which were further subdivided (n= 5/subgroup) based on the sampling time (24, 48, and 72 hours). The tendinopathy model was established using collagenase. The skin was surgically prepared and collagenase (100 μg/tendon) was injected percutaneously into the Achilles tendon, approximately 2 mm proximal to the osteotendinous junction. The animals were treated 1 hour after LLLT (830 nm; 50 mW of mean power and 3 J of energy for 60 s, and every 24 hours thereafter until euthanasia. Hyperalgesia was evaluated before euthanasia. The tendons were dissected and stored in a freezer at -80°C for ELISA and western blotting. The G3 group showed decreased hyperalgesia compared to the G2 group (p <0.05). LLLT groups showed a reduction in the expression of Cox 1 and 2, as well IL-6 and TNF-α but an increase in that of IL-10 (both p <0.05) compared with the untreated group. LLLT can decrease inflammatory biomarker levels, with better outcomes at 72 hours post injury, and can increase the nociceptive threshold of older rats.