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Effect of Low Level Laser Therapy on the expression of inflammatory mediators and on neutrophils and macrophages in acute joint inflammation

Abstract

Introduction: Inflammation of the synovial membrane plays an important role in the pathophysiology of osteoarthritis (OA). The synovial tissue of patients with initial OA is characterized by infiltration of mononuclear cells and production of pro-inflammatory cytokines and other mediators of joint injury. Objective: To evaluate the effect of low level laser therapy (LLLT) operating at 50 mW and 100 mW on joint inflammation in rats induced by papain, through histopathological analysis, differential counts of inflammatory cells (macrophages and neutrophils), as well as gene expression of IL-1ß and IL-6, and protein expression of TNF-±. Materials and Methods: Male Wistar rats (60) were randomly divided into 4 groups of 15 animals, namely, a negative control group; an inflammation injury positive control group; a 50 mW LLLT group, subjected to injury and treated with 50 mW LLLT; and a 100 mW LLLT group, subjected to injury and treated with 100 mW LLLT. The animals were subject to joint inflammation (papain solution, 4%) and then treated with LLLT. On the day of euthanasia, articular lavage was collected and immediately centrifuged; the supernatant was saved for analysis of expression of TNF-± protein by ELISA and expression of IL-1ß and IL-6 mRNA by RT-PCR. A histologic examination of joint tissue was also performed. For the statistical analysis, ANOVA with Tukey's post hoc test was used for comparisons between each group. All data are expressed as mean values and standard deviation, with p < 0.05. Results: Both laser treatment modalities were efficient in reducing cellular inflammation, and both decreased the expression of IL-1ß and IL-6. However, the 100 mW treatment led to a higher reduction of TNF-± compared to the 50 mW treatment. Conclusion: LLLT at 50 mW was more efficient in modulating inflammatory mediators (IL-1², IL-6) and inflammatory cells (macrophages and neutrophils), which correlated with the histology that showed a reduction in the inflammatory process. (AU)

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