Background: Rheumatoid arthritis (RA) is a systemic autoimmune disorder that involves inflammation and pain of joints. Low-level laser irradiation is being evaluated for treating RA, however, the effectiveness of linear polarized near infrared light (SuperLizer;SL) irradiation is unclear.
Aim: It has been reported that interleukin 6 (IL-6) plays a key role in the progression of RA. In our previous study, using DNA microarray analysis, we examined the gene expression profiling of human rheumatoid fibroblast-like synoviocyte MH7A in response to IL-1β administration and SL irradiation. As a result, IL-6 was listed in altered gene as increased by IL-1β and decreased by SL irradiation.
Material and methods: The reduction of IL-6 gene expression in MH7A by SL irradiation was confirmed by reverse transcription polymerase chain reaction (RT-PCR) and real-time PCR. Effect of SL irradiation on the RA inflammation in the collagen induced arthritis (CIA) rats was also studied by measuring temperature. IL-6 production in knee joint of rats was analyzed by immunohistochemistry.
Results: Scatter plot analysis demonstrated that an increase in IL-6 gene expression by IL-1β was reduced by SL irradiation. The reduction of IL-6 mRNA level by SL irradiation was successfully confirmed by RT-PCR and real-time PCR. SL irradiation treated CIA rat decreased the temperature of knee joints. The immunohistochemical analysis demonstrated a strong IL-6 staining in synovial membrane tissue of CIA rat joint, and SL irradiation significantly reduced the staining.
Discussion: Since IL-6 has been identified to be an important proinflammatory cytokine in the pathogenesis of RA, the reduction of IL-6 expression is one of mechanisms in reduction of inflammation in RA joints by SL irradiation suggesting that SL irradiation may be useful for RA therapy.
Conclusion: SL irradiation reduced IL-6 gene expression in MH7A, and reduced inflammation and IL-6 protein expression in knee joint of CIA rats