Reduction of Matrix Metalloproteinase-3 Expression in Rheumatoid Arthritis Rat Joints by Light-emitting Diode

Rheumatoid arthritis (RA) is a systemic autoimmune disease that involves inflammation and joint pain and causes bone resorption. Irradiation with light-emitting diodes (LEDs) is being evaluated for the treatment of RA, but the underlying molecular mechanisms are unclear. To determine whether anti-inflammatory effects are provided, LED irradiation was provided for rats with collagen-induced RA (CIA), and total RNA was isolated from the synovial tissues of CIA rat joints. Gene expression profiles were then monitored by DNA microarray. LED irradiation decreased the swelling in CIA rat knee joints. DNA microarray analysis demonstrated that expression of many genes was altered in RA, including increased MMP3 mRNA levels, while MMP3 mRNA levels were reduced by LED irradiation. These reductions in MMP3 mRNA levels by LED irradiation were confirmed by RT-PCR and real-time PCR. Immunohistochemical analysis demonstrated strong staining for MMP3 in the CIA group, and LED irradiation significantly reduced this staining. Clinical features of reduced swelling in CIA knee joints suggest that LED irradiation might be useful as RA therapy. Since MMP3 has been identified as an important factor in the pathogenesis of RA, reducing MMP3 expression by LED irradiation might offer an important mechanism for reducing inflammation in RA.