Effect of Low Level Laser Irradiation on CXCR3 Gene Expression in Rheumatoid Arthritis Joint

Abstract

Rheumatoid arthritis (RA) is characterized by the infiltration of leukocytes into the synovial tissue and synovial fluid of joints, ultimately leading to destruction of cartilage and bone. Low-level laser irradiation (LLLI) is evaluated for treating RA, however, the molecular basis mechanism underlying the effectiveness of LLLI is unclear. Chemokines and those receptors play a central role in the progression of RA inflammation. CXCR3 may be recruited directly from the circulation into the synovial sublining regions by its ligand, CXCL9, produced by synovial fibroblasts. The objectives of this study were to determine whether LLLI decreased production of CXCR3 and CXCL9 in RA joints of type II collagen induced RA (CIA) rats. Total RNA was isolated from rat knee joints with or without treatment of 830 nm LLLI irradiation, and gene expression profiles were analyzed by DNA microarray (Affymetrix, 41,000 genes). As results, LLLI significantly reduced CXCR3 mRNA level, but not significantly reduced CXCL9. The reduction of CXCR3 mRNA levels was confirmed by RT-PCR and real-time PCR. Since CXCR3 plays an important role of the progression of RA, the reduction of CXCR3 gene expression may be one of important mechanisms in reduction of inflammation in RA joints by LLLI.