Reduction of monocyte chemoattractant protein-1 expression in rheumatoid arthritis rat joints with light-emitting diode phototherapy.

Abstract

Rheumatoid arthritis (RA) is a systemic autoimmune disorder that involves inflammation and pain of the joints. Light-Emitting Diode (LED) irradiation is being evaluated for treating RA; however, the mechanism is unclear. Monocyte chemotaxis protein (MCP)-1 is a key chemokine in the inflammatory status of RA, and MCP-1 levels in plasma are described as a marker for joint inflammation in RA. To understand the mechanism of the anti-inflammatory effect of LED irradiation on RA, the expression of MCP-1 was examined in the knee joints of collagen-induced arthritis (CIA) rats. The rats were immunized with type II collagen and CIA development was confirmed. CIA rat joints were irradiated with LED energy (3 sessions/week, 2 weeks. 840 nm, 2 J/cm(2)). Total RNA was isolated from the rat knee joint tissues and the MCP-1 mRNA levels were monitored with the reverse transcription polymerase chain reaction (RT-PCR) technique and real-time PCR. MCP-1 production in the rat knee joints was analyzed immunohistochemically. RT-PCR analysis demonstrated that MCP-1 mRNA levels had increased in CIA animals when compared to controls, and LED irradiation significant reduced the gene expression in CIA rats. Real-time PCR analysis confirmed a significant reduction in MCP-1 gene expression. The immunohistochemical analysis demonstrated strong MCP-1 staining in CIA rat joint synovial membrane tissue, and LED irradiation significantly reduced the staining. Since MCP-1 has been identified as an important chemokine in the pathogenesis of RA, the reduction of MCP-1 expression would appear to be one of the mechanisms in the reduction of inflammation by LED irradiation. LED irradiation reduced RA-related inflammation through the reduction of MCP-1 gene expression in CIA rat knee joint synovial tissue.