High-frequency near-infrared diode laser irradiation suppresses IL-1β-induced inflammatory cytokine expression and NF-κB signaling pathways in human primary chondrocytes

Osteoarthritis (OA) and rheumatoid arthritis (RA) are common inflammation-associated cartilage degenerative diseases. Recent studies have shown that low-level diode laser treatment can reduce inflammatory cytokine expressions in cartilage. We recently reported that high-frequency low-level diode laser irradiation attenuates matrix metalloproteinases (MMPs) expression in human primary chondrocytes. However, the molecular mechanism underlying the effect of high-frequency low-level diode laser on chondrocytes remains unclear. Therefore, we aimed to elucidate the effect of high-frequency low-level diode laser irradiation on inflammatory cytokine expression in human primary chondrocytes. Normal human articular chondrocytes were treated with recombinant interleukin-1 beta (IL-1β) for 30 min or 24 h and irradiated with a high-frequency NIR diode laser at 8 J/cm 2 . The expression of IL-1β, interleukin-6, and tumor necrosis factor-alpha was assessed using western blot analysis. To evaluate the nuclear factor-kappa B (NF-κB) signaling pathway, the phosphorylation, translocation, and DNA-binding activity of NF-κB were detected using western blot analysis, immunofluorescence analysis, electrophoretic mobility shift assay, and enzyme-linked immunosorbent assay analysis. High-frequency low-level diode laser irradiation decreased inflammatory cytokine expression in IL-1β-treated chondrocytes. Moreover, high-frequency low-level diode laser irradiation decreased the phosphorylation, nuclear translocation, and DNA-binding activity of NF-κB in the IL-1β-treated state. However, irradiation alone did not affect NF-κB activity. Thus, high-frequency low-level diode laser irradiation at 8 J/cm 2 can reduce inflammatory cytokine expressions in normal human articular chondrocytes through NF-κB regulation. These findings indicate that high-frequency low-level diode laser irradiation may reduce the expression of inflammatory cytokines in OA and RA.