Photobiomodulation control the expression of MMP, TNF-α and NK-1 receptors, improving allodynia and cartilage resistance in rheumatoid arthritis model.

Rheumatoid arthritis (RA) is a chronic, systemic, and progressive autoimmune disease that leads to irreversible cartilage destruction and affects multiple tissues. In vivo experimental studies have demonstrated that photobiomodulation therapy (PBM) produces beneficial effects on inflammation and pain modulation. This study aimed to evaluate the effects of topical PBM on the expression of matrix metalloproteinases (MMP-2, MMP-9, MMP-13), tumor necrosis factor-alpha (TNF-α), neurokinin-1 (NK1) receptors, mechanical allodynia, and cartilage mechanical resistance in a rat model of RA. RA was induced using type II collagen and Freund's adjuvant, followed by PBM treatment (808 nm, 2 J, 50 mW, three times per week). Euthanasia was performed at 7 and 14 days using an overdose of anesthetics, and knee cartilage samples were collected for subsequent analyses. PBM significantly reduced the expression of TNF-α and MMPs, preserved cartilage mechanical resistance, and decreased NK1 receptor expression, resulting in improved mechanical allodynia. Topical PBM (808 nm, 2 J, 50 mW) effectively minimized cartilage degradation and attenuated pain sensitivity in rats with induced RA.