Adjunctive zinc supplementation with methotrexate improves therapeutic outcomes in an animal model of arthritis

Zinc is an essential micronutrient necessary for regulating numerous physiological functions and cellular mechanisms, including bone remodelling and immune regulation. Zinc deficiency is associated with rheumatoid arthritis (RA), as loss of zinc homeostasis can impair the activation and maturation of immune cells. An imbalanced immune response is a hallmark of RA. This study aimed to compare the potential of methotrexate (MTX) monotherapy with a combination of MTX and two organic zinc compounds—zinc aspartate and zinc citrate—administered at a therapeutic dose of 50 mg/day, on clinical, biochemical, immunological, and radiological parameters of polyarthritis in a collagen-induced arthritis (CIA) model. Results showed that combination treatments with zinc compounds at this therapeutic level significantly improved oxidative stress markers (GSH, CAT, SOD, NO, MPO, ELA, LPO), serological biomarkers (anti-CCP, CRP), pro-inflammatory mediators (COX-2, NF-κB-p65), pro-inflammatory cytokines (IL-6, IL-1β, TNF-α, IFN-γ), and anti-inflammatory cytokines (IL-10, TGF-β1) compared to the CIA group and MTX monotherapy. Clinical signs, molecular, radiological, and histological analyses of the ankle joints in arthritic rats aligned with these findings. Overall, the results suggest that combining zinc compounds with MTX yields better outcomes in reducing arthritis severity, oxidative stress, and inflammatory markers compared to MTX monotherapy.