TNF and osteoarthritis: In a male Sprague–Dawley rat model of early-stage osteoarthritis induced by immobilizing the left knee joints, nicotine (50 μg/ml) added to the drinking water ameliorated cartilage damage, promoted matrix production, and had an anti-inflammatory effect by reducing the serum levels of TNF-α and the expression of TNF-α in the synovial tissue via stimulating α7 nAChR, indicating that nicotine may have potential as a therapeutic strategy for early osteoarthritis (68).