Peng Teng demonstrated that stimulation of α7nAChR by nicotine attenuated monosodium iodoacetate-induced cartilage degradation and osteoarthritis pain, this protective effect of nicotine is associated with the inhibition of MMP-9 overexpression via the PI3K/Akt/NF-kB signaling pathway (50). Here, MMP9 is linked to osteoarthritis.