TNF and rheumatoid arthritis: Protocatechuic acid inhibits the secretion of MMP-3, MMP-13, TNF-α, IL-1β, and IL-6; regulates the expression of p-p65 and IκBα; and reduces the phosphorylation level of Akt and mTOR, and exerts anti-RA effects by inhibiting the NF-κB and Akt/mTOR signaling pathways [29].