Tripterygium wilfordii Hook F extract suppresses proinflammatory cytokine-induced expression of matrix metalloproteinase genes in articular chondrocytes by inhibiting activating protein-1 and nuclear factor-kappa B activities - Sylvester, J; Liacini, A; Li, W Q; Dehnade, F; Zafarullah, M (Mol Pharmacol, 2001)