Effects of piperine on signaling pathways and transnuclear migration. (a) Interleukin (IL)1β-stimulated fibroblast-like synoviocytes (FLSs) treated with piperine were analyzed by western blot. Piperine treatment did not inhibit the degradation of inhibitor of κB (IκB)α, but slightly inhibited the phosphorylation of extracellular-regulated kinase (ERK)1/2 in the MAP kinase signaling pathways was slightly inhibited in the presence of piperine. (b) The nuclear levels of nuclear factor (NF)κB and activator protein 1 (AP-1) were measured by ELISA detecting p65 and c-FOS from nuclear extracts, respectively, on an ELISA. Piperine inhibited the level of AP-1 in the nucleus, but not NFκB levels. Values are expressed ± standard error of the mean (SEM). ***P < 0.001 vs IL1β treated group without piperine or piperine alone.