The JNK and Akt pathways are required for peripheral blood-macrophage-conditioned medium (PB-MCM)-induced urokinase-type PA (uPA) expression. Cells were untreated (CL) or stimulated with PB-MCM for 2 hours. The results shown are the mean ± SEM from three to four independent experiments. Before culturing as CL or PB-MCM-stimulated cells, chondrocytes were pretreated with PD98059 (PD; 30 μM), SP600125 (SP; 20 μM), SB203580 (SB; 10 μM), or LY294002 (LY, 30 μM) individually or in combination for 1 hour (A), or transfected with control siRNA (si-CL), control pcDNA3 vector (vec), or siRNAs targeting ERK (si-ERK), JNK (si-JNK), p38 (si-p38), or dominant negative mutant of Akt (DN-Akt) (B). *P < 0.05 versus CL. #P < 0.05 versus DMSO-treated, control siRNA (si-CL)-, or control pcDNA3 vector (vec)-transfected cells under PB-MCM stimulation. **P < 0.05 versus SP- or LY-pretreated cells under PB-MCM stimulation. (C, D) Control (CL) or PB-MCM-stimulated chondrocytes were maintained for the times indicated. The phosphorylation of JNK (C) and Akt (D) in these cells is indicated by the band densities (normalized to total protein levels) relative to CL. *P < 0.05 versus CL cells.