Hydroxynonenal-induced microsomal prostaglandin E
synthase-1 protein and mRNA expression in human osteoarthritis chondrocytes. Cells were stimulated (a), (c) with 10 μM 4-hydroxynonenal (HNE) once or (b), (c) repeatedly with 10 μM HNE every 2 hours for different incubation periods, as indicated above. Microsomal prostaglandin E2 synthase-1 (mPGES-1) (a), (b) protein and (c) mRNA were measured respectively by western blotting and real-time RT-PCR. Data are means ± standard errors of the mean, n = 4, expressed as percentages of untreated cells. Student's unpaired t test: *P < 0.05, **P < 0.01, ***P < 0.001.