Effect of diacerein and rhein on subchondral bone osteoblast intracellular mitogen-activated protein (MAP) kinase pathways. Subchondral bone osteoblasts were pre-incubated for 2 hours with diacerein or rhein at 20 μg/mL and incubated for 30 minutes in the presence or absence of interleukin-1-beta (IL-1β) (100 pg/mL). Levels of phosphorylated (a) extracellular signal-regulated kinase-1/2 (ERK1/2), (b) p38, and (c) stress-activated protein kinase/c-jun N-terminal kinase (SAPK/JNK) (p46 and p54) MAP kinases were studied by Western blot and quantified by densitometry as described in Materials and methods. Data are expressed as fold changes compared with IL-1β-treated control, which was assigned a value of 1. Statistical analysis was performed versus IL-1β-treated control.