HSP70 suppresses TNF-α induced phosphorylation of MAPKs in human FLSs. Rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLSs) were incubated with heat shock protein (HSP)70 at 0.1 to 10 μg/ml for 1 hour, and the FLSs were washed and exposed to tumour necrosis factor (TNF)-α (20 ng/ml) for 30 minutes. The cell lysates were immunoblotted with (a) anti-phospho-p38 (p-p38) and anti-total p38 (t-p38), (b) anti-phospho-ERK (p-ERK) and anti-total ERK (t-ERK), and (c) anti-phospho-JNK (p-JNK) and anti-total JNK (t-JNK). Antibodies (Abs) against t-p38, t-ERK, or t-JNK served as controls. The levels of p38, extracellular signal-regulated protein kinase (ERK), and c-Jun amino-terminal kinase (JNK) were estimated by densitometry. Shown in the left panels are representative Western blots, and in the right panels are presented the means ± standard deviation of three independent experiments. *P < 0.05 versus the TNF-α group. MAPK, mitogen-activated protein kinase.