To study mitogen-activated protein kinase (MAPKs) activation in fibroblast-like synoviocytes (FLS) of rheumatoid arthritis (RA) under the stimulation of IL-1 beta, and to elucidate the role of protein tyrosine kinase (PTK) in the activation of MAPKs.
Primary cultures of RA FLS were used. Western blot was applied to examine transient changes in protein tyrosine phosphorylation status and MAPKs activation in RA FLS stimulated with IL-1 beta at various doses, and over different periods. Genistein, the specific PTK inhibitor, was used to evaluate the inhibitory role in activation of MAPKs by IL-1 beta.
IL-1 beta transiently increased protein tyrosine phosphorylation, and activated the MAPKs cascades (mainly ERK2, JNK2 and P38) in RA FLS. There was no obvious difference in MAPKs activation among different doses of IL-1 beta (1 IU/ml, 10 IU/ml, 100 IU/ml), but the peak activation of ERK2, JNK2 and P38 took place at 5 min, 15 min and 1 min, respectively, after stimulation with IL-1 beta. The activation of ERK2 was inhibited by genistein, but the inhibitory role on that of JNK and P38 was relatively weak.
During signal transduction of IL-1 beta in RA FLS, tyrosine phosphorylation was increased transiently, the MAPKs cascade was activated in a few minutes, and there was heterogenicity in the activation among three subfamily members. PTK had a role in the activation of ERK, but had weak effects on that of JNK and P38.