Expression and function of β-arrestin 2 stimulated by IL-1β in human fibroblast-like synoviocytes and the effect of paeoniflorin

The aim of this study was to explore the expression and function of β-arrestin 2 in human fibroblast-like synoviocytes (FLS) stimulated by IL-1β and the effect of paeoniflorin (Pae). We isolated and cultured human FLS, which were stimulated by IL-1β. The FLS proliferations were detected by [3H] thymidine incorporation. The level of cAMP stimulated by IL-1β on different times was investigated by radioimmunoassay, and the activity of PKA was measured by luminescent kinase assay. The expression of β-arrestin 2 was measured by western blot. We found that the human FLS proliferation increased apparently in 24 h, and the activities of PKA and cAMP accumulation increased significantly in 6 h after stimulated by IL-1β, while cAMP accumulation and the activities of PKA decreased especially in 24 h when the expression of β-arrestin 2 increased significantly. Decreased cAMP accumulation and the increased expression of β-arrestin 2 may reveal a positive correlation with the FLS proliferation. Pae (10- 5, 10- 6, 10-7 mol
- L- 1) in vitro could suppress the FLS proliferation and the high expression of β-arrestin 2. The expression of β-arrestin 2 may have a positive correlation with the human FLS proliferation, while the activities of PKA and cAMP accumulation have a negative correlation with the proliferation. The increased β-arrestin 2 may down-regulate cAMP-PKA signaling pathway and promote FLS proliferation. Pae may suppress the expression of β-arrestin 2 and up-regulate cAMP-PKA signaling, which may be one of the mechanisms for the effects of Pae on inhibiting human FLS proliferation.

► Expression of β-arrestin 2 has a positive correlation with the human FLS proliferation. ► The level of PKA and cAMP has a negative correlation with the FLS proliferation. ► β-Arrestin 2 may down-regulate cAMP-PKA signals in FLS and promote proliferation. ► Pae suppress β-arrestin 2 and up-regulate cAMP-PKA signals and inhibit proliferation.