Abstract: Objective: An animal model of collagen-induced arthritis (CIA) was used to investigate the effects of norepinephrine (NE) and α1-adrenoreceptor (α1-AR) on Treg cells in CIA. Methods: Thirty-two male DBA/1 mice were randomly divided into control group and CIA model group. CIA was prepared by intradermal injection of collagen type II (CII, 100 μl) at the tail base of DBA/1 mice. On the 41^th day following primary immunization, co-expression of CD4⁺T and α1-AR in mouse spleens was observed. Protein expressions of α1-AR in the ankle joints and the spleens of mice were measured by Western blot analysis. The CD4⁺ T cells were isolated from the mouse spleen tissues in CIA mice and treated with NE or α1-AR agonist phenylephrine. Percentage of Treg cells in mouse CD4⁺ T cells of CIA mice was determined by flow cytometry. Expressions of α1-AR, transforming growth factor-β (TGF-β) and IL-10 in CD4⁺T cells of CIA mice were assessed by Western blot. Results: Co-expression of CD4 and α1-AR was observed in spleens of both intact and CIA mice. Compared with intace mice, α1-AR expressions in the ankle joints and spleens were down-regulated in CIA mice. NE increased the function of Treg cells in CD4⁺ T cells of CIA mice compared with that of nothing-treated CD4⁺T cells of CIA mice. Moreover, the α1-AR agonist phenylephrine increased the Treg cell function in CD4⁺ T cells of CIA mice relative to that of nothing-treated CD4⁺T cells of CIA mice. Conclusion: Activating α1-AR on CD4⁺T cells of CIA mice enhances Treg cell function,facilitating a shift of CD4⁺T cells toward Treg polarization.

Key words: mice, collagen-induced arthritis, Treg cells, norepinephrine, α1-adrenoreceptor