Impaired. function of regulatory T cells in patients with psoriasis is mediated by phosphorylation of STAT3

Background: Psoriasis is a T cell-mediated chronic inflammatory skin disease. Regulatory T cells (Tregs) are crucial in suppressing immune response to maintain the immune balance. Wheras Tregs from psoriatic patients showed poorly activity in suppressing activation of responder T cells (Tresp), the mechanisms involved in this process are still unknown. Objectives: In this study, we investigated the possible role of STAT3 pathway in the pathogenesis of dysfunctional Tregs in psoriasis. Methods: The suppressive function and the proliferative activity of Tregs were detected from psoriatic patients and normal healthy controls. Expression of phospho-STAT3 in psoriatic Tregs was evaluated by flow cytometry and immunofluorescence. Furthermore, Tregs were treated with Stattic V (STAT3 inhibitor) in order to investigate the role of STAT3 pathway in the function of Tregs. In addition, IL-6, IL-21 and IL-23 treatments were performed to identify the upstream molecules of STAT3 pathway in Tregs. Results: Tregs from peripheral blood of psoriatic patients showed decreased suppressive function, together with phosphorylation of STAT3. In addition, Tregs isolated from psoriatic patients could produce IFN-gamma, TNE-alpha and IL-17. In the co-culture system of Tregs and Tresp isolated from psoriatic patients, addition of STAT3 inhibitor partially restored the suppressive function of Tregs and restrained the expressions of IFN-gamma, TNF-alpha and IL-17 in psoriatic patients. Moreover, we found that IL-6, IL-21 and IL-23 induced the phosphorylation of STAT3 in Tregs. Conclusions: Our findings suggest that psoriatic Tregs experience a predominant STAT3 phosphorylation by exposure to pro-inflammatory cytokines, leading to their impaired functions in suppressing Tresp activation. (C) 2015 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.