Dysfunction of regulatory T cells in patients with psoriasis and related mechanisms of regulation by the STAT3 signaling pathway

Abstract

Objective To evaluate the function of regulatory T (Treg) cells in peripheral blood from patients with psoriasis, and to explore the possible role of the STAT3 signaling pathway in Treg cell dysfunction. Methods Totally, 81 patients with psoriasis vulgaris, who all presented with chronic plaques and had a psoriasis area and severity index (PASI) score of 10-30, were enrolled into this study. Forty-six healthy blood donors served as the control group. Venous blood samples were collected from these subjects followed by isolation of Treg cells and responder T (Tresp) cells. Flow cytometry was performed to determine the proportion of Treg cells in peripheral blood as well as that of cells secreting phosphorylated-STAT3 (p-STAT3), interferon γ (IFN-γ), tumor necrosis factor α (TNF-α) and interleukin 17 (IL-17) in Treg cells, and quantitative real-time PCR (qRT-PCR) to measure the expression levels of IFN-γ, TNF-α and IL-17 mRNAs in Treg cells. Some Treg cells and Tresp cells were cultured in vitro alone or in combination, and flow cytometry was conducted to estimate cellular proliferative activity on day 7 after stimulation with IL-2. Some patient-derived Treg cells were classified into several groups to be cultured alone or in combination with Tresp cells with or without the presence of the STAT3 pathway inhibitor, Stattic V (10 or 50 μg/L), for 7 days. Subsequently, flow cytometry was performed to evaluate the proliferative activity of Tresp cells, and qRT-PCR to measure the expression levels of IFN-γ, TNF-α and IL-17 mRNAs in Treg cells. Results No significant differences were observed in the proportion of Treg cells in peripheral blood between the patient group and control group (6.437% ± 0.186% vs. 6.812% ± 0.241%, t = 1.224, P> 0.05). Compared with control-derived Treg cells, the patient-derived Treg cells showed significantly decreased proliferative activity and inhibitory effects on Tresp cells, but increased proportion of cells secreting p-STAT3, IFN-γ, TNF-α and IL-17 (all P< 0.05). After the treatment with 50 μg/L Stattic V, a significant increase was observed in the inhibitory effect of patient-derived Treg cells on Tresp cells (inhibition rate: 61.670% ± 4.640% vs. 28.820% ± 11.490%, P< 0.05), but a significant decrease in the mRNA expressions of IFN-γ (2-△△Ct: 1.654 ± 0.879 vs. 23.350 ± 6.721, P< 0.05), TNF-α (0.850 ± 0.705 vs. 4.847 ± 1.525, P< 0.05) and IL-17 (0.572 ± 0.135 vs. 3.095 ± 0.650, all P< 0.05) in patient-derived Treg cells compared with untreated patient-derived Treg cells. Conclusions The negative regulatory effect of Treg cells on Tresp cells is decreased in patients with psoriasis, which may be associated with abnormal activation of the STAT3 signaling pathway, and inhibition of the pathway may restore the function of Treg cells to a certain extent. Key words: Psoriasis; T-lymphocytes, regulatory; STAT3 transcription factor; Interferon-gamma; Tumor necrosis factor-alpha; Interleukin-17; Stattic V