The Role Of T Regulatory Cells In The Pathogenesis Of Psoriasis

Objective To investigate the role of T regulatory cells(Treg cells) in the pathogenesis of psoriasis. To further study the mechanisms by which Treg cells contribute to psoriasis.Methods We collected blood samples from 81 patients in the progressive stage of psoriasis and 46 healthy volunteers. After blood collection, CD4+CD25+Foxp3+ was defined as Treg cells, and its frequency was detected by flow cytometry(FCM). Suppressive activities and proliferative activities of Treg cells were evaluated by co-culture of CD4+CD25+CD127-Treg cells and CD4+CD25- CD127+ T effective cells(Teff cells) model. Gene expressions prolife of Treg cells were detected by microarray. q PCR and FCM assay were performed to identify these gene expressions in Treg cells. According to the results of microarray, q PCR, Western blot and immunofluorescence were performed to detect AKT and Foxo1 expression in Treg cells from psoriatic patients and healthy controls. Then,to investigate whether psoriatic serum contribute to the dysfunction of Treg cells and the AKT-Foxo1 pathway, serum from psoriatic patients and healthy controls were added in the culture of Treg and Teff cells. Lentivirus was used for Foxo1 sh RNA delivery to investigate the impact of Foxo1 on the function of Treg cells and the expression of T-bet and IFN-γ. Finally, the in vivo psoriasis-like animal model were established by topical application of imiquimod(IMQ) on the skin of Rag2-/- mice. Subcutaneous injection of Teff cells with or without Treg cells to investigate the role of Treg cells in the pathogenesis of psoriasis. Treg cells from Foxo1-/- or WT mice were subcutaneous injected to study the impact of Foxo1 on the function of Treg cells in psoriasis.Results We found that the frequency of Treg cells in psoriasis patients was comparable with healthy volunteers(P = 0.1365). The the frequency of Treg cells in psoriasis patients showed positive correlation with the severity of psoriasis(R2 = 0.2580, P < 0.001). However, psoriatic Treg cells were impaired in proliferative activity and suppressive activity. To investigate the mechanism, we preformed m RNA array to study the gene expression profile of psoriatic Treg cells. Interestingly, the results showed that the gene expression of psoriatic Treg cells had the similar expression pattern with Foxo1-/-Treg cells, such as producing more pro-inflammatory cytokines. By using q PCR assay, we found that the m RNA level of Foxo1 were equivalent in Treg cells from psoriatic patients and healthy controls, while the m RNA encoding AKT were increased in Treg cells from psoriatic patients. By using both western blotting and immunofluorescence, we found the ratio of p AKT/AKT and p Foxo1/Foxo1 were increased, Foxo1 located more in cytoplasm in psoriatic Treg cells compare with healthy Treg cells. To further investigate what caused this decreased transcriptional activity of Foxo1 in psoriatic Treg cells, we used serum from psoriatic patients or healthy volunteers to treat Treg cell from healthy volunteers, respectively. We found that serum from patients significantly promoted the nuclear exclusion of Foxo1, and increased the phosphorylation of AKT and Foxo1, compared with healthy volunteers. Next, by using sh RNA to knockdown Foxo1 expression in Treg cells from healthy controls, these Treg cells showed decreased proliferative and suppressive activity and expressed more T-bet and IFN-γ. Finally, in the IMQ induced psoriasis-like animal model, we found that local injection of Treg cells ameliorated the process of psoriasis, but Foxo1-/-Treg cells were impaired in negatively regulating the inflammatory process to alleviate the hyperproliferation of epidermis in psoriasis.Conclusion Our findings suggest that the impaired function of Treg cells contribute to the pathogenesis of psoriasis. Further, we provide strong evidence shown that the dis-regulation of Foxo1 may be a critical cause in the dysfunction of Treg cells in psoriasis. These study provide new insight into the mechanism of the pathogenesis of psoriasis.