CDC6 expression is upregulated in epidermal cells in psoriatic lesions and it could be induced by IL-22/STAT3 signaling, a key signaling pathway involved in the pathogenesis of psoriasis, in keratinocytes.
Flow cytometry was used to measure levels of the cytokines IFN-γ, IL-13, IL-9, IL-17, and IL-22 in CD4<sup>+</sup>/CD8<sup>+</sup> T cells in the blood of 19 patients with moderate-to-severe nonsegmental/generalized vitiligo, moderate-to-severe AA (n = 32), psoriasis (n = 24), or AD (n = 43) and control subjects (n = 30).
The JAK1/JAK2/STAT1 and JAK1/TYK2/STAT3 pathways triggered by IFN-<i>γ</i> and IL-22, respectively, are aberrantly activated in psoriasis, as highlighted by the peculiar STAT1 and STAT3 signatures in psoriatic skin lesions.
Our data may represent the significant differences between human psoriasis and murine psoriasis model, and further studies using other models will be required to elucidate the role of IL-21 in psoriasis pathogenesis.
Although its pathogenesis is not fully understood, Th17 cells and the cytokines they produce, such as IL-17, IL-22 and IL-23, play critical roles in the pathogenesis of psoriasis.
IL-22 and IL-17, signature cytokines of type 17 inflammation, as well as IL-4 and IL-13, signature cytokines of type 2 inflammation, both of which are positively correlated with the pathogenesis of psoriasis and allergic diseases, respectively, can induce expression of SCCA1/2 in airway epithelial cells and/or keratinocytes, leading to high expression of SCCA1/2 in these diseases.
Psoriasis is a common, worldwide autoinflammatory, incurable skin disease. miR-197 has therapeutic potential for psoriasis since it can down-regulate the expression of both IL-22RA1 and IL-17RA, subunits of the receptors of IL-22 and IL-17, respectively, which are key cytokines in the disease.
There are three common pathways leading to psoriasis: (1) Th17 cells secrete IL-17, which is stimulated by IL-23; (2) Th1 cells secrete IL-21, TNF-[Formula: see text] and IFN-[Formula: see text], with the help of Th17 cells; (3) Th22 cells secrete IL-22 under the stimulation of Th17 cells.
Together, our results reveal a novel regulatory mechanism of IL-22 expression by STAT1 through directly antagonizing STAT3, and the importance of the balance between STAT3 and STAT1 in IL-22 regulation and psoriasis pathogenesis.
In addition, compared with healthy donors, circulating CD3<sup>+</sup> CD20<sup>+</sup> T cells in patients with psoriasis produced more cytokines, interleukin (IL)-17A, tumour necrosis factor (TNF)-α and IL-21, but not IL-4 and IFN-γ.
Increasing evidence indicates that interleukin-22 (IL-22) holds tremendous potential as a protective agent in preventing liver injury, but its pleiotropic effects and pathogenic role in carcinogenesis, rheumatoid arthritis and psoriasis restrict its systemic application.