Xiaoyin Jiedu Granules may alleviate psoriasis-like skin diseases in mice by regulating sphingosine 1-phosphate receptor expression and reducing Th17 cells

Abstract

Sphingosine-1-phosphate (S1P) is associated with the onset and severity of psoriasis, a chronic inflammatory skin disease linked to innate and adaptive immune responses. This study explores the therapeutic effect of Xiaoyin Jiedu Granules, a combination of traditional Chinese medicines, on psoriasis-like skin lesions in mice and the underlying mechanism. We used imiquimod (IMQ) to induce psoriasis-like dermatitis in mice; the effects of Xiaoyin Jiedu Granules on S1P receptors (S1PRs) were investigated using histology and immunohistochemistry. The effects of Xiaoyin Jiedu Granules on the proliferation, differentiation, and activation of the NF-κB pathway in keratinocytes were verified using quantitative polymerase chain reaction (qPCR) and western blotting analyses. CD4⁺Th17 cells were screened using flow cytometry; the effects of Xiaoyin Jiedu Granules on the differentiation of Th17 cells and the content of related inflammatory factors were also verified. S1PR1-5 was highly expressed in psoriatic lesions. Xiaoyin Jiedu Granules significantly inhibited the secretion of proliferation-related proteins (K6, K16, K17, and IL-36γ) and proinflammatory cytokines (IL-17 and IL-22), transformation of Th17 cells, and activation of the NF-κB pathway and effectively alleviated IMQ-induced psoriasis-like dermatitis. Overall, our findings indicate that Xiaoyin Jiedu Granules have anti-inflammatory activity against S1PR expression, keratinocytes, and immune cells and can therefore mitigate psoriasis. Inhibiting the expression of S1PRs may be an effective treatment strategy against psoriasis.

Keywords: NF-κB; Psoriasis; S1P; S1PRs; Th17.

Fig. 1

Scores of skin lesions and disease severity of mice in each group. (A) Skin lesions on the backs of mice in each group; (B) comparison of PASI scores; (C) histopathological staining ( × 200); and (D) comparison of epidermal thickness.

Fig. 2

Expression of S1PR1-5 in mouse skin lesions detected using immunohistochemistry (IHC). (A) IHC staining results ( × 100); (B) comparison of the expression of S1PR1, S1PR2, S1PR3, S1PR4, and S1PR5 in skin tissues of mice in each group. IMQ, imiquimod; S1PR, sphingosine-1-phosphate receptor.

Fig. 3

Comparison of gene expression levels related to keratinocyte proliferation in mouse skin tissue of each group. (A) Quantitative polymerase chain reaction (qPCR) detection of expression of proliferation-related genes K6, K16, and K17; (B) qPCR detection of the expression of differentiation-related genes K1 and INV; see also Fig. S1; (C) western blotting of the relative expression levels of K6, K16, K17, K1, and INV; (D) western blotting results; (E) ELISA detection of IL-36γ content in mouse skin or serum.

Fig. 4

Proportion of CD4⁺IL-17⁺T cells in the spleens of mice in each group and the expression of related inflammatory factors. (A) CD4⁺ and IL-17⁺ T cells detected using flow cytometry; (B) Immunofluorescence double staining of CD4⁺T cells and S1PR1 was performed in the psoriatic skin lesions of mice ( × 400); (C) CD4⁺IL-17⁺ T cell ratio in each group; (D) IL-17 content in the skin and serum of each group; and (E) IL-22 content in the skin and serum of each group. IMQ, IMQ, imiquimod.

Fig. 5

Expression of inflammation-related signaling pathway proteins in mice in each group. (A) IHC detection of p-Akt, p-p65, and p-STAT3 in mouse skin lesions ( × 400), see also Fig. S2; (B) western blotting of Akt, p65, STAT3, and p-Akt, p-p65, p-STAT3 in skin tissue; (C) relative expression of p65, p-p65; (D) relative expression of STAT3, p-STAT3, Akt, and p-Akt; (E) western blotting of Ikka, p-Ikka, and Ikba levels in skin tissue, See also Fig. S3; (F) relative expression levels of Ikka, p-Ikka, and Ikba.