Fig 2: STAT3 activation abolishes the S1PR3 inhibition-mediated anti-proliferation.A Venn diagram showing overlap between upregulated ATAC-seq peaks in psoriasis patients and downregulated genes after TY treatment in HaCaT cells (10 μM TY and 25 μg/mL IL-6), including K16 and K17. B IGV visualization of K17 expression in psoriasis patients via ATAC-seq (n = 14) (PRJNA597655) and in HaCaT cells treated with IL-6 or IL-6 plus TY via RNA-seq (n = 3). C EdU staining demonstrates that TY inhibits IL-6-induced HaCaT cells proliferation. Scale bars: 20 μm. D. qRT‒PCR analysis of inflammatory mediators and chemokines (IL6, CXCL5, S100A9, and IL8) in HaCaT cells cotreated with IL-6 and TY for 24 h. E Western blot analysis and quantification of Ki67, K17, and P-STAT3 expression in HaCaT cells treated with TY and IL-6 or IL-22. F Western blot analysis and quantification of P-STAT3, STAT3, K17, and S1PR3 in HaCaT cells transfected with S1PR3 siRNA and treated with IL-6 for 24 h. G, H Western blot analysis (G) and quantification (H) of K17 and P-STAT3 in HaCaT cells transfected with the STAT3C plasmid and then treated with IL-6 alone or in combination with TY. The data are presented as the mean ± SD. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001.

Fig 3: S1PR3 inhibition alleviates psoriasis-like lesions in IMQ-treated mice.A Representative macroscopic images and histological staining (H&E, Masson’s trichrome, and PAS) of mouse dorsal skin treated with TY (3 mg/kg/day) or the solvent control prior to daily topical application of IMQ (62.5 mg/day). B PASI scores for assessing erythema, scaling, and skin thickness in IMQ-induced psoriasis-like lesions (n = 4). Higher scores indicate more severe psoriasis. C Representative immunohistochemistry images showing the expression of CD31, K16, K17, Ki67, P-STAT3, and Src in dorsal skin sections from mice treated with solvent control, IMQ, IMQ + TY, or TY alone. D Western blot analysis of Ki67, K16, K17, P-STAT3, STAT3, P-Src, and Src protein levels in dorsal skin lysates from mice treated with solvent control, IMQ, IMQ + TY, or TY alone. GAPDH served as a loading control. E qRT‒PCR analysis of the mRNA levels of the psoriasis-associated proinflammatory mediators Il1b, S100a9, Il1a, and Il23 in mouse skin (n = 3). The data are presented as the mean ± SD. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.

Fig 4: Inhibition of S1PR alleviates IMQ-induced psoriasiform dermatitis in mice.A Representative macroscopic images and histological staining (H&E, Masson’s trichrome, and PAS) of dorsal skin from mice treated with FTY720 (1 mg/kg/day, i.p.) or the solvent control vehicle prior to daily topical IMQ application. B PASI scores for assessing erythema, scaling, and skin thickness in IMQ-induced psoriatic lesions on day 7 (n = 4 mice per group). Higher scores indicate more severe psoriasis. C Spleen indices (spleen weight/body weight ratios) of control, IMQ-, and IMQ + FTY720-treated mice (n = 4 mice per group). D Representative immunohistochemistry images showing Ki67 and K17 expression in dorsal skin sections from control, FTY720-, IMQ-, and IMQ + FTY720-treated mice. E Western blot analysis of Ki67, K16, P-STAT3, STAT3, and GAPDH protein levels in dorsal skin lysates from control, IMQ-, IMQ + FTY720-, and FTY720-treated mice. F qRT‒PCR analysis of the mRNA levels of the proinflammatory cytokines Il17, Tnf, Il6, and Il22 in the dorsal skin of control, IMQ, and IMQ + FTY720-treated mice (n = 3). G Western blot analysis of P-STAT3 (Y705), STAT3, P-AKT (S473), P-AKT (T308), AKT, S1PR3, S1PR2, K16, Survivin, and GAPDH protein levels in HaCaT cells stimulated with IL-6 or IL-22 in the presence or absence of FTY720 pretreatment. The data are presented as the mean ± SD. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.

Fig 5: S1PR3 knockout attenuates IMQ-induced psoriasiform dermatitis.A Macroscopic appearance of dorsal skin (top row), skin-draining lymph nodes (middle row), and histological staining (H&E) of the back skin of WT mice and S1PR3-KO mice with and without IMQ treatment. Scale bars: 100 μm. B Representative immunofluorescence images of K17 (red) and P-STAT3 (green) in psoriasis-like lesions from WT and S1PR3-KO mice with and without IMQ treatment. Nuclei were counterstained with DAPI (blue). Scale bars: 50 μm. C Western blot analysis of K16, P-STAT3, and total STAT3 expression in lesional skin from WT and S1PR3-KO mice with and without IMQ treatment. D qRT‒PCR analysis of key psoriasis-associated inflammatory mediators (Il1b, S100a9, Il1a, and Il23) in the skin of WT, S1PR3-KO, IMQ-treated WT and S1PR3-KO mice (n = 4). E Schematic illustration of keratinocyte-specific S1PR3 knockdown workflow by AAV9-shS1PR3 intradermal injection. F Macroscopic appearance of dorsal skin, and histological staining (H&E staining) of the back skin of WT mice and KC-S1PR3-KD mice with and without IMQ treatment. G Representative immunofluorescence images of K17 (red) and P-STAT3 (green) in psoriatic lesions from WT and S1PR3-KO mice with and without IMQ treatment. H Western blot analysis of Ki67, K16, P-STAT3, STAT3, and S1PR3 expression in the lesion skin from WT and S1PR3-KO mice with and without IMQ treatment. The data are presented as the mean ± SD. *p < 0.05; **p < 0.01; ***p < 0.001.