Fig 1: Immunochemistry and RT-qPCR of RBP4 and STRA6 expression. (a) Lesional skin had a higher level of RBP4 mRNA expression compared with non-lesional areas (p = 0.273). Immunohistochemistry results of RBP4 in the control groups (b), normal skin from group A (c), lesional skin from group A (d), non-lesional skin from group B (e), and lesional skin from group B (f). Protein levels of RBP4 accumulated in the epidermis over time. (g) Compared with normal skin, the STRA6 mRNA level was significantly higher in IMQ lesional skin (p = 0.021). STRA6 immunohistochemistry results of the control groups’ skin (h), normal skin of group A (i), lesional skin of group A (j), normal skin of group B (k), and lesional skin of group B (l). IMQ induced psoriasis-like skin lesion that contained a relatively higher level of STRA6. b-f and h-l: DAB, original magnification × 200
Fig 2: Immunohistochemistry for detecting the expression of APOD, CTLA4, CXCR4, DKK1, INHBA, NPR1, PENK, PROC, RBP4, S100A12, and STC1 in 5 paired gastric cancer and normal tissues. Bar = 20 μm. Magnification, ×200.
Fig 3: ELISA of serum changes in the study groups. Levels of IL-23 (a), IL-17A (b), and TNF-α (c) increased remarkably in the IMQ groups compared with controls. Between the two IMQ groups, a conspicuous increasing trend could be seen in IL-17A and TNF-α in group B. (d) RBP4 accumulated gradually in the circulation with the application of IMQ. Groups A and B both showed significantly increased RBP4 levels. (e) STRA6 levels showed a profound increase after 3 days of IMQ application; by day 7, STRA6 levels were just slightly higher than controls. (f) Retinol levels were slightly elevated in group A, but there were no statistically significant differences in all groups
Fig 4: Proposed vitamin A metabolic alterations in the psoriasis model mouse. The need for retinol in psoriasis lesional skin was increased. To meet this need, RBP4 and STRA6 were upregulated in both serum and psoriatic skin to transfer more retinol inside target cells. The transformation from retinol to RA was also accelerated, by further binding with its receptor, RA induced more synthesis of STRA6, forming a positive feedback loop
Fig 5: ELISA of vitamin A-related molecules and typical pro-inflammatory cytokines in the skin of the study groups. All results describe comparison with the control groups. (a) Retinol levels were slightly higher in lesional skin (p = 0.364). (b) RBP4 expression was elevated in the IMQ groups (p = 0.142). (c) STRA6 expression also showed an increasing trend in the IMQ groups (p = 0.395). No obvious differences were observed in the two IMQ groups. (d) IL-23 increased sharply in the lesional skin of group A (**p = 0.0092) and B (***p < 0.001). Between the two IMQ groups, more IL-23 accumulated in group B (*p = 0.031). (e) IL-17A increased in the lesional skin of both IMQ groups (***p < 0.001). Group B had a higher level of IL-17A in lesional skin (***p < 0.001). (f) TNF-a expression was highest in group B lesional skin compared with group A (*p = 0.030) and the controls (***p < 0.001)
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