Fig 2: UVB-induced changes in norepinephrine and gene expression in mouse skin. A Norepinephrine protein levels in the plasma of UVB-irradiated mice were measured via ELISA. B Norepinephrine protein levels in the skin tissues of UVB-irradiated mice measured via ELISA. C Determination of norepinephrine in the plasma of acutely and chronically UVB-irradiated mice via ELISA. D Expression of Mitf, Tyr, and Tyrp-1 mRNAs in the skin of UVB-irradiated mice (n = 3). The mRNA level in the control skin was normalized to 1. E Gene expression profiles were analyzed via RNA-seq, and the expression of melanogenic paracrine cytokine genes was visualized with a heatmap. The P values for each comparison are represented by different colors. F GSEA was performed using the “melanogenesis” and “melanocyte differentiation” gene sets to demonstrate the sequential transition in gene expression from the acute UVB irradiation group to the normal mouse skin group. The values are expressed as the means ± SDs from three independent experiments. (ns: not statistically significant, *p < 0.05; **p < 0.01; ***p < 0.001)

Fig 3: The sympathetic nervous system is crucial for melanin synthesis induced by UVB in mice. A Representative immunofluorescence images of mouse skin sections stained for TH (sympathetic nerves, green), K14 (keratinocytes, red), and DAPI (nuclei, blue) (n = 3). B Norrenaline protein levels in mouse plasma were measured via ELISA after sympathetic nerve ablation. C Tyrosinase activity in the skin tissues of sympathetically ablated mice exposed to UVB was measured via a Dopa oxidation test (n = 3). D and E RT-qPCR analysis of MITF and TYR expression in sympathetically ablated mice after UVB exposure (n = 3). Scale bar: 50 μm. The values are expressed as the means ± SDs from three independent experiments. (ns: not statistically significant, *p < 0.05; **p < 0.01; ***p < 0.001)

Fig 4: UVB-induced β2-AR silencing in keratinocytes regulates AP-1 activity. A After UVB irradiation, two pairs of siRNA sequences were selected and validated via Western blotting. B MITF and TYR expression in A375 cells was detected by Western blot after the addition of the supernatants. C Gene expression profiles were analyzed using RNA-seq, and the expression of AP-1-associated genes was visualized with a heatmap. The P values for each comparison are represented by different colors. D Volcano plots showing the fold change (FC) on the x-axis versus significance on the y-axis. Many genes were significantly dysregulated after UVB irradiation in HaCaT cells compared with those in control cells. The genes highlighted in red were both statistically significant and at least twofold dysregulated relative to the controls. Note that p-values are shown on a -log10 scale and that FC values are shown on a log2 scale. FC was calculated as UVB/control, with n = 3 for irradiated HaCaT cells and n = 3 for non irradiated cells. Adjusted p-values were calculated via the FDR method. (E) RT-qPCR was used to assess the mRNA expression of JUN and FOS in HaCaT cells after UVB irradiation and siRNA treatment. (F) Representative Western blots showing the expression of C-FOS, C-JUN, P–C-FOS, and P–C-JUN in HaCaT cells following siβ2-AR treatment. The values are expressed as the means ± SDs from three independent experiments. (ns: not statistically significant, *p < 0.05; **p < 0.01; ***p < 0.001)