Figure 6.
UVB and PAF, but not cis-UCA or signals working via P2X7 receptors upregulates IL-33 in the skin. Mice were exposed to either the (A) UVA or (B) UVB components of 80 kJ/m2 ssUV (74.25 kJ/m2 UVA only or 5.75 kJ/m2 UVB only). Arrowheads indicate IL-33–positive cells within the dermis. Frozen skin sections were then labeled for IL-33 as described for Figure 1B. The white line highlights the junction between the epidermis (e) and dermis (d). Scale bar = 100 μm. Whole frozen 7-μm skin sections from P2X7 receptor-expressing wild-type (C) or P2X7 receptor-deficient (D) mice exposed to 80 kJ/m2 UV 72 hours earlier were labeled with antibodies to mouse IL-33 (green). In all images (A–G), DAPI (blue) was used to identify nuclei. The white line highlights the dermal–epidermal junction. Arrowheads point to IL-33–positive cells deep within the dermis of both strains of mice. E–G: Murine embryonic fibroblasts at 80% confluence were cultured with control PBS (E), 100 μg/mL cis-UCA (F), or 1 μmol/L PAF (G) in vitro. The images displayed were taken after 1 hour of exposure to the respective reagents, at which point the cells were fixed and stained for IL-33. Scale bar = 100 μm. H: Quantitative image analysis of IL-33 expression was performed on the cell cultures as described for Figure 2C (n = 2 for each treatment group and time point) and presented as a percentage of the 1-hour control group. Mean ± SEM are shown, with *P < 0.05, **P < 0.01 by one-way analysis of variance and Bonferroni's multiple comparison post-test.