The epidermal barrier function is very important to maintain proper moisture in the human skin and protect inner body homeostasis. The stratum corneum (SC) is the major player in epidermal barrier function. Interleukin (IL)-33 is a tissue-derived cytokine, mainly expressed in epithelial and endothelial cells, and activates Th2 lymphocytes, mast cells, ILC2, and eosinophils. We aimed to study the role of IL-33 in skin barrier function in a steady state. Wild-type (WT), and IL-33 knockout (IL-33KO) mice were tape stripped, and trans-epidermal water loss (TEWL) was monitored. Skin samples were collected, and hematoxylin and eosin staining, immunohistochemical (IHC) analyses, and western blotting were performed. Total RNA was extracted from the skin samples and real-time (RT) PCR was performed. Tape stripping increased TEWL both in IL-33KO and in WT mice (p<0.0001) to similar levels, and there was no statistical difference between WT and IL-33KO mice (n.s.). Tape stripping increased epidermal thickness with an increase of granular layer in IL-33KO mice compared to WT mice. We observed an increased filaggrin (FLG) staining in IHC analyses on days 1, 2, and 3 after tape-stripping in IL-33KO compared to WT mice. Tape-stripping induced the expression of acid ceramidase (ASAH1 and ASAH1.2) both in IHC and real-time PCR analysis in WT (p<0.0001) mice, but not in IL-33KO mice. Filaggrin has been implicated in epidermal barrier function, and acid ceramidase has recently been postulated to decrease ceramide levels in cornified layers in atopic dermatitis patients. IL-33KO mice showed higher filaggrin protein levels and lower acid ceramidase levels after tape-stripping than WT mice, but TEWL levels were comparable to WT mice. These results suggest that there would be other molecules involved in controlling TEWL levels than filaggrin and acid ceramidase.

ESDR209 - IL-33 deficiency increases filaggrin protein level with no impact on TEWL increase after tape-stripping.

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.