title: Mast cells are required for phototolerance induction and scratching abatement.
abstract: Dermal mast cells protect the skin from inflammatory effects of ultraviolet (UV) radiation and are required for UV-induced immune suppression. We sought to determine a potential mechanistic role of mast cells in reducing the sensitivity to UV radiation (i.e. phototolerance induction) through photohardening. We administered single UV exposures as well as a chronic UV irradiation regime to mast cell-deficient Kit(W-Sh/W-Sh) mice and their controls. The chronic irradiation protocol was similar to that given for prophylaxis in certain photodermatoses in humans. Compared to controls, UV-exposed Kit(W-Sh/W-Sh) mice were more susceptible to epidermal hyperplasia and dermal oedema which was linked to blood vessel dilation. Unexpectedly, Kit(W-Sh/W-Sh) mice exhibited an excessive scratching behaviour following broadband UVB plus UVA or solar simulated UV irradiation at doses far below their minimal skin-swelling dose. Protection from this UV-induced scratching phenotype was dependent on mast cells, as engraftment of bone marrow-derived cultured mast cells abated it entirely. Kit(W-Sh/W-Sh) mice were entirely resistant to phototolerance induction by photohardening treatment. Compared to controls, these mice also showed reduced numbers of regulatory T cells and neutrophils in the skin 24 h after UV irradiation. While it is well known that mast cell-deficient mice are resistant to UV-induced immune suppression, we have discovered that they are prone to develop photo-itch and are more susceptible to UV-induced epidermal hyperplasia and skin oedema.
authors.affiliation: Research Unit for Photodermatology, Department of Dermatology, Medical University of Graz, Graz, Austria.|Center for Medical Research, Medical University of Graz, Graz, Austria.
authors.forename: Nina A
authors.initials: NA
authors.lastname: Schweintzger
authors.affiliation: Research Unit for Photodermatology, Department of Dermatology, Medical University of Graz, Graz, Austria.
authors.forename: Isabella
authors.initials: I
authors.lastname: Bambach
authors.affiliation: Research Unit for Photodermatology, Department of Dermatology, Medical University of Graz, Graz, Austria.|Center for Medical Research, Medical University of Graz, Graz, Austria.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Reginato
authors.affiliation: Research Unit for Photodermatology, Department of Dermatology, Medical University of Graz, Graz, Austria.
authors.forename: Gerlinde
authors.initials: G
authors.lastname: Mayer
authors.affiliation: Department of Immunology, UT MD Anderson Cancer Center, Houston, TX, USA.|Laboratory of Immunology, Faculty of Medicine, Universidad Autonoma de Nuevo León, Monterrey, Mexico.
authors.forename: Alberto Y
authors.initials: AY
authors.lastname: Limón-Flores
authors.affiliation: Department of Immunology, UT MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Ullrich
authors.affiliation: Department of Immunology, UT MD Anderson Cancer Center, Houston, TX, USA.|Cellular Photoimmunology Group, Infectious Diseases and Immunology, Sydney Medical School, The Charles Perkins Centre Hub at The University of Sydney, Sydney, NSW, Australia.
authors.forename: Scott N
authors.initials: SN
authors.lastname: Byrne
authors.affiliation: Research Unit for Photodermatology, Department of Dermatology, Medical University of Graz, Graz, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Wolf
mesh_terms: D000818:Animals; D004487:Edema / Q000209:etiology / Q000276:immunology; D006965:Hyperplasia; D007108:Immune Tolerance / Q000528:radiation effects; D008407:Mast Cells / Q000276:immunology* / Q000502:physiology / Q000528:radiation effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009504:Neutrophils / Q000276:immunology / Q000528:radiation effects; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics / Q000276:immunology; D011537:Pruritus / Q000209:etiology / Q000276:immunology / Q000503:physiopathology; D012867:Skin / Q000276:immunology* / Q000473:pathology / Q000528:radiation effects*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology / Q000528:radiation effects; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014664:Vasodilation / Q000276:immunology / Q000528:radiation effects
chemical_list: D019009:Proto-Oncogene Proteins c-kit
keywords: Tregs; immunosuppression; mast cells; photohardening; scratching phenotype