Characterization of sunburn cells after exposure to ultraviolet light

Abstract

Sunburn cells (SBCs) appear in the epidermis shortly after acute UV damage, especially after exposure to UVB light. As yet, the mode of their formation remains to be satisfactorily elucidated. In order to characterize these cells, the expression of various markers of epidermal differentiation following UV exposure was investigated using immunhistochemical procedures. These were applied to paraffin-embedded (microwave technique) and frozen specimens of human skin 24 h after irradiation with 4 times the minimal erythema doses(MED). Normal nonirradiated skin without irradiation served as the control. We used a battery of antibodies directed against the following: cytokeratins (CKs) 5, 10, 17, and 19, actin, cell-adhesion proteins (desmoplakins, desmogleins), markers of terminal epidermal differentiation (filaggrin, involucrin and loricrin), markers of proliferation (PCNA, MIB, K6,16), a marker of endocytosis (clathrin) and markers of cell growth, (transforming growth factor [TGF-alpha]) and B-cell leukemia/lymphoma-2 [bcl-2]. After UV irradiation it was found that CK 5, which is typically confined to basal keratinocytes, was also expressed in suprabasal keratinocytes. The CKs 1 and 10/11 exhibit a normal suprabasal localization, but suprisingly, SBCs were negative for these CKs. Although CK 6,16, and 17 are not usually found in normal epidermis, UVB exposure induced their expression in suprabasal keratinocytes, but again failed to elicit their expression in SBCs. Antibodies specific for markers of late epidermal differentiation (filaggrin, involucrin and loricrin), cell-junction proteins (desmogleins, desmoplakins), proliferation (PCNA and MIB), and endocytosis (clathrin) also failed to produce positive staining of SBCs. Even though TGF-alpha immunoreactivity became detectable in most keratinocytes after UV exposure, this was not the case for SBCs. The number of basally located dendritic cells, most probably melanocytes, exhibiting bcl-2 staining was markedly reduced 6 and 12 h after irradiation as compared with normal skin. SBCs do not express any late differentiation markers, but they do contain proteins typical of basal keratinocytes (CK 5). It can be concluded that SBCs do not develop beyond a more basal-like differentiation pattern, probably as a result of cell death and migration through the epidermis.

Epidermal transit of replication-arrested, undifferentiated keratinocytes in UV-exposed XPC mice: An alternative to in situ apoptosis

“…It has been described that apoptotic cells (located in first suprabasal layers of the epidermis) do not develop beyond a ''basal-like'' differentiation pattern and also retain K5 (18). However, the arrested cells in Xpc…”

Desmosomes: Regulators of Cellular Signaling and Adhesion in Epidermal Health and Disease

“…UV-induced sunburn cells (defined by pyknotic nuclei and eosinophilic cytoplasm) stain negatively for Dsgs and Dps (Bayerl et al 1995) and reduced desmosome molecule transcripts are frequently observed in UV-exposed keratinocytes (Li et al 2001;Murakami et al 2001;Sesto et al 2002;Rundhaug et al 2005). UVC (below 290 nm wavelength) results in caspase-dependent cleavage of Dsg1 and redistribution of Dsg1 from cell borders into the cytoplasm (Dusek et al 2006).…”

Mechanistic Effects of Long-Term Ultraviolet B Irradiation Induce Epidermal and Dermal Changes in Human Skin Xenografts

“…Keratins K6, K16, and/or K17, which are not usually expressed in the innate state of normal epidermis, have been reported to initially induce in the suprabasal layers as early as 6 hours after injury or during the first 24 to 48 hours of UVB irradiation. 48,[77][78][79][80][81] The increase of these epidermal keratins has a direct impact on epidermal cytoarchitectural alteration and its migratory behavior during re-epithelization. The presence of these keratins has been documented in early hair germs and in the companion layer of the outer root sheath during embryonic development and the mature hair follicle anagen.…”