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- Title
Ultraviolet-B-Induced Apoptosis of Keratinocytes: Evidence for Partial Involvement of Tumor Necrosis Factor-α in the Formation of Sunburn Cells.
- Authors
Schwarz, Agatha; Bhardwaj, Ranjit; Aragane, Yoshinori; Mahnke, Karsten; Riemann, Helge; Metze, Dieter; Luger, Thomas A.; Schwarz, Thomas
- Abstract
Irradiation with ultraviolet (UV) B radiation results in the formation of apoptotic keratinocytes called sunburn cells. Recently, it was demonstrated that keratinocytes can release tumor necrosis factor-α (TNF-α), which is known to cause apoptosis in particular cells. In addition, it has been shown that UVB light induces the release of TNF-α by keratinocytes and that keratinocytes express the 55-kD receptor for TNF-α. Therefore, we investigated whether TNF-α is involved in UV-induced apoptosis of kerationocytes. Normal human keratinocytes and HaCaT cells were exposed to UVB light, and apoptosis was examined by nick translation evaluated by fluorescence-activated cell sorter analysis. UVP induced apoptosis in a dose-dependent manner, which was confirmed by electron microscopy. Addition of a polyclonal antibody directed against human TNF-α immediately after UVB exposure was able to reduce DNA fragmentation. However, it was not possible to rescue all cells from apoptosis. To prove whether TNF-α is also involved <em>in vivo</em> in UVB-induced apoptosis of keratinocytes, Balb/c mice were exposed to UVB on their abdomens, skin biopsies were performed 24 h later, and sunburn cells were counted. A single dose of 2000J/M² caused a significant induction of sunburn cells. Subcutaneous injection of a polyclonal antibody directed against murine TNF-α immediately after UVB treatment resulted in a significant but incomplete reduction of sunburn cells, whereas injection of a rabbit IgG as a control had no effect. In both the <em>in vitro</em> and <em>in vivo</em> systems, application of recombinant TNF-α alone either to untreated keratinocytes or into normal murine skin did not induce sunburn cells. Thus, these data demonstrate that TNF-α is involved in UVB-induced apoptosis, but by itself is not able to induce sunburn cells. This further supports the notion that UVB-induced apoptosis of keratinocytes is a multifactorial event.
- Subjects
KERATINOCYTES; APOPTOSIS; TUMOR necrosis factors; SUNBURN; CELLS; PHOTOSENSITIVITY disorders
- Publication
Journal of Investigative Dermatology, 1995, Vol 104, Issue 6, p922
- ISSN
0022-202X
- Publication type
Article
- DOI
10.1111/1523-1747.ep12606202