Schwarz A, Bhardwaj R, Aragane Y, Mahnke K, Riemann H, Metze D, Luger T A, Schwarz T
Ludwig Boltzmann Institute for Cell Biology and Immunobiology of the Skin, Department of Dermatology, University Münster, Germany.
J Invest Dermatol. 1995 Jun;104(6):922-7. doi: 10.1111/1523-1747.ep12606202.
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-alpha (TNF-alpha), which is known to cause apoptosis in particular cells. In addition, it has been shown that UVB light induces the release of TNF-alpha by keratinocytes and that keratinocytes express the 55-kD receptor for TNF-alpha. Therefore, we investigated whether TNF-alpha is involved in UV-induced apoptosis of keratinocytes. 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. UVB induced apoptosis in a dose-dependent manner, which was confirmed by electron microscopy. Addition of a polyclonal antibody directed against human TNF-alpha 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-alpha is also involved in vivo 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 2000 J/m2 caused a significant induction of sunburn cells. Subcutaneous injection of a polyclonal antibody directed against murine TNF-alpha 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 in vitro and in vivo systems, application of recombinant TNF-alpha alone either to untreated keratinocytes or into normal murine skin did not induce sunburn cells. Thus, these data demonstrate that TNF-alpha 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.
用紫外线B（UVB）照射会导致形成被称为晒伤细胞的凋亡角质形成细胞。最近，有研究表明角质形成细胞能够释放肿瘤坏死因子-α（TNF-α），已知该因子可导致特定细胞发生凋亡。此外，已有研究显示UVB光可诱导角质形成细胞释放TNF-α，且角质形成细胞表达TNF-α的55-kD受体。因此，我们研究了TNF-α是否参与UV诱导的角质形成细胞凋亡。将正常人角质形成细胞和HaCaT细胞暴露于UVB光下，通过荧光激活细胞分选分析评估的缺口平移法检测凋亡情况。UVB以剂量依赖方式诱导凋亡，这一点通过电子显微镜得到证实。在UVB照射后立即添加针对人TNF-α的多克隆抗体能够减少DNA片段化。然而，不可能使所有细胞免于凋亡。为了证明TNF-α在体内是否也参与UVB诱导的角质形成细胞凋亡，将Balb/c小鼠腹部暴露于UVB下，24小时后进行皮肤活检，并对晒伤细胞进行计数。单次剂量2000 J/m2可显著诱导晒伤细胞形成。在UVB处理后立即皮下注射针对鼠TNF-α的多克隆抗体，可使晒伤细胞数量显著但不完全减少，而注射兔IgG作为对照则无效果。在体外和体内系统中，单独将重组TNF-α应用于未处理的角质形成细胞或正常鼠皮肤均未诱导晒伤细胞形成。因此，这些数据表明TNF-α参与UVB诱导的凋亡，但自身不能诱导晒伤细胞形成。这进一步支持了UVB诱导的角质形成细胞凋亡是一个多因素事件的观点。
