1,25-Dihydroxyvitamin D3, Transforming Growth Factor β1, Calcium, and Ultraviolet B Radiation Induce Apoptosis in Cultured Human Keratinocytes

Abstract

Apoptosis is a cellular process of self-directed suicide that plays a key role during morphogenesis and in the maintenance of homeostasis in continuously renewing tissues. Currently, apoptosis is detected mainly by gel electrophoresis of fragmented DNA and by typical ultrastructural features such as cell shrinkage and chromatin condensation. Recently, an in situ technique was developed that allows the detection of the apoptotic process in cells and the quantitation of apoptosis in cell populations. We applied this technique to evaluate the apoptotic process in cultured normal human keratinocytes under basic conditions and after stimulation with factors and agents that are presumed but have never been proved to induce apoptosis in these cells. Apoptosis was analyzed after stimulation with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], transforming growth factor beta1 (TGFbeta1), calcium, UVB, or tumor necrosis factor alpha (TNFalpha). All these factors except TNFalpha induced apoptosis in human keratinocytes. Whereas UVB and calcium were good apoptogenic stimuli at 6 and 24 h, respectively, the vitamin D derivative and TGFbeta1 induced apoptosis after 5 and 6 d in culture. Apoptosis was also established by DNA fragmentation and electron microscopy. Finally, TUNEL technique showed that the number of apoptotic cells increases slightly (5-10%) from 24 to 144 h even in untreated keratinocytes. Our studies indicate that factors normally involved in the regulation of cell growth and differentiation can also control apoptosis.

TGF-β3, but Not TGF-β1, Protects Keratinocytes against 12-O-Tetradecanoylphorbol-13-acetate-induced Cell Deathin Vitro and in Vivo

“…3A). As previously reported for human keratinocytes (22,23), TGF-␤1 treatment was also by itself sufficient to increase the number of TUNEL-positive cells. Interestingly, no such effect was observed with TGF-␤3 (Fig.…”

The Role of H2O2as a Mediator of UVB-induced Apoptosis in Keratinocytes

“…By using morphological criteria, these cells have been recognized as keratinocytes undergoing apoptosis. By applying more advanced techniques, it was latter confirmed that UV light induces apoptosis in keratinocytes and epithelial cell lines (Casciola-Rosen et al, 1994;Schwarz et al, 1995;Benassi et al, 1997;Gniadecki et al, 1997;Leverkus et al, 1997). The functional role of sunburn cells was regarded as a marker for severity of sun damage.…”

Inducible expression of filaggrin increases keratinocyte susceptibility to apoptotic cell death

“…Although different cell types vary greatly in their response to various noxious stimuli, 21 ultraviolet radiation has been shown to reproducibly induce apoptosis in keratinocytes. 22,23 Therefore, UVB was used initially to test the apoptotic capabilities of the cell lines. The filaggrin expressing lines consistently rounded up and lifted off from the culture dish at lower doses of UVB and at shorter time points compared to the b-galactosidase expressing lines (Figure 1c,d).…”