Studies for the induction of apoptosis in human junctional and gingival epithelial cells and for protective effect of HGF against apoptosis of these cells

点击翻译按钮获取中文摘要

Hepatocyte growth factor (HGF), also known as the scatter factor and tumor cytotoxic factor, is a most potent mitogen for many epithelial cells and is suggested to support the process of normal development and tissue regeneration.In this study, we first examined the induction of apoptosis in human junctional and gingival epithelial cells induced by serum deprivation, and investgated the protective effect of HGF against apoptosis of these cells. At present, we obtained following results :1. When these cells were cultured in serum-free medium for 24h, the cells underwent apoptosis, judged by generation of oligonucleosomal fragmentation of nuclear DNA and by in situ detection of fragmented DNA by TUNEL method. However, DNA fragmentation was markedly inhibited when the cells were incubated with HGF (10 ng/ml) in serum-free medium.2. We measured interleukin-1beta converting enzyme (ICE, named recently as caspase-1)-like protease activity in these cell extracts after incubation for 24h in serum-free medium and found that caspase-3 activity, but not caspase-1 activity, was increased about 2 times as compared with those of control cells incubated in the presence of 10% serum.3. Specific inhibitor for caspase-3, acetyl-Asp-Glu-Val-Asp-aldehyde inhibited not only the activation of caspase-3 but also the DNA fragmentation induced by serum deprivation, suggesting that activation of caspase-3 is involved in induction of apoptosis in these cells by serum deprivation.4. We examined the effect of HGF on the expression of Bcl-2, which is one of apoptosis suppressor proteins, by Western blotting analysis, and found that HGF increased the expression of Bcl-2.These results suggest that serum deprivation induces apoptosis in human junctional and gingival epithelial cells by increasing caspase-3 activity and that HGF suppresses the apoptosis by increasing the expression of Bcl-2, followed by inhibiting caspase-3 activation.