Ji L, Zhang G, Hirabayashi Y
Laboratory for Glyco Cell Biology, Institute of Chemical and Physical Research (Riken), Saitama, Japan.
Biochem Biophys Res Commun. 1995 Jul 17;212(2):640-7. doi: 10.1006/bbrc.1995.2017.
In many tumor cell lines, tumor necrosis factor alpha (TNF alpha) causes apoptosis with characteristic internucleosomal DNA fragmentation. However, the mechanism is largely unknown. Here we examined the involvement of protein tyrosine kinases by using their inhibitors. Among various tyrosine kinase inhibitors tested, only herbimycin A was found to inhibit internucleosomal DNA fragmentation but not apoptotic morphological changes and cell death induced by TNF alpha in U937 cells. Herbimycin A was able to block DNA fragmentation when it was added to the cell culture as late as 1.5 h after TNF alpha treatment. These results demonstrate that herbimycin A selectively inhibits a later event involved in the process of apoptois that results in internucleosomal DNA fragmentation. Sphingomyelinase and ceramide (Cer) induced internucleosomal DNA fragmentation was also inhibited by herbimycin A, supporting the hypothesis that Cer may be a novel second messenger mediating the cytotoxic effect of TNF alpha.
在许多肿瘤细胞系中，肿瘤坏死因子α（TNFα）可导致细胞凋亡，并伴有特征性的核小体间DNA片段化。然而，其机制在很大程度上尚不清楚。在此，我们通过使用蛋白酪氨酸激酶抑制剂来研究其参与情况。在测试的各种酪氨酸激酶抑制剂中，仅发现除莠霉素A可抑制U937细胞中核小体间DNA片段化，但不抑制TNFα诱导的凋亡形态变化和细胞死亡。当在TNFα处理后1.5小时这么晚的时候将除莠霉素A添加到细胞培养物中时，它能够阻断DNA片段化。这些结果表明，除莠霉素A选择性抑制凋亡过程中导致核小体间DNA片段化的一个后期事件。鞘磷脂酶和神经酰胺（Cer）诱导的核小体间DNA片段化也被除莠霉素A抑制，支持了Cer可能是介导TNFα细胞毒性作用的一种新型第二信使的假说。
