Hollenbach P W, Zilli D L, Laster S M
Department of Microbiology, North Carolina State University, Raleigh 27695.
J Biol Chem. 1992 Jan 5;267(1):39-42.
In this report we have examined the ability of tumor necrosis factor-alpha (TNF) to induce the activity of phospholipase A2 (PLA2) in the cell line C3HA, a murine 3T3-like cell line which is normally resistant to TNF-induced cytolysis but can be sensitized with inhibitors of transcription and translation. Our results show that TNF is normally unable to induce the activity of PLA2 in this cell, as measured by the release of [3H]arachidonic acid. We find, however, that in the presence of either actinomycin D (Act D) or cycloheximide (CHI), TNF is indeed able to induce phospholipase activity and that the TNF-induced activation of PLA2 occurs 2-4 h before the onset of 51Cr release. The release of [3H]arachidonic acid was inhibited by 40-50% by pretreatment with 1 microM dexamethasone. Treatment with dexamethasone also inhibited cytolysis by 40-50% indicating that the CHI-dependent, TNF-induced activation of PLA2 is a cause, not an effect of cytolysis. The ability of TNF to induce the activity of PLA2 was also tested in two other cell types which are resistant to TNF except in the presence of Act D or CHI: SK-MEL-28, a human melanoma-derived cell line, and pVBETK-1cl15.2, an SV40-transformed murine L cell line. Our results were the same, treatment with a combination of Act D and TNF or CHI and TNF was required to cause activation of PLA2.
在本报告中，我们研究了肿瘤坏死因子-α（TNF）诱导磷脂酶A2（PLA2）在C3HA细胞系中活性的能力，C3HA是一种鼠源3T3样细胞系，通常对TNF诱导的细胞溶解具有抗性，但可被转录和翻译抑制剂致敏。我们的结果表明，以[3H]花生四烯酸的释放量来衡量，TNF通常无法在该细胞中诱导PLA2的活性。然而，我们发现，在放线菌素D（Act D）或环己酰亚胺（CHI）存在的情况下，TNF确实能够诱导磷脂酶活性，并且TNF诱导的PLA2激活发生在51Cr释放开始前2 - 4小时。用1 microM地塞米松预处理可使[3H]花生四烯酸的释放量降低40 - 50%。地塞米松处理也使细胞溶解降低40 - 50%，这表明CHI依赖性、TNF诱导的PLA2激活是细胞溶解的原因，而非结果。还在另外两种除了在Act D或CHI存在时对TNF具有抗性的细胞类型中测试了TNF诱导PLA2活性的能力：SK - MEL - 28，一种人黑色素瘤衍生细胞系，以及pVBETK - 1cl15.2，一种SV40转化的鼠L细胞系。我们得到了相同的结果，需要用Act D和TNF或CHI和TNF的组合处理才能引起PLA2的激活。
