Yamada H, Martin P, Suzuki K
Brain and Development Research Center, School of Medicine, University of North Carolina at Chapel Hill 27599-7525, USA.
Brain Res. 1996 Apr 29;718(1-2):138-44. doi: 10.1016/0006-8993(96)00098-4.
Twitcher (twi/twi) is a murine model of globoid cell leukodystrophy in humans caused by a genetic deficiency in activity of galactosylceramidase. Our previous study demonstrated that the rate of Schwann cell proliferation in twi/twi was considerably lower than that of the control (+/+) in vitro. We hypothesize that the lower mitotic rate in twi/twi results from the metabolic perturbation of Schawann cells caused by an accumulation of the toxic metabolite of galactosylceramidase, psychosine, a potent inhibitor of protein kinase C (PKC). Mouse Schwann cells are known to be stimulated to divide by growth factors in media containing fetal bovine serum. The stimulation by glial growth factor (GGF) or platelet-derived growth factor-BB (PDGF-BB) is though to be through the PKC pathway, but not by the basic fibroblast growth factor (bFGF) or transforming growth factor-beta (TGF-beta). Thus, we tested responses of twi/twi and +/+ Schwann cells to these growth factors. Schwann cells were isolated from the dorsal root ganglia at 30 days of age and the experiments were carried out at 21 days in vitro. In media containing PDGF-BB or bovine pituitary extract (BPE), the mitotic rate of twi/twi Schwann cells was 76% or 69% of the +/+ value, respectively, while significant differences were detected between twi/twi and +/+ in cultures containing TGF-beta or bFGF. When phorbol 12,13-dibutyrylate, a specific activator of PKC, was added to the media containing PDGF-BB or BPE, the mitotic rate of twi/twi Schwann cells improved up to 90% of +/+ cells. Staurosporine, an inhibitor of PKC. suppressed the proliferation of both twi/twi and +/+ Schwann cells. However, proliferation of twi/twi Schwann cells was suppressed by one-tenth of the concentration required for +/+ Schwann cells. These results are consistent with an accumulation of psychosine, an inhibitor of PKC, and suggest that the signal transduction system through PKC is impaired in the twi/twi Schwann cells.
颤抖小鼠（twi/twi）是人类球状细胞脑白质营养不良的一种小鼠模型，由半乳糖神经酰胺酶活性的遗传缺陷引起。我们之前的研究表明，在体外，twi/twi小鼠雪旺细胞的增殖速率明显低于对照（+/+）小鼠。我们推测，twi/twi小鼠有丝分裂率较低是由于半乳糖神经酰胺酶的有毒代谢产物——鞘氨醇（一种蛋白激酶C（PKC）的强效抑制剂）积累导致雪旺细胞代谢紊乱所致。已知在含有胎牛血清的培养基中，生长因子可刺激小鼠雪旺细胞分裂。神经胶质生长因子（GGF）或血小板衍生生长因子-BB（PDGF-BB）的刺激作用被认为是通过PKC途径，而碱性成纤维细胞生长因子（bFGF）或转化生长因子-β（TGF-β）则不是。因此，我们测试了twi/twi和+/+雪旺细胞对这些生长因子的反应。在30日龄时从背根神经节分离雪旺细胞，并在体外培养21天时进行实验。在含有PDGF-BB或牛垂体提取物（BPE）的培养基中，twi/twi雪旺细胞的有丝分裂率分别为+/+小鼠的76%或69%，而在含有TGF-β或bFGF的培养物中，twi/twi和+/+之间检测到显著差异。当将PKC的特异性激活剂佛波酯12,13 - 二丁酸盐添加到含有PDGF-BB或BPE的培养基中时，twi/twi雪旺细胞的有丝分裂率提高到+/+细胞的90%。PKC抑制剂星形孢菌素抑制了twi/twi和+/+雪旺细胞的增殖。然而，抑制twi/twi雪旺细胞增殖所需的浓度是+/+雪旺细胞的十分之一。这些结果与PKC抑制剂鞘氨醇的积累一致，并表明twi/twi雪旺细胞中通过PKC的信号转导系统受损。
