Park T H, Mytilineou C
Department of Neurology, Mount Sinai School of Medicine, New York, NY 10029.
Brain Res. 1992 Dec 18;599(1):83-97. doi: 10.1016/0006-8993(92)90855-4.
Several peptide growth factors can maintain survival or promote recovery of injured central neurons. In the present study, the effects of epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) on the toxicity produced by the dopaminergic neurotoxin, 1-methyl-4-phenylpyridinium (MPP+), were investigated in rat mesencephalic dopaminergic neurons in culture. High affinity [3H]DA uptake and morphometric analyses of tyrosine hydroxylase immunostained neurons were used to assess the extent of MPP+ toxicity, dopaminergic neuronal survival and growth of neurites. Consistent with previous reports, EGF and bFGF treatments stimulated neuritic outgrowth in dopaminergic neurons, increased DA uptake and enhanced their long-term survival in vitro. These growth factors also stimulated proliferation of astrocytes. The time course of EGF and bFGF effects on dopaminergic neurons coincided with the increase in glial cell density, suggesting that proliferation of glia mediates their trophic effects. Several findings from our study support this possibility. When MPP+ was applied to cultures at 4 days in vitro, before glial cells had proliferated, the damage to dopaminergic neurons was not affected by EGF or bFGF pretreatments. However, when cultures maintained in the presence of the growth factors for 10 days were exposed to MPP+, after they had become confluent with dividing glial cells, the MPP(+)-induced decreases in DA uptake and cell survival were significantly attenuated. Furthermore, when glial cell proliferation was inhibited by 5-fluoro-2'-deoxyuridine, the protective effects of EGF and bFGF against MPP+ toxicity were abolished. Continuous treatment of MPP(+)-exposed cultures with EGF or bFGF resulted in the stimulation of process regrowth of damaged dopaminergic neurons with concomitant recovery of DA uptake, suggesting that the injured neurons are able to respond to the trophic effects of EGF and bFGF. In summary, our study shows that the trophic effects of EGF and bFGF on mesencephalic dopaminergic neurons include protection from the toxicity produced by MPP+ and promotion of recovery of MPP(+)-damaged neurons. Stimulation of glial cell proliferation is necessary for these effects.
几种肽生长因子可维持受损中枢神经元的存活或促进其恢复。在本研究中，我们在培养的大鼠中脑多巴胺能神经元中研究了表皮生长因子（EGF）和碱性成纤维细胞生长因子（bFGF）对多巴胺能神经毒素1-甲基-4-苯基吡啶鎓（MPP+）产生的毒性的影响。利用高亲和力[3H]多巴胺摄取以及酪氨酸羟化酶免疫染色神经元的形态计量分析来评估MPP+毒性的程度、多巴胺能神经元的存活以及神经突的生长。与先前的报道一致，EGF和bFGF处理可刺激多巴胺能神经元的神经突生长，增加多巴胺摄取并增强其在体外的长期存活。这些生长因子还可刺激星形胶质细胞的增殖。EGF和bFGF对多巴胺能神经元作用的时间进程与胶质细胞密度的增加相吻合，这表明胶质细胞的增殖介导了它们的营养作用。我们研究中的几个发现支持了这种可能性。当在体外培养4天时，即在胶质细胞增殖之前将MPP+应用于培养物中时，多巴胺能神经元的损伤不受EGF或bFGF预处理的影响。然而，当在生长因子存在下维持培养10天的培养物在与分裂的胶质细胞汇合后暴露于MPP+时，MPP+诱导的多巴胺摄取减少和细胞存活减少显著减轻。此外，当用5-氟-2'-脱氧尿苷抑制胶质细胞增殖时，EGF和bFGF对MPP+毒性的保护作用被消除。用EGF或bFGF持续处理暴露于MPP+的培养物会刺激受损多巴胺能神经元的突起再生，并伴随多巴胺摄取的恢复，这表明受损神经元能够对EGF和bFGF的营养作用作出反应。总之，我们的研究表明，EGF和bFGF对中脑多巴胺能神经元的营养作用包括保护其免受MPP+产生的毒性以及促进MPP+损伤神经元的恢复。胶质细胞增殖的刺激对于这些作用是必要的。
