Michel P P, Vyas S, Anglade P, Ruberg M, Agid Y
INSERM U289, Hôpital de la Salpêtrière, Paris, France.
Eur J Neurosci. 1994 Apr 1;6(4):577-86. doi: 10.1111/j.1460-9568.1994.tb00302.x.
The mechanisms that lead ultimately to neuronal death in pathological ageing of the brain remain mostly unknown as in the case of Parkinson's disease where there is a progressive and selective loss of dopaminergic neurons within the substantia nigra. Dopamine-expressing PC12 cells that were neuronally differentiated by nerve growth factor treatment were chosen as a culture model in which to study some of the changes that may occur during the course of the degenerative process. They were exposed to the calcium ionophore A23187 in order to produce a sustained rise in cytoplasmic calcium, a phenomenon related to various pathological conditions. The degenerative effects of the ionophore were dose- and time-dependent. They were characterized by early fragmentation of the neurites followed ultimately by a loss in cell viability. Biochemical changes, such as a decrease in [3H]dopamine uptake and modulations of the tyrosine hydroxylase gene, were detected before macroscopic evidence of cell suffering (e.g. neurite fragmentation) could be observed. Although an ongoing degenerative process was occurring in cell somata, PC12 cells were able to recover upon ionophore withdrawal. Characteristics of apoptosis such as chromatin condensation and DNA fragmentation were detectable in a small population of dying cells. DNA fragmentation could be prevented by the endonuclease inhibitor aurintricarboxylic acid. New protein synthesis was not required, as cycloheximide failed to prevent degeneration. Taken together, these results suggest that differentiated PC12 cells react to calcium stress through a sequence of regulatory processes which appears to be independent of the apoptotic pathway.
在大脑病理性衰老过程中最终导致神经元死亡的机制，就像帕金森病的情况一样，大多仍然未知，在帕金森病中，黑质内多巴胺能神经元会进行性且选择性地丧失。经神经生长因子处理后分化为神经元的表达多巴胺的PC12细胞被选作一种培养模型，用于研究在退行性过程中可能发生的一些变化。它们被暴露于钙离子载体A23187，以导致细胞质钙持续升高，这一现象与各种病理状况相关。离子载体的退行性作用具有剂量和时间依赖性。其特征是神经突早期断裂，最终导致细胞活力丧失。在能够观察到细胞受损的宏观证据（如神经突断裂）之前，就检测到了生化变化，如[3H]多巴胺摄取减少和酪氨酸羟化酶基因的调节。尽管细胞体中正在发生进行性退行性过程，但PC12细胞在撤除离子载体后能够恢复。在一小部分濒死细胞中可检测到凋亡特征，如染色质浓缩和DNA片段化。DNA片段化可被核酸内切酶抑制剂金精三羧酸阻止。由于环己酰亚胺未能阻止退变，因此不需要新的蛋白质合成。综上所述，这些结果表明，分化的PC12细胞通过一系列调节过程对钙应激做出反应，这一过程似乎独立于凋亡途径。
