Gaytan-Garcia S, Kim H, Strong M J
The John P. Robart Research Institute, London, Ontario, Canada.
Toxicology. 1996 Apr 15;108(1-2):17-24. doi: 10.1016/s0300-483x(95)03266-i.
It has previously been shown that a single intracisternal inoculum of AlCl3 in young adult New Zealand white rabbits will induce a dose-dependent phosphatase resistance of high molecular weight neurofilament protein (NFH) that is proportionate to the extent of neurofilamentous inclusion formation (Strong and Jakowec, 1994). To determine if the potential for dissolution of aluminum-induced neurofilamentous inclusions was dependent on the degree of NFH phosphatase resistance, we have examined NFH phosphatase sensitivity in a reversible chronic model of aluminum neurotoxicity. Rabbits receiving repeated intracisternal inoculums of 100 microgram AlCl3 at 28 day intervals until day 267 develop spinal motor neuron perikaryal and neuroaxonal neurofilamentous aggregates in a stereotypic, dose-dependent fashion. In the rabbits receiving inoculums until day 156 with survival until day 267 without further aluminum exposure, neuroaxonal spheroids remained prominent while perikaryal inclusions largely resolved. Immunoreactivity to a monoclonal antibody recognizing phosphorylated NFH (SMI 31) was abolished in perikaryal aggregates at each time interval by dephosphorylation with bovine alkaline phosphatase. However, neuroaxonal spheroids maintained their immunoreactivity. Using time-course dephosphorylation studies of spinal cord homogenates, we observed a significant reduction in the rate of dephosphorylation of NFH following 267 days of AlCl3 exposure (P < 0.05). These observations suggest that neuroaxonal spheroids contain phosphatase-resistant NFH isoforms and that the potential for resolution of intraneuronal neurofilamentous inclusions correlates with the susceptibility of NF within these inclusions to enzymatic dephosphorylation.
先前的研究表明，在年轻成年新西兰白兔的脑池内单次接种氯化铝会诱导高分子量神经丝蛋白（NFH）产生剂量依赖性的磷酸酶抗性，且这种抗性与神经丝包涵体形成的程度成正比（斯特朗和亚科韦克，1994年）。为了确定铝诱导的神经丝包涵体溶解的可能性是否取决于NFH磷酸酶抗性的程度，我们在铝神经毒性的可逆慢性模型中检测了NFH对磷酸酶的敏感性。每隔28天接受100微克氯化铝脑池内重复接种直至第267天的兔子，会以刻板的、剂量依赖性的方式出现脊髓运动神经元胞体和神经轴突神经丝聚集物。在接受接种直至第156天且存活至第267天且不再接触铝的兔子中，神经轴突球状体仍然突出，而胞体包涵体大多消退。在每个时间间隔，通过用牛碱性磷酸酶去磷酸化，识别磷酸化NFH的单克隆抗体（SMI 31）的免疫反应性在胞体聚集体中消失。然而，神经轴突球状体保持其免疫反应性。通过对脊髓匀浆进行时间进程去磷酸化研究，我们观察到在氯化铝暴露267天后，NFH的去磷酸化速率显著降低（P < 0.05）。这些观察结果表明，神经轴突球状体含有抗磷酸酶的NFH异构体，并且神经元内神经丝包涵体消退的可能性与这些包涵体内NF对酶促去磷酸化的敏感性相关。
