Van Den Bosch L, Schwaller B, Vleminckx V, Meijers B, Stork S, Ruehlicke T, Van Houtte E, Klaassen H, Celio M R, Missiaen L, Robberecht W, Berchtold M W
Neurobiology, Laboratory of Physiology, Campus Gasthuisberg, Herestraat 49, Leuven, Belgium.
Exp Neurol. 2002 Apr;174(2):150-61. doi: 10.1006/exnr.2001.7858.
The mechanism responsible for the selective vulnerability of motor neurons in amyotrophic lateral sclerosis (ALS) is poorly understood. Several lines of evidence indicate that susceptibility of motor neurons to Ca(2+) overload induced by excitotoxic stimuli is involved. In this study, we investigated whether the high density of Ca(2+)-permeable AMPA receptors on motor neurons gives rise to higher Ca(2+) transients in motor neurons compared to dorsal horn neurons. Dorsal horn neurons were chosen as controls as these cells do not degenerate in ALS. In cultured spinal motor neurons, the rise of the cytosolic Ca(2+) concentration induced by kainic acid (KA) and mediated by the AMPA receptor was almost twice as high as in spinal neurons from the dorsal horn. Furthermore, we investigated whether increasing the motor neuron's cytosolic Ca(2+)-buffering capacity protects them from excitotoxic death. To obtain motor neurons with increased Ca(2+) buffering capacity, we generated transgenic mice overexpressing parvalbumin (PV). These mice have no apparent phenotype. PV overexpression was present in the central nervous system, kidney, thymus, and spleen. Motor neurons from these transgenic mice expressed PV in culture and were partially protected from KA-induced death as compared to those isolated from nontransgenic littermates. PV overexpression also attenuated KA-induced Ca(2+) transients, but not those induced by depolarization. We conclude that the high density of Ca(2+)-permeable AMPA receptors on the motor neuron's surface results in high Ca(2+) transients upon stimulation and that the low cytosolic Ca(2+)-buffering capacity of motor neurons may contribute to the selective vulnerability of these cells in ALS. Overexpression of a high-affinity Ca(2+) buffer such as PV protects the motor neuron from excitotoxicity and this protective effect depends upon the mode of Ca(2+) entry into the cell.
肌萎缩侧索硬化症（ALS）中运动神经元选择性易损性的机制尚不清楚。多项证据表明，运动神经元对兴奋性毒性刺激诱导的Ca(2+)超载的易感性与之有关。在本研究中，我们调查了与背角神经元相比，运动神经元上高密度的Ca(2+)通透型AMPA受体是否会导致运动神经元中更高的Ca(2+)瞬变。选择背角神经元作为对照，因为这些细胞在ALS中不会退化。在培养的脊髓运动神经元中，由红藻氨酸（KA）诱导并由AMPA受体介导的胞质Ca(2+)浓度升高几乎是背角脊髓神经元的两倍。此外，我们研究了增加运动神经元的胞质Ca(2+)缓冲能力是否能保护它们免受兴奋性毒性死亡。为了获得具有增强Ca(2+)缓冲能力的运动神经元，我们培育了过表达小白蛋白（PV）的转基因小鼠。这些小鼠没有明显的表型。PV在中枢神经系统、肾脏、胸腺和脾脏中过表达。与从非转基因同窝小鼠分离的运动神经元相比，这些转基因小鼠的运动神经元在培养中表达PV，并部分免受KA诱导的死亡。PV过表达也减弱了KA诱导的Ca(2+)瞬变，但没有减弱去极化诱导的Ca(2+)瞬变。我们得出结论，运动神经元表面高密度的Ca(2+)通透型AMPA受体导致刺激时出现高Ca(2+)瞬变，并且运动神经元低的胞质Ca(2+)缓冲能力可能导致这些细胞在ALS中的选择性易损性。过表达高亲和力Ca(2+)缓冲剂如PV可保护运动神经元免受兴奋性毒性，这种保护作用取决于Ca(2+)进入细胞的方式。
