Abushik P A, Karelina T V, Sibarov D A, Stepanenko J D, Giniatullin R, Antonov S M
Zh Evol Biokhim Fiziol. 2015 Jul-Aug;51(4):258-65.
Homocysteine, a sulfur-containing amino acid, exhibits neurotoxic effects and is involved in the pathogenesis of several major neurodegenerative disorders. In contrast to well studied excitoxicity of glutamate, the mechanism of homocysteine neurotoxicity is not clearly understood. By using whole-cell patch-clamp, calcium imaging (fluo-3) and measurements of mitochondrial membrane potential (rhodamine 123) we studied transmembrane currents, calcium signals and changes in mitochondrial membrane potential induced by homocysteine versus responses induced by NMDA and glutamate in cultured rat cortical neurons. L-homocysteine (50 µM) induced inward currents that could be completely blocked by the selective antagonist of NMDA receptors - AP-5. In contrast to NMDA-induced currents, homocysteine-induced currents had a smaller steady-state amplitude. Comparison of calcium responses to homocysteine, NMDA or glutamate demonstrated that in all cortical neurons homocysteine elicited short, oscillatory-type calcium responses, whereas NMDA or glutamate induced sustained increase of intracellular calcium. Analysis of mitochondrial changes demonstrated that in contrast to NMDA homocysteine did not cause a drop of mitochondrial membrane potential at the early stages of action. However, after its long-term action, as in the case of NMDA and glutamate, the changes in mitochondrial membrane potential were comparable with the full drop of respiratory chain induced by protonophore FCCP. Our data suggest that in cultured rat cortical neuron homocysteine at the first stages of action induces neurotoxic effects through activation of NMDA-type ionotropic glutamate receptors with strong calcium influx through the channels of these receptors. The long-term action of homocysteine may lead to mitochondrial disfuction and appears as a drop of mitochondrial membrane potential.
同型半胱氨酸是一种含硫氨基酸，具有神经毒性作用，参与多种主要神经退行性疾病的发病机制。与已充分研究的谷氨酸兴奋性毒性相反，同型半胱氨酸神经毒性的机制尚不清楚。我们利用全细胞膜片钳、钙成像（fluo-3）和线粒体膜电位测量（罗丹明123），研究了同型半胱氨酸诱导的跨膜电流、钙信号和线粒体膜电位变化，以及与NMDA和谷氨酸在培养的大鼠皮质神经元中诱导的反应的比较。L-同型半胱氨酸（50 μM）诱导内向电流，该电流可被NMDA受体的选择性拮抗剂AP-5完全阻断。与NMDA诱导的电流相反，同型半胱氨酸诱导的电流具有较小的稳态幅度。对同型半胱氨酸、NMDA或谷氨酸的钙反应比较表明，在所有皮质神经元中，同型半胱氨酸引发短暂的振荡型钙反应，而NMDA或谷氨酸诱导细胞内钙持续增加。线粒体变化分析表明，与NMDA相反，同型半胱氨酸在作用早期不会导致线粒体膜电位下降。然而，在其长期作用后，与NMDA和谷氨酸的情况一样，线粒体膜电位的变化与质子载体FCCP诱导的呼吸链完全下降相当。我们的数据表明，在培养的大鼠皮质神经元中，同型半胱氨酸在作用的第一阶段通过激活NMDA型离子型谷氨酸受体诱导神经毒性作用，通过这些受体的通道有强烈的钙内流。同型半胱氨酸的长期作用可能导致线粒体功能障碍，并表现为线粒体膜电位下降。
