Collapse of Neuronal Energy Balance As a Basis of L-Homocysteine Neurotoxicity

• Published in: Biochemistry (Moscow). Supplement series A, Membrane and cell biology Membrane and cell biology, 2018-10, Vol.12 (4), p.360-368
• Main Authors: Sitnikova, L. S., Ivanova, M. A., Stepanenko, Yu. D., Karelina, T. V., Giniatullin, R., Sibarov, D. A., Abushik, P. A., Antonov, S. M.
• Format: Article
• Language: English
• Subjects: Apoptosis; Biomedical and Life Sciences; Calcium (intracellular); Calcium ions; Cell Biology; Cell culture; Cerebellum; Energy balance; Fluo-3; Fluorescence; Glutamic acid; Glutamic acid receptors (ionotropic); Homocysteine; Intracellular; L-Homocysteine; Life Sciences; Membrane potential; Mitochondria; N-Methyl-D-aspartic acid receptors; Necrosis; Neurons; Neurotoxicity; Reagents; Rodents
• ISSN: 1990-7478; 1990-7494
• DOI: 10.1134/S1990747818050069

Using fluorescence detection methods, neurotoxic effects of L -homocysteine (HCY), L -glutamate (Glu), and N-methyl- D -aspartate (NMDA) on primary culture of rat cerebellar neurons were compared and the agonist-evoked intracellular Ca 2+ responses and changes in mitochondrial membrane potential were studied. Long-term (5 h) action of HCY, Glu, or NMDA caused neuronal apoptosis and necrosis that was followed by a decrease of quantity of live cells to 40%. It was revealed using Fluo-3 that neurons differed by intracellular Ca 2+ responses to 2-min applications of HCY. In response to all studied agonists, a brief peak or gradual increase of intracellular Ca 2+ concentration was observed. Some neurons did not respond to HCY, but all responded to Glu and NMDA. A prolonged (60 min) treatment with agonists caused a rapid or delayed Ca 2+ overload, while only a small portion of neurons were able to compensate the intracellular Ca 2+ elevation. Six-minute applications of HCY or Glu to neurons induced similar changes of mitochondrial potential (φ mit ) measured by rhodamine123. In this protocol, the ability of the NMDA receptor agonists to cause the mitochondrial dysfunction could be arranged in the following order: NMDA > Glu = HCY. After a 60-min treatment the observed difference vanished because all of the agonists reduced φ mit so that an uncoupling agent FCCP did not cause any additional changes in φ mit . Thus, HCY-induced neurotoxicity in cerebellar neurons is comparable to that of Glu. In this feature cerebellar neurons differ from cortical neurons, in which HCY did not significantly change φ mit during short-term application. This difference could be related with peculiarities of the HCY action on NMDA receptor subtypes expressed by cerebellar neurons.