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J Neurochem. 2014 Apr;129(2):264-74. doi: 10.1111/jnc.12615. Epub 2013 Dec 4.

The role of NMDA and mGluR5 receptors in calcium mobilization and neurotoxicity of homocysteine in trigeminal and cortical neurons and glial cells.

Author information

1
Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland; Laboratory of Comparative Physiology of Cerebellum, Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Science, Saint-Petersburg, Russia.

Abstract

Recent studies suggested contribution of homocysteine (HCY) to neurodegenerative disorders and migraine. However, HCY effect in the nociceptive system is essentially unknown. To explore the mechanism of HCY action, we studied short- and long-term effects of this amino acid on rat peripheral and central neurons. HCY induced intracellular Ca²⁺ transients in cultured trigeminal neurons and satellite glial cells (SGC), which were blocked by the NMDA antagonist AP-5 in neurons, but not in SGCs. In contrast, 3-((2-Methyl-4-thiazolyl)ethynyl)pyridine (MTEP), the metabotropic mGluR5 (metabotropic glutamate receptor 5 subtype) antagonist, preferentially inhibited Ca²⁺ transients in SGCs. Prolonged application of HCY induced apoptotic cell death of both kinds of trigeminal cells. The apoptosis was blocked by AP-5 or by the mGluR5 antagonist MTEP. Likewise, in cortical neurons, HCY-induced cell death was inhibited by AP-5 or MTEP. Imaging with 2',7'-dichlorodihydrofluorescein diacetate or mitochondrial dye Rhodamine-123 as well as thiobarbituric acid reactive substances assay did not reveal involvement of oxidative stress in the action of HCY. Thus, elevation of intracellular Ca²⁺ by HCY in neurons is mediated by NMDA and mGluR5 receptors while SGC are activated through the mGluR5 subtype. Long-term neurotoxic effects in peripheral and central neurons involved both receptor types. Our data suggest glutamatergic mechanisms of HCY-induced sensitization and apoptosis of trigeminal nociceptors.

KEYWORDS:

NMDA receptor; homocysteine; mGluR5; neurodegeneration; pain sensitization; trigeminal ganglion

PMID:
24266734
DOI:
10.1111/jnc.12615
[Indexed for MEDLINE]
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