Inhibition of Synaptic Glutamate Exocytosis and Prevention of Glutamate Neurotoxicity by Eupatilin from Artemisia argyi in the Rat Cortex

Abstract

The inhibition of synaptic glutamate release to maintain glutamate homeostasis contributes to the alleviation of neuronal cell injury, and accumulating evidence suggests that natural products can repress glutamate levels and associated excitotoxicity. In this study, we investigated whether eupatilin, a constituent of Artemisia argyi, affected glutamate release in rat cortical nerve terminals (synaptosomes). Additionally, we evaluated the effect of eupatilin in an animal model of kainic acid (KA) excitotoxicity, particularly on the levels of glutamate and N-methyl-D-aspartate (NMDA) receptor subunits (GluN2A and GluN2B). We found that eupatilin decreased depolarization-evoked glutamate release from rat cortical synaptosomes and that this effect was accompanied by a reduction in cytosolic Ca2+ elevation, inhibition of P/Q-type Ca2+ channels, decreased synapsin I Ca2+-dependent phosphorylation and no detectable effect on the membrane potential. In a KA-induced glutamate excitotoxicity rat model, the administration of eupatilin before KA administration prevented neuronal cell degeneration, glutamate elevation, glutamate-generating enzyme glutaminase increase, excitatory amino acid transporter (EAAT) decrease, GluN2A protein decrease and GluN2B protein increase in the rat cortex. Taken together, the results suggest that eupatilin depresses glutamate exocytosis from cerebrocortical synaptosomes by decreasing P/Q-type Ca2+ channels and synapsin I phosphorylation and alleviates glutamate excitotoxicity caused by KA by preventing glutamatergic alterations in the rat cortex. Thus, this study suggests that eupatilin can be considered a potential therapeutic agent in the treatment of brain impairment associated with glutamate excitotoxicity.

Sodium Houttuyfonate Prevents Seizures and Neuronal Cell Loss by Maintaining Glutamatergic System Stability in Male Rats with Kainic Acid-Induced Seizures

“…Moreover, we also observed significant alterations in the subunits of the AMPA (GluA1 and GluA2) and NMDA (GluN2A and GluN2B) glutamate receptors, including decreased GluA1, GluA2, and GluN2A levels and increased GluN2B levels, in the hippocampus after KA treatment. These alterations are consistent with the results of previous studies [ 20 , 38 , 39 ]. GluA2-containing AMPA receptors are Ca 2+ -impermeable [ 40 ].…”

“…hippocampus after KA treatment. These alterations are consistent with the results of previous studies [20,38,39]. GluA2-containing AMPA receptors are Ca 2+ -impermeable [40].…”

“…Astrocytic EAAT1, EAAT2, and neuronal EAAT3 remove extracellular glutamate, GS converts glutamate to glutamine within astrocytes, and glutaminase converts glutamine into glutamate in neurons [ 33 , 34 , 35 ]. Previous studies have shown that decreased EAAT1, EAAT2, EAAT3, and GS or increased glutaminase cause an increase in glutamate concentrations in the brain and subsequent excitotoxicity [ 34 , 36 , 37 , 38 ]. Similarly, we found that KA treatment significantly decreased the protein levels of EAAT1, EAAT2, EAAT3, and GS in the hippocampus, which suggests that the decreased uptake of glutamate leads to increased glutamate levels in kainic acid-treated rats.…”

Gypenoside XVII Reduces Synaptic Glutamate Release and Protects against Excitotoxic Injury in Rats

“…In the present study, a significant decrease in the protein level of GluN2A and a marked increase in the protein level of GluN2B were detected in the cortex of KA-treated rats. These results were consistent with those of previous studies [29,35,54]. Additionally, these alterations in GluN2A and GluN2B protein levels were reversed by pretreatment with GP-17.…”

“…We also elucidated the effect of GP-17 on neuronal injury in a rat model of excitotoxicity induced by systemic administration of KA, an excitotoxic glutamate analog. Consistent with previous studies [35,53,54], I.P. administration of 15 mg/kg KA induced seizures and neuronal injury in the entorhinal cortex.…”