Alleviation of cognitive deficits in a rat model of glutamate-induced excitotoxicity, using an N-type voltage-gated calcium channel ligand, extracted from Agelena labyrinthica crude venom

Abstract

Excitotoxicity is a common pathological process in Alzheimer’s disease (AD) which is caused by the over-activity of N-Methyl-D-Aspartate receptors (NMDARs). The release of neurotransmitters depends on the activity of voltage-gated calcium channels (VGCCs). Hyper-stimulation of NMDARs can enhance the releasement of neurotransmitters through the VGCCs. This malfunction of channels can be blocked by selective and potent N-type VGCCs ligand. Under excitotoxicity condition, glutamate has negative effects on the pyramidal cells of the hippocampus, which ends in synaptic loss and elimination of these cells. These events leads to learning and memory elimination through the hippocampus circuit’s dysfunction. A suitable ligand has a high affinity to receptor or channel and is selective for its target. The bioactive small proteins of venom have these characteristics. Therefore, peptides and small proteins of animal venom are precious sources for pharmacological applications. The omega-agatoxin-Aa2a was purified, and identified from Agelena labyrinthica specimens, as an N-type VGCCs ligand for this study. The effect of the omega-agatoxin-Aa2a on the glutamate-induced excitotoxicity in rats was evaluated through behavioral tests including Morris Water Maze, and Passive avoidance. The syntaxin1A (SY1A), synaptotagmin1 (SYT1), and synaptophysin (SYN) genes expression were measured via Real-Time PCR. The local expression of synaptosomal-associated protein, 25 k Da (SNAP-25) was visualized using an immunofluorescence assay for synaptic quantification. Electrophysiological amplitude of field excitatory postsynaptic potentials (fEPSPs) in the input–output and LTP curves of mossy fiber were recorded. The cresyl violet staining of hippocampus sections was performed for the groups. Our results demonstrated that the omega-agatoxin-Aa2a treatment could recover the learning, and memory impairment caused by NMDA-induced excitotoxicity in rat hippocampus.

The synergic effects of presynaptic calcium channel antagonists purified from spiders on memory elimination of glutamate-induced excitotoxicity in the rat hippocampus trisynaptic circuit

“…They were fed with crickets and mealworms. Taxonomic keys (particularly by epigyne of female spiders) were used to identify the specimens ( Nentwig et al, 2017 ; Keimasi et al, 2023a ; Keimasi et al, 2023b ).…”

“…Absorbance at 280 nm was obtained for the fractions, which were then accumulated in a 0.75 mL fraction. The selected fractions, marked on the graph, were accumulated and injected into a capillary electrophoresis instrument ( Keimasi et al, 2022 ; Keimasi et al, 2023a ).…”

“…LTP plays a crucial role in increasing dendrites and synaptic plasticity in the brain ( Bin Ibrahim et al, 2022 ). Overstimulation of these receptors by agonists, such as NMDA, glutamate, aspartate, and kainic acid, can lead to destructive reactions in neuronal cells ( Jarrard, 2002 ; Zhang et al, 2014 ; Hosseini-Sharifabad et al, 2021 ; Keimasi et al, 2022 ; Keimasi et al, 2023a ). This hyper-stimulation may be due to the over-activity of the presynaptic voltage-gated calcium channels (VGCCs), which are involved in glutamate release ( Schurr, 2004 ; Nimmrich and Gross, 2012 ; Sousa et al, 2013 ; Mochida, 2019 ).…”

“…The UniProt database has shown that the venoms of the Lycosidae and Agelenidae spider families contain high levels of Lycotoxin ( Liu et al, 2009 ) and Agatoxin proteins ( Consortium, 2019 ), which are related to L-, P/Q-, and N-type VGCC modulators and blockers ( Nimmrich and Gross, 2012 ; Sousa et al, 2013 ). Therefore, omega-Lsp-IA and omega-agatoxin-Aa2a can be considered as P/Q-type and N-type VGCC modulators, respectively ( Consortium, 2019 ; Keimasi et al, 2022 ; Keimasi et al, 2023a ).…”

Sensorineural hearing loss and cognitive impairment: three hypotheses

“…Glu was found to be involved in regulating the channel opening of NMDARs ( Wang et al, 2021 ), and overstimulation of NMDARs enhances the release of Glu via calcium channels. Under excitotoxic conditions, Glu leads to synaptic loss and elimination in hippocampal pyramidal cells ( Companys-Alemany et al, 2022 ; Keimasi et al, 2023 ). It is now widely accepted that over-activation of NMDARs leads to the development of AD ( Xu et al, 2021 ; Abad-Perez et al, 2023 ).…”