The Effect of Isosaponarin Derived from Wasabi Leaves on Glutamate Release in Rat Synaptosomes and Its Underlying Mechanism

Synaptic endocytosis in adult adipose stromal cell-derived neurons

Synapses are essential for facilitating the transmission of information between neurons and for executing neurophysiological processes. Following the exocytosis of neurotransmitters, the synaptic vesicle may quickly undergo endocytosis to preserve the structural integrity of the synapse. When converting adipose-derived stromal cells (ADSCs) into neurons, the ADSCs have already demonstrated comparable morphology, structure, and electrophysiological characteristics to neurons. Nevertheless, there is currently no published study on the endocytotic function of neurons that are produced from ADSCs. This study aimed to examine synaptic endocytosis in neurons derived from ADSCs by qualitatively and quantitatively analyzing the presence of Ap-2, Clathrin, Endophilin, Dynamin, and Hsc70, which are the key proteins involved in clathrin-mediated endocytosis (CME), as well as by using FM1-43 and cadmium selenide quantum dots (CdSe QDs). Additionally, single-cell RNA sequencing (scRNA-seq) was used to look at the levels of both neuronal markers and markers related to CME at the same time. The results of this study provide evidence that synapses in neurons produced from ADSCs have a role in endocytosis, mainly through the CME route.

Well-known polypeptides of deer antler velvet with key actives: modern pharmacological advances

Deer antler velvet, with kidney tonifying, promoting the production of essence and blood, strengthening tendons and bones, not only has a thousand-year medicinal history but also its modern pharmacology mainly focuses on its active polypeptides on motor, nerve, and immune systems. The purpose of this report is to fill the gap in the comprehensive, systematic, and detailed review of polypeptides during the recent 30 years (1992-2023). The research method was to review 53 pharmacological articles from the Public Medicine, Web of science, ACS, and Science Direct database sources by searching the keywords "pilose antler," "deer velvet," "Pilose Antler Peptide (PAP) and Velvet Antler Polypeptide (VAP)." The results showed that deer antler polypeptides (DAPs), by regulating EGF, EGFR, MAPK, P38, ERK, NF-κB, Wnt, PI3K, Akt, MMP, AMPK, Stir1, NLRP3, HO-1, Nrf, Rho, TLR, TGF-β, Smad, Ang II, etc., revealed their effects on seven system-related diseases and their mechanisms, including osteoarthritis, intervertebral disc degeneration, osteoporosis, Alzheimer's, Parkinson's, triple-negative breast cancer, liver injury, liver fibrosis, cardiovascular disease, acute lung injury, and late-onset hypogonadism. In conclusion, DAPs have good effects on motor and other system-related diseases, but the secondary and tertiary structures of DAPs (0.5-1800 KDa) need to be further elucidated, and the structure-activity relationship study is still unavailable and needs to be covered. It is expected that this review may provide the necessary literature support for further research. The activities and mechanisms of polypeptides from the past 30 years (1992-2023) are summarized covering seven systems, related diseases, and its regulatory genes and proteins.

Cynarin, a caffeoylquinic acid derivative in artichoke, inhibits exocytotic glutamate release from rat cortical nerve terminals (synaptosomes)

The purpose of this study was to evaluate the effect of cynarin, a caffeoylquinic acid derivative in artichoke, on glutamate release elicited by 4-aminopyridine (4-AP) in rat cortical nerve terminals (synaptosomes). We observed that cynarin decreased 4-aminopyridine-elicited glutamate release, which was prevented by the removal of external free Ca²⁺ with ethylene glycol bis (β-aminoethyl ether)-N,N,N,N-tetraacetic acid (EGTA) or the blockade of P/Q-type calcium channels with ω-agatoxin IVA. Molecular docking also revealed that cynarin formed a hydrogen bond with the P/Q-type Ca²⁺ channel, indicating a mechanism of action involving Ca²⁺ influx inhibition. Additionally, the inhibitory effect of cynarin on glutamate release is associated with a change in the available synaptic vesicles, as cynarin decreased 4-AP-elicited FM1-43 release or hypertonic sucrose-evoked glutamate release from synaptosomes. Furthermore, the suppression of protein kinase A (PKA) prevented the effect of cynarin on 4-AP-elicited glutamate release. 4-AP-elicited PKA and synapsin I or synaptosomal-associated protein of 25 kDa (SNAP-25) phosphorylation at PKA-specific residues were also attenuated by cynarin. Our data indicate that cynarin, through the suppression of P/Q-type Ca²⁺ channels, inhibits PKA activation and attenuates synapsin I and SNAP-25 phosphorylation at PKA-specific residues, thus decreasing synaptic vesicle availability and contributing to glutamate release inhibition in cerebral cortex terminals.

Mangiferin depresses vesicular glutamate release in synaptosomes from the rat cerebral cortex by decreasing synapsin I phosphorylation

Mangiferin is a glucosyl xanthone that has been shown to be a neuroprotective agent against brain disorders involving excess glutamate. However, the effect of mangiferin on the function of the glutamatergic system has not been investigated. In this study, we used synaptosomes from the rat cerebral cortex to investigate the effect of mangiferin on glutamate release and identify the possible underlying mechanism. We observed that mangiferin produced a concentration-dependent reduction in the release of glutamate elicited by 4-aminopyridine with an IC₅₀ value of 25 μM. Inhibition of glutamate release was blocked by removing extracellular calcium and by treatment with the vacuolar-type H⁺-ATPase inhibitor bafilomycin A1, which prevents the uptake and storage of glutamate in vesicles. Moreover, we showed that mangiferin decreased the 4-aminopyridine-elicited FM1-43 release and synaptotagmin 1 luminal domain antibody (syt1-L ab) uptake from synaptosomes, which correlated with decreased synaptic vesicle exocytosis. Transmission electron microscopy in synaptosomes also showed that mangiferin attenuated the 4-aminopyridine-elicited decrease in the number of synaptic vesicles. In addition, antagonism of Ca²⁺/calmodulin-dependent kinase II (CaMKII) and protein kinase A (PKA) counteracted mangiferin's effect on glutamate release. Mangiferin also decreased the phosphorylation of CaMKII, PKA, and synapsin I elicited by 4-aminopyridine treatment. Our data suggest that mangiferin reduces PKA and CaMKII activation and synapsin I phosphorylation, which could decrease synaptic vesicle availability and lead to a subsequent reduction in vesicular glutamate release from synaptosomes.

Plantainoside D Reduces Depolarization-Evoked Glutamate Release from Rat Cerebral Cortical Synaptosomes

Inhibiting the excessive release of glutamate in the brain is emerging as a promising therapeutic option and is efficient for treating neurodegenerative disorders. The aim of this study is to investigate the effect and mechanism of plantainoside D (PD), a phenylenthanoid glycoside isolated from Plantago asiatica L., on glutamate release in rat cerebral cortical nerve terminals (synaptosomes). We observed that PD inhibited the potassium channel blocker 4-aminopyridine (4-AP)-evoked release of glutamate and elevated concentration of cytosolic Ca²⁺. Using bafilomycin A1 to block glutamate uptake into synaptic vesicles and EDTA to chelate extracellular Ca²⁺, the inhibitory effect of PD on 4-AP-evoked glutamate release was prevented. In contrast, the action of PD on the 4-AP-evoked release of glutamate in the presence of dl-TBOA, a potent nontransportable inhibitor of glutamate transporters, was unaffected. PD does not alter the 4-AP-mediated depolarization of the synaptosomal membrane potential, suggesting that the inhibitory effect of PD on glutamate release is associated with voltage-dependent Ca²⁺ channels (VDCCs) but not the modulation of plasma membrane potential. Pretreatment with the Ca²⁺ channel blocker (N-type) ω-conotoxin GVIA abolished the inhibitory effect of PD on the evoked glutamate release, as did pretreatment with the protein kinase C inhibitor GF109203x. However, the PD-mediated inhibition of glutamate release was eliminated by applying the mitochondrial Na⁺/Ca²⁺ exchanger inhibitor CGP37157 or dantrolene, which inhibits Ca²⁺ release through ryanodine receptor channels. These data suggest that PD mediates the inhibition of evoked glutamate release from synaptosomes primarily by reducing the influx of Ca²⁺ through N-type Ca²⁺ channels, subsequently reducing the protein kinase C cascade.