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Yi Chang,Chi-Feng Hung,Horng Huey Ko,Su-Jane Wang 한국식품영양과학회 2021 Journal of medicinal food Vol.24 No.3
Decreasing synaptic release of glutamate may counteract glutamate excitotoxicity in many neurological diseases. In this study, we investigated the effect of albanin A, a constituent in the root bark of Morus alba L., on the release of glutamate in rat cerebral cortex nerve endings (synaptosomes). We found that albanin A at 5–30μM suppressed 4-aminopyridine (4-AP)-induced release of glutamate. This phenomenon was abolished by extracellular calcium removal or by vesicular transporter inhibition, and was associated with a decrease in intrasynaptosomal Ca2+ levels. However, albanin A had no effect on the synaptosomal membrane potential. The inhibition of N- and P/Q-type Ca2+ channels, calmodulin, adenylate cyclase (AC), and protein kinase A, abolished the effect of albanin A on the glutamate release evoked by 4-AP. Moreover, the albanin A-mediated inhibition of glutamate release was prevented by the Ca2+/calmodulin-stimulated AC1 inhibitor. Western blot showed that AC1, but not AC8, was presented in the synaptosomes, and albanin A reduced 4-AP-induced increases in synaptosomal cyclic adenosine monophosphate content. In addition, albanin A pretreatment substantially attenuated neuronal damage in a rat model of kainic acid-induced glutamate excitotoxicity. Our data reveal that albanin A suppresses glutamate release by decreasing Ca2+/calmodulin/AC1 activation in synaptosomes and exerts neuroprotective effect in vivo.
( Anna Chang ),( Chi-Feng Hung ),( Pei-Wen Hsieh ),( Horng-Huey Ko ),( Su-Jane Wang ) 한국응용약물학회 2021 Biomolecules & Therapeutics(구 응용약물학회지) Vol.29 No.6
Eupafolin, a constituent of the aerial parts of Phyla nodiflora, has neuroprotective property. Because reducing the synaptic release of glutamate is crucial to achieving pharmacotherapeutic effects of neuroprotectants, we investigated the effect of eupafolin on glutamate release in rat cerebrocortical synaptosomes and explored the possible mechanism. We discovered that eupafolin depressed 4-aminopyridine (4-AP)-induced glutamate release, and this phenomenon was prevented in the absence of extracellular calcium. Eupafolin inhibition of glutamate release from synaptic vesicles was confirmed through measurement of the release of the fluorescent dye FM 1-43. Eupafolin decreased 4-AP-induced [Ca<sup>2+</sup>]<sub>i</sub> elevation and had no effect on synaptosomal membrane potential. The inhibition of P/Q-type Ca<sup>2+</sup> channels reduced the decrease in glutamate release that was caused by eupafolin, and docking data revealed that eupafolin interacted with P/Q-type Ca<sup>2+</sup> channels. Additionally, the inhibition of calcium/calmodulindependent protein kinase II (CaMKII) prevented the effect of eupafolin on evoked glutamate release. Eupafolin also reduced the 4-AP-induced activation of CaMK II and the subsequent phosphorylation of synapsin I, which is the main presynaptic target of CaMKII. Therefore, eupafolin suppresses P/Q-type Ca<sup>2+</sup> channels and thereby inhibits CaMKII/synapsin I pathways and the release of glutamate from rat cerebrocortical synaptosomes.