Lin TK, Hung CF, Weng JR, Hsieh TY, Wang SJ.
Kaempferol 3-Rhamnoside on Glutamate Release from Rat Cerebrocortical Nerve Terminals Involves P/Q-Type Ca
2+ Channel and Ca
2+/Calmodulin-Dependent Protein Kinase II-Dependent Pathway Suppression.
Molecules 2022;
27:molecules27041342. [PMID:
35209129 PMCID:
PMC8879690 DOI:
10.3390/molecules27041342]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 02/12/2022] [Accepted: 02/14/2022] [Indexed: 11/22/2022]
Abstract
Excess synaptic glutamate release has pathological consequences, and the inhibition of glutamate release is crucial for neuroprotection. Kaempferol 3-rhamnoside (KR) is a flavonoid isolated from Schima superba with neuroprotective properties, and its effecton the release of glutamate from rat cerebrocortical nerve terminals was investigated. KR produced a concentration-dependent inhibition of 4-aminopyridine (4-AP)-evoked glutamate release with half-maximal inhibitory concentration value of 17 µM. The inhibition of glutamate release by KR was completely abolished by the omission of external Ca2+ or the depletion of glutamate in synaptic vesicles, and it was unaffected by blocking carrier-mediated release. In addition, KR reduced the 4-AP-evoked increase in Ca2+ concentration, while it did not affect 4-AP-evoked membrane potential depolarization. The application of selective antagonists of voltage-dependent Ca2+ channels revealed that the KR-mediated inhibition of glutamate release involved the suppression of P/Q-type Ca2+ channel activity. Furthermore, the inhibition of release was abolished by the calmodulin antagonist, W7, and Ca2+/calmodulin-dependent protein kinase II (CaMKII) inhibitor, KN62, but not by the protein kinase A (PKA) inhibitor, H89, or the protein kinase C (PKC) inhibitor, GF109203X. We also found that KR reduced the 4-AP-induced increase in phosphorylation of CaMKII and its substrate synapsin I. Thus, the effect of KR on evoked glutamate release is likely linked to a decrease in P/Q-type Ca2+ channel activity, as well as to the consequent reduction in the CaMKII/synapsin I pathway.
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