Glutamate gradually elevates [Zn2+]i via the CaM–CaMKII–NOS cascade in primary cultured rat embryonic cortical neurons

Abstract

Abstract Zn 2+ is essential for neuronal signaling, but imbalance cause cell death and neurodegenerative disorders. While the buffering system maintains low cytosolic Zn 2+ concentration ([Zn 2+ ] i ), the details on physiological stimuli elevating [Zn 2+ ] i for neuronal processes remain limited. Our previous reports have demonstrated that dopamine elevates [Zn 2+ ] i through the cAMP−NO pathway, activating autophagy and inflammation in neurons. In this study, we adopted the Zn 2+ imaging technique to verify how glutamate elevated [Zn 2+ ] i in cultured cortical neurons and examined the inflammatory response. Our results showed that glutamate elevates the [Zn 2+ ] i , by activating ionotropic glutamate receptors. Inhibitors of calmodulin (CaM), CaM-dependent protein kinase II (CaMKII), and NO synthase (NOS) blocked the glutamate-induced Zn 2+ response. High-K + buffer induced-membrane depolarization significantly elevated the intracellular Ca 2+ concentration ([Ca 2+ ] i ) but only slightly increased [Zn 2+ ] i and NO production. Glutamate also transiently increased NOS phosphorylation at Ser 1417 within 15 min. The Zn 2+ chelator, TPEN suppressed glutamate-induced inflammasome formation. These results indicate that glutamate-induced local increment in [Ca 2+ ] i via the ionotropic glutamate receptors activates the CaM−CaMKII−NOS complex to produce NO and elevate [Zn 2+ ] i . which trigger inflammation in cultured neurons. Henceforth, this novel glutamate−Zn 2+ signaling pathway after glutamate depolarization elevates [Ca 2+ ] i indicates the involvement of Zn 2+ in modulating long-term neuronal activities.