<p>Zn<sup>2+</sup> is essential for neuronal signaling, but imbalance cause cell death and neurodegenerative disorders. While the buffering system maintains low cytosolic Zn<sup>2+</sup> concentration ([Zn<sup>2+</sup>]<sub>i</sub>), the details on physiological stimuli elevating [Zn<sup>2+</sup>]<sub>i</sub> for neuronal processes remain limited. Our previous reports have demonstrated that dopamine elevates [Zn<sup>2+</sup>]<sub>i</sub> through the cAMP−NO pathway, activating autophagy and inflammation in neurons. In this study, we adopted the Zn<sup>2+</sup> imaging technique to verify how glutamate elevated [Zn<sup>2+</sup>]<sub>i</sub> in cultured cortical neurons and examined the inflammatory response. Our results showed that glutamate elevates the [Zn<sup>2+</sup>]<sub>i</sub>, by activating ionotropic glutamate receptors. Inhibitors of calmodulin (CaM), CaM-dependent protein kinase II (CaMKII), and NO synthase (NOS) blocked the glutamate-induced Zn<sup>2+</sup> response. High-K<sup>+</sup> buffer induced-membrane depolarization significantly elevated the intracellular Ca<sup>2+</sup> concentration ([Ca<sup>2+</sup>]<sub>i</sub>) but only slightly increased [Zn<sup>2+</sup>]<sub>i</sub> and NO production. Glutamate also transiently increased NOS phosphorylation at Ser<sup>1417</sup> within 15&#xa0;min. The Zn<sup>2+</sup> chelator, TPEN suppressed glutamate-induced inflammasome formation. These results indicate that glutamate-induced local increment in [Ca<sup>2+</sup>]<sub>i</sub> via the ionotropic glutamate receptors activates the CaM−CaMKII−NOS complex to produce NO and elevate [Zn<sup>2+</sup>]<sub>i</sub>. which trigger inflammation in cultured neurons. Henceforth, this novel glutamate−Zn<sup>2+</sup> signaling pathway after glutamate depolarization elevates [Ca<sup>2+</sup>]<sub>i</sub> indicates the involvement of Zn<sup>2+</sup> in modulating long-term neuronal activities.</p>

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

  • Hui-Chiun Tseng,
  • Yong-Sheng Wang,
  • Chien-Yuan Pan

摘要

Zn2+ is essential for neuronal signaling, but imbalance cause cell death and neurodegenerative disorders. While the buffering system maintains low cytosolic Zn2+ concentration ([Zn2+]i), the details on physiological stimuli elevating [Zn2+]i for neuronal processes remain limited. Our previous reports have demonstrated that dopamine elevates [Zn2+]i through the cAMP−NO pathway, activating autophagy and inflammation in neurons. In this study, we adopted the Zn2+ imaging technique to verify how glutamate elevated [Zn2+]i in cultured cortical neurons and examined the inflammatory response. Our results showed that glutamate elevates the [Zn2+]i, by activating ionotropic glutamate receptors. Inhibitors of calmodulin (CaM), CaM-dependent protein kinase II (CaMKII), and NO synthase (NOS) blocked the glutamate-induced Zn2+ response. High-K+ buffer induced-membrane depolarization significantly elevated the intracellular Ca2+ concentration ([Ca2+]i) but only slightly increased [Zn2+]i and NO production. Glutamate also transiently increased NOS phosphorylation at Ser1417 within 15 min. The Zn2+ chelator, TPEN suppressed glutamate-induced inflammasome formation. These results indicate that glutamate-induced local increment in [Ca2+]i via the ionotropic glutamate receptors activates the CaM−CaMKII−NOS complex to produce NO and elevate [Zn2+]i. which trigger inflammation in cultured neurons. Henceforth, this novel glutamate−Zn2+ signaling pathway after glutamate depolarization elevates [Ca2+]i indicates the involvement of Zn2+ in modulating long-term neuronal activities.