Cytosolic zinc release and clearance in hippocampal neurons exposed to glutamate – the role of pH and sodium

• Published in: Journal of neurochemistry 2011-04, Vol.117 (2), p.231-243
• Main Author: Kiedrowski, Lech
• Format: Article
• Language: English
• Subjects: Acidification; Adult and adolescent clinical studies; Animals; BCECF; Biological and medical sciences; Calcium (intracellular); Calcium - metabolism; Calcium influx; Cells, Cultured; Chelating Agents - pharmacology; Cytosol - drug effects; Cytosol - metabolism; Data processing; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Dose-Response Relationship, Drug; Edetic Acid - pharmacology; Embryo, Mammalian; Ethylenediamines - pharmacology; Excitatory Amino Acid Agonists - pharmacology; Excitotoxicity; FluoZin‐3; Fura-2 - metabolism; Fura‐2FF; Glutamic acid; Glutamic Acid - pharmacology; Glycine; Glycine - pharmacology; Hippocampus; Hippocampus - cytology; Homeostasis; Hydrogen; Hydrogen-Ion Concentration - drug effects; intracellular pH; intracellular Zn2+ stores; Ischemia; Medical sciences; Mice; N-Methylaspartate - pharmacology; Neurology; Neurons; Neurons - cytology; Organic mental disorders. Neuropsychology; pH effects; Polycyclic Compounds - metabolism; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Sodium; Sodium - metabolism; Statistics, Nonparametric; Temperature effects; TPEN; Zinc; Zinc - metabolism
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2011.07194.x

J. Neurochem. (2011) 117, 231–243. Although Zn2+ homeostasis in neurons is tightly regulated and its destabilization has been linked to a number of pathologies including Alzheimer’s disease and ischemic neuronal death, the primary mechanisms affecting intracellular Zn2+ concentration ([Zn2+]i) in neurons exposed to excitotoxic stimuli remain poorly understood. The present work addressed these mechanisms in cultured hippocampal neurons exposed to glutamate and glycine (Glu/Gly). [Zn2+]i and intracellular Ca2+ concentration were monitored simultaneously using FluoZin‐3 and Fura‐2FF, and intracellular pH (pHi) was studied in parallel experiments using 2′,7′‐bis‐(2‐carboxyethyl)‐5(6)‐carboxyfluorescein. Glu/Gly applications under Na+‐free conditions (Na+ substituted with N‐methyl‐d‐glucamine+) caused Ca2+ influx, pHi drop, and Zn2+ release from intracellular stores. Experimental maneuvers resulting in a pHi increase during Glu/Gly applications, such as stimulation of Na+‐dependent pathways of H+ efflux, forcing H+ efflux via gramicidin‐formed channels, or increasing extracellular pH counteracted [Zn2+]i elevations. In the absence of Na+, the rate of [Zn2+]i decrease could be correlated with the rate of pHi increase. In the presence of Na+, the rate of [Zn2+]i decrease was about twice as fast as expected from the rate of pHi elevation. The data suggest that Glu/Gly‐induced cytosolic acidification promotes [Zn2+]i elevations and that Na+ counteracts the latter by promoting pHi‐dependent and pHi‐independent mechanisms of cytosolic Zn2+ clearance.