Intracellular pH regulation in single cultured astrocytes from rat forebrain

Boyarsky, G.; Ransom, Bruce R.; Schlue, Wolf-R.; Davis, Marion B. E.; Boron, Walter F.

doi:10.1002/glia.440080404

Cited by 136 publications

(92 citation statements)

References 34 publications

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“…The amplitudes of the second and third Glu-evoked changes, compared with the first, were 87 Ϯ 34% (mean Ϯ SD) and 83 Ϯ 44%, respectively (n ϭ Ϫ -carrying transporters (see Fig. 1) (Boyarski et al, 1993;Deitmer and Rose, 1996 In CO 2 / HCO 3 Ϫ -free saline the amplitude of the Glu-induced acid shift increased about threefold to 43.7 nM (Table 1), and its maximal slope increased to 45.0 nM/min (Fig. 3B).…”

Section: Resultsmentioning

confidence: 94%

Mechanisms of H⁺and Na⁺Changes Induced by Glutamate, Kainate, and d-Aspartate in Rat Hippocampal Astrocytes

1996

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The excitatory transmitter glutamate (Glu), and its analogs kainate (KA), andd-aspartate (d-Asp) produce significant pH changes in glial cells. Transmitter-induced pH changes in glial cells, generating changes in extracellular pH, may represent a special form of neuronal–glial interaction. We investigated the mechanisms underlying these changes in intracellular H+concentration ([H+]i) in cultured rat hippocampal astrocytes and studied their correlation with increases in intracellular Na+concentration ([Na+]i), using fluorescence ratio imaging with 2′,7′-bis(carboxyethyl)-5,6-carboxyfluorescein (BCECF) or sodium-binding benzofuran isophthalate (SBFI). Glu, KA, ord-Asp evoked increases in [Na+]i; Glu ord-Asp produced parallel acidifications. KA, in contrast, evoked biphasic changes in [H+]i, alkaline followed by acid shifts, which were unaltered after Ca2+removal and persisted in 0 Cl−-saline, but were greatly reduced in CO2/HCO−3-free or Na+-free saline, or during 4,4′-diisothiocyanato-stilbene-2,2′-disulphonic acid (DIDS) application. The non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) blocked KA-evoked changes in [H+]iand [Na+]i, indicating that they were receptor–ionophore mediated. In contrast, CNQX increased the [H+]ichange and decreased the [Na+]ichange induced by Glu.d-Asp, which is transported but does not act at Glu receptors, induced [H+]iand [Na+]ichanges that were virtually unaltered by CNQX. Our study indicates that [Na+]iincreases are not primarily responsible for Glu- or KA-induced acidifications in astrocytes. Instead, intracellular acidifications evoked by Glu ord-Asp are mainly caused by transmembrane movement of acid equivalents associated with Glu/Asp-uptake into astrocytes. KA-evoked biphasic [H+]ichanges, in contrast, are probably attributable to transmembrane ion movements mediated by inward, followed by outward, electrogenic Na+/HCO−3cotransport, reflecting KA-induced biphasic membrane potential changes.

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Section: Resultsmentioning

confidence: 94%

Mechanisms of H⁺and Na⁺Changes Induced by Glutamate, Kainate, and d-Aspartate in Rat Hippocampal Astrocytes

1996

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“…Images were collected using the Princeton Instruments MicroMax CCD camera, and analyzed with MetaFluor image-processing software (Universal Imaging Corp.). The ratio of the fluorescence emissions (F 490 /F 440 ) was calibrated using the high K ϩ /nigericin technique (14). NH 4 ϩ /NH 3 solutions (30 mM, 2 min) were used to induce an acid load as described before (4).…”

Section: Methodsmentioning

confidence: 99%

ERK1/2-p90RSK-mediated Phosphorylation of Na+/H+ Exchanger Isoform 1

Luo

Kintner

Shull

et al. 2007

Journal of Biological Chemistry

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The function and regulation of Na ؉ /H ؉ exchanger isoform 1 (NHE1) following cerebral ischemia are not well understood. In this study, we demonstrate that extracellular signal-related kinases (ERK1/2) play a role in stimulation of neuronal NHE1 following in vitro ischemia. NHE1 activity was significantly increased during 10 -60 min reoxygenation (REOX) after 2-h oxygen and glucose deprivation (OGD). OGD/REOX not only increased the V max for NHE1 but also shifted the K m toward decreased [H ؉ ] i . These changes in NHE1 kinetics were absent when MAPK/ERK kinase (MEK) was inhibited by the MEK inhibitor U0126. There were no changes in the levels of phosphorylated ERK1/2 (p-ERK1/2) after 2 h OGD. The p-ERK1/2 level was significantly increased during 10 -60 min REOX, which was accompanied by nuclear translocation. U0126 abolished REOX-induced elevation and translocation of p-ERK1/2. We further examined the ERK/90-kDa ribosomal S6 kinase (p90 RSK ) signaling pathways. At 10 min REOX, phosphorylated NHE1 was increased with a concurrent elevation of phosphorylation of p90 RSK , a known NHE1 kinase. Inhibition of MEK activity with U0126 abolished phosphorylation of both NHE1 and p90 RSK . Moreover, neuroprotection was observed with U0126 or genetic ablation or pharmacological inhibition of NHE1 following OGD/REOX. Taken together, these results suggest that activation of ERK1/2-p90 RSK pathways following in vitro ischemia phosphorylates NHE1 and increases its activity, which subsequently contributes to neuronal damage. The Naϩ /H ϩ exchanger (NHE) 2 family is a group of membrane transport proteins that catalyzes the secondary active electroneurtral exchange of one Na ϩ for one H ϩ . To date, nine NHE isoforms (NHE1-9) have been cloned in mammalian tissues (1). Na ϩ /H ϩ exchanger isoform 1 (NHE1) is the most abundant NHE isoform in the rat central nervous system (2) and crucial in regulation of neuronal pH i (3, 4). We have recently reported that NHE1 activity plays an important role in neuronal damage in both in vitro and in vivo ischemic models (4). Inhibition of NHE1 activity during OGD/REOX prevents intracellular Na ϩ and Ca 2ϩ overload and thus reduces the Ca 2ϩ -mediated cascade of deleterious events (4). In acutely isolated CA1 neurons, an anoxia-triggered intracellular alkalization depends on activation of NHE1 (5). We also found that NHE1 activity is stimulated in cortical astrocytes following in vitro ischemia (6). However, whether NHE1 activity is overstimulated in cortical neurons following in vitro ischemia remains unknown.NHE1 has two large functional domains. The N-terminal transmembrane domain (ϳ500 amino acids) is responsible for cation translocation, and the cytoplasmic C-terminal domain (ϳ315 amino acids) is the main regulatory site for the NHE1 activity (7). The distal C-terminal tail of NHE1 contains a number of serine and threonine residues that are phosphorylated by several protein kinases, including extracellular signal-related kinases (ERK1/2) and 90-kDa ribosomal S6 kinase (p90 RSK ) (8). Activa...

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“…Images were collected using a Princeton Instruments MicroMax CCD camera and analyzed with MetaFluor image-processing software. The ratio of the fluorescence emissions (F 490 /F 440 ) was calibrated using the high K ϩ /nigericin technique (Boyarsky et al, 1993). NH 4 ϩ /NH 3 solutions were prepared by replacing 10 mM NaCl in the HEPES-buffered solution with an equimolar concentration of NH 4 Cl.…”

Section: Namentioning

confidence: 99%

Decreased Neuronal Death in Na⁺/H⁺Exchanger Isoform 1-Null Mice afterIn VitroandIn VivoIschemia

Luo¹,

Chen²,

Kintner³

et al. 2005

J. Neurosci.

111

178

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Na ϩ /Hϩ exchanger isoform 1 (NHE1) is a major acid extrusion mechanism after intracellular acidosis. We hypothesized that stimulation of NHE1 after cerebral ischemia contributes to the disruption of Na ϩ homeostasis and neuronal death. In the present study, expression of NHE1 was detected in cultured mouse cortical neurons. Three hours of oxygen and glucose deprivation (OGD) followed by 21 h of reoxygenation ( ϩ/ϩ mice. NHE1 ϩ/ϩ mice treated with HOE 642 or NHE1 heterozygous mice exhibited a ϳ33% decrease in infarct size ( p Ͻ 0.05). These results imply that NHE1 activity disrupts Na ϩ and Ca 2ϩ homeostasis and contributes to ischemic neuronal damage.

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Intracellular pH regulation in single cultured astrocytes from rat forebrain

Cited by 136 publications

References 34 publications

Mechanisms of H⁺and Na⁺Changes Induced by Glutamate, Kainate, and d-Aspartate in Rat Hippocampal Astrocytes

Mechanisms of H⁺and Na⁺Changes Induced by Glutamate, Kainate, and d-Aspartate in Rat Hippocampal Astrocytes

ERK1/2-p90RSK-mediated Phosphorylation of Na+/H+ Exchanger Isoform 1

Decreased Neuronal Death in Na⁺/H⁺Exchanger Isoform 1-Null Mice afterIn VitroandIn VivoIschemia

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Intracellular pH regulation in single cultured astrocytes from rat forebrain

Cited by 136 publications

References 34 publications

Mechanisms of H+and Na+Changes Induced by Glutamate, Kainate, and d-Aspartate in Rat Hippocampal Astrocytes

Mechanisms of H+and Na+Changes Induced by Glutamate, Kainate, and d-Aspartate in Rat Hippocampal Astrocytes

ERK1/2-p90RSK-mediated Phosphorylation of Na+/H+ Exchanger Isoform 1

Decreased Neuronal Death in Na+/H+Exchanger Isoform 1-Null Mice afterIn VitroandIn VivoIschemia

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Mechanisms of H⁺and Na⁺Changes Induced by Glutamate, Kainate, and d-Aspartate in Rat Hippocampal Astrocytes

Mechanisms of H⁺and Na⁺Changes Induced by Glutamate, Kainate, and d-Aspartate in Rat Hippocampal Astrocytes

Decreased Neuronal Death in Na⁺/H⁺Exchanger Isoform 1-Null Mice afterIn VitroandIn VivoIschemia