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Na(+)/H (+) Exchangers and Intracellular pH in Perinatal Brain Injury.

Uria-Avellanal, C; Robertson, NJ; (2014) Na(+)/H (+) Exchangers and Intracellular pH in Perinatal Brain Injury. Transl Stroke Res , 5 (1) pp. 79-98. 10.1007/s12975-013-0322-x. Green open access

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Abstract

Encephalopathy consequent on perinatal hypoxia-ischemia occurs in 1-3 per 1,000 term births in the UK and frequently leads to serious and tragic consequences that devastate lives and families, with huge financial burdens for society. Although the recent introduction of cooling represents a significant advance, only 40 % survive with normal neurodevelopmental function. There is thus a significant unmet need for novel, safe, and effective therapies to optimize brain protection following brain injury around birth. The Na(+)/H(+) exchanger (NHE) is a membrane protein present in many mammalian cell types. It is involved in regulating intracellular pH and cell volume. NHE1 is the most abundant isoform in the central nervous system and plays a role in cerebral damage after hypoxia-ischemia. Excessive NHE activation during hypoxia-ischemia leads to intracellular Na(+) overload, which subsequently promotes Ca(2+) entry via reversal of the Na(+)/Ca(2+) exchanger. Increased cytosolic Ca(2+) then triggers the neurotoxic cascade. Activation of NHE also leads to rapid normalization of pHi and an alkaline shift in pHi. This rapid recovery of brain intracellular pH has been termed pH paradox as, rather than causing cells to recover, this rapid return to normal and overshoot to alkaline values is deleterious to cell survival. Brain pHi changes are closely involved in the control of cell death after injury: an alkalosis enhances excitability while a mild acidosis has the opposite effect. We have observed a brain alkalosis in 78 babies with neonatal encephalopathy serially studied using phosphorus-31 magnetic resonance spectroscopy during the first year after birth (151 studies throughout the year including 56 studies of 50 infants during the first 2 weeks after birth). An alkaline brain pHi was associated with severely impaired outcome; the degree of brain alkalosis was related to the severity of brain injury on MRI and brain lactate concentration; and a persistence of an alkaline brain pHi was associated with cerebral atrophy on MRI. Experimental animal models of hypoxia-ischemia show that NHE inhibitors are neuroprotective. Here, we review the published data on brain pHi in neonatal encephalopathy and the experimental studies of NHE inhibition and neuroprotection following hypoxia-ischemia.

Type: Article
Title: Na(+)/H (+) Exchangers and Intracellular pH in Perinatal Brain Injury.
Open access status: An open access version is available from UCL Discovery
DOI: 10.1007/s12975-013-0322-x
Publisher version: http://dx.doi.org/10.1007/s12975-013-0322-x
Additional information: # The Author(s) 2014. This article is published with open access at Springerlink.com. This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Population Health Sciences > UCL EGA Institute for Womens Health
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Population Health Sciences > UCL EGA Institute for Womens Health > Neonatology
URI: https://discovery.ucl.ac.uk/id/eprint/1422308
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