Na+/H+ exchanger isoform 1 (NHE1) is the most abundantly expressed isoform in the central nervous system (CNS) and carries H+ extrusion in exchange with Na+ influx (1:1 ratio) in regulation of cellular pH. In the previous funding periods, using in vitro and in vivo cerebral ischemia models, we have established that excessive stimulation of NHE1 activity led to dysregulation of intracellular Na+ and Ca2+ homeostasis in conjunction of reversal activation of Na+/Ca2+ exchange (NCXrev) in neurons and astrocytes. We also discovered novel findings that NHE1 plays a primary role in H+ extrusion and maintaining the optimal pHi for NADPH oxidase (NOX) function during the respiratory burst of the activated microglia. Pharmacological inhibition of NHE1 activity with its potent inhibitor cariporide (HOE 642) or global transgenic knockout protected neurons and astrocytes from ischemic damage in ischemic models. It also abolished production of superoxide (O2-.) and pro-inflammatory cytokines (IL- 1?, TNF?) in the activated microglia. In this renewal proposal, we created Nhe1flox/flox mouse line (Nhe1f/f) with exon 5 of Nhe1 flanked with two flox sites in attempt to selectively ablate NHE1 in neurons, astrocytes, or microglia. Using ischemic stroke model (a transient middle cerebral artery occlusion, tMCAO), we detected neuroprotection and less neurological function deficits in hGfapCreER/+;Nhe1f/f mice treated with tamoxifen. Most importantly, selective knockout of astrocytic Nhe1 in GFAP+ astrocytes prevented reactive astrocyte formation, decreased S100? release, reduced microvessel damage and BBB leakage after ischemia. These novel findings suggest that astrocytic NHE1 protein plays an important role in reactive astrocyte-mediated brain damage. We hypothesize that NHE1 activation in reactive astrocytes not only disrupts astrocytic ionic homeostasis, as we demonstrated previously, but it also alters perivascular astrocytic functions at the blood brain barrier (BBB). n this renewal application, we focus to investigate the possible cellular mechanisms underlying deletion of astrocytic NHE1 protein and its impact on reducing reactive astrogliosis, and BBB damage after ischemic stroke. To date, numerous studies have used GfapCreER/+ approaches to selectively alter astrocytes functions. To our knowledge, GfapCreER/+;Nhe1f/f mouse line is the first to exhibit less reactive astrogliosis in ischemic brains. Better understanding the underlying mechanisms will bring new insights into roles of NHE1 protein in dysregulation and dysfunction of reactive astrocytes in ischemic stroke.

Public Health Relevance

Na+/H+ exchanger isoform 1 (NHE1) is the most abundantly expressed isoform in the central nervous system. This proposal is to study roles of NHE1 in ischemic brain damage. The long-term goal of the research is to understand how ion transport proteins and their kinases contribute to disruption of ionic homeostasis and brain damage following ischemia and to determine whether these proteins are potential targets for developing more effective stroke treatments.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS048216-13
Application #
9420638
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Bosetti, Francesca
Project Start
2005-02-04
Project End
2021-02-28
Budget Start
2018-03-01
Budget End
2019-02-28
Support Year
13
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Pittsburgh
Department
Neurology
Type
Schools of Medicine
DUNS #
004514360
City
Pittsburgh
State
PA
Country
United States
Zip Code
15213
Begum, Gulnaz; Song, Shanshan; Wang, Shaoxia et al. (2018) Selective knockout of astrocytic Na+ /H+ exchanger isoform 1 reduces astrogliosis, BBB damage, infarction, and improves neurological function after ischemic stroke. Glia 66:126-144
Dong, Shuying; Maniar, Shelly; Manole, Mioara D et al. (2018) Cerebral Hypoperfusion and Other Shared Brain Pathologies in Ischemic Stroke and Alzheimer's Disease. Transl Stroke Res 9:238-250
Yin, Yan; Sun, George; Li, Eric et al. (2017) ER stress and impaired autophagy flux in neuronal degeneration and brain injury. Ageing Res Rev 34:3-14
Zhao, Hanshu; Carney, Karen E; Falgoust, Lindsay et al. (2016) Emerging roles of Na?/H? exchangers in epilepsy and developmental brain disorders. Prog Neurobiol 138-140:19-35
Boscia, Francesca; Begum, Gulnaz; Pignataro, Giuseppe et al. (2016) Glial Na(+) -dependent ion transporters in pathophysiological conditions. Glia 64:1677-97
Zhu, Wen; Carney, Karen E; Pigott, Victoria M et al. (2016) Glioma-mediated microglial activation promotes glioma proliferation and migration: roles of Na+/H+ exchanger isoform 1. Carcinogenesis 37:839-851
Chang, He Benny; Gao, Xin; Nepomuceno, Rachel et al. (2015) Na(+)/H(+) exchanger in the regulation of platelet activation and paradoxical effects of cariporide. Exp Neurol 272:11-6
Leng, Tiandong; Shi, Yejie; Xiong, Zhi-Gang et al. (2014) Proton-sensitive cation channels and ion exchangers in ischemic brain injury: new therapeutic targets for stroke? Prog Neurobiol 115:189-209
Cengiz, Pelin; Kintner, Douglas B; Chanana, Vishal et al. (2014) Sustained Na+/H+ exchanger activation promotes gliotransmitter release from reactive hippocampal astrocytes following oxygen-glucose deprivation. PLoS One 9:e84294
Cong, Damin; Zhu, Wen; Shi, Yejie et al. (2014) Upregulation of NHE1 protein expression enables glioblastoma cells to escape TMZ-mediated toxicity via increased H? extrusion, cell migration and survival. Carcinogenesis 35:2014-24

Showing the most recent 10 out of 39 publications