title: Time-dependent activity of Na+/H+ exchanger isoform 1 and homeostasis of intracellular pH in astrocytes exposed to CoCl2 treatment.
abstract: Hypoxia causes injury to the central nervous system during stroke and has significant effects on pH homeostasis. Na+/H+ exchanger isoform 1 (NHE1) is important in the mechanisms of hypoxia and intracellular pH (pHi) homeostasis. As a well-established hypoxia-mimetic agent, CoCl2 stabilizes and increases the expression of hypoxia inducible factor‑1α (HIF-1α), which regulates several genes involved in pH balance, including NHE1. However, it is not fully understood whether NHE1 is activated in astrocytes under CoCl2 treatment. In the current study, pHi and NHE activity were analyzed using the pHi‑sensitive dye BCECF‑AM. Using cariporide (an NHE1‑specific inhibitor) and EIPA (an NHE nonspecific inhibitor), the current study demonstrated that it was NHE1, not the other NHE isoforms, that was important in regulating pHi homeostasis in astrocytes during CoCl2 treatment. Additionally, the present study observed that, during the early period of CoCl2 treatment (the first 2 h), NHE1 activity and pHi dropped immediately, and NHE1 mRNA expression was reduced compared with control levels, whereas expression levels of the NHE1 protein had not yet changed. In the later period of CoCl2 treatment, NHE1 activity and pHi significantly increased compared with the control levels, as did the mRNA and protein expression levels of NHE1. Furthermore, the cell viability and injury of astrocytes was not changed during the initial 8 h of CoCl2 treatment; their deterioration was associated with the higher levels of pHi and NHE1 activity. The current study concluded that NHE1 activity and pHi homeostasis are regulated by CoCl2 treatment in a time-dependent manner in astrocytes, and may be responsible for the changes in cell viability and injury observed under hypoxia-mimetic conditions induced by CoCl2 treatment.
authors.affiliation: Department of Basic Medicine, Nursing College, Zhengzhou University, Zhengzhou, Henan 450052, P.R. China.
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.affiliation: Department of Palliative and Hospice Care, The Ninth People's Hospital of Zhengzhou, Zhengzhou, Henan 450053, P.R. China.
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Basic Medicine, Nursing College, Zhengzhou University, Zhengzhou, Henan 450052, P.R. China.
authors.forename: Zhenxiang
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Clinical Pharmacology Base, Department of Infectious Disease, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 450052, P.R. China.
authors.forename: Quancheng
authors.initials: Q
authors.lastname: Kan
authors.affiliation: Department of Neuroimmunology, Henan Academy of Medical and Pharmaceutical Sciences, Zhengzhou University, Zhengzhou, Henan 450052, P.R. China.
authors.forename: Feng
authors.initials: F
authors.lastname: Gao
authors.affiliation: Department of Basic Medicine, Nursing College, Zhengzhou University, Zhengzhou, Henan 450052, P.R. China.
authors.forename: Suyan
authors.initials: S
authors.lastname: Chen
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000096:biosynthesis*; D015687:Cell Hypoxia / Q000187:drug effects; D002460:Cell Line; D003035:Cobalt / Q000633:toxicity*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006706:Homeostasis / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D051379:Mice; D008807:Mice, Inbred BALB C; D020033:Protein Isoforms / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000096:biosynthesis*
chemical_list: D027682:Cation Transport Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; C490997:Slc9a1 protein, mouse; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D003035:Cobalt; C018021:cobaltous chloride