Late expression of Na+/H+ exchanger 1 (NHE1) and neuroprotective effects of NHE inhibitor in the gerbil hippocampal CA1 region induced by transient ischemia.
Although acidosis may be involved in neuronal death, the participation of Na(+)/H(+) exchanger (NHE) in delayed neuronal death in the hippocampal CA1 region induced by transient forebrain ischemia has not been well established. In the present study, we investigated the chronological alterations of NHE1 in the hippocampal CA1 region using a gerbil model after ischemia/reperfusion. In the sham-operated group, NHE1 immunoreactivity was weakly detected in the CA1 region. Two and 3 days after ischemia/reperfusion, NHE1 immunoreactivity was observed in glial components, not in neurons, in the CA1 region. Four days after ischemia/reperfusion, NHE1 immunoreactivity was markedly increased in CA1 pyramidal neurons as well as glial cells. These glial cells were identified as astrocytes based on double immunofluorescence staining. Western blot analysis also showed that NHE protein level in the CA1 region began to increase 2 days after ischemia/reperfusion. The treatment of 10 mg/kg 5-(N-ethyl-N-isopropyl) amiloride, a NHE inhibitor, significantly reduced the ischemia-induced hyperactivity 1 day after ischemia/reperfusion. In addition, NHE inhibitor potently protected CA1 pyramidal neurons from ischemic damage, and NHE inhibitor attenuated the activation of astrocytes and microglia in the ischemic CA1 region. In addition, NHE inhibitor treatment blocked Na(+)/Ca(2+) exchanger 1 immunoreactivity in the CA1 region after transient forebrain ischemia. These results suggest that NHE1 may play a role in the delayed death, and the treatment with NHE inhibitor protects neurons from ischemic damage.
Hwang
In Koo
IK
Department of Anatomy and Cell Biology, College of Veterinary Medicine and BK21 Program for Veterinary Science, Seoul National University, Seoul 151-742, South Korea.
Yoo
Ki-Yeon
KY
An
Sung-Jin
SJ
Li
Hua
H
Lee
Choong Hyun
CH
Choi
Jung Hoon
JH
Lee
Jae-Yong
JY
Lee
Bong-Hee
BH
Kim
Young-Myeong
YM
Kwon
Young-Guen
YG
Won
Moo-Ho
MH
D000584:Amiloride / Q000031:analogs & derivatives* / Q000627:therapeutic use; D000818:Animals; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D005849:Gerbillinae; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006624:Hippocampus / Q000473:pathology*; D016023:Integrins / Q000378:metabolism; D002546:Ischemic Attack, Transient / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D017966:Pyramidal Cells / Q000187:drug effects* / Q000378:metabolism*; D015424:Reperfusion; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013997:Time Factors
D004791:Enzyme Inhibitors; D005904:Glial Fibrillary Acidic Protein; D016023:Integrins; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; C039614:ethylisopropylamiloride