Overexpression of alpha7 nicotinic acetylcholine receptor prevents G1-arrest and DNA fragmentation in PC12 cells after hypoxia.
We investigated the neuroprotective function of alpha7 nicotinic acetylcholine receptor (alpha7nAChR) after transient hypoxia (12 h) and reoxygenation (0-72 h), comparing rat pheochromocytoma (PC12) cells overexpressing FLAG-tagged alpha7nAChR (alpha7pCMV cells) and control PC12 cells (non-transfected or transfected with vector only) in medium with and without nicotine. Plasma membrane degradation in the early phase after hypoxia was inhibited in PC12 cells with nicotine, and more profoundly in alpha7pCMV cells with nicotine. Inhibition of DNA fragmentation in the late phase after hypoxia was most remarkable in alpha7pCMV cells with nicotine, but, surprisingly, it was more remarkable in alpha7pCMV cells without nicotine than in PC12 cells with nicotine. G1-arrest of the cell cycle, observed in control PC12 cells at 12 h after hypoxia, preceding DNA fragmentation, was not evident in alpha7pCMV cells, with or without nicotine. Furthermore, in alpha7pCMV cells with and without nicotine, the basal expression levels of total Akt were approximately 1.5-fold higher, and the up-regulation of Akt phosphorylated at Ser473 after hypoxia was strikingly enhanced, compared with control PC12 cells. These findings suggest that alpha7nAChR functions constitutively in PC12 cells, that its overexpression raises tolerance against G1-arrest and DNA fragmentation after hypoxia, and that it can be considered a candidate target for treatment against hypoxia-induced acute membrane degradation and delayed DNA fragmentation in neurons.
Utsugisawa
Kimiaki
K
Department of Neurology, Iwate Medical University, Uchimaru, Morioka, Japan.
Nagane
Yuriko
Y
Obara
Daiji
D
Tohgi
Hideo
H
D000818:Animals; D002453:Cell Cycle / Q000502:physiology; D015687:Cell Hypoxia / Q000502:physiology*; D019610:Cytoprotection; D053938:DNA Fragmentation / Q000187:drug effects; D016193:G1 Phase / Q000502:physiology*; D015870:Gene Expression; D005822:Genetic Vectors / Q000235:genetics / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D009538:Nicotine / Q000494:pharmacology; D016716:PC12 Cells; D010673:Pheochromocytoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D012333:RNA, Messenger; D051381:Rats; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D014162:Transfection; D015854:Up-Regulation / Q000502:physiology; D064569:alpha7 Nicotinic Acetylcholine Receptor
C579165:Chrna7 protein, rat; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D011978:Receptors, Nicotinic; D011993:Recombinant Fusion Proteins; D064569:alpha7 Nicotinic Acetylcholine Receptor; D009538:Nicotine; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt