title: Mitochondrial hyperpolarization after transient oxygen-glucose deprivation and subsequent apoptosis in cultured rat hippocampal neurons.
abstract: Mitochondrial membrane potential (MMP) regulates the production of high-energy phosphate and apoptotic cascade, both occurring after ischemic impact. The timed profile of MMP differing from grading ischemic impact has to be determined. Primary rat hippocampal cultures were exposed to oxygen-glucose deprivation (OGD) for 30, 60, and 90 min and then were reoxygenated. MMP was expressed as a voltage-dependent dye, JC-1 fluorescence, under confocal microscopy. Cell viability was assessed by calcein AM and ethidium homodimer, each at 3 hours and 24 hours after 30, 60, and 90 min of OGD. The appearance of apoptosis was also evaluated by the TUNEL method at 24 hours. Hyperpolarization of MMP (2.31+/-0.94 normalized JC-1 fluorescence ratio between red and green) was observed during reoxygenation after 30 min OGD, while 60 min OGD induced depolarization (0.66+/-0.22, Valinomycin (potassium ionophore)-induced depolarization: 0.53+/-0.19). The fluorescence of mitochondria became weak after 90 min OGD. Most of the neurons were shrunken after 90 min and neurons were TUNEL-positive 24 hours after 30 min OGD, although most neurons were viable at 3 hours. A longer period of OGD induced necrosis, and most neurons remained viable after only 3 hours. Our data present that the short (30 min) OGD induced hyperpolarization of MMP during reoxygenation, while a longer OGD (60 or 90 min) induced depolarization and acute necrosis. Neurons were still viable even during hyperpolarization of mitochondria, but this hyperpolarization appears to be linked to subsequent apoptotic change.
authors.affiliation: Department of Anesthesiology, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka City 181-8611, Tokyo, Japan. iijmt@kyorin-u.ac.jp
authors.forename: Takehiko
authors.initials: T
authors.lastname: Iijima
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Mishima
authors.forename: Kimio
authors.initials: K
authors.lastname: Akagawa
authors.forename: Yasuhide
authors.initials: Y
authors.lastname: Iwao
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000941:Antigens / Q000378:metabolism; D017209:Apoptosis; D001562:Benzimidazoles / Q000378:metabolism; D001973:Bromodeoxyuridine / Q000378:metabolism; D039481:CD11b Antigen / Q000378:metabolism; D002232:Carbocyanines / Q000378:metabolism; D016923:Cell Death; D002470:Cell Survival; D002478:Cells, Cultured; D005452:Fluoresceins / Q000378:metabolism; D005699:Galactosylceramides / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005947:Glucose / Q000172:deficiency* / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology*; D006801:Humans; D000860:Hypoxia; D020287:In Situ Nick-End Labeling / Q000379:methods; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008928:Mitochondria / Q000502:physiology*; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D009836:Oligodendroglia / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D051381:Rats; D013997:Time Factors; D014841:von Willebrand Factor / Q000276:immunology
chemical_list: D000941:Antigens; D001562:Benzimidazoles; D039481:CD11b Antigen; D002232:Carbocyanines; D005452:Fluoresceins; D005699:Galactosylceramides; D005904:Glial Fibrillary Acidic Protein; D008869:Microtubule-Associated Proteins; C029417:Von Willebrand antigen; C002454:galactocerebroside; D014841:von Willebrand Factor; C085925:calcein AM; C068624:5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolocarbocyanine; D001973:Bromodeoxyuridine; D005947:Glucose; D010100:Oxygen