Effects of continuous hypoxia on energy metabolism in cultured cerebro-cortical neurons.
Mechanisms underlying hypoxia-induced neuronal adaptation have not been fully elucidated. In the present study we investigated glucose metabolism and the activities of glycolytic and TCA cycle enzymes in cerebro-cortical neurons exposed to hypoxia (3 days in 1% of O2) or normoxia (room air). Hypoxia led to increased activities of LDH (194%), PK (90%), and HK (24%) and decreased activities of CS (15%) and GDH (34%). Neurons were incubated with [1-(13)C]glucose for 45 and 120 min under normoxic or hypoxic (120 min only) conditions and 13C enrichment determined in the medium and cell extract using 1H-{13C}-NMR. In hypoxia-treated neurons [3-(13)C]lactate release into the medium was 428% greater than in normoxia-treated controls (45-min normoxic incubation) and total flux through lactate was increased by 425%. In contrast glucose oxidation was reduced significantly in hypoxia-treated neurons, even when expressed relative to total cellular protein, which correlated with the reduced activities of the measured mitochondrial enzymes. The results suggest that surviving neurons adapt to prolonged hypoxia by up-regulation of glycolysis and down-regulation of oxidative energy metabolism, similar to certain other cell types. The factors leading to adaptation and survival for some neurons but not others remain to be determined.
Malthankar-Phatak
Gauri H
GH
Campus Box 8334, Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy and Biomedical Research Institute, Idaho State University, Pocatello, ID 83209, USA.
Patel
Anant B
AB
Xia
Ying
Y
Hong
Soonsun
S
Chowdhury
Golam M I
GM
Behar
Kevin L
KL
Orina
Isaac A
IA
Lai
James C K
JC
D000818:Animals; D002247:Carbon Isotopes / Q000378:metabolism; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology*; D002540:Cerebral Cortex / Q000166:cytology*; D002950:Citrate (si)-Synthase / Q000378:metabolism; D004622:Embryo, Mammalian; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005947:Glucose / Q000378:metabolism; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D006593:Hexokinase / Q000378:metabolism; D000860:Hypoxia / Q000503:physiopathology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009474:Neurons / Q000502:physiology*; D011247:Pregnancy; D011770:Pyruvate Kinase / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D002247:Carbon Isotopes; D019344:Lactic Acid; D007770:L-Lactate Dehydrogenase; D005969:Glutamate Dehydrogenase; D002950:Citrate (si)-Synthase; D006593:Hexokinase; D011770:Pyruvate Kinase; D005947:Glucose