Acidosis has opposite effects on neuronal survival during hypoxia and reoxygenation.
To study the effect of extracellular acidosis on apoptosis and necrosis during ischemia and reoxygenation, we exposed human post-mitotic NT2-N neurones to oxygen and glucose deprivation (OGD) followed by reoxygenation. In some experiments, pH of the cell medium was lowered to 5.9 during either OGD or reoxygenation or both. Staurosporine, used as a positive control for apoptosis, caused Poly(ADP-ribose)-polymerase (PARP) cleavage and nuclear fragmentation, but no PARP cleavage and little fragmentation were seen after OGD. Low molecular weight DNA fragments were found after staurosporine treatment, but not after OGD. No protective effect of caspase inhibitors was seen after 3 h of OGD and 21 h of reoxygenation, but after 45 h of reoxygenation caspase inhibition induced a modest improvement in 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide (MTT) cleavage. While acidosis during OGD accompanied by neutral medium during reoxygenation protected the neurones (MTT: 228 +/- 117% of neutral medium, p < 0.001), acidosis during reoxygenation only was detrimental (MTT: 38 +/- 25%, p < 0.01). We conclude that apoptotic mechanisms play a minor role after OGD in NT2-N neurones. The effect of acidosis on neuronal survival depends on the timing of acidosis, as acidosis was protective during OGD and detrimental during reoxygenation.
Almaas
Runar
R
Department of Pediatric Research, Rikshospitalet, N-0027 Oslo, Norway. runaralm@start.no
Pytte
Morten
M
Lindstad
Julie K
JK
Wright
Marianne
M
Saugstad
Ola Didrik
OD
Pleasure
David
D
Rootwelt
Terje
T
D000138:Acidosis / Q000139:chemically induced / Q000378:metabolism*; D017209:Apoptosis / Q000502:physiology; D061945:Caspase Inhibitors; D016923:Cell Death / Q000187:drug effects; D015687:Cell Hypoxia / Q000502:physiology*; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology*; D003470:Culture Media / Q000494:pharmacology; D053938:DNA Fragmentation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D005947:Glucose / Q000172:deficiency / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D016202:N-Methylaspartate / Q000494:pharmacology; D009336:Necrosis; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010100:Oxygen / Q000494:pharmacology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology
D061945:Caspase Inhibitors; D003470:Culture Media; D004791:Enzyme Inhibitors; D018690:Excitatory Amino Acid Agonists; D005609:Free Radicals; D016202:N-Methylaspartate; D011065:Poly(ADP-ribose) Polymerases; D019311:Staurosporine; D005947:Glucose; D010100:Oxygen