Extracellular acidity and neuronal injury in NT2-N cells induced by oxygen and glucose deprivation

Introduction: We tested the hypothesis that extracellular acidity protects human neuronal cells (NT2-N) from injury induced by oxygen and glucose deprivation. Neuronal protection from acidosis has been studied in numerous in vitro systems, most of which use fetal rat or mouse neurons and not human neurons. Methods: NT2-N cells were cultured. Cells were washed with DMEM with 5.5 mM glucose for control group and 0 mM glucose for experimental groups, 25 mM HEPES, 4 mM glutamine, 100 IU/ml penicillin, 100 μg/ml streptomycin. Wells were divided into 3 main groups: 1) Control: nonnoxia (FiO₂ 0.21) and normoglycemia at 37°C; 2) Anoxia and 0 mM glucose for 6 hours with normoxic normoglycemic recovery; 3) Anoxia and 0 mM glucose for 6 hours with normoxic, normoglycemic recovery and MK801 (NMDA receptor antagonist). The effect of pH on these groups was tested at a pH of 7.4 and a pH of 6.5. Release of the cytoplasmk enzyme lactate dehydrogenase (LDH) was used as a measure of cell viability at 24 hours (LDH supernatant/LDH total × 100). Data were analyzed by ANOVA. Results: %LDH is higher in the oxygen and glucose deprivation groups with and without MK801 (p<0.05) at pH 7.4 and 6.5 compared to control. There is no statistically significant difference between each group at pH 7.4 and pH 6.5. There is no statistically significant difference between the oxygen and glucose deprivation groups with and without MK801 at pH 7.4 and 6.5. Conclusions: Oxygen and glucose deprivations cause a large release of LDH in NT2-N cells. Extracellular acidity does not protect NT2-N cells during anoxia and glucose deprivation. NMDA receptor blockade does not appear to play a role in human neuronal injury induced by oxygen and glucose deprivation.