In order to understand dementia and other ailments associated with high altitude hypoxia, adult Sprague Dawley male rats were exposed to simulated conditions of high altitude (7,500 m above sea level, 59 mmHg) for a period of 5 days and analyzed for changes in neuronal proteome by 2-D sodium dodecyl sulfate polyacrylamide gel electrophoresis. Protein extracts obtained from the brain cortex and hippocampus of the hypoxic rats were separated by 2-D gel electrophoresis. Differentially expressed proteins (analysis by 2-D gel analysis software, Bio-2D, Vilber-Lourmat, France and Delta2d, Decodon, Germany) were subjected to matrix-assisted laser desorption/ionization time-of-flight analysis. Among the proteins identified, the spot corresponding to pI 5.4 and molecular weight 21 kDa, identified as phosphatidylethanolamine binding protein (PEBP1), was consistently lowered (54%) in hypoxic cortex samples. PEBP1, also known as Raf kinase inhibitor protein, is a precursor of hippocampus cholinergic neurostimulatory peptide (HCNP). Western blot analysis revealed elevated phospho-extracellular signal-regulated kinase in hypoxic rat cortex samples, indicating activation of Raf/mitogen-activated protein kinase pathway under hypoxia. Lowered HCNP levels leading to 23% decrease in choline acetyltransferase and 63% increase in acetylcholinesterase activity were detected in hypoxic rat brain cortex, while no significant change was noted in hippocampus. Since PEBP1 is lowered in a number of neurological disorders associated with dementia, we speculate that lowered expression of PEBP1 might be responsible for dementia associated with high-altitude hypoxia. Further studies targeting PEBP1 might give clues about signaling pathways associated with hypoxia and dementia.

J. Neurochem. (2011) 118, 176–186. Abstract β‐N‐Oxalyl‐l‐α,β‐diaminopropionic acid (l‐ODAP) an α‐amino‐3‐hydroxy‐5‐ methyl‐4‐isoxazole propionic acid (AMPA) receptor agonist activates protein kinase C in white leghorn chick brain. The current study focuses on the protein kinase C downstream signaling targets associated with l‐ODAP excitotoxicity in SK‐N‐MC human neuroblastoma cells and white leghorn male chick (Gallus domesticus) brain extracts. l‐ODAP treatment in SK‐N‐MC cells (1.5 mM) and chicks (0.5 mg/g body weight) results in a decreased expression and increased phosphorylation of phosphatidylehthanolamine‐binding protein 1 (PEBP1) up to 4 h which however, returns to normal by 8 h. d‐ODAP, the non‐toxic enantiomer however, did not affect PEBP1 levels in either chick brain or SK‐N‐MC cells. Decreased PEBP1 expression correlated with subsequent activation of Raf‐1, MEK and ERK signaling components of the mitogen‐activated protein kinase cascade and nuclear translocation of hypoxia inducible factor‐1α (HIF‐1α) in chick brain nuclear extracts and SK‐N‐MC cells. SK‐N‐MC cells over‐expressing PEBP1 inhibited nuclear translocation of HIF‐1α when treated with l‐ODAP, indicating that down‐regulation of PEBP1 is responsible for HIF‐1α stabilization and nuclear localization. Excitotoxicity of l‐ODAP may thus be the result of phosphorylation and down‐regulation of PEBP1, a crucial signaling protein regulating diverse signaling cascades. l‐ODAP induced convulsions and seizures in chicks could be the result of a hypoxic insult to brain.