ACETYL-L-CARNITINE (ALCAR) PREVENTS HYPOBARIC HYPOXIA-INDUCED SPATIAL MEMORY IMPAIRMENT THROUGH EXTRACELLULAR RELATED KINASE-MEDIATED NUCLEAR FACTOR ERYTHROID 2-RELATED FACTOR 2 PHOSPHORYLATION

Exposure to hypobaric hypoxia, a condition involving decreased availability of oxygen is known to be associated with oxidative stress, neurodegeneration and memory impairment. The multifactorial response of the brain and the complex signaling pathways involved therewith limits the therapeutic efficacy of several antioxidants in ameliorating hypobaric hypoxia-induced memory impairment. The present study was therefore aimed at investigating the potential of acetyl-L-carnitine (ALCAR), a known antioxidant that has been reported to augment neurotrophin-mediated survival mechanisms, in ameliorating hypoxia-induced neurodegeneration and memory impairment. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key transcription factor involved in the cellular defense mechanism against oxidative stress related to brain injury and neurological disorders. The study was designed to understand the mechanisms involving Nrf2 stabilization following exposure to hypobaric hypoxia. The results displayed reference memory impairment in Sprague-Dawley rats exposed to hypobaric hypoxia (7620 m) for 14 consecutive days which however improved on administration of ALCAR during hypoxic exposure. The study also revealed Nrf2 regulated augmented antioxidant response on administration of ALCAR which was through a novel tyrosine kinase A (TrkA) receptor-mediated mechanism. A decrease in free radical generation, lipid peroxidation and protein oxidation was also observed along with a concomitant increase in thioredoxin and reduced glutathione levels on administration of ALCAR during exposure to hypobaric hypoxia. The present study therefore reveals the therapeutic potential of ALCAR under conditions of hypobaric hypoxia and elucidates a novel mechanism of action of the drug. (C) 2009 IBRO. Published by Elsevier Ltd. All rights reserved.