Preconditioning induces prolonged expression of transcription factors pCREB and NF-κB in the neocortex of rats before and following severe hypobaric hypoxia

Preconditioning using mild repetitive hypobaric hypoxia is known to increase a tolerance of brain neurons to severe hypoxia and other injurious exposures. In the present study, the effects of mild hypoxic preconditioning on the expression of transcription factors NF-kappa B and phosphorylated CREB (pCREB) has been studied in the neocortex of rats exposed to severe hypobaric hypoxia. As revealed by quantitative immunocytochemistry, the injurious severe hypobaric hypoxia (180 Torr, 3 h) remarkably reduced the neocortical levels of pCREB and NF-kappa B. The three-trial hypoxic preconditioning (360 Torr, 2 h, 3 days) induced persistent up-regulation of pCREB and NF-kappa B expression in the neocortex of rats 3-24 h following the severe hypoxia. In addition, the preconditioning alone which was not followed by the severe hypoxia, considerably increased neocortical pCREB and NF-kappa B levels. The findings suggest a role for transcription factors cAMP response element-binding protein and NF-kappa B in the neuroprotective mechanisms activated by the hypoxic preconditioning.