Enhanced phosphorylation of cyclic AMP response element binding protein in the brain of mice following repetitive hypoxic exposure.

Cerebral ischemic/hypoxic preconditioning (I/HPC) is a phenomenon of endogenous protection that renders the brain tolerant to sustained ischemia/hypoxia. This profound protection induced by I/HPC makes it an attractive target for developing potential clinical therapeutic approaches. However, the molecular mechanism of I/HPC is unclear. Cyclic AMP (cAMP) response element binding protein (CREB), a selective nuclear transcriptional factor, plays a key role in the neuronal functions. Phosphorylation of CREB on Ser-133 may facilitate its transcriptional activity in response to various stresses. In the current study, we observed the changes in CREB phosphorylation (Ser-133) and protein expression in the brain of auto-hypoxia-induced HPC mice by using Western blot analysis. We found that the levels of phosphorylated CREB (Ser-133), but not protein expression of CREB, increased significantly (p<0.05) in the hippocampus and the frontal cortex of mice after repetitive hypoxic exposure (H2-H4, n=6 for each group), when compared to that of the normoxic (H0, n=6) or hypoxic exposure once group (H1, n=6). In addition, a significant enhancement (p<0.05) of CREB phosphorylation (Ser-133) could also be found in the nuclear extracts from the whole hippocampus of hypoxic preconditioned mice (H2-H4, n=6 for each group). These results suggest that the phosphorylation of CREB might be involved in the development of cerebral hypoxic preconditioning.