[Effect of repetitive hypoxia on MMP-2/9 expression and activation in murine brain]

To explore the changes of MMP-2/9 protein expression and excitation in brain of repetitive hypoxic mice.

The biochemistry techniques of SDS-PAGE, Western bolt and Gel Goc Image Analysis System were applied to determine the level of MMP-2 and MMP-9 expression and activation in cortex and hippocampus of mice. The animals were randomly divided into 5 groups: the normal control group (H0), acute hypoxic (H1, hypoxic exposure once), repetitive hypoxic groups (H2-H4, repetitive hypoxia for 2-4 runs respectively).

(1) The MMP- 2 expression level was increased first then decreased in hippocampus and the significant decrease was found in H4 group (P < 0.05, n=6), but no significant changes among the 5 groups in cortex. In addition, no activated form of 66 kD MMP-2 had been detected both in hippocampus and cortex. (2) Along with the development of brain hypoxic preconditioning, the level MMP-9 protein expression also increased first then decreased gradually in hippocampus, and the significant changes were found both in H1 and H4 groups (P < 0.05, n=7 for each group). The same trace of changes was also found in the activation of MMP-9 (include 82 and 78 kD forms) in hippocampus, and the significance both in H1 and H4 (P < 0.05, n=7 for each group) were detected. However, there was not any significant change in the level of MMP-9 protein expression or activation to be found in cortex.

These results suggested that MMP-2 and MMP-9 might play certain role in the development of cerebral hypoxic preconditioning, the different changes of MMP-2/9 protein expression and activation both in cortex and hippocampus might be involved in their selective vulnerability to hypoxia.