Abstract
We measured the expression of cell cycle proteins (CyclinD 1, Cdk 2, Cdk 4, Cdk 6, PCNA) and proteins associated with DNA damage and repair (M30, P21, P53, Bcl-2) by immunohistochemistry after induction of cortical cold injury in the rat brain (n=28) and evaluated the relationship between cell cycle protein expression and apoptosis. Measurements were taken at 1, 4, 7, 10 and 14 days (n=4 per time point) . Sham-operated rats (n=4) and normal rats, which were not subjected to any surgical procedure (n=4), were used as controls for temporal profile determination. On day 4, Cdk 2, Cdk 4 and CyclinD1, which are key G1-S regulators, were strongly expressed in the injured rat brains. At day 7, expression of all these proteins had spread to contralateral non-injured brain, then had decreased by day 10, and was no longer detectable by day 14. At day 7, M30, P21, P53, Cdk4, and CyclinD1 were detected in the same region of the superficial cortex, suggesting that expression of Cdk 4 and CyclinD1 may play a role in apoptosis. The fact that expression of Cdk 4 and PCNA was detected in periventricular areas, where M30 was not expressed, suggests that Cdk 4 may play an important role in DNA repair in this area. We concluded that apoptosis and DNA repair might occur in different areas following cold injury in the rat brain.
