p53-independent transient p21(WAF1/CIP1) mRNA induction in the rat brain following experimental traumatic injury

The expression of the cyclin-dependent kinase inhibitor p21(WAF1/CIP1) mRNA after traumatic brain injury in rats was investigated using an in situ hyb ridization technique, along with regulating gene p53 and stress response ge ne hsp70 mRNA levels. At 3h postinjury, p21(WAF1/CIP1) mRNA was markedly in creased in the cortex, white matter, thalamus, CA2, a part of CA1,3 and den tate gyrus of the injured side. Hybridization signals remained elevated at bh in injured cortex and hippocampus and returned to the baseline by 24h po st-insult. On the other hand, p53 mRNA induction was not observed in any br ain sections throughout the post-injury time course. Slight expression of h sp70 mRNA was detected in the injured cortex 3-6h following injury and this was similar to the temporary pattern of p21(WAF1/CIP1) mRNA expression. Th is study showed p21(WAF1/CIP1) mRNA to be transiently induced after traumat ic brain injury, independent of p53, this possibly being an early stress re sponse to protect cells by arresting them in the cycle and allow DNA repair . NeuroReport 11:2073-2078 (C) 2000 Lippincott Williams & Wilkins.