p53 mRNA Expression after Hypoxia and Reoxygenation in Hippocampal CA1 and CA3 Regions

Jung, Yong Wook; Kim, Hong Tae; Shin, Dong Hoon; Ahn, Jae Hong; Jeon, Sang Sin; Lee, Il Gi; Ko, Bok Hyun

Abstract

In the present study, we examined the p53 mRNA expression in neuronal cell injury using a hypoxia and reoxygenation model of neuronal toxicity in hippocampal CA1 and CA3 regions. Reoxygenation for 6 hours to 3 days, after an exposure to hypoxic condition for 2 hours, produced a significant increase in p53 mRNA expression both in CA1 and CA3 regions compared to those in the control. In order to determine whether these changes in p53 mRNA expression in CA1 and CA3 have an effect on hypoxia-induced apoptotic or necrotic changes, TUNEL and H & E staining were applied to the hippocampal neurons. Interestingly, the CA1 region only showed most of strong TUNEL positive reaction whereas TUNEL positive reaction was weak in the CA3 region at reoxygenation time points. In addition, one of the particular morphological changes in CA1 neurons is the shrinkage of some neurons although most of neurons showed normal. However, the prominent neuronal changes in the CA3 region was that there were extensive red neurons containing eosinophilic cytoplasm and several dark neurons showing pyknotic nuclei, expanded perineuronal spaces, and cork-screw processes which are considered to typical necrotic degeneration. These results suggest that increased p53 expression might play important roles in hippocampal cell injury and their molecular mechanisms underlying cell injury may strongly depends upon the different properties of each hippocampal regions.