Hippocampal bcl-2 and bax expressions and neuronal apoptosis after moderate hypothermic cardiopulmonary extracorporeal circulation in rats
- VernacularTitle:中度低温体外循环后大鼠海马bcl-2和bax的表达与神经元凋亡
- Author:
Tingjie ZHANG
- Publication Type:Journal Article
- From:
Chinese Journal of Tissue Engineering Research
2005;9(17):212-215
- CountryChina
- Language:Chinese
-
Abstract:
BACKGROUND: Hippocampus injury is wildly believed to involve in neurocognitive dysfunction; the establishment of a rat model of cardiopulmonary bypass(CPB) allows us to investigate the mechanism of CPB-related hippocampus injury.OBJECTIVE: To investigate the effects of moderate hypothermic CPB with a hemodilution on hippocampal bcl-2 and bax gene expression and neuronal apoptosis in rats.DESIGN: A randomized group division study based on the experimental animals.SETTING: Department of anesthesiology in a university hospital.MATERIALS: Thirty Sprague-Dawley (SD) rats were randomly divided into two groups, CPB group and sham-CPB group with 15 rats in each group.METHODS: Total 15 rats of CPB group were subjected to 60-minute moderate hypothermic nonpulsatile CPB using a peristaltic pump and a membrane oxygenator. The CPB circuit was primed with approximately 20 mL 1:1crystaloid-colloid liquid, while another 15 rats of sham-CPB group underwent identical anesthetic and surgical procedures(including cannulation) except CPB itself. At 1 hour post-CPB, six rats in each group were decapitated, and hippocampi were removed, homogenized, and processed for apoptotic gene ( bcl-2 and bax) mRNAs detection. Reverse transcriptase polymerase chain reaction(RT-PCR) is used to detect expression of mRNA by comparing the PCR product of bcl-2 or bax to those of β-actin housekeeping gene. Immunohistochemistry is used to detect bcl-2 and bax protein expressions and terminal deoxynucleiotidyl transferase-mediated dUTP-biotion nick end labeling(TUNEL) staining method was used to detect neuronal apoptosis at 6 hours post-CPB ( n = 6 in each group) . The protein expression was quantitated as percentage of the positively stained area in the total stained. In addition, hippocampal neuronal ultrastructures were studied by electron microscopy at 6 hours post-CPB( n = 3 in each group).ronal apoptosis and ultrastructure changes between the two groups.RESULTS: At 1 hour post-CPB, the expressions of bcl-2 and bax gene, and the ratio of bax to bcl-2 in CPB group were significantly increased compared with those of sham-CPB group( P ＜ 0.05) . At 6 hours post-CPB, the expressions of Bcl-2 and Bax protein in hippocampal CA1 region had significantly increased in CPB group(P ＜ 0.05) . TUNEL staining showed that hippocampal CA1 neuronal apoptosis was significantly increased in CPB group compared with sham-CPB group at 6 hours post-CPB( P ＜ 0. 05).Electron Microscopy demostrated that, at 6 hours post-CPB, neuronal ultrastructures in CPB group had obvious abnormalities, many mitochondria being moderately to severely swollen with vacuolation as well as decreasing number of mitochondrial cristae, some neurons having characteristic morphological changes of earlier periods of apoptosis such as neuronal pycnosis, irregular nucleus, nuclear membrane with notchs, chromatin condensation, and nucleoli movement to the nuclear periphery, etc.CONCLUSION: Moderate hypothermic CPB with a hemodilution can induce hippocampal bax, bcl-2 gene expression and neuronal apoptosis in rats,which maybe partly explain the mechanism of post-CPB neurocognitive dysfunction.
