Effects On ERK Pathway And Apoptosis In The Hippocampal Neurocyte Of Rats Exposed Under Serious Chronic Intermittent Hypoxia

Objective a rat model of serious chronic intermittent hypoxia was established, the changes of ERK pathway and apoptosis in hippocampal neurocyte was observed, and effects of ERK pathway on nervous injury were explored.Method Adult male Wistar rats (n=48) were randomly divided into 5% intermittent hypoxia group (5%CIH group), control group (UC group), According to different time points each group was divided into four sub-groups:respectively 2,4,6,8w. 5%CIH group were given alternating cycle of different nitrogen and compressed air flow rate (each cycle of 120s, so that 5%CIH group inside the minimum oxygen concentration to 5%, and then recovered to 21%, 8h/d); UC group were not given any treatment. Respectively after 2,4,6,8w of intermittent hypoxia,By immunohistochemical method to detect expression of c-fos and ERK1/2 protein in hippocampal neurocyte;By TUNEL method to detect serious chronic intermittent hypoxia induced neuronal apoptosis in hippocampal neurocyte. To analyze c-fos and ERK1/2 protein semi-quantitatively by Motic Medical image analysis system. The results with the 40 millimeter test optical density (IOD) value indicate. Changes of ERK1/2,c-fos protein and apoptotic index at 2,4,6,8w were observed in hippocampal neurocyte.Statistical analysis SPSS13.0 statistical package used for data analysis, the data with mean±standard deviation(xˉ±s). Independent-Sample T test was used to the comparison between groups. One-Way ANOVA was used to the comparison within group, LSD method was used on multiple comparisons, P <0.05 was considered statistically significant. Result1 Effects on ERK1/2 protein in hippocampal neurocyte after serious chronic intermittent hypoxia.1.1 Most of the cytoplasm of positive cells stained in brown or pale yellow was observed under Optical microscope. Rats of each group have positive cells. The degrees of positive cells are different. UC group shows scattered positive cells; 5%CIH group of positive cells were significantly increased, most of positive cells were in CA1 of hippocampus.1.2 In CA1 of hippocampus,expression of ERK1/2 protein in IOD values in CIH 5% Group is more than in UC Group at 2,4,6,8w (P <0.05); Expression of ERK1/2 protein in IOD values in UC Group at different times there was no significant difference in CA1 of hippocampus (P > 0.05); expression of ERK1/2 protein in IOD values in 5%CIH group at different time levels were significantly different in CA1 of hippocampus (P <0.05), as follows: it roses to the peak at 6w and then decreased.2 Effects on c-fos protein in hippocampal neurocyte after serious chronic intermittent hypoxia.2.1 Most of the nuclei of positive cells stained in brown or pale yellow were observed under Optical microscope. Rats of each group have positive cells. The degrees of positive cells are different. UC group shows scattered positive cells; 5%CIH group of positive cells were significantly increased, most of positive cells were in CA1 of hippocampus.2.2 In CA1 of hippocampus,expression of ERK1/2 protein in IOD values in CIH 5% Group is more than in UC Group at 2,4,6,8w (P <0.05); Expression of ERK1/2 protein in IOD values in UC Group at different times there was no significant difference in CA1 of hippocampus (P > 0.05); expression of ERK1/2 protein in IOD values in 5%CIH group at different time levels were significantly different in CA1 of hippocampus (P <0.05), as follows: it roses to the peak at 6w and then decreased.3. Effects on neuronal apoptosis in hippocampal neurocyte after serious chronic intermittent hypoxia. 3.1 Under Optical microscope , apoptotic cells stained in brown or tan color were round or oval nuclei, shape was broken form, which is not regular, size inconsistency, non-apoptotic cell nuclei were stained with hematoxylin blue, nuclei were relatively large, more consistent shape and size. Rats of each group were apoptotic neurons, UC group showed scattered apoptotic cells, Apoptotic cell of 5%CIH group was significantly increased; Apoptotic cells of 5%CIHare widely distributed, mainly in CAl of hippocampus.3.2 In CA1 of hippocampus,apoptotic index in 5%CIH Group is more than in UC Group at 2,4,6,8w (P <0.05); Apoptotic index in UC Group at different times there was no significant difference in CA1 of hippocampus (P > 0.05); Apoptotic index in 5%CIH group at different time levels were significantly different in CA1 of hippocampus (P <0.05), as follows: it roses to the peak at 6w and then decreased.Conclusionl Serious chronic intermittent hypoxia activated ERK pathway and induced apoptosis in hippocampal cells of rats.2 ERK pathway lead to the formation of early brain damage in serious intermittent hypoxia through which mediated apoptosis in hippocampal cells of rats.