Cerebral lymphatic blockage aggravates apoptosis of hippocampal neurons after subarachnoid hemorrhage in rats

Abstract

Objective To investigate the influence of cerebral lymphatic blockade (CLB) on apoptosis of hippocampal neurons after subarachnoid hemorrhage (SAH) in rats. Methods Healthy adult Wistar rats were randomly assigned to normal control group,SAH group and SAH + CLB group. SAH model was induced by double injection of autologous blood into the cistema magna. On day 3 after second injection, hippocampal cell shape structure of each group were determined by hematoxylin-eosin staining (HE) and propidium iodide (PI) staining. Terminal-deoxynucleotidy transferase mediated nick end labeling (TUNEL) fluorescent was used to determine the situ apoptosis. Immunohistochemistry was conducted to study the expression of caspase-3 and Bcl-2 in hippocampal neurons. Results (1) HE staining and PI staining showed the hippocampal neurons of SAH rats were partly shrink,and nuclei showed wavy or folded seam-like,some crescent-shaped; the hippocampal neurons in SAH + CLB group distributed sparsely,nuclear fragmentation,apoptotic bodies could be seen,surrounded by vacuole formation, Compared with the SAH group, the number of apoptotic cells in SAH + CLB group was significantly increased(the number of apoptotic cells: 0.71 ±0.05,25.36 ±4. 02,37. 82 ±5.93, P<0.01). (2) The fluorescence intensity of positive cells by TUNEL stain in SAH group and SAH + CLB group was higher than in normal control group,while the SAH + CLB group was significantly higher than the SAH group (the fluorescence intensity: 0.19 ±0.03,1.70 ±0.37,2.54±0.53, P<0.01). (3) The fluorescence intensity of caspase-3 in SAH group and SAH + CLB group was higher than the normal control group, while the SAH + CLB group was significantly higher than the SAH group (the fluorescence intensity: 0.14 ±0.03,2.45 ±0.49,2.96 ±0.44, P<0.01). (4) The fluorescence intensity of Bcl-2 in SAH group and SAH + CLB group was higher than the normal control group, while the SAH + CLB group was significantly lower than the SAH group(the fluorescence intensity: 0.58 ±0.08, 3.40 ±0.61,2.67 ±0.44, P<0.01). Conclusion Cerebral lymphatic blockade induce the apoptosis of hipp-ocampal neurons in rats after SAH,which mechanism may be related to high expression of caspase-3 and low ex-pression of Bcl-2. Key words: Cerebral lymphatic drainage; Subarachnoid hemorrhage; Apoptosis; Caspase-3; Bcl-2