Effects Of Double Stress Of Ischemic Stroke And Cadmium On The Cerebrum Of Mice

Cadmium is a heavy metal element with high carcinogenicity.Cadmium has a toxic effect on the nervous system in addition to damaging the liver and kidneys of the human body.Stroke is a common vascular disease that causes great damage to the central nervous system.It is unclear whether cadmium toxcity will affect the pathological progression of ischemic tissue.In this study,we plan to explore whether cadmium poisoning will lead to an increase in ischemic damage.Wild type mouse C57BL/6,Thy1-YFP H-line transgenic mouse in which the pyramidal neurons in the fifth layer of the cerebral cortex are labeled with yellow fluorescent protein?YFP?and Cx3Cr1^GFP/+transgenic mouse in which all microglia are labeled with green fluorescent protein?GFP?were used in this study,a cadmium poisoning model was established by intraperitoneal injection of cadmium chloride and a fixed-point photothrombosis stroke model was made by injecting rose bengal dye from the tail vein.There are four different groups in this experiment:Sham group,CdCl₂ group,Stroke group and Stroke+CdCl₂ group.Whether cadmium poisoning will lead to an increase in stroke was investigated through behavioral tests,histochemical staining,immunofluorescence staining,western blotting,and confocal microscopy at the behavioral,tissue,cel ular and molecular levels.The results of the behavioral performance and Fluoro-Jade C staining showed that forelimb grip strength and total distance decreased,respectively,and the density of degenerative neurons in peri-infarct region increased in the Stroke+4 mg/kg CdCl₂group,while there was no significant changes in the Stroke+2 mg/kg CdCl₂ group,compared with the Stroke group.Therefore,4 mg/kg CdCl₂ was selected for further experiments.The result of Nissl staining showed no change in infarct volume in mice of each group.Our data showed that the neurons in the ischemic boundary were damaged more severely,the distribution area of partially damaged neurons in the ischemic boundary was smaller,and the density of survived neurons was lower in the Stroke+CdCl₂ group,compared with the Stroke group.The results of BrdU staining showed that microglial proliferation of the Stroke+CdCl₂ group in the accumulation zone was significantly increased compared with that in the Stroke group.Analysis of phenotype of microglia showed that the density of M1 microglia?iNOS?and M2microglia?Arg1?in the accumulation zone increased significantly in the Stroke+CdCl₂ group compared with the Stroke group.The results of GFAP staining showed that the density of astrocytes in the Stroke+CdCl₂ group had no significant change in the accumulation zone compared with that in the Stroke group.Inflammatory cytokines were analyzed by western blot.Compared with the Stroke group,the expression levels of pro-inflammatory factors?iNOS,IL-1??and anti-inflammatory factors?TGF-?,Arg1?increased significantly in the Stroke+CdCl₂group.The result of this study,suggest that cadmium poisoning will aggravate ischemic damage to a certain extent.This study provides a new theoretical basis for future studies of the susceptibility of heavy metal exposure on neurological diseases such as stroke.