The Animal Models Of Infectious Brain Edema Induced By Pneumolysin

Background and ObjectiveInfectious brain edema including intracranial infection (purulent meningitis, viral encephalitis, tuberculous meningitis) and extracranial infection (toxic pneumonia, poisoning dysentery, septicemia, etc) induced biain edema, is one common and critically ill of pediatric, bacterial infection is a common cause of it, and G+ bactaria is a common pathogens of central nervous system infections in infants。Streptococus pneumoniae is widely distributed in nature, often dwelling on the normal nasopharyngeal cavity,children's nasopharyngeal carrier rate of up to 24%-32%, is the major pathogen of bacterial pneumonia and meningitis, also is the pathogen have the highest disability and to be died of children meningitis.post-infection showed that sudden onset, associated symptoms are convulsions, high fever and coma etc, have a higher mortality and disability, after the autopsy can be found in brain tissue swelling, congestion, brain weight and volume had increased。PLY is resulting from the collapse of G+, it plays an important role in the infectious brain edema, but the occurrence and development of the exact mechanisms are not yet fully clarified。PLY is an intracellular protein, belongs to thiol activated toxin family, and all streptococcus pneumoniae have it。High concentrations of PLY, can be assembled into oligomers in the membrane, to make transparent membrane pore-forming, causing cell lysis; Low concentrations of PLY, can stimulate cytokine production, ciliated respiratory epithelial cells inhibited the swing, destruction of the upper respiratory tract and alveolar epithelial cells in monolayer, reduce the movement of granulocytes and bactericidal activity, inhibit lymphocyte proliferation and antibody synthesis。Has been found that to contain colonies of streptococus pneumoniae in mice injected with normal saline intra-arterial, used to produce animal model of post-meningitis, can disrupt the connection of BBB。Use purified PLY in vitro experiments can induce microglia and neurons apoptosiso However, scholars at home and abroad more adopt open injury to CNS or cell culture in vitro to establishment the infectious brain edema model, PLY direct-injection experiments with animals approach also have not been reported, therefore, this study will be based on the process of human disease, in an objective way to simulate blood flow in infants and young children through the process of the establishment of cerebral edema animal model of infection.In this experiment, we shall use the major virulence factors of G+ bactaria-PLY injected directly into the arterial blood flow in experimental animals, to reach the brain tissue, which leads to pathological changes, thus be able to more in-depth, comprehensive and objective study of infection in the pathogenesis of brain edema lay the foundation。Material and MethodsProcided by the animal center of zhengzhou university, one hundred and sixty 1-month-old healthy Sprangne-Dawley (SD) rats, weight varied 100～120g, were randomly divided into two groups。PLY group(n= 80), PLY(0.2ml(7μg)) (from Biological Technology Co, Ltd. Shanghai) was injected via carotid for every rat; Control group(NS group, n=80), NS(equal volume with the PLY) was injected each rat by the same methods as PLY group; and sham-operated group 10 ratS。PLY group according to the different observation time points after injection (6h,12h,24h,48h) is further divided into four sub-groups, each sub-group were 10 ratS。The above mentioned sub-group, ten rats injected EB, at different time points for the determination of brain tissue EB。Within 1～2 minutes, injected EB group were given 2%EB via right external jugular vein with 2ml/Kg。Remains to be seen after treatment in each group to the corresponding point in time。At different time points, rats were decapitated to take brain tissue samples。The water content of brain tissue were recorded by measuring both wet and dry weight。By the formamide methods, the EB content of brain tissue was meteraged。The expression of NSE and GFAP protein were investigateed by immunohisto-chemistry technology。Statistical Package for Social Sciences (SPSS), version 16.0, for Windows, was used for Statistical analyses。Results were expressed as mean±standard deviation(SD)。The two-samples t-test for paired sample, was used to assess differences。P values less than 0.05 were considered to be statistically significant。Results1. Histopathologic:In PLY groups, compared with the NS control group, inflammatory cell infiltration, the clearance around vessels became broader, their cubage augmented than before and gliocyte cells became swelled。Nuclear appeared apoptosis among nerve cells and vacuolar degeneration occurred2. Brain EB and BWC content: At 6h of inject PLY, the Brain EB and BWC content of PLY group started to rise, reached peak at 12h, and was still higher than that of control groups at 48h。In PLY groups, The content of twe indexes were significant difference compared with those in corresponding NS sub-group at various time points (P<0.05)。3. Brain EB content, NSE, GFAP protein:In PLY groups,6h after PLY was given, The levels of NSE, GFAP protein in brain started to rise, reaching peak at 24h, maintain higher level at 48h, and still at a high level of expression than 6h。In PLY groups, The content of twe indexes were significant difference compared with those in corresponding NS sub-group at various time points (P<0.05)。4. Relative correlation analysis:PLY group's brain water content NSE protain and BWC, BWC and GFAP protain, EB concent and NSE protain, EB concent and GFAP protain, NSE protain and GFAP protain all appear positive correlation, the r value was 0.607,0.595,0.493,0.532,0.615 and 0.563 (p<0.05)。Conclusion1. After injected PLY via carotid artery to the rat, the brain water content increased, the brain tissue EB content increased, BBB permeability-increasing, the brain NSE protain and the GFAP protain's expression all increased, morphology found in cell toxicity and pathological changes in vasogenic brain edama, means that blood-brain barrier damaged, cerebral edama formationed, degeneration and necrosis of neurons, reactive astrocyts gummosis, shows that the method can be successfully established PLY-induced infectious brain edema model rats。2. In the PLY-induced infectious brain edema model, the brain tissue water and EB content were correlated positively, NSE protein and GFAP protein and BWC content and EB content were correlated positively, it suggested that they were involved in the destruction of BBB, and also may have contributed to the PLY-induced infectious brain edema。...