Dexamethasone Intervened Intrauterine Infection Caused Neonatal Rats White Matter Damage TNF-a And Nogo-A Expression Changes

Objectives: Studyed intrauterine infection caused neonatal rats white matterdamage and speculated it related with tumor necrosis factor-а and neurite outgrowthinhibitor-A; Dexamethasone may reduced the expression of TNF-а、Nogo-A,had hadprotective effect on intrauterine infection caused neonatal rats white matter damage.Methods:1. Establishment of models and grouping:36Sprague-Dawley female rats and12SD male rats,adapt to the environment a week,3:1got in a same cage. Observe thematernal vagina every morning, found vagina vaginal denoted the first day of thepregnancy,unfound vagina vaginal chosen the vaginal swab pictures, microscopeapprea sperm recorded as pregnancy.30pregnancy SD female rats were randomlydivided into normal saline group, LPS group and Dex group,each group10.NS groupintraperitoneal injection normal saline0.35mg/kg.d on gestational day15,16,total2days;LPS group intraperitoneal injection lipopolysccharide0.35mg/kg.d ongestational day15,16,total2days;Dex group lipopolysccharide intraperitonealinjection lipopolysccharide0.35mg/kg.d,1hour later same way inject dexamethasone0.5mg/kg.d on gestational day15,16,total2days.2.Sample collection: removed the pups whose gestation age less than22dayswere preterm pups.After delivering rat, the neonatal rats were sacrificed bydecapitation at postnatal (6h,12h,24h,48h) n=8, and the brains were fixed in10%neutral formaldehyde12h, then conventional dehydration and paraffin-embedded.The brain tissue from each group and each point pathological morphology andstructure were observed by HE staining under optical microscope. Taken out theuterus,distilled water washing fixed in10%neutral formaldehyde12h, thenconventional dehydration and paraffin-embedded.Randomly selected NS,LPS andDex group female rats n=2, executed and picked out placenta and the same wayfixed the placenta. HE stained observed female rats’ uterus and placentapathological morphology,structure and numbers of neutrophilie. 3. Observed projects:Streptavidin-Perosidase immunohistochemistry methodsdetected the expressions of TNF-a and Nogo-A signal protein in newborn rat braintissue from three groups at postnatal (6h,12h,24h,48h).Results:1.The pathological changes of placenta and uterus by HE stained:each grouputerus had trophoblastic cells represented pregnant.NS group: the uterus and placentaoutline were clear,cells arranged in neat rows, microscopic occasionalneutrophils.LPS group: the uterus and placenta were inflammation,contourblurred,blood vessels thickened,the lumen irregular, a large amount of neutrophilicgranulocyte appeared.Dex group: the uterus and placenta contour were normal,showed a small amount of reactive neutrophils.2. The pathological changes of brain tissue by HE stained:NS group: Brain tissuestructure did not change significantly,cells arranged rules,the neuronal cell membraneintegrity, uniform nuclear staining, interstitial in nerve cells were normal, each timepoint was no significant difference.LPS group: cells were weak staining andrarefaction; neuronal cell membrane incomplete visible sunken change, unevennuclear chromatin, nuclear matrix destruction visible nuclear fragmentation andcondensation, interstitial of the nerve cells were edema. Each time showeddifferences.Dex group: brain tissue were mild edema, no tissue was sparse, cellsstained were still clear. Nerve cell membranes complete, occasionally appeareddefects, nuclear visible little fragmentation, no nuclear condensation, the nerve cellshad the interstitia ledema,each point was similar, had no significant difference.3. TNF-а expression: TNF-а expression each point had no significant differencein NS group,LPS group TNF-а expression began to increase at6h,reached peak at12h,after peak maintain at a higher lever,each point had differernce but nostatistically significant.Dex group TNF-а expression lever higher than NS group,each point had no significant difference. Inter-group comparison in the same pointLPS group TNF-а expression lever stronger than NS group（P <0.01）、Dex group（P<0.05）,difference had statistically significant, expression of NS group and Dex groupwere different,but no significant difference（P>0.05）. 4. Nogo-A expression: NS group. Nogo-A expression lever was weakly positive,each time point had no significant difference. LPS group brain tissue Nogo-Aexpression began to increase after birth6h,12h increased rapidly and reached thepeak,24h was still in high lever but decreased,48h slightly decreased. Comparison6h(P <0.01),24h (P <0.01),48h (P <0.01)expression of Nogo-A with12h in LPSgroup,the difference was statistically significant. Dex group Nogo-A expression isweak, no significant difference in the group at each time point.6h,12h,24h LPS groupNogo-A expression higher than NS group（P <0.01）,48h（P <0.05）,,the differencehad statistically significant.Except48h Nogo-A expression LPS group compare withDex group （P <0.05）,but48h（P>0.05）difference was no statistically significant.Nogo-A expression at each point higher than NS（P>0.05）, no statisticallysignificant.Conclusions:1. Female rats’ uterus and placenta were inflammation,focal rarefaction ofcerebral white matter, hippocampus neuronal cell membrane incomplete, nuclearstaining weakly, interstitial of the nerve cells were edemain in neonatal rat brainsafter intraperitonel injection lipopolysccharide,suggest that LPS caused intrauterineinfection and intrauterine infection could lead white matter damage.2. TNF-а expression of neonatal rat brains in LPS group, began to increase at6h,reached peak at12h,after peak maintain at a higher lever,the expression leverstronger than NS group （P <0.01）, speculating intrauterine infection caused whitematter damage associate with the cytokine TNF-а.3. Nogo-A expression of neonatal rat brains in LPS group increase after birth6h,12h increased rapidly and reached the peak,24h was still in high lever butdecreased,48h slightly decreased. Nogo-A expression in LPS group compared withNS group,the differences were statistically significant. Speculating Nogo-A may hascertain relation with intrauterine infection which root in damaged neonatal rat brainand has effect on the process of white matter damage.4. Intrauterine infection pregnant rats intervened to Dex，the uterine and placentacould saw a small amount of neutrophils, no significant inflammation. Neonatal ratbrain tissue showed edema, no obvious loose change, nerve cell appeared no obvious necrotic change, all the histological changes weaker than LPS group.Expression ofTNF-а and Nogo-A,Dex group fewer than LPS group,had differences with NSgroup,but the difference did not had statistically significant（P>0.05）. SpeculateingDex plays an important role in alleviating white matter damage caused by intrauterineinfection.