| Objective: To establish the intrauterine infection model of rat through intraperitonealinjection with bacterial lipopolysaccharide to pregnant rats, investigate the effects andmechanisms of melatonin (MT) on ability of anti-injury of fetal brain induced byintrauterine infection of the fetal rat brain damage caused by bacterial lipopolysaccharide,for the further study of the clinical application of MT in a obstetric experimental basis.Methods: The19th days of pregnant Sprague-Dawley rats were randomly dividedinto three groups:the blank control group, the intrauterine infection group(LPS group) andthe melatonin group (MT group). To establish the models, fetal rat brain damage made bylipopolysaccharide (LPS) induced intrauterine infection. In LPS group, the pregnant ratsreceived an intraperitoneal injection of LPS (500μg/kg). In MT group, the rats weretreated with LPS500μg/kg and MT10mg/kg simultaneously. Then, according thedifferent observation time after injection, the pregnant rats were divided into six timepoints (n=4) respectively:1h,6h,12h,24h,48h,72h. Pregnant rats were sacrificed at theappropriate point quickly by caesarean section on the ice box, and remove the fetal ratbrain and placental tissues.Detected the activities of Glutathione peroxidase (GSH-Px) infetal brain homogenates and the levels of iNOS mRNA expression in fetal rat brain tissueby Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) and to compare thedifferences between the groups,Meanwhile, the pathological changes of placenta and braintissues were observed under light microscope by HE staining, in addition, also detectedbrain cell-apoptotic protein Bax by immunohistochemical method and to compare thedifferences between these groups. Results:1. The intrauterine infection models of rat were constructed successfully, there werehistopathological inflammation changes in placenta and fetal brain tissues which wereobserved under light microscope by HE staining in the intrauterine infection group.Wefound that the infiltration of neutrophils in intrauterine infection placental，light staining offetal rat cerebral cortex, the loose structure was like sieve, and nerve fibers were disorder,uneven thickness,2. Compared the intrauterine infection group and the control group with the infectiontime extention, GSH-Px activity in the brains of fetal rats gradually decreased with theinfection time, reached the lowest point after72hours, the content of iNOSmRNA firstincreased and then decreased, brain tissue iNOSmRNA content began to rise at1hour,6hours increased significantly and up to peak in12hours. There were significantly higherthan the control group each time period (P<0.001); apoptotic protein Bax were obviouslyincreased in brain cells6hours, and24huors reached the peak, then decreased gradually,still higher than the control group in72huous.With the extension of infection time, therewere significantly changes (P<0.05).3. MT had improved the GSH-Px activities of fetal brain tissues, meanwhile, reduceedthe level of iNOS mRNA, meanwhile, reduceed the number of apoptotic protein cells offetal brains and there were significant differences (P<0.05).Conclusions:1. Our study demonstrated that pregnant mice by intraperitoneal injection of LPS leadto fetal rat brain damage, which demonstrated that intrauterine infection was an importantfactor in fetal brain injury.2. There was free radical damage, lipid peroxidation, more apoptotic brain cells infetal rat brains due to intrauterine infection; With the extension of infection time the fetalbrain damage increaseed progressively.3. Intrauterine infections not only cause necrosis of brain cells, but also causesecondary brain cell apoptosis, intrauterine infections induced apoptosis of brain cells isrelevant to the increasing apoptotic protein Bax.4. MT had antagonistic effects on oxidative damage of fetal brain, and also inhibited intrauterine infection-induced apoptosis proteins of brain cells, which indicating that MTprotested the fetal brain damage suffered from intrauterine infection through antioxidantand anti-apoptotic. |
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