Effect Of NGF On Fas And FasL In Brain Tissue After Hypoxic-ischemic Brain Damage In Neonatal Rats

Objective:Neonatal hypoxic-ischemic encephalopathy (HIE) is a common neonatal disease. It can cause neonatal death and permanent nervous system injury later in childhood. There is no effective therapeutic method in clinic at present. Our study established hypoxic-ischemic brain damage (HIBD) model and gave nerve growth factor (NGF) treatment to observe the expression of Fas and FasL in brain tissue, to probe into that one of mechanisms of NGF's brain protective function is to reduce Fas and the FasL expression.Methods:A total of 120 seven-day Wistar rats were randomly divided into three groups (n=40): group A (sham operation control group), group B (HIBD group), group C (HIBD+NGF treatment group). Then each group were divided into five sub-groups (eight cases each) based on different time points after HIBD (6 hours,12 hours,24 hours,48 hours,72 hours), HIBD rat model were established, Rats of group C were given NGF treatment (50μg/kg/d, coeliac) right after HIBD for three days. Animals were executed at different time points, expressions of Fas and FasL in brain tissue of all rats were detected with immunohistochemistry.Results:(1) Neonatal rats had various abnormal behaviors after HIBD. (2) Various morphologic abnormality of brain tissue of rats in HIBD model group at different time points had been observed. However, there were no obvious morphology changes of brain tissue of rats in NGF treatment group. (3) HE staining:Cellular layer was distinct and cellular morphology was normal in sham operation group rats. Different degrees of cellular swelling and degeneration were found at 6h,12h after HIBD in HIBD model group rats. Cellular necrosis became apparent at 24h,48h:cellular nuclear fragmentation, solution, cellular necrosis was more significant at 72h, and gliocyte proliferation were observed. Karyopyknosis and nuclear fragmentation could be observed in the center of focus. In NGF treatment group rats, pathological changes of brain tissue lessened significantly compared with HIBD model group, and cell arranged regularly.(4) Expressions of Fas and FasL:Both Fas and FasL positive staining showed buffy fine grain deposition, positive cells were found in cerebral cortex and hippocampus, and positive staining was mainly in cytoplasm of nerve cell. There were no obvious Fas and FasL positive cells in brain tissue in sham operation group at each time point. Fas and FasL positive cells increased gradually in brain tissue in HIBD model group after HIBD, the peak time of positive expression was 24-48h after HIBD. Afterward positive expressions decreased gradually. There were statistical significant differences in terms of Fas and FasL positive expressions at different time points in HIBD model group rats (P<0.01), and the expressions between Fas and FasL (P<0.01). Fas and FasL positive cells were obvious in brain tissue in NGF treatment group at each time point. And expressions of Fas and FasL positive cells were decreased significantly compared with HIBD model group rats respectively at the each time point (P<0.01).Conclusions:(1) NGF treatment after HIBD in neonatal rats can reduce pathological changes of brain tissue. (2) Expressions of Fas and FasL increased in brain tissue of neonatal rats after HIBD, which suggests the two factors has some effect in the morning apoptosis period of HIBD. (3) NGF treatment can decrease expressions of Fas and FasL in brain tissue of neonatal rats after HIBD, alleviate pathological injury in the course of HIBD, inhibited neuronal apoptosis, provided a protective effect of hypoxia-ischemia-induced neuronal injury.