Cytokine induction in fetal rat brains and brain injury in neonatal rats after maternal lipopolysaccharide administration
Cytokine induction in fetal rat brains and brain injury in neonatal rats after maternal lipopolysaccharide administration
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DOI：
10.1203/00006450-200001000-00013
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发表时间：
2000-01-01
影响因子：
3.6
通讯作者：
Rhodes, PG
中科院分区：
文献类型：
--
作者：
Cai, ZW;Pan, ZL;Rhodes, PG
促炎细胞因子的诱导被认为是产前母体宫内感染与新生儿脑损伤之间的联系。众所周知，细菌感染期间释放的内毒素脂多糖（LPS）会穿过胎盘。通过逆转录酶-聚合酶链反应法测定母体给予LPS后胎鼠脑中细胞因子的诱导。在妊娠 18 天时，将 LPS 混悬于无热原盐水中（腹腔注射）给怀孕大鼠。对照组用无热原盐水治疗。给予LPS 1小时后，胎鼠脑中促炎细胞因子、肿瘤坏死因子-α和IL 1-β mRNA的表达以剂量依赖性方式增加。仅在注射LPS（4mg/kg）后1小时观察到IL-1βmRNA表达的大幅增加，而在LPS注射后4至24小时仍可检测到肿瘤坏死因子-α表达的增加。对妊娠第18、19天连续给予LPS（500μg/kg）或无热原生理盐水的母鼠所生的8日龄幼鼠进行脑损伤检查。LPS组和对照组均未发现明显的坏死组织损伤。对照组大鼠脑内囊和海马伞均清晰地观察到作为髓磷脂标志物的髓磷脂碱性蛋白染色，而LPS处理组大鼠脑内髓磷脂碱性蛋白染色明显较少且较弱。在对照组和 LPS 处理组中均观察到胶质纤维酸性蛋白阳性星形胶质细胞。与对照组相比，LPS治疗组的海马和大脑皮层区域似乎有更多的神经胶质原纤维酸性蛋白阳性星形胶质细胞。免疫印迹数据显示，LPS处理组大鼠大脑皮层或海马中胶质纤维酸性蛋白含量高于对照组。给予母体 LPS 后，8 日龄大鼠大脑中小胶质细胞的 OX-42 阳性染色（3 型补体受体的标记）大大减少。然而，番茄凝集素的组织化学显示，LPS 处理的大鼠脑中变形虫和分枝小胶质细胞的染色与对照组相似。总体结果表明，母体 LPS 给药可诱导胎儿大脑中 IL-1 β 和肿瘤坏死因子 α mRNA 的表达增加。母体 LPS 给药还会增加神经胶质原纤维酸性蛋白阳性星形胶质细胞的数量，减少髓磷脂碱性蛋白的含量，并改变子代大脑中小胶质细胞的免疫反应性。尽管目前的研究结果没有提供直接证据将脂多糖诱导的细胞因子与新生大鼠大脑异常联系起来，但我们的动物模型可能适合探索母体感染对后代大脑神经胶质细胞影响的机制。
Induction of proinflammatory cytokines has been proposed to be a link between prenatal maternal intrauterine infection and neonatal brain damage. It is known that the endotoxin, lipopolysaccharide (LPS), released during bacterial infection crosses the placenta. Cytokine induction in the fetal rat brain after maternal administration of LPS was determined by reverse transcriptase-polymerase chain reaction method. LPS suspension in pyrogen-free saline wits administered (i.p.) to pregnant rats at 18 d of gestation. The control group was treated with pyrogen-free saline. Expression of the proinflammatory cytokines, tumor necrosis factor-alpha and IL 1-beta mRNA, in the fetal rat brain was increased in a dose-dependent manner at 1 h after LPS administration. The great increase in expression of IL-1 beta mRNA was only observed at 1 h after injection of LPS (4 mg/kg), whereas the increased expression of tumor necrosis factor-alpha was still detectable from 4 to 24 h after LPS administration. Brain injuries were examined by immunohistochemistry in 8-d-old rat pups born to the dams that were consecutively treated with LPS (500 mu g/kg) or pyrogen-free saline on gestation d 18 and 19. No apparent necrotic tissue damage was found in either the LPS group or the control group. Myelin basic protein staining, as a marker of myelin, was clearly observed in the internal capsule and the fimbria hippocampus in the rat brain from the control group, Myelin basic protein staining was much less and weaker in the brains of the LPS-treated group. Glial fibrillary acidic protein-positive astrocytes were observed in both the control and the LPS-treated groups. The LPS-treated group appeared to have more glial fibrillary acidic protein-positive astrocytes in the hippocampal and the cortex areas of the brain than the control group. Immunoblotting data showed that glial fibrillary acidic protein content in the cortex or the hippocampus of the LPS-treated rat brain was higher than in the control group. OX-42-positive staining (a marker of the type 3 complement receptors) of microglial cells was greatly reduced in the 8-d-old rat brain after maternal LPS administration. However, histochemistry with tomato lectin showed that staining of both amoeboid and ramified microglial cells in the LPS-treated rat brain was similar to that in the control group. The overall results indicate that maternal LPS administration induces an increased expression of IL-1 beta and tumor necrosis factor-alpha mRNA in the fetal brain. Maternal LPS administration also increases glial fibrillary acidic protein-positive astrocytes, decreases myelin basic protein and alters immunoreactivity of microglia in the brain of offspring. Although results from the current study do not provide direct evidence linking LPS-induced cytokines with the abnormalities in the neonatal rat brain, our animal model may be appropriate for exploring the mechanisms involved in the effects of maternal infection on glial cells in the brains of offspring.