胚胎期脂多糖暴露可通过钟样受体4引起出生后多巴胺能神经元减少

Toll-like receptor 4 mediating prenatal lipopolysaccharide exposure-induced the loss of dopaminergic neurons in the postnatal brain

目的观察钟样受体4(TLR-4)在胚胎期脂多糖(LPS)暴露引起的出生后个体脑内多巴胺(DA)能神经元减少中的作用。方法 TLR-4突变型C57BL/10ScNCr小鼠和野生型C57BL/10ScSn小鼠各15只,在妊娠期第10.5天给小鼠腹腔注射LPS或肽聚糖(PDG),出生后4月龄时收集大脑组织标本(n=5),通过免疫组织化学染色和体视学技术定量DA能神经元和小胶质细胞数量,高效液相色谱法测定DA及其代谢物水平,免疫荧光法结合流式细胞术测定TNF-α和IL-1β蛋白水平。结果出生前接触过LPS的4月龄C57BL/10ScSn小鼠,与注射生理盐水的对照小鼠比较,黑质DA能神经元减少(25.3±2.1)%,纹状体DA含量降低(33.5±5.0)%,黑质小胶质细胞数量增加(294±24)%,黑质和纹状体TNF-α和IL-1β蛋白水平也明显增高;但是出生前接触过LPS的TLR-4突变型C57BL/10ScNCr小鼠脑内无相应变化。出生前接触过TLR-2配体PDG的4月龄C57BL/10ScNCr和C57BL/10ScSn小鼠均出现脑内DA能神经元减少和免疫炎症改变。结论胚胎期接触LPS可通过TLR-4引起出生后个体脑内DA能神经元减少。

Objective To observe the role of ＇Foil like receptor 4 （TI,R-4） in the ahcrnation of nigral-striatal dopamine system and innate immunity in postnatal brains following prenatal exposure to lipopolysaccharidc （LPS）. Methods A total of 15 timed-pregnant TLR-4 deficient C57BL/lOScNCr mice and 15 wild type （WT） C57BL/10ScSn mice at embryonic day 10.5 （E10. 5） were used in this study. The mouse was injected intraperitoneally with LPS or TLR- 2 ligand peptidoglycan （PDG） or saline. A total of 5 brains with different prenatal exposure and TLR-4 genutyping were harvested at postnatal day of 120. The dopaminergic （DA） neurons and microglial cells were quantified by immunohistochemistry staining and sterology. Striatal DA content and DA metabolites were measured by high performance liquid chromatography （HPLC）. Luminex 100 multiplex cytokine assay was used to determine the protein levels lot the cytokines tumor necrosis factor α （TNF-α） and interleukin 1β （ IL-1β）. Results Compared to the saline control, a prenatal LPS exposure led to a （25.3 ± 2. 1 ） % reduction of DA neurons in the postnatal substantia nigra （ SN ） nf4-month- old C57BL/10ScSn mice, which was associated with reduced striatal DA level （33.5 ± 5.0 ）% and an increase in homovanillic acid to DA ratio. Moreover, the prenatal I,PS exposure resulted in an increase of the total number of microglia （294 ± 24） % and the elevation of TNF-α and IL-1Ψβin striatum and SN. On the contrary, there wcrc no significant changes of SN DA neurons and inflammatory response in postnatal brain of C57BL/10ScNCr mice prenatally exposed to LPS. Prenatal PDG exposure led to similar alternations of nigral-striatal dopamine system and innate immunity in postnatal brains of both C57BL/10ScNCr and C57BL/10ScSn mice. Conclusion These results suggest that TLR-4 mediated prenatal lipopolysaccharide exposure induces the loss of DA neurons in the postnatal brain.