细菌脂多糖对不同成熟度新生小鼠脑发育的影响

目的 探讨细菌脂多糖(LPS)对不同成熟度新生小鼠脑发育的影响.方法 2日龄新生小鼠80只随机分成4组,分别腹腔注射不同剂量(0.3 mg·kg-1、0.6 mg·kg-1、0.9 mg·kg-1)的LPS和等容积的9g·L-1盐水,观察给药后小鼠的一般情况；测定给药后脑组织IL-6水平、体质量变化以及相对肝质量；2日龄和7日龄的新生小鼠各20只,不同日龄的新生小鼠随机分成感染组(腹腔注射0.6 ng·kg-1LPS)和对照组(腹腔注射等容积的9g·L-1盐水),连续给药5d,均至12日龄时,灌注取脑,应用免疫组织化学技术检测各组小鼠脑组织碱性髓鞘蛋白(MBP)、神经元特异性烯醇化酶(NSE)、半胱氨酸天冬氨酸蛋白酶3(Caspase-3)的表达情况.结果0.6 mg· kg-1 LPS腹腔注射可导致新生小鼠体质量增长缓慢、肝大、脑组织IL-6水平升高(Pa＜0.05),随着LPS剂量增加,病死率增高,IL-6水平未再升高.2日龄感染组小鼠MBP、NSE表达均明显减少,而Caspase-3的表达明显增多(Pa＜0.05)；7日龄感染组的MBP表达无明显减少(P＞0.05),而NSE的表达明显减少,Caspase-3的表达明显增多(Pa＜0.05).结论 新生小鼠腹腔注射0.6 mg· kg-1 LPS可以模拟临床感染；2日龄新生小鼠感染不仅影响脑白质髓鞘发育,同时也影响灰质神经元；而脑发育相对成熟的7日龄新生小鼠感染主要影响皮质神经元的发育.

Effects of Bacterial Lipopolysaccharide on Brain Development of Neonatal Mice at Different Maturity Levels

Objective To explore the effects of bacterial lipopolysaccharide(LPS) on brain development of neonatal mice at different maturity levels. Methods The newborn mice(n=80) of 2 days were randomly assigned into 4 groups,and were injected either with different doses of LPS(0.3 mg·kg-1,0.6 mg·kg-1,0.9 mg·kg-1) or with equal volume of 9 g·L-1 saline.The mice were sacrificed and the relative liver weight vs the body was calculated,and the level of interleukin-6(IL-6) in the brain was measured by using ELISA.Two days and seven-day old mice(each for 20) were randomly divided into infection group(intra-abdominal injection of LPS)and control group(intra-abdominal injection of equal volume 9 g·L-1 of saline),and each neonatal mouse was injected LPS or 9 g·L-1 of saline for 5 days,and brains were perfused and collected at 12 days.The expression of myelin basic protein(MBP),neuron specific enolase(NSE) and active Caspase-3 in the brain were detected by immunohistochemistry staining. Results The newborn mice were injected with 0.6 mg·kg-1 of LPS showed growth retardation,liver enlargement and increased IL-6 in the brain(Pa<0.05).Mortality increased with the doses of LPS,but not the levels of IL-6.The expression of brain MBP and NSE levels in two-day-old infected mice were reduced significantly,and the expression of Caspase-3 was increased significantly(Pa<0.05).In seven-day-old infected mice,the expression of NSE was reduced significantly,but not the expression of MBP(P>0.05).The expression of Caspase-3 was increased significantly(P<0.05). Conclusions Newborn mice by intraperitoneal injection of 0.6 mg·kg-1 of LPS can mimic clinical chronic infection.Newborn mice with infection at two days after birth induce both white matter and gray matter injury,but not for seven-day-old newborn mice,the injury is only observed in the cortical neurons only.