细菌脂多糖对不同成熟度新生小鼠脑发育的影响

摘要

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.%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 ELJSA. Two days and seven - day old mice (each for 20) were randomly divided into infection group(infra -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 itnmunohistochemistry 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.