髓样相关蛋白MRP8/14在小鼠肺炎链球菌性脑膜炎脑损伤中的作用

The effects of Myeloid-related protein 8/14 on the brain injury in mice with Streptococcus Pneumoniae meningitis

细菌性脑膜炎是各种细菌侵入中枢神经系统引起的脑实质、脑膜或血管的中枢神经系统感染性疾病,而肺炎链球菌(Streptococcus Pneumoniae,SP)是目前细菌性脑膜炎最常见和最主要的致病菌之一.研究SP性脑膜炎脑损伤的发生发展机制可为寻求该疾病新的治疗手段提供初步的实验和理论依据.通过探讨髓样相关蛋白MRP8/14对小鼠脑组织中IgG,Albumin,NSE,caspase3的影响,探讨MRP8/14在小鼠肺炎链球菌性脑膜炎脑损伤中的作用.将48只1. 5~2个月健康雄性BALB/C小鼠随机分为四组:磷酸缓冲盐溶液对照组(PBS组)、MRP8/14蛋白组(MRP8/14组)、肺炎链球菌组(SP组)、肺炎链球菌+MRP8/14蛋白组(SP+MRP8/14组),每组12只;经侧脑室穿刺分别注入PBS、MRP8/14蛋白、SP混悬液、SP+MRP8/14建立动物模型.注射后6,24,48 h对小鼠进行神经行为学评分和体质量的变化率测定;处死小鼠取脑,记录脑组织含水量变化;观察不同时间点小鼠脑组织中Nissl染色阳性细胞及其数量的改变;制备脑组织匀浆,采用ELISA法测定血脑屏障通透性指标IgG,Albumin水平;采用免疫组织化学方法检测脑组织中脑损伤标志物NSE、凋亡相关蛋白caspase3蛋白的表达.结果显示,侧脑室注射6,24,48 h后,SP组小鼠与PBS组相比神经行为学评分明显降低,脑组织含水量明显增加,Nissl染色阳性神经细胞数量减少,IgG和Albumin浓度明显增加,NSE阳性细胞数明显减少,caspase3表达明显升高;SP+MRP8/14组与SP组相比神经行为学评分降低,脑组织含水量增加,Nissl染色阳性神经细胞数量减少,IgG和Albumin浓度增加,NSE阳性细胞数减少,caspase3表达升高趋势更加明显.因此,在小鼠SP性脑膜炎模型中,髓样相关蛋白MRP8/14加剧了SP性脑膜炎小鼠的临床症状、脑水肿、脑组织神经元丢失及脑损伤.

As a central nervous system infectious disease of the brain parenchyma, meninges, or blood vessels, bacterial meningitis is caused by various bacteria invading the central nervous system. Streptococcus Pneumoniae(SP) is one of the most common and major pathogens of bacterial meningitis. Further research on the mechanisms of the development of brain injury in SP meningitis can provide preliminary experimental and theoretical basis for seeking new treatments for this disease.This study was designed to investigate the effects of MRP8/14 on brain damage caused by pneumococcal meningitis in mice by exploring the effects of MRP8/14 on the expressions of IgG, Albumin, neuron-specific enolase(NSE) and caspase3 in mouse brain tissues. 48 healthy male BALB/C mice(1.5~2 months) were randomly divided into four groups: phosphate buffered saline control group(PBS group),MRP8/14 protein group(MRP8/14 group),Streptococcus Pneumoniae group(SP group) and Streptococcus Pneumoniae+MRP8/14 protein group(SP+MRP8/14 group). PBS, MRP8/14 protein, SP suspension,SP+MRP8/14 were injected into the lateral ventricle to establish SP mice model,respectively. The mice were subjected to measure neurobehavioral scores and body mass reduction rates at 6 h,24 h and 48 h after injection. And at all time points observed,the mice were then sacrificed and the brain water content was recorded. The changes of Nissl staining positive cells and the number in the brain tissue of mice at different time points were observed. The levels of IgG and Albumin were measured by ELISA in brain homogenate. The expression of NSE and caspase3 protein in brain tissues were detected by immunohistochemistry. The results showed that at 6 h, 24 h and 48 h after injection, as compared with PBS group,the neurobehavioral scores of the SP group were significantly lower than that in PBS group,at 6 h,24 h and 48 h after injection. And as compared with PBS group, in mice of SP group, the water content of the brain tissue was significantly increased, and the number of Nissl staining positive neurons was decreased. The concentration of IgG and Albumin was significantly increased. The number of NSE positive cells was significantly decreased, and the expression of caspase3 was significantly increased. SP+MRP8/14 group had lower neurobehavioral scores, increased brain tissue water content,decreased number of Nissl staining positive neurons,decreased number of NSE positive cells,as well as increased IgG and Albumin concentrations, as compared with SP group. In conclusion, in a mouse model of SP meningitis, Myeloid-related protein-8/14 could aggravate the clinical symptoms,brain edema,brain tissue neuron loss and brain damage.