前炎症细胞因子对不同年龄小鼠脑室周带神经元存活的影响

THE EFFECT OF PRO-INFLAMMATORY CYTOKINES ON NEURONAL SURVIVAL IN THE PERIVENTRICULAR PARENCHYMA AT DIFFERENT AGED MICE

探讨前炎症细胞因子(PIC)丙种干扰素(IFN-γ)和肿瘤坏死因子(TNF-α)的混合物对不同年龄小鼠脑神经元存活的影响及神经元和神经胶质细胞在对抗炎症反应时的相互关系。采用抗凋亡蛋白Bcl-2免疫组织化学染色以及GFAP/Bcl-2免疫荧光双重标记技术,观察了小鼠单次注射联合细胞因子入侧脑室后,Bcl-2阳性神经元在脑内的分布、神经元Bcl-2的表达和时程变化以及GFAP阳性星形胶质细胞与Bcl-2阳性神经元之间的关系。结果表明,Bcl-2阳性神经元主要分布在第一、二运动皮质第ⅴ层、躯体感觉皮质、隔核、斜角带核、海马和中脑红核等结构。Bcl-2阳性产物位于胞质及突起内,呈棕色,胞核不显色。对照组中Bcl-2阳性神经元在PBS注射2d后,老龄动物脑皮质及海马内Bcl-2表达上调,与青年动物相比有显著性差异(P<0.01)。实验组中细胞因子注射2d后,每个年龄组动物皮质及海马内Bcl-2表达均上调,胞质及突起内Bcl-2阳性产物着色加深,持续到注射后4d,与对照组比较存在显著性差异。与青年组动物比较,老龄动物脑皮质和海马内Bcl-2阳性细胞数目和光密度在PIC注射两天后明显增加,存在显著性差异(P<0.01)。此外,GFAP/Bcl-2染色结果显示皮质、海马和胼胝体内激活的星形胶质细胞表达Bcl-2,部分Bcl-2阳性神经元周围被星形胶质细胞的突起包绕或接触。以上结果提示老龄动物脑的神经元对于炎症刺激的易感性增强。表达Bcl-2的星形胶质细胞可能参与了自身保护机制的调节,且神经元和星形胶质细胞在参与脑内的免疫调节和保护性反应中存在相互作用。

To investigate the effect of proinflammatory cytokine （PIC） on neuronal survival in the pefiventricular parenchyma at different aged mice and the interaction between activated glial cells and neurons after intracerebroventricular （icv） injection of mixed interferon-γ, （IFN-γ） and tumor necrosis factor-α （TNF-α） （recombinant PICs）, Bcl-2 immunohistochemistry and GFAP/Bcl-2 double-labeling immunnfluorescent methods were used to observe the expression of Bcl-2 protein in brain neurons and astrocytes after icv injection of recombinant PICs. It was found that Bcl-2-immunopositive cells were distributed widely in the cortex, diagonal band, hippocampus, septum and red nucleus of the midbrain. Bcl-2 stained neurons were consisted of brownish reaction products localized mostly in the cytoplasm and processes of the neurons. In control group with PBS injection, the density of Bel-2-immunopositive elements was higher in brain neurons of the old mice than that in the younger animals, especially within the hippocampus and cortex. Two days after PICs injections, the density of Bcl-2-positive neurons increased in the cortex and hippocampus beth in the old and young aged groups and began to decrease on the next 4 days later. Compared with the control group, the difference was significant （ P 〈 0.01 ）. Furthermore, PICs induced Bcl-2 expression varied with age, which was more notable in old mice than that in young mice at 2 days after PIC/02 injections. On the other hand, GFAP/ Bcl-2 double staining showed some GFAP-positive astrocytes expressed Bcl-2 and some Bcl-2-positive neurons were also attached or sur-rounded by GFAP-positive processes of the astrocytes. The present results suggest that the old aged brain is more susceptible to inflammatory stimuli than that of young subject. Glial cells with Bcl-2 expression in the cortex, septum, hippocampus and corpus callosum are implicated to interact with neurons in a self-protective response to the inflammatory challenge.