电针预处理对肢体缺血再灌注大鼠生存、脑损伤及认知功能的影响

 目的：观察电针（EA）预处理对肢体缺血再灌注（LI/R）大鼠生存情况、脑损伤及认知功能的影响,探讨相关机制。方法：清洁级、健康成年雄性SD大鼠132 只,体重255～300 g,采用随机数字表法,将其随机分为3 组：假手术(sham)组、LI/R组和LI/R+EA预处理 (LI/R+EA) 组。LI/R组采用动脉夹夹闭双后肢股动脉3 h,建立LI/R模型;sham组只暴露股动脉,不夹闭;LI/R+EA组于模型制备前14 d行电针治疗,针刺穴位为“百会”、“足三里”及“血海”。观察各组大鼠7 d生存率;于再灌注48 h,用Morris水迷宫方法测试大鼠认知功能的变化;其余大鼠于再灌注48 h后处死取材,用干湿重法测定脑含水量;免疫组织化学法测定小胶质细胞标志物Iba1;采用Western blotting检测cleaved caspase-3的表达水平;原位末端标记(TUNEL)法检测神经细胞凋亡并计算凋亡指数;光镜下观察海马病理结构变化;化学法测定活性氧（ROS）、丙二醛（MDA）含量及髓过氧化物酶(MPO)、超氧化物歧化酶(SOD)活性。结果：与sham组比较,LI/R组及LI/R+EA组大鼠7 d生存率下降,潜伏期和游泳距离增加,穿越平台次数减少,海马Iba1阳性细胞数增加,cleaved caspase-3蛋白表达量增加,凋亡指数明显增加,神经元减少,ROS、MDA含量及MPO活性增加,SOD活性降低(P<0.05或P<0.01);与LI/R组相比,LI/R+EA组上述指标得到明显改善(P<0.05或P<0.01)。结论：电针预处理能提高LI/R大鼠生存率,减轻脑损伤及改善大鼠认知功能障碍,其机制可能与抑制小胶质细胞激活、减轻氧化应激损伤有关。     

粒细胞集落刺激因子通过调节小胶质细胞活化改善缺氧致脑室周围白质损伤

目的 探讨粒细胞集落刺激因子通过影响小胶质细胞的活化对缺氧导致的脑室周围白质损伤（PWMD）的保护作用。方法 将1d龄新生小鼠108只随机分为对照组、损伤组及治疗组,后两组经缺氧箱缺氧法制备脑室周围白质损伤模型,造模前及造模后2h给予治疗组存活鼠腹腔注射粒细胞集落刺激因子,之后每日1次,1d、3d、7d后各处死3组部分动物。取全脑切片进行免疫荧光双标检测小胶质细胞的募集以及炎性因子的分泌情况;取脑室周围白质,采用酶联免疫吸附剂测定法检测炎性因子分泌水平;利用RT-PCR法检测致炎因子和抑炎因子的分泌以及两类活化小胶质细胞的数量和比例变化情况;治疗组结束给药于7d,分别于5d、8d、10d、12d、30d进行神经行为学实验,观察其感觉运动功能的发育。结果 粒细胞集落刺激因子能够促进小鼠运动功能恢复,改善脑瘫症状,改变活化小胶质细胞中M1型细胞和M2型细胞的数量和比例,使促炎性因子分泌降低,抑炎因子及神经营养因子分泌升高,改善损伤导致的神经发育异常及神经行为缺陷。结论 利用粒细胞集落刺激因子干预脑室周围白质损伤可以抗炎,并可以诱导小胶质细胞向神经保护方向转化,调节炎性因子和神经营养因子的分泌。     

Gene expression changes in aging retinal microglia: relationship to microglial support functions and regulation of activation

Microglia, the resident immune cells of the central nervous system (CNS), are thought to contribute to the pathogenesis of age-related neurodegenerative disorders. It has been hypothesized that microglia undergo age-related changes in gene expression patterns that give rise to pathogenic phenotypes. We compared the gene expression profiles in microglia isolated ex vivo from the retinas of mice ranging from early adulthood to late senescence. We discovered that microglial gene expression demonstrated progressive change with increasing age, and involved genes that regulate microglial supportive functions and immune activation. Molecular pathways involving immune function and regulation, angiogenesis, and neurotrophin signaling demonstrated age-related change. In particular, expression levels of complement genes, C3 and CFB, previously associated with age-related macular degeneration (AMD), increased with aging, suggesting that senescent microglia may contribute to complement dysregulation during disease pathogenesis. Taken together, senescent microglia demonstrate age-related gene expression changes capable of altering their constitutive support functions and regulation of their activation status in ways relating to neuroinflammation and neurodegeneration in the CNS.     

Neuroinflammatory phenotype in early Alzheimer's disease

Alzheimer's disease (AD) involves progressive neurodegeneration in the presence of misfolded proteins and poorly-understood inflammatory changes. However, research has shown that AD is genetically, clinically, and pathologically heterogeneous. In frozen brain samples of frontal cortex (diseased) and cerebellum (nondiseased) from the University of Kentucky Alzheimer's Disease Center autopsy cohort, we performed gene expression analysis for genes categorizing inflammatory states (termed M1 and M2) from early and late stage AD, and age-matched nondemented controls. We performed analysis of the serum samples for a profile of inflammatory proteins and examined the neuropathologic data on these samples. Striking heterogeneity was found in early AD. Specifically, early-stage AD brain samples indicated apparent polarization toward either the M1 or M2 brain inflammatory states when compared with age-matched nondisease control tissue. This polarization was observed in the frontal cortex and not in cerebellar tissue. We were able to detect differences in AD neuropathology, and changes in serum proteins that distinguished the individuals with apparent M1 versus M2 brain inflammatory polarization.     

Peripheral dendritic cells are essential for both the innate and adaptive antiviral immune responses in the central nervous system

Intranasal application of vesicular stomatitis virus (VSV) causes acute infection of the central nervous system (CNS). However, VSV encephalitis is not invariably fatal, suggesting that the CNS may contain a professional antigen-presenting cell (APC) capable of inducing or propagating a protective antiviral immune response. To examine this possibility, we first characterized the cellular elements that infiltrate the brain as well as the activation status of resident microglia in the brains of normal and transgenic mice acutely ablated of peripheral dendritic cells (DCs) in vivo. VSV encephalitis was characterized by a pronounced infiltrate of myeloid cells (CD45^highCD11b⁺) and CD8⁺ T cells containing a subset that was specific for the immunodominant VSV nuclear protein epitope. This T cell response correlated temporally with a rapid and sustained upregulation of MHC class I expression on microglia, whereas class II expression was markedly delayed. Ablation of peripheral DCs profoundly inhibited the inflammatory response as well as infiltration of virus-specific CD8⁺ T cells. Unexpectedly, the VSV-induced interferon-gamma (IFN-γ) response in the CNS remained intact in DC-deficient mice. Thus, both the inflammatory and certain components of the adaptive primary antiviral immune response in the CNS are dependent on peripheral DCs in vivo.     

Factors involved in inflammation-induced developmental white matter damage

Developmental white matter damage is a brain pathology associated with several long-term neurological disorders. An inflammatory insult has been suggested as the major instigating event. This study investigated the relative influence of inflammation, blood–brain barrier permeability and glial ontogeny in white matter damage. Systemic inflammation was induced in Monodelphis domestica (opossum) by serial intraperitoneal injections of lipopolysaccharide at different stages of brain development. Volume of white matter was estimated for the external capsule. Blood–brain barrier permeability was assessed immunocytochemically. Quantitative RT-PCR was used to measure relative levels of mRNA for IL-1β, IL-6 and COX-2. Developmental changes in numbers and appearance of microglia and astrocytes were estimated. Results showed that in response to systemic inflammation, white matter was reduced in the external capsule during a circumscribed period only. At the same developmental stage blood–brain barrier permeability was altered, cerebral inflammatory response was present and numbers of microglia increased. However, the periods of altered blood–brain barrier permeability and the cerebral inflammatory response were longer than the period of the external capsule's susceptibility to white matter damage, which coincided with the developmental increase in the number of astrocytes in this tract. Thus, the mechanism of white matter damage following systemic inflammation is multifactorial, including cerebral inflammation and breakdown of brain barriers occurring simultaneously at specific stages of glial cell development.     

Bone marrow-derived mesenchymal stem cells reduce brain amyloid-β deposition and accelerate the activation of microglia in an acutely induced Alzheimer's disease mouse model

The therapeutic potential of bone marrow-derived mesenchymal stem cells (BM-MSCs) has recently been explored in various pathological conditions of the central nervous system (CNS). However, the application of BM-MSCs in acutely induced Alzheimer's disease (AD) has not yet been reported. Herein the feasibility of using the BM-MSCs, as a therapeutic agent for AD has been tested. To assess this possibility, an acutely induced AD model induced by injecting amyloid-β (Aβ) into the dentate gyrus (DG) of hippocampus of C57BL/6 mice was used. Intracerebral transplantation of BM-MSCs into the brain of an induced AD model reduced their Aβ levels when compared to sham-transplanted animals. The diminution of Aβ deposits was accompanied by the activation of microglia. In addition, the activated microglia was located near the Aβ deposits, and their morphology was changed from ramified to ameboid as a sign of microglial phagocytosis. This study provides evidence that BM-MSCs can promote the reduction of Aβ through the microglial activation in this acutely induced AD brain, suggesting a potential therapeutic agent against AD.     

Regulation of Fcγ receptors and immunoglobulin G-mediated phagocytosis in mouse microglia

As resident macrophages in the CNS, microglia can transform from a surveillance state to an activated phenotype in response to brain injury. During this transition microglia become highly capable phagocytic cells. Invading pathogens undergo opsonization with immunoglobulins and microglia recognize these opsonized pathogens through interaction with their cognate F_c receptors. In mice, both FcγRI and FcγRIIb receptors are involved in IgG-mediated phagocytosis of opsonzied pathogens. At sites of inflammation, microglial activity is regulated by T-cell derived cytokines. Here we first investigated the effects of IFN-γ, IL-4, IL-13 and GM-CSF on expression of FcγRI and FcγRIIb mRNA levels in both primary microglia and microglial cell line N9. Using quantitative real-time PCR we show that IFN-γ induced a 4-fold increase in the mRNA level of FcγRI but did not induce changes in FcγRIIb expression. IL-4 and IL-13 induced approximately 2-fold increases in expression of FcγRIIb mRNA, but had no effect on FcγRI expression. GM-CSF increased both FcγRI and FcγRIIb mRNA expression. We then characterized the ability of these same cytokines to regulate phagocytosis of immune complexes composed of IgG and the bacteria Staphylococcus aureus. IFN-γ and GM-CSF both induced approximately 2-fold increases in IgG-mediated phagocytosis whereas IL-4 and IL-13 both decreased IgG-mediated phagocytosis by about one-third. None of the cytokines influenced basal levels of phagocytosis. These findings demonstrate a highly selective cytokine-induced regulation of both phagocytosis-related Fcγ receptor subtypes and IgG-mediated phagocytosis itself in microglia. This selective regulation has implications for our understanding of the pathophysiology of CNS infection and autoimmune disease.     

活化的小胶质细胞在大鼠海马神经元缺氧损伤中的作用

目的 探讨缺氧诱导活化的小胶质细胞在SD大鼠海马神经元缺氧损害中的作用机制.方法 建立共培养体系,应用原位缺口末端标记(TUNEL)法、化学发光法探讨不同组别神经元生长状况以及Caspase-3活性;采用免疫荧光法、格里斯试剂法(Griess Reagent)、还原WST-1法、酶联免疫吸咐测定(ELISA)等方法检测各组培养液中NO、O-2以及TNF-α的表达水平.结果 缺氧12h, N9细胞培养液可抑制常规培养的神经元生长增殖活力,同时可加重由缺氧抑制的共培养体系中神经元活力;既可诱导常规培养的神经元凋亡,又可促进共缺氧培养的神经元凋亡;较之于单纯神经元培养系和常规共培养系,共缺氧培养系的培养液中NO、O-2、TNF-α 3类应激性神经毒性因子产量最高.结论 小胶质细胞活化在缺氧诱发的神经元损害中发挥了重要的作用,其活化后产生的神经毒性分子是效应分子.     

Expression of the repulsive guidance molecule RGM and its receptor neogenin after spinal cord injury in sea lamprey

The sea lamprey recovers normal-appearing locomotion after spinal cord transection and its spinal axons regenerate selectively in their correct paths. However, among identified reticulospinal neurons some are consistently bad regenerators and only about 50% of severed reticulospinal axons regenerate through the site of injury. We previously suggested (Shifman, M. I., and Selzer, M. E., 2000a. Expression of netrin receptor UNC-5 in lamprey brain; modulation by spinal cord transection. Neurorehabilitation and Neural Repair 14, 49–58; Shifman, M. I., and Selzer, M. E., 2000b. In situ hybridization in wholemounted lamprey spinal cord: localization of netrin mRNA expression. Journal of Neuroscience Methods 104, 19–25) that selective chemorepulsion might explain why some neurons are bad regenerators and others not. To explore the role of additional chemorepulsive axonal guidance molecules during regeneration, we examined the expression of the repulsive guidance molecule (RGM) and its receptor neogenin by in situ hybridization and quantitative PCR. RGM mRNA was expressed in the spinal cord, primarily in neurons of the lateral gray matter and in dorsal cells. Following spinal cord transection, RGM message was downregulated in neurons close (within 10 mm) to the transection at 2 and 4 weeks, although it was upregulated in reactive microglia at 2 weeks post-transection. Neogenin mRNA expression was unchanged in the brainstem after spinal cord transection, and among the identified reticulospinal neurons, was detected only in “bad regenerators”, neurons that are known to regenerate well never expressed neogenin. The downregulation of RGM expression in neurons near the transection may increase the probability that regenerating axons will regenerate through the site of injury and entered caudal spinal cord.