脑缺血后TLR4作用与小胶质细胞的激活

脑缺血性损伤早期小胶质细胞即被激活。激活的小胶质细胞既有细胞毒性又有神经营养作用。小胶质细胞行使免疫功能的信号转导受体之一是TLR4（toll-like receptor 4）。TLR4在脑内主要表达在小胶质细胞，是一种模式识别受体（pattern recognition receptor，PRR）, 识别一些外源性和内源性的配体。最近的研究表明，TLR4信号通路在脑缺血再灌注损伤中起重要作用。TLR4通过激活小胶质细胞，大量表达炎症因子，加重脑缺血性损伤。     

脑缺血性损伤中灯盏乙素对小胶质细胞介导的神经炎症反应作用的研究进展

<正>脑卒中是严重威胁人类健康的主要疾病之一,其中脑缺血约占80%,具有发病率高、致残率高和病死率高等特点[1]。脑缺血机制复杂,临床表现多样,有关脑缺血的发病机制及其防治一直是基础与临床医学研究的热点,也取得了重要的研究进展。大量研究显示,激活的小胶质细胞介导的炎症反应在中枢神经系统各种神经病理进程中起重要作用。小胶质细胞激活是脑神经病理学改变的重要标志。尽管激活小胶质细胞的物质途径不同,但其激活所致的炎症反应过     

星形胶质细胞在脑缺血诱导的炎症反应中的作用及其机制

脑缺血诱发的炎症反应在急性期可引发脑水肿,挤压缺血灶周围正常脑组织,从而加重神经功能损伤;而在卒中恢复期,对神经组织进行修复具有重要保护作用。近年研究发现星形胶质细胞(Ast)也参与脑缺血后的炎症反应,通过产生抑炎/促炎因子及形成胶质瘢痕/胶质限制对脑组织兼具保护和损伤双重作用,多条信号通路参与这一过程,此外,其与小胶质细胞协同作用也越来越受到重视。靶向调控星形胶质细胞调节脑缺血后炎症反应、促进康复为缺血性卒中治疗和新药研发指明了新的方向。     

小胶质细胞在大鼠暂时性局灶脑缺血再灌注后脑损伤区活化反应的初步研究

目的:探讨暂时性局灶脑缺血后小胶质细胞的反应规律,进一步探讨小胶质细胞在脑缺血损伤中的作用。方法:采用线栓法建立大鼠大脑中动脉阻塞(middle cerebral artery occlusion,MCAO)再灌注模型,应用组织学、免疫组化染色及免疫荧光双标技术,观察大脑中动脉阻塞30 min,再灌注0.5、3、6 h以及1、3、7、14 d和28 d后脑组织的损伤情况,小胶质细胞的形态学和数量变化。结果:组织学观察结果显示:MACO30 min再灌注0.5 h后,梗死区出现神经元肿胀,脑水肿;再灌注3 h和6 h,脑水肿加重,部分神经元出现核固缩,对侧脑组织也出现水肿。脑水肿和神经元固缩在再灌注1 d时最重。再灌注3 d开始,脑水肿程度逐渐减弱,缺血区浸润的小胶质细胞增多。再灌注7 d时,缺血灶小胶质细胞浸润最明显,伴胶质结节形成,再灌注14 d,胶质瘢痕逐渐减小。再灌注28 d,大多数动物梗死区仅存少量小胶质细胞,个别未能修复的坏死灶液化并形成囊腔。免疫组化和免疫荧光双标记结果显示:假手术组小胶质细胞的胞体小,突起细长柔和。脑缺血30 min再灌注0.5 h可见小胶质细胞的体积增大,突起少而短。缺血再灌注6 h,小胶质细胞的胞体增大,突起减少或消失。再灌注1 d和3 d,小胶质细胞的数量明显多于假手术组(P0.05)。再灌注7 d,细胞数量增加达到高峰。再灌注14 d以后,小胶质细胞的数量进一步减少,再灌注28 d后小胶质细胞的数量少于再灌注7 d,但仍多于假手术组和缺血再灌注3 d(P0.05)。结论:暂时性局灶脑缺血能够引起小胶质细胞活化和增生,经历损伤性、反应性、效应性和恢复性变化四个阶段。小胶质细胞在脑缺血损伤组织的清除和损伤修复等方面发挥重要作用。     

长托宁抑制NLRP3炎症小体调节脑缺血再灌注大鼠小胶质细胞极化改善脑损伤

目的 探究长托宁对大鼠脑缺血再灌注致脑损伤的保护作用及可能的机制。方法 30只SD大鼠随机分成假手术组、模型组及长托宁组,每组10只。水迷宫实验检测大鼠认知能力变化;HE染色观察脑组织形态学变化;TUNEL方法检测脑组织神经元细胞凋亡;免疫荧光检测脑组织小胶质细胞极化;ELISA方法检测脑组织炎症因子水平;Western blot检测NLRP3炎症小体相关蛋白表达。结果 长托宁治疗增加脑缺血再灌注损伤大鼠认知能力,改善大鼠脑组织形态,降低脑组织神经元细胞凋亡水平、M2型小胶质细胞比例、IL-1β和IL-18水平及NLRP3、caspase-1和ASC蛋白表达水平,增加脑组织M1型小胶质细胞比例。结论 长托宁减轻大鼠脑缺血再灌注脑损伤,其作用机制可能与抑制NLRP3炎症小体有关。     

利福平通过抑制小胶质细胞活化对大鼠全脑缺血发挥保护作用

目的:探讨利福平对大鼠全脑缺血/再灌注损伤的保护作用及对小胶质活化的影响。方法:采用双侧颈总动脉夹闭合并低血压建立全脑缺血/再灌注大鼠模型,成年雄性SD大鼠42只,随机分成3组,假手术组(S),缺血再灌注组(I/R),利福平干预组(I/R+RFP)。利福平(20 mg/kg)在缺血后30 min腹腔注射。采用Morris水迷宫测定大鼠认知功能改变,HE染色观察海马CA1区病理学变化,免疫组织化学方法检测海马CA1区小胶质细胞活化情况,酶联免疫法(ELISA法)测定各组大鼠海马组织IL-1β、IL-6和TNF-α的表达水平。结果:利福平对大鼠急性全脑缺血/再灌注损伤后的行为学有明显的改善作用,I/R+RFP组大鼠的寻台潜伏期明显缩短,同时,该组大鼠海马神经元损伤数目也显著减少。此外,利福平处理后全脑缺血/再灌注大鼠海马CA1区小胶质细胞活化明显受到抑制,海马组织内IL-1β、IL-6和TNF-α表达显著下调。结论:利福平对全脑缺血/再灌注大鼠脑损伤有明显的保护作用,其机制可能与抑制小胶质细胞活化,减少IL-1β、IL-6和TNF-α等炎症因子的释放,从而抑制炎症反应相关。     

大鼠脑缺血再灌流时神经元损伤与星形胶质细胞的反应

为探讨星形胶质细胞在缺血性神经元损伤中的作用及其与神经元损伤的关系 ,本实验阻塞大鼠大脑中动脉 2 h,再灌流0 .5～ 48h建立短暂局灶性脑缺血模型 ,进行 H-E染色 ;通过胶质原纤维酸性蛋白和细胞核增殖抗原免疫组化单重或双重反应 ,TU NEL和胶质原纤维酸性蛋白免疫组化双重反应观察了神经元和星形胶质细胞的反应。结果表明 :再灌流 2 4h缺血区面积最大 ,再灌流 6h开始出现神经元不可逆变性 ,2 4h梗塞成熟 ;星形胶质细胞表现为反应性、营养不良性和退形变三种不同的形态特点。再灌流 48h时星形胶质细胞数量开始增多。 48h之内星形胶质细胞无增生 ,且有少量星形胶质细胞凋亡。这些结果提示脑缺血时星形胶质细胞反应与神经元损伤密切相关 ,反应性星形胶质细胞是其积极应答神经元损伤的结果 ,在维持神经元存活中起作用。     

小胶质细胞在神经退行性疾病发生发展中的双重作用

小胶细胞是中枢神经系统的主要免疫细胞,当中枢神经系统受到损伤时,就被激活,一方面产生大量致炎性细胞因子和神经元毒性介质,介导脑内慢性炎症反应、细胞凋亡,导致神经元损伤、死亡;另一方面激活的小胶质细胞也发挥吞噬作用和分泌神经生长因子,具有保护中枢神经系统的功能。本文着重阐述小胶质细胞的双重作用,并对目前一些针对小胶细胞治疗作个介绍。     

右美托咪定对大鼠脑缺血再灌注损伤后星形胶质细胞的影响

目的: 通过观察右美托咪定(DEX)对大鼠脑缺血再灌注损伤后星形胶质细胞的影响,探讨DEX对抗脑缺血再灌注损伤的作用及其机制。方法: 采用大脑中动脉栓塞法建立大鼠局灶性脑缺血再灌注模型,将SD大鼠随机分为假手术组、单纯脑缺血再灌注组、DEX预处理1组(缺血前30 min腹腔给予DEX 20 μg/kg)及DEX预处理2组(缺血前30 min腹腔给予DEX 40 μg/kg)。缺血再灌注24 h后,观察大鼠神经功能缺失评分,通过HE染色了解脑梗塞后脑组织的病理学变化,采用免疫组化和蛋白免疫印迹方法观察缺血后脑组织星形胶质细胞的变化。结果: DEX预处理能显著改善大鼠神经功能缺失评分,减小大鼠梗死面积,减少缺血区胶质纤维酸性蛋白(GFAP)阳性星形胶质细胞和肿瘤坏死因子α(TNF-α)阳性星形胶质细胞,降低GFAP表达水平。结论: DEX对缺血再灌注损伤的脑组织具有保护作用,其作用机制可能与抑制星形胶质细胞激活有关。     

NLRP3炎症小体参与脑缺血再灌注损伤的研究进展北大核心CSCD

脑缺血再灌注损伤是指脑组织供血不足,恢复血流灌注后引发缺血组织活性氧(ROS)积累导致的进一步损伤。这一过程引发固有免疫应答并导致炎症级联反应。随着近年对脑缺血再灌注损伤机制的深入研究,Nod样受体蛋白3(NLRP3)作为一种重要的模式识别受体,被发现参与了脑缺血再灌注的炎症损伤过程。而NLRP3炎症小体具有错综复杂的基础机制,尚未完全阐明。本文就NLRP3炎症小体结构、在脑缺血再灌注中的功能及基于NLRP3炎症小体衍生的潜在治疗方法进行综述。     

The anti-inflammatory effects of D-allose contribute to attenuation of cerebral ischemia-reperfusion injury

It has been proved that multiple independently lethal mechanisms are involved in cerebral ischemia-reperfusion injury. Inflammatory processes, mediated by activated leukocytes, have been implicated in the mechanisms of cerebral ischemia-reperfusion injury. In addition, the leukocytes accumulated in the perivascular areas during the inflammatory responses after reperfusion will transform oxygen to reactive free radicals, release cytotoxic products and vasoactive substances, which further promotes brain injury. So activated leukocytes play an important role in the pathophysiologic process of cerebral I/R injury. D-allose, a rare sugar produced from D-ribose, attracts increased attention from researchers in recent years. It has been proved that D-allose can produce inhibitory effects on activated leukocytes in liver, kidney and retina, including immunosuppressive effects, anti-inflammatory effects, as well as anti-oxyradical effects. Furthermore, recent research work of our colleagues has demonstrated that D-allose could attenuate cerebral I/R injury by anti-oxyradical effects. However, inflammatory responses play an important role in the mechanisms of cerebral I/R injury. So we hypothesize that D-allose might perform neuroprotection against cerebral ischemia-reperfusion injury by its anti-inflammatory effects.     

miR-203 protects microglia mediated brain injury by regulating inflammatory responses via feedback to MyD88 in ischemia

Much evidence demonstrates that microglia mediated inflammatory responses play an important role in brain injury in ischemia. miRNA is the important factor in regulation of inflammation. However, the effect of miRNA in microglia mediated inflammatory responses has not been well studied. In the study, we demonstrate that miR-203 negatively regulates ischemia induced microglia activation by targeting MyD88, an important adapter protein involved in most Toll-like receptors (TLRs) and interleukin-1 receptor (IL-1R) pathways. Through negative feedback, enforced expression of miR-203 or MyD88 siRNA silencing inhibits downstream NF-κβ signaling and microglia activation, thereby alleviating neuronal injury. These findings reveal that miR-203 represents a novel target regulating neuroinflammation and brain injury, thus offering a new therapeutical strategy for cerebral hypoxic diseases.     

Effects of monocyte chemoattractant protein 1 on blood-borne cell recruitment after transient focal cerebral ischemia in mice

Monocyte chemoattractant protein 1 (MCP-1) plays an important role in inflammatory reactions following cerebral ischemia. It is known that MCP-1 overexpression leads to increased infarct volume and elevated hematogenous cell recruitment, while MCP-1-deficient mice develop smaller infarcts. It was supposed that MCP-1 dependent macrophage recruitment might be the underlying mechanism of ischemic brain damage but a precise distinction of local microglia and invading macrophages was not performed. In this study we investigated the differential role of MCP-1 on inflammatory cells in MCP-1-deficient mice, using green fluorescent protein (GFP) transgenic bone marrow chimeras. After 30-min of focal cerebral ischemia microglia was rapidly activated and was not different between MCP-1-deficient mice and wild type controls. Activated microglia outnumbered GFP-positive macrophages over the study period. Furthermore, macrophage infiltration was significantly reduced at day 7 in MCP-1-deficient animals (31.2±20.1 cells/mm²) compared to MCP-1 wild type mice (131.5±66.7 cells/mm², P<0.001). Neutrophils were also significantly reduced in MCP-1-deficient mice (62% on day 4% and 87% on day 7; P<0.001). This is the first investigation in cerebral ischemia showing that MCP-1 is necessary for recruiting blood-borne cells to the injury site whereas it does not affect the microglia activation and migration. However, the remarkable predominance of activated microglia and the additional attenuation of invading macrophages suggest that different mechanisms than macrophage recruitment are responsible for the MCP-1-mediated neuroprotective effects after experimental stroke.     

小胶质细胞极化介导炎症反应在脊髓损伤中的作用

背景:小胶质细胞极化参与脊髓损伤后的炎症反应,并在其中发挥关键作用。相关研究表明,有效诱导小胶质细胞从M1促炎表型向M2抗炎表型极化,可以减轻脊髓损伤后的炎症反应,促进组织的修复再生和神经功能的恢复。目的:文章对小胶质细胞的功能和极化、小胶质细胞极化对脊髓损伤的影响及其潜在调控策略以及脊髓损伤后炎症反应进行综述。方法:检索PubMed、Web of Science和中国知网数据库,英文检索词为“microglia,polarization,spinal cord injury,inflammation”,中文检索词为“小胶质细胞、极化、脊髓损伤、炎症”,按纳入和排除标准共纳入80篇文献进行总结。结果与结论:①由小胶质细胞介导的稳定而持续的炎症反应,对脊髓损伤的预后至关重要。②在生理条件下,小胶质细胞处于M0静止表型,但在脊髓损伤后,小胶质细胞活化,进而极化成M1促炎表型,导致神经组织修复能力降低和出现持续性神经炎症。③在脊髓损伤的炎症反应过程中,调控小胶质细胞向M2表型极化或至少向M2表型倾斜,有利于抑制氧化应激反应、调节突触重塑、促进轴突再生和血管生成,是一种有效的调控策略。④截止到目前的研究表明,间充质干细胞、外泌体、临床药物、天然产物、miRNAs和靶点分子可调控小胶质细胞在M1和M2表型之间的转换,这为脊髓损伤后神经组织的修复提供了一种新的思路,未来需进一步研究小胶质细胞在脊髓损伤过程中调控极化的详细机制。     

钆塞酸二钠增强磁共振成像评估小鼠脑缺血再灌注损伤中炎症动态变化

目的：利用钆塞酸二钠增强磁共振成像研究小鼠脑缺血再灌注损伤炎症反应的动态变化。方法：通过封闭缝合线阻断右侧大脑中动脉,建立C57BL/6n小鼠脑缺血再灌注模型。随后,小鼠尾静脉注射钆塞酸二钠,在相应时间点进行磁共振扫描,观察信号变化。此外,免疫组织化学技术用于测量脑组织炎症因子的水平。结果：在大脑中动脉闭塞（MCAO）组和MCAO+钆塞酸二钠组之间,脑组织炎症因子肿瘤坏死因子-α(TNF-α)和白细胞介素1β(IL-1β)水平无显著性差异。在注射钆塞酸二钠的小鼠再灌注后负增强区的最低信号比降低。结论：钆塞酸二钠注射液不影响脑缺血再灌注急性期的炎症反应,钆塞酸二钠增强磁共振成像可作为监测脑缺血再灌注损伤急性期炎症反应的有效手段。     

葛根素对大鼠局灶性脑缺血再灌注损伤后炎症反应的抑制作用

目的： 观察葛根素对大鼠局灶性脑缺血再灌注损伤后炎症反应的抑制作用并探讨其作用机制。方法: 采用大鼠大脑中动脉内栓线阻断法（MCAO）复制大鼠脑缺血再灌注损伤模型，于缺血开始及再灌注即刻由尾静脉注射葛根素18 mg·kg-1，缺血 2 h 再灌注 24 h 后取缺血侧脑组织，HE染色观察海马存活锥体细胞数，比色法测定脑组织MPO活性观察脑组织中性粒细胞浸润程度，Western blotting及RT-PCR法测定脑组织中ICAM-1 蛋白及mRNA表达情况及NF-κB p65亚基核转位情况。结果: 葛根素组缺血侧脑组织海马存活锥体细胞数明显高于缺血再灌注损伤组（P<0.01）， MPO活性明显低于缺血再灌注损伤组（P<0.01），ICAM-1 蛋白及mRNA表达较缺血再灌注损伤组明显减少（P<0.01），NF-κB p65蛋白亚基核转位明显少于缺血再灌注损伤组（P<0.01）。结论: 葛根素可减轻大鼠脑缺血再灌注损伤后炎症反应，这可能是其发挥脑保护作用的机制之一。     

Human bone marrow mesenchymal stem cells-derived exosomes protect against nerve injury via regulating immune microenvironment in neonatal hypoxic-ischemic brain damage model

Neonatal hypoxic-ischemic (HI) brain injury is a serious injury caused by various perinatal factors, which has become a heavy mental burden to the family. The molecular mechanism underlying neonatal hypoxic-ischemic brain injury remains largely unknown. Human bone marrow mesenchymal stem cells (hBMSCs) have caused wide public concern due to the immunomodulatory properties. Exosomes can polarize human microglia and thus changed it into an anti-inflammatory phenotype to reduce the release of pro-inflammatory factors. However, it is unclear whether hBMSCs-exosomes have effect on neonatal hypoxic-ischemic brain injury. In this study, we aimed at investigating the role of hBMSCs-exosomes in regulating immune response and nerve injury in neonatal hypoxic-ischemic brain damage model. In the research, we identified the exosome secretion of hBMSCs could transferred into human microglia (HMC). Moreover, we determined the importance of hBMSCs-exosomes in regulating HMC polarization and inflammatory response. Our research findings might provide a new insight into slowing the disease progression of neonatal hypoxic-ischemic brain injury.     

DDIT4对脑缺血再灌注损伤中自噬的调控作用

正脑卒中(stroke)是危害人类健康与生命的常见病和多发病,是造成我国居民死亡的首位原因~([1]),其中缺血性脑卒中(ischemia stroke)的发病率及致死致残率更是居高不下,约占全部脑血管病的60%~80%~([2])。脑缺血再灌注损伤(cerebral ischemia-reperfusion injury,CIRI)是缺血性脑卒中的重要病理生理     

Inflammation in ischemic brain injury: timing is important

Inflammation is a defense reaction against diverse insults that serves to remove noxious agents and to limit their detrimental effects. There is increasing evidence that post-ischemic inflammation plays an important role in brain ischemia. However, whether inflammatory processes are deleterious or beneficial to recovery is presently a matter of debate and controversy. Experimentally and clinically, stroke is followed by an acute and a prolonged inflammatory response characterized by the production of inflammatory cytokines, leukocyte and monocyte infiltration in the brain, and the activation of resident glial cells. These events may contribute to ischemic brain injury. Several groups report conflicting results regarding the role of inflammation and effects of anti-inflammatory treatments in cerebral ischemia. Experimental studies employing knockout mice for different cytokines and chemokines provide only partial answers. This highlights the importance of clarifying the role of the immune response in pathological changes at the site of ischemic lesions in the brain. Here, we describe dual effects of the brain's inflammatory response and new evidence for a neuroprotective role of proliferating microglial cells in ischemia. In addition, we discuss a potential role of post-ischemic inflammation in brain regeneration and modulation of synaptic plasticity.     

Association of Microglia with Amyloid Plaques in Brains of APP23 Transgenic Mice

Microglia are a key component of the inflammatory response in the brain and are associated with senile plaques in Alzheimer's disease (AD). Although there is evidence that microglial activation is important for the pathogenesis of AD, the role of microglia in cerebral amyloidosis remains obscure. The present study was undertaken to investigate the relationship between beta-amyloid deposition and microglia activation in APP23 transgenic mice which express human mutated amyloid-beta precursor protein (betaPP) under the control of a neuron-specific promoter element. Light microscopic analysis revealed that the majority of the amyloid plaques in neocortex and hippocampus of 14- to 18- month-old APP23 mice are congophilic and associated with clusters of hypertrophic microglia with intensely stained Mac-1- and phosphotyrosine-positive processes. No association of such activated microglia was observed with diffuse plaques. In young APP23 mice, early amyloid deposits were already of dense core nature and were associated with a strong microglial response. Ultrastructurally, bundles of amyloid fibrils, sometimes surrounded by an incomplete membrane, were observed within the microglial cytoplasm. However, microglia with the typical characteristics of phagocytosis were associated more frequently with dystrophic neurites than with amyloid fibrils. Although the present observations cannot unequivocally determine whether microglia are causal, contributory, or consequential to cerebral amyloidosis, our results suggest that microglia are involved in cerebral amyloidosis either by participating in the processing of neuron-derived betaPP into amyloid fibrils and/or by ingesting amyloid fibrils via an uncommon phagocytotic mechanism. In any case, our observations demonstrate that neuron-derived betaPP is sufficient to induce not only amyloid plaque formation but also amyloid-associated microglial activation similar to that reported in AD. Moreover, our results are consistent with the idea that microglia activation may be important for the amyloid-associated neuron loss previously reported in these mice.