小胶质细胞内与神经炎症相关的信号通路

小胶质细胞遍布整个中枢系统,是中枢神经系统的免疫效应细胞,小胶质细胞及其介导的神经炎症在中枢神经系统损伤及疾病处理过程中起着非常重要的作用。本文从NF-κB信号通路、Toll样受体信号通路、MAPK信号通路、JAKSTAT信号通路、PPAR信号通路、Notch信号通路几个方面介绍小胶质细胞内与炎症相关的信号通路。     

S100A9通过增加小鼠星形胶质细胞的谷氨酸分泌促进神经元损伤

目的:研究钙防卫蛋白S100A9刺激体外星形胶质细胞后细胞外谷氨酸浓度变化及其对神经元影响和调控机制。方法:分离培养新生C57BL/6小鼠大脑皮层星形胶质细胞和神经元；Amplite荧光法检测星形胶质细胞培养上清谷氨酸浓度；Real time RT-PCR和Western Blot分别检测星形胶质细胞谷氨酸转运体(GLT-1) mRNA和蛋白表达；Fluo-4荧光探针法检测星形胶质细胞胞内Ca²⁺浓度；转录组测序并结合KEGG分析筛选星形胶质细胞谷氨酸浓度变化的调控机制；S100A9刺激星形胶质细胞的培养上清(CS)干预神经元后，末端脱氧核苷酸转移酶标记法(TUNEL)检测神经元凋亡，CCK-8试剂盒检测神经元存活。结果:S100A9刺激星形胶质细胞后细胞外谷氨酸浓度增加，GLT-1 mRNA和蛋白表达减少，细胞内Ca²⁺浓度增加。差异表达基因KEGG富集在核因子-κB(NF-κB)信号通路、toll样受体(TLRs)信号通路和肿瘤坏死因子(TNF)信号通路等。培养上清组神经元凋亡率高于对照组。结论:S100A9可能通过激活TLR4/NF-κ...     

抑制水通道蛋白4可降低脊髓后角胶质细胞细胞外调节蛋白激酶信号的活化改善坐骨神经损伤导致的神经病理性疼痛

目的 探讨腰椎间盘突出引起的坐骨神经痛中,抑制水通道蛋白4（AQP4）对脊髓胶质细胞以及丝裂原活化蛋白激酶（MAPK）信号通路活化的影响。 方法 取8周龄雄性SD大鼠90只,分为假手术组18只,坐骨神经慢性压迫损伤(CCI)+DMSO组36只, CCI+TGN-020组（AQP4抑制剂）36只。CCI模型应用动物行为学,Western blotting方法,免疫荧光（双重染色）等方法检测。 结果 Western blotting显示,细胞外调节蛋白激酶（ERK）、c-Jun氨基末端激酶（JNK）、 p38MAPK信号通路及星形胶质细胞在神经损伤之后活化;免疫荧光在AQP4的表达被TGN-020抑制之后,胶质细胞及ERK、JNK、p38MAPK信号通路的活化被削弱,p-ERK和胶质纤维酸性蛋白（GFAP）共定位的细胞数量在损伤后明显增多,而TGN-020可减少之。 结论 抑制AQP4可抑制坐骨神经损伤引发的脊髓后角星形胶质细胞活化及MAPK信号通路活化,且可以通过抑制脊髓后角ERK通路的活化来抑制星形胶质细胞的活化,从而改善坐骨神经损伤所致神经病理性疼痛。     

细胞周期蛋白依赖性激酶PFTK1在少突胶质前体细胞分化中的潜在作用

背景:少突胶质细胞主要来自少突胶质前体细胞,该分化过程被多种因子严格调控。一些细胞周期蛋白依赖性激酶可以调控少突胶质前体细胞分化的早期阶段,对少突胶质细胞形成具有重要意义。目的:分析细胞周期蛋白依赖性激酶PFTK1在少突胶质前体细胞分化中的潜在作用及相应机制。方法:利用siRNA技术和Western印迹实验来检测OLN-93细胞分化的相关分子标志物及相应信号通路的活化情况。结果与结论:撤去血清后,少突胶质前体细胞系OLN-93细胞可进行自发分化。形态观察表明,用siRNA技术沉默PFTK1基因表达后,OLN-93细胞的分化得以明显加快。Western印迹实验显示PFTK1基因沉默后,OLN-93分化的相关分子标志物环核苷酸磷酸二酯酶和髓鞘少突胶质细胞糖蛋白的诱导出现显著增加。对PFTK1相关信号通路的研究则发现,PFRK1基因的沉默表达可诱发PI3K/AKT信号通路的活化。而对PI3K/AKT信号通路的特异性抑制可抵消PFTK1沉默对OLN-93细胞分化的促进效果。实验结果首次发现细胞周期蛋白依赖性激酶PFTK1可通过PI3K/AKT信号通路抑制少突胶质前体细胞的分化,为脱髓鞘引起的神经退化性疾病的治疗提供了重要的理论参考。     

脊髓损伤后微环境改变与炎症通路研究进展

创伤性脊髓损伤导致轴索变性,神经元、少突胶质细胞死亡,胶质疤痕产生,最终影响神经功能的恢复。脊髓损伤后,中性粒细胞、巨噬细胞、T细胞等共同介导炎症反应,各细胞在不同时段发挥不同的作用。NF-κB通路是介导脊髓损伤后炎症反应的核心,IKKβ在整个激活过程当中起到主要的作用,损伤早期高表达;丝裂原活化蛋白激酶是信号从细胞表面传导到细胞核内部的重要传递者,通过依次磷酸化将上游信号传递至下游应答分子共同调节着细胞的生长、分化、对环境的应激适应、炎症反应等多种重要的细胞生理/病理过程。JAK/STAT是细胞内信号传导通路,与SCI后星形胶质细胞的分化及炎性胶质瘢痕的形成相关;Wnt/β-cantenin经典通路与炎症反应密切相关,且与细胞治疗抑制SCI炎症反应相关。     

大鼠C6脑胶质瘤模型的基因表达谱分析

目的:筛选和分析大鼠胶质瘤模型与正常星型胶质细胞中的差异表达基因。方法:构建大鼠C6颅内胶质瘤模型,利用Illumina Hi Seq 4000技术对大鼠胶质瘤模型的胶质细胞和正常星形胶质细胞进行转录组测序并对测序结果进行功能注释。以q值0. 05为标准筛选差异表达基因,并通过GO和KEGG数据库分析其功能和参与的信号通路。结果:较之正常星形胶质细胞,大鼠胶质瘤模型组细胞共筛选得到9221个差异表达基因,其中4604个基因表达上调,4617个基因表达下调; GO富集结果表明:这些差异表达基因共映射到575个GO term,与各类结合相关的分子如蛋白结合、离子结合、小分子结合、核苷酸结合等功能富集显著; KEGG富集结果表明:差异表达基因共参与22条通路,富集最多的是癌症发生通路、MAPK通路、胞吞通路和黏着斑通路。结论:成功获取大鼠胶质瘤模型细胞与正常胶质细胞的基因表达谱,差异表达基因富集在癌症发生通路、MAPK通路、胞吞作用通路和黏着斑等生物学通路,这些信号通路可能在胶质瘤发生发展过程中发挥重要作用,对其进一步分析将为临床治疗胶质瘤提供新的靶点。     

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。     

褪黑素对AD模型小鼠脑内小胶质细胞的影响

目的探讨褪黑素对APP/PS1转基因AD模型小鼠脑内小胶质细胞和炎症细胞因子COX-2的抑制效应。方法 AD转基因小鼠随机分为褪黑素处理组和对照组。14 d后,取海马通过免疫荧光化学染色检测小胶质细胞、老年斑位置情况;Western blot、ELISA方法分别检测CD11b、COX-2的变化;Western blot检测炎症信号通路TLR/NF-κB的变化。结果免疫荧光化学显示,老年斑周围有大量活化的小胶质细胞聚集;Western blot、ELISA结果显示褪黑素组小鼠脑内CD11b、COX-2表达显著减少;褪黑素组小鼠TLR/NF-κB炎症信号通路的TLR2、NF-κB-p65表达减少。结论褪黑素可能通过抑制TLR/NF-κB炎症信号通路来抑制小胶质细胞活化并抑制炎症细胞因子COX-2的分泌。     

The different mechanisms of peripheral and central TLR4 on chronic postsurgical pain in rats

Chronic postsurgical pain (CPSP) is a common complication after surgery; however, the underlying mechanisms of CPSP are poorly understood. As one of the most important inflammatory pathways, the Toll-like receptor 4/nuclear factor-kappa B (TLR4/NF-κB) signaling pathway plays an important role in chronic pain. However, the precise role of the TLR4/NF-κB signaling pathway in CPSP remains unclear. In the present study, we established a rat model of CPSP induced by skin/muscle incision and retraction (SMIR) and verified the effects and mechanisms of central and peripheral TLR4 and NF-κB on hyperalgesia in SMIR rats. The results showed that TLR4 expression was increased in both the spinal dorsal horn and dorsal root ganglia (DRGs) of SMIR rats. However, the TLR4 expression pattern in the spinal cord was different from that in DRGs. In the spinal cord, TLR4 was expressed in both neurons and microglia, whereas it was expressed in neurons but not in satellite glial cells in DRGs. Further results demonstrate that the central and peripheral TLR4/NF-κB signaling pathway is involved in the SMIR-induced CPSP by different mechanisms. In the peripheral nervous system, we revealed that the TLR4/NF-κB signaling pathway induced upregulation of voltage-gated sodium channel 1.7 (Nav1.7) in DRGs, triggering peripheral hyperalgesia in SMIR-induced CPSP. In the central nervous system, the TLR4/NF-κB signaling pathway participated in SMIR-induced CPSP by activating microglia in the spinal cord. Ultimately, our findings demonstrated that activation of the peripheral and central TLR4/NF-κB signaling pathway involved in the development of SMIR-induced CPSP.     

CD40-CD40L interactions induce chemokine expression by human microglia: implications for human immunodeficiency virus encephalitis and multiple sclerosis

CD40 is a protein on microglia that is up-regulated with interferon (IFN)-gamma and is engaged by CD40L, found on CD4+ T cells, B cells, and monocytes. These interactions may be important in central nervous system inflammatory diseases. Microglia have been shown to be a source of chemokines, whose expression plays a key role in central nervous system pathologies. We examined the expression of CD40 on microglia in human immunodeficiency virus (HIV) encephalitic brain, and the effects of CD40-CD40L interactions on the expression of chemokines by cultured microglia. We found significantly increased numbers of CD40-positive microglia in HIV-infected brain tissue. Treatment of cultured microglia with IFN-gamma and CD40L increased expression of several chemokines. IFN-gamma- and CD40L-induced MCP-1 protein was mediated by activation of the ERK1/2 MAPK pathway, and Western blot analysis demonstrated phosphorylation of ERK1/2 upon stimulation of microglia. In contrast, IFN-gamma- and CD40L-induced IP-10 protein production was mediated by the p38 MAPK pathway. Our data suggest a mechanism whereby CD40L+ cells can induce microglia to secrete chemokines, amplifying inflammatory processes seen in HIV encephalitis and multiple sclerosis, and implicate CD40-CD40L interactions as a target for interventional strategies.     

Microglia-inhibiting activity of Parkinson's disease drug amantadine

Amantadine is currently used as an antiviral and an antiparkinsonian drug. Although the drug is known to bind a viral proton channel protein, the mechanism of action in Parkinson's disease (PD) remains to be determined. This study investigated whether the drug has an inhibitory effect on microglial activation and neuroinflammation, which have been implicated in the progression of neurodegenerative processes. Using cultured microglial cells, it was demonstrated that the drug inhibited inflammatory activation of microglia and a signaling pathway that governs the microglial activation. The drug reduced the expression and production of proinflammatory mediators in bacterial lipopolysaccharide-stimulated microglia cells. The microglia-inhibiting activity of amantadine was also demonstrated in a microglia/neuron coculture and animal models of neuroinflammation and Parkinson's disease. Collectively, our results suggest that amantadine may act on microglia in the central nervous system to inhibit their inflammatory activation, thereby attenuating neuroinflammation. These results provide a molecular basis of the glia-targeted mechanism of action for amantadine.     

Roles of NF-κB and MAPK signaling pathways in morphological and cytoskeletal responses of microglia to double-stranded RNA

Following virus infection of the central nervous system, microglia become activated and undergo morphological as well as functional transformations, thereby initiating effective antiviral actions. Herein, we have examined the contribution of nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways to cell shape determination and cytoskeletal organization in microglia upon stimulation with double-stranded RNA (dsRNA), a conserved molecular pattern of virus infection. Under non-proliferative condition, microglial MG6-1 cells displayed a distinctive morphology with spinescent processes and small somata. Following dsRNA stimulation, the process-bearing microglial cells exhibited swift and drastic changes in cell morphology, filamentous actin (F-actin) structure, and intracellular signaling. In the dsRNA-stimulated microglial cells, the activation of c-Jun N-terminal kinase (JNK) pathway was involved in morphological alteration into an ameboid state. We also found that p38 signaling pathway negatively regulates the formation of cytoplasmic vacuoles in microglial cells. Furthermore, the dsRNA-induced accumulation of F-actin was partly mediated by NF-κB, JNK, and p38 pathways. These results indicate that NF-κB and MAPK signaling pathways mediate morphological and cytoskeletal changes during dsRNA-induced microglial activation.     

The endocytic pathway in microglia during health,aging and Alzheimer’s disease

Microglia, the main phagocytes of the central nervous system (CNS), are involved in the surveillance and maintenance of nervous tissue. During normal tissue homeostasis, microglia migrates within the CNS, phagocytose dead cells and tissue debris, and modulate synapse pruning and spine formation via controlled phagocytosis. In the event of an invasion by a foreign body, microglia are able to phagocytose the invading pathogen and process it proteolytically for antigen presentation. Internalized substrates are incorporated and sorted within the endocytic pathway and thereafter transported via complex vesicular routes. When targeted for degradation, substrates are delivered to acidic late endosomes and lysosomes. In these, the enzymatic degradation relies on pH and enzyme content. Endocytosis, sorting, transport, compartment acidification and degradation are regulated by complex signaling mechanisms, and these may be altered during aging and pathology. In this review, we discuss the endocytic pathway in microglia, with insight into the mechanisms controlling lysosomal biogenesis and pH regulation. We also discuss microglial lysosome function associated with Alzheimer’s disease (AD) and the mechanisms of amyloid-beta (Aβ) internalization and degradation. Finally, we explore some therapies currently being investigated to treat AD and their effects on microglial response to Aβ, with insight in those involving enhancement of lysosomal function.     

Regulation of microglial survival and proliferation in health and diseases

Microglia play an important role in the development and maintenance of the central nervous system (CNS) under homeostatic conditions as well as during neurodegenerative diseases. Recent observations in human genomics and advances in genetic mouse models have provided insights into signaling pathways that control development, survival, proliferation and function of microglia. Alteration of these pathways contributes to the pathogenesis of CNS diseases. Here we review the current literature regarding the roles of these microglial pathways in both the normal and diseased brain and discuss areas that require further investigation.     

Minocycline suppresses hypoxic activation of rodent microglia in culture

Hypoxia is one of the important physiological stimuli that are often associated with a variety of pathological states such as ischemia, respiratory diseases, and tumorigenesis. In the central nervous system, hypoxia that is accompanied by cerebral ischemia not only causes neuronal cell injury, but may also induce pathological microglial activation. We have previously shown that hypoxia induces inflammatory activation of cultured microglia, and the hypoxic induction of nitric oxide production in microglia is mediated through p38 mitogen-activated protein kinase pathway. Now, we present evidence that minocycline, a tetracycline derivative, suppresses the hypoxic activation of cultured microglia by inhibiting p38 mitogen-activated protein kinase pathway. The drug markedly inhibited hypoxia-induced production of inflammatory mediators such as nitric oxide, TNFalpha, and IL-1beta as well as iNOS protein expression. The signal transduction pathway that leads to the activation of p38 mitogen-activated protein kinase was the molecular target of minocycline. Thus, the known neuroprotective effects of minocycline in animal models of cerebral ischemia may be partly due to its direct actions on brain microglia.     

Reactive oxygen species and p47phox activation are essential for the Mycobacterium tuberculosis-induced pro-inflammatory response in murine microglia

Background  

Activated microglia elicits a robust amount of pro-inflammatory cytokines, which are implicated in the pathogenesis of tuberculosis in the central nervous system (CNS). However, little is known about the intracellular signaling mechanisms governing these inflammatory responses in microglia in response to Mycobacterium tuberculosis (Mtb).     

焦亡信号通路炎症小体与中枢神经系统疾病研究进展

焦亡是一种新发现并证实与炎症相关的细胞死亡方式,其特征为依赖于半胱天冬氨酸蛋白酶-1(caspase-1)的细胞程序性死亡,并伴有促炎症因子的释放,主要为白细胞介素1β和IL-18.虽然焦亡与坏死和凋亡有相似之处,但它们是迥然不同的生物学过程.越来越多的研究发现,焦亡相关信号通路在中枢神经系统疾病中起重要作用,包括急性脑感染、神经变性疾病、急性无菌性脑损伤和慢性无菌性中枢神经系统炎症.     

Purinoceptors in microglia and neuropathic pain

Emerging evidence indicates that microglia play a critical role in the pathogenesis of neuropathic pain, a debilitating chronic pain condition that can occur after peripheral nerve damage caused by disease, infection, or physical injury. Microglia are immunocompetent cells of the central nervous system and express various ionotropic P2X and metabotropic P2Y purinoceptors. After injury to a peripheral nerve, microglia in the spinal cord become activated and upregulate expression of the P2X4 receptor. Recent findings suggest that activation of P2X4 receptors evokes release of brain-derived neurotrophic factor from microglia and that this mediates microglia–neuron signaling leading to pain hypersensitivity. Thus, P2X4 receptors and the intracellular signaling mediators in microglia are promising therapeutic targets for the development of novel pharmacological agents in the management of neuropathic pain.