胶质细胞在癫癎发病机制中的作用研究进展

癫癎是神经系统疾病中的一种严重危害人类健康的常见病、多发病,患病率约为1%,发病机制非常复杂.胶质细胞是神经系统的重要组成部分,胶质细胞占脑细胞总数的约90%,包括星形胶质细胞、少突胶质细胞和小胶质细胞,其在生理与病理状态下对维护神经系统功能的作用至今未明.胶质细胞不仅与脑的正常生理活动、发育以及神经病理过程有明显关系,而且与神经元的功能活动以及损伤与修复过程有千丝万缕的联系.近年来研究表明胶质细胞在癫癎的发病机制中扮演重要角色.本文就癎性发作时胶质细胞功能改变(细胞形态改变、免疫表型改变和细胞增殖活动)、胶质细胞与神经元之间物质、信息交流方面的研究进展进行综述.     

癫痫分子病理机制的研究进展:来自中国的报道

癫癎是一种临床常见的中枢神经系统疾病。近年来,随着科学技术的发展,癫癎发病机制的研究已逐步转向分子水平,本文对过去5年PubMed所收录的中国癫癎研究者有关癫癎分子病理机制研究的学术论文的主要内容进行复习,并结合部分非中国学者的研究内容进行分析讨论,旨在让读者了解中国研究者在癫癎研究中的作用。     

难治性癫(癎)患者颞叶GFAP表达的变化

目的 观察难治性癫(癎)患者手术切除的颞叶脑组织中GFAP表达的变化,以探讨颞叶癫(癎)的发病机制.方法 以12例难治性癫(癎)患者为实验组,2例意外死亡的健康人为对照组,采用免疫组织化学方法观察2组颞叶脑组织中GFAP表达的变化.结果 与对照组相比,实验组颞叶GFAP的表达显著升高(P＜0.05).结论 反应性胶质细胞增生参与了癫(癎)发生的病理过程,GFAP的表达上调可能是难治性癫(癎)发病的分子学机制之一.     

突触素与癫(癎)

癫(癎)(epilepsy)是最常见的神经系统疾病之一,其发病机制复杂,目前认为癫(癎)发病是由于中枢神经系统兴奋与抑制性不平衡导致大脑神经元异常放电所致.     

癫癎发生的分子机制研究进展

癫癎是神经系统常见疾病,以大量神经元反复发作异常放电引起的中枢神经系统短暂性功能失调为特征。对癫癎发生分子机制的研究一直是全球神经科学界关注的焦点。其病因多种多样、机制复杂,涉及离子通道、谷氨酸能系统、γ-氨基丁酸能系统、神经营养因子和炎性介质等多方面。本文拟对癫癎发病的分子机制进行综述,以为研制新型抗癫癎药物寻找新的线索和突破点。     

线粒体在癫癎发病中的作用

中枢神经系统的线粒体功能障碍可以导致癫癎发作,肌阵挛性癫癎与线粒体tRNALys和tRNASer基因突变有关,其几种突变类型中均可出现全面性癫癎发作。部分性癫癎发作常出现在线粒体脑病中,这一类疾病与线粒体tRNALeu基因突变有关。在动物模型及人类癫癎中均证实,线粒体异常与导致神经元死亡的过程密切相关,线粒体功能障碍在癫癎发病机制和难治性癫癎的进展过程中起着重要作用。     

胍丁胺对戊四氮诱导慢性癫癎大鼠的保护作用和海马星形胶质细胞表达的影响

目的:探讨不同剂量胍丁胺对戊四氮诱导的慢性癫癎大鼠模型的保护作用及对海马区星形胶质细胞表达的影响。方法:连续28 d腹腔注射戊四氮35 mg.kg-1建立大鼠慢性癫癎模型。不同剂量胍丁胺(20、40、80 mg.kg-1)进行干预。观察大鼠癫癎发作行为学及海马的形态学变化,检测海马星形胶质细胞的表达。结果:胍丁胺40、80 mg.kg-1可降低癫癎发作的日均等级评分,减少海马神经元丢失及星形胶质细胞增生。结论:胍丁胺40、80 mg.kg-1可抑制慢性癫癎大鼠发作,降低惊厥发作后海马星形胶质细胞的异常增生及神经元损伤。     

胶质细胞介导内环境变化对癫■发病的影响

癫■是神经系统常见慢性疾病,其特征为脑内神经元同步化异常放电,对癫■发病机制的研究多以神经元为主。但近来对神经功能网络中胶质细胞的作用研究日益深入,文中就胶质细胞介导内环境变化导致癫■的可能机制研究进行综述,介绍胶质细胞调节细胞外空间离子浓度、神经递质、细胞外基质、细胞因子等在癫发病机制中的作用。     

癫(癎)患儿血清白介素-6、肿瘤坏死因子水平测定

癫(癎)的发病机制极为复杂,且尚未完全阐明,神经免疫调节网络失衡是其发生、发展的重要因素之一,诸多细胞因子参与癫(癎)的发病过程[1].白介素-6(IL-6)和肿瘤坏死因子(TNF)是具有广泛生物学作用的细胞因子,参与了细胞免疫调节作用.本文检测了癫(癎)患儿血清中IL-6和TNF的水平,旨在探讨癫(癎)的免疫作用机制.     

癫癎发病机制研究

癫癎是一种常见的神经系统疾病,发病率(2～5)/1 000人,严重影响患者的生活、工作和学习,成为中枢神经系统疾病中的一大顽疾.因此,对癫发病机制的研究成为当今国际神经科学领域的重要课题.通过对动物模型和人类癫手术切除的海马标本研究,癫的发病机制可能是由于兴奋性异常增高、抑制机制不足或两者兼有之而导致的癫灶内神经元兴奋性过高,从而导致这些神经元的失控性自发性异常放电,进而引起了癫的反复性发作[1-2].     

Connexins and pannexins: At the junction of neuro‐glial homeostasis & disease

In the central nervous system (CNS), connexin (Cx)s and pannexin (Panx)s are an integral component of homeostatic neuronal excitability and synaptic plasticity. Neuronal Cx gap junctions form electrical synapses across biochemically similar GABAergic networks, allowing rapid and extensive inhibition in response to principle neuron excitation. Glial Cx gap junctions link astrocytes and oligodendrocytes in the pan‐glial network that is responsible for removing excitotoxic ions and metabolites. In addition, glial gap junctions help constrain excessive excitatory activity in neurons and facilitate astrocyte Ca²⁺ slow wave propagation. Panxs do not form gap junctions in vivo, but Panx hemichannels participate in autocrine and paracrine gliotransmission, alongside Cx hemichannels. ATP and other gliotransmitters released by Cx and Panx hemichannels maintain physiologic glutamatergic tone by strengthening synapses and mitigating aberrant high frequency bursting. Under pathological depolarizing and inflammatory conditions, gap junctions and hemichannels become dysregulated, resulting in excessive neuronal firing and seizure. In this review, we present known contributions of Cxs and Panxs to physiologic neuronal excitation and explore how the disruption of gap junctions and hemichannels lead to abnormal glutamatergic transmission, purinergic signaling, and seizures.     

Pannexin1 is expressed by neurons and glia but does not form functional gap junctions

Pannexins are a newly described family of proteins that may form gap junctions. We made antisera against mouse pannexin1 (Panx1). HeLa cells expressing Panx1 have cell surface labeling, but not gap junction plaques, and do not transfer small fluorescent dyes or neurobiotin in a scrape-loading assay. Neuro2a cells expressing Panx1 are not electrophysiologically coupled. Intracellular Panx1-immunoreactivity, but not gap junction plaques, is seen in cultured oligodendrocytes, astrocytes, and hippocampal neurons. Thus, at least in these mammalian cells lines, Panx1 does not form morphological or functional gap junctions, and it remains to be demonstrated that Panx1 forms gap junction-forming protein in the CNS.     

Growing axons in fish optic nerve are accompanied by astrocytes interconnected by tight junctions

Mammalian astrocytes are in general interconnected by gap but not by tight junctions and play an ambiguous and controversially discussed role in central nervous system regeneration. At different neuroanatomical sites, fish astrocytes are interconnected by tight junctions and desmosomes and are involved in the successful regeneration of lesioned fiber tracts. In fish, newly generated retinal ganglion cells continuously grow new axons to the optic tectum but the interrelationship between glial tight junctions and axonal growth is undefined so far. We therefore investigated the occurrence of tight junctional structures and molecules within the ribbon-shaped optic nerve of a teleost fish (Astatotilapia burtoni) and found a predominant expression of zonula occludens protein-1 and claudin-1 in astrocytes where axons of new ganglion cells are assembled retinotopically within the optic nerve. This may support a previously formulated hypothesis according to that different properties of astrocytic membranes could be responsible for different glio-neuronal interactions which in turn may determine the micro-environmental conditions of growing axons.     

脑内缝隙连接

缝隙连接普遍存在于动物组织中，具有重要的生理功能。近年来，由于分子生物学等技术的应用，对许多组织的缝隙连接蛋白的特性及其功能的研究取得了很大进展。本文重点介绍脑内缝隙连接蛋白的类型，分布及其生物物理学和药理学特性，并阐述胶质细胞之间、神经元之间缝隙连接的作用，以及缝隙连接与脑发育和癫痫等神经系统疾病的关系。     

Gap Junctions Couple Astrocytes and Oligodendrocytes

In vertebrates, a family of related proteins called connexins form gap junctions (GJs), which are intercellular channels. In the central nervous system (CNS), GJs couple oligodendrocytes and astrocytes (O/A junctions) and adjacent astrocytes (A/A junctions), but not adjacent oligodendrocytes, forming a “glial syncytium.” Oligodendrocytes and astrocytes each express different connexins. Mutations of these connexin genes demonstrate that the proper functioning of myelin and oligodendrocytes requires the expression of these connexins. The physiological function of O/A and A/A junctions, however, remains to be illuminated.     

Glial cells in the guinea pig myenteric plexus are dye coupled

Glial cells in the myenteric plexus of the guinea pig small intestine were stained intracellularly with Lucifer yellow and horseradish peroxidase. The cells were identified by both their electrophysiological characteristics and by their morphology. Injection of Lucifer yellow, which is known to cross gap junctions, resulted in the staining of many (up to about 100) glial cells. The staining pattern was comparable to the immunostaining of glia with an antiserum for S-100 protein. In contrast to Lucifer yellow, horseradish peroxidase (which does not cross these junctions), was confined to the injected cell. It is concluded that enteric glia are coupled, presumably by gap junctions. This finding indicates that in addition to structural and biochemical similarities, enteric glia may share certain physiological characteristics with central nervous system astrocytes.     

Inflammation induced by innate immunity in the central nervous system leads to primary astrocyte dysfunction followed by demyelination

Primary loss and dysfunction of astrocytes may trigger demyelination, as seen in neuromyelitis optica, an inflammatory disease of the central nervous system. In most patients affected by this disease, injury to astrocytes is initiated by the action of autoantibodies targeting aquaporin 4 (AQP-4), a water channel on astrocytes. We show here that damage of astrocytes and subsequent demyelination can also occur in the absence of autoantibody-mediated mechanisms. Following injection of lipopolysaccharide into the white matter initial microglia activation is followed by a functional disturbance of astrocytes, mainly reflected by retraction of astrocytic foot processes at the glia limitans and loss of AQP-4 and connexins, which are involved in the formation of gap junctions between astrocytes and oligodendrocytes. Demyelination and oligodendrocyte degeneration in this model follows astrocyte pathology. Similar structural abnormalities were also seen in a subset of active lesions in multiple sclerosis. Our studies suggest that astrocyte injury may be an important early step in the cascade of lesion formation in brain inflammation.     

Pannexin expression in the cerebellum

Pannexin1 and pannexin2 are members of the pannexin gene family which are widely expressed in the central nervous system. Here we present an overview of pannexin expression and distribution in the mouse cerebellum. Pannexin1 and pannexin2 are expressed in the Purkinje cells and in some cells of the granule cell layer. Pannexin2 is also expressed in the stellate cells of the molecular layer. A differential expression of pannexin1 and pannexin2 mRNA is observed during cerebellar development. These findings constitute the first indication of the involvement of pannexin molecules in the developing cerebellum. Although the functional relevance of these molecules remains currently unknown, the abundance of pannexins in the Purkinje cells suggests that they may contribute to the generation of cerebellar rhythms.     

Connexin26 in adult rodent central nervous system: demonstration at astrocytic gap junctions and colocalization with connexin30 and connexin43.

The connexin family of proteins (Cx) that form intercellular gap junctions in vertebrates is well represented in the mammalian central nervous system. Among these, Cx30 and Cx43 are present in gap junctions of astrocytes. Cx32 is expressed by oligodendrocytes and is present in heterologous gap junctions between oligodendrocytes and astrocytes as well as at autologous gap junctions between successive myelin layers. Cx36 mRNA has been identified in neurons, and Cx36 protein has been localized at ultrastructurally defined interneuronal gap junctions. Cx26 is also expressed in the CNS, primarily in the leptomeningeal linings, but is also reported in astrocytes and in neurons of developing brain and spinal cord. To establish further the regional, cellular, and subcellular localization of Cx26 in neural tissue, we investigated this connexin in adult mouse brain and in rat brain and spinal cord using biochemical and immunocytochemical methods. Northern blotting, western blotting, and immunofluorescence studies indicated widespread and heterogeneous Cx26 expression in numerous subcortical areas of both species. By confocal microscopy, Cx26 was colocalized with both Cx30 and Cx43 in leptomeninges as well as along blood vessels in cortical and subcortical structures. It was also localized at the surface of oligodendrocyte cell bodies, where it was coassociated with Cx32. Freeze-fracture replica immunogold labeling (FRIL) demonstrated Cx26 in most gap junctions between cells of the pia mater by postnatal day 4. By postnatal day 18 and thereafter, Cx26 was present at gap junctions between astrocytes and in the astrocyte side of most gap junctions between astrocytes and oligodendrocytes. In perinatal spinal cord and in five regions of adult brain and spinal cord examined by FRIL, no evidence was obtained for the presence of Cx26 in neuronal gap junctions. In addition to its established localization in leptomeningeal gap junctions, these results identify Cx26 as a third connexin (together with Cx30 and Cx43) within astrocytic gap junctions and suggest a further level of complexity to the heterotypic connexin channel combinations formed at these junctions.     

Heterogeneity in gap junction expression in astrocytes cultured from different brain regions.

Heterogeneity among astrocytes suggests that their role in the central nervous system is more complex than is commonly recognized. This paper describes just such a functional difference, comparing gap junctions in astrocytes derived from two brain regions. Astrocytes, both in situ and in culture, employ gap junctions as a means of intercellular communication. Recent evidence utilizing cultured rat cortical and striatal astrocytes has shown that these channels consist of subunits of connexin 43, the same protein as that composing cardiac gap junctions. Here we report that astrocytes cultured from neonatal rat hypothalamus contain a greater number of functional channels than astrocytes from the striatum, a difference reflected in both connexin 43 protein and mRNA. Specifically, in hypothalamic astrocytes the level of connexin 43 protein was approximately four times that found in comparable cultures from the striatum, as determined by immunoblotting. Complementary results from immunocytochemical experiments using an antibody specific for connexin 43 reveal significantly greater fluorescence in astrocytes cultured from the hypothalamus as compared to those from the striatum. Northern blot analysis showed that connexin 43 mRNA levels were also approximately 4-fold greater in the hypothalamic cultures, consistent with the difference seen by immunoblotting. Finally, dye coupling studies using confluent cultures consistently showed that within 1 min Lucifer Yellow injected into striatal astrocytes spread to immediately surrounding cells while in hypothalamic astrocytes dye often spread to apparent third or fourth order neighbors within the same time period. Thus, the higher level of connexin 43 expression seen in hypothalamic astrocytes results in cells with greater numbers of functional channels.(ABSTRACT TRUNCATED AT 250 WORDS)