脑源性神经营养因子研究进展

脑源性神经营养因子是一种小分子二聚体蛋白质,在结构上与神经生长因子相关。对中枢神经系统的多种类型神经元的生长、发育、分化、维护和再生部具有重要作用,对于治疗运动神经元病变以及神经系统迟行性疾病有显疗效。本对其细胞与分子生物学特征、生物学功能进行阐述。     

长期运动对幼龄大鼠下丘脑脑源性神经营养因子表达的影响

目的：探讨下丘脑脑源性神经营养因子（BDNF）与幼龄大鼠长期运动中摄食调节活动的关系。方法：3周龄断乳SD大鼠随机分为运动组（E）和对照组（C）,运动组进行9周的游泳运动（每天1次,每周6 d）,运动时间由开始每次30 min逐渐增加到每次90 min。12周龄时用ELISA法测试血清BDNF含量,RT-PCR和Western blot方法检测下丘脑中BDNF mRNA、pro-BDNF和BDFN蛋白表达水平。结果：与C组比较,E组大鼠在运动第1周、第9周以及整个实验期间摄食量无变化。12周龄时与C组相比,E组血清BDNF含量和下丘脑BDNF mRNA表达水平无变化,但下丘脑pro-BDNF和BDNF蛋白表达水平升高（P〈0.05）。结论：长期运动使幼龄大鼠下丘脑BDNF和pro-BDNF蛋白表达水平同时升高。     

脑源性神经营养因子前体蛋白生物学效应研究进展

神经营养因子是一类分泌性多肽类生长因子,可促进中枢和外周神经元的生长、存活以及分化,但其前体分子却具有不同的生物学活性,也有着不同的受体以及细胞内信号通路。本文对近年来关于脑源性神经营养因子前体蛋白的研究予以综述,着重讨论其在神经损伤与情绪障碍和神经退行性变疾病模型中的作用。     

人脑源性神经营养因子基因表达

用聚合酶链式反应(PCR)从人基因组DNA中扩增了人脑源性神经营养因子(hBDNF) cDNA和hBDNF成熟蛋白编码片段,分别克隆到pUC18中.经测序确认两个插入片段序列正确.hBDNF cDNA在CMV启动子控制下在NIH/3T3细胞中表达,用RT-PCR检测转染细胞确有BDNF mRNA存在.BDNF成熟蛋白编码序列在T7启动子控制下在E.coli中表达,SDS-PAGE表明,BDNF得到表达,以包涵体形式存在.     

大鼠肠道菌群变化影响其大脑海马脑源性神经营养因子的表达

目的探讨大鼠肠道菌群变化对海马脑源性神经营养因子(Brain-Derived Neurotropic Factor,BDNF)的影响。方法在雄性SD大鼠的饮用水中添加肠道不吸收的抗生素(新霉素、杆菌肽和游霉素),饮用1周、3周之后检测大鼠体重,采用变性梯度凝胶电泳(Denaturing Gradient Gel Electrophoresis,DGGE)的方法检测大鼠粪便中菌群的组成,并用实时定量PCR检测大鼠大脑海马BDNF的表达水平。结果与对照组相比,饮用抗生素的大鼠体重无明显差异,而肠道菌群有显著变化;抗生素饮用组海马BDNF的表达水平升高(P0.05)。结论肠道菌群变化可以影响大脑海马BDNF的表达。     

神经营养素3和脑源性神经生长因子在大鼠脊髓中的定位表达

神经营养素3（NT－3）和脑源性神经生长因子（BDNF）是神经生长因子（NGF）的同源物,体外实验表明NT－3和BDNF能促进感觉神经元和交感神经元的存活,但是NT－3和BDNF在脊髓中的生物学作用和定位分布还不十分清楚。本用免疫组化ABC法观察了NT－3和BDNF的免疫阳性反应物在大鼠脊髓中的分布。结果表明：呈NT－3样免疫阳性反应的胶质细胞分布于脊髓的后索、侧索和前索中;免疫反应阳性的神经元主要见于脊髓前角,少数见于脊髓后角。BDNF位于大鼠的脊髓前角动物神经元;在脊髓Ⅱ板层中还可见较多的BDNF免疫反应阳性的神经终末。提示NT－3和BDNF在维持脊髓神经元和胶质细胞的生理功能中可能起重要作用。     

大熊猫脑源性神经营养因子基因的克隆与表达

参照人ＢＤＮＦ基因序列设计出一对引物和利用聚合酶链式反应（ＰＣＲ）,首次从大熊猫基因组ＤＮＡ中扩增和克隆到ＢＤＮＦ基因,并使其在大肠杆菌中得到了表达。序列分析表明,大熊猫和人的ＢＤＮＦ基因的核苷酸序列同源性高达９４％。在推导的多肽序列中,除在前导肽区有两个氨基酸的差异外,大熊猫ＢＤＮＦ的成熟区与人和其它已报道的哺乳动物ＢＤＮＦ成熟区的氨基酸序列完全一致,显示了极高的保守性。本文首次在分子生物学水平上对大熊猫核基因组功能基因进行研究分析,其结果为深入开展大熊猫的神经系统疾病防治,神经生理以及分子进化,系统发育等方面的研究奠定了重要基础。     

马来熊脑源性神经营养因子基因编码区的克隆与序列分析

参照人脑源性神经神经生长因子（ＢＤＮＦ）基因序列设计出一对引物，利用聚合酶链式反应，首次从马来熊基因组ＤＮＡ中扩增和克隆到ＢＤＮＦ基因的编码区。对该基因所作的序列分析表明，马来熊和人ＢＤＮＦ基因编码区的核苷酸序列同源性为９４％，而与大熊猫ＢＤＮＦ基因的核苷酸序列同源性高达９９％。在推导的多肽序列中，除在前导肽区有两个氨基酸的差异外，马来熊ＢＤＮＦ的成熟区与人和其他已报道的哺乳动物ＢＤＮＦ成熟区的氨     

脑源性神经营养因子及其临床研究进展

脑源性神经营养因子 (BDNF)是继神经生长因子 (NGF)后发现的第二个神经营养因子 ,在神经系统的发育、功能维持和神经元群的成形性上起重要作用。国内外正积极开发 BDNF用于神经损伤的治疗。本文就 BDNF的结构、功能、信号传导以及临床研究等作一综述     

胶质细胞源性神经营养因子在不同年龄大鼠小脑及海马中的表达差异

目的观察胶质细胞源性神经营养因子（GDNF）在青年和老年大鼠小脑和海马中的表达特征。方法采用免疫组织化学方法显示GDNF在青年及老年大鼠小脑和海马的分布变化。应用计算机图像分析系统对免疫组织化学反应切片进行检测。结果青年组小脑蒲肯野细胞GDNF阳性反应明显强于老年组;但在青年和老年大鼠海马区,GDNF免疫细胞反应的差别并不明显。结论GDNF在蒲氏细胞内含量的增龄性变化提示它影响蒲肯野细胞及小脑其它神经元的功能与存活,对于小脑神经细胞的老化有重要意义。     

腺病毒介导BDNF基因对无血清培养SH-SY5Y细胞的生物学作用研究

目的 :为了有效的将腺病毒介导的脑源性神经营养因子 (BDNF)用于神经损伤的保护治疗。方法 :在体外用BDNF重组腺病毒 (Ad BDNF)对SH SY5Y细胞进行感染 ,在无血清培养条件下对细胞的生长分化进行了形态学的观察 ,利用MTT法检测不同浓度的Ad BDNF对SH SY5Y细胞的促存活作用 ,并对细胞凋亡作用进行了检测。结果和结论 :腺病毒介导的BDNF可有效的促进感染后的SH SY5Y细胞的存活 ,生长和分化 ,并可有效的抑制无血清状态下细胞凋亡的发生     

Progranulin contributes to endogenous mechanisms of pain defense after nerve injury in mice

Progranulin haploinsufficiency is associated with frontotemporal dementia in humans. Deficiency of progranulin led to exaggerated inflammation and premature aging in mice. The role of progranulin in adaptations to nerve injury and neuropathic pain are still unknown. Here we found that progranulin is up-regulated after injury of the sciatic nerve in the mouse ipsilateral dorsal root ganglia and spinal cord, most prominently in the microglia surrounding injured motor neurons. Progranulin knockdown by continuous intrathecal spinal delivery of small interfering RNA after sciatic nerve injury intensified neuropathic pain-like behaviour and delayed the recovery of motor functions. Compared to wild-type mice, progranulin-deficient mice developed more intense nociceptive hypersensitivity after nerve injury. The differences escalated with aging. Knockdown of progranulin reduced the survival of dissociated primary neurons and neurite outgrowth, whereas addition of recombinant progranulin rescued primary dorsal root ganglia neurons from cell death induced by nerve growth factor withdrawal. Thus, up-regulation of progranulin after neuronal injury may reduce neuropathic pain and help motor function recovery, at least in part, by promoting survival of injured neurons and supporting regrowth. A deficiency in this mechanism may increase the risk for injury-associated chronic pain.     

Expression profiles of BDNF splice variants in cultured DRG neurons stimulated with NGF

Expression of brain-derived neurotrophic factor (BDNF) mRNA is increased in the dorsal root ganglion (DRG) in response to peripheral inflammation. Nerve growth factor (NGF) from inflammatory tissue is thought to induce expression of BDNF. Recently, it was reported that the BDNF gene has eight non-coding exons that are transcribed independently into several splice variants. Expression of these splice variants in DRG neurons stimulated with NGF has not been studied. We examined changes in expression of BDNF splice variants in a rat model of peripheral inflammation and in cultured DRG neurons exposed to NGF. Total BDNF mRNA was increased by inflammation in vivo and by NGF in vitro. Among all splice variants, exon 1-9 showed the greatest increase in expression in both experiments. Our results indicate that exon 1-9 contributes to changes in total BDNF levels and may play an important role in the acute response of DRG to NGF.     

Direct evidence for the involvement of brain-derived neurotrophic factor in the development of a neuropathic pain-like state in mice

Thermal hyperalgesia and tactile allodynia induced by sciatic nerve ligation were completely suppressed by repeated intrathecal (i.t.) injection of a TrkB/Fc chimera protein, which sequesters endogenous brain-derived neurotrophic factor (BDNF). In addition, BDNF heterozygous (+/-) knockout mice exhibited a significant suppression of nerve ligation-induced thermal hyperalgesia and tactile allodynia compared with wild-type mice. After nerve ligation, BDNF-like immunoreactivity on the superficial laminae of the ipsilateral side of the spinal dorsal horn was clearly increased compared with that of the contralateral side. It should be noted that a single i.t. injection of BDNF produced a long-lasting thermal hyperalgesia and tactile allodynia in normal mice, and these responses were abolished by i.t. pre-treatment with either a Trk-dependent tyrosine kinase inhibitor K-252a or a selective protein kinase C (PKC) inhibitor Ro-32-0432. Supporting these findings, we demonstrated here for the first time that the increase in intracellular Ca2+ concentration by application of BDNF in cultured mouse spinal neurons was abolished by pre-treatment with either K-252a or Ro-32-0432. Taken together, these findings suggest that the binding of spinally released BDNF to TrkB by nerve ligation may activate PKC within the spinal cord, resulting in the development of a neuropathic pain-like state in mice.     

白鱀豚BDNF基因的扩增和序列分析

利用聚合酶链式反应,首次从白鱀豚基因组DNA 中扩增和克隆到脑源神经营养因子的编码区。在该段序列中含有一个长为747 bp 的开放阅读框,无内含子,编码一个由248 个氨基酸组成的蛋白质,预计分子量为27 953.7道尔顿。其中包括由18 个氨基酸残基组成的信号肽区,111 个氨基酸残基组成的前肽区及119 个氨基酸残基组成的成熟区。序列分析表明,白鱀豚脑源神经营养因子基因编码区的核苷酸序列与其它哺乳动物相似性超过90%,而与猪牛相似性相对较高（分别为95% 和94.7%）。氨基酸序列比较发现,白鱀豚BDNF 前体蛋白的氨基酸序列与其它哺乳动物具有94.5% ～99.5%的相似性,显示了极高的保守性。通过邻接法进行的系统发生分析中,鲸目和食肉目的物种分别聚为单系;与其它哺乳动物相比,鲸类与有蹄类的牛和猪的亲缘关系相对较近,这与鲸类和有蹄类之间具有相对较近的亲缘关系相符。
     

Acute role of the brain-derived neurotrophic factor (BDNF) on the respiratory neural network activity in mice in vitro

In humans, several pathologies are associated with disturbances of the respiratory control, some of them including alteration in the brain-derived neurotrophic factor (BDNF) signalling pathway. BDNF has long been known as a neurotrophic factor involved in survival, differentiation and maintenance of neuronal populations in the peripheral and central nervous system. More recently BDNF has also been discovered to be a potent neuromodulator with acute effects on neuronal excitability and synaptic plasticity. Animals deleted for the gene encoding BDNF exhibit respiratory alteration suggesting an important but yet undefined role of the neurotrophin in respiratory rhythmogenesis either by a trophic and/or an acute action. The possibility that BDNF might exert an acute regulatory role on the rhythmic activity of the respiratory generator of the pre-B?tzinger complex has been recently examined in newborn mice in vitro. Results obtained, reviewed in the present paper, will help getting insights in respiratory rhythm regulatory mechanisms that involve BDNF signalling.     

Synaptogenesis in Co-Culture of Neurons of Dorsal Root Ganglia and Spinal Cord

In co-culture of spinal cord and dorsal root ganglion (DRG) neurons, we studied at different terms of culturing postsynaptic currents in DRG neurons evoked by direct electrical stimulation of single spinal neurons using a voltage-clamp technique in the whole-cell configuration. According to the reversal potential and sensitivity to bicuculline, these currents were classified as inhibitory postsynaptic currents (IPSC) carried by Cl^- ions through GABA_A receptors. During neuronal development in dissociated co-culture, the amplitude of evoked IPSC and their time to peak significantly increased. The time to peak of spontaneous IPSC (sIPSC) in DRG neurons remained unchanged, while the frequency of these currents increased with increasing culturing time. It is concluded that under culturing conditions spinal neurons establish inhibitory synaptic contacts with the somata of DRG neurons, and the number of such functional contacts increases in the course of culturing. Our findings show that in dissociated co-culture the process of formation of inhibitory synapses on the axon terminals of primary afferent neurons is akin to that realized in vivo, but with dissimilar topography of distribution of such synapses.     

Combined brain‐derived neurotrophic factor with extinction training alleviate impaired fear extinction in an animal model of post‐traumatic stress disorder

Impaired fear memory extinction (Ext) is one of the hallmark symptoms of post‐traumatic stress disorder (PTSD). However, since the precise mechanism of impaired Ext remains unknown, effective interventions have not yet been established. Recently, hippocampal‐prefrontal brain‐derived neurotrophic factor (BDNF) activity was shown to be crucial for Ext in naïve rats. We therefore examined whether decreased hippocampal‐prefrontal BDNF activity is also involved in the Ext of rats subjected to a single prolonged stress (SPS) as a model of PTSD. BDNF levels were measured by enzyme‐linked immunosorbent assay (ELISA), and phosphorylation of TrkB was measured by immunohistochemistry in the hippocampus and medial prefrontal cortex (mPFC) of SPS rats. We also examined whether BDNF infusion into the ventral mPFC or hippocampus alleviated the impaired Ext of SPS rats in the contextual fear conditioning paradigm. SPS significantly decreased the levels of BDNF in both the hippocampus and mPFC and TrkB phosphorylation in the ventral mPFC. Infusion of BDNF 24 hours after conditioning in the infralimbic cortex (ILC), but not the prelimbic cortex (PLC) nor hippocampus, alleviated the impairment of Ext. Since amelioration of impaired Ext by BDNF infusion did not occur without extinction training, it seems the two interventions must occur consecutively to alleviate impaired Ext. Additionally, BDNF infusion markedly increased TrkB phosphorylation in the ILC of SPS rats. These findings suggest that decreased BDNF signal transduction might be involved in the impaired Ext of SPS rats, and that activation of the BDNF‐TrkB signal might be a novel therapeutic strategy for the impaired Ext by stress.     

B型酪氨酸激酶受体的轴浆转运

脑源性神经营养因子(brain-derived neurotrophic factor,BDNF)在发育及成熟的中枢神经系统(central nervoussystem,CNS)中起到举足轻重的调节作用,而其中绝大部分作用由其B型酪氨酸激酶受体(tyrosine kinase receptortype B,TrkB)介导,因此TrkB在神经元中的轴浆转运过程显得尤为重要。本文从动力蛋白、潜在调节分子、细胞骨架蛋白等方面对TrkB轴浆转运分子机制的研究进展进行综述,并就其进一步研究提出一系列的问题与展望。