Preferential neurotrophic activity of fibroblast growth factor-20 for dopaminergic neurons through fibroblast growth factor receptor-1c

Degeneration of dopaminergic neurons of the substantia nigra causes Parkinson's disease. Therefore, neurotrophic factors for dopaminergic neurons are of substantial clinical interest. Fibroblast growth factor (FGF)-20 preferentially expressed in the substantia nigra pars compacta (SNPC) of the rat brain significantly enhanced the survival of midbrain dopaminergic neurons. Here we examined the mechanism of action of FGF-20 on dopaminergic neurons. FGF-20 slightly enhanced the survival of total neurons of the midbrain, indicating that it preferentially enhanced the survival of dopaminergic neurons. FGF receptor (FGFR)-1c was found to be expressed abundantly in dopaminergic neurons in the SNPC but at much lower levels in neurons of other midbrain regions by in situ hybridization. FGF-20 was also found to bind FGFR-1c with high affinity with the BIAcore system. Furthermore, FGF-20 activated the mitogen-activated protein kinase (MAPK) pathway, which is the major intracellular signaling pathway of FGFs. Both the FGFR-1 inhibitor SU5402 and the MAPK pathway inhibitor PD98059 also significantly inhibited the activation of the MAPK pathway by FGF-20 and the neurotrophic activity of FGF-20. The present findings indicate that the activation of the MAPK pathway by FGF-20 signaling through FGFR-1c plays important roles in the survival of dopaminergic neurons in the SNPC.     

Expression patterns of epidermal growth factor receptor and fibroblast growth factor receptor 1 mRNA in fetal human brain

Factors that interact with the epidermal growth factor and fibroblast growth factor receptors have numerous effects in the central nervous system (CNS), inducing the proliferation of CNS stem cells and astrocytes and the survival and differentiation of neurons. Both receptors are expressed in the embryonic rodent brain in proliferative and nonproliferative regions, suggesting roles in numerous developmental processes. However, the roles of these factors in human brain development are not known. In the current study, we examined the expression of human epidermal growth factor receptor (HEGFR) and human fibroblast growth factor receptor 1 (HFGFR1) mRNAs in the human fetal brain. The expression of both receptors is strikingly conserved relative to previously reported patterns in the rodent. In the germinal zones, the sites of cellular proliferation, HFGFR1 was expressed primarily in the ventricular zone, whereas HEGFR was expressed in the subventricular zone, suggesting different roles in CNS progenitor proliferation. Differential expression was also observed in other brain areas examined, including the hippocampus and the cerebellum. The current study suggests that HEGFR and HFGFR1 are likely to play different roles during human brain development, but that these roles will be similar to those observed in the rodent brain.     

外源性碱性成纤维细胞生长因子对缺血大鼠脑内源性碱性成纤维细胞生长因子表达的影响

目的 研究外源性碱性成纤维细胞生长因子(bFGF)缩小局灶性脑缺血梗死灶的机制。方法 用免疫组化ABC法检测在局灶性脑缺血模型上给予生理盐水或bFGF后早期生长反应蛋白-1(Egr-1)，bFGF，碱性成纤维细胞生长因子受体(bFGFR)的动态表达。结果 给药组在3h～3d各时间段梗死灶均有不同程度的缩小。对照组和给药组Egr-1表达均表现为3～6h的增强过程，但给药组更强于对照组。对照组12h见有bFGF表达增强，而bFGFR表达3h到达高峰，6h起下降，12h时bFGFR的表达已恢复至正常水平(出现了配体和受体表达时相上不匹配)。给药组bFGF表达提前且增强，3h即见有bFGF表达增强，6h时出现第一峰，从而与bFGFR 3～6h的表达增强过程相吻合。结论 外源性bFGF能缩小梗死灶，该神经保护作用是通过Egr-1蛋白高表达使内源性bFGF的表达增高且提前，从而与bFGFR的表达增强过程重叠而实现的。     

Vascular endothelial growth factor increases neurogenesis after traumatic brain injury

Activation of endogenous stem cells has been proposed as a novel form of therapy in a variety of neurologic disorders including traumatic brain injury (TBI). Vascular endothelial growth factor (VEGF) is expressed in the brain after TBI and serves as a potent activator of angiogenesis and neurogenesis. In this study, we infused exogenous VEGF into the lateral ventricles of mice for 7 days after TBI using mini-osmotic pumps to evaluate the effects on recovery and functional outcome. The results of our study show that VEGF significantly increases the number of proliferating cells in the subventricular zone and in the perilesion cortex. Fate analysis showed that most newborn cells differentiated into astrocytes and oligodendroglia and only a few cells differentiated into neurons. Functional outcome was significantly better in mice treated with VEGF compared with vehicle-treated animals after TBI. Injury size was significantly smaller at 90 days after TBI in VEGF-treated animals, suggesting additional neuroprotective effects of VEGF. In conclusion, VEGF significantly augments neurogenesis and angiogenesis and reduces lesion volumes after TBI. These changes are associated with significant improvement in recovery rates and functional outcome.     

Basic fibroblast growth factor-enhanced neurogenesis contributes to cognitive recovery in rats following traumatic brain injury

Stem/progenitor cells reside throughout the adult CNS and are actively dividing in the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampus. This neurogenic capacity of the SVZ and DG is enhanced following traumatic brain injury (TBI) suggesting that the adult brain has the inherent potential to restore populations lost to injury. This raises the possibility of developing strategies aimed at harnessing the neurogenic capacity of these regions to repair the damaged brain. One strategy is to enhance neurogenesis with mitogenic factors. As basic fibroblast growth factor (bFGF) is a potent stem cell mitogen, we set out to determine if an intraventricular administration of bFGF following TBI could affect the levels of injury-induced neurogenesis in the SVZ and DG, and the degree to which this is associated with cognitive recovery. Specifically, adult rats received a bFGF intraventricular infusion for 7 days immediately following TBI. BrdU was administered to animals daily at 2-7 days post-injury to label cell proliferation. At 1 or 4 weeks post-injury, brain sections were immunostained for BrdU and neuronal or astrocytic markers. We found that injured animals infused with bFGF exhibited significantly enhanced cell proliferation in the SVZ and the DG at 1 week post-TBI as compared to vehicle-infused animals. Moreover, following bFGF infusion, a greater number of the newly generated cells survived to 4 weeks post-injury, with the majority being neurons. Additionally, animals infused with bFGF showed significant cognitive improvement. Collectively, the current findings suggest that bFGF-enhanced neurogenesis contributes to cognitive recovery following TBI.     

Basic fibroblast growth factor in neuronal cultures of human fetal brain

The presence of basic fibroblast growth factor (bFGF) was investigated in neuronal cells derived from 12 and 18 week-old human fetal brain cultures. To this purpose, the ability of bFGF to stimulate plasminogen activator (PA) production in fetal bovine aortic endothelial GM 7373 cells was used as an assay for this molecule in neuronal cell extracts. The identity of the PA-stimulating activity of neuronal cell extract with bFGF was confirmed by its high affinity for heparin and by its cross-reactivity with polyclonal antibodies to human placental bFGF. These antibodies recognized a Mr 18,000 cell-associated protein both in Western blot and in immuno-precipitation experiments. All the neurons showed bFGF immunoreactivity, as demonstrated by immunocytochemical staining, while nonneuronal cells were unstained. The data demonstrate for the first time that cultured human fetal brain neurons contain and synthesize bFGF.     

Diversity in fibroblast growth factor receptor 1 regulation: learning from the investigation of Kallmann syndrome

The unravelling of the genetic basis of the hypogonadotrophic hypogonadal disorders, including Kallmann syndrome (KS), has led to renewed interest into the developmental biology of gonadotrophin-releasing hormone (GnRH) neurones and, more generally, into the molecular mechanisms of reproduction. KS is characterised by the association of GnRH deficiency with diminished olfaction. Until recently, only two KS-associated genes were known: KAL1 and KAL2. KAL1 encodes the cell membrane and extracellular matrix-associated secreted protein anosmin-1 which is implicated in the X-linked form of KS. Anosmin-1 shows high affinity binding to heparan sulphate (HS) and its function remains the focus of ongoing investigation, although a role in axonal guidance and neuronal migration, which are processes essential for normal GnRH ontogeny and olfactory bulb histogenesis, has been suggested. KAL2, identified as the fibroblast growth factor receptor 1 (FGFR1) gene, has now been recognised to be the underlying genetic defect for an autosomal dominant form of KS. The diverse signalling pathways initiated upon FGFR activation can elicit pleiotropic cellular responses depending on the cellular context. Signalling through FGFR requires HS for receptor dimerisation and ligand binding. Current evidence supports a HS-dependent interaction between anosmin-1 and FGFR1, where anosmin-1 serves as a co-ligand activator enhancing the signal activity, the finer details of whose mechanism remain the subject of intense investigation. Recently, mutations in the genes encoding prokineticin 2 (PK2) and prokineticin receptor 2 (PKR2) were reported in a cohort of KS patients, further reinforcing the view of KS as a multigenic trait involving divergent pathways. Here, we review the historical and current understandings of KS and discuss the latest findings from the molecular and cellular studies of the KS-associated proteins, and describe the evidence that suggests convergence of several of these pathways during normal GnRH and olfactory neuronal ontogeny.     

Anatomy of neurogenesis in the early zebrafish brain

The detailed architecture of postembryonic (i.e. secondary, as opposed to primary) neurogenesis in the zebrafish brain at 2 days postfertilization was investigated by studying expression domains of various proneural basic helix-loop-helix genes (i.e. neuroD=nrd, neurogenin1=ngn1, Zash-1b) and neurogenic genes (i.e. Notch-1a, deltaA) on the level of in situ-hybridized sectioned material and compared with brain sections of the same age immunostained for PCNA (a proliferation marker) or for Hu-proteins (marker for early neuronal differentiation). Whereas both Notch-1a and deltaA domains are present in all proliferative zones of the brain, only the more diffuse and scattered deltaA expression appears to extend additionally into the adjacent postmitotic gray matter. Zash-1b is the first achaete-scute orthologue shown here to be expressed exclusively in all proliferative central nervous zones (except for the eye). The ngn1 and nrd genes are typically both expressed in overlapping fashion in many-but not all-brain regions, with ngn1 being more restricted towards the ventricular proliferative zones and nrd extending more laterally. This fact as well as comparisons with PCNA- and Hu-immunostains indicate that a great proportion of ngn1-positive cells are mitotic, but some appear to extend into the postmitotic gray matter where the nrd-domains lie. A comparison of the relative extents of PCNA- (proliferative), nrd- (freshly determined) and Hu-positive (differentiating) cell populations allows to determine the relative maturation state of a given brain part. Similar to findings in late embryonic amniote brains, expression of nrd is absent (from 2 to 5 days) in the zebrafish subpallium, ventral preoptic region, ventral thalamus and hypothalamus. These four regions are also free of ngn1 expression (with the exception of an unusual peripheral ngn1 domain in the preoptic region), indicating that a neurogenetic network not involving nrd and ngn1 is at work there. Our characterization of locally distinct patterns and dynamics of secondary neurogenesis in the entire early (2 dpf) postembryonic zebrafish brain delivers the blueprint for more specialized functional studies.     

The complex morphology of reactive astrocytes controlled by fibroblast growth factor signaling

Astrocytes are the most abundant cell‐type of the human brain and play a variety of roles in brain homeostasis and synaptic maturation, under normal conditions. However, astrocytes undergo dramatic pathological changes in response to brain injury, such as reactive gliosis and glial scar formation. Although abnormal hypertrophy and massive proliferation of astrocytes are obvious, the molecular identity and cues that dictate the structural changes in reactive astrocytes remain unclear. This study proposes that fibroblast growth factor (FGF) signaling is responsible for making astrocyte morphology more complex and hypertrophic in response to an inflammatory stimulus such as lipopolysaccharide. Primary astrocytes isolated from perinatal brains developed more branches in the presence of FGF8 or lesser branches in the presence of FGF2. Introduction of the constitutively active form of the FGF receptor 3 (caFGFR3) into the brain increases the structural complexity, with greater glial fibrillary acidic protein level in astrocytes, while overexpression of a dominant‐negative form of FGFR3 (dnFGFR3) reduces it. Treatment of FGF8 facilitated the wound‐healing process of primary astrocytes in vitro by changing their morphology, indicating that the FGF signal may control the responsiveness of astrocytes in injury conditions. Finally, the blockade of FGF signaling by introducing dnFGFR3 at the site of reactive gliosis reduces astrocyte branch formation and minimizes hypertrophic responses during reactive gliosis. Taken together, these results indicate that FGF8–FGFR3 signaling controls structural changes in astrocytes during reactive gliosis, under pathogenic conditions. GLIA 2014;62:1328–1344     

Neuroprotective effect of acidic fibroblast growth factor on seizure-associated brain damage

Abstract

The neuroprotective effect of acidic fibroblast growth factor (aFCF) has been analysed in a rat model of seizures-associated brain damage. We report that after treatment with a convulsivant dose of Kainic acid, systemically administered aFCF prevents neuronal degeneration in specific brain areas, mainly in the hyppocampal formation. Our findings extend the potential pharmacological use of fibroblast growth factors and afford new data to understand the neurophysiology of these proteins. [Neurol Res 1994; 16: 365-369]     

经鼻给予酸性成纤维细胞生长因子对脑梗死大鼠的血管和神经再生作用

目的研究经鼻给予酸性成纤维细胞生长因子（acidic fibroblast growth factor, aFGF）对脑梗死后神经和血管再生及神经功能恢复的影响。方法健康雄性SD大鼠30只,随机分为aFGF组（n=12）、对照组（n=12）和假手术组（n=6）;aFGF组和对照组大鼠建立大脑中动脉闭塞模型,脑缺血再灌注24h后经鼻分别给予10μg aFGF（200μl）和等容积生理盐水,1次／d,连续7d;同时腹腔注射5-溴脱氧尿核苷（Bromodeoxyuridine,BrdU）50mg／kg,1次/d,连续13d;假手术组操作过程和给药与对照组相同,但不用线栓阻塞大脑中动脉;分别在术前和术后第1、7、14d采用改良神经功能评分评价大鼠神经功能改变情况,并于术后第14d经尾静脉注入异硫氰酸荧光素右旋糖酐（FITC—dextran）,采用免疫组化及激光共聚焦方法分别检测梗死灶周、室管膜下区和纹状体BrdU阳性细胞及微血管的数量。结果术后第7及14d aFGF组神经功能评分显著低于对照组;术后第14d aFGF组缺血侧室管膜下区和纹状体BrdU阳性细胞数与对照组相比均显著增高（P〈0.01）,假手术组仅见少量BrdU阳性细胞;激光共聚焦显示aFGF组梗死灶周微血管数较对照组显著增加（P〈0.05）;同时,与对照组相比经鼻给予aFGF能增加Brdu阳性细胞在血管内皮细胞中的百分比,且有统计学意义（P〈0.05）。结论经鼻给予aFGF能有效促进神经和血管再生,改善脑缺血后神经功能评分,对于治疗脑梗死具有潜在的应用前景。     

Differential induction of nerve growth factor and basic fibroblast growth factor mRNA in neonatal and aged rat brain

Stimulation of glucocorticoid or β-adrenergic receptors (BAR) has been shown to increase nerve growth factor (NGF) biosynthesis in adult rat brain. Little is known about the role of these receptors in the regulation of NGF expression in neonatal and aged brain. We have examined the effect of the synthetic glucocorticoid dexamethasone (DEX) and the BAR agonist clenbuterol (CLE) on the levels of NGF mRNA in neonatal (8 day old), adult (3 month old) and aged (24 month old) rats. By 3 h, DEX (0.5 mg/kg, s.c.) evoked a comparable increase in NGF mRNA in the cerebral cortex and hippocampus in both 8-day and 3-month-old rats. In contrast, CLE (10 mg/kg, i.p.) failed to change NGF mRNA levels in neonatal rats, while increasing (2–3-fold) NGF mRNA levels in the cerebral cortex of adult rats. In 24-month-old rats, both DEX and CLE elicited only a modest increase in NGF mRNA. This increase was, however, anatomically and temporally similar to that observed in adult animals. The weak effect of DEX or CLE was not related to a down-regulation of receptor function because both DEX and CLE were able to elicit a comparable increase in the mRNA levels for basic fibroblast growth factor (FGF2) in neonatal, adult and aged rat brain. Our data demonstrate that induction of NGF expression by neurotransmitter/hormone receptor activation varies throughout life and suggest that pharmacological agents might be useful tools to enhance trophic support in aging.     

Epigenetic regulation of neurogenesis in the adult mammalian brain

Epigenetic regulation represents a fundamental mechanism to maintain cell-type-specific gene expression during development and serves as an essential mediator to interface the extrinsic environment and the intrinsic genetic programme. Adult neurogenesis occurs in discrete regions of the adult mammalian brain and is known to be tightly regulated by various physiological, pathological and pharmacological stimuli. Emerging evidence suggests that various epigenetic mechanisms play important roles in fine-tuning and coordinating gene expression during adult neurogenesis. Here we review recent progress in our understanding of various epigenetic mechanisms, including DNA methylation, histone modifications and non-coding RNAs, as well as cross-talk among these mechanisms, in regulating different aspects of adult mammalian neurogenesis.     

Perspectives on disrupted-in-schizophrenia 1 signaling in neurogenesis

<正>New neurons are generated and integrate into existing circuitry within the hippocampal dentate gyrus and the olfactory bulb of most mammals(Gage and Temple,2013).Neurogenesis in the hippocampus persists through adulthood,and while its function and importance remains unclear,it appears to be required in the formation of specific types of     

Developmental expression of the basic fibroblast growth factor gene in rat brain.

Basic fibroblast growth factor (bFGF) is a trophic factor for a variety of neuronal/glial cell populations. The RNase protection assay, with a cRNA complementary to the coding region of bFGF mRNA, was used to investigate the brain distribution and developmental regulation of bFGF mRNA expression. In adult rats bFGF mRNA is distributed throughout the brain, the highest levels being observed in cerebral cortex, hippocampus and spinal cord. The levels of bFGF mRNA in all the brain structures are low in newborn rats, increase thereafter to reach a peak of expression around postnatal day 21. bFGF mRNA levels are significantly different between various brain structures during the first and second postnatal week. Adult and aged rats (Fisher 344) express the same levels of bFGF mRNA in the various brain regions. The onset of bFGF mRNA expression suggests that this growth factor is important for the maturation as well as for the maintenance of different cell populations of the central nervous system.