Expression of acidic fibroblast growth factor mRNA in the developing and adult rat brain

Fibroblast Growth Factor 2-Mediated Regulation of Neuronal Exosome Release Depends on VAMP3/Cellubrevin in Hippocampal Neurons

Extracellular vesicles (EVs) are endogenous membrane-derived vesicles that shuttle bioactive molecules between glia and neurons, thereby promoting neuronal survival and plasticity in the central nervous system (CNS) and contributing to neurodegenerative conditions. Although EVs hold great potential as CNS theranostic nanocarriers, the specific molecular factors that regulate neuronal EV uptake and release are currently unknown. A combination of patch-clamp electrophysiology and pH-sensitive dye imaging is used to examine stimulus-evoked EV release in individual neurons in real time. Whereas spontaneous electrical activity and the application of a high-frequency stimulus induce a slow and prolonged fusion of multivesicular bodies (MVBs) with the plasma membrane (PM) in a subset of cells, the neurotrophic factor basic fibroblast growth factor (bFGF) greatly increases the rate of stimulus-evoked MVB-PM fusion events and, consequently, the abundance of EVs in the culture medium. Proteomic analysis of neuronal EVs demonstrates bFGF increases the abundance of the v-SNARE vesicle-associated membrane protein 3 (VAMP3, cellubrevin) on EVs. Conversely, knocking-down VAMP3 in cultured neurons attenuates the effect of bFGF on EV release. The results determine the temporal characteristics of MVB-PM fusion in hippocampal neurons and reveal a new function for bFGF signaling in controlling neuronal EV release.

Neural Stem Cells, Neural Progenitors, and Neurotrophic Factors

Neural stem cells (NSCs) have been proposed as a promising cellular source for the treatment of diseases in nervous systems. NSCs can self-renew and generate major cell types of the mammalian central nervous system throughout adulthood. NSCs exist not only in the embryo, but also in the adult brain neurogenic region: the subventricular zone (SVZ) of the lateral ventricle. Embryonic stem (ES) cells acquire NSC identity with a default mechanism. Under the regulations of leukemia inhibitory factor (LIF) and fibroblast growth factors, the NSCs then become neural progenitors. Neurotrophic and differentiation factors that regulate gene expression for controlling neural cell fate and function determine the differentiation of neural progenitors in the developing mammalian brain. For clinical application of NSCs in neurodegenerative disorders and damaged neurons, there are several critical problems that remain to be resolved: 1) how to obtain enough NSCs from reliable sources for autologous transplantation; 2) how to regulate neural plasticity of different adult stem cells; 3) how to control differentiation of NSCs in the adult nervous system. In order to understand the mechanisms that control NSC differentiation and behavior, we review the ontogeny of NSCs and other stem cell plasticity of neuronal differentiation. The role of NSCs and their regulation by neurotrophic factors in CNS development are also reviewed.

Long-Term Estrogen Receptor Beta Agonist Treatment Modifies the Hippocampal Transcriptome in Middle-Aged Ovariectomized Rats

Estradiol (E2) robustly activates transcription of a broad array of genes in the hippocampal formation of middle-aged ovariectomized rats via estrogen receptors (ERα, ERβ, and G protein-coupled ER). Selective ERβ agonists also influence hippocampal functions, although their downstream molecular targets and mechanisms are not known. In this study, we explored the effects of long-term treatment with ERβ agonist diarylpropionitrile (DPN, 0.05 mg/kg/day, sc.) on the hippocampal transcriptome in ovariectomized, middle-aged (13 month) rats. Isolated hippocampal formations were analyzed by Affymetrix oligonucleotide microarray and quantitative real-time PCR. Four hundred ninety-seven genes fulfilled the absolute fold change higher than 2 (FC > 2) selection criterion. Among them 370 genes were activated. Pathway analysis identified terms including glutamatergic and cholinergic synapse, RNA transport, endocytosis, thyroid hormone signaling, RNA degradation, retrograde endocannabinoid signaling, and mRNA surveillance. PCR studies showed transcriptional regulation of 58 genes encoding growth factors (Igf2, Igfb2, Igf1r, Fgf1, Mdk, Ntf3, Bdnf), transcription factors (Otx2, Msx1), potassium channels (Kcne2), neuropeptides (Cck, Pdyn), peptide receptors (Crhr2, Oprm1, Gnrhr, Galr2, Sstr1, Sstr3), neurotransmitter receptors (Htr1a, Htr2c, Htr2a, Gria2, Gria3, Grm5, Gabra1, Chrm5, Adrb1), and vesicular neurotransmitter transporters (Slc32a1, Slc17a7). Protein-protein interaction analysis revealed networking of clusters associated with the regulation of growth/troph factor signaling, transcription, translation, neurotransmitter and neurohormone signaling mechanisms and potassium channels. Collectively, the results reveal the contribution of ERβ-mediated processes to the regulation of transcription, translation, neurogenesis, neuromodulation, and neuroprotection in the hippocampal formation of ovariectomized, middle-aged rats and elucidate regulatory channels responsible for DPN-altered functional patterns. These findings support the notion that selective activation of ERβ may be a viable approach for treating the neural symptoms of E2 deficiency in menopause.

Implementing neuronal plasticity in NeuroAIDS: the experience of brain-derived neurotrophic factor and other neurotrophic factors

Human immunodeficiency virus type-1 (HIV) causes mild or severe neurological problems, termed HIV-associated neurocognitive disorder (HAND), even when HIV patients receive antiretroviral therapy. Thus, novel adjunctive therapies are necessary to reduce or abolish the neurotoxic effect of HIV. However, new therapies require a better understanding of the molecular and cellular mechanisms of HIV-induced neurotoxicity. HAND subjects are characterized by being profoundly depressed, and they experience deficits in memory, learning and movements. Experimental evidence has also shown that HIV reduces neurogenesis. These deficits resemble those occurring in premature brain aging or in a brain with impaired neural repair properties. Thus, it appears that HIV diminishes neuronal survival, along with reduced neuronal connections. These two phenomena should not occur in the adult and developing brain when synaptic plasticity is promoted by neurotrophic factors, polypeptides that are present in adult synapses. This review will outline experimental evidence as well as present emerging concepts for the use of neurotrophic factors and in particular brain-derived neurotrophic factor as an adjunct therapy to prevent HIV-mediated neuronal degeneration and restore the loss of synaptic connections.

Fibroblast growth factor signaling in the developing neuroendocrine hypothalamus

Fibroblast growth factor (FGF) signaling is pivotal to the formation of numerous central regions. Increasing evidence suggests FGF signaling also directs the development of the neuroendocrine hypothalamus, a collection of neuroendocrine neurons originating primarily within the nose and the ventricular zone of the diencephalon. This review outlines evidence for a role of FGF signaling in the prenatal and postnatal development of several hypothalamic neuroendocrine systems. The emphasis is placed on the nasally derived gonadotropin-releasing hormone neurons, which depend on neurotrophic cues from FGF signaling throughout the neurons' lifetime. Although less is known about neuroendocrine neurons derived from the diencephalon, recent studies suggest they also exhibit variable levels of dependence on FGF signaling. Overall, FGF signaling provides a broad spectrum of cues that ranges from genesis, cell survival/death, migration, morphological changes, to hormone synthesis in the neuroendocrine hypothalamus. Abnormal FGF signaling will deleteriously impact multiple hypothalamic neuroendocrine systems, resulting in the disruption of diverse physiological functions.

Expression and Functions of Fibroblast Growth Factor 2 (FGF-2) in Hippocampal Formation

Among the 23 members of the fibroblast growth factor (FGF) family, FGF-2 is the most abundant one in the central nervous system. Its impact on neural cells has been profoundly investigated by in vitro and in vivo studies as well as by gene knockout analyses during the past 2 decades. Key functions of FGF-2 in the nervous system include roles in neurogenesis, promotion of axonal growth, differentiation in development, and maintenance and plasticity in adulthood. From a clinical perspective, its prominent role for the maintenance of lesioned neurons (e.g., ischemia and following transection of fiber tracts) is of particular relevance. In the unlesioned brain, FGF-2 is involved in synaptic plasticity and processes attributed to learning and memory. The focus of this review is on the expression of FGF-2 and its receptors in the hippocampal formation and the physiological and pathophysiological roles of FGF-2 in this region during development and adulthood.

High-level expression and purification of Tat-haFGF19-154

Human acidic fibroblast growth factor (haFGF) stimulates repair and regeneration of central and peripheral nerves after various injuries. However, it is unable to cross the blood-brain barrier (BBB). To produce a therapeutic haFGF with cell-permeable activity, we fused the haFGF(19-154) gene with Tat-PTD. After its construction by a single-step insertion of a polymerase chain reaction (PCR)-amplified coding sequence, the vector pTat-haFGF(19-154)-His was expressed in Escherichia coli BL21 (DE3) cells. The optimal expression level of the soluble fusion protein was up to 36.7% of the total cellular protein. The recombinant Tat-haFGF(19-154)-His was purified by a combination of Ni-NTA affinity, Sephadex G-25, and heparin affinity chromatography to 95% as detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The final yield was 171 mg/l culture. Purified Tat-haFGF(19-154)-His had distinct mitogenic activity in Balb/c 3T3 cells, as measured by methylthiazoletetrazolium (MTT) assay and its ED(50) was 3.931 x 10(-4) micromol/l. Tat-haFGF(19-154)-His protein intravenously injected at the dose of 10 mg/kg could be detected in the pallium and hippocampi.

Fibroblast growth factor blocks Sonic hedgehog signaling in neuronal precursors and tumor cells

The Sonic hedgehog (Shh) and FGF signaling pathways regulate growth and differentiation in many regions of the nervous system, but interactions between these pathways have not been studied extensively. Here, we examine the relationship between Shh and FGF signaling in granule cell precursors (GCPs), which are the most abundant neural progenitors in the cerebellum and the putative cell of origin for the childhood brain tumor medulloblastoma. In these cells, Shh induces a potent proliferative response that is abolished by coincubation with basic FGF. FGF also inhibits transcription of Shh target genes and prevents activation of a Gli-responsive promoter in fibroblasts, which suggests that it blocks Shh signaling upstream of Gli-mediated transcription. FGF-mediated inhibition of Shh responses requires activation of FGF receptors and of ERK and JNK kinases, because it can be blocked by inhibitors of these enzymes. Finally, FGF promotes differentiation of GCPs in vitro and in vivo and halts proliferation of tumor cells from patched (ptc) mutant mice, a model for medulloblastoma. These findings suggest that FGF is a potent inhibitor of Shh signaling and may be a useful therapy for tumors involving activation of the hedgehog pathway.

Neurotrophic factors and amyotrophic lateral sclerosis

The cause of motor neuron death in amyotrophic lateral sclerosis (ALS) remains a mystery. Initial implications of neurotrophic factor impairment involved in disease progression causing selective motor neuron death were brought forward in the late 1980s. These implications were based on several in vitro studies of motor neuron cultures in which a near to complete rescue of axotomized neonatal motor neurons in the presence of supplementary neurotrophic factors were revealed. These findings pawed the way for extensive investigations in experimental animal models of ALS. Neurotrophic factor administration in rodent ALS models demonstrated a remarkable effect on survival of degenerating motor neurons and rescue of axotomized motor neurons, both in vivo and in vitro. In the absence of efficient therapy for ALS, some of these promising neurotrophic factors have been administered to groups of ALS patients, as they appeared available for clinical trials. Up to date, none of tested factors has lived up to expectations, altering the outcome of the disease. This review summarizes current findings on neurotrophic factor expression in ALS tissue and these factors' potential/debatable clinical relevance to ALS and the treatment of ALS. It also discusses possible interventions improving clinical trial design to obtain efficacy of neurotrophic factor treatment in patients suffering from ALS.

Fibroblast growth factor 1 is produced prior to apolipoprotein E in the astrocytes after cryo-injury of mouse brain

We recently reported that fibroblast growth factor 1 (FGF-1) upregulates apolipoprotein E (apoE) synthesis and its secretion as high density lipoprotein (HDL) in cultured astrocytes potentially by an autocrine or paracrine mechanism [Biochim. Biopys. Acta 1589 (2002) 261]. In order to examine pathophysiological relevance of this reaction, we studied association of the production of FGF-1 and apoE in the post-injury mouse brain. After the spot-injury of the brain by liquid nitrogen, the surface size of the wound shrunk more rapidly in the C57BL/6 wild-type mice than the apoE-knock out C57BL/6 mice. Immunohistochemical analysis of the lesions revealed that production of FGF-1 was identified in the reactive astrocytes by the day 2 after the injury in both types of mouse, prior to the production of apoE confirmed by the day 4 in the wild-type. These findings were consistent with our in-vitro observations and hypothesis that FGF-1 upregulates apoE synthesis and subsequently HDL production in the reactive astrocytes by an autocrine or paracrine manner. FGF-1 thus would exert its effect after the CNS damage through apoE secretion.

Cyclic AMP/protein kinase a signal attenuates Ca2+-induced fibroblast growth factor-1 synthesis in rat cortical neurons

Fibroblast growth factor (FGF)-1 is increased in particular brain regions after birth, suggesting an involvement of some regulatory neuronal circuits. To address the neuronal activity responsible for FGF-1 synthesis, effects of various neurotransmitter receptor activation on cellular FGF-1 content were examined using cultured rat cortical neurons. Histamine, glutamate, carbachol, serotonin or gamma-aminobutyric acid (GABA) caused an increase of FGF-1 content. Because this effect was mimicked by (1) N-methyl-D-aspartate, a glutamatergic agonist; (2) Ca(2+) ionophore; (3) depolarization with high concentration of KCl, but was abolished in Ca(2+)-free medium, Ca(2+) influx was thought to trigger FGF-1 synthesis. Such Ca(2+)-mediated enhancement of FGF-1 synthesis, however, did not occur in the presence of norepinephrine (NE), but was restored by KT-5720, an inhibitor of protein kinase A (PKA), suggesting an interplay between Ca(2+)-activated and cAMP/PKA signals for neuronal FGF-1 synthesis. This mechanism was proved to function in vivo by stimulation of FGF-1 expression in neurons of the cerebral cortex after intracerebral administration of propranolol, an antagonist of adrenergic beta receptors. This demonstrates that FGF-1 synthesis is essentially upregulated by Ca(2+) influx through excitatory neuronal activities, but such an effect is abolished by neurotransmission that evokes cAMP/PKA signals. FGF-1 produced is thought to act on establishment and maintenance of particular neuronal circuits in the brain, which may be one of the ways neurotransmitters regulate brain function.

Fibroblast growth factors as regulators of central nervous system development and function

Fibroblast growth factors (FGFs) are multifunctional signaling proteins that regulate developmental processes and adult physiology. Over the last few years, important progress has been made in understanding the function of FGFs in the embryonic and adult central nervous system. In this review, I will first discuss studies showing that FGF signaling is already required during formation of the neural plate. Next, I will describe how FGF signaling centers control growth and patterning of specific brain structures. Finally, I will focus on the function of FGF signaling in the adult brain and in regulating maintenance and repair of damaged neural tissues.

An acidic fibroblast growth factor-like factor secreted into the brain cell culture medium upregulates apoE synthesis, HDL secretion and cholesterol metabolism in rat astrocytes

Production and release of apolipoprotein (apo) E and cholesterol were highly upregulated in the astrocytes prepared by 1-week secondary culture after 1-month primary culture of rat fetal brain cells (M/W cells) in comparison to the cells prepared by a conventional method of 1-week primary and 1-week secondary culture (W/W cells). Both cell preparations were mostly composed of astrocytes with small population of other glial cells, except that type-2 astrocyte-like cells accounted for 5-15% of M/W cells indicating more activated and/or matured status. The conditioned medium of the 1-month primary culture stimulated W/W cells to increase the release of apoE and cholesterol into the medium. The treatment of W/W cells by acidic fibroblast growth factor (aFGF) similarly upregulated biosyntheses and release of apoE and cholesterol. The effect of the conditioned medium was completely inhibited by pretreatment with an anti-aFGF antibody. The increase of the aFGF message was demonstrated in the brain cells after 1-month primary culture. The findings suggested that an aFGF-like trophic factor upregulates biosynthesis and secretion of apoE-high density lipoprotein (HDL) in astrocytes probably by autocrine stimulation in this culture system. Since this cytokine is highly expressed in the development or post-injury period of the brain, it putatively activates intercellular cholesterol transport to support construction or recovery of the brain.

Acidic fibroblast growth factor (FGF-1) in the anterior horn cells of ALS and control cases

The expression and localization of acidic fibroblast growth factor (aFGF; FGF-1) were examined in the spinal cord of patients with amyotrophic lateral sclerosis (ALS) and controls by reverse transcription-polymerase chain reaction (RT-PCR) method and immunohistochemistry. The RT-PCR experiments demonstrated that aFGF amplification products were clearly detected in all control cases but could be scarcely seen in ALS patients. aFGF immunoreactivity was detected in the anterior horn cells of the spinal cord. Double immunostaining for aFGF and choline acetyltransferase revealed that the majority (95.9%) of cholinergic neurons expressed aFGF. In ALS cases, the number and the staining intensity of aFGF-positive neurons were markedly decreased. These results suggest that aFGF is involved in ALS pathology.

Extensive neuronal localization and neurotrophic function of fibroblast growth factor 8 in the nervous system

Fibroblast growth factor (FGF) 8 has been well established to play a critical role in the early development of the central nervous system (CNS). We report here extensive neuronal localization and neurotrophic function of FGF8 in the nervous system. In sections of mouse embryos at E10.5, FGF8 was immunohistochemically found in neurons at the marginal zones of the CNS and in the dorsal root ganglia (DRG). Neuronal localization of FGF8 was marked at later embryonic stages and in adults, involving most of the central and peripheral neurons, including intermuscular enteric neurons, DRGs, and paraaortic sympathetic ganglia. Functionally, FGF8 promoted neurite outgrowth in human neuroblastoma SK-N-MC cells as well as in rat pheochromocytoma PC12 cells, suggesting that FGF8 acts as a neurotrophic factor. FGF8 also supported neuronal survival and differentiation in cultured human neural progenitor cells. In a cell growth assay, treatment with 50 ng/ml FGF8 on human cultured neuroblastoma SK-N-MC and IMR32 cells attenuated the growth of both. In accordance with these in vitro findings, the immunohistochemical analysis on human neurological diseases showed that FGF8 expression is evident in differentiating histological types of neuroblastoma and ganglioneuroblastoma, and that the levels of FGF8 immunoreactivity in the substantia nigra from Parkinson's disease are significantly lower than those in age-matched controls. Taken together, the present findings strongly suggest that FGF8 acts as a more generalized neurotrophic factor than previously reported.

BMP-2 augments FGF-induced differentiation of PC12 cells through upregulation of FGF receptor-1 expression

When exposed to various neurotrophic factors, including fibroblast growth factors (FGF)-1 and -2, rat pheochromocytoma-derived PC12 cells differentiate into sympathetic neuron-like cells possessing elongated neurites. We found that while bone morphogenetic protein-2 (BMP-2) exerted little effect by itself on the differentiation of PC12 cells, in combination with FGF it strongly induced neurite outgrowth, even at subthreshold concentrations of FGF. Analysis of gene expression revealed that FGF receptor-1 (FGFR-1) mRNA was abundantly expressed in PC12 cells and that its expression was upregulated by pretreating the cells with BMP-2. Crosslinking the receptors with (125)I-FGF-2 and then immunoprecipitating them confirmed that expression of FGFR-1, but not other FGF receptor types, was enhanced by BMP-2. Furthermore, Scatchard analyses revealed that the numbers of FGF-2 binding sites were increased by approximately 40% after BMP-2 treatment. Pretreatment with BMP-2 also enhanced peak and sustained levels of FGF-induced ERK1/2 phosphorylation in PC12 cells. Finally, the augmentation of neurotrophic activity by BMP-2 was inhibited by SU5402, an FGFR-1 inhibitor. These findings indicate that BMP-2 augments FGF-induced differentiation of PC12 cells through selective upregulation of FGFR-1 expression, and suggest that BMP-2 and FGF act in concert to regulate cell differentiation in the nervous system.

Detection of spatial localization of Hst-1/Fgf-4 gene expression in brain and testis from adult mice

HST-1, a member of the fibroblast growth factor (FGF) family (FGF-4), has been shown to be a signaling molecule whose expression is essential for embryonic development. However, HST-1/FGF-4 expression has not been detected or reported in adult tissues so far analysed. To investigate whether there is a possible role of HST-1/FGF-4 in adult stage, we have carried out a highly sensitive RT-PCR analysis of Hst-1/Fgf-4 gene expression in adult mice tissues. Results show Hst-1/Fgf-4 gene expression in the nervous system, intestines, and testis of normal adult mice. In situ hybridization technique was used to localize Hst-1/Fgf-4 gene expression in the cerebellum and testis from 10-week-old mice. Cell type-specific gene expression was detected: Purkinje cells in the cerebellum and Sertoli cells in testis. These findings suggest that the Hst-1/Fgf-4 gene also plays an important role in adult tissues, and may offer insights into the biological significance of HST-1/FGF-4 in cerebellar and testicular functions.

Phosphorylation of mitogen-activated protein kinase is altered in neuroectodermal cells overexpressing the human amyloid precursor protein 751 isoform

The aberrant expression or processing of the amyloid precursor protein (APP) is the only known genetic basis for presenile familial Alzheimer's disease, and the molecular connection between APP and tau has been perplexing. Attention has focused on proline-directed serine/threonine kinases as mediating the cytoskeletal modifications of Alzheimer's disease, and we show that overexpression of APP can influence the activation of a candidate kinase, the mitogen-activated protein kinase (MAPK). In murine embryonal carcinoma cells stably transfected with the human 751 isoform of APP, we observed steady-state hyperactivation of p42(MAPK) concomitant with APP overexpression 3 days after neuroectodermal differentiation. In more mature differentiated cells, immunocytochemical analysis revealed enhanced basal somatic and nuclear immunoreactivity for phosphorylated MAPK coupled with an attenuated phosphorylation response to growth factor stimulation. Our results suggest that APP can influence the MAPK signaling pathway in such a way that the absolute and time-dependent activation required for discrimination of the appropriate downstream response are compromised. Such an effect would have important consequences for the functioning of cells coincidentally expressing both proteins, a situation that occurs in neuronal populations vulnerable to Alzheimer's disease pathology.

In vivo actions of fibroblast growth factor-2 and insulin-like growth factor-I on oligodendrocyte development and myelination in the central nervous system

The in vivo effects of fibroblast growth factor-2 (FGF-2) and insulin-like growth factor-I (IGF-I) on oligodendrocytes and CNS myelination were determined in the postnatal rat anterior medullary velum (AMV) following injection of both cytokines into the cerebrospinal fluid. Either FGF-2, IGF-I, or saline were administered via the lateral ventricle, twice daily commencing at postnatal day (P) 6. At P9, AMV were immunohistochemically labeled with the Rip antibody, to enable analysis of the numbers of myelin sheaths and of promyelinating and myelinating oligodendrocytes; promyelinating oligodendrocytes are a recognisable immature phenotype which express myelin-related proteins prior to forming myelin sheaths. In parallel experiments, AMV were treated for Western blot analysis to determine relative changes in expression of the myelin proteins 2', 3'-cyclic nucleotide 3'-phosphohydrolase (CNP) and myelin oligodendrocyte glycoprotein (MOG), which, respectively, characterise early and late stages of myelin maturation. In FGF-2-treated AMV, the number of promyelinating oligodendrocytes increased by 87% compared to saline-injected controls. The numbers of myelinating oligodendrocytes and myelin sheaths were not decreased, but conspicuous unmyelinated gaps within fibre tracts were indications of retarded myelination following FGF-2 treatment. Western blot analysis demonstrated decreased expression of CNP and a near-total loss of MOG, confirming that FGF-2 decreased myelin maturation. In contrast, IGF-I had no effect on the number of promyelinating oligodendrocytes, but increased the numbers of myelinating oligodendrocytes and myelin sheaths by 100% and 93%, respectively. Western blot analysis showed that the amount of CNP was increased following IGF-I treatment, correlating with the greater number of oligodendrocytes, but that MOG expression was lower than in controls, suggesting that the increased number of myelin sheaths in IGF-I was not matched by increased myelin maturation. The results provide in vivo evidence that FGF-2 and IGF-I control the numbers of oligodendrocytes in the brain and, respectively, retard and promote myelination.

Regulation of tyrosine hydroxylase gene expression during transdifferentiation of striatal neurons: changes in transcription factors binding the AP-1 site

We have shown previously that the synergistic interaction of acidic fibroblast growth factor (aFGF) and a coactivator (dopamine, protein kinase A, or protein kinase C activator) will induce the novel expression of tyrosine hydroxylase (TH) in neurons of the developing striatum. In this study we sought to determine whether, concomitant with TH expression, there were unique changes in transcription factors binding the AP-1 regulatory element on the TH gene. Indeed, we found a significant recruitment of proteins into TH-AP-1 complexes as well as a shift from low- to high-affinity binding. Supershift experiments further revealed dramatic changes in the proteins comprising the AP-1 complexes, including recruitment of the transcriptional activators c-Fos, a novel Fos protein, Fos-B, and Jun-D. Concomitantly, there was a decrease in repressor-type factors ATF-2 and CREM-1. aFGF appeared to play a central but insufficient role, requiring the further participation of at least one of the coactivating substances. Experiments examining the signal transduction pathway involved in mediating these nuclear events demonstrated that the presence of only an FGF (1, 2, 4, 9) competent to induce TH caused the phosphorylation of mitogen-activated protein kinase (MAPK). Moreover, the treatment of cells with MEK/ERK inhibitors (apigenin or PD98059) eliminated TH expression and the associated AP-1 changes, suggesting that MAPK was a critical mediator of these events. We conclude that, during transdifferentiation, signals may be transmitted via MAPK to the TH-AP-1 site to increase activators and reduce repressors, helping to shift the balance in favor of TH gene expression at this and possibly other important regulatory sites on the gene.

Impaired cerebral cortex development and blood pressure regulation in FGF-2-deficient mice

Fibroblast growth factor-2 (FGF-2) has been implicated in various signaling processes which control embryonic growth and differentiation, adult physiology and pathology. To analyze the in vivo functions of this signaling molecule, the FGF-2 gene was inactivated by homologous recombination in mouse embryonic stem cells. FGF-2-deficient mice are viable, but display cerebral cortex defects at birth. Bromodeoxyuridine pulse labeling of embryos showed that proliferation of neuronal progenitors is normal, whereas a fraction of them fail to colonize their target layers in the cerebral cortex. A corresponding reduction in parvalbumin-positive neurons is observed in adult cortical layers. Neuronal defects are not limited to the cerebral cortex, as ectopic parvalbumin-positive neurons are present in the hippocampal commissure and neuronal deficiencies are observed in the cervical spinal cord. Physiological studies showed that FGF-2-deficient adult mice are hypotensive. They respond normally to angiotensin II-induced hypertension, whereas neural regulation of blood pressure by the baroreceptor reflex is impaired. The present genetic study establishes that FGF-2 participates in controlling fates, migration and differentiation of neuronal cells, whereas it is not essential for their proliferation. The observed autonomic dysfunction in FGF-2-deficient adult mice uncovers more general roles in neural development and function.

A splice variant of E2-2 basic helix-loop-helix protein represses the brain-specific fibroblast growth factor 1 promoter through the binding to an imperfect E-box

We previously demonstrated that a cis-element (-489 to -467) in the brain-specific fibroblast growth factor (FGF)-1 promoter (FGF-1.B) binds multiple nuclear factors, and this binding enhances transcriptional activity of this promoter. Here we report the isolation of three cDNA clones, VL1, VL2 and VL3, from a human brain stem cDNA expression library using four tandem repeats of the 26-base pair sequence (-492 to -467) as the probe. These cDNA clones represent the variant of bHLH protein E2-2/SEF2-1 in having 12 additional nucleotides encoding the amino acids RSRS. The glutathione S-transferase (GST) fusion proteins of VLl, VL2, and VL3 immunologically react with anti-E2-2 antibody and anti-GST-VL2 antibody. Electrophoretic mobility shift assay and methylation interference assay revealed that the GST fusion proteins specifically bind to an imperfect E-box sequence (GACCTG) present in the 26-base pair sequence. Transient expression of the full-length E2-2 without RSRS in U1240MG glioblastoma cells resulted in repression of FGF-1.B promoter activity. We further showed a significant repression of promoter activity (>40 fold) by E2-2 (lacking the amino acid sequence RSRS) when the E47 reporter construct, containing a hexameric E-box site, was used. In contrast, the E2-2 variant containing the RSRS sequence has no significant effect on either the FGF-1 promoter or E47 promoter. These results suggest that the relative abundance of the two splice variants of E2-2 in brain could be an important determinant for the expression of FGF-1.

Identification and characterization of a novel member of the fibroblast growth factor family

A new member of the fibroblast growth factor (FGF) family, FGF-13, has been molecularly cloned as a result of high throughput sequencing of a human ovarian cancer cell library. The open reading frame of the novel human gene (1419 bp) encodes for a protein of 216 a.a. with a molecular weight of 22 kDa. The FGF-13 sequence contains an amino-terminal hydrophobic region of 23 a.a. characteristic of a signal secretion sequence. FGF-13 is most homologous, 70% similarity at the amino acid level, to FGF-8. Northern hybridization analysis demonstrated prominent expression of FGF-13 in human foetal and adult brain, particularly in the cerebellum and cortex. In proliferation studies with BaF3 cells, FGF-13 preferentially activates cell clones expressing either FGF receptor variant, 3-IIIc or 4. The signal transduction pathways of FGF-13 and FGF-2 were compared in rat hippocampal astrocytes. The two FGFs induce an equivalent level of tyrosine phosphorylation of mitogen-activated protein kinase (MAPK) and c-raf activation. However, FGF-13 is more effective than FGF-2 in inducing the phosphorylation of phospholipase C-gamma (PLC-gamma). Treatment of neuronal cultures from rat embryonic cortex with FGF-13 increases the number of glutamic acid decarboxylase immunopositive neurons, the level of high-affinity gamma-aminobutyric acid (GABA) uptake, and choline acetyltransferase enzyme activity. The GABAergic neuronal response to FGF-13 treatment is rapid with a significant increase occurring within 72 h. We have identified a novel member of the FGF family that is expressed in the central nervous system (CNS) and increases the number as well as the level of phenotypic differentiation of cortical neurons in vitro.

Acute intermittent nicotine treatment produces regional increases of basic fibroblast growth factor messenger RNA and protein in the tel- and diencephalon of the rat

Several findings show a neuroprotective effect of nicotine treatment in different experimental models, and a negative correlation has been observed between cigarette smoking and the incidence of Parkinson's disease. It seems possible that nicotine may in part exert its neuroprotective actions by favouring the synthesis of neurotrophic factors. The aim of this study was to determine whether the nicotine treatment could be associated with the induction of a neurotrophic factor in brain regions with nicotinic receptors. Thus, we analysed by in situ hybridization and RNAse protection assay the effects of (-)nicotine on basic fibroblast growth factor messenger RNA and by immunocytochemistry fibroblast growth factor-2 protein in the tel- and diencephalon of rats following single or acute intermittent (-)nicotine treatment. The present results showed that acute intermittent (-)nicotine treatment (four i.p. injections at intervals of 30 min), but not single injections, lead to a substantial and dose-related (0.1-2 mg/kg) up-regulation of fibroblast growth factor-2 messenger RNA levels in the cerebral cortex, in the hippocampus, in the striatum and ventral midbrain. This induction of fibroblast growth factor-2 expression peaked 4 h after the first injection and returned to normal levels within 24 h. The change of fibroblast growth factor-2 messenger RNA levels was associated with increased fibroblast growth factor-2 immunoreactivity mainly localized to nerve cells. The treatment was effective also when repeated in the same animals three or five days after the first injection. The pre-treatment with the non-competitive (-)nicotine receptor antagonist mecamylamine blocked the (-)nicotine effects on fibroblast growth factor-2 messenger RNA levels. In the above areas, no changes were observed in the fibroblast growth factor-1, 2 and 3 receptor messenger RNA levels nor in brain-derived neurotrophic factor messenger RNA levels. The present data indicate an ability of intermittent (-)nicotine to increase fibroblast growth factor-2 in many tel- and diencephalic areas. In view of the trophic function of fibroblast growth factor-2, the previously observed neuroprotective effects of (-)nicotine may at least in part involve an activation of the neuronal fibroblast growth factor-2 signalling, and open up new avenues for treatment of Parkinson's disease and Alzheimer's disease based on the existence of nicotinic receptor subtypes enhancing fibroblast growth factor-2 signalling in many regions of the tel- and diencephalon.

Novel receptor protein tyrosine phosphatase (RPTPrho) and acidic fibroblast growth factor (FGF-1) transcripts delineate a rostrocaudal boundary in the granule cell layer of the murine cerebellar cortex

We have identified a novel receptor-like protein tyrosine phosphatase (RPTPrho) transcript whose expression in the cerebellar cortex is restricted to the granule cell layer of lobules 1-6. Acidic fibroblast growth factor (FGF-1) mRNA follows a similar cerebellar expression pattern. Together, the two markers define a sharp boundary in lobule 6, slightly caudal to the primary fissure. Anterior and posterior compartments became discernible only during postnatal weeks two and six, for RPTPrho and FGF-1, respectively. A rostrocaudal boundary in lobule 6 of the murine cerebellar cortex has also been identified morphologically by the effects of the meander tail mutation. The position of the RPTPrho and FGF-1 boundary on the rostrocaudal axis of the cerebellar cortex was close to, but not coincident with, the caudal extent of the disorganized anterior lobe of meander tail and the rostral extent of Otx-2 expression. The restricted pattern of FGF-1 and RPTPrho implies that these molecules may have specific signaling roles in the tyrosine phosphorylation/dephosphorylation pathway in the anterior compartment of the adult cerebellar cortex.

Changing responsiveness of developing midbrain dopaminergic neurons for extracellular growth factors

Numerous purified growth factors as well as yet-unidentified neurotrophic activities within mesencephalic glia support the survival of dopaminergic neurons. To further characterize the functional role of these multiple growth factor influences in dopaminergic cell development, various purified growth factors as well as mesencephalic glial-conditioned medium (CM) were screened for effects on dopaminergic cell survival and glial numbers in serum-free low density cultures of the dissociated embryonic day (E) 15 and E17 rat mesencephalon. In E15 mesencephalic cultures, dopaminergic cell survival increased with brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), basic fibroblast growth factor (bFGF), transforming growth factor alpha (TGFalpha), insulin-like growth factor-1 (IGF-1), platelet-derived growth factor-BB (PDGF-BB), and interleukin-6 (IL-6). bFGF, TGFalpha, PDGF, and IL-6 also stimulated glial proliferation as demonstrated by autoradiographic labeling for 3H-thymidine. Moreover, CM derived from the mesencephalic glial cell line Mes42 completely prevented the death of E15 dopaminergic neurons within the initial days of cultivation. In E17 mesencephalic cultures, survival-promoting effects on dopaminergic neurons were present with BDNF, GDNF, and bFGF. TGFalpha, IGF-1, PDGF-BB, and IL-6 stimulated glial proliferation but did not affect dopaminergic cell survival. Similarly, mesencephalic glial-CM completely failed to support the survival of E17 dopaminergic neurons. These observations demonstrate that during embryonic development, dopaminergic cell survival sequentially depends on distinct sets of growth factors. The concomitant loss of sensitivity of developing dopaminergic neurons for mesencephalic glial-CM as well as TGFalpha, IGF-1, PDGF-BB, and IL-6 further provides evidence that these growth factors indirectly affect early dopaminergic neurons through glial-mediated processes and suggests a crucial role of glia during the initial stages of neuronal development.

Neuronal localization of fibroblast growth factor-9 immunoreactivity in human and rat brain

Fibroblast growth factor-9 (FGF-9) is a relatively new member of the FGF family isolated from the conditioned medium of a human glioblastoma cell line as a secreting-type factor that exhibits a growth-stimulating effect on cultured glial cells. In order to elucidate the roles of FGF-9 in the central nervous system, we investigated in detail the distribution of FGF-9 proteins in the normal human and rat brains by immunohistochemistry using two different antibodies specific to FGF-9. In both human and rat, a strong expression of FGF-9 immunoreactivity was localized mainly in neurons throughout the normal brain. Immunoreactive glial cells were rarely encountered. In the human brain, strong and uniform immunoreactivity was observed in neurons of cerebral cortex, hippocampus, substantia nigra, motor nuclei of the brainstem, and Purkinje cell layer. A detailed mapping in the rat brain showed a distribution of FGF-9 immunoreactivity in a widespread population of neurons, though the intensity varied between different locations and even among the same nucleus. The most prominent expression in rat was observed in neurons of the mitral cell layer of the olfactory bulb, red nucleus, mesencephalic trigeminal nucleus, motor trigeminal nucleus, facial nucleus, reticular nucleus and Purkinje cell layer. These findings suggest that FGF-9 plays an important role in the central nervous system and may have a potential function closely connected to neurons in the normal brain.

Transcriptional activation of fibroblast growth factor 1.B promoter is mediated through an 18-base pair cis-acting element

Four different transcripts encoding fibroblast growth factor 1 (FGF-1, also known as aFGF) have been previously identified in our laboratory. Among them, FGF-1.B is the major transcript expressed specifically in the neuronal cells in brain tissue. Using the transient transfection experiment in a glioblastoma cell line, U1240MG, that expresses 1.B, we previously identified two regulatory regions (RR1 and RR2) in the brain-specific promoter, FGF-1.B. In the present study, we showed that the minimal region required for the DNA-protein interaction in RR2 resides in an 18-base pair (-484 to -467) sequence, by using DNase I footprinting and methylation interference studies and electrophoretic mobility shift assays. This minimal cis-acting element was found to be sufficient in enhancing the reporter activity driven by the heterologous herpes simplex virus thymidine kinase promoter in the 1.B-positive U1240MG cell line. This enhancing effect, however, was not detected in a glioblastoma cell line, U1242MG, which is negative for 1.B expression. By electrophoretic mobility shift assays, we also identified a specific DNA-protein complex, namely complex I, which is specific for 1.B-positive cell lines and human brain tissue. By in situ UV cross-linking experiment, we further showed that complex I contains two major DNA-binding proteins of apparent molecular masses of 37 and 98 kDa. Our results suggest that the formation of complex I, resulting from the heterodimerization of a 37-kDa protein (1.B-specific) and a 98-kDa protein (ubiquitous) may likely be a prerequisite for the enhanced expression of 1.B transcript in neuronal cells.

Nitric oxide and fibroblast growth factor in autonomic nervous system: short- and long-term messengers in autonomic pathway and target-organ control

The freely diffusible messenger nitric oxide (NO), generated by NO synthase (NOS)-containing "nitroxergic" (NO-ergic) neurons, is unique among classical synaptic chemical transmitters because of its "non-specificity", molecular "NO-receptors" (e.g. guanylyl cyclase, iron complexes, nitrosylated proteins or DNA) in target cells, intracellular targeting, regulated biosynthesis, and growth factor/cytokine-dependence. In the nervous system, expression of NOS is particularly intriguing in central and peripheral autonomic pathways and their targets. Here, anatomical and functional links appear to exist between NOS, its associated catalytic NADPH-diaphorase enzyme activity (NOSaD) and fibroblast growth factor-2 (FGF-2), a pleiotropic cytokine with mitogenic actions, suggesting mutual "short- and long-term" actions. Several recent studies performed in the rat sympathoadrenal system, an anatomically and neurochemically well-defined autonomic pathway with target-specific functional units of sympathetic preganglionic neurons (SPNs) in the spinal cord, provide evidence for this hypothesis. The NO and cytokine signals may interact at the level of gene expression, transcription factors, post-transcriptional control or second messenger cross-talk. Thus, unique biological roles of FGF-2 and the NO system are likely to exist in neuroendocrine actions, vasomotory perfusion control as well as in neurotrophic actions in sympathetic innervation of the adrenal gland. In view of their anatomical co-existence, functional interplay and synchronizing effects on neuronal networks, multiple roles are suggested for both "short- and long-term" signalling molecules in neuroendocrine functions and integrated autonomic target organ control.

Localization, differential expression and retrograde axonal transport suggest physiological role of FGF-2 in spinal autonomic neurons of the rat

Fibroblast growth factor-2 (FGF-2) has marked pharmacological neurotrophic effects on lesioned spinal autonomic neurons following target removal of the adrenal medulla, yet expression and axonal transport in autonomic neurons remain to be shown. We show here FGF-2 and FGF receptor type 1 (FGFR1) protein and mRNA expression in preganglionic intermediolateral neurons of the rat thoracic spinal cord. While immunoreactivity of both FGF-2 and FGFR1 co-localize to intermediolateral neurons, mRNA transcripts of FGFR1, but not of FGF-2, are detectable in intermediolateral preparations by RNase protection analysis, suggesting protein translocation in vivo. Unilateral microinjection of 125iodinated FGF-2 into the adrenal medulla (a major target of intermediolateral neurons) results in significant accumulation of specific radioactivity in thoracic spinal cord tissue, including the intermediolateral neurons, and the ipsilateral splanchnic nerve. Emulsion autoradiography demonstrated labelling over ipsilateral intermediolateral neurons only. Neuronal co-localization of FGF-2/FGFR1 protein, differential mRNA expression, specific retrograde axonal transport and the known neurotrophic actions in vivo, strongly suggest unique physiological roles of FGF-2 in the autonomic nervous system.

Fibroblast growth factor decreases locomotor activity in rats

The spontaneous locomotor behavior of rats receiving subcutaneous administration of either acidic or basic fibroblast growth factors was recorded in an activity cage. We report that doses between 1 and 100 micrograms/kg significantly decreased the horizontal and vertical activity, as well as the exploratory and stereotypy behavior of the rats. These effects of fibroblast growth factors seem to be specific since (i) they were cancelled by protein hydrolysis and anti-fibroblast growth factor antibodies, (ii) they were unrelated to their hypotensive activity and (iii) they were not attributable to their high structural similarity with the cytokine interleukin-1. Thus fibroblast growth factors did not show any thermogenic activity, did not affect the hypothalamic output of corticotropin-releasing factor and did not change the plasma levels of corticosterone. Pretreatment of the rats with a specific inhibitor of brain nitric oxide synthase prevented the effects of fibroblast growth factors, suggesting the involvement of nitric oxide in these behavioral modifications. Our results contribute to the accumulating evidence describing non-mitogenic activities of fibroblast growth factors.

Characterization of the 1B promoter of fibroblast growth factor 1 and its expression in the adult and developing mouse brain

The present study elucidates the molecular structure of a murine fibroblast growth factor 1 (FGF-1) promoter and describes its distribution in the adult and developing mouse brain. A cDNA clone coding for FGF-1 was isolated from a mouse brain cDNA library. Nucleotide sequence analysis revealed that the clone contained, in addition to the protein coding region, an untranslated exon (FGF-1B) 34 base pairs upstream of the translation start codon ATG. The mouse cDNA clone corresponded to the sole FGF-1 transcript in the brain. An RNase protection assay was used to map the transcription start site of the 1B promoter. The sequences upstream from the major transcription initiation site lacked consensus TATA or CAAT boxes. In situ hybridization with cRNA probes specific for the 1B transcript showed the message to be restricted largely to sensory and motor nuclei in the brainstem, and to the ventral spinal cord and cerebellum. Although occasional brainstem nuclei were labeled at low levels by embryonic day 18, the majority of nuclei became detectable autoradiographically during postnatal weeks 1 and 2, and adult levels of grain density were reached during the 3rd and 4th postnatal weeks. FGF-1B mRNA was expressed in phylogenetically older brain regions, which are involved primarily in processing information from exteroceptive sensory mechanoreceptors and in motor control. The relatively late developmental expression suggests a role for FGF-1 in neuronal maturation, rather than in neurogenesis.

Basic fibroblast growth factor (FGF-2) affects development of acoustico-vestibular neurons in the chick embryo brain in vitro

The effects of basic fibroblast growth factor (FGF-2) on presumptive auditory and vestibular neurons from the medulla were studied in primary cell cultures. The part of the rhombic lip that forms nucleus magnocellularis (homologue of the mammalian anteroventral cochlear nucleus) was explanted from white leghorn chicken embryos at Hamburger-Hamilton stage 28 (E5.5), the time when precursors of the magnocellularis bushy cells migrate and begin to differentiate in situ. In vitro the neuroblasts migrated onto 2-D substrates of purified collagen, differentiated, and expressed neuronal markers. One-half of the cultures were supplemented with human recombinant FGF-2 (10 ng/ml daily) for 5-7 days; the others, with fetal bovine serum. FGF-2 more than doubled the length of neurite outgrowth during the first 3 day treatment compared to serum, but the number of migrating neuroblasts was unaffected. Although neurites attained greater lengths in FGF-2, they usually degenerated after 4-5 days; in serum their growth continued for several weeks. Differentiation of neuronal structure, including axons and dendrites, began within 1-2 days in bFGF but required at least 5-7 days in serum. Histochemical observations in vitro and in situ with antibodies to FGF receptor demonstrated immunopositive patches on acoustico-vestibular neuroblasts at stage 28, when they are migrating and first forming their axons. The findings suggest that FGF-2 stimulates neurite outgrowth in the cochlear and vestibular nuclei. FGF-2 may accelerate cell death by overstimulating neuroblasts, but other factors are needed to sustain their further development.

Expression of the fibroblast growth factor family and their receptor family genes during mouse brain development

The fibroblast growth factor (FGF) family is composed of nine members and four genes encode protein tyrosine kinase receptors for them. To gain insight into the involvement of FGFs and their receptors in the development of nervous system, their expression in brains of perinatal and adult mice was examined by semi-quantitative reverse transcription-linked polymerase chain reactions and in situ hybridization. Although all the genes, with the exception of FGF-4, were found to be expressed, FGF-3, FGF-6, FGF-7 and FGF-8 genes demonstrated higher expression in the late embryonic stages than in postnatal stages, suggesting that these members are involved in the late stages of brain development. In contrast, expression of FGF-1 and FGF-5 increased after birth. Interestingly, FGF-6 expression in perinatal mice was restricted to the central nervous system and skeltal muscles, with intense signals in the developing cerebrum in embryos but in cerebellum in 5-day-old neonates. Furthermore, FGF-receptor (FGFR)-4, a cognate receptor for FGF-6, demonstrated similar spatiotemporal expression, suggesting that FGF-6 and FGFR-4 plays significant roles in the maturation of nervous system as a ligand-receptor system. The results indicate that individual member of the fibroblast growth factor and their receptor family are expressed either sequentially or simultaneously in brain development, strongly suggesting their involvement in the regulation of a variety of developmental processes of brain, i.e., proliferation and migration of neuronal progenitor cells, neuron and glia differentiation, neurite extensions, and synapse formations.

Basic fibroblast growth factor (FGF-2) affects development of acoustico-vestibular neurons in the chick embryo brain in vitro

The effects of basic fibroblast growth factor (FGF-2) on presumptive auditory and vestibular neurons from the medulla were studied in primary cell cultures. The part of the rhombic lip that forms nucleus magnocellularis (homologue of the mammalian anteroventral cochlear nucleus) was explanted from white leghorn chicken embryos at Hamburger-Hamilton stage 28 (E5.5), the time when precursors of the magnocellularis bushy cells migrate and begin to differentiate in situ. In vitro the neuroblasts migrated onto 2-D substrates of purified collagen, differentiated, and expressed neuronal markers. One-half of the cultures were supplemented with human recombinant FGF-2 (10 ng/ml daily) for 5-7 days; the others, with fetal bovine serum. FGF-2 more than doubled the length of neurite outgrowth during the first 3 day treatment compared to serum, but the number of migrating neuroblasts was unaffected. Although neurites attained greater lengths in FGF-2, they usually degenerated after 4-5 days; in serum their growth continued for several weeks. Differentiation of neuronal structure, including axons and dendrites, began within 1-2 days in bFGF but required at least 5-7 days in serum. Histochemical observations in vitro and in situ with antibodies to FGF receptor demonstrated immunopositive patches on acoustico-vestibular neuroblasts at stage 28, when they are migrating and first forming their axons. The findings suggest that FGF-2 stimulates neurite outgrowth in the cochlear and vestibular nuclei. FGF-2 may accelerate cell death by overstimulating neuroblasts, but other factors are needed to sustain their further development.

Cells expressing preproenkephalin mRNA in the rat pineal gland are not serotonin-producing pinealocytes: evidence using in situ hybridization combined with immunocytochemistry for serotonin

1. Preproenkephalin (PPEnk) mRNA expressing cells have been identified in rat pineal gland using radioactive in situ hybridization histochemistry. 2. Approximately 7% of the cells in the pineal gland (7.5 +/- 0.86, mean +/- 95% CI) express PPEnk mRNA. These cells are distributed throughout the pineal as either scattered single cells or small groups of cells with large round or oval nuclei. 3. Using in situ hybridization combined with ABC immunocytochemistry for serotonin (5-HT) in the same pineal sections, the PPEnk mRNA labeling cells are found not to be serotonin-immunoreactive cells. These data indicate that the PPEnk mRNA is expressed in a certain discrete subpopulation of cells in the rat pineal gland and these cells are not serotonin-producing pinealocytes. 4. The physiologic role of PPEnk-derived peptides in the pineal remains unknown. It is possible that these peptides either are synthesized and secreted as hormones or act as pineal paracrine signals.

Differential effects of the intraventricular administration of 6-hydroxydopamine on the induction of type II beta-tubulin and tyrosine hydroxylase mRNA in the locus coeruleus of the aging Fischer 344 rat

Noradrenergic neurons of the locus coeruleus have been shown to respond to injury by increasing the synthesis of neurotransmitter (via the activation and induction of tyrosine hydroxylase, the rate-limiting catalyst in the production of catecholamines) and initiating compensatory axonal sprouting. However, this laboratory has recently described a significant deficit in the activation of tyrosine hydroxylase in the aged Fischer 344 rat, in contrast to the young and mature rat, following partial damage to cortical and hippocampal noradrenergic terminals induced by the neurotoxin 6-hydroxydopamine. To extend these observations, we measured changes in the relative levels of neuron-specific type II beta-tubulin and tyrosine hydroxylase mRNA in locus coeruleus neurons of 2, 12, and 24-month-old Fischer 344 rats following intraventricular infusions of 6-hydroxydopamine by using in situ hybridization histochemistry. These measures were used as markers of the responsiveness of these neurons to injury. 6-Hydroxydopamine treatment induced a persistent increase (at least 10 days) in the expression of type II beta-tubulin mRNA only in 2-month-old animals; this marker decreased in the 12 and 24-month-old animals. Relative levels of tyrosine hydroxylase mRNA increased in 2 and 12-month-old lesioned animals both 3 and 10 days post-treatment. In contrast, the induction of tyrosine hydroxylase mRNA in 24-month-old animals, seen three days post-treatment, was attenuated by 10 days. These data indicate that the capacity of locus coeruleus neurons to compensate for injury by either initiating a potential sprouting response or increasing their capacity to synthesize neurotransmitter is reduced in older animals.

Co-existence of NADPH-diaphorase, fibroblast growth factor-2 and fibroblast growth factor receptor in spinal autonomic system suggests target-specific actions

In the rat spinal cord, we found substantial co-existence of fibroblast growth factor-2, fibroblast growth factor receptor (type-1 or flg) immunoreactivity and reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity (a histochemical marker for neuronal nitric oxide synthase) in preganglionic autonomic cell groups of intermediate layers VI, VII and X. Anti-fibroblast growth factor-2 and anti-nitric oxide synthase binding sites were confined to the cytoplasm of reactive neurons as judged by immunogold electron microscopy. Within the major autonomic nucleus, i.e. intermediolateral column, three different populations were identified: (i) fibroblast growth factor and fibroblast growth factor receptor, (ii) fibroblast growth factor/NADPH-diaphorase and (iii) NADPH-diaphorase-only stained cell groups. Sympathoadrenal neurons were prelabelled with fluorescent tracer Fast Blue and co-stained for fibroblast growth factor-like protein and NADPH-diaphorase, suggesting heterologous diversification of neuronal phenotypes and functional organization in the spinal autonomic system. Our findings suggest intriguing roles for nitric oxide and fibroblast growth factor-2 cytokine in the preganglionic sympathetic spinal cord system: The "short-term" diffusible messenger nitric oxide may act as "tonic" and/or "phasic" signal within rostrocaudally oriented function-specific preganglionic units necessary for integrated target control. The "long-term" messenger fibroblast growth factor-2 may be involved in, for example, cytokine-dependent regulation of neuronal NADPH-diaphorase/nitric oxide synthase. Furthermore, co-existence of NADPH-diaphorase, fibroblast growth factor-2 and receptor in sympathoadrenal neurons suggest mutual target-specific regulatory functions, e.g. hormone release and blood perfusion or maintenance of phenotype and plasticity responsiveness of adrenal medullary tissue.

Distribution of acidic fibroblast growth factor mRNA-expressing neurons in the adult mouse central nervous system

The distribution of acidic fibroblast growth factor (aFGF) mRNA-expressing neurons was studied throughout the adult mouse central nervous system (CNS) with in situ hybridization histochemistry using a radiolabelled synthetic oligodeoxynucleotide probe complementary to the mRNA of human aFGF. We report here a widespread distribution of aFGF mRNA in several defined functional systems of the adult mouse brain, whereby the highest levels of aFGF mRNA were found in large somatomotor neurons in the nuclei of the oculomotor, trochlear, abducens, and hypoglossal nerves; in the motoneurons of the ventral spinal cord and the special visceromotor neurons in the motor nucleus of the trigeminal nerve; and in the facial and ambiguus nuclei. Labelled perikarya were also detected in all central structures of the auditory pathway including the level of the inferior colliculus, i.e., the lateral and medial superior nuclei; the trapezoid, cochlear, and lateral lemniscal nuclei; and parts of the anterior colliculus. Furthermore, many aFGF-positive cell bodies were found in the vestibular system and other structures projecting to the cerebellum, in the deep cerebellar nuclei, in somatosensory structures of the medulla (i.e., in the gracile, cuneate, and external cuneate nuclei), as well as in the spinal nucleus of the trigeminal nerve. The findings that aFGF mRNA is expressed in all components of several well-defined systems (i.e., in sensory structures) as well as in central neurons that process sensory information and, finally, in some efferent projections point towards a concept of aFGF expression primarily within certain neuronal circuitries.

Developmental time course of acidic and basic fibroblast growth factors' expression in distinct cellular populations of the rat central nervous system

Acidic and basic fibroblast growth factors (aFGF and bFGF, respectively) are expressed in high levels in adult central nervous system (CNS). We report the time course of developmental appearance and distribution of these factors and of two FGF receptors, FGFR-1 and FGFR-2, in the CNS of rats ranging in age from embryonic day 16 to adult. Immunohistochemical analysis showed that sensory neurons in the midbrain were the first cells to contain detectable aFGF immunoreactivity at embryonic day 18. The next cell group to contain aFGF were motor neurons, which were found to be aFGF-positive at the day of birth. A number of other subcortical neuronal populations were observed to contain aFGF immunoreactivity after postnatal day 7. Adult levels and distribution patterns of aFGF were reached in all CNS areas by postnatal day 28. Basic FGF immunoreactivity was observed at postnatal day 0 in neurons in the CA2 subfield of hippocampus. Astrocytes contained detectable bFGF immunoreactivity, starting at postnatal day 7. Adult levels and patterns of distribution of bFGF were reached in all CNS areas by postnatal day 28. These immunohistochemical observations were confirmed by using bioassay and Western blot techniques. FGFR-1 and FGFR-2 mRNA were expressed in significant levels in all CNS areas at all time points analyzed. The observation that aFGF and bFGF appear in specific and distinct cellular populations at relatively late developmental times suggests that these FGFs may be involved in specific mechanisms of CNS maturation, maintenance, and repair.

Mechanisms of damage and repair in multiple sclerosis--a review

Pathological features of MS include perivascular inflammation and demyelination with oligodendrocyte loss; in addition, attempts at remyelination are often unsuccessful and may culminate in astrocytic scarring. One approach to investigating the biological principles underlying these processes is to use in vitro systems to analyse single-cell behaviour as well as cell-cell interactions. This paper reviews such data concerned with cell injury and repair which illuminate both demyelination and remyelination. In tissue culture oligodendrocytes are susceptible to injury via cell-mediated and humoral mechanisms. Substances including complement and tumour necrosis factor are capable of killing rat oligodendrocytes in vitro; surface complement activation also initiates a number of intracellular processes within oligodendrocytes as well as providing ligands for phagocytic interactions. The reasons for oligodendrocyte complement activation are discussed, but it appears that species differences exist when extrapolating these data to humans. Myelination and remyelination can also be studied both in vitro and in vivo using defined cell populations. Results from these studies may eventually help to explain some pathological features of MS, including astrocytosis and factors governing the limits of remyelination.

Localization of fibroblast growth factor-9 mRNA in the rat brain

We examined the localization of fibroblast growth factor-9 (FGF-9) mRNA in the rat brain by in situ hybridization. FGF-9 mRNA was moderately or weakly expressed in widespread regions including the olfactory bulb, caudate putamen, cerebral cortex, hippocampus, thalamus, hypothalamus, midbrain, brainstem and cerebellum. However, FGF-9 mRNA was also strongly expressed in several specific nuclei including the red nucleus and oculomotor nucleus in the midbrain, the vestibular nucleus and facial nucleus in the brainstem and the medial cerebellar nucleus, interposed cerebellar nucleus and lateral cerebellar nucleus in the cerebellum. The cellular localization of FGF-9 mRNA indicated that the mRNA in the rat brain was expressed preferentially in neurons, although FGF-9 was originally isolated from human glioma cells. The localization profile of FGF-9 mRNA is different from those of aFGF, bFGF and FGF-5 mRNAs reported previously. The present findings indicate that FGF-9 has a unique role in the brain.

Expression of acidic FGF mRNA in rat auditory brainstem during postnatal maturation

In situ hybridization was used to investigate the mRNA distribution of acidic and basic fibroblast growth factor (aFGF and bFGF) in the auditory brainstem of neonatal and adult rats. bFGF mRNA was not detected at any age. In adult rats, aFGF mRNA was strongly expressed in the principal neurons of the anteroventral and posteroventral cochlear nuclei, but not in the octopus cells. In the dorsal cochlear nucleus, aFGF mRNA was seen only in scattered smaller vertical cells. aFGF was strongly expressed in the nucleus of the trapezoid body and in all periolivary cell groups, but not in the medial and lateral olivary nuclei. No expression was observed in the lemniscal nuclei or in the central nucleus of the inferior colliculus, but large neurons in the external zone of the colliculus were labeled. Developmentally, low levels of aFGF expression appeared in the cochlear nuclei and olivary nuclei between P0 and P6. This expression increased rapidly during the onset of hearing, between P10 and P14, and reached adult level by P14-P17. Labeling in collicular neurons appeared slightly later. The results suggest that the appearance of strong aFGF mRNA expression is related to the onset of function.