Neuroprotection by scatter factor/hepatocyte growth factor and FGF-1 in cerebellar granule neurons is phosphatidylinositol 3-kinase/akt-dependent and MAPK/CREB-independent

Metabolic Messengers: fibroblast growth factor 1

While fibroblast growth factor (FGF) 1 is expressed in multiple tissues, only adipose-derived and brain FGF1 have been implicated in the regulation of metabolism. Adipose FGF1 production is upregulated in response to dietary stress and is essential for adipose tissue plasticity in these conditions. Similarly, in the brain, FGF1 secretion into the ventricular space and the adjacent parenchyma is increased after a hypercaloric challenge induced by either feeding or glucose infusion. Potent anorexigenic properties have been ascribed to both peripheral and centrally injected FGF1. The ability of recombinant FGF1 and variants with reduced mitogenicity to lower glucose, suppress adipose lipolysis and promote insulin sensitization elevates their potential as candidates in the treatment of type 2 diabetes mellitus and associated comorbidities. Here, we provide an overview of the known metabolic functions of endogenous FGF1 and discuss its therapeutic potential, distinguishing between peripherally or centrally administered FGF1.

HGF and MET: From Brain Development to Neurological Disorders

Hepatocyte growth factor (HGF) and its tyrosine kinase receptor, encoded by the MET cellular proto-oncogene, are expressed in the nervous system from pre-natal development to adult life, where they are involved in neuronal growth and survival. In this review, we highlight, beyond the neurotrophic action, novel roles of HGF-MET in synaptogenesis during post-natal brain development and the connection between deregulation of MET expression and developmental disorders such as autism spectrum disorder (ASD). On the pharmacology side, HGF-induced MET activation exerts beneficial neuroprotective effects also in adulthood, specifically in neurodegenerative disease, and in preclinical models of cerebral ischemia, spinal cord injuries, and neurological pathologies, such as Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS). HGF is a key factor preventing neuronal death and promoting survival through pro-angiogenic, anti-inflammatory, and immune-modulatory mechanisms. Recent evidence suggests that HGF acts on neural stem cells to enhance neuroregeneration. The possible therapeutic application of HGF and HGF mimetics for the treatment of neurological disorders is discussed.

Fibroblast Growth Factor 1-Transfected Adipose-Derived Mesenchymal Stem Cells Promote Angiogenic Proliferation

The aim of this study was to investigate, for the first time, the effects of using adipose-derived mesenchymal stem cells (AD-MSCs) transfected with an episomal plasmid encoding fibroblast growth factor 1 (FGF1) (AD-MSCsFGF1), in providing the microenvironment required for angiogenic proliferation. The isolated rat AD-MSCs were positive for mesenchymal (CD29 and CD90) and negative for hematopoietic (CD34 and CD45) surface markers. Adipogenic and osteogenic differentiation of the AD-MSCs also occurred in the proper culture media. The presence of FGF1 in the conditioned medium from the AD-MSCsFGF1 was confirmed by Western blotting. G418 and PCR were used for selection of transfected cells and confirmation of the presence of FGF1 mRNA, respectively. Treatment with the AD-MSCFGF1-conditioned medium significantly increased the NIH-3T3 cell proliferation and human umbilical vein endothelial cell (HUVEC) tube formation compared to conditioned medium from nontransfected AD-MSCs (p < 0.001). In conclusion, the AD-MSCsFGF1 efficiently secreted functional FGF1, which promoted angiogenic proliferation. Using AD-MSCsFGF1 may provide a useful strategy in cell therapy, which can merge the beneficial effects of stem cells with the positive biological effects of FGF1 in various disorders, especially tissue defects, neurodegenerative, cardiovascular and diabetes endocrine pathologies, which remain to be tested in preclinical and clinical studies.

Inhibition of endoplasmic reticulum stress is involved in the neuroprotective effect of aFGF in neonatal hypoxic-ischaemic brain injury

Acidic fibroblast growth factor (aFGF) has been shown to exert neuroprotective effects in experimental models and human patients. In this study, we investigated whether aFGF intranasal-treatment protected against neonatal hypoxic-ischaemic brain injury and evaluated the role of endoplasmic reticulum stress. The Rice-Vannucci model of neonatal hypoxic-ischaemic brain injury was used in 7-day-old rats, which were subjected to unilateral carotid artery ligation followed by 2.5 h of hypoxia. Intranasal aFGF or vehicle was administered immediately after hypoxic-ischaemic injury (100 ng/g) and then twice a day for 1 week to evaluate the long-term effects. Here we reported that intranasal-treatment with aFGF significantly reduced hypoxic-ischaemic brain infarct volumes and the protective effects were at least partially via inhibiting endoplasmic reticulum stress. In addition, aFGF exerted long-term neuroprotective effects against brain atrophy and neuron loss at 7-day after injury. Our data indicate that therapeutic strategies targeting endoplasmic reticulum stress may be promising to the treatment of neonatal hypoxic-ischaemic brain injury.

The synthetic progesterone Norgestrel is neuroprotective in stressed photoreceptor-like cells and retinal explants, mediating its effects via basic fibroblast growth factor, protein kinase A and glycogen synthase kinase 3β signalling

The synthetic progesterone Norgestrel has been shown to have proven neuroprotective efficacy in two distinct models of retinitis pigmentosa: the rd10/rd10 (B6.CXBI-Pde6b(rd10)/J) mouse model and the Balb/c light-damage model. However, the cellular mechanism underlying this neuroprotection is still largely unknown. Therefore, this study aimed to examine the downstream signalling pathways associated with Norgestrel both in vitro and ex vivo. In this work, we identify the potential of Norgestrel to rescue stressed 661W photoreceptor-like cells and ex vivo retinal explants from cell death over 24 h. Norgestel is thought to work through an upregulation of neuroprotective basic fibroblast growth factor (bFGF). Analysis of 661W cells in vitro by real-time polymerase chain reaction (rt-PCR), enzyme-linked immunosorbent assay (ELISA) and Western blotting revealed an upregulation of bFGF in response to Norgestrel over 6 h. Specific siRNA knockdown of bFGF abrogated the protective properties of Norgestrel on damaged photoreceptors, thus highlighting the crucial importance of bFGF in Norgestrel-mediated protection. Furthermore, Norgestrel initiated a bFGF-dependent inactivation of glycogen synthase kinase 3β (GSK3β) through phosphorylation at serine 9. The effects of Norgestrel on GSK3β were dependent on protein kinase A (PKA) pathway activation. Specific inhibition of both the PKA and GSK3β pathways prevented Norgestrel-mediated neuroprotection of stressed photoreceptor cells in vitro. Involvement of the PKA pathway following Norgestrel treatment was also confirmed ex vivo. Therefore, these results indicate that the protective efficacy of Norgestrel is, at least in part, due to the bFGF-mediated activation of the PKA pathway, with subsequent inactivation of GSK3β.

Distinct intracellular signaling mediates C-MET regulation of dendritic growth and synaptogenesis

Hepatocyte growth factor (HGF) activation of the MET receptor tyrosine kinase influences multiple neurodevelopmental processes. Evidence from human imaging and mouse models shows that, in the forebrain, disruptions in MET signaling alter circuit formation and function. One likely means of modulation is by controlling neuron maturation. Here, we examined the signaling mechanisms through which MET exerts developmental effects in the neocortex. In situ hybridization revealed that hgf is located near MET-expressing neurons, including deep neocortical layers and periventricular zones. Western blot analyses of neocortical crude membranes demonstrated that HGF-induced MET autophosphorylation peaks during synaptogenesis, with a striking reduction in activation between P14 and P17 just before pruning. In vitro analysis of postnatal neocortical neurons assessed the roles of intracellular signaling following MET activation. There is rapid, HGF-induced phosphorylation of MET, ERK1/2, and Akt that is accompanied by two major morphological changes: increases in total dendritic growth and synapse density. Selective inhibition of each signaling pathway altered only one of the two distinct events. MAPK/ERK pathway inhibition significantly reduced the HGF-induced increase in dendritic length, but had no effect on synapse density. In contrast, inhibition of the PI3K/Akt pathway reduced HGF-induced increases in synapse density, with no effect on dendritic length. The data reveal a key role for MET activation during the period of neocortical neuron growth and synaptogenesis, with distinct biological outcomes mediated via discrete MET-linked intracellular signaling pathways in the same neurons. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1160-1181, 2016.

Early gestation chorionic villi-derived stromal cells for fetal tissue engineering

AIM: To investigate the potential for early gestation placenta-derived mesenchymal stromal cells (PMSCs) for fetal tissue engineering.

METHODS: PMSCs were isolated from early gestation chorionic villus tissue by explant culture. Chorionic villus sampling (CVS)-size tissue samples (mean = 35.93 mg) were used to test the feasibility of obtaining large cell numbers from CVS within a clinically relevant timeframe. We characterized PMSCs isolated from 6 donor placentas by flow cytometry immunophenotyping, multipotency assays, and through immunofluorescent staining. Protein secretion from PMSCs was examined using two cytokine array assays capable of probing for over 70 factors in total. Delivery vehicle compatibility of PMSCs was determined using three common scaffold systems: fibrin glue, collagen hydrogel, and biodegradable nanofibrous scaffolds made from a combination of polylactic acid (PLA) and poly(lactic-co-glycolic acid) (PLGA). Viral transduction of PMSCs was performed using a Luciferase-GFP-containing lentiviral vector and efficiency of transduction was tested by fluorescent microscopy and flow cytometry analysis.

RESULTS: We determined that an average of 2.09 × 10⁶ (SD ± 8.59 × 10⁵) PMSCs could be obtained from CVS-size tissue samples within 30 d (mean = 27 d, SD ± 2.28), indicating that therapeutic numbers of cells can be rapidly expanded from very limited masses of tissue. Immunophenotyping by flow cytometry demonstrated that PMSCs were positive for MSC markers CD105, CD90, CD73, CD44, and CD29, and were negative for hematopoietic and endothelial markers CD45, CD34, and CD31. PMSCs displayed trilineage differentiation capability, and were found to express developmental transcription factors Sox10 and Sox17 as well as neural-related structural proteins NFM, Nestin, and S100β. Cytokine arrays revealed a robust and extensive profile of PMSC-secreted cytokines and growth factors, and detected 34 factors with spot density values exceeding 10³. Detected factors had widely diverse functions that include modulation of angiogenesis and immune response, cell chemotaxis, cell proliferation, blood vessel maturation and homeostasis, modulation of insulin-like growth factor activity, neuroprotection, extracellular matrix degradation and even blood coagulation. Importantly, PMSCs were also determined to be compatible with both biological and synthetic material-based delivery vehicles such as collagen and fibrin hydrogels, and biodegradable nanofiber scaffolds made from a combination of PLA and PLGA. Finally, we demonstrated that PMSCs can be efficiently transduced (> 95%) with a Luciferase-GFP-containing lentiviral vector for future in vivo cell tracking after transplantation.

CONCLUSION: Our findings indicate that PMSCs represent a unique source of cells that can be effectively utilized for in utero cell therapy and tissue engineering.

Genetic deletion of neuronal pentraxin 1 expression prevents brain injury in a neonatal mouse model of cerebral hypoxia-ischemia

Neonatal hypoxic-ischemic (HI) brain injury is a leading cause of mortality and morbidity in infants and children for which there is no promising therapy at present. Previously, we reported induction of neuronal pentraxin 1 (NP1), a novel neuronal protein of the long-pentraxin family, following HI injury in neonatal brain. Here, we report that genetic deletion of NP1 expression prevents HI injury in neonatal brain. Elevated expression of NP1 was observed in neurons, not in astrocytes, of the ipsilateral cortical layers (I-IV) and in the hippocampal CA1 and CA3 areas of WT brains following hypoxia-ischemia; brain areas that developed infarcts (at 24-48 h), showed significantly increased numbers of TUNEL-(+) cells and tissue loss (at 7 days). In contrast, NP1-KO mice showed no evidence of brain infarction and tissue loss after HI. The immunofluorescence staining of brain sections with mitochondrial protein COX IV and subcellular fractionation analysis showed increased accumulation of NP1 in mitochondria, pro-death protein Bax activation and NP1 co-localization with activated caspase-3 in WT, but not in the NP1-KO brains; corroborating NP1 interactions with the mitochondria-derived pro-death pathways. Disruption of NP1 translocation to mitochondria by NP1-siRNA in primary cortical cultures significantly reduced ischemic neuronal death. NP1 was immunoprecipitated with activated Bax [6A7] proteins; HI caused increased interactions of NP1 with Bax, thereby, facilitating Bax translocation to mitochondrial and neuronal death. To further delineate the specificity of NPs, we found that NP1 but not the NP2 induction is specifically involved in brain injury mechanisms and that knockdown of NP1 only results in neuroprotection. Furthermore, live in vivo T2-weighted magnetic resonance imaging (MRI) including fractional anisotropy (FA) mapping showed no sign of delayed brain injury or tissue loss in the NP1-KO mice as compared to the WT at different post-HI periods (4-24 weeks) examined; indicating a long-term neuroprotective efficacy of NP1 gene deletion. Collectively, our results demonstrate a novel mechanism of neuronal death and predict that inhibition of NP1 expression is a promising strategy to prevent hypoxic-ischemic injury in immature brain.

Critical role of extracellularly secreted neuronal pentraxin 1 in ischemic neuronal death

Background

Developing brain is highly susceptible to hypoxic-ischemic injury leading to severe neurological disabilities in surviving infants and children. Previously we reported induction of neuronal pentraxin 1 (NP1) in hypoxic-ischemic injury in neonatal brain and NP1 co-localization with the excitatory AMPA receptors GluR1 at the synaptic sites. However, how NP1 contributes to hypoxic-ischemic neuronal injury is not completely understood.

Results

Here we report that extracellular secretion of NP1 is required for ischemic neuronal death. Primary cortical neurons at days in vitro (DIV) 12 were subjected to oxygen glucose deprivation (OGD), an in vitro model of ischemic stroke, for different time periods (2–8 h). Oxygen glucose deprivation showed characteristic morphological changes of dying cells, OGD time-dependent induction of NP1 (2-4-fold) and increased neuronal death. In contrast, the NP1-KO cortical neurons were healthy and showed no sign of dying cells under similar conditions. NP1gene silencing by NP1-specific small interfering RNA (NP1-siRNA) protected cortical neurons from OGD-induced death. Conditioned media (CM) collected from OGD exposed WT cortical cultures caused neurotoxicity when added to a subset of DIV 12 normoxia control WT cortical cultures. In contrast, CM from OGD-exposed NP1-KO cultures did not induce cell toxicity in control WT cultures, suggesting a role for extracellular NP1 in neuronal death. However, NP1-KO neurons, which showed normal neuronal morphology and protection against OGD, sustained enhanced death following incubation with CM from WT OGD-exposed cultures. Western blot analysis of OGD exposed WT CM showed temporal increase of NP1 protein levels in the CM. Most strikingly, in contrast to NP1-KO CM, incubation of normal cortical cultures with CM from OGD exposed NP2-KO cultures showed neurotoxicity similar to that observed with CM from OGD exposed WT neuronal cultures. Western immunoblotting further confirmed the increased presence of NP1 protein in OGD-exposed NP2-KO CM. Live immunofluorescence analysis show intense cell surface clustering of NP1 with AMPA GluR1 receptors.

Conclusions

Collectively, our results demonstrate that extracellular release of NP1 promote hypoxic-ischemic neuronal death possibly via surface clustering with GluR1 at synaptic sites and that NP1, not its family member NP2, is involved in the neuronal death mechanisms.

The development of small molecule angiotensin IV analogs to treat Alzheimer's and Parkinson's diseases

Alzheimer's (AD) and Parkinson's (PD) diseases are neurodegenerative diseases presently without effective drug treatments. AD is characterized by general cognitive impairment, difficulties with memory consolidation and retrieval, and with advanced stages episodes of agitation and anger. AD is increasing in frequency as life expectancy increases. Present FDA approved medications do little to slow disease progression and none address the underlying progressive loss of synaptic connections and neurons. New drug design approaches are needed beyond cholinesterase inhibitors and N-methyl-d-aspartate receptor antagonists. Patients with PD experience the symptomatic triad of bradykinesis, tremor-at-rest, and rigidity with the possibility of additional non-motor symptoms including sleep disturbances, depression, dementia, and autonomic nervous system failure. This review summarizes available information regarding the role of the brain renin-angiotensin system (RAS) in learning and memory and motor functions, with particular emphasis on research results suggesting a link between angiotensin IV (AngIV) interacting with the AT4 receptor subtype. Currently there is controversy over the identity of this AT4 receptor protein. Albiston and colleagues have offered convincing evidence that it is the insulin-regulated aminopeptidase (IRAP). Recently members of our laboratory have presented evidence that the brain AngIV/AT4 receptor system coincides with the brain hepatocyte growth factor/c-Met receptor system. In an effort to resolve this issue we have synthesized a number of small molecule AngIV-based compounds that are metabolically stable, penetrate the blood-brain barrier, and facilitate compromised memory and motor systems. These research efforts are described along with details concerning a recently synthesized molecule, Dihexa that shows promise in overcoming memory and motor dysfunctions by augmenting synaptic connectivity via the formation of new functional synapses.

A Network Map of FGF-1/FGFR Signaling System

Fibroblast growth factor-1 (FGF-1) is a well characterized growth factor among the 22 members of the FGF superfamily in humans. It binds to all the four known FGF receptors and regulates a plethora of functions including cell growth, proliferation, migration, differentiation, and survival in different cell types. FGF-1 is involved in the regulation of diverse physiological processes such as development, angiogenesis, wound healing, adipogenesis, and neurogenesis. Deregulation of FGF-1 signaling is not only implicated in tumorigenesis but also is associated with tumor invasion and metastasis. Given the biomedical significance of FGFs and the fact that individual FGFs have different roles in diverse physiological processes, the analysis of signaling pathways induced by the binding of specific FGFs to their cognate receptors demands more focused efforts. Currently, there are no resources in the public domain that facilitate the analysis of signaling pathways induced by individual FGFs in the FGF/FGFR signaling system. Towards this, we have developed a resource of signaling reactions triggered by FGF-1/FGFR system in various cell types/tissues. The pathway data and the reaction map are made available for download in different community standard data exchange formats through NetPath and NetSlim signaling pathway resources.

Sex differences in mitochondrial biogenesis determine neuronal death and survival in response to oxygen glucose deprivation and reoxygenation

Background

Mitochondrial dysfunction has been linked to neuronal death and a wide array of neurodegenerative diseases. Previously, we have shown sex differences in mitochondria-mediated cell death pathways following hypoxia-ischemia. However, the role of mitochondrial biogenesis in hypoxic-ischemic brain injury between male vs. female has not been studied yet.

Results

Primary cerebellar granule neurons (CGNs), isolated from P7 male and female mice (CD-1) segregated based on visual inspection of sex, were exposed to 2 h of oxygen glucose deprivation (OGD) followed by 6–24 h of reoxygenation (Reox). Mitochondrial membrane potential (ΔΨ_m) and cellular ATP levels were reduced significantly in XX CGNs as compared to XY CGNs. Mitochondrial DNA (mtDNA) content was increased (>2-fold) at 2 h OGD in XY CGNs and remained increased up to 24 h of Reox compared to XX neurons and normoxia controls. The expression of mitochondrial transcription factor A (Tfam), the nuclear respiratory factor-1 (NRF-1) and the peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), a master regulator of mitochondrial biogenesis, were up-regulated (2-fold, ***p < 0.001) in XY CGNs but slightly reduced or remained unchanged in XX neurons. Similarly, the TFAM and PGC-1α protein levels and the mitochondrial proteins HSP60 and COXIV were increased in XY neurons only. Supportively, a balanced stimulation of fusion (Mfn 1and Mfn 2) and fission (Fis 1 and Drp 1) genes and enhanced formation of donut-shaped mitochondria were observed in XY CGNs vs. XX neurons (**p < 0.01).

Conclusions

Our results demonstrate that OGD/Reox alters mitochondrial biogenesis and morphological changes in a sex-specific way, influencing neuronal injury/survival differently in both sexes.

Critical role of neuronal pentraxin 1 in mitochondria-mediated hypoxic-ischemic neuronal injury

Developing brain is highly susceptible to hypoxic-ischemic (HI) injury leading to severe neurological disabilities in surviving infants and children. Previously, we have reported induction of neuronal pentraxin 1 (NP1), a novel neuronal protein of long-pentraxin family, following HI neuronal injury. Here, we investigated how this specific signal is propagated to cause the HI neuronal death. We used wild-type (WT) and NP1 knockout (NP1-KO) mouse hippocampal cultures, modeled in vitro following exposure to oxygen glucose deprivation (OGD), and in vivo neonatal (P9-10) mouse model of HI brain injury. Our results show induction of NP1 in primary hippocampal neurons following OGD exposure (4-8 h) and in the ipsilateral hippocampal CA1 and CA3 regions at 24-48 h post-HI compared to the contralateral side. We also found increased PTEN activity concurrent with OGD time-dependent (4-8 h) dephosphorylation of Akt (Ser473) and GSK-3β (Ser9). OGD also caused a time-dependent decrease in the phosphorylation of Bad (Ser136), and Bax protein levels. Immunofluorescence staining and subcellular fractionation analyses revealed increased mitochondrial translocation of Bad and Bax proteins from cytoplasm following OGD (4 h) and simultaneously increased release of Cyt C from mitochondria followed by activation of caspase-3. NP1 protein was immunoprecipitated with Bad and Bax proteins; OGD caused increased interactions of NP1 with Bad and Bax, thereby, facilitating their mitochondrial translocation and dissipation of mitochondrial membrane potential (ΔΨ(m)). This NP1 induction preceded the increased mitochondrial release of cytochrome C (Cyt C) into the cytosol, activation of caspase-3 and OGD time-dependent cell death in WT primary hippocampal neurons. In contrast, in NP1-KO neurons there was no translocation of Bad and Bax from cytosol to the mitochondria, and no evidence of ΔΨ(m) loss, increased Cyt C release and caspase-3 activation following OGD; which resulted in significantly reduced neuronal death. Our results indicate a regulatory role of NP1 in Bad/Bax-dependent mitochondrial release of Cyt C and caspase-3 activation. Together our findings demonstrate a novel mechanism by which NP1 regulates mitochondria-driven hippocampal cell death; suggesting NP1 as a potential therapeutic target against HI brain injury in neonates.

MET and AKT genetic influence on facial emotion perception

BACKGROUND

Facial emotion perception is a major social skill, but its molecular signal pathway remains unclear. The MET/AKT cascade affects neurodevelopment in general populations and face recognition in patients with autism. This study explores the possible role of MET/AKT cascade in facial emotion perception.

METHODS

One hundred and eighty two unrelated healthy volunteers (82 men and 100 women) were recruited. Four single nucleotide polymorphisms (SNP) of MET (rs2237717, rs41735, rs42336, and rs1858830) and AKT rs1130233 were genotyped and tested for their effects on facial emotion perception. Facial emotion perception was assessed by the face task of Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT). Thorough neurocognitive functions were also assessed.

RESULTS

Regarding MET rs2237717, individuals with the CT genotype performed better in facial emotion perception than those with TT (p = 0.016 by ANOVA, 0.018 by general linear regression model [GLM] to control for age, gender, and education duration), and showed no difference with those with CC. Carriers with the most common MET CGA haplotype (frequency = 50.5%) performed better than non-carriers of CGA in facial emotion perception (p = 0.018, df = 1, F = 5.69, p = 0.009 by GLM). In MET rs2237717/AKT rs1130233 interaction, the C carrier/G carrier group showed better facial emotion perception than those with the TT/AA genotype (p = 0.035 by ANOVA, 0.015 by GLM), even when neurocognitive functions were controlled (p = 0.046 by GLM).

CONCLUSIONS

To our knowledge, this is the first study to suggest that genetic factors can affect performance of facial emotion perception. The findings indicate that MET variances and MET/AKT interaction may affect facial emotion perception, implicating that the MET/AKT cascade plays a significant role in facial emotion perception. Further replication studies are needed.

Overexpression of HGF attenuates the degeneration of Purkinje cells and Bergmann glia in a knockin mouse model of spinocerebellar ataxia type 7

Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant disorder associated with cerebellar neurodegeneration caused by expansion of a CAG repeat in the ataxin-7 gene. Hepatocyte growth factor (HGF), a pleiotrophic growth factor, displays highly potent neurotrophic activities on cerebellar neurons. A mutant c-met/HGF receptor knockin mouse model has revealed a role for HGF in the postnatal development of the cerebellum. The present study was designed to elucidate the effect of HGF on cerebellar neurodegeneration in a knockin mouse model of SCA7 (SCA7-KI mouse). SCA7-KI mice were crossed with transgenic mice overexpressing HGF (HGF-Tg mice) to produce SCA7-KI/HGF-Tg mice that were used to examine the phenotypic differences following HGF overexpression. The Purkinje cellular degeneration is thought to occur via cell-autonomous and non-cell autonomous mechanisms mediated by a reduction of glutamate transporter levels in Bergmann glia. The Purkinje cellular degeneration and reduced expression of glutamate transporters in the cerebellum of SCA7-KI mice were largely attenuated in the SCA7-KI/HGF-Tg mice. Moreover, phenotypic impairments exhibited by SCA7-KI mice during rotarod tests were alleviated in SCA7-KI/HGF-Tg mice. The bifunctional nature of HGF on both Purkinje cells and Bergmann glia highlight the potential therapeutic utility of this molecule for the treatment of SCA7 and related disorders.

Regulation of chondroitin sulphate proteoglycan and reactive gliosis after spinal cord transection: effects of peripheral nerve graft and fibroblast growth factor 1

AIMS

The combined treatment of peripheral nerve (PN) graft and fibroblast growth factor (FGF)-1 for spinal cord injury produces functional recovery, but how it affects injury events is still unknown. This project studied the effect of PN graft and FGF-1 on white matter degeneration following spinal cord injury.

METHODS

Rats were divided into four groups: (i) complete spinal cord transection and T8 segment removed; the remaining three groups underwent transection followed by (ii) PN grafting; (iii) supply of exogenous FGF-1; and (iv) PN grafting plus FGF-1 treatment. Chondroitin sulphate proteoglycan (CSPG) deposition, astrocytes and macrophage activation, cavity size, and calcitonin gene-related peptide and synaptophysin immunoreactivity were compared.

RESULTS

Peripheral nerve grafting increased CSPG levels compared to transection surgery alone. This CSPG was associated with the proximity to the PN graft. FGF-1 reduced CSPG deposition in grafted animals regardless of the proximity to the graft. The CSPG reduction was accompanied by reduced GFAP expression and macrophage activation. The amount of CSPG with dissociated glycosaminoglycan did not differ between groups. FGF-1 in Schwann cell-astrocyte coculture did not reduce CSPG deposition. Furthermore, the PN graft increased the calcitonin gene-related peptide immunoreactivity and altered the distribution of synaptophysin-positive axons.

CONCLUSION

Peripheral nerve graft supported sensory re-innervation and partial protection of the grey matter, but up-regulated CSPG in the graft-stump junction compared to non-grafted rats. The reduction of CSPG was caused by FGF-1-PN synergy, and did not involve dissociation of CSPG or the suppression of a general immune response.

The functional deficiency of bone marrow mesenchymal stromal cells in ALS patients is proportional to disease progression rate

Amyotrophic lateral sclerosis (ALS) is caused by motor neuron death. The relationship between the prognosis of ALS patients and the function of their bone marrow mesenchymal stromal cells (BM-MSCs) is unclear. We designed this study to assess the correlation between the progression rate of the ALS Functional Rating Scale-revised version (ΔFS), which is reported to predict prognosis, and the pluripotency and trophic factor secreting capacity of ALS patients' BM-MSCs. We evaluated ΔFS in 23 ALS patients and isolated BM-MSCs from those patients and five healthy people. Levels of Nanog, Oct-4, and Nestin mRNA were examined to evaluate pluripotency, and levels of BDNF, ECGF1, bFGF-2, HGF, IGF-1, PGF, TGF-1β, SDF-1α, GDNF, VEGF, and ANG mRNA were examined to assess trophic factor secreting capacity. In addition, we measured the protein levels of Nanog, Oct-4, Nestin, SDF-1α, ANG, bFGF-2, VEGF, IGF-1, GDNF, and BDNF. mRNA levels of Nanog, Oct-4, ECGF1, bFGF-2, HGF, IGF-1, PGF, TGF-1β, SDF-1α, GDNF, VEGF, and ANG were negatively correlations with ΔFS. However, those of Nestin and BDNF were not significantly correlated with ΔFS. Similarly, Nanog, Oct-4, SDF-1α, ANG, bFGF-2, VEGF, IGF-1, and GDNF protein levels had a significant negative correlation with ΔFS. Results indicate that the pluripotency and trophic factor secreting capacity of the BM-MSCs of ALS patients are reduced in proportion to a poorer prognosis. We therefore suggest that healthy allogeneic BM-MSCs might be a better option for cell therapy in ALS patients.

Hepatocyte growth factor protects retinal ganglion cells by increasing neuronal survival and axonal regeneration in vitro and in vivo

Hepatocyte growth factor (HGF) is known to promote the survival and foster neuritic outgrowth of different subpopulations of CNS neurons during development. Together with its corresponding receptor c-mesenchymal-epithelial transition factor (Met), it is expressed in the developing and the adult murine, rat and human CNS. We have studied the role of HGF in paradigms of retinal ganglion cell (RGC) regeneration and cell death in vitro and in vivo. After application of recombinant HGF in vitro, survival of serum-deprived RGC-5 cells and of growth factor-deprived primary RGC was significantly increased. This was shown to be correlated to the phosphorylation of c-Met and subsequent activation of serine/threonine protein kinase Akt and MAPK downstream signalling pathways involved in neuronal survival. Furthermore, neurite outgrowth of primary RGC was stimulated by HGF. In vivo, c-Met expression in RGC was up-regulated after optic nerve axotomy lesion. Here, treatment with HGF significantly improved survival of axotomized RGC and enhanced axonal regeneration after optic nerve crush. Our data demonstrates that exogenously applied HGF has a neuroprotective and regeneration-promoting function for lesioned CNS neurons. We provide strong evidence that HGF may represent a trophic factor for adult CNS neurons, which may play a role as therapeutic target in the treatment of neurotraumatic and neurodegenerative CNS disorders.

Sex-specific activation of cell death signalling pathways in cerebellar granule neurons exposed to oxygen glucose deprivation followed by reoxygenation

Neuronal death pathways following hypoxia-ischaemia are sexually dimorphic, but the underlying mechanisms are unclear. We examined cell death mechanisms during OGD (oxygen-glucose deprivation) followed by Reox (reoxygenation) in segregated male (XY) and female (XX) mouse primary CGNs (cerebellar granule neurons) that are WT (wild-type) or Parp-1 [poly(ADP-ribose) polymerase 1] KO (knockout). Exposure of CGNs to OGD (1.5 h)/Reox (7 h) caused cell death in XY and XX neurons, but cell death during Reox was greater in XX neurons. ATP levels were significantly lower after OGD/Reox in WT-XX neurons than in XY neurons; this difference was eliminated in Parp-1 KO-XX neurons. AIF (apoptosis-inducing factor) was released from mitochondria and translocated to the nucleus by 1 h exclusively in WT-XY neurons. In contrast, there was a release of Cyt C (cytochrome C) from mitochondria in WT-XX and Parp-1 KO neurons of both sexes; delayed activation of caspase 3 was observed in the same three groups. Thus deletion of Parp-1 shunted cell death towards caspase 3-dependent apoptosis. Delayed activation of caspase 8 was also observed in all groups after OGD/Reox, but was much greater in XX neurons, and caspase 8 translocated to the nucleus in XX neurons only. Caspase 8 activation may contribute to increased XX neuronal death during Reox, via caspase 3 activation. Thus, OGD/Reox induces death of XY neurons via a PARP-1-AIF-dependent mechanism, but blockade of PARP-1-AIF pathway shifts neuronal death towards a caspase-dependent mechanism. In XX neurons, OGD/Reox caused prolonged depletion of ATP and delayed activation of caspase 8 and caspase 3, culminating in greater cell death during Reox.

Neuronal pentraxin 1 induction in hypoxic-ischemic neuronal death is regulated via a glycogen synthase kinase-3α/β dependent mechanism

Intracellular signaling pathways that regulate the production of lethal proteins in central neurons are not fully characterized. Previously, we reported induction of a novel neuronal protein neuronal pentraxin 1 (NP1) in neonatal brain injury following hypoxia-ischemia (HI); however, how NP1 is induced in hypoxic-ischemic neuronal death remains elusive. Here, we have elucidated the intracellular signaling regulation of NP1 induction in neuronal death. Primary cortical neurons showed a hypoxic-ischemia time-dependent increase in cell death and that NP1 induction preceded the actual neuronal death. NP1 gene silencing by NP1-specific siRNA significantly reduced neuronal death. The specificity of NP1 induction in neuronal death was further confirmed by using NP1 (-/-) null primary cortical neurons. Declines in phospho-Akt (i.e. deactivation) were observed concurrent with decreased phosphorylation of its downstream substrate GSK-3α/β (at Ser21/Ser9) (i.e. activation) and increased GSK-3α and GSK-3β kinase activities, which occurred prior to NP1 induction. Expression of a dominant-negative inhibitor of Akt (Akt-kd) blocked phosphorylation of GSK-3α/β and subsequently enhanced NP1 induction. Whereas, overexpression of constitutively activated Akt (Akt-myr) or wild-type Akt (wtAkt) increased GSK-α/β phosphorylation and attenuated NP1 induction. Transfection of neurons with GSK-3α siRNA completely blocked NP1 induction and cell death. Similarly, overexpression of the GSK-3β inhibitor Frat1 or the kinase mutant GSK-3βKM, but not the wild-type GSK-3βWT, blocked NP1 induction and rescued neurons from death. Our findings clearly implicate both GSK-3α- and GSK-3β-dependent mechanism of NP1 induction and point to a novel mechanism in the regulation of hypoxic-ischemic neuronal death.

Transplantation of patient-derived adipose stem cells in YAC128 Huntington's disease transgenic mice

Huntington’s disease (HD) is a genetic neurodegenerative disorder caused by abnormal expansion of CAG in the huntingtin gene. In R6/2 HD transgenic mice, human adipose-derived stem cells (ASCs) can slow disease progression via secretion of multiple paracrine growth factors. In order to prompt autologous ASCs transplantation in HD, we isolated ASCs from subcutaneous adipose tissues from a HD patient and a normal volunteer. ASCs were grown in two different types of stem cell culture media, EGM-2MV (endothelial growth medium-2 MV) or mesenchymal culture medium (MesenPRO). Cell-surface markers CD13, CD29, CD31, CD34, and CD44 were characterized by flow cytometry. BDNF, HGF, IGF, LIF, NGF, and VEGF expressions were determined by RT-PCR. Cell surface markers for HD ASCs were similar to those for normal ASCs. HD ASCs expressed multiple growth factors, and were similar to normal ASCs, except for NGF; however, they can be altered by culture medium. ASCs were transplanted in bilateral striata of 8 month-old YAC128 mice. At 12 months of age, normal ASCs reduced striatal atrophy, while HD ASCs failed to prevent it. Compared to the control YAC128 group, no improvement in Rotarod performance was observed in any of the transplanted YAC128 mice. However, when normal ASCs were transplanted at 12 months, Rotarod performance was maintained for 4 weeks, with detectable transplanted cells in the striatum and periventricular area. In summary, cultured HD patient-derived ASCs express multiple growth factors with the same cell surface markers as those of normal ASCs in vitro. The efficacy of ASCs transplantation in YAC128 transgenic models can be modified, depending on the time window.

Hepatocyte growth factor protects human embryonic stem cell derived-neural progenitors from hydrogen peroxide-induced apoptosis

Promoting human embryonic stem cell (hESC)-derived-neural progenitor survival in the pro-apoptotic niche is pivotal for stem cell replacement therapy. The present study was designed to investigate the protective effect of hepatocyte growth factor (HGF) on hESC-derived neural progenitor injured by hydrogen peroxide (H(2)O(2)) exposure. Treatment of hESC-derived neural progenitor cells with HGF prior to H(2)O(2) exposure conferred protective effect against oxidative stress-induced apoptosis. HGF treatment increased both phosphoinositide 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase1/2 (ERK1/2) phosphorylation. However, selective inhibition of each pathway supported that the activation of PI3K/AKT, but not ERK1/2, provides survival advantage to the neural progenitor cells. Further investigation indicated that HGF pretreatment could attenuate the decrease of the expression of Bcl-2 protein induced by H(2)O(2), whereas the level of Bax was not affected. Additionally, we observed that H(2)O(2)-induced decrease of mitochondrial transmembrane potential, release of cytochrome c and increase of caspase-3 activation were alleviated by HGF pretreatment. These effects of HGF could be reversed by inhibition of the PI3K/Akt and ERKs pathways, indicating PI3K/Akt and ERKs signaling might be involved in HGF-mediated regulation of mitochondrial apoptotic pathway mediated by H(2)O(2). The neuroprotective effect of HGF might potentially be useful in stem cell-based therapies for neurodegenerative disorders.

Slowed progression in models of Huntington disease by adipose stem cell transplantation

OBJECTIVE

Adipose-derived stem cells (ASCs) are readily accessible and secrete multiple growth factors. Here, we show that ASC transplantation rescues the striatal pathology of Huntington disease (HD) models.

METHODS

ASCs were isolated from human subcutaneous adipose tissue. In a quinolinic acid (QA)-induced rat model of striatal degeneration, human ASCs (1 million cells) were transplanted into the ipsilateral striatal border immediately after the QA injection. In 60-day-old R6/2 mice transgenic for HD, ASCs (0.5 million cells) were transplanted into each bilateral striata. In in vitro experiments, we treated mutant huntingtin gene-transfected cerebral neurons with ASC-conditioned media.

RESULTS

In the QA model, human ASCs reduced apomorphine-induced rotation behavior, lesion volume, and striatal apoptosis. In R6/2 transgenic mice, transplantation of ASCs improved Rota-Rod performance and limb clasping, increased survival, attenuated the loss of striatal neurons, and reduced the huntingtin aggregates. ASC-transplanted R6/2 mice expressed elevated levels of peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) and reactive oxygen defense enzymes and showed activation of the Akt/cAMP-response element-binding proteins. ASC-conditioned media decreased the level of N-terminal fragments of mutant huntingtin and associated apoptosis, and increased PGC-1alpha expression.

INTERPRETATION

Collectively, ASC transplantation slowed striatal degeneration and behavioral deterioration of HD models, possibly via secreted factors.

Stem cells as tools in regenerative therapy for retinal degeneration

OBJECTIVE

To describe the use of stem cells (SCs) for regeneration of retinal degenerations. Regenerative medicine intends to provide therapies for severe injuries or chronic diseases where endogenous repair does not sufficiently restore the tissue. Pluripotent SCs, with their capacity to give rise to specialized cells, are the most promising candidates for clinical application. Despite encouraging results, a combination with up-to-date tissue engineering might be critical for ultimate success.

DESIGN

The focus is on the use of SCs for regeneration of retinal degenerations. Cell populations include embryonic, neural, and bone marrow-derived SCs, and engineered grafts will also be described.

RESULTS

Experimental approaches have successfully replaced damaged photoreceptors and retinal pigment epithelium using endogenous and exogenous SCs.

CONCLUSIONS

Stem cells have the potential to significantly impact retinal regeneration. A combination with bioengineering may bear even greater promise. However, ethical and scientific issues have yet to be solved.

The genetic and neurobiologic compass points toward common signaling dysfunctions in autism spectrum disorders

Autism spectrum disorder (ASD) is a common neurodevelopmental disorder with high heritability. Here, we discuss data supporting the view that there are at least two distinct genetic etiologies for ASD: rare, private (de novo) single gene mutations that may have a large effect in causing ASD; and inherited, common functional variants of a combination of genes, each having a small to moderate effect in increasing ASD risk. It also is possible that a combination of the two mechanisms may occur in some individuals with ASD. We further discuss evidence from individuals with a number of different neurodevelopmental syndromes, in which there is a high prevalence of ASD, that some private mutations and common variants converge on dysfunctional ERK and PI3K signaling, which negatively impacts neurodevelopmental events regulated by some receptor tyrosine kinases.

Hepatocyte growth factor and sonic Hedgehog expression in cerebellar neural progenitor cells costimulate medulloblastoma initiation and growth

Medulloblastomas are malignant brain tumors that arise by transformation of neural progenitor cells in the cerebellum in children. Treatment-related neurotoxicity has created a critical need to identify signaling molecules that can be targeted therapeutically to maximize tumor growth suppression and minimize collateral neurologic injury. In genetically engineered mice, activation of Sonic Hedgehog (Shh) signaling in neural stem cells in the developing cerebellum induces medulloblastomas. Hepatocyte growth factor (HGF) and its cell surface receptor c-Met are highly expressed in human medulloblastomas, and elevated levels of c-Met and HGF mRNA predict an unfavorable prognosis for patients. HGF is neuroprotective for cerebellar granule cells and promotes growth of human medulloblastoma cells in culture and in murine xenografts. We modeled the ability of HGF to induce medulloblastomas in mice using a version of the RCAS/tv-a system that allows gene transfer to cerebellar neural progenitors during their postnatal expansion phase when these cells are highly susceptible to transformation. Here, we report a high frequency of medulloblastoma formation in mice after postnatal expression of HGF in cooperation with Shh. Some tumors showed neurocytic differentiation similar to that in human nodular medulloblastomas with activated Shh signaling. Systemic administration of a monoclonal antibody against HGF prolonged survival of mice bearing Shh + HGF-induced medulloblastomas by stimulating apoptosis. These findings indicate a role for HGF in medulloblastoma initiation and growth and show efficacy of HGF-targeted therapy in a mouse model of endogenously arising tumors.

pCREB is involved in neural induction of mouse embryonic stem cells by RA

Mouse embryonic stem (ES) cells can be induced by various chemicals to differentiate into a variety of cell types in vitro. In our study, retinoic acid (RA), one of the most important inducers, used at a concentration of 5 microM, was found to induce the differentiation of ES cells into neural progenitor cells (NPCs). During embryoid body (EB) differentiation, the level of active cyclic AMP response element-binding protein (CREB) was relatively high when 5 microM RA treatment was performed. Inhibition of CREB activity committed EBs to becoming other germ layers, whereas increased expression of CREB enhanced NPC differentiation. Moreover, RA increased the expression of active CREB by enhancing the activity of JNK. Our research suggests that CREB plays a role in RA-induced NPC differentiation by increasing the expression of active JNK.

Nuclear translocation of X-linked inhibitor of apoptosis (XIAP) determines cell fate after hypoxia ischemia in neonatal brain

The inhibitors of apoptosis (IAPs) are emerging as key proteins in the control of cell death. In this study, we evaluated the expression and subcellular distribution of the antiapoptotic protein X-linked IAP (XIAP), and its interactions with the XIAP-associated factor 1 (XAF1) in neonatal rat brain following hypoxia-ischemia (HI). HI triggered the mitochondrial release of cytochrome c, Smac/DIABLO, and caspase 3 activation. Confocal microscopy detected XIAP-specific immunofluorescence in the cytoplasm under normal condition, which exhibited a diffuse distribution at 6 h post-HI and by 12 h the majority of XIAP was redistributed into the nucleus. XIAP nuclear translocation was confirmed by subcellular fractionations and by expressing FLAG-tagged XIAP in primary cortical neurons. Over-expression of XIAP significantly reduced, whereas XIAP gene silencing further enhanced cell death, demonstrating a specific requirement of cytoplasmic XIAP for cell survival. An elevated level of cytosolic XIAP was also evident under the conditions of neuroprotection by fibroblast growth factor-1. XAF1 expression was increased temporally and there was increased nuclear co-localization with XIAP in hypoxic-ischemic cells. XIAP co-immunoprecipitated > 9-fold XAF1 protein concurrent with decreased association with caspases 9 and 3. This is evidenced by the enhanced caspase 3 activity and neuronal death. Our findings implicate XIAP nuclear translocation in neuronal death and point to a novel mechanism in the regulation of hypoxic-ischemic brain injury.

Impact of opiate-HIV-1 interactions on neurotoxic signaling

Opiate drug abuse exacerbates the pathogenesis of human immunodeficiency virus-1 (HIV-1) in the central nervous system through direct actions on glia and neurons. Opiate abuse causes widespread disruption of astroglial and microglial function, and significant increases in astroglial-derived proinflammatory cytokines and chemokines, which likely contributes to neuronal dysfunction, death, and HIV encephalitis. Neurons are also directly affected by opiate-HIV-1 interactions. HIV-1 and the viral proteins gp120 and Tat activate multiple caspase-dependent and caspase-independent proapoptotic pathways in neurons involving phosphatidylinositol 3-kinase (PI3 kinase)/Akt, as well as p38, c-Jun N-terminal kinase (JNK) and/or other mitogen-activated protein kinases (MAPKs). Opiates appear to decrease the threshold for HIV-1-mediated neurotoxicity by sending convergent signals that exacerbate proapoptotic events induced by viral and cellular toxic products. The synergistic proinflammatory and neurotoxic effects of opiate drugs on glia and neurons are largely mediated through mu opioid receptors, which are expressed by subpopulations of astroglia, microglia, and neurons. Opiate abuse intrinsically modifies the host response to HIV-1. Identification of how this occurs is providing considerable insight toward understanding the mechanisms underlying HIV-1-associated dementia.

Basic fibroblast growth factor-induced protection from light damage in the mouse retina in vivo

Basic fibroblast growth factor (bFGF) has proven neuroprotective efficacy in the rodent retina against a diverse array of injurious stimuli. However, there is no consensus to date as to the molecular mechanisms underlying this neuroprotection. The study presented herein demonstrates increased expression of endogenous bFGF in the albino mouse retina in response to acute exposure to sublethal levels of light stress. The increased expression correlates with significant photoreceptor protection from light damage. The neuroprotection is likely to be mediated by bFGF as we demonstrate that a shorter exposure to bright light stress that does not up-regulate bFGF fails to protect photoreceptors from light damage. Furthermore, intravitreal bFGF injection into the retina of mice 3 h prior to light damage affords almost complete photoreceptor protection from light-induced degeneration. In addition, injected bFGF induces the activation of protein kinase B and extracellular signal-regulated kinase 1/2 signalling which correlate directly with the pathways we find to be activated in response to light stress and up-regulated bFGF. Moreover, we demonstrate that both bright light pre-conditioning and intravitreal bFGF injection result in dramatic increases in levels of inactive glycogen synthase kinase 3beta and cyclic AMP response element binding protein phosphorylation indicating a potential mechanism by which bFGF promotes survival of photoreceptors in vivo.

Enhanced cell death in MeCP2 null cerebellar granule neurons exposed to excitotoxicity and hypoxia

Rett syndrome (RTT) is associated with mutations in the transcriptional repressor gene MeCP2. Although the clinical and neuropathological signs of RTT suggest disrupted synaptic function, the specific role of methyl-CpG binding protein 2 (MeCP2) in postmitotic neurons remains relatively unknown. We examined whether MeCP2 deficiency in central neurons contributes to the neuropathogenesis in RTT. Primary cerebellar granule neuronal cultures from wild-type (WT) and MeCP2-/- mice were exposed to N-methyl-d-aspartate (NMDA) and AMPA-induced excitotoxicity and hypoxic-ischemic insult. The magnitude of cell death in MeCP2-/- cells after excitotoxicity and hypoxia was greater than in the WT littermate control cultures and occurred after shorter exposures that usually, in the WT, would not cause cell death. Pretreatment with the growth factor fibroblast growth factor 1 (FGF-1) under conditions at which WT cells showed complete neuroprotection, only partially protected MeCP2-/- cells. To elucidate specifically the effects of MeCP2 knockout (KO) on cell death, we examined two death cascade pathways. MeCP2-/- neurons exposed to 6 h of hypoxia exhibited enhanced activation of the proapoptotic caspase-3 and increased mitochondrial release of apoptosis inducing factor (AIF) compared with WT neurons, which did not show significant changes. However, pretreatment with the caspase inhibitor ZVAD-FMK had little or no effect on AIF release and its subcellular translocation to the nucleus, suggesting caspase-independent AIF release and their independent contribution to hypoxia-induced cell death. Reintroduction of intact MeCP2 gene in MeCP2-/- cells or MeCP2 gene silencing by MeCP2siRNA in WT cells further confirmed the differential sensitivity of the WT and MeCP2-/- cells and suggest a direct role of MeCP2 in cell death. These results clearly demonstrate increased cell death occurred in neurons lacking MeCP2 expression via both caspase- and AIF-dependent apoptotic mechanisms. Our findings suggest a novel, yet unknown, role for MeCP2 in central neurons in the control of neuronal response to cell death.

Hepatocyte growth factor promotes the number of PSD-95 clusters in young hippocampal neurons

Hepatocyte growth factor (HGF) and its receptor are expressed in various regions of the brain and have protective effects against excitotoxic injuries. However, their effects on synapse formation remain to be elucidated. To determine whether HGF has the ability to alter synaptic function during development, we investigated changes in the number of synapse detected by double immunostaining for NMDA receptor subunits and a presynaptic marker in cultured young hippocampal neurons. Whereas application of HGF increased the number of cluster of synapsin, a presynaptic protein, the clusters of NMDA receptor subunits NR1 and NR2B were not altered. Interestingly, colocalization of PSD-95, a scaffolding protein of the receptor, with synapsin was increased by HGF treatment without a change in the total amount of it. In addition, we investigated the expression of surface NMDA receptor, neuroligin, and neurexin, which were assessed by use of a cell-surface biotinylation assay. The application of HGF did not change the surface expression of these proteins. Furthermore, we determined the release of glutamate in response to depolarization. Treatment with HGF promoted depolarization-evoked release of glutamate. These results suggest that HGF modulates the expression of the scaffolding protein of the NMDA receptor at the synapse and promotes maturation of excitatory synapses in young hippocampal neurons.

Activation of protein kinase B/Akt in the periphery contributes to pain behavior induced by capsaicin in rats

Protein kinase B (PKB/Akt) is a member of the second-messenger regulated subfamily of protein kinases. It is implicated in signaling downstream of growth factors, insulin receptor tyrosine kinases and phosphoinositide 3-kinase (PI3K). Current studies indicate that nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and PI3K help mediate inflammatory hyperalgesia. However, little is known about the role of PKB/Akt in the nociceptive system. In this study, we investigated whether PKB/Akt in primary sensory neurons is activated after noxious stimulation and contributes to pain behavior induced in rats by capsaicin. We demonstrated that phospho-PKB/Akt (p-PKB/Akt) is increased in dorsal root ganglia (DRG) at 5 min after intradermal injection of capsaicin. p-PKB/Akt is distributed predominantly in small- and medium-sized DRG cells. After capsaicin injection, p-PKB/Akt (473) is colocalized with isotectin-B4 (IB4), tyrosine kinase A (TrkA), and calcitonin gene-related peptide (CGRP). Furthermore, most transient receptor potential vanilloid type 1 (TRPV1) positive DRG neurons double label for p-PKB/Akt. Behavioral experiments show that intradermal injection of a PI3K (upstream of PKB/Akt) inhibitor, wortmannin, dose-dependently inhibits the changes in exploratory behavior evoked by capsaicin injection. The PKB/Akt inhibitor, Akt inhibitor IV, has the same effect. The results suggest that the PKB/Akt signaling pathway in the periphery is activated by noxious stimulation and contributes to pain behavior.

Adenoviral gene transfer of hepatocyte growth factor prevents death of injured adult motoneurons after peripheral nerve avulsion

Hepatocyte growth factor (HGF) exhibits strong neurotrophic activities on motoneurons both in vitro and in vivo. We examined survival-promoting effects of an adenoviral vector encoding human HGF (AxCAhHGF) on injured adult rat motoneurons after peripheral nerve avulsion. The production of HGF in COS1 cells infected with AxCAhHGF and its bioactivity were confirmed by ELISA, Western blot and Madin-Darby canine kidney (MDCK) cell scatter assay. The facial nerve or the seventh cervical segment (C7) ventral and dorsal roots of 3-month-old Fischer 344 male rats were then avulsed and removed from the stylomastoid or vertebral foramen, respectively, and AxCAhHGF, AxCALacZ (adenovirus encoding beta-galactosidase gene) or phosphate-buffered saline (PBS) was inoculated in the lesioned foramen. Treatment with AxCAhHGF after avulsion significantly prevented the loss of injured facial and C7 ventral motoneurons as compared to AxCALacZ or PBS treatment and ameliorated choline acetyltransferase immunoreactivity in these neurons. These results indicate that HGF may prevent the degeneration of motoneurons in adult humans with motoneuron injury and motor neuron diseases.

Protective Effects of Neurotrophic Factors on Tumor Necrosis Factor-related Apoptosis-inducing Ligand (TRAIL)-mediated Apoptosis of Murine Adrenal Chromaffin Cell Line tsAM5D

We previously established the murine adrenal chromaffin cell line tsAM5D, which was immortalized with the temperature-sensitive simian virus 40 large T-antigen. tsAM5D cells have the capacity to differentiate into neuron-like cells in response to neurotrophic factors when the culture temperature is shifted from 33 to 39 degrees C. In this model system, the temperature shift in the absence of neurotrophic factors led to cell death. Hoechst staining analysis revealed that typical apoptotic nuclei appeared in a time-dependent manner after the temperature shift. Upon shifting to 39 degrees C, the degradation of T-antigen was accompanied by the transcriptional activation of p53 protein. Among the p53 target genes, death receptor 5 (DR5), which is the receptor for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), showed the highest level of induction. Interestingly, TRAIL-neutralizing antibody protected tsAM5D cells from the temperature shift-induced apoptotic cell death by blocking the activation of caspase-8 and -3, indicating the involvement of TRAIL-mediated death signaling in the temperature shift-induced apoptosis. Glial cell line-derived neurotrophic factor (GDNF) inhibited the TRAIL-mediated activation of caspase-8 in tsAM5D cells exposed to 39 degrees C and cooperated with basic fibroblast growth factor and ciliary neurotrophic factor. Interestingly, the temperature shift induced oligomerization of DR5, which is the earliest process necessary for transduction of the death signal. This oligomerization was inhibited by treatment with GDNF plus ciliary neurotrophic factor but not by that with GDNF alone or GDNF plus basic fibroblast growth factor. These results are discussed with respect to the intracellular mechanism underlying the protective function of neurotrophic factors against TRAIL-mediated death signaling.

Transgenic expression of human FGF-1 protects against hypoxic-ischemic injury in perinatal brain by intervening at caspase-XIAP signaling cascades

Perinatal hypoxia-ischemia (HI) is a major cause of neurological disability and mortality in infant and children. In the present study, we explored the neuroprotective efficacy of FGF-1 in a rat model of perinatal HI. Carotid ligation combined with hypoxia caused marked infarctions in the ipsilateral cerebral hemisphere with significant loss of ipsilateral striatal, cortical and hippocampal volumes. Morphological analyses revealed both apoptotic and necrotic form of neuronal death determined by Nissl histology, dark-field microscopy and TUNEL staining. HI induced a marked increase in activated caspase-9, caspase-3 and PARP cleavage at 12 h to 7 days after HI in brain areas displaying TUNEL (+) cells. In addition, expression of the anti-apoptotic protein X-linked inhibitor of apoptosis (XIAP) was decreased under similar conditions of HI. Expression of human FGF-1 in brain significantly reduced the extent of both apoptotic and necrotic injury caused by HI. FGF-1 attenuated the HI-induced increase in activated caspase-3, caspase-9 and cleaved PARP protein levels and markedly blocked the HI-induced decrease in XIAP expression under the conditions at which FGF-1 showed significant neuroprotection. These findings demonstrate that FGF-1 prevents the onset of both apoptotic and necrotic death in neurons otherwise "destined to die" following hypoxic-ischemic injury by intervening at the level of caspase-signaling cascades and by restoring prosurvival protein XIAP expression in central neurons.

Effects of hepatocyte growth factor on phosphorylation of extracellular signal-regulated kinase and hippocampal cell death in rats with transient forebrain ischemia

Hepatocyte growth factor (HGF) has been implicated in protection against several types of cell injuries. We investigated the effects of human recombinant HGF (hrHGF) on the selective neuronal cell death in the hippocampal CA1 region after transient forebrain ischemia in rats and explored the nature of the intracellular signaling pathway for the protection against this neuronal injury. hrHGF was injected continuously into the hippocampal CA1 region directly using an osmotic pump from 10 min to 72 h after the start of reperfusion. The marked increase in the number of TUNEL-positive cells found in the CA1 region after ischemia was almost completely abolished by the hrHGF treatment. Akt phosphorylation as well as IkappaB phosphorylation, which has been implicated in events downstream of the Akt, was not affected by hrHGF treatment. Extracellular signal-regulated kinase (ERK) phosphorylation was decreased in the CA1 region with time after ischemia. hrHGF increased or recovered ERK phosphorylation without changing the total amount of ERK protein. Immunohistochemical analysis demonstrated that phosphorylated ERK was colocalized with a neuronal nucleus marker NeuN in the hippocampal CA1 region of ischemic rats with hrHGF treatment at the early period after reperfusion. These results suggest that the protective effects of hrHGF against neuronal death in the hippocampal CA1 after transient forebrain ischemia could be related to an ERK-dependent pathway.

The scatter factor/hepatocyte growth factor: c-met pathway in human embryonal central nervous system tumor malignancy

Embryonal central nervous system (CNS) tumors, which comprise medulloblastoma, are the most common malignant brain tumors in children. The role of the growth factor scatter factor/hepatocyte growth factor (SF/HGF) and its tyrosine kinase receptor c-Met in these tumors has been until now completely unknown. In the present study, we show that human embryonal CNS tumor cell lines and surgical tumor specimens express SF/HGF and c-Met. Furthermore, c-Met mRNA expression levels statistically significantly correlate with poor clinical outcome. Treatment of medulloblastoma cells with SF/HGF activates c-Met and downstream signal transduction as evidenced by c-Met, mitogen-activated protein kinase, and Akt phosphorylation. SF/HGF induces tumor cell proliferation, anchorage-independent growth, and cell cycle progression beyond the G1-S checkpoint. Using dominant-negative Cdk2 and a degradation stable p27 mutant, we show that cell cycle progression induced by SF/HGF requires Cdk2 function and p27 inhibition. SF/HGF also protects medulloblastoma cells against apoptosis induced by chemotherapy. This cytoprotective effect is associated with reduction of proapoptotic cleaved poly(ADP-ribose) polymerase and cleaved caspase-3 proteins and requires phosphoinositide 3-kinase activity. SF/HGF gene transfer to medulloblastoma cells strongly enhances the in vivo growth of s.c. and intracranial tumor xenografts. SF/HGF-overexpressing medulloblastoma xenografts exhibit increased invasion and morphologic changes that resemble human large cell anaplastic medulloblastoma. This first characterization establishes SF/HGF:c-Met as a new pathway of malignancy with multifunctional effects in human embryonal CNS tumors.

Kynurenic Acid Inhibits the Release of the Neurotrophic Fibroblast Growth Factor (FGF)-1 and Enhances Proliferation of Glia Cells, in vitro

1. Kynurenic (KYNA) and quinolinic (QUIN) acids are neuroactive tryptophan metabolites formed along the kynurenine pathway: the first is considered a non-competitive antagonist and the second an agonist of glutamate receptors of NMDA type. The affinity of these compounds for glutamate receptors is, however, relatively low and does not explain KYNA neuroprotective actions in models of post-ischemic brain damage. 2. We evaluated KYNA effects on the release of fibroblast growth factor (FGF)-1, a potent neurotrophic cytokine. Because KYNA exhibits a neuroprotective profile in vitro and in vivo, we anticipated that it could function as an autocrine/paracrine inducer of FGF-1 release. Studies were performed in several models of FGF-1 secretion (FGF-1 transfected NIH 3T3 cells exposed to heat shock, A375 melanoma cells exposed to serum starvation, growth factor deprived human endothelial cells). To our surprise, KYNA, at low concentration, inhibited FGF-1 release in all cellular models. QUIN, a compound having opposite effects on glutamate receptors, also reduced this release, but its potency was significantly lower than that of KYNA. 3. KYNA and QUIN also displayed a major stimulatory effect on the proliferation rate of mouse microglia and human glioblastoma cells, in vitro. 4. Our data suggest that minor changes of local KYNA concentration may modulate FGF-1 release, cell proliferation, and ultimately tissue damage in different pathological conditions.

Molecular mediators of hypoxic-ischemic injury and implications for epilepsy in the developing brain

Perinatal hypoxia-ischemia (HI) is the most common cause of cerebral palsy, and an important consequence of perinatal HI is epilepsy. Epilepsy is a disorder in which the balance between cerebral excitability and inhibition is tipped toward uncontrolled excitability. Selected neuronal circuits as well as certain populations of glial cells die from the excitotoxicity triggered by HI. Excitotoxicity, a term referring to cell death caused by overstimulation of the excitatory glutamate neurotransmitter receptors, plays a critical role in brain injury caused by perinatal HI. Ample evidence suggests distinct differences between the immature and mature brain with respect to the pathology and consequences of hypoxic-ischemic brain injury. Thus, the intrinsic vulnerability of specific cell types and systems in the developing brain is particularly important in determining the final pattern of damage and functional disability caused by perinatal HI. These patterns of neuronal vulnerability are associated with clinical syndromes of neurologic disorders such as cerebral palsy, epilepsy, and seizures. Recent studies have uncovered important molecular and cellular aspects of hypoxic-ischemic brain injury. The cascade of biochemical and histopathological events initiated by HI can extend for days to weeks after the insult is triggered, which may provide a "therapeutic window" for intervening in the pathogenesis in the developing brain. Activation of apoptotic programs accounts for the majority of HI-induced pathophysiology in neonatal brain disorders. New experimental approaches to protecting brain tissue from the effects of neonatal HI include administration of neuronal growth factors and effective inhibition of the death effector pathways, such as caspase cascade, and their downstream targets, which execute apoptosis and/or induction of their regulatory cellular proteins. Our recent findings that a novel neuronal protein, neuronal pentraxin 1 (NP1), is induced following HI in neonatal brain and that NP1 gene silencing is neuroprotective suggest that NP1 could be a new molecular target in the central neurons for preventing HI injury in developing brain. Most importantly, the specific interactions between NP1 and the excitatory glutamate receptors and their colocalization further implicate a role for this novel neuronal protein in the excitotoxic cascade. Recent experimental work suggests that these approaches may be effective during a longer therapeutic window after the insult, as they are acting on events that are relatively delayed, creating the potential for therapeutic interventions for these lifelong neurological disabilities.

Inhibition of apoptosis-inducing factor translocation is involved in protective effects of hepatocyte growth factor against excitotoxic cell death in cultured hippocampal neurons

Although hepatocyte growth factor (HGF) and its receptor are expressed in various regions of the brain, their effects and mechanism of action under pathological conditions remain to be determined. Over-activation of the N-methyl-d-aspartate (NMDA) receptor, an ionotropic glutamate receptor, has been implicated in a variety of neurological and neurodegenerative disorders. We investigated the effects of HGF on the NMDA-induced cell death in cultured hippocampal neurons and sought to explore their mechanisms. NMDA-induced cell death and increase in the number of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL)-positive cells were prevented by HGF treatment. Although neither the total amounts nor the mitochondrial localization of Bax, Bcl-2 and Bcl-xL were affected, caspase 3 activity was increased after NMDA exposure. Treatment with HGF partially prevented this NMDA-induced activation of caspase 3. Although the amount of apoptosis-inducing factor (AIF) was not altered, translocation of AIF into the nucleus was detected after NMDA exposure. This NMDA-induced AIF translocation was reduced by treatment with HGF. In addition, increased poly(ADP-ribose) polymer formation after NMDA exposure was attenuated by treatment with HGF. These results suggest that the protective effects of HGF against NMDA-induced neurotoxicity are mediated via the partial prevention of caspase 3 activity and the inhibition of AIF translocation to the nucleus.

Targeting the c-Met Pathway Potentiates Glioblastoma Responses to γ-Radiation

PURPOSE

Resistance to current cytotoxic therapies limits the treatment of most solid malignancies. This results, in part, from the overactivation of receptor tyrosine kinases and their downstream pathways in tumor cells and their associated vasculature. In this report, we ask if targeting the multifunctional mitogenic, cytoprotective, and angiogenic scatter factor/hepatocyte growth factor (SF/HGF)/c-Met pathway potentiates antitumor responses to gamma-radiation.

EXPERIMENTAL DESIGN

Endogenous expression of SF/HGF and c-Met was targeted in U87 MG human malignant glioma cells and xenografts using chimeric U1/ribozymes. The effects of U1/ribozymes +/- gamma-radiation on glioma cell proliferation, apoptosis, xenograft growth, and animal survival were examined.

RESULTS

U1/ribozymes knocked down SF/HGF and c-Met mRNA and protein levels, sensitized cells to gamma-radiation (P < 0.005), and enhanced radiation-induced caspase-dependent cytotoxicity in vitro (P < 0.005). Intravenous U1/ribozyme therapy as liposome/DNA complexes or radiation alone modestly and transiently inhibited the growth of s.c. U87 xenografts. Combining the therapies caused tumor regression and a 40% tumor cure rate. In animals bearing intracranial xenografts, long-term survival was 0% in response to radiation, 20% in response to intratumoral adenoviral-based U1/ribozyme delivery, and 80% (P < 0.0005) in response to combining U1/ribozymes with radiation. This apparent synergistic antitumor response was associated with a approximately 70% decrease in cell proliferation (P < 0.001) and a approximately 14- to 40-fold increase in apoptosis (P < 0.0001) within xenografts.

CONCLUSIONS

Targeting the SF/HGF/c-Met pathway markedly potentiates the anti-glioma response to gamma-radiation. Clinical trials using novel SF/HGF/c-Met pathway inhibitors in glioma and other malignancies associated with c-Met activation should ultimate include concurrent radiation and potentially other cytotoxic therapeutics.

Mechanisms of aging in senescence-accelerated mice

BACKGROUND

Progressive neurological dysfunction is a key aspect of human aging. Because of underlying differences in the aging of mice and humans, useful mouse models have been difficult to obtain and study. We have used gene-expression analysis and polymorphism screening to study molecular senescence of the retina and hippocampus in two rare inbred mouse models of accelerated neurological senescence (SAMP8 and SAMP10) that closely mimic human neurological aging, and in a related normal strain (SAMR1) and an unrelated normal strain (C57BL/6J).

RESULTS

The majority of age-related gene expression changes were strain-specific, with only a few common pathways found for normal and accelerated neurological aging. Polymorphism screening led to the identification of mutations that could have a direct impact on important disease processes, including a mutation in a fibroblast growth factor gene, Fgf1, and a mutation in and ectopic expression of the gene for the chemokine CCL19, which is involved in the inflammatory response.

CONCLUSION

We show that combining the study of inbred mouse strains with interesting traits and gene-expression profiling can lead to the discovery of genes important for complex phenotypes. Furthermore, full-genome polymorphism detection, sequencing and gene-expression profiling of inbred mouse strains with interesting phenotypic differences may provide unique insights into the molecular genetics of late-manifesting complex diseases.

Local expression of GH and IGF-1 in the hippocampus of GH-deficient long-lived mice

Beneficial effects of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) on the development and function of the central nervous system are well documented. In spite of primary deficiency of GH and secondary IGF-1 deficiency, Ames dwarf mice live considerably longer than normal animals, exhibit apparently normal cognitive functions and maintain them into advanced age. In an attempt to reconcile these findings, we have examined local expression of GH and IGF-1 in the hippocampus of normal and Ames dwarf mice. We found that both hippocampal GH and IGF-1 protein levels are increased and the corresponding mRNAs are normal in Ames dwarf as compared with normal mice. Increased phosphorylation of Akt and cyclic AMP responsive element-binding protein (CREB) were detected in the hippocampus of Ames dwarf mice. Our results suggest that increase in hippocampal GH and IGF-1 protein expression and subsequent activation of PI3K/Akt-CREB signal transduction cascade might contribute to the maintenance of cognitive function and is likely to be responsible for the integrity of neuronal structure, and maintenance of youthful levels of cognitive function in these long-lived mice during aging.

Bone marrow mononuclear cell transplantation into heart elevates the expression of angiogenic factors

The expression of angiogenic factors was measured to elucidate the mechanism of angiogenesis after bone marrow stem cells transplantation. The left anterior descending coronary (LAD) artery was ligated in male Lewis rats to induce an acute myocardial infarction (AMI); of which, some rats received bone marrow mononuclear cells transplantation (BMT). The expression of cytokines and their receptors was assessed by RT-PCR. The expression of c-met was upregulated in the AMI animals and was further increased when the animals received BMT (P < 0.01). The other cytokines and their receptors remained unchanged after BMT compared with AMI samples. Normal bone marrow mononuclear cells have higher expression level of hepatocyte growth factor (HGF) than those in normal hearts. In conclusion, BMT could increase the expression of c-met. Not all angiogenic cytokines and their receptors were upregulated after BMT. The higher expression of hepatocyte growth factor in bone marrow may contribute to the upregulation of c-met.