Neurotrophins

As a female transitions into motherhood, many neurobiological adaptations are required to meet the demands presented by her offspring. In addition to the traditional maternal responses (e.g. crouching, nursing, retrieving, grooming), our laboratories have observed several behavioural modifications accompanying parity, especially in the areas of foraging and emotional resilience. Additionally, brain modifications have been observed in the hippocampus and amygdala, providing support for neural plasticity extending beyond the expected hypothalamic alterations. Interestingly, we have observed parenting-induced neuroplasticity to persist into late adulthood, even providing protection against age-related brain and memory deficits. Although the majority of work on the parental brain has been conducted on females, preliminary research suggests similar changes in the biparental male California deer mouse. Taken together, research suggests that the parental brain is dynamic and changeable as it undergoes diverse and, in some cases, long-lasting, modifications to facilitate the production and care of offspring.

Nerve Growth Factor (NGF) receptors, TrKA and p75NTR, are being investigated in cancer therapy. Our previous data show that, in HTB114 uterine leiomyosarcoma cells, p75NTR-dependent apoptosis is inducible by cytotoxic drugs, and can suppress NGF-dependent growth. Although amitriptyline can kill cancer cells and bind TrKA/B, its effects on p75NTR-dependent apoptosis are unknown. Objective: the aim of this paper was to evaluate the antineoplastic potential of amitriptyline, and the role of p75NTR-dependent apoptosis in the chemoresistant uterine HTB114 leiomyosarcoma. Methods and results: using proliferation assays and FACS-analysis, we found that amitriptyline caused a dramatic reduction of HTB114 cell viability, associated to the parallel up-regulation of p75NTR expression. This converted the TrKA+-proliferating cells into TrKA+/p75NTR+, leading to down-regulation of TrKA-pro-survival signaling (AKT) and activation of p75NTR-dependent apoptosis (via caspase-3). Conclusions: overall, we provide novel evidence that HTB114 uterine leiomyosarcoma cells are highly sensitive to amitriptyline, supporting the role of p75NTR-dependent apoptosis as a novel cytotoxic mechanism of this drug, and of p75NTR as an inducible stress receptor and a novel target in clinical oncology.

The Nerve Growth Factor (NGF) is the prototypic member of the neurotrophin (NT) family, which plays an essential role in the development and functioning of the vertebrate nervous system. Although originally defined by their actions on neuronal survival and differentiation in the peripheral (PNS) and central nervous systems (CNS), accumulating data indicate the presence of extensive interactions between the NTs and the immune system. NTs are released normally during lymphocyte and leukocyte development by the bone marrow and the thymus and later by secondary lymph organs to maintain responsiveness of these circulating naïve and memory immune cells. Functional NT receptors have been detected on the cells of the immune system and increased levels of NGF protein are found during the acute phase of various diseases with a significant inflammatory component. Furthermore, in certain conditions such as allergic asthma, the released NTs exacerbate the severity of the inflammation and prolong the diseased state. However, in the CNS, if one can control homeostasis of the internal environment, then the natural response of the infiltrating immune cells to release these NTs can be used to intervene at key points in the disease progression. These wider functions are likely to be of concern in any attempted therapeutic use of NGF or related NTs.

Inner ear hair cells have been suggested as attractors for growing afferent fibers, possibly through the release of the neurotrophin brain-derived neurotrophic factor (BDNF). Atoh1 null mice never fully differentiate hair cells and supporting cells and, therefore, may show aberrations in the growth and/or retention of their innervation. We investigated the distribution of cells positive for Atoh1- or Bdnf-mediated β-galactosidase expression in Atoh1 null and Atoh1 heterozygotic mice and correlated the distribution of these cells with their innervation. Embryonic day (E) 18.5 Atoh1 null and heterozygotic littermates show Atoh1- and BDNF-β-galactosidase–positive cells in comparable distributions in the canal cristae and the cochlea apex. Atoh1-β-galactosidase–positive but only occasional Bdnf-β-galactosidase–positive cells are found in the utricle, saccule, and cochlea base of Atoh1 null mutant mice. Absence of Bdnf-β-galactosidase expression in the utricle and saccule of Atoh1 null mice is first noted at E12.5, a time when Atoh1-β-galactosidase expression is also first detected in these epithelia. These data suggest that expression of Bdnf is dependent on ATOH1 protein in some but does not require ATOH1 protein in other inner ear cells. Overall, the undifferentiated Atoh1- and Bdnf-β-galactosidase–positive cells show a distribution reminiscent of that in the six sensory epithelia in control mice, suggesting that ear patterning processes can form discrete patches of Atoh1 and Bdnf expression in the absence of ATOH1 protein. The almost normal growth of afferent and efferent fibers in younger embryos suggests that neither fully differentiated hair cells nor BDNF are necessary for the initial targeted growth of fibers. E18.5 Atoh1 null mice have many afferent fibers to the apex of the cochlea, the anterior and the posterior crista, all areas with numerous Bdnf-β-galactosidase–positive cells. Few fibers remain to the saccule, utricle, and the base of the cochlea, all areas with few or no Bdnf-β-galactosidase–positive cells. Thus, retention of fibers is possible with BDNF, even in the absence of differentiated hair cells. Developmental Dynamics 233:570–583, 2005. © 2005 Wiley-Liss, Inc.

Background Neurotrophins (NTs) are a family of growth factors, including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin3 (NT-3) that are involved in inflammation. Serum and induced sputum NT levels are increased in asthma and in cough because of idiopathic pulmonary fibrosis, respectively. Neurogenic inflammation is implicated in the pathogenesis of chronic cough in individuals with normal chest radiography, but the role of NTs in this condition is unknown.Objective To assess if NT levels are elevated in the serum and airways in subjects with chronic persistent cough.Methods Eighty-one subjects with chronic cough persistent for over 1 year; with normal chest radiography and spirometry were included. Thirty healthy subjects were controls. Serum NGF, BDNF and NT-3 were measured by enzyme immumoassay. In a subset, NGF was measured in induced sputum. Sputum cell counts and allergen-specific serum IgE were measured and all patients received specific sequential treatment trials to achieve a final diagnosis for the cough.Results There was no significant difference either in the levels of serum or sputum NTs in chronic cough subjects compared with controls or between the most common causes of cough: post-nasal drip syndrome, gastro-oesophageal reflux disease, asthma and bronchiectasis. The median (inter-quartile range) for sputum NGF (pg/mL) was 516 (296–772) in healthy controls and 580 (312–880) in subjects with chronic cough (P=0.284). There was no correlation between NT levels and sputum cell counts. Sputum NGF levels correlated with duration of cough (r=0.34, P=0.002).Conclusion: NTs are not elevated in induced sputum or serum of subjects with chronic persistent cough. This implies that NTs do not have a central role in perpetuating airway inflammation in chronic persistent cough.

It is well established that individuals with Down syndrome develop Alzheimer's disease neuropathology by middle age. Both in Alzheimer's disease and Down syndrome, this is accompanied by the atrophy of NGF-dependent cholinergic neurons of the basal forebrain. An NGF trophic compromise in Alzheimer's disease had been early suspected. This hypothesis was discarded with the finding of unaltered NGF mRNA synthesis and of increased NGF precursor levels (proNGF) in post-mortem Alzheimer's disease brains. The possibility of an NGF trophic disconnection has been recently revisited at the light of a newly discovered extracellular NGF metabolic pathway; where proNGF is released in an activity-dependent manner and converted by plasmin to mature NGF in the extracellular space. Mature NGF is ultimately degraded by the metalloprotease MMP-9. This pathway has been shown to be compromised in Alzheimer's disease and Down syndrome brains, thus reviving the trophic factor hypothesis to explain the atrophy of basal forebrain cholinergic neurons in these disorders. This chapter will discuss the physiological role of NGF and its biological significance to cho-linergic neurons of the CNS, and present the evidence for a dysregulation of the NGF metabolism in Alzheimer's disease and Down syndrome.

Neurospheres can be generated from the mouse fetal forebrain by exposing multipotent neural stem cells
(NSCs) to epidermal growth factor (EGF). In the presence of EGF, NSCs can proliferate continuously while retaining the
potential to differentiate into neurons, astrocytes and oligodendrocytes. We examined the expression pattern of the
neurotrophin (NT) receptors tropomysin-related kinase (TRK)-A, TRK-B, TRK-C and p75 neurotrophin receptor
(p75NTR) in NSCs and the corresponding lineage cells. Furthermore, we analyzed the action of the NT Brain-Derived
Neurotrophic Factor (BDNF) on NSCs’ behavior. The effects of BDNF on NSC proliferation and differentiation were
examined together with the signaling pathways by which BDNF receptors transduce signaling effects. We found that all
the known NT receptors, including the truncated isoforms of TRK-B (t-TRK-B) and TRK-C (t-TRK-C), were expressed
by Nestin-positive cells within the neurosphere. Proliferation was enhanced in Nestin-positive and BrdU-positive cells in
the presence of BDNF. In particular, we show that t-TRK-B was abundantly expressed in NSCs and the corresponding
differentiated glia cells while full length TRK-B (fl-TRK-B) was expressed in fully differentiated post-mitotic neurons
such as the neuronal cells of the newborn mouse cortex, suggesting that BDNF may exert its proliferative effects on NSCs
through the t-TRK-B receptor. Finally, we analyzed the cell fates of NSCs differentiated with BDNF in the absence of
EGF and we demonstrate that BDNF stimulated the formation of differentiated cell types in different proportions through
the MAP kinase, AKT and STAT-3 signaling pathways. Thus, the in-vivo regulation of neurogenesis may be mediated by
the summation of signals from the BDNF receptors, in particular the t-TRK-B receptor, regulating physiological fates as
diverse as normal neural replacement, excessive neural loss, or tumor development.

Ovarian cancer is the most lethal gynecological neoplasm, and epithelial ovarian cancer (EOC) accounts for 90% of ovarian malignancies. The 5-year survival is less than 45%, and, unlike other types of cancer, the proportion of women who die from this disease has not improved in recent decades. Nerve growth factor (NGF) and tropomyosin kinase A (TRKA), its high-affinity receptor, play a crucial role in pathogenesis through cell proliferation, angiogenesis, invasion, and migration. NGF/TRKA increase their expression during the progression of EOC by upregulation of oncogenic proteins as vascular endothelial growth factor (VEGF) and c-Myc. Otherwise, the expression of most oncoproteins is regulated by microRNAs (miRs). Our laboratory group reported that the tumoral effect of NGF/TRKA depends on the regulation of miR-145 levels in EOC. Currently, mitochondria have been proposed as new therapeutic targets to activate the apoptotic pathway in the cancer cell. The mitochondria are involved ...

Exploitation of the biologic activity of neurotrophins is desirable for medical purposes, but their protein nature intrinsically bears adverse pharmacokinetic properties. Here, we report synthesis and biologic characterization of a novel class of low molecular weight, non-peptidic compounds with NGF (nerve growth factor)-mimetic properties. MT2, a representative compound, bound to Trk (tropomyosin kinase receptor)A chain on NGF-sensitive cells, as well as in cell-free assays, at nanomolar concentrations and induced TrkA autophosphorylation and receptor-mediated internalization. MT2 binding involved at least two amino-acid residues within TrkA molecule. Like NGF, MT2 increased phosphorylation of extracellular signal-regulated kinase1/2 and Akt proteins and production of MKP-1 phosphatase (dual specificity phosphatase 1), modulated p38 mitogen-activated protein kinase activation, sustained survival of serum-starved PC12 or RDG cells, and promoted their differentiation. However, the intensity of such responses was heterogenous, as the ability of maintaining survival was equally possessed by NGF and MT2, whereas the induction of differentiation was expressed at definitely lower levels by the mimetic. Analysis of TrkA autophosphorylation patterns induced by MT2 revealed a strong tyrosine (Tyr)490 and a limited Tyr785 and Tyr674/675 activation, findings coherent with the observed functional divarication. Consistently, in an NGF-deprived rat hippocampal neuronal model of Alzheimer Disease, MT2 could correct the biochemical abnormalities and sustain cell survival. Thus, NGF mimetics may reveal interesting investigational tools in neurobiology, as well as promising drug candidates.

Background Neurotrophins (NTs) are a family of growth factors, including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin3 (NT-3) that are involved in inflammation. Serum and induced sputum NT levels are increased in asthma and in cough because of idiopathic pulmonary fibrosis, respectively. Neurogenic inflammation is implicated in the pathogenesis of chronic cough in individuals with normal chest radiography, but the role of NTs in this condition is unknown.Objective To assess if NT levels are elevated in the serum and airways in subjects with chronic persistent cough.Methods Eighty-one subjects with chronic cough persistent for over 1 year; with normal chest radiography and spirometry were included. Thirty healthy subjects were controls. Serum NGF, BDNF and NT-3 were measured by enzyme immumoassay. In a subset, NGF was measured in induced sputum. Sputum cell counts and allergen-specific serum IgE were measured and all patients received specific sequential treatment trials to achieve a final diagnosis for the cough.Results There was no significant difference either in the levels of serum or sputum NTs in chronic cough subjects compared with controls or between the most common causes of cough: post-nasal drip syndrome, gastro-oesophageal reflux disease, asthma and bronchiectasis. The median (inter-quartile range) for sputum NGF (pg/mL) was 516 (296–772) in healthy controls and 580 (312–880) in subjects with chronic cough (P=0.284). There was no correlation between NT levels and sputum cell counts. Sputum NGF levels correlated with duration of cough (r=0.34, P=0.002).Conclusion: NTs are not elevated in induced sputum or serum of subjects with chronic persistent cough. This implies that NTs do not have a central role in perpetuating airway inflammation in chronic persistent cough.

Experimental evidence has revealed the role of mitochondria in various aspects of neuronal physiology. Mitochondrial failure results in alterations that underlie the pathogeneses of many neurodegenerative disorders, such as Parkinson's disease, Alzheimer's disease, Huntington's disease (HD) and amyotrophic lateral sclerosis. The mitochondrial toxin 3-nitropropionic acid (3-NP) has been used to model failure; for example, systemic administration of 3-NP imitates the striatal degeneration that is exhibited in the postmortem tissue of patients afflicted with HD. We have demonstrated that low, sub-chronic doses of 3-NP are sufficient to initiate the damage to striatal neurons that is associated with changes in neurotrophin expression levels. However, the mechanisms underlying the alterations in neuronal activity and neurotransmission due to 3-NP-induced mitochondrial dysfunction remain to be elucidated. In this paper, we focus on how corticostriatal transmission and its modulation by neurotrophins are altered in vivo after 5 days of mitochondrial inhibition with 3-NP. Recordings of population spikes and a paired pulse (PP) stimulation protocol were used to document changes in corticostriatal synapses in 3-NP-treated brain slices. The corticostriatal synapses were modulated by neurotrophins but displayed differential amplitude increases in the presence of brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), or neurotrophin-4/5 (NT-4/5) under control conditions. Neurotrophin-mediated synaptic modulation was decreased in slices from 3-NP-treated mice. The protein and mRNA levels of neurotrophins and their receptors were also modified in the 3-NP-treated tissue. Neuronal structural evaluation demonstrated that synaptic length and density were reduced in the 3-NP-treated mice, which partially explained the changes in the amplitudes of the synaptic field responses. Our results demonstrate that corticostriatal synapses are differentially modulated by neurotrophins and that this modulation is altered by mitochondrial failure. Mitochondrial dysfunction also affects neurotransmitter release in corticostriatal synapses, neurotrophin availability, dendritic arborization and the lengths of the striatal medium spiny neurons (MSNs).

This review seeks to give an overview of the current approaches to drug delivery from scaffolds for neural tissue engineering applications. The challenges presented by attempting to replicate the three types of nervous tissue (brain, spinal cord, and peripheral nerve) are summarized. Potential scaffold materials (both synthetic and natural) and target drugs are discussed with the benefits and drawbacks given. Finally, common methods of drug delivery, including degradable/diffusion-based delivery systems, affinity-based delivery systems, immobilized drug delivery systems, and electrically controlled drug delivery systems, are examined and critiqued. Based on the current body of work, suggestions for future directions of research in the field of neural tissue engineering are presented.

Mucopolysaccharidosis IIIB (MPS IIIB; Sanfilippo syndrome type B) is characterized by profound neurological deterioration. Because a murine model of MPS IIIB disease is available, we focused on analysis of gene expression in the brain and cerebellum of 7-month-old MPS IIIB mice by pathway-specific filter microarrays designed to probe apoptotic-related, neurotrophic signalling molecules and inflammatory cytokines and receptors. Moreover, we extended the analysis with real-time PCR performed at 1, 3, 7 months after birth. Bdnf was down-regulated in the brain but up-regulated in the cerebellum at 7 months of age, both at RNA and at protein levels. Cbln1 presented a threefold increase in the oldest brains while remaining unaltered in the cerebellum. Ccl3, Casp11, gp91phox, p67phox, and p47phox showed an increased expression in both brain and cerebellum at each examined time point. Ccl3, in particular, exhibited in both organs and at all times tested approximately a tenfold increase in its expression. Insofar as p47phox, p67phox, and gp91phox are all components of the phagocyte NADPH oxidase, our results suggest the possible involvement of the reactive oxygen species in the genesis of neurodegeneration in MPS IIIB disease. © 2006 Wiley-Liss, Inc.