Early days of the nerve growth factor proteins

Chitosan-based thermosensitive hydrogel with long-term release of murine nerve growth factor for neurotrophic keratopathy

Neurotrophic keratopathy is a persistent defect of the corneal epithelium, with or without stromal ulceration, due to corneal nerve deficiency caused by a variety of etiologies. The treatment options for neurotrophic keratopathy are limited. In this study, an ophthalmic solution was constructed from a chitosan-based thermosensitive hydrogel with long-term release of murine nerve growth factor (CTH-mNGF). Its effectiveness was evaluated in corneal denervation (CD) mice and patients with neurotrophic keratopathy. In the preclinical setting, CTH-mNGF was assessed in a murine corneal denervation model. CTH-mNGF was transparent, thermosensitive, and ensured sustained release of mNGF for over 20 hours on the ocular surface, maintaining the local mNGF concentration around 1300 pg/mL in vivo. Corneal denervation mice treated with CTH-mNGF for 10 days showed a significant increase in corneal nerve area and total corneal nerve length compared with non-treated and CTH treated mice. A subsequent clinical trial of CTH-mNGF was conducted in patients with stage 2 or 3 neurotrophic keratopathy. Patients received topical CTH-mNGF twice daily for 8 weeks. Fluorescein sodium images, Schirmer's test, intraocular pressure, Cochet-Bonnet corneal perception test, and best corrected visual acuity were evaluated. In total, six patients (total of seven eyes) diagnosed with neurotrophic keratopathy were enrolled. After 8 weeks of CTH-mNGF treatment, all participants showed a decreased area of corneal epithelial defect, as stained by fluorescence. Overall, six out of seven eyes had fluorescence staining scores < 5. Moreover, best corrected visual acuity, intraocular pressure, Schirmer's test and Cochet-Bonnet corneal perception test results showed no significant improvement. An increase in corneal nerve density was observed by in vivo confocal microscopy after 8 weeks of CTH-mNGF treatment in three out of seven eyes. This study demonstrates that CTH-mNGF is transparent, thermosensitive, and has sustained-release properties. Its effectiveness in healing corneal epithelial defects in all eyes with neurotrophic keratopathy suggests CTH-mNGF has promising application prospects in the treatment of neurotrophic keratopathy, being convenient and cost effective.

Nerve Growth Factor and the Role of Inflammation in Tumor Development

Nerve growth factor (NGF) plays a dual role both in inflammatory states and cancer, acting both as a pro-inflammatory and oncogenic factor and as an anti-inflammatory and pro-apoptotic mediator in a context-dependent way based on the signaling networks and its interaction with diverse cellular components within the microenvironment. This report aims to provide a summary and subsequent review of the literature on the role of NGF in regulating the inflammatory microenvironment and tumor cell growth, survival, and death. The role of NGF in inflammation and tumorigenesis as a component of the inflammatory system, its interaction with the various components of the respective microenvironments, its ability to cause epigenetic changes, and its role in the treatment of cancer have been highlighted in this paper.

Nerve Growth Factor and Autoimmune Diseases

NGF plays a crucial immunomodulatory role and increased levels are found in numerous tissues during autoimmune states. NGF directly modulates innate and adaptive immune responses of B and T cells and causes the release of neuropeptides and neurotransmitters controlling the immune system activation in inflamed tissues. Evidence suggests that NGF is involved in the pathogenesis of numerous immune diseases including autoimmune thyroiditis, chronic arthritis, multiple sclerosis, systemic lupus erythematosus, mastocytosis, and chronic granulomatous disease. Furthermore, as NGF levels have been linked to disease severity, it could be considered an optimal early biomarker to identify therapeutic approach efficacy. In conclusion, by gaining insights into how these molecules function and which cells they interact with, future studies can devise targeted therapies to address various neurological, immunological, and other disorders more effectively. This knowledge may pave the way for innovative treatments based on NGF manipulation aimed at improving the quality of life for individuals affected by diseases involving neurotrophins.

Distinct conformational changes occur within the intrinsically unstructured pro-domain of pro-Nerve Growth Factor in the presence of ATP and Mg2

Nerve growth factor (NGF), the prototypical neurotrophic factor, is involved in the maintenance and growth of specific neuronal populations, whereas its precursor, proNGF, is involved in neuronal apoptosis. Binding of NGF or proNGF to TrkA, p75NTR , and VP10p receptors triggers complex intracellular signaling pathways that can be modulated by endogenous small-molecule ligands. Here, we show by isothermal titration calorimetry and NMR that ATP binds to the intrinsically disordered pro-peptide of proNGF with a micromolar dissociation constant. We demonstrate that Mg2+ , known to play a physiological role in neurons, modulates the ATP/proNGF interaction. An integrative structural biophysics analysis by small angle X-ray scattering and hydrogen-deuterium exchange mass spectrometry unveils that ATP binding induces a conformational rearrangement of the flexible pro-peptide domain of proNGF. This suggests that ATP may act as an allosteric modulator of the overall proNGF conformation, whose likely distinct biological activity may ultimately affect its physiological homeostasis.

Mechanisms of Peripheral and Central Sensitization in Osteoarthritis Pain

Pain, the primary symptom of osteoarthritis (OA), reduces both the quality and quantity of life for patients. The pathophysiology of OA pain is complex and often difficult to explain solely by radiological structural changes. One reason for this discrepancy is pain sensitization (peripheral sensitization [PS] and central sensitization [CS]) in OA. Thus, an understanding of pain sensitization is important when considering treatment strategies and development for OA pain. In recent years, pro-inflammatory cytokines, nerve growth factors (NGFs), and serotonin have been identified as causative agents that induce peripheral and central sensitization and are becoming therapeutic targets for OA pain. However, the characteristics of the clinical manifestations of pain sensitization elicited by these molecules remain unclear, and it is not well understood who among OA patients should receive the therapeutic intervention. Thus, this review summarizes evidence on the pathophysiology of peripheral and central sensitization in OA pain and the clinical features and treatment options for this condition. While the majority of the literature supports the existence of pain sensitization in chronic OA pain, clinical identification and treatment of pain sensitization in OA are still in their infancy, and future studies with good methodological quality are needed.

First-in-human study to assess the safety, tolerability, pharmacokinetics and immunogenicity of DS002, an anti-nerve growth factor monoclonal antibody

Purpose: To evaluate the safety, tolerability, pharmacokinetics and immunogenicity of DS002 injection, an anti-nerve growth factor (anti-NGF) monoclonal antibody for treating pain conditions, in healthy Chinese subjects. Methods: This study was a single-center, randomized, double-blind, single-dose escalation, placebo-controlled design (CTR20210155). A total of 53 healthy subjects, 27 male and 26 female, were enrolled in this study, and one subject withdrew from the study before administration. Seven dose groups were set up, which were 0.5 mg, 1.0 mg, 2.0 mg, 4.0 mg, 7.0 mg, 12.0 mg and 20.0 mg, respectively. The drug was administered by single subcutaneous injection. Four subjects were enrolled in the first dose group (0.5 mg) received DS002. Other dose groups enrolled eight subjects each, six of whom received DS002 while the other two received a placebo. Safety, tolerability, pharmacokinetic parameters and immunogenicity of DS002 were assessed. Results: DS002 was well tolerated; all adverse events were Grade 1-2, and did not reach the termination standard of dose increment within the range of 0.5-20.0 mg. Adverse event rates were generally similar across treatments. After a single subcutaneous injection, the median T_max in different dose groups ranged 167.77-337.38 h; mean t_1/2 ranged 176.80-294.23 h, the volume of distribution (V_z) ranged 5265.42-7212.00 ml, and the clearance rate (CL) ranged 12.69-24.75 ml/h. In the dose range of 0.5-20.0 mg, C_max ranged from 51.83 ± 22.74 ng/ml to 2048.86 ± 564.78 ng/ml, AUC_0-t ranged from 20615.16 ± 5698.28 h·ng/mL to 1669608.11 ± 387246.36 h·ng/mL, and AUC_0-inf ranged from 21852.45 ± 5920.21 h·ng/mL to 1673504.66 ± 389106.13 h·ng/mL. They all increased with dose escalation, and C_max and AUC_0-t did not have a significant dose-linear relationship, whilst AUC_0-t was not dose-dependent at all. anti-drug antibody test results of each group of all subjects in this trial were negative. Conclusion: DS002 showed satisfactory safety within the dose range of 0.5 mg-20.0 mg. The absorption and metabolism of DS002 were slow, it exhibited a low volume of distribution and the clearance rate was low. These data suggest that DS002, by blocking nerve growth factor, is expected to become a novel, safe and non-addictive treatment for pain conditions.

Targeting the Cation-Chloride Co-Transporter NKCC1 to Re-Establish GABAergic Inhibition and an Appropriate Excitatory/Inhibitory Balance in Selective Neuronal Circuits: A Novel Approach for the Treatment of Alzheimer's Disease

GABA, the main inhibitory neurotransmitter in the adult brain, depolarizes and excites immature neurons because of an initially higher intracellular chloride concentration [Cl^-]i due to the delayed expression of the chloride exporter KCC2 at birth. Depolarization-induced calcium rise via NMDA receptors and voltage-dependent calcium channels is instrumental in shaping neuronal circuits and in controlling the excitatory (E)/inhibitory (I) balance in selective brain areas. An E/I imbalance accounts for cognitive impairment observed in several neuropsychiatric disorders. The aim of this review is to summarize recent data on the mechanisms by which alterations of GABAergic signaling alter the E/I balance in cortical and hippocampal neurons in Alzheimer's disease (AD) and the role of cation-chloride co-transporters in this process. In particular, we discuss the NGF and AD relationship and how mice engineered to express recombinant neutralizing anti-NGF antibodies (AD11 mice), which develop a neurodegenerative pathology reminiscent of that observed in AD patients, exhibit a depolarizing action of GABA due to KCC2 impairment. Treating AD and other forms of dementia with bumetanide, a selective KCC2 antagonist, contributes to re-establishing a proper E/I balance in selective brain areas, leading to amelioration of AD symptoms and the slowing down of disease progression.

Electrophysiological and pathological changes in the vastus medialis and vastus lateralis muscles after early patellar reduction and nerve growth factor injection in rabbits with patellar dislocation

BACKGROUND

Patellar dislocation can cause a series of changes in the trochlear groove and patella. However, the influence of patellar dislocation on the medialis (VM) and vastus lateralis (VL) muscles and whether nerve growth factor (NGF) is beneficial to proprioceptive rehabilitation for patellar dislocation are unknown. The purpose of this study was to investigate the effects on VM and VL after the injection of NGF and early reduction in rabbits for patellar dislocation with electrophysiological and pathological analysis.

METHODS

Sixty 2-month-old rabbits were randomly divided into four groups (15 rabbits in each group). Rabbits in Group 1, Group 2, and Group 3 underwent patellar dislocation surgery, and rabbits in Group 4 underwent sham surgery. One month later, patellar reduction was performed in Groups 1 and 2. NGF was injected into the rabbits of Group 1. The electrophysiological and pathological changes in VM and VL were analyzed at 1 month and 3 months after patellar reduction.

RESULTS

The electrophysiological and pathological indices in Groups 1 and 2 were significantly different from those in Group 3 at 1 and 3 months after patellar reduction. There were significant differences between NGF injection Group 1 and Group 2 without NGF injection. There was no significant difference between Group 1 and Group 4 at 3 months after patellar reduction.

CONCLUSIONS

Patellar dislocation can cause abnormal electrophysiological and pathological effects on VM and VL. Patellar reduction should be performed as early as possible, and NGF injection may be beneficial to the rehabilitation of proprioception.

The Critical Role of Growth Factors in Gastric Ulcer Healing: The Cellular and Molecular Mechanisms and Potential Clinical Implications

In this article we review the cellular and molecular mechanisms of gastric ulcer healing. A gastric ulcer (GU) is a deep defect in the gastric wall penetrating through the entire mucosa and the muscularis mucosae. GU healing is a regeneration process that encompasses cell dedifferentiation, proliferation, migration, re-epithelialization, formation of granulation tissue, angiogenesis, vasculogenesis, interactions between various cells and the matrix, and tissue remodeling, all resulting in scar formation. All these events are controlled by cytokines and growth factors (e.g., EGF, TGFα, IGF-1, HGF, bFGF, TGFβ, NGF, VEGF, angiopoietins) and transcription factors activated by tissue injury. These growth factors bind to their receptors and trigger cell proliferation, migration, and survival pathways through Ras, MAPK, PI3K/Akt, PLC-γ, and Rho/Rac/actin signaling. The triggers for the activation of these growth factors are tissue injury and hypoxia. EGF, its receptor, IGF-1, HGF, and COX-2 are important for epithelial cell proliferation, migration, re-epithelialization, and gastric gland reconstruction. VEGF, angiopoietins, bFGF, and NGF are crucial for blood vessel regeneration in GU scars. The serum response factor (SRF) is essential for VEGF-induced angiogenesis, re-epithelialization, and blood vessel and muscle restoration. Local therapy with cDNA of human recombinant VEGF165 in combination with angiopoietin1, or with the NGF protein, dramatically accelerates GU healing and improves the quality of mucosal restoration within ulcer scars. The future directions for accelerating and improving healing include local gene and protein therapies with growth factors, their combinations, and the use of stem cells and tissue engineering.

Knockdown of astrocytic Grin2a aggravates β-amyloid-induced memory and cognitive deficits through regulating nerve growth factor

Synapse degeneration correlates strongly with cognitive impairments in Alzheimer's disease (AD) patients. Soluble Amyloid-beta (Aβ) oligomers are thought as the major trigger of synaptic malfunctions. Our earlier studies have demonstrated that Aβ oligomers interfere with synaptic function through N-methyl-D-aspartate receptors (NMDARs). Our recent in vitro study found the neuroprotective role of astrocytic GluN2A in the promotion of synapse survival and identified nerve growth factor (NGF) derived from astrocytes, as a likely mediator of astrocytic GluN2A buffering against Aβ synaptotoxicity. Our present in vivo study focused on exploring the precise mechanism of astrocytic GluN2A influencing Aβ synaptotoxicity through regulating NGF. We generated an adeno-associated virus (AAV) expressing an astrocytic promoter (GfaABC1D) shRNA targeted to Grin2a (the gene encoding GluN2A) to perform astrocyte-specific Grin2a knockdown in the hippocampal dentate gyrus, after 3 weeks of virus vector expression, Aβ were bilaterally injected into the intracerebral ventricle. Our results showed that astrocyte-specific knockdown of Grin2a and Aβ application both significantly impaired spatial memory and cognition, which associated with the reduced synaptic proteins PSD95, synaptophysin and compensatory increased NGF. The reduced astrocytic GluN2A can counteract Aβ-induced compensatory protective increase of NGF through regulating pNF-κB, Furin and VAMP3, which modulating the synthesis, mature and secretion of NGF respectively. Our present data reveal, for the first time, a novel mechanism of astrocytic GluN2A in exerting protective effects on synapses at the early stage of Aβ exposure, which may contribute to establish new targets for AD prevention and early therapy.

Role of nerve growth factor in the reproductive physiology of female rabbits: A review

Rabbit does are reflex ovulators such that coitus is needed to release GnRH and elicit the LH surge that triggers the ovulation of mature oocytes. However, the mechanisms eliciting ovulation in this species remain unclear. One of the most promising recently discovered candidates with a role in female reproductive physiology is nerve growth factor beta (β-NGF). This neurotrophin and its high-affinity receptor TrkA and low affinity receptor p75, is present in all compartments of the ovary, oviduct and uterus suggesting a physiologic role in ovarian folliculogenesis, steroidogenesis, ovulation, luteogenesis and embryo development. Besides, evidence exists that β-NGF found in seminal plasma could exert a modulatory role in the female hypothalamus-pituitary-ovarian axis contributing to the adrenergic and cholinergic neuronal stimulus of GnRH neurons in an endocrine manner during natural mating. Probably, the paracrine and local roles of the neurotrophin in steroidogenesis and ovulation reinforce the neuroendocrine pathway that leads to ovulation. This review updates knowledge of the role of β-NGF in rabbit reproduction, including its possible contribution to the mechanisms of action that induce ovulation, and discusses perspectives for the future applications of this neurotrophin on rabbit farms.

Different responses of PC12 cells to different pro-nerve growth factor protein variants

The present work aimed to explore the innovative hypothesis that different transcript/protein variants of a pro-neurotrophin may generate different biological outcomes in a cellular system. Nerve growth factor (NGF) is important in the development and progression of neurodegenerative and cancer conditions. Mature NGF (mNGF) originates from a precursor, proNGF, produced in mouse in two major variants, proNGF-A and proNGF-B. Different receptors bind mNGF and proNGF, generating neurotrophic or neurotoxic outcomes. It is known that dysregulation in the proNGF/mNGF ratio and in NGF-receptors expression affects brain homeostasis. To date, however, the specific roles of the two major proNGF variants remain unexplored. Here we attempted a first characterization of the possible differential effects of proNGF-A and proNGF-B on viability, differentiation and endogenous ngf gene expression in the PC12 cell line. We also investigated the differential involvement of NGF receptors in the actions of proNGF. We found that native mouse mNGF, proNGF-A and proNGF-B elicited different effects on PC12 cell survival and differentiation. Only mNGF and proNGF-A promoted neurotrophic responses when all NGF receptors are exposed at the cell surface. Tropomyosine receptor kinase A (TrkA) blockade inhibited cell differentiation, regardless of which NGF was added to culture media. Only proNGF-A exerted a pro-survival effect when TrkA was inhibited. Conversely, proNGF-B exerted differentiative effects when the p75 neurotrophin receptor (p75^NTR) was antagonized. Stimulation with NGF variants differentially regulated the autocrine production of distinct proNgf mRNA. Overall, our findings suggest that mNGF and proNGF-A may elicit similar neurotrophic effects, not necessarily linked to activation of the same NGF-receptor, while the action of proNGF-B may be determined by the NGF-receptors balance. Thus, the proposed involvement of proNGF/NGF on the development and progression of neurodegenerative and tumor conditions may depend on the NGF-receptors balance, on specific NGF trancript expression and on the proNGF protein variant ratio.

Increased Brain-Derived Neurotrophic Factor in Lumbar Dorsal Root Ganglia Contributes to the Enhanced Exercise Pressor Reflex in Heart Failure

An exaggerated exercise pressor reflex (EPR) is associated with excessive sympatho-excitation and exercise intolerance in the chronic heart failure (CHF) state. We hypothesized that brain-derived neurotrophic factor (BDNF) causes the exaggerated EPR via sensitizing muscle mechanosensitive afferents in CHF. Increased BDNF expression was observed in lumbar dorsal root ganglia (DRGs) from CHF rats compared to sham rats. Immunofluorescence data showed a greater increase in the number of BDNF-positive neurons in medium and large-sized DRG subpopulations from CHF rats. Patch clamp data showed that incubation with BDNF for 4–6 h, significantly decreased the current threshold-inducing action potential (AP), threshold potential and the number of APs during current injection in Dil-labeled isolectin B4 (IB4)-negative medium-sized DRG neurons (mainly mechano-sensitive) from sham rats. Compared to sham rats, CHF rats exhibited an increased number of APs during current injection in the same DRG subpopulation, which was significantly attenuated by 4-h incubation with anti-BDNF. Finally, chronic epidural delivery of anti-BDNF attenuated the exaggerated pressor response to either static contraction or passive stretch in CHF rats whereas this intervention had no effect on the pressor response to hindlimb arterial injection of capsaicin. These data suggest that increased BDNF in lumbar DRGs contributes to the exaggerated EPR in CHF.

Nerve Growth Factor: Early Studies and Recent Clinical Trials

Since its discovery, nerve growth factor (NGF) has long occupied a critical role in developmental and adult neurobiology for its many important regulatory functions on the survival, growth and differentiation of nerve cells in the peripheral and central nervous system. NGF is the first discovered member of a family of neurotrophic factors, collectively indicated as neurotrophins, (which include brain-derived neurotrophic factor, neurotrophin-3 and neurotrophin 4/5). NGF was discovered for its action on the survival and differentiation of selected populations of peripheral neurons. Since then, an enormous number of basic and human studies were undertaken to explore the role of purified NGF to prevent the death of NGF-receptive cells. These studies revealed that NGF possesses important therapeutic properties, after topical administration, on human cutaneous pressure ulcer, corneal ulcers, glaucoma, retinal maculopathy, Retinitis Pigmentosa and in pediatric optic gliomas and brain traumas. The aim of this review is to present our previous, recent and ongoing clinical studies on the therapeutic properties of NGF.

Expression pattern of high-affinity tyrosine kinase Aduring the development of human fetal spinal cord

High-affinity tyrosine kinase A (TrkA) is responsible for the biological activities of nerve growth factor. Most studies of the molecular mechanisms of TrkA that underlie the development of the spinal cord have been conducted in animals and the expression pattern of TrkA during the development of the human fetal spinal cord is not well characterized. We investigated 45 3-28-week-old (G3W-G28W) human fetuses. We assessed the expression pattern of TrkA in the human fetal spinal cord using immunohistochemistry, western blot and reverse transcription polymerase chain reaction to clarify the spatiotemporal developmental changes and to determine the role TrkA plays in development. TrkA immunoreactive products were detected widely in the alar and basal plates, ependyma, glial cells, gray and white matter, internal limiting membrane, mantle layer, marginal layer, neuroepithelium and neurons during this period of development. Expression levels of TrkA mRNA and protein peaked at G12W and G16W, respectively. The strong expression of TrkA was closely related to the formation of the dorsal and ventral horns, and the differentiation of somatic motor neurons during late embryonic development. Our findings suggest that TrkA receptors play crucial roles during the development of human fetal spinal cord. The characteristic expression patterns may clarify the developmental characteristics of the human spinal cord.

Distinct effects on the dendritic arbor occur by microbead versus bath administration of brain-derived neurotrophic factor

Proper communication among neurons depends on an appropriately formed dendritic arbor, and thus, aberrant changes to the arbor are implicated in many pathologies, ranging from cognitive disorders to neurodegenerative diseases. Due to the importance of dendritic shape to neuronal network function, the morphology of dendrites is tightly controlled and is influenced by both intrinsic and extrinsic factors. In this work, we examine how brain-derived neurotrophic factor (BDNF), one of the most well-studied extrinsic regulators of dendritic branching, affects the arbor when it is applied locally via microbeads to cultures of hippocampal neurons. We found that local application of BDNF increases both proximal and distal branching in a time-dependent manner and that local BDNF application attenuates pruning of dendrites that occurs with neuronal maturation. Additionally, we examined whether cytosolic PSD-95 interactor (cypin), an intrinsic regulator of dendritic branching, plays a role in these changes and found strong evidence for the involvement of cypin in BDNF-promoted increases in dendrites after 24 but not 48 h of application. This current study extends our previous work in which we found that bath application of BDNF for 72 h, but not shorter times, increases proximal dendrite branching and that this increase occurs through transcriptional regulation of cypin. Moreover, this current work illustrates how dendritic branching is regulated differently by the same growth factor depending on its spatial localization, suggesting a novel pathway for modulation of dendritic branching locally.

Nerve Growth Factor and Related Substances: A Brief History and an Introduction to the International NGF Meeting Series

Nerve growth factor (NGF) is a protein whose importance to research and its elucidation of fundamental mechanisms in cell and neurobiology far outstrips its basic physiological roles. It was the first of a broad class of cell regulators, largely acting through autocrine and paracrine interactions which will be described herein. It was of similar significance in establishing the identity and unique roles of neurotrophic factors in the development and maintenance of the peripheral and central nervous systems. Finally, it contributed to many advances in the elaboration of cell surface receptor mechanisms and intracellular cell signaling. As such, it can be considered to be a “molecular Rosetta Stone”. In this brief review, the highlights of these various studies are summarized, particularly as illustrated by their coverage in the 13 NGF international meetings that have been held since 1986.

The Role of Neurotrophins in Inflammation and Allergy

Allergic inflammation is the result of a specific pattern of cellular and humoral responses leading to the activation of the innate and adaptive immune system, which, in turn, results in physiological and structural changes affecting target tissues such as the airways and the skin. Eosinophil activation and the production of soluble mediators such as IgE antibodies are pivotal features in the pathophysiology of allergic diseases. In the past few years, however, convincing evidence has shown that neurons and other neurosensory structures are not only a target of the inflammatory process but also participate in the regulation of immune responses by actively releasing soluble mediators. The main products of these activated sensory neurons are a family of protein growth factors called neurotrophins. They were first isolated in the central nervous system and identified as important factors for the survival and differentiation of neurons during fetal and postnatal development as well as neuronal maintenance later in life. Four members of this family have been identified and well defined: nerve growth factor, brain-derived neurotrophic factor, neurotrophin 3, and neurotrophin 4/5. Neurotrophins play a critical role in the bidirectional signaling mechanisms between immune cells and the neurosensory network structures in the airways and the skin. Pruritus and airway hyperresponsiveness, two major features of atopic dermatitis and asthma, respectively, are associated with the disruption of the neurosensory network activities. In this chapter, we provide a comprehensive description of the neuroimmune interactions underlying the pathophysiological mechanisms of allergic and inflammatory diseases.

Pumping the Brakes: Neurotrophic Factors for the Prevention of Cognitive Impairment and Dementia after Traumatic Brain Injury

Traumatic brain injury (TBI) is the leading cause of disability and death worldwide, affecting as many as 54,000,000-60,000,000 people annually. TBI is associated with significant impairments in brain function, impacting cognitive, emotional, behavioral, and physical functioning. Although much previous research has focused on the impairment immediately following injury, TBI may have much longer-lasting consequences, including neuropsychiatric disorders and cognitive impairment. TBI, even mild brain injury, has also been recognized as a significant risk factor for the later development of dementia and Alzheimer's disease. Although the link between TBI and dementia is currently unknown, several proposed mechanisms have been put forward, including alterations in glucose metabolism, excitotoxicity, calcium influx, mitochondrial dysfunction, oxidative stress, and neuroinflammation. A treatment for the devastating long-term consequences of TBI is desperately needed. Unfortunately, however, no such treatment is currently available, making this a major area of unmet medical need. Increasing the level of neurotrophic factor expression in key brain areas may be one potential therapeutic strategy. Of the neurotrophic factors, granulocyte-colony stimulating factor (G-CSF) may be particularly effective for preventing the emergence of long-term complications of TBI, including dementia, because of its ability to reduce apoptosis, stimulate neurogenesis, and increase neuroplasticity.

NGF and proNGF Reciprocal Interference in Immunoassays: Open Questions, Criticalities, and Ways Forward

The homeostasis between mature neurotrophin NGF and its precursor proNGF is thought to be crucial in physiology and in pathological states. Therefore, the measurement of the relative amounts of NGF and proNGF could serve as a footprint for the identification of disease states, for diagnostic purposes. Since NGF is part of proNGF, their selective identification with anti-NGF antibodies is not straightforward. Currently, many immunoassays for NGF measurement are available, while the proNGF assays are few and not validated by published information. The question arises, as to whether the commercially available assays are able to distinguish between the two forms. Also, since in biological samples the two forms coexist, are the measurements of one species affected by the presence of the other? We describe experiments addressing these questions. For the first time, NGF and proNGF were measured together and tested in different immunoassays. Unexpectedly, NGF and proNGF were found to reciprocally interfere with the experimental outcome. The interference also calls into question the widely used NGF ELISA methods, applied to biological samples where NGF and proNGF coexist. Therefore, an immunoassay, able to distinguish between the two forms is needed. We propose possible ways forward, toward the development of a selective assay. In particular, the use of the well validated anti-NGF αD11 antibody in an alphaLISA assay with optimized incubation times would be a solution to avoid the interference in the measurement of a mixed sample containing NGF and proNGF. Furthermore, we explored the possibility of measuring proNGF in a biological sample. But the available commercial kit for the detection of proNGF does not allow the measurement of proNGF in mouse brain tissues. Therefore, we validated an SPR approach for the measurement of proNGF in a biological sample. Our experiments help in understanding the technical limits in the measurement of the NGF/proNGF ratio in biological samples, and propose concrete solutions toward the solution of this problem.

[Basic Research on Neurotrophic Factors and Its Application to Medical Uses]

The author has studied nerve growth factor (NGF) and its family of neurotrophic factors (neurotrophins) for over 40 years. During the first 20 years, my laboratory established a highly sensitive enzyme immunoassay for NGF and analyzed the regulatory mechanism of NGF synthesis in cultured primary cells. Fibroblast cells cultured from peripheral organs such as the heart and astrocytes from the brain produced a substantial amount of NGF in a growth-dependent manner. Furthermore, synthesis of NGF in these cells could be upregulated by catechol compounds including catecholamines. This observation might explain a physiological relation between the level of NGF mRNA and the density of innervation in the peripheral sympathetic nervous systems. Over the subsequent 20 years, my laboratory investigated the physiological functions of neurotrophic factors, including neurotrophins, during development or post-injury and found that brain-derived neurotrophic factor (BDNF) plays a role in the formation of the laminar structure of the cerebral cortex. In addition, my laboratory discovered that endogenous glial cell line-derived neurotrophic factor (GDNF) contributes to the amelioration of motor activity after spinal cord injury. Therefore we aimed to develop low-molecular weight compounds that generate neurotrophic factor-like intracellular signals to protect or ameliorate neurological/psychiatric diseases. 2-Decenoic acid derivatives and other similar molecules could protect or ameliorate in animal models of mood disorders such as depression and enhance recovery from spinal cord injury-induced motor paralysis. Compounds that can generate neurotrophin-like signals in neurons are expected to be developed as therapeutic drugs for certain neurological or psychiatric disorders.

Population pharmacokinetics of tanezumab in phase 3 clinical trials for osteoarthritis pain

Aims

The aims were to 1) develop the pharmacokinetics model to describe and predict observed tanezumab concentrations over time, 2) test possible covariate parameter relationships that could influence clearance and distribution and 3) assess the impact of fixed dosing vs. a dosing regimen adjusted by body weight.

Methods

Individual concentration–time data were determined from 1608 patients in four phase 3 studies conducted to assess efficacy and safety of intravenous tanezumab. Patients received two or three intravenous doses (2.5, 5 or 10 mg) every 8 weeks. Blood samples for assessment of tanezumab PK were collected at baseline, 1 h post‐dose and at weeks 4, 8, 16 and 24 (or early termination) in all studies. Blood samples were collected at week 32 in two studies. Plasma samples were analyzed using a sensitive, specific, validated enzyme‐linked immunosorbent assay.

Results

A two compartment model with parallel linear and non‐linear elimination processes adequately described the data. Population estimates for clearance (CL), central volume (V₁), peripheral volume (V₂), inter‐compartmental clearance, maximum elimination capacity (VM) and concentration at half‐maximum elimination capacity were 0.135 l day^–1, 2.71 l, 1.98 l, 0.371 l day^–1, 8.03 μg day^–1 and 27.7 ng ml^–1, respectively. Inter‐individual variability (IIV) was included on CL, V₁, V₂ and VM. A mixture model accounted for the distribution of residual error. While gender, dose and creatinine clearance were significant covariates, only body weight as a covariate of CL, V₁ and V₂ significantly reduced IIV.

Conclusions

The small increase in variability associated with fixed dosing is consistent with other monoclonal antibodies and does not change risk : benefit.

Real-time investigation of cytochrome c release profiles in living neuronal cells undergoing amyloid beta oligomer-induced apoptosis

Intracellular Cyt c release profiles in living human neuroblastoma undergoing amyloid β oligomer (AβO)-induced apoptosis, as a model Alzheimer's disease-associated pathogenic molecule, were analysed in a real-time manner using plasmon resonance energy transfer (PRET)-based spectroscopy.

Neurotrophic factors and their effects in the treatment of multiple sclerosis

Neurotrophins are small molecules of polypeptides, which include nerve growth factor (NGF) family, glial cell line–derived neurotrophic factor (GDNF) family ligands, and neuropoietic cytokines. These factors have an important role in neural regeneration, remyelination, and regulating the development of the peripheral and central nervous systems (PNS and CNS, respectively) by intracellular signaling through specific receptors. It has been suggested that the pathogenesis of human neurodegenerative disorders may be due to an alteration in the neurotrophic factors and their receptors. The use of neurotrophic factors as therapeutic agents is a novel strategy for restoring and maintaining neuronal function during neurodegenerative disorders such as multiple sclerosis. Innate and adaptive immune responses contribute to pathology of neurodegenerative disorders. Furthermore, autoimmune and mesenchymal stem cells, by the release of neurotrophic factors, have the ability to protect neuronal population and can efficiently suppress the formation of new lesions. So, these cells may be an alternative source for delivering neurotrophic factors into the CNS.

Ligand-induced dynamics of neurotrophin receptors investigated by single-molecule imaging approaches

Neurotrophins are secreted proteins that regulate neuronal development and survival, as well as maintenance and plasticity of the adult nervous system. The biological activity of neurotrophins stems from their binding to two membrane receptor types, the tropomyosin receptor kinase and the p75 neurotrophin receptors (NRs). The intracellular signalling cascades thereby activated have been extensively investigated. Nevertheless, a comprehensive description of the ligand-induced nanoscale details of NRs dynamics and interactions spanning from the initial lateral movements triggered at the plasma membrane to the internalization and transport processes is still missing. Recent advances in high spatio-temporal resolution imaging techniques have yielded new insight on the dynamics of NRs upon ligand binding. Here we discuss requirements, potential and practical implementation of these novel approaches for the study of neurotrophin trafficking and signalling, in the framework of current knowledge available also for other ligand-receptor systems. We shall especially highlight the correlation between the receptor dynamics activated by different neurotrophins and the respective signalling outcome, as recently revealed by single-molecule tracking of NRs in living neuronal cells.

A comparative analysis of the structural, functional and biological differences between Mouse and Human Nerve Growth Factor

NGF is the prototype member of the neurotrophin family of proteins that promote the survival and growth of selected neurons in the central and peripheral nervous systems. As for all neurotrophins, NGF is translated as a pre-pro-protein. Over the years, NGF and proNGF of either human or mouse origin, given their high degree of homology, have been exploited for numerous applications in biomedical sciences. The mouse NGF has been considered the golden-standard for bioactivity. Indeed, due to evolutionary relatedness to human NGF and to its ready availability and by assuming identical properties to its human counterpart, the mouse NGF, isolated and purified from sub-maxillary glands, has been tested not only in laboratory practice and in preclinical models, but it has also been evaluated in several human clinical trials. Aiming to validate this assumption, widely believed, we performed a comparative study of the biochemical and biophysical properties of the mouse and human counterparts of NGF and proNGF. The mature and the precursor proteins of either species strikingly differ in their biophysical profiles and, when tested for ligand binding to their receptors, in their in vitro biological activities. We provide a structural rationale that accounts for their different functional behaviors. Despite being highly conserved during evolution, NGF and proNGF of mouse and human origins show distinct properties and therefore special care must be taken in performing experiments with cross-species systems in the laboratory practice, in developing immunoassays, in clinical trials and in pharmacological treatments.

NGF and ProNGF: Regulation of neuronal and neoplastic responses through receptor signaling

Nerve growth factor (NGF) and its precursor (proNGF) are primarily considered as regulators of neuronal function that induce their responses via the tyrosine kinase receptor TrkA and the pan-neurotrophin receptor p75NTR. It has been generally held that NGF exerts its effects primarily through TrkA, inducing a cascade of tyrosine kinase-initiated responses, while proNGF binds more strongly to p75NTR. When this latter entity interacts with a third receptor, sortilin, apoptotic responses are induced in contrast to the survival/differentiation associated with the other two. Recent studies have outlined portions of the downstream phosphoproteome of TrkA in the neuronal PC12 cells and have clarified the contribution of individual docking sites in the TrkA endodomain. The patterns observed showed a similarity with the profile induced by the epidermal growth factor receptor, which is extensively associated with oncogenesis. Indeed, as with other neurotrophic factors, the distribution of TrkA and p75NTR is not limited to neuronal tissue, thus providing an array of targets outside the nervous systems. One such source is breast cancer cells, in which NGF and proNGF stimulate breast cancer cell survival/growth and enhance cell invasion, respectively. This latter activity is exerted via TrkA (as opposed to p75NTR) in conjunction with sortilin. Another tissue overexpressing proNGF is prostate cancer and here the ability of cancer cells to induce neuritogenesis has been implicated in cancer progression. These studies show that the non-neuronal functions of proNGF/NGF are likely integrated with their neuronal activities and point to the clinical utility of these growth factors and their receptors as biomarkers and therapeutic targets for metastasis and cancer pain.

proNGF/NGF mixtures induce gene expression changes in PC12 cells that neither singly produces

BACKGROUND

Growing evidence shows that, in vivo, the precursor of Nerve Growth Factor (NGF), proNGF, displays biological activities different from those of its mature NGF counterpart, mediated by distinct, and somewhat complementary, receptor binding properties. NGF and proNGF induce distinct transcriptional signatures in target cells, highlighting their different bioactivities. In vivo, proNGF and mature NGF coexist. It was proposed that the relative proNGF/NGF ratio is important for their biological outcomes, especially in pathological conditions, since proNGF, the principal form of NGF in Central Nervous System (CNS), is increased in Alzheimer's disease brains. These observations raise a relevant question: does proNGF, in the presence of NGF, influence the NGF transcriptional response and viceversa? In order to understand the specific proNGF effect on NGF activity, depending on the relative proNGF/NGF concentration, we investigated whether proNGF affects the pattern of well-known NGF-regulated mRNAs.

RESULTS

To test any influence of proNGF on pure NGF expression fingerprinting, the expression level of a set of candidate genes was analysed by qReal-Time PCR in rat adrenal pheochromocytoma cell line PC12, treated with a mixture of NGF and proNGF recombinant proteins, in different stoichiometric ratios. These candidates were selected amongst a set of genes well-known as being rapidly induced by NGF treatment. We found that, when PC12 cells are treated with proNGF/NGF mixtures, a unique pattern of gene expression, which does not overlap with that deriving from treatment with either proNGF or NGF alone, is induced. The specific effect is also dependent on the stoichiometric composition of the mixture. The proNGF/NGF equimolar mixture seems to partially neutralize the specific effects of the proNGF or NGF individual treatments, showing a weaker overall response, compared to the individual contributions of NGF and proNGF alone.

CONCLUSIONS

Using gene expression as a functional read-out, our data demonstrate that the relative availability of NGF and proNGF in vivo might modulate the biological outcome of these ligands.

Prospects for improving brain function in individuals with Down syndrome

Down syndrome (DS), which results from an extra copy of chromosome 21 (trisomy 21), is the most common genetically defined cause of intellectual disability. Although no pharmacotherapy aimed at counteracting the cognitive and adaptive deficits associated with this genetic disorder has been approved at present, there have been several new promising studies on pharmacological agents capable of rescuing learning/memory deficits seen in mouse models of DS. Here, we will review the available mouse models for DS and provide a comprehensive, albeit not exhaustive review of the following preclinical research strategies: (1) SOD1 and antioxidant agents; (2) APP and γ-secretase inhibitors; (3) DYRK1A and the polyphenol epigallocatechin gallate (EGCG); (4) GIRK2 and fluoxetine; (5) adrenergic receptor agonists; (6) modulation of GABAA and GABAB receptors; (7) agonism of the hedgehog signaling pathway; (8) nerve growth factor (NGF) and other neurotrophic factors; (9) anticholinesterase (AChE) agents; and (10) antagonism of NMDA receptors. Finally, we will review briefly five different strategies in DS that have led to clinical studies that either have been concluded or are currently underway: (1) antioxidant therapy; (2) AChE therapy; (3) green tea extract therapy; (4) RG1662 therapy; and (5) memantine therapy. These are exciting times in DS research. Within a decade or so, it is well into the realm of possibility that new forms of pharmacotherapies might become valuable tools in the armamentarium of developmental clinicians, as adjutants to more traditional and proven forms of habilitative interventions aimed at improving the quality of life of individuals with DS.

Oral carcinoma with perineural invasion has higher nerve growth factor expression and worse prognosis

BACKGROUND

This study elucidated the association between histopathological factors and the prognosis of oral carcinoma. As the histopathological factors were determined from the surgical specimen and this can only be used for the choices of postoperative regimens, this study also investigated the linkage between prognostic factors and the expression of key molecules to examine the feasibility of markers as predictors.

METHODS

Clinicopathological factors of 101 oral carcinomas were cross-analyzed with disease-free survival. The expression of nerve growth factor (NGF) and its receptor, tyrosine kinase A receptor, was assayed with immunohistochemistry.

RESULTS

Nodal metastasis was the most crucial clinical predictor for disease-free survival. Perineural invasion (PNI) was an independent histopathological predictor for both nodal metastasis (P = 0.004) and disease-free survival (P = 0.019). Patients with advanced tumor and PNI exhibited the high hazard for tumor progression and poor disease-free survival. NGF immunoreactivity in tumors was correlated with PNI (P = 0.005) and neck lymph node metastasis (P = 0.036).

CONCLUSION

Perineural invasion is the indicator of worst prognosis. As NGF immunoreactivity was found to be associated with PNI and nodal metastasis, the NGF immunoreactivity of oral carcinoma revealed by diagnostic biopsy suggests that alternative therapeutic approaches might be appropriate.

Nerve growth factor and Alzheimer's disease: new facts for an old hypothesis

Understanding sporadic Alzheimer's disease (AD) onset and progression requires an explanation of what triggers the common core of abnormal processing of the amyloid precursor protein and tau processing. In the quest for upstream drivers of sporadic, late-onset AD neurodegeneration, nerve growth factor (NGF) has a central role. Initially connected to AD on a purely correlative basis, because of its neurotrophic actions on basal forebrain cholinergic neurons, two independent lines of research, reviewed in this article, place alterations of NGF processing and signaling at the center stage of a new mechanism, leading to the activation of amyloidogenesis and tau processing. Thus, experimental studies on NGF deficit induced neurodegeneration in transgenic mice, as well as the mechanistic studies on the anti-amyloidogenic actions of NGF/TrkA signaling in primary neuronal cultures demonstrated a novel causal link between neurotrophic signaling deficits and Alzheimer's neurodegeneration. Around these results, a new NGF hypothesis can be built, with neurotrophic deficits of various types representing an upstream driver of the core AD triad pathology. According to the new NGF hypothesis for AD, therapies aimed at reestablishing a correct homeostatic balance between ligands (and receptors) of the NGF pathway appear to have a clear and strong rationale, not just as long-term cholinergic neuroprotection, but also as a truly disease-modifying approach.

Crystal structure and functional implication of the RUN domain of human NESCA

NESCA, a newly discovered signaling adapter protein in the NGF-pathway, contains a RUN domain at its N-terminus. Here we report the crystal structure of the NESCA RUN domain determined at 2.0-Å resolution. The overall fold of the NESCA RUN domain comprises nine helices, resembling the RUN domain of RPIPx and the RUN1 domain of Rab6IP1. However, compared to the other RUN domains, the RUN domain of NESCA has significantly different surface electrostatic distributions at the putative GTPase-interacting interface. We demonstrate that the RUN domain of NESCA can bind H-Ras, a downstream signaling molecule of TrkA, with high affinity. Moreover, NESCA RUN can directly interact with TrkA. These results provide new insights into how NESCA participates in the NGF-TrkA signaling pathway.

Nerve growth factor regulates axial rotation during early stages of chick embryo development

Nerve growth factor (NGF) was discovered because of its neurotrophic actions on sympathetic and sensory neurons in the developing chicken embryo. NGF was subsequently found to influence and regulate the function of many neuronal and non neuronal cells in adult organisms. Little is known, however, about the possible actions of NGF during early embryonic stages. However, mRNAs encoding for NGF and its receptors TrkA and p75(NTR) are expressed at very early stages of avian embryo development, before the nervous system is formed. The question, therefore, arises as to what might be the functions of NGF in early chicken embryo development, before its well-established actions on the developing sympathetic and sensory neurons. To investigate possible roles of NGF in the earliest stages of development, stage HH 11-12 chicken embryos were injected with an anti-NGF antibody (mAb αD11) that binds mature NGF with high affinity. Treatment with anti-NGF, but not with a control antibody, led to a dose-dependent inversion of the direction of axial rotation. This effect of altered rotation after anti NGF injection was associated with an increased cell death in somites. Concurrently, a microarray mRNA expression analysis revealed that NGF neutralization affects the expression of genes linked to the regulation of development or cell proliferation. These results reveal a role for NGF in early chicken embryo development and, in particular, in the regulation of somite survival and axial rotation, a crucial developmental process linked to left-right asymmetry specification.

Pro-nerve growth factor induces autocrine stimulation of breast cancer cell invasion through tropomyosin-related kinase A (TrkA) and sortilin protein

The precursor of nerve growth factor (proNGF) has been described as a biologically active polypeptide able to induce apoptosis in neuronal cells, via the neurotrophin receptor p75(NTR) and the sortilin receptor. Herein, it is shown that proNGF is produced and secreted by breast cancer cells, stimulating their invasion. Using Western blotting and mass spectrometry, proNGF was detected in a panel of breast cancer cells as well as in their conditioned media. Immunohistochemical analysis indicated an overproduction of proNGF in breast tumors, when compared with benign and normal breast biopsies, and a relationship to lymph node invasion in ductal carcinomas. Interestingly, siRNA against proNGF induced a decrease of breast cancer cell invasion that was restored by the addition of non-cleavable proNGF. The activation of TrkA, Akt, and Src, but not the MAP kinases, was observed. In addition, the proNGF invasive effect was inhibited by the Trk pharmacological inhibitor K252a, a kinase-dead TrkA, and siRNA against TrkA sortilin, neurotensin, whereas siRNA against p75(NTR) and the MAP kinase inhibitor PD98059 had no impact. These data reveal the existence of an autocrine loop stimulated by proNGF and mediated by TrkA and sortilin, with the activation of Akt and Src, for the stimulation of breast cancer cell invasion.

BDNF-promoted increases in proximal dendrites occur via CREB-dependent transcriptional regulation of cypin

Alterations in dendrite branching and morphology are present in many neurodegenerative diseases. These variations disrupt postsynaptic transmission and affect neuronal communication. Thus, it is important to understand the molecular mechanisms that regulate dendritogenesis and how they go awry during disease states. Previously, our laboratory showed that cypin, a mammalian guanine deaminase, increases dendrite number when overexpressed and decreases dendrite number when knocked down in cultured hippocampal neurons. Here, we report that exposure to brain-derived neurotrophic factor (BDNF), an important mediator of dendrite arborization, for 72 h but not for 24 h or less increases cypin mRNA and protein levels in rat hippocampal neurons. BDNF signals through cypin to regulate dendrite number, since knocking down cypin blocks the effects of BDNF. Furthermore, BDNF increases cypin levels via mitogen-activated protein kinase and transcription-dependent signaling pathways. Moreover, the cypin promoter region contains putative conserved cAMP response element (CRE) regions, which we found can be recognized and activated by CRE-binding protein (CREB). In addition, exposure of the neurons to BDNF increased CREB binding to the cypin promoter and, in line with these data, expression of a dominant negative form of CREB blocked BDNF-promoted increases in cypin protein levels and proximal dendrite branches. Together, these studies suggest that BDNF increases neuronal cypin expression by the activation of CREB, increasing cypin transcription leading to increased protein expression, thus identifying a novel pathway by which BDNF shapes the dendrite network.

Conformational plasticity of proNGF

Nerve Growth Factor is an essential protein that supports neuronal survival during development and influences neuronal function throughout adulthood, both in the central and peripheral nervous system. The unprocessed precursor of NGF, proNGF, seems to be endowed with biological functions distinct from those of the mature protein, such as chaperone-like activities and apoptotic and/or neurotrophic properties. We have previously suggested, based on Small Angle X-ray Scattering data, that recombinant murine proNGF has features typical of an intrinsically unfolded protein. Using complementary biophysical techniques, we show here new evidence that clarifies and widens this hypothesis through a detailed comparison of the structural properties of NGF and proNGF. Our data provide direct information about the dynamic properties of the pro-peptide and indicate that proNGF assumes in solution a compact globular conformation. The N-terminal pro-peptide extension influences the chemical environment of the mature protein and protects the protein from proteolytic digestion. Accordingly, we observe that unfolding of proNGF involves a two-steps mechanism. The distinct structural properties of proNGF as compared to NGF agree with and rationalise a different functional role of the precursor.

NGF and proNGF regulate functionally distinct mRNAs in PC12 cells: an early gene expression profiling

The biological activities of NGF and of its precursor proNGF are quite distinct, due to different receptor binding profiles, but little is known about how proNGF regulates gene expression. Whether proNGF is a purely pro-apoptotic molecule and/or simply a “less potent NGF” is still a matter of debate. We performed experiments to address this question, by verifying whether a proNGF specific transcriptional signature, distinct from that of NGF, could be identified. To this aim, we studied gene expression regulation by proNGF and NGF in PC12 cells incubated for 1 and 4 hours with recombinant NGF and proNGF, in its wild-type or in a furin-cleavage resistant form. mRNA expression profiles were analyzed by whole genome microarrays at early time points, in order to identify specific profiles of NGF and proNGF. Clear differences between the mRNA profiles modulated by the three neurotrophin forms were identified. NGF and proNGF modulate remarkably distinct mRNA expression patterns, with the gene expression profile regulated by NGF being significantly more complex than that by proNGF, both in terms of the total number of differentially expressed mRNAs and of the gene families involved. Moreover, while the total number of genes modulated by NGF increases dramatically with time, that by proNGFs is unchanged or reduced. We identified a subset of regulated genes that could be ascribed to a “pure proNGF” signalling, distinct from the “pure NGF” one. We also conclude that the composition of mixed NGF and proNGF samples, when the two proteins coexist, influences the profile of gene expression. Based on this comparison of the gene expression profiles regulated by NGF and its proNGF precursor, we conclude that the two proteins activate largely distinct transcriptional programs and that the ratio of NGF to proNGF in vivo can profoundly influence the pattern of regulated mRNAs.

New therapeutic approaches in the treatment of diabetic keratopathy: a review

The cornea is densely innervated, and the integrity of these nerve fibres is critical in maintaining the refractive and protective functions of the cornea. Many ocular and systemic diseases can adversely affect corneal sensory nerves and consequently impair their function, with vision loss being the inevitable consequence of severe corneal neurotrophic ulceration. However, current standard treatments regimens are often ineffective. Over the past three decades, the role of growth factors in maintaining the normal structure and function of the cornea, and in corneal epithelial healing, has become increasingly evident. Many preclinical and clinical trials have shown that growth factors and cytokines can significantly enhance epithelialization (epithelial proliferation and migration) and consequently accelerate wound healing. More recently, local/topical administration of insulin, naltrexone (opioid antagonist) and nicergoline (ergoline derivatives) were found to improve, and significantly increase, the corneal wound healing rate. This report reviews the major attributes of these growth factors and therapeutic agents that may be used in ameliorating impaired corneal wound healing, and presents a perspective on the potential clinical use of these agents as a new generation of ophthalmic pharmaceuticals for the treatment of diabetic keratopathy.

Nerve growth factor in cancer cell death and survival

One of the major challenges for cancer therapeutics is the resistance of many tumor cells to induction of cell death due to pro-survival signaling in the cancer cells. Here we review the growing literature which shows that neurotrophins contribute to pro-survival signaling in many different types of cancer. In particular, nerve growth factor, the archetypal neurotrophin, has been shown to play a role in tumorigenesis over the past decade. Nerve growth factor mediates its effects through its two cognate receptors, TrkA, a receptor tyrosine kinase and p75NTR, a member of the death receptor superfamily. Depending on the tumor origin, pro-survival signaling can be mediated by TrkA receptors or by p75NTR. For example, in breast cancer the aberrant expression of nerve growth factor stimulates proliferative signaling through TrkA and pro-survival signaling through p75NTR. This latter signaling through p75NTR promotes increased resistance to the induction of cell death by chemotherapeutic treatments. In contrast, in prostate cells the p75NTR mediates cell death and prevents metastasis. In prostate cancer, expression of this receptor is lost, which contributes to tumor progression by allowing cells to survive, proliferate and metastasize. This review focuses on our current knowledge of neurotrophin signaling in cancer, with a particular emphasis on nerve growth factor regulation of cell death and survival in cancer.

Quantitative analysis of nerve growth factor in the amniotic fluid during chick embryonic development

Nerve growth factor (NGF) and most neurotrophic factors support the proliferation and survival of particular types of neurons. Besidesthe pivotal role of NGF in the development of neuronal cells, it also has important functions on non-neuronal cells. The amnion surrounds the embryo, providing an aqueous environment for the embryo. A wide range of proteins has been identified in human amniotic fluid (AF). In this study, total protein concentration (TPC) and NGF level in AF samples from chick embryos were measured using a Bio-Rad protein assay, enzyme linked immunosorbent assay (ELISA) and Western blot. TPC increased from days E10 to day E18. There was a rapid increase in AF TPC on day E15 when compared to day E16. No significant changes in NGF levels have been seen from day E10 to day E14. There was a rapid increase in NGF content on days E15 and E16, and thereafter the levels decreased from day E16 to day E18. Since, NGF is important in brain development and changes in AF NGF levels have been seen in some CNS malformations, changes in the TPC and NGF levels in AF during chick embryonic development may be correlated with cerebral cortical development. It is also concluded that NGF is a constant component of the AF during chick embryogenesis.

Natural and synthetic inhibitors of kallikrein-related peptidases (KLKs)

Including the true tissue kallikrein KLK1, kallikrein-related peptidases (KLKs) represent a family of fifteen mammalian serine proteases. While the physiological roles of several KLKs have been at least partially elucidated, their activation and regulation remain largely unclear. This obscurity may be related to the fact that a given KLK fulfills many different tasks in diverse fetal and adult tissues, and consequently, the timescale of some of their physiological actions varies significantly. To date, a variety of endogenous inhibitors that target distinct KLKs have been identified. Among them are the attenuating Zn(2+) ions, active site-directed proteinaceous inhibitors, such as serpins and the Kazal-type inhibitors, or the huge, unspecific compartment forming α(2)-macroglobulin. Failure of these inhibitory systems can lead to certain pathophysiological conditions. One of the most prominent examples is the Netherton syndrome, which is caused by dysfunctional domains of the Kazal-type inhibitor LEKTI-1 which fail to appropriately regulate KLKs in the skin. Small synthetic inhibitory compounds and natural polypeptidic exogenous inhibitors have been widely employed to characterize the activity and substrate specificity of KLKs and to further investigate their structures and biophysical properties. Overall, this knowledge leads not only to a better understanding of the physiological tasks of KLKs, but is also a strong fundament for the synthesis of small compound drugs and engineered biomolecules for pharmaceutical approaches. In several types of cancer, KLKs have been found to be overexpressed, which makes them clinically relevant biomarkers for prognosis and monitoring. Thus, down regulation of excessive KLK activity in cancer and in skin diseases by small inhibitor compounds may represent attractive therapeutical approaches.

Nerve growth factor and tyrosine kinase A receptor in oral squamous cell carcinoma: is there an association with perineural invasion?

PURPOSE

Perineural invasion (PNI) in oral squamous cell carcinoma (SCC) is recognized as a significant predictor of outcome. PNI is associated with locoregional recurrence and decreased survival of patients with head and neck SCC. Nerve growth factor (NGF) has been shown to be involved in PNI in several malignancies, including breast, prostate, and pancreatic cancers. We investigated the hypothesis that NGF and its high-affinity receptor tyrosine kinase A (TrkA) are highly expressed in cases of oral SCC that have histologic evidence of PNI.

MATERIALS AND METHODS

We performed immunohistochemistry on archived oral tongue SCC specimens from the established oral and general pathology databases at the University of California, San Francisco. The following groups were evaluated: 1) 21 T1/T2 oral tongue SCC cases with PNI and 2) 21 T1/T2 oral tongue SCC cases without histologic evidence of PNI.

RESULTS

Strong homogeneous cytoplasmic staining for NGF and TrkA was detected in the malignant cells in the PNI-positive group of tumors. In group II (PNI negative) NGF and TrkA were detected in the stroma cells or were very weakly expressed by the malignant cells. We were able to show the presence of NGF and TrkA in the cytoplasm of malignant squamous cells in tumors with histologic evidence of PNI. Immunostaining for NGF (P = .0001) and TrkA (P = .039) was significantly higher in the PNI-positive oral SCC group than in the PNI-negative oral SCC group.

CONCLUSION

This study shows that oral SCC with evidence of PNI shows increased expression of NGF and TrkA and suggests that NGF and TrkA are involved with the mechanism leading to PNI. Further investigations are warranted to determine the potential for use of NGF and TrkA as candidate biomarkers to predict progression and outcome.

Changes in cerebrospinal fluid nerve growth factor levels during chick embryonic development

In the early stages of brain development, cells within the ependymal lining of the neural tube are thought to secrete cerebrospinal fluid (CSF), the so-called neural tube fluid (NTF), whereas before fusion of the neural folds, the neuroepithelium that lines the inside of the neural tube is in contact with amniotic fluid. As the neural tube closes, a membrane formed from these cells invaginates to form the specialized choroid plexus. The choroid plexus is a highly vascularized epithelial cell structure that secretes proteins, including growth factors, into the CSF. Embryonic CSF (e-CSF) contains high concentrations of proteins compared to adult CSF. CSF has been reported to contain nerve growth factor (NGF) and other neurotrophic factors. In this study, total protein concentration and NGF level in e-CSF samples from chick embryos were measured using a dye-based protein assay, enzyme-linked immunosorbent assay (ELISA) and Western blot. The total protein concentration and NGF levels in the CSF decreased from days E10 to E16. There was a rapid increase in total protein content on days E17 and E18, and thereafter the levels decreased from day E19 to day E21. Days E17 and E18 coincide with the onset of neuron migration, proliferation and organization of the cytoarchitecture of the developing cerebral cortex. After that time the total protein concentration and NGF levels decrease until hatching. Since CSF is in contact with the cerebral cortical germinal epithelium, changes in the protein concentration in the CSF could affect neuroepithelial cell proliferation, survival and migration. It is concluded that NGF is not only a constant component of CSF during chick embryogenesis but it might also be involved in cerebral cortical development.

Systemic disease-induced salivary biomarker profiles in mouse models of melanoma and non-small cell lung cancer

Background

Saliva (oral fluids) is an emerging biofluid poised for detection of clinical diseases. Although the rationale for oral diseases applications (e.g. oral cancer) is intuitive, the rationale and relationship between systemic diseases and saliva biomarkers are unclear.

Methodology/Principal Findings

In this study, we used mouse models of melanoma and non-small cell lung cancer and compared the transcriptome biomarker profiles of tumor-bearing mice to those of control mice. Microarray analysis showed that salivary transcriptomes were significantly altered in tumor-bearing mice vs. controls. Significant overlapping among transcriptomes of mouse tumors, serum, salivary glands and saliva suggests that salivary biomarkers have multiple origins. Furthermore, we identified that the expression of two groups of significantly altered transcription factors (TFs) Runx1, Mlxipl, Trim30 and Egr1, Tbx1, Nr1d1 in salivary gland tissue of melanoma-bearing mice can potentially be responsible for 82.6% of the up-regulated gene expression and 62.5% of the down-regulated gene expression, respectively, in the saliva of melanoma-bearing mice. We also showed that the ectopic production of nerve growth factor (NGF) in the melanoma tumor tissue as a tumor-released mediator can induce expression of the TF Egr-1 in the salivary gland.

Conclusions

Taken together, our data support the conclusion that upon systemic disease development, significant changes can occur in the salivary biomarker profile. Although the origins of the disease-induced salivary biomarkers may be both systemic and local, stimulation of salivary gland by mediators released from remote tumors plays an important role in regulating the salivary surrogate biomarker profiles.