Nerve growth factor (NGF) reduces and NGF antibody exacerbates retinal damage induced in rabbit by experimental ocular hypertension

Encapsulated cell technology: Delivering cytokines to treat posterior ocular diseases

Encapsulated cell technology (ECT) is a targeted delivery method that uses the genetically engineered cells in semipermeable polymer capsules to deliver cytokines. Thus far, ECT has been extensively utilized in pharmacologic research, and shows enormous potentials in the treatment of posterior segment diseases. Due to the biological barriers within the eyeball, it is difficult to attain effective therapeutic concentration in the posterior segment through topical administration of drug molecules. Encouragingly, therapeutic cytokines provided by ECT can cross these biological barriers and achieve sustained release at the desired location. The encapsulation system uses permeable materials that allow growth factors and cytokines to diffuse efficiently into retinal tissue. Moreover, the ECT based treatment can be terminated timely when we need to retrieve the implant, which makes the therapy reversible and provides a safer alternative for intraocular gene therapy. Meanwhile, we also place special emphasis on optimizing encapsulation materials and enhancing preservation techniques to achieve the stable release of growth factors and cytokines in the eyeball. This technology holds great promise for the treatment of patients with dry AMD, RP, glaucoma and MacTel. These findings would enrich our understandings of ECT and promote its future applications in treatment of degenerative retinopathy. This review comprises articles evaluating the exactness of artificial intelligence-based formulas published from 2000 to March 2024. The papers were identified by a literature search of various databases (PubMed/MEDLINE, Google Scholar, Cochrane Library and Web of Science).

A, B, C's of Trk Receptors and Their Ligands in Ocular Repair

Neurotrophins are a family of closely related secreted proteins that promote differentiation, development, and survival of neurons, which include nerve growth factor (NGF), brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-4. All neurotrophins signal through tropomyosin receptor kinases (TrkA, TrkB, and TrkC) which are more selective to NGF, brain-derived neurotrophic factor, and neurotrophin-3, respectively. NGF is the most studied neurotrophin in the ocular surface and a human recombinant NGF has reached clinics, having been approved to treat neurotrophic keratitis. Brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-4 are less studied neurotrophins in the ocular surface, even though brain-derived neurotrophic factor is well characterized in glaucoma, retina, and neuroscience. Recently, neurotrophin analogs with panTrk activity and TrkC selectivity have shown promise as novel drugs for treating dry eye disease. In this review, we discuss the biology of the neurotrophin family, its role in corneal homeostasis, and its use in treating ocular surface diseases. There is an unmet need to investigate parenteral neurotrophins and its analogs that activate TrkB and TrkC selectively.

Nerve Growth Factor Promotes Retinal Neurovascular Unit Repair: A Review

Purpose: The purpose of this paper is to investigate how the imbalance of neurogenic factor (NGF) and its precursor (pro-NGF) mediates structural and functional impairment of retinal neurovascular unit (RNVU) that plays a role in retinal degenerative diseases.Methods: A literature search of electronic databases was performed.Results: The pro-apoptotic effect of pro-NGF and the pro-growth effect of NGF are essential for the pathological and physiological activities of RNVU. Studies show that NGF-based treatment of retinal degenerative diseases, including glaucoma, age-related macular degeneration, retinitis pigmentosa, and diabetic retinopathy, has achieved remarkable efficacy.Conclusions: RNVU plays a complex and multifaceted role in retinal degenerative diseases. The exploration of the differential signaling expression of proNGF-NGF homeostasis under physiological and pathological conditions, and the corresponding pathological processes induced by its regulation, has prompted us to focus on earlier retinal neuroprotective therapeutic strategies to prevent retinal degenerative diseases.

Innervation in organogenesis

Proper innervation of peripheral organs helps to maintain physiological homeostasis and elicit responses to external stimuli. Disruptions to normal function can result in pathophysiological consequences. The establishment of connections and communication between the central nervous system and the peripheral organs is accomplished through the peripheral nervous system. Neuronal connections with target tissues arise from ganglia partitioned throughout the body. Organ innervation is initiated during development with stimuli being conducted through several types of neurons including sympathetic, parasympathetic, and sensory. While the physiological modulation of mature organs by these nerves is largely understood, their role in mammalian development is only beginning to be uncovered. Interactions with cells in target tissues can affect the development and eventual function of several organs, highlighting their significance. This chapter will cover the origin of peripheral neurons, factors mediating organ innervation, and the composition and function of organ-specific nerves during development. This emerging field aims to identify the functional contribution of innervation to development which will inform future investigations of normal and abnormal mammalian organogenesis, as well as contribute to regenerative and organ replacement efforts where nerve-derived signals may have significant implications for the advancement of such studies.

A Review of Potential Novel Glaucoma Therapeutic Options Independent of Intraocular Pressure

Glaucoma, a progressive optic neuropathy characterized by retinal ganglion cell degeneration and visual field loss, is the leading cause of irreversible blindness worldwide. Intraocular pressure (IOP) is presently the only modifiable risk factor demonstrated to slow or halt disease progression; however, glaucomatous damage persists in almost 50% of patients despite significant IOP reduction. Many studies have investigated the non-IOP-related risk factors that contribute to glaucoma progression as well as interventions that can prevent or delay glaucomatous neurodegeneration and preserve vision throughout life, independently of IOP. A vast number of experimental studies have reported effective neuroprotection in glaucoma, and clinical studies are ongoing attempting to provide strong evidence of effectiveness of these interventions. In this review, we look into the current understanding of the pathophysiology of glaucoma and explore the recent advances in non-IOP related strategies for neuroprotection and neuroregeneration in glaucoma.

Nerve Growth Factor as an Ocular Therapy: Applications, Challenges, and Future Directions

Nerve growth factor (NGF), the prototypical neurotrophin first discovered in the 1950s, has recently garnered increased interest as a therapeutic agent promoting neuronal health and regeneration. After gaining orphan drug status within the last decade, NGF-related research and drug development has accelerated. The purpose of this article is to review the preclinical and clinical evidence of NGF in various applications, including central and peripheral nervous system, skin, and ophthalmic disorders. We focus on the ophthalmic applications including not only the FDA-approved indication of neurotrophic keratitis but also retinal disease and glaucoma. NGF represents a promising therapy whose therapeutic profile is evolving. The challenges related to this therapy are reviewed, along with possible solutions and future directions.

Neurotrophic Factors in Glaucoma and Innovative Delivery Systems

Glaucoma is a neurodegenerative disease and a worldwide leading cause of irreversible vision loss. In the last decades, high efforts have been made to develop novel treatments effective in inducing protection and/or recovery of neural function in glaucoma, including neurotrophic factors (NTFs). These approaches have shown encouraging data in preclinical setting; however, the challenge of sustained, targeted delivery to the retina and optic nerve still prevents the clinical translation. In this paper, the authors review and discuss the most recent advances for the use of NTFs treatment in glaucoma, including intraocular delivery. Novel strategies in drug and gene delivery technology for NTFs are proving effective in promoting long-term retinal ganglion cells (RGCs) survival and related functional improvements. Results of experimental and clinical studies evaluating the efficacy and safety of biodegradable slow-release NTF-loaded microparticle devices, encapsulated NTF-secreting cells implants, mimetic ligands for NTF receptors, and viral and non-viral NTF gene vehicles are discussed. NTFs are able to prevent and even reverse apoptotic ganglion cell death. Nevertheless, neuroprotection in glaucoma remains an open issue due to the unmet need of sustained delivery to the posterior segment of the eye. The recent advances in intraocular delivery systems pave the way for possible future use of NTFs in clinical practice for the treatment of glaucoma.

Topical recombinant human Nerve growth factor (rh-NGF) is neuroprotective to retinal ganglion cells by targeting secondary degeneration

Optic neuropathy is a major cause of irreversible blindness worldwide, and no effective treatment is currently available. Secondary degeneration is believed to be the major contributor to retinal ganglion cell (RGC) death, the endpoint of optic neuropathy. Partial optic nerve transection (pONT) is an established model of optic neuropathy. Although the mechanisms of primary and secondary degeneration have been delineated in this model, until now how this is influenced by therapy is not well-understood. In this article, we describe a clinically translatable topical, neuroprotective treatment (recombinant human nerve growth factor, rh-NGF) predominantly targeting secondary degeneration in a pONT rat model. Topical application of rh-NGF twice daily for 3 weeks significantly improves RGC survival as shown by reduced RGC apoptosis in vivo and increased RGC population in the inferior retina, which is predominantly affected in this model by secondary degeneration. Topical rh-NGF also promotes greater axonal survival and inhibits astrocyte activity in the optic nerve. Collectively, these results suggest that topical rh-NGF exhibits neuroprotective effects on retinal neurons via influencing secondary degeneration process. As topical rh-NGF is already involved in early clinical trials, this highlights its potential in multiple indications in patients, including those affected by glaucomatous optic neuropathy.

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.

Recombinant Human Nerve Growth Factor Treatment Promotes Photoreceptor Survival in the Retinas of Rats with Retinitis Pigmentosa

PURPOSE

Increasing evidence suggests that nerve growth factor (NGF) exerts protective effects against retinal degeneration in animal models of retinitis pigmentosa (RP). This study aims at investigating the effects of intravitreal injection of recombinant human NGF (rhNGF) on retinal photoreceptors apoptosis in an animal model of RP, the Royal College of Surgeons (RCS) rats.

METHODS

Thirty-six RCS rats were treated with intravitreal injection of rhNGF or murine NGF (mNGF) or vehicle at 20 postnatal days (pd) and sacrificed at 40 pd. The eyes were enucleated and evaluated by histology, flow cytometric analysis for rhodopsin expression, Western blot for TrkA and activated (phosphorylated) TrkA (pTrkA) levels, and TUNEL assay for apoptosis' detection.

RESULTS

RCS rats showed a significant retinal degeneration associated with cell apoptosis at 40 pd when compared to wild-type animals. Histology showed that rhNGF intravitreal treatment significantly increased retinal thickness when compared to untreated eyes. Photoreceptors' number evaluated by flow cytometry was significantly increased in both intravitreal rhNGF- and mNGF-treated groups when compared to untreated eyes. This protective effect was associated with an increase in TrkA and activated pTrkA levels and an inhibition of apoptosis. Intravitreal NGF injection was well tolerated and did not show clinical and histological signs of adverse effects.

CONCLUSIONS

Intravitreal rhNGF injection proved safe and effective in favoring retinal cell survival in RCS rats. This is the first report showing that the novel rhNGF already proved safe in a phase I study exerts a biologic effect similar to the well-characterized mNGF-induced retinal protection. These results may trigger further studies to investigate rhNGF administration for the treatment of progressive degenerative retinal disorders such as retinitis pigmentosa.

NGF/anti-VEGF combined exposure protects RCS retinal cells and photoreceptors that underwent a local worsening of inflammation

PURPOSE

Our previous study highlighted the potential nerve growth factor (NGF) effect on damaged photoreceptors from a rat model of spontaneous Retinitis Pigmentosa (RP). Herein, we tested the combined NGF/anti-vascular endothelial growth factor (αVEGF) effect on cultured retinal cells isolated from Royal College of Surgeons (RCS) rats receiving an intravitreal VEGF injection (iv-VEGF) to exacerbate retinal inflammation/neovascularization.

METHODS

RCS (n = 75) rats were equally grouped as untreated (n = 25), iv-saline (single saline intravitreal injection; n = 25) and iv-VEGF (single VEGF intravitreal injection; n = 25). Morphological and biochemical analysis or in vitro stimulations with the biomolecular investigation were carried out on explanted retinas. Isolated retinal cells were treated with NGF and αVEGF, either alone or in combination, for 6 days and cells were harvested for morphological and biomolecular analyses.

RESULTS

Infiltrating inflammatory cells were detected in iv-VEGF exposed RCS retinas, indicative of exacerbated inflammation and neovascularization. In cell cultures, NGF/αVEGF significantly increased retinal cell survival as well as rhodopsin expression and neurite outgrowth in photoreceptors. Particularly, NGF/αVEGF upregulated Bcl-2 mRNA, downregulated Bax mRNA, upregulated trkA^NGFR mRNA and finally upregulated both NGF mRNA and protein.

CONCLUSIONS

These data confirm and extend our previous findings on NGF-photoreceptor crosstalk, highlighting that the NGF/αVEGF combination might be an interesting approach for improving neuroprotection of RCS retinal cells and likewise photoreceptors in the presence of neovascularization. Further studies are required to translate this in vitro approach into clinical practice.

Ultrasound Microbubbles Enhance the Neuroprotective Effect of Mouse Nerve Growth Factor on Intraocular Hypertension-Induced Neuroretina Damage in Rabbits

Ultrasound microbubble combined optic protection drugs have obvious protective effect on optic nerve damage. This way of targeting drug delivery is becoming more simple, not through the whole body metabolism, avoiding drug via blood circulation when facing the decomposition and the environment in the interference and destruction process of drugs, to maximize the guarantee to reach target organs of drug concentration and to reache the maximum therapeutic effect. The technique of ultrasound microbubbles is safe, controllable, nonimmunogenic, and repeatable. It provides us with a novel idea in the administration of neuroprotective drugs.

Nerve Growth Factor: A Focus on Neuroscience and Therapy

Nerve growth factor (NGF) is the firstly discovered and best characterized neurotrophic factor, known to play a critical protective role in the development and survival of sympathetic, sensory and forebrain cholinergic neurons. NGF promotes neuritis outgrowth both in vivo and in vitro and nerve cell recovery after ischemic, surgical or chemical injuries. Recently, the therapeutic property of NGF has been demonstrated on human cutaneous and corneal ulcers, pressure ulcer, glaucoma, maculopathy and retinitis pigmentosa. NGF eye drops administration is well tolerated, with no detectable clinical evidence of systemic or local adverse effects. The aim of this review is to summarize these biological properties and the potential clinical development of NGF.

Human β-NGF gene transferred to cat corneal endothelial cells

AIM

To transfect the cat corneal endothelial cells (CECs) with recombinant human β-nerve growth factor gene adeno-associated virus (AAV-β-NGF) and to observe the effect of the expressed β-NGF protein on the proliferation activity of cat CECs.

METHODS

The endothelium of cat cornea was torn under the microscope and rapidly cultivated in Dulbecco's modified Eagle's medium (DMEM) to form single layer CECs and the passage 2 endothelial cells were used in this experiment. The recombinant human AAV-β-NGF was constructed. The recombinant human AAV-β-NGF was transferred into cat CECs directly. Three groups were as following: normal CEC control group, CEC-AAV control group and recombinant CEC-AAV-β-NGF group. Forty-eight hours after transfection, the total RNA was extracted from the CEC by Trizol. The expression of the β-NGF target gene detected by fluorescence quantitative polymerase chain reaction; proliferation activity of the transfected CEC detected at 48h by MTT assay; the percentage of G1 cells among CECs after transfect was detected by flow cytometry method (FCM); cell morphology was observed under inverted phase contrast microscope.

RESULTS

The torn endothelium culture technique rapidly cultivated single layer cat corneal endothelial cells. The self-designed primers for the target gene and reference gene were efficient and special confirmed through electrophoresis analysis and DNA sequencing. Forty-eight hours after transfect, the human β-NGF gene mRNA detected by fluorescence quantitative polymerase chain reaction showed that there was no significant difference between normal CEC control group and CEC-AAV control group (P>0.05); there was significant difference between two control groups and recombinant CEC-AAV-β-NGF group (P<0.05). MTT assay showed that transfect of recombinant AAV-β-NGF promoted the proliferation activity of cat CEC, while there was no significant difference between normal CEC control group and CEC-AAV control group (P>0.05). FCM result showed that the percentage of G1cells in CEC-AAV-NGF group was 76.8% while that in normal CEC control group and CEC-AAV control group was 46.6% and 49.8%.

CONCLUSION

Recombinant AAV-β-NGF promotes proliferation in cat CECs by expressing bioactive β-NGF protein in high efficiency and suggests that its modulation can be used to treat vision loss secondary to corneal endothelial dysfunction.

Discovery of Molecular Therapeutics for Glaucoma: Challenges, Successes, and Promising Directions

Glaucoma, a heterogeneous ocular disorder affecting ∼60 million people worldwide, is characterized by painless neurodegeneration of retinal ganglion cells (RGCs), resulting in irreversible vision loss. Available therapies, which decrease the common causal risk factor of elevated intraocular pressure, delay, but cannot prevent, RGC death and blindness. Notably, it is changes in the anterior segment of the eye, particularly in the drainage of aqueous humor fluid, which are believed to bring about changes in pressure. Thus, it is primarily this region whose properties are manipulated in current and emerging therapies for glaucoma. Here, we focus on the challenges associated with developing treatments, review the available experimental methods to evaluate the therapeutic potential of new drugs, describe the development and evaluation of emerging Rho-kinase inhibitors and adenosine receptor ligands that offer the potential to improve aqueous humor outflow and protect RGCs simultaneously, and present new targets and approaches on the horizon.

Experimental and clinical evidence of neuroprotection by nerve growth factor eye drops: Implications for glaucoma

Elevated intraocular pressure (IOP) in glaucoma causes loss of retinal ganglion cells (RGCs) and damage to the optic nerve. Although IOP is controlled pharmacologically, no treatment is available to restore retinal and optic nerve function. We evaluated the effects of NGF eye drops in a rat model of glaucoma. We also treated 3 patients with progressive visual field defects despite IOP control. Glaucoma was induced in rats through injection of hypertonic saline into the episcleral vein. Initially, 2 doses of NGF (100 and 200 mug/mL) were tested on 24 rats, and the higher dose was found to be more effective. Glaucoma was then induced in an additional 36 rats: half untreated and half treated with 200 mug/mL NGF QID for 7 weeks. Apoptosis/survival of RGCs was evaluated by histological, biochemical, and molecular analysis. Three patients with advanced glaucoma underwent psychofunctional and electrofunctional tests at baseline, after 3 months of NGF eye drops, and after 3 months of follow-up. Seven weeks of elevated IOP caused RGC degeneration resulting in 40% cell death. Significantly less RGC loss was observed with NGF treatment (2,530 +/- 121 vs. 1,850 +/- 156 RGCs/mm(2)) associated with inhibition of cell death by apoptosis. Patients treated with NGF demonstrated long lasting improvements in visual field, optic nerve function, contrast sensitivity, and visual acuity. NGF exerted neuroprotective effects, inhibiting apoptosis of RGCs in animals with glaucoma. In 3 patients with advanced glaucoma, treatment with topical NGF improved all parameters of visual function. These results may open therapeutic perspectives for glaucoma and other neurodegenerative diseases.

A Pro-Nerve Growth Factor (proNGF) and NGF Binding Protein, α2-Macroglobulin, Differentially Regulates p75 and TrkA Receptors and Is Relevant to Neurodegeneration Ex Vivo and In Vivo

Nerve growth factor (NGF) is generated from a precursor, proNGF, that is proteolytically processed. NGF preferentially binds a trophic tyrosine kinase receptor, TrkA, while proNGF binds a neurotrophin receptor (NTR), p75(NTR), that can have neurotoxic activity. Previously, we along with others showed that the soluble protein α2-macroglobulin (α2M) is neurotoxic. Toxicity is due in part to α2M binding to NGF and inhibiting trophic activity, presumably by preventing NGF binding to TrkA. However, the mechanisms remained unclear. Here, we show ex vivo and in vivo three mechanisms for α2M neurotoxicity. First, unexpectedly the α2M-NGF complexes do bind TrkA receptors but do not induce TrkA dimerization or activation, resulting in deficient trophic support. Second, α2M makes stable complexes with proNGF, conveying resistance to proteolysis that results in more proNGF and less NGF. Third, α2M-proNGF complexes bind p75(NTR) and are more potent agonists than free proNGF, inducing tumor necrosis factor alpha (TNF-α) production. Hence, α2M regulates proNGF/p75(NTR) positively and mature NGF/TrkA negatively, causing neuronal death ex vivo. These three mechanisms are operative in vivo, and α2M causes neurodegeneration in a p75(NTR)- and proNGF-dependent manner. α2M could be exploited as a therapeutic target, or as a modifier of neurotrophin signals.

MicroRNA target prediction in glaucoma

Glaucoma is a progressive optic neuropathy and is one of the leading causes of blindness in the industrialized countries. The aim of this study is to investigate microRNA (miRNA) regulation in glaucoma and other neurodegenerative diseases, that share similar pathways, by means of in silico approaches such as bibliographic search and access to bioinformatic resources. First of all, data mining was carried out on Human miRNA Disease Database (HMDD) and miR2Disease databases. Then, predictions of deregulated miRNAs were carried out accessing to microrna.org database. Finally, the potential combinatorial effect of miRNAs, on regulation of biochemical pathways, was studied by an enrichment analysis performed by DIANA-miRPath v.2.0. We found, from literature search, 8 deregulated miRNAs in glaucoma and 9 and 23 in age-related macular degeneration (AMD) and Alzheimer's disease (AD), respectively. One miRNA is commonly deregulated in glaucoma and AMD (miR-23a). Two miRNAs (miR-29a, miR-29b) are common to glaucoma and AD, and four miRNAs were identified to be commonly deregulated in AMD and AD (miR-9, miR-21, miR-34a, miR-146a). The match of the miRNA common to glaucoma and the other two neurodegenerative diseases (AMD and AD) did not generate any output. Enrichment of information has been reached through miRNAs prediction: 88 predicted miRNAs are common to glaucoma and AMD, 19 are common to glaucoma and AD, and 9 are common to AMD and AD. Indeed, predicted miRNAs common to the three neurodegenerative diseases are nine (miR-107, miR-137, miR-146a, miR-181c, miR-197, miR-21, miR-22, miR-590, miR-9). DIANA-miRPath predicted that those nine miRNAs might regulate pathways involved in inflammation. The findings hereby obtained provide a valuable hint to assess deregulation of specific miRNA, as potential biomarkers and therapeutic targets, in glaucoma and other neurodegenerative diseases by means of preclinical and clinical studies.

Nerve growth factor protects retinal ganglion cells against injury induced by retinal ischemia-reperfusion in rats

In this study, we investigated the protective effect of mouse nerve growth factor (NGF) on retinal ganglion cell (RGC) injury induced by retinal ischemia-reperfusion (RIR) in rats and explored its possible mechanisms of action. RIR caused a significant injury to RGCs and an obvious impairment of the inner retina functions, which could be seen from flash electroretinogram and flash visual evoked potential recordings. RIR also increased the expression of the apoptotic protein Bax while decreasing the expression of Bcl-2 and the phosphorylation of protein kinase B (Akt) in RGCs. Preinjection (i.m.) of NGF for 22 d reversed the injury induced by RIR and ameliorated the inner retina functions. NGF also reduced the expression of Bax and reversed the reduction of Bcl-2 and the phosphorylated Akt induced by RIR. These results indicate that NGF produces a neuroprotective effect on RGCs against RIR injury and the protective effect of NGF is mainly mediated by the PI-3K/Akt signaling pathway.

Nerve growth factor modulation of retinal ganglion cell physiology

Nerve growth factor (NGF) is an endogenous neurotrophin involved in the development, maintenance and regeneration of mammalian sympathetic and sensory neurons. Additionally, NGF is known to have trophic and differentiating activity on several populations of cholinergic neurons of the central nervous system (CNS), and to act as a differentiation factor in the development of the visual cortex. The paramount functions of NGF in the visual system are also highlighted by the presence of this neurotrophin and both its receptors TrkA and p75 in most intra-ocular tissues, including lens, vitreous, choroid, iris, and trabecular meshwork. In the retina, NGF is produced and utilized specifically by retinal ganglion cells (RGC), bipolar neurons and glial cells, and is thought to have crucial protective effects in several disease states. Studies on the role of NGF on RGCs survival following optic nerve transection, ischemic injury, ocular hypertension and glaucoma are discussed in this review.

Characterization of NGF, trkA (NGFR) , and p75 (NTR) in Retina of Mice Lacking Reelin Glycoprotein

Both Reelin and Nerve Growth Factor (NGF) exert crucial roles in retinal development. Retinogenesis is severely impaired in E-reeler mice, a model of Reelin deficiency showing specific Green Fluorescent Protein expression in Rod Bipolar Cells (RBCs). Since no data are available on Reelin and NGF cross-talk, NGF and trkA^NGFR/ p75^NTR expression was investigated in retinas from E-reeler versus control mice, by confocal microscopy, Western blotting, and real time PCR analysis. A scattered increase of NGF protein was observed in the Ganglion Cell Layer and more pronounced in the Inner Nuclear Layer (INL). A selective increase of p75^NTR was detected in most of RBCs and in other cell subtypes of INL. On the contrary, a slight trend towards a decrease was detected for trkA^NGFR, albeit not significant. Confocal data were validated by Western blot and real time PCR. Finally, the decreased trkA^NGFR/ p75^NTR ratio, representative of p75^NTR increase, significantly correlated with E-reeler versus E-control. These data indicate that NGF-trkA^NGFR/ p75^NTR is affected in E-reeler retina and that p75^NTR might represent the main NGF receptor involved in the process. This first NGF-trkA^NGFR/ p75^NTR characterization suggests that E-reeler might be suitable for exploring Reelin-NGF cross-talk, representing an additional information source in those pathologies characterized by retinal degeneration.

NGF and VEGF effects on retinal ganglion cell fate: new evidence from an animal model of diabetes

PURPOSE

To investigate if the survival effects of nerve growth factor (NGF) eyedrops on retinal ganglion cell (RGCs) are related to vascular endothelial growth factor (VEGF) in a rat model of diabetic retinopathy.

METHODS

Diabetes was induced in adult rats by streptozotocin injection and changes in the NGF/TrkA and VEGF retina levels were related to the progression of RGC loss. Diabetic rats were subjected to administration of NGF eyedrops or intraocular injection of anti-NGF antibody. All morphologic, immunohistochemical, and biochemical analyses were performed on whole retinas dissected after 7 or 11 weeks after diabetes induction.

RESULTS

Diabetes was successfully induced in rats as shown by glycemic levels >250 mg/dL. The NGF levels increased in diabetic retinas at 7 weeks and decreased at 11 weeks, while VEGF levels increased at all time points. The RGC loss in diabetic retinopathy worsened with anti-NGF administration, which did not alter retina VEGF levels significantly. Administration of NGF eyedrops restored TrkA levels in the retina, and protected RGCs from degeneration without influencing VEGF levels.

CONCLUSIONS

The early increase of NGF in diabetic retina might be an endogenous response for protecting RGCs from degeneration. This protective mechanism is impaired at 11 weeks following diabetes induction, and results in a marked RGC degeneration that is improved by exogenous NGF administration and worsened by anti-NGF. The observed NGF-induced neuroprotection on damaged RGCs was not associated with changes in VEGF retina levels, which were constantly high in diabetic rats and were not altered by anti-NGF administration.

Nerve growth factor: basic studies and possible therapeutic applications

The nerve growth factor (NGF) belongs to a family of neurotrophic factors called neurotrophins. It was discovered as a molecule that stimulates the survival and maturation of developing neurons in the peripheral nervous system and has later been shown to protect adult neurons in the degenerating mammalian brain. Basic and clinical studies have been undertaken to use NGF as a therapeutic agent aimed at restoring and maintaining neuronal function in the central nervous system and to determine the mechanisms to safely deliver the molecule into the brain. Recent studies have also recognized that the role of NGF extends far beyond the horizon of nerve cells and even beyond the peripheral and central nervous system. Studies published from our laboratory have shown that topical application of NGF possesses a protective action on human pressure ulcer, corneal ulcer and glaucoma. Here, we will review these studies, supporting the therapeutic potential of NGF.

Nerve growth factor: from the early discoveries to the potential clinical use

The physiological role of the neurotrophin nerve growth factor (NGF) has been characterized, since its discovery in the 1950s, first in the sensory and autonomic nervous system, then in central nervous, endocrine and immune systems. NGF plays its trophic role both during development and in adulthood, ensuring the maintenance of phenotypic and functional characteristic of several populations of neurons as well as immune cells. From a translational standpoint, the action of NGF on cholinergic neurons of the basal forebrain and on sensory neurons in dorsal root ganglia first gained researcher's attention, in view of possible clinical use in Alzheimer's disease patients and in peripheral neuropathies respectively. The translational and clinical research on NGF have, since then, enlarged the spectrum of diseases that could benefit from NGF treatment, at the same time highlighting possible limitations in the use of the neurotrophin as a drug. In this review we give a comprehensive account for almost all of the clinical trials attempted until now by using NGF. A perspective on future development for translational research on NGF is also discussed, in view of recent proposals for innovative delivery strategies and/or for additional pathologies to be treated, such as ocular and skin diseases, gliomas, traumatic brain injuries, vascular and immune diseases.

Rapamycin sensitive mTOR activation mediates nerve growth factor (NGF) induced cell migration and pro-survival effects against hydrogen peroxide in retinal pigment epithelial cells

Patients with age related macular degeneration (AMD) have a loss of vision in the center of the visual field. Oxidative stress plays an important role in this progress. Nerve growth factor (NGF) is important for the survival and maintenance of sympathetic and sensory neurons and NGF eye drops improve visual acuity and electro-functional activity in patients with AMD. However, the molecular mechanisms and signaling events involved in this have not been fully investigated. Using cultured human retinal pigment epithelial (RPE) cells, we demonstrate here that NGF protects RPE cells against hydrogen peroxide (H(2)O(2))-induced cell apoptosis. NGF also induces RPE cell migration, the latter is important for retinal regeneration and the recovery from AMD. H(2)O(2) decreases S6 phosphorylation and cell viability, which is restored by NGF. Rapamycin, the pharmacologic inhibitor of mammalian target of rapamycin (mTOR), diminished NGF-induced S6 phosphorylation, cell migration and protective effects against oxidative stress. Collectively, we conclude that activation of rapamycin sensitive mTOR signaling mediates NGF induced cell migration and pro-survival effects in H(2)O(2) treated RPE cells.

Time-dependent activation of c-fos in limbic brain areas by ocular administration of nerve growth factor in adult rats

PURPOSE

The ocular administration of the neurotrophin nerve growth factor (NGF) has been successfully used in humans to recover damaged ocular tissues. Studies on animal models have demonstrated the ability of ocular applied NGF to reach the retina and the optic nerve and affect brain visual areas. The aim of this study was to examine whether the ocular application of NGF as eye drops might affect brain areas other than the primary visual centers.

METHODS

Two drops (10 μL) of NGF solution (200 μg/mL) or saline were applied as collyrium to both eyes of adult male Sprague-Dawley rats. The animals were sacrificed at 4, 8, or 24 h after treatment and the brains were fixed through intracardiac perfusion. Coronal brain sections were cut with a cryostat and used for immunohistochemical time series and double immunofluorescence studies using c-fos and NeuN as markers for neuronal activation.

RESULTS

The immunohistochemical studies show a time-dependent effect of NGF eye drop treatment. At 4 h after NGF ocular administration, the increase in c-fos immunoreactivity is mainly observed in areas belonging to the central visual system, such as the lateral geniculate nucleus and visual cortex. At 8 h posttreatment, c-fos expression is enhanced in several limbic structures, including the frontal cortex, hippocampus, amygdala, and hypothalamus. The effects of NGF on c-fos distribution persist at 24 h postadministration. Specificity of NGF-induced c-fos in brain was confirmed using inactivated NGF. The neuronal nature of the NGF-activated cells was demonstrated by confocal microscopy observation of c-fos and NeuN colocalization.

CONCLUSION

This study demonstrates that NGF, when applied on ocular surface, is able to activate c-fos in several areas of the limbic system in a time-dependent manner. These findings suggest that the effects of NGF eye drops are not restricted to the primary visual areas, but are extended to all the retinal central targets, including the forebrain structure. Based on these data, the use of NGF eye drops as a strategy to produce NGF-mediated protective and reparative actions in brain is hypothesizable.

Topical nerve growth factor as a visual rescue strategy in pediatric optic gliomas: a pilot study including electrophysiology

BACKGROUND

To date, no specific therapy is available for optic glioma (OG)-induced visual loss.

OBJECTIVE

To evaluate the effects on visual function of murine nerve growth factor (NGF) eye drop administration in children with severe visual impairment due to low-grade OGs.

METHODS

Five patients with OGs and advanced optic nerve atrophy were assessed before and after a single 10-day course of 1 mg murine NGF topical administration by clinical evaluation, visual evoked potentials (VEPs), and brain magnetic resonance imaging (MRI). VEPs, the main functional outcome measure, were recorded at baseline and 1, 30, 45, 90, and 180 days posttreatment. MRI examinations were performed at baseline and at 180 days after NGF treatment. Six untreated control patients with OGs also underwent serial VEPs, clinical testing, and MRI assessments.

RESULTS

After NGF treatment, median VEPs amplitude showed a progressive increase from the baseline values (P < .01). VEPs reached a maximum amplitude at 90 days (170% increase) and declined at 180 days, still remaining above the baseline level. Perception of spontaneous visual phosphenes was noted in all patients after NGF administration. MRI showed stable tumor size. In controls, clinical findings and VEPs did not show any significant change over the observation period.

CONCLUSIONS

The findings from the study show that NGF administration may be an effective and safe adjunct therapy in children with optic atrophy due to OGs. The beneficial effect on optic nerve function suggests a visual rescuing mechanism exerted by murine NGF on the residual viable optic pathways.

Nerve growth factor eye drop administration improves visual function in a patient with optic glioma

BACKGROUND

Spontaneous visual improvement in people with an optic glioma (OG) of the anterior or retrochiasmatic optic pathways is rare.

OBJECTIVE

To evaluate the effects on visual function of nerve growth factor (NGF) eye drop administration in a patient with severe visual impairment due to a low-grade OG.

METHODS

A 45-year-old woman with OG and long-standing optic nerve atrophy was assessed before and after 2 NGF treatment courses. The drug used was 2.5S murine NGF. One milligram of NGF, diluted in saline solution, was administered onto the conjunctiva of both eyes for 10 consecutive days 3 times a day for each treatment. The follow-up was performed by clinical, neuroradiologic, and electrophysiological tests (electroretinogram and visual evoked potentials [VEPs]) at the end of each treatment and 30 and 60 days later.

RESULTS

A repeated subjective and objective improvement of visual function (>3 lines visual acuity; >40° visual field; >50% VEP amplitude increase, Wilcoxon test P < .01) was recorded after NGF treatment. These measures tended to deteriorate toward baseline values 60 days from the end of each NGF treatment. No ocular or systemic side effects were observed throughout treatment.

CONCLUSIONS

Conjunctival NGF may be a beneficial adjunct therapy for visual loss in patients with OG, possibly exerting its effects on residual viable optic pathways.

Glaucoma alters the expression of NGF and NGF receptors in visual cortex and geniculate nucleus of rats: effect of eye NGF application

We investigated the effect of glaucoma (GL) on nerve growth factor (NGF) presence in two brain visual areas. Rats with elevated intraocular pressure (EIOP), induced by hypertonic saline injection in the episcleral vein, were treated with eye topical application of saline or NGF. Rats were subsequently sacrificed, and brain tissues were used for immunohistochemical, biochemical, and molecular analyses. We found that GL alters the basal level of NGF and NGF receptors in brain visual centers and that NGF eye application normalized these deficits. These findings demonstrate that the reduced presence of NGF can arise due to degenerative events in retinal and brain visual areas.

Reduced NGF level and TrkA protein and TrkA gene expression in the optic nerve of rats with experimentally induced glaucoma

Glaucoma (GL) is an optic neuropathy characterized by progressive loss of visual field due to retinal cell death and optic nerve (ON) degeneration, usually in response to abnormal elevated intraocular pressure (EIOP). It has previously demonstrated that cells of the ON express nerve growth factor (NGF) and NGF-receptors. Relatively little is known, however, about their role on the ON of the glaucomatous eye. The aim of the study was to elucidate this aspect. Using a rat model of GL we investigated the response of NGF and NGF-receptors in the ON of subjects with experimentally induced EIOP. Our results show that EIOP significantly impairs the presence of NGF and NGF-receptor proteins and TrkA gene expression in the ON of glaucomatous eye. These findings suggest that NGF and NGF-receptor might be important signals for the ON response in the EIOP.

Retinal p75 and bax overexpression is associated with retinal ganglion cells apoptosis in a rat model of glaucoma

PURPOSE

The administration of neurotrophins has been clearly demonstrated to support survival of retina cells during a variety of insults. Increased levels of neurotrophins, such as the nerve growth factor (NGF), have been found in experimental models of glaucoma. Nevertheless, loss of retinal cells does occur in the course of ocular hypertension. Therefore, this study sought to address whether timely changes in NGF and its receptors, trkA(NGFR) and p75(NTR), might explain the progression of retinal damage during experimental glaucoma.

METHODS

A well-characterized technique to induce glaucoma in rats was utilized. The animals were sacrificed after 10, 20 and 35 days from induction of glaucoma. Retinal ganglion cell (RGC) apoptosis, retinal expression of NGF protein as well as Bcl-2, Bax, trkA(NGFR) and p75(NTR) transcript expression were detected. The balance between trkA(NGFR) and p75(NTR) was examined, considering their anti- and pro-apoptotic role in cell death, respectively.

RESULTS

We demonstrated that in our model of experimental glaucoma, the loss of retinal ganglion cells (RGCs) is accompanied by a timely increase of retinal NGF. Moreover, we found that the trkA(NGFR)/p75(NTR) mRNA ratio and the Bcl-2/Bax mRNA were both decreased, indicating a p75(NGFR) and Bax over-expression.

CONCLUSIONS

Retinal NGF is over-expressed in experimental glaucoma, but this NGF increase is not sufficient to support survival of RGCs. The failure of NGF trophic support might be associated with the progressive up-regulation of p75(NTR) in relation to trkA(NGFR).

Limitations in assessing nerve growth factor levels in aqueous humor samples from human eyes

Background

Nerve growth factor (NGF) helps in the healing and survival of ganglion cells, photoreceptors, and optic nerve after injury and has been implicated to have a role in pathophysiology of glaucoma. So far, in animal studies, injury to iris in vitro has revealed an increase in NGF levels in aqueous. There is a great interest in investigating the levels of NGF in human aqueous in glaucomatous eyes, as suggested by animal studies, to gain a better understanding of the pathophysiology of glaucoma.

Findings

In this study, we examined the presence of NGF levels in aqueous humor collected from human eyes and the limitations in determining the NGF levels in human samples. NGF was assessed by ELISA immunoassay in undiluted aqueous samples collected from 32 consecutive patients undergoing surgery for cataract (control) or primary open angle glaucoma (POAG). Recombinant NGF was used as positive control. NGF levels were below undetectable levels in aqueous humor from eyes with POAG and controls by immunoassay. Less than 10% of samples had detectable NGF levels and these were considered outliers.

Conclusion

Our result highlights the undetectable levels of NGF in human aqueous samples.

Effects of nerve growth factor for retinal cell survival in experimental retinal detachment

PURPOSE

To investigate the neuron protective effect of recombined nerve growth factor (rNGF) on retinal cell damage induced by experimental retinal detachment.

METHODS

Experimental retinal detachment models were created in Sprague-Dawley rats by subretinal injection of sodium hyaluronate. Intravitreal injection of rNGF (5 microg/eye) or phosphate-buffered saline (PBS) was separately applied every 4 days after retinal detachment. The rat eyes were then observed and sacrificed at various time points. Morphologic changes were observed by light microscopy, electron microscopy, and cell counts. Apoptosis of retinal cells was detected by TUNEL assay.

RESULTS

After retinal detachment, most eyes from NGF-treated groups showed better organized structure of retinal cells than those from the PBS-treated control groups. Cell counts indicated that the nuclei numbers in the outer nuclear layer (ONL), inner nuclear layer (INL), and ganglion cell layer (GCL) of NGF-treated groups were significantly more than those from PBS-treated control group (p < 0.05) after retinal reattachment. TUNEL-positive cells were identified in ONL, INL, and GCL. They peaked at the fourth day after retinal detachment in both the NGF-treated groups and the control groups. But the cell counts of apoptosis revealed that the NGF-treated retina had less TUNEL-positive cells than the control groups (p < 0.05).

CONCLUSIONS

The results showed that intravitreal injection of exogenous NGF can protect retinal cells from degeneration and apoptosis in experimental retinal detachment. It may exert its neuroprotection effect by preventing the apoptosis of retinal cells after retinal detachment.

Neurotrophic rationale in glaucoma: A TrkA agonist, but not NGF or a p75 antagonist, protects retinal ganglion cellsin vivo

Glaucoma is a major cause of vision impairment, which arises from the sustained and progressive apoptosis of retinal ganglion cells (RGC), with ocular hypertension being a major risk or co-morbidity factor. Because RGC death often continues after normalization of ocular hypertension, growth factor-mediated protection of compromised neurons may be useful. However, the therapeutic use of nerve growth factor (NGF) has not proven effective at delaying RGC death in glaucoma. We postulated that one cause for the failure of NGF may be related to its binding to two receptors, TrkA and p75. These receptors have distinct cellular distribution in the retina and in neurons they induce complex and sometimes opposing activities. Here, we show in an in vivo therapeutic model of glaucoma that a selective agonist of the pro-survival TrkA receptor was effective at preventing RGC death. RGC loss was fully prevented by combining the selective agonist of TrkA with intraocular pressure-lowering drugs. In contrast, neither NGF nor an antagonist of the pro-apoptotic p75 receptor protected RGCs. These results further a neurotrophic rationale for glaucoma.

Nerve growth factor involvement in the visual system: implications in allergic and neurodegenerative diseases

The purpose of this review is to outline the main role of nerve growth factor (NGF) in the visual system and particularly in the ocular surface in physiological and pathological conditions. The present review of experimental and clinical studies will highlight old and recent strategies for treating ocular surface and tear disorders with NGF.

Changes in retinal expression of neurotrophins and neurotrophin receptors induced by ocular hypertension

Open angle glaucoma is defined as a progressive and time-dependent death of retinal ganglion cells concomitant with high intraocular pressure, leading to loss of visual field. Because neurotrophins are a family of growth factors that support neuronal survival, we hypothesized that quantitative and qualitative changes in neurotrophins or their receptors may take place early in ocular hypertension, preceding extensive cell death and clinical features of glaucoma. We present molecular, biochemical, and phenotypic evidence that significant neurotrophic changes occur in retina, which correlate temporally with retinal ganglion cell death. After 7 days of ocular hypertension there is a transient up-regulation of retinal NGF, while its receptor TrkA is up-regulated in a sustained fashion in retinal neurons. After 28 days of ocular hypertension there is sustained up-regulation of retinal BDNF, but its receptor TrkB remains unchanged. Throughout, NT-3 levels remain unchanged but there is an early and sustained increase of its receptor TrkC in Müller cells but not in retinal ganglion cells. These newly synthesized glial TrkC receptors are truncated, kinase-dead isoforms. Expression of retinal p75 also increases late at day 28. Asymmetric up-regulation of neurotrophins and neurotrophin receptors may preclude efficient neurotrophic rescue of RGCs from apoptosis. A possible rationale for therapeutic intervention with Trk receptor agonists and p75 receptor antagonists is proposed.

Nerve growth factor and wound healing

The wound healing process following tissue injury consists of a highly regulated sequence of events. Besides many biological activities on both neuronal and nonneuronal cells, nerve growth factor (NGF) has been proposed as an important component of wound healing and tissue repair process in vivo and in vitro. For example, NGF accelerates the rate of wound healing both in normal mice and healing-impaired diabetic mice, and has a potent pharmacological effect in the treatment for ulcer of the skin and cornea in humans. This review summarizes the evidence for the role of NGF in wound healing and tissue repair, and introduces its clinical utility as a therapeutic agent for various diseases.

Nerve growth factor, human skin ulcers and vascularization. Our experience

Cutaneous wound is known to elicit a series of typical cellular responses that include clotting, inflammatory infiltration, reepithelialization, the formation of granulation tissue, including new blood vessel, followed by tissue remodeling and wound contraction. The regulatory molecules implicated in these events are not well known. Neurotrophins and their receptors are trophic factors that are known to play important roles in cutaneous tissues, nerve development and reconstruction after injury. Among the neurotrophins, the nerve growth factor (NGF) was one of the earliest used for clinical studies. NGF has been tested for potential therapeutic application in neuropathies of the central and peripheral nervous system and more recently in human corneal and cutaneous ulcers. Here, I present and discuss data obtained in the last few years on the healing action of NGF in human and domestic animal skin ulcers.

Nerve growth factor (NGF) and lenses: effects of NGF in an in vitro rat model of cataract

BACKGROUND

The aims of this study are to investigate the presence and production of nerve growth factor (NGF) in the rat lens in basal conditions and to evaluate, in vitro, the role of NGF in a model of xylose-induced cataract.

METHODS

Rat lenses were dissected and the expression of NGF, NGF mRNA and high-affinity NGF-receptor (TrkA) was evaluated by immunohistochemistry, immunoenzymatic assay (ELISA) and in-situ hybridization (ISH) techniques. To investigate the role of NGF in cataract formation we used an in vitro model of sugar-induced cataract by culturing rat lenses for 48 h in Eagle's minimum essential medium (MEM) supplemented with xylose. To evaluate the potential protective effect of NGF on xylose-induced cataract formation, exogenous NGF at different concentrations or antibodies neutralizing endogenous NGF (NGF-Ab) or aspecific antibodies were added to xylose-cultured lenses, and the following cataract-related parameters were evaluated and compared to xylose-treated lenses. Cataract formation was evaluated using three different parameters: staging of the cataract by lens photography, quantification of lens transparency in terms of gray level medium (GLM) and evaluation of the hydration percentage (H%) of the lens. To investigate the role of endogenous NGF in cataract onset, NGF levels were evaluated and compared in lenses cultured in xylose supplemented medium versus lenses cultured in control culture medium.

RESULTS

The epithelium from fresh rat lenses expresses NGF-receptor, NGF protein and NGF-mRNA. NGF levels in fresh lens were 54.0 +/- 24.5 pg/g as quantified by ELISA. Xylose-cultured lenses develop cataract changes, including a decrease of GLM and an increase in hydration percentage, associated with a decrease in NGF levels when compared to lenses cultured in the control culture medium. The addition of NGF to xylose-cultured lenses reduces cataract formation, increasing GLM and decreasing the hydration percentage as compared to xylose-treated lenses. On the other hand, the addition of NGF-Ab induces an increase in cataract formation and lens hydration.

CONCLUSIONS

This study demonstrates that rat lens epithelium expresses and synthesizes NGF. Moreover, immunohistochemistry shows that lens epithelial cells also express the NGF receptor. Although the functional significance of TrkA on lens epithelium is at present not clear, the expression of NGF and its high-affinity receptor on the same cells together with our experimental results suggest that NGF is involved in supporting trophism and/or the function of the lens epithelium.

Postnatal changes in nerve growth factor and brain derived neurotrophic factor levels in the retina, visual cortex, and geniculate nucleus in rats with retinitis pigmentosa

Royal College of Surgeons (RCS) rats are a well established animal model of inherited retinitis pigmentosa (RP). Using RCS rats we examined the distribution of nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) in the visual cortex, geniculate nucleus and retina at three different postnatal ages. It was found that the retina of rats with RP expresses low amounts of NGF and BDNF in young and adult life. Altered levels of these factors were found in the visual cortex and in the geniculate nucleus. Our findings indicate that NGF and BDNF are differentially affected in the visual system of developing and adult RCS rats, suggesting that neurotrophins may be implicated in the pathogenesis of inherited RP.

Anti-semaphorin 3A antibodies rescue retinal ganglion cells from cell death following optic nerve axotomy

Damage to the optic nerve in mammals induces retrograde degeneration and apoptosis of the retinal ganglion cell (RGC) bodies. The mechanisms that mediate the response of the neuronal cells to the axonal injury are still unknown. We have previously shown that semaphorins, axon guidance molecules with repulsive cues, are capable of mediating apoptosis in cultured neuronal cells (Shirvan, A., Ziv, I., Fleminger, G., Shina, R., He, Z., Brudo, I., Melamed, E., and Brazilai, A. (1999) J. Neurochem. 73, 961-971). In this study, we examined the involvement of semaphorins in an in vivo experimental animal model of complete axotomy of the rat optic nerve. We demonstrate that a marked induction of type III semaphorin proteins takes place in ipsilateral retinas at early stages following axotomy, well before any morphological signs of RGC apoptosis can be detected. Time course analysis revealed that a peak of expression occurred after 2-3 days and then declined. A small conserved peptide derived from semaphorin 3A that was previously shown to induce neuronal death in culture was capable of inducing RGC loss upon its intravitreous injection into the rat eye. Moreover, we demonstrate a marked inhibition of RGC loss when axotomized eyes were co-treated by intravitreous injection of function-blocking antibodies against the semaphorin 3A-derived peptide. Marked neuronal protection from degeneration was also observed when the antibodies were applied 24 h post-injury. We therefore suggest that semaphorins are key proteins that modulate the cell fate of axotomized RGC. Neutralization of the semaphorin repulsive function may serve as a promising new approach for treatment of traumatic injury in the adult mammalian central nervous system or of ophthalmologic diseases such as glaucoma and ischemic optic neuropathy that induce apoptotic RGC death.

Enhanced survival and regeneration of axotomized retinal ganglion cells by a mixture of herbal extracts

The aim of this study is to investigate the effects of Panax quinquefolius L. extract (PQE), Ginkgo biloba extract (GBE), and Hypericum perforatum extract (HPE), in combination or alone, on the survival and regeneration of axotomized retinal ganglion cells (RGCs) in an optic nerve transection model in adult hamsters. Unilateral transection of the optic nerve was performed to evaluate the effects of herbal extracts on the survival of axotomized RGCs. Effects of the herbal extracts on axonal regeneration of axotomized RGCs, on the other hand, were studied by attaching a peripheral nerve graft onto the transected ocular stump to induce regeneration. Operated animals received daily oral administration of vehicle or herbal extracts (PQE, GBE, and HPE), alone or in combination, for 7 and 21 days, respectively, in the survival and regeneration experiments. Surviving and regenerating RGCs were retrogradely labeled with Fluoro-Gold. The eyes were then enucleated and the retinas were flat-mounted for the counting of the labeled RGCs. Treatment with PQE, GBE and HPE alone failed to offer neuroprotection to injured RGCs. However, treatment with Menta-FX, a mixture of PQE, GBE, and HPE, significantly augmented RGC survival 7 days postaxotomy. Treatment with Menta-FX also induced a significant (87%) increase in the number of regenerating RGCs 21 days after optic nerve transection. This study demonstrates that herbs can act as a potential neuroprotective agent for damaged RGCs. It also suggests that the therapeutic value of herbal remedies can be maximized by the use of mixtures of appropriate herbs.

Nerve growth factor levels and mast cell distribution in human coronary atherosclerosis

Nerve growth factor (NGF), in addition to its neurotrophic function, acts on a variety of non-neuronal cells including immune cells and vascular smooth muscle cells. The aim of the present study was to determine the NGF levels and the distribution of NGF and low-affinity NGF receptor (p75NGFR) and mast cells (MC) in human atherosclerotic coronary arteries. Specimens of human coronary arteries obtained from autopsy cases (n=12, subjects with atherosclerotic lesions; n=9, subjects without atherosclerotic lesions/controls) were used. The present study showed that in the atherosclerosis-lesioned arteries, the amount of NGF decreased, whereas the expression of p75NGFR immunoreactivity and the number, both of MC and vasa vasorum, particularly in the adventitia, significantly increased, compared with the control arteries. Cumulatively, our findings help to set the neurotrophic theory and its currently extended neuroimmune framework into the context of pathobiology of atherosclerosis, suggesting that altered presence of NGF, p75NGFR, and MC may play a role in neuroimmune mechanisms of human coronary atherosclerosis.

Altered nerve growth factor level in the optic nerve of patients affected by multiple sclerosis

In this study we measured with a highly sensitive two-site immunoenzymatic assay the levels of nerve growth factor (NGF) in human optic nerve affected by multiple sclerosis (MS). The result of this study showed an elevated increase of NGF in the MS optic nerves, as compared to the level of NGF found in the optic nerves non-affected by this demyelinating disorder. Moreover, the results showed that the optic nerves also expressed trkA NGF receptor and NGFmRNA, most likely by oligodendrocytes, implying that NGF is locally produced and suggesting that the presence of NGF might be regulated by an autocrine mechanism. These and other ongoing studies on animal models indicate that altered NGF levels are among one of the early symptoms of these demyelinating diseases. The physiopathological role of NGF in the optic nerve during demyelinating disorders remains however to be defined.