An autocrine function of nerve growth factor for cell cycle regulation of vascular endothelial cells

Do Neurotrophins Connect Neurological Disorders and Heart Diseases?

Neurotrophins (NTs) are one of the most characterized neurotrophic factor family members and consist of four members in mammals. Growing evidence suggests that there is a complex inter- and bi-directional relationship between central nervous system (CNS) disorders and cardiac dysfunction, so-called "brain-heart axis". Recent studies suggest that CNS disorders, including neurodegenerative diseases, stroke, and depression, affect cardiovascular function via various mechanisms, such as hypothalamic-pituitary-adrenal axis augmentation. Although this brain-heart axis has been well studied in humans and mice, the involvement of NT signaling in the axis has not been fully investigated. In the first half of this review, we emphasize the importance of NTs not only in the nervous system, but also in the cardiovascular system from the embryonic stage to the adult state. In the second half, we discuss the involvement of NTs in the pathogenesis of cardiovascular diseases, and then examine whether an alteration in NTs could serve as the mediator between neurological disorders and heart dysfunction. The further investigation we propose herein could contribute to finding direct evidence for the involvement of NTs in the axis and new treatment for cardiovascular diseases.

Screening and identification of NOTCH1, CDKN2A, and NOS3 as differentially expressed autophagy-related genes in erectile dysfunction

Background

Loss of function of key autophagy genes are associated with a variety of diseases. However specific role of autophagy-related genes in erectile dysfunction ED remains unclear. This study explores the autophagy-related differentially expressed genes (ARGs) profiles and related molecular mechanisms in Corpus Cavernosum endothelial dysfunction, which is a leading cause of ED.

Methods

The Gene Expression Omnibus (GEO) database was used to identify the key genes and pathways. Differentially expressed genes (DEGs) were mined using the limma package in R language. Next, ARGs were obtained by matching DEGs and autophagy-related genes from GeneCard using Venn diagrams. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of ARGs were described using clusterProfiler and org.Hs.eg.db in R. Moreover, hub ARGs were screened out through protein-protein interaction (PPI), gene-microRNAs, and gene-transcription factors (TFs) networks then visualized using Cytoscape. Of note, the rat model of diabetic ED was established to validate some hub ARGs with qRT-PCR and Western blots.

Results

Twenty ARGs were identified from four ED samples and eight non-ED samples. GO analysis revealed that molecular functions (MF) of upregulated ARGs were mainly enriched in nuclear receptor activity. Also, MF of downregulated ARGs were mainly enriched in oxidoreductase activity, acting on NAD(P)H and heme proteins as acceptors. Moreover, six hub ARGs were identified by setting high degrees in the network. Additionally, hsa-mir-24-3p and hsa-mir-335-5p might play a central role in several ARGs regulation, and the transcription factors-hub genes network was centered with 13 ARGs. The experimental results further showed that the expression of Notch1, NOS3, and CDKN2A in the diabetic ED group was downregulated compared to the control.

Conclusions

Our study deepens the autophagy-related mechanistic understanding of endothelial dysfunction of ED. NOTCH1, CDKN2A, and NOS3 are involved in the regulation of endothelial dysfunction and may be potential therapeutic targets for ED by modulating autophagy.

Neuropeptides and neurohormones in immune, inflammatory and cellular responses to ultraviolet radiation

Humans are exposed to varying amounts of ultraviolet radiation (UVR) through sunlight. UVR penetrates into human skin leading to release of neuropeptides, neurotransmitters and neuroendocrine hormones. These messengers released from local sensory nerves, keratinocytes, Langerhans cells (LCs), mast cells, melanocytes and endothelial cells (ECs) modulate local and systemic immune responses, mediate inflammation and promote differing cell biologic effects. In this review, we will focus on both animal and human studies that elucidate the roles of calcitonin gene-related peptide (CGRP), substance P (SP), nerve growth factor (NGF), nitric oxide and proopiomelanocortin (POMC) derivatives in mediating immune and inflammatory effects of exposure to UVR as well as other cell biologic effects of UVR exposure.

Peripheral Nerve Regeneration Is Independent From Schwann Cell p75NTR Expression

Schwann cell reprogramming and differentiation are crucial prerequisites for neuronal regeneration and re-myelination to occur following injury to peripheral nerves. The neurotrophin receptor p75^NTR has been identified as a positive modulator for Schwann cell myelination during development and implicated in promoting nerve regeneration after injury. However, most studies base this conclusion on results obtained from complete p75^NTR knockout mouse models and cannot dissect the specific role of p75^NTR expressed by Schwann cells. In this present study, a conditional knockout model selectively deleting p75^NTR expression in Schwann cells was generated, where p75^NTR expression is replaced with that of an mCherry reporter. Silencing of Schwann cell p75^NTR expression was confirmed in the sciatic nerve in vivo and in vitro, without altering axonal expression of p75^NTR. No difference in sciatic nerve myelination during development or following sciatic nerve crush injury was observed, as determined by quantification of both myelinated and unmyelinated nerve fiber densities, myelinated axonal diameter and myelin thickness. However, the absence of Schwann cell p75^NTR reduced motor nerve conduction velocity after crush injury. Our data indicate that the absence of Schwann cell p75^NTR expression in vivo is not critical for axonal regrowth or remyelination following sciatic nerve crush injury, but does play a key role in functional recovery. Overall, this represents the first step in redefining the role of p75^NTR in the peripheral nervous system, suggesting that the Schwann cell-axon unit functions as a syncytium, with the previous published involvement of p75^NTR in remyelination most likely depending on axonal/neuronal p75^NTR and/or mutual glial-axonal interactions.

NGF increases FGF2 expression and promotes endothelial cell migration and tube formation through PI3K/Akt and ERK/MAPK pathways in human chondrocytes

OBJECTIVE

Vascular invasion is observed at the osteochondral junction in osteoarthritis (OA). Nerve growth factor (NGF) as an angiogenic factor is expressed in OA. This study is to investigate the effects of NGF on angiogenesis in vitro in human chondrocytes.

DESIGN

Articular cartilages of knee joints were harvested from healthy and OA patients. Expressions of NGF and tropomyosin-related kinase A (TrkA) were detected by western blot, Safranin-O and fast green staining and immunohistochemistry in cartilage. Expression of fibroblast growth factor 2 (FGF2) was detected by western blot in cultured chondrocytes. Chondrocytes were transfected by lentiviral vectors to knock down TrkA. Migration and tube formation of human microvascular endothelial cell (HMVEC) were assessed by using transwell co-culture with chondrocyte after treatment of NGF.

RESULTS

We confirmed expressions of NGF and TrkA were significantly up-regulated in OA. NGF induced expression of FGF2 in a time- and dose-dependent manner. Angiogenic activities of endothelial cells were greatly enhanced after co-cultured with NGF pre-treated chondrocytes, while knock-down of TrkA significantly abolished the above effects. We further found that NGF-induced expression of FGF2 promoted angiogenic activities of endothelial cells through PI3K/Akt and ERK/MAPK signaling pathways.

CONCLUSIONS

NGF promotes expression of FGF2 in vitro via PI3K/Akt and ERK/MAPK signaling pathways in human chondrocytes and it increases angiogenesis, which is mediated by TrkA. NGF could be responsible for vascular up-growth from subchondral bone in OA.

Immunoregulatory Effects of Neuropeptides on Endothelial Cells: Relevance to Dermatological Disorders

Many skin diseases, including psoriasis and atopic dermatitis, have a neurogenic component. In this regard, bidirectional interactions between components of the nervous system and multiple target cells in the skin and elsewhere have been receiving increasing attention. Neuropeptides released by sensory nerves that innervate the skin can directly modulate functions of keratinocytes, Langerhans cells, dermal dendritic cells, mast cells, dermal microvascular endothelial cells and infiltrating immune cells. As a result, neuropeptides and neuropeptide receptors participate in a complex, interdependent network of mediators that modulate the skin immune system, skin inflammation, and wound healing. In this review, we will focus on recent studies demonstrating the roles of α-melanocyte-stimulating hormone, calcitonin gene-related peptide, substance P, somatostatin, vasoactive intestinal peptide, pituitary adenylate cyclase-activating peptide, and nerve growth factor in modulating inflammation and immunity in the skin through their effects on dermal microvascular endothelial cells.

Evaluation of nerve growth factor (NGF) treated mesenchymal stem cells for recovery in neurotmesis model of peripheral nerve injury

BACKGROUND

Peripheral nerve damages are a relatively common type of the nervous system injuries. Although peripheral nerves show some capacity of regeneration after injury, the extent of regeneration is not remarkable. The present study aimed to evaluate the effect of NGF treated mesenchymal stem cells on regeneration of transected sciatic nerve.

MATERIALS AND METHODS

In this experimental study, forty-two male Wistar.rats (180-200 g) were randomly divided into 6 groups (n = 7) including control, Membrane + Cell (Mem + Cell), NGF group, NGF + Cell group, NGF + Mem group and NGF + Mem + Cell group. Regeneration of sciatic nerve was evaluated using behavioral analysis, electrophysiological assessment and histological examination.

RESULTS

The rats in the NGF + Mem + Cell group showed significant decrease in sciatic functional index (SFI) and hot water paw immersion test during the 2nd to 8th weeks after surgery. (p < 0.001). At 8 weeks after surgery, electrophysiological findings showed that amplitude increased and latency decreased significantly in NGF + Mem + Cell group (p < 0.001). Measured histological parameters showed that number of nerve fibers, number of vessels and percent of vessel area also increased significantly in NGF + Mem + Cell group (p < 0.05).

CONCLUSION

The present study showed that NGF in accompany with mesenchymal stem cells improved electrophysiological and histological indices.

Reduced NGF in Gastric Endothelial Cells Is One of the Main Causes of Impaired Angiogenesis in Aging Gastric Mucosa

BACKGROUND & AIMS

Aging gastric mucosa has increased susceptibility to injury and delayed healing owing to impaired angiogenesis, but the mechanisms are not fully known. We examined whether impairment of angiogenesis in aging gastric mucosa is caused by deficiency of nerve growth factor (NGF) in gastric endothelial cells (ECs), and whether NGF therapy could reverse this impairment.

METHODS

In gastric mucosal ECs (GECs) isolated from young and aging rats we examined the following: (1) in vitro angiogenesis, (2) NGF expression, and (3) the effect of NGF treatment on angiogenesis, GEC proliferation and migration, and dependence on serum response factor. In in vivo studies in young and aging rats, we examined NGF expression in gastric mucosa and the effect of NGF treatment on angiogenesis and gastric ulcer healing. To determine human relevance, we examined NGF expression in gastric mucosal biopsy specimens of aging (≥70 y) and young (≤40 y) individuals.

RESULTS

In cultured aging GECs, NGF expression and angiogenesis were reduced significantly by 3.0-fold and 4.1-fold vs young GECs. NGF therapy reversed impairment of angiogenesis in aging GECs, and serum response factor silencing completely abolished this response. In gastric mucosa of aging rats, NGF expression in GECs was reduced significantly vs young rats. In aging rats, local NGF treatment significantly increased angiogenesis and accelerated gastric ulcer healing. In aging human subjects, NGF expression in ECs of gastric mucosal vessels was 5.5-fold reduced vs young individuals.

CONCLUSIONS

NGF deficiency in ECs is a key mechanism underlying impaired angiogenesis and delayed ulcer healing in aging gastric mucosa. Local NGF therapy can reverse these impairments.

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.

Nerve growth factor promotes killing of Leishmania donovani by macrophages through the induction of hydrogen peroxide

Visceral leishmaniasis is protozoonosis that occurs worldwide and still requires effective therapies with less toxicity. In this study, we examined the antileishmanial effect of nerve growth factor (NGF) using a murine infection model. NGF blocked the infection of macrophages by Leishmania donovani, which was completely cancelled by a hydrogen peroxide inhibitor. In vivo, not only did NGF show antileishmanial effects, but combination therapy of NGF and sodium stibogluconate synergistically exhibited the activity more potently than each monotherapy. These results indicate that NGF exerts antileishmanial effect by stimulating hydrogen peroxide production in macrophages and can be a novel therapy for leishmaniasis.

Vascular endothelial growth factor coordinates islet innervation via vascular scaffolding

Neurovascular alignment is a common anatomical feature of organs, but the mechanisms leading to this arrangement are incompletely understood. Here, we show that vascular endothelial growth factor (VEGF) signaling profoundly affects both vascularization and innervation of the pancreatic islet. In mature islets, nerves are closely associated with capillaries, but the islet vascularization process during embryonic organogenesis significantly precedes islet innervation. Although a simple neuronal meshwork interconnects the developing islet clusters as they begin to form at E14.5, the substantial ingrowth of nerve fibers into islets occurs postnatally, when islet vascularization is already complete. Using genetic mouse models, we demonstrate that VEGF regulates islet innervation indirectly through its effects on intra-islet endothelial cells. Our data indicate that formation of a VEGF-directed, intra-islet vascular plexus is required for development of islet innervation, and that VEGF-induced islet hypervascularization leads to increased nerve fiber ingrowth. Transcriptome analysis of hypervascularized islets revealed an increased expression of extracellular matrix components and axon guidance molecules, with these transcripts being enriched in the islet-derived endothelial cell population. We propose a mechanism for coordinated neurovascular development within pancreatic islets, in which endocrine cell-derived VEGF directs the patterning of intra-islet capillaries during embryogenesis, forming a scaffold for the postnatal ingrowth of essential autonomic nerve fibers.

Mechanisms and targets of angiogenesis and nerve growth in osteoarthritis

During osteoarthritis (OA), angiogenesis is increased in the synovium, osteophytes and menisci and leads to ossification in osteophytes and the deep layers of articular cartilage. Angiogenic and antiangiogenic factors might both be upregulated in the osteoarthritic joint; however, vascular growth predominates, and the articular cartilage loses its resistance to vascularization. In addition, blood vessel growth is increased at--and disrupts--the osteochondral junction. Angiogenesis in this location is dependent on the creation of channels from subchondral bone spaces into noncalcified articular cartilage. Inflammation drives synovial angiogenesis through macrophage activation. Blood vessel and nerve growth are linked by common pathways that involve the release of proangiogenic factors, such as vascular endothelial growth factor, β-nerve growth factor and neuropeptides. Proangiogenic factors might also stimulate nerve growth, and molecules produced by vascular cells could both stimulate and guide nerve growth. As sensory nerves grow along new blood vessels in osteoarthritic joints, they eventually penetrate noncalcified articular cartilage, osteophytes and the inner regions of menisci. Angiogenesis could, therefore, contribute to structural damage and pain in OA and provide potential targets for new treatments.

Nerve growth factor as an angiogenic factor

Nerve growth factor (NGF), a neurotrophin that plays a crucial role in promoting neurotrophic and neurotropic effects in sympathetic neurons, has recently been identified as a novel angiogenic molecule, which exerts a variety of effects in the cardiovascular system and on endothelial cells. In fact, NGF may contribute to maintenance, survival, and function of endothelial cells by autocrine and/or paracrine mechanisms. This review summarizes the involvement of NGF in the regulation of angiogenesis in both normal and pathological conditions.

Cardiac NGF and GDNF expression during Trypanosoma cruzi infection in rats

In rats, autonomic nerve endings are damaged during Trypanosoma cruzi-induced myocarditis. Gradual recovery occurs after the acute phase. The present work shows the cardiac levels of glial cell line-derived neurotrophic factor (GDNF) and nerve growth factor (NGF), and their cellular sources during T. cruzi infection in rats. Atrial and ventricular NGF levels (ELISA) increased significantly at day 20 post inoculation, the time-point of maximal sympathetic denervation. ELISA failed to show significant increase of cardiac GDNF levels. However immunohistochemistry showed a significant increase of anti-GDNF gold particles over atrial granules at day 20. Light microscopy showed stronger NGF immunostaining in atrial cardiomyocytes and several blood capillaries. In situ hybridization showed NGF and GDNF mRNAs in atrial and ventricular myocytes of both infected and uninfected animals. Endothelial cells exhibited NGF mRNA and protein only in infected rats. No evidence of neurotrophic factor expression by the infiltrating mononuclear cells was found. This is the first report on neurotrophic factor expression during T. cruzi infection. Our findings indicate an important role for NGF in the regenerative phenomena subsequent to a myocarditis able to damage sympathetic nerve endings, with preservation of preterminals and nerve trunks. GDNF could have a minor or a more transient participation.

Topical application with a new NF-kappaB inhibitor improves atopic dermatitis in NC/NgaTnd mice

Growing evidence has demonstrated the crucial role of NF-kappaB activation on disease severity in allergic disorders. In this study, we examined the clinical relevance of a novel NF-kappaB inhibitor, IMD-0354, for atopic dermatitis (AD) by its topical application. To investigate the in vivo efficacy, 1% IMD-0354 ointment was applied daily to NC/NgaTnd mice with severe dermatitis, which served as a model for human AD. During 2 weeks of treatment, scratching behavior decreased and severity of dermatitis reduced in mice treated with IMD-0354 as well as FK506 without diverse effects. Based on histological examinations, the hyperplasia of keratinocytes and infiltration of inflammatory cells were significantly reduced in the skin of IMD-0354-treated mice. The expressions of T-helper 2 cytokines and tumor necrosis factor-alpha at the affected skin sites were downregulated in IMD-0354-treated mice. Furthermore, IMD-0354 suppressed the proliferation of various immunocompetent cells, neurite outgrowth of nerve growth factor-stimulated pheochromocytoma cells, IgE production from splenic B cells, and IgE-mediated activation of mast cells in vitro. IMD-0354 effectively reduced the allergic inflammation in NC/NgaTnd mice in vivo. Thus, a drug that interferes with NF-kappaB activity may provide an alternative therapeutic strategy for the treatment of AD.

Nerve growth factor (NGF) promotes angiogenesis in the quail chorioallantoic membrane

Angiogenesis, the formation of new blood vessels, is tightly regulated by growth factors, such as vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). The authors hypothesize that nerve growth factor (NGF), a well known neurotrophin, may play a direct angiogenic role. To test this hypothesis, the authors measured the effects of NGF on the natural vascularization of the quail chorioallantoic membrane (CAM). The angiogenic effect of NGF was compared to that of human recombinant VEGF165 (rhVEGF) and basic FGF (rhbFGF). In comparison to phosphate-buffered saline-treated controls, NGFs from different biological sources (mouse, viper, and cobra) increased the rate of angiogenesis in a dose-dependent fashion from 0.5 to 5 microg. For quantitative morphometry, grayscale images of the blood vessels end points of the CAM arteries were binarized for visualization and skeletonized for quantization by fractal analysis. In mouse NGF-treated embryos the fractal dimension (Df), indicative of arterial vessel length and density, increased to 1.266 +/- 0.021 compared to 1.131 +/- 0.018 (p < .001) for control embryos. This effect was similar to that of 0.5 microg rhVEGF (1.290 +/- 0.021, p < .001) and 1.5 microg rhbFGF (1.264 +/- 0.028, p < .001). The mouse NGF-induced angiogenic effect was blocked by 1 microM K252a (1.149 +/- 0.018, p < .001), an antagonist of the NGF/trkA receptor, but not by 1 microM SU-5416 (1.263 +/- 0.029, p < .001), the VEGF/Flk1 receptor antagonist, indicating a direct, selective angiogenic effect of NGF via quail embryo trkA receptor activation. These results confirm previous observations that NGF has angiogenic activity and suggest that this neurotrophin may also play an important role in the cardiovascular system, besides its well-known effects in the nervous system. The angiogenic properties of NGF may be beneficial in engineering new blood vessels and for developing novel antiangiogenesis therapies for cancer.

Nerve growth factor-induced migration of endothelial cells

Nerve growth factor (NGF) is a well known neurotropic and neurotrophic agonist in the nervous system, which recently was shown to also induce angiogenic effects in endothelial cells (ECs). To measure NGF effects on the migration of cultured ECs, an important step in neoangiogenesis, we optimized an omnidirectional migration assay using human aortic endothelial cells (HAECs) and validated the assay with human recombinant basic fibroblast growth factor (rhbFGF) and human recombinant vascular endothelial growth factor (rhVEGF). The potencies of nerve growth factor purified from various species (viper, mouse, and recombinant human) to stimulate HAEC migration was similar to that of VEGF and basic fibroblast growth factor (bFGF) (EC50 of approximately 0.5 ng/ml). Recombinant human bFGF was significantly more efficacious than either viper NGF or rhVEGF, both of which stimulated HAEC migration by approximately 30% over basal spontaneous migration. NGF-mediated stimulation of HAEC migration was completely blocked by the NGF/TrkA receptor antagonist K252a [(8R*,9S*,11S*)-(/)-9-hydroxy-9-methoxycarbonyl-8-methyl-2,3,9,10-tetrahydro-8,11-epoxy-1H,-8H,11H-2,7b,11a-triazadibenzo(a,g)cycloocta(c,d,e)trindene-1-one] (30 nM) but not by the VEGF/Flk receptor antagonist SU-5416 [3-[(2,4-dimethylpyrrol-5-yl) methylidenyl]-indolin-2-one] (250 nM), indicating a direct effect of NGF via TrkA receptor activation on HAEC migration. Viper NGF stimulation of HAEC migration was additively increased by either rhVEGF or rhbFGF, suggesting a potentiating interaction between their tyrosine kinase receptor signaling pathways. Viper NGF represents a novel pharmacological tool to investigate possible TrkA receptor subtypes in endothelial cells. The ability of NGF to stimulate migration of HAEC cells in vitro implies that this factor may play an important role in the cardiovascular system besides its well known effects in the nervous system.

Endogenous NGF regulates CGRP expression in human monocytes, and affects HLA-DR and CD86 expression and IL-10 production

Our recent results on autocrine nerve growth factor (NGF) synthesis in B lymphocytes, which directly regulates the expression and release of calcitonin gene-related peptide (CGRP), a neuropeptide known to down-regulate immune response, led us to propose an anti-inflammatory action of NGF. In the present work, we investigated whether the endogenous synthesis of NGF can regulate the expression of CGRP in other antigen-presenting cells, such as monocytes, and whether this may have a functional effect. Our data indicate that human monocytes synthesize basal levels of NGF and CGRP and that, following lipopolysaccharide (LPS) stimulation, NGF and CGRP expression are both up-regulated. When endogenous NGF is neutralized, the up-regulation of CGRP expression induced by LPS is inhibited. The expression of membrane molecules involved in T-cell activation such as human leukocyte antigen-DR (HLA-DR) and CD86 is affected by endogenous NGF, and similar effects were obtained using a CGRP(1) receptor antagonist. In addition, NGF deprivation in LPS-treated monocytes significantly decreases interleukin 10 (IL-10) synthesis. Our findings indicate that endogenous NGF synthesis has a functional role and may represent a physiologic mechanism to down-regulate major histocompatibility complex (MHC) class II and CD86 expression and alter the development of immune responses.

Stress alters vascular?endothelial growth factor expression in rat arteries: Role of nerve growth factor

The aim of this study was to investigate the role of stress and nerve growth factor (NGF) on the expression of vascular-endothelial growth factor (VEGF) and NGF high-affinity receptor (tyrosine kinase A, TrKA) in the ascending and abdominal aorta.Adult male rats were exposed to immobilization stress for one hour or injected with purified murine NGF. Four hours after treatments, rats were sacrificed and VEGF, NGF and TrkA expression in ascending and abdominal aorta evaluated. The effects of anti-NGF treatment on arterial VEGF expression and on stress-induced arterial cell proliferation were also studied in control and stressed rats.The data indicated that both stress and NGF injection induced a rapid increase of arterial VEGF associated with an elevated level of NGF and TrkA in arterial tissues. Blocking NGF action by neutralizing NGF-antibodies, results in down-regulation of stress-induced VEGF expression by arteries and in the blockade of stress-induced proliferation of cells from the arterial wall.Overall our data demonstrated that NGF is involved in the regulation of VEGF and in cardiac vessels response after emotional stress.

Nerve growth factor supplementation reverses the impairment, induced by Type 1 diabetes, of hindlimb post-ischaemic recovery in mice

AIMS/HYPOTHESIS

Type 1 diabetes increases the risk of peripheral ischaemia and impairs recovery once ischaemia occurs, probably because the healing process is hampered by diabetes-induced endothelial dysfunction. In normoglycaemic mice subjected to limb ischaemia, blockade of nerve growth factor (NGF) compromises reparative angiogenesis. In the present study, we evaluated if expressional alterations of endogenous NGF system components are associated with diabetes-related impairment in neovascularisation. In addition, we tested whether the correction of NGF liabilities benefits post-ischaemic healing of Type 1 diabetic animals.

METHODS

Unilateral hindlimb ischaemia was produced in streptozotocin-induced Type 1 diabetic mice. Purified murine NGF (20 microg daily for 14 days) or PBS were injected into ischaemic adductors. Non-diabetic mice given PBS served as controls. Hindlimb blood flow was analysed sequentially for up to 14 days. At necroscopy, adductors were removed for quantification of microvessel density, endothelial cell apoptosis and NGF receptor expression. NGF content was determined by ELISA three days after ischaemia. In vitro, we tested whether NGF protects endothelial cells from apoptosis induced by high glucose and whether vascular endothelial growth factor-A (VEGF-A) is involved in this beneficial effect.

RESULTS

Muscles removed from Type 1 diabetic mice showed reduced NGF content and up-regulation of the NGF p75 receptor. NGF supplementation promoted capillarisation and arteriogenesis, reduced apoptosis, and accelerated blood flow recovery. NGF stimulated VEGF-A production by human endothelial cells incubated in high-glucose medium and conferred resistance against high-glucose-induced apoptosis via a VEGF-A-mediated mechanism.

CONCLUSIONS/INTERPRETATION

NGF protects endothelial cells from apoptosis induced by Type 1 diabetes and facilitates reparative neovascularisation. The findings may open up new therapeutic options for the treatment of diabetic complications.