Caspase-3 and the regulation of hypoxic neuronal death by vascular endothelial growth factor

Modulation of neurotrophic factors in the treatment of dementia, stroke and TBI: Effects of Cerebrolysin

Neurotrophic factors (NTFs) are involved in the pathophysiology of neurological disorders such as dementia, stroke and traumatic brain injury (TBI), and constitute molecular targets of high interest for the therapy of these pathologies. In this review we provide an overview of current knowledge of the definition, discovery and mode of action of five NTFs, nerve growth factor, insulin-like growth factor 1, brain derived NTF, vascular endothelial growth factor and tumor necrosis factor alpha; as well as on their contribution to brain pathology and potential therapeutic use in dementia, stroke and TBI. Within the concept of NTFs in the treatment of these pathologies, we also review the neuropeptide preparation Cerebrolysin, which has been shown to resemble the activities of NTFs and to modulate the expression level of endogenous NTFs. Cerebrolysin has demonstrated beneficial treatment capabilities in vitro and in clinical studies, which are discussed within the context of the biochemistry of NTFs. The review focuses on the interactions of different NTFs, rather than addressing a single NTF, by outlining their signaling network and by reviewing their effect on clinical outcome in prevalent brain pathologies. The effects of the interactions of these NTFs and Cerebrolysin on neuroplasticity, neurogenesis, angiogenesis and inflammation, and their relevance for the treatment of dementia, stroke and TBI are summarized.

Advances of neurovascular protective potential of 3-N-butylphthalide and its derivatives in diabetic related diseases

3-N-butylphthalide (NBP) is a component isolated from seeds of Chinese celery, and it was firstly approved for the treatment of ischemic stroke. With the gradual in-depth understanding of its pharmacological action, it was found that it may have potential effects on treating diabetes and its complications. This review aims to illustrate the researches on the properties of NBP and its therapeutic efficacy in diabetic related diseases. This review will discuss the results of experiments in vitro and in vivo to make progress in understanding the beneficial effects of NBP and its derivatives on diabetic complications including diabetic vascular diseases, diabetic peripheral neuropathy, diabetic brain related diseases and diabetic cataract. We will also demonstrate NBP's numerous molecular targets and interactions with multiple cellular signaling pathways such as oxidative stress, inflammatory responses, apoptosis and autophagy. NBP is proved to be a potential therapeutic approach for treating diabetic complications.

Astrocytic responses to high glucose impair barrier formation in cerebral microvessel endothelial cells

Hyperglycemic conditions are prodromal to blood-brain barrier (BBB) impairment. The BBB comprises cerebral microvessel endothelial cells (CMECs) that are surrounded by astrocytic foot processes. Astrocytes express high levels of gap junction connexin 43 (Cx43), which play an important role in autocrine and paracrine signaling interactions that mediate gliovascular cross talk through secreted products. One of the key factors of the astrocytic "secretome" is vascular endothelial growth factor (VEGF), a potent angiogenic factor that can disrupt BBB integrity. We hypothesize that high-glucose conditions change the astrocytic expression of Cx43 and increase VEGF secretion leading to impairment of CMEC barrier properties in vitro and in vivo. Using coculture of neonatal rat astrocytes and CMEC, we mimic hyperglycemic conditions using high-glucose (HG) feeding media and show a significant decrease in Cx43 expression and the corresponding increase in secreted VEGF. This result was confirmed by the analyses of Cx43 and VEGF protein levels in the brain cortex samples from the type 2 diabetic rat (T2DN). To further characterize inducible changes in BBB, we measured transendothelial cell electrical resistance (TEER) and tight junction protein levels in cocultured conditioned astrocytes with isolated rat CMEC. The coculture monolayer's integrity and permeability were significantly compromised by HG media exposure, which was indicated by decreased TEER without a change in tight junction protein levels in CMEC. Our study provides insight into gliovascular adaptations to increased glucose levels resulting in impaired cellular cross talk between astrocytes and CMEC, which could be one explanation for cerebral BBB disruption in diabetic conditions.

A combined experimental and computational framework to evaluate the behavior of therapeutic cells for peripheral nerve regeneration

Recent studies have explored the potential of tissue‐mimetic scaffolds in encouraging nerve regeneration. One of the major determinants of the regenerative success of cellular nerve repair constructs (NRCs) is the local microenvironment, particularly native low oxygen conditions which can affect implanted cell survival and functional performance. In vivo, cells reside in a range of environmental conditions due to the spatial gradients of nutrient concentrations that are established. Here we evaluate in vitro the differences in cellular behavior that such conditions induce, including key biological features such as oxygen metabolism, glucose consumption, cell death, and vascular endothelial growth factor secretion. Experimental measurements are used to devise and parameterize a mathematical model that describes the behavior of the cells. The proposed model effectively describes the interactions between cells and their microenvironment and could in the future be extended, allowing researchers to compare the behavior of different therapeutic cells. Such a combinatorial approach could be used to accelerate the clinical translation of NRCs by identifying which critical design features should be optimized when fabricating engineered nerve repair conduits.

The Cause of Alzheimer's Disease: The Theory of Multipathology Convergence to Chronic Neuronal Stress

The field of Alzheimer's disease (AD) research critically lacks an all-inclusive etiology theory that would integrate existing hypotheses and explain the heterogeneity of disease trajectory and pathologies observed in each individual patient. Here, we propose a novel comprehensive theory that we named: the multipathology convergence to chronic neuronal stress. Our new theory reconsiders long-standing dogmas advanced by previous incomplete theories. Firstly, while it is undeniable that amyloid beta (Aβ) is involved in AD, in the seminal stage of the disease Aβ is unlikely pathogenic. Instead, we hypothesize that the root cause of AD is neuronal stress in the central nervous system (CNS), and Aβ is expressed as part of the physiological response to protect CNS neurons from stress. If there is no return to homeostasis, then Aβ becomes overexpressed, and this includes the generation of longer forms that are more toxic and prone to oligomerization. Secondly, AD etiology is plausibly not strictly compartmentalized within the CNS but may also result from the dysfunction of other physiological systems in the entire body. This view implies that AD may not have a single cause, but rather needs to be considered as a spectrum of multiple chronic pathological modalities converging to the persistent stressing of CNS neurons. These chronic pathological modalities, which include cardiovascular disease, metabolic disorders, and CNS structural changes, often start individually, and over time combine with other chronic modalities to incrementally escalate the amount of stress applied to CNS neurons. We present the case for considering Aβ as a marker of neuronal stress in response to hypoxic, toxic, and starvation events, rather than solely a marker of AD. We also detail numerous human chronic conditions that can lead to neuronal stress in the CNS, making the link with co-morbidities encountered in daily clinical AD practice. Finally, we explain how our theory could be leveraged to improve clinical care for AD and related dementia in personalized medicine paradigms in the near future.

In vitro modulation of Schwann cell behavior by VEGF and PDGF in an inflammatory environment

Peripheral glial cell transplantation with Schwann cells (SCs) is a promising approach for treating spinal cord injury (SCI). However, improvements are needed and one avenue to enhance regenerative functional outcomes is to combine growth factors with cell transplantation. Vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) are neuroprotective, and a combination of these factors has improved outcomes in rat SCI models. Thus, transplantation of SCs combined with VEGF and PDGF may further improve regenerative outcomes. First, however, we must understand how the two factors modulate SCs. In this in vitro study, we show that an inflammatory environment decreased the rate of SC-mediated phagocytosis of myelin debris but the addition of VEGF and PDGF (alone and combined) improved phagocytosis. Cytokine expression by SCs in the inflammatory environment revealed that addition of PDGF led to significantly lower level of pro-inflammatory cytokine, TNF-α, but IL-6 and anti-inflammatory cytokines (TGF-β and IL-10), remained unaltered. Further, PDGF was able to decrease the expression of myelination associated gene Oct6 in the presence of inflammatory environment. Overall, these results suggest that the use of VEGF and/or PDGF combined with SC transplantation may be beneficial in SCI therapy.

Diabetic retinal neurodegeneration as a form of diabetic retinopathy

PURPOSE

To review the evidence supporting diabetic retinal neurodegeneration (DRN) as a form of diabetic retinopathy.

METHOD

Review of literature.

RESULTS

DRN is recognized to be a part of retinopathy in patients with diabetes mellitus (DM), in addition to the well-established diabetic retinal vasculopathy (DRV). DRN has been noted in the early stages of DM, before the onset of clinically evident diabetic retinopathy. The occurrence of DRN has been confirmed in animal models of DM, histopathological examination of donor's eyes from diabetic individuals and assessment of neural structure and function in humans. DRN involves alterations in retinal ganglion cells, photoreceptors, amacrine cells and bipolar cells, and is thought to be driven by glutamate, oxidative stress and dysregulation of neuroprotective factors in the retina. Potential therapeutic options for DRN are under evaluation.

CONCLUSIONS

Literature is divided on the temporal relation between DRN and DRV, with evidence of both precedence and simultaneous occurrence. The relationship between DRN and multi-system neuropathy in DM is yet to be evaluated critically.

Chronic Exposure to Tramadol Induces Neurodegeneration in the Cerebellum of Adult Male Rats

Tramadol is a centrally acting synthetic opioid analgesic and SNRI (serotonin/norepinephrine reuptake-inhibitor) that structurally resembles codeine and morphine. Given the tramadol neurotoxic effect and the body of studies on the effect of tramadol on the cerebellum, this study aims to provide deeper insights into molecular and histological alterations in the cerebellar cortex related to tramadol administration. In this study, twenty-four adult male albino rats were randomly and equally divided into two groups: control and tramadol groups. The tramadol group received 50 mg/kg of tramadol daily for 3 weeks via oral gavage. The functional and structural change of the cerebellum under chronic exposure of tramadol were measured. Our data revealed that treating rats with tramadol not only lead to cerebellum atrophy but also resulted in the actuation of microgliosis, neuroinflammatoin, and apoptotic biomarkers. Our results illustrated a significant drop in VEGF (vascular endothelial growth factor) level in the tramadol group. Additionally, tramadol impaired motor coordination and neuromuscular activity. We also identified several signaling cascades chiefly related to neurodegenerative disease and energy metabolism that considerably deregulated in the cerebellum of tramadol-treated rats. Overall, the outcomes of this study suggest that tramadol administration has a neurodegeneration effect on the cerebellar cortex via several pathways consisting of microgliosis, apoptosis, necroptosis, and neuroinflammatoin.

Purinergic Receptor Blockade with Suramin Increases Survival of Postnatal Neural Progenitor Cells In Vitro

Neural progenitor cells (NPCs) are self-renewing and multipotent cells that persist in the postnatal and adult brain in the subventricular zone and the hippocampus. NPCs can be expanded in vitro to be used in cell therapy. However, expansion is limited, since the survival and proliferation of adult NPCs decrease with serial passages. Many signaling pathways control NPC survival and renewal. Among these, purinergic receptor activation exerts differential effects on the biology of adult NPCs depending on the cellular context. In this study, we sought to analyze the effect of a general blockade of purinergic receptors with suramin on the proliferation and survival of NPCs isolated from the subventricular zone of postnatal rats, which are cultured as neurospheres. Treatment of neurospheres with suramin induced a significant increase in neurosphere diameter and in NPC number attributed to a decrease in apoptosis. Proliferation and multipotency were not affected. Suramin also induced an increase in the gap junction protein connexin43 and in vascular endothelial growth factor, which might be involved in the anti-apoptotic effect. Our results offer a valuable tool for increasing NPC survival before implantation in the lesioned brain and open the possibility of using this drug as adjunctive therapy to NPC transplantation.

VEGF/VEGFR-2 system exerts neuroprotection against Phoneutria nigriventer spider envenomation through PI3K-AKT-dependent pathway

This study was undertaken to elucidate why VEGF/VEGFR-2 is elevated in the hippocampus of rats injected with Phoneutria nigriventer spider venom (PNV). PNV delays Na⁺ channels inactivation; blocks Ca²⁺ and K⁺ channels, increases glutamate release, causes blood-brain breakdown (BBBb), brain edema and severe excitotoxicity. Analytical FT-IR spectroscopy showed profound alteration in molecular biochemical state, with evidences for VEGFR-2 (KDR/Flk-1) signaling mediation. By blocking VEGF/VEGFR-2 binding via pre-treatment with itraconazole we demonstrated that animals' condition was deteriorated soon at 1-2 h post-PNV exposure concurrently with decreased expression of VEGF, BBB-associated proteins, ZO-1, β-catenin, laminin, P-gp (P-glycoprotein), Neu-N (neuron's viability marker) and MAPKphosphorylated-p38, while phosphorylated-ERK and Src pathways were increased. At 5 h and coinciding with incipient signs of animals' recuperation, the proteins associated with protection (HIF-1α, VEGF, VEGFR-1, VEGFR-2, Neu-N, occludin, β-catenin, laminin, P-gp efflux protein, phosphorylated-p38) increased thus indicating p38 pathway activation together with paracellular route strengthening. However, the BBB transcellular trafficking and caspase-3 increased (pro-apoptotic pathway activation). At 24 h, the transcellular route reestablished physiological state but the pro-survival pathway PI3K/(p-Akt) dropped in animals underwent VEGF/VEGFR-2 binding inhibition, whereas it was significantly activated at matched interval in PNV group without prior itraconazole; these results demonstrate impaired VEGF' survival effects at 24 h. The inhibition of VEGF/VEGFR-2 binding identified 5 h as turning point at which multi-level dynamic interplay was elicited to reverse hippocampal damage. Collectively, the data confirmed VEGFR-2 signaling via serine-threonine kinase Akt as neuroprotective pathway against PNV-induced damage. Further studies are needed to elucidate mechanisms underlying PNV effects.

Recent Advances on the Role of GSK3β in the Pathogenesis of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a common neurodegenerative disease characterized by progressive motor neuron degeneration. Although several studies on genes involved in ALS have substantially expanded and improved our understanding of ALS pathogenesis, the exact molecular mechanisms underlying this disease remain poorly understood. Glycogen synthase kinase 3 (GSK3) is a multifunctional serine/threonine-protein kinase that plays a critical role in the regulation of various cellular signaling pathways. Dysregulation of GSK3β activity in neuronal cells has been implicated in the pathogenesis of neurodegenerative diseases. Previous research indicates that GSK3β inactivation plays a neuroprotective role in ALS pathogenesis. GSK3β activity shows an increase in various ALS models and patients. Furthermore, GSK3β inhibition can suppress the defective phenotypes caused by SOD, TDP-43, and FUS expression in various models. This review focuses on the most recent studies related to the therapeutic effect of GSK3β in ALS and provides an overview of how the dysfunction of GSK3β activity contributes to ALS pathogenesis.

Empagliflozin alleviates neuronal apoptosis induced by cerebral ischemia/reperfusion injury through HIF-1α/VEGF signaling pathway

Ischemic stroke is a serious condition associated with severe functional disability and high mortality, however; effective therapy remains elusive. Empagliflozin, a sodium-glucose cotransporter 2 inhibitor, has been shown to exert additional non-glycemic benefits including anti-apoptotic effects in different disease settings. Thereby, this study was designed to investigate the ameliorative effect of empagliflozin on the neuronal apoptosis exhibited in cerebral ischemia/reperfusion (I/R) in a rat model targeting HIF-1α/VEGF signaling which is involved in this insult. Global cerebral I/R injury was induced in male Wistar rats through occlusion of the bilateral common carotid arteries for 30 min followed by one-hour reperfusion. Empagliflozin doses of 1 and 10 mg/kg were administered 1 and 24 h after reperfusion. In I/R-injured rats, empagliflozin treatments significantly reduced infarct size and enhanced neurobehavioral functions in a dose-dependent manner. The drug alleviated neuronal death and cerebral injury inflicted by global ischemia as it suppressed neuronal caspase-3 protein expression. In parallel, protein expressions of HIF-1α and its downstream mediator VEGF were upregulated in the ischemic brain following empagliflozin treatment. The results indicated that empagliflozin attenuates cerebral I/R-induced neuronal death via the HIF-1α/VEGF cascade.

Vitamin D Auto-/Paracrine System Is Involved in Modulation of Glucocorticoid-Induced Changes in Angiogenesis/Bone Remodeling Coupling

Osteoporosis is a devastating side effect of chronic glucocorticoid (GC) treatment. Despite the crucial role of vitamin D (VD) in bone homeostasis, the precise molecular mechanisms of its action on GC-induced disturbances of bone remodeling remain undefined. The study was performed to elucidate the relation of VD status to GC-induced changes of the angiogenesis/osteogenesis/bone resorption coupling in bone tissue. Female Wistar rats received prednisolone (5 mg/kg of b.w.) with or without VD₃ (1000 IU/kg of b.w., for 30 days). Biomechanical parameters of rat femurs were assessed by the three-point bending test. The levels of calcium, inorganic phosphate, activity of total alkaline phosphatase (ALP), and its isoenzymes were determined spectrophotometrically. Vascular endothelial growth factor-A (VEGF-A) and caspase-3 protein levels were detected by western blotting. Vdr and Cyp27b1 mRNAs were measured by qRT-PCR. Receptor activator of nuclear factor κB (RANK) expression in bone sections was visualized immunohistochemically. Serum 25(OH)D was assayed by ELISA. GC administration led to a decrease in maximal load (by 1.2-fold) and stiffness and toughness (by 1.3-fold), which was accompanied by a 3-fold reduction of 25(OH)D level, an elevation of the ALP bone isoenzyme activity in serum, hypocalcaemia, and hypophosphatemia. Along with prednisolone-induced VD deficiency, an impaired synthesis of Vdr (-30%) and Cyp27b1 (+71%) mRNA was observed, reflecting deregulation of bone tissue VD-auto-/paracrine system. GC caused an increase in caspase-3 content, suppressed the synthesis of the osteoclastic marker RANK, and altered angiogenesis/osteogenesis coupling by significantly reducing the level of VEGF-A.VD₃ treatment restored serum 25(OH)D content and the expression of key components of the VD-auto-/paracrine system. VD₃ supplementation diminished cell apoptosis and strongly improved angiogenesis/osteogenesis coupling as well as mineral metabolism and biomechanical parameters of femurs in GC-administered rats. Thus, VD₃ can have a beneficial effect on the correction of GC-induced pathological changes in bone remodeling.

The role of edible bird's nest and mechanism of averting lead acetate toxicity effect on rat uterus

Aim

This study aimed to evaluate the protective effect of edible bird's nest (EBN) supplement on the uteri of rats exposed to lead acetate (LA) toxicity.

Materials and Methods

Five treatment groups were established as follows: Group 1 (C), which was given distilled water; Group 2 (T0), which was administered with LA (10 mg/kg body weight [BW]); and Groups 3 (T1), 4 (T2), and 5 (T3), which were given LA (10 mg/kg BW) plus graded concentrations of 30, 60, and 120 mg/kg BW of EBN, respectively. Rats were euthanized at week 5 to collect blood for superoxide dismutase (SOD) assay, and uterus for histomorphological study and expression analyses of epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), and proliferating cell nuclear antigen (PCNA).

Results

Results revealed that LA causes destruction of uterine lining cells and necrosis of uterine glands of exposed rats without EBN supplement while the degree of damage decreased among EBN treated groups; T3 showed the highest ameliorating effect against LA toxicity, as well as an increased number of uterine glands. Increased levels of SOD were also achieved in EBN supplemented groups than the controls. Results of immunohistochemistry showed significantly higher expressions of EGF, VEGF, and PCNA levels (p<0.05) in T3 compared to other treatments. EBN maintained upregulation of antioxidant - reactive oxygen species balance.

Conclusion

The findings showed that EBN could ameliorate the detrimental effects of LA toxicity on the uterus possibly by enhancing enzymatic antioxidant (SOD) activity as well as expressions of EGF, VEGF, and PCNA with cell proliferation roles.

The role of neurogenesis in neurorepair after ischemic stroke

Stroke consists of an abrupt reduction of cerebral blood flow resulting in hypoxia that triggers an excitotoxicity, oxidative stress, and neuroinflammation. After the ischemic process, neural precursor cells present in the subventricular zone of the lateral ventricle and subgranular zone of the dentate gyrus proliferate and migrate towards the lesion, contributing to the brain repair. The neurogenesis is induced by signal transduction pathways, growth factors, attractive factors for neuroblasts, transcription factors, pro and anti-inflammatory mediators and specific neurotransmissions. However, this endogenous neurogenesis occurs slowly and does not allow a complete restoration of brain function. Despite that, understanding the mechanisms of neurogenesis could improve the therapeutic strategies for brain repair. This review presents the current knowledge about brain repair process after stroke and the perspectives regarding the development of promising therapies that aim to improve neurogenesis and its potential to form new neural networks.

CNS-Wide over Expression of Fractalkine Improves Cognitive Functioning in a Tauopathy Model

Accumulating evidence increasingly implicates regulation of neuroinflammation as a potential therapeutic target in Alzheimer’s disease and other neurodegenerative disorders. Fractalkine (FKN) is a unique chemokine that is expressed and secreted by neurons and reduces expression of pro-inflammatory genes. To further demonstrate the utility of agents that increase FKN signaling throughout the central nervous system as possible therapies for AD, we assessed the impact of soluble FKN (sFKN) over expression on cognition in tau depositing rTg450 mice after the onset of cognitive deficits. Using adeno-associated virus serotype 4, we infected cells lining the ventricular system with soluble FKN to increase FKN signaling over a larger fraction of the brain than achieved with intraparenchymal injections. We found that soluble FKN over expression by cells lining the ventricles significantly improved cognitive performance on the novel mouse recognition and radial arm water maze tasks. These benefits were achieved without detectable reductions in tau hyperphosphorylation, hippocampal atrophy, or microglial CD45 expression. Utilizing qPCR, we report a significant increase in Vegfa expression, indicating an increase in trophic support and possible neovascularization in AAV-sFKN-injected mice. To our knowledge, this is the first demonstration that FKN over expression can rescue cognitive function in a tau depositing mouse line.

Graphical Abstract

Vascular Endothelial Growth Factor (VEGF) Prevents the Downregulation of the Cholinergic Phenotype in Axotomized Motoneurons of the Adult Rat

Vascular endothelial growth factor (VEGF) was initially characterized by its activity on the vascular system. However, there is growing evidence indicating that VEGF also acts as a neuroprotective factor, and that its administration to neurons suffering from trauma or disease is able to rescue them from cell death. We questioned whether VEGF could also maintain damaged neurons in a neurotransmissive mode by evaluating the synthesis of their neurotransmitter, and whether its action would be direct or through its well-known angiogenic activity. Adult rat extraocular motoneurons were chosen as the experimental model. Lesion was performed by monocular enucleation and immediately a gelatine sponge soaked in VEGF was implanted intraorbitally. After 7 days, abducens, trochlear, and oculomotor nuclei were examined by immunohistochemistry against choline acetyltransferase (ChAT), the biosynthetic enzyme of the motoneuronal neurotransmitter acetylcholine. Lesioned motoneurons exhibited a noticeable ChAT downregulation which was prevented by VEGF administration. To explore whether this action was mediated via an increase in blood vessels or in their permeability, we performed immunohistochemistry against laminin, glucose transporter-1 and the plasmatic protein albumin. The quantification of the immunolabeling intensity against these three proteins showed no significant differences between VEGF-treated, axotomized and control animals. Therefore, the present data indicate that VEGF is able to sustain the cholinergic phenotype in damaged motoneurons, which is a first step for adequate neuromuscular neurotransmission, and that this action seems to be mediated directly on neurons since no sign of angiogenic activity was evident. These data reinforces the therapeutical potential of VEGF in motoneuronal diseases.

Effects of dexmedetomidine post‑treatment on BDNF and VEGF expression following cerebral ischemia/reperfusion injury in rats

Brain‑derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) serves a significant role in neural protection by activating the phosphatidylinositol 3‑kinase (PI3K)/Akt signaling pathway, which also was associated with the neuroprotective the treatment with dexmedetomidine (DEX). The present study aimed to further explore whether treatment with DEX post‑IR increased the expression level of BDNF and VEGF in the rat brain. A total of 30 healthy, clean male Wistar rats were randomly divided into 3 experimental groups: Control group, ischemia/reperfusion (I/R) group and DEX treatment group. Subsequently, BDNF and VEGF mRNA and protein expression levels were analyzed. The results indicated that the mRNA expression levels of BDNF and VEGF were higher in the I/R and DEX groups compared with expression levels in the Control group at 6 h and 1 day post‑treatment; the levels of BNDF mRNA expression were higher in the DEX group compared with the I/R group. The levels of BDNF and VEGF protein expression in the I/R and DEX groups were also significantly higher compared with those in the Control group. I/R surgery significantly increased the expression of BDNF and VEGF protein DEX group at 6 h, day 1 and day 3 compared with expression levels in the I/R group. Results from the present study indicated that post‑surgical treatment with DEX may increase the expression of BDNF and VEGF following I/R, which may serve a role in nerve protection.

GV1001 Induces Apoptosis by Reducing Angiogenesis in Renal Cell Carcinoma Cells Both In Vitro and In Vivo

OBJECTIVE

To investigate the anticancer effects of GV1001 and its biological mechanism of action in renal cell carcinoma (RCC).

METHODS

The effects of GV1001 on cell survival and apoptosis in RCC cells were examined in vitro using cell viability assay, fluorescence-activated cell sorting, and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. To evaluate the effect of GV1001 on migration, invasion, and angiogenesis, we used wound healing, invasion, endothelial cell tube formation assay, and western blot analysis. Furthermore, we used an RCC xenograft model with either phosphate buffered saline or GV1001 to confirm the anticancer effect of GV1001 in vivo. Tumor volume was monitored during treatment, and tumor weight was measured after animals were killed. Apoptosis and angiogenesis of the tumor tissue were assessed using hematoxylin and eosin staining, immunohistochemistry, and western blot analysis.

RESULTS

GV1001 reduced cell viability and induced apoptosis in RCC cells in vitro. Furthermore, GV1001 suppressed the migration and invasion of RCC cells through regulation of matrix metalloproteinases and tissue inhibitors of metalloproteinases. In addition, GV1001 reduced angiogenesis via regulation of hypoxia-inducible factor 1α. In xenograft mouse model experiment, GV1001 reduced tumor growth and induced apoptosis. As in the in vitro results, GV1001 significantly reduced angiogenesis through regulation of hypoxia-inducible factor 1α in vivo.

CONCLUSION

Our data demonstrated that GV1001 induced apoptosis through suppression of angiogenesis in RCCs both in vitro and in vivo, which suggests that GV1001 may be a potential therapeutic target for RCC.

VEGF attenuates 2-VO induced cognitive impairment and neuronal injury associated with the activation of PI3K/Akt and Notch1 pathway

Vascular endothelial growth factor (VEGF) has been identified as a potential treatment for effectively improving cognitive function in several neuropathological conditions. However, the underlying mechanism and the relevant downstream protective pathways that are activated in neurons by VEGF remain elusive, especially in chronic global cerebral ischemia. In this study, we intended to investigate the signaling mechanisms of VEGF in cognitive protection and anti-apoptosis in a rat model of chronic global cerebral ischemia induced by permanent bilateral common carotid artery occlusion (2-VO). The results showed that intranasal administration of VEGF (72h post-ischemia for 6 successive days) caused a significant improvement in the cognitive deficits induced by 2-VO, accompanied by a reversal of oxidative stress and VEGF depletion in the hippocampus. In addition, VEGF-treatment decreased the expression of Bax and Caspase-3, increased the expression of anti-apoptotic Bcl-xl and the main protein involved in energy homeostasis AMP-activated protein kinase (AMPK), which may account for the anti-apoptotic effects of VEGF. Importantly, VEGF administration upregulated the phosphorylation levels of Akt (pAkt) and PI3K, activated Notch1 pathway in 2-VO hippocampus. These findings suggested that intranasal administration of VEGF alleviated cognitive impairment induced by 2-VO injury, and attenuated oxidative damage and neuronal injury in hippocampus associated with the regulation of PI3K/Akt and Notch1 signaling pathway, which might be the underlying mechanisms of VEGF on global chronic cerebral ischemia.

Anti-VEGF treatment improves neurological function in tumors of the nervous system

Research of various diseases of the nervous system has shown that VEGF has direct neuroprotective effects in the central and peripheral nervous systems, and indirect effects on improving neuronal vessel perfusion which leads to nerve protection. In the tumors of the nervous system, VEGF plays a critical role in tumor angiogenesis and tumor progression. The effect of anti-VEGF treatment on nerve protection and function has been recently reported - by normalizing the tumor vasculature, anti-VEGF treatment is able to relieve nerve edema and deliver oxygen more efficiently into the nerve, thus reducing nerve damage and improving nerve function. This review aims to summarize the divergent roles of VEGF in diseases of the nervous system and the recent findings of anti-VEGF therapy in nerve damage/regeneration and function in tumors, specifically, in Neurofibromatosis type 2 associated schwannomas.

The Effect of Dexamethasone Intravitreal Implant on Retinal Nerve Fiber Layer in Patients Diagnosed with Branch Retinal Vein Occlusion

PURPOSE

To evaluate the effect of a single dose of intravitreal dexamethasone (DEX) implant on retinal nerve fiber layer (RNFL) thickness in patients with branch retinal vein occlusion (BRVO) in a 6-month period.

MATERIALS AND METHODS

This retrospective observational study included the patients with BRVO who received intravitreal DEX implant and whose assessment included the baseline RNFL thickness measurements. The data of 26 eyes of 24 patients were retrospectively analyzed. Spectral domain optic coherence tomography was used to measure peripapillary RNFL thickness in six regional subfields. Intraocular pressure (IOP) values at each visit were recorded. The data of single dose DEX implant during 6 months were assessed.

RESULTS

The mean preoperative and postoperative 6th month nasal RNFL values were 85.4 ± 23.0 μm and 82.1 ± 17.6 μm, respectively, and the difference between the measurements was not statistically significant (p = 0.372). There was a slight decrease in the mean RNFL values postoperatively compared to the baseline values in all quadrants except supero-temporal quadrant; however, none of them reached statistically significant level (p > 0.05). The mean IOP values before and 6 months after implantation were 15.7 ± 2.9 mmHg and 16.5 ± 4.2 mmHg, respectively. The difference between the 6th month IOP values and baseline IOP values was not statistically significant (p = 0.236).

CONCLUSION

Intravitreal DEX implant seems to have no adverse effect on RNFL thickness in BRVO patients in a 6-month period.

VEGF treatment during status epilepticus attenuates long-term seizure-associated alterations in astrocyte morphology

Vascular endothelial growth factor (VEGF) treatment during pilocarpine-induced status epilepticus (SE) causes sustained preservation of behavioral function in rats in the absence of enduring neuroprotection (Nicoletti et al., 2010), suggesting the possibility that other cells or mechanisms could be involved in the beneficial effects of VEGF during SE. Astrocytes have been reported to contribute to epileptiform discharges in the hippocampus (Tian et al., 2005; Kang et al., 1998) and to express VEGF receptors (Krum & Rosenstein, 2002). We report here that VEGF treatment significantly alters multiple astrocyte parameters. This study investigated astrocyte morphology one month after SE in animals treated with VEGF or inactivated VEGF control protein during SE. Individual GFAP-immunostained astrocytes from CA1 and dentate gyrus hilus were traced and morphologically quantified, and both somatic and process structures were analyzed. VEGF treatment during SE significantly prevented post-SE increases in number of branch intersections, process length, and node count. Furthermore, analysis of distance to nearest neighboring astrocytes revealed that VEGF treatment significantly increased inter-astrocyte distance. Overall, VEGF treatment during SE did not significantly alter the shape of the astrocytes, but did prevent SE-induced changes in branching complexity, size, and spatial patterning. Because astrocyte morphology may be related to astrocyte function, it is possible that VEGF's enduring effects on astrocyte morphology may impact the functioning of the post-seizure hippocampus.

Contrasting roles of immune cells in tissue injury and repair in stroke: The dark and bright side of immunity in the brain

Despite considerable efforts in research and clinical studies, stroke is still one of the leading causes of death and disability worldwide. Originally, stroke was considered a vascular thrombotic disease without significant immune involvement. However, over the last few decades it has become increasingly obvious that the immune responses can significantly contribute to both tissue injury and protection following stroke. Recently, much research has been focused on the immune system's role in stroke pathology and trying to elucidate the mechanism used by immune cells in tissue injury and protection. Since the discovery of tissue plasminogen activator therapy in 1996, there have been no new treatments for stroke. For this reason, research into understanding how the immune system contributes to stroke pathology may lead to better therapies or enhance the efficacy of current treatments. Here, we discuss the contrasting roles of immune cells to stroke pathology while emphasizing myeloid cells and T cells. We propose that focusing future research on balancing the beneficial-versus-detrimental roles of immunity may lead to the discovery of better and novel stroke therapies.

Potential Roles of Adropin in Central Nervous System: Review of Current Literature

Adropin is a 4.9 kDa peptide that is important for maintenance of metabolic and non-metabolic homeostasis. It regulates glucose and fatty acid metabolism and is involved in endothelial cell function and endothelial nitric oxide (NO) synthase bioactivity as well as physical activity and motor coordination. Adropin is expressed in many tissues and organs including central nervous system (CNS). This peptide plays a crucial role in the development of various CNS disorders such as stroke, schizophrenia, bipolar disorder as well as Alzheimer's, Parkinson's, and Huntington's diseases. In this comprehensive review, the potential roles of adropin in cellular signaling pathways that lead to pathogenesis and/or treatment of CNS disorders will be discussed.

Bone marrow stromal cell transplantation through tail vein injection promotes angiogenesis and vascular endothelial growth factor expression in cerebral infarct area in rats

BACKGROUND AIMS

This study sought to identify correlations between vascular endothelial growth factor (VEGF) expression after tail-vein injection of rat-derived bone marrow stromal cells (BMSCs) and neurogenesis and angiogenesis in cerebral infarct of rats.

METHODS

Rats with intraluminal middle cerebral artery occlusion were injected in a tail vein with Hoechst-labeled BMSCs. Functional recovery from cerebral infarction was observed through the use of a locomotion score. The brains of injected rats were sliced, and Hoechst-labeled BMSCs in the infarct and peri-infarct areas and subventricular zone (SVZ) were detected with the use of fluorescence microscopy. Ki-67 (as a cell proliferation marker) and VEGF expression were determined by means of immunohistochemistry. Neurofibril formation and angiogenesis were examined by means of Bielschowsky staining.

RESULTS

Within 1 to 2 weeks after BMSC injection, rats showed significantly improved locomotion scores compared with rats without BMSC injection (P < 0.01). Viable BMSCs were found in the peri-infarct area. The numbers of Ki-67-positive and VEGF-positive cells in the peri-infarct area and SVZ of injected rats were significantly increased compared with the control group (P < 0.01). Numerous new vessels, neurofibrils and anastomosed vasculatures were present in the infarct area. These neurofibrils mainly surrounded the neovasculatures.

CONCLUSIONS

These results indicate that BMSC-transplantation in rats through tail vein injection can increase neurogenesis, perhaps as the result of VEGF-mediated and/or Ki-67-mediated angiogenesis.

Transplantation of vascular endothelial growth factor-modified neural stem/progenitor cells promotes the recovery of neurological function following hypoxic-ischemic brain damage

Neural stem/progenitor cell (NSC) transplantation has been shown to effectively improve neurological function in rats with hypoxic-ischemic brain damage. Vascular endothelial growth factor (VEGF) is a signaling protein that stimulates angiogenesis and improves neural regeneration. We hypothesized that transplantation of VEGF-transfected NSCs would alleviate hypoxic-ischemic brain damage in neonatal rats. We produced and transfected a recombinant lentiviral vector containing the VEGF₁₆₅ gene into cultured NSCs. The transfected NSCs were transplanted into the left sensorimotor cortex of rats 3 days after hypoxic-ischemic brain damage. Compared with the NSCs group, VEGF mRNA and protein expression levels were increased in the transgene NSCs group, and learning and memory abilities were significantly improved at 30 days. Furthermore, histopathological changes were alleviated in these animals. Our findings indicate that transplantation of VEGF-transfected NSCs may facilitate the recovery of neurological function, and that its therapeutic effectiveness is better than that of unmodified NSCs.

Neurogenic effect of VEGF is related to increase of astrocytes transdifferentiation into new mature neurons in rat brains after stroke

To study the cellular mechanism of vascular endothelial growth factor (VEGF)-enhanced neurogenesis in ischemic brain injury, we used middle cerebral artery occlusion (MCAO) model to induce transient focal ischemic brain injury. The results showed that ischemic injury significantly increased glial fibrillary acidic protein immunopositive (GFAP(+)) and nestin(+) cells in ipsilateral striatum 3 days following MCAO. Most GFAP(+) cells colocalized with nestin (GFAP(+)-nestin(+)), Pax6 (GFAP(+)-Pax6(+)), or Olig2 (GFAP(+)-Olig2(+)). VEGF further increased GFAP(+)-nestin(+) and GFAP(+)-Pax6(+) cells, and decreased GFAP(+)-Olig2(+) cells. We used striatal injection of GFAP targeted enhanced green fluorescence protein (pGfa2-EGFP) vectors combined with multiple immunofluorescent staining to trace the neural fates of EGFP-expressing (GFP(+)) reactive astrocytes. The results showed that MCAO-induced striatal reactive astrocytes differentiated into neural stem cells (GFP(+)-nestin(+) cells) at 3 days after MCAO, immature (GFP(+)-Tuj-1(+) cells) at 1 week and mature neurons (GFP(+)-MAP-2(+) or GFP(+)-NeuN(+) cells) at 2 weeks. VEGF increased GFP(+)-NeuN(+) and BrdU(+)-MAP-2(+) newborn neurons after MCAO. Fluorocitrate, an astrocytic inhibitor, significantly decreased GFAP and nestin expression in ischemic brains, and also reduced VEGF-enhanced neurogenic effects. This study is the first time to report that VEGF-mediated increase of newly generated neurons is dependent on the presence of reactive astrocytes. The results also illustrate cellular mechanism of VEGF-enhanced neural repair and functional plasticity in the brains after ischemic injury. We concluded that neurogenic effect of VEGF is related to increase of striatal astrocytes transdifferentiation into new mature neurons, which should be very important for the reconstruction of neurovascular units/networks in non-neurogenic regions of the mammalian brain.

Perivascular Arrest of CD8+ T Cells Is a Signature of Experimental Cerebral Malaria

There is significant evidence that brain-infiltrating CD8⁺ T cells play a central role in the development of experimental cerebral malaria (ECM) during Plasmodium berghei ANKA infection of C57BL/6 mice. However, the mechanisms through which they mediate their pathogenic activity during malaria infection remain poorly understood. Utilizing intravital two-photon microscopy combined with detailed ex vivo flow cytometric analysis, we show that brain-infiltrating T cells accumulate within the perivascular spaces of brains of mice infected with both ECM-inducing (P. berghei ANKA) and non-inducing (P. berghei NK65) infections. However, perivascular T cells displayed an arrested behavior specifically during P. berghei ANKA infection, despite the brain-accumulating CD8⁺ T cells exhibiting comparable activation phenotypes during both infections. We observed T cells forming long-term cognate interactions with CX₃CR1-bearing antigen presenting cells within the brains during P. berghei ANKA infection, but abrogation of this interaction by targeted depletion of the APC cells failed to prevent ECM development. Pathogenic CD8⁺ T cells were found to colocalize with rare apoptotic cells expressing CD31, a marker of endothelial cells, within the brain during ECM. However, cellular apoptosis was a rare event and did not result in loss of cerebral vasculature or correspond with the extensive disruption to its integrity observed during ECM. In summary, our data show that the arrest of T cells in the perivascular compartments of the brain is a unique signature of ECM-inducing malaria infection and implies an important role for this event in the development of the ECM-syndrome.

Cerebral malaria is the most severe complication of Plasmodium falciparum infection. Utilizing the murine experimental model of cerebral malaria (ECM), it has been found that CD8⁺ T cells are a key immune cell type responsible for development of cerebral pathology during malaria infection. To identify how CD8⁺ T cells cause cerebral pathology during malaria infection, in this study we have performed detailed in vivo analysis (two photon imaging) of CD8⁺ T cells within the brains of mice infected with strains of malaria parasites that cause or do not cause ECM. We found that CD8⁺ T cells appear to accumulate in similar numbers and in comparable locations within the brains of mice infected with parasites that do or do not cause ECM. Importantly, however, brain accumulating CD8⁺ T cells displayed significantly different movement characteristics during the different infections. CD8⁺ T cells interacted with myeloid cells within the brain during infection with parasites causing ECM, but this association was not required for development of cerebral complications. Furthermore, our results suggest that CD8⁺ T cells do not cause ECM through the widespread killing of brain microvessel cells. The results in this study significantly improve our understanding of the ways through which CD8⁺ T cells can mediate cerebral pathology during malaria infection.

Anti-VEGF treatment improves neurological function and augments radiation response in NF2 schwannoma model

Hearing loss is the main limitation of radiation therapy for vestibular schwannoma (VS), and identifying treatment options that minimize hearing loss are urgently needed. Treatment with bevacizumab is associated with tumor control and hearing improvement in neurofibromatosis type 2 (NF2) patients; however, its effect is not durable and its mechanism of action on nerve function is unknown. We modeled the effect anti-VEGF therapy on neurological function in the sciatic nerve model and found that it improves neurological function by alleviating tumor edema, which may further improve results by decreasing muscle atrophy and increasing nerve regeneration. Using a cranial window model, we showed that anti-VEGF treatment may achieve these effects via normalizing the tumor vasculature, improving vessel perfusion, and delivery of oxygenation. It is known that oxygen is a potent radiosensitizer; therefore, we further demonstrated that combining anti-VEGF with radiation therapy can achieve a better tumor control and help lower the radiation dose and, thus, minimize radiation-related neurological toxicity. Our results provide compelling rationale for testing combined therapy in human VS.

The effect of intravitreal vascular endothelial growth factor on inner retinal oxygen delivery and metabolism in rats

Vascular endothelial growth factor (VEGF) is stimulated by hypoxia and plays an important role in pathologic vascular leakage and neovascularization. Increased VEGF may affect inner retinal oxygen delivery (DO2) and oxygen metabolism (MO2), however, quantitative information is lacking. We tested the hypotheses that VEGF increases DO2, but does not alter MO2. In 10 rats, VEGF was injected intravitreally into one eye, whereas balanced salt solution (BSS) was injected into the fellow eye, 24 h prior to imaging. Vessel diameters and blood velocities were determined by red-free and fluorescent microsphere imaging, respectively. Vascular PO2 values were derived by phosphorescence lifetime imaging of an intravascular oxyphor. Retinal blood flow, vascular oxygen content, DO2 and MO2 were calculated. Retinal arterial and venous diameters were larger in VEGF-injected eyes compared to control eyes (P < 0.03), however no significant difference was observed in blood velocity (P = 0.21). Thus, retinal blood flow was greater in VEGF-injected eyes (P = 0.007). Retinal vascular PO2 and oxygen content were similar between control and VEGF-injected eyes (P > 0.11), while the arteriovenous oxygen content difference was marginally lower in VEGF-injected eyes (P = 0.05). DO2 was 950 ± 340 and 1380 ± 650 nL O2/min in control and VEGF-injected eyes, respectively (P = 0.005). MO2 was 440 ± 150 and 490 ± 190 nL O2/min in control and VEGF-injected eyes, respectively (P = 0.31). Intravitreally administered VEGF did not alter MO2 but increased DO2, suggesting VEGF may play an offsetting role in conditions characterized by retinal hypoxia.

Evaluating the SERCA2 and VEGF mRNAs as Potential Molecular Biomarkers of the Onset and Progression in Huntington's Disease

Abnormalities of intracellular Ca²⁺ homeostasis and signalling as well as the down-regulation of neurotrophic factors in several areas of the central nervous system and in peripheral tissues are hallmarks of Huntington’s disease (HD). As there is no therapy for this hereditary, neurodegenerative fatal disease, further effort should be made to slow the progression of neurodegeneration in patients through the definition of early therapeutic interventions. For this purpose, molecular biomarker(s) for monitoring disease onset and/or progression and response to treatment need to be identified. In the attempt to contribute to the research of peripheral candidate biomarkers in HD, we adopted a multiplex real-time PCR approach to analyse the mRNA level of targeted genes involved in the control of cellular calcium homeostasis and in neuroprotection. For this purpose we recruited a total of 110 subjects possessing the HD mutation at different clinical stages of the disease and 54 sex- and age-matched controls. This study provides evidence of reduced transcript levels of sarco-endoplasmic reticulum-associated ATP2A2 calcium pump (SERCA2) and vascular endothelial growth factor (VEGF) in peripheral blood mononuclear cells (PBMCs) of manifest and pre-manifest HD subjects. Our results provide a potentially new candidate molecular biomarker for monitoring the progression of this disease and contribute to understanding some early events that might have a role in triggering cellular dysfunctions in HD.

Effects of ischemic preconditioning on VEGF and pFlk-1 immunoreactivities in the gerbil ischemic hippocampus after transient cerebral ischemia

Ischemia preconditioning (IPC) displays an important adaptation of the CNS to sub-lethal ischemia. In the present study, we examined the effect of IPC on immunoreactivities of VEGF-, and phospho-Flk-1 (pFlk-1) following transient cerebral ischemia in gerbils. The animals were randomly assigned to four groups (sham-operated-group, ischemia-operated-group, IPC plus (+) sham-operated-group, and IPC+ischemia-operated-group). IPC was induced by subjecting gerbils to 2 min of ischemia followed by 1 day of recovery. In the ischemia-operated-group, a significant loss of neurons was observed in the stratum pyramidale (SP) of the hippocampal CA1 region (CA1) alone 5 days after ischemia-reperfusion, however, in all the IPC+ischemia-operated-groups, pyramidal neurons in the SP were well protected. In immunohistochemical study, VEGF immunoreactivity in the ischemia-operated-group was increased in the SP at 1 day post-ischemia and decreased with time. Five days after ischemia-reperfusion, strong VEGF immunoreactivity was found in non-pyramidal cells, which were identified as pericytes, in the stratum oriens (SO) and radiatum (SR). In the IPC+sham-operated- and IPC+ischemia-operated-groups, VEGF immunoreactivity was significantly increased in the SP. pFlk-1 immunoreactivity in the sham-operated- and ischemia-operated-groups was hardly found in the SP, and, from 2 days post-ischemia, pFlk-1 immunoreactivity was strongly increased in non-pyramidal cells, which were identified as pericytes. In the IPC+sham-operated-group, pFlk-1 immunoreactivity was significantly increased in both pyramidal and non-pyramidal cells; in the IPC+ischemia-operated-groups, the similar pattern of VEGF immunoreactivity was found in the ischemic CA1, although the VEGF immunoreactivity was strong in non-pyramidal cells at 5 days post-ischemia. In brief, our findings show that IPC dramatically augmented the induction of VEGF and pFlk-1 immunoreactivity in the pyramidal cells of the CA1 after ischemia-reperfusion, and these findings suggest that the increases of VEGF and Flk-1 expressions may be necessary for neurons to survive from transient ischemic damage.

Apoptosis inducing effects of Kuding tea polyphenols in human buccal squamous cell carcinoma cell line BcaCD885

Tea polyphenols are functional substances present in tea. Kuding tea as a traditional drink also contains these compounds. After 25, 50 and 100 μg/mL of Kuding tea polyphenol treatment for 48 h, cell proliferation of human buccal squamous cell carcinoma cell line BcaCD885 was inhibited, and the 100 μg/mL of Kuding tea polyphenol showed the highest inhibitory rate at 72.3%. Compared to the lower concentration, the 100 μg/mL of Kuding tea polyphenols significantly (p < 0.05) induced apoptosis as determined by flow cytometry analysis, the content of sub-G1 cancer cells was 32.7%. By RT-PCR and western blot assays, Kuding tea polyphenol significantly induced apoptosis in BcaCD885 cancer cells (p < 0.05) by upregulating caspase-3, caspase-8, caspase-9, Fas/FasL, Bax, p53, p21, E2F1, p73 and downregulating Bcl-2, Bcl-xL, HIAP-1, and HIAP-2 mRNA and protein expressions. Kuding tea polyphenols thus present apoptosis inducing effects in vitro.

Protective or pathogenic effects of vascular endothelial growth factor (VEGF) as potential biomarker in cerebral malaria

Cerebral malaria (CM) is the major lethal complication of Plasmodium falciparum infection. It is characterized by persistent coma along with symmetrical motor signs. Several clinical, histopathological, and laboratory studies have suggested that cytoadherence of parasitized erythrocytes, neural injury by malarial toxin, and excessive inflammatory cytokine production are possible pathogenic mechanisms. Although the detailed pathophysiology of CM remains unsolved, it is thought that the binding of parasitized erythrocytes to the cerebral endothelia of microvessels, leading to their occlusion and the consequent angiogenic dysregulation play a key role in the disease pathogenesis. Recent evidences showed that vascular endothelial growth factor (VEGF) and its receptor-related molecules are over-expressed in the brain tissues of CM patients, as well as increased levels of VEGF are detectable in biologic samples from malaria patients. Whether the modulation of VEGF is causative agent of CM mortality or a specific phenotype of patients with susceptibility to fatal CM needs further evaluation. Currently, there is no biological test available to confirm the diagnosis of CM and its complications. It is hoped that development of biomarkers to identify patients and potential risk for adverse outcomes would greatly enhance better intervention and clinical management to improve the outcomes. We review and discuss here what it is currently known in regard to the role of VEGF in CM as well as VEGF as a potential biomarker.

VEGF ameliorates cognitive impairment in in vivo and in vitro ischemia via improving neuronal viability and function

Vascular endothelial growth factor (VEGF) has recently been proved to be a potential therapeutic drug in ischemic disorders depending on the dose, route and time of administration, especially in focal cerebral ischemia. Whether VEGF could exert protection in a long-term total cerebral ischemic model is still uncertain, and the cellular mechanism has not been clarified so far. In order to answer the above issue, an experiment was performed in non-invasively giving exogenous VEGF to a total cerebral ischemic model rats and examining their spatial cognitive function by performing Morris water maze and long-term potential test. Moreover, we performed in vitro experiment to explore the cellular mechanism of VEGF protection effect. In an in vitro ischemia model oxygen-glucose deprivation (OGD), whole-cell patch-clamp recording was employed to examine neuronal function. Additionally, hematoxylin-eosin and propidium iodide staining were applied in vivo and in vitro in the neuropathological and viability study, separately. Our results showed that intranasal administration of VEGF could improve the cognitive function, synaptic plasticity and damaged hippocampal neurons in a global cerebral ischemia model. In addition, VEGF could retain the membrane potential, neuronal excitability and spontaneous excitatory postsynaptic currents in the early stage of ischemia, which further demonstrated that there was an acute effect of VEGF in OGD-induced pyramidal neurons. Simultaneously, it was also found that the death of CA1 pyramidal neuronal was significantly reduced by VEGF, but there was no similar effect in VEGF coexists with SU5416 group. These results indicated that VEGF could ameliorate cognitive impairment and synaptic plasticity via improving neuronal viability and function through acting on VEGFR-2.

Signaling through the vascular endothelial growth factor receptor VEGFR-2 protects hippocampal neurons from mitochondrial dysfunction and oxidative stress

Vascular endothelial growth factor VEGF (VEGF-A or VEGF₁₆₅) is a potent angiogenic factor that also signals neuroprotection through activation of its cognate receptor VEGFR-2. In this capacity, VEGF signaling can rescue neurons from the damage induced by stressful stimuli many of which elicit oxidative stress. However, the regulatory role that VEGFR-2 plays in providing neuroprotection remains elusive. Therefore, we investigated the effects of VEGFR-2 inhibition on primary cultures of mature hippocampal neurons undergoing nutritional stress. We found that neurons cultured under nutritional stress had increased expression of VEGF and its receptors, VEGFR-1, VEGFR-2, and NP-1, as well as enhanced levels of VEGFR-2 phosphorylation. These neurons also showed increased activation of the prosurvival pathways for MEK/ERK1/2 and PI3K/Akt, enhanced phosphorylation (inactivation) of the proapoptotic BAD, and higher levels of the antiapoptotic protein Bcl-xL, all of which were augmented by treatments with exogenous VEGF and blocked by VEGFR-2 inhibition. The blockade of VEGFR-2 function also elicited a cytotoxicity that was accompanied by caspase-3 activation, induction of hemeoxygenase-1 (HO-1), oxidative stress, and a collapse in the mitochondrial membrane potential (ΔΨ(m)). Knockdown of VEGFR-2 by siRNA generated a similar pattern of redox change and mitochondrial impairment. Pretreatments with VEGF, VEGF-B, or the antioxidant N-acetylcysteine (NAC) rescued SU1498 or siRNA-treated neurons from the mitochondrial dysfunction and oxidative stress induced by VEGFR-2 inhibition in a timely fashion. These findings suggested that VEGF or VEGF-B can provide neuroprotection by signaling through an alternate VEGF receptor. Together, our findings suggest that VEGF signaling through VEGFR-2 plays a critical regulatory role in protecting stressed hippocampal neurons from the damaging effects of an oxidative insult. These findings also implicate VEGFR-1 or NP-1 as compensatory receptors that mediate neuroprotection when VEGFR-2 function is blocked.

Dose-dependent neuroprotection of VEGF₁₆₅ in Huntington's disease striatum

Huntington's disease (HD) is a devastating neurodegenerative disorder caused by abnormal polyglutamine expansion in the huntingtin protein (Exp-Htt). Currently, there are no effective treatments for HD. We used bidirectional lentiviral transfer vectors to generate in vitro and in vivo models of HD and to test the therapeutic potential of vascular endothelial growth factor 165 (VEGF₁₆₅). Lentiviral-mediated expression of Exp-Htt caused cell death and aggregate formation in human neuroblastoma SH-SY5Y and rat primary striatal cultures. Lentiviral-mediated VEGF₁₆₅ expression was found to be neuroprotective in both of these models. Unilateral stereotaxic vector delivery of Exp-Htt vector in adult rat striatum led to progressive inclusion formation and striatal neuron loss at 10 weeks post-transduction. Coinjection of a lower dose VEGF₁₆₅ significantly attenuated DARPP-32(+) neuronal loss, enhanced NeuN staining and reduced Exp-Htt aggregation. A tenfold higher dose VEGF₁₆₅ led to overt neuronal toxicity marked by tissue damage, neovascularization, extensive astrogliosis, vascular leakage, chronic inflammation and distal neuronal loss. No overt behavioral phenotype was observed in these animals. Expression of VEGF₁₆₅ at this higher dose in the brain of wild-type rats led to early mortality with global neuronal loss. This report raises important safety concerns about unregulated VEGF₁₆₅ CNS applications.

Mechanisms of neuroprotection from hypoxia-ischemia (HI) brain injury by up-regulation of cytoglobin (CYGB) in a neonatal rat model

This study was designed to investigate the expression profile of CYGB, its potential neuroprotective function, and underlying molecular mechanisms using a model of neonatal hypoxia-ischemia (HI) brain injury. Cygb mRNA and protein expression were evaluated within the first 36 h after the HI model was induced using RT-PCR and Western blotting. Cygb mRNA expression was increased at 18 h in a time-dependent manner, and its level of protein expression increased progressively in 24 h. To verify the neuroprotective effect of CYGB, a gene transfection technique was employed. Cygb cDNA and shRNA delivery adenovirus systems were established (Cygb-cDNA-ADV and Cygb-shRNA-ADV, respectively) and injected into the brains of 3-day-old rats 4 days before they were induced with HI treatment. Rats from different groups were euthanized 24 h post-HI, and brain samples were harvested. 2,3,5-Triphenyltetrazolium chloride, TUNEL, and Nissl staining indicated that an up-regulation of CYGB resulted in reduced acute brain injury. The superoxide dismutase level was found to be dependent on expression of CYGB. The Morris water maze test in 28-day-old rats demonstrated that CYGB expression was associated with improvement of long term cognitive impairment. Studies also demonstrated that CYGB can up-regulate mRNA and protein levels of VEGF and increase both the density and diameter of the microvessels but inhibits activation of caspase-2 and -3. Thus, this is the first in vivo study focusing on the neuroprotective role of CYGB. The reduction of neonatal HI injury by CYGB may be due in part to antioxidant and antiapoptotic mechanisms and by promoting angiogenesis.

VEGF-A is necessary and sufficient for retinal neuroprotection in models of experimental glaucoma

Vascular endothelial growth factor A (VEGF-A) is a validated therapeutic target in several angiogenic- and vascular permeability–related pathological conditions, including certain cancers and potentially blinding diseases, such as age-related macular degeneration and diabetic retinopathy. We and others have shown that VEGF-A also plays an important role in neuronal development and neuroprotection, including in the neural retina. Antagonism of VEGF-A function might therefore present a risk to neuronal survival as a significant adverse effect. Herein, we demonstrate that VEGF-A acts directly on retinal ganglion cells (RGCs) to promote survival. VEGF receptor-2 signaling via the phosphoinositide-3-kinase/Akt pathway was required for the survival response in isolated RGCs. These results were confirmed in animal models of staurosporine-induced RGC death and experimental hypertensive glaucoma. Importantly, we observed that VEGF-A blockade significantly exacerbated neuronal cell death in the hypertensive glaucoma model. Our findings highlight the need to better define the risks associated with use of VEGF-A antagonists in the ocular setting.

Vascular endothelial growth factor modulates voltage-gated Na(+) channel properties and depresses action potential firing in cultured rat hippocampal neurons

Vascular endothelial growth factor (VEGF), an angiogenic factor, was found to modulate synaptic plasticity by affecting K(+) and Ca(2+) channels and protect neuron from death by depressing glutamatergic transmission. However, whether VEGF also modulates neuronal activity through modulating voltage-gated Na(+) channels (VGSCs), a main determinant of neuronal excitability, we observed the effects of VEGF on Na(+) channel properties and function on cultured rat hippocampal neurons through whole-cell patch-clamp recording. We found that VEGF decreased the Na(+) channel excitability by shifting the voltage-dependence of steady-state inactivation to more hyperpolarized direction, and increasing the time constants of recovery from inactivation without significantly affecting the activation process. The effect of VEGF on Na(+) channel steady-state inactivation was inhibited by the specific VEGF Flk-1 receptor antagonist SU1498, but was not affected by protein kinase C (PKC)-activator 1-oleoyl-2-acetyl-sn-glycerol (OAG). Furthermore, the inhibition of Na(+) currents by VEGF was frequency-dependent. In addition, the frequency of neuron firing evoked by current injection was reversibly depressed by VEGF. Therefore, our results suggest a potential role of VGSCs in the modulation of VEGF on neuronal excitability.

Age-related decrease in cerebrovascular-derived neuroprotective proteins: effect of acetaminophen

As the population ages, the need for effective methods to maintain brain function in older adults is increasingly pressing. Vascular disease and neurodegenerative disorders commonly co-occur in older persons. Cerebrovascular products contribute to the neuronal milieu and have important consequences for neuronal viability. In this regard vascular derived neuroprotective proteins, Such as vascular endothelial growth factor (VEGF), pigment epithelium-derived factor (PEDF), and pituitary adenylate cyclase activating peptide (PACAP) are important for maintaining neuronal viability, especially in the face of injury and disease. The objective of this study is to measure and compare levels of VEGF, PEDF and PACAP released from isolated brain microvessels of Fischer 344 rats at 6, 12, 18, and 24 months of age. Addition of acetaminophen to isolated brain microvessels is employed to determine whether this drug affects vascular expression of these neuroprotective proteins. Experiments on cultured brain endothelial cells are performed to explore the mechanisms/mediators that regulate the effect of acetaminophen on endothelial cells. The data indicate cerebrovascular expression of VEGF, PEDF and PACAP significantly decreases with age. The age-associated decrease in VEGF and PEDF is ameliorated by addition of acetaminophen to isolated brain microvessels. Also, release of VEGF, PEDF, and PACAP from cultured brain endothelial cells decreases with exposure to the oxidant stressor menadione. Acetaminophen treatment upregulates VEGF, PEDF and PACAP in brain endothelial cells exposed to oxidative stress. The effect of acetaminophen on cultured endothelial cells is in part inhibited by the selective thrombin inhibitor hirudin. The results of this study suggest that acetaminophen may be a useful agent for preserving cerebrovascular function. If a low dose of acetaminophen can counteract the decrease in vascular-derived neurotrophic factors evoked by age and oxidative stress, this drug might be useful for improving brain function in the elderly.