Neuroprotection of ischemic brain by vascular endothelial growth factor is critically dependent on proper dosage and may be compromised by angiogenesis

The protective effects of Axitinib on blood-brain barrier dysfunction and ischemia-reperfusion injury in acute ischemic stroke

BACKGROUND AND PURPOSE

The pathophysiological features of acute ischemic stroke (AIS) often involve dysfunction of the blood-brain barrier (BBB), characterized by the degradation of tight junction proteins (Tjs) leading to increased permeability. This dysfunction can exacerbate cerebral injury and contribute to severe complications. The permeability of the BBB fluctuates during different stages of AIS and is influenced by various factors. Developing effective therapies to restore BBB function remains a significant challenge in AIS treatment. High levels of vascular endothelial growth factor (VEGF) in the early stages of AIS have been shown to worsen BBB breakdown and stroke progression. Our study aimed to investigate the protective effects of the VEGF receptor inhibitor Axitinib on BBB dysfunction and cerebral ischemia/reperfusion-induced injury.

METHODS

BEnd3 cell exposed to oxygen-glucose deprivation (OGD) model was constructed to estimate pharmacological activity of Axitinib (400 ng/ml) on anti-apoptosis and pathological barrier function recovery. In vivo, rats were subjected to a 1 h transient middle cerebral artery occlusion and 23 h reperfusion (tMCAO/R) to investigate the permeability of BBB and cerebral tissue damage. Axitinib was administered through the tail vein at the beginning of reperfusion. BBB integrity was assessed by Evans blue leakage and the expression levels of Tjs claudin-5 and occludin.

RESULTS

Our research revealed that co-incubation with Axitinib enhanced the cell viability of OGD-insulted bEnd3 cells, decreased LDH leakage rate, and suppressed the expression of apoptosis-related proteins cytochrome C and Bax. Axitinib also mitigated the damage to Tjs and facilitated the restoration of transepithelial electrical resistance in OGD-insulted bEnd.3 cells. In vivo, Axitinib administration reduced intracerebral Evans blue leakage and up-regulated the expression of Tjs in the penumbra brain tissue in tMCAO/R rats. Notably, 10 mg/kg Axitinib exerted a significant anti-ischemic effect by decreasing cerebral infarct volume and brain edema volume, improving neurological function, and reducing pro-inflammatory cytokines IL-6 and TNF-α in the brain.

CONCLUSIONS

Our study highlights Axitinib as a potent protectant of blood-brain barrier function, capable of promoting pathological blood-brain barrier recovery through VEGF inhibition and increased expression of tight junction proteins in AIS. This suggests that VEGF antagonism within the first 24 h post-stroke could be a novel therapeutic approach to enhance blood-brain barrier function and mitigate ischemia-reperfusion injury.

VEGF and Neuronal Survival

Vascular endothelial growth factor (VEGF) is well known for its angiogenic activity, but recent evidence has revealed a neuroprotective action of this factor on injured or diseased neurons. In the present review, we summarize the most relevant findings that have contributed to establish a link between VEGF deficiency and neuronal degeneration. At issue, 1) mutant mice with reduced levels of VEGF show adult-onset muscle weakness and motoneuron degeneration resembling amyotrophic lateral sclerosis (ALS), 2) administration of VEGF to different animal models of motoneuron degeneration improves motor performance and ameliorates motoneuronal degeneration, and 3) there is an association between low plasmatic levels of VEGF and human ALS. Altogether, the results presented in this review highlight VEGF as an essential motoneuron neurotrophic factor endowed with promising therapeutic potential for the treatment of motoneuron disorders.

The Circadian System Is Essential for the Crosstalk of VEGF-Notch-mediated Endothelial Angiogenesis in Ischemic Stroke

Ischemic stroke is a major public health problem worldwide. Although the circadian clock is involved in the process of ischemic stroke, the exact mechanism of the circadian clock in regulating angiogenesis after cerebral infarction remains unclear. In the present study, we determined that environmental circadian disruption (ECD) increased the stroke severity and impaired angiogenesis in the rat middle cerebral artery occlusion model, by measuring the infarct volume, neurological tests, and angiogenesis-related protein. We further report that Bmal1 plays an irreplaceable role in angiogenesis. Overexpression of Bmal1 promoted tube-forming, migration, and wound healing, and upregulated the vascular endothelial growth factor (VEGF) and Notch pathway protein levels. This promoting effect was reversed by the Notch pathway inhibitor DAPT, according to the results of angiogenesis capacity and VEGF pathway protein level. In conclusion, our study reveals the intervention of ECD in angiogenesis in ischemic stroke and further identifies the exact mechanism by which Bmal1 regulates angiogenesis through the VEGF-Notch1 pathway.

The Association of Biochemical and Genetic Biomarkers in VEGF Pathway with Depression

VEGF is an important neurotrophic and vascular factor involved in mental disorders. The objective of this study was to verify the effect of genetic polymorphisms in the VEGF pathway on the risk for depression, symptom intensity, and suicide attempts. To examine the association between the VEGF pathway and depression, we genotyped polymorphisms and measured the plasma concentrations of VEGF, KDR, and FLT1 proteins. The participants were 160 patients with depression and 114 healthy controls. The questionnaires that assessed the clinical profile of the patients were the MINI-International Neuropsychiatric Interview, GRID-HAMD₂₁, CTQ, BSI, and the number of suicide attempts. Genotyping of participants was performed using the real-time PCR and protein measurements were performed using the enzyme-linked immunosorbent assay (ELISA). VEGF and its inhibitors were reduced in depression. Individuals with depression and displaying the homozygous AA of the rs699947 polymorphism had higher plasma concentrations of VEGF (p-value = 0.006) and were associated with a greater number of suicide attempts (p-value = 0.041). Individuals with depression that were homozygous for the G allele of the FLT1 polymorphism rs7993418 were associated with lower symptom severity (p-value = 0.040). Our results suggest that VEGF pathway polymorphisms are associated with the number of suicide attempts and the severity of depressive symptoms.

VEGF is an essential retrograde trophic factor for motoneurons

VEGF was initially discovered due to its angiogenic activity and therefore named "vascular endothelial growth factor." However, its more recently discovered neurotrophic activity may be evolutionarily more ancient. Our previous work showed that all the changes produced by axotomy on the firing activity and synaptic inputs of abducens motoneurons were completely restored after VEGF administration. Therefore, we hypothesized that the lack of VEGF delivered by retrograde transport from the periphery should also affect the physiology of otherwise intact abducens motoneurons. For VEGF retrograde blockade, we chronically applied a neutralizing VEGF antibody to the lateral rectus muscle. Recordings of extracellular single-unit activity and eye movements were made in alert cats before and after the application of the neutralizing antibody. Our data revealed that intact, noninjured abducens motoneurons retrogradely deprived of VEGF exhibited noticeable changes in their firing pattern. There is a general decrease in firing rate and a significant reduction in eye position and eye velocity sensitivity (i.e., a decrease in the tonic and phasic components of their discharge, respectively). Moreover, by means of confocal immunocytochemistry, motoneurons under VEGF blockade showed a marked reduction in the density of afferent synaptic terminals contacting with their cell bodies. Altogether, the present findings demonstrate that the lack of retrogradely delivered VEGF renders abducens motoneurons into an axotomy-like state. This indicates that VEGF is an essential retrograde factor for motoneuronal synaptic drive and discharge activity.

Snake venom vascular endothelial growth factors (svVEGFs): Unravelling their molecular structure, functions, and research potential

Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis, a physiological process characterized by the formation of new vessels from a preexisting endothelium. VEGF has also been implicated in pathologic states, such as neoplasias, intraocular neovascular disorders, among other conditions. VEGFs are distributed in seven different families: VEGF-A, B, C, D, and PIGF (placental growth factor), which are identified in mammals; VEGF-E, which are encountered in viruses; and VEGF-F or svVEGF (snake venom VEGF) described in snake venoms. This is the pioneer review of svVEGF family, exploring its distribution among the snake venoms, molecular structure, main functions, and potential applications.

Proteomic Characterization of Human Neural Stem Cells and Their Secretome During in vitro Differentiation

Cell therapies represent a promising approach to slow down the progression of currently untreatable neurodegenerative diseases (e.g., Alzheimer's and Parkinson's disease or amyotrophic lateral sclerosis), as well as to support the reconstruction of functional neural circuits after spinal cord injuries. In such therapies, the grafted cells could either functionally integrate into the damaged tissue, partially replacing dead or damaged cells, modulate inflammatory reaction, reduce tissue damage, or support neuronal survival by secretion of cytokines, growth, and trophic factors. Comprehensive characterization of cells and their proliferative potential, differentiation status, and population purity before transplantation is crucial to preventing safety risks, e.g., a tumorous growth due to the proliferation of undifferentiated stem cells. We characterized changes in the proteome and secretome of human neural stem cells (NSCs) during their spontaneous (EGF/FGF2 withdrawal) differentiation and differentiation with trophic support by BDNF/GDNF supplementation. We used LC-MS/MS in SWATH-MS mode for global cellular proteome profiling and quantified almost three thousand cellular proteins. Our analysis identified substantial protein differences in the early stages of NSC differentiation with more than a third of all the proteins regulated (including known neuronal and NSC multipotency markers) and revealed that the BDNF/GDNF support affected more the later stages of the NSC differentiation. Among the pathways identified as activated during both spontaneous and BDNF/GDNF differentiation were the HIF-1 signaling pathway, Wnt signaling pathway, and VEGF signaling pathway. Our follow-up secretome analysis using Luminex multiplex immunoassay revealed significant changes in the secretion of VEGF and IL-6 during NSC differentiation. Our results further demonstrated an increased expression of neuropilin-1 as well as catenin β-1, both known to participate in the regulation of VEGF signaling, and showed that VEGF-A isoform 121 (VEGF121), in particular, induces proliferation and supports survival of differentiating cells.

VEGF Modulates the Neural Dynamics of Hippocampal Subregions in Chronic Global Cerebral Ischemia Rats

Theta and gamma rhythms in hippocampus are important to cognitive performance. The cognitive impairments following cerebral ischemia is linked with the dysfunction of theta and gamma oscillations. As the primary mechanism for learning and memory, synaptic plasticity is in connection with these neural oscillations. Although vascular endothelial growth factor (VEGF) is thought to protect synaptic function in the ischemia rats to relieve cognitive impairment, little has been done on its effect of neural dynamics with this process. The present study investigated whether the alternation of neural oscillations in the hippocampus of ischemia rats is one of the potential neuroprotective mechanisms of VEGF. Rats were treated with the intranasal administration of VEGF at 72 h following chronic global cerebral ischemia procedure. Then local field potentials (LFPs) in hippocampal CA1 and CA3 regions were recorded and analyzed. Our results showed that VEGF can improve the power of theta and gamma rhythms in CA1 region after ischemia. Chronic global cerebral ischemia reduced the theta-gamma phase-amplitude coupling (PAC) not only within CA1 area but also in the pathway from CA3 to CA1, while VEGF alleviated the decreased coupling strength. Despite these notable differences, there were no obvious changes in the PAC within CA3 region. Surprisingly, the ischemia state did not affect the phase-phase interaction of hippocampus. In conclusion, our findings demonstrated that VEGF enhanced the theta-gamma PAC strength of CA3-CA1 pathway in ischemia rats, which may futher improve the information transmission within the hippocampus. These results illustrated the potential electrophysiologic mechanism of VEGF on cognitive improvement.

Serum vascular endothelial growth factor as a biomarker for prognosis of minor ischemic stroke

Objectives Although vascular endothelial growth factor (VEGF) is a well-known molecule involved with neuronal survival and angiogenesis. there are no prospective studies directed at evaluating a potential association between serum VEGF and minor ischemic stroke. The goal of this study was to investigate the utility of serum VEGF as an index for assessing the 90-day prognosis of minor ischemic stroke patients. Methods Records of acute minor stroke patients (N = 225) and those of age- and gender-matched healthy control subjects (N = 225) were prospectively reviewed. Clinical, laboratory, and imaging data were evaluated. Serum samples collected from these stroke patients immediately after admission were assessed for VEGF levels and compared with those of control subjects. Results Serum VEGF levels were significantly increased in stroke patients (40.01 ± 16.48 pg/mL) as compared with those of controls (32.98 ± 10.35 pg/mL). No statistically significant differences in serum VEGF levels were obtained among the three stroke subtypes analyzed in this study (large-artery atherosclerosis, small-artery occlusion and other types of brain infarction). Multivariate regression analysis revealed that serum VEGF levels and cerebral artery stenosis ≥ 50 % were independently associated with an unfavorable outcome. Unfavorable outcome rates were significantly greater in stroke patients showing VEGF levels in the upper quartiles of the distribution, and these VEGF levels were found to serve as a significant predictor of unfavorable outcomes in these minor ischemic stroke patients. Conclusion Increased serum VEGF may serve as an independent predictor of an unfavorable outcome in minor ischemic stroke.

A Single Intraventricular Injection of VEGF Leads to Long-Term Neurotrophic Effects in Axotomized Motoneurons

Vascular endothelial growth factor (VEGF) has been recently demonstrated to induce neuroprotective and synaptotrophic effects on lesioned neurons. Hitherto, the administration of VEGF in different animal models of lesion or disease has been conducted following a chronic protocol of administration. We questioned whether a single dose of VEGF, administered intraventricularly, could induce long-term neurotrophic effects on injured motoneurons. For this purpose, we performed in cats the axotomy of abducens motoneurons and the injection of VEGF into the fourth ventricle in the same surgical session and investigated the discharge characteristics of axotomized and treated motoneurons by single-unit extracellular recordings in the chronic alert preparation. We found that injured motoneurons treated with a single VEGF application discharged with normal characteristics, showing neuronal eye position (EP) and velocity sensitivities similar to control, thereby preventing the axotomy-induced alterations. These effects were present for a prolonged period of time (50 d) after VEGF administration. By confocal immunofluorescence we also showed that the synaptic stripping that ensues lesion was not present, rather motoneurons showed a normal synaptic coverage. Moreover, we demonstrated that VEGF did not lead to any angiogenic response pointing to a direct action of the factor on neurons. In summary, a single dose of VEFG administered just after motoneuron axotomy is able to prevent for a long time the axotomy-induced firing and synaptic alterations without any associated vascular sprouting. We consider that these data are of great relevance due to the potentiality of VEGF as a therapeutic agent in neuronal lesions and diseases.

Dynamic Changes in miR-126 Expression in the Hippocampus and Penumbra Following Experimental Transient Global and Focal Cerebral Ischemia-Reperfusion

miR-126 which is considered one of the most important miRNAs for maintaining vascular integrity, plays an important role in neuroprotection after cerebral ischemia-reperfusion (I-R). Moreover, vascular endothelial growth factor A (VEGFA), sprouty-related EVH1 domain-containing protein 1 (SPRED1), and Raf-1 are also involved in physiological processes of vascular endothelial cells (ECs). This study investigated how miR-126 changes with reperfusion time in different brain tissues after global cerebral ischemia and focal cerebral ischemia and examined the underlying mechanism miR-126 involving VEGFA, SPRED1, and Raf-1 after I-R. The results indicated decreases in the levels of miR-126-3p and miR-126-5p expression in mice and gerbils after I-R, consistent with the results after oxygen and glucose deprivation and reperfusion (OGD/R) in PC12 cells. Glial cells were activated as neuronal damage gradually increased after I-R. Inhibition of miR-126-3p exacerbated the OGD/R-induced cell death and reduced cell viability. After miR-126-3p inhibition, the levels of SPRED1 and VEGFA expression were increased, and p-Raf-1 expression was decreased after OGD/R. Moreover, based on the intervention of miR-126-3p inhibition, we found that the expression of p-Raf-1 was significantly increased after the intervention of siSPRED1, while it was not statistically significant after intervention of siVEGFA. The reduction of miR-126 expression after global and focal cerebral ischemia exacerbated neuronal death, which was closely related to increasing the SPRED1 activation and inhibiting the Raf-1 expression.

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 ischemic post-conditioning on neuronal VEGF regulation and microglial polarization in a rat model of focal cerebral ischemia

Ischemic postconditioning is increasingly being investigated as a therapeutic approach for cerebral ischemia. However, the majority of studies are focused on the acute protection of neurons per se. Whether and how postconditioning affects multiple cells in the recovering neurovascular unit remains to be fully elucidated. Here, we asked whether postconditioning may modulate help-me signaling between injured neurons and reactive microglia. Rats were subjected to 100 min of focal cerebral ischemia, then randomized into a control versus postconditioning group. After 3 days of reperfusion, infarct volumes were significantly reduced in animals treated with postconditioning, along with better neurologic outcomes. Immunostaining revealed that ischemic postconditioning increased expression of vascular endothelial growth factor (VEGF) in neurons within peri-infarct regions. Correspondingly, we confirmed that VEGFR2 was expressed on Iba1-positive microglia/macrophages, and confocal microscopy showed that in postconditioned rats, these cells were polarized to a ramified morphology with higher expression of M2-like markers. Treating rats with a VEGF receptor 2 kinase inhibitor negated these effects of postconditioning on microglia/macrophage polarization. In vitro, postconditoning after oxygen-glucose deprivation up-regulated VEGF release in primary neuron cultures, and adding VEGF to microglial cultures partly shifted their M2-like markers. Altogether, our findings support the idea that after postconditioning, injured neurons may release VEGF as a 'help-me' signal that promotes microglia/macrophage polarization into potentially beneficial phenotypes.

The Janus Face of VEGF in Stroke

The family of vascular endothelial growth factors (VEGFs) are known for their regulation of vascularization. In the brain, VEGFs are important regulators of angiogenesis, neuroprotection and neurogenesis. Dysregulation of VEGFs is involved in a large number of neurodegenerative diseases and acute neurological insults, including stroke. Stroke is the main cause of acquired disabilities, and normally results from an occlusion of a cerebral artery or a hemorrhage, both leading to focal ischemia. Neurons in the ischemic core rapidly undergo necrosis. Cells in the penumbra are exposed to ischemia, but may be rescued if adequate perfusion is restored in time. The neuroprotective and angiogenic effects of VEGFs would theoretically make VEGFs ideal candidates for drug therapy in stroke. However, contradictory to what one might expect, endogenously upregulated levels of VEGF as well as the administration of exogenous VEGF is detrimental in acute stroke. This is probably due to VEGF-mediated blood–brain-barrier breakdown and vascular leakage, leading to edema and increased intracranial pressure as well as neuroinflammation. The key to understanding this Janus face of VEGF function in stroke may lie in the timing; the harmful effect of VEGFs on vessel integrity is transient, as both VEGF preconditioning and increased VEGF after the acute phase has a neuroprotective effect. The present review discusses the multifaceted action of VEGFs in stroke prevention and therapy.

Synaptic loss and firing alterations in Axotomized Motoneurons are restored by vascular endothelial growth factor (VEGF) and VEGF-B

Vascular endothelial growth factor (VEGF), also known as VEGF-A, was discovered due to its vasculogenic and angiogenic activity, but a neuroprotective role for VEGF was later proven for lesions and disorders. In different models of motoneuronal degeneration, VEGF administration leads to a significant reduction of motoneuronal death. However, there is no information about the physiological state of spared motoneurons. We examined the trophic role of VEGF on axotomized motoneurons with recordings in alert animals using the oculomotor system as the experimental model, complemented with a synaptic study at the confocal microscopy level. Axotomy leads to drastic alterations in the discharge characteristics of abducens motoneurons, as well as to a substantial loss of their synaptic inputs. Retrograde delivery of VEGF completely restored the discharge activity and synaptically-driven signals in injured motoneurons, as demonstrated by correlating motoneuronal firing rate with motor performance. Moreover, VEGF-treated motoneurons recovered a normal density of synaptic boutons around motoneuronal somata and in the neuropil, in contrast to the low levels of synaptic terminals found after axotomy. VEGF also reduced the astrogliosis induced by axotomy in the abducens nucleus to control values. The administration of VEGF-B produced results similar to those of VEGF. This is the first work demonstrating that VEGF and VEGF-B restore the normal operating mode and synaptic inputs on injured motoneurons. Altogether these data indicate that these molecules are relevant synaptotrophic factors for motoneurons and support their clinical potential for the treatment of motoneuronal disorders.

Therapeutic hypothermia for ischemic stroke; pathophysiology and future promise

Therapeutic hypothermia, or cooling of the body or brain for the purposes of preserving organ viability, is one of the most robust neuroprotectants at both the preclinical and clinical levels. Although therapeutic hypothermia has been shown to improve outcome from related clinical conditions, the significance in ischemic stroke is still under investigation. Numerous pre-clinical studies of therapeutic hypothermia has suggested optimal cooling conditions, such as depth, duration, and temporal therapeutic window for effective neuroprotection. Several studies have also explored mechanisms underlying the mechanisms of neuroprotection by therapeutic hypothermia. As such, it appears that cooling affects multiple aspects of brain pathophysiology, and regulates almost every pathway involved in the evolution of ischemic stroke. This multifaceted mechanism is thought to contribute to its strong neuroprotective effect. In order to carry out this therapy in optimal clinical settings, methodological and pathophysiological understanding is crucial. However, more investigation is still needed to better understand the underlying mechanisms of this intervention, and to overcome clinical barriers which seem to preclude the routine use therapeutic hypothermia in stroke. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

The Role of Endothelial Progenitor Cells in Ischemic Cerebral and Heart Diseases

Ischemic heart and cerebral diseases are complex clinical syndromes. Endothelial dysfunction caused by dysfunctional endothelial progenitor cells (EPCs) is thought to play a major role in pathophysiology of both types of disease. Healthy EPCs may be able to replace the dysfunctional endothelium through endogenous repair mechanisms. EPC levels are changed in patients with ischemic cerebrovascular and cardiovascular disease and EPCs may play a role in the pathophysiology of these diseases. EPCs are also a marker for preventive and therapeutic interventions. Homing of EPCs to ischemic sites is a mechanism of ischemic tissue repair, and molecules such as stromal-derived factor-1 and integrin may play a role in EPC homing in ischemic disease. Potentiation of the function and numbers of EPCs as well as combining EPCs with other pharmaceutical agents may improve the condition of ischemia patients. However, the precise role of EPCs in ischemic heart and cerebral disease and their therapeutic potential still remain to be explored. Here, we discuss the identification, mobilization, and clinical implications of EPCs in ischemic diseases.

Intracerebral Transplantation of Genetically Engineered Cells for Parkinson's Disease: Toward Clinical Application

Over the last decade, molecular biology has progressively developed, leading to new technology with subsequent clinical application for various cerebral diseases including Parkinson's disease (PD), one of the most investigated neurodegenerative disorders. The therapy for PD is mainly composed of medication, including drug replacement therapy, surgical treatment, and cell transplantation. Cell therapy for PD has been explored by using fetal nigral cells as an allo- or xenograft, autologous sympathetic ganglion, adrenal medulla, and carotid body in clinical settings. In addition, neurotrophic factors, including glial cell line-derived neurotrophic factor (GDNF), have a strong potency to rescue degenerating dopaminergic cells. Protein and/or gene therapy also might be a therapeutic option for PD. In this review, genetically engineered cell transplantation for animal models of PD, including catecholamine/neurotrophic factor-secreting cell transplantation with or without encapsulation, as performed in our laboratories, and their potential future as clinical applications are described with recent clinical studies in this field.

Catalpol stimulates VEGF production via the JAK2/STAT3 pathway to improve angiogenesis in rats' stroke model

ETHNOBOTANICAL RELEVANCE

Catalpol is the main active component of the radix from Rehmannia glutinosa Libosch, which has pleiotropic protective effects in neurodegenerative diseases, ischemic stroke, metabolic disorders and others

AIM

Catalpol has been shown to have neuroprotective, neurorepair, and angiogenesis effects following ischemic brain injury. However, its molecular mechanisms are still poorly understood. In previous studies, the JAK2/STAT3 signaling pathway was found to play a role in neuroprotection and angiogenesis. This study investigated the role of catalpol in stimulating angiogenesis via the JAK2/STAT3 pathway after permanent focal cerebral ischemia (pMCAO).

METHODS

Rats were subjected to right middle cerebral artery occlusion through electrocoagulation and were treated with catalpol (5mg/kg), AG490 was also used to inhibit STAT3 phosphorylation (pSTAT3).

RESULTS

Following stroke, Catalpol improved the neuroethology deficit, increased the cerebral blood flow (CBF) of infarcted brain and upregulated EPO and EPOR. AG490 suppressed the phosphorylation of signal transducer and activator of transcription 3 (STAT3), ultimately inhibited VEGF mRNA expression, which reduced VEGF protein expression and inhibited stroke-induced angiogenesis. However, Catalpol enhanced stroke-induced STAT3 activation and subsequently restored STAT3 activity through the recovery of STAT3 binding to VEGF. Moreover, Catalpol reversed the effect of AG490 on STAT3 activation and nuclear translocation, restored the transcriptional activity of the VEGF promoter by recruiting STAT3 to the VEGF promoter, improved VEGF mRNA and protein expression, increased angiogenesis, reduced the difference in CBF between the infarcted and intact brain and ameliorated the neuroethology behaviors after stroke.

CONCLUSION

Catalpol affects neuroprotection and angiogenesis via the JAK2/STAT3 signaling pathway, which is mediated by STAT3 activation and VEGF expression. Catalpol may be used as a potential therapeutic drug for stroke.

Inhibition of Vascular Endothelial Growth Factor Receptor 2 Exacerbates Loss of Lower Motor Neurons and Axons during Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE) are inflammatory demyelinating and neurodegenerative diseases in the central nervous system (CNS). It is believed that MS and EAE are initiated by autoreactive T lymphocytes that recognize myelin antigens; however, the mechanisms responsible for neurodegeneration in these diseases remain elusive. Data indicate that vascular endothelial growth factor A (VEGF-A) plays a role in the development of MS and EAE. Interestingly, VEGF-A is regarded as a neurotrophic factor in the CNS that promotes neuron survival and neurogenesis in various neurodegenerative diseases by activating VEGF receptor 2 (VEGFR2). In this study, we sought to explore the role of the VEGF-A/VEGFR2 signaling in neurodegeneration in MS and EAE. We showed that the expression of VEGF-A was decreased in the spinal cord during EAE and that VEGFR2 was activated in lower motor neurons in the spinal cord of EAE mice. Interestingly, we found that treatment with SU5416, a selective VEGFR2 inhibitor, starting after the onset of EAE clinical symptoms exacerbated lower motor neuron loss and axon loss in the lumbar spinal cord of mice undergoing EAE, but did not alter Purkinje neuron loss in the cerebellum or upper motor neuron loss in the cerebral cortex. Moreover, SU5416 treatment had a minimal effect on EAE clinical symptoms as well as inflammation, demyelination, and oligodendrocyte loss in the lumbar spinal cord. These results imply the protective effects of the VEGF-A/VEGFR2 signaling on lower motor neurons and axons in the spinal cord in MS and EAE.

Ethyl 3,4-dihydroxybenzoate (EDHB): a prolyl hydroxylase inhibitor attenuates acute hypobaric hypoxia mediated vascular leakage in brain

Sudden exposure to altitude hypoxia is responsible for acute mountain sickness (AMS) in un-acclimatized persons. If not treated in time, AMS can worsen and leads to high altitude cerebral edema, which can be fatal. Present study explores the efficacy of ethyl 3,4-dihydroxybenzoate (EDHB), a prolyl hydroxylase enzyme inhibitor, in modulating adaptive responses to hypobaric hypoxia (HH) in rat brain. Male Sprague-Dawley rats treated with EDHB (75 mg/kg for 3 days), were subjected to acute HH exposure at 9144 m (30,000 ft) for 5 h. Animals were assessed for transvascular leakage and edema formation in brain and role of key inflammatory markers along with hypoxia responsive genes. HH stress increased transvascular permeability and edema formation in conjunction with upregulation of nuclear factor-κB (NF-κB) and its regulated proteins. There was surge in pro-inflammatory cytokines tumor necrosis factor-α, interleukin-6, interferon-γ, monocyte chemoattractant protein-1 and decrement in anti-inflammatory cytokine interleukin-10. Further, upregulation of vascular endothelial growth factor (VEGF), a vascular permeability marker and down-regulation of antioxidant and anti-inflammatory proteins hemoxygenase (HO-1) and metallothionein (MT-1) was also observed under hypoxia. EDHB supplementation effectively scaled down HH induced cerebral edema with concomitant downregulation of brain NF-κB expression. There was significant curtailment of pro-inflammatory cytokines and cell adhesion molecules. There was significant downregulation of permeability factor VEGF by EDHB with concomitant increment in hypoxia inducible factor (HIF1α) and anti-inflammatory proteins HO-1 and MT-1 compared to HH control thus accentuating the potential of EDHB as effective hypoxic preconditioning agent in ameliorating HH mediated injury in brain.

Ischemic preconditioning protects against ischemic brain injury

In this study, we hypothesized that an increase in integrin α_vβ₃ and its co-activator vascular endothelial growth factor play important neuroprotective roles in ischemic injury. We performed ischemic preconditioning with bilateral common carotid artery occlusion for 5 minutes in C57BL/6J mice. This was followed by ischemic injury with bilateral common carotid artery occlusion for 30 minutes. The time interval between ischemic preconditioning and lethal ischemia was 48 hours. Histopathological analysis showed that ischemic preconditioning substantially diminished damage to neurons in the hippocampus 7 days after ischemia. Evans Blue dye assay showed that ischemic preconditioning reduced damage to the blood-brain barrier 24 hours after ischemia. This demonstrates the neuroprotective effect of ischemic preconditioning. Western blot assay revealed a significant reduction in protein levels of integrin α_vβ₃, vascular endothelial growth factor and its receptor in mice given ischemic preconditioning compared with mice not given ischemic preconditioning 24 hours after ischemia. These findings suggest that the neuroprotective effect of ischemic preconditioning is associated with lower integrin α_vβ₃ and vascular endothelial growth factor levels in the brain following ischemia.

Neuroprotective effects of Ilexonin A following transient focal cerebral ischemia in rats

Ilexonin A is a compound isolated from the root of a plant commonly used in traditional Chinese medicine. The aim of the present study was to investigate the possible protective mechanism of Ilexonin A in rats subjected to occlusion of the middle cerebral artery (MCAO). Transient focal cerebral ischemia was induced by 2 h of MCAO, followed by reperfusion. Ilexonin A at doses of 20, 40 and 80 mg/kg were administered via intraperitoneal injection immediately following ischemia/reperfusion. The expression levels of glial fibrillary acidic protein (GFAP), ionized calcium‑binding adapter molecule‑1 (Iba‑1), vascular endothelial growth factor (VEGF), fetal liver kinase‑1 (Flk‑1) and Nestin were examined using immunostaining and Western blot analysis of the peri‑infarct region following ischemia/reperfusion. Ilexonin A significantly decreased the infarct volume and improved neurological deficits in a dose‑dependent manner. The expression levels of VEGF, Flk‑1 and Nestin were significantly increased in the rats treated with Ilexonin A, compared with the rats administered with saline. Following treatment with Ilexonin A, a higher number of GFAP‑positive astrocytes were found in the Ilexonin A‑treated rats at 1, 3 and 7 days, compared with the rats exposed to ischemia only, however, there were fewer astrocytes at 14 days, compared with the ischemia group. Ilexonin A significantly decreased the protein expression of Iba‑1. The results of the present study suggested that the protective effects of Ilexonin A were associated with revascularization, neuronal regeneration, and the regulation of astrocyte and microglia cell activation.

Impacts of N-Butylphthalide on expression of growth factors in rats with focal cerebral ischemia

This study investigates the impacts of n-butylphthalide (NBP) on the expression of vascular endothelial growth factor (VEGF) and transforming growth factor-β1 (TGF-β1) in rats with focal cerebral ischemia. The thread embolization method was used to prepare the rat model of cerebral ischemia-reperfusion (CIR). The animals were divided into a sham operation group, a model control group and NBP treatment group. The NBP group was orally administered 25 mg/kg NBP twice a day after the surgery. The immunohistochemistry and reverse transcription-polymerase chain reaction were performed to observe the protein and mRNA expressions of VEGF and TGF-β 16 hours, 1 day and 2 days after inducing CIR. The mRNA and protein expressions of VEGF and TGF-β1 in the model control group and the NBP treatment group were all increased after CIR, and those of the NBP treatment group at each post-CIR time point were higher than the model control group (p < 0.01). After CIR, the expressions of VEGF and TGF-β1 increased, suggesting that VEGF and TGF-β1 exhibited protective effects towards the ischemic brain injuries, and that NBP could upregulate the expressions of VEGF and TGF-β1 in the peri-infarcted area, thus possibly protecting the ischemic brain tissues through this mechanism.

Neuroprotective Effect of VEGF-Mimetic Peptide QK in Experimental Brain Ischemia Induced in Rat by Middle Cerebral Artery Occlusion

We investigated the effect of the VEGF-mimetic peptide, QK, on ischemic brain damage and on blood-brain barrier permeability in the rat. QK administered by the intracerebroventricular, intravenous, or intranasal route caused a 40% decrease in ischemic brain damage induced by permanent occlusion of the middle cerebral artery relative to that in controls. No increase in the volume of the ischemic hemisphere compared to that of the contralateral nonischemic hemisphere was observed in rats treated with QK, suggesting that this peptide did not cause brain edema. The effect of QK on vessel permeability was evaluated by intravital pial microvessel videoimaging, a technique that allows the pial vessels to be visualized through a surgically prepared open cranial window. The results showed that QK did not cause any leakage of intravenously injected fluorescein-dextran conjugates after intracarotid administration or topical application to the brain cortex. Collectively, these data suggest that QK may exert neuroprotective activity in the context of stroke without promoting any increase in vascular permeability. Because VEGF's neuroprotective activity may be overshadowed by the appearance of brain edema and microbleeds, QK could represent a significant step forward in stroke treatment.

Vascular endothelial growth factor-A mRNA gene expression in clinical phases of multiple sclerosis

Background

Vascular endothelial growth factor A stimulates angiogenesis, but is also pro-inflammatory and plays an important role in the development of neurological disease. This study aimed to investigate whether vascular endothelial growth factor A mRNA expression could be used as a marker for the prediction of susceptibility to multiple sclerosis and relate vascular endothelial growth factor to the clinical phases of multiple sclerosis.

Methods

This was a cross-sectional study, consisting of a total of 60 subjects with multiple sclerosis and 20 healthy controls. Subjects were subjected to history taking, neurological examination and peripheral blood sampling for vascular endothelial growth factor A mRNA gene expression. Vascular endothelial growth factor A gene expression was measured by real-time polymerase chain reaction using the SYBR Green technique.

Results

Vascular endothelial growth factor A mRNA gene expression level was significantly lower in the multiple sclerosis group than in the healthy control group ( P < 0.001). Vascular endothelial growth factor A mRNA gene expression level was higher in relapsing remitting multiple sclerosis (RRMS) patients than in those in remission ( P < 0.001) and in relapsing remitting multiple sclerosis compared with secondary progressive multiple sclerosis ( P < 0.001). There was no correlation between vascular endothelial growth factor A gene expression levels and duration of disease, multiple sclerosis progression index or expanded disability status scale.

Conclusions

A lower vascular endothelial growth factor A mRNA gene expression level was independently associated with a higher risk of multiple sclerosis.

Endothelin-1 increases the expression of VEGF-R1/Flt-1 receptors in rat cultured astrocytes through ETB receptors

Expressions of vascular endothelial growth factor (VEGF) receptors in astrocytes are increased in damaged brains. To clarify the regulatory mechanisms of VEGF receptors, the effects of endothelin-1 (ET-1) were examined in rat cultured astrocytes. Expressions of VEGF-R1 and -R2 receptor mRNA were at similar levels, whereas the mRNA expressions of VEGF-R3 and Tie-2, a receptor for angiopoietins, were lower. Placenta growth factor, a selective agonist of the VEGF-R1 receptor, induced phosphorylation of focal adhesion kinase (FAK) and extracellular signal regulated kinase 1/2 (ERK1/2). Phosphorylations of FAK and ERK 1/2 were also stimulated by VEGF-E, a selective VEGF-R2 agonist. Increased phosphorylations of FAK and ERK1/2 by VEGF165 were reduced by selective antagonists for VEGF-R1 and -R2. Treatment with ET-1 increased VEGF-R1 mRNA and protein levels. The effects of ET-1 on VEGF-R1 mRNA were mimicked by Ala(1,3,11,15) -ET-1, a selective agonist for ETB receptors, and inhibited by BQ788, an ETB antagonist. ET-1 did not affect the mRNA levels of VEGF-R2, -R3, and Tie-2. Pre-treatment with ET-1 potentiated the effects of placenta growth factor on phosphorylations of FAK and ERK1/2. These findings suggest that ET-1 induces up-regulation of VEGF-R1 receptors in astrocytes, and potentiates VEGF signals in damaged nerve tissues. To clarify the regulatory mechanisms of vascular endothelial growth factor (VEGF) receptors, the effects of endothelin-1 (ET-1) were examined in rat cultured astrocytes. Effects of selective VEGF-R1 and R2 agonist showed that these receptors were linked to focal adhesion kinase (FAK) and extracellular signal regulated kinase 1/2 (ERK1/2). Treatment with ET-1 increased expression of VEGF-R1, which was mediated by ETB receptors. Pre-treatment with ET-1 potentiated the VEGF-R1-mediated activations of FAK and ERK1/2. These findings suggest that ET-1 induces up-regulation of VEGF-R1 receptors in astrocytes.

Role of vascular endothelial growth factor and other growth factors in post-stroke recovery

Stroke is a major health problem world-wide and its burden has been rising in last few decades. Until now tissue plasminogen activator is only approved treatment for stroke. Angiogenesis plays a vital role for striatal neurogenesis after stroke. Administration of various growth factors in an early post ischemic phase, stimulate both angiogenesis and neurogenesis and lead to improved functional recovery after stroke. However vascular endothelial growth factors (VEGF) is the most potent angiogenic factor for neurovascularization and neurogenesis in ischemic injury can be modulated in different ways and thus can be used as therapy in stroke. In response to the ischemic injury VEGF is released by endothelial cells through natural mechanism and leads to angiogenesis and vascularization. This release can also be up regulated by exogenous administration of Mesenchymal stem cells, by various physical therapy regimes and electroacupuncture, which further potentiate the efficacy of VEGF as therapy in post stroke recovery. Recent published literature was searched using PubMed and Google for the article reporting on methods of up regulation of VEGF and therapeutic potential of growth factors in stroke.

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.

Distinct roles of endogenous vascular endothelial factor receptor 1 and 2 in neural protection after spinal cord injury

Secondary degeneration after spinal cord injury (SCI) is caused by increased vascular permeability, infiltration of inflammatory cells, and subsequent focal edema. Therapeutic interventions using neurotrophic factors have focused on the prevention of such reactions to reduce cell death and promote tissue regeneration. Vascular endothelial growth factor (VEGF) is a potent angiogenic and vascular permeability factor. However, the effect of VEGF on SCI remains controversial. VEGF signaling is primarily regulated through two primary receptors, VEGF receptor 1 (VEGF-R1) and VEGF receptor 2 (VEGF-R2). The purpose of this study was to examine the effects of intraperitoneal administration of VEGF-R1- and VEGF-R2-neutralizing antibodies on a mouse model of SCI. VEGF-R1 blockade, but not VEGF-R2 blockade, decreased the permeability and infiltration of inflammatory cells, and VEGF-R2 blockade caused a significant increase in neuronal apoptosis in the acute phase of SCI. VEGF-R2 blockade decreased the residual tissue area and the number of neural fibers in the chronic phase of SCI. VEGF-R2 blockade worsened the functional recovery and prolonged the latency of motor evoked potentials. These data suggest that endogenous VEGF-R2 plays a crucial role in neuronal protection after SCI.

SMND-309, a novel derivative of salvianolic acid B, protects rat brains ischemia and reperfusion injury by targeting the JAK2/STAT3 pathway

SMND-309 is a novel derivative of salvianolic acid B, and has shown protective effects against rat cortical neuron damage in vitro and in vivo. However the molecular mechanisms through which SMND-309 affords this protection are unclear. The present study aimed to investigate the mechanisms associated with the protective activities of SMND-309 in a cerebral ischemia and reperfusion injury rat model. In this study, we used AG490, a specific inhibitor of the signaling pathway involving the Janus Kinase 2 (JAK2)/Signal Transducers and Activators of Transcription 3 (STAT3) signaling molecules and suramin, a potent inhibitor of vascular endothelial growth factor (VEGF), to investigate the mechanisms of SMND-309. The cerebral ischemia and reperfusion injury model was induced by performing middle cerebral artery occlusion (MCAO) in the rats. SMND-309 mitigated the effects of ischemia and reperfusion injury on brain by decreasing the infract volume, improving neurological function, increasing the survival of neurons and promoting angiogenesis by increasing the levels of erythropoietin (EPO), erythropoietin receptor (EPOR), phosphorylated JAK2 (P-JAK2), phosphorylated STAT3 (P-STAT3), VEGF and VEGF receptor 2 (Flk-1) in the brain. Our results suggest that SMND-309 provides significant neuroprotective effects against cerebral ischemia and reperfusion injury. The mechanisms of this protection may be attributed to the increased VEGF expression occurring from the JAK2/STAT3 pathway, activated by the increased EPO/EPOR expression in the brain.

The impact of experimental preconditioning using vascular endothelial growth factor in stroke and subarachnoid hemorrhage

Vascular endothelial growth factor (VEGF) stimulating angiogenesis was shown to be a potential novel therapeutic approach for the treatment of ischemic vascular diseases. The goal of the present study was to examine whether transfection of VEGF before occurrence of major stroke (part I) and cerebral vasospasm after experimental subarachnoid hemorrhage (SAH; part II) develops neuroprotective qualities. A total of 25 (part I) and 26 (part II) brains were analyzed, respectively. In part one, a significant reduction of infarct volume in the VEGF-treated stroke animals (43% reduction, P < 0.05) could be detected. In part two, significant vasospasm was induced in all hemorrhage groups (P < 0.02). Analyzing microperfusion, a significant higher amount of perfused vessels could be detected (P < 0.01), whereas no significant effect could be detected towards macroperfusion. Histologically, no infarctions were observed in the VEGF-treated SAH group and the sham-operated group. Minor infarction in terms of vasospasm-induced small lesions could be detected in the control vector transduced group (P = 0.05) and saline-treated group (P = 0.09). The present study demonstrates the preconditioning impact of systemic intramuscular VEGF injection in animals after major stroke and induced severe vasospasm after SAH.

Transplantation of adipose-derived stem cells is associated with neural differentiation and functional improvement in a rat model of intracerebral hemorrhage

AIMS

To examine whether transplantation of adipose-derived stem cells (ADSCs) induces neural differentiation and improves neural function in a rat intracerebral hemorrhage (ICH) model.

METHODS

Adipose-derived stem cells cells were isolated from inguinal fat pad of rat. ICH was induced by injection of collagenase type IV into the right basal ganglia of rat. Forty-eight hours after ICH, ADSCs cells (10 μL of 2-4 × 10(7) cells/mL) were injected into the right lateral cerebral ventricle. The differentiation of ADSCs was detected in vitro and in vivo. The neural function was evaluated with Zea Longa 5-grade scale at day 1, 3, 7, 14, or 28.

RESULTS

Our data demonstrated that ADSCs differentiated into cells that shared the similarities of neurons or astrocytes in vitro. Transplantation of ADSCs decreased cell apoptosis and the transplanted ADSCs were able to differentiate into neuron-like and astrocyte-like cells around the hematoma, accompanied with upregulation of vascular endothelial growth factor expression and improvement of neural function.

CONCLUSIONS

Our data suggest that transplantation of ADSCs could be a therapeutic approach for ICH stroke.

Thrombin activity associated with neuronal damage during acute focal ischemia

Mechanisms of ischemic neuronal and vascular injury remain obscure. Here we test the hypothesis that thrombin, a blood-borne coagulation factor, contributes to neurovascular injury during acute focal ischemia. Stroke was induced in adult Sprague Dawley rats by occluding the middle cerebral artery. Intra-arterial thrombin infusion during ischemia significantly increased vascular disruption and cellular injury. Intravenous infusion of argatroban, a direct thrombin inhibitor, alleviated neurovascular injury. Immunostaining showed thrombin on neurons in the ischemic core. Using an activatable cell-penetrating peptide engineered to detect thrombin activity, we discovered that thrombin proteolytic activity was specifically associated with neuronal damage during ischemia. Protease activated receptor-1, the presumptive thrombin receptor, appeared to mediate ischemic neurovascular injury. Furthermore, rats receiving thrombin during ischemia showed cognitive deficit, whereas rats receiving argatroban retained intact learning and memory. These results suggest a potential role for thrombin contributing to neurovascular injury and several potential avenues for neuroprotection.

Imaging of perfusion, angiogenesis, and tissue elasticity after stroke

Blood flow interruption in a cerebral artery causes brain ischemia and induces dramatic changes of perfusion and metabolism in the corresponding territory. We performed in parallel positron emission tomography (PET) with [(15)O]H(2)O, single photon emission computed tomography (SPECT) with [(99m)Tc]hexamethylpropylene-amino-oxime ([(99m)Tc]HMPAO) and ultrasonic ultrafast shear wave imaging (SWI) during, immediately after, and 1, 2, 4, and 7 days after middle cerebral artery occlusion (MCAO) in rats. Positron emission tomography and SPECT showed initial hypoperfusion followed by recovery at immediate reperfusion, hypoperfusion at day 1, and hyperperfusion at days 4 to 7. Hyperperfusion interested the whole brain, including nonischemic areas. Immunohistochemical analysis indicated active angiogenesis at days 2 to 7, strongly suggestive that hyperperfusion was supported by an increase in microvessel density in both brain hemispheres after ischemia. The SWI detected elastic changes of cerebral tissue in the ischemic area as early as day 1 after MCAO appearing as a softening of cerebral tissue whose local internal elasticity decreased continuously from day 1 to 7. Taken together, these results suggest that hyperperfusion after cerebral ischemia is due to formation of neovessels, and indicate that brain softening is an early and continuous process. The SWI is a promising novel imaging method for monitoring the evolution of cerebral ischemia over time in animals.

Vascular endothelial growth factor (VEGF) and its role in the central nervous system: a new element in the neurotrophic hypothesis of antidepressant drug action

Vascular endothelial growth factor (VEGF) is a well-known cellular mitogen, and a vascular growth factor and permeability regulator. It participates in physiological and pathological processes of angiogenesis and in the development of lymphatic vessels. In addition to the proangiogenic activity, studies of recent years have revealed neurotrophic and neuroprotective potential of VEGF both in the peripheral and central nervous system. VEGF directly influences Schwann cells, neuronal progenitor cells, astrocytes and microglia. This factor plays an import role in developmental processes of the nervous tissue since it is implicated in neurogenesis and the regulation of neuronal development, and in the differentiation and formation of vessels in the brain. VEGF elicits its biological effect via an interaction with three VEGF receptor subtypes: VEGFR1, VEGFR2 and VEGFR3. In the nervous system, VEGFR2 signaling prevails. VEGF as a trophic factor, influencing both vascular endothelial cells and brain cells is a focus of the studies on neuropsychiatric disorders and psychotropic drug action. Antidepressant drugs were shown to induce hippocampal expression of VEGF. In addition, the experiments in animals models of depression have demonstrated that VEGFR2 signaling is indispensable for cellular and behavioral response to antidepressant drugs. Acquiring a deeper knowledge into the signaling pathways engaged in neurogenic and behavioral VEGF actions can unravel new targets for more efficient and quick acting antidepressant drugs.

Paradoxical exacerbation of neuronal injury in reperfused stroke despite improved blood flow and reduced inflammation in early growth response-1 gene-deleted mice

OBJECTIVES

Early growth response gene-1 (Egr-1) coordinates the rapid upregulation of diverse inflammatory and coagulation-related genes following ischemia/reperfusion. Genetic deletion of Egr-1 results in attenuated post-ischemic injury in diverse tissue systems. In the present study, we utilized a murine model of transient middle cerebral artery occlusion to probe the functional effects of Egr-1 deletion following cerebral ischemia/reperfusion.

METHODS

The time course of Egr-1 expression was established by Northern/Western blot analysis, and immunocytochemistry localized Egr-1 to specific cell populations. Flow cytometry was then employed to characterize the ischemic cellular infiltrate of both wild-type (+/+) and Egr-1-null (-/-) mice. Next, the functional effect of Egr-1 deletion was investigated in Egr-1-deficient mice and their wild-type littermates subjected to middle cerebral artery occlusion. Infarct volumes, neurological scores, and reperfusion cerebral blood flow were compared between cohorts.

RESULTS

Rapid upregulation of Egr-1 was observed in the ischemic hemisphere, and localized primarily to neurons and mononuclear cells. Egr-1 deletion led to a suppression of infiltrating neutrophils and activated microglia/macrophages (P<0.001). Additionally, although Egr-1 deletion enhanced post-ischemic cerebral blood flow, Egr-1-deficient mice suffered larger infarcts (P=0.01) and demonstrated a trend towards worse neurological scores (P=0.06) than wild-type controls.

DISCUSSION

Despite a reduction in the proportion of infiltrating inflammatory cells/activated microglia and improvement in post-ischemic reperfusion, Egr-1-deficient animals suffer larger infarcts in our model. Therefore, cerebral Egr-1 expression may function to protect neurons despite its adverse modulatory consequences for inflammation and thrombosis.

The immunology of stroke: from mechanisms to translation

Immunity and inflammation are key elements of the pathobiology of stroke, a devastating illness second only to cardiac ischemia as a cause of death worldwide. While the immune system participates in the brain damage produced by ischemia, the damaged brain, in turn, exerts a powerful immunosuppressive effect that promotes fatal intercurrent infections and threatens the survival of stroke patients. Inflammatory signaling is instrumental in all stages of the ischemic cascade, from the early damaging events triggered by arterial occlusion, to the late regenerative processes underlying post-ischemic tissue repair. Recent developments have revealed that stroke, like multiple sclerosis, engages both innate and adaptive immunity. But, unlike multiple sclerosis, adaptive immunity triggered by newly exposed brain antigens does not have an impact on the acute phase of the damage. Nevertheless, modulation of adaptive immunity exerts a remarkable protective effect on the ischemic brain and offers the prospect of new stroke therapies. However, immunomodulation is not devoid of deleterious side effects, and gaining a better understanding of the reciprocal interaction between the immune system and the ischemic brain is essential to harness the full therapeutic potential of the immunology of stroke.

The expression of VEGF-A is down regulated in peripheral blood mononuclear cells of patients with secondary progressive multiple sclerosis

BACKGROUND

Most patients with relapsing-remitting multiple sclerosis (RRMS) eventually enter a secondary progressive (SPMS) phase, characterized by increasing neurological disability. The mechanisms underlying transition to SPMS are unknown and effective treatments and biomarkers are lacking. Vascular endothelial growth factor-A (VEGF-A) is an angiogenic factor with neuroprotective effects that has been associated with neurodegenerative diseases. SPMS has a prominent neurodegenerative facet and we investigated a possible role for VEGF-A during transition from RRMS to SPMS.

METHODOLOGY/PRINCIPAL FINDINGS

VEGF-A mRNA expression in peripheral blood mononuclear (PBMC) and cerebrospinal fluid (CSF) cells from RRMS (n = 128), SPMS (n = 55) and controls (n = 116) were analyzed using real time PCR. We demonstrate reduced expression of VEGF-A mRNA in MS CSF cells compared to controls (p<0.001) irrespective of disease course and expression levels are restored by natalizumab treatment(p<0.001). VEGF-A was primarily expressed in monocytes and our CSF findings in part may be explained by effects on relative monocyte proportions. However, VEGF-A mRNA expression was also down regulated in the peripheral compartment of SPMS (p<0.001), despite unchanged monocyte counts, demonstrating a particular phenotype differentiating SPMS from RRMS and controls. A possible association of allelic variability in the VEGF-A gene to risk of MS was also studied by genotyping for six single nucleotide polymorphisms (SNPs) in MS (n = 1114) and controls (n = 1234), which, however, did not demonstrate any significant association between VEGF-A alleles and risk of MS.

CONCLUSIONS/SIGNIFICANCE

Expression of VEGF-A in CSF cells is reduced in MS patients compared to controls irrespective of disease course. In addition, SPMS patients display reduced VEGF-A mRNA expression in PBMC, which distinguish them from RRMS and controls. This indicates a possible role for VEGF-A in the mechanisms regulating transition to SPMS. Decreased levels of PBMC VEGF-A mRNA expression should be further evaluated as a biomarker for SPMS.