Inhibition of integrin alphavbeta3 reduces blood-brain barrier breakdown in focal ischemia in rats

α7nACh receptor, a promising target to reduce BBB damage by regulating inflammation and autophagy after ischemic stroke

Increased blood-brain barrier (BBB) permeability can lead to cerebral vasogenic edema and hemorrhagic transformation (HT) after reperfusion with tissue plasminogen activator (tPA), the only United States Food and Drug Administration (FDA)-approved treatment for acute ischemia stroke (AIS). The therapeutic benefits of tPA after AIS are partially outweighed by a more than a six-fold increase in the risk of symptomatic intracerebral hemorrhage. Therefore, strategies to protect the integrity of BBB are urgently needed to reduce HT and vasogenic edema after tPA thrombolysis or endovascular thrombectomy. Interestingly, an NIH study showed that smokers treated with tPA had a significantly lower prevalence of brain hemorrhage than nonsmokers, suggesting that cigarette smoking may protect patients treated with tPA from the side effects of cerebral hemorrhage. Importantly, we recently showed that treatment with nicotine reduces AIS-induced BBB damage and that modulating α7nAChR by modulation could reduce ischemia/reperfusion-induced BBB damage, suggesting that α7nAChR could be a potential target to reduce BBB after AIS. In this review, we first provide an overview of stroke and the impact of α7nAChR activation on BBB damage. Next, we discuss the features and mechanism of BBB destruction after AIS. We then discuss the effect of nicotine effect on BBB integrity as well as the mechanism underlying those effects. Finally, we discuss the side effects and potential strategies for modulating α7nAChR to reduce AIS-induced BBB damage.

Cell-specific expression and function of laminin at the neurovascular unit

Laminin, a major component of the basal lamina (BL), is a heterotrimeric protein with many isoforms. In the CNS, laminin is expressed by almost all cell types, yet different cells synthesize distinct laminin isoforms. By binding to its receptors, laminin exerts a wide variety of important functions. However, due to the reciprocal and cell-specific expression of laminin in different cells at the neurovascular unit, its functions in blood-brain barrier (BBB) maintenance and BBB repair after injury are not fully understood. In this review, we focus on the expression and functions of laminin and its receptors in the neurovascular unit under both physiological and pathological conditions. We first briefly introduce the structures of laminin and its receptors. Next, the expression and functions of laminin and its receptors in the CNS are summarized in a cell-specific manner. Finally, we identify the knowledge gap in the field and discuss key questions that need to be answered in the future. Our goal is to provide a comprehensive overview on cell-specific expression of laminin and its receptors in the CNS and their functions on BBB integrity.

Female-specific neuroprotection after ischemic stroke by vitronectin-focal adhesion kinase inhibition

We found that blood vitronectin (VTN) leaks into the brain and exacerbates tissue loss after stroke by increasing pro-inflammatory IL-6 expression in female, but not male, mice. VTN signals through integrins and downstream focal adhesion kinase (FAK). Here, a two day systemic treatment with a small molecule FAK inhibitor starting 6 h after middle cerebral artery occlusion reduced ipsilateral brain injury size by ∼40-45% at 7 and 14 d, as well as inflammation and motor dysfunction in wild-type female, but not male, mice. FAK inhibition also reduced IL-6 expression in the injured female striatum at 24 h by 62%. Inducible selective gene deletion of FAK in astrocytes also reduced acute IL-6 expression by 72% only in females, and mitigated infarct size by ∼80% and inflammation at 14 d after stroke. Lastly, VTN-/- females had better outcomes, but FAK inhibitor treatment had no additional protective or anti-inflammatory effects. Altogether, this suggests that VTN is detrimental in females primarily through FAK and that FAK inhibition provides neuroprotection (cerebroprotection) by reducing VTN-induced IL-6 expression in astrocytes. Thus, VTN signaling can be targeted to mitigate harmful inflammation with relevance to treatments for women with ischemic stroke, who often have worse outcomes than men.

VEGF, a Key Factor for Blood Brain Barrier Injury After Cerebral Ischemic Stroke

Blood brain barrier (BBB) injury is an important factor affecting the prognosis of ischemic stroke. Extensive research on BBB injury has revealed that blood vessels and neural networks are interdependent and interrelated during and after the development of the brain. An array of signaling molecules, known as angioneurins, can affect both blood vessels and neural networks simultaneously. Angioneurins not only regulate the angiogenesis and remodeling process of the vascular system, but also act as neurotrophic and neuroprotective factors, or serve as guide molecules for axons. Vascular endothelial growth factor (VEGF) is a type of angioneurin that is expressed in neurons, astrocytes, macrophages, and vascular endothelial cells in ischemic and hypoxic brain tissues after cerebral ischemia. VEGF can increase and induce the destruction of the endothelial barrier in the early stages of cerebral ischemia. Both the upregulation of endogenous VEGF levels and the use of exogenous VEGF are harmful in the acute stage of stroke. However, the harmful effects of VEGF on vascular integrity are transient. Several studies have shown that VEGF regulates angiogenesis, neurogenesis, neurite growth and brain edema after cerebral ischemia. Therefore, it is crucial to understand the dual role of VEGF in ischemic stroke. The following will focus on the damage caused by VEGF to the BBB in the context of cerebral ischemic stroke, as well as therapeutic studies targeting VEGF.

EGCG Promotes Neurite Outgrowth through the Integrin β1/FAK/p38 Signaling Pathway after Subarachnoid Hemorrhage

The abnormal neurites have long been regarded as the main player contributing to the poor outcome of patients with subarachnoid hemorrhage (SAH). (-)-Eigallocatechin-3-gallate (EGCG), the major biological component of tea catechin, exhibited strong neuroprotective effects against central nervous system diseases; however, the role of EGCG-mediated neurite outgrowth after SAH has not been delineated. Here, the effect of reactive oxygen species (ROS)/integrin β1/FAK/p38 pathway on neurite outgrowth was investigated. As expected, oxyhemoglobin- (OxyHb-) induced excessive ROS level was significantly reduced by EGCG as well as antioxidant N-acetyl-l-cysteine (NAC). Consequently, the expression of integrin β1 was significantly inhibited by EGCG and NAC. Meanwhile, EGCG significantly inhibited the overexpression of phosphorylated FAK and p38 to basal level after SAH. As a result, the abnormal neurites and cell injury were rescued by EGCG, which eventually increased energy generation and neurological score after SAH. These results suggested that EGCG promoted neurite outgrowth after SAH by inhibition of ROS/integrin β1/FAK/p38 signaling pathway. Therefore, EGCG might be a new pharmacological agent that targets neurite outgrowth in SAH therapy.

Repairing blood-CNS barriers: Future therapeutic approaches for neuropsychiatric disorders

Central nervous system (CNS) drug development faces significant difficulties that translate into high rates of failure and lack of innovation. The pathophysiology of neurological and psychiatric disorders often results in the breakdown of blood-CNS barriers, disturbing the CNS microenvironment and worsening disease progression. Therefore, restoring the integrity of blood-CNS barriers may have a beneficial influence in several CNS disorders and improve treatment outcomes. In this review, pathways that may be modulated to protect blood-CNS barriers from neuroinflammatory and oxidative insults are featured. First, the participation of the brain endothelium and glial cells in disruption processes is discussed. Then, the relevance of regulatory systems is analysed, specifically the hypothalamic-pituitary axis, the renin-angiotensin system, sleep and circadian rhythms, and glutamate neurotransmission. Lastly, compounds of endogenous and exogenous origin that are known to mediate the repair of blood-CNS barriers are presented. We believe that enhancing the protection of blood-CNS barriers is a promising therapeutic strategy to pursue in the future.

Mechanisms in blood-brain barrier opening and metabolism-challenged cerebrovascular ischemia with emphasis on ischemic stroke

Stroke is the leading cause of disability among adults as well as the 2nd leading cause of death globally. Ischemic stroke accounts for about 85% of strokes, and currently, tissue plasminogen activator (tPA), whose therapeutic window is limited to up to 4.5 h for the appropriate population, is the only FDA approved drug in practice and medicine. After a stroke, a cascade of pathophysiological events results in the opening of the blood-brain barrier (BBB) through which further complications, disabilities, and mortality are likely to threaten the patient's health. Strikingly, tPA administration in eligible patients might cause hemorrhagic transformation and sustained damage to BBB integrity. One must, therefore, delineate upon stroke onset which cellular and molecular factors mediate BBB permeability as well as what key roles BBB rupture plays in the pathophysiology of stroke. In this review article, given our past findings of mechanisms underlying BBB opening in stroke animal models, we elucidate cellular, subcellular, and molecular factors involved in BBB permeability after ischemic stroke. The contribution of each factor to stroke severity and outcome is further discussed. Determinant factors in BBB permeability and stroke include mitochondria, miRNAs, matrix metalloproteinases (MMPs), immune cells, cytokines, chemokines, and adhesion proteins. Once these factors are interrogated and their roles in the pathophysiology of stroke are determined, novel targets for drug discovery and development can be uncovered in addition to novel therapeutic avenues for human stroke management.

A Novel Octapeptide Derived From G Protein-Coupled Receptor 124 Improves Cognitive Function Via Pro-Angiogenesis In A Rat Model Of Chronic Cerebral Hypoperfusion-Induced Vascular Dementia

PURPOSE

The lack of effective therapies mandates the development of new treatment strategies for vascular dementia (VaD). G protein-coupled receptor 124 (GPR124) may be a therapeutic target for angiogenesis-related diseases of CNS, including VaD. The GCPF peptide is a truncated and screened fragment of the GPR124 extracellular domain. The potential use of GCPF for VaD treatment, angiogenesis and targeting of integrin αvβ3 are evaluated.

METHODS AND RESULTS

First, the in vivo results indicated that the GCPF peptide could decrease mean escape latency and increase platform crossing times in BCCAO rats. Second, the in vitro and ex vivo results indicated that the GCPF peptide was an active angiogenic peptide and could promote hCMEC/D3 cell migration and adhesion to ECM molecules. Third, in silico analyses predicted that GCPF could specifically interact with integrin αvβ3; the ∆G of GCPF binding to the binding pocket was -16.402 KJ/mol. The molecular characteristics indicated that highly hydrophilic GCPF with a pI of 11.70 had a short half-life in mammals (~1 hr). Finally, the ELISA experiments indicated that low dissociation constant (Kd= 2.412±0.455 nM) corresponds to the high affinity of GCPF for integrin αvβ3.

CONCLUSION

The data indicate that adhesion of GCPF immobilized on ECM surface to endothelial cells via integrin αvβ3 modulates cellular functions to promote angiogenesis and improve cognitive function. This is the first report to prove that GCPF, a novel octapeptide, may be an effective strategy for VaD therapy.

Sex differences in the expression of cell adhesion molecules on microvesicles derived from cultured human brain microvascular endothelial cells treated with inflammatory and thrombotic stimuli

Background

There are sex differences in risk for stroke and small vessel ischemic disease in the brain. Microvesicles (MV) derived from activated cells vary by cell of origin and the stimulus initiating their release. MV released from cells activated by inflammatory and thrombotic factors have the potential to disrupt endothelial cells of the brain microvasculature. Therefore, experiments were designed to identify sex differences in the phenotype of MV released from cultured human brain microvascular endothelial cells (HBMEC) in response to inflammatory and thrombotic stimuli.

Methods

Cultured HBMEC derived from 20- to 30-year-old male and female donors were treated for 20 h with medium supplemented with tumor necrosis factor alpha (TNFα; 20 ng/ml), thrombin (THR; 2 U/ml), or vehicle (i.e., control). MV were isolated from the conditioned media by high-speed centrifugation and quantified by digital flow cytometry by labeling with fluorophore-conjugated primary antibodies against PECAM-1, integrin αvβ3, ICAM-1, E-selectin, or MCAM. In addition, temporal uptake of labeled MV into control HBMEC was examined by confocal microscopy.

Results

Under control conditions, male HBMEC released fewer MV expressing each antigen, except for PECAM-1, than female cells (P < 0.05). Neither TNFα nor THR reduced cell viability. However, TNFα induced apoptosis in female and male cells, whereas THR increased apoptosis marginally only in male cells. TNFα increased expression of all antigens tested on MV in male cells, but only increased expression of integrin αvβ3, ICAM-1, and E-selectin on MV from female cells. THR increased expression of PECAM-1, ICAM-1, and MCAM-1 on MV from male but not female cells. MV were internalized and localized to lysosomes within 90 min after their application to HBMEC.

Conclusions

There are sex differences in expression of cell adhesion molecules on MV released from HBMEC under control conditions and upon activation by TNFα or THR. MV taken up by unstimulated HBMEC may impact the integrity of the brain microvasculature and account, in part, for sex differences in vascular pathologies in the brain.

Roles of blood-brain barrier integrins and extracellular matrix in stroke

Ischemicstroke is a leading cause of death and disability in the United States, but recent advances in treatments [i.e., endovascular thrombectomy and tissue plasminogen activator (t-PA)] that target the stroke-causing blood clot, while improving overall stroke mortality rates, have had much less of an impact on overall stroke morbidity. This may in part be attributed to the lack of therapeutics targeting reperfusion-induced injury after the blood clot has been removed, which, if left unchecked, can expand injury from its core into the surrounding at risk tissue (penumbra). This occurs in two phases of increased permeability of the blood-brain barrier, a physical barrier that under physiologic conditions regulates brain influx and efflux of substances and consists of tight junction forming endothelial cells (and transporter proteins), astrocytes, pericytes, extracellular matrix, and their integrin cellular receptors. During, embryonic development, maturity, and following stroke reperfusion, cerebral vasculature undergoes significant changes including changes in expression of integrins and degradation of surrounding extracellular matrix. Integrins, heterodimers with α and β subunits, and their extracellular matrix ligands, a collection of proteoglycans, glycoproteins, and collagens, have been modestly studied in the context of stroke compared with other diseases (e.g., cancer). In this review, we describe the effect that various integrins and extracellular matrix components have in embryonic brain development, and how this changes in both maturity and in the poststroke environment. Particular focus will be on how these changes in integrins and the extracellular matrix affect blood-brain barrier components and their potential as diagnostic and therapeutic targets for ischemic stroke.

Preparation and Characterization of Functionalized Graphene Oxide Carrier for siRNA Delivery

A successful siRNA delivery system is dependent on the development of a good siRNA carrier. Graphene oxide (GO) has gained great attention as a promising nanocarrier in recent years. It has been reported that GO could be used to deliver a series of drugs including synthetic compounds, proteins, antibodies, and genes. Our previous research indicated that functionalized GO could deliver siRNA into tumor cells and induce a gene silencing effect, to follow up the research, in this research, GO-R8/cRGDfV(GRcR) was designed and prepared for VEGF-siRNA delivery as a novel carrier. The Zeta potential and particle size of the new designed GRcR carrier was measured at (29.46 ± 5.32) mV and (135.7 ± 3.3) nm respectively, and after transfection, the VEGF mRNA level and protein expression level were down-regulated by 48.22% (p < 0.01) and 38.3% (p < 0.01) in HeLa cells, respectively. The fluorescent images of the treated BALB/c nude mice revealed that GRcR/VEGF-siRNA could conduct targeted delivery of VEGF-siRNA into tumor tissues and showed a gene silencing effect as well as a tumor growth inhibitory effect (p < 0.01) in vivo. Further studies showed that GRcR/VEGF-siRNA could effectively inhibit angiogenesis by suppressing VEGF expression. Histology and immunohistochemistry studies demonstrated that GRcR/VEGF-siRNA could inhibit tumor tissue growth effectively and have anti-angiogenesis activity, which was the result of VEGF protein downregulation. Both in vitro and in vivo results demonstrated that GRcR/VEGF-siRNA could be used as an ideal nonviral tumor-targeting vector for VEGF-siRNA delivery in gene therapy.

Fc-saxatilin suppresses hypoxia-induced vascular leakage by regulating endothelial occludin expression

Vascular leakage due to compromised integrity of the endothelial barrier is closely associated with brain damage in several neurological disorders, including ischaemic stroke. Saxatilin, a snake venom disintegrin containing the Arg-Gly-Asp (RGD) motif, exerts thrombolytic and antiplatelet effects by interacting with multiple integrins on platelets. Integrin signalling is indispensable for regulation of endothelial permeability. Saxatilin may play a role in vascular leakage after ischaemia because it has high affinity for endothelial integrins. Here, we determined whether Fc-saxatilin, an Fc-fusion protein of saxatilin, could prevent vascular leakage under hypoxic or ischaemic conditions. In mouse brain microvascular endothelial cells, hypoxia increased the permeability to FITC-dextran, and this effect was attenuated by Fc-saxatilin treatment. Fc-saxatilin also blocked vascular leakage of Evans Blue in the ischaemic brain induced by middle cerebral artery occlusion in mice. Furthermore, the expression of occludin, a tight junction protein, was reduced by hypoxia in endothelial cells. This downregulation of occludin was attenuated by Fc-saxatilin treatment. We also determined the activity of matrix metalloproteinases (MMPs) 2 and 9 because they are implicated in the degradation of occludin and of the microvascular basal lamina. Hypoxia increased MMP-9 activity, and this increase was attenuated by Fc-saxatilin treatment. Fc-saxatilin specifically bound to integrin α_vβ₃ of the endothelial cells and inhibited hypoxia-induced activation of FAK, a downstream signalling molecule in integrin-dependent signal transduction. Taken together, these results provide new insights into the mechanism via which Fc-saxatilin, as an integrin antagonist, prevents vascular leakage under ischemic conditions by regulating occludin expression in endothelial tight junctions.

LXW7 ameliorates focal cerebral ischemia injury and attenuates inflammatory responses in activated microglia in rats

Inflammation plays a pivotal role in ischemic stroke, when activated microglia release excessive pro-inflammatory mediators. The inhibition of integrin αvβ3 improves outcomes in rat focal cerebral ischemia models. However, the mechanisms by which microglia are neuroprotective remain unclear. This study evaluated whether post-ischemic treatment with another integrin αvβ3 inhibitor, the cyclic arginine-glycine-aspartic acid (RGD) peptide-cGRGDdvc (LXW7), alleviates cerebral ischemic injury. The anti-inflammatory effect of LXW7 in activated microglia within rat focal cerebral ischemia models was examined. A total of 108 Sprague-Dawley rats (250–280 g) were subjected to middle cerebral artery occlusion (MCAO). After 2 h, the rats were given an intravenous injection of LXW7 (100 μg/kg) or phosphate-buffered saline (PBS). Neurological scores, infarct volumes, brain water content (BWC) and histology alterations were determined. The expressions of pro-inflammatory cytokines [tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β)], and Iba1-positive activated microglia, within peri-ischemic brain tissue, were assessed with ELISA, western blot and immunofluorescence staining. Infarct volumes and BWC were significantly lower in LXW7-treated rats compared to those in the MCAO + PBS (control) group. The LXW7 treatment lowered the expression of pro-inflammatory cytokines. There was a reduction of Iba1-positive activated microglia, and the TNF-α and IL-1β expressions were attenuated. However, there was no difference in the Zea Longa scores between the ischemia and LXW7 groups. The results suggest that LXW7 protected against focal cerebral ischemia and attenuated inflammation in activated microglia. LXW7 may be neuroprotective during acute MCAO-induced brain damage and microglia-related neurodegenerative diseases.

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.

Rosiglitazone ameliorates astrocyte over-activation and inflammatory cytokine release induced by global cerebral ischemia/reperfusion

Global cerebral ischemia (GCI) is a leading cause of mortality worldwide and remains the primary cause of long-term neurological disability. Astrocyte over-activation and extensive neuron loss in the ischemic brain are the characteristic pathological features of cerebral ischemia. Rosiglitazone (RSG) is a peroxisome-proliferating activating receptor-γ agonist known for its anti-inflammatory activity. Previous studies have suggested that RSG is able to exert neuroprotection in numerous acute and chronic brain injury models. However, whether RSG treatment is involved in astrocyte over-activation and inflammatory reaction in the cortex remains unclear. The aim of the present study was to investigate whether RSG treatment improved functional impairment induced following GCI and protected against cortex neuron loss, and to elucidate the potential mechanisms underlying these functions. Rats were randomly divided into three groups: Sham-operated, GCI and RSG treatment groups. The RSG treatment group was treated with 2 mg/kg RSG immediately following GCI. The results demonstrated that RSG treatment significantly reduced infarct volume and neuron survival rates in addition to increasing function recovery. Furthermore, these results correlate with a reduction in astrocyte over-activation and inflammatory cytokines in the rat cortex. However, no significant changes in glutamate transporter-1 expression levels were observed following RSG treatment compared with the GCI rats. The results of this investigation provide in vivo evidence that RSG significantly protected rats against ischemia-reperfusion-induced brain injury. In addition, RSG may exert neuroprotective effects by inhibiting astrocyte over-activation, and thereby reducing the levels of inflammatory cytokines in the GCI-injured brain. All data revealed that RSG may be a potential neuroprotective agent for cerebral ischemia.

Protective role of isoflurane pretreatment in rats with focal cerebral ischemia and the underlying molecular mechanism

Inflammation and immunity are important in the pathogenesis of cerebral ischemia. Toll-like receptor 4 (TLR4) is involved in the inflammatory responses of injured brain tissues. Emerging studies have focused on the effect of isoflurane (ISO) pretreatment on cerebral ischemia, however, the association between ISO pretreatment and TLR4 during cerebral ischemia remains to be elucidated. In the present study, the protective role of ISO pretreatment in rats with focal cerebral ischemia reperfusion was investigated and the molecular mechanism was discussed. Using a middle cerebral artery occlusion (MCAO) model, triphenyltetrazolium chloride staining was utilized to measure the infarct volume and brain edema and immunofluorescence staining was used to detect the MCAO-induced TLR4 expression and localization. Western blot analyses were conducted to quantify the protein expression levels of TLR4, myeloid differentiation primary response 88 (MyD88) and nuclear factor (NF)-κB in ischemic brain tissue at different time points. The results demonstrated that, following ISO pretreatment, the neurological deficits, brain edema and cerebral infarct size caused by ischemia/reperfusion were attenuated. The astrocyte and microglial activation in the brain tissue was decreased. In addition, the expression levels of TLR4, MyD88 and NF-κB were decreased. The present study indicated that ISO pretreatment may protect the brain from ischemic damage by downregulating the expression levels of TLR4, MyD88 and NF-κB.

Brain endothelial cell specific integrins and ischemic stroke

Ischemic stroke, a devastating event caused by the blockage of a blood vessel(s) supplying the brain, continues to affect thousands of people in the USA every year. While no true advances in stroke therapy have arisen to further improve patient outcomes since the introduction of the blood clot buster tissue plasminogen activator and mechanical clot removal, fewer people are dying from the immediate stroke insult. Instead, patients often suffer significant morbidity due to post-recanalization secondary damage. Central to this damage is the breakdown of the blood-brain barrier, which, in addition to contributing to edema and inflammation, triggers an upregulation in angiogenic growth factors in the brain's attempt to salvage and repair itself. Recent studies have begun to improve our understanding of the post-stroke angiogenic response of brain endothelial cells in the ischemic penumbra, which has long been held to be an important site for medical intervention. These studies suggest that endothelial cell integrin matrix receptors play an important and therapeutically significant role in moderating cellular responses to ischemic brain injury.

Effects of integrins and integrin αvβ3 inhibitor on angiogenesis in cerebral ischemic stroke

Integrins such as αvβ3, α5β1 play a key role in angiogenesis regulation, invasion and metastasis, inflammation, wound healing, etc. The up-regulation of integrin αvβ3 after cerebral ischemic stroke can promote angiogenesis, which in turn improves functional recovery. In addition, the integrin αvβ3 inhibitor can block the blood-brain barrier (BBB) leakage induced by vascular endothelial growth factor (VEGF) and also can reduce inflammatory reaction, decrease the deposition of fibrinogen. Other studies showed that integrin αvβ3 is not essential in revascularization. Therefore, the effect of integrin αvβ3 in the whole process of brain function recovery merits further study.

w007B protects brain against ischemia-reperfusion injury in rats through inhibiting inflammation, apoptosis and autophagy

This study was designed to investigate the effect of w007B, a newly synthesized derivative of honokiol, on MCAO reperfusion, and its therapeutic time window and related mechanisms in rats. Neurological deficit scores, infarct size and brain water content were measured after 24 h reperfusion following 2 h ischemia. The results showed that w007B (10 and 50 μg/kg, IV immediately after reperfusion) markedly decreased neurological deficit scores, reduced infarct size and alleviated brain water content, and then 50 μg/kg w007B given within 3 h after reperfusion (5 h after ischemia) significantly attenuated ischemia-induced brain injury. Additionally, no sign of toxicity was observed when a single dose of 50mg/kg w007B (1000 times of the highest effective dose, IP) was administered. To explore the underlying mechanisms, the expression level of apoptosis, inflammation and autophagy-related markers in brain tissue were detected with kits or by western blot. It was observed that w007B rapidly and significantly reduced caspase-3 activity and NO production in the injured semi-brain, and also lowered the level of the p65 subunit of NF-κB in the nucleus. Besides, it also reduced the expression of Beclin-1 and LC3B-II, and increased the level of p62, the autophagy-related proteins in I/R-injured hemisphere. In conclusion, w007B exerts neuroprotective effect on cerebral ischemia-reperfusion injury with wider therapeutic time window and better safety; its mechanisms may be associated with its anti-inflammation, anti-apoptosis and anti-autophagy action. These results suggest that w007B shows strong potential as a clinical neuroprotective candidate for the treatment of ischemic stroke.

A model of rat embolic cerebral infarction with a quantifiable, autologous arterial blood clot

We developed a novel model of a rat embolic cerebral infarction with a quantifiable autologous arterial blood clot. The left femoral artery had 0.15 ml of blood withdrawn and mixed with 10 units of thrombin in 50 μl saline. After 30 min, the clot was suctioned into a 4-French polyvinyl chloride tube. A 24-gage catheter was inserted up through the internal carotid artery via the external carotid artery stump. The 1-cm clot, at a volume of 7.2 mm3, was pushed and inserted into the internal carotid artery via the catheter. After withdrawing the catheter, the ICA blood flow recovered. We checked neurological status after 24 h (neurological free was 15, and worst was 1) and measured the infarction volume by the TTC method. Twelve rats were examined, and five sham-operated rats were included. Two rats were not able to achieve an 80% reduction in CBF. One rat died due to cerebral infarction. The success rate in producing infarction was 83%. The total infarction volume was 368.5 mm3±61.2 se. Median neurological score was 6. Hemorrhagic transformation was not detected. Sham-operated rats revealed no infarction and no neurological deficit. The volume of infarction correlated significantly with the neurological score. We conclude that this embolic stroke model is useful in producing a human, severe cardioembolic cerebral infarction.

Cilengitide affects tumor compartment, vascularization and microenvironment in experimental bone metastases as shown by longitudinal ¹⁸F-FDG PET and gene expression analysis

PURPOSE

Aim of this study was to investigate the specific treatment effects of inhibiting αvβ3/αvβ5 integrins by cilengitide in an animal model of breast cancer bone metastases using dynamic (18)F-FDG PET and gene expression analysis.

METHODS

For this purpose, nude rats bearing bone metastases were treated with cilengitide, a small molecule inhibitor of αvβ3 and αvβ5 integrins, from day 30 to 55 after tumor cell inoculation of MDA-MB-231 breast cancer cells (25 mg/kg, 5 days per week; n = 8 rats) and compared to control rats (n = 8). Dynamic (18)F-FDG PET data were assessed at days 30, 35 and 55 after tumor cell inoculation determining the vascular fraction VB and the metabolic variables k1-k4. At day 55, genome-wide mRNA expression analysis was performed to assess the treatment-specific expression changes from cilengitide-treated and control rats.

RESULTS

In a longitudinal (18)F-FDG PET study, the vascular fraction VB was significantly decreased in bone metastases between days 30/35, 30/55 and 35/55, whereas the kinetic parameters k1 and k4 were significantly decreased between days 30/55 in skeletal lesions of treated animals. Gene expression analysis from bone metastases at day 55 revealed that tumor-produced integrins (αvβ5) as well as factors relevant for angiogenesis (αvβ3, VEGF, PDGF), bone resorption (PTHrP and RANKL), extracellular matrix remodeling (collagen, CD44) and bone marrow microenvironment (CXCR4) were significantly reduced upon therapy with cilengitide.

CONCLUSIONS

Here, we provide evidence that cilengitide inhibits pivotal factors of all compartments of bone metastases including tumor cells, vasculature and bone microenvironment in vivo and by whole-genome transcriptome analysis.

Astrocytic αVβ3 integrin inhibits neurite outgrowth and promotes retraction of neuronal processes by clustering Thy-1

Thy-1 is a membrane glycoprotein suggested to stabilize or inhibit growth of neuronal processes. However, its precise function has remained obscure, because its endogenous ligand is unknown. We previously showed that Thy-1 binds directly to α(V)β(3) integrin in trans eliciting responses in astrocytes. Nonetheless, whether α(V)β(3) integrin might also serve as a Thy-1-ligand triggering a neuronal response has not been explored. Thus, utilizing primary neurons and a neuron-derived cell line CAD, Thy-1-mediated effects of α(V)β(3) integrin on growth and retraction of neuronal processes were tested. In astrocyte-neuron co-cultures, endogenous α(V)β(3) integrin restricted neurite outgrowth. Likewise, α(V)β(3)-Fc was sufficient to suppress neurite extension in Thy-1(+), but not in Thy-1(-) CAD cells. In differentiating primary neurons exposed to α(V)β(3)-Fc, fewer and shorter dendrites were detected. This effect was abolished by cleavage of Thy-1 from the neuronal surface using phosphoinositide-specific phospholipase C (PI-PLC). Moreover, α(V)β(3)-Fc also induced retraction of already extended Thy-1(+)-axon-like neurites in differentiated CAD cells as well as of axonal terminals in differentiated primary neurons. Axonal retraction occurred when redistribution and clustering of Thy-1 molecules in the plasma membrane was induced by α(V)β(3) integrin. Binding of α(V)β(3)-Fc was detected in Thy-1 clusters during axon retraction of primary neurons. Moreover, α(V)β(3)-Fc-induced Thy-1 clustering correlated in time and space with redistribution and inactivation of Src kinase. Thus, our data indicates that α(V)β(3) integrin is a ligand for Thy-1 that upon binding not only restricts the growth of neurites, but also induces retraction of already existing processes by inducing Thy-1 clustering. We propose that these events participate in bi-directional astrocyte-neuron communication relevant to axonal repair after neuronal damage.

An angiogenic inhibitor, cyclic RGDfV, attenuates MPTP-induced dopamine neuron toxicity

We previously demonstrated that several dopamine (DA) neurotoxins produced punctate areas of FITC-labeled albumin (FITC-LA) leakage in the substantia nigra and striatum suggesting blood brain barrier (BBB) dysfunction. Further, this leakage was co-localized with αvβ3 integrin up-regulation, a marker for angiogenesis. This suggested that the FITC-LA leakage might have been a result of angiogenesis. To assess the possible role of angiogenesis in DA neuron loss, we treated mice with 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine (MPTP) and on the following day treated with cyRGDfV, a cyclic peptide that binds to integrin αvβ3 and prevents angiogenesis. Post-treatment for 3 days (b.i.d.) with cyRGDfV blocked the MPTP-induced upregulation of integrin β3 immunoreactivity (a marker for angiogenesis), leakage of FITC-LA into brain parenchyma (a marker for BBB disruption) as well as the down regulation of Zona Occludin-1 (ZO-1; a marker for tight junction integrity). In addition, cyRGDfV also completely prevented tyrosine hydroxylase immunoreactive cell loss (a marker for DA neurons) and markedly attenuated the up-regulation of activated microglia (Iba1 cell counts and morphology). These data suggest that cyRGDfV, and perhaps other anti-angiogenic drugs, are neuroprotective following acute MPTP treatment and may suggest that compensatory angiogenesis and BBB dysfunction may contribute to inflammation and DA neuron loss.

A novel quantification of blood-brain barrier damage and histochemical typing after embolic stroke in rats

Treatment strategies in acute ischemic stroke are still limited. Considering numerous translation failures, research is tending to a preferred use of human-like animal models, and a more-complex perspective of tissue salvaging involving endothelial, glial and neuronal components according to the neurovascular unit (NVU) concept. During ischemia, blood-brain barrier (BBB) alterations lead to brain edema and hemorrhagic transformation affecting NVU components. The present study aims on a novel quantification method of BBB damage and affected tissue following experimental cerebral ischemia, closely to the human condition. Wistar rats underwent embolic middle cerebral artery occlusion, followed by an intravenous application of fluorescein isothiocyanate (FITC)-tagged albumin (≈70kDa) and/or biotinylated rat IgG (≈150kDa) as BBB permeability markers. Both fluorescent agents revealed similar leakage and allow quantification of BBB permeability by fluorescence microscopy, and after immunohistochemical conversion into a permanent diaminobenzidine label at light-microscopical level. The following markers were identified for sufficient detection of NVU components: Rat endothelial cell antigen-1 (RECA) and laminin for vessels, Lycopersicon esculentum and Griffonia simplicifolia agglutinin for vessels and microglial subpopulations, ionized calcium binding adaptor molecule 1 (Iba1), CD68 and CD11b for macrophages, activated microglia, monocytes and neutrophils, S100β for astroglia, as well as NeuN and HuC/D for neurons. This is the first report confirming the usefulness of simultaneously applied FITC-albumin and biotinylated rat IgG as BBB permeability markers in experimental stroke, and, specifying antibodies and lectins for multiple fluorescence labeling of NVU components. Newly elaborated protocols might facilitate a more-complex outcome measurement in drug development for cerebral ischemia.

Activation of liver X receptor reduces global ischemic brain injury by reduction of nuclear factor-kappaB

Recent studies have found that liver X receptors (LXRs) agonists decrease brain inflammation and exert neuroprotective effect. The aim of this study was to examine the mechanisms of action of liver X receptor agonist GW3965 against brain injury following global cerebral ischemia in the rat. The 48 male SD (Sprague-Dawley) rats were randomly partitioned into three groups: sham, global ischemia (4-vessel occlusion for 15 min; 4VO) treated with vehicle and global ischemia treated with GW3965 (20 mg/kg, via i.p. injection at 10 min after reperfusion). The functional outcome was determined by neurological evaluation at 24 h post ischemia and by testing rats in T maze at 3 and 7 days after reperfusion. The rats' daily body weight, incidence of seizures and 72 h mortality were also determined. After Nissl staining and TUNEL in coronal brain sections, the numbers of intact and damaged cells were counted in the CA1 sector of the hippocampus. The expression of phosphorylated inhibitor of kappaB (p-IkappaBalpha), nuclear factor-kappaB (NF-kappaB) subunit p65, and cyclo-oxygenase-2 (COX-2) were analyzed with Western blot at 12 h after reperfusion. GW3965 tended to reduce 72 h mortality and the incidence of post-ischemic seizures. GW3965-treated rats showed an improved neuronal survivability in CA1 and a significant increase in the percentage of spontaneous alternations detected in T-maze on day 7 after ischemia. GW3965-induced neuroprotection was associated with a significant reduction in nuclear translocation of NF-kB p65 subunit and a decrease in the hippocampal expression of NF-kB target gene, COX-2. LXR receptor agonist protects against neuronal damage following global cerebral ischemia. The mechanism of neuroprotection may include blockade of NF-kappaB activation and the subsequent suppression of COX-2 in the post ischemic brain.

Novel rat middle cerebral artery occlusion model: Trans-femoral artery approach combined with preservation of the external carotid artery

We developed a novel trans-femoral artery approach to the rat middle cerebral artery occlusion model (TF-MCAO) without sacrificing the external carotid artery (ECA) with/without the pterygopalatine artery, which is important for chewing food. To make the TF-MCAO we first dissect the left common carotid artery (CCA), ECA, and internal carotid artery (ICA). Transient occlusion clips are applied to the proximal ECA and the pterygopalatine artery; we never sacrifice the ECA branch. A 24-gage catheter is inserted into the left femoral artery. We insert a slightly bent 0.014in. hydrophilically coated guide wire via a haemostasis valve. Anatomically, the left common carotid artery is located rostral to the descending aorta, permitting a straight-forward, blind approach to the CCA. The guide wire is gently advanced about 17mm from the bifurcation of the CCA until slight resistance is encountered. The guide wire and temporary occlusion clips are withdrawn after 90min. Rats were sacrificed 24h after reperfusion. Eleven rats were examined. One rat died before occlusion due to deep anesthesia. The success rate for producing infarction was 80%. The mean infarction volume of the basal ganglia was 94.4mm(3)+/-9.4 se and mean infarction volume of the cerebral cortex was 124.2mm(3)+/-21.6 se. No rat died due to cerebral infarction and no rat suffered subarachnoid hemorrhage. We conclude that TF-MCAO was useful for producing a cerebral infarction.

Inhibition of integrin alphavbeta3 prevents urokinase plasminogen activator-mediated impairment of cerebrovasodilation after cerebral hypoxia/ischemia

Cerebral hypoxia (10 min) followed immediately by ischemia (20 min) (H/I) impairs cerebrovasodilation in response to hypercapnia and hypotension in the newborn pig; exogenous urokinase plasminogen activator (uPA) potentiates this effect, whereas the blockade of endogenous uPA-mediated vasoactivity prevents it completely. This study investigated the role of integrin alpha(V)beta(3) in the uPA-mediated impairment of cerebrovasodilation after H/I in piglets equipped with a closed cranial window. Pial artery dilation induced by hypercapnia (Pco(2), 75 mmHg) and hypotension (mean arterial blood pressure, decreased by 45%) was blunted after H/I, reversed to vasconstriction in piglets treated with uPA (10(-7) M), a concentration observed in cerebrospinal fluid after H/I, but reverted to a dilation no different than preinsult in piglets administered an anti-alpha(V)beta(3) antibody (10 ng/ml) in addition to uPA (26 +/- 1, 9 +/- 1, -10 +/- 3, and 22 +/- 3% for hypercapnia before H/I, after H/I, after H/I with uPA, and after H/I with combined uPA and anti-alpha(V)beta(3) antibody, respectively). Responses to isoproterenol were unchanged after H/I and combined uPA and anti-alpha(V)beta(3) antibody. Similar results were obtained for the combined administration of uPA with the alpha(V)beta(3) antagonist Arg-Gly-Asp-d-Phe-Val and Arg-Gly-Asp-Ser, but not for the inactive analog Arg-Gly-Asp-Glu-Ser acetate. These data show that the activation of the integrin alpha(V)beta(3) contributes to the uPA-mediated impairment of pial artery dilation after H/I. These data suggest that the inhibition of uPA and integrin signaling may preserve cerebrohemodynamic control after H/I.

Anti-angiogenic effects of non-peptide integrin alphavbeta3 specific antagonist on laser-induced choroidal neovascularization in mice

BACKGROUND

To evaluate the anti-angiogenic effects of integrin alphavbeta3 specific antagonist BS-1417 on laser-induced choroidal neovascularization (CNV) in mice.

METHODS

Male C57BL/6 mice were treated with daily intraperitoneal injections of BS-1417 or saline starting at the onset (day 0) of experiments. CNV was induced by laser photocoagulation the next day. Fluorescein angiograms (FA) and choroidal flatmount FITC-dextran perfusion were performed on experimental day 8. Histological and immunohistochemical examinations were performed with consecutive cryosections. Sub-confluent human vascular endothelial cells (HUVEC) were grown in vitro under various concentrations (0-10 microg/ml) of BS-1417 and the numbers of cell were measured at 48 hours of incubation. After fixation, immunocytochemistry was performed.

RESULTS

BS-1417 significantly decreased the area of dye leakage determined by FA (40% of control, p = 0.0008) and reduced the CNV size found on choroidal flatmount (18% of control, p = 0.007). In histological findings, BS-1417 apparently suppressed the size of laser-induced CNV. Immunoreactivities for VEGF and integrin alphav were remarkably attenuated with BS-1417 compared to control. BS-1417 inhibited the growth and VEGF expression of HUVEC in vitro.

CONCLUSIONS

The integrin alphavbeta3 may play a key role in the induction of laser-induced CNV. The antagonists for integrin alphavbeta3 may have therapeutic effects in CNV associated diseases such as age-related macular degenerations.

Preconditioning with a TLR2 specific ligand increases resistance to cerebral ischemia/reperfusion injury

The brain's resistance to ischemic injury can be transiently augmented by prior exposure to a sub-lethal stress stimulus, i.e. preconditioning. It has been reported that Toll-like receptors (TLRs) are involved in the preconditioning-induced protective effect against ischemic brain injury. In this study, we investigated the effect of preconditioning with a TLR2 specific ligand, Pam3CSK4, on focal cerebral ischemia/reperfusion (I/R) injury in mice. Pam3CSK4 was administered systemically 24 h before the mice were subjected to focal cerebral ischemia (1 h) followed by reperfusion. Cerebral infarct size was determined, blood brain barrier (BBB) permeability was evaluated, and expression of tight-junction proteins were examined after focal cerebral I/R. Results showed that pre-treatment with Pam3CSK significantly reduced brain infarct size (1.9+/-0.5% vs 9.4+/-2.2%) compared with the untreated I/R group. Pam3CSK4 pre-treatment also significantly reduced acute mortality (4.3% vs 24.2%), preserved neurological function (8.22+/-0.64 vs 3.91+/-0.57), and attenuated brain edema (84.61+/-0.08% vs 85.29+/-0.09%) after cerebral I/R. In addition, Pam3CSK4 pre-treatment preserved BBB function as evidenced by decreased leakage of serum albumin (0.528+/-0.026 vs 0.771+/-0.059) and Evans Blue (9.23+/-0.72 microg/mg vs 12.56+/-0.65 microg/mg) into brain tissue. Pam3CSK4 pre-treatment also attenuated the loss of the tight junction protein occludin in response to brain I/R injury. These results suggest that TLR2 is a new target of ischemic preconditioning in the brain and preconditioning with a TLR2 specific ligand will protect the brain from I/R injury.

Multiple effects of 2ME2 and D609 on the cortical expression of HIF-1alpha and apoptotic genes in a middle cerebral artery occlusion-induced focal ischemia rat model

Despite 2-methoxyestradiol (2ME2) and tricyclodecan-9-yl-xanthogenate (D609) having multiple effects on cancer cells, mechanistically, both of them down-regulate hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF). We hypothesize HIF-1alpha plays an essential role in cerebral ischemia as a pro-apoptosis regulator; 2ME2 and D609 decrease the levels of HIF-1alpha and VEGF, that might contribute to protecting brain from ischemia injury. A total of 102 male Sprague-Dawley rats were split into five groups: sham, middle cerebral artery occlusion (MCAO), MCAO + dimethyl sulfoxide, MCAO + 2ME2, and MCAO + D609. 2ME2 and D609 were injected intraperitoneally 1 h after reperfusion. Rats were killed at 24 h and 7 days. At 24 h, 2ME2 and D609 reduce the levels of HIF-1alpha and VEGF (enzyme-linked immunosorbent assay), depress the expression of HIF-1alpha, VEGF, BCL2/adenovirus E1B 19 kDa interacting protein 3 (BNIP3) and cleaved caspase 3 (western blot and immunohistochemistry) in the brain infarct area. Double fluorescence labeling shows HIF-1alpha positive immunoreactive materials are co-localized with BNIP3 and terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling inside the nuclei of neurons. At 7 days, 2ME2 and D609 reduce the infarct volume (2,3,7-triphenyltetrazolium chloride) and blood-brain barrier extravasation, decrease the mortality and improve the neurological deficits. In conclusion, 2ME2 and D609 are powerful agents to protect brain from cerebral ischemic injury by inhibiting HIF-1alpha expression, attenuating the superfluous expression of VEGF to avoid blood-brain barrier disruption and suppressing neuronal apoptosis via BNIP3 pathway.