Peroxynitrite mediates nitric oxide-induced blood-brain barrier damage

From Neurodevelopmental to Neurodegenerative Disorders: The Vascular Continuum

Structural and functional integrity of the cerebral vasculature ensures proper brain development and function, as well as healthy aging. The inability of the brain to store energy makes it exceptionally dependent on an adequate supply of oxygen and nutrients from the blood stream for matching colossal demands of neural and glial cells. Key vascular features including a dense vasculature, a tightly controlled environment, and the regulation of cerebral blood flow (CBF) all take part in brain health throughout life. As such, healthy brain development and aging are both ensured by the anatomical and functional interaction between the vascular and nervous systems that are established during brain development and maintained throughout the lifespan. During critical periods of brain development, vascular networks remodel until they can actively respond to increases in neural activity through neurovascular coupling, which makes the brain particularly vulnerable to neurovascular alterations. The brain vasculature has been strongly associated with the onset and/or progression of conditions associated with aging, and more recently with neurodevelopmental disorders. Our understanding of cerebrovascular contributions to neurological disorders is rapidly evolving, and increasing evidence shows that deficits in angiogenesis, CBF and the blood-brain barrier (BBB) are causally linked to cognitive impairment. Moreover, it is of utmost curiosity that although neurodevelopmental and neurodegenerative disorders express different clinical features at different stages of life, they share similar vascular abnormalities. In this review, we present an overview of vascular dysfunctions associated with neurodevelopmental (autism spectrum disorders, schizophrenia, Down Syndrome) and neurodegenerative (multiple sclerosis, Huntington's, Parkinson's, and Alzheimer's diseases) disorders, with a focus on impairments in angiogenesis, CBF and the BBB. Finally, we discuss the impact of early vascular impairments on the expression of neurodegenerative diseases.

Continuous Monitoring Reveals Protective Effects of N-Acetylcysteine Amide on an Isogenic Microphysiological Model of the Neurovascular Unit

Microphysiological systems mimic the in vivo cellular ensemble and microenvironment with the goal of providing more human-like models for biopharmaceutical research. In this study, the first such model of the blood-brain barrier (BBB-on-chip) featuring both isogenic human induced pluripotent stem cell (hiPSC)-derived cells and continuous barrier integrity monitoring with <2 min temporal resolution is reported. Its capabilities are showcased in the first microphysiological study of nitrosative stress and antioxidant prophylaxis. Relying on off-stoichiometry thiol-ene-epoxy (OSTE+) for fabrication greatly facilitates assembly and sensor integration compared to the prevalent polydimethylsiloxane devices. The integrated cell-substrate endothelial resistance monitoring allows for capturing the formation and breakdown of the BBB model, which consists of cocultured hiPSC-derived endothelial-like and astrocyte-like cells. Clear cellular disruption is observed when exposing the BBB-on-chip to the nitrosative stressor linsidomine, and the barrier permeability and barrier-protective effects of the antioxidant N-acetylcysteine amide are reported. Using metabolomic network analysis reveals further drug-induced changes consistent with prior literature regarding, e.g., cysteine and glutathione involvement. A model like this opens new possibilities for drug screening studies and personalized medicine, relying solely on isogenic human-derived cells and providing high-resolution temporal readouts that can help in pharmacodynamic studies.

Modulating neuroinflammation in neurodegeneration-related dementia: can microglial toll-like receptors pull the plug?

Neurodegeneration-associated dementia disorders (NADDs), namely Alzheimer and Parkinson diseases, are developed by a significant portion of the elderly population globally. Extensive research has provided critical insights into the molecular basis of the pathological advancements of these diseases, but an efficient curative therapy seems elusive. A common attribute of NADDs is neuroinflammation due to a chronic inflammatory response within the central nervous system (CNS), which is primarily modulated by microglia. This response within the CNS is positively regulated by cytokines, chemokines, secondary messengers or cyclic nucleotides, and free radicals. Microglia mediated immune activation is regulated by a positive feedback loop in NADDs. The present review focuses on evaluating the crosstalk between inflammatory mediators and microglia, which aggravates both the clinical progression and extent of NADDs by forming a persistent chronic inflammatory milieu within the CNS. We also discuss the role of the human gut microbiota and its effect on NADDs as well as the suitability of targeting toll-like receptors for an immunotherapeutic intervention targeting the deflation of an inflamed milieu within the CNS.

Cancer Chemotherapy Related Cognitive Impairment and the Impact of the Alzheimer's Disease Risk Factor APOE

Cancer related cognitive impairment (CRCI) is a serious impairment to maintaining quality of life in cancer survivors. Cancer chemotherapy contributes to this condition through several potential mechanisms, including damage to the blood brain barrier, increases in oxidative stress and inflammation in the brain, and impaired neurogenesis, each of which lead to neuronal dysfunction. A genetic predisposition to CRCI is the E4 allele of the Apolipoprotein E gene (APOE), which is also the strongest genetic risk factor for Alzheimer's disease. In normal brains, APOE performs essential lipid transport functions. The APOE4 isoform has been linked to altered lipid binding, increased oxidative stress and inflammation, reduced turnover of neural progenitor cells, and impairment of the blood brain barrier. As chemotherapy also affects these processes, the influence of APOE4 on CRCI takes on great significance. This review outlines the main areas where APOE genotype could play a role in CRCI. Potential therapeutics based on APOE biology could mitigate these detrimental cognitive effects for those receiving chemotherapy, emphasizing that the APOE genotype could help in developing personalized cancer treatment regimens.

Blood-brain barrier dysfunction: the undervalued frontier of hypertension

The blood-brain barrier (BBB) constitutes the complex anatomic and physiologic interface between the intravascular compartment and the central nervous system, and its integrity is paramount for the maintenance of the very sensitive homeostasis of the central nervous system. Arterial hypertension is a leading cause of morbidity and mortality. The BBB has been shown to be disrupted in essential hypertension. BBB integrity is important for central autonomic control and this may be implicated in the pathophysiology of hypertension. On the other hand, evidence from experimental studies indicates that BBB disruption can be present in both hypertensive disease and dementia syndromes, suggesting a possibly key position of loss of BBB integrity in the pathophysiological pathways linking arterial hypertension with cognitive decline. Although much still remains to be elucidated with respect to the exact underlying mechanisms, the discovery of novel pathological pathways has changed our understanding of adult dementia and central nervous system disease overall, pointing out-in parallel-new potential therapeutic targets. The aim of this review is to summarize current scientific knowledge relevant to the pathophysiologic pathways that are involved in the disruption of the BBB function and potentially mediate hypertension-induced cognitive impairment. In parallel, we underline the differential cognition-preserving effect of several antihypertensive agents of similar blood pressure-lowering capacity, highlighting the presence of previously under-recognized BBB-protective actions of these drugs.

Electrohypersensitivity as a Newly Identified and Characterized Neurologic Pathological Disorder: How to Diagnose, Treat, and Prevent It

Since 2009, we built up a database which presently includes more than 2000 electrohypersensitivity (EHS) and/or multiple chemical sensitivity (MCS) self-reported cases. This database shows that EHS is associated in 30% of the cases with MCS, and that MCS precedes the occurrence of EHS in 37% of these EHS/MCS-associated cases. EHS and MCS can be characterized clinically by a similar symptomatic picture, and biologically by low-grade inflammation and an autoimmune response involving autoantibodies against O-myelin. Moreover, 80% of the patients with EHS present with one, two, or three detectable oxidative stress biomarkers in their peripheral blood, meaning that overall these patients present with a true objective somatic disorder. Moreover, by using ultrasonic cerebral tomosphygmography and transcranial Doppler ultrasonography, we showed that cases have a defect in the middle cerebral artery hemodynamics, and we localized a tissue pulsometric index deficiency in the capsulo-thalamic area of the temporal lobes, suggesting the involvement of the limbic system and the thalamus. Altogether, these data strongly suggest that EHS is a neurologic pathological disorder which can be diagnosed, treated, and prevented. Because EHS is becoming a new insidious worldwide plague involving millions of people, we ask the World Health Organization (WHO) to include EHS as a neurologic disorder in the international classification of diseases.

Impact of Metabolic Syndrome on Neuroinflammation and the Blood-Brain Barrier

Metabolic syndrome, which includes diabetes and obesity, is one of the most widespread medical conditions. It induces systemic inflammation, causing far reaching effects on the body that are still being uncovered. Neuropathologies triggered by metabolic syndrome often result from increased permeability of the blood-brain-barrier (BBB). The BBB, a system designed to restrict entry of toxins, immune cells, and pathogens to the brain, is vital for proper neuronal function. Local and systemic inflammation induced by obesity or type 2 diabetes mellitus can cause BBB breakdown, decreased removal of waste, and increased infiltration of immune cells. This leads to disruption of glial and neuronal cells, causing hormonal dysregulation, increased immune sensitivity, or cognitive impairment depending on the affected brain region. Inflammatory effects of metabolic syndrome have been linked to neurodegenerative diseases. In this review, we discuss the effects of obesity and diabetes-induced inflammation on the BBB, the roles played by leptin and insulin resistance, as well as BBB changes occurring at the molecular level. We explore signaling pathways including VEGF, HIFs, PKC, Rho/ROCK, eNOS, and miRNAs. Finally, we discuss the broader implications of neural inflammation, including its connection to Alzheimer's disease, multiple sclerosis, and the gut microbiome.

Melatonin ameliorates hypoglycemic stress-induced brain endothelial tight junction injury by inhibiting protein nitration of TP53-induced glycolysis and apoptosis regulator

Severe hypoglycemia has a detrimental impact on the cerebrovasculature, but the molecular events that lead to the disruption of the integrity of the tight junctions remain unclear. Here, we report that the microvessel integrity was dramatically compromised (59.41% of wild-type mice) in TP53-induced glycolysis and apoptosis regulator (TIGAR) transgenic mice stressed by hypoglycemia. Melatonin, a potent antioxidant, protects against hypoglycemic stress-induced brain endothelial tight junction injury in the dosage of 400 nmol/L in vitro. FRET (fluorescence resonance energy transfer) imaging data of endothelial cells stressed by low glucose revealed that TIGAR couples with calmodulin to promote TIGAR tyrosine nitration. A tyrosine 92 mutation interferes with the TIGAR-dependent NADPH generation (55.60% decreased) and abolishes its protective effect on tight junctions in human brain microvascular endothelial cells. We further demonstrate that the low-glucose-induced disruption of occludin and Caludin5 as well as activation of autophagy was abrogated by melatonin-mediated blockade of nitrosative stress in vitro. Collectively, we provide information on the detailed molecular mechanisms for the protective actions of melatonin on brain endothelial tight junctions and suggest that this indole has translational potential for severe hypoglycemia-induced neurovascular damage.

Plasma Kallikrein Inhibitors in Cardiovascular Disease: An Innovative Therapeutic Approach

Plasma prekallikrein is the liver-derived precursor of the trypsin-like serine protease plasma kallikrein, and circulates in plasma bound to high molecular weight kininogen. Plasma prekallikrein is activated to plasma kallikrein by activated factor XII or prolylcarboxypeptidase. Plasma kallikrein regulates the activity of multiple proteolytic cascades in the cardiovascular system such as the intrinsic pathway of coagulation, the kallikrein-kinin system, the fibrinolytic system, the renin-angiotensin system, and the complement pathways. As such, plasma kallikrein plays a central role in the pathogenesis of thrombosis, inflammation, and blood pressure regulation. Under physiological conditions, plasma kallikrein serves as a cardioprotective enzyme. However, its increased plasma concentration or hyperactivity perpetuates cardiovascular disease (CVD). In this article, we review the biochemistry and cell biology of plasma kallikrein and summarize data from preclinical and clinical studies that have established important functions of this serine protease in CVD states. Finally, we propose plasma kallikrein inhibitors as a novel class of drugs with potential therapeutic applications in the treatment of CVDs.

Tempol alleviates intracerebral hemorrhage-induced brain injury possibly by attenuating nitrative stress

Intracerebral hemorrhage (ICH)-induced brain injury leads to irreversible disruption of the blood-brain barrier (BBB) and fatality brain edema with massive cell death. Although secondary damage could, in principle, be preventable, no effective treatment approaches currently exist for patients with ICH. Tempol, a catalytic scavenger of peroxynitrite (ONOO)-derived free radicals, has been proven to ameliorate brain injury in several types of brain insults. This study aims to investigate the potential neuroprotective effect of tempol after ICH and to explore the underlying mechanisms. Collagenase-induced ICH was performed in rats. Tempol was administered immediately after ICH. The effects of tempol on ICH were evaluated by assessing neurological deficits, BBB permeability, brain edema, and apoptotic cell death. The mechanisms of action of tempol, with its clear ability on the derivative of ONOO [3-nitrotyrosine (3-NT), ONOO, and its derivative-mediated nitration marker] and expression of tight junction protein [zonula occludens-1 (ZO-1)], were also investigated. Perihematomal 3-NT increased significantly following ICH and expressed around vessels accompanied by reduced and discontinuous expression of ZO-1. Tempol treatment significantly suppressed 3-NT formation and preserved ZO-1 levels, and led to improvement in neurological outcomes and reduction of BBB leakiness, brain edema, and apoptosis. In conclusion, tempol has neuroprotective potential in experimental ICH and may help combat ICH-induced brain injury in patients.

Overproduction of nitric oxide intensifies brain infarction and cerebrovascular damage through reduction of claudin-5 and ZO-1 expression in striatum of ischemic brain

Nitric oxide (NO) overproduction has been demonstrated from different NO-synthase overexpression or hyperactivity after brain ischemia. Here, we examined the effects of inhibition of NO overproduction on brain infarction, cerebrovascular damage and expression of claudin-5 and zonula occludens-1 (ZO-1) in striatum of ischemic brain. The experiment was performed in three groups of rats; sham, control ischemia and ischemic treatment. Brain ischemia was induced by 60min of middle cerebral artery occlusion (MCAO) followed by 24h of reperfusion. Treated rats received L-NAME 30min before induction of ischemia (1mg/kg, i.p.). Infarct volume and histopathological changes of ischemic striatum were assessed by TTC and LFB staining methods, respectively. Ultimately, quantitative RT-PCR was used for assessment of claudins-5 and ZO-1 expression. MCAO in the control group induced infarction (135±25mm³) at large areas of striatum in accompany with neuronal damages, whereas L-NAME significantly reduced infarction (87±16mm³) and neuronal injuries. The mRNA of ZO-1 and claudin-5 decreased in ischemic striatum, whereas inhibition of NO overproduction by L-NAME attenuated this reduction for these genes. Our findings indicated that NO overproduction after brain ischemia plays a crucial role in neuronal damage especially at striatal regions. Hence, inhibition of excessive NO production may save striatal cerebrovascular integrity of ischemic brain.

Pharmacological modulation of dietary lipid-induced cerebral capillary dysfunction: Considerations for reducing risk for Alzheimer's disease

An increasing body of evidence suggests that cerebrovascular dysfunction and microvessel disease precede the evolution of hallmark pathological features that characterise Alzheimer's disease (AD), consistent with a causal association for onset or progression. Recent studies, principally in genetically unmanipulated animal models, suggest that chronic ingestion of diets enriched in saturated fats and cholesterol may compromise blood-brain barrier (BBB) integrity resulting in inappropriate blood-to-brain extravasation of plasma proteins, including lipid macromolecules that may be enriched in amyloid-β (Aβ). Brain parenchymal retention of blood proteins and lipoprotein bound Aβ is associated with heightened neurovascular inflammation, altered redox homeostasis and nitric oxide (NO) metabolism. Therefore, it is a reasonable proposition that lipid-lowering agents may positively modulate BBB integrity and by extension attenuate risk or progression of AD. In addition to their robust lipid lowering properties, reported beneficial effects of lipid-lowering agents were attributed to their pleiotropic properties via modulation of inflammation, oxidative stress, NO and Aβ metabolism. The review is a contemporary consideration of a complex body of literature intended to synthesise focussed consideration of mechanisms central to regulation of BBB function and integrity. Emphasis is given to dietary fat driven significant epidemiological evidence consistent with heightened risk amongst populations consuming greater amounts of saturated fats and cholesterol. In addition, potential neurovascular benefits associated with the use of hypolipidemic statins, probucol and fenofibrate are also presented in the context of lipid-lowering and pleiotropic properties.

Nitroproteins in Human Astrocytomas Discovered by Gel Electrophoresis and Tandem Mass Spectrometry

Protein tyrosine nitration is involved in the pathogenesis of highly fatal astrocytomas, a type of brain cancer. To understand the molecular mechanisms of astrocytomas and to discover new biomarkers/therapeutic targets, we sought to identify nitroproteins in human astrocytoma tissue. Anti-nitrotyrosine immunoreaction-positive proteins from a high-grade astrocytoma tissue were detected with two-dimensional gel electrophoresis (2DGE)-based nitrotyrosine immunoblots, and identified with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Fifty-seven nitrotyrosine immunopositive protein spots were detected. A total of 870 proteins (nitrated and non-nitrated) in nitrotyrosine-immunopositive 2D gel spots were identified, and 18 nitroproteins and their 20 nitrotyrosine sites were identified with MS/MS analysis. These nitroproteins participate in multiple processes, including drug-resistance, signal transduction, cytoskeleton, transcription and translation, cell proliferation and apoptosis, immune response, phenotypic dedifferentiation, cell migration, and metastasis. Among those nitroproteins that might play a role in astrocytomas was nitro-sorcin, which is involved in drug resistance and metastasis and might play a role in the spread and treatment of an astrocytoma. Semiquantitative immune-based measurements of different sorcin expressions were found among different grades of astrocytomas relative to controls, and a semiquantitative increased nitration level in high-grade astrocytoma relative to control. Nitro-β-tubulin functions in cytoskeleton and cell migration. Semiquantitative immunoreactivity of β-tubulin showed increased expression among different grades of astrocytomas relative to controls and semiquantitatively increased nitration level in high-grade astrocytoma relative to control. Each nitroprotein was rationalized and related to the corresponding functional system to provide new insights into tyrosine nitration and its potential role in the pathogenesis of astrocytoma formation. Graphical Abstract ᅟ.

Peroxynitrite decomposition catalyst prevents matrix metalloproteinase-9 activation and neurovascular injury after hemoglobin injection into the caudate nucleus of rats

Hemoglobin (Hb) is a major constituent of blood and a potent mediator of oxidative or nitrative stress after intracerebral hemorrhage (ICH). Our previous study demonstrated that Hb could induce abundant peroxynitrite (ONOO(-)) formation in vivo, which may be involved in the blood-brain barrier (BBB) disruption, however, the drug intervention is absent and also the underlying mechanism. Using an experimental stroke model by injecting Hb into the caudate nucleus of male Sprague-Dawley rats, we assessed the role of ONOO(-) decomposition catalyst, 5,10,15,20-tetrakis (4-sulfonatophenyl) porphyrinato iron(III) [FeTPPS] in the activation of MMP-9 and Hb-induced neurovascular injuries. 3-Nitrotyrosine (3-NT, as an index of ONOO(-) formation) and NF-κB expression was measured by western blot (WB) and immunohistochemistry (IHC)/immunofluorescence (IF). Activity of MMP was evaluated by in situ zymography. Neurovascular injury was assessed using zonula occludens-1 (ZO-1) by WB and IF, fibronectin (FN) and neuron-specific nuclear protein (NeuN) IHC. Perihematomal cell death was determined by TUNEL assay. Behavioral outcome was measured by modified neurological severity score (mNSS) test. At the injured striata, profuse 3-NT was produced and mainly expressed in neutrophils and microglia/macrophages. 3-NT formation significantly colocalized with nuclear factor-κB (NF-κB) expression. In situ zymography showed that gelatinase activity was mostly co-localized with neurons and blood vessel walls and partly with neutrophils and microglia/macrophages. Enhanced 3-NT production, NF-κB induction and MMP-9 activation were obviously reduced after FeTPPS treatment. Hb-induced injury to tight junction protein (ZO-1), basal lamina of FN-immunopositive microvasculature and neural cells was evidently ameliorated by FeTPPS. In addition, apoptotic cell numbers as well as behavioral deficits were also improved. The present study shows that the administration of the ONOO(-) decomposition catalyst FeTPPS protects against Hb-induced neurovascular injuries and improves neurological function, which possibly in part by suppressing MMP-9 activation.

Therapeutic potential of peroxynitrite decomposition catalysts: a patent review

INTRODUCTION

Peroxynitrite is a cytotoxic oxidant species implicated in a host of pathologies, including inflammatory and neurodegenerative diseases, cancer, radiation injury and chronic pain. With the recognition of the role of peroxynitrite in disease, numerous experimental and therapeutic tools have arisen to probe peroxyntirite's pathophysiological contribution and attenuate its oxidative damage. Peroxynitrite decomposition catalysts (PNDCs) are redox-active compounds that detoxify peroxynitrite by catalyzing its isomerization or reduction to nitrate or nitrite.

AREAS COVERED

This review discusses recent research articles and patents published 1995 - 2014 on the development and therapeutic use of PNDCs. Iron and manganese metalloporphyrin PNDCs attenuate the toxic effects of peroxynitrite and are currently being developed for clinical applications. Additionally, some Mn porphyrin-based PNDCs have optimized pharmaceutical properties such that they exhibit greater peroxynitrite selectivity. Other classes of PNDC agents, including bis(hydroxyphenyl)dipyrromethenes and metallocorroles, have demonstrated preclinical efficacy, oral availability and reduced toxicity risk.

EXPERT OPINION

Interest in the drug-like properties of peroxynitrite-neutralizing agents has grown with the realization that PNDCs will be powerful tools in the treatment of disease. The design of compounds with enhanced oral availability and peroxynitrite selectivity is a critical step toward the availability of safe, effective and selective redox modulators for the treatment of peroxynitrite-associated pathologies.

Reliable disease biomarkers characterizing and identifying electrohypersensitivity and multiple chemical sensitivity as two etiopathogenic aspects of a unique pathological disorder

Much of the controversy over the causes of electro-hypersensitivity (EHS) and multiple chemical sensitivity (MCS) lies in the absence of both recognized clinical criteria and objective biomarkers for widely accepted diagnosis. Since 2009, we have prospectively investigated, clinically and biologically, 1216 consecutive EHS and/or MCS-self reporting cases, in an attempt to answer both questions. We report here our preliminary data, based on 727 evaluable of 839 enrolled cases: 521 (71.6%) were diagnosed with EHS, 52 (7.2%) with MCS, and 154 (21.2%) with both EHS and MCS. Two out of three patients with EHS and/or MCS were female; mean age (years) was 47. As inflammation appears to be a key process resulting from electromagnetic field (EMF) and/or chemical effects on tissues, and histamine release is potentially a major mediator of inflammation, we systematically measured histamine in the blood of patients. Near 40% had a increase in histaminemia (especially when both conditions were present), indicating a chronic inflammatory response can be detected in these patients. Oxidative stress is part of inflammation and is a key contributor to damage and response. Nitrotyrosin, a marker of both peroxynitrite (ONOO°-) production and opening of the blood-brain barrier (BBB), was increased in 28% the cases. Protein S100B, another marker of BBB opening was increased in 15%. Circulating autoantibodies against O-myelin were detected in 23%, indicating EHS and MCS may be associated with autoimmune response. Confirming animal experiments showing the increase of Hsp27 and/or Hsp70 chaperone proteins under the influence of EMF, we found increased Hsp27 and/or Hsp70 in 33% of the patients. As most patients reported chronic insomnia and fatigue, we determined the 24 h urine 6-hydroxymelatonin sulfate (6-OHMS)/creatinin ratio and found it was decreased (<0.8) in all investigated cases. Finally, considering the self-reported symptoms of EHS and MCS, we serially measured the brain blood flow (BBF) in the temporal lobes of each case with pulsed cerebral ultrasound computed tomosphygmography. Both disorders were associated with hypoperfusion in the capsulothalamic area, suggesting that the inflammatory process involve the limbic system and the thalamus. Our data strongly suggest that EHS and MCS can be objectively characterized and routinely diagnosed by commercially available simple tests. Both disorders appear to involve inflammation-related hyper-histaminemia, oxidative stress, autoimmune response, capsulothalamic hypoperfusion and BBB opening, and a deficit in melatonin metabolic availability; suggesting a risk of chronic neurodegenerative disease. Finally the common co-occurrence of EHS and MCS strongly suggests a common pathological mechanism.

Nitric oxide as a regulatory factor for aquaporin-1 and 4 gene expression following brain ischemia/reperfusion injury in rat

Although the role of aquaporin-4 (AQP4) and aquaporin-1 (AQP1) channels in ischemia-induced brain edema has been previously reported, nitric oxide (NO) modulation of these channels has not been investigated. The aim of this study was to evaluate the NO modulation of AQPs gene expression after brain ischemia/reperfusion (I/R) in rats. The experiment was performed in three groups of rats: sham, control ischemic and L-NAME pretreated (1 mg/kg). Brain ischemia was induced by 60 min middle cerebral artery occlusion (MCAO) under continuous recording of regional cerebral blood flow (rCBF) followed by 12 h reperfusion. Brain edema was assessed by dry/wet method, and Quantitative RT-PCR was used for assessment of mRNA levels of AQPs. There was 80% reduction in rCBF during MCAO. Brain cerebral ischemia elevated the brain water content from 78.66±0.17% to 81.93±0.60%, and inhibition of NO production by L-NAME significantly reduced this elevation (79.74±0.79%). The mRNA expression of AQP1 increased, but AQP4 decreased in response to I/R. l-NAME pretreatment significantly decreased AQP1 mRNA and prevented the reduction of AQP4 mRNA. The findings of this study indicated that brain I/R injury provokes brain edema by alterations of AQPs expression, and the NO is the main signaling factor that modulates gene expression of these channels.

Nitrosative stress induces peroxiredoxin 1 ubiquitination during ischemic insult via E6AP activation in endothelial cells both in vitro and in vivo

AIMS

Although there is accumulating evidence that increased formation of reactive nitrogen species in cerebral vasculature contributes to the progression of ischemic damage, but the underlying molecular mechanisms remain elusive. Peroxiredoxin 1 (Prx1) can initiate the antioxidant response by scavenging free radicals. Therefore, we tested the hypothesis that Prx1 regulates the susceptibility to nitrosative stress damage during cerebral ischemia in vitro and in vivo.

RESULTS

Proteomic analysis in endothelial cells revealed that Prx1 was upregulated after stress-related oxygen-glucose deprivation (OGD). Although peroxynitrite upregulated Prx1 rapidly, this was followed by its polyubiquitination within 6 h after OGD mediated by the E3 ubiquitin ligase E6-associated protein (E6AP). OGD colocalized E6AP with nitrotyrosine in endothelial cells. To assess translational relevance in vivo, mice were studied after middle cerebral artery occlusion (MCAO). This was accompanied by Prx1 ubiquitination and degradation by the activation of E6AP. Furthermore, brain delivery of a lentiviral vector encoding Prx1 in mice inhibited blood-brain barrier leakage and neuronal damage significantly following MCAO.

INNOVATION AND CONCLUSIONS

Nitrosative stress during ischemic insult activates E6AP E3 ubiquitin ligase that ubiquitinates Prx1 and subsequently worsens cerebral damage. Thus, targeting the Prx1 antioxidant defense pathway may represent a novel treatment strategy for neurovascular protection in stroke.

Advances in Herbal Medicine for Treatment of Ischemic Brain Injury

Ischemic brain injury is one of the leading causes of death worldwide and has attracted a lot of attention in the field of drug discovery. Cerebral ischemia is a complex pathological process involving a series of mechanisms, including generation of free radicals, oxidative stress, disruption of the membrane function, release of neurotransmitters and apoptosis. Thrombolytic therapy is the most effective therapeutic strategy, but the benefits are far from being absolute. Increased attention in the field of drug discovery has been focused on using natural compounds from traditional medicinal herbs for neuroprotection, which appears to be a promising therapeutic option for cerebral ischemia with minimal systemic adverse effects that could limit their long term use. The scenario calls for extensive investigations which can result in the development of lead molecules for neuroprotection in the future. In this context, the present review focuses on possible mechanisms underlying the beneficial effects of herbal drugs in patients with cerebral ischemic injury. Natural compounds have been demonstrated to have neurofunctional regulatory actions with antioxidative, anti-inflammatory, calcium antagonizing and anti-apoptotic activities. Among the several leads obtained from plant sources as potential neuroprotective agents, resveratrol, EGb761, curcumin and epigallocatechin-3-gallate have shown significant therapeutic benefits in cerebral ischemic conditions. However, ligustilide, tanshinone, scutellarin and shikonin are the few lead molecules which are under investigation for treatment of cerebral ischemia.

Serotonin depletion can enhance the cerebrovascular responses induced by cortical spreading depression via the nitric oxide pathway

Serotonin (5-HT) is an important neurotransmitter involved in the control of neural and vascular responses. 5-HT depletion can induce several neurological disorders, including migraines. Studies on a cortical spreading depression (CSD) migraine animal model showed that the cortical neurons sensitivity, vascular responses, and nitric oxide (NO) production were significantly increased in 5-HT depletion. However, the involvement of NO in the cerebrovascular responses in 5-HT depletion remains unclear. This study aimed to investigate the role of NO in the CSD-induced alterations of cerebral microvessels in 5-HT depletion. Rats were divided into four groups: control, control with L-NAME treatment, 5-HT depleted, and 5-HT depleted with L-NAME treatment. 5-HT depletion was induced by intraperitoneal injection with para-chlorophenylalanine (PCPA) 3 days before the experiment. The CSD was triggered by KCl application. After the second wave of CSD, N-nitro-l-arginine methyl ester (L-NAME) or saline was intravenously injected into the rats with or without L-NAME treatment groups, respectively. The intercellular adhesion molecules-1 (ICAM-1), cell adhesion molecules-1 (VCAM-1), and the ultrastructural changes of the cerebral microvessels were examined. The results showed that 5-HT depletion significantly increased ICAM-1 and VCAM-1 expressions in the cerebral cortex. The number of endothelial pinocytic vesicles and microvilli was higher in the 5-HT depleted group when compared to the control. Interestingly, L-NAME treatment significantly reduced the abnormalities observed in the 5-HT depleted group. The results of this study demonstrated that an increase of NO production is one of the mechanisms involved in the CSD-induced alterations of the cerebrovascular responses in 5-HT depletion.

Blood-brain barrier disruption induced by hemoglobin in vivo: Involvement of up-regulation of nitric oxide synthase and peroxynitrite formation

Accumulating evidence has demonstrated that up-regulation of nitric oxide synthase (NOS) and subsequent peroxynitrite (ONOO(-)) formation exert a devastating effect on the damage of BBB in multiple diseases. However, considerably less attention has been focused on the role of NOS/ONOO(-) in BBB disruption after intracerebral hemorrhage (ICH). Using an experimental stroke model by injecting hemoglobin (Hb) into the caudate nucleus of male Sprague Dawley rats, we explored the role of NOS/ONOO(-) in BBB disruption after ICH. Brain edema content, behavioral changes, alterations of TJ proteins (claudin-5 and ZO-1), expression of neuronal NOS (nNOS), inducible NOS (iNOS) and endothelial NOS (eNOS), formation of 3-nitrotyrosine (3-NT), as well as NO production were investigated. Hb in the rat brain led to a significant brain edema production and neurological deficits. Overexpressed NOS was concomitant with large quantities of 3-NT formation. Moreover, sites of enhanced nNOS, iNOS, eNOS and 3-NT immunoreactivity were colocalized with diminished or discontinuous ZO-1 and/or claudin-5 staining as evidenced by Western blot and immunofluorescence, indicating the involvement of NOS and ONOO(-) in the BBB disruption. Meaningfully, levels of 3-NT in serum, which had a similar tendency with that of in brain tissues (r=0.934, P<0.001), had a marked correlation with brain edema content (r=0.782, P<0.001) and neurological deficits (r=0.851, P<0.001). We concluded that ONOO(-) formation by the upregulation of NOS may play a central role in promoting the BBB damage following ICH. Moreover, ONOO(-) may be a promising biomarker for the judgment or prediction of brain injury and clinical prognosis after ICH.

Inflammation and hepatic encephalopathy

Hepatic encephalopathy (HE) is a neuropsychiatric syndrome associated with both acute and chronic liver dysfunction, spanning a spectrum that ranges from mild neuropsychological disturbances to coma. The central role of ammonia in the pathogenesis of HE remains incontrovertible however, there is a robust evidence base indicating the important role of inflammation in exacerbating the neurological effects of HE. Inflammation can arise directly within the brain itself as a result of deranged nitrogen and energy homeostasis, with resultant neuronal, astrocyte and microglial dysfunction. Inflammation may also originate in the peripheral circulation and exert effects on the brain indirectly, via the release of pro-inflammatory mediators which directly signal to the brain via the vagus nerve. This review summarises the data that demonstrate the synergistic relationship of inflammation and ammonia that culminates in the manifestation of HE. Sterile inflammation arising from the inflamed or necrotic liver, circulating endotoxin arising from the gut (bacterial translocation) inducing immune dysfunction, and superimposed sepsis will be comprehensively discussed. Finally, this review will provide an overview of the existing and novel treatments on the horizon which can target the inflammatory response, and how they might translate into clinical practise as therapies in the prophylaxis and treatment of HE.

Hemoglobin-induced nitric oxide synthase overexpression and nitric oxide production contribute to blood-brain barrier disruption in the rat

Hemoglobin (Hb) released from extravasated erythrocytes may have a critical role in the process of blood-brain barrier (BBB) disruption and subsequent edema formation after intracerebral hemorrhage (ICH). Excessive nitric oxide (NO) production synthesized by nitric oxide synthase (NOS) has been well documented to contribute to BBB disruption. However, considerably less attention has been focused on the role of NO in Hb-induced BBB disruption. This study was designed to examine the hypothesis that Hb-induced NOS overexpression and excessive NO production may contribute to the changes of tight junction (TJ) proteins and subsequent BBB dysfunction. Hemoglobin was infused with stereotactic guidance into the right caudate nucleus of male Sprague Dawley rats. Then, we investigated the effect of Hb on the BBB permeability, changes of TJ proteins (claudin-5, occludin, zonula occludens-1 (ZO-1), and junctional adhesion molecule-1 (JAM-1)), iron deposition, expression of inducible NOS (iNOS) and endothelial NOS (eNOS), as well as NO production. Hb injection caused a significant increase in BBB permeability. Significant reduction of claudin-5, ZO-1, and JAM-1 was observed after Hb injection as evidenced by PCR and immunofluorescence. After a decrease at early stage, occludin showed a fivefold increase in mRNA level at 7 days. Significant iron deposition was detectable from 48 h to 7 days in a time-dependent manner. The iNOS and eNOS levels dramatically increased after Hb injection concomitantly with large quantities of NO released. Furthermore, enhanced iNOS or eNOS immunoreactivity was co-localized with diffused or diminished claudin-5 staining. We concluded that overexpressed NOS and excessive NO production induced by Hb may contribute to BBB disruption, which may provide an important potential therapeutic target in the treatment of ICH.

Targeting reactive nitrogen species: a promising therapeutic strategy for cerebral ischemia-reperfusion injury

Ischemic stroke accounts for nearly 80% of stroke cases. Recanalization with thrombolysis is a currently crucial therapeutic strategy for re-building blood supply, but the thrombolytic therapy often companies with cerebral ischemia-reperfusion injury, which are mediated by free radicals. As an important component of free radicals, reactive nitrogen species (RNS), including nitric oxide (NO) and peroxynitrite (ONOO(-)), play important roles in the process of cerebral ischemia-reperfusion injury. Ischemia-reperfusion results in the production of nitric oxide (NO) and peroxynitrite (ONOO(-)) in ischemic brain, which trigger numerous molecular cascades and lead to disruption of the blood brain barrier and exacerbate brain damage. There are few therapeutic strategies available for saving ischemic brains and preventing the subsequent brain damage. Recent evidence suggests that RNS could be a therapeutic target for the treatment of cerebral ischemia-reperfusion injury. Herein, we reviewed the recent progress regarding the roles of RNS in the process of cerebral ischemic-reperfusion injury and discussed the potentials of drug development that target NO and ONOO(-) to treat ischemic stroke. We conclude that modulation for RNS level could be an important therapeutic strategy for preventing cerebral ischemia-reperfusion injury.

Hyperglycemia as a Risk Factor of Ischemic Stroke

Diabetes is considered a major risk factor for stroke and is associated with worsened stroke outcomes. Here, we discuss and summarize the mechanisms that have been associated with the increased risk of stroke due to the hyperglycemia in diabetes mellitus. In diabetic stroke models, hyperglycemia exaggerates the following damaging processes: acidosis, accumulation of reactive oxygen species/reactive nitrogen, inflammation and mitochondrial dysfunction. Understanding the mechanism of diabetes acting as a stroke risk factor will definitely assist to reveal issues related to drug metabolism and toxicity in diabetic stroke. In addition, it is suggested that future studies may focus on the mechanisms mediating blood-brain barrier and astrocytes dysfunction under hyperglycemic stroke.

Intestinal ischemia-reperfusion injury leads to inflammatory changes in the brain

Intestinal ischemia-reperfusion (I/R) injury is a well-established animal model of systemic inflammation and can lead to multiple organ failure as well as severe and lasting morbidity and even death. It can occur in humans as a result of vascular surgery or as secondary sequelae to many common conditions including low blood pressure, myocardial infarction, and necrotizing enterocolitis. Systemic inflammation induced through kidney I/R injury has been shown previously to lead to encephalopathic adverse effects, and it was theorized that intestinal injury would also cause secondary central nervous system effects. This study presents evidence that over a 6-h time frame, mouse intestinal I/R injury does not cause neuronal cell death in the brain in vivo. However, at the genetic level, certain inflammatory mediators such as endothelial nitric oxide synthase, intercellular adhesion molecule 1, P selectin, TNF-α, and IL-6 are significantly upregulated. There was a significant increase in brain edema observed in sham-operated animals as well as in fasted and nonfasted I/R groups, but neurons were not apoptotic, in the 6-h time period. Conversely, Iba1-expressing activated microglia cells and glial fibrillary acidic protein-expressing astrocytes were found to be markedly increased in fasted and nonfasted I/R mice compared with controls and sham-operated animals. These data demonstrate that intestinal I/R injury induces inflammatory changes in the brain.

Oxidative stress and blood-brain barrier dysfunction under particular consideration of matrix metalloproteinases

A cell's "redox" (oxidation and reduction) state is determined by the sum of all redox processes yielding reactive oxygen species (ROS), reactive nitrogen species (RNS), and other reactive intermediates. Low amounts of ROS/RNS are generated by different mechanisms in every cell and are important regulatory mediators in many signaling processes (redox signaling). When the physiological balance between the generation and elimination of ROS/RNS is disrupted, oxidative/nitrosative stress with persistent oxidative damage of the organism occurs. Oxidative stress has been suggested to act as initiator and/or mediator of many human diseases. The cerebral vasculature is particularly susceptible to oxidative stress, which is critical since cerebral endothelial cells play a major role in the creation and maintenance of the blood-brain barrier (BBB). This article will only contain a focused introduction on the biochemical background of redox signaling, since this has been reported already in a series of excellent recent reviews. The goal of this work is to increase the understanding of basic mechanisms underlying ROS/RNS-induced BBB disruption, with a focus on the role of matrix metalloproteinases, which, after all, appear to be a key mediator in the initiation and progression of BBB damage elicited by oxidative stress.

Contribution of nitric oxide synthase (NOS) in blood-brain barrier disruption during acute focal cerebral ischemia in normal rat

Endogenous level of nitric oxide (NO) is increased in the brain following the stroke, and deactivation of NO synthase has been shown to attenuate its destructive actions in animal stroke models using middle cerebral artery occlusion (MCAO) procedures. However, little is known about the effects of NO in cerebral vascular integrity and edema during acute cerebral ischemia. Here we investigated whether NO plays any role in the progression of blood-brain barrier (BBB) disruption and edema formation in ischemia/reperfusion injury. Intraperitoneal administration of NO substrate l-arginine (300mg/kg), or NOS inhibitor (l-NAME, 1mg/kg), was done in normal rats at 20min before a 60-min MCAO. Mean arterial blood pressures (MAP) and regional cerebral blood flow (rCBF) were continuously recorded during experiment. Neurological deficit score (NDS) was evaluated 12h after termination of MCAO followed with evaluations of cerebral infarction volume (CIV), edema formation and cerebral vascular permeability (CVP), as determined by the Evans blue dye extravasations (EBE) technique. No significant changes were observed in the values of MAP and rCBF with l-arginine or l-NAME during ischemia or reperfusion periods. There was a 75-85% reduction in rCBF in during MCAO which returned back to its pre-occlusion level during reperfusion. Acute cerebral ischemia with or without l-arginine augmented NDS (4.00±0.44 and 3.00±0.30), in conjunction with increased CIV (518±57mm(3) and 461±65mm(3)), provoked edema (3.09±0.45% and 3.30±0.49%), and elevated EBE (8.28±2.04μg/g and 5.09±1.41μg/g). Inhibition of NO production by l-NAME significantly improved NDS (1.50±0.22), diminished CIV (248±56mm(3)), edema (1.18±0.58%) and EBE (1.37±0.12μg/g). This study reconfirms the cerebroprotective properties of reduced tissue NO during acute ischemic stroke, and it also validates the deleterious actions of increased NOS activity on the disruption of cerebral microvascular integrity and edema formation of ischemia/reperfusion injuries in normal rat, without changing arterial blood pressure or blood flows to ischemic regions.

Reduction of electrical coupling between microvascular endothelial cells by NO depends on connexin37

We have previously shown that increased nitric oxide (NO) production in sepsis impairs arteriolar-conducted vasoconstriction cGMP independently and that the gap junction protein connexin (Cx) 37 is required for this conducted response. In the present study, we hypothesized that NO impairs interendothelial electrical coupling in sepsis by targeting Cx37. We examined the effect of exogenous NO on coupling in monolayers of cultured microvascular endothelial cells derived from the hindlimb skeletal muscle of wild-type (WT), Cx37 null, Cx40 null, and Cx43(G60S) (nonfunctional mutant) mice. To assess coupling, we measured the spread of electrical current injected in the monolayer and calculated the monolayer intercellular resistance (inverse measure of coupling). The NO donor 2,2'-(hydroxynitrosohydrazino)bis-ethanamine (DETA) rapidly and reversibly reduced coupling in cells from WT mice, cGMP independently. NO scavenger HbO(2) did not affect baseline coupling, but it eliminated DETA-induced reduction in coupling. Reduced coupling in response to DETA was also seen in cells from Cx40 null and Cx43(G60S) mice, but not in cells from Cx37 null mice. DETA did not alter the expression of Cx37, Cx40, and Cx43 in WT cells analyzed by immunoblotting and immunofluorescence. Furthermore, neither the peroxynitrite scavenger 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato iron (III), superoxide scavenger Mn(III)tetrakis(4-benzoic acid)porphyrin chloride, nor preloading of WT cells with the antioxidant ascorbate affected this reduction. We conclude that NO-induced reduction of electrical coupling between microvascular endothelial cells depends on Cx37 and propose that NO in sepsis impairs arteriolar-conducted vasoconstriction by targeting Cx37 within the arteriolar wall.

A comparative evaluation of the response to peroxynitrite by a brain endothelial cell line and control of the effects by drug targeting

The potent oxidant peroxynitrite (ONOO(-)) is formed after the combination of nitric oxide with superoxide and has been closely associated with the pathology of inflammatory disease. In particular, the generation of ONOO(-) has been linked to central nervous system disorders including Alzheimer's and Parkinson's disease, multiple sclerosis and bacterial and viral meningitis. Specifically, ONOO(-) has been implicated in the loss of blood-brain barrier (BBB) integrity during neuroinflammation, but the precise mechanisms through which the molecule acts to mediate neurovascular breakdown have not been established. The disruptive effects of ONOO(-) could be mediated by either direct or indirect actions on the endothelial cells that comprise the major component of the BBB. The current study has comparatively assessed the direct toxic effects of ONOO(-) on the brain endothelial cell line, b.End3 and C6 astrocytoma and NA neuroblastoma preparations. b.End3 cells were relatively resistant to ONOO(-)-induced cell death compared with C6 and NA cultures. The indirect involvement of ONOO(-) in neuroendothelial disruption was pharmacologically determined via adhesion molecule expression and immunocompetent cell attachment to b.End3 cells. ONOO(-)-targeted drugs, including the selective free radical scavenger, uric acid, the decomposition catalyst 5,10,15,20-tetrakis (4-sulphonatophenyl) porphyrinatoiron (III) (FeTPPS) and the poly(ADP-ribose) polymerase inhibitor N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-(N,N-dimethylamino) acetamide hydrochloride (PJ34) revealed that ONOO(-) was only partly involved in E-selectin, ICAM-1 and VCAM-1 expression on b.End3 cells and also cytokine-induced T-lymphocyte attachment to the cell line. The results indicate that ONOO(-) contributes to b.End3 cell disruption but is not exclusively responsible for the breakdown of neuroendothelial function.

Mechanisms of C-reactive protein-induced blood-brain barrier disruption

BACKGROUND AND PURPOSE

Increased mortality after stroke is associated with brain edema formation and high plasma levels of the acute phase reactant C-reactive protein (CRP). The aim of this study was to examine whether CRP directly affects blood-brain barrier stability and to analyze the underlying signaling pathways.

METHODS

We used a cell coculture model of the blood-brain barrier and the guinea pig isolated whole brain preparation.

RESULTS

We could show that CRP at clinically relevant concentrations (10 to 20 microg/mL) causes a disruption of the blood-brain barrier in both approaches. The results of our study further demonstrate CRP-induced activation of surface Fcgamma receptors CD16/32 followed by p38-mitogen-activated protein kinase-dependent reactive oxygen species formation by the NAD(P)H-oxidase. The resulting oxidative stress increased myosin light chain kinase activity leading to an activation of the contractile machinery. Blocking myosin light chain phosphorylation prevented the CRP-induced blood-brain barrier breakdown and the disruption of tight junctions.

CONCLUSIONS

Our data identify a previously unrecognized mechanism linking CRP and brain edema formation and present a signaling pathway that offers new sites of therapeutic intervention.

Expression of VEGF, iNOS, and eNOS is increased in cochlea of diabetic rat

CONCLUSION

The results of this study indicate that diabetes causes up-regulation of vascular endothelial growth factor (VEGF), inducible nitric oxide synthase (iNOS), and endothelial nitric oxide synthase (eNOS), which may be involved in the pathogenesis of cochlea functional loss.

OBJECTIVE

To investigate the underlying mechanisms that may be responsible for diabetic microangiopathy in the inner ear, we studied the expression of VEGF, iNOS, and eNOS in the streptozotocin (STZ)-induced diabetic rat cochlea.

MATERIALS AND METHODS

The immunofluorescence studies were performed by using FITC-labelled specific antibodies to VEGF, iNOS, and eNOS on paraffin sections of the cochlea. The expression levels of VEGF, iNOS, and eNOS were quantified by means of Western blot analysis of cochlea protein extracts. Evans blue (EB) was used to investigate blood-labyrinth barrier (BLB) permeability in the cochlea.

RESULTS

Increased cochlear expression of VEGF, iNOS, and eNOS was detected in the diabetic rat. Furthermore, increased permeability of BLB was evidenced by increased cochlear EB extravasation in the diabetic rat.

Human neutrophil-pulmonary microvascular endothelial cell interactions in vitro: differential effects of nitric oxide vs. peroxynitrite

Sepsis-induced acute lung injury is characterized by activation and injury of pulmonary microvascular endothelial cells (PMVEC), increased neutrophil-PMVEC adhesion and migration, and trans-PMVEC high-protein edema. Inducible NO synthase (iNOS) inhibits septic murine neutrophil migration in vivo and in vitro. The effects of NO in human neutrophil-PMVEC interactions are not known. We isolated human PMVEC using magnetic bead-bound anti-PECAM antibody. Confluent PMVEC at passage 3-4 were co-cultured with human neutrophils for assessment of neutrophil-PMVEC adhesion, and trans-PMVEC neutrophil migration and Evans-Blue dye-labeled albumin leak. Two NO donors (spermine-NONOate, S-nitroso-N-acetylpenicillamine) attenuated both cytomix-enhanced neutrophil-PMVEC adhesion by 64+/-14% (p<0.01) and 32+/-3% (p<0.05), respectively, and cytomix-induced trans-PMVEC neutrophil migration by 85+/-16% (p<0.01) and 43+/-5% (p<0.01), respectively. Correspondingly, iNOS inhibition with 1400W enhanced cytomix-stimulated neutrophil migration by 52+/-3% (p<0.01), but had no effect on neutrophil-PMVEC adhesion. Conversely, a peroxynitrite donor (SIN-1) increased both neutrophil-PMVEC adhesion (38+/-2% vs. 14+/-1% control, p<0.01) and trans-PMVEC neutrophil migration; with both effects were completely inhibited by scavenging of NO, superoxide, or peroxynitrite (p<0.05 for each). Scavenging of peroxynitrite also eliminated cytomix-induced neutrophil adhesion and migration. Blocking CD18-dependent neutrophil adhesion prevented cytomix-stimulated trans-PMVEC EB-albumin leak (p<0.05), while inhibiting neutrophil migration paradoxically enhanced cytomix-stimulated EB-albumin leak (11+/-1% vs. 7+/-0.5%, p<0.01). FMLP-induced neutrophil migration had no effect on trans-PMVEC EB-albumin leak. In summary, we report differential effects, including the inhibitory action of NO and stimulatory effect of ONOO(-) on human neutrophil-PMVEC adhesion and trans-PMVEC migration under cytomix stimulation. Moreover, neutrophil-PMVEC adhesion, but not trans-PMVEC migration, contributes to human PMVEC barrier dysfunction.

Fluvastatin prevents glutamate-induced blood-brain-barrier disruption in vitro

Glutamate is an important excitatory amino acid in the central nervous system. Under pathological conditions glutamate levels dramatically increase. Aim of the present study was to examine whether the HMG-CoA inhibitor fluvastatin prevents glutamate-induced blood-brain-barrier (BBB) disruption. Measurements of transendothelial electrical resistance (TEER) were performed to analyze BBB integrity in an in vitro co-culture model of brain endothelial and glial cells. Myosin light chain (MLC) phosphorylation was detected by immunohistochemistry, or using the in-cell western technique. Intracellular Ca2+ and reactive oxygen species (ROS) levels were analyzed using the fluorescence dyes Ca-green or DCF. Glutamate induced a time- (1-3 h) and concentration- (0.25-1 mmol/l) dependent decrease of TEER values that was blocked by the NMDA-receptor antagonist MK801, the Ca2+ chelator BAPTA, the NAD(P)H-oxidase inhibitor apocynin and the MLC-kinase inhibitor ML-7. Furthermore we observed a concentration-dependent increase of intracellular Ca2+ and ROS after glutamate application. Glutamate caused an increase of MLC phosphorylation that was antagonized by apocynin, or BAPTA, indicating that Ca2+ and ROS signaling is involved in the activation of the contractile machinery. Fluvastatin (10-25 micromol/l) completely abolished the glutamate-induced barrier disruption and oxidative stress. The BBB-protecting effect of fluvastatin was completely lost if the cells were treated with the nitric oxide (NO) synthase inhibitor L-NMMA (300 micromol/l). In the present study we demonstrated that glutamate-induced BBB disruption involves Ca2+ signalling via NMDA receptors, which is followed by an increased ROS generation by the NAD(P)H-oxidase. This oxidative stress then activates the MLC kinase. Fluvastatin preserves barrier function in a NO-dependent way and reduces glutamate-induced oxidative stress.

Curcuma oil modulates the nitric oxide system response to cerebral ischemia/reperfusion injury

The antioxidant activity of C.oil in cerebral stroke has been reported earlier. We have attempted here to clarify the mechanisms underlying the neuroprotection against experimental cerebral ischemia by Curcuma oil (C.oil), isolated from the rhizomes of Curcuma longa. C.oil (250 mg/kg i.p.) was given 30 min before focal ischemia in rats caused by occlusion of the middle cerebral artery (1h of occlusion, 24h of reflow). Ischemia, leads to elevation in [Ca(2+)] this sets into motion a cascades of ischemic injury which was attenuated by C.oil. C.oil reduced post-ischemic brain neutrophil infiltration in the ischemic area, controlled tissue NOx levels and the neuronal levels of nitric oxide, peroxynitrite and reactive oxygen species when measured after 24h of reflow. Double immunofluorescence staining analysis and Western immunoblot analysis with C.oil treatment showed that the expression of nitric oxide synthase (NOS) isoforms were decreased significantly compared to the untreated ischemia group. Ischemia is associated with increased in TUNEL (TdT-mediated dUTP nick-end labeling) positive cells in brain sections indicating DNA fragmentation. The C.oil treated group showed a significant decrease in numbers of apoptotic cells compared to the untreated ischemia group, as seen in the flowcytometric analysis of the neurons. Results of immunohistochemistry and Western immunoblot indicate that C.oil suppressed the elevated protein level of Bax, and aided mitochondrial translocation and activation of Bcl-2 by altered mitochondrial membrane potential. It also inhibits the cytosolic release of apoptogenic molecules like cytochrome c, inhibits the activation of caspase-3 and the expression of p53 ultimately inhibiting apoptosis. Our observations suggest that high levels of NO generated by NOS isoforms are partially responsible for exacerbating the neuronal damage induced by MCAo by intraluminal filament.

Accumulation of beta-amyloid in the brain microvessels accompanies increased hyperphosphorylated tau proteins following microsphere embolism in aged rats

To define mechanisms underlying neurovascular injury following brain embolism-induced neurodegeneration, we investigated temporal and spatial pathological changes in brain microvessels up to 12 weeks after microsphere embolism (ME) induction in aged male rats. Mild ME upregulated endothelial nitric oxide synthase (eNOS) and protein tyrosine nitration in brain microvessels. Strong beta-amyloid immunoreactivity coincident with increased eNOS immunoreactivity was observed in microvessels. Immunoblotting of purified brain microvessels revealed that beta-amyloid accumulation significantly increased 1 week after ME induction and remained elevated for 12 weeks. Importantly, beta-amyloid accumulation in brain parenchyma was also observed in areas surrounding injured microvessels at 12 weeks. Levels of Alzheimer's-related hyperphosphorylated tau proteins also concomitantly increased in neurons surrounding regions of beta-amyloid accumulation 12 weeks after ME induction, as did glycogen synthase kinase (GSK3beta) (Tyr-216) phosphorylation. Taken together, ME-induced aberrant eNOS expression and subsequent protein tyrosine nitration in microvessels preceded beta-amyloid accumulation both in microvessels and brain parenchyma, leading to hyperphosphorylation of neuronal tau proteins through GSK3beta activation.

Palmitate-induced NO production has a dual action to reduce cell death through NO and accentuate cell death through peroxynitrite formation

The objective of this study was to determine the role of palmitate-induced stimulation of nitric oxide synthase (NOS) on palmitate-induced cell death, specifically distinguishing the effects of the subtype NOS2 from NOS3, defining the effect of NO on mitochondria death pathways, and determining whether palmitate induces peroxynitrite formation which may impact cardiomyocyte cell survival. Cardiomyocytes from embryonic chick hearts were treated with palmitate 300-500 microM. Cell death was assessed by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. The ability of palmitate to induce NO production and its consequences were tested by using the NOS inhibitor 7-nitroindazole (7-N) and the peroxynitrite scavenger (5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato iron (III) chloride) (FeTPPS). The effect of palmitate on the mitochondria was assessed by Western blotting for cytochrome c release into the cytosol, and assessment of mitochondrial transmembrane potential (DeltaPsi(m)) by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzimidazolyl-carbocyanine iodide staining and immunocytochemistry. The NOS inhibitor 7-N, which is selective for NOS2 and not for NOS3, significantly (p<0.05) increased palmitate-induced cell death. In contrast, 7-N did not alter cell death produced by the combination of potassium cyanide and deoxyglucose, which, respectively, inhibit glycolysis and oxidative phosphorylation. The mitochondrial actions of palmitate, specifically palmitate-induced translocation of mitochondrial cytochrome c to cytosol and loss of mitochondrial transmembrane potential, were not altered by pretreatment with 7-N. FeTPPS, which isomerizes peroxynitrite to nitrate and thereby reduces the toxic effects of peroxynitrite, produced a significant reduction in palmitate-induced cell death. In summary, these data suggest that palmitate stimulates NO production, which has a dual action to protect against cell death or to induce cell death. Palmitate-induced cell death is mediated, in part, through NO generation, which leads to peroxynitrite formation. The protective effect of NO is operative through stimulation of NOS2 but not NOS3. The actions of NO on palmitate-induced cell death are independent of mitochondrial cell death pathways.

Peroxynitrite: biochemistry, pathophysiology and development of therapeutics

Peroxynitrite--the product of the diffusion-controlled reaction of nitric oxide with superoxide radical--is a short-lived oxidant species that is a potent inducer of cell death. Conditions in which the reaction products of peroxynitrite have been detected and in which pharmacological inhibition of its formation or its decomposition have been shown to be of benefit include vascular diseases, ischaemia-reperfusion injury, circulatory shock, inflammation, pain and neurodegeneration. In this Review, we first discuss the biochemistry and pathophysiology of peroxynitrite and then focus on pharmacological strategies to attenuate the toxic effects of peroxynitrite. These include its catalytic reduction to nitrite and its isomerization to nitrate by metalloporphyrins, which have led to potential candidates for drug development for cardiovascular, inflammatory and neurodegenerative diseases.

Inducible NO synthase (iNOS) in human neutrophils but not pulmonary microvascular endothelial cells (PMVEC) mediates septic protein leak in vitro

Sepsis-induced acute lung injury (ALI) is characterized by injury of the pulmonary microvascular endothelial cells (PMVEC) leading to high-protein pulmonary edema. Inducible NO synthase (iNOS) mediates trans-PMVEC protein leak in septic mice in vivo and in murine PMVEC under septic conditions in vitro, but the role of iNOS in human PMVEC protein leak has not been addressed. We hypothesized that iNOS in human neutrophils, but not human PMVEC, mediates septic trans-PMVEC protein leak in vitro. We isolated human PMVEC from lung tissue using magnetic bead-bound anti-PECAM antibody and assessed Evans blue albumin leak across human PMVEC monolayers under septic conditions in the presence/absence of human neutrophils. PMVEC were used at passages 3-4, seeded on 3 mum Transwell inserts and grown to confluence. Cytomix-stimulated trans-PMVEC albumin leak was not attenuated by pre-treatment with 1400 W, a selective iNOS inhibitor, or l-NAME, a non-selective NOS inhibitor. In neutrophil-PMVEC co-culture, basal unstimulated trans-EB-albumin leak was 0.6+/-0.3%, which was increased by cytomix stimulation to 11.5+/-4.4%, p<0.01. Cytomix-stimulated EB-albumin leak in neutrophil-PMVEC co-cultures was inhibited by pre-treatment with 1400 W (3.8+/-1.0%, p<0.05) or l-NAME (4.0+/-1.1%, p<0.05). Pre-treatment of neutrophil-PMVEC co-cultures with PEG-SOD (superoxide scavenger) and FeTPPS (peroxynitrite scavenger) also significantly attenuated neutrophil-dependent cytomix-stimulated leak (4.7+/-3.0%, p<0.05; 0.5+/-1.0%, p<0.01, respectively). In conclusion, trans-human PMVEC albumin leak under septic conditions is dependent on iNOS activity specifically in neutrophils, but not in PMVEC themselves. Septic neutrophil-dependent trans-PMVEC albumin leak may be mediated by peroxynitrite.

Neuroprotective effect of curcumin on focal cerebral ischemic rats by preventing blood–brain barrier damage

Curcumin, a member of the curcuminoid family of compounds, is a yellow colored phenolic pigment obtained from powdered rhizome of C. longa Linn. Recent studies have demonstrated that curcumin has protective effects against cerebral ischemia/reperfusion injury. However, little is known about its mechanism. Disruption of the blood-brain barrier occurs after stroke. Protection of the blood-brain barrier has become an important target of stroke interventions in experimental therapeutic. The objective of the present study was to determine whether curcumin prevents cerebral ischemia/reperfusion injury by protecting blood-brain barrier integrity. We report that a single injection of curcumin (1 and 2 mg/kg, i.v.) 30 min after focal cerebral ischemia/reperfusion in rats significantly diminished infarct volume, improved neurological deficit, decreased mortality, reduced the water content of the brain and the extravasation of Evans blue dye in ipsilateral hemisphere in a dose-dependent manner. In cultured astrocytes, curcumin significantly inhibited inducible nitric oxide synthase (iNOS) expression and NO(x) (Nitrites/nitrates contents) production induced by lipopolysaccharide (LPS)/tumor necrosis factor alpha (TNF(alpha)). Furthermore, curcumin prevented ONOO(-) donor SIN-1-induced cerebral capillaries endothelial cells damage. We concluded that curcumin ameliorates cerebral ischemia/reperfusion injury by preventing ONOO(-) mediated blood-brain barrier damage.

Microsphere embolism-induced endothelial nitric oxide synthase expression mediates disruption of the blood-brain barrier in rat brain

Microsphere embolism (ME)-induced up-regulation of endothelial nitric oxide synthase (eNOS) in endothelial cells of brain microvessels was observed 2-48 h after ischemia. eNOS induction preceded disruption of the blood-brain barrier (BBB) observed 6-72 h after ischemia. In vascular endothelial cells, ME-induced eNOS expression was closely associated with protein tyrosine nitration, which is a marker of generation of peroxynitrite. Leakage of rabbit IgG from microvessels was also evident around protein tyrosine nitration-immunoreactive microvessels. To determine whether eNOS expression and protein tyrosine nitration in vascular endothelial cells mediates BBB disruption in the ME brain, we tested the effect of a novel calmodulin-dependent NOS inhibitor, 3-[2-[4-(3-chloro-2-methylphenyl)-1-piperazinyl]ethyl]-5,6-dimethoxy-1-(4-imidazolylmethyl)-1H-indazole dihydrochloride 3.5 hydrate (DY-9760e), which inhibits eNOS activity and, in turn, protein tyrosine nitration. Concomitant with inhibition of protein tyrosine nitration in vascular endothelial cells, DY-9760e significantly inhibited BBB disruption as assessed by Evans blue (EB) excretion. DY-9760e also inhibited cleavage of poly (ADP-ribose) polymerase as a marker of the apoptotic pathway in vascular endothelial cells. Taken together with previous evidence in which DY-9760e inhibited brain edema, ME-induced eNOS expression in vascular endothelial cells likely mediates BBB disruption and, in turn, brain edema.

Tumor necrosis factor-alpha increases cerebral blood flow and ultrastructural capillary damage through the release of nitric oxide in the rat brain

Tumor necrosis factor-alpha (TNFalpha) is a proinflammatory cytokine implicated in cerebrovascular pathology. The aim of the present study was to characterize the simultaneous effects of an intracarotid administration of TNFalpha on cerebral blood flow (CBF) and the ultrastructure of the blood-brain barrier (BBB) and to determine whether nitric oxide (NO) is a mediator of the TNFalpha-induced alterations in CBF and BBB. TNFalpha (2.5 microg/kg) or saline was infused into the right common carotid artery of male Wistar rats (n = 70). NO production was inhibited with L-NAME (20 mg/kg, i.v.). CBF was monitored for 2 h with laser-Doppler flowmetry. Tissue samples were taken from the unilateral frontoparietal cortex and prepared for electron microscopy. The proportion of capillaries with swollen astrocytic endfeet and the lumen diameter of the capillaries were measured. TNFalpha significantly increased CBF, which reached a maximum of 190% of the baseline 1 h after the cessation of TNFalpha infusion. L-NAME completely prevented the increase in CBF. TNFalpha elevated the swelling of the astrocytic endfeet from a baseline value of 22.4 +/- 9.35% to 64.9 +/- 3.16%. The administration of L-NAME before TNFalpha infusion prevented the astrocytic swelling. These results demonstrate that TNFalpha increases CBF and the swelling of astrocytes through the production of NO. Our data additionally demonstrate that the breakdown of the BBB by circulating TNFalpha may involve the astrocytic endfeet.

Intracerebral administration of neuronal nitric oxide synthase antiserum attenuates traumatic brain injury-induced blood-brain barrier permeability, brain edema formation, and sensory motor disturbances in the rat

The role of nitric oxide (NO) in traumatic brain injury (TBI)-induced sensory motor function and brain pathology was examined using intracerebral administration of neuronal nitric oxide synthase (nNOS) antiserum in a rat model. TBI was produced by a making a longitudinal incision into the right parietal cerebral cortex limited to the dorsal surface of the hippocampus. Focal TBI induces profound edematous swelling, extravasation of Evans blue dye, and up-regulation of nNOS in the injured cerebral cortex and the underlying subcortical areas at 5 hours. The traumatized animals exhibited pronounced sensory motor deficit, as seen using Rota-Rod and grid-walking tests. Intracerebral administration of nNOS antiserum (1 : 20) 5 minutes and 1 hour after TBI significantly attenuated brain edema formation, Evans blue leakage, and nNOS expression in the injured cortex and the underlying subcortical regions. The nNOS antiserum-treated rats showed improved sensory motor functions. However, administration of nNOS antiserum 2 hours after TBI did not influence these parameters significantly. These novel observations suggest that NO participates in blood-brain barrier disruption, edema formation, and sensory motor disturbances in the early phase of TBI, and that nNOS antiserum has some potential therapeutic value requiring additional investigation.

Nitric oxide mediates neurodegeneration and breakdown of the blood-brain barrier in tPA-dependent excitotoxic injury in mice

Stroke and many neurodegenerative diseases culminate in neuronal death through a mechanism known as excitotoxicity. Excitotoxicity proceeds through a complex signaling pathway that includes the participation of the serine protease tissue plasminogen activator (tPA). tPA mediates neurotoxic effects on resident central nervous system cells as well alters blood-brain barrier (BBB) permeability, which further promotes neurodegeneration. Another signaling molecule that promotes neurodegeneration and BBB dysfunction is nitric oxide (NO), although its precise role in pathological progression remains unclear. We examine here the potentially interrelated roles of tPA, NO and peroxynitrite (ONOO-), which is the toxic metabolite of NO, in BBB breakdown and neurodegeneration following intrahippocampal injection of the glutamate analog kainite (KA). We find that NO and ONOO- production are linked to tPA-mediated excitotoxic injury, and demonstrate that NO provision suffices to restore the toxic effects of KA in tPA-deficient mice that are normally resistant to excitotoxicity. NO also promotes BBB breakdown and excitotoxicity. Interestingly, BBB breakdown in itself does not suffice to elicit neurodegeneration; a subsequent ONOO(-)-mediated event is required. In conclusion, NO and ONOO- function as downstream effectors of tPA-mediated excitotoxicity.

Isolation and culture of microvascular endothelial cells from gliomas of different WHO grades

Gliomas are the most common intrinsic brain tumors. The degree of vascularization corresponds to malignancy and is related to prognosis. In order to retrieve information about tumor behavior in situ, the use of primary tissue material for experiments is advantageous. With increasing evidence for the importance of microenvironment and vascularization in tumor biology, we concentrated on the isolation of endothelial cells (EC) from primary tumor material to investigate the role of endothelium within tumor tissue. We developed a method for isolation and purification of tumor-derived endothelial cells. EC were isolated and cultivated from normal brain using tissue digestion and Percoll density gradient centrifugation resulting in a <95% of EC culture. For isolation of EC from gliomas of different malignancy grades a combination of tissue digestion, Percoll gradient centrifugation and magnetic bead sorting by anti-CD31, -VE-Cadherin and -CD 105 was employed. This approach provided a purity of <98%. Cells were classified and characterized by testing expression of CD105, CD31, VE-Cadherin, vWF, UEA-1 and measuring DiI-Ac-LDL-uptake. To exclude contamination, staining and negative selection with anti-SMA, -GFAP, and -CD68 was performed. Tumors were histopathologically diagnosed according to WHO classification. We isolated EC from normal brain (NBEC, n = 11), low-grade gliomas WHO II (LGEC, n = 22), and high-grade gliomas WHO III & IV (HGEC, n = 11). There were no clear differences in EC morphology between the different tumor grades. However, a significantly higher proliferation rate of HGEC compared to LGEC was observed as well as distinctive antigen expression. Already in early passages isolated EC showed a rapid change in antigen expression indicating a phenotypic shift under culture conditions. We could establish a protocol for reliable and reproducible isolation and culture of EC from gliomas with different WHO grading. In first phenotypical and functional analyses, NBEC, LGEC and HGEC show remarkable differences. EC from all tumors could be grown in culture. However, passage related changes of EC phenotype demand very early passages to work with.