The induction of ICAM-1 in human cerebromicrovascular endothelial cells (HCEC) by ischemia-like conditions promotes enhanced neutrophil/HCEC adhesion

Neuroprotective Effects of Guanosine in Ischemic Stroke-Small Steps towards Effective Therapy

Guanosine (Guo) is a nucleotide metabolite that acts as a potent neuromodulator with neurotrophic and regenerative properties in neurological disorders. Under brain ischemia or trauma, Guo is released to the extracellular milieu and its concentration substantially raises. In vitro studies on brain tissue slices or cell lines subjected to ischemic conditions demonstrated that Guo counteracts destructive events that occur during ischemic conditions, e.g., glutaminergic excitotoxicity, reactive oxygen and nitrogen species production. Moreover, Guo mitigates neuroinflammation and regulates post-translational processing. Guo asserts its neuroprotective effects via interplay with adenosine receptors, potassium channels, and excitatory amino acid transporters. Subsequently, guanosine activates several prosurvival molecular pathways including PI3K/Akt (PI3K) and MEK/ERK. Due to systemic degradation, the half-life of exogenous Guo is relatively low, thus creating difficulty regarding adequate exogenous Guo distribution. Nevertheless, in vivo studies performed on ischemic stroke rodent models provide promising results presenting a sustained decrease in infarct volume, improved neurological outcome, decrease in proinflammatory events, and stimulation of neuroregeneration through the release of neurotrophic factors. In this comprehensive review, we discuss molecular signaling related to Guo protection against brain ischemia. We present recent advances, limitations, and prospects in exogenous guanosine therapy in the context of ischemic stroke.

Vascular Risk Factors and Alzheimer's Disease: Blood-Brain Barrier Disruption, Metabolic Syndromes, and Molecular Links

Alzheimer's disease (AD) is a neurodegenerative disorder, marked by cortical and hippocampal deposition of amyloid-β (Aβ) plaques and neurofibrillary tangles and cognitive impairment. Studies indicate a prominent link between cerebrovascular abnormalities and the onset and progression of AD, where blood-brain barrier (BBB) dysfunction and metabolic disorders play key risk factors. Pericyte degeneration, endothelial cell damage, astrocyte depolarization, diminished tight junction integrity, and basement membrane disarray trigger BBB damage. Subsequently, the altered expression of low-density lipoprotein receptor-related protein 1 and receptor for advanced glycation end products at the microvascular endothelial cells dysregulate Aβ transport across the BBB. White matter lesions and microhemorrhages, dyslipidemia, altered brain insulin signaling, and insulin resistance contribute to tau and Aβ pathogenesis, and oxidative stress, mitochondrial damage, inflammation, and hypoperfusion serve as mechanistic links between pathophysiological features of AD and ischemia. Deregulated calcium homeostasis, voltage gated calcium channel functioning, and protein kinase C signaling are also common mechanisms for both AD pathogenesis and cerebrovascular abnormalities. Additionally, APOE polymorphic alleles that characterize impaired cerebrovascular integrity function as primary genetic determinants of AD. Overall, the current review enlightens key vascular risk factors for AD and underscores pathophysiologic relationship between AD and vascular dysfunction.

Integrated analysis of the proteome and transcriptome in a MCAO mouse model revealed the molecular landscape during stroke progression

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DIA proteomics was applied to MCAO mice detection for the first time.

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Proteomics and bioinformatics revealed relationship between stroke process and immunity, especially inflammation.

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C3, Apoa4 and S100a9 were highlighted as a marker or drug targets for stroke.

Strokes usually results in long-term disability and death, and they occur worldwide. Recently, increased research on both on the physiopathological mechanisms and the transcriptome during stroke progression, have highlighted the relationship between stroke progression and immunity, with a special focus on inflammation. Here, we applied proteome analysis to a middle carotid artery occlusion (MCAO) mouse model at 0 h, 6 h, 12 h and 24 h, in which proteome profiling was performed with 23 samples, and 41 differentially expressed proteins (DEPs) were identified. Bioinformatics studies on our data revealed the importance of the immune response and particularly identified the inflammatory response, cytokine- cytokine receptor interactions, the innate immune response and reactive oxygen species (ROS) during stroke progression. In addition, we compared our data with multiple gene expression omnibus (GEO) datasets with and without a time series, in which similar pathways were identified, and three proteins, C3, Apoa4 and S100a9, were highlighted as markers or drug targets for stroke; these three proteins were significantly upregulated in the MCAO model, both in our proteomic data and in the GEO database.

Prioritization of Therapeutic Targets of Inflammation Using Proteomics, Bioinformatics, and In Silico Cell-Cell Interactomics

Protein-protein interactions play key roles in leukocyte extravasation process into the brain and have been attractive therapeutic targets for inhibiting brain inflammation using blocking (or neutralizing) antibodies. These targets include protein-protein interactions between cytokines (or chemokines) and their receptors on leukocytes and between adhesion molecules of leukocyte and brain endothelium. While a number of therapeutics against these targets are currently used in clinic for treatment of brain autoimmune and inflammatory disorders (e.g., multiple sclerosis), they are associated with side effects partly due to the off-target actions (i.e., nonspecific targets). There is a need for novel targets involved in the leukocyte extravasation process that are specific to leukocyte subsets or to individual inflammatory disorder and are amenable for drug development (i.e., druggable). We recently described the blood-brain barrier (BBB) Carta Project as a comprehensive collection of molecular "maps" consisting of multiple experimental omics (including RNA sequencing, proteomics, glycoproteomics, glycomics, metabolomics) and in silico informatics analyses on a number of mammalian species from hundreds of internal, publically available, or curated datasets. Utilizing the datasets and tools from the BBB Carta Project, we describe a methodology to identify novel "druggable" targets involving protein-protein interactions between activated leukocytes and brain endothelial cells using a combination of proteomics, bioinformatics, and in silico interactomics. The result is a prioritized list of protein-protein interactions in a network consisting of leukocyte-brain endothelial cell communication and contacts. These interactions can be further pursued for development of therapeutics such as neutralizing antibodies and their validation through preclinical testing. In addition to targeting brain inflammation, the method described here is applicable for peripheral inflammation and provides the opportunity to target important cell-cell interactions and communications that are more specific/selective for inflammatory disorders and improve currently available therapies.

Contributions of sex to cerebrovascular function and pathology

Sex differences exist in how cerebral blood vessels function under both physiological and pathological conditions, contributing to observed sex differences in risk and outcomes of cerebrovascular diseases (CBVDs), such as vascular contributions to cognitive impairment and dementia (VCID) and stroke. Throughout most of the lifespan, women are protected from CBVDs; however, risk increases following menopause, suggesting sex hormones may play a significant role in this protection. The cerebrovasculature is a target for sex hormones, including estrogens, progestins, and androgens, where they can influence numerous vascular functions and pathologies. While there is a plethora of information on estrogen, the effects of progestins and androgens on the cerebrovasculature are less well-defined. Estrogen decreases cerebral tone and increases cerebral blood flow, while androgens increase tone. Both estrogens and androgens enhance angiogenesis/cerebrovascular remodeling. While both estrogens and androgens attenuate cerebrovascular inflammation, pro-inflammatory effects of androgens under physiological conditions have also been demonstrated. Sex hormones exert additional neuroprotective effects by attenuating oxidative stress and maintaining integrity and function of the blood brain barrier. Most animal studies utilize young, healthy, gonadectomized animals, which do not mimic the clinical conditions of aging individuals likely to get CBVDs. This is also concerning, as sex hormones appear to mediate cerebrovascular function differently based on age and disease state (e.g. metabolic syndrome). Through this review, we hope to inspire others to consider sex as a key biological variable in cerebrovascular research, as greater understanding of sex differences in cerebrovascular function will assist in developing personalized approaches to prevent and treat CBVDs.

Berberine alleviates amyloid β25-35-induced inflammatory response in human neuroblastoma cells by inhibiting proinflammatory factors

The present study investigated the effect of berberine (BBR) on amyloid β 25-35 (Aβ25-35)-induced inflammatory response in human neuroblastoma cells. To model the inflammatory response observed in the central nervous system of patients with Alzheimer's disease, SH-SY5Y and SK-N-SH neuroblastoma cells were induced by Aβ25-35 (5 µM) for 24 h. Subsequently, cells were treated with BBR or indomethacin for 2 h. The cell survival rate was determined by the MTT assay. The activity of lactate dehydrogenase (LDH) in the cell culture medium was examined by spectrophotometry. The expression levels of inflammatory factors prostaglandin E2 (PGE2) and tumor necrosis factor-α (TNF-α) were determined by ELISA assays. The mRNA and protein expression levels of interleukin (IL)-1β, cyclooxygenase 2 (COX-2) and tumor necrosis factor receptor 1 (TNFR1) were measured by reverse-transcription-quantitative polymerase chain reaction and Western blotting, respectively. The results indicated that, treatment with Aβ25-35 increased the expression levels of PGE2 and TNF-α, increased the activity of LDH, and up-regulated the mRNA and protein expression of COX-2, IL-1β, and TNFR1. Treatment with BBR down-regulated the expression levels of PGE2 and TNF-α, decreased the activity of LDH, and downregulated the mRNA and protein expression of COX-2, IL-1β, and TNFR1. Taken together, the present results suggested that BBR suppressed the inflammatory response induced by Aβ25-35 in neuroblastoma cells. The mechanism of action may be associated with the inhibition of proinflammatory factors.

No-reflow phenomenon in the heart and brain

The no-reflow phenomenon refers to the observation that when an organ is made ischemic by occlusion of a large artery supplying it, restoration of patency in that artery does not restore perfusion to the microvasculature supplying the parenchyma of that organ. This has been observed after prolonged arterial occlusions in the heart (30–90 min), brain, skin, and kidney. In experimental models, zones of no reflow in the heart are characterized by ultrastructural microvascular damage, including focal endothelial swelling obstructing the lumen of small vessels. Blood elements such as neutrophil plugs, platelets, and stacking of erythrocytes have also been implicated. No reflow is associated with poor healing of the myocardial infarction. In patients, no reflow is associated with a poor clinical outcome independent of infarct size, suggesting that therapy for no reflow may be an important approach to improving outcome for ST elevation myocardial infarction. No reflow occurs after reperfusion of experimental cerebral ischemia and may be observed after only 5-min episodes of ischemia. Aggregation of blood elements may play a greater role than in cardiac no reflow. No reflow in the brain may involve cortical spreading depression with disturbed local vascular control and high, vasculotonic levels of extracellular K+ concentration, postischemic swelling in endothelial cells and abutting end feet of pericytes, pericyte contraction and death, interstitial edema with collapse of cerebral capillaries, and inflammatory reaction. New guidelines suggesting that reperfusion for stroke may be considered as late as 24 h after the onset of symptoms suggest that clinicians may be seeing more no reflow in the future.

Stroke, Vascular Dementia, and Alzheimer's Disease: Molecular Links

Stroke is a brain disease that occurs when blood flow stops, resulting in reduced oxygen supply to neurons. Stroke occurs at any time and at any age, but increases after the age of 55. It is the second leading cause of death and the third leading cause of disability-adjusted, life-years. The pathophysiology of ischemic stroke is complex and recent molecular, cellular, and animal models and postmortem brain studies have revealed that multiple cellular changes have been implicated, including oxidative stress/mitochondrial dysfunction, inflammatory responses, micro RNA alterations, and marked changes in brain proteins. These cellular changes provide new information for developing therapeutic strategies for ischemic stroke treatment. Research also revealed that stroke increases with a number of modifiable factors and most strokes can be prevented and/or controlled through pharmacological or surgical interventions and lifestyle changes. Ischemic stroke is the major risk factor for vascular dementia and Alzheimer's disease. This review summarizes the latest research findings on stroke, including causal factors and molecular links between stroke and vascular disease/Alzheimer's disease.

Peripheral immune cells infiltrate into sites of secondary neurodegeneration after ischemic stroke

Experimental stroke leads to microglia activation and progressive neuronal loss at sites of secondary neurodegeneration (SND). These lesions are remote from, but synaptically connected to, primary infarction sites. Previous studies have demonstrated that immune cells are present in sites of infarction in the first hours and days after stroke, and are associated with increased neurodegeneration in peri-infarct regions. However, it is not known whether immune cells are also present in more distal sites where SND occurs. Our study aimed to investigate whether immune cells are present in sites of SND and, if so, how these cell populations compare to those in the peri-infarct zone. Cells were isolated from the thalamus, the main site of SND, and remaining brain tissue 14days post-stroke. Analysis was performed using flow cytometry to quantify microglia, myeloid cell and lymphocyte numbers. We identified a substantial infiltration of immune cells in the ipsilateral (stroked) compared to the contralateral (control) thalamus, with a significant increase in the percentage of CD4⁺ and CD8⁺ T cells. This result was further quantified using immunofluorescent labelling of fixed tissue. In the remaining ipsilateral hemisphere tissue, there were significant increases in the frequency of CD4⁺ and CD8⁺ T lymphocytes, B lymphocytes, Ly6G⁺ neutrophils and both Ly6G^-Ly6C^LO and Ly6G^-Ly6C^HI monocytes. Our results indicate that infiltrating immune cells persist in ischemic tissue after the acute ischemic phase, and are increased in sites of SND. Importantly, immune cells have been shown to play pivotal roles in both damage and repair processes after stroke. Our findings indicate that immune cells may also be involved in the pathogenesis of SND and further clinical studies are warranted to characterise the nature of inflammatory cell infiltrates in human disease.

Methane ameliorates spinal cord ischemia-reperfusion injury in rats: Antioxidant, anti-inflammatory and anti-apoptotic activity mediated by Nrf2 activation

Methane is reported to have antioxidant, anti-inflammatory and anti-apoptotic properties. We investigated the potential neuroprotective effects of methane-rich saline (MS) on spinal cord ischemia-reperfusion injury and determined that its therapeutic benefits are associated with the activation of nuclear factor erythroid 2-related factor 2 (Nrf2). Rats received 9min of spinal cord ischemia induced by occlusion of the descending thoracic aorta plus systemic hypotension followed by a single MS treatment (10ml/kg, ip) and 72h reperfusion. MS treatment attenuated motor sensory deficits and produced high concentrations of methane in spinal cords during reperfusion, which increased Nrf2 expression and transcriptional activity in neurons, microglia and astrocytes in the ventral, intermediate and dorsal gray matter of lumbar segments. Heme oxygenase-1, superoxide dismutase, catalase and glutathione were upregulated; and glutathione disulfide, superoxide, hydrogen peroxide, malondialdehyde, 8-hydroxy-2-deoxyguanosine and 3-nitrotyrosine were downregulated in MS-treated spinal cords. MS treatment reduced neuronal apoptosis in gray matter zones, which was consistent with the suppression of cytochrome c release to the cytosol from the mitochondria and the activation of caspase-9 and -3. Throughout the gray matter, the activation of microglia and astrocytes was inhibited; the nuclear accumulation of phosphorylated nuclear factor-kappa B p65 was reduced; and tumor necrosis factor α, interleukin 1β, chemokine (C-X-C motif) ligand 1, intercellular adhesion molecule 1 and myeloperoxidase were decreased. MS treatment attenuated blood-spinal cord barrier dysfunction by preventing the expression and activity of matrix metallopeptidase-9 and disrupting tight junction proteins. Consecutive intrathecal injection of specific siRNAs targeting Nrf2 at 24-h intervals 3 days before ischemia reduced the beneficial effects of MS. Our data indicate that MS treatment prevents IR-induced spinal cord damage via antioxidant, anti-inflammatory and anti-apoptotic activities that involve the activation of Nrf2 signaling. Thus, methane may serve as a novel promising therapeutic agent for treating ischemic spinal cord injury.

Inflammatory responses in brain ischemia

Brain infarction causes tissue death by ischemia due to occlusion of the cerebral vessels and recent work has shown that post stroke inflammation contributes significantly to the development of ischemic pathology. Because secondary damage by brain inflammation may have a longer therapeutic time window compared to the rescue of primary damage following arterial occlusion, controlling inflammation would be an obvious therapeutic target. A substantial amount of experimentall progress in this area has been made in recent years. However, it is difficult to elucidate the precise mechanisms of the inflammatory responses following ischemic stroke because inflammation is a complex series of interactions between inflammatory cells and molecules, all of which could be either detrimental or beneficial. We review recent advances in neuroinflammation and the modulation of inflammatory signaling pathways in brain ischemia. Potential targets for treatment of ischemic stroke will also be covered. The roles of the immune system and brain damage versus repair will help to clarify how immune modulation may treat stroke.

Glial Cell-Elicited Activation of Brain Microvasculature in Response to Brucella abortus Infection Requires ASC Inflammasome-Dependent IL-1β Production

Blood-brain barrier activation and/or dysfunction are a common feature of human neurobrucellosis, but the underlying pathogenic mechanisms are largely unknown. In this article, we describe an immune mechanism for inflammatory activation of human brain microvascular endothelial cells (HBMEC) in response to infection with Brucella abortus Infection of HBMEC with B. abortus induced the secretion of IL-6, IL-8, and MCP-1, and the upregulation of CD54 (ICAM-1), consistent with a state of activation. Culture supernatants (CS) from glial cells (astrocytes and microglia) infected with B. abortus also induced activation of HBMEC, but to a greater extent. Although B. abortus-infected glial cells secreted IL-1β and TNF-α, activation of HBMEC was dependent on IL-1β because CS from B. abortus-infected astrocytes and microglia deficient in caspase-1 and apoptosis-associated speck-like protein containing a CARD failed to induce HBMEC activation. Consistently, treatment of CS with neutralizing anti-IL-1β inhibited HBMEC activation. Both absent in melanoma 2 and Nod-like receptor containing a pyrin domain 3 are partially required for caspase-1 activation and IL-1β secretion, suggesting that multiple apoptosis-associated speck-like protein containing CARD-dependent inflammasomes contribute to IL-1β-induced activation of the brain microvasculature. Inflammasome-mediated IL-1β secretion in glial cells depends on TLR2 and MyD88 adapter-like/TIRAP. Finally, neutrophil and monocyte migration across HBMEC monolayers was increased by CS from Brucella-infected glial cells in an IL-1β-dependent fashion, and the infiltration of neutrophils into the brain parenchyma upon intracranial injection of B. abortus was diminished in the absence of Nod-like receptor containing a pyrin domain 3 and absent in melanoma 2. Our results indicate that innate immunity of the CNS set in motion by B. abortus contributes to the activation of the blood-brain barrier in neurobrucellosis and IL-1β mediates this phenomenon.

Picroside II Inhibits the MEK-ERK1/2-COX2 Signal Pathway to Prevent Cerebral Ischemic Injury in Rats

The objective of this study is to explore the neuroprotective effect and mechanism of picroside II on ERK1/2-COX2 signal transduction pathway after cerebral ischemic injury in rats. Focal cerebral ischemic models were established by inserting monofilament threads into the middle cerebral artery in 200 Wistar rats. Twenty four rats were randomly selected into control group, while the other rats were randomly divided into six groups: model group, picroside group, lipopolysaccharide (LPS) with picroside group, U0126 with picroside group, LPS group, and U0126 group with each group containing three subgroups with ischemia at 6, 12, and 24 h. Neurobehavioral function in the rats was evaluated by modified neurological severity score points (mNSS) test; structure of neurons was observed using hematoxylin-eosin (HE) staining; apoptotic cells were counted using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay; expressions of phosphorylated mitogen/extracellular signal-regulated kinase kinas1/2 (pMEK1/2), phosphorylated extracellular signal-regulated protein kinase1/2 (pERK1/2), and cyclooxygenase (COX2) in the cortex were determined using immunohistochemistry (IHC) and Western blot (WB); and real-time PCR was used to determine the level of COX2 mRNA. The neurological behavioral malfunction appeared in all rats with middle cerebral artery occlusion (MCAO). In the model group, neuron damage was extensive, while the neurobehavioral function score, apoptotic cell index, expression of pMEK1/2, pERK1/2, and COX2 and the level of COX2 mRNA increased significantly when compared to the control group. The peak COX2 mRNA level was in ischemia 12 h, prior to the peak in COX2 protein expression. In the picroside and U0126 groups, the neurological behavioral function was improved, and the number of apoptotic cells and the expression of pMEK1/2, pERK1/2, and COX2 decreased significantly when compared to the model group. In the LPS with picroside group, at ischemia 6 h neuron damage was extensive, and pMEK1/2, pERK1/2, and COX2 expression were much higher than in the model group. But at ischemia 12 and 24 h, the expression of pMEK1/2, pERK1/2, and COX2 decreased slightly, and the neurobehavioral function also improved slightly. In LPS group, neuron damage was extensive, pMEK1/2, pERK1/2, and COX2 expression was still at a high level, and COX2 mRNA peak arrived at ischemic 12 h. Picroside II downregulates COX2 expression after MCAO by inhibiting MEK-ERK1/2 in rats to protect neurons from apoptosis and inflammation.

Phosphodiesterase-5 Inhibitors: Action on the Signaling Pathways of Neuroinflammation, Neurodegeneration, and Cognition

Phosphodiesterase type 5 inhibitors (PDE5-Is) have recently emerged as a potential therapeutic strategy for neuroinflammatory, neurodegenerative, and memory loss diseases. Mechanistically, PDE5-Is produce an anti-inflammatory and neuroprotection effect by increasing expression of nitric oxide synthases and accumulation of cGMP and activating protein kinase G (PKG), the signaling pathway of which is thought to play an important role in the development of several neurodiseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). The aim of this paper was to review present knowledge of the signaling pathways that underlie the use of PDE5-Is in neuroinflammation, neurogenesis, learning, and memory.

Prostaglandin E₂-induced intercellular adhesion molecule-1 expression is mediated by cAMP/Epac signalling modules in bEnd.3 brain endothelial cells

BACKGROUND AND PURPOSE

Prostaglandin E₂ (PGE₂) has been implicated in the regulation of adhesion molecules, leukocyte adhesion and infiltration into inflamed site. However, the underlying mechanism therein involved remains ill-defined. In this study, we explored its cellular mechanism of action in the regulation of the intercellular adhesion molecule-1 (ICAM-1) expression in the brain endothelial cells.

EXPERIMENTAL APPROACH

bEnd.3 cells, the murine cerebrovascular endothelial cell line and primary mouse brain endothelial cells were treated with PGE₂ with or without agonists/antagonists of PGE₂ receptors and associated signalling molecules. ICAM-1 expression, Akt phosphorylation and activity of NF-κB were determined by reverse transcription polymerase chain reaction (RT-PCR), immunoblot analysis, luciferase assay and immunocytochemistry.

KEY RESULTS

PGE₂ significantly up-regulated the expression of ICAM-1, which was blocked by EP4 antagonist (ONO-AE2-227) and knock-down of EP4. PGE₂ effects were mimicked by forskolin, dibutyryl cAMP (dbcAMP) and an exchange protein directly activated by cAMP (Epac) activator (8-Cpt-cAMP) but not a protein kinase A activator (N⁶-Bnz-cAMP). PGE₂-induced ICAM-1 expression was reduced by knock-down of Epac1. A PI3K specific inhibitor (LY294002), Akt inhibitor VIII (Akti) and NF-κB inhibitors (Bay-11-7082 and MG-132) attenuated the induction of ICAM-1 by PGE₂. PGE₂, dbcAMP and 8-Cpt-cAMP induced the phosphorylation of Akt, IκB kinase and IκBα and the translocation of p65 to the nucleus and increased NF-κB dependent reporter gene activity, which was diminished by Akti.

CONCLUSION AND IMPLICATIONS

Our findings suggest that PGE₂ induces ICAM-1 expression via EP4 receptor and Epac/Akt/NF-κB signalling pathway in bEnd.3 brain endothelial cells, supporting its pathophysiological role in brain inflammation.

Neuroimmune regulation of microglial activity involved in neuroinflammation and neurodegenerative diseases

Neuroinflammation constitutes a fundamental process involved in the progression of several neurodegenerative disorders, such as Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis and multiple sclerosis. Microglial cells play a central role in neuroinflammation, promoting neuroprotective or neurotoxic microenvironments, thus controlling neuronal fate. Acquisition of different microglial functions is regulated by intercellular interactions with neurons, astrocytes, the blood-brain barrier, and T-cells infiltrating the central nervous system. In this study, an overview of the regulation of microglial function mediated by different intercellular communications is summarised and discussed. Afterward, we focus in T-cell-mediated regulation of neuroinflammation involved in neurodegenerative disorders.

Hippocampal neuronal metal ion imbalance related oxidative stress in a rat model of chronic aluminum exposure and neuroprotection of meloxicam

Neurodegenerative diseases remain a significant unresolved societal burden afflicting millions of people worldwide. Neurons in the brain are highly sensitive to oxidative stress, which can be induced by metal toxicity. In this paper, a chronic aluminum overload-induced model of neurodegeneration was used to investigate whether metal ions (Al, Fe, Mn, Cu and Zn)-related oxidative stress was involved in neurodegenerative mechanism and to identify the protective action of meloxicam against rat hippocampal neuronal injury. The metal ion contents, activity of superoxide dismutase (SOD), and content of malondialdehyde (MDA) were detected. The results showed that the spatial learning and memory (SLM) function was significantly impaired in chronic aluminum overload rats. Considerable karyopycnosis was observed in hippocampal neurons. The SOD activity was weakened and the MDA content increased both significantly. In the hippocampus, Al, Fe, Mn, Cu, and Zn contents increased by 184.1%, 186.1%, 884.2%, 199.4% and 149.2%, respectively. Meloxicam administration (without Al) had no effect compared with the control group, while meloxicam treatment with aluminum exposure significantly protected rats from SLM function impairment, neuron death, lower SOD activity, higher MDA content and brain metal ion imbalance. Our findings suggest that the cerebral metal ion imbalance-related oxidative stress is involved in mechanism of cerebral injury and neurodegeneration induced by chronic Al overload in rats, and that meloxicam protects neurons by reducing metal ion imbalance-related oxidative stress.

Prioritization of therapeutic targets of inflammation using proteomics, bioinformatics, and in silico cell-cell interactomics

Leukocyte extravasation is a multistep process, involving the movement of leukocytes out of the circulatory system, through vascular endothelium and to the site of tissue damage or infection. Protein-protein interactions play key roles in the extravasation process and have been attractive therapeutic targets for inhibiting inflammation using blocking (or neutralizing) antibodies. These targets include protein-protein interactions between cytokines (or chemokines) and their receptors on leukocytes and between adhesions molecules involving leukocyte-endothelium contacts. A number of therapeutics against these targets are currently used in clinic for treatment of inflammatory disorders, however, they are associated with side-effects partly due to the off-target actions (i.e., nonspecific targets). There is a need for novel targets involved in the leukocyte extravasation process that are specific to leukocyte subsets or to individual inflammatory disorder, and are amenable for drug development (i.e., duggable). In this chapter, we describe a methodology to identify novel "druggable" targets involving protein-protein interactions between activated leukocytes and endothelial cells using a combination of proteomics, bioinformatics and in silico interactomics. The result is a prioritized list of protein-protein interactions in a network consisting of leukocyte-endothelial cell communication and contacts. These prioritized targets can be pursued for the development of therapeutics such as neutralizing antibodies and for their validation through preclinical testing. The method described here provides the workflow to identify and clinically target important cell-cell interactions that are specific/selective for particular inflammatory disorders and to improve currently available therapies.

Herbal medicines for ischemic stroke: combating inflammation as therapeutic targets

Stroke is a debilitating disease for which limited therapeutic approaches are available currently. Thus, there is an urgent need for developing novel therapies for stroke. Astrocytes, endothelial cells and pericytes constitute a neurovascular network for metabolic requirement of neurons. During ischemic stroke, these cells contribute to post-ischemic inflammation at multiple stages of ischemic cascades. Upon ischemia onset, activated resident microglia and astrocytes, and infiltrated immune cells release multiple inflammation factors including cytokines, chemokines, enzymes, free radicals and other small molecules, not only inducing brain damage but affecting brain repair. Recent progress indicates that anti-inflammation is an important therapeutic strategy for stroke. Given a long history with direct experience in the treatment of human subjects, Traditional Chinese Medicine and its related natural compounds are recognized as important sources for drug discovery. Last decade, a great progress has been made to identify active compounds from herbal medicines with the properties of modulating post-ischemic inflammation for neuroprotection. Herein, we discuss the inflammatory pathway in early stage and secondary response to injured tissues after stroke from initial artery occlusion to brain repair, and review the active ingredients from natural products with anti-inflammation and neuroprotection effects as therapeutic agents for ischemic stroke. Further studies on the post-ischemic inflammatory mechanisms and corresponding drug candidates from herbal medicine may lead to the development of novel therapeutic strategies in stroke treatment.

Dysfunctional nucleus tractus solitarius: its crucial role in promoting neuropathogenetic cascade of Alzheimer's dementia--a novel hypothesis

The pathophysiological mechanism(s) underlying Alzheimer's disease (AD) still remain unclear, and no disease-modifying or prophylactic therapies are currently available. Unraveling the fundamental neuropathogenesis of AD is an important challenge. Several studies on AD have suggested lesions in a number of CNS areas including the basal forebrain, hippocampus, entorhinal cortex, amygdale/insula, and the locus coeruleus. However, plausible unifying studies on the upstream factors that involve these heterogeneous regions and herald the onset of AD pathogenesis are not available. The current article presents a novel nucleus tractus solitarius (NTS) vector hypothesis that underpins several disparate biological mechanisms and neural circuits, and identifies relevant hallmarks of major presumptive causative factor(s) linked to the NTS, in older/aging individuals. Aging, obesity, infection, sleep apnea, smoking, neuropsychological states, and hypothermia-all activate inflammatory cytokines and oxidative stress. The synergistic impact of systemic proinflammatory mediators activates microglia and promotes neuroinflammation. Acutely, the innate immune response is protective defending against pathogens/toxins; however, when chronic, it causes neuroinflammation and neuronal dysfunction, particularly in brainstem and neocortex. The NTS in the brainstem is an essential multiple signaling hub, and an extremely important central integration site of baroreceptor, chemoreceptor, and a multitude of sensory afferents from gustatory, gastrointestinal, cardiac, pulmonary, and upper airway systems. Owing to persistent neuroinflammation, the dysfunctional NTS exerts deleterious impact on nucleus ambiguus, dorsal motor nucleus of vagus, hypoglossal, parabrachial, locus coeruleus and many key nuclei in the brainstem, and the hippocampus, entorhinal cortex, prefrontal cortex, amygdala, insula, and basal forebrain in the neocortex. The neuronal and synaptic dysfunction emanating from the inflamed NTS may affect its interconnected pathways impacting almost the entire CNS--which is already primed by neuroinflammation, thus promoting cognitive and neuropsychiatric symptoms. The upstream factors discussed here may underpin the neuropathopgenesis of AD. AD pathology is multifactorial; the current perspective underscores the value of attenuating disparate upstream factors--in conjunction with anticholinesterase, anti-inflammatory, immunosuppressive, and anti-oxidant pharmacotherapy. Amelioration of the NTS pathology may be of central importance in countering the neuropathological cascade of AD. The NTS, therefore, may be a potential target of novel therapeutic strategies.

Intercellular interactomics of human brain endothelial cells and th17 lymphocytes: a novel strategy for identifying therapeutic targets of CNS inflammation

Leukocyte infiltration across an activated brain endothelium contributes to the neuroinflammation seen in many neurological disorders. Recent evidence shows that IL-17-producing T-lymphocytes (e.g., Th17 cells) possess brain-homing capability and contribute to the pathogenesis of multiple sclerosis and cerebral ischemia. The leukocyte transmigration across the endothelium is a highly regulated, multistep process involving intercellular communications and interactions between the leukocytes and endothelial cells. The molecules involved in the process are attractive therapeutic targets for inhibiting leukocyte brain migration. We hypothesized and have been successful in demonstrating that molecules of potential therapeutic significance involved in Th17-brain endothelial cell (BEC) communications and interactions can be discovered through the combination of advanced membrane/submembrane proteomic and interactomic methods. We describe elements of this strategy and preliminary results obtained in method and approach development. The Th17-BEC interaction network provides new insights into the complexity of the transmigration process mediated by well-organized, subcellularly localized molecular interactions. These molecules and interactions are potential diagnostic, therapeutic, or theranostic targets for treatment of neurological conditions accompanied or caused by leukocyte infiltration.

Effects of chlorogenic acid on neutrophil locomotion functions in response to inflammatory stimulus

AIM OF THE STUDY

Species of Lychnophora are used in Brazilian folk medicine as analgesic and anti-inflammatory agents. Chlorogenic acid (CGA) and their analogues are important components of polar extracts of these species, as well in several European and Asian medicinal plants. Some of these phenolic compounds display anti-inflammatory effects. In this paper we report the isolation of CGA from Lychnophora salicifolia and its effects on functions involved in neutrophils locomotion.

MATERIALS AND METHODS

LC-MS(n) data confirmed the presence of CGA in the plant. Actions of CGA were investigated on neutrophils obtained from peritoneal cavity of Wistar rats (4h after 1% oyster glycogen solution injection; 10 ml), and incubated with vehicle or with 50, 100 or 1000 μM CGA in presence of lipopolysaccharide from Escherichia coli (LPS, 5 μg/ml). Nitric oxide (NO; Griess reaction); prostaglandin E(2) (PGE(2)), interleukin-1β (IL-1β) and tumor necrosis factor-α [TNF-α; enzyme-linked immunosorbent assay (EIA)]; protein (flow cytometry) and gene (RT-PCR) expression of L-selectin, β(2)integrin and platelet-endothelial cell adhesion molecule-1 (PECAM-1) were quantified. In vitro neutrophil adhesion to primary culture of microvascular endothelial cell (PMEC) and neutrophil migration in response to formyl-methionil-leucil-phenilalanine (fMLP, 10(-8)M, Boyden chamber) was determined.

RESULTS

CGA treatment did not modify the secretion of inflammatory mediators, but inhibited L-selectin cleavage and reduced β(2) integrin, independently from its mRNA synthesis, and reduced membrane PECAM-1 expression; inhibited neutrophil adhesion and neutrophil migration induced by fMLP.

CONCLUSIONS

Based on these findings, we highlight the direct inhibitory actions of CGA on adhesive and locomotion properties of neutrophils, which may contribute to its anti-inflammatory effects and help to explain the use of Lychnophora salicifolia as an anti-inflammatory agent.

Experimental models for assaying microvascular endothelial cell pathophysiology in stroke

It is important to understand the molecular mechanisms underlying neuron death following stroke in order to develop effective neuroprotective strategies. Since studies on human stroke are extremely limited due to the difficulty in collecting post-mortem tissue at different time points after the onset of stroke, brain ischaemia research focuses on information derived from in-vitro models of neuronal death through ischaemic injury [1]. This review aims to provide an update on the different in-vitro stroke models with brain microvascular endothelial cells that are currently being used. These models provide a physiologically relevant tool to screen potential neuroprotective drugs in stroke and to study the molecular mechanisms involved in brain ischaemia.

Amelioration of inflammation and cytotoxicity by dipyridamole in brain endothelial cells

BACKGROUND

Increasing evidence suggests that beyond its antiplatelet properties, dipyridamole may have pleiotropic effects on other cells within the neurovascular elements of the brain. In this experimental cellular study, we asked whether dipyridamole can ameliorate brain endothelial injury after exposure to inflammatory and metabolic insults.

METHODS

Human brain endothelial cells were grown in culture, and exposed to TNFalpha (continuously for 20 h) or subjected to oxygen-glucose deprivation (OGD; 6 h of insult followed by 18 h recovery). Expression of ICAM-1, VCAM-1 and PECAM-1 were measured by immunoblotting. Matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) in the conditioned media were quantified via zymography. MTT mitochondrial activity was measured to assess endothelial cell viability.

RESULTS

Exposure of human brain endothelial cells to TNFalpha (12.5-50 ng/ml) induced a clear increase in protein levels of ICAM-1, VCAM-1 and MMP-9. TNFalpha did not alter PECAM-1. Dipyridamole (1-5 muM) significantly attenuated ICAM-1 and MMP-9 levels after this inflammatory insult. No significant effects of dipyridamole were noted for VCAM-1. Six-hour OGD induced moderate endothelial cell death accompanied by a release of MMP-9. Dipyridamole significantly decreased MMP-9 levels and cell death after this metabolic insult.

CONCLUSIONS

These results suggest that dipyridamole may ameliorate brain endothelial injury after inflammation and/or metabolic insults. How these putative cellular mechanisms may relate to clinical outcomes and conditions in stroke patients remains to be elucidated.

Inflammation and brain injury: acute cerebral ischaemia, peripheral and central inflammation

Inflammation is a classical host defence response to infection and injury that has many beneficial effects. However, inappropriate (in time, place and magnitude) inflammation is increasingly implicated in diverse disease states, now including cancer, diabetes, obesity, atherosclerosis, heart disease and, most relevant here, CNS disease. A growing literature shows strong correlations between inflammatory status and the risk of cerebral ischaemia (CI, most commonly stroke), as well as with outcome from an ischaemic event. Intervention studies to demonstrate a causal link between inflammation and CI (or its consequences) are limited but are beginning to emerge, while experimental studies of CI have provided direct evidence that key inflammatory mediators (cytokines, chemokines and inflammatory cells) contribute directly to ischaemic brain injury. However, it remains to be determined what the relative importance of systemic (largely peripheral) versus CNS inflammation is in CI. Animal models in which CI is driven by a CNS intervention may not accurately reflect the clinical condition; stroke being typically induced by atherosclerosis or cardiac dysfunction, and hence current experimental paradigms may underestimate the contribution of peripheral inflammation. Experimental studies have already identified a number of potential anti-inflammatory therapeutic interventions that may limit ischaemic brain damage, some of which have been tested in early clinical trials with potentially promising results. However, a greater understanding of the contribution of inflammation to CI is still required, and this review highlights some of the key mechanism that may offer future therapeutic targets.

Neutrophils block permeability increases induced by oxygen glucose deprivation in a culture model of the human blood-brain barrier

Experimentally, oxygen glucose deprivation (OGD) has been widely used to mimic the environmental conditions present during cerebral ischemia-reperfusion (IR) injury. OGD is known to increase permeability across cultured cerebral endothelial cells, which models the effect of IR on permeability across the blood-brain barrier (BBB); however, studies have yet to be performed in a human model. The effect of neutrophils on the increase in BBB permeability associated with IR injury has yet to be modeled in vitro. To address these questions, the human brain endothelial cell line hCMEC/D3 was exposed to OGD with reoxygenation, and permeability was measured for a range of OGD exposure times (1-24h). One hour of exposure to OGD induced a reversible increase in permeability, unassociated with cytotoxicity (assessed from lactate dehydrogenase release). However, 12-24h OGD exposures induced sustained increases in permeability associated with cytotoxicity. The 1h permeability increase was inhibited with the nitric oxide synthase inhibitors l-NAME (10(-)(7)mol/l) and 1400W (10(-)(7)mol/l). Neutrophils (5x10(6)/ml) blocked the permeability increase associated with 1h OGD, whether applied during or after OGD exposure. Permeability remained low if neutrophils were activated with leukotriene (Lt)B(4) (10(-)(7)mol/l) or exposed to a transendothelial gradient of LtB(4), while neutrophil activation with phorbyl myristate acetate (4x10(-)(8)mol/l) induced a small increase. Neutrophils had no effect on the permeability increase induced by 12h OGD exposure. This study finds that OGD induces reversible increases in permeability linked to nitric oxide synthesis in a human culture model of the BBB and shows that neutrophils mitigate permeability increases in this context.

ABCG2 is upregulated in Alzheimer's brain with cerebral amyloid angiopathy and may act as a gatekeeper at the blood-brain barrier for Abeta(1-40) peptides

Alzheimer's disease (AD) is characterized by accumulation and deposition of Abeta peptides in the brain. Abeta deposition in cerebrovessels occurs in many AD patients and results in cerebral amyloid angiopathy (AD/CAA). Since Abeta can be transported across blood-brain barrier (BBB), aberrant Abeta trafficking across BBB may contribute to Abeta accumulation in the brain and CAA development. Expression analyses of 273 BBB-related genes performed in this study showed that the drug transporter, ABCG2, was significantly upregulated in the brains of AD/CAA compared with age-matched controls. Increased ABCG2 expression was confirmed by Q-PCR, Western blot, and immunohistochemistry. Abcg2 was also increased in mouse AD models, Tg-SwDI and 3XTg. Abeta alone or in combination with hypoxia/ischemia failed to stimulate ABCG2 expression in BBB endothelial cells; however, conditioned media from Abeta-activated microglia strongly induced ABCG2 expression. ABCG2 protein in AD/CAA brains interacted and coimmunoprecipitated with Abeta. Overexpression of hABCG2 reduced drug uptake in cells; however, interaction of Abeta(1-40) with ABCG2 impaired ABCG2-mediated drug efflux. The role of Abcg2 in Abeta transport at the BBB was investigated in Abcg2-null and wild-type mice after intravenous injection of Cy5.5-labeled Abeta(1-40) or scrambled Abeta(40-1). Optical imaging analyses of live animals and their brains showed that Abcg2-null mice accumulated significantly more Abeta in their brains than wild-type mice. The finding was confirmed by immunohistochemistry. These results suggest that ABCG2 may act as a gatekeeper at the BBB to prevent blood Abeta from entering into brain. ABCG2 upregulation may serve as a biomarker of CAA vascular pathology in AD patients.

Cell adhesion molecules and ischemic stroke

OBJECTIVE

To describe the role of adhesion molecules in ischemic stroke.

METHODS

A PubMed search of literature pertaining to this study was conducted in April 2008 using specific keyword search terms pertaining to stroke and various listed subtopics related to adhesion molecules.

RESULTS

An important contribution of beta2-integrins (CD11/CD18), intercellular adhesion molecule and P-selectin in the recruitment of leukocytes as well as platelets in the post-ischemic cerebral microvasculature has been defined in related studies. Immunoblockade or genetic deletion of these adhesion molecules has been shown to reduce infarct volume, edema, behavioral deficits and/or mortality in different animal models of ischemic stroke. Anti-adhesion agents also appear to widen the therapeutic window for thrombolytic therapy in these experimental models. An emerging role of inflammatory signaling pathways has also been addressed in modulating adhesion properties of post-ischemic cerebral microvasculature. Despite the promising data obtained from animal studies, few clinical trials assessing anti-adhesion therapy in ischemic stroke have failed to show efficacy.

DISCUSSION

Several experiments using cell surface adhesion molecules as targets of stroke therapy are promising yet inadequate. Clinical trials using immune blockade of adhesion molecules by antibodies have failed due to immune reactions of the host. Further clinical trials are needed to test the efficacy of humanized antibodies or non-immunogenic agents that interfere with cell adhesion mechanisms. Adhesion blocking strategies seem to be effective particularly at reperfusion and use of these strategies with thrombolytic therapies justifies a continued effort to define the role of adhesion molecules in the pathophysiology of cerebral ischemia-reperfusion.

Inhibition of COX 1 and 2 prior to renal ischemia/reperfusion injury decreases the development of fibrosis

Ischemia and reperfusion injury (IRI) contributes to the development of chronic interstitial fibrosis/tubular atrophy in renal allograft patients. Cyclooxygenase (COX) 1 and 2 actively participate in acute ischemic injury by activating endothelial cells and inducing oxidative stress. Furthermore, blockade of COX 1 and 2 has been associated with organ improvement after ischemic damage. The aim of this study was to evaluate the role of COX 1 and 2 in the development of fibrosis by performing a COX 1 and 2 blockade immediately before IRI. We subjected C57Bl/6 male mice to 60 min of unilateral renal pedicle occlusion. Prior to surgery mice were either treated with indomethacin (IMT) at days -1 and 0 or were untreated. Blood and kidney samples were collected 6 wks after IRI. Kidney samples were analyzed by real-time reverse transcription-polymerase chain reaction for expression of transforming growth factor beta (TGF-beta), monocyte chemoattractant protein 1 (MCP-1), osteopontin (OPN), tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-1 beta, IL-10, heme oxygenase 1 (HO-1), vimentin, connective-tissue growth factor (CTGF), collagen I, and bone morphogenic protein 7 (BMP-7). To assess tissue fibrosis we performed morphometric analyses and Sirius red staining. We also performed immunohistochemical analysis of anti-actin smooth muscle. Renal function did not significantly differ between groups. Animals pretreated with IMT showed significantly less interstitial fibrosis than nontreated animals. Gene transcript analyses showed decreased expression of TGF-beta, MCP-1, TNF-alpha, IL-1-beta, vimentin, collagen I, CTGF, and IL-10 mRNA (all P < 0.05). Moreover, HO-1 mRNA was increased in animals pretreated with IMT (P < 0.05). Conversely, IMT treatment decreased osteopontin expression and enhanced BMP-7 expression, although these levels did not reach statistical significance when compared with control expression levels. The blockade of COX 1 and 2 resulted in less tissue fibrosis, which was associated with a decrease in proinflammatory cytokines and enhancement of the protective cellular response.

Angiotensin II controls occludin function and is required for blood brain barrier maintenance: relevance to multiple sclerosis

The blood-brain barrier (BBB) restricts molecular and cellular trafficking between the blood and the CNS. Although astrocytes are known to control BBB permeability, the molecular determinants of this effect remain unknown. We show that angiotensinogen (AGT) produced and secreted by astrocytes is cleaved into angiotensin II (AngII) and acts on type 1 angiotensin receptors (AT1) expressed by BBB endothelial cells (ECs). Activation of AT1 restricts the passage of molecular tracers across human BBB-derived ECs through threonine-phosphorylation of the tight junction protein occludin and its mobilization to lipid raft membrane microdomains. We also show that AGT knock-out animals have disorganized occludin strands at the level of the BBB and a diffuse accumulation of the endogenous serum protein plasminogen in the CNS, compared with wild-type animals. Finally, we demonstrate a reduction in the number of AGT-immunopositive perivascular astrocytes in multiple sclerosis (MS) lesions, which correlates with a reduced expression of occludin similarly seen in the CNS of AGT knock-out animals. Such a reduction in astrocyte-expressed AGT and AngII is dependent, in vitro, on the proinflammatory cytokines tumor necrosis factor-alpha and interferon-gamma. Our study defines a novel physiological role for AngII in the CNS and suggests that inflammation-induced downregulation of AngII production by astrocytes is involved in BBB dysfunction in MS lesions.

Death receptor expression and function at the human blood brain barrier

The blood brain barrier (BBB) is composed of specialized endothelial cells tightly anastomosed to one another and surrounded by a thick extracellular matrix, the basement membrane. Together these components restrict the diffusion of cells and molecules from the periphery into the central nervous system (CNS), providing immune privilege and homeostasis. Dysregulation of the BBB and trans-endothelial migration of immune cells are amongst the earliest CNS changes partaking in lesion formation in multiple sclerosis (MS). Death receptors are members of the tumor necrosis factor receptor (TNFR) super-family. They are expressed on a variety of tissues including endothelium, but the consequence of their triggering appears to be cell type specific. In this study, we describe the expression of death receptors TNFR1, Fas and DR5 on primary cultures of human BBB-derived endothelial cells (ECs), as well as the effects of receptor activation on human brain endothelial cell (HBEC) function. We show that HBECs are resistant to cell death mediated via TNFalpha, FasL and TRAIL and that neither receptor ligation induces cellular proliferation of HBECs. TNFR1 ligation induces NFkappaB activation and the upregulation of chemokines MCP-1 and IL-8, as well as adhesion molecules ICAM-1 and VCAM-1, while Fas and DR5 triggering activate the extracellular signal regulated kinases-1 and -2 (Erk 1/2, p42/44 MAPK) inducing the release of matrix metalloproteinase 9 (MMP9) by BBB-derived ECs.

CEREBROVASCULAR EFFECTS OF OESTROGEN: MULTIPLICITY OF ACTION

1. Cerebral vessels express oestrogen receptors (ER) in both the smooth muscle and endothelial cell layers of cerebral blood vessels. Levels of ERalpha are higher in female rats chronically exposed to oestrogen, either endogenous or exogenous. 2. Chronic exposure to oestrogen, either endogenous (normally cycling females) or exogenous (ovariectomized with oestrogen replacement), results in cerebral arteries that are more dilated than arteries from ovariectomized counterparts when studied in vitro. This effect is primarily mediated by an increase in the production of vasodilator factors, including nitric oxide (NO) and prostacylin. In contrast, oestrogen appears to suppress the production of endothelial-derived hyperpolarizing factor. Oestrogen treatment increases cerebrovascular levels of endothelial nitric oxide synthase (eNOS), cyclo-oxygenase (COX)-1 and prostacyclin synthase. In addition, via activation of the phosphatidylinositol 3-kinase/Akt pathway, both acute and chronic oestrogen exposure increases eNOS phosphorylation, increasing NO production. 3. Oestrogen receptors have also been localized to cerebrovascular mitochondria and exposure to oestrogen increases the efficiency of energy production while simultaneously reducing mitochondrial production of reactive oxygen species. Oestrogen increases the production of mitochondrial proteins encoded by both mitochondrial and nuclear DNA, including cytochrome c, subunits I and IV of complex IV and Mn-superoxide dismutase. Oestrogen treatment increases the activity of citrate synthase and complex IV and decreases mitochondrial production of H(2)O(2). 4. Oestrogen also has potent anti-inflammatory effects in the cerebral circulation that may have important implications for the incidence and severity of cerebrovascular disease. Administration of lipopolysaccharide or interleukin-1beta to ovariectomized female rats induces cerebrovascular COX-2 and inducible nitric oxide synthase (iNOS) protein expression and increases prostaglandin E(2) expression. Levels of COX-2 and iNOS expression vary with the stage of the oestrous cycle, and the cerebrovascular inflammatory response is suppressed in ovariectomized animals treated with oestrogen. Interleukin-1beta induction of COX-2 protein is prevented by treatment with a nuclear factor (NF)-kappaB inhibitor, and oestrogen treatment reduces cerebrovascular NF-kappaB activity. 5. Cerebrovascular dysfunction and pathology contribute to the pathogenesis of stroke, brain trauma, oedema and dementias, such as Alzheimer's disease. A better understanding of the action of oestrogen on cerebrovascular function holds promise for the development of new therapeutic entities that could be useful in preventing or treating a wide variety of cerebrovascular diseases.

Hypoxia-inducible factor-1 (HIF-1) is involved in the regulation of hypoxia-stimulated expression of monocyte chemoattractant protein-1 (MCP-1/CCL2) and MCP-5 (Ccl12) in astrocytes

Background

Neuroinflammation has been implicated in various brain pathologies characterized by hypoxia and ischemia. Astroglia play an important role in the initiation and propagation of hypoxia/ischemia-induced inflammation by secreting inflammatory chemokines that attract neutrophils and monocytes into the brain. However, triggers of chemokine up-regulation by hypoxia/ischemia in these cells are poorly understood. Hypoxia-inducible factor-1 (HIF-1) is a dimeric transcriptional factor consisting of HIF-1α and HIF-1β subunits. HIF-1 binds to HIF-1-binding sites in the target genes and activates their transcription. We have recently shown that hypoxia-induced expression of IL-1β in astrocytes is mediated by HIF-1α. In this study, we demonstrate the role of HIF-1α in hypoxia-induced up-regulation of inflammatory chemokines, human monocyte chemoattractant protein-1 (MCP-1/CCL2) and mouse MCP-5 (Ccl12), in human and mouse astrocytes, respectively.

Methods

Primary fetal human astrocytes or mouse astrocytes generated from HIF-1α^+/+ and HIF-1α^+/- mice were subjected to hypoxia (<2% oxygen) or 125 μM CoCl₂ for 4 h and 6 h, respectively. The expression of HIF-1α, MCP-1 and MCP-5 was determined by semi-quantitative RT-PCR, western blot or ELISA. The interaction of HIF-1α with a HIF-1-binding DNA sequence was examined by EMSA and supershift assay. HIF-1-binding sequence in the promoter of MCP-1 gene was cloned and transcriptional activation of MCP-1 by HIF-1α was analyzed by reporter gene assay.

Results

Sequence analyses identified HIF-1-binding sites in the promoters of MCP-1 and MCP-5 genes. Both hypoxia and HIF-1α inducer, CoCl₂, strongly up-regulated HIF-1α expression in astrocytes. Mouse HIF-1α^+/- astrocytes had lower basal levels of HIF-1α and MCP-5 expression. The up-regulation of MCP-5 by hypoxia or CoCl₂ in HIF-1α^+/+ and HIF-1α^+/- astrocytes was correlated with the levels of HIF-1α in cells. Both hypoxia and CoCl₂ also up-regulated HIF-1α and MCP-1 expression in human astrocytes. EMSA assay demonstrated that HIF-1 activated by either hypoxia or CoCl₂ binds to wild-type HIF-1-binding DNA sequence, but not the mutant sequence. Furthermore, reporter gene assay demonstrated that hypoxia markedly activated MCP-1 transcription but not the mutated MCP-1 promoter in transfected astrocytes.

Conclusion

These findings suggest that both MCP-1 and MCP-5 are HIF-1 target genes and that HIF-1α is involved in transcriptional induction of these two chemokines in astrocytes by hypoxia.

Expression of Adhesion Factors Induced by Epileptiform Activity in the Endothelium of the Isolated Guinea Pig Brain In Vitro

PURPOSE

Brain inflammation has been recently considered in the pathogenesis of focal epilepsies. Synthesis of pro-inflammatory mediators in the brain was described both in experimental models of seizures and in human postsurgical tissue. Inflammatory mediators may up-regulate endothelial adhesion molecules, therefore promoting adhesion and homing of leucocytes into the brain. In the present study, expression of inducible adhesion factors in brain endothelium was verified after pharmacological induction of seizure-like activity in specific brain areas of the in vitro isolated guinea pig brain.

METHODS

Experiments were performed in isolated guinea-pig brains maintained in vitro by arterial perfusion. In this preparation, brief application of the GABAa receptor-antagonist, bicuculline, consistently induced focal ictal discharges in the limbic region that secondarily diffuse to the neocortex, as verified by simultaneous electrophysiological recording of extracellular activity. At the end of the electrophysiological experiment (after 5 h in vitro), brains were fixed and immunostaining for adhesion molecules P-selectin and ICAM-1 and for Fos protein was evaluated.

RESULTS

Immunohistochemical analysis of isolated brains in which seizure-like activity was induced revealed expression of inducible adhesion factors P-selectin and ICAM-1 in the endothelium of small-medium size brain vessels. In particular, the expression of these molecules was consistently observed in all areas involved in epileptic seizure-like ictal activity (limbic cortices and neocortex), and was infrequently found in regions that generated interictal spiking (piriform cortex), suggesting a trigger role played by seizures for endothelial activation. An increase in Fos protein expression was evident in all analyzed limbic areas and in the neocortex, indicating a correlation between the areas of neuronal and endothelial activation. In control brains maintained in vitro for comparable times without induction of epileptiform activity, no immunoreactivity for Fos and adhesion molecules was observed.

CONCLUSIONS

Seizure-like activity in an in vitro isolated brain preparation induces the expression of adhesion molecules in the cerebral endothelium. These observations indicate that local endothelial activation may represent a crucial step for the development of an inflammatory response induced by seizures, and suggest a possible novel pathogenic mechanism during the process of epileptogenesis.

Post-ischaemic treatment with the cyclooxygenase-2 inhibitor nimesulide reduces blood-brain barrier disruption and leukocyte infiltration following transient focal cerebral ischaemia in rats

Several studies suggest that cyclooxygenase (COX)-2 plays a pivotal role in the progression of ischaemic brain damage. In the present study, we investigated the effects of selective inhibition of COX-2 with nimesulide (12 mg/kg) and selective inhibition of COX-1 with valeryl salicylate (VAS, 12-120 mg/kg) on prostaglandin E(2) (PGE(2)) levels, myeloperoxidase (MPO) activity, Evans blue (EB) extravasation and infarct volume in a standardized model of transient focal cerebral ischaemia in the rat. Post-ischaemic treatment with nimesulide markedly reduced the increase in PGE(2) levels in the ischaemic cerebral cortex 24 h after stroke and diminished infarct size by 48% with respect to vehicle-treated animals after 3 days of reperfusion. Furthermore, nimesulide significantly attenuated the blood-brain barrier (BBB) damage and leukocyte infiltration (as measured by EB leakage and MPO activity, respectively) seen at 48 h after the initial ischaemic episode. These studies provide the first experimental evidence that COX-2 inhibition with nimesulide is able to limit BBB disruption and leukocyte infiltration following transient focal cerebral ischaemia. Neuroprotection afforded by nimesulide is observed even when the treatment is delayed until 6 h after the onset of ischaemia, confirming a wide therapeutic window of COX-2 inhibitors in experimental stroke. On the contrary, selective inhibition of COX-1 with VAS had no significant effect on the evaluated parameters. These data suggest that COX-2 activity, but not COX-1 activity, contributes to the progression of focal ischaemic brain injury, and that the beneficial effects observed with non-selective COX inhibitors are probably associated to COX-2 rather than to COX-1 inhibition.

Inflammation in stroke and focal cerebral ischemia

BACKGROUND

A growing number of recent investigations have established a critical role for leukocytes in propagating tissue damage after ischemia and reperfusion in stroke. Experimental data obtained from animal models of middle cerebral artery occlusion implicate inflammatory cell adhesion molecules, chemokines, and cytokines in the pathogenesis of this ischemic damage.

METHODS

Data from recent animal and human studies were reviewed to demonstrate that inflammatory events occurring at the blood-endothelium interface of the cerebral capillaries underlie the resultant ischemic tissue damage.

RESULTS

After arterial occlusion, the up-regulated expression of cytokines including IL-1, and IL-6 act upon the vascular endothelium to increase the expression of intercellular adhesion molecule-1, P-selectin, and E-selectin, which promote leukocyte adherence and accumulation. Integrins then serve to structurally modify the basal lamina and extracellular matrix. These inflammatory signals then promote leukocyte transmigration across the endothelium and mediate inflammatory cascades leading to further cerebral infarction.

CONCLUSIONS

Inflammatory interactions that occur at the blood-endothelium interface, involving cytokines, adhesion molecules, chemokines and leukocytes, are critical to the pathogenesis of tissue damage in cerebral infarction. Exploring these pathophysiological mechanisms underlying ischemic tissue damage may direct rational drug design in the therapeutic treatment of stroke.

Selective COX-2 inhibition reduces leukocyte sticking and improves the microcirculation in TNBS colitis

The role of cyclooxygenase-2 inhibitors in the course of experimental colitis is controversially discussed. The aim of this study was to evaluate leukocyte-endothelium interaction and colitis activity after applying the selective cyclooxygenase-2 inhibitor NS-398 in a rat trinitrobenzene sulfonic acid (TNBS) colitis model. The acute phase of TNBS colitis is characterized by a significant reduction of capillary blood flow, capillary density, diuresis, and weight and a significant increase in capillary permeability, leukocyte sticking, and hematocrit. Applying the selective cyclooxygenase-2 inhibitor NS-398 leads to a significant improvement of all microcirculatory parameters and clinical findings compared to the (untreated) colitis group. There are no histopathological differences between the individual colitis groups. Acute colitis is characterized by an extensive disturbance of microcirculation together with signs of systemic inflammatory response syndrome. These alterations are significantly improved by inhibiting cyclooxygenase-2. The results support the described correlation between cyclooxygenase activation and leukocyte-endothelium interaction. Moreover, they underscore the postulated relation between leukocyte-endothelium interaction and capillary blood flow.

Evidence that hypoxia-inducible factor-1 (HIF-1) mediates transcriptional activation of interleukin-1beta (IL-1beta) in astrocyte cultures

Hypoxia-inducible factor-1 (HIF-1) is a heterodimeric transcription factor composed of HIF-1alpha and HIF-1beta subunits and involved in the regulation of gene expression in adaptive response to hypoxia. This study reports that the inflammatory cytokine interleukin-1beta (IL-1beta) shares common features of other known HIF-1alpha-regulated genes. Both human and mouse IL-1beta genes carry multiple HIF-1-binding sites in their promoter regions and are up-regulated by hypoxia and CoCl2 in human and mouse astrocytes in parallel with up-regulation of HIF-1alpha mRNA and protein. Inhibition of HIF-1alpha degradation by proteasome inhibitor, MG-132, potentiated hypoxia-induced IL-1beta release from human astrocytes, and this response was blocked in the presence of CdCl2. Mouse astrocytes with Hif1alpha+/- genotype demonstrated attenuated up-regulation of both HIF-1alpha and IL-1beta by hypoxia and CoCl2. Mutation of HIF-1-binding sites in the IL-1beta promoter abolished hypoxia-induced transactivation of the reporter gene transfected into human astrocytes. Similarly, HIF-1 binding "decoy" oligonuleotide transfected into astrocytes inhibited both hypoxia-induced transactivation of the HIF-1 reporter gene and IL-1beta secretion from transfected astrocytes. Collectively, the evidence suggests that the transcriptional activation of IL-1beta in astrocytes exposed to hypoxia occurs via HIF-1.

Cyclooxygenase-2-specific inhibitor improves functional outcomes, provides neuroprotection, and reduces inflammation in a rat model of traumatic brain injury

OBJECTIVE

Increases in brain cyclooxygenase-2 (COX2) are associated with the central inflammatory response and with delayed neuronal death, events that cause secondary insults after traumatic brain injury. A growing literature supports the benefit of COX2-specific inhibitors in treating brain injuries.

METHODS

DFU [5,5-dimethyl-3(3-fluorophenyl)-4(4-methylsulfonyl)phenyl-2(5)H)-furanone] is a third-generation, highly specific COX2 enzyme inhibitor. DFU treatments (1 or 10 mg/kg intraperitoneally, twice daily for 3 d) were initiated either before or after traumatic brain injury in a lateral cortical contusion rat model.

RESULTS

DFU treatments initiated 10 minutes before injury or up to 6 hours after injury enhanced functional recovery at 3 days compared with vehicle-treated controls. Significant improvements in neurological reflexes and memory were observed. DFU initiated 10 minutes before injury improved histopathology and altered eicosanoid profiles in the brain. DFU 1 mg/kg reduced the rise in prostaglandin E2 in the brain at 24 hours after injury. DFU 10 mg/kg attenuated injury-induced COX2 immunoreactivity in the cortex (24 and 72 h) and hippocampus (6 and 72 h). This treatment also decreased the total number of activated caspase-3-immunoreactive cells in the injured cortex and hippocampus, significantly reducing the number of activated caspase-3-immunoreactive neurons at 72 hours after injury. DFU 1 mg/kg amplified potentially anti-inflammatory epoxyeicosatrienoic acid levels by more than fourfold in the injured brain. DFU 10 mg/kg protected the levels of 2-arachidonoyl glycerol, a neuroprotective endocannabinoid, in the injured brain.

CONCLUSION

These improvements, particularly when treatment began up to 6 hours after injury, suggest exciting neuroprotective potential for COX2 inhibitors in the treatment of traumatic brain injury and support the consideration of Phase I/II clinical trials.