Tannic acid protects aged brain against cerebral hypoperfusion via modulation of Nrf2 and inflammatory pathways.

Current study purposed to investigate the neuroprotective effects of Tannic Acid (TA) on mild chronic cerebral hypoperfusion model in rats. Male Wistar rats were subjected to permanent Unilateral Common Carotid Artery Occlusion (UCCAO), followed by TA treatment (0.05% w/v) in drinking water for one month. Nuclear factor erythroid 2-related factor 2 (Nrf2), NAD(P)H: quinone oxidoreductase 1 (NQO-1), heme oxygenase-1 (HO-1), factor kappa-light-chain-enhancer of activated B cells (NF-κB), tumor necrosis factor-α (TNF-α), B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), caspase-3, blood triglyceride, blood glucose, and liver enzymes' activity were detected after the experimental period. Also, behavioral tests, hematoxylin and eosin (H&E) staining, and PET scan were performed after treatment. Post-treatment of TA improved locomotion and memory function (P < 0.001), and reduced neural cell death (P < 0.001) in the treatment group compared to UCCAO rats. Furthermore, long-term TA treatment significantly increased the levels of Nrf2 (P < 0.001), NQO-1 (P < 0.001), and HO-1 (P < 0.001) in the hippocampus of the treatment group compared to the UCCAO group. TA consumption in the treatment group applied its anti-inflammatory effects via reducing the activity of NF-κB and TNF-α in comparison with the UCCAO group (P < 0.001 for both). Blood triglyceride, blood glucose, and liver enzymes did not change considerably in the groups (P > 0.05). The current results indicate that long-term post-treatment of TA exhibits protective effects against memory deficit and motor dysfunction. The cellular mechanism of TA in hypoperfused rats might be associated with the activation of antioxidant pathways, especially the Nrf2 pathway, and suppressing inflammatory factors like NF-κB and TNF-α.

Dual microglia effects on blood brain barrier permeability induced by systemic inflammation.

Microglia survey brain parenchyma, responding to injury and infections. Microglia also respond to systemic disease, but the role of blood-brain barrier (BBB) integrity in this process remains unclear. Using simultaneous in vivo imaging, we demonstrated that systemic inflammation induces CCR5-dependent migration of brain resident microglia to the cerebral vasculature. Vessel-associated microglia initially maintain BBB integrity via expression of the tight-junction protein Claudin-5 and make physical contact with endothelial cells. During sustained inflammation, microglia phagocytose astrocytic end-feet and impair BBB function. Our results show microglia play a dual role in maintaining BBB integrity with implications for elucidating how systemic immune-activation impacts neural functions.

The anatomy and immunology of vasculature in the central nervous system.

Barriers between circulation and the central nervous system (CNS) play a key role in the development and modulation of CNS immune responses. Structural variations in the vasculature traversing different anatomical regions within the CNS strongly influence where and how CNS immune responses first develop. Here, we provide an overview of cerebrovascular anatomy, focusing on the blood-CNS interface and how anatomical variations influence steady-state immunology in the compartment. We then discuss how CNS vasculature is affected by and influences the development of different pathophysiological states, such as CNS autoimmune disease, cerebrovascular injury, cerebral ischemia, and infection.

Microvascular fluid exchange during CPB with deep hypothermia circulatory arrest or low flow.

OBJECTIVE: Use of deep hypothermic low-flow (DHLF) cardiopulmonary bypass (CPB) has been associated with higher fluid loading than the use of deep hypothermia circulatory arrest (DHCA). We evaluated whether these perfusion strategies influenced fluid extravasation rates and edema generation differently per-operatively. MATERIALS AND METHODS: Twelve anesthetized pigs, randomly allocated to DHLF (n = 6) or DHCA (n = 6), underwent 2.5 hours CPB with cooling to 20°C for 30 minutes (min), followed by 30 min arrested circulation (DHCA) or 30 min low-flow circulation (DHLF) before 90 min rewarming to normothermia. Perfusion of tissues, fluid requirements, plasma volumes, colloid osmotic pressures and total tissue water contents were recorded and fluid extravasation rates calculated. During the experiments, cerebral microdialysis was performed in both groups. RESULTS: Microvascular fluid homeostasis was similar in both groups, with no between-group differences, reflected by similar fluid extravasation rates, plasma colloid osmotic pressures and total tissue water contents. Although extravasation rates increased dramatically from 0.10 (0.11) ml/kg/min (mean with standard deviation in parentheses) and 0.16 (0.02) ml/kg/min to 1.28 (0.58) ml/kg/min and 1.06 (0.41) ml/kg/min (DHCA and DHLF, respectively) after the initiation of CPB, fluid filtrations during both cardiac arrest and low flow were modest and close to baseline values. Cerebral microdialysis indicated anaerobic metabolism and ischemic brain injury in the DHCA group. CONCLUSION: No differences in microvascular fluid exchange could be demonstrated as a direct effect of DHCA compared with DHLF. Thirty minutes of DHCA was associated with anaerobic cerebral metabolism and possible brain injury.

Response of the cerebral vasculature following traumatic brain injury.

The critical role of the vasculature and its repair in neurological disease states is beginning to emerge particularly for stroke, dementia, epilepsy, Parkinson's disease, tumors and others. However, little attention has been focused on how the cerebral vasculature responds following traumatic brain injury (TBI). TBI often results in significant injury to the vasculature in the brain with subsequent cerebral hypoperfusion, ischemia, hypoxia, hemorrhage, blood-brain barrier disruption and edema. The sequalae that follow TBI result in neurological dysfunction across a host of physiological and psychological domains. Given the importance of restoring vascular function after injury, emerging research has focused on understanding the vascular response after TBI and the key cellular and molecular components of vascular repair. A more complete understanding of vascular repair mechanisms are needed and could lead to development of new vasculogenic therapies, not only for TBI but potentially vascular-related brain injuries. In this review, we delineate the vascular effects of TBI, its temporal response to injury and putative biomarkers for arterial and venous repair in TBI. We highlight several molecular pathways that may play a significant role in vascular repair after brain injury.

CD28 superagonist-mediated boost of regulatory T cells increases thrombo-inflammation and ischemic neurodegeneration during the acute phase of experimental stroke.

While the detrimental role of non-regulatory T cells in ischemic stroke is meanwhile unequivocally recognized, there are controversies about the properties of regulatory T cells (Treg). The aim of this study was to elucidate the role of Treg by applying superagonistic anti-CD28 antibody expansion of Treg. Stroke outcome, thrombus formation, and brain-infiltrating cells were determined on day 1 after transient middle cerebral artery occlusion. Antibody-mediated expansion of Treg enhanced stroke size and worsened functional outcome. Mechanistically, Treg increased thrombus formation in the cerebral microvasculature. These findings confirm that Treg promote thrombo-inflammatory lesion growth during the acute stage of ischemic stroke.

The effect of diesel exhaust exposure on blood-brain barrier integrity and function in a murine model.

Epidemiological studies indicate that exposure to diesel exhaust (DE) is associated with vascular-based disorders. To investigate the effect of DE on blood-brain barrier (BBB) function and integrity, 8-week-old BALB/c mice were randomized to DE in a cyclical treatment regimen over a 2-week period. Functional integrity of BBB was determined by considering brain parenchymal abundance of IgG within the hippocampal formation and cortex at 6 h and 24 h intervals following final exposure treatment. Neurovascular inflammation was expressed as the abundance of glial fibrillar acidic protein. Two doses of DE were studied and compared to air-only treated mice. Mice exposed to DE had substantially greater abundance of parenchymal IgG compared to control mice not exposed to DE. Increased parenchymal glial fibrillar acidic protein at 24 h post-DE exposure suggested heightened neurovascular inflammation. Our findings are proof-of-concept that inhalation of DE can compromise BBB function and support the broader contention that DE exposure may contribute to neurovascular disease risk.

Cerebral blood volume estimation by ferumoxytol-enhanced steady-state MRI at 9.4 T reveals microvascular impact of α1 -adrenergic receptor antibodies.

Cerebrovascular abnormality is frequently accompanied by cognitive dysfunctions, such as dementia. Antibodies against the α1 -adrenoceptor (α1 -AR) can be found in patients with Alzheimer's disease with cerebrovascular disease, and have been shown to affect the larger vessels of the brain in rodents. However, the impact of α1 -AR antibodies on the cerebral vasculature remains unclear. In the present study, we established a neuroimaging method to measure the relative cerebral blood volume (rCBV) in small rodents with the ultimate goal to detect changes in blood vessel density and/or vessel size induced by α1 -AR antibodies. For this purpose, mapping of R2 * and R2 was performed using MRI at 9.4 T, before and after the injection of intravascular iron oxide particles (ferumoxytol). The change in the transverse relaxation rates (ΔR2 *, ΔR2 ) showed a significant rCBV decrease in the cerebrum, cortex and hippocampus of rats (except hippocampal ΔR2 ), which was more pronounced for ΔR2 * than for ΔR2 . Immunohistological analyses confirmed that the α1 -AR antibody induced blood vessel deficiencies. Our findings support the hypothesis that α1 -AR antibodies lead to cerebral vessel damage throughout the brain, which can be monitored by MRI-derived rCBV, a non-invasive neuroimaging method. This demonstrates the value of rCBV estimation by ferumoxytol-enhanced MRI at 9.4 T, and further underlines the significance of this antibody in brain diseases involving vasculature impairments, such as dementia.

Characterization of platelet-monocyte complexes in HIV-1-infected individuals: possible role in HIV-associated neuroinflammation.

HIV-1-associated neuroinflammation persists even with effective combined antiretroviral therapy, and it is associated with the presence of activated monocytes/macrophages within the CNS. To infiltrate the CNS, monocytes transmigrate across the selectively permeable blood-brain barrier, which is compromised during HIV-1 infection. Interestingly, platelet-derived excess soluble CD40 ligand found in the plasma and cerebrospinal fluid of HIV-1-infected individuals with cognitive impairment has previously been implicated in increased blood-brain barrier permeability. In this study we show that soluble CD40 ligand also promotes the formation of complexes between inflammatory monocytes and activated platelets (PMCs), which are detected by flow cytometry as monocytes that express excess of CD61, a platelet marker, and that these complexes are increased in individuals with HIV-1 infection. PMCs exhibit an enhanced ability to adhere to human brain microvascular endothelial cells as compared with monocytes alone, and they migrate across the transendothelial barrier. These complexes can be found marginalized in the lumen of postcapillary venules in postmortem brain tissue derived from cases of HIV-1-associated encephalitis. The extravasation of monocytes across the brain endothelium may exacerbate neuroinflammation, indicating that enhancing this event via platelet interaction may be a contributing factor in the development of cognitive impairment. Thus, dampening platelet activation, and in turn PMC formation, with antiplatelet agents may prove beneficial in developing adjunctive therapies for use in combination with combined antiretroviral therapy in an effort to reduce HIV-1-associated neurologic deficit.

[Vascular factors in the pathogenesis of Alzheimer's disease]. / Vaskuläre Faktoren in der Pathogenese der Alzheimer-Krankheit.

According to the amyloid hypothesis of Alzheimer's disease (AD), the amyloid ß (Aß) peptide, as the primary neurotoxic species, plays a key role in the pathogenesis of the disease. However, many lines of recent evidence also point towards a major importance of early cerebrovascular dysfunction at least for the most common form of the disease, sporadic AD. In the preclinical course not only neuronal but also vascular damage frequently occurs. Cerebral hypoperfusion, blood-brain barrier dysfunction and vascular oxidative stress are typical features of this stage of the disease. Most importantly, such alterations precede the classical pathological hallmarks, such as parenchymal deposition of extracellular amyloid and intracellular neurofibrillary tangles. In this article recent epidemiological, clinical pathological and experimental evidence for an integrative vascular neuronal pathogenetic model of sporadic AD is reviewed.

Inflammatory proteins and the severity of dilated Virchow-Robin Spaces in the elderly.

Recent studies suggest dilated Virchow-Robin Spaces (dVRS) could be a manifestation of cerebral small-vessel disease, but little is known about their risk factors. As inflammation has been associated with other brain MRI findings, we investigated whether interleukin-6 and C-reactive protein were associated with the severity of dVRS in the eldery. dVRS were assessed in basal ganglia and white matter and rated on a severity scale. We found that elevated interleukin-6 levels were associated with higher severity of dVRS in basal ganglia, suggesting that inflammation might be associated with the burden of dVRS in the elderly.

Antibodies to the α1-adrenergic receptor cause vascular impairments in rat brain as demonstrated by magnetic resonance angiography.

BACKGROUND: Circulating agonistic autoantibodies acting at G protein-coupled receptors have been associated with numerous sever pathologies in humans. Antibodies directed predominantly against the α(1)-adrenergig receptor were detected in patients suffering from widespread diseases such as hypertension and type 2 diabetes. Their deleterious action has been demonstrated for peripheral organs. We postulate that antibodies to the α(1)-adrenergig receptor are relevant pathomolecules in diseases of the central nervous system associated with vascular impairments. METHODOLOGY/PRINCIPAL FINDINGS: Using a rat model we studied the long-term action of antibodies against the α(1)-adrenergig receptor either induced by immunization with a receptor peptide or applied by intravenous injection. The vasculature in the rat brains was investigated by time-of-flight magnetic resonance angiography using a 9.4 Tesla small animal MR imaging system. Visual examination of maximum-intensity-projections (MIPs) of brain angiographs revealed the development of vascular defects in antibody- exposed animals between three and eight months of treatment. Relative vascular areas were derived from representative MIP image sections by grayscale analysis and used to form an index of vascular circulation. Animals exposed to the action of α(1)-adrenergig receptor antibodies showed significantly reduced vascular areas (p<0.05). Calculated index values indicated attenuated blood flow in both antibody-treated cohorts compared to their respective controls reaching with (relative units ± standard error, n = 10) 0.839 ± 0.026 versus 0.919 ± 0.026 statistical significance (p<0.05) for peptide-immunized rats. CONCLUSION/SIGNIFICANCE: We present evidence that antibodies to the α(1)-adrenergig receptor cause cerebrovascular impairments in the rat. Our findings suggest the pathological significance of these antibodies in pathologies of the human central nervous system linked to impairments of brain vasculature such as stroke and dementia.

[Clinical and prognostic value of inflammatory genetic markers in traumatic brain injury].

The paper analyses the published data about association of polymorphic gene markers of different bioactive agents (interleukins, angiotensin convertase, catechol-O-methyltransferase, dopamine receptors etc.) with traumatic brain injury. Analysis of the entire pool of data concerning clinical and experimental studies of association of different polymorphic markers of candidate genes with outcome of traumatic brain injury allows to conclude that IL 1alpha and IL 1beta, IL 6, catechol-O-methyltransferase, angiotensin convertase, D2 dopamine receptors in fact play important role in neuroinflammatory response to injury and recovery of the brain ant its functions. Moreover presence or absence of certain polymorphic gene markers differentially influence separate pathogenetic mechanisms of brain injury (e.g., severity of brain edema, cerebral blood flow, cognitive functions). Consequently each of the investigated genes contributes in outcome after traumatic brain injury.

Neutrophil cerebrovascular transmigration triggers rapid neurotoxicity through release of proteases associated with decondensed DNA.

Cerebrovascular inflammation contributes to diverse CNS disorders through mechanisms that are incompletely understood. The recruitment of neutrophils to the brain can contribute to neurotoxicity, particularly during acute brain injuries, such as cerebral ischemia, trauma, and seizures. However, the regulatory and effector mechanisms that underlie neutrophil-mediated neurotoxicity are poorly understood. In this study, we show that mouse neutrophils are not inherently toxic to neurons but that transendothelial migration across IL-1-stimulated brain endothelium triggers neutrophils to acquire a neurotoxic phenotype that causes the rapid death of cultured neurons. Neurotoxicity was induced by the addition of transmigrated neutrophils or conditioned medium, taken from transmigrated neutrophils, to neurons and was partially mediated by excitotoxic mechanisms and soluble proteins. Transmigrated neutrophils also released decondensed DNA associated with proteases, which are known as neutrophil extracellular traps. The blockade of histone-DNA complexes attenuated transmigrated neutrophil-induced neuronal death, whereas the inhibition of key neutrophil proteases in the presence of transmigrated neutrophils rescued neuronal viability. We also show that neutrophil recruitment in the brain is IL-1 dependent, and release of proteases and decondensed DNA from recruited neutrophils in the brain occurs in several in vivo experimental models of neuroinflammation. These data reveal new regulatory and effector mechanisms of neutrophil-mediated neurotoxicity (i.e., the release of proteases and decondensed DNA triggered by phenotypic transformation during cerebrovascular transmigration). Such mechanisms have important implications for neuroinflammatory disorders, notably in the development of antileukocyte therapies.

Adiponectin-deficiency exaggerates sepsis-induced microvascular dysfunction in the mouse brain.

Obesity increases circulating cell-endothelial cell interactions; an early marker of inflammation in laboratory model of sepsis, but little is known about the effect of different adipokines. Adiponectin is an anti-inflammatory adipokine secreted by adipocytes. Adiponectin deficiency is implicated in exaggerated proinflammatory phenotype in both obesity and sepsis via increased proinflammatory cytokine expression. However the effect of adiponectin deficiency on circulating cell-endothelial cell interactions in polymicrobial sepsis is unknown. Furthermore although brain dysfunction in septic patients is a known predictor of death, the pathophysiology involved is unknown. In the current study, we examined the effects of adiponectin deficiency on leukocyte (LA) and platelet adhesion (PA) in cerebral microcirculation of septic mice. Adiponectin deficient (Adipoq(-/-): Adko) and background strain C57Bl/6 (wild type (WT)) mice were used. Sepsis was induced using cecal ligation and puncture (CLP). We studied LA and PA in the cerebral microcirculation using intravital fluorescent video microscopy (IVM), blood brain barrier (BBB) dysfunction using Evans Blue (EB) leakage method and E-selectin expression using dual radiolabeling technique in different WT and Adko mice with CLP. Adiponectin deficiency significantly exaggerated LA (WT-CLP:201 ± 17; Adko-CLP: ± 53 cells/mm(2); P < 0.05) and PA (WT-CLP:125 ± 17; Adko-CLP:188 ± 20 cells/mm(2); P < 0.05) in cerebral microcirculation, EB leakage (WT-CLP:10 ± 3.7; Adko-CLP:24 ± 4.3 ng/g × µl plasma; P < 0.05) and E-selectin expression (WT-CLP:0.06 ± 0.11; Adko-CLP:0.44 ± 0.053 ng/g; P < 0.05) in the brain tissue of the mice with CLP. Furthermore, E-selectin monoclonal antibody (mAb) treatment attenuated cell adhesion and BBB dysfunction of Adko-CLP mice. Adiponectin deficiency is associated with exaggerated leukocyte and PA in cerebral microcirculation of mice with CLP via modulation of E-selectin expression.

RB4CD12 epitope expression and heparan sulfate disaccharide composition in brain vasculature.

RB4CD12 is a phage display antibody that recognizes a heparan sulfate (HS) glycosaminoglycan epitope. The epitope structure is proposed to contain a trisulfated disaccharide, [-IdoA(2-OSO(3))-GlcNSO(3) (6-OSO(3))-], which supports HS binding to various macromolecules such as growth factors and cytokines in central nervous tissues. Chemically modified heparins that lack the trisulfated disaccharides failed to inhibit the RB4CD12 recognition of HS chains. To determine the localization of the RB4CD12 anti-HS epitope in the brain, we performed an immunohistochemical analysis for cryocut sections of mouse brain. The RB4CD12 staining signals were colocalized with laminin and were detected abundantly in the vascular basement membrane. Bacterial heparinases eliminated the RB4CD12 staining signals. The RB4CD12 epitope localization was confirmed by immunoelectron microscopy. Western blotting analysis revealed that the size of a major RB4CD12-positive molecule is ∼460 kDa in a vessel-enriched fraction of the mouse brain. Disaccharide analysis with reversed-phase ion-pair HPLC showed that [-IdoA(2-OSO(3))-GlcNSO(3) (6-OSO(3))-] trisulfated disaccharide residues are present in HS purified from the vessel-enriched brain fraction. These results indicated that the RB4CD12 anti-HS epitope exists in large quantities in the brain vascular basement membrane.

Platelet and leukocyte adhesion in the microvasculature at the cerebral surface immediately after subarachnoid hemorrhage.

OBJECTIVE: Pathophysiology after subarachnoid hemorrhage (SAH) caused by aneurysmal rupture has not been well examined. The purpose of this study was to observe platelet-leukocyte-endothelial cell interactions as indexes of inflammatory and prothrombogenic responses in the acute phase of SAH, using an in vivo cranial window method. METHODS: Subarachnoid hemorrhage was induced in C57Bl/6J mice by using the endovascular perforation method. Intravital microscopy was used to monitor the rolling and adhesion of platelets and leukocytes that were labeled with different fluorochromes. Regional cerebral blood flow was measured with laser Doppler flowmetry. The platelet-leukocyte-endothelial cell interactions were observed 30 minutes, 2 hours, and 8 hours after SAH. The effect of P-selectin antibody and apocynin, an inhibitor of nicotinamide adenine dinucleotide phosphate oxidase, on these responses was examined at 2 hours after SAH, and compared with a different SAH model in which autologous blood was injected into the foramen magna. RESULTS: SAH was accompanied by a 60% decrease in regional cerebral blood flow, whereas no changes in regional cerebral blood flow were observed on the contralateral side. SAH elicited time- and size-dependent increases in rolling and adherent platelets and leukocytes in cerebral venules. All of these interactions were attenuated by treatment with a P-selectin antibody or apocynin. There was no significant blood cell recruitment observed in the blood-injected SAH model. CONCLUSION: SAH at the skull base induced P-selectin- and oxygen radical-mediated platelet-leukocyte-endothelial cell interactions in venules at the cerebral surface. These early inflammatory and prothrombogenic responses may cause a whole-brain injury immediately after SAH.

Reversible encephalopathy after cardiac transplantation: histologic evidence of endothelial activation, T-cell specific trafficking, and vascular endothelial growth factor expression.

Reversible encephalopathy after transplantation is well recognized. The condition is commonly thought to be related to immune suppression, and a characteristic brain imaging pattern is typically recognized with vasogenic edema in the parietal and occipital regions, typically termed posterior reversible encephalopathy syndrome (PRES). We report the case of a patient with reversible encephalopathy after cardiac transplantation with brain biopsy evidence of endothelial activation, selective intravascular/perivascular T-cell trafficking, and VEGF expression in astrocytes, neurons, and the endothelium.