Lipopolysaccharide-activated microglia induce dysfunction of the blood-brain barrier in rat microvascular endothelial cells co-cultured with microglia

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

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

Blood-brain barrier integrity in the pathogenesis of Alzheimer's disease

The blood-brain barrier (BBB) tightly controls the molecular exchange between the brain parenchyma and blood. Accumulated evidence from transgenic animal Alzheimer's disease (AD) models and human AD patients have demonstrated that BBB dysfunction is a major player in AD pathology. In this review, we discuss the role of the BBB in maintaining brain integrity and how this is mediated by crosstalk between BBB-associated cells within the neurovascular unit (NVU). We then discuss the role of the NVU, in particular its endothelial cell, pericyte, and glial cell constituents, in AD pathogenesis. The effect of substances released by the neuroendocrine system in modulating BBB function and AD pathogenesis is also discussed. We perform a systematic review of currently available AD treatments specifically targeting pericytes and BBB glial cells. In summary, this review provides a comprehensive overview of BBB dysfunction in AD and a new perspective on the development of therapeutics for AD.

Inflammation: major denominator of obesity, Type 2 diabetes and Alzheimer's disease-like pathology?

Adipose tissue is an active metabolic organ that contributes to processes such as energy storage and utilization and to the production of a number of metabolic agents, such as adipokines, which play a role in inflammation. In this review, we try to elucidate the connections between peripheral inflammation at obesity and Type 2 diabetes and the central inflammatory process. Multiple lines of evidence highlight the importance of peripheral inflammation and its link to neuroinflammation, which can lead to neurodegenerative diseases such as dementia, Alzheimer's disease (AD) and Parkinson's disease. In addition to the accumulation of misfolded amyloid beta (Aβ) peptide and the formation of the neurofibrillary tangles of hyperphosphorylated tau protein in the brain, activated microglia and reactive astrocytes are the main indicators of AD progression. They were found close to Aβ plaques in the brains of both AD patients and rodent models of Alzheimer's disease-like pathology. Cytokines are key players in pro- and anti-inflammatory processes and are also produced by microglia and astrocytes. The interplay of seemingly unrelated pathways between the periphery and the brain could, in fact, have a common denominator, with inflammation in general being a key factor affecting neuronal processes in the brain. An increased amount of white adipose tissue throughout the body seems to be an important player in pro-inflammatory processes. Nevertheless, other important factors should be studied to elucidate the pathological processes of and the relationship among obesity, Type 2 diabetes and neurodegenerative diseases.

Oxidative Damage of Blood Platelets Correlates with the Degree of Psychophysical Disability in Secondary Progressive Multiple Sclerosis

The results of past research studies show that platelets are one of the main sources of reactive oxygen species (ROS) and reactive nitrogen species (RNS) to be found in the course of many pathological states. The aim of this study was to determine the level of oxidative/nitrative stress biomarkers in blood platelets obtained from multiple sclerosis (MS) patients (n = 110) and to verify their correlation with the clinical parameters of the psychophysical disability of patients. The mitochondrial metabolism of platelets was assessed by measuring the intracellular production of ROS using the fluorescence method with DCFH-DA dye and by identification of changes in the mitochondrial membrane potential of platelets using the JC-1 dye. Moreover, we measured the mRNA expression for the gene encoding the cytochrome c oxidase subunit I (MTCO-1) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) in platelets and megakaryocytes using the RT-qPCR method, as well as the concentration of NADPH oxidase (NOX-1) by the ELISA method. Our results proved an increased level of oxidative/nitrative damage of proteins (carbonyl groups, 3-nitrotyrosine) (p < 0.0001) and decreased level of -SH in MS (p < 0.0001) and also a pronounced correlation between these biomarkers and parameters assessed by the Expanded Disability Status Scale and the Beck's Depression Inventory. The application of fluorescence methods showed mitochondrial membrane potential disruption (p < 0.001) and higher production of ROS in platelets from MS compared to control (p < 0.0001). Our research has also confirmed the impairment of red-ox metabolism in MS, which was achieved by increasing the relative mRNA expression in platelets for the genes studied (2-fold increase for the MTCO-1 gene and 1.5-fold increase in GAPDH gene, p < 0.05), as well as the augmented concentration of NOX-1 compared to control (p < 0.0001). Our results indicate that the oxidative/nitrative damage of platelets is implicated in the pathophysiology of MS, which reflects the status of the disease.

Platelet regulates neuroinflammation and restores blood-brain barrier integrity in a mouse model of traumatic brain injury

Neuroinflammation accompanied by microglial activation triggers multiple cell death after traumatic brain injury (TBI). The secondary injury caused by inflammation may persist for a long time. Recently, platelet C-type lectin-like 2 receptor (CLEC-2) has been shown to regulate inflammation in certain diseases. However, its possible effects on TBI remain poorly understood. Here, we aimed to investigate the role of platelet CLEC-2 in the pathological process of neuroinflammation after TBI. In this study, mice were subjected to sham or controlled cortical impact injury, and arbitrarily received recombinant platelet CLEC-2. In parallel, BV2 cells were treated with lipopolysaccharide (LPS) to mimic microglial activation after TBI. Primary endothelial cells were also subjected to LPS in order to replicate the inflammatory damage caused by TBI. We used western blot analysis, reverse transcription polymerase chain reaction (RT-PCR), and immunostaining to evaluate the role of platelet CLEC-2 in TBI. In conditional knock out platelet CLEC-2 mice, trauma worsened the integrity of the blood-brain barrier and amplified the release of inflammatory cytokines. In wild type mice subjected to controlled cortical impact injury, recombinant platelet CLEC-2 administration altered the secretion of inflammatory cytokines, reduced brain edema, and improved neurological function. In vitro, the polarization phenotype of microglia induced by LPS was transformed by recombinant platelet CLEC-2, and this conversion depended on the mammalian target of rapamycin (mTOR) pathway. Endothelial cell injury by LPS was ameliorated when microglia expressed mostly M2 phenotype markers. In conclusion, platelet CLEC-2 regulates trauma-induced neuroinflammation and restores blood-brain barrier integrity.

ABC Transporters at the Blood-Brain Interfaces, Their Study Models, and Drug Delivery Implications in Gliomas

Drug delivery into the brain is regulated by the blood-brain interfaces. The blood-brain barrier (BBB), the blood-cerebrospinal fluid barrier (BCSFB), and the blood-arachnoid barrier (BAB) regulate the exchange of substances between the blood and brain parenchyma. These selective barriers present a high impermeability to most substances, with the selective transport of nutrients and transporters preventing the entry and accumulation of possibly toxic molecules, comprising many therapeutic drugs. Transporters of the ATP-binding cassette (ABC) superfamily have an important role in drug delivery, because they extrude a broad molecular diversity of xenobiotics, including several anticancer drugs, preventing their entry into the brain. Gliomas are the most common primary tumors diagnosed in adults, which are often characterized by a poor prognosis, notably in the case of high-grade gliomas. Therapeutic treatments frequently fail due to the difficulty of delivering drugs through the brain barriers, adding to diverse mechanisms developed by the cancer, including the overexpression or expression de novo of ABC transporters in tumoral cells and/or in the endothelial cells forming the blood-brain tumor barrier (BBTB). Many models have been developed to study the phenotype, molecular characteristics, and function of the blood-brain interfaces as well as to evaluate drug permeability into the brain. These include in vitro, in vivo, and in silico models, which together can help us to better understand their implication in drug resistance and to develop new therapeutics or delivery strategies to improve the treatment of pathologies of the central nervous system (CNS). In this review, we present the principal characteristics of the blood-brain interfaces; then, we focus on the ABC transporters present on them and their implication in drug delivery; next, we present some of the most important models used for the study of drug transport; finally, we summarize the implication of ABC transporters in glioma and the BBTB in drug resistance and the strategies to improve the delivery of CNS anticancer drugs.

Interleukin-13 Gene Modification Enhances Grafted Mesenchymal Stem Cells Survival After Subretinal Transplantation

Mesenchymal stem cells (MSCs) hold great potential for cell- and gene-based therapies for retinal degeneration. Limited survival is the main obstacle in achieving successful subretinal transplantation of MSCs. The present study sought to evaluate the effect of interleukin-13 (IL-13) gene modification on the phenotypic alteration of retinal microglia (RMG) and the survival of MSCs following subretinal grafting. In this study, LPS-activated RMG were cocultured with MSCs or IL-13-expressing MSCs (IL-13-MSCs) for 24 h, and activated phenotypes were detected in vitro. Western blotting was performed to quantify cytokine secretion by light-injured retinas following subretinal transplantation. The numbers of activated RMG and surviving grafted cells were analysed, and the integrity of the blood-retinal barrier (BRB) was examined in vivo. We found that, compared with normal MSCs, cocultured IL-13-MSCs suppressed the expression of pro-inflammatory factors and major histocompatibility complex II, promoted the expression of anti-inflammatory cytokines by activated RMG and simultaneously inhibited the proliferation of and phagocytosis by RMG. The subretinal transplantation of IL-13-MSCs increased the expression of neurotrophic factors, IL-13 and tight junction proteins in the host retina, decreased the number of phagocytic RMG and improved the survival of grafted cells. Furthermore, IL-13-MSCs alleviated BRB breakdown induced by subretinal injection. Our results demonstrate that IL-13-MSCs can polarize activated RMG to the neuroprotective M2 phenotype and enhance the survival of grafted MSCs against the damage stress induced by subretinal transplantation.

Neuroimaging of traumatic brain injury in military personnel: An overview

BACKGROUND

The incidence of blunt-force traumatic brain injury (TBI) is especially prevalent in the military, where the emergency care admission rate has been reported to be 24.6-41.8 per 10,000 soldier-years. Given substantial advancements in modern neuroimaging techniques over the past decade in terms of structural, functional, and connectomic approaches, this mode of exploration can be viewed as best suited for understanding the underlying pathology and for providing proper intervention at effective time-points.

APPROACH

Here we survey neuroimaging studies of mild-to-severe TBI in military veterans with the intent to aid the field in the creation of a roadmap for clinicians and researchers whose aim is to understand TBI progression.

DISCUSSION

Recent advancements on the quantification of neurocognitive dysfunction, cellular dysfunction, intracranial pressure, cerebral blood flow, inflammation, post-traumatic neuropathophysiology, on blood serum biomarkers and on their correlation to neuroimaging findings are reviewed to hypothesize how they can be used in conjunction with one another. This may allow clinicians and scientists to comprehensively study TBI in military service members, leading to new treatment strategies for both currently-serving as well as veteran personnel, and to improve the study of TBI more broadly.

Obesity-related cognitive impairment: The role of endothelial dysfunction

Obesity is a global pandemic associated with macro- and microvascular endothelial dysfunction. Microvascular endothelial dysfunction has recently emerged as a significant risk factor for the development of cognitive impairment. In this review, we present evidence from clinical and preclinical studies supporting a role for obesity in cognitive impairment. Next, we discuss how obesity-related hyperinsulinemia/insulin resistance, systemic inflammation, and gut dysbiosis lead to cognitive impairment through induction of endothelial dysfunction and disruption of the blood brain barrier. Finally, we outline the potential clinical utility of dietary interventions, exercise, and bariatric surgery in circumventing the impacts of obesity on cognitive function.

Microglial Cells: The Main HIV-1 Reservoir in the Brain

Despite efficient combination of the antiretroviral therapy (cART), which significantly decreased mortality and morbidity of HIV-1 infection, a definitive HIV cure has not been achieved. Hidden HIV-1 in cellular and anatomic reservoirs is the major hurdle toward a functional cure. Microglial cells, the Central Nervous system (CNS) resident macrophages, are one of the major cellular reservoirs of latent HIV-1. These cells are believed to be involved in the emergence of drugs resistance and reseeding peripheral tissues. Moreover, these long-life reservoirs are also involved in the development of HIV-1-associated neurocognitive diseases (HAND). Clearing these infected cells from the brain is therefore crucial to achieve a cure. However, many characteristics of microglial cells and the CNS hinder the eradication of these brain reservoirs. Better understandings of the specific molecular mechanisms of HIV-1 latency in microglial cells should help to design new molecules and new strategies preventing HAND and achieving HIV cure. Moreover, new strategies are needed to circumvent the limitations associated to anatomical sanctuaries with barriers such as the blood brain barrier (BBB) that reduce the access of drugs.

Potentiating a non-neuronal cardiac cholinergic system reinforces the functional integrity of the blood brain barrier associated with systemic anti-inflammatory responses

We previously reported that the heart-specific choline acetyltransferase (ChAT) gene overexpressing mice (ChAT tg) show specific phenotypes including ischemic tolerance and the CNS stress tolerance. In the current study, we focused on molecular mechanisms responsible for systemic and localized anti-inflammatory phenotypes of ChAT tg. ChAT tg were resistant to systemic inflammation induced by lipopolysaccharides due to an attenuated cytokine response. In addition, ChAT tg, originally equipped with less reactive Kupffer cells, were refractory to brain cold injury, with decreased blood brain barrier (BBB) permeability and reduced inflammation. This is because ChAT tg brain endothelial cells expressed more claudin-5, and their astrocytes were less reactive, causing decreased hypertrophy. Moreover, reconstruction of the BBB integrity in vitro confirmed the consolidation of ChAT tg. ChAT tg were also resistant to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neuronal toxicity due to lower mortality rate and neuronal loss of substantia nigra. Additionally, ChAT tg subjected to MPTP showed attenuated BBB disruption, as evident from reduced sodium fluorescein levels in the brain parenchyma. The activated central cholinergic pathway of ChAT tg lead to anti-convulsive effects like vagus nerve stimulation. However, DSP-4, a noradrenergic neuron-selective neurotoxin against the CNS including the locus ceruleus, abrogated the beneficial phenotype and vagotomy attenuated expression of claudin-5, suggesting the link between the cholinergic pathway and BBB function. Altogether, these findings indicate that ChAT tg possess an anti-inflammatory response potential, associated with upregulated claudin-5, leading to the consolidation of BBB integrity. These characteristics protect ChAT tg against systemic and localized inflammatory pathological disorders, which targets the CNS.

Neuroprotective Effects of BHDPC, a Novel Neuroprotectant, on Experimental Stroke by Modulating Microglia Polarization

This study mainly investigated the therapeutic effects of BHDPC on ischemic stroke and its underlying mechanisms. In vivo, the transient middle cerebral artery occlusion (MCAO) was used to induce ischemic model. In vitro, oxygen and glucose deprivation/reperfusion (OGD/R)-induced ischemic stroke in BV-2 microglia and primary neurons, and bEnd.3 mouse cerebral microvascular endothelial cells (ECs) were also used. First, we found that BHDPC exerts considerable neuroprotection against MCAO-induced ischemic injury to mice via alleviating neurological deficits and brain infarcts, inhibiting neuronal cell loss and apoptosis, and attenuating blood-brain barrier disruption and tight junction protein changes. Next, we observed that BHDPC significantly reduced microglial M1 activation but enhanced M2 polarization in MCAO-induced ischemic brain. Further experiments in vitro indicated that BHDPC suppressed microglial activation but promoted M2 microglial polarization in OGD/R-induced BV-2 microglia. In addition, conditioned medium (CM) experiments showed that CM from BHDPC-treated BV-2 microglia provided protections against OGD/R-induced ischemic damage in primary neurons and bEnd.3 ECs. Moreover, we found that BHDPC actions on microglial inflammation were associated with the inactivation of NF-κB signaling. Interestingly, we also found that BHDPC enhanced phosphorylation of protein kinase A (PKA) and cAMP-response element-binding protein (CREB). The pharmacological inhibition or gene knockdown of PKA/CREB signaling diminished BHDPC-promoted microglial M2 polarization. In summary, BHDPC conferred neuroprotection against ischemic injury in experimental stroke models. Modulating microglial activation and polarization contributes to BHDPC-mediated neuroprotective actions, which in part were mediated by nuclear factor kappa B and PKA/CREB signaling pathway.

Retinal microglia initiate neuroinflammation in ocular autoimmunity

Autoimmune uveitis is a sight-threatening ocular inflammatory condition in which the retina and uveal tissues become a target of autoreactive immune cells. While microglia have been studied extensively in autoimmune uveitis, their exact function remains uncertain. The objective of the current study was to determine whether resident microglia are necessary and sufficient to initiate and amplify retinal inflammation in autoimmune uveitis. In this study, we clearly demonstrate that microglia are essential for initiating infiltration of immune cells utilizing a murine model of experimental autoimmune uveoretinitis (EAU) and the recently identified microglia-specific marker P2ry12. Initiating disease is the primary function of microglia in EAU, since eliminating microglia during the later stages of EAU had little effect, indicating that the function of circulating leukocytes is to amplify and sustain destructive inflammation once microglia have triggered disease. In the absence of microglia, uveitis does not develop, since leukocytes cannot gain entry through the blood-retinal barrier, illustrating that microglia play a critical role in regulating infiltration of inflammatory cells into the retina.

Microglial Cells: The Main HIV-1 Reservoir in the Brain

Despite efficient combination of the antiretroviral therapy (cART), which significantly decreased mortality and morbidity of HIV-1 infection, a definitive HIV cure has not been achieved. Hidden HIV-1 in cellular and anatomic reservoirs is the major hurdle toward a functional cure. Microglial cells, the Central Nervous system (CNS) resident macrophages, are one of the major cellular reservoirs of latent HIV-1. These cells are believed to be involved in the emergence of drugs resistance and reseeding peripheral tissues. Moreover, these long-life reservoirs are also involved in the development of HIV-1-associated neurocognitive diseases (HAND). Clearing these infected cells from the brain is therefore crucial to achieve a cure. However, many characteristics of microglial cells and the CNS hinder the eradication of these brain reservoirs. Better understandings of the specific molecular mechanisms of HIV-1 latency in microglial cells should help to design new molecules and new strategies preventing HAND and achieving HIV cure. Moreover, new strategies are needed to circumvent the limitations associated to anatomical sanctuaries with barriers such as the blood brain barrier (BBB) that reduce the access of drugs.

Contributions of Drug Transporters to Blood-Brain Barriers

Blood-brain interfaces comprise the cerebral microvessel endothelium forming the blood-brain barrier (BBB) and the epithelium of the choroid plexuses forming the blood-cerebrospinal fluid barrier (BCSFB). Their main functions are to impede free diffusion between brain fluids and blood; to provide transport processes for essential nutrients, ions, and metabolic waste products; and to regulate the homeostasis of central nervous system (CNS), all of which are attributed to absent fenestrations, high expression of tight junction proteins at cell-cell contacts, and expression of multiple transporters, receptors, and enzymes. Existence of BBB is an important reason that systemic drug administration is not suitable for the treatment of CNS diseases. Some diseases, such epilepsy, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and diabetes, alter BBB function via affecting tight junction proteins or altering expression and function of these transporters. This chapter will illustrate function of BBB, expression of transporters, as well as their alterations under disease status.

KY-226 Protects Blood-brain Barrier Function Through the Akt/FoxO1 Signaling Pathway in Brain Ischemia

KY-226 is a protein tyrosine phosphatase 1B (PTP1B) inhibitor that protects neurons from cerebral ischemic injury. KY-226 restores Akt (protein kinase B) phosphorylation and extracellular signal-regulated kinase (ERK) reduction in transient middle cerebral artery occlusion (tMCAO) damage. However, the mechanisms underlying the neuroprotective effects of KY-226 are unclear. To address this, the effects of KY-226 on blood-brain barrier (BBB) dysfunction were examined in tMCAO mice. KY-226 (10 mg/kg, i.p.) was administered to ICR mice 30 min after 2 h of tMCAO. To assess Akt or ERK involvement, wortmannin (i.c.v.) or U0126 (i.v.), selective inhibitors of PI3K and ERK, respectively, were administered to mice 30 min before ischemia. BBB integrity was assessed by Evans blue leakage 24 h post-reperfusion. The levels of tight junction (TJ) proteins, ZO-1 and occludin, were measured by western blotting; ZO-1 mRNA level was measured by RT-PCR. Compared to vehicle, KY-226 treatment prevented BBB breakdown and reduction in TJ protein levels. KY-226 treatment restored ZO-1 mRNA levels post-reperfusion. Pre-administration of wortmannin or U0126 blocked the protective effects of KY-226 on ZO-1 protein and mRNA reduction in tMCAO mice. In bEnd.3 cells, lipopolysaccharide treatment reduced mRNA and protein levels of ZO-1, an effect rescued by KY-226 treatment. Further, KY-226 treatment restored phosphorylation of pAkt (T308) and its downstream target forkhead box protein O1 (FoxO1) (S256) in bEnd.3 cells. Collectively, we demonstrate that KY-226 protects BBB integrity by restoration of TJ proteins, an effect partly mediated by Akt/FoxO1 pathway activation. Thus, protection of BBB integrity likely underlies KY-226-induced neuroprotection in tMCAO mice.

Hypothalamic Microglial Activation in Obesity: A Mini-Review

Emerging data demonstrate that microglia activation plays a pivotal role in the development of hypothalamic inflammation in obesity. Early after the introduction of a high-fat diet, hypothalamic microglia undergo morphological, and functional changes in response to excessive dietary saturated fats. Initially the resident microglia are affected; however, as diet-induced obesity persists, bone marrow-derived myeloid cells gradually replace resident microglia. Genetic and pharmacological approaches aimed at dampening the inflammatory activity in the hypothalamus of experimental models of obesity have proven beneficial to correct the obese phenotype and improve metabolic abnormalities commonly associated with obesity. These approaches provide an experimental proof-of-concept that hypothalamic inflammation is central to the pathophysiology of obesity; understanding the details of the roles played by microglia in this process may help the development of preventive and therapeutic advances in the field. In this review, we discuss the potential mechanisms underlying hypothalamic microglial activation in high-fat induced obesity.

Neuroinflammatory mechanisms of blood-brain barrier damage in ischemic stroke

As part of the neurovascular unit, the blood-brain barrier (BBB) is a unique, dynamic regulatory boundary that limits and regulates the exchange of molecules, ions, and cells between the blood and the central nervous system. Disruption of the BBB plays an important role in the development of neurological dysfunction in ischemic stroke. Blood-borne substances and cells have restricted access to the brain due to the presence of tight junctions between the endothelial cells of the BBB. Following stroke, there is loss of BBB tight junction integrity, leading to increased paracellular permeability, which results in vasogenic edema, hemorrhagic transformation, and increased mortality. Thus, understanding principal mediators and molecular mechanisms involved in BBB disruption is critical for the development of novel therapeutics to treat ischemic stroke. This review discusses the current knowledge of how neuroinflammation contributes to BBB damage in ischemic stroke. Specifically, we provide an updated overview of the role of cytokines, chemokines, oxidative and nitrosative stress, adhesion molecules, matrix metalloproteinases, and vascular endothelial growth factor as well as the role of different cell types in the regulation of BBB permeability in ischemic stroke.

Leaky brain in neurological and psychiatric disorders: Drivers and consequences

BACKGROUND

The blood-brain barrier acts as a highly regulated interface; its dysfunction may exacerbate, and perhaps initiate, neurological and neuropsychiatric disorders.

METHODS

In this narrative review, focussing on redox, inflammatory and mitochondrial pathways and their effects on the blood-brain barrier, a model is proposed detailing mechanisms which might explain how increases in blood-brain barrier permeability occur and can be maintained with increasing inflammatory and oxidative and nitrosative stress being the initial drivers.

RESULTS

Peripheral inflammation, which is causatively implicated in the pathogenesis of major psychiatric disorders, is associated with elevated peripheral pro-inflammatory cytokines, which in turn cause increased blood-brain barrier permeability. Reactive oxygen species, such as superoxide radicals and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide and peroxynitrite, play essential roles in normal brain capillary endothelial cell functioning; however, chronically elevated oxidative and nitrosative stress can lead to mitochondrial dysfunction and damage to the blood-brain barrier. Activated microglia, redox control of which is mediated by nitric oxide synthases and nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, secrete neurotoxic molecules such as reactive oxygen species, nitric oxide, prostaglandin, cyclooxygenase-2, quinolinic acid, several chemokines (including monocyte chemoattractant protein-1 [MCP-1], C-X-C motif chemokine ligand 1 [CXCL-1] and macrophage inflammatory protein 1α [MIP-1α]) and the pro-inflammatory cytokines interleukin-6, tumour necrosis factor-α and interleukin-1β, which can exert a detrimental effect on blood-brain barrier integrity and function. Similarly, reactive astrocytes produce neurotoxic molecules such as prostaglandin E2 and pro-inflammatory cytokines, which can cause a 'leaky brain'.

CONCLUSION

Chronic inflammatory and oxidative and nitrosative stress is associated with the development of a 'leaky gut'. The following evidence-based approaches, which address the leaky gut and blood-brain barrier dysfunction, are suggested as potential therapeutic interventions for neurological and neuropsychiatric disorders: melatonin, statins, probiotics containing Bifidobacteria and Lactobacilli, N-acetylcysteine, and prebiotics containing fructo-oligosaccharides and galacto-oligosaccharides.

Microglia enhanced the angiogenesis, migration and proliferation of co-cultured RMECs

Background

Attention is increasingly being given to microglia-related inflammation in neovascular diseases, such as diabetic retinopathy and age-related macular disease. Evidence shows that activated microglia contribute to disruption of the blood–retinal barrier, however, the mechanism is unclear. In this study, we aimed to clarify whether and how microglia affect the function of retinal microvascular endothelial cells (RMECs).

Methods

We activated microglia by Lipopolysaccharides (LPS) stimulation. After co-culturing static or activated microglia with RMECs using the Transwell system, we evaluated the function of RMECs. Vascular endothelial growth factor-A (VEGF-A) and platelet-derived growth factor-BB (PDGF-BB) levels in the supernatant from the lower chamber were evaluated by ELISA. Angiogenesis, migration, and proliferation of RMECs were assessed by tube formation, wound healing, and WST-1 assays. The expression levels of tight junction proteins (ZO-1 and occludin) and endothelial markers (CD31 and CD34) were examined by Western blot analysis.

Results

We successfully established an LPS-activated microglia model and co-culture system of static or activated microglia with RMECs. In the co-culture system, we showed that microglia, especially activated microglia stimulated VEGF-A and PDGF-BB expression, enhanced angiogenesis, migration, proliferation, and permeability, and altered the phenotype of co-cultured RMECs.

Conclusions

Microglia, especially activated microglia, play important roles in angiogenesis and maintenance of vascular function hemostasis in the retinal microvasculature. The mechanism needs further investigation and clarification.

The role of stress in the mosaic of autoimmunity: An overlooked association

Stress is defined as the pscyophysiological reaction in which the steady state is disturbed or threatened. Stress is not always perceived as a negative response. Stress results when environmental demands exceed an individuals' adaptive capacities. Autoimmune diseases are heterogeneous group of chronic diseases which occur secondary to loss of self antigen tolerance. The etiopathogenesis of autoimmune disease is uncertain. Genetic factors as well as environmental factors appear to interplay, leading to a cascade of events resulting in disease onset. Stress has been postulated to play a role in disease onset in the genetically susceptible patients. During the stress response, catecholamines and glucocorticoids are released from locus coeruleus and adrenal gland. These biomolecules exert control over various immune cells in the innate and adaptive arms of the immune system, thereby altering the cytokine profile released. The increase of IL-4 promotes T-helper 2 (T_h2) cell differentiation, while the decrease in IL-12 and the increased IL-10 production reduce the number of T-helper 1 (T_h1) cells. The relationship between stress and autoimmune diseases is intricate. Stress has been shown to be associated with disease onset, and disease exacerbations in rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel disease, multiple sclerosis, Graves' disease as well as other autoimmune conditions. In certain conditions such as psoriasis, stress has been implicated in delaying lesion clearance upon the application of standard treatment regimes. Finally, psychological therapy and cognitive behavioral therapy aimed to reduce stress levels was shown to be effective in influencing better outcomes in many autoimmune diseases. The purpose of this paper is to closer inspect the clinical evidence regarding the role of stress on influencing the various aspects of disease entities.

Potentially Common Therapeutic Targets for Multiple Sclerosis and Ischemic Stroke

Ischemic stroke (IS) and multiple sclerosis (MS) are two pathologies of the central nervous system (CNS). At the first look, this appears to be the only similarity between the two diseases, as they seem quite different. Indeed IS has an acute onset compared to MS which develops chronically; IS is consecutive to blood clot migrating to cerebral blood vessels or decrease in cerebral blood flow following atherosclerosis or decreases in cardiac output, whereas MS is an immune disease associated with neurodegeneration. However, both pathologies share similar pathologic pathways and treatments used in MS have been the object of studies in IS. In this mini-review we will discuss similarities between IS and MS on astrocytes and neuroinflammation hallmarks emphasizing the potential for treatments.

Microglia in the Neurovascular Unit: Blood-Brain Barrier-microglia Interactions After Central Nervous System Disorders

Over the past few decades, microglial cells have been regarded as the main executor of inflammation after acute and chronic central nervous system (CNS) disorders, responding rapidly to exogenous stimuli during acute trauma or infections, or signals released by cells undergoing cell death during conditions such as stroke, Alzheimer's disease (AD) and Parkinson's disease (PD). Barriers of the nervous system, and in particular the blood-brain barrier (BBB), play a key role in the normal physiological and cognitive functions of the brain. Being at the interface between the central and peripheral compartment, the BBB is regarded as a sensor of homeostasis, and any disruption within the brain or the systemic compartment triggers BBB dysfunction and neuroinflammation, both contributing to the pathogenesis of cerebrovascular disease. This involves a dynamic response mediated by all components of the neurovascular unit (NVU), and ongoing research suggests that BBB-microglia interaction is critical to dictate the microglial response to NVU injury. The present review aims to give an up-to-date account of the emerging critical role of BBB-microglia interactions during neuroinflammation, and how these could be targeted for the therapeutic treatment of major central inflammatory disease.

Blood–brain barrier and its function during inflammation and autoimmunity

The blood–brain barrier (BBB) is an important physiologic barrier that separates CNS from soluble inflammatory mediators and effector immune cells from peripheral circulation. The optimum function of the BBB is necessary for the homeostasis, maintenance, and proper neuronal function. The clinical and experimental findings have shown that BBB dysfunction is an early hallmark of various neurologic disorders ranging from inflammatory autoimmune, neurodegenerative, and traumatic diseases to neuroinvasive infections. Significant progress has been made in the understanding of the regulation of BBB function under homeostatic and neuroinflammatory conditions. Several neurologic disease-modifying drugs have shown to improve the BBB function. However, they have a broad-acting immunomodulatory function and can increase the risk of life-threatening infections. The recent development of in vitro multicomponent 3-dimensional BBB models coupled with fluidics chamber as well as a cell-type specific reporter and knockout mice gave a new boost to our understanding of the dynamics of the BBB. In the review, we discuss the current understanding of BBB composition and recent findings that illustrate the critical regulatory elements of the BBB function under physiologic and inflammatory conditions, and also suggested the strategies to control BBB structure and function.

Blood–brain barrier and its function during inflammation and autoimmunity

The blood–brain barrier (BBB) is an important physiologic barrier that separates CNS from soluble inflammatory mediators and effector immune cells from peripheral circulation. The optimum function of the BBB is necessary for the homeostasis, maintenance, and proper neuronal function. The clinical and experimental findings have shown that BBB dysfunction is an early hallmark of various neurologic disorders ranging from inflammatory autoimmune, neurodegenerative, and traumatic diseases to neuroinvasive infections. Significant progress has been made in the understanding of the regulation of BBB function under homeostatic and neuroinflammatory conditions. Several neurologic disease-modifying drugs have shown to improve the BBB function. However, they have a broad-acting immunomodulatory function and can increase the risk of life-threatening infections. The recent development of in vitro multicomponent 3-dimensional BBB models coupled with fluidics chamber as well as a cell-type specific reporter and knockout mice gave a new boost to our understanding of the dynamics of the BBB. In the review, we discuss the current understanding of BBB composition and recent findings that illustrate the critical regulatory elements of the BBB function under physiologic and inflammatory conditions, and also suggested the strategies to control BBB structure and function.

Blood–brain barrier and its function during inflammation and autoimmunity

The blood–brain barrier (BBB) is an important physiologic barrier that separates CNS from soluble inflammatory mediators and effector immune cells from peripheral circulation. The optimum function of the BBB is necessary for the homeostasis, maintenance, and proper neuronal function. The clinical and experimental findings have shown that BBB dysfunction is an early hallmark of various neurologic disorders ranging from inflammatory autoimmune, neurodegenerative, and traumatic diseases to neuroinvasive infections. Significant progress has been made in the understanding of the regulation of BBB function under homeostatic and neuroinflammatory conditions. Several neurologic disease-modifying drugs have shown to improve the BBB function. However, they have a broad-acting immunomodulatory function and can increase the risk of life-threatening infections. The recent development of in vitro multicomponent 3-dimensional BBB models coupled with fluidics chamber as well as a cell-type specific reporter and knockout mice gave a new boost to our understanding of the dynamics of the BBB. In the review, we discuss the current understanding of BBB composition and recent findings that illustrate the critical regulatory elements of the BBB function under physiologic and inflammatory conditions, and also suggested the strategies to control BBB structure and function.

Blood–brain barrier and its function during inflammation and autoimmunity

The blood–brain barrier (BBB) is an important physiologic barrier that separates CNS from soluble inflammatory mediators and effector immune cells from peripheral circulation. The optimum function of the BBB is necessary for the homeostasis, maintenance, and proper neuronal function. The clinical and experimental findings have shown that BBB dysfunction is an early hallmark of various neurologic disorders ranging from inflammatory autoimmune, neurodegenerative, and traumatic diseases to neuroinvasive infections. Significant progress has been made in the understanding of the regulation of BBB function under homeostatic and neuroinflammatory conditions. Several neurologic disease-modifying drugs have shown to improve the BBB function. However, they have a broad-acting immunomodulatory function and can increase the risk of life-threatening infections. The recent development of in vitro multicomponent 3-dimensional BBB models coupled with fluidics chamber as well as a cell-type specific reporter and knockout mice gave a new boost to our understanding of the dynamics of the BBB. In the review, we discuss the current understanding of BBB composition and recent findings that illustrate the critical regulatory elements of the BBB function under physiologic and inflammatory conditions, and also suggested the strategies to control BBB structure and function.

Blood–brain barrier and its function during inflammation and autoimmunity

The blood–brain barrier (BBB) is an important physiologic barrier that separates CNS from soluble inflammatory mediators and effector immune cells from peripheral circulation. The optimum function of the BBB is necessary for the homeostasis, maintenance, and proper neuronal function. The clinical and experimental findings have shown that BBB dysfunction is an early hallmark of various neurologic disorders ranging from inflammatory autoimmune, neurodegenerative, and traumatic diseases to neuroinvasive infections. Significant progress has been made in the understanding of the regulation of BBB function under homeostatic and neuroinflammatory conditions. Several neurologic disease-modifying drugs have shown to improve the BBB function. However, they have a broad-acting immunomodulatory function and can increase the risk of life-threatening infections. The recent development of in vitro multicomponent 3-dimensional BBB models coupled with fluidics chamber as well as a cell-type specific reporter and knockout mice gave a new boost to our understanding of the dynamics of the BBB. In the review, we discuss the current understanding of BBB composition and recent findings that illustrate the critical regulatory elements of the BBB function under physiologic and inflammatory conditions, and also suggested the strategies to control BBB structure and function.

Blood–brain barrier and its function during inflammation and autoimmunity

The blood–brain barrier (BBB) is an important physiologic barrier that separates CNS from soluble inflammatory mediators and effector immune cells from peripheral circulation. The optimum function of the BBB is necessary for the homeostasis, maintenance, and proper neuronal function. The clinical and experimental findings have shown that BBB dysfunction is an early hallmark of various neurologic disorders ranging from inflammatory autoimmune, neurodegenerative, and traumatic diseases to neuroinvasive infections. Significant progress has been made in the understanding of the regulation of BBB function under homeostatic and neuroinflammatory conditions. Several neurologic disease-modifying drugs have shown to improve the BBB function. However, they have a broad-acting immunomodulatory function and can increase the risk of life-threatening infections. The recent development of in vitro multicomponent 3-dimensional BBB models coupled with fluidics chamber as well as a cell-type specific reporter and knockout mice gave a new boost to our understanding of the dynamics of the BBB. In the review, we discuss the current understanding of BBB composition and recent findings that illustrate the critical regulatory elements of the BBB function under physiologic and inflammatory conditions, and also suggested the strategies to control BBB structure and function.

Blood–brain barrier and its function during inflammation and autoimmunity

The blood–brain barrier (BBB) is an important physiologic barrier that separates CNS from soluble inflammatory mediators and effector immune cells from peripheral circulation. The optimum function of the BBB is necessary for the homeostasis, maintenance, and proper neuronal function. The clinical and experimental findings have shown that BBB dysfunction is an early hallmark of various neurologic disorders ranging from inflammatory autoimmune, neurodegenerative, and traumatic diseases to neuroinvasive infections. Significant progress has been made in the understanding of the regulation of BBB function under homeostatic and neuroinflammatory conditions. Several neurologic disease-modifying drugs have shown to improve the BBB function. However, they have a broad-acting immunomodulatory function and can increase the risk of life-threatening infections. The recent development of in vitro multicomponent 3-dimensional BBB models coupled with fluidics chamber as well as a cell-type specific reporter and knockout mice gave a new boost to our understanding of the dynamics of the BBB. In the review, we discuss the current understanding of BBB composition and recent findings that illustrate the critical regulatory elements of the BBB function under physiologic and inflammatory conditions, and also suggested the strategies to control BBB structure and function.

TNF-α-sensitive brain pericytes activate microglia by releasing IL-6 through cooperation between IκB-NFκB and JAK-STAT3 pathways

Interleukin (IL)-6 is an important mediator of neurovascular dysfunction, neurodegeneration and/or neuroinflammation. We previously reported that brain pericytes released higher levels of IL-6 than did glial cells (astrocytes and microglia) in response to tumor necrosis factor (TNF)-α. Moreover, pericytes stimulated with TNF-α enhanced activation of BV-2 microglia. In this study, we investigated the mechanisms of TNF-α mediated induction of IL-6 release from brain pericytes and astrocytes and whether pericyte-derived IL-6 would facilitate activation of BV-2 microglia. Using rat brain pericyte and astrocyte primary cultures and pharmacological inhibitors, we found that, TNF-α induced the highest levels of IL-6 release from pericytes by activating the inhibitor kappa B (IκB)-nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) and Janus family of tyrosine kinase (JAK)-signal transducer and activator of transcription (STAT)3 pathways. STAT3 contributed to TNF-α induced nuclear translocation of phospho-NFκB in pericytes. TNF-α-induced IL-6 release in astrocytes was mediated by NFκB but not by STAT3. The presence of pericytes amplified TNF-α-induced iNOS mRNA expression in BV-2 microglia. This effect was blocked by a neutralizing antibody for IL-6. These findings indicated that crosstalk between the IκB-NFκB and JAK-STAT3 pathways is a pericyte specific mechanism, not occurring in astrocytes, for TNF-α-induced IL-6 release. IL-6 derived from pericytes enhanced microglial activation. Our findings increase understanding of the role of pericyte-microglia crosstalk in the brain under neuroinflammatory conditions and suggest a potentially attractive therapeutic target for brain inflammation.

Blood-brain barrier and its function during inflammation and autoimmunity

The blood-brain barrier (BBB) is an important physiologic barrier that separates CNS from soluble inflammatory mediators and effector immune cells from peripheral circulation. The optimum function of the BBB is necessary for the homeostasis, maintenance, and proper neuronal function. The clinical and experimental findings have shown that BBB dysfunction is an early hallmark of various neurologic disorders ranging from inflammatory autoimmune, neurodegenerative, and traumatic diseases to neuroinvasive infections. Significant progress has been made in the understanding of the regulation of BBB function under homeostatic and neuroinflammatory conditions. Several neurologic disease-modifying drugs have shown to improve the BBB function. However, they have a broad-acting immunomodulatory function and can increase the risk of life-threatening infections. The recent development of in vitro multicomponent 3-dimensional BBB models coupled with fluidics chamber as well as a cell-type specific reporter and knockout mice gave a new boost to our understanding of the dynamics of the BBB. In the review, we discuss the current understanding of BBB composition and recent findings that illustrate the critical regulatory elements of the BBB function under physiologic and inflammatory conditions, and also suggested the strategies to control BBB structure and function.

The blood-brain barrier in Alzheimer's disease

Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by the pathological accumulation of amyloid beta (Aβ) peptides and neurofibrillary tangles containing hyperphosphorylated neuronal tau protein. AD pathology is also characterized by chronic brain inflammation, which promotes disease pathogenesis. In this context, the blood-brain barrier (BBB), a highly specialized endothelial cell membrane that lines cerebral microvessels, represents the interface between neural cells and circulating cells of the immune system. The BBB thus plays a key role in the generation and maintenance of chronic inflammation during AD. The BBB operates within the neurovascular unit (NVU), which includes clusters of glial cells, neurons and pericytes. The NVU becomes dysfunctional during AD, and each of its components may undergo functional changes that contribute to neuronal injury and cognitive deficit. In transgenic animals with AD-like pathology, recent studies have shown that circulating leukocytes migrate through the activated brain endothelium when certain adhesion molecules are expressed, penetrating into the brain parenchyma, interacting with the NVU components and potentially affecting their structural integrity and functionality. Therefore, migrating immune system cells in cerebral vessels act in concert with the modified BBB and may be integrated into the dysfunctional NVU. Notably, blocking the adhesion mechanisms controlling leukocyte-endothelial interactions inhibits both Aβ deposition and tau hyperphosphorylation, and reduces memory loss in AD models. The characterization of molecular mechanisms controlling vascular inflammation and leukocyte trafficking could therefore help to determine the basis of BBB dysfunction during AD and may lead to the development of new therapeutic approaches.

Blood-brain barrier dysfunction and recovery after ischemic stroke

The blood-brain barrier (BBB) plays a vital role in regulating the trafficking of fluid, solutes and cells at the blood-brain interface and maintaining the homeostatic microenvironment of the CNS. Under pathological conditions, such as ischemic stroke, the BBB can be disrupted, followed by the extravasation of blood components into the brain and compromise of normal neuronal function. This article reviews recent advances in our knowledge of the mechanisms underlying BBB dysfunction and recovery after ischemic stroke. CNS cells in the neurovascular unit, as well as blood-borne peripheral cells constantly modulate the BBB and influence its breakdown and repair after ischemic stroke. The involvement of stroke risk factors and comorbid conditions further complicate the pathogenesis of neurovascular injury by predisposing the BBB to anatomical and functional changes that can exacerbate BBB dysfunction. Emphasis is also given to the process of long-term structural and functional restoration of the BBB after ischemic injury. With the development of novel research tools, future research on the BBB is likely to reveal promising potential therapeutic targets for protecting the BBB and improving patient outcome after ischemic stroke.

Linking lipid peroxidation and neuropsychiatric disorders: focus on 4-hydroxy-2-nonenal

4-hydroxy-2-nonenal (HNE) is considered to be a strong marker of oxidative stress; the interaction between HNE and cellular proteins leads to the formation of HNE-protein adducts able to alter cellular homeostasis and cause the development of a pathological state. By virtue of its high lipid concentration, oxygen utilization, and the presence of metal ions participating to redox reactions, the brain is highly susceptible to the formation of free radicals and HNE-related compounds. A variety of neuropsychiatric disorders have been associated with elevations of HNE concentration. For example, increased levels of HNE were found in the cortex of bipolar and schizophrenic patients, while HNE plasma concentrations resulted high in patients with major depression. On the same line, high brain concentrations of HNE were found associated with Huntington's inclusions. The incidence of high HNE levels is relevant also in the brain and cerebrospinal fluid of patients suffering from Parkinson's disease. Intriguingly, in this case the increase of HNE was associated with an accumulation of iron in the substantia nigra, a brain region highly affected by the pathology. In the present review we recapitulate the findings supporting the role of HNE in the pathogenesis of different neuropsychiatric disorders to highlight the pathogenic mechanisms ascribed to HNE accumulation. The aim of this review is to offer novel perspectives both for the understanding of etiopathogenetic mechanisms that remain still unclear and for the identification of new useful biological markers. We conclude suggesting that targeting HNE-driven cellular processes may represent a new more efficacious therapeutical intervention.

Characterization of Sepsis and Sepsis-Associated Encephalopathy

BACKGROUND

Sepsis and sepsis-associated encephalopathy (SAE) are common intensive care unit (ICU) diseases; the morbidity and mortality are high. The present study analyzed the sensitivity of different diagnostic criteria of sepsis 1.0 and 3.0, epidemiological characteristics of sepsis and SAE, and explored its risk factors for death, short-term, and long-term prognosis.

METHODS

The retrospective study included patients in ICU from January 2015 to June 2016. After excluding 58 patients, 175 were assigned to either an SAE or a non-SAE group (patients with sepsis but no encephalopathy). The sensitivity of the diagnostic criteria was compared between sepsis 1.0 and 3.0, respectively. Between-group differences in baseline data, Acute Physiology and Chronic Health Evaluation II score (APACHE II score), Sequential Organ Failure Assessment score (SOFA score), etiological data, biochemical indicators, and 28-day and 180-day mortality rates were analyzed. Survival outcomes and long-term prognosis were observed, and risk factors for death were analyzed through 180-day follow-up.

RESULTS

The sensitivity did not differ significantly between the diagnostic criteria of sepsis 1.0 and 3.0 (P = .286). The 42.3% incidence of SAE presented a significantly high APACHE II and SOFA scores as well as 28-day mortality and 180-day mortality (all P < .001). The incidence of death was 37.1%. The multivariate stepwise regression analysis demonstrated that the risk of death in SAE group was significantly higher than the non-SAE group (P < .001). Sepsis-associated encephalopathy is a risk factor for sepsis-related death (relative risk [RR] = 2.868; 95% confidence interval: 1.730-4.754; P < .001). Although males showed a significantly high rate of 28-day and 180-day mortality (P = .035 and .045), it was not an independent risk factor for sepsis-related death (P = .072). The long-term prognosis of patients with sepsis was poor with decreased quality of life. No significant difference was observed in prognosis between the SAE and non-SAE groups (P > .05).

CONCLUSION

Both diagnostic criteria cause misdiagnosis, and the sensitivity did not differ significantly. The incidence of SAE was high, and 28-day and 180-day mortality rates were significantly higher than those without SAE. Sepsis-associated encephalopathy is a risk factor for poor outcome. The overall long-term prognosis of patients with sepsis was poor, and the quality of life decreased.

NOSH-NBP, a Novel Nitric Oxide and Hydrogen Sulfide- Releasing Hybrid, Attenuates Ischemic Stroke-Induced Neuroinflammatory Injury by Modulating Microglia Polarization

NOSH-NBP, a novel nitric oxide (NO) and hydrogen sulfide (H2S)-releasing hybrid, protects brain from ischemic stroke. This study mainly aimed to investigate the therapeutic effect of NOSH-NBP on ischemic stroke and the underlying mechanisms. In vivo, transient middle cerebral artery occlusion (tMCAO) was performed in C57BL/6 mice, with NO-NBP and H2S-NBP as controls. NO and H2S scavengers, carboxy-PTIO and BSS, respectively, were used to quench NO and H2S of NOSH-NBP. In vitro, BV2 microglia/BMDM were induced to the M1/2 phenotype, and conditioned medium (CM) experiments in BV2 microglia, neurons and b.End3 cerebral microvascular endothelial cells (ECs) were performed. Microglial/macrophage activation/polarization was assessed by flow cytometry, Western blot, RT-qPCR, and ELISA. Neuronal and EC survival was measured by TUNEL, flow cytometry, MTT and LDH assays. Transmission electron microscopy, EB extravasation, brain water content, TEER measurement and Western blot were used to detect blood-brain barrier (BBB) integrity and function. Interestingly, NOSH-NBP significantly reduced cerebral infarct volume and ameliorated neurological deficit, with superior effects compared with NO-NBP and/or H2S-NBP in mice after tMCAO. Both NO and H2S-releasing groups contributed to protection by NOSH-NBP. Additionally, NOSH-NBP decreased neuronal death and attenuated BBB dysfunction in tMCAO-treated mice. Furthermore, NOSH-NBP promoted microglia/macrophage switch from an inflammatory M1 phenotype to the protective M2 phenotype in vivo and in vitro. Moreover, the TLR4/MyD88/NF-κB pathway and NLRP3 inflammasome were involved in the inhibitory effects of NOSH-NBP on M1 polarization, while peroxisome proliferator activated receptor gamma signaling contributed to NOSH-NBP induced M2 polarization. These findings indicated that NOSH-NBP is a potential therapeutic agent that preferentially promotes microglial/macrophage M1-M2 switch in ischemic stroke.

Microglia: Housekeeper of the Central Nervous System

Microglia, of myeloid origin, play fundamental roles in the control of immune responses and the maintenance of central nervous system homeostasis. These cells, just like peripheral macrophages, may be activated into M1 pro-inflammatory or M2 anti-inflammatory phenotypes by appropriate stimuli. Microglia do not respond in isolation, but form part of complex networks of cells influencing each other. This review addresses the complex interaction of microglia with each cell type in the brain: neurons, astrocytes, cerebrovascular endothelial cells, and oligodendrocytes. We also highlight the participation of microglia in the maintenance of homeostasis in the brain, and their roles in the development and progression of age-related neurodegenerative disorders.

Development and Function of the Blood-Brain Barrier in the Context of Metabolic Control

Under physiological conditions, the brain consumes over 20% of the whole body energy supply. The blood-brain barrier (BBB) allows dynamic interactions between blood capillaries and the neuronal network in order to provide an adequate control of molecules that are transported in and out of the brain. Alterations in the BBB structure and function affecting brain accessibility to nutrients and exit of toxins are found in a number of diseases, which in turn may disturb brain function and nutrient signaling. In this review we explore the major advances obtained in the understanding of the BBB development and how its structure impacts on function. Furthermore, we focus on the particularities of the barrier permeability in the hypothalamus, its role in metabolic control and the potential impact of hypothalamic BBB abnormities in metabolic related diseases.

Role of thrombin-PAR1-PKCθ/δ axis in brain pericytes in thrombin-induced MMP-9 production and blood-brain barrier dysfunction in vitro

Thrombin, an essential component in the coagulation cascade, participates in the pathogenesis of brain diseases, such as ischemic stroke, intracerebral hemorrhage, Alzheimer's disease and Parkinson's disease through blood-brain barrier (BBB) dysfunction. It is thought that the thrombin-matrix metalloproteinase (MMP)-9 axis is an important process in the pathogenesis of neurovascular disease, such as BBB dysfunction. We recently reported that brain pericytes are the most MMP-9-releasing cells in response to thrombin stimulation among the BBB-constituting cells. This thrombin-induced MMP-9 release is partially due to protease-activated receptor (PAR1), one of the specific thrombin receptors. Then, we evaluated the intracellular signaling pathways involved in MMP-9 release and the contribution of thrombin-reactive brain pericytes to BBB dysfunction. PKC activator evoked MMP-9 release from brain pericytes. The thrombin-induced MMP-9 release was inhibited by U0126, LY294002, Go6976, and Go6983. However, Go6976 decreased phosphorylation levels of PKCθ and Akt, and Go6983 decreased phosphorylation levels of PKCδ and extracellular signal-regulated kinase (ERK). Additionally, treatment of pericytes with thrombin or PAR1-activating peptide stimulated PKCδ/θ signaling. These substances impaired brain endothelial barrier function in the presence of brain pericytes. Brain pericytes function through two independent downstream signaling pathways via PAR1 activation to release MMP-9 in response to thrombin - the PKCθ-Akt pathway and the PKCδ-ERK1/2 pathway. These pathways participate in PAR1-mediated MMP-9 release from pericytes, which leads to BBB dysfunction. Brain pericytes and their specific signaling pathways could provide novel therapeutic targets for thrombin-induced neurovascular diseases.

The interplay between Angiotensin II, TLR4 and hypertension

Hypertension is a multifactorial disease. Although a number of different underlying mechanisms have been learned from the various experimental models of the disease, hypertension still poses challenges for treatment. Angiotensin II plays an unquestionable role in blood pressure regulation acting through central and peripheral mechanisms. During hypertension, dysregulation of the Renin-Angiotensin System is associated with increased expression of pro-inflammatory cytokines and reactive oxygen species causing kidney damage, endothelial dysfunction, and increase in sympathetic activity, among other damages, eventually leading to decline in organ function. Recent studies have shown that these effects involve both the innate and the adaptive immune response. The contribution of adaptive immune responses involving different lymphocyte populations in various models of hypertension has been extensively studied. However, the involvement of the innate immunity mediating inflammation in hypertension is still not well understood. The innate and adaptive immune systems intimately interact with one another and are essential to an effectively functioning of the immune response; hence, the importance of a better understanding of the underlying mechanisms mediating innate immune system during hypertension. In this review, we aim to discuss mechanisms linking Angiotensin II and the innate immune system, in the pathogenesis of hypertension. The newest research investigating Angiotensin II triggering toll like receptor 4 activation in the kidney, vasculature and central nervous system contributing to hypertension will be discussed. Understanding the role of the innate immune system in the development of hypertension may bring to light new insights necessary to improve hypertension management.

Vascular inter-regulation of inflammation: molecular and cellular targets for CNS therapy

Angiogenesis and inflammation are clearly interconnected and interdependent processes that are dysregulated in a series of systemic and brain pathologies. Herein, key aspects regarding endothelial cell function and tissue remodelling that are particularly affected or aggravated by inflammation are presented. Most importantly, the cellular and molecular mechanisms involved in the vascular regulation of the inflammatory processes occurring in several brain disorders and how they impact on disease/injury progression are detailed, highlighting potential targets for therapy. Finally, nanomedicine-based approaches designed to overcome limitations pertaining to low systemic bioavailability, light, pH and temperature sensitivity and/or rapid degradation of these targets, and to optimize their mode of action are discussed. Ultimately, we expect this review to provide new insight and to suggest novel approaches for the treatment of blood-brain barrier dysfunction per se or as a means to treat the injured or diseased central nervous system.

A2A Adenosine Receptor Antagonism Reverts the Blood-Brain Barrier Dysfunction Induced by Sleep Restriction

Chronic sleep restriction induces blood-brain barrier disruption and increases pro-inflammatory mediators in rodents. Those inflammatory mediators may modulate the blood-brain barrier and constitute a link between sleep loss and blood-brain barrier physiology. We propose that adenosine action on its A_2A receptor may be modulating the blood-brain barrier dynamics in sleep-restricted rats. We administrated a selective A_2A adenosine receptor antagonist (SCH58261) in sleep-restricted rats at the 10^th day of sleep restriction and evaluated the blood-brain barrier permeability to dextrans coupled to fluorescein (FITC-dextrans) and Evans blue. In addition, we evaluated by western blot the expression of tight junction proteins (claudin-5, occludin, ZO-1), adherens junction protein (E-cadherin), A_2A adenosine receptor, adenosine-synthesizing enzyme (CD73), and neuroinflammatory markers (Iba-1 and GFAP) in the cerebral cortex, hippocampus, basal nuclei and cerebellar vermis. Sleep restriction increased blood-brain barrier permeability to FITC-dextrans and Evans blue, and the effect was reverted by the administration of SCH58261 in almost all brain regions, excluding the cerebellum. Sleep restriction increased the expression of A_2A adenosine receptor only in the hippocampus and basal nuclei without changing the expression of CD73 in all brain regions. Sleep restriction reduced the expression of tight junction proteins in all brain regions, except in the cerebellum; and SCH58261 restored the levels of tight junction proteins in the cortex, hippocampus and basal nuclei. Finally, sleep restriction induced GFAP and Iba-1 overexpression that was attenuated with the administration of SCH58261. These data suggest that the action of adenosine on its A_2A receptor may have a crucial role in blood-brain barrier dysfunction during sleep loss probably by direct modulation of brain endothelial cell permeability or through a mechanism that involves gliosis with subsequent inflammation and increased blood-brain barrier permeability.

The restorative role of annexin A1 at the blood-brain barrier

Annexin A1 is a potent anti-inflammatory molecule that has been extensively studied in the peripheral immune system, but has not as yet been exploited as a therapeutic target/agent. In the last decade, we have undertaken the study of this molecule in the central nervous system (CNS), focusing particularly on the primary interface between the peripheral body and CNS: the blood-brain barrier. In this review, we provide an overview of the role of this molecule in the brain, with a particular emphasis on its functions in the endothelium of the blood-brain barrier, and the protective actions the molecule may exert in neuroinflammatory, neurovascular and metabolic disease. We focus on the possible new therapeutic avenues opened up by an increased understanding of the role of annexin A1 in the CNS vasculature, and its potential for repairing blood-brain barrier damage in disease and aging.

The role of macrophage polarization on bipolar disorder: Identifying new therapeutic targets

OBJECTIVE

Bipolar disorder is a chronic, severe and disabling disease; however, its pathophysiology remains poorly understood. Recent evidence has suggested that inflammation and immune dysregulation play a significant role in the pathophysiology of bipolar disorder. This review is aimed to highlight the importance of systemic inflammation in modulating the inflammatory response of microglia and hence its potential involvement with bipolar disorder. We also discuss novel therapeutic strategies that emerge from this new research.

METHOD

This article presents a theoretical synthesis of the effects of systemic inflammation on the immune response of the central nervous system in bipolar disorder. The complex relationship between stress, pro-inflammatory cytokines and microglial dysfunction is summarized, emphasizing the role of the kynurenine pathway in this process and, consequently, their effects on neuronal plasticity.

RESULTS

Bipolar patients demonstrate increased serum levels of pro-inflammatory cytokines (interleukin-1β, interleukin-6 and tumor necrosis factor-α) and lower hypothalamic-pituitary-adrenal axis sensitivity. This imbalance in the immune system promotes a change in blood-brain barrier permeability, leading to an inflammatory signal spread in the central nervous system from the periphery, through macrophages activation (M1 polarization). Chronic microglial activation can result in neuronal apoptosis, neurogenesis inhibition, hippocampal volume reduction, lower neurotransmitters synthesis and cytotoxicity, by increasing glutamate production and kynurenine metabolism.

CONCLUSIONS

This review provides an overview of the mechanisms involved in the immune system imbalance and its potential involvement in the pathophysiology of bipolar disorder. Consequently, new strategies that normalize the immune-inflammatory pathways may provide a valuable therapeutic target for the treatment of these disorders.

Microglia-blood vessel interactions: a double-edged sword in brain pathologies

Microglia are long-living resident immune cells of the brain, which secure a stable chemical and physical microenvironment necessary for the proper functioning of the central nervous system (CNS). These highly dynamic cells continuously scan their environment for pathogens and possess the ability to react to damage-induced signals in order to protect the brain. Microglia, together with endothelial cells (ECs), pericytes and astrocytes, form the functional blood-brain barrier (BBB), a specialized endothelial structure that selectively separates the sensitive brain parenchyma from blood circulation. Microglia are in bidirectional and permanent communication with ECs and their perivascular localization enables them to survey the influx of blood-borne components into the CNS. Furthermore, they may stimulate the opening of the BBB, extravasation of leukocytes and angiogenesis. However, microglia functioning requires tight control as their dysregulation is implicated in the initiation and progression of numerous neurological diseases. Disruption of the BBB, changes in blood flow, introduction of pathogens in the sensitive CNS niche, insufficient nutrient supply, and abnormal secretion of cytokines or expression of endothelial receptors are reported to prime and attract microglia. Such reactive microglia have been reported to even escalate the damage of the brain parenchyma as is the case in ischemic injuries, brain tumors, multiple sclerosis, Alzheimer's and Parkinson's disease. In this review, we present the current state of the art of the causes and mechanisms of pathological interactions between microglia and blood vessels and explore the possibilities of targeting those dysfunctional interactions for the development of future therapeutics.