The blood-brain barrier and the inflammatory response

Blood urea nitrogen to albumin ratio is associated with cerebral small vessel diseases

Blood urea nitrogen (BUN) to albumin ratio (BAR) is a comprehensive parameter that reflects renal, inflammatory, nutritional, and endothelial functions. BAR has been shown to be associated with various cancers, pneumonia, sepsis, and pulmonary and cardiovascular diseases; however, few studies have been conducted on its association with cerebrovascular diseases. In this study, we evaluated the association between BAR and cerebral small vessel disease (cSVD) in health check-up participants. We assessed consecutive health check-up participants between January 2006 and December 2013. For the cSVD subtype, we quantitatively measured the volume of white matter hyperintensity (WMH) and qualitatively measured the presence of lacune and cerebral microbleeds (CMBs). The BAR was calculated by dividing BUN by albumin as follows: BAR = BUN (mg/dl)/albumin (g/dl). A total of 3012 participants were evaluated. In multivariable linear regression analysis, BAR showed a statistically significant association with WMH volume after adjusting for confounders [β = 0.076, 95% confidence interval (CI): 0.027-0.125]. In multivariable logistic regression analyses, BAR was significantly associated with lacunes [adjusted odds ratio (aOR) = 1.20, 95% CI: 1.00-1.44] and CMBs (aOR = 1.28, 95% CI: 1.06-1.55). BAR was associated with all types of cSVD in the health check-up participants.

Crotalphine Modulates Microglia M1/M2 Phenotypes and Induces Spinal Analgesia Mediated by Opioid-Cannabinoid Systems

Pain is a worldwide public health problem and its treatment is still a challenge since clinically available drugs do not completely reverse chronic painful states or induce undesirable effects. Crotalphine is a 14 amino acids synthetic peptide that induces a potent and long-lasting analgesic effect on acute and chronic pain models, peripherally mediated by the endogenous release of dynorphin A and the desensitization of the transient receptor potential ankyrin 1 (TRPA1) receptor. However, the effects of crotalphine on the central nervous system (CNS) and the signaling pathway have not been investigated. Thus, the central effect of crotalphine was evaluated on the partial sciatic nerve ligation (PSNL)-induced chronic neuropathic pain model. Crotalphine (100 µg/kg, p.o.)-induced analgesia on the 14th day after surgery lasting up to 24 h after administration. This effect was prevented by intrathecal administration of CB1 (AM251) or CB2 (AM630) cannabinoid receptor antagonists. Besides that, crotalphine-induced analgesia was reversed by CTOP, nor-BNI, and naltrindole, antagonists of mu, kappa, and delta-opioid receptors, respectively, and also by the specific antibodies for β-endorphin, dynorphin-A, and met-enkephalin. Likewise, the analgesic effect of crotalphine was blocked by the intrathecal administration of minocycline, an inhibitor of microglial activation and proliferation. Additionally, crotalphine decreased the PSNL-induced IL-6 release in the spinal cord. Importantly, in vitro, crotalphine inhibited LPS-induced CD86 expression and upregulated CD206 expression in BV-2 cells, demonstrating a polarization of microglial cells towards the M2 phenotype. These results demonstrated that crotalphine, besides activating opioid and cannabinoid analgesic systems, impairs central neuroinflammation, confirming the neuromodulatory mechanism involved in the crotalphine analgesic effect.

Expression of antimicrobial host defence peptides in the central nervous system during health and disease

Antimicrobial host defence peptides (HDP) are critical for the first line of defence against bacterial, viral, and fungal pathogens. Over the past decade we have become more aware that, in addition to their antimicrobial roles, they also possess the potent immunomodulatory capacity. This includes chemoattracting immune cells, activating dendritic cells and macrophages, and altering T-cell differentiation. Most examinations of their immunomodulatory roles have focused on tissues in which they are very abundant, such as the intestine and the inflamed skin. However, HDP have now been detected in the brain and the spinal cord during a number of conditions. We propose that their presence in the central nervous system (CNS) during homeostasis, infection, and neurodegenerative disease has the potential to contribute to immunosurveillance, alter host responses and skew developing immunity. Here, we review the evidence for HDP expression and function in the CNS in health and disease. We describe how a wide range of HDP are expressed in the CNS of humans, rodents, birds, and fish, suggesting a conserved role in protecting the brain from pathogens, with evidence of production by resident CNS cells. We highlight differences in methodology used and how this may have resulted in the immunomodulatory roles of HDP being overlooked. Finally, we discuss what HDP expression may mean for CNS immune responses.

Computational and Experimental Assessments of Magnolol as a Neuroprotective Agent and Utilization of UiO-66(Zr) as Its Drug Delivery System

The phenolic natural product magnolol exhibits neuroprotective properties through β-amyloid toxicity in PC-12 cells and ameliorative effects against cognitive deficits in a TgCRND8 transgenic mice model. Its bioavailability and blood-brain barrier crossing ability have been significantly improved using the metal-organic framework (MOF) UiO-66(Zr) as a drug delivery system (DDS). To investigate the neuroprotective effects of the Zr-based DDS, magnolol and magnolol-loaded-UiO-66(Zr) (Mag@UiO-66(Zr)) were evaluated for inhibitory activity against β-secretase and AlCl₃-induced neurotoxicity. Due to the moderate inhibition observed for magnolol in vitro, in silico binding studies were explored against β-secretase along with 11 enzymes known to affect Alzheimer's disease (AD). Favorable binding energies against CDK2, CKD5, MARK, and phosphodiesterase 3B (PDE3B) and dynamically stable complexes were noted through molecular docking and molecular dynamic simulation experiments, respectively. The magnolol-loaded DDS UiO-66(Zr) also showed enhanced neuroprotective activity against two pathological indices, namely, neutrophil infiltration and apoptotic neurons, in addition to damage reversal compared to magnolol. Thus, MOFs are promising drug delivery platforms for poorly bioavailable drugs.

Delivering Antisense Oligonucleotides across the Blood-Brain Barrier by Tumor Cell-Derived Small Apoptotic Bodies

The blood-brain barrier (BBB) is the most restrictive and complicated barrier that keeps most biomolecules and drugs from the brain. An efficient brain delivery strategy is urgently needed for the treatment of brain diseases. Based on the studies of brain-targeting extracellular vesicles (EVs), the potential of using small apoptotic bodies (sABs) from brain metastatic cancer cells for brain-targeting drug delivery is explored. It is found that anti-TNF-α antisense oligonucleotide (ASO) combined with cationic konjac glucomannan (cKGM) can be successfully loaded into sABs via a transfection/apoptosis induction process and that the sABs generated by B16F10 cells have an extraordinarily high brain delivery efficiency. Further studies suggest that ASO-loaded sABs (sCABs) are transcytosed by b. End3 (brain microvascular endothelial cells, BMECs) to penetrate the BBB, which is mediated by CD44v6, and eventually taken up by microglial cells in the brain. In a Parkinson's disease (PD) mouse model, sCABs dramatically ameliorate PD symptoms via the anti-inflammatory effect of ASO. This study suggests that sABs from brain metastatic cancer cells are excellent carriers for brain-targeted delivery, as they have not only an extraordinary delivery efficiency but also a much higher scale-up production potential than other EVs.

The Use of Alternative Strategies for Enhanced Nanoparticle Delivery to Solid Tumors

Nanomaterial (NM) delivery to solid tumors has been the focus of intense research for over a decade. Classically, scientists have tried to improve NM delivery by employing passive or active targeting strategies, making use of the so-called enhanced permeability and retention (EPR) effect. This phenomenon is made possible due to the leaky tumor vasculature through which NMs can leave the bloodstream, traverse through the gaps in the endothelial lining of the vessels, and enter the tumor. Recent studies have shown that despite many efforts to employ the EPR effect, this process remains very poor. Furthermore, the role of the EPR effect has been called into question, where it has been suggested that NMs enter the tumor via active mechanisms and not through the endothelial gaps. In this review, we provide a short overview of the EPR and mechanisms to enhance it, after which we focus on alternative delivery strategies that do not solely rely on EPR in itself but can offer interesting pharmacological, physical, and biological solutions for enhanced delivery. We discuss the strengths and shortcomings of these different strategies and suggest combinatorial approaches as the ideal path forward.

A Destruction Model of the Vascular and Lymphatic Systems in the Emergence of Psychiatric Symptoms

The lymphatic system is important for antigen presentation and immune surveillance. The lymphatic system in the brain was originally introduced by Giovanni Mascagni in 1787, while the rediscovery of it by Jonathan Kipnis and Kari Kustaa Alitalo now opens the door for a new interpretation of neurological diseases and therapeutic applications. The glymphatic system for the exchanges of cerebrospinal fluid (CSF) and interstitial fluid (ISF) is associated with the blood-brain barrier (BBB), which is involved in the maintenance of immune privilege and homeostasis in the brain. Recent notions from studies of postmortem brains and clinical studies of neurodegenerative diseases, infection, and cerebral hemorrhage, implied that the breakdown of those barrier systems and infiltration of activated immune cells disrupt the function of both neurons and glia in the parenchyma (e.g., modulation of neurophysiological properties and maturation of myelination), which causes the abnormality in the functional connectivity of the entire brain network. Due to the vulnerability, such dysfunction may occur in developing brains as well as in senile or neurodegenerative diseases and may raise the risk of emergence of psychosis symptoms. Here, we introduce this hypothesis with a series of studies and cellular mechanisms.

The Brain Entangled: The Contribution of Neutrophil Extracellular Traps to the Diseases of the Central Nervous System

Under normal conditions, neutrophils are restricted from trafficking into the brain parenchyma and cerebrospinal fluid by the presence of the brain–blood barrier (BBB). Yet, infiltration of the central nervous system (CNS) by neutrophils is a well-known phenomenon in the course of different pathological conditions, e.g., infection, trauma or neurodegeneration. Different studies have shown that neutrophil products, i.e., free oxygen radicals and proteolytic enzymes, play an important role in the pathogenesis of BBB damage. It was recently observed that accumulating granulocytes may release neutrophil extracellular traps (NETs), which damage the BBB and directly injure surrounding neurons. In this review, we discuss the emerging role of NETs in various pathological conditions affecting the CNS.

Accessing neuroinflammation sites: Monocyte/neutrophil-mediated drug delivery for cerebral ischemia

Cerebral ischemia (CI) results from inadequate blood flow to the brain. The difficulty of delivering therapeutic molecules to lesions resulting from CI hinders the effective treatment of this disease. The inflammatory response following CI offers a unique opportunity for drug delivery to the ischemic brain and targeted cells because of the recruitment of leukocytes to the stroke core and penumbra. In the present study, neutrophils and monocytes were explored as cell carriers after selectively carrying cRGD liposomes, which effectively transmigrated the blood-brain barrier, infiltrated the cerebral parenchyma, and delivered therapeutic molecules to the injured sites and target cells. Our results showed the successful comigration of liposomes with neutrophils/monocytes and that both monocytes and neutrophils were important for successful delivery. Enhanced protection against ischemic injury was achieved in the CI/reperfusion model. The strategy presented here shows potential in the treatment of CI and other diseases related to inflammation.

HLA and killer cell immunoglobulin-like receptor (KIRs) genotyping in patients with acute ischemic stroke

INTRODUCTION

In humans, a major component of natural killer (NK) and T cell target recognition depends on the surveillance of human leukocyte antigen (HLA) class I molecules by killer immunoglobulin-like receptors (KIRs).

AIMS

To implement the knowledge about the immunological genetic background of acute ischemic stroke susceptibility in relation to the frequency of the KIR genes and HLA alleles.

METHODS

Subjects with acute ischemic stroke and subjects without stroke were genotyped for the presence of KIR genes and of the three major KIR ligand groups, HLA-C1, HLA-C2, and HLA-Bw4, both HLA-B and HLA-A loci.

RESULTS

Between November 2013 and February 2016, consecutive patients with acute ischemic stroke were recruited. As healthy controls, we enrolled subjects without acute ischemic stroke. Subjects with acute ischemic stroke in comparison with controls showed a higher frequency of 2DL3, 2DL5B, 2DS2, and 2DS4 KIR genes and a lower frequency of HLA-B-Bw4^I alleles. Subjects without acute ischemic stroke showed a higher frequency of interaction between KIR 2DS2 and HLAC2. We also observed a higher frequency of 2DL3 and 2 DL4 KIR genes in subjects with atherosclerotic (LAAS) subtype. Multiple logistic regression analysis showed a protective effect towards stroke of HLA-B-Bw4^I and interaction between KIR 2DL2 and HLAC1 and 2DS2-HLAC2 and a detrimental effect of 2DL2-HLA-C1_A interactions.

CONCLUSION

Our findings of a higher frequency of activating KIR genes seem to be consistent with findings previously reported patients with coronary syndrome. This higher frequency of "proinflammatory" genes in subjects with ischemic stroke could also explain the immunoinflammatory activation of the acute phase of stroke.

The Role of the CXCL12/CXCR4/ACKR3 Axis in Autoimmune Diseases

Chemokine receptors are members of the G protein-coupled receptor superfamily. These receptors are intimately involved in cell movement, and thus play a critical role in several physiological and pathological situations that require the precise regulation of cell positioning. CXCR4 is one of the most studied chemokine receptors and is involved in many functions beyond leukocyte recruitment. During embryogenesis, it plays essential roles in vascular development, hematopoiesis, cardiogenesis, and nervous system organization. It has been also implicated in tumor progression and autoimmune diseases and, together with CD4, is one of the co-receptors used by the HIV-1 virus to infect immune cells. In contrast to other chemokine receptors that are characterized by ligand promiscuity, CXCR4 has a unique ligand-stromal cell-derived factor-1 (SDF1, CXCL12). However, this ligand also binds ACKR3, an atypical chemokine receptor that modulates CXCR4 functions and is overexpressed in multiple cancer types. The CXCL12/CXCR4/ACKR3 axis constitutes a potential therapeutic target for a wide variety of inflammatory diseases, not only by interfering with cell migration but also by modulating immune responses. Thus far, only one antagonist directed against the ligand-binding site of CXCR4, AMD3100, has demonstrated clinical relevance. Here, we review the role of this ligand and its receptors in different autoimmune diseases.

The Role of VE-cadherin in Blood-brain Barrier Integrity Under Central Nervous System Pathological Conditions

The blood-brain barrier (BBB) is a layer between the blood circulation and neural tissue. It plays a pivotal role in maintaining the vulnerable extracellular microenvironment in the neuronal parenchyma. Neuroinflammatory events can result in BBB dysregulation by disturbing adherens junctions (AJs) and tight junctions (TJs). VE-cadherin, as one of the most im-portant components of the vascular system, is specifically responsible for the assembly of AJs and BBB architecture. Here, we present a review, which highlights recently available insights into the relationship between

the neuroinflammation and BBB dysregulation. We then explore the specific interaction between VE-cadherin and BBB. Fi-nally, we discuss the changes of VE-cadherin with different neurological diseases from both experimental and clinical stud-ies. An understanding of VE-cadherin in BBB regulation may indicate that VE-cadherin can partially be a biomarker of neu-roinflammation disease and lead to novel approaches for abating BBB dysregulation under pathological conditions and the opening of the BBB following central nervous system (CNS) drug delivery.

Superparamagnetic iron oxide nanocolloids in MRI studies of neuroinflammation

Iron oxide (IO) nanocolloids are being increasingly used to image cellular contribution to neuroinflammation using MRI, as these particles are capable of labeling circulating cells with phagocytic activity, allowing to assess cell trafficking from the blood to neuroinflammation sites. The use of IOs relies on the natural phagocytic properties of immune cells, allowing their labeling either in vitro or directly in vivo, following intravenous injection. Despite concerns on the specificity of the latter approach, the widespread availability and relatively low cost of these techniques, coupled to a sensitivity that allows to reach single cell detection, have promoted their use in several preclinical and clinical studies. In this review, we discuss the results of currently available preclinical and clinical IO-enhanced MRI studies of immune cell trafficking in neuroinflammation, examining the specificity of the existing findings, in view of the different possible mechanisms underlying IO accumulation in the brain. From this standpoint, we assess the implications of the temporal and spatial differences in the enhancement pattern of IOs, compared to gadolinium-based contrast agents, a clinically established MRI marker blood-brain barrier breakdown. While concerns on the specificity of cell labeling obtained using the in-vivo labeling approach still need to be fully addressed, these techniques have indeed proved able to provide additional information on neuroinflammatory phenomena, as compared to conventional Gadolinium-enhanced MRI.

Tail Vein Infusion of Adipose-Derived Mesenchymal Stem Cell Alleviated Inflammatory Response and Improved Blood Brain Barrier Condition by Suppressing Endoplasmic Reticulum Stress in a Middle Cerebral Artery Occlusion Rat Model

BACKGROUND The current study was designed to explore the pathway through which adipose-derived mesenchymal stem cells (ADMSCs) affect brain ischemic injury. MATERIAL AND METHODS The improving effect of ADMSCs on the brain function and structure was evaluated in a middle cerebral artery occlusion (MCAO) rat model. The permeability of the brain-blood barrier (BBB), inflammatory response, and endoplasmic reticulum (ER) stress-related signaling induced by ischemia were determined. RESULTS The administration of ADMSCs decreased neurological severity score when compared with that in the MCAO group and also restricted the brain infarction area as well as cell apoptosis. ADMSCs suppressed the inflammation in brains by decreasing the expressions of IL-1β, IL-6, and TNF-α, contributing to the decreased permeability of the BBB. The expressions of pro-apoptosis factors in ER stress were inhibited while that of anti-apoptosis factors were induced. CONCLUSIONS ADMSCs affected brain injury in multiple ways, not only by suppressing inflammation in the brain infarction area, but also by blocking ER stress-induced apoptosis.

Cytokine networks in neuroinflammation

Cytokines provide cells with the ability to communicate with one another and orchestrate complex multicellular behaviour. There is an emerging understanding of the role that cytokines play in normal homeostatic tissue function and how dysregulation of these cytokine networks is associated with pathological conditions. The central nervous system (CNS), where few blood-borne immune cells circulate, seems to be particularly vulnerable to dysregulated cytokine networks. In degenerative diseases, such as proteopathies, CNS-resident cells are the predominant producers of pro-inflammatory cytokines. By contrast, in classical neuroinflammatory diseases, such as multiple sclerosis and encephalitides, pro-inflammatory cytokines are mainly produced by tissue-invading leukocytes. Whereas the effect of dysregulated cytokine networks in proteopathies is controversial, cytokines delivered to the CNS by invading immune cells are in general detrimental to the tissue. Here, we summarize recent observations on the impact of dysregulated cytokine networks in neuroinflammation.

The role of Toll-like receptors in multiple sclerosis and possible targeting for therapeutic purposes

The interaction between the immune and nervous systems suggests invaluable mechanisms for several pathological conditions, especially neurodegenerative disorders. Multiple sclerosis (MS) is a potentially disabling chronic autoimmune disease, characterized by chronic inflammation and neurodegenerative pathology of the central nervous system. Toll-like receptors (TLRs) are an important family of receptors involved in host defense and in recognition of invading pathogens. The role of TLRs in the pathogenesis of autoimmune disorders such as MS is only starting to be uncovered. Recent studies suggest an ameliorative role of TLR3 and a detrimental role of other TLRs in the onset and progression of MS and experimental autoimmune encephalomyelitis, a murine model of MS. Thus, modulating TLRs can represent an innovative immunotherapeutic approach in MS therapy. This article outlines the role of these TLRs in MS, also discussing TLR-targeted agonist or antagonists that could be used in the different stages of the disease.

Multiple sclerosis: myeloperoxidase immunoradiology improves detection of acute and chronic disease in experimental model

PURPOSE

To test if MPO-Gd, a gadolinium-based magnetic resonance (MR) imaging probe that is sensitive and specific for the proinflammatory and oxidative enzyme myeloperoxidase (MPO), which is secreted by certain inflammatory cells, is more sensitive than diethylenetriaminepentaacetic acid (DTPA)-Gd in revealing early subclinical and chronic disease activity in the brain in experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis.

MATERIALS AND METHODS

The protocol for animal experiments was approved by the institutional animal care committee. A total of 61 female SJL mice were induced with EAE. Mice underwent MPO-Gd- or DTPA-Gd-enhanced MR imaging on days 6, 8, and 10 after induction, before clinical disease develops, and during chronic disease at remission and the first relapse. Brains were harvested at these time points for flow cytometric evaluation of immune cell subtypes and immunohistochemistry. Statistical analysis was performed, and P < .05 was considered to indicate a significant difference.

RESULTS

MPO-Gd helps detect earlier (5.2 vs 2.3 days before symptom onset, P = .004) and more (3.1 vs 0.3, P = .008) subclinical inflammatory lesions compared with DTPA-Gd, including in cases in which there was no evidence of overt blood-brain barrier (BBB) breakdown detected with DTPA-Gd enhancement. The number of MPO-Gd-enhancing lesions correlated with early infiltration of MPO-secreting monocytes and neutrophils into the brain (r = 0.91). MPO-Gd also helped detect more lesions during subclinical disease at remission (5.5 vs 1.3, P = .006) and at the first relapse (9.0 vs 2.7, P = .03) than DTPA-Gd, which also correlated well with the presence and accumulation of MPO-secreting inflammatory cells in the brain (r = 0.93).

CONCLUSION

MPO-Gd specifically reveals lesions with inflammatory monocytes and neutrophils, which actively secrete MPO. These results demonstrate the feasibility of detection of subclinical inflammatory disease activity in vivo, which is different from overt BBB breakdown.

Inhibition of monocyte adhesion to brain-derived endothelial cells by dual functional RNA chimeras

Because adhesion of leukocytes to endothelial cells is the first step of vascular-neuronal inflammation, inhibition of adhesion and recruitment of leukocytes to vascular endothelial cells will have a beneficial effect on neuroinflammatory diseases. In this study, we used the pRNA of bacteriophage phi29 DNA packaging motor to construct a novel RNA nanoparticle for specific targeting to transferrin receptor (TfR) on the murine brain-derived endothelial cells (bEND5) to deliver ICAM-1 siRNA. This RNA nanoparticle (FRS-NPs) contained a FB4 aptamer targeting to TfR and a siRNA moiety for silencing the intercellular adhesion molecule-1 (ICAM-1). Our data indicated that this RNA nanoparticle was delivered into murine brain-derived endothelial cells. Furthermore, the siRNA was released from the FRS-NPs in the cells and knocked down ICAM-1 expression in the TNF-α–stimulated cells and in the cells under oxygen-glucose deprivation/reoxygenation (OGD/R) condition. The functional end points of the study indicated that FRS-NPs significantly inhibited monocyte adhesion to the bEND5 cells induced by TNF-α and OGD/R. In conclusion, our approach using RNA nanotechnology for siRNA delivery could be potentially applied for inhibition of inflammation in ischemic stroke and other neuroinflammatory diseases, or diseases affecting endothelium of vasculature.

Age-dependent modifications in vascular adhesion molecules and apoptosis after 48-h reperfusion in a rat global cerebral ischemia model

Stroke is one of the leading causes of death and permanent disability in the elderly. However, most of the experimental studies on stroke are based on young animals, and we hypothesised that age can substantially affect the stroke response. The two-vessel occlusion model of global ischemia by occluding the common carotid arteries for 15 min at 40 mmHg of blood pressure was carried out in 3- and 18-month-old male Sprague-Dawley rats. The adhesion molecules E- and P-selectin, cell adhesion molecules (CAMs), both intercellular (ICAM-1) and vascular (VCAM-1), as well as glial fibrillary acidic protein (GFAP), and cleaved caspase-3 were measured at 48 h after ischemia in the cerebral cortex and hippocampus using Western blot, qPCR and immunofluorescence techniques. Diametric expression of GFAP and a different morphological pattern of caspase-3 labelling, although no changes in the cell number, were observed in the neurons of young and old animals. Expression of E-selectin and CAMs was also modified in an age- and ischemia/reperfusion-dependent manner. The hippocampus and cerebral cortex had similar response patterns for most of the markers studied. Our data suggest that old and young animals present different time-courses of neuroinflammation and apoptosis after ischemic damage. On the other hand, these results suggest that neuroinflammation is dependent on age rather than on the different vulnerability described for the hippocampus and cerebral cortex. These differences should be taken into account in searching for therapeutic targets.

The blood-brain barrier: structure, function and therapeutic approaches to cross it

The blood-brain barrier (BBB) is constituted by a specialized vascular endothelium that interacts directly with astrocytes, neurons and pericytes. It protects the brain from the molecules of the systemic circulation but it has to be overcome for the proper treatment of brain cancer, psychiatric disorders or neurodegenerative diseases, which are dramatically increasing as the population ages. In the present work we have revised the current knowledge on the cellular structure of the BBB and the different procedures utilized currently and those proposed to cross it. Chemical modifications of the drugs, such as increasing their lipophilicity, turn them more prone to be internalized in the brain. Other mechanisms are the use of molecular tools to bind the drugs such as small immunoglobulins, liposomes or nanoparticles that will act as Trojan Horses favoring the drug delivery in brain. This fusion of the classical pharmacology with nanotechnology has opened a wide field to many different approaches with promising results to hypothesize that BBB will not be a major problem for the new generation of neuroactive drugs. The present review provides an overview of all state-of-the-art of the BBB structure and function, as well as of the classic strategies and these appeared in recent years to deliver drugs into the brain for the treatment of Central Nervous System (CNS) diseases.

Transcriptional targeting of sphingosine-1-phosphate receptor S1P2 by epigallocatechin-3-gallate prevents sphingosine-1-phosphate-mediated signaling in macrophage-differentiated HL-60 promyelomonocytic leukemia cells

Background

Macrophage chemotaxis followed by blood–brain barrier transendothelial migration is believed to be associated with inflammation in the central nervous system. Antineuroinflammatory strategies have identified the dietary-derived epigallocatechin-3-gallate (EGCG) as an efficient agent to prevent neuroinflammation-associated neurodegenerative diseases by targeting proinflammatory mediator signaling.

Methods

Given that high levels of sphingosine kinase and its product, sphingosine-1-phosphate (S1P), are present in brain tumors, we used quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and immunoblotting to test whether EGCG may impact on S1P receptor gene expression and prevent S1P response in undifferentiated and in terminally differentiated macrophages.

Results

Promyelomonocytic human leukemia (HL)-60 cells were differentiated into macrophages, and S1P triggered phosphorylation in extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and P38 mitogen-activated protein kinase (MAPK) intracellular signaling, as shown by Western blot analysis. Pretreatment of cells with EGCG prior to differentiation inhibited the response to S1P in all three pathways, while EGCG abrogated P38 MAPK phosphorylation when present only during differentiation. Terminally-differentiated macrophages were, however, insensitive to EGCG treatment. Using qRT-PCR, gene expression of the S1P receptors S1P1, S1P2, and S1P5 was predominantly induced in terminally-differentiated macrophages, while the S1P2 was decreased by EGCG treatment.

Conclusion

Our data suggest that diet-derived EGCG achieves efficient effects as a preventive agent, targeting signaling pathways prior to cell terminal differentiation. Such properties could impact on cell chemotaxis through the blood–brain barrier and prevent cancer-related neuroinflammation.

cRGD mediated liposomes enhanced antidepressant-like effects of edaravone in rats

The delayed onset of therapeutic outcomes is a major drawback of the current antidepressants. The blood-brain barrier is the most important bottleneck impeding drug transport into the brain. Therefore, development of novel antidepressant medications with rapid onset and sustained activity is urgent. RGD liposomes showed an excellent effect of brain-targeting drug delivery and increased the entering rate to the brain. In the present study, we prepared cyclic RGD liposomes loaded with edaravone (cRGD-ERLs) and evaluated the potential antidepressant-like effects of this drug delivery system in rats. The results showed single injection of cRGD-ERLs produced significant antidepressant-like effects in both forced swim and novelty suppressed feeding test. Moreover, acute cRGD-ERLs increased the expression of c-fos in the medial prefrontal cortex, suggesting that cRGD-ERLs could activate the neuronal function. Furthermore, cRGD-ERLs reversed the increase of lipopolysaccharides (LPS)-induced plasma cytokine IL-1β and IL-6, suggesting that normalization of cytokine level might be involved in the behavioral response of cRGD-ERLs. Finally, cRGD-ERLs prevented the increase of immobility induced by LPS in the forced swim test. Overall, the current data revealed a novel brain-target drug delivery system, which can be used to improve the therapeutic outcomes of antidepressants by increase of crossing rate to the brain.

Antibody, T-cell and dendritic cell immunotherapy for malignant brain tumors

Modest improvement in brain tumor patient survival has been achieved through advances in surgical, adjuvant radiation and chemotherapeutic strategies. However, these traditional approaches have been unsuccessful in permanently controlling these aggressive tumors, with recurrence being quite common. Hence, there is a need for novel therapeutic approaches that specifically target the molecularly diverse brain tumor cell population. The ability of the immune system to recognize altered tumor cells while avoiding surrounding normal cells offers an enormous advantage over the nonspecific nature of the conventional treatment schemes. Therefore, immunotherapy represents a promising approach that may supplement the standard therapies in eliminating the residual brain tumor cells. This review summarizes different immunotherapeutic approaches currently being tested for malignant brain tumor treatment.

Chemokines and chemokine receptors in multiple sclerosis

Multiple sclerosis is an autoimmune disease with classical traits of demyelination, axonal damage, and neurodegeneration. The migration of autoimmune T cells and macrophages from blood to central nervous system as well as the destruction of blood brain barrier are thought to be the major processes in the development of this disease. Chemokines, which are small peptide mediators, can attract pathogenic cells to the sites of inflammation. Each helper T cell subset expresses different chemokine receptors so as to exert their different functions in the pathogenesis of MS. Recently published results have shown that the levels of some chemokines and chemokine receptors are increased in blood and cerebrospinal fluid of MS patients. This review describes the advanced researches on the role of chemokines and chemokine receptors in the development of MS and discusses the potential therapy of this disease targeting the chemokine network.

Porcine brain microvessel endothelial cells show pro-inflammatory response to the size and composition of metallic nanoparticles

The purpose of the current studies was to determine if systemic exposure of various metallic nanoparticles differing in size and composition [silver (Ag-NPs, 25, 40 and 80 nm), copper-oxide (Cu-NPs, 40 and 60 nm) or gold (Au-NPs, 3 and 5 nm)] can induce the release of pro-inflammatory mediators that influence the restrictive nature of the blood-brain barrier (BBB) in vitro. Confluent porcine brain microvessel endothelial cells (pBMECs) (8-12 days) were treated with various metallic nanoparticles (15 μg/ml). Extracellular concentrations of pro-inflammatory mediators (IL-1β, TNFα and PGE2) were evaluated using ELISA. pBMECs were cultured in standard 12-well Transwell® inserts, and permeability was evaluated by measuring the transport of fluorescein across the pBMEC monolayers. PGE2 release following Cu-NP exposure was significantly increased when compared to the control. Similar results were observed for Ag-NPs but not Au-NPs. The secretion of TNFα and IL-1β was observed for both Cu-NPs and Ag-NPs but not in response to Au-NPs. The post-treatment time profiles of TNFα and IL-1β revealed that the IL-1β response was more persistent. The permeability ratios (exposure/control) were significantly greater following exposure to Cu-NPs or Ag-NPs, compared to Au-NPs. Together, these data suggest that the composition and size of NPs can cause significant pro-inflammatory response that can influence the integrity of the BBB.

The Changes of P-glycoprotein Activity by Interferon-γ and Tumor Necrosis Factor-α in Primary and Immortalized Human Brain Microvascular Endothelial Cells

The purpose of this study was to investigate the modification of expression and functionality of the drug transporter P-glycoprotein (P-gp) by tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) at the blood-brain barrier (BBB). We used immortalized human brain microvessel endothelial cells (iHBMEC) and primary human brain microvessel endothelial cells (pHBMEC) as in vitro BBB model. To investigate the change of p-gp expression, we carried out real time PCR analysis and Western blotting. To test the change of p-gp activity, we performed rhodamin123 (Rh123) accumulation study in the cells. In results of real time PCR analysis, the P-gp mRNA expression was increased by TNF-α or IFN-γ treatment for 24 hr in both cell types. However, 48 hr treatment of TNF-α or IFN-γ did not affect P-gp mRNA expression. In addition, co-treatment of TNF-α and IFN-γ markedly increased the P-gp mRNA expression in both cells. TNF-α or IFN-γ did not influence P-gp protein expression whatever the concentration of cytokines or duration of treatment in both cells. However, P-gp expression was increased after treatments of both cytokines together in iHBMEC cells only compared with untreated control. Furthermore, in both cell lines, TNF-α or IFN-γ induced significant decrease of P-gp activity for 24 hr treatment. And, both cytokines combination treatment also decreased significantly P-gp activity. These results suggest that P-gp expression and function at the BBB is modulated by TNF-α or/and IFN-γ. Therefore, the distribution of P-gp depending drugs in the central nervous system can be modulated by neurological inflammatory diseases.

Matrix metalloproteinases and their tissue inhibitors in serum and cerebrospinal fluid of children with Japanese encephalitis virus infection

The expression of matrix metalloproteinases (MMPs) is tightly regulated at the level of gene transcription, conversion of pro-enzyme to active MMPs, and the action of tissue inhibitors of metalloproteinases (TIMPs). The present study aimed to investigate the expression of some specific MMPs (2, 7, 9) and TIMPs (1, 2, 3) in serum and cerebrospinal fluid (CSF) of children with Japanese encephalitis virus (JEV) infection. Serum and CSF levels of MMPs and TIMPs in children with JEV infection and disease control (DC) were compared. The CSF and serum concentrations of MMP-2, TIMP-2 and TIMP-3 were significantly higher in children with JEV infection compared to DC. The concentration of MMP-9 in serum was significantly higher in children with JEV infection than in the DC and healthy control (HC), while in the CSF, no significant difference was observed compared to DC. The MMP-7 serum concentration was significantly higher in children with JEV infection compared to HC, but no significant difference was observed compared to DC. MMP-7 concentration was undetectable in CSF in both groups. The TIMP-1 CSF concentration was significantly higher, while the serum concentration was significantly lower, in children with JEV infection compared to DC. No correlation was found between the levels of each biomolecule measured in CSF and serum, suggesting that the levels in CSF represent local production within the CNS rather than production in the periphery. We also observed leucocytosis, mononuclear pleocytosis and elevated protein concentrations in the CSF of children with JEV infection compared to DC.

Depression after myocardial infarction: TNF-α-induced alterations of the blood-brain barrier and its putative therapeutic implications

Patients experiencing an acute myocardial infarction (AMI) have a three times higher chance to develop depression. Vice versa, depressive symptoms increase the risk of cardiovascular events. The co-existence of both conditions is associated with substantially worse prognosis. Although the underlying mechanism of the interaction is largely unknown, inflammation is thought to be of pivotal importance. AMI-induced peripheral cytokines release may cause cerebral endothelial leakage and hence induces a neuroinflammatory reaction. The neuroinflammation may persist even long after the initial peripheral inflammation has subsided. Among those selected brain regions that are prone to blood-brain barrier dysfunction, the paraventricular nucleus of the hypothalamus (PVN), a major center for cardiovascular autonomic regulation, is indicated to play a mediating role. Optimal cardiovascular therapy improves cardiovascular prognosis without major effects on depression. By the same token, antidepressant therapy in cardiovascular disease is associated with modest improvement in depressive symptoms, however without improvement in cardiac outcome. The failure of current antidepressants and the growing number of patients suffering from both conditions legitimize the search for better antidepressive therapies, from patients as well as society perspectives. Though we appreciate the mutual character of the interaction between depression and AMI, the present review focuses on the side of AMI induced depression and discusses the role of inflammation, represented by the proinflammatory cytokine TNF-α, as potential underlying mechanism. It is conceivable that inhibition of the inflammatory response post-AMI, through targeted anti-inflammatory pharmacotherapeutical agents may prevent the development of depressive symptoms and ultimately may improve cardiovascular outcomes.

Mast cell activation and neutrophil recruitment promotes early and robust inflammation in the meninges in EAE

The meninges are often considered inert tissues that house the CSF and provide protection for the brain and spinal cord. Yet emerging data demonstrates that they are also active sites of immune responses. Furthermore, the blood-CSF barrier surrounding meningeal blood vessels, together with the blood-brain barrier (BBB), is postulated to serve as a gateway for the pathological infiltration of immune cells into the CNS in multiple sclerosis (MS). Our previous studies using mast cell-deficient (Kit(W/Wv)) mice demonstrated that mast cells resident in the dura mater and pia mater exacerbate experimental autoimmune encephalomyelitis (EAE), a rodent model of MS, by facilitating CNS inflammatory cell influx. Here we examined the underlying mechanisms that mediate these effects. We demonstrate that there are dramatic alterations in immune associated gene expression in the meninges in pre-clinical disease, including those associated with mast cell and neutrophil function. Meningeal mast cells are activated within 24 h of disease induction, but do not directly compromise CNS vascular integrity. Rather, through production of TNF, mast cells elicit an early influx of neutrophils, cells known to alter vascular permeability, into the meninges. These data add to the growing evidence that inflammation in the meninges precedes CNS immune cell infiltration and establish that mast cells are among the earliest participants in these disease-initiating events. We hypothesize that mast cell-dependent neutrophil recruitment and activation in the meninges promotes early breakdown of the local BBB and CSF-blood barrier allowing initial immune cell access to the CNS.

Magnetic resonance imaging of blood brain/nerve barrier dysfunction and leukocyte infiltration: closely related or discordant?

Unlike other organs the nervous system is secluded from the rest of the organism by the blood brain barrier (BBB) or blood nerve barrier (BNB) preventing passive influx of fluids from the circulation. Similarly, leukocyte entry to the nervous system is tightly controlled. Breakdown of these barriers and cellular inflammation are hallmarks of inflammatory as well as ischemic neurological diseases and thus represent potential therapeutic targets. The spatiotemporal relationship between BBB/BNB disruption and leukocyte infiltration has been a matter of debate. We here review contrast-enhanced magnetic resonance imaging (MRI) as a non-invasive tool to depict barrier dysfunction and its relation to macrophage infiltration in the central and peripheral nervous system under pathological conditions. Novel experimental contrast agents like Gadofluorine M (Gf) allow more sensitive assessment of BBB dysfunction than conventional Gadolinium (Gd)-DTPA enhanced MRI. In addition, Gf facilitates visualization of functional and transient alterations of the BBB remote from lesions. Cellular contrast agents such as superparamagnetic iron oxide particles (SPIO) and perfluorocarbons enable assessment of leukocyte (mainly macrophage) infiltration by MR technology. Combined use of these MR contrast agents disclosed that leukocytes can enter the nervous system independent from a disturbance of the BBB, and vice versa, a dysfunctional BBB/BNB by itself is not sufficient to attract inflammatory cells from the circulation. We will illustrate these basic imaging findings in animal models of multiple sclerosis, cerebral ischemia, and traumatic nerve injury and review corresponding findings in patients.

Systemic immune activation shapes stroke outcome

Stroke is a major cause of morbidity and mortality, and activation of the immune system can impact on stroke outcome. Although the majority of research has focused on the role of the immune system after stroke there is increasing evidence to suggest that inflammation and immune activation prior to brain injury can influence stroke risk and outcome. With the high prevalence of co-morbidities in the Western world such as obesity, hypertension and diabetes, pre-existing chronic 'low-grade' systemic inflammation has become a customary characteristic of stroke pathophysiology that needs to be considered in the search for new therapies. The importance of the immune system in stroke has been demonstrated in a number of ways, both experimentally and in the clinical setting. This review will focus on the effect of immune activation arising from systemic inflammatory conditions and infection, how it affects the incidence and outcomes of stroke, and the possible underlying mechanisms involved. This article is part of a Special Issue entitled 'Neuroinflammation in neurodegeneration and neurodysfunction'.

Upregulated expression of matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in BALB/c mouse brain challenged with Japanese encephalitis virus

BACKGROUND

Uncontrolled immune responses in the nervous system are potentially damaging following Japanese encephalitis virus (JEV) infection. Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) act together to control the proteolysis of extracellular matrix. Disbalances in the MMP/TIMP system during virally induced neurodegenerative processes and inflammations are responsive to changes in the progression of diseases.

METHODS

The expression of MMP-2, MMP-7, MMP-9, TIMP-1, and TIMP-3 in JEV-infected mouse brain was analyzed by RT-PCR for semiquantitation and ELISA for estimation of protein along with brain histopathology at different days postinoculation (dpi). Gelatin gel zymography was performed for MMP-2 and MMP-9 activities.

RESULTS

In the virus-infected group, expression of MMP-2, MMP-7, MMP-9, TIMP-1, and TIMP-3 was found to be increased from 1 dpi to 6 dpi as compared to controls by both RT-PCR and ELISA. The expressions of MMPs and TIMPs at mRNA and protein levels were in concordance with each other. Post hoc multiple comparison analysis between days revealed that, in the virus-infected groups, significant increases (p < 0.05) in MMP and TIMP levels were observed between various dpi at both mRNA and protein levels. Only the MMP-7 protein level at 6 dpi was not significant compared to 5 dpi (p = 0.99).

CONCLUSION

Overexpression of MMPs and TIMPs is associated with disease severity in the central nervous system (CNS) during JEV infection. Our results showed that JEV infection can alter the expression of MMPs and TIMPs in the CNS. Thus, assessing these important immune mediators in CNS infection appears to play an important role in the development of symptoms and may help to understand the JEV-induced neurological disorders. More studies are required on this important enzymatic system to study their role in immune mediated pathogenesis.

Systemic and central immunity in Alzheimer's disease: therapeutic implications

Clinical pharmaceutical trials aimed at modulating the immune system in Alzheimer's Disease have largely focused on either dampening down central proinflammatory innate immunity or have manipulated adaptive immunity to facilitate the removal of centrally deposited beta amyloid. To date, these trials have had mixed clinical therapeutic effects. However, a number of clinical studies have demonstrated disturbances of both systemic and central innate immunity in Alzheimer's Disease and attention has been drawn to the close communication pathways between central and systemic immunity. This paper highlights the need to take into account the potential systemic effects of drugs aimed at modulating central immunity and the possibility of developing novel therapeutic approaches based on the manipulation of systemic immunity and its communication with the central nervous system.

Brain microvessel endothelial cells responses to gold nanoparticles: In vitro pro-inflammatory mediators and permeability

This report examined blood-brain barrier (BBB) related proinflammatory mediators and permeability changes in response to various sized gold nanoparticles (Au-NPs) (3, 5, 7, 10, 30 and 60 nm) in vitro using primary rat brain microvessel endothelial cells (rBMEC). The Au-NPs were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and laser Doppler velocimetry (LDV). The accumulation of Au-NPs was determined spectrophotometrically. The rBMEC cytotoxicity of Au-NPs was evaluated by cell proliferation assay (XTT) (concentration range 0.24-15.63 μg/cm², for 24 h). The time-dependent changes (0, 2, 4 and 8 h) of several proinflammatory mediators (IL-1β, IL-2, TNFα and PGE₂) were evaluated by ELISA. The smaller Au-NPs (3-7 nm) showed higher rBMEC accumulation compared to larger Au-NPs (10-60 nm), while only moderate decreased cell viability was observed with small Au-NPs (3 nm) at high concentrations (≥ 7.8 μg/cm²). Even though slight changes in cell viability were observed with small Au-NPs, the basal levels of the various proinflammatory mediators remained unchanged with all treatments except LPS (positive control). rBMEC morphology appeared unaffected 24 h after exposure to Au-NPs with only mild changes in fluorescein permeability indicating BBB integrity was unaltered. Together, these data suggest the responses of the cerebral microvasculature to Au-NPs have a significant relationship with the Au-NPs unique size-dependent physiochemical properties.

X-ray fluorescence analysis of long-term changes in the levels and distributions of trace elements in the rat brain following mechanical injury

This paper describes the results of the application of X-ray fluorescence microscopy to the qualitative, topographic and quantitative elemental analysis of nervous tissue from rats with neocortical brain injury. The tissue samples were analyzed with a 15 μm beam defined by the size of the polycapillary focus. Raster scanning of the samples generated 2D cartographies, revealing the distributions of elements such as P, S, Cl, K, Ca, Fe, Cu, and Zn. Special emphasis was placed on the analysis of the areas neighboring the lesion site and the hippocampal formation tissue. The results obtained for rats with mechanical brain injuries were compared with those recorded for controls and animals with pilocarpine-induced seizures. There were no significant differences in the elemental compositions of gray and white matter between injured and uninjured brain hemispheres. A higher level of Ca was observed in the gray matter of both of the hemispheres in brains with neocortical injuries. A similar relation was noticed for Fe in the white matter. A comparative study of hippocampal formation tissue showed a statistically significant decrease in the mass per unit area of P in the dentate gyrus (DG) and the hilus (H) of DG for animals with brain lesions in comparison with the control group. Analogous relations were found for Cu in the DG and Zn in sector 3 of Ammon’s horn (CA3) and the DG. It is important to note that identical changes in the same areas were observed for animals with pilocarpine-induced seizures in our previous study.

Silver nanoparticle induced blood-brain barrier inflammation and increased permeability in primary rat brain microvessel endothelial cells

The current report examines the interactions of silver nanoparticles (Ag-NPs) with the cerebral microvasculature to identify the involvement of proinflammatory mediators that can increase blood-brain barrier (BBB) permeability. Primary rat brain microvessel endothelial cells (rBMEC) were isolated from adult Sprague-Dawley rats for an in vitro BBB model. The Ag-NPs were characterized by transmission electron microscopy (TEM), dynamic light scattering, and laser Doppler velocimetry. The cellular accumulation, cytotoxicity (6.25-50 μg/cm(3)) and potential proinflammatory mediators (interleukin [IL]-1β, IL-2, tumor necrosis factor [TNF] α, and prostaglandin E(2) [PGE(2)]) of Ag-NPs (25, 40, or 80 nm) were determined spectrophotometrically, cell proliferation assay (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide) and ELISA. The results show Ag-NPs-induced cytotoxic responses at lower concentrations for 25 and 40 nm when compared with 80-nm Ag-NPs. The proinflammatory responses in this study demonstrate both Ag-NPs size and time-dependent profiles, with IL-1B preceding both TNF and PGE(2) for 25 nm. However, larger Ag-NPs (40 and 80 nm) induced significant TNF responses at 4 and 8 h, with no observable PGE(2) response. The increased fluorescein transport observed in this study clearly indicates size-dependent increases in BBB permeability correlated with the severity of immunotoxicity. Together, these data clearly demonstrate that larger Ag-NPs (80 nm) had significantly less effect on rBMEC, whereas the smaller particles induced significant effects on all the end points at lower concentrations and/or shorter times. Further, this study suggests that Ag-NPs may interact with the cerebral microvasculature producing a proinflammatory cascade, if left unchecked; these events may further induce brain inflammation and neurotoxicity.

Magnetic nanoformulation of azidothymidine 5'-triphosphate for targeted delivery across the blood-brain barrier

Despite significant advances in highly active antiretroviral therapy (HAART), the prevalence of neuroAIDS remains high. This is mainly attributed to inability of antiretroviral therapy (ART) to cross the blood–brain barrier (BBB), thus resulting in insufficient drug concentration within the brain. Therefore, development of an active drug targeting system is an attractive strategy to increase the efficacy and delivery of ART to the brain. We report herein development of magnetic azidothymidine 5′-triphosphate (AZTTP) liposomal nanoformulation and its ability to transmigrate across an in vitro BBB model by application of an external magnetic field. We hypothesize that this magnetically guided nanoformulation can transverse the BBB by direct transport or via monocyte-mediated transport. Magnetic AZTTP liposomes were prepared using a mixture of phosphatidyl choline and cholesterol. The average size of prepared liposomes was about 150 nm with maximum drug and magnetite loading efficiency of 54.5% and 45.3%, respectively. Further, magnetic AZTTP liposomes were checked for transmigration across an in vitro BBB model using direct or monocyte-mediated transport by application of an external magnetic field. The results show that apparent permeability of magnetic AZTTP liposomes was 3-fold higher than free AZTTP. Also, the magnetic AZTTP liposomes were efficiently taken up by monocytes and these magnetic monocytes showed enhanced transendothelial migration compared to normal/non-magnetic monocytes in presence of an external magnetic field. Thus, we anticipate that the developed magnetic nanoformulation can be used for targeting active nucleotide analog reverse transcriptase inhibitors to the brain by application of an external magnetic force and thereby eliminate the brain HIV reservoir and help to treat neuroAIDS.

Current immunotherapeutic strategies for central nervous system tumors

Immunotherapy has emerged as a promising tool in the management of malignant central nervous system tumors. Despite improvement in patient survival, traditional approaches, which consist mostly of surgery, radiotherapy, and chemotherapy, have been largely unsuccessful in permanently controlling these aggressive tumors. Immunotherapeutic strategies offer not only a novel approach but also an advantage in a way other modalities have been failing. Specifically, the capabilities of the immune system to recognize altered cells while leaving normal cells intact offer tremendous advantage over the conventional therapeutic approaches. This article summarizes our current understanding of immunotherapeutic treatment modalities used in clinical trials for management of malignant central nervous system tumors.

Glutamate receptor expression in multiple sclerosis lesions

Blockade of receptors for the excitatory neurotransmitter glutamate ameliorates neurological clinical signs in models of the CNS inflammatory demyelinating disease multiple sclerosis (MS). To investigate whether glutamate excitoxicity may play a role in MS pathogenesis, the cellular localization of glutamate and its receptors, transporters and enzymes was examined. Expression of glutamate receptor (GluR) 1, a Ca(++)-permeable ionotropic AMPA receptor subunit, was up-regulated on oligodendrocytes in active MS lesion borders, but Ca(++)-impermeable AMPA GluR2 subunit levels were not increased. Reactive astrocytes in active plaques expressed AMPA GluR3 and metabotropic mGluR1, 2/3 and 5 receptors and the GLT-1 transporter, and a subpopulation was immunostained with glutamate antibodies. Activated microglia and macrophages were immunopositive for GluR2, GluR4 and NMDA receptor subunit 1. Kainate receptor GluR5-7 immunostaining showed endothelial cells and dystrophic axons. Astrocyte and macrophage populations expressed glutamate metabolizing enzymes and unexpectedly the EAAC1 transporter, which may play a role in glutamate uptake in lesions. Thus, reactive astrocytes in MS white matter lesions are equipped for a protective role in sequestering and metabolizing extracellular glutamate. However, they may be unable to maintain glutamate at levels low enough to protect oligodendrocytes rendered vulnerable to excitotoxic damage because of GluR1 up-regulation.

Body Distributioin of RGD-mediated Liposome in Brain-targeting Drug Delivery

RGD conjugation liposomes (RGD-liposomes) were evaluated for brain-targeting drug delivery. The flow cytometric in vitro study demonstrated that RGD-liposomes could bind to monocytes and neutrophils effectively. Ferulic acid (4-hydroxy-3-methoxycinnamic, FA) was loaded into liposomes. Rats were subjected to intrastriatal microinjections of 100 units of human recombinant IL-1beta to produce brain inflammation and caudal vein injection of three formulations (FA solution, FA liposome and RGD-coated FA liposome). Animals were sacrificed 15, 30, 60 and 120 min after administration to study the body distribution of the FA in the three formulations. HPLC was used to determine the concentration of FA in vivo with salicylic acid as internal standard. The results of body distribution indicated that RGD-coated liposomes could be mediated into the brain with a 6-fold FA concentration compared to FA solution and 3-fold in comparison to uncoated liposome. Brain targeted delivery was achieved and a reduction in dosage might be allowed.

Multiple sclerosis: a battle between destruction and repair

Multiple sclerosis (MS) is a chronic neurodegenerative disease of the CNS in which an unrelenting attack from the innate and adaptive arms of the immune system results in extensive demyelination, loss of oligodendrocytes and axonal degeneration. This review summarizes advances in the understanding of the cellular and molecular pathways involved in neurodegeneration following autoimmune-mediated inflammation in the CNS. The mechanisms underlying myelin and axonal destruction and the equally important interaction between degenerative and repair mechanisms are discussed. Recent studies have revealed that the failure of CNS regeneration may be in part a result of the presence of myelin-associated growth inhibitory molecules in MS lesions. Successful therapeutic intervention in MS is likely to require suppression of the inflammatory response, in concert with blockade of growth inhibitory molecules and possibly the mobilization or transplantation of stem cells for regeneration.

Surface Modification of RGD-Liposomes for Selective Drug Delivery to Monocytes/Neutrophils in Brain

In the present study, RGD peptide was coupled with ferulic acid (FA) liposomes for binding to monocytes and neutrophils in peripheral blood for brain targeting in response to leukocyte recruitment. Cholesterol (Ch) was esterified with succinic anhydride to introduce a carboxylic end group (Ch-COOH). Soybean phosphatidylcholine, cholesterol and Ch-COOH were in a molar ratio of 1 : 0.23 : 0.05. FA was loaded into liposomes with 80.2+/-5.2% entrapment efficiency (EE) using a calcium acetate gradient method since it was difficult to load FA by other methods. RGD peptide was a novel compound coupled with Ch-COOH via carbodiimide and N-hydroxysulfosuccinimide. The results of the in vitro flow cytometric study showed that RGD conjugation liposomes (RGD-liposomes) could bind to monocytes/neutrophils efficiently. The rats were subjected to intrastriatal microinjections of 100 microl of human recombinant IL-1beta to produce brain inflammation and subsequently sacrificed after 15, 30, 60 and 120 min of administration of three formulations (FA solution, FA liposome, RGD-coated FA liposome). The body distribution results showed that RGD-liposomes could be directed to the target site, i.e. the brain, by cell selectivity in case of an inflammatory response. For RGD coated liposomes, the concentration of FA in brain was 6-fold higher than that of FA solution and 3-fold higher than that of uncoated liposomes. MTT assay and flow cytometry were used in the pharmacodynamic studies where it was found that FA liposomes exhibited greater antioxidant activity to FA solution on U937 cell.

CNS immune privilege: hiding in plain sight

Central nervous system (CNS) immune privilege is an experimentally defined phenomenon. Tissues that are rapidly rejected by the immune system when grafted in sites, such as the skin, show prolonged survival when grafted into the CNS. Initially, CNS immune privilege was construed as CNS isolation from the immune system by the blood-brain barrier (BBB), the lack of draining lymphatics, and the apparent immunoincompetence of microglia, the resident CNS macrophage. CNS autoimmunity and neurodegeneration were presumed automatic consequences of immune cell encounter with CNS antigens. Recent data have dramatically altered this viewpoint by revealing that the CNS is neither isolated nor passive in its interactions with the immune system. Peripheral immune cells can cross the intact BBB, CNS neurons and glia actively regulate macrophage and lymphocyte responses, and microglia are immunocompetent but differ from other macrophage/dendritic cells in their ability to direct neuroprotective lymphocyte responses. This newer view of CNS immune privilege is opening the door for therapies designed to harness autoreactive lymphocyte responses and also implies (i) that CNS autoimmune diseases (i.e. multiple sclerosis) may result as much from neuronal and/or glial dysfunction as from immune system dysfunctions and (ii) that the severe neuronal and glial dysfunction associated with neurodegenerative disorders (i.e. Alzheimer's disease) likely alters CNS-specific regulation of lymphocyte responses affecting the utility of immune-based therapies (i.e. vaccines).

(Peri)vascular production and action of pro-inflammatory cytokines in brain pathology

In response to tissue injury or infection, the peripheral tissue macrophage induces an inflammatory response through the release of IL-1β (interleukin-1β) and TNFα (tumour necrosis factor α). These cytokines stimulate macrophages and endothelial cells to express chemokines and adhesion molecules that attract leucocytes into the peripheral site of injury or infection. The aims of the present review are to (i) discuss the relevance of brain (peri)vascular cells and compartments to bacterial meningitis, HIV-1-associated dementia, multiple sclerosis, ischaemic and traumatic brain injury, and Alzheimer's disease, and (ii) to provide an overview of the production and action of pro-inflammatory cytokines by (peri)vascular cells in these pathologies of the CNS (central nervous system). The brain (peri)vascular compartments are highly relevant to pathologies affecting the CNS, as infections are almost exclusively blood-borne. Insults disrupt blood and energy flow to neurons, and active brain-to-blood transport mechanisms, which are the bottleneck in the clearance of unwanted molecules from the brain. Perivascular macrophages are the most reactive cell type and produce IL-1β and TNFα after infection or injury to the CNS. The main cellular target for IL-1β and TNFα produced in the brain (peri)vascular compartment is the endothelium, where these cytokines induce the expression of adhesion molecules and promote leucocyte infiltration. Whether this and other effects of IL-1 and TNF in the brain (peri)vascular compartments are detrimental or beneficial in neuropathology remains to be shown and requires a clear understanding of the role of these cytokines in both damaging and repair processes in the CNS.

What is the blood-brain barrier (not)?

In 1900, summarizing his experiments with toxins and Ehrlich's earlier observations with intravital dyes, the Berlin physician Lewandowski concluded that "brain capillaries must hold back certain molecules". Illustrating this phenomenon with persuasive beauty, the subsequently evolving metaphor of a 'Bluthirnschranke' (blood-brain barrier, BBB) gained wide acceptance, but the extension of its meaning into the context of inhibiting leukocyte recruitment into the brain is imprecise. On the basis of the original work by Ehrlich, Lewandowski and Goldmann we re-define the BBB as a capillary barrier for solutes, and clarify that leukocyte recruitment requires two differentially regulated steps: (i) passage across postcapillary venules into Virchow-Robin spaces, and (ii) subsequent progression across the glia limitans into the neuropil. We propose that the second step frequently involves perivascular antigen-recognition and the induction of ectoenzymes, for example matrix metalloproteinases (MMPs).

Abnormal endothelial tight junctions in active lesions and normal-appearing white matter in multiple sclerosis

Blood-brain barrier (BBB) breakdown, demonstrable in vivo by enhanced MRI is characteristic of new and expanding inflammatory lesions in relapsing-remitting and chronic progressive multiple sclerosis (MS). Subtle leakage may also occur in primary progressive MS. However, the anatomical route(s) of BBB leakage have not been demonstrated. We investigated the possible involvement of interendothelial tight junctions (TJ) by examining the expression of TJ proteins (occludin and ZO-1 ) in blood vessels in active MS lesions from 8 cases of MS and in normal-appearing white (NAWM) matter from 6 cases. Blood vessels (10-50 per frozen section) were scanned using confocal laser scanning microscopy to acquire datasets for analysis. TJ abnormalities manifested as beading, interruption, absence or diffuse cytoplasmic localization of fluorescence, or separation of junctions (putative opening) were frequent (affecting 40% of vessels) in oil-red-O-positive active plaques but less frequent in NAWM (15%), and in normal (< 2%) and neurological controls (6%). Putatively "open" junctions were seen in vessels in active lesions and in microscopically inflamed vessels in NAWM. Dual fluorescence revealed abnormal TJs in vessels with pre-mortem serum protein leakage. Abnormal or open TJs, associated with inflammation may contribute to BBB leakage in enhancing MRI lesions and may also be involved in subtle leakage in non-enhancing focal and diffuse lesions in NAWM. BBB disruption due to tight junctional pathology should be regarded as a significant form of tissue injury in MS, alongside demyelination and axonopathy.