ICAM 1 expression and fluid phase endocytosis of cultured brain microvascular endothelial cells following exposure to interferon beta-1a and TNFalpha

Advancing brain barriers RNA sequencing: guidelines from experimental design to publication

BACKGROUND

RNA sequencing (RNA-Seq) in its varied forms has become an indispensable tool for analyzing differential gene expression and thus characterization of specific tissues. Aiming to understand the brain barriers genetic signature, RNA seq has also been introduced in brain barriers research. This has led to availability of both, bulk and single-cell RNA-Seq datasets over the last few years. If appropriately performed, the RNA-Seq studies provide powerful datasets that allow for significant deepening of knowledge on the molecular mechanisms that establish the brain barriers. However, RNA-Seq studies comprise complex workflows that require to consider many options and variables before, during and after the proper sequencing process.

MAIN BODY

In the current manuscript, we build on the interdisciplinary experience of the European PhD Training Network BtRAIN ( https://www.btrain-2020.eu/ ) where bioinformaticians and brain barriers researchers collaborated to analyze and establish RNA-Seq datasets on vertebrate brain barriers. The obstacles BtRAIN has identified in this process have been integrated into the present manuscript. It provides guidelines along the entire workflow of brain barriers RNA-Seq studies starting from the overall experimental design to interpretation of results. Focusing on the vertebrate endothelial blood-brain barrier (BBB) and epithelial blood-cerebrospinal-fluid barrier (BCSFB) of the choroid plexus, we provide a step-by-step description of the workflow, highlighting the decisions to be made at each step of the workflow and explaining the strengths and weaknesses of individual choices made. Finally, we propose recommendations for accurate data interpretation and on the information to be included into a publication to ensure appropriate accessibility of the data and reproducibility of the observations by the scientific community.

CONCLUSION

Next generation transcriptomic profiling of the brain barriers provides a novel resource for understanding the development, function and pathology of these barrier cells, which is essential for understanding CNS homeostasis and disease. Continuous advancement and sophistication of RNA-Seq will require interdisciplinary approaches between brain barrier researchers and bioinformaticians as successfully performed in BtRAIN. The present guidelines are built on the BtRAIN interdisciplinary experience and aim to facilitate collaboration of brain barriers researchers with bioinformaticians to advance RNA-Seq study design in the brain barriers community.

Significance of correlation between interferon-γ and soluble intercellular adhesion molecule-1 and interleukin-17 in hepatitis B virus-related cirrhosis

BACKGROUND AND OBJECTIVE

Hepatitis B virus (HBV)-related cirrhosis is known to be associated with chronic hepatic inflammation. The present study aimed to examine the correlation between inflammatory mediators INF-γ, IL-17, and sICAM-1 in HBV cirrhotic patients.

METHODS

The levels of sICAM-1, interleukin-17, and IFN-γ were measured with enzyme-linked immunosorbent assays in 120 cirrhotic patients with HBV and 270 sex- and age-matched healthy controls. Total bilirubin (TB) was measured and the association between TB and IFN-γ, sICAM-1, interleukin-17 were analyzed. The levels of these cytokines in serum and the association between IFN-γ and sICAM-1 as well as interleukin-17 were investigated. Relationships between these cytokines and Child-Pugh classes were analyzed in patients.

RESULTS

Age and sex were similar, but TB values were significantly different between the two groups (P<0.001). Serum levels of sICAM-1, interleukin-17, and IFN-γ were significantly higher in cirrhotic patients with HBV than in controls (P<0.001 for both). TB levels were positively correlated with IFN-γ, interleukin-17 and sICAM-1 levels. Significantly positive correlations were also found between IFN-γ and interleukin-17 as well as sICAM-1 (r=0.817 and r=0.561, respectively, P<0.01). There were significant differences between the studied cytokines (sICAM-1, interleukin-17, and IFN-γ) and Child-Pugh classes (P<0.01).

CONCLUSIONS

The increased IFN-γ level was correlated with both IL-17 and sICAM-1, and it may primarily play a role as cytokines trigger in liver injury. Both IL-17 and sICAM-1 may synergistically contribute to liver damage.

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.

Endocytosis and intracellular processing of platelet microparticles by brain endothelial cells

Platelet-derived microparticles (PMP) bind and modify the phenotype of many cell types including endothelial cells. Recently, we showed that PMP were internalized by human brain endothelial cells (HBEC). Here we intend to better characterize the internalization mechanisms of PMP and their intracellular fate. Confocal microscopy analysis of PKH67-labelled PMP distribution in HBEC showed PMP in early endosome antigen 1 positive endosomes and in LysoTracker-labelled lysosomes, confirming a role for endocytosis in PMP internalization. No fusion of calcein-loaded PMP with HBEC membranes was observed. Quantification of PMP endocytosis using flow cytometry revealed that it was partially inhibited by trypsin digestion of PMP surface proteins and by extracellular Ca²⁺ chelation by EDTA, suggesting a partial role for receptor-mediated endocytosis in PMP uptake. This endocytosis was independent of endothelial receptors such as intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 and was not increased by tumour necrosis factor stimulation of HBEC. Platelet-derived microparticle internalization was dramatically increased in the presence of decomplemented serum, suggesting a role for PMP opsonin-dependent phagocytosis. Platelet-derived microparticle uptake was greatly diminished by treatment of HBEC with cytochalasin D, an inhibitor of microfilament formation required for both phagocytosis and macropinocytosis, with methyl-β-cyclodextrin that depletes membrane cholesterol needed for macropinocytosis and with amiloride that inhibits the Na⁺/H⁺ exchanger involved in macropinocytosis. In conclusion, PMP are taken up by active endocytosis in HBEC, involving mechanisms consistent with both phagocytosis and macropinocytosis. These findings identify new processes by which PMP could modify endothelial cell phenotype and functions.

Functional defects of CD46-induced regulatory T cells to suppress airway inflammation in mite allergic asthma

Defective recruitment of regulatory T cells (Treg) function to the airway is important in the pathogenesis of allergic asthma. Complement regulatory protein (CD46) is a newly defined costimulatory molecule for Treg activation, which together with IL-10/granzyme B production may aid in suppressing asthmatic inflammation. This study examines chemotaxis and adhesion molecule expression on CD3/CD46-activated CD4(+) T cells (Tregs) from patients with and without asthma to suppress mite allergen-induced respiratory epithelial cells inflammation and to elucidate the mechanism of CD46-mediated Treg activation. Diminished IL-10/granzyme B and CCR4 expression from CD3/CD46-activated Tregs appeared in asthmatic subjects. CD3/CD46-activated Tregs from asthma patients co-cultured with BEAS-2B cells suppressed Dermatophagoides pteronyssinus 2 induced nuclear factor-κB/p65 by cell contact inhibition. Decreased interaction of CD3/CD46-mediated Tregs and BEAS-2B cells from asthmatics was associated with downregulated phosphorylation of protein kinase B (AKT) expression. Results provide the first evidence that decreased interaction between CD46-mediated Tregs and lung epithelial cells with less IL-10/granzyme B production may cause airway inflammation in allergic asthma.

The mechanism of action of interferon-β in relapsing multiple sclerosis

Multiple sclerosis (MS) is characterized by autoimmune inflammation and subsequent neurodegeneration. It is believed that early in the disease course, proinflammatory T cells that are activated in the periphery by antigen presentation cross the blood-brain barrier (BBB) into the CNS directed by various chemotaxic agents. However, to date, there has been no formal demonstration of a specific precipitating antigen. Once inside the CNS, activated T cells including T helper-1 (T(h)1), T(h)17, γδ and CD8+ types are believed to secrete proinflammatory cytokines. Decreased levels of T(h)2 cells also correlate with relapses and disease progression in MS, since T(h)2-derived cytokines are predominantly anti-inflammatory. In healthy tissue, inflammatory effects are opposed by specific subsets of regulatory T cells (T(regs)) including CD4+, CD25+ and FoxP3+ cells that have the ability to downregulate the activity of proinflammatory T cells, allowing repair and recovery to generally follow inflammatory insult. Given their function, the pathogenesis of MS most likely involves deficits of T(reg) function, which allow autoimmune inflammation and resultant neurodegeneration to proceed relatively unchecked. Interferons (IFNs) are naturally occurring cytokines possessing a wide range of anti-inflammatory properties. Recombinant forms of IFNβ are widely used as first-line treatment in relapsing forms of MS. The mechanism of action of IFNβ is complex, involving effects at multiple levels of cellular function. IFNβ appears to directly increase expression and concentration of anti-inflammatory agents while downregulating the expression of proinflammatory cytokines. IFNβ treatment may reduce the trafficking of inflammatory cells across the BBB and increase nerve growth factor production, leading to a potential increase in neuronal survival and repair. IFNβ can also increase the number of CD56bright natural killer cells in the peripheral blood. These cells are efficient producers of anti-inflammatory mediators, and may have the ability to curb neuron inflammation. The mechanistic effects of IFNβ manifest clinically as reduced MRI lesion activity, reduced brain atrophy, increased time to reach clinically definite MS after the onset of neurological symptoms, decreased relapse rate and reduced risk of sustained disability progression. The mechanism of action of IFNβ in MS is multifactorial and incompletely understood. Ongoing and future studies will increase our understanding of the actions of IFNβ on the immune system and the CNS, which will in turn aid advances in the management of MS.

Cloning and characterization of the murine claudin-5 promoter

Claudin-5, an integral tight junction protein component, plays a critical role in permeability of the endothelial cell barrier. Recently, we have shown that claudin-5 protein is down-regulated by the proinflammatory cytokine TNF alpha and its levels restored by dexamethasone treatment. In order to investigate the regulation of claudin-5 at the transcriptional level, we have cloned the murine claudin-5 promoter. The claudin-5 promoter sequence (1131 bp) showed no consensus TATA-box. We identified putative transcription factor binding sites, including six full and two half sites degenerated glucocorticoid-response elements (GREs), two NFkappaB, three Sp1, one Sp2, one Ap2, as well as three E-boxes. Serially deleted promoter constructs showed high basal activity. TNF alpha significantly reduced the promoter activity and mRNA levels of claudin-5 in brain cEND and myocardial MyEND endothelial cells. Dexamethasone treatment led to a significant increase of the murine claudin-5 promoter activity and mRNA levels in cEND cells. However, no claudin-5 induction could be observed in MyEND cells in response to dexamethasone. Our studies suggest tissue-specific regulation of the claudin-5 gene via glucocorticoids and a high vulnerability of claudin-5 to TNF alpha. This could be an important mechanism in diseases accompanied by the release of proinflammatory cytokines, for example in patients with chronic heart failure or multiple sclerosis.

Flupirtine as neuroprotective add-on therapy in autoimmune optic neuritis

Multiple sclerosis (MS) is a common inflammatory disease of the central nervous system that results in persistent impairment in young adults. During chronic progressive disease stages, there is a strong correlation between neurodegeneration and disability. Current therapies fail to prevent progression of neurological impairment during these disease stages. Flupirtine, a drug approved for oral use in patients suffering from chronic pain, was used in a rat model of autoimmune optic neuritis and significantly increased the survival of retinal ganglion cells, the neurons that form the axons of the optic nerve. When flupirtine was combined with interferon-beta, an established immunomodulatory therapy for MS, visual functions of the animals were improved during the acute phase of optic neuritis. Furthermore, flupirtine protected retinal ganglion cells from degeneration in a noninflammatory animal model of optic nerve transection. Although flupirtine was shown previously to increase neuronal survival by Bcl-2 up-regulation, this mechanism does not appear to play a role in flupirtine-mediated protection of retinal ganglion cells either in vitro or in vivo. Instead, we showed through patch-clamp investigations that the activation of inwardly rectifying potassium channels is involved in flupirtine-mediated neuroprotection. Considering the few side effects reported in patients who receive long-term flupirtine treatment for chronic pain, our results indicate that this drug is an interesting candidate for further evaluation of its neuroprotective potential in MS.

Interferon-β stabilizes barrier characteristics of the blood–brain barrier in four different species in vitro

Background

Blood–brain barrier (BBB) breakdown is an early event in the pathogenesis of multiple sclerosis (MS). In a previous study we have found a direct stabilization of barrier characteristics after treatment of bovine brain capillary endothelial cells (BCECs) with human recombinant interferon-β-1a (IFN-β-1a) in an in vitro BBB model. In the present study we examined the effect of human recombinant IFN-β-1a on the barrier properties of BCECs derived from four different species including humans to predict treatment efficacy of IFN-β-1a in MS patients.

Methods

We used primary bovine and porcine BCECs, as well as human and murine BCEC cell lines. We investigated the influence of human recombinant IFN-β-1a on the paracellular permeability for 3H-inulin and 14C-sucrose across monolayers of bovine, human, and murine BCECs. In addition, the transendothelial electrical resistance (TEER) was determined in in vitro systems applying porcine and murine BCECS.

Results

We found a stabilizing effect on the barrier characteristics of BCECs after pretreatment with IFN-β-1a in all applied in vitro models: addition of IFN-β-1a resulted in a significant decrease of the paracellular permeability across monolayers of human, bovine, and murine BCECs. Furthermore, the TEER was significantly increased after pretreatment of porcine and murine BCECs with IFN-β-1a.

Conclusion

Our data suggest that BBB stabilization by IFN-β-1a may contribute to its beneficial effects in the treatment of MS. A human in vitro BBB model might be useful as bioassay for testing the treatment efficacy of drugs in MS.

Activation of human monocytes after infection by human coronavirus 229E

Human coronaviruses (HCoV) are recognized respiratory pathogens that may be involved in other pathologies such as central nervous system (CNS) diseases. To investigate whether leukocytes could participate in respiratory pathologies and serve as vector for viral spread towards other tissues, the susceptibility of human leukocytic cell lines and peripheral blood mononuclear cells (PBMC) to HCoV-229E and HCoV-OC43 infection was investigated. Human primary monocytes/macrophages were susceptible to HCoV-229E infection, but strongly restricted HCoV-OC43 replication. Moreover, productive HCoV-229E infection of primary monocytes and of the THP-1 monocytic cell line led to their activation, as indicated by the production of pro-inflammatory mediators, including TNF-alpha, CCL5, CXCL10 and CXCL11 and MMP-9. Moreover, an in vitro chemotaxis assay showed that motility towards chemokines of THP-1 cells and primary monocytes was increased following an acute or persistent HCoV-229E infection. Taken together, these results suggest that infected monocytes could serve as a reservoir for HCoV-229E, become activated, participate in the exacerbation of pulmonary pathologies, as well as serve as potential vectors for viral dissemination to host tissues, where it could be associated with other pathologies.

Mechanisms of the blood-brain barrier disruption in HIV-1 infection

(1) Alterations of brain microvasculature and the disruption of the blood-brain barrier (BBB) integrity are commonly associated with human immunodeficiency virus type 1 (HIV-1) infection. These changes are most frequently found in human immunodeficiency virus-related encephalitis (HIVE) and in human immunodeficiency virus-associated dementia (HAD). (2) It has been hypothesized that the disruption of the BBB occurs early in the course of HIV-1 infection and can be responsible for HIV-1 entry into the CNS. (3) The current review discusses the mechanisms of injury to brain endothelial cells and alterations of the BBB integrity in HIV-infection with focus on the vascular effects of HIV Tat protein. In addition, this review describes the mechanisms of the BBB disruption due to HIV-1 or Tat protein interaction with selected risk factors for HIV infection, such as substance abuse and aging.

Why study transport of peptides and proteins at the neurovascular interface

The blood-brain barrier (BBB) is an immense neurovascular interface. In neurodegenerative, ischemic, and traumatic disorders of the central nervous system (CNS), the BBB may hinder the delivery of many therapeutic peptides and proteins to the brain and spinal cord. Fortunately, the mistaken dogma that peptides and proteins do not cross the BBB has been corrected during the past two decades by the accumulating evidence that peptides and proteins in the periphery exert potent effects in the CNS. Not only can peptides and proteins serve as carriers for selective therapeutic agents, but they themselves may directly cross the BBB after delivery into the bloodstream. Their passage may be mediated by simple diffusion or specific transport, both of which can be affected by interactions in the blood compartment (outside the BBB) and within the endothelial cells (at the BBB level). Although the majority of current delivery strategies focuses on modification of the molecule to be delivered, understanding the mechanisms of transport will eventually facilitate regulation of the BBB directly. We review the different aspects of interactions and discuss recent advances in the cell biology of peptide/protein transport across the BBB. Better understanding of the nature and regulation of the transport systems at the BBB will provide a new direction to enhance the interactions of peripheral peptides and proteins with the CNS.

Interferon-beta stabilizes barrier characteristics of brain endothelial cells in vitro

Multiple sclerosis (MS) is accompanied by a breakdown of the blood-brain barrier (BBB) leading to edema formation and aggravation of the disease. Interferon-beta (IFN-beta) has been approved for the treatment of MS and besides its immunomodulatory effects has been demonstrated to lead to a stabilization of BBB integrity in vivo. To investigate whether human recombinant IFN-beta exerts direct effects on the BBB, we used an in vitro BBB model in which brain endothelial cells in coculture with astrocytes form a tight permeability barrier for 3H-inulin and 14C-sucrose. Removal of the astrocytes from the coculture or alternatively addition of histamine resulted in an increased paracellular permeability for small tracers across the brain endothelial cell monolayer. Strikingly, in the presence of IFN-beta, permeability increase under both conditions was inhibited. Permeability changes were accompanied by minor changes in the staining for tight junction-associated proteins in brain endothelial cell monolayers. Taken together, our data demonstrate a direct stabilizing effect of IFN-beta on BBB cerebral endothelial cells in vitro that might significantly contribute to the beneficial effects of IFN-beta treatment in MS in vivo.

Cadmium stimulates the expression of ICAM-1 via NF-kappaB activation in cerebrovascular endothelial cells

Cadmium (Cd), a ubiquitous heavy metal, has been shown to accumulate in the central nervous system, especially outside of the blood-brain barrier (BBB), suggesting a potential toxicity to nervous tissue. Thus, we investigated the effect of Cd on intercellular adhesion molecule-1 (ICAM-1) expression, as an indicator of BBB injury, in mouse brain microvessel endothelial cells (bEnd.3 cells). The treatment with Cd increased the expression of ICAM-1 at the levels of protein and mRNA, and these increases were almost completely inhibited by a specific NF-kappaB inhibitor SN50. The treatment with Cd induced the translocation of NF-kappaB from cytosolic to membrane fraction and increased DNA binding activity of NF-kappaB, and this NF-kappaB activation was inhibited by SN50. Interestingly, Cd did not trigger the degradation of IkappaBalpha, suggesting that Cd-induced ICAM-1 expression is mediated through IkappaBalpha degradation-independent pathway. Instead, tyrosine phosphorylation of IkappaBalpha was significantly elevated by Cd treatment, and this elevation was blocked by genistein, a protein tyrosine kinase inhibitor. In summary, the present results suggest that Cd stimulates the expression of ICAM-1 in bEnd.3 cells, via NF-kappaB activation that is mediated by the tyrosine phosphorylation of IkappaBalpha.

Role of ICAM-1 and P-selectin expression in the development and effector function of CD4+CD25+regulatory T cells

Dynamic regulatory mechanisms prevent autoreactive T cell activation. Upon T cell receptor crosslinking, CD4+CD25+ T regulatory (T(R)) cells block both the proliferation and cytokine production of CD4+CD25- effector cells in an apparent antigen non-specific manner. Within the T(R)population, L-selectin (CD62L)(hi)T(R)cells have been described as more efficient suppressors of T cell proliferation than CD62L(low)T(R)cells. We have previously reported that CD4+CD25+CD62L(hi)T(R)cells express elevated levels of two additional adhesion molecules, ICAM-1 (CD54) and P-selectin (CD62P) in comparison to non-T(R)cells. In the current study, we investigated the functional contribution of CD54 and CD62P expression to the suppressive phenotype of T(R)cells both in vitro and in vivo. While the CD4+CD25+ T(R)cell population was demonstrated to be significantly larger in CD62P-/- mice than in wild-type C57BL/6 mice, CD62P-/- T(R)cell function was deficient in vitro, but not in vivo. Interestingly, we detected no deficiencies in T(R)cell numbers or effector function in CD54-/- mice suggesting that T(R)cells may differ from effector CD4+ T cells in the requirement for CD54 expression within the immunological synapse. Collectively, these findings indicate that CD62P may influence T(R)cell differentiation/development and that T(R)cell activation occurs independently of CD54 expression.

Interferon-beta blocks infiltration of inflammatory cells and reduces infarct volume after ischemic stroke in the rat

The inflammatory response that exacerbates cerebral injury after ischemia is an attractive therapeutic target: it progresses over days and strongly contributes to worsening of the neurologic outcome. The authors show that, after transient ischemic injury to the rat brain, systemic application of interferon-beta (IFN-beta), a cytokine with antiinflammatory properties, attenuated the development of brain infarction. Serial magnetic resonance imaging (MRI) showed that IFN-beta treatment reduced lesion volume on diffusion-weighted MRI by 70% (P < 0.01) at 1 day after stroke. IFN-beta attenuated the leakage of contrast agent through the blood-brain barrier (P < 0.005), indicating a better-preserved blood-brain barrier integrity. Both control and IFN-beta-treated animals showed a similar degree of relative hyperperfusion of the lesioned hemisphere, indicating that neuroprotection by IFN-beta was not mediated by improved cerebral perfusion as assessed 24 hours after stroke onset. IFN-beta treatment resulted in an 85% reduction (P < 0.0001) in infarct volume 3 weeks later, as determined from T2-weighted MRI and confirmed by histology. This effect was achieved even when treatment was started 6 hours after stroke onset. Quantitative immunohistochemistry at 24 hours after stroke onset showed that IFN-beta almost completely prevented the infiltration of neutrophils and monocytes into the brain. Gelatinase zymography showed that this effect was associated with a decrease in matrix metalloproteinase-9 expression. In conclusion, treatment with the antiinflammatory cytokine IFN-beta affords significant neuroprotection against ischemia/reperfusion injury, and within a relatively long treatment window. Because IFN-beta has been approved for clinical use, it may be rapidly tested in a clinical trial for its efficacy against human stroke.

Adhesion molecules and matrix metalloproteinases in Multiple Sclerosis: effects induced by Interferon-beta

In Multiple Sclerosis (MS) pathology, early inflammation involves leukocyte migration across the blood-brain barrier (BBB) within the central nervous system. In this process, adhesion molecules (AMs), both membrane-bound and soluble-circulating forms, and matrix metalloproteinases (MMPs) certainly play a regulatory role. In MS, recombinant Interferon-beta (rIFNbeta) is effective in reducing gadolinium contrast-enhancing lesions on magnetic resonance imaging and this suggests that it may reduce BBB damage or even restore its integrity by different mechanisms that include interference with both AM and MMP pathways. This review will highlight the effects induced by rIFNbeta, both in vitro and in vivo, on cell-bound and soluble forms of AMs and on MMPs.

Regulation and functional effects of monocyte migration across human brain-derived endothelial cells

We have used human brain-derived endothelial cells (HBECs) maintained under basal culture conditions in a Boyden chamber assay system as an in vitro model of migration of cells of systemic immune origin across the blood brain barrier (BBB) during the initiation of a CNS-directed inflammatory response. In this study we evaluated the molecular mechanisms that regulate passage of ex vivo peripheral blood-derived monocytes across this barrier and the effects of such migration on the properties of both the HBECs and the monocytes. Our results indicate that monocytes can migrate across HBECs in the absence of inflammatory conditions, at rates exceeding those of lymphocytes. Monocyte migration could be significantly inhibited by the addition of blocking antibodies to intercellular adhesion molecule (ICAM)-1, very late antigen (VLA)-4 integrin, and monocyte chemoattractant protein (CCL-2/MCP-1), or treatment with tissue inhibitor of metalloproteinase (TIMP-1). Following monocyte migration there was a significant increase in permeability of soluble molecules and an enhanced rate of T cell migration across HBECs. The enhanced permeability could be partially prevented with anti-TNF-alpha antibody. The migration process did not induce the upregulation of either co-stimulatory molecules or chemokine receptors on the monocytes. These studies emphasize the functional role of monocyte-endothelial interactions in permitting target access of a CNS-directed cell-mediated immune response.

Serial analysis of soluble intercellular adhesion molecule-1 level in relapsing-remitting multiple sclerosis patients during IFN-beta1b treatment

In this controlled study, we investigated the serum and cerebrospinal fluid (CSF) levels of soluble intercellular adhesion molecule-1 (sICAM-1) in relapsing-remitting multiple sclerosis (RRMS) patients and changes in the levels of this adhesion molecule during interferon-beta1b (IFN-beta1b) treatment. We also investigated the changes in the levels of sICAM-1 in correlation with disease activity and with findings on magnetic resonance images (MRI). The study included 24 patients (16 females and 8 males) who were confirmed to have RRMS based on the criteria of Poser et al. Sixteen of the patients received IFN-beta1b (Betaseron, Berlex Laboratories, Schering AG Germany, Berlin) treatment, and 8 did not receive this therapy. The levels of sICAM-1 in the MS patients' serum and CSF were significantly higher than levels in individuals with noninflammatory neurologic disease (p = 0.0081 and p = 0.0001, respectively). In the first 3 months of the study, MS patients treated with IFN-beta1b showed a significant rise in sICAM-1 levels (p = 0.0023), whereas their untreated counterparts showed no significant change. Neither of the groups showed a significant correlation between sICAM-1 level and disease activity demonstrated by MRI or between sICAM-1 level and clinical disease activity. The findings suggest that IFN-beta1b treatment may have a short-term upregulating effect on sICAM-1.

Interferon-beta counteracts inflammatory mediator-induced effects on brain endothelial cell tight junction molecules-implications for multiple sclerosis

To elucidate mechanisms of endothelial cell (EC) dysfunction in CNS inflammatory responses and beneficial effects of interferon-beta (IFN-gamma) in multiple sclerosis (MS), we analyzed effects of individual and combinations of soluble inflammatory mediators on the intracellular localization of the EC tight junction-associated molecules zonula occludens-1 and -2 (ZO-1 and ZO-2) in human brain ECs. The cytoplasm in the majority of cells in control EC cultures was clear; ZO-1 and ZO-2 were localized peripherally near sites of cell contact and associated with submembranous cytoplasmic filaments. H2O2 induced reversible time- and concentration-dependent translocation of ZO-1 and ZO-2 to a random distribution within EC cytoplasm and retraction of EC borders. For low concentrations, these effects were accompanied by less prominent submembranous filaments but not by evidence of cytotoxicity, increased cell death or altered amounts of ZO-1. Tumor necrosis factor-beta induced similar alterations but interferon-y did not. Co-treatment with either cytokine increased H2O2 effects whereas IFN-beta reversed H2O2-induced effects. In control white matter samples, EC cytoplasm was clear and ZO-1 was located on cell borders. In inflammatory/demyelinating lesions, EC ZO-1 was diffuse, indicating that the alterations induced in vitro mimic those in active MS lesions. These findings suggest that in MS patients, IFN-beta treatment may counteract inflammatory mediator effects on CNS EC tight junction molecules, thereby preserving EC barrier function.

The adhesion molecule ICAM-1 and its regulation in relation with the blood-brain barrier

The blood-brain barrier (BBB) is formed by high resistance tight junctions within the capillary endothelium perfusing the vertebrate brain. Normal BBB maintains a unique microenvironment within the central nervous system (CNS). In neurodegenerative disorders (for example multiple sclerosis, MS), the BBB becomes impaired. Perivascular cells (astrocytes, macrophages and microglial cells) and brain microvascular endothelial cells (BMEC) produce various inflammatory factors that affect the BBB permeability and the expression of adhesion molecules. Indeed, cytokines can stimulate the expression of several adhesion molecules on brain microvascular endothelial cells. Among these adhesion molecules, the intercellular adhesion molecule-1 (ICAM-1) binds to its leukocyte ligands and allows activated leukocytes entry into the CNS. This review is dealing with the expression and regulation of ICAM-1 in relation with several properties of the BBB. Particularly, the role of ICAM-1 in the control of the leukocyte traffic into the CNS, as well as in cerebral malaria and in CNS infection by viruses, is discussed.

Innate immune responses in viral encephalitis

The innate immune system is multifaceted, comprised of preformed factors, cells, and many proteins and lipid mediators produced by those cells. In the CNS these are critical in initiation and amplification of the inflammatory response and in the subsequent elicitation of the specific T cell response to viral encephalitis. Cells that are resident in brain parenchyma and peripheral cells that are recruited both play key roles in the hosts's responses. Unlike the peripheral compartments, in the CNS, non-cytolytic means of eliminating viral infections have been critical, since, in contrast to columnar epithelial cells, neurons are non-renewing. When the innate immune responses are inefficient or absent in viral encephalitis, pathology is more likely. Much more work remains to elucidate all of the critical cells and their mediators, as well as to develop new therapies for infections of the CNS.

Interferon-beta directly influences monocyte infiltration into the central nervous system

Interferon-beta (IFN-beta) has beneficial effects on the clinical symptoms of multiple sclerosis (MS) patients, but its exact mechanism of action is yet unknown. We here suggest that IFN-beta directly modulates inflammatory events at the level of cerebral endothelium. IFN-beta treatment resulted in a marked reduction of perivascular infiltrates in acute experimental allergic encephalomyelitis (EAE), the rat model for MS, which was coupled to a major decrease in the expression of the adhesion molecules ICAM-1 and VCAM-1 on brain capillaries. In vitro, IFN-beta reduced the mRNA levels and protein expression of adhesion molecules of brain endothelial cell cultures and diminished monocyte transendothelial migration. Monocyte adhesion and subsequent migration was found to be predominantly regulated by VCAM-1. These data indicate that IFN-beta exerts direct antiinflammatory effects on brain endothelial cells thereby contributing to reduced lesion formation as observed in MS patients.

In vitro modulation of adhesion molecules, adhesion phenomena, and fluid phase endocytosis on human umbilical vein endothelial cells and brain-derived microvascular endothelium by IFN-beta 1a

Administration of interferon-beta (IFN-beta) in multiple sclerosis (MS) patients provides clinical benefits, although its mechanism(s) of action are not completely understood. We addressed the issue of whether concentrations of IFN-beta1a close to those reached in the serum of treated MS patients could modulate either adhesion molecules or adhesion of peripheral blood mononuclear cells (PBMC) as well as fluid phase endocytosis (FPE) in human umbilical vein endothelial cells (HUVEC) and in brain-derived microvascular endothelial cells (HBMEC). Adhesion was assessed by flow cytometry, and FPE was evaluated by peroxidase uptake. In our study, 200 U/ml IFN-beta1a induced a reduction in adhesion of PBMC to HUVEC. The information reported herein may contribute to further elucidating some of the mechanisms of action of IFN-beta on vascular endothelium.

LFA-1 expression on CD4(+)CD45RO(+) peripheral blood T-lymphocytes in RR MS: effects induced by rIFNbeta-1a

We investigate the in vivo and in vitro effects of short-term treatment with recombinant Interferon beta-1a (rIFNbeta-1a) on CD4(+)CD45RO(+) activated/memory peripheral blood T-lymphocytes (PBTLs) expressing Leukocyte Function Antigen-1 (LFA-1; CD11a/CD18) in relapsing-remitting (RR) Multiple Sclerosis (MS) patients. Blood samples were obtained from 10 RR MS patients before and after 2, 4 and 6 months of rIFNbeta-1a (Avonex) treatment. For each sample, the percentage of CD4(+)CD45RO(+)CD11a(+) (CD11a(dim) and CD11a(bright)) T-cells was evaluated in in vivo PBTLs and in untreated or rIFNbeta-1a (1000 U/ml) or recombinant soluble Intercellular Adhesion Molecule-1 (ICAM-1, the ligand for LFA-1) (400 ng/ml) treated cultured PBTLs by triple fluorescence flow-cytometry (FACS analysis). Soluble ICAM-1 (sICAM-1) serum levels were evaluated by ELISA. In vivo, the percentage of CD4(+)CD45RO(+), CD4(+)CD45RO(+)CD11a(+), CD4(+)CD45RO(+)CD11a(dim) PBTLs increased after 4 and 6 months of rIFNbeta-1a treatment compared to pretreatment and 2 months of treatment (p<0.05). The CD11a expression per se did not change during the time course. Soluble ICAM-1 (sICAM-1) serum levels also increased (p<0.05) after 4 and 6 months of treatment. When T-cells, obtained from the blood of the same patients before and during in vivo treatment, were cultured either untreated or treated with rIFNbeta-1a, they showed an increase in the percentage of CD4(+)CD45RO(+) T-cells expressing CD11a(bright) (p<0.05). The addition of recombinant sICAM-1 to untreated cultures decreased the percentage of CD4(+)CD45RO(+) T-cells expressing CD11a. This last finding seems to support an indirect effect in vivo of rIFNbeta-1a via sICAM-1 on this T-cell subset, since the ICAM-1 soluble form, induced in vivo in serum by rIFNbeta-1a but lacking in in vitro conditions, keeps the percentage of CD11a(+) unchanged within CD4(+)CD45RO(+) T-cells and induces their expression of CD11a(dim), probably preventing T-cells from transmigrating.

Interferon beta-1a downregulates TNFalpha-induced intercellular adhesion molecule 1 expression on brain microvascular endothelial cells through a tyrosine kinase-dependent pathway

TNFalpha (100 U/ml, 24 h) upregulated intercellular adhesion molecule 1 (ICAM1) expression on brain microvascular endothelial cell (BMEC) culture. The tyrosine kinase (TK) inhibitor genestein (100 microgram/ml), the protein kinase C (PKC) inhibitor staurosporin (1 nM), and interferon (IF) beta-1a (1000 U/ml) antagonized TNFalpha effect. When an ineffective dose of IFbeta-1a (100 U/ml) was challenged with ineffective doses of either genestein (10 microgram/ml) or staurosporin (0.1 nM), the combination IFbeta-1a-genestein significantly reduced TNFalpha-induced ICAM1 expression whereas IFbeta-1a-staurosporin did not. These findings indicate that a TK- rather than a PKC-dependent mechanism is involved in the modulation of TNFalpha response by IFbeta-1a on BMECs.

Inhibition of protein kinase C counteracts TNFalpha-induced intercellular adhesion molecule 1 expression and fluid phase endocytosis on brain microvascular endothelial cells

TNFalpha (100 U/ml, 24 h) upregulated intercellular adhesion molecule 1 (ICAM1) expression and fluid phase endocytosis (FPE) of horseradish peroxidase on brain microvascular endothelial cell (BMEC) culture. The protein kinase C (PKC) inhibitor staurosporin (0. 5-10 nM) antagonized ICAM1 expression and FPE due to TNFalpha, whereas the protein kinase A inhibitor H89 (0.5-10 nM) did not. These findings indicate that a PKC-dependent mechanism may affect TNFalpha signalling on different barrier properties of BMECs.

MRI and clinical activity in MS patients after terminating treatment with interferon beta-1b

Monthly MRI activity and clinical disability were evaluated in two relapsing-remitting multiple sclerosis (RRMS) patients for 4 years during a cross-over treatment trial with IFNbeta-1b, and for a mean of 21 months after terminating treatment with IFNbeta-1b. Post-treatment MRI activity was compared to baseline activity in these patients. Although contrast enhancing lesions (CEL) and the bulk white matter lesion load (BWMLL) on T2-weighted images eventually returned to baseline values, there was a refractory period of 6 - 10 months after terminating treatment, before baseline MRI activity was restored. Although the mechanism for a sustained effect of IFNbeta-1b is unclear at this time, these results have important implications for enrollment of such patients into new treatment protocols that rely on contrast enhancing lesion frequency as an outcome measure.

Interferon beta-1a prevents the effects of lipopolysaccharide on embryonic brain microvessels

By means of light and electron microscopy we have studied the effect of interferon beta-1a (IFNbeta-1a) in the optic tecta of 20-day-old chick embryos under normal conditions and after exposure to lipopolysaccharide (LPS) which mimics the blood-brain barrier (BBB) disruption in meningoencephalitis. Optic tecta were examined for: (i) ultrastructure by means of transmission electron microscopy; (ii) the immunohistochemical localization of HT7 antigen, a specific marker of differentiation of the brain microvessels; (iii) the brain microvessel permeability, by means of horseradish peroxidase (HRP) tracer; (iv) the expression of microvessel glycoconjugates, by means of lectin histochemistry, using Ricinus communis agglutinin-I (RCA-I), specific for beta-D-galactosyl moieties and Wheat Germ agglutinin (WGA) specific for sialyl and N-acetylglucosaminyl moieties. A morphometric evaluation of brain microvessel permeability and of glycoconjugate expression was also performed. In control- and in IFNbeta-1a-treated embryos, HRP was confined to the vessel lumina which were sealed by the interendothelial tight junctions. RCA-I binding sites were recognizable both in the basal membranes and in the tight junctions, while WGA sites were present on the luminal side of the endothelial cells. HRP was blocked in the vessels lumina by the interendothelial tight junctions. After LPS treatment, HRP showed an extravascular localization and the labeling of microvessels by anti-HT7 antibodies disappeared. RCA-I binding was only found ultrastructurally and appeared as irregularly clustered gold particles, in the cleft of damaged tight junctions, but were no longer detectable in the endothelial basement membranes. After pretreatment of LPS-treated embryos with IFNbeta-1a, the vessel permeability to HRP strongly decreased and the vessels showed the normal pattern of HT7 protein and of the RCA-I binding sites. These results indicate that the changes induced by LPS in the endothelial cells are prevented by IFNbeta-1a.

Tumor necrosis factor-alpha increases lactoferrin transcytosis through the blood-brain barrier

Lactoferrin (Lf) is an iron-binding protein involved in host defense against infection and severe inflammation, which accumulates in the brain during neurodegenerative disorders. Prior to determining Lf function in pathological brain tissues, we investigated its transport through the blood-brain barrier (BBB) in inflammatory conditions. For this purpose, we used a reconstituted BBB model consisting of the coculture of bovine brain capillary endothelial cells (BBCECs) and astrocytes in the presence of tumor necrosis factor-alpha (TNF-alpha). As TNF-alpha can be either synthesized by brain glial cells or present in circulating blood, BBCECs were exposed to this cytokine at their luminal or abluminal side. We have been able to demonstrate that in the presence of TNF-alpha, whatever the type of exposure, BBCECs were activated and Lf transport through the activated BBCECs was markedly increased. Lf was recovered intact at the abluminal side of the cells, suggesting that increased Lf accumulation may occur in immune-mediated pathophysiology. This process was transient as 20 h later, cells were in a resting state and Lf transendothelial traffic was back to normal. The enhancement of Lf transcytosis seems not to involve the up-regulation of the Lf receptor but rather an increase in the rate of transendothelial transport.