E-selectin expression on human brain microvascular endothelial cells

Sepsis-Exacerbated Brain Dysfunction After Intracerebral Hemorrhage

Sepsis susceptibility is significantly increased in patients with intracerebral hemorrhage (ICH), owing to immunosuppression and intestinal microbiota dysbiosis. To date, ICH with sepsis occurrence is still difficult for clinicians to deal with, and the mortality, as well as long-term cognitive disability, is still increasing. Actually, intracerebral hemorrhage and sepsis are mutually exacerbated via similar pathophysiological mechanisms, mainly consisting of systemic inflammation and circulatory dysfunction. The main consequence of these two processes is neural dysfunction and multiple organ damages, notably, via oxidative stress and neurotoxic mediation under the mediation of central nervous system activation and blood-brain barrier disruption. Besides, the comorbidity-induced multiple organ damages will produce numerous damage-associated molecular patterns and consequently exacerbate the severity of the disease. At present, the prospective views are about operating artificial restriction for the peripheral immune system and achieving cross-tolerance among organs via altering immune cell composition to reduce inflammatory damage.

TNF-α enhancement of CD62E mediates adhesion of non-small cell lung cancer cells to brain endothelium via CD15 in lung-brain metastasis

BACKGROUND

CD15, which is overexpressed on various cancers, has been reported as a cell adhesion molecule that plays a key role in non-CNS metastasis. However, the role of CD15 in brain metastasis is largely unexplored. This study provides a better understanding of CD15/CD62E interaction, enhanced by tumor necrosis factor-α (TNF-α), and its correlation with brain metastasis in non-small cell lung cancer (NSCLC).

METHODS

CD15 and E-selectin (CD62E) expression was demonstrated in both human primary and metastatic NSCLC cells using flow cytometry, immunofluorescence, and Western blotting. The role of CD15 was investigated using an adhesion assay under static and physiological flow live-cell conditions. Human tissue sections were examined using immunohistochemistry.

RESULTS

CD15, which was weakly expressed on hCMEC/D3 human brain endothelial cells, was expressed at high levels on metastatic NSCLC cells (NCI-H1299, SEBTA-001, and SEBTA-005) and at lower levels on primary NSCLC (COR-L105 and A549) cells (P < .001). The highest expression of CD62E was observed on hCMEC/D3 cells activated with TNF-α, with lower levels on metastatic NSCLC cells followed by primary NSCLC cells. Metastatic NSCLC cells adhered most strongly to hCMEC/D3 compared with primary NSCLC cells. CD15 immunoblocking decreased cancer cell adhesion to brain endothelium under static and shear stress conditions (P < .0001), confirming a correlation between CD15 and cerebral metastasis. Both CD15 and CD62E expression were detected in lung metastatic brain biopsies.

CONCLUSION

This study enhances the understanding of cancer cell-brain endothelial adhesion and confirms that CD15 plays a crucial role in adhesion in concert with TNF-α activation of its binding partner, CD62E.

A Pathophysiological Insight into Sepsis and Its Correlation with Postmortem Diagnosis

BACKGROUND

Sepsis is among the leading causes of death worldwide and is the focus of a great deal of attention from policymakers and caregivers. However, sepsis poses significant challenges from a clinical point of view regarding its early detection and the best organization of sepsis care. Furthermore, we do not yet have reliable tools for measuring the incidence of sepsis. Methods based on analyses of insurance claims are unreliable, and postmortem diagnosis is still challenging since autopsy findings are often nonspecific.

AIM

The objective of this review is to assess the state of our knowledge of the molecular and biohumoral mechanisms of sepsis and to correlate them with our postmortem diagnosis ability.

CONCLUSION

The diagnosis of sepsis-related deaths is an illustrative example of the reciprocal value of autopsy both for clinicians and for pathologists. A complete methodological approach, integrating clinical data by means of autopsy and histological and laboratory findings aiming to identify and demonstrate the host response to infectious insults, is mandatory to illuminate the exact cause of death. This would help clinicians to compare pre- and postmortem findings and to reliably measure the incidence of sepsis.

Sepsis-induced brain dysfunction

Systemic infection is often revealed by or associated with brain dysfunction, which is characterized by alteration of consciousness, ranging from delirium to coma, seizure or focal neurological signs. Its pathophysiology involves an ischemic process, secondary to impairment of cerebral perfusion and its determinants and a neuroinflammatory process that includes endothelial activation, alteration of the blood-brain barrier and passage of neurotoxic mediators. Microcirculatory dysfunction is common to these two processes. This brain dysfunction is associated with increased mortality, morbidity and long-term cognitive disability. Its diagnosis relies essentially on neurological examination that can lead to specific investigations, including electrophysiological testing or neuroimaging. In practice, cerebrospinal fluid analysis is indisputably required when meningitis is suspected. Hepatic, uremic or respiratory encephalopathy, metabolic disturbances, drug overdose, sedative or opioid withdrawal, alcohol withdrawal delirium or Wernicke's encephalopathy are the main differential diagnoses. Currently, treatment consists mainly of controlling sepsis. The effects of insulin therapy and steroids need to be assessed. Various drugs acting on sepsis-induced blood-brain barrier dysfunction, brain oxidative stress and inflammation have been tested in septic animals but not yet in patients.

Mechanisms of dendritic cell trafficking across the blood-brain barrier

Although the central nervous system (CNS) is considered to be an immunoprivileged site, it is susceptible to a host of autoimmune as well as neuroinflammatory disorders owing to recruitment of immune cells across the blood-brain barrier into perivascular and parenchymal spaces. Dendritic cells (DCs), which are involved in both primary and secondary immune responses, are the most potent immune cells in terms of antigen uptake and processing as well as presentation to T cells. In light of the emerging importance of DC traficking into the CNS, these cells represent good candidates for targeted immunotherapy against various neuroinflammatory diseases. This review focuses on potential physiological events and receptor interactions between DCs and the microvascular endothelial cells of the brain as they transmigrate into the CNS during degeneration and injury. A clear understanding of the underlying mechanisms involved in DC migration may advance the development of new therapies that manipulate these mechanistic properties via pharmacologic intervention. Furthermore, therapeutic validation should be in concurrence with the molecular imaging techniques that can detect migration of these cells in vivo. Since the use of noninvasive methods to image migration of DCs into CNS has barely been explored, we highlighted potential molecular imaging techniques to achieve this goal. Overall, information provided will bring this important leukocyte population to the forefront as key players in the immune cascade in the light of the emerging contribution of DCs to CNS health and disease.

Inflammatory cytokines regulate endothelial cell survival and tissue repair functions via NF-κB signaling

Inflammation contributes to the development of fibrotic and malignant diseases. We assessed the ability of inflammatory cytokines to modulate endothelial cell survival and functions related to tissue repair/remodeling. Treatment with interleukin (IL)-1β or tumor necrosis factor (TNF)-α (2 ng/mL) led to human pulmonary artery endothelial cells becoming spindle-shaped fibroblast-like cells. However, immunoblot and DNA microarray showed no change in most endothelial and mesenchymal markers. In the presence of IL-1β or TNF-α, cells were resistant to apoptosis induced by deprivation of serum and growth factor, and were more migratory. In addition, cells treated with IL-1β or TNF-α contracted collagen gels more robustly. In contrast, transforming growth factor-β1 did not induce these responses. RNA interference targeting nuclear factor (NF)-κB p65 blocked the effects of IL-1β or TNF-α on cell morphologic change, survival, migration, and collagen gel contraction. These results suggest that endothelial cells may contribute to tissue repair/remodeling via the NF-κB signaling in a milieu of airway inflammation.

Sepsis-associated encephalopathy and its differential diagnosis

Sepsis-associated encephalopathy (SAE) is defined as a diffuse cerebral dysfunction resulting from the systemic inflammatory response to an infection without direct infestation of the CNS. Although the pathophysiology of SAE is as yet unknown, some mechanisms have been suggested that involve BBB disruption as a consequence of proinflammatory mediators’ effects on endothelial cells. This leads to an increased passage of neurotoxic and proinflammatory mediators into the brain parenchyma, as well as an impairment of the movements of oxygen and metabolites through the BBB. Both neurons and glial cells are affected, resulting in neural functioning and neurotransmission impairment. The clinical translation of this process is an alteration of consciousness and awareness. SAE is a frequent condition in septic patients. Despite being considered reversible, SAE appears to be associated with long-term cognitive impairment. Detection and diagnosis can be challenging; it requires daily neurological assessment with the assistance of clinical scores. Use of biomarkers and neurophysiological testing is discussed. The aim of this article is to provide practical tools for detection of SAE, as well as an updated overview of its pathophysiology and therapeutic perspectives.

Platelet interleukin-1alpha drives cerebrovascular inflammation

White blood cell infiltration across an activated brain endothelium contributes to neurologic disease, including cerebral ischemia and multiple sclerosis. Identifying mechanisms of cerebrovascular activation is therefore critical to our understanding of brain disease. Platelet accumulation in microvessels of ischemic mouse brain was associated with endothelial activation in vivo. Mouse platelets expressed interleukin-1alpha (IL-1alpha), but not IL-1beta, induced endothelial cell adhesion molecule expression (ICAM-1 and VCAM-1), and enhanced the release of CXC chemokine CXCL1 when incubated with primary cultures of brain endothelial cells from wild-type or IL-1alpha/beta-deficient mice. A neutralizing antibody to IL-1alpha (but not IL-1beta) or application of IL-1 receptor antagonist inhibited platelet-induced endothelial activation by more than 90%. Platelets from IL-1alpha/beta-deficient mice did not induce expression of adhesion molecules in cerebrovascular endothelial cells and did not promote CXCL1 release in vitro. Conditioned medium from activated platelets induced an IL-1alpha-dependent activation of mouse brain endothelial cells and supported the transendothelial migration of neutrophils in vitro. Thus, we have identified platelets as a key source of IL-1alpha and propose that platelet activation of brain endothelium via IL-1alpha is a critical step for the entry of white blood cells, major contributors to inflammation-mediated injury in the brain.

Inhibition of complement C5a prevents breakdown of the blood-brain barrier and pituitary dysfunction in experimental sepsis

Introduction

Septic encephalopathy secondary to a breakdown of the blood-brain barrier (BBB) is a known complication of sepsis. However, its pathophysiology remains unclear. The present study investigated the effect of complement C5a blockade in preventing BBB damage and pituitary dysfunction during experimental sepsis.

Methods

Using the standardised caecal ligation and puncture (CLP) model, Sprague-Dawley rats were treated with either neutralising anti-C5a antibody or pre-immune immunoglobulin (Ig) G as a placebo. Sham-operated animals served as internal controls.

Results

Placebo-treated septic rats showed severe BBB dysfunction within 24 hours, accompanied by a significant upregulation of pituitary C5a receptor and pro-inflammatory cytokine expression, although gene levels of growth hormone were significantly attenuated. The pathophysiological changes in placebo-treated septic rats were restored by administration of neutralising anti-C5a antibody to the normal levels of BBB and pituitary function seen in the sham-operated group.

Conclusions

Collectively, the neutralisation of C5a greatly ameliorated pathophysiological changes associated with septic encephalopathy, implying a further rationale for the concept of pharmacological C5a inhibition in sepsis.

The encephalopathy in sepsis

Brain dysfunction is a severe complication of sepsis with an incidence ranging from 9% to 71% that is associated with increased morbidity and mortality. Its diagnosis relies mainly on neurologic examination with clinical manifestations ranging from confusion to coma. An electroencephalogram, somatosensory evoked potentials, and measurement of plasma S-100b protein and neuron-specific enolase can be useful for the detection of brain dysfunction. Brain MRI can identify brain lesions such as cerebral infarction, posterior reversible encephalopathy syndrome, and leukoencephalopathy. The mechanism of sepsis-associated encephalopathy involves inflammatory and non-inflammatory processes that affect endothelial cells, glial cells, and neurons and induce blood-brain barrier breakdown, derangements of intracellular metabolism, and cell death. Specific treatments for sepsis-associated encephalopathy need to be developed. Currently, treatment is mainly the management of sepsis.

Sepsis-associated delirium

OBJECTIVE

Sepsis-associated delirium is a common and poorly understood neurological complication of sepsis. This review provides an update of the diagnostic criteria and treatment strategies and the current knowledge about the mechanisms involved in sepsis associated brain dysfunction.

DATA SOURCES

Articles published between 1981 and 2006 were identified through a Medline search for "encephalopathy" and "sepsis" and by hand searching of articles cited in the identified publications. The immune response to sepsis results in multiorgan failure including brain dysfunction.

DISCUSSION

The potential mechanisms for sepsis-associated delirium include vascular damage, endothelial activation, breakdown of the blood-brain barrier, metabolic disorders, brain inflammation and apoptosis. On the other hand, there is evidence for distinct neuroprotective factors, such as anti-inflammatory mediators and glial cell activity.

CONCLUSIONS

The diagnosis of sepsis-associated delirium relies mainly on clinical and electrophysiological criteria, and its treatment is entirely based on general management of sepsis.

Differential expression of selectins by mouse brain capillary endothelial cells in vitro in response to distinct inflammatory stimuli

Increased lymphocyte trafficking across blood-brain barrier (BBB) is a prominent and early event in inflammatory and immune-mediated CNS diseases. The adhesion molecules that control the entry of leukocytes into the brain have not been fully elucidated. Although the role of ICAM-1 and VCAM-1 has been well documented, the expression and role of selectins is still a matter of controversy. In a mouse syngenic in vitro BBB model, highly relevant for examining immunological events, mouse brain capillary endothelial cells (MBCECs) do not express selectins. Treatment of MBCECs with LPS, induced E- and P-selectin expression, whereas TNF-alpha or IFN-gamma treatments did not. Finally, P-selectin but not E-selectin expression was induced in IL-1beta treated MBCECs. Thus, our study suggests that diverse inflammatory stimuli could differentially regulate selectin expression at the BBB.

Science review: The brain in sepsis--culprit and victim

On one side, brain dysfunction is a poorly explored complication of sepsis. On the other side, brain dysfunction may actively contribute to the pathogenesis of sepsis. The current review aimed at summarizing the current knowledge about the reciprocal interaction between the immune and central nervous systems during sepsis. The immune-brain cross talk takes part in circumventricular organs that, being free from blood-brain-barrier, interface between brain and bloodstream, in autonomic nuclei including the vagus nerve, and finally through the damaged endothelium. Recent observations have confirmed that sepsis is associated with excessive brain inflammation and neuronal apoptosis which clinical relevance remains to be explored. In parallel, damage within autonomic nervous and neuroendocrine systems may contribute to sepsis induced organ dysfunction.

L-gamma-Glutamyl-L-cysteinyl-glycine (glutathione; GSH) and GSH-related enzymes in the regulation of pro- and anti-inflammatory cytokines: a signaling transcriptional scenario for redox(y) immunologic sensor(s)?

Of the antioxidant/prooxidant mechanisms mediating the regulation of inflammatory mediators, particularly cytokines, oxidative stress-related pathways remain a cornerstone. It is conspicuous that there is a strong association between free radical accumulation (ROS/RNS; oxidative stress) and the evolution of inflammation and inflammatory-related responses. The scenario that upholds a consensus on the aforementioned is still evolving to unravel, from an immunologic perspective, the molecular mechanisms associated with ROS/RNS-dependent inflammation. Cytokines are keynote players when it comes to defining an intimate relationship among reduction-oxidation (redox) signals, oxidative stress and inflammation. How close we are to identifying the molecular basis of this intricate association should be weighed against the involvement of specific signaling molecules and, potentially, transcription factors. L-gamma-Glutamyl-L-cysteinyl-glycine, or glutathione (GSH), an antioxidant thiol, has shaped, and still is refining, the face of oxidative signaling in terms of regulating the milieu of inflammatory mediators, ostensibly via the modulation (expression/repression) of oxygen- and redox-responsive transcription factors, hence termed redox(y)-sensitive cofactors. When it comes to the arena of oxygen sensing, oxidative stress and inflammation, nuclear factor-kappaB (NF-kappaB) and hypoxia-inducible factor-1alpha (HIF-1alpha) are key players that determine antioxidant/prooxidant responses with oxidative challenge. It is the theme therein to underlie current understanding of the molecular association hanging between oxidative stress and the evolution of inflammation, walked through an elaborate discussion on the role of transcription factors and cofactors. Would that classify glutathione and other redox signaling cofactors as potential anti-inflammatory molecules emphatically remains of particular interest, especially in the light of identifying upstream and downstream molecular pathways for conceiving therapeutic, alleviating strategy for oxidant-mediated, inflammatory-related disease conditions.

Reactive oxygen species mediate endotoxin-induced human dermal endothelial NF-kappaB activation

BACKGROUND

Microvascular endothelial cell "activation" by endotoxin is an early and critical phenomenon underlying organ dysfunction related to sepsis. Dermal endothelial cells contribute to many of the manifestations of septic shock, such as cutaneous interstitial edema and loss of peripheral vasomotor regulation. Human dermal endothelial cell activation by endotoxin (lipopolysaccharide [LPS]) is characterized by the generation of reactive oxygen species (ROS) that enhance nuclear translocation of the transcription factor kappa-B (NF-kappaB).

METHODS

We tested our hypothesis by stimulating human dermal microvascular endothelial cells (HMEC.1) with endotoxin and assaying for endothelial generation of ROS and nuclear translocation of NF-kappaB subunits. HMEC.1 cultures were treated individually with LPS, hydrogen peroxide, or xanthine, xanthine oxidase, and ferrous sulfate (xanthine/XO/Fe(2+)). Nuclear proteins were isolated and consensus sequence binding was assessed by electrophoretic mobility shift assay (EMSA). 2',7'-Dichlorofluorescin diacetate and confocal microscopy were used to examine ROS production in LPS-stimulated HMEC.1.

RESULTS

Nuclear translocation of the p65/p50 NF-kappaB heterodimer was detectable 30 min after stimulation with LPS alone or the xanthine/XO/Fe(2+) combination, but not with hydrogen peroxide. Antioxidant N-acetylcysteine (NAC) inhibited LPS-stimulated ROS production in HMEC.1. Antioxidant prior to or simultaneously with LPS exposure, but not following LPS, also prevented NF-kappaB activation. NAC was ineffective at inhibiting NF-kappaB translocation at increased LPS concentrations.

CONCLUSIONS

Dermal endothelial cells, a microvascular cell type that may contribute to the systemic response to blood-borne endotoxemia, generate ROS in the absence of other inflammatory cells. These LPS-activated endothelial cells, in turn, rapidly translocate transcription factor NF-kappaB to cell nuclei, a process regulated in part by intracellular ROS.

Dexamethasone affects cytokine-mediated adhesion of HL-60 human promyelocytic leukemia cells to cultured dermal microvascular endothelial cells

Leukocyte endothelial adhesion (LEA) is the prelude to a complex cascade of reactions following an immunological challenge. Recently, LEA has been implicated in the molecular basis of several dermatological disorders. While the role of proinflammatory cytokines, such as interleukin-1 beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), in LEA has been investigated using nondermal models, limited data exist regarding their effects on LEA in dermal models. This study shows that cotreatment of cultured human dermal endothelial cells (CADMEC) with IL-1beta and TNF-alpha resulted in a marked increase in the adherence of human promyelocytic leukemia (HL-60) cells to CADMEC and an increase in expression of intercellular adhesion molecule-1 and E-selectin. Pretreatment of CADMEC with dexamethasone, a long-lasting glucocorticoid, resulted in a decrease in both HL-60 cell adhesion to CADMEC and adhesion molecule expression. Taken together, these data demonstrate that LEA may play a role in inflammatory skin conditions and in the mechanisms underlying the potential use of glucocorticoids as a treatment option.

Human lactoferrin interacts with soluble CD14 and inhibits expression of endothelial adhesion molecules, E-selectin and ICAM-1, induced by the CD14-lipopolysaccharide complex

Lipopolysaccharides (LPS), either in the free form or complexed to CD14, a LPS receptor, are elicitors of the immune system. Lactoferrin (Lf), a LPS-chelating glycoprotein, protects animals against septic shock. Since optimal protection requires administration of Lf prior to lethal doses of LPS, we hypothesized that interactions between Lf and soluble CD14 (sCD14) exist. In a first step, human sCD14 and human Lf (hLf) were used to determine the kinetic binding parameters of hLf to free sCD14 in an optical biosensor. The results demonstrated that hLf bound specifically and with a high affinity (K(d) = 16+/-7 nM) to sCD14. Affinity chromatography studies showed that hLf interacted not only with free sCD14 but also, though with different binding properties, with sCD14 complexed to LPS or lipid A-2-keto-3-deoxyoctonic acid-heptose. In a second step, we have investigated whether the capacity of hLf to interact with sCD14 could modulate the expression of endothelial-leukocyte adhesion molecule 1 (E-selectin) or intercellular adhesion molecule 1 (ICAM-1) induced by the sCD14-LPS complex on human umbilical vein endothelial cells (HUVEC). Our experiments show that hLf significantly inhibited both E-selectin and ICAM-1 expressions at the surface of HUVEC. In conclusion, these observations suggest that the anti-inflammatory effects of hLf are due not only to the ability of the molecule to chelate LPS but also to its ability to interact with sCD14 and with the sCD14 complexed to LPS, thus modifying the activation of endothelial cells.

Treatment of established relapsing experimental autoimmune encephalomyelitis with the proteasome inhibitor PS-519

PLP139-151-induced relapsing experimental autoimmune encephalomyelitis (R-EAE) in SJL mice is a Th1-mediated autoimmune demyelinating disease model for multiple sclerosis (MS) in which the primary disease relapse is mediated by T cells specific for the endogenous PLP178-191 epitope. This complex inflammatory process requires the co-ordinated expression of a wide variety of immune-related genes active at a variety of stages of the autoimmune process which are regulated, in part, by the transcription factor nuclear factor (NF)-kappaB which is activated via the ubiquitin-proteasome pathway. We asked if in vivo administration of a selective inhibitor of the ubiquitin-proteasome pathway, PS-519, which downregulates activation of NF-kappaB, could downregulate ongoing R-EAE. Administration of PS-519 during the remission phase, following acute clinical disease was effective in significantly reducing the incidence of clinical relapses, CNS histopathology, and T cell responses to both the initiating and relapse-associated PLP epitopes. The inhibition of clinical disease was dependent upon continuous administration of PS-519 in that recovery of T cell function and onset of disease relapses developed within 10-14 days of drug withdrawal. The data suggest that targeting the ubiquitin proteasome pathway, in particular NF-kappaB, may offer a novel and efficacious approach for the treatment of progressive autoimmune diseases, including MS.

Matrix metalloproteinases contribute to brain damage in experimental pneumococcal meningitis

The present study was performed to evaluate the role of matrix metalloproteinases (MMP) in the pathogenesis of the inflammatory reaction and the development of neuronal injury in a rat model of bacterial meningitis. mRNA encoding specific MMPs (MMP-3, MMP-7, MMP-8, and MMP-9) and the inflammatory cytokine tumor necrosis factor alpha (TNF-alpha) were significantly (P < 0.04) upregulated, compared to the beta-actin housekeeping gene, in cortical homogenates at 20 h after infection. In parallel, concentrations of MMP-9 and TNF-alpha in cerebrospinal fluid (CSF) were significantly increased in rats with bacterial meningitis compared to uninfected animals (P = 0.002) and showed a close correlation (r = 0.76; P < 0. 001). Treatment with a hydroxamic acid-type MMP inhibitor (GM6001; 65 mg/kg intraperitoneally every 12 h) beginning at the time of infection significantly lowered the MMP-9 (P < 0.02) and TNF-alpha (P < 0.02) levels in CSF. Histopathology at 25.5 +/- 5.7 h after infection showed neuronal injury (median [range], 3.5% [0 to 17.5%] of the cortex), which was significantly (P < 0.01) reduced to 0% (0 to 10.8%) by GM6001. This is the first report to demonstrate that MMPs contribute to the development of neuronal injury in bacterial meningitis and that inhibition of MMPs may be an effective approach to prevent brain damage as a consequence of the disease.

Free radical scavengers: chemical concepts and clinical relevance

Free radicals are involved in the pathology of many CNS disorders, like Parkinson's disease, Alzheimer's disease, or stroke. This discovery lead to the development of many radical scavengers for the clinical treatment of neurodegenerative diseases. In this review, the different chemical concepts for free radical scavenging will be discussed: nitrons, thiols, iron chelators, phenols, and catechols. Especially catechols, like the naturally occurring flavonols, the synthetic drug nitecapone, or the endogenous catacholamines and their metabolites, are of great interest, as they combine iron chelating with radical scavenging activity. We present data on the radical scvenging activity of dopamine and apomorphine, which prevent lipid peroxidation in rat brain mitochondria and protect PC12 cells against H2O2-toxicity.

Upregulation of intercellular adhesion molecule-1 expression on human endothelial cells by tumour necrosis factor-alpha in an in vitro model of the blood-brain barrier

Adhesion molecules on the endothelial surface of the blood-brain barrier (BBB) play an important role in the pathogenesis of many encephalopathies, including multiple sclerosis (MS) and cerebral malaria (CM). The expression of four surface molecules of relevance to MS and CM on the immortalized human umbilical vein endothelial cell line, ECV304, was investigated using immunofluorescence flow cytometry. We found that ECV304 cells express intercellular adhesion molecule-1 (ICAM-1) and low levels of CD36, but not vascular cell adhesion molecule-1 (VCAM-1) or E-selectin. This expression pattern was unaltered on ECV304 cells which were co-cultured with C6 glioma cells; conditions under which the endothelial cells display enhanced barrier formation. Tumour necrosis factor-alpha (TNF-alpha), which is elevated in MS and CM, decreased the integrity of the barrier in co-cultured endothelial cells and upregulated the expression of ICAM-1 nine-fold. The significance of elevated ICAM-1 expression in relation to the binding of parasitised erythrocytes at the BBB in CM is discussed.

Detection of soluble E-selectin, ICAM-1, VCAM-1, and L-selectin in the cerebrospinal fluid of patients after subarachnoid hemorrhage

OBJECT

The goal of this study was to explore whether the levels of soluble adhesion molecules were elevated in cerebrospinal fluid (CSF) after subarachnoid hemorrhage (SAH). This association was suggested by the known inflammatory response in vasospasm and the role of vascular adhesion molecules in regulating leukocytic adhesion to, and migration across, vascular endothelium.

METHODS

A prospective analysis was performed on CSF samples obtained in 17 patients who had suffered a recent aneurysmal SAH and in 16 control patients by using quantitative enzyme-linked immunosorbent assays for E-selectin, intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), and L-selectin. Levels of soluble forms of E-selectin (p=0.0013), ICAM-1 (p=0.0001), and VCAM-1 (p=0.048) were found to be elevated in the CSF of patients after SAH compared with levels in the CSF of norminal controls, patients with unruptured aneurysms, and patients tested months after SAH occurred. In addition, individual patients tested at the time of their initial ictus demonstrated a fall in adhesion molecule levels over time. Levels of E-selectin (p=0.044) were highest in patients who later developed moderate or severe vasospasm.

CONCLUSIONS

Adhesion molecules are known to be involved in white cell adherence to the endothelium and subsequent diapedesis and migration in which a role in initiation of tissue damage is postulated. The authors have demonstrated the elevation of three adhesion molecules, with severely elevated levels of E-selectin seen in patients who later develop vasospasm. A correlation with a role of vascular adhesion molecules in the pathogenesis of cerebral vasospasm is suggested.

E-selectin expression in human endothelial cells by TNF-alpha-induced oxidant generation and NF-kappaB activation

Because reactive oxygen species (ROS) can function as second messengers and regulate the activation of the transcription factor nuclear factor (NF)-kappaB, we investigated the possible role of tumor necrosis factor-alpha (TNF-alpha)-induced ROS generation in endothelial cells in signaling E-selectin gene transcription. We demonstrated that stimulation of human pulmonary artery endothelial cells with TNF-alpha (100 U/ml) resulted in ROS production using the oxidant-sensitive dye 5 (and 6)-carboxy-2',7'-dichlorodihydrofluorescein diacetate bis(acetoxymethyl)ester. Pretreatment with N-acetyl-L-cysteine (NAC) or pyrrolidine dithiocarbamate (PDTC) for 0.5 h inhibited TNF-alpha-induced generation of ROS as well as activation of NF-kappaB and E-selectin mRNA and the cell surface protein expression. These findings indicate that TNF-alpha induces NF-kappaB activation and the resultant E-selectin gene expression by a pathway that involves formation of ROS and that E-selectin expression can be inhibited by the antioxidant action of NAC or PDTC. The results support the hypothesis that generation of ROS in endothelial cells induced by proinflammatory cytokines such as TNF-alpha is a critical signal mediating E-selectin expression.

Endothelial cell monolayers as a tool for studying microvascular pathophysiology

Endothelial cells contribute to a variety of biological responses that facilitate organ function. This critical role of the endothelial cell has resulted in the development of different in vitro models that utilize monolayers of cultured cells to simulate conditions that exist in the intact animal. This review focuses on endothelial cell monolayers as a model system for research on certain pathophysiological conditions affecting the gastrointestinal tract. The advantages and limitations of endothelial cell monolayers are addressed, along with evolving technologies and strategies that hold promise for extending the utility of this in vitro model for studies of gastrointestinal function and disease.

Cerebral lupus vasculopathy. Mechanisms and clinical relevance

The most common neuropathological findings in SLE are a small vessel cerebral vasculopathy and microinfarcts. These findings may reflect the end result of repeated episodes of acute inflammation in the small vessels in the brain. There is experimental support for the local Shwartzman reaction as a paradigm to explain some of the CNS manifestations in SLE. Activation or "priming" of cerebral microvascular endothelial cells by anticardiolipin antibodies or other immunoglobulins in concert with intravascular activation of the complement system may combine to elicit leukothrombosis in the brain. Therapies aimed at inhibiting leukocyte-endothelial cell interactions in the brain may be of use in CNS lupus.