Gold nanoparticle-based colorimetric biosensors

Gold nanoparticles (AuNPs) provide excellent platforms for the development of colorimetric biosensors as they can be easily functionalised, displaying different colours depending on their size, shape and state of aggregation. In the last decade, a variety of biosensors have been developed to exploit the extent of colour changes as nano-particles (NPs) either aggregate or disperse, in the presence of analytes. Of critical importance to the design of these methods is that the behaviour of the systems has to be reproducible and predictable. Much has been accomplished in understanding the interactions between a variety of substrates and AuNPs, and how these interactions can be harnessed as colorimetric reporters in biosensors. However, despite these developments, only a few biosensors have been used in practice for the detection of analytes in biological samples. The transition from proof of concept to market biosensors requires extensive long-term reliability and shelf life testing, and modification of protocols and design features to make them safe and easy to use by the population at large. Developments in the next decade will see the adoption of user friendly biosensors for point-of-care and medical diagnosis as innovations are brought to improve the analytical performances and usability of the current designs. This review discusses the mechanisms, strategies, recent advances and perspectives for the use of AuNPs as colorimetric biosensors.

Expression of ADAMTS-1, -4, -5 and TIMP-3 in normal and multiple sclerosis CNS white matter

ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) -1, -4 and -5 proteases have been identified in the CNS at the mRNA level. These glutamyl endopeptidases, inhibited by tissue inhibitor of metalloproteinases (TIMP)-3, are key enzymes in the degradation of the aggregating chondroitin sulphate proteoglycans (CSPGs), and may therefore play a role in CNS extracellular matrix (ECM) changes in multiple sclerosis (MS). We have investigated ADAMTS and TIMP-3 expression in normal and MS CNS white matter by real-time RT-PCR, western blotting and immunohistochemistry. We report for the first time the presence of ADAMTS-1, -4 and -5 in normal and MS white matter. Levels of ADAMTS-1 and -5 mRNA were decreased in MS compared to normal tissue, with no significant change in ADAMTS-4 mRNA levels. Protein levels of ADAMTS-4 were significantly higher in MS tissue compared to normal tissue. Immunohistochemical studies demonstrated that ADAMTS-4 was associated predominantly with astrocytes with increased expression within MS lesions. TIMP-3 mRNA was significantly decreased in MS compared to controls. These studies suggest a role for ADAMTS-4 in the pathogenesis of MS. Further studies on the activity of ADAMTS-4 will enable a better understanding of its role in the turnover of the ECM of white matter in MS.

CCL2 binding is CCR2 independent in primary adult human astrocytes

Chemokines are low relative molecular mass proteins, which have chemoattractant actions on many cell types. The chemokine, CCL2, has been shown to play a major role in the recruitment of monocytes in central nervous system (CNS) lesions in multiple sclerosis (MS). Since resident astrocytes constitute a major source of chemokine synthesis including CCL2, we were interested to assess the regulation of CCL2 by astrocytes. We showed that CCL2 bound to the cell surface of astrocytes and binding was not modulated by inflammatory conditions. However, CCR2 protein was not detected nor was activation of the classical CCR2 downstream signaling pathways. Recent studies have shown that non-signaling decoy chemokine receptors bind and modulate the expression of chemokines at site of inflammation. Here, we show that the D6 chemokine decoy receptor is constitutively expressed by primary human adult astrocytes at both mRNA and protein level. In addition, CCL3, which binds to D6, but not CCL19, which does not bind to D6, displaced CCL2 binding to astrocytes; indicating that CCL2 may bind to this cell type via the D6 receptor. Our results suggest that CCL2 binding to primary adult human astrocytes is CCR2-independent and is likely to be mediated via the D6 decoy chemokine receptor. Therefore we propose that astrocytes are implicated in both the establishment of chemokine gradients for the migration of leukocytes into and within the CNS and in the regulation of CCL2 levels at inflammatory sites in the CNS.

Brevican and phosphacan expression and localization following transient middle cerebral artery occlusion in the rat

The ECM (extracellular matrix) is a complex molecular framework that provides physical support to cells and tissues, while also providing signals for cell growth, migration, differentiation and survival. The ECM of the CNS (central nervous system) is unusual in that it is rich in CSPGs (chondroitin sulfate proteoglycans), hyaluronan and tenascins. The CSPGs are widely expressed throughout the developing and adult CNS and have a role in guiding or limiting neurite outgrowth and cell migration. Alterations in the synthesis or breakdown of the ECM may contribute to disease processes. Here, we examine changes in the brain-specific CSPGs, brevican and phosphacan, following transient middle cerebral artery occlusion, a model of stroke in the rat. We have investigated their expression at various time points as well as their spatial relationship with ADAMTS-4 (adisintegrin and metalloprotease with thrombospondin motifs 4). The co-localization of ADAMTS or its activity may indicate a functional role for this matrix–protease pair in degeneration/regeneration processes that occur in stroke.

Upregulation of ADAM-17 expression in active lesions in multiple sclerosis

ADAM-17, a disintegrin and metalloproteinase, is the major proteinase responsible for the cleavage of membrane-bound tumour necrosis factor (TNF) as well as being an active sheddase of other cytokines, cytokine receptors, growth factors and adhesion molecules. TNF is a major proinflammatory cytokine that has been identified as having a pathogenic role in inflammatory diseases within the CNS including multiple sclerosis (MS). Here we report the cellular origin and distribution of ADAM-17 expression within clinically and neuropathologically confirmed MS and normal control white matter, assessed by immunohistochemistry, western blotting and PCR. ADAM-17 expression was associated with the blood vessel endothelium, activated macrophages/microglia and parenchymal astrocytes in MS white matter. Increased levels of ADAM-17 immunoreactivity were displayed in active lesions with evidence of recent myelin breakdown. Further studies into the functional role of ADAM-17 in the pathogenesis of MS and other inflammatory conditions are required.

ADAMTS-1 and -4 are up-regulated following transient middle cerebral artery occlusion in the rat and their expression is modulated by TNF in cultured astrocytes

ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) enzymes are a recently described group of metalloproteinases. The substrates degraded by ADAMTS-1, -4 and -5 suggest that they play a role in turnover of extracellular matrix in the central nervous system (CNS). ADAMTS-1 is also known to exhibit anti-angiogenic activity. Their main endogenous inhibitor is tissue inhibitor of metalloproteinases (TIMP)-3. The present study was designed to investigate ADAMTS-1, -4 and -5 and TIMP-3 expression after experimental cerebral ischaemia and to examine whether cytokines known to be up-regulated in stroke could alter their expression by astrocytes in vitro. Focal cerebral ischaemia was induced by transient middle cerebral artery occlusion in the rat using the filament method. Our results demonstrate a significant increase in expression of ADAMTS-1 and -4 in the occluded hemisphere but no significant change in TIMP-3. This was accompanied by an increase in mRNA levels for interleukin (IL)-1beta, IL-1 receptor antagonist (IL-1ra) and tumour necrosis factor (TNF). ADAMTS-4 mRNA and protein were up-regulated by TNF in primary human astrocyte cultures. The increased ADAMTS-1 and -4 in experimental stroke, together with no change in TIMP-3, may promote ECM breakdown after stroke, enabling infiltration of inflammatory cells and contributing to brain injury. In vitro studies suggest that the in vivo modulation of ADAMTS-1 and -4 may be controlled in part by TNF.

Differential expression of ADAMTS-1, -4, -5 and TIMP-3 in rat spinal cord at different stages of acute experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an animal model of inflammatory demyelination, a pathological event common to multiple sclerosis (MS). During CNS inflammation there are alterations in the extracellular matrix (ECM). A Disintegrin and Metalloproteinase with Thrombospondin motifs (ADAMTS)-1, -4 and -5 are proteases present in the CNS, which are able to cleave the aggregating chondroitin sulphate proteoglycans, aggrecan, phosphacan, neurocan and brevican. It is therefore important to investigate changes in their expression in different stages of EAE induction. We have investigated expression of ADAMTS-1, -4, -5 and tissue inhibitor of metalloproteinase (TIMP)-3, by real-time RT-PCR. We have also examined protein expression of ADAMTS-1, -4 and -5 by western blotting and immunocytochemistry in spinal cord from animals at different stages of disease progression. Our study demonstrated a decrease in ADAMTS-4 mRNA and protein expression. TIMP-3 was decreased at the mRNA level although protein levels were increased in diseased animals compared to controls. Our study identifies changes in ADAMTS expression during the course of CNS inflammation which may contribute to ECM degradation and disease progression.

Cytokine regulation of MCP-1 expression in brain and retinal microvascular endothelial cells

Chemokines have a pivotal role in the selective mediation and amplification of inflammation. The CNS vascular endothelial cells, which form part of the blood-brain barrier (BBB) and blood-retinal barrier (BRB), are ideally situated to present chemokines to circulating lymphocytes leading to their recruitment. Monocyte-chemoattractant protein-1 (MCP-1), also known as CCL2, a potent chemoattractant of T cells and monocytes, has been implicated in inflammatory and angio-proliferative brain and retinal disease. In this study, MCP-1 expression by CNS endothelial cells was investigated in vitro. Rat brain (GP8/3.9) and retinal (JG2/1) vascular endothelial cell lines expressed MCP-1 constitutively in vitro as assessed by immunocytochemistry and enzyme linked immunosorbant assay (ELISA). Upregulation of secreted MCP-1 was observed following activation with the pro-inflammatory cytokines TNF-alpha, IL-1 beta and IFN-gamma, and was reduced following dexamethasone treatment. Functional chemotactic activity of brain and retinal endothelial cell supernatants was demonstrated in an in vitro chemotaxis assay, which was inhibited by anti-MCP-1 antibodies. These findings suggest that endothelial cell-derived MCP-1 plays a key role in leukocyte recruitment across the blood-brain and blood-retinal barriers in vivo.

Longitudinal study of chemokine receptor expression on peripheral lymphocytes in multiple sclerosis: CXCR3 upregulation is associated with relapse

The interaction between chemokines and their receptors leads to selective recruitment of cells to foci of inflammation. Cross-sectional studies have reported significantly different expression of chemokine receptors CXCR3, CCR5 and CCR2 on peripheral blood lymphocytes in multiple sclerosis (MS) compared with controls. Cells expressing these receptors are likely to play a pathogenic role as suggested by studies of experimental autoimmune encephalomyelitis. Also, immunogenetic studies of nonfunctional CCR5 receptors in MS patients, due to 32delta deletion, demonstrated a delay in time to next relapse. The aims of this study were to detect any changes in the serial expression of chemokine receptors CCR2, CCR3, CCR5 and CXCR3 on peripheral blood CD4+ lymphocytes from patients with MS and to correlate the changes with relapses. Upregulation of CXCR3 expression on peripheral blood CD4+ lymphocytes was associated with all relapses and CCR5 expression was significantly affected with all relapses. Clinical recovery, with or without intravenous methylprednisolone treatment, coincided with the return of CXCR3 towards baseline in all but one case. Fluctuation in the expression of CXCR3 and CCR5 was also significantly greater in clinically stable patients with MS compared with controls, which may be due to subclinical disease activity. These findings provide further support for the view that CXCR3 and CCR5 antagonists could have a therapeutic value in MS.

Expression of chemokines in cerebrospinal fluid and serum of patients with chronic inflammatory demyelinating polyneuropathy

Chemokines are likely to contribute to the pathogenesis of chronic inflammatory demyelinating polyneuropathy (CIDP), as evidenced by data from experimental autoimmune neuritis. The alpha and beta chemokines in the cerebrospinal fluid (CSF) and serum from patients with CIDP were analysed using an enzyme linked immunosorbent assay. CXCL9, CXCL10, and CCL3 were raised in the CSF in CIDP compared with controls and non-demyelinating neuropathies (p < 0.001). Although the CSF levels of CCL2 were significantly higher than the serum levels for all groups, the difference between groups was not significant. CXCL9, CXCL10, and CCL3 may contribute to the pathogenesis of CIDP by recruiting inflammatory T cells and monocytes to spinal nerve roots, while CCL2 is likely to play a physiological role.

Expression of chemokines in the CSF and correlation with clinical disease activity in patients with multiple sclerosis

OBJECTIVE

To define the chemokine profile in the CSF of patients with multiple sclerosis (MS) and compare it with three control groups; patients with benign headache (headache), non-inflammatory neurological diseases (NIND), and other inflammatory neurological diseases (IND). In addition, the correlations of CSF chemokine concentrations with chemokine receptor expression on CSF CD4(+) T cells and with clinical disease activity were assessed.

METHODS

Forty three patients with MS, 24 with IND, 44 with NIND, and 12 with benign headache undergoing diagnostic or therapeutic lumbar puncture were included. Supernatant fluid from CSF was analysed for four beta (CCL2, CCL3, CCL4, CCL5) and two alpha (CXCL9, CXCL10)chemokines by enzyme linked immunosorbent assay (ELISA). Chemokine receptors CCR3, CCR5, and CXCR3 on CD4(+) T cells from eight patients with MS were analysed using directly conjugated fluorescent labelled monoclonal antibodies and flow cytometry.

RESULTS

CXCL10, formerly interferon-gamma inducible protein-10 (IP-10), was significantly increased and CCL2, formerly monocyte chemoattractant protein-1 (MCP-1), was significantly reduced in the CSF of patients with MS and IND compared with those with benign headache and NIND. Concentrations of CXCL10 were significantly greater in patients with relapsing-remitting compared with secondary progressive MS and correlated significantly with CXCR3 expression on CSF CD4(+) T cells from patients with MS. Concentrations of CXCL10 decreased and CCL2 concentrations increased as time from the last relapse increased in patients with MS.

CONCLUSION

Increased CXCL10 and decreased CCL2 concentrations in the CSF are associated with relapses in MS. Although serial values from individual patients were not available, this study suggests that CXCL10 and CCL2 may return towards baseline concentrations after a relapse. Correlation of CXCL10 with CD4(+) T cell expression of CXCR3 was consistent with its chemoattractant role for activated lymphocytes. Thus CXCL10 neutralising agents and CXCR3 receptor antagonists may be therapeutic targets in MS.

Astrocyte and endothelial cell expression of ADAM 17 (TACE) in adult human CNS

ADAM 17, also known as TACE, is an important sheddase for a number of proteins, including tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-alpha (TGF-alpha), L-selectin, p75, and p55 TNF receptors, and interleukin-1 receptor II (IL-1RII). The presence of ADAM 17 mRNA in adult mouse and rat CNS was recently reported (Karkkainen et al. Mol Cell Neurosci 15:547-560, 2000). However, the cellular origin of ADAM 17 remains unknown. In this study, we have used an anti-ADAM 17 antibody in an immunohistochemical study of its distribution in human adult CNS tissue. Cells with astrocytic and endothelial morphology were ADAM 17-positive. This finding was further confirmed using double immunofluorescence with antibodies against GFAP and von Willebrand factor, which label astrocytes and endothelial cells, respectively. This study demonstrates that ADAM 17 is expressed by astrocytes and endothelial cells in normal brain tissue and may have a role in normal brain function.

Immunoregulation of microglial functional properties

Microglia are the resident tissue macrophages of the central nervous system (CNS) parenchyma and are key players in the initiation of an inflammatory response. Microglia rapidly transform from a resting to an activated morphology in response to a variety of disease states. However, they can also be the target of infections, as in the case of HIV. Many of the effector properties of microglia can be attributed to the array of substances they secrete in response to stimuli such as bacterial lipopolysaccharide, cytokines, and chemokines. The products of activated microglia include: cytokines (pro- and anti-inflammatory), chemokines, nitric oxide, superoxide radicals, and proteases. Furthermore, microglia have the ability to present antigen to T cells, migrate in response to chemotactic stimuli, and phagocytose cell debris. This report focuses on the immunomodulatory functions of microglia, with particular attention to chemokines, and highlights their pivotal role in the CNS.

Extracellular nucleotides differentially regulate interleukin-1beta signaling in primary human astrocytes: implications for inflammatory gene expression

The cytokine interleukin-1beta (IL-1beta) is a potent activator of human astrocytes, inducing or modulating expression of multiple proinflammatory genes via activation of the transcription factors nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1). In this study, we examined whether IL-1beta signaling is regulated in these cells by extracellular nucleotides that are released at high concentrations under inflammatory conditions and act as ligands for members of the P2 receptor family. Using reporter constructs and electromobility shift assays, we found that cotreatment of astrocyte cultures with ATP (1-100 microm) significantly potentiated IL-1beta-mediated activation of NF-kappaB and AP-1 and that ATP alone activated AP-1. These effects were blocked by the P2 receptor antagonists XAMR 0721, periodate-oxidized ATP, and suramin. A role for ATP in modulating IL-1beta-mediated inflammatory gene expression was supported further by the observation that ATP potentiated the IL-1beta-induced expression of IL-8 mRNA and protein but strongly downregulated IP-10 expression. Reverse transcription-PCR and cloning demonstrated expression of the ATP-responsive P2 receptor subtypes P2Y(1), P2Y(2), and P2X(7), as well as the ATP-insensitive receptor P2Y(4). ADP, a selective agonist for P2Y(1), produced results similar to or greater than those obtained using ATP, whereas 2'-3'-O-(4-benzoyl-benzoyl)-ATP, a selective agonist for P2X(7), was less effective than ATP. In contrast, UTP, a selective agonist for P2Y(2) and P2Y(4), was ineffective. These studies indicate that different P2 receptor subtypes play distinct roles in the modulation of IL-1beta-mediated signal transduction in human astrocytes, and that signaling via P2 receptors may fine-tune the transcription of genes involved in inflammatory responses in the human CNS.

Expression of the beta-chemokine receptors CCR2, CCR3 and CCR5 in multiple sclerosis central nervous system tissue

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) characterised by perivascular inflammatory cell infiltrates and plaques of demyelination. Chemokines have been shown to play an important role in the activation and directional migration of cells to sites of CNS inflammation. The action of chemokines requires the expression of their complementary chemokine receptors by their target cells. We have examined the expression of the beta-chemokine receptors CCR2, CCR3 and CCR5 in post-mortem MS CNS tissue using single- and double-labelling immunocytochemistry techniques. Low levels of CCR2, CCR3 and CCR5 were expressed by microglial cells throughout control CNS tissue. In chronic active MS lesions CCR2, CCR3 and CCR5 were associated with foamy macrophages and activated microglia. CCR2 and CCR5 were also present on large numbers of infiltrating lymphocytes. A smaller number of CCR3-positive lymphocytes were present, but we also noted CCR3 and CCR5 on astrocytes in five of the 14 cases of MS investigated, particularly associated with processes around vessels and at the glia limitans. Ligands for CCR2 and CCR3 include MCP-1 and MCP-3 which were co-localised around vessels with the infiltrating leukocytes, but were also present in unaffected areas of cortex. The elevated expression of CCR2, CCR3 and CCR5 in the CNS in MS suggests these beta-chemokine receptors and their ligands play a role in the pathogenesis of MS.

Dexamethasone regulation of matrix metalloproteinase expression in CNS vascular endothelium

Matrix metalloproteinases (MMPs) have been implicated in the early breakdown of the blood-brain barrier in neuroinflammatory disease. Although expression of these enzymes by resident glial cells and recruited immune cells has been described, altered expression of MMPs by the CNS vascular endothelial cells may also contribute to barrier disruption. In the present study, the in vitro expression of MMP-2 and -9 as well as tissue inhibitor of metalloproteinase (TIMP)-2 by rat CNS microvascular endothelial cells has been determined and compared with that by endothelial cell lines derived from rat aorta and high endothelial venules. Primary cultures of rat brain microvascular endothelial cells as well as the rat brain (GP8/3.9) and rat retinal endothelial (JG2/1) cell lines constitutively expressed MMP-2, -9 and TIMP-2. In vitro activation of CNS endothelium with the pro-inflammatory cytokines, tumour necrosis factor-alpha and interleukin-1beta, resulted in selective upregulation of MMP-9 activity, whereas no significant changes were seen in MMP-2 or TIMP-2 levels at 24 h. The addition of dexamethasone partially inhibited the cytokine-induced upregulation of MMP-9. Treatment of GP8/3.9 brain endothelial cells with active MMP-9 caused subtle but distinct alterations in the expression of the junctional protein, ZO-1. Quantitative differences found between CNS and non-CNS endothelial cells in the expression of both MMP-2 and -9, and in the expression of TIMP-2 demonstrate that CNS vascular endothelium is functionally distinct from non-CNS endothelium. These results suggest that cytokine-induced upregulation of MMP-9 expression by the CNS vascular endothelium may play a role in the pathogenesis of blood-brain and blood-retinal barrier breakdown in vivo.

Expression of the interferon-gamma-inducible chemokines IP-10 and Mig and their receptor, CXCR3, in multiple sclerosis lesions

The recruitment of leucocytes to sites of inflammation is an important feature of multiple sclerosis (MS) pathology. Chemokines are involved in the activation and specific directional migration of monocytes and T-lymphocytes to sites of inflammation. Using immunocytochemistry, the expression of the alpha-chemokines, interferon (IFN)-gamma-inducible protein-10 (IP-10) and monokine induced by IFN-gamma (Mig), and their receptor CXCR3 have been examined in post-mortem central nervous system (CNS) tissue from MS cases at different stages of lesion development. In actively demyelinating lesions both IP-10 and Mig protein were predominantly expressed by macrophages within the plaque and by reactive astrocytes in the surrounding parenchyma. CXCR3 was expressed by T cells and by astrocytes within the plaque. Interferon-gamma may stimulate glial cells to express IP-10 and Mig, which continue the local inflammatory response by selectively recruiting activated T-lymphocytes into the CNS.

Chemokine modulation of matrix metalloproteinase and TIMP production in adult rat brain microglia and a human microglial cell line in vitro

Matrix metalloproteinases (MMPs) are a family of zinc-dependent enzymes, capable of degrading proteins found in the extracellular matrix. MMPs 2 and 9 are known to be produced by microglia, the resident macrophages of the central nervous system. The control of the secretion of these proteases and the activation of proenzymes by other proteases such as plasmin, as well as the balance between MMP secretion and the secretion of their natural inhibitors (TIMPs), have an important relevance in the pathogenesis of multiple sclerosis (MS). The in vitro control of MMPs 2 and 9, TIMPs 1 and 2, and urokinase-type plasminogen activator by microglia was examined in response to a panel of chemokines (chemotactic cytokines), using ELISA and zymography techniques. The chemokines MCP1, MIP1beta, RANTES, IL-8, and Fractalkine were all found significantly to increase the secretion of MMPs and TIMPs by a human foetal microglial cell line, CHME3, after 24 h stimulation. The chemokines tested, MCP1, MIP1beta, and Fractalkine, were also shown to increase MMP9 secretion by primary isolated rat brain microglia in vitro. MCP1, MIP1alpha/beta, and RANTES significantly decreased the secretion of uPA into culture supernatants in ELISA experiments. These findings suggest an important potential role for the involvement of chemokines in the breakdown of the blood-brain barrier and also the destruction of myelin basic protein in MS.

Chemokines induce migration and changes in actin polymerization in adult rat brain microglia and a human fetal microglial cell line in vitro

Microglia, the resident macrophages of the central nervous system, are the primary cells to respond to injury in the brain, both in inflammation, e.g., in multiple sclerosis, and trauma. Chemokines are potential mediators of microglial cell recruitment to sites of injury; thus, the ability of microglia to migrate in response to a number of chemokines was assessed. The chemokines monocyte chemoattractant protein 1, macrophage inflammatory protein 1alpha, macrophage inflammatory protein 1beta, RANTES (regulated upon activation normal T cell expressed and secreted), interleukin 8, and IP-10 (interferon gamma inducible protein-10), induce migration and changes in the distribution of f-actin in adult rat microglia and a human microglial cell line, CHME3, in vitro. Both cell types show a significant migration response, above control levels, to all the chemokines tested in a typical dose-dependent manner. These chemokines also induced a reorganization of the actin cytoskeleton of the cells. This study indicates that chemokines play an important role in the recruitment of microglia to areas of central nervous system inflammation.

Expression of monocyte chemoattractant protein-1 and other beta-chemokines by resident glia and inflammatory cells in multiple sclerosis lesions

Beta-chemokines induce the directional migration of monocytes and T lymphocytes and are thus associated with chronic inflammation. Using immunocytochemistry and in situ hybridisation (ISH) techniques, we have examined the expression of the beta-chemokines monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and RANTES (regulated upon activation, normal T cell expressed and secreted) in post-mortem human brain from multiple sclerosis (MS) cases, at different stages of lesion development. In actively demyelinating MS plaques RANTES expression was restricted to the blood vessel endothelium, perivascular cells and surrounding astrocytes, suggesting a role in the recruitment of inflammatory cells from the circulation. MCP-1 was expressed by astrocytes and macrophages within acute MS lesions, but was restricted to reactive astrocytes in the parenchyma surrounding the lesion. MIP-1alpha was expressed by astrocytes and macrophages within the plaque, while MIP-1beta was expressed by macrophages and microglia within the lesion, and by microglia in surrounding white matter. Glial cells may be stimulated to produce chemokines and continue the local inflammatory response by forming chemotactic gradients to attract T cells and mononuclear phagocytes from the circulation and surrounding tissue.

Inhibitory effect of interferon-gamma on LPS-induced interleukin 1 beta production by isolated adult rat brain microglia

The effect of interferon-gamma (IFN-gamma) on lipopolysaccharide (LPS)-induced cytokine production has been examined in adult rat brain microglia. Following treatment of isolated cells in vitro with LPS, interleukin-1 (IL-1) and interleukin-6 (IL-6) levels in culture supernatants, determined by bioassay, were increased in a dose-dependent manner. IL-6 was particularly sensitive to LPS-stimulation. Using in situ hybridisation techniques, the induction by LPS of IL-1 and IL-6 mRNA in cultured microglia has been demonstrated. When IFN-gamma was included, LPS-induced production of both IL-1 and IL-6 by microglia was significantly reduced and this effect was particularly marked in the case of IL-1. Comparisons with peritoneal macrophages demonstrate that whilst both cell types produce IL-1 and IL-6 in response to LPS, IFN-gamma had no significant effect on this response in peritoneal macrophages. This suggests potential control mechanisms which may be effective in down-regulating cytokine production by microglia in vivo.

Expression of costimulatory molecules B7-1 (CD80), B7-2 (CD86), and interleukin 12 cytokine in multiple sclerosis lesions

Resting autoreactive T cells are present in the circulation of normal individuals without pathologic consequences. In autoimmune animal models, stimulation of these self-reactive T cells in the presence of costimulatory molecules B7-1 results in T cell-mediated autoimmune disease, whereas B7-2 stimulation generates regulatory autoreactive T cells that abrogate disease severity. Thus, reactivation in the brain of myelin-autoreactive T cells by antigen with costimulatory molecules may be a critical event in the pathophysiology of multiple sclerosis (MS), a putative autoimmune disease of central nervous system (CNS) myelin. We investigated the expression of cytokines and costimulatory molecules in a panel of 41 histologically characterized CNS specimens from 15 MS and 10 control cases using semiquantitative reverse transcriptase-polymerase chain reaction and immunocytochemistry. In four cases, vascular CNS infarcts with inflammation were compared with MS plaques from the same brain. We observed increased expression of B7-1 and interleukin (IL) 12p40 in acute MS plaques, particularly from early disease cases but not in inflammatory infarcts. B7-1 staining was localized predominantly to the lymphocytes in perivenular inflammatory cuffs but not the parenchyma. In contrast, B7-2 was expressed predominantly on macrophages both in MS lesions of varied time duration and in inflammatory infarcts. These findings indicate that an early event in the initiation of MS involves upregulation of B7-1 and IL-12, resulting in conditions that maximally stimulate T cell activation and induction of T helper 1-type immune responses.

Cytokine production in the central nervous system

Cytokines participate in normal physiologic events within the CNS. At times of infection and inflammation, their role is emphasized by the upregulation of cytokines and their receptors within the CNS, with concomitant effects on brain function. Cytokines produced by glial cells, T cells, and macrophages interact within the CNS to determine the outcome of the inflammatory reaction. Cytokines have been implicated in the pathogenesis of many CNS diseases, including multiple sclerosis (MS), and their role continues to be intensely investigated. The possibility of novel cytokine therapies, such as anticytokine antibodies or receptor antagonists acting on the cytokine network, provides an optimistic future for treatment of MS and other CNS diseases in which cytokines have been implicated.

In situ hybridization in neuropathology

In situ hybridization (ISH) allows the demonstration and localization of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in tissue sections, cells and chromosomes by utilizing a specific interaction with a labelled nucleotide probe of known composition. Although this technique has been employed for many years using radiolabelled probes, the recent development of nonisotopic labelling systems and the greatly increased availability of synthetic nucleic acids has allowed an enormous expansion in the potential applications of ISH. The technique is now applicable to unfixed and fixed tissues, including archival material. The use of enzyme-linked antibody techniques to detect labelled probes has greatly increased the sensitivity of non-isotopic ISH without a loss of specificity. The successful use of ISH demands careful selection of labelled probes, adequate tissue pretreatment to allow access of the probe, control of the stringency of probe binding and a sensitive reporter system, in addition to adequate controls. The accurate localization of nucleotides in the central nervous system (CNS) has many current research applications in the study of gene expression in multiple sclerosis and other inflammatory disorders, and a wide range of neurodegenerative disorders, viral infections and neoplasms. The technique is of diagnostic value in viral disorders, particularly where multiple infections occur. The combination of non-isotopic ISH with immunocytochemistry electron microscopy and quantitative image analysis greatly increases its research potential, while the development of a related method, the in situ polymerase chain reaction, offers an additional opportunity for further enhancing the sensitivity of this technique.

Increased expression of high affinity IL-2 receptors and beta-adrenoceptors on peripheral blood mononuclear cells is associated with clinical and MRI activity in multiple sclerosis

Enhanced expression of beta-adrenoceptor densities on peripheral blood mononuclear cells (PBMCs) in progressive multiple sclerosis patients has been observed in a number of independent studies. A link between increased number of beta-adrenoceptors and inflammatory disease has been further indicated by studies in rheumatoid arthritis and relapsing-remitting multiple sclerosis patients. In a serial monthly assessment of relapsing-remitting multiple sclerosis patients, we have demonstrated that increased beta-adrenoceptors on PBMCs correlate with the expression of high affinity interleukin-2 receptors (IL-2Rs) and disease activity as determined by clinical and MRI findings. Magnetic resonance imaging activity was strongly correlated with IL-2R expression and it appears to be a sensitive marker of PBMC immunoactivation in multiple sclerosis. In vitro studies showed that beta-agonist stimulation of PBMCs reduces the IL-2R expression and suppresses cell proliferation following mitogenic stimulation. This observation may indicate a recovery role for the enhanced beta-adrenoceptor expression in multiple sclerosis. However, its therapeutic importance remains to be tested by appropriate trials using either beta-agonists or agents activating the second messenger system, c-AMP, in lymphocytes.

Myelin basic protein content of aggregating rat brain cell cultures treated with cytokines and/or demyelinating antibody: effects of macrophage enrichment

The demyelinative potential of the cytokines interleukin-1 alpha (IL-1 alpha), interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha) has been investigated in myelinating aggregate brain cell cultures. Treatment of myelinated cultures with these cytokines resulted in a reduction in myelin basic protein (MBP) content. This effect was additively increased by anti-myelin/oligodendrocyte glycoprotein (alpha-MOG) in the presence of complement. Qualitative immunocytochemistry demonstrated that peritoneal macrophages, added to the fetal telencephalon cell suspensions at the start of the culture period, successfully integrated into aggregate cultures. Supplementing the macrophage component of the cultures in this fashion resulted in increased accumulation of MBP. The effect of IFN-gamma on MBP content of cultures was not affected by the presence of macrophages in increased numbers.

Cytokine mRNA expression in inflammatory multiple sclerosis lesions: detection by non-radioactive in situ hybridization

The predominant pathological features in the central nervous system (CNS) in multiple sclerosis (MS) are perivascular inflammation and demyelination. The cells in the inflammatory cuff consist mainly of T lymphocytes and macrophages. Cytokines produced by inflammatory cells within the CNS have the potential to enhance local inflammation and promote phagocytosis of myelin by macrophages, resulting in demyelination. Resident brain cells, microglia and astrocytes, also produce cytokines after stimulation in vitro. We have applied the technique of non-radioactive in situ hybridization to examine which cells in the CNS are producing cytokines in MS. Using digoxigenin-labelled oligonucleotide probes we have detected expression of the cytokines IL-1 alpha, IL-2, IL-4, IL-6, IL-10, IFN-gamma, TGF beta 1 & 2 and TNF-alpha in frozen sections of CNS tissue from MS cases. The intensity and distribution of the staining for mRNA is cytokine specific, IL-6, IFN-gamma and TNF-alpha predominating in the perivascular inflammatory cuffs, the others being more weakly expressed. Expression of all cytokine mRNAs is stronger in perivascular cells rather than in parenchymal cells, suggesting that circulating inflammatory cells which have crossed the blood brain barrier are the major source of cytokines in MS tissue.

Modulation of interferon-gamma-induced major histocompatibility complex class II and Fc receptor expression on isolated microglia by transforming growth factor-beta 1, interleukin-4, noradrenaline and glucocorticoids

Interleukin-4 (IL-4) enhances Fc receptor (FcR) expression on isolated rat brain microglia and peritoneal macrophages but has little effect on major histocompatibility complex (MHC) class II antigen expression. In contrast transforming growth factor-beta 1 (TGF-beta 1) causes a reduction in expression of MHC class II on macrophages and of FcR on both cell types. Both microglia and peritoneal macrophages demonstrate enhanced expression of FcR and MHC class II on treatment with interferon-gamma (IFN-gamma). The effect of IL-4 or TGF-beta 1 in combination with IFN-gamma, added either sequentially or simultaneously, has been investigated. TGF-beta 1 down-regulates IFN-gamma-induced effects in both microglia and macrophages when present before or during the activation stage. In combination, IL-4 and IFN-gamma can be additive or antagonistic, depending on their concentrations and the sequence in which cells are exposed to the cytokines. Non-cytokine mediators present during stimulation, such as noradrenaline, dexamethasone and corticosterone, are also potent inhibitors of IFN-gamma-induced activation of microglia and macrophages.

Regulation of Fc receptor and major histocompatibility complex antigen expression on isolated rat microglia by tumour necrosis factor, interleukin-1 and lipopolysaccharide: effects on interferon-gamma induced activation

Isolated rat brain microglia display enhanced expression of Fc receptors on treatment with interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) and lipopolysaccharide (LPS), whereas major histocompatibility complex (MHC) antigen expression is enhanced only by IFN-gamma. Although TNF and LPS individually have no effect on MHC expression by microglia, they both antagonize IFN-gamma-induced expression. The enhanced expression of Fc receptors observed in the presence of IFN-gamma, TNF or LPS is significantly inhibited by the combination of IFN-gamma with either LPS or TNF. IL-1 alpha has little effect on IFN-gamma-induced MHC or Fc receptor expression by microglia. Peritoneal macrophages behave similarly to microglia, with the notable exception that IL-1 alpha enhances IFN-gamma-induced FcR expression. These observations suggest that the functional activity of microglia during inflammation or demyelination in the central nervous system can be influenced by the changing profile of cytokines present during lesion development.

Detection of interleukin-1 and interleukin-6 in adult rat brain, following mechanical injury, by in vivo microdialysis: evidence of a role for microglia in cytokine production

In vivo levels of interleukin-1 (IL-1) and IL-6, present in the interstitial spaces of brain, have been repeatedly monitored up to 7 days after insertion of a microdialysis probe, designed to induce mechanical trauma to the brain. IL-1 is barely detectable immediately after implantation but over a 24-48 h period a 15-fold increase is seen. In contrast IL-6 levels at day 0 are high, increasing slightly (10%) by day 1 but decreasing to 40% by day 2. The temporal pattern of IL-6 recovery in the cerebrospinal fluid was similar to that in the dialysate but the levels were significantly lower and may reflect diffusion from the site of the probe lesion. Cellular sources of these cytokines include macrophages and neutrophils, which have infiltrated the lesion and microglia resident in the brain, which can be identified at the lesion site within 24 h of probe implantation. The astrocytic response to injury, evidenced by increased glial fibrillary acidic protein staining occurs much later, by day 7, and is unlikely to be responsible for IL-1 and IL-6 production found at 24-48 h. Since upon isolation and stimulation of microglia in vitro with lipopolysaccharide IL-1 and IL-6 can be measured in the supernatant, it would appear that they have the capacity to produce cytokines in vivo. Localised synthesis of cytokines at sites of brain injury by microglia would further stimulate microglia in an autocrine manner and also propagate the astrocytic reaction.

Histopathology of multiple sclerosis lesions detected by magnetic resonance imaging in unfixed postmortem central nervous system tissue

Postmortem unfixed whole brains from 17 multiple sclerosis and 6 control cases were examined by magnetic resonance imaging (MRI) using a T2-weighted spin echo sequence and histology to determine the relationship between areas of abnormal MRI signal and underlying pathological change. In group 1, small MRI lesions and correspondingly small plaques, most of which were chronic, were detected histologically in 5 brains. In 4 brains there were more extensive areas of both abnormal signal and histological plaques which were more often active (group 2). However, in a further 5 brains extensive MRI abnormalities were observed when only small periventricular plaques were present histologically (group 3). Lesions in the hindbrain and cerebral grey matter were infrequently observed by MRI. The extensive MRI abnormalities seen in areas in which only small histological plaques were found may be the result of vascular permeability changes in the normal-appearing white matter surrounding plaques.

Fc receptor density, MHC antigen expression and superoxide production are increased in interferon-gamma-treated microglia isolated from adult rat brain

Treatment of microglia isolated from adult rat brain with interferon-gamma (IFN-gamma) at a concentration of 1 U/ml resulted in enhanced expression of Fc receptors and major histocompatibility complex (MHC) antigens and increased production of superoxide anions. Neonatal microglia and peritoneal macrophages, isolated and cultured in the same manner, displayed functional properties very similar to those of adult microglia, indicating a common origin for different macrophage populations. The Fc binding capacity of microglia was found to be significantly greater than that of peritoneal cells, thus underlining the potential role of microglia in immune-mediated demyelination.

The nature of inflammatory components during demyelination in multiple sclerosis

Immune reactivity in the central nervous system (CNS) in multiple sclerosis (MS) can be fuelled by activated T lymphocytes sequestered in the brain and those entering systemically. The perivascular cuff of the inflammatory lesion consists predominantly of T cells and macrophages, while the hypercellular interface between normal and degenerating myelin is comprised mainly of macrophages and activated microglia. MHC class II+ cells are abundant in the hypercellular zone and expression of both the polymorphic and invariant chains of the molecule are expressed beyond the plaque edge in the white matter where the staining is restricted largely to microglia. Under carefully controlled staining conditions expression of MHC class II can be demonstrated on microglia in control white matter. Thus the immunological privilege of the CNS does not appear to preclude constitutive expression of MHC antigens or prevent the traffic of activated lymphocytes into the brain parenchyma. However, the antigens priming the immune reaction in the CNS in MS and the role of antibodies in the demyelinating process remain a matter for speculation and the exact mechanisms of demyelination are as yet unresolved.

Characterisation of microglia isolated from adult human and rat brain

A method has been developed to isolate microglia from adult human and rat brain cell suspensions by rosette formation via Fc receptors. Immunocytochemical characterisation of the cells immediately following isolation and after 7-10 days in vitro with a panel of monoclonal antibodies has demonstrated that microglia from adult brain have the phenotypic characteristics and phagocytic capacity of mononuclear phagocytes, but lack the hydrolytic enzyme, non-specific esterase. The ability to isolate rapidly a purified population of microglia from adult brain provides a means for investigating mechanisms of activation and differentiation of tissue macrophages, which could elucidate their role in inflammation of the central nervous system.

Microglia are the major cell type expressing MHC class II in human white matter

In normal human white matter the predominant cell type expressing MHC Class II is the microglia. This population of cells reacts with the pan macrophage marker, EBM/11, and constitutes about 13% of the glial cell population. The intensity of staining was enhanced and the absolute number of Class II+ microglia increased in normal appearing white matter from multiple sclerosis (MS) brain. As T cell activation in MS may occur in the brain the upregulation of microglia bearing MHC Class II may reflect their function as antigen presenting cells in the development of inflammatory lesions.

Distribution of glial fibrillary acidic protein in gliosed human white matter

Glial fibrillary acidic protein (GFAP) in gliosed white matter from multiple sclerosis plaques and cerebral infarcts was examined by polyacrylamide gel electrophoresis and immunoblotting. Using a monoclonal antibody raised against human GFAP, up to 11 GFAP polypeptide bands of molecular weight 37-49 kilodaltons were identified in particulate and supernatant fractions of CNS tissue homogenates. Soluble GFAP constituted about one-quarter of the total GFAP in normal cerebral white matter. In brain lesions in which reactive astrocytes were observed microscopically, the proportion of soluble GFAP was increased, with a greater representation of the lower-molecular-weight forms. In brain chronic sclerotic plaques, almost all of the GFAP was in the particulate form. Purified particulate GFAP was susceptible to proteolysis at acid but not at neutral pH in the presence of CNS homogenates. In tissue autolysis studies, GFAP was stable in situ for periods well in excess of average CNS postmortem times.

Immunocytochemical characterisation of the immune reaction in the central nervous system in multiple sclerosis. Possible role for microglia in lesion growth

As there is evidence that in multiple sclerosis T-cell activation occurs in the central nervous system rather than outside, the inflammatory lesion may be extended through antigen presentation by cells at the edge of the plaque. In this study we present an immunocytochemical report on CNS tissue from an active case of MS, with an analysis of the distribution of CD4 and CD8 binding T cells and the expression of class I and II MHC determinants in plaques and white matter. Perivascular cuffs of early lesions, as judged by hypercellularity and minimal demyelination, contained activated T (Tac+) cells, which reacted with an anti-IL-2 monoclonal antibody. Thus sufficient T-cell growth factor would appear to be present to fuel the immune reaction in a growing lesion. The preponderance of T cells of the cytotoxic/suppressor (CD8) phenotype in the CNS parenchyma was found in conjunction with widespread staining of class I MHC antigen, a prerequisite for activity of cytotoxic T cells. Potential antigen presenting cells were demonstrated in MS plaques with a monoclonal antibody against the cytoplasmic, invariant chain of class II MHC. Macrophages and astrocytes, contributed to the staining in the hypercellular plaque border while the distribution of class II+ microglia in white matter suggest they may also be of importance in local antigen presentation.

Human muscle cell surface antigen 16.3A5 is encoded by a gene on chromosome 11

A monoclonal antibody (McAb), 16.3A5, has been characterized that reacts with a cell surface antigen of human muscle cells and a variety of nonmuscle cells. The gene controlling synthesis of 16.3A5 antigen has been assigned to human chromosome 11 by assessing McAb reactivity on a panel of mouse-human cell hybrids. The 16.3A5 has a novel specificity distinct from other chromosome 11-encoded antigens such as W6/34, F10.44.2, TRA1.10, and 4D12 antigens.

An analysis of contractile proteins in developing chick heart by SDS polyacrylamide gel electrophoresis and electron microscopy

Chick heart development was studied using transmission electron microscopy and SDS-polyacrylamide gel electrophoresis in combination with densitometry. Myosin heavy chain, alpha-actinin, actin and tropomyosin accumulations were analysed in developing hearts from preheartbeat stage 9 (Hamburger-Hamilton staging series) through 2 days after hatching. At the preheartbeat stage, electron microscopy revealed a significant number of thin filaments scattered throughout the cytoplasm of the myoblasts; however, very few thick filaments were seen. There was no obvious association between the two filament types. SDS-polyacrylamide tube gels of heart muscle homogenates demonstrated the presence of all five proteins in hearts at the preheartbeat stage. Further analyses of the proteins by gel densitometry indicated that both actin and myosin accumulated rapidly during heart development while alpha-actinin and tropomyosin levels remained relatively static. Our results show that detectable quantities of myosin heavy chain, alpha-actinin, actin and tropomyosin accumulate in myocardial cells prior to the appearance of myofibrils and initiation of the contractile function.

Evidence for the importance of arginine residues in pig kidney alkaline phosphatase

The arginine-specific reagents 2,3-butanedione and phenylglyoxal inactivate pig kidney alkaline phosphatase. As inactivation proceeds there is a progressive fall in Vmax. of the enzyme, but no demonstrable change in the Km value for substrate. Pi, a competitive inhibitor, and AMP, a substrate of the enzyme, protect alkaline phosphatase against the arginine-specific reagents. These effects are explicable by the assumption that the enzyme contains an essential arginine residue at the active site. Protection is also afforded by the uncompetitive inhibitor NADH through a partially competive action against the reagents. Enzyme that has been exposed to the reagents has a decreased sensitivity to NADH inhibition. It is suggested that an arginine residue is important for NADH binding also, although this residue is distinct from that at the catalytic site. The protection given by NADH against loss of activity is indicative of the close proximity of the active and NADH sites.