Immunohistological analysis of macrophages in the central nervous system of Lewis rats with acute experimental allergic encephalomyelitis

The Role of the Intestinal Microbiome in Multiple Sclerosis-Lessons to Be Learned from Hippocrates

Based on recent advances in research of chronic inflammatory conditions, there is a growing body of evidence that suggests a close correlation between the microbiota of the gastrointestinal tract and the physiologic activity of the immune system. This raises the idea that disturbances of the GI ecosystem contribute to the unfolding of chronic diseases including neurodegenerative pathologies. Here, we overview our current understanding on the putative interaction between the gut microbiota and the immune system from the aspect of multiple sclerosis, one of the autoimmune conditions accompanied by severe chronic neuroinflammation that affects millions of people worldwide.

Inhibition of N-acylethanolamine-hydrolyzing acid amidase reduces T cell infiltration in a mouse model of multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis (MS), in which myeloid cells sustain inflammation, take part in priming, differentiation, and reactivation of myelin-specific T cells, and cause direct myelin damage. N-Acylethanolamine-hydrolyzing acid amidase (NAAA) is a proinflammatory enzyme induced by phlogosis and overexpressed in macrophages and microglia of EAE mice. Targeting these cell populations by inhibiting NAAA may be a promising pharmacological strategy to modulate the inflammatory aspect of MS and manage disease progression. To address this goal, we used ARN16186, a small molecule specifically designed and synthesized as a pharmacological tool to inhibit NAAA. We assessed whether enzyme inhibition affected the severity of neurological symptoms and modulated immune cell infiltration into the central nervous system of EAE mice. We found that preventive chronic treatment with ARN16186 was efficacious in slowing disease progression and preserving locomotor activity in EAE mice. Furthermore, NAAA inhibition reduced the number of immune cells infiltrating the spinal cord and modulated the overactivation of NF-kB and STAT3 transcription factors, leading to less expansion of Th17 cells over the course of the disease.

Dopaminergic Receptor Targeting in Multiple Sclerosis: Is There Therapeutic Potential?

Dopamine is a neurotransmitter that mediates neuropsychological functions of the central nervous system (CNS). Recent studies have shown the modulatory effect of dopamine on the cells of innate and adaptive immune systems, including Th17 cells, which play a critical role in inflammatory diseases of the CNS. This article reviews the literature data on the role of dopamine in the regulation of neuroinflammation in multiple sclerosis (MS). The influence of dopaminergic receptor targeting on experimental autoimmune encephalomyelitis (EAE) and MS pathogenesis, as well as the therapeutic potential of dopaminergic drugs as add-on pathogenetic therapy of MS, is discussed.

Serotoninergic system targeting in multiple sclerosis: the prospective for pathogenetic therapy

Serotonin (5-hydroxytryptamine) (5-HT) is a neurotransmitter, which mediates neuropsychological functions of the central nervous system (CNS). Recent studies have shown the modulatory effect of 5-HT on gut microbiota functions, which play an essential role in developing CNS inflammatory diseases. Finally, 5-HT is a direct mediator of neuroimmune interaction. The article reviews the literature data on the role of 5-HT in the regulation of neuroinflammation in multiple sclerosis (MS). The influence of 5-HT and selective serotonin reuptake inhibitors (SSRIs) on experimental autoimmune encephalomyelitis (EAE) and MS pathogenesis, as well as the therapeutic potential of serotoninergic drugs as a pathogenetic therapy of MS, are discussed.

Nanomodulation of Macrophages in Multiple Sclerosis

Multiple Sclerosis (MS) is a chronic demyelinating autoimmune disease primarily affecting young adults. Despite an unclear causal factor, symptoms and pathology arise from the infiltration of peripheral immune cells across the blood brain barrier. Accounting for the largest fraction of this infiltrate, macrophages are functionally heterogeneous innate immune cells capable of adopting either a pro or an anti-inflammatory phenotype, a phenomenon dependent upon cytokine milieu in the CNS. This functional plasticity is of key relevance in MS, where the pro-inflammatory state dominates the early stage, instructing demyelination and axonal loss while the later anti-inflammatory state holds a key role in promoting tissue repair and regeneration in later remission. This review highlights a potential therapeutic benefit of modulating macrophage polarisation to harness the anti-inflammatory and reparative state in MS. Here, we outline the role of macrophages in MS and look at the role of current FDA approved therapeutics in macrophage polarisation. Moreover, we explore the potential of particulate carriers as a novel strategy to manipulate polarisation states in macrophages, whilst examining how optimising macrophage uptake via nanoparticle size and functionalisation could offer a novel therapeutic approach for MS.

Analysis of the direct injury effector of oligodendroglia cells or myelin sheath in an experimental allergic encephalomyelitis model induced by the MOG35-55 peptide

The aim of the present study was to investigate the possible role of cytotoxic T lymphocytes (CTL) and mononuclear macrophages in the pathogenic processes of experimental animals. To construct a chronic experimental allergic encephalomyelitis (EAE) model, an artificially synthesized myelin oligodendrocyte glycoprotein (MOG)35‑55 peptide was used to induce C57BL/6 mice. Subsequently, the experimental animals were investigated at the level of their nervous function, and histopathological, immunohistochemical and fluorescence immunohistochemical experiments were performed at different time points following immunization. The expression of immune molecules and cytokines associated with the activation of the mononuclear macrophages and CTL during the different stages was assessed by western blotting and reverse transcription‑quantitative polymerase chain reaction. As a result, the MOG35‑55 peptide was identified as being successful at inducing C57BL/6 mice for the development of the EAE model. A modest level of mononuclear macrophage and lymphocyte infiltration was observed in the central nervous system (CNS), although no infiltration of neutrophils was observed. A sporadic flaky deletion of the myelin sheath was also identified. The activation and proliferation of mononuclear macrophages, including microglia cells, was clearly demonstrated. Furthermore, the expression levels of major histocompatibility complex class I and II molecules and interleukin‑12 in the brain, which is associated with the activation and proliferation of mononuclear macrophages, increased over the duration of the experiment compared with less pronounced changes in the expression levels of interferon (IFN)‑γ, Fas and perforin in the CNS, which are associated with the function of CTL. The secretion of IFN‑γ in the spleen increased during the morbidity peak, however, any noticeable activation and proliferation of CD8+ T cells was absent. These results demonstrated that the induced immune response mediated by mononuclear macrophages made a more important contribution compared with CTL towards the pathological process of myelin sheath injury. Mononuclear macrophages are therefore, identified as being one of the most significant effector cell types to directly injure the myelin sheath in the CNS.

Sialoadhesin - a macrophage-restricted marker of immunoregulation and inflammation

Sialoadhesin (Sn, also known as Siglec-1 and CD169) is a macrophage-restricted cell surface receptor that is conserved across mammals. Sn is a member of the sialic acid-binding IgG-like lectin (Siglec) family of proteins characterized by affinity to specifically sialylated ligands, and under normal conditions is expressed on subsets of macrophages in secondary lymphoid tissues, such as lymph node and spleen. However, Sn-positive macrophages can also be found in a variety of pathological conditions, including (autoimmune) inflammatory infiltrates and tumours. Sn has been shown to contribute to sialylated pathogen uptake, antigen presentation and lymphocyte proliferation, and to influence both immunity and tolerance. This review presents Sn as a macrophage-specific marker of inflammation and immunoregulation with the potential to becoming an important biomarker for immunologically active macrophages and a target for therapy.

Anti-inflammatory effects of the anticonvulsant drug levetiracetam on electrophysiological properties of astroglia are mediated via TGFβ1 regulation

BACKGROUND AND PURPOSE

The involvement of astrocytes as immune-competent players in inflammation and the pathogenesis of epilepsy and seizure-induced brain damage has recently been recognized. In clinical trials and practice, levetiracetam (LEV) has proven to be an effective antiepileptic drug (AED) in various forms of epileptic seizures, when applied as mono- or added therapy. Little is known about the mechanism(s) of action of LEV. Evidence so far suggests a mode of action different from that of classical AEDs. We have shown that LEV restored functional gap junction coupling and basic membrane properties in an astrocytic inflammatory model in vitro.

EXPERIMENTAL APPROACH

Here, we used neonatal rat astrocytes co-cultured with high proportions (30%) of activated microglia or treated with the pro-inflammatory cytokine interleukin-1β to provoke inflammatory responses. Effects of LEV (50 µg·mL⁻¹) on electrophysiological properties of astrocytes (by whole cell patch clamp) and on secretion of TGFβ1 (by (ELISA)) were studied in these co-cultures.

KEY RESULTS

LEV restored impaired astrocyte membrane resting potentials via modification of inward and outward rectifier currents, and promoted TGFβ1 expression in inflammatory and control co-cultures. Furthermore, LEV and TGFβ1 exhibited similar facilitating effects on the generation of astrocyte voltage-gated currents in inflammatory co-cultures and the effects of LEV were prevented by antibody to TGFβ1.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that LEV is likely to reduce the harmful spread of excitation elicited by seizure events within the astro-glial functional syncytium, with stabilizing consequences for neuronal-glial interactions.

Sialoadhesin-deficient mice exhibit subtle changes in B- and T-cell populations and reduced immunoglobulin M levels

Sialoadhesin (Sn, also called Siglec-1 or CD169) is a transmembrane receptor and the prototypic member of the Siglec family of sialic acid binding immunoglobulin-like lectins. It is expressed on specialized subsets of resident macrophages in hematopoietic and lymphoid tissues and on inflammatory macrophages. In order to investigate its function, we generated Sn-deficient mice and confirmed that these mice are true nulls by fluorescence-activated cell sorter analysis and immunohistochemistry. Mice deficient in Sn were viable and fertile and showed no developmental abnormalities. Analysis of cell populations revealed no differences in bone marrow, peritoneal cavity, and thymus, but there was a small increase in CD8 T cells and a decrease in B220-positive cells in spleens and lymph nodes of Sn-deficient mice. Furthermore, in spleen there was a slight decrease in follicular B cells with an increase in numbers of marginal zone B cells. B- and T-cell maturation as well as responses to stimulation with thioglycolate were only slightly affected by Sn deficiency. Immunoglobulin titers in Sn-deficient mice were significantly decreased for immunoglobulin M (IgM) but similar for IgG subclasses. These results suggest a role for sialoadhesin in regulating cells of the immune system rather than in influencing steady-state hematopoiesis.

Effects of cytokines on microglial phenotypes and astroglial coupling in an inflammatory coculture model

Cytokines play an important role in the onset, regulation, and propagation of immune and inflammatory responses within the central nervous system (CNS). The main source of cytokines in the CNS are microglial cells. Under inflammatory conditions, microglial cells are capable of producing pro- and antiinflammatory cytokines, which convey essential impact on the glial and neuronal environment. One paramount functional feature of astrocytes is their ability to form a functionally coupled syncytium. The structural link, which is responsible for the syncytial behavior of astrocytes, is provided by gap junctions. The present study was performed to evaluate the influence of inflammation related cytokines on an astroglial/microglial inflammatory model. Primary astrocytic cultures of newborn rats were cocultured with either 5% (M5) or 30% (M30) microglial cells and were incubated with the following proinflammatory cytokines: tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interferon-gamma (IFN-gamma), and the antiinflammatory cytokines transforming growth factor-beta1 (TGF-beta1) and IFN-beta. Under these conditions, i.e., incubation with the inflammatory cytokines and the high fraction of microglia (M30), microglial cells revealed a significant increase of activated round phagocytotic cells accompanied by a reduction of astroglial connexin 43 (Cx43) expression, a reduced functional coupling together with depolarization of the membrane resting potential (MRP). When the antiinflammatory mediator TGF-beta1 was added to proinflammatory altered M30 cocultures, a reversion of microglial activation and reconstitution of functional coupling together with recovery of the astroglial MRP was achieved. Finally IFN-beta, added to M5 cocultures was able to prevent the effects of the proinflammatory cytokines TNF-alpha, IL-1beta, and IFN-gamma.

Discovery and Pharmacological Characterization of a Novel Rodent-Active CCR2 Antagonist, INCB3344

This report describes the characterization of INCB3344, a novel, potent and selective small molecule antagonist of the mouse CCR2 receptor. The lack of rodent cross-reactivity inherent in the small molecule CCR2 antagonists discovered to date has precluded pharmacological studies of antagonists of this receptor and its therapeutic relevance. In vitro, INCB3344 inhibits the binding of CCL2 to mouse monocytes with nanomolar potency (IC(50) = 10 nM) and displays dose-dependent inhibition of CCL2-mediated functional responses such as ERK phosphorylation and chemotaxis with similar potency. Against a panel of G protein-coupled receptors that includes other CC chemokine receptors, INCB3344 is at least 100-fold selective for CCR2. INCB3344 possesses good oral bioavailability and systemic exposure in rodents that allows in vivo pharmacological studies. INCB3344 treatment results in a dose-dependent inhibition of macrophage influx in a mouse model of delayed-type hypersensitivity. The histopathological analysis of tissues from the delayed-type hypersensitivity model demonstrates that inhibition of CCR2 leads to a substantial reduction in tissue inflammation, suggesting that macrophages play an orchestrating role in immune-based inflammatory reactions. These results led to the investigation of INCB3344 in inflammatory disease models. We demonstrate that therapeutic dosing of INCB3344 significantly reduces disease in mice subjected to experimental autoimmune encephalomyelitis, a model of multiple sclerosis, as well as a rat model of inflammatory arthritis. In summary, we present the first report on the pharmacological characterization of a selective, potent and rodent-active small molecule CCR2 antagonist. These data support targeting this receptor for the treatment of chronic inflammatory diseases.

Antigenized antibodies expressing Vbeta8.2 TCR peptides immunize against rat experimental allergic encephalomyelitis

Background

Immunity against the T cell receptor (TCR) is considered to play a central role in the regulation of experimental allergic encephalomyelitis (EAE), a model system of autoimmune disease characterized by a restricted usage of TCR genes. Methods of specific vaccination against the TCR of pathogenetic T cells have included attenuated T cells and synthetic peptides from the sequence of the TCR. These approaches have led to the concept that anti-idiotypic immunity against antigenic sites of the TCR, which are a key regulatory element in this disease.

Methods

The present study in the Lewis rat used a conventional idiotypic immunization based on antigenized antibodies expressing selected peptide sequences of the Vβ8.2 TCR (⁹³ASSDSSNTE¹⁰¹ and ³⁹DMGHGLRLIHYSYDVNSTEKG⁵⁹).

Results

The study demonstrates that vaccination with antigenized antibodies markedly attenuates, and in some instances, prevents clinical EAE induced with the encephalitogenic peptide ⁶⁸GSLPQKSQRSQDENPVVHF⁸⁸ in complete Freunds' adjuvant (CFA). Antigenized antibodies induced an anti-idiotypic response against the Vβ8.2 TCR, which was detected by ELISA and flowcytometry. No evidence was obtained of a T cell response against the corresponding Vβ8.2 TCR peptides.

Conclusions

The results indicate that antigenized antibodies expressing conformationally-constrained TCR peptides are a simple means to induce humoral anti-idiotypic immunity against the TCR and to vaccinate against EAE. The study also suggests the possibility to target idiotypic determinants of TCR borne on pathogenetic T cells to vaccinate against disease.

Microglia activation influences dye coupling and Cx43 expression of the astrocytic network

Under inflammatory conditions, activated microglia are capable of producing proinflammatory cytokines that are reported to influence cell-to-cell communication. The present study was performed to evaluate the influence of microglial activation on the coupling efficiency of the astroglial network. Primary astrocyte cultures of newborn rats were cocultured with either 5% (M5) or 30% (M30) microglia. Microglial activation (rounded phagocytotic phenotype) was investigated using the monoclonal anti-ED1 antibody, and immunofluorescence with a polyclonal anti-Cx43 antibody was used to study astroglial Cx43 expression and distribution. Functional coupling of astrocytes was evaluated by monitoring the transfer of microinjected Lucifer yellow into neighboring cells. The data obtained can be summarized as follows: astroglia/M30 cocultures contained significantly fewer resting microglia and significantly more activated microglia than the M5 cocultures; significantly reduced astroglial Cx43 staining was found in M30 cocultures concurrently with a reduced number of dye coupled astrocytes; and the positive correlation of percent activated microglia with reduced astroglial Cx43 expression was highly significant, indicating that the degree of intercellular communication in the astroglial network may be modulated by the activation of microglia under in vitro conditions.

Development of Neurons and Glial Cells in Cerebral Cortex, Cultured in the Presence or Absence of Bioelectric Activity: Morphological Observations

Chronic blockade of bioelectric activity (BEA) has been shown to increase neuronal cell death in tissue culture, but the effects of this treatment on non-neuronal cells have not been investigated. To determine which cell types are affected by chronic suppression of BEA, we investigated their morphological development in primary cultures of rat cerebral cortex, grown with or without the sodium channel blocker tetrodotoxin (TTX). Morphological development was monitored by phase-contrast microscopy and by immunofluorescent staining of markers specific for neurons (NSE, MAP2, B-50, and the 200 kD neurofilament protein), astrocytes (GFAP), oligodendrocytes (galactocerebroside), macrophages (ED-1) and fibroblasts (fibronectin). Neurons in control cultures steadily increased in size and elaborated a dense network of axons and dendrites during the first 3 weeks. Astrocytes proliferated strongly and formed a 'bottom-layer' on which other cells grew. Part of the astrocytes migrated into the peripheral area of the culture, but retracted to the centre after 14 days in vitro (DIV). Oligodendrocytes and macrophages also increased in number, but oligodendrocytes were completely lost by 28 DIV. After 3 weeks, axons that had grown into the periphery of the culture gradually retracted and/or degenerated, following the retracting astrocytes. Some of the neurons died after 21 DIV, but a large part persisted until 42 DIV. Upon TTX treatment from 5/6 DIV, cultures with few macrophages showed an increase in the proportion of necrotic nuclei at 14 and 21 DIV. The retraction of peripherally located fibres was accelerated by 3 - 4 days and their degeneration was augmented. Neuronal density decreased to zero between 21 and 42 DIV. Astrocytes showed a clear decrease in density from 28 DIV. Conversely, the density of macrophages was increased about two-fold from 14 DIV. These results indicate that both neurons and glia are affected by chronic TTX treatment.

Fractalkine expression and the recruitment of CX3CR1+ cells in the prolonged mesangial proliferative glomerulonephritis

BACKGROUND

We established the reversible and the prolonged models of mesangial proliferative glomerulonephritis (GN) with anti-Thy 1 antibody 1-22-3. However, the essential factors leading to the prolonged glomerular alterations have not been identified.

METHODS

The expressions of several chemokines and cytokines were compared in the reversible and the prolonged models. Expression of fractalkine and the number of the fractalkine receptor CX3CR1-positive cells in the glomeruli in the prolonged model were significantly higher than those in the reversible model. Then, the localization of fractalkine and the characteristics of CX3CR1+ cells were analyzed in glomeruli. To elucidate the significance of the fractalkine expression, we analyzed the expression in the model treated with angiotensin II receptor antagonist, candesartan.

RESULTS

Immunostaining of fractalkine was detected on endothelial cells on the fifth day, and fractalkine staining also was detected in the mesangial area on day 14. Major parts of the CX3CR1+ cells in the glomeruli were macrophages, especially ED3+ cells. Candesartan treatment ameliorated the glomerular morphological findings at six weeks after disease induction. Although the treatment did not ameliorate the morphological finding at two weeks, decreased expression of fractalkine and CX3CR1+ were already detected at two weeks in rats treated with candesartan.

CONCLUSIONS

Fractalkine expression and the recruitment of CX3CR1+ cells in glomeruli might play an important role in the development of the prolonged disease. These expressions could be predictors of the prolonged disease of the mesangial proliferative glomerulonephritis.

FK506 ameliorates proteinuria and glomerular lesions induced by anti-Thy 1.1 monoclonal antibody 1-22-3

BACKGROUND

We have previously reported that CD4 T lymphocytes and their cytokines contribute to development of Thy 1.1 glomerulonephritis (GN). FK506 is reported to suppress the production of Th1 cytokines. The aims of this study were to elucidate the role of Th1 cytokines on mesangial alteration and to examine whether FK506 is available for therapy of mesangial proliferative GN.

METHODS

The effects of daily treatments of FK506 from day -5 and from day +1 of Thy 1.1 GN induction on glomerular alterations were analyzed.

RESULTS

FK506 treatment with 1.0 and 0.3 mg/kg body weight (BW) daily from day 1 to day 4 significantly reduced the glomerular expression of mRNA for interferon-gamma (IFN-gamma; 1.0 mg/kg BW FK506, 32.4% to the placebo group, P < 0.01) and IL-2 (55.6%, P < 0.01) on day 5. FK506 treatment from day -5 of GN induction reduced proteinuria and glomerular alteration in a dose-dependent manner. Although no side effects were detected in rats with 0.3 mg/kg BW of FK506 treatment from day +1, the treatment also ameliorated proteinuria (day 14, 3.7 +/- 0.89 vs. 19.8 +/- 12.3 mg/100 g BW/day P < 0.05) and glomerular alterations [total cell number, 63.1 +/- 3.1 vs. 80.2 +/- 7.4, P < 0.01; matrix expansion, 0.90 +/- 0.30 vs. 1.34 +/- 0.27, P < 0.05; alpha-smooth muscle actin (alphaSMA) expression; 1.20 +/- 0.12 vs. 1.96 +/- 0.29, P < 0.01] on day 14.

CONCLUSION

Th1 cytokines may play an important role in the development of mesangial proliferative glomerulonephritis, and could be targets for therapy. FK506 might be available for clinical use.

Cutting edge: CD43 functions as a T cell counterreceptor for the macrophage adhesion receptor sialoadhesin (Siglec-1)

Sialoadhesin (Siglec-1) is a macrophage-restricted sialic acid-binding receptor that mediates interactions with hemopoietic cells, including lymphocytes. In this study, we identify sialoadhesin counterreceptors on T lymphocytes. Several major glycoproteins (85, 130, 240 kDa) were precipitated by sialoadhesin-Fc fusion proteins from a murine T cell line (TK-1). Binding of sialoadhesin to these glycoproteins was sialic acid dependent and was abolished by mutation of a critical residue (R97A) of the sialic acid binding site in the membrane distal Ig-like domain of sialoadhesin. The 130- and 240-kDa sialoadhesin-binding glycoproteins were identified as the sialomucins CD43 and P-selectin glycoprotein ligand 1 (CD162), respectively. CD43 expressed in COS cells supported increased binding to immobilized sialoadhesin. Finally, sialoadhesin bound different glycoforms of CD43 expressed in Chinese hamster ovary cells, including unbranched (core 1) and branched (core 2) O:-linked glycans, that are normally found on CD43 in resting and activated T cells, respectively. These results identify CD43 as a T cell counterreceptor for sialoadhesin and suggest that in addition to its anti-adhesive role CD43 may promote cell-cell interactions.

The detection and quantitation of inflammation in the central nervous system during experimental allergic encephalomyelitis using the radiopharmaceutical 99mTc-RP128

RP128 is a novel agent which readily chelates 99mTc to form a radiopharmaceutical which binds in vivo to the tuftsin receptor located specifically on neutrophils and monocyte-macrophages, therefore removing the need for in vitro cell labelling prior to intravenous administration. We have assessed the ability of 99mTc-RP128 to detect central nervous system (CNS) inflammation in experimental allergic encephalomyelitis (EAE), an animal model of the human disease multiple sclerosis. The radiopharmaceutical was recorded at significantly increased levels in all EAE diseased CNS tissues, compared to normal and control samples, at 0.5, 1 and 3 h post-injection using a dual radioisotope technique to correct for non-extravasated tracer (P<0.05). Moreover, extravascular accumulation of the agent could be clearly demonstrated in inflammatory tissues with minimal loss of sensitivity when the secondary isotopic correction for blood volume was omitted. In addition, 99mTc-RP128 successfully monitored glucocorticoid suppression of inflammation (P<0.05), recording a typical dose-response to increasing steroid concentration. Clearly, 99mTc-RP128 can quantitatively detect CNS inflammation and assess responses to therapy indicating potential value as an imaging agent both clinically and as a research aid. Furthermore, the rapid in vivo labelling by 99mTc-RP128 of specific inflammatory cells combined with the ability to monitor the progress of anti-inflammatory therapeutics may recommend the agent for use in a variety of inflammatory conditions.

Infiltration of lymphocytes in the limbic brain following stimulation of subclinical cellular immunity and low dosages of lithium and a cholinergic agent

This experiment was designed to investigate the hypothesis that single small dosages of lithium (1.5 mEq/kg), the muscarinic agent pilocarpine (15 mg/kg) and spinal cord emulsion encourage perivascular infiltration of lymphocytes into the brain even when overt symptoms of experimental allergic encephalomyelitis are not apparent. The brains of rats that had received this small dosage of lithium and pilocarpine exhibited discernable infiltrations of lymphocytes within limbic tracts but no discernable neuronal loss. Although the brains of the rats that displayed overt seizures following larger dosages of lithium (3 mEq/kg) and pilocarpine (30 mg/kg) exhibited the usual pattern of neuronal loss within multiple thalamic and limbic structures and conspicuous foci of lymphocytic infiltration (particularly within the hippocampal formation) the correlation between the numbers of foci and the proportions of neuronal damage in these structures was not significant statistically. These results indicate that infiltrations of lymphocytes into brain parenchyma are not simple artifacts of the amount of neuronal damage and may be sensitive toxicological markers for subclinical interactions between drugs and immune responses.

Dose and scanning delay using USPIO for central nervous system macrophage imaging

RATIONALE AND OBJECTIVES

In experimental allergic encephalomyelitis (EAE), central nervous system (CNS) macrophage imaging is achievable by MRI using AMI-227 an ultra-small particle iron oxide contrast agent at a dose of 300 micromol/kg Fe. The objective was to test the feasibility at the human recommended dose of 45 micromol/kg Fe.

METHODS

Two groups of EAE rats were tested with AMI-227 using 45 and 300 micromol/kg Fe respectively. Following i.v. injection of AMI-227, they were scanned after a delay of 4-6 and 20-24 h.

RESULTS

With a high dose of AMI-227, all animals showed low signal intensity related to iron-loaded macrophages in the CNS. At low dose no abnormalities were found in the CNS. Furthermore, a delay of 4-6 h failed to demonstrate abnormalities even at high dose.

CONCLUSIONS

Dose, scanning delay after administration and blood half-life are major parameters for T2* CNS macrophage imaging.

Depletion of blood-borne macrophages does not reduce demyelination in mice infected with a neurotropic coronavirus

Mice infected with the neurotropic coronavirus mouse hepatitis virus strain JHM (MHV-JHM) develop a chronic demyelinating disease with symptoms of hindlimb paralysis. Histological examination of the brains and spinal cords of these animals reveals the presence of large numbers of activated macrophages/microglia. In two other experimental models of demyelination, experimental allergic encephalomyelitis and Theiler's murine encephalomyelitis virus-induced demyelination, depletion of hematogenous macrophages abrogates the demyelinating process. In both of these diseases, early events in the demyelinating process are inhibited by macrophage depletion. From these studies, it was not possible to determine whether infiltrating macrophages were required for late steps in the process, such as myelin removal. In this study, we show that when macrophages are depleted with either unmodified or mannosylated liposomes encapsulating dichloromethylene diphosphate, the amount of demyelination detected in MHV-infected mice is not affected. At a time when these cells were completely depleted from the liver, approximately equivalent numbers of macrophages were present in the spinal cords of control and drug-treated animals. These results suggest that blood-borne macrophages are not required for MHV-induced demyelination and also suggest that other cells, such as perivascular macrophages or microglia, perform the function of these cells in the presence of drug.

Type IV phosphodiesterase inhibition in experimental allergic encephalomyelitis of Lewis rats: sequential gene expression analysis of cytokines, adhesion molecules and the inducible nitric oxide synthase

Type IV phosphodiesterase inhibitors are able to suppress EAE. To investigate the effects of this therapy in the central nervous system, we serially analyzed from days 7 to 17 postinoculation the gene expression pattern of tumor necrosis factor (TNF), lymphotoxin, interferon-gamma, interleukin-1beta, the inducible nitric oxide synthase (iNOs), interleukin-10, the vascular cell adhesion molecule-1 (VCAM-1) and the intercellular adhesion molecule-1 (ICAM-1) in the spinal cord of Lewis rats with actively induced EAE, treated with Rolipram. Treated rats had a delayed and milder disease, and reduced numbers of infiltrates in the nervous tissue. The gene expression profile was similar to that of untreated rats, although delayed, with no evidence of IL-10 upregulation during the observation period. The delayed inflammation was not associated with changes in the expression of VCAM-1 and ICAM-1. In peripheral blood mononuclear cells, TNF mRNA levels were decreased and interleukin-10 was unchanged. This therapy did not alter the proliferative ability of T lymphocytes against myelin basic protein. The encephalitogenic potential of splenocytes from treated animals was also unaffected. The high levels of both iNOs mRNA and nitric oxide (NO) found before the appearance of clinical signs, suggests that NO generation might be a contributing factor to the therapeutic benefit achieved by Rolipram in the rat.

Two- and three-dimensional computer graphic evaluation of the subacute spinal cord injury

We have evaluated three-week-old compression lesions of the rat spinal cord using two-dimensional and three-dimensional morphometry, reconstruction, and visualization techniques. We offer a new computer assisted method to determine the number and density of macrophages within the spinal lesion using the macrophage specific monoclonal label ED1. We also provide quantitative information on pathological cyst formation and cavitation. This technique does not require: (1) subjective identification of the cell type, (2) human interaction with the data during the phase of quantification, and (3) can be applied to any sampling paradigm based on immunocytochemical labeling. Using novel algorithms based on solutions to 'correspondence' and 'branching' problems inherent in cross-sectional histological data, we provide three-dimensional reconstructions and visualizations of the macrophagic lesions and cysts imbedded within it. Our three-dimensional surface reconstructions can be interrogated to determine volumes and surface areas of structures within the data set. Using these methods we have learned that macrophage numbers approach the maximum density possible for such isodiametric cells (approximately 12 microm diameter) in the central lesion ranging from 4000-7000 cells per mm2 of lesion. At the time point studied, macrophage numbers would have peaked following the initial insult, and would not be expected to decline for several months. While the density of macrophages is highest in the region of most tissue damage, we show that the central regions of cavitated and cystic spinal parenchyma is not. We discuss how this density of cells may effect the secondary pathological responses of the spinal cord to injury.

Depletion of T lymphocytes with immunotoxin retards the progress of experimental allergic encephalomyelitis in rhesus monkeys

FN18-CRM9 is an anti-rhesus anti-CD3 immunotoxin that can transiently deplete T cells to 1% of initial values in both the blood and lymph node compartments and can induce long-term tolerance to mismatched renal allografts. We have investigated the ability of this immunotoxin to interdict the course of an experimental rhesus T-cell-driven autoimmune disease, experimental allergic encephalomyelitis (EAE) induced by myelin basic protein. Monkeys showing CSF pleocytosis were then treated with FN18-CRM9 alone or in combination with cranial irradiation (325 or 650 cGy). EAE in nontreated control monkeys progressed rapidly. Paralysis occurred 4-6 days after CSF pleocytosis. Paralysis was either delayed or never occurred in treated monkeys, and histopathology revealed few inflammatory plaques that were notable for their low or absent T cell content. While T cells repopulate in the periphery posttreatment, they do not return to the CNS in large numbers, suggesting that the newly repopulated T cells have lost their previously acquired CNS homing capability. Anti-CD3 immunotoxin may be useful in treating clinical T-cell-driven autoimmune diseases such as rheumatoid arthritis and multiple sclerosis.

Ganglioside spinal cord changes in chronic relapsing experimental allergic encephalomyelitis induced in the Lewis rats

Chronic relapsing experimental allergic encephalomyelitis (CREAE) was induced in Lewis rats by inoculation with guinea-pig myelin and complete Freund's adjuvant followed by treatment with low-dose cyclosporin A. Rats were sacrified at different phases of the disease (just before the onset of clinical signs, during the first clinical episode of CREAE and during the first recovery). Gangliosides were extracted from the spinal cord, analysed after purification by two-dimensional chromatography and quantified densitometrically. An increase of GM 1, the main rat myelin ganglioside, and a decrease of GT1b, suggested to play a role in mediating the interactions between oligodendroglia and axons, were observed during the development of the CREAE. These findings indicating significant ganglioside changes in CREAE give further support to the concept concerning the involvement of gangliosides in autoimmune demyelination.

Reversible inhibitory effects of interferon-gamma and tumour necrosis factor-alpha on oligodendroglial lineage cell proliferation and differentiation in vitro

We have investigated the effects of the two prominent inflammatory cytokines, interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha), on oligodendroglial lineage cell development and survival. Purified oligodendrocytes and oligodendrocyte precursors obtained from neonatal rat brain primary cultures were subcultured in a defined, serum-free medium and exposed to IFN-gamma (1-100 U/ml, TNF-alpha (25-100 ng/ml) or both (100 U/ml and 50 ng/ml respectively) from day 1 to day 3 or from day 3 to day 6. While cell survival was not affected in any of the conditions tested, IFN-gamma dose-dependently inhibited [3H]thymidine or bromodeoxyuridine incorporation (by up to 50%) and the reduction of the tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT; by up to 33%). TNF-alpha synergized with IFN-gamma, but was ineffective by itself. Moreover, IFN-gamma totally antagonized the induction by basic fibroblast growth factor and platelet-derived growth factor of the proliferation of the oligodendroglial lineage cell population under study. IFN-gamma also blocked the differentiation of oligodendrocyte precursors, as evidenced by cell morphology, immunostaining for early and late differentiation markers (galactocerebroside and myelin basic protein respectively) and activity of ceramide galactosyl transferase. Again, the effect of IFN-gamma was potentiated by TNF-alpha, which was ineffective when tested alone. The inhibitory activity of IFN-gamma was rapidly reversible: 3 days after removal of the cytokine, administered from day 1 to day 3, complete recovery of cll proliferation and differentiation could be documented. The cytokine-induced arrest in the expression of differentiation antigens was accompanied by perturbations in the expression of the corresponding mRNAs, revealed by a semiquantitative reverse transcription-polymerase chain reaction method. In particular, the message for myelin basic protein (and, in the case of treatment from days 3 to 6, also that for myelin associated glycoprotein) was decreased in cultures exposed to IFN-gamma, and further depressed in cultures treated with IFN-gamma and TNF-alpha, while TNF-alpha alone was ineffective. The above observations may help explain the role of IFN-gamma and TNF-alpha in the pathogenesis of inflammatory demyelinating diseases, in which increases in the levels of these substances have been described. In particular, in the case of multiple sclerosis, our results may bear on the problem of defective remyelination and are consistent with the frequent relapsing-remitting course of the disease.

Dexamethasone and colchicine reduce inflammation and delayed oedema following experimental brain contusion

The effect of anti-inflammatory treatment on monocyte/macrophage infiltration, major histocompatibility complex molecules (MHC) class II expression and delayed oedema following experimental brain contusion was studied by immunohistochemistry and tissue-specific gravity measurement in 44 rats. Colchicine, chloroquine and dexamethasone administered once daily for five days after the trauma reduced inflammation and oedema. The difference was statistically significant with colchicine and dexamethasone. The findings comprise further evidence of a pathogenetically important inflammation after experimental contusion. It is probable that anti-inflammatory agents may prevent secondary neurological damage due to elevated intracranial pressure and cell to cell- or cytokine-mediated neuronal degeneration and demyelination.

Aggravation of experimental allergic encephalomyelitis (EAE) by administration of nitric oxide (NO) synthase inhibitors

Macrophages constitute a large proportion of the inflammatory cells that infiltrate the central nervous system (CNS) of animals with EAE. Through the production of inflammatory mediators these infiltrating macrophages can contribute to the regulation of the immune reaction within the CNS, that eventually results in neurological deficits associated with EAE. NO, a free radical produced by macrophages and other cell types, has been put forward as such an immune mediator. In the present study we show that macrophages isolated from the CNS of Lewis rats with clinical signs of EAE produce elevated amounts of NO. We treated rats, in which EAE was induced, with N(omega) -nitro-L-arginine-methylester or N(g)-monomethyl-L-arginine, inhibitors of NO synthase, either systemically via intraperitoneal injection, or intracerebrally via a cannula placed in the lateral ventricle. Both treatments resulted in a marked aggravation of clinical signs of EAE. These data point to an important role of NO, produced by infiltrating macrophages, as an immune-suppressor in the disease process during EAE.

The role of macrophage subpopulations in autoimmune disease of the central nervous system

In this review the role of various subpopulations of macrophages in the pathogenesis of experimental autoimmune encephalomyetitis is discussed. Immunohistochemistry with macrophage markers shows that in this disease different populations of macrophages (i.e. perivascular cells, microglia and infiltrating blood-borne macrophages) are present in the central nervous system. These subpopulations partially overlap in some functional activity while other activities seem to be restricted to a distinct subpopulation, indicating that these subpopulations have different roles in the pathogenesis of encephalomyelitis. The studies discussed in this review reveal that immunocytochemical and morphological studies, combined with new techniques such as in situ nick translation and experimental approaches like the use of bone marrow chimeras and macrophage depletion techniques, give valuable information about the types and functions of cells involved in central nervous system inflammation. The review is divided in three parts. In the first part the experimental autoimmune encephalomyelitis model is introduced. The second part gives an overview of the origin, morphology and functions of the various subpopulations. In the third part the role of these subpopulations is discussed in relation to the various stages (i.e. preclinical, clinical and recovery) of the experimental disease.

Increased activity of hypothalamic corticotropin-releasing hormone neurons in multiple sclerosis

Clinical observations and animal studies suggest that the hypothalamo-pituitary-adrenal (HPA) axis plays a role in the susceptibility to and the recovery from multiple sclerosis (MS). Since the HPA-axis is under the control of corticotropin-releasing hormone (CRH) neurons of the hypothalamus, we determined 2 parameters for activation of the CRH neurons in the hypothalamic paraventricular nucleus (PVN) in MS patients. Since the HPA-axis is more activated in MS, we expected an increased activity of CRH neurons. We also expected to see an age-related increase in CRH activity, because of the possible role of the HPA-axis in the age-related decrease in susceptibility to MS. The number of CRH cell profiles and the proportion of CRH neurons co-expressing vasopressin were used as parameters for activity. CRH cell population became more activated both in control and MS patients, from 40 years of age onwards, when the prevalence of MS starts to decrease in the population. The CRH neurons showed a significantly higher level of activation in MS patients than in controls, as appeared from the 3-fold increase in CRH cell number and the 4.5-fold increase in cells co-expressing CRH and vasopressin (AVP).

Production and function of monocyte chemoattractant protein-1 and other beta-chemokines in murine glial cells

Monocyte chemoattractant protein-1 (MCP-1), formerly termed JE, is a member of the beta-chemokine (C-C chemokine) family and has been shown to be produced by a variety of cell types. Recently, mRNA of JE/MCP-1 was detected in astrocytes during the acute phase of experimental allergic encephalomyelitis (EAE). In addition, supernatants collected from human cultured astrocytes have recently been found to be chemotactic for monocytes. However, chemokine production and function in glial cells has not been fully examined. Using a sandwich ELISA assay, we have now quantitated MCP-1 levels and assessed MCP-1 function on murine glial cells. Lipopolysaccharide (LPS), interleukin (IL)-1 beta and tumor necrosis factor (TNF)-alpha induced MCP-1 secretion by astrocytes, but not microglia. In addition, pretreatment with interferon (IFN)-gamma significantly augmented MCP-1 production by either LPS or the above cytokines. In contrast, LPS preferentially induced production of another beta-chemokine, macrophage inflammatory protein-1 alpha (MIP-1 alpha) from microglial cells. MCP-1 induced chemotaxis of microglial cells and macrophages. Similarly, another beta-chemokine, TCA3, which is produced by encephalitogenic T lymphocytes, also induced chemotaxis of microglia and macrophages. These findings suggested that astrocytes and microglial cells differentially produce chemokines in the central nervous system, and that both astrocytes and T cells may facilitate recruitment and activation of microglial cells via production of beta-chemokines.

Macrophages in T cell line-mediated, demyelinating, and chronic relapsing experimental autoimmune encephalomyelitis in Lewis rats

About 50% of the mononuclear cells in the perivascular lesions in the central nervous system (CNS) of rats suffering from experimental allergic encephalomyelitis (EAE) are blood-borne macrophages. In this study we investigated the role of these macrophages in different variants of EAE, using a liposome-mediated macrophage depletion technique. Intravenously injected liposomes containing dichloromethylene diphosphonate (Cl2MDP) are ingested by macrophages and cause temporary and selective elimination of these cells. Macrophage depletion during EAE induced by a T cell line specific for myelin basic protein (MBP; T cell-EAE) suppresses development of neurological signs of EAE. T cell-EAE with pronounced demyelination as induced by an additionally injected MoAb directed against myelin oligodendrocyte glycoprotein (MOG) was also significantly ameliorated after macrophage depletion. During chronic relapsing EAE (CR-EAE) the occurrence of relapses was prevented or suppressed, provided that the liposomes were injected before the initiation of a putative relapse. A chronic progressive course of CR-EAE was not modified by Cl2MDP containing liposome treatment. Histologic examination of the CNS of liposome-treated animals confirmed decreased infiltration of macrophages into the parenchyma in the rats with T cell and AD-EAE, whereas T cells were still present.

Preparation of a monoclonal antibody to a glycidic epitope of the epidermal growth factor receptor that recognizes inhibitors of astrocyte proliferation and reactive microglia

A mouse monoclonal antibody (5B9), directed against a carbohydrate epitope of human epidermal growth factor receptor (EGFR), recognized an 81-kDalton glycoprotein in buffer-soluble and detergent-solubilized rat brain extracts (BE). The glycoprotein was more abundant in extracts prepared from injured brain than in those from normal tissue. Removal from BE of the antigens recognized by 5B9 increased their astrocyte mitogenic activity. Sections of injured rat brain and cultures derived from damaged brain, enriched in microglia, showed 5B9 immunoreactivity in ED1-positive cells. The abundance of the glycoprotein recognized by 5B9 in injured, relative to normal, tissue, suggested that molecules with EGFR immunoreactivity may be expressed in reactive microglial cells and released after injury.

The influence of antiadhesion therapies on leukocyte subset accumulation in central nervous system ischemia in rats

Although treatment with agents that block leukocyte function, including anti-ICAM-1 and doxycycline, reduces experimental central nervous system (CNS) ischemic injury, it is not known how leukocyte subset accumulation is affected by these agents. Using the rat two-vessel occlusion model and immunohistochemistry, we investigated granulocyte (PMN) and monocyte/macrophage (M phi) accumulation at 1 and 4 d postischemia. A total of 24 animals were randomized to sham surgery, or to ischemia with saline, anti-ICAM-1, or doxycycline treatments. No leukocytes were observed in sham animals. At 24 h postischemia, there was a moderate infiltration of PMN and M phi in untreated animals that was significantly decreased with either treatment. At 4 d after ischemia no PMN were identified, with extensive M phi accumulation occurring in untreated animals that was only partially reduced with doxycycline treatment. These results confirm that both anti-ICAM-1 and doxycycline treatments reduce PMN and M phi infiltration at 24 h. Delayed M phi accumulation occurs despite treatment, suggesting that some of these cells represent transformed resident microglia.

Intracerebral inflammatory response to experimental brain contusion

The inflammatory reaction following experimental brain contusion was studied by immunohistochemistry in 22 rats during the first 16 days after trauma. An inflammatory mononuclear cell response was evident on day 2, with a maximum on days 5-6 and signs remained still 16 days after the trauma. The time course of the cellular infiltration adjacent to the lesion correlated with blood brain barrier dysfunction in the contralateral side of the traumatized hemisphere. The cellular infiltrate comprised NK cells, T-helper cells and T-cytotoxic/suppressor cells as well as monocytes/macrophages. Most of the macrophages appeared to be activated by T-cells. Surprisingly, polymorphonuclear cells appeared less engaged than mononuclear cells in the inflammation. The demonstration of immunocompetent cells and the induction of MHC-1 and MHC-II antigen provides a substrate for inflammatory reactions similar to those that cause neurological damage in inflammatory diseases such as viral infections, multiple sclerosis and experimental allergic encephalitis. Our observations indicate that the role of the inflammatory reactions may have a role, hitherto neglected, in the pathogenesis of secondary traumatic brain injury.

Adenovirus-mediated gene therapy of experimental gliomas

The efficacy of adenovirus (ADV)-mediated gene therapy to treat brain tumors was tested in a syngeneic glioma model. Tumor cells were transduced in situ with a replication-defective ADV carrying the herpes simplex virus thymidine kinase (HSV-tk) gene controlled by the Rous sarcoma virus promoter. Expression of the HSV-tk gene enables the transduced cell to convert the drug ganciclovir to a form that is cytotoxic to dividing cells. Tumors were generated in Fischer 344 rats by stereotaxic implantation of 9L gliosarcoma cells into the caudate nucleus. Eight days later, the tumors were injected either with the ADV carrying the HSV-tk (ADV-tk) gene or a control ADV vector containing the beta-galactosidase (ADV-beta gal) gene and the rats were treated with either ganciclovir or saline. Tumor size was measured 20 days after implantation of 9L cells or at death. Rats treated with ADV-beta gal and ganciclovir or with ADV-tk and saline had large tumors. No tumors were detected in animals treated with ADV-tk and with ganciclovir at doses > or = 80 mg/kg. An infiltrate of macrophages and lymphocytes at the injection site in animals treated with ADV-tk and ganciclovir indicated an active local immune reaction. In survival studies, all animals treated with ADV-tk and ganciclovir have remained alive longer than 80 and up to 120 days after tumor induction whereas all untreated animals died by 22 days. These results demonstrate that ADV-mediated transfer of HSV-tk to glioma cells in vivo confers sensitivity to ganciclovir, and represents a potential method of treatment of brain tumors.

Synthesis of 1,25-dihydroxyvitamin D3 by rat brain macrophages in vitro

Cultured microglial cells were examined for their ability to metabolize 25-hydroxyvitamin D3 (25-(OH) D3). Upon exposure to lipopolysaccharide, microglial cells produced a vitamin D metabolite which comigrated with synthetic 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) in two different systems of high performance liquid chromatography. This metabolite had the same affinity as synthetic 1,25-(OH)2D3 for the chick intestinal 1,25-(OH)2D3 receptor. Lipopolysaccharide-stimulated microglial cells incubated with 3 nM of 25-(OH) D3 synthesized up to 5.76 fmol 1,25-(OH)2D3/8 x 10(5) cells/2 hr. Microglial cells stimulated for 48 hr with interferon-gamma also produced a significant amount of 1,25-(OH)2D3 (4.17 fmol/8 x 10(5) cells/2 hr). In contrast, levels of 1,25-(OH)2D3 produced by resting microglial cells were barely detectable. It is concluded that activated brain macrophages may be committed to synthesize 1,25-(OH)2D3 in vitro. This raises the possibility that activation of microglial cells in vivo may be followed by an increase in the level of 1,25-(OH)2D3 in the central nervous system (CNS). These results support the emerging concept that the brain constitutes a target tissue for vitamin D metabolites.

Nitric oxide mediates the toxoplasmastatic activity of murine microglial cells in vitro

Toxoplasma gondii (T. gondii), an opportunistic protozoan, is an important cause of central nervous system (CNS) infections in immunosuppressed patients. The present study focused on the interaction between T. gondii and microglial cells from the brain of neonatal Balb/c mice. Preincubation of the murine microglial cells with recombinant interferon-gamma (rIFN-gamma) and lipopolysaccharide (LPS) induced significant inhibition of T. gondii replication in a dose dependent manner. This antiparasitic effect in microglial cells was correlated with the induction of the L-arginine-dependent generation of reactive nitrogen intermediates (RNIs). Tumor necrosis factor-alpha (TNF-alpha) was also involved in the toxoplasmastatic activity. Microglial cells incubated with recombinant TNF-alpha in combination with a non-activating concentration of rIFN-gamma released substantial amount of RNIs. Neutralizing antibodies against mouse TNF-alpha inhibited the release of RNI by rIFN-gamma activated macrophages. In summary, the present results show that activation of microglial cells by rIFN-gamma and LPS induce the production of nitric oxide (NO) by these cells via an L-arginine dependent pathway. NO appears to be the effector molecule mediating the toxoplasmastatic effects in these cells.

Lipocortin 1 (annexin 1) immunoreactivity in the cervical spinal cord of Lewis rats with acute experimental allergic encephalomyelitis

Spontaneous recovery from acute experimental allergic encephalomyelitis (EAE) by the Lewis rat is probably mediated by endogenous corticosteroids. It has been proposed that the anti-inflammatory actions of the glucocorticoids may be effected via the induction of mediator proteins termed lipocortins and recently we have demonstrated increased levels of lipocortin 1 in the central nervous system (CNS) of EAE-diseased rats (Bolton C., A-J. Elderfield and R.J. Flower (1990), J. Neuroimmunol. 29: 173-181). In this study, utilizing antisera raised against recombinant human lipocortin 1, immunohistochemistry and light microscopy have been used to determine the distribution of the protein in the cervical spinal cord of Lewis rats during EAE. In normal animals lipocortin 1 immunoreactivity was localized predominantly in the walls of larger blood vessels and to a lesser extent capillaries. The same staining pattern was found in adjuvant-inoculated controls. In sections from EAE-inoculated animals there was no change during the induction phase, but with the onset of clinical symptoms and the appearance of inflammatory infiltrates in the CNS, a marked increase in lipocortin 1 immunostaining was observed. This additional staining was due to widespread immunoreactivity of the lesions, was maximal at the height of disease and decreased following recovery and lesion regression. Within the lesions the vast majority of infiltrating lymphocytes and macrophages were positive for lipocortin 1, including some very heavily stained macrophage-like cells. Measurement of corticosterone in the sera of these animals showed that changes in lipocortin 1 immunostaining in the CNS during EAE closely parallel serum corticosterone levels.

Differential recognition of sequences within the encephalitogenic region of myelin basic protein capable of eliciting cell-mediated immune responses in experimental autoimmune encephalomyelitis

The fine specificity of myelin basic protein (MBP) epitopes capable of eliciting in vivo delayed-type hypersensitivity responses in Lewis rats with experimental autoimmune encephalomyelitis (EAE) was compared to those eliciting in vitro antigen-specific T cell proliferation and augmentation of disease transfer. Utilizing a panel of synthetic peptides with sequences representing the 68-86 region of guinea pig (GP-) or bovine myelin basic protein (B-MBP), animals were primed with one species of peptide and subsequently challenged with either the same peptide or peptides with truncations or substitutions representative of the other species of MBP. In regard to minimal length sequences capable of eliciting delayed-type hypersensitivity (DTH), rats primed with GP-MBP and complete Freund's adjuvant (CFA) exhibited a hierarchical pattern of responsiveness to challenge with a series of truncated peptides, ranking as follows: GP-68-86 > GP-72-86 > GP-68-84 > > GP-75-86 = no activity. This response pattern corresponds to that previously reported for T cell proliferation and activation for disease transfer. Furthermore, a comparison of these T cell-mediated immune parameters, as elicited by the substituted peptides, revealed the response patterns of DTH reactivity to be similar to that previously described for in vitro T cell proliferation with significant DTH responses generated only by the peptide species for which the animal was primed. In contrast, a cross-reactive pattern of recognition was observed in cells mediating disease transfer, with all four 68-86 sequences capable of augmenting activation for adoptive transfer of disease, regardless of the peptide species for which the animal was primed.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphodiesterase inhibitor pentoxifylline, a selective suppressor of T helper type 1- but not type 2-associated lymphokine production, prevents induction of experimental autoimmune encephalomyelitis in Lewis rats

The phosphodiesterase inhibitor pentoxifylline (POX), which is known to have pharmacological effects in animal models of multiorgan failure and endotoxin-mediated shock, was tested for its immunosuppressive potential on T lymphocyte activation in vitro and in vivo. POX was found to have a profound inhibitory effect on both mitogen- and antigen-induced proliferation of CD4+ T cells in vitro. This inhibitory activity of the drug could be reproduced by treating T lymphocytes with cAMP analogues during stimulation. Responses of repeatedly in vitro stimulated cells were much more strongly inhibited by the drug and by cAMP analogues than responses of fresh resting lymphocytes. Furthermore, POX could drastically down-regulate tumor necrosis factor regulate production and to a lesser extent interleukin (IL)-2 secretion in activated T cells, but an excess of exogenous IL-2 did not override the antiproliferative effect of the drug. In contrast, the same doses of POX had no inhibitory effect on spontaneous or induced IL-4 and IL-6 production by short-term cultured T lymphocytes, indicating a selective sparing of T helper type 2 (Th2)-associated lymphokine functions by the drug. To test a potential use of POX as an antiinflammatory agent in T cell-mediated autoimmune disease, the influence of POX on myelin basic protein (MBP)-induced experimental autoimmune encephalomyelitis (EAE) was assessed. The onset of EAE in Lewis rats could almost completely be abrogated by oral administration of POX during the induction phase of disease. Lack of clinical symptoms in POX-treated animals coincided with a marked suppression of MBP-specific T cell reactivity in vitro, without any evidence for a generalized impairment of T cell activity. Collectively, our data suggest the potential use of xanthine derivatives of the POX type as a supporting antiinflammatory therapeutic agent in Th1 CD4+ T cell-mediated autoimmune diseases in animal models and possibly in man.

Macrophage populations in different stages of induced hepatic metastases in rats: an immunohistochemical analysis

Macrophages play a role in the host defence against cancer. Little is known about changes in macrophage populations during early metastatic growth. To evaluate the distribution, number and phenotype of macrophages in the development of hepatic metastases in a rat model (Wag/Rij rats and syngeneic CC531 colon carcinoma cell line), an immunohistochemical study was performed with the monoclonal antibodies ED1 (monocytes, and all macrophages), ED2 (resident tissue macrophages, like Kupffer cells) and ED3 (a subpopulation of macrophages which may play a role in the recruitment of lymphocytes). OX19 and His14 were used to identify lymphocytes. In this study a new monoclonal antibody CC52 is described, which recognizes the CC531 tumour cell line. Liver metastases were induced by injection of CC531 colon carcinoma cells into a mesenteric vein. Rats were killed at various intervals. Results show three major macrophage populations during hepatic tumour growth: (1) on day 3, infiltrates are observed around the micrometastases, which contain mainly newly recruited macrophages (ED1+ and ED2-); (2) after 7 days, ED3-positive (ED3+) macrophages together with T lymphocytes are found in the infiltrates; (3) an increase in the number of ED2-positive (ED2+) Kupffer cells is observed in the liver parenchyma after 14 days. In conclusion, the present results suggest that various populations of macrophages, newly recruited (ED1+) as well as resident Kupffer cells (ED2+), are involved in the immune response against tumour cell deposits in the liver.

Early changes of macrophage-like immunoreactivity in the rat inferior olive after intraperitoneal 3-acetylpyridine injection

Early changes of macrophage-like immunoreactivity were observed in the inferior olive after intraperitoneal injection of 3-acetylpyridine (3AP) using seven monoclonal antibodies recognizing macrophage subpopulations (OX-42, OX-6, ED-1, RM-1, TRPM-1, TRPM-2, and TRPM-3). Both resting and activated forms of microglia were stained with OX-42 and TRPM-2. Some of activated microglia reacted to OX-6 and/or ED-1. Neither resting nor activated microglia reacted to any of RM-1, TRPM-1, and TRPM-3. Four h after 3AP injection, the processes of OX-42-positive microglia had increased in number and became thicker than resting microglia. Between 24 h and the 7th day after 3AP injection (day 7), OX-42-positive microglia gradually increased in number. At 24 h after 3AP injection, round cells appeared that stained with all seven antibodies. These disappeared by day 3. Double staining indicated that OX-42-positive activated microglia on day 7 were divided into subpopulations by their immunoreactivity to ED-1. We suggest that the round cells derived from blood monocytes and entered the brain only transiently while OX-42-positive activated microglia originated from parenchymal resting microglia and continued to increase in number after the disappearance of the round cells.

Detection of lysosomal cysteine proteinases in microglia: flow cytometric measurement and histochemical localization of cathepsin B and L

The activation and differentiation of microglia is a prominent pathophysiological process in numerous inflammatory and demyelinating diseases of the central nervous system, including Alzheimer's disease and the AIDS encephalopathy. The tissue damage during these diseases has partly been attributed to lipid peroxidating reactive oxygen intermediates for which activated microglia are a major source. The destruction of tissue may also involve the release of proteolytic enzymes, such as the lysosomal cysteine proteinases cathepsin B and L, which are present notably in phagocytic cells. The cathepsins B and L are endopeptidases with a substrate specificity including important proteins, like myelin basic protein, extracellular matrix components, or the class II major histocompatibility complex. Because of this pathophysiological relevance the cathepsins B and L were chosen for histochemical demonstration in isolated and cultured rat microglia and measurement by a new flow cytometric method. Cathepsin B/L activity was measured flow cytometrically in single viable cells by the intracellular cleavage of non-fluorescent (Z-Phe-Arg)2-rhodamine 110 to the green fluorescent monoamide Z-Phe-Arg-rhodamine 110 and rhodamine 110. In microglia we measured a cathepsin B/L activity that was 2.5 times higher than in thioglycolate-elicited, i.e., inflammatory peritoneal rat macrophages. In elicited peritoneal macrophages the formation of fluorescent product was 6.2 times higher than in unstimulated resident peritoneal macrophages, demonstrating that the activation and differentiation of mononuclear phagocytes is accompanied by an increased cathepsin B/L enzyme activity. The subcellular localization of cathepsin B/L activity in plated viable microglia was demonstrated histochemically by the use of Z-Ala-Arg-Arg-4-methoxy-2-naphthylamide. Its blue fluorescent cleavage product 4-methoxy-2-naphthylamide was found in lysosomes. Our study shows that activated microglia are an important potential source of cathepsin B/L. This is particularly interesting as enzymatically active cathepsins have recently been found extracellularly at high levels in the senile plaques of Alzheimer's disease, which are known to contain many activated microglia. The release of proteinases by microglia may play a crucial role in the pathomechanism of tissue-destructing diseases in the brain.

Characterization of microglia and macrophages in the central nervous system of rats: definition of the differential expression of molecules using standard and novel monoclonal antibodies in normal CNS and in four models of parenchymal reaction

This report describes the development of a new panel of monoclonal antibodies produced following immunization of mice with cultured rat microglial cells. Using these new reagents and previously defined antibodies that bind to microglia or macrophages, the responses of parenchymal microglia, perivascular "microglial" cells, and infiltrating macrophage/monocytes were examined in 4 divergent models of central nervous system reaction. These were brain abscess, experimental allergic encephalomyelitis, Wallerian degeneration, and stab wound. No single new antibody was specific only for microglia; all antibodies positively staining microglial cells also labeled various subsets of macrophage/monocytic cells in normal tissues of the immune system. Moreover, the results indicate that microglia are capable of different levels and a variety of types of response, as defined by the molecules they elaborate. These findings suggest that these CNS resident cells belong to the extended monocyte/macrophage/dendritic cell family and that they do not respond in a stereotypic manner to all forms of CNS insult.