Expression of chemokine receptors CCR1 and CCR5 reflects differential activation of mononuclear phagocytes in pattern II and pattern III multiple sclerosis lesions

Fluorophore-Labeled Pyrrolones Targeting the Intracellular Allosteric Binding Site of the Chemokine Receptor CCR1

In this study, we describe the structure-based development of the first fluorescent ligands targeting the intracellular allosteric binding site (IABS) of the CC chemokine receptor type 1 (CCR1), a G protein-coupled receptor (GPCR) that has been pursued as a drug target in inflammation and immune diseases. Starting from previously reported intracellular allosteric modulators of CCR1, tetramethylrhodamine (TAMRA)-labeled ligands were designed, synthesized, and tested for their suitability as fluorescent tracers to probe binding to the IABS of CCR1. In the course of these studies, we developed LT166 (12) as a highly versatile fluorescent CCR1 ligand, enabling cell-free as well as cellular NanoBRET-based binding studies in a nonradioactive and high-throughput manner. Besides the detection of intracellular allosteric ligands by direct competition with 12, we were also able to monitor the binding of extracellular antagonists due to their positive cooperative binding with 12. Thereby, we provide a straightforward and nonradioactive method to easily distinguish between ligands binding to the IABS of CCR1 and extracellular negative modulators. Further, we applied 12 for the identification of novel chemotypes for intracellular CCR1 inhibition that feature high binding selectivity for CCR1 over CCR2. For one of the newly identified intracellular CCR1 ligands (i.e., 23), we were able to show CCR1 over CCR2 selectivity also on a functional level and demonstrated that this compound inhibits basal β-arrestin recruitment to CCR1, thereby acting as an inverse agonist. Thus, our fluorescent CCR1 ligand 12 represents a highly promising tool for future studies of CCR1-targeted pharmacology and drug discovery.

A novel phenotype of B cells associated with enhanced phagocytic capability and chemotactic function after ischemic stroke

Accumulating evidence has demonstrated the involvement of B cells in neuroinflammation and neuroregeneration. However, the role of B cells in ischemic stroke remains unclear. In this study, we identified a novel phenotype of macrophage-like B cells in brain-infiltrating immune cells expressing a high level of CD45. Macrophage-like B cells characterized by co-expression of B-cell and macrophage markers, showed stronger phagocytic and chemotactic functions compared with other B cells and showed upregulated expression of phagocytosis-related genes. Gene Ontology analysis found that the expression of genes associated with phagocytosis, including phagosome- and lysosome-related genes, was upregulated in macrophage-like B cells. The phagocytic activity of macrophage-like B cells was verified by immunostaining and three-dimensional reconstruction, in which TREM2-labeled macrophage-like B cells enwrapped and internalized myelin debris after cerebral ischemia. Cell-cell interaction analysis revealed that macrophage-like B cells released multiple chemokines to recruit peripheral immune cells mainly via CCL pathways. Single-cell RNA sequencing showed that the transdifferentiation to macrophage-like B cells may be induced by specific upregulation of the transcription factor CEBP family to the myeloid lineage and/or by downregulation of the transcription factor Pax5 to the lymphoid lineage. Furthermore, this distinct B cell phenotype was detected in brain tissues from mice or patients with traumatic brain injury, Alzheimer's disease, and glioblastoma. Overall, these results provide a new perspective on the phagocytic capability and chemotactic function of B cells in the ischemic brain. These cells may serve as an immunotherapeutic target for regulating the immune response of ischemic stroke.

Dynamics of reactive astrocytes fosters tissue regeneration after cuprizone-induced demyelination

Demyelination in the central nervous system (CNS) is a hallmark of many neurodegenerative diseases such as multiple sclerosis (MS) and others. Here, we studied astrocytes during de- and remyelination in the cuprizone mouse model. To this end, we exploited the ribosomal tagging (RiboTag) technology that is based on Cre-mediated cell type-selective HA-tagging of ribosomes. Analyses were performed in the corpus callosum of GFAP-Cre+/- Rpl22HA/wt mice 5 weeks after cuprizone feeding, at the peak of demyelination, and 0.5 and 2 weeks after cuprizone withdrawal, when remyelination and tissue repair is initiated. After 5 weeks of cuprizone feeding, reactive astrocytes showed inflammatory signatures with enhanced expression of genes that modulate leukocyte migration (Tlr2, Cd86, Parp14) and they produced the chemokine CXCL10, as verified by histology. Furthermore, demyelination-induced reactive astrocytes expressed numerous ligands including Cx3cl1, Csf1, Il34, and Gas6 that act on homeostatic as well as activated microglia and thus potentially mediate activation and recruitment of microglia and enhancement of their phagocytotic activity. During early remyelination, HA-tagged cells displayed reduced inflammatory response signatures, as indicated by shutdown of CXCL10 production, and enhanced expression of osteopontin (SPP1) as well as of factors that are relevant for tissue remodeling (Timp1), regeneration and axonal repair. During late remyelination, the signatures shifted towards resolving inflammation by active suppression of lymphocyte activation and differentiation and support of glia cell differentiation. In conclusion, we detected highly dynamic astroglial transcriptomic signatures in the cuprizone model, which reflects excessive communication among glia cells and highlights different astrocyte functions during neurodegeneration and regeneration.

Immunophenotyping of Monocyte Migration Markers and Therapeutic Effects of Selenium on IL-6 and IL-1β Cytokine Axes of Blood Mononuclear Cells in Preoperative and Postoperative Coronary Artery Disease Patients

Multivessel coronary artery disease (CAD) is characterized by underlying chronic vascular inflammation and occlusion in the coronary arteries, where these patients undergo coronary artery bypass grafting (CABG). Since post-cardiotomy inflammation is a well known phenomenon after CABG, attenuation of this inflammation is required to reduce perioperative morbidity and mortality. In this study, we aimed to phenotype circulating frequencies and intensities of monocyte subsets and monocyte migration markers, respectively, and to investigate the plasma level of inflammatory cytokines and chemokines between preoperative and postoperative CAD patients and later, to intervene the inflammation with sodium selenite. We found a higher amplitude of inflammation, postoperatively, in terms of CCR1high monocytes and significantly increased pro-inflammatory cytokines, IL-6, IL-8, and IL-1RA. Further, in vitro intervention with selenium displayed mitigating effects on the IL-6/STAT-3 axis of mononuclear cells derived from postoperative CAD patients. In addition, in vitro selenium intervention significantly reduced IL-1β production as well as decreased cleaved caspase-1 (p20) activity by preoperative (when stimulated) as well as postoperative CAD mononuclear cells. Though TNF-α exhibited a positive correlation with blood troponin levels in postoperative CAD patients, there was no obvious effect of selenium on the TNF-α/NF-κB axis. In conclusion, anti-inflammatory selenium might be utilized to impede systemic inflammatory cytokine axes to circumvent aggravating atherosclerosis and further damage to the autologous bypass grafts during the post-surgical period.

CCR4 and CCR5 Involvement in Monocyte-Derived Macrophage Migration in Neuroinflammation

Microglia, resident macrophages in the brain, play major roles in neuroinflammation after an acute many neurological diseases, including stroke. Our recent animal stroke model showed that interleukin (IL)-4 and IL-13 released by microglia are converted into monocyte-derived macrophages. However, the correlation with the migration mechanism of these cells is still unclear. This study aimed to clarify the effect of these cells on their migration and to identify potential targets that influence neuroinflammatory conditions. Inflammatory conditions were induced by lipopolysaccharide (LPS) treatment in in vitro and in vivo models. Cell migration was observed using transwell assay, and target chemokines were screened using the proteome profiler array in the in vitro model. Intravital, IVIS, and CLARITY imaging were used in the in vivo model. After LPS (1 ng/ml) treatment in BV2 (microglia cell line) and J774 (monocyte/macrophage cell line) cells, BV2 migration was approximately two-fold more enhanced compared to J774 migration. Overall, six types of chemokine C-C motif ligands (CCLs) were detected from the BV2 conditioned medium with LPS. These CCLs were related to C-C motif receptor (CCR)4 and CCR5. In the in vivo model, CCR4 and CCR5 antagonist significantly inhibited the migration of monocyte-derived macrophages to brain tissue following LPS (5 µg) treatment. In conclusion, the chemokines released by microglia may influence migration of monocyte-derived macrophages in necroinflammation conditions inducted by microglial activation. CCR4 and CCR5 expressed on monocyte-derived macrophages interacted with these chemokines and induced migration. Therefore, CCR4 and CCR5 may be explored as new therapeutic targets for neuroinflammation.

Weathering the Storm: Harnessing the Resolution of Inflammation to Limit COVID-19 Pathogenesis

The resolution of inflammation is a temporally and spatially coordinated process that in its innate manifestations, primarily involves neutrophils and macrophages. The shutdown of infection or injury-induced acute inflammation requires termination of neutrophil accumulation within the affected sites, neutrophil demise, and clearance by phagocytes (efferocytosis), such as tissue-resident and monocyte-derived macrophages. This must be followed by macrophage reprogramming from the inflammatory to reparative and consequently resolution-promoting phenotypes and the production of resolution-promoting lipid and protein mediators that limit responses in various cell types and promote tissue repair and return to homeostatic architecture and function. Recent studies suggest that these events, and macrophage reprogramming to pro-resolving phenotypes in particular, are not only important in the acute setting, but might be paramount in limiting chronic inflammation, autoimmunity, and various uncontrolled cytokine-driven pathologies. The SARS-CoV-2 (COVID-19) pandemic has caused a worldwide health and economic crisis. Severe COVID-19 cases that lead to high morbidity are tightly associated with an exuberant cytokine storm that seems to trigger shock-like pathologies, leading to vascular and multiorgan failures. In other cases, the cytokine storm can lead to diffuse alveolar damage that results in acute respiratory distress syndrome (ARDS) and lung failure. Here, we address recent advances on effectors in the resolution of inflammation and discuss how pro-resolution mechanisms with particular emphasis on macrophage reprogramming, might be harnessed to limit the universal COVID-19 health threat.

Iron Heterogeneity in Early Active Multiple Sclerosis Lesions

OBJECTIVE

Multiple sclerosis (MS) is a heterogeneous inflammatory demyelinating disease. Iron distribution is altered in MS patients' brains, suggesting iron liberation within active lesions amplifies demyelination and neurodegeneration. Whether the amount and distribution of iron are similar or different among different MS immunopatterns is currently unknown.

METHODS

We used synchrotron X-ray fluorescence imaging, histology, and immunohistochemistry to compare the iron quantity and distribution between immunopattern II and III early active MS lesions. We analyzed archival autopsy and biopsy tissue from 21 MS patients.

RESULTS

Immunopattern II early active lesions contain 64% more iron (95% confidence interval [CI] = 17-127%, p = 0.004) than immunopattern III lesions, and 30% more iron than the surrounding periplaque white matter (95% CI = 3-64%, p = 0.03). Iron in immunopattern III lesions is 28% lower than in the periplaque white matter (95% CI = -40 to -14%, p < 0.001). When normalizing the iron content of early active lesions to that of surrounding periplaque white matter, the ratio is significantly higher in immunopattern II (p < 0.001). Microfocused X-ray fluorescence imaging shows that iron in immunopattern II lesions localizes to macrophages, whereas macrophages in immunopattern III lesions contain little iron.

INTERPRETATION

Iron distribution and content are heterogeneous in early active MS lesions. Iron accumulates in macrophages in immunopattern II, but not immunopattern III lesions. This heterogeneity in the two most common MS immunopatterns may be explained by different macrophage polarization, origin, or different demyelination mechanisms, and paves the way for developing new or using existing iron-sensitive magnetic resonance imaging techniques to differentiate among immunopatterns in the general nonbiopsied MS patient population. ANN NEUROL 2021;89:498-510.

CCR5-Positive Inflammatory Monocytes are Crucial for Control of Sepsis

Neutrophils and inflammatory monocytes control sepsis by migration to the site of infection via their chemokine receptors. CCR5 is a chemokine receptor that is not expressed on neutrophils and inflammatory monocytes under homeostatic conditions. However, it has been demonstrated that CCR5 can become expressed on these cells during different models of inflammation. In the present study, we investigated if CCR5 is also expressed on neutrophil and inflammatory monocytes during sepsis, exerting an important role in the migration of these cells to the infectious focus. Using cecal ligation and puncture model to induce polymicrobial sepsis, we demonstrated that the expression of CCR5 is induced on CD11bLy6GLy6C inflammatory monocytes, but not on neutrophils (CD11bLy6GLy6C). Furthermore, CCR5 plays an important role for the migration of the inflammatory monocytes to infection focus during sepsis. CCR5-expressing inflammatory monocytes migrate from the bone marrow to the circulation and then into the site of infection, where they phagocytize and kill the bacteria. Consequently, CCR5 mice showed increased systemic inflammatory response and mortality compared to wild-type mice. These data therefore demonstrate a hitherto unrecognized protective role of CCR5 in sepsis.

Differences in the Reponses to Apheresis Therapy of Patients With 3 Histopathologically Classified Immunopathological Patterns of Multiple Sclerosis

Importance

Plasma exchange and immunoadsorption are second-line apheresis therapies for patients experiencing multiple sclerosis relapses. Early active multiple sclerosis lesions can be classified into different histopathological patterns of demyelination. Pattern 1 and 2 lesions show T-cell- and macrophage-associated demyelination, and pattern 2 is selectively associated with immunoglobulin and complement deposits, suggesting a humoral immune response. Pattern 3 lesions show signs of oligodendrocyte degeneration. Thus it is possible that pathogenic heterogeneity might predict therapy response.

Objective

To evaluate the apheresis response in relation to histopathologically defined immunopathological patterns of multiple sclerosis.

Design, Setting and Participants

This single-center cohort study recruited 69 patients nationwide between 2005 and 2016. All included patients had a diagnosis of early active inflammatory demyelination consistent with multiple sclerosis; were classified into patterns 1, 2, or 3 based on brain biopsy analysis; and underwent apheresis treatments. Patients who had concomitant severe disease, neuromyelitis optica, or acute disseminated encephalomyelitis were excluded.

Main Outcomes and Measures

The primary therapy outcome was a functionally relevant improvement of the relapse-related neurological deficit. Radiological and Expanded Disability Status Scale changes were secondary outcome parameters.

Results

The mean (SD) age of patients was 36.6 (13.3) years; 46 of the 69 participants (67%) were female. Overall, 16 patients (23%) exhibited pattern 1 lesions, 40 (58%) had pattern 2 lesions, and 13 (19%) had pattern 3 lesions. A functional therapy response was observed in 5 of the 16 patients with pattern 1 disease (31%) and 22 of the 40 patients with pattern 2 disease (55%), but none of the 13 patients with pattern 3 disease exhibited improvement (pattern 2 vs 3 P < .001). Radiological improvements were found in 4 (25%), 22 (56%), and 1 (11%) of patients with patterns 1, 2, and 3, respectively. The respective rates of response measured by changes in Expanded Disability Status Scale scores were 25%, 40%, and 0%. Brainstem involvement was a negative predictive factor for the functional therapy response (logarithmic odds ratio [logOR], -1.43; 95% CI, -3.21 to 0.17; P = .03), while immunoadsorption (as compared with plasma exchange) might be a positive predictive factor (logOR, 3.26; 95% CI, 0.75 to 8.13; P = .01).

Conclusions and Relevance

This cohort study provides evidence that the response to apheresis treatment is associated with immunopathological patterns. Patients with both patterns 1 and 2 improved clinically after apheresis treatment, but pattern 2 patients who showed signs of a humoral immune response benefited most. Apheresis appears unlikely to benefit patients with pattern 3 lesions.

Cortical and meningeal pathology in progressive multiple sclerosis: a new therapeutic target?

Multiple sclerosis (MS) is an inflammatory and neurodegenerative disease that involves an intricate interaction between the central nervous system and the immune system. Nevertheless, its etiology is still unknown. MS exhibits different clinical courses: recurrent episodes with remission periods ('relapsing-remitting') that can evolve to a 'secondary progressive' form or persistent progression from the onset of the disease ('primary progressive'). The discovery of an effective treatment and cure has been hampered due to the pathological and clinical heterogeneity of the disease. Historically, MS has been considered as a disease exclusively of white matter. However, patients with progressive forms of MS present with cortical lesions associated with meningeal inflammation along with physical and cognitive disabilities. The pathogenesis of the cortical lesions has not yet been fully described. Animal models that represent both the cortical and meningeal pathologies will be critical in addressing MS pathogenesis as well as the design of specific treatments. In this review, we will address the state-of-the-art diagnostic and therapeutic alternatives and the development of strategies to discover new therapeutic approaches, especially for the progressive forms.

A proliferation-inducing ligand-mediated anti-inflammatory response of astrocytes in multiple sclerosis

OBJECTIVE

The two related tumor necrosis factor members a proliferation-inducing ligand (APRIL) and B-cell activation factor (BAFF) are currently targeted in autoimmune diseases as B-cell regulators. In multiple sclerosis (MS), combined APRIL/BAFF blockade led to unexpected exacerbated inflammation in the central nervous system (CNS) of patients. Here, we investigate the role of the APRIL/BAFF axis in the CNS.

METHODS

APRIL expression was analyzed in MS lesions by immunohistochemistry. The in vivo role of APRIL was assessed in the murine MS model, experimental autoimmune encephalitis (EAE). Functional in vitro studies were performed with human and mouse astrocytes.

RESULTS

APRIL was expressed in lesions from EAE. In its absence, the disease was worst. Lesions from MS patients also showed APRIL expression upon infiltration of macrophages. Notably, all the APRIL secreted by these macrophages specifically targeted astrocytes. The upregulation of chondroitin sulfate proteoglycan, sometimes bearing chondroitin sulfate of type E sugar moieties, binding APRIL, in reactive astrocytes explained the latter selectivity. Astrocytes responded to APRIL by producing a sufficient amount of IL-10 to dampen antigen-specific T-cell proliferation and pathogenic cytokine secretion. Finally, an intraspinal delivery of recombinant APRIL before disease onset, shortly reduced EAE symptoms. Repeated intravenous injections of recombinant APRIL before and even at disease onset also had an effect.

INTERPRETATION

Our data show that APRIL mediates an anti-inflammatory response from astrocytes in MS lesions. This protective activity is not shared with BAFF. ANN NEUROL 2019;85:406-420.

Loss of 'homeostatic' microglia and patterns of their activation in active multiple sclerosis

Microglia and macrophages accumulate at the sites of active demyelination and neurodegeneration in the multiple sclerosis brain and are thought to play a central role in the disease process. We used recently described markers to characterize the origin and functional states of microglia/macrophages in acute, relapsing and progressive multiple sclerosis. We found microglia activation in normal white matter of controls and that the degree of activation increased with age. This microglia activation was more pronounced in the normal-appearing white matter of patients in comparison to controls and increased with disease duration. In contrast to controls, the normal-appearing white matter of patients with multiple sclerosis showed a significant reduction of P2RY12, a marker expressed in homeostatic microglia in rodents, which was completely lost in active and slowly expanding lesions. Early stages of demyelination and neurodegeneration in active lesions contained microglia with a pro-inflammatory phenotype, which expressed molecules involved in phagocytosis, oxidative injury, antigen presentation and T cell co-stimulation. In later stages, the microglia and macrophages in active lesions changed to a phenotype that was intermediate between pro- and anti-inflammatory activation. In inactive lesions, the density of microglia/macrophages was significantly reduced and microglia in part converted to a P2RY12+ phenotype. Analysis of TMEM119, which is expressed on microglia but not on recruited macrophages, demonstrated that on average 45% of the macrophage-like cells in active lesions were derived from the resident microglia pool. Our study demonstrates the loss of the homeostatic microglial signature in active multiple sclerosis with restoration associated with disease inactivity.

The impact of multiple sclerosis relapse treatment on migration of effector T cells--Preliminary study

Migration of inflammatory cells from the blood to the central nervous system (CNS) is crucial for development of multiple sclerosis (MS). Inhibition of this process would allow to control disease activity. The first step confirming this approach would be the analysis of the impact of effective MS relapse therapy on migration of effector T cells. The aim of the study was to analyze the influence of methylprednisolone (MP) on the migratory activity of effector CD4+ T cells from MS patients. Moreover, to study the potential mechanism of this process we studied expression of chemokine receptors on migrating cells.

MATERIAL AND METHODS

Peripheral blood samples were obtained from relapsing-remitting MS (RR-MS) patients during relapse (n=23) and from control group (n=23). After isolation CD4+ T cells were incubated with various concentrations of MP. Then they were stimulated in chemotaxis assay with chemokines CCL3 or CXCL10 or were used to CCR1 and CXCR3 expression analysis.

RESULTS

CXCL10- and CCL3-stimulated migration of CD4+ T cells was significantly increased in MS. MP was able to reduce in vitro migration of effector T cells induced by CXCL10, but not by CCL3. Inhibition by MP was dose-dependent. Expression of analyzed chemokine receptors was unaltered after MP incubation.

CONCLUSIONS

MP reduced CD4+ T cells migration induced by CXCL10 without affecting CXCR3 expression. These observations demonstrate one of the potential mechanisms of MP action in MS, distinct from inducing cell apoptosis, and suggests the new targets for development of more effective MS treatments.

Elucidation of the CCR1- and CCR5-binding modes of MIP-1α by application of an NMR spectra reconstruction method to the transferred cross-saturation experiments

C-C chemokine receptor 1 (CCR1) and CCR5 are involved in various inflammation and immune responses, and regulate the progression of the autoimmune diseases differently. However, the number of residues identified at the binding interface was not sufficient to clarify the differences in the CCR1- and CCR5-binding modes to MIP-1α, because the NMR measurement time for CCR1 and CCR5 samples was limited to 24 h, due to their low stability. Here we applied a recently developed NMR spectra reconstruction method, Conservation of experimental data in ANAlysis of FOuRier, to the amide-directed transferred cross-saturation experiments of chemokine receptors, CCR1 and CCR5, embedded in lipid bilayers of the reconstituted high density lipoprotein, and MIP-1α. Our experiments revealed that the residues on the N-loop and β-sheets of MIP-1α are close to both CCR1 and CCR5, and those in the C-terminal helix region are close to CCR5. These results suggest that the genetic influence of the single nucleotide polymorphisms of MIP-1α that accompany substitution of residues in the C-terminal helix region, E57 and V63, would provide clues toward elucidating how the CCR5-MIP-1α interaction affects the progress of autoimmune diseases.

Central role of Th2/Tc2 lymphocytes in pattern II multiple sclerosis lesions

OBJECTIVE

Multiple sclerosis (MS) is a disease of the central nervous system with marked heterogeneity in several aspects including pathological processes. Based on infiltrating immune cells, deposition of humoral factors and loss of oligodendrocytes and/or myelin proteins, four lesion patterns have been described. Pattern II is characterized by antibody and complement deposition in addition to T-cell infiltration. MS is considered a T-cell-mediated disease, but until now the study of pathogenic T cells has encountered major challenges, most importantly the limited access of brain-infiltrating T cells. Our objective was to identify, isolate, and characterize brain-infiltrating clonally expanded T cells in pattern II MS lesions.

METHODS

We used next-generation sequencing to identify clonally expanded T cells in demyelinating pattern II brain autopsy lesions, subsequently isolated these as T-cell clones from autologous cerebrospinal fluid and functionally characterized them.

RESULTS

We identified clonally expanded CD8(+) but also CD4(+) T cells in demyelinating pattern II lesions and for the first time were able to isolate these as live T-cell clones. The functional characterization shows that T cells releasing Th2 cytokines and able to provide B cell help dominate the T-cell infiltrate in pattern II brain lesions.

INTERPRETATION

Our data provide the first functional evidence for a putative role of Th2/Tc2 cells in pattern II MS supporting the existence of this pathogenic phenotype and questioning the protective role that is generally ascribed to Th2 cells. Our observations are important to consider for future treatments of pattern II MS patients.

The role of immune cells, glia and neurons in white and gray matter pathology in multiple sclerosis

Multiple sclerosis is one of the most common causes of chronic neurological disability beginning in early to middle adult life. Multiple sclerosis is idiopathic in nature, yet increasing correlative evidence supports a strong association between one's genetic predisposition, the environment and the immune system. Symptoms of multiple sclerosis have primarily been shown to result from a disruption in the integrity of myelinated tracts within the white matter of the central nervous system. However, recent research has also highlighted the hitherto underappreciated involvement of gray matter in multiple sclerosis disease pathophysiology, which may be especially relevant when considering the accumulation of irreversible damage and progressive disability. This review aims at providing a comprehensive overview of the interplay between inflammation, glial/neuronal damage and regeneration throughout the course of multiple sclerosis via the analysis of both white and gray matter lesional pathology. Further, we describe the common pathological mechanisms underlying both relapsing and progressive forms of multiple sclerosis, and analyze how current (as well as future) treatments may interact and/or interfere with its pathology. Understanding the putative mechanisms that drive disease pathogenesis will be key in helping to develop effective therapeutic strategies to prevent, mitigate, and treat the diverse morbidities associated with multiple sclerosis.

The plasticity of inflammatory monocyte responses to the inflamed central nervous system

Over the last three decades it has become increasingly clear that monocytes, originally thought to have fixed, stereotypic responses to foreign stimuli, mediate exquisitely balanced protective and pathogenic roles in disease and immunity. This balance is crucial in core functional organs, such as the central nervous system (CNS), where minor changes in neuronal microenvironments and the production of immune factors can result in significant disease with fatal consequences or permanent neurological sequelae. Viral encephalitis and multiple sclerosis are examples of important human diseases in which the pathogenic contribution of monocytes recruited from the bone marrow plays a critical role in the clinical expression of disease, as they differentiate into macrophage or dendritic cells in the CNS to carry out effector functions. While antigen-specific lymphocyte populations are central to the adaptive immune response in both cases, in viral encephalitis a prominent macrophage infiltration may mediate immunopathological damage, seizure induction, and death. However, the autoimmune response to non-replicating, non-infectious, but abundant, self antigen has a different disease progression, associated with differentiation of significant numbers of infiltrating monocytes into dendritic cells in the CNS. Whilst a predominant presence of macrophages or dendritic cells in the inflamed CNS in viral encephalitis or multiple sclerosis is well described, the way in which the inflamed CNS mobilizes monocytes in the bone marrow to migrate to the CNS and the key drivers that lead to these specific differentiation pathways in vivo are not well understood. Here we review the current understanding of factors facilitating inflammatory monocyte generation, migration and entry into the brain, as well as their differentiation towards macrophages or dendritic cells in viral and autoimmune disease in relation to their respective disease outcomes.

Pathologic heterogeneity persists in early active multiple sclerosis lesions

OBJECTIVE

Multiple sclerosis (MS) lesions demonstrate immunopathological heterogeneity in patterns of demyelination. Previous cross-sectional studies reported immunopatterns of demyelination were identical among multiple active demyelinating lesions from the same individual, but differed between individuals, leading to the hypothesis of intraindividual pathological homogeneity and interindividual heterogeneity. Other groups suggested a time-dependent heterogeneity of lesions. The objective of our present study was to analyze tissue samples collected longitudinally to determine whether patterns of demyelination persist over time within a given patient.

METHODS

Archival tissue samples derived from patients with pathologically confirmed central nervous system inflammatory demyelinating disease who had undergone either diagnostic serial biopsy or biopsy followed by autopsy were analyzed immunohistochemically. The inclusion criteria consisted of the presence of early active demyelinating lesions--required for immunopattern classification--obtained from the same patient at 2 or more time points.

RESULTS

Among 1,321 surgical biopsies consistent with MS, 22 cases met the study inclusion criteria. Twenty-one patients (95%) showed a persistence of immunopathological patterns in tissue sampled from different time points. This persistence was demonstrated for all major patterns of demyelination. A single patient showed features suggestive of both pattern II and pattern III on biopsy, but only pattern II among all active lesions examined at autopsy.

INTERPRETATION

These findings continue to support the concept of patient-dependent immunopathological heterogeneity in early MS and suggest that the mechanisms and targets of tissue injury may differ among patient subgroups. These observations have potentially significant implications for individualized therapeutic approaches.

The autoimmune disease-associated transcription factors EOMES and TBX21 are dysregulated in multiple sclerosis and define a molecular subtype of disease

We have identified a marked over-representation of transcription factors controlling differentiation of T, B, myeloid and NK cells among the 110 MS genes now known to be associated with multiple sclerosis (MS). To test if the expression of these genes might define molecular subtypes of MS, we interrogated their expression in blood in three independent cohorts of untreated MS (from Sydney and Adelaide) or clinically isolated syndrome (CIS, from San Francisco) patients. Expression of the transcription factors (TF) controlling T and NK cell differentiation, EOMES, TBX21 and other TFs was significantly lower in MS/CIS compared to healthy controls in all three cohorts. Expression was tightly correlated between these TFs, with other T/NK cell TFs, and to another downregulated gene, CCL5. Expression was stable over time, but did not predict disease phenotype. Optimal response to therapy might be indicated by normalization of expression of these genes in blood.

Pathology of demyelinating diseases

There has been significant progress in our understanding of the pathology and pathogenesis of central nervous system inflammatory demyelinating diseases. Neuropathological studies have provided fundamental new insights into the pathogenesis of these disorders and have led to major advances in our understanding of multiple sclerosis (MS) heterogeneity, the substrate of irreversible progressive disability in MS, the relationship between inflammation and neurodegeneration in MS, the neuroimaging correlates of MS lesions, and the pathogenesis of other central nervous system inflammatory disorders, including neuromyelitis optica, acute disseminated encephalomyelitis, and Balo's concentric sclerosis. Herein, we review the pathological features of these central nervous system inflammatory demyelinating disorders and discuss neuropathological studies that have yielded novel insights into potential mechanisms involved in the formation of the demyelinated lesion.

Glatiramer acetate increases phagocytic activity of human monocytes in vitro and in multiple sclerosis patients

Beside its effects on T cells, a direct influence on cells of the myelo-monocytic lineage by GA becomes evident. Recently, we demonstrated that GA drives microglia to adopt properties of type II antigen presenting cells (APC) and increases their phagocytic activity. In the present work, we focused on human blood monocytes in order to examine whether GA may increase phagocytic activity in vivo and to evaluate the molecular mechanisms explaining this new discovered mode of action.

Peripheral blood mononuclear cells (PBMC) were obtained using a Biocoll-Isopaque gradient and monocytes were subsequently isolated by using CD14 MicroBeads. Phagocytic activity was determined by flow cytometric measurement of the ingestion of fluorescent beads. Flow cytometry was also used to assess monocytic differentiation and expression of phagocytic receptors. Monocytes of GA treated MS patients exhibited a significantly higher phagocytic activity than those of healthy controls or non-treated MS patients. In vitro, a significant phagocytic response was already detectable after 1 h of GA treatment at the concentrations of 62.5 and 125 µg/ml. A significant increase at all concentrations of GA was observed after 3 h and 24 h, respectively. Only monocytes co-expressing CD16, particularly CD14⁺⁺CD16⁺ cells, were observed to phagocytose. Treatment of monocytes with IL-10 and supernatants from GA-treated monocytes did not alter phagocytosis. We observed a decrease in CD11c expression by GA while no changes were found in the expression of CD11b, CD36, CD51/61, CD91, TIM-3, and CD206. In our blocking assays, treatment with anti-CD14, anti-CD16, anti-TIM3, anti-CD210, and particularly anti-CD36 antibodies led to a decrease in phagocytosis.

Our results demonstrate a new mechanism of action of GA treatment that augments phagocytic activity of human monocytes in vivo and in vitro. This activity seems to arise from the CD14⁺⁺CD16⁺ monocyte subset.

Oligodendrocytes and the early multiple sclerosis lesion

There is little agreement among neuropathologists regarding the timing and nature of oligodendrocyte loss in multiple sclerosis (MS). This review describes changes that accompany acute oligodendrocyte loss in new lesions. Included is a description of the immunopathology of new lesions in 23 severe early cases selected from a bank of 300 MS autopsies. Oligodendrocytes in prephagocytic lesions exhibit cytopathic changes that include apoptosis of oligodendrocytes immunoreactive for caspase 3, phagocytosis of apoptotic oligodendrocytes, swelling of cells with abnormal nuclei, complement deposition, and lysis. These are nonspecific changes that provide no clue as to the cause of oligodendrocyte injury. Associated changes include the presence of enlarged immunoglobulin (IgG)(+) microglia and early macrophages, the presence nearby of a focus of inflammatory demyelination, an open blood-brain barrier, and the presence of rare CD8 T cells. Myelin contacted by IgG(+) macrophages is immunoreactive for complement but not for IgG. It is likely that macrophage activity in evolving white and gray matter plaques is scavenging activity directed at nonvital myelin secondary to oligodendrocytes loss. One feature of MS that is not understood is the extraordinarily close resemblance the disease shows pathologically to neuromyelitis optica (NMO), including that demyelination in both is secondary to a loss of caspase 3-positive apoptotic oligodendrocytes. These similarities raise the possibility that like NMO, MS is an autoimmune disease in which oligodendrocyte apoptosis is determined by injury to some other glial or mesenchymal component.

Monocyte function and trafficking in cardiovascular disease

Monocytes are key effectors of the immune homeostasis and play a crucial role in (vascular) injury repair. Despite their role in immune defense and tissue repair mechanisms, monocytes are also involved in several pathological conditions such as autoimmune and cardiovascular diseases as well as cancer. This suggests that monocytes can be used as diagnostic and as therapeutic targets. A better understanding and characterisation of monocytes and their function in both physiological and pathological situations is thus of great interest. This review focuses on recent advances on the role of monocytes in cardiovascular diseases and describes the value of monocytes as either disease marker or therapeutic target for (cardio)vascular diseases.

A novel highly potent therapeutic antibody neutralizes multiple human chemokines and mimics viral immune modulation

Chemokines play a key role in leukocyte recruitment during inflammation and are implicated in the pathogenesis of a number of autoimmune diseases. As such, inhibiting chemokine signaling has been of keen interest for the development of therapeutic agents. This endeavor, however, has been hampered due to complexities in the chemokine system. Many chemokines have been shown to signal through multiple receptors and, conversely, most chemokine receptors bind to more than one chemokine. One approach to overcoming this complexity is to develop a single therapeutic agent that binds and inactivates multiple chemokines, similar to an immune evasion strategy utilized by a number of viruses. Here, we describe the development and characterization of a novel therapeutic antibody that targets a subset of human CC chemokines, specifically CCL3, CCL4, and CCL5, involved in chronic inflammatory diseases. Using a sequential immunization approach, followed by humanization and phage display affinity maturation, a therapeutic antibody was developed that displays high binding affinity towards the three targeted chemokines. In vitro, this antibody potently inhibits chemotaxis and chemokine-mediated signaling through CCR1 and CCR5, primary chemokine receptors for the targeted chemokines. Furthermore, we have demonstrated in vivo efficacy of the antibody in a SCID-hu mouse model of skin leukocyte migration, thus confirming its potential as a novel therapeutic chemokine antagonist. We anticipate that this antibody will have broad therapeutic utility in the treatment of a number of autoimmune diseases due to its ability to simultaneously neutralize multiple chemokines implicated in disease pathogenesis.

Migration of monocytes after intracerebral injection at entorhinal cortex lesion site

The lack of classical lymph vessels within brain tissue complicates immune surveillance of the CNS, and therefore, cellular emigration out of the CNS parenchyma requires alternate pathways. Whereas invasion of blood-derived mononuclear cells and their transformation into ramified, microglia-like cells in areas of axonal degeneration across an intact BBB have been demonstrated, it still remained unclear whether these cells reside permanently, undergo apoptosis, or leave the brain to present antigen in lymphoid organs. With the use of ECL of mice and injection of GFP-expressing monocytes, we followed the appearance of injected cells in spleen and LNs and the migratory pathways in whole-head histological sections. Monocytes migrated from the lesion site to deep CLNs, peaking in number at Day 7, but they were virtually absent in spleen and in superficial CLNs and inguinal LNs until Day 21 after lesion/injection. In whole-head sections, GFP monocytes were found attached to the olfactory nerves and located within the nasal mucosa at 48 hpi. Thus, monocytes are capable of migrating from lesioned brain areas to deep CLNs and use the cribriform plate as an exit route.

Monocyte recruitment during infection and inflammation

Monocytes originate from progenitors in the bone marrow and traffic via the bloodstream to peripheral tissues. During both homeostasis and inflammation, circulating monocytes leave the bloodstream and migrate into tissues where, following conditioning by local growth factors, pro-inflammatory cytokines and microbial products, they differentiate into macrophage or dendritic cell populations. Recruitment of monocytes is essential for effective control and clearance of viral, bacterial, fungal and protozoal infections, but recruited monocytes also contribute to the pathogenesis of inflammatory and degenerative diseases. The mechanisms that control monocyte trafficking under homeostatic, infectious and inflammatory conditions are being unravelled and are the focus of this Review.

Plasmacytoid dendritic cells in multiple sclerosis: chemokine and chemokine receptor modulation by interferon-beta

Plasmacytoid dendritic cells (pDCs) are present in peripheral blood, leptomeninges and demyelinating lesions in patients with multiple sclerosis (MS). The ability of pDCs to produce chemokines and express the chemokine receptor CCR7 in MS is not known. We studied pDCs in MS patients and healthy subjects. The ability of pDCs to up-regulate CCR7 was significantly increased in untreated MS patients as compared to healthy subjects. IFN-beta treatment significantly inhibited TLR9 agonist-specific secretion of chemokines, which are ligands for CCR5-positive Th1 cells (CCL3, CCL4, and CCL5), and impaired TLR9 agonist-induced up-regulation of CCR7 and IFN-alpha in MS patients. This finding represents a new immunomodulatory effect of IFN-beta in patients with multiple sclerosis.

CXCR2-positive neutrophils are essential for cuprizone-induced demyelination: relevance to multiple sclerosis

Multiple sclerosis is an inflammatory demyelinating disorder of the CNS. Recent studies have suggested diverse mechanisms as underlying demyelination, including a subset of lesions induced by an interaction between metabolic insult to oligodendrocytes and inflammatory mediators. For mice of susceptible strains, cuprizone feeding results in oligodendrocyte cell loss and demyelination of the corpus callosum. Remyelination ensues and has been extensively studied. Cuprizone-induced demyelination remains incompletely characterized. We found that mice lacking the type 2 CXC chemokine receptor (CXCR2) were relatively resistant to cuprizone-induced demyelination and that circulating CXCR2-positive neutrophils were important for cuprizone-induced demyelination. Our findings support a two-hit process of cuprizone-induced demyelination, supporting the idea that multiple sclerosis pathogenesis features extensive oligodendrocyte cell loss. These data suggest that cuprizone-induced demyelination is useful for modeling certain aspects of multiple sclerosis pathogenesis.

Multiple sclerosis: distribution of inflammatory cells in newly forming lesions

OBJECTIVE

CD4 T-cell-dependent macrophage activation directed against a myelin or oligodendrocyte antigen is generally thought to be the mechanism causing myelin destruction in multiple sclerosis (MS). However, areas within expanding MS lesions may exhibit prominent oligodendrocyte loss and apoptosis in the absence of infiltrating lymphocytes. The present study was designed to further investigate the inflammatory profile of different regions within rapidly expanding MS lesions.

METHODS

Twenty-six active lesions from 11 patients with early MS were serially sectioned and immunostained for T and B cells, plasma cells, ramified microglia, macrophages, monocytes, and CD209-positive dendritic cells. Cell counts were compared in prephagocytic, phagocytic, and immediately postphagocytic areas.

RESULTS

Parenchymal T and B cells were largely absent in areas of initial oligodendrocyte loss and in areas of degenerate and dead myelin infiltrated by myelin phagocytes. In contrast, trailing areas of complete demyelination packed with lipid macrophages, and, in some lesions, regenerating oligodendrocytes, showed large numbers of T cells, B cells, and immunoglobulin G (IgG)-positive plasma cells. Lesions in 2 exceptionally early cases contained relatively few T and B cells, and no IgG-positive plasma cells.

INTERPRETATION

Early loss of oligodendrocytes is a prominent feature in tissue bordering rapidly expanding MS lesions. Macrophage activity is largely an innate scavenging response to the presence of degenerate and dead myelin. Adaptive immune activity involving T and B cells is conspicuous chiefly in recently demyelinated tissue, which may show signs of oligodendrocyte regeneration. The findings suggest that plaque formation has some basis other than destructive cell-mediated immunity directed against a myelin or oligodendrocyte antigen.

HIV Coreceptors and Their Roles in Leukocyte Trafficking During Neuroinflammatory Diseases

Due to the increasing resistance of HIV-1 to antiretroviral therapies, there has been much emphasis on the discovery and development of alternative therapeutics for HIV-1-infected individuals. The chemokine receptors CXCR4 (Bleul et al. 1996a; Feng et al. 1996; Nagasawa et al. 1996; Oberlin et al. 1996) and CCR5 (Alkhatib et al. 1996; Deng et al. 1996; Dragic et al. 1996) were identified as target molecules from the time their role as coreceptors for HIV-1 entry into leukocytes was first discovered 10 years ago. Initial studies focused on the use of the chemokine ligands, or altered derivatives, of CXCR4 and CCR5 to prevent the entrance of HIV-1 into immune cells (Schols 2006). While these studies showed some initial promise, there was evidence of significant caveats to their use, including selection of alternative coreceptor utilizing strains (Marechal et al. 1999; Mosier et al. 1999) and the potential to cause inflammatory side effects. These data prompted the development and study of small molecule inhibitors of CXCR4 and CCR5, which have also been used to examine the roles of these molecules in a variety of inflammatory and infectious diseases.

The pathological spectrum of CNS inflammatory demyelinating diseases

Inflammatory demyelinating diseases of the central nervous system (CNS) occur throughout the world and are the leading cause of nontraumatic neurological disability in young adults. They represent a broad spectrum of disorders that vary in their clinical course, regional distribution, and pathology. However, there can be a considerable overlap between at least some of these disorders, leading to misdiagnoses or diagnostic uncertainty. Multiple sclerosis (MS), the most common inflammatory demyelinating CNS disease affecting approximately one million adults, shares the basic pathological hallmark of CNS inflammatory demyelination. Advances based on recent systematic clinicopathologic-serologic correlative approaches have led to novel insights with respect to the classification of this disorder, the pathologic substrate of disability, a better understanding of the underlying pathogenic mechanisms involved in lesion formation, as well as the clinical relevance of cortical demyelination and normal appearing white matter pathology. In addition to prototypic MS, these diseases include Marburg variant of acute MS, Balo's concentric sclerosis, neuromyelitis optica, acute disseminated encephalomyelitis, and tumefactive MS. The last decade has seen a resurgence of interest in examining the lesions of these inflammatory demyelinating CNS disorders with newer and more sophisticated immunological and molecular tools. Herein, we review the clinicopathologic features of these CNS inflammatory demyelinating disorders and discuss recent advances in understanding their immunopathogenesis.

Double-label nonradioactive in situ hybridization for the analysis of chemokine receptor expression in the central nervous system

Chemokines are a family of mainly-secreted proteins, traditionally associated with regulation of leukocyte trafficking during host defense and pathological immune/inflammatory reactions. All chemokines signal to G protein-coupled receptors. Recent studies show that chemokines and their receptors are also expressed by neuroepithelial cells, and govern developmental, physiological and pathological processes through actions towards these cells, as well as infiltrating and resident hematopoietic cells. Understanding chemokine action at the tissue level therefore requires defining which cells express chemokine receptors. At a first level of approximation (and lacking appropriate immunohistochemical reagents) this determination can be made by in situ hybridization (ISH), which localizes mRNA expression for chemokines and their receptors at the cellular level. Here we provide a protocol for ISH and demonstrate its application for localizing mRNA encoding two chemokine receptors, CXCR4 and CXCR7 in murine CNS tissues.

CCR5 expression on macrophages/microglia is associated with early remyelination in multiple sclerosis lesions

Remyelination in multiple sclerosis (MS) occurs spontaneously and extensively. The underlying mechanisms, however, are only partly understood. Findings in experimental animal settings suggest that inflammation promotes remyelination and repair. Here, we characterized the chemokine receptor expression profiles of macrophages/microglia in early remyelinating and completely remyelinated lesions compared with active demyelinating and inactive demyelinated MS lesions obtained in the early disease course. Biopsy material consisting of 16 MS cases was available for this study. We found that macrophages/microglia within early remyelinating lesions expressed predominantly CCR5. Our findings implicate a possible role of CCR5(+) cells in initiating remyelination.

CCL genes in multiple sclerosis and systemic lupus erythematosus

This follow up study aims to refine the roles of previously suggested candidate genes (CC chemokine ligands or CCLs) in multiple sclerosis (MS), and to test these markers in another autoimmune disorder, systemic lupus erythematosus (SLE). After stringent correction for multiple testing, we reject the importance of previously suggested borderline associations with CCLs in MS. A new finding is the differential distribution of CCL8 marker alleles and a haplotype in extreme severity subgroups of MS. In SLE, this study reveals strong associations with a marker and a haplotype encompassing the CCL14 gene, which suggests that a lupus relevant variant may lie within or in the proximity of this haplotype.

Multiple sclerosis: chemokine receptor expression on circulating lymphocytes in correlation with radiographic measures of tissue injury

BACKGROUND

Leukocytes expressing inflammatory chemokine receptors (CKRs), most consistently CCR2, CCR5, and CXCR3, have been identified in multiple sclerosis (MS) tissue lesions and provide attractive therapeutic targets. Our previous studies found large inter-individual differences in expression of these CKRs but stable levels over time within subjects. This observation suggests a CKR "set-point" within individuals, which might relate to inflammatory injury in MS. We evaluated the correlation between CKR levels and magnetic resonance imaging (MRI) measures of disease activity.

METHODS

Fifty-five relapsing remitting MS (RRMS) and secondary progressive MS (SPMS) patients were prospectively followed with annual CKR and MRI studies. Multiparameter flow cytometry was used to determine CCR2, CCR5, and CXCR3 expression on CD4 and CD8 cells. Simultaneous cranial MRIs were performed, and quantitative measures of T2, T1, and gadolinium lesions, brain parenchymal fraction (BPF), and whole brain and fractionated magnetization transfer ratio (MTR) were performed using automated software. Spearman's rank correlations evaluated the relationship between CKR levels and MRI measures.

RESULTS

Significant correlations were observed between CXCR3 expression on CD8 cells and measures of new (T1) and total (T1, T2) lesion volumes, lesion MTR, and BPF; higher levels of CXCR3 expression were correlated with greater injury on MRI (|r| = 0.27-0.42). In contrast, CD4 cell CKR expression was only minimally correlated with MRI measures.

CONCLUSIONS

Over 2 years, we observed significant correlations between the percent of CD8 cells expressing CXCR3 and MRI measures of MS inflammatory activity and tissue destruction. These observations are consistent with a pathogenic role for cytotoxic T cells in MS brain and have significant implications regarding T-cell targeted therapeutic strategies.

Mitochondrial defects in acute multiple sclerosis lesions

Multiple sclerosis is a chronic inflammatory disease, which leads to focal plaques of demyelination and tissue injury in the CNS. The structural and immunopathological patterns of demyelination suggest that different immune mechanisms may be involved in tissue damage. In a subtype of lesions, which are mainly found in patients with acute fulminant multiple sclerosis with Balo's type concentric sclerosis and in a subset of early relapsing remitting multiple sclerosis, the initial myelin changes closely resemble those seen in white matter stroke (WMS), suggesting a hypoxia-like tissue injury. Since mitochondrial injury may be involved in the pathogenesis of such lesions, we analysed a number of mitochondrial respiratory chain proteins in active lesions from acute multiple sclerosis and from WMS using immunohistochemistry. Functionally important defects of mitochondrial respiratory chain complex IV [cytochrome c oxidase (COX)] including its catalytic component (COX-I) are present in Pattern III but not in Pattern II multiple sclerosis lesions. The lack of immunohistochemically detected COX-I is apparent in oligodendrocytes, hypertrophied astrocytes and axons, but not in microglia. The profile of immunohistochemically detected mitochondrial respiratory chain complex subunits differs between multiple sclerosis and WMS. The findings suggest that hypoxia-like tissue injury in Pattern III multiple sclerosis lesions may be due to mitochondrial impairment.

Chemokines and chemokine receptors in neurological disease: raise, retain, or reduce?

Chemokines and chemokine receptors comprise a large number of molecules implicated in a wide range of physiological and pathological functions. Numerous studies have demonstrated the roles of chemokines and chemokine receptors: 1) during development, by regulating hematopoiesis, cardiogenesis, and vascular and cerebellar development; 2) during tumor biology, by controlling cell proliferation, angiogenesis, and metastasis; and 3), especially during leukocyte migration, by acting on firm adhesion, locomotion, diapedesis, and chemotaxis. This review focuses on chemokine and chemokine receptor involvement in diverse neurological diseases and their therapeutic potentials. Because of its induction or upregulation during CNS pathologies, members of the chemokine system can be used as biological markers. CXCR4 and CXCL12, by the correlation between their expression and the glioblastoma tumor progression, could be a marker to grade this type of CNS tumor. CCR1, by virtue of specific expression in Abeta plaques, may be a marker for Alzheimer pathology. Downregulation of CCL2 in cerebrospinal fluid may be a candidate to characterize multiple sclerosis (MS), but needs additional investigation. Moreover, chemokines and chemokine receptors represent interesting therapeutic targets. Using chemokine receptor antagonists, several studies provided exciting findings for potential neurological disease treatment. Chemokine receptor antagonists reduce disease severity in animal models of MS. In glioblastoma, a CXCR4 antagonist (AMD3100) showed an inhibition of tumor growth. Inhibition of chemokine receptor signaling is not the only therapeutic strategy: for example, CXCR4-CXCL12 has anti-inflammatory properties and CX3CL1-CX3CR1 controls neurotoxicity. Thus, chemokine biology suggests several approaches for treating neurological disease.

The pathology of MS: new insights and potential clinical applications

BACKGROUND

The pathological hallmarks of the multiple sclerosis (MS) lesion consist of focal demyelination, inflammation, scar formation, and variable axonal destruction. Despite years of classical histopathological study and more recent intensive use of magnetic resonance technology, the MS lesion is incompletely understood. How it is initiated, how it changes over time, how it correlates with clinical symptoms and other markers of disease activity, and how it is impacted by therapeutic intervention are all largely unknown. As the site of disease pathology, the MS lesion remains the target of attack for therapy. Therefore it is essential we better understand MS lesion evolution and its clinical as well as paraclinical correlates.

REVIEW SUMMARY

In this review, we focus on what can be learned about MS from detailed pathological analysis. We discuss the literature on both the traditional and more recent changing concepts about MS pathogenesis. We also review the work of the Multiple Sclerosis Lesion Project, an international collaborative effort to study the pathologic, clinical, and radiologic correlates of the MS lesion.

CONCLUSIONS

The introduction of new technologies has contributed to a better appreciation regarding the complexity of the MS lesion. The discovery of heterogeneity in demyelinating lesions has suggested that different mechanisms may be involved in MS pathogenesis. This observation may be important for future studies on the etiology and therapy of the disease. However the potential to apply these findings to the clinic will rely on the development of technologies that allow the stratification of MS subtypes without being dependent on brain biopsies.

Temporal expression and cellular origin of CC chemokine receptors CCR1, CCR2 and CCR5 in the central nervous system: insight into mechanisms of MOG-induced EAE

Background

The CC chemokine receptors CCR1, CCR2 and CCR5 are critical for the recruitment of mononuclear phagocytes to the central nervous system (CNS) in multiple sclerosis (MS) and other neuroinflammatory diseases. Mononuclear phagocytes are effector cells capable of phagocytosing myelin and damaging axons. In this study, we characterize the regional, temporal and cellular expression of CCR1, CCR2 and CCR5 mRNA in the spinal cord of rats with myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (MOG-EAE). While resembling human MS, this animal model allows unique access to CNS-tissue from various time-points of relapsing neuroinflammation and from various lesional stages: early active, late active, and inactive completely demyelinated lesions.

Methods

The expression of CCR1, CCR2 and CCR5 mRNA was studied with in situ hybridization using radio labelled cRNA probes in combination with immunohistochemical staining for phenotypic cell markers. Spinal cord sections from healthy rats and rats with MOG-EAE (acute phase, remission phase, relapse phase) were analysed. In defined lesion stages, the number of cells expressing CCR1, CCR2 and CCR5 mRNA was determined. Data were statistically analysed by the nonparametric Mann-Whitney U test.

Results

In MOG-EAE rats, extensive up-regulation of CCR1 and CCR5 mRNA, and moderate up-regulation of CCR2 mRNA, was found in the spinal cord during episodes of active inflammation and demyelination. Double staining with phenotypic cell markers identified the chemokine receptor mRNA-expressing cells as macrophages/microglia. Expression of all three receptors was substantially reduced during clinical remission, coinciding with diminished inflammation and demyelination in the spinal cord. Healthy control rats did not show any detectable expression of CCR1, CCR2 or CCR5 mRNA in the spinal cord.

Conclusion

Our results demonstrate that the acute and chronic-relapsing phases of MOG-EAE are associated with distinct expression of CCR1, CCR2, and CCR5 mRNA by cells of the macrophage/microglia lineage within the CNS lesions. These data support the notion that CCR1, CCR2 and CCR5 mediate recruitment of both infiltrating macrophages and resident microglia to sites of CNS inflammation. Detailed knowledge of expression patterns is crucial for the understanding of therapeutic modulation and the validation of CCR1, CCR2 and CCR5 as feasible targets for therapeutic intervention in MS.

Influence of CCR5-Δ32 genotype in Spanish population with multiple sclerosis

A number of association studies have explored the relationship between the CCR5-Delta32 allele and the risk of developing multiple sclerosis (MS), with varying results. In light of the results of several studies that have analyzed the role of the allele in MS, it has been proposed that the allele is involved in the etiopathogeny of the disease. Our study revealed a statistically significant difference between the study group and the control group for the carriers of at least one deleted allele (P = 0.027). The allele was more frequent in the control group, which suggests a possible protective effect of this deletion against MS. When ethnic origin was taken into account in the same analysis, we saw that the bulk of the difference was attributable to the Basque group, although the trend was also visible in the control group. Consideration of ethnic origin is therefore essential for the analysis of our sample. CCR5-Delta32 allele distribution was higher in the Basque control population than in the Basque MS population, which suggests that it confers a protective effect against MS. Relevant values were a P value of 0.008 and an odds ratio of 0.168 (95% confidence interval, 0.038 to 0.737).

CCR5 expression on monocytes and T cells: modulation by transmigration across the blood-brain barrier in vitro

Observational studies in multiple sclerosis (MS) demonstrated altered expression of chemokine receptors (CkRs) on comparable populations of mononuclear cells (e.g. CD4(+)/CD45RO(+) T-cells) in brain sections compared with blood. These findings raised questions about the regulation of CkRs on trafficking cells. Regulatory processes for CkRs are complex: examples include down-regulation following ligand engagement during migration and either up- or down-regulation following activation. Additionally, CkRs that mediate transmigration without being down-regulated will be selectively enriched on migrating cells in the inflammatory site. Finally, CkRs may act as functionally neutral markers of activated cells capable of undergoing transmigration. Clarifying CkR regulation may aid in the selection and application of antagonists for treating neuroinflammation. Mechanisms of receptor regulation during transmigration cannot be studied by descriptive methods. We evaluated CCR5 expression on CD14(+) monocytes and CD3(+) T-cells following CCL5-driven transmigration through an in vitro blood-brain barrier (IVBBB), as both T-cells and monocytes in MS lesions express CCR5. CCR5 expression was augmented on non-migrating CD14(+) but not CD3(+) cells, suggesting selective activation of monocytes by incubation in contact with endothelial cells. As proposed from observational studies, CCR5 was enriched on monocytes that migrated spontaneously in the absence of exogenous chemokine. Addition of the CCR5 ligand CCL5 to the lower chamber led to enhanced CD3(+) T-cell migration. Interestingly, CCR5 was down-regulated on both CD14(+) monocytes and CD3(+) T cells during CCL5-driven migration. These results are distinct from those obtained in comparable studies of CCR2 and CXCR3, suggesting that the specifics for CkR expression should be studied for individual receptors on each leukocyte subpopulation during the design of strategies for pharmacological blockade in neuroinflammation.

Chemokines, mononuclear cells and the nervous system: heaven (or hell) is in the details

Chemokines and their receptors are essential elements in leukocyte trafficking during health and disease. There are three (or more) distinct routes of leukocyte entry into the central nervous system (CNS), and molecular mechanisms of physiological and neuroinflammatory leukocyte recruitment to the CNS are slowly coming into view. Migration of immune cells into cerebrospinal fluid supports CNS immunosurveillance. Current knowledge of the trafficking determinants that direct the leukocyte recruitment in CNS pathology relies in large part on studies of multiple sclerosis and its models including experimental autoimmune encephalomyelitis. Overlapping molecular signals are responsible for the migration of specific cells into the CNS during pathological inflammation and host defense, raising challenges and opportunities for therapeutic manipulation.

Analyses of a MS-associated haplotype encompassing the CCL3 gene

Our previous studies showed the association of multiple sclerosis with the same marker haplotype encompassing the CCL3 gene in two independent sets of families. Here we present that sequencing of this haplotype and its flanking regions detected no new mutation, but 16 single nucleotide polymorphisms (SNP) and 1 insertion/deletion variant in both affected and unaffected individuals. Transmission distortion analyses of the newly identified variants in the second set of families revealed no individual marker association. In the absence of a single disease relevant variant within the MS associated haplotype and the surrounding linkage disequilibrium block, the highlighted haplotype may itself indicate a functionally relevant allelic combination or interaction.