Astrocytes are the major intracerebral source of macrophage inflammatory protein-3alpha/CCL20 in relapsing experimental autoimmune encephalomyelitis and in vitro

GFAP-independent inflammatory competence and trophic functions of astrocytes generated from murine embryonic stem cells

The directed generation of pure astrocyte cultures from pluripotent stem cells has proven difficult. Generation of defined pluripotent-stem-cell derived astrocytes would allow new approaches to the investigation of plasticity and heterogeneity of astrocytes. We here describe a two-step differentiation scheme resulting in the generation of murine embryonic stem cell (mESC) derived astrocytes (MEDA), as characterized by the upregulation of 19 astrocyte-associated mRNAs, and positive staining of most cells for GFAP (glial fibrillary acidic protein), aquaporin-4 or glutamine synthetase. The MEDA cultures could be cryopreserved, and they neither contained neuronal, nor microglial cells. They also did not react to the microglial stimulus lipopolysaccharide, while inflammatory activation by a complete cytokine mix (CCM) or its individual components (TNF-α, IL1-β, IFN-γ) was readily observed. MEDA, stimulated by CCM, became susceptible to CD95 ligand-induced apoptosis and produced NO and IL-6. This was preceded by NF-kB activation, and up-regulation of relevant mRNAs. Also GFAP-negative astrocytes were fully inflammation-competent. Neurotrophic support by MEDA was found to be independent of GFAP expression. In summary, we described here the generation and functional characterization of microglia-free murine astrocytes, displaying phenotypic heterogeneity as is commonly observed in brain astrocytes.

Lateral fluid percussion injury of the brain induces CCL20 inflammatory chemokine expression in rats

Background

Traumatic brain injury (TBI) evokes a systemic immune response including leukocyte migration into the brain and release of pro-inflammatory cytokines; however, the mechanisms underlying TBI pathogenesis and protection are poorly understood. Due to the high incidence of head trauma in the sports field, battlefield and automobile accidents identification of the molecular signals involved in TBI progression is critical for the development of novel therapeutics.

Methods

In this report, we used a rat lateral fluid percussion impact (LFPI) model of TBI to characterize neurodegeneration, apoptosis and alterations in pro-inflammatory mediators at two time points within the secondary injury phase. Brain histopathology was evaluated by fluoro-jade (FJ) staining and terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay, polymerase chain reaction (qRT PCR), enzyme linked immunosorbent assay (ELISA) and immunohistochemistry were employed to evaluate the CCL20 gene expression in different tissues.

Results

Histological analysis of neurodegeneration by FJ staining showed mild injury in the cerebral cortex, hippocampus and thalamus. TUNEL staining confirmed the presence of apoptotic cells and CD11b⁺ microglia indicated initiation of an inflammatory reaction leading to secondary damage in these areas. Analysis of spleen mRNA by PCR microarray of an inflammation panel led to the identification of CCL20 as an important pro-inflammatory signal upregulated 24 h after TBI. Although, CCL20 expression was observed in spleen and thymus after 24h of TBI, it was not expressed in degenerating cortex or hippocampal neurons until 48 h after insult. Splenectomy partially but significantly decreased the CCL20 expression in brain tissues.

Conclusion

These results demonstrate that the systemic inflammatory reaction to TBI starts earlier than the local brain response and suggest that spleen- and/ or thymus-derived CCL20 might play a role in promoting neuronal injury and central nervous system inflammation in response to mild TBI.

Regulatory T cells exhibit enhanced migratory characteristics, a feature impaired in patients with multiple sclerosis

Migration of immune cells characterizes inflammation and plays a key role in autoimmune diseases such as MS. CD4(+)Foxp3(+) regulatory T cells (Treg) have the potential to dampen immune responses but show functional impairment in patients with MS. We here show that murine Treg exhibit higher constitutive cell motility in horizontal migration on laminin, surpass non-Treg in transwell assays through microporous membranes as well as across primary brain endothelium and are present in the naïve CNS to a significantly higher extent compared to spleen, lymph nodes and blood. Likewise, human Treg from healthy donors significantly exceed non-Treg in migratory rates across primary human brain endothelium. Finally, we investigated whether the propensity to migrate is impaired as a feature of autoimmunity and therefore tested patients with MS. Treg from patients with stable relapsing-remitting MS show significantly impaired migratory capacity under non-inflammatory conditions compared to healthy donors. We hypothesize that the enhanced propensity to migrate is a feature of Treg that allows for an equilibrium in parenchymal immune surveillance, e.g. of the CNS. Impaired Treg migration across the intact blood-brain barrier, as observed for Treg from patients with MS, indicates a broader functional deficiency hypothetically contributing to early CNS lesion development or phases of MS remissions.

IL-9 promotes Th17 cell migration into the central nervous system via CC chemokine ligand-20 produced by astrocytes

Newly discovered IL-9-producing helper T cells (Th9) reportedly exert both aggravating and suppressive roles on experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. However, it is still unclear whether Th9 is a distinct Th cell subset and how IL-9 functions in the CNS. In this study, we show that IL-9 is produced by naive CD4(+) T cells that were stimulated with anti-CD3 and anti-CD28 Abs under the conditions of Th2-, inducible regulatory T cell-, Th17-, and Th9-polarizing conditions and that IL-9 production is significantly suppressed in the absence of IL-4, suggesting that IL-4 is critical for the induction of IL-9 by each producing cell. The IL-9 receptor complex, IL-9R and IL-2Rγ, is constitutively expressed on astrocytes. IL-9 induces astrocytes to produce CCL-20 but not other chemokines, including CCL-2, CCL-3, and CXCL-2 by astrocytes. The conditioned medium of IL-9-stimulated astrocytes induces Th17 cell migration in vitro, which is cancelled by adding anti-CCL-20 neutralizing Abs. Treating with anti-IL-9 neutralizing Abs attenuates experimental autoimmune encephalomyelitis, decreases the number of infiltrating Th17 cells, and reduces CCL-20 expression in astrocytes. These results suggest that IL-9 is produced by several Th cell subsets in the presence of IL-4 and induces CCL-20 production by astrocytes to induce the migration of Th17 cells into the CNS.

Absence of PAF receptor alters cellular infiltrate but not rolling and adhesion of leukocytes in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a condition induced in some susceptible species to the study of multiple sclerosis (MS). The platelet activating factor (PAF) is an important mediator of immune responses and seems to be involved in MS. However, the participation of PAF in EAE and MS remains controversial. Thus, in this study, we aimed to evaluate the role of PAF receptor in the pathogenesis of EAE. EAE was induced using an emulsion containing MOG(35-55). EAE-induced PAF receptor knock out (PAFR(-/-)) mice presented milder disease when compared to C57BL/6 wild type (WT) animals. PAFR(-/-) animals had lower inflammatory infiltrates in central nervous system (CNS) tissue when compared to WT mice. However, intravital microscopy in cerebral microvasculature revealed similar levels of rolling and adhering leukocytes in both WT and PAFR(-/-) mice. Interleukine (IL)-17 and chemokines C-C motif legends (CCL)2 and CCL5 were significantly lower in PAFR(-/-) mice when compared to WT mice. Brain infiltrating cluster of differentiation (CD)4(+) leukocytes and IL-17(+) leukocytes was diminished in PAFR(-/-) when compared to WT mice. Taken together, our results suggest that PAF receptor is important in the induction and development of EAE, although it has no influence in rolling and adhesion steps of cell recruitment. The absence of PAF receptor results in milder disease by altering the type of inflammatory mediators and cells that are present in CNS tissue.

Molecular mechanisms underlying hypothermia-induced neuroprotection

Stroke is a dynamic event in the brain involving heterogeneous cells. There is now compelling clinical evidence that prolonged, moderate cerebral hypothermia initiated within a few hours after severe ischemia can reduce subsequent neuronal death and improve behavioral recovery. The neuroprotective role of hypothermia is also well established in experimental animals. However, the mechanism of hypothermic neuroprotection remains unclear, although, presumably involves the ability of hypothermia to suppress a broad range of injurious factors. In this paper, we addressed this issue by utilizing comprehensive gene and protein expression analyses of ischemic rat brains. To predict precise target molecules, we took advantage of the therapeutic time window and duration of hypothermia necessary to exert neuroprotective effects. We proposed that hypothermia contributes to protect neuroinflammation, and identified candidate molecules such as MIP-3α and Hsp70 that warrant further investigation as targets for therapeutic drugs acting as “hypothermia-like neuroprotectants.”

An immune paradox: how can the same chemokine axis regulate both immune tolerance and activation?: CCR6/CCL20: a chemokine axis balancing immunological tolerance and inflammation in autoimmune disease

Chemokines (chemotactic cytokines) drive and direct leukocyte traffic. New evidence suggests that the unusual CCR6/CCL20 chemokine receptor/ligand axis provides key homing signals for recently identified cells of the adaptive immune system, recruiting both pro-inflammatory and suppressive T cell subsets. Thus CCR6 and CCL20 have been recently implicated in various human pathologies, particularly in autoimmune disease. These studies have revealed that targeting CCR6/CCL20 can enhance or inhibit autoimmune disease depending on the cellular basis of pathogenesis and the cell subtype most affected through different CCR6/CCL20 manipulations. Here, we discuss the significance of this chemokine receptor/ligand axis in immune and inflammatory functions, consider the potential for targeting CCR6/CCL20 in human autoimmunity and propose that the shared evolutionary origins of pro-inflammatory and regulatory T cells may contribute to the reason why both immune activation and regulation might be controlled through the same chemokine pathway.

Clinical study on CXCL13, CCL17, CCL20 and IL-17 as immune cell migration navigators in relapsing-remitting multiple sclerosis patients

BACKGROUND

There has been a growing evidence for the role of chemokines in the pathology of multiple sclerosis. Recently, there has been great emphasis placed on humoral immunity and the T(H)-17 response, which has not yet been thoroughly described in MS. The aim of this study was to investigate the role of specific chemokines involved in B-cell migration (CXCL13) and in the T(H)-17 immune response (IL-17, CCL17, CCL20).

METHODS

Using ELISA, the chosen chemokine concentrations were measured in the serum and cerebrospinal fluid of relapsing-remitting MS patients with both active and stable disease, and the relapse prediction rate was calculated.

RESULTS

We found that the CSF concentrations of CXCL13 in patients with RRMS both, during relapse and remission, were significantly higher than in controls. CCL17 and CCL20 were not detected in CSF in either of the groups, whereas serum CCL20 level was significantly higher in remission than during relapse. Intravenous methylprednisolone treatment of patients with relapse did not influence serum CXCL13 and CCL20 levels. However, it did lower CCL17 and IL-17 concentrations.

CONCLUSIONS

CXCL13 is an important mediator in MS that is strongly linked to the neuroinflammatory activity of the disease. However, more studies are needed for elucidating the roles of CCL17, CCL20 and IL-17 in MS pathology.

Neutralizing endogenous chemokines with small molecules. Principles and potential therapeutic applications

Regulation of cellular responses to external stimuli such as hormones, neurotransmitters, or cytokines is achieved through the control of all steps of the complex cascade starting with synthesis, going through maturation steps, release, distribution, degradation and/or uptake of the signalling molecule interacting with the target protein. One possible way of regulation, referred to as scavenging or neutralization of the ligand, has been increasingly studied, especially for small protein ligands. It shows innovative potential in chemical biology approaches as well as in disease treatment. Neutralization of protein ligands, as for example cytokines or chemokines can lead to the validation of signalling pathways under physiological or pathophysiological conditions, and in certain cases, to the development of therapeutic molecules now used in autoimmune diseases, chronic inflammation and cancer treatment. This review explores the field of ligand neutralization and tries to determine to what extent small chemical molecules could substitute for neutralizing antibodies in therapeutic approaches.

CCR6 regulates EAE pathogenesis by controlling regulatory CD4+ T-cell recruitment to target tissues

The T-cell subsets, characterized by their cytokine production profiles and immune regulatory functions, depend on correct in vivo location to interact with accessory or target cells for effective immune responses. Differentiation of naive CD4(+) T cells into effectors is accompanied by sequentially regulated expression of the chemokine receptors responsible for cell recruitment to specific tissues. We studied CCR6 function in EAE, a CD4(+) T-cell-mediated CNS disease characterized by mononuclear infiltration and demyelination. CCR6(-/-) mice showed an altered time course of EAE development, with delayed onset, a higher clinical score, and more persistent symptoms than in controls. An imbalanced cytokine profile and reduced Foxp3(+) cell frequency characterized CNS tissues from CCR6(-/-) compared with CCR6(+/+) mice during the disease effector phase. Transfer of CCR6(+/+) Treg to CCR6(-/-) mice the day before EAE induction reduced the clinical score associated with an increased in infiltrating Foxp3(+) cells and recovery of the cytokine balance in CCR6(-/-) mouse CNS. Competitive assays between CCR6(+/+) and CCR6(-/-) Treg adoptively transferred to CCR6(-/-) mice showed impaired ability of CCR6(-/-) Treg to infiltrate CNS tissues in EAE-affected mice. Our data indicate a CCR6 requirement by CD4(+) Treg to downregulate the CNS inflammatory process and neurological signs associated with EAE.

Mice deficient for CCR6 fail to control chronic experimental autoimmune encephalomyelitis

Chemokines are a superfamily of chemotactic cytokines that play an important role in leukocyte trafficking and have been implicated as functional mediators of immunopathology in experimental autoimmune encephalomyelitis (EAE). In the present study, we investigated the role of the CCL20 receptor, CCR6, in chronic EAE. After immunization with myelin oligodendrocyte glycoprotein 35-55 in CFA, CCR6(-/-) mice developed a significantly more severe chronic EAE as compared to wild type immunized animals. CCR6 expression was not required by T cells to induce EAE. Measurement of peripheral T cell responses showed differences in IFN-gamma and IL-17 responses between CCR6(-/-) and wild type mice. At the time when CCR6(-/-) mice showed significantly more severe chronic EAE there was a significant decrease in PD-L1-expressing mDC in the spleens and no differences in Foxp3 Treg. Furthermore, add back of mDC with increased PD-L1 expression to CCR6(-/-) mice reduced the severe chronic EAE disease phase to that of wild type controls. The results suggest a role for CCR6-expressing PDL1(+) mDC in regulating EAE progression.

Bone marrow stromal cell therapy reduces proNGF and p75 expression in mice with experimental autoimmune encephalomyelitis

Demyelination is prominent in experimental autoimmune encephalomyelitis (EAE). The receptor p75 and its high affinity ligand proNGF are required for oligodendrocyte death after injury. We hypothesize that bone marrow stromal cells (BMSCs) provide therapeutic benefit in EAE mice by reducing proNGF/p75 expression. PBS or BMSCs (2 x 10(circumflex)6) were administered intravenously on the day of EAE onset. Neurological function and demyelination areas were measured. Immunohistochemical staining was used to measure apoptotic oligodendrocytes, expression of proNGF and p75, and the relationship between proNGF and p75 in neural cells. proNGF was used to treat oligodendrocytes in culture with or without BMSCs. EAE mice exhibited neurological function deficit and demyelination, and expression of proNGF and p75 was increased. BMSC treatment improved functional recovery, reduced demyelination area and apoptotic oligodendrocytes, decreased expression of proNGF and p75 compared with PBS treatment. proNGF(+) cells colocalized with neural cell markers, while p75 colocalized with an oligodendrocytic marker, and proNGF colocalized with p75. proNGF induced apoptosis of oligodendrocytes in vitro, and p75 antibody blocked this apoptotic activity. BMSCs reduced p75 expression and apoptotic activity in oligodendrocytes with proNGF treatment. BMSC treatment benefits on EAE mice may be fostered by decreasing the cellular expression of proNGF and p75, thereby reducing oligodendrocyte death.

C-C chemokine receptor 6-regulated entry of TH-17 cells into the CNS through the choroid plexus is required for the initiation of EAE

Interleukin 17-producing T helper cells (T(H)-17 cells) are important in experimental autoimmune encephalomyelitis, but their route of entry into the central nervous system (CNS) and their contribution relative to that of other effector T cells remain to be determined. Here we found that mice lacking CCR6, a chemokine receptor characteristic of T(H)-17 cells, developed T(H)-17 responses but were highly resistant to the induction of experimental autoimmune encephalomyelitis. Disease susceptibility was reconstituted by transfer of wild-type T cells that entered into the CNS before disease onset and triggered massive CCR6-independent recruitment of effector T cells across activated parenchymal vessels. The CCR6 ligand CCL20 was constitutively expressed in epithelial cells of choroid plexus in mice and humans. Our results identify distinct molecular requirements and ports of lymphocyte entry into uninflamed versus inflamed CNS and suggest that the CCR6-CCL20 axis in the choroid plexus controls immune surveillance of the CNS.

Cytokines and myelination in the central nervous system

Myelin abnormalities that reflect damage to developing and mature brains are often found in neurological diseases with evidence of inflammatory infiltration and microglial activation. Many cytokines are virtually undetectable in the uninflamed central nervous system (CNS), so that their rapid induction and sustained elevation in immune and glial cells contributes to dysregulation of the inflammatory response and neural cell homeostasis. This results in aberrant neural cell development, cytotoxicity, and loss of the primary myelin-producing cells of the CNS, the oligodendrocytes. This article provides an overview of cytokine and chemokine activity in the CNS with relevance to clinical conditions of neonatal and adult demyelinating disease, brain trauma, and mental disorders with observed white matter defects. Experimental models that mimic human disease have been developed in order to study pathogenic and therapeutic mechanisms, but have shown mixed success in clinical application. However, genetically altered animals, and models of CNS inflammation and demyelination, have offered great insight into the complexities of neuroimmune interactions that impact oligodendrocyte function. The intracellular signaling pathways of selected cytokines have also been highlighted to illustrate current knowledge of receptor-mediated events. By learning to interpret the actions of cytokines and by improving methods to target appropriate predictors of disease risk selectively, a more comprehensive understanding of altered immunoregulation will aid in the development of advanced treatment options for patients with inflammatory white matter disorders.

Tracing functional antigen-specific CCR6 Th17 cells after vaccination

Background

The function of T helper cell subsets in vivo depends on their location, and one hallmark of T cell differentiation is the sequential regulation of migration-inducing chemokine receptor expression. CC-chemokine receptor 6 (CCR6) is a trait of tissue-homing effector T cells and has recently been described as a receptor on T helper type 17 (Th17) cells. Th17 cells are associated with autoimmunity and the defence against certain infections. Although, the polarization of Th cells into Th17 cells has been studied extensively in vitro, the development of those cells during the physiological immune response is still elusive.

Methodology/Principal Findings

We analysed the development and functionality of Th17 cells in immune-competent mice during an ongoing immune response. In naïve and vaccinated animals CCR6⁺ Th cells produce IL-17. The robust homeostatic proliferation and the presence of activation markers on CCR6⁺ Th cells indicate their activated status. Vaccination induces antigen-specific CCR6⁺ Th17 cells that respond to in vitro re-stimulation with cytokine production and proliferation. Furthermore, depletion of CCR6⁺ Th cells from donor leukocytes prevents recipients from severe disease in experimental autoimmune encephalomyelitis, a model for multiple sclerosis in mice.

Conclusions/Significance

In conclusion, we defined CCR6 as a specific marker for functional antigen-specific Th17 cells during the immune response. Since IL-17 production reaches the highest levels during the immediate early phase of the immune response and the activation of Th17 cells precedes the Th1 cell differentiation we tent to speculate that this particular Th cell subset may represent a first line effector Th cell subpopulation. Interference with the activation of this Th cell subtype provides an interesting strategy to prevent autoimmunity as well as to establish protective immunity against infections.

Lymphoid chemokines in chronic neuroinflammation

Lymphoid chemokines play an essential role in the establishment and maintenance of lymphoid tissue microarchitecture and have been implicated in the formation of tertiary (or ectopic) lymphoid tissue in chronic inflammatory conditions. Here, we review recent advances in lymphoid chemokine research in central nervous system inflammation, focusing on multiple sclerosis and the animal model experimental autoimmune encephalomyelitis. We also highlight how the study of lymphoid chemokines, particularly CXCL13, has led to the identification of intrameningeal B-cell follicles in the multiple sclerosis brain paving the way to the discovery that these abnormal structures are highly enriched in Epstein–Barr virus-infected B cells and plasma cells.

Gene expression in the rat brain during prostaglandin D2 and adenosinergically-induced sleep

Previous studies have supported the hypothesis that macromolecular synthesis occurs in the brain during sleep as a response to prior waking activities and that prostaglandin D2 (PGD2) is an endogenous sleep substance whose effects are dependent on adenosine A2a receptor-mediated signaling. We compared gene expression in the cerebral cortex, basal forebrain, and hypothalamus during PGD2-induced and adenosinergically-induced sleep to results from our previously published study of recovery sleep (RS) after sleep deprivation (SD). Immediate early gene expression in the cortex during sleep induced by PGD2- or by the selective adenosine A2a agonist CGS21680 showed limited similarity to that observed during RS while, in the basal forebrain and hypothalamus, widespread activation of immediate early genes not seen during RS occurred. In all three brain regions, PGD2 and CGS21680 reduced the expression of arc, a transcript whose expression is elevated during SD. Using GeneChips, the majority of genes induced by either PGD2 or CGS21680 were induced by both, suggesting activation of the same pathways. However, gene expression induced in the brain after PGD2 or CGS21680 treatment was distinct from that described during RS after SD and apparently involves glial cell gene activation and signaling pathways in neural-immune interactions.

Preferential recruitment of CCR6-expressing Th17 cells to inflamed joints via CCL20 in rheumatoid arthritis and its animal model

This report shows that interleukin (IL) 17–producing T helper type 17 (Th17) cells predominantly express CC chemokine receptor (CCR) 6 in an animal model of rheumatoid arthritis (RA). Th17 cells induced in vivo in normal mice via homeostatic proliferation similarly express CCR6, whereas those inducible in vitro by transforming growth factor β and IL-6 additionally need IL-1 and neutralization of interferon (IFN) γ and IL-4 for CCR6 expression. Forced expression of RORγt, a key transcription factor for Th17 cell differentiation, induces not only IL-17 but also CCR6 in naive T cells. Furthermore, Th17 cells produce CCL20, the known ligand for CCR6. Synoviocytes from arthritic joints of mice and humans also produce a large amount of CCL20, with a significant correlation (P = 0.014) between the amounts of IL-17 and CCL20 in RA joints. The CCL20 production by synoviocytes is augmented in vitro by IL-1β, IL-17, or tumor necrosis factor α, and is suppressed by IFN-γ or IL-4. Administration of blocking anti-CCR6 monoclonal antibody substantially inhibits mouse arthritis. Thus, the joint cytokine milieu formed by T cells and synovial cells controls the production of CCL20 and, consequently, the recruitment of CCR6⁺ arthritogenic Th17 cells to the inflamed joints. These results indicate that CCR6 expression contributes to Th17 cell function in autoimmune disease, especially in autoimmune arthritis such as RA.

Proliferation, differentiation, and cytokine secretion of human umbilical cord blood-derived mononuclear cells in vitro

OBJECTIVE

Human umbilical cord blood (hUCB)-derived mononuclear cells were previously shown to exert therapeutic effects in a number of animal models of nervous system impairment. However, the mechanisms underlying the structural and functional improvements are still unclear. As cell replacement seems to be a rare or absent event in vivo, we suggest secondary mechanisms, by which the therapeutic effect of transplanted mononuclear cells might be mediated. We investigated the potential of hUCB-derived mononuclear cells in vitro to proliferate, differentiate, and to secrete factors possibly beneficial for the host brain tissue in vivo.

METHODS

Using a succession of distinct culture media, mononuclear cells were stimulated by growth factor combinations, e.g., epidermal growth factor (EGF)/fibroblast growth factor-2 (FGF-2) or nerve growth factor (NGF)/retinoic acid (RA). Expression of hematological and neural marker proteins was investigated by immunoblotting, immunocytochemistry, and fluorescence-activated cell analysis. Secretion of proteins was assayed using a human cytokine antibody array, and quantified via enzyme-linked immunosorbent assay.

RESULTS

Mononuclear cells were shown to undergo proliferation in the presence of EGF/FGF-2. When cells were cultured in NGF/RA-containing medium, neuronal and glial marker proteins were expressed, indicating differentiation. In the presence of either growth factor combination, cells in vitro secrete interleukins, growth factors, and chemotactic proteins.

CONCLUSION

Although capable of incipient differentiation, cytokine secretion of hUCB-derived mononuclear cells envisages the potential of an indirect effect in vivo. Most factors detected in conditioned medium are renowned for their anti-inflammatory, neuroprotective, angiogenic, or chemotactic actions, thus, providing the means for a therapeutic outcome mediated by secondary effects.

The immunity of splenic and peritoneal F4/80(+) resident macrophages in mouse mixed allogeneic chimeras

Mixed allogeneic chimeras are emerging as a prospective approach to induce immune tolerance in clinics. However, the immunological function of macrophages in mixed chimeras has not been evaluated. Using a B6-->BALB/c mixed chimera model, we investigated the phenotype and function of F4/80(+) resident peritoneal exudate macrophage (PEMs) and splenic macrophages (SPMs) in vitro and in vivo. Recipient F4/80(+)PEMs and SPMs in mixed chimeras expressed significantly lower levels of MHC-II, CD54, and CD23 than those in non-chimeric mice before lipopolysaccharide stimulation. Recipient F4/80(+)PEMs and SPMs in mixed chimeras induced normal cell proliferation and delayed-type hypersensitivity of allo-T cells, but they induced more IFN-gamma and IL-2 products and less IL-10 and TGF-beta products of allo-T cells compared with those of non-chimeras. Furthermore, recipient F4/80(+)PEMs and SPMs had significantly higher phagocytotic capacity against chicken red blood cells or allo-T cells than those of controls while they had normal phagocytosis to Escherichia coli. Although some slight but significant alterations of recipient macrophages have been detected, these results provide direct evidences for the efficient immunity of recipient macrophages in mixed allogeneic chimeras. The present study also, for the first time, offered basic information for macrophages maturing in heterogeneous environments.

Protective immunity and delayed type hypersensitivity reaction are uncoupled in experimental Leishmania major infection of CCR6-negative mice

The chemokine receptor CCR6 is expressed on naïve B cells, dendritic cell and T-cell subpopulations and is involved in cell navigation during organogenesis and recruitment in response to inflammatory stimuli. Gene-deficient C57BL/6 CCR6(-/-) mice infected with the protozoan parasite Leishmania (L.) major were able to mount a protective immune response and survived the infection. Whereas macrophage production of nitric oxide (NO), the key leishmanicidal effector molecule during the immune response to L. major, did not require CCR6, the migration of CD4(+) T cells to the site of infection was reduced in CCR6(-/-) mice. Furthermore, the induction of a T-cell-dependent delayed-type-hypersensitivity (DTH) reaction was defective in CCR6(-/-) mice, whereas resistance to re-infection was maintained in the absence of CCR6. We conclude that CCR6 contributes to the recruitment of T cells to the site of infection, but is largely dispensable for the control of L. major parasites during primary or secondary infection.

Identification of genes involved in the initiation of human Th1 or Th2 cell commitment

The differentiation of naïve T helper (Th) cells is induced by TCR activation and IL-12/STAT4 or IL-4/STAT6 signaling pathways, forming Th1 and Th2 cells, respectively. In this study, oligonucleotide arrays were used to identify genes regulated during the initiation of human Th1 and Th2 cell differentiation at 2 and 6 h in presence or absence of immunosuppressive TGF-beta. As a result the immediate targets of IL-12, IL-4 and TGF-beta were identified. The effects of IL-12 at this early stage were minimal and consistent with the known kinetics of IL-12Rbeta2 expression. IL-4, however, was observed to rapidly regulate 63 genes, 26 of which were differentially expressed at both the 2- and 6-h time points. Of these IL-4 regulated genes, one-third have previously been observed to display expression changes in the later phases of the polarization process. Similarly to the key regulators, TBX21 and GATA3, the transcription factors SATB1, TCF7 and BCL6 were differentially regulated at the protein level during early Th1 and Th2 cell polarization. Moreover, the developing Th1 and Th2 cells were demonstrated to be responsive to the immunosuppressive TGF-beta and IL-10. In this study, a panel of novel factors that may be important regulators of the differentiation process was identified.

Astrocytes produce dendritic cell-attracting chemokines in vitro and in multiple sclerosis lesions

As a result of their close association with the blood-brain barrier, astrocytes play an important role in regulating the homing of different leukocyte subsets to the inflamed central nervous system (CNS). In this study, we investigated whether human astrocytes produce chemokines that promote the migration of myeloid dendritic cells (DCs). By reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay, we show that cultured human astrocytes stimulated with interleukin-1beta and tumor necrosis factor produce CCL2, CCL3, CCL4, CCL5, CCL20, and CXCL12 that act on immature DCs, but not CCL19 and CCL21, 2 chemokines specific for mature DCs. Compared with controls, supernatants of cytokine-stimulated astrocytes are more effective in promoting the migration of immature monocyte-derived DCs (iMDDCs). Desensitization of CXCR4 (receptor for CXCL12), CCR1-3-5 (shared receptors for CCL3-4-5), and CCR6 (receptor for CCL20) on iMDDC reduces cell migration toward astrocyte supernatants, indicating that astrocytes release biologically relevant amounts of iMDDC-attracting chemokines. By immunohistochemistry, we show that CXCL12 and, to a lesser extent, CCL20 are expressed by reactive astrocytes in multiple sclerosis lesions. These data lend support to the idea that astrocyte-derived chemokines may contribute to immature DC recruitment to the inflamed CNS.

Patterns of protein expression in infectious meningitis: a cerebrospinal fluid protein array analysis

Seventy-nine cytokines, chemokines, and growth factors were measured by protein array analysis in the cerebrospinal fluid of patients with meningitis and controls. Several factors were found to be regulated, which have not been studied in the CNS before, e.g., macrophage inflammatory protein-1delta (CCL15) and neutrophil-activating peptide-2 (CXCL7). In pneumococcal meningitis, other new observations were an increase of macrophage migration inhibitory factor, monocyte chemoattractant protein-2 (CCL8), pulmonary and activation-regulated chemokine (CCL18), and macrophage inflammatory protein-3alpha (CCL20), and a sustained upregulation of several growth factors. In viral meningitis, new findings were an elevation of CCL8, thrombopoietin, and vascular endothelial growth factor.

Immunological patterns identifying disease course and evolution in multiple sclerosis patients

Reliable, and easy to measure, immunological markers able to denote disease characteristics in multiple sclerosis (MS) patients are still lacking. We applied a multivariate statistical analysis on results obtained by measuring-by real-time RT-PCR-mRNA levels of 25 immunological relevant molecules in PBMCs from 198 MS patients. The combined measurement of mRNA levels of IL-1beta, TNF-alpha, TGF-beta, CCL20 and CCR3 was able to distinguish MS patients from healthy individuals. CXCR5, CCL5, and CCR3 combined mRNA levels identify primary progressive MS patients while TNF-alpha, IL-10, CXCL10 and CCR3 differentiate relapsing MS patients. Our results indicate that multi-parametric analysis of mRNA levels of immunological relevant molecules in PBMCs may represent a successful strategy for the identification of putative peripheral markers of disease state and disease activity in MS patients.

Effects of estradiol on lipopolysaccharide and Pam3Cys stimulation of CCL20/macrophage inflammatory protein 3 alpha and tumor necrosis factor alpha production by uterine epithelial cells in culture

We have previously demonstrated that rat uterine epithelial cells (UEC) produce CCL20/macrophage inflammatory protein 3 alpha (MIP3alpha) and tumor necrosis factor alpha (TNF-alpha) in response to live and heat-killed Escherichia coli and to the pathogen-associated molecular patterns (PAMP) lipopolysaccharide (LPS) and Pam3Cys. To determine whether estradiol (E2) modulates PAMP-induced CCL20/MIP3alpha and TNF-alpha secretion, primary cultures of rat UEC were incubated with E2 for 24 h and then treated with LPS or Pam3Cys or not treated for an additional 12 h. E2 inhibited the constitutive secretion of TNF-alpha and CCL20/MIP3alpha into culture media. Interestingly, E2 pretreatment enhanced CCL20/MIP3alpha secretion due to LPS and Pam3Cys administration. In contrast, and at the same time, E2 lowered the TNF-alpha response to both PAMP. To determine whether estrogen receptors (ER) mediated the effects of E2, epithelial cells were incubated with E2 and/or ICI 182,780, a known ER antagonist. ICI 182,780 had no effect on E2 inhibition of constitutive TNF-alpha and CCL20/MIP3alpha secretion. In contrast, ICI 182,780 reversed the stimulatory effect of E2 on LPS- and/or Pam3Cys-induced CCL20/MIP3alpha secretion as well as partially reversed the inhibitory effect of E2 on TNF-alpha production by epithelial cells. Overall, these results indicate that E2 regulates the production of TNF-alpha and CCL20/MIP3alpha by UEC in the absence as well as presence of PAMP. Since CCL20/MIP3alpha has antimicrobial activity and is chemotactic for immune cells, these studies suggest that regulation of CCL20/MIP3alpha and TNF-alpha by E2 and PAMP may have profound effects on innate and adaptive immune responses to microbial challenge in the female reproductive tract.

CCL2 and CCL5 mediate leukocyte adhesion in experimental autoimmune encephalomyelitis—an intravital microscopy study

Experimental autoimmune encephalomyelitis (EAE) models multiple sclerosis (MS) and is characterized by marked mononuclear cell influx in the brain. Several studies have demonstrated a role for chemokines during EAE. It remains to be determined whether these mediators modulate EAE primarily by mediating leukocyte influx into the CNS or by modifying lymphocyte activation and/or trafficking into lymphoid organs. After induction of EAE with MOG(35-55), leukocyte recruitment peaked on day 14 and correlated with symptom onset, TNF-alpha production and production of CCL2 and CCL5. Levels of CXCL-10 and CCL3 were not different from control animals. Using intravital microscopy, we demonstrated that leukocyte rolling and adhesion also peaked at day 14. Treatment with anti-CCL2 or anti-CCL5 antibodies just prior to the intravital microscopy prevented leukocyte adhesion, but not rolling. Our data suggest that induction of leukocyte adhesion to the brain microvasculature is an important mechanism by which CCL2 and CCL5 participate in the pathophysiology of EAE.

Statins and their potential targets in multiple sclerosis therapy

Multiple sclerosis (MS) is a CNS-demyelinating disease characterised by relapsing and chronic neurological impairment. While traditionally CNS autoantigen-specific CD4(+) T cells have been considered the culprits in the initial phase of the disease, recent observations have altered this concept. It is now recognised that other T lymphocyte subclasses can initiate CNS demyelination. In addition, other cell types and molecules may play an important role in MS pathogenesis. There is overwhelming evidence that MS is a dynamic process, in which recurrent episodes of blood-brain barrier disruption and CNS inflammation play a crucial role in early disease stages, leading eventually to the largely irreversible changes of demyelination, gliosis and axonal degeneration. These observations may have important therapeutic implications. Within the last ten years, several medications have been approved for MS treatment. These agents, all of which are given parenterally, are only partially effective and are often associated with adverse effects and potential toxicities. The number and different types of medications used for MS are likely to increase in the near future, as several novel therapies are currently tested in clinical trials. 3-hydroxy-3-methyglutaryl coenzyme A reductase inhibitors, 'statins', are cholesterol-lowering drugs that are given orally, are safe and have biological effects independent of their cholesterol-reducing properties. Recent reports have shown that statins have anti-inflammatory and neuroprotective properties that may be beneficial in the treatment of MS. This article will outline experimental evidence that suggests potential clinical benefits of statins for MS patients.

Preferential expression and function of Toll-like receptor 3 in human astrocytes

In contrast to other tissues, the central nervous system (CNS) is essentially devoid of MHC expression and shielded from antibodies by the blood-brain barrier. Therefore, a rapid local innate immune response by resident brain cells is required to effectively fight infectious agents. This study analyzed the expression and function of Toll-like receptors (TLRs) in cultured human astrocytes. Quantitative PCR for TLRs 1 to 10 showed a basal expression of TLR3 that could be enhanced by IFN-gamma, IL-1beta, and IFN-beta. The other TLRs were barely detectable and not inducible by the same cytokines. IFN-gamma-activated astrocytes responded to TLR3 ligand poly (I:C) engagement with IL-6 production, while ligands of other TLRs, like LPS, lipoteichoic acid, peptidoglycan, flagellin, and CpG, had no effect. Poly (I:C) also triggered astrocyte production of TNF-alpha and the chemokines CCL2/MCP-1, CCL5/RANTES, CCL20/MIP-3alpha, and CXCL10/IP-10. The adapter molecules MyD88 (full length and short isoform), TIRAP/Mal, and TICAM-1/TRIF, which are required for TLR signaling, were all expressed by astrocytes. Thus, resting and activated human astrocytes express preferentially TLR3 and, upon TLR3 engagement, produce IL-6 and chemokines active on T cells, B cells, monocytes, and dendritic cells. These data indicate that astrocytes function as sentinels for viral infections in the CNS.

CCR6 expression defines regulatory effector/memory-like cells within the CD25(+)CD4+ T-cell subset

Regulatory CD25(+)CD4+ T cells (Treg cells) are a central element of peripheral tolerance. Little is known, however, about phenotypic and functional characteristics of these cells with regard to memory. In this study we show that the chemokine receptor CCR6 is expressed on a distinct subset of mouse Treg cells. Similar to their CD25- counterparts, CCR6+ Treg cells exhibit markers of activation, memory, and expansion that are indicative for an effector-memory function. They are memory-like cells, generated in vivo from CCR6(-)CD25+ T cells after the encounter of antigen. As conventional CD25- effector-memory T cells, they have a high turnover rate and, in contrast to CCR6- Treg cells, they respond rapidly to restimulation in vitro with up-regulation of interleukin 10. CCR6+ Treg cells are enriched in the peripheral blood and accumulate in the central nervous system after induction of experimental autoimmune encephalomyelitis (EAE). This subset therefore seems to represent a population of regulatory effector-memory T cells (T(REM)), destined to control potentially destructive immune responses directly in inflamed tissues. Importantly, these cells are also present in humans. Here the expression of CCR6 fully cosegregates with CD45RO, an established marker of human memory T cells.

Chemokines and glial cells: a complex network in the central nervous system

Chemokines are small secreted proteins that are essential for the recruitment and activation of specific leukocyte subsets at sites of inflammation and for the development and homeostasis of lymphoid and nonlymphoid tissues. During the past decade, chemokines and their receptors have also emerged as key signaling molecules in neuroinflammatory processes and in the development and functioning of the central nervous system. Neurons and glial cells, including astrocytes, oligodendrocytes, and microglia, have been identified as cellular sources and/or targets of chemokines produced in the central nervous system in physiological and pathological conditions. In this article, we provide an update of chemokines and chemokine receptors expressed by glial cells focusing on their biological functions and implications in neurological diseases.

Is damage in central nervous system due to inflammation?

The aim of this work was to review the inflammatory factors involved in central nervous system (CNS) inflammation and the damage associated to their participation in an inflammatory disease of CNS, multiple sclerosis in humans and experimental allergic encephalomyelitis in the murine model. Inflammation has an important repairing function, nevertheless frequently in the CNS inflammation is the cause of damage and it does not fulfill this repairing function as it happens in other compartments of the body. The inflammatory response in the CNS involves the participation of different cellular types of the immune system (macrophages, mast cells, T and B lymphocytes, dendritic cells) and resident cells of the CNS (microglia, astrocytes, neurons), adhesion molecules, cytokines and chemokines among other proteic components. During neuroinflammation chemotaxis is an important event in the recruitment of cells to the CNS. The lymphocyte recruitment implies the presence of chemokines and chemokine receptors, the expression of adhesion molecules, the interaction between lymphocytes and the bloodbrain barrier (BBB) endothelium, and finally their passage through the BBB to arrive at the site of inflammation. If this process is not controlled, is prolonged, inflammation loses its repairing function and can be the cause of damage. Usually neuroinflammation has the tendency to decline to damage, which would explain most of the CNS pathologies.

Statins as potential therapeutic agents in multiple sclerosis

3-Hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors (ie, statins) are oral cholesterol-lowering drugs. Statins are well tolerated and have an excellent safety record. These agents competitively inhibit HMG CoA reductase, which is the enzyme that catalyzes the conversion of HMG CoA to L-mevalonate. Although L-mevalonate is a key intermediate in cholesterol synthesis, several of its metabolites are involved in post-translational modification of specific proteins involved in cell proliferation and differentiation. Thus, independent of their cholesterol-reducing properties, statins have important pleiotropic biologic effects. Recent reports indicate that statins have anti-inflammatory and neuroprotective properties. Whether statins will be of clinical benefit for patients with multiple sclerosis and other neurodegenerative diseases of the central nervous system will only be known after they are evaluated in prospective randomized clinical trials.

Identification of differentially regulated transcripts in mouse striatum following methamphetamine treatment - an oligonucleotide microarray approach

Methamphetamine is an addictive drug of abuse that can produce neurotoxic effects in dopamine nerve endings of the striatum. The purpose of this study was to identify new genes that may play a role in the highly complex cascade of events associated with methamphetamine intoxication. Using Affymetrix oligonucleotide arrays, 12 488 genes were simultaneously interrogated and there were 152 whose expression levels were changed following methamphetamine treatment. The genes are grouped into broad functional categories with inflammatory/immune response elements, receptor/signal transduction components and ion channel/transport proteins among the most populated. Many genes within these categories can be linked to ion regulation and apoptosis, both of which have been implicated in methamphetamine toxicity, and numerous factors associated with microglial activation emerged with significant changes in expression. For example, brain-derived neurotrophic factor (BDNF), chemokine (C-C) receptor 6 (CCr6) and numerous chemokine transcripts were increased or decreased in expression more than 2.8-fold. These results point to activated microglia as a potential source of the reactive oxygen/nitrogen species and cytokines that have been previously associated with methamphetamine toxicity and other neurotoxic conditions.

The CC chemokine CCL20 and its receptor CCR6

CCL20, alternatively named liver and activation-regulated chemokine (LARC), macrophage inflammatory protein-3alpha (MIP-3alpha) or Exodus-1, is the only chemokine known to interact with CC chemokine receptor 6 (CCR6), a property shared with the antimicrobial beta-defensins. The ligand-receptor pair CCL20-CCR6 is responsible for the chemoattraction of immature dendritic cells (DC), effector/memory T-cells and B-cells and plays a role at skin and mucosal surfaces under homeostatic and inflammatory conditions, as well as in pathology, including cancer and rheumatoid arthritis. In this review, the discovery, the gene and protein structure, the in vitro biological activities, the cell and inducer specific expression and the tissue distribution of CCL20 and CCR6 are discussed.