CC chemokine receptor 8 in the central nervous system is associated with phagocytic macrophages

Human Primary Astrocytes Differently Respond to Pro- and Anti-Inflammatory Stimuli

For a long time, astrocytes were considered a passive brain cell population. However, recently, many studies have shown that their role in the central nervous system (CNS) is more active. Previously, it was stated that there are two main functional phenotypes of astrocytes. However, nowadays, it is clear that there is rather a broad spectrum of these phenotypes. The major goal of this study was to evaluate the production of some inflammatory chemokines and neurotrophic factors by primary human astrocytes after pro- or anti-inflammatory stimulation. We observed that only astrocytes induced by inflammatory mediators TNFα/IL-1a/C1q produced CXCL10, CCL1, and CXCL13 chemokines. Unstimulated astrocytes and those cultured with anti-inflammatory cytokines (IL-4, IL-10, or TGF-β1) did not produce these chemokines. Interestingly, astrocytes cultured in proinflammatory conditions significantly decreased the release of neurotrophic factor PDGF-A, as compared to unstimulated astrocytes. However, in response to anti-inflammatory cytokine TGF-β1, astrocytes significantly increased PDGF-A production compared to the medium alone. The production of another studied neurotrophic factor BDNF was not influenced by pro- or anti-inflammatory stimulation. The secretory response was accompanied by changes in HLA-DR, CD83, and GFAP expression. Our study confirms that astrocytes differentially respond to pro- and anti-inflammatory stimuli, especially to inflammatory cytokines TNF-α, IL-1a, and C1q, suggesting their role in leukocyte recruitment.

Chemokine CCL18 Promotes Phagocytosis Through Its Receptor CCR8 Rather than PITPNM3 in Human Microglial Cells

CCL18 is a CC chemokine that exhibits diverse functions through interaction with various cell subsets with both proinflammatory anti-inflammatory properties through its receptors CCR8 (CC chemokine receptor 8) and PITPNM3 (phosphatidylinositol transfer protein 3). However, the function of CCL18 in microglia remains unclear. In this study, we show that CCL18 did not change the expression of the inflammatory factors, interleukin (IL)-1β, IL-6, tumor necrosis factor alpha (TNF-α), or inducible nitric oxide synthase (iNOS), but significantly induced expression of the macrophage markers, MRC-1 and ARG-1 M2, in a human microglial clone 3 cell line (HMC3). Phagocytosis by HMC3 cells was significantly enhanced in the presence of CCL18, indicated by uptake of amyloid-β and dextran. CCR8 and PITPNM3 were both expressed on HMC3 cells, but selective knockdown of CCR8 and PITPNM3 showed that only the former played a dominant role in phagocytosis of HMC3 through the nuclear factor kappa B (NF-κB)/Src signaling pathway. Our results suggest that CCL18 could have anti-inflammatory activity and activate the phagocytic function of microglia, which is involved in neural development, homeostasis, and repair mechanisms.

Dynamic Responses of Microglia in Animal Models of Multiple Sclerosis

Microglia play an essential role in maintaining central nervous system (CNS) homeostasis, as well as responding to injury and disease. Most neurological disorders feature microglial activation, a process whereby microglia undergo profound morphological and transcriptional changes aimed at containing CNS damage and promoting repair, but often resulting in overt inflammation that sustains and propagates the neurodegenerative process. This is especially evident in multiple sclerosis (MS), were microglial activation and microglia-driven neuroinflammation are considered key events in the onset, progression, and resolution of the disease. Our understanding of microglial functions in MS has widened exponentially in the last decade by way of new tools and markers to discriminate microglia from other myeloid populations. Consequently, the complex functional and phenotypical diversity of microglia can now be appreciated. This, in combination with a variety of animal models that mimic specific features and processes of MS, has contributed to filling the gap of knowledge in the cascade of events underlying MS pathophysiology. The purpose of this review is to present the most up to date knowledge of the dynamic responses of microglia in the commonly used animal models of MS, specifically the immune-mediated experimental autoimmune encephalomyelitis (EAE) model, and the chemically-induced cuprizone and lysolecithin models. Elucidating the spectrum of microglial functions in these models, from detrimental to protective, is essential to identify emerging targets for therapy and guide drug discovery efforts.

Changes in Chemokines and Chemokine Receptors Expression in a Mouse Model of Alzheimer's Disease

The amyloid precursor protein plus presenilin-1 (APP/PS1) mice are a frequently-used model for Alzheimer's disease studies (AD). However, the data relevant to which proteins are involved in inflammatory mechanism are not sufficiently well-studied using the AD mouse model. Using behavioral studies, quantitative RT-PCR and Western-blot techniques, significant findings were determined by the expression of proteins involved in inflammation comparing APP/PS1 and Wild type mice. Increased GFAP expression could be associated with the elevation in number of reactive astrocytes. IL-3 is involved in inflammation and ABDF1 intervenes normally in the transport across cell membranes and both were found up-regulated in APP/PS1 mice compared to Wild type mice. Furthermore, CCR5 expression was decreased and both CCL3 and CCL4 chemokines were highly expressed indicating a possible gliosis and probably an increase in chemotaxis from lymphocytes and T cell generation. We also noted for the first time, a CCR8 increase expression with diminution of its CCL1 chemokine, both normally involved in protection from bacterial infection and demyelination. Control of inflammatory proteins will be the next step in understanding the progression of AD and also in determining the mechanisms that can develop in this disease.

Glycosylated extracellular vesicles released by glioblastoma cells are decorated by CCL18 allowing for cellular uptake via chemokine receptor CCR8

Cancer cells release extracellular vesicles (EVs) that contain functional biomolecules such as RNA and proteins. EVs are transferred to recipient cancer cells and can promote tumour progression and therapy resistance. Through RNAi screening, we identified a novel EV uptake mechanism involving a triple interaction between the chemokine receptor CCR8 on the cells, glycans exposed on EVs and the soluble ligand CCL18. This ligand acts as bridging molecule, connecting EVs to cancer cells. We show that glioblastoma EVs promote cell proliferation and resistance to the alkylating agent temozolomide (TMZ). Using in vitro and in vivo stem-like glioblastoma models, we demonstrate that EV-induced phenotypes are neutralised by a small molecule CCR8 inhibitor, R243. Interference with chemokine receptors may offer therapeutic opportunities against EV-mediated cross-talk in glioblastoma.

Role of chemokine C-C motif ligand-1 in acute and chronic pulmonary inflammations

Background

Chemokine C-C motif ligand 1 (CCL1) accumulates C-C motif chemokine receptor 8 positive leukocytes to the inflammatory sites. Single-nucleotide polymorphisms in the chemokine CCL1 gene are associated with exacerbation of chronic obstructive lung disease. However, it is unclear whether CCL1 has immunomodulatory functions during pulmonary inflammation. This study aimed to elucidate this issue using newly generated transgenic mice that express CCL1 in the lungs (SPC-CCL1 mice).

Methods

To evaluate the phenotypes of these mice, lung section and bronchoalveolar lavage (BAL) fluid analyses were performed. We intratracheally administered lipopolysaccharide (LPS) or Mycobacterium bovis as a model of acute or chronic lung inflammation, respectively.

Results

No histological differences were observed between lung tissue from SPC-CCL1 Tg and wild-type mice in the resting condition and after LPS administration. In the resting condition, the total BAL cell concentration was lower in SPC-CCL1 Tg mice than in wild-type mice (P = 0.0097). Flow cytometric analyses showed that SPC-CCL1 Tg mice had fewer F4/80-positive cells than wild-type mice (P = 0.0278). After intratracheal LPS administration, CCL1 overexpression changed neither the total numbers nor population of BAL cells. After mycobacterial administration, pulmonary granuloma formation was significantly enhanced. The degree of Immunostaining for endoplasmic reticulum to nucleus signaling 1, a molecule associated with granuloma formation and endoplasmic reticulum stress, was significantly enhanced in the granuloma regions of SPC-CCL1 mice treated with Mycobacterium, compared to those of wild-type mice.

Conclusions

CCL1 overexpression in the lungs did not change the acute inflammatory response induced by LPS, but enhanced granuloma formation after mycobacterial treatment, possibly through enhancing endoplasmic reticulum stress.

Important role of mast cells in multiple sclerosis

Autoimmunity is a disease that occurs when the body tissue is attacked by its own immune system. Multiple sclerosis (MS) is an autoimmune illness which triggers neurological progressive and persistent functions. MS is associated with an abnormal B-cell response and upregulation of T-cell reactivity against a multitude of antigens. Mast cells are the first line of the innate immune system and act by degranulating and secreting chemical mediators and cytokines. Their participation on the central nervous system has been recognized since the beginning of the last century. They have an important role in autoimmune disease, including MS where they mediate inflammation and demyelinization by presenting myelin antigens to T cells or disrupting the blood-brain barrier and permitting entry of inflammatory cells and cytokines. The participation of mast cells in MS is demonstrated by gene overexpression of chemical mediators and inflammatory cytokines. Here we report the relationship and involvement between mast cells and multiple sclerosis.

Systematic Review of the Neurobiological Relevance of Chemokines to Psychiatric Disorders

Psychiatric disorders are highly prevalent and disabling conditions of increasing public health relevance. Much recent research has focused on the role of cytokines in the pathophysiology of psychiatric disorders; however, the related family of immune proteins designated chemokines has been relatively neglected. Chemokines were originally identified as having chemotactic function on immune cells; however, recent evidence has begun to elucidate novel, brain-specific functions of these proteins of relevance to the mechanisms of psychiatric disorders. A systematic review of both human and animal literature in the PubMed and Google Scholar databases was undertaken. After application of all inclusion and exclusion criteria, 157 references were remained for the review. Some early mechanistic evidence does associate select chemokines with the neurobiological processes, including neurogenesis, modulation of the neuroinflammatory response, regulation of the hypothalamus–pituitary–adrenal axis, and modulation of neurotransmitter systems. This early evidence however does not clearly demonstrate any specificity for a certain psychiatric disorder, but is primarily relevant to mechanisms which are shared across disorders. Notable exceptions include CCL11 that has recently been shown to impair hippocampal function in aging – of distinct relevance to Alzheimer’s disease and depression in the elderly, and pre-natal exposure to CXCL8 that may disrupt early neurodevelopmental periods predisposing to schizophrenia. Pro-inflammatory chemokines, such as CCL2, CCL7, CCL8, CCL12, and CCL13, have been shown to drive chemotaxis of pro-inflammatory cells to the inflamed or injured CNS. Likewise, CX3CL has been implicated in promoting glial cells activation, pro-inflammatory cytokines secretion, expression of ICAM-1, and recruitment of CD4+ T-cells into the CNS during neuroinflammatory processes. With further translational research, chemokines may present novel diagnostic and/or therapeutic targets in psychiatric disorders.

Thymic stromal lymphopoietin deficiency attenuates experimental autoimmune encephalomyelitis

In the present study we examined the role of thymic stromal lymphopoietin (TSLP) in experimental autoimmune encephalomyelitis (EAE). Here, we report that TSLP knock-out (KO) mice display a delayed onset of disease and an attenuated form of EAE. This delayed onset was accompanied by a reduced number of encephalitogenic T helper type 1 (Th1) cells in the central nervous system (CNS) of TSLP KO mice. In addition, CD4(+) and CD8(+) T cells from CNS of TSLP KO mice show a reduced activation status in comparison to wild-type mice. It is noteworthy that we could also show that lymph node cells from TSLP KO mice expanded less efficiently and that interleukin (IL)-6-, interferon (IFN)-γ and tumour necrosis factor (TNF)-α levels were reduced. Furthermore, CD3(+) T cells isolated in the preclinical phase from myelin oligodendrocyte glycoprotein peptide 35-55 (MOG(35-55))-immunized TSLP KO mice showed a reduced response after secondary exposure to MOG(35-55), indicating that differentiation of naive T cells into MOG(35-55)-specific effector and memory T cells was impaired in KO mice. The addition of recombinant TSLP enhanced T cell proliferation during MOG(35-55) restimulation, showing that T cells also respond directly to TSLP. In summary, these data demonstrate that expression of, and immune activation by, TSLP contributes significantly to the immunopathology of EAE.

Analysis of chemokines and receptors expression profile in the myelin mutant taiep rat

Taiep rat has a failure in myelination and remyelination processes leading to a state of hypomyelination throughout its life. Chemokines, which are known to play a role in inflammation, are also involved in the remyelination process. We aimed to demonstrate that remyelination-stimulating factors are altered in the brainstem of 1- and 6-month-old taiep rats. We used a Rat RT² Profiler PCR Array to assess mRNA expression of 84 genes coding for cytokines, chemokines, and their receptors. We also evaluated protein levels of CCL2, CCR1, CCR2, CCL5, CCR5, CCR8, CXCL1, CXCR2, CXCR4, FGF2, and VEGFA by ELISA. Sprague-Dawley rats were used as a control. PCR Array procedure showed that proinflammatory cytokines were not upregulated in the taiep rat. In contrast, some mRNA levels of beta and alpha chemokines were upregulated in 1-month-old rats, but CXCR4 was downregulated at their 6 months of age. ELISA results showed that CXCL1, CCL2, CCR2, CCR5, CCR8, and CXCR4 protein levels were decreased in brainstem at the age of 6 months. These results suggest the presence of a chronic neuroinflammation process with deficiency of remyelination-stimulating factors (CXCL1, CXCR2, and CXCR4), which might account for the demyelination in the taiep rat.

Mast cell FcεRI-induced early growth response 2 regulates CC chemokine ligand 1-dependent CD4+ T cell migration

Mast cells are well positioned in host tissue for detecting environmental signals, including allergens, leading to activation of the high-affinity IgE receptor FcεRI, and initiating a signaling cascade that perpetuates the production of biologically potent mediators, including chemokines. We have identified a novel target of mast cell FcεRI activity in the transcription factor early growth response 2 (Egr2) and sought to characterize its function therein. Egr2 was transiently activated following FcεRI-mediated signaling, targeted the promoter of the chemokine CCL1, and was critical for allergen-induced mast cell CCL1 production. Egr2-deficient mast cells were incapable of directing CD4(+) T cell migration via the CCL1-CCR8 axis. In a model of allergic asthma, reconstitution of mast cell-deficient mice with Egr2-deficient mast cells demonstrated that mast cell Egr2 was essential for migration of CD4(+) T cells to the inflamed lung. These findings position Egr2 as a critical regulator of mast cell-directed CD4(+) T cell migration.

Quantitative GPCR and ion channel transcriptomics in primary alveolar macrophages and macrophage surrogates

BACKGROUND

Alveolar macrophages are one of the first lines of defence against invading pathogens and play a central role in modulating both the innate and acquired immune systems. By responding to endogenous stimuli within the lung, alveolar macrophages contribute towards the regulation of the local inflammatory microenvironment, the initiation of wound healing and the pathogenesis of viral and bacterial infections. Despite the availability of protocols for isolating primary alveolar macrophages from the lung these cells remain recalcitrant to expansion in-vitro and therefore surrogate cell types, such as monocyte derived macrophages and phorbol ester-differentiated cell lines (e.g. U937, THP-1, HL60) are frequently used to model macrophage function.

METHODS

The availability of high throughput gene expression technologies for accurate quantification of transcript levels enables the re-evaluation of these surrogate cell types for use as cellular models of the alveolar macrophage. Utilising high-throughput TaqMan arrays and focussing on dynamically regulated families of integral membrane proteins, we explore the similarities and differences in G-protein coupled receptor (GPCR) and ion channel expression in alveolar macrophages and their widely used surrogates.

RESULTS

The complete non-sensory GPCR and ion channel transcriptome is described for primary alveolar macrophages and macrophage surrogates. The expression of numerous GPCRs and ion channels whose expression were hitherto not described in human alveolar macrophages are compared across primary macrophages and commonly used macrophage cell models. Several membrane proteins known to have critical roles in regulating macrophage function, including CXCR6, CCR8 and TRPV4, were found to be highly expressed in macrophages but not expressed in PMA-differentiated surrogates.

CONCLUSIONS

The data described in this report provides insight into the appropriate choice of cell models for investigating macrophage biology and highlights the importance of confirming experimental data in primary alveolar macrophages.

Osteoblastic and cytokine gene expression of implant-adherent cells in humans

OBJECTIVES

Implant surface topography is a key determinant affecting osteoblastic differentiation and cell-cell signaling of implant-adherent cells.

MATERIALS AND METHODS

To assess the early osteoinductive and cell-cell signaling events in adherent cells, commercially pure titanium implants (2.2 × 5 mm) with nanotopography (HF-treated TiO2 grit-blasted) were compared with micron-scale topography TiO2 grit-blasted (micron-scale, control) implants in vivo. Six implants (n = 3/surface) were placed in 10 systemically healthy subjects and removed by reverse threading at 1, 3, and 7 days. Gene expression profiles of adherent cells were interrogated using low-density RT-PCR arrays.

RESULTS

Osteoinduction was not observed at day 1 on either surface. At 3 days, elevated levels of BMP6, osteopontin, and osterix (OSX) were observed in RNA of cells adherent to both micron-scale and nanotopography surfaces. Both surfaces supported osteoinductive gene expression at 7 days; however, modest elevations of most mRNAs and significantly higher OSX mRNA levels were measured for cells adhered to nanotopography implants. Further, chemokine and cytokine profiles including CXCL10, CXCL14, IL-9, IL-22, and TOLLIP were upregulated on nanotopographic surfaces as compared with microtopographic surfaces.

CONCLUSIONS

Implants with superimposed nanoscale topography generate a greater induction of genes linked to osteogenesis and cell-cell signaling during the early phases of osseointegration.

G protein-coupled receptors as therapeutic targets for multiple sclerosis

G protein-coupled receptors (GPCRs) mediate most of our physiological responses to hormones, neurotransmitters and environmental stimulants. They are considered as the most successful therapeutic targets for a broad spectrum of diseases. Multiple sclerosis (MS) is an inflammatory disease that is characterized by immune-mediated demyelination and degeneration of the central nervous system (CNS). It is the leading cause of non-traumatic disability in young adults. Great progress has been made over the past few decades in understanding the pathogenesis of MS. Numerous data from animal and clinical studies indicate that many GPCRs are critically involved in various aspects of MS pathogenesis, including antigen presentation, cytokine production, T-cell differentiation, T-cell proliferation, T-cell invasion, etc. In this review, we summarize the recent findings regarding the expression or functional changes of GPCRs in MS patients or animal models, and the influences of GPCRs on disease severity upon genetic or pharmacological manipulations. Hopefully some of these findings will lead to the development of novel therapies for MS in the near future.

CCR8 signaling influences Toll-like receptor 4 responses in human macrophages in inflammatory diseases

CCR8 immunity is generally associated with Th2 responses in allergic diseases. In this study, we demonstrate for the first time a pronounced attenuated influx of macrophages in ovalbumin (OVA)-challenged CCR8 knockout mice. To explore whether macrophages in human inflamed lung tissue also were CCR8 positive, human lung tissue from patients with chronic obstructive pulmonary disease (COPD) was evaluated. Indeed, CCR8 expression was pronounced in invading monocytes/macrophages from lungs of patients with Global Initiative for Obstructive Lung Disease (GOLD) stage IV COPD. Given this expression pattern, the functional role of CCR8 on human macrophages was evaluated in vitro. Human peripheral blood monocytes expressed low levels of CCR8, while macrophage colony-stimulating factor (M-CSF)-derived human macrophages expressed significantly elevated surface levels of CCR8. Importantly, CCL1 directly regulated the expression of CD18 and CD49b and hence influenced the adhesion capacity of human macrophages. CCL1 drives chemotaxis in M-CSF-derived macrophages, and this could be completely inhibited by lipopolysaccharide (LPS). Whereas both CCL1 and LPS monotreatment inhibited spontaneous superoxide release in macrophages, CCL1 significantly induced superoxide release in the presence of LPS in a dose-dependent manner. Finally, CCL1 induced production of proinflammatory cytokines such as tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) and could inhibit LPS-induced cytokine production in a dose-dependent manner. Our data demonstrate, for the first time, the presence of CCR8 on inflammatory macrophages in human COPD lung tissue. Importantly, the functional data from human macrophages suggest a potential cross talk between the CCR8 and the Toll-like receptor 4 (TLR4) pathways, both of which are present in COPD patients.

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.

Ly6c+ "inflammatory monocytes" are microglial precursors recruited in a pathogenic manner in West Nile virus encephalitis

In a lethal West Nile virus (WNV) model, central nervous system infection triggered a threefold increase in CD45^int/CD11b⁺/CD11c⁻ microglia at days 6–7 postinfection (p.i.). Few microglia were proliferating, suggesting that the increased numbers were derived from a migratory precursor cell. Depletion of “circulating” (Gr1⁻(Ly6C^lo)CX3CR1⁺) and “inflammatory” (Gr1^hi/Ly6C^hi/CCR2⁺) classical monocytes during infection abrogated the increase in microglia. C57BL/6 chimeras reconstituted with cFMS–enhanced green fluorescent protein (EGFP) bone marrow (BM) showed large numbers of peripherally derived (GFP⁺) microglia expressing GR1⁺(Ly6C⁺) at day 7 p.i., suggesting that the inflammatory monocyte is a microglial precursor. This was confirmed by adoptive transfer of labeled BM (Ly6C^hi/CD115⁺) or circulating inflammatory monocytes that trafficked to the WNV-infected brain and expressed a microglial phenotype. CCL2 is a chemokine that is highly expressed during WNV infection and important in inflammatory monocyte trafficking. Neutralization of CCL2 not only reduced the number of GFP⁺ microglia in the brain during WNV infection but prolonged the life of infected animals. Therefore, CCL2-dependent inflammatory monocyte migration is critical for increases in microglia during WNV infection and may also play a pathogenic role during WNV encephalitis.

A promising therapeutic approach for multiple sclerosis: recombinant T-cell receptor ligands modulate experimental autoimmune encephalomyelitis by reducing interleukin-17 production and inhibiting migration of encephalitogenic cells into the CNS

Recombinant T-cell receptor ligands (RTLs) can prevent and reverse clinical and histological signs of experimental autoimmune encephalomyelitis (EAE) in an antigen-specific manner and are currently in clinical trials for treatment of subjects with multiple sclerosis (MS). To evaluate regulatory mechanisms, we designed and tested RTL551, containing the alpha1 and beta1 domains of the I-A(b) class II molecule covalently linked to the encephalitogenic MOG-35-55 peptide in C57BL/6 mice. Treatment of active or passive EAE with RTL551 after disease onset significantly reduced clinical signs and spinal cord lesions. Moreover, RTL551 treatment strongly and selectively reduced secretion of interleukin-17 and tumor necrosis factor alpha by transferred green fluorescent protein-positive (GFP+) MOG-35-55-reactive T-cells and almost completely abrogated existent GFP+ cellular infiltrates in affected spinal cord sections. Reduced inflammation in spinal cords of RTL551-treated mice was accompanied by a highly significant downregulation of chemokines and their receptors and inhibition of VCAM-1 (vascular cell adhesion molecule-1) and ICAM-1 (intercellular adhesion molecule-1) expression by endothelial cells. Thus, RTL therapy cannot only inhibit systemic production of encephalitogenic cytokines by the targeted myelin oligodendrocyte glycoprotein-reactive T-cells but also impedes downstream local recruitment and retention of inflammatory cells in the CNS. These findings indicate that targeted immunotherapy of antigen-specific T-cells can result in a reversal of CNS lesion formation and lend strong support to the application of the RTL approach for therapy in MS.

Recruitment and activation of macrophages by pathogenic CD4 T cells in type 1 diabetes: evidence for involvement of CCR8 and CCL1

Adoptive transfer of diabetogenic CD4 Th1 T cell clones into young NOD or NOD.scid recipients rapidly induces onset of diabetes and also provides a system for analysis of the pancreatic infiltrate. Although many reports have suggested a role for macrophages in the inflammatory response, there has been little direct characterization of macrophage activity in the pancreas. We showed previously that after migration to the pancreas, diabetogenic CD4 T cell clones produce a variety of inflammatory cytokines and chemokines, resulting in the recruitment of macrophages. In this study, we investigated mechanisms by which macrophages are recruited and activated by T cells. Analysis of infiltrating cells after adoptive transfer by the diabetogenic T cell clone BDC-2.5 indicates that large numbers of cells staining for both F4/80 and CD11b are recruited into the pancreas where they are activated to make IL-1beta, TNF-alpha, and NO, and express the chemokine receptors CCR5, CXCR3, and CCR8. Diabetogenic CD4 T cell clones produce several inflammatory chemokines in vitro, but after adoptive transfer we found that the only chemokine that could be detected ex vivo was CCL1. These results provide the first evidence that CCR8/CCL1 interaction may play a role in type 1 diabetes through macrophage recruitment and activation.

Expression of chemokine receptors CCR7 and CCR8 in the CNS during ChREAE

Chemokines and their receptors are important players in organism homeostasis, development and immune response to inflammatory stimuli. It has been recently confirmed that they are also involved in the development of several autoimmune diseases. In this study, we analysed the expression of two recently identified CC chemokine receptors, CCR7 and CCR8, in the central nervous system (CNS) and in peripheral tissues during chronic relapsing experimental autoimmune encephalomyelitis (ChREAE) -- an animal model of the human demyelinating disease multiple sclerosis (MS). We observed upregulation of both chemokine receptors in the CNS during the first and second attacks of ChREAE, whereas disease remission was characterized by a lower expression of those receptors. An analysis of the kinetics of CCR7 and CCR8 expression in the CNS during the first attack of the disease showed a constant increase in the first few days after the onset of clinical signs. This expression correlated with the clinical severity of ChREAE. CCR7-positive mononuclear cells were detected mostly in perivascular inflammatory cuffs in the CNS. In peripheral tissues (the spleen and kidneys) expression of both receptors was not upregulated during active ChREAE. These findings suggest that CCR7 and CCR8 may play a significant role in the pathogenesis of EAE and probably MS.

CCR7, CCR8, CCR9 and CCR10 in the mouse hippocampal CA1 area and the dentate gyrus during and after pilocarpine-induced status epilepticus

The present study showed CCR7, CCR8, CCR9 and CCR10 in the normal Swiss mouse hippocampus at both protein and mRNA levels. CCR7, CCR9 and CCR10 were mainly localized in hippocampal principal cells and some interneurons. CCR9 was also found in the mossy fibres and/or terminals, suggesting an axonal or presynaptic localization, and CCR10 in apical dendrites of pyramidal neurons in the CA1 area. CCR8 was observed in interneurons. Double-labelling immunocytochemistry revealed that most of calbindin (CB)-, calretinin (CR)- and parvalbumin (PV)-immunopositive neurons expressed CCR7-10, except CR-immunopositive cells in which only 10 to 12% expressed CCR8. During and after pilocarpine-induced status epilepticus, progressive changes of each of CCR7, CCR8, CCR9 and CCR10 proteins occurred in different patterns at various time points. Sensitive real-time PCR showed similar change patterns at mRNA level. At the chronic stage, i.e. at 2 months after pilocarpine-induced status epilepticus, significant reduction of CCR7-10 expression in CB-, CR- and PV-immunpositive interneurons may suggest the phenotype change of surviving interneurons. Double labelling of CCR7, CCR8 and CCR9 with glial fibrillary acidic protein (GFAP) at the chronic stage may suggest an induced expression in reactive astrocytes. The present study may, therefore, for the first time, provide evidence that CCR7-10 may be involved in normal hippocampal activity. The demonstration of the progressive changes of CCR7-10 during and after status epilepticus may open a new area to reveal the mechanism of neuronal loss after status epilepticus and of epileptogenesis.

Design, Synthesis, and Evaluation of Naphthalene-Sulfonamide Antagonists of Human CCR8

The design, synthesis, and structure-activity relationship development of naphthalene-derived human CCR8 antagonists is described. In vitro binding assay results of these investigations are reported, critical interactions of the antagonists with CCR8 are defined, and preliminary physicochemical and pharmacokinetic data for the naphthalene scaffold are presented.

Inflammation in adult and neonatal stroke

This chapter will discuss the current knowledge of the contribution of systemic and local inflammation in acute and sub-chronic stages of experimental stroke in both the adult and neonate. It will review the role of specific cell types and interactions among blood cells, endothelium, glia, microglia, the extracellular matrix and neurons - cumulatively called "neurovascular unit" - in stroke induction and evolution. Intracellular inflammatory signaling pathways such as nuclear factor kappa beta and mitogen-activated protein kinases, and mediators produced by inflammatory cells such as cytokines, chemokines, reactive oxygen species and arachidonic acid metabolites, as well as the modifying role of age on these mechanisms, will be reviewed as well as the potential for therapy in stroke and hypoxic-ischemic injury.

Microglia and inflammation: impact on developmental brain injuries

Inflammation during the perinatal period has become a recognized risk factor for developmental brain injuries over the past decade or more. To fully understand the relationship between inflammation and brain development, a comprehensive knowledge about the immune system within the brain is essential. Microglia are resident immune cells within the central nervous system and play a critical role in the development of an inflammatory response within the brain. Microglia are critically involved with both the innate and adaptive immune system, regulating inflammation and cell damage within the brain via activation of Toll-like receptors, production of cytokines, and a myriad of other intracellular and intercellular processes. In this article, microglial physiology is reviewed along with the role of microglia in developmental brain injuries in humans and animal models. Last, microglial functions within the innate and adaptive immune system will be summarized. Understanding the processes of inflammation and microglial activation is critical for formulating effective preventative and therapeutic strategies for developmental brain injuries.

Design, synthesis, and progress toward optimization of potent small molecule antagonists of CC chemokine receptor 8 (CCR8)

Activation of CCR8 by its ligand CCL1 may play an important role in diseases such as asthma, multiple sclerosis, and cancer. The study of small molecule CCR8 antagonists will help establish the validation of these hypotheses. We report the design, synthesis, and progress toward optimization of potent small molecule CCR8 antagonists identified from a high-throughput screen. These analogues exhibit good potency in binding and chemotaxis assays, show good selectivity versus the hERG channel, and have good eADME (early absorption, distribution, metabolism, and excretion) profiles.

Absence of CC chemokine receptor 8 enhances innate immunity during septic peritonitis

An effective clearance of microbes is crucial in host defense during infection. In the present study, we demonstrate that CC chemokine receptor 8 (CCR8) skews innate immune response during septic peritonitis induced by cecal ligation and puncture (CLP). CCR8 was expressed in resident peritoneal macrophages and elicited leukocytes during CLP in the wild-type CCR8+/+ mice. CCR8-/- mice were resistant to CLP-induced lethality relative to CCR8+/+ mice, and this resistance was associated with an augmented bacterial clearance in CCR8-/- mice. In vitro, peritoneal macrophages from CCR8-/- mice, but not neutrophils, exhibited enhanced bactericidal activities relative to those from CCR8+/+ mice. Upon stimulation with the bacterial component LPS, elevated levels of superoxide generation, lysosomal enzyme release, and nitric oxide generation, effector molecules for bacterial killing were detected in CCR8-/- macrophages relative to CCR8+/+ macrophages. In addition, CCR8-/- macrophages produced significantly higher levels than CCR8+/+ macrophages of several cytokines and chemokines known to augment bactericidal activities of leukocytes that include TNF-alpha, IL-12, macrophage-derived chemokine (MDC/CCL22), macrophage inflammatory protein (MIP)-2, and KC. Altogether, these results indicate that CCR8 may have a negative impact on host defense during septic peritonitis, providing a new paradigm for the role of CCR8 in innate immunity.

Identification and Characterization of U83A Viral Chemokine, a Broad and Potent β-Chemokine Agonist for Human CCRs with Unique Selectivity and Inhibition by Spliced Isoform

Leukotropic human herpesvirus 6 (HHV-6) establishes a persistent infection associated with inflammatory diseases and encodes chemokines that could chemoattract leukocytes for infection or inflammation. HHV-6 variant A encodes a distant chemokine homolog, U83A, and a polymorphism promoting a secreted form was identified. U83A and three N-terminal modifications were expressed and purified, and activities were compared with a spliced truncated isoform, U83A-Npep. U83A efficiently and potently induced calcium mobilization in cells expressing single human CCR1, CCR4, CCR6, or CCR8, with EC50 values <10 nM. U83A also induced chemotaxis of Th2-like leukemic cells expressing CCR4 and CCR8. High-affinity binding, 0.4 nM, was demonstrated to CCR1 and CCR5 on monocytic/macrophage cells, and pretreatment with U83A or modified forms could block responses for endogenous ligands. U83A-Npep acted only as antagonist, efficiently blocking binding of CCL3 to CCR1 or CCR5 on differentiated monocytic/macrophage leukemic cells. Furthermore, CCL3 induction of calcium signaling via CCR1 and CCL1 induced chemotaxis via CCR8 in primary human leukocytes was inhibited. Thus, this blocking by the early expressed U83A-Npep could mediate immune evasion before finishing the replicative cycle. However, late in infection, when full-length U83A is made, chemoattraction of CCR1-, CCR4-, CCR5-, CCR6-, and CCR8-bearing monocytic/macrophage, dendritic, and T lymphocyte cells can facilitate dissemination via lytic and latent infection of these cells. This has further implications for neuroinflammatory diseases such as multiple sclerosis, where both cells bearing CCR1/CCR5 plus their ligands, as well as HHV-6A, have been linked. Applications also discussed include novel vaccines/immunotherapeutics for cancer and HIV as well as anti-inflammatories.

Chemokine receptor CXCR3: an unexpected enigma

CXCR3, the receptor for CXCL9/MIG, CXCL10/IP-10, and CXCL11/I-TAC, is preferentially expressed on activated Th1 T cells and has been predicted to play an important role in their trafficking. However, this simplistic view of the function of CXCR3 and its ligands has not been borne out by studies of disease models, including experimental autoimmune encephalomyelitis (EAE), using varied methods of receptor blockade, as well as knockout or transgenic mice. This review focuses on the current understanding of the enigmatic role of CXCR3 and its ligands in CNS inflammatory/autoimmune disorders. The conflicting results among varied models of CNS inflammation suggest complex and multiple roles for CXCR3 and its ligands in the pathogenesis of CNS inflammatory/autoimmune diseases. Thus, further study is needed to determine how CXCL10 neutralizing agents or CXCR3 receptor antagonists might be applied to treating human disease.

Brain microglia and blood-derived macrophages: molecular profiles and functional roles in multiple sclerosis and animal models of autoimmune demyelinating disease

Microglia and macrophages, one a brain-resident, the other a mostly hematogenous cell type, represent two related cell types involved in the brain pathology in multiple sclerosis and its autoimmune animal model, the experimental allergic encephalomyelitis. Together, they perform a variety of different functions: they are the primary sensors of brain pathology, they are rapidly recruited to sites of infection, trauma or autoimmune inflammation in experimental allergic encephalomyelitis and multiple sclerosis and they are competent presenters of antigen and interact with T cells recruited to the inflamed CNS. They also synthesise a variety of molecules, such as cytokines (TNF, interleukins), chemokines, accessory molecules (B7, CD40), complement, cell adhesion glycoproteins (integrins, selectins), reactive oxygen radicals and neurotrophins, that could exert a damaging or a protective effect on adjacent axons, myelin and oligodendrocytes. The current review will give a detailed summary on their cellular response, describe the different classes of molecules expressed and their attribution to the blood derived or brain-resident macrophages and then discuss how these molecules contribute to the neuropathology. Recent advances using chimaeric and genetically modified mice have been particularly telling about the specific, overlapping and nonoverlapping roles of macrophages and microglia in the demyelinating disease. Interestingly, they point to a crucial role of hematogenous macrophages in initiating inflammation and myelin removal, and that of microglia in checking excessive response and in the induction and maintenance of remission.

Involvement of beta-chemokines in the development of inflammatory demyelination

The importance of β-chemokines (or CC chemokine ligands – CCL) in the development of inflammatory lesions in the central nervous system of patients with multiple sclerosis and rodents with experimental allergic encephalomyelitis is strongly supported by descriptive studies and experimental models. Our recent genetic scans in families identified haplotypes in the genes of CCL2, CCL3 and CCL11-CCL8-CCL13 which showed association with multiple sclerosis. Complementing the genetic associations, we also detected a distinct regional expression regulation for CCL2, CCL7 and CCL8 in correlation with chronic inflammation in multiple sclerosis brains. These observations are in consensus with previous studies, and add new data to support the involvement of CCL2, CCL7, CCL8 and CCL3 in the development of inflammatory demyelination. Along with our own data, here we review the literature implicating CCLs and their receptors (CCRs) in multiple sclerosis and experimental allergic encephalomyelitis. The survey reflects that the field is in a rapid expansion, and highlights some of the pathways which might be suitable to pharmaceutical interventions.

Chemokine receptors in the central nervous system: role in brain inflammation and neurodegenerative diseases

Chemokines were originally described as chemotactic cytokines involved in leukocyte trafficking. Research over the last decade, however, has shown that chemokine receptors are not restricted to leukocytes. In the brain, chemokine receptors are not only found in microglia (a brain macrophage), but also in astrocytes, oligodendrocytes and neurons. In this review, we describe the spatial and cellular distribution of chemokine receptors in the brain, distinguishing between constitutively and inducibly expressed receptors. We then discuss possible physiological functions, including neuronal migration, cell proliferation and synaptic activity. Evidence is emerging that chemokine receptors are also involved in neuronal death and hence neurodegenerative diseases. Chemokines may induce neuronal death either indirectly (e.g. through activation of microglia killing mechanisms) or directly through activation of neuronal chemokine receptors. Disease processes in which chemokines and their receptors are likely to be involved include multiple sclerosis (MS), Alzheimer's disease (AD), HIV-associated dementia (HAD) and cerebral ischemic disease. The study of chemokines and their receptors in the central nervous system (CNS) is not only relevant for the understanding of brain physiology and pathophysiology, but may also lead to the development of targeted treatments for neurodegenerative diseases.

Role of Microglia and Macrophages in Eae

Microglia and macrophages are related cell types that play an important role in the pathogenesis of MS and EAE. This chapters reviews the role of these cells in the normal brain and their contribution to inflammatory demyelinating disease, including their role in antigen presentation, co-stimulation, and production of cytokines and other inflammatory mediators

Role of CCR8 and other chemokine pathways in the migration of monocyte-derived dendritic cells to lymph nodes

Studying the influence of chemokine receptors (CCRs) on monocyte fate may reveal information about which subpopulations of monocytes convert to dendritic cells (DCs) and the migration pathways that they use. First, we examined whether prominent CCRs on different monocyte subsets, CCR2 or CX3CR1, mediated migration events upstream of the accumulation of monocyte-derived DCs in lymph nodes (LNs). Monocytes were labeled and traced by uptake of latex microspheres in skin. Unexpectedly, neither CCR2 nor CX3CR1 were required. However, absence of CCR2 led to an increased labeling of the minor Gr-1int monocyte population, and the number of latex+ DCs that emigrated to LNs was correspondingly increased. Characterization of Gr-1int monocytes revealed that they selectively expressed CCR7 and CCR8 mRNA in blood. CCR7 and CCR8 pathways were used by monocyte-derived DCs during mobilization from skin to LNs. The role of CCR8 in emigration from tissues also applied to human monocyte-derived cells in a model of transendothelial trafficking. Collectively, the data suggest that Gr-1int monocytes may be most disposed to become a lymphatic-migrating DCs. When these monocyte-derived DCs exit skin to emigrate to LNs, they use not only CCR7 but also CCR8, which was not previously recognized to participate in migration to LNs.

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.

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

Multiple sclerosis (MS) is an inflammatory demyelinating disorder of the CNS. A recent study identified 4 patterns of demyelination in active MS lesions. The characteristics of pattern II lesions suggested a primary inflammatory mechanism of myelin injury, while pattern III lesions showed features consistent with dying-back oligodendrogliopathy. The recruitment, differentiation, and activation of mononuclear phagocytes are dependent on the expression of chemokine receptors. Using immunohistochemistry we quantified cellular expression of CCR1 and CCR5 in pattern II (n = 21) and pattern III (n = 17) lesion areas of differing demyelinating activity. Infiltrating monocytes in both lesion patterns co-expressed CCR1 and CCR5, suggesting conserved mechanisms of monocyte recruitment into the CNS. In pattern II lesions, the number of cells expressing CCR1 significantly decreased while CCR5 increased in late active compared with early active demyelinating regions. In striking contrast, numbers of cells expressing CCR1 and CCR5 were equal in all regions of pattern III lesions. As hypoxia-like mechanisms may play a role in pattern III lesions, we extended these studies to white matter infarcts (n = 7) in which the expression of CCR1 better resembled pattern III than pattern II lesions. As judged by mononuclear phagocyte chemokine receptor expression, there appear to be distinct tissue environments in pattern II and III MS lesions.

Genetic fusions with viral chemokines target delivery of nonimmunogenic antigen to trigger antitumor immunity independent of chemotaxis

The ideal vaccine carrier should be able to target antigen delivery and possibly recruit antigen-presenting cells (APC) and deliver an activation signal to promote adaptive immune responses. Ligands for chemokine receptors expressed on APC may be attractive candidates, as they can both target and attract APC. To investigate the requirement for APC recruitment, we used a pair of viral chemokines, agonist herpes simplex virus 8-derived macrophage inflammatory protein-I (vMIP-I) and antagonist MC148, which induce and suppress chemotaxis, respectively. Chemokine-antigen fusions efficiently delivered a model nonimmunogenic tumor antigen to APC for processing and presentation to antigen-specific T cells in vitro. Physical linkage of chemokine and antigen and specific binding of chemokine receptor by the fusion protein were required. Mice immunized with vMIP-I or MC148 fusion DNA vaccines elicited protection against tumor challenge. Therefore, vaccine efficacy depends primarily on the ability of the carrier to target antigen delivery to APC for subsequent processing and presentation, and chemotaxis directly induced by the chemokine moiety in the fusion may not be necessary.