An antibody to IP-10 is a potent antagonist of cell migration in vitro and in vivo and does not affect disease in several animal models of inflammation

Chemokine CXCL10 and Coronavirus-Induced Neurologic Disease

Chemokines (chemotactic cytokines) are involved in a wide variety of biological processes. Following microbial infection, there is often robust chemokine signaling elicited from infected cells, which contributes to both innate and adaptive immune responses that control growth of the invading pathogen. Infection of the central nervous system (CNS) by the neuroadapted John Howard Mueller (JHM) strain of mouse hepatitis virus (JHMV) provides an excellent example of how chemokines aid in host defense as well as contribute to disease. Intracranial inoculation of the CNS of susceptible mice with JHMV results in an acute encephalomyelitis characterized by widespread dissemination of virus throughout the parenchyma. Virus-specific T cells are recruited to the CNS, and control viral replication through release of antiviral cytokines and cytolytic activity. Sterile immunity is not acquired, and virus will persist primarily in white matter tracts leading to chronic neuroinflammation and demyelination. Chemokines are expressed and contribute to defense as well as chronic disease by attracting targeted populations of leukocytes to the CNS. The T cell chemoattractant chemokine CXCL10 (interferon-inducible protein 10 kDa, IP-10) is prominently expressed in both stages of disease, and serves to attract activated T and B lymphocytes expressing CXC chemokine receptor 3 (CXCR3), the receptor for CXCL10. Functional studies that have blocked expression of either CXCL10 or CXCR3 illuminate the important role of this signaling pathway in host defense and neurodegeneration in a model of viral-induced neurologic disease.

Age-Associated Resident Memory CD8 T Cells in the Central Nervous System Are Primed To Potentiate Inflammation after Ischemic Brain Injury

Aging is associated with an increase in basal inflammation in the CNS and an overall decline in cognitive function and poorer recovery following injury. Growing evidence suggests that leukocyte recruitment to the CNS is also increased with normal aging, but, to date, no systematic evaluation of these age-associated leukocytes has been performed. In this work, the effect of aging on CNS leukocyte recruitment was examined. Aging was associated with more CD45(high) leukocytes, primarily composed of conventional CD8(+) T cells. These results were strain independent and seen in both sexes. Intravascular labeling and immunohistology revealed the presence of parenchymal CD8(+) T cells in several regions of the brain, including the choroid plexus and meninges. These cells had effector memory (CD44(+)CD62L(-)) and tissue-resident phenotypes and expressed markers associated with TCR activation. Analysis of TCRvβ repertoire usage suggested that entry into the CNS is most likely stochastic rather than Ag driven. Correlational analyses revealed a positive association between CD8 T cell numbers and decreased proinflammatory function of microglia. However, the effects of cerebral ischemia and ex vivo stimulation of these cells dramatically increased production of TNF, IFN-γ, and MCP-1/CCL2. Taken together, we identified a novel population of resident memory, immunosurveillant CD8 T cells that represent a hallmark of CNS aging and appear to modify microglia homeostasis under normal conditions, but are primed to potentiate inflammation and leukocyte recruitment following ischemic injury.

Emerging importance of chemokine receptor CXCR3 and its ligands in cardiovascular diseases

The CXC chemokines, CXCL4, -9, -10, -11, CXCL4L1, and the CC chemokine CCL21, activate CXC chemokine receptor 3 (CXCR3), a cell-surface G protein-coupled receptor expressed mainly by Th1 cells, cytotoxic T (Tc) cells and NK cells that have a key role in immunity and inflammation. However, CXCR3 is also expressed by vascular smooth muscle and endothelial cells, and appears to be important in controlling physiological vascular function. In the last decade, evidence from pre-clinical and clinical studies has revealed the participation of CXCR3 and its ligands in multiple cardiovascular diseases (CVDs) of different aetiologies including atherosclerosis, hypertension, cardiac hypertrophy and heart failure, as well as in heart transplant rejection and transplant coronary artery disease (CAD). CXCR3 ligands have also proven to be valid biomarkers for the development of heart failure and left ventricular dysfunction, suggesting an underlining pathophysiological relation between levels of these chemokines and the development of adverse cardiac remodelling. The observation that several of the above-mentioned chemokines exert biological actions independent of CXCR3 provides both opportunities and challenges for developing effective drug strategies. In this review, we provide evidence to support our contention that CXCR3 and its ligands actively participate in the development and progression of CVDs, and may additionally have utility as diagnostic and prognostic biomarkers.

Anti-inflammatory mechanisms of IFN-γ studied in experimental autoimmune encephalomyelitis reveal neutrophils as a potential target in multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) mediated by T helper (h)1 and/or Th17 CD4 T cells that drive inflammatory lesion development along with demyelination and neuronal damage. Defects in immune regulatory mechanisms are thought to play a role in the pathogenesis of MS. While an early clinical trial indicated that IFN-γ administration was detrimental to MS, studies in the mouse model of MS, experimental autoimmune encephalomyelitis (EAE), indicated that IFN-γ exhibits a number of anti-inflammatory properties within the CNS. These mechanisms include inhibition of IL-17 production, induction of regulatory T cells, T cell apoptosis and regulation of chemokine production. Mice deficient in IFN-γ or its receptor were instrumental in deciphering the anti-inflammatory properties of IFN-γ in the CNS. In particular, they revealed that IFN-γ is a major regulator of neutrophil recruitment into the CNS, which by a variety of mechanisms including disruption of the blood-brain-barrier (BBB) and production of reactive oxygen species are thought to contribute to the onset and progression of EAE. Neutrophils were also shown to be instrumental in EAE relapses. To date neutrophils have not been appreciated as a driver of MS, but more recently based largely on strong EAE data this view is being reevaluated by some investigators in the field.

Deletion of astroglial CXCL10 delays clinical onset but does not affect progressive axon loss in a murine autoimmune multiple sclerosis model

Multiple sclerosis (MS) is characterized by central nervous system (CNS) inflammation, demyelination, and axonal degeneration. CXCL10 (IP-10), a chemokine for CXCR3⁺ T cells, is known to regulate T cell differentiation and migration in the periphery, but effects of CXCL10 produced endogenously in the CNS on immune cell trafficking are unknown. We created floxed cxcl10 mice and crossed them with mice carrying an astrocyte-specific Cre transgene (mGFAPcre) to ablate astroglial CXCL10 synthesis. These mice, and littermate controls, were immunized with myelin oligodendrocyte glycoprotein peptide 35-55 (MOG peptide) to induce experimental autoimmune encephalomyelitis (EAE). In comparison to the control mice, spinal cord CXCL10 mRNA and protein were sharply diminished in the mGFAPcre/CXCL10^fl/fl EAE mice, confirming that astroglia are chiefly responsible for EAE-induced CNS CXCL10 synthesis. Astroglial CXCL10 deletion did not significantly alter the overall composition of CD4⁺ lymphocytes and CD11b⁺ cells in the acutely inflamed CNS, but did diminish accumulation of CD4⁺ lymphocytes in the spinal cord perivascular spaces. Furthermore, IBA1+ microglia/macrophage accumulation within the lesions was not affected by CXCL10 deletion. Clinical deficits were milder and acute demyelination was substantially reduced in the astroglial CXCL10-deleted EAE mice, but long-term axon loss was equally severe in the two groups. We concluded that astroglial CXCL10 enhances spinal cord perivascular CD4⁺ lymphocyte accumulation and acute spinal cord demyelination in MOG peptide EAE, but does not play an important role in progressive axon loss in this MS model.

Th1-mediated experimental autoimmune encephalomyelitis is CXCR3 independent

Drugs that block leukocyte trafficking ameliorate multiple sclerosis (MS). Occurrences of opportunistic infection, however, highlight the need for novel drugs that modulate more restricted subsets of T cells. In this context, chemokines and their receptors are attractive therapeutic targets. CXCR3, a Th1-associated chemokine receptor, is preferentially expressed on T cells that accumulate in MS lesions and central nervous system (CNS) infiltrates of mice with experimental autoimmune encephalomyelitis (EAE). Surprisingly, mice genetically deficient in either CXCR3 or CXCL10 succumb to EAE following active immunization with myelin antigens. EAE is mediated by a heterogeneous population of T cells in myelin-immunized mice. Hence, disease might develop in the absence of CXCR3 secondary to the compensatory action of encephalitogenic CCR6(+) Th17 cells. However, in the current study, we show for the first time that blockade or genetic deficiency of either CXCR3 or of its primary ligand has no impact on clinical EAE induced by the adoptive transfer of highly polarized Th1 effector cells. Our data illustrate the fact that, although highly targeted immunotherapies might have more favorable side effect profiles, they are also more likely to be rendered ineffective by inherent redundancies in chemokine and cytokine networks that arise at sites of neuroinflammation.

Enhanced expression of CXCL10 in inflammatory bowel disease: potential role of mucosal Toll-like receptor 3 stimulation

BACKGROUND

We explored the gene expression in colonic biopsies of active and inactive inflammatory bowel disease (IBD) in an extensive material of ulcerative colitis (UC) and Crohn's disease (CD). The chemokine CXCL10 and its receptor CXCR3 were among the upregulated genes. This study examined the expression of CXCL10 and the mechanisms for its release in patients with UC or CD and in intestinal epithelial cell (IEC) lines.

METHODS

A microarray gene expression analysis was done on colonic biopsies (n = 133) from patients with IBD. Biopsies were studied with immunohistochemistry for CXCL10 and CXCR3 expression. Mechanisms for CXCL10 release in peripheral blood mononuclear cells (PBMCs) and in the colonic epithelial cell lines HT-29 and SW620 were studied upon pattern recognition receptor (PRR) stimulation.

RESULTS

CXCL10 and CXCR3 mRNA abundances were increased in biopsies from active UC and CD compared to inactive disease and controls. CXCL10 was mainly localized to mucosal epithelial cells, with increased immunostaining in active IBD. CXCR3-positive cells were scattered in the lamina propria. CXCL10 was secreted from the colonic epithelial cell lines in response to the Toll-like receptor 3 (TLR3) ligand polyinosinic: polycytidylic acid (poly(I:C)). This ligand also induced a marked release of CXCL10 in PBMCs from IBD patients and controls.

CONCLUSIONS

We identified CXCL10 and CXCR3 as upregulated genes in colonic mucosa in active IBD. The TLR3-ligand poly(I:C) markedly increased release of CXCL10 in colonic epithelial cell lines, suggesting a TLR3-mediated CXCL10 release from mucosal epithelial cells in IBD patients.

IFN-γ-induced apoptosis of human embryonic stem cell derived oligodendrocyte progenitor cells is restricted by CXCR2 signaling

Engraftment of human embryonic stem cell (hESC)-derived OPCs in animal models of demyelination results in remyelination and clinical recovery, supporting the feasibility of cell replacement therapies in promoting repair of damaged neural tissue. A critical gap in our understanding of the mechanisms associated with repair revolves around the effects of the local microenvironment on transplanted cell survival. We have determined that treatment of human ESC-derived OPCs with the pleiotropic cytokine IFN-γ promotes apoptosis that is associated with mitochondrial cytochrome c released into the cytosol with subsequent caspase 3 activation. IFN-γ-induced apoptosis is mediated, in part, by secretion of the CXC chemokine ligand 10 (CXCL10) from IFN-γ-treated cells. Signaling through the chemokine receptor CXCR2 by the ligand CXCL1 functions in a tonic manner by muting apoptosis and this is associated with reduced levels of cytosolic cytochrome c and impaired cleavage of caspase 3. These findings support a role for both IFN-γ and CXCL10 in contributing to neuropathology by promoting OPC apoptosis. In addition, these data suggest that hOPCs used for therapeutic treatment for human neurologic disease/damage are susceptible to death through exposure to local inflammatory cytokines present within the inflammatory milieu.

A selective and potent CXCR3 antagonist SCH 546738 attenuates the development of autoimmune diseases and delays graft rejection

BACKGROUND

The CXCR3 receptor and its three interferon-inducible ligands (CXCL9, CXCL10 and CXCL11) have been implicated as playing a central role in directing a Th1 inflammatory response. Recent studies strongly support that the CXCR3 receptor is a very attractive therapeutic target for treating autoimmune diseases, such as rheumatoid arthritis, multiple sclerosis and psoriasis, and to prevent transplant rejection. We describe here the in vitro and in vivo pharmacological characterizations of a novel and potent small molecule CXCR3 antagonist, SCH 546738.

RESULTS

In this study, we evaluated in vitro pharmacological properties of SCH 546738 by radioligand receptor binding and human activated T cell chemotaxis assays. In vivo efficacy of SCH 546738 was determined by mouse collagen-induced arthritis, rat and mouse experimental autoimmune encephalomyelitis, and rat cardiac transplantation models. We show that SCH 546738 binds to human CXCR3 with a high affinity of 0.4 nM. In addition, SCH 546738 displaces radiolabeled CXCL10 and CXCL11 from human CXCR3 with IC50 ranging from 0.8 to 2.2 nM in a non-competitive manner. SCH 546738 potently and specifically inhibits CXCR3-mediated chemotaxis in human activated T cells with IC90 about 10 nM. SCH 546738 attenuates the disease development in mouse collagen-induced arthritis model. SCH 546738 also significantly reduces disease severity in rat and mouse experimental autoimmune encephalomyelitis models. Furthermore, SCH 546738 alone achieves dose-dependent prolongation of rat cardiac allograft survival. Most significantly, SCH 546738 in combination with CsA supports permanent engraftment.

CONCLUSIONS

SCH 546738 is a novel, potent and non-competitive small molecule CXCR3 antagonist. It is efficacious in multiple preclinical disease models. These results demonstrate that therapy with CXCR3 antagonists may serve as a new strategy for treatment of autoimmune diseases, including rheumatoid arthritis and multiple sclerosis, and to prevent transplant rejection.

Validation of urinary CXCL10 as a marker of borderline, subclinical, and clinical tubulitis

BACKGROUND

Renal allograft injury secondary to subclinical and clinical tubulitis remains an important cause of allograft fibrosis and loss despite modern immunosuppression. The goal of this study was to validate the previously reported use of urinary CXCL10 (interferon-γ-induced protein of 10 kDa) as a noninvasive marker of tubulitis in an independent clinical cohort.

METHODS

Urine samples (n=102) from 91 patients with protocol or indication biopsies were assayed for urinary CXCL10 using ELISA. The groups analyzed were as follows: normal histology (n=22); interstitial fibrosis and tubular atrophy (IFTA) (n=20); IFTA and borderline tubulitis (n=13); borderline (n=13), subclinical (n=17); and clinical tubulitis (n=17) without IFTA.

RESULTS

The ratio of urinary CXCL10 to creatinine (CXCL10: Cr) was found to distinguish borderline, subclinical and clinical tubulitis from normal histology, and IFTA. The area under the curve receiver operating characteristic curve to distinguish normal versus borderline and subclinical tubulitis was 0.845 (OR 1.407, P=0.0184); normal versus borderline, subclinical and clinical tubulitis was 0.835 (OR 1.400, P=0.0127). CXCL10: Cr demonstrated a sensitivity of 73.3% and specificity of 72.7% for normal versus borderline and subclinical tubulitis at a cut-off of 1.97 ng CXCL10/mmol Cr.

CONCLUSION

This study validates urinary CXCL10 as a noninvasive, sensitive, and specific marker for tubulitis in an independent cohort. The straightforward urine processing is accessible to clinical laboratories. We propose that CXCL10 may be useful as a supplementary noninvasive screening test for tubulitis in renal transplant patients, with a level more than 1.97 ng CXCL10/mmol Cr being a threshold to consider biopsy.

Shining a light on intestinal traffic

Inflammatory bowel disease (IBD), encompassing Crohn's disease and ulcerative colitis, is associated with enhanced leukocyte infiltration to the gut, which is directly linked to the clinical aspects of these disorders. Thus, leukocyte trafficking is a major target for IBD therapy. Past and emerging techniques to study leukocyte trafficking both in vitro and in vivo have expanded our knowledge of the leukocyte migration process and the role of inhibitors. Various strategies have been employed to target chemokine- and integrin-ligand interactions within the multistep adhesion cascade and the S1P/S1PR1 axis in leukocyte migration. Though there is an abundance of preclinical data demonstrating efficacy of leukocyte trafficking inhibitors, many have yet to be confirmed in clinical studies. Vigilance for toxicity and further research is required into this complex and emerging area of IBD therapy.

Targeting chemokine receptors in chronic inflammatory diseases: an extensive review

The traffic of the different types of immune cells is an important aspect in the immune response. Chemokines are soluble peptides that are able to attract cells by interaction with chemokine receptors on their target cells. Several different chemokines and receptors exist enabling the specific trafficking of different immune cells. In chronic inflammatory disorders there is abundance of immune cells present at the inflammatory site. This review focuses on the role of chemokine receptors in chronic inflammatory disorders of the lungs, intestine, joints, skin and nervous system and the potential of targeting these receptors as therapeutic intervention in these disorders.

Synoviocyte innate immune responses: TANK-binding kinase-1 as a potential therapeutic target in rheumatoid arthritis

OBJECTIVES

Innate immune responses in the rheumatoid synovium contribute to inflammation and joint destruction in RA. Two IκB kinase (IKK)-related kinases, TNF receptor associated factor (TRAF) family member-associated nuclear factor κ-light-chain enhancer of activated B cells (NF-κB) activator (TANK)-binding kinase 1 (TBK1) and IKKε, potentially regulate synovitis by activating IFN response genes. These kinases induce the expression of inflammatory mediators such as C-X-C motif ligand 10 (CXCL10)/IFN-γ-induced protein 10 kDa (IP-10) in fibroblast-like synoviocytes (FLS). Since IP-10 is a promising therapeutic target in RA, we evaluated whether blocking TBK1 might be an effective way to modulate IP-10 expression.

METHODS

Wild-type (WT) and IKKε(-/-) FLS were transfected with TBK1 or control small interfering RNA (siRNA) and stimulated with polyinosinic acid : polycytidylic acid [poly(I:C)]. Gene expression was assayed using quantitative PCR. Cytokine production in culture supernatants was measured by Luminex multiplex analysis. IFN-regulatory factor (IRF3) dimerization was determined by native PAGE. IFN-β and IP-10 promoter activity was measured using luciferase reporter constructs.

RESULTS

Initial studies showed that siRNA markedly decreased TBK1 expression in cultured FLS. Poly(I:C)-induced IRF7 gene expression was inhibited in the absence of TBK1, but not IKKε. IRF3 gene expression was similar to WT cells in TBK1 or IKKε-deficient FLS. IRF3 dimerization required both TBK1 and IKKε. Surprisingly, IRF3-mediated gene and protein expression of IFN-β and IP-10 was dependent on TBK1, not IKKε. Promoter constructs showed that TBK1 decreased IP-10 gene transcription and IP-10 mRNA stability was unaffected by TBK1 deficiency.

CONCLUSION

Based on the selective regulation of IP-10 in FLS, TBK1 appears to be the optimal IKK-related kinase to target in RA.

Monoclonal antibodies to B and T lymphocyte attenuator (BTLA) have no effect on in vitro B cell proliferation and act to inhibit in vitro T cell proliferation when presented in a cis, but not trans, format relative to the activating stimulus

B and T lymphocyte attenuator (BTLA) is an immunoglobulin superfamily member surface protein expressed on B and T cells. Its ligand, herpesvirus entry mediator (HVEM), is believed to act as a monomeric agonist that signals via the CRD1 of HVEM to inhibit lymphocyte activation: HVEM is also the receptor for lymphotoxin-α and LIGHT, which both bind in the CRD2 and CRD3 domains of the HVEM molecule, and for CD160 which competes with BTLA. We have shown that recombinant HVEM and a panel of different monoclonal antibodies specifically bind murine BTLA on both B and T cells and that some antibodies inhibit anti-CD3ε-induced T cell proliferation in vitro, but only when constrained appropriately with a putatively cross-linking reagent. The antibodies had no significant effect on in vitro T cell proliferation in a mixed lymphocyte reaction (MLR) assay nor on in vitro DO11.10 antigen-induced T cell proliferation. None of these antibodies, nor HVEM-Fc, had any significant effect on in vitro B cell proliferation induced by anti-immunoglobulin M antibodies (±anti-CD40) or lipopolysaccharide. We further elucidated the requirements for inhibition of in vitro T cell proliferation using a beads-based system to demonstrate that the antibodies that inhibited T cell proliferation in vitro were required to be presented to the T cell in a cis, and not trans, format relative to the anti-CD3ε stimulus. We also found that antibodies that inhibited T cell proliferation in vitro had no significant effect on the antibody captured interleukin-2 associated with the in vivo activation of DO11.10 T cells transferred to syngeneic recipient BALB/c mice. These data suggest that there may be specific structural requirements for the BTLA molecule to exert its effect on lymphocyte activation and proliferation.

Appearance of Cxcl10-expressing cell clusters is common for traumatic brain injury and neurodegenerative disorders

Traumatic brain injury (TBI) in the mouse results in the rapid appearance of scattered clusters of cells expressing the chemokine Cxcl10 in cortical and subcortical areas. To extend the observation of this unique pattern, we used neuropathological mouse models using quantitative reverse transcriptase-polymerase chain reaction, gene array analysis, in-situ hybridization and flow cytometry. As for TBI, cell clusters of 150-200 mum expressing Cxcl10 characterize the cerebral cortex of mice carrying a transgene encoding the Swedish mutation of amyloid precursor protein, a model of amyloid Alzheimer pathology. The same pattern was found in experimental autoimmune encephalomyelitis in mice modelling multiple sclerosis. In contrast, mice carrying a SOD1(G93A) mutant mimicking amyotrophic lateral sclerosis pathology lacked such cell clusters in the cerebral cortex, whereas clusters appeared in the brainstem and spinal cord. Mice homozygous for a null mutation of the Cxcl10 gene did not show detectable levels of Cxcl10 transcript after TBI, confirming the quantitative reverse transcriptase-polymerase chain reaction and in-situ hybridization signals. Moreover, unbiased microarray expression analysis showed that Cxcl10 was among 112 transcripts in the neocortex upregulated at least threefold in both TBI and ageing TgSwe mice, many of them involved in inflammation. The identity of the Cxcl10(+) cells remains unclear but flow cytometry showed increased numbers of activated microglia/macrophages as well as myeloid dendritic cells in the TBI and experimental autoimmune encephalomyelitis models. It is concluded that the Cxcl10(+) cells appear in the inflamed central nervous system and may represent a novel population of cells that it may be possible to target pharmacologically in a broad range of neurodegenerative conditions.