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

G protein-coupled receptors (GPCRs): advances in structures, mechanisms, and drug discovery

G protein-coupled receptors (GPCRs), the largest family of human membrane proteins and an important class of drug targets, play a role in maintaining numerous physiological processes. Agonist or antagonist, orthosteric effects or allosteric effects, and biased signaling or balanced signaling, characterize the complexity of GPCR dynamic features. In this study, we first review the structural advancements, activation mechanisms, and functional diversity of GPCRs. We then focus on GPCR drug discovery by revealing the detailed drug-target interactions and the underlying mechanisms of orthosteric drugs approved by the US Food and Drug Administration in the past five years. Particularly, an up-to-date analysis is performed on available GPCR structures complexed with synthetic small-molecule allosteric modulators to elucidate key receptor-ligand interactions and allosteric mechanisms. Finally, we highlight how the widespread GPCR-druggable allosteric sites can guide structure- or mechanism-based drug design and propose prospects of designing bitopic ligands for the future therapeutic potential of targeting this receptor family.

Structural insights into the activation and inhibition of CXC chemokine receptor 3

The chemotaxis of CD4+ type 1 helper cells and CD8+ cytotoxic lymphocytes, guided by interferon-inducible CXC chemokine 9-11 (CXCL9-11) and CXC chemokine receptor 3 (CXCR3), plays a critical role in type 1 immunity. Here we determined the structures of human CXCR3-DNGi complexes activated by chemokine CXCL11, peptidomimetic agonist PS372424 and biaryl-type agonist VUF11222, and the structure of inactive CXCR3 bound to noncompetitive antagonist SCH546738. Structural analysis revealed that PS372424 shares a similar orthosteric binding pocket to the N terminus of CXCL11, while VUF11222 buries deeper and activates the receptor in a distinct manner. We showed an allosteric binding site between TM5 and TM6, accommodating SCH546738 in the inactive CXCR3. SCH546738 may restrain the receptor at an inactive state by preventing the repacking of TM5 and TM6. By revealing the binding patterns and the pharmacological properties of the four modulators, we present the activation mechanisms of CXCR3 and provide insights for future drug development.

Research progress of CXCR3 inhibitors

The human CXCR3 receptor was initially identified and cloned in the mid-1990s. In the process of understanding CXCR3, it gradually found that it plays an important role in the process of a variety of diseases, including inflammation, immune diseases, cancer, cardiovascular diseases, central nervous system diseases, etc., which attracted the attention of many researchers. Subsequently, some small molecule inhibitors targeting CXCR3 receptors were also developed. Unfortunately, no CXCR3 inhibitors have been approved for marketing by FDA. Up to now, only one CXCR3 small molecule inhibitor has entered the clinical trial stage, but it has not achieved ideal results in the end. Therefore, there is still much to think about and explore for the development of CXCR3 inhibitors. This article reviews the important role of CXCR3 in various physiological and pathological processes and some small molecule inhibitors of CXCR3.

Mediators and mechanisms of immune checkpoint inhibitor-associated myocarditis: Insights from mouse and human

The broad application of immune checkpoint inhibitors (ICIs) has led to significant gains in cancer outcomes. By abrogating inhibitory signals, ICIs promote T cell targeting of cancer cells but can frequently trigger autoimmune manifestations, termed immune-related adverse events (irAEs), affecting essentially any organ system. Among cardiovascular irAEs, immune-related myocarditis (irMyocarditis) is the most described and carries the highest morbidity. The currently recommended treatment for irMyocarditis is potent immunosuppression with corticosteroids and other agents, but this has limited evidence basis. The cellular pathophysiology of irMyocarditis remains poorly understood, though mouse models and human data have both implicated effector CD8+ T cells, some of which are specific for the cardiomyocyte protein α-myosin. While the driving molecular signals and transcriptional programs are not well defined, the involvement of chemokine receptors such as CCR5 and CXCR3 has been proposed. Fundamental questions regarding why only approximately 1% of ICI recipients develop irMyocarditis and why irMyocarditis carries a much worse prognosis than other forms of lymphocytic myocarditis remain unanswered. Further work in both murine systems and with human samples are needed to identify better tools for diagnosis, risk-stratification, and treatment.

A review of the pleiotropic actions of the IFN-inducible CXC chemokine receptor 3 ligands in the synovial microenvironment

Chemokines are pivotal players in instigation and perpetuation of synovitis through leukocytes egress from the blood circulation into the inflamed articulation. Multitudinous literature addressing the involvement of the dual-function interferon (IFN)-inducible chemokines CXCL9, CXCL10 and CXCL11 in diseases characterized by chronic inflammatory arthritis emphasizes the need for detangling their etiopathological relevance. Through interaction with their mutual receptor CXC chemokine receptor 3 (CXCR3), the chemokines CXCL9, CXCL10 and CXCL11 exert their hallmark function of coordinating directional trafficking of CD4+ TH1 cells, CD8+ T cells, NK cells and NKT cells towards inflammatory niches. Among other (patho)physiological processes including infection, cancer, and angiostasis, IFN-inducible CXCR3 ligands have been implicated in autoinflammatory and autoimmune diseases. This review presents a comprehensive overview of the abundant presence of IFN-induced CXCR3 ligands in bodily fluids of patients with inflammatory arthritis, the outcomes of their selective depletion in rodent models, and the attempts at developing candidate drugs targeting the CXCR3 chemokine system. We further propose that the involvement of the CXCR3 binding chemokines in synovitis and joint remodeling encompasses more than solely the directional ingress of CXCR3-expressing leukocytes. The pleotropic actions of the IFN-inducible CXCR3 ligands in the synovial niche reiteratively illustrate the extensive complexity of the CXCR3 chemokine network, which is based on the intercommunion of IFN-inducible CXCR3 ligands with distinct CXCR3 isoforms, enzymes, cytokines, and infiltrated and resident cells present in the inflamed joints.

Chemokines and chemokine receptors as promising targets in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease that commonly causes inflammation and bone destruction in multiple joints. Inflammatory cytokines, such as IL-6 and TNF-α, play important roles in RA development and pathogenesis. Biological therapies targeting these cytokines have revolutionized RA therapy. However, approximately 50% of the patients are non-responders to these therapies. Therefore, there is an ongoing need to identify new therapeutic targets and therapies for patients with RA. In this review, we focus on the pathogenic roles of chemokines and their G-protein-coupled receptors (GPCRs) in RA. Inflamed tissues in RA, such as the synovium, highly express various chemokines to promote leukocyte migration, tightly controlled by chemokine ligand-receptor interactions. Because the inhibition of these signaling pathways results in inflammatory response regulation, chemokines and their receptors could be promising targets for RA therapy. The blockade of various chemokines and/or their receptors has yielded prospective results in preclinical trials using animal models of inflammatory arthritis. However, some of these strategies have failed in clinical trials. Nonetheless, some blockades showed promising results in early-phase clinical trials, suggesting that chemokine ligand-receptor interactions remain a promising therapeutic target for RA and other autoimmune diseases.

Design, Synthesis, and Pharmacological Evaluation of Benzimidazolo-thiazoles as Potent CXCR3 Antagonists with Therapeutic Potential in Autoimmune Diseases: Discovery of ACT-672125

The chemokine receptor CXCR3 allows the selective recruitment of innate and adaptive inflammatory immune cells into inflamed tissue. CXCR3 ligands are secreted after exposure to pro-inflammatory cytokines. Upon binding to CXCR3 ligands, CXCR3 expressing T-lymphocytes migrate toward sites of inflammation and can promote tissue damage. Therefore, antagonizing this receptor may provide clinical benefits for patients suffering from autoimmune diseases characterized by high concentrations of CXCR3 ligands. Herein, we report the second part of our CXCR3 discovery program where we explored the benzimidazolo-thiazole core scaffold. The optimization of potency and the mitigation of an hERG liability are described. Further pharmacokinetic considerations led to the identification of the potent CXCR3 antagonist ACT-672125 (29). The compound showed good physicochemical properties and safety profile. In a proof-of-mechanism model of lung inflammation, ACT-672125 inhibited the recruitment of CXCR3 expressing T cells into the inflamed lung in a dose-dependent manner.

Absence of TSC1 Accelerates CD8+ T cell-mediated Acute Cardiac Allograft Rejection

Tuberous sclerosis complex (TSC) is an autosomal dominant disease caused by inactivating mutations in TSC1 or TSC2.Patients with TSC often require organ transplantation after organ failure. TSC1 serves as an important control node in immune cell development and responses; however, its effect on T cells in transplant immunity has not yet been explored. Here, we characterized the effect of TSC1 deficiency in T cells on acute allograft rejection using a mouse cardiac transplantation model. We observed compromised allograft survival in mice with TSC1-deficient T cells. Notably, the allografts in mice transferred with TSC1-deficient CD8⁺T cells showed accelerated acute allograft rejection. TSC1 deficiency triggered the increased accumulation of CD8⁺ T cells in allografts due to augmented infiltration caused by increased CXCR3 expression levels and elevated in-situ proliferation of TSC1-deficient CD8⁺ T cells. Compared to CD8⁺ T cells from wild-type (WT) mice, TSC1-deficient CD8⁺ T cells exhibited enhanced cell proliferation and increased expression levels of interferon-γ and granzyme B after alloantigen stimulation. Rapamycin, an inhibitor of mammalian target of rapamycin (mTOR), is used to treat patients with TSC and prevent rejection after solid-organ transplantation. Although rapamycin induced most cardiac allografts to survive beyond 100 d in WT mice, rapamycin-treated cardiac allografts in TSC1-deficient mice were rejected within 60 d. These results suggest that TSC1-deficient recipients may be more resistant to rapamycin-mediated immunosuppression during organ transplantation. Collectively, TSC1 significantly accelerates acute allograft rejection by enhancing the alloreactivity of CD8⁺ T cells, making them more resistant to mTOR inhibitor-mediated immunosuppression.

C-X-C Motif Chemokine Ligand 9 and Its CXCR3 Receptor Are the Salt and Pepper for T Cells Trafficking in a Mouse Model of Gaucher Disease

Gaucher disease is a lysosomal storage disease, which happens due to mutations in GBA1/Gba1 that encodes the enzyme termed as lysosomal acid β-glucosidase. The major function of this enzyme is to catalyze glucosylceramide (GC) into glucose and ceramide. The deficiency of this enzyme and resultant abnormal accumulation of GC cause altered function of several of the innate and adaptive immune cells. For example, augmented infiltration of T cells contributes to the increased production of pro-inflammatory cytokines, (e.g., IFNγ, TNFα, IL6, IL12p40, IL12p70, IL23, and IL17A/F). This leads to tissue damage in a genetic mouse model (Gba1^9V/-) of Gaucher disease. The cellular mechanism(s) by which increased tissue infiltration of T cells occurs in this disease is not fully understood. Here, we delineate role of the CXCR3 receptor and its exogenous C-X-C motif chemokine ligand 9 (CXCL9) in induction of increased tissue recruitment of CD4⁺ T and CD8⁺ T cells in Gaucher disease. Intracellular FACS staining of macrophages (Mϕs) and dendritic cells (DCs) from Gba1^9V/- mice showed elevated production of CXCL9. Purified CD4⁺ T cells and the CD8⁺ T cells from Gba1^9V/- mice showed increased expression of CXCR3. Ex vivo and in vivo chemotaxis experiments showed CXCL9 involvement in the recruitment of Gba1^9V/- T cells. Furthermore, antibody blockade of the CXCL9 receptor (CXCR3) on T cells caused marked reduction in CXCL9- mediated chemotaxis of T cells in Gba1^9V/- mice. These data implicate abnormalities of the CXCL9-CXCR3 axis leading to enhanced tissue recruitment of T cells in Gaucher disease. Such results provide a rationale for blockade of the CXCL9/CXCR3 axis as potential new therapeutic targets for the treatment of inflammation in Gaucher disease.

Promising Therapeutic Targets for Treatment of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic poly-articular chronic autoimmune joint disease that mainly damages the hands and feet, which affects 0.5% to 1.0% of the population worldwide. With the sustained development of disease-modifying antirheumatic drugs (DMARDs), significant success has been achieved for preventing and relieving disease activity in RA patients. Unfortunately, some patients still show limited response to DMARDs, which puts forward new requirements for special targets and novel therapies. Understanding the pathogenetic roles of the various molecules in RA could facilitate discovery of potential therapeutic targets and approaches. In this review, both existing and emerging targets, including the proteins, small molecular metabolites, and epigenetic regulators related to RA, are discussed, with a focus on the mechanisms that result in inflammation and the development of new drugs for blocking the various modulators in RA.

Establishing Classification Tree Models in Rheumatoid Arthritis Using Combination of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry and Magnetic Beads

Background: There is no simple method for early diagnosis and evaluation of rheumatoid arthritis (RA). This study aimed to determine potential biomarkers and establish diagnostic patterns for RA using proteomic fingerprint technology combined with magnetic beads.

Methods: The serum protein profiles of 97 RA patients and 76 healthy controls (HCs) were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) with weak cationic exchange (WCX) magnetic beads. Samples were randomly divided into training (83 RA patients and 56 HCs) and test sets (14 RA patients and 20 HCs). Patients were classified according to their Disease Activity Score: in remission, n = 28; with low disease activity, n = 17; with moderate disease activity, n = 21; with high disease activity, n = 31. There are 44 RA patients alone, 22 RA patients with interstitial lung disease (RA-ILD), 18 RA patients with secondary Sjögren's syndrome (RA-sSS), 6 RA patients with osteonecrosis of the femoral head (RA-ONFH), and 7 RA patients with other complications. Eleven patients were treated with etanercept only for half a year, after which their serum protein profiles were detected. The proteomic pattern was identified by Biomarker Patterns Software, and the potential biomarkers for RA diagnosis were further identified and quantified by enzyme-linked immunosorbent assay.

Results: The diagnostic pattern with four potential protein biomarkers, mass-to-charge (m/z) 3,448.85, 4,716.71, 8,214.29, and 10,645.10, could accurately recognize RA patients from HCs (specificity, 91.57%; sensitivity, 92.86%). The test set were correctly classified by this model (sensitivity, 95%; specificity, 100%). The components containing the four biomarkers were preliminarily retrieved through the ExPasy database, including the C-C motif chemokine 24 (CCL24), putative metallothionein (MT1DP), sarcolipin (SLN), and C-X-C motif chemokine 11 (CCXL11). Only the CCL24 level was detected to have a significant decrease in the serum of RA patients as compared with HCs (p < 0.05). No significant difference was found in others, but a decreasing trend consistent with the down-regulation of the four biomarkers detected by MALDI-TOF-MS was observed. The diagnostic models could effectively discriminate between RA alone and RA with complications (RA-ILD: m/z 10,645.10 and 12,595.86; RA-sSS: m/z 6,635.62 and 33,897.72; RA-ONFH: m/z 2,071.689). The classification model, including m/z 1,130.776, 1,501.065, 2,091.198, and 11,381.87, could distinguish between RA patients with disease activity and those in remission. RA with low disease activity could be efficiently discriminated from other disease activity patients by specific protein biomarkers (m/z 2,032.31, 2,506.214, and Z9286.495). Two biomarkers (m/z 2,032.31 and 4,716.71) were applied to build the classification model for RA patients with moderate and high disease activities. Biological markers for etanercept (m/z 2,671.604064, 5,801.840579, 8,130.195641, and 9,286.49499) were observed between the responder (n = 7) and non-responder groups (n = 4) (p < 0.05).

Conclusion: We successfully established a series of diagnostic models involving RA and RA with complications as well as assessed disease activity. Furthermore, we found that CCL24 may be a valuable auxiliary diagnostic indicator for RA. These results provide reference values for clinical practice in the future.

Inhibition of the CXCL9-CXCR3 axis suppresses the progression of experimental apical periodontitis by blocking macrophage migration and activation

Apical periodontitis (AP) is an acute or chronic inflammatory disease caused by complex interactions between infected root canal and host immune system. It results in the induction of inflammatory mediators such as chemokines and cytokines leading to periapical tissue destruction. To understand the molecular pathogenesis of AP, we have investigated inflammatory-related genes that regulate AP development. We found here that macrophage-derived CXCL9, which acts through CXCR3, is recruited by progressed AP. The inhibition of CXCL9 by a CXCR3 antagonist reduced the lesion size in a mouse AP model with decreasing IL-1β, IL-6 and TNFα expression. The treatment of peritoneal macrophages with CXCL9 and LPS induced the transmigration and upregulation of osteoclastogenic cytokines such as IL-1β, IL-6 and matrix metalloprotease 2, a marker of activated macrophages. This suggests that the CXCL9-CXCR3 axis plays a crucial role in the development of AP, mediated by the migration and activation of macrophages for periapical tissue destruction. Our data thus show that CXCL9 regulates the functions of macrophages which contribute to AP pathogenesis, and that blocking CXCL9 suppresses AP progression. Knowledge of the principal factors involved in the progression of AP, and the identification of related inflammatory markers, may help to establish new therapeutic strategies.

Biased agonism at chemokine receptors

In the human chemokine system, interactions between the approximately 50 known endogenous chemokine ligands and 20 known chemokine receptors (CKRs) regulate a wide range of cellular functions and biological processes including immune cell activation and homeostasis, development, angiogenesis, and neuromodulation. CKRs are a family of G protein-coupled receptors (GPCR), which represent the most common and versatile class of receptors in the human genome and the targets of approximately one third of all Food and Drug Administration-approved drugs. Chemokines and CKRs bind with significant promiscuity, as most CKRs can be activated by multiple chemokines and most chemokines can activate multiple CKRs. While these ligand-receptor interactions were previously regarded as redundant, it is now appreciated that many chemokine:CKR interactions display biased agonism, the phenomenon in which different ligands binding to the same receptor signal through different pathways with different efficacies, leading to distinct biological effects. Notably, these biased responses can be modulated through changes in ligand, receptor, and or the specific cellular context (system). In this review, we explore the biochemical mechanisms, functional consequences, and therapeutic potential of biased agonism in the chemokine system. An enhanced understanding of biased agonism in the chemokine system may prove transformative in the understanding of the mechanisms and consequences of biased signaling across all GPCR subtypes and aid in the development of biased pharmaceuticals with increased therapeutic efficacy and safer side effect profiles.

Evaluating the Role of CXCR3 in Pain Modulation: A Literature Review

CXCR3 is a well-known receptor involved in immune cell recruitment and inflammation. Pathological inflammation leads to pain stimulation and hence nociception. Therefore, we decided to review the recent research on CXCR3 to identify its precise role in the modulation of pain in a variety of clinical conditions targeting various regions of the body. Studies were selected from PubMed Medline, which relate CXCR3 to the progression of diseases with either bone cancer pain, neuropathic pain, cystitis pain, osteoarthritis and rheumatoid arthritis pain, dental pain, in particular, periodontitis and pulpitis. In all the diseases studied, a high prevalence of CXCR3 and/or its ligand were identified where CXCR3 is a key player in the pathophysiological process of many inflammatory conditions. CXCR3 and its ligands, particularly CXCL10, modulate nociception via actions in the dorsal root ganglia and dorsal horn of the spinal cord, in cases of bone cancer pain, neuropathic, and joint pain. However, with the other studied disease, no direct link to pain has been made, although it contributes to the pathological progression of the diseases and hence would be a causal factor for the pain. Furthermore, CXCR3 appears to play a role in desensitizing the opioid receptor in the descending modulatory pathway within the brain stem as well as modulating opioid-induced hyperalgesia in the dorsal horn of the spinal cord. Further research is required for understanding the exact mechanisms of CXCR3 in pain modulation centrally and peripherally. A greater understanding of the immunological activities and pharmacological consequence of CXCR3 and its ligands could help in the discovery of newer drugs for modulating pain arising from pathogenic or inflammatory sources. Given the significance of the CXCR3 for nociception, its utilization may prove to be beneficial as a target for analgesia.

In Vitro Immunological Effects of CXCR3 Inhibitor AMG487 on Dendritic Cells

AMG 487 is the targeted blocker of chemokine receptor CXCR3 and improves inflammatory symptoms by blocking the inflammatory cycle. Here we investigated whether AMG 487 affects dendritic cell (DC) biology and function. The expression of co-stimulatory markers on DCs was reduced, indicating the semi-mature state of DC when AMG 487 was added throughout the in vitro differentiation period. Additionally, when added solely during the final lipopolysaccharide-induced activation step, AMG 487 inhibited DC activation, as demonstrated by a decreased expression of activation markers. AMG487 also promoted the expression of PD-L2 and impaired the ability to induce antigen-specific T cell responses. Our results demonstrated that AMG 487 significantly affects DC maturity in vitro and function leading to impaired T cell activation, inducing DCs to have characteristics similar to tolerogenic DCs. AMG 487 may directly play an immunomodulatory role during DC development and functional shaping.

Effective Treatments for Bladder Cancer Affecting CXCL9/CXCL10/CXCL11/CXCR3 Axis: A Review

Bladder cancer (BC) originates mainly from the epithelial compartment of the bladder, which is defined as transitional cell carcinoma or urothelial cell carcinoma. About 70% of patients with BC will survive five years from diagnosis. Previous studies revealed that the immune system and its mediators, particularly chemokines, play a crucial role in modulating responses against BC. Chemokines, which serve as chemoattractants for leukocytes, are small proteins that can initiate inflammatory and anti-inflammatory immune responses and also are associated with many aspects of both regulation and progression of mentioned responses. Additionally, these immune mediators can interfere with the other tumor-related processes, including tumor proliferation, neovascularization, and metastases. Among these chemokines, CXC chemokines, including CXCL9, CXCL10, and CXCL11, are recognized as the main ligands of C-X-C motif chemokine receptor 3 (CXCR3) and contribute to related immune responses after therapeutic strategies for BC. Evidence suggests that the production of these chemokines can have two important implications. First, these mediators can trigger the accumulation of CD8+ T cells that can contribute to the elimination of the tumor. Secondly, the production of these chemokines by tumor tissue may trigger the migration and activation of immune cells including myeloid-derived suppressor cells and regulatory T cells, which act in favor of the tumor and its progress. Therefore, in this review, we describe the latest therapeutic approaches based on targeting this axis's components and subsequent immune phenomenon.

Role of Chemokines and Chemokine Receptors in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is one of the most prevalent autoimmune diseases and a prototypic inflammatory disease, affecting the small joints of the hands and feet. Chemokines and chemokine receptors play a critical role in RA pathogenesis via immune cells recruitment. Several chemokines and chemokine receptors are abundant in the peripheral blood and in the local inflamed joints of RA. Furthermore, synthetic and biologics disease modifying anti rheumatic drugs have been reported to affect chemokines expression. Thus, many studies have focused on targeting chemokines and chemokine receptors, where some have shown positive promising results. However, most of the chemokine blockers in human trials of RA treatment displayed some failures that can be attributed to several reasons in their structures and binding affinities. Nevertheless, targeting chemokines will continue to be under development, in order to improve their therapeutic potentials in RA and other autoimmune diseases. In this review we provide an up-to-date knowledge regarding the role of chemokines and chemokine receptors in RA with an emphasis on their activities on immune cells. We also discussed the effects of drugs targeting those molecules in RA. This knowledge might provide impetus for developing new therapeutic modalities to treat this chronic disease.

The CC and CXC chemokines: major regulators of tumor progression and the tumor microenvironment

Chemokines are a family of soluble cytokines that act as chemoattractants to guide the migration of cells, in particular of immune cells. However, chemokines are also involved in cell proliferation, differentiation, and survival. Chemokines are associated with a variety of human diseases including chronic inflammation, immune dysfunction, cancer, and metastasis. This review discusses the expression of CC and CXC chemokines in the tumor microenvironment and their supportive and inhibitory roles in tumor progression, angiogenesis, metastasis, and tumor immunity. We also specially focus on the diverse roles of CXC chemokines (CXCL9-11, CXCL4 and its variant CXCL4L1) and their two chemokine receptor CXCR3 isoforms, CXCR3-A and CXCR3-B. These two distinct isoforms have divergent roles in tumors, either promoting (CXCR3-A) or inhibiting (CXCR3-B) tumor progression. Their effects are mediated not only directly in tumor cells but also indirectly via the regulation of angiogenesis and tumor immunity. A full comprehension of their mechanisms of action is critical to further validate these chemokines and their receptors as biomarkers or therapeutic targets in cancer.

CXCR3 antagonist AMG487 suppresses rheumatoid arthritis pathogenesis and progression by shifting the Th17/Treg cell balance

Rheumatoid arthritis (RA) is an autoimmune disease that is characterized by uncontrolled joint inflammation and damage to bone and cartilage. Previous studies have shown that chemokine receptors have important roles in RA development, and that blocking these receptors effectively inhibits RA progression. Our study was undertaken to investigate the role of AMG487, a selective CXCR3 antagonist, in DBA/1J mice bearing collagen-induced arthritis (CIA). Following induction of CIA, animals were treated with 5 mg/kg AMG487 intraperitoneally every 48 h, starting from day 21 until day 41 and evaluated for clinical score, and histological hallmarks of arthritic inflammation. We further investigated the effect of AMG487 on Th1 (T-bet), Th17 (IL-17A, RORγt, STAT3), Th22 (IL-22), and T regulatory (Treg; Foxp3 and IL-10) cells in splenic CXCR3⁺ and CD4⁺ T cells using flow cytometry. We also assessed the effect of AMG487 on T-bet, RORγt, IL-17A, IL-22, Foxp3, and IL-10 at both mRNA and protein levels using RT-PCR and Western blot analyses of knee samples. The severity of clinical scores, and histological inflammatory damage decreased significantly in AMG487-treated compared with CIA control mice. Moreover, the percentage of Th1, Th17, and Th22 cells decreased significantly and that of Treg cells increased in AMG487-treated mice. We further observed that AMG487-treatment downregulated T-bet, IL-17A, RORγt, and IL-22, whereas it upregulated Foxp3 and IL-10 mRNA and protein levels. This study demonstrates the antiarthritic effects of AMG487 in CIA animal model and supports the development of CXCR3 antagonists as a novel strategy for the treatment of inflammatory and arthritic conditions.

CXCR3 regulates CD4+ T cell cardiotropism in pressure overload-induced cardiac dysfunction

Heart failure (HF) is associated in humans and mice with increased circulating levels of CXCL9 and CXCL10, chemokine ligands of the CXCR3 receptor, predominantly expressed on CD4+ Th1 cells. Chemokine engagement of receptors is required for T cell integrin activation and recruitment to sites of inflammation. Th1 cells drive adverse cardiac remodeling in pressure overload-induced cardiac dysfunction, and mice lacking the integrin ligand ICAM-1 show defective T cell recruitment to the heart. Here, we show that CXCR3+ T cells infiltrate the heart in humans and mice with pressure overload-induced cardiac dysfunction. Genetic deletion of CXCR3 disrupts CD4+ T cell heart infiltration and prevents adverse cardiac remodeling. We demonstrate that cardiac fibroblasts and cardiac myeloid cells that include resident and infiltrated macrophages are the source of CXCL9 and CXCL10, which mechanistically promote Th1 cell adhesion to ICAM-1 under shear conditions in a CXCR3-dependent manner. To our knowledge, our findings identify a previously unrecognized role for CXCR3 in Th1 cell recruitment into the heart in pressure overload-induced cardiac dysfunction.

Protective effects of CXCR3/HO‑1 gene‑modified BMMSCs on damaged intestinal epithelial cells: Role of the p38‑MAPK signaling pathway

The purpose of the present study was to investigate whether bone marrow mesenchymal stem cells (BMMSCs) modified by CXC-chemokine receptor type 3 (CXCR3) and heme oxygenase-1 (HO-1) genes can repair damaged intestinal epithelial cells in vitro, and the role of the p38 mitogen-activated protein kinase (p38-MAPK) pathway in this process. A model of intestinal epithelial crypt cell line-6 (IEC-6) damage was created, and BMMSCs were transfected with either the CXCR3 and/or HO-1 gene in vitro. There were nine experimental groups in which the damaged IEC-6 cells were co-cultured with differentially-treated BMMSCs and lymphocytes for 24 h. Reverse transcription-quantitative polymerase chain reaction analysis, immunohistochemistry and a western blot analysis were performed to detect stem cell transfection, the repair of damaged intestinal epithelial cells and the expression of related molecules in the P38-MAPK pathway, respectively. Crystal violet staining and live cell imaging were used to detect the chemotaxis of BMMSCs. Flow cytometry was used to detect T lymphocyte activity and the surface markers expressed on BMMSCs. An ELISA was used to quantify cytokine production. The adenovirus (Ad)-CXCR3/MSCs exhibited the characteristics of stem cells and exhibited chemotaxis. The Ad-CXCR3/MSCs and Ad-(CXCR3 + HO)/MSCs exhibited increased expression of tight junction protein zonula occludens-1 (ZO-1) and anti-proliferating cell nuclear antigen in the damaged IEC-6 cells, and apoptosis of the damaged IEC-6 cells was decreased. BMMSCs inhibited the phosphorylation of p38, in addition to downstream molecules of the p38MAPK signaling pathway. The Ad-CXCR3/MSCs and Ad-(CXCR3 + HO)/MSCs exhibited significantly decreased expression levels of downstream molecules, including phosphorylated (p)-p38, p-activated transcription factor 2, p-C/EBP homologous protein-10, and p-myocyte enhancer factor 2C, and target molecules (e.g., apoptotic bodies). The effects of Ad-(CXCR3 + HO)/MSCs on the repair of the damaged intestinal tract and inhibition of the p38-MAPK pathway was more marked than those in other groups on day 7 post-surgery in the rejection model for small bowel transplantation. BMMSCs modified by the CXCR3 and HO-1 genes exhibited superior ability to repair damaged intestinal epithelial cells and served this role via the p38-MAPK pathway.

Upregulation of chemokine CXCL10 enhances chronic pulmonary inflammation in tree shrew collagen-induced arthritis

Chronic pulmonary inflammation (CPI) gives rise to serious lung injuries in rheumatoid arthritis (RA) patients. However, the molecular mechanism underlying the pathogenesis of RA-associated CPI remains little understood. Here we established a novel tree shrew-based collagen-induced arthritis (TsCIA) model to study RA-associated CPI. Our results showed that typical CPI but not fibrosis developed pathologically in the TsCIA model. Furthermore, abnormal up-regulation of pulmonary chemokine CXCL10 was directly associated with lung damage. Specific blockage of CXCR3 (a CXCL10 receptor) significantly decreased the severity of CPI by decreasing the recruitment of inflammatory cells. Therefore, CXCL10 is proposed as a key player responsible for the development of TsCIA-associated CPI. Our findings also suggest that CXCR3 could be developed as a potential diagnosis biomarker for RA-associated CPI.

Regulatory T cells control endothelial chemokine production and migration of T cells into intestinal tumors of APCmin/+ mice

Tumor-infiltrating lymphocytes are crucial for anti-tumor immunity. We have previously shown that regulatory T cells (Treg) are able to reduce T-cell transendothelial migration in vitro and accumulation of effector T cells in intestinal tumors in vivo. Treg depletion also resulted in increased levels of the chemokines CXCL9 and CXCL10 specifically in the tumors. In this study, we investigated the mechanisms for Treg mediated suppression of T-cell migration into intestinal tumors in the APCmin/+ mouse model. By breeding APCmin/+ mice with DEREG mice, which harbour a high affinity diphtheria toxin receptor under the control of the FOXP3 promoter, we were able to deplete Treg in tumor-bearing mice. Using adoptive transfer experiments, we could document a markedly increased migration of T cells specifically into Treg depleted tumors, and that Treg depletion results in increased production of the CXCR3 ligand CXCL10 from endothelial cells in the tumors. Furthermore, we were able to demonstrate that T cells use CXCR3 to migrate into intestinal tumors. In addition, human colon adenocarcinomas express high levels of mRNA CXCR3 ligands and tumor endothelial cells produce CXCL9 and CXCL10 ex vivo. In conclusion, this study demonstrates that Treg reduce endothelial CXCL10 production, inhibit T-cell migration into tumors and that CXCR3 mediated signalling is crucial for lymphocyte accumulation in intestinal tumors. Thus, immunotherapy aimed at Treg depletion may be effective by increasing not only T effector cell activity, but also their accumulation in tumors.

CXCR3 blockade combined with cyclosporine A alleviates acute graft-versus-host disease by inhibiting alloreactive donor T cell responses in a murine model

Chemotaxis of T cells to acute graft-versus-host disease (aGvHD) target tissues directed by chemokines and their receptors plays a key role in the pathogenesis of aGvHD. Blockade of lymphocyte migration by targeting chemokine receptors may be a viable strategy for the prevention and treatment of aGvHD, which is quite distinguishable from typical efforts to use immunosuppressive medications that have been associated with some side effects. CXCR3 and its ligands have been reported to be correlated with aGvHD pathogenesis. Using the small-molecule CXCR3 antagonist AMG487, we demonstrated that AMG487 combined with cyclosporine A (CsA) effectively alleviated aGvHD with a prolonged mean survival time and significantly inhibited the infiltration of inflammatory cells in aGvHD target tissues in a murine aGvHD model. In addition, AMG487 combined with CsA inhibited the activation, proliferation and differentiation of donor-derived T cells in the spleens. Further results showed that the concentrations of Th1 cells associated with pro-inflammatory cytokines such as IFN-γ and TNFα in serum were decreased. In addition, AMG487 treatment did not alter CXCR3 and CCR5 expression in donor-derived T cells but elevated the serum CXCL9 and CXCL10 levels. This novel and effective approach has the potential to develop a new clinical method to prevent and treat aGvHD.

C19, a C-terminal peptide of CKLF1, decreases inflammation and proliferation of dermal capillaries in psoriasis

Psoriasis is a chronic inflammatory autoimmune disease with undefined etiology. Chemokine-like factor 1 (CKLF1), a human cytokine that is a functional ligand for CCR4, displays chemotactic activities in a wide spectrum of leukocytes and plays an important role in psoriasis development. In previous study, our laboratory found that the expression of CKLF1 increased in psoriatic lesions. C19 as a CKLF1's C-terminal peptide has been reported to exert inhibitory effects on a variety of diseases. However, the protective roles of C19 in endothelial cells proliferation and inflammatory cells chemotaxis remain elusive in psoriasis. In this study we examined the protective effect of C19 on both the cellular model and the animal model. The effects of C19 on endothelial cells proliferation and inflammatory cells chemotaxis were investigated in cultured human umbilical vein endothelial cells (HUVECs) and imiquimod-induced psoriasiform inflammation of BALB/c mice based on techniques including immunohistochemical analysis, quantitative real-time PCR (qRT-PCR), western blot, transwell, and EdU assay. This study shows that CKLF1-C19 significantly protects against psoriasis by inhibiting the infiltration of inflammatory cells and proliferation of microvascular cells, possibly via inhibiting MAPK pathways.

Ligand activation induces different conformational changes in CXCR3 receptor isoforms as evidenced by plasmon waveguide resonance (PWR)

The chemokine receptor CXCR3 plays important roles in angiogenesis, inflammation and cancer. Activation studies and biological functions of CXCR3 are complex due to the presence of spliced isoforms. CXCR3-A is known as a pro-tumor receptor whereas CXCR3-B exhibits anti-tumor properties. Here, we focused on the conformational change of CXCR3-A and CXCR3-B after agonist or antagonist binding using Plasmon Waveguide Resonance (PWR). Agonist stimulation induced an anisotropic response with very distinct conformational changes for the two isoforms. The CXCR3 agonist bound CXCR3-A with higher affinity than CXCR3-B. Using various concentrations of SCH546738, a CXCR3 specific inhibitor, we demonstrated that low SCH546738 concentrations (≤1 nM) efficiently inhibited CXCR3-A but not CXCR3-B’s conformational change and activation. This was confirmed by both, biophysical and biological methods. Taken together, our study demonstrates differences in the behavior of CXCR3-A and CXCR3-B upon ligand activation and antagonist inhibition which may be of relevance for further studies aimed at specifically inhibiting the CXCR3A isoform.

A fully humanized IgG-like bispecific antibody for effective dual targeting of CXCR3 and CCR6

Chemokines and their receptors are pivotal for the trafficking of leukocytes during immune responses, and host defense. However, immune cell migration also contributes to a wide variety of autoimmune and chronic inflammatory diseases. Compelling evidence suggests that both CXCR3 and CCR6 chemokine receptors play crucial roles in the migration of pathological Th1 and Th17 cells during the course of certain inflammatory diseases. The use of two or more receptors by pathogenic cells may explain why targeting of individual receptors has proven disappointing in the clinic. We therefore hypothesized that simultaneous targeting of both CXCR3 and CCR6 with a bispecific antibody (BsAb) might result in decreased chemotaxis and/or specific depletion of pro-inflammatory T cell subsets. In this study, we designed and characterized a fully humanized BsAb. We show that the BsAb binds to both chemokine receptors, as demonstrated by Flow Cytometry and Surface Plasmon Resonance analysis. Furthermore, we demonstrate that the BsAb effectively blocks cell chemotaxis and induces specific antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro. Therefore, we propose that dual targeting of CXCR3 and CCR6 with a fully humanized BsAb may display a potent interventional approach for the treatment of inflammatory and autoimmune diseases.

Protein Tyrosine Phosphatase Inhibition Prevents Experimental Cerebral Malaria by Precluding CXCR3 Expression on T Cells

Cerebral malaria induced by Plasmodium berghei ANKA infection is dependent on the sequestration of cytotoxic T cells within the brain and augmentation of the inflammatory response. Herein, we demonstrate that inhibition of protein tyrosine phosphatase (PTP) activity significantly attenuates T cell sequestration within the brain and prevents the development of neuropathology. Mechanistically, the initial upregulation of CXCR3 on splenic T cells upon T cell receptor stimulation was critically decreased through the reduction of T cell-intrinsic PTP activity. Furthermore, PTP inhibition markedly increased IL-10 production by splenic CD4⁺ T cells by enhancing the frequency of LAG3⁺CD49b⁺ type 1 regulatory cells. Overall, these findings demonstrate that modulation of PTP activity could possibly be utilized in the treatment of cerebral malaria and other CXCR3-mediated diseases.

Pancreatic islet inflammation: an emerging role for chemokines

Both type 1 and type 2 diabetes exhibit features of inflammation associated with alterations in pancreatic islet function and mass. These immunological disruptions, if unresolved, contribute to the overall pathogenesis of disease onset. This review presents the emerging role of pancreatic islet chemokine production as a critical factor regulating immune cell entry into pancreatic tissue as well as an important facilitator of changes in tissue resident leukocyte activity. Signaling through two specific chemokine receptors (i.e., CXCR2 and CXCR3) is presented to illustrate key points regarding ligand-mediated regulation of innate and adaptive immune cell responses. The prospective roles of chemokine ligands and their corresponding chemokine receptors to influence the onset and progression of autoimmune- and obesity-associated forms of diabetes are discussed.

Killer cells in atherosclerosis

Cytotoxic lymphocytes (killer cells) play a critical role in host defence mechanisms, protecting against infections and in tumour surveillance. They can also exert detrimental effects in chronic inflammatory disorders and in autoimmune diseases. Tissue cell death and necrosis are prominent features of advanced atherosclerotic lesions including vulnerable/unstable lesions which are largely responsible for most heart attacks and strokes. Evidence for accumulation of killer cells in both human and mouse lesions together with their cytotoxic potential strongly suggest that these cells contribute to cell death and necrosis in lesions leading to vulnerable plaque development and potentially plaque rupture. Killer cells can be divided into two groups, adaptive and innate immune cells depending on whether they require antigen presentation for activation. Activated killer cells detect damaged or stressed cells and kill by cytotoxic mechanisms that include perforin, granzymes, TRAIL or FasL and in some cases TNF-α. In this review, we examine current knowledge on killer cells in atherosclerosis, including CD8 T cells, CD28- CD4 T cells, natural killer cells and γδ-T cells, mechanisms responsible for their activation, their migration to developing lesions and effector functions. We also discuss pharmacological strategies to prevent their deleterious vascular effects by preventing/limiting their cytotoxic effects within atherosclerotic lesions as well as potential immunomodulatory therapies that might better target lesion-resident killer cells, to minimise any compromise of the immune system, which could result in increased susceptibility to infections and reductions in tumour surveillance.

NF-κB signaling regulates cell-autonomous regulation of CXCL10 in breast cancer 4T1 cells

The chemokine CXCL10 and its receptor CXCR3 play a role in breast cancer metastasis to bone and osteoclast activation. However, the mechanism of CXCL10/CXCR3-induced intracellular signaling has not been fully investigated. To evaluate CXCL10-induced cellular events in the mouse breast cancer cell line 4T1, we developed a new synthetic CXCR3 antagonist JN-2. In this study, we observed that secretion of CXCL10 in the supernatant of 4T1 cells was gradually increased during cell growth. JN-2 inhibited basal and CXCL10-induced CXCL10 expression and cell motility in 4T1 cells. Treatment of 4T1 cells with CXCL10 increased the expression of P65, a subunit of the NF-κB pathway, via activation of the NF-κB transcriptional activity. Ectopic overexpression of P65 increased CXCL10 secretion and blunted JN-2-induced suppression of CXCL10 secretion, whereas overexpression of IκBα suppressed CXCL10 secretion. These results indicate that the CXCL10/CXCR3 axis creates a positive feedback loop through the canonical NF-κB signaling pathway in 4T1 cells. In addition, treatment of osteoblasts with conditioned medium from JN-2-treated 4T1 cells inhibited the expression of RANKL, a crucial cytokine for osteoclast differentiation, which resulted in an inhibitory effect on osteoclast differentiation in the co-culture system of bone marrow-derived macrophages and osteoblasts. Direct intrafemoral injection of 4T1 cells induced severe bone destruction; however, this effect was suppressed by the CXCR3 antagonist via downregulation of P65 expression in an animal model. Collectively, these results suggest that the CXCL10/CXCR3-mediated NF-κB signaling pathway plays a role in the control of autonomous regulation of CXCL10 and malignant tumor properties in breast cancer 4T1 cells.

Designing small molecule CXCR3 antagonists

INTRODUCTION

By virtue of its specificity for chemokines induced in Th1-associated pathologies, CXCR3 has attracted considerable attention as a target for therapeutic intervention. Several pharmacologically distinct small molecules with in vitro and in vivo potency have been described in the literature, although to date, none have shown efficacy in clinical trials. Areas covered: In this article, the author outlines the rationale for targeting CXCR3 and discusses the potential pitfalls in targeting receptors in poorly understood areas of chemokine biology. Furthermore, they cover emerging therapeutic areas outside of the 'traditional' Th1 arena in which CXCR3 antagonists may ultimately bear fruit. Finally, they discuss the design of recently discovered small molecules targeting CXCR3. Expert opinion: CXCR3 and its ligands appear to play roles in a multitude of diverse diseases in humans. In vitro studies suggest that CXCR3 is inherently 'druggable' and that potent, efficacious small molecules targeting CXCR3 antagonists will find a clinical niche. However, the well-trodden path to failure of small molecule chemokine receptor antagonists in clinical trials suggests that a cautious approach should be undertaken. Ideally, unequivocal evidence elucidating the precise role of CXCR3 should be obtained before targeting the receptor in a particular disease cohort.

Activation of STING-Dependent Innate Immune Signaling By S-Phase-Specific DNA Damage in Breast Cancer

Background

Previously we identified a DNA damage response-deficient (DDRD) molecular subtype within breast cancer. A 44-gene assay identifying this subtype was validated as predicting benefit from DNA-damaging chemotherapy. This subtype was defined by interferon signaling. In this study, we address the mechanism of this immune response and its possible clinical significance.

Methods

We used immunohistochemistry (IHC) to characterize immune infiltration in 184 breast cancer samples, of which 65 were within the DDRD subtype. Isogenic cell lines, which represent DDRD-positive and -negative, were used to study the effects of chemokine release on peripheral blood mononuclear cell (PBMC) migration and the mechanism of immune signaling activation. Finally, we studied the association between the DDRD subtype and expression of the immune-checkpoint protein PD-L1 as detected by IHC. All statistical tests were two-sided.

Results

We found that DDRD breast tumors were associated with CD4+ and CD8+ lymphocytic infiltration (Fisher's exact test P < .001) and that DDRD cells expressed the chemokines CXCL10 and CCL5 3.5- to 11.9-fold more than DNA damage response-proficient cells (P < .01). Conditioned medium from DDRD cells statistically significantly attracted PBMCs when compared with medium from DNA damage response-proficient cells (P < .05), and this was dependent on CXCL10 and CCL5. DDRD cells demonstrated increased cytosolic DNA and constitutive activation of the viral response cGAS/STING/TBK1/IRF3 pathway. Importantly, this pathway was activated in a cell cycle-specific manner. Finally, we demonstrated that S-phase DNA damage activated expression of PD-L1 in a STING-dependent manner.

Conclusions

We propose a novel mechanism of immune infiltration in DDRD tumors, independent of neoantigen production. Activation of this pathway and associated PD-L1 expression may explain the paradoxical lack of T-cell-mediated cytotoxicity observed in DDRD tumors. We provide a rationale for exploration of DDRD in the stratification of patients for immune checkpoint-based therapies.

Pediatric Kawasaki Disease and Adult Human Immunodeficiency Virus Kawasaki-Like Syndrome Are Likely the Same Malady

Background.  Pediatric Kawasaki disease (KD) and human immunodeficiency virus (HIV)⁺ adult Kawasaki-like syndrome (KLS) are dramatic vasculitides with similar physical findings. Both syndromes include unusual arterial histopathology with immunoglobulin (Ig)A⁺ plasma cells, and both impressively respond to pooled Ig therapy. Their distinctive presentations, histopathology, and therapeutic response suggest a common etiology. Because blood is in immediate contact with inflamed arteries, we investigated whether KD and KLS share an inflammatory signature in serum. Methods.  A custom multiplex enzyme-linked immunosorbent assay (ELISA) defined the serum cytokine milieu in 2 adults with KLS during acute and convalescent phases, with asymptomatic HIV⁺ subjects not taking antiretroviral therapy serving as controls. We then prospectively collected serum and plasma samples from children hospitalized with KD, unrelated febrile illnesses, and noninfectious conditions, analyzing them with a custom multiplex ELISA based on the KLS data. Results.  Patients with KLS and KD subjects shared an inflammatory signature including acute-phase reactants reflecting tumor necrosis factor (TNF)-α biologic activity (soluble TNF receptor I/II) and endothelial/smooth muscle chemokines Ccl1 (Th2), Ccl2 (vascular inflammation), and Cxcl11 (plasma cell recruitment). Ccl1 was specifically elevated in KD versus febrile controls, suggesting a unique relationship between Ccl1 and KD/KLS pathogenesis. Conclusions.  This study defines a KD/KLS inflammatory signature mirroring a dysfunctional response likely to a common etiologic agent. The KD/KLS inflammatory signature based on elevated acute-phase reactants and specific endothelial/smooth muscle chemokines was able to identify KD subjects versus febrile controls, and it may serve as a practicable diagnostic test for KD.

CXCR3 Blockade Inhibits T Cell Migration into the Skin and Prevents Development of Alopecia Areata

Alopecia areata (AA) is an autoimmune disease of the hair follicle that results in hair loss of varying severity. Recently, we showed that IFN-γ-producing NKG2D(+)CD8(+) T cells actively infiltrate the hair follicle and are responsible for its destruction in C3H/HeJ AA mice. Our transcriptional profiling of human and mouse alopecic skin showed that the IFN pathway is the dominant signaling pathway involved in AA. We showed that IFN-inducible chemokines (CXCL9/10/11) are markedly upregulated in the skin of AA lesions, and further, that the IFN-inducible chemokine receptor, CXCR3, is upregulated on alopecic effector T cells. To demonstrate whether CXCL9/10/11 chemokines were required for development of AA, we treated mice with blocking Abs to CXCR3, which prevented the development of AA in the graft model, inhibiting the accumulation of NKG2D(+)CD8(+) T cells in the skin and cutaneous lymph nodes. These data demonstrate proof of concept that interfering with the Tc1 response in AA via blockade of IFN-inducible chemokines can prevent the onset of AA. CXCR3 blockade could be approached clinically in human AA with either biologic or small-molecule inhibition, the latter being particularly intriguing as a topical therapeutic.

Elevated CXC chemokines in urine noninvasively discriminate OAB from UTI

Overlapping symptoms of overactive bladder (OAB) and urinary tract infection (UTI) often complicate the diagnosis and contribute to overprescription of antibiotics. Inflammatory response is a shared characteristic of both UTI and OAB and here we hypothesized that molecular differences in inflammatory response seen in urine can help discriminate OAB from UTI. Subjects in the age range of (20-88 yr) of either sex were recruited for this urine analysis study. Urine specimens were available from 62 UTI patients with positive dipstick test before antibiotic treatment. Six of these patients also provided urine after completion of antibiotic treatment. Subjects in cohorts of OAB (n = 59) and asymptomatic controls (n = 26) were negative for dipstick test. Urinary chemokines were measured by MILLIPLEX MAP Human Cytokine/Chemokine Immunoassay and their association with UTI and OAB was determined by univariate and multivariate statistics. Significant elevation of CXCL-1, CXCL-8 (IL-8), and CXCL-10 together with reduced levels for a receptor antagonist of IL-1A (sIL-1RA) were seen in UTI relative to OAB and asymptomatic controls. Elevated CXCL-1 urine levels predicted UTI with odds ratio of 1.018 and showed a specificity of 80.77% and sensitivity of 59.68%. Postantibiotic treatment, reduction was seen in all CXC chemokines with a significant reduction for CXCL-10. Strong association of CXCL-1 and CXCL-10 for UTI over OAB indicates mechanistic differences in signaling pathways driving inflammation secondary of infection in UTI compared with a lack of infection in OAB. Urinary chemokines highlight molecular differences in the paracrine signaling driving the overlapping symptoms of UTI and OAB.

Chemokine release from human rhinovirus-infected airway epithelial cells promotes fibroblast migration

BACKGROUND

Thickening of the lamina reticularis, a feature of remodeling in the asthmatic airways, is now known to be present in young children who wheeze. Human rhinovirus (HRV) infection is a common trigger for childhood wheezing, which is a risk factor for subsequent asthma development. We hypothesized that HRV-infected epithelial cells release chemoattractants to recruit fibroblasts that could potentially contribute to thickening of the lamina reticularis.

OBJECTIVE

We sought to investigate whether conditioned medium from HRV-infected epithelial cells can trigger directed migration of fibroblasts.

METHODS

Human bronchial epithelial cells were exposed to medium alone or infected with HRV-16. Conditioned medium from both conditions were tested as chemoattractants for human bronchial fibroblasts in the xCELLigence cell migration apparatus.

RESULTS

HRV-conditioned medium was chemotactic for fibroblasts. Treatment of fibroblasts with pertussis toxin, an inhibitor of Gαi-coupled receptors, prevented their migration. Production of epithelial chemoattractants required HRV replication. Multiplex analysis of epithelial supernatants identified CXCL10, CXCL8, and CCL5 as Gαi-coupled receptor agonists of potential interest. Subsequent analysis confirmed that fibroblasts express CXCR3 and CXCR1 receptors and that CXCL10 and, to a lesser extent, CXCL8, but not CCL5, are major contributors to fibroblast migration caused by HRV-conditioned medium.

CONCLUSION

CXCL10 and CXCL8 produced from HRV-infected epithelial cells are chemotactic for fibroblasts. This raises the possibility that repeated HRV infections in childhood could contribute to the initiation and progression of airway remodeling in asthmatic patients by recruiting fibroblasts that produce matrix proteins and thicken the lamina reticularis.

CXC chemokine receptor 3 promotes steatohepatitis in mice through mediating inflammatory cytokines, macrophages and autophagy

BACKGROUND & AIMS

CXC chemokine receptor 3 (CXCR3) is involved in virus-related chronic liver inflammation. However, the role of CXCR3 in non-alcoholic steatohepatitis (NASH) remains unclear. We aimed to investigate the role of CXCR3 in NASH.

METHODS

Human liver tissues were obtained from 24 non-alcoholic fatty liver disease (NAFLD) patients and 20 control subjects. CXCR3 knockout (CXCR3(-/-)), obese db/db mice and their wild-type (WT) littermates were used in both methionine-and-choline-deficient (MCD) diet and high-fat high-carbohydrate high-cholesterol (HFHC) diet-induced NASH models. In addition, MCD-fed WT mice were administrated with CXCR3 specific antagonists.

RESULTS

CXCR3 was significantly upregulated in liver tissues of patients with NAFLD and in dietary-induced NASH animal models. Compared with WT littermates, CXCR3(-/-) mice were more resistant to both MCD and HFHC diet-induced steatohepatitis. Induction of CXCR3 in dietary-induced steatohepatitis was associated with the increased expression of hepatic pro-inflammatory cytokines, activation of NF-κB, macrophage infiltration and T lymphocytes accumulation (Th1 and Th17 immune response). CXCR3 was also linked to steatosis through inducing hepatic lipogenic genes. Moreover, CXCR3 is associated with autophagosome-lysosome impairment and endoplasmic reticulum (ER) stress in steatohepatitis as evidenced by LC3-II and p62/SQSTM1 accumulation and the induction of GRP78, phospho-PERK and phospho-eIF2α. Inhibition of CXCR3 using CXCR3 antagonist significantly suppressed MCD-induced steatosis and hepatocytes injury in AML-12 hepatocytes. Blockade of CXCR3 using CXCR3 antagonists in mice reversed the established steatohepatitis.

CONCLUSIONS

CXCR3 plays a pivotal role in NASH development by inducing production of cytokines, macrophage infiltration, fatty acid synthesis and causing autophagy deficiency and ER stress.

Successes and failures of chemokine-pathway targeting in rheumatoid arthritis

Chemokines and chemokine receptors are involved in leukocyte recruitment and angiogenesis underlying the pathogenesis of rheumatoid arthritis (RA) and other inflammatory rheumatic diseases. Numerous chemokines, along with both conventional and atypical cell-surface chemokine receptors, are found in inflamed synovia. Preclinical studies carried out in animal models of arthritis involving agents targeting chemokines and chemokine receptors have yielded promising results. However, most human trials of treatment of RA with antibodies and synthetic compounds targeting chemokine signalling have failed to show clinical improvements. Chemokines can have overlapping actions, and their activities can be altered by chemical modification or proteolytic degradation. Effective targeting of chemokine pathways must take acount of these properties, and can also require high levels of receptor occupancy by therapeutic agents to prevent signalling. CCR1 is a promising target for chemokine-receptor blockade.

CXCL10/CXCR3 signaling mediates inhibitory action by interferon-gamma on CRF-stimulated adrenocorticotropic hormone (ACTH) release

Secretion of hormones by the anterior pituitary gland can be stimulated or inhibited by paracrine factors that are produced during inflammatory reactions. The inflammation cytokine interferon-gamma (IFN-γ) is known to inhibit corticotropin-releasing factor (CRF)-stimulated adrenocorticotropin (ACTH) release but its signaling mechanism is not yet known. Using rat anterior pituitary, we previously demonstrated that the CXC chemokine ligand 10 (CXCL10), known as interferon-γ (IFN-γ) inducible protein 10 kDa, is expressed in dendritic cell-like S100β protein-positive (DC-like S100β-positive) cells and that its receptor CXCR3 is expressed in ACTH-producing cells. DC-like S100β-positive cells are a subpopulation of folliculo-stellate cells in the anterior pituitary. In the present study, we examine whether CXCL10/CXCR3 signaling between DC-like S100β-positive cells and ACTH-producing cells mediates inhibition of CRF-activated ACTH-release by IFN-γ, using a CXCR3 antagonist in the primary pituitary cell culture. We found that IFN-γ up-regulated Cxcl10 expression via JAK/STAT signaling and proopiomelanocortin (Pomc) expression, while we reconfirmed that IFN-γ inhibits CRF-stimulated ACTH-release. Next, we used a CXCR3 agonist in primary culture to analyze whether CXCL10 induces Pomc-expression and ACTH-release using a CXCR3 agonist in the primary culture. The CXCR3 agonist significantly stimulated Pomc-expression and inhibited CRF-induced ACTH-release, while ACTH-release in the absence of CRF did not change. Thus, the present study leads us to an assumption that CXCL10/CXCR3 signaling mediates inhibition of the CRF-stimulated ACTH-release by IFN-γ. Our findings bring us to an assumption that CXCL10 from DC-like S100β-positive cells acts as a local modulator of ACTH-release during inflammation.

Small Molecule CXCR3 Antagonists

Chemokines and their receptors are known to play important roles in disease. More than 40 chemokine ligands and 20 chemokine receptors have been identified, but, to date, only two small molecule chemokine receptor antagonists have been approved by the FDA. The chemokine receptor CXCR3 was identified in 1996, and nearly 20 years later, new areas of CXCR3 disease biology continue to emerge. Several classes of small molecule CXCR3 antagonists have been developed, and two have shown efficacy in preclinical models of inflammatory disease. However, only one CXCR3 antagonist has been evaluated in clinical trials, and there remain many opportunities to further investigate known classes of CXCR3 antagonists and to identify new chemotypes. This Perspective reviews the known CXCR3 antagonists and considers future opportunities for the development of small molecules for clinical evaluation.

Adverse local tissue reaction (ALTR) associated with corrosion products in metal-on-metal and dual modular neck total hip replacements is associated with upregulation of interferon gamma-mediated chemokine signaling

Adverse local tissue reactions (ALTR) associated with tribocorrosion following total hip arthroplasty (THA) have become a significant clinical concern in recent years. In particular, implants featuring metal-on-metal bearing surfaces and modular femoral stems have been reported to result in elevated rates of ALTR. These tribocorrosion-related tissue reactions are characterized by marked necrosis and lymphocytic infiltration, which contrasts sharply with the macrophagic and foreign body giant cell inflammation associated with polyethylene wear particle induced peri-implant osteolysis. In this study, we characterize tribocorrosion-associated ALTR at a molecular level. Gene expression profiling of peri-implant tissue around failing implants identifies upregulation of numerous inflammatory mediators in ALTR, including several interferon gamma inducible factors, most notably the chemokines MIG/CXCL9 and IP-10/CXCL10. This expression profile is distinct from that associated with polyethylene wear induced osteolysis, which is characterized by induction of markers of alternative macrophage activation, such as chitotriosidase (CHIT-1). Importantly, MIG/CXCL9 and IP-10/CXCL10 are also elevated at the protein level in the synovial fluid and, albeit more moderately, the serum, of ALTR patients, raising the possibility that these factors may serve as circulating biomarkers for the early detection of ALTR in at-risk patients.

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.

Metabolic profiling of ligands for the chemokine receptor CXCR3 by liquid chromatography-mass spectrometry coupled to bioaffinity assessment

Chemokine receptors belong to the class of G protein-coupled receptors and are important in the host defense against infections and inflammation. However, aberrant chemokine signaling is linked to different disorders such as cancer, central nervous system and immune disorders, and viral infections [Scholten DJ et al. (2012) Br J Pharmacol 165(6):1617–1643]. Modulating the chemokine receptor function provides new ways of targeting specific diseases. Therefore, discovery and development of drugs targeting chemokine receptors have received considerable attention from the pharmaceutical industry in the past decade. Along with that, the determination of bioactivities of individual metabolites derived from lead compounds towards chemokine receptors is crucial for drug selectivity, pharmacodynamics, and potential toxicity issues. Therefore, advanced analytical methodologies are in high demand. This study is aimed at the optimization of a new analytical method for metabolic profiling with parallel bioaffinity assessment of CXCR3 ligands of the azaquinazolinone and piperazinyl-piperidine class and their metabolites. The method is based on mass spectrometric (MS) identification after liquid chromatographic (LC) separation of metabolic mixtures. The bioaffinity assessment is performed “at-line” via high-resolution nanofractionation onto 96-well plates allowing direct integration of radioligand binding assays. This new method enables identification of metabolites from lead compounds with associated estimation of their individual bioaffinity. Moreover, the identification of the metabolite structures via accurate mass measurements and MS² allows the identification of liable metabolic “hotspots” for further lead optimization. The efficient combination of chemokine receptor ligand binding assays with analytical techniques, involving nanofractionation as linking technology, allows implementation of comprehensive metabolic profiling in an early phase of the drug discovery process.