Signal transduction by the chemokine receptor CXCR3: activation of Ras/ERK, Src, and phosphatidylinositol 3-kinase/Akt controls cell migration and proliferation in human vascular pericytes

The differences in cytokine signatures between severe fever with thrombocytopenia syndrome (SFTS) and hemorrhagic fever with renal syndrome (HFRS)

Severe fever with thrombocytopenia syndrome (SFTS) virus and hantavirus are categorized under the Bunyavirales order. The severe disease progression in both SFTS and hemorrhagic fever with renal syndrome (HFRS) is associated with cytokine storms. This study aimed to explore the differences in cytokine profiles and immune responses between the two diseases. A cross-sectional, single-center study involved 100 participants, comprising 46 SFTS patients, 48 HFRS patients, and 6 healthy controls. The study employed the Luminex cytokine detection platform to measure 48 cytokines. The differences in cytokine profiles and immune characteristics between the two diseases were further analyzed using multiple linear regression, principal component analysis, and random forest method. Among the 48 cytokines tested, 30 showed elevated levels in SFTS and/or HFRS compared to the healthy control group. Furthermore, there were 19 cytokines that exhibited significant differences between SFTS and HFRS. Random forest analysis suggested that TRAIL and CTACK were predictive of SFTS, while IL2Ralpha, MIG, IL-8, IFNalpha2, HGF, SCF, MCP-3, and PDGFBB were more common with HFRS. It was further verified by the receiver operating characteristic with area under the curve >0.8 and P-values <0.05, except for TRAIL. Significant differences were observed in the cytokine profiles of SFTS and HFRS, with TRAIL, IL2Ralpha, MIG, and IL-8 being the top 4 cytokines that most clearly distinguished the two diseases.

IMPORTANCE

SFTS and HFRS differ in terms of cytokine immune characteristics. TRAIL, IL-2Ralpha, MIG, and IL-8 were the top 4 that differed markedly between SFTS and HFRS.

Modulating cancer mechanopathology to restore vascular function and enhance immunotherapy

Solid tumor pathology, characterized by abnormalities in the tumor microenvironment (TME), challenges therapeutic effectiveness. Mechanical factors, including increased tumor stiffness and accumulation of intratumoral forces, can determine the success of cancer treatments, defining the tumor's "mechanopathology" profile. These abnormalities cause extensive vascular compression, leading to hypoperfusion and hypoxia. Hypoperfusion hinders drug delivery, while hypoxia creates an unfavorable TME, promoting tumor progression through immunosuppression, heightened metastatic potential, drug resistance, and chaotic angiogenesis. Strategies targeting TME mechanopathology, such as vascular and stroma normalization, hold promise in enhancing cancer therapies with some already advancing to the clinic. Normalization can be achieved using anti-angiogenic agents, mechanotherapeutics, immune checkpoint inhibitors, engineered bacterial therapeutics, metronomic nanomedicine, and ultrasound sonopermeation. Here, we review the methods developed to rectify tumor mechanopathology, which have even led to cures in preclinical models, and discuss their bench-to-bedside translation, including the derivation of biomarkers from tumor mechanopathology for personalized therapy.

Platelet factor 4(PF4) and its multiple roles in diseases

Platelet factor 4 (PF4) combines with heparin to form an antigen that could produce IgG antibodies and participate in heparin-induced thrombocytopenia (HIT). PF4 has attracted wide attention due to its role in novel coronavirus vaccine-19 (COVID-9)-induced immune thrombotic thrombocytopenia (VITT) and cognitive impairments. The electrostatic interaction between PF4 and negatively charged molecules is vital in the progression of VITT, which is similar to HIT. Emerging evidence suggests its multiple roles in hematopoietic and angiogenic inhibition, platelet coagulation interference, host inflammatory response promotion, vascular inhibition, and antitumor properties. The emerging pharmacological effects of PF4 may help deepen the exploration of its mechanism, thus accelerating the development of targeted therapies. However, due to its pleiotropic properties, the development of drugs targeting PF4 is at an early stage and faces many challenges. Herein, we discussed the characteristics and biological functions of PF4, summarized PF4-mediated signaling pathways, and discussed its multiple roles in diseases to inform novel approaches for successful clinical translational research.

Phosphorylation barcodes direct biased chemokine signaling at CXCR3

G protein-coupled receptor (GPCR)-biased agonism, selective activation of certain signaling pathways relative to others, is thought to be directed by differential GPCR phosphorylation "barcodes." At chemokine receptors, endogenous chemokines can act as "biased agonists", which may contribute to the limited success when pharmacologically targeting these receptors. Here, mass spectrometry-based global phosphoproteomics revealed that CXCR3 chemokines generate different phosphorylation barcodes associated with differential transducer activation. Chemokine stimulation resulted in distinct changes throughout the kinome in global phosphoproteomics studies. Mutation of CXCR3 phosphosites altered β-arrestin 2 conformation in cellular assays and was consistent with conformational changes observed in molecular dynamics simulations. T cells expressing phosphorylation-deficient CXCR3 mutants resulted in agonist- and receptor-specific chemotactic profiles. Our results demonstrate that CXCR3 chemokines are non-redundant and act as biased agonists through differential encoding of phosphorylation barcodes, leading to distinct physiological processes.

RSV-induced expanded ciliated cells contribute to bronchial wall thickening

Viral infection, particularly respiratory syncytial virus (RSV), causes inflammation in the bronchiolar airways (bronchial wall thickening, also known as bronchiolitis). This bronchial wall thickening is a common pathophysiological feature in RSV infection, but it causes more fatalities in infants than in children and adults. However, the molecular mechanism of RSV-induced bronchial wall thickening remains unknown, particularly in healthy adults. Using highly differentiated pseudostratified airway epithelium generated from primary human bronchial epithelial cells, we revealed RSV-infects primarily ciliated cells. The infected ciliated cells expanded substantially without compromising epithelial membrane integrity and ciliary functions and contributed to the increased height of the airway epithelium. Furthermore, we identified multiple factors, e.g., cytoskeletal (ARP2/3-complex-driven actin polymerization), immunological (IP10/CXCL10), and viral (NS2), contributing to RSV-induced uneven epithelium height increase in vitro. Thus, RSV-infected expanded cells contribute to a noncanonical inflammatory phenotype, which contributes to bronchial wall thickening in the airway, and is termed cytoskeletal inflammation.

Phosphorylation barcodes direct biased chemokine signaling at CXCR3

G protein-coupled receptor (GPCR) biased agonism, the activation of some signaling pathways over others, is thought to largely be due to differential receptor phosphorylation, or "phosphorylation barcodes." At chemokine receptors, ligands act as "biased agonists" with complex signaling profiles, which contributes to the limited success in pharmacologically targeting these receptors. Here, mass spectrometry-based global phosphoproteomics revealed that CXCR3 chemokines generate different phosphorylation barcodes associated with differential transducer activation. Chemokine stimulation resulted in distinct changes throughout the kinome in global phosphoproteomic studies. Mutation of CXCR3 phosphosites altered β-arrestin conformation in cellular assays and was confirmed by molecular dynamics simulations. T cells expressing phosphorylation-deficient CXCR3 mutants resulted in agonist- and receptor-specific chemotactic profiles. Our results demonstrate that CXCR3 chemokines are non-redundant and act as biased agonists through differential encoding of phosphorylation barcodes and lead to distinct physiological processes.

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.

Reciprocal expression of the immune response genes CXCR3 and IFI44L as module hubs are associated with patient survivals in primary central nervous system lymphoma

PURPOSE

Here, we investigated expression modules reflecting the reciprocal expression of the cancer microenvironment and immune response-related genes associated with poor prognosis in primary central nervous system lymphoma (PCNSL).

METHODS

Weighted gene coexpression network analysis revealed representative modules, including neurogenesis, immune response, anti-virus, microenvironment, gene expression and translation, extracellular matrix, morphogenesis, and cell adhesion in the transcriptome data of 31 PCNSL samples. RESULTS : Gene expression networks were also reflected by protein-protein interaction networks. In particular, some of the hub genes were highly expressed in patients with PCNSL with prognoses as follows: AQP4, SLC1A3, GFAP, CXCL9, CXCL10, GBP2, IFI6, OAS2, IFIT3, DCN, LRP1, and LUM with good prognosis; and STAT1, IFITM3, GZMB, ISG15, LY6E, TGFB1, PLAUR, MMP4, FTH1, PLAU, CSF3R, FGR, POSTN, CCR7, TAS1R3, small ribosomal subunit genes, and collagen type 1/3/4/6 genes with poor prognosis. Furthermore, prognosis prediction formulae were constructed using the Cox proportional-hazards regression model, which demonstrated that the IP-10 receptor gene CXCR3 and type I interferon-induced protein gene IFI44L could predict patient survival in PCNSL.

CONCLUSION

These results indicate that the differential expression and balance of immune response and microenvironment genes may be required for PCNSL tumor growth or prognosis prediction, which would help understanding the mechanism of tumorigenesis and potential therapeutic targets in PCNSL.

iNKT17 cells play a pathogenic role in ethinylestradiol-induced cholestatic hepatotoxicity

IL-17 is closely associated with inflammation in intrahepatic cholestasis (IHC). Targeting IL-17 ameliorates IHC in mice. Invariant natural killer T (iNKT) cells are predominantly enriched in the liver and they mediate drug-induced liver injury through their secreted cytokines. However, whether iNKT17 cells are involved in ethinylestradiol (EE)-induced IHC remains unclear. In the present study, the administration of EE (10 mg/kg in vivo and 6.25 μM in vitro) promoted the activation and expansion of iNKT17 cells, which contributed to a novel hepatic iNKT17/Treg imbalance. iNKT cell-deficient Jα18^-/- mice and the RORγt inhibitor digoxin (20 μg) alleviated EE-induced cholestatic hepatotoxicity and downregulated the IL-17 signalling pathway. In contrast, the co-administration of EE with recombinant IL-17 (1 μg) to Jα18^-/- mice induced cholestatic hepatotoxicity and increased the infiltration of hepatic neutrophils and monocytes. Importantly, the administration of IL-17^-/- iNKT cells (3.5 × 10⁵) to Jα18^-/- mice resulted in the attenuation of hepatotoxicity and the recruitment of fewer hepatic neutrophils and monocytes than the adoptive transfer of wild-type iNKT cells. These results indicated that iNKT17 cells could exert pathogenic effects. The recruitment and activation of iNKT17 cells could be attributed to the high level of CXCR3 expression on their surface. CXCL10 deficiency ameliorated EE-induced cholestatic liver damage, reduced hepatic CXCR3⁺ iNKT cells and inhibited RORγt expression. These findings suggest that iNKT17 cells play a key role in EE-induced cholestatic liver injury via CXCR3-mediated recruitment and activation. Our study provides new insights and therapeutic targets for cholestatic diseases.

EGFR-Tyrosine Kinase Inhibitors Induced Activation of the Autocrine CXCL10/CXCR3 Pathway through Crosstalk between the Tumor and the Microenvironment in EGFR-Mutant Lung Cancer

CXCL10 is a cytokine that is elevated during EGFR-TKI treatment in the tumor microenvironment of lung cancer. Here, we report an original study that the impact of the CXCL10/CXCR3 pathway on EGFR-TKI resistance in EGFR-mutant lung cancer through a cytokine array analysis during in vitro coculture with tumor cells and activated PBMCs treated with EGFR-TKI, as well as the serial analysis of CXCL10 in EGFR-mutant lung cancer transgenic mice during EGFR-TKI treatment. In EGFR-mutant tumor cells cocultured with activated PBMCs, EGFR-TKI treatment increased CXCL10 in the supernatant; this activated CXCR3 in the tumor cells to induce the phosphorylation of Src and the NF-κB subunit, p65, and the expression of HIF-1α. CXCL10 siRNA treatment of EGFR-mutant tumor cells also decreased CXCL10 in the supernatant from coculturing with activated PBMCs, suggesting that the effects of CXCL10 occur via autocrine and paracrine pathways. Importantly, elevated CXCL10/CXCR3 signaling was recapitulated in a transgenic lung cancer mouse model. Our results show that increased CXCL10 levels during early EGFR-TKI treatment stimulate oncogenic signaling of persistent tumor cells to contribute to EGFR-TKI resistance via autocrine and paracrine pathways.

The Extended N-Terminal Domain Confers Atypical Chemokine Receptor Properties to CXCR3-B

The chemokine receptor CXCR3 plays a critical role in immune cell recruitment and activation. CXCR3 exists as two main isoforms, CXCR3-A and CXCR3-B, resulting from alternative splicing. Although the two isoforms differ only by the presence of an N-terminal extension in CXCR3-B, they have been attributed divergent functional effects on cell migration and proliferation. CXCR3-B is the more enigmatic isoform and the mechanisms underlying its function and signaling remain elusive. We therefore undertook an in-depth cellular and molecular comparative study of CXCR3-A and CXCR3-B, investigating their activation at different levels of the signaling cascades, including G protein coupling, β-arrestin recruitment and modulation of secondary messengers as well as their downstream gene response elements. We also compared the subcellular localization of the two isoforms and their trafficking under resting and stimulated conditions along with their ability to internalize CXCR3-related chemokines. Here, we show that the N-terminal extension of CXCR3-B drastically affects receptor features, modifying its cellular localization and preventing G protein coupling, while preserving β-arrestin recruitment and chemokine uptake capacities. Moreover, we demonstrate that gradual truncation of the N terminus leads to progressive recovery of surface expression and G protein coupling. Our study clarifies the molecular basis underlying the divergent effects of CXCR3 isoforms, and emphasizes the β-arrestin-bias and the atypical nature of CXCR3-B.

Evolution, Expression and Functional Analysis of CXCR3 in Neuronal and Cardiovascular Diseases: A Narrative Review

Chemokines form a sophisticated communication network wherein they maneuver the spatiotemporal migration of immune cells across a system. These chemical messengers are recognized by chemokine receptors, which can trigger a cascade of reactions upon binding to its respective ligand. CXC chemokine receptor 3 (CXCR3) is a transmembrane G protein-coupled receptor, which can selectively bind to CXCL9, CXCL10, and CXCL11. CXCR3 is predominantly expressed on immune cells, including activated T lymphocytes and natural killer cells. It thus plays a crucial role in immunological processes like homing of effector cells to infection sites and for pathogen clearance. Additionally, it is expressed on several cell types of the central nervous system and cardiovascular system, due to which it has been implicated in several central nervous system disorders, including Alzheimer's disease, multiple sclerosis, dengue viral disease, and glioblastoma, as well as cardiovascular diseases like atherosclerosis, Chronic Chagas cardiomyopathy, and hypertension. This review provides a narrative description of the evolution, structure, function, and expression of CXCR3 and its corresponding ligands in mammals and zebrafish and the association of CXCR3 receptors with cardiovascular and neuronal disorders. Unraveling the mechanisms underlying the connection of CXCR3 and disease could help researchers investigate the potential of CXCR3 as a biomarker for early diagnosis and as a therapeutic target for pharmacological intervention, along with developing robust zebrafish disease models.

Rhinovirus infection of bronchial epithelium induces specific bronchial smooth muscle cell migration of severe asthmatic patients

BACKGROUND

Patients with severe asthma show an increase in both exacerbation frequency and bronchial smooth muscle (BSM) mass. Rhinovirus (RV) infection of the bronchial epithelium (BE) is the main trigger of asthma exacerbations. Histological analysis of biopsies shows that a close connection between BE and hypertrophic BSM is a criterion for severity of asthma.

OBJECTIVE

We hypothesized that RV infection of BE specifically increases asthmatic BSM cell migration.

METHODS

Serum samples, biopsies or BSM cells were obtained from 86 patients with severe asthma and 31 non-asthmatic subjects. BE cells from non-asthmatic subjects were cultured in an air-liquid interface and exposed to RV-16. Migration of BSM cells was assessed in response to BE supernatant using chemotaxis assays. Chemokine concentrations were analyzed by transcriptomics and ELISAs. Immunocytochemistry, western blotting and flow cytometry were used to quantify CXCR3 isoform distribution. CXCR3 downstream signaling pathways were assessed by calcium imaging and western blots.

RESULTS

BSM cells from severe asthmatic patients specifically migrated toward RV-infected BE, whereas those from non-asthmatic subjects did not. This specific migration is driven by BE CXCL10, which was increased in vitro in response to RV infection as well as in vivo in serum from exacerbating patients with severe asthma. The mechanism is related to both decreased expression and activation of the CXCR3-B-specific isoform in severe asthmatic BSM cells.

CONCLUSION

We have demonstrated a novel mechanism of BSM remodeling in severe asthmatic patients following RV exacerbation. This study highlights the CXCL10/CXCR3-A axis as a potential therapeutic target in severe asthma.

Integrated Molecular Characterization to Reveal the Association between Kynurenine 3-Monooxygenase Expression and Tumorigenesis in Human Breast Cancers

Kynurenine 3-monooxygenase (KMO) is overexpressed in several tumors and participates in the progression of breast cancer tumorigenesis, including cancer types such as triple-negative breast cancer (TNBC). This malignant gene is an enzyme in the kynurenine pathway, which is involved in the carcinogenesis of cancer through immune function manipulation. However, it remains unclear whether the role of the KMO contributes to tumorigenesis and immune functions in human breast cancer. In this study, we found that KMO was highly expressed in different types of tumors, especially in invasive ductal breast carcinoma. In addition, KMO expression was positively correlated with the malignant clinical features of patients with breast cancer, such as TNBC and a nodal-positive status, along with patients with a higher Nottingham prognostic index (NPI). Furthermore, the top ten KMO-correlated genes were the chemokines and pro-inflammatory cytokines known to be involved in the progression of various cancers, therefore, KMO may facilitate breast cancers via synergistically regulating inflammatory responses in tumors with these hub genes. Taken together, these findings highlight the tumor-promotion role of KMO in breast cancers and suggest that KMO can serve as a biomarker for prognosis prediction in breast cancer patients.

Recent Advances in Glioma Therapy: Combining Vascular Normalization and Immune Checkpoint Blockade

Glioblastoma (GBM) accounts for more than 50% of all primary malignancies of the brain. Current standard treatment regimen for GBM includes maximal surgical resection followed by radiation and adjuvant chemotherapy. However, due to the heterogeneity of the tumor cells, tumor recurrence is often inevitable. The prognosis of patients with glioma is, thus, dismal. Glioma is a highly angiogenic tumor yet immunologically cold. As such, evolving studies have focused on designing strategies that specifically target the tyrosine kinase receptors of angiokines and encourage immune infiltration. Recent promising results from immunotherapies on other cancer types have prompted further investigations of this therapy in GBM. In this article, we reviewed the pathological angiogenesis and immune reactivity in glioma, as well as its target for drug development, and we discussed future directions in glioma therapy.

TNF-α augments CXCL10/CXCR3 axis activity to induce Epithelial-Mesenchymal Transition in colon cancer cell

Chronic inflammation-induced metastases have long been regarded as one of the significant obstacles in treating cancer. Tumor necrosis factor-α (TNF-α), a main inflammation mediator within tumor microenvironment, affects tumor development by inducing multiple chemokines to establish a complex network. Recent reports have revealed that CXCL10/CXCR3 axis affects cancer cells invasiveness and metastases, and Epithelial-mesenchymal transition (EMT) is the main reason for frequent proliferation and distant organ metastases of colon cancer (CC) cells, However, it is unclear whether TNF-α- mediated chronic inflammation can synergically enhance EMT-mediated CC metastasis through promoting chemokine expression. According to this study, TNF-α activated the PI3K/Akt and p38 MAPK parallel signal transduction pathways, then stimulate downstream NF-κB pathway p65 into the nucleus to activate CXCL10 transcription. CXCL10 enhanced the metastases of CC-cells by triggering small GTPases such as RhoA and cdc42. Furthermore, overexpression of CXCL10 significantly enhanced tumorigenicity and mobility of CC cells in vivo. We further clarified that CXCL10 activated the PI3K/Akt pathway through CXCR3, resulting in suppression of GSK-3β phosphorylation and leading to upregulation of Snail expression, thereby regulating EMT in CC cells. These outcomes lay the foundation for finding new targets to inhibit CC metastases.

Vascular normalization in immunotherapy: A promising mechanisms combined with radiotherapy

Leakage and compression of blood vessels may result in deprivation of blood flow to a large number of tumor tissues, which can lead to tumor hypoxia. Hypoxia induces an increase in the expression of hypoxia-inducible factor 1 in tumor cells, which induces angiogenesis in tumors through the high expression of vascular endothelial growth factor, thereby forming a positive feedback vicious circle. Improving hypoxia by normalizing blood vessels and improving radiosensitivity by immunotherapy has emerged as a new application of combined immunotherapy and radiotherapy. Interferon γ produced by CD4 + /CD8 + T cells, induced by immune checkpoint inhibitors, plays an important role in the normalization of blood vessels; tumor-associated eosinophils also play a role in the process of immunotherapy-induced blood vessel normalization. In addition, the reduction in regulatory T cells induced by immune checkpoint inhibitors can increase eosinophil levels, which promotes the further development of vascular normalization mechanisms. This review focuses on the mechanism of immunotherapy to normalize blood vessels, and proposes a good prospect for improving hypoxia. Due to the narrow vascular normalization window of anti-angiogenesis therapy, discovery of the vascular normalization effect of immunotherapy provides a new idea for the combined application of immunotherapy and radiotherapy. The enlarged vascular normalization window and improved hypoxia provide a good opportunity for the subsequent implementation of radiotherapy. The above sorting and analysis may pave the way for a promising strategy for cancer treatment via combined immunotherapy and radiotherapy.

CXCL10 and CXCR3 in the Trigeminal Ganglion Contribute to Trigeminal Neuropathic Pain in Mice

Purpose

Trigeminal neuropathic pain is very common clinically, but effective treatments are lacking. Chemokines and their receptors have been implicated in the pathogenesis of chronic pain. This study explored the role of the chemokine CXCL10 and its receptor, CXCR3, in trigeminal neuropathic pain in mice.

Materials and Methods

Trigeminal neuropathic pain was established by partial infraorbital nerve ligation (pIONL) in wild-type and Cxcr3^−/− mice. Facial mechanical allodynia was evaluated by behavioral testing. A lentivirus containing Cxcr3 shRNA (LV-Cxcr3 shRNA) was microinjected into the trigeminal ganglion (TG) to knock down Cxcr3 expression. Quantitative polymerase chain reaction assays and immunofluorescence staining were used to examine Cxcl10/Cxcr3 mRNA expression and protein distribution. Western blotting was performed to examine activation of extracellular signal-regulated kinase (ERK) and AKT in the TG. Intra-TG injection of an AKT inhibitor was performed to examine the role of AKT in trigeminal neuropathic pain.

Results

pIONL induced persistent trigeminal neuropathic pain, which was alleviated in Cxcr3^−/− mice. Intra-TG injection of LV-Cxcr3 shRNA attenuated pIONL-induced mechanical allodynia. Furthermore, pIONL increased the expression of CXCR3 and its major ligand, CXCL10, in TG neurons. Intra-TG injection of CXCL10 induced pain hypersensitivity in wild-type mice but not in Cxcr3^−/− mice. CXCL10 also induced activation of ERK and AKT in the TG of wild-type mice. Finally, pIONL-induced activation of ERK and AKT was reduced in Cxcr3^−/− mice. Intra-TG injection of the AKT inhibitor alleviated pIONL-induced mechanical allodynia in WT mice but not in Cxcr3^−/− mice.

Conclusion

CXCL10 acts on CXCR3 to induce ERK and AKT activation in TG neurons and contributes to the maintenance of trigeminal neuropathic pain.

Ketohexokinase inhibition improves NASH by reducing fructose-induced steatosis and fibrogenesis

Background & Aims

Increasing evidence highlights dietary fructose as a major driver of non-alcoholic fatty liver disease (NAFLD) pathogenesis, the majority of which is cleared on first pass through the hepatic circulation by enzymatic phosphorylation to fructose-1-phosphate via the ketohexokinase (KHK) enzyme. Without a current approved therapy, disease management emphasises lifestyle interventions, but few patients adhere to such strategies. New targeted therapies are urgently required.

Methods

We have used a unique combination of human liver specimens, a murine dietary model of NAFLD and human multicellular co-culture systems to understand the hepatocellular consequences of fructose administration. We have also performed a detailed nuclear magnetic resonance-based metabolic tracing of the fate of isotopically labelled fructose upon administration to the human liver.

Results

Expression of KHK isoforms is found in multiple human hepatic cell types, although hepatocyte expression predominates. KHK knockout mice show a reduction in serum transaminase, reduced steatosis and altered fibrogenic response on an Amylin diet. Human co-cultures exposed to fructose exhibit steatosis and activation of lipogenic and fibrogenic gene expression, which were reduced by pharmacological inhibition of KHK activity. Analysis of human livers exposed to ¹³C-labelled fructose confirmed that steatosis, and associated effects, resulted from the accumulation of lipogenic precursors (such as glycerol) and enhanced glycolytic activity. All of these were dose-dependently reduced by administration of a KHK inhibitor.

Conclusions

We have provided preclinical evidence using human livers to support the use of KHK inhibition to improve steatosis, fibrosis, and inflammation in the context of NAFLD.

Lay summary

We have used a mouse model, human cells, and liver tissue to test how exposure to fructose can cause the liver to store excess fat and become damaged and scarred. We have then inhibited a key enzyme within the liver that is responsible for fructose metabolism. Our findings show that inhibition of fructose metabolism reduces liver injury and fibrosis in mouse and human livers and thus this may represent a potential route for treating patients with fatty liver disease in the future.

CXCL10/CXCR3 Signaling in the DRG Exacerbates Neuropathic Pain in Mice

Chemokines and receptors have been implicated in the pathogenesis of chronic pain. Here, we report that spinal nerve ligation (SNL) increased CXCR3 expression in dorsal root ganglion (DRG) neurons, and intra-DRG injection of Cxcr3 shRNA attenuated the SNL-induced mechanical allodynia and heat hyperalgesia. SNL also increased the mRNA levels of CXCL9, CXCL10, and CXCL11, whereas only CXCL10 increased the number of action potentials (APs) in DRG neurons. Furthermore, in Cxcr3^-/- mice, CXCL10 did not increase the number of APs, and the SNL-induced increase of the numbers of APs in DRG neurons was reduced. Finally, CXCL10 induced the activation of p38 and ERK in ND7-23 neuronal cells and DRG neurons. Pretreatment of DRG neurons with the P38 inhibitor SB203580 decreased the number of APs induced by CXCL10. Our data indicate that CXCR3, activated by CXCL10, mediates p38 and ERK activation in DRG neurons and enhances neuronal excitability, which contributes to the maintenance of neuropathic pain.

Expression and role of MIG/CXCR3 axis in mantle cell lymphoma

Mantle cell lymphoma (MCL) is a unique subtype of B-cell non-Hodgkin lymphoma with a generally aggressive and heterogeneous clinical course. Chemokines are one of the complex components in the tumor microenvironment (TME), and they play a vital role in tumor progression and metastasis. There is no information about the monokine induced by gamma interferon (MIG)/CXC chemokine receptor 3 (CXCR3) axis in patients with MCL. In the present study, we discovered that CXCR3 was highly expressed in MCL tissues and some cell lines including Maver, Z138, and Jeko-1, and significantly associated with clinical factors reflecting high tumor burden in MCL patients. Moreover, elevated serum MIG at diagnosis showed a close relationship with advanced disease and poor prognosis in MCL patients. Additionally, the role of CXCR3 in promoting the proliferation and inhibiting the apoptosis of primary MCL cells and Jeko-1 cells was validated by in vitro experiments. Further research indicated that the MIG/CXCR3 axis mediated MCL cell migration to the TME through the PI3K/AKT signaling pathway. Therefore, the MIG/CXCR3 axis might be a potential target with fewer off-target side effects than other targets in MCL.

CXCR3A promotes the secretion of the antifibrotic decoy receptor sIL-13Rα2 by pulmonary fibroblasts

CXC chemokine receptor 3 (CXCR3) A and its IFN-inducible ligands CXCL9 and CXCL10 regulate vascular remodeling and fibroblast motility. IL-13 is a profibrotic cytokine implicated in the pathogenesis of inflammatory and fibroproliferative conditions. Previous work from our laboratory has shown that CXCR3A is negatively regulated by IL-13 and is necessary for the basal regulation of the IL-13 receptor subunit IL-13Rα2. This study investigates the regulation of fibroblast phenotype, function, and downstream IL-13 signaling by CXCR3A in vitro. CXCR3A was overexpressed via transient transfection. CXCR3A^-/- lung fibroblasts were isolated for functional analysis. Additionally, the contribution of CXCR3A to tissue remodeling following acute lung injury was assessed in vivo with wild-type (WT) and CXCR3^-/- mice challenged with IL-13. CXCR3 and IL-13Rα2 displayed a reciprocal relationship after stimulation with either IL-13 or CXCR3 ligands. CXCR3A reduced expression of fibroblast activation makers, soluble collagen production, and proliferation. CXCR3A enhanced the basal expression of pERK1/2 while inducing IL-13-mediated downregulation of NF-κB-p65. CXCR3A^-/- pulmonary fibroblasts were increasingly proliferative and displayed reduced contractility and α-smooth muscle actin expression. IL-13 challenge regulated expression of the CXCR3 ligands and soluble IL-13Rα2 levels in lungs and bronchoalveolar lavage fluid (BALF) of WT mice; this response was absent in CXCR3^-/- mice. Alveolar macrophage accumulation and expression of genes involved in lung remodeling was increased in CXCR3^-/- mice. We conclude that CXCR3A is a central antifibrotic factor in pulmonary fibroblasts, limiting fibroblast activation and reducing extracellular matrix (ECM) production. Therefore, targeting of CXCR3A may be a novel approach to regulating fibroblast activity in lung fibrosis and remodeling.

Potential therapeutic manipulations of the CXCR3 chemokine axis for the treatment of inflammatory fibrosing diseases

Chemokines play important roles in homeostasis and inflammatory processes. While their roles in leukocyte recruitment are well-appreciated, chemokines play additional roles in the body, including mediating or regulating angiogenesis, tumor metastasis and wound healing. In this opinion article, we focus on the role of CXCR3 and its ligands in fibrotic processes. We emphasize differences of the effects of each ligand, CXCL9, CXCL10 and CXCL11, on fibroblasts in different tissues of the body. We include discussions of differences in signaling pathways that may account for protective or pro-fibrotic effects of each ligand in different experimental models and ex vivo analysis of human tissues. Our goal is to highlight potential reasons why there are disparate findings in different models, and to suggest ways in which this chemokine axis could be manipulated for the treatment of fibrosis.

NLRP3 Is Involved in the Maintenance of Cerebral Pericytes

Pericytes play a central role in regulating the structure and function of capillaries in the brain. However, molecular mechanisms that drive pericyte proliferation and differentiation are unclear. In our study, we immunostained NACHT, LRR and PYD domains-containing protein 3 (NLRP3)-deficient and wild-type littermate mice and observed that NLRP3 deficiency reduced platelet-derived growth factor receptor β (PDGFRβ)-positive pericytes and collagen type IV immunoreactive vasculature in the brain. In Western blot analysis, PDGFRβ and CD13 proteins in isolated cerebral microvessels from the NLRP3-deficient mouse brain were decreased. We further treated cultured pericytes with NLRP3 inhibitor, MCC950, and demonstrated that NLRP3 inhibition attenuated cell proliferation but did not induce apoptosis. NLRP3 inhibition also decreased protein levels of PDGFRβ and CD13 in cultured pericytes. On the contrary, treatments with IL-1β, the major product of NLRP3-contained inflammasome, increased protein levels of PDGFRβ, and CD13 in cultured cells. The alteration of PDGFRβ and CD13 protein levels were correlated with the phosphorylation of AKT. Inhibition of AKT reduced both protein markers and abolished the effect of IL-1β activation in cultured pericytes. Thus, NLRP3 activation might be essential to maintain pericytes in the healthy brain through phosphorylating AKT. The potential adverse effects on the cerebral vascular pericytes should be considered in clinical therapies with NLRP3 inhibitors.

Role of Chemokines in the Biology of Cholangiocarcinoma

Cholangiocarcinoma (CCA), a heterogeneous tumor with poor prognosis, can arise at any level in the biliary tree. It may derive from epithelial cells in the biliary tracts and peribiliary glands and possibly from progenitor cells or even hepatocytes. Several risk factors are responsible for CCA onset, however an inflammatory milieu nearby the biliary tree represents the most common condition favoring CCA development. Chemokines play a key role in driving the immunological response upon liver injury and may sustain tumor initiation and development. Chemokine receptor-dependent pathways influence the interplay among various cellular components, resulting in remodeling of the hepatic microenvironment towards a pro-inflammatory, pro-fibrogenic, pro-angiogenic and pre-neoplastic setting. Moreover, once tumor develops, chemokine signaling may influence its progression. Here we review the role of chemokines in the regulation of CCA development and progression, and the modulation of angiogenesis, metastasis and immune control. The potential role of chemokines and their receptors as possible biomarkers and/or therapeutic targets for hepatobiliary cancer is also discussed.

Increased Osteoblastic Cxcl9 Contributes to the Uncoupled Bone Formation and Resorption in Postmenopausal Osteoporosis

Introduction

Estrogen deficiency leads to bone loss in postmenopausal osteoporosis, because bone formation, albeit enhanced, fails to keep pace with the stimulated osteoclastic bone resorption. The mechanism driving this uncoupling is central to the pathogenesis of postmenopausal osteoporosis, which, however, remains poorly understood. We previously found that Cxcl9 secreted by osteoblasts inhibited osteogenesis in bone, while the roles of Cxcl9 on osteoclastic bone resorption and osteoporosis are unclear.

Materials and Methods

Postmenopausal osteoporosis mouse model was established by bilateral surgical ovariectomy (OVX). In situ hybridization was performed to detect Cxcl9 mRNA expression in bone. ELISA assay was conducted to assess Cxcl9 concentrations in bone and serum. Cxcl9 activity was blocked by its neutralizing antibody. Micro-CT was performed to determine the effects of Cxcl9 neutralization on bone structure. Cell Migration and adhesion assay were conducted to evaluate the effects of Cxcl9 on osteoclast activity. TRAP staining and Western blot were performed to assess osteoclast differentiation. CXCR3 antagonist NBI-74,330 or ERK antagonist SCH772984 was administered to osteoclast to study the effects of Cxcl9 on CXCR3/ERK signaling.

Results

Cxcl9 was expressed and secreted increasingly in OVX mice bone. Neutralizing Cxcl9 in bone marrow prevented bone loss in the mice by facilitating bone formation as well as inhibiting bone resorption. In vitro, Cxcl9 secreted from osteoblasts facilitated osteoclast precursors adhesion, migration and their differentiation into mature osteoclasts. The positive role of osteoblastic Cxcl9 on osteoclasts was eliminated by blocking CXCR3/ERK signaling in osteoclasts. Estrogen negatively regulated Cxcl9 expression and secretion in osteoblasts, explaining the increased Cxcl9 concentration in OVX mice bone.

Conclusion

Our study illustrates the roles of Cxcl9 in inhibiting bone formation and stimulating bone resorption in osteoporotic bone, therefore providing a possible therapeutic target to the treatment of postmenopausal osteoporosis.

The Chemokine Receptor CCR7 Uses Distinct Signaling Modules With Biased Functionality to Regulate Dendritic Cells

Chemotaxis is a molecular mechanism that confers leukocytes the ability to detect gradients of chemoattractants. Chemokine receptors are well-known regulators of chemotaxis in leukocytes; however, they can regulate several other activities in these cells. This information has been often neglected, probably due to the paramount role of chemotaxis in the immune system and in biology. Therefore, the experimental data available on the mechanisms used by chemokine receptors to regulate other functions of leukocytes is sparse. The results obtained in the study of the chemokine receptor CCR7 in dendritic cells (DCs) provide interesting information on this issue. CCR7 guides the DCs from the peripheral tissues to the lymph nodes, where these cells control T cell activation. CCR7 can regulate DC chemotaxis, survival, migratory speed, cytoarchitecture, and endocytosis. Biochemical and functional analyses show: first, that CCR7 uses in DCs the PI3K/Akt pathway to control survival, the MAPK pathway to control chemotaxis, and the RhoA pathways to regulate actin dynamics, which in turn controls migratory speed, cytoarchitecture, and endocytosis; second, that these three signaling pathways behave as modules with a high degree of independence; and third, that although each one of these routes can regulate several functions in different settings, CCR7 promotes in DCs a functional bias in each pathway. The data uncover an interesting mechanism used by CCR7 to regulate the DCs, entailing multifunctional signaling pathways organized in modules with biased functionality. A similar mechanism could be used by other chemoattractant receptors to regulate the functions of leukocytes.

CXCL9 chemokine promotes the progression of human pancreatic adenocarcinoma through STAT3-dependent cytotoxic T lymphocyte suppression

Chemokines play essential roles in the progression of various human cancers; however, the expression and role of CXC chemokines in pancreatic adenocarcinoma (PAAD) have not yet been identified. The aim of this study is to identify the expression patterns, clinical significance and mechanisms of CXC chemokines in regulating tumour microenvironment of PAAD. Three CXC chemokines, including CXCL5, CXCL9, and CXCL10, were significantly overexpressed in PAAD tissues, which were correlated with the poor survival of the patients. CXCL9/10 was associated with change of immune cell pattern in the tumour microenvironment, and supplementation of CXCL9 in the orthotopic murine PAAD model promoted tumour progression. In particular, CXCL9 reduced the CD8+ cytotoxic T lymphocytes in the tumour microenvironment of PAAD, which could be attributed to the reduced CD8+ T cell proliferation, activation, and secretion of anti-tumour cytokines. In vitro treatment of CXCL9 directly led to the suppression of the proliferation, activation, and secretion of anti-tumour cytokines of isolated CD8+ T cells. Inhibition of STAT3 recovered the CXCL9-inhibited proliferation, activation, and secretion of anti-tumour cytokines of CD8+ T cells. Our study indicates CXCL9 as a potential target of immunotherapy in PAAD treatment by regulating the CD8+ T lymphocytes in the tumour microenvironment.

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.

Drp1 Controls Effective T Cell Immune-Surveillance by Regulating T Cell Migration, Proliferation, and cMyc-Dependent Metabolic Reprogramming

Mitochondria are key players in the regulation of T cell biology by dynamically responding to cell needs, but how these dynamics integrate in T cells is still poorly understood. We show here that the mitochondrial pro-fission protein Drp1 fosters migration and expansion of developing thymocytes both in vitro and in vivo. In addition, we find that Drp1 sustains in vitro clonal expansion and cMyc-dependent metabolic reprogramming upon activation, also regulating effector T cell numbers in vivo. Migration and extravasation defects are also exhibited in Drp1-deficient mature T cells, unveiling its crucial role in controlling both T cell recirculation in secondary lymphoid organs and accumulation at tumor sites. Moreover, the observed Drp1-dependent imbalance toward a memory-like phenotype favors T cell exhaustion in the tumor microenvironment. All of these findings support a crucial role for Drp1 in several processes during T cell development and in anti-tumor immune-surveillance.

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The pro-fission protein Drp1 sustains correct thymocyte maturation

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Drp1 promotes T cell metabolic reprogramming and expansion upon activation

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Drp1 allows efficient T cell extravasation from blood and infiltration into tumors

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An optimal T cell anti-tumor response requires Drp1

The role of CXC receptors signaling in early stages of mouse embryonic stem cell differentiation

Interplay between CXCR7 and other CXC receptors, namely CXCR4 or CXCR3, binding such ligands as SDF-1 or ITAC, was shown to regulate multiple cellular processes. The developmental role of signaling pathways mediated by these receptors was proven by the phenotypes of mice lacking either functional CXCR4, or CXCR7, or SDF-1, showing that formation of certain lineages relies on these factors. In this study, using in vitro differentiating mouse embryonic stem cells that lacked the function of CXCR7, we asked the question about the role of CXCR mediated signaling during early steps of differentiation. Our analysis showed that interaction of SDF-1 or ITAC with CXC receptors is necessary for the regulation of crucial developmental regulators expression and that CXCR7 is involved in the control of ESC pluripotency and differentiation into mesodermal lineages.

The Synthetic Dipeptide Pidotimod Shows a Chemokine-Like Activity through CXC Chemokine Receptor 3 (CXCR3)

In recent years immunomodulators have gained a strong interest and represent nowadays an active expanding area of research for the control of microbial diseases and for their therapeutic potential in preventing, treating and reducing the morbidity and mortality of different diseases. Pidotimod (3-L-pyroglutamyl-L-thiaziolidine-4carboxylic acid, PDT) is a synthetic dipeptide, which possesses immunomodulatory properties and exerts a well-defined pharmacological activity against infections, but its real mechanism of action is still undefined. Here, we show that PDT is capable of activating tyrosine phosphorylation-based cell signaling in human primary monocytes and triggering rapid adhesion and chemotaxis. PDT-induced monocyte migration requires the activation of the PI3K/Akt signaling pathway and chemokine receptor CXCR3. Indeed, a mAb to CXCR3 and a specific receptor inhibitor suppressed significantly PDT-dependent chemotaxis, and CXCR3-silenced primary monocytes lost responsiveness to PDT chemoattraction. Moreover, our results highlighted that the PDT-induced migratory activity is sustained by the CXCR3A isoform, since CXCR3-transfected L1.2 cells acquired responsiveness to PDT stimulation. Finally, we show that PDT, as CXCR3 ligands, is also able to direct the migration of IL-2 activated T cells, which express the highest levels of CXCR3 among CXCR3-expressing cells. In conclusion, our study defines a chemokine-like activity for PDT through CXCR3A and points on the possible role that this synthetic dipeptide may play in leukocyte trafficking and function. Since recent studies have highlighted diverse therapeutic roles for molecules which activates CXCR3, our findings call for an exploration of using this dipeptide in different pathological processes.

Senescent human melanocytes drive skin ageing via paracrine telomere dysfunction

Cellular senescence has been shown to contribute to skin ageing. However, the role of melanocytes in the process is understudied. Our data show that melanocytes are the only epidermal cell type to express the senescence marker p16^INK4A during human skin ageing. Aged melanocytes also display additional markers of senescence such as reduced HMGB1 and dysfunctional telomeres, without detectable telomere shortening. Additionally, senescent melanocyte SASP induces telomere dysfunction in paracrine manner and limits proliferation of surrounding cells via activation of CXCR3-dependent mitochondrial ROS. Finally, senescent melanocytes impair basal keratinocyte proliferation and contribute to epidermal atrophy in vitro using 3D human epidermal equivalents. Crucially, clearance of senescent melanocytes using the senolytic drug ABT737 or treatment with mitochondria-targeted antioxidant MitoQ suppressed this effect. In conclusion, our study provides proof-of-concept evidence that senescent melanocytes affect keratinocyte function and act as drivers of human skin ageing.

Antitumor Activity of a Novel Fibroblast Growth Factor Receptor Inhibitor for Intrahepatic Cholangiocarcinoma

Fibroblast growth factor receptor 2 (FGFR2) might have an important role in the pathogenesis and biology of cholangiocarcinoma (CCA). We examined FGFR expression in CCA tumor specimens obtained from patients and CCA cell lines, and then determined the effects of the novel FGFR inhibitor, derazantinib (DZB; formally, ARQ 087), which is currently in clinical phase 2 trials for intrahepatic CCA. DZB inhibited the growth of CCA cell lines in a dose-dependent manner, and extracellular signal-regulated kinase 1/2 and AKT. It also activated apoptotic and cell growth arrest signaling. DZB reduced the in vitro invasiveness and the expression of key epithelial-mesenchymal transition genes. The in vitro data correlated with the expression of FGFRs in human CCA specimens by immunohistochemistry (FGFR1, 30% positive; and FGFR2, 65% positive) and the CCA cell lines assayed by Western blot analysis. These correlated in vitro studies suggest that FGFR may play an important role in the pathogenesis and biology of CCA. Our findings support the notion that FGFR inhibitors, like DZB, should be further evaluated at the clinical stage as targeted therapy for CCA treatment.

The Distinct Roles of CXCR3 Variants and Their Ligands in the Tumor Microenvironment

First thought to orchestrate exclusively leukocyte trafficking, chemokines are now acknowledged for their multiple roles in the regulation of cell proliferation, differentiation, and survival. Dysregulation of their normal functions contributes to various pathologies, including inflammatory diseases and cancer. The two chemokine receptor 3 variants CXCR3-A and CXCR3-B, together with their cognate chemokines (CXCL11, CXCL10, CXCL9, CXCL4, and CXCL4L1), are involved in the control but also in the development of many tumors. CXCR3-A drives the infiltration of leukocytes to the tumor bed to modulate tumor progression (paracrine axis). Conversely, tumor-driven changes in the expression of the CXCR3 variants and their ligands promote cancer progression (autocrine axis). This review summarizes the anti- and pro-tumoral activities of the CXCR3 variants and their associated chemokines with a focus on the understanding of their distinct biological roles in the tumor microenvironment.

Targeting Drp1 and mitochondrial fission for therapeutic immune modulation

Mitochondria are dynamic organelles whose processes of fusion and fission are tightly regulated by specialized proteins, known as mitochondria-shaping proteins. Among them, Drp1 is the main pro-fission protein and its activity is tightly regulated to ensure a strict control over mitochondria shape according to the cell needs. In the recent years, mitochondrial dynamics emerged as a new player in the regulation of fundamental processes during T cell life. Indeed, the morphology of mitochondria directly regulates T cell differentiation, this by affecting the engagment of alternative metabolic routes upon activation. Further, Drp1-dependent mitochondrial fission sustains both T cell clonal expansion and T cell migration and invasivness. By this review, we aim at discussing the most recent findings about the roles played by the Drp1-dependent mitochondrial fission in T cells, and at highlighting how its pharmacological modulation could open the way to future therapeutic approaches to modulate T cell response.

CXCR7 contributes to the aggressive phenotype of cholangiocarcinoma cells

Development of cholangiocarcinoma (CCA) is dependent on a cross-talk with stromal cells, which release different chemokines including CXCL12, that interacts with two different receptors, CXCR4 and CXCR7. The aim of the present study was to investigate the role of CXCR7 in CCA cells. CXCR7 is overexpressed by different CCA cell lines and in human CCA specimens. Knock-down of CXCR7 in HuCCT-1 cells reduced migration, invasion, and CXCL12-induced adhesion to collagen I. Survival of CCA was also reduced in CXCR7-silenced cells. The ability of CXCL12 to induce cell migration and survival was also blocked by CCX733, a CXCR7 antagonist. Similar effects of CXCR7 activation were observed in CCLP-1 cells and in primary iCCA cells. Enrichment of tumor stem-like cells by a 3D culture system resulted in increased CXCR7 expression compared to cells grown in monolayers, and genetic knockdown of CXCR7 robustly reduced sphere formation both in HuCCT-1 and in CCLP-1 cells. In HuCCT-1 cells CXCR7 was found to interact with β-arrestin 2, which was necessary to mediate CXCL12-induced migration, but not survival. In conclusion, CXCR7 is widely expressed in CCA, and contributes to the aggressive phenotype of CCA cells, inducing cell migration, invasion, adhesion, survival, growth and stem cell-like features. Cell migration induced by CXCR7 requires interaction with β-arrestin 2.

Biased agonists of the chemokine receptor CXCR3 differentially control chemotaxis and inflammation

The chemokine receptor CXCR3 plays a central role in inflammation by mediating effector/memory T cell migration in various diseases; however, drugs targeting CXCR3 and other chemokine receptors are largely ineffective in treating inflammation. Chemokines, the endogenous peptide ligands of chemokine receptors, can exhibit so-called biased agonism by selectively activating either G protein- or β-arrestin-mediated signaling after receptor binding. Biased agonists might be used as more targeted therapeutics to differentially regulate physiological responses, such as immune cell migration. To test whether CXCR3-mediated physiological responses could be segregated by G protein- and β-arrestin-mediated signaling, we identified and characterized small-molecule biased agonists of the receptor. In a mouse model of T cell-mediated allergic contact hypersensitivity (CHS), topical application of a β-arrestin-biased, but not a G protein-biased, agonist potentiated inflammation. T cell recruitment was increased by the β-arrestin-biased agonist, and biopsies of patients with allergic CHS demonstrated coexpression of CXCR3 and β-arrestin in T cells. In mouse and human T cells, the β-arrestin-biased agonist was the most efficient at stimulating chemotaxis. Analysis of phosphorylated proteins in human lymphocytes showed that β-arrestin-biased signaling activated the kinase Akt, which promoted T cell migration. This study demonstrates that biased agonists of CXCR3 produce distinct physiological effects, suggesting discrete roles for different endogenous CXCR3 ligands and providing evidence that biased signaling can affect the clinical utility of drugs targeting CXCR3 and other chemokine receptors.

The Role of Monocyte/Macrophage and CXCR3 in Differentiation between Recurrent Hepatitis C and Acute Cellular Rejection Postliver Transplantation

Objective

Liver transplantation (LT) is the recommended treatment for patients with advanced liver disease and cirrhosis in all guidelines, mostly as a complication of HCV. The distinction between reinfection of the graft with HCV and acute cellular rejection (ACR) is essential because they are managed differently. Hepatic macrophages, which can either arise from circulating blood-derived monocytes (BDM) or from resident tissue Kupffer cells, are central in the pathogenesis of chronic liver injury. The aim of this work was to evaluate whether the origin of macrophages and the immune mediator CXCR3 could help in differentiating between acute recurrent HCV and ACR after liver transplantation.

Methods

Twenty-nine cases of recurrent hepatitis C and 26 cases of ACR were included in this study. The expression of CD 68 (macrophage marker), CD11b (BDM marker), and CxCR3 in the postliver transplant biopsy using immunohistochemistry was determined.

Results

CD11b expression highlighting macrophages of BDM origin was in favor of recurrent hepatitis C (P < 0.001) than in ACR (P = 0.44), while CXCR3 expression by hepatocytes was in favor of ACR (P = 0.001).

Conclusion

Macrophage infiltrating liver tissue post LT can distinguish between ACR by upregulation of CXCR3 and recurrent hepatitis C by predominant CD11b.

A humanized mouse model of liver fibrosis following expansion of transplanted hepatic stellate cells

Hepatic stellate cells (HSCs) are major contributors to liver fibrosis, as hepatic injuries may cause their transdifferentiation into myofibroblast-like cells capable of producing excessive extracellular matrix proteins. Also, HSCs can modulate engraftment of transplanted hepatocytes and contribute to liver regeneration. Therefore, understanding the biology of human HSCs (hHSCs) is important, but effective methods have not been available to address their fate in vivo. To investigate whether HSCs could engraft and repopulate the liver, we transplanted GFP-transduced immortalized hHSCs into immunodeficient NOD/SCID mice. Biodistribution analysis with radiolabeled hHSCs showed that after intrasplenic injection, the majority of transplanted cells rapidly translocated to the liver. GFP-immunohistochemistry demonstrated that transplanted hHSCs engrafted alongside hepatic sinusoids. Prior permeabilization of the sinusoidal endothelial layer with monocrotaline enhanced engraftment of hHSCs. Transplanted hHSCs remained engrafted without relevant proliferation in the healthy liver. However, after CCl₄ or bile duct ligation-induced liver damage, transplanted hHSCs expanded and contributed to extracellular matrix production, formation of bridging cell-septae and cirrhosis-like hepatic pseudolobules. CCl₄-induced injury recruited hHSCs mainly to zone 3, whereas after bile duct ligation, hHSCs were mainly in zone 1 of the liver lobule. Transplanted hHSCs neither transdifferentiated into other cell types nor formed tumors in these settings. In conclusion, a humanized mouse model was generated by transplanting hHSCs, which proliferated during hepatic injury and inflammation, and contributed to liver fibrosis. The ability to repopulate the liver with transplanted hHSCs will be particularly significant for mechanistic studies of cell-cell interactions and fibrogenesis within the liver.

An alternatively spliced variant of CXCR3 mediates the metastasis of CD133+ liver cancer cells induced by CXCL9

Metastasis of liver cancer is closely linked to tumor microenvironment, in which chemokines and their receptors act in an important role. The CXCR3, the receptor of chemokine CXCL9, belongs to a superfamily of rhodopsin-like seven transmembrane GPCRs and CXCR subfamily. In HCC tissues, CXCR3 was frequently upregulated and correlated with tumor size, tumor differentiation, portal invasion and metastasis. In the study, CXCR3-A isoform that was bound by CXCL9 was found to cause significant change of ERK1/2 phosphorylation level in the MAPK signaling pathway, consequently upregulating the MMP2 and MMP9 expression and promoting invasion and metastasis of CD133+ liver cancer cells. Also, CXCR3-A suppressed the adhesion ability of CD133+ liver cancer cells that stimulated by CXCL9 for 24h. These findings suggest that CXCR3 and its ligand CXCL9 could promote the metastasis of liver cancer cells and might be a potential target for the intervention of liver cancer metastasis.

Dihydroartemisinin attenuates autoimmune thyroiditis by inhibiting the CXCR3/PI3K/AKT/NF-κB signaling pathway

Dihydroartemisinin (DHA) is the first generation of naturally occurring artemisinin derivatives with antimalarial activity. Recent research showed that this drug also features immunosuppressive and anti-inflammatory properties. Autoimmune thyroiditis (AIT) is a common organ-specific autoimmune disease with no available effective drug treatment. In this study, we investigated effects of DHA on AIT in vitro and in vivo. Results showed that DHA can visibly reduce antithyroglobulin antibody and thyroid peroxidase antibody levels and regulate T helper cells (Th) 1/Th2 imbalance of experimental AIT mice. DHA also dose-dependently suppressed proliferation of lymphocytes induced by lipopolysaccharide and concanavalin A. DHA inhibited binding of C-X-C chemokine ligand 10 (CXCL10) and its receptor (C–X–C motif) receptor 3 (CXCR3), thus inhibiting calcium flow. DHA can also reduce expression levels of PI3-kinase (PI3K), p-PI3K, protein kinase B (AKT), p-AKT, nuclear factor (NF)-κB/p65, and p-NF-κB/p65. In conclusion, DHA may serve as treatment drug for AIT by inhibiting the CXCR3/PI3K/AKT/NF-kB signaling pathway.

The role of CXCR3/LRP1 cross-talk in the invasion of primary brain tumors

CXCR3 plays important roles in angiogenesis, inflammation, and cancer. However, the precise mechanism of regulation and activity in tumors is not well known. We focused on CXCR3-A conformation and on the mechanisms controlling its activity and trafficking and investigated the role of CXCR3/LRP1 cross talk in tumor cell invasion. Here we report that agonist stimulation induces an anisotropic response with conformational changes of CXCR3-A along its longitudinal axis. CXCR3-A is internalized via clathrin-coated vesicles and recycled by retrograde trafficking. We demonstrate that CXCR3-A interacts with LRP1. Silencing of LRP1 leads to an increase in the magnitude of ligand-induced conformational change with CXCR3-A focalized at the cell membrane, leading to a sustained receptor activity and an increase in tumor cell migration. This was validated in patient-derived glioma cells and patient samples. Our study defines LRP1 as a regulator of CXCR3, which may have important consequences for tumor biology.

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.

Pathogenic roles of CXCL10 signaling through CXCR3 and TLR4 in macrophages and T cells: relevance for arthritis

BACKGROUND

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by uncontrolled joint inflammation and destruction of bone and cartilage. We previously reported that C-X-C motif chemokine 10 (CXCL10; also called IP-10) has important roles in joint inflammation and bone destruction in arthritis. However, the specific mechanisms by which CXCL10 regulates the recruitment of inflammatory cells and the production of osteoclastogenic cytokines in RA progression are not fully understood.

METHODS

Bone marrow-derived macrophages and CD4⁺ T cells were isolated from wild-type (WT), Cxcl10 ^-/-, and Cxcr3 ^-/- mice. CXCL10-induced migration was performed using a Boyden chamber, and CXCL10-stimulated production of osteoclastogenic cytokines was measured by quantitative real-time PCR and ELISA. Collagen antibody-induced arthritis (CAIA) was induced by administration of collagen type II antibodies and lipopolysaccharide to the mice. Clinical scores were analyzed and hind paws were collected for high-resolution micro-CT, and histomorphometry. Serum was used to assess bone turnover and levels of osteoclastogenic cytokines.

RESULTS

CXCL10 increased the migration of inflammatory cells through C-X-C chemokine receptor 3 (CXCR3)-mediated, but not toll-like receptor 4 (TLR4)-mediated, ERK activation. Interestingly, both receptors CXCR3 and TLR4 were simultaneously required for CXCL10-stimulated production of osteoclastogenic cytokines in CD4⁺ T cells. Furthermore, calcineurin-dependent NFATc1 activation was essential for CXCL10-induced RANKL expression. In vivo, F4/80⁺ macrophages and CD4⁺ T cells robustly infiltrated into synovium of WT mice with CAIA but were significantly reduced in both Cxcl10 ^-/- and Cxcr3 ^-/- mice. Serum concentrations of osteoclastogenic cytokines and bone destruction were also reduced in the knockout mice, leading to attenuated progression of arthritis.

CONCLUSION

These findings highlight the importance of CXCL10 signaling in the pathogenesis of RA and provide previously unidentified details of the mechanisms by which CXCL10 promotes the development of arthritis.

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.

Mutual regulation of tumour vessel normalization and immunostimulatory reprogramming

Blockade of angiogenesis can retard tumour growth, but may also paradoxically increase metastasis^1,2. Vessel normalization (VN) may resolve this paradox³. VN involves increased pericyte coverage, improved tumour vessel perfusion, reduced vascular permeability, and consequently mitigated hypoxia³. While these processes alter tumour progression, their regulation is poorly understood. Here we show that Type 1 T helper (Th1) cells play a crucial role in VN. Bioinformatic analyses revealed that gene expression features related to VN correlate with immunostimulatory pathways, especially T lymphocyte (TL) infiltration/activities. To delineate the causal relationship, we employed various mouse models with VN or TL deficiencies. While VN disruption reduced TL infiltration as expected⁴, reciprocal depletion or inactivation of CD4⁺-TLs decreased VN, indicating a mutually-regulatory loop. Additionally, CD4⁺-TL activation by immune checkpoint blockade (ICB) increased VN. IFNγ⁺ Th1 cells are the major population associated with VN. Patient-derived xenograft (PDX) tumours growing in immunodeficient animal hosts exhibited enhanced hypoxia compared to the original tumours in immunocompetent human hosts, which was reduced by adoptive Th1 transfer. Our findings elucidate an unexpected role of Th1 in vasculature and immune reprogramming. Th1 cells may be a marker and a determinant of both ICB and anti-angiogenesis efficacies.

IP-10/CXCR3 Axis Promotes the Proliferation of Vascular Smooth Muscle Cells through ERK1/2/CREB Signaling Pathway

Excessive proliferation of vascular smooth muscle cells is one of the main pathological processes leading to atherosclerosis and intimal hyperplasia after vascular interventional therapy. Our previous study has shown that interferon-γ inducible protein-10 contributes to the proliferation of vascular smooth muscle cell. However, the underlying mechanisms remain unclear. Extracellular signal-regulated kinase 1/2, serine/threonine kinase Akt, and cAMP response element binding protein are signaling pathways, which are considered to play important roles in the processes of vascular smooth muscle cell proliferation. Moreover, chemokine receptor 3 and Toll-like receptor 4 are potential receptors of inducible protein-10 in this process. In the present study, IP-10 was found to directly induce vascular smooth muscle cell proliferation, and exposure to inducible protein-10 activated extracellular signal-regulated kinase 1/2, serine/threonine kinase, and cAMP response element binding protein signaling. Inhibitor of extracellular signal-regulated kinase 1/2, rather than inhibitor of serine/threonine kinase, inhibited the phosphorylation of cAMP response element binding protein and reduced inducible protein-10-stimulated vascular smooth muscle cell proliferation. Knockdown of cAMP response element binding protein by siRNA inhibited inducible protein-10-induced vascular smooth muscle cell proliferation. Moreover, anti-CXCR3 IgG, instead of anti-Toll-like receptor 4 IgG, reduced inducible protein-10-induced vascular smooth muscle cell proliferation and inducible protein-10-stimulated extracellular signal-regulated kinase 1/2 and cAMP response element binding protein activation. Together, these results indicate that inducible protein-10 promotes vascular smooth muscle cell proliferation via chemokine receptor 3 and activation of extracellular signal-regulated kinase 1/2 inducible protein-10-induced vascular smooth muscle cell proliferation. These data provide important targets for future studies to modulate atherosclerosis and restenosis after vascular interventional therapy.

Chemokine Receptor Signaling and the Hallmarks of Cancer

The chemokines are a family of chemotactic cytokines that mediate their activity by acting on seven-transmembrane-spanning G protein-coupled receptors. Both the ability of the chemokines and their receptors to form homo- and heterodimers and the promiscuity of the chemokine-chemokine receptor interaction endow this protein family with enormous signaling plasticity and complexity that are not fully understood at present. Chemokines were initially identified as essential regulators of homeostatic and inflammatory trafficking of innate and adaptive leucocytes from lymphoid organs to tissues. Chemokines also mediate the host response to cancer. Nevertheless, chemokine function in this response is not limited to regulating leucocyte infiltration into the tumor microenvironment. It is now known that chemokines and their receptors influence most-if not all-hallmark processes of cancer; they act on both neoplastic and untransformed cells in the tumor microenvironment, including fibroblasts, endothelial cells (blood and lymphatic), bone marrow-derived stem cells, and, obviously, infiltrating leucocytes. This review begins with an overview of chemokine and chemokine receptor structure, to better define how chemokines affect the proliferation, survival, stemness, and metastatic potential of neoplastic cells. We also examine the main mechanisms by which chemokines regulate tumor angiogenesis and immune cell infiltration, emphasizing the pro- and antitumorigenic activity of this protein superfamily in these interrelated processes.