CXC Chemokine Receptor 2 Antagonist Research Articles

Cathelicidin boosts the antifungal activity of neutrophils and improves prognosis during Aspergillus fumigatus keratitis.

Aspergillus fumigatus (A. fumigatus) is one of the common pathogens of fungal keratitis. Fungal growth and invasion cause excessive inflammation and corneal damage, leading to severe vision loss. Neutrophils are the primary infiltrating cells critical for fungal clearance. Cathelicidin [LL-37 in humans and cathelicidin-related antimicrobial peptide (CRAMP) in mice], a natural antimicrobial peptide, can directly inhibit the growth of many pathogens and regulate immune responses. However, the role of cathelicidin and its effect on neutrophils in A. fumigatus keratitis remain unclear. By establishing A. fumigatus keratitis mouse models, we found that cathelicidin was increased in A. fumigatus keratitis. It could reduce fungal loads, lower clinical scores, and improve corneal transparency. Restriction of CRAMP on fungal proliferation was largely counteracted in CD18-/- mice, in which neutrophils cannot migrate into infected sites. When WT neutrophils were transferred into CD18-/- mice, corneal fungal loads were distinctly reduced, indicating that neutrophils are vital for CRAMP-mediated resistance. Furthermore, cathelicidin promoted neutrophils to phagocytose and degrade conidia both in vitro and in vivo. CXC chemokine receptor 2 (CXCR2) was reported to be a functional receptor of LL-37 on neutrophils. CXCR2 antagonist SB225002 or phospholipase C (PLC) inhibitor U73122 weakened LL-37-induced phagocytosis. Meanwhile, LL-37 induced PLC γ phosphorylation, which was attenuated by SB225002. SB225002 or the autophagy inhibitors Bafilomycin-A1 and 3-Methyladenine weakened LL-37-induced degradation of conidia. Transmission electron microscopy (TEM) observed that LL-37 increased autophagosomes in Aspergillus-infected neutrophils. Consistently, LL-37 elevated autophagy-associated protein expressions (Beclin-1 and LC3-II), but this effect was weakened by SB225002. Collectively, cathelicidin reduces fungal loads and improves the prognosis of A. fumigatus keratitis. Both in vitro and in vivo, cathelicidin promotes neutrophils to phagocytose and degrade conidia. LL-37/CXCR2 activates PLC γ to amplify neutrophils' phagocytosis and induces autophagy to eliminate intracellular conidia.

CXCR2 inhibition overcomes ponatinib intolerance by eradicating chronic myeloid leukemic stem cells through PI3K/Akt/mTOR and dipeptidylpeptidase Ⅳ (CD26)

This study explores the therapeutic potential of targeting CXCR2 in patients afflicted with ponatinib-resistant chronic myeloid leukemia (CML). Ponatinib, a third-generation tyrosine kinase inhibitor (TKI), was initially designed for treating patients with CML harboring the T315I mutation. However, resistance or intolerance issues may lead to treatment discontinuation. Additionally, TKIs have exhibited limitations in eradicating quiescent CML stem cells. Our investigation reveals the activation of CXC chemokine receptor 2 (CXCR2) signaling in response to chemotherapeutic stress. Treatment with the CXCR2 antagonist, SB225002, effectively curtails cell proliferation and triggers apoptosis in ponatinib-resistant CML cells. SB225002 intervention also results in the accumulation of reactive oxygen species and disruption of mitochondrial function, phenomena associated with TKI chemoresistance and apoptosis. Furthermore, we demonstrate that activated CXCR2 expression induces the activity of dipeptidylpeptidase Ⅳ (DPP4/CD26), a CML leukemic stem cell marker, and concomitantly inhibits the PI3K/Akt/mTOR pathway cascades. These findings underscore the novel role of CXCR2 in the regulation of not only ponatinib-resistant CML cells, but also CML leukemic stem cells. Consequently, our study proposes that targeting CXCR2 holds promise as a viable therapeutic strategy for addressing patients with CML grappling with ponatinib resistance.

Fluorescent Ligands Enable Target Engagement Studies for the Intracellular Allosteric Binding Site of the Chemokine Receptor CXCR2.

Herein, we report the structure-based development of fluorescent ligands targeting the intracellular allosteric binding site (IABS) of CXC chemokine receptor 2 (CXCR2), a G protein-coupled receptor (GPCR) that has been pursued as a drug target in oncology and inflammation. Starting from the cocrystallized intracellular CXCR2 antagonist 00767013 (1), tetramethylrhodamine (TAMRA)-labeled CXCR2 ligands were designed, synthesized, and tested for their suitability as fluorescent reporters to probe binding to the IABS of CXCR2. By means of these studies, we developed Mz438 (9a) as a high-affinity and selective fluorescent CXCR2 ligand, enabling cell-free as well as cellular NanoBRET-based binding studies in a nonisotopic and high-throughput manner. Further, we show that 9a can be used as a tool to visualize intracellular target engagement for CXCR2 via fluorescence microscopy. Thus, our small-molecule-based fluorescent CXCR2 ligand 9a represents a promising tool for future studies of CXCR2 pharmacology.

Discovery of Benzocyclic Sulfone Derivatives as Potent CXCR2 Antagonists for Cancer Immunotherapy.

Increasing evidence shows that the CXC chemokine receptor 2 (CXCR2) signaling pathway is essentially implicated in the recruitment of myeloid-derived suppressor cells (MDSCs) to the tumor microenvironment and leads to MDSC-mediated immune suppression. Therefore, CXCR2 has recently emerged as a promising drug target for cancer immunotherapy. In this paper, benzocyclic sulfone derivatives were designed as potent CXCR2 antagonists. Structure-activity relationship studies resulted in two lead compounds 9b and 11h, which demonstrated double-digit nanomolar potencies against CXCR2 and significantly inhibited neutrophil infiltration into the air pouch in an in vivo setting. More importantly, 9b and 11h dose-dependently inhibited the tumor growth through oral administration in the Pan02 mouse model. Further cytometry and immunohistochemical analyses revealed that 9b and 11h could reduce the infiltration of neutrophils and MDSCs and enhance the infiltration of CD3+ T lymphocytes into the Pan02 tumor tissues, shedding light on their mechanisms of action in cancer immunotherapy.

CXCR2, a novel target to overcome tyrosine kinase inhibitor resistance in chronic myelogenous leukemia cells

Chronic myeloid leukemia (CML) is a reciprocal translocation disorder driven by a breakpoint cluster region (BCR)-Abelson leukemia virus (ABL) fusion gene that stimulates abnormal tyrosine kinase activity. Tyrosine kinase inhibitors (TKIs) are effective in treating Philadelphia chromosome (Ph) + CML patients. However, the appearance of TKI-resistant CML cells is a hurdle in CML treatment. Therefore, it is necessary to identify novel alternative treatments targeting tyrosine kinases. This study was designed to determine whether C-X-C chemokine receptor 2 (CXCR2) could be a novel target for TKI-resistant CML treatment. Interleukin 8 (IL-8), a CXCR2 ligand, was significantly increased in the bone marrow serum of initially diagnosed CML patients and TKI-resistant CML cell conditioned media. CXCR2 antagonists suppressed the proliferation of CML cells via cell cycle arrest in the G2/M phase. CXCR2 inhibition also attenuated mTOR, c-Myc, and BCR-ABL expression, leading to CML cell apoptosis, irrespective of TKI responsiveness. Moreover, SB225002, a CXCR2 antagonist, caused higher cell death in TKI-resistant CML cells than TKIs. Using a mouse xenograft model, we confirmed that SB225002 suppresses tumor growth, with a prominent effect on TKI-resistant CML cells. Our findings demonstrate that IL-8 is a prognostic factor for the progression of CML. Inhibiting the CXCR2-mTOR-c-Myc cascade is a promising therapeutic strategy to overcome TKI-sensitive and TKI-insensitive CML. Thus, CXCR2 blockade is a novel therapeutic strategy to treat CML, and SB225002, a commercially available CXCR2 antagonist, might be a candidate drug that could be used to treat TKI-resistant CML.

Administration of a CXC Chemokine Receptor 2 (CXCR2) Antagonist, SCH527123, Together with Oseltamivir Suppresses NETosis and Protects Mice from Lethal Influenza and Piglets from Swine-Influenza Infection

Excessive neutrophil influx, their released neutrophil extracellular traps (NETs), and extracellular histones are associated with disease severity in influenza-infected patients. Neutrophil chemokine receptor CXC chemokine receptor 2 (CXCR2) is a critical target for suppressing neutrophilic inflammation. Herein, temporal dynamics of neutrophil activity and NETosis were investigated to determine the optimal timing of treatment with the CXCR2 antagonist, SCH527123 (2-hydroxy-N,N-dimethyl-3-[2-([(R)-1-(5-methyl-furan-2-yl)-propyl]amino)-3,4-dioxo-cyclobut-1-enylamino]-benzamide), and its efficacy together with antiviral agent, oseltamivir, was tested in murine and piglet influenza-pneumonia models. SCH527123 plus oseltamivir markedly improved survival of mice infected with lethal influenza, and diminished lung pathology in swine-influenza-infected piglets. Mechanistically, addition of SCH527123 in the combination treatment attenuated neutrophil influx, NETosis, in both mice and piglets. Furthermore, neutrophils isolated from influenza-infected mice showed greater susceptibility to NETotic death when stimulated with a CXCR2 ligand, IL-8. In addition, CXCR2 stimulation induced nuclear translocation of neutrophil elastase, and enhanced citrullination of histones that triggers chromatin decondensation during NET formation. Studies on temporal dynamics of neutrophils and NETs during influenza thus provide important insights into the optimal timing of CXCR2 antagonist treatment for attenuating neutrophil-mediated lung pathology. These findings reveal that pharmacologic treatment with CXCR2 antagonist together with an antiviral agent could significantly ameliorate morbidity and mortality in virulent and sublethal influenza infections.

The protective effect of CXC chemokine receptor 2 antagonist on experimental bronchopulmonary dysplasia induced by postnatal systemic inflammation.

BackgroundAnimal studies have shown that a leukocyte influx precedes the development of bronchopulmonary dysplasia (BPD) in premature sheep. The CXC chemokine receptor 2 (CXCR2) pathway has been implicated in the pathogenesis of BPD because of the predominance of CXCR2 ligands in tracheal aspirates of preterm infants who later developed BPD.PurposeTo test the effect of CXCR2 antagonist on postnatal systemic and pulmonary inflammation and alveolarization in a newborn Sprague-Dawley rat model of BPD.MethodsLipopolysaccharide (LPS) was injected intraperitoneally (i.p.) into the newborn rats on postnatal day 1 (P1), P3, and P5 to induce systemic inflammation and inhibit alveolarization. In the same time with LPS administration, CXCR2 antagonist (SB-265610) or vehicle was injected i.p. to investigate whether CXCR2 antagonist can alleviate the detrimental effect of LPS on alveolarization by attenuating inflammation. On P7 and P14, bronchoalveolar lavage fluid (BALF) and peripheral blood (PB) were collected from the pups. To assess alveolarization, mean cord length and alveolar surface area were measured on 4 random nonoverlapping fields per animal in 2 distal lung sections at ×100 magnification.ResultsEarly postnatal LPS administration significantly increased neutrophil counts in BALF and PB and inhibited alveolarization, which was indicated by a greater mean cord length and lesser alveolar surface area. CXCR2 antagonist significantly attenuated the increase of neutrophil counts in BALF and PB and restored alveolarization as indicated by a decreased mean cord length and increased alveolar surface area in rat pups exposed to early postnatal systemic LPS.ConclusionCXCR2 antagonist preserved alveolarization by alleviating pulmonary and systemic inflammation induced by early postnatal systemic LPS administration. These results suggest that CXCR2 antagonist can be considered a potential therapeutic agent for BPD that results from disrupted alveolarization induced by inflammation.

CXCR2 antagonist for patients with chronic obstructive pulmonary disease with chronic mucus hypersecretion: a phase 2b trial

BackgroundOral CXC chemokine receptor 2 (CXCR2) antagonists have been shown to inhibit neutrophil migration and activation in the lung in preclinical and human models of neutrophilic airway inflammation. A previous study with danirixin, a reversible CXCR2 antagonist, demonstrated a trend for improved respiratory symptoms and health status in patients with COPD.MethodsThis 26-week, randomised, double-blind, placebo-controlled phase IIb study enrolled symptomatic patients with mild-to-moderate COPD at risk for exacerbations. Patients received danirixin 5, 10, 25, 35 or 50 mg twice daily or placebo in addition to standard of care. Primary end-points were the dose response of danirixin compared with placebo on the incidence and severity of respiratory symptoms (Evaluating Respiratory Symptoms in COPD [E-RS:COPD] scores) and safety. Secondary end-points included the incidence of moderate-severe exacerbations, health status (COPD Assessment test, CAT) and health-related quality of life HRQoL (St. George Respiratory Questionnaire-COPD, SGRQ-C).ResultsA total of 614 participants were randomized to treatment. There were no improvements in E-RS:COPD, CAT or SGRQ-C scores in participants treated with any dose of danirixin compared to placebo; a larger than expected placebo effect was observed. There was an increased incidence of exacerbation in the danirixin-treated groups and an increased number of pneumonias in participants treated with danirixin 50 mg.ConclusionsThe robust placebo and study effects prohibited any conclusions on the efficacy of danirixin. However, the absence of a clear efficacy benefit and the observed increase in exacerbations in danirixin-treated groups suggests an unfavorable benefit-risk profile in patients with COPD.Trial registrationThis study was registered with clinicaltrials.gov, NCT03034967.

Discovery, structure-activity relationship study and biological evaluation of 2-thioureidothiophene-3-carboxylates as a novel class of C-X-C chemokine receptor 2 (CXCR2) antagonists

The C-X-C motif ligand 8 and C-X-C chemokine receptor 2 (CXCL8-CXCR2) axis is involved in pathogenesis of various diseases including inflammation and cancers. Various CXCR2 antagonists are under development for several diseases. Our previous high-throughput cell-based assay specific for CXCR2 has identified a pyrimidine-based compound CX797 acting on CXCR2 down-stream signaling. A lead optimization campaign through scaffold-hopping strategy led to a series of 2-thioureidothiophene-3-carboxylates (TUTP) as novel CXCR2 antagonists. Structure-activity relationship study of TUTPs led to the identification of compound 52 that significantly inhibited CXCR2-mediated β-arrestin recruitment signaling (IC50 = 1.1±0.01 μM) with negligible effect on CXCL8-mediated cAMP signaling and calcium flux. Similar to the known CXCR2 antagonist SB265610, compound 52 inhibited CXCL8-CXCR2 induced phosphorylation of ERK1/2. TUTP compounds also inhibited CXCL8-mediated cell migration and showed synergy with doxorubicin in ovarian cancer cells, thereby supporting TUTPs as promising compounds for cancer treatment.

CXCR2 antagonism promotes oligodendrocyte precursor cell differentiation and enhances remyelination in a mouse model of multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune demyelinating disease characterized by the autoimmune attack of oligodendrocytes, leading to demyelination and progressive functional deficits. CXC chemokine receptor 2 (CXCR2) is recently reported to orchestrate the migration, proliferation and differentiation of oligodendrocyte precursor cells (OPCs), which implies its possible involvement in the demyelinating process. Here, we used a CXCR2 antagonist, compound 2, as a tool to investigate the role of CXCR2 in demyelination and the underlying mechanism. The primary cultured oligodendrocytes and cuprizone (CPZ)-intoxicated mice were applied in the present study. The results showed that compound 2 significantly promoted OPC proliferation and differentiation. In the demyelinated lesions of CPZ-intoxicated mice, vigorous OPC proliferation and myelin repair was observed after compound 2 treatment. Subsequent investigation of the underlying mechanisms identified that upon inhibition of CXCR2, compound 2 treatment upregulated Ki67, transcription factor 2 (Olig2) and Caspr expression, activated PI3K/AKT/mTOR signaling, ultimately promoted OPCs differentiation and enhanced remyelination. In conclusion, our results demonstrated that CXCR2 antagonism efficiently promoted OPC differentiation and enhanced remyelination in CPZ-intoxicated mice, supporting CXCR2 as a promising therapeutic target for the treatment of chronic demyelinating diseases such as MS.

Cell-specific regulatory effects of CXCR2 on cholestatic liver injury.

The CXC chemokine receptor 2 (CXCR2) is critical for neutrophil recruitment and hepatocellular viability but has not been studied in the context of cholestatic liver injury following bile duct ligation (BDL). The present study sought to elucidate the cell-specific roles of CXCR2 on acute liver injury after BDL. Wild-type and CXCR2-/- mice were subjected BDL. CXCR2 chimeric mice were created to assess the cell-specific role of CXCR2 on liver injury after BDL. SB225002, a selective CXCR2 antagonist, was administrated intraperitoneally after BDL to investigate the potential of pharmacological inhibition. CXCR2-/- mice had significantly less liver injury than wild-type mice at 3 and 14 days after BDL. There was no difference in biliary fibrosis among groups. The chemokines CXCL1 and CXCL2 were induced around areas of necrosis and biliary structures, respectively, both areas where neutrophils accumulated after BDL. CXCR2-/- mice showed significantly less neutrophil accumulation in those injured areas. CXCR2Liver+/Myeloid+ and CXCR2Liver-/Myeloid- mice recapitulated the wild-type and CXCR2-knockout phenotypes, respectively. CXCR2Liver+/Myeloid+ mice suffered higher liver injury than CXCR2Liver+/Myeloid- and CXCR2Liver-/Myeloid+; however, only those chimeras with knockout of myeloid CXCR2 (CXCR2Liver+/Myeloid- and CXCR2Liver-/Myeloid-) showed reduction of neutrophil accumulation around areas of necrosis. Daily administration of SB225002 starting after 3 days of BDL reduced established liver injury at 6 days. In conclusion, neutrophil CXCR2 guides the cell to the site of injury, while CXCR2 on liver cells affects liver damage independent of neutrophil accumulation. CXCR2 appears to be a viable therapeutic target for cholestatic liver injury.NEW & NOTEWORTHY This study is the first to reveal cell-specific roles of the chemokine receptor CXCR2 in cholestatic liver injury caused by bile duct ligation. CXCR2 on neutrophils facilitates neutrophil recruitment to the liver, while CXCR2 on liver cells contributes to liver damage independent of neutrophils. CXCR2 may represent a viable therapeutic target for cholestatic liver injury.

Emerging therapies in adult and paediatric bronchiectasis.

Bronchiectasis is a chronic respiratory disorder characterized by persistent productive cough and recurrent chest infections secondary to permanent structural airway damage. The current treatment strategies for this debilitating disorder are limited to prompt antibiotic treatment of infective exacerbations and regular airway clearance techniques. Despite its high morbidity and associated mortality across all age groups, it has been a neglected area of research in respiratory medicine and there remain no licensed disease-modifying therapies. In this review, we have explored the numerous potential therapeutic targets to break the vicious cycle of infection and inflammation seen in these patients and the novel therapeutic agents that have been developed to target them. We have reviewed the role of novel anti-inflammatory agents designed to target the persistent neutrophilic inflammatory infiltrate seen in bronchiectatic airways, including neutrophil elastase inhibitors, CXCR2 (CXC chemokine receptor 2) antagonists, DPP-1 (dipeptidyl peptidase 1) inhibitors, PDE4 (phosphodiesterase 4) inhibitors and statins. Furthermore, we have explored novel targets to improve mucociliary clearance, namely ENaC (epithelial sodium channel) inhibitors, and discussed the potential of alternative antimicrobial strategies such as inhaled phages. Our review highlights the importance of a multi-faceted approach to bronchiectasis management, which aims not only to eradicate or suppress bronchial infection but also to break the cycle of persistent airway inflammation that results in progressive lung damage in these patients.

Abstract LB-064: The discovery of novel small molecular CXCR2 antagonist by using ligand-based pharmacophore model

Abstract Tumor metastasis has become a fatal disease progress which greatly influence cancer treatment and prognosis. Generally, the metastatic progression can be classified into three main processes: the cancer cells leave the original “tumor home”, travel through “vessel highway”, and settle down in a new “tissue house”. Many agents with various machnisms have been developed for the treatment of cancer cell metastasis, including VEGFR inhibitors, integrin inhibitors, or MMP (matrix metallo protease) inhibitors. Recently a growing interest has been shown for the CXC chemokine receptor 2 (CXCR2), due to their involvement in metastasis physiology. Once CXCR2 is triggered by upstream effectors, it can cause the activation of downstream signals such as serine/threonine kinases, tyrosine kinases. Its essential role in influencing tumor microenvironment makes CXCR2 an important target for anti-tumor metastasis treatment. The first non-peptide CXCR2 antagonist SB225002 was discovered in the mid-1990s by GSK Company. To date, four drug candidates are in clinical trials, including Danirixin, AZD5069, Reparixin and Ladarixin. The clinical indications of AZD5069 were expanded to metastatic head & neck cancer and metastatic pancreatic cancer, in combination with MEDI4736 (a PDL-1 inhibitor). As an excellent computational tool, the pharmacophore model, has been rapidly developed for the identification of novel hit/lead compounds for various targets, especially for proteins without crystal structures. An extensive effort has been made in the attempt to apply pharmacophore model to identify novel VEGFR inhibitors, MMP inhibitors as anti-cancer metastasis agents, revealing that ligand-based pharmacophore model is the best approach when the target geometry is not available, or the binding mode is not elucidated. At present, the binding mode of CXCR2 with its antagonists has not been fully discovered, however, the group of N. Neamati have been trying to establishing a ligand-based pharmacophore model which could be applied for virtual screening to find novel scaffolds of CXCR2 antagonist; this work, for the first time, indicated the feasibility of applying pharmacophore model for the discovery of CXCR2 antagonist. Although a bunch of CXCR2 antagonists have been identified, the anti-tumor metastasis effect of CXCR2 antagonists is not considered in most cases. In our study, a convenient pharmacophore model was built with HipHop program, by screening a mini-database contained compounds which were designed based on the known structure-activity relationship (SAR) of the diarylurea series CXCR2 antagonists. Several novel skeletons with moderate to potent CXCR2 antigonitic activiites were identified. Following optimization resulted in the discovery of compound D45 which showed not only potent CXCR2 antagonist activity with an IC50 value of 10 nM and 910-fold selectivity against CXCR1, but also good in vitro anti-tumor metastatic effect in wound healing assay. Moreover, compound D45 exhibitored promising druglikeness with more than 90% bioavailability in rat. Citation Format: Wen-Hai Huang, Zhi-Long Wang, Jin-Xin Che, Hai-Chao Sheng, Feng Huang, Yong-Zhou Hu, You-Hong Hu, Xin Xie, Xiao-Wu Dong. The discovery of novel small molecular CXCR2 antagonist by using ligand-based pharmacophore model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-064.

Ligand-based pharmacophore model for the discovery of novel CXCR2 antagonists as anti-cancer metastatic agents.

Metastatic cancer is considered a fatal progression of cancer worldwide. It has been shown that a key player in this scenario is the CXC chemokine receptor 2 (CXCR2). To identify novel CXCR2 antagonists, a pharmacophore model was built with the HipHop program by screening a database containing compounds which were designed based on the known structure–activity relationship (SAR) of the diarylurea series CXCR2 antagonists. Compound 1a bearing the novel skeleton was selected from database screening and subjected to the in vitro biological test which showed a moderate CXCR2 antagonist potential. With further modification and exploration of SAR, compound 1e demonstrated improved CXCR2 antagonist activity with an IC50 value of 14.8 µM. Furthermore, wound healing assay using the NCI-H1299 cell line indicated that 1e showed an excellent anti-cancer metastatic effect (72% inhibition in cell migration at 50 µg ml−1).

Different Effects of Human Umbilical Cord Mesenchymal Stem Cells on Glioblastoma Stem Cells by Direct Cell Interaction or Via Released Soluble Factors.

Glioblastoma (GBM), the most common primary brain tumor in adults, is an aggressive, fast-growing and highly vascularized tumor, characterized by extensive invasiveness and local recurrence. In GBM and other malignancies, cancer stem cells (CSCs) are believed to drive invasive tumor growth and recurrence, being responsible for radio- and chemo-therapy resistance. Mesenchymal stem cells (MSCs) are multipotent progenitors that exhibit tropism for tumor microenvironment mediated by cytokines, chemokines and growth factors. Initial studies proposed that MSCs might exert inhibitory effects on tumor development, although, to date, contrasting evidence has been provided. Different studies reported either MSC anti-tumor activity or their support to tumor growth. Here, we examined the effects of umbilical cord (UC)-MSCs on in vitro GBM-derived CSC growth, by direct cell-to-cell interaction or indirect modulation, via the release of soluble factors. We demonstrate that UC-MSCs and CSCs exhibit reciprocal tropism when co-cultured as 3D spheroids and their direct cell interaction reduces the proliferation of both cell types. Contrasting effects were obtained by UC-MSC released factors: CSCs, cultured in the presence of conditioned medium (CM) collected from UC-MSCs, increased proliferation rate through transient ERK1/2 and Akt phosphorylation/activation. Analysis of the profile of the cytokines released by UC-MSCs in the CM revealed a strong production of molecules involved in inflammation, angiogenesis, cell migration and proliferation, such as IL-8, GRO, ENA-78 and IL-6. Since CXC chemokine receptor 2 (CXCR2), a receptor shared by several of these ligands, is expressed in GBM CSCs, we evaluated its involvement in CSC proliferation induced by UC-MSC-CM. Using the CXCR2 antagonist SB225002, we observed a partial but statistically significant inhibition of CSC proliferation and migration induced by the UC-MSC-released cytokines. Conversely, CXCR2 blockade did not reduce the reciprocal tropism between CSCs and UC-MSCs grown as spheroids. In conclusion, we show that direct (cell-to-cell contact) or indirect (via the release of soluble factors) interactions between GBM CSCs and UC-MSCs in co-culture produce divergent effects on cell growth, invasion and migration, with the former mainly causing an inhibitory response and the latter a stimulatory one, involving a paracrine activation of CXCR2.

Danirixin: A Reversible and Selective Antagonist of the CXC Chemokine Receptor 2.

CXC chemokine receptor 2 (CXCR2) is a key receptor in the chemotaxis of neutrophils to sites of inflammation. The studies reported here describe the pharmacological characterization of danirixin, a CXCR2 antagonist in the diaryl urea chemical class. Danirixin has high affinity for CXCR2, with a negative log of the 50% inhibitory concentration (pIC50) of 7.9 for binding to Chinese hamster ovary cell (CHO)-expressed human CXCR2, and 78-fold selectivity over binding to CHO-expressed CXCR1. Danirixin is a competitive antagonist against CXCL8 in Ca2+-mobilization assays, with a KB (the concentration of antagonist that binds 50% of the receptor population) of 6.5 nM and antagonist potency (pA2) of 8.44, and is fully reversible in washout experiments over 180 minutes. In rat and human whole-blood studies assessing neutrophil activation by surface CD11b expression following CXCL2 (rat) or CXCL1 (human) challenge, danirixin blocks the CD11b upregulation with pIC50s of 6.05 and 6.3, respectively. Danirixin dosed orally also blocked the influx of neutrophils into the lung in vivo in rats following aerosol lipopolysaccharide or ozone challenge, with median effective doses (ED50s) of 1.4 and 16 mg/kg respectively. Thus, danirixin would be expected to block chemotaxis in disease states in which neutrophils are increased in response to inflammation, such as pulmonary diseases. In comparison with navarixin, a CXCR2 antagonist from a different chemical class, the binding characterization of danirixin is distinct. These observations may offer insight into the previously observed clinical differences in induction of neutropenia between these compounds.

The Chemokine Receptor CXCR2 Supports Nociceptive Sensitization after Traumatic Brain Injury.

Chronic pain after traumatic brain injury (TBI) is very common, but the mechanisms linking TBI to pain and the pain-related interactions of TBI with peripheral injuries are poorly understood. Chemokine receptors play an important role in both pain and brain injury. In the current work, we pursued the hypothesis that the epigenetically regulated CXC chemokine receptor 2 (CXCR2) is a crucial modulator of nociceptive sensitization induced by TBI. For these studies, we used the rat lateral fluid percussion model of TBI. Histone actyltransferase activity was blocked using anacardic acid beginning immediately following injury, or delayed for seven days prior to administration. The selective CXCR2 antagonist SCH527123 administered systemically or intrathecally was used to probe the role of chemokine signaling on mechanical hindpaw sensitization after TBI. The expression of the CXCR2 receptor was accomplished using real-time PCR, immunohistochemistry, and Western blotting, while epigenetic regulation was assessed using chromatin immunoprecipitation assay. The spinal levels of several pain-related mediators including CXCL1, an endogenous ligand for CXCR2, as well as brain-derived neurotrophic factor and prodynorphin were measured by enzyme-linked immunosorbent assay. We observed that anacardic acid potently blocked and reversed mechanical hindpaw sensitization after TBI. The same drug was able to prevent the upregulation of CXCR2 after TBI, but did not affect the spinal expression of other pain mediators. On the other hand, both systemically and intrathecally administered SCH527123 reversed hindpaw allodynia after TBI. Most of the spinal CXCR2 appeared to be expressed by spinal cord neurons. Chromatin immunoprecipitation experiments demonstrated TBI-enhanced association of the CXCR2 promoter with acetylated-H3K9 histone protein that was also reversible using anacardic acid. Taken together, our findings suggested that TBI causes the upregulation of spinal CXCR2 through an epigenetic mechanism ultimately supporting nociceptive sensitization. The use of CXCR2 antagonists may, therefore, be useful in pain resulting from TBI.

Neutrophil elastase-induced elastin degradation mediates macrophage influx and lung injury in 60% O2-exposed neonatal rats.

Neutrophil (PMNL) influx precedes lung macrophage (LM) influx into the lung following exposure of newborn pups to 60% O2. We hypothesized that PMNL were responsible for the signals leading to LM influx. This was confirmed when inhibition of PMNL influx with a CXC chemokine receptor-2 antagonist, SB-265610, also prevented the 60% O2-dependent LM influx, LM-derived nitrotyrosine formation, and pruning of small arterioles. Exposure to 60% O2 was associated with increased lung contents of neutrophil elastase and α-elastin, a marker of denatured elastin, and a decrease in elastin fiber density. This led us to speculate that neutrophil elastase-induced elastin fragments were the chemokines that led to a LM influx into the 60% O2-exposed lung. Inhibition of neutrophil elastase with sivelestat or elafin attenuated the LM influx. Sivelestat also attenuated the 60% O2-induced decrease in elastin fiber density. Daily injections of pups with an antibody to α-elastin prevented the 60% O2-dependent LM influx, impaired alveologenesis, and impaired small vessel formation. This suggests that neutrophil elastase inhibitors may protect against neonatal lung injury not only by preventing structural elastin degradation, but also by blocking elastin fragment-induced LM influx, thus preventing tissue injury from LM-derived peroxynitrite formation.

The safety and tolerability of oral AZD5069, a selective CXCR2 antagonist, in patients with moderate-to-severe COPD

BackgroundChronic obstructive pulmonary disease (COPD) is characterized by neutrophil-dominated airway mucosal inflammation and elevated neutrophil counts in sputum and lung tissue. CXC chemokine receptor 2 (CXCR2) is predominantly expressed on neutrophils and mediates the migration of neutrophils to inflammatory sites. AZD5069 is a small molecule CXCR2 antagonist with the potential to inhibit neutrophil migration into the airways in patients with COPD. MethodsThis 4-week, randomized, double-blind, placebo-controlled, parallel-group, multi-center, Phase IIa study evaluated the safety and tolerability of AZD5069 in patients with moderate-to-severe COPD (ClinicalTrials.gov identifier: NCT01233232). The pharmacokinetics and effect of AZD5069 on blood neutrophil counts were also assessed. Patients completed daily diary cards and attended weekly clinic visits for safety assessments. Results87 patients (mean FEV1 56% pred; mean age 64 years; 69% male) were randomized to receive placebo (n = 29), AZD5069 50 mg bid (n = 30) or AZD5069 80 mg bid (n = 28) for 4 weeks. AZD5069 was well tolerated with adverse events (AEs) reported in 9 (31%), 10 (33%) and 6 (21%) patients in the placebo, AZD5069 50 mg and AZD5069 80 mg groups, respectively. AEs were generally mild or moderate in severity. The incidence of infections, the most commonly reported AE, was similar across the three groups (17%, 17% and 11% of patients in the placebo, AZD5069 50 and 80 mg groups, respectively). Blood neutrophil counts decreased on average from baseline by 14–40% and 13–36% in the AZD5069 50 mg and 80 mg groups, respectively, and 4 patients discontinued from the study due to decreased neutrophil count, 3 in the AZD5069 50 mg group and 1 in the 80 mg group. The systemic exposure (AUC and Cmax) of AZD5069 increased less than in proportion to the dose and there was a large overlap in the individual exposures between the two dose levels. ConclusionsAZD5069 was well tolerated overall in those patients who completed study treatment, with no increase in infection rates in either dosage group compared with placebo. Further studies with AZD5069 appear to be warranted.

Importance of CXC Chemokine Receptor 2 in Alveolar Neutrophil and Exudate Macrophage Recruitment in Response to Pneumococcal Lung Infection

Sustained neutrophilic infiltration is known to contribute to organ damage, such as acute lung injury. CXC chemokine receptor 2 (CXCR2) is the major receptor regulating inflammatory neutrophil recruitment in acute and chronic inflamed tissues. Whether or not the abundant neutrophil recruitment observed in severe pneumonia is essential for protective immunity against Streptococcus pneumoniae infections is incompletely defined. Here we show that CXCR2 deficiency severely perturbs the recruitment of both neutrophils and exudate macrophages associated with a massive bacterial outgrowth in distal airspaces after infection with S. pneumoniae, resulting in 100% mortality in knockout (KO) mice within 3 days. Moreover, irradiated wild-type mice reconstituted with increasing amounts of CXCR2 KO bone marrow (10, 25, 50, and 75% KO) have correspondingly decreased numbers of both neutrophils and exudate macrophages, which is associated with a stepwise increase in bacterial burden and a reciprocal stepwise decrease in survival in S. pneumoniae-induced pulmonary infection. Finally, application of the CXCR2 antagonist SB-225002 resulted in decreased alveolar neutrophil and exudate macrophage recruitment in mice along with increased lung bacterial loads after infection with S. pneumoniae. Together, these data show that CXC chemokine receptor 2 serves a previously unrecognized nonredundant role in the regulation of both neutrophil and exudate macrophage recruitment to the lung in response to S. pneumoniae infection. In addition, we demonstrate that a threshold level of 10 to 25% of reduced neutrophil recruitment is sufficient to cause increased mortality in mice infected with S. pneumoniae.