Identification of a potent, selective non-peptide CXCR2 antagonist that inhibits interleukin-8-induced neutrophil migration

Analogues of ERβ ligand chloroindazole exert immunomodulatory and remyelinating effects in a mouse model of multiple sclerosis

Pharmaceutical agents currently approved for the treatment of multiple sclerosis reduce relapse rates, but do not reverse or prevent neurodegeneration nor initiate myelin repair. The highly selective estrogen receptor (ER) β ligand chloroindazole (IndCl) shows particular promise promoting both remyelination while reducing inflammatory cytokines in the central nervous system of mice with experimental autoimmune encephalomyelitis. To optimize these benefits, we developed and screened seven novel IndCl analogues for their efficacy in promoting primary oligodendrocyte (OL) progenitor cell survival, proliferation, and differentiation in vitro by immunohistochemistry. Two analogues, IndCl-o-chloro and IndCl-o-methyl, induced proliferation and differentiation equivalent to IndCl and were selected for subsequent in vivo evaluation for their impact on clinical disease course, white matter pathology, and inflammation. Both compounds ameliorated disease severity, increased mature OLs, and improved overall myelination in the corpus callosum and white matter tracts of the spinal cord. These effects were accompanied by reduced production of the OL toxic molecules interferon-γ and chemokine (C-X-C motif) ligand, CXCL10 by splenocytes with no discernable effect on central nervous system-infiltrating leukocyte numbers, while IndCl-o-methyl also reduced peripheral interleukin (IL)−17. In addition, expression of the chemokine CXCL1, which is associated with developmental oligodendrogenesis, was upregulated by IndCl and both analogues. Furthermore, callosal compound action potential recordings from analogue-treated mice demonstrated a larger N1 component amplitude compared to vehicle, suggesting more functionally myelinated fibers. Thus, the o-Methyl and o-Chloro IndCl analogues represent a class of ERβ ligands that offer significant remyelination and neuroprotection as well as modulation of the immune system; hence, they appear appropriate to consider further for therapeutic development in multiple sclerosis and other demyelinating diseases.

Blastemal progenitors modulate immune signaling during early limb regeneration

Blastema formation, a hallmark of limb regeneration, requires proliferation and migration of progenitors to the amputation plane. Although blastema formation has been well described, the transcriptional programs that drive blastemal progenitors remain unknown. We transcriptionally profiled dividing and non-dividing cells in regenerating stump tissues, as well as the wound epidermis, during early axolotl limb regeneration. Our analysis revealed unique transcriptional signatures of early dividing cells and, unexpectedly, repression of several core developmental signaling pathways in early regenerating stump tissues. We further identify an immunomodulatory role for blastemal progenitors through interleukin 8 (IL-8), a highly expressed cytokine in subpopulations of early blastemal progenitors. Ectopic il-8 expression in non-regenerating limbs induced myeloid cell recruitment, while IL-8 knockdown resulted in defective myeloid cell retention during late wound healing, delaying regeneration. Furthermore, the il-8 receptor cxcr-1/2 was expressed in myeloid cells, and inhibition of CXCR-1/2 signaling during early stages of limb regeneration prevented regeneration. Altogether, our findings suggest that blastemal progenitors are active early mediators of immune support, and identify CXCR-1/2 signaling as an important immunomodulatory pathway during the initiation of regeneration.

L-selectin expression is regulated by CXCL8-induced reactive oxygen species produced during human neutrophil rolling

Neutrophils destroy invading microorganisms by phagocytosis by bringing them into contact with bactericidal substances, among which ROS are the most important. However, ROS also function as important physiological regulators of cellular signaling pathways. Here, we addressed the involvement of oxygen derivatives in the regulation of human neutrophil rolling, an essential component of the inflammatory response. Flow experiments using dihydroethidium-preloaded human neutrophils showed that these cells initiate an early production of intracellular ROS during the rolling phase of the adhesion cascade, a phenomenon that required cell rolling, and the interaction of the chemokine receptor CXCR2 with their ligand CXCL8. Flow cytometry experiments demonstrated that L-selectin shedding in neutrophils is triggered by ROS through an autocrine-paracrine mechanism. Preincubation of neutrophils with the NADPH oxidase complex inhibitor diphenyleniodonium chloride significantly increased the number of rolling neutrophils on endothelial cells. Interestingly, the same effect was observed when CXCL8 signaling was interfered using either a blocking monoclonal antibody or an inhibitor of its receptor. These findings indicate that, in response to CXCL8, neutrophils initiate ROS production during the rolling phase of the inflammatory response. This very early ROS production might participate in the modulation of the inflammatory response by inducing L-selectin shedding in neutrophils.

Differential Effects of Posttranslational Modifications of CXCL8/Interleukin-8 on CXCR1 and CXCR2 Internalization and Signaling Properties

CXCL8 or interleukin (IL)-8 directs neutrophil migration and activation through interaction with CXCR1 and CXCR2 that belong to the family of G protein-coupled receptors (GPCRs). Naturally occurring posttranslational modifications of the NH₂-terminal region of CXCL8 affect its biological activities, but the underlying molecular mechanisms are only partially understood. Here, we studied the implications of site-specific citrullination and truncation for the signaling potency of CXCL8. Native CXCL8(1-77), citrullinated [Cit5]CXCL8(1-77) and the major natural isoform CXCL8(6-77) were chemically synthesized and tested in internalization assays using human neutrophils. Citrullinated and truncated isoforms showed a moderately enhanced capacity to induce internalization of CXCR1 and CXCR2. Moreover, CXCL8-mediated activation of Gαi-dependent signaling through CXCR1 and CXCR2 was increased upon modification to [Cit5]CXCL8(1-77) or CXCL8(6-77). All CXCL8 variants promoted recruitment of β-arrestins 1 and 2 to CXCR1 and CXCR2. Compared to CXCL8(1-77), CXCL8(6-77) showed an enhanced potency to recruit β-arrestin 2 to both receptors, while for [Cit5]CXCL8(1-77) only the capacity to induce β-arrestin 2 recruitment to CXCR2 was increased. Both modifications had no biasing effect, i.e., did not alter the preference of CXCL8 to activate either Gαi-protein or β-arrestin-dependent signaling through its receptors. Our results support the concept that specific chemokine activities are fine-tuned by posttranslational modifications.

Angiogenic Properties of 'Leukocyte- and Platelet-Rich Fibrin'

Leukocyte- and Platelet-Rich Fibrin (L-PRF) is an autologous platelet concentrate, consisting of a fibrin matrix enriched with platelets, leukocytes and a plethora of cytokines and growth factors. Since L-PRF is produced bedside from whole blood without the use of an anti-coagulant, it is becoming a popular adjuvant in regenerative medicine. While other types of platelet concentrates have been described to stimulate blood vessel formation, little is known about the angiogenic capacities of L-PRF. Therefore, this study aimed to fully characterize the angiogenic potential of L-PRF. With an antibody array, the growth factors released by L-PRF were determined and high levels of CXC chemokine receptor 2 (CXCR-2) ligands and epidermal growth factor (EGF) were found. L-PRF induced in vitro key steps of the angiogenic process: endothelial proliferation, migration and tube formation. In addition, we could clearly demonstrate that L-PRF is able to induce blood vessel formation in vivo, the chorioallantoic membrane assay. In conclusion, we could demonstrate the angiogenic capacity of L-PRF both in vitro and in vivo, underlying the clinical potential of this easy-to-use platelet concentrate.

Involvement of Prokineticin 2-expressing Neutrophil Infiltration in 5-Fluorouracil-induced Aggravation of Breast Cancer Metastasis to Lung

Adjuvant chemotherapy is used for human breast cancer patients, even after curative surgery of primary tumor, to prevent tumor recurrence primarily as a form of metastasis. However, anticancer drugs can accelerate metastasis in several mouse metastasis models. Hence, we examined the effects of postsurgical administration with 5-fluorouracil (5-FU), doxorubicin, and cyclophosphamide, on lung metastasis process, which developed after the resection of the primary tumor arising from the orthotopic injection of a mouse triple-negative breast cancer cell line, 4T1. Only 5-FU markedly increased the numbers and sizes of lung metastasis foci, with enhanced tumor cell proliferation and angiogenesis as evidenced by increases in Ki67-positive cell numbers and CD31-positive areas, respectively. 5-FU-mediated augmented lung metastasis was associated with increases in intrapulmonary neutrophil numbers and expression of neutrophilic chemokines, Cxcl1 and Cxcl2 in tumor cells, with few effects on intrapulmonary T-cell or macrophage numbers. 5-FU enhanced Cxcl1 and Cxcl2 expression in 4T1 cells in a NFκB-dependent manner. Moreover, the administration of a neutrophil-depleting antibody or a Cxcr2 antagonist, SB225002, significantly attenuated 5-FU-mediated enhanced lung metastasis with depressed neutrophil infiltration. Furthermore, infiltrating neutrophils and 4T1 cells abundantly expressed prokineticin-2 (Prok2) and its receptor, Prokr1, respectively. Finally, the administration of 5-FU after the resection of the primary tumor failed to augment lung metastasis in the mice receiving Prokr1-deleted 4T1 cells. Collectively, 5-FU can enhance lung metastasis by inducing tumor cells to produce Cxcl1 and Cxcl2, which induced the migration of neutrophils expressing Prok2 with a capacity to enhance 4T1 cell proliferation. Mol Cancer Ther; 17(7); 1515-25. ©2018 AACR.

Therapeutic inhibition of CXC chemokine receptor 2 by SB225002 attenuates LPS-induced acute lung injury in mice

INTRODUCTION

Sustained neutrophilic infiltration is known to contribute to organ damage, such as acute lung injury (ALI). CXC chemokine receptor 2 (CXCR2) is the major receptor regulating inflammatory neutrophil recruitment in acute and chronic inflamed tissues. The purpose of this study was to investigate the functional relevance of the CXCR2 inhibitor SB225002 in LPS-induced acute lung injury.

MATERIAL AND METHODS

Male C57BL/6 mice were randomly divided into the following four experimental groups (n = 10 per group): untreated group (control group, Ctr); LPS-treated ALI group (LPS group, LPS); LPS + PBS-treated group (LPS + PBS); and SB225002-treated ALI group (LPS + SB225002). Twenty-four hours after treatment, the blood, bronchoalveolar lavage fluid (BALF), and lung tissue were collected and wet/dry ratio, protein concentration, myeloperoxidase (MPO) activity, neutrophil infiltration, and inflammatory cytokine secretion in lung tissue were measured. The pathologic changes in the lungs were examined using optical microscopy. Survival rates were recorded at 120 h in all four groups, in other experiments.

RESULTS

Histology findings revealed that the SB225002-treated group had significantly milder lung injury compared to the LPS-induced ALI and the PBS-treated control groups. Treatment with SB225002 significantly attenuated LPS-induced lung injury and suppressed the inflammatory responses in damaged lung tissue. Compared to the PBS-treated control group, treatment with SB225002 dramatically decreased the lung wet/dry ratio, protein concentration, and infiltration of neutrophils in lung tissue. Therefore, SB225002 treatment appeared to inhibit the production of inflammatory cytokines and increase survival time compared to the PBS-treated control group.

CONCLUSIONS

Together, these data demonstrated that inhibition of CXCR2 signaling by SB225002 could ameliorate LPS-induced acute lung injury, by reducing neutrophil recruitment and vascular permeability. SB225002 may be further developed as a potential novel treatment for LPS-induced ALI.

Tumor conditions induce bone marrow expansion of granulocytic, but not monocytic, immunosuppressive leukocytes with increased CXCR2 expression in mice

Myeloid-derived suppressor cells (MDSCs) promote tumor growth through, in part, inhibiting T-cell immunity. However, mechanisms underlying MDSC expansion and guidance of MDSCs toward the tumor microenvironment remain unclear. Employing Percoll density gradients, we separate bone marrow (BM) leukocytes from tumor-bearing mice into four density-increasing bands with myeloid leukocytes enriched in bands III and IV. Band III comprises monocytes and low-density granulocytes, both confirmed to be M-MDSCs and G-MDSCs, respectively, by displaying potent inhibition of T-cell proliferation. However, monocytes act as M-MDSCs not only under tumor conditions but also the healthy condition. In contrast, band IV contains non-inhibitory, mature granulocytes. Only band III G-MDSCs display significant expansion in mice bearing B16 melanoma, Lewis lung carcinoma, or MC38 colon carcinoma. The expanded G-MDSCs also show increased CXCR2 expression, which guides egress out of BM, and produce arginase-1 and ROS upon encountering antigen-activated T cells. Adoptive transfer assays demonstrate that both G-MDSCs and mature granulocytes infiltrate tumors, but only the former displays sustention and accumulation. Intratumoral administrations of granulocytes further demonstrate that G-MDSCs promote tumor growth, whereas mature granulocytes exert minimal effects, or execute powerful anti-tumor effects providing the presence of PMN activation mechanisms in the tumor microenvironment.

Small molecule screen in embryonic zebrafish using modular variations to target segmentation

Small molecule in vivo phenotypic screening is used to identify drugs or biological activities by directly assessing effects in intact organisms. However, current screening designs may not exploit the full potential of chemical libraries due to false negatives. Here, we demonstrate a modular small molecule screen in embryonic zebrafish that varies concentration, genotype and timing to target segmentation disorders, birth defects that affect the spinal column. By testing each small molecule in multiple interrelated ways, this screen recovers compounds that a standard screening design would have missed, increasing the hit frequency from the chemical library three-fold. We identify molecular pathways and segmentation phenotypes, which we share in an open-access annotated database. These hits provide insight into human vertebral segmentation disorders and myopathies. This modular screening strategy is applicable to other developmental questions and disease models, highlighting the power of relatively small chemical libraries to accelerate gene discovery and disease study.

Developmental Vitamin D Availability Impacts Hematopoietic Stem Cell Production

Vitamin D insufficiency is a worldwide epidemic affecting billions of individuals, including pregnant women and children. Despite its high incidence, the impact of active vitamin D3 (1,25(OH)D3) on embryonic development beyond osteo-regulation remains largely undefined. Here, we demonstrate that 1,25(OH)D3 availability modulates zebrafish hematopoietic stem and progenitor cell (HSPC) production. Loss of Cyp27b1-mediated biosynthesis or vitamin D receptor (VDR) function by gene knockdown resulted in significantly reduced runx1 expression and Flk1+cMyb+ HSPC numbers. Selective modulation in vivo and in vitro in zebrafish indicated that vitamin D3 acts directly on HSPCs, independent of calcium regulation, to increase proliferation. Notably, ex vivo treatment of human HSPCs with 1,25(OH)D3 also enhanced hematopoietic colony numbers, illustrating conservation across species. Finally, gene expression and epistasis analysis indicated that CXCL8 (IL-8) was a functional target of vitamin D3-mediated HSPC regulation. Together, these findings highlight the relevance of developmental 1,25(OH)D3 availability for definitive hematopoiesis and suggest potential therapeutic utility in HSPC expansion.

Microtubule Depolymerization by Kinase Inhibitors: Unexpected Findings of Dual Inhibitors

Microtubule-targeting agents are widely used as clinical drugs in the treatment of cancer. However, some kinase inhibitors can also disrupt microtubule organization by directly binding to tubulin. These unexpected effects may result in a plethora of harmful events and/or a misinterpretation of the experimental results. Thus, further studies are needed to understand these dual inhibitors. In this review, I discuss the roles of dual inhibitors of kinase activity and microtubule function as well as describe the properties underlining their dual roles. Since both kinase and microtubule inhibitors cause cell toxicity and cell cycle arrest, it is difficult to determine which inhibitor is responsible for each phenotype. A discrimination of cell cycle arrest at G0/G1 or G2/M and/or image analyses of cellular phenotype may eventually lead to new insights on drug duality. Because of the indispensable roles of microtubules in mitosis and vesicle transport, I propose a simple and easy method to identify microtubule depolymerizing compounds.

Dysregulated Chemokine Signaling in Cystic Fibrosis Lung Disease: A Potential Therapeutic Target

CF lung disease is characterized by a chronic and non-resolving activation of the innate immune system with excessive release of chemokines/cytokines including IL-8 and persistent infiltration of immune cells, mainly neutrophils, into the airways. Chronic infection and impaired immune response eventually lead to pulmonary damage characterized by bronchiectasis, emphysema, and lung fibrosis. As a complete knowledge of the pathways responsible for the exaggerated inflammatory response in CF lung disease is lacking, understanding these pathways could reveal new therapeutic targets, and lead to novel treatments. Therefore, there is a strong rationale for the identification of mechanisms and pathways underlying the exaggerated inflammatory response in CF lung disease. This article reviews the role of inflammation in the pathogenesis of CF lung disease, with a focus on the dysregulated signaling involved in the overexpression of chemokine IL-8 and excessive recruitment of neutrophils in CF airways. The findings suggest that targeting the exaggerated IL-8/IL-8 receptor (mainly CXCR2) signaling pathway in immune cells (especially neutrophils) may represent a potential therapeutic strategy for CF lung disease.

The Matrikine Acetylated Proline-Glycine-Proline Couples Vascular Inflammation and Acute Cardiac Rejection

The extracellular matrix (ECM) is a dynamic, bioactive structure critical to organ development, structure and function. Excessive remodeling of the ECM is a hallmark of a variety of inflammatory conditions including vascular disease. Endothelin-1 (ET1) synthesis is understood to promote cardiovascular diseases including acute cardiac transplant rejection; however, the contribution of ECM-derived chemokines (matrikines) to vascular inflammation remains poorly understood. Herein we report that the matrikine acetylated Pro-Gly-Pro (PGP) stimulates vascular inflammation through activation of endothelial CXC Chemokine Receptor 2 (CXCR2) and production of endothelin-1 both in vitro and in vivo. As a proof of hypothesis, we demonstrate that coronary PGP levels associate with both circulating endothelin-1 and acute rejection in cardiac transplant patients (sensitivity of 100% and specificity of 86%). These findings establish PGP as a novel mediator in cardiovascular disease, and implicate bioactive matrix fragments as underappreciated agents potentially active in numerous conditions propagated by progressive vascular inflammation.

Host non-inflammatory neutrophils mediate the engraftment of bioengineered vascular networks

Notwithstanding remarkable progress in vascular network engineering, implanted bioengineered microvessels largely fail to form anastomoses with the host vasculature. Here, we demonstrate that implants containing assembled human vascular networks (A-Grafts) fail to engraft due to their inability to engage non-inflammatory host neutrophils upon implantation into mice. In contrast, unassembled vascular cells (U-Grafts) readily engage alternatively polarized neutrophils, which in turn serve as indispensable mediators of vascular assembly and anastomosis. The depletion of host neutrophils abrogated vascularization in U-Grafts, whereas an adoptive transfer of neutrophils fully restored vascularization in myeloid-depleted mice. Neutrophil engagement was regulated by secreted factors and was progressively silenced as the vasculature matured. Exogenous addition of factors from U-Grafts reengaged neutrophils and enhanced revascularization in A-Grafts, a process that was recapitulated by blocking Notch signaling. Our data suggest that the pro-vascularization potential of neutrophils can be harnessed to improve the engraftment of bioengineered tissues.

Sex-Dependent Glial Signaling in Pathological Pain: Distinct Roles of Spinal Microglia and Astrocytes

Increasing evidence suggests that spinal microglia regulate pathological pain in males. In this study, we investigated the effects of several microglial and astroglial modulators on inflammatory and neuropathic pain following intrathecal injection in male and female mice. These modulators were the microglial inhibitors minocycline and ZVEID (a caspase-6 inhibitor) and the astroglial inhibitors L-α-aminoadipate (L-AA, an astroglial toxin) and carbenoxolone (a connexin 43 inhibitor), as well as U0126 (an ERK kinase inhibitor) and D-JNKI-1 (a c-Jun N-terminal kinase inhibitor). We found that spinal administration of minocycline or ZVEID, or Caspase6 deletion, reduced formalin-induced inflammatory and nerve injury-induced neuropathic pain primarily in male mice. In contrast, intrathecal L-AA reduced neuropathic pain but not inflammatory pain in both sexes. Intrathecal U0126 and D-JNKI-1 reduced neuropathic pain in both sexes. Nerve injury caused spinal upregulation of the astroglial markers GFAP and Connexin 43 in both sexes. Collectively, our data confirmed male-dominant microglial signaling but also revealed sex-independent astroglial signaling in the spinal cord in inflammatory and neuropathic pain.

Cxcl8b and Cxcr2 Regulate Neutrophil Migration through Bloodstream in Zebrafish

Neutrophils play an essential role during an inflammatory response, which is dependent on their rapid recruitment from the bone marrow to the vasculature. However, there is no information about the molecular signals that regulate neutrophil entry to circulation during an inflammatory process in humans. This is mainly due to the lack of a suitable model of study that contains similar set of molecules and that allows in vivo analyses. In this study, we used the zebrafish to assess the role of Cxcl8a, Cxcl8b, and Cxcr2 in neutrophil migration to blood circulation after injury. Using Tg(BACmpx:GFP)ⁱ¹¹⁴ transgenic embryos and two damage models (severe and mild), we developed in vivo lack of function assays. We found that the transcription levels of cxcl8a, cxcl8b, and cxcr2 were upregulated in the severe damage model. In contrast, only cxcr2 and cxcl8a mRNA levels were increased during mild damage. After knocking down Cxcl8a, neutrophil quantity decreased at the injury site, while Cxcl8b decreased neutrophils in circulation. When inhibiting Cxcr2, we observed a decrease in neutrophil entry to the bloodstream. In conclusion, we identified different functions for both Cxcl8 paralogues, being the Cxcl8b/Cxcr2 axis that regulates neutrophil entry to the bloodstream, while Cxcl8a/Cxcr2 regulates the migration to the affected area.

Chemokine Signaling and the Regulation of Bidirectional Leukocyte Migration in Interstitial Tissues

Motile cells navigate through complex tissue environments that include both attractive and repulsive cues. In response to tissue wounding, neutrophils, primary cells of the innate immune response, exhibit bidirectional migration that is orchestrated by chemokines and their receptors. Although progress has been made in identifying signals that mediate the recruitment phase, the mechanisms that regulate neutrophil reverse migration remain largely unknown. Here, we visualize bidirectional neutrophil migration to sterile wounds in zebrafish larvae and identify specific roles for the chemokine receptors Cxcr1 and Cxcr2 in neutrophil recruitment to sterile injury and infection. Notably, we also identify Cxcl8a/Cxcr2 as a specific ligand-receptor pair that orchestrates neutrophil chemokinesis in interstitial tissues during neutrophil reverse migration and resolution of inflammation. Taken together, our findings identify distinct receptors that mediate bidirectional leukocyte motility during interstitial migration depending on the context and type of tissue damage in vivo.

Adiponectin promotes human jaw bone marrow mesenchymal stem cell chemotaxis via CXCL1 and CXCL8

Adiponectin (APN) is known to promote the osteogenic differentiation of human jaw bone marrow mesenchymal stem cells (h‐JBMMSCs). However, the underlying mechanism has not been fully elucidated. Previously, we showed that APN could promote h‐JBMMSC osteogenesis via APPL1‐p38 by up‐regulating osteogenesis‐related genes. Here, we aimed to determine whether APN could promote h‐JBMMSC chemotaxis through CXCL1/CXCL8. The CCK‐8, wound healing and transwell assays were used to evaluate the proliferation, migration and chemotaxis of h‐JBMMSCs with or without APN treatment. Chemotaxis‐related genes were screened using RNA‐seq, and the results were validated using real‐time PCR and ELISA. We also performed Western blot using the AMPK inhibitor, WZ4003, and the p38 MAPK inhibitor, SB203580, to identify the signalling pathway involved. We found that APN could promote h‐JBMMSC chemotaxis in the co‐culture transwell system. CXCL1 and CXCL8 were screened and confirmed as the up‐regulated target genes. The APN‐induced CXCL1/8 up‐regulation to promote chemotaxis could be blocked by CXCR2 inhibitor SB225002. Western blot revealed that the phosphorylation of AMPK and p38 MAPK increased in a time‐dependent manner with APN treatment. Additionally, WZ4003 and SB203580 could suppress the APN‐induced overexpression of CXCL1 and CXCL8. The results of the transwell chemotaxis assay also supported the above results. Our data suggest that APN can promote h‐JBMMSC chemotaxis by up‐regulating CXCL1 and CXCL8.

Upregulation of TH/IL-17 Pathway-Related Genes in Human Coronary Endothelial Cells Stimulated with Serum of Patients with Acute Coronary Syndromes

Background

Inflammation plays an essential role in the development and complications of atherosclerosis plaques, including acute coronary syndromes (ACS). Indeed, previous reports have shown that within the coronary circulation of ACS patients, several soluble mediators are released. Moreover, it has been demonstrated that endothelial dysfunction might play an important role in atherosclerosis as well as ACS pathophysiology. However, the mechanisms by which these soluble mediators might affect endothelial functions are still largely unknown. We have evaluated whether soluble mediators contained in serum from coronary circulation of ACS patients might promote changes of gene profile in human coronary endothelial cells (HCAECs).

Methods

HCAECs were stimulated in vitro for 12 h with serum obtained from the coronary sinus (CS) and the aorta (Ao) of ACS patients; stable angina (SA) patients served as controls. Gene expression profiles of stimulated cells were evaluated by microarray and real-time PCR.

Results

HCAECs stimulated with serum from CS of ACS patients showed a significant change (upregulation and downregulation) in gene expression profile as compared with cells stimulated with serum from CS of SA patients. Moreover, ad hoc sub analysis indicated the upregulation of Th-17/IL-17 pathway-related genes.

Conclusion

This study demonstrates that, in ACS patients, the chemical mediators released in the coronary circulation might be able to perturb coronary endothelial cells (ECs) modifying their gene profile. These modified ECs, through downregulation of protective gene and, mainly, through upregulation of gene able to modulate the Th-17/IL-17 pathway, might play a key role in progression of coronary atherosclerosis and in developing future acute events.

The inflammatory chemokine Cxcl18b exerts neutrophil-specific chemotaxis via the promiscuous chemokine receptor Cxcr2 in zebrafish

Cxcl18b is a chemokine found in zebrafish and in other piscine and amphibian species. Cxcl18b is a reliable inflammatory marker; however, its function is yet to be elucidated. Here, we found that Cxcl18b is chemotactic towards neutrophils, similarly to Cxcl8a/Interleukin-8, the best characterised neutrophil chemoattractant in humans and teleosts. Like Cxcl8a, Cxcl18b-dependent recruitment required the chemokine receptor Cxcr2, while it was unaffected by depletion of the other two neutrophil receptors cxcr1 and cxcr4b. To visualise cxcl18b induction, we generated a Tg(cxcl18b:eGFP) reporter line. The transgene is induced locally upon bacterial infection with the fish pathogen Mycobacterium marinum, but strikingly is not directly expressed by infected cells. Instead, cxcl18b is induced by non-phagocytic uninfected cells that compose the stroma of the granulomas, typical inflammatory lesions formed upon mycobacterial infections. Together, these results suggest that Cxcl18b might be an important contributor to neutrophil chemotaxis in the inflammatory microenvironment and indicate that the zebrafish model could be explored to further investigate in vivo the biological relevance of different Cxcl8-like chemokine lineages.

Downregulation of transgelin blocks interleukin-8 utilization and suppresses vasculogenic mimicry in breast cancer cells

Vasculogenic mimicry (VM) is a non-classical mechanism recently described in many tumors, whereby cancer cells, rather than endothelial cells, form blood vessels. Transgelin is an actin-binding protein that has been implicated in multiple stages of cancer development. In this study, we investigated the role of transgelin in VM and assessed its effect on the expression of endothelial and angiogenesis-related genes during VM in MDA-MB-231 breast cancer cells. We confirmed the ability of MDA-MB-231 cells to undergo VM through a tube formation assay. Flow cytometry analysis revealed an increase in the expression of the endothelial-related markers VE-cadherin and CD34 in cells that underwent VM, compared with those growing in a monolayer, which was confirmed by immunocytochemistry. We employed siRNA to silence transgelin, and knockdown efficiency was determined by western blot analyses. Downregulation of transgelin suppressed cell proliferation and tube formation, but increased IL-8 levels in Matrigel cultures. RT-PCR analyses revealed that the expression of IL-8, VE-cadherin, and CD34 was unaffected by transgelin knockdown, indicating that increased IL-8 expression was not due to enhanced transcriptional activity. More importantly, the inhibition of IL-8/CXCR2 signaling also resulted in suppression of VM with increased IL-8 levels, confirming that increased IL-8 levels after transgelin knockdown was due to inhibition of IL-8 uptake. Our findings indicate that transgelin regulates VM by enhancing IL uptake. These observations are relevant to the future development of efficient antivascular agents. Impact statement Vasculogenic mimicry (VM) is an angiogenic-independent mechanism of blood vessel formation whereby aggressive tumor cells undergo formation of capillary-like structures. Thus, interventions aimed at angiogenesis might not target the entire tumor vasculature. A more holistic approach is therefore needed in the development of improved antivascular agents. Transgelin, an actin-binding protein, has been associated with multiple stages of cancer development such as proliferation, migration and invasion, but little is known about its role in vasculogenic mimicry. We present here, an additional mechanism by which transgelin promotes malignancy by way of its association with the occurrence of VM. Although transgelin knockdown did not affect the transcript levels of most of the angiogenesis-related genes in this study, it was associated with the inhibition of the uptake of IL-8, accompanied by suppressed VM, indicating that transgelin is required for VM. These observations are relevant to the future development of efficient antivascular agents.

Modulation of infection-mediated migration of neutrophils and CXCR2 trafficking by osteopontin

Osteopontin (OPN) is a pro-inflammatory protein that paradoxically protects against inflammation and bone destruction in a mouse model of endodontic infection. Here we have tested the hypothesis that this effect of OPN is mediated by effects on migration of innate immune cells to the site of infection. Using the air pouch as a model of endodontic infection in mice, we showed that neutrophil accumulation at the site of infection with a mixture of endodontic pathogens is significantly reduced in OPN-deficient mice. Reduced neutrophil accumulation in the absence of OPN was accompanied by an increase in bacterial load. OPN-deficiency did not affect neutrophil survival, CXCR2 ligand expression, or the production of inflammatory cytokines in the air pouch. In vitro, OPN enhanced neutrophil migration to CXCL1, whereas in vivo, inhibition of CXCR2 suppressed cellular infiltration in air pouches of infected wild-type mice by > 50%, but had no effect in OPN-deficient mice. OPN increased cell surface expression of CXCR2 on bone marrow neutrophils in an integrin-α_v -dependent manner, and suppressed the internalization of CXCR2 in the absence of ligand. Together, these results support a model where the protective effect of OPN results from enhanced initial neutrophil accumulation at sites of infection resulting in optimal bacterial killing. We describe a novel mechanism for this effect of OPN: integrin-α_v -dependent suppression of CXCR2 internalization in neutrophils, which increases the ability of these cells to migrate to sites of infection in response to CXCR2 ligands.

Cellular Dielectric Spectroscopy: A Label-Free Technology for Drug Discovery

Cellular dielectric spectroscopy (CDS) provides realtime, label-free, universal measurements, enabling comprehensive pharmacological evaluation of cell surface receptors in living cells. The sensitivity of the measurement allows monitoring of ligand-mediated activation of endogenous receptors, therefore generating physiologically relevant data. Activation of receptors results in CDS response profiles that are characteristic of main subsets of G-protein coupled receptors (GPCRs) within a cell line. This allows cluster analysis of response profiles that may be used in several important applications, which include identification of the G-protein coupling of orphan GPCRs and the cataloging of active endogenous receptors in cells. In this study, CDS technology is used in the pharmacological evaluation of multiple receptors in many cell types, including primary cells. Specifically, data is presented demonstrating hit confirmation, receptor selectivity analysis, ligand potency, and Schild analysis of receptor-selective antagonists. CDS results compare favorably to other cell-based assays, and the robustness and reproducibility of CDS assays are reflected by low assay coefficient of variation (CVs) and reliable Z'-scores of the data. Because CDS requires no stable or transiently transfected cells or special reagents, assay development and data acquisition is simple and fast. The ease of use, universality, and label-free nature of the CDS-based platform make it well suited to secondary screening applications in drug discovery.

HIV infection-induced transcriptional program in renal tubular epithelial cells activates a CXCR2-driven CD4+ T-cell chemotactic response

OBJECTIVE

Viral replication and interstitial inflammation play important roles in the pathogenesis of HIV-associated nephropathy. Cell-cell interactions between renal tubule epithelial cells (RTECs) and HIV-infected T cells can trigger efficient virus internalization and viral gene expression by RTEC. To understand how HIV replication initiates HIV-associated nephropathy, we studied the cellular response of RTECs to HIV, examining the transcriptional profiles of primary RTECs exposed to cell-free HIV or HIV-infected T cells.

METHODS

HIV-induced gene expression in hRTECs was examined in vitro by Illumina RNA deep sequencing and revealed an innate response to HIV, which was subclassified by gene ontology biological process terms. Chemokine responses were examined by CD4 T-cell chemotaxis assays.

RESULTS

As compared with cell-free virus infection, exposure to HIV-infected T cells elicited a stronger upregulation of inflammatory and immune response genes. A major category of upregulated genes are chemokine/cytokine families involved in inflammation and immune response, including inflammatory cytokines CCL20, IL6 and IL8-related chemokines: IL8, CXCL1, CXCL2, CXCL3, CXCL5 and CXCL6. Supernatants from virus-exposed RTECs contained strong chemoattractant activity on primary CD4 T cells, which was potently blocked by a CXCR2 antagonist that antagonizes IL8-related chemokines. We observed a preferential migration of CXCR2-expressing, central memory CD4 T cells in response to HIV infection of RTECs.

CONCLUSION

Interactions between primary RTECs and HIV-infected T cells result in potent induction of inflammatory response genes and release of cytokines/chemokines from RTECs that can attract additional T cells. Activation of these genes reflects an innate response to HIV by nonimmune cells.

PLAG (1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol) augments the therapeutic effect of pegfilgrastim on gemcitabine-induced neutropenia

Granulocyte colony-stimulating factor (G-CSF) is widely used for preventing neutropenia during chemotherapy. Polyethylene glycol-conjugated granulocyte colony-stimulating factor (PEG-G-CSF, pegfilgrastim) serves the same purpose but has a longer half-life and greater stability than G-CSF. In this study, we investigated whether 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol, acetylated diglyceride (PLAG), augments the therapeutic effect of pegfilgrastim on chemotherapy-induced neutropenia. We compared neutrophil counts in four groups of mice: control mice, gemcitabine-treated mice, gemcitabine/pegfilgrastim-treated mice, and gemcitabine/pegfilgrastim/PLAG-treated mice. PLAG (50 mg/kg) was orally administered every day during the treatment course. CBC analysis showed that the group treated with PLAG experienced a dramatically increased neutrophil counts on the third day following pegfilgrastim treatment. PLAG had no effect on blood cell apoptosis and neutrophil release from bone marrow. Additionally, pegfilgrastim-induced CXCR2 expression in neutrophils was markedly decreased in PLAG-treated animals. These results suggest that PLAG plays a role in inhibiting neutrophil extravasation, giving rise to an increased number of circulating neutrophils when used with pegfilgrastim during gemcitabine treatment. These data support the potential for PLAG to be used with pegfilgrastim to treat or prevent chemotherapy-induced neutropenia by modulating neutrophil transmigration.

Periprostatic adipocytes act as a driving force for prostate cancer progression in obesity

Obesity favours the occurrence of locally disseminated prostate cancer in the periprostatic adipose tissue (PPAT) surrounding the prostate gland. Here we show that adipocytes from PPAT support the directed migration of prostate cancer cells and that this event is strongly promoted by obesity. This process is dependent on the secretion of the chemokine CCL7 by adipocytes, which diffuses from PPAT to the peripheral zone of the prostate, stimulating the migration of CCR3 expressing tumour cells. In obesity, higher secretion of CCL7 by adipocytes facilitates extraprostatic extension. The observed increase in migration associated with obesity is totally abrogated when the CCR3/CCL7 axis is inhibited. In human prostate cancer tumours, expression of the CCR3 receptor is associated with the occurrence of aggressive disease with extended local dissemination and a higher risk of biochemical recurrence, highlighting the potential benefit of CCR3 antagonists in the treatment of prostate cancer.

The CXCR1/2 Pathway: Involvement in Diabetes Pathophysiology and Potential Target for T1D Interventions

Although numerous chemokine/chemokine receptor pathways have been described to be implicated in the pathogenesis of type 1 diabetes (T1D), the CXCR1/2 axis has recently been proved to be crucial for leucocyte recruitment involved in insulitis and β cell damage. Multiple strategies blocking the CXCR1/2 pathway are available such as neutralizing antibodies, small molecules and peptide-derived inhibitors. They were firstly and widely used in cancer thanks to their anti-tumorigenic activity and only recently they were tested as a new interventional approach for T1D. As well, CXCR1/2 inhibition has been demonstrated to prevent inflammation- and autoimmunity-mediated damage of the pancreatic islets through inhibiting the migration of CXCR1/2-expressing cells. Among them, neutrophils, macrophages, and, although to a smaller extent, lymphoid cells are the main CXCR1/2-expressing cells. These results supported the active role of the innate immunity in the autoimmune process and opened new interventional approaches for the management of T1D.

SB225002 Induces Cell Death and Cell Cycle Arrest in Acute Lymphoblastic Leukemia Cells through the Activation of GLIPR1

Acute Lymphoblastic Leukemia (ALL) is the most frequent childhood malignancy. In the effort to find new anti-leukemic agents, we evaluated the small drug SB225002 (N-(2-hydroxy-4-nitrophenyl)-N’-(2-bromophenyl)urea). Although initially described as a selective antagonist of CXCR2, later studies have identified other cellular targets for SB225002, with potential medicinal use in cancer. We found that SB225002 has a significant pro-apoptotic effect against both B- and T-ALL cell lines. Cell cycle analysis demonstrated that treatment with SB225002 induces G2-M cell cycle arrest. Transcriptional profiling revealed that SB225002-mediated apoptosis triggered a transcriptional program typical of tubulin binding agents. Network analysis revealed the activation of genes linked to the JUN and p53 pathways and inhibition of genes linked to the TNF pathway. Early cellular effects activated by SB225002 included the up-regulation of GLIPR1, a p53-target gene shown to have pro-apoptotic activities in prostate and bladder cancer. Silencing of GLIPR1 in B- and T-ALL cell lines resulted in increased resistance to SB225002. Although SB225002 promoted ROS increase in ALL cells, antioxidant N-Acetyl Cysteine pre-treatment only modestly attenuated cell death, implying that the pro-apoptotic effects of SB225002 are not exclusively mediated by ROS. Moreover, GLIPR1 silencing resulted in increased ROS levels both in untreated and SB225002-treated cells. In conclusion, SB225002 induces cell cycle arrest and apoptosis in different B- and T-ALL cell lines. Inhibition of tubulin function with concurrent activation of the p53 pathway, in particular, its downstream target GLIPR1, seems to underlie the anti-leukemic effect of SB225002.

Boronic acid-containing CXCR1/2 antagonists: Optimization of metabolic stability, in vivo evaluation, and a proposed receptor binding model

Blockade of undesired neutrophil migration to sites of inflammation remains an area of substantial pharmaceutical interest. To effect this blockade, a validated therapeutic target is antagonism of the chemokine receptor CXCR2. Herein we report the discovery of 6-(2-boronic acid-5-trifluoromethoxy-benzylsulfanyl)-N-(4-fluoro-phenyl)-nicotinamide 6, an antagonist with activity at both CXCR1 and CXCR2 receptors (IC50 values 31 and 21 nM, respectively). Compound 6 exhibited potent inhibition of neutrophil influx in a rat model of pulmonary inflammation, and is hypothesized to interact with a unique intracellular binding site on CXCR2. Compound 6 (SX-576) is undergoing further investigation as a potential therapy for pulmonary inflammation.

Macrophages and β-cells are responsible for CXCR2-mediated neutrophil infiltration of the pancreas during autoimmune diabetes

Autoimmune type 1 diabetes (T1D) development results from the interaction between pancreatic β-cells, and the innate and the adaptive immune systems culminating with the destruction of the insulin-secreting β-cells by autoreactive T cells. This diabetogenic course starts during the first postnatal weeks by the infiltration of the pancreatic islets by innate immune cells and particularly neutrophils. Here, we aim to determine the cellular and molecular mechanism leading to the recruitment of this neutrophils in the pancreatic islets of non-obese diabetic (NOD) mice. Here, we show that neutrophil recruitment in the pancreatic islets is controlled by inflammatory macrophages and β-cells themselves. Macrophages and β-cells produce the chemokines CXCL1 and CXCL2, recruiting CXCR2-expressing neutrophils from the blood to the pancreatic islets. We further show that pancreatic macrophages secrete IL-1β-inducing CXCR2 ligand production by the β-cells. Finally, the blockade of neutrophil recruitment at early ages using CXCR2 antagonist dampens the diabetogenic T-cell response and the later development of autoimmune diabetes, supporting the therapeutic potential of this approach.

Subject Categories Immunology; Metabolism

The matrikine N-α-PGP couples extracellular matrix fragmentation to endothelial permeability

The compartmentalization and transport of proteins and solutes across the endothelium is a critical biologic function altered during inflammation and disease, leading to pathology in multiple disorders. The impact of tissue damage and subsequent extracellular matrix (ECM) fragmentation in regulating this process is unknown. We demonstrate that the collagen-derived matrikine acetylated proline-glycine-proline (N-α-PGP) serves as a critical regulator of endothelial permeability. N-α-PGP activates human endothelial cells via CXC-chemokine receptor 2 (CXCR2), triggering monolayer permeability through a discrete intracellular signaling pathway. In vivo, N-α-PGP induces local vascular leak after subcutaneous administration and pulmonary vascular permeability after systemic administration. Furthermore, neutralization of N-α-PGP attenuates lipopolysaccharide-induced lung leak. Finally, we demonstrate that plasma from patients with acute respiratory distress syndrome (ARDS) induces VE-cadherin phosphorylation in human endothelial cells, and this activation is attenuated by N-α-PGP blockade with a concomitant improvement in endothelial monolayer impedance. These results identify N-α-PGP as a novel ECM-derived matrikine regulating paracellular permeability during inflammatory disease and demonstrate the potential to target this ligand in various disorders characterized by excessive matrix turnover and vascular leak such as ARDS.

A novel phenylcyclohex-1-enecarbothioamide derivative inhibits CXCL8-mediated chemotaxis through selective regulation of CXCR2-mediated signalling

BACKGROUND AND PURPOSE

Since the CXC chemokine receptor CXCR2 and its cognate ligand CXCL8 (IL-8) critically regulate neutrophil trafficking during inflammation, they have been implicated in a number of inflammatory lung diseases. Several CXCR2 antagonists have been described and the blockade of CXCR2 has shown promise in pre-clinical disease models and early clinical trials. However, given its potential, there are fewer distinct classes of antagonists of CXCR2 than of other clinically relevant molecular targets. Thus, we sought to identify additional classes of compounds that alter CXCR2 function.

EXPERIMENTAL APPROACH

We used the CXCR2 Tango(TM) assay to screen an in-house library of highly diverse chemical compounds. CX4338 [2-(benzylamino)-4,4-dimethyl-6-oxo-N-phenylcyclohex-1-enecarbothioamide] was identified from our screen and additional studies to characterize the compound were performed. Receptor internalization and second-messenger assays were used to assess the effects of CX4338 on CXCR2-mediated signalling. Wound healing, transwell cell migration and LPS-induced lung inflammation in mice were used to determine the in vitro and in vivo effects of CX4338.

KEY RESULTS

CX4338 selectively inhibited CXCR2-mediated recruitment of β-arrestin-2 and receptor internalization, while enhancing CXCR2-mediated MAPK activation. Additionally, CX4338 inhibited CXCL8-induced chemotaxis in CXCR2-overexpressing cells and human neutrophils. In vivo, CX4338 significantly reduced neutrophils in bronchoalveolar lavage induced by LPS in mice.

CONCLUSIONS AND IMPLICATIONS

A novel compound CX4338 inhibited CXCR2-mediated cell migration with a mechanism of action not previously reported. Also, selective inhibition of CXCR2-mediated β-arrestin-2 activation is sufficient to inhibit CXCL8-mediated chemotaxis.

Nucleotide receptors control IL-8/CXCL8 and MCP-1/CCL2 secretions as well as proliferation in human glioma cells

Glioma cells release cytokines to stimulate inflammation that facilitates cell proliferation. Here, we show that Lipopolysaccharide (LPS) treatment could induce glioma cells to proliferate and this process was dependent on nucleotide receptor activation as well as interleukin-8 (IL-8/CXCL8) secretion. We observed that extracellular nucleotides controlled IL-8/CXCL8 and monocyte chemoattractant protein 1 (MCP-1/CCL2) release by U251MG and U87MG human glioma cell lines via P2X7 and P2Y6 receptor activation. The LPS-induced release of these cytokines was also modulated by purinergic receptor activation since IL-8 and MCP-1 release was decreased by the nucleotide scavenger apyrase as well as by the pharmacological P2Y6 receptor antagonists suramin and MRS2578. In agreement with these observations, the knockdown of P2Y6 expression decreased LPS-induced IL-8 release as well as the spontaneous release of IL-8 and MCP-1, suggesting an endogenous basal release of nucleotides. Moreover, high millimolar concentrations of ATP increased IL-8 and MCP-1 release by the glioma cells stimulated with suboptimal LPS concentration which were blocked by P2X7 and P2Y6 antagonists. Altogether, these data suggest that extracellular nucleotides control glioma growth via P2 receptor-dependent IL-8 and MCP-1 secretions.

Discovery of 2-[5-(4-Fluorophenylcarbamoyl)pyridin-2-ylsulfanylmethyl]phenylboronic Acid (SX-517): Noncompetitive Boronic Acid Antagonist of CXCR1 and CXCR2

The G protein-coupled chemokine receptors CXCR1 and CXCR2 play key roles in inflammatory diseases and carcinogenesis. In inflammation, they activate and recruit polymorphonuclear cells (PMNs) through binding of the chemokines CXCL1 (CXCR1) and CXCL8 (CXCR1 and CXCR2). Structure-activity studies that examined the effect of a novel series of S-substituted 6-mercapto-N-phenyl-nicotinamides on CXCL1-stimulated Ca(2+) flux in whole human PMNs led to the discovery of 2-[5-(4-fluorophenylcarbamoyl)pyridin-2-ylsulfanylmethyl]phenylboronic acid (SX-517), a potent noncompetitive boronic acid CXCR1/2 antagonist. SX-517 inhibited CXCL1-induced Ca(2+) flux (IC50 = 38 nM) in human PMNs but had no effect on the Ca(2+) flux induced by C5a, fMLF, or PAF. In recombinant HEK293 cells that stably expressed CXCR2, SX-517 antagonized CXCL8-induced [(35)S]GTPγS binding (IC50 = 60 nM) and ERK1/2 phosphorylation. Inhibition was noncompetitive, with SX-517 unable to compete the binding of [(125)I]-CXCL8 to CXCR2 membranes. SX-517 (0.2 mg/kg iv) significantly inhibited inflammation in an in vivo murine model. SX-517 is the first reported boronic acid chemokine antagonist and represents a novel pharmacophore for CXCR1/2 antagonism.

Control of CXCR2 activity through its ubiquitination on K327 residue

Background

The interleukin-8 chemokine (IL-8) G-protein coupled receptor CXCR2 governs pro-inflammatory and pro-angiogenic responses in leukocytes and endothelial cells. At a molecular standpoint, CXCR2 is widely reported to operate through calcium flux, phosphoinoisitide 3 kinase (PI3K) and mitogen-activated protein kinase (MAPK). While CXCR2 trafficking is suspected to be intertwined with its signaling, the exact mechanism is not fully elucidated.

Results

Here, we identified the lysine 327 within the CXCR2 C-terminal tail as a key residue for ubiquitination, internalization, and signaling. First, the substitution to an arginine of K327 mutation was associated with a reduction in CXCR2 poly-ubiquitination. While WT CXCR2 was rapidly internalized following IL-8 administration, K327R mutant remained at the plasma membrane. Finally, K327R mutant failed to promote the recruitment of β-arrestin2, as estimated by imagery and bioluminescence resonance transfer. As a consequence, the activation of intracellular signaling, including both early events such as ERK phosphorylation and the increase in calcium flux, and the latter activation of the AP1 and NF-κB transcription factors, was blunted.

Conclusions

Overall, our results demonstrate that CXCR2 ubiquitination on K327 residue modulates agonist-activated CXCR2 cell sorting and intracellular signaling. Thus, the inhibition of K327 ubiquitination might emerge as an effective mean to curb exacerbated CXCR2 signaling in several pathological conditions, such as inflammatory diseases and cancer.

Pharmacological inhibition of CXCR2 chemokine receptors modulates paraquat-induced intoxication in rats

Paraquat (PQ) is an agrochemical agent commonly used worldwide, which is allied to potential risks of intoxication. This herbicide induces the formation of reactive oxygen species (ROS) that ends up compromising various organs, particularly the lungs and the brain. This study evaluated the deleterious effects of paraquat on the central nervous system (CNS) and peripherally, with special attempts to assess the putative protective effects of the selective CXCR2 receptor antagonist SB225002 on these parameters. PQ-toxicity was induced in male Wistar rats, in a total dose of 50 mg/kg, and control animals received saline solution at the same schedule of administration. Separate groups of animals were treated with the selective CXCR2 antagonist SB225002 (1 or 3 mg/kg), administered 30 min before each paraquat injection. The major changes found in paraquat-treated animals were: decreased body weight and hypothermia, nociception behavior, impairment of locomotor and gait capabilities, enhanced TNF-α and IL-1β expression in the striatum, and cell migration to the lungs and blood. Some of these parameters were reversed when the antagonist SB225002 was administered, including recovery of physiological parameters, decreased nociception, improvement of gait abnormalities, modulation of striatal TNF-α and IL-1β expression, and decrease of neutrophil migration to the lungs and blood. Taken together, our results demonstrate that damage to the central and peripheral systems elicited by paraquat can be prevented by the pharmacological inhibition of CXCR2 chemokine receptors. The experimental evidence presented herein extends the comprehension on the toxicodynamic aspects of paraquat, and opens new avenues to treat intoxication induced by this herbicide.

Exploring inflammatory disease drug effects on neutrophil function

Neutrophils are critical inflammatory cells; thus, it is important to characterize the effects of drugs on neutrophil function in the context of inflammatory diseases. Herein, chemically guided neutrophil migration, known as chemotaxis, is studied in the context of drug treatment at the single cell level using a microfluidic platform, complemented by cell viability assays and calcium imaging. Three representative drugs known to inhibit surface receptor expression, signaling enzyme activity, and the elevation of intracellular Ca(2+) levels, each playing a significant role in neutrophil chemotactic pathways, are used to examine the in vitro drug effects on cellular behaviors. The microfluidic device establishes a stable concentration gradient of chemokines across a cell culture chamber so that neutrophil migration can be monitored under various drug-exposure conditions. Different time- and concentration-dependent regulatory effects were observed by comparing the motility, polarization, and effectiveness of neutrophil chemotaxis in response to the three drugs. Viability assays revealed distinct drug capabilities in reducing neutrophil viability while calcium imaging clarified the role of Ca(2+) in the neutrophil chemotaxis. This study provides mechanistic insight into the drug effects on neutrophil function, facilitating comparison of current and potential pharmaceutical approaches.

Connexin-43 induces chemokine release from spinal cord astrocytes to maintain late-phase neuropathic pain in mice

Accumulating evidence suggests that spinal cord astrocytes play an important role in neuropathic pain sensitization by releasing astrocytic mediators (e.g. cytokines, chemokines and growth factors). However, it remains unclear how astrocytes control the release of astrocytic mediators and sustain late-phase neuropathic pain. Astrocytic connexin-43 (now known as GJ1) has been implicated in gap junction and hemichannel communication of cytosolic contents through the glial syncytia and to the extracellular space, respectively. Connexin-43 also plays an essential role in facilitating the development of neuropathic pain, yet the mechanism for this contribution remains unknown. In this study, we investigated whether nerve injury could upregulate connexin-43 to sustain late-phase neuropathic pain by releasing chemokine from spinal astrocytes. Chronic constriction injury elicited a persistent upregulation of connexin-43 in spinal astrocytes for >3 weeks. Spinal (intrathecal) injection of carbenoxolone (a non-selective hemichannel blocker) and selective connexin-43 blockers (connexin-43 mimetic peptides (43)Gap26 and (37,43)Gap27), as well as astroglial toxin but not microglial inhibitors, given 3 weeks after nerve injury, effectively reduced mechanical allodynia, a cardinal feature of late-phase neuropathic pain. In cultured astrocytes, TNF-α elicited marked release of the chemokine CXCL1, and the release was blocked by carbenoxolone, Gap26/Gap27, and connexin-43 small interfering RNA. TNF-α also increased connexin-43 expression and hemichannel activity, but not gap junction communication in astrocyte cultures prepared from cortices and spinal cords. Spinal injection of TNF-α-activated astrocytes was sufficient to induce persistent mechanical allodynia, and this allodynia was suppressed by CXCL1 neutralization, CXCL1 receptor (CXCR2) antagonist, and pretreatment of astrocytes with connexin-43 small interfering RNA. Furthermore, nerve injury persistently increased excitatory synaptic transmission (spontaneous excitatory postsynaptic currents) in spinal lamina IIo nociceptive synapses in the late phase, and this increase was suppressed by carbenoxolone and Gap27, and recapitulated by CXCL1. Together, our findings demonstrate a novel mechanism of astrocytic connexin-43 to enhance spinal cord synaptic transmission and maintain neuropathic pain in the late-phase via releasing chemokines.

Blockade of CXCR2 signalling: A potential therapeutic target for preventing neutrophil-mediated inflammatory diseases

Polymorphonuclear neutrophils (PMN) play a key role in host innate immune responses by migrating to the sites of inflammation. Furthermore, PMN recruitment also plays a significant role in the pathophysiology of a plethora of inflammatory disorders such as chronic obstructive pulmonary disease (COPD), gram negative sepsis, inflammatory bowel disease (IBD), lung injury, and arthritis. Of note, chemokine-dependent signalling is implicated in the amplification of immune responses by virtue of its role in PMN chemotaxis in most of the inflammatory diseases. It has been clinically established that impediment of PMN recruitment ameliorates disease severity and provides relief in majority of other immune-associated disorders. This review focuses on different novel approaches clinically proven to be effective in blocking chemokine signalling associated with PMN recruitment that includes CXCR2 antagonists, chemokine analogs, anti-CXCR2 monoclonal antibodies, and CXCR2 knock-out models. It also highlights the significance of the utility of nanoparticles in drugs used for blocking migration of PMN to the sites of inflammation.

Combinatorial cytokine code generates anti-viral state in dendritic cells

The physiological function of the immune system and the response to therapeutic immunomodulators may be sensitive to combinatorial cytokine micro-environments that shape the responses of specific immune cells. Previous work shows that paracrine cytokines released by virus-infected human dendritic cells (DC) can dictate the maturation state of naïve DCs. To understand the effects of paracrine signaling, we systematically studied the effects of combinations cytokines in this complex mixture in generating an anti-viral state. After naïve DCs were exposed to either IFNβ or to paracrine signaling released by DCs infected by Newcastle disease virus (NDV), microarray analysis revealed a large number of genes that were differently regulated by the DC-secreted paracrine signaling. In order to identify the cytokine mechanisms involved, we identified 20 cytokines secreted by NDV infected DCs for which the corresponding receptor gene is expressed in naïve DCs. By exposing cells to all combinations of 19 cytokines (leave-one-out studies), we identified five cytokines (IFNβ, TNFα, IL-1β, TNFSF15, and IL28) as candidates for regulating DC maturation markers. Subsequent experiments identified IFNβ, TNFα, and IL1β as the major contributors to this anti-viral state. This finding was supported by infection studies in vitro, by T-cell activation studies and by in vivo infection studies in mouse. Combination of cytokines can cause response states in DCs that differ from those achieved by the individual cytokines alone. These results suggest that the cytokine microenvironment may act via a combinatorial code to direct the response state of specific immune cells. Further elucidation of this code may provide insight into responses to infection and neoplasia as well as guide the development of combinatorial cytokine immunomodulation for infectious, autoimmune, and immunosurveillance-related diseases.

CXCR2 modulators: a patent review (2009 - 2013)

INTRODUCTION

Small-molecule antagonists of CXC chemokine receptor 2 (CXCR2) have attracted a considerable amount of attention due to the key central role that this receptor plays in inflammatory conditions. Recently, several CXCR2 receptor antagonists have demonstrated promising proof of activity in early pulmonary clinical trials, which has stimulated additional efforts to identify new CXCR2 receptor antagonists.

AREAS COVERED

During the period 2009 - 2013, there were numerous patent publications from various companies claiming the discovery of novel CXCR2 receptor antagonists. Herein, an interpretation of these new patent publications combined with emerging disclosures from the peer-reviewed literature during this time frame is given. This review highlights the preferred or representative compounds from the patent applications along with relevant biological characterization.

EXPERT OPINION

Many of the new CXCR2 receptor antagonists described in this review represent closely related analogs to previously disclosed clinical candidates. With the recent discontinuation of several CXCR2 receptor antagonists in the clinic, additional clinical trial information for CXCR2 receptor antagonists, both past and present, will determine the long-term therapeutic potential of these compounds for the treatment of a variety of inflammatory disorders.