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

Probing the role of CXC motif in chemokine CXCL8 for high affinity binding and activation of CXCR1 and CXCR2 receptors

All chemokines share a common structural scaffold that mediate a remarkable variety of functions from immune surveillance to organogenesis. Chemokines are classified as CXC or CC on the basis of conserved cysteines, and the two subclasses bind distinct sets of GPCR class of receptors and also have markedly different quaternary structures, suggesting that the CXC/CC motif plays a prominent role in both structure and function. For both classes, receptor activation involves interactions between chemokine N-loop and receptor N-domain residues (Site-I), and between chemokine N-terminal and receptor extracellular/transmembrane residues (Site-II). We engineered a CC variant (labeled as CC-CXCL8) of the chemokine CXCL8 by deleting residue X (CXC → CC), and found its structure is essentially similar to WT. In stark contrast, CC-CXCL8 bound poorly to its cognate receptors CXCR1 and CXCR2 (K(i) > 1 μm). Further, CC-CXCL8 failed to mobilize Ca(2+) in CXCR2-expressing HL-60 cells or recruit neutrophils in a mouse lung model. However, most interestingly, CC-CXCL8 mobilizes Ca(2+) in neutrophils and in CXCR1-expressing HL-60 cells. Compared with the WT, CC-CXCL8 binds CXCR1 N-domain with only ∼5-fold lower affinity indicating that the weak binding to intact CXCR1 must be due to its weak binding at Site-II. Nevertheless, this level of binding is sufficient for receptor activation indicating that affinity and activity are separable functions. We propose that the CXC motif functions as a conformational switch that couples Site-I and Site-II interactions for both receptors, and that this coupling is critical for high affinity binding but differentially regulates activation.

CXCL7-Mediated Stimulation of Lymphangiogenic Factors VEGF-C, VEGF-D in Human Breast Cancer Cells

Increased expression of lymphangiogenesis factors VEGF-C/D and heparanase has been correlated with the invasion of cancer. Furthermore, chemokines may modify matrix to facilitate metastasis, and they are associated with VEGF-C and heparanase. The chemokine CXCL7 binds heparin and the G-protein-linked receptor CXCR2. We investigated the effect of CXCR2 blockade on the expression of VEGF-C/D, heparanase, and on invasion. CXCL7 siRNA and a specific antagonist of CXCR2 (SB225002) were used to treat CXCL7 stably transfected MCF10AT cells. Matrigel invasion assays were performed. VEGF-C/D expression and secretion were determined by real-time PCR and ELISA assay, and heparanase activity was quantified by ELISA. SB225002 blocked VEGF-C/D expression and secretion (P < .01). CXCL7 siRNA knockdown decreased heparanase (P < .01). Both SB225002 and CXCL7 siRNA reduced the Matrigel invasion (P < .01). The MAP kinase signaling pathway was not involved. The CXCL7/CXCR2 axis is important for cell invasion and the expression of VEGF-C/D and heparanase, all linked to invasion.

Targeting CXCR1/CXCR2 receptor antagonism in malignant melanoma

IMPORTANCE OF THE FIELD

The incidence of malignant melanoma is increasing throughout the world and is currently rising faster than any other cancer in men and second only to lung cancer in women. Current strategies focused on systemic therapy for treatment of melanoma have shown no effect on survival. Therefore there is a pressing need for developing novel targeted therapeutics.

AREAS COVERED IN THIS REVIEW

Our goal is to provide an overview regarding targeting CXCR1/2 in malignant melanoma, the rationale behind these approaches and the future perspective.

WHAT THE READER WILL GAIN

This review illustrates our current understanding of CXCR1/2 receptor in melanoma progression and metastasis. We describe approaches that are being developed to block CXCR1/2 activation, including low-molecular-weight antagonists, modified chemokines and antibodies directed against ligands and receptors.

TAKE HOME MESSAGE

The chemokine receptors CXCR1 and CXCR2 and their ligands play an important role in the pathogenesis of malignant melanoma. Recent reports demonstrated that CXCR1 is constitutively expressed in all melanoma cases irrespective of stage and grade, however, CXCR2 expression was restricted to aggressive melanoma tumors,. Furthermore, modulation of CXCR1/2 expression and/or activity has been shown to regulate malignant melanoma growth, angiogenesis and metastasis, suggesting CXCR1/2 targeting as a novel therapeutic approach for malignant melanoma.

Overview of novel therapeutic targets for asthma and chronic obstructive pulmonary disease

Obstructive lung diseases, in particular asthma and chronic obstructive pulmonary disease, are a worldwide health problem that is increasing in incidence. While significant progress has been made in the control of symptoms, further advances must be made in modifying the clinical situation in terms of disease progression. Numerous pathogenetic studies have demonstrated that inflammatory responses play a crucial role in the development of chronic lung obstruction, while current molecular findings have provided a myriad of new and promising therapeutic targets. The aim of this article is to provide an overview of clinically and pharmacologically relevant targets for asthma and chronic obstructive pulmonary diseases, considering currently investigated therapeutic approaches.

Anti-chemokine small molecule drugs: a promising future?

IMPORTANCE OF THE FIELD

Chemokines have principally been associated with inflammation due to their role in the control of leukocyte migration, but just over a decade ago chemokine receptors were also identified as playing a pivotal role in the entry of the HIV virus into cells. Chemokines activate seven transmembrane G protein-coupled receptors, making them extremely attractive therapeutic targets for the pharmaceutical industry.

AREAS COVERED IN THIS REVIEW

Although there are now a large number of molecules targeting chemokines and chemokine receptors including neutralizing antibodies in clinical trials for inflammatory diseases, the results to date have not always been positive, which has been disappointing for the field. These failures have often been attributed to redundancy in the chemokine system. However, other difficulties have been encountered in drug discovery processes targeting the chemokine system, and these will be addressed in this review.

WHAT THE READER WILL GAIN

In this review, the reader will get an insight into the hurdles that have to be overcome, learn about some of the pitfalls that may explain the lack of success, and get a glimpse of the outlook for the future.

TAKE HOME MESSAGE

In 2007, the FDA approved maraviroc, an inhibitor of CCR5 for the prevention of HIV infection, the first triumph for a small-molecule drug acting on the chemokine system. The time to market, 11 years from discovery of CCR5, was fast by industry standards. A second small-molecule drug, a CXCR4 antagonist for hematopoietic stem cell mobilization, was approved by the FDA at the end of 2008. The results of a Phase III trial with a CCR9 inhibitor for Crohn's disease are also promising. This could herald the first success for a chemokine receptor antagonist as an anti-inflammatory therapeutic and confirms the importance of chemokine receptors as a target class for anti-inflammatory and autoimmune diseases.

CXCL8 and its cognate receptors in melanoma progression and metastasis

The incidence of melanoma is rising at an alarming rate and we are still awaiting an effective treatment for this malignancy. In its early stage, melanoma can be cured by surgical removal, but once metastasis has occurred there is no effective treatment. Recent findings have suggested multiple functional implications of CXCL8 and its cognate receptors, CXCR1 and CXCR2, in melanoma pathogenesis, thus underscoring their importance as targets for cancer therapy. This review provides an update on the roles of CXCL8 and its receptors in melanoma progression and metastasis.

Dynamic regulation of CXCR1 and CXCR2 homo- and heterodimers

Although homo- and heterodimerization are reported for some chemokine receptors, it remains unclear whether these functional states are in dynamic equilibrium and how receptor/ligand levels influence oligomerization. In human neutrophils and in cell lines that coexpress the chemokine receptors CXCR1 and CXCR2, we used fluorescence resonance energy transfer techniques to show that these two receptors form homo- and heterodimers. Receptor expression and ligand activation were found to regulate the balance between these complexes, adapting the response to changes in the milieu. CXCL8, a ligand for both receptors, alters heterodimeric complexes, whereas it stabilizes homodimers and promotes receptor internalization. Oligomerization of receptors, together with the regulation of their expression and desensitization, could thus contribute to the fine control of chemokine functions.

Evidence that cathelicidin peptide LL-37 may act as a functional ligand for CXCR2 on human neutrophils

LL-37, derived from human cathelicidin, stimulates immune responses in neutrophils. Although FPR2 and P2X7 were proposed as LL-37 receptors, we have shown that among 21 neutrophil receptors only CXCR2 was down-regulated by LL-37. LL-37 functions similarly to CXCR2-specific chemokines CXCL1 and CXCL7 in terms of receptor down-regulation and intracellular calcium mobilization on freshly isolated neutrophils. Neutrophils pretreated with CXCL8, a chemokine that binds both CXCR1/2, completely blocked the calcium mobilization in response to LL-37, while LL-37 also partially inhibited (125)I-CXCL8 binding to neutrophils. SB225002, a selective CXCR2 antagonist, blocked LL-37-induced calcium mobilization and migration of neutrophils. LL-37 stimulates calcium mobilization in CXCR2-transfected HEK293 cells, CXCR2(+) THP-1 cells and monocytes, but not in CXCR1-transfected HEK293 cells. WKYMVm peptide (ligand for FPR2) does not block LL-37-stimulated calcium flux in either THP-1 (FPR2(-)) or monocytes (FPR2(high)), further confirming the specificity of LL-37 for CXCR2 and not FPR2. Among all ligands tested (ATP, BzATP, WKYMVm, CXCL1, and LL-37), only LL-37 stimulated migration of monocytes (CXCR2(+) and FPR2(+)) and migration was inhibited by the CXCR2 inhibitor SB225002. Moreover, CXCR2 but not CXCR1 was internalized in LL-37-treated neutrophils. Thus, our data provide evidence that LL-37 may act as a functional ligand for CXCR2 on human neutrophils.

Prostaglandin F(2alpha)-F-prostanoid receptor regulates CXCL8 expression in endometrial adenocarcinoma cells via the calcium-calcineurin-NFAT pathway

Pro-inflammatory mediators, like prostaglandin (PG) and chemokines, promote tumourigenesis by enhancing cell proliferation, migration of immune cells and recruitment of blood vessels. Recently we showed elevated expression of the chemokine (C-X-C motif) receptor 2 (CXCR2) in endometrial adenocarcinomas localized to neutrophils and neoplastic epithelial and vascular cells. Furthermore we found that PGF_2α-F-prostanoid (FP) receptor regulates the expression of the CXCR2 ligand CXCL1, to promote neutrophil chemotaxis in endometrial adenocarcinomas. In the present study we identified another CXCR2 ligand, CXCL8 as a target for PGF_2α-FP receptor signalling which enhances epithelial cell proliferation in endometrial adenocarcinoma cells in vitro and in nude mice in vivo. We found that PGF_2α-FP receptor interaction induces CXCL8 expression in endometrial adenocarcinoma cells via the protein kinase C–calcium–calcineurin–NFAT signaling pathway. Promoter analysis revealed that CXCL8 transcriptional activation by PGF_2α signaling is mediated by cooperative interactions between the AP1 and NFAT binding sites. Furthermore, PGF_2α via the FP receptor induced the expression of the regulator of calcineurin 1 isoform 4 (RCAN1-4) via the calcineurin/NFAT pathway in a reciprocal manner to CXCL8. Using an adenovirus to overexpress RCAN1-4, we found that RCAN1-4 is a negative regulator of CXCL8 expression in endometrial adenocarcinoma cells. Taken together our data have elucidated the molecular and cellular mechanism whereby PGF_2α regulates CXCL8 expression via the FP receptor in endometrial adenocarcinomas and have highlighted RCAN1-4 as a negative regulator of CXCL8 expression which may be exploited therapeutically to inhibit CXCL8-mediated tumour development.

Characterization of contraction-inducible CXC chemokines and their roles in C2C12 myocytes

Physical exercise triggers the release of several cytokines/chemokines from working skeletal muscles, but the underlying mechanism(s) by which skeletal muscles decipher and respond to highly complex contractile stimuli remains largely unknown. In an effort to investigate the regulatory mechanisms of the expressions of two contraction-inducible CXC chemokines, CXCL1/KC and CXCL5/LIX, in contracting skeletal muscle cells, we took advantage of our in vitro exercise model using highly developed contractile C(2)C(12) myotubes, which acquire properties similar to those of in vivo skeletal muscle via manipulation of Ca(2+) transients with electric pulse stimulation (EPS). Production of these CXC chemokines was immediately augmented by EPS-evoked contractile activity in a manner dependent on the activities of JNK and NF-kappaB, but not p38, ERK1/2, or calcineurin. Intriguingly, exposure of myotubes to cyclic mechanical stretch also induced expression of these CXC chemokines; however, a much longer period of stimulation (approximately 12 h) was required, despite rapid JNK phosphorylation. We also demonstrate herein that CXCL1/KC and CXCL5/LIX have the ability to raise intracellular Ca(2+) concentrations via CXCR2-mediated activation of pertussis toxin-sensitive Galpha(i) proteins in C(2)C(12) myoblasts, an action at least partially responsible for their migration and differentiation. Although we revealed a possible negative feedback regulation of their own production in response to the contractile activity in differentiated myotubes, exogenous administration of these CXC chemokines did not acutely influence either insulin-induced Akt phosphorylation or GLUT4 translocation in C(2)C(12) myotubes. Taken together, these data shed light on the fundamental characteristics of contraction-inducible CXC chemokine production and their potential roles in skeletal muscle cells.

Nicotinamide glycolates antagonize CXCR2 activity through an intracellular mechanism

The chemokine receptors CXCR1/2 are involved in a variety of inflammatory diseases, including chronic obstructive pulmonary disease. Several classes of allosteric small-molecule CXCR1/2 antagonists have been developed. The data presented here describe the cellular pharmacology of the acid and ester forms of the nicotinamide glycolate pharmacophore, a potent antagonist of CXCR2 signaling by the chemokines CXCL1 and CXCL8. Ester forms of the nicotinamide glycolate antagonized CXCL1-stimulated chemotaxis (IC(50) = 42 nM) and calcium flux (IC(50) = 48 nM) in human neutrophils, but they were inactive in cell-free assays of (125)I-CXCL8/CXCR2 binding and CXCL1-stimulated guanosine 5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPgammaS) exchange. Acid forms of the nicotinamide glycolate were inactive in whole-cell assays of chemotaxis and calcium flux, but they inhibited (125)I-CXCL8/CXCR2 binding and CXCL1-stimulated [(35)S]GTPgammaS exchange. The (3)H ester was internalized by neutrophils and rapidly converted to the (3)H acid in a concentrative process. The (3)H acid was not internalized by neutrophils but was sufficient alone to inhibit CXCL1-stimulated calcium flux in neutrophils that were permeabilized by electroporation to permit its direct access to the cell interior. Neutrophil efflux of the acid was probenecid-sensitive, consistent with an organic acid transporter. These data support a mechanism wherein the nicotinamide glycolate ester serves as a lipophilic precursor that efficiently translocates into the intracellular neutrophil space to liberate the active acid form of the pharmacophore, which then acts at an intracellular site. Rapid inactivation by plasma esterases precluded use in vivo, but the mechanism elucidated provided insight for new nicotinamide pharmacophore classes with therapeutic potential.

Modulation of CXC chemokine receptor expression and function in human neutrophils during aging in vitro suggests a role in their clearance from circulation

In mice, differential regulation of CXC chemokine receptor expression in circulating polymorphonuclear neutrophils (PMNs) undergoing senescence results in homing to the bone marrow. However, the role of this compartment and of the chemokine receptor CXCR4 is still under discussion, and only scarce data exist about CXCR4 function in human PMN. In our study, we provide evidence that also in human neutrophils, expression (cell surface and mRNA), chemotactic and signaling functions of the homing-related chemokine receptor CXCR4 are upregulated during aging in vitro, independent of addition of stimulatory cytokines (TNF, IL-1, IL-8, G-CSF). In contrast, interleukin-8 receptors are downmodulated (CXCR2) or remain unchanged (CXCR1), suggesting that human PMNs undergoing senescence acquire a phenotype that impairs inflammatory extravasation and favors homing to the bone marrow or other tissues involved in sequestration. Partially retained responsiveness to interleukin-8 may be important for neutrophil function when senescence occurs after extravasation in inflamed tissues.

CXC ligand 5 is an adipose-tissue derived factor that links obesity to insulin resistance

We show here high levels of expression and secretion of the chemokine CXC ligand 5 (CXCL5) in the macrophage fraction of white adipose tissue (WAT). Moreover, we find that CXCL5 is dramatically increased in serum of human obese compared to lean subjects. Conversely, CXCL5 concentration is decreased in obese subjects after a weight reduction program, or in obese non-insulin-resistant, compared to insulin-resistant, subjects. Most importantly we demonstrate that treatment with recombinant CXCL5 blocks insulin-stimulated glucose uptake in muscle in mice. CXCL5 blocks insulin signaling by activating the Jak2/STAT5/SOCS2 pathway. Finally, by treating obese, insulin-resistant mice with either anti-CXCL5 neutralizing antibodies or antagonists of CXCR2, which is the CXCL5 receptor, we demonstrate that CXCL5 mediates insulin resistance. Furthermore CXCR2-/- mice are protected against obesity-induced insulin resistance. Taken together, these results show that secretion of CXCL5 by WAT resident macrophages represents a link between obesity, inflammation, and insulin resistance.

Small-molecule antagonists for CXCR2 and CXCR1 inhibit human melanoma growth by decreasing tumor cell proliferation, survival, and angiogenesis

PURPOSE

Melanoma, the most aggressive form of skin cancer, accounts for 75% of all skin cancer-related deaths and current therapeutic strategies are not effective in advanced disease. In the current study, we have investigated the efficacy of orally active small-molecule antagonist targeting CXCR2/CXCR1.

EXPERIMENTAL DESIGN

Human A375SM melanoma cells were treated with SCH-479833 or SCH-527123, and their effect on proliferation, motility, and invasion was evaluated in vitro. We examined the downstream signaling events in the cells following treatment with antagonists. For in vivo studies, A375SM cells were implanted subcutaneously into athymic nude mice followed by administration of SCH-479833, SCH-527123, or hydroxypropyl-beta-cyclodextrin (20%) orally for 21 days and their effect on tumor growth and angiogenesis was evaluated.

RESULTS

Our data show that SCH-479833 or SCH-527123 inhibited the melanoma cell proliferation, chemotaxis, and invasive potential in vitro. Treatment of melanoma cells with SCH-479833 or SCH-527123 also inhibited tumor growth. Histologic and histochemical analyses showed significant (P < 0.05) decreases in tumor cell proliferation and microvessel density in tumors. Moreover, we observed a significant increase in melanoma cell apoptosis in SCH-479833- or SCH-527123-treated animals compared with controls.

CONCLUSION

Together, these studies show that selectively targeting CXCR2/CXCR1 with orally active small-molecule inhibitors is a promising therapeutic approach for inhibiting melanoma growth and angiogenesis.

The effects of the selective and non-peptide CXCR2 receptor antagonist SB225002 on acute and long-lasting models of nociception in mice

This study evaluated the antinociceptive effects of the selective and non-peptide CXCR2 antagonist SB225002 in mouse models of pain. As assessed in different tests of spontaneous nociception, intraperitoneal (i.p.) administration of SB225002 caused consistent and dose-related reduction of acetic acid-induced abdominal constrictions, whereas it did not significantly affect the nociception evoked by formalin, capsaicin, glutamate or phorbol ester acetate (PMA). Systemic treatment with SB225002 strikingly reduced the spontaneous nociception induced by 8-bromo-cAMP (8-Br-cAMP), or mechanical hypernociception induced by prostaglandin E(2) (PGE(2)), epinephrine, or the keratinocyte-derived chemokine (KC). In the carrageenan model, SB225002 markedly reduced mechanical hypernociception when administered by i.p., intrathecal (i.t.) or intracerebroventricular (i.c.v.) routes, or even when co-administered with carrageenan into the mouse paw, indicating peripheral and central sites of action for SB225002. In addition, i.p. treatment with SB225002 significantly attenuated the increase in MPO activity or the elevation of IL-1beta, TNFalpha or KC levels following carrageenan injection. In the persistent models of pain evoked by complete Freund's adjuvant (CFA) or by the partial ligation of the sciatic nerve (PLSN), the repeated administration of SB225002 displayed prominent and long-lasting antinociceptive effects. Notably, SB225002 did not evoke unspecific central effects, as evaluated in the open-field and rota-rod tests, or even in the latency responses for thermal stimuli. Our data confirm the previous notion on the critical role exerted by chemokines in pain, indicating that selective CXCR2 antagonists, such as SB225002, might well represent interesting and innovative alternatives for the management of both acute and chronic pain.

A role for a CXCR2/phosphatidylinositol 3-kinase gamma signaling axis in acute and chronic vascular permeability

Most proangiogenic polypeptide growth factors and chemokines enhance vascular permeability, including vascular endothelial growth factor (VEGF), the main target for anti-angiogenic-based therapies, and interleukin-8 (IL-8), a potent proinflammatory mediator. Here, we show that in endothelial cells IL-8 initiates a signaling route that converges with that deployed by VEGF at the level of the small GTPase Rac1 and that both act through the p21-activated kinase to promote the phosphorylation and internalization of VE-cadherin. However, whereas VEGF activates Rac1 through Src-related kinases, IL-8 specifically signals to Rac1 through its cognate G protein-linked receptor, CXCR2, and the stimulation of the phosphatidylinositol 3-kinase gamma (PI3Kgamma) catalytic isoform, thereby providing a specific molecular targeted intervention in vascular permeability. These results prompted us to investigate the potential role of IL-8 signaling in a mouse model for retinal vascular hyperpermeability. Importantly, we observed that IL-8 is upregulated upon laser-induced retinal damage, which recapitulates enhanced vascularization, leakage, and inflammatory responses. Moreover, blockade of CXCR2 and PI3Kgamma was able to limit neovascularization and choroidal edema, as well as macrophage infiltration, therefore contributing to reduce retinal damage. These findings indicate that the CXCR2 and PI3Kgamma signaling pathway may represent a suitable target for the development of novel therapeutic strategies for human diseases characterized by vascular leakage.

Nonpeptidergic allosteric antagonists differentially bind to the CXCR2 chemokine receptor

The chemokine receptor CXCR2 is involved in different inflammatory diseases, like chronic obstructive pulmonary disease, psoriasis, rheumatoid arthritis, and ulcerative colitis; therefore, it is considered an attractive drug target. Different classes of small CXCR2 antagonists have been developed. In this study, we selected seven CXCR2 antagonists from the diarylurea, imidazolylpyrimide, and thiazolopyrimidine class and studied their mechanisms of action at human CXCR2. All compounds are able to displace (125)I-CXCL8 and inhibit CXCL8-induced beta-arrestin2 recruitment. Detailed studies with representatives of each class showed that these compounds displace and antagonize CXCL8, most probably via a noncompetitive, allosteric mechanism. In addition, we radiolabeled the high-affinity CXCR2 antagonist SB265610 [1-(2-bromophenyl)-3-(4-cyano-1H-benzo[d] [1,2,3]-triazol-7-yl)urea] and subjected [(3)H]SB265610 to a detailed analysis. The binding of this radioligand was saturable and reversible. Using [(3)H]SB265610, we found that compounds of the different chemical classes bind to distinct binding sites. Hence, the use of a radiolabeled low-molecular weight CXCR2 antagonist serves as a tool to investigate the different binding sites of CXCR2 antagonists in more detail.

Inducible cutaneous inflammation reveals a protumorigenic role for keratinocyte CXCR2 in skin carcinogenesis

Transgenic mice that overexpress PKCalpha in the epidermis (K5-PKCalpha mice) exhibit acute CXCR2-mediated intraepidermal neutrophilic inflammation and a strong epidermal hyperplasia in response to application of 12-O-tetradecanoylphorbol-13-acetate (TPA). We now show that hyperplasia is independent of infiltrating neutrophils. Furthermore, when K5-PKCalpha mice were initiated with 7,12-dimethylbenz(a)anthracene (DMBA) and promoted with a low dose of TPA, 58% of K5-PKCalpha mice developed skin papillomas that progressed to carcinoma, whereas wild-type mice did not develop tumors. We confirmed that CXCR2 is expressed by keratinocytes and showed that transformation by oncogenic ras (a hallmark of DMBA initiation) or TPA exposure induced all CXCR2 ligands. Ras induction of CXCR2 ligands was mediated by autocrine activation of epidermal growth factor receptor and nuclear factor-kappaB, and potentiated by PKCalpha. Oncogenic ras also induced CXCR2 ligands in keratinocytes genetically ablated for CXCR2. However, ras transformed CXCR2 null keratinocytes formed only small skin tumors in orthotopic skin grafts to CXCR2 intact hosts, whereas transformed wild-type keratinocytes produced large tumors. In vitro, CXCR2 was essential for CXCR2 ligand-stimulated migration of ras-transformed keratinocytes and for ligand activation of the extracellular signal-regulated kinase (ERK) and Akt pathways. Both migration and activation of ERK and Akt were restored by CXCR2 reconstitution of CXCR2 null keratinocytes. Thus, activation of CXCR2 on ras-transformed keratinocytes has both promigratory and protumorigenic functions. The up-regulation of CXCR2 ligands after initiation by oncogenic ras and promotion with TPA in the mouse skin model provides a mechanism to stimulate migration by both autocrine and paracrine pathways and contribute to tumor development.

Therapeutic effect of blocking CXCR2 on neutrophil recruitment and dextran sodium sulfate-induced colitis

Dextran sodium sulfate (DSS)-induced colitis in mice is characterized by polymorphonuclear neutrophil (PMN) infiltration into the colonic mucosa and lumen. The mechanism by which this occurs is unclear. To begin to understand the mechanism, we determined the role of the PMN chemokine receptor, CXCR2, in DSS-induced colitis by using CXCR2(-/-) mice or by neutralizing CXCR2. DSS was administered through drinking water to CXCR2(-/-) and BALB/c mice for 5 days followed by regular water for 1 day. In the neutralization study, mice were injected with control serum or goat anti-CXCR2 antiserum. BALB/c mice receiving DSS and control serum-injected mice receiving DSS lost weight and showed considerable clinical illness. Histological observation revealed submucosal edema, PMN infiltration into the submucosa and mucosa, extensive crypt damage with abscesses, and ulceration. In contrast, both the CXCR2(-/-) and anti-CXCR2 antiserum-treated mice gained weight and had significantly lower symptom scores. Histology of these mice showed submucosal edema but relatively intact crypt architecture and very few ulcers. Significantly fewer PMNs were found in the mucosa in anti-CXCR2 anti-serum compared with control serum-injected inflamed mice, but no significant difference in eosinophil infiltration was observed between the groups. Our experiments identify a role for CXCR2 in DSS-induced colitis and suggest that antagonizing CXCR2 provides some therapeutic efficacy, possibly by impeding PMN recruitment into the mucosa. Antagonizing CXCR2 may form the basis for therapeutic drugs directed at controlling colitis.

Novel role of CXCR2 in regulation of gamma-secretase activity

Alzheimer's disease (AD) is a progressive chronic disorder that leads to cognitive decline. Several studies have associated up-regulation of some of the chemokines and/or their receptors with altered APP processing leading to increased production of beta-amyloid protein (Abeta) and AD pathological changes. However, there is no direct evidence to date to determine whether the altered processing of APP results in up-regulation of these receptors or whether the up-regulation of the chemokine receptors causes modulated processing of APP. In the current study, we demonstrate that treatment of the chemokine receptor CXCR2 with agonists leads to enhancement of Abeta production and treatment with antagonists or immunodepletion of CXCR2's endogenous agonists leads to Abeta inhibition. Further, we found that the inhibitory effect of the antagonist of CXCR2 on Abeta40 and Abeta42 is mediated via gamma-secretase, specifically through reduction in expression of presenilin (PS), one of the gamma-secretase components. Also, in vivo chronic treatment with a CXCR2 antagonist blocked Abeta40 and Abeta42 production. Using small interfering RNAs for CXCR2, we further showed that knockdown of CXCR2 in vitro accumulates gamma-secretase substrates C99 and C83 with reduced production of both Abeta40 and Abeta42. Taken together, these findings strongly suggest for the first time that up-regulation of the CXCR2 receptor can be the driving force in increased production of Abeta. Our findings unravel new mechanisms involving the CXCR2 receptor in the pathogenesis of AD and pose it as a potential target for developing novel therapeutics for intervention in this disease. Also, we propose here a new chemical series of interest that can serve as a prototype for drug development.

CXC chemokines and their receptors: a case for a significant biological role in cutaneous wound healing

Wound healing requires a complex series of reactions and interactions among cells and their mediators, resulting in an overlapping series of events including coagulation, inflammation, epithelialization, formation of granulation tissue, matrix and scar formation. Cytokines and chemokines promote inflammation, angiogenesis, facilitate the passage of leukocytes from circulation into the tissue, and contribute to the regulation of epithelialization. They integrate inflammatory events and reparative processes that are important for modulating wound healing. Thus both cytokines and chemokines are important targets for therapeutic intervention. The chemokine-mediated regulation of angiogenesis is highly sophisticated, fine tuned, and involves pro-angiogenic chemokines, including CXCL1-3, 5-8 and their receptors, CXCR1 and CXCR2. CXCL1 and CXCR2 are expressed in normal human epidermis and are further induced during the wound healing process of human burn wounds, especially during the inflammatory, epithelialization and angiogenic processes. Human skin explant studies also show CXCR2 is expressed in wounded keratinocytes and Th/1/Th2 cytokine modulation of CXCR2 expression correlates with proliferation of epidermal keratinocytes. Murine excision wound healing, chemical burn wounds and skin organ culture systems are valuable models for examining the role of inflammatory cytokines and chemokines in wound healing.

CXCR2 antagonists for the treatment of pulmonary disease

Chemokines have long been implicated in the initiation and amplification of inflammatory responses by virtue of their role in leukocyte chemotaxis. The expression of one of the receptors for these chemokines, CXCR2, on a variety of cell types and tissues suggests that these receptors may have a broad functional role under both constitutive conditions and in the pathophysiology of a number of acute and chronic diseases. With the development of several pharmacological, immunological and genetic tools to study CXCR2 function, an important role for this CXC chemokine receptor subtype has been identified in chronic obstructive pulmonary disease (COPD), asthma and fibrotic pulmonary disorders. Interference with CXCR2 receptor function has demonstrated different effects in the lungs including inhibition of pulmonary damage induced by neutrophils (PMNs), antigen or irritant-induced goblet cell hyperplasia and angiogenesis/collagen deposition caused by lung injury. Many of these features are common to inflammatory and fibrotic disorders of the lung. Clinical trials evaluating small molecule CXCR2 antagonists in COPD, asthma and cystic fibrosis are currently underway. These studies hold considerable promise for identifying novel and efficacious treatments of pulmonary disorders.

The angiogenic response of the aorta to injury and inflammatory cytokines requires macrophages

The purpose of this study was to define early events during the angiogenic response of the aortic wall to injury. Rat aortic rings produced neovessels in collagen culture but lost this capacity over time. These quiescent rings responded to vascular endothelial growth factor but not to a mixture of macrophage-stimulatory cytokines and chemokines that was angiogenically active on fresh rings. Analysis of cytokine receptor expression revealed selective loss in quiescent rings of the proangiogenic chemokine receptor CXCR2, which was expressed predominantly in aortic macrophages. Pharmacologic inhibition of CXCR2 impaired angiogenesis from fresh rings but had no effect on vascular endothelial growth factor-induced angiogenesis from quiescent explants. Angiogenesis was also impaired in cultures of aortic rings from CXCR2-deficient mice. Reduced CXCR2 expression in quiescent rat aortic rings correlated with marked macrophage depletion. Pharmacologic ablation of macrophages from aortic explants blocked formation of neovessels in vitro and reduced aortic ring-induced angiogenesis in vivo. The angiogenic response of macrophage-depleted rings was completely restored by adding exogenous macrophages. Moreover, angiogenesis from fresh rings was promoted by macrophage CSF (CSF-1) and inhibited with anti-CSF-1 Ab. Thus, aortic angiogenic sprouting following injury is strongly influenced by conditions that modulate resident macrophage numbers and function.

Hepatocyte signaling through CXC chemokine receptor-2 is detrimental to liver recovery after ischemia/reperfusion in mice

CXC chemokines and their receptor, CXC chemokine receptor-2 (CXCR2), are important components of the hepatic inflammatory response to ischemia/reperfusion (I/R). However, direct effects of CXC chemokines on hepatocytes during this response have not been studied. Wild-type and CXCR2(-/-) mice were subjected to 90 minutes of partial hepatic ischemia followed by up to 96 hours of reperfusion. CXCR2(-/-) mice had significantly less liver injury at all reperfusion times compared with wild-type mice. Early neutrophil recruitment (12 hours) was diminished in CXCR2(-/-) mice, but within 24 hours it was the same as that of wild-type mice. Hepatocyte proliferation and regeneration was accelerated in CXCR2(-/-) mice compared with wild-type mice. These effects were associated with increased activation of nuclear factor kappaB and signal transducers and activators of transcription-3, despite there being no difference in the expression of proliferative factors such as tumor necrosis factor alpha, interleukin-6, and hepatocyte growth factor. To establish whether the accelerated proliferation and regeneration observed in CXCR2(-/-) mice was due to effects on hepatocytes rather than just a generalized decrease in acute inflammatory injury, mice were treated with the CXCR2 antagonist, SB225002, after neutrophil recruitment and injury were maximal (24 hours after reperfusion). SB225002 treatment increased hepatocyte proliferation and regeneration in a manner identical to that observed in CXCR2(-/-) mice. Treatment of primary wild-type hepatocytes with macrophage inflammatory protein-2 revealed that low concentrations protected against cell death, whereas high concentrations induced cell death. These effects were absent in hepatocytes from CXCR2(-/-) mice.

CONCLUSION

Our data suggest that hepatocyte CXCR2 regulates proliferation and regeneration after I/R injury and reveal important differences in the role of this receptor in liver regeneration and repair induced under different conditions that may be related to ligand concentration.

Identification of a putative intracellular allosteric antagonist binding-site in the CXC chemokine receptors 1 and 2

The chemokine receptors CXCR1 and CXCR2 are G-protein-coupled receptors (GPCRs) implicated in mediating cellular functions associated with the inflammatory response. Potent CXCR2 receptor antagonists have been discovered, some of which have recently entered clinical development. The aim of this study was to identify key amino acid residue differences between CXCR1 and CXCR2 that influence the relative antagonism by two compounds that have markedly different chemical structures. By investigating the effects of domain switching and point mutations, we found that the second extracellular loop, which contained significant amino acid sequence diversity, was not important for compound antagonism. We were surprised to find that switching the intracellular C-terminal 60 amino acid domains of CXCR1 and CXCR2 caused an apparent reversal of antagonism at these two receptors. Further investigation showed that a single amino acid residue, lysine 320 in CXCR2 and asparagine 311 in CXCR1, plays a predominant role in describing the relative antagonism of the two compounds. Homology modeling studies based on the structure of bovine rhodopsin indicated a potential intracellular antagonist binding pocket involving lysine 320. We conclude that residue 320 in CXCR2 forms part of a potential allosteric binding pocket on the intracellular side of the receptor, a site that is distal to the orthosteric site commonly assumed to be the location of antagonist binding to GPCRs. The existence of a common intracellular allosteric binding site at GPCRs related to CXCR2 may be of value in the design of novel antagonists for therapeutic intervention.

The selective nonpeptide CXCR2 antagonist SB225002 ameliorates acute experimental colitis in mice

Although neutrophils are strongly implicated in eliminating pathogens, excessive recruitment may cause tissue damage. Therefore, reducing cell influx during an inflammatory process may be a potential target for treating inflammatory bowel diseases (IBD). As CXCR2 is involved in neutrophil migration, this study aimed to evaluate whether the systemic therapeutic treatment with selective CXCR2 antagonist SB225002 ameliorates experimental colitis, which was induced in mice by 2,4,6-trinitrobenzene sulfonic acid (TNBS). After colitis establishment (24 h), mice were treated with SB225002. At later time-points, up to 72 h, mice were monitored for body weight loss and overall mortality. At the time of sacrifice, colonic tissues were scored for macro- and microscopic damage, and cytokine levels, myeloperoxidase (MPO) activity, and protein expression were analyzed. TNBS administration induced macro- and microscopic damage in colon tissue, leading in most cases to animal death. Curative treatment with SB225002 significantly reduced all of the parameters analyzed, leading to an improvement of inflammatory signs. SB225002 reduced neutrophil influx, MPO activity, IL-1beta, MIP-2, and keratinocyte-derived chemokine (KC) levels and the expression of vascular endothelial growth factor, inducible NO synthase, and cyclooxygenase-2 proteins into the colon tissue. Levels of IL-4 and IL-10 were increased significantly in the colons of animals treated with SB225002. Additionally, curative treatment with mouse anti-KC significantly reduced MPO activity and colonic damage. These results taken together demonstrate that a selective blockade of CXCR2 consistently reduced TNBS-induced colitis, suggesting that the use of SB225002 is a potential therapeutic approach for the treatment of IBD and other related inflammatory disorders.

CXCR2 chemokine receptor antagonism enhances DOP opioid receptor function via allosteric regulation of the CXCR2-DOP receptor heterodimer

Opioid agonists have a broad range of effects on cells of the immune system, including modulation of the inflammatory response, and opioid and chemokine receptors are co-expressed by many white cells. Hetero-oligomerization of the human DOP opioid and chemokine CXCR2 receptors could be detected following their co-expression by each of co-immunoprecipitation, three different resonance energy transfer techniques and the construction of pairs of individually inactive but potentially complementary receptor G-protein α subunit fusion proteins. Although DOP receptor agonists and a CXCR2 antagonist had no inherent affinity for the alternative receptor when either receptor was expressed individually, use of cells that expressed a DOP opioid receptor construct constitutively, and in which expression of a CXCR2 receptor construct could be regulated, demonstrated that the CXCR2 antagonist enhanced the function of DOP receptor agonists only in the presence of CXCR2. This effect was observed for both enkephalin- and alkaloid-based opioid agonists, and the effective concentrations of the CXCR2 antagonist reflected CXCR2 receptor occupancy. Entirely equivalent results were obtained in cells in which the native DOP opioid receptor was expressed constitutively and in which expression of the isolated CXCR2 receptor could be induced. These results indicate that a CXCR2 receptor antagonist can enhance the function of agonists at a receptor for which it has no inherent direct affinity by acting as an allosteric regulator of a receptor that is a heterodimer partner for the CXCR2 receptor. These results have novel and important implications for the development and use of small-molecule therapeutics.

Deregulation of a STAT3-interleukin 8 signaling pathway promotes human glioblastoma cell proliferation and invasiveness

Inactivation of the tumor suppressor phosphatase and tensin homolog (mutated in multiple advanced cancers 1) (PTEN) is recognized as a major event in the pathogenesis of the brain tumor glioblastoma. However, the mechanisms by which PTEN loss specifically impacts the malignant behavior of glioblastoma cells, including their proliferation and propensity for invasiveness, remain poorly understood. Genetic studies suggest that the transcription factor signal transducers and activators of transcription 3 (STAT3) harbors a PTEN-regulated tumor suppressive function in mouse astrocytes. Here, we report that STAT3 plays a critical tumor suppressive role in PTEN-deficient human glioblastoma cells. Endogenous STAT3 signaling is specifically inhibited in PTEN-deficient glioblastoma cells. Strikingly, reactivation of STAT3 in PTEN-deficient glioblastoma cells inhibits their proliferation, invasiveness, and ability to spread on myelin. We also identify the chemokine interleukin 8 (IL8) as a novel target gene of STAT3 in human glioblastoma cells. Activated STAT3 occupies the endogenous IL8 promoter and directly represses IL8 transcription. Consistent with these results, IL8 is upregulated in PTEN-deficient human glioblastoma tumors. Importantly, IL8 repression mediates STAT3 inhibition of glioblastoma cell proliferation, invasiveness, and spreading on myelin. Collectively, our findings uncover a novel link between STAT3 and IL8, the deregulation of which plays a key role in the malignant behavior of PTEN-deficient glioblastoma cells. These studies suggest that STAT3 activation or IL8 inhibition may have potential in patient-tailored treatment of PTEN-deficient brain tumors.

Leukocyte adhesion molecule and chemokine production through lipoteichoic acid recognition by toll-like receptor 2 in cultured human lymphatic endothelium

We have recently reported that the human lymphatic endothelium has toll-like receptor 4 (TLR4)-mediated lipopolysaccharide recognition mechanisms that induce the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Although ligand engagement with TLR2 enables activation of the MyD88-dependent pathway similarly to TLR4, whether TLR2 ligands such as lipoteichoic acid (LTA) trigger the activation of lymphatic endothelium remains unclear. This study has been designed to investigate the expression dynamics of LTA-induced leukocyte adhesion molecules and chemokines in cultured human lymphatic endothelium (LEC). Reverse transcription/polymerase chain reaction (RT-PCR) and real-time quantitative PCR analyses have shown that LEC usually expresses TLR2 and increases TLR2 gene expression on LTA treatment. Indeed, LTA-treated LEC increases the expression of E-selectin, ICAM-1, and VCAM-1 but does not alter the gene expression of ICAM-2, ICAM-3, junctional adhesion molecule-1 (JAM-1), JAM-3, or platelet endothelial cell adhesion molecule-1 (PECAM-1). The expression of LTA-induced E-selectin, ICAM-1, and VCAM-1 in LEC is suppressed by anti-TLR2 but not by anti-TLR4 and is also suppressed by TLR2-specific short interfering RNA (siRNA) but not by siRNA for TLR4. The expression of CCL2, CCL5, and CCL20 (Cys-Cys motif chemokines) and of CXCL1, CXCL3, CXCL5, CXCL6, and CXCL8 (Cys-X-Cys motif chemokines) was induced in LEC with LTA. These data suggest that the human lymphatic endothelial phenotype has TLR2-mediated LTA-recognition mechanisms, resulting in increased expression of inflammatory leukocyte adhesion molecules and phagocyte-attractive chemokines. The human lymphatic endothelium may thus function to collect leukocytes from tissues into lymphatic vessels by means of immunologically functional molecules.

The expression of E-selectin and chemokines in the cultured human lymphatic endothelium with lipopolysaccharides

This study investigated the expression of selectins and chemokines in cultured human lymphatic endothelial cells stimulated with lipopolysaccharides. In microarray, vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 gene expressions in the lymphatic endothelium with lipopolysaccharides did not change at 0.5 h but increased two- to three-fold at 12 h, whereas E-selectin increased 10-fold at 0.5 h and 68-fold at 12 h compared with untreated cells. The E-selectin mRNA and protein increased in the lymphatic endothelial cells with lipopolysaccharides at more than two-fold levels compared with human umbilical vein endothelial cells. Induction of Cys-Cys chemokine ligand 2, 3, 5, 7, 8 and 20 mRNAs in the lymphatic endothelial cells with lipopolysaccharides was detected in microarray and real-time PCR. The Cys-Cys chemokine ligand 2, 5 and 20 mRNA amounts in cells with high concentration lipopolysaccharides were larger in the lymphatic endothelial cells than in human umbilical vein endothelial cells. The Cys-Cys chemokine ligand 3 and 8 mRNAs were not detected in human umbilical vein endothelial cells. Induction of Cys-X-Cys chemokine ligand 1, 3, 5, 6 and 8 mRNAs was detected in the lymphatic endothelial cells with lipopolysaccharides. The Cys-X-Cys chemokine ligand 3, 5 and 8 mRNA amounts in cells with high concentration lipopolysaccharides were larger in the lymphatic endothelial cells than in human umbilical vein endothelial cells. In conclusion, it was demonstrated that the cultured human lymphatic endothelial cells express E-selectin and phagocyte-attractive chemokine genes.

Carboxylic acid bioisosteres acylsulfonamides, acylsulfamides, and sulfonylureas as novel antagonists of the CXCR2 receptor

A series of novel acylsulfonamide, acylsulfamide, and sulfonylurea bioisosteres of carboxylic acids were prepared as CXCR2 antagonists. Structure-activity relationships are reported for these series. One potent orally bioavailable inhibitor had excellent PK properties and was active in a lung injury model in hyperoxia-exposed newborn rats.

Oxidative stress induces extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase in cystic fibrosis lung epithelial cells: Potential mechanism for excessive IL-8 expression

Cystic fibrosis (CF) is a lethal disease caused by defective function of the cftr gene product, the CF transmembrane conductance regulator (CFTR) that leads to oxidative damage and excessive inflammatory response in lungs of CF patients. We here report the effects of oxidative stress (hyperoxia, 95% O(2)) on the expression of pro-inflammatory interleukin (IL)-8 and CXCR1/2 receptors in two human CF lung epithelial cell lines (IB3-1, with the heterozygous F508del/W1282X mutation and CFBE41o- with the homozygous F508del/F508del mutation) and two control non-CF lung epithelial cell lines (S9 cell line derived from IB3-1 after correction with wtCFTR and the normal bronchial cell line 16HBE14o-). Under oxidative stress, the expression of IL-8 and CXCR1/2 receptors was increased in CF, corrected and normal lung cell lines. The effects of oxidative stress were also investigated by measuring the transcription nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1) activities. Under oxidative stress, no increase of NF-kappaB activation was observed in CF lung cells in contrast to that observed in normal and corrected CF lung cells. The signalling of mitogen-activated protein (MAP) kinases was further studied. We demonstrated that extracellular signal-regulated kinase (ERK1/2) and AP-1 activity was markedly enhanced in CF but not non-CF lung cells under oxidative stress. Consistently, inhibition of ERK1/2 in oxidative stress-exposed CF lung cells strongly decreased both the IL-8 production and CXCR1/2 expression. Therefore, targeting of ERK1/2 MAP kinase may be critical to reduce oxidative stress-mediated inflammation in lungs of CF patients.

Aspects on pathophysiological mechanisms in COPD

Chronic obstructive pulmonary disease (COPD) is a condition which is characterized by irreversible airway obstruction due to narrowing of small airways, bronchiolitis, and destruction of the lung parenchyma, emphysema. It is the fourth most common cause of mortality in the world and is expected to be the third most common cause of death by 2020. The main cause of COPD is smoking but other exposures may be of importance. Exposure leads to airway inflammation in which a variety of cells are involved. Besides neutrophil granulocytes, macrophages and lymphocytes, airway epithelial cells are also of particular importance in the inflammatory process and in the development of emphysema. Cell trafficking orchestrated by chemokines and other chamoattractants, the proteinase-antiproteinase system, oxidative stress and airway remodelling are central processes associated with the development of COPD. Recently systemic effects of COPD have attracted attention and the importance of systemic inflammation has been recognized. This seems to have direct therapeutic implications as treatment with inhaled glucocorticosteroids has been shown to influence mortality. The increasing body of knowledge regarding the inflammatory mechanism in COPD will most likely have implications for future therapy and new drugs, specifically aimed at interaction with the inflammatory processes, are currently being developed.

Th1/Th2 cytokines reciprocally regulate in vitro pulmonary angiogenesis via CXC chemokine synthesis

Hypervascularity is known as an important element of airway remodeling in bronchial asthma. However, it remains obscure how allergic inflammation relates to angiogenesis in the lung. In this study, we examined the in vitro effects of inflammatory cytokines on endothelial cell functions, particularly angiogenesis. Human microvascular endothelial cells from normal lung (HMVEC-Ls) were cultured with TNF-alpha, IFN-gamma, IL-4, a combination of TNF-alpha and IFN-gamma, or a combination of TNF-alpha and IL-4, and the cell proliferation and tube-forming activities were evaluated. IL-4 slightly enhanced the proliferation of HMVEC-Ls in the presence of vascular endothelial growth factor (VEGF), whereas TNF-alpha and IFN-gamma tended to inhibit it. Synergistic inhibition was observed when TNF-alpha and IFN-gamma were simultaneously added to the culture medium. The combination of IL-4 and TNF-alpha markedly promoted tube formation by HMVEC-Ls, even in the absence of VEGF. The IL-4 and TNF-alpha combination induced autocrine production of CXCR2 chemokines, which are known to have angiogenic activity, whereas the production of angiostatic CXCR3 chemokines was dramatically up-regulated when TNF-alpha and IFN-gamma were present. The marked IL-4- and TNF-alpha-induced tube formation was inhibited by a selective CXCR2 antagonist. These results suggest that, in the presence of TNF-alpha, IL-4 and IFN-gamma reciprocally regulate tube formation by HMVEC-Ls through autocrine synthesis of CXCR2 and CXCR3 chemokines, respectively. Of note, the CXCR2 chemokine-induced tube formation was independent of VEGF. Therefore, CXCR2 chemokines may represent potential therapeutic targets for bronchial asthma.

ELR+-CXC chemokines and their receptors in early metanephric development

Although originally identified as mediators of inflammation, it is now apparent that chemokines play a fundamental role in tissue development. In this study, ELR(+)-CXC chemokine family members CXCL2 and CXCL7, along with their preferred receptor CXCR2, were expressed at the earliest stages of metanephric development in the rat, and signaling through this receptor was required for the survival and maintenance of the undifferentiated metanephric mesenchyme (MM). A specific antagonist of the CXCR2 receptor SB225002 induced apoptosis in this population but did not affect more mature structures or cells in the ureteric bud. CXCL7 treatment of isolated MM elicited an angiogenic response by upregulation of matrix metalloprotease 9 and endothelial and mesangial markers (platelet-endothelial cell adhesion molecule, Megsin, Thy-1, PDGF receptor alpha, and vascular alpha-actin) and induced SB225002-sensitive cell invasion through a matrix. Because Wilms' tumor cells may similarly depend on CXCR2 signaling for survival, primary tumor samples were analyzed, and 15 of 16 Wilms' tumors were found to be CXCR2 positive, whereas grossly normal kidney tissues from tumor patients or renal cell carcinomas were CXCR2 negative. Furthermore, cell lines derived from Wilms' tumors but not those from renal cell carcinomas were sensitive to SB225002-induced apoptosis. These data provide evidence for a prosurvival and proangiogenic role of ELR(+)-CXC chemokines and their receptor CXCR2 during metanephric development and suggest a novel mechanism for chemotherapeutic intervention in Wilms' tumor.

3-Arylamino-2H-1,2,4-benzothiadiazin-5-ol 1,1-dioxides as novel and selective CXCR2 antagonists

A series of 3-arylamino-2H-1,2,4-benzothiadiazin-5-ol 1,1-dioxides were prepared and shown to be novel and selective antagonists of the CXCR2 receptor. Synthesis, structure and activity relationships, selectivity, and some developability properties are described.

Pharmacological characterization of Sch527123, a potent allosteric CXCR1/CXCR2 antagonist

In neutrophils, growth-related protein-alpha (CXCL1) and interleukin-8 (CXCL8), are potent chemoattractants (Cytokine 14:27-36, 2001; Biochemistry 42:2874-2886, 2003) and can stimulate myeloperoxidase release via activation of the G protein-coupled receptors CXCR1 and CXCR2. The role of CXCR1 and CXCR2 in the pathogenesis of inflammatory responses has encouraged the development of small molecule antagonists for these receptors. The data presented herein describe the pharmacology of 2-hydroxy-N,N-dimethyl-3-{2-[[(R)-1-(5-methyl-furan-2-yl)-propyl]amino]-3,4-dioxo-cyclobut-1-enylamino}-benzamide (Sch527123), a novel antagonist of both CXCR1 and CXCR2. Sch527123 inhibited chemokine binding to (and activation of) these receptors in an insurmountable manner and, as such, is categorized as an allosteric antagonist. Sch527123 inhibited neutrophil chemotaxis and myeloperoxidase release in response to CXCL1 and CXCL8 but had no effect on the response of these cells to C5a or formyl-methionyl-leucyl-phenylalanine. The pharmacological specificity of Sch527123 was confirmed by testing in a diversity profile against a panel of enzymes, channels, and receptors. To measure compound affinity, we characterized [(3)H]Sch527123 in both equilibrium and nonequilibrium binding analyses. Sch527123 binding to CXCR1 and CXCR2 was both saturable and reversible. Although Sch527123 bound to CXCR1 with good affinity (K(d) = 3.9 +/- 0.3 nM), the compound is CXCR2-selective (K(d) = 0.049 +/- 0.004 nM). Taken together, our data show that Sch527123 represents a novel, potent, and specific CXCR2 antagonist with potential therapeutic utility in a variety of inflammatory conditions.

Chemokines and their receptors as potential targets for the treatment of asthma

Asthma is a chronic and sometimes fatal disease, which affects people of all ages throughout the world. Important hallmarks of asthma are airway inflammation and remodelling, with associated bronchial hyperresponsiveness and variable airflow obstruction. These features are orchestrated by cells of both the innate (eosinophils, neutrophils and mast cells) and the adaptive (T(H)2 T cells) immune system, in concert with structural airway cells. Chemokines are important for the recruitment of both immune and structural cells to the lung, and also for their microlocalisation within the lung tissue. Specific blockade of the responses elicited by chemokines and chemokine receptors responsible for the pathological migration of airway cells could therefore be of great therapeutic interest for the treatment of asthma.

Comparison of N,N′-diarylsquaramides and N,N′-diarylureas as antagonists of the CXCR2 chemokine receptor

N,N'-diarylsquaramides were prepared and evaluated as antagonists of CXCR2. The compounds were found to be potent and selective antagonists of CXCR2. Significant differences in SAR was observed relative to the previously described N,N'-diarylurea series. As was the case in the N,N'-diarylurea series, placing sulfonamide substituent adjacent to the acidic phenol significantly reduced the clearance in rat pharmacokinetic studies.

The DEK nuclear autoantigen is a secreted chemotactic factor

The nuclear DNA-binding protein DEK is an autoantigen that has been implicated in the regulation of transcription, chromatin architecture, and mRNA processing. We demonstrate here that DEK is actively secreted by macrophages and is also found in synovial fluid samples from patients with juvenile arthritis. Secretion of DEK is modulated by casein kinase 2, stimulated by interleukin-8, and inhibited by dexamethasone and cyclosporine A, consistent with a role as a proinflammatory molecule. DEK is secreted in both a free form and in exosomes, vesicular structures in which transcription-modulating factors such as DEK have not previously been found. Furthermore, DEK functions as a chemotactic factor, attracting neutrophils, CD8+ T lymphocytes, and natural killer cells. Therefore, the DEK autoantigen, previously described as a strictly nuclear protein, is secreted and can act as an extracellular chemoattractant, suggesting a direct role for DEK in inflammation.

Differential calcium signaling in dairy cows with specific CXCR1 genotypes potentially related to interleukin-8 receptor functionality

Neutrophil migration and activation are critical components of innate immunity and are mediated by a variety of inflammatory mediators, which include interleukin-8 (IL-8) and epithelial-derived neutrophil activating peptide-78 (ENA-78). Limited knowledge on the expression of receptors for these inflammatory mediators (CXCR1 and CXCR2) in bovine, in addition to the association of a polymorphism (G-->C) in position +777 of the CXCR1 gene with impaired neutrophil function, prompted evaluation of CXCR1 and CXCR2 mRNA and protein expression, ligand binding affinity, and intracellular receptor signaling in neutrophils from cows with different CXCR1 genotypes. Initial observations revealed that overall IL-8 receptor numbers appeared to be lower in cows with a CC genotype compared to cows with a GG genotype. However, in the presence of SB225002, a CXCR2 inhibitor, CXCR1 affinity was about fivefold lower in cows with a CC genotype and may have resulted in an underestimation of receptor numbers in cows with this genotype. In addition, intracellular calcium ([Ca++]i) release was lower in cows with a CC genotype when cells were stimulated with IL-8 but not ENA-78. Furthermore, when neutrophils were stimulated with an optimal dose of IL-8 in the presence of SB225002, [Ca++]i release was lower in cows with a CC genotype, suggesting differential CXCR1 signaling among genotypes. These findings offer knowledge of the role that each of these receptors plays in the inflammatory response in the bovine and provide insight into the potential mechanisms that may be affected in neutrophils of cows with different CXCR1 genotypes.