Cloning of a cDNA encoding a mouse homolog of the interleukin-8 receptor

Neutrophil extracellular traps induced by chemotherapy inhibit tumor growth in murine models of colorectal cancer

Neutrophil extracellular traps (NETs), a web-like structure of cytosolic and granule proteins assembled on decondensed chromatin, kill pathogens and cause tissue damage in diseases. Whether NETs can kill cancer cells is unexplored. Here, we report that a combination of glutaminase inhibitor CB-839 and 5-FU inhibited the growth of PIK3CA-mutant colorectal cancers (CRCs) in xenograft, syngeneic, and genetically engineered mouse models in part through NETs. Disruption of NETs by either DNase I treatment or depletion of neutrophils in CRCs attenuated the efficacy of the drug combination. Moreover, NETs were present in tumor biopsies from patients treated with the drug combination in a phase II clinical trial. Increased NET levels in tumors were associated with longer progression-free survival. Mechanistically, the drug combination induced the expression of IL-8 preferentially in PIK3CA-mutant CRCs to attract neutrophils into the tumors. Further, the drug combination increased the levels of ROS in neutrophils, thereby inducing NETs. Cathepsin G (CTSG), a serine protease localized in NETs, entered CRC cells through the RAGE cell surface protein. The internalized CTSG cleaved 14-3-3 proteins, released BAX, and triggered apoptosis in CRC cells. Thus, our studies illuminate a previously unrecognized mechanism by which chemotherapy-induced NETs kill cancer cells.

Association between CXCR2 and IL-22BP expression indicate a poor outcome for gastric adenocarcinoma progression

C-X-C motif chemokine receptor type 2 (CXCR2), a key regulatory protein, has been associated with multiple roles in the progression of numerous tumors, including gastric adenocarcinoma (GA). However, the mechanism of CXCR2 in the development of tumors remains controversial and unclear. In a previous study, the expression of CXCR2 and interleukin-22 receptor 2 (IL-22BP) was observed in GA. This promoted the present study, which aimed to explore the association between the two proteins, and to further analyze their roles in GA. CXCR2 and IL-22BP protein expression was analyzed by immunohistochemistry and reverse transcription-quantitative polymerase chain reaction assays in gastric cancer (GC) tissue, additionally confirmed via western blotting and immunocytochemical analysis in the MKN-45, BGC-823 and SGC-7901 cell lines. The association between expression levels and clinicopathological characteristics was evaluated by the Mann-Whitney U and Kruskal-Wallis tests. Using Kaplan-Meier plots and Cox proportional hazard models, overall survival (OS) was analyzed. Compared with non-cancerous tissue, CXCR2 and IL-22BP were over expressed (P<0.001 and P<0.001, respectively), and were observed mainly in the cytoplasm (P=0.022 and P=0.014, respectively) in GA. The associated protein and messenger RNA levels were analyzed, and coexpression was identified. Increased expression and more positive cases of CXCR2 and IL-22BP were observed with advanced pathological tumor-node-metastasis (p-TNM) stage in GC (P<0.001 and P<0.001, respectively), as well as the presence and absence of lymph node metastasis (LNM) (P=0.003 and P=0.041, respectively) and deep or superficial muscular invasion (P=0.002 and P=0.004, respectively). In addition, an association between IL-22BP and tumor diameter was indicated (P=0.021). In a Kaplan-Meier analysis, compared with negative expression, the two proteins identified a group of patients with the shortest OS. Cox proportional hazard models revealed that the two proteins, in addition to p-TNM stage, LNM and depth of invasion, predicted a short time to OS. The coexpression of CXCR2 and IL-22BP was demonstrated in GA, which may indicate that CXCR2 is involved in more complex mechanisms and roles, and indicate a poor outcome in GA progression.

Role of chemokine receptor CXCR2 expression in mammary tumor growth, angiogenesis and metastasis

BACKGROUND

Chemokines and their receptors have long been known to regulate metastasis in various cancers. Previous studies have shown that CXCR2 expression is upregulated in malignant breast cancer tissues but not in benign ductal epithelial samples. The functional role of CXCR2 in the metastatic phenotype of breast cancer still remains unclear. We hypothesize that the chemokine receptor, CXCR2, mediates tumor cell invasion and migration and promotes metastasis in breast cancer. The objective of this study is to investigate the potential role of CXCR2 in the metastatic phenotype of mouse mammary tumor cells.

MATERIALS AND METHODS

We evaluated the functional role of CXCR2 in breast cancer by stably downregulating the expression of CXCR2 in metastatic mammary tumor cell lines Cl66 and 4T1, using short hairpin RNA (shRNA). The effects of CXCR2 downregulation on tumor growth, invasion and metastatic potential were analyzed in vitro and in vivo.

RESULTS

We demonstrated knock down of CXCR2 in Cl66 and 4T1 cells (Cl66-shCXCR2 and 4T1-shCXCR2) cells by reverse transcriptase polymerase chain reaction (RT-PCR) at the transcriptional level and by immunohistochemistry at the protein level. We did not observe a significant difference in in vitro cell proliferation between vector control and CXCR2 knock-down Cl66 or 4T1 cells. Next, we examined the invasive potential of Cl66-shCXCR2 cells by in vitro Matrigel invasion assay. We observed a significantly lower number (52 ± 5) of Cl66-shCXCR2 cells invading through Matrigel compared to control cells (Cl66-control) (182 ± 3) (P < 0.05). We analyzed the in vivo metastatic potential of Cl66-shCXCR2 using a spontaneous metastasis model by orthotopically implanting cells into the mammary fat pad of female BALB/c mice. Animals were sacrificed 12 weeks post tumor implantation and tissue samples were analyzed for metastatic nodules. CXCR2 downregulation significantly inhibited tumor cell metastasis. All the mice (n = 10) implanted with control Cl66 cells spontaneously developed lung metastasis, whereas a significantly lower number of mice (40%) implanted with Cl66-shCXCR2 cells exhibited lung metastases.

CONCLUSIONS

Together, these results suggest that CXCR2 may play a critical role in breast cancer invasion and metastasis.

The functional significance behind expressing two IL-8 receptor types on PMN

PMN are critical to innate immunity and are fundamental to antibacterial defense. To localize to sites of infection, PMN possess receptors that detect chemoattractant stimuli elicited at the site, such as chemokines, complement split products, or bioactive lipids. Signaling through these receptors stimulates chemotaxis toward the site of infection but also activates a number of biochemical processes, with the result that PMN kill invading bacteria. PMN possess two receptors, CXCR1 and CXCR2, for the N-terminal ELR motif-containing CXC chemokines, although only two chemokine members bind both receptors and the remainder binding only CXCR2. This peculiar pattern in receptor specificity has drawn considerable interest and investigation into whether signaling through each receptor might impart unique properties on the PMN. Indeed, at first glance, CXCR1 and CXCR2 appear to be functionally redundant; however, there are differences. Considering these proinflammatory activities of activating PMN through chemokine receptors, there has been great interest in the possibility that blocking CXCR1 and CXCR2 on PMN will provide a therapeutic benefit. The literature examining CXCR1 and CXCR2 in PMN function during human and modeled diseases will be reviewed, asking whether the functional differences can be perceived based on alterations in the role PMN play in these processes.

Effect of interleukin-8 gene silencing with liposome-encapsulated small interfering RNA on ovarian cancer cell growth

BACKGROUND

Interleukin-8 (IL-8) is a proangiogenic cytokine that is overexpressed in many human cancers. We investigated the clinical and biologic significance of IL-8 in ovarian carcinoma using human samples and orthotopic mouse models.

METHODS

Tumor expression of IL-8 was assessed by immunohistochemistry among ovarian cancer patients (n = 102) with available clinical and survival data. We examined the effect of IL-8 gene silencing with small interfering RNAs incorporated into neutral liposomes (siRNA-DOPCs), alone and in combination with docetaxel, on in vivo tumor growth, angiogenesis (microvessel density), and tumor cell proliferation in mice (n = 10 per treatment group) bearing orthotopic taxane-sensitive (HeyA8 and SKOV3ip1) and taxane-resistant (SKOV3ip2.TR) ovarian tumors. All statistical tests were two-sided.

RESULTS

Of the 102 cancer specimens, 43 (42%) had high IL-8 expression and 59 (58%) had low or no IL-8 expression; high IL-8 expression was associated with advanced tumor stage (P = .019), high tumor grade (P = .031), and worse survival (median survival for patients with high vs low IL-8 expression: 1.62 vs 3.79 years; P < .001). Compared with empty liposomes, IL-8 siRNA-DOPC reduced the mean tumor weight by 32% (95% confidence interval [CI] = 14% to 50%; P = .03) and 52% (95% CI = 27% to 78%; P = .03) in the HeyA8 and SKOV3ip1 mouse models, respectively. In all three mouse models, treatment with IL-8 siRNA-DOPC plus the taxane docetaxel reduced tumor growth the most compared with empty liposomes (77% to 98% reduction in tumor growth; P < .01 for all). In the HeyA8 and SKOV3ip1 models, tumors from mice treated with IL-8 siRNA-DOPC alone had lower microvessel density than tumors from mice treated with empty liposomes (HeyA8: 34% lower, 95% CI = 32% to 36% lower [P = .002]; SKOV3ip1: 39% lower, 95% CI = 34% to 44% lower [P = .007]). Compared with empty liposomes, IL-8 siRNA-DOPC plus docetaxel reduced tumor cell proliferation by 35% (95% CI = 25% to 44%; P < .001) and 38% (95% CI = 28% to 48%; P < .001) in the HeyA8 and SKOV3ip1 models, respectively.

CONCLUSIONS

Increased IL-8 expression is associated with poor clinical outcome in human ovarian carcinoma, and IL-8 gene silencing decreases tumor growth through antiangiogenic mechanisms.

Murine CXCR1 is a functional receptor for GCP-2/CXCL6 and interleukin-8/CXCL8

Functional interleuin-8 (IL-8) receptors (IL-8RA and IL-8RB: CXCR1 and CXCR2, respectively) have been described in human, monkey, dog, rabbit, and guinea pig. Although three IL-8R homologues have been found in rat, only one of these, rat CXCR2, appears to be functional based on responsiveness to ligands. Similarly, CXC chemokines induce biological responses through the murine homolog of CXCR2, but the identification of functional rodent CXCR1 homologues has remained elusive. We have identified and characterized the mouse CXCR1 homologue (mCXCR1). Murine CXCR1 shares 68 and 88% amino acid identity with its human and rat counterparts, respectively. Similar to the tissue distribution pattern of rat CXCR1, we found murine CXCR1 mRNA expression predominantly in lung, stomach, bone marrow, and leukocyte-rich tissues. In contrast to previous reports, we determined that mCXCR1 is a functional receptor. We show predominant engagement of this receptor by mouse GCP-2/CXCL6, human GCP-2, and IL-8/CXCL8 by binding, stimulation of GTPgammaS exchange, and chemotaxis of mCXCR1-transfected cells. Furthermore, murine CXCR1 is not responsive to the human CXCR2 ligands ENA-78/CXCL5, NAP-2/CXCL7, GRO-alpha, -beta, -gamma/CXCL1-3, or rat CINC-1-3. In addition, we show concomitant elevation of mCXCR1 and its proposed major ligand, GCP-2, positively correlated with paw swelling in murine collagen-induced arthritis. This report represents the first description of a functional CXCR1-like receptor in rodents.

Interleukin-1-dependent sequential chemokine expression and inflammatory cell infiltration in ischemia-reperfusion injury

OBJECTIVE

Ischemia-reperfusion injury is known to cause organ failure, but the mechanisms of pathogenesis remain unclear. Inflammation is a factor in tissue destruction in ischemia reperfusion injury, and interleukin (IL)-1 is a key promoter of inflammation.

DESIGN

Prospective, randomized, and controlled study.

SETTING

University laboratory.

SUBJECTS

Male mice 6-8 wks of age, in which genes for IL-1alpha and IL-1beta (IL-1alpha/beta deficient) and IL-1 receptor antagonist (IL-1RA deficient) are deleted by homologous recombination, and wild-type controls on a Balb/c background.

INTERVENTIONS

In this study, the role of IL-1 on inflammatory cascades, including chemokine expression, inflammatory cell infiltration, and tissue destruction, was investigated in 45 mins of unilateral renal ischemic injury using IL-1alpha/beta-deficient mice and IL-1RA-deficient mice. In addition, the effects of IL-1 on chemokine expression in cultured tubular epithelial cells were investigated.

MEASUREMENTS AND MAIN RESULTS

In vivo study revealed that the number of interstitial infiltrated neutrophils and macrophages, which accompanied the increase of the serum levels of keratinocyte-derived chemokine (KC) and macrophage inflammatory protein (MIP)-1alpha, respectively, significantly increased in IL-1RA-deficient mice. The number of interstitial infiltrated neutrophils correlated well with serum levels of KC at 24 hrs after reperfusion, whereas the number of interstitial infiltrated macrophages correlated well with the serum levels of MIP-1alpha and monocyte chemoattractant protein (MCP)-1 at 24 and 48 hrs after reperfusion, respectively. Likewise, in vitro study revealed that stimulation of tubular epithelial cells by IL-1beta and/or H2O2 sequentially induced KC, MIP-1alpha, and MCP-1 in both protein and messenger RNA levels, which is consistent with in vivo results.

CONCLUSION

IL-1-dependent inflammatory cascades, followed by inflammatory cell infiltration and subsequent tissue destruction, may affect pathogenesis of renal ischemia-reperfusion injury.

Overexpression of IL-8 in the cornea induces ulcer formation in the SCID mouse

AIMS

Although interleukin 8 (IL-8) is not produced in the normal cornea, it has been detected there in several pathological conditions. In this study, the direct effects of IL-8 overexpression on the cornea was examined.

METHODS

The corneal surface of severe combined immunodeficiency mice was infected by the adenovirus vector encoding human IL-8 (IL-8/Ad5) and clinical and pathological changes were observed at various time points.

RESULTS

Clinically, marked angiogenesis and ulcer formation in the cornea were observed by 12 hours and 24 hours, respectively. Histologically, prominent angiogenesis was observed in the corneal stroma at 12 hours. Cleft formation between the corneal epithelium and stroma, and neutrophil infiltration into the corneal stroma were seen at 16 hours. By 24 hours after the infection with IL-8/Ad5, a shallow ulcer was formed in the cornea. In contrast, infection with the control adenovirus carrying the beta galactosidase gene (LacZ) showed neither corneal ulceration nor neutrophil infiltration. Immunohistochemical analysis showed that infection with IL-8/Ad5 resulted in the production of IL-8 by corneal and conjunctival stromal cells.

CONCLUSION

Our results indicate that IL-8 overexpression in corneal tissue causes ulcer formation in the cornea through chemoattraction of neutrophils, suggesting the aetiological role of IL-8 in some types of corneal ulcers.

A homolog of the human chemokine receptor CXCR1 is expressed in the mouse

Two distinct genes are present in the human genome encoding receptors for human interleukin-8 (hCXCL8), referred to as hCXCR1 and hCXCR2. While it seems clear that orthologous genes are present in the genomes of several mammals, the existence of a gene encoding an ortholog of hCXCR1 in the mouse has thus far been controversial. We have isolated a cDNA that is highly similar to the cDNAs of hCXCR1 and hCXCR2, but is clearly distinct from the cDNA encoding mouse CXCR2 (mCXCR2). The encoded protein, designated mouse CXCR1-like (mCXCR1-like), shares 64, 57, 57, and 89% identical amino acids with hCXCR1, hCXCR2, mCXCR2, and rCXCR1-like, respectively. The gene encoding mCXCR1-like was mapped to mouse chromosome 1 and its genomic organization was determined to be very similar to the organization of the gene encoding hCXCR1. Like hCXCR1, mCXCR1-like was found to be expressed at the mRNA level in neutrophils. In addition, mRNA encoding mCXCR1-like was detected in liver, kidney, and spleen. In spleen, mCXCR1-like transcripts were predominantly found in CD4+ T cells. In liver, mCXCR1-like transcripts were identified in residual CD3+ T cells and macrophages, suggesting that mCXCR1-like may regulate inflammatory and immunological processes in the liver. When expressed as a recombinant protein, mCXCR1-like was not activated by a large panel of known CXC chemokines of human and murine origin. These findings suggest that a homolog or ortholog of hCXCR1 is expressed in the mouse to be activated by a hitherto unknown CXC chemokine of the mouse.

CXCR2 is critical for dsRNA-induced lung injury: relevance to viral lung infection

BACKGROUND: Respiratory viral infections are characterized by the infiltration of leukocytes, including activated neutrophils into the lung that can lead to sustained lung injury and potentially contribute to chronic lung disease. Specific mechanisms recruiting neutrophils to the lung during virus-induced lung inflammation and injury have not been fully elucidated. Since CXCL1 and CXCL2/3, acting through CXCR2, are potent neutrophil chemoattractants, we investigated their role in dsRNA-induced lung injury, where dsRNA (Poly IC) is a well-described synthetic agent mimicking acute viral infection. METHODS: We used 6-8 week old female BALB/c mice to intratracheally inject either single-stranded (ssRNA) or double-stranded RNA (dsRNA) into the airways. The lungs were then harvested at designated timepoints to characterize the elicited chemokine response and resultant lung injury following dsRNA exposure as demonstrated qualititatively by histopathologic analysis, and quantitatively by FACS, protein, and mRNA analysis of BAL fluid and tissue samples. We then repeated the experiments by first pretreating mice with an anti-PMN or corresponding control antibody, and then subsequently pretreating a separate cohort of mice with an anti-CXCR2 or corresponding control antibody prior to dsRNA exposure. RESULTS: Intratracheal dsRNA led to significant increases in neutrophil infiltration and lung injury in BALB/c mice at 72 h following dsRNA, but not in response to ssRNA (Poly C; control) treatment. Expression of CXCR2 ligands and CXCR2 paralleled neutrophil recruitment to the lung. Neutrophil depletion studies significantly reduced neutrophil infiltration and lung injury in response to dsRNA when mice were pretreated with an anti-PMN monoclonal Ab. Furthermore, inhibition of CXCR2 ligands/CXCR2 interaction by pretreating dsRNA-exposed mice with an anti-CXCR2 neutralizing Ab also significantly attenuated neutrophil sequestration and lung injury. CONCLUSION: These findings demonstrate that CXC chemokine ligand/CXCR2 biological axis is critical during the pathogenesis of dsRNA-induced lung injury relevant to acute viral infections.

Cloning and characterization of mouse homolog of the CXC chemokine receptor CXCR1

CXCR2/IL-8RB was the only receptor previously reported in mice for ELR+ CXC chemokines, whereas the receptors for these chemokines in human include both CXCR1 and CXCR2. In this study, we cloned the full length cDNA of the mouse CXCR1 (mCXCR1) gene. The deduced amino acid of mCXCR1 was 77% and 58% identical to the rat and human CXCR1, respectively. RT-PCR and Northern blot analysis showed that mCXCR1 mRNA was expressed in lung, spleen, thymus, peripheral blood leukocytes, as well as in the isolated neutrophils. In a mouse respiratory inflammation model induced by lipopolysaccharide, a large number of neutrophils infiltrated into the lung and, meanwhile, the mCXCR1 expression was significantly increased in the recruited neutrophils, suggesting that mCXCR1 may mediate the recruitment of neutrophils to the inflammation site under certain infections.

Cloning and Pharmacological Characterization of CXCR1 and CXCR2 fromMacaca fascicularis

Two genes with high sequence homology to human CXCR1 (hCXCR1) and CXCR2 (hCXCR2) were cloned from blood of cynomolgus monkey (Macaca fascicularis). Comparison of the expression pattern of these receptors in different species demonstrated that, like in humans, cynomolgus CXCR1 (cCXCR1) and CXCR2 (cCXCR2) are highly expressed in blood. Membranes from transfected BaF3 cells expressing cCXCR1 bind interleukin (IL)-8 with an affinity similar to hCXCR1 (Kd values, 170 +/- 87 and 103 +/- 37 pM, respectively) and show low binding affinity to Gro-alpha. Cynomolgus CXCR2 also binds hIL-8 but with somewhat higher affinity than the hCXCR2 (46 +/- 28 and 220 +/- 14 pM, respectively). Surprisingly, cCXCR2 has a reduced binding affinity to hGro-alpha (3.7 +/- 2.2 nM), a specific ligand of hCXCR2 (540 +/- 140 pM). Furthermore, the CXCR2-specific antagonist SB225002 [N-(2-hydroxy-4-nitrophenyl)-N'-(2-bromophenyl)urea] is 10-fold more potent in inhibiting IL-8 binding to hCXCR2 than to cCXCR2, suggesting that some of the observed differences in the amino acid sequences of the human and monkey receptor affect ligand binding sites or the conformation of the receptor. Both cynomolgus receptors were functionally active in inducing guanosine 5'-O-(3-thio)triphosphate exchange on membranes in response to IL-8 and Gro-alpha and in mediating chemotactic activity of recombinant BA/F3 cells in response to IL-8 and Gro-alpha. These results identify the products of the novel cynomolgus genes as functional homologs of hCXCR1 and hCXCR2.

Critical role for CXCR2 and CXCR2 ligands during the pathogenesis of ventilator-induced lung injury

Mortality related to adult respiratory distress syndrome (ARDS) ranges from 35% to 65%. Lung-protective ventilator strategies can reduce mortality during ARDS. The protective strategies limit tidal volumes and peak pressures while maximizing positive end-expiratory pressure. The efficacy of this approach is due to a reduction of shear-stress of the lung and release of inflammatory mediators. Ventilator-induced lung injury (VILI) is characterized by inflammation. The specific mechanism(s) that recruit leukocytes during VILI have not been elucidated. Because the murine CXC chemokines KC/CXCL1 and MIP-2/CXCL2/3, via CXCR2, are potent neutrophil chemoattractants, we investigated their role in a murine model of VILI. We compared two ventilator strategies in C57BL/6 mice: high peak pressure and high stretch (high peak pressure/stretch) versus low peak pressure/stretch for 6 hours. Lung injury and neutrophil sequestration from the high-peak pressure/stretch group were greater than those from the low-peak pressure/stretch group. In addition, lung expression of KC/CXCL1 and MIP-2/CXCL2/3 paralleled lung injury and neutrophil sequestration. Moreover, in vivo inhibition of CXCR2/CXC chemokine ligand interactions led to a marked reduction in neutrophil sequestration and lung injury. These findings were confirmed using CXCR2(-/-) mice. Together these experiments support the notion that increased expression of KC/CXCL1 and MIP-2/CXCL2/3 and their interaction with CXCR2 are important in the pathogeneses of VILI.

Disruption of neutrophil migration in a conditional transgenic model: evidence for CXCR2 desensitization in vivo

We developed transgenic mice conditionally expressing the neutrophil chemoattracting chemokine KC and the beta-galactosidase gene in multiple tissues. In these transgenic mice, doxycycline treatment induced a strong up-regulation in the expression of KC in several tissues, including heart, liver, kidney, skin, and skeletal muscle. Expression of KC within these tissues led to a rapid and substantial increase in the serum levels of KC (serum KC levels were higher than 200 ng/ml 24 h after treatment). Accordingly, beta-galactosidase expression was also detected after injection of doxycycline and was highest in skeletal muscle, pancreas, and liver. Surprisingly, despite expression of KC in multiple tissues, no neutrophil infiltration was observed in any of the tissues examined, including skin. Doxycycline treatment of nontransgenic mice grafted with transgenic skin caused dense neutrophilic infiltration of the grafts, but not the surrounding host skin, indicating that the KC produced in transgenic tissues was biologically active. In separate experiments, neutrophil migration toward a localized source of recombinant KC was impaired in animals overexpressing KC but was normal in response to other neutrophil chemoattractants. Analysis of transgenic neutrophils revealed that high concentrations of KC in transgenic blood had no influence on L-selectin cell surface expression but caused desensitization of the receptor for KC, CXCR2. These results confirm the neutrophil chemoattractant properties of KC and provide a mechanistic explanation for the paradoxical lack of leukocyte infiltration observed in the presence of elevated concentrations of this chemokine.

Chemokine-dependent neutrophil recruitment in a murine model of Legionella pneumonia: potential role of neutrophils as immunoregulatory cells

The roles of CXC chemokine-mediated host responses were examined with an A/J mouse model of Legionella pneumophila pneumonia. After intratracheal inoculation of 10(6) CFU of L. pneumophila, the bacterial numbers in the lungs increased 10-fold by day 2; this increase was accompanied by the massive accumulation of neutrophils. Reverse transcription-PCR data demonstrated the up-regulation of CXC chemokines, such as keratinocyte-derived chemokine, macrophage inflammatory protein 2 (MIP-2), and lipopolysaccharide-induced CXC chemokine (LIX). Consistent with these data, increased levels of KC, MIP-2, and LIX proteins were observed in the lungs and peaked at days 1, 2, and 2, respectively. Although the administration of anti-KC or anti-MIP-2 antibody resulted in an approximately 20% decrease in neutrophil recruitment on day 2, no increase in mortality was observed. In contrast, the blockade of CXC chemokine receptor 2 (CXCR2), a receptor for CXC chemokines, including KC and MIP-2, strikingly enhanced mortality; this effect coincided with a 67% decrease in neutrophil recruitment. Interestingly, anti-CXCR2 antibody did not affect bacterial burden by day 2, even in the presence of a lethal challenge of bacteria. Moreover, a significant decrease in interleukin-12 (IL-12) levels, in contrast to the increases in KC, MIP-2, and LIX levels, was demonstrated for CXCR2-blocked mice. These data indicated that CXCR2-mediated neutrophil accumulation may play a crucial role in host defense against L. pneumophila pneumonia in mice. The increase in lethality without a change in early bacterial clearance suggested that neutrophils may exert their protective effect not through direct killing but through more immunomodulatory actions in L. pneumophila pneumonia. We speculate that a decrease in the levels of the protective cytokine IL-12 may explain, at least in part, the high mortality in the setting of reduced neutrophil recruitment.

Large and sustained induction of chemokines during impaired wound healing in the genetically diabetic mouse: prolonged persistence of neutrophils and macrophages during the late phase of repair

Chemokines are seen as the stimuli that largely control leukocyte migration. To assess whether the severely impaired process of cutaneous repair observed in genetically diabetic db/db mice is associated with a dysregulated infiltration of immune cells, we determined the expressional kinetics for the murine growth-regulated oncogene/melanoma growth stimulatory activity homolog macrophage inflammatory protein-2, and the macrophage chemoattractant protein-1, respectively. Wound repair in db/db mice was characterized by a sustained inflammatory response and a prolonged expression of macrophage inflammatory protein-2 and macrophage chemoattractant protein-1. Immuno-histochemistry revealed that keratinocytes at the wound margins expressed macrophage chemoattractant protein-1, whereas macrophage inflammatory protein-2 immunopositive signals were observed only in keratinocytes of hair follicles located adjacent to the wound site. Inactivation studies using neutralizing antibodies against macrophage chemoattractant protein-1 or macrophage inflammatory protein-2 indicated that sustained expression of these chemokines participated in a prolonged presence of neutrophils and macrophages at the wound site during diabetic repair. Furthermore, our data provide evidence that late infiltration (day 13 after injury) of neutrophils and macrophages into wounds in db/db mice was associated with a simultaneous downregulation of mRNA for receptors specific for macrophage inflammatory protein-2 and macrophage chemoattractant protein-1 in these animals.

The isolation and sequence of canine interleukin-8 receptor

A cDNA corresponding to canine IL-8 receptor has been cloned and sequenced. The cDNA was synthesized using RT-PCR, with oligonucleotide primers designed from conserved regions of published IL-8 receptors. The 5'-end was cloned by 5'-RACE and the 3'-end was cloned by 3'-RACE. The cDNA encodes a predicted full length IL-8r protein of 356 amino acids. At the nucleic acid level, the canine cDNA shows 83.9%, 82.4%/78.8%, 81.5%/78%, 81.4%/77.7%, 77.8% and 77.3%/71.9% identity to published sequences of bovine, human, gorilla, rabbit, mouse and rat IL8RB/IL8RA, respectively. The derived protein from the cDNA sequences shows 75.3%/70.3%, 75.3%/70.1%, 74.8%/69.4%, 70%/59%, and 69.7% identity to that of human, rabbit, gorilla, rat and mouse IL8RB/IL8RA homolog.

Bacterial clearance and survival are dependent on CXC chemokine receptor-2 ligands in a murine model of pulmonary Nocardia asteroides infection

Survival from murine pulmonary nocardiosis is highly dependent on CXC chemokine receptor-2 (CXCR2) ligand-mediated neutrophil chemotaxis and subsequent clearance of the infectious agent Nocardia asteroides. Intratracheal inoculation of N. asteroides rapidly up-regulated the CXC chemokines macrophage inflammatory protein-2 (MIP-2) and KC within 24 h, with levels remaining elevated through day 3 before returning to near baseline levels by day 7. Coinciding with elevated MIP-2 and KC were the rapid recruitment of neutrophils and clearance of the organism. Anti-Ly-6G Ab-mediated neutrophil depletion before bacterial challenge resulted in strikingly increased mortality to N. asteroides infection. The relative contribution of MIP-2 in neutrophil recruitment was examined by anti-MIP-2 Ab treatment before nocardial infection. MIP-2 neutralization had no detrimental effects on survival, neutrophil recruitment, or bacterial clearance, suggesting the usage of additional or alternative CXCR2-binding ligands. The importance of the CXC family of chemokines was determined by the administration of an anti-CXCR2 Ab capable of blocking ligand binding in vivo. Anti-CXCR2 treatment greatly increased mortality by preventing neutrophil migration into the lung. Paralleling this impaired neutrophil recruitment was a 100-fold increase in lung bacterial burden. Combined, these observations indicate a critical role for neutrophils and CXC chemokines during nocardial pneumonia. These data directly link CXCR2 ligands and neutrophil recruitment and lend further support to the concept of CXC chemokine redundancy. For infections highly dependent on neutrophils, such as nocardial pneumonia, this is of critical importance.

CXC chemokines interleukin-8 (IL-8) and growth-related gene product alpha (GROalpha) modulate Purkinje neuron activity in mouse cerebellum

We give here evidence that Purkinje neurons (PNs) of mouse cerebellar slices studied with patch clamp technique combined with laser confocal microscopy, respond to human IL-8 and GROalpha by (i) a cytosolic Ca2+ transient compatible with inositol (1,4,5) trisphosphate (InsP3) formation; (ii) an enhancement of the neurotransmitter release; and (iii) an impairment of the long-term depression of synaptic strength (LTD). It was also found the expression of IL-8 receptor type 2 in PN and granule cells by immunofluorescence, immunoblotting and RT-PCR analysis. Considered together these findings suggest that IL-8 and GROalpha may play a neuromodulatory role on mouse cerebellum.

Representational difference analysis of a committed myeloid progenitor cell line reveals evidence for bilineage potential

In this study we have sought to characterize a committed myeloid progenitor cell line in an attempt to isolate general factors that may promote differentiation. We used cDNA representational difference analysis (RDA), which allows analysis of differential gene expression, to compare EML and EPRO cells. We have isolated nine differentially expressed cDNA fragments as confirmed by slot blot, Northern, and PCR analysis. Three of nine sequences appear to be novel whereas the identity of the remaining fragments suggested that the EPRO cell line is multipotent. Among the isolated sequences were eosinophilic, monocytic, and neutrophilic specific genes. Therefore, we tested the ability of EPRO cells to differentiate along multiple myeloid lineages and found that EPRO cells exhibited morphologic maturation into either monocyte/macrophages or neutrophils, but not eosinophils. Furthermore, when EPRO cells were exposed to ATRA, neutrophil specific genes were induced, whereas monocytic markers were induced by phorbol ester treatment. This study highlights the use of cDNA RDA in conjunction with the EML/EPRO cell line to isolate markers associated with macrophage and neutrophil differentiation and establishes the usefulness of this system in the search for factors involved in myeloid commitment.

Physiologic Regulation of Postovulatory Neutrophil Migration into Vagina in Mice by a C-X-C Chemokine(s)

Leukocytes, particularly neutrophils, infiltrate into female genital organs after ovulation in both humans and mice. In mice, a female sexual cycle consists of 5 phases: proestrus, estrus, metestrus-1, metestrus-2, and diestrus. Ovulation occurs at estrus; at metestrus-2, a large number of neutrophils infiltrate into the vaginal epithelium accompanied by an increased neutrophil number in vaginal lavage fluid. Concomitantly, concentrations of a functional IL-8 homologue, murine macrophage inflammatory protein (MIP)-2, were increased significantly in vaginal lavage fluid at metestrus-2 as compared with other phases. On the contrary, MIP-2 was not detected in plasma during the whole course of a sexual cycle. Moreover, immunohistochemical analyses demonstrated that MIP-2 protein expression was prominent at the upper layer of the vaginal epithelium at metestrus-2, in contrast to a marginal staining in the vaginal epithelium at proestrus and estrus. These results suggest that a C-X-C chemokine, MIP-2, was produced physiologically in the vaginal epithelium in a sexual cycle-dependent manner. Furthermore, the administration of neutralizing anti-IL-8R homologue Abs at proestrus abrogated leukocyte infiltration into the vagina at metestrus. However, anti-MIP-2 Abs reduced leukocyte influx at metestrus by ∼50%. Thus, a murine IL-8 homologue, MIP-2, and its related molecules physiologically regulate neutrophil migration into the vagina in a sexual cycle-dependent manner.

Chemokine receptor expression in cultured glia and rat experimental allergic encephalomyelitis

Chemokines are a group of pro-inflammatory peptides that mediate leukocyte migration and activation. Several members of the chemokine family have been shown to be synthesized by cells of the central nervous system (CNS). To begin to address the role of chemokine receptors in CNS physiology, we identified, by molecular cloning techniques, the rat orthologs of the chemokine receptors, CCR2, CCR3, CCR5, and CXCR4. CCR2 and CCR5 expression was detected in rat spleen, lung, kidney, thymus and macrophages; CCR5 mRNA was also detected in rat brain. Primary cultures of rat microglia expressed CCR5 mRNA that was regulated by IFN-gamma, while both cultured astrocytes and microglia were found to contain mRNA for CXCR4 and CX3CR1. Induction of experimental allergic encephalomyelitis (EAE) in the rat was accompanied by increased levels of CCR2, CCR5, CXCR4, and CX3CR1 mRNAs in the lumbar spinal cords of animals displaying clinical signs of the disease. These data identify the rat orthologs of chemokine receptors and demonstrate that brain, spinal cord, and cultured glial cells express chemokine receptors that can be regulated both in vitro and in vivo.

Molecular cloning and characterization of a cDNA encoding the rat interleukin-8 receptor

In this study we present the cloning, characterization and expression analysis of a cDNA encoding a rat interleukin-8 receptor (rIL-8R). A 1324 bp cDNA containing an open reading of 359 amino acids with an 86.1% overall identity with the previously characterized mouse IL-8R was isolated. Genomic DNA analysis using several restriction enzymes revealed a single band suggesting that the rIL-8R gene exists as a single-copy, which is in contrast to humans where there are two different IL-8Rs genes. Expression of rIL-8R mRNA was found in several tissues including spleen, heart, lung, liver, skeletal muscle and kidney. In brain and testis rIL-8R mRNA was not detectable. Rat IL-8R mRNA expression at the cellular level was studied in the spleen using RNA-RNA in situ hybridization and immunohistochemistry. IL-8R mRNA containing cells were predominately found in the mantle zone of the germinal center. These cells were identified as B lymphocytes using the OX-33 monoclonal antibody.

Identification of two rat genes orthologous to the human interleukin-8 receptors

The genes encoding two functional human interleukin-8 (IL-8) receptors have been identified by molecular cloning techniques and they are members of the rhodopsin G-protein coupled receptor (GCR) superfamily. We report the molecular cloning of two rat GCR genes (rat CXCR1-like and rat CXCR2) whose conceptualized amino acid sequences are approximately 70% identical to the human IL-8 A and B receptor subtypes. The murine GRO-like peptide, macrophage inflammatory peptide-2 (MIP-2), elevates intracellular calcium levels in HEK293 cells expressing the rat CXCR2 receptor. Southern blot analysis of restriction-digested rodent and human genomic DNAs indicate that rat CXCR1-like and CXCR2 are: 1) each single copy genes in the rat genome; 2) most closely related to the human IL-8 receptor genes; and 3) orthologous to two previously identified murine genes. CXCR2 mRNA is detected in adult rat lung, spleen, and neutrophils. CXCR1-like mRNA can be detected in adult rat lung, native rat macrophages, and a rat alveolar macrophage cell line (NR8383). These data identify the rat orthologs of the human IL-8 receptors, and describe cellular and tissue targets of rat C-X-C chemokine peptides.

Characterization of interleukin-8 receptors in non-human primates

Interleukin-8 is a chemokine with a potent neutrophil chemoattractant activity. In humans, two different cDNAs encoding human IL8 receptors designated IL8RA and IL8RB have been cloned. IL8RA binds IL8, while IL8RB binds IL8 as well as other alpha-chemokines. Both human IL8Rs are encoded by two genes physically linked on chromosome 2. The IL8RA and IL8RB genes have open reading frames (ORF) lacking introns. By direct sequencing of the polymerase chain reaction products, we sequenced the IL8R genes of cell lines from four non-human primates: chimpanzee, gorilla, orangutan, and macaca. The IL8RB encodes an ORF in the four non-human primates, showing 95% - 99% similarity to the human IL8RB sequence. The IL8RA homologue in gorilla and chimpanzee consisted of two ORF 98% - 99% identical to the human sequence. The macaca and orangutan IL8RA homologues are pseudogenes: a 2 base pair insertion generated a sequence with several stop codons. In addition, we describe the physical linkage of these genes in the four non-human primates and discuss the evolutionary implications of these findings.

Activation of protein kinase C enhances the phosphorylation of the type B interleukin-8 receptor and stimulates its degradation in non-hematopoietic cells

We have previously characterized the stably transfected, clonally selected human placental cell line, 3ASubE P-3, which overexpresses the type B interleukin-8 receptor (IL-8RB) and responds to the chemokine melanoma growth stimulatory activity (MGSA) with enhanced phosphorylation of this receptor. In work described here, we demonstrate that the MGSA-enhanced phosphorylation of this receptor is mediated via a process involving pertussis toxin-sensitive G proteins. Furthermore, treatment of the 3ASubE P-3 cells with either 12-O-tetradecanoylphorbol 13-acetate (TPA) or 1,2-dioctanoyl-sn-glycerol (diC8), two different activators of protein kinase C (PKC), results in a concentration-dependent increase in the phosphorylation of the IL-8RB. Inhibition of PKC, by treatment with staurosporin (50 nM for 2 h), or down-regulation of PKC, by prolonged treatment with TPA (400 nM for 40 h) suppresses the TPA-enhanced receptor phosphorylation, but has no effect on the MGSA-enhanced receptor phosphorylation. These data suggest that the isoforms of PKC that are sensitive to these manipulations may not play a role in mediating the MGSA-enhanced phosphorylation of the IL-8RB. TPA treatment also results in a time-dependent decrease in 125I-MGSA binding to the 3ASubE P-3 cells. A 30-min treatment with 400 nM TPA results in approximately a 50% decrease in binding, whereas a 2-h treatment essentially eliminates specific binding of 125I-MGSA to these cells. The TPA-induced decrease in 125I-MGSA binding is accompanied by enhanced degradation of the IL-8RB, as indicated by Western blot analysis and pulse-chase experiments, suggesting a potential role for PKC as a negative regulator of the IL-8RB. MGSA treatment (50 nM for 2 h) also stimulates receptor degradation in the 3ASubE P-3 cells, indicating that this receptor is down-regulated in response to prolonged exposure to its ligand. In similar studies conducted on the promonocytic cell line, U937, MGSA treatment of the U937 cells resulted in receptor phosphorylation, whereas PKC activation failed to significantly modulate the phosphorylation state of the IL-8RB. Treatment of the U937 cells with MGSA, TPA, or diC8 resulted in a loss of receptor protein present in these cell types. These data imply that MGSA signaling through the IL-8RB is similar in both the non-hematopoietic and hematopoietic cell types, whereas activation of PKC by TPA or diC8 elicits different responses in these two distinct cell types.

The orphan mouse receptor interleukin (IL)-8R beta binds N51. Structure-function analysis using N51/IL-8 chimeric molecules

We have demonstrated that the orphan receptor representing the putative mouse (mu) homolog of the human (hu) interleukin-8 receptor beta (IL-8R beta) binds the mouse N51 cytokine, also known as KC. The muIL-8R beta gene was constitutively expressed in NIH 3T3 cells (NIH-muIL-8R beta). Cells and plasma membranes from the NIH-muIL-8R beta clone showed binding of 125I-N51 that was displaced by unlabeled N51. Other related cytokines were assayed for their ability to displace 125I-N51. MIP-2 and GRO alpha/MGSA competed as well as N51 for the receptor, but huIL-8 and NAP-2 did not compete at all. Chimeric molecules between IL-8 and N51 were used to extend the binding analysis. The segment between the conserved cysteines 2 and 3, named domain I; cysteines 3 and 4, domain II; and cysteine 4 and the C terminus, domain III of IL-8 were replaced by the corresponding domains of N51 and vice versa. When studying the binding of 125I-N51 and the hybrid molecules to the receptor, we observed that chimeras of N51 containing either domain I, II, or III of IL-8 were agonists of N51, and chimeras of IL-8 containing domain II or III of N51 were partial agonists of N51. These results demonstrate that domain I of N51 does not confer binding specificity and suggest that the region from the third cysteine to the C terminus of the N51 molecule is more important for binding to muIL-8R beta.

Interleukin-8 induces motile behavior and loss of focal adhesions in primary fibroblasts

Interleukin-8 (IL-8) is a proinflammatory cytokine that promotes neutrophil migration. Although fibroblasts are known to secrete IL-8, the actions of this cytokine on fibroblasts have not been previously reported. We have found that in subconfluent populations of cultured primary fibroblasts, IL-8 causes an increase in the percentage of cells lacking focal adhesions. Most of the IL-8-stimulated cells not only exhibit a lack of focal adhesions but also have a migratory phenotype that includes a protrusive leading edge and trailing tail. In addition, IL-8 was found to promote primary fibroblast chemotaxis in modified Boyden chambers as well as chemokinesis on serum-coated coverslips. Human primary fibroblasts were also found to specifically bind to IL-8 with high affinity. We have previously shown that a lack of focal structures in primary fibroblasts can be used as an index of chemokinetic locomotion and have fully characterized this system using newborn rat heart conditioned medium. The main stimulus in heart conditioned medium that is responsible for the lack of focal adhesions in the majority of cells can be immunoprecipitated using a polyclonal antibody against recombinant human IL-8. Additionally, video microscopy assays using heart conditioned medium depleted with the IL-8 antibody show an increase in the percentage of stationary cells, a consequent decrease in the percentage of migrating cells, and a twofold increase in the mitotic rate. Interleukin-1 alpha and tumor necrosis factor-alpha, which are early inflammatory cytokines, have been previously shown to stimulate IL-8 production in macrophages, fibroblasts, endothelial and epithelial cells. Our findings indicate that these two cytokines also cause an increase in the percentage of fibroblasts without focal adhesions. Additionally, this increase in cells lacking focal structures can be largely attributed to the production and subsequent autocrine action of a factor immunoprecipitated with an IL-8 antibody. Conversely, GRO-alpha, which has a high homology with IL-8, does not cause a similar increase in the percentage of cells lacking focal adhesions, but was not antagonistic to the effects of IL-8.