Chemokines--chemotactic cytokines that mediate inflammation

Redox regulation of chemokine receptor expression

Cytokines and reactive oxygen intermediates (ROI) are frequent companions at sites of acute inflammation. We have shown previously that in human monocytes, bacterial lipopolysaccharide, IL-1, and tumor necrosis factor-alpha induce a rapid down-regulation of the monocyte chemotactic protein-1 receptor CCR2 (CC chemokine receptor-2). These stimuli also induce production of ROI. In this paper, we investigate the influence of antioxidants and/or ROI on chemokine-receptor expression. In human monocytes, the antioxidant pyrrolidine dithiocarbamate (PDTC) rapidly inhibited CCR2 (95-100% of inhibition) and CCR5 (77-100% of inhibition) mRNA expression by strongly decreasing transcript stability. CCR2 half-life was decreased from 1.5 h to 45 min; CCR5 half-life was decreased from 2 h to 70 min. This inhibitory activity also included CXCR4 (CXC chemokine receptor-4) but not CXCR2 receptor and, although to a lesser extent, was shared by the antioxidants N-acetyl-l-cysteine and 2-mercaptoethanol. In contrast, the ROI-generating system xanthine/xanthine oxidase increased CCR5 and CXCR4 mRNA expression and counteracted the inhibitory effect of PDTC. Accordingly, H(2)O(2) and the glutathione-depleting drug buthionine sulfoximine increased to different extents CCR2, CCR5, and CXCR4 mRNA expression. The PDTC-mediated inhibition of CCR5 and CXCR4 mRNA expression was associated with decreased chemotactic responsiveness (>90% inhibition) and with a marked inhibition of surface-receptor expression. In contrast, xanthine/xanthine oxidase opposed the bacterial lipopolysaccharide- and tumor necrosis factor-alpha-mediated inhibition of CCR5 and CXCR4 mRNA expression and increased both the CCR5 surface expression and the cell migration (3-fold) in response to macrophage inflammatory protein-1beta. These results suggest that the redox status of cells is a crucial determinant in the regulation of the chemokine system.

Endothelial cell expression of monocyte chemotactic protein-1, tissue factor, and thrombomodulin on hydrophilic plasma polymers

Endothelial cells (EC) from human aortas, microvessels, and pulmonary arteries were examined for their expression and activity of monocyte chemotactic protein-1 (MCP-1), tissue factor, and thrombomodulin in response to tumor necrosis factor-alpha (TNFalpha) on the hydrophilic plasma polymers gamma-butyrolactone (GBL) and N-vinyl-2-pyrrolidone (NVP), along with a fibronectin (FN) control. RNAs isolated from EC grown on these substrates were subjected to reverse transcription-polymerase chain reaction (RT-PCR) and dot-blot analysis. EC expression of MCP-1 and tissue factor was very low in the absence of TNFalpha but high for constitutively expressed thrombomodulin. TNFalpha induced EC expression and activity of MCP-1 and tissue factor and suppressed that of thrombomodulin on all substrates. Greater differences were seen with regard to cell origin, but little difference was seen among substrates. Basal secretion of MCP-1 was very low in aortic and pulmonary artery EC and even less in microvascular EC. TNFalpha increased MCP-1 secretion significantly in aortic and pulmonary artery EC but to a lesser extent in microvascular EC. In contrast, tissue factor expression was greater in pulmonary artery EC compared to microvascular and aortic EC. Basal expression of thrombomodulin was largely comparable for all three cell types grown on different surfaces, but TNFalpha suppressed thrombomodulin to different extents depending on the origin of the EC. The activity of tissue factor and thrombomodulin and the secretion of MCP-1 by EC were largely correlated with the expression of these genes. We conclude that EC origin may be an important determinant of cellular function on hydrophilic plasma polymer substrates. However, the differences in cellular function due to variations in substrate surface hydrophilicity could have been masked by the extracellular matrix remodeling that presumably occurred during EC growth to confluence.

RANTES binding and down-regulation by a novel human herpesvirus-6 beta chemokine receptor

The human herpesvirus 6 (HHV-6) U51 gene defines a new family of betaherpesvirus-specific genes encoding multiple transmembrane glycoproteins with similarity to G protein-coupled receptors, in particular, human chemokine receptors. These are distinct from the HHV-6 U12 and HCMV US28 family. In vitro transcription and translation as well as transient cellular expression of U51 showed properties of a multiple transmembrane protein with a 30-kDa monomer as well as high m.w. aggregates or oligomers. Transient cellularly expressed U51 also appeared to form dimeric intermediates. Despite having only limited sequence similarity to chemokine receptors, U51 stably expressed in cell lines showed specific binding of the CC chemokine RANTES and competitive binding with other beta chemokines, such as eotaxin; monocyte chemoattractant protein 1, 3, and 4; as well as the HHV-8 chemokine vMIPII. In epithelial cells already secreting RANTES, U51 expression resulted in specific transcriptional down-regulation. This correlated with reduced secretion of RANTES protein into the culture supernatants. Regulation of RANTES levels may alter selective recruitment of circulating inflammatory cells that the virus can infect and thus could mediate the systemic spread of the virus from initial sites of infection in epithelia. Alternatively, chemokine regulation could modulate a protective inflammatory response to aid the spread of virus by immune evasion. Such mimicry, by viral proteins, of host receptors leading to down-regulation of chemokine expression is a novel immunomodulatory mechanism.

Localisation of mRNA for JE/MCP-1 and its receptor CCR2 in atherosclerotic lesions of the ApoE knockout mouse

MCP-1 has potent chemotactic activity for monocytes and is strongly implicated in the pathogenesis of atherosclerosis. In the present study, we have used in situ hybridisation to examine the gene expression of JE, the murine homologue of MCP-1, and its receptor, CCR2, during the development of atherosclerotic lesions in the ApoE knockout mouse. Interestingly, the earliest expression of JE detected during lesion development was found to be localised in mesenchymal cells in the adventitia and not in the intima. Macrophages were subsequently found to accumulate in these affected regions of the adventitia and these cells were found to express high levels of JE. At this stage, early macrophage-rich lesions with high expression of JE were also seen in the intima, but expression of mRNA for the receptor for JE (CCR2) was only found on adventitial macrophages and not in the intima. This sequence of events suggests that adventitial inflammation may be an important early event in lesion development and responsible for the subsequent accumulation of macrophages in the intima possibly by recruitment from the adventitia as well as via the vessel lumen.

Distinct patterns of stimulus-inducible chemokine mRNA accumulation in human fetal astrocytes and microglia

Interferon-gamma-inducible 10 kd protein (IP-10) is an ELR (Glu-Leu-Arg)(-) alpha chemokine with known chemotactic effects on T cells and monocytes, as well as anti-viral, anti-angiogenic, and anti-tumor effects. Previous studies have demonstrated that in cultured rat astrocytes and microglia, stimulation with LPS or virus can induce the expression of IP-10. In this study, we determined the pattern of IP-10 gene induction in primary human microglia and astrocytes by cytokines and LPS using ribonuclease protection assay. The expression of IP-10 mRNA was compared with that of other alpha (IL-8) and beta chemokines. The results showed that in human microglia, IP-10 expression was induced equally potently by LPS, IFNbeta or IFNgamma. "Proinflammatory" cytokines IL-1beta or TNFalpha also induced small amounts of IP-10 mRNA. "Anti-inflammatory" cytokines IL-4, IL-10 and TGFbeta were ineffective in inducing IP-10 in microglia. In human astrocytes, induction of IP-10 mRNA by cytokines was similar to that in microglia. LPS, however, was ineffective in inducing IP-10 in human astrocytes. The monocyte chemoattractant beta-chemokine I-309 mRNA was induced in human astrocytes and microglia by IFNbeta or IFNgamma, or by LPS in microglia, showing a tight co-regulation with IP-10 mRNA expression. In contrast to the potent induction of IP-10 and I-309 by IFNs in human glia, the ELR(+) alpha chemokine IL-8 mRNA was induced by IL-1beta and TNFalpha, and to a lesser extent by IFNbeta in microglia. IFNbeta but not IFNgamma was effective in inducing the expression of beta chemokines MIP-1alpha and MIP-1beta in human microglia, with the levels of mRNA similar to those induced by IL-1beta or TNFalpha. Neither MIP-1alpha nor MIP-1beta mRNAs were induced by any stimulation in human astrocytes. The induction of RANTES mRNA in microglia by IFNbeta, IL-1beta or TNFalpha was variable, showing no to low level expression depending on the case, whereas LPS provided a consistent inducing signal. In astrocytes, only cytokine combinations (IFN + IL-1beta) effectively induced the RANTES mRNA. These results demonstrate that distinct sets of chemokine genes are induced in human glial cells by cytokines and interferons. These results may have wide implications for inflammatory, vascular and neoplastic diseases of the CNS.

Expression and contribution of endogenous IL-13 in an experimental model of sepsis

IL-13 has been shown to exert potent anti-inflammatory properties. In this study, we elucidated the functional role of endogenous IL-13 in a murine model of septic peritonitis induced by cecal ligation and puncture (CLP). Initial studies demonstrated that the level of IL-13 increased in tissues including liver, lung, and kidney, whereas no considerable increase was found in either peritoneal fluid or serum after CLP. Immunohistochemically, IL-13-positive cells were Kupffer cells in liver, alveolar macrophages in lung, and epithelial cells of urinary tubules in kidney. IL-13 blockade with anti-IL-13 Abs significantly decreased the survival rate of mice after CLP from 53% to 14% on day 7 compared with control. To determine the potential mechanisms whereby IL-13 exerted a protective role in this model, the effects of anti-IL-13 Abs on both local and systemic inflammation were investigated. Administration of anti-IL-13 Abs did not alter the leukocyte infiltration and bacterial load in the peritoneum after CLP but dramatically increased the neutrophil influx in tissues after CLP, an effect that was accompanied by significant increases in the serum levels of aspartate transaminase, alanine transaminase, blood urea nitrogen, and creatinine. Tissue injury caused by IL-13 blockade was associated with increases in mRNA and the protein levels of CXC chemokines macrophage inflammatory protein-2 and KC as well as the CC chemokine macrophage inflammatory protein-1alpha and the proinflammatory cytokine TNF-alpha. Collectively, these results suggest that endogenous IL-13 protected mice from CLP-induced lethality by modulating inflammatory responses via suppression of overzealous production of inflammatory cytokines/chemokines in tissues.

Pentoxifylline inhibits ICAM-1 expression and chemokine production induced by proinflammatory cytokines in human pulmonary epithelial cells

Airway epithelium participates in inflammatory reactions by producing chemokines and expressing cell-surface adhesion molecules which aid in the selective recruitment of effector cells. Previous studies showed that proinflammatory cytokines, interleukin 1 (IL-1) and tumor necrosis factor alpha (TNF alpha), induce surface expression of intercellular adhesion molecule 1 (ICAM-1) and the production of the chemokines interleukin 8 (IL-8) and monocyte chemoattractant protein (MCP-1) on pulmonary epithelial cell lines in vitro. In this study, the dose response of four cytokines, IL-1alpha, IL-1beta, TNF alpha and TNF beta, in inducing ICAM-1 expression and production of IL-8 and MCP-1 on pulmonary A549 epithelial cells was examined. Both IL-1alpha and IL-1beta induced ICAM-1 expression and IL-8 and MCP-1 production at lower doses than TNF alpha or TNF beta. Pentoxifylline, an anti-inflammatory agent used to treat vascular diseases, was tested for its ability to inhibit the activation of airway epithelial cells by these cytokines. Pentoxifylline completely inhibited the surface expression of ICAM-1 and the production of IL-8 and MCP-1 by cytokine-activated epithelial cells. As elevated levels of chemokines are often present in bronchial lavage fluids of patients suffering from various acute respiratory diseases, pentoxifylline may be useful for preventing the rapid development of immune reactions leading to lung injury.

CD4(+ )T cells play an important role in acute experimental pancreatitis in mice

BACKGROUND & AIMS

Few data are available on the potential role of T lymphocytes in experimental acute pancreatitis. The aim of this study was to characterize their role in the inflammatory cascade of acute pancreatitis.

METHODS

To type this issue, acute pancreatitis was induced by repeated injections of cerulein in nude mice and in vivo CD4(+) or CD8(+) T cell-depleted mice. The role of T lymphocyte-costimulatory pathways was evaluated using anti-CD40 ligand or anti-B7-1 and -B7-2 monoclonal blocking antibodies. The role of Fas-Fas ligand was explored using Fas ligand-targeted mutant (generalized lymphoproliferative disease) mice. Severity of acute pancreatitis was assessed by serum hydrolase levels and histology. Intrapancreatic interleukin 12, interferon gamma, Fas ligand, and CD40 ligand messenger RNA were detected by reverse-transcription polymerase chain reaction. Intrapancreatic T lymphocytes were identified by immunohistochemistry.

RESULTS

In control mice, T cells, most of them CD4(+) T cells, are present in the pancreas and are recruited during acute pancreatitis. In nude mice, histological lesions and serum hydrolase levels are significantly decreased. T-lymphocyte transfer into nude mice partially restores the severity of acute pancreatitis and intrapancreatic interferon gamma, interleukin 12, and Fas ligand gene transcription. The severity of pancreatitis is also reduced by in vivo CD4(+) (but not CD8(+)) T-cell depletion and in Fas ligand-targeted mutant mice. Blocking CD40-CD40 ligand or B7-CD28 costimulatory pathways has no effect on the severity of pancreatitis.

CONCLUSIONS

T lymphocytes, particularly CD4(+) T cells, play a pivotal role in the development of tissue injury during acute experimental pancreatitis in mice.

Chemokines and myeloid cell recruitment

Chemokine-chemokine receptor interactions mediate constitutive leukocyte trafficking and leukocyte recruitment to sites of infection and inflammation. We suggest that a multiplicity of leukocyte chemoattractants exists to increase the selectivity of leukocyte recruitment in a range of physiological and pathological settings.

Transplantation into genetically alymphoid mice as an approach to dissect the roles of uterine natural killer cells during pregnancy--a review

Mice genetically deficient in the natural killer (NK) cell lineage lack uterine (uNK cells) and demonstrate morphometrically-quantifiable histopathology within their implantation sites. Two particular mouse strains, tg(epsilon),26 and RAG-2 null x gamma(c) null, have been used successfully as transplant recipients to address questions relating to the biology of uNK cells. uNK cells did not differentiate within decidualized uterine graft segments from normal mice, which were anastomosed orthotopically into immunodeficient hosts. uNK cells did appear in similar grafts placed into immunocompetent hosts, indicating that uNK cells or their progenitors must home to the uterus. This was confirmed by splenocyte transplantation into pregnant uNK cell deficient recipients. Only splenocytes from pregnant donors, not those from non-pregnant donors, homed to the uterus. Homing in this in vivo assay was independent of the CC-chemokine receptors, CCR-2 and CCR-5. Longer-term bone marrow cell reconstitution of neonatal or virgin adult uNK cell-deficient mice has identified a functional role for uNK cells in modification of the decidual arterioles which is mediated by IFN-gamma. By utilizing mutant and gene-ablated mice as donors for tissue or haematopoietic cell transplants to uNK cell deficient mice, it should be possible to fully characterize the in vivo regulation and functions of these pregnancy-specific uterine lymphocytes.

The preterm prediction study: granulocyte colony-stimulating factor and spontaneous preterm birth. National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network

OBJECTIVE

Granulocyte colony-stimulating factor is elevated in the amniotic fluid and plasma of women with chorioamnionitis and active preterm labor. We investigated the relationship between plasma granulocyte colony-stimulating factor and subsequent spontaneous preterm birth in pregnant women without symptoms.

STUDY DESIGN

We performed a nested case-control study involving 194 women who had a singleton spontaneous preterm birth and 194 matched term control subjects from the patient pool (n = 2929) enrolled in the Preterm Prediction Study. Plasma collected at 24 and 28 weeks' gestation was analyzed for granulocyte colony-stimulating factor, and the results were compared with subsequent spontaneous preterm birth.

RESULTS

Compared with term control subjects, women who were delivered of their infants spontaneously at <28 weeks' gestation had increased mean granulocyte colony-stimulating factor values at 24 weeks' gestation (84.7 +/- 38.4 vs 67.7 +/- 28.6 pg/mL; P =.049), and women who were delivered of their infants at <32 weeks' gestation had increased mean plasma granulocyte colony-stimulating factor values at 28 weeks' gestation (80.4 +/- 24.1 vs 55.9 +/- 16.5 pg/mL; P =. 001). At 24 weeks' gestation a granulocyte colony-stimulating factor value >75th percentile in control subjects (approximately 80 pg/mL) was found in 48.9% (23/47) of all women delivered of their infants at <32 weeks' gestation versus 14.9% (7/47) of the term control subjects (adjusted odds ratio, 6.2; 95% confidence interval, 1.8-20. 8). At 28 weeks' gestation a granulocyte colony-stimulating factor value >75th percentile was found in 36.8% (7/19) of women delivered of their infants at <32 weeks' gestation versus 5.3% (1/19) of term control subjects (adjusted odds ratio, 25.7; 95% confidence interval, 1.5-470.4). When measured at 24 or 28 weeks' gestation, granulocyte colony-stimulating factor did not predict spontaneous preterm birth at 32 to 34 weeks' gestation or at 35 to 36 weeks' gestation.

CONCLUSION

In pregnant women without symptoms at 24 and 28 weeks' gestation, elevated plasma granulocyte colony-stimulating factor levels are associated with subsequent early (<32 weeks' gestation) spontaneous preterm birth, especially within the next 4 weeks, but not with late spontaneous preterm birth. These data provide further evidence that early spontaneous preterm birth is associated with an inflammatory process that is identifiable by the presence of a cytokine in maternal plasma several weeks before the early spontaneous preterm birth; however, later spontaneous preterm birth is not associated with this process.

Molecular mechanisms that lead to reduced expression of duffy antigens

BACKGROUND

In the Duffy blood group system, the null phenotype Fy(a-b-) has been classically associated with a mutated GATA box, while the Fy(x) phenotype weak Fy(b) is associated with Arg89Cys and Ala100Thr mutations. This report assesses the prevalence of the Duffy GATA box and the Fy(x)-associated mutations in white and African American (black) donors and investigates the molecular mechanism underlying the Fy(x) phenotype.

STUDY DESIGN AND METHODS

PCR RFLP Duffy genotyping was performed on blood samples from blacks and whites. Duffy antigen expression (Fy(a), Fy(b), Fy6, Fy3) on RBCs was measured by flow cytometry. By site-directed mutagenesis, the relevance of each Fy(x)-associated mutation to Duffy (mRNA, antigen, and protein) expression was analyzed in transfectants by Northern blotting, flow cytometry, and immunoblotting.

RESULTS

The mutated GATA box occurred at a high allele frequency (0.8) in blacks and was rare among whites. Conversely, the Fy(x)-associated mutations were absent in blacks, but present in 3.5 percent of whites. By flow cytometry, Duffy antigens (Fy(a) or Fy(b), Fy6 and Fy3) showed a dosage effect in RBC samples that were transcriptionally silenced by the GATA box mutation in one allele. By contrast, the reduced (10%) Duffy protein in Fy(x) RBCs was shown by heterologous expression analysis not to be due to reduced RNA levels, but to protein instability caused by Arg89Cys.

CONCLUSIONS

Reduced Duffy expression can result from mutations affecting transcription (mutated GATA box in one allele) or instability of the translated protein (Arg89Cys). The frequencies of these mutations vary among populations.

Human vascular smooth muscle cells possess functional CCR5

CC chemokine receptors are important modulators of inflammation. Although CC chemokine receptors have been found predominantly on leukocytes, recent studies have suggested that vascular smooth muscle cells respond to CC chemokines. We now report that human smooth muscle cells express CCR5, a co-receptor for human immunodeficiency virus. CCR5 mRNA was detectable by RNA blot hybridization in human aortic and coronary artery smooth muscle cells. The cDNA generated by reverse transcription-polymerase chain reaction from aortic smooth muscle cells had 100% identity throughout the entire coding region with the CCR5 cloned from THP-1 cells. By immunohistochemistry, CCR5 and the CCR5 ligand, macrophage inflammatory protein-1beta (MIP-1beta), were detected in smooth muscle cells and macrophages of the atherosclerotic plaque. In smooth muscle cell culture, MIP-1beta induced a significant increase in intracellular calcium concentrations, which was blocked by an antibody to CCR5. In addition, MIP-1beta caused a calcium-dependent increase in tissue factor activity. Tissue factor is the initiator of coagulation and is thought to play a key role in arterial thrombosis. These data suggest that human arterial smooth muscle cells express functional CCR5 receptors and MIP-1beta is an agonist for these cells.

Central role for G protein-coupled phosphoinositide 3-kinase gamma in inflammation

Phosphoinositide 3-kinase (PI3K) activity is crucial for leukocyte function, but the roles of the four receptor-activated isoforms are unclear. Mice lacking heterotrimeric guanine nucleotide-binding protein (G protein)-coupled PI3Kgamma were viable and had fully differentiated neutrophils and macrophages. Chemoattractant-stimulated PI3Kgamma-/- neutrophils did not produce phosphatidylinositol 3,4,5-trisphosphate, did not activate protein kinase B, and displayed impaired respiratory burst and motility. Peritoneal PI3Kgamma-null macrophages showed a reduced migration toward a wide range of chemotactic stimuli and a severely defective accumulation in a septic peritonitis model. These results demonstrate that PI3Kgamma is a crucial signaling molecule required for macrophage accumulation in inflammation.

Species selectivity of a small molecule antagonist for the CCR1 chemokine receptor

The species specificity of a small molecule antagonist for the human CCR1 chemokine receptor, 2-2-diphenyl-5-(4-chlorophenyl)piperidin-1-yl)valeronitrile (CCR1 antagonist 1), has been examined using cloned CCR1 receptors from various species. The compound was able to bind to rabbit, marmoset, and human CCR1, and was able to block the functional activation of these receptors. However, it failed to significantly displace radiolabeled macrophage inflammatory protein-1alpha (MIP-1alpha) binding to mouse CCR1 at concentrations up to 10 microM. These data suggested that the antagonist binding site is well-conserved in rabbit, marmoset and human CCR1, but not in mouse CCR1. The functional selectivity and mechanism of action for CCR1 antagonist 1 were further characterized. CCR1 antagonist 1 blocked the increase in intracellular Ca(2+) stimulated by CCR1 agonists, but had no effect on N-formyl-Met-Leu-Phe (FMLP), monocyte chemotactic protein-1 (MCP-1) and stromal-derived factor 1alpha (SDF1alpha)-induced Ca(2+) mobilization, demonstrating functional selectivity for CCR1. Since CCR1 antagonist 1 is a functional antagonist of marmoset and rabbit CCR1 receptors, it should be possible to test its efficacy in animal models of disease.

The stromal cell-derived factor-1 chemokine is a potent platelet agonist highly expressed in atherosclerotic plaques

Chemokines are chemotactic cytokines that activate and direct the migration of leukocytes. However, their role in modulating platelet function has not been shown. We studied the direct effect of chemokines on human platelets and found that of the 16 tested only stromal cell-derived factor (SDF)-1 induced platelet aggregation, accompanied by a rise in intracellular calcium. Platelets expressed the SDF-1 receptor, CXCR4, and an antibody to CXCR4 and pertussis toxin inhibited SDF-1-induced platelet aggregation, confirming that this effect is mediated through CXCR4, a Galphai-coupled receptor. SDF-1-induced platelet aggregation was also inhibited by wortmannin, LY294002, and genistein, suggesting that phosphatidylinositol 3-kinase and tyrosine kinase are likely involved in SDF-1-induced platelet aggregation. Because chemokines are produced from multiple vascular cells and atherosclerotic vessels are prone to develop platelet-rich thrombi, we examined the expression of SDF-1 in human atheroma. SDF-1 protein was highly expressed in smooth muscle cells, endothelial cells, and macrophages in human atherosclerotic plaques but not in normal vessels. Our studies demonstrate a direct effect of a chemokine in inducing platelet activation and suggest a role for SDF-1 in the pathogenesis of atherosclerosis and thrombo-occlusive diseases.

Expression of the chemokine eotaxin and its receptor, CCR3, in human endometrium

Eosinophils are present in human endometrium only immediately before and during menstruation, suggesting a role in that process. The expression of the eosinophil chemoattractant, eotaxin, and its receptor, CCR3, within the human endometrium were investigated by immunohistochemical analysis of tissue sections spanning the entire menstrual cycle. Eotaxin was localized to perivascular cells in the late secretory phase, and it was also identified in eosinophils. However, the highest levels of this chemokine were present in both luminal and glandular epithelial cells during the proliferative and secretory phases of the cycle. Treatment of endometrial tissue with monensin, which blocks protein secretion, increased epithelial immunoreactive eotaxin, substantiating synthesis in these cells. Although the CCR3 receptor was expressed by eosinophils, it was also strongly expressed by endometrial epithelial cells. The CCR3 receptor on purified, cultured endometrial epithelial cells was functional, as assessed by a transient Ca(2+) flux in response to eotaxin. These analyses demonstrate that eotaxin is expressed by endometrial cells and may therefore be involved in the recruitment of eosinophils into this tissue premenstrually. However, the observation that this chemokine and the CCR3 molecule are strongly expressed by epithelial cells throughout the cycle suggests that these proteins may have additional important functions within the endometrium.

Chemokines and chemokine receptors in the pathogenesis of multiple sclerosis

In recent years we have seen growing evidence for the role of chemokines in the pathogenesis of several infectious and non-infectious inflammatory CNS disease states, including Multiple Sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE). An increase in proinflammatory chemokines has been associated with demyelinating lesions and clinical neurological dysfunction in patients with MS; these chemokines could be potential targets for MS therapy. Besides a clearly defined role in mediating leukocyte migration, these and other chemokines may act as immunoregulatory molecules in the driving to Th1/Th2 responses, switch of cytokine profiles, and the induction of tolerance. Since chemokine receptors have now been identified on macrophages, microglia, astrocytes, and endothelial cells as well as neurons in the CNS, chemokine/receptor interactions may mediate functional responses in a variety of CNS cell types during the course of inflammatory disease states. Therefore, clarification of the roles of chemokines and their receptors in the pathogenesis of EAE and MS will be useful in establishing immunotherapeutic strategies for these neurological autoimmune disorders.

Sepsis Syndrome

A clinical syndrome including fever, leukocytosis, elevated cardiac output, and reduced systemic vascular resistance has been associated with severe infection (i.e., sepsis). However, during the last 15 years, many patients have demonstrated all of the findings that have traditionally been associated with “sepsis” but have not had demonstrated sources of infection. This led to the term “sepsis syndrome” to refer to that population of patients who appeared to have a physiologic and metabolic response associated with, but who did not have, severe infection. More commonly called the systemic inflammatory response syndrome (SIRS), the sepsis syndrome is now associated with the nonspecific systemic activation of the human inflammatory cascade by any of a number of clinical events. The management of the SIRS patient has been ineffective because of incomplete definition of the mechanisms responsible for the syndrome. It is argued that all of the biological mechanisms that are operative in a simple wound and are beneficial are negative for the host when activated systemically. Thus, SIRS is seen in three separate scenarios at present: (1) invasive infection; (2) dissemination of microbes secondary to failure of host defense mechanisms; and (3) severe activation of inflammation by injury, shock, severe soft tissue inflammation, and other noninfectious but proinflammatory events. Newer treatment strategies will need to focus not on the inciting event itself but on better control of the complex responses of the host.

Quantitative analysis of a synthetic peptide, NR58-3.14.3, in serum by LC-MS with inclusion of a diastereomer as internal standard

A method for quantifying an intramolecularly linked all-d-amino acid peptide, NR58-3.14.3, in rat serum by LC-MS using selected ion monitoring with inclusion of a diastereomer as internal standard was developed. The reproducible quantitation of multiply charged compounds by LC-MS using single ion or selective reaction monitoring is often a challenge as the intensity ratio of the ions in a series of different charge states can vary. Good precision was obtained in the selected ion monitoring mode by integrating the summed ion currents of the singly, doubly, and triply charged molecular ions. Since stable isotope analogs are costly and integration of residual unlabeled material can be of concern, a diastereomer of NR58-3.14.3, NR58-3.14.5, was used as internal standard. The diastereomers were indistinguishable by electrospray MS, but fully separated by reversed-phase LC. Consequently, interference due to isotopic impurities or coelution was not encountered. The calibration plot was linear throughout a concentration range of 0.2 to 200.0 microg/ml (r(2) = 0.9996). Intraday precision of the standards analyzed was less than 12% RSD over the calibration range and the accuracy within +/-11% RE. Serum pharmacokinetics were in good agreement with the pharmacokinetic profiles of small, ionic, and polar molecules.

Differential in situ distribution of interleukin-8, monocyte chemoattractant protein-1 and Rantes in human chronic periapical granuloma

In situ distribution of three prototype chemokines interleukin (IL)-8, monocyte chemoattractant protein (MCP)-1 and Rantes was determined in chronic human periapical granulomas by immunohistochemistry using monoclonal antibodies. IL-8 was found primarily in the cytoplasm of the Malassez epithelial cells. MCP-1 immunoreactivity was confined to the endothelial cells that lined small venules. Each of the three investigated chemokines, including Rantes, exhibited a characteristic binding pattern to the extracellular matrix of the lesion. The observed chemokines may play a role in establishing the cellular composition of chronic apical periodontitis, thus augmenting the intensity of local inflammation and tissue damage.

Hyperoxia synergistically increases TNF-alpha-induced interleukin-8 gene expression in A549 cells

Interleukin (IL)-8 is an important mediator of acute lung injury. Hyperoxia induces IL-8 production in some cell types, but its effect on IL-8 gene expression in respiratory epithelium is not well described. In addition, IL-8 gene expression resulting from the combined effects of hyperoxia and proinflammatory cytokines has not been well characterized. We treated cultured respiratory epithelial-like cells (A549 cells) with hyperoxia alone, tumor necrosis factor (TNF)-alpha alone, or the combination of TNF-alpha and hyperoxia and evaluated IL-8 gene expression. Hyperoxia alone had a minimal effect on IL-8 gene expression, and TNF-alpha alone increased IL-8 gene expression in a time-dependent manner. In contrast, the combination of TNF-alpha and hyperoxia synergistically increased IL-8 gene expression as measured by ELISA (TNF-alpha alone for 24 h = 769 +/- 89 pg/ml vs. hyperoxia + TNF-alpha for 24 h = 1, 189 +/- 89 pg/ml) and Northern blot analyses. Experiments involving IL-8 promoter-reporter assays, electromobility shift assays, and Western blot analyses demonstrated that hyperoxia augmented TNF-alpha-mediated activation of the IL-8 promoter by a nuclear factor (NF)-kappaB-dependent mechanism and increased the duration of NF-kappaB nuclear translocation after concomitant treatment with TNF-alpha. Additional reporter gene assays demonstrated, however, that increased activation of NF-kappaB does not fully account for the synergistic effect of hyperoxia and that the NF-IL-6 site in the IL-8 promoter is also required for the synergistic effect of hyperoxia. We conclude that hyperoxia alone has a minimal effect on IL-8 gene expression but synergistically increases IL-8 gene expression in the presence of TNF-alpha by a mechanism involving cooperative interaction between the transcription factors NF-kappaB and NF-IL-6.

Modulating chemokines: more lessons from viruses

Chemokines are crucial effector molecules involved in orchestrating the host inflammatory response against invading pathogens. Viruses have devised several strategies for exploiting or neutralizing chemokines or their receptors to further their own propagation or elude host defenses. Insight into strategies used by viruses to modulate chemokines might help generate novel approaches for treating viral diseases and chemokine-mediated inflammatory disorders.

CCR5 delta32, matrix metalloproteinase-9 and disease activity in multiple sclerosis

Chemokines and matrix metalloproteinases (MMPs) appear to be crucial in leukocyte recruitment to the central nervous system in multiple sclerosis (MS). CCR5 delta32, a truncated allele of the CC chemokine receptor CCR5 gene encoding a non-functional receptor, did not confer protection from MS. CCR5 delta32 was, however, associated with a lower risk of recurrent clinical disease activity. High CSF levels of MMP-9 activity were also associated with recurrent disease activity. These results directly link intrathecal inflammation to disease activity in patients with MS, suggesting that treatments targeting CCR5 or treatment with MMP inhibitors may attenuate disease activity in MS.

Experimental gliosarcoma induces chemokine receptor expression in rat brain

Macrophage/microglial infiltration is a characteristic feature of brain tumors. The functional role(s) of these cells is complex and could include both trophic and suppressive effects on tumors. Information has recently emerged about the molecular signals that regulate the accumulation and function of monocytes in pathological disorders. Recent data indicate that the chemokine, monocyte chemoattractant protein-1 (MCP-1), a potent monocyte activating and chemotactic factor, is a primary regulator of the macrophage response in brain tumors. We hypothesized that if MCP-1 regulates macrophage/microglial infiltration, then expression of the specific MCP-1 receptor, CCR2, will be induced in peritumoral tissue and/or within brain tumors. Identification of a specific receptor that is preferentially expressed in brain tumors could be important both in terms of tumor biology and as a potential therapeutic target. We used an established experimental gliosarcoma model, induced by intracranial transplantation of cultured 9L cells into adult rat brain, to test this hypothesis. RT-PCR analysis showed high levels of both MCP-1 and CCR2 mRNA and Western blot analysis demonstrated increased CCR2 protein in tumor extracts. Immunocytochemistry showed CCR2 immunoreactive microglia in peritumoral tissue and, unexpectedly, that intrinsic tumor cells, rather than monocytes, were the predominant source of CCR2. These results demonstrate that CCR2 expression is markedly upregulated in this brain tumor model.

Host-pathogen studies in the post-genomic era

Several studies are starting to show the power of DNA microarrays to identify interactions between animal hosts and their pathogens, and have revealed interesting correlations between host responses to different infectious agents.

Novel therapy for asthma

The health burden of asthma is increasing globally at an alarming rate, providing a strong impetus for the development of new therapeutics. Currently available inhaled bronchodilators and anti-inflammatory drugs are effective in most asthmatics, but this palliative therapy requires long-term daily administration. Despite considerable efforts by the pharmaceutical industry, it has been difficult to develop novel therapeutic agents; the leukotriene antagonists and synthesis inhibitors being the only new class of asthma treatments to have been licensed in the last 30 years. It is clearly important to understand more about the underlying mechanisms of asthma and about how current drugs work before rational improvements in therapy can be expected. There are numerous therapies in clinical development that combat the inflammation found in asthma, specifically targeting eosinophils, IgE, adhesion molecules, cytokines and chemokines, inflammatory mediators and cell signalling. In particular, there is the obvious need for new therapy for severe asthma that is poorly controlled by high doses of corticosteroids, as well as agents to counter acute emergency asthma. A long-term goal is to develop disease-modifying immunotherapy, that could be introduced in childhood to alter the natural history of asthma. Thanks to the extensive efforts of the pharmaceutical industry, in the near future we can expect the introduction of a range of novel therapies for asthma.

Chemokines, chemokine receptors, and renal disease: from basic science to pathophysiologic and therapeutic studies

Leukocyte trafficking from peripheral blood into affected tissues is an essential component of the inflammatory reaction to virtually all forms of injury and is an important factor in the development of many kidney diseases. Advances in the past few years have highlighted the central role of a family of chemotactic cytokines called chemokines in this process. Chemokines help to control the selective migration and activation of inflammatory cells into injured renal tissue. Chemokines and their receptors are expressed by intrinsic renal cells as well as by infiltrating cells during renal inflammation. This study summarizes the in vitro and in vivo data on chemokines and chemokine receptors in renal diseases with a special focus on potential therapeutic effects on inflammatory processes.

Chemokine production by the BEAS-2B human bronchial epithelial cells: differential regulation of eotaxin, IL-8, and RANTES by TH2- and TH1-derived cytokines

BACKGROUND

Bronchial epithelial cells produce many types of chemokines and may contribute to lung inflammation by recruiting inflammatory cells. The CC chemokine eotaxin is a potent, eosinophil-specific chemoattractant that has been detected in the bronchial epithelium of patients with asthma.

OBJECTIVES

The aim of this study was to investigate the regulatory mechanisms of chemokine production from bronchial epithelium by inflammatory cytokines, especially T(H)2- and T(H)1-derived cytokines, in bronchial asthma.

METHODS

BEAS-2B human bronchial epithelial cells were cultured with TNF-alpha, IL-4, IL-13, and IFN-gamma alone or in combination, after which supernatants were assayed for eotaxin, IL-8, and RANTES proteins with ELISA. Reverse transcription-PCR was also performed.

RESULTS

TNF-alpha induced production of eotaxin, IL-8, and RANTES in a concentration-dependent manner. Both IL-4 and IL-13 synergistically enhanced TNF-alpha-induced eotaxin production, whereas IL-8 production induced by TNF-alpha was significantly down-regulated by the T(H)2-derived cytokines. IFN-gamma, a T(H)1 cytokine, counteracted the enhancing effects of IL-4 and IL-13 on eotaxin production. RANTES production by TNF-alpha was not affected by IL-4 and IL-13 but was markedly enhanced by IFN-gamma.

CONCLUSIONS

These results suggest that T(H)2 cytokines are involved in preferential recruitment of eosinophils in bronchial asthma by enhancing eotaxin and reducing IL-8 production from bronchial epithelial cells and that T(H)1 cytokines counteract the effects of T(H)2 cytokines by reducing eotaxin production.

The chemokine receptor antagonist AOP-RANTES reduces monocyte infiltration in experimental glomerulonephritis

The chemokine receptor antagonist AOP-RANTES reduces monocyte infiltration in experimental glomerulonephritis.

BACKGROUND

This study was designed to evaluate the role of the novel chemokine receptor antagonist amino-oxypentane RANTES (AOP-RANTES), which blocks the binding of macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, and RANTES to the chemokine receptor-5 (CCR-5) on the infiltration of monocytes in experimental glomerulonephritis.

METHODS

Rats were treated twice daily with 12.5 microg AOP-RANTES following an induction of anti-rat-thymocyte antibody-mediated glomerulonephritis. The white blood cell count, glomerular monocyte infiltration, chemokine expression, and collagen type IV deposition were assessed.

RESULTS

The induction of glomerulonephritis increased glomerular monocyte/macrophage (M/M) infiltration at 24 hours and at 5 days was still higher than in controls. AOP-RANTES prevented glomerular M/M infiltration at 24 hours and at 5 days. This was paralleled by reduced glomerular collagen type IV deposition as a fibrotic marker in nephritic animals.

CONCLUSION

These data show that the CCR-5 chemokine receptor antagonist AOP-RANTES ameliorates M/M infiltration and improves glomerular pathology in experimental glomerulonephritis. The use of chemokine receptor antagonists may offer a new therapeutic option in inflammatory renal injuries.

Chemokine and Chemokine Receptor Interactions Provide a Mechanism for Selective T Cell Recruitment to Specific Liver Compartments Within Hepatitis C-Infected Liver

The role played by chemokines in regulating the selective recruitment of lymphocytes to different tissue compartments in disease is poorly characterized. In hepatitis C infection, inflammation confined to portal areas is associated with a less aggressive course, whereas T cell infiltration of the liver parenchyma is associated with progressive liver injury and cirrhosis. We propose a mechanism to explain how lymphocytes are recruited to hepatic lobules during bursts of necroinflammatory activity in chronic hepatitis C infection. We report here that lymphocytes infiltrating hepatitis C-infected liver express high levels of the chemokine receptors CCR5 and CXCR3. However, whereas the CCR5 ligands macrophage inflammatory protein-1α and -1β were largely confined to vessels within portal tracts, the CXCR3 ligands IFN-inducible protein-10 and monokine-induced by IFN-γ were selectively up-regulated on sinusoidal endothelium. In vitro, human hepatic sinusoidal endothelial cells secreted IFN-inducible protein-10 and monokine-induced by IFN-γ in response to stimulation with IFN-γ in combination with either IL-1 or TNF-α. This suggests that intrahepatic Th1 cytokines drive the increased expression of IFN-inducible protein-10 and monokine-induced by IFN-γ and thereby promote the continuing recruitment of CXCR3-expressing T cells into the hepatic lobule in chronic hepatitis C infection.

Endogenous Monocyte Chemoattractant Protein-1 (MCP-1) Protects Mice in a Model of Acute Septic Peritonitis: Cross-Talk Between MCP-1 and Leukotriene B4

We investigated the involvement of monocyte chemoattractant protein (MCP)-1 in a murine model of septic peritonitis induced by cecal ligation and puncture (CLP). Initial studies demonstrated that CLP induced a dramatic increase in MCP-1 production in the peritoneum, followed by an increase in the recruitment of leukocytes. MCP-1 blockade with anti-MCP-1 antiserum significantly decreased the survival rate following CLP, which was accompanied by an enhanced recovery of viable bacteria from the peritoneum. This was likely due to the reduction in the recruitment and activation of both macrophages and neutrophils. To understand the mechanisms whereby MCP-1 may influence neutrophil infiltration, levels of chemokines known to attract neutrophils were monitored, which showed that peritoneal levels of macrophage-inflammatory protein (MIP)-2, KC, and MIP-1α were not altered with anti-MCP-1 Abs. However, anti-MCP-1 Abs reduced the peritoneal levels of leukotriene B4 (LTB4) by 59%. The i.p. injection of MCP-1 into normal mice resulted in elevated levels of LTB4 in the peritoneum. In vitro, MCP-1 stimulated the production of LTB4 from peritoneal macrophages, in a dose-dependent manner. A specific LTB4 receptor antagonist (CP-105,696) inhibited CLP-induced recruitment of both neutrophils and macrophages, which was accompanied by a reduced level of MCP-1 in the peritoneum. Finally, administration of CP-105,696 was extremely detrimental to the survival of mice following CLP. These experiments demonstrate that endogenous MCP-1 serves as an indirect mediator to attract neutrophils via the production of LTB4, and suggest the cross-talk can occur between MCP-1 and the lipid mediator LTB4 during septic peritonitis.

NH2- and COOH-Terminal Truncations of Murine Granulocyte Chemotactic Protein-2 Augment the In Vitro and In Vivo Neutrophil Chemotactic Potency

Chemokines are important mediators of leukocyte migration during the inflammatory response. Post-translational modifications affect the biological potency of chemokines. In addition to previously identified NH2-terminally truncated forms, COOH-terminally truncated forms of the CXC chemokine murine granulocyte chemotactic protein-2 (GCP-2) were purified from conditioned medium of stimulated fibroblasts. The truncations generated 28 natural murine GCP-2 isoforms containing 69–92 residues, including most intermediate forms. Both NH2- and COOH-terminal truncations of GCP-2 resulted in enhanced chemotactic potency for human and murine neutrophils in vitro. The truncated isoform GCP-2(9–78) was 30-fold more potent than intact GCP-2(1–92)/LPS-induced CXC chemokine (LIX) at inducing an intracellular calcium increase in human neutrophils. After intradermal injection in mice, GCP-2(9–78) was also more effective than GCP-2(1–92)/LIX at inducing neutrophil infiltration. Similar to human IL-8 and GCP-2, murine GCP-2(9–78) and macrophage inflammatory protein-2 (MIP-2) induced calcium increases in both CXCR1 and CXCR2 transfectants. Murine GCP-2(9–78) could desensitize the calcium response induced by MIP-2 in human neutrophils and vice versa. Furthermore, MIP-2 and truncated GCP-2(9–78), but not intact GCP-2(1–92)/LIX, partially desensitized the calcium response to human IL-8 in human neutrophils. Taken together, these findings point to an important role of post-translationally modified GCP-2 to replace IL-8 in the mouse.

Cytokine, chemokine and chemokine receptor mRNA expression in different strains of normal mice: implications for establishment of a Th1/Th2 bias

The resistance or susceptibility of inbred strains of mice to various pathogens and autoimmune diseases such as EAE has been linked to differences in the balance between cytokines associated with Th1- and Th2-type immune responses. Previous work from this laboratory on the mouse strain specific resistance to mouse adenovirus type I (MAV-1)-induced encephalopathy revealed subtle differences in the transcription rates of several immunologically important molecules that was evident prior to infection. In this study, we show striking differences in cytokine, chemokine and chemokine receptor mRNA expression in the spleens of normal, immunologically naive C57BL/6J, BALB/cJ and SJL/J mice. Messenger RNAs for interferon (IFN)-gamma and the chemokine IFN gamma inducible protein (IP)-10 were preferentially expressed in C57BL/6J spleens, whereas in BALB/cJ spleens mRNAs for lymphotoxin-beta, interferon-beta, transforming growth factor-beta, and the chemokine receptors CCR3 and CXCR4 predominated. A unique profile of chemokine receptors was found in spleens from normal SJL/J mice that correlated with the presence of polymorphisms within the CCR-3 gene. The patterns of gene expression fit well into the Th1/Th2 paradigm for C57BL/6J and BALB/cJ strains and suggest an important role for chemokines, as well as cytokines, in contributing to the genetic basis of the immune response.

The CC-chemokine receptor 5 (CCR5) is a marker of, but not essential for the development of human Th1 cells

The CC-chemokine receptor 5 (CCR5) has recently been described as a surface marker of human T cells producing type 1 (Th1) cytokines. Here we confirm that CCR5 is expressed on human Th1 but not on Th2 T-cell clones. Using intracellular cytokine staining, we show that alloantigen specific CD4+ T-cell lines derived from a CCR5-deficient individual (delta32 allele homozygote) contain high numbers of both interferon gamma (IFN-gamma) and interleukin (IL)-2 producing cells, low numbers of IL-10 producing cells and no IL4 or IL-5 producing cells when stimulated with phorbol ester and ionomycin in vitro. These results were similar to those obtained from alloantigen specific CD4+ T-cell lines derived from CCR5 expressing individuals. An enzyme-linked immunoabsorbent assay (ELISA) confirmed that the Th1 cytokine-positive cells from the CCR5-deficient individual were able to produce equal amounts of cytokines when compared to T-cell lines from CCR5-expressing individuals, These results demonstrate that CCR5-negative T cells display the same capacity of Th1 T-cell differentiation as T cells derived from CCR5-expressing individuals. Thus, CCR5 expression is not essential for differentiation of human Th1 T cells.

The equine herpesvirus 2 E1 open reading frame encodes a functional chemokine receptor

Several herpesviruses contain open reading frames (ORFs) that encode potential homologs of eucaryotic genes. Equine herpesvirus 2 (EHV-2) is a gammaherpesvirus related to other lymphotropic herpesviruses such as herpesvirus saimiri and Epstein-Barr virus. The E1 ORF of EHV-2, a G protein-coupled receptor homolog, shows 31 to 47% amino acid identity with known CC chemokine receptors. To investigate whether E1 may encode a functional receptor, we cloned the E1 ORF and expressed it in stably transfected cell lines. We report here the identification of the CC chemokine eotaxin as a functional ligand for the EHV-2 E1 receptor. Chemokines are likely to play a role in the regulation of immune functions in equine hosts during EHV-2 infection and, via interaction with E1, may affect viral replication and/or escape from immune responses.

Chemokines and atherosclerosis

Chemokines or chemotactic cytokines represent an expanding family of structurally related small molecular weight proteins, recognised as being responsible for leukocyte trafficking and activation. Soon after the discovery of this class of cytokines, about a decade ago, monocyte chemoattractant protein-1 (MCP-1) was found to be highly expressed in human atherosclerotic lesions and postulated to be central in monocyte recruitment into the arterial wall and developing lesions. In this review, we will discuss our present knowledge about MCP-1 and its receptor CCR2 and their role in atherogenesis. Although less well established, other chemokines such as RANTES, MIP-1alpha and MIP-1beta have also been implicated in atherosclerotic lesion formation as are a number of more recently discovered chemokines like MCP-4, ELC and PARC. The role of these chemokines in the progression of atherosclerosis will be discussed as well as the emerging role of IL-8, mostly know for its effects on neutrophils. Particular attention will be given not only to the involvement of chemokines in the inflammatory recruitment of monocytes/macrophages, but also to their role in the related local immune responses and vascular remodelling which occur during the formation of unstable atherosclerotic plaques.

Role for interactions between IP-10/Mig and CXCR3 in proliferative glomerulonephritis

The mechanisms responsible for mesangial cell proliferation in proliferative glomerulonephritis are only partially understood. This article reports the results of an immunohistochemical study showing high expression of the chemokine receptor CXCR3 by mesangial cells of patients with IgA nephropathy, membranoproliferative glomerulonephritis, or rapidly progressive glomerulonephritis. CXCR3 was also detectable by flow cytometry in cultured human mesangial cells, in which it appeared to be functionally active, as determined by the ability of its ligand, the (interferon-gamma)-inducible protein of 10 kD (IP-10) to induce intracellular Ca2+ influx. Both IP-10 and the monokine induced by interferon-gamma (Mig) were also effective in inducing proliferation of human mesangial cells. These data suggest that in patients with proliferative glomerulonephritis, the chemokines IP-10 and/or Mig not only may act as chemoattractants for infiltrating mononuclear cells in the inflamed tissue, but also may directly induce the proliferation of mesangial cells.

Interactions between mycoplasma lipoproteins and the host immune system

Mycoplasmas typically have a number of distinct lipoproteins anchored on the outer face of the plasma membrane. These surface antigens have a potent modulin activity and are preferential targets of the host immune response. However, the variation of some of these lipoproteins provides mycoplasmas with an effective means of evading the host immune defence system.