Signal transduction by the chemokine receptor CXCR3: activation of Ras/ERK, Src, and phosphatidylinositol 3-kinase/Akt controls cell migration and proliferation in human vascular pericytes

The small GTPase Rac-1 is a regulator of mesangial cell morphology and thrombospondin-1 expression

Thrombospondin-1 (TSP-1), which is synthesized by mesangial cells, is known for its anti-angiogenic activity and its ability to activate latent TGF-beta. TSP-1 is upregulated in renal diseases associated with tissue remodeling. Therefore, we hypothesized that the expression of TSP-1 might be modulated by changes in cell morphology involving proteins of the Rho family. Spreading of mesangial cells after detachment and reseeding was characterized by the formation of lamellipodia and focal adhesions, pointing toward a Rac-1-mediated rearrangement of actin structures. Clustering of focal adhesion proteins was also observed in a model system of nocodazole-induced disruption of microtubules. These morphological alterations were impeded by pharmacological inhibition of Src family kinases, of the small GTPase Rac-1, or by downregulation of Rac-1 by siRNA. Upon cell spreading, TSP-1 was upregulated in the absence and much more prominently in the presence of serum, but also after nocodazole treatment. TSP-1 upregulation was controlled by activation of Src family kinases, ERK 1/2 and Rac-1, whereas activation of RhoA-ROCK signaling was not linked to TSP-1 induction. We thus provide evidence that TSP-1 expression is induced by common signaling pathways, which are activated by morphological alterations of renal mesangial cells or by soluble factors as contained in serum, and these pathways include Src family kinases, ERK 1/2 and Rac-1. Our data suggest that tissue remodeling activates gene expression of pathophysiologically relevant proteins such as TSP-1.

Ephrin-A1 stimulates migration of CD8+CCR7+ T lymphocytes

We have previously demonstrated that binding of ephrin-A1 to Eph receptors on human CD4+ T cells stimulates migration. Here, we show that a distinct population of CD8+ T lymphocytes, expressing the chemokine receptor CCR7, also binds ephrin-A1 and is stimulated to migrate after binding. The Eph receptor signaling pathway taking part in the migration event was here investigated. Induced tyrosine phosphorylation of several proteins was seen after ephrin-A1 binding. In particular, induced phosphorylation and kinase activity of the Src kinase family member Lck was observed. An Lck inhibitor inhibited ephrin-A1-induced migration, indicating the involvement of Lck in the migration event. In addition, we observed an induced association of the focal adhesion-like kinase proline-rich tyrosine kinase 2 (Pyk2) and the guanidine exchange factor Vav1 with Lck. PI3K inhibitors also inhibited migration, and studies in transfectants indicate an association of PI3K with EphA1. Further, ephrin-A1-induced migration could be related to the activation of Rho GTPases. This was also observed by using an inhibitor of the Rho-associated kinase ROCK, a downstream effector of Rho. Our results suggest that stimulation of Eph receptors on CD8+CCR7+ T cells leads to migration involving activation of Lck, Pyk2, PI3K, Vav1 and Rho GTPase.

Role of chemokines in endocrine autoimmune diseases

Chemokines are a group of peptides of low molecular weight that induce the chemotaxis of different leukocyte subtypes. The major function of chemokines is the recruitment of leukocytes to inflammation sites, but they also play a role in tumoral growth, angiogenesis, and organ sclerosis. In the last few years, experimental evidence accumulated supporting the concept that interferon-gamma (IFN-gamma) inducible chemokines (CXCL9, CXCL10, and CXCL11) and their receptor, CXCR3, play an important role in the initial stage of autoimmune disorders involving endocrine glands. The fact that, after IFN-gamma stimulation, endocrine epithelial cells secrete CXCL10, which in turn recruits type 1 T helper lymphocytes expressing CXCR3 and secreting IFN-gamma, thus perpetuating autoimmune inflammation, strongly supports the concept that chemokines play an important role in endocrine autoimmunity. This article reviews the recent literature including basic science, animal models, and clinical studies, regarding the role of these chemokines in autoimmune endocrine diseases. The potential clinical applications of assaying the serum levels of CXCL10 and the value of such measurements are reviewed. Clinical studies addressing the issue of a role for serum CXCL10 measurement in Graves' disease, Graves' ophthalmopathy, chronic autoimmune thyroiditis, type 1 diabetes mellitus, and Addison's disease have been considered. The principal aim was to propose that chemokines, and in particular CXCL10, should no longer be considered as belonging exclusively to basic science, but rather should be used for providing new insights in the clinical management of patients with endocrine autoimmune diseases.

Temporal analysis of E2 transcriptional induction of PTP and MKP and downregulation of IGF-I pathway key components in the mouse uterus

17beta-Estradiol (E2) is well known to be associated with uterine cancer, endometriosis, and leiomyomas. Although insulin-like growth factor I (IGF-I) has been identified as a mediator of the uterotrophic effect of E2 in several studies, this mechanism is still not well understood. In the present study, identification of the genes modulated by a physiological dose of E2, in the uterus, has been done in ovariectomized mice using Affymetrix microarrays. The E2-induced genomic profile shows that multiple genes belonging to the IGF-I pathway are affected after exposure to E2. Two phases of regulation could be identified. First, from 0 to 6 h, the expression of genes involved in the cell cycle, growth factors, protein tyrosine phosphatases, and MAPK phosphatases is quickly upregulated by E2, while IGF-I receptor and several genes of the MAPK and phosphatidylinositol 3-kinase pathways are downregulated. Later, i.e., from 6 to 24 h, transporters and peptidases/proteases are stimulated, whereas defense-related genes are differentially regulated by E2. Finally, cytoarchitectural genes are modulated later. The present data show that a physiological dose of E2 induces, within 24 h, a series of transcriptional events that promote the uterotrophic effect. Among these, the E2-mediated activation of the IGF-I pathway seems to play a pivotal role in the uterotrophic effect. Furthermore, the protein tyrosine phosphatases and MAPK phosphatases are likely to modulate the estrogenic uterotrophic action by targeting, at different steps, the IGF-I pathway.

Molecular mechanisms of hepatic fibrogenesis

Liver fibrosis, a wound-healing response to a variety of chronic stimuli, is characterized by excessive deposition of extracellular matrix (ECM) proteins, of which type I collagen predominates. This alters the structure of the liver leading to organ dysfunction. The activated hepatic stellate cell (HSC) is primarily responsible for excess collagen deposition during liver fibrosis. Two important aspects are involved in mediating the fibrogenic response: first the HSC becomes directly fibrogenic by synthesizing ECM proteins; second, the activated HSC proliferates, effectively amplifying the fibrogenic response. Although the precise mechanisms responsible for HSC activation remain elusive, substantial insight is being gained into the molecular mechanisms responsible for ECM production and cell proliferation in the HSC. The activated HSC becomes responsive to both proliferative (platelet-derived growth factor) and fibrogenic (transforming growth factor-beta[TGF-beta]) cytokines. It is becoming clear that these cytokines activate both mitogen-activated protein kinase (MAPK) signaling, involving p38, and focal adhesion kinase-phosphatidylinositol 3-kinase-Akt-p70 S6 kinase (FAK-PI3K-Akt-p70(S6K)) signaling cascades. Together, these regulate the proliferative response, activating cell cycle progression as well as collagen gene expression. In addition, signaling by both TGF-beta, mediated by Smad proteins, and p38 MAPK influence collagen gene expression. Smad and p38 MAPK signaling have been found to independently and additively regulate alpha1(I) collagen gene expression by transcriptional activation while p38 MAPK, but not Smad signaling, increases alpha1(I) collagen mRNA stability, leading to increased synthesis and deposition of type I collagen. It is anticipated that by understanding the molecular mechanisms responsible for HSC proliferation and excess ECM production new therapeutic targets will be identified for the treatment of liver fibrosis.

Migratory Pathways of T Cells and Response to CXCR3 and CXCR4 Ligands: Adhesion Molecules Involved and Implications for Multiple Sclerosis Pathogenesis

Gammadelta T lymphocytes are thought to be involved in multiple sclerosis (MS) pathogenesis. In this work, we discuss the characteristics of these cells and possible implications in the pathogenesis of MS, focusing on the mechanism(s) underlying extravasation and tissue localization. Phenotype and transendothelial migration of gammadelta T cells from healthy donors and patients with relapsing-remitting MS were studied. In MS patients the V delta 2 T cell subset, expressing NKRP1A/CD161 adhesion molecule, is expanded and capable of transendothelial migration. V delta 1/V delta 2 subsets use distinct signal transduction pathways: V delta 1 cells lack NKRP1A and express PECAM-1/CD31, which drives transmigration, while V delta 2 cells are PECAM-1 negative and use NKRP1A. V delta 2 migration is coupled with CAMKII, whereas V delta 1 depend on PI-3K. NKRP1A and PECAM-1 selectively activate the two pathways: indeed, oligomerization of NKRP1A on V delta 2 T cells leads to CAMKII activation, occupancy of PECAM-1 on V delta 1 cells triggers the PI-3K-dependent Akt/PKB pathway. Moreover, V delta 2 T cells are CXCR3(bright)CXCR4(dull), while V delta 1 are mostly CXCR4(+). V delta 1 and V delta 2 cells transmigrate in response to IP-10/CXCL10 and SDF-1/CXCL12 according to the expression of their specific receptors. In a fraction of V delta 1 T cells coexpressing CXCR3 and CXCR4, the homeostatic chemokine 6Ckine/SLC/CCL21 is more effective. IP-10/CXCL10 or 6Ckine/SLC/CCL21 and SDF-1/CXCL12-induced transmigration is coupled to PI-3K/Akt/PKB, but only CXCR3 is capable of inducing CAMKII activation. We suggest that both subsets of gammadelta T lymphocytes may migrate to the site of lesion in MS using two different signaling pathways to extravasate and responding to different chemokines.

CXCL10 promotes invasion-related properties in human colorectal carcinoma cells

CXCL10 was recently shown to exert antimalignancy functions by influencing the tumor microenvironment. Here, we have taken a different approach, investigating the effects of CXCL10 directly on tumor-promoting functions in colorectal carcinoma (CRC) cells. CXCL10 expression was detected in preferred metastatic sites of CRC (liver, lungs, and lymph nodes), and its CXCR3 receptor was expressed by eight CRC cell lines (detected: reverse transcription-PCR and/or flow cytometry). Detailed analysis was done on two cell lines derived from primary CRC tumors (SW480, KM12C) and their metastatic descendents (SW620 and KM12SM). The three known variants of CXCR3 (CXCR3-A, CXCR3-B, and CXCR3-alt) were detected in all four cell lines. CXCR3 expression was also observed on colorectal tumor cells in biopsies of CRC patients (immunohistochemistry). CXCL10 and CXCR3 expression were potently induced in CRC cells by Interferon gamma and all four CRC cell lines responded to CXCL10 by extracellular signal-regulated kinase 1/2 dephosphorylation. The chemokine did not affect tumor cell growth or angiogenesis-related functions in the tumor cells, such as CXCL8 and vascular endothelial growth factor secretion. Importantly, CXCL10 significantly up-regulated invasion-related properties in CRC cells: It promoted matrix metalloproteinase 9 expression and induced CRC cell migration. Of note, CXCL10-induced migration was detected only in the two metastatic cells and not in their primary counterparts. Also, CXCL10 promoted the adhesion of metastatic cells to laminin. These results suggest that CXCL10 can be exploited by CRC cells toward their progression, thus possibly antagonizing the antimalignancy effects of the chemokine on the tumor microenvironment. Therefore, care should be taken when considering CXCL10 as a therapeutic antitumor modality for CRC treatment.

CXCL5 overexpression is associated with late stage gastric cancer

PURPOSE

Chemokines play multiple roles in the development and progression of many different tumors. Our cDNA array data suggested that chemokine CXCL5 was upregulated in gastric cancer. Here, we analyzed CXCL5 protein expression in gastric cancer and investigated the clinical implications of CXCL5 upregulation.

METHODS

Immunostaining for CXCL5 was performed on gastric tissue microarrays of tissue specimens obtained by gastrectomy. The intensity of immunostaining in tumor tissue was considered strong when tumor tissue staining was more intense than in normal tissue; the intensity was null when staining was weaker in the tumor than in normal tissue; and the intensity was weak when staining was similar in both tissues. Serum CXCL5 levels and microvascular density in tumor tissue were measured by ELISA and monoclonal antibody to Factor VIII.

RESULTS

Strong CXCL5 expression correlated with tumor stage. CXCL5 expression did not correlate with T stage. However, N stage positively correlated with CXCL5 expression. Serum CXCL5 levels in late stage (IIIB, IV) gastric cancer patients were higher than in patients with benign conditions. Microvascular density was higher in tumors with strong CXCL5 expression, but the correlation with CXCL5 was not linear. Multiple logistic regression analyses showed that, compared to no or weak expression, strong expression of CXCL5 was a significant risk factor for high N stage (N2, N3).

CONCLUSIONS

CXCL5 overexpression was associated with late stage gastric cancer and high N stage. These results suggest a role for CXCL5 in the progression of gastric cancer, specifically in lymph node metastasis.

IL-22-mediated liver cell regeneration is abrogated by SOCS-1/3 overexpression in vitro

The IL-10-like cytokine IL-22 is produced by activated T cells. In this study, we analyzed the role of this cytokine system in hepatic cells. Expression studies were performed by RT-PCR and quantitative PCR. Signal transduction was analyzed by Western blot experiments and ELISA. Cell proliferation was measured by MTS and [(3)H]thymidine incorporation assays. Hepatocyte regeneration was studied in in vitro restitution assays. Binding of IL-22 to its receptor complex expressed on human hepatic cells and primary human hepatocytes resulted in the activation of MAPKs, Akt, and STAT proteins. IL-22 stimulated cell proliferation and migration, which were both significantly inhibited by the phosphatidylinositol 3-kinase inhibitor wortmannin. IL-22 increased the mRNA expression of suppressor of cytokine signaling (SOCS)-3 and the proinflammatory cytokines IL-6, IL-8, and TNF-alpha. SOCS-1/3 overexpression abrogated IL-22-induced STAT activation and decreased IL-22-mediated liver cell regeneration. Hepatic IL-22 mRNA expression was detectable in different forms of human hepatitis, and hepatic IL-22 mRNA levels were increased in murine T cell-mediated hepatitis in vivo following cytomegalovirus infection, whereas no significant differences were seen in an in vivo model of ischemia-reperfusion injury. In conclusion, IL-22 promotes liver cell regeneration by increasing hepatic cell proliferation and hepatocyte migration through the activation of Akt and STAT signaling, which is abrogated by SOCS-1/3 overexpression.

Identification of carboxypeptidase of glutamate like-B as a candidate suppressor in cell growth and metastasis in human hepatocellular carcinoma

PURPOSE

We have previously done large-scale cDNA transfection screening on human hepatocellular carcinoma (HCC) cells and have identified 3,806 cDNA genes that possess the ability of either stimulating or inhibiting cell growth. In this study, we characterized one of these growth suppressor genes, carboxypeptidase of glutamate like-B (CPGL-B), in HCC.

EXPERIMENTAL DESIGN

Semiquantitative reverse-transcription PCR was used to examine the expression levels of CPGL-B. The cellular localization and functions of CPGL-B were investigated by enforced expression of CPGL-B in HCC cells.

RESULTS

From our previous cDNA transfection screening, we identified a gene named CPGL and its isoform, CPGL-B. With computational analysis, CPGL was located at chromosome 18q22.3 and was a homologue of peptidase family M20. CPGL was expressed in all adult and fetal tissues, whereas its isoform, CPGL-B, lacking exons 3 and 4, was expressed in all fetal tissues but only in liver and placenta of adult tissues. In HCC, CPGL-B was frequently underexpressed (35 of 90, 38.9%) in tumorous tissues compared with the corresponding nontumorous livers. Intriguingly, the underexpression was significantly associated with the presence of venous invasion (P=0.018) and tumor microsatellite formation (P=0.004). Stable transfection of CPGL-B in SMMC7721 HCC cells showed significant inhibition in cell viability, colony formation, cell invasion, and tumor formation in nude mice. CPGL-B also down-regulated CXCR3, matrix metalloproteinase 11, and CD44s, which are involved in cell growth and cell migration.

CONCLUSIONS

These findings suggest that the frequent underexpression of CPGL-B may be associated with cell growth and metastasis of HCC.

CXCR3-mediated T-cell chemotaxis involves ZAP-70 and is regulated by signalling through the T-cell receptor

The chemokine receptor CXCR3 is critical for the function of activated T cells. We studied the molecular mechanisms of CXCR3 signalling. The addition of CXCR3 ligands to normal human T cells expressing CXCR3 led to the tyrosine phosphorylation of multiple proteins. Addition of the same ligands to Jurkat T cells engineered to express CXCR3 induced tyrosine phosphorylation of proteins with molecular weights similar to those in normal cells. Immunoblotting with phosphotyrosine-specific antibodies identified Zeta-associated protein of 70,000 molecular weight (ZAP-70), linker for the activation of T cells (LAT), and phospholipase-C-gamma1 (PLCgamma1) to be among the proteins that become phosphorylated upon CXCR3 activation. ZAP-70 was phosphorylated on tyrosine 319, LAT on tyrosines 171 and 191, and PLCgamma1 on tyrosine 783. The ZAP-70 inhibitor piceatannol reduced CXCR3-mediated tyrosine phosphorylation of ZAP-70, LAT, PLCgamma1 and mitogen-activated protein kinase Erk and it reduced CXCL10-mediated chemotaxis of both CXCR3-transfected Jurkat T cells and normal T cells expressing CXCR3. These results are consistent with the involvement of ZAP-70 in CXCR3-mediated protein tyrosine phosphorylation and CXCR3-induced T-cell chemotaxis. Studies with the Lck-deficient Jurkat T-cell line, JCAM1.6, demonstrated that phosphorylation of ZAP-70 after CXCR3 activation is a Lck-dependent process. Finally, stimulating CXCR3-expressing Jurkat T cells and normal T cells expressing CXCR3 through the T-cell receptor attenuated CXCR3-induced tyrosine phosphorylation and CXCR3-mediated T-cell migration, indicating the occurrence of cross-talk between T-cell receptor and CXCR3-signalling pathways. These results shed light on the mechanisms of CXCR3 signalling. Such information could be useful when designing therapeutic strategies to regulate T-cell function.

Resistin as an intrahepatic cytokine: overexpression during chronic injury and induction of proinflammatory actions in hepatic stellate cells

Obesity and insulin resistance accelerate the progression of fibrosis during chronic liver disease. Resistin antagonizes insulin action in rodents, but its role in humans is still controversial. The aims of this study were to investigate resistin expression in human liver and to evaluate whether resistin may affect the biology of activated human hepatic stellate cells (HSCs), key modulators of hepatic fibrogenesis. Resistin gene expression was low in normal human liver but was increased in conditions of severe fibrosis. Up-regulation of resistin during chronic liver damage was confirmed by immunohistochemistry. In a group of patients with alcoholic hepatitis, resistin expression correlated with inflammation and fibrosis, suggesting a possible action on HSCs. Exposure of cultured HSCs to recombinant resistin resulted in increased expression of the proinflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, through activation of nuclear factor (NF)-kappaB. Resistin induced a rapid increase in intracellular calcium concentration, mainly through calcium release from intracellular inositol triphosphate-sensitive pools. The intracellular calcium chelator BAPTA-AM blocked resistin-induced NF-kappaB activation and monocyte chemoattractant protein-1 expression. In conclusion, this study shows a role for resistin as an intrahepatic cytokine exerting proinflammatory actions in HSCs, via a Ca2+/NF-kappaB-dependent pathway and suggests involvement of this adipokine in the pathophysiology of liver fibrosis.

Resistin as an intrahepatic cytokine: overexpression during chronic injury and induction of proinflammatory actions in hepatic stellate cells

Obesity and insulin resistance accelerate the progression of fibrosis during chronic liver disease. Resistin antagonizes insulin action in rodents, but its role in humans is still controversial. The aims of this study were to investigate resistin expression in human liver and to evaluate whether resistin may affect the biology of activated human hepatic stellate cells (HSCs), key modulators of hepatic fibrogenesis. Resistin gene expression was low in normal human liver but was increased in conditions of severe fibrosis. Up-regulation of resistin during chronic liver damage was confirmed by immunohistochemistry. In a group of patients with alcoholic hepatitis, resistin expression correlated with inflammation and fibrosis, suggesting a possible action on HSCs. Exposure of cultured HSCs to recombinant resistin resulted in increased expression of the proinflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, through activation of nuclear factor (NF)-kappaB. Resistin induced a rapid increase in intracellular calcium concentration, mainly through calcium release from intracellular inositol triphosphate-sensitive pools. The intracellular calcium chelator BAPTA-AM blocked resistin-induced NF-kappaB activation and monocyte chemoattractant protein-1 expression. In conclusion, this study shows a role for resistin as an intrahepatic cytokine exerting proinflammatory actions in HSCs, via a Ca2+/NF-kappaB-dependent pathway and suggests involvement of this adipokine in the pathophysiology of liver fibrosis.

Differential effects of immunosuppressive drugs on T-cell motility

The best-characterized mechanism of the action of immunosuppressive drugs is to prevent T-cell clonal expansion, thus containing the magnitude of the ensuing immune response. As T-cell recruitment to the inflammatory site is another key step in the development of T-cell-mediated inflammation, we analyzed and compared the effects of two commonly used immunosuppressants, cyclosporin A (CsA) and the rapamycin-related compound SDZ-RAD, on the motility of human CD4+ T cells. We show that CsA, but not SDZ-RAD, inhibits T-cell transendothelial migration in vitro. CsA selectively impaired chemokine-induced T-cell chemotaxis while integrin-mediated migration was unaffected. The inhibition of T-cell chemotaxis correlated with reduced AKT/PKB but not ERK activation following exposure to the chemokine CXCL-12/SDF-1. In addition, CsA, but not SDZ-RAD, prevents some T-cell receptor-mediated effects on T-cell motility. Finally, we show that CsA, but not SDZ-RAD inhibits tissue infiltration by T cells in vivo. Our data suggest a prominent antiinflammatory role for CsA in T-cell-mediated tissue damage, by inhibiting T-cell trafficking into tissues in addition to containing clonal expansion.

A proteomic screen identified stress-induced chaperone proteins as targets of Akt phosphorylation in mesangial cells

The serine-threonine kinase Akt regulates mesangial cell apoptosis, proliferation, and hypertrophy. To define Akt signaling pathways in mesangial cells, we performed a functional proteomic screen for rat mesangial cell proteins phosphorylated by Akt. A group of chaperone proteins, heat shock protein (Hsp) 70, Hsp90alpha, Hsp90beta, Glucose-regulated protein (Grp) Grp78, Grp94, and protein disulfide isomerase (PDI) were identified as potential Akt substrates by two techniques: (a) in vitro phosphorylation of mesangial cell lysate by recombinant active Akt followed by protein separation by SDS-PAGE or 2-DE and phosphoprotein identification by peptide mass fingerprinting using MALDI-MS, or (b) immunoblot analysis of proteins from PDGF-stimulated mesangial cells using an anti-Akt phospho-motif antibody. In vitro kinase reactions using recombinant proteins confirmed that Akt phosphorylates Hsp70, Hsp90alpha and beta, Grp94, and PDI. Immunoprecipitation of Akt from mesangial cell lysate coprecipitated Grp78 and Hsp70. PDGF stimulation of mesangial cells caused an acidic shift in the isoelectric point of Hsp70, Hsp90, and PDI that was dependent on PI-3K activity for Hsp70 and Hsp90. The data suggest that Akt-mediated phosphorylation of stress-induced chaperones represents a mechanism for regulation of chaperone function during mesangial cell responses to physiologic and pathologic stimuli.

Cell differentiation dependent expressed CCR6 mediates ERK-1/2, SAPK/JNK, and Akt signaling resulting in proliferation and migration of colorectal cancer cells

The expression of CCL20 (MIP-3alpha), which chemoattracts leukocytes to sites of inflammation, has been shown in intestinal epithelial cells (IEC). Aim of this study was to analyze the role of the CCL20 receptor CCR6 in IEC and colorectal cancer (CRC) cells. Expression of CCR6 and CCL20 was analyzed by RT-PCR and immunohistochemistry. Signaling was investigated by Western blotting, proliferation by MTS assays and chemotactic cell migration by wounding assays. The effect of CCL20 on Fas-induced apoptosis was determined by flow cytometry. CCR6 and its ligand CCL20 are expressed in IEC. Moreover, CRC and CRC metastases express CCR6, which is upregulated during IEC differentiation. Stimulation of IEC with CCL20 and proinflammatory stimuli (TNF-alpha, IL-1beta, LPS) significantly upregulates CCL20 mRNA expression. CCL20 expression was significantly increased in inflamed colonic lesions in Crohn's disease and correlated significantly with the IL-8 mRNA expression in these lesions (r = 0.71) but was downregulated in CRC metastases. CCL20 activated Akt, ERK-1/2, and SAPK/JNK MAP kinases and increased IL-8 protein expression. The CCL20 mediated activation of these pathways resulted in a 2.6-fold increase of cell migration (P = 0.001) and in a significant increase of cell proliferation (P < 0.05) but did not influence Fas-induced apoptosis. In conclusion, IEC and CRC express CCL20 and its receptor CCR6. CCL20 expression is increased in intestinal inflammation, while CCR6 is upregulated during cell differentiation. CCR6 mediated signals result in increased IEC migration and proliferation suggesting an important role in intestinal homeostasis and intestinal inflammation by mediating chemotaxis of IEC but also in mediating migration of CRC cells.

Fractalkine stimulates angiogenesis by activating the Raf-1/MEK/ERK- and PI3K/Akt/eNOS-dependent signal pathways

Fractalkine (FKN) has been implicated in modulation of angiogenesis and vascular inflammation, but the underlying mechanism has not been elucidated. We have investigated the molecular mechanism by which FKN regulates angiogenesis. We found that recombinant FKN increases in vitro proliferation, migration, and tube formation of human umbilical vein endothelial cells and stimulates in vivo angiogenesis. FKN-induced angiogenesis was accompanied by phosphorylation of ERK, Akt, and endothelial nitric oxide (NO) synthase (eNOS), as well as an increase in NO production. These biochemical events and angiogenesis were completely inhibited by the G protein-coupled receptor inhibitor pertussis toxin. Inhibitors of Raf-1, MEK, phosphatidylinositol 3-kinase (PI3K), and eNOS or transfection with dominant-negative forms of ERK and Akt significantly suppressed the angiogenic activity of FKN. However, inhibitors of Raf-1 and MEK or a dominant-negative ERK mutant blocked FKN-induced ERK, but not Akt and eNOS, phosphorylation. The PI3K inhibitor and a dominant-negative mutant of Akt suppressed Akt and eNOS phosphorylation and NO production. Our results demonstrated that FKN stimulated angiogenesis by activating the Raf-1/MEK/ERK and PI3K/Akt/eNOS/NO signal pathways via the G protein-coupled receptor CX3CR1, indicating that two pathways are required for full angiogenic activity of FKN. This study suggests that FKN may play an important role in the pathophysiological process of inflammatory angiogenesis.

Fas ligand is responsible for CXCR3 chemokine induction in CD4+ T cell-dependent liver damage

Immune-mediated hepatic damage has been demonstrated in the pathogenesis of hepatitis C virus (HCV) and other hepatotrophic infections. Fas/Fas ligand (FasL) interaction plays a critical role in immune-mediated hepatic damage. To understand the molecular mechanism(s) of FasL-mediated liver inflammation, we examined the effect of CD4(+) T cells expressing high levels of FasL on the initiation of hepatic damage through analysis of chemokine and chemokine receptor expression in HCV core x TCR (DO11.10) double-transgenic mice. In vivo antigenic stimulation triggers a marked influx of core-expressing Ag-specific CD4(+) T cells into the liver of the immunized core(+) TCR mice but not their core(-) TCR littermates. Strikingly, the inflammatory process in the liver of core(+) TCR mice was accompanied by a dramatic increase in IFN-inducible protein 10 and monokine induced by IFN-gamma production. The intrahepatic lymphocytes were primarily CXCR3-positive and anti-CXCR3 Ab treatment abrogates migration of CXCR3(+) lymphocytes into the liver and hepatic damage. Importantly, the blockade of Fas/FasL interaction reduces the expression of IFN-inducible protein 10 and monokine induced by IFN-gamma and cellular infiltration into the liver. These findings suggest that activated CD4(+) T cells with elevated FasL expression are involved in promoting liver inflammation and hepatic damage through the induction of chemokines.

Down-regulation of CXCL5 inhibits squamous carcinogenesis

We report a novel role for the CXC-chemokine, CXCL5, in the proliferation and invasion of head and neck squamous cell carcinoma (HNSCC). Previously, we reported transcriptional up-regulation of CXCL5 in metastatic cells. In this study, we provide biological validation of these findings and show that CXCL5 is intimately involved in tumor cell proliferation, migration, and invasion. Cells derived from a lymph node metastasis, but not from a synchronous primary tumor, secreted CXCL5 as judged by Western blotting of conditioned media. We used RNA interference to generate cell lines (shL5) in which CXCL5 expression was greatly reduced, and tested whether this modulated the cell phenotype. shL5 cells showed decreased proliferation compared with cells harboring nontargeting control sequences. In addition, we found that the ability of shL5 cells to migrate and invade in vitro through a basement membrane substitute was greatly impaired compared with control cells. Finally, whereas control cells were highly tumorigenic in nude mice, the tumorigenic potential in vivo of shL5 cells was found to be ablated. Taken together, these data suggest that CXCL5 production contributes to both enhanced proliferation and invasion of squamous cell carcinomas and that targeting of chemokine pathways may represent a potential therapeutic modality for these lesions.

IL-22 is increased in active Crohn's disease and promotes proinflammatory gene expression and intestinal epithelial cell migration

IL-22 is produced by activated T cells and signals through a receptor complex consisting of IL-22R1 and IL-10R2. The aim of this study was to analyze IL-22 receptor expression, signal transduction, and specific biological functions of this cytokine system in intestinal epithelial cells (IEC). Expression studies were performed by RT-PCR. Signal transduction was analyzed by Western blot experiments, cell proliferation by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay and Fas-induced apoptosis by flow cytometry. IEC migration was studied in wounding assays. The IEC lines Caco-2, DLD-1, SW480, HCT116, and HT-29 express both IL-22 receptor subunits IL-22R1 and IL-10R2. Stimulation with TNF-alpha, IL-1beta, and LPS significantly upregulated IL-22R1 without affecting IL-10R2 mRNA expression. IL-22 binding to its receptor complex activates STAT1/3, Akt, ERK1/2, and SAPK/JNK MAP kinases. IL-22 significantly increased cell proliferation (P = 0.002) and phosphatidylinsitol 3-kinase-dependent IEC cell migration (P < 0.00001) as well as mRNA expression of TNF-alpha, IL-8, and human beta-defensin-2. IL-22 had no effect on Fas-induced apoptosis. IL-22 mRNA expression was increased in inflamed colonic lesions of patients with Crohn's disease and correlated highly with the IL-8 expression in these lesions (r = 0.840). Moreover, IL-22 expression was increased in murine dextran sulfate sodium-induced colitis. IEC express functional receptors for IL-22, which increases the expression of proinflammatory cytokines and promotes the innate immune response by increased defensin expression. Moreover, our data indicate intestinal barrier functions for this cytokine-promoting IEC migration, which suggests an important function in intestinal inflammation and wound healing. IL-22 is increased in active Crohn's disease and promotes proinflammatory gene expression and IEC migration.

CXCR3 chemokine receptor-induced chemotaxis in human airway epithelial cells: role of p38 MAPK and PI3K signaling pathways

Human airway epithelial cells (HAEC) constitutively express the CXC chemokine receptor CXCR3, which regulates epithelial cell movement. In diseases such as chronic obstructive pulmonary disease and asthma, characterized by denudation of the epithelial lining, epithelial cell migration may contribute to airway repair and reconstitution. This study compared the potency and efficacy of three CXCR3 ligands, I-TAC/CXCL11, IP-10/CXCL10, and Mig/CXCL9, as inducers of chemotaxis in HAEC and examined the underlying signaling pathways involved. Studies were performed in cultured HAEC from normal subjects and the 16-HBE cell line. In normal HAEC, the efficacy of I-TAC-induced chemotaxis was 349 +/- 88% (mean +/- SE) of the medium control and approximately one-half the response to epidermal growth factor, a highly potent chemoattractant. In normal HAEC, Mig, IP-10, and I-TAC induced chemotaxis with similar potency and a rank order of efficacy of I-TAC = IP-10 > Mig. Preincubation with pertussis toxin completely blocked CXCR3-induced migration. Of interest, intracellular [Ca(2+)] did not rise in response to I-TAC, IP-10, or Mig. I-TAC induced a rapid phosphorylation (5-10 min) of two of the three MAPKs, i.e., p38 and ERK1/2. Pretreatment of HAEC with the p38 inhibitor SB 20358 or the PI3K inhibitor wortmannin dose-dependently inhibited the chemotactic response to I-TAC. In contrast, the ERK1/2 inhibitor U0126 had no effect on chemotaxis. These data indicate that in HAEC, CXCR3-mediated chemotaxis involves a G protein, which activates both the p38 MAPK and PI3K pathways in a calcium-independent fashion.

CCL2 and CXCL1 trigger calcitonin gene-related peptide release by exciting primary nociceptive neurons

Chemokines are important mediators in immune responses and inflammatory processes. Calcitonin gene-related peptide (CGRP) is produced in dorsal root ganglion (DRG) neurons. In this study, CGRP radioimmunoassay was used to investigate whether the chemokines CCL2 and CXCL1 could trigger CGRP release from cultured DRG neurons of neonatal rats and, if so, which cellular signaling pathway was involved. The results showed that CCL2 and CXCL1 ( approximately 5-100 ng/ml) evoked CGRP release and intracellular calcium elevation in a pertussis toxin (PTX)-sensitive manner. The CGRP release by CCL2 and CXCL1 was significantly inhibited by EGTA, omega-conotoxin GVIA (an N-type calcium channel blocker), thapsigargin, and ryanodine. Pretreatment of DRG neurons for 30 min with the inhibitors of phospholipase C (PLC) and protein kinase C (PKC) but not mitogen-activated protein kinases (MAPKs) significantly reduced CCL2- or CXCL1-induced CGRP release and intracellular calcium elevation. Intraplantar injection of CCL2 or CXCL1 produced hyperalgesia to thermal and mechanical stimulation in rats. These data suggest that CCL2 and CXCL1 can stimulate CGRP release and intracellular calcium elevation in DRG neurons. PLC-, PKC-, and calcium-induced calcium release from ryanodine-sensitive calcium stores signaling pathways are involved in CCL2- and CXCL1-induced CGRP release from primary nociceptive neurons, in which chemokines produce painful effects via direct actions on chemokine receptors expressed by nociceptive neurons.

Thrombopoietin stimulates migration and activates multiple signaling pathways in hepatoblastoma cells

Thrombopoietin (TPO), a cytokine that participates in the differentiation and maturation of megakaryocytes, is produced in the liver, but only limited information is available on the biological response of liver-derived cells to TPO. In this study, we investigated whether HepG2 cells express c-Mpl, the receptor for TPO, and whether TPO elicits biological responses and intracellular signaling in this cell type. Specific transcripts for c-Mpl were detected in HepG2 cells by RT-PCR, and expression of the protein was demonstrated by Western blot analysis and immunofluorescence. Exposure of HepG2 cells to TPO was associated with a dose-dependent increase in cell migration and chemoinvasion through Matrigel-coated filters. A checkerboard analysis showed that the effects of TPO on cell migration were dependent on both chemotaxis and chemokinesis. Exposure of HepG2 cells to TPO resulted in the activation of different members of the MAPK family, including ERK and JNK, as assessed using phosphorylation-specific antibodies and immune complex kinase assays. TPO also activated phosphatidylinositol 3-kinase (PI3K) and the downstream kinase Akt in a time-dependent manner. Finally, activation of c-Mpl was associated with increased activation of nuclear factor-kappaB. With the use of specific inhibitors, tyrosine phosphorylation and activation of PI3K were found to be required for the induction of migration in response to TPO. We conclude that TPO exerts biological actions on cultured hepatoblastoma cells via activation of c-Mpl and its downstream signaling.

Identification and characterization of a potent, selective nonpeptide agonist of the CC chemokine receptor CCR8

In this study, we report the first example of a nonpeptide chemokine receptor agonist, 2-{2-[4-(3-phenoxybenzyl)piperazin-1-yl]ethoxy}ethanol (ZK 756326), for the CC chemokine receptor CCR8. ZK 756326 inhibited the binding of the CCR8 ligand I-309 (CCL1), with an IC(50) value of 1.8 muM. Furthermore, ZK 756326 was a full agonist of CCR8, dose-responsively eliciting an increase in intracellular calcium and cross-desensitizing the response of the receptor to CCL1. In addition, ZK 756326 stimulated extracellular acidification in cells expressing human CCR8. The ability of ZK 756326 to induce a response was receptor-specific and mediated through Galpha(i), because it could be blocked by treatment with pertussis toxin. The CCR8 agonist activated cells expressing murine CCR8, eliciting their chemotaxis and inducing phosphorylation of extracellular signal-regulated kinase ERK1/2. Like CCL1, ZK 756326 inhibited human immunodeficiency virus (HIV) fusion of cells expressing CD4 and CCR8. Finally, unlike mCCL1, ZK 756326 bound to and activated a form of mCCR8 that was mutated to eliminate O-linked sulfation at tyrosines 14 and 15. Therefore, ZK 756326 is most probably not binding in the same manner as CCL1 but can activate the switch mechanism involved in transducing signaling events. In summary, we have identified a nonpeptide agonist of CCR8. This compound may be useful in evaluating the physiological role of CCR8 in HIV infection, as well as in the general study of CCR8 biology without the constraints inherent to the use of protein agonists such as its natural ligand.

Role of CXCR3 carboxyl terminus and third intracellular loop in receptor-mediated migration, adhesion and internalization in response to CXCL11

The chemokine receptor CXCR3 is predominantly expressed on activated T and natural killer (NK) cells. CXCR3 and its ligands, CXCL11, CXCL10, and CXCL9, play a major role in T-helper 1 (Th1)-dependent inflammatory responses. CXCL11 is the most dominant physiological inducer of adhesion, migration, and internalization of CXCR3. To study the role of CXCR3 carboxyl-terminus and the third intracellular (3i) loop in chemokine-mediated migration, adhesion, and CXCR3 internalization, we generated CXCR3 receptors mutated in their distal (Ser-Thr domain) or proximal (trileucine domain) membrane carboxyl terminus, and/or the third intracellular loop. We found that migration of CXCR3-expressing HEK 293 cells toward CXCL11 was pertussis toxin-dependent and required the membrane proximal carboxyl terminus of CXCR3. Internalization induced by CXCL11 and protein kinase C (PKC) activation was also regulated by the membrane proximal carboxyl terminus; however, only CXCL11-induced internalization required the LLL motif of this region. Internalization and Ca(2+) flux induced by CXCL11 were independent of the 3i loop S245, whereas migration at high CXCL11 concentrations, integrin-dependent adhesion, and actin polymerization were S245 dependent. Our findings indicate that CXCL11-dependent CXCR3 internalization and cell migration are regulated by the CXCR3 membrane proximal carboxyl terminus, whereas adhesion is regulated by the 3i loop S245. Thus, distinct conformational changes induced by a given CXCR3 ligand trigger different downstream effectors of adhesion, motility, and CXCR3 desensitization.

The chemokines CXCL9, CXCL10, and CXCL11 differentially stimulate G alpha i-independent signaling and actin responses in human intestinal myofibroblasts

Intestinal myofibroblasts have been implicated in the pathogenesis of chronic inflammatory conditions such as Crohn's disease via interactions with an elaborate network of cytokines, growth factors, and other inflammatory mediators. CXCR3 is a Galpha(i) protein-coupled receptor that binds the proinflammatory chemokines CXCL9, CXCL10, and CXCL11, which are released from the intestinal epithelium. The three CXCR3 ligands shared the ability to activate biochemical (e.g., PI3K and MAPK activation) and functional events (actin reorganization) in intestinal myofibroblasts. However, CXCL11 is unique in its ability to elevate intracellular calcium. Surprisingly, although CXCR3 mRNA is detectable in these myofibroblasts, there is no detectable surface expression of CXCR3. Furthermore, the biochemical responses and actin reorganization stimulated by the CXCR3 ligands in intestinal myofibroblasts are insensitive to the Galpha(i) inhibitor, pertussis toxin. This suggests either the existence of differential receptor coupling mechanisms in myofibroblasts for CXCR3 that are distinct from those observed in PBLs and/or that these cells express a modified or variant CXCR3 compared with the CXCR3 expressed on PBLs.

CXCR3 surface expression in human airway epithelial cells: cell cycle dependence and effect on cell proliferation

We recently demonstrated that human bronchial epithelial cells (HBEC) constitutively express the CXC chemokine receptor CXCR3, which when activated, induces directed cell migration. The present study in HBEC examined the relative expression of the CXCR3 splice variants CXCR3-A and -B, cell cycle dependence of CXCR3 expression, and the effects of the CXCR3 ligand, the interferon-gamma-inducible CXC chemokine I-TAC/CXCL11, on DNA synthesis and cell proliferation. Both CXCR3-A and -B mRNA, assessed by real-time RT-PCR, were expressed in normal HBEC (NHBEC) and the HBEC line 16-HBE. However, CXCR3-B mRNA was 39- and 6-fold greater than CXCR3-A mRNA in NHBEC and 16-HBE, respectively. Although most HBEC (>80%) assessed by flow cytometry and immunofluorescence microscopy contained intracellular CXCR3, only a minority (<40%) expressed it on the cell surface. In this latter subset of cells, most (>75%) were in the S + G(2)/M phases of the cell cycle. Stimulation of CXCR3 with I-TAC enhanced thymidine incorporation and cell proliferation and increased p38 and ERK1/2 phosphorylation. These data indicate that 1) human airway epithelial cells primarily express CXCR3-B mRNA, 2) surface expression of CXCR3 is largely confined to the S + G(2)/M phases of the cell cycle, and 3) activation of CXCR3 induces DNA synthesis, cell proliferation, and activation of MAPK pathways. We speculate that activation of CXCR3 exerts a mitogenic effect in HBEC, which may be important during airway mucosal injury in obstructive airway diseases such as asthma and chronic obstructive pulmonary disease.

CXCR4 and CXCL12 are inversely expressed in colorectal cancer cells and modulate cancer cell migration, invasion and MMP-9 activation

Colorectal cancer (CRC) is characterized by a distinct metastatic pattern resembling chemokine-induced leukocyte trafficking. This prompted us to investigate expression, signal transduction and specific functions of the chemokine receptor CXCR4 in CRC cells and metastases. Using RT-PCR analysis and Western blotting, we demonstrated CXCR4 and CXCL12 expression in CRC and CRC metastases. Cell differentiation increases CXCL12 mRNA levels. Moreover, CXCR4 and its ligand are inversely expressed in CRC cell lines with high CXCR4 and low or not detectable CXCL12 expression. CXCL12 activates ERK-1/2, SAPK/JNK kinases, Akt and matrix metalloproteinase-9. These CXCL12-induced signals mediate reorganization of the actin cytoskeleton resulting in increased cancer cell migration and invasion. Moreover, CXCL12 increases vascular endothelial growth factor (VEGF) expression and cell proliferation but has no effect on CRC apoptosis. Therefore, the CXCL12/CXCR4 system is an important mediator of invasion and metastasis of CXCR4 expressing CRC cells.

Review article: the pathogenesis of fibrosis in non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis has been recognized as a significant cause of end-stage liver disease and hepatic decompensation. Despite the growing interest in this condition, the molecular mechanisms underlying the development of fibrosis in this setting are only partially understood. In this article, the cellular and molecular basis of fibrosis in chronic liver disease are briefly outlined. In addition, mechanisms specifically operating in the context of fatty liver and steatohepatitis are examined, including: insulin resistance, oxidative stress, and inflammation. Finally, recent developments indicating the possible contribution of cytokines derived from adipose tissue (adipokines) to liver fibrosis is discussed.

Intracellular signal cascade in CD4+ T-lymphocyte migration stimulated by interferon-gamma-inducible protein-10

The intracellular signal cascades involved in chemokine-stimulated migration of in vitro activated human peripheral blood CD4+ T-lymphocytes were investigated. IP-10-mediated chemotactic response of lymphocytes was decreased in the presence of selective inhibitors of Src-kinases (by 40-45%), PI3-kinases (35-40%), and MAP-kinases ERK1/2 (35-40%) and p38 (20%). Combined addition of specific inhibitors of Src-kinases and PI3-kinases and inhibitors of Src-kinases and ERK1/2 MAP-kinases did not result in the further increase of the inhibitory effect, while the combined addition of specific inhibitors of PI3-kinases and ERK1/2 MAP-kinases decreased migration of CD4+ T-lymphocytes more effectively (by 55-60%) than any individual inhibitor. Immunoblotting analysis of activation of MAP-kinases ERK1/2 and p38 revealed increased level of phosphorylation of ERK1/2 and p38 MAP-kinases in the presence IP-10. Selective inhibitors of Src-kinases and PI3-kinases significantly inhibited phosphorylation of p38 but did not influence phosphorylation of ERK1/2 MAP-kinases. Our results suggest that Src-kinases, PI3-kinases, and ERK1/2 MAP-kinases are involved in intracellular signal cascade activated during IP-10-stimulated migration of T-lymphocytes, whereas p38 MAP-kinases do not participate in the migration process, although its activation induced by IP-10 depends on Src-kinases and PI3-kinases.

Heterologous regulation of chemokine receptor signaling by the lipid phosphatase SHIP in lymphocytes

The SH2 domain-containing inositol polyphosphate 5-phosphatase (SHIP) is known to play an important role in the negative regulation by FcgammaRIIB of PI3K-dependent signaling cascades activated by the B cell antigen receptor (BCR) as well as several tyrosine-kinase coupled cytokine receptors. However, to date the role of SHIP in the regulation of PI3K-dependent signals elicited by G-protein-coupled receptors (GPCR) such as chemokine receptors has not been investigated. In this study, we report that ligation of the G-protein-coupled chemokine receptor CXCR4 by SDF-1/CXCL12 has no effect on the tyrosine phosphorylation of SHIP in the murine B cell lymphoma A20. However, co-ligation of the B cell antigen receptor and FcgammaRIIB inhibits the PI3K-dependent phosphorylation of PKB and ERK1/2 in response to CXCL12. We have also utilised a constitutively active membrane-localised SHIP mutant expressed in the Jurkat leukaemic T cell line (which do not normally express SHIP), in order to investigate the effect of this mutant on CXCL12 stimulated PI3K-dependent signaling events. Experiments have revealed that CXCL12-mediated PKB phosphorylation, chemotaxis and lipid accumulation are inhibited in the presence of this SHIP mutant. Thus, it appears that heterologous activation of SHIP by non-G-protein-coupled receptor-mediated routes can impinge on PI3K-dependent signaling pathways activated by independently ligated G-protein-coupled chemokine receptors.

Divergent roles of c-Src in controlling platelet-derived growth factor-dependent signaling in fibroblasts

The vast complexity of platelet-derived growth factor (PDGF)-induced downstream signaling pathways is well known, but the precise roles of critical players still elude us due to our lack of specific and temporal control over their activities. Accordingly, although Src family members are some of the better characterized effectors of PDGFbeta signaling, considerable controversy still surrounds their precise functions. To address these questions and limitations, we applied a chemical-genetic approach to study the role of c-Src at the cellular level, in defined signaling cascades; we also uncovered novel phosphorylation targets and defined its influence on transcriptional events. The spectacular control of c-Src on actin reorganization and chemotaxis was delineated by global substrate labeling and transcriptional analysis, revealing multiple cytoskeletal proteins and chemotaxis promoting genes to be under c-Src control. Additionally, this tool revealed the contrasting roles of c-Src in controlling DNA synthesis, where it transmits conflicting inputs via the phosphatidylinositol 3 kinase and Ras pathways. Finally, this study reveals a mechanism by which Src family kinases may control PDGF-mediated responses both at transcriptional and translational levels.

CD14+CD34low cells with stem cell phenotypic and functional features are the major source of circulating endothelial progenitors

Endothelial progenitor cells (EPCs) seem to be a promising tool for cell therapy of acute myocardial infarction, but their nature is still unclear. We show here that EPCs obtainable from peripheral blood (PB) derive from the adhesion-related selection in culture of a subset of CD14+ cells, which, when assessed by the highly-sensitive antibody-conjugated magnetofluorescent liposomes (ACMFL) technique, were found to express CD34. These CD14+CD34low cells represented a variable proportion at individual level of CD14+ cells, ranging from 0.6% to 8.5% of all peripheral-blood leukocytes, and constituted the dominant population among circulating KDR+ cells. By using the ACMFL technique, virtually all CD14+ cells present in the bone marrow were found to be CD14+CD34low double-positive cells. EPCs, as well as purified circulating CD14+CD34low cells, exhibited high expression of embryonic stem cell (SC) markers Nanog and Oct-4, which were downregulated in a STAT3-independent manner when they differentiated into endothelial cells (ECs). Moreover, circulating CD14+CD34low cells, but not CD14+CD34- cells, proliferated in response to SC growth factors, and exhibited clonogenicity and multipotency, as shown by their ability to differentiate not only into ECs, but also into osteoblasts, adipocytes, or neural cells. The results of this study may reconcile apparently contradictory data of the literature, showing the generation of PB-derived EPCs from either CD34+ or CD14+ cells. We suggest that the use of this previously unrecognized population of circulating CD14+CD34low cells, which exhibit both phenotypic and functional features of SCs, may be useful in improving cell-based therapies of vascular and tissue damage.

High CXCL10 expression in rejected kidneys and predictive role of pretransplant serum CXCL10 for acute rejection and chronic allograft nephropathy

BACKGROUND

Several experimental models have shown that CXCL10 is required for initiation and development of graft failure caused by both acute and chronic rejection.

METHODS

CXCL10 expression and distribution was investigated in tissue specimens obtained from 22 patients suffering from acute rejection (AR) or chronic allograft nephropathy (CAN) by using in situ hybridization. Furthermore, pretransplantation sera of 316 cadaveric kidney-graft recipients were tested retrospectively for serum CXCL10 levels by a quantitative sandwich immunoassay.

RESULTS

Bioptic specimens obtained from patients with CAN were characterized by wide CXCL10 expression not only at level of infiltrating inflammatory cells but also of vascular, tubular, and glomerular structures. In addition, assessment of pretransplant serum CXCL10 levels in 316 graft recipients and stratification of patients in three groups according to serum CXCL10 levels (<100 pg/mL, n=163; 100-150 pg/mL, n=69; >150 pg/mL, n=84) showed highly significant differences in 5-year survival rates for the two extreme groups (95.7% vs. 79.7%, P=0.0002). Accordingly, patients who developed severe, early AR (277.14+/-65.08 p=0.004) and those who developed CAN also showed increased pretransplant serum CXCL10 levels (193.2+/-36.9, P=0.03). Multivariate analysis demonstrated that among the analyzed variables, CXCL10 (relative risk [RR] 2.801) and delayed graft function (RR 3.728) had the highest predictive power of graft loss.

CONCLUSIONS

These results suggest that pretransplant serum CXCL10 levels greater than 150 pg/mL confer an increased risk of early, severe, AR and subsequent CAN, finally resulting in renal-allograft failure. This finding might be used for the individualization of immunosuppressive therapies.

MAPKs mediate the activation of cytosolic phospholipase A2 by amyloid β(25–35) peptide in bovine retina pericytes

We have previously shown that, in bovine retina pericytes, amyloid beta(1-42) and its truncated form containing amino acids 25-35, after 24 h treatment, stimulate arachidonic acid (AA) release and phosphatidylcholine hydrolysis, by activation of both cytosolic (cPLA(2)) and Ca(2+)-independent (iPLA(2)) phospholipase A(2). A putative role for MAP kinases in this process emerged. Here we studied the role of the MAP-kinase family as well as both cPLA(2) and iPLA(2) mRNA expression by a semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) in the same sublethal model of amyloid-beta (Abeta) damage to pericytes in vitro. Abeta(25-35) peptide evoked AA release as well as stimulated phosphorylation of ERK1/2, p38 MAPKs and cPLA(2), but not c-Jun N-terminal kinase (JNK/SAPK). PD98059, an inhibitor of ERK-activating kinase MEK-1, and SB203580, an inhibitor of p38 protein kinase, abolished the stimulation of AA release and MAPK activities. In cells stimulated by Abeta(25-35) peptide, Western blotting and confocal microscopy analyses confirmed either an increase in the phosphorylated form of ERKs and p38 or their nuclear translocation. A complete inhibition of MAPK activation and AA release was also observed when pericytes were treated with GF109203X, a general PKC inhibitor, indicating the important role of both PKC and the two MAPKs in mediating the Abeta peptide response. Compared with samples untreated or treated with reverse Abeta(35-25) peptide, pretreatment with 50 microM Abeta(25-35) for 24 h significantly increased the level of constitutively expressed iPLA(2) mRNA by 25%, which seems to depend on the activation of kinases. By contrast, the level of cPLA(2) mRNA remained unchanged. Together, these data link either the stimulation of PKC-ERK-p38 cascades or PLA(2) activity by Abeta peptide to prooxidant mechanism induced by amyloid, which may initially stimulate the cell reaction as well as metabolic repair, such as during inflammation.

CXCR3-/- mice mount an efficient Th1 response but fail to control Leishmania major infection

Chemokines play a critical role in recruitment of leukocytes to the site of infection, which is essential for host defense. We analyzed the role of CXC chemokine receptor 3 (CXCR3) in the control of cutaneous leishmaniasis using CXCR3-/- C57BL/6 mice. We found that Leishmania major-infected CXCR3-/- mice mount an efficient Th1 response as evident by markedly increased serum levels of Th1-associated IgG2a and significant production of IFN-gamma and IL-12 by the draining lymph node cells, restrict systemic spread of infection, but fail to control parasite replication at the site of infection and develop chronic non-healing lesions. Furthermore, the inability of CXCR3-/- mice to control cutaneous L. major growth was associated with fewer CD4+ and CD8+ T cells and significantly lower levels of IFN-gamma in their lesions as compared to CXCR3+/+ mice. These results demonstrate that CXCR3 plays a critical role in the host defense against cutaneous leishmaniasis caused by L. major. Furthermore, they also suggest that the susceptibility of CXCR3-/- mice to L. major is due to impaired CD4+ and CD8+ T cell trafficking and decreased production of IFN-gamma at the site of infection rather than to their inability to mount a parasite-specific Th1 response.

Oxysterols inhibit phosphatidylcholine synthesis via ERK docking and phosphorylation of CTP:phosphocholine cytidylyltransferase

Surfactant deficiency contributes to acute lung injury and may result from the elaboration of bioactive lipids such as oxysterols. We observed that the oxysterol 22-hydroxycholesterol (22-HC) in combination with its obligate partner, 9-cis-retinoic acid (9-cis-RA), decreased surfactant phosphatidylcholine (PtdCho) synthesis by increasing phosphorylation of the regulatory enzyme CTP:phosphocholine cytidylyltransferase-alpha (CCTalpha). Phosphorylation of CCTalpha decreased its activity. 22-HC/9-cis-RA inhibition of PtdCho synthesis was blocked by PD98059 or dominant-negative ERK (p42 kinase). Overexpression of constitutively active MEK1, the kinase upstream of p42 kinase, increased CCTalpha phosphorylation. Expression of truncated CCTalpha mutants lacking proline-directed sites within the C-terminal phosphorylation domain partially blocked oxysterol-mediated inhibition of PtdCho synthesis. Mutagenesis of Ser315 within CCTalpha was both required and sufficient to confer significant resistance to 22-HC/9-cis-RA inhibition of PtdCho synthesis. A novel putative ERK-docking domain N-terminal to this phosphoacceptor site was mapped within the CCTalpha membrane-binding domain (residues 287-300). The results are the first demonstration of a physiologically relevant phosphorylation site and docking domain within CCTalpha that serve as targets for ERKs, resulting in inhibition of surfactant synthesis.

Alteration of podocytes in a murine model of crescentic glomerulonephritis

Recent observations suggest a central role of podocytes in crescent formation. In experimental glomerulonephritis podocytes disrupt the parietal epithelial layer and attach on its basement membrane, thus forming bridges between the tuft and Bowman's capsule, and they are a major constituent of crescents. In order to explain these findings we hypothesize that inflammation triggers motility in podocytes. In the present study we asked whether podocytes display alterations which suggest a migratory behavior in glomerulonephritis. Glomerulonephritis was induced in mice by injection of a rabbit serum against the glomerular basement membrane. The kidneys were perfusion-fixed 6 days later and examined by light and electron microscopy as well as by immunohistochemistry. In glomerulonephritis the apical cytoplasm of podocytes displayed numerous actin-containing microprotrusions. Cortactin, a protein involved in the regulation of actin polymerization, was predominantly expressed in foot processes of podocytes in control mice. It was redistributed to the cell body in glomerulonephritis. In untreated mice betal-integrin was restricted to the foot processes. In glomerulonephritis it was additionally found in the cytoplasm and in the apical cell membrane. Recycling of integrins is a crucial event in initiation of cell migration. ICAM-1 and CD44, the ligation of which induces migratory behaviors, were absent from healthy podocytes but expressed by some podocytes in glomerulonephritis. Thus, in glomerulonephritis podocytes display some characteristic features of migrating cells. This might explain their ability to break through the parietal epithelium and to become a constituent of early crescents.

Impairment in postischemic neovascularization in mice lacking the CXC chemokine receptor 3

Inflammatory cell infiltration is a feature of postischemic neovascularization. However, mechanisms leading to leukocyte attraction to the site of neovascularization are still undefined. We hypothesized that the CXC chemokine receptor 3 (CXCR3) may contribute to leukocyte accumulation and subsequently to blood vessel growth in the ischemic area. Ischemia induced by femoral artery ligature improved the number of CXCR3-expressing cells and the level of its ligand, CXCL10. Angiographic score, blood flow recovery measurement, and capillary density analysis showed a significant decrease of ischemic/nonischemic leg ratio in CXCR3-deficient mice when compared with controls (P<0.05), at day 21 after ischemia. Interestingly, this impairment was as important as that observed in mice deficient for the well known CC-chemokine monocyte chemoattractant protein-1 (MCP-1). At day 7 of ischemic injury, the number of CD3-positive T cells and Mac-3-positive monocytes/macrophages was 38% and 45% lower, respectively, in the ischemic leg of CXCR3-deficient mice compared with the control group (P<0.05), suggesting an important role for CXCR3 in leukocyte recruitment into the ischemic area. VEGF protein content, a classical proangiogenic factor, was also markedly reduced (80% reduction) in ischemic leg of CXCR3-deficient mice (P<0.01). Injection of bone marrow-derived mononuclear cells (BM-MNCs) isolated from wild-type animals restored the neovascularization reaction in CXCR3-deficient mice whereas BM-MNCs from CXCR3-deficient mice was ineffective. In conclusion, CXCR3 plays a key role in neovascularization and provides novel information on the mechanisms leading to leukocyte infiltration in the vessel growth area.

Cellular characteristics of neuroblastoma cells: regulation by the ELR--CXC chemokine CXCL10 and expression of a CXCR3-like receptor

Bone marrow stroma cells secrete the chemokine CXCL12 that may support bone marrow metastasis formation by neuroblastoma cells. The present study demonstrates that bone marrow stroma cell lines also secrete CXCL10, a chemokine that was shown in the past to have anti-malignancy functions. A receptor recognized by antibodies against CXCR3 was shown to be expressed by six neuroblastoma cell lines. Further detailed analysis was performed on the NUB6 and SK-NMC neuroblastoma cells, showing that CXCL10 induced potent Erk phosphorylation in a G(alpha)i-dependent manner. The role of a CXCR3-like receptor in Erk phosphorylation was substantiated by the ability of CXCL11, another potent CXCR3 ligand, to induce Erk phosphorylation in the NUB6 and SK-NMC cells. Further characterization of CXCL10 activities indicated that CXCL10 partly inhibited the growth of the NUB6 and SK-NMC cells. Both NUB6 and SK-NMC cells did not migrate to CXCL10, although their migratory machinery was intact, as evidenced by their migration to bone marrow constituents. Altogether, these results suggest that CXCL10 interacts with a CXCR3-like receptor in neuroblastoma cell lines, raising the possibility that following the homing of the tumor cells to the bone marrow (through a CXCL10-independent mechanism), CXCL10 may partly inhibit neuroblastoma cell growth at this site.

The chemokine CXCL10 modulates excitatory activity and intracellular calcium signaling in cultured hippocampal neurons

In this study, we provide evidence for direct modulatory effects of the chemokine, CXCL10, on the physiology of hippocampal neurons maintained in primary culture. CXCL10 elicited a rise in intracellular Ca2+ and enhanced both spontaneous and evoked electrical activity of hippocampal neurons. CXCL10-induced elevations in intracellular Ca2+ were associated with an increase in neuronal firing and an alteration in the relationship between the evoked Ca2+ signal and neuronal activity. The effects of CXCL10 were not accompanied by a shift in resting membrane potential (RMP) or input resistance. Expression of the CXCR3 chemokine receptor supports a direct effect of CXCL10 on hippocampal neurons.

Induction of mast cell interactions with blood vessel wall components by direct contact with intact T cells or T cell membranes in vitro

BACKGROUND

Mast cells exert profound pleiotropic effects on immune cell reactions at inflammatory sites, where they are most likely influenced not only by the extracellular matrix (ECM) and inflammatory mediators but also by the proximity of activated T lymphocytes. We recently reported that activated T cells induce mast cell degranulation with the release of TNF-alpha, and that this activation pathway is mediated by lymphocyte function-associated antigen-1 (LFA-1)/intercellular adhesion molecule-1 (ICAM-1) binding.

OBJECTIVE

To determine how this contact between the two cell types can modulate mast cell behaviour in an inflammatory milieu by examining the adhesion of mast cells to endothelial cells and ECM ligands in an integrin-dependent manner.

METHODS

Human mast cells (HMC-1) were co-cultured with resting or activated T cells followed by testing their adhesion to endothelial cell and ECM ligands, stromal derived factor-1alpha (SDF-1alpha)-induced migration, and western blotting.

RESULTS

Co-culturing HMC-1 with activated, but not with resting T cells resulted in marked stimulation of mast cell adhesion to vascular cell adhesion molecule-1 and ICAM-1 in a very late antigen-4- and LFA-1-dependent fashion. In addition, activated T cells or T cell membranes promoted HMC-1 adhesion to fibronectin (FN) and laminin. This effect was accompanied by the phosphorylation of extracellular regulated kinase and p38, but not of c-Jun N-terminal kinase. Importantly, the adhesive property of mast cells depended exclusively on the direct contact between the two cell types, since neither supernatants from activated T cells nor separation of the two cell populations with a porous membrane affected mast cell adhesion to FN. Furthermore, similar results were obtained when mast cells were incubated with purified membranes from activated T cells. These results suggest that, in addition to stimulating mast cell degranulation, the proximity of activated T lymphocytes to mast cells can mediate the adhesion of mast cell precursors to the endothelial ligands and ECM. Activated T cells also stimulated SDF-1alpha-induced mast cell migration.

CONCLUSION

This symbiotic relationship between the two types of immune cells may serve to direct mast cells to specific sites of inflammation where their effector functions are required.

Acute exposure to CXC chemokine ligand 10, but not its chronic astroglial production, alters synaptic plasticity in mouse hippocampal slices

Brain levels of CXC chemokine ligand 10 (CXCL10) are elevated in a number of neuropathological conditions. To determine its impact on neuronal function, we measured synaptic transmission and plasticity in hippocampal slices prepared from transgenic (TG) mice with chronic astroglial production of CXCL10. We also tested the acute effect of recombinant CXCL10 applied to slices from normal C57Bl/6J mice, CXCL10 TG mice and CXCR3 knock out (KO) mice. Chronic production of CXCL10 did not alter synaptic plasticity. By contrast, exogenous CXCL10 (10 ng/ml) significantly inhibited long-term potentiation (LTP) in slices from normal C57Bl/6J mice and CXCL10 TG. The effect was probably receptor-mediated because CXCL10-induced inhibition of LTP was not observed in CXCR3 KO mice. Our findings suggest that acute exposure to CXCL10 alters synaptic plasticity via CXCR3 in mouse hippocampus.

High pretransplant serum levels of CXCL10/IP-10 are related to increased risk of renal allograft failure

In experimental models, the chemokine CXCL10/IP-10 is required for graft failure owing to both acute and chronic rejection. In the present study, pretransplantation sera from 316 cadaver kidney graft recipients were tested for serum CXCL10 and CCL22/MDC levels by an ELISA assay. Kidney graft recipients with normally functioning grafts showed significantly lower serum CXCL10 levels than patients who experienced graft failure, whereas no differences for serum CCL22 levels were observed. After the assignment of all patients to four groups according to serum CXCL10 levels, the death-censored survival rates of grafts were 97.5%, 93.6%, 89.7%, 78.7% (p = 0.0006) at 5 years, while no influence was observed on patient survival. Accordingly, patients with the highest CXCL10 levels showed an increased frequency and severity of rejection episodes. Serum C-reactive protein (CRP) level was also assayed in the same samples. Increase of serum CRP levels represented a predictive parameter for death, but not for graft failure. Multivariate analysis demonstrated that among the analyzed variables, CXCL10 had the highest predictive power of graft loss (RR 2.787). Thus, measurement of pretransplant serum CXCL10 levels might represent a clinically useful parameter to identify subjects who are at high risk of severe rejection and graft failure.

Identification of genes differentially expressed in T cells following stimulation with the chemokines CXCL12 and CXCL10

BACKGROUND

Chemokines are involved in many biological activities ranging from leukocyte differentiation to neuronal morphogenesis. Despite numerous reports describing chemokine function, little is known about the molecular changes induced by cytokines.

METHODS

We have isolated and identified by differential display analysis 182 differentially expressed cDNAs from CXCR3-transfected Jurkat T cells following treatment with CXCL12 or CXCL10. These chemokine-modulated genes were further verified using quantitative RT-PCR and Western blot analysis.

RESULTS

One hundred and forty-six of the cDNAs were successfully cloned, sequenced, and identified by BLAST. Following removal of redundant and non-informative clones, seventeen mRNAs were found to be differentially expressed post treatment with either chemokine ligand with several representing known genes with established functions. Twenty-one genes were upregulated in these transfected Jurkat cells following both CXCL12 and CXCL10, four genes displayed a discordant response and seven genes were downregulated upon treatment with either chemokine. Identified genes include geminin (GEM), thioredoxin (TXN), DEAD/H box polypeptide 1 (DDX1), growth hormone inducible transmembrane protein (GHITM), and transcription elongation regulator 1 (TCERG1). Subsequent analysis of several of these genes using semi-quantitative PCR and western blot analysis confirmed their differential expression post ligand treatment.

CONCLUSIONS

Together, these results provide insight into chemokine-induced gene activation and identify potentially novel functions for known genes in chemokine biology.

Differential requirement of members of the MAPK family for CCL2 expression by hepatic stellate cells

Hepatic stellate cells (HSC) coordinate the liver wound-healing response through secretion of several cytokines and chemokines, including CCL2 (formerly known as monocyte chemoattractant protein-1). In this study, we evaluated the role of different proteins of the MAPK family (ERK, p38(MAPK), and JNK) in the regulation of CCL2 expression by HSC, as an index of their proinflammatory activity. Several mediators activated all three MAPK, including TNF, IL-1, and PDGF. To assess the relative role of the different MAPKs, specific pharmacological inhibitors were used; namely, SB203580 (p38(MAPK)), SP600125 (JNK), and PD98059 (MEK/ERK). The efficacy and specificity of the different inhibitors in our cellular system were verified analyzing the enzymatic activity of the different MAPKs using in vitro kinase assays and/or testing the inhibition of phosphorylation of downstream substrates. SB203580 and SP600125 dose-dependently inhibited CCL2 secretion and gene expression induced by IL-1 or TNF. In contrast, inhibition of ERK did not affect the upregulation of CCL2 induced by the two cytokines. Finally, activin A was also found to stimulate CCL2 expression and to activate ERK, JNK, p38, and their downstream targets. Unlike in cells exposed to proinflammatory cytokines, all three MAPKs were required to induce CCL2 secretion in response to activin. We conclude that members of the MAPK family differentially regulate cytokine-induced chemokine expression in human HSC.

Activation of Phosphoinositide 3-Kinases by the CCR4 Ligand Macrophage-Derived Chemokine Is a Dispensable Signal for T Lymphocyte Chemotaxis

Macrophage-derived chemokine (MDC/CC chemokine ligand 22 (CCL22)) mediates its cellular effects principally by binding to its receptor CCR4, and together they constitute a multifunctional chemokine/receptor system with homeostatic and inflammatory roles in the body. We report the CCL22-induced accumulation of phosphatidylinositol-(3,4,5)-trisphosphate (PI(3,4,5)P(3)) in the leukemic T cell line CEM. CCL22 also had the ability to chemoattract human Th2 cells and CEM cells in a pertussis toxin-sensitive manner. Although the PI(3,4,5)P(3) accumulation along with the pertussis toxin-susceptible phosphorylation of protein kinase B were sensitive to the two phosphoinositide 3-kinase inhibitors, LY294002 and wortmannin, cell migration was unaffected. However, cell migration was abrogated with the Rho-dependent kinase inhibitor, Y-27632. These data demonstrate that although there is PI(3,4,5)P(3) accumulation downstream of CCR4, phosphoinositide 3-kinase activity is a dispensable signal for CCR4-stimulated chemotaxis of Th2 cells and the CEM T cell line.