Changes in CXCL12/CXCR4-chemokine expression during onset of colorectal malignancies

Chemokines have been proposed to contribute to tumour growth and metastatic spread of several cancer entities. Here, we examined the relative levels of CXCL12/CXCR4 in resection specimens from patients with different malignant and non-malignant colorectal diseases as well as colorectal liver metastases (CRLM). CXCL12/CXCR4 mRNA and protein expression profiles were assessed by quantitative real-time PCR, Western blot analysis, enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry in resection specimens from patients with ulcerative colitis (UC; n = 15), colorectal adenoma (CRA; n = 15), colorectal adenocarcinoma (CRC; n = 47) and CRLM (n = 16). Corresponding non-affected tissues served as control. In contrast to UC tissues, CXCL12 showed a distinct down-regulation in CRA, CRC and CRLM specimens, whereas the corresponding receptor CXCR4 demonstrated a significant up-regulation in CRC and CRLM related to corresponding non-affected tissues (p < 0.05, respectively). Our results strongly suggest an association between CXCL12/CXCR4 expression and the induction of CRA, CRC and the development of CRLM. Therefore, CXCR4 may be a potential target for specific therapeutic interventions.

Functional expression of CCR1, CCR3, CCR4, and CXCR4 chemokine receptors on human platelets

Platelets are known to contain platelet factor 4 and beta-thromboglobulin, alpha-chemokines containing the CXC motif, but recent studies extended the range to the beta-family characterized by the CC motif, including RANTES and Gro-alpha. There is also evidence for expression of chemokine receptors CCR4 and CXCR4 in platelets. This study shows that platelets have functional CCR1, CCR3, CCR4, and CXCR4 chemokine receptors. Polymerase chain reaction detected chemokine receptor messenger RNA in platelet RNA. CCR1, CCR3, and especially CCR4 gave strong signals; CXCR1 and CXCR4 were weakly positive. Flow cytometry with specific antibodies showed the presence of a clear signal for CXCR4 and weak signals for CCR1 and CCR3, whereas CXCR1, CXCR2, CXCR3, and CCR5 were all negative. Immunoprecipitation and Western blotting with polyclonal antibodies to cytoplasmic peptides clearly showed the presence of CCR1 and CCR4 in platelets in amounts comparable to monocytes and CCR4 transfected cells, respectively. Chemokines specific for these receptors, including monocyte chemotactic protein 1, macrophage inflammatory peptide 1alpha, eotaxin, RANTES, TARC, macrophage-derived chemokine, and stromal cell-derived factor 1, activate platelets to give Ca(++) signals, aggregation, and release of granule contents. Platelet aggregation was dependent on release of adenosine diphosphate (ADP) and its interaction with platelet ADP receptors. Part, but not all, of the Ca(++) signal was due to ADP release feeding back to its receptors. Platelet activation also involved heparan or chondroitin sulfate associated with the platelet surface and was inhibited by cleavage of these glycosaminoglycans or by heparin or low molecular weight heparin. These platelet receptors may be involved in inflammatory or allergic responses or in platelet activation in human immunodeficiency virus infection.

HIV-1 coreceptor usage and CXCR4-specific viral load predict clinical disease progression during combination antiretroviral therapy

BACKGROUND: Although combination antiretroviral therapy (cART) dramatically reduces rates of AIDS and death, a minority of patients experience clinical disease progression during treatment. OBJECTIVE: To investigate whether detection of CXCR4(X4)-specific strains or quantification of X4-specific HIV-1 load predict clinical outcome. METHODS: From the Swiss HIV Cohort Study, 96 participants who initiated cART yet subsequently progressed to AIDS or death were compared with 84 contemporaneous, treated nonprogressors. A sensitive heteroduplex tracking assay was developed to quantify plasma X4 and CCR5 variants and resolve HIV-1 load into coreceptor-specific components. Measurements were analyzed as cofactors of progression in multivariable Cox models adjusted for concurrent CD4 cell count and total viral load, applying inverse probability weights to adjust for sampling bias. RESULTS: Patients with X4 variants at baseline displayed reduced CD4 cell responses compared with those without X4 strains (40 versus 82 cells/microl; P = 0.012). The adjusted multivariable hazard ratio (HR) for clinical progression was 4.8 [95% confidence interval (CI) 2.3-10.0] for those demonstrating X4 strains at baseline. The X4-specific HIV-1 load was a similarly independent predictor, with HR values of 3.7 (95% CI, 1.2-11.3) and 5.9 (95% CI, 2.2-15.0) for baseline loads of 2.2-4.3 and > 4.3 log10 copies/ml, respectively, compared with < 2.2 log10 copies/ml. CONCLUSIONS: HIV-1 coreceptor usage and X4-specific viral loads strongly predicted disease progression during cART, independent of and in addition to CD4 cell count or total viral load. Detection and quantification of X4 strains promise to be clinically useful biomarkers to guide patient management and study HIV-1 pathogenesis.

Chemokine receptor 4 (CXCR4) is part of the lipopolysaccharide "sensing apparatus"

Recognition of bacterial lipopolysaccharide (LPS) by the innate immune system involves at least three receptor molecules: CD14, TLR4 and MD-2. Additional receptor components such as heat shock proteins, chemokine receptor 4 (CXCR4), or CD55 have been suggested to be part of this activation cluster; possibly acting as additional LPS transfer molecules. Our group has previously identified CXCR4 as a component of the "LPS-sensing apparatus". In this study we aimed to elucidate the role that CXCR4 plays in innate immune responses to LPS. Here we demonstrate that CXCR4 transfection results in responsiveness to LPS. Fluorescence correlation spectroscopy experiments further showed that LPS directly interacts with CXCR4. Our data suggest that CXCR4 is not only involved in LPS binding but is also responsible for triggering signalling, especially mitogen-activated protein kinases in response to LPS. Finally, co-clustering of CXCR4 with other LPS receptors seems to be crucial for LPS signalling, thus suggesting that CXCR4 is a functional part of the multimeric LPS "sensing apparatus".

CXC receptor-4 mRNA silencing abrogates CXCL12-induced migration of colorectal cancer cells

Background Interactions between CXCR4 and its ligand CXCL12 have been shown to be involved in cancer progression in colorectal cancer (CRC). We performed a comparative CXCL12/CXCR4 expression analysis and assessed the effect of external CXCL12 stimulation on migration of CRC cells without and with CXCR4 inhibition. Methods Expression of CXCL12/CXCR4 was assessed by quantitative real-time PCR, ELISA and immunohistochemistry in resection specimens of 50 CRC patients as well as in the corresponding normal tissues and in three human CRC cell lines with different metastatic potential (Caco-2, SW480 and HT-29). Migration assays were performed after stimulation with CXCL12 and CXCR4 was inhibited by siRNA and neutralizing antibodies. Results In CRC tissues CXCL12 was significantly down-regulated and CXCR4 was significantly up-regulated compared to the corresponding normal tissues. In cell lines CXCR4 was predominantly expressed in SW480 and less pronounced in HT-29 cells. CXCL12 was only detectable in Caco-2 cells. CXCL12 stimulation had no impact on Caco-2 cells but significantly increased migration of CXCR4 bearing SW480 and HT-29 cells. This effect was significantly abrogated by neutralizing anti-CXCR4 antibody as well as by CXCR4 siRNAs (P < 0.05). Conclusions CXCR4 expression was up-regulated in CRC and CXCL12 stimulation increased migration in CXCR4 bearing cell lines. Migration was inhibited by both neutralizing CXCR4 antibodies and CXCR4 siRNAs. Thus, the expression and functionality of CXCR4 might be associated with the metastatic potential of CRC cells and CXCL12/CXCR4 interactions might therefore constitute a promising target for specific treatment interventions.

Identification of a highly conserved valine-glycine-phenylalanine amino acid triplet required for HIV-1 Nef function

Background The Nef protein of HIV facilitates virus replication and disease progression in infected patients. This role as pathogenesis factor depends on several genetically separable Nef functions that are mediated by interactions of highly conserved protein-protein interaction motifs with different host cell proteins. By studying the functionality of a series of nef alleles from clinical isolates, we identified a dysfunctional HIV group O Nef in which a highly conserved valine-glycine-phenylalanine (VGF) region, which links a preceding acidic cluster with the following proline-rich motif into an amphipathic surface was deleted. In this study, we aimed to study the functional importance of this VGF region. Results The dysfunctional HIV group O8 nef allele was restored to the consensus sequence, and mutants of canonical (NL4.3, NA-7, SF2) and non-canonical (B2 and C1422) HIV-1 group M nef alleles were generated in which the amino acids of the VGF region were changed into alanines (VGF→AAA) and tested for their capacity to interfere with surface receptor trafficking, signal transduction and enhancement of viral replication and infectivity. We found the VGF motif, and each individual amino acid of this motif, to be critical for downregulation of MHC-I and CXCR4. Moreover, Nef’s association with the cellular p21-activated kinase 2 (PAK2), the resulting deregulation of cofilin and inhibition of host cell actin remodeling, and targeting of Lck kinase to the trans-golgi-network (TGN) were affected as well. Of particular interest, VGF integrity was essential for Nef-mediated enhancement of HIV virion infectivity and HIV replication in peripheral blood lymphocytes. For targeting of Lck kinase to the TGN and viral infectivity, especially the phenylalanine of the triplet was essential. At the molecular level, the VGF motif was required for the physical interaction of the adjacent proline-rich motif with Hck. Conclusion Based on these findings, we propose that this highly conserved three amino acid VGF motif together with the acidic cluster and the proline-rich motif form a previously unrecognized amphipathic surface on Nef. This surface appears to be essential for the majority of Nef functions and thus represents a prime target for the pharmacological inhibition of Nef.

Anti-HIV state but not apoptosis depends on IFN signature in CD4+ T cells

To gain insights into the molecular mechanisms underlying early host responses to HIV in the CD4(+) T cell target population, we examined gene expression in CD4(+) T cells isolated 24 h after ex vivo HIV infection of lymphocyte aggregate cultures derived from human tonsils. Gene profiling showed a distinct up-regulation of genes related to immune response and response to virus, notably of IFN-stimulated genes (ISGs), irrespective of the coreceptor tropism of the virus. This mostly IFN-alpha-dependent gene signature suggested the involvement of plasmacytoid dendritic cells, a principal component of the antiviral immune response. Indeed, depletion of plasmacytoid dendritic cells before HIV inoculation abrogated transcriptional up-regulation of several ISGs and resulted in increased levels of HIV replication. Treatment with a blocking anti-IFN-alphaR Ab yielded increased HIV replication; conversely, HIV replication was decreased in pDC-depleted cultures treated with IFN-alpha. Among up-regulated ISGs was also TRAIL, indicating a potential role of the IFN signature in apoptosis. However, a blocking anti-TRAIL Ab did not abrogate apoptosis of CD4(+) T cells in CXCR4-tropic HIV-infected cultures, suggesting the involvement of pathways other than TRAIL mediated. We conclude that acute HIV infection of lymphoid tissue results in up-regulation of ISGs in CD4(+) T cells, which induces an anti-HIV state but not apoptosis.

Disseminated and sustained HIV infection in CD34+ cord blood cell-transplanted Rag2-/-gamma c-/- mice

Because of species selectivity, HIV research is largely restricted to in vitro or clinical studies, both limited in their ability to rapidly assess new strategies to fight the virus. To prospectively study some aspects of HIV in vivo, immunodeficient mice, transplanted with either human peripheral blood leukocytes or human fetal tissues, have been developed. Although these are susceptible to HIV infection, xenoreactivity, and short infection spans, resource and ethical constraints, as well as biased HIV coreceptor tropic strain infection, pose substantial problems in their use. Rag2(-/-)gamma(c)(-/-) mice, transplanted as newborns with human CD34(+) cells, were recently shown to develop human B, T, and dendritic cells, constituting lymphoid organs in situ. Here we tested these mice as a model system for HIV-1 infection. HIV RNA levels peaked to up to 2 x 10(6) copies per milliliter of plasma early after infection, and viremia was observed for up to 190 days, the longest time followed. A marked relative CD4(+) T cell depletion in peripheral blood occurred in CXCR4-tropic strain-infected mice, whereas this was less pronounced in CCR5-tropic strain-infected animals. Thymus infection was almost exclusively observed in CXCR4-tropic strain-infected mice, whereas spleen and lymph node HIV infection occurred irrespective of coreceptor selectivity, consistent with respective coreceptor expression on human CD4(+) T cells. Thus, this straightforward to generate and cost-effective in vivo model closely resembles HIV infection in man and therefore should be valuable to study virus-induced pathology and to rapidly evaluate new approaches aiming to prevent or treat HIV infection.

Platelet chemokines and their receptors: what is their relevance to platelet storage and transfusion practice?

The role of platelets as inflammatory cells is demonstrated by the fact that they can release many growth factors and inflammatory mediators, including chemokines, when they are activated. The best known platelet chemokine family members are platelet factor 4 (PF4) and beta-thromboglobulin (beta-TG), which are synthesized in megakaryocytes, stored as preformed proteins in alpha-granules and released from activated platelets. However, platelets also contain many other chemokines such as interleukin-8 (IL-8), growth-regulating oncogene-alpha(GRO-alpha), epithelial neutrophil-activating protein 78 (ENA-78), regulated on activation normal T expressed and secreted (RANTES), macrophage inflammatory protein-1alpha (MIP-1alpha), and monocyte chemotactic protein-3 (MCP-3). They also express chemokine receptors such as CCR4, CXCR4, CCR1 and CCR3. Platelet activation is a feature of many inflammatory diseases such as heparin-induced thrombocytopenia, acquired immunodeficiency syndrome, and congestive heart failure. Substantial amounts of PF4, beta-TG and RANTES are released from platelets on activation, which may occur during storage. Although very few data are available on the in vivo effects of transfused chemokines, it has been suggested that the high incidence of adverse reactions often observed after platelet transfusions may be attributed to the chemokines present in the plasma of stored platelet concentrates.

Identification of mesenchymal stromal cells in human lung parenchyma capable of differentiating into aquaporin 5-expressing cells

The lack of effective therapies for end-stage lung disease validates the need for stem cell-based therapeutic approaches as alternative treatment options. In contrast with exogenous stem cell sources, the use of resident progenitor cells is advantageous considering the fact that the lung milieu is an ideal and familiar environment, thereby promoting the engraftment and differentiation of transplanted cells. Recent studies have shown the presence of multipotent 'mesenchymal stem cells' in the adult lung. The majority of these reports are, however, limited to animal models, and to date, there has been no report of a similar cell population in adult human lung parenchyma. Here, we show the identification of a population of primary human lung parenchyma (pHLP) mesenchymal stromal cells (MSCs) derived from intraoperative normal lung parenchyma biopsies. Surface and intracellular immunophenotyping by flow cytometry revealed that cultures do not contain alveolar type I epithelial cells or Clara cells, and are devoid of the following hematopoietic markers: CD34, CD45 and CXCR4. Cells show an expression pattern of surface antigens characteristic of MSCs, including CD73, CD166, CD105, CD90 and STRO-1. As per bone marrow MSCs, our pHLP cells have the ability to differentiate along the adipogenic, osteogenic and chondrogenic mesodermal lineages when cultured in the appropriate conditions. In addition, when placed in small airway growth media, pHLP cell cultures depict the expression of aquaporin 5 and Clara cell secretory protein, which is identified with that of alveolar type I epithelial cells and Clara cells, respectively, thereby exhibiting the capacity to potentially differentiate into airway epithelial cells. Further investigation of these resident cells may elucidate a therapeutic cell population capable of lung repair and/or regeneration.

Inhibition of Notch signaling induces extensive intussusceptive neo-angiogenesis by recruitment of mononuclear cells

Notch is an intercellular signaling pathway related mainly to sprouting neo-angiogenesis. The objective of our study was to evaluate the angiogenic mechanisms involved in the vascular augmentation (sprouting/intussusception) after Notch inhibition within perfused vascular beds using the chick area vasculosa and MxCreNotch1(lox/lox) mice. In vivo monitoring combined with morphological investigations demonstrated that inhibition of Notch signaling within perfused vascular beds remarkably induced intussusceptive angiogenesis (IA) with resultant dense immature capillary plexuses. The latter were characterized by 40 % increase in vascular density, pericyte detachment, enhanced vessel permeability, as well as recruitment and extravasation of mononuclear cells into the incipient transluminal pillars (quintessence of IA). Combination of Notch inhibition with injection of bone marrow-derived mononuclear cells dramatically enhanced IA with 80 % increase in vascular density and pillar number augmentation by 420 %. Additionally, there was down-regulation of ephrinB2 mRNA levels consequent to Notch inhibition. Inhibition of ephrinB2 or EphB4 signaling induced some pericyte detachment and resulted in up-regulation of VEGFRs but with neither an angiogenic response nor recruitment of mononuclear cells. Notably, Tie-2 receptor was down-regulated, and the chemotactic factors SDF-1/CXCR4 were up-regulated only due to the Notch inhibition. Disruption of Notch signaling at the fronts of developing vessels generally results in massive sprouting. On the contrary, in the already existing vascular beds, down-regulation of Notch signaling triggered rapid augmentation of the vasculature predominantly by IA. Notch inhibition disturbed vessel stability and led to pericyte detachment followed by extravasation of mononuclear cells. The mononuclear cells contributed to formation of transluminal pillars with sustained IA resulting in a dense vascular plexus without concomitant vascular remodeling and maturation.

HGF Expressing Stem Cells in Usual Interstitial Pneumonia Originate from the Bone Marrow and Are Antifibrotic

BACKGROUND Pulmonary fibrosis may result from abnormal alveolar wound repair after injury. Hepatocyte growth factor (HGF) improves alveolar epithelial wound repair in the lung. Stem cells were shown to play a major role in lung injury, repair and fibrosis. We studied the presence, origin and antifibrotic properties of HGF-expressing stem cells in usual interstitial pneumonia. METHODS Immunohistochemistry was performed in lung tissue sections and primary alveolar epithelial cells obtained from patients with usual interstitial pneumonia (UIP, n = 7). Bone marrow derived stromal cells (BMSC) from adult male rats were transfected with HGF, instilled intratracheally into bleomycin injured rat lungs and analyzed 7 and 14 days later. RESULTS In UIP, HGF was expressed in specific cells mainly located in fibrotic areas close to the hyperplastic alveolar epithelium. HGF-positive cells showed strong co-staining for the mesenchymal stem cell markers CD44, CD29, CD105 and CD90, indicating stem cell origin. HGF-positive cells also co-stained for CXCR4 (HGF+/CXCR4+) indicating that they originate from the bone marrow. The stem cell characteristics were confirmed in HGF secreting cells isolated from UIP lung biopsies. In vivo experiments showed that HGF-expressing BMSC attenuated bleomycin induced pulmonary fibrosis in the rat, indicating a beneficial role of bone marrow derived, HGF secreting stem cells in lung fibrosis. CONCLUSIONS HGF-positive stem cells are present in human fibrotic lung tissue (UIP) and originate from the bone marrow. Since HGF-transfected BMSC reduce bleomycin induced lung fibrosis in the bleomycin lung injury and fibrosis model, we assume that HGF-expressing, bone-marrow derived stem cells in UIP have antifibrotic properties.

Naive B-cell trafficking is shaped by local chemokine availability and LFA-1-independent stromal interactions.

It is not known how naive B cells compute divergent chemoattractant signals of the T-cell area and B-cell follicles during in vivo migration. Here, we used two-photon microscopy of peripheral lymph nodes (PLNs) to analyze the prototype G-protein-coupled receptors (GPCRs) CXCR4, CXCR5, and CCR7 during B-cell migration, as well as the integrin LFA-1 for stromal guidance. CXCR4 and CCR7 did not influence parenchymal B-cell motility and distribution, despite their role during B-cell arrest in venules. In contrast, CXCR5 played a nonredundant role in B-cell motility in follicles and in the T-cell area. B-cell migration in the T-cell area followed a random guided walk model, arguing against directed migration in vivo. LFA-1, but not α4 integrins, contributed to B-cell motility in PLNs. However, stromal network guidance was LFA-1 independent, uncoupling integrin-dependent migration from stromal attachment. Finally, we observed that despite a 20-fold reduction of chemokine expression in virus-challenged PLNs, CXCR5 remained essential for B-cell screening of antigen-presenting cells. Our data provide an overview of the contribution of prototype GPCRs and integrins during naive B-cell migration and shed light on the local chemokine availability that these cells compute.

In vivo TCR Signaling in CD4(+) T Cells Imprints a Cell-Intrinsic, Transient Low-Motility Pattern Independent of Chemokine Receptor Expression Levels, or Microtubular Network, Integrin, and Protein Kinase C Activity

Intravital imaging has revealed that T cells change their migratory behavior during physiological activation inside lymphoid tissue. Yet, it remains less well investigated how the intrinsic migratory capacity of activated T cells is regulated by chemokine receptor levels or other regulatory elements. Here, we used an adjuvant-driven inflammation model to examine how motility patterns corresponded with CCR7, CXCR4, and CXCR5 expression levels on ovalbumin-specific DO11.10 CD4(+) T cells in draining lymph nodes. We found that while CCR7 and CXCR4 surface levels remained essentially unaltered during the first 48-72 h after activation of CD4(+) T cells, their in vitro chemokinetic and directed migratory capacity to the respective ligands, CCL19, CCL21, and CXCL12, was substantially reduced during this time window. Activated T cells recovered from this temporary decrease in motility on day 6 post immunization, coinciding with increased migration to the CXCR5 ligand CXCL13. The transiently impaired CD4(+) T cell motility pattern correlated with increased LFA-1 expression and augmented phosphorylation of the microtubule regulator Stathmin on day 3 post immunization, yet neither microtubule destabilization nor integrin blocking could reverse TCR-imprinted unresponsiveness. Furthermore, protein kinase C (PKC) inhibition did not restore chemotactic activity, ruling out PKC-mediated receptor desensitization as mechanism for reduced migration in activated T cells. Thus, we identify a cell-intrinsic, chemokine receptor level-uncoupled decrease in motility in CD4(+) T cells shortly after activation, coinciding with clonal expansion. The transiently reduced ability to react to chemokinetic and chemotactic stimuli may contribute to the sequestering of activated CD4(+) T cells in reactive peripheral lymph nodes, allowing for integration of costimulatory signals required for full activation.

Regulation of peripheral classical and non-classical monocytes on infliximab treatment in patients with rheumatoid arthritis and ankylosing spondylitis.

OBJECTIVE To investigate the regulatory effect of tumour necrosis factor (TNF) blockade with infliximab on the distribution of peripheral blood monocyte subpopulations in patients with rheumatoid arthritis (RA) and ankylosing spondylitis (AS). METHODS Purified CD11b+CD14+ monocytes from 5 patients with RA and 5 AS were analysed ex vivo before and after infliximab treatment by flow cytometry for CD16, CD163, CD11b, C-C chemokine receptor type 2 (CCR2) and CXC chemokine receptor 4 (CXCR4) at baseline and at days 2, 14, 84 and 168 after the first infliximab administration. Serum levels of the stromal cell-derived factor (SDF)-1 and monocyte chemotactic peptide (MCP)-1 at different time points were measured in either patient group before and on infliximab treatment. RESULTS Anti-TNF treatment with infliximab led to a significant increase of circulating CD11b+ non-classical and a concomitantly decrease of CD11b+ classical monocytes, to a decline in SDF-1 levels and reduced expression of CCR2 and CXCR4 on non-classical monocyte subpopulation. CONCLUSIONS Our study shows, that TNFα blockade by infliximab resulted in a dichotomy of the regulation of classical and non-classical monocytes that might have substantial impact on inhibition of osteoclastogenesis and of subsequent juxta-articular bone destruction and systemic bone loss in RA and AS.