The chemokine ESkine/CCL27 displays novel modes of intracrine and paracrine function

Roles of CCR10/CCL27-CCL28 axis in tumour development: mechanisms, diagnostic and therapeutic approaches, and perspectives

Cancer is now one of the major causes of death across the globe. The imbalance of cytokine and chemokine secretion has been reported to be involved in cancer development. Meanwhile, CC chemokines have received considerable interest in cancer research. CCR10, as the latest identified CC chemokine receptor (CCR), has been implicated in the recruitment and infiltration of immune cells, especially lymphocytes, into epithelia such as skin via ligation to two ligands, CCL27 and CCL28. Other than homoeostatic function, several mechanisms have been shown to dysregulate CCR10/CCL27-CCL28 expression in the tumour microenvironment. As such, these receptors and ligands mediate T-cell trafficking in the tumour microenvironment. Depending on the types of lymphocytes recruited, CCR10/CCL27-CCL28 interaction has been shown to play conflicting roles in cancer development. If they were T helper and cytotoxic T cells and natural killer cells, the role of this axis would be tumour-suppressive. In contrast, if CCR10/CCL27-CCL28 recruited regulatory T cells, cancer-associated fibroblasts or myeloid-derived suppressor cells, it would lead to tumour progression. In addition to the trafficking of lymphocytes and immune cells, CCR10 also leads to the migration of tumour cells or endothelial cells (called angiogenesis and lymphangiogenesis) to promote tumour metastasis. Furthermore, CCR10 signalling triggers tumour-promoting signalling such as PI3K/AKT and mitogen-activated protein kinase/extracellular signal-regulated kinase, resulting in tumour cell growth. Since CCR10/CCL27-CCL28 is dysregulated in the tumour tissues, it is suggested that analysis and measurement of them might predict tumour development. Finally, it is hoped using therapeutic approaches based on this axis might increase our knowledge to overcome tumour progression.

Rapid Internalization and Nuclear Translocation of CCL5 and CXCL4 in Endothelial Cells

The chemokines CCL5 and CXCL4 are deposited by platelets onto endothelial cells, inducing monocyte arrest. Here, the fate of CCL5 and CXCL4 after endothelial deposition was investigated. Human umbilical vein endothelial cells (HUVECs) and EA.hy926 cells were incubated with CCL5 or CXCL4 for up to 120 min, and chemokine uptake was analyzed by microscopy and by ELISA. Intracellular calcium signaling was visualized upon chemokine treatment, and monocyte arrest was evaluated under laminar flow. Whereas CXCL4 remained partly on the cell surface, all of the CCL5 was internalized into endothelial cells. Endocytosis of CCL5 and CXCL4 was shown as a rapid and active process that primarily depended on dynamin, clathrin, and G protein-coupled receptors (GPCRs), but not on surface proteoglycans. Intracellular calcium signals were increased after chemokine treatment. Confocal microscopy and ELISA measurements in cell organelle fractions indicated that both chemokines accumulated in the nucleus. Internalization did not affect leukocyte arrest, as pretreatment of chemokines and subsequent washing did not alter monocyte adhesion to endothelial cells. Endothelial cells rapidly and actively internalize CCL5 and CXCL4 by clathrin and dynamin-dependent endocytosis, where the chemokines appear to be directed to the nucleus. These findings expand our knowledge of how chemokines attract leukocytes to sites of inflammation.

CCL27 Signaling in the Tumor Microenvironment

Chemokines are a group of small proteins which play an important role in leukocyte migration and invasion. They are also involved in the cellular proliferation and migration of tumor cells.Chemokine CCL27 (cutaneous T cell-attracting chemokine, CTACK) is mainly expressed by keratinocytes of the normal epidermis. It is well known that this chemokine plays an important role in several inflammatory diseases of the skin, such as atopic dermatitis, contact dermatitis, and psoriasis. Moreover, several studies have shown an association between CCL27 expression and a variety of neoplasms including skin cancer.In this chapter, we address the role of chemokine CCL27 in the tumor microenvironment in the most relevant cancers of the skin and other anatomical locations. We also make a brief comment on future perspectives and the potential relation of CCL27 with different immunotherapeutic modalities.

CC Chemokines in a Tumor: A Review of Pro-Cancer and Anti-Cancer Properties of Receptors CCR5, CCR6, CCR7, CCR8, CCR9, and CCR10 Ligands

CC chemokines (or β-chemokines) are 28 chemotactic cytokines with an N-terminal CC domain that play an important role in immune system cells, such as CD4⁺ and CD8⁺ lymphocytes, dendritic cells, eosinophils, macrophages, monocytes, and NK cells, as well in neoplasia. In this review, we discuss human CC motif chemokine ligands: CCL1, CCL3, CCL4, CCL5, CCL18, CCL19, CCL20, CCL21, CCL25, CCL27, and CCL28 (CC motif chemokine receptor CCR5, CCR6, CCR7, CCR8, CCR9, and CCR10 ligands). We present their functioning in human physiology and in neoplasia, including their role in the proliferation, apoptosis resistance, drug resistance, migration, and invasion of cancer cells. We discuss the significance of chemokine receptors in organ-specific metastasis, as well as the influence of each chemokine on the recruitment of various cells to the tumor niche, such as cancer-associated fibroblasts (CAF), Kupffer cells, myeloid-derived suppressor cells (MDSC), osteoclasts, tumor-associated macrophages (TAM), tumor-infiltrating lymphocytes (TIL), and regulatory T cells (T_reg). Finally, we show how the effect of the chemokines on vascular endothelial cells and lymphatic endothelial cells leads to angiogenesis and lymphangiogenesis.

Convergent inactivation of the skin-specific C-C motif chemokine ligand 27 in mammalian evolution

The appearance of mammalian-specific skin features was a key evolutionary event contributing for the elaboration of physiological processes such as thermoregulation, adequate hydration, locomotion, and inflammation. Skin inflammatory and autoimmune processes engage a population of skin-infiltrating T cells expressing a specific C-C chemokine receptor (CCR10) which interacts with an epidermal CC chemokine, the skin-specific C-C motif chemokine ligand 27 (CCL27). CCL27 is selectively produced in the skin by keratinocytes, particularly upon inflammation, mediating the adhesion and homing of skin-infiltrating T cells. Here, we examined the evolution and coding condition of Ccl27 in 112 placental mammalian species. Our findings reveal that a number of open reading frame inactivation events such as insertions, deletions, and start and stop codon mutations independently occurred in Cetacea, Pholidota, Sirenia, Chiroptera, and Rodentia, totalizing 18 species. The diverse habitat settings and lifestyles of Ccl27-eroded lineages probably implied distinct evolutionary triggers rendering this gene unessential. For example, in Cetacea, the rapid renewal of skin layers minimizes the need for an elaborate inflammatory mechanism, mirrored by the absence of epidermal scabs. Our findings suggest that the convergent and independent loss of Ccl27 in mammalian evolution concurred with unique adaptive roads for skin physiology.

KiSS‑1‑mediated suppression of the invasive ability of human pancreatic carcinoma cells is not dependent on the level of KiSS‑1 receptor GPR54

The onset of local invasion and lymphatic metastasis in pancreatic cancer limits survival following surgical intervention and additional therapies. Reduced expression of KiSS‑1 in pancreatic cancer is associated with cancer metastasis. Previous studies have indicated that kisspeptin, the KiSS‑1 peptide, is able to bind to its receptor‑GPR54 (hOT7T175) and suppress the migration of PANC‑1 pancreatic cancer cells. Whether the metastatic suppression of KiSS‑1 is dependent on the levels of GPR54 in pancreatic cancer cell lines remains unclear. Human BxPC‑3 pancreatic carcinoma cells are highly differentiated without exhibiting metastasis, however PANC‑1 pancreatic carcinoma cells are poorly differentiated and exhibit local and lymph node metastasis. Compared with primary cultured trophoblasts, BxPc‑3 and PANC‑1 cells were observed to express low levels of KiSS‑1 mRNA and protein, measured using reverse transcription‑quantitative polymerase chain reaction and western blotting, respectively. However, greater mRNA and protein expression levels of GPR54 were observed in PANC‑1 cells compared with BxPc‑3 cells. An MTT assay was used to investigate the effect of KiSS‑1 on BxPc‑3 and PANC‑1 cell proliferation. There were no significant differences in proliferation following transfection with KiSS‑1 in BxPc‑3 and PANC‑1 cells compared with the controls (P>0.05). A Transwell assay with chambers coated with Matrigel was used to evaluate the in vitro invasive ability of BxPc‑3 and PANC‑1 cells, with the invasion index of BxPc‑3 and PANC‑1 cells significantly reduced following 48 h of KiSS‑1 overexpression (P<0.05). The mRNA and protein expression levels of KiSS‑1 were significantly increased in BxPc‑3 and PANC‑1 cells 48 h subsequent to transfection with KiSS‑1 (P<0.05), while GPR54 expression was not altered (P>0.05). KiSS‑1 is a metastasis suppressor gene of pancreatic cancer, and this suppression is not dependent on the expression levels of GPR54. Therefore, KiSS‑1 is potentially a novel target for gene therapy.

Overview of the mechanisms regulating chemokine activity and availability

Physiological leukocyte homing and extravasation of leukocytes during inflammatory processes is directed by a number of proteins including adhesion molecules, proteases, cytokines and chemokines. Tight regulation of leukocyte migration is essential to ensure appropriate migration. A number of mechanisms exist that regulate leukocyte migration including up- or down-regulation of chemokine or chemokine receptor gene expression. However, chemokine availability in vivo also depends on the interaction of chemokines with specific glycosaminoglycans such as heparan sulfate on the surface of endothelial layers. Modification of the interaction of chemokines with these glycosaminoglycans alters the presentation of chemokines to chemokine receptors on circulating leukocytes. On top, binding of chemokines to atypical chemokine receptors that do not signal through G proteins affects chemokine availability on the endothelial layers. In addition to mechanisms that modulate chemokine availability, this review summarizes mechanisms that fine-tune chemokine function. These include synergy or antagonism between chemokines and alternative splicing of chemokine genes. Moreover, chemokines may be posttranslationally modified leading to molecules with enhanced or reduced potency to bind to G protein-coupled receptors or GAGs or generating chemokines with altered receptor specificity. Cross-talk between these different mechanisms generates a complex regulatory network that allows the organism to modulate leukocyte migration in a highly specific manner.

Chemotactic and mitogenic stimuli of neuronal apoptosis in patients with medically intractable temporal lobe epilepsy

To identify the upstream signals of neuronal apoptosis in patients with medically intractable temporal lobe epilepsy (TLE), we evaluated by immunohistochemistry and confocal microscopy brain tissues of 13 TLE patients and 5 control patients regarding expression of chemokines and cell-cycle proteins. The chemokine RANTES (CCR5) and other CC-chemokines and apoptotic markers (caspase-3, -8, -9) were expressed in lateral temporal cortical and hippocampal neurons of TLE patients, but not in neurons of control cases. The chemokine RANTES is usually found in cytoplasmic and extracellular locations. However, in TLE neurons, RANTES was displayed in an unusual location, the neuronal nuclei. In addition, the cell-cycle regulatory transcription factor E2F1 was found in an abnormal location in neuronal cytoplasm. The pro-inflammatory enzyme cyclooxygenase-2 and cytokine interleukin-1β were expressed both in neurons of patients suffering from temporal lobe epilepsy and from cerebral trauma. The vessels showed fibrin leakage, perivascular macrophages and expression of IL-6 on endothelial cells. In conclusion, the cytoplasmic effects of E2F1 and nuclear effects of RANTES might have novel roles in neuronal apoptosis of TLE neurons and indicate a need to develop new medical and/or surgical neuroprotective strategies against apoptotic signaling by these molecules. Both RANTES and E2F1 signaling are upstream from caspase activation, thus the antagonists of RANTES and/or E2F1 blockade might be neuroprotective for patients with medically intractable temporal lobe epilepsy. The results have implications for the development of new medical and surgical therapies based on inhibition of chemotactic and mitogenic stimuli of neuronal apoptosis in patients with medically intractable temporal lobe epilepsy.

Expression and regulation in the brain of the chemokine CCL27 gene locus

The chemokine CCL27 has chemoattractant properties for memory T cells and has been implicated in skin allergic reactions. The present study reports the expression in the brain of two CCL27 splice variants localized in the cerebral cortex and limbic regions. CCL27-like immunoreactivity was identified mainly in neurons. Variant 1 was found elevated in the olfactory bulbs during allergic inflammation induced by intranasal challenge with allergen. This was accompanied by the presence of T cells in the olfactory bulbs. Intranasal administration of neutralizing antibodies against CCL27 reduced the presence of T cells in the olfactory bulbs suggesting a function in T cell activity in the brain.

An alternatively spliced CXCL16 isoform expressed by dendritic cells is a secreted chemoattractant for CXCR6+ cells

DC are professional APCs that initiate and regulate adaptive immune responses by interacting with naïve and memory T cells. Chemokines released by DC play an essential role in T cell recruitment and in the maintenance of antigen-specific T cell-DC conjugates. Here, we characterized the expression of the T cell-attracting chemokine CXCL16 by murine DC. We demonstrate that through alternative RNA splicing, DC not only express the previously characterized transmembrane CXCL16 isoform, which can be cleaved from the cell surface, but also a novel isoform lacking the transmembrane and cytoplasmic domains. Transfection of HEK293 cells shows that this novel isoform, termed CXCL16v, is not expressed on the cell membrane but is secreted as a protein of approximately 10 kDa. Quantitative PCR demonstrates that CXCL16v is broadly expressed in lymphoid and nonlymphoid tissues resembling the tissue distribution of DC. Indeed, CXCL16v mRNA is expressed significantly by spleen DC and BM-DC. Moreover, we show that mature DC have increased CXCL16v mRNA levels and express transmembrane and soluble CXCL16 proteins. Finally, we show that CXCL16v specifically attracts cells expressing the chemokine receptor CXCR6. Our data demonstrate that mature DC express secreted, transmembrane, and cleaved CXCL16 isoforms to recruit and communicate efficiently with CXCR6(+) lymphoid cells.

A chemokine targets the nucleus: Cxcl12-gamma isoform localizes to the nucleolus in adult mouse heart

Chemokines are extracellular mediators of complex regulatory circuits involved principally in cell-to-cell communication. Most studies to date of the essential chemokine Cxcl12 (Sdf-1) have focused on the ubiquitously expressed secreted isoforms α and β. Here we show that, unlike these isoforms and all other known chemokines, the alternatively transcribed γ isoform is an intracellular protein that localizes to the nucleolus in differentiated mouse Cardiac tissue. Our results demonstrate that nucleolar transportation is encoded by a nucleolar-localization signal in the unique carboxy-terminal region of Sdf-1γ, and is competent both in vivo and in vitro. The molecular mechanism underlying these unusual chemokine properties involves cardiac-specific transcription of an mRNA containing a unique short-leader sequence lacking the signal peptide and translation from a non-canonical CUG codon. Our results provide an example of genome economy even for essential and highly conserved genes such as Cxcl12, and suggest that chemokines can exert tissue specific functions unrelated to cell-to-cell communication.

Effects of facial nerve axotomy on Th2- and Th1-associated chemokine expression in the facial motor nucleus of wild-type and presymptomatic mSOD1 mice

We have previously demonstrated a neuroprotective mechanism of facial motoneuron (FMN) survival after facial nerve axotomy that is dependent on CD4(+) Th2 cell interaction with peripheral antigen-presenting cells, as well as CNS resident microglia. To investigate this mechanism, we chose to study the Th2-associated chemokine, CCL11, and Th1-associated chemokine, CXCL11, in wild-type and presymptomatic mSOD1 mice after facial nerve axotomy. In this report, the results indicate that CCL11 is constitutively expressed in the uninjured facial motor nucleus, but CXCL11 is not expressed at all. Facial nerve axotomy induced a shift in CCL11 expression from FMN to astrocytes, whereas CXCL11 was induced in FMN. Differences in the number of CCL11- and CXCL11-expressing cells were observed between WT and mSOD1 mice after facial nerve axotomy.

Cytoplasmic CXCR4 expression in breast cancer: induction by nitric oxide and correlation with lymph node metastasis and poor prognosis

Background

Lymph nodes constitute the first site of metastasis for most malignancies, and the extent of lymph node involvement is a major criterion for evaluating patient prognosis. The CXC chemokine receptor 4 (CXCR4) has been shown to play an important role in lymph node metastasis. Nitric oxide (NO) may also contribute to induction of metastatic ability in human cancers.

Methods

CXCR4 expression was analyzed in primary human breast carcinoma with long-term follow-up. The relationship between nitrotyrosine levels (a biomarker for peroxynitrate formation from NO in vivo) and lymph node status, CXCR4 immunoreactivity, and other established clinico-pathological parameters, as well as prognosis, was analyzed. Nitrite/nitrate levels and CXCR4 expressions were assessed in MDA-MB-231 and SK-BR-3 breast cancer cell lines after induction and/or inhibition of NO synthesis.

Results

CXCR4 staining was predominantly cytoplasmic; this was observed in 50%(56/113) of the tumors. Cytoplasmic CXCR4 expression was significantly correlated with nitrotyrosine levels and lymph node metastasis. Kaplan-Meier survival curves showed that cytoplasmic CXCR4 expression was associated with reduced disease-free and overall survival. In multivariate analysis, cytoplasmic CXCR4 expression emerged as a significant independent predictor for overall and disease-free survival. Cytoplasmic expression of functional CXCR4 in MDA-MB-231 and SK-BR-3 cells was increased by treatment with the NO donor DETA NONOate. This increase was abolished by L-NAME, an inhibitor of NOS.

Conclusion

Our data showed a role for NO in stimulating cytoplasmic CXCR4 expression in vitro. Formation of the biomarker nitrotyrosine was also correlated with CXCR4 expression and lymph node metastasis in vivo. In addition, cytoplasmic CXCR4 expression may serve as a significant prognostic factor for long-term survival in breast cancer.

Nuclear expression of CXCR4 in tumor cells of non-small cell lung cancer is correlated with lymph node metastasis

The stromal-derived factor 1alpha (CXCL12)/chemokine receptor CXCR4 system plays an important role in the metastatic process of a variety of cancers, with CXCR4 frequently expressed by tumor cells homing to CXCL12-rich compartments. The current study evaluated a possible association of CXCR4 expression with lymph node metastasis in primary non-small cell lung cancer. CXCR4 expression levels were evaluated using immunohistology in 46 non-small cell lung cancer specimens of patients without or with lymph node involvement (N0 = 24, N1/N2/N3 = 22). Evaluation of immunostaining was performed semiquantitatively by visual assessment. Statistical analyses with multiple testing adjustments for confirmatory comparisons were performed to assess relevant parameters associated with lymph node metastases. In all samples of non-small cell lung cancer, tumor cells stained positively for cytoplasmic CXCR4. The intensity of the CXCR4 staining varied considerably between specimens: 2 (4%) tumors demonstrated weak cytoplasmic CXCR4, 22 (48%) intermediate, and 22 (48%) strong staining. Membranous staining was absent; however, nuclear staining of CXCR4 was observed in 5 non-small cell lung cancer samples. Statistical analyses of the association between presence of lymph node metastases and CXCR4 expression levels revealed that cytoplasmic CXCR4 expression was not associated with the presence of lymph node metastases. However, nuclear CXCR4 was significantly correlated with increasing lymph node stage (P = .008), linear-to-linear association. The association between aberrant expression of CXCR4 in the nucleus of non-small cell lung cancer and metastasis to lymph nodes points toward a potential tumor metastasis promoting function of nuclear CXCR4.

The chemokine network. II. On how polymorphisms and alternative splicing increase the number of molecular species and configure intricate patterns of disease susceptibility

In this second review on chemokines, we focus on the polymorphisms and alternative splicings and on their consequences in disease. Because chemokines are key mediators in the pathogenesis of inflammatory, autoimmune, vascular and neoplastic disorders, a large number of studies attempting to relate particular polymorphisms of chemokines to given diseases have already been conducted, sometimes with contradictory results. Reviewing the published data, it becomes evident that some chemokine genes that are polymorphic have alleles that are found repeatedly, associated with disease of different aetiologies but sharing some aspects of pathogenesis. Among CXC chemokines, single nucleotide polymorphisms (SNPs) in the CXCL8 and CXCL12 genes stand out, as they have alleles associated with many diseases such as asthma and human immunodeficiency virus (HIV), respectively. Of CC chemokines, the stronger associations occur among alleles from SNPs in CCL2 and CCL5 genes and a number of inflammatory conditions. To understand how chemokines contribute to disease it is also necessary to take into account all the isoforms resulting from differential splicing. The first part of this review deals with polymorphisms and the second with the diversity of molecular species derived from each chemokine gene due to alternative splicing phenomena. The number of molecular species and the level of expression of each of them for every chemokine and for each functionally related group of chemokines reaches a complexity that requires new modelling algorithms akin to those proposed in systems biology approaches.

TNF family molecule LIGHT regulates chemokine CCL27 expression on mouse embryonic stem cell-derived dendritic cells through NF-kappaB activation

Cytokine LIGHT is a type II transmembrane protein belonging to the TNF family that was originally identified as a weak inducer of apoptosis. It plays a role in inducing maturation of dendritic cells, such as upregulating CD80, CD86 expression on dendritic cells. However, whether LIGHT induces CC chemokine expression in DC and promotes their migration remains unknown. In this study, we found that esDC express CCR7 and CCR10 (the receptor of CCL27) upon the LIGHT stimulation. LIGHT also upregulates CCL27, but not CCL19 and CCL21 expression in esDC. The esDC migration potential has been increased in LIGHT activated DCs compared with control cells. LIGHT activated DCs autocrine CCL27 which regulate their migration as Blockage of CCL27 on esDC using neutralizing antibody reduces migration potential. In signaling study, we identified that LIGHT activated NF-kappaB in esDC and inhibition of NF-kappaB activation by specific inhibitor can partly attenuate the effect of LIGHT in regulation of CCL27 expression. Moreover, Shp-2 is required in LIGHT activated NF-kappaB because Knockdown of Shp-2 affects the NF-kappaB activation induced by LIGHT and consequently influences LIGHT mediated CCL27 expression. TRAF6 is critical in DC maturation in recent reports; however, knockdown of TRAF6 expression using siRNA did not alter CCL27 expression in LIGHT matured DCs. Our study demonstrates that LIGHT stimulation enhances CCL27 expression through activation of NF-kappaB in DCs.

Potential role of CCL27 and CCR10 expression in melanoma progression and immune escape

Aim of this study was to investigate using immunohistochemistry techniques the interrelation between T immunoreactive cells and the expression of CCR10 and its ligand CCL27 in 59 cutaneous melanocytic lesions. In malignant melanomas, T lymphocyte density was significantly decreased from thin melanomas to intermediate and thick ones (P<0.0005). CCR10 expression was found both in benign and malignant lesions and it was directly correlated with the Breslow depth (P=0.0298) and inversely with T lymphocyte density (P=0.0231). Moreover, cases with positive sentinel lymph node tended to have a higher CCR10 expression compared to cases with negative sentinel lymph node (P=0.0281). When CCR10 and CCL27 expression were evaluated together, CCR10-/CCL27-melanomas tended to have a higher mean density of CD3+ and CD8+ lymphocytes. Our results suggest that in human melanomas CCR10 and CCL27 may act to increase the ability of neoplastic cells to grow, invade tissue, disseminate to lymph nodes and to escape the host immune response.

IL-1beta and TNF-alpha induce increased expression of CCL28 by airway epithelial cells via an NFkappaB-dependent pathway

CCL28 is a mucosal chemokine that attracts eosinophils and T cells via the receptors CCR3 and CCR10. Consequently, it is a candidate mediator of the pathology associated with asthma. This study examined constitutive and induced expression of CCL28 by A549 human airway epithelial-like cells. Real-time RT-PCR and ELISA of cultured cells and supernatants revealed constitutive levels of CCL28 expression to be low, whereas IL-1beta and TNF-alpha, induced significantly increased expression. Observations from induced sputum and human airway biopsies supported this. Signal transduction studies revealed that IL-1beta and TNF-alpha stimulation induced NFkappaB phosphorylation in A549 cells, but antagonist inhibition of NFkappaB p50-p65 phosphorylation correlated with marked reduction of IL-1beta or TNF-alpha induced CCL28 expression. Together these studies imply a role for CCL28 in the orchestration of airway inflammation, and suggest that CCL28 is one link between microbial insult and the exacerbation of pathologies such as asthma, through an NFkappaB-dependent mechanism.

The anatomy of mucosal immune responses

It remains unclear how and where unresponsiveness to fed antigens is induced. This "oral tolerance" is probably necessary to prevent the array of immune effector mechanisms required to counteract pathogens of the mucosae from being misdirected against food antigens or commensal flora. It will obviously be important to dissect where, when, and how such immunological homeostasis is maintained in the gut, but it will also be necessary to determine whether similar inductive and effector mechanisms are required for the therapeutic applications of oral tolerance systemically. This may be influenced by anatomical and microenvironmental effects on the phenotype and/or activation state of the antigen-presenting cell (APC), which presents orally delivered antigen. Fed antigen passes from the intestinal lumen either via the villus epithelium and M cells in the Peyer's patches (PP) or the mucosal lamina propria to the organized lymphoid tissues of the PP and mesenteric lymph nodes (MLN). In addition, there is evidence that mucosally administered antigen also gains access directly to peripheral lymphoid organs. Each of these sites contains distinctive populations of APCs and has unique local microenvironments that may influence the immune response in different ways. We propose that feeding antigen in high doses may induce clonal anergy, deletion, or altered differentiation because it gains direct access to resting APCs in the T cell areas of both the gut-associated lymphoid tissues (GALT) and peripheral lymphoid organs, with presentation occurring in the absence of productive costimulation. By contrast, low doses of tolerizing antigen may be taken up and presented preferentially by APCs in the GALT, where the local environment may favor the induction of regulatory T cells. This is consistent with our own and others findings, using adoptive transfer of TcR tg T cells. These studies have shown that antigen-specific CD4(+) T cells are activated simultaneously in all peripheral and gut-associated lymphoid organs after feeding high doses of proteins, but that this may be more restricted to local tissues when lower doses are used. Another level of anatomical control is imposed within lymphoid organs, where migration of T cells through distinct anatomical compartments can affect their differentiation. We find that, in contrast to orally primed T cells, orally tolerized T cells are unable to migrate into B cell follicles during their initial exposure to antigen. This affects their differentiation as upon subsequent challenge with antigen in adjuvant, tolerized T cells can be found in follicles but are unable to provide the B cell help that primed T cells can deliver. We hypothesize that the initial defective migration of tolerized T cells prevents them from receiving signals from antigen-specific B cells in follicles and results in abortive differentiation. Thus, both gross and fine anatomical location of fed antigen presentation may be important in mucosal immunoregulation.

The Tie-2 ligand angiopoietin-2 destabilizes quiescent endothelium through an internal autocrine loop mechanism

The angiopoietins Ang-1 and Ang-2 have been identified as ligands of the endothelial receptor tyrosine kinase Tie-2, which controls vascular assembly and endothelial quiescence. The largely complementary phenotypes of Ang-1-deficient mice and Ang-2-overexpressing mice have led to an antagonistic model in which Ang-1 acts as Tie-2-activating agonist and Ang-2 acts as a Tie-2-inhibiting antagonist. To date, no mechanistic equivalent of the antagonistic Ang-1/Ang-2 model has been established and the mechanisms of Ang-2 function in particular remain mysterious. We have studied the effector functions of Ang-1 and Ang-2 on quiescent endothelial cells using a three-dimensional co-culture model of endothelial cells and smooth-muscle cells. Endothelial-cell monolayer integrity in this model is dependent on Tie-2 signaling, as evidenced by detaching endothelial cells following exposure to the small molecular weight Tie-2 inhibitor A-422885.66, which cannot be overcome by exogenous Ang-1. Accordingly, exogenous Ang-2 rapidly destabilizes the endothelial layer, which can be observed within 30-60 minutes and leads to prominent endothelial-cell detachment within 4 hours. Exogenous Ang-2-mediated endothelial-cell detachment can be rescued by Ang-1, soluble Tie-2 and vascular endothelial growth factor. Similar findings were obtained in an umbilical-vein explant model. Ang-2 is mainly produced by endothelial cells and therefore acts primarily in an autocrine manner. Thus, stimulated release of endogenous Ang-2 or overexpression of Ang-2 in endothelial cells perturbs co-culture spheroid integrity, which can be rescued by exogenous Ang-1 and vascular endothelial growth factor. However, autocrine Ang-2-mediated endothelial-cell detachment cannot be blocked by soluble Tie-2. Taken together, the data demonstrate for the first time the antagonistic Ang-1/Ang-2 concept in a defined cellular model and identify Ang-2 as a rapidly acting autocrine regulator of the endothelium that acts through an internal autocrine loop mechanism.

Post-translational control of chemokines: a role for decoy receptors?

It is well-established that chemokines play a critical role in the orchestration of inflammation and immunity. Interactions between chemokines and their receptors are essential for the homing of specific subsets of leukocytes to their functional microenvironments. They also influence other diverse biological processes such as development, leukocyte activation, Th1/Th2 polarisation, tumour metastasis, angiogenesis, and HIV pathogenesis. However, despite their importance, only now are we beginning to understand the complex regulation brought to bear on these molecules. In this review, we discuss a number of these key chemokine regulators that exert their influence once these proteins have been synthesised. We examine (i) chemokine storage, release, and presentation, (ii) protease regulation, (iii) viral manipulation of host chemokines, and (iv) natural mammalian receptor antagonists. Principally, the growing evidence for a role for decoy receptors in the chemokine system is discussed. In particular, the potential decoy function of the 'silent' pro-inflammatory chemokine receptor D6 is described alongside two other candidate decoy receptor molecules, DARC, and CCX-CKR. Dissecting the biological and pathological function of these chemokine controllers will lead to a deeper understanding of chemokine regulation, and may reveal novel strategies to therapeutically modify the chemokine system.

Chemokines in innate and adaptive host defense: basic chemokinese grammar for immune cells

Chemokines compose a sophisticated communication system used by all our cell types, including immune cells. Chemokine messages are decoded by specific receptors that initiate signal transduction events leading to a multitude of cellular responses, leukocyte chemotaxis and adhesion in particular. Critical determinants of the in vivo activities of chemokines in the immune system include their presentation by endothelial cells and extracellular matrix molecules, as well as their cellular uptake via "silent" chemokine receptors (interceptors) leading either to their transcytosis or to degradation. These regulatory mechanisms of chemokine histotopography, as well as the promiscuous and overlapping receptor specificities of inflammation-induced chemokines, shape innate responses to infections and tissue damage. Conversely, the specific patterns of homeostatic chemokines, where each chemokine is perceived by a single receptor, are charting lymphocyte navigation routes for immune surveillance. This review presents our current understanding of the mechanisms that regulate the cellular perception and pathophysiologic meaning of chemokines.

Efficient proliferation and adipose differentiation of human adipose tissue-derived vascular stromal cells transfected with basic fibroblast growth factor gene

Human vascular stromal (VS) cells obtained from mature adipose tissue were transfected with an adenovirus vector carrying the basic fibroblast growth factor (bFGF) gene. bFGF protein was observed in VS cell nuclei 24 h after transfection and in the cytoplasm and extracellular space 72 h after transfection. Naive VS cells were almost static in vitro and proliferated in a dose-dependent manner on stimulation with recombinant bFGF (rbFGF). However, bFGF-transfected VS cells proliferated spontaneously to the same extent as naive VS cells when stimulated with rbFGF at 100 ng/ml. The former cells started to proliferate on day 3 after transfection and the proliferation pattern was similar to that of the latter cells, although only a slight amount of bFGF protein was detected in the culture medium when the bFGF-transfected cells started to proliferate. The proliferation of bFGF-transfected VS cells was completely inhibited by bFGF neutralizing antibody, which also completely inhibited the proliferation of naive VS cells stimulated with rbFGF. Under conditions favoring differentiation to adipocytes, bFGF-transfected VS cells stopped proliferating and started to accumulate lipid in the cytoplasm. bFGF-transfected VS cells, which spontaneously and efficiently proliferate while preserving their ability to differentiate into adipocytes, may be an adequate cell source for human adipose tissue regeneration.

Alternative splicing generates a novel non-secretable resistin isoform in Wistar rats1

Resistin is a secreted adipose tissue hormone that belongs to the resistin-like molecule family. We report here a new alternatively spliced isoform of the rat resistin gene, named S-resistin (short resistin), detected in adipose tissue by reverse transcription-polymerase chain reaction (RT-PCR). A comparison of this cDNA variant and genomic sequences indicates the lack of the second exon containing the secretory consensus signal. Both cDNAs, resistin and S-resistin, were carboxy-tagged with FLAG epitope and transiently expressed in cultured cell lines. While the resistin-FLAG construct gives the expected pattern for a secretion protein, the S-resistin-FLAG construct yielded a predominant nuclear staining. These results indicate that this splicing event regulates the fate and probably the function of the mature protein.

Immune evasion by murine melanoma mediated through CC chemokine receptor-10

Human melanoma cells frequently express CC chemokine receptor (CCR)10, a receptor whose ligand (CCL27) is constitutively produced by keratinocytes. Compared with B16 murine melanoma, cells rendered more immunogenic via overexpression of luciferase, B16 cells that overexpressed both luciferase and CCR10 resisted host immune responses and readily formed tumors. In vitro, exposure of tumor cells to CCL27 led to rapid activation of Akt, resistance to cell death induced by melanoma antigen-specific cytotoxic T cells, and phosphatidylinositol-3-kinase (PI3K)–dependent protection from apoptosis induced by Fas cross-linking. In vivo, cutaneous injection of neutralizing antibodies to endogenous CCL27 blocked growth of CCR10-expressing melanoma cells. We propose that CCR10 engagement by locally produced CCL27 allows melanoma cells to escape host immune antitumor killing mechanisms (possibly through activation of PI3K/Akt), thereby providing a means for tumor progression.

The intracrine hypothesis and intracellular peptide hormone action

There is evidence that many peptide growth factors and hormones act in the intracellular space after either internalization or retention in their cells of synthesis. These factors, commonly called intracrines, are structurally diverse while sharing some common functional features. Reports of intracellular peptide hormone binding and action are reviewed here. Also, this laboratory has made proposals regarding the origin and actions of intracrines and these areas are further explored. Intracrine interactions and the relationship of intracrines to transcription factors are discussed. The intracellular/intracrine renin-angiotensin system (iRAS) is reviewed to illustrate the intracrine analogue of a well-established physiological system. The role of intracrine action in metazoan development is also considered.

CCL27/PESKY: a novel paradigm for chemokine function

Chemokines play a central role in regulating leukocyte migration. The recently discovered CC chemokine ligand 27 (CCL27), through interaction with its cognate receptor, CC chemokine receptor 10 (CCR10), appears to be involved in attracting a subset of memory T cells to the skin during some cutaneous inflammatory responses. Strangely, CCL27 can also be produced as a non-secreted form, as a result of alternative splicing. This protein, termed PESKY, is targeted to the nucleus where it is able to modulate transcription and alter cell morphology. Specifically, PESKY induces a rearrangement of the actin cytoskeleton, manifest by the disruption of stress fibres. This consequently enhances cell motility. Surprisingly, secreted CCL27 can also reach the nucleus after CCR10-mediated internalisation, where it may also be capable of directly modulating transcription to alter cell behaviour. This review will discuss these unprecedented findings.