The role of chemokines and chemokine receptors in mucosal inflammation

Chemokines represent a large family of small cytokines, the main function of which is the attraction of leukocytes to different tissues. Several chemokines and their receptors have been shown to play a critical role in lymphoid development, mucosal immunity, and inflammation. In this article we review recent advances in chemokine physiology and their potential role in the pathogenesis of mucosal inflammation. We also discuss the potential for the use of chemokine or chemokine receptor antagonists as novel therapies for inflammatory bowel disease.     

RNA、lnc-EGFR对肝细胞癌免疫逃避调节的相关性

目的探讨RNA、表皮生长因子受体长链非编码RNA(lnc-EGFR)对肝细胞癌(HCC)免疫逃避调节的相关性。方法通过医院病理档案室随机选择保定市第一中心病医院2017年1月至2019年1月收集的HCC标本30份和癌旁正常组织30份,采用RT-PCR法检测各组织中RNA、lnc-EGFR表达水平;蛋白质印迹法检测HCC组织中化学因子和细胞免疫因子表达情况,并分析RNA、lnc-EGFR与其相关性;将HCC细胞株随机分为两组,分别为RNA、lnc-EGFR抑制组(n=15)与空白对照组(n=15),MTT法检测细胞增殖情况,流式细胞仪检测细胞凋亡情况与细胞周期分布情况。结果癌旁正常组织中RNA、lnc-EGFR表达水平分别为(0.46±0.12)和(0.62±0.15)低于HCC组织(0.22±0.06)和(0.14±0.05)(P<0.05)。HCC组织中CXCL12-CXCR4表达水平低于癌旁正常组织(P<0.05);HCC组织中CCL20-CCR6、CX3CLI-CX3CR1高于癌旁正常组织(P<0.05);HCC组织中细胞免疫因子IL-6、IL-10、TGF-β、TNF-α表达水平高于癌旁正常组织(P<0.05);RNA、lnc-EGFR表达水平与CXCL12-CXCR4呈显著负相关(P<0.05),与CCL20-CCR6、CX3CLI-CX3CR1、IL-6、IL-10、TGF-β、TNF-α呈显著正相关关系(P<0.05);HCC、癌旁正常组织中细胞相对吸光度、细胞凋亡率、细胞周期占比均具有统计学差异(P<0.05)。结论RNA、lnc-EGFR在HCC组织中呈高表达水平,可通过上调组织中化学因子和细胞免疫因子水平来提高癌细胞免疫逃避调节水平,与HCC免疫逃避调节具有显著相关性。     

Structural diversity of heparan sulfate binding domains in chemokines

Heparan sulfate (HS) molecules are ubiquitous in animal tissues where they function as ligands that are dramatically involved in the regulation of the proteins they bind. Of these, chemokines are a family of small proteins with many biological functions. Their well-conserved monomeric structure can associate in various oligomeric forms especially in the presence of HS. Application of protein surface analysis and energy calculations to all known chemokine structures leads to the proposal that four different binding modes are created by the folding and oligomerization of these proteins. So, based on the present state of our knowledge, four different clusters of amino acids should be involved in the recognition process. Our results help to rationalize how unique sequences of HS specifically bind any given chemokine. The conclusions open the route for a rational design of compounds of therapeutical interest that could influence chemokine activity.     

Migration of T cells in vivo: molecular mechanisms and clinical implications

T cells play an important role in the pathogenesis of chronic and autoimmune inflammatory diseases. They are found in high numbers in involved tissues, such as the lamina propria of the gut in patients with Crohn disease. Modifying T-cell number and function may therefore be of therapeutic value. In principle, two mechanisms may be responsible for the development of such T-cell infiltrates: 1) an increased rate of T-cell immigration into involved tissues or 2) an increased proliferation rate, decreased T-cell death (apoptosis) rate, and prolonged retention of T cells already in the tissue. Based on the theory that T cells selectively target affected tissues through organ-specific adhesion-molecule pathways, current anti-adhesion-molecule therapy aims to interfere selectively with T-cell entry to stop tissue damage. However, the traffic of labeled T cells in unmanipulated animals shows that the entry of T-cell subsets into tissues is not organ-specific, even under conditions of differing adhesion molecule and chemokine receptor expression. In contrast, within various tissues, both movement and survival of T-cell subsets differ considerably. These observations suggest that the differential expression of adhesion molecules and chemokine receptors on T cells serves at least two functions in vivo. First, during migration of T cells out of the bloodstream, the different adhesion-molecule pathways provide redundancy, which guarantees that T-cell subsets are able to enter the different tissues in sufficient numbers (security). Second, adhesion molecules and chemokine receptors mediate T-cell interactions within the tissue that are characteristic for each subset and each microenvironment and determine the nature of the ensuing immune response (selectivity). Shifting the focus of anti-adhesion-molecule therapy toward the T cells in diseased tissue may lead to new treatment options.     

Chemokines in islet allograft rejection

Chemokines have emerged as important regulators in the development, differentiation, and anatomic distribution of leukocytes. Studies of renal and cardiac allograft biopsies have revealed that the expression of many chemokine receptors and their ligands was associated with acute allograft rejection. However, the importance of these chemokine receptor systems varies in the host response to a particular allograft. In this regard, CXCR3 appears to play a more important role in cardiac allograft rejection than CCR2 and CCR5. We have found that CCR2, CCR5, and CXCR3 and their ligands, as well as Th1 cytokines are induced to high levels in rejecting islet allografts. Interestingly, targeting CCR5 resulted in a significant prolongation of islet allograft survival. This prolongation was associated with a Th2 response. Our data indicate that in the process of acute rejection, the temporal expression and the ultimate function of a given chemokine vary among different organs or tissues. Hence, each organ or tissue may require a unique set of chemokines to generate acute rejection. Targeting the appropriate chemokine receptors may provide a clinically useful strategy to prevent islet allograft rejection.     

Distribution of the human immunodeficiency virus coreceptors CXCR4 and CCR5 in fetal lymphoid organs: implications for pathogenesis in utero

HIV entry into a cell requires the coordinate cell surface expression of CD4 and one of several chemokine coreceptors. Here we have examined the expression of the two most widely utilized HIV coreceptors, CXCR4 and CCR5, on various lymphoid tissues derived from the fetus. CXCR4 and CCR5 are differentially expressed on lymphocytes in different lymphoid organs, which may reflect the maturational and functional status of cells within the organ. The different levels of coreceptor expression on CD4+ cells in the various organs may directly affect the targeting of CXCR4- and CCR5-tropic strains of HIV toward different fetal lymphoid tissues during in utero infection.     

CXCL13 (BCA-1) is produced by follicular lymphoma cells: role in the accumulation of malignant B cells

Follicular lymphomas (FLs) localize in lymphoid tissues and recapitulate the structure of normal secondary follicles. The chemokine/chemokine receptor pair CXCL13/CXCR5 is required for the architectural organization of B cells within lymphoid follicles. In this study, we showed that CXCL13 was secreted by FL cells. FL cells expressed CXCR5 and migrated in response to CXCL13. Furthermore, we observed a synergistic effect between CXCL13 and CXCL12 (SDF-1), a chemokine produced by stromal cells in lymphoid tissues. The production of CXCL13 by FL cells and CXCL12 by stromal cells probably directs and participates in the accumulation of FL cells within specific anatomic sites.     

Autoantigen signalling through chemokine receptors

PURPOSE OF REVIEW: Recent studies have shown that disease-associated self-antigens activate chemokine receptors. This review focuses on the mechanics of autoantigen interaction with select chemokine receptors, how these migratory signals are amplified and discusses the possibility that chemokine receptors can be valuable therapeutic targets in the prevention and treatment of autoimmune disease. RECENT FINDINGS: We have recently shown that most autoantigens are chemotactic for immature dendritic cells, suggesting that autoantigens have the potential to bridge the innate and adaptive immune systems. Autoantigens also induce other leukocytes expressing their responsive chemokine receptor to migrate. These newly recruited leukocytes, in response to proinflammatory mediators, simulate the surrounding tissues to release chemokines. Several groups have reported increases in both select chemokines and chemokine receptors in inflamed tissues. Taken together, these studies suggest that autoantigens initiate leukocyte migration into damaged and inflamed tissue that leads to the subsequent amplification of the inflammatory response. SUMMARY: Most autoantigens induce chemokine receptor mediated cell migration, therefore targeting chemokine receptors for either prevention or therapy has great potential to limit autoimmune diseases.     

Recruitment of CCR6-expressing Th17 cells by CCL 20 secreted from IL-1 beta-, TNF-alpha-, and IL-17A-stimulated endometriotic stromal cells

In a novel paradigm of T cell differentiation, type 17 T helper (Th17) cells may play a significant role in endometriosis, a chronic inflammatory disease. However, the mechanism regulating the accumulation of Th17 cells in endometriotic tissues remains unknown. We hypothesized that Th17 cells migrate to endometriotic tissues through an interaction of the chemokine CC chemokine ligand (CCL)20 and its receptor CCR6. Using endometriotic tissues from women with endometriosis, we demonstrated, by flow cytometry, that Th17 cells in endometriotic tissues express CC chemokine receptor (CCR)6. Immunohistochemistry also revealed that CCL20 was expressed in the epithelial cells and stromal cells beneath the epithelium of endometriotic tissues. CCR6+ cells were small and round and scattered in the stroma in which abundant CCL20+ cells were detected. CCL20 caused selective migration of Th17 cells in the peripheral blood in a migration assay. IL-1β, TNF-α, and IL-17A increased the secretion of CCL20 in cultured endometriotic stromal cells. Inhibitors of p38- and p42/44-MAPKs, and stress-activated protein kinase/c-Jun kinase suppressed the secretion of CCL20 increased by IL-1β, TNF-α, and IL-17A. This suggests that the CCL20/CCR6 system is involved in the migration of Th17 cells to endometriotic tissues and that proinflammatory cytokines contribute to the development of endometriosis via up-regulation of CCL20 secretion from endometriotic stromal cells.     

Inhibition of HIV-1 replication in human lymphoid tissues ex vivo by measles virus

Human immunodeficiency virus (HIV) type 1 replication and disease progression are enhanced by various pathogens in coinfected individuals. However, acute infection with measles virus (MV) has been found to suppress HIV-1 replication in coinfected children. We investigated the mechanisms of this phenomenon using human lymphoid tissues coinfected ex vivo with HIV-1 and MV. MV inhibited both CXCR4-tropic (X4) and CCR5-tropic (R5) HIV-1, but the inhibitory effect was particularly profound for R5 virus, which transmits infection and dominates the early stages of HIV-1 disease. MV inhibits the replication of R5 HIV-1 in coinfected tissues by up-regulation of the CC chemokine RANTES, a well-known inhibitor of R5 HIV-1 infection, and this up-regulation is augmented in tissues coinfected with R5 HIV-1. Deciphering the molecular mechanisms by which MV and other pathogens alter local cytokine/chemokine networks and cause tissue microenvironments to become detrimental to HIV-1 may significantly contribute to the development of effective anti-HIV therapies.     

Disparate lymphoid chemokine expression in mice and men: no evidence of CCL21 synthesis by human high endothelial venules

T-cell homing to secondary lymphoid tissues generally depends on chemokine-induced firm adhesion in high endothelial venules (HEVs) and is primarily mediated through the CC chemokine receptor 7 (CCR7) on lymphocytes. The CCR7 ligand designated CCL21 is considered the most important trigger because it appears constitutively expressed by murine HEVs. Surprisingly, when we analyzed human tissues, no CCL21 mRNA could be detected in HEVs. In fact, CCL21 mRNA was only expressed in extravascular T-zone cells and lymphatics, whereas immunostaining revealed CCL21 protein within HEVs. This suggests that T-cell recruitment to human lymphoid tissues depends on the transcytosis of lymphoid chemokines through HEV cells because there is at present no evidence of alternative chemokine production in these cells that could explain the attraction of naive T lymphocytes.     

Suppressive effects of cyclosporine A on neutrophils and T cells may be related to therapeutic benefits in patients with steroid-resistant ulcerative colitis

An intravenous infusion of cyclosporine A (CsA) shows clinical benefits in patients with steroid-resistant ulcerative colitis (UC). To clarify its mechanisms, we investigated the ability of CsA to inhibit the functions of neutrophils and T cells. The cytotoxic activity by mucosal T cells was analyzed by anti-CD3-triggered cytotoxicity after lamina propria mononuclear cells were cultured with recombinant interleukin (IL)-2. The chemotactic response, the generation of superoxide, and the production of chemokines, IL-8, and macrophage inflammatory protein-1alpha by neutrophils were examined using a multiple-well chamber assay, a chemiluminescence method, and an enzyme-linked immunosorbent assay (ELISA), respectively. Mucosal chemokine activity was determined by an ELISA using the organ culture supernatant of mucosal biopsy tissues. Pretreatment with CsA caused consistent inhibitions of cytotoxic activity by mucosal T cells and chemotactic migration, superoxide generation, and chemokine production by neutrophils mostly in a dose-dependent manner. In patients who received an intravenous infusion of CsA, mucosal chemokine activity decreased after therapy in parallel with decreases in the numbers of neutrophils and mononuclear cells in the biopsy tissues. These results suggest that suppressive effects of CsA on neutrophils and T cells may be related to therapeutic benefits in patients with steroid-resistant UC.     

Up-regulation of the chemokine receptor CCR7 in classical but not in lymphocyte-predominant Hodgkin disease correlates with distinct dissemination of neoplastic cells in lymphoid organs

Chemokines and chemokine receptors are key mediators for regulating cell traffic and positioning in both homeostatic and inflammatory conditions. It is also presumed that chemokines and their receptors are likely to play a critical role in the localization of malignant hematopoietic cells in their target organs. This study analyzed chemokine and chemokine receptor expression in several Hodgkin disease (HD)-derived cell lines and in HD tumors. All HD-derived cell lines expressed functional CCR7 and CXCR4 receptors. CCR7 up-regulation was mediated by constitutive NF-kappaB activity. Lymphoid tissues in HD revealed differential expression levels of CCR7, CXCR4, and CXCR5, depending on the distinct subtypes of HD. HD of the classical subtypes, predominantly located in the interfollicular zone, showed strong CCR7 and CXCR4 expression and moderate CXCR5 expression. In contrast, the nodular lymphocyte-predominant HD (NLP) subtype, regularly associated with follicular structures, exhibited no CCR7 reactivity but abundant CXCR4 staining. Their respective chemokine ligands showed marked expression by reactive cells within the tumors of classical HD and outside of the tumor nodules in NLPHD. Functionally, such differential chemokine receptor expression might contribute to specific localization and confinement of neoplastic cells within the target organs in the distinct HD entities.     

A rich chemokine environment strongly enhances leukocyte migration and activities

The migration of leukocytes in immune surveillance and inflammation is largely determined by their response to chemokines. While the chemokine specificities and expression patterns of chemokine receptors are well defined, it is still a matter of debate how leukocytes integrate the messages provided by different chemokines that are concomitantly produced in physiologic or pathologic situations in vivo. We present evidence for a novel regulatory mechanism of leukocyte trafficking. Our data are consistent with a mode of action where CC-chemokine receptor 7 (CCR7) agonists and unrelated, nonagonist chemokines first form a heteromeric complex, in the presence of which the triggering of CCR7 can occur at a much lower agonist concentration. The increase is synergistic and can be evoked by many but not all chemokines. Chemokine-induced synergism might provide an amplification system in "chemokine-rich" tissues, rendering leukocytes more competent to respond to migratory cues.     

Bone marrow mesenchymal stem cells express a restricted set of functionally active chemokine receptors capable of promoting migration to pancreatic islets

Bone marrow-derived mesenchymal stem cells (BM-MSCs) are stromal cells with the ability to proliferate and differentiate into many tissues. Although they represent powerful tools for several therapeutic settings, mechanisms regulating their migration to peripheral tissues are still unknown. Here, we report chemokine receptor expression on human BM-MSCs and their role in mediating migration to tissues. A minority of BM-MSCs (2% to 25%) expressed a restricted set of chemokine receptors (CXC receptor 4 [CXCR4], CX3C receptor 1 [CX3CR1], CXCR6, CC chemokine receptor 1 [CCR1], CCR7) and, accordingly, showed appreciable chemotactic migration in response to the chemokines CXC ligand 12 (CXCL12), CX3CL1, CXCL16, CC chemokine ligand 3 (CCL3), and CCL19. Using human pancreatic islets as an in vitro model of peripheral tissue, we showed that islet supernatants released factors able to attract BM-MSCs in vitro, and this attraction was principally mediated by CX3CL1 and CXCL12. Moreover, cells with features of BM-MSCs were detected within the pancreatic islets of mice injected with green fluorescent protein (GFP)-positive BM. A population of bona fide MSCs that also expressed CXCR4, CXCR6, CCR1, and CCR7 could be isolated from normal adult human pancreas. This study defines the chemokine receptor repertoire of human BM-MSCs that determines their migratory activity. Modulation of homing capacity may be instrumental for harnessing the therapeutic potential of BM-MSCs.     

结直肠癌趋化因子单核细胞超化蛋白-1的表达

目的：通过检测结直肠癌组织中单核细胞超化蛋白－1（MPC－1）的表达情况，研究MCP－1的表达与结直肠癌生物学行为的关系。方法：采用RT－PCR方法，检测临床收集的新鲜结肠癌组织标本中MCP－1mRNA的表达；采用免疫组化方法，检测结直肠癌组织中MCP－1蛋白的表达，结果：12例结直肠癌组织均可出现MCP－1mRNA的表达，40例结直肠癌组织MCP－1蛋白表达的阳性率为90％，结直肠癌组织MCP－1蛋白的表达与结直肠癌的转移及Dukes分期有关，表达强者，转移发生率低，Dukes分期早，结论：结直肠组织中MCP－1的表达能影响结直肠癌的生物学行为。     

CCL7 and CCL21 overexpression in gastric cancer is associated with lymph node metastasis and poor prognosis

AIM: To investigate how a complex network of CC chemokine ligands (CCLs) and their receptors influence the progression of tumor and metastasis.METHODS: In the present study, we used immunohistochemistry to examine the expression of CCL7, CCL8 and CCL21 in 194 gastric cancer samples and adjacent normal tissues. We analyzed their correlation with tumor metastasis, clinicopathologic parameters and clinical outcome.RESULTS: We found that the higher expression of CCL7 and CCL21 in cancer tissues than in normal tissues was significantly correlated with advanced depth of wall invasion, lymph node metastasis and higher tumor node metastasis stage. Moreover, Kaplan-Meier survival analysis revealed that CCL7 and CCL21 overexpression in cancer tissues was correlated with poor prognosis.CONCLUSION: These results suggest that overexpression of these two CC chemokine ligands is associated with tumor metastasis and serves as a prognostic factor in patients with gastric cancer.     

Coexpression of the chemokines ELC and SLC by T zone stromal cells and deletion of the ELC gene in the plt/plt mouse

The spontaneous mutant mouse strain, plt/plt, lacks the secondary lymphoid organ chemokine (SLC)-ser gene and has disrupted trafficking of T cells and dendritic cells (DCs) to lymphoid tissues. We demonstrate here that the gene for the related chemokine, Epstein-Barr virus-induced molecule-1 ligand chemokine (ELC), is also deleted in this immunodeficient mouse strain. Using a combination of approaches, including bone marrow reconstitution and double in situ hybridization, we show in wild-type mice that ELC is expressed by T zone stromal cells that also make SLC. Smaller amounts of ELC are made by DCs, predominantly of the CD8(+) phenotype. We propose that ELC- and SLC-expressing T zone stromal cells play a central role in bringing naive T cells and DCs together for the initiation of immune responses.