Prostate tumor CXC-chemokine profile correlates with cell adhesion to endothelium and extracellular matrix

Though chemokines of the CXC family are thought to play key roles in neoplastic transformation and tumor invasion, information about CXC chemokines in prostate cancer is sparse. To evaluate the involvement of CXC chemokines in prostate cancer, we analyzed the CXC coding mRNA of both chemokine ligands (CXCL) and chemokine receptors (CXCR), using the prostate carcinoma cell lines PC-3, DU-145 and LNCaP. CXCR proteins were further evaluated by Western blot, CXCR surface expression by flow cytometry and confocal microscopy. The expression pattern was correlated to adherence of the tumor cells to an endothelial cell monolayer or to extracellular matrix components. Based on growth and adhesion capacity, PC-3 and DU-145 were identified to be highly aggressive tumor cells (PC-3>DU-145), whereas LNCaP belonged to the low aggressive phenotype. CXCL1, CXCL3, CXCL5 and CXCL6 mRNA, chemokines with pro-angiogenic activity, were strongly expressed in DU-145 and PC-3, but not in LNCaP. CXCR3 and CXCR4 surface level differed in the following order: LNCaP>DU-145>PC-3. The differentiation factor, fatty acid valproic acid, induced intracellular CXCR accumulation. Therefore, prostate tumor malignancy might be accompanied by enhanced synthesis of angiogenesis stimulating CXC chemokines. Further, shifting CXCR3 and CXCR4 from the cell surface to the cytoplasm might activate pro-tumoral signalling events and indicate progression from a low to a highly aggressive phenotype.     

The expression and role of CXC chemokines in colorectal cancer

Cancer is a life-threatening disease world-wide and colorectal cancer is the second common cause of cancer mortality. The interaction between tumor cells and stromal cells plays a crucial role in tumor initiation and progression and is partially mediated by chemokines. Chemokines predominantly participate in the chemoattraction of leukocytes to inflammatory sites. Nowadays, it is clear that CXC chemokines and their receptors (CXCR) may also modulate tumor behavior by several important mechanisms: regulation of angiogenesis, activation of a tumor-specific immune response by attracting leukocytes, stimulation of tumor cell proliferation and metastasis. Here, we review the expression and complex roles of CXC chemokines (CXCL1 to CXCL16) and their receptors (CXCR1 to CXCR6) in colorectal cancer. Overall, increased expression levels of CXC chemokines correlate with poor prognosis.     

Chemokine receptor trio: CXCR3, CXCR4 and CXCR7 crosstalk via CXCL11 and CXCL12

Although chemokines are well established to function in immunity and endothelial cell activation and proliferation, a rapidly growing literature suggests that CXC Chemokine receptors CXCR3, CXCR4 and CXCR7 are critical in the development and progression of solid tumors. The effect of these chemokine receptors in tumorigenesis is mediated via interactions with shared ligands I-TAC (CXCL11) and SDF-1 (CXCL12). Over the last decade, CXCR4 has been extensively reported to be overexpressed in most human solid tumors and has earned considerable attention toward elucidating its role in cancer metastasis. To enrich the existing armamentarium of anti-cancerous agents, many inhibitors of CXCL12–CXCR4 axis have emerged as additional or alternative agents for neo-adjuvant treatments and even many of them are in preclinical and clinical stages of their development. However, the discovery of CXCR7 as another receptor for CXCL12 with rather high binding affinity and recent reports about its involvement in cancer progression, has questioned the potential of “selective blockade” of CXCR4 as cancer chemotherapeutics. Interestingly, CXCR7 can also bind another chemokine CXCL11, which is an established ligand for CXCR3. Recent reports have documented that CXCR3 and their ligands are overexpressed in different solid tumors and regulate tumor growth and metastasis. Therefore, it is important to consider the interactions and crosstalk between these three chemokine receptors and their ligand mediated signaling cascades for the development of effective anti-cancer therapies. Emerging evidence also indicates that these receptors are differentially expressed in tumor endothelial cells as well as in cancer stem cells, suggesting their direct role in regulating tumor angiogenesis and metastasis. In this review, we will focus on the signals mediated by this receptor trio via their shared ligands and their role in tumor growth and progression.     

CXCR4/CXCL12 axis promotes VEGF-mediated tumor angiogenesis through Akt signaling pathway

CXC chemokine receptor 4 (CXCR4) has been shown to play a critical role in chemotaxis and homing, which are key steps in cancer metastasis. There is also increasing evidence that links this receptor to angiogenesis; however, its molecular basis remains elusive. Vascular endothelial growth factor (VEGF), one of the major angiogenic factors, promotes the formation of leaky tumor vasculatures that are the hallmarks of tumor progression. Here, we investigated whether CXCR4 induces the expression of VEGF through the PI3K/Akt pathway. Our results showed that CXCR4/CXCL12 induced Akt phosphorylation, which resulted in upregulation of VEGF at both the mRNA and protein levels. Conversely, blocking the activation of Akt signaling led to a decrease in VEGF protein levels; blocking CXCR4/CXCL12 interaction with a CXCR4 antagonist suppressed tumor angiogenesis and growth in vivo. Furthermore, VEGF mRNA levels correlated well with CXCR4 mRNA levels in patient tumor samples. In summary, our study demonstrates that the CXCR4/CXCL12 signaling axis can induce angiogenesis and progression of tumors by increasing expression of VEGF through the activation of PI3K/Akt pathway. Our findings suggest that targeting CXCR4 could provide a potential new anti-angiogenic therapy to suppress the formation of both primary and metastatic tumors.     

The role of CXC chemokines in the transition of chronic inflammation to esophageal and gastric cancer

Chronic inflammation may increase the risk to develop cancer, for instance esophagitis or gastritis may lead to development of esophageal or gastric cancer, respectively. The key molecules attracting leukocytes to local inflammatory sites are chemokines. We here provide a systematic review on the impact of CXC chemokines (binding the receptors CXCR1, CXCR2, CXCR3 and CXCR4) on the transition of chronic inflammation in the upper gastrointestinal tract to neoplasia. CXCR2 ligands, including GRO-α,β,γ/CXCL1,2,3, ENA-78/CXCL5 and IL-8/CXCL8 chemoattract pro-tumoral neutrophils. In addition, angiogenic CXCR2 ligands stimulate the formation of new blood vessels, facilitating tumor progression. The CXCR4 ligand SDF-1/CXCL12 also promotes tumor development by stimulating angiogenesis and by favoring metastasis of CXCR4-positive tumor cells to distant organs producing SDF-1/CXCL12. Furthermore, these angiogenic chemokines also directly enhance tumor cell survival and proliferation. In contrast, the CXCR3 ligands Mig/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11 are angiostatic and attract anti-tumoral T lymphocytes and may therefore mediate tumor growth retardation and regression. Thus, chemokines exert diverging, sometimes dual roles in tumor biology as described for esophageal and gastric cancer. Therefore extensive research is needed to completely unravel the complex chemokine code in specific cancers. Possibly, chemokine-targeted cancer therapy will have to be adapted to the individual's chemokine profile.     

The role of CXC chemokines in the transition of chronic inflammation to esophageal and gastric cancer

Chronic inflammation may increase the risk to develop cancer, for instance esophagitis or gastritis may lead to development of esophageal or gastric cancer, respectively. The key molecules attracting leukocytes to local inflammatory sites are chemokines. We here provide a systematic review on the impact of CXC chemokines (binding the receptors CXCR1, CXCR2, CXCR3 and CXCR4) on the transition of chronic inflammation in the upper gastrointestinal tract to neoplasia. CXCR2 ligands, including GRO-α,β,γ/CXCL1,2,3, ENA-78/CXCL5 and IL-8/CXCL8 chemoattract pro-tumoral neutrophils. In addition, angiogenic CXCR2 ligands stimulate the formation of new blood vessels, facilitating tumor progression. The CXCR4 ligand SDF-1/CXCL12 also promotes tumor development by stimulating angiogenesis and by favoring metastasis of CXCR4-positive tumor cells to distant organs producing SDF-1/CXCL12. Furthermore, these angiogenic chemokines also directly enhance tumor cell survival and proliferation. In contrast, the CXCR3 ligands Mig/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11 are angiostatic and attract anti-tumoral T lymphocytes and may therefore mediate tumor growth retardation and regression. Thus, chemokines exert diverging, sometimes dual roles in tumor biology as described for esophageal and gastric cancer. Therefore extensive research is needed to completely unravel the complex chemokine code in specific cancers. Possibly, chemokine-targeted cancer therapy will have to be adapted to the individual's chemokine profile.     

CXCR4/CXCL12 在肿瘤中的研究进展

研究表明趋化因子及其受体在胚胎发育、干细胞迁移以及各种免疫反应中发挥重要作用,是许多生理及病理过程中细胞运动的重要因素。趋化因子受体CXCR4是一个由352个氨基酸构成的、7次跨膜的G蛋白偶联受体。趋化因子CXCL12为其特异性受体。研究发现,CXCR4/CXCL12在多种肿瘤中都有表达,在肿瘤的生长、血管生成、转移等方面发挥着重要作用。与正常组织相比,肿瘤组织及转移灶CXCR4高表达。因此,对CXCR4/CXCL12轴在肿瘤病生理中的作用机制进行进一步研究,很可能为肿瘤的治疗及对肿瘤转移的预防提供一个新的思路。我们现在就对其在肿瘤病生理中的作用做一综述。     

Opposing effects of high- and low-molecular weight hyaluronan on CXCL12-induced CXCR4 signaling depend on CD44

The tumor microenvironment makes a decisive contribution to the development and dissemination of cancer, for example, through extracellular matrix components such as hyaluronan (HA), and through chemokines that regulate tumor cell behavior and angiogenesis. Here we report a molecular link between HA, its receptor CD44 and the chemokine CXCL12 in the regulation of cell motility and angiogenesis. High-molecular-weight HA (hHA) was found to augment CXCL12-induced CXCR4 signaling in both HepG2iso cells and primary human umbilical vein endothelial cells, as evidenced by enhanced ERK phosphorylation and increased cell motility. The augmentation of CXCR4 signaling translated into increased vessel sprouting and angiogenesis in a variety of assays. Small HA oligosaccharides (sHA) efficiently inhibited these effects. Both siRNA-mediated reduction of CD44 expression and antibodies that block the interaction of CD44 with HA provided evidence that CXCL12-induced CXCR4 signaling depends on the binding of hHA to CD44. Consistently, CD44 and CXCR4 were found to physically interact in the presence of CXCL12, an interaction that could be inhibited by sHA. These findings provide novel insights into how microenvironmental components interact with cell surface receptors in multi-component complexes to regulate key aspects of tumor growth and progression.     

The role of CXC chemokine ligand 4/CXC chemokine receptor 3-B in breast cancer progression

Chemokines and their receptors participate in the development of cancers by enhancing tumor cell proliferation, angiogenesis, invasion, metastasis and penetration of tumor immune cells. It remains unclear whether CXC chemokine ligand 4 (CXCL4)/CXC chemokine receptor 3-B (CXCR3-B) can be used as an independent molecular marker for establishing prognosis for breast cancer patients. We evaluated CXCL4 and CXCR3-B expression in 114 breast cancer tissues and 30 matched noncancerous tissues using immunohistochemistry and western blot, and determined the correlation between their expression and clinicopathologic findings. We observed that breast cancer tissues express CXCL4 strongly and CXCR3-B weakly compared to noncancerous tissues. Strong CXCL4 expression was detected in 94.7% and weak CXCR3-B expression was detected in 78.9% of the tissues. Therefore, CXCL4/CXCR3-B might play a crucial role in breast cancer progression. We found no significant correlation between CXCL4 and age, tumor stage, tumor grade or TNM stage. CXCR3-B was associated significantly with tumor grade. Moreover, the Chi-square test of association showed that the expression of CXCL4/CXCR3-B might be an independent prognostic marker for breast cancer. Therefore, we suggest that CXCR3-B is an indicator of poor prognosis and may also be a chemotherapeutic target.     

CXCR6/CXCL16 functions as a regulator in metastasis and progression of cancer

Metastasis is considered the obvious mark for most aggressive cancers. However, little is known about the molecular mechanism of the regulation of cancer metastasis. Recent evidence increasingly suggests that the interaction between chemokines and chemokine receptors is pivotal in the process of metastasis. The chemokine receptor CXCR4 and its ligand CXCL12, for example, have been reported to play a vital role in cancer metastasis. Another chemokine and chemokine receptor pair, the CXCL16/CXCR6 axis, has been studied by several independent research groups. Here, we summarize recent advances in our knowledge of the function of CXC chemokine receptor CXCR6 and its ligand CXCL16 in regulating metastasis and invasion of cancer. CXCR6 and CXCL16 are up-regulated in multiple cancer tissue types and cancer cell lines relative to normal tissues and cell lines. In addition, both CXCR6 and CXCL16 levels increase as tumor malignancy increases. Trans-membranous CXCL16 chemokine reduces proliferation while soluble CXCL16 chemokine enhances proliferation and migration. TM-CXCL16 functions as an inducer for lymphocyte build-up around tumor sites. High trans-membranous CXCL16 expression correlates with a good prognosis. Moreover, the Akt/mTOR signal pathway is involved in activating the CXCR6/CXCL16 axis. These findings suggest multiple opportunities for blocking the CXCR6/CXCL16 axis and the Akt/mTOR signal pathway in novel cancer therapies.     

The CXC chemokine receptor 2, CXCR2, is the putative receptor for ELR+ CXC chemokine-induced angiogenic activity

We have previously shown that members of the ELR(+) CXC chemokine family, including IL-8; growth-related oncogenes alpha, beta, and gamma; granulocyte chemotactic protein 2; and epithelial neutrophil-activating protein-78, can mediate angiogenesis in the absence of preceding inflammation. To date, the receptor on endothelial cells responsible for chemotaxis and neovascularization mediated by these ELR(+) CXC chemokines has not been determined. Because all ELR(+) CXC chemokines bind to CXC chemokine receptor 2 (CXCR2), we hypothesized that CXCR2 is the putative receptor for ELR(+) CXC chemokine-mediated angiogenesis. To test this postulate, we first determined whether cultured human microvascular endothelial cells expressed CXCR2. CXCR2 was detected in human microvascular endothelial cells at the protein level by both Western blot analysis and immunohistochemistry using polyclonal Abs specific for human CXCR2. To determine whether CXCR2 played a functional role in angiogenesis, we determined whether this receptor was involved in endothelial cell chemotaxis. We found that microvascular endothelial cell chemotaxis in response to ELR(+) CXC chemokines was inhibited by anti-CXCR2 Abs. In addition, endothelial cell chemotaxis in response to ELR(+) CXC chemokines was sensitive to pertussis toxin, suggesting a role for G protein-linked receptor mechanisms in this biological response. The importance of CXCR2 in mediating ELR(+) CXC chemokine-induced angiogenesis in vivo was also demonstrated by the lack of angiogenic activity induced by ELR(+) CXC chemokines in the presence of neutralizing Abs to CXCR2 in the rat corneal micropocket assay, or in the corneas of CXCR2(-/-) mice. We thus conclude that CXCR2 is the receptor responsible for ELR(+) CXC chemokine-mediated angiogenesis.     

Depletion of CXCR2 inhibits tumor growth and angiogenesis in a murine model of lung cancer

The Glu-Leu-Arg(+) (ELR(+)) CXC chemokines are potent promoters of angiogenesis and have been demonstrated to induce a significant portion of nonsmall cell lung cancer-derived angiogenic activity and support tumorigenesis. ELR(+) CXC chemokines share a common chemokine receptor, CXCR2. We hypothesized that CXCR2 mediates the proangiogenic effects of ELR(+) CXC chemokines during tumorigenesis. To test this postulate, we used syngeneic murine Lewis lung cancer (LLC; 3LL, H-2(b)) heterotopic and orthotopic tumor model systems in C57BL/6 mice replete (CXCR2(+/+)) and deficient in CXCR2 (CXCR2(-/-)). We first demonstrated a correlation of the expression of endogenous ELR(+) CXC chemokines with tumor growth and metastatic potential of LLC tumors. Next, we found that LLC primary tumors were significantly reduced in growth in CXCR2(-/-) mice. Moreover, we found a marked reduction in the spontaneous metastases of heterotopic tumors to the lungs of CXCR2(-/-) mice. Morphometric analysis of the primary tumors in CXCR2(-/-) mice demonstrated increased necrosis and reduced vascular density. These findings were further confirmed in CXCR2(+/+) mice using specific neutralizing Abs to CXCR2. The results of these studies support the notion that CXCR2 mediates the angiogenic activity of ELR(+) CXC chemokines in a preclinical model of lung cancer.     

CXC chemokines in angiogenesis

CXC chemokines display pleiotropic effects in immunity, regulating angiogenesis, and mediating organ-specific metastases of cancer. In the context of angiogenesis, CXC chemokines are a unique family of cytokines, known for their ability to behave in a disparate manner in the regulation of angiogenesis. Members that contain the ‘ELR’ motif are potent promoters of angiogenesis, and mediate their angiogenic activity via binding and activating CXCR2 on endothelium. In contrast, members, in general, those are inducible by interferons and lack the ELR motif (ELR⁻) are potent inhibitors of angiogenesis, and bind to CXCR3 on endothelium. This review will discuss the biology of these angiogenic and angiostatic CXC chemokines and discuss their disparate angiogenic activity in the context of a variety of disorders.     

NMR structure of CXCR3 binding chemokine CXCL11 (ITAC)

CXCL11 (ITAC) is one of three chemokines known to bind the receptor CXCR3, the two others being CXCL9 (Mig) and CXCL10 (IP-10). CXCL11 differs from the other CXCR3 ligands in both the strength and the particularities of its receptor interactions: It has a higher affinity, is a stronger agonist, and behaves differently when critical N-terminal residues are deleted. The structure of CXCL11 was determined using solution NMR to allow comparison with that of CXCL10 and help elucidate the source of the differences. CXCL11 takes on the canonical chemokine fold but exhibits greater conformational flexibility than has been observed for related chemokines under the same sample conditions. Unlike related chemokines such as IP-10 and IL-8, ITAC does not appear to form dimers at millimolar concentrations. The origin for this behavior can be found in the solution structure, which indicates a beta-bulge in beta-strand 1 that distorts the dimerization interface used by other CXC chemokines.     

TNFα-exposed Bone Marrow-derived Mesenchymal Stem Cells Promote Locomotion of MDA-MB-231 Breast Cancer Cells through Transcriptional Activation of CXCR3 Ligand Chemokines

Bone marrow-derived mesenchymal stem cells (BM-MSCs) are often recruited to solid tumors, integrate into the tumor stroma, and contribute to tumor development. TNFα is a major inflammatory cytokine present in the tumor microenvironment and has a profound influence on the progression of tumor development. This study was aimed to investigate the role of BM-MSCs in tumor promotion in response to TNFα. Quantitative real-time PCR arrays show that diverse cytokines/chemokines were induced in TNFα-treated BM-MSCs; in particular, CXCR3 ligand chemokines, including CXCL9, CXCL10, and CXCL11, were potently induced. A serial and site-directed mutation analysis in the CXCL9, CXCL10, and CXCL11 promoters revealed that NF-κB binding elements were responsible for TNFα-induced promoter activation of CXCR3 ligand chemokines. TNFα stimulated NF-κB activity, and ectopic expression of NF-κB enhanced TNFα-induced promoter activities of the CXCR3 ligand chemokines. Gel shift and supershift assays showed that NF-κB was associated with CXCR3 ligand chemokine promoters in response to TNFα treatment. All three CXCR3 ligand chemokines enhanced the migration and invasive motility of MDA-MB-231 breast cancer cells expressing CXCR3. Treatment of MDA-MB-231 cells with CXCL10 activated small GTPase of Rho family proteins, such as RhoA and Cdc42. CXCL9-, CXCL10-, or CXCL11-induced invasive capability of MDA-MB-231 cells was completely abrogated in the presence of a neutralizing anti-CXCR3 antibody in the culture medium. Moreover, CXCL9, CXCL10, and CXCL11 stimulated the expression of MMP-9, but not MMP-2, in MDA-MB-231 cells. These results suggest that BM-MSCs promote the locomotion of breast cancer cells through CXCR3 ligand-mediated actin rearrangement by TNFα in the tumor microenvironment.     

The role of CXCR2/CXCR2 ligand biological axis in renal cell carcinoma

Renal cell carcinoma (RCC) accounts for 3% of new cancer incidence and mortality in the United States. Studies in RCC have predominantly focused on VEGF in promoting tumor-associated angiogenesis. However, other angiogenic factors may contribute to the overall angiogenic milieu of RCC. We hypothesized that the CXCR2/CXCR2 ligand biological axis represents a mechanism by which RCC cells promote angiogenesis and facilitate tumor growth and metastasis. Therefore, we first examined tumor biopsies and plasma of patients with metastatic RCC for levels of CXCR2 ligands, and RCC tumor biopsies for the expression of CXCR2. The proangiogenic CXCR2 ligands CXCL1, CXCL3, CXCL5, and CXCL8, as well as VEGF were elevated in the plasma of these patients and found to be expressed within the tumors. CXCR2 was found to be expressed on endothelial cells within the tumors. To assess the role of ELR(+) CXC chemokines in RCC, we next used a model of syngeneic RCC (i.e., RENCA) in BALB/c mice. CXCR2 ligand and VEGF expression temporally increased in direct correlation with RENCA growth in CXCR2(+/+) mice. However, there was a marked reduction of RENCA tumor growth in CXCR2(-/-) mice, which correlated with decreased angiogenesis and increased tumor necrosis. Furthermore, in the absence of CXCR2, orthotopic RENCA tumors demonstrated a reduced potential to metastasize to the lungs of CXCR2(-/-) mice. These data support the notion that CXCR2/CXCR2 ligand biology is an important component of RCC tumor-associated angiogenesis and tumorigenesis.     

趋化因子SD-1及其受体CXCR4在卵巢癌中的研究进展

基质细胞衍生因子-1(Stromal cell derived factor-1,SDF-1)是CXC趋化因子家族的重要成员,系统命名为CXCL12,能与它的唯一受体CXC趋化因子受体-4(CXC chemokine receptor-4,CXCR4)形成CXCL12-CXCR4生物学轴,CXCL12-CXCR4生物学轴在肿瘤生长、侵袭、转移过程中发生重要作用。到目前为止,已发现CXCL12-CXCR4在卵巢癌、胰腺癌、肝癌等多种肿瘤组织中表达。然而,国内目前还没有关于CXCL12-CXCR4与卵巢癌关系的相关综述,本文将从趋化因子CXCL12及其受体CXCR4,CXCL12/CXCR4轴与卵巢癌细胞系实验研究,CXCL12-CXCR4轴与卵巢癌的临床研究,CXCL12/CXCR4与卵巢癌预后,CXCL12/CXCR4与卵巢癌治疗展望等五个方面对CXCL12-CXCR4生物轴与卵巢癌的关系,及其在卵巢癌治疗中的应用展开综述。     

Activating and inhibitory Ly49 receptors modulate NK cell chemotaxis to CXC chemokine ligand (CXCL) 10 and CXCL12

NK cells can migrate into sites of inflammatory responses or malignancies in response to chemokines. Target killing by rodent NK cells is restricted by opposing signals from inhibitory and activating Ly49 receptors. The rat NK leukemic cell line RNK16 constitutively expresses functional receptors for the inflammatory chemokine CXC chemokine ligand (CXCL)10 (CXCR3) and the homeostatic chemokine CXCL12 (CXCR4). RNK-16 cells transfected with either the activating Ly49D receptor or the inhibitory Ly49A receptor were used to examine the effects of NK receptor ligation on CXCL10- and CXCL12-mediated chemotaxis. Ligation of Ly49A, either with Abs or its MHC class I ligand H2-D(d), led to a decrease in chemotactic responses to either CXCL10 or CXCL12. In contrast, Ly49D ligation with Abs or H2-D(d) led to an increase in migration toward CXCL10, but a decrease in chemotaxis toward CXCL12. Ly49-dependent effects on RNK-16 chemotaxis were not the result of surface modulation of CXCR3 or CXCR4 as demonstrated by flow cytometry. A mutation of the Src homology phosphatase-1 binding motif in Ly49A completely abrogated Ly49-dependent effects on both CXCL10 and CXCL12 chemotaxis, suggesting a role for Src homology phosphatase-1 in Ly49A/chemokine receptor cross-talk. Ly49D-transfected cells were pretreated with the Syk kinase inhibitor Piceatannol before ligation, which abrogated the previously observed changes in migration toward CXCL10 and CXCL12. Piceatannol also abrogated Ly49A-dependent inhibition of chemotaxis toward CXCL10, but not CXCL12. Collectively, these data suggest that Ly49 receptors can influence NK cell chemotaxis within sites of inflammation or tumor growth upon interaction with target cells.     

Effects of CXCL4/CXCR3 on the lipopolysaccharide-induced injury in human umbilical vein endothelial cells

Chemokines and inflammatory response of endothelial cells is crucial in the development and progression of inflammatory disease. Lipopolysaccharide (LPS) is a well-known factor to trigger inflammatory response and induce damage of endothelial cells. The present study used lipopolysaccharide (LPS)-treated human vascular endothelial cells (HUVECs) to investigate the function of chemokine CXC chemokine ligand 4 (CXCL4) and its receptor CXC chemokine receptor 3 (CXCR3) in inflammatory-induced endothelial injury. LPS exposure (50, 100, 200 ng/ml) to HUVECs induced a dose- and time-dependent increase in CXCL4 and CXCR3 expression at both mRNA and protein levels. The LPS-induced endothelium hyperpermeability was inhibited by the addition of CXCL4 neutralizing antibody. Moreover, the addition of CXCL4 neutralizing antibody abolished the effects of LPS on tight junction (TJ) protein expression (occludin claudin-4 and Zonula occluden-1[ZO-1]) and p38 phosphorylation, which is supported by the observation of increased TJ protein expression and decreased p38 phosphorylation in LPS-treated HUVECs. SB203580, a p38 inhibitor, protected HUVECs from CXCL4-stimulated damage. In conclusion, CXCL4/CXCR3, which was enhanced by LPS, may be involved in endothelial proliferation, apoptosis, and permeability via the p38 signaling pathway.     

Cell surface heparan sulfate participates in CXCL1-induced signaling

The CXC subfamily of chemokines plays an important role in diverse processes, including inflammation, wound healing, growth regulation, angiogenesis, and tumorigenesis. The ELR-CXC chemokine, CXCL1 or MGSA/GROalpha, is traditionally considered to attract neutrophils to sites of inflammation. The non-ELR-CXC chemokine, CXCL10 or IP-10, is chemotactic for monocytes, B cells, and activated T lymphocytes. In addition to its role in leukocyte migration, CXCL10 inhibits the angiogenic functions of the ELR-CXC chemokines as well as bFGF and VEGF. Heparan sulfate proteoglycans (HSPGs) are required for the interaction of bFGF and vEGF ligands and their receptors. However, the role of HSPGs in regulating the ELR-chemokines signaling and biological functions is poorly understood. We show here that the CXCL1 maximal binding to CXCR2 expressed on HEK293 and CHO-K1 cells is dependent on the presence of cell surface HSPGs. The cell surface HSPGs on cells are required for CXCL1-induced PAK1 activation. Moreover, CXCL10 can inhibit CXCL1-induced PAK1 and ERK activation as well as the CXCL1-induced chemotaxis through decreasing CXCL1 binding to cell surface heparan sulfate. These data indicate that HSPGs are involved in modulating CXCL1-induced PAK1 activation and chemotaxis through regulating CXCL1 binding activity to CXCR2 receptor. CXCL10 inhibits CXCL1-induced PAK1 activation and chemotaxis by interfering with appropriate binding of CXCL1 to CXCR2 receptor.