Pharmacological evidence for complex and multiple site interaction of CXCR4 with SDF-1alpha: implications for development of selective CXCR4 antagonists

The C-X-C chemokine SDF-1 and its receptor CXCR4, mediate a pivotal role in the pathophysiology of HIV-1 infection and vascular inflammatory diseases. In this study, we investigated the pharmacological properties of SDF-1alpha interaction with CXCR4 in human leukemia cell lines. Our data, based on [125I]-SDF-1alpha radioligand binding, SDF-1alpha-induced [35S]-GTPgammaS binding and use of specific CXCR4 antagonist AMD3100 reveals the complex nature of SDF-1alpha-CXCR4 interaction. Firstly, homologous competition with cold SDF-1alpha revealed a bimodal ligand displacement curve and secondly, although AMD3100 inhibited both SDF-1alpha-mediated chemotaxis (IC(50)=4.7 nM) and [35S]-GTPgammaS binding (IC(50)=7.4 nM) with high affinity, it was intriguingly up to 3000-fold less potent (IC(50)=15.2 microM) in the radioligand binding assay. These results provide pharmacological evidence for the recently described two-site model for SDF-1alpha-CXCR4 interaction. Accordingly, inhibition of SDF-1alpha binding to one of the receptor sites is sufficient to antagonize function, without causing its complete displacement from the receptor. Furthermore, these findings have important implications in the development and evaluation of CXCR4-selective small molecule antagonists for therapeutic use.     

The many facets of SDF-1alpha, CXCR4 agonists and antagonists on hematopoietic progenitor cells

Stromal cell-derived factor-1alpha (SDF-1alpha) has pleiotropic effects on hematopoietic progenitor cells (HPCs). We have monitored podia formation, migration, proliferation, and cell-cell adhesion of human HPC under the influence of SDF-1alpha, a peptide agonist of CXCR4 (CTCE-0214), a peptide antagonist (CTCE-9908), and a nonpeptide antagonist (AMD3100). Whereas SDF-1alpha induced migration of CD34(+) cells in a dose-dependent manner, CTCE-0214, CTCE-9908, and AMD3100 did not induce chemotaxis in this concentration range albeit the peptides CTCE-0214 and CTCE-9908 increased podia formation. Cell-cell adhesion of HPC to human mesenchymal stromal cells was impaired by the addition of SDF-1alpha, CTCE-0214, and AMD3100. Proliferation was not affected by SDF-1alpha or its analogs. Surface antigen detection of CXCR4 was reduced upon treatment with SDF-1alpha or AMD3100 and it was enhanced by CTCE-9908. Despite the fact that all these molecules target the same CXCR4 receptor, CXCR4 agonists and antagonists have selective effects on different functions of the natural molecule.     

Construction of intrakine mutant SDF-1alpha/54/KDEL and its inhibiting effects upon CXCR4 expression on cell membrane

To investigate the impact of phenotypic knockout of CXCR4 on Molt-4 cells via intrakine technology,the C-terminal alpha-helix gene SDF-1alpha/54/KDEL of human stromal cell-derived Faceor-1 deletion is fused to a retention signal 4-peptide -KDEL that retains the newly synthesized receptor within the Molt-4 cells endoplasimc reticulum. Subsequently, PCR is used to amplify the target gene SDF-1alpha/54/ KDEL from the constructed plasmid SDF-WT-Gly x 4-Dec/PET-30a(+) at its C-terminal and subclone it into eukaryotic expression vectors pEGFP-C3 for generating recombinant vector cells by lipEGFP-C3/SDF-1alpha/54/KDEL, and then have it sequenced. After the transfection of recombinant plasmids into COS-7 posome, SDF-1alpha/54/KDEL protein is confirmed with Western blot. The recombinant plasmids pEGFP-C3/SDF-1alpha/54/KDEL are isolated and transiently transfected in Molt-4 cells by electroporation. Flow cytometric analysis shows a dramatic reduction of CXCR4 expression on Molt-4 cells. The conclusion is that SDF-1alpha/54/KDEL could assume a role in the phenotypic knockout of CXCR4, and the findings suggest that the inhibiting effect of SDF-1alpha/54 against CXCR4 is not influenced by the deletion of SDF-1alpha helix at the C terminal.     

Maturation decreases responsiveness of human bone marrow B lineage cells to stromal-derived factor 1 (SDF-1).

We compared the chemotactic responsiveness of different subsets of human B lineage cells to stromal derived factor-1 (SDF-1). High percentages (30-40% of input) of purified bone marrow progenitors including non-B lineage progenitors, pro-B cells, and pre-B cells migrated to SDF-1alpha, demonstrating that SDF-1 is an efficacious chemoattractant of these cells. Pro-B cells responded optimally to a lower concentration of SDF-1 than other subsets, demonstrating that SDF-1 is a more potent chemoattractant of this subset. A lower percentage (10-15% of input) of mature B lymphocytes migrated to SDF-1alpha than pro-B cells, demonstrating that responsiveness of B lineage cells to SDF-1 decreases during differentiation. Inhibition by anti-CXCR4 mAb demonstrated that migration of B lineage cells to SDF-1 was completely dependent on CXC chemokine receptor-4 (CXCR4). Mature B cells expressed higher levels of CXCR4 receptors than uncommitted progenitors and pro-B cells, despite differences in responsiveness to SDF-1. CXCR4 receptors expressed by unresponsive and SDF-1-responsive B cells bound SDF-1alpha with similar affinities (K(D) = 1.7-3.3 x 10(-9) M). Therefore, elements downstream from CXCR4 appear to regulate responsiveness of B cells to SDF-1. We speculate that SDF-1 and CXCR4 direct migration of progenitor cells in microenvironments that promote B lymphopoiesis.     

SDF-1α/CXCR4轴通过诱导胰腺癌上皮-间充质转化促进肿瘤迁移和侵袭

目的:探讨SDF-1α/CXCR4轴对胰腺癌细胞迁移和侵袭能力的影响及其作用机制。方法:应用RT-qPCR检测4种胰腺癌细胞株CXCR4 mRNA的表达。Transwell实验检测外源性SDF-1α及其受体CXCR4靶向抑制剂AMD3100对胰腺癌细胞迁移和侵袭能力的影响。MTS法检测外源性SDF-1α及AMD3100对胰腺癌细胞活力的影响。Western blot法检测外源性SDF-1α及AMD3100对胰腺癌细胞上皮-间充质转化(EMT)相关标志物表达的影响。结果:(1) 4种胰腺癌细胞株均不同程度地表达CXCR4 mRNA,其中PANC-1细胞株表达量最高。(2)外源性SDF-1α可增强PANC-1细胞的迁移和侵袭能力,该作用可被AMD3100所阻断。(3)外源性SDF-1α处理PANC-1细胞72 h可增强细胞活力,该作用可被AMD3100阻断。(4)外源性SDF-1α通过上调SNAIL和TWIST促使PANC-1细胞发生EMT,该作用可被AMD3100所阻断。结论:SDF-1/CXCR4轴通过促进胰腺癌细胞发生EMT而促进肿瘤迁移和侵袭。     

Limbal epithelial stem/progenitor cells attract stromal niche cells by SDF-1/CXCR4 signaling to prevent differentiation

Corneal epithelial stem cells (SCs) are an ideal model for investigating how adult lineage-committed epithelial SCs are regulated by an anatomically defined and accessible niche, that is, limbal palisades of Vogt, located between the cornea and the conjunctiva. We have used collagenase digestion to isolate the entire limbal epithelial SCs and subjacent mesenchymal cells, and we have demonstrated that their close association is crucial for promoting epithelial clonal growth, implying that the latter serves as niche cells (NCs). After their close association was disrupted by trypsin/EDTA, single SCs and NCs could reunite to generate sphere growth in three-dimensional Matrigel in the embryonic SC medium, and that such sphere growth initiated by SC-NC reunion was mediated by SDF-1 uniquely expressed by limbal epithelial progenitor cells and its receptor CXCR4, but not CXCR7, strongly expressed by limbal stromal NCs. Inhibition of CXCR4 by AMD3100 or a blocking antibody to CXCR4 but not CXCR7 disrupted their reunion and yielded separate spheres with a reduced size, while resultant epithelial spheres exhibited more corneal differentiation and a notable loss of holoclones. For the first time, these results provide strong evidence supporting that limbal SC function depends on close physical association with their native NCs via SDF-1/CXCR4 signaling. This novel in vitro model of sphere growth with NCs can be used for investigating how limbal SC self-renewal and fate decision might be regulated in the limbal niche.     

SDF-1/CXCR4在滋养层细胞中的表达及其在母-胎免疫耐受中的作用

目的:研究趋化因子SDF1及其配体CXCR4在滋养层细胞中的表达及其在母胎免疫耐受中的作用。方法:取早孕期的绒毛,分离纯化培养绒毛外滋层养细胞(extravilloustrophoblast,EVT),用免疫细胞化学染色法检测SDF1与CXCR4在绒毛中的表达。用流式细胞术筛选源于滋养层细胞高表达CXCR4的绒癌细胞株用于体外微孔隔离室迁移实验,以分析SDF1的趋化活性。用免疫组织化学染色法检测早孕期绒毛及足月妊娠胎盘中SDF1及CXCR4的表达。结果:在EVT中可检出SDF1和CXCR4的表达,在一定范围内,SDF1的趋化活性与其浓度呈正相关(r=0.68,P<0.01)。10μg/L的SDF1趋化作用最强,最大趋化指数CI为1.62±0.12。在早孕期的绒毛及足月胎盘中,滋养层细胞的胞膜和细胞质中均检出SDF1和CXCR4的表达,但在足月胎盘中的表达强度明显低于早孕期的绒毛组织(P<0.01)。结论:SDF1/CXCR4在妊娠中发挥着重要作用,对维系母胎免疫耐受具有重要意义。     

Increase of CCR1 and CCR5 expression and enhanced functional response to MIP-1 alpha during differentiation of human monocytes to macrophages

Chemokines and their receptors regulate migration of leukocytes under normal and inflammatory conditions. In this study, we analyzed the CC chemokine receptor (CCR) expression of monocytes differentiating in vitro to macrophages. We observed a time-dependent change of expression and functional responsiveness of CCR1, CCR2, and CCR5 within 48 h. Whereas freshly harvested monocytes were strongly attracted by monocyte chemotactic protein 1 (MCP-1), a specific ligand for CCR2, only a weak response was observed to macrophage inflammatory protein 1alpha (MIP-1alpha), which binds to CCR1 and CCR5. In striking contrast, differentiated macrophages displayed a strong chemotactic response to MIP-1alpha and only a weak response to MCP-1. These findings were paralleled by intracellular calcium shifts. During the time course of monocyte to macrophage differentiation, mRNA levels and surface expression of CCR2 decreased, whereas that of CCR1 and CCR5 increased. The time-dependent switch from CCR2 on monocytes to CCR1 and CCR5 on mature macrophages reflects a functional change belonging to the differentiation process of monocytes to macrophages and may form the basis for a differential responsiveness of monocytes and macrophages to distinct sets of chemokines.     

Alginates induce differentiation and expression of CXCR7 and CXCL12/SDF-1 in human keratinocytes-The role of calcium

Alginates from seaweed are used in chronic wound management, though the molecular and cellular effects of various alginate dressings are not well documented. We have developed ultrapure sodium-alginates from Pseudomonas fluorescens with different content and distribution of single guluronic acid (G) residues (0-45% G), and tested their biological activities on human primary keratinocytes (KCs). The alginates inhibited KC migration and induced expression of differentiation markers. The potency of the alginates correlated with the increasing percentage of single G residues. These findings were explained by different binding and release of ionic calcium (Ca++) from the alginates which subsequently triggered differentiation. Ca-free alginates had no effect on KC migration and differentiation, but the chemokine receptor CXCR7 was upregulated. Q-PCR revealed that also CXCL12/SDF-1, one of two known CXCR7-ligands, was induced by the alginates. Both CXCR7 and CXCL12-induction was dependent on the alginate G-content, and highest upregulation was induced by an alginate with 19% single G residues. In the epidermis, CXCR7 expression was restricted to the basal layer. This study defines two biological effects of ultrapure alginates on KCs, both being dependent on the alginate structure, and being either dependent or independent of Ca. ? 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A 100A:2803-2812, 2012.     

趋化因子基质细胞衍生因子1(SDF-1)及其受体CXCR4

趋化因子及其受体在免疫和炎症反应、造血以及HIV感染等方面发挥重要作用,其中基质细胞衍生因子-1SDF-1及其受体CXCR4由于在造血干细胞迁移、归巢以及HIV感染中的作用而受到关注,并对其作用机制进行了探讨,现就SDF-1及其受体CXCR4的有关内容作一综述。     

基质细胞衍生因子-1及其受体CXCR4在肿瘤转移中的作用

基质细胞衍生因子-1(Stromal cell-derived factor-1,SDF-1)及其受体CXCR4与人类多种肿瘤转移密切相关,CXCR4在一些肿瘤细胞系、原发肿瘤组织均呈高表达。SDF-1在肿瘤细胞潜在转移靶器官的表达量比非常规转移靶器官高,肿瘤细胞利用CXCR4与其天然配体间的趋化效应实现远距离转移。SDF-1/CXCR4驱动癌细胞转移模式的提出及其相互作用机制的深入研究对于肿瘤治疗具有重要的指导意义。     

Chemokine receptor CXCR4-dependent internalization and resecretion of functional chemokine SDF-1 by bone marrow endothelial and stromal cells

Regulation of the availability of chemokine SDF-1 (CXCL12) in bone marrow is still not fully understood. Here we describe a unique function for the chemokine receptor CXCR4 expressed on bone marrow endothelial cells, which efficiently internalize circulating SDF-1, resulting in its translocation into the bone marrow. Translocated SDF-1 increased the homing of transplanted human CD34(+) hematopoietic progenitors to the bone marrow. The chemokine transporter function of CXCR4 was a characteristic of endothelial and stromal cells but not of hematopoietic cells. Thus, chemokine translocation across the blood-bone marrow barrier allows effective transfer of functional SDF-1 from the periphery to the stem cell niche in the bone marrow during both homeostasis and 'alarm' situations.     

SDF-1/CXCR4轴通过调控间充质干细胞定向分化修复缺氧缺血性脑损伤

目的:探讨基质细胞衍生因子-1(stromalcell-derivedfactor-1,SDF-1)/CXC趋化因子受体4(CXCchemokinereceptor4,CXCR4)轴调控间充质干细胞定向分化、修复缺氧缺血性脑损伤的作用。方法:大鼠间充质干细胞(ratmesenchymalstemcells,rMSCs)经缺氧培养不同时点(0h、6h、12h、24h、48h、72h)或SDF-1α(10μg/L)孵育后,采用RT-PCR、Westernblotting和流式细胞术检测其表面CXCR4表达的变化;建立大鼠缺氧缺血性脑损伤模型,运用RT-PCR和Westernblotting检测造模后不同时点(1d、3d、5d、7d、14d、21d)大鼠脑部海马组织中SDF-1αmRNA转录和蛋白表达的改变情况;用AMD3100(CXCR4拮抗剂)拮抗rMSCs表面CXCR4后,免疫细胞化学和Westernblotting检测rMSCs诱导向神经细胞分化中神经元特异性烯醇化酶(neuron-specificenolase,NSE)和胶质纤维酸性蛋白(glialfibrillaryacidicprotein,GFAP)等神经细胞特异性标志物的阳性率及表达变化情况。结果:低氧培养6h及12h的rMSCsCXCR4mRNA及蛋白表达水平均较常氧培养组明显增加(P<0.01),10μg/LSDF-1α孵育后rMSCs的CXCR4表达水平明显增加(P<0.01);缺氧缺血性脑损伤模型的大鼠脑内SDF-1α蛋白表达显著增加(P<0.01);5mg/LAMD3100处理后的rMSCs在向神经细胞诱导分化中NSE和GFAP蛋白的表达明显减少。结论:微小剂量的SDF-1α可诱导低氧培养的rMSCs表面CXCR4的表达,而在缺氧缺血性脑损伤模型的大鼠脑内SDF-1α表达增加,从而使SDF-1/CXCR4轴的生物学效应得以增强;CXCR4拮抗的rMSCs在分化中神经细胞特异性标志物NSE和GFAP的表达降低,表明SDF-1/CXCR4轴在rMSCs定向神经分化修复缺血缺氧脑损伤中具有重要的调控作用。     

SDF-1:CXCR4 axis is fundamental for tissue preservation and repair

This Commentary discusses the role of the SDF-1:CXCR4 axis in tissue preservation and repair.Adult stem cell therapy has demonstrated the potential for tissue preservation and repair in multiple organ systems including the heart,¹ liver,² brain,³ skin,⁴ and kidney.⁵ In some organ systems, such as the liver, there is evidence of real regeneration,⁶ whereas in other organ systems, such as the heart, there is little evidence for tissue regeneration.^7,8 Regardless of whether tissue is regenerated in a given organ system, consistent evidence exists across all organ systems for modulation of cell death, leading to preservation of organ-specific tissue function. The similarity of tissue preservation across systems suggests that there may exist a common mechanism of use for adult stem cell therapy; furthermore, the findings that conditioned media from adult stem cells led to tissue preservation suggested that the effect was due, at least in part, to paracrine factor expression by the adult stem cells.^8,9Early in the investigation of the mechanisms related to stem cell-based tissue repair, the stromal cell-derived factor-1 (SDF-1):CXCR4 axis was identified as a key factor in the recruitment of stem cells to areas of tissue injury in multiple organ systems.^10,11,12 These findings led us to propose that the reestablishment of SDF-1 expression late after tissue injury could serve as a strategy to induce tissue repair;^10,13 this hypothesis is now the focus of an on-going clinical trial in patients with chronic heart failure ({"type":"clinical-trial","attrs":{"text":"NCT01082094","term_id":"NCT01082094"}}NCT01082094, clinicaltrials.gov). More recently, studies by our group and others have demonstrated that the expression of SDF-1 at the time of acute injury induces the recruitment of endogenous tissue-specific stem cells¹⁴ as well as direct preservation of end-organ cells such as cardiac myocytes.⁸Further demonstrating the importance of the SDF-1 in tissue repair, in this issue of the journal, Otsuka et al¹⁵ demonstrate the role of SDF-1 in inhibiting photoreceptor cell loss in retinal detachment. These investigators quantified the levels of vascular endothelial growth factor and SDF-1 in the vitreous of patients with retinal detachment (RD) and proliferative diabetic retinopathy as well as other pathologies. Vascular endothelial growth factor and SDF-1 levels are increased in proliferative diabetic retinopathy;^16,17 however, only SDF-1 levels were increased in RD. Interestingly, the up-regulation of SDF-1 in RD did not lead to proliferation of the vasculature of the retina. Consistent with the up-regulation of SDF-1 in response to RD is the correlation of vitreous SDF-1 levels with the extent and duration of RD.The investigators took their observation of increased SDF-1 in the vitreous of patients with RD and nicely investigated the effects of SDF-1 in the R28 retinal precursor cell line and a rat model of RD. Their data demonstrate that there is minimal SDF-1 expression in the normal eye but that within 3 days of experimentally induced RD there is increased SDF-1 expression in the anti-glial fibrillary acidic protein-positive astrocytes. Based on the known biology of the SDF-1, the increased expression of SDF-1 in the vitreous could have multiple effects including recruitment of bone marrow-derived stem cells and local inhibition of cell death in CXCR4-expressing cells.The lack of vascular changes associated with increased SDF-1 expression in patients with RD suggests that SDF-1 expression is not associated with significant recruitment of bone marrow-derived endothelial progenitor cells because it is associated with SDF-1-mediated myocardial healing.^8,10 Rather, the mechanism of SDF-1-mediated healing or tissue preservation in the eye seems to be more related to that seen in the skin, the healing of which is also not associated with vascular growth.¹⁸Otsuka et al¹⁵ demonstrate that SDF-1 expression in the eye in the setting of RD is associated with preservation of photoreceptors in the outer nuclear layer. Further demonstrating that the effects of SDF-1 are specific in response to injury, inhibition of SDF-1 signaling in the normal eye had no effects on cells in the outer nuclear layer. Of importance, the specificity of the SDF-1 response was mediated by the expression of CXCR4 by photoreceptors in the outer nuclear layer. CXCR4 expression in the normal retina was limited to the ganglion cell and the inner nuclear layers; however, in response to RD, there was significant CXCR4 expression in the outer nuclear layer and photoreceptor inner segments of the detached retina. The importance of the SDF-1:CXCR4 axis on cell survival was confirmed in studies using the R28 retinal precursor cell line in the setting of serum starvation, similar to what we have previously demonstrated in the setting of hypoxia and serum starvation using mesenchymal stem cells.⁸Perhaps directly in the eye¹⁵ and skin¹⁸ and more circuitously in other organ systems including the heart¹⁰ and brain,¹⁹ up-regulation of the SDF-1:CXCR4 axis is a fundamental response to tissue injury and modulating SDF-1⁸ and CXCR4²⁰ expression can serve as a strategy to preserve and restore end-organ function. The sequence of events after tissue injury is generalized in Figure 1: i) After tissue injury there is a local up-regulation of SDF-1 expression. The increased SDF-1 expression leads to homing of endogenous and bone marrow-derived stem cells in some organ system. ii) The end-organ cells up-regulate CXCR4 expression. The local up-regulation of CXCR4 can lead to cellular dysfunction²¹ but renders the cell responsive to SDF-1-mediated survival.Open in a separate windowFigure 1Schematic representation of the effects of tissue injury on SDF-1:CXCR4 expression and the local and remote effects of modulating their local expression.As delineated in Figure 1, the up-regulation of SDF-1 can lead to stem cell homing and engraftment that seems to be associated with neovascularization. In the absence of stem cell homing as seen in this study by Otsuka et al¹⁵ and in recent studies on SDF-1-mediated surgical wound healing,¹⁸ SDF-1 expression does not seem to induce neovascularization.One recurring question regarding the importance of the SDF-1:CXCR4 axis in tissue repair is if the axis is so critical, why does the up-regulation of CXCR4 on end-organ cells often occur at a time when SDF-1 expression is declining²²? We have recently demonstrated that although SDF-1:CXCR4 coexpression is required for normal cardiac development,²³ once cardiac myocyte fate is determined, CXCR4 expression is no longer required.²⁴ Thus, one hypothesis is that because SDF-1:CXCR4 expression is intimately involved in tumor metastases,^25,26 evolution has favored mammals that, in adulthood, have SDF-1 expression temporally misaligned with organ CXCR4 expression.The study of Otsuka et al¹⁵ extends the end-organ systems involved in SDF-1:CXCR4 tissue preservation and repair. It also raises some important and interesting questions for future studies. In particular, the eye in response to RD, like the bone marrow, seems to have sustained SDF-1 expression. In most organ systems studied to date, SDF-1 is rapidly up- and then down-regulated.²² Previous studies have suggested that SDF-1 expression in stroke and myocardial infarction is due to modulation of intracellular hypoxia-inducible factor-1α.²⁰ The lack of vascular endothelial growth factor expression in the vitreous of RD suggests that hypoxia-inducible factor-1α is not responsible for SDF-1-mediated expression in RD. Thus, the mechanism of SDF-1 up-regulation in RD remains to be elucidated.In summary, the study by Otsuka et al¹⁵ elucidates an important role for SDF-1 expression in preservation of photoreceptors and the outer nuclear layer of the eye after retinal detachment. These findings suggest that CXCR4 expression in the eye is modulated in injury and that exogenous SDF-1 delivery may serve as a strategy to further preserve tissue structure during healing. Future studies need to be focused not only on the therapeutic potential of SDF-1 in ocular disease states but also on the molecular mechanisms associated with SDF-1 up-regulation in the eye after retinal detachment as well as the mechanisms associated with specific CXCR4 expression in specific tissue layers of the eye.     

胎盘中SDF-1/CXCR4的表达与妊娠期高血压疾病的关系

目的研究趋化因子SDF-1及其受体CXCR4在妊娠期高血压疾病患者胎盘中的表达,分析其表达水平变化与妊娠期高血压疾病发病之间的关系。方法采用免疫组织化学法检测妊娠期高血压疾病患者胎盘组织中SDF-1、CXCR4的表达强度及表达范围。结果随着妊娠期高血压疾病病情程度的加重,胎盘组织中SDF-1及CXCR4表达强度及范围均呈渐进性下降趋势,且SDF-1的表达强度及范围明显优于CXCR4的表达强度及范围。结论 SDF-1、CXCR4表达强度及范围的变化与妊娠期高血压疾病的发病有重要关系。     

Production of stromal cell-derived factor-1 (SDF-1)and expression of CXCR4 in human bone marrow endothelial cells

This study investigated the production of stromal cell-derived factor-1 (SDF-1) and the expression of CXCR4 in human bone marrow endothelial cells (BMECs). Human BMEC cell line BMEC-1 cells expressed SDF-1 mRNA, and conditioned medium induced chemoattraction of CD34+ cells. Migration was not inhibited by pretreating the input cells with pertussis toxin, indicating that the chemoattractive activity was not dependent on SDF-1. Three-day culture of BMEC-1 and primary human BMEC cells produced 1,710+/-204 and 1,050+/-153 pg/mL SDF-1alpha, respectively, which was much less than primary human BM stromal cells (29,536+/-532 pg/ mL). By immuno-histochemistry, CXCR4 was detected in the endothelial cells lining sinusoids, arterioles, and venules in the bone marrow. However, cultured BMECs and BMEC-1 cells did not express CXCR4 on their surfaces. These results indicate that BMECs produce and release small amounts of SDF-1 and express CXCR4 in vivo only.     

Mobilization of myeloma cells involves SDF-1/CXCR4 signaling and downregulation of VLA-4

Adhesion molecules and stromal cell-derived factor-1 (SDF-1)/CXCR4 signaling play key roles in homing and mobilization of hematopoietic stem cells (HSC). Active signaling through SDF-1/CXCR4 and upregulation of adhesion molecules are required for homing, whereas downregulation of adhesion molecules and disruption of SDF-1/CXCR4 signaling are required for mobilization of HSC. We studied the surface expression of CXCR4 very late activation antigen (VLA)-4 and VLA-5 on myeloma cells mobilized with cyclophosphamide and GM-CSF in 12 multiple myeloma patients undergoing HSC mobilization for autologous transplantation. We also studied the plasma levels of SDF-1 in apheresis collection of these patients. We observed a statistically significant decrease in the levels of SDF-1 and surface expression of CXCR4 on myeloma cells in four consecutive apheresis collections compared with premobilization bone marrow specimens. We also observed a statistically significant decrease in surface expression of VLA-4 in myeloma cells in the apheresis collections compared with premobilization bone marrow samples. Furthermore, myeloma cells derived from apheresis collections had decreased adhesion and trans-stromal migration in response to SDF-1, which could be reversed by short incubation with interleukin-6. Hence, mobilization of myeloma cells involves SDF-1/CXCR4 signaling and downregulation of VLA-4.     

SDF-1/CXCR4信号通路在骨性关节炎病理进程中的作用

背景：骨性关节炎的发病机制错综复杂,其预防与治疗是当今医学界的难题之一,与其相关的信号通路的研究已成为国内外研究的热点,其靶向治疗有望成为攻克骨性关节炎的关键。 目的：总结SDF-1/CXCR4信号通路在诸多疾病尤其是在骨性关节炎发病中的作用,为骨性关节炎的靶向治疗提供科学依据。 方法：应用计算机检索PubMed和CBM数据库中2008-09/2010-07发表的相关文献。以主题检索为主要检索方法,结合限定检索等方法,以“SDF-1/CXCR4信号通路、骨性关节炎”和“SDF-1/CXC4 signaling pathway, osteoarthritis”为中英文检索词,选择与骨性关节炎SDF-1/CXCR4信号通路有关的文献,排除内容陈旧、重复的文章。 结果与结论：共检索到2 147篇文章,按纳入和排除标准对文献进行筛选,保留32篇文章进行综述。目前,SDF-1/CXCR4信号通路在诸多疾病的发生发展过程中具有重要作用,已成为目前世界医学的研究热点之一。有研究表明,SDF-1/CXCR4信号通路可能在骨性关节炎的发病中具有重要作用,而对该信号通路的干预可能成为预防与治疗骨性关节炎的靶点,有望成为今后骨性关节炎防治方面研究的热点。