Stimulation of beta adrenoceptors in a human monocyte cell line (U937) up-regulates cyclic AMP-specific phosphodiesterase activity.

Experiments were conducted using undifferentiated U937 cells, a human monocytic cell line, to establish an in vitro model to examine the hormonal regulation of the cyclic AMP (cAMP)-specific phosphodiesterase (PDE IV). Standard chromatographic techniques, coupled with the use of inhibitors and activators that are selective for various phosphodiesterase (PDE) isozymes, were used to establish the PDE isozyme profile in supernatant fractions of U937 cells. When PDE activity was assessed using 1 microM [3H]cAMP as a substrate, 70 to 90% of the total U937 cell supernatant activity in the major peak eluting from anion-exchange columns was inhibited by 30 microM rolipram, a selective inhibitor of PDE IV. The remaining activity was nearly abolished by 10 microM siguazodan or 10 microM cyclic GMP (cGMP,) selective inhibitors of the cGMP-inhibited PDE. Kinetic analyses of the enzyme activity contained within this major peak of PDE activity revealed a cAMP Km = 3 microM and a rolipram Ki = 0.5 microM, values characteristic of PDE IV. Additional studies revealed the presence of a small amount of Ca++/calmodulin-stimulated PDE, but no cGMP-stimulated PDE or cGMP-specific PDE activity. In an effort to induce PDE activity in intact U937 cells by producing a sustained increase in cAMP content, cells were treated for 4 hr with salbutamol (1 microM), rolipram (30 microM) or a combination of both agents. The combination of salbutamol and rolipram produced a 2- to 3-fold increase in PDE activity in U937 cells; when used alone, rolipram was without effect whereas salbutamol induced an increase that was approximately one-half of that observed with the combination. Isozyme isolation and characterization revealed that the overall elevation of cellular PDE activity could be accounted for by a 2- to 3-fold increase in the Vmax of PDE IV with no change in its Km. The induction of PDE IV by salbutamol was: 1) concentration- and time-dependent; 2) detectable only after prolonged (2-4 hr) agonist exposure; 3) preceded by an increase in cAMP content and an activation of cAMP-dependent protein kinase; 4) mimicked by 8-bromo-cAMP and prostaglandin E2; 5) reversible within 3 hr of salbutamol removal; and 6) abolished by cycloheximide or actinomycin D. Collectively, these results indicate that the major PDE isozyme in the soluble fraction of U937 cells is PDE IV and that the activity of this enzyme is increased markedly in cells after prolonged exposure to agents that increase cAMP content.     

1,25-Dihydroxyvitamin D3 induces collagen binding to the human monocyte line U937

Interactions of cells with components of the extracellular matrix can modulate cellular functions. We measured binding of a major matrix protein to U937 cells, a human promonocytic line. Radioiodinated type I or type III human collagen was bound only to U937 cells differentiated to a more mature phenotype with 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). Binding was observed at 4 degrees C and was saturable; Scatchard analysis of the binding to 1,25-(OH)2D3-pretreated U937 cells indicated a single class of high-affinity binding sites. Preincubation of U937 cells with interferon gamma did not induce collagen binding. Collagen binding did not appear to be dependent on fibronectin binding. Surface proteins of U937 cells were 125I labeled and cell membrane proteins resolved by affinity chromatography on collagen-Sepharose. Major specifically labeled bands of 180, 155, and 125 kD were identified in membrane fractions from 1,25-(OH)2D3-pretreated U937 cells only. 1,25-(OH)2D3 appears to specifically regulate collagen binding to monocyte precursors.     

Coated fibronectin induces adhesion in the human monocytic cell line U937

The differentiation inducing effect of coated human fibronectin (HFN) on U937 was investigated. U937 cells usually proliferate without stimuli. HFN induced the adhesion of about 20% of U937 cells in a serum free medium. HFN did not inhibit cell growth nor induce CD14 expression. The adhesion inducing activity of HFN was completely blocked by addition of anti-HFN antibody. Phorbor 12-myristate 13-acetate (PMA), another differentiation inducing agent, inhibited the growth of U937 cells but did not induce adhesion in the serum free medium. These data imply that HFN has a differentiation inducing effect on a human monocytic cell line and could be used as a biological response modifier.     

Properties of monocyte chemotactic and activating factor (MCAF) purified from a human fibrosarcoma cell line

A monocyte chemotactic and activating factor (MCAF) has been purified from TNF-stimulated 8387 human fibrosarcoma cell line-conditioned media. The purified MCAF showed microheterogeneity yielding two bands on SDS-PAGE analysis. Fibrosarcoma-derived MCAF specifically competed with THP-1 (a human monocytic cell line)-derived 125I-labeled MCAF in binding to human PBMC, whereas a similar basic heparin-binding leukocyte chemoattractant, IL-8, did not. The purified MCAF stimulated superoxide anion and N-acetyl beta-D glucosaminidase-releasing activity in human monocytes, as well as monocyte cytostatic augmenting activity against tumor cells and chemotactic activity for monocytes. When injected subcutaneously into Lewis rat ears, the purified human MCAF also induced considerable in vivo local monocyte infiltration beginning at 3 h and becoming maximal at 18 h. In conclusion, the data presented in this paper indicate that MCAF is a potent activator of monocytes as well as a monocyte recruitment factor that acts through receptors that are specific for this novel molecule. This novel cytokine might have an important role in tumor growth control due to its ability to attract and activate monocytes.     

Human granulocyte-macrophage colony-stimulating factor induces expression of the tumor necrosis factor gene by the U937 cell line and by normal human monocytes.

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) exerts profound effects on the proliferation, differentiation, and effector function of myeloid lineage cells. In contrast to its growth-promoting effects on normal myeloid progenitor cells, we found that GM-CSF unexpectedly inhibited the colony growth of U937 cells in agar culture. Furthermore, medium conditioned by recombinant GM-CSF(rGM-CSF)-treated U937 cells was found to exert an inhibitory effect on subsequent U937 colony growth that was partially due to the presence of tumor necrosis factor (TNF). By Northern blot analysis, rGM-CSF was shown to induce expression of the TNF gene in U937 cells and in T-lymphocyte-depleted, monocyte-enriched peripheral blood mononuclear cells. Furthermore, rGM-CSF was observed to significantly enhance TNF secretion by monocytes stimulated with endotoxin and phorbol myristate acetate (PMA). These data suggest that some of the biological effects of GM-CSF may be amplified through the release of monokines such as TNF.     

Specific binding of the human monocytic cell line U937 to the alternatively spliced connecting segment (IIICS) of fibronectin

U937 cells attach to the RGDS-containing 80-kD fragment of fibronectin (Fn). The present report examined whether these cells recognize other domains of Fn. U937 cells attach to a 38-kD fragment derived from the A chain of Fn, which includes the Hep II domain and most of the alternatively spliced IIICS region. U937 did not bind to a 58-kD fragment derived from the B chain (which lacks IIICS) and has the Hep II site. They also did not bind to a 31-kD COOH-terminal fibrin-binding fragment or to a 29-kD fragment containing the Hep I domain. Cell adhesion to the 38-kD fragment was not inhibited by the 80-kD fragment, by GRGDSPC synthetic peptides, or by a mAb directed to the RGDS-containing domain of Fn. Attachment was completely inhibited by the 38-kD fragment and by the synthetic peptide CS-1, comprising the first 25 amino acid residues of IIICS. These results indicate that U937 cells interact with two sites of Fn, the RGDS-containing region, and the IIICS region.     

Isolation and expression of cDNA clones encoding a human receptor for IgG (Fc gamma RII)

We have cloned and expressed a cDNA encoding a human receptor for IgG (Fc gamma R) from the monocyte cell line U937. The deduced structure is a 35-kD transmembrane protein with homology to the mouse Fc[gamma 2b/gamma 1] receptor amino acid sequence of approximately 60% in the extracellular domain. The signal sequence is homologous to the mouse Fc gamma R alpha cDNA clone, while the transmembrane domain shares homology with mouse Fc gamma R beta cDNAs. The cytoplasmic domain is apparently unique. The extracellular domain shows significant homology to proteins of the Ig gene superfamily, including the human c-fms protooncogene/CSF-1 receptor. Mouse Ltk- cells transfected with the human Fc gamma R cDNA express a cell-surface receptor that selectively binds human IgG and is recognized by the anti-Fc gamma RII mAb IV.3. Antibodies against peptides derived from the human Fc gamma R sequence specifically stain U937 cells, but not an Fc gamma RII-bearing B-lymphoblastoid cell line (Daudi). These results identify the human Fc gamma RII as the homologue of mouse Fc[gamma 2b/gamma 1] R, and provide evidence for heterogeneity of Fc gamma RII expressed on monocytes and B cells.     

人骨肉瘤细胞株U2-OS中分离并鉴定肿瘤干细胞

目的:采用无血清培养法从人骨肉瘤细胞株U2-OS中分离肿瘤干细胞,检测肿瘤干细胞特异性标志物Stro-1的表达。方法:实验于2006-02/2007-02在兰州大学第二医院骨科研究所完成。①实验材料:人骨肉瘤细胞株U2-OS由中国科学院细胞库提供;DMEM/F12(1∶1)培养基(Gibco公司);胎牛血清(杭州四季青公司);PCR引物由上海生物工程公司合成。②实验方法:取原代培养的骨肉瘤细胞经胰蛋白酶消化制备单细胞悬液,用含表皮生长因子20μg/L、碱性成纤维细胞生长因子20μg/L、L-谷氨酰胺2mmol/L、胰岛素4U/L、青霉素100U/mL和链霉素100U/mL,pH7.2～7.5的无血清DMEM/F12培养基重悬细胞,常规培养5～7d,待培养基中悬浮的肉瘤细胞球体积较大后,用无血清培养基重新吹打成单细胞悬液,按1∶2或1∶3比例传代。③实验评估:从上述骨肉瘤细胞株中分离出的肿瘤细胞球,用MTT法检测其增殖能力,免疫磁珠分选Stro-1阳性细胞,反转录-聚合酶链法检测Stro-1阳性细胞中Stro-1 mRNA的表达,免疫细胞化学染色的方法检测分化后成骨细胞特异性抗原的表达。结果:①肿瘤干细胞增殖活性:增殖潜伏期约为24h,传代后1～2d即可见肿瘤干细胞形成,以后体积逐渐增大。第7天吸光度值最高,与0d吸光度值比较差异有显著性意义(P<0.01)。②免疫磁珠法分选Stro-1阳性细胞:分选的Stro-1 细胞接种于无血清培养基后,24～48h即可形成和原代肿瘤干细胞球形态一样的干细胞球,而Stro-1-细胞却不能形成肿瘤细胞球。③骨肉瘤干细胞中Stro-1mRNA的表达:Stro-1 细胞和Stro-1-细胞mRNA扩增产物的吸光度值二者比较差异有显著性意义(P<0.05)。④肿瘤干细胞分化:分化2周的肿瘤干细胞骨形态蛋白及Ⅰ型胶原酶均呈阳性表达。结论:骨肉瘤细胞株中存在骨肉瘤干细胞,并具有自我更新和多向分化的能力。     

Establishment of long-term monocyte suspension cultures from normal human peripheral blood

The long-term suspension growth of normal, immature myeloid cells from fresh human cord blood was recently reported and required cells separated on supplemented discontinuous Percoll gradients, growth in media containing hydrocortisone and vitamins D3, and gentle, continuous agitation (13). When normal adult bone marrow (six donors) or blood from Epstein-Barr virus (EBV)-seropositive donors (nine donors) was used as a source of fresh human leukocytes, only short-term proliferation of myeloid cells was achieved with the same techniques. However, when leukocytes prepared from EBV seronegative normal adult peripheral blood were used, pure populations of monocytes and macrophages that replicate slowly in liquid suspension culture for greater than 5 mo were repeatedly obtained from three independent donors. These cultures consists of several morphologically distinguishable monocytic cell types, including an approximately 20% adherent macrophage population. The monocytic nature of these cultures was confirmed by cytochemical, immunological, and functional criteria. These monocytes retain a normal chromosome pattern and can be induced to differentiate to phagocytic cells by treatment with tetradecanylphorbal acetate. Eventually, the cultures terminate as nonreplicating mature macrophages. These liquid suspension cultures should be a valuable resource for morphological, biochemical, and functional studies of developing monocyte-macrophages and their interaction with other cell types in normal and various pathological situations.     

Effect of a marine toxin on human peripheral blood monocytes

The effect of okadaic acid (OA), a non-TPA (12-0- tetradecanoylphorbol-13-acetate)-type tumor promoter, on interleukin 1 (IL-1) synthesis in human peripheral blood monocytes in vitro was examined using immunofluorescence and the mouse thymocyte assays. Stimulation of IL-1 was shown with 0.05 microgram OA/ml (the peak response), while concentrations of greater than 1.0 micrograms OA/ml showed significant inhibition of IL-1 synthesis by monocytes in the immunofluorescence analysis. Okadaic acid added directly to mouse thymocytes showed a peak response in IL-1 synthesis at 0.01 microgram OA/ml, while significant inhibition was shown for concentrations of OA greater than 0.1 microgram OA/ml. Supernatants of monocytes exposed to OA gave maximum stimulation at 0.05 microgram OA/ml for both 24 and 48 hr exposures. Significant inhibition of IL-1 synthesis in monocytes was shown by supernatants obtained from monocytes exposed 24 hr with 1.0 microgram OA/ml. Addition of various concentrations of OA to monocyte cultures in the presence of increasing concentrations of monoclonal antibody to OA showed significant reduction of the inhibition of IL-1 synthesis by OA at the 0.10 microgram level, but more significantly at the 1.0 microgram OA/ml level. The higher levels of OA associated with inhibition of IL-1 synthesis in monocytes in this study were comparable to the concentrations used in the tumor promotion studies by others. The reversal of the inhibitory effect of OA by the monoclonal antibody to OA is of interest and should be applicable to further studies on the mechanism of OA tumor promotion.     

全反式维甲酸对人白血病细胞系U937细胞生长的影响及其机制分析

目的 研究全反式维甲酸(ATRA)作用于人白血病细胞系U937细胞后,对细胞生长的影响及可能的机制.方法 收集1 μmol/L ATRA作用后的U937细胞,利用流式细胞术检测细胞周期分布,Western blot法检测细胞周期相关蛋白(cyclinA、p16、021、027及p27相关分子skp2)表达水平的变化,采用免疫沉淀方法检测U937细胞中027与Skp2的结合情况.结果 流式细胞术分析显示,在1μmol/L ATRA作用72 h后,72%的U937细胞被阻滞在G0/G1期.Western blot分析显示,ATRA能诱导cyclinA、Skp2表达下凋,p21、p27表达上调.免疫沉淀法检测结果显示在U937细胞中p27与skp2存在相互结合的情况.结论 ATRA可能主要通过诱导p27表达上调引起U937细胞生长阻滞,其过程是由p27相关分子Skp2所介导的.     

Characterization of the adhesion of the human monocytic cell line U937 to cultured endothelial cells.

Adhesion of blood-borne monocytes to the vascular endothelium is the first step in the infiltration of this leukocyte into the vessel wall or the interstitial space during inflammation. A significant role for the monocyte in both wound healing and atherogenesis is now well accepted. The molecular interactions involved in monocyte attachment to the endothelium are unknown. To study this phenomenon we have developed an in vitro system that uses the human monocytic tumor cell line U937 as a model for the blood-borne monocyte. 51Cr-labeled U937 cells were found to adhere with high affinity to cultured endothelial cells (ECs) from several sources. Much less binding was observed to either smooth muscle cells or fibroblasts from several species. Conditioned medium and cocultivation experiments ruled out the possibility that target cells could affect U937 cell binding by secretion of factors. Binding of U937 cells to porcine aortic ECs reached equilibrium after 30 min at 37 degrees C and 90 min at 4 degrees C with similar extent of binding at the two temperatures. Binding of U937 to the endothelium reached saturation at 9-12 U937 per porcine aortic EC (semi-confluent) with half-maximal binding at 1.5 X 10(6) U937 cells/ml. Bound cells dissociated with a half-life of 20 h at 37 degrees C. Adhesion of U937 cells was blocked by prior incubation of ECs with normal monocytes but not with platelets, lymphocytes, or neutrophils. Trypsin treatment or detergent solubilization of ECs inhibited U937 cell binding. A striking effect of EC density on monocytic cell adhesion was observed with bovine, rat, and porcine ECs. Confluent cultures of these cells exhibited negligible binding of U937, but when plated sparsely, the same cells were excellent targets for U937 cell adhesion. In addition, when confluent cultures of bovine aortic ECs were "wounded" with a cotton swab and then allowed to recover for 24 h at 37 degrees C, U937 cells were found to adhere most readily to the ECs migrating into the wound and neighboring the wound but not to ECs in the confluent monolayer away from the wound edge. These latter results may have implications for the focal adhesion of monocytes to the vessel wall in vivo.     

1 alpha,25-dihydroxyvitamin D3 induces maturation of the human monocyte cell line U937, and, in association with a factor from human T lymphocytes, augments production of the monokine, mononuclear cell factor

The monocyte factor, interleukin 1, or other factors homologous with interleukin 1, modulates functions of a variety of cells, including T and B lymphocytes, synovial cells, and chondrocytes. We have reported that a human monocyte cell line, U937, produces interleukin 1 when incubated with a soluble factor from lectin-stimulated T lymphocytes. We have also shown that U937 cells have a specific cytosolic receptor for 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25[OH]2D3). We now report that 1 alpha,25(OH)2D3(10(-11)-10(-10) M) induces maturational changes in the U937 cells similar to those produced by conditioned medium from lectin-stimulated T lymphocytes (increase in Fc receptors and OKM1 binding and decrease in proliferation), but does not induce monokine production as measured by mononuclear cell factor activity. 1 alpha,25(OH)2D3 is 200-300-fold more effective than 25-hydroxyvitamin D3, which is consistent with the known biological potency of these vitamin D3 metabolites. 1 alpha,25(OH)2D3 and the lymphokine together markedly augment maturational effects and, in addition, augment monokine production. The specificity of the interaction is further demonstrated by the lack of augmentation of monokine production with 1 beta,25-dihydroxyvitamin D3 in the presence of lymphokine. These interactions of a classical hormone and the hormonelike product(s) of the immune system with U937 cells serve as a model for human monocyte/macrophage differentiation and suggest a role for these interactions in some aspects of inflammation.     

人外周血树突状细胞的分离与鉴定

目的:体外分离培养并鉴定人外周血树突状细胞,并观察其抗原呈递功能。方法:实验于2005-05/2006-11在南方医科大学南方医院肿瘤中心生物治疗实验室完成。从人类白细胞抗原A2表达阳性的健康人外周血中分离获得单个核细胞。培养5h后洗涤贴壁细胞,加入含有10%人AB血清的RPMI1640培养基,及重组人粒细胞-巨噬细胞集落刺激因子和重组人白细胞介素4,于培养的第1,3,6天对树突状细胞的形态、表型进行分析,并定期检测树突状细胞的纯度与得率。抽取与以上树突状细胞不同来源的其他健康人外周血。经淋巴细胞分离液分离后,获取非贴壁细胞,用含10%人AB血清的1640培养基重悬,加入白细胞介素2继续孵育6d,作为同种异体T淋巴细胞。将树突状细胞分为两组,一组按常规方法培养6d,另一组在培养至第5天时加入黑色素瘤抗原基因A3编码的多肽继续培养24h。在经紫外线处理后的96孔板中,分别加入树突状细胞悬液1×104,5×103,2×103,1×103细胞/每孔,以自身T淋巴细胞作为对照,每孔设3个复孔,分别加入1×105淋巴细胞/每孔。评价树突状细胞刺激T淋巴细胞增殖的能力。结果:①单个核细胞体外培养至第6天,可获得大量、90.81%高纯度的树突状细胞,能够较高地表达21.8?1a、99.0%HLA-DR、63.4?80、18.9?83和80.6?86。②将诱导培养6d获得的两组树突状细胞作为刺激细胞,以不同的浓度与同种异体淋巴细胞混合,均可产生增殖反应;经过黑色素瘤抗原基因A3编码的多肽处理的各种比例的树突状细胞,较相应未经黑色素瘤抗原基因A3编码的多肽处理的树突状细胞激发淋巴细胞增殖的能力明显增强,浓度相对较高的树突状细胞刺激效果最明显,能够强烈地激发同种混合淋巴细胞增殖。结论:得到了一群较高程度表达CD83、CD86和HLA-DR分子、体外可强烈激发同种异体T淋巴细胞增殖的树突状细胞群。     

Isolation and purification of the Rh(D) blood group receptor component from human erythrocyte membrane

The Rh(D) antigen of human red blood cell membranes has been isolated as a homogeneous immunologically intact component. The method of preparation was as follows: Red cell membranes were prepared free of hemoglobin and components were solubilized using ethylenediaminetetraacetic acid (EDTA) followed by sodium chloride. Diaflo® ultrafilter membranes were used to separate solubilized membrane components into different molecular weight classes. The Rh(D) activity was demonstrated in the molecular weight class between 10 000 and 20 000. This fraction, which had six components by disc gel electrophoresis, was further purified by isoelectric focusing on a pH gradient of 3 to 10, followed by a pH gradient of 5 to 8. The Rh(D) antigen was eluted as a single component, migrated as a discrete band on disc gel electrophoresis, and inhibited the agglutination of anti-Rh(D) antibody. When the Rh(D) antigen was injected into guinea pigs, a high titer of anti-Rh(D) antibody was obtained.     

Isolation and partial characterization of a specific alpha-fetoprotein receptor on human monocytes.

Since a large body of data has suggested a significant role for alpha-fetoprotein (AFP) in the regulation of the immune response at a number of levels, we examined the possibility of a specific receptor for AFP on the immune recognition cell, the monocyte/macrophage. Microscopic autoradiography exhibited an obvious binding of AFP almost exclusively on human peripheral monocytes but not on lymphocytes. In a human monocyte cell line (U937) Scatchard plot analysis indicated the presence of two distinct AFP-specific binding sites with a Kd of 5 x 10(-11) M, 49 binding sites per cell, and 2.5 x 10(-7) M, 7,800 binding sites per cell. 125I-ASD-AFP, AFP-radiolabeled bifunctional photoactivatable thio-cleavable cross-linker, was used to isolate the AFP binding protein from U937 cells. After ultraviolet photoactivation, 125I-sulfosuccinimidyl 2-(p-azido-salicylamido)ethyl-1,3'-dithiopropionate was covalently linked to the putative receptor. Autoradiography of SDS gradient PAGE under reducing conditions showed a major radiolabeled band at between 62 and 65 kD. To confirm the specificity of the finding, recombination of AFP with the isolated receptor was examined in artificially reconstituted membrane vesicles, which also resulted in a single band at approximately 62-65 kD by SDS-PAGE autoradiography. From the data above, we concluded that human monocytes possess a specific AFP binding protein on the membrane, a putative receptor, which may be involved with the physiological regulation of the immune response.     

地塞米松对人单核细胞糖皮质激素受体蛋白表达的影响

目的研究不同浓度的地塞米松,在不同的刺激时间下对人单核细胞糖皮质激素受体蛋白(GRα,GRβ)表达的影响。方法对培养的人单核细胞株THP1给予不同浓度的地塞米松,在不同的刺激时间下,采用Westernblotting检测细胞中GRα、CRβ蛋白表达。结果人的单核细胞中存在GRQ、GRB受体。GRQ表达量在相同浓度地塞米松刺激下,随刺激时间的延长表现出下调;GRB表达量随地塞米松刺激浓度的增加以及刺激时间的延长而上调。结论GRα表达量随地塞米松刺激时间的延长表现出下调。GRβ表达量随地塞米松浓度的增加、刺激时间的延长而上调,具有一定的剂量和时间依赖性。GRα、GRβ的表达受糖皮质激素的调节。     

人外周血单核细胞体外诱导树突状细胞的形态学观察与功能研究

目的：探讨从人外周血单核细胞体外培养扩增的树突状细胞(dendritic cell,DC)形态学特征及其活性。方法：人外周血常规分离单个核细胞，粘附6h后去除悬浮细胞，以细胞因子粒细胞-巨噬细胞集落刺激因子(GM-CSF)、白细胞介素-4(IL-4)进行诱导培养7d，并进行形态学特征，细胞表型和淋巴细胞刺激能力鉴定。结果：培养1周即可得到大量DC，形态学观察可见细胞形态不规则，细胞表面大量突起，为典型的DC特征，免疫组化和间接免疫荧光显示CDla阳性表达率达80％～95％，并能刺激同种淋巴细胞增殖反应。结论：人外周血单核细胞可经GM-CSF、IL-4诱导培养成DC，具有典型的树突状细胞的形态学特征及抗原呈递能力。