Expression of surface antigen and mRNA for the CD11c (alpha X, p150) subunit of the human leukocyte adherence receptor family in hematopoietic cells

Saliva Suppresses Osteoclastogenesis in Murine Bone Marrow Cultures

Saliva can reach mineralized surfaces in the oral cavity; however, the relationship between saliva and bone resorption is unclear. Herein, we examined whether saliva affects the process of osteoclastogenesis in vitro. We used murine bone marrow cultures to study osteoclast formation. The addition of fresh sterile saliva eliminated the formation of multinucleated cells that stained positive for tartrate-resistant acid phosphatase (TRAP). In line with the histochemical staining, saliva substantially reduced gene expression of cathepsin K, calcitonin receptor, and TRAP. Addition of saliva led to considerably decreased gene expression of receptor activator of nuclear factor kappa-B (RANK) and, to a lesser extent, that of c-fms. The respective master regulators of osteoclastogenesis (c-fos and NFATc1) and the downstream cell fusion genes (DC-STAMP and Atp6v0d2) showed decreased expression after the addition of saliva. Among the costimulatory molecules for osteoclastogenesis, only OSCAR showed decreased expression. In contrast, CD40, CD80, and CD86—all costimulatory molecules of phagocytic cells—were increasingly expressed with saliva. The phagocytic capacity of the cells was confirmed by latex bead ingestion. Based on these in vitro results, it can be concluded that saliva suppresses osteoclastogenesis and leads to the development of a phagocytic cell phenotype.

Resident alveolar macrophages are susceptible to and permissive of Coxiella burnetii infection

Coxiella burnetii, the causative agent of Q fever, is a zoonotic disease with potentially life-threatening complications in humans. Inhalation of low doses of Coxiella bacteria can result in infection of the host alveolar macrophage (AM). However, it is not known whether a subset of AMs within the heterogeneous population of macrophages in the infected lung is particularly susceptible to infection. We have found that lower doses of both phase I and phase II Nine Mile C. burnetii multiply and are less readily cleared from the lungs of mice compared to higher infectious doses. We have additionally identified AM resident within the lung prior to and shortly following infection, opposed to newly recruited monocytes entering the lung during infection, as being most susceptible to infection. These resident cells remain infected up to twelve days after the onset of infection, serving as a permissive niche for the maintenance of bacterial infection. A subset of infected resident AMs undergo a distinguishing phenotypic change during the progression of infection exhibiting an increase in surface integrin CD11b expression and continued expression of the surface integrin CD11c. The low rate of phase I and II Nine Mile C. burnetii growth in murine lungs may be a direct result of the limited size of the susceptible resident AM cell population.

Attenuation of allergen-induced responses in CCR6-/- mice is dependent upon altered pulmonary T lymphocyte activation

We have established a defect in CCR6-/- mice in response to a cockroach allergen airway challenge characterized by decreased IL-5 production, reduced CD4+ T and B cells as well as decreased eosinophil accumulation. To determine the nature of the defect in CCR6-/- mice T lymphocyte populations from allergen-sensitized wild-type mice were transferred into sensitized CCR6-/- mice. The reconstituted response was characterized by an increase in IL-5 levels, eosinophil accumulation, and serum IgE levels in recipient CCR6-/- mice. Analysis of lymphocytes from draining lymph nodes of CCR6+/+ and CCR6-/- sensitized or challenged mice demonstrated a significant decrease in IL-5 and IL-13 production in CCR6-/- mice. In contrast, the systemic response in allergen-rechallenged spleen cells demonstrated no significant alteration in allergen-induced cytokine production. Transfer of isolated splenic T lymphocytes from sensitized CCR6+/+ mice induced airway hyperresponsiveness in wild-type but not CCR6-/- naive mice, suggesting that T cells alone were not sufficient to induce airway hyperresponsiveness in CCR6-/- mice. Additional analysis demonstrated decreased CD11c+, CD11b+ and CD11c, and B220 subsets of dendritic cells in the lungs of CCR6-/- mice after allergen challenge. Using in vitro cell mixing studies with isolated pulmonary CD4+ T cells and CD11c+ cells from CCR6+/+ or CCR6-/- mice, we demonstrate alterations in both CCR6-/- T cells and CCR6-/- pulmonary APCs to elicit IL-5 responses. Altogether, the defect in CCR6-/- mice appears to be primarily due to an alteration in T cell activation, but also appears to include local pulmonary APC defects.

Production of inducible nitric oxide is required for monocytic differentiation of U937 cells induced by vitamin E-succinate

Many putative differentiating agents arrest cell growth prior to progression of the cell through differentiation. Vitamin E-succinate is known to be a potent modulator of haematopoietic differentiation as well as an inhibitor of cell growth in vitro and in vivo. In this study, we examined whether vitamin E-succinate could modulate the monocytic differentiation of U937 human monoblasts. Treatment with vitamin E-succinate for 1–4 days inhibited the proliferation of U937 cells. Vitamin E-succinate also induced monocytic differentiation as indicated by the increase in nitro blue tetrazolium reduction activity, and the expression of monocyte specific cell surface antigen, CD11c, and integrins alpha5 and beta1. The monocytic differentiation of U937 cells was also induced when the cells were cultured in fibronectin-coated wells. Monocytic differentiation was enhanced when the cells were treated with both vitamin E-succinate and fibronectin, suggesting that vitamin E-succinate and fibronectin synergistically act on monocytic differentiation of U937 cells. During monocytic differentiation of U937 cells induced by vitamin E-succinate and/or fibronectin, nitric oxide was detected in supernatants. The production of nitric oxide was not detected when monocytic differentiation of U937 cells was induced by phorbol-12 myristate 13-acetate, a well known inducer of macrophage-like cell differentiation. Vitamin E-succinate and/or fibronectin induced monocytic differentiation was blocked by the treatment of nitric oxide synthase inhibitor, N-G-monomethyl-L-arginine. In contrast, treatment of cells with sodium nitroprusside, a chemical nitric oxide donor, stimulated monocytic differentiation of U937 cells at an early time point. Taken together, these results suggest that nitric oxide is an important intermediator at an early stage of vitamin E-succinate- and/or fibronectin-induced monocytic differentiation of U937 cells.

CD11c integrin gene promoter activity during myeloid differentiation

The integrin CD11c/CD18 functions as a cell surface receptor for numerous soluble factors and proteins (LPS, fibrinogen, iC3b), mediates leukocyte interactions with other cell types and is a signal transducing receptor. CD11c/CD18 is found primarily on myeloid cells, where its expression is regulated both during differentiation and during monocyte maturation into tissue macrophages. To determine the transcription factors and cis-acting elements driving the developmentally-regulated expression of CD11c/CD18 the proximal regulatory region of the CD11c gene has been structurally and functionally characterized using the U937 and HL-60 cell lines as myeloid differentiation models. The tissue-specific activity of the CD11c promoter is conferred by two Sp1-binding sites and an adjacent C/EBP-binding element, with a likely contribution from other transcription factors with a more limited tissue distribution (PU.1, Oct-2, Myb). The participation of Sp1 in the transcription of the CD11c gene strongly suggests that CD11c/CD18 expression is dependent on the proliferative state of the cell, thus establishing a first level of control for the regulated expression of CD11c/CD18 during myeloid differentiation. The differentiation responsiveness of the CD11c promoter has been mapped to an AP-1-binding site whose mutation greatly decreases the inducibility of the promoter during the PMA-triggered differentiation of U937 cells. Although AP-1 mediates the responsiveness to several other differentiating agents including GM-CSF, additional elements are required for induction of the CD11c promoter activity upon Sodium Butyrate-triggered differentiation. In fact, the Sodium Butyrate-responsiveness and the presence of both AP-1- and C/EBP-binding sites suggests that the proximal regulatory region of the CD11c promoter might include an extracellular matrix-response element. As a whole, the transcription of the CD11c gene appears to be controlled by the proliferative state of the cell and is tightly coupled to progression along the myeloid differentiation pathway. The differentiation inducibility of the CD11c promoter has been further demonstrated after stable transfection into U937 cells, where the -361/+43 fragment retains the capacity to drive luciferase expression upon PMA-, GM-CSF- or Sodium Butyrate-triggered myeloid differentiation. Thus, while the characterization of the transcription factors regulating CD11c expression is still in progress, the CD11c promoter has been shown to constitute a very useful tool for the identification of myeloid-differenting agents which might be of potential therapeutical interest.

Differentiation of U-937 promonocytic cells by etoposide and ICRF-193, two antitumour DNA topoisomerase II inhibitors with different mechanisms of action

We have compared the action on U-937 human promonocytic leukemia cells of two DNA topoisomerase II inhibitors, namely the epipodophyllotoxin etoposide and the bisdioxopiperazine ICRF-193. One hour pulse-treatment with 3 microM etoposide caused topoisomerase associated, primary DNA breakage, which was rapidly followed by apoptosis. By contrast, these effects were not observed upon pulse-treatment with 6 microM ICRF-193. However, continuous treatments with subcytotoxic concentrations of etoposide (0.15 microM) and ICRF-193 (0.3 microM) produced several similar effects, namely decreased cell proliferation, accumulation of cells at G2, increase in cell mass, and induction of differentiation. Under these conditions, etoposide produced a biphasic activation of protein kinase C, which consisted in an early transient activation (from hours 1 to 6) of the membrane-bound enzyme followed by a later activation (hour 48) of the total, membrane-bound and cytosolic enzyme. By contrast, ICRF-193 only provoked a late activation (from hours 72 to 96) of the total enzyme. When used at differentiation-inducing concentrations, both topoisomerase inhibitors caused a great stimulation of AP-1 binding activity, with maximum value at hour 12 in etoposide-treated cells and at hour 48 in ICRF-193-treated cells. By contrast, the binding activity of the NF-kappa(B) and EGR-1 transcription factors was little affected. It is concluded that topoisomerase II inhibitors may induce the differentiation of promonocytic cells, independently of their capacity to cause DNA strand breaks. However, there are other effects, such as the early activation of protein kinase C, which are probably derived from the production of primary DNA breakage by some anti-topoisomerase drugs.

Premature parturition is characterized by in utero activation of the fetal immune system

OBJECTIVE

At birth the fetus emerges from a sterile environment into a nonsterile one. This process is associated with activation of the fetal immune system which protects the fetus against infection in the newborn period. We conducted this study to determine whether activation of the monocyte-neutrophil system occurs in fetuses before premature birth.

STUDY DESIGN

Forty patients in premature labor with intact membranes underwent cordocentesis for research purposes. Fetal blood was analyzed with the use of flow cytometry to measure the cell surface markers CD11c, CD13, CD15, and CD67, which are associated with monocyte and neutrophil activation, and CD14 and CD63, which were used as controls.

RESULTS

Twenty-eight percent (11/40) of the infants were delivered prematurely within 72 hours of entering the study while the remainder were delivered at term. Our data clearly indicate that premature infants delivered within 72 hours had a higher percentage of CD11c, CD13, CD15, and CD67 than those delivered at term. In contrast, there were no significant differences in the percentages of CD14 and CD63.

CONCLUSION

Activation of the monocyte-neutrophil system exists in fetuses destined for premature delivery. These findings indicate that premature parturition is associated with in utero immune system activation.

Modulation of HSP70 and HSP27 gene expression by the differentiation inducer sodium butyrate in U-937 human promonocytic leukemia cells

The treatment of U-937 human promonocytic cells with the differentiation inducer sodium butyrate (0.75 mM) transiently increased heat-shock protein 70 (HSP70) mRNA levels between 3 and 6 h, and heat-shock protein 27 (HSP27) mRNA levels between 12 and 24 h, as indicated by northern blot assays. Gel retardation assays indicated that butyrate also stimulated heat-shock factor (HSF) binding activity between 3 and 6 h, suggesting that the activation of HSP70 gene expression was mediated by the heat-shock factor DNA response element (HSE). In addition, the treatment provoked a biphasic alteration of the c-fos mRNA level, consisting of a slight increase between 0.5 and 3 h followed by a greater increase between 12 and 48 h, while it caused a single increase between 12 and 48 h in c-jun mRNA level. The possible involvement of the heat-shock protein genes in the butyrate-induced differentiation of U-937 cells is discussed.

Vitamin E succinate induction of HL-60 cell adhesion: a role for fibronectin and a 72-kDa fibronectin-binding molecule

HL-60 cells, growing as single cells in suspension, exhibit marked cell-cell adhesion when treated for 24 hours with 10 micrograms/ml RRR-alpha-tocopheryl succinate, also called vitamin E succinate (VES). VES-induced cell-cell adhesion is dependent on divalent cations and a functional cytoskeleton and is protein mediated. Cell adhesion molecules CD11a/CD18, CD11b/CD18, CD29, and CD54 do not appear to be mediating VES-induced cell adhesion. HL-60 cells treated with VES adhere to fibronectin-coated plastic and secrete elevated levels of fibronectin. A 72-kDa fibronectin-binding membrane molecule was detected on VES-treated HL-60 cells, and antibodies to fibronectin were shown to inhibit VES-induced cell aggregation. VES induction of HL-60 cell-cell adhesion is proposed to result from increased amounts of extracellular fibronectin binding to VES-induced cell surface fibronectin-binding molecules.

The action of the DNA intercalating agents 4'-(9-acridinylamino) methanesulphon-m-anisidide and 1,4-bis(butylamino) benzo[g]phthalazine in U-937 human promonocytic cells: relationship between cell cycle and differentiation

The action of two structurally related DNA intercalating agents has been studied and compared, namely 4'-(9-acridinylamino) methanesulphon-m-anisidide (amsacrine, mAMSA) and 1,4-bis(butylamino)benzo[g]phthalazine (ABP) on the cell cycle and differentiation of U-937 human promonocytic leukemia cells. mAMSA (0.1 microM) and ABP (4 microM) reduced the proliferation activity to a similar extent and caused little cell mortality. At these subcytotoxic concentrations mAMSA induced the cells to accumulate at the G2 phase of the cycle, while cycle inhibition provoked by ABP was not phase specific. In addition, mAMSA caused an increase in the cell mass while ABP provoked cell shrinkage. This was consistent with the fact that ABP considerably inhibited protein synthesis, while mAMSA did not significantly affect this activity. SDS/K+DNA precipitation assays indicated that mAMSA, but not ABP, stimulated protein-DNA covalent complex formation. Finally, it was found that mAMSA, but not ABP, elicited the expression of differentiation markers, namely nitroblue tetrazolium reduction, activation of vimentin and leukocyte integrin (CD11b/CD18 and CD11c/CD18) expression, and downregulation of c-myc expression. The DNA intercalators doxorubicin and mitoxantrone, which like mAMSA induced the cells to accumulate at the G2 phase and increased the cell mass, induced the expression of differentiation markers. In contrast, the intercalators aclarubicin and caffeine and the non-intercalator novobiocin, which produced minor alterations on cell-cycle distribution and caused cell shrinkage, did not significantly elicit differentiation. These results support the conclusion that differentiation of myeloid leukemia cells by cytostatic drugs depends on the perturbations of the cell cycle, leading to disproportionate increases in cell mass.

Enhanced ICAM-1-dependent adhesion of myelomonocytic cells expressing increased levels of beta 2-integrins and CD43

Interaction of ICAM-1 and its ligands plays an important role in the leukocyte binding to endothelium. The best characterized ICAM-ligands belong to the family of beta 2-integrins (CD11/CD18), but recently it has been suggested that CD43, a molecule with no structural resemblance to integrins binds ICAM-1 also. On the leukocytes the main regulatory pathway for ICAM-mediated binding is believed to be a short-term regulation of the avidity of CD11/CD18. In this study the authors investigated whether a quantitative increase in the surface expression of ICAM-ligands also can lead to enhanced binding to purified ICAM-1. PMA-treatment differentiates myelomonocytic cell lines into macrophages with a concomitant increase in the surface expression and mRNA-levels of the beta 2-integrin alpha- and beta-chains as well as that of CD43, another ICAM-ligand. The binding of the PMA-treated THP-1 cells to ICAM-1 was increased simultaneously compared to non-treated cells. The binding was blocked completely with antibodies to CD18 and ICAM-1. It is concluded that in addition to the transient qualitative regulation, a long-term quantitative regulation of ICAM-1 ligands also plays a role in increasing the adhesiveness of myelomonocytic cells. This may be relevant in chronic inflammation episodes.

Adherence between Entamoeba histolytica trophozoites and undifferentiated or DMSO-induced HL-60 cells

Differentiation of promyelocytic HL-60 cells along the pathway toward granulocytes using dimethyl-sulfoxide (DMSO) led to increased expression of the adhesion molecules CD11b (Mac-1), CD11c (p150,95), and CD35 (CR1). Undifferentiated and differentiated HL-60 cells adhered similarly to Entamoeba histolytica trophozoites, and monoclonal antibodies against adhesion molecules CD11b and CD11c did not inhibit adherence. We therefore suggest that CD11b and CD11c are not involved in the adherence between polymorphonuclear granulocytes and E. histolytica trophozoites.