Regulation of Fc gamma receptor subtype expression on a human eosinophilic leukemia cell line EoL-3: participation of cAMP and protein kinase C in the effects of interferon-gamma and phorbol ester

Assessing and managing risks arising from exposure to endocrine-active chemicals

Managing risks to human health and the environment produced by endocrine-active chemicals (EAC) is dependent on sound principles of risk assessment and risk management, which need to be adapted to address the uncertainties in the state of the science of EAC. Quantifying EAC hazard identification, mechanisms of action, and dose-response curves is complicated by a range of chemical structure/toxicology classes, receptors and receptor subtypes, and nonlinear dose-response curves with low-dose effects. Advances in risk science including toxicogenomics and quantitative structure-activity relationships (QSAR) along with a return to the biological process of hormesis are proposed to complement existing risk assessment strategies, including that of the Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC 1998). EAC represents a policy issue that has captured the public's fears and concerns about environmental health. This overview describes the process of EAC risk assessment and risk management in the context of traditional risk management frameworks, with emphasis on the National Research Council Framework (1983), taking into consideration the strategies for EAC management in Canada, the United States, and the European Union.

Membrane receptor-mediated apoptosis and caspase activation in the differentiated EoL-1 eosinophilic cell line

Caspases are key molecules in the control of apoptosis, but relatively little is known about their contribution to eosinophil apoptosis. We examined caspase-3, -8, and -9 activities in receptor ligation-dependent apoptosis induction in the differentiated human eosinophilic cell line EoL-1. Differentiated EoL-1 exhibited bi-lobed nuclei, eosinophil-associated membrane receptors, and basic granule proteins. Annexin-V fluorescein isothiocyanate binding to EoL-1 revealed significant (P<0.01) apoptosis induction in cells cultured for 20 h with monoclonal antibodies (mAb) specific for CD45 (71%+/-4.3), CD45RA (58%+/-2.3), CD45RB (68%+/-2.4), CD95 (47%+/-2.6), and CD69 (52%+/-2.1) compared with control (23%+/-1.6) or CD45RO mAb (27%+/-3.9). The pan-caspase inhibitor Z-Val-Ala-Asp-fluoromethylketone (fmk) and inhibitors of caspase-8 (Z-Ile-Glu-Thr-Asp-fmk) and caspase-9 (Z-Leu-Glu-His-Asp-fmk) significantly inhibited mAb-induced apoptosis of EoL-1 but had no effect on constitutive (baseline) apoptosis at 16 and 20 h. Caspase activity was analyzed using the novel CaspaTag trade mark technique and flow cytometry. EoL-1 treated with pan-CD45, CD45RA, CD45RB, and CD95 mAb exhibited caspase-3 and -9 activation at 12 h post-treatment, which increased at 16 and 20 h. Activated caspase-8 was detected 12 and 16 h after ligation with CD45, CD45RA, CD45RB, and CD95 mAb followed by a trend toward basal levels at 20 h. CD69 ligation resulted in caspase-3 activation, a modest but significant activation of caspase-8, and a loss in mitochondrial transmembrane potential but had no significant effect on activation of caspase-9. Thus, the intrinsic and extrinsic caspase pathways are involved in controlling receptor ligation-mediated apoptosis induction in human eosinophils, findings that may aid the development of a more targeted, anti-inflammatory therapy for asthma.

Interaction between galectin-3 and FcgammaRII induces down-regulation of IL-5 gene: implication of the promoter sequence IL-5REIII

Our previous work demonstrated the capacity of galectin-3 (a beta-galactoside binding animal lectin) to inhibit IL-5 gene expression in different cell types, but the interaction of lectin with the cells and the pathways for the inhibition process are unknown. One of the purposes of this work was to study the cellular ligand for galectin-3. We have demonstrated that galectin-3 can bind to the low affinity IgG receptor (FcgammaRII or CD32) by using different experimental approaches, such as flow cytometry, fusion protein GST technology, and with a model of FcgammaRII-deficient mice. To further analyze the interaction between FcgammaRII and galectin-3, and its implication in IL-5 gene down-regulation we used FcgammaRII-deficient mice. When PBMC from these mice were incubated with galectin-3, the expression of the IL-5 gene was unchanged. However, when PBMC from wild type mice and FcgammaRIII-deficient mice were incubated with galectin-3, IL-5 gene expression was down-regulated. Finally, we studied the implication of the negative regulatory sequence in the IL-5 gene promoter. In the presence of galectin-3, a DNA-protein complex was formed with the IL-5REIII region. This complex was not observed when unrelated oligonucleotide was used. So, galectin-3 induces a pathway, which activates a transcription factor that binds to IL-5REIII. This interaction is capable of inhibiting IL-5 gene transcription.

The direct effect of interferon-gamma on human eosinophilic leukemia cell lines: the induction of interleukin-5 mRNA and the presence of an interferon-gamma receptor

The EoL-1 and EoL-3, human eosinophilic leukemia cell lines, have been used as models for studying the maturation and the function of human eosinophils. We investigated the effects of interferon-gamma (IFN-gamma) on superoxide anion (O2-) production of these cell lines and interleukin-5 (IL-5) mRNA expression in the EoL-1. O2- was measured by chemiluminescence of MCLA, one of cypridina luciferin analogs. The O2- production of fMLP-stimulated EoL-1 and EoL-3 was increased by the IFN-gamma treatment. IL-5 mRNA expression was detected in the IFN-gamma-treated EoL-1 by reverse transcription-polymerase chain reaction (RT-PCR). Further, we examined IFN-gamma receptor 1 mRNA expression in these cell lines and peripheral blood eosinophils by means of northern blot hybridization. IFN-gamma receptor 1 mRNA was detected in the EoL-3 and the IFN-gamma-treated EoL-1. A weak expression of IFN-gamma receptor 1 mRNA was detected in peripheral blood eosinophils isolated from a patient with eosinophilia. These results suggest that IFN-gamma may act on eosinophils directly through its receptor.

Induction of phosphatidylinositol-linked Fc gamma receptor III expression on an eosinophilic cell line, EoL-1, by dibutyryl cyclic AMP and interferon-gamma

The expression of Fc gamma receptor III (Fc gamma RIII) on a human eosinophilic leukemia cell line, EoL-1, was examined and compared with its expression on normal blood eosinophils. Surface Fc gamma RIII expression on EoL-1 cells could be induced in vitro with a combination of dibutyryl cAMP (dbcAMP) and gamma-interferon (IFN-gamma), but not with IFN-gamma or dbcAMP alone. Pretreatment of EoL-1 cells with dbcAMP induced EoL-1 cells to express Fc gamma RIII when stimulated with IFN-gamma, but EoL-1 cells pretreated with IFN-gamma and then stimulated with dbcAMP failed to express Fc gamma RIII. Cyclic AMP was shown to play a role in the effect of dbcAMP. Both the treatment with phosphatidyl-inositol-specific phospholipase C (PI-PLC) and the restriction enzyme digestion of Fc gamma RIII cDNA showed that the Fc gamma RIII on EoL-1 cells was a phosphatidylinositol-linked form. On the other hand, freshly isolated blood eosinophils constitutively expressed few, if any, Fc gamma RIII, and IFN-gamma induced Fc gamma RIII expression on them in vitro. Dibutyryl cAMP did not induce Fc gamma RIII expression and even suppressed the IFN-gamma-induced Fc gamma RIII expression on normal eosinophils. The EoL-1 cell line appears to be a useful in vitro model for the expression and function of the phosphatidylinositol-linked form of Fc gamma RIII on eosinophils.

Cholera toxin (choleragen)-polymorphonuclear leukocyte interactions: effect on migration in vitro and Fc gamma R-dependent phagocytic and bactericidal activity

PMNL leukocytosis is a feature common to many types of infectious and inflammatory diseases. How PMNL are recruited to tissues is not yet clear although it is a question that has considerable clinical importance. We investigated the function of PMNL which migrated through an artificial barrier (Chinese hamster ovary (CHO) cells, collagen and nylon cloth membrane) subjected to CT or choleragenoid treatment toward plain medium (the same RPMI in the upper and lower chamber) or medium containing chemotactic factor (fMLP or LPS or ZAS). CT treatment significantly (P < 0.01) reduced the Fc gamma R expression on the surface of PMNL. The PMNL functions, namely, migration, phagocytic activity and intracellular killing of staphylococci, also have been reduced significantly (P < 0.01). Fc gamma R expression and some functions of PMNL that migrate to chemoattractants were reduced, irrespective of the presence or absence of CT; however, the inhibitory effect of CT on PMNL function was observed only when PMNL migrate to the lower chamber without chemotactic factor. On the other hand choleragenoid treatment of CHO cells did not have any significant influence on PMNL function and Fc gamma R expression. In conclusion, our experiments demonstrate that CT reduces EAFc rosetting and the Fc gamma R-dependent phagocytic and bactericidal activity of bovine blood PMNL.

Regulation of the expression of leukocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) on a human eosinophilic leukemia cell line EoL-3

The effects of several cytokines and phorbol myristate acetate (PMA) on LFA-1 and ICAM-1 expression on a human eosinophilic leukemia cell line, EoL-3, were investigated and compared with those of a human monocytic leukemia cell line, U937. EoL-3 cells expressed large amounts of LFA-1 and small amounts of ICAM-1, and their expression was regulated similarly in EoL-3 cells and U937 cells. Interferon-gamma (IFN-gamma) enhanced ICAM-1 expression but not LFA-1 expression, and PMA augmented both LFA-1 and ICAM-1 expression. IFN-gamma and PMA showed an additive effect on ICAM-1 expression. These results collectively suggest that expression of LFA-1 and ICAM-1 is regulated differently and that IFN-gamma and PMA regulate the expression through different mechanisms. PMA but not IFN-gamma induced homotypic adhesion of EoL-3 and U937 cells, suggesting that PMA but not IFN-gamma activated the adhesive function of these cells. Staurosporin, an inhibitor of protein kinases (PKs), partly suppressed IFN-gamma- and PMA-augmented expression of ICAM-1 on EoL-3 and U937 cells, but did not affect PMA-augmented LFA-1 expression, suggesting that staurosporin-sensitive PKs are involved in IFN-gamma- and PMA-augmented ICAM-1 expression but not in PMA-augmented LFA-1 expression. The role of protein kinase C (PK-C) in these mechanisms was not revealed because a PK-C inhibitor, H-7, did not show any definitive effect on IFN-gamma- and PMA-induced expression of LFA-1 and ICAM-1. Moreover, cyclic AMP (cAMP)- and cGMP-dependent pathways were not shown to be involved in the augmentation of the expression of these molecules.

EoL-1, a human eosinophilic cell line

EoL-1 cells, a recently established human eosinophilic leukemia cell line, have cytological features of myeloblasts under normal culture conditions, and differentiate not only phenotypically but also functionally into eosinophils by a number of stimuli. EoL-1 cells are particularly useful for analyzing leukemic cell differentiation and the properties of malignant eosinophils. EoL-1 cells are also a useful in vitro model for studying human eosinophil functions and their regulation.