Human neutrophilic and eosinophilic granulocytes display different levels of c-fos proto-oncogene expression: an in situ hybridization study

Inflammatory cytokine expression is independent of the c-Jun N-terminal kinase/AP-1 signaling cascade in human neutrophils

In the last decade, the ability of neutrophils to generate proinflammatory cytokines has become firmly established. Because neutrophils typically infiltrate inflammatory sites in large numbers, they could significantly contribute to the cytokine environment and even represent a substantial source of cytokines in chronic inflammatory disorders in which they predominate over other cell types. To date, however, most studies have focused on identifying which mediators are produced by neutrophils, as opposed to elucidating the molecular bases underlying this process. We previously showed that most stimuli of cytokine production in neutrophils also activate NF-kappaB in these cells. In this report, we turned our attention to another transcription factor that plays a central role in inflammation, AP-1. Among Jun/Fos proteins, only JunD and c-Fos are abundantly expressed in neutrophils, and they are mainly cytoplasmic. Both the cellular levels and distribution of the Jun/Fos proteins remain unaffected by various neutrophil stimuli, including those that are known to increase the corresponding mRNA transcripts. Similarly, c-Jun N-terminal kinase (JNK) 1 is overwhelmingly cytoplasmic in neutrophils and does not translocate to the nucleus upon cell activation. Although JNK is not activatable under most circumstances, specific conditions do allow its phosphorylation in response to TNF. However, no experimental condition (even those leading to JNK activation) resulted in the induction of genuine AP-1 complexes in neutrophils. Accordingly, the potent JNK inhibitor, SP 600125, failed to inhibit inflammatory cytokine gene expression in neutrophils. Collectively, our findings strongly suggest that the JNK/AP-1 signaling pathway has little or no impact on the generation of inflammatory mediators in neutrophils.

Fos immunoreactivity assessment on human normal and pathological bronchial biopsies

The transcription factor Fos is involved in cell proliferation and differentiation. Its expression in normal and pathological adult human tissues and cells has rarely been studied. We therefore studied bronchial biopsies obtained from 14 normal subjects (NS), 18 non-steroid-treated asthmatics, 10 corticosteroid-treated asthmatics and 10 patients with chronic bronchitis (CB), in addition to 34 patients with lung cancer (LC), by immunofluorescence for Fos immunoreactivity, using a highly specific polyclonal antibody. Bronchial tissue of 0/10 NS, 11/18 non-steroid-treated asthmatics, 1/10 steroid-treated asthmatics, 0/10 CB and 1/34 LC expressed Fos. In asthmatic patients, the expression was heterogeneous, localized to epithelial cells and correlated with the epithelium shedding (tau = 0.45, P = 0.0001). Corticosteroid-treated patients rarely expressed Fos, suggesting a role for this proto-oncogene in asthmatic bronchial inflammation. Fos was rarely expressed in the normal and pathological (CB, LC) proliferative compartment of the human bronchi, suggesting its low role in cell proliferation of the large airways.

Mice lacking c-fos have normal hematopoietic stem cells but exhibit altered B-cell differentiation due to an impaired bone marrow environment

Mice lacking c-fos develop severe osteopetrosis with deficiencies in bone remodeling and exhibit extramedullary hematopoiesis, thymic atrophy, and altered B-cell development. In this study, we have used these mice to characterize in detail the developmental potential of hematopoietic stem cells lacking c-fos and to analyze how the lymphoid differentiation is altered. In c-fos -/- mice, B-cell numbers are reduced in the spleen, lymph nodes, and the peripheral blood as a result of a marked reduction (> 90%) in the number of clonogenic B-cell precursors. In contrast, the number and lineage distribution of myeloid progenitor cells are not affected. The thymic defects observed in a large number of these mice correlate with their health status, suggesting that this may be an indirect effect of the c-fos mutation. In vitro differentiation and bone marrow reconstitution experiments demonstrated that hematopoietic stem cells lacking c-fos can give rise to all mature myeloid as well as lymphoid cells, suggesting that the observed B lymphopenia in the mutant mice is due to an altered environment. Transplantation of wild-type bone marrow cells into newborn mutant mice resulted in the establishment of a bone marrow space and subsequent correction of the B-cell defect. These results demonstrate that hematopoietic stem cells lacking Fos have full developmental potential and that the observed defect in B-cell development is most likely due to the impaired bone marrow environment as a consequence of osteopetrosis.

Mice lacking c-fos have normal hematopoietic stem cells but exhibit altered B-cell differentiation due to an impaired bone marrow environment

Mice lacking c-fos develop severe osteopetrosis with deficiencies in bone remodeling and exhibit extramedullary hematopoiesis, thymic atrophy, and altered B-cell development. In this study, we have used these mice to characterize in detail the developmental potential of hematopoietic stem cells lacking c-fos and to analyze how the lymphoid differentiation is altered. In c-fos -/- mice, B-cell numbers are reduced in the spleen, lymph nodes, and the peripheral blood as a result of a marked reduction (> 90%) in the number of clonogenic B-cell precursors. In contrast, the number and lineage distribution of myeloid progenitor cells are not affected. The thymic defects observed in a large number of these mice correlate with their health status, suggesting that this may be an indirect effect of the c-fos mutation. In vitro differentiation and bone marrow reconstitution experiments demonstrated that hematopoietic stem cells lacking c-fos can give rise to all mature myeloid as well as lymphoid cells, suggesting that the observed B lymphopenia in the mutant mice is due to an altered environment. Transplantation of wild-type bone marrow cells into newborn mutant mice resulted in the establishment of a bone marrow space and subsequent correction of the B-cell defect. These results demonstrate that hematopoietic stem cells lacking Fos have full developmental potential and that the observed defect in B-cell development is most likely due to the impaired bone marrow environment as a consequence of osteopetrosis.

Detection of Epstein-Barr virus in lymphoid tissues of patients with infectious mononucleosis by in situ hybridization

Although the immunological response during infectious mononucleosis (IMN) has been studied in detail, little is known about the spread of Epstein-Barr virus (EBV) in lymphoid organs or the topographical distribution of the infected cells. In this study, EBV was detected in 11 lymph nodes, 4 tonsils, and 1 spleen of 16 patients with IMN. The predominant cell type positive for the EBV genome was identified as small lymphocytes localized chiefly within typical T areas, preferentially in perifollicular and interfollicular regions of the lymph node. A few endothelia of epithelioid venules were also found to be positive. Furthermore, a small number of sinus lining cells of lymph nodes exhibited labelling. Altogether, only a small number of cells, not exceeding 1 per cent of all cells, were infected with EBV. Our results show that only a small number of lymphocytes carry the EBV and that besides B lymphocytes, other cell constituents of lymphatic tissues are infected by EBV during IMN.

Expression of c-jun, jun B and jun D proto-oncogenes in human peripheral-blood granulocytes

We have found that purified human peripheral-blood granulocytes express constitutively significant levels of proto-oncogenes c-jun, jun B and jun D mRNA. Upon functional activation of granulocytes by 4 beta-phorbol 12-myristate 13-acetate (PMA), the levels of c-jun, jun B and jun D transcripts were increased. The three jun genes showed a similar time course in their induction by PMA, maximal mRNA levels being reached after 60 min of induction. These results suggest that expression of c-jun, jun B and jun D genes might be involved in terminal granulocyte differentiation or in regulating granulocyte functionality.

Early protooncogene expression during hemin-induced differentiation of human erythroleukemic cells

In situ hybridization was used to study the effects of hemin on the expression of the oncogenes c-myc, c-fos, and myb, and on the mRNA level of erythroid porphobilinogen deaminase (PBG-D) and alpha-globin in HEL cells during differentiation. The technique was effective in detecting changes in mRNA levels in small numbers of HEL cells. Hemin stimulation of HEL cells results in an early increase in myb and c-myc expression and a decrease in c-fos mRNA, while increased PBG-D and alpha-globin expression is not seen until 8 h after hemin treatment. Blast-like cells display expression of c-myc, alpha-globin and PBG-D, while the more differentiated cells give a positive response to both c-fos and myb. During HEL cell differentiation, the mechanism of hemin stimulation appears to be through the up regulation of myb and c-myc mRNA and down regulation of c-fos. The subsequent expression of PBG-D and alpha-globin may indicate that early increases in protooncogene expression are first required for the normal progression of erythropoiesis to occur.

Detection of fos oncogene products by monoclonal antibody FO-120 in lymphoproliferative disorders

We investigated the expression of fos oncogene proteins in lymphoproliferative disorders, using a monoclonal antibody (FO-120) that was prepared against a synthetic oligopeptide of fos protein (amino acid sequence from 127 to 152). Although peripheral blood leukocytes were rarely positive for FO-120, they were transiently stained after lectin (PHA) stimulation. After culture with IL-2 for 1 or 2 weeks, less than 40% of the lymphocytes weakly reacted with FO-120, whereas strongly positive cells were detected in more than 70% of cells in half the T-cell lines established from preleukemic state of adult T-cell leukemia (pre-ATL) and all of ATL derived T-cell lines. All in vivo specimens of non-Hodgkin's malignant lymphomas, except for one case of T-cell lymphoma were also strongly positive. In addition, the extent of the antibody reactivity correlated with the histopathological grade of malignancy in B-cell lymphoma. The reactivity to most AILD-IBL lesions overlapped with that to T-lymphomas, and could be distinguished from that to reactive lesions. FO-120 appears to be a useful tool for detecting early neoplastic changes in lymphoproliferative disorders.

Persistent and enhanced expression of c-fos gene products in various kinds of human hematopoietic cell lines. Immunofluorescence study using prepared monoclonal antibodies

Two kinds of monoclonal antibodies recognizing fos proto-oncogene (c-fos) products were prepared using a synthetic oligopeptide corresponding to amino acids 127-152 of the fos oncogene products. These monoclonal antibodies (FO-120 & FO-145) detected fos gene products induced in a human monocyte cell line (U-937) by phorbol acetate (TPA) and induced in both human and mouse fibroblast cell lines (284, BALB/c 3T3) by serum-stimulation. One of the monoclonal antibodies (FO-120) reacted with 50-kDa and 42-kDa proteins and the other antibody (FO-145) reacted with a 30-33-kDa protein. The expression of the fos gene in various human hematopoietic cell lines was investigated using these prepared monoclonal antibodies. While almost all hematopoietic cell lines tested reacted with these monoclonal antibodies to various degrees, the majority of normal peripheral blood lymphocytes cultured with lectin (PHA) and interleukin 2 (IL-2) did not, suggesting that cells of some permanent hematopoietic cell lines, irrespective of their lineage specificity and growth factor dependency, continuously express the fos oncogene. These monoclonal antibodies may be useful for detecting early neoplastic changes in hematopoietic cells.

c-fos expression interferes with thymus development in transgenic mice

To study the function of the proto-oncogene c-fos in hematopoietic tissues, transgenic mice were generated that express c-fos from the H2-Kb promoter in several organs. These H2-c-fos mice have enlarged spleens and hyperplastic thymuses containing an increased number of thymic epithelial cells. The exogenous c-fos expression specifically affects T cell development in the thymus, thereby increasing the fraction of mature thymocytes. Results obtained with bone marrow radiation chimeras suggest that the altered distribution of T cell subsets is not a direct effect of c-fos expression within the T cell lineage. No changes in the proportion of hematopoietic cell lineages are seen in the spleen, and these mice do not develop lymphoid malignancies. B and T cell function, however, is impaired, and H2-c-fos mice are immune deficient. It appears that c-fos specifically stimulates the proliferation of thymic epithelial cells, and may thus indirectly affect T cell development.