| Macrophage colony-stimulating factor (M-CSF) is a hematopoietic growth factor that induces differentiation, proliferation, and survival of mononuclear phagocytes. Previously our lab demonstrated that M-CSF stimulated human monocytes to produce the pro-angiogenic factor VEGF, and here we investigated the signaling mechanism of this action. Using the Matrigel(TM) plug angiogenesis assay, we demonstrated increased numbers of macrophages (F4/80+ cells), VEGF, and angiogenesis (vonWillebrand factor+ endothelial cells forming complete circles) in plugs containing M-CSF. Importantly, neutralizing VEGF within plugs containing M-CSF, reduced the amount of angiogenesis to control levels. In Chapter 2, we illustrate the ERK- and Sp1-dependent mechanism for M-CSF-induced VEGF production from human monocytes and demonstrate for the first time the ability of M-CSF to induce angiogenesis in vivo.;Levels of glucocorticoids can be increased exogenously by external administration of steroids or endogenously with an overactive stress response. Glucocorticoids have been shown to alter cytokine receptor expression, so in Chapter 3, we hypothesize that glucocorticoids would affect GM-CSF-induced sVEGFR-1 production. To assess the in vivo effects of steroids on GM-CSF-induced sVEGFR-1 production, we injected Matrigel(TM) plugs containing GM-CSF + VEGF subcutaneously into mice and treated mice with water control or Dexamethasone. Previously, our lab has shown that GM-CSF induces the secretion of sVEGFR-1 within these plugs, blocking VEGF-dependent angiogenesis. We observed a significant increase the level of VEGF in plugs taken from mice treated with Dexamethasone compared to control treated mice. These data illustrate the ability of glucocorticoids to effect the production of angiogenic factors from immune cells.;Glucocorticoids are increased during the stress response, so we investigated the global effects of stress on breast cancer growth and metastases in Chapter 4. To define the biochemical pathway regulating these events, we next inhibited pathways of the stress response with daily treatment of a glucocorticoid receptor antagonist (RU486), a beta-adrenergic receptor antagonist (Nadolol), or an opioid receptor antagonist (Naltrexone) during restraint stress. We observed no effect on stress-enhanced tumor growth by any of the inhibitors. To investigate the role of stress in the tumor microenvironment, we performed flow cytometry for immune cell populations and immunohistochemistry for immune cell markers within the tumors. The percentage of CD3+CD4+ T-helper cells and neutrophil numbers were increased in breast tumors from restraint-stressed mice compared to controls. No difference was observed in the amount of NK cells but less cytolytic activity was displayed by cells taken from restraint-stressed mice. We observed no difference in the proliferation of tumor cells (Ki67+ cells) in restraint-stressed mice.;Finally, in Chapter 5, we investigated the effects of stress on lung inflammation. Social disruption stress (SDR) has been shown to induce glucocorticoid-resistance in immune cells, causing an over-active inflammatory response with no regulatory mechanism in place. We investigated the effects of SDR on the lung microenvironment and found that SDR alone induced pulmonary inflammation, as assessed by lung pathology and lung tissue myeloperoxidase levels. Idiopathic pulmonary fibrosis (IPF) is a disease of the lung interstium that is thought to be affected by lung inflammation. Therefore, we investigated of the effects of SDR on bleomycin-induced pulmonary fibrosis, a mouse model for IPF. Social disruption stress given before or after bleomycin treatment did not exacerbate symptoms of bleomycin-induced pulmonary fibrosis. While SDR did not affect pulmonary fibrosis symptoms, the pulmonary inflammation observed with only SDR demonstrates the effects of microenvironment on immune cell responses. (Abstract shortened by UMI.)... |
