No abstract

Eosinophil-mediated diseases, such as allergic asthma, eosinophilic fasciitis, and certain hypersensitivity pulmonary disorders, are characterized by eosinophil infiltration and tissue injury. Mast cells and T cells often colocalize to these areas. Recent data suggest that mast cells can contribute to eosinophil-mediated inflammatory responses. Activation of mast cells can occur by antigen and immunoglobulin E (IgE) via the high-affinity receptor (FcepsilonRI) for IgE. The liberation of proteases, leukotrienes, lipid mediators, and histamine can contribute to tissue inflammation and allow recruitment of eosinophils to tissue. In addition, the synthesis and expression of a plethora of cytokines and chemokines (such as granulocyte-macrophage colony-stimulating factor [GM-CSF], interleukin-1 [IL-1], IL-3, IL-5, tumor necrosis factor-alpha [TNF-alpha], and the chemokines IL-8, regulated upon activation normal T cell expressed and secreted [RANTES], monocyte chemotactic protein-1 [MCP-1], and eotaxin) by mast cells can influence eosinophil biology. Stem cell factor (SCF)-c-kit, cytokine-cytokine receptor, and chemokine-chemokine receptor (CCR3) interactions leading to nuclear factor kappaB (NF-kappaB), mitogen-activated protein kinase (MAPK) expression, and other signaling pathways can modulate eosinophil function. Eosinophil hematopoiesis, activation, survival, and elaboration of mediators can all be regulated thus by mast cells in tissue. Moreover, because eosinophils can secrete SCF, eosinophils can regulate mast cell function in a paracrine manner. This two-way interaction between eosinophils and mast cells can pave the way for chronic inflammatory responses in a variety of human diseases. This review summarizes this pivotal interaction between human mast cells and eosinophils.

Abstract

Fibroblast-derived cytokines may play crucial roles in airway inflammation. In this study, we analyzed expression of the inflammatory cytokine, granulocyte-macrophage colony-stimulating factor (GM-CSF), a major eosinophilopoietin, by normal human lung fibroblast (NHLF) cells and its regulation by monokines and macrophage contact. NHLFs were stimulated with interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) and were cocultured with the U937 myelomonocytic cell line. The expression of GM-CSF transcripts was analyzed by reverse transcription-polymerase chain reaction (RT-PCR), and GM-CSF protein was detected by ELISA. Nuclear translocation of nuclear factor-kappaB (NF-kappaB), an important transcription factor for inflammatory gene expression, was assessed by electrophoretic mobility shift assay (EMSA). Both IL-1beta and TNF-alpha significantly enhanced the production of GM-CSF by NHLF. Coculturing of peripheral blood mononuclear cells (PBMC) with NHLF induced GM-CSF expression. This phenomenon was also seen on coculturing U937 cells or membranes derived from U937 with NHLF but was inhibited when the two types of cells were separated, suggesting a need for cell-cell contact. U937 membranes, as well as IL-1beta and TNF-alpha, induced nuclear translocation of NF-kappaB. These data support a prominent role for macrophage-fibroblast interactions in airway inflammation and fibrosis.