The focus of this project is to define factors and signal transduction pathways involved in the modulation of human monocyte functions that may contribute to the immunopathology associated with various disease states. Connective tissue destruction is associated with many diseases in which the monocyte/macrophage is a prominent cell. Since matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) are believed to play a major role in the destruction and remodeling of connective tissue, a major emphasis has been placed on how these enzymes and inhibitors are regulated. Our recent studies have demonstrated that monocyte MMPs and TIMP-1 are differentially regulated by cytokines, such as TNFa, GM-CSF, IL-1b, or IFN-g. Experiments with LPS stimulated monocytes indicate that monocyte MMPs, such as MMP-9 and MMP-1, are differentially regulated as a result of their induction through different MAP kinase pathways which in turn activate MMP specific transactivating factors. Monocytes/ macrophages also play a crucial role in cardiovascular diseases due to their potential for development into foam cells, a prominent cell type found in atherosclerotic plaques. Since MMPs may be involved in the rupture of plaques resulting in the ischemic events associated with stroke we are studying the effect of causative (oxidized LDL) and putative therapeutic agents (estrogen, raloxifene, and L-arginine) for atherosclerosis on monocyte MMP and cytokine production. These agents are being tested in vitro on normal monocytes and by examining functional responses of monocytes obtained from patients with high cholesterol/LDL levels that are on a clinical protocol involving treatment with estrogen, raloxifene, and L-arginine.
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