Elevation of blood triglycerides, primarily as triglyceride-rich lipoproteins (TGRL), is a known risk factor for the development of atherosclerotic cardiovascular disease and increasingly linked to vascular inflammation. TGRL consist of chylomicrons, very low density-lipoproteins (VLDL), and their remnant particles. Our previous work on this project, "Interactions of lipoproteins with the vascular wall" HL55667, years 8-11, has provided new observations that frame the renewal of this project: TGRL lipolysis products in moderate to high concentrations cause release of transforming growth factor (TGF)-21 from endothelial cells, increase reactive oxygen species (ROS) formation and activate nuclear transcription factors in endothelial cells, and increase endothelial barrier permeability and VLDL remnant particle accumulation in the artery wall. The overall goals of this proposal are to examine the mechanisms of VLDL lipolysis product-induced release of TGF-21 from endothelial cells, cell signaling pathways associated with VLDL lipolysis product treatments and lipolysis product-induced changes in endothelial layer permeability and VLDL remnant particle accumulation. Aim 1: To test the hypothesis that fatty acids released by VLDL lipolysis up regulate NADPH oxidase, generating ROS that cause release of TGF-21 from latent TGF-21 binding protein (LTBP). Aim 2: To test the hypothesis that VLDL lipolysis products alter endothelial cell function through a TGF-21 / Smad-mediated pathway. Aim 3: To test the hypothesis that VLDL lipolysis products increase endothelial layer permeability through paracellular pathways induced by TGF-21. The proposed experiments raise the possibility of identifying new mechanisms for autocrine and/or paracrine stimulation of endothelial cells that could initiate or modulate pro-inflammatory actions on vascular cells. Further, these data could provide us with clues about otherwise unsuspected cell signaling pathways initiated by lipolysis of TGRL, a biological process occurring continuously but magnified after every meal. Finally, increased concentrations of TGRL lipolysis products increase arterial endothelial layer permeability and remnant particle accumulation by mechanisms yet to be determined, but likely to be important in early atherosclerotic lesions. New pathophysiological mechanisms, identified in this project, then can be probed for potential therapeutic opportunities to reduce vascular inflammation and atherosclerosis. PUBLIC HEALTH RELEVANCE: Studies from our laboratories and others have shown that some of the pathophysiological effects of very low- density lipoprotein (VLDL) in vascular inflammation and atherosclerosis may be related to VLDL lipolysis product effects on endothelial cells. Endothelial cells are exposed to high concentrations of a broad array of lipolysis products because of the strategic location of lipoprotein lipase, which is anchored to endothelial cells. Further, the matrix, which covers the endothelial cell, also is exposed to high concentrations of VLDL lipolysis products. This proposal will ask specific questions about the effects of VLDL lipolysis products on the endothelial cell matrix, cell signaling and effects on nuclear transcription factors, and mechanisms of endothelial cell layer-mediated permeability and VLDL remnant accumulation. The knowledge gained from this project will enable us to understand better the alternative pathways by which VLDL could cause vascular inflammation and atherosclerosis. Completion of this project will help us to design strategies that utilize our knowledge of these pro- and anti-inflammatory lipids and proteins to evaluate cardiovascular disease risk and prevent and treat atherosclerotic cardiovascular disease.