Oxidized low‐density lipoprotein increases endothelial intracellular calcium and alters cytoskeletal f‐actin distribution

Abstract

Central to the pathogenesis of atherosclerosis is an abnormally functioning endothelium and a consequent loss of vascular integrity. These abnormalities may be induced by haemodynamic factors, biochemical substances, and also by oxidatively modified low-density lipoprotein (LDL). To understand the mechanism by which oxidized LDL causes endothelial dysfunction, human umbilical vein endothelial cells (HUVECs) were loaded with FURA-2, and intracellular calcium mobilization was studied in acute (seconds after LDL was injected) or chronic (24 h after LDL was injected) preparations. Our results demonstrate that 100 microg mL(-1) oxidized LDL increases HUVEC intracellular calcium. In contrast, native LDL at this same concentration had no effect. In addition, chronic exposure (24 h) of HUVECs to oxidized LDL significantly increases HUVEC intracellular calcium. Fluorescent photomicrographs of HUVECs stained with BODIPY-phalloidin f-actin indicates that oxidized LDL causes a reorganization of microfilaments. The results of this study demonstrate that the mechanism by which oxidized LDL causes a loss of vascular integrity could be through activation of endothelial cells to increase cytosolic calcium, which alters the endothelial barrier by reorganizing the cytoskeleton.

oxLDL facilitates flow-induced realignment of aortic endothelial cells

“…These observations are in agreement with earlier studies showing that acute exposure to oxLDL induces formation of F-actin stress fibers, increases endothelial contractility (14), and induces activation of RhoA (14,18,36), which is well known to induce stress fiber formation. A longer (24 h) exposure to oxLDL resulted in disappearance of individual stress fibers and clustering of F-actin in the peripheral regions of the cells (43). Formation of actin stress fibers and formation of peripheral an actin band were suggested to contribute to an increase in endothelial permeability (14,43).…”

“…A longer (24 h) exposure to oxLDL resulted in disappearance of individual stress fibers and clustering of F-actin in the peripheral regions of the cells (43). Formation of actin stress fibers and formation of peripheral an actin band were suggested to contribute to an increase in endothelial permeability (14,43). oxLDL was also reported to induce actin polymerization in macrophages (26,27).…”

Intercellular signalling within vascular cells under high D-glucose involves free radical-triggered tyrosine kinase activation

“…Notably, endothelial Ca 2+ signalling has been shown to be a suitable marker for cell dysfunction initiated by a variety of stimuli such as E. coli lipopolysaccharides (LPS; [19]), peroxides [20,21,22], oxidized low density lipoprotein [23], streptozotocininduced diabetes [24,25] and hyperglycaemia [10,11,26]. The latter was causally linked to generation of · O 2 -in EC [10,27].…”

The Human Paraoxonase Gene Cluster As a Target in the Treatment of Atherosclerosis

“…OxLDL also affects the expression of various key genes in endothelial cells, thus altering endothelial function (126). In addition, oxLDL can also induce cytoskeletal rearrangements such as F-actin distribution, cell contraction, and the formation of intercellular gaps (92,364). Lastly, oxLDL can induce endothelial cells to express and secrete various inflammatory and adhesive molecules such as intercellular adhesion molecule 1 (ICAM-1) and monocyte chemotactic protein 1 (MCP-1), which facilitate the adherence and migration of monocytes and T lymphocytes to injured sites.…”