Oxidized LDL signals through Rho-GTPase to induce endothelial cell stiffening and promote capillary formation

Abstract

Oxidative modifications of LDL are a major risk factor in the development of vascular disease and are known to induce endothelial dysfunction, one of the earliest manifestations of atherosclerosis (1, 2). Our studies focus on the oxidized LDL (oxLDL)-induced impact on endothelial biomechanics and its role in vascular dysfunction.Our recent studies showed that the stiffness of aortic endothelial cells (ECs) is significantly increased by exposing the cells to oxLDL in vitro or by dyslipidemia in the dietinduced porcine atherosclerosis model in vivo (3, 4). An increase in endothelial stiffness was accompanied by an increase in endothelial contractile forces generated on the cell-substrate interface and an enhanced ability of ECs to form branching networks in 3D cultures (3, 4), which is considered a prerequisite of angiogenesis (5). Moreover, earlier studies demonstrated a correlation between increased endothelial force and network formation across several endothelial subtypes (6). We proposed, therefore, that oxLDL-induced endothelial stiffening may lead to increased angiogenic activity of ECs during the development of atherosclerotic plaques. This process is expected to be of major clinical importance because neovascularization of the plaques is increasingly recognized as a critical process and a major risk factor for plaque vulnerability (7). The goal of this study is to elucidate the mechanism of oxLDL-induced endothelial stiffening and evaluate a link between this effect and the ability of ECs to form functional capillaries. Abstract Endothelial biomechanics is

Molecular-Scale Biophysical Modulation of an Endothelial Membrane by Oxidized Phospholipids

“…Recently, it was shown that endothelial cell stiffness per se plays a role in adhesion and transmigration of immune cells (84,85). Our previous studies also demonstrate that an increase in endothelial cell stiffness and force generation enhances endothelial angiogenic potential in 3D cultures in vitro (10,11) and in matrigels inserted in vivo (56). Most recently, Busik et al demonstrated that a decrease in membrane fluidity, which is expected to reflect a decrease in lipid order, correlates with migration and homing of bone-marrow-derived circulating stem cells (86).…”

“…Moreover, our studies further demonstrate that exposure to oxLDL induces an increase in F-actin stress fibers (80) and that endothelial stiffening induced by cholesterol depletion critically depends on the integrity of F-actin (6). In terms of the mechanism that links insertion of oxidized lipids to endothelial cell stiffening, our recent study demonstrates that for oxLDL and oxysterols, stiffening is mediated by the activation of the RhoA/Rock/PLCP/MLC2 pathway (56). oxPAPCs, however, were shown to activate two other members of the Rho-GTPase family, Rac1 and CDC42, while attenuating thrombin-induced RhoA activation (18,82).…”

“…First, samples were analyzed for the presence of LPC, POVPC, and PGPC. Next, cholesterol and oxysterols were analyzed as acetate derivatives after acetylation with a mixture of acetic anhydride/pyridine (1:2, v/v) at 55 C for 30 min, as described in (56). To quantify POVPC and PGPC, standard curves of responses of variable amounts of POVPC and PGPC versus a fixed amount of the internal standard (13:0-LPC) were created.…”

Context-Dependent Role of Oxidized Lipids and Lipoproteins in Inflammation

“…Noticeably, in addition to oxidized fatty acyls, oxysterols play important roles in macrophage and EC biology [70, 71] (Box 1). As the esterified oxidized PUFA decompose to produce so-called oxidation end products, namely, short carbon chain aldehydes and ketones, they become uniformly proinflammatory.…”

“…Oxysterols, found both intracellularly and in OxLDL, induce a large number of profound cellular responses. For example, 7-ketocholesterol, a product of ROS-mediated cholesterol oxidation in OxLDL, regulates endothelial biomechanics and induces expression of inflammatory genes [70, 71]; enzymatically produced 25-hydroxycholesterol (25-OHC), among other oxysterols, activates the anti-inflammatory liver X receptor and other nuclear receptors and regulates function of insulin-induced gene 1. As is the case with oxidized PUFA products, oxysterols mediate both pro- and anti- inflammatory responses.…”