Perilipin 2 (PLIN2)-deficiency does not increase cholesterol-induced toxicity in macrophages.

Interventions on macrophages/foam cells to redirect intracellular cholesterol towards efflux pathways could become a very valuable addition to our therapeutic arsenal against atherosclerosis. However, certain manipulations of the cholesteryl ester cycle, such as the inhibition of ACAT1, an ER-resident enzyme that re-esterifies cholesterol, are not well tolerated. Previously we showed that targeting perilipin-2 (PLIN2), a major lipid droplet (LD)-associated protein in macrophages, prevents foam cell formation and protects against atherosclerosis. Here we have assessed the tolerance of PLIN2-deficient bone marrow derived macrophages (BMM) to several lipid loading conditions similar to the found during atherosclerosis development, including exposure to modified low-density lipoprotein (mLDL) and 7-ketocholesterol (7-KC), a free cholesterol (FC) metabolite, in media with or without cholesterol acceptors. BMM isolated from mice that do or do not express PLIN2 were tested for apoptosis (TUNEL and cleaved caspase-3), ER stress (CHOP induction and XBP-1 splicing), and inflammation (TNF-α and IL-6 mRNA levels). Like in other cell types, PLIN2 deficiency impairs LD buildup in BMM. However, while most stress parameters were elevated in macrophages under ACAT inhibition and 7-KC loading, PLIN2 inactivation was well tolerated. The data support the safety of targeting PLIN2 to prevent foam cell formation and atherosclerosis.

Epigallocatechin gallate preserves endothelial function by reducing the endogenous nitric oxide synthase inhibitor level.

Asymmetric dimethylarginine (ADMA), the endogenous nitric oxide synthase inhibitor, is thought to be a key factor contributing to endothelial dysfunction. Tea catechins can cause an endothelium-dependent vasorelaxation. The present study examined the effect of epigallocatechin gallate (EGCG), the major component of tea catechins, on endothelial dysfunction induced by native low density lipoprotein (LDL) in rats and oxidized LDL (ox-LDL) in cultured endothelial cells, and whether the protective effect of EGCG is related to reduction of ADMA level. A single injection of LDL (4 mg x kg(-1), i.v.) markedly reduced endothelium-dependent relaxation and the serum nitrite/nitrate (NO) level, and increased serum concentrations of ADMA, malondialdehyde (MDA), and tumor necrosis factor-alpha (TNF-alpha). EGCG (10 or 50 mg x kg(-1), i.p.) significantly attenuated the inhibition of vasodilator response to acetylcholine and the decreased serum nitrite/nitrate level, and reduced the elevated levels of ADMA, MDA, and TNF-alpha. Exposure of endothelial cells to ox-LDL (100 microg x mL(-1)) for 24 h markedly increased the medium levels of lactate dehydrogenase (LDH), ADMA, TNF-alpha, and MDA, and decreased the level of nitrite/nitrate in the medium and the activity of dimethylarginine dimethylaminohydrolase (DDAH) in the endothelial cells. EGCG (10 and 100 microg x mL(-1)) significantly decreased the levels of LDH, ADMA, TNF-alpha, and MDA, and increased the level of nitrite/nitrate and the activity of DDAH. These results suggest that EGCG protects endothelial dysfunction induced by native LDL in vivo or by ox-LDL in endothelial cells, and the protective effect of EGCG on the endothelium is related to decrease in ADMA level via increasing of DDAH activity.

Participación de la lipoproteína de baja densidad oxidada en el desarrollo de la placa aterosclerótica / The role played by oxidised low-density lipoprotein in the development of the atherosclerotic plaque

Objetivo. Exponer cuáles son los mecanismos por los cuales los lípidos plasmáticos, y concretamente la lipoproteína de baja densidad (LDL) oxidada, contribuyen al desarrollo de la placa ateromatosa. Desarrollo. La disfunción endotelial y la formación de la estría grasa constituyen la etapa inicial en el desarrollo de la arterioesclerosis. La hipercolesterolemia favorece la oxidación de LDL en contacto con radicales libres de oxígeno liberados por células endoteliales, macrófagos y células musculares lisas, y su captación y acumulación incontrolada por macrófagos subendoteliales, que se transforman en células espumosas. El acúmulo de estas células, con un leve engrosamiento intimal, constituye la estría grasa. La LDL oxidada estimula la quimiotaxis de células inflamatorias, su adhesión a células endoteliales y su migración al interior de la pared vascular; además, promueve la proliferación de células musculares lisas y su infiltración en el espacio subintimal; induce la apoptosis en el núcleo de la placa, favorece un estado protrombótico y reduce la función fibrinolítica. Así, participa en la progresión de las lesiones hacia placas ateromatosas bien estructuradas. La aplicación terapéutica de suplementos dietéticos de antioxidantes y –más importante en la actualidad– la administración de estatinas pueden retrasar la progresión de lesiones arterioescleróticas. Conclusiones. La hipercolesterolemia, a través de la LDL oxidada, ejerce un papel fundamental en el proceso de la aterogénesis. El conocimiento de su mecanismo de actuación es importante para el cirujano vascular, ya que supone una eficaz diana terapéutica

AIM. To present how plasma lipids, and particularly oxidized low-density lipoprotein (LDL), participate in the development of the atheromatous plaque. DEVELOPMENT. Endotelial dysfunction and the development of fatty streaks are the initial events in the process of plaque formation. Hypercholesterolemia favours the oxidation of LDL in contact with oxygen-derived free radicals released by endothelial cells, macrophages and smooth muscle cells, and their uncontrolled uptake and accumulation by subendothelial macrophages, which turn into foam cells. The accumulation of these cells, together with a slight intimal thickening, makes up the fatty streak. The oxidized LDL stimulates the chemoattraction of inflammatory cells, their adhesion to endothelial cells and their migration into the structure of the vascular wall. It promotes the proliferation of smooth muscle cells and their infiltration into the subintimal space. It induces cell apoptosis in the core of the plaque, and it favours a prothrombotic state by reducing the fibrinolytic activity. Thus, it participates in the progression of the vascular lesions towards well-structured atheromatous plaques. The therapeutic application of diet supplements of antioxidants or, more important nowadays, the prescription of statins, can slow down the progression of atherosclerotic lesions. CONCLUSIONS. Hypercholesterolemia, by means of the oxidized LDL, plays an essential role in the atherosclerotic development. It is important for the vascular surgeon to be familiar with this process because it is an effective therapeutic target

Early pathological changes of endothelia in a model using LDL perfusion at physiological LDL-cholesterol concentration.

The aim of the present research was to provide further insight into the debated problem of the existence of modified LDL in vivo. For this purpose a novel model was devised for studying LDL injurious effect on endothelial cells (EC) by infusing native cholesterol rich LDL, diluted to physiological LDL cholesterol concentration. Normal rabbits were infused with LDL separated from rabbits previously fed either with standard food (I-LDL Group), 1% cholesterol (II-LDL Group) or 1% cholesterol plus probucol (IV-LDL Group). Cu++ modified II-LDL was infused as well (III-LDL Group). After dilution as above, lipid oxide (LP) significantly increased in III- and II-LDL media, as compared to I- and IV-LDL media. EC of III- and II-LDL Groups showed irregular shape and surface pattern. Further, they showed adhering clusters of monocytes, platelets and erythrocytes. Endocytic vesicles and ruthenium red-positive particles increased too. EC of IV-LDL Group were only slightly affected as compared to I-LDL Group. These data suggest that native LDL from hypercholesterolemic rabbits contain an oxidized form which is noxious to EC even when LDL is infused at physiological LDL-cholesterol concentration. This early injury is in part LP-associated and actively involves platelets and monocytes.