Abstract
High levels of circulating lipoprotein constitute a risk factor for cardiovascular diseases, and in this context, the specific role of the very-low-density lipoproteins (VLDL) is poorly understood. The response of human umbilical vein endothelial cells (HUVEC) to VLDL exposure was studied, especially focusing on the pathways involved in alteration of redox homeostasis and nitric oxide (NO) bioavailability. The results obtained by the analysis of the expression level of genes implicated in the NO metabolism and oxidative stress response indicated a strong activation of inducible NO synthase (iNOS) upon 24 h exposure to VLDL, particularly if these have been preventively oxidised. Simultaneously, both mRNA and protein expression of endothelial NO synthase (eNOS) were decreased and its phosphorylation pattern, at the key residues Tyr495 and Ser1177, strongly suggested the occurrence of the eNOS uncoupling. The results are consistent with the observed increased production of nitrites and nitrates (NOx), reactive oxygen species (ROS), 3-nitrotyrosine (3-NT), and, at mitochondrial level, a deficit in mitochondrial O2 consumption. Altogether, these data suggest that the VLDL, particularly if oxidised, when allowed to persist in contact with endothelial cells, strongly alter NO bioavailability, affecting redox homeostasis and mitochondrial function.
Highlights
Atherosclerosis, one of the principal causes of morbidity and mortality in occidental countries, is a disease affecting large and medium-sized muscular arteries, characterised by endothelial dysfunction and vascular inflammation [1,2,3]
P values were considered statistically significant by analysis of variance (ANOVA)
The transcriptional activity of human umbilical vein endothelial cells (HUVEC) exposed to 140 μg/mL n-very-low-density lipoproteins (VLDL) or oxidised VLDL (ox-VLDL) was investigated by targeting genes related to nitric oxide (NO) metabolism and to oxidative stress
Summary
Atherosclerosis, one of the principal causes of morbidity and mortality in occidental countries, is a disease affecting large and medium-sized muscular arteries, characterised by endothelial dysfunction and vascular inflammation [1,2,3]. Evidence has been collected suggesting that, as reported for the LDL [5], the oxidation of VLDL triggers a cascade of proatherogenic and proinflammatory cell responses [12]. These include lipoprotein retention in the arterial wall and Oxidative Medicine and Cellular Longevity recruitment of macrophages at the vessel level; under these conditions, foam cells are formed and eventually the atherosclerotic plaque builds up [13, 14]
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