High Concentration of Low-Density Lipoprotein Results in Disturbances in Mitochondrial Transcription and Functionality in Endothelial Cells.

Stefanie Gonnissen,Joachim Altschmied,Judith Haendeler,Heiner Schaal,Wolfgang Kaisers,Jörg Timm,Johannes Ptok,Kirsten Jander,Olaf Eckermann,Florian Von Ameln,Philipp Jakobs,Niloofar Ale-Agha,Christine Goy

doi:10.1155/2019/7976382

Abstract

Concentrations of low-density lipoprotein (LDL) above 0.8 mg/ml have been associated with increased risk for cardiovascular diseases and impaired endothelial functionality. Here, we demonstrate that high concentrations of LDL (1 mg/ml) decreased NOS3 protein and RNA levels in primary human endothelial cells. In addition, RNA sequencing data, in particular splice site usage analysis, showed a shift in NOS3 exon-exon junction reads towards those specifically assigned to nonfunctional transcript isoforms further diminishing the functional NOS3 levels. The reduction in NOS3 was accompanied by decreased migratory capacity, which depends on intact mitochondria and ATP formation. In line with these findings, we also observed a reduced ATP content. While mitochondrial mass was unaffected by high LDL, we found an increase in mitochondrial DNA copy number and mitochondrial RNA transcripts but decreased expression of nuclear genes coding for respiratory chain proteins. Therefore, high LDL treatment most likely results in an imbalance between respiratory chain complex proteins encoded in the mitochondria and in the nucleus resulting in impaired respiratory chain function explaining the reduction in ATP content. In conclusion, high LDL treatment leads to a decrease in active NOS3 and dysregulation of mitochondrial transcription, which is entailed by reduced ATP content and migratory capacity and thus, impairment of endothelial cell functionality.

Highlights

Diet plays a crucial role in the development and prevention of cardiovascular diseases
As the Mitochondrial DNA (mtDNA) content was increased upon high low-density lipoprotein (LDL) without a concomitant change in mitochondrial mass, we investigated the expression of protein coding mitochondrial RNA (mtRNA) transcripts and mitochondrial ribosomal RNAs
The major findings of our study are that treatment of human primary endothelial cells with 1 mg/ml LDL for seven days decreases the NOS3 protein levels, increases inactive NOS3 splice variants, and reduces mitochondrial functionality in endothelial cells, which results in dramatically reduced migratory capacity and endothelial cell impairment

Summary

Introduction

Diet plays a crucial role in the development and prevention of cardiovascular diseases. A diet high in saturated fat increases the risk of heart disease and stroke. It is estimated to cause about 31% of coronary heart disease and 11% of stroke worldwide. Cholesterol is carried through our blood by particles called lipoproteins: high-density lipoprotein (HDL) and low-density lipoprotein (LDL). HDL cholesterol reduces the risk of cardiovascular disease as it carries cholesterol away from the bloodstream. High levels of LDL cholesterol lead to atherosclerosis increasing the risk of heart attack and ischemic stroke. Already in 2002, Minamino et al demonstrated that human atherosclerotic lesions contain vascular endothelial cells with senescence-associated phenotypes [1]. We have previously demonstrated for the first time that

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