Acyl Chain-Dependent Effect of Lysophosphatidylcholine on Endothelium-Dependent Vasorelaxation

Peer reviewe

Reduced expression of adipose triglyceride lipase decreases arachidonic acid release and prostacyclin secretion in human aortic endothelial cells

<p><b>Background:</b> Vascular endothelial cells represent an important source of arachidonic acid (AA)-derived mediators involved in the generation of anti- or proatherogenic environments. Evidence emerged (in mast cells), that in addition to phospholipases, neutral lipid hydrolases as adipose triglyceride lipase (ATGL) also participate in this process.</p> <p><b>Objective:</b> To examine the impact of ATGL on AA-release from cellular phospholipids (PL) and on prostacyclin secretion in human aortic endothelial cells (HAEC).</p> <p><b>Methods and results:</b> siRNA-mediated silencing of ATGL promoted lipid droplet formation and TG accumulation in HAEC (nile red stain). ATGL knockdown decreased the basal and A23187 (calcium ionophore)-induced release of ¹⁴C-AA from (¹⁴C-AA-labeled) HAEC. In A23187-stimulated ATGL silenced cells, this was accompanied by a decreased content of ¹⁴C-AA in cellular PL and a decreased secretion of prostacyclin (determined by 6-keto PGF1α EIA).</p> <p><b>Conclusions:</b> In vascular endothelial cells, the efficiency of stimulus-induced AA release and prostacyclin secretion is dependent on ATGL.</p

Low Valine Serum Levels Predict Increased 1-Year Mortality in Acute Heart Failure Patients

Considering the relationship between disease severity and the extent of metabolic derangement in heart failure, we hypothesized that the serum levels of metabolites may have prognostic value for 1-year mortality in acute heart failure (AHF). The AHF study was a prospective, observational study enrolling consecutive patients hospitalized due to AHF. Metabolites were measured in serum collected at admission using NMR spectroscopy. Out of 315 AHF patients, 118 (37.5%) died within 1 year after hospitalization for AHF. The serum levels of 8 out of 49 identified metabolites were significantly different between patients who were alive and those who died within 1 year after hospitalization for AHF. Of these, only valine was significantly associated with 1-year mortality (hazard ratio 0.73 per 1 standard deviation increase, 95% confidence interval: 0.59–0.90, p = 0.003) in the multivariable Cox regression analyses. Kaplan–Maier analysis showed significantly higher survival rates in AHF patients with valine levels above the median (>279.2 µmol/L) compared to those with valine levels ≤ 279.2 µmol/L. In a receiver operating characteristics curve analysis, valine was able to discriminate between the two groups with an area under the curve of 0.65 (95% CI 0.59–0.72). We conclude that valine serum levels might be of prognostic value in AHF

Associations between Endothelial Lipase, High-Density Lipoprotein, and Endothelial Function Differ in Healthy Volunteers and Metabolic Syndrome Patients

Metabolic syndrome (MS) is characterized by endothelial- and high-density lipoprotein (HDL) dysfunction and increased endothelial lipase (EL) serum levels. We examined the associations between EL serum levels, HDL (serum levels, lipid content, and function), and endothelial function in healthy volunteers (HV) and MS patients. Flow-mediated dilation (FMD), nitroglycerin-mediated dilation (NMD), serum levels of HDL subclasses (measured by nuclear magnetic resonance (NMR) spectroscopy), and EL serum levels differed significantly between HV and MS patients. The serum levels of triglycerides in large HDL particles were significantly positively correlated with FMD and NMD in HV, but not in MS patients. Cholesterol (C) and phospholipid (PL) contents of large HDL particles, calculated as HDL1-C/HDL1-apoA-I and HDL1-PL/HDL1-apoA-I, respectively, were significantly negatively correlated with FMD in HV, but not in MS patients. Cholesterol efflux capacity and arylesterase activity of HDL, as well as EL, were correlated with neither FMD nor NMD. EL was significantly negatively correlated with HDL-PL/HDL-apoA-I in HV, but not in MS patients, and with serum levels of small dense HDL containing apolipoprotein A-II in MS patients, but not in HV. We conclude that MS modulates the association between HDL and endothelial function, as well as between EL and HDL. HDL cholesterol efflux capacity and arylesterase activity, as well as EL serum levels, are not associated with endothelial function in HV or MS patients

ROS are induced by LPC and contribute to LPC-induced impairment of relaxation.

<p>A) The rings were equilibrated in 100 µl PSS buffer containing 10 µM DETCA and 10 µM lucigenin at 37°C for 30 minutes, followed by addition of PSS (control) or LPC (10 µM). Emitted light (RLU) was recorded every 10 seconds for 30 seconds. The RLU were normalised to protein content of respective aortic rings and expressed as percentage of control set to 100%. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065155#s3" target="_blank">Results</a> are means ± SEM of three separate experiments, each performed with three rings for each LPC. The rings were preincubated without (no LPC) or with 10 µM LPC 18:1 (B), 18:2 (C), 20:4 (D) or 16:0 (E) in the absence or presence of 200 µM Tempol for 30 minutes, followed by precontraction with NE and cumulative addition of ACh. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065155#s3" target="_blank">Results</a> for each condition are mean ± SEM of 12 rings from 6 mice. *P<0.05, **P<0.01.</p

ACh-induced relaxation of mouse aortic rings is attenuated by LPC.

<p>The rings were preincubated without (no LPC) or with 10 µM LPC 16:0 (A), 18:1 (B), 18:2 (C) or 20:4 (D) for 30 minutes, followed by precontraction with NE and cumulative addition of ACh. Relaxation values were expressed as a percentage of the NE-induced contraction. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065155#s3" target="_blank">Results</a> of each experimental condition are mean ± SEM of 24 rings for each case from 6 mice. *P<0.05, **P<0.01***P<0.001.</p

Inhibition of TXA₂- and PGI₂- synthase improves relaxation attenuated by LPC 20:4.

<p>The rings were preincubated without (no LPC) or with LPC 20:4 in the absence or presence of 10 µM furegrelate, a TXA₂ synthase inhibitor (A) or 10 µM tranylcypromine, a PGI₂ synthase inhibitor (B) or a combination of both (C) for 30 minutes, followed by precontraction with NE and cumulative addition of ACh. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065155#s3" target="_blank">Results</a> are mean ± SEM of 12 rings from 6 mice. *P<0.05, **P<0.01.</p

Prostanoid release from LPC-treated aortic rings.

<p>The rings were incubated in 200 µl aerated PSS under cell culture conditions at 37°C for 1 h. Thereafter, buffer was replaced with fresh PSS supplemented with PSS (control) or 10 µM LPC followed by further incubation under cell culture conditions at 37°C for 1 h. (A) 6-keto PGF_1α, a stable degradation product of PGI₂ (B), TXB₂, a stable degradation product of TXA₂, (C) PGE₂ and (D) PGF_2α were quantified by EIA assays and rings were solubilized for protein quantification. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0065155#s3" target="_blank">Results</a> shown in A and B are means ± SD of four experiments and those in C and D of three experiments, done in triplicates. *P<0.05, **P<0.01***P<0.001.</p

Endothelial Lipase Modulates Paraoxonase 1 Content and Arylesterase Activity of HDL

International audienceEndothelial lipase (EL) is a strong modulator of the high-density lipoprotein (HDL) structure, composition, and function. Here, we examined the impact of EL on HDL paraoxonase 1 (PON1) content and arylesterase (AE) activity in vitro and in vivo. The incubation of HDL with EL-overexpressing HepG2 cells decreased HDL size, PON1 content, and AE activity. The EL modification of HDL did not diminish the capacity of HDL to associate with PON1 when EL-modified HDL was incubated with PON1-overexpressing cells. The overexpression of EL in mice significantly decreased HDL serum levels but unexpectedly increased HDL PON1 content and HDL AE activity. Enzymatically inactive EL had no effect on the PON1 content of HDL in mice. In healthy subjects, EL serum levels were not significantly correlated with HDL levels. However, HDL PON1 content was positively associated with EL serum levels. The EL-induced changes in the HDL-lipid composition were not linked to the HDL PON1 content. We conclude that primarily, the interaction of enzymatically active EL with HDL, rather than EL-induced alterations in HDL size and composition, causes PON1 displacement from HDL in vitro. In vivo, the EL-mediated reduction of HDL serum levels and the consequently increased PON1-to-HDL ratio in serum increase HDL PON1 content and AE activity in mice. In humans, additional mechanisms appear to underlie the association of EL serum levels and HDL PON1 content