THP-1 macrophage cholesterol efflux is impaired by palmitoleate through Akt activation.

Jenika D Marshall,Bronwyn A Woolfrey,Madeline N Fitzpatrick,Robert J Brown,Emily R Courage,Andrea F Lopez-Clavijo,Anne D Kim,Ryan F Elliott,Michael J O Wakelam,Mireille Ouimet,Laura Calabresi

doi:10.1371/journal.pone.0233180

Jenika D Marshall, Bronwyn A Woolfrey + Show 9 more

Open Access

https://doi.org/10.1371/journal.pone.0233180

Copy DOI

Journal: PloS one	Publication Date: May 21, 2020
Citations: 4	License type: CC BY 4.0

Affiliation: Babraham Institute, University of Ottawa

Abstract

Lipoprotein lipase (LPL) is upregulated in atherosclerotic lesions and it may promote the progression of atherosclerosis, but the mechanisms behind this process are not completely understood. We previously showed that the phosphorylation of Akt within THP-1 macrophages is increased in response to the lipid hydrolysis products generated by LPL from total lipoproteins. Notably, the free fatty acid (FFA) component was responsible for this effect. In the present study, we aimed to reveal more detail as to how the FFA component may affect Akt signalling. We show that the phosphorylation of Akt within THP-1 macrophages increases with total FFA concentration and that phosphorylation is elevated up to 18 hours. We further show that specifically the palmitoleate component of the total FFA affects Akt phosphorylation. This is tied with changes to the levels of select molecular species of phosphoinositides. We further show that the total FFA component, and specifically palmitoleate, reduces apolipoprotein A-I-mediated cholesterol efflux, and that the reduction can be reversed in the presence of the Akt inhibitor MK-2206. Overall, our data support a negative role for the FFA component of lipoprotein hydrolysis products generated by LPL, by impairing macrophage cholesterol efflux via Akt activation.

Highlights

Lipoprotein lipase (LPL) is an extracellular enzyme required for the hydrolysis of triacylglycerols (TAG), and to a much lesser extent phospholipids, from TAG-rich lipoproteins within the bloodstream [1,2]
We hypothesized that one or more specific fatty acids that exist within the total free fatty acid (FFA) component of lipoprotein hydrolysis products that are generated by LPL impair cholesterol efflux through the activation of Akt. To test this hypothesis, using THP-1 macrophages, we examined the activation of Akt in response to various FFA mixtures that contain the concentrations of FFA species that we previously reported to be found within LPL hydrolysis products from total lipoproteins [16]
We previously showed using antibody arrays that the hydrolysis products liberated by LPL from total lipoproteins (ρ

Summary

Introduction

Lipoprotein lipase (LPL) is an extracellular enzyme required for the hydrolysis of triacylglycerols (TAG), and to a much lesser extent phospholipids, from TAG-rich lipoproteins within the bloodstream [1,2]. LPL is anchored to the outside of the endothelial cells lining the luminal surface of capillaries in several tissues via heparan sulfate proteoglycans [3,4,5], and as a headto-tail homodimer to glycerophosphatidylinositol high-density lipoprotein binding protein-1 [6]. LPL is expressed by several tissues, including adipose, skeletal, cardiac, breast, adrenal tissues, and macrophages [3,4]. In addition to its catalytic function, LPL actively. Palmitoleate inhibits cholesterol efflux via Akt activation

Objectives

Methods

Results

Conclusion