Eicosapentaenoic Acid and Docosahexaenoic Acid Regulate Modified LDL Uptake and Macropinocytosis in Human Macrophages

Abstract

There is evidence that long chain n-3 PUFA (such as from fish oils) provide atheroprotection through, in part, changes in macrophage function although it has not been fully determined whether these n-3 PUFA target cellular mechanisms that control macrophage foam cell formation. Therefore, we investigated whether the n-3 PUFA, EPA and DHA, modulate modified low-density lipoprotein (LDL) uptake by human macrophages. The uptake of fluorophore labeled acetylated LDL (AcLDL) and/or oxidized LDL (OxLDL) by THP-1 macrophages and primary human monocyte-derived macrophages were measured by flow cytometry following co-incubation with EPA or DHA in vitro. DHA inhibited both AcLDL and OxLDL uptake in human macrophages whilst EPA reduced AcLDL and increased OxLDL uptake. These effects were only partly explained by changes in the mRNA and protein expression of key scavenger receptors, such as CD36 and scavenger receptor-A, in these cells suggesting the involvement of a scavenger receptor-independent mechanism. EPA and DHA inhibited macropinocytosis, as measured by Lucifer Yellow uptake, in human macrophages and attenuated the expression of Syndecan-4, which has been implicated in the uptake of other modified forms of LDL. EPA and DHA reduced modified LDL uptake by human macrophages through a mechanism that is in part scavenger receptor-independent and may involve inhibition of macropinocytosis and Syndecan-4 expression. This suggests that both EPA and DHA are capable of regulating macrophage foam cell formation and adds to the evidence describing an atheroprotective role for n-3 PUFA, implicating them as potential therapeutic agents for the treatment of clinical atherosclerosis.

The Phosphoinositide 3‐Kinase Signaling Pathway is Involved in the Control of Modified Low‐Density Lipoprotein Uptake by Human Macrophages

“…Total cell lysates were size-fractionated on SDS-polyacrylamide gels (Life Technologies) and then analyzed by Western blot analysis as previously described [7, 9, 10]. Antibodies were either from Santacruz Biotechnology [SR-A (sc-20660), CD36 (sc-9154)] or Sigma-Aldrich (β-actin).…”

“…The process involves actin-dependent ruffling of the plasma membrane and the subsequent fusion of the membrane to itself to form intracellular fluid filled vacuoles 0.5–5 μM in diameter [5, 6]. Although an important role for macropinocytosis in the uptake of native LDL is well established [5, 6], our recent studies have extended the role of this process to the uptake of modified LDL by macrophages [7, 8]. Previous studies have shown that PI3K plays a potentially important role in macropinocytosis, including the uptake of native LDL, under certain conditions [5, 6].…”

Oral omega-3 fatty acids promote resolution in chemical peritonitis

“…In this study, we demonstrate that oral fish oil supplementation induced a significant increase in have begun to uncover some as-of-yet unclear associations 17,29,[47][48][49] . Akin to our results, one study displayed a 26% decrease in PPARγ mRNA in mouse aortas following a 12 week fish oil diet; in another study TNFα decreased PPARγ synthesis in macrophages 50 , perhaps providing a mechanism for the M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 13 decreased PPARγ mRNA, unchanged particle phagocytosis and unchanged macrophage vacuolization in this study.…”

The natural compound berberine positively affects macrophage functions involved in atherogenesis

“…We tested the potential inhibitory effect of BBR on macropinocytosis evaluating the uptake of lucifer yellow (LY) [23] in THP-1 macrophages through confocal microscopy. When cells were in basal conditions, macropinocytosis was clearly detectable after 2 h incubation with LY ( Fig.…”