Quantification of In Vitro Macrophage Cholesterol Efflux and In Vivo Macrophage-Specific Reverse Cholesterol Transport

The intake of olive oil (OO) enriched with phenolic compounds (PCs) promotes ex vivo HDL-mediated macrophage cholesterol efflux in humans. We aimed to determine the effects of PC-enriched virgin OO on reverse cholesterol transport (RevCT) from macrophages to feces in vivo. Female C57BL/6 mice were given intragastric doses of refined OO (ROO) and a functional unrefined virgin OO enriched with its own PC (FVOO) for 14 days. Our experiments included two independent groups of mice that received intragastric doses of the phenolic extract (PE) used to prepare the FVOO and the vehicle solution (saline), as control, for 14 days. FVOO intake led to a significant increase in serum HDL cholesterol and its ability to induce macrophage cholesterol efflux in vitro when compared with ROO group. This was concomitant with the enhanced macrophage-derived [3H]cholesterol transport to feces in vivo. PE intake per se also increased HDL cholesterol levels and significantly promoted in vivo macrophage-to-feces RevCT rate when compared with saline group. PE upregulated the expression of the main macrophage transporter involved in macrophage cholesterol efflux, the ATP binding cassettea1. Our data provide direct evidence of the crucial role of OO PCs in the induction of macrophage-specific RevCT in vivo.

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HDL mediates reverse cholesterol transport from ram spermatozoa and induces hyperactivated motility

Biology of Reproduction ◽

10.1093/biolre/ioab035 ◽

2021 ◽

Author(s):

Naomi C Bernecic ◽

Simon P Graaf ◽

Tamara Leahy ◽

Bart M Gadella

Keyword(s):

Reverse Cholesterol Transport ◽

Cholesterol Efflux ◽

Scavenger Receptor ◽

High Density Lipoproteins ◽

In Vitro Fertilisation ◽

Critical Event ◽

Cholesterol Transport ◽

Type I

ABSTRACT Reverse Cholesterol Transport or cholesterol efflux is part of an extensive plasma membrane remodelling process in spermatozoa that is imperative for fertilisation. For ram spermatozoa, sheep serum is well known to support in vitro fertilisation (IVF), but knowledge of its explicit role is limited. Though, it is postulated to elicit cholesterol efflux owing to the presence of high density lipoproteins (HDLs) that interact with transmembrane cholesterol transporters, such as ATP-binding cassette transporter A1 (ABCA1) and scavenger receptor class B, type I (SR-BI). In this study, we report that both sheep serum and HDLs were able to elicit cholesterol efflux alone by up to 20–40% (as measured by the BODIPY-cholesterol assay). Furthermore, when the antagonists glibenclamide and valspodar were used to inhibit the function of ABCA1 and SR-BI or ABCA1 alone, respectively, cholesterol efflux was only marginally reduced (8–15)%. Nevertheless, it is likely that in ram spermatozoa, a specific facilitated pathway of cholesterol efflux is involved in the interaction between cholesterol acceptors and transporters. Interestingly, exposure to HDLs also induced hyperactivated motility, another critical event required for successful fertilisation. Taken together, this study details the first report of the dual action of HDLs on ram spermatozoa, providing both an insight into the intricacy of events leading up to fertilisation in vivo as well as demonstrating the possible application of HDL supplementation in media for IVF.

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Abstract 316: Paraoxonase 1 (PON1) Promotes the Cholesterol Efflux and Regulates the Reverse Cholesterol Transport (RCT)

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.35.suppl_1.316 ◽

2015 ◽

Vol 35 (suppl_1) ◽

Author(s):

Souade Ikhlef ◽

Hicham Berrougui ◽

Abdelouahed Khalil

Keyword(s):

Reverse Cholesterol Transport ◽

Cholesterol Efflux ◽

Oxidized Ldl ◽

Paraoxonase 1 ◽

Pon1 Activity ◽

Cholesterol Transport ◽

Phospholipase Activity ◽

Gene And Protein Expression

Paraoxonase 1 (PON1) is a High Density Lipoprotein (HDL) associated enzyme which contributes to the antioxidant and anti-inflammatory properties of HDL. It also stimulates cholesterol efflux mediated by HDL. The purpose of this study is to determine the mechanism by which PON1 regulates this antiatherogenic activity of HDL. The oxidized phospholipids hydrolysis by PON1 results in the formation of Lysophosphatidylcholine (LPC). The phospholipase PON1 activity effect on the cholesterol efflux and the gene and protein expression were determined in vitro on J774 macrophages cells and was also determined in vivo on C57/BL6 male mice. Our results show that due to its phospholipase activity, PON1 hydrolyzes oxidized LDL (oxLDL) and contributes to the formation of LPC, which stimulates cholesterol efflux from macrophages. Our results show that PON1 induced the expression of ABCA1 cholesterol transporters. Western blot as well as qPCR analysis show that PON1 stimulate PPARγ and LXRα nuclear receptors expression. Moreover, the use of ABCA1, PPARγ and LXRα inhibitors (respectively DIDS, GGPP and GW9662) affects the capacity of PON1 to stimulate cholesterol efflux, in particular by decreasing the proteins expression of interest (ABCA1, PPARγ and LXRα). Incubation of macrophages with purified LPC with macrophages induces a high expression of PPARγ-LXRα-ABCA1 pathway. Incubation of macrophages with PON1-oxLDL mixture and their injection to mice increase significantly the reverse cholesterol transport. Our results show that tPON1 stimulate both cholesterol efflux and RCT. via the regulation of the PPARγ-LXRα-ABCA1 pathway. This effect is attributed to the phospholipase activity of PON1 which mediates the hydrolysis of ox-LDL to form LPC.

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