Atherosclerosis 202 (2009) 461–469 Di-oleoyl phosphatidylcholine (PC-18:1) stimulates paraoxonase 1 (PON1) enzymatic and biological activities: In vitro and in vivo studies Michal Efrat a , Mira Rosenblat a , Saeed Mahmood b , Jacob Vaya b , Michael Aviram a,∗ a The Lipid Research Laboratory, Technion Faculty of Medicine, The Rappaport Family Institute for Research in the Medical Sciences, Rambam Medical Center, Haifa 31096, Israel b TheLaboratory of Natural Compounds for Medical Use, Migal, Galilee Technological Center, Israel Received 6 March 2008; received in revised form 1 May 2008; accepted 5 May 2008 Available online 15 May 2008 Abstract Objective: Paraoxonase 1 (PON1) is a high-density lipoprotein (HDL)-associated enzyme which possess anti-atherogenic properties. Our aim was to analyze the effect of HDL phospholipids on HDL-associated paraoxonase (PON1) catalytic and biological activities. Methods and results: In HDL isolated from di-oleoyl-phosphatidylcholine (PC-18:1)-enriched serum, HDL–PC-18:1 levels, as well as PON1 lactonase, arylesterase and paraoxonase activities were increased by 23%, 35%, 47% and 63%, respectively, as compared to control HDL (p < 0.01). Furthermore, PON1 contribution to HDL-mediated cholesterol efflux from J774A.1 macrophages was higher in PC-18:1-enriched HDL in comparison to control HDL. In vivo olive oil consumption by Balb C mice increased HDL phospholipids/protein (30%), and HDL–PON1 arylesterase (150%) and lactonase (94%) activities (p < 0.01). Furthermore, in the olive oil-treated mice PON1 contribution to HDL-mediated macrophage cholesterol efflux was higher by 100%, in comparison to placebo mouse HDL (p < 0.01). Similarly, olive oil consumption by healthy subjects increased HDL–PC-18:1 levels, HDL–PON1 arylesterase (88%), lactonase (52%), paraoxonase (140%) activities and PON1 stimulatory effect on HDL-mediated cholesterol efflux (53%) as compared to HDL before treatment (p < 0.01). PC-18:1 stimulatory effect on recombinant PON1 mutant (lacks 20 amino acids at the N-terminal region) paraoxonase and lactonase activities was lower by 56% and 57%, respectively, in comparison to its effect on wild type PON1 (p < 0.01). Conclusion: Intervention to increase PON1 activities by HDL enrichment with PC-18:1 could be proven as a beneficial anti-atherogenic therapy. © 2008 Elsevier Ireland Ltd. All rights reserved. Keywords: Paraoxonase 1; HDL; Di-oleoyl phosphatidylcholine; Lactonase activity; Macrophages; Cholesterol efflux 1. Introduction Serum paraoxonase 1 (PON1) is associated mostly with high-density lipoprotein (HDL) and to a minor extent also with chylomicrons or VLDL [1]. PON1 exhibits a wide range of hydrolytic activities such as arylesterase, phos- photriesterase and lactonase (which is its primary native function [2]). Human serum PON1 activity was shown to be inversely related to the risk of cardiovascular diseases ∗ Corresponding author. Tel.: +972 4 8542970; fax: +972 4 8542130. E-mail address: aviram@tx.technion.ac.il (M. Aviram). [3]. Low PON1 activities were observed in atherosclerotic, hypercholesterolemic and diabetic patients [4], as well as in the atherosclerotic apolipoprotein E-deficient (E 0 ) mice [5], and in rabbits fed an atherogenic diet [6]. The role of PON1 in atherosclerosis development was demonstrated in studies using mice lacking PON1 [7,8] or over-expressing PON1 [9]. PON1 anti-atherogenic properties include protec- tion of LDL, HDL and macrophages against oxidative stress [10], attenuation of oxidized-LDL uptake by macrophages [11], inhibition of macrophages cholesterol biosynthesis [12] and stimulation of HDL-mediated cholesterol efflux from the cells [13]. 0021-9150/$ – see front matter © 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.atherosclerosis.2008.05.016