Oxidative Stress Is Markedly Elevated in Lecithin:Cholesterol Acyltransferase-deficient Mice and Is Paradoxically Reversed in the Apolipoprotein E Knockout Background in Association with a Reduction in Atherosclerosis

Dominic S Ng,Graham F Maguire,John Wylie,Amir Ravandi,Wanli Xuan,Zakaria Ahmed,Mohammad Eskandarian,Arnis Kuksis,Philip W Connelly

doi:10.1074/jbc.m112320200

Abstract

Complete lecithin:cholesterol acyltransferase (LCAT) deficiency is a rare cause of severe hypoalphalipoproteinemia, but the affected subjects are surprisingly not particularly prone to premature coronary heart disease. We studied oxidative stress in lcat-/- mice and their cross-breed with apolipoprotein-E knockout mice (apoE-/-xlcat-/-) by measuring vascular ring superoxide production and plasma phospholipid (PL)-bound F2-isoprostane levels and their relationship with aortic atherosclerosis. Compared with wild type control (lcat+/+), lcat-/- and lcat+/- mice showed a 4.9- (p = 0.003) and a 2.1-fold (p = 0.04) increase in plasma PL-F2-isoprostane levels, respectively. There was also a 3.6- (p < 0.0001) and 2.9-fold (p = 0.003) increase in the area under the curve for the aortic ring superoxide excursion by lucigenin-derived chemiluminescence. A comparison of apoE-/-xlcat+/+ mice with wild type control mice showed a more modest 2.1- (p = 0.04) and 2.2-fold (p < 0.00001) increase in these respective markers. Surprisingly, the apoE-/-xlcat-/- mice showed a paradoxical normalization in both oxidation markers. Furthermore, by fast protein liquid chromatography separation, we observed an associated retention and redistribution of serum paraoxonase activities to the non-high density lipoprotein fractions in both the apoE-/-xlcat-/- and apoE-/-xlcat+/- mice. Aortic atherosclerotic lesions in male apoE-/-xlcat-/- and apoE-/-xlcat+/- mice were reduced by 52 (p = 0.02) and 24% (p = 0.46), respectively. Our data suggest that LCAT-deficient mice are associated with an increased oxidative stress that is paradoxically reversed in a hyperlipidemic background, possibly due to the redistribution of paraoxonase. This modulation of oxidative stress may in part contribute to the reduced atherosclerosis seen in the apoE-/- xlcat-/- mice.

Highlights

Lecithin:cholesterol acyltransferase (LCAT)1 plays a central role in the reverse cholesterol transport process by mediating the esterification of tissue-derived free cholesterol (FC) and is responsible for the majority of esterified cholesterol (CE) in the circulation [1]
Lipoprotein analyses on the Fast protein liquid chromatography (FPLC) fractions showed a preservation of the accumulation of “VLDL” fractions in the apoEϪ/ϪxlcatϪ/Ϫ and apoEϪ/Ϫxlcatϩ/Ϫ mice in comparison with the apoEϪ/Ϫ xlcatϩ/ϩ control mice (Fig. 1)
The IDL/low density lipoproteins (LDL) shoulder showed a 23% reduction in the apoEϪ/ϪxlcatϪ/Ϫ mice compared with apoEϪ/Ϫxlcatϩ/ϩ and apoEϪ/Ϫxlcatϩ/Ϫ littermates (Fig. 1), consistent with the significant up-regulation of the LDL receptor found in LCAT ko mice [23]

Summary

Introduction

Lecithin:cholesterol acyltransferase (LCAT)1 plays a central role in the reverse cholesterol transport process by mediating the esterification of tissue-derived free cholesterol (FC) and is responsible for the majority of esterified cholesterol (CE) in the circulation [1]. Gene-Gene Interactions on Oxidative Markers and PON1 Activity—Two-way ANOVA analyses on the six genotypic groups showed strong interaction between lcat and apoE alleles on LDCL-AUC, F2-isoP, and PON1 activities with their respective F values being 92.19 (p Ͻ 0.0001), 10.5 (p ϭ 0.0003), and 22.73 (p Ͻ 0.0001).

Results

Conclusion