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      Lipid‐Free Apolipoprotein A‐I Reduces Progression of Atherosclerosis by Mobilizing Microdomain Cholesterol and Attenuating the Number of CD131 Expressing Cells: Monitoring Cholesterol Homeostasis Using the Cellular Ester to Total Cholesterol Ratio

      , MS 1 , , PhD 1 , , MS 5 , , MS 1 , , BS 5 , , BS 1 , , PhD 5 , , MA 5 , , MS 1 , , BS 2 , , MS 1 , 3 , 4 , , PhD 1 , 3 , 4 , , PhD 2 , , PhD , 1 , 2

      Journal of the American Heart Association: Cardiovascular and Cerebrovascular Disease

      John Wiley and Sons Inc.

      apolipoprotein, apolipoprotein A‐I, cholesterol, chronic inflammation, high‐density lipoprotein, inflammation, lipid rafts, microdomains, signaling pathways, Atherosclerosis, Lipids and Cholesterol, Cell Signalling/Signal Transduction, Basic Science Research, Vascular Biology

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          Atherosclerosis is a chronic inflammatory disorder whose development is inversely correlated with high‐density lipoprotein concentration. Current therapies involve pharmaceuticals that significantly elevate plasma high‐density lipoprotein cholesterol concentrations. Our studies were conducted to investigate the effects of low‐dose lipid‐free apolipoprotein A‐I (apoA‐I) on chronic inflammation. The aims of these studies were to determine how subcutaneously injected lipid‐free apoA‐I reduces accumulation of lipid and immune cells within the aortic root of hypercholesterolemic mice without sustained elevations in plasma high‐density lipoprotein cholesterol concentrations.

          Methods and Results

          Ldlr −/− and Ldlr −/− apoA‐I −/− mice were fed a Western diet for a total of 12 weeks. After 6 weeks, a subset of mice from each group received subcutaneous injections of 200 μg of lipid‐free human apoA‐I 3 times a week, while the other subset received 200 μg of albumin, as a control. Mice treated with lipid‐free apoA‐I showed a decrease in cholesterol deposition and immune cell retention in the aortic root compared with albumin‐treated mice, regardless of genotype. This reduction in atherosclerosis appeared to be directly related to a decrease in the number of CD131 expressing cells and the esterified cholesterol to total cholesterol content in several immune cell compartments. In addition, apoA‐I treatment altered microdomain cholesterol composition that shifted CD131, the common β subunit of the interleukin 3 receptor, from lipid raft to nonraft fractions of the plasma membrane.


          ApoA‐I treatment reduced lipid and immune cell accumulation within the aortic root by systemically reducing microdomain cholesterol content in immune cells. These data suggest that lipid‐free apoA‐I mediates beneficial effects through attenuation of immune cell lipid raft cholesterol content, which affects numerous types of signal transduction pathways that rely on microdomain integrity for assembly and activation.

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          Most cited references 101

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          Protein measurement with the Folin phenol reagent.

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            Major lipids, apolipoproteins, and risk of vascular disease.

            Associations of major lipids and apolipoproteins with the risk of vascular disease have not been reliably quantified. To assess major lipids and apolipoproteins in vascular risk. Individual records were supplied on 302,430 people without initial vascular disease from 68 long-term prospective studies, mostly in Europe and North America. During 2.79 million person-years of follow-up, there were 8857 nonfatal myocardial infarctions, 3928 coronary heart disease [CHD] deaths, 2534 ischemic strokes, 513 hemorrhagic strokes, and 2536 unclassified strokes. Hazard ratios (HRs), adjusted for several conventional factors, were calculated for 1-SD higher values: 0.52 log(e) triglyceride, 15 mg/dL high-density lipoprotein cholesterol (HDL-C), 43 mg/dL non-HDL-C, 29 mg/dL apolipoprotein AI, 29 mg/dL apolipoprotein B, and 33 mg/dL directly measured low-density lipoprotein cholesterol (LDL-C). Within-study regression analyses were adjusted for within-person variation and combined using meta-analysis. The rates of CHD per 1000 person-years in the bottom and top thirds of baseline lipid distributions, respectively, were 2.6 and 6.2 with triglyceride, 6.4 and 2.4 with HDL-C, and 2.3 and 6.7 with non-HDL-C. Adjusted HRs for CHD were 0.99 (95% CI, 0.94-1.05) with triglyceride, 0.78 (95% CI, 0.74-0.82) with HDL-C, and 1.50 (95% CI, 1.39-1.61) with non-HDL-C. Hazard ratios were at least as strong in participants who did not fast as in those who did. The HR for CHD was 0.35 (95% CI, 0.30-0.42) with a combination of 80 mg/dL lower non-HDL-C and 15 mg/dL higher HDL-C. For the subset with apolipoproteins or directly measured LDL-C, HRs were 1.50 (95% CI, 1.38-1.62) with the ratio non-HDL-C/HDL-C, 1.49 (95% CI, 1.39-1.60) with the ratio apo B/apo AI, 1.42 (95% CI, 1.06-1.91) with non-HDL-C, and 1.38 (95% CI, 1.09-1.73) with directly measured LDL-C. Hazard ratios for ischemic stroke were 1.02 (95% CI, 0.94-1.11) with triglyceride, 0.93 (95% CI, 0.84-1.02) with HDL-C, and 1.12 (95% CI, 1.04-1.20) with non-HDL-C. Lipid assessment in vascular disease can be simplified by measurement of either total and HDL cholesterol levels or apolipoproteins without the need to fast and without regard to triglyceride.
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              Macrophages in atherosclerosis: a dynamic balance.

              Atherosclerosis is a chronic inflammatory disease that arises from an imbalance in lipid metabolism and a maladaptive immune response driven by the accumulation of cholesterol-laden macrophages in the artery wall. Through the analysis of the progression and regression of atherosclerosis in animal models, there is a growing understanding that the balance of macrophages in the plaque is dynamic and that both macrophage numbers and the inflammatory phenotype influence plaque fate. In this Review, we summarize recently identified pro- and anti-inflammatory pathways that link lipid and inflammation biology with the retention of macrophages in plaques, as well as factors that have the potential to promote their egress from these sites.

                Author and article information

                J Am Heart Assoc
                J Am Heart Assoc
                Journal of the American Heart Association: Cardiovascular and Cerebrovascular Disease
                John Wiley and Sons Inc. (Hoboken )
                07 November 2016
                November 2016
                : 5
                : 11 ( doiID: 10.1002/jah3.2016.5.issue-11 )
                © 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

                This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.

                Figures: 8, Tables: 0, Pages: 13, Words: 13234
                Funded by: National Institutes of Health
                Award ID: DK 071895
                Award ID: DK65598
                Award ID: R01HL112270
                Award ID: R01HL127649
                Funded by: TOPS Club, Inc.
                Original Research
                Original Research
                Coronary Heart Disease
                Custom metadata
                November 2016
                Converter:WILEY_ML3GV2_TO_NLMPMC version:4.9.8 mode:remove_FC converted:21.11.2016


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