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Macrophage-specific apoE gene repair reduces diet-induced hyperlipidemia and atherosclerosis in hypomorphic Apoe mice.

Gaudreault N, Kumar N, Olivas VR, Eberlé D, Rapp JH, Raffai RL - PLoS ONE (2012)

Bottom Line: Although the liver is the major source of plasma apoE, extra-hepatic sources of apoE, including from macrophages, account for up to 10% of plasma apoE levels.This difference in atherosclerosis lesions size was proportional to the observed reduction in plasma cholesterol.Macrophage-derived apoE raises plasma apoE levels in response to diet-induced hyperlipidemia and by such reduces atherosclerosis proportionally to the extent to which it lowers plasma cholesterol levels.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgery, University of California San Francisco, VA Medical Center, San Francisco, California, United States of America.

ABSTRACT

Background: Apolipoprotein (apo) E is best known for its ability to lower plasma cholesterol and protect against atherosclerosis. Although the liver is the major source of plasma apoE, extra-hepatic sources of apoE, including from macrophages, account for up to 10% of plasma apoE levels. This study examined the contribution of macrophage-derived apoE expression levels in diet-induced hyperlipidemia and atherosclerosis.

Methodology/principal findings: Hypomorphic apoE (Apoe(h/h)) mice expressing wildtype mouse apoE at ∼2-5% of physiological levels in all tissues were derived by gene targeting in embryonic stem cells. Cre-mediated gene repair of the Apoe(h/h) allele in Apoe(h/h)LysM-Cre mice raised apoE expression levels by 26 fold in freshly isolated peritoneal macrophages, restoring it to 37% of levels seen in wildtype mice. Chow-fed Apoe(h/h)LysM-Cre and Apoe(h/h) mice displayed similar plasma apoE and cholesterol levels (55.53±2.90 mg/dl versus 62.70±2.77 mg/dl, n = 12). When fed a high-cholesterol diet (HCD) for 16 weeks, Apoe(h/h)LysM-Cre mice displayed a 3-fold increase in plasma apoE and a concomitant 32% decrease in plasma cholesterol when compared to Apoe(h/h) mice (602.20±22.30 mg/dl versus 888.80±24.99 mg/dl, n = 7). On HCD, Apoe(h/h)LysM-Cre mice showed increased apoE immunoreactivity in lesional macrophages and liver-associated Kupffer cells but not hepatocytes. In addition, Apoe(h/h)LysM-Cre mice developed 35% less atherosclerotic lesions in the aortic root than Apoe(h/h) mice (167×10(3)±16×10(3) µm(2) versus 259×10(3)±56×10(3) µm(2), n = 7). This difference in atherosclerosis lesions size was proportional to the observed reduction in plasma cholesterol.

Conclusions/significance: Macrophage-derived apoE raises plasma apoE levels in response to diet-induced hyperlipidemia and by such reduces atherosclerosis proportionally to the extent to which it lowers plasma cholesterol levels.

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Lesional macrophage-derived apoE.Immunofluorescent images of Apoeh/hLysM-Cre (A,C) and Apoeh/h mice (B,D; scale bar = 250 µm) aortic roots; anti-Mac-2 (green), and apoE (red). Quantification of lesion area (E), macrophage positive and % of area (F–G); n = 7. Quantification of apoE fluorescence intensity (FI), (H); n = 7, mean±sem, *P<0.05, **P<0.01, ***P<0.001.
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pone-0035816-g005: Lesional macrophage-derived apoE.Immunofluorescent images of Apoeh/hLysM-Cre (A,C) and Apoeh/h mice (B,D; scale bar = 250 µm) aortic roots; anti-Mac-2 (green), and apoE (red). Quantification of lesion area (E), macrophage positive and % of area (F–G); n = 7. Quantification of apoE fluorescence intensity (FI), (H); n = 7, mean±sem, *P<0.05, **P<0.01, ***P<0.001.

Mentions: Additional characterizations of aortic root atheromas with immunofluorescence microscopy (Fig. 5) revealed 46% less macrophage positive area in Apoeh/hLysM-Cre mice than in Apoeh/h mice (141×103±16×103 µm2 versus 259×103±12×103 µm2, p<0.01; Fig. 5A,B&F). However, when normalized to the aortic root intimae area (Fig. 5E), the lesions in both groups of mice contained the same percentage of macrophages (Fig. 5G). We also observed a 2.4-fold increase in apoE fluorescence intensity within the atheroma of Apoeh/hLysM-Cre mice compared to that of Apoeh/h mice (465.3±81.2a.u./µm2 versus 190.8±25.9a.u./µm2, p = 0.01; Fig. 5C,D&H).


Macrophage-specific apoE gene repair reduces diet-induced hyperlipidemia and atherosclerosis in hypomorphic Apoe mice.

Gaudreault N, Kumar N, Olivas VR, Eberlé D, Rapp JH, Raffai RL - PLoS ONE (2012)

Lesional macrophage-derived apoE.Immunofluorescent images of Apoeh/hLysM-Cre (A,C) and Apoeh/h mice (B,D; scale bar = 250 µm) aortic roots; anti-Mac-2 (green), and apoE (red). Quantification of lesion area (E), macrophage positive and % of area (F–G); n = 7. Quantification of apoE fluorescence intensity (FI), (H); n = 7, mean±sem, *P<0.05, **P<0.01, ***P<0.001.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3351426&req=5

pone-0035816-g005: Lesional macrophage-derived apoE.Immunofluorescent images of Apoeh/hLysM-Cre (A,C) and Apoeh/h mice (B,D; scale bar = 250 µm) aortic roots; anti-Mac-2 (green), and apoE (red). Quantification of lesion area (E), macrophage positive and % of area (F–G); n = 7. Quantification of apoE fluorescence intensity (FI), (H); n = 7, mean±sem, *P<0.05, **P<0.01, ***P<0.001.
Mentions: Additional characterizations of aortic root atheromas with immunofluorescence microscopy (Fig. 5) revealed 46% less macrophage positive area in Apoeh/hLysM-Cre mice than in Apoeh/h mice (141×103±16×103 µm2 versus 259×103±12×103 µm2, p<0.01; Fig. 5A,B&F). However, when normalized to the aortic root intimae area (Fig. 5E), the lesions in both groups of mice contained the same percentage of macrophages (Fig. 5G). We also observed a 2.4-fold increase in apoE fluorescence intensity within the atheroma of Apoeh/hLysM-Cre mice compared to that of Apoeh/h mice (465.3±81.2a.u./µm2 versus 190.8±25.9a.u./µm2, p = 0.01; Fig. 5C,D&H).

Bottom Line: Although the liver is the major source of plasma apoE, extra-hepatic sources of apoE, including from macrophages, account for up to 10% of plasma apoE levels.This difference in atherosclerosis lesions size was proportional to the observed reduction in plasma cholesterol.Macrophage-derived apoE raises plasma apoE levels in response to diet-induced hyperlipidemia and by such reduces atherosclerosis proportionally to the extent to which it lowers plasma cholesterol levels.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgery, University of California San Francisco, VA Medical Center, San Francisco, California, United States of America.

ABSTRACT

Background: Apolipoprotein (apo) E is best known for its ability to lower plasma cholesterol and protect against atherosclerosis. Although the liver is the major source of plasma apoE, extra-hepatic sources of apoE, including from macrophages, account for up to 10% of plasma apoE levels. This study examined the contribution of macrophage-derived apoE expression levels in diet-induced hyperlipidemia and atherosclerosis.

Methodology/principal findings: Hypomorphic apoE (Apoe(h/h)) mice expressing wildtype mouse apoE at ∼2-5% of physiological levels in all tissues were derived by gene targeting in embryonic stem cells. Cre-mediated gene repair of the Apoe(h/h) allele in Apoe(h/h)LysM-Cre mice raised apoE expression levels by 26 fold in freshly isolated peritoneal macrophages, restoring it to 37% of levels seen in wildtype mice. Chow-fed Apoe(h/h)LysM-Cre and Apoe(h/h) mice displayed similar plasma apoE and cholesterol levels (55.53±2.90 mg/dl versus 62.70±2.77 mg/dl, n = 12). When fed a high-cholesterol diet (HCD) for 16 weeks, Apoe(h/h)LysM-Cre mice displayed a 3-fold increase in plasma apoE and a concomitant 32% decrease in plasma cholesterol when compared to Apoe(h/h) mice (602.20±22.30 mg/dl versus 888.80±24.99 mg/dl, n = 7). On HCD, Apoe(h/h)LysM-Cre mice showed increased apoE immunoreactivity in lesional macrophages and liver-associated Kupffer cells but not hepatocytes. In addition, Apoe(h/h)LysM-Cre mice developed 35% less atherosclerotic lesions in the aortic root than Apoe(h/h) mice (167×10(3)±16×10(3) µm(2) versus 259×10(3)±56×10(3) µm(2), n = 7). This difference in atherosclerosis lesions size was proportional to the observed reduction in plasma cholesterol.

Conclusions/significance: Macrophage-derived apoE raises plasma apoE levels in response to diet-induced hyperlipidemia and by such reduces atherosclerosis proportionally to the extent to which it lowers plasma cholesterol levels.

Show MeSH
Related in: MedlinePlus