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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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Related in: MedlinePlus

Macrophage-derived apoE levels in atherosclerosis.Histological sections of oil-red-O stained aortic roots from Apoeh/hLysM-Cre (A) and Apoeh/h mice (B; scale bar = 250 µm). Quantification of oil-red-O positive area (n = 7; mean±sem, **P<0.01; C), aortic wall area (D), and % of oil-red-O (E). Correlation analysis between oil-red-O area and plasma cholesterol (n = 14; **P<0.01; F).
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pone-0035816-g004: Macrophage-derived apoE levels in atherosclerosis.Histological sections of oil-red-O stained aortic roots from Apoeh/hLysM-Cre (A) and Apoeh/h mice (B; scale bar = 250 µm). Quantification of oil-red-O positive area (n = 7; mean±sem, **P<0.01; C), aortic wall area (D), and % of oil-red-O (E). Correlation analysis between oil-red-O area and plasma cholesterol (n = 14; **P<0.01; F).

Mentions: We next assessed the contribution of macrophage-derived apoE expression levels on atherosclerosis in Apoeh/h and Apoeh/hLysM-Cre mice fed a HCD. As shown in Fig. 4, the aortic root oil-red O positive area was 35.5% smaller in Apoeh/hLysM-Cre mice than in Apoeh/h mice (167×103±16×103 µm2 versus 259×103±56×103 µm2; p<0.01; Fig. 4A,B&C). However, normalizing the oil-red O positive area to that of the aortic root wall area (Fig. 4D) revealed that in both groups of mice, the atheroma within the aortic root contained the same percentage of neutral lipids (Fig. 4E). In addition, in Apoeh/h mice but not in Apoeh/hLysM-Cre mice, the oil-red O positive area was directly proportional to plasma cholesterol levels (Fig. 4F; r2 = 0.86, p<0.01, and r2 = 0.06, respectively).


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)

Macrophage-derived apoE levels in atherosclerosis.Histological sections of oil-red-O stained aortic roots from Apoeh/hLysM-Cre (A) and Apoeh/h mice (B; scale bar = 250 µm). Quantification of oil-red-O positive area (n = 7; mean±sem, **P<0.01; C), aortic wall area (D), and % of oil-red-O (E). Correlation analysis between oil-red-O area and plasma cholesterol (n = 14; **P<0.01; F).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0035816-g004: Macrophage-derived apoE levels in atherosclerosis.Histological sections of oil-red-O stained aortic roots from Apoeh/hLysM-Cre (A) and Apoeh/h mice (B; scale bar = 250 µm). Quantification of oil-red-O positive area (n = 7; mean±sem, **P<0.01; C), aortic wall area (D), and % of oil-red-O (E). Correlation analysis between oil-red-O area and plasma cholesterol (n = 14; **P<0.01; F).
Mentions: We next assessed the contribution of macrophage-derived apoE expression levels on atherosclerosis in Apoeh/h and Apoeh/hLysM-Cre mice fed a HCD. As shown in Fig. 4, the aortic root oil-red O positive area was 35.5% smaller in Apoeh/hLysM-Cre mice than in Apoeh/h mice (167×103±16×103 µm2 versus 259×103±56×103 µm2; p<0.01; Fig. 4A,B&C). However, normalizing the oil-red O positive area to that of the aortic root wall area (Fig. 4D) revealed that in both groups of mice, the atheroma within the aortic root contained the same percentage of neutral lipids (Fig. 4E). In addition, in Apoeh/h mice but not in Apoeh/hLysM-Cre mice, the oil-red O positive area was directly proportional to plasma cholesterol levels (Fig. 4F; r2 = 0.86, p<0.01, and r2 = 0.06, respectively).

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