Limits...
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.

Show MeSH

Related in: MedlinePlus

Atherosclerotic plaque composition.Immunofluorescent images of Apoeh/hLysM-Cre (A) and Apoeh/h mice (B; scale bar = 50 µm) aortic roots; anti-smooth-muscle-cell-α-actin (SMCs, red), anti-Mac-2 (Macrophages, green) and nuclei (blue). Sirius Red stained aortic roots (brightfield (C–D) and polarized light (E–F)) from Apoeh/hLysM-Cre (C,E) and Apoeh/h mice (D,F); (scale bar = 250 µm). Collagen quantification (G–H, n = 7, mean±sem).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3351426&req=5

pone-0035816-g006: Atherosclerotic plaque composition.Immunofluorescent images of Apoeh/hLysM-Cre (A) and Apoeh/h mice (B; scale bar = 50 µm) aortic roots; anti-smooth-muscle-cell-α-actin (SMCs, red), anti-Mac-2 (Macrophages, green) and nuclei (blue). Sirius Red stained aortic roots (brightfield (C–D) and polarized light (E–F)) from Apoeh/hLysM-Cre (C,E) and Apoeh/h mice (D,F); (scale bar = 250 µm). Collagen quantification (G–H, n = 7, mean±sem).

Mentions: To determine whether macrophage-derived apoE in atheroma had a local effect on plaque composition, we assessed the presence of smooth muscle cells and collagen levels in aortic root lesions of both mouse models. As shown in Figure 6A&B, the immunoreactivity for smooth muscle α-actin in the intimae of the lesions confirmed the presence of fibrous caps in both groups of mice. In addition, we found a similar percentage of total collagen content in the lesions of both Apoeh/hLysM-Cre and Apoeh/h mice (44.0±4.6% versus 43.1±4.7%; Fig. 6C–H). Taken together, these results demonstrate that despite a 40% decrease in lesion area and two-fold increase in apoE immunoreactivity, the lesions of Apoeh/hLysM-Cre mice were at a similar stage of complexity as those of Apoeh/h mice.


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)

Atherosclerotic plaque composition.Immunofluorescent images of Apoeh/hLysM-Cre (A) and Apoeh/h mice (B; scale bar = 50 µm) aortic roots; anti-smooth-muscle-cell-α-actin (SMCs, red), anti-Mac-2 (Macrophages, green) and nuclei (blue). Sirius Red stained aortic roots (brightfield (C–D) and polarized light (E–F)) from Apoeh/hLysM-Cre (C,E) and Apoeh/h mice (D,F); (scale bar = 250 µm). Collagen quantification (G–H, n = 7, mean±sem).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0035816-g006: Atherosclerotic plaque composition.Immunofluorescent images of Apoeh/hLysM-Cre (A) and Apoeh/h mice (B; scale bar = 50 µm) aortic roots; anti-smooth-muscle-cell-α-actin (SMCs, red), anti-Mac-2 (Macrophages, green) and nuclei (blue). Sirius Red stained aortic roots (brightfield (C–D) and polarized light (E–F)) from Apoeh/hLysM-Cre (C,E) and Apoeh/h mice (D,F); (scale bar = 250 µm). Collagen quantification (G–H, n = 7, mean±sem).
Mentions: To determine whether macrophage-derived apoE in atheroma had a local effect on plaque composition, we assessed the presence of smooth muscle cells and collagen levels in aortic root lesions of both mouse models. As shown in Figure 6A&B, the immunoreactivity for smooth muscle α-actin in the intimae of the lesions confirmed the presence of fibrous caps in both groups of mice. In addition, we found a similar percentage of total collagen content in the lesions of both Apoeh/hLysM-Cre and Apoeh/h mice (44.0±4.6% versus 43.1±4.7%; Fig. 6C–H). Taken together, these results demonstrate that despite a 40% decrease in lesion area and two-fold increase in apoE immunoreactivity, the lesions of Apoeh/hLysM-Cre mice were at a similar stage of complexity as those of Apoeh/h mice.

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