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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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Plasma apoE and lipid levels.Representative Western blot (A) and quantification (B; n = 3) of the band intensity of plasma apoE from wild type (WT), Apoe−/− (E−/−), Apoeh/h and Apoeh/hLysM-Cre mice either fed a chow diet or a high cholesterol diet (HCD); mean±sem, two-way ANOVA Bonferonni post-tests, **p<0.01 and t-test #p<0.05. Plasma cholesterol (n = 7; mean±sem, one-way ANOVA post-test, ***p<0.001; C) and lipoprotein cholesterol distribution (pooled of 7 mice; D) are shown; inset: Western blot of apoB and quantification (n = 3); mean±sem, two-way ANOVA Bonferonni post-tests, **p<0.01, ***p<0.001. Representative Western Blot of apoE distribution in lipoprotein fractions (E).
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pone-0035816-g002: Plasma apoE and lipid levels.Representative Western blot (A) and quantification (B; n = 3) of the band intensity of plasma apoE from wild type (WT), Apoe−/− (E−/−), Apoeh/h and Apoeh/hLysM-Cre mice either fed a chow diet or a high cholesterol diet (HCD); mean±sem, two-way ANOVA Bonferonni post-tests, **p<0.01 and t-test #p<0.05. Plasma cholesterol (n = 7; mean±sem, one-way ANOVA post-test, ***p<0.001; C) and lipoprotein cholesterol distribution (pooled of 7 mice; D) are shown; inset: Western blot of apoB and quantification (n = 3); mean±sem, two-way ANOVA Bonferonni post-tests, **p<0.01, ***p<0.001. Representative Western Blot of apoE distribution in lipoprotein fractions (E).

Mentions: Because macrophage-derived apoE has been shown to reduce plasma cholesterol levels [6], [7], we investigated whether a 26-fold increase in macrophage-derived apoE expression would modulate circulating levels of plasma apoE in Apoeh/hLysM-Cre mice relative to Apoeh/h mice. Interestingly, as shown in Figure 2A&B, Apoeh/hLysM-Cre had modestly more plasma apoE than Apoeh/h mice when fed a chow diet, corresponding to 1.7% and 0.8% of levels seen in WT mice fed a chow diet, respectively. Following 16 weeks of HCD consumption, Apoeh/hLysM-Cre mice showed a 3-fold increase in plasma apoE levels relative to Apoeh/h mice (Fig. 2A&B) reaching nearly 10% of WT levels.


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)

Plasma apoE and lipid levels.Representative Western blot (A) and quantification (B; n = 3) of the band intensity of plasma apoE from wild type (WT), Apoe−/− (E−/−), Apoeh/h and Apoeh/hLysM-Cre mice either fed a chow diet or a high cholesterol diet (HCD); mean±sem, two-way ANOVA Bonferonni post-tests, **p<0.01 and t-test #p<0.05. Plasma cholesterol (n = 7; mean±sem, one-way ANOVA post-test, ***p<0.001; C) and lipoprotein cholesterol distribution (pooled of 7 mice; D) are shown; inset: Western blot of apoB and quantification (n = 3); mean±sem, two-way ANOVA Bonferonni post-tests, **p<0.01, ***p<0.001. Representative Western Blot of apoE distribution in lipoprotein fractions (E).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3351426&req=5

pone-0035816-g002: Plasma apoE and lipid levels.Representative Western blot (A) and quantification (B; n = 3) of the band intensity of plasma apoE from wild type (WT), Apoe−/− (E−/−), Apoeh/h and Apoeh/hLysM-Cre mice either fed a chow diet or a high cholesterol diet (HCD); mean±sem, two-way ANOVA Bonferonni post-tests, **p<0.01 and t-test #p<0.05. Plasma cholesterol (n = 7; mean±sem, one-way ANOVA post-test, ***p<0.001; C) and lipoprotein cholesterol distribution (pooled of 7 mice; D) are shown; inset: Western blot of apoB and quantification (n = 3); mean±sem, two-way ANOVA Bonferonni post-tests, **p<0.01, ***p<0.001. Representative Western Blot of apoE distribution in lipoprotein fractions (E).
Mentions: Because macrophage-derived apoE has been shown to reduce plasma cholesterol levels [6], [7], we investigated whether a 26-fold increase in macrophage-derived apoE expression would modulate circulating levels of plasma apoE in Apoeh/hLysM-Cre mice relative to Apoeh/h mice. Interestingly, as shown in Figure 2A&B, Apoeh/hLysM-Cre had modestly more plasma apoE than Apoeh/h mice when fed a chow diet, corresponding to 1.7% and 0.8% of levels seen in WT mice fed a chow diet, respectively. Following 16 weeks of HCD consumption, Apoeh/hLysM-Cre mice showed a 3-fold increase in plasma apoE levels relative to Apoeh/h mice (Fig. 2A&B) reaching nearly 10% of WT levels.

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