Cited by 194Atherosclerosis and Cardiovascular DiseasesCholesterol and Lipid MetabolismLipoproteins and Cardiovascular Health

The DOI matches its Crossref record; 23 of the 23 references it cites were found in a registry or an index; none of the 17 sources its claims cite is checked for support yet.

Macrophage Sortilin Promotes LDL Uptake, Foam Cell Formation, and Atherosclerosis

Open access

Abstract

Rationale: Noncoding gene variants at the SORT1 locus are strongly associated with low-density lipoprotein cholesterol (LDL-C) levels, as well as with coronary artery disease. SORT1 encodes a protein called sortilin, and hepatic sortilin modulates LDL metabolism by targeting apolipoprotein B–containing lipoproteins to the lysosome. Sortilin is also expressed in macrophages, but its role in macrophage uptake of LDL and in atherosclerosis independent of plasma LDL-C levels is unknown. Objective: To determine the effect of macrophage sortilin expression on LDL uptake, foam cell formation, and atherosclerosis. Methods and Results: We crossed Sort1 −/− mice onto a humanized Apobec1 −/− ; hAPOB transgenic background and determined that Sort1 deficiency on this background had no effect on plasma LDL-C levels but dramatically reduced atherosclerosis in the aorta and aortic root. To test whether this effect was a result of macrophage sortilin deficiency, we transplanted Sort1 −/− ;LDLR −/− or Sort1 +/+ ;LDLR −/− bone marrow into Ldlr −/− mice and observed a similar reduction in atherosclerosis in mice lacking hematopoetic sortilin without an effect on plasma LDL-C levels. In an effort to determine the mechanism by which hematopoetic sortilin deficiency reduced atherosclerosis, we found no effect of sortilin deficiency on macrophage recruitment or lipopolysaccharide-induced cytokine release in vivo. In contrast, sortilin-deficient macrophages had significantly reduced uptake of native LDL ex vivo and reduced foam cell formation in vivo, whereas sortilin overexpression in macrophages resulted in increased LDL uptake and foam cell formation. Conclusions: Macrophage sortilin deficiency protects against atherosclerosis by reducing macrophage uptake of LDL. Sortilin-mediated uptake of native LDL into macrophages may be an important mechanism of foam cell formation and contributor to atherosclerosis development.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

Macrophage sortilin promotes native LDL uptake, foam cell formation, and atherosclerosis in mouse models, independent of plasma LDL-C levels. Sort1 deficiency in hematopoietic cells reduces atherosclerosis, whereas sortilin overexpression increases macrophage LDL uptake.

Key findings

  • Total-body Sort1 deficiency on the Apobec1−/−; hAPOB Tg background did not change plasma LDL-C but reduced atherosclerosis: 68% reduction in en face aorta lesion area (P<0.0001) and 87% reduction in aortic root lesion area (P<0.0001).
  • Hematopoietic Sort1 deficiency after bone marrow transplantation into Ldlr−/− mice also reduced atherosclerosis without affecting plasma LDL-C: 69% reduction in en face aortic lesion area (P<0.00001) and 34% reduction in aortic root lesion area (P<0.01).
  • Sortilin-deficient macrophages had reduced foam cell formation: 28% lower total cellular cholesterol, 25% lower free cholesterol, and 32% lower cholesteryl ester (P<0.05); in vivo foam cells showed a 33% reduction in cellular cholesterol (P<0.05).
  • Sortilin deficiency reduced 125I-LDL uptake by 48% in thioglycollate-elicited macrophages and 33% in bone marrow-derived macrophages (P<0.05 for both), by 39% in the absence of LDLR (P<0.05), and by 38% with cytochalasin D (P<0.05); Sort1 overexpression in J774 macrophages increased LDL uptake by 29% (P<0.05). No effect was found on thioglycollate-elicited monocyte recruitment or LPS-induced cytokine release in vivo.

Methods

  • Atherosclerosis studies used Sort1−/− mice crossed onto the Apobec1−/−; hAPOB Tg background, fed a western-type diet for 18 weeks, with lesion area assessed en face and in aortic roots.
  • Bone marrow from Sort1−/−;LDLR−/− or Sort1+/+;LDLR−/− donors was transplanted into irradiated Ldlr−/− recipients; after 6 weeks, mice received western diet for 18 weeks before atherosclerosis assessment.
  • Macrophage studies used thioglycollate-elicited peritoneal macrophages and bone marrow-derived macrophages, with 125I-LDL uptake/degradation, Oil Red O staining, cholesterol measurements, and lentiviral Sort1 overexpression in J774 cells; statistics used 2-tailed paired Student’s t test and 1-way ANOVA with Bonferroni correction for the LPS experiment.

Limitations

  • The paper does not include a formal limitations section. It states that the mechanisms of LDL-induced macrophage Sort1 upregulation require further exploration.
  • Evident from the text: all causal data are from mouse atherosclerosis models and ex vivo mouse macrophages; bone marrow transplantation implicates hematopoietic cells but does not isolate macrophages from other hematopoietic cell types.
  • Evident from the text: no human interventional or macrophage-specific in vivo data are presented, and the authors note mechanistic differences from another study using a different mouse model and LDL-labeling approach.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1161/circresaha.116.305811

Cites

23 of 23 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

21 Own result · 10 Own interpretation · 7 Not checked yet · 2 Own method · 1 No basis given

Verify all 17 references — free account

Show all 28 claims

  • Probably not a substantial claim. 6
  • It may state two separate claims as one. 9
13 of 13
  • The paper relies on this without support.

    Thioglycollate-elicited peritoneal macrophages and bone-marrow-derived macrophages are representative of arterial macrophages for LDL uptake and foam cell formation.

    “For studies of macrophage LDL uptake, both thioglycollate-elicited peritoneal macrophages and bone-marrow derived macrophages were used.”
  • The paper relies on this without support.

    Cytochalasin D completely inhibits macropinocytosis under the experimental conditions, so residual LDL uptake is independent of macropinocytosis.

    “LDL uptake studies were performed in bone marrow derived macrophages in the presence of cytochalasin D, a potent inhibitor of actin polymerization and macropinocytosis.”
  • The paper relies on this without support.

    LPS-induced cytokine release in vivo is a valid measure of the inflammatory pathways that contribute to atherosclerosis in this model.

    “To determine if Sort1−/− mice have reduced cytokine levels, cytokine multiplexing assays were performed on Sort1−/− and Sort1+/+ mice injected with lipopolysaccharide (LPS).”
3 of 3

Citations

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Metadata

Authors
Patel, K. M., Strong, A., Tohyama, J., Jin, X., Morales, C. R., Billheimer, J., Millar, J., Kruth, H., & Rader, D. J.
Affiliations
National Institutes of Health (US)
Venue
Circulation Research
Published
2015-02-27
Volume
116
Issue
5
Pages
789-796
ISSN
  • 0009-7330 (ISSN-L)
  • 1524-4571
OpenAlex
W2039791966
Cited by
194
References
23
Citations by year
2026: 10 · 2025: 11 · 2024: 19 · 2023: 10 · 2022: 24 · 2021: 15 · 2020: 21 · 2019: 20 · 2018: 22 · 2017: 17 · 2016: 15 · 2015: 10
FWCI
9.29
Type
journal article
Language
en
Open access
Locations
  • Circulation Research (publishedVersion)
  • PubMed (publishedVersion)
  • Europe PMC (PubMed Central) (acceptedVersion)
  • PubMed Central (acceptedVersion)
Funders
  • National Heart, Lung, and Blood Institute (R01HL109489)
  • National Institute of General Medical Sciences (T32GM008076)
Topics
  • Life Sciences › Immunology and Microbiology › Immunology › Atherosclerosis and Cardiovascular Diseases
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biochemistry › Cholesterol and Lipid Metabolism
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Lipoproteins and Cardiovascular Health
Keywords
sortilin, SORT1, macrophages, LDL uptake, foam cell formation, atherosclerosis, LDL receptor, apolipoprotein B, coronary artery disease, bone marrow transplantation, humanized mice, lipid metabolism
MeSH terms
APOBEC-1 Deaminase, Sortilin, Animals, Aortic Diseases, Bone Marrow Cells, Cytidine Deaminase, Female, Foam Cells, Lipoproteins, LDL, Cholesterol, LDL, Macrophages, Male, Mice, Transgenic, Radiation Chimera, Receptors, LDL, Macrophages, Peritoneal, Mice, Knockout, Adaptor Proteins, Vesicular Transport, Atherosclerosis, Mice, Diet, Western

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