Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2008 Jun 24;117(25):3227-37.
doi: 10.1161/CIRCULATIONAHA.108.771048. Epub 2008 Jun 2.

P-selectin glycoprotein ligand-1 is highly expressed on Ly-6Chi monocytes and a major determinant for Ly-6Chi monocyte recruitment to sites of atherosclerosis in mice

Guangyu An  1 , Huan Wang, Rong Tang, Tadayuki Yago, J Michael McDaniel, Samuel McGee, Yuqing Huo, Lijun Xia
Affiliations

P-selectin glycoprotein ligand-1 is highly expressed on Ly-6Chi monocytes and a major determinant for Ly-6Chi monocyte recruitment to sites of atherosclerosis in mice

Guangyu An et al. Circulation. .

Abstract

Background: Ly-6C(hi) monocytes are key contributors to atherosclerosis in mice. However, the manner in which Ly-6C(hi) monocytes selectively accumulate in atherosclerotic lesions is largely unknown. Monocyte homing to sites of atherosclerosis is primarily initiated by rolling on P- and E-selectin expressed on endothelium. We hypothesize that P-selectin glycoprotein ligand-1 (PSGL-1), the common ligand of P- and E-selectin on leukocytes, contributes to the preferential homing of Ly-6C(hi) monocytes to atherosclerotic lesions.

Methods and results: To test this hypothesis, we examined the expression and function of PSGL-1 on Ly-6C(hi) and Ly-6C(lo) monocytes from wild-type mice, ApoE(-/-) mice, and mice lacking both ApoE and PSGL-1 genes (ApoE(-/-)/PSGL-1(-/-)). We found that Ly-6C(hi) monocytes expressed a higher level of PSGL-1 and had enhanced binding to fluid-phase P- and E-selectin compared with Ly-6C(lo) monocytes. Under in vitro flow conditions, more Ly-6C(hi) monocytes rolled on P-, E-, and L-selectin at slower velocities than Ly-6C(lo) cells. In an ex vivo perfused carotid artery model, Ly-6C(hi) monocytes interacted preferentially with atherosclerotic endothelium compared with Ly-6C(lo) monocytes in a PSGL-1-dependent manner. In vivo, ApoE(-/-) mice lacking PSGL-1 had impaired Ly-6C(hi) monocyte recruitment to atherosclerotic lesions. Moreover, ApoE(-/-)/PSGL-1(-/-) mice exhibited significantly reduced monocyte infiltration in wire injury-induced neointima and in atherosclerotic lesions. ApoE(-/-)/PSGL-1(-/-) mice also developed smaller neointima and atherosclerotic plaques.

Conclusions: These data indicate that PSGL-1 is a new marker for Ly-6C(hi) monocytes and a major determinant for Ly-6C(hi) cell recruitment to sites of atherosclerosis in mice.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Ly-6Chi monocytes have significantly increased PSGL-1 expression. A. Peripheral murine leukocytes were stained with mAbs to CD90, B220, CD49b, NK1.1, Ly-6G, and CD11b. Cells in gate M were defined as monocytes. B. Representative dot plots showing expression of Ly-6C and PSGL-1 in the total monocytes (gate M). Percentages in the upper right panels represent Ly-6ChiPSGL-1hi monocytes. C. Comparisons of the number of Ly-6Chi monocytes in ApoE-/- and ApoE-/-/PSGL-1-/- mice on the Western diet with ApoE-/- mice fed the chow diet. D. Representative PSGL-1 expression on Ly-6Chi and Ly-6Clo monocytes from an ApoE-/- mouse fed the chow diet. E. Quantification of PSGL-1 expression (MFI, mean fluorescence intensity) on Ly-6Chi and Ly-6Clo monocytes from WT and ApoE-/- mice. F. Real-time PCR quantification (fold changes) of PSGL-1 transcripts of Ly-6Chi and Ly-6Clo monocyte subsets from WT mice. The fluorescent intensities of both axes (A and B) or x axis (D) are on a log scale. Data are means ± SEM (A-E: n = 17 mice/group; F, n = 9 mice/group).
Figure 2
Figure 2
PSGL-1 is highly expressed on murine CX3CR1loCD11b+ monocytes as well as on human CD14+CD16- monocytes. A. Representative dot plot showing CX3CR1loCD11b+ (R1 region, red) and CX3CR1hiCD11b+ (R2 region, blue) monocytes. Cells in the gated R1 and R2 regions were examined for expression of PSGL-1 (B) and for interactions with P-selectin (C) and E-selectin (D). Labels on both axes are on a log scale. The data represent at least three experiments. E. Representative histogram showing PSGL-1 expression on human CD14+CD16- monocytes. Labels on x axis is on a log scale. Shown are the results of three independent experiments.
Figure 3
Figure 3
Ly-6Chi monocytes exhibit enhanced rolling on P-, E- and L-selectin under flow, and increased PSGL-1-dependent interactions with atherosclerotic endothelium. A and B. Representative histograms compare PSGL-1-dependent P-selectin and E-selectin binding activities of Ly-6Chi and Ly-6Clo monocytes from WT mice fed chow. 4RA10 is a blocking mAb to PSGL-1. Shaded histograms represent isotype controls. The fluorescent intensity of x axis is on a log scale. C, D and E. Accumulation of rolling Ly-6Chi and Ly-6Clo monocytes over P-selectin (P-sel) or E-selectin (E-sel), or L-selectin (L-sel). Shown are the mean ± SEM of three independent experiments. F and G. Rolling and adhesion of WT Ly-6Chi and Ly-6Clo as well as PSGL-1-/- Ly-6Chi monocytes on atherosclerotic endothelium in an ex vivo carotid artery model. Shown are the mean ± SEM of three independent experiments.
Figure 4
Figure 4
The Western diet does not change the expression profiles of other adhesion molecules or the chemokine receptor CCR2 on Ly-6Chi and Ly-6Clo monocytes. Representative histograms compare expression of L-selectin, CD44, CD18, CD49d, and CCR2 on both Ly-6Chi and Ly-6Clo monocytes from WT or ApoE-/- mice. Shaded histograms represent isotype controls. The fluorescent intensity of x axis of each histogram is on a log scale. Shown are the results of three independent experiments.
Figure 5
Figure 5
ApoE-/-/PSGL-1-/- mice have reduced macrophage accumulation in atherosclerotic lesions and develop smaller atherosclerotic plaques. A. Macrophage staining (light brown color) in aortic root cross-sections of atherosclerotic lesions in ApoE-/- and ApoE-/-/PSGL-1-/- mice that were fed the Western diet for 12 weeks. B. Quantitative analysis of the macrophages (n = 8 mice/group). Data are means ± SEM. C and D. Oil-Red O-stained (red color) en face preparations of aortas (C), and aortic root cross-sections (D) from atherosclerotic lesions in ApoE-/- and ApoE-/-/PSGL-1-/- mice that were fed the Western diet for 12 weeks. E and F. Quantitative analysis of atherosclerotic lesion area in the entire aorta (E, n = 10 mice/group) and aortic root cross-sections (F, 8 sections/mouse, n = 12 mice/group) using NIH Image J software. Data are means ± SEM. Scale bars: A and D = 100 mm; C = 1 cm.
Figure 6
Figure 6
Lack of PSGL-1 results in reduced monocyte infiltration in neointima, impaired Ly-6C-positive monocyte recruitment to injured arterial walls and reduced formation of neointimal lesions. A. Macrophage staining (dark brown color) in neointima of carotid arteries of ApoE-/- and ApoE-/-/PSGL-1-/- mice after wire-induced injury. B. Quantification of the macrophage staining of neointima. Data are means ± SEM (n = 8 mice/group). C and D. Representative immunofluorescence staining of Ly-6C-positive monocytes (arrows) of ApoE-/- (C) or ApoE-/-/PSGL-1-/- (D) carotid arterial cryosections after wire-induced injury. Arrowheads indicate autofluorescence of vascular elastic membranes. E. Movat stained neointimas in ApoE-/- and ApoE-/-/PSGL-1-/- carotid arteries after wire injury. F. Quantification of the sizes of neointima and media (n = 8). Scale bars: A, C, and E = 100 mm.
Figure 7
Figure 7
Model for PSGL-1-mediated selective homing of Ly-6Chi monocytes. A. Ly-6Chi monocytes that are also PSGL-1hi and L-selectin+ preferentially interact with P- and E-selectin on activated endothelium/adherent platelets (primary tethering) or with L-selectin on a rolling/adherent leukocyte or a leukocyte fragment (a neutrophil in this case, secondary tethering) under flow. B. Ly-6Clo monocytes that are also PSGL-1lo and L-selectin- cannot efficiently interact with activated endothelium under flow because of low-level surface expression of PSGL-1, and, possibly, lack of L-selectin.
See this image and copyright information in PMC

Comment in

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Ross R. Atherosclerosis--an inflammatory disease. N Engl J Med. 1999;340:115–126. - PubMed
    1. Libby P. Inflammation in atherosclerosis. Nature. 2002;420:868–874. - PubMed
    1. Geissmann F, Jung S, Littman DR. Blood monocytes consist of two principal subsets with distinct migratory properties. Immunity. 2003;19:71–82. - PubMed
    1. Swirski FK, Libby P, Aikawa E, Alcaide P, Luscinskas FW, Weissleder R, Pittet MJ. Ly-6Chi monocytes dominate hypercholesterolemia-associated monocytosis and give rise to macrophages in atheromata. J Clin Invest. 2007;117:195–205. - PMC - PubMed
    1. Tacke F, Alvarez D, Kaplan TJ, Jakubzick C, Spanbroek R, Llodra J, Garin A, Liu J, Mack M, van Rooijen N, Lira SA, Habenicht AJ, Randolph GJ. Monocyte subsets differentially employ CCR2, CCR5, and CX3CR1 to accumulate within atherosclerotic plaques. J Clin Invest. 2007;117:185–194. - PMC - PubMed

Publication types

MeSH terms