Document Type

Thesis - Open Access

Award Date

2016

Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

Natalie Thiex

Keywords

atherosclerosis, colony stimulating factor one, CSF-1, foam cells, lipid droplets, macrophages

Abstract

Atherosclerosis is a serious disease affecting a large portion of the world’s population. In atherosclerosis, macrophages become filled with lipid droplets and form fatty plaques in artery walls. The formation of these atherosclerotic plaques is dependent on the macrophage growth factor colony stimulating factor-1 (CSF-1); however, understanding the changes in CSF-1 signaling and related pathways in foam cells remain poorly investigated. Lipid-laden macrophages were formed through exposure of murine bone marrow derived macrophages to 100 μg/ml acetylated LDL for 24 h. Non-LDL treated macrophages were grown in parallel for each experiment and used for comparison. Immunofluorescent staining was used to visualize and quantify CSF-1R, pAkt, pERK, pCSF-1R, and Ki67. To synchronize the signaling process, macrophages were deprived of CSF-1 supplemented media before experiments. The lipid-laden macrophages had a decreased rate of CSF-1R expression. The degradation of CSF-1R was unchanged after the initial CSF-1 stimulation, but the level of phosphorylated receptor was lower in lipid-laden macrophages. The phosphorylation of Akt was unchanged during the first hour but increased in non-LDL exposed cells after 10 h. The phosphorylation of ERK spiked in non-LDL exposed cells at 7 min indicating a possible differential activation of pathways. Macrophage proliferation, as measured by Ki67 staining, increased while the cells had lipid droplets then leveled as lipid droplets cleared from the cells. Lipid-laden macrophages also did not display differences in CSF-1 stimulated macropinocytosis as observed with live-cell microscopy. Flow cytometry analysis revealed lipid laden macrophages had an increase in CD68, with decreased expression of CD11B and CD80. Differences in activation of signaling molecules highlight cellular functions affected by lipid droplets that can be targeted to prevent the proliferation of macrophages in plaques and promote plaque clearance.

Library of Congress Subject Headings

Atherosclerosis

Atherosclerotic plaque

Macrophages

Colony-stimulating factors (Physiology)

Lipids

Description

Includes bibliographical references (page 59-60)

Format

application/pdf

Number of Pages

72

Publisher

South Dakota State University

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Rights Statement

In Copyright