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Updated: Jul 24, 2025
Quantification of Atherosclerosis in Mice
Published on: June 12, 2019
The effect of HLA-DRB1*04:01 on a mouse model of atherosclerosis
Garth Blackler1, James Akingbasote1, Ewa Cairns1,2
1Department of Microbiology and Immunology, Western University, London, Ontario, Canada.
Insights
The HLA-DRB1 gene variant increases cardiovascular risk in rheumatoid arthritis (RA) patients. This study found HLA-DRB1 expression elevates oxidized LDL and reduces sex-based differences in atherosclerosis development in mice.
Area of Science:
- Immunogenetics
- Cardiovascular Science
- Rheumatology
Background:
- Rheumatoid arthritis (RA) patients carrying the HLA-DRB1 gene variant face a higher risk of cardiovascular disease.
- Atherosclerotic cardiovascular disease (ASCVD) is a significant concern in RA, with potential links to specific genetic factors.
- Understanding the role of HLA-DRB1 in atherogenesis is crucial for developing targeted prevention strategies in RA.
Purpose of the Study:
- To investigate the direct impact of human leukocyte antigen (HLA)-DRB1 expression on the development of atherosclerotic cardiovascular disease (ASCVD).
- To utilize a novel mouse model combining HLA-DRB1 transgenicity with low-density lipoprotein receptor deficiency to study ASCVD.
- To assess the influence of HLA-DRB1 on lipid profiles, inflammatory markers, and atherosclerotic plaque characteristics.
Main Methods:
- Mice expressing HLA-DRB1*04:01 (DR4tg) were crossed with low-density lipoprotein receptor knockout (Ldlr-/-) mice.
- Mice were fed a high-fat, high-cholesterol (HFHC) diet or a regular diet for 12 weeks to induce atherosclerosis.
- Serum lipoproteins, C-reactive protein (CRP), oxidized LDL (OxLDL), and aortic plaque burden were analyzed; plaque citrullination was assessed.
Main Results:
- While Ldlr-/- mice had higher LDL-C, DR4tg Ldlr-/- mice exhibited a greater ratio of pro-atherogenic OxLDL to LDL and increased CRP levels.
- Aortic plaque burden and citrullination were similar between DR4tg Ldlr-/- and Ldlr-/- mice, but OxLDL and CRP were elevated in DR4tg Ldlr-/-.
- HLA-DRB1 expression reduced the male predominance typically observed in atherosclerosis in Ldlr-/- mice.
Conclusions:
- HLA-DRB1 expression in this mouse model promotes a pro-atherogenic lipid profile (elevated OxLDL) and inflammatory response (increased CRP).
- The presence of HLA-DRB1 mitigates the sex-specific differences in atherosclerosis development seen in Ldlr-/- mice.
- These findings suggest a direct role for HLA-DRB1 in modulating ASCVD risk factors, potentially explaining its association with cardiovascular disease in RA patients.
Objectives:
HLA-DRB1 is associated with an increased risk of cardiovascular disease in patients with rheumatoid arthritis (RA). This study aimed to determine the effect of HLA-DRB1 on atherosclerotic cardiovascular disease (ASCVD) using a novel mouse model.
Methods:
Mice transgenic for HLA-DRB1*04:01 (DR4tg) were crossed with low density lipoprotein receptor knock-out (Ldlr) mice that develop atherosclerosis when fed a high fat, high cholesterol (HFHC) diet. Male and female DR4tgLdlr (n = 48), Ldlr (n = 24), DR4tg (n = 24), and C57Bl/6 (B6) background (n = 24) mice were fed HFHC or regular diet (RD) for 12 weeks. Blood samples were analyzed for serum lipoproteins using a colorimetric assay. C-reactive protein (CRP) and oxidized LDL (OxLDL) were measured using ELISA. Atherosclerosis in the aortas was assessed using the lipid stain, Sudan IV. The presence of citrulline in atherosclerotic plaque was determined by immunohistochemistry.
Results:
Sera low-density lipoprotein cholesterol (LDL-C) levels were higher in HFHC-fed Ldlr versus DR4tgLdlr-; p = 0.0056, but the aortic plaque burden and degree of citrullination in the plaque were similar for these two strains. The ratio of pro-atherogenic OxLDL to LDL levels was higher in DR4tgLdlr than Ldlrmice; p = 0.0017. All mice had an increase in CRP when fed a HFHC diet, most pronounced for DR4tgLdlr; p = 0.0009. There were no significant sex differences for DR4tgLdlr mice; however, male Ldlr mice had worse atherosclerosis. B6 and DR4tg mice did not have significant elevations in serum cholesterol levels and did not develop atherosclerosis.
Conclusions:
Expression of HLA-DRB1 resulted in an elevation of OxLDL and a reduction in the male bias for atherosclerosis, mimicking what is observed in RA.
