Β-carotene promotes atherosclerosis resolution and alleviates liver inflammation in a reversible murine model of atherosclerosis: A potential role of regulatory T cells

Background: β-carotene has several health benefits on lipid metabolism, most of which are mediated through its provitamin A activity. Our laboratory has recently shown that β-carotene conversion to vitamin A is associated with reduced circulating cholesterol levels in mice and humans. Objective: To study the effect of β-carotene on atherosclerosis regression and hepatic inflammation. Methods: We utilized various animal models to study atherosclerosis regression: In our first model, we used weekly injections of an antisense oligonucleotide targeting the expression of the low-density lipoprotein receptor (LDLR ASO). To facilitate the development of atherosclerotic lesions, we fed these mice a Western diet (0.3% cholesterol, 41% of calories from fat) deficient in vitamin A (WD-VAD) for 16 weeks, after which we harvested the baseline group. The remaining mice underwent regression by stopping the LDLR ASO injections and injecting them once with LDLR SO, which binds and deactivates LDLR ASO. To study the role of β-carotene on atherosclerosis regression, we maintained a subset of mice on the same diet (WD-VAD), and another subset fed with a WD-VAD supplemented with 50 mg/kg of β-carotene (WD-β-carotene) for three weeks. To test the implication of regulatory T cells (Tregs) in β-carotene-induced atherosclerosis regression, we treated a group of mice with an anti-CD25 monoclonal antibody to deplete Tregs during regression. For all experiments, aortic roots, plasma, and tissues were collected and analyzed using morphometric and biochemical methods. Liver samples were harvested for RNA sequencing and histological analyses. Results: Baseline mice showed an increase in cholesterol levels in comparison to all regression groups, independently of the presence of β-carotene in the diet. These changes occurred independently of alterations in body weight. For the LDLR ASO model, histological analyses of aortic roots failed to show differences in atherosclerotic lesion area between groups, although we observed a reduction in the macrophage content in both regression groups that was more pronounced in WD-β-carotene-fed mice; baseline vs regression-VAD (~30%, P=0.053), and baseline vs regression-β-carotene (~42%, P<0.005). Collagen content in plaques, an indicator of plaque stability in humans, showed an increase in both regression groups; baseline vs regression-VAD (~217%, P <0.005), and baseline vs regression-β-carotene (~308%, P<0.0001). Lastly, anti-CD25 infusions decreased Tregs content in plasma and spleen. We also analyzed the liver using RNA sequencing and immunostaining. We found that the baseline mice showed a significant increase in hepatic macrophage accumulation in comparison to both regression groups. However, β-carotene showed a more pronounced effect on reducing hepatic inflammation compared to VAD. Conclusion: β-carotene enhances atherosclerosis resolution, as observed by a reduction in plaque macrophage content accompanied with an increase in collagen content. Atherosclerosis resolution is associated with a reduction in hepatic macrophage content and β-carotene enhances these positive effects.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Nutritional Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Albakri, Asma'a Ghaleb Ali

Contributors dc:contributor

• Amengual, Jaume
• Swanson, Kelly
• Nakamura, Manabu
• Erdman, John

• β-carotene
• atherosclerosis regression
• low density lipoprotein
• regulatory T cells
• Hepatic inflammation

Statement dc:rights

• Copyright 2021 Asma’a Ghaleb Ali Albakri

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/113308

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/113308