Related Experiment Video
Updated: Jul 16, 2026
Isolation of Primary Patient-specific Aortic Smooth Muscle Cells and Semiquantitative Real-time Contraction Measurements In Vitro
Published on: February 15, 2022
Anti-atherosclerotic effects of sirolimus on human vascular smooth muscle cells
Kun L Ma1, Xiong Z Ruan, Stephen H Powis
1Centre for Nephrology, Royal Free & Univ. College Medical School, University College London, London, UK.
Abstract:
Sirolimus is a potent immunosuppressive agent and has an anti-atherosclerotic effect through its anti-proliferative property. The present study was undertaken to investigate the effect of sirolimus on intracellular cholesterol homeostasis in human vascular smooth muscle cells (VSMCs) in the presence of inflammatory cytokine IL-1 beta. We explored the effect of sirolimus on the lipid accumulation of VSMCs in the presence of IL-1 beta, using Oil Red O staining and quantitative measurement of intracellular cholesterol. The effect of sirolimus on the gene and protein expression of lipoprotein receptors and ATP binding cassettes (ABCA1 and ABCG1) was examined by real-time PCR and Western blotting, respectively. Furthermore, the effect of sirolimus on cholesterol efflux from VSMCs in the presence or absence of IL-1 beta was also investigated using [(3)H] cholesterol efflux. Finally, we examined the effect of sirolimus on the production of inflammatory cytokines in VSMCs using ELISA. Sirolimus reduced intracellular lipid accumulation in VSMCs mediated by IL-1 beta possibly due to the reduction of expression of low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) receptors. Sirolimus increased cholesterol efflux from VSMCs and overrode the suppression of cholesterol efflux induced by IL-1 beta. Sirolimus also increased ABCA1 and ABCG1 genes expression, even in the presence of IL-1 beta. We further confirmed that sirolimus inhibited mRNA and protein expression of inflammatory cytokines IL-6, tumor necrosis factor-alpha, IL-8, and monocyte chemoattractant protein-1. Inhibition of lipid uptake together with increasing cholesterol efflux and the inhibition of inflammatory cytokines are all important aspects of the anti-atherosclerotic effects of sirolimus on VSMCs.
Insights
Sirolimus reduces cholesterol buildup in vascular cells by lowering lipid uptake and increasing cholesterol removal. It also suppresses inflammatory cytokines, contributing to its anti-atherosclerotic effects.
Area of Science:
- Cardiovascular Biology
- Immunology
- Pharmacology
Background:
- Sirolimus (rapamycin) is an immunosuppressant with anti-proliferative properties relevant to atherosclerosis.
- Vascular smooth muscle cells (VSMCs) play a critical role in atherogenesis, and their lipid metabolism is influenced by inflammatory cytokines like IL-1 beta.
Purpose of the Study:
- To investigate the effects of sirolimus on intracellular cholesterol homeostasis in human VSMCs under IL-1 beta stimulation.
- To elucidate the mechanisms underlying sirolimus's anti-atherosclerotic potential in VSMCs.
Main Methods:
- Oil Red O staining and cholesterol quantification for lipid accumulation.
- Real-time PCR and Western blotting for gene and protein expression analysis (lipoprotein receptors, ABCA1, ABCG1).
- Radioactive cholesterol efflux assays and ELISA for cytokine analysis.
Main Results:
- Sirolimus decreased IL-1 beta-induced lipid accumulation in VSMCs, potentially via reduced LDL and VLDL receptor expression.
- Sirolimus enhanced cholesterol efflux from VSMCs, counteracting IL-1 beta's suppressive effect, and upregulated ABCA1 and ABCG1 expression.
- Sirolimus significantly inhibited the expression of inflammatory cytokines (IL-6, TNF-alpha, IL-8, MCP-1) in VSMCs.
Conclusions:
- Sirolimus modulates cholesterol homeostasis in VSMCs by inhibiting lipid uptake and promoting cholesterol efflux.
- Sirolimus exhibits anti-atherosclerotic properties by reducing VSMC lipid accumulation and suppressing inflammatory cytokine production.
