Leonurine Prevents Atherosclerosis Via Promoting the Expression of ABCA1 and ABCG1 in a Pparγ/Lxrα Signaling Pathway-Dependent Manner

Background/aims: Previous studies have demonstrated that leonurine, a unique alkaloid compound of Herba leonuri, can exert anti-oxidative and anti-inflammatory effects on the development of atherosclerosis (AS). This study was designed to investigate the effects of leonurine on Cholesterol efflux from THP-1 macrophage-derived foam cells and development of atherosclerotic lesions in apoE-/- mice, and further determine the potential mechanisms.

Methods: Human THP-1 cells were fully differentiated into foam cells by the pre-treatment with phorbol-12-myristate-13-acetate (PMA) and oxidized density lipoproteins (ox-LDL). After cells were incubated with various concentrations of leonurine, Oil Red O staining and high-performance liquid chromatography (HPLC) assays were utilized to detect cellular lipid accumulation and Cholesterol content, respectively. Cellular Cholesterol efflux was determined by liquid scintillation counting. The mRNA and protein levels of ATP-binding cassette transporter A1/G1 (ABCA1/G1), Peroxisome Proliferator-activated Receptor γ (PPARγ) and liver X receptor α (LXRα) in foam cells were assessed using real-time quantitative PCR (RT-qPCR) and western blot analyses, respectively. Plasma triglyceride (TG), total Cholesterol (TC), high-density lipoprotein-cholesterol (HDL-C) and low-density lipoprotein-cholesterol (LDL-C) levels in apoE-/- mice were evaluated using enzymatic methods. The atherosclerotic lesion sizes and collagen contents in aortic roots were determined by Oil Red O and Masson's trichrome staining, respectively.

Results: Oil Red O staining and liquid scintillation counting assays showed that leonurine significantly inhibited lipid accumulation and promoted 3H-cholesterol efflux in human THP-1 macrophage-derived foam cells in a concentration-dependent manner. Besides, both the mRNA and protein levels of ABCA1/G1, PPARγ and LXRα were enhanced by leonurine, which were attenuated by LXRα siRNA or PPARγ siRNA transfection. Finally, leonurine improved plasma lipid profile, decreased atherosclerotic lesion sizes, increased collagen contents and amplified PPARγ, LXRα and ABCA1/G1 expressions in aortic roots of apoE-/- mice.

Conclusions: Leonurine can promote Cholesterol efflux and alleviate cellular lipid accumulation by magnifying the expression of ABCA1/G1 in a PPARγ/LXRα signaling pathway-dependent manner in human THP-1 macrophage-derived foam cells and abate atherogenesis in apoE-/- mice, which may offer a promising therapeutic intervention of leonurine in protecting against AS.