Decaffeinated coffee and green tea extract inhibit foam cell atherosclerosis by lowering inflammation and improving cholesterol influx/efflux balance through upregulation of PPARγ and miR-155

Abstract

Background: Foam cells are markers of atherosclerosis and characterise advanced atherosclerotic plaque, stimulated by inflammation caused by high lipid levels in macrophages. The combination of decaffeinated coffee and green tea extract (DCGTE) has been suggested to have a role in foam cell inhibition. Objective: we investigated the inhibiting role of DCGTE against foam cell formation, through modulation of the inflammation process and cholesterol metabolism in macrophage colony stimulating factor- (M-CSF) and oxidized low-density lipoprotein (oxLDL)-exposed macrophages. Methods: Coffee and green tea were extracted by filtration and infusion respectively, and underwent decaffeination using active carbon and blanching methods, respectively. Cells were administered 160/160 and 320/320μg/ml of DCGTE. Foam cell formation was observed using a light microscope after staining with Oil Red O (ORO), and the accumulation of lipids in macrophages with ELISA. Observations of lipid influx and efflux were determined through semiquantitative cluster differentiation 36 (CD36) and ATP binding cassette transporter A1 (ABCA1) expression through immunofluorescence. The inflammation process was quantified using inflammatory/anti-inflammatory markers, e.g., tumor necrosis factor α (TNFα) and interleukin 10 (IL10) with ELISA. Peroxisome proliferator activated response γ (PPARγ) expression and activity were assessed with PCR and ELISA, respectively. The expression of microRNA 155 (miR-155) was examined using qPCR. Results: DCGTE at the above concentrations tended to reduce foam cell numbers, significantly inhibited lipid accumulation (p=0.000), reduced CD36 expression (p=0.000) and TNFα secretion (p=0.000) in Raw264.7 exposed to M-CSF 50ng/ml and oxLDL 50μg/ml. PPARγ expression (p=0.00) and activity (p=0.001), miR-155 relative expression (p=0.000), and IL10 production (p=0.000) also increased. Conclusion: DCGTE lowered foam cell numbers, possibly through attenuation of the inflammatory process and improvement of lipid/efflux mechanisms in M-CSF and oxLDL-stimulated Raw264.7 cells, via upregulation of PPARγ and miR-155. Our results suggest DCGTE may help prevent atherosclerosis-based diseases.