Effect of essential oils from introduced and local plants on cholesterol metabolism in hepatic and foam cells. A search for natural antiatherogenic compounds

CASTRO A; OTERO C.; DUMRAUF B.; RODENAK KLADNIEW B; MONTERO VILLEGAS S; VIÑA S; GARCÍA DE BRAVO M ; CRESPO R.

Salta

Congreso; Joint LV Annual SAIB Meeting and XIV PABMB Congress.; 2019

SAIB

High blood cholesterol levels constitute one of the main risk factors for the development of cardiovascular diseases, including atherosclerosis. The aim of this study was to analyze the effects of essential oils (EOs) on cholesterol metabolism through its pathway of synthesis, the mevalonate pathway (MVP), and its intracellular accumulation, looking for EOs of local production plants that show the greatest potential to prevent or decrease the atherogenic process. Human hepatic cell line (HepG2) and human THP-1 derived foam cells were treated with Citrus reticulata, Lippia alba (chemotypes tagetenone, linalool and dihydrocarvone) and Melissa calamintha EOs and with D-limonene and 1,8-cineole (components of the EOs). MTT assays were used to determine working concentrations. Cholesterol synthesis was assessed by incorporation of [14C]acetate in HepG2 cells, and Ro 48-8071 was used as lanosterol synthase (LSS) inhibitor. Nonsaponifiable lipids were evaluated by radio-TLC. Foam cells were produced using 40 𝜇g/mL oxidized low-density lipoproteins (oxLDL). Lipid droplets content was quantified spectrophotometrically by Oil Red O staining and cholesterol (total, free, and esterified) by commercial kits and TLC. A three-dimensional (3D) foam cell spheroid model was developed using the hanging droplet culture method. Results show that in hepatic cells EOs of C. reticulata and L. alba decrease the incorporation of [14C]acetate in lanosterol and cholesterol, suggesting an inhibition of the enzyme lanosterol synthase (LSS) and or squalene synthase of MVP. The incorporation of [14C]acetate in squalene is up and down but always increases in cells incubated with its major components, D-limonene and 1,8-cineole, indicating LSS inhibition. In all cases, the levels of 2,3-oxidosqualene and / or ubiquinone are increased. Foam cells in 2D cultures show different IC50 values of cell viability in cells treated with the EOs, and the lowest values were obtained with the M. calamintha (IC50 =130 µL/L) treatment. Foam cells also show great variability on the content of lipid droplets, mainly cholesterol, when they were incubated with the EOs. C. reticulata and L. alba significantly decreased intracellular lipid levels and cholesterol synthesis. Preliminary assays performed in the foam cells in 3D culture model suggest similar results. We conclude that EOs from well adapted to local conditions plant species decrease cholesterol synthesis in hepatic cells by LSS inhibition, an enzyme of a post-squalene reaction without diminishing essential isoprenoids as ubiquinone, and decrease cholesterol accumulation in foam cells. These results suggest that these EOs have great potential as natural drugs against atherosclerogenesis.