Sesamin, a Naturally Occurring Lignan, Inhibits Ligand-Induced Lipogenesis through Interaction with Liver X Receptor Alpha (LXRα) and Pregnane X Receptor (PXR)

Figure 6

Sesamin (SSM) attenuates rifampin- (RIF-) induced transient transcriptional assays of S14 and SCD reporter activity, PXR target genes mRNA and protein expressions, and lipid contents. (a) HepG2 cells were cotransfected with a PXR expression plasmid and S14-Luc and SCD-Luc reporter genes and treated with 20 or 40 μM SSM and in combination with 20 μM RIF for 24 h. Data represent the mean ± SE; n = 4; ; ; compared with control or RIF-treated groups as indicated. (b) Differentiated HepaRG cells treated with 20 or 40 μM SSM alone or in combination with 20 μM RIF for 24 h. Quantitative real-time PCR (real-time PCR) results of gene expression levels of S14, FAS, and SCD are shown. β-actin was used as an internal control. Data represent the mean ± SE; n = 3; ; compared with control or RIF-treated groups, respectively, as indicated. (c) Differentiated HepaRG cells treated with RIF or SSM alone or in combination for 24 h were harvested, and their protein levels of PXR target genes and β-actin (internal control) were analyzed via western blot. Quantitation of the indicated protein bands was corrected by β-actin expression. The representative blot shown was quantified with ImageJ software. Data represent the mean ± SE; n = 3; ; compared with control or RIF-treated groups as indicated. (d) Differentiated HepaRG cells were repeatedly exposed to (A) solvent, (B) 20 μM RIF, (C) 20 μM RIF + 5 μM SSM, and (D) 20 μM RIF + 10 μM SSM for 14 days. Lipid accumulation was then assessed using Oil Red O staining, which allows the detection of triglycerides and cholesterol esters. HepaRG cells were observed and photographed under a phase‐contrast microscope (original magnification ×400). Oil red O dye was then extracted using isopropanol and quantified with a microplate reader at 510 nm. Values represent the mean ± SE; n = 3; compared with control or RIF-treated groups as indicated.

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