REGULATION OF APOLIPOPROTEIN A‐1 AND APOLIPOPROTEIN B100 GENES BY THYMOQUINONE RICH FRACTION AND THYMOQUINONE IN HEPG2 CELLS

Abstract

ABSTRACT Thymoquinone (TQ) rich fraction (TQRF) extracted from Nigella sativa seeds using a supercritical fluid extraction technique was prepared. The regulatory effects of TQRF at 80 µg/mL and commercial TQ at 2 µg/mL on apolipoprotein B100 (Apo B100) and apolipoprotein A‐1 (Apo A‐1) genes in the presence or absence of 25‐hydroxycholesterol (25OH), were investigated in human HepG2 cell line using quantitative real‐time polymerase chain reaction. Incubating HepG2 cells in 10% human lipoprotein deficient serum (HLPDS) for 24 h in the presence of 2 µg/mL 25OH showed a significant increase in Apo B100 mRNA expression level by twofold compared to the control cells; on the other hand, no significant change in Apo A‐1 mRNA level was observed. When cells were incubated with HLPDS in the absence of 25OH and treated with TQRF and TQ, the mRNA level of Apo B100 was down‐regulated by 70 and 49%, respectively, in TQRF and TQ treated cells compared to untreated cells. Apo A‐1 gene was up‐regulated by four‐ and twofold in TQRF and TQ treated cells, respectively, compared to that observed in untreated cells. The present study clearly shows that TQRF and TQ are effective in regulating Apo A‐1 and Apo B100 genes that influence cholesterol metabolism in HepG2 cells. PRACTICAL APPLICATIONSCardiovascular diseases (CVDs), including coronary heart disease, are considered as frequent cause of most deaths in the world. Hypercholesterolemia is the major risk of CVD. The plasma levels of Apo B100 and Apo A‐1 have been reported to be a risk of developing CVD. Natural products that are able to up‐regulate Apo A‐1 and down‐regulate Apo B100 genes are candidates for preventing and treating hypercholesterolemia. The regulatory effect of thymoquinone rich fraction extracted from Nigella sativa seeds using supercritical fluid extraction on Apo A‐1 and Apo B100 genes may play an important role in controlling the plasma cholesterol level, and thus, may reduce the risk of CVD.