Regulation of low-density lipoprotein receptor and 3-hydroxy-3-methylglutaryl coenzyme A reductase gene expression by thymoquinone-rich fraction and thymoquinone in HepG2 cells.
OBJECTIVE
Nigella sativa and its active constituent thymoquinone (TQ) have been exploited for their various health benefits. This work was aimed to investigate the regulatory effects of TQ-rich fraction (TQRF) and commercial TQ on the low-density lipoprotein receptor (LDLR) and 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) genes in HepG2 cells.


RESULTS
TQRF was extracted from N. sativa seeds using supercritical fluid extraction. The regulatory effects of TQRF at 80 microg/ml and TQ at 2 microg/ml on LDLR and HMGCR gene expression were investigated in HepG2 cells using quantitative real-time PCR. The TQ content in TQRF was 2.77% (w/w) and was obtained at a temperature of 40 degrees C and a pressure of 600 bar. Treatment of cells with TQRF and TQ resulted in a 7- and 2-fold upregulation of LDLR mRNA level, respectively, compared with untreated cells. The mRNA level of HMGCR was downregulated by 71 and 12%, respectively, compared with untreated cells.


CONCLUSIONS
TQRF and TQ regulated genes involved in cholesterol metabolism by two mechanisms, the uptake of low-density lipoprotein cholesterol via the upregulation of the LDLR gene and inhibition of cholesterol synthesis via the suppression of the HMGCR gene.
Al-Naqeep
Ghanya
G
Nutraceuticals and Nutrigenomics Programme, Laboratory of Molecular Biomedicine, Institute of Bioscience, Universiti Putra Malaysia, Serdang, Malaysia.
Ismail
Maznah
M
Allaudin
Zeenathul
Z
D016227:Benzoquinones / Q000302:isolation & purification / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D018076:DNA, Complementary / Q000235:genetics; D004273:DNA, Neoplasm / Q000235:genetics; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D056945:Hep G2 Cells / Q000187:drug effects / Q000473:pathology; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000187:drug effects / Q000235:genetics*; D031881:Nigella sativa; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D012334:RNA, Neoplasm / Q000235:genetics / Q000302:isolation & purification; D011973:Receptors, LDL / Q000187:drug effects / Q000235:genetics*
D016227:Benzoquinones; D018076:DNA, Complementary; D004273:DNA, Neoplasm; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D011973:Receptors, LDL; D006903:Hydroxymethylglutaryl CoA Reductases; C003466:thymoquinone