The Nuclear Oxysterol, 5-Cholesten-3{beta}, 25-Diol 3-Sulfate, Decreases Cholesterol Biosynthesis by Inhibiting Expression of HMG CoA Reductase in HepG2 Cells

A novel oxysterol, 5-cholesten-3ƒÒ, 25-diol 3-sulfate (25HC3S), was recently found in human liver nuclei as the nuclear oxysterol and its levels increased dramatically in the nuclei and the mitochondria following overexpression of a mitochondrial cholesterol delivery protein, StAR, in primary rat hepatocytes. In the present study, the nuclear oxysterol was chemically synthesized using 25-hydroxycholesterol and the triethylamine-sulfur trioxide complex. MS and NMR analysis shows that the product has one sulfonate group which is located at 3-position of 25-hydroxycholesterol, suggesting that 5-cholesten-3ƒÒ, 25-diol 3-sulfate is successfully synthesized. The addition of the product, 25HC3S, dramatically inhibited cholesterol biosynthesis and significantly decreased the intracellular microsomal cholesterol in HepG2 cells. Real time RT-PCR and Western blot analysis shows that 25HC3S strongly inhibited expression of HMG CoA reductase at the transcriptional level, which is time and dose dependent. We concluded that 25HC3S plays an important role in the maintenance of intracellular cholesterol homeostasis in the hepatocytes.