Exposure to azide markedly decreases mRNAs encoding cholesterol synthetic enzymes and inhibits cholesterol biosynthesis

Exposure of Clone 9 cells to azide for 24 h decreased the abundance of mRNA transcripts encoding sequential cholesterol biosynthetic enzymes assayed by mircroarray analysis. The decreased abundance of these transcripts was verified by real‐time PCR. Treatment with azide also decreased the abundance of SREBP‐1c and SREBP‐2 transcripts. Exposure to azide decreased cellular content of cholesterol by 30% and markedly inhibited the biosynthesis of cholesterol (by ~90%), measured by 2 H‐ labeling techniques. 25‐OH cholesterol, an inhibitor of cholesterol synthesis, decreased cholesterol but not palmitate synthesis. 24‐h exposure of HepG2 cells to azide yielded similar results. Treatment of Clone 9 cells and HepG2 cells with AICAR, a stimulator of AMP‐activated protein kinase (AMPK) also inhibited cholesterol synthesis. However, and in sharp contrast to azide, exposure to AICAR resulted in a modest increase in the abundance of mRNA transcripts encoding the cholesterol synthetic enzymes and that of SREBP‐1c. It is concluded that a) prolonged incubation in the presence of azide inhibits cholesterol synthesis, b) exposure to azide results in a decrease in the abundance of several mRNAs encoding cholesterol biosynthetic enzymes and that of SREBPs 1c and 2, and c) that the effect of azide on the observed mRNA abundances is not mediated by stimulation of AMPK. This work is supported by a grant from NIH‐DK45945.