5α-hydroxy-6-keto Cholesterol (6-oxo-3,5,-diol) is a major metabolite of cholesterol formed during exposure of lung epithelial cells to ozone, with formation of 5β,6β-epoxycholesterol as a predominant precursor. Exposure of C57BL/6J mice to 0.5-3 ppm ozone produced a dose-dependent formation of 6-oxo-3,5,-diol which was detectable in the bronchalveolar lavage fluid, lavaged cells, and lung homogenates. 6-Oxo-3,5-diol is a potent inhibitor of cholesterol synthesis in human bronchial epithelial cells with an IC50 of 350 nM and exhibits significant cytotoxicity in the low μM range.
