Interindividual variability in the expression and NNK carbonyl reductase activity of 11β-hydroxysteroid dehydrogenase 1 in human lung

The balance between metabolic activation and detoxification is critical in determining the susceptibility to lung cancer upon exposure to the tobacco specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Carbonyl reduction of NNK, followed by glucuronidation, is the main detoxification pathway of this lung carcinogen in humans. Recently, we have identified 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD 1) as microsomal NNK carbonyl reductase in liver and lung. In the present study, the interindividual variability of 11β-HSD 1 expression and NNK-carbonyl reductase activity was examined in human lung by RT–PCR, Western blot analysis and enzyme activity. Levels of 11β-HSD 1 mRNA varied over an almost 20-fold range among different subjects. Levels of NNK carbonyl reductase activity in lung microsomes closely resembled the relative amounts of immunoreactive protein as determined by Western blot analysis. In view of the large interindividual differences in the susceptibility of tobacco smoke related lung cancer, we present the first data on the variability of 11β-HSD 1 expression and NNK carbonyl reduction in human lung.