Application of a ligand-based theoretical approach to derive conversion paths and ligand conformations in CYP11B2-mediated aldosterone formation.

The biosynthesis of the mineralocorticoid hormone aldosterone involves a multistep hydroxylation of 11-deoxycorticosterone at the 11- and 18-positions, resulting in the formation of corticosterone and 18-hydroxycorticosterone, the final precursor of aldosterone. Two members of the cytochrome P450 11B family, CYP11B1 and CYP11B2, are known to catalyze these 11- and 18-hydroxylations, however, only CYP11B2 can oxidize 18-hydroxycorticosterone to aldosterone. It is unknown what sequence of hydroxylations leads to the formation of 18-hydroxycorticosterone. In this study we have investigated which of the possible conversion paths towards formation of 18-hydroxycorticosterone and aldosterone are most likely from the ligand perspective. Therefore, we combined quantum mechanical investigations on the steroid conformations of 11-deoxycorticosterone and its ensuing reaction intermediates with Fukui indices calculations to predict the reactivity of their carbon atoms for an attack by the iron-oxygen species. Both F(-) and F(0) were calculated to account for different mechanisms of substrate conversion. We show which particular initial conformations of 11-deoxycorticosterone and which conversion paths are likely to result in the successful synthesis of aldosterone, and thereby may be representative for the mechanism of aldosterone biosynthesis by CYP11B2. Moreover, we found that the most likely path for aldosterone synthesis coincides with the substrate conformation proposed in an earlier publication. To summarize, we show that on a theoretical and strictly ligand-directed basis only a limited number of reaction paths in the conversion of 11-deoxycorticosterone to aldosterone is possible. Despite its theoretical nature, this knowledge may help to understand the catalytic function of CYP11B1 and CYP11B2.

Synthesis, biological evaluation, and molecular modeling of 1-benzyl-1H-imidazoles as selective inhibitors of aldosterone synthase (CYP11B2).

Reducing aldosterone action is beneficial in various major diseases such as heart failure. Currently, this is achieved with mineralocorticoid receptor antagonists, however, aldosterone synthase (CYP11B2) inhibitors may offer a promising alternative. In this study, we used three-dimensional modeling of CYP11B2 to model the binding modes of the natural substrate 18-hydroxycorticosterone and the recently published CYP11B2 inhibitor R-fadrozole as a rational guide to design 44 structurally simple and achiral 1-benzyl-1H-imidazoles. Their syntheses, in vitro inhibitor potencies, and in silico docking are described. Some promising CYP11B2 inhibitors were identified, with our novel lead MOERAS115 (4-((5-phenyl-1H-imidazol-1-yl)methyl)benzonitrile) displaying an IC(50) for CYP11B2 of 1.7 nM, and a CYP11B2 (versus CYP11B1) selectivity of 16.5, comparable to R-fadrozole (IC(50) for CYP11B2 6.0 nM, selectivity 19.8). Molecular docking of the inhibitors in the models enabled us to generate posthoc hypotheses on their binding modes, providing a valuable basis for future studies and further design of CYP11B2 inhibitors.