Endocrine Abstracts

The aldosterone synthase (CYP11B2), being 93 % identical in its primary structure to CYP11B1, catalyses the 11beta-hydroxylation, 18-hydroxylation and 18-oxidation of deoxycorticosterone to form aldosterone. CYP11B2 is an important target for the development of drugs, since overproduction of aldosterone may lead to hypertension as well as heart failure. Thus, besides the mineralocorticoid receptor, CYP11B2 seems to be a potent target for drug development. To find specific inhibitors for these enzymes, test systems containing the respective human enzymes are necessary. We have created recombinant cells expressing human CYP11B1 or CYP11B2. For this, we have cloned CYP11B1 and CYP11B2 from normal human adrenals and expressed them in V79 cells and in the fission yeast Schizosaccharomyces pombe, respectively. Surprisingly, both cell systems did not need co-expression of the autologous electron donor system, consisting of an iron-sulfur protein, adrenodoxin, and a FAD containing reductase. It could be demonstrated that recombinant V79 as well as recombinant yeast cells can be used for studying effects of potential inhibitors. Usage of cells expressing CYP11B1 or CYP11B2, moreover, allows to evaluate the specificity of a given inhibitor. The development of a medium-throughput system for the screening of potential inhibitors of CYP11B2 which are valuable lead compounds for the discovery of drugs against hypertension and myocardial fibrosis will be presented which allowed the screening of >1000 compounds. The new screening system displayed high reproducibility and was applied to investigate a library of pharmacologically active compounds. 1268 compounds were investigated during this study which revealed 5 selective inhibitors of CYP11B2 (after validation against CYP11B1). The new inhibitors of CYP11B2 are already existing drugs that could be used either in the treatment of hyperaldosteronism-related diseases or as lead compounds that could further be optimized to achieve safer and selective inhibitors of aldosterone synthase. Very recently, we were also able to express CYP11B1 and CYP11B2 in E. coli and purify the proteins from there. They can be used for in-vitro characterization of inhibitors as well as naturally occurring mutants. The advantages and disadvantages of the different test systems will be discussed.

Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.