Investigation of the Potential of Bile Acid Methyl Esters as Inhibitors of Aldo-keto Reductase 1C2: Insight from Molecular Docking, Virtual Screening, Experimental Assays and Molecular Dynamics.

Human aldo-keto reductase 1C isoforms (AKR1C1-C4) catalyze reduction of endogenous and exogenous compounds, including therapeutic drugs, and are associated with chemotherapy resistance. AKR1C2 is involved in metastatic processes and is a target for the treatment of various cancers. Here we used molecular docking to explore the potential of a series of eleven bile acid methyl esters as AKR1C2 inhibitors. Autodock 4.2 ranked 10 of the 11 test compounds above a decoy set generated based on ursodeoxycholic acid, a known AKR1C2 inhibitor, while 5 of these 10 ranked above 94 % of decoys in Autodock Vina. Seven inactives reported in the literature not to inhibit AKR1C2 ranked below the decoy threshold: 5 of these are specific inhibitors of AKR1C3, a related isoform. Using the same parameters, Autodock Vina identified steroidal analogs of AKR1C substrates, bile acids, and AKR1C inhibitors in the top 5 % of a virtual screen of a natural product library. In experimental assays, 6 out of 11 of the tested bile acid methyl esters inhibited >50 % of AKR1C2 activity, while 2 compounds were strong AKR1C3 inhibitors. Potential off-target interactions with the glucocorticoid receptor were measured using a yeast-based fluorescence assay, where results suggest that the methyl ester could interfere with binding. The top ranking compound based on docking and experimental results showed dose-dependent inhibition of AKR1C2 with an IC50 of ∼3.6 µM. Molecular dynamics simulations (20 ns) were used to explore potential interactions between a bile acid methyl ester and residues in the AKR1C2 active site. Our molecular docking results identify AKR1C2 as a target for bile acid methyl esters, which combined with virtual screening results could provide new directions for researchers interested in synthesis of AKR1C inhibitors.

Microwave-assisted green synthesis of bile acid derivatives and evaluation of glucocorticoid receptor binding.

Herein, we present microwave-assisted AlCl3 catalyzed oxidation of bile acid hydroxyl groups in the presence of Oxone® in water media. Significant rate enhancements were observed for Wolff-Kishner reduction of synthesized bile acids oxo derivatives to the 5ß-cholanic acid. Reaction of amidation of the simplest bile acid and aminolysis of the deoxycholic acid was accomplished in the absence of solvent and catalysts under sealed vessel microwave conditions. Because 5ß-cholanic acid reportedly modulates glucocorticoid receptor signaling in cell models of Parkinson's disease, we tested the affinity of 5ß-cholanic acid and deoxycholic acid derivatives for the glucocorticoid receptor in vitro using a yeast-based fluorescent screen. Treatment of GR-expressing yeast with prednisolone resulted in a dose-dependent increase in fluorescence; whereas 5ß-cholanic acid binds to the glucocorticoid receptor with more moderate affinity. Similarly, molecular docking also suggests that 5ß-cholanic acid can bind to the glucocorticoid receptor, with similar geometry to known GR ligands.