<strong>In silico computer simulation risk assessment of triazole fungicides on human cytochrome p450 aromatase enzyme: cyp19a1 inhibition by triazoles using autodock software.<br /></strong>

Abstract

Biosynthesis of estrogens from androgens is catalyzed by cytochrome P450 aromatase. Target enzymes of triazoles in steroidogenesis are the sterol 14-alfa-demethylase (encoded by the CYP51 gene) and the aromatase (encoded by the CYP19 gene). Aromatase inhibition by the triazole compounds Letrozole (LTZ) and Anastrozole is a prevalent therapy for estrogen-dependent postmenopausal breast cancer. Triazole containing compounds as systemic fungicides are widely used in agriculture due to its high efficiency, broad spectrum, low toxicity and long effectiveness. They target 14α-demethylase, but some were previously shown to inhibit aromatase, thereby raising the possibility of endocrine disruptive effects. However, mechanistic analysis of their inhibition has never been undertaken. In this study inhibitory effect of triazole fungicides were evaluated on the human aromatase enzyme and compared with the Letrozole (LTZ), the most potent inhibitor of aromatase, which is used as anti-estrogen for breast cancer treatment. For this study was used software AUTODOCK to calculate inhibition energy (IE) of triazoles on aromatase enzyme CYP19A1. As triazole moieties are widely used in fungicides, some studies reported that agricultural triazole pesticides are culprits for the development of resistance to other triazole containing drugs. To avoid the risk of possible development of resistance to other triazole drugs and to reduce toxicity of aromatase inhibitors in the treatment of breast cancer, there are used different methods in order to find out new preventive strategies. Hypothesis of this study is that common agricultural triazole fungicides may express inhibitory effect on human aromatase enzyme Cyp19A1, in this way contributing to drug resistance and increased risk of cumulative toxicity of anti-estrogen medications. In our study we performed virtual screening of 15 fungicides and AI reference drug Letrozole to measure inhibitory effect on human aromatase. In this way we aim to range which pesticides are most potent inhibitors of Cyp19A1 enzyme to predict and prevent possible summative cumulating effect of fungicide undesirably overlapping with the activity of anticancer drugs. In our docking study we used together the X-ray structure of human cytochrome P450 aromatase Cyp19A1 (PDB code 3S79, resolution 2.75 Å) associated with the metabolism of estrogens and carcinogens with breast cancer, with a collection of commercially available compounds, particularly, 15 triazole fungicides and anticancer drug Letrozole as reference standard. The binding affinity was evaluated by the binding energies, docking energy, inhibition constant, intermolecular energy, and RMSD values. It was demonstrated that the docking protocol could reliably reproduce the interaction of aromatase with its substrate with an RMSD of 0 Å. We found that four triazole fungicides compounds: Triticonazole, Tebuconazole, Metconazole and Fluquinconazole, exhibited minimal inhibition constant (IC). These compounds with minimal binding energy are safer in terms of toxicity and resistance of other prescription drugs like non-steroid AIs like Letrosole.