Alkylphenols disrupt estrogen homeostasis via diradical cross-coupling reactions: A novel pathway of endocrine disruption

• Published in: Environment international Vol. 183; p. 108428
• Main Authors: Liu, Liu, Guo, Fangjie, Cui, Hongyang, Ji, Li, Yang, Yi, Jiao, Ling, Huang, Yixuan, Wan, Yi
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01.01.2024; Elsevier
• Subjects: CYP450 enzymes; Cytochrome P-450 CYP3A; Density functional theory calculations; Diradical mechanism; Endocrine Disruptors; Estradiol - metabolism; Estrogens - metabolism; Homeostasis; Phenolic cross-coupling reactions; Phenols; Spin aromatic delocalization; CYP450 enzymes; Phenolic cross-coupling reactions; Diradical mechanism; Density functional theory calculations; Spin aromatic delocalization
• ISSN: 0160-4120; 1873-6750
• DOI: 10.1016/j.envint.2024.108428

[Display omitted] •Abundant metabolites of cross-coupling reaction of alkylphenols and estrogens were identified.•The coupling reactions were catalyzed by CYP3A4 and verified in general populations.•Alkylphenols disrupt estrogen homeostasis via cross-coupling reactions.•Spin-trapping screening and DFT calculations revealed the diradical mechanism of cross-coupling reactions. Estrogen, being an essential class of sex hormone, is an important target of endocrine disruption chemicals. It is well known that environmental disruptors could activate or inhibit estrogen receptors, acting as agonists or antagonists, and thus affect the circulating estrogen concentrations. Here, we report enzyme-mediated diradical cross-coupling reactions between alkylphenols (e.g., 2,4-di-tert-butylphenol [DBP], 4-nonylphenol [4-NP], and 4-tert-octylphenol [4-t-OP]) and estrogens (e.g., estradiol [E2]) that generate coupling metabolites and disrupt estrogen homeostasis. Among the phenolic xenobiotics, the screening of metabolic products revealed that alkylphenols had the highest reaction activities and generated coupling metabolites with high abundances (DBP-O-E2, 4-t-OP-O-E2, and 4-NP-O-E2). The coupling reactions were catalyzed by cytochrome P450 3A4 (CYP3A4) and verified by the detection of the coupling products in general populations. In vitro and in vivo exposures together with CYP3A4 inhibition demonstrated that cross-coupling reactions of phenols and E2 significantly reduced the normal levels of E2. We further established a unique spin-trapping-based high-throughput screening method to show the existence of diradicals in the coupling reaction. Density functional theory calculations revealed that spin aromatic delocalization was the fundamental cause of the high rebound barrier and sufficient lifetime of phenoxy radicals that enabled phenolic cross-coupling triggered by cytochrome P450. The identified mechanistic details for diradical cross-coupling reactions provide a novel pathway for phenolic chemicals to disrupt estrogen homeostasis.