Newly Observed Spontaneous Activation of Ethephon as a Butyrylcholinesterase Inhibitor

Exposure to ethephon compromises endometrial decidualization in mice during early pregnancy via GPR120

Exposure to ethephon (ETH), a plant growth regulator commonly used for several purposes, can potentially decrease sperm numbers and viability. Occasional findings regarding ETH effects on female reproduction during early pregnancy have also been reported. During early pregnancy, endometrial decidualization is a critical event for embryo implantation and pregnancy maintenance. Thus, we aimed to explore the effect and mechanism of ETH on endometrial decidualization both in vivo and in vitro. Mice were gavaged with 0 and 285 mg/kg b.w. ETH from gestational days (GD)1 until sacrifice, whereas pseudopregnant mice from pseudopregnant day 1 (PPD-1) until PPD-8. Primary mouse endometrial stromal cells (mESCs) received 640 ug/ml ETH and added E2 and P4 to induce decidualization. Results indicated female albino CD1 mice exposed to high dose of ETH (285 mg/kg b.w.) by oral gavage, the number of embryo implantation sites on GD6 and GD8 were significantly decreased, the levels of serum E2 and P4 on GD8 were significantly decreased. Compared with the control group, the decidualization response artificially induced by corn oil in pseudopregnant mice and by E2 and P4 in primary mouse endometrial stromal cells (mESCs) was weakened in the high dose of ETH treated group. The high dose, 285 mg/kg b.w ETH treated group altered the expression of endometrial decidual markers on GD6 and GD8. The triglyceride and fatty acid metabolism-related genes were significantly increased after female albino CD1 mice exposed to high does, 285 mg/kg b.w ETH on GD6 and GD8. GPR120 was substantially reduced after ETH treatment. When overexpression of GPR120, the compromised decidualization induced by ETH treatment was rescued. Furthermore, molecular docking presented Thr234 and His251 of GPR120 as preferred binding sites for ETH. Mutation of these two sites rescued the compromised decidualization induced by ETH. In conclusion, we demonstrated that ETH exposure could impair decidualization during early pregnancy. GPR120 expression and binding between GPR120 and ETH are crucial for impaired decidualization mediated via ETH.

Organophosphorus Xenobiotic Toxicology

Originally, organophosphorus (OP) toxicology consisted of acetylcholinesterase inhibition by insecticides and chemical threat agents acting as phosphorylating agents for serine in the catalytic triad, but this is no longer the case. Other serine hydrolases can be secondary OP targets, depending on the OP structure, and include neuropathy target esterase, lipases, and endocannabinoid hydrolases. The major OP herbicides are glyphosate and glufosinate, which act in plants but not animals to block aromatic amino acid and glutamine biosynthesis, respectively, with safety for crops conferred by their expression of herbicide-tolerant targets and detoxifying enzymes from bacteria. OP fungicides, pharmaceuticals including calcium retention agents, industrial chemicals, and cytochrome P450 inhibitors act by multiple noncholinergic mechanisms, often with high potency and specificity. One type of OP-containing fire retardant forms a highly toxic bicyclophosphate γ-aminobutyric acid receptor antagonist upon combustion. Some OPs are teratogenic, mutagenic, or carcinogenic by known mechanisms that can be avoided as researchers expand knowledge of OP chemistry and toxicology for future developments in bioregulation.

Unexpected Metabolic Reactions and Secondary Targets of Pesticide Action

Pesticides provide a fascinating combination of substituents not present in other environmental chemicals, leading to unexpected metabolites and toxicological effects in pests, mammals, and other organisms. The parent compound and/or metabolites of some pesticides have multiple targets, requiring identification of the causal agents and their modes of action. This review considers a few of the author's observations in the past six decades, some solved and others still puzzling. It illustrates that a new substituent combination not only confers specific chemical and physical properties to a class of compounds but often yields metabolites with a surprising variety of biological activities. Examples considered include proinsecticides, procyclic phosphates, CYP inhibitors as synergists, thiocarbamate sulfoxides, promutagens, carcinogens, and hepatotoxins, and stress tolerance inducers in plants. Although the discoveries considered are based on pesticide toxicology, they are broadly applicable to environmental toxicology and xenobiotics in animals, plants, and microorganisms.

Review of human butyrylcholinesterase structure, function, genetic variants, history of use in the clinic, and potential therapeutic uses

Phase I clinical trials have shown that pure human butyrylcholinesterase (BChE) is safe when administered to humans. A potential therapeutic use of BChE is for prevention of nerve agent toxicity. A recombinant mutant of BChE that rapidly inactivates cocaine is being developed as a treatment to help recovering cocaine addicts avoid relapse into drug taking. These clinical applications rely on knowledge of the structure, stability, and properties of BChE, information that is reviewed here. Gene therapy with a vector that sustains expression for a year from a single injection is a promising method for delivering therapeutic quantities of BChE.

Characterization of the transient oxaphosphetane BChE inhibitor formed from spontaneously activated ethephon

The major plant growth regulator ethephon degrades to ethylene and phosphate in aqueous solutions and plants and is spontaneously activated to a butyrylcholinesterase (BChE) inhibitor in alkaline solutions and animal tissues. In the present ³¹P NMR kinetic study of the reactions of ethephon in pH 7.4 carbonate buffer, we observed a transient peak at 28.11 ppm. The time course for the appearance and disappearance of this peak matches the activation/degradation kinetic profile of the BChE inhibitor, and the chemical shift supports the proposed 2-oxo-2-hydroxy-1,2-oxaphosphetane structure.