Metabolic activation of (R)-(+)-pulegone to a reactive enonal that covalently binds to mouse liver proteins

McClanahan, Robert H.; Thomassen, David G.; Slattery, John T.; Nelson, Sidney D.

doi:10.1021/tx00011a013

Cited by 66 publications

(74 citation statements)

References 14 publications

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“…M4 and M7 are also hydroxybutyryl and carboxypropionic acid-containing metabolites, respectively, and are consistent with Kobayashi's observations. Semicarbazide has been used to trap an unsaturated ␥-keto-␣,␤-unsaturated aldehyde derived from pulegone (McClanahan et al, 1989) as a pyridazine product, and we also successfully trapped the ␥-keto-␣,␤-unsaturated aldehyde (M15) derived from prazosin with semicarbazide. Finally, semicarbazide greatly reduced the formation of M4 and M7 (Fig.…”

Section: Discussionmentioning

confidence: 99%

Metabolism of Prazosin in Rat, Dog, and Human Liver Microsomes and Cryopreserved Rat and Human Hepatocytes and Characterization of Metabolites by Liquid Chromatography/Tandem Mass Spectrometry

Erve¹,

Vashishtha²,

DeMaio³

et al. 2007

Drug Metab Dispos

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ABSTRACT:Prazosin (2-[4-(2-furanoyl)-piperazin-1-yl]-4-amino-6,7-dimethoxyquinazoline) is an antihypertensive agent that was introduced to the market in 1976. It has since established an excellent safety record. However, in vitro metabolism of prazosin has not been investigated. This study describes the in vitro biotransformation of prazosin in liver microsomes from rats, dogs, and humans, as well as rat and human cryopreserved hepatocytes and characterization of metabolites using liquid chromatography/tandem mass spectrometry. The major in vivo biotransformation pathways reported previously in rats and dogs include demethylation, amide hydrolysis, and O-glucuronidation. These metabolic pathways were also confirmed in our study. In addition, several new metabolites were characterized, including a stable carbinolamine, an iminium species, and an enamine-all formed via oxidation of the piperazine ring. Two ring-opened metabolites generated following oxidative cleavage of the furan ring were also identified. Using semicarbazide hydrochloride as a trapping agent, an intermediate arising from opening of the furan ring was captured as a pyridazine product. In the presence of glutathione, three glutathione conjugates were detected in microsomal incubations, although they were not detected in cryopreserved hepatocytes. These data support ring opening of the furan via a reactive ␥-keto-␣,␤-unsaturated aldehyde intermediate. In the presence of UDP-glucuronic acid, prazosin underwent conjugation to form an N-glucuronide not reported previously. Our in vitro investigations have revealed additional metabolic transformations of prazosin and have shown the potential of prazosin to undergo bioactivation through metabolism of the furan ring to a reactive intermediate.Prazosin (Fig. 1), a short-acting vasodilator discovered in the mid1970s, has been widely used in treating hypertension and congestive heart failure (Constantine, 1974;Althuis and Hess, 1977;Stanaszek et al., 1983). It was the first of a new class of direct-acting vasodilators acting by ␣-adrenoreceptor blockade. Prazosin was introduced to the U.S. market as MINIPRESS by Pfizer (New York, NY) in 1976. Prazosin is well tolerated, with the most common side effect associated with treatment being postural hypotension. Although no longer a major drug among the antihypertensive agents, based on prazosin's ability to antagonize centrally located ␣ 1 -adrenergic receptors, a new indication for treatment of post-traumatic stress disorders (PTSD) encountered during civilian life is being explored in clinical studies (Taylor and Raskind, 2002). In addition, prazosin is also being investigated in treating combat-related nightmares characteristic of PTSD among soldiers recently returned from Operation Iraqi Freedom (Daly et al., 2005).In vitro metabolism of prazosin in animals or humans has not been reported. Early metabolism studies with 14 C-labeled prazosin (label in quinazoline ring) in rats and dogs revealed that it undergoes extensive hepatic metabolism with biliary excret...

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Section: Discussionmentioning

confidence: 99%

Metabolism of Prazosin in Rat, Dog, and Human Liver Microsomes and Cryopreserved Rat and Human Hepatocytes and Characterization of Metabolites by Liquid Chromatography/Tandem Mass Spectrometry

Erve¹,

Vashishtha²,

DeMaio³

et al. 2007

Drug Metab Dispos

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“…This hypothesis is supported by the observation that a tetrahydrofuran analogue is not toxic (25). By analogy to other furan-containing compounds, such as methylfuran, furosemide, 4-ipomeanol, menthofuran, and aflatoxin (28-35), 1,4-enedials or possible epoxide precursors are the likely reactive metabolites (Scheme 2) (34)(35)(36)(37).…”

Section: Introductionmentioning

confidence: 89%

Identification of the Protein Targets of the Reactive Metabolite of Teucrin A in Vivo in the Rat

Druckova

Mernaugh

Ham

et al. 2007

Chem. Res. Toxicol.

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Covalent modification of proteins is associated with the toxicity of many electrophiles, and the identification of relevant in vivo protein targets is a desirable but challenging goal. Here, we describe a strategy for the enrichment of adducted proteins utilizing single-chain fragment variable (ScFv) antibodies selected using phage-display technology. Teucrin A is a furan-containing diterpenoid found in the herb germander that is primarily responsible for the herb's hepatotoxicity in rodents and humans following metabolic activation by cytochrome P450 enzymes. Conjugates of the 1,4-enedial derivative of teucrin A, its presumed toxic metabolite, with lysine-and cysteine-containing peptides were synthesized and used to select ScFvs from a rodent phage-displayed library, which recognized the terpenoid moiety of the teucrin-derived adducts. Immunoaffinity isolation of adducted proteins from rat liver homogenates following administration of a toxic dose of teucrin A afforded a family of proteins that were identified by liquid chromatography/tandem mass spectrometry. Of the 46 proteins identified in this study, most were of mitochondrial and endoplasmic reticulum origin. Several cytosolic proteins were found, as well as four peroxisomal and two secreted proteins. Using Ingenuity Pathway Analysis software, two significant networks involving the target genes were identified that had major functions in gene expression, small molecule biochemistry, and cellular function and maintenance. These included proteins involved in lipid, amino acid, and drug metabolism. This study illustrates the utility of chemically synthesized biological conjugates of reactive intermediates and the potential of the phage display technology for the generation of affinity reagents for the isolation of adducted proteins.

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“…12) Despite its use in traditional medicine, pennyroyal oil is known to be extremely hepatotoxic and neurotoxic. Pulegone causes extensive liver damage in laboratory animals, 13) and human intoxication with pennyroyal oil (or with mint tea containing this oil) is associated with the loss of renal function, hepatotoxicity, dizziness, epileptic encephalopathy and, in severe cases, death. 14) Although the hepatotoxic effects of pulegone have been extensively demonstrated and studied, the behavioral effects of this terpenic compound have only recently gained attention in the field.…”

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confidence: 99%

The Aversive, Anxiolytic-Like, and Verapamil-Sensitive Psychostimulant Effects of Pulegone

Silveira

Oliveira-Silva

Lamanes

et al. 2014

Biological & Pharmaceutical Bulletin

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We investigated the psychostimulant, rewarding, and anxiolytic-like effects of pulegone. Possible interactions between pulegone and menthol concerning their psychostimulant effect were also analyzed. General mouse activity after pulegone treatment, and the interacitons between pulegone and menthol, were determined in the open field. The anxiolytic-like activity, motor coordination and strength force were evaluated using the elevated plus maze (EPM), rotarod test and grasping test, respectively. The motivational properties of pulegone were evaluated by pairing the drug effects on the mice with the least preferred compartment (previously determined) of a conditioned place preference (CPP) apparatus. Pulegone increased mouse locomotor activity and immobilization time. Verapamil, but not diltiazem, haloperidol or picrotoxin, decreased the psychostimulation induced by pulegone. Pulegone also decreased grooming and rearing behaviors and caused motor incoordination and weakness at high doses. Pulegone increased the time spent by mice in the open arms of the EPM, and flumazenil pre-treatment did not alter this effect. Pulegone either produced no CPP or induced conditioned place aversion. The changes in mouse ambulatory activity caused by the association of pulegone with menthol were either lower than those predicted by the theoretical curve or not different from the predicted values. Therefore, pulegone induces a verapamil-sensitive psychostimulant effect that appears to independ on the opening of L-type calcium channels. Pulegone has negative reinforcing properties and seems to possess anxiolytic-like actions unrelated to the benzodiazepine site of the γ-aminobutyric acid type A (GABA A ) receptor. Finally, pulegone might act in an addictive or synergic way with menthol.

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Metabolic activation of (R)-(+)-pulegone to a reactive enonal that covalently binds to mouse liver proteins

Cited by 66 publications

References 14 publications

Metabolism of Prazosin in Rat, Dog, and Human Liver Microsomes and Cryopreserved Rat and Human Hepatocytes and Characterization of Metabolites by Liquid Chromatography/Tandem Mass Spectrometry

Metabolism of Prazosin in Rat, Dog, and Human Liver Microsomes and Cryopreserved Rat and Human Hepatocytes and Characterization of Metabolites by Liquid Chromatography/Tandem Mass Spectrometry

Identification of the Protein Targets of the Reactive Metabolite of Teucrin A in Vivo in the Rat

The Aversive, Anxiolytic-Like, and Verapamil-Sensitive Psychostimulant Effects of Pulegone

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