In vivo Role of Cytochrome P450 2E1 and Glutathione-S-Transferase Activity for Acrylamide Toxicokinetics in Humans

Abstract

Acrylamide, a potential food carcinogen in humans, is biotransformed to the epoxide glycidamide in vivo. Both acrylamide and glycidamide are conjugated with glutathione, possibly via glutathione-S-transferases (GST), and bind covalently to proteins and nucleic acids. We investigated acrylamide toxicokinetics in 16 healthy volunteers in a four-period change-over trial and evaluated the respective role of cytochrome P450 2E1 (CYP2E1) and GSTs. Participants ingested selfprepared potato chips containing acrylamide (1 mg) without comedication, after CYP2E1 inhibition (500 mg disulfiram, single dose) or induction (48 g/d ethanol for 1 week), and were phenotyped for CYP2E1 with chlorzoxazone (250 mg, single dose). Unchanged acrylamide and the mercapturic acids N -acetyl-S-(2-carbamoylethyl)-cysteine (AAMA) and N-acetyl-S -(2-hydroxy-2-carbamoylethyl)-cysteine (GAMA) accounted for urinary excretion [geometric mean (percent coefficient of variation)] of 2.9% (42), 65% (23), and 1.7% (65) of the acrylamide dose in the reference period.Hemoglobin adducts increased clearly following the acrylamide test-meal. The cumulative amounts of acrylamide, AAMA, and GAMA excreted and increases in AA adducts changed significantly during CYP2E1 blockade [point estimate (90% confidence interval)] to the 1.34-fold (1.14-1.58), 1.18-fold (1.02-1.36), 0.44-fold (0.31-0.61), and 1.08-fold (1.02-1.15) of the reference period, respectively, but were not changed significantly during moderate CYP2E1 induction. Individual baseline CYP2E1 activity, CYP2E1*6, GSTP1 313A>G and 341T>C single nucleotide polymorphisms, and GSTM1-and GSTT1-null genotypes had no major effect on acrylamide disposition. The changes in acrylamide toxicokinetics upon CYP2E1 blockade provide evidence that CYP2E1 is a major but not the only enzyme mediating acrylamide epoxidation in vivo to glycidamide in humans. No obvious genetic risks or protective factors in xenobiotic-metabolizing enzymes could be determined for exposed subjects. (Cancer Epidemiol

Mechanism-Based Inactivation of Human CYP2E1 by Diethyldithocarbamate

“…The use of disulfiram in studies aimed to inactivate CYP2E1 in vivo has been reported recently (Doroshyenko et al, 2009); however, the mechanism by which it causes inactivation has not been reported. We report here that disulfiram is not the compound directly responsible for inactivation of CYP2E1, but that its reduced form, diethyldithiocarbamate, is responsible for the inactivation (Fig.…”

“…CYP2E1 is involved in the metabolism of numerous low-molecular-weight xenobiotics including acetaminophen, benzene, and chlorzoxazone, as well as anesthetics such as halothane (Koop, 1992;Lieber, 1997). Disulfiram has been used for a long time as an inhibitor of CYP2E1 in various in vivo studies (Doroshyenko et al, 2009). It has also been proposed that inhibition by disulfiram could be used to prevent the activation of nitrosamine carcinogens by CYP2E1 (Wattenberg et al, 1989).…”

Toxicology and risk assessment of acrolein in food

“…The authors concluded from the excretion kinetics that the exposure to acrolein is attributable to the intake of the test meal. The deep-frozen urine samples examined during these analyses originated from a study conducted earlier [97,98]. Test subjects consumed self-made potato chips with relatively high acrylamide content (acrylamide dose 1 mg).…”

Diverse action of acrylamide on cytochrome P450 and glutathione S-transferase isozyme activities, mRNA levels and protein levels in human hepatocarcinoma cells

“…Glycidamide is mutagenic, and it is able to bind to DNA and cause genetic damage (Adler et al 2000;Yousef and El-Demerdash 2006). Glycidamide is subsequently metabolized through either GSH conjugation by GST or hydrolysis by epoxide hydrolase (Paulsson et al 2005;Doroshyenko et al 2009). …”

“…CYP2E1 is the classical alcohol-inducible CYP isoform which catalyzes several pro-carcinogens such as benzene, N-nitrosodimethylamine, styrene, into their carcinogenic forms. CYP2E1 is also a polymorphic enzyme (Ulusoy et al 2007a, b;Doroshyenko et al, 2009). While it was shown that acrylamide is metabolized primarily by liver CYP2E1, the effects of acrylamide on cytochrome-dependent drug metabolizing enzymes have not yet been characterized.…”