Sulfoxidation of Mercapturic Acids Derived from Tri- and Tetrachloroethene by Cytochromes P450 3A:  A Bioactivation Reaction in Addition to Deacetylation and Cysteine Conjugate β-Lyase Mediated Cleavage

Werner, Michael; Birner, Gerhard; Dekant, W.

doi:10.1021/tx950075u

Cited by 52 publications

(45 citation statements)

References 52 publications

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“…The findings that TCVC oxidation was NADPH-dependent, stereoselective, and inhibited by methimazole or 1-benzylimidazole are consistent with the involvement of FMO3 and P450s in this sulfoxidation reaction (Ripp et al, 1997(Ripp et al, , 1999Krause et al, 2003). N-Acetyl-S-(1,2,2-trichlorovinyl)-L-cysteine, the mercapturic acid of TCVC, is metabolized to its corresponding sulfoxide by the isozymes of the cytochrome P450 3A family (Werner et al,1996).…”

Section: Discussionmentioning

confidence: 59%

“…TCVC (150 l) was added to the enzymatic incubation to start the metabolic reaction; the pH of the reaction mixture was approximately pH 7.6 after the addition of TCVC solution (final concentration 5 mM). The kidney microsomal experiments were carried out in the presence of 0.1 mM AOAA to inhibit any ␤-lyase-mediated reaction (Lash et al, 1994;Werner et al, 1996). To terminate the reaction, ice-cold 0.75% perchloric acid (0.15 ml) was added.…”

Section: Methodsmentioning

confidence: 99%

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S-(1,2,2-Trichlorovinyl)-l-cysteine Sulfoxide, a Reactive Metabolite ofS-(1,2,2-Trichlorovinyl)-l-cysteine Formed in Rat Liver and Kidney Microsomes, Is a Potent Nephrotoxicant

Elfarra¹,

Krause²

2007

J Pharmacol Exp Ther

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Previously, we have provided evidence that cytochromes P450 (P450s) and flavin-containing monooxygenases (FMOs) are involved in the oxidation of S-(1,2,2-trichlorovinyl)-L-cysteine (TCVC) in rabbit liver microsomes to yield the reactive metabolite TCVC sulfoxide (TCVCS). Because TCVC is a known nephrotoxic metabolite of tetrachloroethylene, the nephrotoxic potential of TCVCS in rats and TCVCS formation in rat liver and kidney microsomes were investigated. At 5 mM TCVC, rat liver microsomes formed TCVCS at a rate nearly 5 times higher than the rate measured with rat kidney microsomes, whereas at 1 mM TCVC only the liver activity was detectable. TCVCS formation in liver and kidney microsomes was dependent upon the presence of NADPH and was inhibited by the addition of methimazole or 1-benzylimidazole, but not superoxide dismutase,

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Section: Discussionmentioning

confidence: 59%

Section: Methodsmentioning

confidence: 99%

S-(1,2,2-Trichlorovinyl)-l-cysteine Sulfoxide, a Reactive Metabolite ofS-(1,2,2-Trichlorovinyl)-l-cysteine Formed in Rat Liver and Kidney Microsomes, Is a Potent Nephrotoxicant

Elfarra¹,

Krause²

2007

J Pharmacol Exp Ther

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“…cysteine, and N-acetyl-S-(4-methoxybenzyl)-L-cysteine were synthesized and characterized as described before Werner et al, 1997;Scholz et al, 2005)…”

Section: Methodsmentioning

confidence: 99%

Specificity of Aminoacylase III-Mediated Deacetylation of Mercapturic Acids

et al. 2006

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ABSTRACT:Trichloroethylene (TCE) and other halogenated alkenes are known environmental contaminants with cytotoxic and nephrotoxic effects, and are potential carcinogens. Their metabolism via the mercapturate metabolic pathway was shown to lead to their detoxification. The final products of this pathway, mercapturic acids or N-acetyl-L-cysteine S-conjugates, are secreted into the lumen in the renal proximal tubule. The proximal tubule may also deacetylate mercapturic acids, and the resulting cysteine S-conjugates are transformed by cysteine S-conjugate ␤-lyases to nephrotoxic reactive thiols. The specificity and rate of mercapturic acid deacetylation may determine the toxicity of certain mercapturic acids; however, the exact enzymologic processes involved are not known in detail. In the present study we characterized the kinetics of the recently cloned mouse aminoacylase III (AAIII) toward a wide spectrum of halogenated mercapturic acids and N-acetylated amino acids. In general, the V max value of AAIII was significantly larger with chlorinated and brominated mercapturic acids, whereas fluorination significantly decreased it. The enzyme deacetylated mercapturic acids derived from the TCE metabolism including N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine (NA-1,2-DCVC) and N-acetyl-S-(2,2-dichlorovinyl)-L-cysteine (NA-2,2-DCVC). Both mercapturic acids induced cytotoxicity in mouse proximal tubule mPCT cells expressing AAIII, which was decreased by an inhibitor of ␤-lyase, aminooxyacetate. The toxic effect of NA-2,2-DCVC was smaller than that of NA-1,2-DCVC, indicating that factors other than the intracellular activity of AAIII mediate the cytotoxicity of these mercapturic acids. Our results indicate that in proximal tubule cells, AAIII plays an important role in deacetylating several halogenated mercapturic acids, and this process may be involved in their cyto-and nephrotoxicity.Trichloroethylene (TCE) and other industrial solvents are shown to cause nephrotoxicity and hepatotoxicity, and are probable human carcinogens (Maltoni et al., 1988;Cummings and Lash, 2000). One of the TCE toxicity mechanisms involves the conjugation with glutathione, which is transformed by ␥-glutamyltransferase and dipeptidase to cysteine S-conjugates Berrnauer et al., 1996;Anders and Dekant, 1998). The formation of cysteine S-conjugates takes place mainly in liver and, to some extent, also in kidney. Cysteine S-conjugates may be acetylated in the liver and kidney into corresponding N-acetyl S-conjugates (mercapturic acids) and transported from the liver into the kidney. In the kidney proximal tubules, mercapturic acids may be secreted or deacetylated by aminoacylases into cysteine S-conjugates Dekant, 1994, 1998). The deacetylation reaction may play an important role in the renal nephrotoxicity since cysteine S-conjugates, but not mercapturates, are transformed by cysteine conjugate ␤-lyases into toxic metabolites (Hayden and Stevens, 1990;Commandeur et al., 1995). Cysteine S-conjugates also may be transformed by flavoprotein monooxygenase...

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“…and N-acetyl-S-purinyl-L-cysteine were synthesized and characterized as described previously [20,21]. [22], and rat liver microsomes were kindly supplied by F. Hoffmann-La Roche (Basel, Switzerland).…”

Section: Chemicalsmentioning

confidence: 99%

Rapid detection and identification of N-acetyl-L-cysteine thioethers using constant neutral loss and theoretical multiple reaction monitoring combined with enhanced product-ion scans on a linear ion trap mass spectrometer

Scholz

Dekant

Völkel

et al. 2005

J. Am. Soc. Mass Spectrom.

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A sensitive and specific liquid chromatography-mass spectrometry (LC-MS) method based on the combination of constant neutral loss scans (CNL) with product ion scans was developed on a linear ion trap. The method is applicable for the detection and identification of analytes with identical chemical substructures (such as conjugates of xenobiotics formed in biological systems) which give common CNLs. A specific CNL was observed for thioethers of N-acetyl-L-cysteine (mercapturic acids, MA) by LC-MS/MS. MS and HPLC parameters were optimized with 16 MAs available as reference compounds. All of these provided a CNL of 129 Da in the negative-ion mode. To assess sensitivity, a multiple reaction monitoring (MRM) mode with 251 theoretical transitions using the CNL of 129 Da combined with a product ion scan (IDA thMRM) was compared with CNL combined with a product ion scan (IDA CNL). An information-dependent acquisition (IDA) uses a survey scan such as MRM (multiple reaction monitoring) to generate "informations" and starting a second acquisition experiment such as a product ion scan using these "informations." Th-MRM means calculated transitions and not transitions generated from an available standard in the tuning mode. The product ion spectra provide additional information on the chemical structure of the unknown analytes. All MA standards were spiked in low concentrations to rat urines and were detected with both methods with LODs ranging from 60 pmol/mL to 1.63 nmol/mL with IDA thMRM. The expected product ion spectra were observed in urine. Application of this screening method to biological samples indicated the presence of a number of MAs in urine of unexposed rats, and resulted in the identification of 1,4-dihydroxynonene mercapturic acid as one of these MAs by negative and positive product ion spectra. These results show that the developed methods have a high potential to serve as both a prescreen to detect unknown MAs and to identify these analytes in complex matrix. (J Am Soc Mass Spectrom 2005, 16, 1976 -1984

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Sulfoxidation of Mercapturic Acids Derived from Tri- and Tetrachloroethene by Cytochromes P450 3A: A Bioactivation Reaction in Addition to Deacetylation and Cysteine Conjugate β-Lyase Mediated Cleavage

Cited by 52 publications

References 52 publications

S-(1,2,2-Trichlorovinyl)-l-cysteine Sulfoxide, a Reactive Metabolite ofS-(1,2,2-Trichlorovinyl)-l-cysteine Formed in Rat Liver and Kidney Microsomes, Is a Potent Nephrotoxicant

S-(1,2,2-Trichlorovinyl)-l-cysteine Sulfoxide, a Reactive Metabolite ofS-(1,2,2-Trichlorovinyl)-l-cysteine Formed in Rat Liver and Kidney Microsomes, Is a Potent Nephrotoxicant

Specificity of Aminoacylase III-Mediated Deacetylation of Mercapturic Acids

Rapid detection and identification of N-acetyl-L-cysteine thioethers using constant neutral loss and theoretical multiple reaction monitoring combined with enhanced product-ion scans on a linear ion trap mass spectrometer

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