The formation of styrene glutathione adducts catalyzed by prostaglandin H synthase. A possible new mechanism for the formation of glutathione conjugates.

B H Stock,J R Bend,T E Eling

doi:10.1016/s0021-9258(17)38477-6

Abstract

The metabolism of styrene by prostaglandin hydroperoxidase and horseradish peroxidase was examined. Ram seminal vesicle microsomes in the presence of arachidonic acid or hydrogen peroxide and glutathione converted styrene to glutathione adducts. Neither styrene 7,8-oxide nor styrene glycol was detected as a product in the incubation. Also, the addition of styrene 7,8-oxide and glutathione to ram seminal vesicle microsomes did not yield styrene glutathione adducts. The peroxidase-generated styrene glutathione adducts were isolated by high pressure liquid chromatography and characterized by NMR and tandem mass spectrometry as a mixture of (2R)- and (2S)-S-(2-phenyl-2-hydroxyethyl)glutathione. (1R)- and (1S)-S-(1-phenyl-2-hydroxyethyl)glutathione were not formed by the peroxidase system. The addition of phenol or aminopyrine to incubations, which greatly enhances the oxidation of glutathione to a thiyl radical by peroxidases, increased the formation of styrene glutathione adducts. We propose a new mechanism for the formation of glutathione adducts that is independent of epoxide formation but dependent on the initial oxidation of glutathione to a thiyl radical by the peroxidase, and the subsequent reaction of the thiyl radical with a suitable substrate, such as styrene.

Highlights

The metabolism ofstyrene by prostaglandin hydro- Epoxides are further metabolized by epoxide hydrolase to peroxidase and horseradish peroxidawsaes examined. the corresponding diols, or they areconjugated with glutathi
We studied prostaformation of glutathione adducts that is independent glandin hydroperoxidase-dependent styrene metabolism
Dation of glutathione toa thiyl radical by the peroxi- oxide we detected the formation of S-substituted dase, and the subsequent reaction of thtehiyl radical styrene glutathione adductswhen glutathione was present in with a suitable substrate, sucahs styrene

Summary

A POSSIBLE NEW MECHANISM FOR THE FORMATION OF GLUTATHIONE CONJUGATES*

Oxidases, increased the formationof styrene glutathi- oxide byperoxyl radicals generated during prostaglandin biooneadducts. To investigate this possibility, we studied prostaformation of glutathione adducts that is independent glandin hydroperoxidase-dependent styrene metabolism. Dation of glutathione toa thiyl radical by the peroxi- oxide we detected the formation of S-substituted dase, and the subsequent reaction of thtehiyl radical styrene glutathione adductswhen glutathione was present in with a suitable substrate, sucahs styrene. Our data suggest a new mechanism for the formation of glutathione adductsthat is independent of epoxide formation but dependent on initial oxidation of Epoxidation is an important step in the enzymatic activation of many chemicals, including carcinogens, in biological systems. Certain dihydrodiol metabolites of poglutathione to a thiyl radical by the peroxidase andthe subsequent reaction of this radical with a suitable substrate, such asstyrene. Lycyclic aromatic hydrocarbons are epoxidized to ultimate carcinogenic electrophiles, which react with DNA and form

EXPERIMENTAL PROCEDURES

Methods

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