Analysis of the inhibition of mammalian thioredoxin, thioredoxin reductase, and glutaredoxin by cis-diamminedichloroplatinum (II) and its major metabolite, the glutathione-platinum complex

Citation
Esj. Arner et al., Analysis of the inhibition of mammalian thioredoxin, thioredoxin reductase, and glutaredoxin by cis-diamminedichloroplatinum (II) and its major metabolite, the glutathione-platinum complex, FREE RAD B, 31(10), 2001, pp. 1170-1178
Citations number
58
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
FREE RADICAL BIOLOGY AND MEDICINE
ISSN journal
0891-5849 → ACNP
Volume
31
Issue
10
Year of publication
2001
Pages
1170 - 1178
Database
ISI
SICI code
0891-5849(20011115)31:10<1170:AOTIOM>2.0.ZU;2-0
Abstract
Several studies have demonstrated a correlation between cellular toxicity o f cis-diamminedichloroplatinum (II) (cisplatin, CDDP) and inhibited intrace llular activity of the thioredoxin system, i.e,, thioredoxin (Trx), thiored oxin reductase (TrxR), and NADPH. Conversely, increased cellular activity o f the Trx system confers resistance to CDDP. In this study, we have analyze d the interaction of CDDP with Trx and TrxR in order to clarify the mechani sm. The inhibition with time-dependent kinetics by CDDP of NADPH-reduced (b ut not oxidized) TrxR was irreversible, strongly suggesting covalent modifi cation of the reduced selenocysteine-containing active site. Assuming secon d order kinetics, the rate constant of TrxR inhibition by CDDP was 21 +/- 3 M(-1)s(-1). Transplatin was found to be an even more efficient inhibitor, with a second order rate constant of 84 +/- 22 M(-1)s(-1), whereas carbopla tin (up to 1 mM) gave no inhibition of the enzyme under the same conditions . Escherichia coli Trx or human or bacterial glutaredoxin (Grx) activities were in comparison only slightly or not at all inhibited by either CDDP, tr ansplatin, or carboplatin. However, glutaredoxins were found to be inhibite d by the purified glutathione adduct of cisplatin, bis-(glutathionato)plati niim(II) (GS-Platinum complex, GS-Pt), with an IC50 = 350 muM in the standa rd beta -hydroxyethyl disulfide-coupled assay for human Grx. Also the mamma lian Trx system was inhibited by GS-Pt with similar efficiency (IC50 = 325 muM), whereas neither the E. coli Trx system nor glutathione reductase were inhibited. Formation of GS-Pt is a major route for cellular elimination of CDDP. The fact that GS-Pt inhibits the mammalian Trx as well as Grx system s shows that CDDP may exert effects at several stages of its metabolism, in cluding after conjugation with GSH, which are intimately linked with the ce llular disulfide/dithiol redox regulatory systems. (C) 2001 Elsevier Scienc e Inc.