Changes in the concentrations of protein-mixed disulfides (XS-SP) of glutathione (GSH), cysteine (CSH), and cysteinylglycine (CGSH) were studied in human platelets treated with diamide and t-BOOH in timecourse experiments (time range, 1-30 min) in order to understand the contribution of minor thiols CSH and CGSH to the regulation of glutathione-protein mixed disulfides (GS-SP). Diamide was much more potent than t-BOOH in altering the platelet thiol composition of XS-SP (threshold dose: diamide, 0.03 mM; t-BOOH, 0.5 mM) and caused reversible XS-SP peaks whose magnitude was related to the concentration of free thiols in untreated cells. Thus maximum levels of GS-SP (8 min after 0.4 mM diamide) were about 16-fold higher than those of controls (untreated platelets, GS-SP = 0.374 nmol/109 platelets), whereas those of CS-SP and CGS-SP were only 4-fold increased (untreated platelets, CS-SP = 0.112 nmol/109 platelets; CGS-SP = 0.024 nmol/109 platelets). The greater effects of diamide with respect to t-BOOH were explained on the basis of the activities of fast reactive protein SH groups for diamide and glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G-6-PDH) for t-BOOH. The addition of cysteine (0.3 mM, at 4 min) after treatment of platelets with 0.4 mM diamide increased the rate of reversal of GS-SP peaks to normal values, but also caused a relevant change in CGS-SP with respect to that of platelets treated with diamide alone. An increased γ-glutamyltranspeptidase activity was found in platelets treated with diamide. Moreover, untreated platelets were found to release and hydrolyze GSH to CGSH and CSH. Ratios of thiols/disulfides (XSH/XSSX) and activities of GR and G-6PDH were also related to a high reducing potential exerted by GSH but not by minor thiols. The lower mass and charge of minor thiols is a likely requisite of the regulation of GS-SP levels in platelets. (C) 2000 Academic Press.

Giustarini, D., Campoccia, G., Fanetti, G., Rossi, R., Giannerini, F., Lusini, L., et al. (2000). Minor thiols cysteine and cysteinylglycine regulate the competition between glutathione and protein SH groups in human platelets subjected to oxidative stress. ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS, 380(1), 1-10 [10.1006/abbi.2000.1847].

Minor thiols cysteine and cysteinylglycine regulate the competition between glutathione and protein SH groups in human platelets subjected to oxidative stress

Giustarini, Daniela;Rossi, Ranieri;Cherubini di Simplicio, Paolo
2000-01-01

Abstract

Changes in the concentrations of protein-mixed disulfides (XS-SP) of glutathione (GSH), cysteine (CSH), and cysteinylglycine (CGSH) were studied in human platelets treated with diamide and t-BOOH in timecourse experiments (time range, 1-30 min) in order to understand the contribution of minor thiols CSH and CGSH to the regulation of glutathione-protein mixed disulfides (GS-SP). Diamide was much more potent than t-BOOH in altering the platelet thiol composition of XS-SP (threshold dose: diamide, 0.03 mM; t-BOOH, 0.5 mM) and caused reversible XS-SP peaks whose magnitude was related to the concentration of free thiols in untreated cells. Thus maximum levels of GS-SP (8 min after 0.4 mM diamide) were about 16-fold higher than those of controls (untreated platelets, GS-SP = 0.374 nmol/109 platelets), whereas those of CS-SP and CGS-SP were only 4-fold increased (untreated platelets, CS-SP = 0.112 nmol/109 platelets; CGS-SP = 0.024 nmol/109 platelets). The greater effects of diamide with respect to t-BOOH were explained on the basis of the activities of fast reactive protein SH groups for diamide and glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G-6-PDH) for t-BOOH. The addition of cysteine (0.3 mM, at 4 min) after treatment of platelets with 0.4 mM diamide increased the rate of reversal of GS-SP peaks to normal values, but also caused a relevant change in CGS-SP with respect to that of platelets treated with diamide alone. An increased γ-glutamyltranspeptidase activity was found in platelets treated with diamide. Moreover, untreated platelets were found to release and hydrolyze GSH to CGSH and CSH. Ratios of thiols/disulfides (XSH/XSSX) and activities of GR and G-6PDH were also related to a high reducing potential exerted by GSH but not by minor thiols. The lower mass and charge of minor thiols is a likely requisite of the regulation of GS-SP levels in platelets. (C) 2000 Academic Press.
2000
Giustarini, D., Campoccia, G., Fanetti, G., Rossi, R., Giannerini, F., Lusini, L., et al. (2000). Minor thiols cysteine and cysteinylglycine regulate the competition between glutathione and protein SH groups in human platelets subjected to oxidative stress. ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS, 380(1), 1-10 [10.1006/abbi.2000.1847].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11365/43331
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