The effects of age and hyperhomocysteinemia on the redox forms of plasma thiols.
We assayed the redox forms of cysteine (reduced [CSH], oxidized [CSSC], and bound to protein [CS-SP]), cysteinylglycine (CGSH; cysteinylgycine disulfide [CGSSGC] and cysteinylglycine-protein mixed disulfide [CGS-SP]), glutathione (GSH; glutathione disulfide [GSSG] and glutathione-protein mixed disulfide [GS-SP]), homocysteine (Hcy; homocystine [HcyS] and homocystine-protein mixed disulfides [bHcy]), and protein sulfhydryls in the plasma of healthy subjects (divided into 8 groups ranging in age from birth to 70 years) and patients with mild hyperhomocysteinemia associated with cardiovascular disease (heart-transplant patients) or vascular atherosclerosis, with or without renal failure. In healthy individuals, levels of disulfides and protein-mixed disulfides were more abundant than those of thiols, and those of protein-thiol mixed disulfides were higher than disulfides. Concentrations of CSH, GSH, and CGSH in the various groups had profiles characterized by a maximum over time. The concentration of Hcy was unchanged up to the age of 30 years, after which it increased. CSSC concentration increased gradually with age, whereas concentrations of the other disulfides were essentially unchanged. By contrast, the concentrations of all protein-thiol mixed disulfides, especially those with CSH, increased gradually with age. Ranks of distribution of the reduced forms changed with age (at birth, CSH > CGSH > GSH > Hcy; in 1- to 2-year-olds, CSH > GSH > CGSH > Hcy; and in 51- to 70-year-olds, CSH > CGSH = GSH > Hcy), whereas those of disulfides and protein-thiol mixed disulfides were substantially unchanged (in all age groups, CSSC > CGSSGC > GSSG = HcyS and CS-SP > CGS-SP > bHcy > GS-SP). In patients with pathologic conditions, plasma levels of disulfide forms CSSC, HcyS, CS-SP, and bHcy were significantly increased, whereas other redox forms of thiols were unchanged or showed variations opposite (increasing or decreasing) to control values. Maximal increases in disulfides and protein-thiol mixed disulfides were associated with renal failure. Our data suggest that increases in plasma bHcy concentrations in subjects with pathologic conditions were more likely the result of activation of thiol-disulfide exchange reactions between free reduced Hcy and CS-SP than of a direct action of reactive oxygen species.
Di Giuseppe
Danila
D
Department of Neuroscience, Pharmacology Unit, University of Sienna, Sienna, Italy.
Frosali
Simona
S
Priora
Raffaella
R
Di Simplicio
Francesca Cherubini
FC
Buonocore
Giuseppe
G
Cellesi
Carla
C
Capecchi
Pier Leopoldo
PL
Pasini
Franco Laghi
FL
Lazzerini
Pietro Enea
PE
Jakubowski
Hieronim
H
Di Simplicio
Paolo
P
D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000097:blood*; D001161:Arteriosclerosis / Q000097:blood; D001798:Blood Proteins / Q000378:metabolism; D002318:Cardiovascular Diseases / Q000097:blood; D002648:Child; D002675:Child, Preschool; D003545:Cysteine / Q000097:blood; D004220:Disulfides / Q000097:blood; D005998:Glycine / Q000097:blood; D016027:Heart Transplantation; D006801:Humans; D020138:Hyperhomocysteinemia / Q000097:blood*; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D010084:Oxidation-Reduction; D011485:Protein Binding; D051437:Renal Insufficiency / Q000097:blood; D013438:Sulfhydryl Compounds / Q000097:blood*
D001798:Blood Proteins; D004220:Disulfides; D013438:Sulfhydryl Compounds; D003545:Cysteine; D005998:Glycine