Sgaravatti ÃnM; Vargas BnA; Zandoná, BR; Deckmann KtB; Rockenbach, FJ; Moraes, TB; Monserrat, JM; Sgarbi, MB; Pederzolli, CD; Wyse, ATS; Wannmacher CvMD; Wajner, M; Dutra-Filho, CS
Abstract: Tyrosine accumulates in inborn errors of tyrosine catabolism, especially in tyrosinemia type II, where tyrosine levels are highly elevated in tissues and physiological fluids of affected patients. In tyrosinemia type II, high levels of tyrosine are correlated with eyes, skin and central nervous system disturbances. Considering that the mechanisms of brain damage in these disorders are poorly known, in the present study, we investigated whether oxidative stress is elicited by l-tyrosine in cerebral cortex homogenates of 14-day-old Wistar rats. The in vitro effect of 0.1–4.0mM l-tyrosine was studied on the following oxidative stress parameters: total radical-trapping antioxidant potential (TRAP), total antioxidant reactivity (TAR), ascorbic acid content, reduced glutathione (GSH) content, spontaneous chemiluminescence, thiobarbituric acid-reactive substances (TBA-RS), thiol-disulfide redox state (SH/SS ratio), protein carbonyl content, formation of DNA-protein cross-links, and the activities of the enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glucose-6-phosphate dehydrogenase (G6PDH). TRAP, TAR, ascorbic acid content, SH/SS ratio and CAT activity were significantly diminished, while formation of DNA-protein cross-link was significantly enhanced by l-tyrosine in vitro. In contrast, l-tyrosine did not affect the other parameters of oxidative stress evaluated. These results indicate that l-tyrosine decreases enzymatic and non-enzymatic antioxidant defenses, changes the redox state and stimulates DNA damage in cerebral cortex of young rats in vitro. This suggests that oxidative stress may represent a pathophysiological mechanism in tyrosinemic patients, in which this amino acid accumulates. [Copyright 2008 Elsevier] Copyright of International Journal of Developmental Neuroscience is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts)
TYROSINE; GLUTATHIONE; CEREBROSPINAL fluid; OXYGEN; 2; 2′-azo-bis(2-amidinopropane) ( ABAP ); 2,2′-azo-bis(2-amidinopropane) ( ABAP ); 2,6-dichlorophnolindophenol ( DCIP ); 4-hydroxyphenyllactic acid ( 4-HPLA ); 4-hydroxyphenylpyruvate dioxygenase ( 4-HPPD ); 4-hydroxyphenylpyruvic acid ( 4-HPPA ); 5; 5′-dithio-bis(2-nitrobenzoic acid) ( DTNB ); 5,5′-dithio-bis(2-nitrobenzoic acid) ( DTNB ); 6-dichlorophnolindophenol ( DCIP ); catalase ( CAT ); central nervous system ( CNS ); cerebrospinal fluid ( CSF ); dinitrophenylhydrazine ( DNPH ); dithiothreitol ( DTT ); DNA-protein cross-links ( DNA-PC ); glucose-6-phosphate dehydrogenase ( G6PDH ); glutathione peroxidase ( GPx ); hydrogen peroxide ( H2O2 ); reduced glutathione ( GSH ); sodium dodecyl sulfate ( SDS ); superoxide dismutase ( SOD ); thiobarbituric acid-reactive substances ( TBA-RS ); total antioxidant reactivity ( TAR ); total radical-trapping antioxidant potential ( TRAP ); trichloroacetic acid ( TCA ); tyrosine aminotransferase ( TAT )