Impairment of brain redox homeostasis caused by the major metabolites accumulating in hyperornithinemia-hyperammonemia-homocitrullinuria syndrome in vivo.
Ornithine, ammonia and homocitrulline are the major metabolites accumulating in hyperornithinemia-hyperammonemia-homocitrullinuria syndrome, a genetic disorder characterized by neurological regression whose pathogenesis is still not understood. The present work investigated the in vivo effects of intracerebroventricular administration of ornithine and homocitrulline in the presence or absence of hyperammonemia induced by intraperitoneal urease treatment on a large spectrum of oxidative stress parameters in cerebral cortex from young rats in order to better understand the role of these metabolites on brain damage. Ornithine increased thiobarbituric acid-reactive substances (TBA-RS) levels and carbonyl formation and decreased total antioxidant status (TAS) levels. We also observed that the combination of hyperammonemia with ornithine resulted in significant decreases of sulfhydryl levels, reduced glutathione (GSH) concentrations and the activities of catalase (CAT) and glutathione peroxidase (GPx), highlighting a synergistic effect of ornithine and ammonia. Furthermore, homocitrulline caused increases of TBA-RS values and carbonyl formation, as well as decreases of GSH concentrations and GPx activity. Hcit with hyperammonemia (urease treatment) decreased TAS and CAT activity. We also showed that urease treatment per se was able to enhance TBA-RS levels. Finally, nitric oxide production was not altered by Orn and Hcit alone or in combination with hyperammonemia. Our data indicate that the major metabolites accumulating in hyperornithinemia-hyperammonemia-homocitrullinuria syndrome provoke lipid and protein oxidative damage and a reduction of the antioxidant defenses in the brain. Therefore, it is presumed that oxidative stress may represent a relevant pathomechanism involved in the brain damage found in patients affected by this disease.
Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, UFRGS, Rua Ramiro Barcelos, 2600 - Anexo, 90035-003, Porto Alegre, RS, Brazil.
Carolina Maso
CM
Viegas
Anelise Miotti
AM
Tonin
Angela
A
Zanatta
Bianca
B
Seminotti
Estela Natacha Brandt
EN
Busanello
Carolina Gonçalves
CG
Fernandes
Alana Pimentel
AP
Moura
Guilhian
G
Leipnitz
Moacir
M
Wajner
D000592:Amino Acid Metabolism, Inborn Errors / Q000097:blood / Q000139:chemically induced / Q000378:metabolism*; D000641:Ammonia / Q000097:blood / Q000378:metabolism*; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D002956:Citrulline / Q000031:analogs & derivatives* / Q000378:metabolism / Q000652:urine; D005979:Glutathione Peroxidase / Q000378:metabolism; D006706:Homeostasis / Q000502:physiology*; D007274:Injections, Intraperitoneal; D007276:Injections, Intraventricular; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D009952:Ornithine / Q000097:blood / Q000378:metabolism* / Q000633:toxicity; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000187:drug effects; D050050:Protein Carbonylation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013438:Sulfhydryl Compounds / Q000378:metabolism; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D014510:Urease
D000975:Antioxidants; D013438:Sulfhydryl Compounds; D017392:Thiobarbituric Acid Reactive Substances; C001352:homocitrulline; D002956:Citrulline; D009569:Nitric Oxide; D000641:Ammonia; D009952:Ornithine; D002374:Catalase; D005979:Glutathione Peroxidase; D014510:Urease