RESUMEN
Citrullinemia Type I is an inborn error, which leads to accumulation of citrulline and ammonia in blood and body tissues. We evaluated the in vitro effects of citrulline, ammonia and the influence of resveratrol on oxidative stress parameters in the cerebrum of 30- and 60-day-old male Wistar rats. Citrulline (0.1, 2.5, 5.0 mM), ammonia (0.01, 0.1, 1.0 mM) and resveratrol (0.01, 0.1, 0.5 mM) were added to the assays to measure thiobarbituric acid reactive substances (TBA-RS), total sulfhydryl content and the activity of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). Citrulline (2.5 and 5.0 mM) increased TBA-RS in the cerebellum of 30-day-old and in the cerebral cortex and cerebellum of 60-day-old. Citrulline (5.0 mM) increased SOD and reduced GSH-Px in the hippocampus of 30-day-old, whereas in the cerebellum it increased GSH-Px. In the cerebral cortex, 2.5 and 5.0 mM citrulline reduced GSH-Px. In 60-day-old, 2.5 and 5.0 mM citrulline increased SOD in the cerebellum, increased GSH-Px in the cerebral cortex and 5.0 mM citrulline reduced CAT and increased SOD in the cerebral cortex. Ammonia (0.1 and 1.0 mM) reduced the sulfhydryl content in the cerebral cortex of 30- and 60-day-old, 1.0 mM ammonia increased SOD and reduced GSH-Px in the cerebellum of 30-day-old and increased SOD in the hippocampus and cerebellum of 60-day-old. Resveratrol was able to prevent the majority of these alterations. Thus, citrulline and ammonia induce oxidative stress in the cerebrum of rats; however, resveratrol was able to exert antioxidant effects against these substances.
Asunto(s)
Antioxidantes/farmacología , Encéfalo/metabolismo , Citrulinemia/metabolismo , Fármacos Neuroprotectores/farmacología , Estrés Oxidativo/fisiología , Resveratrol/farmacología , Amoníaco/toxicidad , Animales , Antioxidantes/uso terapéutico , Encéfalo/efectos de los fármacos , Citrulina/toxicidad , Citrulinemia/inducido químicamente , Citrulinemia/prevención & control , Relación Dosis-Respuesta a Droga , Masculino , Fármacos Neuroprotectores/uso terapéutico , Estrés Oxidativo/efectos de los fármacos , Ratas , Ratas Wistar , Resveratrol/uso terapéuticoRESUMEN
We investigated the in vitro effects of citrulline (0.1, 2.5 and 5.0 mM) and ammonia (0.01, 0.1 and 1.0 mM), and the influence of resveratrol (0.01 mM, 0.1 mM and 0.5 mM) on pyruvate kinase, citrate synthase, succinate dehydrogenase (SDH), complex II, and cytochrome c oxidase activities in cerebral cortex, cerebellum and hippocampus homogenates of 60-day-old male Wistar rats. Results showed that 2.5 and 5.0 mM citrulline decreased pyruvate kinase activity in cerebral cortex and, at a concentration of 5.0 mM, increased its activity in hippocampus. Additionally, 5.0 mM citrulline increased citrate synthase activity in the cerebellum of rats. Citrulline (5.0 mM) reduced complex II and cytochrome c oxidase activities in cerebral cortex and hippocampus. With regard to ammonia, at 0.1 and 1.0 mM, decreased complex II activity in cerebral cortex and at 1.0 mM decreased its activity in cerebellum and hippocampus. Ammonia (1.0 mM) also decreased cytochrome c oxidase activity in cerebral cortex and cerebellum of rats. Resveratrol was able to prevent most of the alterations caused by these metabolites in the biomarkers of energy metabolism measured in the cerebrum of rats. Data suggest that these alterations in energy metabolism, caused by citrulline and ammonia, are probably mediated by the generation of free radicals, which can in turn be scavenged by resveratrol.
Asunto(s)
Citrulinemia/tratamiento farmacológico , Metabolismo Energético/efectos de los fármacos , Depuradores de Radicales Libres/farmacología , Resveratrol/farmacología , Amoníaco/administración & dosificación , Amoníaco/toxicidad , Animales , Cerebelo/efectos de los fármacos , Cerebelo/metabolismo , Corteza Cerebral/efectos de los fármacos , Corteza Cerebral/metabolismo , Citrulina/administración & dosificación , Citrulina/toxicidad , Citrulinemia/metabolismo , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Depuradores de Radicales Libres/administración & dosificación , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Masculino , Ratas , Ratas Wistar , Resveratrol/administración & dosificaciónRESUMEN
Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is an autosomal recessive disorder caused by a defect in the mitochondrial ornithine transporter, leading to accumulation of ornithine (Orn), homocitrulline (Hcit) and ammonia. Progressive neurological regression whose pathogenesis is not well established is common in this disease. The present work investigated the in vivo effects of intracerebroventricular administration of Orn and Hcit on important parameters of oxidative stress and energy metabolism in cerebral cortex from young rats. Orn and Hcit significantly increased thiobarbituric acid-reactive substances values and carbonyl formation, indicators of lipid and protein oxidative damage, respectively. Furthermore, N-acetylcysteine and the combination of the free radical scavengers ascorbic acid plus α-tocopherol attenuated the lipid oxidation and totally prevented the protein oxidative damage provoked by Orn and Hcit, suggesting that reactive species were involved in these effects. Hcit, but not Orn administration, also decreased glutathione concentrations, as well as the activity of catalase and glutathione peroxidase, indicating that Hcit provokes a reduction of brain antioxidant defenses. As regards to the parameters of energy metabolism, we verified that Orn and Hcit significantly inhibited the citric acid cycle function (inhibition of CO(2) synthesis from [1-(14)C] acetate), the aerobic glycolytic pathway (reduced CO(2) production from [U-(14)C] glucose) and complex I-III activity of the respiratory chain. Hcit also inhibited the activity of aconitase, an enzyme very susceptible to free radical attack. Taken together, our data indicate that mitochondrial homeostasis is disturbed by Orn and especially by Hcit. It is presumed that the impairment of brain bioenergetics and the oxidative damage induced by these metabolites may possibly contribute to the brain deterioration and neurological symptoms affecting patients with HHH syndrome.