Marked reduction of Na(+), K(+)-ATPase and creatine kinase activities induced by acute lysine administration in glutaryl-CoA dehydrogenase deficient mice.

Glutaric acidemia type I (GA I) is an inherited neurometabolic disorder caused by a severe deficiency of the mitochondrial glutaryl-CoA dehydrogenase activity leading to accumulation of predominantly glutaric (GA) and 3-hydroxyglutaric (3HGA) acids in the brain and other tissues. Affected patients usually present with hypotonia and brain damage and acute encephalopathic episodes whose pathophysiology is not yet fully established. In this study we investigated important parameters of cellular bioenergetics in brain, heart and skeletal muscle from 15-day-old glutaryl-CoA dehydrogenase deficient mice (Gcdh(-/-)) submitted to a single intra-peritoneal injection of saline (Sal) or lysine (Lys - 8 µmol/g) as compared to wild type (WT) mice. We evaluated the activities of the respiratory chain complexes II, II-III and IV, α-ketoglutarate dehydrogenase (α-KGDH), creatine kinase (CK) and synaptic Na(+), K(+)-ATPase. No differences of all evaluated parameters were detected in the Gcdh(-/-) relatively to the WT mice injected at baseline (Sal). Furthermore, mild increases of the activities of some respiratory chain complexes (II-III and IV) were observed in heart and skeletal muscle of Gcdh(-/-) and WT mice after Lys administration. However, the most marked effects provoked by Lys administration were marked decreases of the activities of Na(+), K(+)-ATPase in brain and CK in brain and skeletal muscle of Gcdh(-/-) mice. In contrast, brain α-KGDH activity was not altered in WT and Gcdh(-/-) injected with Sal or Lys. Our results demonstrate that reduction of Na(+), K(+)-ATPase and CK activities may play an important role in the pathogenesis of the neurodegenerative changes in GA I.

Induction of oxidative stress in brain of glutaryl-CoA dehydrogenase deficient mice by acute lysine administration.

In the present work we evaluated a variety of indicators of oxidative stress in distinct brain regions (striatum, cerebral cortex and hippocampus), the liver, and heart of 30-day-old glutaryl-CoA dehydrogenase deficient (Gcdh(-/-)) mice. The parameters evaluated included thiobarbituric acid-reactive substances (TBA-RS), 2-7-dihydrodichlorofluorescein (DCFH) oxidation, sulfhydryl content, and reduced glutathione (GSH) concentrations. We also measured the activities of the antioxidant enzymes glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT), superoxide dismutase (SOD) and glucose-6-phosphate dehydrogenase (G6PD). Under basal conditions glutaric (GA) and 3-OH-glutaric (3OHGA) acids were elevated in all tissues of the Gcdh(-/-) mice, but were essentially absent in WT animals. In contrast there were no differences between WT and Gcdh(-/-) mice in any of the indicators or oxidative stress under basal conditions. Following a single intra-peritoneal (IP) injection of lysine (Lys) there was a moderate increase of brain GA concentration in Gcdh(-/-) mice, but no change in WT. Lys injection had no effect on brain 3OHGA in either WT or Gcdh(-/-) mice. The levels of GA and 3OHGA were approximately 40% higher in striatum compared to cerebral cortex in Lys-treated mice. In the striatum, Lys administration provoked a marked increase of lipid peroxidation, DCFH oxidation, SOD and GR activities, as well as significant reductions of GSH levels and GPx activity, with no alteration of sulfhydryl content, CAT and G6PD activities. There was also evidence of increased lipid peroxidation and SOD activity in the cerebral cortex, along with a decrease of GSH levels, but to a lesser extent than in the striatum. In the hippocampus only mild increases of SOD activity and DCFH oxidation were observed. In contrast, Lys injection had no effect on any of the parameters of oxidative stress in the liver or heart of Gcdh(-/-) or WT animals. These results indicate that in Gcdh(-/-) mice cerebral tissue, particularly the striatum, is at greater risk for oxidative stress than peripheral tissues following Lys administration.

Alterations in oxidative markers in the cerebellum and peripheral organs in MPS I mice.

Mucopolysaccharidosis type I is a lysosomal storage disease with alterations in several organs. Little is known about the pathways that lead to the pathology. Evidences point oxidative stress on lysosomal storage diseases and mucopolysaccharidosis type I. The aim of the present study was to evaluate oxidative biomarkers on mucopolysaccharidosis type I mice model. We evaluated antioxidant enzymatic activity, protein damage and lipid peroxidation in the forebrain, cerebellum, heart, lung, diaphragm, liver, kidney and spleen. Superoxide dismutase activity was increased on cerebellum, lung, diaphragm, liver and kidney of mucopolysaccharidosis type I mice. Catalase activity was increased on cerebellum, spleen and lung. There was no alteration on glutathione peroxidase activity on any of the analyzed organs. Mucopolysaccharidosis type I mice showed increased carbonyl groups on cerebellum, heart and spleen. There was a decrease of thiobarbituric acid-reactive substances on the cerebellum of mucopolysaccharidosis type I mice. The results indicate a oxidative imbalance in this model. As lysosomes are very susceptible to oxidative damage, leading inclusive to cellular death, and lysosomal storage diseases present several alterations on this organelles, this finding can help to elucidate the cellular damage pathways on mucopolysaccharidosis type I.

Long-term memory for aversive training is impaired in Idua(-/-) mice, a genetic model of mucopolysaccharidosis type I.

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disease that leads to neurodegeneration and neurological deficits, among other pathological and clinical consequences. The aim of the present study was to evaluate neurobehavioral parameters in a genetic mouse model of mucopolysaccharidosis type I (MPS I). During exploration of an open field, adult MPS I (Idua(-/-)) mice showed normal locomotion and anxiety but reduced number of rearings. Idua(-/-) mice performed normally in a novel object recognition memory task and showed normal short-term retention of inhibitory avoidance training. By contrast, long-term retention of inhibitory avoidance was impaired in Idua(-/-) mice. The deficit in inhibitory avoidance memory could not be attributed to reduced footshock reactivity. The results indicate that Idua(-/-) mice present deficits in long-term memory for aversive training and reduced exploratory behavior.