Pauline Maciel August

Higher susceptibility of cerebral cortex and striatum to sulfite neurotoxicity in sulfite oxidase-deficient rats

Patients affected by sulfite oxidase (SO) deficiency present severe seizures early in infancy and progressive neurological damage, as well as tissue accumulation of sulfite, thiosulfate and S-sulfocysteine. Since the pathomechanisms involved in the neuropathology of SO deficiency are still poorly established, we evaluated the effects of sulfite on redox homeostasis and bioenergetics in cerebral cortex, striatum, cerebellum and hippocampus of rats with chemically induced SO deficiency. The deficiency was induced in 21-day-old rats by adding 200ppm of tungsten, a molybdenum competitor, in their drinking water for 9weeks. Sulfite (70mg/kg/day) was also administered through the drinking water from the third week of tungsten supplementation until the end of the treatment. Sulfite decreased reduced glutathione concentrations and the activities of glutathione reductase and glutathione S-transferase (GST) in cerebral cortex and of GST in cerebellum of SO-deficient rats. Moreover, sulfite increased the activities of complexes II and II-III in striatum and of complex II in hippocampus, but reduced the activity of complex IV in striatum of SO-deficient rats. Sulfite also decreased the mitochondrial membrane potential in cerebral cortex and striatum, whereas it had no effect on mitochondrial mass in any encephalic tissue evaluated. Finally, sulfite inhibited the activities of malate and glutamate dehydrogenase in cerebral cortex of SO-deficient rats. Taken together, our findings indicate that cerebral cortex and striatum are more vulnerable to sulfite-induced toxicity than cerebellum and hippocampus. It is presumed that these pathomechanisms may contribute to the pathophysiology of neurological damage found in patients affected by SO deficiency.

Bezafibrate prevents mitochondrial dysfunction, antioxidant system disturbance, glial reactivity and neuronal damage induced by sulfite administration in striatum of rats: Implications for a possible therapeutic strategy for sulfite oxidase deficiency

Sulfite accumulates in tissues of patients affected by sulfite oxidase (SO) deficiency, a neurometabolic disease characterized by seizures and progressive encephalopathy, often resulting in early death. We investigated the effects of sulfite on mitochondrial function, antioxidant system, glial reactivity and neuronal damage in rat striatum, as well as the potential protective effects of bezafibrate on sulfite-induced toxicity. Thirty-day-old rats were intrastriatally administered with sulfite (2μmol) or NaCl (2μmol; control) and euthanized 30min after injection for evaluation of biochemical parameters and western blotting, or 7days after injection for analysis of glial reactivity and neuronal damage. Treatment with bezafibrate (30 or 100mg/kg/day) was performed by gavage during 7days before (pre-treatment) or after sulfite administration. Sulfite decreased creatine kinase and citrate synthase activities, mitochondrial mass, and PGC-1α nuclear content whereas bezafibrate pre-treatment prevented these alterations. Sulfite also diminished cytochrome c oxidase (COX) IV-1 content, glutathione levels and the activities of glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST) and glucose-6-phosphate dehydrogenase (G6PDH). On the other hand, catalase activity was increased by sulfite. Bezafibrate pre-treatment prevented the reduction of GPx, GR, GST and G6PDH activities. Finally, sulfite induced glial reactivity and neuronal damage, which were prevented by bezafibrate when administered before or after sulfite administration. Our findings provide strong evidence that sulfite induces neurotoxicity that leads to glial reactivity and neuronal damage. Since bezafibrate exerts neuroprotective effects against sulfite toxicity, it may be an attractive agent for the development of novel therapeutic strategies for SO-deficient patients.

Swimming exercise enhances the hippocampal antioxidant status of female Wistar rats

Abstract Objectives Moderate exercise is known to have health benefits, while both sedentarism and strenuous exercise have pro-oxidant effects. In this study, we assessed the effect of moderate exercise on the antioxidant homeostasis of rats’ hippocampi. Methods Female Wistar rats were submitted to a 30-minute swimming protocol on 5 days a week, for 4 weeks. Control rats were immersed in water and carefully dried. Production of hippocampal reactive species, activity of antioxidant enzymes, and glutathione levels in these animals were determined up to 30 days after completion of the 4-week protocol. Results Production of reactive species and hippocampal glutathione levels were increased 1 day after completion of the 4-week protocol, and returned to control levels after 7 days. Antioxidant enzyme activities were increased both 1 day (catalase) and 7 days (superoxide dismutase and glutathione peroxidase) after completion of the protocol. Thirty days after completion of the protocol, none of the antioxidant parameters evaluated differed from those of controls. Discussion Our results reinforce the benefits of aerobic exercise, which include positive modulation of antioxidant homeostasis in the hippocampi. The effects of exercise are not permanent; rather, an exercise regimen must be continued in order to maintain the neurometabolic adaptations.

Polyols accumulated in ribose-5-phosphate isomerase deficiency increase mitochondrial superoxide production and improve antioxidant defenses in rats' prefrontal cortex.

The ribose‐5‐phosphate isomerase deficiency is an inherited condition, which results in cerebral d‐arabitol and ribitol accumulation. Patients present leukoencephalopathy, mental retardation, and psychomotor impairment. Considering that the pathophysiology of this disorder is still unclear, and literature are sparse and contradictory, reporting pro and antioxidant activities of polyols, the main objective of this study was to investigate some parameters of oxidative homeostasis of prefrontal cortex of rats incubated with d‐arabitol and ribitol. We found evidences that ribitol promoted an increase in antioxidant enzymes activity (superoxide dismutase, catalase, and glutathione peroxidase), probably secondary to enhanced production of superoxide radical, measured by flow cytometry. Oxidation of proteins and lipids was not induced by polyols. Our data allow us to conclude that, at least in our methodological conditions, arabitol and ribitol probably have a secondary effect on the pathophysiology of ribose‐5‐phosphate isomerase deficiency.

Food restriction during pregnancy alters brain's antioxidant network in dams and their offspring.

Abstract Dietary restriction increases life span and protects distinct organisms against a series of diseases, among which, those related to oxidative stress, like neurodegenerative diseases. Interferences in the maternal environment are known to reprogram the offspring metabolism response, impacting in the risk of chronic diseases development in adulthood. We aimed to assess the effects of 40% food restriction on reactive species levels, enzymatic and non-enzymatic antioxidant defenses, and oxidative damage parameters in the cerebellum and total cerebral cortex of pregnant rats and their offspring. Dams and pups showed oxidative modulation caused by food restriction in both structures. Dichlorofluorescein oxidation, reflecting reactive species levels, was reduced in the cerebellum of dams and offspring, while the cerebral cortex was not affected. Decreased mitochondrial superoxide levels were found in the cerebellum and cerebral cortex of pups, while nitric oxide was increased in the cortex. We also measured the activities of important antioxidant enzymes responsible by reactive oxygen species elimination. Superoxide dismutase activity was increased in the cerebellum of dams and in both structures of pups, while it was decreased in dams’ cerebral cortex. Both brain structures were affected concerning to catalase, glutathione peroxidase, and glutaredoxin activities, which were reduced in pups and dams. Non-enzymatic defenses were decreased in pups, while dams showed an adaptive pattern in the cerebellum and no alteration in the cerebral cortex. Even though the results suggest increased oxidative status, lipids and proteins were not oxidatively affected. Our data suggest that intrauterine food restriction may disrupt oxidative status, impairing the antioxidant network.

Effect of maternal antioxidant supplementation and/or exercise practice during pregnancy on postnatal overnutrition induced by litter size reduction: Brain redox homeostasis at weaning

Prenatal and early postnatal environments can permanently influence health throughout life. Early overnutrition increases the risk to develop chronic diseases. Conversely, the intake of flavonoids and exercise practice during pregnancy seem to promote long‐term benefits to offspring. We hypothesized that benefic interventions during pregnancy could protect against possible postnatal neurochemical alterations caused by overnutrition induced by reduced litter size. Female Wistar rats were divided into four groups: (1) sedentary + vehicle, (2) sedentary + naringenin, (3) swimming exercise + vehicle, and (4) swimming exercise + naringenin. One day after birth, the litter was culled to 8 pups (control) or 3 pups (overfed) per dam, yielding control and overfed subgroups for each maternal group. Serum of 21‐days‐old pups was collected, also the cerebellum, hippocampus, and hypothalamus were dissected. Litter size reduction increased fat mass and enhanced body weight. Maternal interventions, when isolated, caused reduced glucose serum levels in offspring nurtured in control litters. In the cerebellum, reducing the litter size decreased the activity of thioredoxin reductase, which was prevented by maternal supplementation with naringenin. Hippocampus and hypothalamus have shown altered antioxidant enzymes activities in response to litter size reduction. Interestingly, when maternal exercise and naringenin supplementation were allied, the effect disappeared, suggesting a concurrent effect of the two maternal interventions. In conclusion, exercise or naringenin supplementation during pregnancy can be important interventions for combating the increasing rates of overweight during the infancy and its related neurochemical changes, especially when applied isolated.