RESUMO
Increased fructose concentrations are the biochemical hallmark of fructosemia, a group of inherited disorders on the metabolic pathway of this sugar. The main clinical findings observed in patients affected by fructosemia include neurological abnormalities with developmental delay, whose pathophysiology is still undefined. In the present work we investigated the in vitro and in vivo effects of fructose on acetylcholinesterase (AchE) activity in brain structures of developing rats. For the in vitro experiments, fructose was added at increasing concentrations to the incubation medium. It was observed that fructose provoked an inhibition of acetylcholinesterase activity in cerebral cortex of 30-day-old-rats, even at low concentrations (0.1 mM). For the in vivo experiments, rats were killed 1 h after a single fructose administration (5 µmol/g). Control group received the same volume of saline solution. We found that AchE activity was increased in cerebral cortex of 30- and 60-day-old rats receiving fructose administration. Finally, we observed that AchE activity was unaffected by acute fructose administration in cerebral cortex, striatum or hippocampus of 15- and 90-day-old rats. The present data suggest that a disruption in cholinergic homeostasis may be involved in the pathophysiology of brain damage observed in young patients affected by fructosemia.
Assuntos
Acetilcolinesterase/farmacologia , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/enzimologia , Frutose/farmacologia , Animais , Masculino , Ratos , Ratos Wistar , Fatores de TempoRESUMO
Phenylketonuria (PKU) is a disease caused by a deficiency of phenylalanine hydroxylase (PAH), resulting in an accumulation of phenylalanine (Phe) in the brain tissue, cerebrospinal fluid, and other tissues of PKU patients. Considering that high levels of Phe are associated with neurological dysfunction and that the mechanisms underlying the neurotoxicity in PKU remain poorly understood, the main objective of this study was to investigate the in vivo and in vitro effects of Phe on DNA damage, as determined by the alkaline comet assay. The results showed that, compared to control group, the levels of DNA migration were significantly greater after acute administration of Phe, p-chlorophenylalanine (p-Cl-Phe, an inhibitor of PAH), or a combination thereof in cerebral cortex and blood, indicating DNA damage. These treatments also provoked increase of carbonyl content. Additionally, when Phe or p-Cl-Phe was present in the incubation medium, we observed an increase in the frequency and index of DNA damage in the cerebral cortex and blood, without affecting lactate dehydrogenase (LDH) release. Our in vitro and in vivo findings indicate that DNA damage occurs in the cerebral cortex and blood of rats receiving Phe, suggesting that this mechanism could be, at least in part, responsible for the neurological dysfunction in PKU patients.