retinol-palmitate and Neurodegenerative-Diseases

Vitamin A has been characterized as a potential neurotoxin, because ingestion of such vitamin - or its derivatives, the retinoids - at moderate to high doses elicits a myriad of deleterious effects, from acute intoxication involving head-ache, confusion, and 'pseudo tumor cerebri' to chronic, and perhaps irreversible, abnormalities, including irritability, anxiety, depression, and suicide ideation. Nevertheless, it still remains to be found the mechanism by which vitamin A induces cognitive decline. Based on the fact that vitamin A at clinical doses is a potent pro-oxidant agent to the central nervous system, we performed the present work to analyze whether a cotreatment with L-NAME at 30 mg/kg (four times a week) was able to prevent (or minimize) the biochemical and/or behavioral disturbances resulting from a 28-day daily supplementation with retinol palmitate at doses from 1000 to 9000 IU/kg/day. Then, we investigated mitochondrial function, redox parameters, and the levels of proteins potentially involved in neurodegenerative events, as for instance α-synuclein and receptor for advanced glycation endproducts. Besides, monoamine oxidase enzyme activity was quantified in this work. We observed that L-NAME cotreatment was not completely effective in preventing the redox disturbances induced by vitamin A supplementation. Moreover, L-NAME cotreatment did not affect the behavioral deficits elicited by vitamin A supplementation. We conclude that other parameters rather than NO levels or its derivatives, as for example ONOO(-), take a more important role in mediating the negative effects triggered by vitamin A supplementation.

Topics: alpha-Synuclein; Animals; Anxiety Disorders; Behavior, Animal; Central Nervous System; Dietary Supplements; Diterpenes; Electron Transport; Glutathione Transferase; Heat-Shock Proteins; Illness Behavior; Locomotion; Male; Manganese; Mitochondria; Monoamine Oxidase; Neurodegenerative Diseases; NG-Nitroarginine Methyl Ester; Nitric Oxide; Oxidation-Reduction; Rats; Rats, Wistar; Receptor for Advanced Glycation End Products; Receptors, Dopamine; Receptors, Immunologic; Retinyl Esters; Superoxide Dismutase; Superoxides; Tyrosine; Vitamin A