Induction of oxidative stress by L-2-hydroxyglutaric acid in rat brain

L-2-hydroxyglutaric acid (LGA) is the biochemical hallmark of L-2-hydroxyglutaric aciduria (L-OHGA), an inherited neurometabolic disorder characterized by progressive neurodegeneration with cerebellar and pyramidal signs, mental deterioration, epilepsy, and subcortical leukoencephalopathy. Because the underlying mechanisms of the neuropathology of this disorder are virtually unknown, in this study we tested the in vitro effect of LGA on various parameters of oxidative stress, namely, chemiluminescence, thiobarbituric acid-reactive substances (TBA-RS), protein carbonyl formation (PCF), total radical-trapping antioxidant potential (TRAP), total antioxidant reactivity (TAR), and the activities of the antioxidant enzymes catalase, glutathione peroxidase, and superoxide dismutase in cerebellum and cerebral cortex of 30-day-old rats. LGA significantly increased chemiluminescence, TBA-RS, and PCF measurements and markedly decreased TAR values in cerebellum, in contrast to TRAP and the activity of the antioxidant enzymes, which were not altered by the acid. Similar but less pronounced effects were provoked by LGA in cerebral cortex. Moreover, the LGA-induced increase of TBA-RS was significantly attenuated by melatonin (N-acetyl-5-methoxytryptamine) and by the combinations of ascorbic acid plus Trolox (soluble alpha-tocopherol) and of superoxide dismutase plus catalase but not by the inhibitor of nitric oxide synthase Nomega-nitro-L-arginine methyl ester (L-NAME), creatine, or superoxide dismutase or catalase alone in either cerebral structure. The data indicate that LGA provokes oxidation of lipids and proteins and reduces the brain capacity to modulate efficiently the damage associated with an enhanced production of free radicals, possibly by inducing generation of superoxide and hydroxyl radicals, which are trapped by the scavengers used. Thus, in case these findings can be extrapolated to human L-OHGA, it may be presumed that oxidative stress is involved in the pathophysiology of the brain damage observed in this disorder.