5-Oxoproline reduces non-enzymatic antioxidant defenses in vitro in rat brain

Metab Brain Dis. 2007 Mar;22(1):51-65. doi: 10.1007/s11011-006-9041-2. Epub 2007 Jan 20.

Abstract

5-Oxoproline (pyroglutamic acid) accumulates in glutathione synthetase deficiency, an inborn metabolic defect of the gamma-glutamyl cycle. This disorder is clinically characterized by hemolytic anemia, metabolic acidosis and severe neurological disorders. Considering that the mechanisms of brain damage in this disease are poorly known, in the present study we investigated whether oxidative stress is elicited by 5-oxoproline. The in vitro effect of (0.5-3.0 mM) 5-oxoproline was studied on various parameters of oxidative stress, such as total radical-trapping antioxidant potential, total antioxidant reactivity, chemiluminescence, thiobarbituric acid-reactive substances, sulfhydryl content, carbonyl content, and 2',7'-dichlorofluorescein fluorescence, as well as on the activities of the antioxidant enzymes catalase, superoxide dismutase and glutathione peroxidase in cerebral cortex and cerebellum of 14-day-old rats. Total radical-trapping antioxidant potential and total antioxidant reactivity were significantly reduced in both cerebral structures. Carbonyl content and 2',7'-dichlorofluorescein fluorescence were significantly enhanced, while sulfhydryl content was significantly diminished. In contrast, chemiluminescence and thiobarbituric acid-reactive substances were not affected by 5-oxoproline. The activities of catalase, superoxide dismutase and glutathione peroxidase were also not altered by 5-oxoproline. These results indicate that 5-oxoproline causes protein oxidation and reactive species production and decrease the non-enzymatic antioxidant defenses in rat brain, but does not cause lipid peroxidation. Taken together, it may be presumed that 5-oxoproline elicits oxidative stress that may represent a pathophysiological mechanism in the disorder in which this metabolite accumulates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antioxidants / metabolism*
  • Brain Diseases, Metabolic / metabolism*
  • Catalase / metabolism
  • Cerebellum / drug effects
  • Cerebellum / metabolism*
  • Cerebral Cortex / drug effects
  • Cerebral Cortex / metabolism*
  • Glutathione Peroxidase / metabolism
  • Glutathione Synthase / deficiency
  • In Vitro Techniques
  • Lipid Peroxidation / drug effects
  • Lipid Peroxidation / physiology
  • Oxidative Stress / drug effects*
  • Oxidative Stress / physiology
  • Pyrrolidonecarboxylic Acid / pharmacology*
  • Rats
  • Rats, Wistar
  • Superoxide Dismutase / metabolism
  • Thiobarbituric Acid Reactive Substances / metabolism

Substances

  • Antioxidants
  • Thiobarbituric Acid Reactive Substances
  • Catalase
  • Glutathione Peroxidase
  • Superoxide Dismutase
  • Glutathione Synthase
  • Pyrrolidonecarboxylic Acid