Disturbance of redox homeostasis by ornithine and homocitrulline in rat cerebellum: a possible mechanism of cerebellar dysfunction in HHH syndrome.

Abstract

AIMS:

Cerebellar ataxia is commonly observed in hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome, an inherited metabolic disorder biochemically characterized by ornithine (Orn), homocitrulline (Hcit) and ammonia accumulation. Since the pathophysiology of cerebellum damage in this disorder is still unknown, we investigated the effects of Hcit and Orn on important parameters of redox and energy homeostasis in cerebellum of young rats.

MATERIAL AND METHODS:

We determined thiobarbituric acid-reactive substance (TBA-RS) levels, carbonyl content, nitrate and nitrite production, hydrogen peroxide production, GSH concentrations, sulfhydryl content, as well as activities of respiratory chain complexes I-IV, creatine kinase, Na(+),K(+)-ATPase, aconitase and α-ketoglutarate dehydrogenase.

KEY FINDINGS:

Orn and Hcit significantly increased TBA-RS levels (lipid oxidation), that was totally prevented by melatonin and reduced glutathione (GSH). We also found that nitrate and nitrite production was not altered by any of the metabolites, in contrast to hydrogen peroxide production which was significantly enhanced by Hcit. Furthermore, GSH concentrations were significantly reduced by Orn and Hcit and sulfhydryl content by Orn, implying an impairment of antioxidant defenses. As regards energy metabolism, Orn and Hcit provoked a significant reduction of aconitase activity, without altering the other parameters. Furthermore, Orn-elicited reduction of aconitase activity was totally prevented by GSH, indicating that the critical groups of this enzyme were susceptible to oxidation caused by this amino acid.

SIGNIFICANCE:

Taken together, our data indicate that redox homeostasis is disturbed by the major metabolites accumulating in HHH syndrome and that this mechanism may be implicated in the ataxia and cerebellar abnormalities observed in this disorder.

• Authors: Angela Zanatta, Carolina Maso Viegas, Anelise Miotti Tonin, Estela Natacha Brandt Busanello, Mateus Grings, Alana Pimentel Moura, Guilhian Leipnitz, Moacir Wajner
• Journal: Life sciences (Life Sci) Vol. 93 Issue 4 Pg. 161-8 (Aug 06 2013) ISSN: 1879-0631 [Electronic] Netherlands
• PMID: 23806752 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2013.

Chemical References

• Nerve Tissue Proteins
• Nitrates
• Nitrites
• Thiobarbituric Acid Reactive Substances
• homocitrulline
• Citrulline
• Hydrogen Peroxide
• Ornithine
• Ketoglutarate Dehydrogenase Complex
• Creatine Kinase
• Aconitate Hydratase
• Sodium-Potassium-Exchanging ATPase
• Glutathione

Topics

• Aconitate Hydratase (metabolism)
• Animals
• Cerebellum (metabolism, pathology)
• Citrulline (analogs & derivatives, pharmacology)
• Creatine Kinase (metabolism)
• Electron Transport
• Glutathione (metabolism)
• Homeostasis (drug effects)
• Hydrogen Peroxide (metabolism)
• Hyperammonemia (metabolism, pathology)
• Ketoglutarate Dehydrogenase Complex (metabolism)
• Nerve Tissue Proteins (metabolism)
• Nitrates (metabolism)
• Nitrites (metabolism)
• Ornithine (deficiency, metabolism, pharmacology)
• Oxidation-Reduction (drug effects)
• Rats
• Rats, Wistar
• Sodium-Potassium-Exchanging ATPase (metabolism)
• Thiobarbituric Acid Reactive Substances (metabolism)
• Urea Cycle Disorders, Inborn (metabolism, pathology)