Bilirubin injury to neurons: Contribution of oxidative stress and rescue by glycoursodeoxycholic acid

Maria A. Brito, Sílvia Lima, Adelaide Fernandes, Ana S. Falcão, Rui F.M. Silva, D. Allan Butterfield, Dora Brites

Research output: Contribution to journalArticlepeer-review

91 Scopus citations

Abstract

It is well established that high levels of unconjugated bilirubin (UCB) can be toxic to the central nervous system, and oxidative stress is emerging as a relevant event in the mechanisms of UCB encephalopathy. In contrast, the hydrophilic bile acid, ursodeoxycholic acid (UDCA), has been reported as a cytoprotective and antioxidant molecule. In this study, we investigated if exposure of rat neurons in primary culture to clinically relevant concentrations of UCB leads to oxidative injury. The contribution of oxidative stress in UCB neurotoxicity was further investigated by examining whether the reduction of NO production by NAME, an inhibitor of nitric oxide synthase, prevents the disruption of the redox status and neuronal damage. Moreover, we evaluated the ability of glycoursodeoxycholic acid (GUDCA), the most relevant conjugated derivative in the serum of patients treated with UDCA, to abrogate the UCB-induced oxidative damage. Cultured rat neurons were incubated with 50 or 100 μM UCB in the presence of 100 μM human serum albumin, alone or in combination with 100 μM NAME or with 50 μM GUDCA, for 4 h at 37 °C. Protein carbonyls, 4-hydroxy-2-nonenal-protein adducts, intracellular glutathione content and cell death were determined. The results obtained showed that UCB induces protein oxidation and lipid peroxidation, while diminishes the thiol antioxidant defences, events that were correlated with the extent of cell death. Moreover, these events were counteracted by NAME and abrogated in the presence of GUDCA. Collectively, this study shows that oxidative stress is one of the pathways associated with neuronal viability impairment by UCB, and that GUDCA significantly prevents such effects from occurring. These findings corroborate the antioxidant properties of the bile acid and point to a new therapeutic approach for UCB-induced neurotoxicity due to oxidative stress.

Original languageEnglish
Pages (from-to)259-269
Number of pages11
JournalNeuroToxicology
Volume29
Issue number2
DOIs
StatePublished - Mar 2008

Bibliographical note

Funding Information:
This work was supported by grants from Fundação para a Ciência e a Tecnologia (FCT-POCI/SAU-MMO/55955/2004) and FEDER, and from Fundação Luso-Americana para o Desenvolvimento (344/03), Lisbon, Portugal.

Keywords

  • Cell death
  • Glycoursodeoxycholic acid
  • Neurons
  • Oxidative stress
  • Unconjugated bilirubin

ASJC Scopus subject areas

  • General Neuroscience
  • Toxicology

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