A carregar...
Publicação
Behind bilirubin neurotoxicity: discovering what’s left at the blood-brain barrier
| Nome: | Descrição: | Tamanho: | Formato: | |
|---|---|---|---|---|
| 96.15 MB | Adobe PDF |
Orientador(es)
Resumo(s)
During neonatal life, elevation of unconjugated bilirubin (UCB) levels may lead to
minor neurological dysfunction or even to bilirubin encephalopathy (kernicterus). The
pathogenesis of this condition involves UCB passage across the blood-brain barrier
(BBB), but it is still unknown the role of this barrier in the consequent brain injury. Thus,
this thesis intended to investigate the response of human brain microvascular
endothelial cells (HBMEC), a simplified in vitro model of the BBB, to UCB, to evaluate
the modulation of these effects by therapeutic molecules, and to dissect the neuro-glialvascular
alterations in brain parenchyma of neonatal kernicterus cases.First, we observed that HBMEC incubation with UCB induced cell death,cytokine release and oxidative stress. As some of the molecules that the HBMEC
produced are known modulators of permeability and angiogenesis, we continued our
studies with the evaluation of barrier integrity. Our second study showed that prolonged
exposure to high concentrations of UCB caused monolayer fragility and compromised
barrier integrity. To complement these studies, we investigated the action of the
neuroprotective bile acids, ursodeoxycholic acid (UDCA) and glycoursodeoxycholic
acid (GUDCA) against UCB toxicity. The bile acids showed optimal protective abilities
in distinct parameters: GUDCA was effective in preventing cell death, while UDCA
reduced the production of angiogenic-related molecules and prevented the elevation of
permeability. Importantly, the bile acids efficiency was demonstrated in a broad window
of opportunity, with both protective and recovery properties. Next, we continued our
work by analysing brain regions with great susceptibility to bilirubin, as the cerebellum,
hippocampus and basal ganglia, which showed marked neuronal loss. Additionally, the
results revealed new players in the neuropathology of kernicterus, including increased
vascularization and dysfunction in several BBB components, as astrocytes, pericytes
and basement membrane.In conclusion, high levels of UCB compromise endothelial integrity, mainly after
prolonged exposure, ultimately leading to BBB breakdown and enhanced UCB
passage into the brain. Additionally, our data shows the potential of UDCA and GUDCA
as preventive, but also restorative therapeutic molecules against UCB-injury. Moreover,
evaluation of kernicterus cases suggests a link between region-specific susceptibility
and marked vascular dysfunction. These findings contribute to a better understanding
of the neurotoxic steps involved in the irreversible brain damage cause by severe
jaundice.
Descrição
Tese de doutoramento, Farmácia (Biologia Celular e Molecular), Universidade de Lisboa, Faculdade de Farmácia, 2013
Palavras-chave
Teses de doutoramento - 2013