title: Cross-talk between neurons and astrocytes in response to bilirubin: early beneficial effects.
abstract: Hyperbilirubinemia remains one of the most frequent clinical diagnoses in the neonatal period. This condition may lead to the deposition of unconjugated bilirubin (UCB) in the central nervous system, causing nerve cell damage by molecular and cellular mechanisms that are still being clarified. To date, all the studies regarding bilirubin-induced neurological dysfunction were performed in monotypic nerve cell cultures. The use of co-cultures, where astrocyte-containing culture inserts are placed on the top of neuron cultures, provides the means to directly evaluate the cross-talk between these two different cell types. Therefore, this study was designed to evaluate whether protective or detrimental effects are produced by astrocytes over UCB-induced neurodegeneration. Our experimental model used an indirect co-culture system where neuron-to-astrocyte signaling was established concomitantly with the 24 h exposure to UCB. In this model astrocytes abrogated the well-known UCB-induced neurotoxic effects by preventing the loss of cell viability, dysfunction and death by apoptosis, as well as the impairment of neuritic outgrowth. To this protection it may have accounted the induced expression of the multidrug resistance-associated protein 1 and the 3.5-fold increase in the values of S100B, when communication between both cells was established independently of UCB presence. In addition, the presence of astrocytes in the neuronal environment preserved the UCB-induced increase in glutamate levels, but raised the basal concentrations of nitric oxide and TNF-α although no UCB effects were noticed. Our data suggest that bidirectional signalling during astrocyte-neuron recognition exerts pro-survival effects, stimulates neuritogenesis and sustains neuronal homeostasis, thus protecting cells from the immediate UCB injury. These findings may help explain why irreversible brain damage usually develops only after the first day of post-natal life.
authors.affiliation: Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL/CPM), Faculty of Pharmacy, University of Lisbon, Avenida Professor Gama Pinto, 1649-003, Lisbon, Portugal.
authors.forename: Ana Sofia
authors.initials: AS
authors.lastname: Falcão
authors.forename: Rui F M
authors.initials: RF
authors.lastname: Silva
authors.forename: Ana Rita
authors.initials: AR
authors.lastname: Vaz
authors.forename: Sandra Leitão
authors.initials: SL
authors.lastname: Silva
authors.forename: Adelaide
authors.initials: A
authors.lastname: Fernandes
authors.forename: Dora
authors.initials: D
authors.lastname: Brites
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology*; D001663:Bilirubin / Q000494:pharmacology / Q000633:toxicity*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D018698:Glutamic Acid / Q000096:biosynthesis; D051556:Hyperbilirubinemia, Neonatal / Q000503:physiopathology; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000096:biosynthesis; D009414:Nerve Growth Factors / Q000096:biosynthesis; D016501:Neurites / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000096:biosynthesis; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D001663:Bilirubin; D018698:Glutamic Acid; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009414:Nerve Growth Factors; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C579158:S100b protein, rat; C421109:multidrug resistance-associated protein 1