title: MAPKs are key players in mediating cytokine release and cell death induced by unconjugated bilirubin in cultured rat cortical astrocytes.
abstract: When activated by unconjugated bilirubin (UCB), astrocytes are important sources of inflammatory mediators such as TNF-alpha, IL-1beta and IL-6, which may contribute for the neurotoxicity observed during severe neonatal hyperbilirubinemia. In the present study, we have addressed the role of the mitogen-activated protein kinases (MAPKs) p38, Jun N-terminal kinase (JNK)1/2 and extracellular signal-regulated kinase (ERK)1/2 pathways and their relation with the nuclear factor kappaB (NF-kappaB) cascade in the signalling events involved in cytokine release and cell death caused by UCB in primary cultures of rat astrocytes. Stimulation of astrocytes with UCB in the presence of all the MAPK inhibitors prevented UCB-induced release of TNF-alpha and IL-6, while IL-1beta secretion was only reduced by JNK1/2 and ERK1/2 inhibitors. In addition, activation of the NF-kappaB transcription factor, needed for cytokine release by UCB-stimulated astrocytes, was shown to be dependent on JNK1/2 and ERK1/2 phosphorylation. Moreover, all MAPK inhibitors prevented astroglial apoptosis triggered by UCB. Interestingly, UCB-induced lactate dehydrogenase release was prevented by blockade of JNK1/2, ERK1/2 and NF-kappaB cascades but enhanced by p38 inhibition. Taken together, our data demonstrate for the first time that MAPK transduction pathways are key players in the UCB-induced inflammatory response and cell death in astrocytes, probably also involving NF-kappaB modulation. These findings contribute to unraveling the complex mechanisms of astrocyte reactivity to UCB and may ultimately prove useful in the development of new therapeutic strategies to prevent nerve cell damage during acute bilirubin encephalopathy.
authors.affiliation: Centro de Patogénese Molecular, Unidade de Biologia Molecular e Biopatologia Experimental, Faculdade de Farmácia, University of Lisbon, Avenida Professor Gama Pinto, 1649-003 Lisbon, Portugal.
authors.forename: Adelaide
authors.initials: A
authors.lastname: Fernandes
authors.forename: Ana S
authors.initials: AS
authors.lastname: Falcão
authors.forename: Rui F M
authors.initials: RF
authors.lastname: Silva
authors.forename: Maria A
authors.initials: MA
authors.lastname: Brito
authors.forename: Dora
authors.initials: D
authors.lastname: Brites
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D001663:Bilirubin / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D016207:Cytokines / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D015870:Gene Expression / Q000187:drug effects; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: D016207:Cytokines; D004791:Enzyme Inhibitors; D007770:L-Lactate Dehydrogenase; D020929:Mitogen-Activated Protein Kinase Kinases; D001663:Bilirubin