title: CNTF protects oligodendrocytes from ammonia toxicity: intracellular signaling pathways involved.
abstract: In pediatric patients, hyperammonemia can provoke irreversible damages to developing CNS like cortical atrophy, ventricular enlargement, demyelination or gray and white matter hypodensities which are concordant with alterations of neurons and oligodendrocytes. Cerebral injury triggers endogenous protective mechanisms that can prevent or limit brain damage. Understanding these mechanisms may lead to new therapeutic strategies. We investigated whether ciliary neurotrophic factor (CNTF), a cytokine-like protein expressed by astrocytes and described as an injury-associated survival factor, was up-regulated by ammonia in developing reaggregated 3D brain cell cultures. We showed that CNTF is up-regulated by ammonia exposure, through mediation of p38 MAPK activation in astrocytes. We also observed that SAPK/JNK and Erk1/2 activations in oligodendrocytes and neurons, respectively, also play indirect roles in CNTF synthesis by astrocytes. Co-treatment with exogenous CNTF demonstrated strong protective effects on oligodendrocytes, but not on neurons, against ammonia toxicity. These protective effects involved JAK/STAT, SAPK/JNK and c-jun proteins.
authors.affiliation: Inborn Errors of Metabolism, Clinical Chemistry Laboratory, Centre Hospitalier Universitaire Vaudois and University of Lausanne, Lausanne, Switzerland.
authors.forename: Laurène
authors.initials: L
authors.lastname: Cagnon
authors.forename: Olivier
authors.initials: O
authors.lastname: Braissant
mesh_terms: D000641:Ammonia / Q000633:toxicity*; D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001921:Brain / Q000166:cytology / Q000378:metabolism; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D020934:Ciliary Neurotrophic Factor / Q000378:metabolism*; D053739:Ciliary Neurotrophic Factor Receptor alpha Subunit / Q000378:metabolism; D018920:Coculture Techniques; D053612:Janus Kinases / Q000378:metabolism; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D009836:Oligodendroglia / Q000187:drug effects / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D050791:STAT Transcription Factors / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D020934:Ciliary Neurotrophic Factor; D053739:Ciliary Neurotrophic Factor Receptor alpha Subunit; D016755:Proto-Oncogene Proteins c-jun; D050791:STAT Transcription Factors; D000641:Ammonia; D053612:Janus Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4