title: Ammonia-induced miRNA expression changes in cultured rat astrocytes.
abstract: Hepatic encephalopathy is a neuropsychiatric syndrome evolving from cerebral osmotic disturbances and oxidative/nitrosative stress. Ammonia, the main toxin of hepatic encephalopathy, triggers astrocyte senescence in an oxidative stress-dependent way. As miRNAs are critically involved in cell cycle regulation and their expression may be regulated by oxidative stress, we analysed, whether astrocyte senescence is a consequence of ammonia-induced miRNA expression changes. Using a combined miRNA and gene microarray approach, 43 miRNA species which were downregulated and 142 genes which were upregulated by NH4Cl (5 mmol/l, 48 h) in cultured rat astrocytes were found. Ammonia-induced miRNA and gene expression changes were validated by qPCR and 43 potential miRNA target genes, including HO-1, were identified by matching upregulated mRNA species with predicted targets of miRNA species downregulated by ammonia. Inhibition of HO-1 targeting miRNAs which were downregulated by NH4Cl strongly upregulated HO-1 mRNA and protein levels and inhibited astrocyte proliferation in a HO-1-dependent way. Preventing ammonia-induced upregulation of HO-1 by taurine (5 mmol/l) as well as blocking HO-1 activity by tin-protoporphyrine IX fully prevented ammonia-induced proliferation inhibition and senescence. The data suggest that ammonia induces astrocyte senescence through NADPH oxidase-dependent downregulation of HO-1 targeting miRNAs and concomitant upregulation of HO-1 at both mRNA and protein level.
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich Heine University, D 40225 Düsseldorf, Germany.
authors.forename: Jessica
authors.initials: J
authors.lastname: Oenarto
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich Heine University, D 40225 Düsseldorf, Germany.
authors.forename: Ayse
authors.initials: A
authors.lastname: Karababa
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich Heine University, D 40225 Düsseldorf, Germany.
authors.forename: Mirco
authors.initials: M
authors.lastname: Castoldi
authors.affiliation: Cecile &Oskar Vogt Institute for Brain Research; Heinrich Heine University, D 40225 Düsseldorf, Germany.
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Bidmon
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich Heine University, D 40225 Düsseldorf, Germany.
authors.forename: Boris
authors.initials: B
authors.lastname: Görg
authors.affiliation: Clinic for Gastroenterology, Hepatology and Infectious Diseases, Heinrich Heine University, D 40225 Düsseldorf, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Häussinger
mesh_terms: D000641:Ammonia / Q000494:pharmacology*; D000818:Animals; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism*; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000187:drug effects / Q000235:genetics; D016000:Cluster Analysis; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D005973:Glutamine / Q000096:biosynthesis; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000235:genetics*; D019255:NADPH Oxidases / Q000378:metabolism; D051381:Rats; D015203:Reproducibility of Results
chemical_list: D035683:MicroRNAs; D005973:Glutamine; D000641:Ammonia; D051547:Heme Oxygenase-1; D019255:NADPH Oxidases