title: Characterization of monoamine oxidases in mesenchymal stem cells: role in hydrogen peroxide generation and serotonin-dependent apoptosis.
abstract: Early death of grafted bone marrow mesenchymal stem cells (MSCs) represents a major limit to their use in cell therapy of solid organs. It is well known that oxidative stress plays a major role in cell death. We have recently shown that the serotonin-degrading enzyme monoamine oxidase A (MAO-A) generates large amount of hydrogen peroxide (H2O2) responsible for cell apoptosis. Hydrogen peroxide generation requires 5-HT internalization into the cell and its degradation by MAO-A. In the present study, we investigated whether MAO-A is expressed in MSCs and we defined its role in serotonin-dependent MSCs apoptosis. RT-PCR analysis and western blots showed that the serotonin transporter (SERT) and the 2 MAO isoenzymes, A and B, are expressed in MSCs. As shown by enzyme assays using [14C]serotonin or [14C]β-phenylethylamine as selective MAO-A or MAO-B substrates, MAO-A is largely predominant in MSCs. Incubation of MSCs with the MAO substrate tyramine led to a time-dependent generation of H2O2 that was prevented by the MAO inhibitor pargyline. Finally, exposure of the cells to serotonin promoted an increase in MSCs apoptosis prevented by pargyline and the SERT inhibitor imipramine. The pro-apoptotic effect of serotonin was associated to a decrease in the expression of the anti-apoptotic factor Bcl-2. In conclusion, these results show for the first time that the 5-HT-degrading enzyme MAO-A is an important source of H2O2 in MSCs and plays a major role in 5-HT-dependent MSCs apoptosis.
authors.affiliation: INSERM, U858, F-31432 Toulouse, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Trouche
authors.forename: Celine
authors.initials: C
authors.lastname: Mias
authors.forename: Marie-Helene
authors.initials: MH
authors.lastname: Seguelas
authors.forename: Catherine
authors.initials: C
authors.lastname: Ordener
authors.forename: Daniel
authors.initials: D
authors.lastname: Cussac
authors.forename: Angelo
authors.initials: A
authors.lastname: Parini
mesh_terms: D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007099:Imipramine / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D008995:Monoamine Oxidase / Q000378:metabolism*; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology; D016877:Oxidants / Q000378:metabolism*; D010293:Pargyline / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D012701:Serotonin / Q000494:pharmacology*; D050486:Serotonin Plasma Membrane Transport Proteins / Q000378:metabolism; D013566:Sympathomimetics / Q000494:pharmacology; D014439:Tyramine / Q000494:pharmacology; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D018759:Adrenergic Uptake Inhibitors; D007527:Isoenzymes; D008996:Monoamine Oxidase Inhibitors; D016877:Oxidants; D019253:Proto-Oncogene Proteins c-bcl-2; D050486:Serotonin Plasma Membrane Transport Proteins; D013566:Sympathomimetics; D051028:bcl-2-Associated X Protein; D012701:Serotonin; D045304:Cytochromes c; D010293:Pargyline; D006861:Hydrogen Peroxide; D008995:Monoamine Oxidase; D007099:Imipramine; D014439:Tyramine