title: Induction of apoptotic cell death by putrescine.
abstract: The polyamines are essential for cellular growth and differentiation. Ornithine decarboxylase (ODC), which catalyses the first step in the biosynthesis of the polyamines, has a very fast turnover and is subject to a strong feedback control by the polyamines. In the present study, we show that overexpression of a metabolically stable ODC in CHO cells induced a massive cell death unless the cells were grown in the presence of the ODC inhibitor alpha-difluoromethylornithine (DFMO). Cells overexpressing wild-type (unstable) ODC, on the other hand, were not dependent on the presence of DFMO for their growth. The induction of cell death was correlated with a dramatic increase in cellular putrescine levels. Analysis using flow cytometry revealed perturbed cell cycle kinetics, with a large accumulation of cells with sub-G1 amounts of DNA, which is a typical sign of apoptosis. Another strong indication of apoptosis was the finding that one of the key enzymes in the apoptotic process, caspase-3, was induced when DFMO was omitted from the growth medium. Furthermore, inhibition of the caspase activity significantly reduced the recruitment of cells to the sub-G1 fraction. In conclusion, deregulation of polyamine homeostasis may negatively affect cell proliferation and eventually lead to cell death by apoptosis if putrescine levels become too high.
authors.affiliation: Department of Experimental Medical Science, Lund University, S-22184 Lund, Sweden.
authors.forename: Koichi
authors.initials: K
authors.lastname: Takao
authors.forename: Mattias
authors.initials: M
authors.lastname: Rickhag
authors.forename: Cecilia
authors.initials: C
authors.lastname: Hegardt
authors.forename: Stina
authors.initials: S
authors.lastname: Oredsson
authors.forename: Lo
authors.initials: L
authors.lastname: Persson
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D016466:CHO Cells; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D000518:Eflornithine / Q000494:pharmacology; D004791:Enzyme Inhibitors; D016193:G1 Phase / Q000187:drug effects; D009955:Ornithine Decarboxylase / Q000378:metabolism; D065108:Ornithine Decarboxylase Inhibitors; D011700:Putrescine / Q000096:biosynthesis / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D065108:Ornithine Decarboxylase Inhibitors; D053148:Caspase 3; D020169:Caspases; D009955:Ornithine Decarboxylase; D011700:Putrescine; D000518:Eflornithine