Downregulation of T cell growth factor production by ornithine decarboxylase and its product putrescine: D,L-alpha-difluoromethylornithine suppresses general protein synthesis but augments simultaneously the production of interleukin-2.
Treatment of EL-4 lymphoma cells with tetradecanoylphorbol-acetate (TPA), a well-known activator of protein kinase C, induces the production of the T cell growth factor interleukin-2 (IL-2) and the expression of IL-2-specific mRNA within 4-8 h. This system is an ideal model for studies on the induction of a differentiated function in a homogeneous lymphoid cell population by a defined signal. TPA induces also an increase of ornithine decarboxylase (ODC) activity and elevates the intracellular concentrations of putrescine and polyamines within 4-8 h. A similar increase of intracellular putrescine and polyamine concentrations can be achieved by administration of 2 mM putrescine to the culture medium. However, putrescine cannot induce the production of IL-2 in the absence of TPA and cannot reconstitute the IL-2 production in cultures with PGE2 or cyclosporine A, i.e., two well-known immunosuppressive substances which inhibit ODC activity. Putrescine has rather a counter-regulatory effect as concluded from the observation that the TPA-induced TCGF production and IL-2-specific mRNA expression are augmented (superinduced) by the ODC inhibitor D,L-alpha-difluoromethylornithine (DFMO) and again suppressed after the administration of putrescine or polyamines to DFMO-treated cultures. The glycolytic activity, general protein synthesis [( 3H]leucine incorporation), and the cell cycle progression from G2/M to G1, in contrast, are inhibited by DFMO and reconstituted by putrescine. This demonstrates that the cells are able to sacrifice to a large extent several vital functions including their general protein synthesis and to devote themselves at the same time to a fulminant production of their functionally most relevant protein IL-2. This process is downregulated by ODC and its product putrescine. A correlation between increased IL-2 production and accumulation of cells in the G2/M phase was also observed in cultures treated with hydroxyurea or with a combination of amethopterin and adenosine.
Mihm
S
S
Institute of Immunology and Genetics, German Cancer Research Center, Heidelberg.
Risso
A
A
Stöhr
M
M
Oberdorfer
F
F
Dröge
W
W
D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D000518:Eflornithine / Q000494:pharmacology*; D006019:Glycolysis / Q000187:drug effects; D007376:Interleukin-2 / Q000096:biosynthesis*; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D008223:Lymphoma / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D008938:Mitosis / Q000187:drug effects; D009955:Ornithine Decarboxylase / Q000502:physiology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D011700:Putrescine / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000276:Adjuvants, Immunologic; D007376:Interleukin-2; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D009955:Ornithine Decarboxylase; D007930:Leucine; D013755:Tetradecanoylphorbol Acetate; D011700:Putrescine; D000518:Eflornithine