Ifenprodil and SL 82.0715 antagonize the effects of NMDA via a polyamine-sensitive modulatory site
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In rat tissues, a decrease in spermidine, accompanied by an increase in spermine was induced by the oral administration (once daily for either 1 week or 1 month) of trans-4-methylcyclohexylamine (4MCHA), a spermidine synthase inhibitor. This is similar to the changes observed in polyamine content when cell growth is arrested. The body-weight gain of the rats tended to decrease with increasing doses of 4MCHA. A decrease in spermidine, combined with a moderate increase in spermine, was observed dose-dependently in all of the tissues tested, with a relatively fast clearance of 4MCHA. Manipulating the polyamine content of tissues, by daily administration of 100 mumol 4MCHA for 1 week, made it possible to estimate the effects of simultaneously added spermidine or spermine on endogenous polyamine contents. The altered polyamine levels, obtained after daily administration for 1 week, were maintained during the extended 1-month period, with growth-dependent alteration. The results show it is possible to produce experimental rats with a higher spermine:spermidine ratio than control rats to investigate the physiological significance of spermidine downregulation and spermine upregulation in vivo.
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Through its role in polyamine acetylation and the back‐conversion pathway, spermidine/spermine N 1 ‐acetyltransferase (SSAT) has the potential to control intracellular polyamine pools by facilitating their catabolism and/or excretion. The possibility that the enzyme is subject to regulation by intracellular polyamine pools was investigated in MALME‐3 human melanoma cells. Increases in intracellular polyamine pools by treatment with 3 μM exogenous spermidine or spermine for 48 h caused SSAT activity to increase 111% and 226%, respectively, and SSAT‐specific mRNA to rise 19% and 66%, respectively. Decreases in polyamine pools by treatment with inhibitors of polyamine biosynthesis caused SSAT activity to decrease by 46% and mRNA to fall by 89%. Both SSAT activity and mRNA were more sensitive to changes in spermine than spermidine. The identification of a positive regulatory relationship between SSAT and intracellular polyamine pools further implicates this enzyme in a proposed model for polyamine pool homeostasis.
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The effects of alpha-difluoromethylornithine, a specific inhibitor of ornithine decarboxylase, on cell growth rate, polyamine content and the content of decarboxylated S-adenosylmethionine in SV-3T3 transformed mouse fibroblasts were studied. DL-alpha-Difluoromethylornithine at 1 mM or higher concentrations decreased the growth rate by over 90% after 2 or more days of exposure, but the cells remained viable, although quiescent for at least 9 days. Addition of 10 microM-spermidine or -spermine or 50 microM-putrescine at any time throughout this period completely reversed the inhibition of growth. Treatment with alpha-difluoromethylornithine decreased putrescine and spermidine contents by more than 98% and that of spermine by 60%, but cells exposed to exogenous polyamines did not require complete replenishment of the polyamine pools to resume growth. In fact, a virtually normal growth rate was obtained in cells lacking putrescine, having 2% of normal spermidine content and 156% of normal spermine. These results suggest that the well-known increase in putrescine and spermidine in cells stimulated for growth is not essential for this to occur and that mammalian cells can utilize spermine as their only polyamine. A substantial reversal of the growth-inhibitory effect of alpha-difluoromethylornithine was produced by a number of polyamines not normally found in mammalian cells, including the spermidine analogues aminopropylcadaverine and sym-homospermidine, which were partially converted into their respective spermine analogues by addition of an aminopropyl group within the cell. The spermine analogue sym-norspermine was also effective, but the maximal growth rate produced by these unphysiological polyamines was only 60-70% of that produced by the normal polyamines. These results indicate that spermidine and spermine have the optimal length for activation of the cellular processes critically dependent on polyamines and should help in identifying these processes. Exposure to alpha-difluoromethylornithine leads to an enormous rise in the concentration of decarboxylated S-adenosylmethionine, which reached a peak at 530-fold after 3 days of exposure and steadily declined to 140-fold after 11 days. This increase was abolished by addition of exogenous polyamines, which rapidly decreased the activity of S-adenosylmethionine decarboxylase. The increase in decarboxylated S-adenosylmethionine is unlikely to be solely responsible for the decrease to the same extent by spermine, sym-norspermidine and sym-homospermidine, which produce 97%, 16% and 60% of the control growth rate, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)
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Red blood cells (RBC) from 69 patients with advanced cancer and 37 healthy controls were subjected to polyamine determination by using high-performance liquid chromatography. The polyamine contents in normal human RBC were spermidine 15.04 ± 3.63 nmol and spermine 8.82 ± 3.12 nmol per 1010 RBC. Spermidine and spermine levels in RBC were elevated in patients with cancer (p < 0.005). Serial studies in seven patients with cancer indicated that both polyamines in RBC were reduced after successful surgery. Our data indicate that the determination of polyamine levels in RBC is clinically useful as a marker of disease activity in patients with cancer.
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In this paper we describe the synthesis and characterization of a series of simple spermine/amino acid conjugates, some of which potently inhibit the uptake of spermidine into MDA-MB-231 breast cancer cells. The presence of an amide in the functionalized polyamine appeared to add to the affinity for the polyamine transporter. The extensive biological characterization of an especially potent analogue from this series, the Lys-Spm conjugate (31), showed this molecule will be an extremely useful tool for use in polyamine research. It was shown that the use of 31 in combination with DFMO led to a cytostatic growth inhibition of a variety of cancer cells, even when used in the presence of an extracellular source of transportable spermidine. It was furthermore shown that this combination effectively reduced the cellular levels of putrescine and spermidine while not affecting the levels of spermine. These facts together with the nontoxic nature of 31 make it a novel lead for further anticancer development.
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Summary In AKR mice that develop spontaneous lymphoid leukemia, the thymus is the organ of primary involvement. Thymic cells from normal mice, as well as from mice with advanced leukemia, were separated according to size by sedimentation in a 1 × g sucrose gradient, the larger cells sedimenting further than the smaller cells. The fractions obtained from this gradient, which correspond to successive phases of the cell cycle, were collected and subjected to polyamine analysis. In the G0 phase of the cell cycle the spermine content was higher than in the G1 phase, whereas the putrescine and spermidine content were similar in these two phases. The cellular content of putrescine, spermidine, and spermine increased progressively as the cells traversed the cell cycle from G1 to M. In fact, the amount of all these amines was increased in the G1 + S fraction. In the fraction corresponding to the G2 + M phases, the polyamine content was twofold that in the G1 phase. This increase in the polyamine content was seen first for putrescine, then for spermidine, and finally for spermine. This sequential pattern reflects the order of synthesis of the polyamines, i.e., putrescine being the precursor of spermidine and spermidine the precursor of spermine.
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Polyamines (putrescine, spermidine, spermine) are closely linked to cellular synthesis of DNA, RNA and protein, and are thought to be an indicator of cell proliferation. Plasma, erythrocytes and tissue polyamine levels in 58 patients with colorectal cancer were measured to survey the relationship between polyamines and stage classification. The polyamine levels of plasma, erythrocytes and tissue in patients were increased significantly compared with those of controls. Plasma spermine and erythrocytes spermidine and spermine levels were increased with the advance of stage. In plasma and erythrocytes, spermidine/spermine ratios were decreased in accordance with the stages. On the contrary, the polyamine levels and the ratio in cancer tissue were not varied in all stages. These results present the following conclusions. Although cancer tissue has higher proliferative activity than normal mucosa, these activities of main tumors in each stage are not fluctuated. The polyamine levels in plasma and erythrocytes are possibly influenced by tumor burden and therefore those could be an useful marker for indicating the stage of colorectal cancer.
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