Role of polyamines in the control of cell proliferation and differentiation

Dietary soy protein is associated with reduced intestinal mucosal polyamine concentration in male Wistar rats

Quantitation of polyamine levels has been correlated with biomarkers of proliferation in the colon mucosa where dysregulated epithelial hyperproliferation is associated with colorectal cancer risk. This study was performed to assess the response of polyamine measurements to dietary factors in an animal model. Male Wistar rats were fed purified diet or diets substituted by 20% lard fat, 20% beet fiber and 20% soy protein. After 2 wk, mucosal polyamines were measured along intestinal tracts by HPLC. In rats fed the control diet (n = 10), mucosal polyamines were found at high levels in the duodenum, jejunum and ileum but at low levels in the cecum, colon and rectum. Compared with rats fed the control diet, those fed the 20% lard diet showed greater polyamine levels in the large intestine (P < 0.05, n = 10), but those fed the 20% fiber diet exhibited lower polyamine levels in the small intestine (P < 0.05, n = 9). However, rats fed the 20% soy protein diet had lower polyamine levels in both small and large intestines (P < 0.05, n = 15). Significant linear correlations were observed between rectal polyamine levels and the dietary energy intakes in these four diet groups (r = 0.972-0.991, P < 0.001). Supplementation of 0.1% soy isoflavones to the basal diet or 0.3% DL-methionine to the 20% soy protein diet for 4 wk did not affect polyamine levels. The results indicate that soy protein reduced mucosal polyamine levels, at least in part, through reduction of energy intakes. Further studies are warranted to verify that polyamine levels in intestinal mucosa are useful as an intermediate endpoint of the dietary risk factors.

Proton MR spectroscopy of prostatic tissue focused on the detection of spermine, a possible biomarker of malignant behavior in prostate cancer

To investigate whether polyamines may be valuable diagnostic and prognostic markers in prostate cancer, the presence of polyamines was studied in various human prostatic tissues using both proton magnetic resonance (MR) spectroscopy and high-pressure liquid chromatography (HPLC). The HPLC results showed that normal and benign hyperplastic prostatic tissues were characterized by a high content of spermine. Spermine levels were reduced in tumor tissue, especially in prostatic carcinoma with metastases, and in xenografts of human prostatic carcinoma cells. These preliminary results indicate that spermine may be used as a biomarker for malignant behavior. The MR spectroscopy study showed that it is possible to detect spermine resonances in prostatic biopsy material by one-dimensional and two-dimensional J-resolved MR spectroscopy at high field (600 MHz). Localized one-dimensional in vitro MR spectra obtained at the clinical field strength of 1.5 T showed spermine signals in the region between 3.0 and 3.3 ppm. In in vivo MR spectra of the human prostate, however, these signals were obscured by resonances of choline (3.2 ppm) and creatine (3.0 ppm).

Polyamines in the lung: polyamine uptake and polyamine-linked pathological or toxicological conditions

The natural polyamines putrescine, cadaverine, spermidine, and spermine are found in all cells. These (poly)cations exert interactions with anions, e.g., DNA and RNA. This feature represents their best-known direct physiological role in cellular functions: cell growth, division, and differentiation. The lung and, more specifically, alveolar epithelial cells appear to be endowed with a much higher polyamine uptake system than any other major organ. In the lung, the active accumulation of natural polyamines in the epithelium has been studied in various mammalian species including rat, hamster, rabbit, and human. The kinetic parameters (Michaelis-Menten constant and maximal uptake) of the uptake system are the same order of magnitude regardless of the polyamine or species studied and the in vitro system used. Also, other pulmonary cells accumulate polyamines but never to the same extent as the epithelium. Although different uptake systems exist for putrescine, spermidine, and spermine in the lung, neither the nature of the carrier protein nor the reason for its existence is known. Some pulmonary toxicological and/or pathological conditions have been related to polyamine metabolism and/or polyamine content in the lung. Polyamines possess an important intrinsic toxicity. From in vitro studies with nonpulmonary cells, it has been shown that spermidine and spermine can be metabolized to hydrogen peroxide, ammonium, and acrolein, which can all cause cellular toxicity. In hyperoxia or after ozone exposure, the increased polyamine synthesis and polyamine content of the rat lung is correlated with survival of the animals. Pulmonary hypertension induced by monocrotaline or hypoxia has also been linked to the increased polyamine metabolism and polyamine content of the lung. In a small number of studies, it has been shown that polyamines can contribute to the suppression of immunologic reactions in the lung.

Polyamine depletion up-regulates c-Myc expression, yet induces G(1) arrest and terminal differentiation of F9 teratocarcinoma stem cells

The ornithine decarboxylase (ODC) gene is a transcriptional target of c-Myc. Exponentially growing cells usually exhibit high c-Myc levels and high ODC levels, whereas stationary phase cells and terminally differentiated cells have low levels of both proteins. Therefore, we were surprised to find that when F9 teratocarcinoma stem cells were blocked in the G(1) phase of their cell cycle and induced to differentiate by irreversible inhibition of the ODC activity, the expression of c-Myc was up-regulated instead of being down-regulated. During the course of differentiation, the c-myc gene was constitutively expressed, and c-Myc protein accumulated. In transfection experiments, using ODC promoter-reporter gene fusion constructs, the accumulation of c-Myc protein, resulting from polyamine depletion, led to increased reporter gene expression. This finding is consistent with the view that depletion of polyamines relieves the suppression that they exert on c-myc mRNA translation, causing an accumulation of c-Myc protein, which in turn transactivates its target gene, the bona fide ODC gene. Thus, the accumulation of an active c-Myc protein does not preclude differentiative events, nor does it override the growth arrest caused by polyamine depletion. These results suggest a new role for polyamines-as negative regulators of c-Myc expression.

Half-lives of ornithine decarboxylase and S-adenosylmethionine decarboxylase activities during the cell cycle of Chinese hamster ovary cells

Cells in mitosis were seeded immediately after being harvested by the mitotic shake off technique from a culture of exponentially growing Chinese hamster ovary cells. At 2, 5, 7, 10, and 12 h after seeding, cycloheximide was added. Cells were sampled at various times after cycloheximide addition and the ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC) activities were determined. Flow cytometric analysis showed that cells sampled at 2, 5, 7, 10, and 12 h after seeding were found in mid G(1), at the G(1)/S transition, in mid S phase, at the S/G(2) transition, and in late G(2), respectively. The half-lives of ODC and AdoMetDC activities varied during the cell cycle. The half-life of ODC activity showed a biphasic pattern with increases in connection to the G(1)/S and S/G(2) transitions while the half-life of AdoMetDC activity increased only at the G(1)/S transition.

Control of filament formation in Candida albicans by polyamine levels

Candida albicans, the most common fungal pathogen, regulates its cellular morphology in response to environmental conditions. The ODC gene, which encodes ornithine decarboxylase, a key enzyme in polyamine biosynthesis, was isolated and disrupted. Homozygous null Candida mutants behaved as polyamine auxotrophs and grew exclusively in the yeast form at low polyamine levels (0.01 mM putrescine) under all conditions tested. An increase in the polyamine concentration (10 mM putrescine) restored the capacity to switch from the yeast to the filamentous form. The strain with a deletion mutation also showed increased sensitivity to salts and calcofluor white. This Candida odc/odc mutant was virulent in a mouse model. The results suggest a model in which polyamine levels exert a pleiotrophic effect on transcriptional activity.

Heterogeneous distribution of polyamines in temporal lobe epilepsy

Polyamine contents were determined in human temporal lobe epilepsy. In the seven patients studied, stereoelectroencephalography (SEEG) located the epileptogenic focus in Ammon's horn and neuropathological findings were limited to hippocampal gliosis and sclerosis. Each polyamine exhibited a specific regional distribution. The most important variations were observed for spermidine and spermine while putrescine levels varied less. The regional variation was predominant in middle > posterior > anterior parts of the temporal lobe. Spermine contents and the spermidine/spermine (SPD/SPM) index varied especially in the middle and posterior parts of the hippocampus. Metabolic SPD/SPM index and spermidine levels were found to be drastically increased in almost all limbic parts when compared to neocortical regions. The opposite was observed for spermine. The heterogeneous distribution of polyamines was compared to abnormal electrical activities recorded by SEEG: SPD/SPM index and spermidine levels were sharply increased in seizure onset areas and high levels of spermine were detected in temporal cortex propagation areas. The presently reported heterogeneity of polyamine contents might contribute to modulate differentially the local control of excitability in human temporal epilepsy.

Recombinant anti-polyamine antibodies: identification of a conserved binding site motif

Polyamines are small linear polycations found ubiquitously in eukaryotic cells. They are involved in nucleic acid and protein synthesis and rises in cellular polyamine levels have been correlated with cell proliferation. Antibodies to these molecules have potential as prognostic indicators of disease conditions and indicators of treatment efficacy. Antipolyamine monoclonal antibodies of differing but defined specificities have been generated in our laboratory using polyamine ovalbumin conjugates as immunogens. These antibodies show small but significant cross reactivities with other polyamine species; IAG-1 cross reacts with spermidine (8%), JAC-1 with spermine (6%) and JSJ-1 with both putrescine (11%) and spermine (6%). We have rescued and sequenced the heavy and light chain variable regions of all three of these antibodies. While the light chains of two antibodies, IAG-1 and JSJ-1, were 93% homologous at the amino acid level, none of the heavy chains displayed any significant sequence homology. However, computer-generated models of all three antibody binding sites revealed a three-dimensionally conserved polyamine binding site motif. The polyamine appears to bind into a negatively charged cleft lined with acidic and polar residues. The cleft is partially or completely closed at one end and the specificity of the interaction is determined by placement of acidic residues in the cleft. Aromatic residues contribute to polyamine binding interacting with the carbon backbone. The polyamine-binding motif we have identified is very similar to that observed in the crystal structure of PotD, the primary receptor of the polyamine transport system in Escherichia coli.

L-arginine metabolites regulate DNA synthesis and nitric oxide synthase activity in cultured human dermal microvascular endothelial cells--potential positive and negative regulators of angiogenesis derived from L-arginine

Human dermal microvascular endothelial cell (HDMVEC) growth and proliferation is important for skin angiogenesis. Our data support the hypothesis that a regulatory switch from an angiogenic to a nonangiogenic stimulus involves a change in l-arginine metabolism from polyamines (PAs) to nitric oxide (NO) and, conversely, a change to an angiogenic stimulus is expected to drive l-arginine metabolism in favor of PA synthesis. Current studies with cultured HDMVECs demonstrated that NO inhibited, whereas the PA putrescine stimulated DNA synthesis. The nitric oxide synthase (NOS) inhibitor NG-nitro l-arginine methyl ester stimulated DNA synthesis with a significant increase from control at 2.5 and 5 mM (p < 0.05); in contrast, the ornithine decarboxylase (ODC) inhibitor alpha-difluoromethyl ornithine (DFMO) inhibited DNA synthesis with a significant decrease from control at 19.65, 29.48, and 39.48 microM (p < 0.05). NO donors sodium nitroprusside dihydrate, S-nitroso-N-penicillamine, and l-hydroxy-2-oxo-3(3-aminopropyl)-3-propyl-triazine all inhibited DNA synthesis. There was a significant increase in NOS activity with DFMO treatment (p < 0.05) and a less pronounced decrease in NOS activity with direct PA treatment. In summary, NO and PAs are important mediators of HDMVEC growth and PAs downregulate NOS activity in these cells. NOS and ODC enzyme products may not only be important components in the regulation of angiogenesis in the skin but they may also regulate their own synthesis via feedback mechanisms.

Changes in ornithine decarboxylase activity and putrescine concentrations after spinal cord compression injury in the rat

Traumatic spinal cord injury results in direct physical damage to structures and the generation of local factors contributing to secondary pathogenesis. In the present study, we investigated changes in polyamine metabolism after spinal cord compression injury in the rat. This is a stress induced metabolic pathway, of which an activation may indicate both, secondary pathogenesis or induction of neuroprotective response. Ornithine decarboxylase (ODC) activity, the rate limiting step of polyamine synthesis, and levels of the diamine putrescine, the product of ornithine decarboxylase reaction, were analyzed in control (non-laminectomized) animals and at 2 and 4 h after laminectomy or compression injury at the L4 segmental level. ODC activity was significantly increased 4 h after laminectomy in L4 and in adjacent L3 and L5 segments and compression to L4 produced a further increase 4 h after injury as compared with the intact control group. Putrescine levels were likewise significantly elevated to the same extend in the laminectomized and injured cord as compared with the intact control group. These findings demonstrate increased ODC and putrescine levels in the laminectomized and traumatized spinal cord and suggest that laminectomy may be an important 'priming event' that contributes to secondary injury after spinal cord compression injury.

The cellular localization of the L-ornithine decarboxylase/polyamine system in normal and diseased central nervous systems

Natural polyamines, spermidine and spermine, and their precursor putrescine, are of considerable importance for the developing and mature nervous system. They exhibit a number of neurophysiological and metabolic effects in the nervous system, including control of nucleic acid and protein synthesis, modulation of ionic channels and calcium-dependent transmitter release. The polyamine system is also known to be involved in various brain pathologic events (seizures, stroke, Alzheimer's disease and others). While cerebral polyamine concentrations and the activities of polyamine-metabolizing enzymes have been studied in great detail, much less is known about the cells that are responsible for cerebral polyamine synthesis and interconversion. With the present review the attempt is made to show how exact knowledge about the regional distribution and cellular localization of polyamines and the polyamine-synthesizing enzymatic machinery (and especially of L-ornithine decarboxylase) may help to better understand the functional interplay between polyamines and other endogenous agents (transmitters, receptors, growth factors neuroactive drugs etc.). Polyamines have been localized both in neurones and glial cells. However, the main cellular locus of the ODC is the neuron--both in the immature and adult central nervous system. Each period of normal brain development and ageing seems to have its own, characteristic temporo-spatial pattern of neuronal ODC expression. During strong functional activation (kindling, epileptic seizures, neural transplantation) astrocytes and other non-neuronal cells do also express ODC and other polyamine-metabolizing enzymes. Astroglial expression of ODC is accompanied by an increase in glial fibrillary acidic protein in these cells. This shift in the cellular mechanisms of polyamine metabolism is currently far from being understood. In human brain diseases (Alzheimer's disease, schizophrenia) certain neurones show an increased expression of ODC, the first and rate-limiting enzyme of polyamine metabolism. Since polyamines are structurally related to psychoactive drugs (neuroleptics, antidepressants) the polyamine system might be of importance as a putative target for drug intervention in psychiatry.

Coordinate changes of polyamine metabolism regulatory proteins during the cell cycle of normal human dermal fibroblasts

In human dermal fibroblasts, brought to quiescence (G0) by serum starvation, the S phase peaked 24 h and G2/M phases 36 h after serum re-addition. Under the same conditions, ornithine decarboxylase mRNA peaked at 12 h, decreased markedly in S phase and remained low until 48 h. Conversely, ornithine decarboxylase antizyme transcript dropped to its lowest level at 12 h, while reaching its highest values between 24 and 48 h. Ornithine decarboxylase activity followed essentially the pattern of its mRNA, but relative changes were much greater. S-Adenosylmethionine decarboxylase transcript and enzyme activity also peaked at around 12 h, decreasing thereafter. Spermidine/spermine N1-acetyltransferase mRNA and activity reached the highest values at 36-48 h. Putrescine concentration increased up to 18 h and fell dramatically in the S phase, remaining low thereafter. Both spermidine and spermine reached peaks at 18 h and decreased in the S phase, but not nearly as much as putrescine. We discuss how this comprehensive study may help to understand the involvement of polyamines in the control of cell proliferation.

Translocation of ornithine decarboxylase to the surface membrane during cell activation and transformation

Ornithine decarboxylase (ODC) is highly up-regulated in proliferating and transforming cells. Here we show that upon induction, an initial cytosolic increase of ODC is followed by translocation of a fraction of the enzyme to the surface membrane. ODC membrane translocation is mediated by a p47(phox) membrane-targeting motif-related sequence, as indicated by reduced ODC activity in the membrane fraction of cells treated with a competing, ODC-derived (amino acids 165-172) peptide, RLSVKFGA, which is homologous to the p47(phox) membrane-targeting sequence. p47(phox) membrane translocation is known to be dependent on the phosphorylation of the targeting motif. Analogously, overexpressed ODC.S167A, a mutant ODC lacking the putative phosphorylation site Ser67, is unable to move to the surface membrane. Cells blocked with the RLSVKFGA peptide showed defective transformation, indicating that the motif-mediated translocation of ODC is prerequisite to its biological function. Constitutive targeting of ODC to the membrane using a plasmid encoding the chimeric protein, wild-type ODC with C-terminal linkage to the farnesylation motif of K-ras, caused impaired cytokinesis with an accumulation of polykaryotic cells. Impaired cytokinesis confirms that ODC is involved in mitotic cytoskeletal rearrangement events and pinpoints the importance of relevant membrane targeting to its physiological function.

Comparative effects of TGFbeta on proliferation of 7- and 14-day-old chick embryo fibroblasts and lack of involvement of the ODC/PA system in the TGFbeta signaling pathway

The growth regulatory activity of transforming growth factor beta (TGFbeta) on chick embryo skin fibroblasts was compared in two developmental ages, days 7 and 14. The time course of 3H-thymidine incorporation, an S-phase marker of replication, was determined during 36 hr of TGFbeta treatment. Seven-day-old cells showed a prereplicative phase of 6 hr, and 14-day-old cells showed a prereplicative phase of 12 hr. DNA synthesis peaked at 24 hr in 7-day-old fibroblasts and was 10 times higher than that in 14-day-old fibroblasts. Ornithine decarboxylase (ODC) activity and content of the natural polyamines spermine (Spm), spermidine (Spd), and putrescine (Put) differed during cell cycle. ODC activity peaked at 12 hr in 7-day-old cells and at 6 hr in 14-day-old cells. Its level was two times higher at day 7 and was associated with a greater content of ODC mRNA. The maximum of polyamine (PA) concentration was determined after 12 hr of treatment in 7-day-old cells and after 36 hr in 14-day-old cells. These findings indicate that the TGFbeta proliferative response of embryo fibroblasts changes during development and is associated with activation of the ODC/PA system. Cotreatment with alpha-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ODC, did not reduced growth rate. Inhibition of ODC resulted in levels of Put and Spd comparable to that of quiescent fibroblasts, whereas Spm concentration remained higher. Because an altered ODC metabolism does not convey the effects of TGFbeta on DNA synthesis, the ODC/PA system may not play a role in the pathway of TGFbeta signaling.

Promotion of intestinal carcinogenesis by dietary methionine

The metabolism of the polyamines spermidine and spermine is known to be enhanced in rapidly proliferating cells. Methionine is a precursor of the aminopropyl moieties of these amines. Therefore, it was of interest to study the effects of a methionine supplemented diet on polyamine metabolism and preneoplastic changes occurring in the intestinal tract of rats treated with the chemical carcinogen azoxymethane (AOM). Adult Wistar rats received 15 mg AOM/kg body wt (i.p.) once each week for 2 weeks. Thereafter, the rats were randomly divided into two groups and received controlled isoenergetic diets containing the same amount of folate, choline and vitamin B12 during 12 weeks: one group was kept on a standard diet; the other was fed the same diet, except that 1% L-methionine was added at the expense of carbohydrates. After 12 weeks, the administration of the methionine-supplemented diet stimulated the turnover rate of ileal epithelial cells, indicating enhanced crypt cell proliferation. Furthermore, in this group, a 2-fold increase in the number of aberrant hyperproliferative crypts and the appearance of tumors was observed in the colon. These effects were accompanied by the increased formation of spermidine and spermine due to the enhancement of S-adenosylmethionine decarboxylase activity and by the upregulation of Cdx-1, a homeobox gene with oncogenic potentials. The experimental data do not support the view of a chemopreventive effect of dietary methionine supplementation on intestinal carcinogenesis in rats, even at an early phase of preneoplastic development, but rather suggest that methionine promotes intestinal carcinogenesis.

Ornithine decarboxylase is a transcriptional target of tumor suppressor WT1

The product of the Wilm's tumor suppressor gene, WT1, is a zinc-finger DNA-binding protein, which is thought to be a transcription factor. Two genes, those encoding epidermal growth factor receptor and syndecan-1, are known to be endogenous targets of WT1. Previous studies had identified binding sites for WT1 in the promoter of the ornithine decarboxylase (ODC) gene. In this paper, we tested whether the endogenous ODC gene might be a target of WT1 by establishing lines of baby hamster kidney (BHK) cells that expressed WT1 isoform A under control of a tetracycline-regulated expression system. When expression of WT1 was activated in BHK cells, the cellular level of ODC mRNA declined, with kinetics that correlated with the increase in WT1 level, demonstrating that the endogenous ODC gene was indeed responsive to cellular level of WT1. WT1 isoforms A and B inhibited the activity of the ODC promoter by approximately fivefold in transiently transfected BHK cells, while isoforms C and D, which have altered DNA binding domains, had no significant effect. The sequence CTCCCCCGC, located at nucleotides -106 to -98 relative to the site of transcriptional initiation in the ODC gene, interacted with the zinc-finger domain of isoforms A and B of WT1 with high affinity and specificity. A mutation in the binding site that disrupted this interaction partially removed the inhibition of ODC promoter activity by WT1, as did mutation of the two E-box sequences in intron I of the ODC gene. Simultaneous mutation of the WT1-binding motif and the two E-boxes completely abolished inhibition by WT1 of ODC promoter activity. These results, taken together, implicate the ODC gene as a downstream target of the tumor suppressor WT1.

Capillary gas chromatographic determination of putrescine and cadaverine in serum of cancer patients using trifluoroacetylacetone as derivatizing reagent

Trifluoroacetylacetone (FAA) derivatives of 1,4-diaminobutane (putrescine) (Pu) and 1,5-diaminopentane (cadaverine) (CA) were prepared and characterized by elemental microanalysis, IR, and mass spectrometry. Diamine derivatives were eluted from capillary gas chromatographic (CGC) column BP1 (12 m x 0.22 mm I.D.) or BP5 (50 m x 0.22 mm) with layer thickness 0.25 microm, using nitrogen as a carrier gas and flame ionization detection (FID). A solvent extraction procedure was developed for the extraction of Pu and CA from aqueous solution with a linear calibration range 0-20 microg/0.2 ml of extract with a detection limit of 0.5-0.6 ng/injection. The method was applied for the determination of Pu and CA in the serum of five cancer patients before and after radiotherapy. The serum of two healthy persons was also analyzed for Pu and CA contents. Pu and CA concentrations were found within the range 1.16-3.96 microg/ml and 0.88-1.46 microg/ml in cancer patients as compared to 0.11-0.16 microg/ml and 0.06-0.075 microg/ml respectively in healthy persons with a coefficient of variation (CV) within 0.62-5.47%. Pu and CA concentrations decreased on radiotherapy in cancer patients, but were much higher than in healthy persons.

Kinetic analysis of spermine binding to NRD convertase

N-arginine dibasic convertase cleaves polypeptides between paired basic residues containing the sequence Arg-Arg or Arg-Lys. The enzyme contains a large anionic domain, which in the rat enzyme consists of 57 acidic residues out of a stretch of 76 amino acids. Polyamines modulate the activity of the enzyme presumably by binding at the anionic domain (Csuhai et al. (1995) Biochemistry 34, 12411-12419). In this study a kinetic analysis of the effect of salts and amines, particularly the polyamine spermine, on the rat enzyme was studied. Simple salts were inhibitory with no apparent specificity for the anion or cation. Inhibition resulted in an increased Km and a decreased Vmax. Evidence that amines bind to an anionic domain was obtained by the finding that N,N-bis [2-hydroxyethyl]-2-aminoethanesulfonic acid, which is structurally related to the inhibitory amine triethanolamine, is noninhibitory. Inhibition exhibited a complex dependence on spermine concentration. The data fit a model in which enzyme-spermine and enzyme-(spermine)2 complexes are formed. A pH-independent Kd ( approximately 0.1 microM) was obtained for enzyme-spermine formation, while enzyme-(spermine)2 formation was dependent on pH; Kd at pH 6.5 = 1 microM and a Kd at pH 8 = approximately 16 microM. Direct binding of spermine was demonstrated by the ability of spermine to increase the thermal stability of the enzyme. The concentration dependence for the spermine-induced increase in thermal stability fits a model in which formation of the enzyme-spermine complex is sufficient to account for the observed changes.

Differentiation-promoting effect of 1-O (2 methoxy) hexadecyl glycerol in human colon cancer cells

Alkylglycerols are naturally occurring bioactive ether lipids found in great abundance in the livers of many marine species. In this study, we evaluated the differentiation-promoting potential of a methoxy substituted alkylglycerol--1-O (2 methoxy) hexadecyl glycerol (MHG)--to promote a more benign or differentiated phenotype in human colon cancer cells. Three cell lines with different biological and phenotypic properties were used. They were the moderately differentiated and growth factor-responsive Moser, the growth factor-unresponsive and malignant HT29, and the poorly differentiated and growth factor-unresponsive HCT116. Treatment of these cell lines with MHG resulted in a downmodulation of cellular proliferation, a reduced propensity for anchorage-independent growth, and a reduced capacity in cellular invasion. Induction of the colon-associated and differentiation-related molecule carcinoembryonic antigen was also observed in the three cell lines. Induction of the transformation-sensitive and differentiation-related glycoprotein fibronectin was observed in the HT29 cells. It is concluded that MHG was biologically active and promoted a more benign or differentiated phenotype in these colon cancer cells. Since differentiation-inducing agents may possess chemoprevention properties, the use of MHG and the alkylglycerols in inducing differentiation or in chemoprevention of malignant diseases warrants further investigation.

Differentiation-inducing effect of retinoic acid, difluoromethylornithine, sodium butyrate and sodium suramin in human colon cancer cells

We investigated the relative effectiveness of four differentiation-inducing chemicals to induce a more normal or benign phenotype in the human colon cancer cell lines Moser and HT29. The differentiation-inducing capability of all-trans retinoic acid (ATRA), difluoromethylornithine (DFMO), sodium butyrate (NaB) and sodium suramin (NaS) was evaluated in terms of the efficacy of these chemicals in inhibiting cellular proliferation, growth in soft agarose, invasion of matrigel and induction of morphological alteration. The relative ability of these chemicals to induce production of the differentiation-related molecules fibronectin and carcinoembryonic antigen was also determined. Overall, ATRA was found to be the most effective chemical in inducing differentiation as measured by these parameters. The Moser cells were more susceptible to differentiation induction by comparison with the HT29 cells. Both similarities and differences in the cellular responses to DFMO, NaB and NaS were also observed for the Moser and HT29 cells. The differences in cellular responses to these chemicals may be due to different phenotypic properties of these two cell lines and different mechanisms of action of these chemicals.

Pre- and post-hatching developmental changes in beta-adrenoceptor subtypes in chick brain

This study used [3H]CGP 12177 as a radioligand to determine the beta1 and beta2-adrenoceptor changes from the pre-hatching E17 stage, where the beta2 subtype is first detected, to the post-hatching P30 stage. While beta1-adrenoceptors were found to be present from E18 and were limited to cerebellum and hyperstriatum in all stages studied, beta2-adrenoceptors showed a wider distribution throughout the brain. In most of the structures analysed both beta1- and beta2-adrenoceptor binding values reached a maximum in the P2 stage, followed by a decrease over the following days. A second increase in both subtypes was detected again in the P15 and P30 stages. These results support the notion of a specific role for beta-adrenoceptors in neural plasticity in the first week after hatching and suggest that the beta2 subtype is the main adrenoceptor in chick brain throughout its development.

QSAR analysis of polyamine transport inhibitors in L1210 cells

PURPOSE

In this paper, the authors attempt to construct a mathematical model to correlate the biological activities of 63 polyamine transport inhibitors in L1210 cells with their physicochemical parameters.

METHOD

The inhibitory constants (Ki) were obtained from the published work of Bergeron et al. Non-weighted least square method was used in deriving the regression equations with a BMDP program. An AM1 subroutine of the HyperChem program was used to optimize the geometry and calculate the molecular dipole moments and the distance between two terminal amino groups. A CQSAR program was used to calculate Clog P (oct./w.).

RESULTS

A good correlation (r2 = 0.81) was obtained by using a five-parameter equation including the distance between two terminal amino groups (d), the number of cationic charge (Charge), molecular weight (MW), dipole moment (mu), and hydrogen bond forming ability (Hb).

CONCLUSION

This model accounts for 81% of the variance in the data and can be used to estimate transport-inhibitory activity of many other polyamine analogues. It gives some quantitative information about the relationship between the polyamine analogues' function as transport inhibitors and their molecular structures.

Involvement of polyamines in retinoblastoma protein phosphorylation

Hepatocyte growth factor (HGF) increased both levels of phosphorylated and non-phosphorylated forms of retinoblastoma protein (RB) in primary cultured rat hepatocytes. Combined treatment of HGF and a specific inhibitor of ornithine decarboxylase (ODC), alpha-difluoromethylornithine (DFMO), reduced the levels of hyper-phosphorylated and hypo-phosphorylated forms of RB and increased the levels of the non-phosphorylated form, compared to HGF alone, but did not affect the total level of RB. Polyamines added exogenously overcame the effects of DFMO; they increased hyper- and hypo-phosphorylated forms and decreased non-phosphorylated RB. TGF-beta1 inhibited the increases in ODC activity, RB phosphorylation, and DNA synthesis induced by HGF. However, polyamines added exogenously could not overcome the inhibition by RB phosphorylation and DNA synthesis by TGF-beta1. These results suggest that polyamines are involved in the phosphorylation of RB, but the inhibition of polyamine biosynthesis by TGF-beta1 did not result in the inhibition of RB phosphorylation and DNA synthesis.

Inhibition of proteasome function prevents thymocyte apoptosis: involvement of ornithine decarboxylase

We have previously shown that polyamine levels rapidly decrease in thymocytes undergoing apoptosis, and that ornithine decarboxylase increases early but too transiently to maintain elevated polyamine levels. These data led us to suppose that a precocious ornithine decarboxylase degradation might be responsible for the imbalance of polyamine metabolism. Ornithine decarboxylase is known to be degraded by the cytosolic 26S proteasome that plays an essential role in thymocyte apoptosis. In this paper we demonstrate that the inhibition of proteasome function preserves ornithine decarboxylase activity and prevents thymocytes from undergoing apoptosis after dexamethasone treatment. Since intracellular polyamine levels are also preserved, ornithine decarboxylase seems to be functionally active in maintaining polyamine homeostasis after proteasome inhibition in thymocytes. Our proposed role for the proteasome in quiescent cells upon an apoptotic stimulus is to degrade proteins like ornithine decarboxylase that are involved in the control of the cell cycle and cell survival.

Exogenous spermidine modulates glycosaminoglycan accumulation and epithelial differentiation in chick embryonic skin

We have previously shown that feather formation in chick embryonic skin depends on accumulation of sulphated glycosaminoglycans in the underlying mesenchyme, and that addition of spermidine to chick embryo fibroblasts increases the extracellular sulphated glycosaminoglycans. In the present work, using histological, histochemical and biochemical procedures, we have investigated the effects on glycosaminoglycan accumulation and on epithelial differentiation of adding spermidine and bis-cyclohexylammonium sulphate, a spermidine inhibitor, to embryonic chick skin cultures. Our results demonstrate that spermidine induces an accumulation of sulphated glycosaminoglycan and an increase in feather formation, suggesting that the morphogenetic effect of spermidine may be dependent on specific glycosaminoglycan accumulation.

Transcription factor ZBP-89 regulates the activity of the ornithine decarboxylase promoter

Appropriate cellular levels of polyamines are required for cell growth and differentiation. Ornithine decarboxylase is a key regulatory enzyme in the biosynthesis of polyamines, and precise regulation of the expression of this enzyme is required, according to cellular growth state. A variety of mitogens increase the level of ornithine decarboxylase activity, and, in most cases, this elevation is due to increased levels of mRNA. A GC box in the proximal promoter of the ornithine decarboxylase gene is required for basal and induced transcriptional activity, and two proteins, Sp1 and NF-ODC1, bind to this region in a mutually exclusive manner. Using a yeast one-hybrid screening method, ZBP-89, a DNA-binding protein, was identified as a candidate for the protein responsible for NF-ODC1 binding activity. Three lines of evidence verified this identification; ZBP-89 copurified with NF-ODC1 binding activity, ZBP-89 antibodies specifically abolished NF-ODC1 binding to the GC box, and binding affinities of 12 different double-stranded oligonucleotides were indistinguishable between NF-ODC1, in nuclear extract, and in vitro translated ZBP-89. ZBP-89 inhibited the activation of the ornithine decarboxylase promoter by Sp1 in Schneider's Drosophila line 2, consistent with properties previously attributed to NF-ODC1.

A unique interaction between polyamine and multidrug resistance (P-glycoprotein) transporters in cultured Chinese hamster ovary cells transfected with mouse mdr-1 gene

We have shown that a functional link exists between the polyamine transporter and the multi-drug resistance (MDR) efflux transporter (P-glycoprotein, P-gp) in MDR-positive cancer cells. To further explore the nature of this interaction, we have examined the effect of reduced polyamine transport activity on cellular expression and activity of P-gp acquired by either selection or transfection. Chinese hamster ovary (CHO) cells and their polyamine transport-deficient mutants (CHOMGBG) were transfected with mouse mdr-1b gene. The activity of P-gp in these cells was quantified by measuring cellular accumulation of radiolabeled taxol and etoposide in the presence and absence of the P-gp modulator SDZ PSC-833 (valspodar; a semisynthetic undecapeptide derived from cyclosporin D). The mdr-1b-transfected CHO cells accumulated 2- to 3-fold less taxol and etoposide than the controls, an accumulation defect reversed by the potent MDR modulator PSC-833. Despite expression of P-gp on the surface of mdr-1b-transfected CHOMGBG cells, this classic MDR phenotype was not observed. Similarly, CHO cells, but not CHOMGBG cells, showed MDR activity after selection with doxorubicin as determined by reduced accumulation of radiolabeled taxol. Treatment with 50 microM of reduced polymer of spermine and glutaraldehyde, a selective blocker of the polyamine transport system, reduced MDR activity in mdr-1-transfected CHO cells and restored cellular accumulation of etoposide and taxol to control levels, effects not observed in mdr-1-transfected CHOMGBG cells. Notably, mdr-1-transfected CHO cells were 4- to 16-fold more resistant to the cytotoxic effects of the P-gp substrates doxorubicin, taxol, and etoposide than were the mdr-1-transfected CHOMGBG cells. CHO cells transfected with the mdr-1 gene exhibited a 23% reduction in cellular uptake of [14C]spermidine compared with untransfected controls; spermidine accumulation in CHOMGBG cells was no different than that in untransfected controls. These data suggest that the existence of a functioning polyamine transport system may be a requirement for MDR transporter activity, while the expression of functioning P-gp appears to reduce polyamine transporter activity.

Responses to maternal separation: mechanisms and mediators

Clinical studies indicate the predominance of psychosocial factors (nurturing environment) in the genesis of the Maternal Deprivation Syndrome. Consequences of disrupting mother-infant interactions range from marked suppression of certain neuroendocrine and physiological systems after short periods of maternal deprivation to retardation of growth and behavioral development after chronic periods. We have shown that maternal separation initiates a complex adaptive biobehavioral response in preweaning rat pups that includes (1) a decrease in the synthesis of ornithine decarboxylase, an obligatory enzyme for normal cell growth and development, (2) a reduction in DNA synthesis, an index of cell multiplication, (3) abnormal patterns of neuroendocrine secretion, and (4) a suppression of cell responses to growth hormone, prolactin and insulin, three major trophic hormones. This unique pattern of adaptation to maternal separation is not related to food or temperature changes but results from a lack of a specific type of tactile stimulation of the pup by the mother. Recently, we have shown that in the absence of "nurturing touch" the brain initiates the suppression of ornithine decarboxylase gene transcription by interfering with the cell's ability to transduce the activating signal induced by the growth promoting hormones. Studies indicate that central endorphinergic pathways may mediate this action. This is accomplished by the downregulation of specific Immediate Early Genes (c-myc and max) that normally promote the synthesis of this critical growth-regulatory enzyme. These studies of short-term maternal separation not only demonstrated that maternal care is a critical regulator of pup physiology and biobehavioral development but that there are marked similarities between this animal model of maternal separation and the delay in growth and development observed in children with the deprivation syndrome or in touch-deprived premature human neonates. Our identification of a specific type of nurturing touch as a neonatal growth requirement led us to test supplemental tactile stimulation in isolated very-premature human babies. The result of our intervention with massage was dramatic. Infants not only showed marked gains in weight and behavioral development, but also a significant enhancement in sympatho-adrenal maturation. We suggest that animal models of maternal deprivation can be used to understand the integrative processing of appropriate sensory input, CNS function and end-organ physiology required to maintain normal development.

A novel technique for visualizing the intracellular localization and distribution of transported polyamines in cultured pulmonary artery smooth muscle cells

The use of a combination of monofluorescein adducts of spermidine (FL-SPD) and spermine (FL-SPM) with confocal laser scanning microscopy (CLSM) provides a useful means for monitoring the fate and time-dependent changes in the distribution of transported polyamines within living cells. Polyamine-fluorescein adducts were synthesized from fluorescein isothiocyanate and the appropriate polyamine. Monofluorescein polyamine adducts (ratio 1:1) were isolated using thin layer chromatography, and the structure and molecular weight of the monofluorescein polyamine adducts were confirmed using NMR and mass spectroscopy, respectively. The covalent linkage of the fluorescent adduct moiety to SPD and SPM did not influence their rate of uptake by bovine pulmonary artery smooth muscle cells (PASMC). Similar to 14C-SPD and 14C-SPM, the rate of uptake of 14C-FL-SPD and 14C-FL-SPM in PASMC was temperature-dependent. Treatment for 24 h with difluoromethylornithine (DFMO), a selective blocker of the enzyme ornithine decarboxylase and an inducer of the polyamine transport system, significantly increased the cellular uptake of 14C-FL-SPD and 14C-FL-SPM compared to that of control cells. When compared to control cells, treatment of PASMC with the pyrrolizidine alkaloid monocrotaline for 24 h also significantly increased the cellular uptake of 14C-FL-SPD and 14C-FL-SPM. On the other hand, 24 h treatment of PASMC with a polymer of SPM, a selective blocker of the polyamine transport system, or with free spermine, markedly reduced the cellular accumulation of 14C-FL-SPD and 14C-FL-SPM. After a 20-min treatment of PASMC with FL-SPD or FL-SPM, CLSM revealed that adduct fluorescence was localized in the cytoplasm of living cells. Treatment with DFMO increased the cytoplasmic accumulation of both FL-SPD and FL-SPM. In addition, the fluorescence observed in the cytoplasm of chinese hamster ovary cells (CHO) was significantly higher than that detected in the cytoplasm of their polyamine transport deficient variants (CHOMGBG). The results of this study provide the first evidence of the utility of a novel method for visualizing the uptake, distribution, and cellular localization of transported polyamines in viable cultured mammalian cells.

Somatic and germline clone analysis in mutants of the S-adenosylmethionine synthetase encoding gene in Drosophila melanogaster

We have analysed the phenotypic consequences of homozygous mutant clones in the S-adenosylmethionine synthetase encoding gene in Drosophila melanogaster. The results suggest that SamS function is required for cell proliferation/growth in embryonic/early larval cells and during development of imaginal disc cells. Homozygous SamS germline clones can, however, develop and give rise to viable heterozygous offspring. This offspring expresses a Minute-like phenotype. We suggest that this phenotype is caused by an obstruction of the polyamine biosynthesis.

Alpha-difluoromethylornithine (DFMO) as a potent arginase activity inhibitor in human colon carcinoma cells

Alpha-difluoromethylornithine (DFMO) is commonly used as a specific ornithine decarboxylase (ODC, EC4.1.1.17) irreversible inhibitor. ODC is the enzyme responsible for polyamine biosynthesis, which has been shown to be strictly necessary for cell proliferation. In HT-29 Glc-/+ cells, L-arginine is the major precursor of these molecules through the sequential actions of arginase, which leads to L-ornithine generation and ODC. L-ornithine, a substrate for ODC, retroinhibits arginase. Since DFMO is an ornithine analogue, we searched for a direct effect of this agent upon arginase. The flux of L-arginine through arginase in intact cells was inhibited by 51+/-11% by 10 mM of DFMO whereas 10 mM of L-valine, a known potent arginase inhibitor, inhibited this flux by 73+/-6%. DFMO equilibrated between extracellular and intercellular spaces and, when used at 10-mM concentration, was without effect on L-arginine net uptake. Measurement of arginase activity in HT-29 cell homogenates with increasing concentrations of DFMO and L-arginine led to an inhibition with a calculated Ki (inhibitory constant) equal to 3.9+/-1.0 mM. L-ornithine was less effective than DFMO in inhibiting arginase activity. Bovine liver arginase, used as another source of the enzyme, was also severely inhibited by DFMO. The inhibitory effect of DFMO upon arginase, one step upstream of the ODC reaction in the metabolic conversion of L-arginine to polyamines, is of potential physiological importance, since it could alter the production of ornithine and thus its metabolism in pathways other than the ODC pathway.

Induction of spermidine/spermine N1-acetyltransferase in human cancer cells in response to increased production of reactive oxygen species

Reactive oxygen species (ROS) are involved in a number of disease states where they are believed to be responsible for cellular damage. In this study we examined the effect of ROS generation on polyamine catabolism. Treatment of human breast cancer cells with either H2O2 or hyperoxia increased the activity of spermidine/spermine N1-acetyltransferase (SSAT). These increases occurred before any significant signs of cellular injury. Agents known to decrease the production of reactive oxygen species such as dimethylthiourea and o-phenanthroline prevented the increase in SSAT activity indicating ROS involvement in the induction process. These results suggest that induction of SSAT may be a protective response to oxidative stress in mammalian cells facilitating removal of polyamines from the cell to prevent their toxic accumulation.

A novel calcium-independent enzyme capable of incorporating putrescine into proteins

A Ca(++)-independent enzyme capable of incorporating [3H]-putrescine into proteins was detected in the rat intestine mucosa. The Ca(++)-independent incorporation of [3H]-putrescine into proteins was temperature-, pH-, time-, and dose-dependent. However, this enzyme was absent in the gastric mucosa. Similar to testicular Ca(++)-dependent transglutaminase, the optimal pH of intestinal Ca(++)-independent enzyme was 9.0. At 10(-5) M or less putrescine concentrations, the Ca(++)-independent enzyme in an intestinal cytosol preparation showed a greater activity than did the Ca(++)-dependent transglutaminase. However, at higher putrescine concentrations, the latter showed a greater activity than did the former. Both the intestinal Ca(++)-dependent and independent enzymes were inhibited by cystamine, thermal labile at 50 degrees C and precipitated by 30 to 50% saturation of ammonium sulfate. The fact that these two enzymes shared many similar characteristics, with the exceptions of Ca(++)-requirement, suggests that they may have similar active site and intrinsic molecular function(s).

Two-stage exposure of Syrian-hamster-embryo cells to environmental carcinogens: superinduction of ornithine decarboxylase correlates with increase of morphological-transformation frequency

As part of environmental toxicology, it is important to assess both the carcinogenic potential of xenobiotics and their mode of action on target cells. Since dysregulation of ornithine decarboxylase (ODC), a rate-limiting enzyme of polyamine biosynthesis, is considered as an early and essential component in the process of multistage carcinogenesis, we have studied the mode of ODC induction in Syrian-hamster-embryo(SHE) cells stage-exposed to carcinogens and to non-carcinogens. One-stage (5 hr) treatment of SHE cells with 50 microM clofibrate (CLF), a non-genotoxic carcinogen, or with 0.4 microM benzo(a)pyrene (BaP), a genotoxic carcinogen, slightly decreased basal ODC activity. Using the 2-stage exposure, 1 hr to carcinogen, then replacement by TPA for 5 hr, the ODC activity was higher than that obtained with TPA alone. This ODC superinduction was not observed when SHE cells were similarly pre-treated with non-carcinogenic compounds. Several environmental chemicals, pesticides, solvents, oxidizers and drugs were investigated with this SHE cell model. With one-stage exposure, some xenobiotics decreased basal ODC activity, while for others ODC changes were not noticeable. With 2-stage exposure (chemical followed by TPA), all carcinogens amplified the TPA-inducing effect, resulting in ODC superinduction. Comparative studies of the action of carcinogens and of non-carcinogens, using 2-stage exposure protocols, clearly show a close relationship between ODC induction rate and morphological transformation frequency.

Polyamine metabolism of rat gastric mucosa after oral administration of hypertonic sodium chloride solution

Oral administration of 1 ml of 3.42 M NaCl solution to rats induced spermidine/spermine N1-acetyltransferase (SSAT) activity in gastric mucosa as well as ornithine decarboxylase (ODC) activity. SSAT activity increased and peaked at 5 h and again at 7 h, whereas ODC activity peaked at 6 h. SSAT mRNA also increased after 3.42 M NaCl administration to an extent similar to the increase in SSAT activity at 5 h. Intracellular putrescine level and DNA synthesis were increased by NaCl administration. A polyamine oxidase inhibitor, N,N'-bis(2,3-butadienyl)-1,4-butanediamine (MDL-72527), but not an ODC inhibitor, alpha-difluoromethylornithine (DFMO), inhibited the increases in putrescine level and DNA synthesis at 5 h. The inhibition of DNA synthesis by MDL-72527 was reversed by putrescine administration. In contrast, both MDL-72527 and DFMO inhibited the increase in putrescine level and DNA synthesis at 16.5 h. These findings suggest that putrescine produced from preexistent spermidine by SSAT is responsible for the initial DNA synthesis after mucosal injury induced by NaCl and that both SSAT and ODC are involved in formation of putrescine, which is required for subsequent DNA synthesis.

Polyamines may regulate S-phase progression but not the dynamic changes of chromatin during the cell cycle

Several studies suggest that polyamines may stabilize chromatin and play a role in its structural alterations. In line with this idea, we found here by chromatin precipitation and micrococcal nuclease (MNase) digestion analyses, that spermidine and spermine stabilize or condense the nucleosomal organization of chromatin in vitro. We then investigated the possible physiological role of polyamines in the nucleosomal organization of chromatin during the cell cycle in Chinese hamster ovary (CHO) cells deficient in ornithine decarboxylase (ODC) activity. An extended polyamine deprivation (for 4 days) was found to arrest 70% of the odc- cells in S phase. MNase digestion analyses revealed that these cells have a highly loosened and destabilized nucleosomal organization. However, no marked difference in the chromatin structure was detected between the control and polyamine-depleted cells following the synchronization of the cells at the S-phase. We also show in synchronized cells that polyamine deprivation retards the traverse of the cells through the S phase already in the first cell cycle. Depletion of polyamines had no significant effect on the nucleosomal organization of chromatin in G1-early S. The polyamine-deprived cells were also capable of condensing the nucleosomal organization of chromatin in the S/G2 phase of the cell cycle. These data indicate that polyamines do not regulate the chromatin condensation state during the cell cycle, although they might have some stabilizing effect on the chromatin structure. Polyamines may, however, play an important role in the control of S-phase progression.

Direct inhibitory effect of uremic toxins and polyamines on proliferation of VERO culture cells

The dialysate fluid of uremic patients exhibits, in vitro, an inhibitory effect on cell growth, owing to urea, guanidino compounds, and substances named middle molecules. The polyamines are compounds which exhibit high levels in biological fluids during either normal development or disease such as psoriasis, uremia, and tumors. Dialysate and middle molecules show toxicity and degeneration of the organotype cultures, whereas the free polyamines and nonrecirculated dialysate do not have any toxic effect. The aim of this study is to analyze the effects of polyamines, nonrecirculated dialysate, and middle molecules of uremic patients in periodic hemodialysis on cultured VERO (fibroblast-like cells) growth. These cells show an inhibition of growth in middle molecules or 2 x 10(-4) M putrescine and a stimulation with nonrecirculated dialysate and 2 x 10(-8) M putrescine. The effect is different because the cultures with middle molecules begin growth again after 24 hr, whereas in the presence of 2 x 10(-4) M putrescine no further growth is observed. Cells maintained in middle molecules + 2 x 10(-8) M putrescine show an irreversible degeneration, attesting a toxic effect due to the low molarities of putrescine. The electron microscopy shows alteration of cytoplasmic, mitochondrial, and nuclear membranes, but no chromatin fragmentation with either middle molecules or 2 x 10(-4) M putrescine: this suggests that the cells do not die of apoptosis. In conclusion, during uremia the polyamines could cause toxic effects, even at low concentrations, on cells stressed by other toxic stimuli.

Polyamines regulate both transcription and translation of the gene encoding ornithine decarboxylase antizyme in mouse

The degradation of ornithine decarboxylase (ODC) is mediated by antizyme, a protein regulated by the end-products of ODC activity, the polyamines. High levels of polyamines induce a +1 ribosomal frameshift in the translation of the rat antizyme message leading to the expression of a full-length protein. We have studied whether the regulation of antizyme expression occurs only at the level of translation or whether polyamine levels also affect the transcription of the antizyme gene. Thus, we have cloned and sequenced the mouse homologues of the rat ODC-antizyme gene and cDNA. Northern blot analysis shows that although high concentrations of polyamines do not affect the steady-state levels of antizyme message in L1210 leukemia cells, polyamine depletion using 2-(difluoromethyl)ornithine [Orn(F2Me)] leads to a marked decrease in mRNA levels. Results of transient transfections of luciferase-reporter-gene constructs driven by antizyme promoter fragments in untreated and Orn(F2Me)-treated Balb/C 3T3 cells indicate that the transcription of the antizyme gene is altered upon polyamine depletion. The amount of antizyme protein on Western blots was also altered by polyamine depletion and addition, and the polysomal distribution of antizyme message suggests a general translational increase of the message when polyamine concentrations are high. These results indicate a role for polyamines in the transcriptional and translational regulation of ornithine decarboxylase antizyme.

JSJ-1, an anti-spermidine monoclonal antibody with potential clinical applications

Polyamines have been implicated in a wide variety of functions including nucleic acid synthesis and protein synthesis. Their levels have been shown to increase in response to cell growth and differentiation. Use of polyamines as prognostic indicators of proliferative disease conditions has been hindered by the lack of suitable rapid and sensitive assays. We report the characterization of an anti-spermidine antibody, JSJ-1, with novel putrescine cross reactivity. JSJ-1 cross-reacts more strongly with putrescine (11%) than with spermine (6%). This suggests that the aminobutyl group common to both putrescine and spermidine is an important element in the antibody-antigen interaction. We have demonstrated that antibody-spermidine binding is effected by increased ionic strength. This finding is consistent with the antibody-antigen interaction being ionic. The JSJ-1 antibody has been successfully used to detect increased polyamine levels in clinical serum samples and identify those with increased polyamine levels.

Neurotoxicity of polyamines and pharmacological neuroprotection in cultures of rat cerebellar granule cells

We have studied in a well-characterized in vitro neuronal system, cultures of cerebellar granule cells, the toxicity of polyamines endogenously present in the brain: spermine, spermidine, and putrescine. Twenty-four-hour exposure of mature (8 days in vitro) cultures to 1-500 microM spermine resulted in a dose-dependent death of granule cells, with the half-maximal effect being reached below 50 microM concentration. Putrescine was moderately toxic but only at 500 microM concentration. Spermidine was tested at 50 and 100 microM concentration and its toxicity was evaluated to be about 50% that of spermine. Neuronal death caused by spermine occurred, at least in part, by apoptosis. Spermine toxicity was completely prevented by competitive (CGP 39551) and noncompetitive (MK-801) antagonists of the NMDA receptor, but was unaffected by a non-NMDA antagonist (NBQX) or by antagonists of the polyamine site present on the NMDA receptor complex, such as ifenprodil. A partial protection from spermine toxicity was obtained through the simultaneous presence of free radical scavengers or through inhibition of the free radical-generating enzyme nitric oxide synthase, known to be partially effective against direct glutamate toxicity. The link between spermine toxicity and glutamate was further strengthened by the fact that, under culture conditions in which glutamate toxicity was ineffective or much reduced, spermine toxicity was absent or very much decreased. Exposure to spermine was accompanied by a progressive accumulation of glutamate in the medium of granule cell cultures. This was attributed to glutamate leaking out from dying or dead cells and was substantially prevented by the simultaneous presence of MK-801 or CGP 39551. The present results demonstrate that polyamines are toxic to granule cells in culture and that this toxicity is mediated through the NMDA receptor by interaction of exogenously added polyamines with endogenous glutamate released by neurons in the medium. The involvement of brain polyamines, in particular spermine and spermidine, in excitotoxic neuronal death is strongly supported by our present results.

Activation of intestinal mitochondrial phospholipase D by polyamines and monoamines

Intestinal mitochondria have a phospholipase D (PLD) activity which was stimulated by polyamines and monoamines resulting in the formation of phosphatidic acid (PA) from endogenous phospholipids. When stimulated by polyamines, mitochondrial PLD utilized endogenous phosphatidylethanolamine (PE) as substrate whereas stimulated by monoamines, both PE and phosphatidylcholine (PC) were hydrolysed. Stimulation of PA formation by spermine was enhanced by the presence of calcium. Since polyamines are known to alter the calcium transport by mitochondria and PA is known to possess an ionophore effect, stimulation of PA formation in mitochondria by polyamines suggests that polyamine-induced alteration in calcium homeostasis might involve a PA related mechanism.

Ordered cell cycle phase perturbations in Chinese hamster ovary cells treated with an S-adenosylmethionine decarboxylase inhibitor

The polyamines putrescine, spermidine, and spermine are needed for normal cell cycle progression and polyamine-depleted cells cease to proliferate. We have investigated cell cycle perturbations in Chinese hamster ovary cells seeded in the presence of 4-amidinoindan-1-one 2'-amidinohydrazone (CGP 48664), a potent inhibitor of S-adenosylmethionine decarboxylase, an enzyme which is essential for the synthesis of spermidine and spermine. At 9 h and at 1, 2, and 3 days after seeding, cells were labelled with the thymidine analog bromodeoxyuridine (BrdUrd) for 30 min, after which the BrdUrd-containing medium was removed and the cells were allowed to progress through the cell cycle in BrdUrd-free medium before sampling (post-labelling time). Using flow cytometry, coupled with an indirect immunofluorenscence technique, utilizing monoclonal anti-BrdUrd and secondary fluorescein-isothiocyanate-conjugated antibodies, and the DNA stain propidium iodide, cellular BrdUrd and DNA contents were quantified. By investigating the movement of BrdUrd-nonlabelled G1 cells into S phase during the post-labelling time, a measure of the G1/S transition was obtained. The time of appearence in G1 of BrdUrd-labelled cells which had divided was used to monitor the length of the G2+M phase. A measure of the S phase length (DNA synthesis time) was obtained by monitoring the progression of BrdUrd-labelled cells through S phase. CGP 48664-induced spermine depletion significantly increased the length of the S phase already 9 h after seeding cells in the presence of the inhibitor. No effects on the G1/S transition or on the length of the G2+M phase were observed until 2 days after seeding.

Polyamine-like immunoreactivity in rat neurons

The localization of polyamine (PA) pools in motor, sensory, and autonomic neurons and in the nerve cells of the hypothalamo-hypophysial system of rats was examined by immunocytochemical method using the monoclonal antibody ASPM-29 specific to spermine (Spm) and spermidine (Spd) fixed in situ. Strong PA immunoreactivity was found in the cytoplasm and dendrites of the large perikaryon of motor neurons in the anterior spinal column, in the Purkinje cells of the cerebellum, in the pyramidal cells of the cerebrum, in the nerve cells of the paraventricular and supraoptic nuclei in the hypothalamus, and in the nerve cells of the spinal and autonomic ganglions. No PA immunoreactivity was seen in the nucleus and nerve terminals of the neurons. The PA immunoreactivities in the motor and sensory neurons were characterized by clustered masses and blocks of immunoreactive cells. Irrespective of location, small and medium-sized neurons were weakly PA-positive. The glia cells, some stellite cells, and Schwann cells were almost completely PA-negative. These results may suggest that in neurons PAs are not transported axonally, but are located in conjunction with Nissl bodies (the rough endoplasmic reticulum), specified as sites for protein synthesis within cells.

Central administration of morphine inhibits brain and liver ornithine decarboxylase activity in neonatal rats: involvement of transcription- and non-transcription-dependent mechanisms

This study examined whether the developmental deficits usually observed in infants born to opiate addicted mothers could involve effects on ornithine decarboxylase, a growth-controlling enzyme. Intracerebroventricular (i.c.v.) injection of a single dose of morphine (2 microg) to 6-day-old rats markedly decreased basal brain and liver ornithine decarboxylase activity as well as the increases in hepatic ornithine decarboxylase activity produced by subcutaneously (s.c.) administered insulin, an important trophic hormone. Centrally applied morphine acts supraspinally to downregulate peripheral ornithine decarboxylase activity, since s.c. administration of the same dose as used i.c.v. decreased neither basal liver ornithine decarboxylase levels nor tissue responsiveness to insulin. This does not imply that the opiate is unable to affect ornithine decarboxylase when applied systemically. In fact, a robust inhibition of both basal and induced liver ornithine decarboxylase activity was obtained in rat pups given 20 microg of morphine s.c. This larger dose is able to trigger the hepatic ornithine decarboxylase effects presumably by stimulating opiate receptors located at central sites after crossing the blood-brain barrier and penetrating into the brain. Concomitant administration of naloxone plus morphine i.c.v. prevented morphine from downregulating ornithine decarboxylase activity, confirming the participation of supraspinal opioid receptors in morphine ornithine decarboxylase actions. Finally, as was the case for insulin induced stimulation of ornithine decarboxylase activity, i.c.v. injection of morphine markedly diminished insulin induced stimulation of hepatic ornithine decarboxylase mRNA accumulation. In turn, contrary to the inhibition of basal ornithine decarboxylase activity, morphine did not lower basal hepatic ornithine decarboxylase mRNA levels when given alone. Thus, CNS morphine can apparently suppress tissue ornithine decarboxylase expression through both transcriptional and posttranscriptional mechanisms. The evidence obtained suggest that postnatal exposure to opiate drugs might detrimentally affect development by altering normal tissue ornithine decarboxylase ontogeny.