Role of polyamines in the control of cell proliferation and differentiation

Ornithine decarboxylase, polyamines and CD11b expression in HL-60 cells during differentiation induced by retinoic acid

Polyamines (PA) and retinoic acid affect mammalian cell growth, differentiation and apoptosis. Retinoic acid induces granulocytic differentiation of mieloid cell lines and, during this process, is responsible for the expression of CD11b, a surface antigen. In this study we investigate the effects of retinoic acid on HL-60 cells, monitoring ornithine decarboxylase (ODC) activity (enzyme rate of PA), putrescine (PUT), spermidine (SPD), spermine (SPM) levels, CD11b myeloid surface marker differentiation, cell cycle, and apoptosis. ODC activity and PUT levels are correlated with mieloid cell differentiation induced by retinoic acid treatment. Only the ODC/PUT ratio is connected with retinoic acid treated HL-60 cells. Treated cultures show a decrease of proliferation and a cell block in the G0/G1 phase, with consequent diminished S phase. The G0/G1 and S phases are significantly related to ODC activity and to PUT and SPD behavior, whereas in differentiating condition only the decrease of PUT is related to the S phase. CD11b expression, stimulated by retinoic acid treatment, is associated with the SPM trend. Total PA behavior agrees with apoptotic cell increase after 96 h of stimulation. Our data show that retinoic acid treatment modifies ODC activity and the turnover of PA. PUT, SPD and SPM, therefore, have a different role, and may be involved in the differentiative/apoptotic program of retinoic acid treated HL-60 cells.

Impact of Topoisomerase II alpha and spermine on the clinical outcome of children with acute lymphoblastic leukemia

It has been reported in the literature that a leukemic cell may be (or become) resistant to anti-cancer treatment because many mechanisms, such as efflux membrane pump (multi-drug resistance, MDR-P170), intracellular transport (LRP, MRP), or different detoxification systems (glutathione transferases, methallothioneines) may be implicated. Topoisomerase II alpha (TopoII) are also reported as responsible for resistance since their main action is to repair DNA breakage. Polyamines are described as having a protective DNA action by stabilizing the double stranded DNA helix. For these reasons we investigated 65 children with acute lymphoblastic leukemia using an immunocytochemical method to elucidate the potential role of Topoisomerase and polyamines in drug resistance. Most children (60/65) were treated with the French (acute lymphoblastic leukemia, ALL) protocol (FRALLE-93) in which B and C arms include (at least) VP16. Children with cytoplasmic TopoII positivity (18 cases) were more resistant since their overall survival was 34 months compared to more than 110 months for negative cases ( P = 0.0003). Polyamines may be associated with drug resistance since the overall survivals were 51 months and 92 months for positive and negative patients, respectively, but the P-value is only 0.13. We conclude that Topoisomerase and polyamines must be tested at diagnosis as new possible markers for chemo-resistance. Larger series are needed to confirm these preliminary results and to verify if the use of anti epipodophillotoxin agents (as it is the case for FRALLE B or C) should be excluded for positive cases.

Differential in vitro development of inflorescences in long and short day Lemna spp.: involvement of ethylene and polyamines

In vitro-development of Lemna inflorescences on minimal medium is known to differ in long day (LDP) and short day (SDP) plants (Z. Pfl, physiol. 77, 395). In LDP pistil growth predominates, while in SDP stamen growth predominates. This indicates that LDP and SDP inflorescences differ in endogenous hormones and depend for a balanced male-female development on different plant-supplied factors (Z. Pfl. physiol. 80, 283 and 298). Here inflorescences of the LDP L. gibba and the SDP L. aequinoctialis were tested for differences in ethylene-polyamine (PA) relations, as ethylene and PAs are inversely related (shared precursor, mutual inhibition of synthesis), and exogenous ethylene has been shown previously to restore male-female balance in SDP inflorescences (Z. Pfl. physiol. 80, 283). Promotion of pistil or stamen growth indicates a predominance of ethylene and PAs in LDP and SDP, respectively. Hence, in LDP, exogenous PAs and inhibitors of ethylene synthesis, and in SDP, an inhibitor of PA-synthesis, were applied to restore the male-female balance in vitro. In L. aequinoctialis (SDP), application of methylglyoxal-bis(guanylhydrazone) (MGBG), an inhibitor of spermidine (SD) synthesis, resulted in near normal development via stamen inhibition and/or pistil promotion. In L. gibba (LDP), ethylene inhibition was effective, especially by aminoethoxyvinylglycine (AVG), which reduced pistil growth. Effects of alpha-aminooxyacetic acid (AOA) were less clear. Putrescine (PUT) promoted stamen growth under certain circumstances, perhaps acting as a precursor for the more active SD. SD effects were concentration-dependent for pistil and stamen. Most importantly, increases in SD turned pistil promotion into inhibition and almost normalised floral development. Spermine (SM) enhanced stamen growth. Results are conclusive that PA-ethylene relationships are involved in inflorescence development in a contrasting manner in LDP and SDP. It is apparent that in whole plants the LDP supplies the inflorescences with factors inhibiting ethylene and/or stimulating PA-synthesis. In SDP the converse is true.

The chemopreventive agent alpha-difluoromethylornithine blocks Ki-ras-dependent tumor formation and specific gene expression in Caco-2 cells

Mutation of the Kirsten-ras (Ki-ras) proto-oncogene occurs frequently in colorectal cancers. alpha-Difluoromethylornithine (DFMO), an irreversible inhibitor of the polyamine biosynthetic enzyme, ornithine decarboxylase (ODC), inhibits Ki-ras transformation and colon tumorigenesis in carcinogen-treated animal models by mechanisms yet to be elucidated. Caco-2 cells transfected with an activated Ki-ras, but not parental cells, formed tumors in severe combined immunodeficient (SCID) mice. DFMO treatment (2% in drinking water) prevented tumor growth. Gene expression profiling was performed to identify Ki-ras-and DFMO-dependent patterns of gene expression. Microarray results were validated with real-time or semi-quantitative RT-PCR and/or Western blot analysis. Genes upregulated in Caco-2 cells expressing an activated Ki-ras encoded cytoskeletal-, transport-, protease-, and gap junction-associated proteins. These genes are important for normal development and maintenance of colonic epithelial tissue. Caco-2 cells transfected with an activated Ki-ras displayed increased expression of the integrin alpha 1 (INGA1) and enhanced cell migration on laminin. These parameters were unaffected by DFMO, but Ki-ras-dependent migration was inhibited by INGA1 antibodies. Other Ki-ras-dependent, but DFMO-independent, genes included transglutaminase (TGase) and kallikrein 6 (KLK6). Ki-ras-transfected cells also expressed increased levels of connexin43 (Cx43) (RNA and protein), tight junction protein, and endothelin 1. DFMO reversed these increases. The results indicated that the Ki-ras oncogene caused changes in experimental cell migration and cell-cell communication genes and that some of these changes could be reversed by DFMO.

Effects of polyamines on mitochondrial Ca2+ transport

Mammalian mitochondria are able to enhance Ca(2+) accumulation in the presence of polyamines by activating the saturable systems of Ca(2+) inward transport and buffering extramitochondrial Ca(2+) concentrations to levels similar to those in the cytosol of resting cells. This effect renders them responsive to regulate free Ca(2+) concentrations in the physioloical range. The mechanism involved is due to a rise in the affinity of the Ca(2+) transport system, induced by polyamines, most probably exhibiting allosteric behaviour. The regulatory site of this mechanism is the so-called S(1) binding site of polyamines, which operates in physiological conditions and is located in the energy well between the two peaks present in the energy profile of mitochondrial spermine transport. Spermine is bidirectionally transported across teh inner membrane by cycling, in which influx and efflux are driven by electrical and pH gradients, respectively. Most probably, polyamine affects the Ca(2+) transport system when it acts from the outside-that is, in the direction of its uniporter channel, in order to reach the S(1) site. Important physiological functions are related to activation of Ca(2+) transport systems by polyamines and their interactions with the S(1) site. These functions include a rise in the metabolic rate for energy supply and modulation of mitochondrial permeability transition induction, with consequent effects on the triggering of the apoptotic pathway.

Transcriptional and translational control of ornithine decarboxylase during Ras transformation

ODC (ornithine decarboxylase) activity is induced following ras activation. However, the Ras effector pathways responsible are unknown. These experiments used NIH-3T3 cells expressing partial-loss-of-function Ras mutants to activate selectively pathways downstream of Ras and examined the contribution of each pathway to ODC induction. Overexpression of Ras12V, a constitutively active mutant, resulted in ODC activities up to 20-fold higher than controls. Stable transfections of Ras partial-loss-of-function mutants and constitutively active forms of MEK (MAPK kinase) and Akt indicated that activation of more than one Ras effector pathway is necessary for the complete induction of ODC activity. The increase in ODC activity in Ras12V-transformed cells is not owing to a substantial change in ODC protein half-life, which increased by <2-fold. Northern-blot analysis and reporter assays suggested that the mechanism of ODC induction involves both a modest increase in the transcription of ODC mRNA and a much more considerable increase in the translation of mRNA into protein. ODC transcription was controlled through a pathway dependent on Raf/MEK/ERK (where ERK stands for extracellular-signal-regulated kinase) activation, whereas activation of the phosphoinositide 3-kinase and the Raf/MEK/ERK pathways were necessary for translational regulation of ODC. The increase in ODC synthesis was accompanied by changes in phosphorylation of eukaryotic initiation factor 4E and its binding protein 4E-BP1. Results show that the phosphoinositide 3-kinase pathway regulates phosphorylation of both proteins, whereas the Raf/MEK/ERK pathway affects only the eukaryotic initiation factor 4E phosphorylation.

Functional GATA- and initiator-like-elements exhibit a similar arrangement in the promoters of Caenorhabditis elegans polyamine synthesis enzymes

Polyamines are essential cell constituents involved in growth processes. In Caenorhabditis elegans the polyamine synthetic pathway consists of three enzymes, ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (AdoMetDC) and spermidine synthase. Their gene expression pattern was determined in C. elegans by microinjection of green fluorescent protein (GFP) reporter gene constructs. All transgenic animals exhibited GFP expression in their intestinal cells. For the AdoMetDC promoter, fluorescence was additionally observed in dopaminergic neurons, while the ODC promoter also drives a male-specific GFP expression in the distal part of the reproductive system. The minimal promoter regions for intestine-specific expression of the AdoMetDC and spermidine synthase genes were determined by deletion mutants. Using the Seqcomp and Family Relation programs, a similar arrangement of putative cis-regulatory elements within these regions and also within the respective regions of the orthologous Caenorhabditis briggsae genes were found. The functional conservation of the latter was confirmed by heterologous transformation experiments. Moreover, the involvement of putative GATA- and initiator-(Inr)-like-elements in gene expression was determined by mutagenesis studies. RNase protection assay revealed that the Inr-like-element does not represent the main transcriptional start site, at least of C. elegans spermidine synthase. In conclusion, a similar minimal promoter architecture was found for C. elegans as well as C. briggsae AdoMetDC and spermidine synthase, two genes that participate in the same metabolic pathway.

A perspective of polyamine metabolism

Polyamines are essential for the growth and function of normal cells. They interact with various macromolecules, both electrostatically and covalently and, as a consequence, have a variety of cellular effects. The complexity of polyamine metabolism and the multitude of compensatory mechanisms that are invoked to maintain polyamine homoeostasis argue that these amines are critical to cell survival. The regulation of polyamine content within cells occurs at several levels, including transcription and translation. In addition, novel features such as the +1 frameshift required for antizyme production and the rapid turnover of several of the enzymes involved in the pathway make the regulation of polyamine metabolism a fascinating subject. The link between polyamine content and human disease is unequivocal, and significant success has been obtained in the treatment of a number of parasitic infections. Targeting the polyamine pathway as a means of treating cancer has met with limited success, although the development of drugs such as DFMO (alpha-difluoromethylornithine), a rationally designed anticancer agent, has revolutionized our understanding of polyamine function in cell growth and provided 'proof of concept' that influencing polyamine metabolism and content within tumour cells will prevent tumour growth. The more recent development of the polyamine analogues has been pivotal in advancing our understanding of the necessity to deplete all three polyamines to induce apoptosis in tumour cells. The current thinking is that the polyamine inhibitors/analogues may also be useful agents in the chemoprevention of cancer and, in this area, we may yet see a revival of DFMO. The future will be in adopting a functional genomics approach to identifying polyamine-regulated genes linked to either carcinogenesis or apoptosis.

Influence of testosterone on regulation of ODC, antizyme, and N1-SSAT gene expression in mouse kidney

Polyamines are involved in the control of the cell cycle and cell growth. In murine kidney, testosterone enhances gene expression of ornithine decarboxylase (ODC), the first enzyme in polyamine biosynthesis. In this study, we document the time course effect of testosterone on 1) gene expression of ODC, antizyme 1 (AZ1), and spermidine/spermine-N1-acetyltransferase (N1-SSAT); 2) ODC activity in proximal convoluted tubules (PCT) and cortical proximal straight tubules (CPST); and 3) renal polyamine levels. Female mice were treated with testosterone for a period of 1, 2, 3, and 5 consecutive days. ODC gene expression was extremely low in kidneys of untreated female mice compared with that of males. Consequently, the renal putrescine level was sevenfold lower in females than in males, whereas spermidine and spermine levels did not differ between sexes. In female kidneys, testosterone treatment sharply increased ODC mRNA and protein levels as well as ODC activity. Testosterone increased the expression of ODC in PCT and CPST over different time courses, which suggests that ODC activity is differentially regulated in distinct tubules. The expression of AZ1 and N1-SSAT mRNA was similar in male and female mouse kidneys. Testosterone treatment enhanced AZ1 and N1-SSAT mRNA levels in a time-dependent manner by unknown molecular mechanisms. Putrescine and spermidine levels increased after testosterone treatment in female kidneys. Surprisingly, although ODC protein and activity were undetectable in female kidneys, the levels of AZ1 mRNA and protein were similar to those in males. Therefore, one may propose that ODC protein could be continuously degraded by AZ1 in female kidneys.

Long-lasting CNS effects of a short-term chemical knockout of ornithine decarboxylase during development: nicotinic cholinergic receptor upregulation and subtle macromolecular changes in adulthood

Ornithine decarboxylase (ODC) and the polyamines play an essential role in brain cell replication and differentiation and polyamines also regulate the function of nicotinic acetylcholine receptors (nAChRs). We administered alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ODC, to neonatal rats on postnatal days 5-12, during the mitotic peak of the cerebellum, a treatment regimen that achieves a chemical knockout of ODC activity and polyamine depletion limited to the treatment period. Although growth inhibition and gross dysmorphology were limited to the cerebellum, both alpha7 and alpha4beta2 nAChRs were upregulated in adulthood in the frontal cortex, hippocampus and thalamus, with the largest effect in the latter region, primarily in females. Receptor upregulation was accompanied by abnormalities in macromolecular indices of cell packing density and cell membrane surface area, but the generalized cellular alterations did not share the regional or sex selectivity shown by the effects on nAChRs. Elevated DNA concentration was most notable in the hippocampus and was associated with augmented levels of glial fibrillary acidic protein, thus implying gliosis as the cause of the increased number of cells. DFMO's effects on both nAChR expression and cellular biomarkers resembled those of developmental exposure to nicotine. Accordingly, some of the effects may represent a specific alteration in nAChR signaling evoked by polyamine depletion during a critical developmental window. Alterations in polyamine gating of cholinergic synaptic signaling may thus contribute to the adverse neurobehavioral effects of numerous neuroteratogens that directly or indirectly disrupt the ODC/polyamine pathway.

Effect of spermine synthase on the sensitivity of cells to anti-tumour agents

The role of spermine in the sensitivity of cells to various established and experimental anti-tumour agents was examined, using paired cell lines that possess or lack spermine synthase. All spermine-synthase-deficient cells had no detectable spermine, and elevated spermidine, content. Spermine content did not alter the cell growth rate. There was little or no difference in sensitivity of immortalized mouse embryonic fibroblasts to doxorubicin, etoposide, cisplatin, methylglyoxal bis(guanylhydrazone) or H(2)O(2) and only a slight increase in sensitivity to vinblastine and nocodazole. However, the absence of spermine clearly increased the sensitivity to 1,3-bis(2-chloroethyl)- N -nitrosourea, suggesting that depletion of spermine may be a useful way to increase the anti-neoplastic effects of anti-tumour agents that form chloroethyl-mediated interstrand DNA cross-links. The effects of spermine on the response to polyamine analogues (which have been proposed to be useful anti-neoplastic agents) were complex, and depended on the compound examined and on the cells tested. Sensitivity to CHENSpm ( N (1)-ethyl- N (11)-[(cycloheptyl)methyl]-4,8-diazaundecane) was substantially greater in immortalized fibroblasts that lack spermine. In contrast, BE-3-4-3 [ N (1), N (12)-bis(ethyl)spermine] and BE-3-3-3 [ N (1), N (11)-bis(ethyl)norspermine] were more active against cells that contained spermine. The presence of spermine correlated with a greater induction of spermidine/spermine- N (1)-acetyltransferase by BE-3-3-3, which is consistent with suggestions that this induction is important for the response to this drug. These findings support the concepts that different polyamine analogues have different sites of action and that CHENSpm has a different site of action from BE-3-3-3.

PKC alpha mediates maternal touch regulation of growth-related gene expression in infant rats

During short-term periods of separation of rat pups from their mothers, the loss of certain sensory signals suppresses the increase in ornithine decarboxylase (ODC) gene expression induced by the growth-promoting hormones prolactin (PRL) and growth hormone (GH). Here, we identify a molecular mechanism through which maternal separation (MS) curtails ODC expression. Our results demonstrate that the absence of specific tactile stimuli provided by the mother limits PRL-evoked stimulation of ODC biosynthesis by interfering with sn-1,2-diacylglycerol's (DAG) ability to activate protein kinase Calpha (PKCalpha) and consequently c-myc mRNA and max mRNA expression. The proteins encoded by these proto-oncogenes function as direct transactivators of the ODC gene. As ODC activity is obligatory for normal cell replication and differentiation, PKCalpha activation by DAG represents an important control point at which 'nurturing touch' regulates growth and development of the neonate. Such a mechanism can explain the maladaptive consequences of disrupting mother-infant tactile interactions as occurs in isolated premature babies. Also, it could provide a basis for developing therapeutic interventions to maximize growth potential in children failing-to-thrive despite normal maternal care.

Antineoplastic activity of honey in an experimental bladder cancer implantation model: in vivo and in vitro studies

OBJECTIVES

The antitumor effect of bee honey against bladder cancer was examined in vitro and in vivo.

METHODS

Three human bladder cancer cell lines (T24, 253J and RT4) and one murine bladder cancer cell line (MBT-2) were used in these experiments. In an in vitro study, the antitumor activity was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, TdT-mediated dUTP-biotin nick end labeling (TUNEL) assay, 5-Bromodeoxyuridine (BrdU) labeling index and flowcytometry (FCM). In the in vivo study, cancer cells were implanted subcutaneously in the abdomens of mice, and the effects were assessed by the tumor growth.

RESULTS

In vitro studies revealed significant inhibition of the proliferation of T24 and MBT-2 cell lines by 1-25% honey and of RT4 and 253J cell lines by 6-25% honey. BrdU labeling index was significantly lower. FCM showed lower S-phase fraction, as well as absence of aneuploidy compared with control cells. In the in vivo studies, intralesional injection of 6 and 12% honey as well as oral ingestion of honey significantly inhibited tumor growth.

CONCLUSION

Bee honey is an effective agent for inhibiting the growth of T24, RT4, 253J and MBT-2 bladder cancer cell lines in vitro. It is also effective when administered intralesionally or orally in the MBT-2 bladder cancer implantation models. Our results are promising, and further research is needed to clarify the mechanisms of the antitumor activity of honey.

The c-myc gene regulates the polyamine pathway in DMSO-induced apoptosis

It is accepted that apoptosis is a gene-controlled process of cellular self-destruction. It occurs during physiological regulation and in pathological situations in the life of a cell. In the immune system, several different intracellular and extracellular factors have been associated with the induction of apoptosis, and the final responses depend on the cell system and the acquired signals. In lymphoid cells, dexamethasone-induced apoptosis is associated with c-myc downregulation in cells that remain in G0-G1 until the point of death. Ornithine decarboxylase (ODC), a key enzyme involved in polyamine biosynthesis, is regulated by c-myc, which is a transcriptional activator implicated not only in the control of cell proliferation and differentiation but also in programmed cell death. As dimethylsulphoxide (DMSO) induces apoptosis in the RPMI-8402 human pre-T cell line, the present study analysed the involvement of the c-myc proto-oncogene and polyamine pathway as mediators of apoptosis. Cell growth, programmed cell death, c-myc expression, ODC activity and intracellular polyamine content were detected after DMSO and difluoromethylornithine (DFMO) treatment. DMSO-treated cells exhibit a decrease in ODC activity and polyamine levels associated with cell growth arrest and programmed cell death induction. The expression of c-myc proto-oncogene, as its mRNA or protein, is specifically down-regulated. DFMO, a well defined polyamine biosynthesis inhibitor, completely blocks ODC activity, resulting in growth inhibition but not apoptosis. Moreover, in these samples no evidence of changes of c-myc expression were found. The results obtained suggest that, in RPMI-8402 cells, DMSO provokes a c-myc-dependent decrease of ODC activity followed by a depletion of intracellular polyamine levels, associated with programmed cell death and cell growth arrest.

Effect of L-arginine on arginase activity in male accessory sex glands of alloxan-treated rats

Arginase activity has been identified in the prostate, and may be important in the synthesis of polyamines in accessory sex glands in the male. Polyamines in turn may mediate the action of androgens. Diabetic patients have disordered androgen synthesis. The purpose of this work was to evaluate the effect of L-arginine on arginase activity in accessory sex glands of male rats under normal and diabetic conditions (alloxan 120 mg/kg, i.p.). Normal and diabetic male rats were untreated or were treated with insulin or L-arginine for 96 h, and sacrificed. Arginase activity was measured in serum and in accessory sex glands. Arginase activity in accessory glands did not change significantly with induction of diabetes. Arginase activity was increased in diabetic insulin-treated rats, but there was no arginase response to L-arginine administration in diabetic animals. These findings stand in contrast to beneficial effects of L-arginine previously observed when this amino acid was administered for a long time (at least 10 days). We suspect that altered arginase activity in accessory sex glands may play a role in the reproductive dysfunction caused by diabetes, inasmuch as arginase activity can be increased in experimentally diabetic rats by the administration of insulin.

The transcript-level-independent activation of ornithine decarboxylase in suspension-cultured BY2 cells entering the cell cycle

The regulation of ornithine decarboxylase (ODC) expression was studied in suspension-cultured tobacco (Nicotiana tabacum L.) BY2 cells. ODC activity increased rapidly 3 h after cells re-entered the cell cycle from the stationary phase, corresponding to the G1 phase, and continued to increase in the subsequent S phase, while the ODC transcript level increased only transiently. ODC activity was suppressed by sucrose-deficiency, while the ODC transcript level was not affected. U0126, a specific inhibitor of mammalian MAPK kinases (MEKs), significantly reduced ODC enzyme activity, but not the ODC transcript level. These results suggest that ODC activity is regulated independently of its transcript level in BY2 cells, and that sucrose and a U0126-sensitive protein kinase are required for the transcript-level-independent activation of ODC.

Combined magnetic resonance imaging and spectroscopic imaging approach to molecular imaging of prostate cancer

Magnetic resonance spectroscopic imaging (MRSI) provides a noninvasive method of detecting small molecular markers (historically the metabolites choline and citrate) within the cytosol and extracellular spaces of the prostate, and is performed in conjunction with high-resolution anatomic imaging. Recent studies in pre-prostatectomy patients have indicated that the metabolic information provided by MRSI combined with the anatomical information provided by MRI can significantly improve the assessment of cancer location and extent within the prostate, extracapsular spread, and cancer aggressiveness. Additionally, pre- and post-therapy studies have demonstrated the potential of MRI/MRSI to provide a direct measure of the presence and spatial extent of prostate cancer after therapy, a measure of the time course of response, and information concerning the mechanism of therapeutic response. In addition to detecting metabolic biomarkers of disease behavior and therapeutic response, MRI/MRSI guidance can improve tissue selection for ex vivo analysis. High-resolution magic angle spinning ((1)H HR-MAS) spectroscopy provides a full chemical analysis of MRI/MRSI-targeted tissues prior to pathologic and immunohistochemical analyses of the same tissue. Preliminary (1)H HR-MAS spectroscopy studies have already identified unique spectral patterns for healthy glandular and stromal tissues and prostate cancer, determined the composition of the composite in vivo choline peak, and identified the polyamine spermine as a new metabolic marker of prostate cancer. The addition of imaging sequences that provide other functional information within the same exam (dynamic contrast uptake imaging and diffusion-weighted imaging) have also demonstrated the potential to further increase the accuracy of prostate cancer detection and characterization.

Decreased ornithine decarboxylase activity in the kidneys of Dahl salt-sensitive rats

To assess the roles of polyamines (putrescine, spermidine, and spermine) and ornithine decarboxylase (ODC), the rate-limiting enzyme of polyamine synthesis, in the development of salt-sensitive hypertension, we evaluated activity and expression of ODC, urinary polyamine excretion, and antizyme (endogenous ODC inhibitor protein) expression in Dahl salt-sensitive (SS) and salt-resistant (SR) rats after they were fed on a low (0.3%) or high (4%) salt diet for 4 weeks. We also examined the effects of spermidine and difluoromethylornithine (DFMO: a specific inhibitor of ODC) on the systolic blood pressure and ODC protein expression in SS rats fed a high salt diet. Renal ODC activity and urinary polyamine excretion in SS rats were lower than those in SR rats after 4 weeks treatment with a low or high salt diet. The renal ODC protein expression of SS rats was paradoxically increased as compared to the SR group. A high salt diet did not alter ODC activity but increased ODC protein only in SS rats. ODC mRNA and antizyme protein expressions were not significantly different among the four groups. Spermidine supplementation attenuated and DFMO exaggerated hypertension in SS rats fed a high salt diet. Spermidine down-regulated and DFMO up-regulated renal ODC protein in SS rats on a high salt diet. ODC activity was decreased but protein was paradoxically increased in kidneys of SS rats. ODC protein was suggested to increase in compensation for the inhibition of its activity. Impaired ODC activity and polyamine production in the kidney may exaggerate salt-sensitive hypertension in SS rats.

Nebivolol inhibits vascular smooth muscle cell proliferation by mechanisms involving nitric oxide but not cyclic GMP

The objective of this study was to elucidate the mechanisms by which nebivolol, a cardio-selective beta-adrenergic receptor antagonist, inhibits rat aortic smooth muscle cell (RASMC) proliferation. Nebivolol was compared with DETA-NO and S-nitroso-N-acetylpenicillamine (SNAP), two nitric oxide (NO) donor agents, and alpha-difluoromethylornithine (DFMO), a known inhibitor of ornithine decarboxylase (ODC). All four test agents inhibited RASMC proliferation in a concentration-dependent manner, with nebivolol being the most potent (IC(50) = 4.5 microM), whereas atenolol, another relatively selective beta(1)-blocker, was inactive. DFMO, nebivolol, and DETA-NO interfered with cell proliferation in a cell-density-dependent manner, the lower the cell density the greater the inhibition of cell proliferation. The cytostatic effects of nebivolol and DETA-NO were completely independent of cyclic GMP, as neither ODQ (cytosolic guanylyl cyclase inhibitor) nor zaprinast (cyclic GMP phosphodiesterase inhibitor) affected the antiproliferative action of nebivolol or DETA-NO. The cytostatic effects of nebivolol, SNAP, and DFMO were largely prevented by the addition of excess putrescine, but not ornithine, to cell cultures. Moreover, nebivolol caused a marked reduction in the intracellular levels of putrescine, spermidine, and spermine. Like DFMO, nebivolol and DETA-NO interfered with the G(1)-phase to S-phase cell cycle transition in RASMC. These observations confirm previous findings that DFMO and NO interfere with RASMC proliferation by inhibiting ODC and polyamine production and provide evidence that nebivolol works by the same mechanism.

Polyamines interact with DNA as molecular aggregates

New compounds, named nuclear aggregates of polyamines, having a molecular mass of 8000, 4800 and < 1000 Da, were found in the nuclear extracts of several replicating cells. Their molecular structure is based on the formation of ionic bonds between polyamine ammonium and phosphate groups. The production of the 4800 Da compound, resulting from the aggregation of five or more < 1000 Da units, was increased in Caco-2 cells treated with the mitogen gastrin. Dissolving single polyamines in phosphate buffer resulted in the in vitro aggregation of polyamines with the formation of compounds with molecular masses identical to those of natural aggregates. After the interaction of the 4800 Da molecular aggregate with the genomic DNA at 37 degrees C, both the absorbance of DNA in phosphate buffer and the DNA mobility in agarose gel increased greatly. Furthermore, these compounds were able to protect the genomic DNA from digestion by DNase I, a phosphodiesterasic endonuclease. Our data indicate that the nuclear aggregate of polyamines interacts with DNA phosphate groups and influence, more efficaciously than single polyamines, both the conformation and the protection of the DNA.

Clusterin (SGP-2) transient overexpression decreases proliferation rate of SV40-immortalized human prostate epithelial cells by slowing down cell cycle progression

Clusterin is a highly conserved, widely distributed glycoprotein whose biological significance is still debated. Involved in many biological processes and disease states, clusterin is induced by cell injury and tissue regression, but is repressed during cell proliferation. We have previously reported that clusterin mRNA induction is associated with epithelial cell atrophy in the rat prostate and both clusterin transcript and protein accumulated in quiescent normal human skin fibroblasts. Here we show that transient clusterin overexpression, in SV40-immortalized human prostate epithelial cells (PNT2), resulted in increased accumulation of cells in the G(0)/G(1) phases of the cell cycle, accompanied by slowdown of cell cycle progression and decrease of DNA synthesis. The activities of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC), and the level of histone H3 mRNA (markers of cell proliferation) concomitantly decreased, while Gas1 mRNA (a marker of cell quiescence) accumulated. Thus it appears that clusterin, by opposing the effect of SV40 on the proliferation rate of PNT2 cells, acts as an anti-oncogene in the prostate, suggesting a role for this gene in controlling proliferation of normal and transformed prostate epithelial cells.

Polyamine uptake is necessary for a normal biochemical maturation of astrocytes in culture

In this study we have explored the importance of polyamine uptake in the proliferation and biochemical maturation of cerebellar astroyctes in culture. The uptake of polyamines paralleled astrocyte proliferation measured as [3H]thymidine incorporation into the DNA. Inhibition of polyamine uptake did not alter the developmental profile of thymidine incorporation, perhaps due to a compensatory increase in ornithine decarboxylase activity but was able to reduce glutamine synthetase (GS) activity, an enzymatic marker for astrocyte biochemical maturation, from 9 days in vitro. The present results suggest that polyamine uptake plays an important role in the biochemical maturation of astrocytes in culture.

High molecular protein of Helicobacter pylori responsible for inhibition of ornithine decarboxylase activity of human gastric cultured cells

BACKGROUND

Ornithine decarboxylase (ODC), a rate-limiting enzyme of polyamine biosynthesis, mediates epithelial cell proliferation and plays a critical role in the optimal repair of gastric mucosal damage. Several studies have shown that Helicobacter pylori inhibits the growth and proliferation of gastric cells in vitro.

AIM

To test whether H. pylori extract affects ODC mRNA expression and its enzyme activity in gastric cells and to examine the partial characterization of the molecule responsible for this effect.

METHODS

Human gastric cells (MKN-45) were used. Bacterial extracts from various E. coli or H. pylori strains, namely (1) cagA+, vacA+, CagA+, VacA+; (2) cagA+, vacA+, CagA+ VacA-; or (3) cagA-, vacA+, CagA-, VacA- were added to the cells. Cell proliferation was assessed by [3H]-thymidine incorporation, viability by MTT assay and LDH release test, ODC enzyme activity by 14CO2 counts from L-[1(14)C]ornithine, and ODC mRNA by Northern blotting.

RESULTS

H. pylori and E. coli extract did not affect viability of gastric cells. H. pylori extract, especially extracts containing a protein greater than 50 kDa, significantly inhibited proliferation and ODC activity of gastric cells while E. coli extract had no effect. Inhibition of ODC activity was found in extracts of all H. pylori strains, irrespective of CagA and VacA protein expression. Serum stimulation induces an increase in ODC mRNA while H. pylori extract did not affect ODC mRNA expression.

CONCLUSION

High molecular weight (greater than 50 kDa) proteins of H. pylori extract without CagA or VacA protein inhibited proliferation and ODC activity of human gastric cells, but did not affect ODC mRNA expression, suggesting that inhibition of ODC activity is regulated at the post-transcriptional level.

Rapid caspase-dependent cell death in cultured human breast cancer cells induced by the polyamine analogue N(1),N(11)-diethylnorspermine

The spermine analogue N(1),N(11)-diethylnorspermine (DENSPM) efficiently depletes the cellular pools of putrescine, spermidine and spermine by down-regulating the activity of the polyamine biosynthetic enzymes and up-regulating the activity of the catabolic enzyme spermidine/ spermine N(1)-acetyltransferase (SSAT). In the breast cancer cell line L56Br-C1, treatment with 10 microm DENSPM induced SSAT activity 60 and 240-fold at 24 and 48 h after seeding, respectively, which resulted in polyamine depletion. Cell proliferation appeared to be totally inhibited and within 48 h of treatment, there was an extensive apoptotic response. Fifty percent of the cells were found in the sub-G(1) region, as determined by flow cytometry, and the presence of apoptotic nuclei was morphologically assessed by fluorescence microscopy. Caspase-3 and caspase-9 activities were significantly elevated 24 h after seeding. At 48 h after seeding, caspase-3 and caspase-9 activities were further elevated and at this time point a significant activation of caspase-8 was also found. The DENSPM-induced cell death was dependent on the activation of the caspases as it was inhibited by the general caspase inhibitor Z-Val-Ala-Asp fluoromethyl ketone. The results are discussed in the light of the L56Br-C1 cells containing mutated BRCA1 and p53, two genes involved in DNA repair.

Synthesis of bis-spermine dimers that are potent polyamine transport inhibitors

A series of novel spermine dimer analogues was synthesized and assessed for their ability to inhibit spermidine transport into MDA-MB-231 breast carcinoma cells. Two spermine molecules were tethered via their N(1) primary amines with naphthalenedisulfonic acid, adamantanedicarboxylic acid and a series of aliphatic dicarboxylic acids. The linked spermine analogues were potent polyamine transport inhibitors and inhibited cell growth cytostatically in combination with a polyamine synthesis inhibitor. Variation in the linker length did not alter polyamine transport inhibition. The amount of charge on the molecule may influence the molecular interaction with the transporter since the most potent spermidine transport inhibitors contained 5-6 positive charges.

Activities of arginase I and II are limiting for endothelial cell proliferation

Polyamines are essential for cell proliferation; therefore, we hypothesized that arginase I or arginase II activities, via production of ornithine for polyamine synthesis, may be limiting for proliferation of endothelial cells (EC). Bovine coronary venular EC stably transfected with a lacZ gene (lacZ-EC, control), rat arginase I cDNA (AI-EC), or mouse arginase II cDNA (AII-EC) were utilized to test this hypothesis. Cell-proliferation assays showed that EC proliferation was markedly increased in AI-EC and AII-EC compared with lacZ-EC. Expression of proliferating cell nuclear antigen was also enhanced in AI-EC and AII-EC. DL-alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase, was used to establish that increased polyamine synthesis was involved in mediating the enhanced growth of AI-EC and AII-EC. Addition of 5 mM DFMO to the culture medium completely abolished the differences in cellular putrescine concentrations and reduced the differences in spermidine concentrations among AI-EC, AII-EC, and lacZ-EC. The DFMO treatment also prevented an increase in AI-EC and AII-EC proliferation compared with lacZ-EC. Addition of 10 and 50 microM putrescine dose-dependently increased AI-EC, AII-EC, and lacZ-EC growth to the same extent. These results demonstrate that either arginase isoform can potentially play a role in modulating EC proliferation by regulating polyamine synthesis.

Disruption of gene YlODC reveals absolute requirement of polyamines for mycelial development in Yarrowia lipolytica

Polyamines are required for cellular growth and differentiation. In mammals and fungi they are synthesized via a pathway involving ornithine decarboxylase (ODC), which transforms ornithine into putrescine. We have cloned and disrupted the gene coding for ODC in Yarrowia lipolytica to analyze the role of polyamines in dimorphism of this fungus. Substrate- and cofactor-binding motifs, as well as two putative PEST boxes were identified in the amino acid sequence. A single transcript 1.7 kb in size was identified by Northern hybridization, and confirmed by rapid amplification of cDNA ends (RACE). Null mutants lacked ODC activity and behaved as polyamine auxotrophs. When low levels of polyamines were supplied to the null mutant, only yeast-like, but not mycelial growth was sustained. This phenomenon was confirmed by introduction of the YlODC gene under the control of an inducible promoter into the null mutant.

Polyamines as cancer markers: applicable separation methods

Spermine, spermidine, putrescine and cadaverine are aliphatic amines widely spread in the human body. Their concentrations together with their acetyl conjugates increase significantly in the biological fluids and the affected tissues of cancer patients. Their concentrations decrease with the improvement in the patient's condition on multiple therapy. Various chromatographic techniques are frequently used in monitoring concentrations of di- and polyamines in cancer. Among these techniques, thin-layer chromatography and liquid chromatography using pre- or postcolumn derivatization, separating on a reversed-phase or an ion-exchange column are the most commonly used. Besides, high-resolution capillary column gas chromatography (GC) is increasingly used over packed column GC, and in recent years, capillary zone electrophoresis has also gained some importance in polyamine determinations. The review examines the prospects and the limitations of polyamines as cancer markers using chromatographic and electrophoretic techniques.

Influence of polyamine architecture on the transport and topoisomerase II inhibitory properties of polyamine DNA-intercalator conjugates

An efficient five-step synthetic method was developed to access a series of spermine derivatives containing appended acridine, anthracene, and 7-chloroquinoline motifs. The derivatives were composed of a spermine fragment covalently tethered at its N4 and N9 positions to an aromatic nucleus via an aliphatic chain (e.g., 8: acridine -[C4 aliphatic tether]-spermine-[C4 aliphatic tether]-acridine). The distance separating the spermine and aromatic nuclei was altered via different tethers composed of four or five methylene units. These bis ligands (8, 9, 12, and 13) were shown to inhibit human DNA topoisomerase II (topo II) activity at 5 microM. Enzymatic activity was assessed as the ability to unknot (decatenate) and cleave kinetoplast DNA (kDNA). Polyamine conjugation did not disrupt the ability of the acridine-spermine conjugates 8 and 9 to inhibit topo II activity as compared with the 9-aminoacridine and 9-(N-butyl)aminoacridine controls (at 5 microM). The parent polyamines, spermine (5 microM) and spermidine (10 microM), had little effect on topo II activity. In general, the bis-substituted spermine derivatives (8, 9, 12, and 13) were more efficient topo II inhibitors at 5 microM than their monosubstituted spermidine counterparts (22-25) at 10 microM. Within the bisintercalator spermine series, insertion of an additional methylene unit (i.e., C5 tethers) increased potency 2-fold (8, bis-C4-acridine, 47 h IC(50) = 40 microM; 9, bis-C5-acridine, IC(50) = 17 microM). Comparison of the bis- and monoacridine spermine motifs (8 and 17) revealed a 4-fold increase in potency for the latter architecture (94 h IC(50) for 8, 74 microM; for 17, 17 microM). In general the bisintercalators (8, 9, 12, and 13) behaved as cytostatic agents, while the monosubstituted acridine and anthracene derivatives (22-25) were cytotoxic. Anthracene-containing conjugates were generally more toxic than their acridine counterparts in an L1210 (murine leukemia) cell assay. Of the conjugates tested the (monointercalator)-spermine motif (e.g., 17) had the highest affinity for the L1210 polyamine transporter as revealed by spermidine protection experiments.

Short- and long-chain natural polyamines play specific roles in adult cricket neuroblast proliferation and neuron differentiation in vitro

In the house cricket (Acheta domesticus) mushroom bodies, neurogenesis still occurs during adulthood. Using in vitro approaches, the respective roles of natural polyamines in neurogenesis were examined. Mushroom body neuroblast proliferation was assayed in organotypic culture using 5-bromo, 2'-deoxyuridine labeling. The number of labeled cells was significantly increased when putrescine was added to culture medium, whereas spermidine and spermine supplementation did not alter cell proliferation. Conversely, in vitro morphometric studies on mushroom body neurons cultured in a defined medium showed that putrescine addition failed to alter any morphological character of these interneurons, whereas addition of the long-chain polyamines, spermidine and spermine, stimulated neuron differentiation. These two polyamines significantly increased total neurite length; moreover, spermidine-treated cells exhibited more branches than the controls. The present data demonstrate that putrescine has a mitogenic effect on mushroom body neuronal precursors, and that spermidine and spermine, which failed to induce neuroblast proliferation, act on neuronal differentiation, inducing neurite outgrowth. Our results indicate that short- and long-chain polyamines play specific roles during neurogenesis, and provide a basis for further studies on neuronal precursor proliferation and differentiation.

Polyamines in the human gut

Intracellular polyamine concentrations are maintained by endogenous synthesis and uptake of exogenous polyamines from the gastrointestinal lumen. Recently, much attention has been focused on the role of polyamines in tumour pathogenesis and the possible therapeutic value of reducing polyamine concentrations in tumour tissue. Unfortunately, polyamines also appear to be essential for the maintenance of normal gastrointestinal structure and function. The immediate analytical challenge is to make progress in laboratory methods for polyamine class analyses and assessment of polyamine metabolism. An obvious gastroenterological target is to make up for past neglect of the function of these important dietary components.

Inhibitory effect of 1-O (2 methoxy) hexadecyl glycerol and phenylbutyrate on the malignant properties of human prostate cancer cells

The ability of the naturally occurring ether lipid, 1-O (2 methoxy) hexadecyl glycerol (MHG), and phenylbutyrate (BP) to inhibit cellular proliferation, anchorage-independent growth and cellular invasion in the human prostate cancer LnCap and DU145 cells was determined. Both MHG and PB inhibited the malignant properties of these prostate cancer cells. The concentrations required to achieve similar inhibitory effect, however, were significantly different for these two agents. MHG inhibited cell growth with equal potency in these cell lines with an IC-50 value of 93 microM for LnCap, and 97 microM for DU145. The IC-50 values for PB were 1.3 mM and 7.3 mM, respectively, for LnCap and DU145 cells. Both MHG and PB (IC-50 concentrations) inhibited the anchorage-independent growth and cellular invasion in these cells. Over 50% inhibition of anchorage-independent growth was achieved for both LnCap and DU145 cells by PB, while a lesser degree of inhibition was achieved with MHG. Both MHG- and PB-treated cells showed a reduced propensity to invade matrigels. Invasion of PB-treated LnCap and DU145 cells was reduced, respectively, by approximate 41 and 30% when compared to untreated control cells, while invasion of MHG-treated LnCap and DU145 cells was reduced to a lesser extent. Because differentiation-inducing agents may possess chemopreventive properties, the use of naturally occurring MHG and nontoxic PB in the chemoprevention of malignant diseases warrants further investigation.

Polyamine metabolism in brain tumours: diagnostic relevance of quantitative biochemistry

OBJECTIVE

Activation of polyamine metabolism is closely associated with cellular proliferation. The purpose was to investigate whether the content of the polyamines putrescine, spermidine, and spermine, and the activity of the first metabolic key enzyme of polyamine metabolism, ornithine decarboxylase (ODC), represent biochemical markers of malignancy in brain tumours.

METHODS

The concentration of putrescine, spermidine, and spermine, and the activity of ODC were biochemically quantified in tissue samples obtained during open microsurgery of 670 patients with brain tumours. Biochemical analysis and histopathological classification were carried out in serial tumour samples.

RESULTS

The activity of ODC was very low in peritumoral non-neoplastic brain tissue (0.9 (SD 0.6) nmol/g/h). It was significantly higher in gliomas and it significantly increased with a higher grade of malignancy (grade I 2.7 (2.8) nmol/g/h, grade II 3.1 (4.0) nmol/g/h, grade III 5.7 (5.6) nmol/g/h, grade IV 10.6 (11.7) nmol/g/h). High enzyme activity was also found in medulloblastomas (25.5 (15.1) nmol/g/h), malignant lymphomas (52.1 (42.1) nmol/g/h), and metastases from carcinoma (14.9 (22.1) nmol/g/h). Lowest values were measured in epidermoid cysts (0.5 (0.2) nmol/g/h), craniopharyngiomas (1.2 (0.9) nmol/g/h), angioblastomas (1.6 (1.7) nmol/g/h), and neurinomas (2.0 (1.8) nmol/g/h). By contrast with ODC activity, polyamine concentrations did not correlate with the grade of malignancy. Correlation of regional biochemical and histomorphological data in rapidly growing neoplasms showed high enzyme activity in solid tumour parts and low activity in necrotic areas.

CONCLUSIONS

Novel data relating ODC activation and polyamine concentrations to neuropathology is presented indicating that high ODC activity represents a biochemical marker of malignancy in brain tumours. This information is important for clinical and therapeutic investigations.

Permeability characteristics of polyamines across intestinal epithelium using the Caco-2 monolayer system: comparison between transepithelial flux and mitogen-stimulated uptake into epithelial cells

The polyamines putrescine, spermidine, and spermine are present in foods in high amounts, and are used for cell growth throughout the body. Surprisingly little is known about the mechanisms of polyamine absorption in the gut. To elucidate the mechanisms, transepithelial transport of polyamines was studied in human enterocytelike Caco-2 cells, grown on permeable filter supports. Transport of all three polyamines across Caco-2 cell monolayers was linear; intraepithelial accumulation of polyamines was higher in confluent than in differentiated Caco-2 cells, but still negligible in comparison with the overall transport across the monolayers. Epidermal growth factor (EGF) enhanced polyamine accumulation in Caco-2 cells four-fold, and basolateral uptake was higher than apical uptake if the cells were stimulated to grow. The amounts of polyamines taken up by the cells were nevertheless negligible in comparison with the net polyamine flux across the monolayers. Basolateral excretion of polyamines was in the picomolar range, whereas their transepithelial transport, occurring presumably by passive diffusion through the paracellular pathway, contributed hundreds of micromoles of polyamines to the basolateral chamber. We conclude that transepithelial transport of polyamines occurs by passive diffusion, and that it is not influenced when epithelial cells are stimulated to proliferate by a potent mitogen such as EGF.

A mechanistic study of proliferation induced by Angelica sinensis in a normal gastric epithelial cell line

It has been reported that an extract from Angelica sinensis mainly consisting of polysaccharides (95%) prevented ethanol- or indomethacin-induced gastric mucosal damage (Cho CH et al. Planta Med 2000;66:348-51). However, it is not known whether Angelica sinensis has a direct stimulatory effect on the healing of gastric mucosal lesions. To study the hypothesis that Angelica sinensis has a direct mucosal healing effect in rats and in isolated gastric epithelial cells, we assessed the wound repair in both animals and normal cell culture (RGM-1), as well as [3H]thymidine incorporation, ornithine decarboxylase (ODC) activity, and ODC protein and c-Myc protein expression after different treatments in RGM-1 cells. We found that Angelica sinensis crude extract (ASCE) dose-dependently enhanced gastric ulcer healing in rats and promoted wound repair in RGM-1 cells. It also significantly stimulated [3H]thymidine incorporation and ODC activity in RGM-1 cells in a concentration-dependent manner. ODC and c-Myc protein expression was also increased as a result of this process. DL-alpha-difluoromethyl-ornithine repressed the [3H]thymidine incorporation and ODC activity induced by ASCE. Pretreatment with c-Myc antisense oligodeoxynucleotides blocked the stimulatory action of ASCE on [3H]thymidine incorporation and ODC protein expression. These data suggest that ASCE has a direct mucosal healing effect on gastric epithelial cells, while ODC and c-Myc are closely associated with this effect.

Significance of arginase and ornithine in malignant tumors of the human skin

During neoplastic development, several aspects of the regulation of polyamine synthesis undergo profound changes. In extrahepatic mammalian tissues in which the urea cycle is not functioning, arginase is believed to supply the cell with ornithine, a non-protein amino acid that is a precursor for biosynthesis of polyamines. Because the activity of ornithine decarboxylase and polyamine levels have been shown to be elevated during carcinogenesis, we decided to investigate the role of arginase in the development of malignant tumors of the human skin and to examine whether arginase activity and ornithine level can be used as biologic markers for distinguishing patients with squamous cell cancer from patients with basal cell cancer. For this purpose, we studied tissue arginase activity and ornithine level in tumor and adjacent normal tissues in 16 patients (55 +/- 10 years of age) with malignant skin tumors (8 of which were squamous cell cancers and 8 of which were basal cell cancers). The mean arginase activity and ornithine levels in tumor tissues (total) were 17.75 +/- 8.54 U/mg protein and 40.89 +/- 14.88 nmol/mg protein, respectively, versus 3.69 +/- 1.71 U/mg protein and 12.98 +/- 6.21 nmol/mg protein, respectively, for normal tissues. The mean specific arginase activity levels in squamous cell and basal cell cancers of the human skin were 18.49 +/- 10.47 U/mg protein and 16.63 +/- 6.00 U/mg protein, respectively. The mean ornithine levels in squamous cell and basal cell cancers of the human skin were 42.45 +/- 19.10 nmol/mg protein and 39.33 +/- 10.19 nmol/mg protein, respectively. Our results indicated that (1) arginase activity and ornithine levels are elevated in squamous cell and basal cell cancers of the human skin; (2) the increased activity of arginase and hence the elevated levels of ornithine may be important in the development of malignant tumors of the human skin; and (3) although arginase activity and ornithine level may be useful for distinguishing patients with malignant skin tumors from healthy subjects, they cannot be used as biologic markers for distinguishing patients with squamous cell cancer from patients with basal cell cancer.

Transepithelial transport of putrescine across monolayers of the human intestinal epithelial cell line, Caco-2

AIM: To study the transepithelial transport characteristics of the polyamine putrescine in human intestinal Caco-2 cell monolayers to elucidate the mechanisms of the putrescine intestinal absorption.

METHODS: The transepithelial transport and the cellular accumulation of putrescine was measured using Caco-2 cell monolayers grown on permeable filters.

RESULTS: Transepithelial transport of putrescine in physiological concentrations ( > 0.5 mM) from the apical to basolateral side was linear. Intracellular accumulation of putrescine was higher in confluent than in fully differentiated Caco-2 cells, but still negligible (less than 0.5%) of the overall transport across the monolayers in apical to basolateral direction.EGF enhanced putrescine accumulation in Caco-2 cells by four fold, as well as putrescine conversion to spermidine and spermine by enhancing the activity of S adenosylmethionine decarboxylase. However, EGF did not have any significant influence on putrescine flux across the Caco- 2 cell monolayers. Excretion of putrescine from Caco-2 cells into the basolateral medium did not exceed 50 picomoles, while putrescine passive flux from the apical to the basolateral chamber, contributed hundreds of micromoles polyamines to the basolateral chamber.

CONCLUSION: Transepithelial transport of putrescine across Caco-2 cell monolayers occurs in passive diffusion, and is not influenced when epithelial cells are stimulated to proliferate by a potent mitogen such as EGF.

Saccharomyces boulardii does not stimulate mucosal hyperplasia after intestinal resection in the rat

BACKGROUND

Polyamines have been shown to be important regulators of the intestinal adaptation process after massive bowel resection. Saccharomyces boulardii is yeast that has the ability to synthesize polyamines. Therefore. S. boulardii may be useful in the treatment of short bowel syndrome.

METHODS

Twenty 150-g male Sprague-Dawley rats were subjected to 80% jejunoileal resection. Another 20 animals received transection and closure and served as pair fed controls. One half of the resected rats and one half of the controls were given S. boulardii 25 mg/day.

RESULTS

After 2 weeks, mucosal mass (mg/cm bowel) did not differ between treated and non-treated animals despite the presence of a marked resection effect. Mucosal DNA, protein, and sucrase activity likewise did not differ. Subsequently, the experiment was repeated four times the original dose (100 mg/day) and found comparable results. In the proximal bowel, mucosal mass was 92+/-6 mg/cm in treated animals versus 107+/-8 mg/cm in untreated rats. In the distal small bowel, comparable values were 85+/-5 mg/cm and 88+/-4 mg/cm. Again, mucosal DNA, protein, and sucrase activity levels paralleled these results.

CONCLUSIONS

Although S. boulardii may stimulate polyamine synthesis, it does not seem to be helpful in augmenting gut adaptation in this animal model of short bowel syndrome.

5'-Methylthioadenosine administration prevents lipid peroxidation and fibrogenesis induced in rat liver by carbon-tetrachloride intoxication

BACKGROUND

5'-Methylthioadenosine (MTA), a product of S-adenosylmethionine (SAM) catabolism, could undergo oxidation by mono-oxygenases and auto-oxidation. MTA and SAM effects on oxidative liver injury were evaluated in CCl4-treated rats.

METHODS

Male Wistar rats were killed 1-48 h after poisoning with a single intraperitoneal CCl4 dose (0.15 ml/100 g) or with the same dose twice a week for 14 weeks. Daily doses of MTA or SAM (384 micromol/kg), started 1 week before acute CCl4 administration or with chronic treatment, were continued up to the time of sacrifice.

RESULTS

Acute and chronic CCl4 intoxication decreased MTA and, to a lesser extent, SAM and reduced glutathione (GSH) liver levels. MTA administration increased liver MTA without affecting SAM and GSH. SAM treatment caused complete/partial recovery of these compounds. MTA and, to a lesser extent, SAM prevented an increase in liver phospholipid hydroperoxides in acutely and chronically intoxicated rats and in prolyl hydroxylase activity and trichrome-positive areas in chronically treated rats. MTA prevented upregulation of Tgf-beta1, Collagen-alpha1 (I) and Tgf-alpha genes in liver of chronically intoxicated rats, and TGF-beta1-induced transdifferentiation to myofibroblasts and growth stimulation by platelet-derived growth factor-b of stellate cells in vitro.

CONCLUSIONS

MTA and SAM protect against oxidative liver injury through partially different mechanisms.

Effects of an aqueous extract of processed bidi tobacco on the growth of hamster tracheal epithelial cells

Inhalation of tobacco dust is responsible for elevated genotoxicity and pulmonary ailments in workers engaged in processing tobacco for the manufacture of bidis, the Indian version of cigarettes. Tracheal tissue being the major site of interaction with tobacco dust, the effects of different concentrations of an aqueous extract of bidi tobacco (ATE) on the growth of a hamster tracheal epithelial cell line (HTE) were investigated. Colony forming efficiency assay revealed that ATE was cytotoxic only at the highest concentration of 5.0 mg/ml. In cultures treated with 1.25 mg/ml ATE, the cell doubling time and growth rate were similar to that of the controls, while a significant increase in cell doubling time (29.4+/-0.3 h vs 14.0+/-3.75 h, P<0.001) was observed at 2.5 mg/ml ATE concentration. Exposure of HTE cells to the non-toxic ATE concentration of 2.5 mg/ml was found to stimulate ornithine decarboxylase (ODC) activity, incorporation of [3H] methyl thymidine into DNA and increase in the S phase fraction was seen by flow cytometry. However, a 56% reduction in the growth rate of cultures treated with 2.5 mg/ml ATE was related to the prolongation of the traverse of cells through S phase. ATE-induced growth suppression was reversed when cultures were grown in ATE-free medium or upon repeated exposure to ATE. The findings suggest that increased tracheal cell proliferation induced by chronic inhalation of tobacco dust may contribute to the development of pulmonary disorders and possibly neoplasia in exposed individuals.

Development of a sandwich ELISA test for arginase measurement based on monoclonal antibodies

Human arginase was purified from liver and two monoclonal antibodies (MAbs), HA1 and HA2, were produced by fusion of spleen cells from an arginase-immunized BALB/c mouse and the NS-1 myeloma cell line. Both MAbs were of the IgG3 subclass and contained the kappa light chain. HA1 inhibited arginase activity, suggesting that it binds to the arginase catalytic site. HA1 and a horseradish peroxidase-conjugated polyclonal rabbit anti-human arginase antibody were used to develop a sandwich enzyme-linked immunoadsorbent assay (ELISA) for the quantification of human arginase, which can be used in the 1 to 300 ng/mL range. Because of its sensitivity and specificity, this MAb can be successfully applied to the ELISA quantification of arginase in serum and culture supernatants.

Neonatal polyamine depletion by alpha-difluoromethylornithine: effects on adenylyl cyclase cell signaling are separable from effects on brain region growth

Ornithine decarboxylase (ODC) and the polyamines play an essential role in brain cell replication and differentiation. We administered alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ODC, to neonatal rats on postnatal days 5-12, during the mitotic peak of the cerebellum, a treatment regimen that leads to selective growth inhibition and dysmorphology. In adulthood, cell signaling responses mediated through the adenylyl cyclase pathway were evaluated in order to determine if synaptic dysfunction extends to regions that appear to be otherwise unaffected by DFMO. Total adenylyl cyclase catalytic activity, evaluated with the direct enzymatic stimulant, Mn(2+), was significantly elevated in male rats both in the cerebellum and in brain regions showing no growth retardation (cerebral cortex, brainstem); there were no significant effects in females. In contrast, signaling mediated through the G proteins that couple neurotransmitter receptors to adenylyl cyclase showed a deficit in the DFMO group, as evaluated with the response to fluoride; in males, there was no corresponding increase in activity as would have been expected solely from the enhancement of adenylyl cyclase, and in females, there was actually a significant decrease in the response to fluoride. Again, the deficits were not restricted to the cerebellum. Stimulation of adenylyl cyclase by isoproterenol, a beta-adrenergic receptor agonist that acts through G(s), likewise displayed deficits in both males and females, and without distinction by brain region. These results indicate that the ODC/polyamine pathway plays a role in the development of cell signaling, and hence in neurotransmission, above and beyond its role in cell replication and differentiation. Given the fact that numerous drugs and environmental contaminants have been shown to alter ODC and the polyamines in the developing brain, our findings suggest that changes in brain region growth or structure are inadequate to predict the targeting of specific neurotransmitter or signaling pathways, and that gender-selective functional defects may be present despite the absence of morphological differences.

Novel lysine-spermine conjugate inhibits polyamine transport and inhibits cell growth when given with DFMO

Polyamines are ubiquitous molecules with multiple intracellular functions. Cells tightly regulate their levels through feedback mechanisms affecting synthesis, intracellular conversion, and transport. Because polyamines have an important role in regulating cell growth, they are a target for cancer therapeutic development. However, to effectively inhibit cell growth through polyamine depletion one needs to inhibit both polyamine synthesis and import. Although the mammalian polyamine transporter has not been cloned, we have identified ORI 1202, an N(1)-spermine-L-lysinyl amide, as an effective polyamine transport inhibitor. ORI 1202 prevents the cellular accumulation of [(3)H]spermidine over a 20-h test period. ORI 1202 (30-100 microM) effectively inhibits cell growth when used in conjunction with the polyamine synthesis inhibitor alpha-difluoromethylornithine (DFMO; > or =230 microM). Human breast, prostate, and bladder carcinoma cell lines and melanoma cell lines show ORI 1202 EC(50) values in the low micromolar range when tested in conjunction with DFMO. This cytostatic effect correlates with a reduction in the intracellular levels of putrescine and spermidine. When ORI 1202 (45 mg/kg, i.p., tidx5) and DFMO (1% in drinking water) were delivered over 14 days, MDA-MB-231 breast tumor xenografts in nude mice showed 50% growth inhibition. Polyamine depletion therapy provides a cytostatic therapy that could be useful against cancer and other diseases resulting from uncontrolled cell growth.

Treatment of cells with the polyamine analog N, N11-diethylnorspermine retards S phase progression within one cell cycle

When Chinese hamster ovary cells were seeded in the presence of the spermine analog N1,N11-diethylnorspermine (DENSPM), cell proliferation ceased; this was clearly apparent by cell counting 2 days after seeding the cells. However, 1 day after seeding there was a slight difference in cell number between control and DENSPM-treated cultures. To investigate the reason for this easily surpassed slight difference, we used a sensitive bromodeoxyuridine/flow cytometry method. Cell cycle kinetics were studied during the first cell cycle after seeding cells in the absence or presence of DENSPM. Our results show that DENSPM treatment did not affect the progression of the cells through G1 or the first G1/S transition that took place after seeding the cells. The first cell cycle effect was a delay in S phase as shown by an increase in the DNA synthesis time. The following G2/M transition was not affected by DENSPM treatment. DENSPM treatment inhibited the transient increases in putrescine, spermidine, and spermine pools that took place within 24 h after seeding. Thus, in conclusion, the first cell cycle phase affected by the inhibition of polyamine biosynthesis caused by DENSPM was the S phase. Prolongation of the other cell cycle phases occurred at later time points, and the G1 phase was affected before the G2/M phase.

Insulin-mediated alterations in S-adenosylmethionine decarboxylase expression in H-ras transformed cells of varying degrees of malignancy

Cell growth regulation is a highly complex process. The present study demonstrates a novel link between alterations in insulin-mediated regulation during malignant conversion and the expression of S-adenosylmethionine decarboxylase, a key regulatory activity in the biosynthesis of polyamines. H-ras transformed mouse 10 T 1/2 cell lines exhibiting increasing malignant potential were investigated for possible insulin-mediated changes in S-adenosylmethionine decarboxylase gene expression. Selective induction of S-adenosylmethionine decarboxylase gene expression was observed, because, in contrast to nontransformed 10T 1/2 cells, only H-ras transformed cells capable of only benign tumour formation or H-ras transformed metastatic cells exhibited marked elevations in S-adenosylmethionine decarboxylase mRNA levels. Evidence for regulation of S-adenosylmethionine decarboxylase gene expression at both transcriptional and post-transcriptional levels was found. Evidence was also found for a cycloheximide sensitive regulator of S-adenosylmethionine decarboxylase gene expression in H-ras transformed metastatic cells, whose effect, in combination with insulin, resulted in a further augmentation of S-adenosylmethionine decarboxylase gene expression. This regulation was not present in H-ras transformed cells capable of only benign tumour formation. These results suggest that insulin can modulate S-adenosylmethionine decarboxylase gene expression in H-ras transformed cells and further suggests a mechanism of insulin stimulation of transformed cells wherein alterations in the regulatory activity of S-adenosylmethionine decarboxylase gene expression are critical and constitutes a part of an altered growth regulatory program associated with cellular transformation.