Inactivation of human immunodeficiency virus type 1 by the amine oxidase-peroxidase system

Human immunodeficiency virus type 1 (HIV-1) is rapidly inactivated by exposure to a naturally occurring antimicrobial system consisting of peroxidase, H2O2, and a halide. Among the potential sources of H2O2 is the amine oxidase system in which mono-, di-, and polyamines are oxidatively deaminated with the formation of H2O2. The polyamine spermine is present at exceptionally high concentrations in semen. We report here that spermine, spermidine, and, to a lesser degree, the synthetic polyamine 15-deoxyspergualin are viricidal to HIV-1 when combined with amine oxidase and myeloperoxidase. Antiviral activity required each component of the spermine-amine oxidase-peroxidase system and was inhibited by azide (a peroxidase inhibitor) and by catalase but not by superoxide dismutase. Heat treatment of catalase largely abolished its inhibitory effect. These findings implicate H2O2 formed by the amine oxidase system in the antiviral effect and raise the possibility that the polyamine-amine oxidase-peroxidase system influences the survival of HIV-1 in semen and in the vaginal canal.

The effect of spermine on calcium requirement for protein kinase C association with phospholipid vesicles

We have previously reported that polyamines interfere with protein kinase C-membrane interactions. With the aim of clarifying the influence of the relationship between calcium and polyamines on this process we have investigated the effect of spermine on the formation of active protein kinase C-membrane complexes as a function of Ca++ concentrations. Protein kinase C, purified from rat brain, was allowed to interact with phospholipid vesicles of defined composition. The active complex protein kinase C-liposomes was determined by its ability to bind radioactive phorbol ester with an exact 1:1 stoichiometry. The results show that, at Ca++ levels below 0.1 microM, spermine inhibits the formation of complexes between protein kinase C and membranes. At higher Ca++ concentrations, spermine does not prevent the association process but does influence the ratio between the enzyme molecules irreversibly inserted into the membrane and those reversibly associated with it. We have also demonstrated that spermine, by reducing the density of acidic component of liposomes, influences the calcium requirement for protein kinase C-membrane binding. This study indicates that spermine may regulate the activation of protein kinase C and affects the calcium requirement for the association of this enzyme with the phospholipid bilayer. The results suggest a possible role for polyamines in signal transduction when protein kinase C is involved.

Nitric oxide inhibition of endothelial cell mitogenesis and proliferation

BACKGROUND

Endothelial cell (EC) proliferation is essential in vascular repair after injury to the vessel wall. Impaired EC proliferation may be an important factor contributing to vessel wall disease. Nitric oxide (NO) inhibits proliferation of many cells, including smooth muscle cells (SMC). We tested the hypothesis that NO inhibits EC proliferation and DNA synthesis.

METHODS

Cultured canine venous ECs were treated with NO donors: S-nitroso-N-acetylpenicillamine (SNAP), S-nitroso-glutathione (GSNO), or spermine NONOate (SP NO). Proliferation was determined by cell counts after 48 hours. Parallel proliferation studies were done with rat aortic SMC. ECs synchronized in S phase were treated with the NO donor diethylamine NONOate (DEA NO), and DNA synthesis was measured as the incorporation of tritiated thymidine. A NO antagonist, cPTIO, was used to reverse the effects of DEA NO:

RESULTS

Concentration-dependent (1 to 100 mmol/L) inhibition of EC proliferation (11% to 71% inhibition; p < 0.05) was seen with SNAP. Similar inhibition of proliferation was noted with the NO donors GSNO and SP NO and in SMC treated with SNAP. DEA NO caused concentration-dependent (0.1 to 1 mmol/L) inhibition of EC DNA synthesis (39% to 85% inhibition; p < 0.05), which was reversed by cPTIO.

CONCLUSIONS

NO inhibits proliferation and mitogenesis of cultured ECs. This may occur in certain pathologic states, where production of NO in plaques and diseased vessels impedes reendothelialization, thus contributing to adverse thrombotic and vasospastic events.

Spermine induces haemoglobin synthesis in murine erythroleukaemia cells

The naturally occurring polyamine spermine induces haemoglobin synthesis in murine erythroleukaemia (MEL) cells. Haemoglobin production was accompanied by accumulation of cytoplasmic beta-globin mRNA and growth inhibition, but not by cell-cycle block or changes in cell volume. Hexamethylene-bisacetamide (HMBA), a well known differentiating agent, also induces haemoglobin production, but causes a G1 block and decreases cell volume. These findings indicate that HMBA and spermine affect MEL cells differently, even though both induce haemoglobin production.

Toxicity and growth-promoting potential of spermine when fed to chicks

Previous studies have shown that the feeding of putrescine, a biogenic amine and the precursor of the mammalian polyamines, can promote whole-body growth of chicks. The current study was undertaken to determine the effect of spermine, also a biogenic amine and the most cationic of the polyamines, under similar conditions. In Exp. 1, 120 week-old chicks were fed purified crystalline amino acid-based diets containing 0, .2, .4, .6, .8, or 1.0% spermine for 14 d. Spermine proved highly toxic and growth rates were reduced compared with controls when even .2% was fed. In Exp. 2, chicks were fed 0, .0375, .0750, or .1000% spermine. These concentrations proved less toxic than those used in Exp. 1. Supplemental dietary cysteine was then provided at 0, .3, .6, and .9% together with 0, .025, .050, or .400% spermine (Exp. 3) because depletion of cellular glutathione has been suggested as contributing to spermine's toxicity. Even high levels of cysteine supplementation did not overcome spermine's toxicity. Subsequent dietary provision of L-2-oxothiazolidine-4-carboxylic acid (OTC, Exp. 4), a cysteine prodrug, showed that depletion of cellular glutathione was not likely a cause of spermine toxicosis. A trend toward increased weight gain and feed efficiency was observed when low concentrations of spermine were fed. It was concluded, however, that dietary spermine was more toxic to chicks than was previously seen for putrescine, that any growth-promoting effects of dietary spermine are small, and that supplements of dietary cysteine or OTC are unlikely to increase these effects by overcoming spermine toxicosis.

A novel polymeric spermine conjugate inhibits polyamine transport in pulmonary artery smooth muscle cells

The polyamines putrescine, spermidine and spermine (SPM) are low molecular weight organic cations that play essential intracellular regulatory roles in cell growth and differentiation. Whereas both de novo polyamine synthesis and transmembrane transport regulate cell polyamine contents, exploitation of pathways as pharmacologic targets has been limited by the lack of agents which specifically block polyamine transport. We now report the synthesis and biologic activity of novel polymeric glutaraldehyde conjugates of putrescine, spermidine and SPM which act at the cell membrane to inhibit polyamine uptake in cultured bovine pulmonary artery smooth muscle cells. Each conjugate caused dose-related inhibition of [14C]polyamine transport in pulmonary artery smooth muscle cells with the polymeric SPM conjugate being most effective in inhibiting the uptake of all three polyamines. Polymeric SPM failed to impair uptake of neutral or charged amino acids or to associate with pulmonary artery smooth muscle cells in a temperature-dependent manner. The polymeric SPM conjugate caused substantial decreases in cell polyamine contents which were associated with concentration-dependent cytotoxicity. Spectroscopic analyses of the polymeric SPM conjugate indicated that its molecular weight was 25 +/- 0.5 kDa, which is equivalent to approximately 90 monomeric--HN(CH2)3NH(CH2)4NH(CH2)3NH(CH2)5--units. These findings indicate that reduced polymeric glutaraldehyde conjugates of the polyamines may function as specific inhibitors of polyamine transport and thus provide a basis for examination of polyamine transport as a pharmacologic target in disorders characterized by dysregulated cell growth and differentiation.

The antioxidant effect of spermine NONOate in human low-density lipoprotein

The nitric oxide (*NO) donor N-[4-[1-(3-aminopropyl)-2-hydroxy-2-nitrosohydrazino]butyl]-1,3- propanediamine, also referred to as Spermine NONOate (SNN), inhibited the copper(II) sulfate-initiated oxidative modification of human low-density lipoprotein (LDL) as measured by the formation of thiobarbituric acid reactive substances, conjugated diene formation, and changes in electrophoretic mobility. The presence of the nitronyl nitroxide 1-oxy-2-[p-(trimethylammoniumyl)phenyl]-4,4,5,5- tetramethylimadazoline 3-oxide, a scavenger of *NO, antagonized the inhibitory activity of SNN. The inhibition of copper-dependent LDL oxidation had a nonlinear dependence on SNN concentration. Low concentrations of SNN ( < 4 microM) were only poorly effective at inhibiting LDL oxidation; however, a dramatic enhancement of inhibition occurred above 4 microM SNN. This behavior was qualitatively different from that of butylated hydroxytoluene, a phenolic chain-breaking antioxidant, which exhibited an approximately linear concentration dependence in this system. Addition of 13[S-(E,Z)]-hydroperoxy-9,11-octadecadienoic acid, a lipid hydroperoxide, to LDL diminished the antioxidant effect of 4 and 8 microM SNN, but not that of 12 microM SNN. SNN inhibited the depletion of alpha-tocopherol during both copper-dependent and 2,2'-azobis(2-amidinopropane)-dependent oxidation of LDL. We propose that a direct reaction is occurring between NO and the lipid peroxyl radical, forming a lipid-nitroso adduct. Formation of this product would not only remove the lipid peroxyl radical, thus preventing chain propagation, but would also prohibit the regeneration of lipid hydroperoxide, thereby stopping further transition metal ion-dependent initiation. The difference in the kinetic behavior between SNN and conventional antioxidants can be explained by this effect.

Differential actions of exogenous and intracellular spermine on contractile activity in smooth muscle of rat portal vein

Effects of the naturally occurring polyamine spermine on electrical and contractile properties of the rat portal vein were studied. 1 mM spermine nearly abolished spike activity and spontaneous contractions and decreased the intracellular Ca2+ concentration ([Ca2+]i). The phasic force responses to 0.1 and 1 microM phenylephrine were partially inhibited, but not the sustain plateau contraction caused by 5 microM phenylephrine. The Ca(2+)-force relation in high-K+ (128 mM)-depolarized veins was shifted to the right, EC50 for Ca2+ increasing from 0.50 +/- 0.03 mM (control, n = 8) to 0.65 +/- 0.06 and to 0.94 +/- 0.03 at 1 (n = 4) and 10 (n = 3) mM spermine, respectively. However, at a Ca2+ concentration of 2.5 mM, giving maximal force, there was no effect of spermine (1 mM) on either force or [Ca2+]i. Whereas extracellular spermine thus reduced contractile activity at moderate levels of stimulation, increased intracellular concentration of spermine potentiated the force response to Ca2+. Intracellular loading of spermine by reversible permeabilization increased its concentration by 2-3 times. The spontaneous activity and response to phenylephrine were unchanged. However, the Ca(2+)-force relation of depolarized veins was shifted to the left, EC50 decreasing from 0.51 +/- 0.04 mM in controls (n = 7) to 0.36 +/- 0.02 mM in the loaded veins (n = 9). Spermine increased Ca(2+)-activated force in portal veins permeabilized with beta-escin. The degree of potentiation was consistent with observed effects in spermine-loaded intact veins. The results suggest that spermine at physiological intracellular concentration may contribute to the determination of Ca2+ sensitivity in vascular smooth muscle cells.

Differential effects of spermine on phosphatidylinositol 3-kinase and phosphatidylinositol phosphate 5-kinase

The metabolism of phosphoinositides plays an important role in the signal transduction pathways. We report here that naturally occurring polyamines affect the activities of phosphatidylinositol (PI) 3-kinase and PI 4-phosphate (PIP) 5-kinase differently. While polyamines inhibited the PI 3-kinase activity, they stimulated the activity of PIP 5-kinase in the order of spermine > spermidine > putrescine. Spermine inhibited the PI 3-kinase activity in a concentration-dependent manner with an IC50 of 100 microM. On the other hand, spermine (5 mM) stimulated the activity of PIP 5-kinase 2-3 fold. Kinetic studies of spermine-mediated inhibition of PI 3-kinase revealed that it was noncompetitive with respect to ATP. The effect of Mg2+ and PIP2 concentration on kinase activity was sigmoidal, with spermine inhibiting PI 3-kinase activity at all PIP2 concentrations. While 1 mM calcium stimulated PI 3-kinase activity at submaximal concentrations of Mg2+ (1.25 mM), inhibition was observed at optimal concentration of Mg2+ (2 mM). We propose that spermine may modulate the cellular signal by virtue of its differential effects on phosphoinositide kinases.

Polyamine effects on purine-purine-pyrimidine triple helix formation by phosphodiester and phosphorothioate oligodeoxyribonucleotides

Utilization of oligodeoxyribonucleotides to inhibit specific gene transcription in vivo (antigene strategy) requires the efficient formation of triple helices under physiological conditions. However, pyrimidine-motif triplexes are not favored at physiological pH, and physiological concentrations of potassium cations hamper purine-motif triplex formation. Here we investigated the effects of polyamines on promoting triplex formation by G/T-rich oligodeoxyribonucleotides containing either phosphodiester or a diastereomeric mixture of phosphorothioate linkages. Compared with Mg2+, equimolar concentrations of polyamines greatly facilitated purine-motif triplex formation with the following order of effectiveness: spermine > spermidine > putrescine. At low polyamine concentrations, phosphorothioate oligonucleotides were better at triplex formation than the corresponding phosphodiester oligonucleotides. Kinetic studies indicated that polyamines facilitated triplex formation by increasing the rate of oligonucleotide-duplex DNA association. However, triplex accumulation with either oligonucleotide was still low under physiological conditions (140 mM K+, 10 mM Mg2+, 1 mM spermine). The inhibitory effects of K+ could be partially overcome with high concentrations of Mg2+ or spermine, with phosphodiester oligonucleotides being better able to form triplexes than phosphorothioates under these conditions.

Slowing proliferation in head and neck tumors: in vitro growth inhibitory effects of the polyamine analog BE-4-4-4-4 in human squamous cell carcinomas

PURPOSE

These preclinical studies were carried out to examine the potential of the antiproliferative polyamine analog 1,19-bis-(ethylamino)-5,10,15-triazanonadecane (BE-4-4-4-4) to serve as a therapy adjuvant to radiation for patients with rapidly dividing tumors of the head and neck (H&N).

METHODS AND MATERIALS

Cytostatic and cytotoxic effects of this polyamine analog were investigated in three squamous cell carcinoma (SCC) cell lines derived from human H&N tumors.

RESULTS

Growth inhibition was achieved in all cell lines within 3-4 days of continuous 10 microM drug exposure, and inhibition of cell cycle proliferation kinetics was confirmed via flow cytometry. Cytotoxicity was pronounced (3-4 log cell kill) in the SCC-38 and SCC-4Y cell lines with continuous 10 microM analog exposure over 5 days, and was minimal in the SCC-13Y cell line. No demonstrable effect of BE-4-4-4-4 on single dose radiation survival was identified in any SCC cell line. Ornithine decarboxylase (ODC) activity was rapidly inhibited (1-2 h) following 10 microM BE-4-4-4-4 exposure in all SCC cell lines (approximately 90%), whereas identical exposure to 10 microM difluoromethylornithine (DFMO) induced animal ODC inhibition (approximately 10%). Dose-dependent depletion of endogenous polyamines (putrescine, spermidine, spermine) was achieved in all SCC cell lines following 1 microM and 10 microM BE-4-4-4-4 exposures. Difluoromethylornithine was significantly less potent than BE-4-4-4-4 in its capacity to deplete endogenous polyamines, with no measureable depletion of spermine pools even with 5 mM x 48 h DFMO exposures.

CONCLUSIONS

These data evaluate cytostatic and cytotoxic properties of the polyamine analog BE-4-4-4-4 in human SCCs, and suggest a role for investigation of such agents as an adjuvant to radiation in the therapeutic approach to rapidly dividing human tumors such as those that occur in the H&N.

Modulation of 2-oxoglutarate dehydrogenase and oxidative phosphorylation by Ca2+ in pancreas and adrenal cortex mitochondria

The effect of external free Ca2+ ([Ca2+]ex) on the 2-oxoglutarate dehydrogenase (2-OGDH) activity and the rate of state 3 respiration was studied in dog pancreas and adrenal cortex mitochondria. A method for the preparation of mitochondria from pancreas, free of zymogen granules, was developed. The mitochondria showed high respiratory control values and maintained adequate ADP/O ratios in the course of several hours. Half-maximal stimulation (K0.5) of 2-OGDH activity and state 3 respiration by Ca2+ was decreased twofold by spermine, in both pancreas and adrenal cortex mitochondria incubated with Mg2+; Na+ increased the K0.5 value for Ca2+ in both kinds of mitochondria. The matrix Ca2+ content was enhanced by spermine at different [Ca2+]ex. The Ca2+ gradient ([Ca2+]m/[Ca2+]ex) determined in Fluo 3-loaded pancreas mitochondria was found to be below 1, either in the presence of Na+ or in the absence of spermine. The protonmotive force was increased by 1 microM Ca2+, in state 3 conditions, by 6-8 mV; lower Ca2+ concentrations kept the H+ gradient rather constant. An increase in the spermine/Mg2+ ratio at constant external Ca2+ resulted in stimulation of the 2-OGDH activity and state 3 respiration. The data indicate that matrix Ca2+ may regulate the rate of ATP synthesis in pancreas and adrenal cortex mitochondria, through the modulation of 2-OGDH and the maintenance of a high H+ gradient. In addition to changes in external Ca2+, the variation in the spermine/Mg2+ ratio may also exert control of oxidative phosphorylation.

Treatment of nude mice with 4-amidinoindan -1- one2 '- amidinohydrazone, a new S-adenosylmethionine decarboxylase inhibitor, delays growth and inhibits metastasis of human melanoma cells

CGP 48664A (4-amidinoindan-1-one2'-amidinohydrazone) is a novel inhibitor of S-adenosyl-methionine decarboxylase (SAMDC), a key enzyme in the biosynthesis of polyamines, which are themselves essential for proliferation of mammalian cells. Seven different human melanoma cell lines were treated in vitro with CGP 48664A. High, intermediate and low levels of cytostasis were induced in four, one and two melanoma lines, respectively. This cytostasis was reversed by the addition of exogenous spermidine or spermine to the culture medium. The heterogeneous low metastatic (CGP 48664A-resistant) A375P cells and highly metastatic (CGP 48664A-sensitive) A375SM cells were implanted into the subcutis or injected intravenously into nude mice. Systemic daily administration of CGP 48664A significantly reduced the size of cutaneous lesions and the number of lung metastases in mice implanted with A375SM cells. No beneficial effects were found in mice injected with A375P cells. Drug activity was dose dependent, and maximal effects were observed when treatment began in mice with small tumour burdens. The data suggest that CGP 48664A is effective against melanoma metastasis in nude mice and that its activity should be tested in combination with other cytoreductive agents.

Suppression of ventricular arrhythmias during ischemia-reperfusion by agents inhibiting Ins(1,4,5)P3 release

BACKGROUND

Reperfusion following myocardial ischemia causes a rapid and transient release of inositol (1,4,5)triphosphate [Ins(1,4,5)P3]. The aim of this study was to test whether this increased Ins(1,4,5)P3 release was important for the development of ventricular arrhythmias and whether agents that inhibit this signal transduction pathway, such as aminoglycoside antibiotics, suppress arrhythmias.

METHODS AND RESULTS

In perfused rat hearts, ventricular tachycardia (VT), ventricular fibrillation (VF), and accumulation of Ins(1,4,5)P3 were measured during early reperfusion. A number of different compounds, including neomycin, gentamicin, streptomycin, spermine, reserpine, and prazosin, were effective in inhibiting the reperfusion-induced Ins(1,4,5)P3 release and the onset of VT and VF in parallel. A strong correlation existed between Ins(1,4,5)P3 content, measured at 2 minutes of reperfusion, and the incidence of reperfusion VT and VF. In addition, intravenous gentamicin suppressed the onset of arrhythmias under ischemic and reperfusion conditions in vivo.

CONCLUSIONS

Our results are consistent with the view that Ins(1,4,5)P3 release plays a pivotal role in mediating arrhythmias during early reperfusion. Agents inhibiting Ins(1,4,5)P3 release are antiarrhythmic and may have potential use clinically.

Polyamines alter sequence-specific DNA-protein interactions

The polyamines are abundant biogenic cations implicated in many biological processes. Despite a plethora of evidence on polyamine-induced DNA conformational changes, no thorough study of their effects on the activities of sequence-specific DNA binding proteins has been performed. We describe the in vitro effects of polyamines on the activities of purified, representative DNA-binding proteins, and on complex protein mixtures. Polyamines at physiological concentrations enhance the binding of several proteins to DNA (e.g. USF, TFE3, Ig/EBP, NF-IL6, YY1 and ICP-4, a herpes simplex virus gene regulator), but inhibit others (e.g. Oct-1). The degree of enhancement correlates with cationic charge; divalent putrescine is ineffective whereas tetravalent spermine is more potent than trivalent spermidine. Polyamine effects on USF and ICP-4 result from increased rate of complex formation rather than a decreased rate of dissociation. DNAse I footprint analysis indicated that polyamines do not alter DNA-protein contacts. Polyamines also facilitate formation of complexes involving binding of more than one protein on a DNA fragment.

Evidence that the effects of phospholipids on the activity of the Ca(2+)-ATPase do not involve aggregation

The Ca(2+)-ATPase of skeletal-muscle sarcoplasmic reticulum, solubilized in monomeric from in C12E8, has been reconstituted by dialysis into sealed vesicles of dioleoyl phosphatidylcholine [di(C18:1)PC], dimyristoleoyl phosphatidylcholine [di(C14:1)PC], dinervonyl phosphatidylcholine [di(C24:1)PC] or dipalmitoyl phosphatidylcholine [di(C16:0)PC] in the gel phase, at a phospholipid/ATPase molar ratio of 10,000: 1. Cross-linking experiments show that ATPase molecules are present in these reconstituted vesicles as isolated monomeric species. ATPase activities for the reconstituted vesicles are about half of those for the ATPase reconstituted with the same lipid in unsealed membrane fragments, attributed to a close to random orientation for the ATPase molecules in the reconstituted vesicles. ATPase activities for the ATPase in reconstituted vesicles of di(C14:1)PC or di(C24:1)PC are less than in vesicles of di(C18:1)PC, and no activity could be detected for the ATPase in di(C16:0)PC in the gel phase. It is concluded that effects of lipids on the activity of the ATPase are independent of any changes in the state of aggregation of the ATPase. Inhibition of ATPase activity by spermine and by the hydrophilic domain of phospholamban are observed both for the unreconstituted ATPase and for the ATPase in reconstituted vesicles, so that inhibition is independent of any aggregation caused by these polycationic species. Stimulation of ATPase activity by jasmone is also observed both for the unreconstituted ATPase and for the ATPase in reconstituted vesicles, so that stimulation of the ATPase also does not follow from any change in the state of aggregation of the ATPase.

Control of proton sensitivity of the NMDA receptor by RNA splicing and polyamines

The function of the N-methyl-D-aspartate (NMDA)-preferring glutamate receptor can be regulated by extracellular pH, a process that may be important during ischemia in the brain or during seizures. Protons inhibit NMDA receptor function by 50 percent at pH 7.3 through interactions with the NR1 subunit, and both polyamines and NR1 exon 5 potentiate receptor function through relief of the tonic proton inhibition present at physiological pH. A single amino acid (lysine 211) was identified that mediates the effects of exon 5 in the rat brain. Electroneutral substitutions at this position restored pH sensitivity and, consequently, polyamine relief of tonic inhibition. This effect, together with the structural similarities between polyamines and the surface loop encoded by exon 5, suggest that exon 5 may act as a tethered pH-sensitive constitutive modulator of NMDA receptor function.

Developmental change of the potentiation of NMDA response by spermine

Developmental change in the potentiation of N-methyl-D-aspartate (NMDA) responses by spermine was investigated on the ventromedial hypothalamic neurones acutely dissociated from the rats aged between 5 and 21 days, using a nystatin perforated patch clamp recording in a whole cell mode. Spermine potentiated the NMDA response in a concentration dependent manner between 10(-5) M and 10(-5) M at all ages examined. This potentiation decreased significantly with age. On the other hand, spermine did not affect the kainate and AMPA responses at any age. This developmental change of the modulation of NMDA responses might influence to or be influenced by the behavioural and neuronal changes related to the VMH in the early postnatal life.

Polyamines antagonize N-methyl-D-aspartate-evoked depolarizations, but reduce Mg2+ block

This study utilized a grease-gap preparation to investigate the effects of polyamines on responses of CA1 hippocampal pyramidal cells to N-methyl-D-aspartate (NMDA) and on the block of the NMDA channel by Mg2+. In the absence of added Mg2+, 1,10-diaminodecane (0.1-1 mM) non-competitively antagonized NMDA-evoked depolarizations. Its antagonism slowly progressed to a stable value, was not use-dependent and did not reverse completely upon washout. Similar results were obtained with 100 microM spermine and 1 mM diethylenetriamine. Addition of 1 mM Mg2+ to the superfusion medium greatly reduced these effects. Conversely, the polyamines attenuated the blocking action of Mg2+. Postnatal treatment with alpha-difluoromethylornithine reduced the total polyamine content of area CA1 in 10- to 15-day-old rats almost to the adult level (although spermine content was unaffected). Mg2+ less potently antagonized NMDA-evoked depolarizations in slices from 10- to 15-day-old rats than in slices from adult rats, and this difference was unaffected by the alpha-difluoromethylornithine treatment. These results suggest (1) that there are rapid and slow components to the antagonism of NMDA-evoked depolarizations by polyamines, both of which may involve permeation of the polyamine into or through the NMDA channel: (2) that polyamine release in brain could modulate the Mg2+ sensitivity of responses to NMDA; and (3) that changes in the total content of endogenous polyamine do not explain developmental differences in the sensitivity of NMDA-evoked depolarizations to Mg2+.

Polyamines may increase the percentage of in-vitro fertilized murine oocytes that develop into blastocysts

This study was designed to investigate whether the polyamines spermine, spermidine and putrescine can prevent the arrest of development of in-vitro fertilized murine oocytes from CD1 strain mice. Development in M16 or Brinster's medium with or without polyamine supplementation was assessed and the ability of blastocysts to attach and grow out on laminin was compared with in-vivo-generated embryo blastocysts. Oocytes from old (20 weeks) females showed lower rates of fertilization and subsequent development in comparison with oocytes from young (6-8 weeks old) females, but in both cases < 5% of in-vitro fertilized oocytes achieved the blastocyst stage. In-vitro fertilized young oocytes showed enhanced development to the blastocyst stage with the addition of the polyamine putrescine, although lesser enhancement was seen with spermine and spermidine; this effect was only evident when the oocytes were grown in Brinster's medium, reflecting the need for a particular set of culture conditions for growth-enhancing agents to be effective. Blastocysts generated in putrescine-supplemented Brinster's medium were able to implant on laminin-coated surfaces in vitro and to respond to the cytokines colony-stimulating factor-1, epidermal growth factor and platelet-derived growth factor with increased trophoblast outgrowth to a greater degree than in-vivo-generated blastocysts. Murine in-vitro fertilized embryo development was not enhanced by co-culture with Vero cells. Putrescine was the most effective polyamine, enhancing the in-vitro fertilized oocyte development to blastocysts in a permissive environment.

[The effect of spermine on protein kinase activity and number of cytosolic estradiol receptors]

Spermine decreased distinctly the activity of Ca2+ -phospholipid-dependent protein kinases, whereas not affected the protein kinase A activity. Content of cytosol estradiol receptors was drastically decreased in rat uterine in presence of the polyamine. The data obtained and literature data suggest that activation of estradiol receptors appears to occur after phosphorylation by means of Ca2+ - dependent protein kinases, which are regulated via phosphoinositide-involving mechanism, i.e. these receptors acquire the ability to bind hormones.

Involvement of ornithine decarboxylase and polyamines in glucocorticoid-induced apoptosis of rat thymocytes

Ornithine decarboxylase (ODC), the first and rate-limiting enzyme of polyamine metabolism, has been shown to be required for entry into and progression through the cell cycle. However, the role of ODC and polyamines in apoptosis remains to be determined. We have examined ODC expression and polyamine levels in thymocytes activated to undergo apoptosis by dexamethasone treatment. We have demonstrated a rapid and reversible induction of ODC (mRNA and activity), as previously reported for the mRNA expression of other "early" genes, c-fos, c-jun, and c-myc, in the same experimental model. Surprisingly, polyamine levels diminished progressively starting at 2-4 h after dexamethasone treatment, and spermine was depleted at 8-12 h. This seemed to be relevant since increasing the intracellular polyamine levels by exogenous spermine administration prevented the DNA "laddering" (2-4 h) and the DNA loss from the nucleus (8-18 h) due to dexamethasone treatment. Moreover, the activities of spermidine/spermine N1-acetyltransferase, which controls the cytosolic polyamine interconversion pathway, and of spermidine N8-acetyltransferase, which regulates the nuclear pool and functions of polyamines, were measured in apoptotic cells. Spermidine/spermine N1-acetyltransferase activity progressively increased and might be responsible for spermidine and spermine excretion as acetyl derivatives. In contrast, spermidine N8-acetyltransferase activity remained unchanged. A completely different scenario was observed in proliferating concanavalin A-treated thymocytes, studied for comparison. In this case, polyamine levels increased, remaining at high values until 12 h. This is likely a consequence of the rapid and prolonged induction of ODC (mRNA and activity), accompanied by that of spermidine/spermine N1-acetyltransferase (mRNA and activity).(ABSTRACT TRUNCATED AT 250 WORDS)

Dual effect of spermine on acrosomal exocytosis in capacitated bovine spermatozoa

The influence on spermine on the acrosomal exocytosis of capacitated bovine spermatozoa was studied. Dual effect of spermine was observed, depending on its concentration. It was shown that 10 microM spermine stimulated acrosomal exocytosis and prostaglandin F2 alpha production, whereas higher concentrations of spermine inhibited these processes. Acrosomal exocytosis induced by spermine was inhibited by staurosporine, a specific protein kinase C (PKC) inhibitor, indicating that PKC may be involved in this stimulation. Also, acrosomal exocytosis induced by the PKC activator phorbol 12-myristate-13-acetate was inhibited by 10 mM spermine. Therefore, these data indicate that spermine is involved in signal transduction events leading to exocytosis. We suggest that the concentration-dependent reversal of the stimulatory action of spermine could be explained by the existence of two binding sites for spermine: high affinity sites involved in inducing acrosomal exocytosis by low spermine concentration and low affinity sites mediating inhibition of acrosomal exocytosis by high concentration of spermine.