Maize polyamine oxidase in the presence of spermine/spermidine induces the apoptosis of LoVo human colon adenocarcinoma cells

Amine oxidases, which contribute to the regulation of polyamine levels, catalyze the oxidative deamination of polyamines to generate H2O2 and aldehyde(s). In this study, and at least to the best of our knowledge, maize polyamine oxidase (ZmPAO) was used for the first time with the aim of identifying a novel strategy for cancer therapy. The cytotoxicity and the mechanisms of cell death induced by the enzymatic oxidation products of polyamine generated by ZmPAO were investigated. Exogenous spermine and ZmPAO treatment decreased cell viability in a spermine dose‑ and time‑dependent manner, particularly, the viability of the multidrug‑resistant (MDR) colon adenocarcinoma cells, LoVo DX, when compared with drug‑sensitive ones (LoVo WT). Further analyses revealed that H2O2 derived from spermine was mainly responsible for the cytotoxicity. Flow cytometric analysis revealed that treatment with ZmPAO and spermine increased the apoptotic population of LoVo WT and LoVo DX cells. In addition, we found that treatment with ZmPAO and spermine markedly reduced mitochondrial membrane potential in the LoVo DX cells, in agreement with the results of cell viability and apoptosis assays. Transmission electron microscopic observations supported the involvement of mitochondrial depolarization in the apoptotic process. Therefore, the dysregulation of polyamine metabolism in tumor cells may be a potential therapeutic target. In addition, the development of MDR tumor cells is recognized as a major obstacle in cancer therapy. Therefore, the design of a novel therapeutic strategy based on the use of this combination may be taken into account, making this approach attractive mainly in treating MDR cancer patients.

Potentiation of apple procyanidin-triggered apoptosis by the polyamine oxidase inactivator MDL 72527 in human colon cancer-derived metastatic cells

Apple procyanidins have chemopreventive properties in a model of colon cancer, they affect intracellular signalling pathways, and trigger apoptosis in a human adenocarcinoma-derived metastatic cell line (SW620). In the present study we investigated relationships between procyanidin-induced alterations in polyamine metabolism and apoptotic effects. Apple procyanidins diminish the activities of ornithine decarboxylase and S-adenosyl-L-methionine decarboxylase, key enzymes of polyamine biosynthesis, and they induce spermidine/spermine N(1)-acetyltransferase, which initiates retroconversion of poly-amines. As a consequence of the enzymatic changes polyamine concentrations are diminished, and N(1)-acetyl-polyamines accumulate in SW620 cells. In contrast with expectations MDL 72527, an inactivator of polyamine oxidase (PAO), improved the anti-proliferative effect of procyanidins, and caused an increase of the proportion of apoptotic cells, although it prevented the formation of hydrogen peroxide and 3-acetamidopropanal, the cytotoxic products of PAO-catalysed degradation of N(1)-acetylspermidine and N1-acetylspermine. Addition of 500 microM N1-acetylspermidine to the culture medium in the presence of procyanidins mimicked the effect of MDL 72527. Therefore we presume that the enhanced procyanidin-triggered apoptosis by MDL 72527 is mediated by the accumulation of N(1)-acetyl-polyamines. The observation that apple procyanidins enhance polyamine catabolism and reduce polyamine biosynthesis activity similar to known inducers of SSAT, without sharing their toxicity, and the potentiation of these effects by low concentrations of MDL 72527 suggests apple procyanidins for chemopreventive and therapeutic interventions.

Properties of recombinant human N1-acetylpolyamine oxidase (hPAO): potential role in determining drug sensitivity

The recent cloning of the mammalian gene coding for N(1)-acetylpolyamine oxidase (PAO) provides the opportunity to directly examine the role of human PAO (hPAO) in polyamine homeostasis as well as its potential role in determining cellular response to antitumor polyamine analogues. To facilitate the study of this enzyme, the production, purification, and characterization of the recombinant hPAO is reported. hPAO oxidizes N(1)-acetylspermidine (K(m)=2.1 microM, K(cat)=15.0 s(-1)) and has very high affinity for N(1)-acetylspermine (K(m)=0.85 microM, K(cat)=31.7 s(-1)). The recombinant hPAO does not efficiently oxidize spermine, thereby demonstrating a significant difference in substrate specificity from the previously described human spermine oxidase PAOh1/SMO. Importantly, hPAO demonstrates the ability to oxidize a subset of antitumor polyamine analogues, suggesting that this oxidase activity could have a significant effect on determining tumor sensitivity to these or similar agents. Transfection of A549 human lung cancer cells with an hPAO-expressing plasmid leads to a profound decrease in sensitivity to those analogues which act as substrates, confirming its potential to alter drug response. One similarity that hPAO shares with human PAOh1/SMO, is that certain oligoamine analogues are potent inhibitors of its oxidase activity. The results of these studies demonstrate how changes in polyamine catabolism may affect drug response.

Effect of methylenetetrahydrofolate reductase 677 C-T, 1298 A-C, and 1317 T-C on factor V 1691 mutation in Turkish deep vein thrombosis patients

Possible effect of three common mutations in (MTHFR 677 C-T; 1317 T-C; 1298 C-A) and FV 1691 G-A mutation was studied in Turkish patients with thrombosis and compared with normal controls. The case-control study included 68 patients with the diagnosis of deep vein thrombosis and 66 controls, consecutively selected among subjects without personal and familial history of atherothrombosis. Patients with deep vein thrombosis were selected if Doppler ultrasonography was positive. Only, the comparison of factor V 1691 G-A mutation revealed statistically significant difference in control (6.06%) and deep vein thrombosis (23.5%) group. Risk assessment of double prothrombotic gene alterations revealed only FV 1691 G-A mutation as an independent risk factor for thrombosis (odds ratio 4.7 [1.5-15.0]), but our data suggested that MTHFR 677 has effect on its own (odds ratio 1.97 [0.6-2.7]) but may have synergy with FV 1691 G-A (odds ratio 8.12 [2.0-25.3]). However, MTHFR 1298 A-C and 1317 T-C does not have any effect; furthermore, being heterozygote at two different loci or homozygosity at least in a locus for 677 and 1298 revealed a significant increase (odds ratio 9 and 24 [1.3-59.3 and 2.3-240.3]) between these two groups.

Modulation of K+ channel currents by serum amineoxidase in neurons

The influence of bovine serum amineoxidase (SAO), a circulating copper-enzyme, on neuronal K+ channels is described. Bovine SAO enhanced K+ channel currents in N1E-115 neuroblastoma cells in a time-dependent manner. Unlike ceruloplasmin (another copper-protein, shown as depolarizing factor in neurons), SAO had no effect on resting potential of neurons. However, pretreatment of cells with SAO inhibited ceruloplasmin-induced membrane depolarization. Although ceruloplasmin alone inhibited K+ channel currents, it further enhanced K+ channel currents in the presence of SAO. Therefore, SAO may be another endogenous modulator of neuronal K+ channels with effect and mechanisms different from those of ceruloplasmin.

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.

H2-forming N5,N10-methylenetetrahydromethanopterin dehydrogenase from Methanobacterium thermoautotrophicum. Studies of the catalytic mechanism of H2 formation using hydrogen isotopes

H2-forming N5,N10-methylenetetrahydromethanopterin dehydrogenase is a novel hydrogenase found in most methanogenic archaea. It catalyzes the reversible conversion of N5,N10-methylenetetrahydromethanopterin (CH2 = H4MPT) to N5,N10-methenyltetrahydromethanopterin (CH identical to H4MPT+) and dihydrogen; CH2 = H4MPT + H+<-->CH identical to H4MPT(+) + H2; delta G degrees ' = + 5 kJ/mol. In the following investigation, the formation of H2, HD and D2 was studied in experiments in which either the methylene group of CH2 = H4MPT or water were deuterium labelled. In the case of CD2 = H4MPT and H2O, the dihydrogen formed immediately after the start of the reaction was composed of approximately 50% HD and 50% of H2 at all pH tested. In the case of CH2 = H4MPT and D2O, the dihydrogen generated was composed of approximately 50% HD and 50% D2 at pD 5.7 and of approximately 85% HD and 15% D2 at pD 7.0. Evidence is presented that the enzyme catalyzes a CH identical to H4MPT(+)-dependent isotopic exchange between HD and H2O and between HD and D2O, yielding H2 and D2, respectively. A catalytic mechanism aimed to explain these findings is discussed.

Cytotoxicity and kinetic analysis of purified bovine serum amine oxidase in the presence of spermine in Chinese hamster ovary cells

Bovine serum amine oxidase (BSAO, EC 1.4.3.6) catalyzes the oxidative deamination of polyamines giving rise to the corresponding aldehydes, ammonia and hydrogen peroxide (H2O2). This study demonstrates that amine oxidase (BSAO) purified from bovine serum and exogenous spermine caused cytotoxicity in Chinese hamster ovary (CHO) cells. Cytotoxicity occurred when cells were exposed to BSAO (0.0164-16.4 micrograms/ml) in the presence of spermine (1.9-340 microM). BSAO and spermine alone were not toxic at these concentrations. Cytotoxicity was dependent on the concentration of spermine and on the incubation time, and was also accelerated at 42 degrees C relative to 37 degrees C. Kinetic analysis of the enzymatic reaction, as a function of spermine concentration, showed Michaelis-Menten saturation kinetics. The apparent Vmax increased from 19.1 +/- 0.4 microM min-1 at 37 degrees C to 23.0 +/- 0.3 microM min-1 at 42 degrees C. The apparent Km decreased from 25.5 +/- 2.6 microM at 37 degrees C to 17.7 +/- 1.3 microM at 42 degrees C. Catalase inhibited cytotoxicity, suggesting that H2O2 was partially responsible for cytotoxicity. This work shows that the oxidation products of polyamines, rather than the polyamines themselves, are responsible for cytotoxicity in mammalian cells. The significance of this study is that amine oxidases could have therapeutic potential in cancer treatment regimens and a beneficial effect is likely when the enzyme is used together with clinical hyperthermia.

Inhibition and killing of fungi by the polyamine oxidase-polyamine system. Antifungal activity of the PAO-polyamine system

Both components of the polyamine oxidase (PAO)-polyamine system are known to be present in phagocytes and have thus been postulated to contribute to the antimicrobial activity of these cells. Therefore, the effects of the PAO-polyamine system on three medically important opportunistic fungi were examined. Yeasts of Cryptococcus neoformans, but not Candida albicans blastoconidia or Aspergillus fumigatus conidia, were efficiently killed by the system. Two putative end products of the system, hydrogen peroxide and acrolein, both killed C. neoformans at concentrations attainable with the whole system. However, catalase failed to inhibit activity of the whole system, making hydrogen peroxide an unlikely mediator of killing. Although C. albicans blastoconidia and A. fumigatus conidia were not killed by the PAO-polyamine system, germ tube formation by the former, and hyphal growth by the latter, were markedly inhibited. These data establish that the PAO-polyamine system possesses antifungal activity.

Fusion-mediated microinjection of active amine and diamine oxidases into cultured cells: effect on protein and DNA synthesis in chick embryo fibroblasts and in glioma cells

Serum amine oxidase and/or porcine kidney diamine oxidase were trapped within reconstituted Sendai virus envelopes, and retained their activity. The trapped enzymes that were detected by radioimmunoblots were microinjected into cultured cells by fusion. When diamine oxidase was microinjected into cultured fibroblasts of chick or rat embryos, a temporary arrest in protein and DNA synthesis was observed. The inhibitory effect was more significant when both serum amine oxidase and kidney diamine oxidase were microinjected into those cultured cells. Fibroblasts of either chick or rat embryos transformed by Rous sarcoma virus were more susceptible to the injected enzymes than the normal cultures, showing a complete arrest in protein and DNA synthesis within 4 hours. Similar results were obtained by microinjecting diamine oxidase into cultured glioma cells. The injected enzyme catalyzed the oxidation of intracellular polyamines. The resulting oxidation product (hydrogen peroxide and aminoaldehydes) apparently caused the arrest in the synthesis of macromolecules.

Effect of microinjected amine and diamine oxidases on the ultrastructure of eukaryotic cultured cells

Diamine oxide and serum amine oxidase, which catalyse the oxidation of diamines and polyamines, respectively, were trapped within reconstituted Sendai virus envelopes. These loaded envelopes were incubated with cultured normal chick fibroblasts or with fibroblasts transformed by Rous sarcoma viruses. The binding of the reconstituted envelopes to the cultured cells was confirmed by scanning electron microscopy. It has been shown that the reconstituted envelopes (1-3 microns diameter) were attached to the eukaryotic cells. No significant changes in the morphology of the normal chick embryo fibroblasts were noted upon treatment with enzyme-loaded envelopes. On the other hand, chick embryo fibroblasts transformed by Rous sarcoma virus were affected by the microinjected amine oxidases. Scanning electron microscopy demonstrated the formation of holes in the microinjected cells. Similar morphological changes were also observed when diamine oxidase was microinjected into cultured glioma cells. These holes may be the result of the ejection of the nucleus. These findings are in line with the observed effect of the injected amine oxidases on macromolecular synthesis in normal and transformed chick embryo fibroblasts.

Differences in sensitivity of Schistosoma mansoni schistosomula, Dirofilaria immitis microfilariae, and Nematospiroides dubius third-stage larvae to damage by the polyamine oxidase-polyamine system

The effect of the polyamine oxidase (PAO)-polyamine system on some helminths was examined in vitro. Both Schistosoma mansoni schistosomula and Dirofilaria immitis microfilariae were highly sensitive to this system, the latter more so than the former. In contrast, exsheathed third-stage larvae of Nematospiroides dubius were resistant to the effects of the PAO-polyamine system. After incubation of microfilariae with either spermine or spermidine in the presence of serum containing PAO (bovine serum or human retroplacental serum) or partially purified PAO, damage of worms occurred, compatible with our criteria for worm death. Similar results were obtained with schistosomula by using spermine. The damage seemed to be mediated by PAO products other than hydrogen peroxide because catalase did not protect either parasite. Our data demonstrate that helminths may be damaged by products of the PAO-polyamine system.

Polyamine oxidase in human retroplacental serum inhibits the growth of Plasmodium falciparum

Human retroplacental serum (RPS) containing polyamine oxidase inhibited the growth of the Camp strain of Plasmodium falciparum in vitro as assayed by the parasite's decreased incorporation of 3H-hypoxanthine. Inhibition was dose-dependent on the concentrations of serum polyamine oxidase and added polyamines. Almost complete inhibition was seen in 96-hr asynchronous cultures containing 10% RPS and in those containing 1.2% RPS plus 50 microM polyamine. Subtle morphologic changes in mature stages and decreased numbers of new rings were associated with inhibition seen in 19-hr synchronous cultures initiated at the trophozoite stage. These incubation times were longer than in previous reports showing inhibition of malaria parasites by bovine polyamine oxidase but not by human polyamine oxidase. Macrophages contain polyamine oxidase, the reaction products of which are known to be similar to those of RPS polyamine oxidase but different from those of bovine polyamine oxidase. It remains to be determined whether human polyamine oxidase, acting upon ubiquitous polyamines, contributes to host defenses against malaria.

[Detection of polyamines by a new enzymatic differential assay. (4). Fundamental study on a new enzymatic differential assay of blood]

The enzymatic method for isolation and determination of urinary polyamines was modified to measure the polyamines in the blood. High recovery rates of polyamine in blood by enzymatic hydrolyzation were obtained, namely, 101.9 +/- 4.4% for diamine, 96.0 +/- 5.4% for spermidine and 104.1 +/- 3.3% for spermine. Furthermore excellent linearity was demonstrated. Within-run precision of polyamine in blood was excellent, namely, in C.V., 1.15% for Reaction 1, 2.11% for Reaction 2 and 2.79% for Reaction 3. This method was compared with high pressure liquid chromatography (HPLC), and a close correlation was demonstrated for all the fractions: diamine r = 0.8824, y = 1.367x+0.0417 (n = 15); spermidine r = 0.9878, y = 0.806x+5.218 (n = 15); spermine r = 0.9764, y = 1.068x-0.9195 (n = 15).

Inhibition of the respiratory burst of human neutrophils by the polyamine oxidase-polyamine system

The addition of the polyamines, spermine and spermidine, to human neutrophils caused a depression of the hexose-monophosphate (HMP) shunt activity of neutrophils stimulated with latex particles but not of unstimulated cells. The effect was dependent on the presence of bovine serum and was not observed when normal human serum was substituted for bovine serum. The polyamine oxidase (PAO) in bovine serum was probably responsible for generating the activity since normal human serum lacks PAO. A role for PAO was further supported by the finding that partially purified bovine PAO in the presence of polyamines similarly mediated inhibition of HMP shunt activity in stimulated neutrophils. Catalase failed to prevent the inhibitory effects of the PAO-polyamine system suggesting that H2O2 is not the responsible product. In addition, our results show that human pregnancy serum known to contain PAO activity in the presence of polyamines mediated a similar inhibition of the respiratory burst.

Stimulation of the hexose monophosphate pathway by pyrroline-5-carboxylate reductase in the lens

Addition of pyrroline-5-carboxylate (P5C) or its precursors to rat lenses cultured for 24 hr in TC-199 medium containing 14C-glucose results in an apparent concentration-dependent increase in hexose monophosphate-pentose (HMP) pathway activity. Addition of proline, the reduction product of P5C, did not result in an increase, suggesting that stimulation of the HMP pathway is related to the reduction of P5C to proline by the enzyme P5C reductase. No apparent feedback inhibition on P5C reductase was observed. Stimulation of HMP pathway activity by P5C was also observed in the lenses of Philly and Nakano mouse, two models of congenital osmotic cataracts. Compared with its genetic control, the Swiss--Webster mouse, generally no difference in the lenticular levels of HMP pathway activity was observed in the Philly mouse--even after the onset of cataract. Stimulation of the HMP pathway in the Philly lens by P5C, however, was consistently lower than its control. In the lenses from the Nakano mouse and its genetic control, the Balb/c mouse, no difference in the percentage stimulation of the HMP pathway resulting from the addition of P5C was observed, but HMP pathway activity in the Nakano lens was consistently lower than that of the control.

Inhibition of human neutrophil locomotion by the polyamine oxidase-polyamine system

The polyamines, spermine and spermidine, in the presence of either bovine serum [containing polyamine oxidase (PAO) activity] or partially purified PAO, inhibited human neutrophil locomotion. This effect could not be produced by either bovine serum, PAO, or the polyamines alone. The results suggested that at least two of the products generated during the oxidation of polyamines by PAO, namely H2O2 and ammonia, are not responsible for the effects on neutrophils. Acrolein, a breakdown product of other products (aminoaldehydes), was found to inhibit the neutrophil functions. Since polyamines, and possibly PAOs, accumulate at inflammatory sites, products of the PAO-polyamine reaction could function as regulators of the inflammatory response.

[Effect of serum polyamine oxidase on normal and tumor cells]

Serum polyamine oxidase was studied for its effect on normal and transformed fibroblasts, Erlich carcinoma, Zaidela hepatoma and experimental Svec leukaemia cells as well as on K-562 human leukaemia cells. It is found that the cell death was induced by dialdehydes generated by polyamine deamination. Autoradiographically it was shown that dialdehydes cross-link the cell plasma membranes. It is suggested that serum polyamine oxidase is one of the factors responsible for the phenomenon of constitutional resistance which provides subsequent realization of the long-term immune defence.

Polyamine oxidase mediates intra-erythrocytic death of Plasmodium falciparum

Using a number of established culture strains of Plasmodium falciparum, the effects of the addition of polyamine oxidase and spermine on the intra-erythrocytic forms were studied. Cultures to which polyamine oxidase and polyamines were added contained only degenerate parasites but if one or other were added alone the cultures were similar to the controls. The effects were confirmed by 35S-methionine incorporation.

Polyamine oxidase-mediated killing of African trypanosomes

African trypanosomes, Trypanosoma brucei brucei, T. vivax and T. congolense, were killed when incubated in vitro with ruminant sera in the presence of exogeneous spermidine, and were non-infective for mice. Purified polyamine oxidase in the presence of spermidine-mediated similar killing of trypanosomes. The abundance of polyamine oxidase activity in ruminant sera which can react with polyamines to produce products with cytotoxic properties may explain the trypanosome killing. This system may contribute to non-specific parasite killing in vivo.

Oxygen-dependent free radicals in spermine oxidation cytostatis and chemiluminescence and the role of superoxide dismutase

Spermine interacted with serum polyamine oxidase (PAO) to arrest proliferation of cultured Bri8 lymphocytes. Arrest was independent of catalase activity and was not directly due to an H(2)O(2) byproduct. Arrest was averted by 3-hydroxybenzyloxyamine, which inactivates the pyridoxal co-factor of PAO. The oxidation of spermine in the presence of different concentrations of PAO was non-linear, which implied complex intermediate events for conversion of spermine to labile di-oxidized spermine (N,N'-bis(3-propionaldehyde)-1,4-butanediamine) with, perhaps, overall generation of free radicals (O(2) (-·) and ·OH) which are damaging to cells. Exogenous free radicals were apparently neither direct participants in cytostasis, nor in the chemiluminescence demonstrable for spermine oxidation. Thiourea, an ·OH scavenger, protected against both proliferation arrest and luminescence. Many other powerful ·OH scavengers, however, were ineffective. Though reaction mixtures reduced ferricytochrome c initially, reduction was not inhibited by superoxide dismutase (SOD) which indicated that the anion O(2) (-·) had not been generated. The powerful reducing capability of di-oxidized spermine itself could have competed against any O(2) (-·) for ferricytochrome c reduction. Nevertheless, O(2) (-·) was generated during further PAO conversion and/or auto-oxidation of di-oxidized spermine. Curiously, addition of SOD to destroy presumptive O(2) (-·) variably potentiated cytotoxicity. Blockage of any anion channels in the cell plasma membrane by stilbene derivatives did not influence cytotoxicity. Thus, findings support our previous evidence that cationic di-oxidized spermine is a potent G(1) inhibitor of cell proliferation. The possibility of intracellular free-radical and thiol involvement is discussed.

Mechanism of action of oxidized polyamines on the metabolism of human spermatozoa

Oxidized spermine, an iminoaldehyde (N,N'-bis (3-propionaldehyde) 1,4-diaminobutane), is a non-competitive inhibitor of fructolysis by human spermatozoa. The inhibition constant is about 0.3 mM. In experiments with [U-14C]fructose the iminoaldehyde caused a more pronounced depression of the formation of CO2 than of lactate. The iminoaldehyde was without influence on the conversion of fructose to lactate by cell-free extracts of spermatozoa, but it markedly decreased the uptake of fructose and lactate by spermatozoa. These findings strongly suggest that inhibition of the fructose metabolism of intact spermatozoa was due to interaction of the iminoaldehyde with sperm membranes and not to inhibition of any enzyme of the glycolytic pathway. Several aliphatic and aromatic aldehydes were also tested for their ability to inhibit sugar utilization of human spermatozoa: only n-hexanal exerted an inhibitory effect, the extent of which approached that of oxidized spermine.