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

Inducible expression of maize polyamine oxidase in the nucleus of MCF-7 human breast cancer cells confers sensitivity to etoposide

In this study, polyamine oxidase from maize (MPAO), which is involved in the terminal catabolism of spermidine and spermine to produce an aminoaldehyde, 1,3-diaminopropane and H(2)O(2), has been conditionally expressed at high levels in the nucleus of MCF-7 human breast cancer cells, with the aim to interfere with polyamine homeostasis and cell proliferation. Recombinant MPAO expression induced accumulation of a high amount of 1,3-diaminopropane, an increase of putrescine levels and no alteration in the cellular content of spermine and spermidine. Furthermore, recombinant MPAO expression did not interfere with cell growth of MCF-7 cells under normal conditions but it did confer higher growth sensitivity to etoposide, a DNA topoisomerase II inhibitor widely used as antineoplastic drug. These data suggest polyamine oxidases as a potential tool to improve the efficiency of antiproliferative agents despite the difficulty to interfere with cellular homeostasis of spermine and spermidine.

The physiological role of biogenic amines redox reactions in mitochondria. New perspectives in cancer therapy

In tumours, polyamines and amine oxidases increase as compared to normal tissues. Cytotoxicity induced by bovine serum amine oxidase (BSAO) and spermine is attributed to H2O2 and aldehydes produced by the reaction. Increasing the incubation temperature from 37 to 42 degrees C enhances cytotoxicity in cells exposed to spermine metabolites. The combination BSAO/spermine prevents tumour growth, particularly well if the enzyme has been conjugated with a biocompatible hydrogel polymer. Since the tumour cells release endogenous substrates of BSAO, the administration of spermine is not required. Combination with hyperthermia improves the cytocidal effect of polyamines oxidation products. Our findings show that multidrug resistant (MDR) cells are more sensitive to spermine metabolites than their wild-type counterparts, due to an increased mitochondrial activity which induces the generation of intracellular ROS prior to the onset of mitochondrial permeability transition (MPT). It makes this new approach attractive, since the development of MDR is one of the major problems of conventional cancer therapy.

Amine oxidases in apoptosis and cancer

Amine oxidases, the major enzymes of biogenic amines metabolism, are considered to be biological regulators, especially for cell growth and differentiation. A primary involvement of amine oxidases in cancer growth inhibition and progression, especially by means of aldehydes, H(2)O(2) and other reactive oxygen species, the amine oxidase-mediated products of biogenic amines oxidation, has been demonstrated. Amine oxidases are involved in cancer growth inhibition because of the higher content in tumour cells of biogenic amines in comparison to normal cells. The cytotoxic effect can be explained by a damage to cell membranes and/or nuclei or, indirectly, through modulation of membrane permeability transition and therefore apoptosis. The oxidation products of biogenic amines appears to be also carcinogenic, while acrolein, produced from the oxidation of spermine and spermidine, should be a key compound both carcinogenic and cytotoxic. The cancer inhibition/promotion effect of amine oxidases could be explained by taking into consideration the full pattern of the enzyme content of the cell. The balance of amine oxidases and antioxidant enzymes appear to be a crucial point for cancer inhibition or progression. A long lasting imbalance of these enzymes appears to be carcinogenic, while, for a short time, amine oxidases are cytotoxic for cancer cells.

Substrate specificity of the bovine serum amine oxidase and in situ characterisation of aminoaldehydes by NMR spectroscopy

The oxidation of spermidine or homospermidine with bovine serum amine oxidase (BSAO) was monitored in situ, using proton nuclear magnetic resonance spectroscopy in water with 10% D(2)O. NMR assignments were performed by spin decoupling and COSY spectra or by comparison with data from synthetic aminoaldehydes. The results represent the first in situ characterisation of the highly reactive aminoaldehydes and showed oxidation at the N(1) amino group of spermidine and homospermidine. Comparison of homospermidine with a variety of substrates revealed that among straight chain di- and polyamines both an aminopropyl group and two primary amino groups separated by seven (norspermidine) or eight (spermidine) carbon atoms were required for optimal substrate ability. However, highest activity was seen with the substrate N-(4-aminobutyl)hexahydropyrimidine, showing that the substrate channel of BSAO has a dual substrate preference, with moderately bulky substituents at the distal end of a diamine contributing equally well as an alkyl amino group. Cytotoxic investigations of a variety of substrates for BSAO, confirmed previous results, that cytotoxicity is primarily linked to polyamines encompassing the aminopropyl moiety. No acrolein was observed at any time during the oxidation showing that it reacts very fast with available amino groups forming a variety of derivatives.

Human aldehyde dehydrogenase. cDNA cloning and primary structure of the enzyme that catalyzes dehydrogenation of 4-aminobutyraldehyde

Human liver aldehyde dehydrogenase (E3 isozyme), with wide substrate specificity and low Km for 4-aminobutyraldehyde, was only recently characterized [Kurys, G., Ambroziak, W. & Pietruszko, R. (1989) J. Biol. Chem. 264, 4715-4721] and in this study we report on its primary structure. Polyclonal antibodies, specific for the E3 isozyme and three oligonucleotide probes derived from amino acid sequence of the E3 protein, were used for isolation of the first cDNA clone encoding the human enzyme (1503 bp; coding for 440 amino acid residues). Additional clones were obtained by using the first isolated clone as a probe. The largest clone of 1635 bp coded for 462 amino acid residues; it was longer at the 3'end of the cDNA non-coding region. The identity of the clone was established by DNA sequencing and by comparison with peptide sequences derived from the E3 protein, which constituted approximately 29% of the total primary structure of the E3 isozyme. The start codon was never encountered despite a variety of different approaches (500 amino acid residues were expected on the basis of SDS-gel molecular-mass determination of the E3 isozyme subunit). Despite the great catalytic similarity between the E3 and E1 isozymes [Ambroziak, W. & Pietruszko, R. (1991) J. Biol. Chem. 266, 13011-13018], the primary structure of the E3 isozyme has only approximately 40.6% of positional identity with that of the E1 isozyme. Sequence comparison with GenBank and Protein Identification Resource database sequences indicated no primary structure of aldehyde dehydrogenase more closely resembling the E3 isozyme than that of Escherichia coli betaine aldehyde dehydrogenase (52.7% positional identity), a prokaryotic enzyme specific for betaine aldehyde.

A specific peroxidase-coupled activity stain for diamine oxidases

A specific peroxidase-coupled activity staining method for diamine oxidase (DAO) was developed. Diaminobenzidine was found to inhibit DAO and to give rise to unspecific staining. Among several other reagents 4-Cl-1-naphthol was found to be most suitable. Using specific activity staining DAO could be visualized in polyacrylamide gels as a high-molecular-weight complex, which could be dissociated by Tween 20 but not by NP-40, Triton X-100, or Chaps.

Cultured hepatocytes bind and internalize bovine serum amine oxidase-gold complexes

Cultured hepatocytes express binding sites for bovine serum amine oxidase on their membrane surfaces as evaluated at the electron microscopic level by using enzyme-gold complexes. Hepatocytes show binding sites as small clusters of gold granules, not bound in a specialized region of the plasma membrane. The binding competition of enzyme-gold ligand to cells was achieved by preincubation with uncoupled bovine serum amine oxidase. In addition, N-acetyl-galactosamine, N-acetyl-glucosamine and Mannose, at the final concentration of 80 mM, partially inhibit the binding.

Prolonged systemic administration of cyclosporin A affects gingival epithelium

Gingival biopsies were obtained from 12 patients suffering from Behcet's disease who were treated with Cyclosporin A (CsA) for up to 20 months. Preparations were made for examination with both light and scanning electron microscopy (SEM). Along with known changes in the gingival epithelial structure observed following CsA treatment, we also found unusual clusters of needle-like crystallites embedded in the epithelium, mostly at the base of the acanthotic projections. Toluidin blue staining revealed increased numbers of both intact and degranulated mast cells in the attached epithelium. It is concluded that CsA affects the gingival epithelium and that the clinically observed enlargement of gingival tissue following prolonged treatment with CsA is due primarily to CsA-epithelial interaction.