No description available.

Six polyamine anthracene conjugates (Ants) were studied that take advantage of the polyamine transporter system (PTS) to target specific cancer. The structural features of the Ants involve planar aromatic anthracene that has highly cytotoxicity properties and a polyamine chain similar to natural polyamine, which is taken up by eukaryote cells expressing the PTS actively. Experimental data show that Ants with di-substituted polyamine chains have significantly higher DNA binding affinities than the mono-substituted anthracene conjugates. The high ionic conditions (~150 mM NaCl and 260 mM KCl) in the eukaryote cell nucleus extensively impair the apparent DNA binding of the Ants, but may further reinforce DNA structural stability. Combining the published cytotoxicity of the PTS data with the DNA interaction data reported here, the di-substituted polyamine anthracene conjugates have the highest potential to, after cellular uptake via PTS, bind to DNA.

Methods for polyamine derivatization with a panel of extrinsic fluorophores followed by HPLC with fluorescence and UV absorption detection have been developed. Four fluorophores were examined using polyamines and aminoglycosides. o-Phthalaldehyde (OPA) and fluorescamine are selective fluorophores that only react with primary amines; 9- fluorenylmethyl chloroformate (FMOC Cl) and dansyl chloride react with both primary and secondary amines. Reaction and HPLC conditions were optimized with each of the above fluorophores using a series of model mono- and diamines and then applied to natural and semi-synthetic polyamines. The amines that have been investigated are natural di- and polyamines: putrescine, cadaverine, spermidine, spermine, thermospermine, aminoglycosides: kanamycin, paramomycin, neomycin, and synthetic polyamine conjugates e.g. N⁴,N⁹-dioleoylspermine, N¹-cholesteryl spermine carbamate. The resultant derivatives were confirmed by off-line high resolution electrospray ionization mass spectrometry (HR ESI MS). The results show that the synthesis of polyamine derivatives in quantitative yield depends on the time of reaction, the temperature and the ratio of fluorophore reagent. Linearity of derivatization was calculated and regression coefficients ranged from 0.968 to 0.999 with good reproducibility. HR ESI MS analysis of the reaction products demonstrated complete derivatization of both primary and secondary amino groups with dansyl and FMOC fluorescence derivatives and of primary amine groups for OPA and fluorescamine derivatives. Under the ionization conditions used the dansyl derivatives showed, in addition to monovalent ions [M+H]⁺, divalent cations [M+2H]²⁺ because this chromophore contains a basic amine that can be easily protonated. FMOC derivatives gave prominent [M+Na]⁺ ions. The OPA derivatization reaction is rapid, but the products have poor stability. The derivatization with fluorescamine gave multiple products with glucosamine due to the presence of a chiral centre in the fluorophore. The relative quantum yields of the polyaminefluorophore derivatives were examined to determine the effect of intramolecular fluorescence quenching. Dansylation is the fluorescent derivatization method of choice.

No description available.

Les progrès considérables effectués durant les trente dernières années permettent de guérir actuellement plus de 75% des enfants atteints d’un cancer. Néanmoins, certains types de tumeur, comme les gliomes de haut grade et les neuroblastomes métastatiques des enfants de plus de un an, gardent un pronostic particulièrement sombre. De nouvelles stratégies thérapeutiques doivent donc être développées dans ces indications. Dans cette optique, nous avons étudié les effets de deux nouvelles molécules ciblées, le cilengitide, inhibiteur des intégrines αvβ3 et αvβ5, et le F14512, inhibiteur de la topoisomérase II dont la délivrance est vectorisée via le système de transport des polyamines, sur des modèles précliniques de gliomes pédiatriques et de neuroblastomes.Nous avons montré pour la première fois l’existence d’une expression variable d’αvβ3 et αvβ5 dans nos modèles de lignées cellulaires pédiatriques, peu modifiée par les radiations ionisantes. Le traitement par cilengitide a entraîné une inhibition dose-dépendante de la croissance des cellules exprimant αvβ3, liée à un rapide détachement cellulaire et à une sensibilité à l’anoïkis. Cette inhibition de croissance et le détachement cellulaire n’étaient pas corrélés au niveau d’expression des intégrines αvβ3 et αvβ5. Néanmoins, nos travaux semblent montrer que la cible principale du cilengitide est l’intégrine αvβ3. Le traitement par radiations ionisantes n’a pas modifié le détachement induit par le cilengitide dans nos modèles.Nous avons également mis en évidence une activité du système de transport des polyamines dans nos modèles, permettant ainsi une incorporation active du F14512 dans nos cellules de neuroblastomes. Nous avons montré une supériorité de la cytotoxicité du F14512 par rapport à l’étoposide in vitro, et son effet antitumoral a été démontré sur un modèle in vivo. Ces résultats, ainsi que l’effet globalement synergique de l’association du F14512 avec les sels de platine, sont de solides arguments pour poursuivre le développement de cette molécule, en phase clinique chez les patients atteints d’un neuroblastome. Par ailleurs, d’autres investigations pourraient être envisagées dans d’autres types tumoraux dans lesquels l’étoposide occupe une place importante. L’effet radiosensibilisant du F14512 pourrait dans ce cadre ouvrir des perspectives dans la prise en charge des médulloblastomes.[...] / Despite the progress made during the past thirty years leading to cure about 75% of children with cancer, the prognosis of high-grade gliomas (HGG) in children and metastatic neuroblastoma remains poor. The aim of the thesis was to study in vitro the mechanisms of action of a novel inhibitor of αvβ3 and αvβ5 integrins, so-called cilengitide , and of a new topoisomerase II inhibitor targeting the polyamine transport system (PTS), so-called F14512, used as a single drug or in combination therapy in neuroblastoma and pediatric gliomas cell lines. Our panel of cell lines included three pediatric HGG, 2 low-grade pediatric glioma and four neuroblastoma cell lines as well as one adult HGG cell line. The first part of the work involved cilengitide, and was based on clinical and preclinical data previously obtained in adult glioblastoma. There was no data concerning the effect of cilengitide on pediatric HGG or neuroblastoma cells nor about its use in combination with radiation therapy in children. Similarly, no data were available about the level of expression of αvβ3 and αvβ5 integrins on the surface of glioma and pediatric neuroblastoma cells. We showed by flow cytometry significant and various αvβ3 and αvβ5 integrin expression levels in our four neuroblastomas and in most of glioma cell lines. Those expression levels were unrelated to tumor grade. UW479 cells expressed only αvβ5 integrin and therefore served as a negative control. Irradiation of glioma cells slightly increased αvβ3 expression in SF188, KNS42 and Res259 cell lines without inducing de novo integrin expression in UW479 cells. Cilengitide treatment resulted in a dose-dependent inhibition of cell growth leading to obtain an IC50 in the three cell lines tested. UW479 cells were not sensitive to Cilengitide, suggesting that Cilengitide’s action largely depends on αvβ3 inhibition. It was not possible to determine an IC50 value in the adult prototypical U87MG cell line.Cilengitide treatment resulted in a rapid and dose -dependent detachment of more than 50% of our cells expressing αvβ3 when cultured in adherent conditions on vitronectin, which is a specific matrix of integrins, whereas it remained without effect when the cells were grown on collagen, a nonspecific matrix. The growth inhibition induced by cilengitide was comparable to that observed when cells were seeded on polyHEMA gel in physically non-adherent conditions. Not surprisingly, the cilengitide induced no detachment of UW479 cells regardless of the matrix used. In contrast, cell viability assays showed a strong growth inhibition when these cells were seeded on polyHEMA gel. Interestingly, U87MG cells remained able to grow despite a strong detachment induced by cilengitide, suggesting a resistance to anoikis. Finally, inhibition of cell growth induced by cilengitide seemed only linked to cell detachment and corresponded to cell death by anoikis. These inhibitions of cell detachment and cell growth were not correlated with the levels of expression of integrins [...].

Abstract The polyamines putrescine, spermidine and spermine are highly regulated polycations present in virtually all cells of higher eukaryotes. They are essential for proper cell growth and differentiation by participating in various physiological processes including DNA, RNA and protein synthesis, apoptosis and interactions with ion-channels. The complexity of polyamine metabolism and the multitude of compensatory mechanisms that are invoked to maintain polyamine homeostasis argue that these molecules are critical for cell survival. The primary aim of this study was to gain a better understanding of the mode of action of polyamines and the regulatory mechanisms in which they are involved. Transgenic mice overexpressing the polyamine biosynthetic enzymes S-AdoMetDC and ODC were found to maintain their polyamine pools by acetylation of spermidine and spermine and an increased export of these acetylated compounds. The expression of various genes was studied as a response to polyamine deprivation in cell- and kidney organ culture. Among these genes acetyl-CoA synthetase and ornithine decarboxylase were demonstrated to be developmentally regulated. Changes in gene expression patterns, with most of the transcripts upregulated in the polyamine-depleted samples, indicated selective stabilization of mRNAs. Polyamines were shown to play an important role in kidney organogenesis as their depletion results in a reduction of ureteric branching and retardation of tubule formation. The selective changes of various genes in the ureteric bud and mesenchyme indicate that polyamines might have a role in the regulation of epithelial-mesenchymal interactions during mouse kidney development.

The polyamines putrescine, spermidine and spermine play essential roles in the proliferation and differentiation of most eukaryotic cells. Inhibition of the polyamine pathway is known to have antitumour and antiparasitic effects and á-difluoromethylornithine (DFMO), a polyamine biosynthesis inhibitor, is clinically used in the treatment of African sleeping sickness caused by Trypanosoma brucei gambiense. Ornithine decarboxylase (ODC) and Sadenosylmethionine decarboxylase (AdoMetDC) are the rate-limiting enzymes in polyamine metabolism. Usually, these enzymes are individually regulated, however, in the malaria parasite, Plasmodium falciparum, these enzymes are part of a unique bifunctional PfAdoMetDC/ODC protein. In addition, compared to homologous proteins, this malarial protein contains six unique parasite-specific inserted regions, which can be targeted with novel drugs. A modified restriction enzyme-mediated inverse PCR method was developed to delete the largest parasite-specific insert (411 bp) from the large PfAdoMetDC/ODC gene (4257 bp). The method was compared to existing deletion mutagenesis PCR protocols and was shown to be the most effective method (80% mutagenesis efficiency) as opposed to the 40% positively mutated clones obtained with the overlapping primer method in deleting a >100 bp region. The independent removal of all three the PfAdoMetDC domain parasite-specific inserts and subsequent activity analysis thereof showed that these inserts are essential for the catalytic activities of both the decarboxylase domains. Plasmodia conserved secondary structures within these inserts were identified and were also shown to be very important for domain activities, possibly through protein-protein interactions across and within the domains of the bifunctional complex for the efficient regulation of intracellular polyamine levels. The N-terminally located O1 insert in the PfODC domain is a highly conserved and structurally distinct insert, which is essential for both domain activities. Previous studies showed that the deletion of this insert prevents dimerisation of the PfODC monomers and as a result influences association of PfODC with the PfAdoMetDC domain to form the bifunctional ~330 kDa complex. In addition, immobilisation of the insert via the mutagenesis of flanking Gly residues and the disruption of a single conserved α-helix within the insert severely affected both PfODC and PfAdoMetDC activities. It was thus hypothesised that the helix is involved in protein-protein interactions and the dimerisation of the PfODC domain. Size-exclusion chromatography of the monofunctional PfODC and bifunctional PfAdoMetDC/ODC proteins with disrupted helices resulted in the elution of only the monomeric (~85 kDa) and heterodimeric PfAdoMetDC/ODC (~160 kDa) proteins, respectively. The mono- and bifunctional wild type and immobile proteins eluted as both dimeric PfODC (~170 kDa) and heterotetrameric (~330 kDa) fractions as a result of intact protein-protein interactions. These results were subsequently exploited in the design and application of a parasite-specific, mechanistically novel, inhibitory peptide specific for this non-homologous insert in the bifunctional protein. A 1000x molar excess of a synthetic peptide, complementary to the α-helix within the O1 insert but opposite in charge, resulted in a ~40% inhibition of the PfODC enzyme. This study thus provides a proof-of-principle for the use of an inhibitory peptide targeting a parasite-specific insert in the dimerisation interface of a uniquely bifunctional malarial protein. / Dissertation (MSc)--University of Pretoria, 2008. / Biochemistry / unrestricted

Because excessive body weight is a major health issue, there is an urgent need to understand all physiological mechanisms relating to control of fat deposition/mobilization. Here we investigated the linkage between polyamine metabolism and fat homeostasis that we recently discovered to operate in mice. Our previous data show that the expression level of spermine/spermidine acetyltransferase (SSAT), a polyamine catabolic enzyme, potently modulates body fat content of mice. In particular, our data indicated that SSAT overexpressing mice (SSAT-Tg) have reduced acetyl CoA levels and are lean while SSAT null mice (SSAT-ko) are obese. Since the acetyl CoA/malonyl CoA levels are critical for control of free fatty acid synthesis and oxidation via malonyl CoA regulation of CPT-1 (carnitine palmitoyltransferase-1), we hypothesized that genetic manipulation of SSAT alters body fat accumulation by activating of AMP-activated protein kinase pathway and thus has a global effect on energy metabolism. To test this hypothesis, we performed a combination of proteomics and antibody based expression studies in white adipose tissue (WAT) of SSAT-ko, SSAT-wt and SSAT-tg: We identified 9 proteins in WAT that show an increasing gradient across SSAT-ko, SSAT-wt and SSAT-tg, all of which have a connection with acetyl-CoA consumption. These include: a) glycolytic enzymes (aldolase, enolase, pyruvate dehydrogenase); b) TCA cycle enzymes (aconitate hydratase, malate dehydrogenase); c) fatty acid lipolysis and beta oxidation enzymes (hormone-sensitive lipase, monoglyceride lipase, 3-hydroxyacyl CoA dehydrogenase). Additional expression studies using Western blots indicated that acetyl CoA regulates metabolism by AMP-activated protein kinase pathway. Furthermore, to determine how tissue-specific changes in SSAT expression will impact fat accumulation and the precise role of SSAT expression status in fat homeostasis and obesity, we generated adipose-specific SAT1 knockout (FSAT1KO) mice using the Cre-Lox method. On 27-week-old, FSAT1KO mice have higher average body weight than wild type mice (WT: 45.13 ± 2.23 g vs. FSAT1KO: 52.28 ± 1.62 g, p<0.05) when fed a high-fat diet. Larger lipid droplets and lipid accumulation were present in FSAT1KO mouse livers compared to the control WT mice. Several proteins involved in fat metabolism were found to be up-regulated in FSAT1KO mice using GeLC-MS proteomics approach. These data indicated that the lack of SSAT activity in adipose tissue, but not liver or muscle, drives the phenotypic changes in SSAT-ko obese mice. Our interpretation of these results is that genetic modulation of SSAT causes a combination of changes in WAT that involve lipolysis, energy metabolism and calorie loss resulting from polyamine export. In summary, the data indicate that modulation of SSAT activity affects fat metabolism and calorie balance. / Biochemistry

Ce projet d’interface Chimie/Biologie repose sur les expertises complémentaires de deux équipes. Il concerne la conception et le développement d’inhibiteurs dirigés contre les Kinétoplastidés (trypanosomes, leishmanies). Il est en effet urgent de développer de nouvelles stratégies thérapeutiques pour répondre à la chimiorésistance et à la toxicité des médicaments actuellement utilisés contre ces parasites. Le métabolisme et le transport des polyamines étant essentiel chez les parasites, ils constituent des cibles thérapeutiques d’intérêt contre les Kinétoplastidés. Le projet intègre la synthèse de nouveaux dérivés polyamines spécifiques des parasites, l’évaluation sur des modèles in vitro de leishmaniose et de trypanosomose africaine, ainsi qu’une évaluation sur trypanothione réductase. La mise au point d’une méthode de quantification du transport de polyamine a également été initiée. Cinquante-quatre composés, répartis en trois séries chimiques, ont été synthétisés et évalués. Un grand nombre d’entre eux présentent des activités antiparasitaires de l’ordre du micromolaire et des évaluations in vivo sont actuellement en cours avec le composé le plus prometteur. / This project is at the interface of chemistry and biology and relies on the expertise of two different teams. This thesis involves the design and development of inhibitors directed against Kinetoplastids. It is urgent to develop new therapeutic strategies to respond to drug resistance and toxicity of currently used drugs against these parasites. Polyamine metabolism and transporter have been demonstrated as essential for parasite growth. Therefore, these systems are potential drug targets for development of antikinetoplastid compounds. We chose to synthesize polyamine derivatives and evaluate their biological activity against Kinetoplatids. Fifty-four compounds, divided into three chemical series, have been synthesized and evaluated. Many have shown a micromolar biological activity in vitro against parasite. In vivo evaluation is foreseen for the most promising derivative.

This dissertation is a compilation of published work and a manuscript that seeks to understand the role of polyamine metabolism in the regulation of pneumococcal physiology. Streptococcus pneumoniae (pneumococcus) is the major cause of community-acquired pneumonia, and otitis media worldwide. Genetic diversity and serotype replacement, and antibiotics resistance to confound existing therapeutic strategies and limit the effectiveness of the available capsule polysaccharide (CPS) based vaccines. Polyamines such as putrescine, spermidine and cadaverine are ubiquitous polycationic hydrocarbons that interact with negatively charged molecules and modulate important cellular processes. Intracellular polyamine concentrations are regulated by biosynthesis, degradation, and transport. This work investigated the impact of the deletion of polyamine biosynthesis gene, SP_0916 (cadA, lysine/arginine decarboxylase covered in the second, third and fourth chapters), on growth, Gram staining characteristics, capsule production, proteome and stress responses of virulent pneumococcal serotype 4 (TIGR4). We identified loss of capsular polysaccharide (CPS) in DELTA SP_0916 strain. Our proteome results showed a shift in metabolism towards the pentose phosphate pathway (PPP) that could reduce the availability of precursors for CPS and could explain the un-encapsulated phenotype of DELTA SP_0916. Since a shift towards the PPP is usually in response to stress, we compared the stress responses of DELTA SP_0916 to that of TIGR4. Our results show that the mutant was more susceptible to oxidative, nitrosative, and acid stress compared to the wild type. In the fifth chapter we compared the transcriptome, metabolome, stress responses and stress susceptibility of the polyamine transport deficient strain (DELTA potABCD) and S. pneumoniae TIGR4. Results in this chapter show that polyamine transport is essential for pneumococcal stress responses, and capsule biosynthesis. The impact of impaired polyamine synthesis (DELTA SP_0916), and transport (DELTA potABCD) on pneumococcal capsule is due to altered expression of Leloir pathway, reduced glycolysis, and increased PPP, possibly in response to impaired stress responses. These results demonstrate that alteration of polyamine pathways affects pneumococcal stress responses which in turn could limit the availability of precursors for capsule synthesis, and thus have an impact on virulence. Thus, polyamine metabolism is an attractive avenue for developing novel interventions for limiting the spread of S. pneumoniae, a versatile human pathogen.