Polyamine Modulation of Anticonvulsant Drug Response: A Potential Mechanism Contributing to Pharmacoresistance in Chronic Epilepsy.

Despite the development of numerous novel anticonvulsant drugs, ∼30% of epilepsy patients remain refractory to antiepileptic drugs (AEDs). Many established and novel AEDs reduce hyperexcitability via voltage- and use-dependent inhibition of voltage-gated Na+ channels. For the widely used anticonvulsant carbamazepine (CBZ), use-dependent block of Na+ channels is significantly reduced both in experimental and human epilepsy. However, the molecular underpinnings of this potential cellular mechanism for pharmacoresistance have remained enigmatic.Here, we describe the mechanism that leads to the emergence of CBZ-resistant Na+ channels. We focused on the endogenous polyamine system, which powerfully modulates Na+ channels in a use-dependent manner. We had shown previously that the intracellular polyamine spermine is reduced in chronic epilepsy, resulting in increased persistent Na+ currents. Because spermine and CBZ both bind use-dependently in spatial proximity within the Na+ channel pore, we hypothesized that spermine loss might also be related to diminished CBZ response. Using the pilocarpine model of refractory epilepsy in male rats and whole-cell patch-clamp recordings, we first replicated the reduction of use-dependent block by CBZ in chronically epileptic animals. We then substituted intracellular spermine via the patch pipette in different concentrations. Under these conditions, we found that exogenous spermine significantly rescues use-dependent block of Na+ channels by CBZ. These findings indicate that an unexpected modulatory mechanism, depletion of intracellular polyamines, leads both to increased persistent Na+ currents and to diminished CBZ sensitivity of Na+ channels. These findings could lead to novel strategies for overcoming pharmacoresistant epilepsy that target the polyamine system.SIGNIFICANCE STATEMENT Pharmacoresistant epilepsy affects ∼18 million people worldwide, and intense efforts have therefore been undertaken to uncover the underlying molecular and cellular mechanisms. One of the key known candidate mechanisms of pharmacoresistance has been a loss of use-dependent Na+ channel block by the anticonvulsant carbamazepine (CBZ), both in human and experimental epilepsies. Despite intense scrutiny, the molecular mechanisms underlying this phenomenon have not been elucidated. We now show that a loss of intracellular spermine in chronic epilepsy is a major causative factor leading to the development of CBZ-resistant Na+ currents. This finding can be exploited both for the screening of anticonvulsants in expression systems, and for novel strategies to overcome pharmacoresistance that target the polyamine system.

Polyamines levels increase in smut teliospores after contact with sugarcane glycoproteins as a plant defensive mechanism.

Previous studies have already highlighted the correlation between Sporisorium scitamineum pathogenicity and sugarcane polyamine accumulation. It was shown that high infectivity correlates with an increase in the amount of spermidine, spermine and cadaverine conjugated to phenols in the sensitive cultivars whereas resistant plants mainly produce free putrescine. However, these previous studies did not clarify the role of these polyamides in the disorders caused to the plant. Therefore, the purpose of this research is to clarify the effect of polyamines on the development of smut disease. In this paper, commercial polyamines were firstly assayed on smut teliospores germination. Secondly, effects were correlated to changes in endogenous polyamines after contact with defense sugarcane glycoproteins. Low concentrations of spermidine significantly activated teliospore germination, while putrescine had no activating effect on germination. Interestingly, it was observed that the diamine caused nuclear decondensation and breakage of the teliospore cell wall whereas the treatment of teliospores with spermidine did not induce nuclear decondensation or cell wall breakdown. Moreover, the number of polymerized microtubules increased in the presence of 7.5 mM spermidine but it decreased with putrescine which indicates that polyamines effects on Sporisorium scitamineum teliospore germination could be mediated through microtubules interaction. An increased production of polyamines in smut teliospores has been related to sugarcane resistance to the disease. Teliospores incubation with high molecular mass glycoproteins (HMMG) from the uninoculated resistant variety of sugarcane, Mayari 55-14, caused an increase of the insoluble fraction of putrescine, spermidine and spermine inside the teliospore cells. Moreover, the level of the soluble fraction of spermidine (S fraction) increased inside teliospores and the excess was released to the medium. The HMMG glycoproteins purified from Mayarí 55-14 plants previously inoculated with the pathogen significantly increased the levels of both retained and secreted soluble putrescine and spermidine. Polyamines levels did not increase in teliospores after incubation with HMMG produced by non resistant variety Barbados 42231 which could be related to the incapacity of these plants to defend themselves against smut disease. Thus, a hypothesis about the role of polyamines in sugarcane-smut interaction is explained.

Comparative studies on the interaction between biogenic polyamines and bovine intestinal alkaline phosphatases: spectroscopic and theoretical approaches.

In this work, the effect of two organic polyamines (spermine and spermidine) on the fluorescence intensity and activity of bovine intestinal alkaline phosphatase (BIALP) are investigated. The interaction of BIALP with spermine and spermidine was studied in a diethanolamine buffer with 0.5 mM magnesium chloride (pH 9.8) and at two temperatures by using the fluorescence quenching method. Furthermore, the activity of enzyme was studied using UV-Vis spectrophotometry in a diethanolamine buffer with 0.5 mM magnesium chloride, at 37 °C, in the absence and presence of different concentrations of each polyamine (0-5 mM). It was demonstrated that both polyamines quenched the intrinsic fluorescence of BIALP by the static quenching process. Based on these results, the values of the binding site for both polyamines were close to each other and decreased by increasing the temperature. The calculated thermodynamic parameters (ΔH° < 0 and ΔS° < 0) also showed that the acting forces in the formation of the complex between BIALP and polyamines were hydrogen bonds and van der Waals forces with an overall favorable Gibbs free energy change (∆G° < 0). In addition, kinetic studies revealed that these polyamines enhanced the enzyme activity of BIALP in a concentration-dependent manner. This result also indicated that spermine had more of an effect on BIALP activity in the same condition. Also, molecular docking as well as thermodynamic parameters showed that hydrogen bonds and van der Waals forces played an important role in the stabilization of BIALP-polyamine complexes.

Polyamine Deacetylase Structure and Catalysis: Prokaryotic Acetylpolyamine Amidohydrolase and Eukaryotic HDAC10.

Polyamines such as putrescine, spermidine, and spermine are small aliphatic cations that serve myriad biological functions in all forms of life. While polyamine biosynthesis and cellular trafficking pathways are generally well-defined, only recently has the molecular basis of reversible polyamine acetylation been established. In particular, enzymes that catalyze polyamine deacetylation reactions have been identified and structurally characterized: histone deacetylase 10 (HDAC10) from Homo sapiens and Danio rerio (zebrafish) is a highly specific N8-acetylspermidine deacetylase, and its prokaryotic counterpart, acetylpolyamine amidohydrolase (APAH) from Mycoplana ramosa, is a broad-specificity polyamine deacetylase. Similar to the greater family of HDACs, which mainly serve as lysine deacetylases, both enzymes adopt the characteristic arginase-deacetylase fold and employ a Zn2+-activated water molecule for catalysis. In contrast with HDACs, however, the active sites of HDAC10 and APAH are sterically constricted to enforce specificity for long, slender polyamine substrates and exclude bulky peptides and proteins containing acetyl-l-lysine. Crystal structures of APAH and D. rerio HDAC10 reveal that quaternary structure, i.e., dimer assembly, provides the steric constriction that directs the polyamine substrate specificity of APAH, whereas tertiary structure, a unique 310 helix defined by the P(E,A)CE motif, provides the steric constriction that directs the polyamine substrate specificity of HDAC10. Given the recent identification of HDAC10 and spermidine as mediators of autophagy, HDAC10 is rapidly emerging as a biomarker and target for the design of isozyme-selective inhibitors that will suppress autophagic responses to cancer chemotherapy, thereby rendering cancer cells more susceptible to cytotoxic drugs.

An overview of polyamine metabolism in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest major cancers, with a five year survival rate of less than 8%. With current therapies only giving rise to modest life extension, new approaches are desperately needed. Even though targeting polyamine metabolism is a proven anticancer strategy, there are no reports, which thoroughly survey the literature describing the role of polyamine biosynthesis and transport in PDAC. This review seeks to fill this void by describing what is currently known about polyamine metabolism in PDAC and identifies new targets and opportunities to treat this disease. Due to the pleiotropic effects that polyamines play in cells, this review covers diverse areas ranging from polyamine metabolism (biosynthesis, catabolism and transport), as well as the potential role of polyamines in desmoplasia, autophagy and immune privilege. Understanding these diverse roles provides the opportunity to design new therapies to treat this deadly cancer via polyamine depletion.

Polyamine Metabolism and Oxidative Protein Folding in the ER as ROS-Producing Systems Neglected in Virology.

Reactive oxygen species (ROS) are produced in various cell compartments by an array of enzymes and processes. An excess of ROS production can be hazardous for normal cell functioning, whereas at normal levels, ROS act as vital regulators of many signal transduction pathways and transcription factors. ROS production is affected by a wide range of viruses. However, to date, the impact of viral infections has been studied only in respect to selected ROS-generating enzymes. The role of several ROS-generating and -scavenging enzymes or cellular systems in viral infections has never been addressed. In this review, we focus on the roles of biogenic polyamines and oxidative protein folding in the endoplasmic reticulum (ER) and their interplay with viruses. Polyamines act as ROS scavengers, however, their catabolism is accompanied by H2O2 production. Hydrogen peroxide is also produced during oxidative protein folding, with ER oxidoreductin 1 (Ero1) being a major source of oxidative equivalents. In addition, Ero1 controls Ca2+ efflux from the ER in response to e.g., ER stress. Here, we briefly summarize the current knowledge on the physiological roles of biogenic polyamines and the role of Ero1 at the ER, and present available data on their interplay with viral infections.

Hepatitis C virus alters metabolism of biogenic polyamines by affecting expression of key enzymes of their metabolism.

Chronic infection with hepatitis C virus (HCV) induces liver fibrosis and cancer. In particular metabolic alterations and associated oxidative stress induced by the virus play a key role in disease progression. Albeit the pivotal role of biogenic polyamines spermine and spermidine in the regulation of liver metabolism and function and cellular control of redox homeostasis, their role in the viral life cycle has not been studied so far. Here we show that in cell lines expressing two viral proteins, capsid and the non-structural protein 5A, expression of the two key enzymes of polyamine biosynthesis and degradation, respectively, ornithine decarboxylase (ODC) and spermidine/spermine-N1-acetyl transferase (SSAT), increases transiently. In addition, both HCV core and NS5A induce sustained expression of spermine oxidase (SMO), an enzyme that catalyzes conversion of spermine into spermidine. Human hepatoma Huh7 cells harboring a full-length HCV replicon exhibited suppressed ODC and SSAT levels and elevated levels of SMO leading to decreased intracellular concentrations of spermine and spermidine. Thus, role of HCV-driven alterations of polyamine metabolism in virus replication and development of HCV-associated liver pathologies should be explored in future.

[Low-molecular-weight regulators of biogenic polyamine metabolism affect cytokine production and expression of hepatitis С virus proteins in Huh7.5 human hepatocarcinoma cells].

Hepatitis C virus (HCV) induces the expression of the genes of proinflammatory cytokines, the excessive production of which may cause cell death, and contribute to development of liver fibrosis and hepatocarcinoma. The relationship between cytokine production and metabolic disorders in HCV-infected cells remains obscure. The levels of biogenic polyamines, spermine, spermidine, and their precursor putrescine, may be a potential regulator of these processes. The purpose of the present work was to study the effects of the compounds which modulate biogenic polyamines metabolism on cytokine production and HCV proteins expression. Human hepatocarcinoma Huh7.5 cells have been transfected with the plasmids that encode HCV proteins and further incubated with the following low-molecular compounds that affect different stages of polyamine metabolism: (1) difluoromethylornithine (DFMO), the inhibitor of ornithine decarboxylase, the enzyme that catalyzes the biosynthesis of polyamines; (2) N,N'-bis(2,3-butane dienyl)-1,4-diaminobutane (MDL72.527), the inhibitor of proteins involved in polyamine degradation; and (3) synthetic polyamine analog N^(I),N^(II)-diethylnorspermine (DENSpm), an inducer of polyamine degradation enzyme. The intracellular accumulation and secretion of cytokines (IL-6, IL-1ß, TNF-α, and TGF-ß) was assessed by immunocytochemistry and in the immunoenzyme assay, while the cytokine gene expression was studied using reverse transcription and PCR. The effects of the compounds under analysis on the expression of HCV proteins were analyzed using the indirect immunofluorescence with anti-HCV monoclonal antibodies. It has been demonstrated that, in cells transfected with HCV genes, DFMO reduces the production of three out of four tested cytokines, namely, TNF-α and TGF-ß in cells that express HCV core, Е1Е2, NS3, NS5A, and NS5B proteins, and IL-1ß in the cells that express HCV core, Е1Е2, and NS3 proteins. MDL72527 and DENSpm decreased cytokine production to a lesser extent. Incubation with DFMO led to a 28-32% decrease in the number of cells expressing NS5B or NS5A, both of which are key components of the HCV replication complex. The results obtained in the work indicate that a further detailed study of the antiviral activity of DFMO is required in order to assess its potential as an anti-hepatitis C therapeutic agent.

A Nascent Peptide Signal Responsive to Endogenous Levels of Polyamines Acts to Stimulate Regulatory Frameshifting on Antizyme mRNA.

The protein antizyme is a negative regulator of cellular polyamine concentrations from yeast to mammals. Synthesis of functional antizyme requires programmed +1 ribosomal frameshifting at the 3' end of the first of two partially overlapping ORFs. The frameshift is the sensor and effector in an autoregulatory circuit. Except for Saccharomyces cerevisiae antizyme mRNA, the frameshift site alone only supports low levels of frameshifting. The high levels usually observed depend on the presence of cis-acting stimulatory elements located 5' and 3' of the frameshift site. Antizyme genes from different evolutionary branches have evolved different stimulatory elements. Prior and new multiple alignments of fungal antizyme mRNA sequences from the Agaricomycetes class of Basidiomycota show a distinct pattern of conservation 5' of the frameshift site consistent with a function at the amino acid level. As shown here when tested in Schizosaccharomyces pombe and mammalian HEK293T cells, the 5' part of this conserved sequence acts at the nascent peptide level to stimulate the frameshifting, without involving stalling detectable by toe-printing. However, the peptide is only part of the signal. The 3' part of the stimulator functions largely independently and acts at least mostly at the nucleotide level. When polyamine levels were varied, the stimulatory effect was seen to be especially responsive in the endogenous polyamine concentration range, and this effect may be more general. A conserved RNA secondary structure 3' of the frameshift site has weaker stimulatory and polyamine sensitizing effects on frameshifting.

Dual Regulatory Role of Polyamines in Adipogenesis.

Adipogenesis is a complex process, accompanied by a chain of interdependent events. Disruption of key events in this cascade may interfere with the correct formation of adipose tissue. Polyamines were demonstrated necessary for adipogenesis; however, the underlying mechanism by which they act has not been established. Here, we examined the effect of polyamine depletion on the differentiation of 3T3-L1 preadipocytes. Our results demonstrate that polyamines are required early in the adipogenic process. Polyamine depletion inhibited the second division of the mitotic clonal expansion (MCE), and inhibited the expression of PPARγ and C/EBPα, the master regulators of adipogenesis. However, it did not affect the expression of their transcriptional activator, C/EBPß. Additionally, polyamine depletion resulted in elevation of mRNA and protein levels of the stress-induced C/EBP homologous protein (CHOP), whose dominant negative function is known to inhibit C/EBPß DNA binding activity. Conditional knockdown of CHOP in polyamine-depleted preadipocytes restored PPARγ and C/EBPα expression, but failed to recover MCE and differentiation. Thus, our results suggest that the need for MCE in the adipogenic process is independent from the requirement for PPARγ and C/EBPα expression. We conclude that de novo synthesis of polyamines during adipogenesis is required for down-regulation of CHOP to allow C/EBPß activation, and for promoting MCE.

Transglutaminase as polyamine mediator in plant growth and differentiation.

Transglutaminases (TGases) are ubiquitous enzymes catalyzing many biological reactions. The best-known TGase activity, namely the transamidation of specific proteins by polyamines (PAs), has been studied in plants to verify if TGase is a mediator of PAs mechanism of action to re-interpret some of PAs effects. Usually, the TGase activity is present at basal level in plant cells, but it can be induced by internal or external events or stresses, like rehydration, wounding, light, developmental differentiation and programmed cell death (PCD). Here, two models of induced growth are presented, namely pollen apical growth and dedifferentiation followed by reacquisition of the pluripotency of already differentiated cells. Moreover, PAs and TGase involvement during the differentiation and the activity of organelles and finally during the terminal organ differentiation or self-incompatibility-induced PCD are reported. In all of these models, TGase plays a role. The enzyme was detected in several cell compartments, like cytosol, chloroplasts and possibly mitochondria, microsomal fraction, cell wall and also extracellularly. The products of TGase catalysis, modified with PAs, mainly consist of high molecular mass complexes. Among the protein substrates until now identified we mention the cytoskeletal proteins, actin and tubulin, whose PA modification also affects their interaction with motor proteins and the dynamic of cytoskeleton. The most widely studied substrates are component of chloroplast photosystems, in particular light-harvesting complexes, whose modification is light dependent and whose differentiation and size are affected by TGase, thereby conditioning photosynthetic efficiency and photoprotection. Finally, modification of cell wall substrates affects wall growth and reinforcement.

Modulation by miR-29b of intestinal epithelium homoeostasis through the repression of menin translation.

Menin regulates distinct cellular functions by regulating gene transcription through its interaction with partner transcription factors, but the exact mechanisms that control menin levels remain largely unknown. In the present study we report that Men1 mRNA, encoding menin, is a novel target of miR-29b and that miR-29b/Men1 mRNA association regulates menin expression post-transcriptionally in rat intestinal epithelial cells (IECs). Overexpression of a miR-29b precursor lowered the levels of Men1 mRNA modestly, but reduced new synthesis of menin robustly; conversely, antagonism of miR-29b enhanced menin protein synthesis and steady-state levels. The repressive effect of miR-29b on menin expression was mediated through a single binding site in the coding region of Men1 mRNA, because point mutation of this site prevented miR-29b-induced repression of menin translation. Increasing cellular polyamines due to overexpression of ornithine decarboxylase (ODC) enhanced menin translation by reducing miR-29b, whereas polyamine depletion by inhibiting ODC increased it, thus suppressing menin expression. Moreover, an increase in menin abundance in an miR-29b-silenced population of IECs led to increased sensitivity to apoptosis, which was prevented by silencing menin. These findings indicate that miR-29b represses translation of Men1 mRNA, in turn affecting intestinal epithelial homoeostasis by altering IEC apoptosis.

Construction of a metabolomics profile of arsenic trioxide effect in gastric carcinoma cell line SGC7901.

Arsenic trioxide (ATO) is highly effective for treating acute promyelocytic leukemia. It also holds the promise for treating solid tumors, including gastric carcinoma. However, the molecular mechanism of the effectiveness of ATO to solid tumor is still poorly understood. In this study, we chosed gastric carcinoma as an example and tried to reveal the antitumor mechanism through metabolomics. Gastric carcinoma cell line SGC7901 was treated with ATO for 6, 12, and 24 h. The global metabolite profiles were monitored by metabolomics analysis using gas chromatography (GC)/mass spectrometry (MS) and liquid chromatography/MS/MS. A total of 281 certified metabolites were reliably detected. Bioinformatics analysis showed that glycerophospholipid synthesis, one-carbon synthesis, and glutathione synthesis were affected dramatically. Other cellular functions/pathways that had been affected included inflammatory response, nicotinamide adenine dinucleotide (NAD(+)), and polyamine biosynthesis pathway. The metabolomics data from this study, in combination with previous transcriptomics and proteomics data, could serve as valuable resources for the understanding of the specific antitumor mechanism of ATO treatment.

Over-expression of mouse ornithine decarboxylase gene under the control of fruit-specific promoter enhances fruit quality in tomato.

Diamine putrescine (Put) and polyamines; spermidine (Spd) and spermine (Spm) are essential component of every cell because of their involvement in the regulation of cell division, growth and development. The aim of this study is to enhance the levels of Put during fruit development and see its implications in ripening and quality of tomato fruits. Transgenic tomato plants over-expressing mouse ornithine decarboxylase gene under the control of fruit-specific promoter (2A11) were developed. Transgenic fruits exhibited enhanced levels of Put, Spd and Spm, with a concomitant reduction in ethylene levels, rate of respiration and physiological loss of water. Consequently such fruits displayed significant delay of on-vine ripening and prolonged shelf life over untransformed fruits. The activation of Put biosynthetic pathway at the onset of ripening in transgenic fruits is also consistent with the improvement of qualitative traits such as total soluble solids, titratable acids and total sugars. Such changes were associated with alteration in expression pattern of ripening specific genes. Transgenic fruits were also fortified with important nutraceuticals like lycopene, ascorbate and antioxidants. Therefore, these transgenic tomatoes would be useful for the improvement of tomato cultivars through breeding approaches.

Polyamines are critical for the induction of the glutamate decarboxylase-dependent acid resistance system in Escherichia coli.

As part of our studies on the biological functions of polyamines, we have used a mutant of Escherichia coli that lacks all the genes for polyamine biosynthesis for a global transcriptional analysis on the effect of added polyamines. The most striking early response to the polyamine addition is the increased expression of the genes for the glutamate-dependent acid resistance system (GDAR) that is important for the survival of the bacteria when passing through the acid environment of the stomach. Not only were the two genes for glutamate decarboxylases (gadA and gadB) and the gene for glutamate-γ-aminobutyrate antiporter (gadC) induced by the polyamine addition, but the various genes involved in the regulation of this system were also induced. We confirmed the importance of polyamines for the induction of the GDAR system by direct measurement of glutamate decarboxylase activity and acid survival. The effect of deletions of the regulatory genes on the GDAR system and the effects of overproduction of two of these genes were also studied. Strikingly, overproduction of the alternative σ factor rpoS and of the regulatory gene gadE resulted in very high levels of glutamate decarboxylase and almost complete protection against acid stress even in the absence of any polyamines. Thus, these data show that a major function of polyamines in E. coli is protection against acid stress by increasing the synthesis of glutamate decarboxylase, presumably by increasing the levels of the rpoS and gadE regulators.

Ethanol-induced impairment of polyamine homeostasis--a potential cause of neural tube defect and intrauterine growth restriction in fetal alcohol syndrome.

INTRODUCTION: Polyamines play a fundamental role during embryogenesis by regulating cell growth and proliferation and by interacting with RNA, DNA and protein. The polyamine pools are regulated by metabolism and uptake from exogenous sources. The use of certain inhibitors of polyamine synthesis causes similar defects to those seen in alcohol exposure e.g. retarded embryo growth and endothelial cell sprouting. METHODS: CD-1 mice received two intraperitoneal injections of 3 g/kg ethanol at 4 h intervals 8.75 days post coitum (dpc). The fetal head, trunk, yolk sac and placenta were collected at 9.5 and 12.5 dpc and polyamine concentrations were determined. RESULTS: No measurable quantity of polyamines could be detected in the embryo head at 9.5 dpc, 12 h after ethanol exposure. Putrescine was not detectable in the trunk of the embryo at that time, whereas polyamines in yolk sac and placenta were at control level. Polyamine deficiency was associated with slow cell growth, reduction in endothelial cell sprouting, an altered pattern of blood vessel network formation and consequently retarded migration of neural crest cells and growth restriction. DISCUSSION: Our results indicate that the polyamine pools in embryonic and extraembryonic tissues are developmentally regulated. Alcohol administration, at the critical stage, perturbs polyamine levels with various patterns, depending on the tissue and its developmental stage. The total absence of polyamines in the embryo head at 9.5 dpc may explain why this stage is so vulnerable to the development of neural tube defect, and growth restriction, the findings previously observed in fetal alcohol syndrome.

Polyamines metabolism and breast cancer: state of the art and perspectives.

Breast cancer (BC) is a common disease that generally occurs in women over the age of 50, and the risk is especially high for women over 60 years of age. One of the major BC therapeutic problems is that tumors initially responsive to chemotherapeutic approaches can progress to more aggressive forms poorly responsive to therapies. Polyamines (PAs) are small polycationic alkylamines, naturally occurring and essential for normal cell growth and development in eukaryotes. The intracellular concentration of PA is maintained within strongly controlled contents, while a dysregulation occurs in BC cells. Polyamines facilitate the interactions of transcription factors, such as estrogen receptors with their specific response element, and are involved in the proliferation of ER-negative and highly invasive BC tumor cells. Since PA metabolism has a critical role in cell death and proliferation, it represents a potential target for intervention in BC. The goal of this study was to perform a literature search reviewing the association between PA metabolism and BC, and the current evidence supporting the BC treatment targeting PA metabolism. We here describe in vitro and in vivo models, as well as the clinical trials that have been utilized to unveil the relationship between PA metabolism and BC. Polyamine pathway is still an important target for the development of BC chemotherapy via enzyme inhibitors. Furthermore, a recent promising strategy in breast anticancer therapy is to exploit the self-regulatory nature of PA metabolism using PA analogs to affect PA homeostasis. Nowadays, antineoplastic compounds targeting the PA pathway with novel mechanisms are of great interest and high social impact for BC chemotherapy.

Molecular basis of the 'anti-aging' effect of spermidine and other natural polyamines - a mini-review.

BACKGROUND: Spermidine, a naturally occurring polyamine, has recently emerged as exhibiting anti-aging properties. Its supplementation increases lifespan and resistance to stress, and decreases the occurrence of age-related pathology and loss of locomotor ability. Its mechanisms of action are just beginning to be understood. OBJECTIVES: An up-to-date overview of the so far identified mechanisms of action of spermidine and other polyamines on aging is presented. METHODS: Studies of aging and of the molecular effects of polyamines in general and spermidine in particular are used to synthesize our knowledge on what molecular mechanisms spermidine and other polyamines trigger to positively affect aging. RESULTS: Autophagy is the main mechanism of action of spermidine at the molecular level. However, recent research shows that spermidine can act via other mechanisms, namely inflammation reduction, lipid metabolism and regulation of cell growth, proliferation and death. It is suggested that the main pathway used by spermidine to trigger its effects is the MAPK pathway. CONCLUSIONS: Given that polyamines can interact with many molecules, it is not surprising that they affect aging via several mechanisms. Many of these mechanisms discovered so far have already been linked with aging and by acting on all of these mechanisms, polyamines may be strong regulators of aging.

Polyamines in cell walls of chlorococcalean microalgae.

Biotechnology of microalgae represents a very attractive alternative as a source of energy and substances of high value when compared with plant cultivation. Cell walls of green microalgae have an extraordinary chemical and mechanical resistance and may impede some steps in the biotechnological/industrial exploitation of algae. The aim of the present contribution was to check the presence of polyamines in the cell walls of chlorococcalean green microalgae. Polyamines are nitrogenous compounds synthesized normally in cells and may affect the properties of the cell wall. Our work included strains either forming or not forming the polymer algaenan, allowing us to conclude that algaenan is not a prerequisite for the presence of polyamines in the cell walls. Polyamines were detected in isolated cell walls of Scenedesmus obliquus, Chlorella fusca, Chlorella saccharophila, and Chlorella vulgaris. Their concentration in isolated cell walls ranged between 0.4 and 8.4 nmol/mg dry weight.

Effect of amphotericin B on the metabolic profiles of Candida albicans.

Amphotericin B (AmB) is a polyene antifungal drug widely used for systemic fungal infections. In this study, a metabonomic method using gas chromatography-mass spectrometry (GC/MS) was developed to characterize the metabolic profiles of Candida albicans cells exposed to AmB. Thirty-one differentially produced metabolites between AmB-treated and the control groups were identified, among which 10 metabolites were upregulated and 21 metabolites were downregulated. These differentially produced metabolites were mainly involved in polyamines synthesis, tricarboxylic acid (TCA) cycle, oxidative stress, glutathione metabolism, lipid synthesis and glycolysis. Further experiments showed that the polyamines including putrescine, spermidine, and spermine played an important role in the sensitivity of C. albicans cells upon AmB treatment, and combined use of AmB and inhibitors of polyamine biosynthesis pathway might be a potential antifungal strategy. This study provided a systemic view of the metabolic pattern in C. albicans upon exposure to AmB, which shed new light on the mechanisms of action of antifungal agents.