Chemically induced oxidative stress increases polyamine levels by activating the transcription of ornithine decarboxylase and spermidine/spermine-N1-acetyltransferase in human hepatoma HUH7 cells

Hepatitis C Virus Dysregulates Polyamine and Proline Metabolism and Perturbs the Urea Cycle

Hepatitis C virus (HCV) is an oncogenic virus that causes chronic liver disease in more than 80% of patients. During the last decade, efficient direct-acting antivirals were introduced into clinical practice. However, clearance of the virus does not reduce the risk of end-stage liver diseases to the level observed in patients who have never been infected. So, investigation of HCV pathogenesis is still warranted. Virus-induced changes in cell metabolism contribute to the development of HCV-associated liver pathologies. Here, we studied the impact of the virus on the metabolism of polyamines and proline as well as on the urea cycle, which plays a crucial role in liver function. It was found that HCV strongly suppresses the expression of arginase, a key enzyme of the urea cycle, leading to the accumulation of arginine, and up-regulates proline oxidase with a concomitant decrease in proline concentrations. The addition of exogenous proline moderately suppressed viral replication. HCV up-regulated transcription but suppressed protein levels of polyamine-metabolizing enzymes. This resulted in a decrease in polyamine content in infected cells. Finally, compounds targeting polyamine metabolism demonstrated pronounced antiviral activity, pointing to spermine and spermidine as compounds affecting HCV replication. These data expand our understanding of HCV's imprint on cell metabolism.

Hazard assessment of complex legacy-contaminated groundwater mixtures using a novel approach method in adult fathead minnows

Traditional risk assessment methods face challenges in the determination of drivers of toxicity for complex mixtures such as those present at legacy-contaminated sites. Bioassay-driven analysis across several levels of biological organization represents an approach to address these obstacles. This study aimed to apply a novel transcriptomics tool, the EcoToxChip, to characterize the effects of complex mixtures of contaminants in adult fathead minnows (FHMs) and to compare molecular response patterns to higher-level biological responses. Adult FHMs were exposed for 4 and 21 days to groundwater mixtures collected from a legacy-contaminated site. Adult FHM showed significant induction of micronuclei in erythrocytes, decrease in reproductive capacities, and some abnormal appearance of liver histology. Parallel EcoToxChip analyses showed a high proportion of upregulated genes and a few downregulated genes characteristic of compensatory responses. The three most enriched pathways included thyroid endocrine processes, transcription and translation cellular processes, and xenobiotics and reactive oxygen species metabolism. Several of the most differentially regulated genes involved in these biological pathways could be linked to the apical outcomes observed in FHMs. We concluded that molecular responses as determined by EcoToxChip analysis show promise for informing of apical outcomes and could support risk assessments of complex contaminated sites.

Investigation of the effects of T-2 toxin in chicken-derived three-dimensional hepatic cell cultures

Despite being one of the most common contaminants of poultry feed, the molecular effects of T-2 toxin on the liver of the exposed animals are still not fully elucidated. To gain more accurate understanding, the effects of T-2 toxin were investigated in the present study in chicken-derived three-dimensional (3D) primary hepatic cell cultures. 3D spheroids were treated with three concentrations (100, 500, 1000 nM) of T-2 toxin for 24 h. Cellular metabolic activity declined in all treated groups as reflected by the Cell Counting Kit-8 assay, while extracellular lactate dehydrogenase activity was increased after 500 nM T-2 toxin exposure. The levels of oxidative stress markers malondialdehyde and protein carbonyl were reduced by the toxin, suggesting effective antioxidant compensatory mechanisms of the liver. Concerning the pro-inflammatory cytokines, IL-6 concentration was decreased, while IL-8 concentration was increased by 100 nM T-2 toxin exposure, indicating the multifaceted immunomodulatory action of the toxin. Further, the metabolic profile of hepatic spheroids was also modulated, confirming the altered lipid and amino acid metabolism of toxin-exposed liver cells. Based on these results, T-2 toxin affected cell viability, hepatocellular metabolism and inflammatory response, likely carried out its toxic effects by affecting the oxidative homeostasis of the cells.

Multi-omics analysis of attenuated variant reveals potential evaluation marker of host damaging for SARS-CoV-2 variants

SARS-CoV-2 continues to threaten human society by generating novel variants via mutation and recombination. The high number of mutations that appeared in emerging variants not only enhanced their immune-escaping ability but also made it difficult to predict the pathogenicity and virulence based on viral nucleotide sequences. Molecular markers for evaluating the pathogenicity of new variants are therefore needed. By comparing host responses to wild-type and variants with attenuated pathogenicity at proteome and metabolome levels, six key molecules on the polyamine biosynthesis pathway including putrescine, SAM, dc-SAM, ODC1, SAMS, and SAMDC were found to be differentially upregulated and associated with pathogenicity of variants. To validate our discovery, human airway organoids were subsequently used which recapitulates SARS-CoV-2 replication in the airway epithelial cells of COVID-19 patients. Using ODC1 as a proof-of-concept, differential activation of polyamine biosynthesis was found to be modulated by the renin-angiotensin system (RAS) and positively associated with ACE2 activity. Further experiments demonstrated that ODC1 expression could be differentially activated upon a panel of SARS-CoV-2 variants of concern (VOCs) and was found to be correlated with each VOCs' pathogenic properties. Particularly, the presented study revealed the discriminative ability of key molecules on polyamine biosynthesis as a predictive marker for virulence evaluation and assessment of SARS-CoV-2 variants in cell or organoid models. Our work, therefore, presented a practical strategy that could be potentially applied as an evaluation tool for the pathogenicity of current and emerging SARS-CoV-2 variants.

Polyamine Dysregulation and Nucleolar Disruption in Alzheimer's Disease

A hypothesis of Alzheimer's disease etiology is proposed describing how cellular stress induces excessive polyamine synthesis and recycling which can disrupt nucleoli. Polyamines are essential in nucleolar functions, such as RNA folding and ribonucleoprotein assembly. Changes in the nucleolar pool of anionic RNA and cationic polyamines acting as counterions can cause significant nucleolar dynamics. Polyamine synthesis reduces S-adenosylmethionine which, at low levels, triggers tau phosphorylation. Also, polyamine recycling reduces acetyl-CoA needed for acetylcholine, which is low in Alzheimer's disease. Extraordinary nucleolar expansion and/or contraction can disrupt epigenetic control in peri-nucleolar chromatin, such as chromosome 14 with the presenilin-1 gene; chromosome 21 with the amyloid precursor protein gene; chromosome 17 with the tau gene; chromosome 19 with the APOE4 gene; and the inactive X chromosome (Xi; aka "nucleolar satellite") with normally silent spermine synthase (polyamine synthesis) and spermidine/spermine-N1-acetyltransferase (polyamine recycling) alleles. Chromosomes 17, 19 and the Xi have high concentrations of Alu elements which can be transcribed by RNA polymerase III if positioned nucleosomes are displaced from the Alu elements. A sudden flood of Alu RNA transcripts can competitively bind nucleolin which is usually bound to Alu sequences in structural RNAs that stabilize the nucleolar heterochromatic shell. This Alu competition leads to loss of nucleolar integrity with leaking of nucleolar polyamines that cause aggregation of phosphorylated tau. The hypothesis was developed with key word searches (e.g., PubMed) using relevant terms (e.g., Alzheimer's, lupus, nucleolin) based on a systems biology approach and exploring autoimmune disease tautology, gaining synergistic insights from other diseases.

Characterization of molecular and apical effects of legacy-contaminated groundwater on early life stages of fathead minnows

Mechanistic toxicology approaches represent a promising alternative to traditional live animal testing; however, the often-noted uncertainties concerning the linkages between effects observed at molecular and apical levels curtails the adoption of such approaches. The objective of this study was to apply a novel transcriptomics tool, EcoToxChips, to characterize the effects of complex mixtures of contaminants in fish and to compare molecular response patterns to higher-level biological responses including swimming behavior, deformities, and mortality. Fathead minnow (FHM) embryos were exposed for seven days to increasing concentrations of groundwater collected from moderate (MIAZ) and high (HIAZ) industrial activity zones of a legacy contaminated site. There was a concentration-dependent disruption of photo-dependent swimming responses associated with avoidance behavior patterns and spinal deformities (HIAZ and MIAZ), and an induction of pericardial edema and mortality (HIAZ-10%). Parallel EcoToxChip analyses showed a shift from a majority of upregulated genes at lower concentrations to a majority of downregulated genes at higher concentrations for both treatment conditions. Many of the significantly differentially regulated genes were involved in biological pathways including induction of oxidative stress, activating of several metabolic processes and growth, cell death, and inhibition of signal transduction signaling processes. Several contaminants present in the groundwater mixtures could have contributed to an exceedance of antioxidant system capacities that possibly led to the deformities, altered swimming behaviours, and mortality observed in FHMs. Therefore, molecular response patterns could be linked to apical outcomes observed in this study. Overall, the results observed in this study demonstrate that transcriptomics approaches such as the EcoToxChip system could be supportive of risk assessment of complex contaminated sites.

Polyamine transport inhibition and cisplatin synergistically enhance tumor control through oxidative stress in murine head and neck cancer models

Background

Surgery and/or platinum-based chemoradiation remain standard of care for patients with head and neck squamous cell carcinoma (HNSCC). While these therapies are effective in a subset of patients, a substantial proportion experience recurrence or treatment resistance. As cisplatin mediates cytotoxicity through oxidative stress while polyamines play a role in redox regulation, we posited that combining cisplatin with polyamine transport inhibitor, AMXT-1501, would increase oxidative stress and tumor cell death in HNSCC cells.

Methods

Cell proliferation was measured in syngeneic mouse HNSCC cell lines treated with cisplatin ± AMXT-1501. Synergy was determined by administering cisplatin and AMXT-1501 at a ratio of 1:10 to cancer cells in vitro . Cancer cells were transferred onto mouse flanks to test the efficacy of treatments in vivo . Reactive oxygen species (ROS) were measured. Cellular apoptosis was measured with flow cytometry using Annexin V/PI staining. High-performance liquid chromatography (HPLC) was used to quantify polyamines in cell lines. Cell viability and ROS were measured in the presence of exogenous cationic amino acids.

Results

The combination of cisplatin and AMXT-1501 synergize in vitro on HNSCC cell lines. In vivo combination treatment resulted in tumor growth inhibition greater than either treatment individually. The combination treatment increased ROS production and induced apoptotic cell death. HPLC revealed the synergistic mechanism was independent of intracellular polyamine levels. Supplementation of cationic amino acids partially rescued cancer cell viability and reduced ROS.

Conclusion

AMXT-1501 enhances the cytotoxic effects of cisplatin in vitro and in vivo in aggressive HNSCC cell lines through a polyamine-independent mechanism.

Characterization and Mechanism of Tea Polyphenols Inhibiting Biogenic Amine Accumulation in Marinated Spanish Mackerel

Putrescine is a low-molecular-weight organic compound that is widely found in pickled foods. Although the intake of biogenic amines is beneficial to humans, an excessive intake can cause discomfort. In this study, the ornithine decarboxylase gene (ODC) was involved in putrescine biosynthesis. After cloning, expression and functional verification, it was induced and expressed in E. coli BL21 (DE3). The relative molecular mass of the recombinant soluble ODC protein was 14.87 kDa. The function of ornithine decarboxylase was analyzed by determining the amino acid and putrescine content. The results show that the ODC protein could catalyze the decarboxylation of ornithine to putrescine. Then, the three-dimensional structure of the enzyme was used as a receptor for the virtual screening of inhibitors. The binding energy of tea polyphenol ligands to the receptor was the highest at -7.2 kcal mol^-1. Therefore, tea polyphenols were added to marinated fish to monitor the changes in putrescine content and were found to significantly inhibit putrescine production (p < 0.05). This study lays the foundation for further research on the enzymatic properties of ODC and provides insight into an effective inhibitor for controlling the putrescine content in pickled fish.

Transcriptome Analysis of Redox Systems and Polyamine Metabolic Pathway in Hepatoma and Non-Tumor Hepatocyte-like Cells

Reactive oxygen species (ROS) play a major role in the regulation of various processes in the cell. The increase in their production is a factor contributing to the development of numerous pathologies, including inflammation, fibrosis, and cancer. Accordingly, the study of ROS production and neutralization, as well as redox-dependent processes and the post-translational modifications of proteins, is warranted. Here, we present a transcriptomic analysis of the gene expression of various redox systems and related metabolic processes, such as polyamine and proline metabolism and the urea cycle in Huh7.5 hepatoma cells and the HepaRG liver progenitor cell line, that are widely used in hepatitis research. In addition, changes in response to the activation of polyamine catabolism that contribute to oxidative stress were studied. In particular, differences in the gene expression of various ROS-producing and ROS-neutralizing proteins, the enzymes of polyamine metabolisms and proline and urea cycles, as well as calcium ion transporters between cell lines, are shown. The data obtained are important for understanding the redox biology of viral hepatitis and elucidating the influence of the laboratory models used.

Hypothesis-driven dragging of transcriptomic data to analyze proven targeted pathways in Rhinella arenarum larvae exposed to organophosphorus pesticides

Transcriptional analysis of the network of transcription regulators and target pathways in exposed organisms may be a hard task when their genome remains unknown. The development of hundreds of qPCR assays, including primer design and normalization of the results with the appropriate housekeeping genes, seems an unreachable task. Alternatively, we took advantage of a whole transcriptome study on Rhinella arenarum larvae exposed to the organophosphorus pesticides azinphos-methyl and chlorpyrifos to evaluate the transcriptional effects on a priori selected groups of genes. This approach allowed us to evaluate the effects on hypothesis-selected pathways such as target esterases, detoxifying enzymes, polyamine metabolism and signaling, and regulatory pathways modulating them. We could then compare the responses at the transcriptional level with previously described effects at the enzymatic or metabolic levels to obtain global insight into toxicity-response mechanisms. The effects of both pesticides on the transcript levels of these pathways could be considered moderate, while chlorpyrifos-induced responses were more potent and earlier than those elicited by azinphos-methyl. Finally, we inferred a prevailing downregulation effect of pesticides on signaling pathways and transcription factor transcripts encoding products that modulate/control the polyamine and antioxidant response pathways. We also tested and selected potential housekeeping genes based on those reported for other species. These results allow us to conduct future confirmatory studies on pesticide modulation of gene expression in toad larvae.

The Impact of Spermidine on C2C12 Myoblasts Proliferation, Redox Status and Polyamines Metabolism under H2O2 Exposure

A central feature of the skeletal muscle is its ability to regenerate through the activation, by environmental signals, of satellite cells. Once activated, these cells proliferate as myoblasts, and defects in this process profoundly affect the subsequent process of regeneration. High levels of reactive oxygen species such as hydrogen peroxide (H₂O₂) with the consequent formation of oxidized macromolecules increase myoblasts’ cell death and strongly contribute to the loss of myoblast function. Recently, particular interest has turned towards the beneficial effects on muscle of the naturally occurring polyamine spermidine (Spd). In this work, we tested the hypothesis that Spd, upon oxidative challenge, would restore the compromised myoblasts’ viability and redox status. The effects of Spd in combination with aminoguanidine (Spd-AG), an inhibitor of bovine serum amine oxidase, on murine C2C12 myoblasts treated with a mild dose of H₂O₂ were evaluated by analyzing: (i) myoblast viability and recovery from wound scratch; (ii) redox status and (iii) polyamine (PAs) metabolism. The treatment of C2C12 myoblasts with Spd-AG increased cell number and accelerated scratch wound closure, while H₂O₂ exposure caused redox status imbalance and cell death. The combined treatment with Spd-AG showed an antioxidant effect on C2C12 myoblasts, partially restoring cellular total antioxidant capacity, reducing the oxidized glutathione (GSH/GSSG) ratio and increasing cell viability through a reduction in cell death. Moreover, Spd-AG administration counteracted the induction of polyamine catabolic genes and PA content decreased due to H₂O₂ challenges. In conclusion, our data suggest that Spd treatment has a protective role in skeletal muscle cells by restoring redox balance and promoting recovery from wound scratches, thus making myoblasts able to better cope with an oxidative insult.

Aspirin eugenol ester alleviates lipopolysaccharide-induced acute lung injury in rats while stabilizing serum metabolites levels

Aspirin eugenol ester (AEE) was a novel drug compound with aspirin and eugenol esterified. AEE had various pharmacological activities, such as anti-inflammatory, antipyretic, analgesic, anti-oxidative stress and so on. In this study, it was aimed to investigate the effect of AEE on the acute lung injury (ALI) induced by lipopolysaccharide (LPS) in rats. In vitro experiments evaluated the protective effect of AEE on the LPS-induced A549 cells. The tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) were measured in the cell supernatant. The Wistar rats were randomly divided into five groups (n = 8): control group, model group (LPS group), LPS + AEE group (AEE, 54 mg·kg−1), LPS + AEE group (AEE, 108 mg·kg−1), LPS + AEE group (AEE, 216 mg·kg−1). The lung wet-to-dry weight (W/D) ratio and immune organ index were calculated. WBCs were counted in bronchoalveolar lavage fluid (BALF) and total protein concentration was measured. Hematoxylin-Eosin (HE) staining of lung tissue was performed. Glutathione (GSH), glutathione peroxidase (GPx), catalase (CAT), antioxidant superoxide dismutase (SOD), total antioxidant capacity (T-AOC), lactate dehydrogenase (LDH), C-reactive protein (CRP), myeloperoxidase (MPO), malondialdehyde (MDA), macrophage mobility inhibitory factor (MIF), TNF-α, IL-6, and IL-1β activity were measured. The metabolomic analysis of rat serum was performed by UPLC-QTOF-MS/MS. From the results, compared with LPS group, AEE improved histopathological changes, reduced MDA, CRP, MPO, MDA, and MIF production, decreased WBC count and total protein content in BALF, pro-inflammatory cytokine levels, immune organ index and lung wet-dry weight (W/D), increased antioxidant enzyme activity, in a dose-dependent manner. The results of serum metabolomic analysis showed that the LPS-induced ALI caused metabolic disorders and oxidative stress in rats, while AEE could ameliorate it to some extent. Therefore, AEE could alleviate LPS-induced ALI in rats by regulating abnormal inflammatory responses, slowing down oxidative stress, and modulating energy metabolism.

Polyamines and Their Metabolism: From the Maintenance of Physiological Homeostasis to the Mediation of Disease

The polyamines spermidine and spermine are positively charged aliphatic molecules. They are critical in the regulation of nucleic acid and protein structures, protein synthesis, protein and nucleic acid interactions, oxidative balance, and cell proliferation. Cellular polyamine levels are tightly controlled through their import, export, de novo synthesis, and catabolism. Enzymes and enzymatic cascades involved in polyamine metabolism have been well characterized. This knowledge has been used for the development of novel compounds for research and medical applications. Furthermore, studies have shown that disturbances in polyamine levels and their metabolic pathways, as a result of spontaneous mutations in patients, genetic engineering in mice or experimentally induced injuries in rodents, are associated with multiple maladaptive changes. The adverse effects of altered polyamine metabolism have also been demonstrated in in vitro models. These observations highlight the important role these molecules and their metabolism play in the maintenance of physiological normalcy and the mediation of injury. This review will attempt to cover the extensive and diverse knowledge of the biological role of polyamines and their metabolism in the maintenance of physiological homeostasis and the mediation of tissue injury.

The Association between Spermidine/Spermine N1-Acetyltransferase (SSAT) and Human Malignancies

Spermidine/spermine N¹-acetyltransferase (SSAT) functions as a critical enzyme in maintaining the homeostasis of polyamines, including spermine, spermidine, and putrescine, in mammalian cells. SSAT is a catalytic enzyme that indirectly regulates cellular physiologies and pathways through interaction with endogenous and exogenous polyamines. Normally, SSAT exhibits only at a low cellular level, but upon tumorigenesis, the expression, protein level, and activities of SSAT are altered. The alterations induce cellular damages, including oxidative stress, cell cycle arrest, DNA dynamics, and proliferation by influencing cellular mechanisms and signaling pathways. The expression of SSAT has been reported in various studies to be altered in different cancers, and it has been correlated with tumor development and progression. Tumor grades and stages are associated with the expression levels of SSAT. SSAT can be utilized as a target for substrate binding, and excreted metabolites may be used as a novel cancer biomarker. There is also potential for SSAT to be developed as a therapeutic target. Polyamine analogs could increase SSAT expression and increase the cytotoxicity of chemotherapy to tumor cells. Drugs targeting polyamines and SSAT expression have the potential to be developed into new cancer treatments in the future.

Oxidative Chemical Stressors Alter the Physiological State of the Nasal Olfactory Mucosa of Atlantic Salmon

The olfactory organs of fish have vital functions for chemosensory and defence. Though there have been some ground-breaking discoveries of their involvement in immunity against pathogens in recent years, little is known about how they respond to non-infectious agents, such as exogenous oxidants, which fish encounter regularly. To this end, we employed Atlantic salmon (Salmo salar) as a model to study the molecular responses at the nasal olfactory mucosa of a teleost fish when challenged with oxidants. Microarray analysis was employed to unravel the transcriptional changes at the nasal olfactory mucosa following two types of in vivo exposure to peracetic acid (PAA), a highly potent oxidative agent commonly used in aquaculture: Trial 1: periodic and low dose (1 ppm, every 3 days over 45 days) to simulate a routine disinfection; and Trial 2: less frequent and high dose (10 ppm for 30 min, every 15 days, 3 times) to mimic a bath treatment. Furthermore, leukocytes from the olfactory organ were isolated and exposed to PAA, as well as to hydrogen peroxide (H₂O₂) and acetic acid (AA)—the two other components of PAA trade products—to perform targeted cellular and molecular response profiling. In the first trial, microarrays identified 32 differentially expressed genes (DEG) after a 45-day oxidant exposure. Erythrocyte-specific genes were overly represented and substantially upregulated following exogenous oxidant exposure. In Trial 2, in which a higher dose was administered, 62 DEGs were identified, over 80% of which were significantly upregulated after exposure. Genes involved in immune response, redox balance and stress, maintenance of cellular integrity and extracellular matrix were markedly affected by the oxidant. All chemical stimuli (i.e., PAA, H₂O₂, AA) significantly affected the proliferation of nasal leukocytes, with indications of recovery observed in PAA- and H₂O₂-exposed cells. The migration of nasal leukocytes was promoted by H₂O₂, but not much by PAA and AA. The three chemical oxidative stressors triggered oxidative stress in nasal leukocytes as indicated by an increase in the intracellular reactive oxygen species level. This resulted in the mobilisation of antioxidant defences in the nasal leukocytes as shown by the upregulation of crucial genes for this response network. Though qPCR revealed changes in the expression of selected cytokines and heat shock protein genes following in vitro challenge, the responses were stochastic. The results from the study advance our understanding of the role that the nasal olfactory mucosa plays in host defence, particularly towards oxidative chemical stressors.

Dengue virus targets RBM10 deregulating host cell splicing and innate immune response

RNA-seq experiments previously performed by our laboratories showed enrichment in intronic sequences and alterations in alternative splicing in dengue-infected human cells. The transcript of the SAT1 gene, of well-known antiviral action, displayed higher inclusion of exon 4 in infected cells, leading to an mRNA isoform that is degraded by non-sense mediated decay. SAT1 is a spermidine/spermine acetyl-transferase enzyme that decreases the reservoir of cellular polyamines, limiting viral replication. Delving into the molecular mechanism underlying SAT1 pre-mRNA splicing changes upon viral infection, we observed lower protein levels of RBM10, a splicing factor responsible for SAT1 exon 4 skipping. We found that the dengue polymerase NS5 interacts with RBM10 and its sole expression triggers RBM10 proteasome-mediated degradation. RBM10 over-expression in infected cells prevents SAT1 splicing changes and limits viral replication, while its knock-down enhances the splicing switch and also benefits viral replication, revealing an anti-viral role for RBM10. Consistently, RBM10 depletion attenuates expression of interferon and pro-inflammatory cytokines. In particular, we found that RBM10 interacts with viral RNA and RIG-I, and even promotes the ubiquitination of the latter, a crucial step for its activation. We propose RBM10 fulfills diverse pro-inflammatory, anti-viral tasks, besides its well-documented role in splicing regulation of apoptotic genes.

Differential effects of azinphos-methyl and chlorpyrifos on polyamine oxidative metabolism during the embryonic development of Rhinella arenarum and its relation to oxidative stress

The organophosphorus pesticides azinphos-methyl (AZM) and chlorpyrifos (CPF) exert their toxic action by inhibition of acetylcholinesterase, but non-target processes such as polyamine metabolism can also be affected. Our objective was to evaluate the effects of different concentrations of AZM (0.5-, 2- and 9 mg L^-1) and CPF (0.5- and 1 mg L^-1) on polyamine oxidative metabolism along Rhinella arenarum embryonic development and to explore its relationship to oxidative stress. Free and conjugated polyamines were measured by HPLC. The activity of spermine oxidase (SMOX), N¹-acetylpolyamine oxidase (PAOX) and diamine oxidase (DAO) were measured through kinetic spectrofluorometry. Free putrescine and spermine were significantly increased in open mouth embryos exposed to AZM. Free polyamine levels were not affected by CPF exposure. In embryos exposed to AZM, DAO was increased in tail bud stage and SMOX was increased in open mouth stage, while embryos exposed to CPF showed an increase of PAOX activity in tail bud stage and a decrease of DAO and SMOX activity in open mouth stage. Polyamine levels and oxidative degradation enzymes respond differently if R. arenarum embryos are exposed to AZM or CPF, despite that both insecticides belong to the same chemical family. The early increase of DAO and PAOX would play a protective role to guarantee the normal progression of embryonic development. The increased production of reactive species might contribute to an oxidative stress situation generated by exposure to the insecticides and to the alteration of the antioxidant defense system. In tail bud stage embryos, PAOX and SMOX were positively correlated to acetylcholinesterase activity and reduced glutathione levels (GSH), and negatively correlated to the antioxidant enzymes catalase (CAT) and glutathione S-transferase (GST). In complete operculum embryos, a negative correlation between antioxidant parameters and polyamine levels and polyamine oxidative metabolism was observed, except for SMOX, which showed a low positive correlation with CAT and GSH and a negative correlation to PAOX and DAO. We suggest the use of DAO and PAOX as biomarkers of exposure to AZM and CPF, respectively, as they respond earlier than the classical biomarker acetylcholinesterase.

Polyamine Catabolism in Acute Kidney Injury

Acute kidney injury (AKI) refers to an abrupt decrease in kidney function. It affects approximately 7% of all hospitalized patients and almost 35% of intensive care patients. Mortality from acute kidney injury remains high, particularly in critically ill patients, where it can be more than 50%. The primary causes of AKI include ischemia/reperfusion (I/R), sepsis, or nephrotoxicity; however, AKI patients may present with a complicated etiology where many of the aforementioned conditions co-exist. Multiple bio-markers associated with renal damage, as well as metabolic and signal transduction pathways that are involved in the mediation of renal dysfunction have been identified as a result of the examination of models, patient samples, and clinical data of AKI of disparate etiologies. These discoveries have enhanced our ability to diagnose AKIs and to begin to elucidate the mechanisms involved in their pathogenesis. Studies in our laboratory revealed that the expression and activity of spermine/spermidine N1-acetyltransferase (SAT1), the rate-limiting enzyme in polyamine back conversion, were enhanced in kidneys of rats after I/R injury. Additional studies revealed that the expression of spermine oxidase (SMOX), another critical enzyme in polyamine catabolism, is also elevated in the kidney and other organs subjected to I/R, septic, toxic, and traumatic injuries. The maladaptive role of polyamine catabolism in the mediation of AKI and other injuries has been clearly demonstrated. This review will examine the biochemical and mechanistic basis of tissue damage brought about by enhanced polyamine degradation and discuss the potential of therapeutic interventions that target polyamine catabolic enzymes or their byproducts for the treatment of AKI.

Polyamine catabolism and oxidative damage

Polyamines (PAs) are indispensable polycations ubiquitous to all living cells. Among their many critical functions, PAs contribute to the oxidative balance of the cell. Beginning with studies by the Tabor laboratory in bacteria and yeast, the requirement for PAs as protectors against oxygen radical-mediated damage has been well established in many organisms, including mammals. However, PAs also serve as substrates for oxidation reactions that produce hydrogen peroxide (H2O2) both intra- and extracellularly. As intracellular concentrations of PAs can reach millimolar concentrations, the H2O2 amounts produced through their catabolism, coupled with a reduction in protective PAs, are sufficient to cause the oxidative damage associated with many pathologies, including cancer. Thus, the maintenance of intracellular polyamine homeostasis may ultimately contribute to the maintenance of oxidative homeostasis. Again, pioneering studies by Tabor and colleagues led the way in first identifying spermine oxidase in Saccharomyces cerevisiae. They also first purified the extracellular bovine serum amine oxidase and elucidated the products of its oxidation of primary amine groups of PAs when included in culture medium. These investigations formed the foundation for many polyamine-related studies and experimental procedures still performed today. This Minireview will summarize key innovative studies regarding PAs and oxidative damage, starting with those from the Tabor laboratory and including the most recent advances, with a focus on mammalian systems.

Glutamate Excitotoxicity Linked to Spermine Oxidase Overexpression

Excitotoxic stress has been associated with several different neurological disorders, and it is one of the main causes of neuronal degeneration and death. To identify new potential proteins that could represent key factors in excitotoxic stress and to study the relationship between polyamine catabolism and excitotoxic damage, a novel transgenic mouse line overexpressing spermine oxidase enzyme in the neocortex (Dach-SMOX) has been engineered. These transgenic mice are more susceptible to excitotoxic injury and display a higher oxidative stress, highlighted by 8-Oxo-2'-deoxyguanosine increase and activation of defense mechanisms, as demonstrated by the increase of nuclear factor erythroid 2-related factor 2 (Nrf-2) in the nucleus. In Dach-SMOX astrocytes and neurons, an alteration of the phosphorylated and non-phosphorylated subunits of glutamate receptors increases the kainic acid response in these mice. Moreover, a decrease in excitatory amino acid transporters and an increase in the system xc- transporter, a Nrf-2 target, was observed. Sulfasalazine, a system xc- transporter inhibitor, was shown to revert the increased susceptibility of Dach-SMOX mice treated with kainic acid. We demonstrated that astrocytes play a crucial role in this process: neuronal spermine oxidase overexpression resulted in an alteration of glutamate excitability, in glutamate uptake and efflux in astrocytes involved in the synapse. Considering the involvement of oxidative stress in many neurodegenerative diseases, Dach-SMOX transgenic mouse can be considered as a suitable in vivo genetic model to study the involvement of spermine oxidase in excitotoxicity, which can be considered as a possible therapeutic target.

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.

Effects of lentivirus-mediated ornithine decarboxylase gene on the proliferation and apoptosis of fibroblast-like synoviocytes in rats with arthritis

OBJECTIVE

This study aimed to explore the effects of lentivirus-mediated ornithine decarboxylase (ODC) gene on the proliferation and apoptosis of fibroblast-like synoviocytes (FLSs) in rats with rheumatoid arthritis (RA).

METHODS

Twenty Lewis rats were randomized into control group (ten rats without processing) and RA group (ten rats of adjuvant-induced arthritis). The third-generation FLSs were randomized into test, control and blank groups. MTT assay and flow cytometry were employed to detect cell proliferation and apoptosis, respectively. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of tumor necrosis factor α (TNF-α), interferon-γ (IFN-γ), and interleukin-2 (IL-2).

RESULTS

Lewis rats in the RA group became ill from 11days on and got seriously ill 18days after modeling. However, rats in the control group had no obvious change. MTT assay showed that the test group had higher cell proliferation than the blank and control groups (P₁<0.001; P₂<0.001). Flow cytometry revealed that the apoptosis of FLSs in the test group was significantly lower than that in the blank and control groups (P₁<0.001; P₂<0.001). ELISA showed that the test group had higher TNF-α, IFN-γ and IL-2 level than the control and blank groups (all P<0.001), but no significant difference was found between the control and blank groups (all P>0.05).

CONCLUSION

The results indicated that overexpression of ODC gene promotes the proliferation while suppressing apoptosis of FLSs in rats with RA.

Ornithine Decarboxylase-Mediated Production of Putrescine Influences Ganoderic Acid Biosynthesis by Regulating Reactive Oxygen Species in Ganoderma lucidum

Putrescine is an important polyamine that participates in a variety of stress responses. Ornithine decarboxylase (ODC) is a key enzyme that catalyzes the biosynthesis of putrescine. A homolog of the gene encoding ODC was cloned from Ganoderma lucidum In the ODC-silenced strains, the transcript levels of the ODC gene and the putrescine content were significantly decreased. The ODC-silenced strains were more sensitive to oxidative stress. The content of ganoderic acid was increased by approximately 43 to 46% in the ODC-silenced strains. The content of ganoderic acid could be recovered after the addition of exogenous putrescine. Additionally, the content of reactive oxygen species (ROS) was significantly increased by approximately 1.3-fold in the ODC-silenced strains. The ROS content was significantly reduced after the addition of exogenous putrescine. The gene transcript levels and the activities of four major antioxidant enzymes were measured to further explore the effect of putrescine on the intracellular ROS levels. Further studies showed that the effect of the ODC-mediated production of putrescine on ROS might be a factor influencing the biosynthesis of ganoderic acid. Our study reports the role of putrescine in large basidiomycetes, providing a basis for future studies of the physiological functions of putrescine in microbes.IMPORTANCE It is well known that ODC and the ODC-mediated production of putrescine play an important role in resisting various environmental stresses, but there are few reports regarding the mechanisms underlying the effect of putrescine on secondary metabolism in microorganisms, particularly in fungi. G. lucidum is gradually becoming a model organism for studying environmental regulation and metabolism. In this study, a homolog of the gene encoding ODC was cloned in Ganoderma lucidum We found that the transcript level of the ODC gene and the content of putrescine were significantly decreased in the ODC-silenced strains. The content of ganoderic acid was significantly increased in the ODC-silenced strains. Further studies showed that the effect of the ODC-mediated production of putrescine on ROS might be a factor influencing the biosynthesis of ganoderic acid. Our study reports the role of putrescine in large basidiomycetes, providing a basis for future studies of the physiological functions of putrescine in microbes.

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.

1H NMR-based metabolomics study of liver damage induced by ginkgolic acid (15:1) in mice

Ginkgolic acid (15:1) is a major toxic component in extracts obtained from Ginkgo biloba (EGb) that has allergic and genotoxic effects. This study is the first to explore the hepatotoxicity of ginkgolic acid (15:1) using a NMR (nuclear magnetic resonance)-based metabolomics approach in combination with biochemistry assays. Mice were orally administered two doses of ginkgolic acid (15:1), and mouse livers and serum were then collected for NMR recordings and biochemical assays. The levels of activity of alanine aminotransferase (ALT) and glutamic aspartate transaminase (AST) observed in the ginkgolic acid (15:1)-treated mice suggested that it had induced severe liver damage. An orthogonal signal correction partial least-squares discriminant analysis (OSC-PLSDA) performed to determine the metabolomic profile of mouse liver tissues indicated that many metabolic disturbances, especially oxidative stress and purine metabolism, were induced by ginkgolic acid (15:1). A correlation network analysis combined with information related to structural similarities further confirmed that purine metabolism was disturbed by ginkgolic acid (15:1). This mechanism might represent the link between the antitumour activity and the liver injury-inducing effect of ginkgolic acid (15:1). A SUS (Shared and Unique Structure) plot suggested that a two-dose treatment of ginkgolic acid (15:1) had generally the same effect on metabolic variations but that its effects were dose-dependent, revealing some of the common features of ginkgolic acid (15:1) dosing. This integrated metabolomics approach helped us to characterise ginkgolic acid (15:1)-induced liver damage in mice.

Putrescine treatment reverses α-tocopherol-induced desynchronization of polyamine and retinoid metabolism during rat liver regeneration

Background

The pre-treatment with α-tocopherol inhibits progression of rat liver proliferation induced by partial hepatectomy (PH), by decreasing and/or desynchronizing cyclin D1 expression and activation into the nucleus, activation and nuclear translocation of STAT-1 and -3 proteins and altering retinoid metabolism. Interactions between retinoic acid and polyamines have been reported in the PH-induced rat liver regeneration. Therefore, we evaluated the effect of low dosage of α-tocopherol on PH-induced changes in polyamine metabolism.

Methods

This study evaluated the participation of polyamine synthesis and metabolism during α-tocopherol-induced inhibition of rat liver regeneration. In PH-rats (Wistar) treated with α-tocopherol and putrescine, parameters indicative of cell proliferation, lipid peroxidation, ornithine decarboxylase expression (ODC), and polyamine levels, were determined.

Results

Pre-treatment with α-tocopherol to PH-animals exerted an antioxidant effect, shifting earlier the increased ODC activity and expression, temporally affecting polyamine synthesis and ornithine metabolism. Whereas administration of putrescine induced minor changes in PH-rats, the concomitant treatment actually counteracted most of adverse actions exerted by α-tocopherol on the remnant liver, restituting its proliferative potential, without changing its antioxidant effect. Putrescine administration to these rats was also associated with lower ODC expression and activity in the proliferating liver, but the temporally shifting in the amount of liver polyamines induced by α-tocopherol, was also “synchronized” by the putrescine administration. The latter is supported by the fact that a close relationship was observed between fluctuations of polyamines and retinoids.

Conclusions

Putrescine counteracted most adverse actions exerted by α-tocopherol on rat liver regeneration, restoring liver proliferative potential and restituting the decreased retinoid levels induced by α-tocopherol. Therefore interactions between polyamines and retinol, mediated by the oxidant status, should be taken into consideration in the development of new therapeutic strategies for pathologies occurring with liver cell proliferation.

Upregulation of energy metabolism-related, p53-target TIGAR and SCO2 in HuH-7 cells with p53 mutation by geranylgeranoic acid treatment

Metabolic alternation in cancer cells is one of the most common characteristics that distinguish malignant cells from normal cells. Many studies have explained the Warburg hypothesis that cancer cells obtain more energy from aerobic glycolysis than mitochondrial respiration. Here, we show that a branched-chain C-20 polyunsaturated fatty acid, geranylgeranoic acid (GGA), induces upregulation of the cellular protein levels of TP53-induced glycolysis and apoptosis regulator (TIGAR) and synthesis of cytochrome c oxidase 2 (SCO2) in human hepatoma-derived HuH-7cells harboring the mutant TP53 gene, suggesting that GGA may shift an energetic state of the tumor cells from aerobic glycolysis to mitochondrial respiration. In addition, UPLC/TOF/MS-based metabolomics analysis supported the GGA-induced energetic shift, as it revealed that GGA induced a time-dependent increase in the cellular contents of fructose 6-phosphate and decrease of fructose 1,6-diphosphate. Furthermore, metabolomics analysis revealed that GGA rapidly induced spermine accumulation with slight decrease of spermidine. Taken together, the present study strongly suggests that GGA may shift HuH-7 cells from aerobic glycolysis to mitochondrial respiration through the immediate upregulation of TIGAR and SCO2 protein levels.

Mitochondria in the middle: exercise preconditioning protection of striated muscle

Cellular and physiological adaptations to an atmosphere which became enriched in molecular oxygen spurred the development of a layered system of stress protection, including antioxidant and stress response proteins. At physiological levels reactive oxygen and nitrogen species regulate cell signalling as well as intracellular and intercellular communication. Exercise and physical activity confer a variety of stressors on skeletal muscle and the cardiovascular system: mechanical, metabolic, oxidative. Transient increases of stressors during acute bouts of exercise or exercise training stimulate enhancement of cellular stress protection against future insults of oxidative, metabolic and mechanical stressors that could induce injury or disease. This phenomenon has been termed both hormesis and exercise preconditioning (EPC). EPC stimulates transcription factors such as Nrf-1 and heat shock factor-1 and up-regulates gene expression of a cadre of cytosolic (e.g. glutathione peroxidase and heat shock proteins) and mitochondrial adaptive or stress proteins (e.g. manganese superoxide dismutase, mitochondrial KATP channels and peroxisome proliferator activated receptor γ coactivator-1 (PGC-1)). Stress response and antioxidant enzyme inducibility with exercise lead to protection against striated muscle damage, oxidative stress and injury. EPC may indeed provide significant clinical protection against ischaemia-reperfusion injury, Type II diabetes and ageing. New molecular mechanisms of protection, such as δ-opioid receptor regulation and mitophagy, reinforce the notion that mitochondrial adaptations (e.g. heat shock proteins, antioxidant enzymes and sirtuin-1/PGC-1 signalling) are central to the protective effects of exercise preconditioning.

Tamoxifen metabolite endoxifen interferes with the polyamine pathway in breast cancer

Tamoxifen is the most widely used drug to treat women with estrogen receptor α (ERα)-positive breast cancer. Endoxifen is recognized as the active metabolite of tamoxifen in humans. We studied endoxifen effects on ERα-positive MCF-7 breast cancer cells. Estradiol increased the proliferation of MCF-7 cells by two- to threefold and endoxifen suppressed its effects. Endoxifen suppressed c-myc, c-fos and Tff1 oncogene expression, as revealed by RT-PCR. Estradiol increased the activity of ornithine decarboxylase (ODC) and adenosyl methioninedecarboxylase (AdoMetDC), whereas endoxifen suppressed these enzyme activities. Endoxifen increased activities of spermine oxidase (SMO) and acetyl polyamine oxidase (APAO) significantly, and reduced the levels of putrescine and spermidine. These data suggest a possible mechanism for the antiestrogenic effects of tamoxifen/endoxifen, involving the stimulation of polyamine oxidase enzymes. Therefore, SMO and APAO stimulation might be useful biomarkers for the efficacy of endoxifen treatment of breast cancer.

The Dysregulation of Polyamine Metabolism in Colorectal Cancer Is Associated with Overexpression of c-Myc and C/EBPβ rather than Enterotoxigenic Bacteroides fragilis Infection

Colorectal cancer is one of the most common cancers in the world. It is well known that the chronic inflammation can promote the progression of colorectal cancer (CRC). Recently, a number of studies revealed a potential association between colorectal inflammation, cancer progression, and infection caused by enterotoxigenic Bacteroides fragilis (ETBF). Bacterial enterotoxin activates spermine oxidase (SMO), which produces spermidine and H2O2 as byproducts of polyamine catabolism, which, in turn, enhances inflammation and tissue injury. Using qPCR analysis, we estimated the expression of SMOX gene and ETBF colonization in CRC patients. We found no statistically significant associations between them. Then we selected genes involved in polyamine metabolism, metabolic reprogramming, and inflammation regulation and estimated their expression in CRC. We observed overexpression of SMOX, ODC1, SRM, SMS, MTAP, c-Myc, C/EBPβ (CREBP), and other genes. We found that two mediators of metabolic reprogramming, inflammation, and cell proliferation c-Myc and C/EBPβ may serve as regulators of polyamine metabolism genes (SMOX, AZIN1, MTAP, SRM, ODC1, AMD1, and AGMAT) as they are overexpressed in tumors, have binding site according to ENCODE ChIP-Seq data, and demonstrate strong coexpression with their targets. Thus, increased polyamine metabolism in CRC could be driven by c-Myc and C/EBPβ rather than ETBF infection.

Preparation of Antispermidine/Spermine-N1-Acetyltransferase Monoclonal Antibodies

Spermidine/spermine N1-acetyltransferase (SSAT) is a catabolic regulator of polyamines, ubiquitous molecules essential for cell proliferation and differentiation. Anti-SSAT antibodies (monoclonal antibodies [mAbs]) of high titer were prepared by immunizing BALB/c mice with multifocal intradermal injections and by fusing high-titer antibody-producing spleen cells with myeloma cells of SP2/0 origin. Four mAbs were selected for further characterization as classes and subclasses. Antibodies were produced by these three clones with high affinities ranging from 10(9) to 10(11) M(-1). These clones were found to be of the immunoglobulin IgG1 subclass with kappa light chain. They could recognize SSAT as determined by Western blot and immunohistochemistry. The specificity of one clone, 4H6, was studied by using the small interfering RNA (siRNA) on SSAT. 4H6 was also compared with the commercial antibody. The produced mAbs will be a useful tool for further investigation of SSAT functions in organisms.

Altering the Mitochondrial Fatty Acid Synthesis (mtFASII) Pathway Modulates Cellular Metabolic States and Bioactive Lipid Profiles as Revealed by Metabolomic Profiling

Despite the presence of a cytosolic fatty acid synthesis pathway, mitochondria have retained their own means of creating fatty acids via the mitochondrial fatty acid synthesis (mtFASII) pathway. The reason for its conservation has not yet been elucidated. Therefore, to better understand the role of mtFASII in the cell, we used thin layer chromatography to characterize the contribution of the mtFASII pathway to the fatty acid composition of selected mitochondrial lipids. Next, we performed metabolomic analysis on HeLa cells in which the mtFASII pathway was either hypofunctional (through knockdown of mitochondrial acyl carrier protein, ACP) or hyperfunctional (through overexpression of mitochondrial enoyl-CoA reductase, MECR). Our results indicate that the mtFASII pathway contributes little to the fatty acid composition of mitochondrial lipid species examined. Additionally, loss of mtFASII function results in changes in biochemical pathways suggesting alterations in glucose utilization and redox state. Interestingly, levels of bioactive lipids, including lysophospholipids and sphingolipids, directly correlate with mtFASII function, indicating that mtFASII may be involved in the regulation of bioactive lipid levels. Regulation of bioactive lipid levels by mtFASII implicates the pathway as a mediator of intracellular signaling.

Changes of polyamine pattern in digestive glands of mussel Mytilus galloprovincialis under exposure to cadmium

Polyamines, in particular spermidine and spermine, have been identified as important antioxidants, highly induced by oxidative stress in a variety of organisms. However, little is known about changes in polyamine content of metal-stressed marine organisms. In the present study, mussels (Mytilus galloprovincialis) were experimentally exposed to 25 μg/L Cd(2+) or 100 μg/L Cd(2+) for up to 15 days. Cd(2+) was progressively accumulated in mussel tissues, leading to a characteristic oxidative-stress status. Free putrescine (PUT) production was noticeably induced in response to Cd(2+) at day 5 and then declined. In contrast, free spermidine (SPD) content was gradually reduced, whereas the concentration of free spermine (SPM) increased. In combination, these changes led to a 69% or 88% reduction in the ratio of (SPD+SPM)/PUT at day 5, dependent on the Cd(2+) concentration used, which subsequently followed an upward trend in values, albeit not reaching those of controls. Conjugated polyamines constantly increased, in particular conjugated spermidine and spermine, tagging along with metallothionein production. Acetylated polyamines showed a diverse profile of changes, but their content was generally kept at low levels throughout the exposure period. Collectively, our results suggest that certain polyamine compounds could play a significant role in the tolerance of mussels against Cd(2+)-mediated stress, and that the ratio (SPD+SPM)/PUT could be a good indicator of the metal-stress status.

Polyamine catabolism in carcinogenesis: potential targets for chemotherapy and chemoprevention

Polyamines, including spermine, spermidine, and the precursor diamine, putrescine, are naturally occurring polycationic alkylamines that are required for eukaryotic cell growth, differentiation, and survival. This absolute requirement for polyamines and the need to maintain intracellular levels within specific ranges require a highly regulated metabolic pathway primed for rapid changes in response to cellular growth signals, environmental changes, and stress. Although the polyamine metabolic pathway is strictly regulated in normal cells, dysregulation of polyamine metabolism is a frequent event in cancer. Recent studies suggest that the polyamine catabolic pathway may be involved in the etiology of some epithelial cancers. The catabolism of spermine to spermidine utilizes either the one-step enzymatic reaction of spermine oxidase (SMO) or the two-step process of spermidine/spermine N (1)-acetyltransferase (SSAT) coupled with the peroxisomal enzyme N (1)-acetylpolyamine oxidase. Both catabolic pathways produce hydrogen peroxide and a reactive aldehyde that are capable of damaging DNA and other critical cellular components. The catabolic pathway also depletes the intracellular concentrations of spermidine and spermine, which are free radical scavengers. Consequently, the polyamine catabolic pathway in general and specifically SMO and SSAT provide exciting new targets for chemoprevention and/or chemotherapy.

Pharmacological potential of biogenic amine-polyamine interactions beyond neurotransmission

Histamine, serotonin and dopamine are biogenic amines involved in intercellular communication with multiple effects on human pathophysiology. They are products of two highly homologous enzymes, histidine decarboxylase and l-aromatic amino acid decarboxylase, and transmit their signals through different receptors and signal transduction mechanisms. Polyamines derived from ornithine (putrescine, spermidine and spermine) are mainly involved in intracellular effects related to cell proliferation and death mechanisms. This review summarizes structural and functional evidence for interactions between components of all these amine metabolic and signalling networks (decarboxylases, transporters, oxidases, receptors etc.) at cellular and tissue levels, distinct from nervous and neuroendocrine systems, where the crosstalk among these amine-related components can also have important pathophysiological consequences. The discussion highlights aspects that could help to predict and discuss the effects of intervention strategies.

Increased polyamines alter chromatin and stabilize autoantigens in autoimmune diseases

Polyamines are small cations with unique combinations of charge and length that give them many putative interactions in cells. Polyamines are essential since they are involved in replication, transcription, translation, and stabilization of macro-molecular complexes. However, polyamine synthesis competes with cellular methylation for S-adenosylmethionine, the methyl donor. Also, polyamine degradation can generate reactive molecules like acrolein. Therefore, polyamine levels are tightly controlled. This control may be compromised in autoimmune diseases since elevated polyamine levels are seen in autoimmune diseases. Here a hypothesis is presented explaining how polyamines can stabilize autoantigens. In addition, the hypothesis explains how polyamines can inappropriately activate enzymes involved in NETosis, a process in which chromatin is modified and extruded from cells as extracellular traps that bind pathogens during an immune response. This polyamine-induced enzymatic activity can lead to an increase in NETosis resulting in release of autoantigenic material and tissue damage.

HCV and oxidative stress in the liver

Hepatitis C virus (HCV) is the etiological agent accounting for chronic liver disease in approximately 2-3% of the population worldwide. HCV infection often leads to liver fibrosis and cirrhosis, various metabolic alterations including steatosis, insulin and interferon resistance or iron overload, and development of hepatocellular carcinoma or non-Hodgkin lymphoma. Multiple molecular mechanisms that trigger the emergence and development of each of these pathogenic processes have been identified so far. One of these involves marked induction of a reactive oxygen species (ROS) in infected cells leading to oxidative stress. To date, markers of oxidative stress were observed both in chronic hepatitis C patients and in various in vitro systems, including replicons or stable cell lines expressing viral proteins. The search for ROS sources in HCV-infected cells revealed several mechanisms of ROS production and thus a number of cellular proteins have become targets for future studies. Furthermore, during last several years it has been shown that HCV modifies antioxidant defense mechanisms. The aim of this review is to summarize the present state of art in the field and to try to predict directions for future studies.

Ornithine decarboxylase and glutamate decarboxylase 65 as prognostic markers of gallbladder malignancy: a clinicopathological study in benign and malignant lesions of the gallbladder

Ornithine decarboxylase (ODC) plays a critical role in cell proliferation and is overexpressed in a variety of cancers. Furthermore, γ-aminobutyric acid (GABA) content and glutamate decarboxylase (GAD) activity are increased in neoplastic tissues in colon and breast cancer. However, few studies have examined these molecules in gallbladder cancer specimens. We observed the expression levels of ODC and GAD65 in benign and malignant lesions of the gallbladder and investigated their clinicopathological significance for the first time. The expression levels of ODC and GAD65 in specimens from gallbladder adenocarcinoma (n=108), peritumoral tissues (n=46), adenomatous polyps (n=15) and chronic cholecystitis (n=35) were detected using immunohistochemical methods. Kaplan-Meier survival and Cox regression analyses were carried out to explore the clinical and pathological correlations. The levels of positive staining of ODC and GAD65 were significantly higher in gallbladder adenocarcinoma than in peritumoral tissues, adenomatous polyps and chronic cholecystitis. The Kaplan‑Meier survival analysis and Cox regression analysis showed that the expression of ODC and GAD65 correlated significantly with the one-year survival rate and the mean survival time of the patients postoperatively. We conclude that the overexpression of ODC and GAD65 are significant in the carcinogenesis and progression of gallbladder adenocarcinoma. They may be important biological markers for the evaluation of biological behaviors and the prognosis of gallbladder adenocarcinoma.