Functional characterization of the human spermidine/spermine N(1)-acetyltransferase gene promoter

The Role of Spermidine and Its Key Metabolites in Important, Pathogenic Human Viruses and in Parasitic Infections Caused by Plasmodium falciparum and Trypanosoma brucei

The triamine spermidine is a key metabolite of the polyamine pathway. It plays a crucial role in many infectious diseases caused by viral or parasitic infections. Spermidine and its metabolizing enzymes, i.e., spermidine/spermine-N¹-acetyltransferase, spermine oxidase, acetyl polyamine oxidase, and deoxyhypusine synthase, fulfill common functions during infection in parasitic protozoa and viruses which are obligate, intracellular parasites. The competition for this important polyamine between the infected host cell and the pathogen determines the severity of infection in disabling human parasites and pathogenic viruses. Here, we review the impact of spermidine and its metabolites in disease development of the most important, pathogenic human viruses such as SARS-CoV-2, HIV, Ebola, and in the human parasites Plasmodium and Trypanosomes. Moreover, state-of-the-art translational approaches to manipulate spermidine metabolism in the host and the pathogen are discussed to accelerate drug development against these threatful, infectious human diseases.

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.

Putative association between the -1415 T/C polymorphism of spermidine/spermine N1-acetyltransferase (SSAT1) gene and alcohol use disorders in women and men

BACKGROUND

The activity of N-methyl-D-aspartate (NMDA) glutamate receptor, which responds to the levels of polyamines, modifies the neurotoxicity caused by ethanol. We aimed to investigate if the functionality of the spermidine/spermine N1-acetyltransferase (SSAT1) gene could be associated with a differential risk for alcoholism.

METHODS

We studied a sample of 586 subjects: 104 alcohol-dependent patients, 273 patients with psychiatric disorders but without substance dependence, and 209 healthy controls. After gender stratification, the allele frequency distribution of the SSAT1 gene was compared between these three groups.

RESULTS

In females, the TC genotype was significantly more frequent in alcohol-dependent patients than in non-alcohol-dependent psychiatric controls (χ(2 )= 7.509 df = 2, p = 0.023). A trend was found when alcohol-dependent females were compared with the healthy control group (χ(2 )= 4.897 df = 2, p = 0.086). No statistical differences were found among the males.

DISCUSSION AND CONCLUSION

Gender differences in the regulation of SSAT1 gene expression may possibly be due to gender-specific effects of stress, ethanol toxicity, and/or polyamines levels. Further studies are needed to confirm our findings.

Lack of evidence for the association of ornithine decarboxylase (+316 G>A), spermidine/spermine acetyl transferase (-1415 T>C) gene polymorphisms with calcium oxalate stone disease

Urolithiasis is a complex and multifactorial disorder characterized by the presence of stones in the urinary tract. Urea cycle is an important process involved in disease progression. L-ornithine is a key amino acid in the urea cycle and is converted to putrescine by ornithine decarboxylase (ODC). Putrescine, spermidine and spermine are natural polyamines that are catabolized by a specific enzyme, spermidine/spermine acetyltransferase (SSAT). The single-nucleotide polymorphisms (SNPs) in the intron region of ODC (+316 G>A) and promoter region of SSAT (-1415 T>C) genes have been found to be associated with the polyamines expression levels. The aim of this study was to examine whether the ODC (+316 G>A) intron 1 region gene polymorphism and SAT-1 promoter region (-1415 T>C) gene polymorphisms are potential genetic markers for susceptibility to urolithiasis. A control group of 104 healthy subjects and a group of 65 patients with recurrent idiopathic calcium oxalate stone disease were enrolled into this study. Polymerase chain reaction (PCR)-based restriction analysis was performed for the ODC intron 1 (+316 G>A) region and SAT-1 (-1415 T>C) promoter gene polymorphisms by PstI and MspI restriction enzyme digestion, respectively. The genotype distribution of polymorphisms studied in the ODC intron 1 region (+316 G>A) and SAT-1 -1415 T>C promoter region did not reveal a significant difference between urolithiasis and the control groups (P=0.713 and 0.853), respectively. Furthermore, no significant difference was observed between the control and patient groups for ODC +316 G>A and SAT-1 -1415 T>C allele frequencies (P=0.877 and 0.644), respectively. In conclusion, results of the present study suggest that ODC + 316 G>A and SAT-1 -1415 T>C gene polymorphisms might not be a risk factor for urolithiasis.

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

Biogenic polyamines spermine and spermidine participate in numerous cellular processes including transcription, RNA processing and translation. Specifically, they counteract oxidative stress, an alteration of cell redox balance involved in generation and progression of various pathological states including cancer. Here, we investigated how chemically induced oxidative stress affects polyamine metabolism, specifically the expression and activities of enzymes catalyzing polyamine synthesis (ornithine decarboxylase; ODC) and degradation (spermidine/spermine-N(1)-acetyltransferase; SSAT), in human hepatoma cells. Oxidative stress induced the up-regulation of ODC and SSAT gene transcription mediated by Nrf2, and in case of SSAT, also by NF-κB transcription factors. Activation of transcription led to the elevated intracellular activities of both enzymes. The balance in antagonistic activities of ODC and SSAT in the stressed hepatoma cells was shifted towards polyamine biosynthesis, which resulted in increased intracellular levels of putrescine, spermidine, and spermine. Accumulation of putrescine is indicating for accelerated degradation of polyamines by SSAT - acetylpolyamine oxidase (APAO) pathway generating toxic products that promote carcinogenesis, whereas accelerated polyamine synthesis via activation of ODC is favorable for proliferation of cells including those sub-lethally damaged by oxidative stress.

Epigenetic regulation of spermidine/spermine N1-acetyltransferase (SAT1) in suicide

We have recently shown that the expression of spermidine/spermine N1-acetyltransferase (SAT1) is downregulated across the brains of suicide completers, and that its expression is influenced by genetic variations in the promoter. Several promoter polymorphisms in SAT1, including rs6526342, have been associated with suicide and other psychiatric disorders, and display haplotype-specific effects on expression. However, these effects cannot explain total variability in SAT1 expression, and other regulatory mechanisms, such as epigenetic factors, may also be at play. In this study, we assessed the involvement of epigenetic factors in controlling SAT1 expression in the prefrontal cortex of suicide completers by mapping CpG methylation across a 1880-bp region of the SAT1 promoter, and measuring levels of tri-methylated histone-3-lysine 27 (H3K27me3) at the promoter in suicide completers and controls. Our results demonstrated that CpG methylation was significantly negatively correlated with SAT1 expression. Although overall or site-specific CpG methylation was not associated with suicide or SAT1 expression, we observed high levels of methylation at the polymorphic CpG site created by rs6526342, indicating a relationship between promoter haplotypes and methylation. There was no association between H3K27me3 and suicide, nor was this modification associated with SAT1 expression. Overall, our results indicate that epigenetic factors in the promoter region of SAT1 influence gene expression levels, and may provide a mechanism for both our previous findings of haplotype-specific effects of promoter variations on SAT1 expression, as well as the widespread downregulation of SAT1 expression observed in the brains of suicide completers.

Androgen receptor requires JunD as a coactivator to switch on an oxidative stress generation pathway in prostate cancer cells

Relatively high oxidative stress levels in the prostate are postulated to be a major factor for prostate carcinogenesis and prostate cancer (CaP) progression. We focused on elucidating metabolic pathways of oxidative stress generation in CaP cells. Previously, we showed that the transcription factor JunD is essential for androgen-induced reactive oxygen species (ROS) production in androgen-dependent human CaP cells. We also recently showed that androgen induces the first and regulatory enzyme spermidine/spermine N1-acetyltransferase (SSAT) in a polyamine catabolic pathway that produces copious amounts of metabolic ROS. Here, we present coimmunoprecipitation and Gaussia luciferase reconstitution assay data that show that JunD forms a complex with androgen-activated androgen receptor (AR) in situ. Our chromatin immunoprecipitation assay data show that JunD binds directly to a specific SSAT promoter sequence only in androgen-treated LNCaP cells. Using a vector containing a luciferase reporter gene connected to the SSAT promoter and a JunD-silenced LNCaP cell line, we show that JunD is essential for androgen-induced SSAT gene expression. The elucidation of JunD-AR complex inducing SSAT expression leading to polyamine oxidation establishes the mechanistic basis of androgen-induced ROS production in CaP cells and opens up a new prostate-specific target for CaP chemopreventive/chemotherapeutic drug development.

Identification and characterization of spermidine/spermine N1-acetyltransferase promoter variants in suicide completers

BACKGROUND

We have previously shown that the expression of spermidine/spermine N1-acetyltransferase (SAT1) is decreased in the brain Brodmann areas (BA)4, BA8/9, and BA11 of suicide completers and found an association between rs6526342, a SAT1 promoter single nucleotide polymorphism (SNP), with suicide completion (1).

METHODS

We genotyped 18 promoter polymorphisms in SAT1 in a French-Canadian population. The relationship between haplotypes and gene expression was assessed with microarray analysis of three brain regions as well as reporter gene assays in three cell lines. Site-directed mutagenesis was used to examine the role of individual polymorphisms in reporter gene expression.

RESULTS

We identified two major and several minor haplotypes in the promoter region of SAT1. Subjects who possessed the haplotype containing the risk allele for rs6526342 demonstrated decreased SAT1 expression in BA4, BA8/9, and BA11. This haplotype was also associated with decreased expression in reporter gene assays. Site-directed mutagenesis identified three polymorphisms-an insertion/deletion (rs6151267), and two SNPs (rs6526342 and rs928931)-that were involved in determining reporter gene expression. These polymorphisms do not seem to exert their effects through the polyamine responsive element, because all constructs were induced to a similar extent in the presence of spermine.

CONCLUSIONS

Our results indicate that genetic variations in the promoter region of SAT1 are involved in determining levels of gene expression and might provide a mechanism for the decreased SAT1 expression observed in suicide completers.

Positive association between SAT-1 -1415T/C polymorphism and anxiety

Limbic glutamatergic neurotransmission plays a pivotal role in the pathogenesis of anxiety disorders. Polyamines modulate the activity of several ionotropic glutamate receptors and have been involved in the regulation of fear-conditioning response. Spermidine/spermine N1-acetyltransferase (SSAT-1) is the main enzyme regulating polyamine catabolism. The aim of the present study was to examine the association between anxiety disorders and the -1415T/C (rs1960264) single nucleotide polymorphism (SNP) of the gene (SAT1) coding for SSAT-1. A case-control design was used in order to compare the genotypes for the -1415T/C (rs1960264) SNP between anxiety patients (n = 218), other non-anxiety psychiatric patients (n = 362), and healthy controls (n = 251). DSM-IV diagnoses were provided using MINI 4.4. Genomic DNA was extracted from peripheral blood samples collected from participants. In males, there was a significant difference in the distribution of the two genotypes (T and C) for the SAT-1 -1415T/C SNP between anxiety patients, non-anxiety psychiatric controls, and healthy controls. The T genotype was significantly more frequent in males suffering from anxiety disorders than in male psychiatric controls and healthy controls. This is the first study linking polymorphic variants of genes involved in polyamine metabolism with anxiety disorders.

SAT-1 -1415T/C polymorphism and susceptibility to schizophrenia

Patients suffering from psychosis show increased blood and fibroblast total polyamine levels. Spermidine/spermine N1-acetyltransferase (SSAT-1) and its coding gene (SAT-1) are the main factors regulating polyamine catabolism. The aim of the present study was to examine the association between the SAT-1 -1415T/C single nucleotide polymorphism (SNP) and schizophrenia. A case-control design was used in order to compare the genotypes for the SNP between schizophrenia patients (n=180, 83 females and 97 males), other non-psychotic psychiatric patients (n=413, 256 females and 157 males), and healthy controls (n=251, 101 females and 150 males). No significant differences in the distribution of the genotypes of the SAT-1 -1415T/C SNP were found groups among groups. We failed to demonstrate a significant association between the SAT-1 -1415T/C SNP and schizophrenia, but a mild association between allele C and psychopathology was found in the female group.

Nuclear and membrane receptor-mediated signalling pathways modulate polyamine biosynthesis and interconversion

Polyamines play an important role in cell growth and differentiation, while their overproduction has potentially oncogenic consequences. Polyamine homoeostasis, a critical determinant of cell fate, is precisely tuned at the level of biosynthesis, degradation and transport. The enzymes ODC (ornithine decarboxylase), AdoMetDC (S-adenosylmethionine decarboxylase) and SSAT (spermidine/spermine N(1)-acetyltransferase) are critical for polyamine pool maintenance. Our experiments were designed to examine the expression of these enzymes in testosterone-induced hypertrophic and antifolate-induced hyperplastic mouse kidney, characterized by activation of AR (androgen receptor) and HGF (hepatocyte growth factor) membrane receptor c-Met respectively. The expression of these key enzymes was up-regulated by antifolate CB 3717 injury-evoked activation of HGF/c-Met signalling. In contrast, activation of the testosterone/AR pathway remarkably induced a selective increase in ODC expression without affecting other enzymes. Studies in catecholamine-depleted kidneys point to a synergistic interaction between the signalling pathways activated via cell membrane catecholamine receptors and AR, as well as c-Met. We found that this cross-talk modulated the expression of ODC and AdoMetDC, enzymes limiting polyamine biosynthesis, but not SSAT. This is in contrast with the antagonistic cross-talk between AR- and c-Met-mediated signalling which negatively regulated the expression of ODC, but affected neither AdoMetDC nor SSAT.

Polyamine analogues down-regulate estrogen receptor alpha expression in human breast cancer cells

The critical role of polyamines in cell growth has led to the development of a number of agents that interfere with polyamine metabolism including a novel class of polyamine analogues, oligoamines. Here we demonstrate that oligoamines specifically suppress the mRNA and protein expression of estrogen receptor alpha (ERalpha) and ERalpha target genes in ER-positive human breast cancer cell lines, whereas neither ERbeta nor other steroid hormonal receptors are affected by oligoamines. The constitutive expression of a cytomegalovirus promoter-driven exogenous ERalpha in ER-negative MDA-MB-231 human breast cancer cells was not altered by oligoamines, suggesting that oligoamines specifically suppress ERalpha transcription rather than affect mRNA or protein stability. Further analysis demonstrated that oligoamines disrupted the DNA binding activity of Sp1 transcription factor family members to an ERalpha minimal promoter element containing GC/CA-rich boxes. Treatment of MDA-MB-231 cells with the JNK-specific inhibitor SP600125 or expression of the c-Jun dominant negative inhibitor TAM67 blocked the oligoamine-activated JNK/c-Jun pathway and enhanced oligoamine-inhibited ERalpha expression, suggesting that AP-1 is a positive regulator of ERalpha expression and that oligoamine-activated JNK/AP-1 activity may antagonize the down-regulation of ERalpha induced by oligoamines. Taken together, these results suggest a novel antiestrogenic mechanism for specific polyamine analogues in human breast cancer cells.

cDNA microarray analysis of isogenic paclitaxel- and doxorubicin-resistant breast tumor cell lines reveals distinct drug-specific genetic signatures of resistance

cDNA microarray analysis is a highly useful tool for the classification of tumors and for prediction of patient prognosis to specific cancers based on this classification. However, to date, there is little evidence that microarray approaches can be used to reliably predict patient response to specific chemotherapy drugs or regimens. This is likely due to an inability to differentiate between genes affecting patient prognosis and genes that play a role in response to specific drugs. Thus, it would be highly useful to identify genes whose expression correlates with tumor cell sensitivity to specific chemotherapy agents in a drug-specific manner. Using cDNA microarray analysis of wildtype MCF-7 breast tumor cells and isogenic paclitaxel-resistant (MCF-7(TAX)) or doxorubicin-resistant (MCF-7(DOX)) derivative cell lines, we have uncovered drug-specific changes in gene expression that accompany the establishment of paclitaxel or doxorubicin resistance. These changes in gene expression were confirmed by quantitative reverse transcription polymerase chain reaction and immunoblotting experiments, with a confirmation rate of approximately 91-95%. The genes identified may prove highly useful for prediction of response to paclitaxel or doxorubicin in patients with breast cancer. To our knowledge this is the first report of drug-specific genetic signatures of resistance to paclitaxel or doxorubicin, based on a comparison of gene expression between isogenic wildtype and drug-resistant tumor cell lines. Moreover, this study provides significant insight into the wide variety of mechanisms through which resistance to these agents may be acquired in breast cancer.

Direct oxidative DNA damage, apoptosis and radio sensitivity by spermine oxidase activities in mouse neuroblastoma cells

In mammals, the polyamines affect cell growth, differentiation, and apoptosis; their levels are increased in malignant and proliferating cells, thus justifying an interest in a chemotherapeutic approach to cancer. The flavoprotein SMO is the most recently characterized catabolic enzyme, preferentially oxidizing SPM to SPD, 3-aminopropanal and H(2)O(2). In this report, we describe a novel functional characterization of the recently cloned splice variant isoforms from mouse brain, encoding, among others, the nuclear co-localized spermine oxidase mSMOmu. The over-expression of the active isoforms mSMOalpha and mSMOmu, and the inactive mSMOdelta and mSMOgamma in mouse neuroblastoma cells, demonstrated the first evidence of the direct oxidative DNA damage by the SMO activities, either alone or, in a higher extent, when associated with radiation exposure, thus working as radio sensitizer. These effects were reverted by treatment with 50 muM and 100 muM doses of the inhibitor of SMO activity MDL 72,527. The over-expression of all SMO isoforms failed to influence the expression of the regulating enzymes of polyamines metabolism ODC and SSAT. Dealing with the unbalanced tissue specific SMO activities, these results could indicate a new direction to tailor chemotherapy-associated radiotherapy, improving dose-rate protocol and allowing the modulation of deleterious side effects on healthy tissues.