Anti-oxidant activity of spermine and spermidine re-evaluated with oxidizing systems involving iron and copper ions

Natural Polyamine Spermidine Inhibits the In Vitro Oxidation of LDL

Spermidine is a natural autophagy-inducer and anti-aging compound. Herein, we investigated a potential autophagy-independent mechanism of spermidine, namely its capability to directly impede LDL oxidation, an early step in atherogenesis. In our in vitro-model, LDL oxidation was induced by the addition of CuCl2 in the presence of increasing concentrations of spermidine, and the degree of oxidation of the lipid, as well as of the protein part of LDL, was measured. We found that spermidine concentration-dependently inhibited the production of lipid hydroperoxides, malondialdehyde, and oxidation-specific immune epitopes in the LDL particle, associated with decreased relative electrophoretic mobilities, respectively. For example, the LPO content was significantly lower when LDL was oxidized in the presence of 500 µg/mL spermidine (26.9 ± 1.6 nmol/mg LDL) than in the absence of spermidine (180.6 ± 7.7 nmol/mg LDL, p < 0.0001). When oxLDL was obtained under increasing spermidine concentrations, its cytotoxicity in EA.hy926 cells concentration-dependently decreased. Quantum chemical calculations show that the reaction between spermidine and hydroxyl radicals is exergonic. We conclude that spermidine is a direct inhibitor of LDL oxidation due to its capability to scavenge hydroxyl radicals. Thus, spermidine supplementation might be a suitable tool to impede atherogenesis and associated (cardio)vascular diseases. Further prospective clinical studies are needed to evaluate the potential atheroprotective/health-promoting effects of spermidine-rich diets.

Promising Effects of Novel Supplement Formulas in Preventing Skin Aging in 3D Human Keratinocytes

Dietary intervention is considered a safe preventive strategy to slow down aging. This study aimed to evaluate the protective effects of a commercially available supplement and six simpler formulations against DNA damage in 3D human keratinocytes. The ingredients used are well known and were combined into various formulations to test their potential anti-aging properties. Firstly, we determined the formulations' safe concentration by evaluating cytotoxicity and cell viability through spectrophotometric assays. We then examined the presence of tumor p53 binding protein 1 and phosphorylated histone H2AX foci, which are markers of genotoxicity. The foci count revealed that a 24-h treatment with the supplement did not induce DNA damage, and significantly reduced DNA damage in cells exposed to neocarzinostatin for 2 h. Three of the simpler formulations showed similar results. Moreover, the antioxidant activity was tested using a recently developed whole cell-based chemiluminescent bioassay; results showed that a 24-h treatment with the supplement and three simpler formulations significantly reduced intracellular H2O2 after pro-oxidant injury, thus suggesting their possible antiaging effect. This study's originality lies in the use of a 3D human keratinocyte cell model and a combination of natural ingredients targeting DNA damage and oxidative stress, providing a robust evaluation of their anti-aging potential.

Synergistic effect of spermidine and ciprofloxacin against Alzheimer's disease in male rat via ferroptosis modulation

Alzheimer's disease (AD) is a prevalent form of neurodegenerative disease with a complex pathophysiology that remains not fully understood, and the exact mechanism of neurodegeneration is uncertain. Ferroptosis has been linked to the progression of degenerative diseases observed in AD models. The present study is designed to investigate the protective effects of spermidine, a potent antioxidant and iron chelator, and its synergistic interactions with ciprofloxacin, another iron chelator, in modulating ferroptosis and mitigating AD progression in rats. This study investigated AD-related biomarkers like neurotoxic amyloid beta (Aβ), arginase I, and serotonin. Spermidine demonstrated an anti-ferroptotic effect in the AD model, evident from the modulation of ferroptosis parameters such as hippocampus iron levels, reduced protein expression of transferrin receptor 1 (TFR1), and arachidonate 15-lipoxygenase (ALOX15). Additionally, the administration of spermidine led to a significant increase in protein expression of phosphorylated nuclear factor erythroid 2-related factor 2 (p-Nrf2) and upregulation of Cystine/glutamate transporter (SLC7A11) gene expression. Moreover, spermidine notably decreased p53 protein levels, acrolein, and gene expression of spermidine/spermine N1-acetyltransferase 1 (SAT1). Overall, our findings suggest that spermidine and/or ciprofloxacin may offer potential benefits against AD by modulating ferroptosis. Furthermore, spermidine enhanced the antioxidant efficacy of ciprofloxacin and reduced its toxic effects.

Varietal Influence on the Formation of Bioactive Amines during the Processing of Fermented Cocoa with Different Pulp Contents

During cocoa processing, there can be the formation of bioactive amines, which are compounds that play relevant roles not only in plant development but also in human health. Thus, we aimed to investigate the presence and levels of bioactive amines during the processing of two important varieties of cocoa (PS 1319 and Parazinho). The seeds were fermented using five different pulp proportions: 100% (E1), 80% (E2), 60% (E3), and 0% (total pulp removal) (E4). The beans were fermented and dried on a farm following traditional procedures. Soon after, they were roasted and processed into chocolates with 60% cocoa in the laboratory. Bioactive amine contents were determined by ion-pair reversed-phase HPLC and fluorometric detection in the samples before, during, and after fermentation, after drying and roasting (nibs), and in the liquor and chocolate. The only amines found before processing in PS 1319 and Parazinho, respectively, in dry weight basis (dwb), were putrescine (pulp, 13.77 and 12.31; seed, 5.88 and 4.58) and serotonin (seed, 2.70 and 2.54). Fermentation was shorter for Parazinho (156 h) compared to PS 1319 (180 h). The changes in amines were affected by the cocoa variety. During drying, the presence of cadaverine stood out, appearing in all treatments of the PS 1319 variety, reaching 17.96 mg/kg dwb, and in two treatments of the Parazinho variety (100 and 60% pulp). During roasting, most of the amines decreased, except for phenylethylamine, which increased up to 2.47 mg/kg dwb for Parazinho and 1.73 mg/kg dwb for PS 1319. Most of the amines formed and built up (e.g., tyramine, putrescine, and cadaverine) during fermentation were not available or were at low levels in the nibs. Most of the amines found during processing did not reach the final product (chocolate), except for cadaverine in PS 1319 without pulp (7.54 mg/kg dwb). Finally, we confirmed how pulp content, processing, and variety influence the content of bioactive amines in cocoa and chocolate. These changes can be better demonstrated through a heatmap and principal component analysis.

Difluoromethylornithine (DFMO) Enhances the Cytotoxicity of PARP Inhibition in Ovarian Cancer Cells

Ovarian cancer accounts for 3% of the total cancers in women, yet it is the fifth leading cause of cancer deaths among women. The BRCA1/2 germline and somatic mutations confer a deficiency of the homologous recombination (HR) repair pathway. Inhibitors of poly (ADP-ribose) polymerase (PARP), another important component of DNA damage repair, are somewhat effective in BRCA1/2 mutant tumors. However, ovarian cancers often reacquire functional BRCA and develop resistance to PARP inhibitors. Polyamines have been reported to facilitate the DNA damage repair functions of PARP. Given the elevated levels of polyamines in tumors, we hypothesized that treatment with the polyamine synthesis inhibitor, α-difluoromethylornithine (DFMO), may enhance ovarian tumor sensitivity to the PARP inhibitor, rucaparib. In HR-competent ovarian cancer cell lines with varying sensitivities to rucaparib, we show that co-treatment with DFMO increases the sensitivity of ovarian cancer cells to rucaparib. Immunofluorescence assays demonstrated that, in the presence of hydrogen peroxide-induced DNA damage, DFMO strongly inhibits PARylation, increases DNA damage accumulation, and reduces cell viability in both HR-competent and deficient cell lines. In vitro viability assays show that DFMO and rucaparib cotreatment significantly enhances the cytotoxicity of the chemotherapeutic agent, cisplatin. These results suggest that DFMO may be a useful adjunct chemotherapeutic to improve the anti-tumor efficacy of PARP inhibitors in treating ovarian cancer.

Harnessing the polyamine transport system to treat BRAF inhibitor-resistant melanoma

BRAF mutations are present in over half of all melanoma tumors. Although BRAF inhibitors significantly improve survival of patients with metastatic melanoma, recurrences occur within several months. We previously reported that BRAF mutant melanoma cells are more sensitive to a novel arylmethyl-polyamine (AP) compound that exploits their increased polyamine uptake compared to that of BRAF wildtype cells. Using an animal model of BRAF inhibitor-resistant melanoma, we show that co-treatment with the BRAF inhibitor, PLX4720, and AP significantly delays the recurrence of PLX4720-resistant melanoma tumors and decreases tumor-promoting macrophages. Development of BRAF inhibitor-resistance enriches for metastatic cancer stem cells (CSC) and increases tumor-promoting macrophages. In vitro studies demonstrated that CD304⁺, CXCR4⁺ spheroid cultures of BRAF mutant melanoma cells are resistant to PLX4720 but are more sensitive to AP compared to monolayer cultures of the same cells. AP significantly inhibited YUMM1.7 melanoma cell invasiveness across a Matrigel-coated filter using the CXCR4 ligand, SDF-1α, as the chemoattractant. AP also blocked the chemotactic effect of SDF-1α on CXCR4⁺ macrophages and inhibited M2 polarization of macrophages. In melanoma-macrophage co-cultures, AP prevented the PLX4720-induced release of pro-tumorigenic growth factors, such as VEGF, from macrophages and prevented the macrophage rescue of BRAF mutant melanoma cells treated with PLX4720. Our study offers a novel therapy (AP) to treat chemo-resistant melanoma. AP is unique because it targets the polyamine transport system in BRAF inhibitor-resistant CSCs and also blocks CXCR4 signaling in invasive melanoma cells and pro-tumorigenic macrophages.

Spermidine improves antioxidant activity and energy metabolism in mung bean sprouts

The effects of exogenous spermidine and dicyclohexylamine (DCHA, spermidine synthesis inhibitor) on the antioxidative system and energy status of germinating mung bean were investigated. Results showed that exogenous spermidine increased the content of total phenolic and ascorbic acid and the antioxidative activity, but reduced activities and gene expressions of peroxidase (POD) and catalase (CAT). These changes might be explained by increased H₂O₂ content and activities of succinic dehydrogenase (SDH), adenosine triphosphatases (ATPases), and cytochrome c oxidase (CCO), resulting in higher adenosine triphosphate (ATP) and energy charge (EC). Interestingly, spermidine down-regulated expressions of SDH, H⁺-ATPase, Ca²⁺-ATPase and CCO whilst DCHA reduced energy metabolism and induced the opposite effects to spermidine, except for ascorbic acid content. Inhibition was reversed by exogenous spermidine. In conclusion, spermidine induced the accumulation of H₂O₂, enhanced the antioxidative system and improved the energy metabolism to enhance the functional quality of mung bean sprouts.

A Novel Polyamine-Targeted Therapy for BRAF Mutant Melanoma Tumors

Mutant serine/threonine protein kinase B-Raf (BRAF) protein is expressed in over half of all melanoma tumors. Although BRAF inhibitors (BRAFi) elicit rapid anti-tumor responses in the majority of patients with mutant BRAF melanoma, the tumors inevitably relapse after a short time. We hypothesized that polyamines are essential for tumor survival in mutant BRAF melanomas. These tumors rely on both polyamine biosynthesis and an upregulated polyamine transport system (PTS) to maintain their high intracellular polyamine levels. We evaluated the effect of a novel arylpolyamine (AP) compound that is cytotoxic upon cellular entry via the increased PTS activity of melanoma cells with different BRAF mutational status. Mutant BRAF melanoma cells demonstrated greater PTS activity and increased sensitivity to AP compared to wild type BRAF (BRAF^WT) melanoma cells. Treatment with an inhibitor of polyamine biosynthesis, α-difluoromethylornithine (DFMO), further upregulated PTS activity in mutant BRAF cells and increased their sensitivity to AP. Furthermore, viability assays of 3D spheroid cultures of mutant BRAF melanoma cells demonstrated greater resistance to the BRAFi, PLX4720, compared to 2D monolayer cultures. However, co-treatment with AP restored the sensitivity of melanoma spheroids to PLX4720. These data indicate that mutant BRAF melanoma cells are more dependent on the PTS compared to BRAF^WT melanoma cells, resulting in greater sensitivity to the PTS-targeted cytotoxic AP compound.

Bioactive amines and phenolic compounds in cocoa beans are affected by fermentation

Cocoa is the target of increased scientific research as it is one of the richest source of bioactive compounds. The formation of bioactive amines and their changes in cocoa beans during seven days of traditional fermentation was investigated for the first time. In addition, total phenolic compounds, anthocyanins contents and the scavenging capacity against ABTS radical were determined to monitor the fermentation process. Only two biogenic amines (tryptamine and tyramine) and two polyamines (spermidine and spermine) were detected in cocoa beans during fermentation. Fermentation was characterized by three stages: i) high levels of tryptamine, phenolics, and scavenging capacity; ii) high contents of spermine, total biogenic amines and total polyamines; and iii) the highest spermidine levels and total acidity, but the lowest total phenolic compounds and anthocyanins contents. The scavenging capacity of cocoa beans during fermentation correlated with total phenolic compounds and anthocyanins contents.

Contribution of inorganic polyphosphate towards regulation of mitochondrial free calcium

BACKGROUND

Calcium signaling plays a key role in the regulation of multiple processes in mammalian mitochondria, from cellular bioenergetics to the induction of stress-induced cell death. While the total concentration of calcium inside the mitochondria can increase by several orders of magnitude, the concentration of bioavailable free calcium in mitochondria is maintained within the micromolar range by the mitochondrial calcium buffering system. This calcium buffering system involves the participation of inorganic phosphate. However, the mechanisms of its function are not yet understood. Specifically, it is not clear how calcium-orthophosphate interactions, which normally lead to formation of insoluble precipitates, are capable to dynamically regulate free calcium concentration. Here we test the hypothesis that inorganic polyphosphate, which is a polymerized form of orthophosphate, is capable to from soluble complexes with calcium, playing a significant role in the regulation of the mitochondrial free calcium concentration.

METHODS

We used confocal fluorescence microscopy to measure the relative levels of mitochondrial free calcium in cultured hepatoma cells (HepG2) with variable levels of inorganic polyphosphate (polyP).

RESULTS

The depletion of polyP leads to the significantly lower levels of mitochondrial free calcium concentration under conditions of pathological calcium overload. These results are coherent with previous observations showing that inorganic polyphosphate (polyP) can inhibit calcium-phosphate precipitation and, thus, increase the amount of free calcium.

CONCLUSIONS

Inorganic polyphosphate plays an important role in the regulation of mitochondrial free calcium, leading to its significant increase.

GENERAL SIGNIFICANCE

Inorganic polyphosphate is a previously unrecognized integral component of the mitochondrial calcium buffering system.

Structural dependence of in vitro cytotoxicity, oxidative stress and uptake mechanisms of poly(propylene imine) dendritic nanoparticles

The in vitro cytotoxic and intracellular oxidative stress responses to exposure to poly(propylene imine) (PPI) dendritic nanoparticles of increasing generation (number of repeated branching cycles) (G0-G4) were assessed in an immortal non-cancerous human keratinocyte cell line (HaCaT). Confocal fluorescence microscopy with organelle staining was used to explore the uptake and intracellular trafficking mechanisms. A generation- and dose-dependent cytotoxic response was observed, increasing according to generation and, therefore, number of surface amino groups. A comparison of the cytotoxic response of G4 PPI and the related G4 poly(amido amine) dendrimer indicates that the PPI with the same number of surface amino groups elicits a significantly higher cytotoxic response. The trend of cytotoxicity versus dendrimer generation and, therefore, size is discontinuous in the region of G2, however, indicating a difference in uptake mechanism for higher compared to lower generations. Whereas the higher generations elicit an oxidative stress response at short exposure times, the lower generations indicate an antioxidant response. Confocal microscopy indicates that, whereas they are prominent at early exposure times for the larger PPI dendrimers, no evidence of early stage endosomes was observed for lower generations of PPI. The results are consistent with an alternative uptake mechanism of physical diffusion across the semipermeable cell membrane for the lower generation dendrimers and are discussed in terms of their implications for predictive models for nanotoxicology and design strategies for nanomedical applications.

Characterization of Staphylococcus aureus responses to spermine stress

Spermine (Spm), a potent bactericidal polyamine, exerts a strong synergistic effect with β-lactams against methicillin-resistant Staphylococcus aureus (MRSA). To explore the Spm-based antibacterial targets in S. aureus, time course-dependent transcriptome analysis was conducted on Mu50 (MRSA) in the absence and presence of Spm. Genes in the sigB regulon and most ATP-producing pathways were found down-regulated when exposure to high dose Spm. In contrast, a number of genes for iron acquisition and regulation showed significant induction, indicating a specific connection between Spm and iron-depletion. The tetM gene for tetracycline (Tc) resistance exhibited most significant fold change among the listed genes. It was specifically upregulated by Tc and Spm but not by other ribosome-targeted drugs or other polyamines; however, such induction of tetM cannot confer resistance to Spm. A set of genes for osmotic balance, including kdpABCDE for potassium ion uptake and regulation, was also induced by Spm stress. Addition of KCl or NaCl, but not high concentration sucrose, was found to increase Spm MIC over 30-fold. In summary, transcriptome analysis demonstrated a specific pattern of response upon Spm exposure, suggesting Spm may alter the intracellular iron status and suppress the SigB regulon to exert its toxicity.

Solving the jigsaw puzzle of wound-healing potato cultivars: metabolite profiling and antioxidant activity of polar extracts

Potato (Solanum tuberosum L.) is a worldwide food staple, but substantial waste accompanies the cultivation of this crop due to wounding of the outer skin and subsequent unfavorable healing conditions. Motivated by both economic and nutritional considerations, this metabolite profiling study aims to improve understanding of closing layer and wound periderm formation and guide the development of new methods to ensure faster and more complete healing after skin breakage. The polar metabolites of wound-healing tissues from four potato cultivars with differing patterns of tuber skin russeting (Norkotah Russet, Atlantic, Chipeta, and Yukon Gold) were analyzed at three and seven days after wounding, during suberized closing layer formation and nascent wound periderm development, respectively. The polar extracts were assessed using LC-MS and NMR spectroscopic methods, including multivariate analysis and tentative identification of 22 of the 24 biomarkers that discriminate among the cultivars at a given wound-healing time point or between developmental stages. Differences among the metabolites that could be identified from NMR- and MS-derived biomarkers highlight the strengths and limitations of each method, also demonstrating the complementarity of these approaches in terms of assembling a complete molecular picture of the tissue extracts. Both methods revealed that differences among the cultivar metabolite profiles diminish as healing proceeds during the period following wounding. The biomarkers included polyphenolic amines, flavonoid glycosides, phenolic acids and glycoalkaloids. Because wound healing is associated with oxidative stress, the free radical scavenging activities of the extracts from different cultivars were measured at each wounding time point, revealing significantly higher scavenging activity of the Yukon Gold periderm especially after 7 days of wounding.

Health effects and occurrence of dietary polyamines: a review for the period 2005-mid 2013

This review continues a previous one (Kalač & Krausová, 2005). Dietary polyamines spermidine and spermine participate in an array of physiological roles with both favourable and injurious effects on human health. Dieticians thus need plausible information on their content in various foods. The data on the polyamine contents in raw food materials increased considerably during the reviewed period, while information on their changes during processing and storage have yet been fragmentary and inconsistent. Spermidine and spermine originate mainly from raw materials. Their high contents are typical particularly for inner organs and meat of warm-blooded animals, soybean and fermented soybean products and some mushroom species. Generally, polyamine contents range widely within the individual food items.

Analgesic, anti-inflammatory, and GC-MS studies on Castanospermum australe A. Cunn. & C. Fraser ex Hook

The present study was aimed to evaluate the analgesic and anti-inflammatory properties of Castanospermum australe and to profile phytochemicals by GC-MS. The ethanolic extracts were prepared by successive solvent extraction using Soxhlet apparatus. The analgesic activity was analyzed by hot plate method and acetic acid-induced writhing test whereas anti-inflammatory study was done by carrageenan induced paw oedema model. The acute toxicity study revealed that ethanol extracts of leaf and bark of C. australe were safe even at a higher dose of 2000 mg/kg whereas ethanol extract of seed was toxic at the same dose. In both hot plate method (5.85 s) and acetic acid-induced writhing test (57%), the leaf ethanol extract exhibited significant analgesic activity (P < 0.001) at a dose of 400 mg/kg. The anti-inflammatory activity of leaf extract was exhibited by the reduction in paw linear diameter by 64.76% at 400 mg/kg in carrageenan induced paw oedema. The GC-MS analysis of the ethanol extract of leaf revealed sixteen major compounds of which 1,7-dimethyl-4,10-dioxa-1,7-diazacyclododecane, (+)-N-methylephedrine, and permethylspermine were found to be pharmaceutically and the most important. These findings justify that C. australe can be a valuable natural analgesic and anti-inflammatory source which seemed to provide potential phytotherapeutics against various ailments.

Radiation protection following nuclear power accidents: a survey of putative mechanisms involved in the radioprotective actions of taurine during and after radiation exposure

There are several animal experiments showing that high doses of ionizing radiation lead to strongly enhanced leakage of taurine from damaged cells into the extracellular fluid, followed by enhanced urinary excretion. This radiation-induced taurine depletion can itself have various harmful effects (as will also be the case when taurine depletion is due to other causes, such as alcohol abuse or cancer therapy with cytotoxic drugs), but taurine supplementation has been shown to have radioprotective effects apparently going beyond what might be expected just as a consequence of correcting the harmful consequences of taurine deficiency per se. The mechanisms accounting for the radioprotective effects of taurine are, however, very incompletely understood. In this article an attempt is made to survey various mechanisms that potentially might be involved as parts of the explanation for the overall beneficial effect of high levels of taurine that has been found in experiments with animals or isolated cells exposed to high doses of ionizing radiation. It is proposed that taurine may have radioprotective effects by a combination of several mechanisms: (1) during the exposure to ionizing radiation by functioning as an antioxidant, but perhaps more because it counteracts the prooxidant catalytic effect of iron rather than functioning as an important scavenger of harmful molecules itself, (2) after the ionizing radiation exposure by helping to reduce the intensity of the post-traumatic inflammatory response, and thus reducing the extent of tissue damage that develops because of severe inflammation rather than as a direct effect of the ionizing radiation per se, (3) by functioning as a growth factor helping to enhance the growth rate of leukocytes and leukocyte progenitor cells and perhaps also of other rapidly proliferating cell types, such as enterocyte progenitor cells, which may be important for immunological recovery and perhaps also for rapid repair of various damaged tissues, especially in the intestines, and (4) by functioning as an antifibrogenic agent. A detailed discussion is given of possible mechanisms involved both in the antioxidant effects of taurine, in its anti-inflammatory effects and in its role as a growth factor for leukocytes and nerve cells, which might be closely related to its role as an osmolyte important for cellular volume regulation because of the close connection between cell volume regulation and the regulation of protein synthesis as well as cellular protein degradation. While taurine supplementation alone would be expected to exert a therapeutic effect far better than negligible in patients that have been exposed to high doses of ionizing radiation, it may on theoretical grounds be expected that much better results may be obtained by using taurine as part of a multifactorial treatment strategy, where it may interact synergistically with several other nutrients, hormones or other drugs for optimizing antioxidant protection and minimizing harmful posttraumatic inflammatory reactions, while using other nutrients to optimize DNA and tissue repair processes, and using a combination of good diet, immunostimulatory hormones and perhaps other nontoxic immunostimulants (such as beta-glucans) for optimizing the recovery of antiviral and antibacterial immune functions. Similar multifactorial treatment strategies may presumably be helpful in several other disease situations (including severe infectious diseases and severe asthma) as well as for treatment of acute intoxications or acute injuries (both mechanical ones and severe burns) where severely enhanced oxidative and/or nitrative stress and/or too much secretion of vasodilatory neuropeptides from C-fibres are important parts of the pathogenetic mechanisms that may lead to the death of the patient. Some case histories (with discussion of some of those mechanisms that may have been responsible for the observed therapeutic outcome) are given for illustration of the likely validity of these concepts and their relevance both for treatment of severe infections and non-infectious inflammatory diseases such as asthma and rheumatoid arthritis.

Yeast response and tolerance to polyamine toxicity involving the drug : H+ antiporter Qdr3 and the transcription factors Yap1 and Gcn4

The yeast QDR3 gene encodes a plasma membrane drug : H(+) antiporter of the DHA1 family that was described as conferring resistance against the drugs quinidine, cisplatin and bleomycin and the herbicide barban, similar to its close homologue QDR2. In this work, a new physiological role for Qdr3 in polyamine homeostasis is proposed. QDR3 is shown to confer resistance to the polyamines spermine and spermidine, but, unlike Qdr2, also a determinant of resistance to polyamines, Qdr3 has no apparent role in K(+) homeostasis. QDR3 transcription is upregulated in yeast cells exposed to spermine or spermidine dependent on the transcription factors Gcn4, which controls amino acid homeostasis, and Yap1, the main regulator of oxidative stress response. Yap1 was found to be a major determinant of polyamine stress resistance in yeast and is accumulated in the nucleus of yeast cells exposed to spermidine-induced stress. QDR3 transcript levels were also found to increase under nitrogen or amino acid limitation; this regulation is also dependent on Gcn4. Consistent with the concept that Qdr3 plays a role in polyamine homeostasis, QDR3 expression was found to decrease the intracellular accumulation of [(3)H]spermidine, playing a role in the maintenance of the plasma membrane potential in spermidine-stressed cells.

Ferric-reducing ability power of selected plant polyphenols and their metabolites: implications for clinical studies on the antioxidant effects of fruits and vegetable consumption

Undeniably, low sensitivities in the ferric-reducing ability power (FRAP) is evident in the detection of the augmentation of plasma antioxidant activity, relative to the rise in circulating polyphenols after ingestion of fruits and vegetables. We investigated in vitro the FRAP of 17 plant polyphenols and their metabolites at submicromolar concentrations commensurate in human plasma. We then explored the in vitro effects of polyphenols and purified apple quercetin glycosides on plasma FRAP. We found that apple quercetin glycosides along with various polyphenols observed this distinct power at submicromolar concentrations. The presence of a catechol structure in the compound molecule was positively associated with FRAP (r = 0.60, P < 0.05). An aliphatic substitute at a catechol ring and a double bond in an aliphatic substitute conjugated with an aromatic ring of catechol contributed to 37% of the variance in the FRAP of compounds with catechol in the backbone structure (n = 11). Plasma supplementation with 0.2 microM mixtures of seven of the most active compounds (catechin, 3,4-dihydroxycinnamic acid, 3,4-dihydroxyhydrocinnamic acid, 3,4-dihydroxyphenylacetic acid, ferulic acid, gallic acid and quercetin) initiated a placid rise in FRAP (23.3 +/- 1.2 versus 28.1 +/- 1.3 nmol of Fe(3+), P < 0.05). Apple quercetin glycosides at 0.5 microM did not elevate plasma FRAP. Plasma alone had 30 times higher power than quercetin glycosides at 0.5 microM. Abounding of FRAP exhibited in human plasma as compared to polyphenols at submicromolar concentrations, may offer elucidation to previous incongruities implicated in insignificant rises of plasma FRAP several days after ingestion of fruits or vegetables. This suggests that intake of food products and/or supplements rich in polyphenols containing a catechol ring with an aliphatic substitute augments the plasma FRAP in human beings.