Oxidative stress is recognized as a trigger of different metabolic events in all organisms. Various factors correlated with oxidation, such as the ␤-oxidation of fatty acids and their enzymatic or nonenzymatic byproducts (e.g., precocious sexual inducer factors and lipoperoxides) have been shown to be involved in aflatoxin formation. In the present study, we found that increased levels of reactive oxygen species (ROS) were correlated with increased levels of aflatoxin biosynthesis in Aspergillus parasiticus. To better understand the role of ROS formation in toxin production, we generated a mutant (⌬ApyapA) having the ApyapA gene deleted, given that ApyapA orthologs have been shown to be part of the antioxidant response in other fungi. Compared to the wild type, the mutant showed an increased susceptibility to extracellular oxidants, as well as precocious ROS formation and aflatoxin biosynthesis. Genetic complementation of the ⌬ApyapA mutant restored the timing and quantity of toxin biosynthesis to the levels found in the wild type. The presence of putative AP1 (ApYapA orthologue) binding sites in the promoter region of the regulatory gene aflR further supports the finding that ApYapA plays a role in the regulation of aflatoxin biosynthesis. Overall, our results show that the lack of ApyapA leads to an increase in oxidative stress, premature conidiogenesis, and aflatoxin biosynthesis.Reactive oxygen species (ROS), such as superoxide anionand lipoperoxides (LOOH), which are formed from unsaturated fatty acids and can be produced in the cell during metabolic processes, can be overproduced following the action of oxidative stressors present in the environment (32,49,57). To counteract the potentially dangerous accumulation of ROS, cells have evolved strategies (49, 61) based on enzymatic or nonenzymatic systems (28,45). The main antioxidant enzymes in cells involved in ROS removal are superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX). If H 2 O 2 exceeds the cell-scavenging capacity, it can generate highly reactive HO ⅐ through a Fenton reaction, which initiates the formation of LOOH in the membrane lipids (32). When ROS accumulation occurs, the oxidant/antioxidant balance is perturbed, which can damage the cell membrane and cell metabolism (free-radical theory of aging) (26). ROS produced at certain time points during the cell's life cycle and at low physiological concentrations play a crucial role in the organism's homeostasis and cell functions. As second messengers, ROS take part in the plant's developmental processes (18,24,31) and in the defense mechanisms against pathogens and abiotic stress (5, 24, 52, 62). Similar effects have been shown in mammals, where ROS at proper levels stimulate antioxidant reactions, immune system modulation, and regulation of cell proliferation (3,4,55,59,65). One of the major objectives of studying the biology of stress is to identify the key factors that control the switch from cytoprotective responses to cell dysfunction following oxidative insult (11)....

Carotenoids are used for systemic photoprotection in humans. Regarding mechanisms underlying photoprotective effects of carotenoids, here we compared the modulation of UVA-related injury by carotenoids. Human dermal fibroblasts (HDF) were exposed to moderate doses of UVA, which stimulated apoptosis, increased levels of reactive oxygen species and thiobarbituric acid reactive substances, decreased antioxidant enzymes activities, promoted membrane perturbation, and induced the expression of heme oxygenase-1 (HO-1). The carotenoids astaxanthin (AX), canthaxanthin (CX) and beta-carotene (betaC) were delivered to HDF 24 h before exposure to UVA. Astaxanthin exhibited a pronounced photoprotective effect and counteracted all of the above-mentioned UVA-induced alterations to a significant extent. beta-Carotene only partially prevented the UVA-induced decline of catalase and superoxide dismutase activities, but it increased membrane damage and stimulated HO-1 expression. Moreover, betaC dose-dependently induced caspase-3 activity following UVA exposure. In contrast, CX had no effect on oxidative damage, except for HO-1 expression, which was augmented. Uptake of AX by fibroblasts was higher than that of the other two carotenoids. The photostability of the three compounds in fibroblasts was AX > CX >> betaC. The data indicate that the oxo-carotenoid AX has a superior preventive effect towards photo-oxidative changes in cell culture.

UV-induced DNA damage can lead to melanoma, the most dangerous form of skin cancer. Understanding the mechanisms employed by melanocytes to protect against UV is therefore a key issue. In melanocytes, catalase is the main enzyme responsible for degrading hydrogen peroxide and we have previously shown that that low basal levels of catalase activity are associated with the light phototype in in vitro and ex vivo models. Here we investigate the possible correlation between its activity and melanogenesis in primary cultures of human melanocytes. We show that while the total melanin concentration is directly correlated to the level of pigmentation, the more the degree of pigmentation increased, the lower the proportion of pheomelanin present. Moreover, in human melanocytes in vitro, catalase-specific mRNA, protein and enzymatic activity were all directly correlated with total cellular melanin content. We also observed that immediately after a peroxidative treatment, the increase in reactive oxygen species was inversely associated with pigmentation level. Darkly pigmented melanocytes therefore possess two protective strategies represented by melanins and catalase activity that are likely to act synergistically to counteract the deleterious effects of UV radiation. By contrast, lightly pigmented melanocytes possess lower levels of melanogenic and catalase activity and are therefore more susceptible to accumulate damage after UV exposition.

Plant immunity is activated through complex and cross-talking transduction pathways that include a mitogen-activated protein kinase phosphorylation cascade. Here, we have investigated the role in immunity of the Arabidopsis (Arabidopsis thaliana) gene subfamily that encodes the mitogen-activated protein triple kinases indicated as ARABIDOPSIS NUCLEUS-AND PHRAGMOPLAST-LOCALIZED KINASE1-RELATED PROTEIN KINASE1 (ANP1), ANP2, and ANP3. For this study, we used representative danger signals (elicitors) belonging to the classes of the damage-and pathogen-associated molecular patterns, i.e. oligogalacturonides, linear fragments derived from the plant cell wall homogalacturonan, and the peptide elf18 derived from the bacterial elongation factor thermo-unstable. Analyses of single and double as well as conditional triple mutants show that ANPs are required for elicitor-triggered defense responses and protection against the necrotrophic fungus Botrytis cinerea. Notably, ANPs are also required for both the elicitor-induced oxidative burst and the transduction of the hydrogen peroxide signal but not for the inhibition of auxin-induced gene expression, indicating that this response can be uncoupled from the activation of defense responses. Our findings point to ANPs as key transduction elements that coordinate damage-and pathogen-associated molecular patterntriggered immunity and orchestrate reactive oxygen species accumulation and signaling.

Summary Tomato fruit ripening is controlled by the hormone ethylene and by a group of transcription factors, acting upstream of ethylene. During ripening, the linear carotene lycopene accumulates at the expense of cyclic carotenoids. Fruit‐specific overexpression of LYCOPENE β‐CYCLASE (LCYb) resulted in increased β‐carotene (provitamin A) content. Unexpectedly, LCYb‐overexpressing fruits also exhibited a diverse array of ripening phenotypes, including delayed softening and extended shelf life. These phenotypes were accompanied, at the biochemical level, by an increase in abscisic acid (ABA) content, decreased ethylene production, increased density of cell wall material containing linear pectins with a low degree of methylation, and a thicker cuticle with a higher content of cutin monomers and triterpenoids. The levels of several primary metabolites and phenylpropanoid compounds were also altered in the transgenic fruits, which could be attributed to delayed fruit ripening and/or to ABA. Network correlation analysis and pharmacological experiments with the ABA biosynthesis inhibitor, abamine, indicated that altered ABA levels were a direct effect of the increased β‐carotene content and were in turn responsible for the extended shelf life phenotype. Thus, manipulation of β‐carotene levels results in an improvement not only of the nutritional value of tomato fruits, but also of their shelf life.

The H(2)O(2)-promoted oxidations of the two nonphenolic beta-O-aryl lignin model trimers 1 and 2, catalyzed by lignin peroxidase (LiP) at pH = 3.5, have been studied. The results have been compared with those obtained in the oxidation of 1 and 2 with the genuine one-electron oxidant potassium 12-tungstocobalt(III)ate. These models present a different substitution pattern of the three aromatic rings, and by one-electron oxidation, they form radical cations with the positive charge, which is localized in the dialkoxylated ring as also evidenced by a pulse radiolysis study. Both the oxidations with the enzymatic and with the chemical systems lead to the formation of products deriving from the cleavage of C-C and C-H bonds in a beta position with respect to the radical cation with the charge residing in the dialkoxylated ring (3,4-dimethoxybenzaldehyde (5) and a trimeric ketone 6 in the oxidation of 1 and a dimeric aldehyde 8 and a trimeric ketone 9 in the oxidation of 2). These products are accompanied by a dimeric aldehyde 7 in the oxidation of 1 and 4-methoxybenzaldehyde (10) in the oxidation of 2. The unexpected formation of these two products has been explained by suggesting that 1.+ and 2.+ can also undergo an intramolecular electron transfer leading to the radical cations 1a.+ and 2a.+ with the charge residing in a monoalkoxylated ring. The fast cleavage of a C-C bond beta to this ring, leading to 7 from 1.+ and to 10 from 2.+, is the driving force of the endoergonic electron transfer. A kinetic steady-state investigation of the LiP-catalyzed oxidation of the trimer 2, the dimeric model 1-(3,4-dimethoxyphenyl)-2-phenoxy-1-ethanol (4), and 3,4-dimethoxybenzyl alcohol (3) has indicated that the turnover number (k(cat)) and the affinity for the enzyme decrease significantly by increasing the size of the model compound. In contrast, the three substrates exhibited a very similar reactivity toward a chemical oxidant [Co(III)W]. This suggests a size-dependent interaction of the enzyme with the substrate which may influence the efficiency of the electron transfer.

a b s t r a c tProject: Oxidative stress (OS) is enhanced in hemodialysis (HD) patients. Lipid peroxidation and oxidative damage to glycids, proteins and nucleic acids are the main consequences of OS and are associated with increased cardiovascular risk. Vitamin E and glutathione peroxidase (GSH-Px) represent the main antioxidant systems in human cells. Selenium (Se), bound to the active sites of GSH-Pxs, plays a critical role in this antioxidant defence system. Statins are widely used and extensively investigated in the prevention of cardiovascular disease, notably in high-risk subjects. Several studies show antioxidant effects of statins not related to their lipid-lowering action. Our study aimed to compare serum Se concentration in ESRD patients on maintenance HD and in homogeneous healthy subjects and to investigate whether chronic treatment with statins may interfere with serum Se concentration in HD patients. Procedure: A total of 103 HD patients and 69 healthy subjects were enrolled; HD patients were divided into patients who were not treated with statins (group A) and patients who assumed statins since 6 months at least (group B). Serum Se was determined by atomic absorption spectrometry. Results: Serum Se was significantly lower in HD patients of group A compared with healthy subjects (81.65719.66 Vs. 96.47715.62 mcg/L, po0.0040). However, in HD patients who assumed statins serum, Se was significantly higher than in HD patients who did not (111.83718.82 vs. 81.65719.66 mcg/L, po0.0001). Conclusions: Our results suggest that in HD patients chronic treatment with statins is related to higherserum Se concentration.

The COP9 signalosome (CSN) is a highly conserved eukaryotic protein complex which regulates the cullin RING family of ubiquitin ligases and carries out a deneddylase activity that resides in subunit 5 (CSN5). Whereas CSN activity is essential for the development of higher eukaryotes, several unicellular fungi including the budding yeast Saccharomyces cerevisiae can survive without a functional CSN. Nevertheless, the budding yeast CSN is biochemically active and deletion mutants of each of its subunits exhibit deficiency in cullins deneddylation, although the biological context of this activity is still unknown in this organism. To further characterize CSN function in budding yeast, we present here a transcriptomic and proteomic analysis of a S. cerevisiae strain deleted in the CSN5/RRI1 gene (hereafter referred to as CSN5), coding for the only canonical subunit of the complex. We show that Csn5 is involved in modulation of the genes controlling amino acid and lipid metabolism and especially ergosterol biosynthesis. These alterations in gene expression correlate with the lower ergosterol levels and increased intracellular zinc content which we observed in csn5 null mutant cells. We show that some of these regulatory effects of Csn5, in particular the control of isoprenoid biosynthesis, are conserved through evolution, since similar transcriptomic and/or proteomic effects of csn5 mutation were previously observed in other eukaryotic organisms such as Aspergillus nidulans, Arabidopsis thaliana and Drosophila melanogaster. Our results suggest that the diverged budding yeast CSN is more conserved than was previously thought.