Low Levels Of Oxidative Stress Research Articles

Distinctive adaptive response to repeated exposure to hydrogen peroxide associated with upregulation of DNA repair genes and cell cycle arrest

Many environmental and physiological stresses are chronic. Thus, cells are constantly exposed to diverse types of genotoxic insults that challenge genome stability, including those that induce oxidative DNA damage. However, most in vitro studies that model cellular response to oxidative stressors employ short exposures and/or acute stress models. In this study, we tested the hypothesis that chronic and repeated exposure to a micromolar concentration of hydrogen peroxide (H2O2) could activate DNA damage responses, resulting in cellular adaptations. For this purpose, we developed an in vitro model in which we incubated mouse myoblast cells with a steady concentration of ~50μM H2O2 for one hour daily for seven days, followed by a final challenge of a 10 or 20X higher dose of H2O2 (0.5 or 1mM). We report that intermittent long-term exposure to this oxidative stimulus nearly eliminated cell toxicity and significantly decreased genotoxicity (in particular, a >5-fold decreased in double-strand breaks) resulting from subsequent acute exposure to oxidative stress. This protection was associated with cell cycle arrest in G2/M and induction of expression of nine DNA repair genes. Together, this evidence supports an adaptive response to chronic, low-level oxidative stress that results in genomic protection and up-regulated maintenance of cellular homeostasis.

Abstract 1673: Optical metabolic imaging of response to radiation in radiation-sensitive and resistant lung cancer cells

Abstract Tumor resistance to radiation therapy is a significant obstacle that patients and doctors face while treating tumors. Meaningful changes in therapy are contingent upon the ability to identify an unfavorable response very early (first week) in the course of treatment. Optical imaging can perform noninvasive, frequent and quantitative measurements of tumor biology at the point of care. The goal of this study was to identify optically measurable metabolic endpoints in a matched model of radiation resistance before and after treatment. A human lung cancer cell line was induced to develop radiation resistance through repeated exposure to a clinically relevant dose of X-ray radiation (2 Gy). We used a fluorescent glucose analog called 2-NBDG to quantify glucose uptake. We measured the endogenous fluorescence of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD), metabolic coenzymes found primarily in the cytoplasm and mitochondria, respectively. We determined the redox ratio [FAD/(NADH + FAD)] in both cell lines. We evaluated the behavior of the cellular antioxidant system by comparing the levels of reactive oxygen species (ROS) and ROS scavengers, such as glutathione (GSH) for each cell group. Finally, we analyzed the oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) using a metabolic flux analyzer. Radiation-resistant A549 lung cancer cells were induced by exposure to 25 fractions of X-ray radiation (2.2 Gy/fraction). Clonogenic assays were performed to confirm radiation resistance. All fluorescence images were obtained using a multiphoton microscope. 2-NBDG, ROS, GSH, NADH, and FAD fluorescence were excited at 960, 930, 780, 755 and 860 nanometers, respectively. The cells were exposed to 2 Gy 60 minutes prior to the Seahorse assay. All experiments were performed in both the parental A549 cell line (A549C) and the radiation-resistant A549 cell line (A549R) at baseline (prior to radiation) and after radiation. At baseline, the A549R cells revealed a significantly lower level of oxidative stress and a higher level of GSH. Interestingly, glucose uptake, quantified using 2-NBDG fluorescence, was significantly lower in the A549R cells compared to the A549C cells at baseline. The redox ratio was significantly higher in the A549R cells prior to radiation, indicating a preference for mitochondrial respiration. However, after radiation, the OCR of the A549R cells was significantly lower than the parental cell line, indicating a lower use of mitochondrial respiration. There were no significant differences in ECAR levels between both cell lines after radiation. Our results indicate that the radiation-resistant A549 lung cancer cells present very distinguishable metabolic properties at baseline and after exposure to radiation relative to the parental cell line that could potentially be exploited in vivo. Citation Format: Kinan Alhallak, Ruud P.M. Dings, Narasimhan Rajaram. Optical metabolic imaging of response to radiation in radiation-sensitive and resistant lung cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1673.

The photoprotective effects of 2-benzoyl-3-phenylquinoxaline 1,4-dioxide against UVB-induced damage in HaCaT cells.

With the increasing levels of atmospheric ozone depletion, there has been much concern about the causal effects of high levels of ultraviolet radiation reaching the Earth's surface on skin cancer. This has led to growing interest in identifying new active ingredients for use in commercial sunscreens. In our study, the chemical compound 2-benzoyl-3-phenylquinoxaline 1,4-dioxide (BPQ) prepared by the Beirut reaction was tested for its ability to protect a human keratinocyte cell line (HaCaT) against ultraviolet B radiation (280-315nm). We show that BPQ exhibited strong absorbance in the UVB range, with an overall absorption spectrum very similar to that of Padimate-O, a well-known active ingredient used in commercial sunscreens. HaCaT cells, which were irradiated with UVB in the presence of multiple doses of BPQ, exhibited, in a dose-dependent fashion, a significantly higher viability and lower oxidative stress levels than cells irradiated in the absence of drug. Our results show that BPQ is a potential photoprotective drug that holds great promise for use as an active ingredient in commercial sunscreens.

The redox protein p66(shc) mediates cochlear vascular dysfunction and transient noise-induced hearing loss.

p66shc, a member of the ShcA protein family, is essential for cellular response to oxidative stress, and elicits the formation of mitochondrial Reactive Oxygen Species (ROS), thus promoting vasomotor dysfunction and inflammation. Accordingly, mice lacking the p66 isoform display increased resistance to oxidative tissue damage and to cardiovascular disorders. Oxidative stress also contributes to noise-induced hearing loss (NIHL); we found that p66shc expression and serine phosphorylation were induced following noise exposure in the rat cochlea, together with markers of oxidative stress, inflammation and ischemia as indicated by the levels of the hypoxic inducible factor (HIF) and the vascular endothelial growth factor (VEGF) in the highly vascularised cochlear lateral region and spiral ganglion. Importantly, p66shc knock-out (p66 KO) 126 SvEv adult mice were less vulnerable to acoustic trauma with respect to wild type controls, as shown by preserved auditory function and by remarkably lower levels of oxidative stress and ischemia markers. Of note, decline of auditory function observed in 12 month old WT controls was markedly attenuated in p66KO mice consistent with delayed inner ear senescence. Collectively, we have identified a pivotal role for p66shc -induced vascular dysfunction in a common pathogenic cascade shared by noise-induced and age-related hearing loss.

Regucalcin counteracts tert-butyl hydroperoxide and cadmium-induced oxidative stress in rat testis.

Regucalcin (RGN) is a calcium (Ca2+ )-binding protein with multiple physiological roles and has also been linked to the suppression of oxidative stress. It is widely known that oxidative stress adversely affects spermatogenesis, disrupting the development of germ cells, and interfering with sperm function. The present study aims to analyze the role of RGN modulating testicular oxidative stress. To address this issue, seminiferous tubules (SeT) from transgenic rats overexpressing RGN (Tg-RGN) and wild-type (WT) were cultured ex vivo for 24 h in the presence/absence of pro-oxidant stimuli, tert-butyl hydroperoxide (TBHP, 250 and 500 μM) and cadmium chloride (Cd, 10 and 20 μM). Noteworthy, SeT from Tg-RGN animals displayed a significantly higher antioxidant capacity and diminished levels of thiobarbituric acid reactive substances relatively to their WT counterparts, both in control and experimental conditions. Regarding the antioxidant defense systems, a significant increase in the activity of glutathione-S-transferase was found in the SeT of Tg-RGN whereas no differences were observed in superoxide dismutase activity throughout experimental conditions. The activity of apoptosis executioner caspase-3 was significantly increased in the SeT of WT rats treated with 250 μM of TBHP or 10 μM of Cd, an effect not seen in Tg-RGN animals. These results showed that the SeT of Tg-RGN animals displayed lower levels of oxidative stress and increased antioxidant defenses, exhibiting protection against oxidative damage and apoptosis. Moreover, the present findings support the antioxidant role of RGN in spermatogenesis, which may be an important issue of further research in the context of male infertility. Copyright © 2016 John Wiley & Sons, Ltd.

Temperature and oxidative stress as triggers for virulence gene expression in pathogenic Leptospira spp.

Leptospirosis is a zooanthroponosis aetiologically caused by pathogenic bacteria belonging to the genus, Leptospira. Environmental signals such as increases in temperatures or oxidative stress can trigger response regulatory modes of virulence genes during infection. This study sought to determine the effect of temperature and oxidative stress on virulence associated genes in highly-passaged L. borgpeterseneii Jules and L. interrogans Portlandvere. Bacteria were grown in EMJH at 30°C, 37°C or at 30°C before being transferred to 37°C. A total of 14 virulence-associated genes (fliY, invA, lenA, ligB, lipL32, lipL36, lipL41, lipL45, loa22, lsa21, mce, ompL1, sph2 and tlyC) were assessed using endpoint PCR. Transcriptional analyses of lenA, lipL32, lipL41, loa22, sph2 were assessed by quantitative real-time RT-PCR at the temperature conditions. To assess oxidative stress, bacteria were exposed to H2O2 for 30 and 60 min with or without the temperature stress. All genes except ligB (for Portlandvere) and ligB and mce (for Jules) were detectable in the strains. Quantitatively, temperature stress resulted in significant changes in gene expression within species or between species. Temperature changes were more influential in gene expression for Jules, particularly at 30oC and upshift conditions; at 37oC, expression levels were higher for Portlandvere. However, compared to Jules, where temperature was influential in two of five genes, temperature was an essential element in four of five genes in Portlandvere exposed to oxidative stress. At both low and high oxidative stress levels, the interplay between genetic predisposition (larger genome size) and temperature was biased towards Portlandvere particularly at 30oC and upshift conditions. While it is clear that expression of many virulence genes in highly passaged strains of Leptospira are attenuated or lost, genetic predisposition, changes in growth temperature and/or oxidative intensity and/or duration were factors which acted in isolation or together with other regulatory cues to contribute to the variable gene expression observed in this study. Overall, differential gene expression in serovar Portlandvere was more responsive to temperature and oxidative stress.

Plasma kallikrein-bradykinin pathway promotes circulatory nitric oxide metabolite availability during hypoxia

Nitric oxide (NO) is an indispensible signalling molecule under hypoxic environment for both ethnic high altitude natives as well as lowland residents at high altitude. Several studies have reported higher levels of NO and bioactive NO products for both high altitude natives as well as healthy high altitude sojourners. But the metabolic pathways regulating the formation of NO and associated metabolites during hypoxia still remain elusive. In the present study, we profiled plasma proteomes of Ladakhi natives (3520 m) and lowland residents (post 1, 4 and 7 days stay) at the same altitude. This has resulted in the identification of 208 hypoxia responsive proteins (p < 0.05) and kininogen-plasma kallikrein-bradykinin as a major pathway regulating eNOS activity during hypoxia. In corroboration, we have also observed significant higher levels of plasma biomarkers for NO production (l-citrulline, nitrite, nitrate) for Ladakhi natives as compared to both lowland individuals healthy high altitude sojourners indicating higher NO availability. Since hypoxia-induced free radicals reduce NO availability, we also measured plasma levels of 8-isoprostanes, protein carbonyls and protein oxidation products in both Ladakhi natives and high altitude sojourners. Interestingly Ladakhi natives had significant lower levels of oxidative stress in comparison to high altitude sojourners but higher than lowland controls. These results suggest that plasma kallikrein-bradykinin-eNOS pathway along with moderate oxidative stress contributes to high altitude adaptation of Ladakhi natives.

Regulation of exercise blood flow: Role of free radicals

During exercise, oxygen and nutrient rich blood must be delivered to the active skeletal muscle, heart, skin, and brain through the complex and highly regulated integration of central and peripheral hemodynamic factors. Indeed, even minor alterations in blood flow to these organs have profound consequences on exercise capacity by modifying the development of fatigue. Therefore, the fine-tuning of blood flow is critical for optimal physical performance. At the level of the peripheral circulation, blood flow is regulated by a balance between the mechanisms responsible for vasodilation and vasoconstriction. Once thought of as toxic by-products of in vivo chemistry, free radicals are now recognized as important signaling molecules that exert potent vasoactive responses that are dependent upon the underlying balance between oxidation–reduction reactions or redox balance. Under normal healthy conditions with low levels of oxidative stress, free radicals promote vasodilation, which is attenuated with exogenous antioxidant administration. Conversely, with advancing age and disease where background oxidative stress is elevated, an exercise-induced increase in free radicals can further shift the redox balance to a pro-oxidant state, impairing vasodilation and attenuating blood flow. Under these conditions, exogenous antioxidants improve vasodilatory capacity and augment blood flow by restoring an “optimal” redox balance. Interestingly, while the active skeletal muscle, heart, skin, and brain all have unique functions during exercise, the mechanisms by which free radicals contribute to the regulation of blood flow is remarkably preserved across each of these varied target organs.

Abstracts from The 12th Symposium of the International Neurotrauma Society February 1-4, 2016 Cape Town, South Africa.

Abstracts from The 12th Symposium of the International Neurotrauma Society February 1-4, 2016 Cape Town, South Africa.

Role of Beclin-1-Mediated Autophagy in the Survival of Pediatric Leukemia Cells

Background/Aims: Acute and chronic leukemia are severe malignant cancers worldwide, and can occur in pediatric patients. Since bone marrow cell transplantation is seriously limited by the availability of the immune-paired donor sources, the therapy for pediatric leukemia (PL) remains challenging. Autophagy is essential for the regulation of cell survival in the harsh environment. However, the role of autophagy in the survival of PL cells under the oxidative stress, e.g. chemotherapy, remain ill-defined. In the current study, we addressed these questions. Methods: We analyzed the effects of oxidative stress on the cell viability of PL cells in vitro, using a CCK-8 assay. We analyzed the effects of oxidative stress on the apoptosis and autophagy of PL cells. We analyzed the levels of Beclin-1 and microRNA-93 (miR-93) in PL cells. Prediction of binding between miR-93 and 3'-UTR of Beclin-1 mRNA was performed by a bioinformatics algorithm and confirmed by a dual luciferase reporter assay. The relationship between levels of miR-93 and patients' survival was analyzed in PL patients. Results: We found that oxidative stress dose-dependently increased autophagy in PL cells. While low-level oxidative stress did not increase apoptosis, high-level oxidative stress increased apoptosis, seemingly from failure of autophagy-mediated cell survival. High-level oxidative stress appeared to suppress the protein levels of an autophagy protein Beclin-1 in PL cells, possibly through induction of miR-93, which inhibited the translation of Beclin-1 mRNA via 3'-UTR binding. Conclusion: Beclin-1-mediated autophagy plays a key role in the survival of PL cells against oxidative stress. Induction of miR-93 may increase the sensitivity of PL cells to oxidative stress during chemotherapy to improve therapeutic outcome.

P53 coordinates with Δ133p53 isoform to promote cell survival under low-level oxidative stress

p53 coordinates with Δ133p53 isoform to promote cell survival under low-level oxidative stress

Heat tolerance of highbush blueberry is related to the antioxidative enzymes and oxidative protein-repairing enzymes

Improving the understanding of the heat-tolerance mechanisms in blueberries (Vaccinium spp.) and screening high heat-tolerant germplasms are critical for the development of this fruit. In the present study, the heat tolerances of the ‘Jersey’ and ‘Diana’ cultivars were compared, which represent the northern and southern highbush blueberry cultivars, respectively. The results showed that exposure to high temperature significantly increased the level of oxidative damage in both highbush blueberries. However, oxidative stress induced by high temperature is significantly lower in ‘Jersey’ than that observed in ‘Diana’. The lower level of oxidative stress in ‘Jersey’ was related to the significantly higher transcript levels of the antioxidative genes and oxidative protein-repairing genes, which may have resulted in the relatively higher semi-lethal high temperature of ‘Jersey’ (48.30°C) than that of the heat-sensitive ‘Diana’(47.32°C). The heat susceptibility of ‘Diana’ was also confirmed by the 3-year field trial, the total death rates of ‘Jersey’ and ‘Diana’ were 7.78 and 12.22%, respectively. Therefore, it can be suggested that some northern highbush blueberry cultivars such as ‘Jersey’ are more heat tolerant than some southern highbush cultivars, and thus suitable for cultivation in lower latitude areas with hot summers.

Mesenchymal Stromal Cells Disrupt mTOR-Signaling and Aerobic Glycolysis During T-Cell Activation.

Mesenchymal stromal cells (MSCs) possess numerous regenerative and immune modulating functions. Transplantation across histocompatibility barriers is feasible due to their hypo-immunogenicity. MSCs have emerged as promising tools for treating graft-versus-host disease following allogeneic stem cell transplantation. It is well established that their clinical efficacy is substantially attributed to fine-tuning of T-cell responses. At the same time, increasing evidence suggests that metabolic processes control T-cell function and fate. Here, we investigated the MSCs' impact on the metabolic framework of activated T-cells. In fact, MSCs led to mitigated mTOR signaling. This phenomenon was accompanied by a weaker glycolytic response (including glucose uptake, glycolytic rate, and upregulation of glycolytic machinery) toward T-cell activating stimuli. Notably, MSCs express indoleamine-2,3-dioxygenase (IDO), which mediates T-cell suppressive tryptophan catabolism. Our observations suggest that IDO-induced tryptophan depletion interferes with a tryptophan-sufficiency signal that promotes cellular mTOR activation. Despite an immediate suppression of T-cell responses, MSCs foster a metabolically quiescent T-cell phenotype characterized by reduced mTOR signaling and glycolysis, increased autophagy, and lower oxidative stress levels. In fact, those features have previously been shown to promote generation of long-lived memory cells and it remains to be elucidated how MSC-induced metabolic effects shape in vivo T-cell immunity.

Lung Disease, Oxidative Stress, and Oxygen Requirements in Preterm Infants.

The role of oxidative stress remains unclear in the multifactorial pathophysiologic mechanism of lung disease in preterm infants. The aim of this study was to examine the associations among chronic lung disease (CLD), oxidative stress, and oxygen requirements in preterm infants. Prospective, longitudinal, and correlational design. Preterm infants born at <32 weeks' gestation (N = 31), median gestation of 29.0 weeks (range 24.9-31.7). The diagnosis of CLD was obtained from the medical record. Oxidative stress was measured using 8-hydroxydeoxyguanosine (8-OHdG) in the cord blood at birth and urine on Days 1 and 7. Oxygen requirements were measured using fraction of inspired oxygen (FIO2) recorded in the first hour after birth/admission and the average FIO2 during the first 12 hr and 7 days after birth. Descriptive statistics are presented. Comparison analyses were performed using Kruskal-Wallis and Fisher's exact tests. Infants with CLD (n = 12) had lower gestational age (p = .04) and weight (p = .04) at birth, more days on the ventilator (p = .004), and longer neonatal intensive care unit stay (p = .04) compared to infants without CLD (n = 19). CLD was associated with lower oxidative stress levels (p = .03) and higher oxygen requirements during the first 12 hr (p = .025) and on Day 7 (p = .001). Lower oxidative stress levels on Day 7 were associated with higher oxygen requirements in the first 12 hr (p = .01) and on Day 7 (p = .03). Our results linking CLD and higher oxygen requirements with low oxidative stress contradict previous reports. Findings identify a gap in knowledge for postresuscitation oxygen therapy in preterm infants and expose the role of oxidative stress from inflammation and intermittent hypoxia in the etiology of CLD.

Red-fleshed sweet orange juice improves the risk factors for metabolic syndrome

Orange juice consumption can promote lower levels of oxidative stress and inflammation due to the antioxidant activity of citrus flavonoids and carotenoids. In addition, red-fleshed sweet orange juice (red orange juice) also contains lycopene. This study investigated the effects of red orange juice consumption on risk factors for metabolic syndrome. Volunteers consumed red orange juice daily for 8 weeks, with clinical and biochemical assessments performed at baseline and on the final day. There was no change in the abdominal obesity, but low-density lipoprotein cholesterol, C-reactive protein decreased, while there was an increase of the antioxidant activity in serum after red orange juice consumption. Insulin resistance and systolic blood pressure were reduced in normal-weight volunteers, while diastolic blood pressure decreased in overweight volunteers after intervention. Red orange juice showed anti-inflammatory, antioxidant, and lipid-lowering properties that may prevent the development of metabolic syndrome.

The impact of oxidative stress on chaperone-mediated human sperm-egg interaction.

How does oxidative stress impact upon human sperm-egg interaction and in particular the formation of zona pellucida-receptor complexes on the sperm surface? Oxidative stress during human sperm capacitation resulted in the chemical alkylation of the molecular chaperone heat shock protein A2 (HSPA2), a concomitant reduction in surface expression of the zona pellucida-receptor arylsulphatase A (ARSA) and a severe loss of zona pellucida binding ability. An inability to bind to the zona pellucida is commonly encountered in the defective spermatozoa generated by male infertility patients; however, the underlying mechanisms remain unresolved. Recent studies have revealed that zona pellucida binding is mediated by molecular chaperones, particularly HSPA2, that facilitate the formation of multimeric zona pellucida-receptor complexes on the surface of mammalian spermatozoa during capacitation. Spermatozoa were collected from healthy normozoospermic donors (n = 15). Low levels of oxidative stress were induced in populations of non-capacitated spermatozoa by a 1 h treatment with 4-hydroxynonenal (4HNE) or hydrogen peroxide (H2O2) and then these insults were removed and cells were capacitated for 3 h. Motility, membrane fluidity, protein tyrosine phosphorylation and lipid raft distribution were evaluated after sperm capacitation to determine the impact of oxidative stress on this process. The surface expression of ARSA and sperm adhesion molecule 1 (SPAM1) was observed using fluorescence microscopy, and the ability of treated cells to interact with homologous human zonae pellucidae was assessed through gamete co-incubation. Proximity ligation was used to evaluate the state of the HSPA2-laden zona pellucida-receptor complex and an immunoprecipitation approach was taken to establish the chemical alkylation of HSPA2 by the cytotoxic lipid aldehyde 4HNE. The validity of these findings was then tested through treatment of oxidatively stressed cells with the nucleophile penicillamine in order to scavenge lipid aldehydes and limit their ability to interact with HSPA2. All experiments were performed on samples pooled from two or more donors per replicate, with a minimum of three replicates. The oxidative treatments employed in this study did not influence sperm motility or capacitation-associated changes in membrane fluidity, tyrosine phosphorylation and lipid raft redistribution. However, they did significantly impair zona pellucida binding compared with the capacitated control (P < 0.01). The reduction in zona pellucida binding was associated with the impaired surface expression (P < 0.02) of a zona pellucida-receptor complex comprising HSPA2, SPAM1 and ARSA. Proximity ligation and immunoprecipitation assays demonstrated that impaired zona pellucida binding was, in turn, associated with the chemical alkylation of HSPA2 with 4HNE and the concomitant disruption of this zona pellucida-receptor complex. The use of penicillamine enabled a partial recovery of ARSA surface expression and zona pellucida adherence in H2O2-treated cells. These data suggest that the ability of low levels of oxidative stress to disrupt sperm function is mediated by the production of lipid aldehydes as a consequence of lipid peroxidation and their adduction to the molecular chaperone HSPA2 that is responsible for co-ordinating the assembly of functional zona pellucida-receptor complexes during sperm capacitation. While these results extend only to one particular zona pellucida-receptor complex, we postulate that oxidative stress may more broadly impact upon sperm surface architecture. In this light, further study is required to assess the impact of oxidative stress on additional HSPA2-laden protein complexes. These findings link low levels of oxidative stress to a severe loss of sperm function. In doing so, this work suggests a potential cause of male infertility pertaining to a loss of zona pellucida recognition ability and will contribute to the more accurate diagnosis and treatment of such conditions.

The MAPKKKs Ste11 and Bck1 jointly transduce the high oxidative stress signal through the cell wall integrity MAP kinase pathway.

Oxidative stress stimulates the Rho1 GTPase, which in turn induces the cell wall integrity (CWI) MAP kinase cascade. CWI activation promotes stress-responsive gene expression through activation of transcription factors (Rlm1, SBF) and nuclear release and subsequent destruction of the repressor cyclin C. This study reports that, in response to high hydrogen peroxide exposure, or in the presence of constitutively active Rho1, cyclin C still translocates to the cytoplasm and is degraded in cells lacking Bck1, the MAPKKK of the CWI pathway. However, in mutants defective for both Bck1 and Ste11, the MAPKKK from the high osmolarity, pseudohyphal and mating MAPK pathways, cyclin C nuclear to cytoplasmic relocalization and destruction is prevented. Further analysis revealed that cyclin C goes from a diffuse nuclear signal to a terminal nucleolar localization in this double mutant. Live cell imaging confirmed that cyclin C transiently passes through the nucleolus prior to cytoplasmic entry in wild-type cells. Taken together with previous studies, these results indicate that under low levels of oxidative stress, Bck1 activation is sufficient to induce cyclin C translocation and degradation. However, higher stress conditions also stimulate Ste11, which reinforces the stress signal to cyclin C and other transcription factors. This model would provide a mechanism by which different stress levels can be sensed and interpreted by the cell.

Oxidative stress is related to both melanin‐ and carotenoid‐based ornaments in the common yellowthroat

Summary Male ornaments are hypothesized to signal the ability of males to produce an effective immune response without extensive oxidative stress and damage to DNA. We examined this hypothesis in male common yellowthroats (Geothlypis trichas), which have two ornaments, a black (eumelanin‐based) facial mask and a yellow (carotenoid‐based) bib. In our study population, only the black mask is sexually selected. As predicted by the oxidative stress hypothesis, males with larger black masks were more resistant to oxidative stress, as measured by an in vitro assay of the resistance of erythrocytes to haemolysis by free radicals. Furthermore, males with larger masks also tended to have lower levels of glutathione, which was predicted because glutathione inhibits eumelanin production. In contrast, mask size was not related to absolute levels of oxidative stress measured in the plasma. Although the yellow bib is not under sexual selection in our population, males with larger bibs and feathers with greater carotenoid chroma had lower levels of oxidative stress. The oxidative stress hypothesis was first proposed for carotenoid‐based ornaments. However, our results suggest that, even in the same individuals, carotenoid and eumelanin‐based plumage ornaments may both signal the ability of males to resist or manage oxidative stress.

Effects of synbiotic on anthropometry, lipid profile and oxidative stress in obese children.

Recent studies have suggested some beneficial effects of probiotics and/or prebiotics on obesity in adults; such experience is limited in children and adolescents. This study was an open-label, randomised, controlled study including children with primary obesity. The first group was treated with a standard method with a reduced calorie intake and increased physical activity. The second group received add-on daily synbiotic supplementation during one month. The aim of this study was to evaluate potential effects of a synbiotic on anthropometric measurements, lipid profile and oxidative stress parameters. One month of supplementation of the synbiotic resulted in a significant reduction of weight (P<0.001) and body mass index (P<0.01). Changes (% reduction comparing to baseline) in anthropometric measurements, were significantly higher in the children receiving the additional synbiotic supplement (P<0.05). The percentage of children with weight loss was higher in the synbiotic group, but not statistically significant (71.4 vs 64.2%, P>0.05). At the 30(th) day of synbiotic intervention, serum total cholesterol, low density lipoprotein cholesterol and total oxidative stress levels significantly declined (P<0.05). Changes in serum lipid levels were significantly higher in the synbiotic group (P<0.05). Changes in serum total oxidative stress levels before and after the intervention period, were significant in synbiotic group (P<0.01). In our study, changes in weight, body mass index, and triceps skinfold thickness were higher in the group receiving the one month synbiotic supplement thin in the standard method group. The supplement tested also had a beneficial effect on lipid profile and total oxidative stress. To the best of our knowledge, this is the first study showing the effects of synbiotics on oxidative stress in obese patients with an additional effect on weight loss regarding to previous studies.

Sestrin2, a Regulator of Thermogenesis and Mitohormesis in Brown Adipose Tissue.

Sestrin2 is a stress-inducible protein that functions as an antioxidant and inhibitor of mTOR complex 1. In a recent study, we found that Sestrin2 overexpression in brown adipocytes interfered with normal metabolism by reducing mitochondrial respiration through the suppression of uncoupling protein 1 (UCP1) expression. The metabolic effects of Sestrin2 in brown adipocytes were dependent on its antioxidant activity, and chemical antioxidants produced similar effects in inhibiting UCP1-dependent thermogenesis. These observations suggest that low levels of reactive oxygen species (ROS) in brown adipocytes can actually be beneficial and necessary for proper metabolic homeostasis. In addition, considering that Sestrins are ROS inducible and perform ROS detoxifying as well as other metabolism-controlling functions, they are potential regulators of mitohormesis. This is a concept in which overall beneficial effects result from low-level oxidative stress stimuli, such as the ones induced by caloric restriction or physical exercise. In this perspective, we incorporate our recent insight obtained from the Sestrin2 study toward a better understanding of the relationship between ROS, Sestrin2, and mitochondrial metabolism in the context of brown adipocyte physiology.