Fibroblasts derived from Gpx1 knockout mice display senescent-like features and are susceptible to H2O2-mediated cell death

Antioxidant Systems as Modulators of Ferroptosis: Focus on Transcription Factors

Ferroptosis is a type of programmed cell death that differs from apoptosis, autophagy, and necrosis and is related to several physio-pathological processes, including tumorigenesis, neurodegeneration, senescence, blood diseases, kidney disorders, and ischemia-reperfusion injuries. Ferroptosis is linked to iron accumulation, eliciting dysfunction of antioxidant systems, which favor the production of lipid peroxides, cell membrane damage, and ultimately, cell death. Thus, signaling pathways evoking ferroptosis are strongly associated with those protecting cells against iron excess and/or lipid-derived ROS. Here, we discuss the interaction between the metabolic pathways of ferroptosis and antioxidant systems, with a particular focus on transcription factors implicated in the regulation of ferroptosis, either as triggers of lipid peroxidation or as ferroptosis antioxidant defense pathways.

Oxidative stress associated with spatial memory impairment and social olfactory deterioration in female mice reveals premature aging aroused by perinatal protein malnutrition

Early-life adversity, like perinatal protein malnutrition, increases the vulnerability to develop long-term alterations in brain structures and function. This study aimed to determine whether perinatal protein malnutrition predisposes to premature aging in a murine model and to assess the cellular and molecular mechanisms involved. To this end, mouse dams were fed either with a normal (NP, casein 20%) or a low-protein diet (LP, casein 8%) during gestation and lactation. Female offspring were evaluated at 2, 7 and 12 months of age. Positron emission tomography analysis showed alterations in the hippocampal CA3 region and the accessory olfactory bulb of LP mice during aging. Protein malnutrition impaired spatial memory, coinciding with higher levels of reactive oxygen species in the hippocampus and sirt7 upregulation. Protein malnutrition also led to higher senescence-associated β-galactosidase activity and p21 expression. LP-12-month-old mice showed a higher number of newborn neurons that did not complete the maturation process. The social-odor discrimination in LP mice was impaired along life. In the olfactory bulb of LP mice, the senescence marker p21 was upregulated, coinciding with a downregulation of Sirt2 and Sirt7. Also, LP-12-month-old mice showed a downregulation of catalase and glutathione peroxidase, and LP-2-month-old mice showed a higher number of newborn neurons in the subventricular zone, which then returned to normal values. Our results show that perinatal protein malnutrition causes long-term impairment in cognitive and olfactory skills through an accelerated senescence phenotype accompanied by an increase in oxidative stress and altered sirtuin expression in the hippocampus and olfactory bulb.

Selenium Deficiency Induces Apoptosis and Necroptosis Through ROS/MAPK Signal in Human Uterine Smooth Muscle Cells

Selenium (Se) is one of the essential trace elements; its deficiency induces ROS production and cell death in cardiomyocytes, skeletal muscle cells, and vascular smooth muscle cells, but it is still not clear the impact of Se deficiency on human uterine smooth muscle cells (HUSMCs). To investigate the effect of low Se on the mRNA expression of selenoproteins, the mRNA and protein expression of apoptosis and necroptosis of HUSMCs and their mechanism, Se deficient HUSMCs mode was established through culturing with 1% FBS containing 0 ng/mL, 0.7 ng/mL, and 7 ng/mL Se, and 10% FBS was as the control group. Then, the apoptosis and necroptosis rates, intracellular ROS content and the expression levels of selenoproteins, apoptosis, necroptosis, MAPK pathway-related genes were examined under different Se concentrations. The results showed that Se deficiency led to the augment of cell apoptosis and necroptosis in HUSMCs (p < 0.05), downregulated (p < 0.05) 19 selenoproteins (GPX1, GPX2, GPX3, GPX4, GPX6, Dio3, Txnrd2, Txnrd3, SEPHS2, SEL15, SELH, SELI, SELM, SELN, SELO, SELS, SELT, SELV, and SELW), while Dio2, SELK, Txnrd1, and MSRB1 were not affected by Se deficiency (p ≥ 0.05). In addition, Se deficiency led to increased intracellular ROS content, p-P38 and p-JNK gene expression levels (p < 0.05), the mitochondrial apoptosis pathway Bax, Casp9 and Cle-Casp3 protein expression levels (p < 0.05), and decreased Bcl2 protein expression level (p < 0.05), simultaneously, increased necroptosis marker genes RIP1, RIP3, and MLKL protein expression levels (p < 0.05) with a dose-dependent pattern. The above results indicate that Se deficiency induces HUSMCs apoptosis and necroptosis through the ROS/MAPK pathway and is closely related to selenoproteins.

MicroRNAs, Long Non-Coding RNAs, and Circular RNAs in the Redox Control of Cell Senescence

Cell senescence is critical in diverse aspects of organism life. It is involved in tissue development and homeostasis, as well as in tumor suppression. Consequently, it is tightly integrated with basic physiological processes during life. On the other hand, senescence is gradually being considered as a major contributor of organismal aging and age-related diseases. Increased oxidative stress is one of the main risk factors for cellular damages, and thus a driver of senescence. In fact, there is an intimate link between cell senescence and response to different types of cellular stress. Oxidative stress occurs when the production of reactive oxygen species/reactive nitrogen species (ROS/RNS) is not adequately detoxified by the antioxidant defense systems. Non-coding RNAs are endogenous transcripts that govern gene regulatory networks, thus impacting both physiological and pathological events. Among these molecules, microRNAs, long non-coding RNAs, and more recently circular RNAs are considered crucial mediators of almost all cellular processes, including those implicated in oxidative stress responses. Here, we will describe recent data on the link between ROS/RNS-induced senescence and the current knowledge on the role of non-coding RNAs in the senescence program.

Identification of Selenoprotein H Isoforms and Impact of Selenoprotein H Overexpression on Protein But Not mRNA Levels of 2 Other Selenoproteins in 293T Cells

BACKGROUND

Selenoprotein H (SELONOH), a member of the thioredoxin-like family proteins, is prioritized to degradation in selenium (Se) insufficiency. Recent studies implicate protective roles of SELENOH in oxidative stress, cellular senescence, and intestinal tumorigenesis. Although the nonselenoprotein H0YE28 is suggested as shortened SELENOH according to genomic and proteomic data repositories, this variant has not been verified biochemically.

OBJECTIVES

We sought to identify SELENOH isoforms and explore the impact of Se flux on selenoprotein expression in SELENOH-overexpressing cells.

METHODS

A vector expressing a FLAG (the DYKDDDDK sequence) tag on the N-terminal end of wild-type SELENOH was constructed and transiently transfected into 293T cells incubated with graded concentrations of Na2SeO3 (0-200 nM). Cells were subjected to immunoprecipitation, LC-MS/MS protein analysis, immunoblotting, qRT-PCR, and senescence assays. Data were analyzed by 1-way or 2-way ANOVA.

RESULTS

Results of anti-FLAG immunoblotting showed that FLAG-SELENOH transfection increased (3.7-fold; P < 0.05) protein levels of the long, but not the short, SELENOH variants in the presence of Na2SeO3 (100 nM). By contrast, SELENOH mRNA levels were increased by 53-fold upon FLAG-SELENOH transfection but were comparable with or without supplemental Se (100 nM). LC-MS/MS analyses of anti-FLAG immunoprecipitates designated both anti-FLAG bands as SELENOH and co-identified three 60S ribosomal and 9 other proteins. Overexpression of FLAG-SELENOH 1) reduced glutathione peroxidase 1 and thioredoxin reductase 1 expression at the protein rather than the mRNA level in the absence but not presence of supplemental Se (100 nM; P < 0.05); 2) increased mRNA levels of 3 heat shock proteins (HSP27, HSP70-1A, and HSP70-1B; P < 0.05); and 3) reduced senescence induced by H2O2 (20 μM, 4 hours; P < 0.05).

CONCLUSIONS

These cellular studies demonstrate a Se-independent, shortened SELENOH variant and suggest competition of overexpressed FLAG-SELENOH with 2 other selenoproteins for the expression at the protein but not the mRNA level in Se insufficiency.

Targeting c-Src Reverses Accelerated GPX-1 mRNA Decay in Chronic Obstructive Pulmonary Disease Airway Epithelial Cells

Enhanced expression of the cellular antioxidant glutathione peroxidase (GPX)-1 prevents cigarette smoke-induced lung inflammation and tissue destruction. Subjects with chronic obstructive pulmonary disease (COPD), however, have decreased airway GPX-1 levels, rendering them more susceptible to disease onset and progression. The mechanisms that downregulate GPX-1 in the airway epithelium in COPD remain unknown. To ascertain these factors, analyses were conducted using human airway epithelial cells isolated from healthy subjects and human subjects with COPD and lung tissue from control and cigarette smoke-exposed A/J mice. Tyrosine phosphorylation modifies GPX-1 expression and cigarette smoke activates the tyrosine kinase c-Src. Therefore, studies were conducted to evaluate the role of c-Src on GPX-1 levels in COPD. These studies identified accelerated GPX-1 mRNA decay in COPD airway epithelial cells. Targeting the tyrosine kinase c-Src with siRNA inhibited GPX-1 mRNA degradation and restored GPX-1 protein levels in human airway epithelial cells. In contrast, silencing the tyrosine kinase c-Abl, or the transcriptional activator Nrf2, had no effect on GPX-1 mRNA stability. The chemical inhibitors for c-Src (saracatinib and dasanitib) restored GPX-1 mRNA levels and GPX-1 activity in COPD airway cells in vitro. Similarly, saracatinib prevented the loss of lung Gpx-1 expression in response to chronic smoke exposure in vivo. Thus, this study establishes that the decreased GPX-1 expression that occurs in COPD lungs is at least partially due to accelerated mRNA decay. Furthermore, these findings show that targeting c-Src represents a potential therapeutic approach to augment GPX-1 responses and counter smoke-induced lung disease.

Naphtho-Gamma-Pyrones Produced by Aspergillus tubingensis G131: New Source of Natural Nontoxic Antioxidants

Seven naphtho-gamma-pyrones (NγPs), including asperpyrone E, aurasperone A, dianhydroaurasperone C, fonsecin, fonsecinone A, fonsecin B, and ustilaginoidin A, were isolated from Aspergillus tubingensis G131, a non-toxigenic strain. The radical scavenging activity of these NγPs was evaluated using ABTS assay. The Trolox equivalent antioxidant capacity on the seven isolated NγPs ranged from 2.4 to 14.6 μmol L^-1. The toxicity and ability of the NγPs to prevent H₂O₂-mediated cell death were evaluated using normal/not cancerous cells (CHO cells). This cell-based assay showed that NγPs: (1) Are not toxic or weakly toxic towards cells and (2) are able to protect cells from oxidant injuries with an IC₅₀ on H₂O₂-mediated cell death ranging from 2.25 to 1800 μmol mL^-1. Our data show that A. tubingensis G131 strain is able to produce various NγPs possessing strong antioxidant activities and low toxicities, making this strain a good candidate for antioxidant applications in food and cosmetic industries.

The hydroxy-analogue of selenomethionine alleviated lipopolysaccharide-induced inflammatory responses is associated with recover expression of several selenoprotein encoding genes in the spleens of Kunming mice

This study aimed to determine whether hydroxy-analogue of selenomethionine (HMSeBA) supplementation could alleviate LPS-induced immunological stress in mice. A total of 90 Kunming mice were randomly assigned into 5 groups. The CON-LPS and CON+LPS groups were fed basal diet (BD), the others were fed BD with different levels of HMSeBA (0.15, 0.30 and 0.45 mg Se per kg) for 4 weeks. Mice were injected with LPS (3 mg per kg BW) or the corresponding physiological saline at 14 d and 28 d. Plasma and spleens were collected at 28 d. The results showed that: (1) LPS injection decreased ADG of mice at the 3^rd week, and increased the concentration of IL-6 and TNF-α in plasma and the spleen index; (2) LPS injection induced immunological stress, up-regulated 8 inflammation-related genes and 3 selenoprotein encoding genes, and down-regulated 16 selenoprotein encoding genes in spleens; (3) compared with the CON+LPS group, HMSeBA supplementation increased ADG of mice at 3 weeks and GSH-Px activity in plasma and spleens, decreased spleen index and plasma IL-6 and TNF-α levels, down-regulated mRNA levels of COX-2, ICAM-1, TNF-α, IL-6, and MCP-1, and up-regulated IL-10 and iNOS in spleens. 0.30 mg Se per kg of HMSeBA exhibited the optimal protective effect; (4) HMSeBA supplementation modestly recovered the expression of 8 selenoprotein encoding genes in the spleens of the stressed mice. The results indicated that HMSeBA supplementation alleviated LPS-induced immunological stress accompanied up-regulation of a subset of selenoprotein encoding genes in spleens of mice.

This study aimed to determine whether hydroxy-analogue of selenomethionine (HMSeBA) supplementation could alleviate LPS-induced immunological stress in mice.

Beneficial and paradoxical roles of selenium at nutritional levels of intake in healthspan and longevity

Accumulation of genome and macromolecule damage is a hallmark of aging, age-associated degeneration, and genome instability syndromes. Although processes of aging are irreversible, they can be modulated by genome maintenance pathways and environmental factors such as diet. Selenium (Se) confers its physiological functions mainly through selenoproteins, but Se compounds and other proteins that incorporate Se nonspecifically also impact optimal health. Bruce Ames proposed that the aging process could be mitigated by a subset of low-hierarchy selenoproteins whose levels are preferentially reduced in response to Se deficiency. Consistent with this notion, results from two selenotranscriptomic studies collectively implicate three low-hierarchy selenoproteins in age or senescence. Experimental evidence generally supports beneficial roles of selenoproteins in the protection against damage accumulation and redox imbalance, but some selenoproteins have also been reported to unexpectedly display harmful functions under sporadic conditions. While longevity and healthspan are usually thought to be projected in parallel, emerging evidence suggests a trade-off between longevity promotion and healthspan deterioration with damage accumulation. We propose that longevity promotion under conditions of Se deficiency may be attributed to 1) stress-response hormesis, an advantageous event of resistance to toxic chemicals at low doses; 2) reduced expression of selenoproteins with paradoxical functions to a lesser extent. In particular, selenoprotein H is an evolutionally conserved nuclear selenoprotein postulated to confer Se functions in redox regulation, genome maintenance, and senescence. This review highlights the need to pinpoint roles of specific selenoproteins and Se compounds in healthspan and lifespan for a better understanding of Se contribution at nutritional levels of intake to healthy aging.

Peroxiredoxin I participates in the protection of reactive oxygen species-mediated cellular senescence

Peroxiredoxin I (Prx I) plays an important role as a reactive oxygen species (ROS) scavenger in protecting and maintaining cellular homeostasis; however, the underlying mechanisms are not well understood. Here, we identified a critical role of Prx I in protecting cells against ROS-mediated cellular senescence by suppression of p16^INK4a expression. Compared to wild-type mouse embryonic fibroblasts (WT-MEFs), Prx I^−/− MEFs exhibited senescence-associated phenotypes. Moreover, the aged Prx I^−/− mice showed an increased number of cells with senescence associated-β-galactosidase (SA-β-gal) activity in a variety of tissues. Increased ROS levels and SA-β-gal activity, and reduction of chemical antioxidant in Prx I^−/− MEF further supported an essential role of Prx I peroxidase activity in cellular senescence that is mediated by oxidative stress. The up-regulation of p16^INK4a expression in Prx I^−/− and suppression by overexpression of Prx I indicate that Prx I possibly modulate cellular senescence through ROS/p16^INK4a pathway.

Blackberry, raspberry and black raspberry polyphenol extracts attenuate angiotensin II-induced senescence in vascular smooth muscle cells

Activation of angiotensin II (Ang II) signaling during aging increases reactive oxygen species (ROS) leading to vascular senescence, a process linked to the onset and progression of cardiovascular diseases (CVD). Consumption of fruits and vegetables, particularly berries, is associated with decreased incidence of CVD, which has mainly been attributed to the polyphenol content of these foods. Thus, the objective of this study was to investigate the role of blackberry (BL), raspberry (RB), and black raspberry (BRB) polyphenol extracts in attenuating Ang II-induced senescence in vascular smooth muscle cells (VSMCs) and to determine the molecular mechanisms involved. BL, RB and BRB polyphenol extracts (200 μg ml^-1) attenuated Ang II-induced senescence, denoted by decreased number of cells positive for senescence associated β-galactosidase (SA-β-gal) and down-regulation of p21 and p53 expression, which were associated with decreased ROS levels and Ang II signaling. BL polyphenol extract increased superoxide dismutase (SOD) 1 expression, attenuated the up-regulation of Nox1 expression and the phosphorylation of Akt, p38MAPK and ERK1/2 induced by Ang II, and reduced senescence in response to Nox1 overexpression. In contrast, RB and BRB polyphenol extracts up-regulated the expression of SOD1, SOD2, and glutathione peroxidase 1 (GPx1), but exerted no effect on Nox1 expression nor on senescence induced by Nox1 overexpression. BRB reduced signaling similar to BL, while RB was unable to reduce Akt phosphorylation. Furthermore, we demonstrated that inhibition of Akt, p38MAPK and ERK1/2 as well as down-regulation of Nox1 by siRNA prevented senescence induced by Ang II. Our findings indicate that Ang II-induced senescence is attenuated by BL polyphenols through a Nox1-dependent mechanism and by RB and BRB polyphenols in a Nox1-independent manner, likely by increasing the cellular antioxidant capacity.

Atherothrombosis and Oxidative Stress: Mechanisms and Management in Elderly

SIGNIFICANCE

The incidence of cardiovascular events (CVEs) increases with age, representing the main cause of death in an elderly population. Aging is associated with overproduction of reactive oxygen species (ROS), which may affect clotting and platelet activation, and impair endothelial function, thus predisposing elderly patients to thrombotic complications. Recent Advances: There is increasing evidence to suggest that aging is associated with an imbalance between oxidative stress and antioxidant status. Thus, upregulation of ROS-producing enzymes such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and myeloperoxidase, along with downregulation of antioxidant enzymes, such as superoxide dismutase and glutathione peroxidase, occurs during aging. This imbalance may predispose to thrombosis by enhancing platelet and clotting activation and eliciting endothelial dysfunction. Recently, gut-derived products, such as trimethylamine N-oxide (TMAO) and lipopolysaccharide, are emerging as novel atherosclerotic risk factors, and gut microbiota composition has been shown to change by aging, and may concur with the increased cardiovascular risk in the elderly.

CRITICAL ISSUES

Antioxidant treatment is ineffective in patients at risk or with cardiovascular disease. Further, anti-thrombotic treatment seems to work less in the elderly population.

FUTURE DIRECTIONS

Interventional trials with antioxidants targeting enzymes implicated in aging-related atherothrombosis are warranted to explore whether modulation of redox status is effective in lowering CVEs in the elderly. Antioxid. Redox Signal. 27, 1083-1124.

Analyses of Selenotranscriptomes and Selenium Concentrations in Response to Dietary Selenium Deficiency and Age Reveal Common and Distinct Patterns by Tissue and Sex in Telomere-Dysfunctional Mice

Background: The hierarchies of tissue selenium distribution and selenotranscriptomes are thought to critically affect healthspan and longevity.Objective: We determined selenium status and selenotranscriptomes in response to long-term dietary selenium deficiency and age in tissues of male and female mice.Methods: Weanling telomerase RNA component knockout C57BL/6 mice were fed a selenium-deficient (0.03 mg Se/kg) Torula yeast-based AIN-93G diet or a diet supplemented with sodium selenate (0.15 mg Se/kg) until age 18 or 24 mo. Plasma, hearts, kidneys, livers, and testes were collected to assay for selenotranscriptomes, selected selenoproteins, and tissue selenium concentrations. Data were analyzed with the use of 2-factor ANOVA (diet × age) in both sexes.Results: Dietary selenium deficiency decreased (P ≤ 0.05) selenium concentrations (65-72%) and glutathione peroxidase (GPX) 3 (82-94%) and selenoprotein P (SELENOP) (17-41%) levels in the plasma of both sexes of mice and mRNA levels (9-68%) of 4, 4, and 12 selenoproteins in the heart, kidney, and liver of males, respectively, and 5, 16, and 14 selenoproteins, respectively, in females. Age increased selenium concentrations and SELENOP levels (27% and 30%, respectively; P ≤ 0.05) in the plasma of males only but decreased (12-46%; P < 0.05) mRNA levels of 1, 5, and 13 selenoproteins in the heart, kidney, and liver of males, respectively, and 6, 5, and 0 selenoproteins, respectively, in females. Among these mRNAs, selenoprotein H (Selenoh), selenoprotein M (Selenom), selenoprotein W (Selenow), methionine-R-sulfoxide reductase 1 (MsrB1), Gpx1, Gpx3, thioredoxin reductase 1 (Txnrd1), Txnrd2, selenoprotein S (Selenos), selenoprotein F (Selenof), and selenoprotein O (Selenoo) responded in parallel to dietary selenium deficiency and age in ≥1 tissue or sex, or both. Dietary selenium deficiency upregulated (40-160%; P ≤ 0.05) iodothyronine deiodinase 2 (Dio2) and selenoprotein N (Selenon) in the kidneys of males. Age upregulated (11-44%; P < 0.05) Selenon in the kidneys of males, selenoprotein K (Selenok) and selenoprotein I (Selenoi) in the kidneys of females, and Selenof and Selenok in the testes.Conclusions: These results illustrate tissue-specific sexual dimorphisms of selenium status and selenotranscriptomes because of dietary selenium deficiency and age.

Advanced glycation end-products decreases expression of endothelial nitric oxide synthase through oxidative stress in human coronary artery endothelial cells

BACKGROUND

Advanced glycation end-products (AGEs) are elevated under diabetic conditions and associated with insulin resistance, endothelial dysfunction and vascular inflammation in humans. It has been demonstrated that AGEs evoke oxidative and inflammatory reactions in endothelial cells through the interaction with a receptor for AGEs (RAGE). Here, we aimed to identify the cellular mechanisms by which AGEs exacerbate the endothelial dysfunction in human coronary artery endothelial cells (HCAECs).

METHODS

30 type 2 diabetic patients with or without coronary artery atherosclerosis were recruited for this study. Plasma levels of AGE peptides (AGE-p) were analyzed using flow injection assay. Endothelial function was tested by brachial artery flow-mediated vasodilatation (FMD). Further investigations were performed to determine the effects and mechanisms of AGEs on endothelial dysfunction in HCAECs.

RESULTS

AGE-p was inversely associated with FMD in diabetic patients with coronary artery atherosclerosis in our study. After treated with AGEs, HCAECs showed significant reductions of eNOS mRNA and protein levels including eNOS and phospho-eNOS Ser1177, eNOS mRNA stability, eNOS enzyme activity, and cellular nitric oxide (NO) levels, whereas superoxide anion production was significantly increased. In addition, AGEs significantly decreased mitochondrial membrane potential, ATP content and catalase and superoxyde dismutase (SOD) activities, whereas it increased NADPH oxidase activity. Treatment of the cells with antioxidants SeMet, SOD mimetic MnTBAP and mitochondrial inhibitor thenoyltrifluoroacetone (TTFA) effectively blocked these effects induced by AGEs. AGEs also increased phosphorylation of the mitogen-activated protein kinases p38 and ERK1/2, whereas the specific inhibitors of p38, ERK1/2, and TTFA effectively blocked AGEs-induced reactive oxygen species production and eNOS downregulation.

CONCLUSIONS

AGEs cause endothelial dysfunction by a mechanism associated with decreased eNOS expression and increased oxidative stress in HCAECs through activation of p38 and ERK1/2.

Opposing impacts on healthspan and longevity by limiting dietary selenium in telomere dysfunctional mice

Selenium (Se) is a trace metalloid essential for life, but its nutritional and physiological roles during the aging process remain elusive. While telomere attrition contributes to replicative senescence mainly through persistent DNA damage response, such an aging process is mitigated in mice with inherently long telomeres. Here, weanling third generation telomerase RNA component knockout mice carrying short telomeres were fed a Se‐deficient basal diet or the diet supplemented with 0.15 ppm Se as sodium selenate to be nutritionally sufficient throughout their life. Dietary Se deprivation delayed wound healing and accelerated incidence of osteoporosis, gray hair, alopecia, and cataract, but surprisingly promoted longevity. Plasma microRNA profiling revealed a circulating signature of Se deprivation, and subsequent ontological analyses predicted dominant changes in metabolism. Consistent with this observation, dietary Se deprivation accelerated age‐dependent declines in glucose tolerance, insulin sensitivity, and glucose‐stimulated insulin production in the mice. Moreover, DNA damage and senescence responses were enhanced and Pdx1 and MafA mRNA expression were reduced in pancreas of the Se‐deficient mice. Altogether, these results suggest a novel model of aging with conceptual advances, whereby Se at low levels may be considered a hormetic chemical and decouple healthspan and longevity.

Glutathione Peroxidase-1 Suppresses the Unfolded Protein Response upon Cigarette Smoke Exposure

Oxidative stress provokes endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR) in the lungs of chronic obstructive pulmonary (COPD) subjects. The antioxidant, glutathione peroxidase-1 (GPx-1), counters oxidative stress induced by cigarette smoke exposure. Here, we investigate whether GPx-1 expression deters the UPR following exposure to cigarette smoke. Expression of ER stress markers was investigated in fully differentiated normal human bronchial epithelial (NHBE) cells isolated from nonsmoking, smoking, and COPD donors and redifferentiated at the air liquid interface. NHBE cells from COPD donors expressed heightened ATF4, XBP1, GRP78, GRP94, EDEM1, and CHOP compared to cells from nonsmoking donors. These changes coincided with reduced GPx-1 expression. Reintroduction of GPx-1 into NHBE cells isolated from COPD donors reduced the UPR. To determine whether the loss of GPx-1 expression has a direct impact on these ER stress markers during smoke exposure, Gpx-1-/- mice were exposed to cigarette smoke for 1 year. Loss of Gpx-1 expression enhanced cigarette smoke-induced ER stress and apoptosis. Equally, induction of ER stress with tunicamycin enhanced antioxidant expression in mouse precision-cut lung slices. Smoke inhalation also exacerbated the UPR response during respiratory syncytial virus infection. Therefore, ER stress may be an antioxidant-related pathophysiological event in COPD.

Inter-relation between brain-derived neurotrophic factor and antioxidant enzymes in bipolar disorder

OBJECTIVES

Accumulating evidence indicates that oxidative stress and neurotrophins have a bidirectional relationship. In this post hoc, exploratory analysis, we investigated the association between plasma brain-derived neurotrophic factor (BDNF) levels and activities of the antioxidant enzymes glutathione peroxidase (GPx) and superoxide dismutase (SOD) in individuals with bipolar disorder (BD) and healthy controls.

METHODS

We measured plasma levels of BDNF and activities of GPx and SOD in individuals with BD (n=59) and healthy controls (n=26). Information related to current and past psychiatric/medical history, as well as to metabolic comorbidities, was also reported.

RESULTS

There were negative correlations between BDNF, GPx (r=-.449, P≤.001) and GPx/SOD ratio (r=-.503, P<.001), and a positive correlation between BDNF and SOD (r=.254, P=.020). There was a moderating effect of body mass index (BMI) on the association between BDNF and GPx/SOD rate ratio [(RR)=1.002, P=.034]; interactions between impaired glucose metabolism (IGM), GPx (RR=1.016, P=.033), and GPx/SOD ratio (RR=1.026, P=.002) were also observed. These results were significant in models that included age, gender, alcohol, tobacco and medication use.

CONCLUSIONS

There was a robust and independent correlation between peripheral BDNF and antioxidant enzyme activities in individuals with BD, which was moderated by metabolic comorbidities. These results reinforce the concept that these systems are associated and further extend knowledge of the putative effect of metabolic comorbidities in the pathophysiological substrates of BD.

NADPH oxidases: key modulators in aging and age-related cardiovascular diseases?

Reactive oxygen species (ROS) and oxidative stress have long been linked to aging and diseases prominent in the elderly such as hypertension, atherosclerosis, diabetes and atrial fibrillation (AF). NADPH oxidases (Nox) are a major source of ROS in the vasculature and are key players in mediating redox signalling under physiological and pathophysiological conditions. In this review, we focus on the Nox-mediated ROS signalling pathways involved in the regulation of 'longevity genes' and recapitulate their role in age-associated vascular changes and in the development of age-related cardiovascular diseases (CVDs). This review is predicated on burgeoning knowledge that Nox-derived ROS propagate tightly regulated yet varied signalling pathways, which, at the cellular level, may lead to diminished repair, the aging process and predisposition to CVDs. In addition, we briefly describe emerging Nox therapies and their potential in improving the health of the elderly population.

Inhibition of hydrogen peroxide induced injuring on human skin fibroblast by Ulva prolifera polysaccharide

Ulva prolifera can protect human skin fibroblast from being injured by hydrogen peroxide. This work studied the composition of Ulva prolifera polysaccharide and identified its physicochemical properties. The results showed that the cell proliferation of 0.5mg/mL crude polysaccharide was 154.4% of that in negative control group. Moreover, ROS detection indices, including DCFH-DA, GSH-PX, MDA and CAT, indicated that crude polysaccharide could improve cellular ability to scavenge free radical and decrease the injury on human skin fibroblast by hydrogen peroxide. In purified polysaccharide, the activity of fraction P1-1 was the highest, with 174.6% of that in negative control group. The average molecular weight of P1-1 was 137kD with 18.0% of sulfate content. This work showed the inhibition of hydrogen peroxide induced injuries on human skin fibroblast by Ulva prolifera polysaccharide, which may further evaluate the application of U. prolifera on cosmetics.

Lack of glutathione peroxidase-1 facilitates a pro-inflammatory and activated vascular endothelium

A critical early event in the pathogenesis of atherosclerosis is vascular inflammation leading to endothelial dysfunction (ED). Reactive oxygen species and inflammation are inextricably linked and declining antioxidant defense is implicated in ED. We have previously shown that Glutathione peroxidase-1 (GPx1) is a crucial antioxidant enzyme in the protection against diabetes-associated atherosclerosis. In this study we aimed to investigate mechanisms by which lack of GPx1 affects pro-inflammatory mediators in primary aortic endothelial cells (PAECs) isolated from GPx1 knockout (GPx1 KO) mice. Herein, we demonstrate that lack of GPx1 prolonged TNF-α induced phosphorylation of P38, ERK and JNK, all of which was reversed upon treatment with the GPx1 mimetic, ebselen. In addition, Akt phosphorylation was reduced in GPx1 KO PAECs, which correlated with decreased nitric oxide (NO) bioavailability as compared to WT PAECs. Furthermore, IκB degradation was prolonged in GPx1 KO PAECS suggesting an augmentation of NF-κB activity. In addition, the expression of vascular cell adhesion molecule (VCAM-1) was significantly increased in GPx1 KO PAECs and aortas. Static and dynamic flow adhesion assays showed significantly increased adhesion of fluorescently labeled leukocytes to GPx1 KO PAECS and aortas respectively, which were significantly reduced by ebselen treatment. Our results suggest that GPx1 plays a critical role in regulating pro-inflammatory pathways, including MAPK and NF-κB, and down-stream mediators such as VCAM-1, in vascular endothelial cells. Lack of GPx1, via effects on p-AKT also affects signaling to eNOS-derived NO. We speculate based on these results that declining antioxidant defenses as seen in cardiovascular diseases, by failing to regulate these pro-inflammatory pathways, facilitates an inflammatory and activated endothelium leading to ED and atherogenesis.

Targeting Mitochondria and Reactive Oxygen Species-Driven Pathogenesis in Diabetic Nephropathy

Diabetic kidney disease is one of the major microvascular complications of both type 1 and type 2 diabetes mellitus. Approximately 30% of patients with diabetes experience renal complications. Current clinical therapies can only mitigate the symptoms and delay the progression to end-stage renal disease, but not prevent or reverse it. Oxidative stress is an important player in the pathogenesis of diabetic nephropathy. The activity of reactive oxygen and nitrogen species (ROS/NS), which are by-products of the diabetic milieu, has been found to correlate with pathological changes observed in the diabetic kidney. However, many clinical studies have failed to establish that antioxidant therapy is renoprotective. The discovery that increased ROS/NS activity is linked to mitochondrial dysfunction, endoplasmic reticulum stress, inflammation, cellular senescence, and cell death calls for a refined approach to antioxidant therapy. It is becoming clear that mitochondria play a key role in the generation of ROS/NS and their consequences on the cellular pathways involved in apoptotic cell death in the diabetic kidney. Oxidative stress has also been associated with necrosis via induction of mitochondrial permeability transition. This review highlights the importance of mitochondria in regulating redox balance, modulating cellular responses to oxidative stress, and influencing cell death pathways in diabetic kidney disease. ROS/NS-mediated cellular dysfunction corresponds with progressive disease in the diabetic kidney, and consequently represents an important clinical target. Based on this consideration, this review also examines current therapeutic interventions to prevent ROS/NS-derived injury in the diabetic kidney. These interventions, mainly aimed at reducing or preventing mitochondrial-generated oxidative stress, improving mitochondrial antioxidant defense, and maintaining mitochondrial integrity, may deliver alternative approaches to halt or prevent diabetic kidney disease.

Mitochondrial Oxidative Stress, Mitochondrial DNA Damage and Their Role in Age-Related Vascular Dysfunction

The prevalence of cardiovascular diseases is significantly increased in the older population. Risk factors and predictors of future cardiovascular events such as hypertension, atherosclerosis, or diabetes are observed with higher frequency in elderly individuals. A major determinant of vascular aging is endothelial dysfunction, characterized by impaired endothelium-dependent signaling processes. Increased production of reactive oxygen species (ROS) leads to oxidative stress, loss of nitric oxide (^•NO) signaling, loss of endothelial barrier function and infiltration of leukocytes to the vascular wall, explaining the low-grade inflammation characteristic for the aged vasculature. We here discuss the importance of different sources of ROS for vascular aging and their contribution to the increased cardiovascular risk in the elderly population with special emphasis on mitochondrial ROS formation and oxidative damage of mitochondrial DNA. Also the interaction (crosstalk) of mitochondria with nicotinamide adenosine dinucleotide phosphate (NADPH) oxidases is highlighted. Current concepts of vascular aging, consequences for the development of cardiovascular events and the particular role of ROS are evaluated on the basis of cell culture experiments, animal studies and clinical trials. Present data point to a more important role of oxidative stress for the maximal healthspan (healthy aging) than for the maximal lifespan.

Glutathione peroxidase-1 deficiency potentiates dysregulatory modifications of endothelial nitric oxide synthase and vascular dysfunction in aging

Recently, we demonstrated that gene ablation of mitochondrial manganese superoxide dismutase and aldehyde dehydrogenase-2 markedly contributed to age-related vascular dysfunction and mitochondrial oxidative stress. The present study has sought to investigate the extent of vascular dysfunction and oxidant formation in glutathione peroxidase-1-deficient (GPx-1(-/-)) mice during the aging process with special emphasis on dysregulation (uncoupling) of the endothelial NO synthase. GPx-1(-/-) mice on a C57 black 6 (C57BL/6) background at 2, 6, and 12 months of age were used. Vascular function was significantly impaired in 12-month-old GPx-1(-/-) -mice as compared with age-matched controls. Oxidant formation, detected by 3-nitrotyrosine staining and dihydroethidine-based fluorescence microtopography, was increased in the aged GPx-1(-/-) mice. Aging per se caused a substantial protein kinase C- and protein tyrosine kinase-dependent phosphorylation as well as S-glutathionylation of endothelial NO synthase associated with uncoupling, a phenomenon that was more pronounced in aged GPx-1(-/-) mice. GPx-1 ablation increased adhesion of leukocytes to cultured endothelial cells and CD68 and F4/80 staining in cardiac tissue. Aged GPx-1(-/-) mice displayed increased oxidant formation as compared with their wild-type littermates, triggering redox-signaling pathways associated with endothelial NO synthase dysfunction and uncoupling. Thus, our data demonstrate that aging leads to decreased NO bioavailability because of endothelial NO synthase dysfunction and uncoupling of the enzyme leading to endothelial dysfunction, vascular remodeling, and promotion of adhesion and infiltration of leukocytes into cardiovascular tissue, all of which was more prominent in aged GPx-1(-/-) mice.

Caveolin-1/PTRF upregulation constitutes a mechanism for mediating p53-induced cellular senescence: implications for evidence-based therapy of delayed wound healing in diabetes

A heightened state of oxidative stress and senescence of fibroblasts constitute potential therapeutic targets in nonhealing diabetic wounds. Here, we studied the underlying mechanism mediating diabetes-induced cellular senescence using in vitro cultured dermal fibroblasts and in vivo circular wounds. Our results demonstrated that the total antioxidant capacity and mRNA levels of thioredoxinreductase and glucose-6-phosphate dehydrogenase as well as the ratio of NADPH/NADP were decreased markedly in fibroblasts from patients with type 2 diabetes (DFs). Consistent with this shift in favor of excessive reactive oxygen species, DFs also displayed a significant increase in senescence-associated β-galactosidase activity and phospho-γ-histone H2AX (pH2AX) level. Moreover, the ability of PDGF to promote cell proliferation/migration and regulate the phosphorylation-dependent activation of Akt and ERK1/2 appears to be attenuated as a function of diabetes. Mechanistically, we found that diabetes-induced oxidative stress upregulated caveolin-1 (Cav-1) and PTRF expression, which in turn sequestered Mdm2 away from p53. This process resulted in the activation of a p53/p21-dependent pathway and the induction of premature senescence in DFs. Most of the aforementioned oxidative stress and senescence-based features observed in DFs were recapitulated in a 10-day-old diabetic wound. Intriguingly, we confirmed that the targeted depletion of Cav-1 or PTRF using siRNA- or Vivo-Morpholino antisense-based gene therapy markedly inhibited diabetes/oxidative stress-induced premature senescence and also accelerated tissue repair in this disease state. Overall, our data illuminate Cav-1/PTRF-1 as a key player of a novel signaling pathway that may link a heightened state of oxidative stress to cellular senescence and impaired wound healing in diabetes.

The canonical NF-κB pathway differentially protects normal and human tumor cells from ROS-induced DNA damage

DNA damage responses (DDR) invoke senescence or apoptosis depending on stimulus intensity and the degree of activation of the p53-p21(Cip1/Waf1) axis; but the functional impact of NF-κB signaling on these different outcomes in normal vs. human cancer cells remains poorly understood. We investigated the NF-κB-dependent effects and mechanism underlying reactive oxygen species (ROS)-mediated DDR outcomes of normal human lung fibroblasts (HDFs) and A549 human lung cancer epithelial cells. To activate DDR, ROS accumulation was induced by different doses of H(2)O(2). The effect of ROS induction caused a G2 or G2-M phase cell cycle arrest of both human cell types. However, ROS-mediated DDR eventually culminated in different end points with HDFs undergoing premature senescence and A549 cancer cells succumbing to apoptosis. NF-κB p65/RelA nuclear translocation and Ser536 phosphorylation were induced in response to H(2)O(2)-mediated ROS accumulation. Importantly, blocking the activities of canonical NF-κB subunits with an IκBα super-repressor or suppressing canonical NF-κB signaling by IKKβ knock-down accelerated HDF premature senescence by up-regulating the p53-p21(Cip1/Waf1) axis; but inhibiting the canonical NF-κB pathway exacerbated H(2)O(2)-induced A549 cell apoptosis. HDF premature aging occurred in conjunction with γ-H2AX chromatin deposition, senescence-associated heterochromatic foci and beta-galactosidase staining. p53 knock-down abrogated H(2)O(2)-induced premature senescence of vector control- and IκBαSR-expressing HDFs functionally linking canonical NF-κB-dependent control of p53 levels to ROS-induced HDF senescence. We conclude that IKKβ-driven canonical NF-κB signaling has different functional roles for the outcome of ROS responses in the contexts of normal vs. human tumor cells by respectively protecting them against DDR-dependent premature senescence and apoptosis.

Physiological regulation of cardiac contractility by endogenous reactive oxygen species

Increased production of reactive oxygen species (ROS) has been linked to the pathogenesis of congestive heart failure. However, emerging evidence suggests the involvement of ROS in the regulation of various physiological cellular processes in the myocardium. In this review, we summarize the latest findings regarding the role of ROS in the acute regulation of cardiac contractility. We discuss ROS-dependent modulation of the inotropic responses to G protein-coupled receptor agonists (e.g. β-adrenergic receptor agonists and endothelin-1), the potential cellular sources of ROS (e.g. NAD(P)H oxidases and mitochondria) and the proposed end-targets and signalling pathways by which ROS affect contractility. Accumulating new data supports the fundamental role of endogenously generated ROS to regulate cardiac function under physiological conditions.

The contribution of oxidative stress to drug-induced organ toxicity and its detection in vitro and in vivo

INTRODUCTION

Nowadays the 'redox hypothesis' is based on the fact that thiol/disulfide couples such as glutathione (GSH/GSSG), cysteine (Cys/CySS) and thioredoxin ((Trx-(SH)2/Trx-SS)) are functionally organized in redox circuits controlled by glutathione pools, thioredoxins and other control nodes, and they are not in equilibrium relative to each other. Although ROS can be important intermediates of cellular signaling pathways, disturbances in the normal cellular redox can result in widespread damage to several cell components. Moreover, oxidative stress has been linked to a variety of age-related diseases. In recent years, oxidative stress has also been identified to contribute to drug-induced liver, heart, renal and brain toxicity.

AREAS COVERED

This review provides an overview of current in vitro and in vivo methods that can be deployed throughout the drug discovery process. In addition, animal models and noninvasive biomarkers are described.

EXPERT OPINION

Reducing post-market drug withdrawals is essential for all pharmaceutical companies in a time of increased patient welfare and tight budgets. Predictive screens positioned early in the drug discovery process will help to reduce such liabilities. Although new and more efficient assays and models are being developed, the hunt for biomarkers and noninvasive techniques is still in progress.

Oxidative stress and diabetes: what can we learn about insulin resistance from antioxidant mutant mouse models?

The development of metabolic dysfunctions like diabetes and insulin resistance in mammals is regulated by a myriad of factors. Oxidative stress seems to play a central role in this process as recent evidence shows a general increase in oxidative damage and a decrease in oxidative defense associated with several metabolic diseases. These changes in oxidative stress can be directly correlated with increased fat accumulation, obesity, and consumption of high-calorie/high-fat diets. Modulation of oxidant protection through either genetic mutation or treatment with antioxidants can significantly alter oxidative stress resistance and accumulation of oxidative damage in laboratory rodents. Antioxidant mutant mice have previously been utilized to examine the role of oxidative stress in other disease models, but have been relatively unexplored as models to study the regulation of glucose metabolism. In this review, we will discuss the evidence for oxidative stress as a primary mechanism linking obesity and metabolic disorders and whether alteration of antioxidant status in laboratory rodents can significantly alter the development of insulin resistance or diabetes.

Glutathione peroxidase-1 in health and disease: from molecular mechanisms to therapeutic opportunities

Reactive oxygen species, such as superoxide and hydrogen peroxide, are generated in all cells by mitochondrial and enzymatic sources. Left unchecked, these reactive species can cause oxidative damage to DNA, proteins, and membrane lipids. Glutathione peroxidase-1 (GPx-1) is an intracellular antioxidant enzyme that enzymatically reduces hydrogen peroxide to water to limit its harmful effects. Certain reactive oxygen species, such as hydrogen peroxide, are also essential for growth factor-mediated signal transduction, mitochondrial function, and maintenance of normal thiol redox-balance. Thus, by limiting hydrogen peroxide accumulation, GPx-1 also modulates these processes. This review explores the molecular mechanisms involved in regulating the expression and function of GPx-1, with an emphasis on the role of GPx-1 in modulating cellular oxidant stress and redox-mediated responses. As a selenocysteine-containing enzyme, GPx-1 expression is subject to unique forms of regulation involving the trace mineral selenium and selenocysteine incorporation during translation. In addition, GPx-1 has been implicated in the development and prevention of many common and complex diseases, including cancer and cardiovascular disease. This review discusses the role of GPx-1 in these diseases and speculates on potential future therapies to harness the beneficial effects of this ubiquitous antioxidant enzyme.

Expression of peroxiredoxin I regulated by gonadotropins in the rat ovary

Objective

Peroxiredoxins (Prxs) play an important role in regulating cellular differentiation and proliferation in several types of mammalian cells. This report examined the expression of Prx isotype I in the rat ovary after hormone treatment.

Methods

Immature rats were injected with 10 IU of pregnant mare's serum gonadotropin (PMSG) to induce the growth of multiple preovulatory follicles and 10 IU of human chorionic gonadotropin (hCG) to induce ovulation. Immature rats were also treated with diethylstilbestrol (DES), an estrogen analogue, to induce the growth of multiple immature follicles. Northern blot analysis was performed to detect gene expression. Cell-type specific localization of Prx I mRNA were detected by in situ hybridization analysis.

Results

During follicle development, ovarian Prx I gene expression was detected in 3-day-old rats and had increased in 21-day-old rats. The levels of Prx I mRNA slightly declined one to two days following treatment with DES. A gradual increase in Prx I gene expression was observed in ovaries obtained from PMSG-treated immature rats. Furthermore, hCG treatment of PMSG-primed rats resulted in a gradual stimulation of Prx I mRNA levels by 24 hours (2.1-fold increase) following treatment, which remained high until 72 hours following treatment. In situ hybridization analysis revealed the expression of the Prx I gene in the granulosa cells of PMSG-primed ovaries and in the corpora lutea of ovaries stimulated with hCG for 72 hours.

Conclusion

These results demonstrate the gonadotropin and granulosa cell-specific stimulation of Prx I gene expression, suggesting its role as a local regulator of follicle development.

Transcriptional up-regulation of antioxidant genes by PPARδ inhibits angiotensin II-induced premature senescence in vascular smooth muscle cells

This study evaluated peroxisome proliferator-activated receptor (PPAR) δ as a potential target for therapeutic intervention in Ang II-induced senescence in human vascular smooth muscle cells (hVSMCs). Activation of PPARδ by GW501516, a specific agonist of PPARδ, significantly inhibited the Ang II-induced premature senescence of hVSMCs. Agonist-activated PPARδ suppressed the generation of Ang II-triggered reactive oxygen species (ROS) with a concomitant reduction in DNA damage. Notably, GW501516 up-regulated the expression of antioxidant genes, such as glutathione peroxidase 1, thioredoxin 1, manganese superoxide dismutase and heme oxygenase 1. siRNA-mediated down-regulation of these antioxidant genes almost completely abolished the effects of GW501516 on ROS production and premature senescence in hVSMCs treated with Ang II. Taken together, the enhanced transcription of antioxidant genes is responsible for the PPARδ-mediated inhibition of premature senescence through sequestration of ROS in hVSMCs treated with Ang II.

Adaptive dysfunction of selenoproteins from the perspective of the triage theory: why modest selenium deficiency may increase risk of diseases of aging

The triage theory proposes that modest deficiency of any vitamin or mineral (V/M) could increase age-related diseases. V/M-dependent proteins required for short-term survival and/or reproduction (i.e., "essential") are predicted to be protected on V/M deficiency over other "nonessential" V/M-dependent proteins needed only for long-term health. The result is accumulation of insidious damage, increasing disease risk. We successfully tested the theory against published evidence on vitamin K. Here, we review about half of the 25 known mammalian selenoproteins; all of those with mouse knockout or human mutant phenotypes that could be used as criteria for a classification of essential or nonessential. Five selenoproteins (Gpx4, Txnrd1, Txnrd2, Dio3, and Sepp1) were classified as essential and 7 (Gpx1, Gpx 2, Gpx 3, Dio1, Dio2, Msrb1, and SelN) nonessential. On modest selenium (Se) deficiency, nonessential selenoprotein activities and concentrations are preferentially lost, with one exception (Dio1 in the thyroid, which we predict is conditionally essential). Mechanisms include the requirement of a special form of tRNA sensitive to Se deficiency for translation of nonessential selenoprotein mRNAs except Dio1. The same set of age-related diseases and conditions, including cancer, heart disease, and immune dysfunction, are prospectively associated with modest Se deficiency and also with genetic dysfunction of nonessential selenoproteins, suggesting that Se deficiency could be a causal factor, a possibility strengthened by mechanistic evidence. Modest Se deficiency is common in many parts of the world; optimal intake could prevent future disease.

Resistin decreases expression of endothelial nitric oxide synthase through oxidative stress in human coronary artery endothelial cells

Resistin is a newly discovered adipocyte-derived cytokine that may play an important role in insulin resistance, diabetes, adipogenesis, inflammation, and cardiovascular disease. However, it is largely unknown whether resistin impairs endothelial functions by affecting the endothelial nitric oxide synthase (eNOS) system. In this study, we determined the effect of human recombinant resistin protein on eNOS expression and regulation in human coronary artery endothelial cells (HCAECs). When cells were treated with clinically relevant concentrations of resistin (40 or 80 ng/ml) for 24 h, the levels of eNOS mRNA, protein, and activity and eNOS mRNA stability were significantly reduced. Cellular nitric oxide levels were also decreased. In addition, the cellular levels of reactive oxygen species (ROS), including superoxide anion, were significantly increased in resistin-treated HCAECs. Mitochondrial membrane potential and the activities of catalase and superoxide dismutase were reduced. Three antioxidants, seleno-L-methionine, ginsenoside Rb1, and MnTBAP (superoxide dismutase mimetic), effectively blocked resistin-induced eNOS downregulation. Meanwhile, resistin activated the mitogen-activated protein kinases p38 and c-Jun NH(2)-terminal kinase (JNK), and the specific p38 inhibitor SB-239063 effectively blocked resistin-induced ROS production and eNOS downregulation. Furthermore, immunoreactivity of resistin was increased in atherosclerotic regions of human aorta and carotid arteries. Thus resistin directly induces eNOS downregulation through overproduction of ROS and activation of p38 and JNK in HCAECs. Resistin-induced mitochondrial dysfunction and imbalance in cellular redox enzymes may be the underlying mechanisms of oxidative stress.

Update on the oxidative stress theory of aging: does oxidative stress play a role in aging or healthy aging?

The oxidative stress theory of aging predicts that manipulations that alter oxidative stress/damage will alter aging. The gold standard for determining whether aging is altered is life span, i.e., does altering oxidative stress/damage change life span? Mice with genetic manipulations in their antioxidant defense system designed to directly address this prediction have, with few exceptions, shown no change in life span. However, when these transgenic/knockout mice are tested using models that develop various types of age-related pathology, they show alterations in progression and/or severity of pathology as predicted by the oxidative stress theory: increased oxidative stress accelerates pathology and reduced oxidative stress retards pathology. These contradictory observations might mean that (a) oxidative stress plays a very limited, if any, role in aging but a major role in health span and/or (b) the role that oxidative stress plays in aging depends on environment. In environments with minimal stress, as expected under optimal husbandry, oxidative damage plays little role in aging. However, under chronic stress, including pathological phenotypes that diminish optimal health, oxidative stress/damage plays a major role in aging. Under these conditions, enhanced antioxidant defenses exert an "antiaging" action, leading to changes in life span, age-related pathology, and physiological function as predicted by the oxidative stress theory of aging.

Aging decreases expression and activity of glutathione peroxidase-1 in human endothelial progenitor cells

The mechanisms underlying effects of aging on functions of pro-angiogenic endothelial progenitor cells (EPCs) are poorly understood. Previous studies demonstrated that human EPCs express high levels of antioxidant enzymes as compared to mature endothelial cells. Here, we hypothesized that aging impairs antioxidant capacity of EPCs. So called "early EPCs" derived from cultured blood mononuclear cells were obtained from healthy young (average=24 years old) and old (average=72 years old) subjects. In EPCs of old subjects, the levels of glutathione peroxidase-1 (GPX1) protein and enzymatic activity were significantly reduced. The serum selenium levels in young and old subjects were not significantly different. Increasing selenium concentration in the cell culture also did not affect the protein levels of GPX1, suggesting the reduced GPX1 in old subject's EPCs is selenium independent. Expressions of catalase, Mn-superoxide dismutase (MnSOD), and CuZnSOD were not affected by aging. EPCs of old subjects were more sensitive to oxidative stress induced by H(2)O(2) as compared with EPCs of young subjects, suggesting that impairment of GPX1 during aging may contribute to low survival ability of EPCs in response to oxidative stress. The results indicate that GPX1 may represent a potential therapeutic target for enhancement of regenerative capacity of EPCs in old subjects.

Inhibition of thioredoxin reductase 1 by caveolin 1 promotes stress-induced premature senescence

Thioredoxin reductase 1 (TrxR1) is an important antioxidant enzyme that controls cellular redox homeostasis. By using a proteomic-based approach, here we identify TrxR1 as a caveolar membrane-resident protein. We show that caveolin 1, the structural protein component of caveolae, is a TrxR1-binding protein by demonstrating that the scaffolding domain of caveolin 1 (amino acids 82-101) binds directly to the caveolin-binding motif (CBM) of TrxR1 (amino acids 454-463). We also show that overexpression of caveolin 1 inhibits TrxR activity, whereas a lack of caveolin 1 activates TrxR, both in vitro and in vivo. Expression of a peptide corresponding to the caveolin 1 scaffolding domain is sufficient to inhibit TrxR activity. A TrxR1 mutant lacking the CBM, which fails to localize to caveolae and bind to caveolin 1, is constitutively active and inhibits oxidative-stress-mediated activation of the p53/p21(Waf1/Cip1) pathway and induction of premature senescence. Finally, we show that caveolin 1 expression inhibits TrxR1-mediated cell transformation. Thus, caveolin 1 links free radicals to activation of the p53/p21(Waf1/Cip1) pathway and induction of cellular senescence by acting as an endogenous inhibitor of TrxR1.

Mice deficient in both Mn superoxide dismutase and glutathione peroxidase-1 have increased oxidative damage and a greater incidence of pathology but no reduction in longevity

To test the impact of increased mitochondrial oxidative stress as a mechanism underlying aging and age-related pathologies, we generated mice with a combined deficiency in two mitochondrial-localized antioxidant enzymes, Mn superoxide dismutase (MnSOD) and glutathione peroxidase-1 (Gpx-1). We compared life span, pathology, and oxidative damage in Gpx1(-/-), Sod2(+/-)Gpx1(+/-), Sod2(+/-)Gpx1(-/-), and wild-type control mice. Oxidative damage was elevated in Sod2(+/-)Gpx1(-/-) mice, as shown by increased DNA oxidation in liver and skeletal muscle and increased protein oxidation in brain. Surprisingly, Sod2(+/-)Gpx1(-/-) mice showed no reduction in life span, despite increased levels of oxidative damage. Consistent with the important role for oxidative stress in tumorigenesis during aging, the incidence of neoplasms was significantly increased in the older Sod2(+/-)Gpx1(-/-) mice (28-30 months). Thus, these data do not support a significant role for increased oxidative stress as a result of compromised mitochondrial antioxidant defenses in modulating life span in mice and do not support the oxidative stress theory of aging.

Impact of inorganic nutrients on maintenance of genomic stability

Maintenance of genome stability is of fundamental importance for counteracting carcinogenesis. Many human genome instability syndromes exhibit a predisposition to cancer. An increasing body of epidemiological evidence has suggested a link between nutrient status and risk of cancer. Like other chemicals, nutrients can be toxic when consumed in excess. It has become clear that both nutritional deficiency and toxicity can compromise the integrity of the genome. This article focuses on roles of inorganic trace nutrients, including selenium, copper, zinc, and iron, in the redox regulation of genome stability and how they relate to the pathologies of genomic instability syndromes and cancer.

Chlamydia heat shock protein 60 decreases expression of endothelial nitric oxide synthase in human and porcine coronary artery endothelial cells

AIMS

Clinically, Chlamydia pneumoniae infection and its heat shock protein 60 (cHSP60) may contribute to atherogenesis; however, its underlying mechanisms are largely unknown. The objective of this study was to determine whether cHSP60 could cause endothelial dysfunction in human coronary artery endothelial cells (HCAECs) and porcine coronary arteries.

METHODS AND RESULTS

When HCAECs were treated with recombinant cHSP60, endothelial nitric oxide synthase (eNOS) mRNA and protein levels, enzyme activities, cellular NO levels, mRNA stability, and promoter activities were significantly decreased. Superoxide anion production was significantly increased due to the inhibition of mitochondrial membrane potential and catalase and superoxide dismutase (SOD) activities as well as activation of NADPH oxidase. Antioxidant seleno-l-methionine (SeMet) or SOD mimetic MnTBAP effectively blocked cHSP60-induced eNOS downregulation. In addition, cHSP60 activated mitogen-activated protein kinases (MAPKs) including p38, c-Jun-N-terminal kinase/stress-activated protein kinase, and extracellular signal-regulated kinases. Specific chemical inhibitors or their dominant-negative mutant forms of these MAPKs effectively blocked cHSP60-induced eNOS downregulation. cHSP60-induced eNOS downregulation and oxidative stress were also demonstrated in porcine coronary artery rings in vitro. Functionally, endothelium-dependent vasorelaxation was significantly reduced in cHSP60-treated vessels.

CONCLUSION

cHSP60 directly induces eNOS downregulation through oxidative stress and MAPK activation in both HCAECs and porcine coronary arteries, thereby causing endothelial dysfunction.

Mechanisms of stress resistance in Snell dwarf mouse fibroblasts: enhanced antioxidant and DNA base excision repair capacity, but no differences in mitochondrial metabolism

Dermal fibroblasts from long-lived Snell dwarf mice can withstand a variety of oxidative and non-oxidative stressors compared to normal littermate controls. Here, we report differences in the levels and activities of intracellular antioxidant and DNA repair enzymes between normal and Snell dwarf mice fibroblasts cultured under a variety of conditions, including: 3% and 20% ambient O(2); the presence and absence of serum; and the addition of an exogenous oxidative stress. The only significant difference between normal and dwarf cells cultured in complete medium, at 20% O(2), was an approximately 40% elevation of glutathione peroxidase (GPx) activity in the mutant cells. Serum deprivation elicited increases in GPx in both genotypes, but these activities remained higher in dwarf mouse cells. Dwarf mouse cells deprived of serum and challenged with exposure to paraquat or hydrogen peroxide showed a generally greater upregulation of catalase and DNA base excision repair enzymes. As these toxins can interact with mitochondria to increase mitochondrial ROS production, we explored whether there were differences in mitochondrial metabolism between normal and dwarf mouse cells. However, neither mitochondrial content nor the apparent mitochondrial membrane potential differed between genotypes. Overall, the results suggest that superior hydrogen peroxide metabolism and a marginally greater DNA base excision repair capacity contribute to the stress resistance phenotype of Snell dwarf mouse fibroblasts.

Peroxiredoxin IV protects cells from radiation-induced apoptosis in head-and-neck squamous cell carcinoma

PURPOSE

Human peroxiredoxins (Prxs) are known as a family of thiol-specific antioxidant enzymes, among which Prx-I and -II play an important role in protecting cells from irradiation-induced cell death. It is not known whether Prx-IV also protects cells from ionizing radiation (IR).

METHODS AND MATERIALS

To evaluate the protective role of Prx-IV in IR, we transfected full-length Prx-IV cDNA into AMC-HN3 cells, which weakly express endogenous Prx-IV, and knocked down the expression of Prx-IV with siRNA methods using AMC-HN7 cells, which express high levels of endogenous Prx-IV. Radiosensitivity profiles in these cells were evaluated using clonogenic assay, FACS analysis, cell viability, and TUNEL assay.

RESULTS

Three Prx-IV expressing clones were isolated. Prx-IV regulated intracellular reactive oxygen species (ROS) levels and made cells more resistant to IR-induced apoptosis. Furthermore, the knockdown of Prx-IV with siRNA made cells more sensitive to IR-induced apoptosis.

CONCLUSION

The results of these studies suggest that Prx-IV may play an important role in protecting cells from IR-induced apoptosis in head-and-neck squamous cell carcinoma.

Glutathione peroxidase-1 regulates mitochondrial function to modulate redox-dependent cellular responses

Glutathione peroxidase-1 (GPx-1) is a selenocysteine-containing enzyme that plays a major role in the reductive detoxification of peroxides in cells. In permanently transfected cells with approximate 2-fold overexpression of GPx-1, we found that intracellular accumulation of oxidants in response to exogenous hydrogen peroxide was diminished, as was epidermal growth factor receptor (EGFR)-mediated Akt activation in response to hydrogen peroxide or EGF stimulation. Knockdown of GPx-1 augmented EGFR-mediated Akt activation, whereas overexpression of catalase decreased Akt activation, suggesting that EGFR signaling is regulated by redox mechanisms. To determine whether mitochondrial oxidants played a role in these processes, cells were pretreated with a mitochondrial uncoupler prior to EGF stimulation. Inhibition of mitochondrial function attenuated EGF-mediated activation of Akt in control cells but had no additional effect in GPx-1-overexpressing cells, suggesting that GPx-1 overexpression decreased EGFR signaling by decreasing mitochondrial oxidants. Consistent with this finding, GPx-1 overexpression decreased global protein disulfide bond formation, which is dependent on mitochondrially produced oxidants. GPx-1 overexpression, in permanently transfected or adenovirus-treated cells, also caused overall mitochondrial dysfunction with a decrease in mitochondrial potential and a decrease in ATP production. GPx-1 overexpression also decreased EGF- and serum-mediated [(3)H]thymidine incorporation, indicating that alterations in GPx-1 can attenuate cell proliferation. Taken together, these data suggest that GPx-1 can modulate redox-dependent cellular responses by regulating mitochondrial function.

The Mn-superoxide dismutase single nucleotide polymorphism rs4880 and the glutathione peroxidase 1 single nucleotide polymorphism rs1050450 are associated with aging and longevity in the oldest old

The free radical theory of aging states that reactive oxygen species (ROS) play a key role in age-related accumulation of cellular damage, and consequently influence aging and longevity. Therefore, variation in genes encoding proteins protecting against ROS could be expected to influence variation in aging and life span. The rs4880 and rs1050450 SNPs in the manganese superoxide dismutase (MnSOD) and glutathione peroxidase 1 (GPX1) genes, respectively, are associated with age-related diseases and appear to affect the activities of the encoded variant proteins. In this study we genotyped these SNPs in 1650 individuals from the Danish 1905 cohort (follow-up time: 1998-2008, age at intake: 92-93 years, number of deaths: 1589 (96.3%)) and investigated the association with aging and longevity. We found decreased mortality of individuals holding either the MnSOD rs4880 C or the GPX1 rs1050450 T alleles (HR (MnSOD(CC/CT))=0.91, P=0, p=0.002 and HR (GPX1(TT/TC))=0.93, p=0.008). Furthermore, a synergetic effect of the alleles was observed (HR=0.76, p=0.001). Finally, moderate positive associations with good self rated health, decreased disability and increased cognitive capacity were observed. Our results thus indicate that genetic variation in MnSOD and GPX1 may be associated with aging and longevity.

Carbachol alleviates oxygen free radical injury in gut during enteral resuscitation of burn shock in rats

AIM: To investigate the effects of carbachol on oxygen free radical injury in gut during enteral resuscitation of burn shock in rats.

METHODS: A 35% TBSA full thickness scald injury was induced in 38 Wistar rats. The rats were divided randomly into four groups: scald with no therapy (scald alone, n = 8), scald with enteral infusing either a glucose electrolyte solution (GES, n = 10) or GES containing carbachol (60 μg/kg, GES/CAR, n = 10), and scald with enteral infusing only carbachol (CAR, n = 10). GES was infused into intestine through a duodenal stomy according to Parkland formula (4 mL·1%TBSA/kg) 30 min after scald and carbachol was administered simultaneously through the same path. Four hours after injury, the initial jejunum was collected for evaluation of xanthine oxidase (XOD), malondialdehyde (MDA), myeloperoxidase (MPO) and assessment of the pathologic damages.

RESULTS: The activity of XOD and MPO, and the MDA level were 13.2%, 21.3% and 21.1% higher in the GES containing carbachol treatment groups than in the scald alone group (P < 0.05). Resuscitation with GES/CAR resulted in significantly lower levels of XOD (1.36 ± 0.37 vs 2.51 ± 0.56, P < 0.01), MDA (3.97 ± 1.57 vs 6.59 ± 1.50, P < 0.01) and MPO (0.47 ± 0.14 vs 0.83 ± 0.21, P < 0.01) than resuscitation with GES. The parameters in the CAR group were the lowest. The gut lesions were mild in the CAR and GES/CAR groups, severe in the CAR alone group, and most severe in the GES group.

CONCLUSION: Carbachol can alleviate gut oxygen free radical injury during enteral resuscitation of burn shock, which might be associated with its anti-inflammation effects, inhibition of XOD activity and generation of oxygen free radicals in gut tissue.

Comparison of mice born after intracytoplasmic sperm injection with in vitro fertilization and natural mating

The procedures of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) are routinely used in modern medicine to overcome infertility and, in animal husbandry, to propagate lines with compromised fertility. However, there remains concern that manual selection and injection of whole sperm into oocytes could contribute to pre- and postnatal developmental defects. To address this, we have used gene expression profiling and immunophenotyping to characterize offspring generated by these procedures. We used gametes from glutathione peroxidase 1 knockout (Gpx1-/-) mice as a sensitized screen responsive to oxidative stress from artificial reproduction technologies (ART). There were no differences between IVF and ICSI derived offspring in gene expression patterns, and minor differences in hematopoietic parameters. Furthermore there were only minor differences between these IVF and ICSI pups and those derived from natural mating. These data demonstrate for the first time in that there is no significant phenotypic affects of ICSI when compared to IVF and we identified a relatively minor influence of the artificial fertilization methods on phenotype of offspring compared with natural mating. These observations would support the use of ICSI for derivation of mutant mouse lines and may be of some importance for the use of this technique in human ART.

Inhibitory effect of peroxiredoxin II (Prx II) on Ras-ERK-NFkappaB pathway in mouse embryonic fibroblast (MEF) senescence

Intracellular reactive oxygen species (ROS) were attenuated by the expression of peroxiredoxin II (Prx II). Cellular senescence as judged by senescence-associated (SA)-beta-galactosidase (Gal) positive cell formation was increased in Prx II-deficient mouse embryonic fibroblast (MEF). Ras expression was increased following passages. The level of Ras expression was higher in Prx II-/- MEF than wild type MEF. ERK activity was also augmented by the deletion of Prx II. SA-beta-Gal-positive cell formation was reduced by PD98059, ERK inhibitor. Activated nuclear transcription factor, nuclear factor-kappaB (NFkappaB) by the deletion of Prx II was inhibited by the treatment with PD98059. In contrast, no changes in SA-beta-Gal-positive cell formation were detected by NFkappaB inhibitor, N-alpha-tosyl-L-phenylalanyl chloromethyl ketone (TPCK). Collectively, results suggest that Prx II deletion activate Ras-ERK-NFkappaB pathways and cellular senescence in Prx II-/- MEF cells was mediated by ERK activation but not by NFkappaB activation.

Glutathione-peroxidase-1 null muscle progenitor cells are globally defective

Mice lacking glutathione peroxidase-1 (Gpx1) have decreased resistance to systemically administered oxidants as well as infections, and sustain increased damage after ischemia-reperfusion injuries. However, stem or progenitor cell function in these animals has not been studied. We characterized patterns of proliferation, apoptosis, and differentiation of primary muscle progenitor cells (myoblasts) from Gpx1(-/-) mice. Myoblasts are the transit amplifying compartment of skeletal muscle. All aspects of myoblast biology are negatively affected by deletion of Gpx1. In particular, passaged, proliferating Gpx1(-/-) myoblasts, when induced to differentiate into fused multinucleated myotubes, show significant impairment, and form only a few immature myotubes. This defect occurs despite increased expression of the core regulators of muscle differentiation, the myogenic basic helix-loop-helix (bHLH) transcription factors, in the Gpx1(-/-) myoblasts. Furthermore, Gpx1(-/-) myoblasts exhibited decreased proliferation and increased apoptosis compared to wild-type cells. In vivo, muscle fiber areas are decreased in Gpx1(-/-) vs wild-type mice. These data suggest that Gpx1 is important for adult muscle progenitor cell function at many levels, is necessary for integrity of muscle differentiation, and that quiescent resident stem cell populations may be particularly vulnerable to peroxide-mediated damage.