Oxygen radicals and signaling

Deconvoluting the role of reactive oxygen species and autophagy in human diseases

Reactive oxygen species (ROS), chemically reactive molecules containing oxygen, can form as a natural byproduct of the normal metabolism of oxygen and also have their crucial roles in cell homeostasis. Of note, the major intracellular sources including mitochondria, endoplasmic reticulum (ER), peroxisomes and the NADPH oxidase (NOX) complex have been identified in cell membranes to produce ROS. Interestingly, autophagy, an evolutionarily conserved lysosomal degradation process in which a cell degrades long-lived proteins and damaged organelles, has recently been well-characterized to be regulated by different types of ROS. Accumulating evidence has demonstrated that ROS-modulated autophagy has numerous links to a number of pathological processes, including cancer, ageing, neurodegenerative diseases, type-II diabetes, cardiovascular diseases, muscular disorders, hepatic encephalopathy and immunity diseases. In this review, we focus on summarizing the molecular mechanisms of ROS-regulated autophagy and their relevance to diverse diseases, which would shed new light on more ROS modulators as potential therapeutic drugs for fighting human diseases.

Superoxide release from contracting skeletal muscle in pulmonary TNF-α overexpression mice

Chronic obstructive pulmonary disease (COPD) often results in increased levels of tumor necrosis factor-α (TNF-α), a proinflammatory cytokine, which circulates in the blood. However, it is not clear whether pulmonary TNF-α overexpression (a COPD mimic) induces excessive reactive oxygen species (ROS) formation in skeletal muscle and thereby may contribute to the muscle impairment often seen in COPD. We hypothesized that ROS generation in contracting skeletal muscle is elevated when there is TNF-α overproduction in the lung and that this can induce muscle dysfunction. Cytochrome c (cyt c) in the perfusate was used to assay superoxide (O2(·-)) release from isolated contracting soleus muscles from transgenic mice of pulmonary TNF-α overexpression (Tg(+)) and wild-type (WT) mice. Our results showed that Tg(+) muscle released significantly higher levels of O2(·-) than WT during a period of intense contractile activity (in nmol/mg wt; 17.5 ± 2.3 vs. 4.4 ± 1.3, respectively; n = 5; P < 0.05). In addition, the soleus muscle demonstrated a significantly reduced fatigue resistance in Tg(+) mice compared with WT mice. Perfusion of the contracting soleus muscle with superoxide dismutase, which specifically scavenges O2(·-) in the perfusate, resulted in significantly less cyt c reduction, thereby indicating that the type of ROS released from the Tg(+) muscles is O2(·-). Our results demonstrate that pulmonary TNF-α overexpression leads to a greater O2(·-) release from contracting soleus muscle in Tg(+) compared with WT and that the excessive formation of O2(·-) in the contracting muscle of Tg(+) mice leads to earlier fatigue.

SIRT5 desuccinylates and activates SOD1 to eliminate ROS

Cu/Zn superoxide dismutase (SOD1) is a key antioxidant enzyme. Deficiency of SOD1 is associated with various human diseases, including cancer. Here, we report that SOD1 is succinylated and that succinylation decreases its activity. SIRT5 binds to, desuccinylates and activates SOD1. SOD1-mediated ROS reduction is increased when SIRT5 is co-expressed. Furthermore, mutation of the SOD1 succinylation site inhibits the growth of lung tumor cells. These results reveal a novel post-translational regulation of SOD1 by means of succinylation and SIRT5-dependent desuccinylation, which is important for the growth of lung tumor cells.

CR108, a novel vitamin K3 derivative induces apoptosis and breast tumor inhibition by reactive oxygen species and mitochondrial dysfunction

Vitamin K3 derivatives have been shown to exert anticancer activities. Here we show a novel vitamin K3 derivative (S)-2-(2-hydroxy-3-methylbutylthio)naphthalene-1,4-dione, which is named as CR108 that induces apoptosis and tumor inhibition through reactive oxygen species (ROS) and mitochondrial dysfunction in human breast cancer. CR108 is more effective on the breast cancer cell death than other vitamin K3 derivatives. Moreover, CR108 induced apoptosis in both the non-HER-2-overexpressed MCF-7 and HER-2-overexpressed BT-474 breast cancer cells. CR108 caused the loss of mitochondrial membrane potential, cytochrome c released from mitochondria to cytosol, and cleaved PARP proteins for apoptosis induction. CR108 markedly increased ROS levels in breast cancer cells. N-acetylcysteine (NAC), a general ROS scavenger, completely blocked the CR108-induced ROS levels, mitochondrial dysfunction and apoptosis. Interestingly, CR108 increased the phosphorylation of p38 MAP kinase but conversely inhibited the survivin protein expression. NAC treatment prevented the activation of p38 MAP kinase and rescued the survivin protein levels. SB202190, a specific p38 MAP kinase inhibitor, recovered the survivin protein levels and attenuated the cytotoxicity of CR108-treated cells. Furthermore, CR108 inhibited the xenografted human breast tumor growth in nude mice. Together, we demonstrate that CR108 is a novel vitamin K3 derivative that induces apoptosis and tumor inhibition by ROS production and mitochondrial dysfunction and associates with the phosphorylation of p38 MAP kinase and the inhibition of survivin in the human breast cancer.

Homeostatic generation of reactive oxygen species protects the zebrafish liver from steatosis

Nonalcoholic fatty liver disease is the most common liver disease in both adults and children. The earliest stage of this disease is hepatic steatosis, in which triglycerides are deposited as cytoplasmic lipid droplets in hepatocytes. Through a forward genetic approach in zebrafish, we found that guanosine monophosphate (GMP) synthetase mutant larvae develop hepatic steatosis. We further demonstrate that activity of the small GTPase Rac1 and Rac1-mediated production of reactive oxygen species (ROS) are down-regulated in GMP synthetase mutant larvae. Inhibition of Rac1 activity or ROS production in wild-type larvae by small molecule inhibitors was sufficient to induce hepatic steatosis. More conclusively, treating larvae with hydrogen peroxide, a diffusible ROS that has been implicated as a signaling molecule, alleviated hepatic steatosis in both GMP synthetase mutant and Rac1 inhibitor-treated larvae, indicating that homeostatic production of ROS is required to prevent hepatic steatosis. We further found that ROS positively regulate the expression of the triglyceride hydrolase gene, which is responsible for the mobilization of stored triglycerides in hepatocytes. Consistently, inhibition of triglyceride hydrolase activity in wild-type larvae by a small molecule inhibitor was sufficient to induce hepatic steatosis.

CONCLUSION

De novo GMP synthesis influences the activation of the small GTPase Rac1, which controls hepatic lipid dynamics through ROS-mediated regulation of triglyceride hydrolase expression in hepatocytes.

Nox enzymes and new thinking on reactive oxygen: a double-edged sword revisited

Reactive oxygen species (ROS) are a chemical class of molecules that have generally been conceptualized as deleterious entities, albeit ones whose destructive properties could be harnessed as antimicrobial effector functions to benefit the whole organism. This appealingly simplistic notion has been turned on its head in recent years with the discovery of the NADPH oxidases, or Noxes, a family of enzymes dedicated to the production of ROS in a variety of cells and tissues. The Nox-dependent, physiological generation of ROS is highly conserved across virtually all multicellular life, often as a generalized response to microbes and/or other exogenous stressors. This review discusses the current knowledge of the role of physiologically generated ROS and the enzymes that form them in both normal biology and disease.

Involvement of reactive oxygen species in PTTH-stimulated ecdysteroidogenesis in prothoracic glands of the silkworm, Bombyx mori

In the present study, the possible involvement of reactive oxygen species (ROS) in prothoracicotropic hormone (PTTH)-stimulated ecdysteroidogenesis of Bombyx mori prothoracic glands (PGs) was investigated. Results showed that PTTH treatment resulted in a rapidly transient increase in the intracellular ROS concentration, as measured using 2',7'-dichlorofluorescin diacetate (DCFDA), an oxidation-sensitive fluorescent probe. The antioxidant, N-acetylcysteine (NAC), abolished PTTH-induced increase in fluorescence. Furthermore, PTTH-induced ROS production was partially inhibited by the NAD(P)H oxidase inhibitor, apocynin, indicating that NAD(P)H oxidase is one of the sources for PTTH-stimulated ROS production. Four mitochondrial oxidative phosphorylation inhibitors (rotenone, antimycin A, the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP), and diphenylene iodonium (DPI)) significantly attenuated ROS production induced by PTTH. These data suggest that the activity of complexes I and III in the electron transport chain and the mitochondrial inner membrane potential (ΔΨ) contribute to PTTH-stimulated ROS production. In addition, PTTH-stimulated ecdysteroidogenesis was greatly inhibited by treatment with either NAC or mitochondrial inhibitors (rotenone, antimycin A, FCCP, and DPI), but not with apocynin. These results indicate that mitochondria-derived, but not membrane NAD(P)H oxidase-mediated ROS signaling, is involved in PTTH-stimulated ecdysteroidogenesis of PGs in B. mori.

Oxidative stress-induced cyclin D1 depletion and its role in cell cycle processing

BACKGROUND

Cyclin D1 is immediately down-regulated in response to reactive oxygen species (ROS) and implicated in the induction of cell cycle arrest in G2 phase by an unknown mechanism. Either treatment with a protease inhibitor alone or expression of protease-resistant cyclin D1 T286A resulted in only a partial relief from the ROS-induced cell cycle arrest, indicating the presence of an additional control mechanism.

METHODS

Cells were exposed to hydrogen peroxide (H2O2), and analyzed to assess the changes in cyclin D1 level and its effects on cell cycle processing by kinase assay, de novo synthesis, gene silencing, and polysomal analysis, etc.

RESULTS

Exposure of cells to excessive H2O2 induced ubiquitin-dependent proteasomal degradation of cyclin D1, which was subsequently followed by translational repression. This dual control mechanism was found to contribute to the induction of cell cycle arrest in G2 phase under oxidative stress. Silencing of an eIF2α kinase PERK significantly retarded cyclin D1 depletion, and contributed largely to rescuing cells from G2 arrest. Also the cyclin D1 level was found to be correlated with Chk1 activity.

CONCLUSIONS

In addition to an immediate removal of the pre-existing cyclin D1 under oxidative stress, the following translational repression appear to be required for ensuring full depletion of cyclin D1 and cell cycle arrest. Oxidative stress-induced cyclin D1 depletion is linked to the regulation of G2/M transit via the Chk1-Cdc2 DNA damage checkpoint pathway.

GENERAL SIGNIFICANCE

The control of cyclin D1 is a gate keeping program to protect cells from severe oxidative damages.

Proteomic profiling and interactome analysis of ER-positive/HER2/neu negative invasive ductal carcinoma of the breast: towards proteomics biomarkers

Breast cancer, especially ER positive/HER2/neu negative IDC, is the predominant subtype of invasive ductal carcinoma. Although proteomic approaches have been used towards biomarker discovery in clinical breast cancer, ER positive/HER2/neu negative IDC is the least studied subtype. To discover biomarkers, as well as to understand the molecular events associated with disease progression of estrogen receptor positive/HER2/neu negative subtype of invasive ductal carcinoma, differential protein expression profiling was performed by using LC-MS(E) (MS at elevated energy). A total of 118 proteins were identified, of which 26 were differentially expressed. These identified proteins were functionally classified and their interactions and coexpression were analyzed by using bioinformatic tools PANTHER (Protein Analysis THrough Evolutionary Relationships) and STRING (Search Tool for the Retrieval of Interacting Genes). These proteins were found to be upregulated and were involved in cytoskeletal organization, calcium binding, and stress response. Interactions of annexin A5, actin, S100 A10, glyceraldehyde 3 phosphate dehydrogenase, superoxide dismutase 1, apolipoprotein, fibrinogen, and heat shock proteins were prominent. Differential expression of these proteins was validated by two-dimensional gel electrophoresis and Western blot analysis. The cluster of these proteins may serve as a signature profile for estrogen receptor positive/ HER2/neu negative subtype.

Principles in redox signaling: from chemistry to functional significance

Reactive oxygen and nitrogen species are currently considered not only harmful byproducts of aerobic respiration but also critical mediators of redox signaling. The molecules and the chemical principles sustaining the network of cellular redox regulated processes are described. Special emphasis is placed on hydrogen peroxide (H(2)O(2)), now considered as acting as a second messenger, and on sulfhydryl groups, which are the direct targets of the oxidant signal. Cysteine residues of some proteins, therefore, act as sensors of redox conditions and are oxidized in a reversible reaction. In particular, the formation of sulfenic acid and disulfide, the initial steps of thiol oxidation, are described in detail. The many cell pathways involved in reactive oxygen species formation are reported. Central to redox signaling processes are the glutathione and thioredoxin systems controlling H(2)O(2) levels and, hence, the thiol/disulfide balance. Lastly, some of the most important redox-regulated processes involving specific enzymes and organelles are described. The redox signaling area of research is rapidly expanding, and future work will examine new pathways and clarify their importance in cellular pathophysiology.

Nutritional supplements and plasma antioxidants in childhood asthma

OBJECTIVE

This study investigated the relationship of plasma antioxidants to airway inflammation and systemic oxidative stress in children suffering from atopic asthma with consideration of the intake of nutritional supplements.

SUBJECTS AND RESEARCH METHODS

A total of 35 asthmatic children (AG) and 21 healthy controls (CG) participated in this study. Plasma levels of vitamins A and E, β-carotene, coenzyme Q10 and malondialdehyde (MDA) were analyzed with high-performance liquid chromatography (HPLC); the total antioxidant capacity (TAC) was measured photometrically, and selenium was determined by atomic absorption spectroscopy (AAS). The volume of fractionated exhaled nitric oxide (FeNO) was measured with the NIOX nitric oxide monitoring system.

RESULTS

The plasma antioxidants vitamins A and E, selenium, and coenzyme Q10 but not β-carotene were significantly (p < 0.05) lower in asthmatics than in controls. Further, asthmatic children had significantly reduced plasma concentrations of TAC (p < 0.01), significantly enhanced levels of MDA (p < 0.001), and exhaled a significantly (p < 0.001) higher mean volume of FENO than healthy children. Regular intake of supplements had a significant positive influence on plasma vitamin E (p < 0.01), selenium (p < 0.01), TAC (p < 0.05), MDA (p < 0.01), and FENO (p < 0.01) in asthmatics but not in controls. Additionally, significant negative associations of vitamin E and MDA (AG: p < 0.01; CG: p < 0.05), and vitamin E and FENO (AG: p < 0.05; CG: p > 0.05) were identified.

CONCLUSION

These results indicate that nutritional supplements beneficially modulate plasma antioxidants and thus might have a positive influence on systemic redox balance and subsequently, pulmonary inflammation in asthmatic children.

Achieving the balance between ROS and antioxidants: when to use the synthetic antioxidants

Free radical damage is linked to formation of many degenerative diseases, including cancer, cardiovascular disease, cataracts, and aging. Excessive reactive oxygen species (ROS) formation can induce oxidative stress, leading to cell damage that can culminate in cell death. Therefore, cells have antioxidant networks to scavenge excessively produced ROS. The balance between the production and scavenging of ROS leads to homeostasis in general; however, the balance is somehow shifted towards the formation of free radicals, which results in accumulated cell damage in time. Antioxidants can attenuate the damaging effects of ROS in vitro and delay many events that contribute to cellular aging. The use of multivitamin/mineral supplements (MVMs) has grown rapidly over the past decades. Some recent studies demonstrated no effect of antioxidant therapy; sometimes the intake of antioxidants even increased mortality. Oxidative stress is damaging and beneficial for the organism, as some ROS are signaling molecules in cellular signaling pathways. Lowering the levels of oxidative stress by antioxidant supplements is not beneficial in such cases. The balance between ROS and antioxidants is optimal, as both extremes, oxidative and antioxidative stress, are damaging. Therefore, there is a need for accurate determination of individual's oxidative stress levels before prescribing the supplement antioxidants.

Physiological roles of mitochondrial reactive oxygen species

Historically, mitochondrial reactive oxygen species (mROS) were thought to exclusively cause cellular damage and lack a physiological function. Accumulation of ROS and oxidative damage have been linked to multiple pathologies, including neurodegenerative diseases, diabetes, cancer, and premature aging. Thus, mROS were originally envisioned as a necessary evil of oxidative metabolism, a product of an imperfect system. Yet few biological systems possess such flagrant imperfections, thanks to the persistent optimization of evolution, and it appears that oxidative metabolism is no different. More and more evidence suggests that mROS are critical for healthy cell function. In this Review, we discuss this evidence following some background on the generation and regulation of mROS.

Oxidative stress and the antioxidant enzyme system in the developing brain

Preterm infants are vulnerable to the oxidative stress due to the production of large amounts of free radicals, antioxidant system insufficiency, and immature oligodendroglial cells. Reactive oxygen species (ROS) play a pivotal role in the development of periventricular leukomalacia. The three most common ROS are superoxide (O2^•-), hydroxyl radical (OH^•), and hydrogen peroxide (H₂O₂). Under normal physiological conditions, a balance is maintained between the production of ROS and the capacity of the antioxidant enzyme system. However, if this balance breaks down, ROS can exert toxic effects. Superoxide dismutase, glutathione peroxidase, and catalase are considered the classical antioxidant enzymes. A recently discovered antioxidant enzyme family, peroxiredoxin (Prdx), is also an important scavenger of free radicals. Prdx1 expression is induced at birth, whereas Prdx2 is constitutively expressed, and Prdx6 expression is consistent with the classical antioxidant enzymes. Several antioxidant substances have been studied as potential therapeutic agents; however, further preclinical and clinical studies are required before allowing clinical application.

Low electric fields induce ligand-independent activation of EGF receptor and ERK via electrochemical elevation of H(+) and ROS concentrations

Physiological electric fields are involved in many biological processes and known to elicit their effects during long exposures ranging from a few hours to days. Following exposure to electric fields of physiological amplitude, epidermal growth factor receptor (EGFR) was demonstrated to be redistributed and upregulated with further intracellular signaling such as the MAPK signaling cascade. In our study we demonstrated EGFR activation and signaling induced by short train of pulsed low electric field (LEF) (10V/cm, pulse-width 180μs, 500Hz, 2min) in serum-free medium, following 24-hour starvation, and in the absence of exogenous EGF ligand, suggesting a ligand-independent pathway for EGFR activation. This ligandless activation was further confirmed by using neutralizing antibodies (LA1) that block the EGFR ligand-binding site. EGFR activation was found to be EGFR kinase dependent, yet with no dimerization following exposure to LEF. ERK activation was found to be mainly a result of EGFR downstream signaling though it partially occurred via EGFR-independent way. We demonstrate that reactive oxygen species and especially decrease in pH generated during exposure to LEF are involved in EGFR ligandless activation. We propose a possible mechanism for the LEF-induced EGFR ligand-independent activation and show activation of other receptor tyrosine kinases following exposure to LEF.

Protective effect of montelukast which is cysteinyl-leukotriene receptor antagonist on gentamicin-induced nephrotoxicity and oxidative damage in rat kidney

Nephrotoxicity is a major complication of gentamicin (GEN). We aimed to evaluate the potential protective effect of montelukast (MK) against GEN-induced nephrotoxicity in rats. Thirty-two rats were randomly divided into four groups, each consisting of eight animals as follows: (1) the rats were control; (2) intraperitoneally injected with GEN 14 consecutive days (100 mg/kg/day); (3) treated with GEN plus distilled water via nasogastric gavage for 14 days; and (4) treated with GEN plus MK (10 mg/kg/day) for 14 days. After 15 days, rats were killed and their kidneys were taken and blood analysis was performed. Twenty-four hours urine collections were obtained in standard metabolic cages a day before the rats were killed. Tubular necrosis and interstitial fibrosis scoring were determined histopathologically in a part of kidneys; nitric oxide (NO), malondialdehyde (MDA), and reduced glutathione (GSH) levels were determined in the other part of kidneys. Statistical analyses were made by the chi-square test and analysis of variance. Serum urea and creatinine levels were significantly higher in rats treated with GEN alone, than the rats in control and GEN + MK groups.The GSH levels in renal tissue of only GEN-treated rats were significantly lower than those in control group, and administration of MK to GEN-treated rats significantly increased the level of GSH. The group that was given GEN and MK had significantly lower MDA and NO levels in kidney cortex tissue than those that was given GEN alone. In rats treated with GEN + MK, despite the presence of mild tubular degeneration and tubular necrosis are less severe, and glomeruli maintained a better morphology when compared with GEN group. We can say that MK prevents kidney damage with antioxidant effect, independently of NO.

Putative role of proteins involved in detoxification of reactive oxygen species in the early response to gravitropic stimulation of poplar stems

Gravity perception and gravitropic response are essential for plant development. In herbaceous species it is widely accepted that one of the primary events in gravity perception involves the displacement of amyloplasts within specialized cells. However the signaling cascade leading to stem reorientation is not fully known especially in woody species in which primary and secondary growth occur. Several different second messengers and proteins have been suggested to be involved in signal transduction of gravitropism. Reactive oxygen species (ROS) have been implicated as second messengers in several plant hormone responses. It has been shown that ROS are asymmetrically generated in roots by gravistimulation to regions of reduced growth. Proteins involved in detoxification of ROS and defense were identified by mass spectrometry: i.e., Thioredoxin h (Trx h), CuZn superoxide dismutase (CuZn SOD), ascorbate peroxidase (APX2), oxygen evolving enhancer 1 (OEE1), oxygen evolving enhancer 2 (OEE2), and ATP synthase. These differentially accumulated proteins that correspond to detoxification of ROS were analyzed at the mRNA level. The mRNA levels showed different expression patterns than those of the corresponding proteins, and revealed that transcription levels were not completely concomitant with translation. Our data showed that these proteins may play a role in the early response to gravitropic stimulation.

The effects of vitamin d on gentamicin-induced acute kidney injury in experimental rat model

Introduction. Acute kidney injury (AKI) pathogenesis is complex. Findings of gentamicin nephrotoxicity are seen in 30% of the AKI patients. Vitamin D has proven to be effective on renin expression, inflammatory response, oxidative stress, apoptosis, and atherosclerosis. We aimed to investigate the effect of vitamin D in an experimental rat model of gentamicin-induced AKI. Methods. Thirty nonuremic Wistar albino rats were divided into 3 groups: Control group, 1 mL saline intramuscular (im) daily; Genta group, gentamicin 100 mg/kg/day (im); Genta + vitamin D, gentamicin 100 mg/kg/day (im) in addition to 1 α , 25 (OH)2D3 0.4 mcg/kg/day subcutaneously for 8 days. Blood pressures and 24-hour urine were measured. Blood urea and creatinine levels and urine tubular injury markers were measured. Renal histology was semiquantitatively assessed. Results. Urea, creatinine and urine neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1 were all increased in Genta group indicating AKI model. Systolic blood pressure decreased, but urine volume and glutathione increased in Genta + Vit D group compared to Control group. Histological scores indicating tubular injury increased in Genta and Genta + Vit D groups. Conclusions. Vitamin D does not seem to be effective on histological findings although it has some beneficial effects via RAS system and a promising effect on antioxidant system.

Hace1 controls ROS generation of vertebrate Rac1-dependent NADPH oxidase complexes

The Hace1-HECT E3 ligase is a tumor suppressor that ubiquitylates the activated GTP-bound form of the Rho family GTPase Rac1, leading to Rac1 proteasomal degradation. Here we show that, in vertebrates, Hace1 targets Rac1 for degradation when Rac1 is localized to the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase holoenzyme. This event blocks de novo reactive oxygen species generation by Rac1-dependent NADPH oxidases, and thereby confers cellular protection from reactive oxygen species-induced DNA damage and cyclin D1-driven hyper-proliferation. Genetic inactivation of Hace1 in mice or zebrafish, as well as Hace1 loss in human tumor cell lines or primary murine or human tumors, leads to chronic NADPH oxidase-dependent reactive oxygen species elevation, DNA damage responses and enhanced cyclin D1 expression. Our data reveal a conserved ubiquitin-dependent molecular mechanism that controls the activity of Rac1-dependent NADPH oxidase complexes, and thus constitutes the first known example of a tumor suppressor protein that directly regulates reactive oxygen species production in vertebrates.

Activation of Stat3 in endothelial cells following hypoxia-reoxygenation is mediated by Rac1 and protein Kinase C

Stat3 is an important transcription factor that regulates both proinflammatory and anit-apoptotic pathways in the heart. This study examined the mechanisms of activation of Stat3 in human endothelial cells following hypoxia/reoxygenation (H/R). By expression of constitutively active Rac1 mutant protein, and by RNA silencing of Rac1, we found that Stat3 forms a multiprotein complex with Rac1 and PKC in an H/R-dependent manner, which at least in part, appears to regulate Stat3 S727 phosphorylation. Selective inhibition of PKC with calphostin C produces a marked suppression of Stat3 S727 phosphorylation. The association of Stat3 with Rax1 occurs predominantly at the cell membrane, but also inside the nucleus, and occurs through the binding of the coiled-coil domain of Stat3 to the 54 NH(2)-terminal residues of Rac1. Transfection with a peptide comprising the NH(2)-terminal 17 amino acid residues of Rac1-dependent signaling pathways resulting in physical association between Rac1 and Stat3 and the formation of a novel multiprotein complex with PKC.

An inverse-Warburg effect and the origin of Alzheimer's disease

Glycolysis and oxidative phosphorylation (OxPhos) are the two major mechanisms involved in brain energetics. In this article we propose that the sporadic forms of Alzheimer's disease (AD) are driven by age-related damage to macromolecules and organelles which results in the following series of dynamic processes. (1) Metabolic alteration: Upregulation of OxPhos activity by dysfunctional neurons. (2) Natural selection: Competition for the limited energy substrates between neurons with normal OxPhos activity [Type (1)] and dysfunctional neurons with increased OxPhos [Type (2)]. (3) Propagation, due to the fact that Type (1) neurons are outcompeted for limited substrate by Type (2) neurons which, because of increased ROS production, eventually become dysfunctional and die. Otto Warburg, in his studies of the origin of cancer, discovered that most cancer cells are characterized by an increase in glycolytic activity-a property which confers a selective advantage in oncologic environments. Accordingly, we propose the term "inverse-Warburg effect" to describe increased OxPhos activity--a property which we propose confers a selective advantage in neuronal environments, and which we hypothesize to underlie the shift from normal to pathological aging and subsequent AD.

Consumption of water containing a high concentration of molecular hydrogen reduces oxidative stress and disease activity in patients with rheumatoid arthritis: an open-label pilot study

BACKGROUND

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by the destruction of bone and cartilage. Although its etiology is unknown, the hydroxyl radical has been suggested to be involved in the pathogenesis of RA. Recently, molecular hydrogen (H2) was demonstrated to be a selective scavenger for the hydroxyl radical. Also, the method to prepare water containing extremely high concentration of H2 has been developed. We hypothesized that H2 in the water could complement conventional therapy by reducing the oxidative stress in RA.

METHODS

Twenty patients with rheumatoid arthritis (RA) drank 530 ml of water containing 4 to 5 ppm molecular hydrogen (high H2 water) every day for 4 weeks. After a 4-week wash-out period, the patients drank the high H2 water for another 4 weeks. Urinary 8-hydroxydeoxyguanine (8-OHdG) and disease activity (DAS28, using C-reactive protein [CRP] levels) was estimated at the end of each 4-week period.

RESULTS

Drinking high H2 water seems to raise the concentration of H2 more than the H2 saturated (1.6 ppm) water in vivo. Urinary 8-OHdG was significantly reduced by 14.3% (p < 0.01) on average. DAS28 also decreased from 3.83 to 3.02 (p < 0.01) during the same period. After the wash-out period, both the urinary 8-OHdG and the mean DAS28 decreased, compared to the end of the drinking period. During the second drinking period, the mean DAS28 was reduced from 2.83 to 2.26 (p < 0.01). Urinary 8-OHdG was not further reduced but remained below the baseline value. All the 5 patients with early RA (duration < 12 months) who did not show antibodies against cyclic citrullinated peptides (ACPAs) achieved remission, and 4 of them became symptom-free at the end of the study.

CONCLUSIONS

The results suggest that the hydroxyl radical scavenger H2 effectively reduces oxidative stress in patients with this condition. The symptoms of RA were significantly improved with high H2 water.

MAP17, a ROS-dependent oncogene

MAP17 is a small 17 kDa non-glycosylated membrane protein previously identified as being overexpressed in carcinomas. Breast tumor cells that overexpress MAP17 show an increased tumoral phenotype with enhanced proliferative capabilities both in the presence or the absence of contact inhibition, decreased apoptotic sensitivity, and increased migration. MAP17-expressing clones also grow better in nude mice. The increased malignant cell behavior induced by MAP17 is associated with an increase in reactive oxygen species (ROS) production, and the treatment of MAP17-expressing cells with antioxidants results in a reduction in the tumorigenic properties of these cells. The MAP17-dependent increase in ROS and tumorigenesis relies on its PDZ-binding domain because disruption of this sequence by point mutations abolishes the ability of MAP17 to enhance ROS production and tumorigenesis. MAP17 is overexpressed in a great variety of human carcinomas, including breast tumors. Immunohistochemical analysis of MAP17 during cancer progression demonstrates that overexpression of the protein strongly correlates with tumoral progression. Generalized MAP17 overexpression in human carcinomas indicates that MAP17 can be a good marker for tumorigenesis and, especially, for malignant progression.

Controlling subcellular delivery to optimize therapeutic effect

This article focuses on drug targeting to specific cellular organelles for therapeutic purposes. Drugs can be delivered to all major organelles of the cell (cytosol, endosome/lysosome, nucleus, nucleolus, mitochondria, endoplasmic reticulum, Golgi apparatus, peroxisomes and proteasomes) where they exert specific effects in those particular subcellular compartments. Delivery can be achieved by chemical (e.g., polymeric) or biological (e.g., signal sequences) means. Unidirectional targeting to individual organelles has proven to be immensely successful for drug therapy. Newer technologies that accommodate multiple signals (e.g., protein switch and virus-like delivery systems) mimic nature and allow for a more sophisticated approach to drug delivery. Harnessing different methods of targeting multiple organelles in a cell will lead to better drug delivery and improvements in disease therapy.

Control of redox potential in hybridoma cultures: effects on MAb production, metabolism, and apoptosis

Culture redox potential (CRP) has proven to be a valuable monitoring tool in several areas of biotechnology; however, it has been scarcely used in animal cell culture. In this work, a proportional feedback control was employed, for the first time, to maintain the CRP at different constant values in hybridoma batch cultures for production of a monoclonal antibody (MAb). Reducing and oxidant conditions, in the range of −130 and +70 mV, were maintained in 1-l bioreactors through automatic control of the inlet gas composition. Cultures at constant DOT, in the range of 3 and 300 %, were used for comparison. The effect of constant CRP on cell concentration, MAb production, metabolism of glucose, glutamine, thiols, oxygen consumption, and programmed cell death, was evaluated. Reducing conditions resulted in the highest viable cell and MAb concentrations and thiols production, whereas specific glucose and glutamine consumption rates remained at the lowest values. In such conditions, programmed cell death, particularly apoptosis, occurred only after nutrient exhaustion. The optimum specific MAb production rate occurred at intermediate CRP levels. Oxidant conditions resulted in a detrimental effect in all culture parameters, increasing the specific glucose, glutamine, and oxygen consumption rates and inducing the apoptotic process, which was detected as early as 24 h even when glutamine and glucose were present at non-limiting concentrations. In most cases, such results were similar to those obtained in control cultures at constant DOT.

Major metabolite of F2-isoprostane in urine may be a more sensitive biomarker of oxidative stress than isoprostane itself

BACKGROUND

There is limited literature on the contributors to isoprostane metabolite 2,3-dinor-5,6-dihydro-15-F(2t)-isoprostane (15-F(2t)-IsoP-M) compared with F(2)-isoprostanes (F(2)-IsoPs) as an oxidative stress biomarker.

OBJECTIVE

The objective of this study was to investigate whether plasma concentrations of antioxidants, urinary excretion rates of polyphenols, and antioxidants in food and dietary supplements are attributable to both urinary F(2)-IsoP and 15-F(2t)-IsoP-M concentrations.

DESIGN

Dietary intake information and blood and urine samples were obtained from 845 healthy middle-aged and elderly female participants of the Shanghai Women's Health Study. Urinary isoprostanes (F(2)-IsoPs and 15-F(2t)-IsoP-M) were measured and adjusted for creatinine concentrations.

RESULTS

Urinary 15-F(2t)-IsoP-M and F(2)-IsoP concentrations were lower in subjects who used a multivitamin. Lower F(2)-IsoP concentrations were observed in ginseng users, whereas lower concentrations of 15-F(2t)-IsoP-M were shown in subjects who used a vitamin E supplement. Plasma concentrations of several antioxidants (ie, β-carotenes, both trans and cis β-carotenes, lycopene other than trans, 5-cis and 7-cis isomers, cis anhydrolutein, and cis β-cryptoxanthin) were inversely associated with 15-F(2t)-IsoP-M but not with F(2)-IsoPs, whereas β-, γ-, and δ-tocopherols were positively associated with 15-F(2t)-IsoP-M but not with F(2)-IsoPs. Urinary polyphenol quercetin was positively associated with both F(2)-IsoPs and 15-F(2t)-IsoP-M.

CONCLUSION

The results suggest that the F(2)-IsoP major metabolite 15-F(2t)-IsoP-M may be a more sensitive marker of endogenous oxidative stress status than are F(2)-IsoPs in the assessment of effects of antioxidants on age-related diseases.

Protein modification as oxidative stress marker in normal and pathological human seminal plasma

OBJECTIVE

Our study aims to assess the oxidative stress status of seminal plasma from normozoospermic, azoospermic, and leukocytospermic males, since abnormal sperm and leukocytes in human ejaculates are the main source of reactive oxygen species (ROS) which lead to oxidative damages. For this purpose we applied a biochemical approach to the assessment of the oxidative stress status by using two-dimensional (2D) electrophoresis to check the level of protein oxidation after specific labeling of free thiol (-SH) groups.

METHODS

Seminal plasma samples from normal and pathological males were analyzed by a luminol-based chemiluminescent assay. The same samples after specific labeling of free -SH groups with 3-N-maleimidopropionyl biocytin, were analyzed by 2D electrophoresis and computer-assisted semiquantitative determination of the amount of free -SH groups.

RESULTS

Using a standard chemiluminescence assay, we demonstrated a high, low and normal level of ROS, respectively, in seminal plasma from leukocytospermic, azoospermic, and normozoospermic subjects. By 2D electrophoresis and streptavidin blotting of specifically labeled free -SH groups of proteins, we detected in the same samples a higher level of oxidated -SH groups comparable between azoospermic and leukocytospermic samples, whereas a significantly higher level of free -SH groups was detected in normozoospermic subjects.

DISCUSSION

Our results demonstrated that a pathological oxidative stress status in seminal plasma may be revealed by the levels of the protein free -SH groups, both in the presence or absence of cells.

Effects of dihydropyridine calcium channel blockers on oxidized low-density lipoprotein induced proliferation and oxidative stress of vascular smooth muscle cells

Background

Dihydropyridine calcium channel blockers (CCBs) are more effective in reducing carotid intima-media thickness (IMT) than other classes of antihypertensive drugs due to their vascular effects. However, the mechanism remains to be elucidated.

Findings

Ox-LDL induced HUVSMCs proliferation in a time- and dose-dependent manner. When pretreated with three CCBs before 50 μg/ml ox-LDL stimulation, 30 μM lacidipine and 3 μM amlodipine exhibited 27% and 18% decrease of pro-proliferative effect induced by ox-LDL, whereas (S-)-amlodipine did not have any anti-proliferative effect. 30 μM lacidipine inhibited about two-thirds of the ox-LDL induced ROS production in HUVSMCs, whereas amlodipine and (S-)-amlodipine did not have influence on ROS production. The MAPKs pathway inhibitors inhibited the ox-LDL induced proliferation of HUVSMCs.

Conclusion

Our study has demonstrated that lipophilic CCBs, such as lacidipine may inhibit ox-LDL induced proliferation and oxidative stress of VSMCs, and that the ROS-MAPKs pathway might be involved in the mechanism.

A hypothesis on chemical mechanism of the effect of hydrogen

Many studies have shown that hydrogen can play important roles on the antioxidant, anti-inflammatory and other protective effects. Ohsawa et al have proved that hydrogen can electively and directly scavenge hydroxyl radical. But this mechanism cannot explain more new experimental results. In this article, the hypothesis, which is inspired by H2 could bind to the metal as a ligand, come up to explain its extensive biology effect: Hydrogen could regulate particular metalloproteins by bonding (M-H2 interaction) it. And then it could affect the metabolization of ROS and signal transduction. Metalloproteins may be ones of the target molecules of H2 action. Metal ions may be appropriate role sites for H2 molecules. The hypothesis pointed out a new direction to clarify its mechanisms.

Lack of p53 decreases basal oxidative stress levels in the brain through upregulation of thioredoxin-1, biliverdin reductase-A, manganese superoxide dismutase, and nuclear factor kappa-B

AIMS

The basal oxidative and nitrosative stress levels measured in cytosol, mitochondria, and nuclei as well as in the whole homogenate obtained from the brain of wild type (wt) and p53 knockout [p53((-/-))] mice were evaluated. We hypothesized that the loss of p53 could trigger the activation of several protective mechanisms such as those involving thioredoxin-1 (Thio-1), the heme-oxygenase-1/biliverdin reductase-A (HO-1/BVR-A) system, manganese superoxide dismutase (MnSOD), the IkB kinase type β (IKKβ)/nuclear factor kappa-B (NF-kB), and the nuclear factor-erythroid 2 (NF-E2) related factor 2 (Nrf-2).

RESULTS

A decrease of protein carbonyls, protein-bound 4-hydroxy-2-nonenal (HNE), and 3-nitrotyrosine (3-NT) was observed in the brain from p53((-/-)) mice compared with wt. Furthermore, we observed a significant increase of the expression levels of Thio-1, BVR-A, MnSOD, IKKβ, and NF-kB. Conversely a significant decrease of Nrf-2 protein levels was observed in the nuclear fraction isolated from p53((-/-)) mice. No changes were found for HO-1.

INNOVATION

This is the first study of basal oxidative/nitrosative stress in in vivo conditions of brain obtained from p53((-/-)) mice. New insights into the role of p53 in oxidative stress have been gained.

CONCLUSION

We demonstrated, for the first time, that the lack of p53 reduces basal oxidative stress levels in mice brain. Due to the pivotal role that p53 plays during cellular stress response our results provide new insights into novel therapeutic strategies to modulate protein oxidation and lipid peroxidation having p53 as a target. The implications of this work are profound, particularly for neurodegenerative disorders.

Methods to monitor classical protein-tyrosine phosphatase oxidation

Reactive oxygen species (ROS), particularly hydrogen peroxide (H(2)O(2)), act as intracellular second messengers in many signaling pathways. Protein-tyrosine phosphatases (PTPs) are now believed to be important targets of ROS. PTPs contain a conserved catalytic cysteine with an unusually low pK(a). This property allows PTPs to execute nucleophilic attack on substrate phosphotyrosyl residues, but also renders them highly susceptible to oxidation. Reversible oxidation, which inactivates PTPs, is emerging as an important cellular regulatory mechanism and might contribute to human diseases, including cancer. Given their potential toxicity, it seems likely that ROS generation is highly controlled within cells to restrict oxidation to those PTPs that must be inactivated for signaling to proceed. Thus, identifying ROS-inactivated PTPs could be tantamount to finding the PTP(s) that critically regulate a specific signaling pathway. This article provides an overview of the methods currently available to identify and quantify PTP oxidation and outlines future challenges in redox signaling.

Cytoprotective effect of trolox against oxidative damage and apoptosis in the NRK-52e cells induced by melamine

An outbreak of urinary stones associated with consumption of melamine-tainted milk products occurred in 2008 in China, leading to serious illness of many infants and even death. However, the toxicity of melamine in kidney epithelial cells remains unclear. We have explored the effects of melamine and trolox on renal NRK-52e (normal rat kidney 52e) cells. The IC(50) of melamine was measured by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] assay. Total SOD (superoxide dismutase) was determined by NBT (Nitro Blue Tetrazolium) staining method. GSH-Px (glutathione peroxidase) activity was detected by UV colorimetric assay, and MDA (malondialdehyde) content was determined by thiobarbituric acid assay. Apoptosis induced by melamine was determined by flow cytometry. The IC(50) increased when NRK-52e cells were treated with both melamine and trolox compared with melamine only. SOD and GSH-Px activities were decreased, but MDA content was increased by melamine in a dose-dependent manner. Trolox significantly enhanced SOD and GSH-Px activity in melamine-treated NRK-52e cells, but it decreased their MDA content. LDH (lactate dehydrogenase) activity and the level of ROS (reactive oxygen species) of the NRK-52e cells were enhanced by melamine compared with the control. Furthermore, the apoptosis rate increased in NRK-52e cells treated with melamine, whereas trolox was protective. These results show that melamine has an obvious adverse effect on proliferation of NRK-52e cells, causing oxidative damage and apoptosis, thus providing a novel insight into renal cytotoxicology of melamine. Trolox ameliorates the effect on melamine toxicity.

Exercise training prevents skeletal muscle afferent sensitization in rats with chronic heart failure

An exaggerated exercise pressor reflex (EPR) contributes to exercise intolerance and excessive sympathoexcitation in the chronic heart failure (CHF) state, which is prevented by exercise training (ExT) at an early stage in the development of CHF. We hypothesized that ExT has a beneficial effect on the exaggerated EPR by improving the dysfunction of muscle afferents in CHF. We recorded the discharge of mechanically sensitive (group III) and metabolically sensitive (group IV) afferents in response to static contraction, passive stretch, and hindlimb intra-arterial injection of capsaicin in sham+sedentary (Sed), sham+ExT, CHF+Sed, and CHF+ExT rats. Compared with sham+Sed rats, CHF+Sed rats exhibited greater responses of group III afferents to contraction and stretch, whereas the responses of group IV afferents to contraction and capsaicin were blunted. ExT prevented the sensitization of group III responses to contraction or stretch and partially prevented the blunted group IV responses to contraction or capsaicin in CHF rats. Furthermore, we investigated whether purinergic 2X (P2X) and transient receptor potential vanilloid 1 (TRPV1) receptors mediate the altered sensitivity of muscle afferents by ExT in CHF. We found that the upregulated P2X and downregulated TRPV1 receptors in L4/5 dorsal root ganglia of CHF rats were normalized by ExT. Hindlimb intra-arterial infusion of a P2X antagonist attenuated the group III response to contraction or stretch in CHF rats to a greater extent than in sham rats, which was normalized by ExT. These findings suggest that ExT improves the abnormal sensitization of muscle afferents in CHF at least, in part, via restoring the dysfunction of P2X and TRPV1 receptors.

MAP17 and the double-edged sword of ROS

Reactive oxygen species, ROS, are beneficially involved in many signaling pathways that control development and maintain cellular homeostasis. In physiological conditions, a tightly regulated redox balance protects cells from injurious ROS activity, but if the balance is altered, it promotes various pathological conditions including cancer. Understanding the duality of ROS as cytotoxic molecules and key mediators in signaling cascades may provide novel opportunities for improved cancer therapy. MAP17 is a small 17-kDa non-glycosylated membrane protein that is overexpressed in many tumors of different origins, including carcinomas. Immunohistochemical analysis of MAP17 during cancer progression demonstrates that overexpression of the protein strongly correlates with the progression of most types of tumor. Tumor cells that overexpress MAP17 show an increased tumoral phenotype associated with an increase in ROS. However, in non-tumor cells MAP17 increases ROS, resulting in senescence or apoptosis. Therefore, in tumor cells, MAP17 could be a marker for increased oxidative stress and could define new therapeutic approaches. Here, we review the role of MAP17 as a putative oncogene, as well as its role in cancer and anticancer therapies.

Reactive oxygen species and epidermal growth factor are antagonistic cues controlling SHP-2 dimerization

The SHP-2 tyrosine phosphatase plays key regulatory roles in the modulation of the cell response to growth factors and cytokines. Over the past decade, the integration of genetic, biochemical, and structural data has helped in interpreting the pathological consequences of altered SHP-2 function. Using complementary approaches, we provide evidence here that endogenous SHP-2 can dimerize through the formation of disulfide bonds that may also involve the catalytic cysteine. We show that the fraction of dimeric SHP-2 is modulated by growth factor stimulation and by the cell redox state. Comparison of the phosphatase activities of the monomeric self-inhibited and dimeric forms indicated that the latter is 3-fold less active, thus pointing to the dimerization process as an additional mechanism for controlling SHP-2 activity. Remarkably, dimers formed by different SHP-2 mutants displaying diverse biochemical properties were found to respond differently to epidermal growth factor (EGF) stimulation. Although this differential behavior cannot be rationalized mechanistically yet, these findings suggest a possible regulatory role of dimerization in SHP-2 function.

Advanced glycation end-products induce injury to pancreatic beta cells through oxidative stress

AIM

This study evaluated the direct effects of advanced glycation end-products (AGEs) on pancreatic β cells, including cellular viability, generation of reactive oxygen species (ROS) and insulin secretion, and also looked for the main source of ROS in INS-1 cells and the possible molecular mechanism(s) of cell injury by AGEs.

METHODS

INS-1 cells were cultured with 100, 200 and 500 mg/L of AGEs for specific periods of time. Cell apoptosis was determined by ELISA and real-time PCR assays. ROS were detected by DCFH-DA and MitoSOX Red probes with a flow cytometer, NADPH oxidase activity was measured by lucigenin chemiluminescence and MAPK phosphorylation was measured by Western blot tests.

RESULTS

Both cell apoptosis and ROS generation increased in AGE-treated cells in a dose-dependent way, and both the mitochondrial electron transport chain and NADPH oxidase pathway participated in ROS generation, although the role of the mitochondrial pathway was earlier and more important. AGEs exerted a toxic effect on insulin secretion that could be largely reversed by inhibiting ROS.

CONCLUSION

AGEs injured INS-1 cells by oxidative stress mainly through the mitochondrial pathway, although the JNK and p38 MAPK signaling pathways were also key modulators in ROS-mediated β-cell death.

The modulatory influence of p-methoxycinnamic acid, an active rice bran phenolic acid, against 1,2-dimethylhydrazine-induced lipid peroxidation, antioxidant status and aberrant crypt foci in rat colon carcinogenesis

We investigated the chemopreventive effect of p-methoxycinnamic acid (p-MCA), an active phenolic acid of rice bran, turmeric, and Kaemperfia galanga against 1,2-dimethylhydrazine-induced rat colon carcinogenesis. Male albino Wistar rats were randomly divided into six groups. Group 1 consisted of control rats that received a modified pellet diet and 0.1% carboxymethyl cellulose. The rats in Group 2 received a modified pellet diet supplemented with p-MCA [80 mg/kg body weight (b.wt.) post-orally (p.o.)] everyday. The rats in Groups 3-6 received 1,2-dimethylhydrazine (DMH) (20 mg/kg b.wt.) via subcutaneous injections once a week for the first 4 weeks; additionally, the rats in Groups 4, 5 and 6 received p-MCA at doses of 20, 40 and 80 mg/kg b.wt./day p.o., respectively, everyday for 16 weeks. The rats were sacrificed at the end of the experimental period of 16 weeks. The DMH-treated rats exhibited an increased incidence of aberrant crypt foci (ACF) development; an increased crypt multiplicity; decreased concentrations of tissue lipid peroxidation markers such as thiobarbituric acid reactive substances (TBARS), conjugated dienes (CD) and lipid hydroperoxides (LOOH); decreased levels of tissue enzymic antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR); and decreased levels of non-enzymic antioxidants such as reduced glutathione (GSH) and vitamins C, E and A in the colon. Supplementation with p-MCA significantly reversed these changes and significantly inhibited the formation of ACF and its multiplicity. Thus, our findings demonstrate that p-MCA exerts a strong chemopreventive activity against 1,2-dimethylhydrazine-induced colon carcinogenesis by virtue of its ability to prevent the alterations in DMH-induced circulatory and tissue oxidative stress and preneoplastic changes. p-MCA was more effective when administered at a dose of 40 mg/kg b.wt. than at the other two doses tested.