Role of redox potential and reactive oxygen species in stress signaling

H2O2 signals via iron induction of VL30 retrotransposition correlated with cytotoxicity

The impact of oxidative stress on mobilization of endogenous retroviruses and their effects on cell fate is unknown. We investigated the action of H2O2 on retrotransposition of an EGFP-tagged mouse LTR-retrotransposon, VL30, in an NIH3T3 cell-retrotransposition assay. H2O2 treatment of assay cells caused specific retrotranspositions documented by UV microscopy and PCR analysis. Flow cytometric analysis revealed an unusually high dose- and time-dependent retrotransposition frequency induced, ∼420,000-fold at 40 μM H2O2 compared to the natural frequency, which was reduced by ectopic expression of catalase. Remarkably, H2O2 moderately induced the RNA expression of retrotransposon B2 without affecting the basal expression of VL30s and L1 and significantly induced the expression of various endogenous reverse transcriptase genes. Further, whereas treatment with 50 μM FeCl2 alone was ineffective, cotreatment with 10 μM H2O2 and 50 μM FeCl2 caused a 6-fold higher retrotransposition induction than H2O2 alone, which was associated with cytotoxicity. H2O2- or H2O2/FeCl2-induced retrotransposition was significantly reduced by the iron chelator DFO or the antioxidant NAC, respectively. Furthermore, both H2O2-induced retrotransposition and associated cytotoxicity were inhibited after pretreatment of cells with DFO or the reverse transcriptase inhibitors efavirenz and etravirine. Our data show for the first time that H2O2, acting via iron, is a potent stimulus of retrotransposition contributing to oxidative stress-induced cell damage.

15-Deoxy-Δ(12,14)-prostaglandin J(2) attenuates the biological activities of monocyte/macrophage cell lines

Monocytes/macrophages link the innate and adaptive immune systems, and in inflammatory disorders their activation leads to tissue damage. 15-Deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)), a natural peroxisome proliferator-activated receptor gamma (PPARγ) ligand, has garnered much interest because it possesses anti-inflammatory properties in a number of experimental models. However, whether it regulates monocytes/macrophage pathophysiology is still unknown. This study was designed to examine the effects of 15d-PGJ(2) on the phagocytosis, proliferation and inflammatory cytokines generation in mouse monocyte/macrophage cell line RAW264.7 and J774A.1 cells upon lipopolysaccharide challenge. Our results showed that 15d-PGJ(2) inhibited the phagocytic activity and cell proliferation in a dose-dependent manner, and suppressed proinflammatory cytokines expression, such as tumor necrosis factor-α, transforming growth factor-β1, interleukin-6, and monocyte chemotactic protein-1. These effects were independent of PPARγ, because PPARγ agonist (troglitazone or ciglitazone) and PPARγ antagonist (GW9662) did not affect these activities mentioned above in cells. Treatment of 15d-PGJ(2) also did not modulate expression and distribution of PPARγ. However, these effects of 15d-PGJ(2) were abrogated by antioxidant N-acetylcysteine. Moreover, treatment of 15d-PGJ(2) induced a significant increase in reactive oxygen species production in RAW264.7 and J774A.1 cells. In conclusion, 15d-PGJ(2) attenuates the biological activities of mouse monocyte/macrophage cell line cells involving oxidative stress, independently of PPARγ. These data further underline the anti-inflammation potential of 15d-PGJ(2).

Beneficial effect of (-)schisandrin B against 3-nitropropionic acid-induced cell death in PC12 cells

Huntington's disease (HD) is characterized by the dysfunction of mitochondrial energy metabolism, which is associated with the functional impairment of succinate dehydrogenase (mitochondrial complex II), and pyruvate dehydrogenase (PDH). Treatment with 3-nitropropionic acid (3-NP), a potent irreversible inhibitor of succinate dehydrogenase, replicates most of the pathophysiological features of HD. In the present study, we investigated the effect of (-)schisandrin B [(-)Sch B, a potent enantiomer of schisandrin B] on 3-NP-induced cell injury in rat differentiated neuronal PC12 cells. The 3-NP caused cell necrosis, as assessed by lactate dehydrogenase (LDH) leakage, and mitochondrion-dependent cell apoptosis, as assessed by caspase-3 and caspase-9 activation, in differentiated PC12 cells. The cytotoxicity induced by 3-NP was associated with a depletion of cellular reduced glutathione (GSH) as well as the activation of redox-sensitive c-Jun N-terminal kinase (JNK) pathway and the inhibition of PDH. (-)Sch B pretreatment (5 and 15 μM) significantly reduced the extent of necrotic and apoptotic cell death in 3-NP-challenged cells. The cytoprotection afforded by (-)Sch B pretreatment was associated with the attenuation of 3-NP-induced GSH depletion as well as JNK activation and PDH inhibition. (-)Sch B pretreatment enhanced cellular glutathione redox status and ameliorated the 3-NP-induced cellular energy crisis, presumably by suppressing the activated JNK-mediated PDH inhibition, thereby protecting against necrotic and apoptotic cell death in differentiated PC12 cells.

Uncaria rhynchophylla and Rhynchophylline Inhibit c-Jun N-Terminal Kinase Phosphorylation and Nuclear Factor-κB Activity in Kainic Acid-Treated Rats

Our previous studies have shown that Uncaria rhynchophylla (UR) can reduce epileptic seizures. We hypothesized that UR and its major component rhynchophylline (RH), reduce epileptic seizures in rats treated with kainic acid (KA) by inhibiting nuclear factor-κB (NF-κB) and activator-protein-1 (AP-1) activity, and by eliminating superoxide anions. Therefore, the level of superoxide anions and the DNA binding activities of NF-κB and AP-1 were measured. Sprague-Dawley (SD) rats were pre-treated with UR (1.0 g/kg, i.p.), RH (0.25 mg/kg, i.p.), or valproic acid (VA, 250 mg/kg, i.p.) for 3 days and then KA was administered intra-peritoneal (i.p.). The results indicated that UR, RH, and VA can reduce epileptic seizures and the level of superoxide anions in the blood. Furthermore, KA was demonstrated to induce the DNA binding activities of NF-κB and AP-1. However, these inductions were inhibited by pre-treatment with UR, RH, or VA for 3 days. Moreover, UR and RH were shown to be involved in the suppression of c-Jun N-terminal kinase (JNK) phosphorylation. This study suggested that UR and RH have antiepileptic effects in KA-induced seizures and are associated with the regulation of the innate immune system via a reduction in the level of superoxide anions, JNK phosphorylation, and NF-κB activation.

Repair of oxidative DNA damage is delayed in the Ser326Cys polymorphic variant of the base excision repair protein OGG1

Gene-environment interactions influence an individual's risk of disease development. A common human 8-oxoguanine DNA glycosylase 1 (OGG1) variant, Cys326-hOGG1, has been associated with increased cancer risk. Evidence suggests that this is due to reduced repair ability, particularly under oxidising conditions but the underlying mechanism is poorly understood. Oxidising conditions may arise due to internal cellular processes, such as inflammation or external chemical or radiation exposure. To investigate wild-type and variant OGG1 regulation and activity under oxidising conditions, we generated mOgg1 (-/-) null mouse embryonic fibroblasts cells stably expressing Ser326- and Cys326-hOGG1 and measured activity, gene expression, protein expression and localisation following treatment with the glutathione-depleting compound L-buthionine-S-sulfoximine (BSO). Assessment of OGG1 activity using a 7,8-dihydro-8-oxodeoxyguanine (8-oxo dG) containing molecular beacon demonstrated that the activity of both Ser326- and Cys326-hOGG1 was increased following oxidative treatment but with different kinetics. Peak activity of Ser326-hOGG1 occurred 12 h prior to that of Cys326-hOGG1. In both variants, the increased activity was not associated with any gene expression or protein increase or change in protein localisation. These findings suggest that up-regulation of OGG1 activity in response to BSO-induced oxidative stress is via post-transcriptional regulation and provide further evidence for impaired Cys326-hOGG1 repair ability under conditions of oxidative stress. This may have important implications for increased mutation frequency resulting from increased oxidative stress in individuals homozygous for the Cys326 hOGG1 allele.

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.

Acidic sphingomyelinase induced by electrophiles promotes proinflammatory cytokine production in human bladder carcinoma ECV-304 cells

Electrophiles in environmental pollutants or cigarette smoke are high risk factors for various diseases caused by cell injuries such as apoptosis and inflammation. Here we show that electrophilic compounds such as diethyl malate (DEM), methyl mercury and cigarette smoke extracts significantly enhanced the expression of acidic sphingomyelinase (ASMase). ASMase activity and the amount of ceramide of DEM-treated cells were approximately 6 times and 4 times higher than these of non-treated cells, respectively. Moreover, we found that DEM pretreatment enhanced the production of IL-6 induced by TNF-α. Knockdown of ASMase attenuated the enhancement of TNF-α-dependent IL-6 production. On the other hand, enhancement of TNF-α-induced IL-6 production was observed in ASMase-overexpressing cells without DEM. Fractionation of the lipid raft revealed that the TNF receptor 1 (TNFR1) was migrated into the lipid raft in DEM-treated cells or ASMase-overexpressing cells. The TNF-α-induced IL-6 expression required the clustering of TNFR1 since IL-6 expression were decreased by the destruction of the lipid raft with filipin. These results demonstrated a new role for ASMase in the acceleration of the production of TNF-induced IL-6 as a pro-inflammatory cytokine and indicated that electrophiles could potentiate inflammation response by up-regulating of ASMase expression following formation of lipid rafts.

Gu-4 suppresses affinity and avidity modulation of CD11b and improves the outcome of mice with endotoxemia and sepsis

Background

Systemic leukocyte activation and disseminated leukocyte adhesion will impair the microcirculation and cause severe decrements in tissue perfusion and organ function in the process of severe sepsis. Gu-4, a lactosyl derivative, could selectively target CD11b to exert therapeutic effect in a rat model of severe burn shock. Here, we addressed whether Gu-4 could render protective effects on septic animals.

Methodology/Principal Findings

On a murine model of endotoxemia induced by lipopolysaccharide (LPS), we found that the median effective dose (ED50) of Gu-4 was 0.929 mg/kg. In vivo treatment of Gu-4 after LPS challenge prominently attenuated LPS-induced lung injury and decreased lactic acid level in lung tissue. Using the ED50 of Gu-4, we also demonstrated that Gu-4 treatment significantly improved the survival rate of animals underwent sepsis induced by cecal ligation and puncture. By adhesion and transwell migration assays, we found that Gu-4 treatment inhibited the adhesion and transendothelial migration of LPS-stimulated THP-1 cells. By flow cytometry and microscopy, we demonstrated that Gu-4 treatment inhibited the exposure of active I-domain and the cluster formation of CD11b on the LPS-stimulated polymorphonuclear leukocytes. Western blot analyses further revealed that Gu-4 treatment markedly inhibited the activation of spleen tyrosine kinase in LPS-stimulated THP-1 cells.

Conclusions/Significance

Gu-4 improves the survival of mice underwent endotoxemia and sepsis, our in vitro investigations indicate that the possible underlying mechanism might involve the modulations of the affinity and avidity of CD11b on the leukocyte. Our findings shed light on the potential use of Gu-4, an interacting compound to CD11b, in the treatment of sepsis and septic shock.

Role of mitochondrial homeostasis and dynamics in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease that affects a staggering percentage of the aging population and causes memory loss and cognitive decline. Mitochondrial abnormalities can be observed systemically and in brains of patients suffering from AD, and may account for part of the disease phenotype. In this review, we summarize some of the key findings that indicate mitochondrial dysfunction is present in AD-affected subjects, including cytochrome oxidase deficiency, endophenotype data, and altered mitochondrial morphology. Special attention is given to recently described perturbations in mitochondrial autophagy, fission-fusion dynamics, and biogenesis. We also briefly discuss how mitochondrial dysfunction may influence amyloidosis in Alzheimer's disease, why mitochondria are a valid therapeutic target, and strategies for addressing AD-specific mitochondrial dysfunction.

Gestational restraint stress and the developing dopaminergic system: an overview

Prenatal stress exerts a strong impact on fetal brain development in rats impairing adaptation to stressful conditions, subsequent vulnerability to anxiety, altered sexual function, and enhanced propensity to self-administer drugs. Most of these alterations have been attributed to changes in the neurotransmitter dopamine (DA). In humans; dysfunction of dopaminergic system is associated with development of several neurological disorders, such as Parkinson disease, schizophrenia, attention-deficit hyperactivity disorder, and depression. Evidences provided by animal research, as well as retrospective studies in humans, pointed out that exposure to adverse events in early life can alter adult behaviors and neurochemical indicators of midbrain DA activity, suggesting that the development of the DA system is sensitive to disruption by exposure to early stressors. The purpose of this article is to provide a general overview of published studies and our own study related to the effect of prenatal insults on the development of DA metabolism and biology, focusing mainly in articles involving prenatal-restraint stress protocols in rats. We will also attempt to make a correlation between theses alterations and DA-related pathological processes in humans.

Protection from palmitate-induced mitochondrial DNA damage prevents from mitochondrial oxidative stress, mitochondrial dysfunction, apoptosis, and impaired insulin signaling in rat L6 skeletal muscle cells

Saturated free fatty acids have been implicated in the increase of oxidative stress, mitochondrial dysfunction, apoptosis, and insulin resistance seen in type 2 diabetes. The purpose of this study was to determine whether palmitate-induced mitochondrial DNA (mtDNA) damage contributed to increased oxidative stress, mitochondrial dysfunction, apoptosis, impaired insulin signaling, and reduced glucose uptake in skeletal muscle cells. Adenoviral vectors were used to deliver the DNA repair enzyme human 8-oxoguanine DNA glycosylase/(apurinic/apyrimidinic) lyase (hOGG1) to mitochondria in L6 myotubes. After palmitate exposure, we evaluated mtDNA damage, mitochondrial function, production of mitochondrial reactive oxygen species, apoptosis, insulin signaling pathways, and glucose uptake. Protection of mtDNA from palmitate-induced damage by overexpression of hOGG1 targeted to mitochondria significantly diminished palmitate-induced mitochondrial superoxide production, restored the decline in ATP levels, reduced activation of c-Jun N-terminal kinase (JNK) kinase, prevented cells from entering apoptosis, increased insulin-stimulated phosphorylation of serine-threonine kinase (Akt) (Ser473) and tyrosine phosphorylation of insulin receptor substrate-1, and thereby enhanced glucose transporter 4 translocation to plasma membrane, and restored insulin signaling. Addition of a specific inhibitor of JNK mimicked the effect of mitochondrial overexpression of hOGG1 and partially restored insulin sensitivity, thus confirming the involvement of mtDNA damage and subsequent increase of oxidative stress and JNK activation in insulin signaling in L6 myotubes. Our results are the first to report that mtDNA damage is the proximal cause in palmitate-induced mitochondrial dysfunction and impaired insulin signaling and provide strong evidence that targeting DNA repair enzymes into mitochondria in skeletal muscles could be a potential therapeutic treatment for insulin resistance.

Impact of oxidative stress on male fertility - a review

Oxidative stress is a state related to increased cellular damage caused by oxygen and oxygen-derived free radicals known as reactive oxygen species (ROS). It is a serious condition, as ROS and their metabolites attack DNA, lipids and proteins, alter enzymatic systems and cell signalling pathways, producing irreparable alterations, cell death and necrosis. While small amounts of ROS have been shown to be required for several functions of spermatozoa, their excessive levels can negatively impact the quality of spermatozoa and impair their overall fertilising capacity. These questions have recently attracted the attention of the scientific community; however, research aimed at exploring the role of oxidative stress and antioxidants associated with male fertility is still at its initial stages. This review summarises the current facts available in this field and intends to stimulate interest in basic and clinical research, especially in the development of effective methods for the diagnosis and therapy of semen damage caused by oxidative stress.

Regulation of reactive oxygen species generation in cell signaling

Reactive oxygen species (ROS) including superoxide anion and hydrogen peroxide (H(2)O(2)) are thought to be byproducts of aerobic respiration with damaging effects on DNA, protein, and lipid. A growing body of evidence indicates, however, that ROS are involved in the maintenance of redox homeostasis and various cellular signaling pathways. ROS are generated from diverse sources including mitochondrial respiratory chain, enzymatic activation of cytochrome p450, and NADPH oxidases further suggesting involvement in a complex array of cellular processes. This review summarizes the production and function of ROS. In particular, how cytosolic and membrane proteins regulate ROS generation for intracellular redox signaling will be detailed.

Role of oxidative stress and antioxidant enzymes in Crohn's disease

There is increasing interest in oxidative stress being a potential aetiological factor and/or a triggering factor in Crohn's disease, rather than a concomitant occurrence during the pathogenesis of the disease. Recent research has shown that the immune mononuclear cells of Crohn's disease patients are induced to produce hydrogen peroxide (H2O2). Similarly, the regulation of antioxidant enzymes during disease in these cells has been unravelled, showing that SOD (superoxide dismutase) activity and GPx (glutathione peroxidase) activity is increased during active disease and returns to normal in remission phases. However, catalase remains constantly inhibited which supports the idea that catalase is not a redox-sensitive enzyme, but a regulator of cellular processes. ROS (reactive oxygen species) can be produced under the stimulus of different cytokines such as TNFα (tumour necrosis factor α). It has been shown in different experimental models that they are also able to regulate apoptosis and other cellular processes. The status of oxidative stress elements in Crohn's disease and their possible implications in regulating cellular processes are reviewed in the present paper.

Rhein induces apoptosis in human breast cancer cells

Human breast cancers cells overexpressing HER2/neu are more aggressive tumors with poor prognosis, and resistance to chemotherapy. This study investigates antiproliferation effects of anthraquinone derivatives of rhubarb root on human breast cancer cells. Of 7 anthraquinone derivatives, only rhein showed antiproliferative and apoptotic effects on both HER2-overexpressing MCF-7 (MCF-7/HER2) and control vector MCF-7 (MCF-7/VEC) cells. Rhein induced dose- and time-dependent manners increase in caspase-9-mediated apoptosis correlating with activation of ROS-mediated activation of NF-κB- and p53-signaling pathways in both cell types. Therefore, this study highlighted rhein as processing anti-proliferative activity against HER2 overexpression or HER2-basal expression in breast cancer cells and playing important roles in apoptotic induction of human breast cancer cells.

Endothelial progenitor cells and exercise-induced redox regulation

Endothelial progenitor cells (EPCs) are thought to participate in endothelial cell regeneration and neovascularization in either a direct or an indirect way. The number of circulating EPCs is influenced by many factors like disease status, medication, age, and fitness level and is an independent predictor of disease progression and cardiovascular events. Experimental as well as clinical studies during the last 10 years clearly demonstrated that physical exercise training has a beneficial effect on endothelial function, which is a clear predictive value for cardiovascular mortality. Over the last years mainly clinical studies provided solid evidence for an exercise training induced mobilization of EPCs from the bone marrow, thereby possibly influencing the regeneration of the endothelial cell layer. This review will discuss the mechanisms how exercise induces mobilization of EPCs from the bone marrow with a focus on the influence on the redox balance.

Anti-inflammatory effects of apocynin, an inhibitor of NADPH oxidase, in airway inflammation

Oxidative stress is implicated in the pathogenesis of allergic asthma and remains an attractive target for the prevention of the disease. Herein, we investigated the anti-inflammatory effects of apocynin, a NADPH oxidase (NOX) inhibitor, in both in vitro and in vivo allergen-induced experimental asthma mediated by Th2 hyperresponsiveness. Apocynin showed potential antioxidant activities and inhibitory effects on the activation of redox-sensitive transcription factors, such as NF-κB and AP-1, induced by pro-inflammatory stimuli, such as TNF-α, lipopolysaccharide and Poly I:C, and that inhibited the production of pro-inflammatory cytokines, such as TNF-α, IL-1β and IL-6. In in vivo experimental asthma model, moreover, apocynin significantly attenuated ovalbumin-induced airway hyperresponsiveness and inflammation, as shown by the attenuation of total inflammatory cell and soluble product influx into bronchoalveolar lavage fluid, such as macrophages, eosinophils, IL-4, IL-5, IL-12, IL-13 and TNF-α. Apocynin also significantly reduced lung inflammation in the tissues. Altogether, these results suggest that apocynin may be useful in the treatment of inflammatory diseases induced by oxidative stress through NOX activity.

Targeting the mitochondria activates two independent cell death pathways in ovarian cancer stem cells

Cancer stem cells are responsible for tumor initiation and chemoresistance. In ovarian cancer, the CD44+/MyD88+ ovarian cancer stem cells are also able to repair the tumor and serve as tumor vascular progenitors. Targeting these cells is therefore necessary to improve treatment outcome and patient survival. The previous demonstration that the ovarian cancer stem cells are resistant to apoptotic cell death induced by conventional chemotherapy agents suggests that other forms of targeted therapy should be explored. We show in this study that targeting mitochondrial bioenergetics is a potent stimulus to induce caspase-independent cell death in a panel of ovarian cancer stem cells. Treatment of these cells with the novel isoflavone derivative, NV-128, significantly depressed mitochondrial function exhibited by decrease in ATP, Cox-I, and Cox-IV levels, and by increase in mitochondrial superoxide and hydrogen peroxide. This promotes a state of cellular starvation that activates two independent pathways: (i) AMPKα1 pathway leading to mTOR inhibition; and (ii) mitochondrial MAP/ERK kinase/extracellular signal-regulated kinase pathway leading to loss of mitochondrial membrane potential. The demonstration that a compound can specifically target the mitochondria to induce cell death in this otherwise chemoresistant cell population opens a new venue for treating ovarian cancer patients.

Weight gain following treatment with valproic acid: pathogenetic mechanisms and clinical implications

In the last years, a growing body of literature indicates an association between valproic acid therapy and weight gain. Weight gain during valproate treatment can be observed within the first 3 months of therapy and women seem to be more susceptible than men. The mechanism through which valproic acid may induce a weight gain is still controversial. The scope of this paper is to investigate the possible causal link between treatment and weight gain in epileptic patients. Systematic review of published epidemiological studies has been done in order to evaluate the real extent of this side effect of valproic acid and its clinical implications, such as an increased risk of insulin resistance and other secondary metabolic abnormalities. The knowledge of the potential of valproic acid to cause significant changes in body weight will help in appropriate selection and modification of antiepileptic therapy to minimize the risk for weight abnormalities. Measurements of body weight before initiation of valproic acid therapy should be done as part of the monitoring of patients with epilepsy to detect changes before there are serious adverse consequences; an increase of 2 kg of body weight after 1 month of treatment should imply considerations to change antiepileptic drug therapy.

The importance of mitochondrial DNA in aging and cancer

Mitochondrial dysfunction has been implicated in premature aging, age-related diseases, and tumor initiation and progression. Alterations of the mitochondrial genome accumulate both in aging tissue and tumors. This paper describes our contemporary view of mechanisms by which alterations of the mitochondrial genome contributes to the development of age- and tumor-related pathological conditions. The mechanisms described encompass altered production of mitochondrial ROS, altered regulation of the nuclear epigenome, affected initiation of apoptosis, and a limiting effect on the production of ribonucleotides and deoxyribonucleotides.

Aldose reductase in keratinocytes attenuates cellular apoptosis and senescence induced by UV radiation

Although aldose reductase (AR) has been implicated in the cellular response to oxidative stress, the role of AR in ultraviolet-B (UVB)-induced cellular injury has not been investigated. Here, we show that an increased expression of AR in human keratinocytes modulates UVB-induced apoptotic cell death and senescence. Overexpression of AR in HaCaT cells significantly attenuated UVB-induced cellular damage and apoptosis, with a decreased generation of reactive oxygen species (ROS) and aldehydes. Ablation of AR with small interfering RNA or inhibition of AR activity abolished these effects. We also show that increased AR activity suppressed UVB-induced activation of the p38 and c-Jun N-terminal kinases, but did not affect the extracellular signal-regulated kinase and phosphatidylinositol 3-kinase pathways. Similarly, UVB-induced translocation of Bax and Bcl-2 to mitochondria and cytosol, respectively, was markedly attenuated in cells overexpressing AR. Knockdown or inhibition of AR activity in primary cultured keratinocytes enhanced UVB-induced cellular senescence and increased the level of a cell-cycle regulatory protein, p53. Finally, cellular apoptosis induced by UVB radiation was significantly reduced in the epidermis of transgenic mice overexpressing human AR. These findings suggest that AR plays an important role in the cellular response to oxidative stress by sequestering ROS and reactive aldehydes generated in keratinocytes.

The beneficial effects of physical exercise on antioxidant status in asthmatic children

BACKGROUND

The pathogenesis of asthma involves both airway inflammation and an oxidant/antioxidant imbalance. It is demonstrated in asthmatic adults that exercise programmes improve lung function, a mechanism yet to be elucidated. The purpose of this study was to investigate the possible beneficial effects of physical exercise on antioxidant status in asthmatic children which may lead to ameliorated lung function.

METHODS

The study enrolled thirteen control and thirty asthmatic children. The asthmatic group was subdivided into two: the first group receiving only pharmacological treatment (n=15) and the second receiving pharmacological treatment with exercise programme (n=15) for 8 weeks. Blood samples were drawn from the subjects before and after treatment periods. As oxidant stress markers blood levels of malondialdehyde (MDA) and total nitric oxide (NO), and as antioxidant status, glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) enzyme activities were assessed.

RESULTS

Before any treatment was initiated, MDA and NO levels in the asthmatic group were significantly higher than the controls (3.40±0.96 nmol/ml vs 2.46±0.58 nmol/ml, and 12.53±2.10 vs 9.40±1.39 micromol/L, respectively). Both SOD (p=0.0001) and GSH-Px (p=0.023) activities were significantly lower in the asthmatic group. Pharmacological treatment and exercise programme together significantly improved lung performance and decreased the levels of oxidant stress markers, in concordance with a significantly increase in antioxidant enzyme activity measures when compared to the pharmacological treatment.

CONCLUSION

Structured exercise programme in asthmatic children resulted in better lung function, which may be attributed to its effect on antioxidant status.

SirT3 suppresses hypoxia inducible factor 1α and tumor growth by inhibiting mitochondrial ROS production

It has become increasing clear that alterations in cellular metabolism have a key role in the generation and maintenance of cancer. Some of the metabolic changes can be attributed to the activation of oncogenes or loss of tumor suppressors. Here, we show that the mitochondrial sirtuin, SirT3, acts as a tumor suppressor via its ability to suppress reactive oxygen species (ROS) and regulate hypoxia inducible factor 1α (HIF-1α). Primary mouse embryo fibroblasts (MEFs) or tumor cell lines expressing SirT3 short-hairpin RNA exhibit a greater potential to proliferate, and augmented HIF-1α protein stabilization and transcriptional activity in hypoxic conditions. SirT3 knockdown increases tumorigenesis in xenograft models, and this is abolished by giving mice the anti-oxidant N-acetyl cysteine. Moreover, overexpression of SirT3 inhibits stabilization of HIF-1α protein in hypoxia and attenuates increases in HIF-1α transcriptional activity. Critically, overexpression of SirT3 decreases tumorigenesis in xenografts, even when induction of the sirtuin occurs after tumor initiation. These data suggest that SirT3 acts to suppress the growth of tumors, at least in part through its ability to suppress ROS and HIF-1α.

Mechanisms associated with mitochondrial-generated reactive oxygen species in cancer

The mitochondria are unique cellular organelles that contain their own genome and, in conjunction with the nucleus, are able to transcribe and translate genes encoding components of the electron transport chain (ETC). To do so, the mitochondria must communicate with the nucleus via the production of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2), which are produced as a byproduct of aerobic respiration within the mitochondria. Mitochondrial signaling is proposed to be altered in cancer cells, where the mitochondria are frequently found to harbor mutations within their genome and display altered functional characteristics leading to increased glycolysis. As signaling molecules, ROS oxidize and inhibit MAPK phosphatases resulting in enhanced proliferation and survival, an effect particularly advantageous to cancer cells. In terms of transcriptional regulation, ROS affect the phosphorylation, activation, oxidation, and DNA binding of transcription factors such as AP-1, NF-kappaB, p53, and HIF-1alpha, leading to changes in target gene expression. Increased ROS production by defective cancer cell mitochondria also results in the upregulation of the transcription factor Ets-1, a factor that has been increasingly associated with aggressive cancers.

Regulation of myocardial growth and death by NADPH oxidase

The NADPH oxidases (Nox) are transmembrane proteins dedicated to producing reactive oxygen species (ROS), including superoxide and hydrogen peroxide, by transferring electrons from NAD(P)H to molecular oxygen. Nox2 and Nox4 are expressed in the heart and play an important role in mediating oxidative stress at baseline and under stress. Nox2 is primarily localized on the plasma membrane, whereas Nox4 is found primarily on intracellular membranes, on mitochondria, the endoplasmic reticulum or the nucleus. Although Nox2 plays an important role in mediating angiotensin II-induced cardiac hypertrophy, Nox4 mediates cardiac hypertrophy and heart failure in response to pressure overload. Expression of Nox4 is upregulated by hypertrophic stimuli, and Nox4 in mitochondria plays an essential role in mediating oxidative stress during pressure overload-induced cardiac hypertrophy. Upregulation of Nox4 induces oxidation of mitochondrial proteins, including aconitase, thereby causing mitochondrial dysfunction and myocardial cell death. On the other hand, Noxs also appear to mediate physiological functions, such as erythropoiesis and angiogenesis. In this review, we discuss the role of Noxs in mediating oxidative stress and both pathological and physiological functions of Noxs in the heart.

The role of intracellular glutathione in the progression of Chlamydia trachomatis infection

The productive internalization in the host cell of Chlamydia trachomatis elementary bodies and their infectivity depends on the degree of reduction of disulfide bonds in the outer envelope of the elementary body. We have hypothesized that the reducing agent may be intracellular glutathione (GSH). Three approaches were used to modulate the intracellular GSH concentration: (1) treatment of cells with buthionine sulfoximine, which causes irreversible inhibition of GSH biosynthesis; (2) hydrogen peroxide-induced oxidation of GSH by intracellular glutathione peroxidases; and (3) treatment of cells with N-acetyl-l-cysteine (NAC), a precursor of glutathione. In the first two cases, we observed a four- to sixfold inhibition of C. trachomatis infection, whereas in NAC-treated cells we detected an increase in the size of chlamydial inclusions. Using a proteomics approach, we showed that the inhibition of chlamydial infection does not combine with alterations in protein expression patterns after cell treatment. These results suggest that GSH plays a key role in the reduction of disulfide bonds in the C. trachomatis outer envelope at an initial stage of the infection.

Taurine prevents free fatty acid-induced hepatic insulin resistance in association with inhibiting JNK1 activation and improving insulin signaling in vivo

We infused the 48 h intralipid plus heparin (IH) to normal rats to elevate plasma free fatty acids (FFAs). Co-infusion of taurine was designed for the purpose of studying the effects of taurine on insulin sensitivity, oxidative stress, c-Jun NH-terminal kinase (JNK)1 activity and insulin signaling in livers of prolonged IH-infused rats. Cannulated rats were infused for 48 h intravenously with either saline or IH, with or without taurine. Hyperinsulinemic-euglycemic clamps with [6-3H] glucose infusion were performed to assess hepatic insulin sensitivity. IH infusion increased plasma 8-isoprostaglandin and hepatic malondialdehyde (MDA). IH also increased JNK1 activity and insulin receptor substrate 1/2 (IRS-1/2) serine phosphorylation, reduced insulin-stimulated IRS-1/2 tyrosine phosphorylation and Akt serine 473 phosphorylation, and induced hepatic insulin resistance. Taurine co-infusion with IH prevented the rise in 8-isoprostaglandin and MDA, inhibited the activation of JNK1, and improved insulin signaling and insulin resistance in liver. The present study has demonstrated that taurine, as an antioxidant, prevented hepatic oxidative stress and ameliorated hepatic insulin resistance. And this effect may be associated with the inhibition of JNK1 activation and the improvement of insulin signaling. This study suggests the therapeutic value of taurine in protecting from hepatic insulin resistance caused by elevated FFAs.

Redox control of protein-DNA interactions: from molecular mechanisms to significance in signal transduction, gene expression, and DNA replication

Protein-DNA interactions play a key role in the regulation of major cellular metabolic pathways, including gene expression, genome replication, and genomic stability. They are mediated through the interactions of regulatory proteins with their specific DNA-binding sites at promoters, enhancers, and replication origins in the genome. Redox signaling regulates these protein-DNA interactions using reactive oxygen species and reactive nitrogen species that interact with cysteine residues at target proteins and their regulators. This review describes the redox-mediated regulation of several master regulators of gene expression that control the induction and suppression of hundreds of genes in the genome, regulating multiple metabolic pathways, which are involved in cell growth, development, differentiation, and survival, as well as in the function of the immune system and cellular response to intracellular and extracellular stimuli. It also discusses the role of redox signaling in protein-DNA interactions that regulate DNA replication. Specificity of redox regulation is discussed, as well as the mechanisms providing several levels of redox-mediated regulation, from direct control of DNA-binding domains through the indirect control, mediated by release of negative regulators, regulation of redox-sensitive protein kinases, intracellular trafficking, and chromatin remodeling.

Estrogen-induced reactive oxygen species-mediated signalings contribute to breast cancer

Elevated lifetime estrogen exposure is a major risk factor for breast cancer. Recent advances in the understanding of breast carcinogenesis clearly indicate that induction of estrogen receptor (ER) mediated signaling is not sufficient for the development of breast cancer. The underlying mechanisms of breast susceptibility to estrogen's carcinogenic effect remain elusive. Physiologically achievable concentrations of estrogen or estrogen metabolites have been shown to generate reactive oxygen species (ROS). Recent data implicated that these ROS induced DNA synthesis, increased phosphorylation of kinases, and activated transcription factors, e.g., AP-1, NRF1, E2F, NF-kB and CREB of non-genomic pathways which are responsive to both oxidants and estrogen. Estrogen-induced ROS by increasing genomic instability and by transducing signal through influencing redox sensitive transcription factors play important role (s) in cell transformation, cell cycle, migration and invasion of the breast cancer. The present review discusses emerging data in support of the role of estrogen induced ROS-mediated signaling pathways which may contribute in the development of breast cancer. It is envisioned that estrogen induced ROS mediated signaling is a key complementary mechanism that drives the carcinogenesis process. ROS mediated signaling however occurs in the context of other estrogen induced processes such as ER-mediated signaling and estrogen reactive metabolite-associated genotoxicity. Importantly, estrogen-induced ROS can function as independent reversible modifiers of phosphatases and activate kinases to trigger the transcription factors of downstream target genes which participate in cancer progression.

Mechanisms of tumor promotion by reactive oxygen species

This review analyzes the available information concerning mechanisms of non-genotoxic action of reactive oxygen species (ROS) during tumor promotion and pathways of their generation under the influence of chemical compounds. Special attention is given to the ability of ROS to induce pseudohypoxia through inhibition of prolyl oxidase, which is an oxygen sensor in the cell. Functions of HIF-1alpha as a main contributor to the ROS-induced promotion are analyzed. Data suggest that an unregulated high level of HIF-1alpha in the cell could induce the development of tumors. Hypothetical possibilities of ROS production under the influence of different environmental pollutants, which are promoters of tumorigenesis, include functioning of cytochrome P450 during oxidation of substrates, functioning of the mitochondrial respiratory chain, and action of peroxisome proliferators.

Inhibition of central angiotensin II-induced pressor responses by hydrogen peroxide

Hydrogen peroxide (H(2)O(2)), important reactive oxygen species produced endogenously, may have different physiological actions. The superoxide anion (O(2)(·-)) is suggested to be part of the signaling mechanisms activated by angiotensin II (ANG II) and central virus-mediated overexpression of the enzyme superoxide dismutase (that dismutates O(2)(·-) to H(2)O(2)) reduces pressor and dipsogenic responses to central ANG II. Whether this result might reflect elevation of H(2)O(2) rather than depletion of O(2)(·-) has not been addressed. Here we investigated the effects of H(2)O(2) injected intracerebroventricularly (i.c.v.) or ATZ (3-amino-1,2,4-triazole, a catalase inhibitor) injected intravenously (i.v.) or i.c.v. on the pressor responses induced by i.c.v. injections of ANG II. Normotensive male Holtzman rats (280-320 g, n=5-13/group) with stainless steel cannulas implanted in the lateral ventricle were used. Prior injection of H(2)O(2) (5 μmol/1 μl) or ATZ (5 nmol/1 μl) i.c.v. almost abolished the pressor responses induced by ANG II (50 ng/1 μl) also injected i.c.v. (7 ± 3 and 5 ± 3 mm Hg, respectively, vs. control: 19 ± 4 mm Hg). Injection of ATZ (3.6 mmol/kg b.wt.) i.v. also reduced central ANG II-induced pressor responses. Injections of H(2)O(2) i.c.v. and ATZ i.c.v. or i.v. alone produced no effect on baseline arterial pressure. Central ANG II, H(2)O(2) or ATZ did not affect heart rate. The results show that central injections of H(2)O(2) and central or peripheral injections of ATZ reduced the pressor responses induced by i.c.v. ANG II, suggesting that exogenous or endogenous H(2)O(2) may inhibit central pressor mechanisms activated by ANG II.

Hyperoxia sensing: from molecular mechanisms to significance in disease

Oxygen therapy using mechanical ventilation with hyperoxia is necessary to treat patients with respiratory failure and distress. However, prolonged exposure to hyperoxia leads to the generation of excessive reactive oxygen species (ROS), causing cellular damage and multiple organ dysfunctions. As the lungs are directly exposed, hyperoxia can cause both acute and chronic inflammatory lung injury and compromise innate immunity. ROS may contribute to pulmonary oxygen toxicity by overwhelming redox homeostasis, altering signaling cascades that affect cell fate, ultimately leading to hyperoxia-induced acute lung injury (HALI). HALI is characterized by pronounced inflammatory responses with leukocyte infiltration, injury, and death of pulmonary cells, including epithelia, endothelia, and macrophages. Under hyperoxic conditions, ROS mediate both direct and indirect modulation of signaling molecules such as protein kinases, transcription factors, receptors, and pro- and anti-apoptotic factors. The focus of this review is to elaborate on hyperoxia-activated key sensing molecules and current understanding of their signaling mechanisms in HALI. A better understanding of the signaling pathways leading to HALI may provide valuable insights on its pathogenesis and may help in designing more effective therapeutic approaches.

gp-91 mediates histone deacetylase inhibition-induced cardioprotection

We have recently shown that the inhibition of histone deacetylases (HDAC) protects the heart against ischemia and reperfusion (I/R) injury. The mechanism by which HDAC inhibition induces cardioprotection remains unknown. We sought to investigate whether the genetic disruption of gp-91, a subunit of NADPH-oxidase, would mitigate cardioprotection of HDAC inhibition. Wild-type and gp-91(-)(/-) mice were treated with a potent inhibitor of HDACs, trichostatin A (TSA, 0.1 mg/kg, i.p.). Twenty-four hours later, the perfused hearts were subjected to 30 min of ischemia and 30 min of reperfusion. HDAC inhibition in wild-type mice produced marked improvements in ventricular functional recovery and the reduction of infarct size. TSA-induced cardioprotection was eliminated with genetic deletion of gp91. Notably, Western blot and immunostaining displayed a significant increase in gp-91 in myocardium following HDAC inhibition, which resulted in a mildly subsequent increase in the production of reactive oxygen species (ROS). The pre-treatment of H9c2 cardiomyoblasts with TSA (50 nmol/l) decreased cell necrosis and increased viability in response to simulated ischemia (SI), which was abrogated by the transfection of cells with gp-91 siRNA, but not by scrambled siRNA. Furthermore, treatment of PLB-985 gp91(+/+) cells with TSA increased the resistance to SI, which also diminished with genetic disruption of gp91 in gp91(phox)-deficient PLB-985 cells. TSA treatment inhibited the increased active caspase-3 in H9c2 cardiomyoblasts and PLB-985 gp91(+/+) cells exposed to SI, which were prevented by knockdown of gp-91 by siRNA. These results suggest that a cascade consisting of gp-91 and HDAC inhibition plays an essential role in orchestrating the cardioprotective effect.

Cooperative induction of CXCL10 involves NADPH oxidase: Implications for HIV dementia

With the increasing prevalence of HIV-associated neurocognititve disorders (HAND), understanding the mechanisms by which HIV-1 induces neuro-inflammation and subsequent neuronal damage is important. The hallmark features of HIV-encephalitis, the pathological correlate of HIV-associated Dementia (HAD), are gliosis, oxidative stress, chemokine dysregulation, and neuronal damage/death. Since neurons are not infected by HIV-1, the current thinking is that these cells are damaged indirectly by pro-inflammatory chemokines released by activated glial cells. CXCL10 is a neurotoxic chemokine that is upregulated in astroglia activated by HIV-1 Tat, IFN-gamma, and TNF-alpha. In this study we have demonstrated that HIV-1 Tat increases CXCL10 expression in IFN-gamma and TNF-alpha stimulated human astrocytes via NADPH oxidase. We have shown that the treatment of astrocytes with a mixture of Tat and cytokines leads to a respiratory burst that is abrogated by apocynin, an NADPH oxidase inhibitor. Pretreatment of Tat, IFN-gamma, and TNF-alpha stimulated astrocytes with apocynin also resulted in concomitant inhibition of CXCL10 expression. Additionally, apocynin was also able to reduce Tat and cytokine-mediated activation of the corresponding signaling molecules Erk1/2, Jnk, and Akt with a decrease in activation and nuclear translocation of NF-kappaB, important regulators of CXCL10 induction. Understanding the mechanisms involved in reducing both oxidative stress and the release of pro-inflammatory agents could lead to the development of therapeutics aimed at decreasing neuro-inflammation in patients suffering from HAD.

The NRF2-heme oxygenase-1 system modulates cyclosporin A-induced epithelial-mesenchymal transition and renal fibrosis

Epithelial-mesenchymal transition (EMT) is an underlying mechanism of tissue fibrosis, generating myofibroblasts, which serve as the primary source of extracellular matrix production from tissue epithelial cells. Recently, EMT has been implicated in immunosuppressive cyclosporin A (CsA)-induced renal fibrosis. In this study, the potential role of NRF2, which is the master regulator of genes associated with the cellular antioxidant defense system, in CsA-induced EMT renal fibrosis has been investigated. Pretreatment of rat tubular epithelial NRK-52E cells with sulforaphane, an activator of NRF2, could prevent EMT gene changes such as the loss of E-cadherin and the increase in alpha-smooth muscle actin (alpha-SMA) expression. Conversely, genetic inhibition of NRF2 in these cells aggravated changes in CsA-induced EMT markers. These in vitro observations could be confirmed in vivo: CsA treatment resulted in severe renal damage and fibrosis with increased expression of alpha-SMA in NRF2-deficient mice compared to wild-type mice. NRF2-mediated amelioration of CsA-caused EMT changes could be accounted for in part by the regulation of heme oxygenase-1 (HO-1). CsA treatment increased HO-1 expression in an NRF2-dependent manner in NRK cells as well as in murine fibroblasts. Induction of HO-1 by CsA seems to be advantageous in that it counteracts EMT gene changes: specific increase in HO-1 expression caused by cobalt protoporphyrin prevented CsA-mediated alpha-SMA induction, whereas genetic inhibition of HO-1 by siRNA substantially enhanced alpha-SMA induction compared to control cells. Collectively, our results suggest that the NRF2-HO-1 system plays a protective role against CsA-induced renal fibrosis by modulating EMT gene changes.

Role of MAP kinases in regulating expression of antioxidants and inflammatory mediators in mouse keratinocytes following exposure to the half mustard, 2-chloroethyl ethyl sulfide

Dermal exposure to sulfur mustard causes inflammation and tissue injury. This is associated with changes in expression of antioxidants and eicosanoids which contribute to oxidative stress and toxicity. In the present studies we analyzed mechanisms regulating expression of these mediators using an in vitro skin construct model in which mouse keratinocytes were grown at an air-liquid interface and exposed directly to 2-chloroethyl ethyl sulfide (CEES), a model sulfur mustard vesicant. CEES (100-1000 microM) was found to cause marked increases in keratinocyte protein carbonyls, a marker of oxidative stress. This was correlated with increases in expression of Cu,Zn superoxide dismutase, catalase, thioredoxin reductase and the glutathione S-transferases, GSTA1-2, GSTP1 and mGST2. CEES also upregulated several enzymes important in the synthesis of prostaglandins and leukotrienes including cyclooxygenase-2 (COX-2), microsomal prostaglandin E synthase-2 (mPGES-2), prostaglandin D synthase (PGDS), 5-lipoxygenase (5-LOX), leukotriene A(4) (LTA(4)) hydrolase and leukotriene C(4) (LTC(4)) synthase. CEES readily activated keratinocyte JNK and p38 MAP kinases, signaling pathways which are known to regulate expression of antioxidants, as well as prostaglandin and leukotriene synthases. Inhibition of p38 MAP kinase suppressed CEES-induced expression of GSTA1-2, COX-2, mPGES-2, PGDS, 5-LOX, LTA(4) hydrolase and LTC(4) synthase, while JNK inhibition blocked PGDS and GSTP1. These data indicate that CEES modulates expression of antioxidants and enzymes producing inflammatory mediators by distinct mechanisms. Increases in antioxidants may be an adaptive process to limit tissue damage. Inhibiting the capacity of keratinocytes to generate eicosanoids may be important in limiting inflammation and protecting the skin from vesicant-induced oxidative stress and injury.

HIV neuropathogenesis: a tight rope walk of innate immunity

During the course of HIV-1 disease, virus neuroinvasion occurs as an early event, within weeks following infection. Intriguingly, subsequent central nervous system (CNS) complications manifest only decades after the initial virus exposure. Although CNS is commonly regarded as an immune-privileged site, emerging evidence indicates that innate immunity elicited by the CNS glial cells is a critical determinant for the establishment of protective immunity. Sustained expression of these protective immune responses, however, can be a double-edged sword. As protective immune mediators, cytokines have the ability to function in networks and co-operate with other host/viral mediators to tip the balance from a protective to toxic state in the CNS. Herein, we present an overview of some of the essential elements of the cerebral innate immunity in HIV neuropathogenesis including the key immune cell types of the CNS with their respective soluble immune mediators: (1) cooperative interaction of IFN-γ with the host/virus factor (platelet-derived host factor (PDGF)/viral Tat) in the induction of neurotoxic chemokine CXCL10 by macrophages, (2) response of astrocytes to viral infection, and (3) protective role of PDGF and MCP-1 in neuronal survival against HIV Tat toxicity. These components of the cerebral innate immunity do not act separately from each other but form a functional immunity network. The ultimate outcome of HIV infection in the CNS will thus be dependent on the regulation of the net balance of cell-specific protective versus detrimental responses.

Roles of oxidative stress in signaling and inflammation induced by particulate matter

This review reports the role of oxidative stress in impairing the function of lung exposed to particulate matter (PM). PM constitutes a heterogeneous mixture of various types of particles, many of which are likely to be involved in oxidative stress induction and respiratory diseases. Probably, the ability of PM to cause oxidative stress underlies the association between increased exposure to PM and exacerbations of lung disease. Mostly because of their large surface area, ultrafine particles have been shown to cause oxidative stress and proinflammatory effects in different in vivo and in vitro studies. Particle components and surface area may act synergistically inducing lung inflammation. In this vein, reactive oxygen species elicited upon PM exposure have been shown to activate a number of redox-responsive signaling pathways and Ca(2+) influx in lung target cells that are involved in the expression of genes that modulate relevant responses to lung inflammation and disease.

Rat mitochondrial manganese superoxide dismutase: amino acid positions involved in covalent modifications, activity, and heat stability

The role of three amino acid residues (Q143, Y34, S82) of rat mitochondrial superoxide dismutase (ratSOD2) in the enzymatic activity, thermostability, and post-translational modification of the enzyme was investigated through site-directed mutagenesis studies. Six recombinant forms of the enzyme were produced, carrying the Q143 or H143 residue with or without the Y34F or S82A replacement. All proteins bound manganese as active cofactor and were organized as homotetramers. The greatest effect on the activity (sixfold reduction) was observed in ratSOD2 forms containing the H143 variant, whereas Y34F and S82A substitutions moderately reduced the enzymatic activity compared to the Q143 form. Heat inactivation studies showed the high thermo-tolerance of ratSOD2 and allowed an evaluation of the related activation parameters of the heat inactivation process. Compared to Q143, the H143 variant was significantly less heat stable and displayed moderately lower enthalpic and entropic factors; the Y34F substitution caused a moderate reduction of heat stability, whereas the S82A replacement slightly improved the thermo-tolerance of the Q143 variant; both substitutions significantly increased enthalpic and entropic factors of heat inactivation, the greatest effect being observed with S82A substitution. All recombinant forms of ratSOD2 were glutathionylated in Escherichia coli, a feature pointing to the high reactivity of ratSOD2 toward glutathione. Moreover, the S82 position of the enzyme was phosphorylated in an in vitro system containing human mitochondrial protein extracts as source of protein kinases. These data highlight the role played by some residues in ratSOD2 and suggest a fine regulation of the enzyme occurring in vivo.

Hydroxyoctadecadienoic acid as a potential biomarker for oxidative stress in patients with chronic hepatitis C

BACKGROUND AND AIM

The possible involvement of oxidative stress in hepatitis C virus (HCV)-induced liver damage and hepatocarcinogenesis has been reported. We have recently developed a novel method to measure total hydroxyoctadecadienoic acid (tHODE) and have proposed its usefulness as a biomarker for lipid peroxidation. The present study was undertaken to evaluate oxidative stress in HCV-infected liver diseases by several potential oxidative stress markers including tHODE and further to validate the biomarkers for evaluating the efficacy of iron reduction therapy.

METHODS

Total hydroxyoctadecadienoic acid, total 8-iso-prostagrandin F(2alpha) (t8-iso-PGF(2alpha)), selenoprotein P and other antioxidant compounds were measured in the plasma and erythrocytes obtained from 42 healthy controls and 78 HCV patients. Plasma levels of biomarkers and antioxidants were also assessed during the iron reduction therapy for 16 weeks in 12 HCV patients.

RESULTS

The concentrations of tHODE in the plasma and erythrocytes and t8-iso-PGF(2alpha) in the plasma of chronic HCV-infected patients were significantly higher than those of healthy controls. Plasma levels of vitamin E and vitamin C of HCV-infected patients were lower than those of the controls. Furthermore, the plasma tHODE significantly correlated with serum aminotransferases and type IV collagen-7S domain in chronic HCV-infected patients. During the iron reduction therapy, the plasma levels of tHODE but not t8-iso-PGF(2alpha) decreased and inversely its stereo-isomer ratio (ZE/EE) increased in parallel with the decreases of serum alanine aminotransferase, ferritin and alpha-fetoprotein.

CONCLUSION

The levels of tHODE in chronic HCV-infected patients can be a useful biomarker for the evaluation of oxidative stress in chronic hepatitis C.