Redox signaling and the emerging therapeutic potential of thiol antioxidants

Lipoic acid as a novel treatment for Alzheimer's disease and related dementias

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that destroys patient memory and cognition, communication ability with the social environment and the ability to carry out daily activities. Despite extensive research into the pathogenesis of AD, a neuroprotective treatment - particularly for the early stages of disease - remains unavailable for clinical use. In this review, we advance the suggestion that lipoic acid (LA) may fulfil this therapeutic need. A naturally occurring precursor of an essential cofactor for mitochondrial enzymes, including pyruvate dehydrogenase (PDH) and alpha-ketoglutarate dehydrogenase (KGDH), LA has been shown to have a variety of properties which can interfere with pathogenic principles of AD. For example, LA increases acetylcholine (ACh) production by activation of choline acetyltransferase and increases glucose uptake, thus supplying more acetyl-CoA for the production of ACh. LA chelates redox-active transition metals, thus inhibiting the formation of hydroxyl radicals and also scavenges reactive oxygen species (ROS), thereby increasing the levels of reduced glutathione. Via the same mechanisms, downregulation redox-sensitive inflammatory processes is also achieved. Furthermore, LA can scavenge lipid peroxidation products such as hydroxynonenal and acrolein. The reduced form of LA, dihydrolipoic acid (DHLA), is the active compound responsible for most of these beneficial effects. R-alpha-LA can be applied instead of DHLA, as it is reduced by mitochondrial lipoamide dehydrogenase, a part of the PDH complex. In this review, the properties of LA are explored with particular emphasis on how this agent, particularly the R-alpha-enantiomer, may be effective to treat AD and related dementias.

Delivery of chemotherapy and antibodies across the blood-brain barrier and the role of chemoprotection, in primary and metastatic brain tumors: report of the Eleventh Annual Blood-Brain Barrier Consortium meeting

Although knowledge of molecular biology and cellular physiology has advanced at a rapid pace, much remains to be learned about delivering chemotherapy and antibodies across the blood-brain barrier (BBB) for the diagnosis and treatment of central nervous system (CNS) disease. A meeting, partially funded by an NIH R13 grant, was convened to discuss the state of the science, current knowledge gaps, and future directions in the delivery of drugs and proteins to the CNS, for the treatment of primary and metastatic brain tumors. Meeting topics included CNS metastases and the BBB, and chemoprotection and chemoenhancement in CNS disorders. The discussions regarding CNS metastases generated possibilities of chemoprotection as a means not only to decrease treatment-related toxicity but also to increase chemotherapy dose intensity. The increasing incidence of sanctuary brain metastasis from breast cancer, in part due to the difficulty of monoclonal antibodies (mAbs) such as herceptin to cross the BBB, was one of the most salient "take home" messages of the meeting.

Antioxidant down-regulates interleukin-18 expression in asthma

An alteration in the balance between a T-helper type 2 cell (Th2) response and a Th1 response may predispose to the development of bronchial asthma. Interleukin-18 (IL-18) has an ability to promote both Th1 and Th2 responses, depending on the surrounding cytokine environment. Reactive oxygen species (ROS) play a crucial role in the pathogenesis of airway inflammation and hyperresponsiveness. Recent studies have demonstrated that antioxidants are able to reduce airway inflammation and hyperreactivity in animal models of asthma. In this study, we used a C57BL/6 mouse model of allergic asthma to examine the effects of antioxidants on the regulation of IL-18 expression. Our present study with ovalbumin-induced murine model of asthma revealed that ROS production in cells from bronchoalveolar lavage fluids was increased and that administration of L-2-oxothiazolidine-4-carboxylic acid or alpha-lipoic acid reduced the increased levels of ROS, the increased expression of IL-18 protein and mRNA, airway inflammation, and bronchial hyperresponsiveness. Our results also showed that antioxidants down-regulated a transcription factor, nuclear factor-kappaB (NF-kappaB), activity. These results indicate that antioxidants may reduce IL-18 expression in asthma by inhibiting the activity of NF-kappaB and suggest that ROS regulate the IL-18 expression.

In vitro and in vivo neuroprotection by γ-glutamylcysteine ethyl ester against MPTP: Relevance to the role of glutathione in Parkinson's disease

Glutathione is an abundant intracellular thiol antioxidant whose levels are reduced both in Parkinson's disease itself and in a widely used animal model of the disorder, systemic MPTP administration. Previous in vitro work from our laboratory has suggested that glutathione depletion may be directly responsible for mitochondrial dysfunction, which ultimately leads to dopaminergic cell death associated with the disease. Here, we demonstrate the ability of gamma-glutamylcysteine ethyl ester, a lipid permeable derivative of the major substrate for scavenger glutathione synthesis, to counteract glutathione loss and neurodegeneration associated with in vitro and in vivo administration of MPTP or its derivatives. This data suggests that prevention of glutathione depletion is a likely therapeutic target for the disease.

N-acetylcysteine selectively protects cerebellar granule cells from 4-hydroxynonenal-induced cell death

4-hydroxynonenal (HNE), an aldehydic product of membrane lipid peroxidation, has been shown to induce neurotoxicity accompanied by multiple events. To clarify mechanisms of neuroprotective compounds on HNE-induced toxicity, the protective effects of N-acetylcysteine (NAC), alpha-tocopherol (TOC), ebselen and S-allyl-L-cysteine (SAC) were compared in cerebellar granule neurons. The decrease in MTT reduction induced by HNE was significantly suppressed by pretreatment of the neurons with 1000 microM NAC or 10 and 100 microM TOC; however, lactate dehydrogenase (LDH) release and propidium iodide (PI) fluorescence studies revealed that neuronal death was suppressed by NAC but not by TOC. Treatment of these neurons with HNE resulted in a drastic reduction of mitochondrial membrane potential, and this reduction was also prevented by NAC but not by TOC. Ebselen and SAC, a garlic compound, were unable to protect these neurons against HNE-induced toxicity. Pretreatment with NAC also prevented HNE-induced depletion of intracellular glutathione (GSH) levels in these neurons. These results suggest that NAC, but not other antioxidants such as TOC, SAC and ebselen, exerts significant protective effects against HNE-induced neuronal death in cerebellar granule neurons, and that this neuroprotective effect is due, at least in part, to preservation of mitochondrial membrane potential and intracellular GSH levels.

Mitoenergetic failure in Alzheimer disease

Brain cells are highly energy dependent for maintaining ion homeostasis during high metabolic activity. During active periods, full mitochondrial function is essential to generate ATP from electrons that originate with the oxidation of NADH. Decreasing brain metabolism is a significant cause of cognitive abnormalities of Alzheimer disease (AD), but it remains uncertain whether this is the cause of further pathology or whether synaptic loss results in a lower energy demand. Synapses are the first to show pathological symptoms in AD before the onset of clinical symptoms. Because synaptic function has high energy demands, interruption in mitochondrial energy supply could be the major factor in synaptic failure in AD. A newly discovered age-related decline in neuronal NADH and redox ratio may jeopardize this function. Mitochondrial dehydrogenases and several mutations affecting energy transfer are frequently altered in aging and AD. Thus, with the accumulation of genetic defects in mitochondria at the level of energy transfer, the issue of neuronal susceptibility to damage as a function of age and age-related disease becomes important. In an aging rat neuron model, mitochondria are both chronically depolarized and produce more reactive oxygen species with age. These concepts suggest that multiple treatment targets may be needed to reverse this multifactorial disease. This review summarizes new insights based on the interaction of mitoenergetic failure, glutamate excitotoxicity, and amyloid toxicity in the exacerbation of AD.

Endogenous anti-oxidants in pregnancy and preeclampsia

Oxidative stress has been implicated in a wide variety of diseases and degenerative states including cancer, rheumatoid arthritis, cardiovascular disease and ageing. There is now considerable evidence to suggest that pregnancy leads to the generation of an increased oxidative burden, but whether this overwhelms the anti-oxidant capacity within the placenta and/or the peripheral circulation remains a point of conjecture. There is little doubt that oxidative stress is a significant contributor in the pathogenesis of preeclampsia. The use of exogenous anti-oxidants such as vitamins C and E in the prevention of preeclampsia is the subject of several large clinical trials currently being conducted in many countries around the world. The results of these studies are eagerly awaited, but what of the endogenous anti-oxidant systems that have evolved to combat the oxidative burden associated with living in an aerobic environment? This review will focus on several important anti-oxidant enzyme systems, their role in pregnancy and the evidence to suggest that endogenous anti-oxidants are important in the development of complications of pregnancy such as preeclampsia.

Arsenic in the aetiology of cancer

Arsenic, one of the most significant hazards in the environment affecting millions of people around the world, is associated with several diseases including cancers of skin, lung, urinary bladder, kidney and liver. Groundwater contamination by arsenic is the main route of exposure. Inhalation of airborne arsenic or arsenic-contaminated dust is a common health problem in many ore mines. This review deals with the questions raised in the epidemiological studies such as the dose-response relationship, putative confounders and synergistic effects, and methods evaluating arsenic exposure. Furthermore, it describes the metabolic pathways of arsenic, and its biological modes of action. The role of arsenic in the development of cancer is elucidated in the context of combined epidemiological and biological studies. However, further analyses by means of molecular epidemiology are needed to improve the understanding of cancer aetiology induced by arsenic.

Molecular Cloning and Functional Characterization of a Cell-permeable Superoxide Dismutase Targeted to Lung Adenocarcinoma Cells

In clinical oncology, many trials with superoxide dismutase (SOD) have failed to demonstrate antitumor ability and in many cases even caused deleterious effects because of low tumor-targeting ability. In the current research, the Nostoc commune Fe-SOD coding sequence was amplified from genomic DNA. In addition, the single chain variable fragment (ScFv) was constructed from the cDNA of an LC-1 hybridoma cell line secreting anti-lung adenocarcinoma monoclonal antibody. After modification, the SOD and ScFv were fused and co-expressed, and the resulting fusion protein produced SOD and LC-1 antibody activity. Tracing SOD-ScFv by fluorescein isothiocyanate and superoxide anions (O2*-) in SPC-A-1 cells showed that the fusion protein could recognize and enter SPC-A-1 cells to eliminate O2*-. The lower oxidative stress resulting from the decrease in cellular O2*- delayed the cell cycle at G1 and significantly slowed SPC-A-1 cell growth in association with the dephosphorylation of the serine-threonine protein kinase Akt and expression of p27kip1. The tumor-targeting fusion protein resulting from this research overcomes two disadvantages of SODs previously used in the clinical setting, the inability to target tumor cells or permeate the cell membrane. These findings lay the groundwork for development of an efficient antitumor drug targeted by the ScFv.

Quebrachitol (2-O-methyl-L-inositol) attenuates 6-hydroxydopamine-induced cytotoxicity in rat fetal mesencephalic cell cultures

Naturally occurring plant substances have the potential to prevent oxidative damage in various pathophysiological conditions including neurodegenerative disorders. Recent findings indicate that impaired energy metabolism plays a prominent role in neurodegeneration. The present study investigated whether quebrachitol (2-O-methyl-L-inositol) (QCT), a sugar like natural compound that was suggested to have both antioxidant and membrane stabilization activity prevents the cytotoxic effect of 6-hydroxydopamine (6-OHDA, 200 microM) on cultured rat fetal mesencephalic cells. While QCT (0.1-100 microg/ml) produced no effect per se on cell viability as measured in the 3[4,5-dimethylthiazole-2il]-2,5-diphenyltetrazolium bromide (MTT) test, it offered concentration-related protection against cell death induced by 6-OHDA. In addition, QCT demonstrated an antioxidant activity against 6-OHDA-induced oxidative stress as evidenced by reduced formation of nitrite-nitrate and thiobarbituric acid-related substances. Fluorescence microscopy using acridine orange/ethidium bromide double staining further affirmed the absence of 6-OHDA (200 microM)-induced morphological changes characteristic of apoptosis/necrosis in cultures pretreated with QCT (100 microg/ml). Also, results of tyrosine hydroxylase immunoreactivity indicated that 6-OHDA induces cell death in mesencephalic cultures affecting both TH+ positive and TH- negative (TH+ and TH-, respectively) and QCT pretreatment protects them from cell death, in a non-specific manner. Our data indicate that QCT has a cytoprotective role due, at least in part, to an antioxidant and free radical scavenging mechanism. Furthermore, the study suggests that inositol compounds might serve as leads in developing drugs for the treatment of various neurodegenerative disorders.

Role of vicinal protein thiols in radiation and cytotoxic responses

Glutathione (GSH) and more recently protein thiols (P-SH) have been found to play a major role in cellular radiation response. However, the effects of protein vicinal thiols, which are important for the functions of several major enzymes, on cellular responses to radiation have not been clearly delineated. Here we investigated the effects of depleting GSH and protein vicinal thiols (HS-P-SH) and P-SH on cell toxicity and radiation response. We used hydroxyethyldisulfide (HEDS, beta-mercaptoethanol-disulfide) alone and in combination with phenylarsine oxide (PAO) to alter P-SH, HS-P-SH and GSH. HEDS, a direct substrate for thioredoxin reductase and an indirect substrate for glutaredoxin (thioltransferase), did not alter protein vicinal thiols in cells. However, PAO, which specifically forms a covalent adduct with vicinal thiols, blocked bioreduction of HEDS; there was a concomitant and yet unexplained decrease in K1 cell GSH in the presence of HEDS and PAO. G6PD+ (K1) and G6PD- (E89) cells treated with L-buthionine sulfoximine (L-BSO) for 72 h to deplete GSH followed by PAO showed an increased cytotoxic response. However, the surviving E89 cells showed a 10,000-fold greater radiation lethality than the K1 cells. The effects of rapid depletion of GSH by a combination of L-BSO and dimethyfumarate (DMF), a glutathione-S-transferase substrate, were also investigated. Under these conditions, PAO radiosensitized the E89 cells more than 1000-fold over the K1 cells. The potential mechanisms for the altered response may be related to the inhibition of thioredoxin reductase and glutaredoxin. Both are key enzymes involved in DNA synthesis, protein homeostasis and cell survival. With GSH removed, vicinal thiols appear to play a critical role in determining cell survival and radiosensitivity. Decreasing P-SH and removing GSH and vicinal thiols is extremely toxic to K1 and E89 cells. We conclude that radiation sensitivity and cell survival are dependent on vicinal thiol and GSH. In the former and latter cases, the protein thiols are also important.

Proteome analysis of hepatocellular carcinoma by laser capture microdissection

Hepatocellular carcinoma (HCC) is one of the most frequent visceral neoplasia worldwide and is a multifactorial and multistage pathogenesis that finally leads to the deregulation of cell homeostasis. Laser capture microdissection (LCM) may allow a more ready identification of differences in protein expression in selected cell types or areas of tissue, and microscopic regions as small as 3-5 microm in diameter can be sampled. Here we applied the LCM to the proteomic study of hepatitis B-related HCC and surrounding non-tumor tissues. Proteome alterations were observed using 2-DE and ESI-MS/MS, and alterations in the proteome were examined. Twenty protein spots were selected, of which 11 proteins were significantly altered in the HCC compared with the surrounding non-tumor tissues. Of the proteins that were selected, peroxiredoxin 2, apolipoprotein A-I precursor, 3-hydroxyacyl-CoA dehydrogenase type II, and 14.5-kDa translational inhibitor protein appear to be novel candidates as useful hepatitis B-related HCC markers. This study indicates that LCM is a useful technological method in the proteomic study of cancer tissue. The proteins revealed in this experiment can be used in the future for studies pertaining to hepatocarcinogenesis, or as diagnostic markers and therapeutic targets for HCC associated with hepatitis B virus infection.

Antagonistic Effects of Oxidized Low Density Lipoprotein and α-Tocopherol on CD36 Scavenger Receptor Expression in Monocytes

Vitamin E deficiency increases expression of the CD36 scavenger receptor, suggesting specific molecular mechanisms and signaling pathways modulated by alpha-tocopherol. We show here that alpha-tocopherol down-regulated CD36 expression (mRNA and protein) in oxidized low density lipoprotein (oxLDL)-stimulated THP-1 monocytes, but not in unstimulated cells. Furthermore, alpha-tocopherol treatment of monocytes led to reduction of fluorescent oxLDL-3,3'-dioctadecyloxacarbocyanine perchlorate binding and uptake. Protein kinase C (PKC) appears not to be involved because neither activation of PKC by phorbol 12-myristate 13-acetate nor inhibition by PKC412 was affected by alpha-tocopherol. However, alpha-tocopherol could partially prevent CD36 induction after stimulation with a specific agonist of peroxisome proliferator-activated receptor-gamma (PPARgamma; troglitazone), indicating that this pathway is susceptible to alpha-tocopherol action. Phosphorylation of protein kinase B (PKB) at Ser473 was increased by oxLDL, and alpha-tocopherol could prevent this event. Expression of PKB stimulated the CD36 promoter as well as a PPARgamma element-driven reporter gene, whereas an inactive PKB mutant had no effect. Moreover, coexpression of PPARgamma and PKB led to additive induction of CD36 expression. Altogether, our results support the existence of PKB/PPARgamma signaling pathways that mediate CD36 expression in response to oxLDL. The activation of CD36 expression by PKB suggests that both lipid biosynthesis and fatty acid uptake are stimulated by PKB.

Oxidative stress in asthma and COPD: antioxidants as a therapeutic strategy

Asthma and chronic obstructive pulmonary disease (COPD) are inflammatory lung diseases that are characterized by systemic and chronic localized inflammation and oxidative stress. Sources of oxidative stress arise from the increased burden of inhaled oxidants, as well as elevated amounts of reactive oxygen species (ROS) released from inflammatory cells. Increased levels of ROS, either directly or via the formation of lipid peroxidation products, may play a role in enhancing the inflammatory response in both asthma and COPD. Moreover, in COPD it is now recognized as the main pathogenic factor for driving disease progression and increasing severity. ROS and lipid peroxidation products can influence the inflammatory response at many levels through its impact on signal transduction mechanisms, activation of redox-sensitive transcriptions factors, and chromatin regulation resulting in pro-inflammatory gene expression. It is this impact of ROS on chromatin regulation by reducing the activity of the transcriptional co-repressor, histone deacetylase-2 (HDAC-2), that leads to the poor efficacy of corticosteroids in COPD, severe asthma, and smoking asthmatics. Thus, the presence of oxidative stress has important consequences for the pathogenesis, severity, and treatment of asthma and COPD. However, for ROS to have such an impact, it must first overcome a variety of antioxidant defenses. It is likely, therefore, that a combination of antioxidants may be effective in the treatment of asthma and COPD. Various approaches to enhance the lung antioxidant screen and clinical trials of antioxidant compounds are discussed.

An introduction to thiol redox proteins in the endoplasmic reticulum and a review of current electrochemical methods of detection of thiols

This aim of this paper is to expound the complexity of thiol redox systems in the endoplasmic reticulum of eukaryotic cells to the electroanalytical community. A summary of the state of the art in electrochemical methods for detection of thiols gives an insight into the challenges that need to be addressed to bridge the disparity between current analytical techniques and applications in a 'real' biological scenario.

The antioxidant role of glutathione and N-acetyl-cysteine supplements and exercise-induced oxidative stress

An increase in exercise intensity is one of the many ways in which oxidative stress and free radical production has been shown to increase inside our cells. Effective regulation of the cellular balance between oxidation and antioxidation is important when considering cellular function and DNA integrity as well as the signal transduction of gene expression. Many pathological states, such as cancer, Parkinson's disease, and Alzheimer's disease have been shown to be related to the redox state of cells. In an attempt to minimize the onset of oxidative stress, supplementation with various known antioxidants has been suggested. Glutathione and N-acetyl-cysteine (NAC) are antioxidants which are quite popular for their ability to minimize oxidative stress and the downstream negative effects thought to be associated with oxidative stress. Glutathione is largely known to minimize the lipid peroxidation of cellular membranes and other such targets that is known to occur with oxidative stress. N-acetyl-cysteine is a by-product of glutathione and is popular due to its cysteine residues and the role it has on glutathione maintenance and metabolism. The process of oxidative stress is a complicated, inter-twined series of events which quite possibly is related to many other cellular processes. Exercise enthusiasts and researchers have become interested in recent years to identify any means to help minimize the detrimental effects of oxidative stress that are commonly associated with intense and unaccustomed exercise. It is possible that a decrease in the amount of oxidative stress a cell is exposed to could increase health and performance.

Redox modifications of protein-thiols: emerging roles in cell signaling

Glutathione represents the major low molecular weight antioxidant redox recycling thiol in mammalian cells and plays a central role in the cellular defence against oxidative damage. Classically glutathione has been known to provide the cell with a reducing environment in addition to maintaining the proteins in a reduced state. Emerging evidences suggest that the glutathione redox status may entail dynamic regulation of protein function by reversible disulfide bond formation. The formation of inter- and intramolecular disulfides as well as mixed disulfides between protein cysteines and glutathione, i.e., S-glutathiolation, has now been associated with the stabilization of extracellular proteins, protection of proteins against irreversible oxidation of critical cysteine residues, and regulation of enzyme functions and transcription. Regulation of DNA binding of redox-dependent transcription factors such as nuclear factor-kappaB, p53, and activator protein-1, has been suggested as one of the mechanisms by which cells may transduce oxidative stress redox signaling into an inducible expression of a wide variety of genes implicated in cellular changes such as proliferation, differentiation, and apoptosis. However, the molecular mechanisms linking the glutathione cellular redox state to a reversible oxidation of various signaling proteins are still poorly understood. This commentary discusses the emerging concept of protein-S-thiolation, protein-S-nitrosation and protein-SH (formation of sulfenic, sulfinic and sulfonic acids) in redox signaling during normal physiology and under oxidative stress in controlling the cellular processes.

Lipoic acid decreases exhaled nitric oxide concentrations in anesthetized endotoxemic rats

We recently demonstrated that lipoic acid suppresses endotoxin-stimulated expression of inducible nitric oxide synthase and nitric oxide production in mouse macrophages. In this study, we tested whether lipoic acid suppresses these inflammatory mediators in the lungs of rats. Rats were assigned to receive either no special treatment, endotoxin alone, or pretreatment with lipoic acid followed by endotoxin. After anesthetizing the rats and injecting them intraperitoneally with lipoic acid (100 mg/kg) at 4 h and again at 1 h before treatment, the rats then received either endotoxin (0.01 mg/kg) or its vehicle solution. Exhaled gas was sampled every 15 min and concentrations of nitric oxide in the samples were measured using a chemiluminescence analyzer. After 150 min of exposure to endotoxin, the lungs were harvested and snap-frozen in liquid nitrogen for subsequent analysis. Lipoic acid attenuated endotoxin-induced increases in exhaled nitric oxide concentrations (P<0.001) and iNOS (P<0.05). These findings support the hypothesis that lipoic acid inhibits endotoxin-stimulated formation of intrapulmonary nitric oxide.

Novel potential neuroprotective agents with both iron chelating and amino acid-based derivatives targeting central nervous system neurons

Antioxidants and iron chelating molecules are known as neuroprotective agents in animal models of neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). In this study, we designed and synthesized a novel bifunctional molecule (M10) with radical scavenging and iron chelating ability on an amino acid carrier likely to be a substrate for system L, thus targeting the compound to the central nervous system (CNS). M10 had a moderate iron affinity in HEPES buffer (pH 7.4) with logK(3)=12.25+/-0.55 but exhibited highly inhibitory action against iron-induced lipid peroxidation, with an IC(50) value (12microM) comparable to that of desferal (DFO). EPR studies indicated that M10 was a highly potent *OH scavenger with an IC(50) of about 0.3 molar ratio of M10 to H(2)O(2). In PC12 cell culture, M10 was at least as potent as the anti-Parkinson drug rasagiline in protecting against cell death induced by serum-deprivation and by 6-hydroxydopamine (6-OHDA). These results suggest that M10 deserves further investigation as a potential agent for the treatment of neurodegenerative disorders such as AD and PD.

[Cerebral oxidative stress: are astrocytes vulnerable to low intracellular glutamate concentrations? Consequences for neuronal viability]

This review describes reactive oxygen species (ROS), their production and effects on crucial biological molecules, the different lines of defense against oxidative stress, with particular attention to glutathione, the main antioxidant in the brain, which neuronal synthesis seems to be dependent on astrocytic precursors. It also focuses on the different ways by which glutamate may induce oxidative stress in the brain. The different mechanisms leading to ROS production, activated during the excitotoxic cascade, are described. Oxidative glutamate toxicity is also briefly described. A novel form of oxidative glutamate toxicity by depletion of transported glutamate that we recently evidenced is detailed. This toxicity induced by pharmacological reversal of glutamate transport, which mimics glutamate transport reversal occurring in ischemia, involves glutathione depletion and oxidative stress, leading to delayed death of cultured striatal astrocytes differentiated by dibutyryl-cAMP, probably through apoptotic processes. Evidence suggesting that this oxidative glutamate toxicity by depletion of transported glutamate is very likely occurring in vivo and its consequences on neuronal survival are discussed.

Vitamin E prevents cell death induced by mild oxidative stress in chicken skeletal muscle cells

Apoptosis and necrosis are two forms of cell death that can occur in response to various agents and oxidative damage. In addition to necrosis, apoptosis contributes to muscle fiber loss in various muscular dystrophies as well participates in the exudative diathesis in chicken, pathology caused by dietary deficiency of vitamin E and selenium, which affects muscle tissue. We have used chicken skeletal muscle cells and bovine fibroblasts to study molecular events involved in the cell death induced by oxidative stress and apoptotic agents. The effect of vitamin E on cell death induced by oxidants was also investigated. Treatment of cells with anti-Fas antibody (50 to 400 ng/mL), staurosporine (0.1 to 100 microM) and TNF-alpha (10 and 50 ng/mL) resulted in a little loss of Trypan blue exclusion ability. Those stimuli conducted cells to apoptosis detected by an enhancement in caspase activity upon fluorogenic substrates but this activity was not fully blocked by the caspase inhibitor Z-VAD-fmk. Oxidative stress induced by menadione (10, 100 and 250 muM) promoted a significant reduction in cell viability (10%, 20% and 35% for fibroblasts; 20%, 30% and 75% for muscle cells, respectively) and caused an increase in caspase activity and DNA fragmentation. H2O2 also promoted apoptosis verified by caspase activation and DNA fragmentation, but in higher doses induced necrosis. Vitamin E protected cells from death induced by low doses of oxidants. Although it was ineffective in reducing caspase activity in fibroblasts, this vitamin diminished the enzyme activity in muscle cells. These data suggested that oxidative stress could activate apoptotic mechanisms; however the mode of cell death will depend on the intensity and duration of the stimulus, and on the antioxidant status of the cells.

The effects of some Mannich bases on heat shock proteins HSC70 and GRP75, and thioredoxin and glutaredoxin levels in Jurkat cells

Mannich bases interact with cellular thiols and inactivate thioredoxin reductase. In this study, the effects of cytotoxic mono-Mannich bases 2, 3 and cyclic Mannich base C1 on the expression of cytoprotective heat shock proteins (HSC70 and GRP75) and on levels of thioredoxin (TRX) and glutaredoxin (GRX) were investigated in Jurkat cells. Cells were exposed to the compounds for 24 h in cell culture medium with 1% FBS. C1 and 2 increased the levels of HSC70 (200% of control) in all the concentrations tested, but 3 did not affect HSC70 levels. Whereas 3 increased GRP75 expression (123-154%), 2 and C1 either did not affect (95-87% for 2, and 88% for C1) or slightly decreased GRP75 expression (82% for 2 and 67% for C1). Mannich bases generally decreased GRX levels (68%, 63-77% and 33-71% for 2, 3 and C1, respectively), but 3 increased GRX levels at 1 microg/ml (142%). Whereas 2 and 3 decreased TRX levels (30-79% and 37-44% of control, respectively), C1 increased the expression of TRX (156-201%). Our results suggest that decreases in GRX and TRX due to the alkylating effects of Mannich bases might have prevented cell division and decreased survival in Jurkat cells, which could not be prevented by increased heat shock protein expression.

Stress-induced activation of the p53 tumor suppressor in leukemia cells and normal lymphocytes requires mitochondrial activity and reactive oxygen species

The p53 system is highly stress sensitive and integrates diverse intracellular signals in a complex and poorly defined manner. We report on the high dependence of stress-induced p53 activation on mitochondrial activity. Down-regulation of mitochondrial transmembrane potential (MTMP) by inhibitors of electron transport (rotenone, thenoyltrifluoroacetone (TTFA)) and adenosine triphosphate (ATP) synthesis (oligomycin) prevented stress-induced p53 protein accumulation and abrogated p53-dependent apoptosis in a wild-type p53 leukemia cell line MOLT-3, in primary leukemia cells and in normal T lymphocytes. Using genome-wide gene expression analysis, stress-induced up-regulation of the p53 transcriptional targets and their specific inhibition by oligomycin has been demonstrated. Oligomycin did not impair p53-independent apoptosis and caused only a slight reduction of intracellular ATP levels. Reactive oxygen species (ROS) localized to mitochondria decreased in the presence of oligomycin, and stress-induced p53 activation showed strong ROS sensitivity both in leukemic and normal cells. These observations identify mitochondrial activity, described by MTMP and ROS levels, as a critical intracellular determinant of the p53 stress sensitivity and suggest potential implications of this linkage in the mechanisms of chemoresistance of acute leukemia cells.

ROS formation and glutathione levels in human oral fibroblasts exposed to TEGDMA and camphorquinone

Glutathione (GSH) is important for the self-protection of cells against oxidative stress and toxic xenobiotics, whereas reactive oxygen species (ROS) at elevated concentrations may cause detrimental alterations of cell membranes, DNA, and other cellular structures. The present investigation addressed the effects of triethylene-glycoldimethacrylate (TEGDMA) and camphorquinone (CQ) on glutathione metabolism and the formation of ROS in oral cells. Primary human pulp fibroblasts were exposed to various concentrations of TEGDMA and CQ (0.1-5 mM). Subsequently, GSH concentration and ROS formation were analyzed with the use of the monobromobimane assay (GSH) and 2',7'-dichlorofluorescein diacetate (DCFH-DA) (ROS). The endogenous ROS hydrogen peroxide (H2O2) was used as a positive control (0.02-2 mM). TEGDMA significantly decreased GSH at concentrations between 0.5 and 5 mM (p<0.05), but did not elevate ROS levels. Contrary, CQ increased ROS formation at concentrations>or=1 mM, but had only a moderate effect on GSH at the highest test concentration. Hydrogen peroxide increased ROS and simultaneously decreased GSH at concentrations of >or=0.2 mM. These data show that the investigated substances may cause cell damage due to various mechanisms, GSH decrease and/or ROS increase. As a consequence, TEGDMA and CQ released into an aqueous environment from resinous materials might interact, thus generating significant cytotoxic effects even at low concentrations.

N-acetylcysteine amide, a novel cell-permeating thiol, restores cellular glutathione and protects human red blood cells from oxidative stress

Oxidative stress plays an important role in the progression of neurodegenerative and age-related diseases, causing damage to proteins, DNA, and lipids. A novel thiol N-acetylcysteine amide (AD4), the amide form of N-acetylcysteine (NAC) and a Cu(2+) chelator, was assessed for its antioxidant and protective effects using human red blood cells (RBCs) as a model. AD4 was shown by flow cytometry to inhibit tert.-butylhydroxyperoxide (BuOOH)-induced intracellular oxidation in RBCs stained with the oxidant-sensitive probe 2',7'-dichlorofluorescein diacetate. In addition, AD4 retarded BuOOH-induced thiol depletion and hemoglobin oxidation. Restoration of the thiol-depleted RBCs by externally applied AD4 was significantly greater compared with NAC and, unlike NAC, was accompanied by hemoglobin protection from oxidation. In a cell-free system we have demonstrated that AD4 reacted with oxidized glutathione (GSSG) to generate reduced glutathione (GSH). The formation of GSH was determined enzymatically using GSH peroxidase and by HPLC. Based on these results a thiol-disulfide exchange between AD4 and GSSG is proposed as the mechanism underlying the antioxidant effects of AD4 on BuOOH-treated RBCs. Together, these studies demonstrate that AD4 readily crosses cell membranes, replenishes intracellular GSH, and, by incorporating into the redox machinery, defends the cell from oxidation. These results provide further evidence for the efficient membrane permeation of AD4 over NAC, and support the possibility that it could be explored for treatment of neurodegeneration and other oxidation-mediated disorders.

L-gamma-Glutamyl-L-cysteinyl-glycine (glutathione; GSH) and GSH-related enzymes in the regulation of pro- and anti-inflammatory cytokines: a signaling transcriptional scenario for redox(y) immunologic sensor(s)?

Of the antioxidant/prooxidant mechanisms mediating the regulation of inflammatory mediators, particularly cytokines, oxidative stress-related pathways remain a cornerstone. It is conspicuous that there is a strong association between free radical accumulation (ROS/RNS; oxidative stress) and the evolution of inflammation and inflammatory-related responses. The scenario that upholds a consensus on the aforementioned is still evolving to unravel, from an immunologic perspective, the molecular mechanisms associated with ROS/RNS-dependent inflammation. Cytokines are keynote players when it comes to defining an intimate relationship among reduction-oxidation (redox) signals, oxidative stress and inflammation. How close we are to identifying the molecular basis of this intricate association should be weighed against the involvement of specific signaling molecules and, potentially, transcription factors. L-gamma-Glutamyl-L-cysteinyl-glycine, or glutathione (GSH), an antioxidant thiol, has shaped, and still is refining, the face of oxidative signaling in terms of regulating the milieu of inflammatory mediators, ostensibly via the modulation (expression/repression) of oxygen- and redox-responsive transcription factors, hence termed redox(y)-sensitive cofactors. When it comes to the arena of oxygen sensing, oxidative stress and inflammation, nuclear factor-kappaB (NF-kappaB) and hypoxia-inducible factor-1alpha (HIF-1alpha) are key players that determine antioxidant/prooxidant responses with oxidative challenge. It is the theme therein to underlie current understanding of the molecular association hanging between oxidative stress and the evolution of inflammation, walked through an elaborate discussion on the role of transcription factors and cofactors. Would that classify glutathione and other redox signaling cofactors as potential anti-inflammatory molecules emphatically remains of particular interest, especially in the light of identifying upstream and downstream molecular pathways for conceiving therapeutic, alleviating strategy for oxidant-mediated, inflammatory-related disease conditions.

Variable effects of exercise intensity on reduced glutathione, thiobarbituric acid reactive substance levels, and glucose concentration

BACKGROUND

Physical exercise may be associated with a 10- to 20-fold increase in whole body oxygen uptake. Generation of free oxygen radicals (FORs) is elevated to a level that overwhelms tissue antioxidant defense systems in exercise. One of the most reliable indices of exercise-induced oxidant production is tissue glutathione oxidation.

METHODS

In this study three different volunteer groups carried out various sports disciplines and worked at least as amateurs for 6-7 years before and after aerobic (Aer)-, anaerobic (Anae)-, or aerobic + anaerobic (Aer-Anae)-dominant exercises. Thiobarbituric acid reactive substances (TBARS) reduced glutathione (GSH) levels, glucose concentration was measured, and we investigated their relationships with different types of exercise. From all groups (n=60, each group comprising 10 females and 10 males), we collected blood samples at the following five different times: before exercise; immediately after exercise, and 4, 24, and 48 h after completion of exercise. These samples were assayed for whole blood GSH, plasma TBARS levels, and glucose concentration.

RESULTS

Significant increase in Aer-Anae was noted in levels of TBARS while decrease was observed in glutathione levels in exercise group as compared with prior levels in all groups. However, no statistical difference was observed in total group levels before and after exercise and in male and female groups compared before and after exercise. When gender differences were taken into account, females generally had higher levels of GSH, whereas TBARS levels were higher in males. When compared either before or after exercise, levels of glucose concentration--especially immediately after exercise period in all groups--were higher. In addition, in Anae groups glucose concentrations were higher at 4 and 24 h in females than in males. Aer exercise caused oxidative stress to a lesser degree, whereas Aer-Anae exercise caused oxidative stress of higher degree that was statistically significant.

CONCLUSIONS

According to our findings, exercise increased TBARS level significantly in all groups, especially more so in Aer-Anae groups. In addition, GSH was increased more in females than in males, while concentration of glucose did not change remarkably. Additionally, it can be stated that women are more resistant to oxidative stress.

Redox modulation of chromatin remodeling: impact on histone acetylation and deacetylation, NF-kappaB and pro-inflammatory gene expression

Reactive oxygen species (ROS), either directly or via the formation of lipid peroxidation products, such as 4-hydroxy-2-nonenal, acrolein and F2-isoprostanes, may play a role in enhancing inflammation through the activation and phosphorylation of stress kinases (JNK, ERK, p38) and redox-sensitive transcription factors such as NF-kappaB and AP-1. This increases the expression of genes regulating a battery of distinct pro-inflammatory mediators. Acetylation by histone acetyltransferase (HAT) of specific lysine residues on the N-terminal tail of core histones, results in uncoiling of the DNA and increased accessibility to transcription factor binding. In contrast, histone deacetylation by histone deacetylase (HDAC) represses gene transcription by promoting DNA winding thereby limiting access to transcription factors. Oxidative stress activates NF-kappaB resulting in expression of pro-inflammatory mediators through the activation of intrinsic HAT activity on co-activator molecules. In addition, oxidative stress also inhibits HDAC activity and in doing so enhances inflammatory gene expression which leads to a chronic inflammatory response. Oxidative stress can also increase complex formation between the co-activator CBP/p300 and the p65 subunit of NF-kappaB suggesting a further role of oxidative stress in chromatin remodeling. The antioxidant and/or anti-inflammatory effects of thiol molecules (glutathione, N-acetyl-L-cysteine and N-acystelyn), dietary polyphenols (curcumin-diferuloylmethane and resveratrol), the bronchodilator theophylline and glucocorticoids have all been shown to play a role in either controlling NF-kappaB activation or chromatin remodeling through modulation of HDAC activity and subsequently inflammatory gene expression in lung epithelial cells. Thus, oxidative stress regulates both signal transduction and chromatin remodeling which in turn impacts on pro-inflammatory responses in the lungs.

Retinal oxidative stress induced by high intraocular pressure

Glaucoma is an optic neuropathy in which retinal ganglion cells die probably through an apoptotic process. Apoptosis is known to involve free radicals in several systems including the retina. In this context, the aim of the present work was to analyze retinal oxidative damage in rats with glaucoma induced by the chronic injection of hyaluronic acid in the eye anterior chamber. The results showed a significant decrease in total retinal superoxide dismutase and catalase activities after 6 and 3 weeks of treatment with hyaluronic acid, respectively. Also, although GPX activity increased after 10 weeks of ocular hypertension, GSH levels significantly decreased at 6 weeks of treatment with hyaluronic acid. Moreover, retinal lipid peroxidation significantly increased in a time-of-hypertension-dependent manner. On the other hand, a significant decrease in both diurnal and nocturnal retinal melatonin content was detected at 3, 6, or 10 weeks of treatment with hyaluronic acid. The present results suggest that retinal oxidative stress may be involved in glaucomatous cell death. Thus, manipulation of intracellular redox status using antioxidants may be a new therapeutic tool to prevent glaucomatous neurodegeneration.

Activation of the ligand-mineralocorticoid receptor functional unit by ancient, classical, and novel ligands. Structure-activity relationship

The mineralocorticoid effect on epithelial cells is the resultant of an intricate net of biochemical regulations that ultimately leads to the maintenance of electrolyte homeostasis. Two key protagonists in this plot are the ligand, which broadcasts the information, and the receptor, which functions as a receiver and transducer. Therefore, the responsibility for the final biological effect is not limited to each individual component but to both of them, so they constitute a functional unit. In addition, several prereceptor regulatory mechanisms are also determinant factors for the final biological response. Because steroids are present in both animals and plants and are derived from common precursors, it is intriguing how these simple molecules have acquired specialization to shape biological development and differentiation. This is particularly true for the function of aldosterone in mammals, which is mimicked by glucocorticoids or progesterone in some particular cases. Inasmuch as the most potent mineralocorticoid in nature, aldosterone, shows a poorly angled steroid nucleus at the A?B-ring junction, and because steroids that possess identical functional groups and different steroidal frames elicit different mineralocorticoid effects, we postulate that a planar conformation of the ligand is a key requirement to acquire potent sodium retention properties. The model takes into consideration all the mechanisms involved in the regulation of the final biological effect, although it does not provide a definitive answer to the original question. It is also discussed how the use of novel mineralocorticoid ligands may shed light on the still obscure mechanism of action of the mineralocorticoid receptor.

Oxidative stress in mothers who have conceived fetus with neural tube defects: the role of aminothiols and selenium

BACKGROUND & AIMS

Methionine metabolic impairment and selenium deficit have been associated to neural tube defects. The relationship between thiol metabolism and selenium is not well known. We assessed the status of aminothiols and selenium, as well as thiolic status and the amino acids involved in arginine synthesis in the case of selenium depletion and repletion, studying their relationship to neural tube defects.

METHODS

We studied 44 women of 37 +/- 8 years (mean +/- SD) who had conceived fetuses with neural tube defects as cases; and 181 women of 39 +/- 7 years (mean +/- SD) with healthy children as controls. We determined selenium, vitamin B12, serum folates, plasma thiol compounds and amino acids. Homocysteine transsulfuration was assessed using total cysteine/total homocysteine ratio (tCys/tHcy), and selenium repletion cut-off value was 1.06 micromol/l (84 microg/l).

RESULTS

Cases showed significantly lower levels (median) than controls of total homocysteine (P = 0.001), total cysteinylglycine (P < 0.001), selenium (P < 0.001) and tryptophane (P = 0.002); and higher tCys/tHcy levels (P < 0.001), glutathione (P = 0.008) and L-arginine (P = 0.001). Cases with selenium depletion (selenium < or = 1.06 micromol/l) had significantly higher levels than controls of cysteine (P = 0.010), glutathione (P = 0.005), tCys/tHcy (P < 0.001), and arginine (P = 0.004), but significantly lower levels than controls of tryptophane (P = 0.027), cysteinylglycine (P < 0.001) and folates (P < 0.001). Only cysteinylglycine was lower than controls (P < 0.001) when selenium > 1.06 micromol/l. Methionine levels were higher in cases with selenium depletion than in repletion (P = 0.029).

CONCLUSIONS

According to our data, a diet deficient in selenium and folates or their absorption impairment, and/or other mechanisms related to polyamines and nitric oxide can lead to oxidant/antioxidant imbalance and to a higher occurrence of these malformations.

Protein s-glutathionylation in retinal pigment epithelium converts heat shock protein 70 to an active chaperone

A disulfide bond between key redox-sensitive cysteine residues and glutathione is one mechanism by which redox related allosteric effectors can regulate protein structure and function. Here we test the hypothesis that glutaredoxin-1 (Grx-1), a member of the oxidoreductase family of enzymes, may be a critical component of redox-sensitive molecular switches by mediating reversible protein S-glutathionylation and enzymatic catalysis of thiol/disulfide exchange. Deglutathionylation of a 70 kDa protein by Grx-1 was detected using a monoclonal antibody specific to protein S-glutathionylation. Heat shock cognate protein 70 (Hsc70) was identified as a substrate of Grx-1 through mass spectrometry. Recombinant Hsc70 was glutathionylated in vitro, and protein S-glutathionylation reversed by Grx-1. Glutathionylated Hsc70 was more effective in preventing luciferase aggregation at 43 degrees C than reduced Hsc70 in a dose dependent fashion. ATP did not effect the chaperone activity of Hsc70-SG but did increase the activity of reduced Hsc70-SG. Reversible glutathionylation of Hsc70 may provide a mechanism for post-translation regulation of chaperone activity.

Stress protein activation by the cyclopentenone prostaglandin 15-deoxy-Δ12,14-prostaglandin J2 in human mesangial cells

BACKGROUND

The cyclopentenone prostaglandin 15-deoxy-delta12,14-prostaglandin J2 (15dPGJ2) affects mesangial proliferation, survival and production of proinflammatory proteins. During a survey of the mesangial cell proteome after treatment with 15dPGJ2, heat shock protein 70 (HSP70) was found to be the most conspicuously up-regulated protein, suggesting that stress proteins are key mediators or modulators of the effects of 15dPGJ2. Because cyclopentenone prostaglandins are highly reactive toward intracellular thiols, the role of intracellular thiol modification in the stress response to 15dPGJ2 was examined.

METHODS

Human mesangial cells were treated with 15dPGJ2 and intracellular thiol status was monitored by the fluorescent thiol probe monobromobimane (MBB). Specific intracellular thiol pools were manipulated by treating the cells with buthionine sulfoximine (BSO) to deplete glutathione (GSH), or phenylarsine oxide (PAO) to modify protein vicinal dithiols. Transcription pathways were examined with reporter gene or adenoviral constructs.

RESULTS

15dPGJ2 decreased mesangial GSH and other intracellular thiols, but depletion of GSH specifically with BSO did not induce HSP70. Thiol-replenishing reagents, which can restore modified protein thiols, attenuated 15dPGJ2-induced HSP70 levels. Furthermore, PAO mimicked the effects of 15dPGJ2 on HSP70. 15dPGJ2 also activated the stress-responsive transcription factor Nrf2, which requires thiol modification of its cytoplasmic inhibitor protein for transcriptional activity, and induced the Nrf2-dependent stress protein heme oxygenase-1 (HO-1).

CONCLUSION

15dPGJ2 activates a stress response in human mesangial cells by covalent modification of protein thiols through its unique cyclopentenone ring structure. This stress response may be beneficial in preventing renal cell injury or death during kidney inflammation or ischemia.

Oxidation-reduction potential regulates RpoS levels in Salmonella Typhimurium

AIMS

The aim of this work was to investigate the connection between oxidation-reduction (redox) potential and stationary phase induction of RpoS in Salmonella Typhimurium.

METHODS AND RESULTS

A lux-based reporter was used to evaluate RpoS activity in S. Typhimurium pure cultures. During growth of S. Typhimurium, a drop in the redox potential of the growth medium occurred at the same time as RpoS induction and entry into stationary phase. An artificially induced decrease in redox potential earlier during growth reduced the time to RpoS induction and Salmonella entered the stationary phase prematurely. In contrast, under high redox conditions, Salmonella grew unaffected and entered the stationary growth phase as normal, although RpoS induction did not occur. As a consequence, stationary phase cells grown in the high redox environment were significantly more heat sensitive (P < 0.05) than those grown under normal conditions.

CONCLUSIONS

This work suggests that redox potential can regulate RpoS levels in S. Typhimurium and can thus, control the expression of genes responsible for thermal resistance.

SIGNIFICANCE AND IMPACT OF THE STUDY

The ability to manipulate RpoS induction and control stationary phase gene expression can have important implications in food safety. Early RpoS induction under low redox potential conditions can lead to enhanced resistance in low cell concentrations to inimical processes such as heat stress. Inhibition of RpoS induction would abolish stationary phase protective properties making cells more sensitive to common food control measures.

Redox regulation of surface protein thiols: identification of integrin alpha-4 as a molecular target by using redox proteomics

Thiols affect a variety of cell functions, an effect known as redox regulation. We show here that treatment (1-2 h) of cells with 0.1-5 mM N-acetyl-L-cysteine (NAC) increases surface protein thiol expression in human peripheral blood mononuclear cells. This effect is not associated with changes in cellular glutathione (GSH) and is also observed with a non-GSH precursor thiol N-acetyl-D-cysteine or with GSH itself, which is not cell-permeable, suggesting a direct reducing action. NAC did not augment protein SH in the cytosol, indicating that they are already maximally reduced under normal, nonstressed, conditions. By using labeling with a non permeable, biotinylated SH reagent followed by two-dimensional gel electrophoresis and analysis by MS, we identified some of the proteins associated with the membrane that are reduced by NAC. These proteins include the following: integrin alpha-4, myosin heavy chain (nonmuscle type A), myosin light-chain alkali (nonmuscle isoform), and beta-actin. NAC pretreatment augmented integrin alpha-4-dependent fibronectin adhesion and aggregation of Jurkat cells without changing its expression by fluorescence-activated cell sorter, suggesting that reduction of surface disulfides can affect proteins function. We postulate that some of the activities of NAC or other thiol antioxidants may not only be due to free radical scavenging or increase of intracellular GSH and subsequent effects on transcription factors, but could modify the redox state of functional membrane proteins with exofacial SH critical for their activity.

The changing faces of glutathione, a cellular protagonist

Glutathione (GSH) has been described for a long time just as a defensive reagent against the action of toxic xenobiotics (drugs, pollutants, carcinogens). As a prototype antioxidant, it has been involved in cell protection from the noxious effect of excess oxidant stress, both directly and as a cofactor of glutathione peroxidases. In addition, it has long been known that GSH is capable of forming disulfide bonds with cysteine residues of proteins, and the relevance of this mechanism ("S-glutathionylation") in regulation of protein function is currently receiving confirmation in a series of research lines. Rather paradoxically, however, recent studies have also highlighted the ability of GSH-and notably of its catabolites-to promote oxidative processes, by participating in metal ion-mediated reactions eventually leading to formation of reactive oxygen species and free radicals. A crucial role in these phenomena is played by membrane bound gamma-glutamyltransferase activity. The significance of GSH as a major factor in regulation of cell life, proliferation, and death, should be regarded as the integrated result of all these roles it can play.

The general case for redox control of wound repair

The orthodox view has been that reactive oxygen species are primarily damaging to cells. There is general agreement that while high (3%) doses of H(2)O(2) may serve as a clinical disinfectant, its overall effect on healing is not positive. Current work shows that at very low concentrations, reactive oxygen species may regulate cellular signaling pathways by redox-dependent mechanisms. Recent discoveries show that almost all cells of the wound microenvironment contain specialized enzymes that utilize O(2) to generate reactive oxygen species. Numerous aspects of wound healing are subject to redox control. An understanding of how endogenous reactive oxygen species are generated in wound-related cells may influence the healing process and could result in new redox-based therapeutic strategies. Current results with growth factor therapy of wounds have not met clinical expectations. Many of these growth factors, such as platelet-derived growth factor, rely on reactive oxygen species for functioning. Redox-based strategies may serve as effective adjuncts to jump-start healing of chronic wounds. The understanding of wound-site redox biology is also likely to provide novel insights into the fundamental mechanisms that would help to optimize conditions for oxygen therapy. While a window of therapeutic opportunity seems to exist under conditions of low concentrations of reactive oxygen species, high levels may complicate regeneration and remodeling of nascent tissue.

Revisiting the essential role of oxygen in wound healing

Hypoxemia, caused by disrupted vasculature, is a key factor that limits wound healing. Correcting hypoxemia through the administration of supplemental oxygen (O(2)) can have significant beneficial impact on wound healing in the perioperative and outpatient settings. Beyond its role as a nutrient and antibiotic, O(2) may support vital processes such as angiogenesis, cell motility, and extracellular matrix formation. Recent discoveries highlight a novel aspect, addressing the role of O(2) in wound healing via the production of reactive oxygen species (ROS). Almost all wound-related cells possess specialized enzymes that generate ROS (including free radicals and H(2)O(2)) from O(2). Defect in these enzymes is associated with impaired healing. Low wound pO(2) is expected to compromise the function of these enzymes. At low concentrations, ROS serve as cellular messengers to support wound healing. The use of systemic hyperbaric O(2) therapy presents potential advantages, as well as risks. There is evidence to suspect that the use of pressure and systemic pure O(2) may not be essential in wound care. Elimination of these factors by using sub-pure systemic O(2) under normobaric conditions may significantly minimize the risk of O(2) toxicity. Furthermore, opportunities to treat dermal wounds using topical O(2) therapy warrant further investigation. Given that many growth factors require ROS for their function, it is reasonable to assume that approaches to correct wound pO(2) will serve as an effective adjunct in treating chronic wounds.

Mitochondrial dysfunction due to mutant copper/zinc superoxide dismutase associated with amyotrophic lateral sclerosis is reversed by N-acetylcysteine

We report that the expression of mutant G93A copper/zinc superoxide dismutase (SOD1), associated with familial amyotrophic lateral sclerosis, specifically causes a decrease in MTT reduction rate and ATP levels and an increase in both cytosolic and mitochondrial reactive oxygen species (ROS) production in human neuroblastoma SH-SY5Y cells compared to cells overexpressing wild-type SOD1 and untransfected cells. Exposure to N-acetylcysteine lowers ROS production and returns mitochondrial functional assays to control levels. No large aggregates of human SOD1 are detectable under basal growth conditions in any of the investigated cell lines. After proteasome activity inhibition, SOD1 aggregates can be detected exclusively in G93A-SOD1 cells, even though they do not per se enhance cell death compared to control cell lines. Our findings indicate that mitochondrial homeostasis is affected by mutant SOD1-generated ROS independently from the formation of aggregates and that this alteration is reversed by antioxidants.

Nitric oxide and mechanisms of redox signaling

Regulation of signal transduction and gene expression is a multifaceted process involving ligands, receptors, and second messengers that trigger cascades of protein kinases and phosphatases and propagate the signal to the nucleus to alter gene expression. Reduction-oxidation (redox)-based regulatory pathways provide additional means of gating signal transduction, and redox-based regulation of gene expression emerges as a fundamental regulatory mechanism in living cells. The cellular redox state is reflected by the degree of oxidation (or reduction) of various redox-active molecules at a specific cellular location at any given time point. The ratio of oxidized/reduced redox species determines the redox potential, which may vary dramatically in time and in different compartments of a cell and consequently alter in a temporally and spatially dynamic process the activity of signaling enzymes that carry redox-active functional groups. Generation and action of free radicals such as nitric oxide, superoxide, and H(2)O(2) that paradigmatically highlight the impact of redox regulation on cellular signal transduction and gene expression are discussed with a special focus on the renal glomerular response to injury.

Lipoic acid supplementation prevents angiotensin II-induced renal injury

BACKGROUND

Angiotensin II (Ang II)-induced renal injury is associated with perivascular inflammation, cell proliferation, and increased superoxide production in the vascular wall. We tested whether lipoic acid, an endogenous antioxidant, protects against the Ang II-induced inflammatory response and end-organ damage.

METHODS

Light microscopy, immunohistochemistry, electrophoretic mobility shift assay, Northern blots, and high-pressure liquid chromatography (HPLC) were used in kidneys from double transgenic rats (dTGR) harboring human renin and angiotensinogen genes and normotensive Sprague Dawley (SD) rats. The effects of lipoic acid supplementation for three weeks were examined in dTGR and SD rats.

RESULTS

Lipoic acid effectively prevented Ang II-induced glomerular and vascular damage in the kidneys and completely prevented the development of albuminuria. Ang II-induced leukocyte infiltration and cell proliferation in the kidney were attenuated. The redox-sensitive transcription factors nuclear factor (kappa) B (NF-kappa B) and activator protein-1 (AP-1) in the kidneys were increased in dTGR compared with SD, and were effectively reduced. Renal glutathione levels were much higher in dTGR than in SD, while the opposite was true for cysteine levels. These results suggested increased renal glutathione oxidation in dTGR, leading to cysteine shortage. Lipoic acid partly prevented renal cysteine depletion and increased hepatic cysteine and glutathione concentrations. This effect was accompanied by increased hepatic gamma-glutamylcysteine synthetase mRNA expression.

CONCLUSION

Our in vivo results suggest that lipoic acid protects against Ang II-induced renal injury through anti-inflammatory/antioxidative mechanisms. The effects are associated with decreased NF-kappa B and AP-1 activation, as well as improved thiol homeostasis.

Anti-angiogenic property of edible berry in a model of hemangioma

Hemangiomas represent a powerful model to study in vivo angiogenesis. Monocyte chemotactic protein 1 (MCP-1) is known to be responsible for recruiting macrophages to sites of infection or inflammation and facilitate angiogenesis. Recently we have demonstrated that edible berry extracts potently suppress inducible vascular endothelial growth factor expression and in vitro angiogenesis. Comparative analysis of several berry extracts led to the observation that wild blueberry and a berry mix were most effective. Our goal was to follow up on our findings with wild blueberry and the berry mix (OptiBerry). The present work rests on our current finding that these two berry powders significantly inhibit inducible MCP-1 expression in endothelioma cells. Therefore, we sought to examine the effects of wild blueberry and berry mix in an in vivo model of experimental angiogenesis. Reporter studies showed that the berry powders significantly inhibited basal MCP-1 transcription and inducible nuclear factor kappaB transcription. Endothelioma cells pre-treated with berry powders showed diminished ability to form hemangioma. Histological analysis demonstrated markedly decreased infiltration of macrophages in hemangioma of treated mice compared to placebo-treated controls. The current results provide the first in vivo evidence substantiating the anti-angiogenic property of edible berries.

Differential roles of hydrogen peroxide and superoxide in mediating IL-1-induced NF-kappa B activation and iNOS expression in bovine articular chondrocytes

Our previous studies showed that reactive oxygen species (ROS) are required for the pro-inflammatory cytokine interleukin-1 beta (IL-1) to induce the activity of the Nuclear transcription Factor-kappa B (NF-kappa B) and the expression of the inducible isoform of the nitric oxide synthase (iNOS) in bovine articular chondrocytes. This study aimed at elucidating the role of hydrogen peroxide (H(2)O(2)) and the superoxide radical, two major ROS, in mediating those IL-1-induced responses. The results obtained show that chondrocytes produce both H(2)O(2) and superoxide radical in response to IL-1. Treatment of the chondrocyte cultures with H(2)O(2) alone did not induce NF-kappa B activation or iNOS expression. Addition of H(2)O(2) simultaneously with IL-1 did neither enhance nor inhibit NF-kappa B activation and iNOS expression, relatively to treatment with IL-1 alone. Accordingly, treatment with catalase did not inhibit those IL-1-induced responses. Treatment with superoxide dismutase, however, effectively prevented IL-1-induced I kappa B-alpha degradation and iNOS expression. Taken together, the results obtained indicate that superoxide mediates IL-1-induced I kappa B-alpha degradation and the consequent NF-kappa B activation and iNOS expression in chondrocytes, whereas H(2)O(2) does not seem to participate in those IL-1-induced responses. In conclusion, the present study identifies the superoxide radical as the ROS involved in mediating the IL-1-induced signaling pathway that leads to NF-kappa B activation and to the expression of NF-kappa B-dependent genes in bovine articular chondrocytes.

Obstructive sleep apnoea syndrome--an oxidative stress disorder

Obstructive sleep apnoea syndrome (OSA) is associated with increased cardiovascular morbidity and mortality. However, the underlying mechanisms are not entirely understood. This review will summarize the evidence that substantiates the notion that the repeated apnoea-related hypoxic events in OSA, similarly to hypoxia/reperfusion injury, initiate oxidative stress. Thus, affecting energy metabolism, redox-sensitive gene expression, and expression of adhesion molecules. A limited number of studies substantiate this hypothesis directly by demonstrating increased free radical production in OSA leukocytes and increased plasma-lipid peroxidation. A great number of studies, however, support this hypothesis indirectly. Increase in circulating levels of adenosine and urinary uric acid in OSA are implicated with increased production of reactive oxygen species (ROS). Activation of redox-sensitive gene expression is suggested by the increase in some protein products of these genes, including VEGF, erythropoietin, endothelin-1, inflammatory cytokines and adhesion molecules. These implicate the participation of redox-sensitive transcription factors as HIF-1 AP-1 and NFkappaB. Finally, adhesion molecule-dependent increased avidity of OSA monocytes to endothelial cells, combined with diminished NO bioavailability, lead to exaggerated endothelial cell damage and dysfunction. Cumulatively, these processes may exacerbate atherogenic sequelae in OSA.

Early oxidative stress in the diabetic kidney: effect of DL-alpha-lipoic acid

Oxidative stress is implicated in the pathogenesis of diabetic nephropathy. The attempts to identify early markers of diabetes-induced renal oxidative injury resulted in contradictory findings. We characterized early oxidative stress in renal cortex of diabetic rats, and evaluated whether it can be prevented by the potent antioxidant, DL-alpha-lipoic acid. The experiments were performed on control rats and streptozotocin-diabetic rats treated with/without DL-alpha-lipoic acid (100 mg/kg i.p., for 3 weeks from induction of diabetes). Malondialdehyde plus 4-hydroxyalkenal concentration was increased in diabetic rats vs. controls (p <.01) and this increase was partially prevented by DL-alpha-lipoic acid. F(2) isoprostane concentrations (measured by GCMS) expressed per either mg protein or arachidonic acid content were not different in control and diabetic rats but were decreased several-fold with DL-alpha-lipoic acid treatment. Both GSH and ascorbate (AA) levels were decreased and GSSG/GSH and dehydroascorbate/AA ratios increased in diabetic rats vs. controls (p <.01 for all comparisons), and these changes were completely or partially (AA) prevented by DL-alpha-lipoic acid. Superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione transferase, and NADH oxidase, but not catalase, were upregulated in diabetic rats vs. controls, and these activities, except glutathione peroxidase, were decreased by DL-alpha-lipoic acid. In conclusion, enhanced oxidative stress is present in rat renal cortex in early diabetes, and is prevented by DL-alpha-lipoic acid.

Alpha-tocopherol induces expression of connective tissue growth factor and antagonizes tumor necrosis factor-alpha-mediated downregulation in human smooth muscle cells

The effect of alpha-tocopherol treatment on gene expression in human aortic vascular smooth muscle cells was analyzed by gene expression arrays. The expression of the connective tissue growth factor (CTGF) gene was induced by alpha-tocopherol 1.8-fold in gene array experiments, and similar results were also obtained by RT-PCR (1.7-fold) and at the protein level (1.4-fold). The antioxidants beta-tocopherol and N-acetylcysteine did not induce CTGF gene expression, suggesting a nonantioxidant mechanism for alpha-tocopherol action. Protein kinase C (PKC) inhibition by alpha-tocopherol has been previously described. However, PKC downregulation did not prevent CTGF induction by alpha-tocopherol, and inhibition of PKC activity with several inhibitors did not increase its expression, suggesting an alternative pathway for the alpha-tocopherol effect. On the other hand, tumor necrosis factor-alpha reduced the expression of CTGF, an effect that was reversed by antioxidants. The data suggest that tumor necrosis factor-alpha inhibition of CTGF gene expression is prevented in an antioxidant-sensitive process and that alpha-tocopherol increases CTGF expression by a PKC-independent, nonantioxidant mechanism. Because CTGF stimulates the synthesis of extracellular matrix, the normalization of CTGF gene expression by alpha-tocopherol may accelerate wound repair and tissue regeneration during atherosclerosis.