Oxidant-induced Damage Research Articles

Protective Effects of Liposomal N-Acetylcysteine against Paraquat-Induced Cytotoxicity and Gene Expression

Paraquat (PQ) is a herbicide that preferentially accumulates in the lung and exerts its cytotoxicity via the generation of reactive oxygen species (ROS). There is no specific treatment for paraquat poisoning. Attempts have been made to increase the antioxidant status in the lung using antioxidants (e.g., superoxide dismutase, vitamin E, N-acetylcysteine) but the outcome from such treatments is limited. Encapsulation of antioxidants in liposomes improves their therapeutic potential against oxidant-induced lung damage because liposomes facilitate intracellular delivery and prolong the retention of entrapped agents inside the cell. In the present study, we compared the effectiveness of conventional N-acetylcysteine (NAC) and liposomal-NAC (L-NAC) against PQ-induced cytotoxicity and examined the mechanism(s) by which these antioxidant formulations conferred cytoprotection. The effects of NAC or L-NAC against PQ-induced cytotoxicity in A549 cells were assessed by measuring cellular PQ uptake, intracellular glutathione content, ROS levels, mitochondrial membrane potential, cellular gene expression, inflammatory cytokine release and cell viability. Pretreatment of cells with L-NAC was significantly more effective than pretreatment with the conventional drug in reducing PQ-induced cytotoxicity, as indicated by the biomarkers used in this study. Our results suggested that the delivery of NAC as a liposomal formulation improves its effectiveness in counteracting PQ-induced cytotoxicity.

The DNA glycosylase Ogg1 defends against oxidant-induced mtDNA damage and apoptosis in pulmonary artery endothelial cells

Emerging evidence suggests that mitochondrial (mt) DNA damage may be a trigger for apoptosis in oxidant-challenged pulmonary artery endothelial cells (PAECs). Understanding the rate-limiting determinants of mtDNA repair may point to new targets for intervention in acute lung injury. The base excision repair (BER) pathway is the only pathway for oxidative damage repair in mtDNA. One of the key BER enzymes is Ogg1, which excises the base oxidation product 8-oxoguanine. Previously we demonstrated that overexpression of mitochondrially targeted Ogg1 in PAECs attenuated apoptosis induced by xanthine oxidase (XO) treatment. To test the idea that Ogg1 is a potentially rate-limiting BER determinant protecting cells from oxidant-mediated death, PAECs transfected with siRNA to Ogg1 were challenged with XO and the extent of mitochondrial and nuclear DNA damage was determined along with indices of apoptosis. Transfected cells demonstrated significantly reduced Ogg1 activity, which was accompanied by delayed repair of XO-induced mtDNA damage and linked to increased XO-mediated apoptosis. The nuclear genome was undamaged by XO in either control PAECs or cells depleted of Ogg1. These observations suggest that Ogg1 plays a critical and possibly rate-limiting role in defending PAECs from oxidant-induced apoptosis by limiting the persistence of oxidative damage in the mitochondrial genome.

Apurinic Apyrimidinic Endonuclease/Redox Effector Factor 1 Immunoreactivity and Grading in Hepatocellular Carcinoma Risk of Relapse After Liver Transplantation

Apurinic apyrimidinic endonuclease (APE1)/redox effector factor 1 (Ref-1), which is a multifunction protein involved in both transcriptional regulation of gene expression during adaptive cellular responses to oxidative stress and in the base excision repair pathway of DNA lesions generated as a consequence of oxidant-induced base damage, contributes to the maintenance of genome stability. APE1/Ref-1 is normally localized in the nucleus; cytoplasmic localization observed in several tumors has been correlated with a poor prognosis. Hepatocellular carcinoma (HCC) grading is an essential tool to predict the risk of relapse and patient prognosis, particularly in patients undergoing liver transplantation (OLT). The aim of this study was to identify the role of APE1/Ref-1 in predicting a posttransplant HCC relapse. We studied 48 patients transplanted for HCC to define grading as well as nuclear and cytoplasmic APE1/Ref-1 expression within neoplastic versus nonneoplastic parenchyma. We defined a cutoff of 60% of cytoplasmic APE1/Ref-1 expression to identify positive cases. At a minimum of 1.5-year follow-up after transplantation, 32 patients are alive and 16 patients are deceased after HCC relapse. Among low-grade HCC (grades 1 and 2), 76% of cases are alive; only 34% showed cytoplasmic APE1/Ref-1 immunoreactivity. Among the high-grade cases (grades 3 and 4), 50% were alive with 64% showing cytoplasmic immunoreactivity. Nuclear reactivity was generally similar either in neoplastic or in cirrhotic livers, irrespective of the grade. These data seemed to support the hypothesis of a predictive role of APE1/Ref-1 for HCC risk of relapse, which together with tumor grade by analysis of a pretransplant needle biopsy should aid decision making for OLT.

Baculovirus P35 protein: An overview of its applications across multiple therapeutic and biotechnological arenas

Baculovirus immediate early P35 protein is well known for its anti-apoptotic as well as anti-oxidant properties. Mechanism of action of P35 involves inhibition of a vast range of initiator to executioner class of caspases. In addition, P35's role in inhibiting oxidant-induced mitochondrial damage, primarily in the apoptotic pathway, has also been extensively investigated. Elucidation of P35's functions during regulation of programmed cell death (PCD) has led to a renewed focus on exploiting this basic knowledge for clinical and other related applications. This review outlines specific biochemical and genetic pathways where P35 intervenes and regulates rate-limiting steps in the apoptotic signaling cascade. Research efforts are underway to utilize P35 as an agent in regulating apoptosis and under certain circumstances, also explore the therapeutic potential of its anti-oxidant features. One of the major outcomes of recent studies include significantly improved effectiveness of cytochrome P450 directed enzyme pro-drug delivery tools when used in conjunction with P35, which may help in alleviating drug resistance in tumor cells and simultaneously prolonging the cytotoxic effects of anti-cancer drugs. Moreover, applied research carried out recently in the fields of diabetes, ischemia-induced neuronal cell death, experimental autoimmune encephalomyelitis (EAE), multiple sclerosis (MS), inflammatory arthritis, cardiovascular and ocular disorders illustrate P35's utilization across diverse therapeutic areas and will certainly make it an attractive biomolecule for the discovery research.

The role of APP processing in oxidant-induced damage in cultured neuroblastoma cells

The role of APP processing in oxidant-induced damage in cultured neuroblastoma cells

Promotion of cardiovascular disease by exposure to the air pollutant ozone

in the decades following the discovery of the chemical nature of environmental air pollutants and the biochemical reactions they could undergo, it was viewed that the primary tissue target of air pollution would be our lungs. This made sense, as the principal constituents of photochemical air

Deletion of Keap1 in the Lung Attenuates Acute Cigarette Smoke–Induced Oxidative Stress and Inflammation

Exposure to cigarette smoke (CS) is the primary factor associated with the development of chronic obstructive pulmonary disease (COPD). CS increases the level of oxidants in the lungs, resulting in a depletion of antioxidants, which promotes oxidative stress and the destruction of alveolar tissue. In response to CS, pulmonary epithelial cells counteract increased levels of oxidants by activating Nrf2-dependent pathways to augment the expression of detoxification and antioxidant enzymes, thereby protecting the lung from injury. We hypothesize that increasing the pathways activated by Nrf2 will afford protection against CS-induced lung damage. To this end we have developed a novel mouse model in which the cytosolic inhibitor of Nrf2, Keap1, is genetically deleted in Clara cells, which predominate in the upper airways in mice. Deletion of Keap1 in Clara cells resulted in increased expression of Nrf2-dependent genes, such as Nqo1 and Gclm, as determined by microarray analysis and quantitative PCR. Deletion of Keap1 in airway epithelium decreased Keap1 protein levels and significantly increased the total level of glutathione in the lungs. Increased Nrf2 activation protected Clara cells against oxidative stress ex vivo and attenuated oxidative stress and CS-induced inflammation in vivo. Expression of KEAP1 was also decreased in human epithelial cells through siRNA transfection, which increased the expression of Nrf2-dependent genes and attenuated oxidative stress. In conclusion, activating Nrf2 pathways in tissue-specific Keap1 knockout mice represents an important genetic approach against oxidant-induced lung damage.

Investigation of Lipid Profiles and Lipid Peroxidation in Patients with Type 2 Diabetes

The aim of this study was to investigat the lipid peroxidation of plasma as a marker of oxidant-induced protein damage the effects of oxygen radicals on glycated-hemoglobin and to find out the relationship between the increase level of Malondialdehyde (MDA) on HbA1C, lipid profiles and FBS (Fasting Blood Sugar) in patients with type 2 diabetes. This randomized study included 200 individuals, 100 cases had history of diabetic for at least 3 years (file in Isfehan hospital, Diabetic Center of Medical Sciences University) and 100 cases as the control group without history of diabetes. In both groups, level of MDA, FBS, lipid profiles and HbA1C were determined in fasting blood samples. Results showed that MDA level in diabetic patients was significantly (p<0.005) higher (0.9222 ± 0.3 μmol/L) than those in the control group (0.7428 ± 0.04μmol/L). The same was also true (p<0.05) for the level of HbA1C (9.387 ± 2.4 mg/dl in diabetic patients and 7.356 ± 1.0 mg/dl in the control group) and the FBS (163.31 ± 56mg/dl in patient group and 85.740 ± 10.1 in the control group). Furthermore, the concentration of, LDL significantly was higher (p<0.05) and the HDL level were significantly lower (p<0.05) in case group as compared to control group. The increased plasma lipid peroxidation and decreased plasma HDL that we observed in patients with type 2 diabetes mellitus indicated that these may predispose to the development of cardiovascular complications. © EuroJournals Publishing, Inc. 2009.

Mitochondrial oxidative stress and dysfunction in myocardial remodelling

Recent experimental and clinical studies have suggested that oxidative stress is enhanced in myocardial remodelling and failure. The production of oxygen radicals is increased in the failing heart, whereas normal antioxidant enzyme activities are preserved. Mitochondrial electron transport is an enzymatic source of oxygen radical generation and can be a therapeutic target against oxidant-induced damage in the failing myocardium. Chronic increases in oxygen radical production in the mitochondria can lead to a catastrophic cycle of mitochondrial DNA (mtDNA) damage as well as functional decline, further oxygen radical generation, and cellular injury. Reactive oxygen species induce myocyte hypertrophy, apoptosis, and interstitial fibrosis by activating matrix metalloproteinases. These cellular events play an important role in the development and progression of maladaptive myocardial remodelling and failure. Therefore, oxidative stress and mtDNA damage are good therapeutic targets. Overexpression of the genes for peroxiredoxin-3 (Prx-3), a mitochondrial antioxidant, or mitochondrial transcription factor A (TFAM), could ameliorate the decline in mtDNA copy number in failing hearts. Consistent with alterations in mtDNA, the decrease in mitochondrial function was also prevented. Therefore, the activation of Prx-3 or TFAM gene expression could ameliorate the pathophysiological processes seen in mitochondrial dysfunction and myocardial remodelling. Inhibition of oxidative stress and mtDNA damage could be novel and effective treatment strategies for heart failure.

The ketogenic diet increases mitochondrial glutathione levels

The ketogenic diet (KD) is a high-fat, low carbohydrate diet that is used as a therapy for intractable epilepsy. However, the mechanism(s) by which the KD achieves neuroprotection and/or seizure control are not yet known. We sought to determine whether the KD improves mitochondrial redox status. Adolescent Sprague-Dawley rats (P28) were fed a KD or control diet for 3 weeks and ketosis was confirmed by plasma levels of beta-hydroxybutyrate (BHB). KD-fed rats showed a twofold increase in hippocampal mitochondrial GSH and GSH/GSSG ratios compared with control diet-fed rats. To determine whether elevated mitochondrial GSH was associated with increased de novo synthesis, the enzymatic activity of glutamate cysteine ligase (GCL) (the rate-limiting enzyme in GSH biosynthesis) and protein levels of the catalytic (GCLC) and modulatory (GCLM) subunits of GCL were analyzed. Increased GCL activity was observed in KD-fed rats, as well as up-regulated protein levels of GCL subunits. Reduced CoA (CoASH), an indicator of mitochondrial redox status, and lipoic acid, a thiol antioxidant, were also significantly increased in the hippocampus of KD-fed rats compared with controls. As GSH is a major mitochondrial antioxidant that protects mitochondrial DNA (mtDNA) against oxidative damage, we measured mitochondrial H2O2 production and H2O2-induced mtDNA damage. Isolated hippocampal mitochondria from KD-fed rats showed functional consequences consistent with the improvement of mitochondrial redox status i.e. decreased H2O2 production and mtDNA damage. Together, the results demonstrate that the KD up-regulates GSH biosynthesis, enhances mitochondrial antioxidant status, and protects mtDNA from oxidant-induced damage.

Protein metabolism in severe childhood malnutrition

The major clinical syndromes of severe childhood malnutrition (SCM) are marasmus (non-oedematous SCM), kwashiorkor and marasmic-kwashiorkor (oedematous SCM). Whereas treatment of marasmus is straightforward and the associated mortality is low, kwashiorkor and marasmic-kwashiorkor are difficult to treat and have high morbidity and mortality rates. Despite extensive research, the pathogenic factors which cause a child to develop the oedematous instead of the non-oedematous form of SCM in response to food deprivation are still not clear. Over the years, two attractive hypotheses have been put forward. The first proposed that a dysadaptation in protein metabolism was involved and the second proposed that free radical damage of cellular membranes might be involved. To address aspects of these hypotheses, in this article we have reviewed work done by our group and by others on protein metabolism and pro-oxidant/anti-oxidant homeostasis in children with the oedematous and non-oedematous syndromes of SCM. A significant finding is that when there is chronic food deprivation children with non-oedematous SCM can maintain body protein breakdown at the same rate as when they are well nourished, but children with oedematous SCM cannot. The slower protein breakdown rate of children with oedematous SCM reduces the supply of most amino acids, resulting in decreased availability for the synthesis of plasma proteins involved in nutrient transport and the acute phase response to infection. Another consistent finding is that children with oedematous SCM have oxidative stress as there is evidence of oxidant-induced cellular damage and impaired synthesis of the primary cellular anti-oxidant glutathione.

Decreased Expression of Peroxiredoxins in Fuchs’ Endothelial Dystrophy

To compare the relative expression of peroxiredoxin (Prx) proteins in normal human corneal endothelium with endothelium in corneas affected by Fuchs' endothelial dystrophy (FED) and between normal human endothelium and epithelial/stromal tissue. Human corneal endothelial cell-Descemet's membrane (HCEC-DM) complexes from normal and FED corneal buttons were dissected from the epithelium/stroma. For proteomic analysis, HCEC-DM protein extracts were separated by using two-dimensional gel electrophoresis. Relative differences in protein spot density was analyzed. Proteins of interest, including Prx isoforms, were identified by MALDI-TOF (matrix-assisted desorption ionization-time of flight) mass spectrometry. Western blot analysis compared the relative expression of Prx isoforms in normal and FED endothelium and between normal endothelium and normal epithelium/stroma. Expression of Prx-2 mRNA was compared by using real-time PCR. Proteomic analysis identified differences in the relative expression of Prx isoforms between normal and FED endothelium. Western blot analysis confirmed that expression of Prx-2, -3, and -5 was significantly decreased (P < 0.05) in FED cells. Normal HCECs expressed significantly (P < 0.05) higher levels of Prx-2 and -3 than did the epithelium/stroma. Expression of Prx-5 was not significantly different (P > 0.05) in the endothelium versus the epithelium/stroma. Real-time PCR analysis revealed that Prx-2 mRNA was significantly decreased (P = 0.027) in FED samples. Prx proteins were identified in human corneal endothelium. The fact that Prx-2 and -3 were expressed at significantly higher levels in HCEC-DM compared with the epithelium/stroma reflects the different physiologic activities of individual corneal cell types. Significantly decreased expression of Prx-2, -3, and -5 in FED may suggest an alteration in the ability of endothelial cells to withstand oxidant-induced damage and may be closely related to the pathogenesis of this disease.

Metallothionein Induction by Hypoxia Involves Cooperative Interactions between Metal-Responsive Transcription Factor-1 and Hypoxia-Inducible Transcription Factor-1α

Mammalian metallothionein (MT) genes are transcriptionally activated by the essential metal zinc as well as by environmental stresses, including toxic metal overload and redox fluctuations. In addition to playing a key role in zinc homeostasis, MT proteins can protect against metal- and oxidant-induced cellular damage, and may participate in other fundamental physiologic and pathologic processes such as cell survival, proliferation, and neoplasia. Previously, our group reported a requirement for metal-responsive transcription factor-1 (MTF-1) in hypoxia-induced transcription of mouse MT-I and human MT-IIA genes. Here, we provide evidence that the protumorigenic hypoxia-inducible transcription factor-1alpha (HIF-1alpha) is essential for induction of MT-1 by hypoxia, but not zinc. Chromatin immunoprecipitation assays revealed that MTF-1 and HIF-1alpha are both recruited to the mouse MT-I promoter in response to hypoxia, but not zinc. In the absence of HIF-1alpha, MTF-1 is recruited to the MT-I promoter but fails to activate MT-I gene expression in response to hypoxia. Thus, HIF-1alpha seems to function as a coactivator of MT-I gene transcription by interacting with MTF-1 during hypoxia. Coimmunoprecipitation studies suggest interaction between MTF-1 and HIF-1alpha, either directly or as mediated by other factors. It is proposed that association of these important transcription factors in a multiprotein complex represents a common strategy to control unique sets of hypoxia-inducible genes in both normal and diseased tissue.

Oxidative Stress and Mitochondrial DNA Damage in Heart Failure

Recent experimental and clinical studies have suggested that oxidative stress is enhanced in heart failure. The production of oxygen radicals is increased in the failing heart while antioxidant enzyme activities are preserved. Mitochondrial electron transport is an enzymatic source of oxygen radical generation and also a target against oxidant-induced damage in the failing myocardium. Chronic increases in oxygen radical production in the mitochondria can lead to a catastrophic cycle of mitochondrial DNA (mtDNA) damage, as well as functional decline, further oxygen radical generation, and cellular injury. Reactive oxygen species induce myocyte hypertrophy, apoptosis, and interstitial fibrosis by activating matrix metalloproteinases. These cellular events play an important role in the development and progression of maladaptive cardiac remodeling and failure. Therefore, oxidative stress and mtDNA damage are good therapeutic targets. Overexpression of peroxiredoxin-3 (Prx-3), mitochondrial antioxidant, or mitochondrial transcription factor A (TFAM) could ameliorate the decline in mtDNA copy number in failing hearts. Consistent with alterations in mtDNA, the decrease in oxidative capacities is also prevented. Therefore, the activation of Prx-3 or TFAM expression could ameliorate the pathophysiological processes seen in myocardial failure. Inhibition of oxidative stress and mtDNA damage could be novel and potentially effective treatment strategies for heart failure.

Sulfur-Containing Compounds in Protecting Against Oxidant-Mediated Lung Diseases

Over 95% of the oxygen we metabolize undergoes a four-electron reduction to produce two molecules of water. Whenever electrons escape from the mitochondrial electron-transport chain and pass directly onto oxygen, oxidants that can cause cytotoxicity are generated. The lung being constantly exposed to atmospheric oxygen is more susceptible to oxidant-induced cellular damage. For instance, increased generation of oxidants is implicated in many pulmonary pathological conditions including emphysema, adult respiratory distress syndrome, idiopathic pulmonary fibrosis and asthma. Sulfur is an essential major inorganic element with a recently described protective cellular role. One of its many biologically important functions is the formation of disulfide bridges between two cysteine molecules thus stabilizing protein conformation. Also, it provides the site for attachment and transfer of 1-C methyl groups via formation of S-adenosylmethionine, and most importantly it is an essential constituent of the antioxidant tripeptide, glutathione, and vitamins like thiamin and biotin. However, its protective role emanates from its antioxidant properties in the context of sulfur-containing compounds (S-adenosylmethionine, cysteine, taurine, glutathione etc) that are known to act in protecting against oxidant-induced lung disease. The efficacy of these sulfur-containing compounds in scavenging oxidants directly or indirectly and consequently protecting against lung diseases is discussed herein.

Flupirtine attenuates sodium nitroprusside-induced damage to retinal photoreceptors, in situ

Flupirtine has been shown to function as a neuroprotectant and is presently used in man to treat a number of conditions. The aim of this study was to investigate the specific antioxidant properties of flupirtine in relation to oxidant-induced damage to retinal photoreceptors. Initial in vitro studies on brain membranes showed that flupirtine was approximately 20 times more potent than trolox (vitamin E analogue) and 8 times more potent than metipranolol at attenuating lipid peroxidation caused by the nitric oxide donor, sodium nitroprusside (SNP). Subsequent immunohistochemical studies revealed that following an intraocular injection of SNP, retinal photoreceptors are the only retinal cell types that appear to be clearly affected. This was supported by electroretinogram (ERG) recordings which showed both the a- and b-wave amplitudes to be significantly reduced. Western blotting techniques showed that SNP caused a significant decrease in photoreceptor-specific markers (RET-P1, rhodopsin kinase), an increase in cleaved caspase-3, Bcl-2, and cleaved PARP proteins that are associated with apoptosis and no change in the ganglion cell specific marker, neurofilament (NF-L). This was supported by RT-PCR data where rhodopsin (photoreceptor specific) mRNA was reduced while Thy-1 and NF-L (ganglion cell specific) mRNAs were unaffected. In addition SNP caused an elevation of glial cell response mRNAs primarily associated with Müller cells (GFAP, CNTF, bFGF) as well as caspase-3 and Bcl-2. Importantly, when flupirtine was co-injected, the effects to the retina caused by SNP on retinal proteins and mRNAs were in most cases significantly blunted. The conclusion reached from this study is that flupirtine is a powerful antioxidant and when injected into the eye with SNP attenuates the detrimental influence of SNP to retinal photoreceptors. Since oxidative stress has been implicated in retinal diseases like age-related macular degeneration (AMD) this study provides “proof of principle” for the idea that flupirtine may help individuals suffering from such retinal diseases.

A review of ozone-induced effects on the forests of central Mexico

The first report on oxidant-induced plant damage in the Valley of Mexico was presented over 30 years ago. Ozone is known to occur in the Mexico City Metropolitan Area and elsewhere as the cause of chlorotic mottling on pine needles that are 2 years old or older as observed in 1976 on Pinus hartwegii and Pinus leiophylla. Visible evidences for the negative effects of ozone on the vegetation of central Mexico include foliar injury expressed as chlorotic mottling and premature defoliation on pines, a general decline of sacred fir, visible symptoms on native forest broadleaved species (e.g. Mexican black cherry). Recent investigations have also indicated that indirect effects are occurring such as limited root colonization by symbiotic fungi on ozone-damaged P. hartwegii trees and a negative influence of the pollutant on the natural regeneration of this species. The negative ozone-induced effects on the vegetation will most likely continue to increase.

The Role of Oxidative Stress in Spontaneous Abortion and Recurrent Pregnancy Loss: A Systematic Review

Human reproduction is not considered a highly efficient biological process. Before the end of the first trimester, 30%-50% of conceptions end in spontaneous abortion. Most losses occur at the time of implantation. 15%-20% of clinical pregnancies end in spontaneous abortions. Recurrent pregnancy loss is a frustrating clinical problem both for clinicians and patients. Recurrent pregnancy loss affects 0.5%-3% of women in the reproductive age group, and between 50%-60% of recurrent pregnancy losses are idiopathic. Oxidative stress-induced damage has been hypothesized to play a role in spontaneous abortion, idiopathic recurrent pregnancy loss, hydatidiform mole, defective embryogenesis, and drug-induced teratogenicity. Some studies implicate systemic and placental oxidative stress in the pathophysiology of abortion and recurrent pregnancy loss. Oxidant-induced endothelial damage, impaired placental vascularization and immune malfunction have all been proposed to play a role in the pathophysiology of idiopathic recurrent pregnancy loss. Oxidative stress-induced placental dysfunction may be a common cause of the multifactorial and polygenic etiologies of abortion, recurrent pregnancy loss, defective embryogenesis, hydatidiform mole, and drug-induced teratogenic effects. Oxidative stress-induced modification of phospholipids has been linked to the formation of antiphospholipid antibodies in the antiphospholipid syndrome. The objective of this review was to examine the association between oxidative stress, spontaneous abortion and recurrent pregnancy loss, based on the published literature. We conducted an extensive literature search utilizing the databases of Medline, CINAHL, and Cochrane from 1986 to 2005. The following keywords were used: oxidative stress, abortion, recurrent pregnancy loss, reactive oxygen species, antioxidants, fetal development, and embryopathies. We conducted an electronic search, as well as a manual search of cross-references. We have included all studies in the English language found in the literature focusing on oxidative stress and its association with abortions, recurrent pregnancy loss and drug-induced teratogenicity. The role of antioxidant vitamins for primary prevention of oxidative stress-induced pathologies needs to be investigated further. Obstetricians & Gynecologists, Family Physicians. After completion of this article, the reader should be able to state that the causes of spontaneous and recurrent abortion are multifaceted, however, some of the causes may be preventable and also explain that the role of oxidative stress during pregnancy and adverse pregnancy outcomes has a basis in pathophysiology, although the role of oxidative stress and the treatment of oxidative stress during or before pregnancy remains speculative.

Good science shows the way: Highlight Commentary on “Redox proteomics analysis of oxidatively modified proteins in G93A–SOD1 transgenic mice—A model of familial amyotrophic lateral sclerosis” ☆

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the degeneration of pyramidal neurons in the motor cortex and motor neurons in the brain stem and spinal cord. There is not cure for ALS and the patients typically die of respiratory failure between 1 and 5 years after diagnostic. The causes of ALS are unknown. Most of the cases are sporadic and 10% of the cases are hereditary (familial ALS) [1]. In 1993, mutations in the gene of the antioxidant enzyme superoxide dismutase were linked to 2–3% of the cases of familial ALS [2]. These reports lead to the oxidative stress hypothesis in ALS, which was first though to be produced by a loss-of-function. Soon after, it becomes clear that the mutations were responsible for a gain-of-function. The mutant SOD gain of toxic function hypothesis was based in the fact that some mutant enzymes had the same activity than wild type SOD, mice deficient for SOD do not develop motor neuron disease and mice transgenic for mutant, but not to wild type SOD develop an ALS-like disease [3]. At the same time markers of oxidative damage were reported in human ALS patients and transgenic mice models of ALS. Although, the oxidative hypothesis to explain the mutant SOD gain-in-function does not have general acceptance [4], the fact that oxidation occurs in ALS patients and animal models of the disease is incontrovertible [5]. However, whether oxidative damage plays a central role in the induction of motor neuron death, or is a co-phenomenon without pathological implications, remains unknown. This unknown has lead to skepticism in many ALS investigators, which consider oxidative stress no more than a secondary phenomenon of little or no importance in the pathogenesis of the disease [4]. The main problem in the research of oxidant-induced damage has been identifying relevant targets of oxidative damage. In 1995, two papers were publishing that brought the strength of powerful analytical methods to oxidative stress in ALS [6,7]. One identified carbonyl formation [6] and the other tyrosine nitration [7] in pre-symptomatic animal models of ALS using two-dimension gel electrophoresis and mass spectrometry analysis. More importantly was the identification of specific target proteins with possible implications in the pathology of the disease. Remarkably, the oxidized proteins identified by Poon et al are present in aggregates in human patients and animal models of ALS [6]. One of the oxidized proteins identified was SOD1 itself. Oxidation of SOD changes its biochemical properties and the metal binding properties. In addition, the paper this report takes a more conservative approach on previously extreme positions. In this publication, the Butterfield group discusses how protein aggregation could be caused by oxidative stress, linking two apparently irreconcilable positions, more because of the attitude of the researches than the nature of the results [6]. It is possible that many investigators dismiss these papers as more of those oxidative stress papers; but the fact the Poon’s report is one of the higher download papers from Free Radical Biology and Medicine indicates it has also awaken the curiosity of many other investigators. It seems that making an interpretation that explains much of the available results attract new interest in continue these important investigations. In this era in which new ideas and hypotheses are embraced as the last “true,” while at the same time old ideas and hypotheses are forget, even those supported by experimental evidence. In which it becomes very difficult to publish anything against the new “dogma,” or that is not “fashionable” anymore and only a few recognizable journals keep reviewing and publishing these “old and out of fashion papers.” Scientist that test the hypothesis using sound and accepted and many times state of the art approaches are always refreshing. When in addition, these papers further advance the knowledge in one field based on evidence and a fair interpretation of the results supported by previous knowledge is always something worthy to read. We are still do not know whether oxidative stress or any of the identified oxidized proteins play a role in ALS. We do not know either whether protein aggregation plays a role in the pathogenesis of ALS. There is not irrefutable evidence linking protein oxidation and aggregation in motor neuron degeneration. Would it not be great to know?

Resistance of quiescent and proliferating airway epithelial cells to H2O2 challenge

Alveolar epithelial cell injury and recovery are important in the pathogenesis of oxidant-induced lung damage. The alveolar cell line A549 was used to study responses of proliferating and quiescent cells in culture to time- and dose-dependent hydrogen peroxide (H(2)O(2)) challenges. Recovery was monitored after 24 h of incubation in fresh medium with 10% serum. The adherent cells were counted and the resistance and recovery of the attached cells was assessed by appearance, by measuring the number of viable, apoptotic and necrotic cells using fluorescent-activated cell sorting, and by determining the intracellular free thiol content. A549 cells recovered from a 1-h challenge with up to 1 mM H(2)O(2) but could not sustain a more prolonged challenge (6 or 24 h) with 0.5 mM or 1.0 mM H(2)O(2). These more severe conditions resulted in: loss of cells by detachment from the plate surface; reduced numbers of viable cells primarily due to necrosis; and a strong reduction of the intracellular free thiol content. Quiescent cells proved to be more sensitive to oxidative stress than proliferating cells. Intracellular free thiol levels apparently play a decisive role in cell survival, preferentially protecting proliferating cells.