4-hydroxynonenal inhibits Na(+)-K(+)-ATPase

Lipid-derived electrophiles inhibit the function of membrane channels during ferroptosis

The therapeutic targeting of ferroptosis requires full understanding of the molecular mechanism of this regulated cell death pathway. While lipid-derived electrophiles (LDEs), including 4-hydroxy-2-nonenal (4-HNE), are important biomarkers of ferroptosis, a functional role for these highly reactive species in ferroptotic cell death execution has not been established. Here, through mechanistic characterization of LDE-detoxification impairment, we demonstrate that LDEs mediate altered protein function during ferroptosis. Applying live cell fluorescence imaging, we first identified that export of glutathione-LDE-adducts through multidrug resistance-associated protein (MRP) channels is inhibited following exposure to a panel of ferroptosis inducers (FINs) with different modes of action (type I-IV FINs erastin, RSL3, FIN56, and FINO2). This channel inhibition was recreated by both initiation of lipid peroxidation and treatment with 4-HNE. Importantly, treatment with radical-trapping antioxidants prevented impaired LDE-adduct export when working with both FINs and lipid peroxidation initiators but not 4-HNE, pinpointing LDEs as the cause of this inhibited MRP activity observed during ferroptosis. Our findings, when combined with reports of widespread LDE alkylation of key proteins following ferroptosis induction, including MRP1, set a precedent for LDEs as critical mediators of ferroptotic cell damage. Lipid hydroperoxide breakdown to form truncated phospholipids and LDEs may fully explain membrane permeabilization and modified protein function downstream of lipid peroxidation, offering a unified explanation of the molecular cell death mechanism of ferroptosis.

Erythritol attenuates testicular dysfunction in diabetic rat via suppression of oxidative stress, inflammation and apoptosis

Hyperglycemia -induced oxidative stress and inflammation have been closely associated with diabetes complications including testicular dysfunction. Conversely, reducing blood glucose and/or use of antioxidant have been associated with reduced diabetes complications. The present study investigated the effect of erythritol (which has both antioxidant and blood glucose lowering function) on diabetes -induced testicular dysfunction in rats. Thirty male Wistar rats (170-200g) were randomly divided into 5 groups: 1) control; 2) erythritol; 3) diabetic; 4) diabetic + erythritol 1000 mg/kg; and 5) diabetic + metformin 300 mg/kg. After 8 weeks of treatment period, blood sample, testes and epididymis were collected for reproductive hormones, biochemical and histological examinations, and sperm analysis respectively. There was a significant (p < 0.05) decrease in sperm count, sperm motility, sperm morphology and serum reproductive hormones (Follicle stimulating hormone (FSH), Leutinizing hormone (LH), testosterone and gonadotropin releasing hormone (GnRH)) of diabetes rat compared to control. Also, diabetes rat showed increase in sperm and testicular malonaldehyde (MDA) and decrease in sperm and testicular superoxide dismutase (SOD) activity and glutathione (GSH) level. Further, diabetes rat showed reduced testicular weight, decreased testicular 17β-HSD and 3β-HSD activity and testicular histo-architectural alteration which were accompanied by decrease testicular vascular endothelial growth factor (VEGF) and concomitant increase in testicular myeloperoxidase activity and level of caspase 3. The present results indicates that induction of diabetes in rat causes reduction in the level of reproductive hormones (Testosterone, LH and FSH) as well as sperm and testicular oxidative stress causing abnormal sperm parameters, and biochemical and histo-architectural alterations in the testes of rats. In addition, the present results suggest that erythritol administration reduced blood glucose and ameliorated hyperglycemia -induced oxidative stress -mediated alterations in both sperm and testes of diabetes rat. Further, the present study suggests that erythritol improved testicular oxidative stress, inflammation and apoptosis by up-regulating VEGF.

Physio-biochemical, metabolic nitrogen excretion and ion-regulatory assessment in largemouth bass (Micropterus salmoides) following exposure to high environmental iron

Iron overload is a significant water quality issue in many parts of the world. Therefore, we evaluated the potential toxic effects of waterborne elevated iron on largemouth bass (Micropterus salmoides), a highly valued sport and aquaculture fish species. First, a 96 h-LC₅₀ toxicity assay was performed to understand the tolerance limit of this species to iron; and was determined to be 22.07 mg/L (as Fe³⁺). Thereafter, to get a better insight on the fish survival during long-term exposure to high environmental iron (HEI) (5.52 mg/L, 25% of the determined 96 h-LC₅₀ value), a suite of physio-biochemical, nitrogenous metabolic and ion-regulatory compensatory responses were examined at 7, 14, 21 and 28 days. Results showed that oxygen consumption dropped significantly at 21 and 28 days of HEI exposure. Ammonia excretion rate (J_amm) was significantly inhibited from day 14 and remained suppressed until the last exposure period. The transcript concentration of Rhesus glycoproteins Rhcg2 declined; likely diminishing ammonia efflux out of gills. These changes were also reflected by a parallel increment in plasma ammonia levels. Under HEI exposure, ion-balance was negatively affected, manifested by reduced plasma [Na⁺] and parallel inhibition in branchial Na⁺/K⁺-ATPase activity. Muscle water content was elevated in HEI-exposed fish, signifying an osmo-regulatory compromise. HEI exposure also increased iron burden in plasma and gills. The iron accumulation pattern in gills was significantly correlated with a suppression of J_amm, branchial Rhcg2 expression and Na⁺/K⁺-ATPase activity. There was also a decline in the glycogen, protein and lipid reserves in the hepatic tissue from 14 days, 28 days and 21 days, respectively. Overall, we conclude that sub-lethal chronic iron exposure can impair normal physio-biochemical and ion-regulatory functions in largemouth bass. Moreover, this data set can be applied in assessing the environmental risk posed by a waterborne iron overload on aquatic life.

Identification of 4-hydroxynonenal-modified proteins in human osteoarthritic chondrocytes

The α,β-unsaturated aldehyde 4-hydroxynonenal (HNE) is formed through lipid peroxidation during oxidative stress. As a highly reactive electrophile, it is able to form adducts with various biomolecules, including proteins. These protein modifications could modulate many signaling pathways, as well as cell differentiation and proliferation, and thus could be highly important in the context of the extracellular matrix and degradation of articular cartilage. This study specifically investigated the role of HNE as a bioactive molecule in chondrocytes of osteoarthritis (OA) patients. Chondrocyte extracts of OA and non-OA patients were analyzed for HNE binding using Western blot and bottom-up LC-MS/MS analyses. HNE-modified histones, H2A and H2B, and histone deacetylase were identified using anti-HNE antibodies. Furthermore, peptide sequencing and database searching revealed 95 distinct HNE-modified proteins and their exact modification sites, with 88 protein adducts being unique to OA chondrocytes. HNE-proteins of specific interest included histone H2A, H2B and H4, collagen alpha-3(VI) chain, eukaryotic initiation factor 4A-I, and nucleolar RNA helicase 2. Comparing their MS/MS spectra to those of HNE-modified standard peptides further validated the six HNE-proteins. SIGNIFICANCE: HNE binding to proteins has been shown to result in multiple abnormalities of chondrocyte phenotype and function, suggesting its contribution in OA development. Considering the increased levels of HNE in OA cartilage, this reactive aldehyde could play a role in OA. This work represents a clinically-relevant in vivo study to demonstrate the pathophysiological role of HNE in human OA. Since HNE binding can alter protein conformation and function, it remains highly relevant to study the effects of this modification in OA.

Expression of Neuronal Na+/K+-ATPase α Subunit Isoforms in the Mouse Brain Following Genetically Programmed or Behaviourally-induced Oxidative Stress

The Na⁺/K⁺-ATPase is a transmembrane ion pump that has a critical homeostatic role within every mammalian cell; however, it is vulnerable to the effects of increased oxidative stress. Understanding how expression of this transporter is influenced by oxidative stress may yield insight into its role in the pathophysiology of neurological and neuropsychiatric diseases. In this study we investigated whether increased oxidative stress could influence Na⁺/K⁺-ATPase expression in various brain regions of mice. We utilized two different models of oxidative stress: a behavioural chronic unpredictable stress protocol and the Aldh2^-/- mouse model of oxidative stress-based and age-related cognitive impairment. We identified distinct regional baseline mRNA and protein expression patterns of the Na⁺/K⁺-ATPase α1 and α3 isoforms within the neocortex, hippocampus, and brainstem of wildtype mice. Consistent with previous studies, there was a higher proportion of α3 expression relative to α1 in the brainstem versus neocortex, but a higher proportion of α1 expression relative to α3 in the neocortex versus the brainstem. The hippocampus had similar expression levels of both α1 and α3. Despite increased staining for oxidative stress in higher brain, no differences in α1 or α3 expression were noted in Aldh2^-/- mice versus wildtype, or in mice exposed to a 28-day chronic unpredictable stress protocol. In both models of oxidative stress, gene and protein expression of Na⁺/K⁺-ATPase α1 and α3 isoforms within the higher and lower brain was remarkably stable. Thus, Na⁺/K⁺-ATPase function previously reported as altered by oxidative stress is not through induced changes in the expression of pump isoforms.

Redox Signaling by Reactive Electrophiles and Oxidants

The concept of cell signaling in the context of nonenzyme-assisted protein modifications by reactive electrophilic and oxidative species, broadly known as redox signaling, is a uniquely complex topic that has been approached from numerous different and multidisciplinary angles. Our Review reflects on five aspects critical for understanding how nature harnesses these noncanonical post-translational modifications to coordinate distinct cellular activities: (1) specific players and their generation, (2) physicochemical properties, (3) mechanisms of action, (4) methods of interrogation, and (5) functional roles in health and disease. Emphasis is primarily placed on the latest progress in the field, but several aspects of classical work likely forgotten/lost are also recollected. For researchers with interests in getting into the field, our Review is anticipated to function as a primer. For the expert, we aim to stimulate thought and discussion about fundamentals of redox signaling mechanisms and nuances of specificity/selectivity and timing in this sophisticated yet fascinating arena at the crossroads of chemistry and biology.

4-Hydroxynonenal (HNE) modified proteins in metabolic diseases

4-Hydroxynonenal (HNE) is one of the quantitatively most important products of lipid peroxidation. Due to its high toxicity it is quickly metabolized, however, a small share of HNE avoids enzymatic detoxification and reacts with biomolecules including proteins. The formation of HNE-protein-adducts is one of the accompanying processes in oxidative stress or redox disbalance. The modification of proteins might occur at several amino acids side chains, leading to a variety of products and having effects on the protein function and fate. This review summarizes current knowledge on the formation of HNE-modified proteins, their fate in mammalian cells and their potential role as a damaging agents during oxidative stress. Furthermore, the potential of HNE-modified proteins as biomarkers for several diseases are highlighted.

Specific ion channels contribute to key elements of pathology during secondary degeneration following neurotrauma

BACKGROUND

Following partial injury to the central nervous system, cells beyond the initial injury site undergo secondary degeneration, exacerbating loss of neurons, compact myelin and function. Changes in Ca²⁺ flux are associated with metabolic and structural changes, but it is not yet clear how flux through specific ion channels contributes to the various pathologies. Here, partial optic nerve transection in adult female rats was used to model secondary degeneration. Treatment with combinations of three ion channel inhibitors was used as a tool to investigate which elements of oxidative and structural damage related to long term functional outcomes. The inhibitors employed were the voltage gated Ca²⁺ channel inhibitor Lomerizine (Lom), the Ca²⁺ permeable AMPA receptor inhibitor YM872 and the P2X₇ receptor inhibitor oxATP.

RESULTS

Following partial optic nerve transection, hyper-phosphorylation of Tau and acetylated tubulin immunoreactivity were increased, and Nogo-A immunoreactivity was decreased, indicating that axonal changes occurred acutely. All combinations of ion channel inhibitors reduced hyper-phosphorylation of Tau and increased Nogo-A immunoreactivity at day 3 after injury. However, only Lom/oxATP or all three inhibitors in combination significantly reduced acetylated tubulin immunoreactivity. Most combinations of ion channel inhibitors were effective in restoring the lengths of the paranode and the paranodal gap, indicative of the length of the node of Ranvier, following injury. However, only all three inhibitors in combination restored to normal Ankyrin G length at the node of Ranvier. Similarly, HNE immunoreactivity and loss of oligodendrocyte precursor cells were only limited by treatment with all three ion channel inhibitors in combination.

CONCLUSIONS

Data indicate that inhibiting any of a range of ion channels preserves certain elements of axon and node structure and limits some oxidative damage following injury, whereas ionic flux through all three channels must be inhibited to prevent lipid peroxidation and preserve Ankyrin G distribution and OPCs.

Previous physical exercise alters the hepatic profile of oxidative-inflammatory status and limits the secondary brain damage induced by severe traumatic brain injury in rats

KEY POINTS

An early inflammatory response and oxidative stress are implicated in the signal transduction that alters both hepatic redox status and mitochondrial function after traumatic brain injury (TBI). Peripheral oxidative/inflammatory responses contribute to neuronal dysfunction after TBI Exercise training alters the profile of oxidative-inflammatory status in liver and protects against acute hyperglycaemia and a cerebral inflammatory response after TBI. Approaches such as exercise training, which attenuates neuronal damage after TBI, may have therapeutic potential through modulation of responses by metabolic organs. The vulnerability of the body to oxidative/inflammatory in TBI is significantly enhanced in sedentary compared to physically active counterparts.

ABSTRACT

Although systemic responses have been described after traumatic brain injury (TBI), little is known regarding potential interactions between brain and peripheral organs after neuronal injury. Accordingly, we aimed to investigate whether a peripheral oxidative/inflammatory response contributes to neuronal dysfunction after TBI, as well as the prophylactic role of exercise training. Animals were submitted to fluid percussion injury after 6 weeks of swimming training. Previous exercise training increased mRNA expression of X receptor alpha and ATP-binding cassette transporter, and decreased inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF)-α and interleukin (IL)-6 expression per se in liver. Interestingly, exercise training protected against hepatic inflammation (COX-2, iNOS, TNF-α and IL-6), oxidative stress (decreases in non-protein sulfhydryl and glutathione, as well as increases in 2',7'-dichlorofluorescein diacetate oxidation and protein carbonyl), which altered hepatic redox status (increases in myeloperoxidase and superoxide dismutase activity, as well as inhibition of catalase activity) mitochondrial function (decreases in methyl-tetrazolium and Δψ, as well as inhibition of citrate synthase activity) and ion gradient homeostasis (inhibition of Na⁺ ,K⁺ -ATPase activity inhibition) when analysed 24 h after TBI. Previous exercise training also protected against dysglycaemia, impaired hepatic signalling (increase in phosphorylated c-Jun NH2-terminal kinase, phosphorylated decreases in insulin receptor substrate and phosphorylated AKT expression), high levels of circulating and neuronal cytokines, the opening of the blood-brain barrier, neutrophil infiltration and Na⁺ ,K⁺ -ATPase activity inhibition in the ipsilateral cortex after TBI. Moreover, the impairment of protein function, neurobehavioural (neuromotor dysfunction and spatial learning) disability and hippocampal cell damage in sedentary rats suggests that exercise training also modulates peripheral oxidative/inflammatory pathways in TBI, which corroborates the ever increasing evidence regarding health-related outcomes with respect to a physically active lifestyle.

Biological fate of food nanoemulsions and the nutrients they carry – internalisation, transport and cytotoxicity of edible nanoemulsions in Caco-2 intestinal cells

Internalisation of edible food nanoemulsions by CaCo-2 intestinal cells. The structure of edible nanoemulsions increases five times upon incorporation of reactive/ROS producing nutrients/APIs.

Modified Lipids and Lipoproteins in Chronic Kidney Disease: A New Class of Uremic Toxins

Chronic kidney disease (CKD) is associated with an enhanced oxidative stress and deep modifications in lipid and lipoprotein metabolism. First, many oxidized lipids accumulate in CKD and were shown to exert toxic effects on cells and tissues. These lipids are known to interfere with many cell functions and to be pro-apoptotic and pro-inflammatory, especially in the cardiovascular system. Some, like F2-isoprostanes, are directly correlated with CKD progression. Their accumulation, added to their noxious effects, rendered their nomination as uremic toxins credible. Similarly, lipoproteins are deeply altered by CKD modifications, either in their metabolism or composition. These impairments lead to impaired effects of HDL on their normal effectors and may strongly participate in accelerated atherosclerosis and failure of statins in end-stage renal disease patients. This review describes the impact of oxidized lipids and other modifications in the natural history of CKD and its complications. Moreover, this review focuses on the modifications of lipoproteins and their impact on the emergence of cardiovascular diseases in CKD as well as the appropriateness of considering them as actual mediators of uremic toxicity.

Signaling by 4-hydroxy-2-nonenal: Exposure protocols, target selectivity and degradation

4-hydroxy-2-nonenal (HNE), a major non-saturated aldehyde product of lipid peroxidation, has been extensively studied as a signaling messenger. In these studies a wide range of HNE concentrations have been used, ranging from the unstressed plasma concentration to far beyond what would be found in actual pathophysiological condition. In addition, accumulating evidence suggest that signaling protein modification by HNE is specific with only those proteins with cysteine, histidine, and lysine residues located in certain sequence or environments adducted by HNE. HNE-signaling is further regulated through the turnover of HNE-signaling protein adducts through proteolytic process that involve proteasomes, lysosomes and autophagy. This review discusses the HNE concentrations and exposure modes used in signaling studies, the selectivity of the HNE-adduction site, and the turnover of signaling protein adducts.

The Role of Na/K-ATPase Signaling in Oxidative Stress Related to Obesity and Cardiovascular Disease

Na/K-ATPase has been extensively studied for its ion pumping function, but, in the past several decades, has been identified as a scaffolding and signaling protein. Initially it was found that cardiotonic steroids (CTS) mediate signal transduction through the Na/K-ATPase and result in the generation of reactive oxygen species (ROS), which are also capable of initiating the signal cascade. However, in recent years, this Na/K-ATPase/ROS amplification loop has demonstrated significance in oxidative stress related disease states, including obesity, atherosclerosis, heart failure, uremic cardiomyopathy, and hypertension. The discovery of this novel oxidative stress signaling pathway, holds significant therapeutic potential for the aforementioned conditions and others that are rooted in ROS.

Concurrent measurement of cellular turbidity and hemoglobin to evaluate the antioxidant activity of plants

In past decades, a multitude of analytical methods for measuring antioxidant activity of plant extracts has been developed. However, when using methods to determine hemoglobin released from human erythrocytes treated with ginger extracts, we found hemoglobin concentrations were significantly higher than in untreated control samples. This suggests in the presence of antioxidants that measuring hemoglobin alone is not sufficient to determine hemolysis. We show concurrent measurement of erythrocyte concentration and hemoglobin is essential in such assays, and describe a new protocol based on simultaneous measurement of cellular turbidity and hemoglobin.

Metabolic methanol: molecular pathways and physiological roles

Methanol has been historically considered an exogenous product that leads only to pathological changes in the human body when consumed. However, in normal, healthy individuals, methanol and its short-lived oxidized product, formaldehyde, are naturally occurring compounds whose functions and origins have received limited attention. There are several sources of human physiological methanol. Fruits, vegetables, and alcoholic beverages are likely the main sources of exogenous methanol in the healthy human body. Metabolic methanol may occur as a result of fermentation by gut bacteria and metabolic processes involving S-adenosyl methionine. Regardless of its source, low levels of methanol in the body are maintained by physiological and metabolic clearance mechanisms. Although human blood contains small amounts of methanol and formaldehyde, the content of these molecules increases sharply after receiving even methanol-free ethanol, indicating an endogenous source of the metabolic methanol present at low levels in the blood regulated by a cluster of genes. Recent studies of the pathogenesis of neurological disorders indicate metabolic formaldehyde as a putative causative agent. The detection of increased formaldehyde content in the blood of both neurological patients and the elderly indicates the important role of genetic and biochemical mechanisms of maintaining low levels of methanol and formaldehyde.

Possible involvement of membrane lipids peroxidation and oxidation of catalytically essential thiols of the cerebral transmembrane sodium pump as component mechanisms of iron-mediated oxidative stress-linked dysfunction of the pump's activity

The precise molecular events defining the complex role of oxidative stress in the inactivation of the cerebral sodium pump in radical-induced neurodegenerative diseases is yet to be fully clarified and thus still open. Herein we investigated the modulation of the activity of the cerebral transmembrane electrogenic enzyme in Fe²⁺-mediated in vitro oxidative stress model. The results show that Fe²⁺ inhibited the transmembrane enzyme in a concentration dependent manner and this effect was accompanied by a biphasic generation of aldehydic product of lipid peroxidation. While dithiothreitol prevented both Fe²⁺ inhibitory effect on the pump and lipid peroxidation, vitamin E prevented only lipid peroxidation but not inhibition of the pump. Besides, malondialdehyde (MDA) inhibited the pump by a mechanism not related to oxidation of its critical thiols. Apparently, the low activity of the pump in degenerative diseases mediated by Fe²⁺ may involve complex multi-component mechanisms which may partly involve an initial oxidation of the critical thiols of the enzyme directly mediated by Fe²⁺ and during severe progression of such diseases; aldehydic products of lipid peroxidation such as MDA may further exacerbate this inhibitory effect by a mechanism that is likely not related to the oxidation of the catalytically essential thiols of the ouabain-sensitive cerebral electrogenic pump.

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Fe²⁺ evoked lipid peroxidation (LPO) and inhibition of sodium pump (SP) in rat brain.

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However, dithiothreitol prevented both Fe²⁺-mediated LPO and inhibition of SP.

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Conversely, vitamin E prevented only Fe²⁺-mediated LPO but not inhibition of SP.

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Thus Fe²⁺ mediated inactivation of SP likely by oxidizing the essential thiol on SP.

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However, malondialdehyde inhibited SP by a mechanism not related to thiol oxidation.

4-Hydroxynonenal in the pathogenesis and progression of human diseases

Metastable aldehydes produced by lipid peroxidation act as 'toxic second messengers' that extend the injurious potential of free radicals. 4-hydroxy 2-nonenal (HNE), a highly toxic and most abundant stable end product of lipid peroxidation, has been implicated in the tissue damage, dysfunction, injury associated with aging and other pathological states such as cancer, Alzheimer, diabetes, cardiovascular and inflammatory complications. Further, HNE has been considered as a oxidative stress marker and it act as a secondary signaling molecule to regulates a number of cell signaling pathways. Biological activity of HNE depends on its intracellular concentration, which can differentially modulate cell death, growth and differentiation. Therefore, the mechanisms responsible for maintaining the intracellular levels of HNE are most important, not only in the defense against oxidative stress but also in the pathophysiology of a number of disease processes. In this review, we discussed the significance of HNE in mediating various disease processes and how regulation of its metabolism could be therapeutically effective.

Interaction of aldehydes derived from lipid peroxidation and membrane proteins

A great variety of compounds are formed during lipid peroxidation of polyunsaturated fatty acids of membrane phospholipids. Among them, bioactive aldehydes, such as 4-hydroxyalkenals, malondialdehyde (MDA) and acrolein, have received particular attention since they have been considered as toxic messengers that can propagate and amplify oxidative injury. In the 4-hydroxyalkenal class, 4-hydroxy-2-nonenal (HNE) is the most intensively studied aldehyde, in relation not only to its toxic function, but also to its physiological role. Indeed, HNE can be found at low concentrations in human tissues and plasma and participates in the control of biological processes, such as signal transduction, cell proliferation, and differentiation. Moreover, at low doses, HNE exerts an anti-cancer effect, by inhibiting cell proliferation, angiogenesis, cell adhesion and by inducing differentiation and/or apoptosis in various tumor cell lines. It is very likely that a substantial fraction of the effects observed in cellular responses, induced by HNE and related aldehydes, be mediated by their interaction with proteins, resulting in the formation of covalent adducts or in the modulation of their expression and/or activity. In this review we focus on membrane proteins affected by lipid peroxidation-derived aldehydes, under physiological and pathological conditions.

Pretreatment with pyridoxamine mitigates isolevuglandin-associated retinal effects in mice exposed to bright light

The benefits of antioxidant therapy for treating age-related macular degeneration, a devastating retinal disease, are limited. Perhaps species other than reactive oxygen intermediates should be considered as therapeutic targets. These could be lipid peroxidation products, including isolevuglandins (isoLGs), prototypical and extraordinarily reactive γ-ketoaldehydes that avidly bind to proteins, phospholipids, and DNA and modulate the properties of these biomolecules. We found isoLG adducts in aged human retina but not in the retina of mice kept under dim lighting. Hence, to test whether scavenging of isoLGs could complement or supplant antioxidant therapy, we exposed mice to bright light and found that this insult leads to retinal isoLG-adduct formation. We then pretreated mice with pyridoxamine, a B6 vitamer and efficient scavenger of γ-ketoaldehydes, and found that the levels of retinal isoLG adducts are decreased, and morphological changes in photoreceptor mitochondria are not as pronounced as in untreated animals. Our study demonstrates that preventing the damage to biomolecules by lipid peroxidation products, a novel concept in vision research, is a viable strategy to combat oxidative stress in the retina.

Apoptosis signalling by 4-hydroxynonenal: a role for JNK–c-Jun/AP-1 pathway

4-Hydroxynonenal (HNE) is one of the most abundant aldehyde components of ox-LDL and it exerts various effects on intracellular and extracellular signaling cascades. In this mini-review, a brief synopsis of HNE-modulated signaling pathways will be presented mainly focused on cell death, including recent studies from our laboratory. The results of a number of studies demonstrate the ability of HNE to induce apoptosis and ROS formation in a dose-dependent manner. Several signaling pathways have been shown to be modulated by HNE, including MAP kinases, PKC isoforms, cell-cycle regulators, receptor tyrosine kinases and caspases. In order to get insight into the mechanisms of apoptotic response by HNE, MAP kinase and caspase activation pathways have been studied in 3T3 fibroblasts; HNE induced early activation of JNK and p38 proteins but down-regulated the basal activity of ERK-1/2. We have shown that HNE-induced release of cytochrome c from mitochondria, caspase-9 and caspase-3 activation. Activation of AP-1 along with increased c-Jun and phospho-c-Jun levels could be inhibited by pretreatment of cells with certain molecules such as resveratrol. Additionally, overexpression of dominant negative c-Jun and JNK1 in 3T3 fibroblasts prevented HNE-induced apoptosis, which indicated a role for JNK-c-Jun/AP-1 pathway. JNK-dependent induction of c-Jun/AP-1 activation data in the literature indicates a critical potential role for JNK in the cellular response against toxic products of lipid peroxidation.

Redox proteomics in selected neurodegenerative disorders: from its infancy to future applications

Several studies demonstrated that oxidative damage is a characteristic feature of many neurodegenerative diseases. The accumulation of oxidatively modified proteins may disrupt cellular functions by affecting protein expression, protein turnover, cell signaling, and induction of apoptosis and necrosis, suggesting that protein oxidation could have both physiological and pathological significance. For nearly two decades, our laboratory focused particular attention on studying oxidative damage of proteins and how their chemical modifications induced by reactive oxygen species/reactive nitrogen species correlate with pathology, biochemical alterations, and clinical presentations of Alzheimer's disease. This comprehensive article outlines basic knowledge of oxidative modification of proteins and lipids, followed by the principles of redox proteomics analysis, which also involve recent advances of mass spectrometry technology, and its application to selected age-related neurodegenerative diseases. Redox proteomics results obtained in different diseases and animal models thereof may provide new insights into the main mechanisms involved in the pathogenesis and progression of oxidative-stress-related neurodegenerative disorders. Redox proteomics can be considered a multifaceted approach that has the potential to provide insights into the molecular mechanisms of a disease, to find disease markers, as well as to identify potential targets for drug therapy. Considering the importance of a better understanding of the cause/effect of protein dysfunction in the pathogenesis and progression of neurodegenerative disorders, this article provides an overview of the intrinsic power of the redox proteomics approach together with the most significant results obtained by our laboratory and others during almost 10 years of research on neurodegenerative disorders since we initiated the field of redox proteomics.

Aldo-keto reductases mediate constitutive and inducible protection against aldehyde toxicity in human neuroblastoma SH-SY5Y cells

Reactive aldehydes including methyl glyoxal, acrolein and 4-hydroxy-2-nonenal (4-HNE) have been implicated in the progression of neurodegenerative diseases. The reduction of aldehydes to alcohols by the aldo-keto reductase (AKR) family of enzymes may represent an important detoxication route within neuronal cells. In this study, the ability of AKR enzymes to protect human neuroblastoma SH-SY5Y cells against reactive aldehydes was assessed. Using gene-specific RNA interference (RNAi), we report that AKR7A2 makes a significant contribution to the reduction of methyl glyoxal in SH-SY5Y cells, with its knockdown altering the IC(50) from 410 to 25.8μM, and that AKR1C3 contributes to 4-HNE reduction, with its knockdown lowering the IC(50) from 1.25 to 0.58μM. In addition, we have shown that pretreatment of cells with sub-lethal concentrations of 4-HNE or methyl glyoxal leads to a significant increase in IC(50) when cells are exposed to higher concentrations of the toxic aldehyde. The IC(50) for methyl glyoxal increased from 410μM to 1.9mM, and the IC(50) for 4-HNE increased from 120 to 690nM. To investigate this protection, we show that pretreatment of cells with the AKR inhibitor sorbinil lead to decreased resistance to aldehydes. We show that AKR1C can be induced 8-fold in SH-SY5Y cells by treatment with sub-lethal concentrations of methyl glyoxal, and 5-fold by 4-HNE treatment. AKR1B is not induced by methyl glyoxal but is induced 10-fold by 4-HNE treatment. Furthermore, we have shown that this adaptive response can also be induced using the chemoprotective agent tert-butyl hydroquinone (t-BHQ), and that this also evokes an increase in the expression and activity of AKR1B and AKR1C. These findings highlight the potential for the interventional upregulation of AKR via non-toxic derivatives or natural compounds as a novel therapeutic approach towards the detoxication of aldehydes, with the aim of halting the progression of aldehyde-dependent neurodegenerative diseases.

Mitochondria as a source and target of lipid peroxidation products in healthy and diseased heart

The heart is a highly oxidative organ in which cardiomyocyte turnover is virtually absent, making it particularly vulnerable to accumulation of lipid peroxidation products (LPP) formed as a result of oxidative damage. Reactive oxygen and nitrogen species are the most common electrophiles formed during lipid peroxidation and lead to the formation of both stable and unstable LPP. Of the LPP formed, highly reactive aldehydes are a well-recognized causative factor in ageing and age-associated diseases, including cardiovascular disease and diabetes. Recent studies have identified that the mitochondria are both a primary source and target of LPP, with specific emphasis on aldehydes in cardiomyocytes and how these affect the electron transport system and Ca(2+) balance. Numerous studies have found that there are functional consequences in the heart following exposure to specific aldehydes (acrolein, trans-2-hexanal, 4-hydroxynonenal and acetaldehyde). Because these LPP are known to form in heart failure, cardiac ischaemia-reperfusion injury and diabetes, they may have an underappreciated role in the pathophysiology of these disease processes. Lipid peroxidation products are involved in the transcriptional regulation of endogenous anti-oxidant systems. Recent evidence demonstrates that transient increases in LPP may be beneficial in cardioprotection by contributing to mitohormesis (i.e. induction of anti-oxidant systems) in cardiomyocytes. Thus, exploitation of the cardioprotective actions of the LPP may represent a novel therapeutic strategy for future treatment of heart disease.

Lipid peroxidation and neurodegenerative disease

Lipid peroxidation is a complex process involving the interaction of oxygen-derived free radicals with polyunsaturated fatty acids, resulting in a variety of highly reactive electrophilic aldehydes. Since 1975, lipid peroxidation has been extensively studied in a variety of organisms. As neurodegenerative diseases became better understood, research establishing a link between this form of oxidative damage, neurodegeneration, and disease has provided a wealth of knowledge to the scientific community. With the advent of proteomics in 1995, the identification of biomarkers for neurodegenerative disorders became of paramount importance to better understand disease pathogenesis and develop potential therapeutic strategies. This review focuses on the relationship between lipid peroxidation and neurodegenerative diseases. It also demonstrates how findings in current research support the common themes of altered energy metabolism and mitochondrial dysfunction in neurodegenerative disorders.

Evidence that hyperprolinemia alters glutamatergic homeostasis in rat brain: neuroprotector effect of guanosine

This study investigated the effects of acute and chronic hyperprolinemia on glutamate uptake, as well as some mechanisms underlying the proline effects on glutamatergic system in rat cerebral cortex. The protective role of guanosine on effects mediated by proline was also evaluated. Results showed that acute and chronic hyperprolinemia reduced glutamate uptake, Na(+), K(+)-ATPase activity, ATP levels and increased lipoperoxidation. GLAST and GLT-1 immunocontent were increased in acute, but not in chronic hyperprolinemic rats. Our data suggest that the effects of proline on glutamate uptake may be mediated by lipid peroxidation and disruption of Na(+), K(+)-ATPase activity, but not by decreasing in glutamate transporters. This probably induces excitotoxicity and subsequent energy deficit. Guanosine was effective to prevent most of the effects promoted by proline, reinforcing its modulator role in counteracting the glutamate toxicity. However, further studies are needed to assess the modulatory effects of guanosine on experimental hyperprolinemia.

Nutrition for brain recovery after ischemic stroke: an added value to rehabilitation

In patients who undergo rehabilitation after ischemic stroke, nutrition strategies are adopted to provide tube-fed individuals with adequate nutrition and/or to avoid the body wasting responsible for poor functional outcome and prolonged stay in the hospital. Investigations have documented that nutrition interventions can enhance the recovery of neurocognitive function in individuals with ischemic stroke. Experimental studies have shown that protein synthesis is suppressed in the ischemic penumbra. In clinical studies on rehabilitation patients designed to study the effects of counteracting or limiting this reduction of protein synthesis by providing protein supplementation, patients receiving such supplementation had enhanced recovery of neurocognitive function. Cellular damage in cerebral ischemia is also partly caused by oxidative damage secondary to free radical formation and lipid peroxidation. Increased oxidative stress negatively affects a patient's life and functional prognosis. Some studies have documented that nutrition supplementation with B-group vitamins may mitigate oxidative damage after acute ischemic stroke. Experimental investigations have also shown that cerebral ischemia changes synaptic zinc release and that acute ischemia increases zinc release, aggravating neuronal injury. In clinical practice, patients with ischemic stroke were found to have a lower than recommended dietary intake of zinc. Patients in whom daily zinc intake was normalized had better recovery of neurological deficits than subjects given a placebo. The aim of this review is to highlight those brain metabolic alterations susceptible to nutrition correction in clinical practice. The mechanisms underlying the relationship between cerebral ischemia and nutrition metabolic conditions are discussed.

Role of antioxidants on Na(+),K (+)-ATPase activity and gene expression in cerebral cortex of hyperprolinemic rats

Considering that Na(+),K(+)-ATPase is an embedded-membrane enzyme and that experimental chronic hyperprolinemia decreases the activity of this enzyme in brain synaptic plasma membranes, the present study investigated the effect of chronic proline administration on thiobarbituric acid-reactive substances, as well as the influence of antioxidant vitamins E plus C on the effects mediated by proline on Na(+),K(+)-ATPase activity in cerebral cortex of rats. The expression of Na(+),K(+)-ATPase catalytic subunits was also evaluated. Results showed that proline increased thiobarbituric acid-reactive substances, suggesting an increase of lipid peroxidation. Furthermore, concomitant administration of vitamins E plus C significantly prevented the increase of lipid peroxidation, as well as the inhibition of Na(+),K(+)-ATPase activity caused by proline. We did not observe any change in levels of Na(+),K(+)-ATPase mRNA transcripts after chronic exposure to proline and vitamins E plus C. These findings provide insights into the mechanisms through which proline exerts its effects on brain function and suggest that treatment with antioxidants may be beneficial to treat neurological dysfunctions present in hyperprolinemic patients.

Homocysteine alters glutamate uptake and Na+,K+-ATPase activity and oxidative status in rats hippocampus: protection by vitamin C

In the present study we investigate the effect of homocysteine on glutamate uptake, Na+,K+-ATPase, enzymatic antioxidant defenses, as well as reactive species levels in hippocampus of rats. The influence of vitamin C, a classic antioxidant, on the effects elicited by homocysteine was also tested. Results showed that chronic hyperhomocysteinemia decreased glutamate uptake and the activities of Na+,K+-ATPase, catalase and superoxide dismutase in hippocampus of rats. Reactive species levels were increased by chronic homocysteine administration. Concomitant administration of vitamin C significantly prevented these alterations caused by homocysteine. According to our results, it seems possible to suggest that the reduction in glutamate uptake and Na+,K+-ATPase activity may be mediated by oxidative stress, since vitamin C prevented these effects. We suggest that the administration of antioxidants should be considered as an adjuvant therapy to specific diet in homocystinuria.

Acute and chronic hypermethioninemia alter Na+ K+-ATPase activity in rat hippocampus: prevention by antioxidants

In the current study we initially investigated the influence of antioxidants (vitamins E plus C) on the effect mediated by acute and chronic administration of methionine (Met) on Na(+),K(+)-ATPase activity in rat hippocampus. We also verified whether the alterations on the enzyme after administration of Met and/or antioxidants were associated with changes in relative expression of Na(+),K(+)-ATPase catalytic subunits (isoforms α1, α2 and α3). For acute treatment, young rats received a single subcutaneous injection of Met or saline (control) and were sacrificed 12 h later. In another set of experiments, rats were pretreated for 1 week with daily intraperitoneal administration of vitamins E (40 mg/kg) and C (100 mg/kg) or saline. After that, rats received a single injection of Met or saline and were killed 12 h later. For chronic treatment, Met was administered to rats from the 6th to the 28th day of life; controls and treated rats were sacrificed 12 h after the last injection. In parallel to chronic treatment, rats received a daily intraperitoneal injection of vitamins E and C from the 6th to the 28th day of life and were killed 12 h after the last injection. Results showed that administration of antioxidants partially prevented the inhibition of enzyme activity caused by acute and chronic hypermethioninemia. Besides, we demonstrated that transcription of catalytic subunits of Na(+),K(+)-ATPase was not altered by chronic and acute exposure to Met and/or vitamins E plus C. These data strongly suggest the oxidative damage as one possible mechanism involved in the reduction of Na(+),K(+)-ATPase activity caused by hypermethioninemia and if confirmed in human beings, we might propose the use of antioxidants as an adjuvant therapy in hypermethioninemic patients.

Aldehyde dehydrogenase 7A1 (ALDH7A1) attenuates reactive aldehyde and oxidative stress induced cytotoxicity

Mammalian aldehyde dehydrogenase 7A1 (ALDH7A1) is homologous to plant ALDH7B1 which protects against various forms of stress such as increased salinity, dehydration and treatment with oxidants or pesticides. Deleterious mutations in human ALDH7A1 are responsible for pyridoxine-dependent and folinic acid-responsive seizures. In previous studies, we have shown that human ALDH7A1 protects against hyperosmotic stress presumably through the generation of betaine, an important cellular osmolyte, formed from betaine aldehyde. Hyperosmotic stress is coupled to an increase in oxidative stress and lipid peroxidation (LPO). In this study, cell viability assays revealed that stable expression of mitochondrial ALDH7A1 in Chinese hamster ovary (CHO) cells provides significant protection against treatment with the LPO-derived aldehydes hexanal and 4-hydroxy-2-nonenal (4HNE) implicating a protective function for the enzyme during oxidative stress. A significant increase in cell survival was also observed in CHO cells expressing either mitochondrial or cytosolic ALDH7A1 treated with increasing concentrations of hydrogen peroxide (H(2)O(2)) or 4HNE, providing further evidence for anti-oxidant activity. In vitro enzyme activity assays indicate that human ALDH7A1 is sensitive to oxidation and that efficiency can be at least partially restored by incubating recombinant protein with the thiol reducing agent β-mercaptoethanol (BME). We also show that after reactivation with BME, recombinant ALDH7A1 is capable of metabolizing the reactive aldehyde 4HNE. In conclusion, ALDH7A1 mechanistically appears to provide cells protection through multiple pathways including the removal of toxic LPO-derived aldehydes in addition to osmolyte generation.

Inhibition by 4-hydroxynonenal (HNE) of Ca2+ transport by SERCA1a: low concentrations of HNE open protein-mediated leaks in the membrane

Exposure of sarcoplasmic reticulum membranes to 4-hydroxy-2-nonenal (HNE) resulted in inhibition of the maximal ATPase activity and Ca(2+) transport ability of SERCA1a, the Ca(2+) pump in these membranes. The concomitant presence of ATP significantly protected SERCA1a ATPase activity from inhibition. ATP binding and phosphoenzyme formation from ATP were reduced after treatment with HNE, whereas Ca(2+) binding to the high-affinity sites was altered to a lower extent. HNE reacted with SH groups, some of which were identified by MALDI-TOF mass spectrometry, and competition studies with FITC indicated that HNE also reacted with Lys(515) within the nucleotide binding pocket of SERCA1a. A remarkable fact was that both the steady-state ability of SR vesicles to sequester Ca(2+) and the ATPase activity of SR membranes in the absence of added ionophore or detergent were sensitive to concentrations of HNE much smaller than those that affected the maximal ATPase activity of SERCA1a. This was due to an increase in the passive permeability of HNE-treated SR vesicles to Ca(2+), an increase in permeability that did not arise from alteration of the lipid component of these vesicles. Judging from immunodetection with an anti-HNE antibody, this HNE-dependent increase in permeability probably arose from modification of proteins of about 150-160kDa, present in very low abundance in longitudinal SR membranes (and in slightly larger abundance in SR terminal cisternae). HNE-induced promotion, via these proteins, of Ca(2+) leakage pathways might be involved in the general toxic effects of HNE.

Roles of 3-nitrotyrosine- and 4-hydroxynonenal-modified brain proteins in the progression and pathogenesis of Alzheimer's disease

Proteins play an important role in normal structure and function of the cells. Oxidative modification of proteins may greatly alter the structure and may subsequently lead to loss of normal physiological cell functions and may lead to abnormal function of cell and eventually to cell death. These modifications may be reversible or irreversible. Reversible protein modifications, such as phosphorylation, can be overcome by specific enzymes that cause a protein to 'revert' back to its original protein structure, while irreversible protein modifications cannot. Several important irreversible protein modifications include protein nitration and HNE modification, both which have been extensively investigated in research on the progression of Alzheimer's disease (AD). From the earliest stage of AD throughout the advancement of the disorder there is evidence of increased protein nitration and HNE modification. These protein modifications lead to decreased enzymatic activity, which correlates directly to protein efficacy and provides support for several common themes in AD pathology, namely altered energy metabolism, mitochondrial dysfunction and reduced cholinergic neurotransmission. The current review summarized some of the findings on protein oxidation related to different stages of Alzheimer's disease (AD) that will be helpful in understanding the role of protein oxidation in the progression and pathogenesis of AD.

Inhibition of aldehyde dehydrogenase 2 by oxidative stress is associated with cardiac dysfunction in diabetic rats

Left ventricular (LV) dysfunction is a common comorbidity in diabetic patients, although the molecular mechanisms underlying this cardiomyopathic feature are not completely understood. Aldehyde dehydrogenase 2 (ALDH2) has been considered a key cardioprotective enzyme susceptible to oxidative inactivation. We hypothesized that hyperglycemia-induced oxidative stress would influence ALDH2 activity, and ALDH2 inhibition would lead to cardiac functional alterations in diabetic rats. Diabetes was induced by intraperitoneal (i.p.) injection of 60 mg/kg streptozotocin. Rats were divided randomly into four groups: control, untreated diabetic, diabetic treated with N-acetylcysteine (NAC) and diabetic treated with α-lipoic acid (α-LA). Cardiac contractile function, oxidative stress markers and reactive oxygen species (ROS) levels were assessed. ALDH2 activity and expression also were determined. The role of ALDH2 activity in change in hyperglycemia-induced mitochondrial membrane potential (Δψ) was tested in cultured neonatal cardiomyocytes. Myocardial MDA content and ROS were significantly higher in diabetic rats than in controls, whereas GSH content and Mn-SOD activity were decreased in diabetic rats. Compared with controls, diabetic rats exhibited significant reduction in LV ejection fraction and fractional shortening, accompanied by decreases in ALDH2 activity and expression. NAC and α-LA attenuated these changes. Mitochondrial Δψ was decreased greatly with hyperglycemia treatment, and high glucose combined with ALDH2 inhibition with daidzin further decreased Δψ. The ALDH2 activity can be regulated by oxidative stress in the diabetic rat heart. ALDH2 inhibition may be associated with LV reduced contractility, and mitochondrial impairment aggravated by ALDH2 inhibition might reflect an underlying mechanism which causes cardiac dysfunction in diabetic rats.

Cell signaling by protein carbonylation and decarbonylation

Reactive oxygen species (ROS) serve as mediators of signal transduction. However, mechanisms of how ROS influence the target molecules to elicit signaling event have not been defined. Our laboratory recently accumulated evidence for the role of protein carbonylation in the mechanism of ROS signaling. This concept originated from experiments in which pulmonary artery smooth muscle cells were treated with endothelin-1 to understand the mechanism of cell growth. Endothelin-1 was found to promote protein carbonylation in an endothelin receptor- and Fenton reaction-dependent manner. Mass spectrometry identified proteins that are carbonylated in response to endothelin-1, including annexin A1. Our experiments generated a hypothesis that endothelin-1-mediated carbonylation and subsequent degradation of annexin A1 promote cell growth. This mechanism was found also to occur in response to other signaling activators such as serotonin and platelet-derived growth factor in smooth muscle cells of pulmonary circulation, systemic circulation, and the airway, as well as in cardiac muscle cells, suggesting the universal role of this pathway. We also discovered a process of decarbonylation that defines transient kinetics of carbonylation signals in certain conditions. We propose that protein carbonylation and decarbonylation serve as a mechanism of signal transduction.

Aldehyde dehydrogenase 2 in cardiac protection: a new therapeutic target?

Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is emerging as a key enzyme involved in cytoprotection in the heart. ALDH2 mediates both the detoxification of reactive aldehydes such as acetaldehyde and 4-hydroxy-2-nonenal and the bioactivation of nitroglycerin to nitric oxide. In addition, chronic nitrate treatment results in ALDH2 inhibition and contributes to nitrate tolerance. Our laboratory recently identified ALDH2 to be a key mediator of endogenous cytoprotection. We reported that ALDH2 is phosphorylated and activated by the survival kinase protein kinase C epsilon and found a strong inverse correlation between ALDH2 activity and infarct size. We also identified a small molecule ALDH2 activator which reduces myocardial infarct size induced by ischemia/reperfusion in vivo. In this review, we discuss evidence that ALDH2 is a key mediator of endogenous survival signaling in the heart, suggest possible cardioprotective mechanisms mediated by ALDH2 and discuss potential clinical implications of these findings.

Activation of aldehyde dehydrogenase 2 (ALDH2) confers cardioprotection in protein kinase C epsilon (PKCvarepsilon) knockout mice

Acute administration of ethanol can reduce cardiac ischemia/reperfusion injury. Previous studies demonstrated that the acute cytoprotective effect of ethanol on the myocardium is mediated by protein kinase C epsilon (PKCvarepsilon). We recently identified aldehyde dehydrogenase 2 (ALDH2) as a PKCvarepsilon substrate, whose activation is necessary and sufficient to confer cardioprotection in vivo. ALDH2 metabolizes cytotoxic reactive aldehydes, such as 4-hydroxy-2-nonenal (4-HNE), which accumulate during cardiac ischemia/reperfusion. Here, we used a combination of PKCvarepsilon knockout mice and a direct activator of ALDH2, Alda-44, to further investigate the interplay between PKCvarepsilon and ALDH2 in cardioprotection. We report that ethanol preconditioning requires PKCvarepsilon, whereas direct activation of ALDH2 reduces infarct size in both wild type and PKCvarepsilon knockout hearts. Our data suggest that ALDH2 is downstream of PKCvarepsilon in ethanol preconditioning and that direct activation of ALDH2 can circumvent the requirement of PKCvarepsilon to induce cytoprotection. We also report that in addition to ALDH2 activation, Alda-44 prevents 4-HNE induced inactivation of ALDH2 by reducing the formation of 4-HNE-ALDH2 protein adducts. Thus, Alda-44 promotes metabolism of cytotoxic reactive aldehydes that accumulate in ischemic myocardium. Taken together, our findings suggest that direct activation of ALDH2 may represent a method of harnessing the cardioprotective effect of ethanol without the side effects associated with alcohol consumption.

Adaptation to oxidative challenge induced by chronic physical exercise prevents Na+,K+-ATPase activity inhibition after traumatic brain injury

Physical exercise is likely to alter brain function and to afford neuroprotection in several neurological diseases. Although the favorable effects of physical exercise on traumatic brain injury (TBI) patients is well known, little information is available regarding the role of free radicals in the improvement induced by physical exercise in an experimental model of TBI induced by fluid percussion injury (FPI). Thus, we investigated whether 6 weeks of swimming training protects against oxidative damage (measured by protein carbonylation and thiobarbituric acid-reactive substances-TBARS) and neurochemical alterations represented by immunodetection of alpha subunit and activity of Na(+),K(+)-ATPase after FPI in cerebral cortex of rats. Statistical analysis revealed that physical training protected against FPI-induced TBARS and protein carbonylation increase. In addition, physical training was effective against Na(+),K(+)-ATPase enzyme activity inhibition and alpha(1) subunit level decrease after FPI. Pearson's correlation analysis revealed that the decrease in levels of catalytic alpha(1) subunit of Na(+),K(+)-ATPase induced FPI correlated with TBARS and protein carbonylation content increase. Furthermore, the effective protection exerted by physical training against FPI-induced free radical correlated with the immunocontent of the catalytic alpha(1) subunit maintenance. These data suggest that TBI-induced reactive oxygen species (ROS) generation decreases Na(+),K(+)-ATPase activity by decreasing the total number of enzyme molecules, and that physical exercise protects against this effect. Therefore, the effective protection of selected targets, such as Na(+),K(+)-ATPase induced by physical training, supports the idea that physical training may exert prophylactic effects on neuronal cell dysfunction and damage associated with TBI.

Oxidative stress and autophagy in the regulation of lysosome-dependent neuron death

Lysosomes critically regulate the pH-dependent catabolism of extracellular and intracellular macromolecules delivered from the endocytic/heterophagy and autophagy pathways, respectively. The importance of lysosomes to cell survival is underscored not only by their unique ability effectively to degrade metalloproteins and oxidatively damaged macromolecules, but also by the distinct potential for induction of both caspase-dependent and -independent cell death with a compromise in the integrity of lysosome function. Oxidative stress and free radical damage play a principal role in cell death induced by lysosome dysfunction and may be linked to several upstream and downstream stimuli, including alterations in the autophagy degradation pathway, inhibition of lysosome enzyme function, and lysosome membrane damage. Neurons are sensitive to lysosome dysfunction, and the contribution of oxidative stress and free radical damage to lysosome dysfunction may contribute to the etiology of neurodegenerative disease. This review provides a broad overview of lysosome function and explores the contribution of oxidative stress and autophagy to lysosome dysfunction-induced neuron death. Putative signaling pathways that either induce lysosome dysfunction or result from lysosome dysfunction or both, and the role of oxidative stress, free radical damage, and lysosome dysfunction in pediatric lysosomal storage disorders (neuronal ceroid lipofuscinoses or NCL/Batten disease) and in Alzheimer's disease are emphasized.

Serum Concentrations of F2-Isoprostanes and 4-Hydroxynonenal in Hemodialysis Patients in Relation to Inflammation and Renal Anemia

Background

Patients with end-stage renal disease (ESRD) undergoing hemodialysis (HD) are apparently exposed to enhanced oxidative stress and to inflammation. It was the aim of this study to characterize the state of systemic oxidative stress of ESRD patients before and following HD using highly specific biomarkers, F₂-isoprostanes and 4-hydroxynonenal (HNE). Furthermore the question should be answered, if there are associations between inflammation and systemic oxidative stress and/or between systemic oxidative stress and renal anemia, which is more or less typical for HD patients.

Patients and methods

Concentrations of F₂-isoprostanes, HNE, C-reactive protein (CRP) as marker of inflammation, and hemoglobin were measured in serum samples of patients with ESRD before and after HD and of healthy control persons for comparison. Total (esterified plus free) F₂-isoprostanes were quantified by highly sensitive gas chromatography/mass spectrometry technique, HNE by thin layer chromatography and HPLC/UV detection, CRP by immunoturbidimetry and hemoglobin by clinico-chemical routine assay.

Results

1. HD patients showed significantly higher serum concentrations of F₂-isoprostanes and HNE than healthy human control subjects. 2. Total (esterified plus free) F₂-isoprostane levels before HD were not significantly different from those after HD, whereas HNE levels were significantly decreased in patients after HD. 3. F₂-isoprostane concentrations in HD patients correlated with the levels of CRP, whereas HNE concentrations inversely correlated with the content of hemoglobin.

Conclusion

Both, F₂-isoprostanes and HNE serum concentrations are useful oxidative stress parameters in ESRD patients undergoing HD. Whereas HNE strongly correlates with the severity of renal anemia, leading to left heart insufficiency, F₂-isoprostanes (sum of free plus esterified) highly correlate with the degree of inflammation.

Mechanism of destruction of microtubule structures by 4-hydroxy-2-nonenal

A major end product of lipid peroxidation, 4-hydroxy-2-nonenal (HNE), is an electrophilic alkenal and produces Michael adducts with cellular proteins. It is known that exposure of cultured cells to HNE causes rapid disappearance of microtubule networks. In this study we addressed the mechanism. Immunochemical studies revealed that HNE preferentially modified alpha-tubulin in rat primary neuronal cells, PC12 cells, and rat fibroblast cell line 3Y1 cells. This was morphologically associated with the disappearance of microtubule structures in those cells. In a purified rat brain microtubule fraction, HNE modified unpolymerized tubulin and impaired its polymerizability, with a concomitant increase in insolubilized tubulin. Nevertheless, HNE had a marginal effect on the stability of pre-polymerized microtubules. These results suggest that disruption of microtubule assembly as a result of HNE modification of unpolymerized tubulin, rather than destruction of assembled microtubules, is responsible for the disappearance of microtubule structures in cells exposed to HNE.