ALDH1L2 Is the Mitochondrial Homolog of 10-Formyltetrahydrofolate Dehydrogenase

Cytosolic 10-formyltetrahydrofolate dehydrogenase (FDH, ALDH1L1) is an abundant enzyme of folate metabolism. It converts 10-formyltetrahydrofolate to tetrahydrofolate and CO₂ in an NADP⁺-dependent reaction. We have identified a gene at chromosome locus 12q24.11 of the human genome, the product of which has 74% sequence similarity with cytosolic FDH. This protein has an extra N-terminal sequence of 22 amino acid residues, predicted to be a mitochondrial translocation signal. Transfection of COS-7 or A549 cell lines with a construct in which green fluorescent protein was introduced between the leader sequence and the rest of the putative mitochondrial FDH (mtFDH) has demonstrated mitochondrial localization of the fusion protein, suggesting that the identified gene encodes a mitochondrial enzyme. Purified pig liver mtFDH displayed dehydrogenase/hydrolase activities similar to cytosolic FDH. Real-time PCR performed on an array of human tissues has shown that although cytosolic FDH mRNA is highest in liver, kidney, and pancreas, mtFDH mRNA is most highly expressed in pancreas, heart, and brain. In contrast to the cytosolic enzyme, which is not detectable in cancer cells, the presence of mtFDH was demonstrated in several human cancer cell lines by conventional and real-time PCR and by Western blot. Analysis of genomes of different species indicates that the mitochondrial enzyme is a later evolutionary product when compared with the cytosolic enzyme. We propose that this novel mitochondrial enzyme is a likely source of CO₂ production from 10-formyltetrahydrofolate in mitochondria and plays an essential role in the distribution of one-carbon groups between the cytosolic and mitochondrial compartments of the cell.     

异柠檬酸脱氢酶在植物抗氧化胁迫中的作用

异柠檬酸脱氢酶(ICDH)是连接C-N代谢酶的关键,它催化三羧酸循环(TCA)中的异柠檬酸氧化脱羧形成α-酮戊二酸的可逆反应。ICDH的另一个重要功能是产生细胞质中的NADPH,NADPH在细胞中无处不在,介导许多氧化还原反应,并影响到几乎所有的代谢途径,涉及植物体内的活性氧(ROS)的生产和消耗,因此是传递胁迫信号的中转站。综述异柠檬酸脱氢酶在植物抗氧化胁迫中的作用,便于更好地理解ICDH在氧化胁迫中的信号传递和化学反应中所起的作用,为抗逆分子育种服务。     

Ethanol-Induced Oxidative Stress: The Role of Binaphthyl Diselenide as a Potent Antioxidant

It is widely accepted that oxidative stress plays a central role in alcohol-induced pathogenesis. The protective effect of binaphthyl diselenide (NapSe)2 was investigated in ethanol (Etoh)-induced brain injury. Thirty male adult Wistar rats were divided randomly into five groups of six animals each and treated as follows: (1) The control group received the vehicle (soy bean oil, 1 mL/kg, p.o.). (2) Ethanol group of animals was administered with ethanol (70% v/v, 2 mL/kg, p.o.). (3) (NapSe)2 1 mg/kg, 1 mL/kg plus ethanol 70% (v/v, 2 mL/kg, p.o. (5) (NapSe)2 10 mg/kg, 1 mL/kg) plus ethanol 70% (v/v, 2 mL/kg, p.o). After acute treatment, all rats were sacrificed by decapitation. Evidence for oxidative stress in rat brain was obtained from the observed levels of thiobarbituric acid reactive species, of non-protein thiol (NPSH) groups, and of ascorbic acid, as well as from the activities of catalase (CAT) and of superoxide dismutase (SOD). (NapSe)2 compensated the deficits in the antioxidant defense mechanisms (CAT, SOD, NPSH, and ascorbic acid), and suppressed lipid peroxidation in rat brain resulting from Etoh administration. It was concluded that ethanol exposure causes alterations in the antioxidant defense system and induces oxidative stress in rat brain. (NaPSe)2 at 5 mg/kg restored the antioxidant defenses in rat brain and mitigated the toxic effects of alcohol, suggesting that could be used as a potential therapeutic agent for alcohol-induced oxidative damage in rat brain.     

Macrophage Glucose-6-Phosphate Dehydrogenase Stimulates Proinflammatory Responses with Oxidative Stress

Glucose-6-phosphate dehydrogenase (G6PD) is a key enzyme that regulates cellular redox potential. In this study, we demonstrate that macrophage G6PD plays an important role in the modulation of proinflammatory responses and oxidative stress. The G6PD levels in macrophages in the adipose tissue of obese animals were elevated, and G6PD mRNA levels positively correlated with those of proinflammatory genes. Lipopolysaccharide (LPS) and free fatty acids, which initiate proinflammatory signals, stimulated macrophage G6PD. Overexpression of macrophage G6PD potentiated the expression of proinflammatory and pro-oxidative genes responsible for the aggravation of insulin sensitivity in adipocytes. In contrast, when macrophage G6PD was inhibited or suppressed via chemical inhibitors or small interfering RNA (siRNA), respectively, basal and LPS-induced proinflammatory gene expression was attenuated. Furthermore, macrophage G6PD increased activation of the p38 mitogen-activated protein kinase (MAPK) and NF-κB pathways, which may lead to a vicious cycle of oxidative stress and proinflammatory cascade. Together, these data suggest that an abnormal increase of G6PD in macrophages promotes oxidative stress and inflammatory responses in the adipose tissue of obese animals.     

植物中磷酸甘油醛-3-磷酸脱氢酶（GAPDH）在氧化胁迫下的生理功能

文章介绍植物中持家蛋白磷酸甘油醛-3-磷酸脱氢酶（GAPDH）在氧化胁迫下抑制活性氧生成、诱发磷酸化过程从而激活MAPK信号级联反应、诱导聚合体形成、参与谷胱甘肽修饰和控制电子转运中的生理功能研究进展。     

Stress Induction of Mitochondrial Formate Dehydrogenase in Potato Leaves

The metabolism of [1-¹³C]glucose in Pisolithus tinctorius cv Coker & Couch, in uninoculated seedlings of Eucalyptus globulus bicostata ex Maiden cv Kirkp., and in the E. globulus-P. tinctorius ectomycorrhiza was studied using nuclear magnetic resonance spectroscopy. In roots of uninoculated seedlings, the ¹³C label was mainly incorporated into sucrose and glutamine. The ratio (¹³C3 + ¹³C2)/¹³C4 of glutamine was approximately 1.0 during the time-course experiment, indicating equivalent contributions of phosphoenolpyruvate carboxylase and pyruvate dehydrogenase to the production of α-ketoglutarate used for synthesis of this amino acid. In free-living P. tinctorius, most of the ¹³C label was incorporated into mannitol, trehalose, glutamine, and alanine, whereas arabitol, erythritol, and glutamate were weakly labeled. Amino acid biosynthesis was an important sink of assimilated ¹³C (43%), and anaplerotic CO₂ fixation contributed 42% of the C flux entering the Krebs cycle. In ectomycorrhizae, sucrose accumulation was decreased in the colonized roots compared with uninoculated control plants, whereas ¹³C incorporation into arabitol and erythritol was nearly 4-fold higher in the symbiotic mycelium than in the free-living fungus. It appears that fungal utilization of glucose in the symbiotic state is altered and oriented toward the synthesis of short-chain polyols.     

Isocitrate Dehydrogenase Is Important for Nitrosative Stress Resistance in Cryptococcus neoformans,but Oxidative Stress Resistance Is Not Dependent on Glucose-6-Phosphate Dehydrogenase

The opportunistic intracellular fungal pathogen Cryptococcus neoformans depends on many antioxidant and denitrosylating proteins and pathways for virulence in the immunocompromised host. These include the glutathione and thioredoxin pathways, thiol peroxidase, cytochrome c peroxidase, and flavohemoglobin denitrosylase. All of these ultimately depend on NADPH for either catalytic activity or maintenance of a reduced, functional form. The need for NADPH during oxidative stress is well established in many systems, but a role in resistance to nitrosative stress has not been as well characterized. In this study we investigated the roles of two sources of NADPH, glucose-6-phosphate dehydrogenase (Zwf1) and NADP⁺-dependent isocitrate dehydrogenase (Idp1), in production of NADPH and resistance to oxidative and nitrosative stress. Deletion of ZWF1 in C. neoformans did not result in an oxidative stress sensitivity phenotype or changes in the amount of NADPH produced during oxidative stress compared to those for the wild type. Deletion of IDP1 resulted in greater sensitivity to nitrosative stress than to oxidative stress. The amount of NADPH increased 2-fold over that in the wild type during nitrosative stress, and yet the idp1Δ strain accumulated more mitochondrial damage than the wild type during nitrosative stress. This is the first report of the importance of Idp1 and NADPH for nitrosative stress resistance.The alveolar macrophage can produce microbicidal amounts of toxic reactive oxygen species (ROS) and reactive nitrogen species (RNS) following phagocytosis (27, 53). Despite this, the opportunistic fungal pathogen Cryptococcus neoformans is able to inhabit and replicate within phagocytes of the mammalian host and to exit these cells unharmed (1, 2, 40). The intracellular pathogenicity of C. neoformans is most likely facilitated by stress resistance mechanisms, including a number of antioxidant proteins and pathways involved in the detoxification of ROS and RNS. Specifically, these include the synthesis of mannitol, a free radical scavenger (9, 20); the small protein flavohemoglobin denitrosylase (Fhb1), which is essential for resistance of C. neoformans to nitrosative stress (10, 14, 32); and the glutathione and thioredoxin antioxidant systems, which are both important for stress resistance and virulence (42, 43, 45).Even with different mechanisms of catalysis and/or cellular localization, one thing that these stress resistance proteins and pathways have in common is the requirement for NADPH as a cofactor. NADPH is used as an electron donor either in recycling of oxidized, inactive enzymes to reduced, active forms or directly in catalytic activity. For example, Fhb1 binds NADPH during its catalytic activity and uses it directly as an electron donor for the reduction of NO· to NO₃ (21). Catalases, which are highly conserved antioxidants that dismute H₂O₂ to molecular oxygen and water, consist of four units each with a molecule of NADPH bound in the core (18, 36, 59). The tripeptide glutathione (GSH) is oxidized to glutathione disulfide (GSSG), a homodimer held together by a disulfide bridge, during its oxidative state. GSSG can be reduced back to GSH by glutathione reductase, an enzyme that requires NADPH for electrons used in reduction. Similarly, glutathione peroxidase and thiol peroxidase ultimately depend on NADPH for recycling from an oxidized, inactive form back to a reduced, active form (57).NADPH is classically recognized as being produced by the highly conserved, cytosolic pentose phosphate pathway. This pathway has been shown to be important for reductive biochemistry during oxidative stress in many organisms. The pentose phosphate pathway is an essential factor in maintaining health of erythrocytes, cells that, due to their biological function, have considerable risk for oxidative damage. Humans deficient in the pathway have hemolytic anemia, as their erythrocytes are unable to maintain sufficient pools of reduced glutathione (68). Also, the pressure of oxidative stress can stimulate the pentose phosphate pathway. This has been shown in human lymphocytes (56); in the rat adrenal gland, liver, and pancreas (15, 16); and in bacteria (63).In fungi, the pentose phosphate pathway has been implicated in both oxidative stress resistance and adaptation to oxidative stress. In the model yeast Saccharomyces cerevisiae, NADPH-generating systems, including the pentose phosphate pathway, are critical for the ability of this organism to resist and adapt to high levels of oxidative stress (35, 47). It has also been shown that the cytosolic copper/zinc superoxide dismutase and the pentose phosphate pathway have overlapping roles in protecting S. cerevisiae from oxidative stress and that both systems are critical for maintaining the intracellular redox state (62). Furthermore, fungi may rely on the pentose phosphate pathway for more than reducing oxidative stress. Aspergillus nidulans requires a functional pentose phosphate pathway for nitrogen metabolism. Four A. nidulans mutants with independent defects in the pentose phosphate pathway were unable to grow on nitrite, nitrate, or various carbon sources, including 1% glucose, d-xylose, or d-glucoronate (28).The pathway has two phases, the oxidative phase and the nonoxidative phase. The oxidative phase consists of two successive oxidations and results in the production of NADPH. The first enzyme in the oxidative phase of the pentose phosphate pathway is glucose-6-phosphate dehydrogenase (Zwf). Zwf catalyzes the oxidation of glucose-6-phosphate to 6-phosphogluconate and is highly specific for NADP⁺ as a cofactor (49, 67). There is abundant evidence supporting the role of Zwf in oxidative stress resistance. In addition to Zwf deficiency causing hemolytic anemia, Zwf has been also been implicated in maintenance of DNA repair systems during oxidative stress, as some cancers and aging disorders have also been linked to Zwf deficiency (30). For instance, Chinese hamster ovarian cells that are Zwf null have enhanced radiation sensitivity and a reduced ability to repair double-strand breaks due to the inactivation of Ku, a heterodimer DNA repair protein. In this case, the inactivation of Ku is the result of overoxidation of key cysteine residues on the protein due to the lack of sufficient reduced GSH (3). In the model yeast Saccharomyces cerevisiae, deletion of ZWF1 results in sensitivity to oxidative stress. ZWF1 is also important for the adaptive response to oxidative stress in S. cerevisiae. ZWF1-null mutants and wild-type cells were pretreated with 0.2 mM H₂O₂ and then challenged with 2 mM H₂O₂. While a large increase in tolerance to the high level of H₂O₂ was observed in the wild-type cells pretreated with 0.2 mM H₂O₂, the zwf1Δ strain was unable to tolerate the higher concentration (33). In Candida albicans, another pathogenic fungus, ZWF1 is upregulated during oxidative stress (38).Another source of NADPH is NADP⁺-dependent isocitrate dehydrogenase (Idp) (55), a ubiquitous enzyme that in systems ranging from humans to yeasts to plants has been found in the cytosol, peroxisomes, or mitochondria (12, 19, 70). Although this enzyme can be targeted to mitochondria, it is distinct from the NAD⁺-dependent isocitrate dehydrogenase (Idh) that functions in the mitochondria as part of the Krebs cycle. However, similarly to Idh, Idp catalyzes the decarboxylation of isocitrate to α-ketoglutarate (29). This reaction can be performed in the mitochondria, in the cytosol, or in peroxisomes using isocitrate formed from citrate exported across the mitochondrial membrane. This allows for the production of NADPH in cellular compartments without reliance of active transport of NADPH across membranes (11). It is important to have reductive power produced directly within organelles for protection from exogenous as well as endogenous stressor. For example, NADPH is consumed in peroxisomes by enzymes such as catalase and uric acid oxidase, that counteract the ROS produced during breakdown of lipids (4, 5, 31). Mitochondria particularly require reductive capability, as these organelles are susceptible to endogenous ROS produced during cellular respiration and also to exogenous RNS (52). The proteins that make up the electron transport chain are prone to damage by nitric oxide, peroxynitrite, and S-nitrosothiols (6). Nitric oxide and peroxynitrite have been shown to cause irreversible damage to cytochrome c reductase, NADH dehydrogenase, and the succinate-ubiquinone complex; the common mechanism of damage is sequestration of iron/sulfur centers of the proteins (54, 69). Thus, without a means of detoxification, the mitochondrial membrane loses potential and the ability to continue respiration, leading to death of the stressed cell. In C. neoformans, some antioxidant enzymes that are located at the mitochondria and dependent on NADPH for function include catalases, superoxide dismutases, cytochrome c peroxidase, and flavohemoglobin denitrosylase (7, 24, 25, 26). These enzymes are important for stress resistance or virulence of C. neoformans due to their role in high-temperature growth (24, 25) or nitrosative stress resistance (10, 14, 26).In humans, there is one IDP gene that results in mitochondrial and peroxisomal products (22). In S. cerevisiae, there are three IDP genes, which encode mitochondrial (IDP1), cytosolic (IDP2), and peroxisomal (IDP3) forms of the protein. Deletion of both ZWF1 and any one of the IDP genes in S. cerevisiae results in sensitivity to oxidative stress, likely due to a substantial decrease in NADPH produced in these double deletion mutants (41). In C. neoformans there is one predicted IDP gene (IDP1). Microarray data have indicated that this gene is upregulated 2.5-fold during nitrosative stress and thus may have a role in resistance to this stressor (44).Since so many factors essential for stress resistance in C. neoformans utilize NADPH, we hypothesize that the sources of this cofactor are likewise critical for stress resistance. Although Zwf1 is important for adaptation to oxidative stress in the fungi S. cerevisiae and C. albicans, we had previously found that C. neoformans is unable to adapt to oxidative stress (S. M. Brown and J. K. Lodge, unpublished data), and thus we had reason to suspect that the role of Zwf1 in C. neoformans may be different than that in other organisms. The role of Idp1 in stress resistance, especially in resistance to nitrosative stress, is relatively unknown. In this study we used biochemical and genetic approaches to compare the roles of Zwf1 and Idp1 in resistance to oxidative and nitrosative stress in C. neoformans. We found that the Zwf1 is dispensable for viability, for resistance to oxidative and nitrosative stress, and for NADPH production. In contrast, we found that Idp1 is important for resistance to nitrosative stress, specifically for maintaining healthy mitochondria during exposure to nitrosative stress.     

Hepatoprotective and Antioxidant Activity of Linden (Tilia platyphyllos L.) Infusion Against Ethanol-Induced Oxidative Stress in Rats

The present study was carried out to evaluate the hepatoprotective effect and antioxidant role of infusion prepared from linden flowers (LF) against ethanol-induced oxidative stress. The hepatoprotective and antioxidant role of the plant’s infusion against ethanol-induced oxidative stress was evaluated by measuring liver damage serum biomarkers, aspartate aminotransferase (AST), alanine aminotransferase, lactate dehydrogenase (LDH), total protein, total albumin, and total cholesterol level; ADS such as GSH, GR, SOD, GST, CAT and GPx, and MDA contents in various tissues of rats. Rats were divided into four experimental groups: I (control), II (20 % ethanol), III (2 % LF), and IV (20 % ethanol + 2 % LF). According to the results, the level of serum marker enzymes, AST and LDH, was significantly increased in group alcohol and group LF as compared to control group, whereas decreased in group IV as compared to ethanol group. With regard to MDA content and ADS constituents, MDA contents of alcohol group in all tissues, except for erythrocytes and heart, and in brain, kidney, and spleen of LF group significantly increased compared to control group, whereas LF beverage extract supplementation did not restore the increased MDA towards close the control level. In addition, while ethanol caused fluctuation in antioxidant defense system constituents level as a result of oxidative stress condition in the rats, it could have not been determined the healing effects of the LF against these fluctuations. The results indicated that LF beverage extract could not be as important as diet-derived antioxidants in preventing oxidative damage in the tissues by reducing the lipid oxidation or inhibiting the production of ethanol-induced free radicals in rats.     

Increased Cerebral Glucose-6-Phosphate Dehydrogenase Activity in Alzheimer''s Disease May Reflect Oxidative Stress

The activities of the hexose monophosphate pathway enzymes glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were measured at autopsy in control and Alzheimer's disease brains. Enzyme activities did not vary between different areas of brain and were unaltered by age. In Alzheimer's disease, the activities of both enzymes were increased, the glucose-6-phosphate dehydrogenase activity being almost double the activity of normal controls. We propose that this increased enzyme activity is a response to elevated brain peroxide metabolism.     

Oxidative Burst and Hypoosmotic Stress in Tobacco Cell Suspensions

Oxidative burst constitutes an early response in plant defense reactions toward pathogens, but active oxygen production may also be induced by other stimuli. The oxidative response of suspension-cultured tobacco (Nicotiana tabacum cv Xanthi) cells to hypoosmotic and mechanical stresses was characterized. The oxidase involved in the hypoosmotic stress response showed similarities by its NADPH dependence and its inhibition by iodonium diphenyl with the neutrophil NADPH oxidase. Activation of the oxidative response by hypoosmotic stress needed protein phosphorylation and anion effluxes, as well as opening of Ca²⁺ channels. Inhibition of the oxidative response impaired Cl⁻ efflux, K⁺ efflux, and extracellular alkalinization, suggesting that the oxidative burst may play a role in ionic flux regulation. Active oxygen species also induced the cross-linking of a cell wall protein, homologous to a soybean (Glycine max L.) extensin, that may act as part of cell volume and turgor regulation through modification of the physical properties of the cell wall.     

A Cyanobacterium Lacking Iron Superoxide Dismutase Is Sensitized to Oxidative Stress Induced with Methyl Viologen but Is Not Sensitized to Oxidative Stress Induced with Norflurazon

A strain of Synechococcus sp. strain PCC 7942 with no functional Fe superoxide dismutase (SOD), designated sodB⁻, was characterized by its growth rate, photosynthetic pigments, and cyclic photosynthetic electron transport activity when treated with methyl viologen or norflurazon (NF). In their unstressed conditions, both the sodB⁻ and wild-type strains had similar chlorophyll and carotenoid contents and catalase activity, but the wild type had a faster growth rate and higher cyclic electron transport activity. The sodB⁻ was very sensitive to methyl viologen, indicating a specific role for the FeSOD in protection against superoxide generated in the cytosol. In contrast, the sodB⁻ mutant was less sensitive than the wild type to oxidative stress imposed with NF. This suggests that the FeSOD does not protect the cell from excited singlet-state oxygen generated within the thylakoid membrane. Another up-regulated antioxidant, possibly the MnSOD, may confer protection against NF in the sodB⁻ strain. These results support the hypothesis that different SODs have specific protective functions within the cell.     

Oxidative Stress Alters Syndecan-1 Distribution in Lungs with Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease characterized by severe, progressive fibrosis. Roles for inflammation and oxidative stress have recently been demonstrated, but despite advances in understanding the pathogenesis, there are still no effective therapies for IPF. This study investigates how extracellular superoxide dismutase (EC-SOD), a syndecan-binding antioxidant enzyme, inhibits inflammation and lung fibrosis. We hypothesize that EC-SOD protects the lung from oxidant damage by preventing syndecan fragmentation/shedding. Wild-type or EC-SOD-null mice were exposed to an intratracheal instillation of asbestos or bleomycin. Western blot was used to detect syndecans in the bronchoalveolar lavage fluid and lung. Human lung samples (normal and IPF) were also analyzed. Immunohistochemistry for syndecan-1 and EC-SOD was performed on human and mouse lungs. In vitro, alveolar epithelial cells were exposed to oxidative stress and EC-SOD. Cell supernatants were analyzed for shed syndecan-1 by Western blot. Syndecan-1 ectodomain was assessed in wound healing and neutrophil chemotaxis. Increases in human syndecan-1 are detected in lung homogenates and lavage fluid of IPF lungs. Syndecan-1 is also significantly elevated in the lavage fluid of EC-SOD-null mice after asbestos and bleomycin exposure. On IHC, syndecan-1 staining increases within fibrotic areas of human and mouse lungs. In vitro, EC-SOD inhibits oxidant-induced loss of syndecan-1 from A549 cells. Shed and exogenous syndecan-1 ectodomain induce neutrophil chemotaxis, inhibit alveolar epithelial wound healing, and promote fibrogenesis. Oxidative shedding of syndecan-1 is an underlying cause of neutrophil chemotaxis and aberrant wound healing that may contribute to pulmonary fibrosis.Idiopathic pulmonary fibrosis (IPF)² is an interstitial lung disease characterized by severe and progressive fibrosis. IPF patients have a mean survival of 3–5 years (1, 2) and no effective therapies (3, 4), other than orthotopic lung transplantation, have proven to improve survival. The pathogenesis of IPF is poorly understood; however, inflammation and oxidant/antioxidant imbalances in the lung are thought to play important roles (5–7). A better understanding of the molecular mechanisms involved in oxidative injury and fibrosis could lead to the development of novel therapeutic targets.Extracellular superoxide dismutase (EC-SOD) is an antioxidant enzyme bound to heparan sulfate in the lung extracellular matrix (8–10), which can inhibit inflammation (11, 12) and prevent subsequent development of fibrosis (13–16). Despite its beneficial role, the mechanisms through which EC-SOD protects the lung remain unknown.The extracellular matrix (ECM) is essential for tissue homeostasis and changes in the ECM microenvironment can be detrimental to cell function during inflammation and wound healing. Heparan sulfate proteoglycans (HSPG) contain a membrane-bound core protein and extracellular carbohydrate side chains. Syndecans are the most abundant HSPG in humans; there are 4 isoforms with variable cell expression (17, 18). Both syndecan-1 and -4 are expressed in the lung, with epithelial cell and ubiquitous expression, respectively (19). Syndecans are essential for ECM homeostasis by binding cytokines and growth factors, acting as co-receptors and soluble effectors. They also have potential roles in inflammation (18, 20, 21), fibrosis (22, 23), and wound healing (24–26). Syndecans are shed under physiological and pathological conditions but the function of shed syndecans is poorly understood (22). Reactive oxygen species (ROS) are capable of fragmenting HSPG (27) and other ECM components. Notably, EC-SOD has been shown to prevent oxidative damage to many ECM components (23, 28, 29). Within the lung, EC-SOD binds to syndecan-1 on the cell surface via a heparin-binding domain (8, 30). Because of the known functions of syndecans and its close interaction with EC-SOD, syndecan-1 is a key target that may contribute to the anti-inflammatory and anti-fibrotic effects of EC-SOD in the lung and in the pulmonary fibrosis.This study was conducted to determine the role of EC-SOD in protecting the ECM from oxidative stress and to investigate our hypothesis that EC-SOD protects the lung from inflammation and fibrosis by inhibiting oxidant-induced shedding of syndecan-1. Our findings suggest that a loss of EC-SOD in the lung leaves syndecan-1 vulnerable to oxidative stress and that oxidatively shed syndecan-1 ectodomain induces neutrophil chemotaxis, impairs epithelial wound healing, and promotes fibrogenesis. The discovery that oxidative stress alters the distribution of syndecan-1 in the lung microenvironment is a novel finding in the context of pulmonary fibrosis. These findings advance the understanding of the pathogenesis of idiopathic pulmonary fibrosis and provide a potential new therapeutic target for intervention in IPF.     

Alcohol Dehydrogenase Accentuates Ethanol-Induced Myocardial Dysfunction and Mitochondrial Damage in Mice: Role of Mitochondrial Death Pathway

Objectives

Binge drinking and alcohol toxicity are often associated with myocardial dysfunction possibly due to accumulation of the ethanol metabolite acetaldehyde although the underlying mechanism is unknown. This study was designed to examine the impact of accelerated ethanol metabolism on myocardial contractility, mitochondrial function and apoptosis using a murine model of cardiac-specific overexpression of alcohol dehydrogenase (ADH).

Methods

ADH and wild-type FVB mice were acutely challenged with ethanol (3 g/kg/d, i.p.) for 3 days. Myocardial contractility, mitochondrial damage and apoptosis (death receptor and mitochondrial pathways) were examined.

Results

Ethanol led to reduced cardiac contractility, enlarged cardiomyocyte, mitochondrial damage and apoptosis, the effects of which were exaggerated by ADH transgene. In particular, ADH exacerbated mitochondrial dysfunction manifested as decreased mitochondrial membrane potential and accumulation of mitochondrial O₂^•−. Myocardium from ethanol-treated mice displayed enhanced Bax, Caspase-3 and decreased Bcl-2 expression, the effect of which with the exception of Caspase-3 was augmented by ADH. ADH accentuated ethanol-induced increase in the mitochondrial death domain components pro-caspase-9 and cytochrome C in the cytoplasm. Neither ethanol nor ADH affected the expression of ANP, total pro-caspase-9, cytosolic and total pro-caspase-8, TNF-α, Fas receptor, Fas L and cytosolic AIF.

Conclusions

Taken together, these data suggest that enhanced acetaldehyde production through ADH overexpression following acute ethanol exposure exacerbated ethanol-induced myocardial contractile dysfunction, cardiomyocyte enlargement, mitochondrial damage and apoptosis, indicating a pivotal role of ADH in ethanol-induced cardiac dysfunction possibly through mitochondrial death pathway of apoptosis.     

乙醛脱氢酶2可减少氧化损伤诱导的心肌细胞凋亡

乙醛脱氢酶2 (aldehyde dehydrogenase 2, ALDH2)是线粒体特异性酶,已被证明参与氧化应激诱导的细胞凋亡,而在心肌细胞中的作用知之甚少。本研究旨在通过用特异性ALDH2抑制剂大豆苷抑制ALDH2活性来研究ALDH2在抗霉素A诱导的心肌细胞凋亡中的作用。应用抗霉素A和大豆苷诱导小鼠心肌细胞,然后测定ALDH2酶活性、细胞内活性氧(reactive oxy gen species, ROS)含量和细胞凋亡,应用RT-PCR和蛋白质印迹法(Western blotting)检测ALDH2 m RNA和蛋白表达。结果表明,抗霉素A (40μg/mL)可诱导新生心肌细胞凋亡,而大豆苷(50μmol/L)能有效地抑制ALDH2活性而对细胞凋亡没有影响,并且可显著增强抗霉素A诱导的心肌细胞凋亡(53.72%～71.33%, p<0.05)。与单独用抗霉素A处理的细胞相比,抗霉素A和大豆苷共处理的心肌细胞中活化的丝裂原活化蛋白激酶(mitogen-activated protein kinase, MAPK)信号传导途径(p38-MAPK)的磷酸化也显著增加。本研究初步表明,改变线粒体ALDH2活性可能是减少氧化损伤诱导的心肌细胞凋亡的潜在选择。