Mitochondrial response to oxidative and nitrosative stress in early stages of diabetes

Diabetes mellitus (DM) is associated with increased production of reactive oxygen and nitrogen species; consequently, an increase in lipid peroxidation and a decrease in antioxidants resulting in mitochondrial dysfunction. Using a rat model of DM induced by streptozotocin, we show the opposite: an increase in NO levels, S-nitrosylation, aconitase activity, and total glutathione and a decrease in lipid peroxidation at early stages of diabetes. These data imply that the decrease in lipid peroxidation is a vital early response to hyperglycemia to prevent escalation of ROS generation in mitochondria. These results also suggest a need for novel therapeutic targets to prevent the neurological consequences of diabetes.     

Glutathione – linking cell proliferation to oxidative stress

SignificanceThe multifaceted functions of reduced glutathione (gamma-glutamyl–cysteinyl–glycine; GSH) continue to fascinate plants and animal scientists, not least because of the dynamic relationships between GSH and reactive oxygen species (ROS) that underpin reduction/oxidation (redox) regulation and signalling. Here we consider the respective roles of ROS and GSH in the regulation of plant growth, with a particular focus on regulation of the plant cell cycle. Glutathione is discussed not only as a crucial low molecular weight redox buffer that shields nuclear processes against oxidative challenge but also a flexible regulator of genetic and epigenetic functions.Recent advancesThe intracellular compartmentalization of GSH during the cell cycle is remarkably consistent in plants and animals. Moreover, measurements of in vivo glutathione redox potentials reveal that the cellular environment is much more reducing than predicted from GSH/GSSG ratios measured in tissue extracts. The redox potential of the cytosol and nuclei of non-dividing plant cells is about −300 mV. This relatively low redox potential maintained even in cells experiencing oxidative stress by a number of mechanisms including vacuolar sequestration of GSSG. We propose that regulated ROS production linked to glutathione-mediated signalling events are the hallmark of viable cells within a changing and challenging environment.Critical issuesThe concept that the cell cycle in animals is subject to redox controls is well established but little is known about how ROS and GSH regulate this process in plants. However, it is increasingly likely that redox controls exist in plants, although possibly through different pathways. Moreover, redox-regulated proteins that function in cell cycle checkpoints remain to be identified in plants. While GSH-responsive genes have now been identified, the mechanisms that mediate and regulate protein glutathionylation in plants remain poorly defined.Future directionsThe nuclear GSH pool provides an appropriate redox environment for essential nuclear functions. Future work will focus on how this essential thiol interacts with the nuclear thioredoxin system and nitric oxide to regulate genetic and epigenetic mechanisms. The characterization of redox-regulated cell cycle proteins in plants, and the elucidation of mechanisms that facilitate GSH accumulation in the nucleus are keep steps to unravelling the complexities of nuclear redox controls.     

Mitochondrial dysfunction in brain aging: role of oxidative stress and cardiolipin

Aging is a biological process characterized by impairment of cellular bioenergetic function, increased oxidative stress, attenuated ability to respond to stresses, increased risk of contracting age-associated disorders that affects many tissues, with a more marked effect on brain and heart function. Oxidative stress is widely thought to underpin many aging processes. The mitochondrion is considered the most important cellular organelle to contribute to the aging process, mainly through respiratory chain dysfunction and formation of reactive oxygen species, leading to damage to mitochondrial proteins, lipids and mitochondrial DNA. Furthermore, exposure to oxidants, especially in the presence of Ca(2+), can induce the mitochondrial permeability transition with deleterious effects on mitochondrial function. Cardiolipin plays a central role in several mitochondrial bioenergetic processes as well as in mitochondrial-dependent steps in apoptosis and mitochondrial membrane stability and dynamics. Alterations to cardiolipin structure, content and acyl chain profile have been associated with mitochondrial dysfunction in multiple tissues in several physiopathological conditions and aging. In this review, we focus on the role played by oxidative stress and cardiolipin in mitochondrial bioenergetic alterations associated with brain aging.     

Immunocytochemical demonstration of the expression and induction of manganese-superoxide dismutase in the adenohypophysis

Immunocytochemistry for manganese-superoxide dismutase (Mn-SOD) was studied in 12 normal adenohypophyses and 38 various pituitary lesions. The proportions of cells with granular immunoreactivity for Mn-SOD in normal adenohypophysis ranged from 9.8% to 29.6% (mean +/- sd; 18.4 +/- 6.2%). Some positive cells tended to accumulate in clusters, distribution of which corresponded well with those immunopositive for mitochondrial protein and cytochrome oxidase. The number of Mn-SOD-positive cells increased in adjacent residual adenohypophysis in eight of nine recent infarcts, in two of five old infarcts, in all four cases of lymphocytic hypophysitis, in two of four abscess cases and in one of three metastatic tumour cases, whereas the immunoreactivities of mitochondrial protein- and cytochrome oxidase-positive cells either did not vary or decreased. The intensity of the histological inflammatory reactions showed a positive correlation with reactivity for Mn-SOD in these lesions. Of eight adenomas, the surrounding area of compressed adenohypophysis showed increased numbers of Mn-SOD- and mitochondrial protein-/cytochrome oxidase-positive cells in four and six cases respectively. It is suggested that positivity for Mn-SOD may be related to some functional activity of mitochondria. It is further suggested that adenohypophysial cells have a high potential to induce Mn-SOD by inflammatory and ischaemic stress and, in addition, by enhanced mitochondrial activity. © 1998 Chapman & Hall     

Requirements for proximal tubule epithelial cell detachment in response to ischemia: role of oxidative stress

Sublethal renal ischemia induces tubular epithelium damage and kidney dysfunction. Using NRK-52E rat proximal tubular epithelial cells, we have established an in vitro model, which includes oxygen and nutrients deprivation, to study the proximal epithelial cell response to ischemia. By means of this system, we demonstrate that confluent NRK-52E cells lose monolayer integrity and detach from collagen IV due to: (i) actin cytoskeleton reorganization; (ii) Rac1 and RhoA activity alterations; (iii) Adherens junctions (AJ) and Tight junctions (TJ) disruption, involving redistribution but not degradation of E-cadherin, beta-catenin and ZO-1; (iv) focal adhesion complexes (FAC) disassembly, entangled by mislocalization of paxillin and FAK dephosphorylation. Reactive oxygen species (ROS) are generated during the deprivation phase and rapidly balanced at recovery involving MnSOD induction, among others. The use of antioxidants (NAC) prevented FAC disassembly by blocking paxillin redistribution and FAK dephosphorylation, without abrogating AJ or TJ disruption. In spite of this, NAC did not show any protective effect on cell detachment. H(2)O(2), as a pro-oxidant treatment, supported the contribution of ROS in tubular epithelial cell-matrix but not cell-cell adhesion alterations. In conclusion, ROS-mediated FAC disassembly was not sufficient for the proximal epithelial cell shedding in response to sublethal ischemia, which also requires intercellular adhesion disruption.     

Effects of Lactobacillus strains on cancer cell proliferation and oxidative stress in vitro

AIMS: The objective of this study was to assess in vitro, whether heat-killed (HK) lactic acid bacteria cells and fractionations of HK cells could suppress the viability of human cancer cells and inhibit the cytotoxicity associated with oxidative stress. METHODS AND RESULTS: Among the strains, the HK cells of Lactobacillus acidophilus 606 and Lactobacillus casei ATCC 393 exhibited the most profound inhibitory activity in all of the tested cell lines. HK cells of L. acidophilus 606 were determined to be less toxic to healthy human embryo fibroblasts (hEF cells) than were HK cells of L. casei ATCC 393. The soluble polysaccharides from L. acidophilus 606 evidenced the most effective anticancer activity, but inhibited hEF cell growth by only 20%. The soluble polysaccharides from L. acidophilus 606 were partly observed to induce apoptosis in the HT-29 cells by DNA fragmentation and propidium iodine staining. Both the HK cells of L. acidophilus 606 and the soluble polysaccharide components of this strain also exhibited potent antioxidative activity. CONCLUSIONS: Our findings suggest that the soluble polysaccharide fraction from L. acidophilus 606 may constitute a novel anticancer agent, which manifests a high degree of selectivity for human cancer cells and antioxidative agent in the food industry. SIGNIFICANCE AND IMPACT OF THE STUDY: These soluble polysaccharide components from Lactobacillus may be applied to various foods, and used as adjuncts for cancer therapy and prevention.     

节杆菌A.pascens DMDC12锰超氧化物歧化酶基因的克隆和表达

利用PCR技术对自行筛选的高度耐盐节杆菌Arthrobacter pascensDMDC12中的超氧化物歧化酶基因进行克隆,获得了节杆菌A.pascensDMDC12的SOD新基因(GenBank收录号为DQ779150)。将该基因与原核表达质粒载体pET-22b( )连接,构建重组质粒pET-sodAP,将质粒转化至表达宿主菌E.coliBL21(DE3),构建基因工程菌BL21/pET-sodAP。用异丙基硫代--βD-半乳糖苷(IPTG)诱导重组SOD蛋白表达,用酶活和SDS-PAGE分析表达产物,表达产物的相对分子质量为2.4×104,与sodAP推测的长度相同。表达目的蛋白占菌体可溶性蛋白的23%,比酶活达915.07 IU.mg-1,是对照菌株的8.73倍,具有较高的表达。本研究为进一步进行重组Mn-SOD的研究和应用奠定了基础。     

Prostate cancer and physical activity: Adaptive response to oxidative stress

Prostate cancer is the most common form of cancer affecting men in the Western world. Its relative incidence increases exponentially with age and a steady increase is observed with extended life span. A sedentary lifestyle represents an important risk factor and a decrease in prostate cancer prevalence is associated with exercise. However, the molecular mechanisms involved in this process remain unknown. We hypothesize that reactive oxygen species generated by physical exercise are a key regulatory factor in prostate cancer prevention. Aging is correlated with increased oxidative stress (OS), which in turn provides a favorable environment for tumorigenesis. Running training is known to enhance the antioxidant defense system, reducing oxidative stress. In this context, the decrease in OS induced by exercise may delay the development of prostate cancer. This review focuses on oxidative stress-based mechanisms leading to prostate cancer sensitization to exercise, which could have some impact on the development of novel cancer therapeutic strategies.     

Mitochondrial oxidative stress plays a key role in aging and apoptosis

Harman first suggested in 1972 that mitochondria might be the biological clock in aging, noting that the rate of oxygen consumption should determine the rate of accumulation of mitochondrial damage produced by free radical reactions. Later in 1980 Miquel and coworkers proposed the mitochondrial theory of cell aging. Mitochondria from postmitotic cells use O2 at a high rate, hence releasing oxygen radicals that exceed the cellular antioxidant defences. The key role of mitochondria in cell aging has been outlined by the degeneration induced in cells microinjected with mitochondria isolated from fibroblasts of old rats, especially by the inverse relationship reported between the rate of mitochondrial production of hydroperoxide and the maximum life span of species. An important change in mitochondrial lipid composition is the age-related decrease found in cardiolipin content. The concurrent enhancement of lipid peroxidation and oxidative modification of proteins in mitochondria further increases mutations and oxidative damage to mitochondrial DNA (mtDNA) in the aging process. The respiratory enzymes containing the defective mtDNA-encoded protein subunits may increase the production of reactive oxygen species, which in turn would aggravate the oxidative damage to mitochondria. Moreover, superoxide radicals produced during mitochondrial respiration react with nitric oxide inside mitochondria to yield damaging peroxynitrite. Treatment with certain antioxidants, such as sulphur-containing antioxidants, vitamins C and E, or the Ginkgo biloba extract EGb 761, protects against the age-associated oxidative damage to mtDNA and the oxidation of mitochondrial glutathione. Moreover, the EGb 761 extract also prevents changes in mitochondrial morphology and function associated with aging of the brain and liver.     

The role of superoxide dismutase in combating oxidative stress in higher plants

Superoxide dismutase (SOD) isozymes are compartmentalized in higher plants and play a major role in combating oxygen radical mediated toxicity. In this review we evaluate the mode of action and effects of the SOD isoforms with respect to oxidative stress resistance, correlating age, species, and specificity of plants during development.     

Diva reduces cell death in response to oxidative stress and cytotoxicity

Diva is a member of the Bcl2 family but its function in apoptosis remains largely unclear because of its specific expression found within limited adult tissues. Previous overexpression studies done on various cell lines yielded conflicting conclusions pertaining to its apoptotic function. Here, we discovered the expression of endogenous Diva in PC12 neuronal-like cell line and rat bone marrow mesenchymal stem cells (BMSCs), leading to their utilisation for the functional study of Diva. Through usage of recombinant Fas ligand, hydrogen peroxide, overexpression and knock down experiments, we discovered that Diva plays a crucial pro-survival role via the mitochondrial death pathway. In addition, immunoprecipitation studies also noted a decrease in Diva's interaction with Bcl2 and Bax following apoptosis induced by oxidative stress. By overexpressing Diva in BMSCs, we had observed an increase in the cells' capacity to survive under oxidative stress and microglial toxicity. The result obtained from our study gives us reason to believe that Diva plays an important role in controlling the survival of BMSCs. Through overexpression of Diva, the viability of these BMSCs may be boosted under adverse conditions.     

Regulation of gamma-glutamylcysteine synthetase expression in response to oxidative stress.

Glutathione (GSH) is synthesized by the activity of two ATP-requiring GSH synthesizing enzymes. Gamma-glutamylcysteine synthetase (gamma-GCS) is the rate limiting enzyme for the GSH synthesis. Gamma-GCS is a heterodimer of heavy, catalytic subunit and light, regulatory subunit and responsive to many stresses, such as heat shock, oxidative stress or cytokines. To know the regulation of the expression of gamma-GCS gene, in the present study, we show evidences that gamma-GCS heavy subunit is upregulated by oxidative stress by ionizing radiation and TNF-alpha mediated by nuclear factor-kappaB (NF-kappaB), and impairment of the expression of gamma-GCS by TNF-alpha in diabetic condition. Furthermore we describe the importance of GSH in the regulation of NF-kappaB subunits.     

Microarray expression profiling of Spodoptera litura in response to oxidative stress

To examine the expression profile of oxidative stress responsive genes in Spodoptera litura, we constructed a cDNA library from S. litura injected with hydrogen peroxide (H(2)O(2)). Using a microarray chip composed of 2,964 cDNAs, we screened gene expression at 1, 3, 5, 7, and 9 h post H(2)O(2) injection. Data were clustered into 15 groups of genes that behave similarly across each time course. Seventy-three genes were identified as being at least twofold up- or downregulated after treatment with H(2)O(2) in S. litura. We constructed expressed sequence tags (ESTs) for genes that changed at least twofold after treatment with H(2)O(2) . The functional classification of these ESTs based on Gene Ontology showed that the ESTs are rich in genes involved in oxidoreductase activity (5.7%), defense (14.3%), cellular process (22.9%), and development (17.1%).     

Role of zinc in pulmonary endothelial cell response to oxidative stress

Although zinc is a well-known inhibitor of apoptosis, it may contribute to oxidative stress-induced necrosis. We noted that N,N,N',N'- tetrakis(2-pyridylmethyl)ethylenediamine (TPEN; >10 microM), a zinc chelator, quenched fluorescence of the zinc-specific fluorophore Zinquin and resulted in an increase in spontaneous apoptosis in cultured sheep pulmonary artery endothelial cells (SPAECs). Addition of exogenous zinc (in the presence of pyrithione, a zinc ionophore) to the medium of SPAECs caused an increase in Zinquin fluorescence and was associated with a concentration-dependent increase in necrotic cell death. Exposure of SPAECs to TPEN (10 microM) resulted in enhanced apoptosis after lipopolysaccharide or complete inhibition of t-butyl hydroperoxide (tBH)-induced necrosis. We further investigated the role of two zinc-dependent enzymes, poly(ADP-ribose) polymerase (PARP) and protein kinase (PK) C, in tBH toxicity. tBH toxicity was only affected by the PARP inhibitors 4-amino-1,8-naphthalimide or 3-aminobenzamide over a narrow range, whereas the PKC inhibitors bisindolylmaleimide and staurosporine significantly reduced tBH toxicity. tBH caused translocation of PKC to the plasma membrane of SPAECs that was partially inhibited by TPEN. Thus pulmonary endothelial cell zinc inhibits spontaneous and lipopolysaccharide-dependent apoptosis but contributes to tBH-induced necrosis, in part, via a PKC-dependent pathway.     

Mitochondrial permeability transition and oxidative stress

Mitochondrial permeability transition (MPT) is a non-selective inner membrane permeabilization that may precede necrotic and apoptotic cell death. Although this process has a specific inhibitor, cyclosporin A, little is known about the nature of the proteinaceous pore that results in MPT. Here, we review data indicating that MPT is not a consequence of the opening of a pre-formed pore, but the consequence of oxidative damage to pre-existing membrane proteins.     

Differential superoxide dismutase expression in ryegrass cultivars in response to short term aluminium stress

Background and aims

Saline soils limit plant production worldwide through osmotic stress, specific-ion toxicities, and nutritional imbalances.

Methods

The ability of Ca²⁺ and K⁺ to alleviate toxicities of Na⁺ and Mg²⁺ was examined using 89 treatments in short-term (48 h) solution culture studies for cowpea (Vigna unguiculata (L.) Walp.) roots. Root elongation was related to ionic activities at the outer surface of the root plasma membrane.

Results

The addition of K⁺ was found to alleviate the toxic effects of Na⁺, and supplemental Ca²⁺ improved growth further in these partially-alleviated solutions where K⁺ was present. Therefore, Na⁺ appears to interfere with K⁺ metabolism, and Ca²⁺ reduces this interference. Interestingly, the ability of Ca²⁺ to improve K-alleviation of Na⁺ toxicity is non-specific, with Mg²⁺ having a similar effect. In contrast, the addition of Ca²⁺ to Na-toxic solutions in the absence of K⁺ did not improve growth, suggesting that Ca²⁺ does not directly reduce Na⁺ toxicity in these short-term studies (for example, by reducing Na⁺ uptake) when supplied at non-deficient levels. Finally, K⁺ did not alleviate Mg²⁺ toxicity, suggesting that Mg²⁺ is toxic by a different mechanism to Na⁺.

Conclusions

Examination of how the toxic effects of salinity are alleviated provides clues as to the underlying mechanisms by which growth is reduced.     

TpMRK regulates cell division of Tetrahymena in response to oxidative stress

TpMRK was identified as a stress‐responsive mitogen activated protein kinase (MAPK)‐related kinase and has been shown to play a critical role in the stress signalling in Tetrahymena cells. Here, we found that the mRNA expression of TpMRK was correlated with cell division of Tetrahymena with decreased expression occurring in cells prior to entering synchronous cell division induced by heat treatment. Notably, cell division was delayed with a lower division index of 40% after exposure to hydrogen peroxide while 85% of cells underwent cell division synchronously at 75 min after heat treatment without the oxidative exposure. Furthermore, inactivation of TpMRK signalling by p38 MAPK inhibitor SB203580 or MEK inhibitor PD 98059 partially derepressed cell division induced by hydrogen peroxide. Our data suggest that oxidative stimuli might cause aberration of synchronous cell division of Tetrahymena through activating the TpMRK cascade. Copyright © 2009 John Wiley & Sons, Ltd.