Loss of thioredoxin function in retinas of mice overexpressing amyloid β

Amyloid β peptides (Aβ) have been implicated in the pathogenesis of age-related macular degeneration (ARMD) and glaucoma. In this study, retinas of mice overexpressing Aβ (Tg) were compared to those of wild-type mice (Wt) and analyzed for oxidative stress parameters. We observed a progressive decrease in all retinal cell layers, which was significantly greater in Tg mice at 14 months and culminated in loss of the outer retina at 18 months of age. We also observed higher levels of reactive oxygen species, glial fibrillary acidic protein, and hydroperoxide in Tg versus Wt mice (14 months). These effects were associated with phosphorylation/activation of the apoptosis signal kinase 1 and the p38 mitogen-activated kinase. Western blotting analysis revealed progressive increases in the levels of thioredoxin 1 and thioredoxin inhibitory protein in Tg compared to Wt mice. No changes were observed in the levels of thioredoxin reductase 1 (TrxR1); however, measurements of TrxR1 activity showed a 42.7±8% reduction in Tg mice versus Wt at 14 months of age. Our data suggest that Aβ-mediated retinal neurotoxicity involves impairment of the thioredoxin system and enhanced oxidative stress, potentially implicating this mechanism in the pathogenesis of ARMD and glaucoma.     

Regulation of HIF-1α activity by overexpression of thioredoxin is independent of thioredoxin reductase status

Berberine (BBR) is one of the major alkaloids and has been reported to have a variety of pharmacologic effects, including inhibition of cell cycle progression. Here, we investigated the mechanisms of BBR protection of neuronal cells from cell death induced by the Parkinson’s disease-related neurotoxin 6-hydroxydopamine (6-OHDA). Pretreatment of SH-SY5Y cells with BBR significantly reduced 6-OHDAinduced generation of reactive oxygen species (ROS), caspase-3 activation, and subsequent cell death. BBR also upregulated heme oxygenase-1 (HO-1) expression, which conferred protection against 6-OHDA-induced dopaminergic neuron injury and besides, effect of BBR on HO-1 was reversed by siRNA-Nrf2. Furthermore, BBR induced PI3K/Akt and p38 activation, which are involved in the induction of Nrf2 expression and neuroprotection. These results suggest that BBR may be useful as a therapeutic agent for the treatment of dopaminergic neuronal diseases.     

Induction of extracellular ATP mediates increase in intracellular thioredoxin in RAW264.7 cells exposed to low-dose γ-rays

We previously showed that low doses (0.25-0.5 Gy) of γ-rays elevated thioredoxin (Trx-1) in various organs of mice after whole-body irradiation. Also, it is reported that extracellular ATP, which is released in response to various stresses, regulates the expression of intracellular antioxidants through activation of P2 receptors. We have recently found that low-dose γ-rays induce ATP release from the exposed cells. However, it is not yet clear whether the radiation-induced extracellular ATP modulates the cellular redox balance. Here, we investigated whether γ-ray irradiation-induced release of extracellular ATP contributes to the induction of the cellular antioxidant Trx-1, using mouse macrophage-like RAW264.7 cells. Irradiation with γ-rays or exogenously added ATP increased the expression of Trx-1, and in both cases the increase was blocked by pretreatment with an ectonucleotidase, apyrase. Then, the involvement of ATP-dependent reactive oxygen species (ROS) generation in the increase in antioxidant capacity was examined. ATP stimulation promoted the generation of intracellular ROS and also increased Trx-1 expression. The increase in Trx-1 expression was significantly suppressed by pretreatment of the cells with antioxidants. In conclusion, the γ-ray irradiation-induced release of extracellular ATP may, at least in part, contribute to the production of ROS via purinergic signaling, leading to promotion of intracellular antioxidants as an adaptive response to an oxidative stress.     

Ascorbate peroxidase–thioredoxin interaction

Proteomics data have suggested ascorbate peroxidase (APX) to be a potential thioredoxin-interacting protein. Using recombinant enzymes, we observed that incubation of pea cytosolic APX with reduced poplar thioredoxins h drastically inactivated the peroxidase. A similar inactivation is induced by reduced glutathione and dithiothreitol, whereas diamide and oxidized glutathione have no effect. Oxygen consumption measurements, modifications of the APX visible spectrum and protection by hydrogen peroxide scavenging enzymes suggest that APX oxidizes thiols leading to the generation of thiyl radicals. These radicals can in turn react with thiyl anions to produce the disulfide radical anions, which are responsible for oxygen reduction and subsequent hydrogen peroxide production. The APX inactivation is not due solely to hydrogen peroxide since fluorimetry indicates that the environment of the APX tryptophan residues is dramatically modified only in the presence of thiol groups. The physiological implications of this interaction are discussed.     

Is human thioredoxin monomeric or dimeric?

We have examined the molecular weight and rotational correlation time of human thioredoxin by analytical ultracentrifugation and NMR spectroscopy, respectively. Two variants of human thioredoxin were studied, namely human thioredoxin identical in amino acid sequence to the one whose NMR structure we previously determined (C62A, C69A, C73A, M74T) and human thioredoxin (C62A, C69A, C73A, M74) containing the wild-type amino acid methionine at position 74. In both cases, the experimental data indicate that the predominant species is monomeric and we find no evidence for the existence of a well-defined dimeric form as was observed in the recently reported crystal structure (Weichsel et al., 1996) of human thioredoxin and the C73S mutant.     

Single cystathionine β-synthase domain-containing proteins modulate development by regulating the thioredoxin system in Arabidopsis

Plant thioredoxins (Trxs) participate in two redox systems found in different cellular compartments: the NADP-Trx system (NTS) in the cytosol and mitochondria and the ferredoxin-Trx system (FTS) in the chloroplast, where they function as redox regulators by regulating the activity of various target enzymes. The identities of the master regulators that maintain cellular homeostasis and modulate timed development through redox regulating systems have remained completely unknown. Here, we show that proteins consisting of a single cystathionine β-synthase (CBS) domain pair stabilize cellular redox homeostasis and modulate plant development via regulation of Trx systems by sensing changes in adenosine-containing ligands. We identified two CBS domain-containing proteins in Arabidopsis thaliana, CBSX1 and CBSX2, which are localized to the chloroplast, where they activate all four Trxs in the FTS. CBSX3 was found to regulate mitochondrial Trx members in the NTS. CBSX1 directly regulates Trxs and thereby controls H(2)O(2) levels and regulates lignin polymerization in the anther endothecium. It also affects plant growth by regulating photosynthesis-related [corrected] enzymes, such as malate dehydrogenase, via homeostatic regulation of Trxs. Based on our findings, we suggest that the CBSX proteins (or a CBS pair) are ubiquitous redox regulators that regulate Trxs in the FTS and NTS to modulate development and maintain homeostasis under conditions that are threatening to the cell.     

The importance of protein–protein interactions for optimising oxygen activity in photosystem II: reconstitution with a recombinant thioredoxin—manganese stabilising protein

In this paper we describe how photosystem II (PSII) from higher plants, which have been depleted, of the extrinsic proteins can be reconstituted with a chimeric fusion protein comprising thioredoxin from Escherichia coli and the manganese stabilising protein from Thermosynechococcus elongatus. Surprisingly, even though E. coli thioredoxin is completely unrelated to PSII, the fusion protein restores higher rates of activity upon rebinding to PSII than either the native spinach MSP, or T. elongatus MSP. PSII reconstituted with the fusion protein also has a lower requirement for calcium than PSII with the small extrinsic proteins removed, or PSII reconstituted with spinach or T. elongatus MSP. The MSP portion of the fusion protein is less thermally stable compared to isolated MSP from T. elongatus, which could be the key to its superior activation capability through greater flexibility. This work reveals the importance of protein–protein interactions in the water splitting activity of PSII and suggests that conformational configurations, which increase flexibility in MSP, are essential to its function, even when these are induced by an unrelated protein.     

Is thioredoxin the physiological vitamin K epoxide reducing agent?

E. coli thioredoxin plus thioredoxin reductase have previously been shown to replace dithiothreitol as the electron donor for mammalian liver microsomal vitamin K epoxide reduction in vitro. Such activity is dependent on detergent disruption of the microsomal membrane integrity. A previously characterized salicylate-inhibitable pathway for electron transfer from endogenous cytosolic reducing agents to the microsomal epoxide reducing warfarin-inhibitable enzyme is not inhibited by known alternate substrates and inhibitors of the thioredoxin system nor by antibodies against thioredoxin.     

Biotransformation of Digitoxin in Cell Cultures of Capsicum frutescens in the Presence of β-cyclodextrin

Cell suspension cultures of Capsicum frutescens accumulated digoxin, purpureaglycoside A and other unknown derivatives when digitoxin, a cardiac glycoside, was used as a precursor. The feeding of digitoxin complexed with &#103 -cyclodextrin increased the accumulation of digoxin, purpureaglycoside A and other unknown derivatives. Control cultures (without digitoxin) did not produce any of these metabolites. The growth of cells was affected by both digitoxin as well as digitoxin- &#103 -cyclodextrin. The accumulation of purpureaglycoside A and digoxin reached a maximum of 1241 and 374 &#119 g 100 ml &#109 1 culture on the 6th and 2nd day, respectively, which was 3.9 and 4.5 fold higher than cultures treated with digitoxin alone (sampled on the 13th day). The other unknown derivatives formed in digitoxin- &#103 -cyclodextrin fed cultures were 15 times higher than digitoxin alone fed C. frutescens cultures. The addition of glucose to digitoxin- &#103 -cyclodextrin treated cultures increased the accumulation of purpureaglycoside A which reached a maximum of 3589 &#119 g 100 ml &#109 1 culture after 12 h incubation, which was a 2.9 fold increase over cultures treated with digitoxin- &#103 -cyclodextrin alone.     

Evolutionary Advantages of Participation of Vasopressin instead of Vasotocin in Regulation of Water–Salt Balance in Mammals

In experiments on non-anesthetized Wistar white rats there was studied reaction of kidney to an intramuscular injection of arginine vasotocin or arginine vasopressin at doses from 0.001 to 0.05 µg/100 g body mass on the background of a water load. Water (5 ml/100 g body mass) was administered through a catheter into stomach to suppress secretion of endogenous antidiuretic hormone (ADH). In experiments with water administration, diuresis increased due to a decrease of osmotic permeability of renal tubules and to excretion of osmotically free water, with the constant clearance of sodium ions. Injection of 0.05 µg arginine vasopressin led to a marked decrease of diuresis due to a rise of reabsorption of osmotically free water without elevation of excretion of osmotically active substances. Injection of the same dose of arginine vasotocin resulted in no increase of diuresis; however, reabsorption of osmotically free water and excretion of osmotically active substances including sodium ions were more pronounced. Hence, both vasotocin and vasopressin increased osmotic permeability of the tubular epithelium, but vasotocin, unlike vasopressin, promoted reduction of reabsorption of sodium ions and their loss with urine. A suggestion is made that one of the reasons for replacement in mammals of the molecular ADH forms (vasotocin by vasopressin) was the absence of the pronounced natriuretic effect in arginine vasopressin. This was of crucial significance to preserve sodium ions in the organism, to maintain water–salt balance in animals adapted to the terrestrial life, and to provide not only osmo-, but also volumoregulation.     

Alteration in virulence characteristics of biofilm cells of Pseudomonas aeruginosa in presence of Tamm-Horsfall protein

Summary Tamm-Horsfall glycoprotein is the most abundant protein in human urine. The present investigation was planned to study the effect of Tamm-Horsfall protein (THP) on elaboration of virulence factors by biofilm cells of Pseudomonas aeruginosa. It was observed that with increase in concentration of THP from 10 to 50 μg/ml there was significant enhancement in elaboration of all the virulence factors by biofilm cells of P. aeruginosa. However, with further increase in concentration of THP from 50 to 70 μg/ml, significant decrease in elaboration of all the virulence traits was observed. Implications of these findings in relation to urinary tract infections caused by P. aeruginosa have been discussed.     

Glycosylation ofα 1 glycoprotein in septic shock: Changes in degree of branching and in expression of sialyl Lewisx groups

The occurrence of differences in acute-phase response, with respect to concentration and glycosylation of ₁-acid glycoprotein (AGP) was studied in the sera of patients surviving or not from septic shock. Crossed affino-immunoelectrophoresis was used with concanavalin A andAleuria aurantia lectin for the detection of the degree of branching and fucosylation, respectively, and the monoclonal CSLEX-1 for the detection of sialyl Lewis^x (SLeX) groups on AGP. Septic shock apparently induced an acute-phase response as indicated by the increased serum levels and changed glycosylation of AGP. In the survivor group a transient increase in diantennary glycan content was accompanied by a gradually increasing fucosylation and SLeX expression, comparable to those observed in the early phase of an acute-inflammatory response. Remarkably, in the non-survivor group a modest increase in diantennary glycan content was accompanied by a strong elevation of the fucosylation of AGP and the expression of SLeX groups on AGP, typical for the late phase of an acute-phase response. Our results suggest that these changes in glycosylation of AGP can have a prognostic value for the outcome of septic shock.Abbreviations AAL Aleuria aurantia lectin - AGP ₁-acid glycoprotein - CAIE crossed affinoimmunoelectrophoresis - Con A Concanavalin A - HSPC human serum protein calibrator - IL-1 interleukin 1 - IL-6 interleukin 6 - LIF leukaemia inhibitory factor - LPS lipopolysaccharide - SLeX sialyl Lewis^x - TNF tumour necrosis factor     

Conservation of Orchids in China

China, as one of the most important Range States of orchids in the world, has about 1300 species withabundant varieties of orchids. However, owing to over, abuse harvest and illegal trades, the wild populations ofthese species have declined dramatically, even bringing some species to the edge of extinction. In response to such challenges, the Chinese government has put conservation of orchids as a priority agenda, taking a series of Innovative and effective measures to protect the orchids in the wild.[第一段]