Redox Components Research Articles

Radiation-Induced Senescence Reprograms Secretory and Metabolic Pathways in Colon Cancer HCT-116 Cells.

Understanding the global metabolic changes during the senescence of tumor cells can have implications for developing effective anti-cancer treatment strategies. Ionizing radiation (IR) was used to induce senescence in a human colon cancer cell line HCT-116 to examine secretome and metabolome profiles. Control proliferating and senescent cancer cells (SCC) exhibited distinct morphological differences and expression of senescent markers. Enhanced secretion of pro-inflammatory chemokines and IL-1, anti-inflammatory IL-27, and TGF-β1 was observed in SCC. Significantly reduced levels of VEGF-A indicated anti-angiogenic activities of SCC. Elevated levels of tissue inhibitors of matrix metalloproteinases from SCC support the maintenance of the extracellular matrix. Adenylate and guanylate energy charge levels and redox components NAD and NADP and glutathione were maintained at near optimal levels indicating the viability of SCC. Significant accumulation of pyruvate, lactate, and suppression of the TCA cycle in SCC indicated aerobic glycolysis as the predominant energy source for SCC. Levels of several key amino acids decreased significantly, suggesting augmented utilization for protein synthesis and for use as intermediates for energy metabolism in SCC. These observations may provide a better understanding of cellular senescence basic mechanisms in tumor tissues and provide opportunities to improve cancer treatment.

Highly Flexible and Tailorable Cobalt-Doped Cross-Linked Polyacrylamide-Based Electrolytes for Use in High-Performance Supercapacitors.

A novel hydrogel polymer electrolyte was prepared by incorporation of 1,4-butanediol diglycidyl ether (BG) to cross-linked polyacrylamide (PAM). The electrolyte (PAMBG) was modified with cobalt (II) sulfate with various doping ratios (PAMBGCoX) to increase the capacitance by increasing faradaic reactions. The supercapacitor device assembly was performed by using active carbon (AC) electrodes and hydrogel polymer electrolytes. The specific capacitance of the PAMBGCo5 device indicated 130 F g-1 , which is at least a seven-fold improvement due to the insertion of Co as a redox component. The electrolyte device, PAMBGCo5, displays superior performance having an energy density of 38 Wh kg-1 at a power density of 500 W kg-1 . Additionally, with the same hydrogel, the device performed 10,000 galvanostatic charge-discharge cycles via retaining 91% of the initial capacitance. A cost-effective electrolyte, PAMBGCo5, was tested in a carbon-based supercapacitor under bent and twisted conditions at various angles, confirming the robustness of the device.

Revealing the effect of paired redox-acid sites on metal oxide catalysts for efficient NOx removal by NH3-SCR

Understanding the nature of active sites on metal oxide catalysts in the selective catalytic reduction (SCR) of NO by NH3 (NH3-SCR) is a crucial prerequisite for the development of novel efficient NH3-SCR catalysts. In this work, two CeO2-based SCR catalyst systems with diverse acidic metal oxides-CeO2 interfaces, i.e., Nb2O5-CeO2 (Nb2O5/CeO2 and CeO2/Nb2O5) and WO3-CeO2 (WO3/CeO2 and CeO2/WO3), were prepared and used to reveal the relationship between NH3-SCR activity and surface acidity/redox properties. In combination with the results of the NH3-SCR activity test and various characterizations, it was found that the NH3-SCR performance of Nb2O5-CeO2 and WO3-CeO2 catalysts was highly dependent on the strong interactions between the redox component (CeO2) and acidic component (Nb2O5 or WO3), as well as the amount of paired redox-acid sites. From a quantitative perspective, an activity-surface acidity/redox property relationship was proposed. For both Nb2O5-CeO2 and WO3-CeO2 catalysts systems operated at the more concerned low-temperature range (200 °C), the NH3-SCR activity in low NOx conversion region (< 40%) was mainly dominated by the surface acidity of catalysts, while the NH3-SCR activity in high NOx conversion region (> 40%) was more determined by redox properties.

Vitamin E beyond Its Antioxidant Label.

Vitamin E, comprising tocopherols and tocotrienols, is mainly known as an antioxidant. The aim of this review is to summarize the molecular mechanisms and signaling pathways linked to inflammation and malignancy modulated by its vitamers. Preclinical reports highlighted a myriad of cellular effects like modulating the synthesis of pro-inflammatory molecules and oxidative stress response, inhibiting the NF-κB pathway, regulating cell cycle, and apoptosis. Furthermore, animal-based models have shown that these molecules affect the activity of various enzymes and signaling pathways, such as MAPK, PI3K/Akt/mTOR, JAK/STAT, and NF-κB, acting as the underlying mechanisms of their reported anti-inflammatory, neuroprotective, and anti-cancer effects. In clinical settings, not all of these were proven, with reports varying considerably. Nonetheless, vitamin E was shown to improve redox and inflammatory status in healthy, diabetic, and metabolic syndrome subjects. The anti-cancer effects were inconsistent, with both pro- and anti-malignant being reported. Regarding its neuroprotective properties, several studies have shown protective effects suggesting vitamin E as a potential prevention and therapeutic (as adjuvant) tool. However, source and dosage greatly influence the observed effects, with bioavailability seemingly a key factor in obtaining the preferred outcome. We conclude that this group of molecules presents exciting potential for the prevention and treatment of diseases with an inflammatory, redox, or malignant component.

Direct Utilization of Photoinduced Charge Carriers to Promote Electrochemical Energy Storage.

Electrochemical energy storage has been regarded as one of the most promising strategies for next-generation energy consumption. To meet the increasing demands of urban electric vehicles, development of green and efficient charging technologies by exploitation of solar energy should be considered for outdoor charging in the future. Herein, a light-sensitive material (copper foam-supported copper oxide/nickel copper oxides nanosheets arrays, namely CF@CuOx @NiCuOx NAs) with hierarchical nanostructures to promote electrochemical charge storage is specifically fabricated. The as-fabricated NAs have demonstrated a high areal specific capacity of 1.452C cm-2 under light irradiation with a light power of 1.76 W, which is 44.8% higher than the capacity obtained without light. Such areal specific capacity (1.452 C cm-2 ) is much higher than that of the conventional supercapacitor structure using a similar active redox component reported recently (NiO nanosheets array@Co3 O4 -NiO FTNs: maximum areal capacity of 623.5 mF cm-2 at 2 mA cm-2 ). This photo-enhancement for charge storage can be attributed to the combination of photo-sensitive Cu2 O and pseudo-active NiO components. Hence, this work may provide new possibilities for direct utilization of sustainable solar energy to realize enhanced capability for energy storage devices.

Thermochemical hydrogen production using Rh/CeO2/γ-Al2O3 catalyst by steam reforming of ethanol and water splitting in a packed bed reactor

This study is focused on investigating the dual performance of Rh/CeO2/γ-Al2O3 catalyst for steam reforming of ethanol (SRE) and thermochemical water splitting (TCWS) using a packed bed reactor. The catalyst is designed to be thermally stable containing an active phase of Rh and the redox component of CeO2 for oxygen exchange, supported on γ-Al2O3. The catalyst has been characterised by SEM, XRD, BET, TPR, TPD, XPS and TGA before testing in the reactor. The optimal temperature for SRE reaction over this catalyst is between 700 °C and 800 °C to produce high concentrations of hydrogen (~60%), and low CO and CH4. The selectivity towards CO and CH4 is higher at low temperatures and drops with rise in reaction temperature. Further, Rh/CeO2/γ-Al2O3 is found to be active for TCWS at relatively low temperatures (≤1200 °C). At temperatures as low as 800 °C, this catalyst is especially found suitable for multiple redox cycles, producing a total of 48.9 mmol/gcat in four redox cycles. The catalyst can be employed for large number of redox cycles when the reactor is operated at lower temperatures. Finally, the reaction pathways have been proposed for both SRE and TCWS on Rh/CeO2/γ-Al2O3 catalyst.

Proteome of Stored RBC Membrane and Vesicles from Heterozygous Beta Thalassemia Donors.

Genetic characteristics of blood donors may impact the storability of blood products. Despite higher basal stress, red blood cells (RBCs) from eligible donors that are heterozygous for beta-thalassemia traits (βThal+) possess a differential nitrogen-related metabolism, and cope better with storage stress compared to the control. Nevertheless, not much is known about how storage impacts the proteome of membrane and extracellular vesicles (EVs) in βThal+. For this purpose, RBC units from twelve βThal+ donors were studied through proteomics, immunoblotting, electron microscopy, and functional ELISA assays, versus units from sex- and aged-matched controls. βThal+ RBCs exhibited less irreversible shape modifications. Their membrane proteome was characterized by different levels of structural, lipid raft, transport, chaperoning, redox, and enzyme components. The most prominent findings include the upregulation of myosin proteoforms, arginase-1, heat shock proteins, and protein kinases, but the downregulation of nitrogen-related transporters. The unique membrane proteome was also mirrored, in part, to that of βThal+ EVs. Network analysis revealed interesting connections of membrane vesiculation with storage and stress hemolysis, along with proteome control modulators of the RBC membrane. Our findings, which are in line with the mild but consistent oxidative stress these cells experience in vivo, provide insight into the physiology and aging of stored βThal+ RBCs.

From Global to Local-New Insights into Features of Pyrethroid Detoxification in Vector Mosquitoes.

Simple SummaryInsecticides are used to reduce the nuisance of biting insects, and, importantly, also to reduce the spread of insect-borne diseases. Over the years, mosquitoes have developed resistance to these insecticides. The most commonly used class of insecticides are the pyrethroids, synthetic versions of plant-derived compounds; they are less toxic to mammals and other animals than some other classes. One problem with all insecticides, though, is the development of resistance by the insect groups they are applied to combat. This review describes new insights into the ways in which mosquitoes have evolved resistance to pyrethroids. For example, before pyrethroids bind to their targets on motoneurons to paralyze mosquitoes, they must first pass through the outer exoskeleton to inner tissues. Resistant mosquitoes have evolved the ability to break down pyrethroids into nontoxic products that are then excreted. This metabolism prevents toxic buildup of the insecticide, which would otherwise be lethal to the mosquitoes. Scientists have identified a variety of changes to mosquito genes that are responsible for insecticide degradation and excretion. In this review, we outline the genes and pathways involved in the breakdown of pyrethroids and the key gene categories that are involved.The threat of mosquito-borne diseases continues to be a problem for public health in subtropical and tropical regions of the world; in response, there has been increased use of adulticidal insecticides, such as pyrethroids, in human habitation areas over the last thirty years. As a result, the prevalence of pyrethroid-resistant genetic markers in natural mosquito populations has increased at an alarming rate. This review details recent advances in the understanding of specific mechanisms associated with pyrethroid resistance, with emphasis on features of insecticide detoxification and the interdependence of multiple cellular pathways. Together, these advances add important context to the understanding of the processes that are selected in resistant mosquitoes. Specifically, before pyrethroids bind to their targets on motoneurons, they must first permeate the outer cuticle and diffuse to inner tissues. Resistant mosquitoes have evolved detoxification mechanisms that rely on cytochrome P450s (CYP), esterases, carboxyesterases, and other oxidation/reduction (redox) components to effectively detoxify pyrethroids to nontoxic breakdown products that are then excreted. Enhanced resistance mechanisms have evolved to include alteration of gene copy number, transcriptional and post-transcriptional regulation of gene expression, as well as changes to cellular signaling mechanisms. Here, we outline the variety of ways in which detoxification has been selected in various mosquito populations, as well as key gene categories involved. Pathways associated with potential new genes of interest are proposed. Consideration of multiple cellular pathways could provide opportunities for development of new insecticides.

Where do the electrons go? How numerous redox processes drive phytochemical diversity

Plants produce structurally and functionally diverse metabolites that are key to many physiological processes such as growth and development, reproduction, defense, and stress responses. Underlying this chemical diversity are numerous enzyme-catalyzed (oxidoreductase) reactions that transfer electrons between molecular species altering their respective oxidation states. Many of these oxidoreductases require redox-active components such as redox-associated electron carriers and/or redox-active metals. Furthermore, many oxidoreductases contain amino acids that are susceptible to redox-driven post-translational modifications. These redox reactions and redox-active components are widely distributed throughout primary and specialized (secondary) metabolism using electrons derived from photosynthesis, respiration, and acquired nutrients. This review illustrates the criticality of collectively analyzing the redox state of plants including the phytochemical reactions that rely on redox components, the redox state of oxidoreductases, and the balance of oxidants and antioxidants. This redox-focused perspective is essential to understanding how plants harness the power of electrons to drive phytochemical diversity for essential functions in dynamic environments. Furthermore, the increasing likelihood of adverse environmental conditions on future plant systems will inevitably alter the production and distribution of electrons resulting in escalating levels of oxidative damage. Therefore, additional protection strategies, likely involving metabolic engineering, will need to be developed to maintain a favorable redox state for plant health and the phytochemical products required for life.

Assessment of Antioxidant and Antimicrobial Activities of Silver Nanoparticles Biosynthesized by Haplophyllum Obtusifolium

Background: Plants comprise great antioxidant sources as a result of their redox and biochemical components, which are rich in secondary metabolites such as phenolic acids, flavonoids, and other constituents. Haplophyllum obtusifolium from polygonaceae is widely used for preventing and managing diabetes. This study investigated the antibacterial and antioxidant activities of silver nanoparticles (AgNPs) biosynthesized by H. obtusifolium. Methods: The aerial parts of H. obtusifolium were gathered from the north of Khorasan Razavi province, Iran and desiccated at the chamber temperature. The shoots were powdered by grinding, 5 g of the powder was mixed with 250 mL of deionized water, and the resultant blend was then filtered. Bactericidal properties and antioxidant activity of the nanoparticles were assessed using disk diffusion and DPPH (2, 2-diphenyl-1-picrylhydrazyl) tests, respectively. Results: The results of this study showed that the biosynthesized nanoparticles exhibited antibacterial activity against a gram-negative (Klebsiella pneumoniae) bacterium, but they had no effects on gram-positive Staphylococcus epidermidis. Antioxidant test results showed that these nanoparticles were capable of eliminating DPPH radicals in a concentration-dependent manner so that a more potent antioxidant activity was seen in higher concentrations of the nanoparticles. Conclusion: Our results suggested that H. obtusifolium can be used as a key source of antioxidants/ antimicrobial agents in food and pharmaceutical industries.

Highly sensitive interfaces of graphene electrical-electrochemical vertical devices for on drop atto-molar DNA detection

The development of novel high-sensitivity DNA-based biosensors is beneficial, as these devices have applications in the identification of genetic risk factors, medical diagnostics, and environmental monitoring. Herein, we report on the first robust device capable of detecting DNA on a microliter drop with a zepto-molar (10−21) concentration. To accomplish this, we engineered an electrical-electrochemical vertical device (EEVD) that comprises a novel drain and source terminal in a short-circuited configuration, paired with an ideal non-polarizable reference electrode. Vertical electron transfer occurs perpendicularly to the graphene plane, while the electronic current flows through the graphene van der Waals (vdW) heterojunctions. Ferrocene adsorbed on graphene was strategically chosen as the vdW heterojunction redox component. Charge carrier insertion into the graphene makes the EEVD 10 times more sensitive than traditional graphene field-effect transistors. Interfacial potential changes were measured for single-stranded DNA detection with an unprecedented zepto-molar limit of detection.

(Invited) Demystifying the Electrode/Electrolyte Interface in Carbon-Based Electrochemical Capacitors with Specs Technique and Electrochemical Dilatometry

It is often said that the highly developed surface area of electrode materials ensures high capacitance, power and energy in electrochemical capacitors. However, the real ‘efficiency’ of the surface exploited in charge storage remains unknown. Recently, it turned out that the Step Potential Electrochemical Spectroscopy (SPECS) technique can be a useful tool for determining it.The SPECS technique allows for the comprehensive analysis of the total current output and evaluation of the capacitive, redox and other components. Together with the physicochemical data from nitrogen and CO2 adsorption techniques, we aim at the determination of the real electrode/electrolyte interface surface.Based on the knowledge gained to date, we assume that the efficiency of the interface ‘exploitation’ depends on many factors: pore size distribution, wettability of the electrode material by electrolyte, as well as the size of the ions. Thus, inappropriate selection of one of these parameters can aggravate the device performance, even if the excellent carbon material is applied as electrode component.The paper will provide the results from SPECS correlated with the physicochemical properties of carbon materials. It appears that the electrochemically accessible surface does not exceed 30% of the values estimated by N2 or CO2adsorption. The results will be supported by the recent findings from electrochemical dilatometry experiments.

(Invited) New Brands of High Energy Electrochemical Capacitors with Hybridized Carbon Electrodes

The main disadvantages of electrical double-layer capacitors – EDLCs, are the relatively low amount of energy stored and the high cost of the devices. For new applications, as powering of e.g., electric vehicles, the concept of hybrid capacitor (HC) appears as a promising approach enabling to enhance the energy output. HCs behave as EDLC (e.g., linear galvanostatic charge/discharge, rectangular cyclic voltammogram, low time constant), while combining capacitive and battery-like electrodes. Since the battery-type electrode operates in a narrow potential range, the potential excursion of the EDL electrode is almost twice larger than in a symmetric EDLC, leading to approximately doubling of the discharge capacitance [1]. Hence, for the same voltage range, the specific energy of the HC is twice higher than for an EDLC. In the last decade, HCs using a redox active electrolyte such as the iodine/iodide system [2] and lithium-ion capacitors (LIC) [3] have emerged as very promising technologies, essentially owing to the fact that carbon electrodes are highly conductive and relatively inexpensive.LICs implement a lithiated graphite negative electrode operating ca 100 mV above the lithium deposition potential and an activated carbon positive electrode using a wide potential range, allowing the charge storage capacity to be approximately doubled, while the maximum cell voltage can reach 4 V. Hence, the specific energy of a LIC is around 4 to 5 times higher than in an EDLC using the same AC at comparable specific power. However, as it is mandatory to pre-intercalate lithium in the negative graphite electrode before operating a LIC, it has been proposed to include an auxiliary metallic lithium electrode [4], what complicates the cell construction, while excess lithium might cause also safety issues. Therefore, we have recently implemented a new strategy based on a sacrificial lithiated material (for example 3,4-dihydroxybenzonitrile dilithium salt – Li2DHBN [5]) added in the positive AC electrode, and from which lithium is irreversibly extracted and intercalated in the graphite anode. In case of Li2DHBN, we have demonstrated that the DOBN oxidized derivative is soluble in the electrolyte, leaving only AC at the positive electrode after lithium extraction. At 1 kW kg-1, the specific energy of the LIC reaches 50 Wh kg-1 against only 12 Wh kg-1 for the EDLC built with the same AC. We will show that this concept can be extended to high performance and low cost sodium-ion capacitors [6].For AC-based hybrid capacitors realized by the implementation of redox active electrolytes, aqueous solutions of iodides have lately prevailed over others, owing to well-separated EDL and battery-like charging mechanisms [1]. However, as the voltage of AC/AC cells with alkali iodides is limited to only 0.8-1.2 V [2], we have proposed to use bi-functional aqueous electrolytes including the redox component (e.g., KI) and a supporting neutral electrolyte (e.g., Li2SO4), enabling to extend the potential range of the negative electrode. The capacitance of the HC is doubled as compared to a typical EDLC, whereas the voltage can reach 1.5 – 1.6 V [7]. Recently, an AC/AC cell based on a mixture of choline iodide and choline nitrate demonstrated the same energy and power performance as a commercial EDLC using an organic electrolyte, while being able to perform down to -40°C [8].Acknowledgements: The Foundation for Polish Science is acknowledged for financially supporting the HYCAP project (research grant TEAM TECH/2016-3/17).References B. Gorska, E. Frackowiak, F. Beguin, Curr. Opin. Electrochem. 9 (2018) 95.G Lota, E. Frackowiak , Electrochem. Comm. 11 (2009) 87.T. Aida, K. Yamada, M. Morita, Electrochem. Solid State Lett. 9 (2006) A534.T. Aida, I. Murayama, K. Yamada, M. Morita, Electrochem. Solid State Lett. 10 (2007) A93.P. Jezowski, O. Crosnier, E. Deunf, P. Poizot, F. Beguin, T. Brousse, Nat. Mater. 17 (2018) 167.X. Pan, A. Chojnacka, P. Jezowski, F. Beguin, Electrochim. Acta 318 (2019) 471.Q. Abbas, P. Babuchowska, E. Frackowiak, F. Beguin, J. Power Sources 326 (2016) 652.P. Przygocki, Q. Abbas, B. Gorska, F. Beguin, J. Power Sources 427 (2019) 283.

Regulation of redox processes in biological systems with the participation of the Keap1/Nrf2/ARE signaling pathway, biogenic selenium nanoparticles as Nrf2 activators

The article is devoted to the mechanisms of regulation of redox processes in cells, a review of the Keap1 / Nrf2 / ARE redox-sensitive signaling system as a fundamental pathway that plays a key role in maintaining cellular redox homeostasis under stressful, inflammatory, carcinogenic and proapoptotic conditions. The structure of the cysteine-rich repressor protein Keap1, which is responsible for sensory perception of electrophiles and reactive oxygen species, the structure and functions of the transcription factor Nrf2, mechanisms of Nrf2 activation through the Keap1 / Nrf2 / ARE signaling system, which regulates the transcription and expression of cellular cytoprotective and antioxidant proteins, are described. Published data on the specificity of the interaction of the components of this cellular signaling pathway, the mechanisms of Keap1 dependent and independent adaptive response to the action of inductors, the role of biogenic selenium nanoparticles synthesized by green chemistry with the participation of bacteria in these processes are analyzed; features of Nrf2 induction depending on the type of bacteria and the stabilizing shell. It has been shown that biogenic selenium nanoparticles (BNSe), synthesized by different types of bacteria, activate the transcription factor Nrf2 using the Keap1-independent activation pathway through mitogen-protein kinases (MAPK): p38, ERK1 / 2 and AKT-mediated phosphorylation of Nrf2, protect the intestinal epithelial barrier function from the effects of oxidative damage, normalize mitochondrial function. A detailed understanding of thiol-dependent and independent redox signaling mechanisms under physiological and pathological conditions will lead to a deeper understanding of the redox component in human and animal diseases. The use of biogenic nanoselen, synthesized with the participation of various bacterial species, has been demonstrated to activate the Keap1 / Nrf2 / ARE signaling pathway, which may be of practical interest as a therapeutic target for many redox-mediated diseases.

Anti-Melanoma Activities of Artemisone and Prenylated Amino-Artemisinins in Combination With Known Anticancer Drugs.

The most frequently occurring cancers are those of the skin, with melanoma being the leading cause of death due to skin cancer. Breakthroughs in chemotherapy have been achieved in certain cases, though only marginal advances have been made in treatment of metastatic melanoma. Strategies aimed at inducing redox dysregulation by use of reactive oxygen species (ROS) inducers present a promising approach to cancer chemotherapy. Here we use a rational combination of an oxidant drug combined with a redox or pro-oxidant drug to optimize the cytotoxic effect. Thus we demonstrate for the first time enhanced activity of the amino-artemisinin artemisone and novel prenylated piperazine derivatives derived from dihydroartemisinin as the oxidant component, and elesclomol-Cu(II) as the redox component, against human malignant melanoma cells A375 in vitro. The combinations caused a dose dependent decrease in cell numbers and increase in apoptosis. The results indicate that oxidant-redox drug combinations have considerable potential and warrant further investigation.

Flavone as a novel matrix for the matrix-assisted laser desorption/ionisation analysis of lanthanide and transition metal salts.

The mass spectral analysis of metal salts, especially lanthanide and transition metal salts, can be challenging. Although getting information on the metal present is usually straightforward, obtaining information on the correct oxidation state and anion composition is challenging. Many ionisation techniques have some redox component to the ionisation process, which commonly results in changing the oxidation state of the metal and the associated loss of ligand and anion information. We present here a simple method for negative ion matrix-assisted laser desorption/ionisation mass spectrometry using the non-acidic flavonoid flavone as a novel matrix. This results in reliable information on the oxidation state of the metal as spectra are dominated by anion adduct ions with very little (typically no) redox processes occurring.

Carnitine metabolism in the human gut: characterization of the two-component carnitine monooxygenase CntAB from Acinetobacter baumannii

Bacterial formation of trimethylamine (TMA) from carnitine in the gut microbiome has been linked to cardiovascular disease. During this process, the two-component carnitine monooxygenase (CntAB) catalyzes the oxygen-dependent cleavage of carnitine to TMA and malic semialdehyde. Individual redox states of the reductase CntB and the catalytic component CntA were investigated based on mutagenesis and electron paramagnetic resonance (EPR) spectroscopic approaches. Protein ligands of the flavin mononucleotide (FMN) and the plant-type [2Fe-2S] cluster of CntB and also of the Rieske-type [2Fe-2S] cluster and the mononuclear [Fe] center of CntA were identified. EPR spectroscopy of variant CntA proteins suggested a hierarchical metallocenter maturation, Rieske [2Fe-2S] followed by the mononuclear [Fe] center. NADH-dependent electron transfer via the redox components of CntB and within the trimeric CntA complex for the activation of molecular oxygen was investigated. EPR experiments indicated that the two electrons from NADH were allocated to the plant-type [2Fe-2S] cluster and to FMN in the form of a flavin semiquinone radical. Single-turnover experiments of this reduced CntB species indicated the translocation of the first electron onto the [Fe] center and the second electron onto the Rieske-type [2Fe-2S] cluster of CntA to finally allow for oxygen activation as a basis for carnitine cleavage. EPR spectroscopic investigation of CntA variants indicated an unusual intermolecular electron transfer between the subunits of the CntA trimer via the "bridging" residue Glu-205. On the basis of these data, a redox catalytic cycle for carnitine monooxygenase was proposed.

On the functionality of a methionine sulfoxide reductase B from Trypanosoma cruzi

BackgroundMethionine is an amino acid susceptible to be oxidized to give a racemic mixture of R and S forms of methionine sulfoxide (MetSO). This posttranslational modification has been reported to occur in vivo under either normal or stress conditions. The reduction of MetSO to methionine is catalyzed by methionine sulfoxide reductases (MSRs), thiol-dependent enzymes present in almost all organisms. These enzymes can reduce specifically one or another of the isomers of MetSO (free and protein-bound). This redox modification could change the structure and function of many proteins, either concerned in redox or other metabolic pathways. The study of antioxidant systems in Trypanosoma cruzi has been mainly focused on the involvement of trypanothione, a specific redox component for these organisms. Though, little information is available concerning mechanisms for repairing oxidized methionine residues in proteins, which would be relevant for the survival of these pathogens in the different stages of their life cycle. MethodsWe report an in vitro functional and in vivo cellular characterization of methionine sulfoxide reductase B (MSRB, specific for protein-bound MetSO R-enantiomer) from T. cruzi strain Dm28c. ResultsMSRB exhibited both cytosolic and mitochondrial localization in epimastigote cells. From assays involving parasites overexpressing MSRB, we observed the contribution of this protein to increase the general resistance against oxidative damage, the infectivity of trypomastigote cells, and intracellular replication of the amastigote stage. Also, we report that epimastigotes overexpressing MSRB exhibit inhibition of the metacyclogenesis process; this suggesting the involvement of the proteins as negative modulators in this cellular differentiation. Conclusions and general significanceThis report contributes to novel insights concerning redox metabolism in T. cruzi. Results herein presented support the importance of enzymatic steps involved in the metabolism of L-Met and in repairing oxidized macromolecules in this parasite.

Thallium Toxicity in Caenorhabditis elegans: Involvement of the SKN-1 Pathway and Protection by S-Allylcysteine.

Monovalent thallium (Tl+) is a cation that can exert complex neurotoxic patterns in the brain by mechanisms that have yet to be completely characterized. To learn more about Tl+ toxicity, it is necessary to investigate its major effects in vivo and its ability to trigger specific signaling pathways (such as the antioxidant SKN-1 pathway) in different biological models. Caenorhabditis elegans (C. elegans) is a nematode constituting a simple in vivo biological model with a well-characterized nervous system, and high genetic homology to mammalian systems. In this study, both wild-type (N2) and skn-1 knockout (KO) mutant C. elegans strains subjected to acute and chronic exposures to Tl+ [2.5-35μM] were evaluated for physiological stress (survival, longevity, and worm size), motor alterations (body bends), and biochemical changes (glutathione S-transferase regulation in a gst-4 fluorescence strain). While survival was affected by Tl+ in N2 and skn-1 KO (worms lacking the orthologue of mammalian Nrf2) strains in a similar manner, the longevity was more prominently decreased in the skn-1 KO strain compared with the wild-type strain. Moreover, chronic exposure led to a greater compromise in the longevity in both strains compared with acute exposure. Tl+ also induced motor alterations in both skn-1 KO and wild-type strains, as well as changes in worm size in wild-type worms. In addition, preconditioning nematodes with the well-known antioxidant S-allylcysteine (SAC) reversed the Tl+-induced decrease in survival in the N2 strain. GST fluorescent expression was also decreased by the metal in the nematode, and recovered by SAC. Our results describe and validate, for the first time, features of the toxic pattern induced by Tl+ in an in vivo biological model established with C. elegans, supporting an altered redox component in Tl+ toxicity, as previously described in mammal models. We demonstrate that the presence of the orthologous SKN-1 pathway is required for worms in evoking an efficient antioxidant defense. Therefore, the nematode represents an optimal model to reproduce mammalian Tl+ toxicity, where toxic mechanisms and novel therapeutic approaches of clinical value may be successfully pursued.

Characterization of Glutamate-Mediated Hormonal Regulatory Pathway of the Drought Responses in Relation to Proline Metabolism in Brassica napus L.

Proline metabolism influences the metabolic and/or signaling pathway in regulating plant stress responses. This study aimed to characterize the physiological significance of glutamate (Glu)-mediated proline metabolism in the drought stress responses, focusing on the hormonal regulatory pathway. The responses of cytosolic Ca2+ signaling, proline metabolism, and redox components to the exogenous application of Glu in well-watered or drought-stressed plants were interpreted in relation to endogenous hormone status and their signaling genes. Drought-enhanced level of abscisic acid (ABA) was concomitant with the accumulation of ROS and proline, as well as loss of reducing potential, which was assessed by measuring NAD(P)H/NAD(P)+ and GSH/GSSG ratios. Glu application to drought-stressed plants increased both salicylic acid (SA) and cytosolic Ca2+ levels, with the highest expression of calcium-dependent protein kinase (CPK5) and salicylic acid synthesis-related ICS1. The SA-enhanced CPK5 expression was closely associated with further enhancement of proline synthesis-related genes (P5CS1, P5CS2, and P5CR) expression and a reset of reducing potential with enhanced expression of redox regulating genes (TRXh5 and GRXC9) in a SA-mediated NPR1- and/or PR1-dependent manner. These results clearly indicate that Glu-activated interplay between SA- and CPK5-signaling as well as Glu-enhanced proline synthesis are crucial in the amelioration of drought stress in Brassica napus.