Inhibition Of O2 Research Articles

Coating seeds with purified-hydrocolloids extracted from conventional activated sludge affects the growth physiology of wheat under gradient salt stress

With continuous innovations in wastewater treatment technology, the use of excess sludge has become a research focus. Purified-hydrocolloids obtained from aerobic granular sludge (AGS) and conventional activated sludge (CAS) have many practical applications, including waterproofing, adsorption, flame retardance, slow-release properties, and seed coating. In this study, purified-hydrocolloids extracted from CAS was used as a new seed coating, which was uniformly sprayed onto the surface of wheat seeds. Purified-hydrocolloids was most effective in resisting salt stress in wheat seedlings at a NaCl concentration of 125 mmol/L (soil salinity 2.74 g/Kg). The germination percentage, plant height, K+/Na+ ratio, soluble sugar and soluble protein contents of purified-hydrocolloids-coated seeds increased by 13.33 %, 46.32 %, 37.25 %, 8.89 %, and 36.22 %, respectively, compared with wheat seeds without purified-hydrocolloids coating. Inhibition of O2− production activity and malondialdehyde content was reduced by 38.62 % and 48.00 %, respectively. Therefore, the purified-hydrocolloids coating had a mitigating effect on wheat seed germination and seedling growth in salt-stressed environments, and this application would be beneficial to the use of saline soil resources and the improvement of ecosystems in coastal areas.

Marine‐Derived Nanozyme‐Crosslinked Self‐Adaptive Hydrogels for Programmed Regulating the Regeneration Process

AbstractSelf‐adaptive hydrogels that can specifically respond to pathological cues and match the highly ordered tissue regeneration process are significantly on‐demand for effective wound management. Herein, multifunctional marine‐derived gold clusterzyme (AuNCs)‐based self‐adaptive hydrogels with microenvironment triggered release behavior are elaborately fabricated for on‐demand antioxidant, anti‐inflammatory and immunoregulation. The marine mussel‐derived catechol ligands (L‐3,4‐dihydroxyphenylalanine) endow AuNCs with enhanced superoxide dismutase‐mimic activity due to their high affinity to superoxide anion free radical (O2−•) and unique electron transfer mechanism, leading to 100% inhibition of O2−•. Upon uniformly crosslinking with phenylboronic acid‐modified marine‐derived sodium alginate (PBA‐Sa), the obtained AuNCs@PBA‐Sa hydrogels exhibit outstanding self‐healing property, tunable degradation and good removability. Meanwhile, AuNCs can greatly enhance the mechanical property and confer the hydrogel with favorable tissue adhesion for rapid hemostasis. Furthermore, injectable AuNCs@PBA‐Sa hydrogels can not only adapt their shape to the irregular wound, but also smartly adapt their microstructure to the physiological microenvironment of diabetic wound, leading to the responsive release of AuNCs upon the break of boronate ester bonds. The released gold clusterzymes can actively induce the generation of M2‐macrophage, demonstrating an outstanding anti‐inflammatory and pro‐regeneration effect. Therefore, the present multifunctional clusterzyme‐based self‐adaptive hydrogels hold great potential for remolding the dynamic tissue regeneration microenvironment and smart wound management.

High-density lipoprotein regulates angiogenesis by affecting autophagy via miRNA-181a-5p.

We previously demonstrated that normal high-density lipoprotein (nHDL) can promote angiogenesis, whereas HDL from patients with coronary artery disease (dHDL) is dysfunctional and impairs angiogenesis. Autophagy plays a critical role in angiogenesis, and HDL regulates autophagy. However, it is unclear whether nHDL and dHDL regulate angiogenesis by affecting autophagy. Endothelial cells (ECs) were treated with nHDL and dHDL with or without an autophagy inhibitor. Autophagy, endothelial nitric oxide synthase (eNOS) expression, miRNA expression, nitric oxide (NO) production, superoxide anion (O2•-) generation, EC migration, and tube formation were evaluated. nHDL suppressed the expression of miR-181a-5p, which promotes autophagy and the expression of eNOS, resulting in NO production and the inhibition of O2•- generation, and ultimately increasing in EC migration and tube formation. dHDL showed opposite effects compared to nHDL and ultimately inhibited EC migration and tube formation. We found that autophagy-related protein 5 (ATG5) was a direct target of miR-181a-5p. ATG5 silencing or miR-181a-5p mimic inhibited nHDL-induced autophagy, eNOS expression, NO production, EC migration, tube formation, and enhanced O2•- generation, whereas overexpression of ATG5 or miR-181a-5p inhibitor reversed the above effects of dHDL. ATG5 expression and angiogenesis were decreased in the ischemic lower limbs of hypercholesterolemic low-density lipoprotein receptor null (LDLr-/-) mice when compared to C57BL/6 mice. ATG5 overexpression improved angiogenesis in ischemic hypercholesterolemic LDLr-/- mice. Taken together, nHDL was able to stimulate autophagy by suppressing miR-181a-5p, subsequently increasing eNOS expression, which generated NO and promoted angiogenesis. In contrast, dHDL inhibited angiogenesis, at least partially, by increasing miR-181a-5p expression, which decreased autophagy and eNOS expression, resulting in a decrease in NO production and an increase in O2•- generation. Our findings reveal a novel mechanism by which HDL affects angiogenesis by regulating autophagy and provide a therapeutic target for dHDL-impaired angiogenesis.

IMT504 protects beta cells against apoptosis and maintains beta cell identity, without modifying proliferation.

We have demonstrated that oligodeoxynucleotide IMT504 promotes significant improvement in the diabetic condition in diverse animal models. Based on these results, here we evaluated whether these effects observed in vivo could be due to direct effects on β-cells. We demonstrate by immunofluorescence that IMT504 enters the cell and locates in cytoplasm where it induces GSK-3β phosphorylation that inactivates this kinase. As GSK-3β tags Pdx1 for proteasomal degradation, by inactivating GSK-3β, IMT504 induces an increase in Pdx1 protein levels, demonstrated by Western blotting. Concomitantly, an increase in Ins2 and Pdx1 gene transcription was observed, with no significant increase in insulin content or secretion. Enhanced Pdx1 is promising since it is a key transcription factor for insulin synthesis and is also described as an essential factor for the maintenance β-cell phenotype and function. Dose-dependent inhibition of H2 O2 -induced apoptosis determined by ELISA as well as decreased expression of Bax was also observed. These results were confirmed in another β-cell line, beta-TC-6 cells, in which a cytokine mix induced apoptosis that was reversed by IMT504. In addition, an inhibitor of IMT504 entrance into cells abrogated the effect IMT504. Based on these results we conclude that the β-cell recovery observed in vivo may include direct effects of IMT504 on β-cells, by maintaining their identity/phenotype and protecting them from oxidative stress and cytokine-induced apoptosis. Thus, this work positions IMT504 as a promising option in the framework of the search of new therapies for type I diabetes treatment.

Photodegradation mechanism of metronidazole on nanostructured material type SBA-15/TiO2

The water quality to supply the human population has been a growing concern throughout the planet, as well as wastewater treatment. In this context, the photodegradation of the antibiotic metronidazole (MTZ) in aqueous solution was evaluated on nanostructured SBA-15/TiO2 under UV irradiation. The structural and optical characterization of SBA-15/TiO2 indicated the formation of a structure similar to the SBA-15 molecular sieve with band gap energy (Eg) equal to 3.23 eV. The photodegradation of MTZ on SBA-15/TiO2 indicated that the concentration was reduced by 87.70 % after 200 min of irradiation, with 75.52 % of degradation after the third reuse cycle. Comparatively, the photodegradation rate was 63.39 % and 56.7 % for commercial TiO2 (P25) and synthesized TiO2 (NP-TiO2), respectively. The effect of radical scavengers at 10-4 mol L-1 concentration demonstrated that inhibition of radicals O2•- and •OH reduces photodegradation by 76.73 % and 86.13 %, respectively. The photodegradation byproducts analysis by LC-MS indicated that the photodegradation of MTZ begins by oxidation of C-OH by radical O2•- and hydroxylation of the imidazole ring. Through chemical actinometry was obtained 10.6 % of the radiation emitted by UV lamps in the photodegradation process. Furthermore, the degradation of MTZ on SBA-15/TiO2 had a cost-effective $ 21.05 m-3 and was better than that of the other powders studied in this work.

BnaWRKY75 positively regulates the resistance against Sclerotinia sclerotiorum in ornamental Brassica napus

With the development of tourism at home and abroad, Rapeseed (Brassica napus) has become an important ornamental plant. However, its ornamental value at the inflorescence stage is greatly reduced by Sclerotinia sclerotiorum. Identification of important genes in the defense responses is critical for molecular breeding, which is an important strategy for controlling the disease. In this study, we isolated a B. napus WRKY transcription factor gene, BnaWRKY75. BnaWRKY75 was found to encode a nucleus-localized protein and exhibited relatively high expression in the stems. Arabidopsis thaliana transgenic plants expressing BnaWRKY75 showed enhanced resistance to S. sclerotiorum, and both ProBnaWRKY75:GUS and gene expression analyses showed that BnaWRKY75 was highly responsive to S. sclerotiorum infection, indicating the involvement of BnaWRKY75 in response to this infection. Furthermore, overexpression (OE) of BnaWRKY75 in B. napus significantly enhanced the resistance to S. sclerotiorum, whereas the resistance was reduced in RNAi transgenic B. napus plants. Moreover, the BnaWRKY75-OE B. napus plants exhibited constitutive activation of salicylic acid-, jasmonic acid-, and ethylene-mediated defense responses and the inhibition of both H2O2 and O2.- accumulation in response to this pathogen. By contrast, BnaWRKY75-RNAi plants showed a reverse pattern, suggesting that BnaWRKY75 is involved in hormonal signaling pathways and in the control of reactive oxygen species accumulation. In conclusion, these data indicate that BnaWRKY75, a regulator of multiple defense responses, positively regulates resistance against S. sclerotiorum, which may guide the improvement of resistance in rapeseed.

AgMYB5, an MYB transcription factor from celery, enhanced β-carotene synthesis and promoted drought tolerance in transgenic Arabidopsis

BackgroundWater shortage caused by global warming seriously affects the yield and quality of vegetable crops. β-carotene, the lipid-soluble natural product with important pharmacological value, is abundant in celery. Transcription factor MYB family extensively disperses in plants and plays regulatory roles in carotenoid metabolism and water scarcity response.ResultsHere, the AgMYB5 gene encoding 196 amino acids was amplified from celery cv. ‘Jinnanshiqin’. In celery, the expression of AgMYB5 exhibited transactivation activity, tissue specificity, and drought-condition responsiveness. Further analysis proved that ectopic expression of AgMYB5 increased β-carotene content and promoted drought tolerance in transgenic Arabidopsis thaliana. Moreover, AgMYB5 expression promoted β-carotene biosynthesis by triggering the expression of AtCRTISO and AtLCYB, which in turn increased antioxidant enzyme activities, and led to the decreased contents of H2O2 and MDA, and the inhibition of O2− generation. Meanwhile, β-carotene accumulation promoted endogenous ABA biosynthesis of transgenic Arabidopsis, which resulted in ABA-induced stomatal closing and delayed water loss. In addition, ectopic expression of AgMYB5 increased expression levels of AtERD1, AtP5CS1, AtRD22, and AtRD29.ConclusionsThe findings indicated that AgMYB5 up-regulated β-carotene biosynthesis and drought tolerance of Arabidopsis.

High photoactivity of ZrxOy-Bi2O2(CO3) composite materials prepared by one-step synthesis for efficient photodegradation of 4-chlorophenol in water

The ZrBi composite materials were prepared in a single step by the chemical co-precipitation method. Bi2O2(CO3) joined ZrxOy modifying the mole percentage from 5 to 11 mol %. ZrBi composites dried at 80 °C were characterized by: XRD, FTIR, DRS, SEM, N2 adsorption, HR-TEM, PL, XPS and EDS-SEM. Later they were evaluated in the photodegradation of 4-Chlorophenol under UV irradiation. The degradation and mineralization percentages were determined after 150 min of reaction by UV–vis spectroscopy and Total Organic Carbon (TOC), respectively. The composite containing 9 mol % of Bi2O2(CO3) (ZrBi-9) with a specific volume of 0.03 m3/kg in solution with specific catalyst density of 1*10−3 kg/L, showed the highest photoactivity with 96 % photodegradation, a higher value compared to that obtained with the reference material TiO2-P25 (72 %). Finally, a possible reaction mechanism was proposed based on recent studies, which allow to follow the formation of active species OH, O2− and h+. The formation of OH radicals was measured by fluorescence spectroscopy while the inhibition of O2− radicals as well as the scavenge of h+ were determined by UV–vis spectroscopy. The results showed that ZrBi composite materials do not promote OH radical formation. The scavenge of h+ showed a total loss of photoactivity and the inhibition of O2− in the reaction medium results in a partial decrease of photoactivity. The formation of heterojunctions, the presence of localized states and oxygen vacancies in the synthesized materials promise an excellent alternative for the rapid photodegradation of 4-Chlorophenol under UV radiation.

Melatonin-Induced Inhibition of Shiraia Hypocrellin A Biosynthesis Is Mediated by Hydrogen Peroxide and Nitric Oxide.

Melatonin (MLT), an evolutionarily conserved pleiotropic molecule, is implicated in numerous physiological processes in plants and animals. However, the effects of MLT on microbes have seldom been reported. In this study, we examined the influence of exogenous MLT on the growth and hypocrellin biosynthesis of bambusicolous fungus Shiraia sp. S9. Hypocrellin A (HA) is a photoactivated and photoinduced perylenequinone (PQ) toxin in Shiraia. Exogenous MLT at 100.00 μM not only decreased fungal conidiation and spore germination but inhibited HA contents significantly in fungal cultures under a light/dark (24 h:24 h) shift. MLT treatment was associated with higher activity of antioxidant enzymes (superoxide dismutase, catalase and peroxidase) and a marked decline in reactive oxygen species (ROS) production in the mycelia. Moreover, MLT induced endogenous nitric oxide (NO) production during the culture. The NO donor sodium nitroprusside (SNP) potentiated MLT-induced inhibition of O2− production, but NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) enhanced O2− production, whereas MLT-induced NO level was increased by the ROS scavenger vitamin C (Vc). The changes in NO and H2O2 were proved to be involved in the MLT-induced downregulation of the expressions of HA biosynthetic genes, leading to the suppression of HA production. This study provides new insight into the regulatory roles of MLT on fungal secondary metabolism activities and a basis for understanding self-resistance in phototoxin-producing fungi.

Unveiling the influential mechanism of O2 on the corrosion of N80 carbon steel under dynamic supercritical CO2 conditions

The influential mechanism of O2 on the corrosion of N80 carbon steel under dynamic supercritical CO2 conditions was explored by mass loss and electrochemical tests, and surface analysis. It is demonstrated that the introduction of O2 inhibits the corrosion of steel. The developed water chemistry model confirms that the decrease in the corrosive species concentration by introducing O2 is not responsible for the inhibition to steel corrosion. The corrosion inhibition of O2 is implemented by promoting the formation of protective FeCO3 film in the initial period owing to the diffusion barrier effect of the formed outer ferric hydroxide/oxide film.

Adansonia digitata L. (Baobab Fruit) Effect on Postprandial Glycemia in Healthy Adults: A Randomized Controlled Trial.

Baobab fruits have been traditionally used in Africa due to their therapeutic properties attributed to their high polyphenol content. The aim of the study was to investigate the effect of baobab fruit on postprandial glycaemia in healthy adults and to measure its bioactive compounds and antioxidant activity. The study (NCT05140629) was conducted on 31 healthy subjects. The participants were randomly allocated in the control group (oral glucose tolerance test (OGTT); n = 16) and in the intervention group (OGTT, followed by administration of 250 mL baobab aqueous extract (BAE); n = 15). Total phenols, proanthocyanins, hydrolyzable tannins, and antioxidant activity (FRAP, DPPH, ABTS, and inhibition of O2•− and NO• methods) were quantified. Repeated measures ANOVA of mixed type and independent samples t-test were used. Glycemia incremental area under the curve (p = 0.012) and glucose maximum concentration (p = 0.029) was significantly lower in the intervention group compared to the control group. The BAE revealed high total contents of phenols, proanthocyanins, and hydrolyzable tannins, as well as a strong capacity to scavenge superoxide anions and nitric oxide radicals and a high antioxidant activity. In conclusion, this study encourages the use of this food component as a promising source of natural antioxidants and a hypoglycemic agent under glucose load acute conditions.

Neuroprotective properties of ethanolic extract of Citrus unshiu Markovich peel through NADPH oxidase 2 inhibition in chemotherapy-induced neuropathic pain animal model.

The present study aimed to determine the antioxidant effect of Citrus unshiu Markovich (CUM) extract in neuronal cell lines under oxidative stress and to investigate the effect of chemotherapy-induced peripheral neuropathy (CIPN) on the nociceptive response in a preclinical mice model. We tested the inhibition of H2 O2 in Neuro2A cells treated with CUM. Experimental animals were treated with oxaliplatin to induce CINP, and then administered oral CUM for 4 weeks in order to observe the effect of CUM. Animals were evaluated weekly for thermal hyperalgesia and digital motor nerve conduction velocity (NCV). Lumbar dorsal root ganglia (DRG) isolated from each animal were evaluated through immunochemical and western blot analysis for nerve damage, inflammatory response, and expression of redox signaling factors. The main mechanisms were determined to be decreased inducible nitric oxide synthase (iNOS) production due to the inhibition of NADPH oxidase 2 (NOX2). To determine the functional role of NOX2 in CINP, we administrated CUM into NOX2-deficient mice with neuropathic pain. Therefore, we suggest that CUM controls the expression levels of inflammatory factors in CINP via NOX2 inactivation. This study demonstrated that a complementary medicine such as CUM might be a potential novel therapeutic agent for the treatment of CINP.

Enzymatic Synthesis of α-Tocopherol Derivative Glycoside, Daidzein Glycoside, Daidzein Oligosaccharide, Resveratrol Oligosaccharide, and Curcumin Oligosaccharides and Their Anti-Allergic Activity and Neuroprotective Activity

Enzymatic glycosylations of an α-tocopherol derivative, daidzein, resveratrol, and curcumin were investigated. The plant polyphenol, resveratrol, was incubated with glucosyltransferase from Phytolacca americana. The resveratrol glycoside obtained was then incubated with cyclodextrin glucanotransferase to obtain resveratrol oligosaccharide. Daidzein and curcumin were also converted into daidzein glycoside, daidzein oligosaccharide, and curcumin oligosaccharides. Also, α-tocopherol derivative, that is, 2, 5,7,8-tetramethyl-2-(4,8-dimethylnonyl)chroman-6-ol, was glycosylated. The glycosides and oligosaccharides had strong anti-allergic activity such as suppression of IgE formation, inhibition of histamine release, and inhibition of O2 - generation. In addition, the glycosides and oligosaccharides showed efficient neuroprotective activity by inhibition of phosphodiesterase.

Abstract 1945: Modulation of intracellular redox milieu regulates Mcl-1 levels and sensitizes venetoclax resistant cancer cells

Abstract Mcl-1, a member of the Bcl-2 family of anti-apoptotic proteins is commonly amplified in malignant cancers and has been implicated in chemotherapy resistance. More recently, it has been reported to mediate resistance to the Bcl-2 specific BH3 mimetic, venetoclax (ABT199). The protein stability of Mcl-1 is regulated largely by post-translational modifications (PTMs) such as phosphorylation and ubiquitination. Where phosphorylation of Thr163 residue at the PEST domain region by kinases result in Mcl-1 stability and extended protein half-life, phosphorylation of Ser159 residue leads to protein degradation via proteasome pathway. Given the importance of PTMs in regulating Mcl-1, identification of signaling pathways that could modulate PTMs of Mcl-1 to thereby sensitize tumors to chemotherapy have been explored extensively. The intracellular redox milieu has been widely reported to modulate protein-protein signaling as well as inducing PTMs, where different reactive oxygen species (ROS) have also been shown to mediate differential effects. For example, enhanced production of O2- (by either inhibition or downregulation of SOD1/SOD2) could mediate tumorigenicity and chemoresistance. To that end, our group and others have also previously reported the oncogenicity of superoxide (O2-), where an elevated O2- level mediates enhanced anti-apoptotic activity against chemotherapeutic agents through sustained Bcl-2 phosphorylation and the inhibition of O2- production conversely sensitized cells to chemotherapy. Nonetheless, the exact mechanisms of how O2- exerts its pro-survival effects remain elusive. Our preliminary findings now suggest that elevated intracellular O2- levels induces Mcl-1 stability in cancer cells through PTMs as a potential mechanism of chemotherapy resistance. Increased intracellular O2- levels induced Mcl-1 through phosphorylation of Thr163 residue of Mcl-1, which in turn reduced ubiquitination dependent degradation of Mcl-1. Importantly, increased O2- level increased resistance to cell death induced by Mcl-1 specific BH3 mimetic, S63845 and conversely, reducing O2- levels resulted in sensitization of intrinsically venetoclax resistant leukemia cells to venetoclax induced cell death. These results provide a novel insight into how the intracellular redox state could impact upon cancer cell viability and therapy resistance. Citation Format: Jolin Xiao Lai, Shazib Pervaiz. Modulation of intracellular redox milieu regulates Mcl-1 levels and sensitizes venetoclax resistant cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1945.

Anionic redox reaction in Na-deficient layered oxide cathodes: Role of Sn/Zr substituents and in-depth local structural transformation revealed by solid-state NMR

Anionic redox reaction (ARR) offers a complementary electron reservoir that affords the egress/ingress of additional Na beyond the conventional cation redox reaction. However, oxygen-related ARR in sodium-ion batteries is universally confronted with several roadblocks such as insufficient reversibility and poor understanding on the functioning mechanisms. We herein attempt to improve the reversibility of oxygen-related ARR in a Na-deficient Li/Mn(IV)-based layered oxide cathode by Sn and Zr substitutions. The as-designed P2-Na0.66Li0.22Mn0.775Sn0.005O2 and P2-Na0.66Li0.22Mn0.775Zr0.005O2 demonstrate much enhanced cycle stability and rate capability (72% capacity retention at 10 mA g−1 after 100 cycles and 92 mAh g−1 reversible capacity at 1 A g−1 for the former). The role of Sn/Zr substituents was meticulously studied, manifesting the effective inhibition of the anisotropic O2−α−Mn4+coupling (0 < α < 2) and the irreversible lattice oxygen loss. More impressively, the local structural transformations studied via 23Na/7Li solid-state NMR substantiate that (i) Li-ions migrate from TM (transition metal) layer to AM (alkali metal) layer upon charge, and do not return to the original sites in TM layer upon discharge; (ii) the egress/ingress of Na follows a solid-solution reaction within 4.5–1.5 V, but the local structural transition is not fully reversible; (iii) Li/Mn migrations continue beyond the initial cycle, bringing about irreversible Li/Mn losses and Na-site local disorder upon prolonged cycling. Altogether, this study provides deep insights into the ARR mechanism of Na-deficient layered oxide cathodes and will pave a new avenue to fully address the intrinsic shortcomings of oxygen-related ARR.

Comparison of Direct and Mediated Electron Transfer for Bilirubin Oxidase from Myrothecium Verrucaria. Effects of Inhibitors and Temperature on the Oxygen Reduction Reaction

One of the processes most studied in bioenergetic systems in recent years is the oxygen reduction reaction (ORR). An important challenge in bioelectrochemistry is to achieve this reaction under physiological conditions. In this study, we used bilirubin oxidase (BOD) from Myrothecium verrucaria, a subclass of multicopper oxidases (MCOs), to catalyse the ORR to water via four electrons in physiological conditions. The active site of BOD, the T2/T3 cluster, contains three Cu atoms classified as T2, T3α, and T3β depending on their spectroscopic characteristics. A fourth Cu atom; the T1 cluster acts as a relay of electrons to the T2/T3 cluster. Graphite electrodes were modified with BOD and the direct electron transfer (DET) to the enzyme, and the mediated electron transfer (MET) using an osmium polymer (OsP) as a redox mediator, were compared. As a result, an alternative resting (AR) form was observed in the catalytic cycle of BOD. In the absence and presence of the redox mediator, the AR direct reduction occurs through the trinuclear site (TNC) via T1, specifically activated at low potentials in which T2 and T3α of the TNC are reduced and T3β is oxidized. A comparative study between the DET and MET was conducted at various pH and temperatures, considering the influence of inhibitors like H2O2, F−, and Cl−. In the presence of H2O2 and F−, these bind to the TNC in a non-competitive reversible inhibition of O2. Instead; Cl− acts as a competitive inhibitor for the electron donor substrate and binds to the T1 site.

Nitrate inhibits primary root growth by reducing accumulation of reactive oxygen species in the root tip in Medicago truncatula

In Medicago truncatula, nitrate, acting as a signal perceived by NITRATE TRANSPORTER1/PEPTIDE TRANSPORTER FAMILY 6.8 (MtNPF6.8), inhibits primary root growth through a reduction of root cell elongation. Since reactive oxygen species (ROS) produced and converted in root tip (O2•− → H2O2 → •OH) have been reported to control cell elongation, the impact of nitrate on the distribution of these ROS in the primary root of M. truncatula was analyzed. We found that nitrate reduced the content of O2•−, H2O2 and •OH in the root tip of three wild type genotypes sensitive to nitrate (R108, DZA, A17), inhibition of root growth and O2•− accumulation being highly correlated. Nitrate also modified the capacity of R108 root tip to produce or remove ROS. The ROS content decrease observed in R108 in response to nitrate is linked to changes in peroxidase activity (EC1.11.1.7) with an increase in peroxidative activity that scavenge H2O2 and a decrease in hydroxylic activity that converts H2O2 into •OH. These changes impair the accumulation of H2O2 and then the accumulation of •OH, the species responsible for cell wall loosening and cell elongation. Accordingly, nitrate inhibitory effect was abolished by externally added H2O2 or mimicked by KI, an H2O2 scavenger. In contrast, nitrate has no effect on ROS production or removal capacities in npf6.8-2, a knockdown line insensitive to nitrate, affected in the nitrate transporter MtNPF6.8 (in R108 background) by RNAi. Altogether, our data show that ROS are mediators acting downstream of MtNPF6.8 in the nitrate signaling pathway.

Reduction of Leukocyte Microvascular Adherence and Preservation of Blood-Brain Barrier Function by Superoxide-Lowering Therapies in a Piglet Model of Neonatal Asphyxia.

Background: Asphyxia is the most common cause of brain damage in newborns. Substantial evidence indicates that leukocyte recruitment in the cerebral vasculature during asphyxia contributes to this damage. We tested the hypothesis that superoxide radical () promotes an acute post-asphyxial inflammatory response and blood-brain barrier (BBB) breakdown. We investigated the effects of removing by superoxide dismutase (SOD) or C3, the cell-permeable SOD mimetic, in protecting against asphyxia-related leukocyte recruitment. We also tested the hypothesis that xanthine oxidase activity is one source of this radical.Methods: Anesthetized piglets were tracheostomized, ventilated, and equipped with closed cranial windows for the assessment of post-asphyxial rhodamine 6G-labeled leukocyte-endothelial adherence and microvascular permeability to sodium fluorescein in cortical venules. Asphyxia was induced by discontinuing ventilation. SOD and C3 were administered by cortical superfusion. The xanthine oxidase inhibitor oxypurinol was administered intravenously.Results: Leukocyte-venular adherence significantly increased during the initial 2 h of post-asphyxial reperfusion. BBB permeability was also elevated relative to non-asphyxial controls. Inhibition of production by oxypurinol, or elimination of by SOD or C3, significantly reduced rhodamine 6G-labeled leukocyte-endothelial adherence and improved BBB integrity, as measured by sodium fluorescein leak from cerebral microvessels.Conclusion: Using three different strategies to either prevent formation or enhance elimination of during the post-asphyxial period, we saw both reduced leukocyte adherence and preserved BBB function with treatment. These findings suggest that agents which lower in brain may be attractive new therapeutic interventions for the protection of the neonatal brain following asphyxia.

Effect of Adansonia digitata L. fruit on postprandial glycaemia in non-diabetic adults

Introduction: Diabetes mellitus is a chronic disease that affect 13% of the Portuguese population, which is estimated to increase to 15.8% in 2035 [1]. Adansonia digitata L. (Baobab) fruit is considered an important nutritional and medicinal resource [2], which is commonly consumed in the African continent. Previous studies have found postprandial hypoglycaemic activity attributed to fruit polyphenol content [3]. This study aimed to verify the effect of Adansonia digitata L. (Baobab) fruit on postprandial glycaemia levels on non-diabetics adults and evaluate compounds related with antioxidant activity. Materials and methods: Following Cooperativa Egas Moniz ethical committee approval 31 nondiabetic adults, with ages between 18 and 40 years, were recruited from the local community. A written informed consent was obtained from volunteers that were randomly allocated in a control group (n = 16), subjected to an oral glucose tolerance test (OGTT), or in an intervention group (n = 15), subjected to OGTT followed by administration of 250 mL Baobab aqueous extract (BAE). Repeated Measures ANOVA of mixed type was used to access the difference between the 2 groups for postprandial BGL at different times. Independent samples t-test was used to access the difference between the 2 groups for AUC, ΔCmax and Cmax. BAE content of total phenols, proanthocyanidins and hydrolysable tannins, as well as its antioxidant activity (FRAP, DPPH, ABTS and inhibition of O2 •− and NO• methods) were quantified. Results: Results revealed that there is no interaction between the independent and repeated measures factors, thus is not possible to infer about differences in PBG in different moments. Results showed higher (Cmáx) PBG in the control group compared with the intervention group (p = 0,029), although no significant variation (ΔCmax) was observed (p = 0.054). PBG area under the curve (AUC) was significantly lower (p = 0.012) on the intervention group. Total phenols, proanthocyanidins and hydrolysable tannins concentrations from BAE were 702.39 ± 11.85, 336.33±10.85 and 237.63±4.71 mg EAT/100g FW, respectively. Antioxidant activity was high, being the reducing power given by the FRAP method 1289.58 ± 34.44 mg ET/100 g FW, the scavenging activities of the DPPH and ABTS radicals 1269.72 ± 129.23 and 1004.42 ± 41.65 mg ET/100g FW, respectively. O2 •− and NO• IC50 were respectively 57.86 ± 2.57 and 29.48 ± 5.17 mg EAG/100g FW. Discussion and conclusions: Results obtained suggest that the BAE could act beneficially for postprandial glycaemic control, as previously stated [3] and a possible correlation with its antioxidant properties.

Respiratory burst oxidase homologue-dependent H2 O2 and chloroplast H2 O2 are essential for the maintenance of acquired thermotolerance during recovery after acclimation.

Thermotolerance is improved by heat stress (HS) acclimation, and the thermotolerance level is "remembered" by plants. However, the underlying signalling mechanisms remain largely unknown. Here, we showed NADPH oxidase-mediated H2 O2 (NADPH-H2 O2 ), and chloroplast-H2 O2 promoted the sustained expression of HS-responsive genes and programmed cell death (PCD) genes, respectively, during recovery after HS acclimation. When spraying the NADPH oxidase inhibitor, diphenylene iodonium, after HS acclimation, the NADPH-H2 O2 level significantly decreased, resulting in a decrease in the expression of HS-responsive genes and the loss of maintenance of acquired thermotolerance (MAT). In contrast, compared with HS acclimation, NADPH-H2 O2 declined but chloroplast-H2 O2 further enhanced during recovery after HS over-acclimation, resulting in the reduced expression of HS-responsive genes and substantial production of PCD. Notably, the further inhibition of NADPH-H2 O2 after HS over-acclimation also inhibited chloroplast-H2 O2 , alleviating the severe PCD and surpassing the MAT of HS over-acclimation treatment. Due to the change in subcellular H2 O2 after HS acclimation, the tomato seedlings maintained a constant H2 O2 level during recovery, resulting in stable and lower total H2 O2 levels during a tester HS challenge conducted after recovery. We conclude that tomato seedlings increase their MAT by enhancing NADPH-H2 O2 content and controlling chloroplast-H2 O2 production during recovery, which enhances the expression of HS-responsive genes and balances PCD levels, respectively.