Superoxide Formation Research Articles

Unveiling the link between NADPH oxidase 2 activation and mitochondrial superoxide formation in leukemic cell killing induced by arsenic trioxide.

This study focused on the interplay between NADPH oxidase 2 (NOX 2) activation and mitochondrial superoxide (mitoO2.-) formation induced by clinically relevant concentrations of arsenic trioxide (ATO; As2O3) in acute promyelocytic leukemia (APL) cells. Carefully controlled inhibitor studies and small interfering RNA mediated downregulation of p47phox (a component of the NOX 2 complex) expression demonstrated that, in an APL cell line, ATO promotes upstream NOX 2 activation critically connected with the formation of mitoO2.- and with the ensuing mitochondrial permeability transition (MPT)-dependent apoptosis. Instead, acute myeloid leukemia (AML) cell lines respond to ATO with low NOX 2 activation, resulting in a state that is non-permissive for mitoO2.- formation. Consistently, through rescue experiments, we demonstrate that pharmacological stimulation of NOX 2 overcomes resistance in these cells, thereby initiating the same cascade of downstream events observed in APL cells. As a final note, several lines of evidence, including measurement of glutathione, catalase and glutathione peroxidase levels, indicated that the antioxidant machinery was similar in APL and AML cells. The results regarding nuclear factor erythroid 2 p45-related factor 2-dependent antioxidant responses were instead of more complex interpretation as NB4 cells appeared particularly responsive to ATO. Our findings allow a novel interpretation of the interplay between NOX 2 activation and mitoO2.- formation induced by ATO, ultimately steering leukemic cells towards MPT-dependent apoptosis. These mechanistic insights provide a rationale for the disparate responses of APL and AML cells to ATO, offering potential avenues for the development of therapeutic intervention tailored to specific leukemia subtypes.

Discovery of 1,3-disubstituted prop-2-en-1-one derivatives as inhibitors of neutrophilic inflammation via modulation of MAPK and Akt pathways

Targeting neutrophil function has gained attention as a propitious therapeutic strategy for diverse inflammatory diseases. Accordingly, a series of enone-based derivatives were developed to inhibit neutrophil-mediated inflammation, showing promise for treating inflammatory diseases. These compounds fall into two clusters with distinct effects: one inhibits neutrophilic superoxide (SO) anion production and elastase release triggered by N-formyl-Met-Leu-Phe (fMLF), with compound 6a being most effective (IC50 values of 1.23 and 1.37 μM, respectively), affecting c-Jun N-terminal kinase (JNK) and Akt phosphorylation. The second cluster suppresses formation of SO anion without affecting elastase levels, surpassed by compound 26a (IC50 of 1.56 μM), which attenuates various mitogen-activated protein kinases (MAPKs) with minimal Akt impact. Notably, none of the tested compounds showed cytotoxicity in human neutrophils, underscoring their potential as therapeutic agents against inflammatory diseases.

Study of the Mechanism and Charge-Transfer Processes in Water Oxidation Catalysis by Nickel Hydroxide and Silk Fibroin: A Spectroelectrochemical Approach

Water electrolysis has emerged as a crucial electrochemical reaction on the generation of sustainable fuels, due to the ongoing climate crisis. To divert from expensive catalysts based on rare noble metals such as Ir and Ru, transition metal oxides seem to be promising candidates and several recent studies have deepened the investigation on the nickel oxide/hydroxide for water oxidation catalysis. It has been proposed that in the presence of elements such as iron and gold, a partial charge-transfer occurs between the nickel and the metal, facilitating the formation of superoxide species and nickel in higher oxidation states that enhance the oxygen evolution reaction (OER). 1–4 Rao et al (2022)5 developed a methodology combining UV-Vis spectroscopy and voltametric techniques to determine the number of these nickel species in higher oxidation levels during the OER for nickel oxides dopped with Zn, Fe, Co and Mn. From their results, they proposed a mechanism for the OER that involves two steps: 1) initial oxidation from NiII to NiIII and superoxide formation, which is limited by the potential and 2) coupling and desorption of the superoxide species, which is limited by rate. Next, they demonstrated that the different dopants modulated the bond strength between the nickel and the oxygen: too weak-bonding limited the ability to oxidize nickel and too strong-bonding limited the combination and desorption of the oxygen.In this work, monolayers of nickel hydroxide were electrodeposited, in the presence and the absence of silk fibroin (SF), on top of electrodes containing gold nanoparticles and used surface-enhanced Raman scattering (SERS)and UV-Vis spectroeletrochemical techniques to study the influence of the gold and SF on the catalytic performance of nickel hydroxide. Our previous results6 showed that the silk protein was able to stabilize the α-Ni(OH)2 nanoparticles and improved its electrochemical activity. Here, we followed the Rao et al’s methodology and found analogous results for the mechanisms of water oxidation. Figure 1A and B shows the number oxidized species and the calculated turnover frequency (TOF) as function of the potential for the samples with 1, 3, 6 and 9 monolayers, containing or not SF. While the number of oxidized species remains comparable across samples with the same number of monolayers, those containing fibroin generally exhibit higher TOFs. A volcano-like graph (Figure 1C) was obtained when the TOFs at an overpotential of 0.3 V is plotted against the NiII-NiIII redox potential, indicating a transition from potential-limited to rate-limited regions as monolayer thickness increases. We propose that this behavior is caused by the charge-transfer effect between nickel and gold, which is strongest for one monolayer and decreases as the number of nickel sites on the bulk moves away the gold surface. Notably, as monolayer thickness increases, samples containing SF show less susceptibility to decrease in TOFs, implying an additional charge-transfer effect between the protein and nickel, which contributes for the balance of the nickel bond strength with oxygen and facilitates its coupling and desorption.In summary, our study advances understanding of OER mechanisms and charge-transfer processes involving nickel hydroxide electrocatalysis, suggesting that proteins like SF can actively contribute to catalytic processes. However, further investigations are needed in order to elucidate the precise role of the protein and how to use them to optimize catalytic performance. REFERENCES 1. Diaz-Morales, O., Ferrus-Suspedra, D. & M. Koper, M. T. Chem. Sci. 7, 2639–2645 (2016).2. Yeo, B. S. & Bell, A. T. J. Phys. Chem. C 116, 8394–8400 (2012).3. Li, C.-F. et al. Angew. Chem. Int. Ed. 61, e202116934 (2022).4. Trotochaud, L., Young, S. L., Ranney, J. K. & Boettcher, S. W. J. Am. Chem. Soc. 136, 6744–6753 (2014).5. Rao, R. R. et al. J. Am. Chem. Soc. 144, 7622–7633 (2022). 6. do Nascimento, E. R. et al. ACS Appl. Electron. Mater. 4, 1214–1224 (2022). Figure 1

Stability of RbO2 As a Discharge Product of Metal–O2 Batteries

The cathode reaction in metal–oxygen batteries, also referred to as metal–air batteries, has been extensively studied for the electrochemical management of the oxygen reduction reaction (ORR) to harness it for energy conversion. Alkali metal–oxygen batteries utilizing non-aqueous electrolytes have garnered interest for their high theoretical energy density, which leverages atmospheric oxygen as the cathode active material. However, their practical application remains limited by the low reversibility of the ORR.The Li–O2 battery, first introduced in 1996,[1] was followed by Na–O2 and K-O2 batteries.[2, 3] The cathode reaction in metal–oxygen batteries involves the reduction and reoxidation of oxygen. In non-aqueous electrolytes that contain alkali metal ions, the formation of alkali metal superoxide (MO2) occurs as a discharge product.[4] MO2 stability is empirically known to be influenced by the ionic radii of the alkali metal ion (M+) and the superoxide ion (O2 -).[5] Lithium superoxide (LiO2), which forms through a one-electron reduction process in lithium-based electrolytes, exhibits a significant ionic radius discrepancy between the lithium ion (Li+ 0.76 Å in octahedral coordination) and the relatively large O2 -. This discrepancy results in instability as an ion pair, allowing lithium superoxide to exist only as a transient reaction intermediate.[6, 7, 8] Consequently, the disproportionation reaction (2LiO2 → Li2O2 + O2) and/or subsequent reduction reaction lead to the formation of lithium peroxide (LiO2 + Li+ + e- → Li2O2).[9] The two-electron reduction product, Li2O2, poses challenges for re-oxidation, causing Li–O2 batteries to experience a significant charge overpotential (1–1.5 V). This overpotential greatly diminishes reversibility and energy efficiency.[10] Conversely, in sodium-based electrolytes (Na+: 1.02 Å), NaO2 can be isolated because of its larger ionic radius compared to Li+, offering different electrochemical properties. Unlike Li2O2, NaO2 can be charged at a relatively low overpotential (approximately 200 mV). However, NaO2 reacts with trace amounts of H2O and CO2 present in the cell, facilitating formation of Na2O2 and its hydrates.[11] In potassium-based electrolytes, which feature an even larger ionic radius (K+: 1.38 Å), KO2 can be isolated, and because of its relative stability, KO2 is commercially available as a chemical reagent.[12] Their high stability against moisture and CO2 has been demonstrated; these cells can undergo repeated charge–discharge cycles over extended periods without significant degradation.[13] Despite the high stability of KO2, it can still gradually contribute to the problems mentioned previously, thus degrading battery performance. In this study, we concentrated on enhancing the stability of MO2 against H2O and CO2. We systematically examined and compared ORR mechanism with those involving rubidium (Rb+: 1.52 Å) and cesium ions (Cs+: 1.67 Å), both of which possess even larger ionic radii than potassium.[References][1] M. Abraham, Z. Jiang, J. Electrochem. Soc., 143, 1 (1996).[2] Hartmann, P. Adelhelm, et al., Nat. Mater, 12, 228 (2013).[3] Ren, Y. Wu, J. Am. Chem. Soc., 135, 2923 (2013).[4] Xiao, Y. Wu, et al., Acc. Chem. Res. 51, 2335-2343 (2018).[5] Qin, Y. Wu, et al., J. Am. Chem. Soc., 142, 11629 (2020).[6] Mahler, I. Persson, Inorg. Chem., 51, 425-438 (2012).[7] D. C. Dietzel, M. Jansen, et al., J. Am. Chem. Soc., 126, 4689 (2004).[8] Z. Foppl, Anorg. Allg. Chem., 291, 12-50 (1957).[9] Wang, Y. C. Lu, Energy Stor. Mater., 28, 235-246 (2020).[10] Padbury, X. Zhang, J. Power Sources, 196, 4436-4444 (2011).[11] Sun, X. Sun, et al., J. Phys. Chem. C, 119, 13433-13441 (2015).[12] Wang, Y. C. Lu, ACS Energy Lett., 5, 3804–3812 (2020).[13] Qin, Y. Wu, et al., Angew. Chem., 132, 10584-10587 (2020).

Impact of Fe3+/Polyphenol Ratio in Iron-gall Ink on Superoxide Formation: Rationalizing Historic Recipes from a Kinetic Study.

Iron-gall inks, a vital part of our written cultural heritage, are at risk of complete loss due to degradation, a potential loss that we must urgently address. These inks are based on Fe3+-complexes with phenolic compounds, which grow to form a complex network of iron oxyhydroxides. Over time, these black inks turn into brownish tones, with extensive degradation in paper support leading to extensive breaking. The kinetics of iron-gall ink preparation explains the use of iron sulfate, FeSO4, in all ancient recipes to obtain a stable amorphous ink. The novelty of this work shows that a low ratio of Fe3+/polyphenol is a crucial factor in allowing the ink's growth without its degradation. This ratio also prevents the formation of superoxide. This was achieved through a comprehensive research methodology involving spectroscopic techniques in the visible and the near-infrared regions, stopped-flow spectrometry and electrochemical studies.

Electron-transfer flavoprotein : ubiquinone-oxidoreductase induces increased superoxide formation upon fatty acid and branched-chain keto-acid Beta-oxidation in INS-1E cells

Electron-transfer flavoprotein : ubiquinone-oxidoreductase induces increased superoxide formation upon fatty acid and branched-chain keto-acid Beta-oxidation in INS-1E cells

Weak magnetic field for enhanced degradation of sulfamethoxazole by the CoFe2O4/PAA system: Insights into performance and mechanism

In this work, a novel approach coupling a heterogeneous weak magnetic field (WMF) with the CoFe2O4/peroxyacetic acid (PAA) system was employed to enhance the degradation of sulfamethoxazole (SMX). Under the optimized conditions of 50 mT WMF, 0.1 g/L CoFe2O4, 0.2 mM PAA, and initial pH 6.0, a complete degradation of 10 μM SMX was achieved in 25 min, exhibiting a high synergistic coefficient of 1.61. This result indicates a significant synergistic effect among WMF, CoFe2O4, and PAA in effectively degrading SMX. The introduction of WMF did not alter the pH application range of the CoFe2O4/PAA system. Furthermore, the degradation efficiency of SMX by the CoFe2O4/PAA/WMF system was significantly reduced in the presence of humic acid (HA) and bicarbonate ions (HCO3−), while chloride ions (Cl−) exhibited a minor inhibitory effect. Quenching experiments and electron paramagnetic resonance (EPR) analysis reveal that WMF did not alter the types of reactive oxygen species (ROS) generated in the CoFe2O4/PAA system. The degradation of SMX in the CoFe2O4/PAA/WMF system involved both radical (CH3C(O)O∙ and CH3C(O)OO∙) and non-radical (1O2) oxidation pathways, driven by the redox cycling between ≡Co2+/≡Co3+ and PAA, as well as the rapid adsorption and transformation of oxygen (O2) at oxygen vacancies (OV), respectively. The presence of WMF enhanced the utilization of PAA by CoFe2O4 by improving the convection and mass transport in the solution, facilitating the formation of superoxide anion (O2∙−) and supplemented lattice oxygen (O2−) through the directional migration of paramagnetic O2 towards the CoFe2O4 surface, thus significantly promoting ROS formation. Additionally, the degradation pathways of SMX in the CoFe2O4/PAA/WMF system were proposed based on density functional theory (DFT) calculations and the detected transformation products (TPs). The toxicity of SMX was effectively reduced, as verified by predictions from the Ecological Structure-Activity Relationship Model (ECOSAR) procedure. The excellent catalytic performance, reusability, and effective degradation of various organic pollutants demonstrated by the CoFe2O4/PAA/WMF system suggest its potential as a promising strategy for water treatment.

Efficient cleavage of Cα[sbnd]Cβ bonds in lignin using tetrabutylammonium tetrafluoroborate as both the catalyst and auxiliary electrolyte

Lignin is a promising alternative to fossil resources due to its abundance of benzene ring monomers. However, the stability of the CαCβ bond in lignin has hindered its efficient depolymerization. Electrochemical methods for breaking this bond are not well-studied. This paper presents a novel approach for catalytic depolymerization of lignin to produce acetals under mild conditions, without the need for additional catalysts. Under room temperature and in an air atmosphere, the combination of tetrabutylammonium tetrafluoroborate (TBABF4) as an auxiliary electrolyte and methanol (MeOH) as a solvent has shown high selectivity in catalyzing the cleavage of CαCβ bonds in lignin. Over 90.0 % of the resulting products are acetals, with the optimal conditions being a substrate concentration of 0.02 M, TBABF4 concentration of 0.008 M, a constant current of 30 mA, and a reaction time of 3 h. This led to a substrate conversion rate of 95.8 % and a product yield of 98.0 % for benzaldehyde dimethyl acetal (Bda). The mechanism study reveals that the tributyl ammonium radical cation decomposed by TBABF4 is adsorbed on the electrode surface. Subsequently, the adsorbed O2 is activated to form superoxide anion radical active species through single electron transfer, which plays a crucial catalytic role. TBABF4 acts as both an auxiliary electrolyte and a catalyst in this process. This research introduces a novel approach for electrocatalytic depolymerization of inert CαCβ bonds in lignin, leading to the selective conversion into acetal chemicals.

NoxO1 Determines the Level of ROS Formation by the Nox1-Centered NADPH Oxidase.

The Nox1-centered NADPH oxidase complex facilitates the transfer of electrons from intracellular NADPH across the cell membrane to extracellular molecular oxygen, resulting in the formation of superoxide. The complex is comprised of two membrane-bound subunits, namely Nox1 and p22phox, and the cytosolic subunits, namely NoxA1 and NoxO1. The presence of NoxO1 facilitates the proximity of all components, thereby enabling the complex to exhibit constitutive activity. Despite the theoretical sufficiency of all subunits in a 1:1 ratio, the precise composition of the Nox1-centered NADPH oxidase remains unknown. Analyses of mRNA expression in different cell lines revealed an unequal expression of the components, with an excess of NoxO1. Furthermore, plasmid-based overexpression of individual components of the Nox1-centered NADPH oxidase resulted in an excess of NoxO1 mRNA. The objective of this study was to analyze the ability of NoxO1 to control the level of ROS formation by the Nox1 complex. To this end, we generated Hek293 cells for constitutive expression of Nox1 and NoxA1, which were then transfected with increasing concentrations of NoxO1. The data presented herein suggests that ROS formation by the Nox1-centered NADPH oxidase is dependent on the concentration of NoxO1. A surplus of NoxO1 has been observed to exert control over the activity of the complex in accordance with a dose-dependent mechanism. We thus conclude that the ratio of Nox1, NoxA1, and NoxO1 complexes does not adhere to a 1:1 ratio. Conversely, the availability of NoxO1 serves to regulate the formation of ROS by the Nox1-centered NADPH oxidase.

Efavirenz: New Hope in Cancer Therapy.

Despite extensiveresearch directedat preventive and treatment strategies, breast cancer remains the leading cause of cancer-related mortality among women. This necessitates the development of a new medication aimed at increasing patient survival and quality of life. A new drug's development from the ground up can cost billions of dollars and take up to ten or more years. Because much of the required safety and pharmacokinetic data are already available from earlier trials, repurposing medications usually results in lower costs and shorter turnaround times. Many antiretroviral medications target biological pathways and enzymes associated with cancer, which becomes an ideal option for repurposing as anticancer medications. Efavirenz is an antiretroviral medication that targets molecular pathways implicated in the growth of breast cancer, such as LINE-1 (long interspersed nuclear elements-1) suppression, hence lowering the proliferation of breast cancer cells and exhibiting anti-cancer properties. Additionally, it suppresses the fatty acid synthase gene and other important genes related to fat metabolism, impairing mitochondrial activity and making cancer cells deprived of energy. Efavirenz also inhibits cancer-initiating stem cells, promotes differentiation, and prevents recurrence. Additionally, efavirenz promotes oxidative damage bythe formation of superoxide in cancer cells. In addition to its anti-cancer properties, efavirenz has the advantage of being a well-established and relatively inexpensive medication with a favorable safety profile. If proven effective, efavirenz could offer a cost-effective therapeutic option, which is an intriguing direction that warrants further investigation.

TNFα Induces DNA and Histone Hypomethylation and Pulmonary Artery Smooth Muscle Cell Proliferation Partly via Excessive Superoxide Formation.

Objective: The level of tumor necrosis factor-α (TNF-α) is upregulated during the development of pulmonary vascular remodeling and pulmonary hypertension. A hallmark of pulmonary arterial (PA) remodeling is the excessive proliferation of PA smooth muscle cells (PASMCs). The purpose of this study is to investigate whether TNF-α induces PASMC proliferation and explore the potential mechanisms. Methods: PASMCs were isolated from 8-week-old male Sprague-Dawley rats and treated with 0, 20, or 200 ng/mL TNF-α for 24 or 48 h. After treatment, cell number, superoxide production, histone acetylation, DNA methylation, and histone methylation were assessed. Results: TNF-α treatment increased NADPH oxidase activity, superoxide production, and cell numbers compared to untreated controls. TNF-α-induced PASMC proliferation was rescued by a superoxide dismutase mimetic tempol. TNF-α treatment did not affect histone acetylation at either dose but did significantly decrease DNA methylation. DNA methyltransferase 1 activity was unchanged by TNF-α treatment. Further investigation using QRT-RT-PCR revealed that GADD45-α, a potential mediator of DNA demethylation, was increased after TNF-α treatment. RNAi inhibition of GADD45-α alone increased DNA methylation. TNF-α impaired the epigenetic mechanism leading to DNA hypomethylation, which can be abolished by a superoxide scavenger tempol. TNF-α treatment also decreased H3-K4 methylation. TNF-α-induced PASMC proliferation may involve the H3-K4 demethylase enzyme, lysine-specific demethylase 1 (LSD1). Conclusions: TNF-α-induced PASMC proliferation may be partly associated with excessive superoxide formation and histone and DNA methylation.

Machine-Learning-Assisted Discovery of Mechanosynthesized Lead-Free Metal Halide Perovskites for the Oxidative Photocatalytic Cleavage of Alkenes.

Lead-free metal halide perovskites can potentially be air- and water-stable photocatalysts for organic synthesis, but there are limited studies on them for this application. Separately, machine learning (ML), a critical subfield of artificial intelligence, has played a pivotal role in identifying correlations and formulating predictions based on extensive datasets. Herein, an iterative workflow by incorporating high-throughput experimental data with ML to discover new lead-free metal halide perovskite photocatalysts for the aerobic oxidation of styrene is described. Through six rounds of ML optimization guided by SHapley Additive exPlanations (SHAP) analysis, BA2CsAg0.95Na0.05BiBr7 as a photocatalyst that afforded an 80% yield of benzoic acid under the standard conditions is identified, which is a 13-fold improvement compared to the 6% with when using Cs2AgBiBr6 as the initial photocatalyst benchmark that is started. BA2CsAg0.95Na0.05BiBr7 can tolerate various functional groups with 22 styrene derivatives, highlighting the generality of the photocatalytic properties demonstrated. Radical scavenging studies and density functional theory calculations revealed that the formation of the reactive oxygen species superoxide and singlet oxygen in the presence of BA2CsAg0.95Na0.05BiBr7 are critical for photocatalysis.

The effects of ecdysterone and enalapril on nitric oxide synthesis and the markers of oxidative stress in streptozotocin-induced diabetes in rats: a comparative study.

Cardiovascular functions in diabetes greatly depend on constitutive NOS (cNOS) activity. A comparative study of the effects of a steroid hormone ecdysterone and enalapril, an ACE inhibitor widely used to treat cardiac disorders on cNOS, inducible NOS (iNOS), xanthine oxidoreductase (XOR) activity, RNS, ROS, and lipid peroxidation in heart tissue in experimental diabetes was conducted. The rat model of diabetes was established by streptozotocin injection. NOS activity, NO2-, NO3-, uric acid, nitrosothiols, hydroperoxide, superoxide, and diene conjugate formation were studied spectrophotomerically. In diabetes, cNOS downregulation correlated with a dramatic fall of NO2- production and ~4.5-fold elevation of nitrosothiols, which agreed with a steep rise of iNOS activity, while NO3- remained close to control. Dramatic activation of XOR was observed, which correlated with the elevation of both superoxide production and nitrate reductase activity and resulted in strong lipid peroxidation. Ecdysterone and enalapril differently affected RNS metabolism. Ecdysterone moderately restored cNOS but strongly suppressed iNOS, which resulted in the reduction of NO3-, but full restoration of NO2- production. Enalapril better restored cNOS but less effectively suppressed iNOS, which promoted NO3- formation. Both drugs similarly inhibited XOR, which equally alleviated oxidative stress and lipid peroxidation. The synergistic action of iNOS and XOR was a plausible explanation for strong lipid peroxidation, abolished by the inhibition of iNOS and XOR by ecdysterone or enalapril. Complementary effects of ecdysterone and enalapril on cNOS, iNOS, and RNS are a promising basis for their combined use in the treatment of cardiovascular disorders caused by cNOS dysfunction in diabetes.

#944 Soluble uric acid inhibits neutrophil functions during infections in patients with kidney disease

Abstract Background and Aims Chronic kidney disease (CKD) is one of the most common diseases affecting 8-16% of the world population. Beside cardiovascular complications, infections including sepsis are the second most common cause of death in patients with acute kidney injury (AKI) and CKD. However, the underlying pathomechanisms that contribute to the secondary immunodeficiency related to kidney disease [1] are not well understood. Recent evidence suggests that CKD-related hyperuricemia characterised by elevated serum uric acid (UA) levels suppresses immune cell functions during sterile inflammation [2]. Whether this is also the case during host defense is subject of our current investigation. In this study, we hypothesized that soluble UA inhibits neutrophil effector functions and therefore contributes to the increased infection risk in patients with kidney disease. Method Blood neutrophils were isolated from healthy individuals as well as from patients with kidney diseases, and incubated ex vivo in the presence or absence of 10 mg/dl soluble UA prior to stimulation with bacterial peptides including LPS. Immune cell functions including cytoskeletal changes, immune cell activation, maturation, endo- and phagocytosis (pHrodo Dextran particles, IgG-FITC beads, pHrodo E. coli bioparticles), ROS production, and neutrophil extracellular trap (NET) formation were analysed and quantified using flow cytometry, fluorescence and colorimetric assays, and fluorescence microscopy. In addition, to verify our results we stimulated neutrophils from healthy individuals with sera from hyperuricemic CKD patients. Results Our results show for the first time that soluble UA significantly inhibits the ability of neutrophils to endocytose small particles and phagocytose beads in neutrophils from healthy individuals comparable to the inhibitory effect of Cytochalasin D, an inhibitor of endo- and phagocytosis. Interestingly, unlike neutrophils from AKI patients, neutrophils from CKD patients were significantly less able to phagocytose beads compared to healthy controls with and without stimulation. To mimic the uptake of pathogens more physiologically, pHrodo E. coli bioparticles were used. We found that soluble UA inhibited the phagocytosis of such bioparticles in neutrophils. In addition, our investigation into the formation of ROS showed that soluble UA inhibited specifically nitric oxide, peroxynitrite, hydroxyl radicals and hydrogen peroxide, but to a lower extent the formation of superoxides in neutrophils from healthy individuals, similar to the effectiveness of the radical scavenger N-acetylcysteine. These data were comparable with our cohort study of neutrophils from CKD patients. To examine the mechanism of reduced ROS production, we inhibited NADPH oxidase (DPI) and MPO (4-ABAH) in neutrophils and found that soluble UA has similar inhibitory effects on ROS production like DPI whereas 4-ABAH was more potent. This indicated that soluble UA modulates NADPH oxidase and ROS production, which subsequently resulted in reduced NET formation in neutrophils. Conclusion Our data identify soluble UA as potential immune regulator of the secondary immunodeficiency in patients with kidney disease by inhibiting the endo- and phagocytosis of particles, NADPH-mediated ROS production and NET formation in neutrophils, processes that are important to kill pathogens and fight an infection. Thus, specifically targeting UA with urate-lowering therapy might overcome the suppressed host defence against infection in patients with kidney disease.

Sphingosine is involved in PAPTP-induced death of pancreas cancer cells by interfering with mitochondrial functions

Pancreas ductal adenocarcinoma belongs to the most common cancers, but also to the tumors with the poorest prognosis. Here, we pharmacologically targeted a mitochondrial potassium channel, namely mitochondrial Kv1.3, and investigated the role of sphingolipids and mutated Kirsten Rat Sarcoma Virus (KRAS) in Kv1.3-mediated cell death. We demonstrate that inhibition of Kv1.3 using the Kv1.3-inhibitor PAPTP results in an increase of sphingosine and superoxide in membranes and/or membranes associated with mitochondria, which is enhanced by KRAS mutation. The effect of PAPTP on sphingosine and mitochondrial superoxide formation as well as cell death is prevented by sh-RNA-mediated downregulation of Kv1.3. Induction of sphingosine in human pancreas cancer cells by PAPTP is mediated by activation of sphingosine-1-phosphate phosphatase and prevented by an inhibitor of sphingosine-1-phosphate phosphatase. A rapid depolarization of isolated mitochondria is triggered by binding of sphingosine to cardiolipin, which is neutralized by addition of exogenous cardiolipin. The significance of these findings is indicated by treatment of mutated KRAS-harboring metastasized pancreas cancer with PAPTP in combination with ABC294640, a blocker of sphingosine kinases. This treatment results in increased formation of sphingosine and death of pancreas cancer cells in vitro and, most importantly, prolongs in vivo survival of mice challenged with metastatic pancreas cancer.Key messagesPancreatic ductal adenocarcinoma (PDAC) is a common tumor with poor prognosis.The mitochondrial Kv1.3 ion channel blocker induced mitochondrial sphingosine.Sphingosine binds to cardiolipin thereby mediating mitochondrial depolarization.Sphingosine is formed by a PAPTP-mediated activation of S1P-Phosphatase.Inhibition of sphingosine-consumption amplifies PAPTP effects on PDAC in vivo.

One pot synthesis of multi-functional B doped g-C3N4-praseodymium oxide nanocomposites for colorimetric detection of Hg2+ ion and solar photocatalytic removal of toxic water pollutants

A novel praseodymium oxide-boron co-doped graphitic carbon nitride composite was synthesized via one-step solid-state thermal condensation of urea, orthoboric acid and praseodymium nitrate precursors. The prepared composites were characterized by various methods. All the prepared composites demonstrated multi-functional activities towards peroxidase-mimetic based colorimetric detection of Hg2+ ions and superior photocatalytic efficiency towards photodegradation of textile colorants, photoreduction of hexavalent chromium and nitro aromatics like para-nitro phenol (PNP) and para-nitro aniline (PNA). The superior photocatalytic activity can be attributed to the formation of type II heterojunction which facilitates charge separation and increases the lifetime of photogenerated charge pairs. As evident from the scavenger studies, these charge pairs are involved in the formation of superoxide and hydroxyl radicals. The superior activity of the optimum composite can be attributed to the porous flaky morphology, decreased optical band gap, heterojunction mediated charge separation, and praseodymium oxide's conductive nature. A linear range of about 0.25–800 nM of Hg2+ ions can be detected with a limit of detection (LOD) of 42.4 nM using the colorimetric strategy. The as-synthesized composite is thus a unique, efficient, economically viable, and excellent candidate for detecting and degrading various hazardous water pollutants.

Role of reactive carbonyls and superoxide radicals in protein damage by cigarette smoke extracts: Comparison of Heat-not-Burn e-cigarettes to conventional cigarettes

Oxidative protein damage involving carbonylation of respiratory tract proteins typically accompanies exposure to tobacco smoke. Such damage can arise via multiple mechanisms, including direct amino acid oxidation by reactive oxygen species or protein adduction by electrophilic aldehydes. This study investigated the relative importance of these pathways during exposure of a model protein to fresh cigarette emission extracts. Briefly, protein carbonyl adducts were estimated in bovine serum albumin following incubation in buffered solutions with whole cigarette emissions extracts prepared from either a single 1R6F research cigarette or a single “Heat-not-Burn” e-cigarette. Although both extracts caused concentration-dependent protein carbonylation, conventional cigarette extracts produced higher adduct yields than e-cigarette extracts. Superoxide radical generation by conventional and e-cigarette emissions was assessed by monitoring nitro blue tetrazolium reduction and was considerably lower in extracts made from “Heat-Not-Burn” e-cigarettes. The superoxide dismutase/catalase mimic EUK-134 strongly suppressed radical production by whole smoke extracts from conventional cigarettes, however, it did not diminish protein carbonyl adduction when incubating smoke extracts with the model protein. In contrast, edaravone, a neuroprotective drug with strong carbonyl-trapping properties, strongly suppressed protein damage without inhibiting superoxide formation. Although these findings require extension to appropriate cell-based and in vivo systems, they suggest reactive aldehydes in tobacco smoke make greater contributions to oxidative protein damage than smoke phase radicals.

Oxidative Stress Induced by Cortisol in Human Platelets.

Hypercortisolism is known to affect platelet function. However, few studies have approached the effect of exogenous cortisol on human platelets, and the results obtained are conflicting and unconvincing. In this study, the effect of exogenous cortisol on several parameters indicative of oxidative status in human platelets has been analysed. We have found that cortisol stimulates ROS production, superoxide anion formation, and lipid peroxidation, with these parameters being in strict correlation. In addition, cortisol decreases GSH and membrane SH-group content, evidencing that the hormone potentiates oxidative stress, depleting platelet antioxidant defence. The involvement of src, syk, PI3K, and AKT enzymes in oxidative mechanisms induced by cortisol is shown. The main sources of ROS in cells can include uncontrolled increase of NADPH oxidase activity and uncoupled aerobic respiration during oxidative phosphorylation. Both mechanisms seem to be involved in ROS formation induced by cortisol, as the NADPH oxidase 1 inhibitor 2(trifluoromethyl)phenothiazine, and rotenone and antimycin A, complex I and III inhibitor, respectively, significantly reduce oxidative stress. On the contrary, the NADPH oxidase inhibitor gp91ds-tat, malate and NaCN, complex II and IV inhibitor, respectively, have a minor effect. It is likely that, in human platelets, oxidative stress induced by cortisol can be associated with venous and arterial thrombosis, greatly contributing to cardiovascular diseases.

Carbon Dot-Mediated Photodynamic Treatment Improves the Quality Attributes of Post-Harvest Goji Berries (Lycium barbarum L.) via Regulating the Antioxidant System.

Carbon dots (CDs) have been proposed as photosensitizers in photodynamic treatment (PDT), owing to their excellent biological attributes and budding fruit preservation applications. In the present study, CDs (4.66 nm) were synthesized for photodynamic treatment to improve the quality attributes in post-harvest goji berries. The prepared CDs extended the storage time of the post-harvest goji berries by 9 d. The CD-mediated PDT postponed the hardness and decay index loss, reduced the formation of malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion (O2•-) significantly, and delayed the loss of vital nutrients like the total protein, phenols, and flavonoids. The CD-mediated PDT improved the catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), phenylalanine ammonia-lyase (PAL), glutathione reductase (GR), and superoxide dismutase (SOD) activities, but did not improve polyphenol oxidase (PPO) activity. In addition, The CD-mediated PDT induced the accumulation of ascorbic acid (ASA) and glutathione (GSH). Overall, a CD-mediated PDT could extend the storage time and augment the quality attributes in post-harvest fresh goji berries by regulating the antioxidant system.

Recyclable and Stable Porphyrin-Based Self-Assemblies by Electrostatic Force for Efficient Photocatalytic Organic Transformation.

Development of efficient, stable, and recyclable photocatalysts for organic synthesis is vital for transformation of traditional thermal organic chemistry into green sustainable organic chemistry. In this work, the study reports an electrostatic approach to assemble meso-tetra (4-sulfonate phenyl) porphyrin (TPPS)tetra (4-sulfonate phenyl) porphyrin (TPPS) as a donor and benzyl viologen (BV) as an acceptor into stable and recyclable photocatalyst for an efficient organic transformation reaction - aryl sulfide oxidation. By use of the electrostatic TPPS-BV photocatalysts, 0.1mmol aryl sulfide with electron-donating group can be completely transformed into aryl sulfoxide in 60min without overoxidation into sulfone, rendering near 100% yield and selectivity. The photocatalyst can be recycled up to 95% when 10mg amount is used. Mechanistic study reveals that efficient charge separation between TPPS and BV results in sufficient formation of superoxide which further reacts with the oxidized sulfide by the photocatalyst to produce the sulfoxide. This mechanistic pathway differs significantly from the previously proposed singlet oxygen-dominated process in homogeneous TPPS photocatalysis.