Oxygen Species Research Articles

Loss of Brain Norepinephrine Elicits Neuroinflammation-Mediated Oxidative Injury and Selective Caudo-Rostral Neurodegeneration.

Environmental toxicant exposure has been strongly implicated in the pathogenesis of Parkinson's disease (PD). Clinical manifestations of non-motor and motor symptoms in PD stem from decades of progressive neurodegeneration selectively afflicting discrete neuronal populations along a caudo-rostral axis. However, recapitulating this spatiotemporal neurodegenerative pattern in rodents has been unsuccessful. The purpose of this study was to generate such animal PD models and delineate mechanism underlying the ascending neurodegeneration. Neuroinflammation, oxidative stress, and neuronal death in mice brains were measured at different times following a single systemic injection of lipopolysaccharide (LPS). We demonstrate that LPS produced an ascending neurodegeneration that temporally afflicted neurons initially in the locus coeruleus (LC), followed by substantia nigra, and lastly the primary motor cortex and hippocampus. To test the hypothesis that LPS-elicited early loss of noradrenergic LC neurons may underlie this ascending pattern, we used a neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) to deplete brain norepinephrine. DSP-4 injection resulted in a time-dependent ascending degenerative pattern similar to that generated by the LPS model. Mechanistic studies revealed that increase in nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-2 (NOX2)-dependent superoxide/reactive oxygen species (ROS) production plays a key role in both LPS- and DSP-4-elicited neurotoxicity. We found that toxin-elicited chronic neuroinflammation, oxidative neuronal injuries, and neurodegeneration were greatly suppressed in mice deficient in NOX2 gene or treated with NOX2-specific inhibitor. Our studies document the first rodent PD model recapturing the ascending neurodegenerative pattern of PD patients and provide convincing evidence that the loss of brain norepinephrine is critical in initiating and maintaining chronic neuroinflammation and the discrete neurodegeneration in PD.

REACTIVE OXYGEN AND NITROGEN SPECIES ROLE IN EXPERIMENTAL PERIODONTITIS DEVELOPMENT

Introduction. Activation of lipid peroxidation is one of the trigger mechanisms of periodontium injury, which is primary caused by cellular damage. Reactive oxygen and nitrogen species (RONS) are able to cause damage to a cell as well as final products of lipid peroxidation, including unsaturated aldehydes and other metabolites. Objective. The aim of the research was to determine the role of RONS and accumulation of lipid peroxidation derivatives in initial development and formation of chronical inflammatory process in periodontium. Methods. Experimental periodontitis was modeled in animals by injection of complex mixtures of microorganisms diluted in egg protein into periodontal tissues. The results of biochemical studies of free radical processes activity in blood serum were evaluated by content of diene, triene conjugates, TBA-active products and total quantity of metabolites of nitric oxide (NO2–+NO3–), which were determined on the 7th, 14th and 30th days of the experiment. Results. Generation of active forms of oxygen is more influential, providing longevity of inflammatory process. This pays attention to typical dynamics of changes in active processes of lipid peroxidation in the development and course of experimental periodontitis. The study of inflammatory process with a bacterial-immune component in the rats’ periodontal complex proved accumulation of lipid peroxidation and nitric oxide metabolites in blood serum.Conclusions. The preservation of increased lipid peroxidation and nitric oxide metabolites in blood serum of the experimental animals with acute periodontitis conduce enhance of alteration and delayed healing that result in its sequel into chronical periodontitis.

Interaction of Neodymium Containing Chloride Melts with Oxygen Species

Alkali chloride based melts can be employed as working media in spent nuclear fuels pyrochemical reprocessing. Oxygen is on of common impurities in technology and oxygen species can seriously influence speciation of metals in molten electrolytes. From the other hand, one of the possible ways of separating uranium from rare earth fission products by selective precipitation of uranium oxide. The present work was aimed at studying reactions taking place in chloride melts containing neodymium (III) and uranium (III and IV) ions upon addition of oxygen species. In particular, reactions with oxygen and oxide ions (introduced in form of lithium oxide) were considered. Thermodynamic modeling of possible reactions was first performed to estimate the possibility of separating uranium from rare earths. The experiments were then conducted in the melts based on LiCl–KCl eutectic, NaCl–KCl equimolar mixture and individual LiCl at 550 oC (for LiCl–KCl) and 750 oC for all the melts). Reaction of the melts containing NdCl3, UCl3 or UCl4 with Li2O (at various O2– to Nd3+ (U3+, U4+) mole ratios) and with O2 was investigated. High temperature electronic absorption spectroscopy was employed to determine the kinetics of the reactions taking place. Phase composition of the solid phases was characterized by X-ray powder diffraction analysis. Size of the particles in the precipitates formed at various conditions was also determined to assess the feasibility of subsequent separation of the solids from the technological melts.

Interaction of Neodymium Containing Chloride Melts with Oxygen Species

Reaction of lithium oxide with neodymium chloride was studied in LiCl, LiCl–KCl and NaCl–KCl based melts at various O2– : Nd3+ mole ratios. The effect of the experimental conditions on the degree and rate of neodymium precipitation, phase composition of the solid reaction products was investigated. Size of the particles in the precipitates formed at various conditions was determined to assess the feasibility of subsequent separation of the solids from the technological melts.

(Invited) Platinum Single-Atom Catalysts for Electrochemical Reactions

As a catalyst, single-atom platinum may provide an ideal structure for platinum minimization. The single-atom catalyst of platinum supported on titanium nitride nanoparticles were successfully prepared with an aid of chlorine ligands. Unlike platinum nanoparticles, the single-atom active sites predominantly produced hydrogen peroxide in the electrochemical oxygen reduction with the highest mass activity reported so far. The electrocatalytic oxidation of small organic molecules, such as formic acid and methanol, also exhibited unique selectivity on the single-atom platinum catalyst. A lack of platinum ensemble sites changed the reaction pathway for oxygen reduction reaction toward two electrons pathway and formic acid oxidation toward direct dehydrogenation, and also induced no activity for methanol oxidation. The single-atom platinum showed high mass activity and unique selectivity for the electrochemical reactions. Additionally, the role of the support may have a significant impact on the catalytic properties similar to that of the ligand molecules in homogeneous catalysts. The support effect was demonstrated by preparing the single-atom platinum catalyst on two different supports, titanium carbide and titanium nitride. The formation of single-atom Pt was confirmed by STEM, EXAFS, and in-situ IR spectroscopy. Pt1/TiC showed higher activity, selectivity, and stability for electrochemical H2O2 production than Pt1/TiN. Density functional theory calculation presented that oxygen species have strong affinity into Pt1/TiN possibly acting as surface poisoning species, and Pt1/TiC preserves oxygen-oxygen bond more with higher selectivity towards H2O2 production. The support in single-atom catalysts actively participates in the surface reaction, not just acting as anchoring sites for single-atoms. The Pt single-atom electrocatalyst was also prepared on Sb-doped SnO2 (Pt1/ATO), and it was used to fabricate direct formic acid fuel cell.

Oxidative stress and neurodegeneration: the involvement of iron

Many evidences indicate that oxidative stress plays a significant role in a variety of human disease states, including neurodegenerative diseases. Iron is an essential metal for almost all living organisms due to its involvement in a large number of iron-containing proteins and enzymes, though it could be also toxic. Actually, free iron excess generates oxidative stress, particularly in brain, where anti-oxidative defences are relatively low. Its accumulation in specific regions is associated with pathogenesis in a variety of neurodegenerative diseases (i.e., Parkinson's disease, Alzheimer's disease, Huntington's chorea, Amyotrophic Lateral Sclerosis and Neurodegeneration with Brain Iron Accumulation). Anyway, the extent of toxicity is dictated, in part, by the localization of the iron complex within the cell (cytosolic, lysosomal and mitochondrial), its biochemical form, i.e., ferritin or hemosiderin, as well as the ability of the cell to prevent the generation and propagation of free radical by the wide range of antioxidants and cytoprotective enzymes in the cell. Particularly, ferrous iron can act as a catalyst in the Fenton reaction that potentiates oxygen toxicity by generating a wide range of free radical species, including hydroxyl radicals (·OH). The observation that patients with neurodegenerative diseases show a dramatic increase in their brain iron content, correlated with the production of reactive oxigen species in these areas of the brain, conceivably suggests that disturbances in brain iron homeostasis may contribute to the pathogenesis of these disorders. The aim of this review is to describe the chemical features of iron in human beings and iron induced toxicity in neurodegenerative diseases. Furthermore, the attention is focused on metal chelating drugs therapeutic strategies.

Silencing of PINK1 represses cell growth, migration and induces apoptosis of lung cancer cells

PTEN induced putative kinase 1 (PINK1) has been found to be up-regulated, which promotes the proliferation and chemoresistance in lung cancer. Nevertheless, the role and detailed mechnisms of PINK1 in lung cancer have not been fully understood, which need to be further clarified. In this study, the resluts showed that silencing of PINK1 inhibited proliferation and blocked cell cycle of lung cancer cells. Furthermore, the apoptosis rate was enhanced by PINK1 suppression, as evidenced by increased protein levels of Bax, cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase (PARP), and decreased level of Bcl-2. The migration and invasion abilities were also restrained by PINK1 silencing. Silencing of PINK1 also resulted in oxygen species (ROS) overproduction and decreased mitochondrial membrane potential. Finally, suppression of PINK1 repressed the growth of xenograft tumor and induced apoptosis in tumor tissues in vivo. This study might lead to PINK1 kinase as a novel therapeutic target for lung cancer treatment.

Heterogeneously Catalyzed Aerobic Oxidation of Sulfides with a BaRuO3 Nanoperovskite.

A rhombohedral BaRuO3 nanoperovskite, which was synthesized by the sol-gel method using malic acid, could act as an efficient heterogeneous catalyst for the selective oxidation of various aromatic and aliphatic sulfides with molecular oxygen as the sole oxidant. BaRuO3 showed much higher catalytic activities than other catalysts, including ruthenium-based perovskite oxides, under mild reaction conditions. The catalyst could be recovered by simple filtration and reused several times without obvious loss of its high catalytic performance. The catalyst effect, 18O-labeling experiments, and kinetic and mechanistic studies showed that substrate oxidation proceeds with oxygen species caused by the solid. The crystal structure of ruthenium-based oxides is crucial to control the nature of the oxygen atoms and significantly affects their oxygen transfer reactivity. Density functional theory calculations revealed that the face-sharing octahedra in BaRuO3 likely are possible active sites in the present oxidation in sharp contrast to the corner-sharing octahedra in SrRuO3, CaRuO3, and RuO2. The superior oxygen transfer ability of BaRuO3 is also applicable to the quantitative conversion of dibenzothiophene into the corresponding sulfone and gram-scale oxidation of 4-methoxy thioanisole, in which 1.20 g (71% yield) of the analytically pure sulfoxide could be isolated.

Heterogeneous reaction mechanism of elemental mercury oxidation by oxygen species over MnO2 catalyst

MnO2-based catalysts have attracted great attention in the field of elemental mercury (Hg0) catalytic oxidation because of their superior catalytic performance and wide temperature window. Quantum chemistry calculations based on density functional theory (DFT) combined with periodic slab models were carried out to investigate the heterogeneous mechanism of Hg0 oxidation by oxygen species (gas-phase O2, chemisorbed oxygen, and lattice oxygen) on MnO2 surface. The results indicate that Hg0 and HgO are chemically adsorbed on MnO2 surface with the adsorption energies of −69.50 and −226.48 kJ/mol, respectively. The adsorption of O2 on MnO2 surface belongs to chemisorption. O2 can decompose on MnO2 surface with an energy barrier of 97.46 kJ/mol to produce two atomic adsorbed oxygen. The perpendicular adsorbed O2 and dissociative adsorbed O2 are more favorable for Hg0 catalytic oxidation than lattice oxygen, and perpendicular adsorbed O2 is the most active oxygen for Hg0 oxidation. The reaction pathway of Hg0 oxidation by perpendicular adsorbed O2 includes three reaction steps: Hg0 → Hg(ads) → HgO(ads) → HgO. The third step (HgO(ads) → HgO) is endothermic by 168.17 kJ/mol with an energy barrier of 179.48 kJ/mol, and it is the rate-limiting step of the whole Hg0 oxidation reaction.

Abstract 2415: HEY1 counteracts hypoxia-induced oxidative stress via transcriptionally repressing PINK1 in hepatocellular carcinoma

Abstract Background and Objective: Excessive accumulation of oxidative stress/reactive oxygen species (ROS) can be harmful to cancer cells. Hypoxia or O2 deprivation, which is commonly found in hepatocellular carcinoma (HCC), is a crucial factor that contributes to elevated ROS level in HCC cells as hypoxia causes inefficient transfer of electrons in the mitochondria. To survive, HCC cells need to devise strategies to counteract and balance hypoxia-induced oxidative stress. While it is known that hypoxia inducible factors (HIFs) are essential to metabolic reprogramming in HCC cells under hypoxia, there are significant gaps in knowledge about underlying mechanisms and transcriptional targets of HIFs. Experimental Procedures: Gene profiling of HCC cell lines (exposed to 20% and 1% O2) was analyzed by transcriptome sequencing to identify novel candidate responsible for counteracting hypoxia-induced oxidative stress. ShRNA-mediated gene silencing and gene activation by CRISPR-dCas9 system were used to modify transcriptional expression of HEY1 for different functional assays. Transmission electron microscopy was used to visualize the mitochondrial structure. Orthotopic and subcutaneous HCC implantation models were used to evaluate the role of HEY1 in HCC progression. Transcriptome sequencing and ChIP assay were performed to identify novel transcriptional targets of HEY1. Results: We showed that transcriptional repressor HEY1 was induced under hypoxia and directly regulated by HIF-1α. Overexpression of HEY1 was associated with poor overall survival in HCC patients. Importantly, we identified PINK1 as a novel repression target of HEY1. PINK1 is known to protect cells against mitochondrial dysfunction. We demonstrated that HEY1 actively repressed PINK1 and downregulation of PINK1 led to loss of mitochondrial mass and impaired mitochondrial cristae formation, subsequently decreasing intracellular ROS level. Downregulation of PINK also associated with poor overall survival and decrease-free in HCC patients. Genetic ablation of HEY1 in HCC cells profoundly reduced tumor growth and lung metastasis while genetic ablation of PINK1 in HCC cells reversely promoted HCC growth. Strikingly, HEY1 and PINK1 expressions reversely correlated in human HCC tissues. Conclusion: This study unprecedentedly identifies an upstream regulatory mechanism of PINK1, which controls the oxidative stress in HCC cells. It also reveals a novel molecular mechanism by which ablation of HEY1 leads to elevation of oxidative stress, making HCC cells more vulnerable. Targeting HEY1 represents an attractive therapeutic approach against HCC. Citation Format: David Kung-Chun Chiu, Iris Ming-Jing Xu, Robin Kit-Ho Lai, Aki Pui-Wah Tse, Dicky Cheuk-Ting Law, Vincent Wai-Hin Yuen, Larry Lai Wei, Hui-Yu Koh, Chun-Ming Wong, Irene Oi-Lin Ng, Carmen Chak-Lui Wong. HEY1 counteracts hypoxia-induced oxidative stress via transcriptionally repressing PINK1 in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2415.

Abstract 2832: Novel therapy for oral squamous cell carcinoma using non-thermal atmospheric pressure biocompatible plasma activated water

Abstract Non-thermal atmospheric pressure biocompatible plasma (NBP) has been reported that was possible to induce apoptosis on various cancer cells including lung, ovary, brain, liver, breast, and pancreas cancer. We developed NBP device, which has been reported to have cytotoxicity on cancer cells induce DNA damage and apoptosis. In particular,reactive oxygen and/or nitrogen species (RONS) were generated by plasma device to give oxidative stress and depolarization of mitochondria membrane in cancer cells. Now we developed a microwave plasma jet system, which could generate nitric oxide (NO) and NO-plasma activated water (NO-PAW). Previously, we found that NO-PAW could induce apoptosis and accumulate ROS in human cervical cancer cells (1). In this study we investigated the efficacy of NO-PAW on oral squamous cancer cells (OSCC), a common malignant tumor of the head and neck (2, 3). We observed that cytotoxicity and apoptotic stimulation by NO-PAW were significantly increased. Also, expression level of caspase and PARP in OSCC was increased after treatment by NO-PAW. However, the apoptosis effect was not observed in human gingival fibroblasts (as normal human cells). Additionally, we found that NO-PAW inhibited cancer progression in vivo. In conclusion, NO-PAW could suppress the progress of OSCC by inducing cell apoptosis. This indicated NO-PAW as a novel tool for OSCC therapy, and probably will be also effective for other oral cancer. Acknowledgments: This work was supported by the Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea (NRF- 2016K1A4A3914113) funded by the Ministry of Science, ICT, and Future Planning (MSIP) of the Korean Government for EH. Choi, I. Han. The Korea government, and the Basic Science Research Program through the NRF of Korea, funded by the Ministry of Education (NRF-2015R1C1A2A01054137) for I. Han.

Three-way catalysis with supported gold catalysts: Poisoning effects of hydrocarbons

Poisoning phenomena recently observed during the conversion of three-way catalysis model feed (CO, NO propene, O2, without or with water) over supported Au catalysts [V. Ulrich et al., Applied Catalysis B 203 (2017) 572] were investigated by reaction studies (replacing propene by propane in model feed, study of CO oxidation without and with relevant additional components), by temperature-programmed oxidation of deposits (TG, TPO), by studying self-regeneration phenomena and by DRIFTS of CO adsorption and co-adsorption of CO and propene under different conditions. During CO oxidation in the presence of other components, two different poisoning phenomena were observed. In the presence of propane, propene, and/or NO, CO oxidation was significantly inhibited below 370 K over Au on Al2O3 or on La-stabilized Al2O3, but not on Au/CeZrOx where activity was relatively low anywhere. DRIFTS data on (co-)adsorption of CO and propene suggest that this poisoning is not merely a result of site blocking by the coadsorbate, but that electron transfer from the co-adsorbates towards the active sites, which are assumed to be at the perimeter of positively charged Au clusters with the support, might have additionally quenched the reaction. At higher temperatures, a different poisoning mechanism operates in propene-containing mixtures. From studies by TPO, TG, and DRIFTS, we conclude the formation of carbonaceous residues, which do not block, however, CO adsorption sites but the support surface around Au clusters instead. While this inhibits CO oxidation involving active support oxygen, the same oxygen species might combust the deposits at higher temperatures. This results in self-regeneration phenomena depending on the redox activity of the support, the temperature and the propene content in the feed. In transient experiments, it was observed that NO is most favorably reduced by intermediates of coke formation from propene. Under stationary conditions, however, NO reduction, mostly by CO, remains insufficient.

Modification of soybean and lupine sprouting conditions: influence on yield, ROS generation, and antioxidative systems

Formation of free radicals’ and antioxidants’ biosynthesis during seeds sprouting strongly depends on plant growth conditions, especially while sprouts are fortified in iron. The influence of watering with FeSO4 solution on soybean and lupine sprouting, yield of iron accumulated in plant tissue, as well as free radical (reactive oxygen and nitrogen species) synthesis and antioxidant activity (capacity) were the objective of this study. Optimal iron accumulation and biomass efficiency were obtained for 3 day watering with water, followed by abiotic stress application (Fe2+ ions). For lupine sprouts, maximal radical formation (up to ~ 5.7 a.u.) took place on the fifth day of culturing in these conditions, while, for soybean sprouts, continuous increase in their activity was observed until the seventh day (up to ~ 5.8 a.u.). Total antioxidant activity in lupine sprouts increased definitely, even more than three times during 7 days of lupine growing, but, for soybean, it was almost steady. The same trend was observed in phenolic compounds and flavonoids contents. For soybean sprouts, these antioxidants were almost steady, while, for lupine sprouts in these conditions, the intensive synthesis of these antioxidants was observed. In response to high iron content applied from the fourth day in the cultivation media, lupine sprouts synthesize low molecular antioxidants effectively. For soybean sprouts, another mechanism of defense against oxidative stress should be expected.

Anti-angiogenic treatment (Bevacizumab) improves the responsiveness of photodynamic therapy in colorectal cancer.

Photodynamic therapy (PDT) is a treatment utilizing the combined action of photosensitizers and light for the treatment of various cancers. The mechanisms for tumor destruction after PDT include direct tumor cell kill by singlet oxygen species (OS), indirect cell kill via vascular damage, and an elicited immune response. However, it has been reported that many cellular activators, including vascular endothelial growth factor (VEGF), are produced by tumor cells after PDT. In this study, we demonstrate that meta-tetra(hydroxyphenyl) chlorin (mTHPC)-based photodynamic therapy combined with bevacizumab (Avastin™), an anti-VEGF neutralizing monoclonal antibody that blocks the binding of VEGF to its receptor, can enhance the effectiveness of each treatment modality. We evaluated the efficacy of bevacizumab-based anti-angiogenesis in combination with PDT as well as the resulting VEGF levels and microvessel density (MVD) in a mouse model of human colon cancer. Enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry (IHC) were performed to assess VEGF concentrations and microvessel density in the various treatment groups, and confocal imaging and high performance liquid chromatography (HPLC) analyses were used to measure the distribution and concentration of mTHPC in tumors. Our results demonstrate that combination of PDT followed by bevacizumab significantly elicits a greater tumor response whereas bevacizumab treatment prior to PDT led to a reduced tumor response. Immunostaining and ELISA analyses revealed a lower expression of VEGF in tumors treated with combination therapy of PDT followed by bevacizumab. However, bevacizumab treatment decreased the accumulation of mTHPC in tumors 24 h after administration, which complemented the results of decreased anti-tumor efficacy of bevacizumab followed by PDT.

Multi-functional thin film coatings formed via nanogrinding

Nanostructured thin films of silicon and titanium disilicide are produced using a nanoscale or colloidal grinding technique based on planetary ball milling in solution. High-purity micron-scale powders are dispersed in solvent and milled at 200–1000 rpm for 10 min to several hours. The resulting films are cast from solution on planar and curved surfaces with individual particle sizes reaching below 100 nm after approximately 45 min of grinding at 400 rpm. X-ray analysis and Raman spectroscopy shows that the crystalline structure of the starting materials is maintained following grinding, with carbon and oxygen species appearing, as grinding time is increased likely the result of surface reactions occurring during the milling process. Surface wettability measurements show the contact angle of nanostructured Si, and TiSi2 films can be tuned from approximately 10 to over 100 degrees resulting in hydrophobic or hydrophilic surfaces depending upon grinding time, speed and solvent. Two-terminal electronic transport data of the thin films show that electrical resistivity can be tuned by more than one order of magnitude depending on grinding conditions. In general, coatings created via nanogrinding possess unique and varied structural, surface, electrical and optical properties, which can be used for advanced multi-functional materials and devices.

Protective Effects of 2-Amino-5,6-dihydro-4H-1,3-thiazine and Its Derivative against Radiation-Induced Hematopoietic and Intestinal Injury in Mice.

Ionizing radiation (IR) acts as an external stimulating factor, when it acts on the body, it will activate NF-B and cause the up-regulation of inducible nitric oxide synthase (iNOS) and induce a large amount of nitric oxide (NO) production. NO and other reactive nitrogen and oxygen species (RNS and ROS) can cause damage to biological molecules and affect their physiological functions. Our study investigated the protective role of 2-amino-5,6-dihydro-4H-1,3-thiazine hydrobromide (2-ADT) and 2-acetylamino-5,6-dihydro-4H-1,3-thiazine hydrobromide (2-AADT), two nitric oxide synthase inhibitors, against radiation-induced hematopoietic and intestinal injury in mice. Pretreatment with 2-ADT and 2-AADT improved the survival of mice exposed to a lethal dose of radiation, especially, the survival rate of the 2-ADT 20 mg/kg group was significantly higher than that of the vehicle group (p < 0.001). Our findings indicated that the radioprotective actions of 2-ADT and 2-AADT are achieved via accelerating hematopoietic system recovery, decreasing oxidative and nitrosative stress by enhancing the antioxidant defense system and reducing NO as well as peroxynitrite (ONOO) content, and mitigating the radiation-induced DNA damage evaluated by comet assay. These results suggest that 2-ADT and 2-AADT may have great application potential in ameliorating the damages of radiotherapy.

Effects of δ-tocotrienol on ochratoxin A-induced nephrotoxicity in rats.

Ochratoxin A (OTA), is a natural contaminant of the food chain worldwide involved in the development of different type of cancers in animals and humans. Several studies suggested that oxidative damage might contribute to increase the cytotoxicity and carcinogenicity capabilities of OTA. The aim of this study was to evaluate the possible protective effect of δ-tocotrienol (Delta), a natural form of vitamin E, against OTA-induced nephrotoxicity. Male Sprague-Dawley rats were treated with OTA and/or Delta by gavage for 14 days. Our results shown that OTA treatment induced the increase of reactive oxigen species production correlated to a strong reduction of Glomerular Filtration Rate (GFR) and absoluted fluid reabsorption (Jv) with conseguent significant increase in blood pressure. Consistent, we noted in the kidney of rats treated with OTA, an increase in malondialdheyde and dihydroethidium production and a reduction of the activity of the catalase, superoxide dismutase, and glutathione peroxidase. Conversly, in the rat group subjected to the concomitant treatment OTA plus Delta, we observed the restored effect, compared the OTA treatment group, on blood pressure, GFR, Jv, and all activities of renal antioxidant enzymes. Finally, as far as concern the tissue damage induced by OTA and measured evaluating fibronectin protein levels, we observed that in OTA plus Delta group this effect is not restored. Our findings releval that a mechanism underlying the renal toxicity induced by OTA is the oxidative stress and provide a new rationale to use a Delta in order to protect, at least in part, against OTA-induced nephrotoxicity.

In-situ analysis of catalytic pyrolysis of Baiyinhua coal with pyrolysis time-of-flight mass spectrometry

Baiyinhua coal was subjected to catalytic pyrolysis over HZSM-5 and Ni-modified HZSM-5 (Ni/HZSM-5) with a novel pyrolysis time-of-flight mass spectrometers (Py-TOF-MS) equipped with vacuum ultraviolet photoionization (VUVPI). The soft ionization of VUVPI allowed the detection of volatile organic compounds. The effect of HZSM-5 and Ni/HZSM-5 on distribution of coal pyrolysis products was online investigated. The coal pyrolysis products including alkanes, phenols, aromatics and sulfur containing compounds (H2S and CH3SH) were detected. In the presence of HZSM-5 and Ni/HZSM-5, the products from coal pyrolysis have higher content of substituted benzene and alkenes and lower content of phenols in comparison with that without catalyst. The catalysts promote the conversion of phenols products to aromatic hydrocarbons via dehydroxylation reaction. Ni/HZSM-5 exhibits better catalytic performance for generating products with higher aromatic content and less oxygen species than HZSM-5 alone. Temperature-evolved profiles of pyrolysis products were also measured. It was found that the peak temperature of alkenes and substituted benzene of catalytic pyrolysis shifts to lower temperature region while that of dihydroxybenzenes moves to higher temperature. This work demonstrates the good performance of Py-TOF-MS for the online study of the coal catalytic pyrolysis process.

Conversion of CO2 in a packed-bed dielectric barrier discharge reactor

The conversion of CO2 into CO and O2 in a quartz cylindrical packed-bed dielectric reactor has been studied using CO2 and Ar gas mixtures at atmospheric pressure and near ambient temperature with quartz wool, γ-Al2O3, and TiO2 packing. The highest energy efficiencies and conversion rates were observed with TiO2 packing in 20% CO2 in Ar: 30% conversion with 2.9% energy efficiency, and 17.5% conversion with 5.0% energy efficiency. Both γ-Al2O3 and quartz wool also showed an enhancement in conversion over an unpacked reactor. The percentage of CO2 to Ar in the range of 20%–60% is shown to have only a minor effect on reactor performance. Conversion as a function of power input and flow rate is studied in detail for γ-Al2O3 and TiO2 packing with similar particle sizes. In both cases, simple chemical kinetic models show that the CO production rate is nearly equal for both materials, while reverse reaction rates to CO2 are doubled for γ-Al2O3 compared to TiO2. From detailed charge–voltage (Q-V) analysis of all four reactor configurations, it is revealed that the electric field at which discharging occurs is higher for both γ-Al2O3 and TiO2 as compared to the empty or quartz wool filled reactors. Comparing kinetic model results with the electrical Q-V analysis, it appears likely that the higher and similar magnitude electric fields occurring with γ-Al2O3 and TiO2 are directly responsible for the increased CO production rates via increased electron energies in the discharge. The higher reverse reaction rates for γ-Al2O3, and its subsequent poorer performance compared to TiO2, can be attributed to a significantly higher effective surface area, which increases undesirable surface reactions between CO and oxygen species.

Steam catalytic cracking of coal tar over iron‐containing mixed metal oxides

AbstractSteam catalytic cracking is deemed as a promising method for the catalytic cracking of coal tar. In this study, a serial of iron‐containing mixed metal oxides including ceria, zirconia, alumina, cobalt, nickel, and barium oxides were prepared for steam catalytic cracking of coal tar and characterized by N2 adsorption‐desorption, X‐ray diffraction, H2 temperature programmed reduction, and Raman spectroscopy, respectively. It was found that the specific surface area and pore volume increase while the crystal size decreases when Fe2O3 was doped with the investigated metal oxides. Among these, iron‐alumina mixed oxide (FeAl) shows the highest specific surface area and pore volume. The H2‐TPR analysis indicated that most of the mixed metal oxides have lower reduction temperature, especially for iron‐ceria mixed oxide (FeCe). The reduction temperature of FeCe is around 500 °C, and its reduction peak shifts to a lower temperature and becomes narrower as compared to other iron‐containing mixed metal oxides. The steam catalytic cracking of coal tar at 550 °C showed that the light tar content (below 360 °C) over FeCe, FeCo, and FeAl are 68.5, 67.0, and 66.5 %, respectively. The increase of CO2 and H2 over iron‐containing mixed metal oxides suggested that oxygen species from iron‐containing mixed metal oxides and steam could participate in the steam catalytic cracking of coal tar.