Enhancement of the mutagenicity of polyphenols by chlorination and nitrosation in Salmonella typhimurium.

The hydrolytic products of lignins, humic acids and industrial waste including hydroquinone, catechol, resorcinol, pyrogallol and 1,2,4-benzenetriol are widely distributed in water sources. These polyphenols can interact with chlorine or nitrite to yield new derivatives. Generally, these new products possess more mutagenic potential than their original compounds. Furthermore, the mutagenicity of these polyphenols and their derivatives can be dramatically reduced by rodent liver microsomal enzymes (S9). The mutagenicity of polyphenols is in this order: hydroquinone greater than 1,2,4-benzenetriol greater than pyrogallol, while catechol, resorcinol and phloroglucinol are non-mutagenic. The ultimate product of chlorination or nitrosation of hydroquinone has been identified to be p-benzoquinone. The formation of active oxygen species including superoxide anion and hydrogen peroxide by polyphenols has been demonstrated and this may contribute partly to the molecular mechanisms of polyphenol mutagenicity.     

Distinct roles of peroxynitrite and hydroxyl radical in triggering stunned myocardium-like impairment of cardiac myocytes in vitro

Myocardial stunning is characterized by the impairment of excitation-contraction coupling via a decrease in myofilament Ca²⁺ responsiveness, thought to be triggered by hydroxyl radicals (·OH) generated upon reperfusion. Since peroxynitrite is also expected to be produced during reperfusion, we examined whether it can induce a stunned myocardium-like impairment of cardiac myocytes. Its effect on cultured cardiac myocytes was compared with that of hydrogen peroxide (H₂O₂), ·OH source. Infusion of peroxynitrite (0.2 mM) induced a decrease in cell motion and a complete arrest in diastole at 2.9 ± 0.3 min, which coincided with an elevation in [Ca²⁺]_i. Arrest induced by infusion of H²O² (10 mM) was not associated with an increase in [Ca²⁺]_i. The ATP content was unaffected by peroxynitrite (control, 34.3 ± 3.4: + peroxynitrite, 32.9 ± 3.5 nmol/mg protein) and the cells remained viable. Sulfhydryl (SH) content was decreased by peroxynitrite, but not by H₂O₂. The membrane fluidity (a measure of peroxidation of the membrane lipids) was not affected by peroxynitrite, but was decreased by H₂O₂. Onset time of arrest was unaffected by deferoxamine (0.2 mM), but was delayed by DTT (10 mM) (from 2.9 ± 0.3 to 19.2 ± 1.6 min). Nitrotyrosine content was unchanged by peroxynitrite, and its augmentation with Fe³⁺/EDTA (1 mM) was not associated with a shortened onset time of arrest. The function of the Na⁺/Ca²⁺ exchanger was impaired by peroxynitrite, but not by H₂O₂. Peroxynitrite and H₂O₂ each induce arrest, but only the former increases [Ca²⁺]_i. One of the mechanisms of the increase in [Ca²⁺]_i is Na⁺/Ca²⁺ exchanger dysfunction. The impairments were induced through SH oxidation by peroxynitrite, but through lipid peroxidation by H₂O₂. Myocardial stunning may be induced by both species in concert.     

Evaluation of hydroxyl radical-scavenging property of purpurogallin using high pressure liquid chromatography

Purpurogallin (PPG) has been used as an additive to edible and non-edible oils or fats to retard oxidation. Its antioxidant mechanism is not known. We investigated the ability of PPG to scavenge exogenously generated hydroxyl radicals (·OH) using a sensitive high pressure liquid chromatographic (HPLC) method. ·OH was generated by photolysis of H₂O₂ (1.25–10 moles) with UV light and was trapped with salicylic acid (500 nmoles). Salicylic acid is hydroxylated to produce ·OH adduct products 2,3-and 2,5-dihydroxybenzoic acid (DHBA). H₂O₂ produced concentration-dependent ·OH as estimated by generation of 2,3- and 2,5-DHBA. PPG (100, 200, 300, 400, 500 and 600 nmoles) produced concentration-dependent decreases in ·OH adduct products (approximately 70% inhibition with 600 nmoles of PPG). It did not affect the peak of standard 2,3- and 2,5-DHBA indicating that the decrease in the adduct product generated by H₂O₂ is due to scavenging of ·OH. These results indicate that photolysis of H₂O₂ by UV light produces ·OH and that PPG scavenges ·OH.     

Chemical Bases of Nonspecific Immunity

Our knowledge on the nature and quantity of reactive O₂forms generated in phagocytes, particularly in neutrophil leucocytes, and their role in nonspecific immunity is reviewed. In thermodynamical terms, oxygen is a very reactive molecule and, hence, can react with most chemical elements and many organic molecules. In kinetic terms, O₂is rather inert. Its reactivity can be increased either by reduction or excitation. After accepting four electrons, O₂is finally reduced to H₂O. Partial reduction resulting in highly reactive intermediates, namely, superoxide anion (O₂ ^·–), hydrogen peroxide (H₂O₂), and hydroxyl radical (^·OH), is possible. Singlet oxygen (¹O₂) is the product of O₂excitation. Phagocytes acting like agents of nonspecific immunity generate such reactive forms of O₂.     

In vitro studies of interactions of NO· donor drugs with superoxide and hydroxyl radicals

Nitric oxide (NO·) is a free radical characterized by a high spontaneous chemical reactivity with many other molecules including the superoxide radical (O₂·^–). This complex interaction may generate a peroxynitrite anion (ONOO^–), which behaves as an important mediator of oxidative stress in many pathological states. In the present study, in vitro experiments were performed to assess directly the O₂·^– and hydroxyl (·OH) radical scavenging effects of various NO· donor drugs, i.e. sodium nitroprusside (SNP), sodium nitrite (NaNO₂), molsidomine and SIN 1, at pH 7.4, 7 or 6. Concentrations of NO· in the incubation medium containing the different NO· donor drugs were measured by the assay based on the reaction of Fe-N-methyl-D-glucamine dithiocarbamate (MGD) with NO· that yields a stable spin-adduct measured by electron paramagnetic resonance (EPR). O₂·^– and ·OH generation was characterized by EPR spin trapping techniques, using the spin trap 5,5-dimethyl-1-pyrroline-1-oxide (DMPO). These free radicals were generated from the enzymatic system xanthine-xanthine oxidase, in phosphate buffer adjusted at pH 7.4, 7 and 6. Under these experimental conditions, SNP exhibited the strongest superoxide scavenging properties, characterized by IC₅₀ values expressed in the µmolar range, which decreased at low pH. Addition of SNP (800 µM) to solution containing MGD and Fe²⁺ (5:1) at pH 7 4 produced a three line EPR spectrum which is identified to [(MGD)₂-Fe²⁺-NO]. In control experiments no EPR signal was observed. We obtained the same results with NaNO₂ and an augmentation of the spin-adduct level was noted with the prolongation of the incubation period. In return, molsidomine (2 mM) did not produce, in our conditions, a detectable production of NO·. NaNO₂ displayed a significant superoxide scavenging effect only at pH 6, whilst neither molsidomine nor SIN 1 had any effect. Therefore, the superoxide scavenging properties of SNP, NaNO₂, and molsidomine appeared to be closely related to their potential for NO· release, which partially depends on the pH conditions. The behaviour of SIN 1 is more complicated, the speed of oxygen diffusion probably acting as a limiting factor in NO· formation in our conditions. The production of NO· was detected in presence of SIN 1. The intensity of the complex is comparable with the signal founded with NaNO₂. By contrast, all molecules exhibited hydroxyl radical scavenging properties, highlighting the capacity of ·OH to react with a wide range of molecules. In conclusion, considering the poor chemical reactivity of O₂·^–, the NO· donor drugs/O₂·^– interactions suggest a special relationship between these two radical species, which, in certain pathological states, could lead to the generation of cytotoxic end-products with strong oxidizing properties.     

Superoxide dismutase and hydrogen peroxide formation in Campylobacter sputorum subspecies bubulus

Cell-free extracts of Campylobacter sputorum subspecies bubulus contained superoxide dismutase. The enzyme was located in the cytoplasmic fraction and insensitive to cyanide. After centrifuging a cell-free extract at 144000 x g for 1.5 h the total activity in the supernatant fraction was threefold higher than in the crude cell-free extract. The pellet fraction thus obtained was shown to have a lowering effect on superoxide dismutase activities from different sources in the assay method used here. C. sputorum responded to a raised oxygen tension in the culture by an increase in the superoxide dismutase activity. The ability to produce superoxide anion radicals (O₂ ^-·) during oxidation of formate and lactate was demonstrated. Furthermore C. sputorum was found to produce H₂O₂ while oxidizing formate. In experiments in which the reduction of cytochrome c by formate was followed, step-wise kinetics were observed. One of the steady states then obtained was attributed to the oxidizing action of H₂O₂, because it was abolished by the addition of catalase and lengthened by H₂O₂ added in addition to H₂O₂ formed as a product of formate oxidation. An overall reaction for formate oxidation by C. sputorum is discussed.Abbreviations O₂ ^-· superoxide anion radical - NBT p-nitro blue tetrazolium chloride - ABTS 2,2-azino-di-[3-ethylbenzthiazoline sulfonate (6)] - TL-medium tryptose-lactate medium     

Photosynthetic production of hydrogen peroxide by Ulva rigida C. Ag. (Chlorophyta)

Production of hydrogen peroxide has been found in Ulva rigida (Chlorophyta). The formation of H₂O₂ was light dependent with a production of 1.2 mol·g FW^–1·h^–1 in sea water (pH 8.2) at an irradiance of 700 mol photons m^–2·s^–1. The excretion was also pH dependent: in pH 6.5 the production was not detectable (< 5 nmol·g FW^–1·h^–1) but at pH 9.0 the production was 5.0 mol·g FW^–1·h^–1. The production of H₂O₂ was totally inhibited by 3-(3,4-dichlorophenyl)-1,1 dimethylurea (DCMU). The ability of U. rigida growing in tanks (7501) under a natural light regime to excrete H₂O₂ was checked and found to be seven times higher at 08.00 hours than other times of the day. The H₂O₂ concentration in the cultivation tank (density: 2 g FW·l^–1) reached the highest value (3 M) at 11.00 hours. Photosynthesis was not influenced by H₂O₂ formation. The H₂O₂ is suggested to come from the Mehler reaction (pseudocyclic photophosphorylation). With an oxygen evolution of 120 mmol·g FW^–1·h^–1 at pH 8.2 and 90 mmol·g FW^–1·h^–1 at pH 9.0, 0.5% and 2.7% of the electrons were used for extracellular H₂O₂ production. The H₂O₂ production is sufficiently high to be of physiological and ecological significance, and is suggested to be a part of the defence against epi and endophytes.Abbreviations ACL artificial, continuous light - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - GNL greenhouse - LDC Luminol-dependent chemiluminescence - SOD Superoxide dismutase This investigation was supported by SAREC (Swedish Agency for Research Cooperation with Developing Countries), Hierta-Retzius Foundation, Marianne and Marcus Wallenberg Foundation, the Swedish Environmental Protection Board, and CICYT Spain.     

Cytochemistry and reactive oxygen species: a retrospective

This retrospective reviews the methodology we have developed over several decades for detecting reactive oxygen species (ROS), using the activated polymorphonuclear leukocyte (PMN) as the paradigm of a cell which vigorously generates ROS through activation of NADPH oxidase. In the seventies, the sites of ROS generation by PMN were not clear from biochemical data, and we sought to develop new methods for the cytochemical localization of O^·– ₂, H₂O₂, and the H₂O₂-myeloperoxidase (MPO)-halide system. The H₂O₂-MPO-halide system in phagocytosing cells was localized at the fine structural level by our development of 3,3-diaminobenzidine (DAB) as a cytochemical probe for detecting peroxidase activities. Using DAB and exogenous H₂O₂, we confirmed that azurophil granules discharged MPO into the phagosome, and using particles coated with DAB and relying on endogenous H₂O₂ to yield oxidized DAB, H₂O₂ was localized to phagolysosomes. The subcellular sites of H₂O₂ generation were shown using cerium ions which react with H₂O₂ and precipitate electron opaque cerium perhydroxides (Ce(OH)₂OOH and Ce(OH)₃OOH). The results suggested that NADPH oxidase is associated with the plasmalemma, and that the enzyme enters the phagosome along with the invaginating plasmalemma, accounting for the presence of H₂O₂ in the phagosome. As O^·– ₂ is the major product of NADPH oxidase, its detection was of some importance. Based on the concept that O^·– ₂ oxidizes Mn²⁺ to Mn³⁺, and Mn³⁺ oxidizes DAB, a medium containing DAB-Mn²⁺ was used to localize sites of O^·– ₂ production in stimulated PMN. The localizations were, as expected, similar to those for H₂O₂. These techniques have been of considerable usefulness and in general provide the foundation for cytochemistry of ROS in other systems.Presented at the 36th Symposium of the Society for Histochemistry, 22 September 1994, Heidelberg, Germany     

Benthic community metabolism of three Austrian pre-alpine lakes of different trophic conditions and its oxygen dependency

Benthic community respiration rates of profundal sediments of Fuschlsee (37.6 mg · O₂ · m^–2 · h^–1 — eutrophic), Mondsee (40.19 mg · O₂ · m^–2 · h^–1 — eutrophic) and Attersee (11.5 mg · O₂ · m^–2 · h^–1 — oligo-mesotrophic) were measuredin situ, and in cores. By exposing the sediments to different oxygen levels in the laboratory it was found that benthic community metabolism reduced with decreasing oxygen concentrations. The slope of the regression lines, relating oxygen uptake rates to oxygen concentrations, differed significantly for the different sites investigated. These results were closely related to the trophic conditions of the lakes.     

Synthesis of copper(II) complexes with 3,5-bis(4,6-dimethylpyrimidin-2-yl)-4H-1,2,4-triazol-4-amine (L). Molecular and crystal structures of L and [Cu2L2Cl4]·2MeCN

A series of copper(II) complexes, i.e. Cu₂LCl₄, CuLCl₂·H₂O and [Cu₂L₂Cl₄]·2MeCN (8), based on a new potentially polytopic ligand, 3,5-bis(4,6-dimethylpyrimidin-2-yl)-4H-1,2,4-triazol-4-amine (3b, L), have been synthesized. The crystal structures of L and [Cu₂L₂Cl₄]·2MeCN were studied by X-ray single crystal analysis. The dinuclear compound [Cu₂L₂Cl₄]·2MeCN represents the first example of structurally characterized metal complexes with 3,5-di(pyrimidin-2-yl)-4H-1,2,4-triazol-4-amines. Both copper atoms have distorted tetragonal-pyramidal 3N + 2Cl environment. Surprisingly, in contrast to the complexes based on 3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-amine (pyridinyl analog of L), the compound [Cu₂L₂Cl₄]·2MeCN adopts a dinuclear trans-(N′,N¹,N²)₂ double bridging binding mode which is due to tridentate coordination of two L molecules linking two copper atoms through N¹,N²-triazole and N′-pyrimidine atoms. It seems to be reasonable that it is methyl groups in pyrimidinyl moiety that obstruct the expected dinuclear (N′,N¹,N²,N″)₂ double bridging coordination being one of the most common for 4-substituted 3,5-di(pyridin-2-yl)-4H-1,2,4-triazoles and 3,5-di(pyridin-2-yl)-1,2,4-triazolates. Due to π-π stacking interactions, molecules of Cu₂L₂Cl₄ in the structure of [Cu₂L₂Cl₄]·2MeCN form 1D chains.     

Cyclic and acyclic compartmental Schiff bases, their reduced analogues and related mononuclear and heterodinuclear complexes

[1+1] macrocyclic and [1+2] macroacyclic compartmental ligands (H₂L), containing one N₂O₂, N₃O₂, N₂O₃, N₄O₂ or O₂N₂O₂ Schiff base site and one O₂O_n (n=3, 4) crown-ether like site, have been prepared by self-condensation of the appropriate formyl- and amine precursors. The template procedure in the presence of sodium ion afforded Na₂(L) or Na(HL) · nH₂O. When reacted with the appropriate transition metal acetate hydrate, H₂L form M(L) · nH₂O, M(HL)(CH₃COO) · nH₂O, M(H₂L)(X)₂ · nH₂O (M=Cu²⁺, Co²⁺, Ni²⁺; X=CH₃COO⁻, Cl⁻) or Mn(L)(CH₃COO) · nH₂O according to the experimental conditions used. The same complexes have been prepared by condensation of the appropriate precursors in the presence of the desired metal ion. The Schiff bases H₂L have been reduced by NaBH₄ to the related polyamine derivatives H₂R, which form, when reacted with the appropriate metal ions, M(H₂R)(X)₂ (M= Co²⁺, Ni²⁺; X=CH₃COO⁻, Cl⁻), Cu(R) · nH₂O and Mn(R)(CH₃COO) · nH₂O. The prepared ligands and related complexes have been characterized by IR, NMR and mass spectrometry. The [1+1] cyclic nature of the macrocyclic polyamine systems and the site occupancy of sodium ion have been ascertained, at least for the sodium (I) complex with the macrocyclic ligand containing one N₃O₂ Schiff base and one O₂O₃ crown-ether like coordination chamber, by an X-ray structural determination. In this complex the asymmetric unit consists of one cyclic molecule of the ligand coordinated to a sodium ion by the five oxygen atoms of the ligand. The coordination geometry of the sodium ion can be described as a pentagonal pyramid with the metal ion occupying the vertex. In the mononuclear complexes with H₂L or H₂R the transition metal ion invariantly occupies the Schiff base site; the sodium ion, on the contrary, prefers the crown-ether like site. Accordingly, the heterodinuclear complexes [MNa(L)(CH₃COO)_x] (M=Cu²⁺, Co²⁺, Ni², x=1; M=Mn³⁺, x=2) have been synthesised by reacting the appropriate formyl and amine precursors in the presence of M(CH₃COO)_n · nH₂O and NaOH in a 1:1:1:2 molar ratio. The reaction of the mononuclear transition metal complexes with Na(CH₃COO) · nH₂O gives rise to the same heterodinuclear complexes. Similarly [MNa(R)(CH₃COO)_x] have been prepared by reaction of the appropriate polyamine ligand H₂R with the desired metal acetate hydrate and NaOH in 1:1:2 molar ratio.     

Generation of hydroxyl radicals by soybean nodule leghaemoglobin

Leghaemoglobin, a protein present in root nodules of soybean (Glycine max (L.) Merr.), generates the highly reactive hydroxyl radical (·OH) upon incubation with hydrogen peroxide (H₂O₂). The H₂O₂ appears to cause breakdown of the haem, releasing iron ions that convert H₂O₂ into ·OH outside the protein. Oxyleghaemoglobin (oxygenated ferrous protein) is more sensitive to attack by H₂O₂ than is metleghaemoglobin (ferric protein). The possibility of oxyleghaemoglobin breakdown by H₂O₂ and formation of damaging ·OH may explain why the root nodule is equipped with iron-storage proteins and enzymes that can remove H₂O₂.     

NO和H2O2诱导大豆根尖和边缘细胞耐铝反应的作用

 NO和H₂O₂是参与植物抗非生物胁迫反应的重要信号分子, 为了确定NO和H₂O₂在大豆(Glycine max)根尖和根边缘细胞(root border cells, RBCs)耐铝反应中的作用及其相互关系, 以‘浙春3号’大豆为材料, 研究了铝毒胁迫下大豆根尖内源NO和H₂O₂的变化, 以及外源NO和H₂O₂诱导大豆根尖和RBCs的耐铝反应。结果表明, 50 μmol·L^–1 Al处理48 h显著抑制大豆根的伸长, 提高Al在根尖的积累, 同时显著增加根尖内源NO和H₂O₂含量。施加0.25 mmol·L^–1外源NO供体亚硝基铁氰化钠(Na₂[Fe(CN)₅NO]·2H₂O, sodium nitroprusside, SNP)和0.1 mmol·L^–1H₂O₂, 能有效地缓解Al对大豆根伸长的抑制、根尖Al积累和RBCs 的死亡, 该缓解作用可以被0.05 mmol·L^–1 NO清除剂2-(4- 羧基苯)-4,4,5,5- 四甲基咪唑-1- 氧-3- 氧化物, 钾盐(C₁₄H₁₆N₂O₄·K, carboxy-PTIO, cPTIO)和150 U·mL^–1 H₂O₂清除酶(catalase, CAT)逆转。并且外源NO能够显著促进根尖H₂O₂的积累, 而外源H₂O₂对根尖NO的含量无显著影响。这表明NO和H₂O₂是诱导大豆根尖及RBCs耐铝反应的两种信号分子, NO可能通过调控H₂O₂的形成, 进而诱导大豆根尖及RBCs的耐铝反应。     

Synthesis and structural characterizations of four polyoxometalate compounds consisting of transition metals or alkaline cations as the bridging units

Four new polyoxometalate compounds, namely [Cu₂(pyrazine)₄][Cu(pyrazine)₂][PMo₁₂O₄₀] · 2H₂O (1), {[K(H₂O)₂]₄H₈PW₁₂O₄₄}F · 8H₂O (2), H₉[K₂KMo₃₆O₁₁₂(H₂O)₃₄] · 35H₂O (3), and H₃Na₃[V₁₀O₂₈] · 15H₂O (4), were prepared and characterized by single crystal X-ray diffraction, elemental analysis and IR spectroscopy. Single crystal X-ray diffraction analysis results reveal that, in compound 1, Keggin anion of [PMoO₁₂O₄₀]³⁻ is enchased in the bowl-like Cu(I)-pyrazine intervals via weak interactions between terminal oxygen atoms and cations of Cu(I). For compound 2, a three-dimensional architecture with pores of 7.70 × 7.70 Å is constructed from the anions of [PW₁₂O₄₄]¹¹⁻ cross-linked via corner-sharing alkali cations of K⁺. The [Mo₃₆O₁₁₂(H₂O)₁₆]¹²⁻ units of compound 3 are linked to form one wave-like chain via cations of K⁺. Whereas, in compound 4, anions of [V₁₀O₂₈]³⁻ are linked via NaO₆ octahedra to form two-dimensional layer structure. On the basis of this two-dimensional layer, a three-dimensional architecture is further formed via hydrogen bonds involving edge-shared NaO₆ double octahedron.     

Hydrothermal synthesis and structural characterization of a network oxide constructed from {Mo12O34(O3AsC6H5)4} clusters and {Cu(terpy)} subunits

The hydrothermal reaction of MoO₃, [Cu(CH₃CO₂)₂] · H₂O, 2,2^′:6^′,2″-terpyridine (terpy), H₂O₃AsC₆H₅, H₂O and H₂SO₄ yields aqua colored crystals of [{Cu(terpy)}₂Mo₁₂O₃₄(O₃AsC₆H₅)₄] · 2.25H₂O (1 · 2.25H₂O). The two-dimensional structure of 1 is constructed from {Mo₁₂O₃₄(O₃AsC₆H₅)₄}⁴⁻ clusters linked through {Cu(terpy)}²⁺ subunits. Each Cu(II) site exhibits {CuN₃O₂} coordination geometry and links two adjacent clusters. In turn, each cluster is associated with four Cu(II) sites through {MoO · Cu} interactions.     

Mechanism of DNA Damage and Apoptosis Induced by Tetrahydropapaveroline, a Metabolite of Dopamine

Tetrahydropapaveroline (THP), a metabolite of dopamine, has been suspected to be associated with dopaminergic neurotoxicity of L-DOPA. THP induced apoptosis in human leukemia cell line HL-60 cells, but did not in its hydrogen peroxide (H₂O₂)-resistant clone HP100. THP-induced DNA ladder formation in HL-60 cells was inhibited by a metal chelator. THP induced damage to ³²P-labeled DNA fragments in the presence of metals. In the presence of Fe(III)EDTA, THP caused DNA damage at every nucleotide. The DNA damage was inhibited by free hydroxy radical (^·OH) scavengers and catalase, suggesting that the Fe(III)EDTA-mediated DNA damage is mainly due to ^·OH generation. In the presence of Cu(II), THP caused DNA damage mainly at T and G of 5′-TG-3′ sequence. The inhibitive effect of catalase and bathocuproine on Cu(II)-mediated DNA damage suggested that H₂O₂ and Cu(I) participate in the DNA damage. This study demonstrated that THP-induced apoptosis via reactive oxygen species generated from reaction of H₂O₂ and metals plays an important role in cytotoxicity of L-DOPA.     

Reactive oxygen species in vascular biology: implications in hypertension

Reactive oxygen species (ROS), including superoxide (·O₂^–), hydrogen peroxide (H₂O₂), and hydroxyl anion (OH-), and reactive nitrogen species, such as nitric oxide (NO) and peroxynitrite (ONOO^–), are biologically important O₂ derivatives that are increasingly recognized to be important in vascular biology through their oxidation/reduction (redox) potential. All vascular cell types (endothelial cells, vascular smooth muscle cells, and adventitial fibroblasts) produce ROS, primarily via cell membrane-associated NAD(P)H oxidase. Reactive oxygen species regulate vascular function by modulating cell growth, apoptosis/anoikis, migration, inflammation, secretion, and extracellular matrix protein production. An imbalance in redox state where pro-oxidants overwhelm anti-oxidant capacity results in oxidative stress. Oxidative stress and associated oxidative damage are mediators of vascular injury and inflammation in many cardiovascular diseases, including hypertension, hyperlipidemia, and diabetes. Increased generation of ROS has been demonstrated in experimental and human hypertension. Anti-oxidants and agents that interrupt NAD(P)H oxidase-driven ·O₂^– production regress vascular remodeling, improve endothelial function, reduce inflammation, and decrease blood pressure in hypertensive models. This experimental evidence has evoked considerable interest because of the possibilities that therapies targeted against reactive oxygen intermediates, by decreasing generation of ROS and/or by increasing availability of antioxidants, may be useful in minimizing vascular injury and hypertensive end organ damage. The present chapter focuses on the importance of ROS in vascular biology and discusses the role of oxidative stress in vascular damage in hypertension.     

Protonated N-heterocycle-templated supramolecular frameworks built of triangular molybdenum(IV) clusters

A series of porous supramolecular complexes (Hoxine)₂ · [Mo₃O₄(C₂O₄)₃(H₂O)₃] · 5H₂O (1),(Hphen)₂ · [Mo₃O₄(C₂O₄)₃(H₂)₃]  · 0.5C₂H₅OH · 7H₂O (2), H₂bpy · [Mo₃O₄(C₂O₄)₃(H₂O)₃] · 2.5H₂O (3), H₂TTD · [Mo₃O₄(C₂O₄)₃(H₂O)₃] · C₂H₅OH · 3H₂O (4), (oxine = 8-hydroxyquinoline, phen = 1,10-phenanthroline, bpy = 4,4′-bipyridine, TTD = triethylene diamine) have been prepared and characterized by single-crystal X-ray crystallography, elemental analysis and infrared spectroscopy. Self-assembly of [Mo₃O₄(C₂O₄)₃(H₂O)₃]²⁻ directed by H-bonding association between the coordination water molecules and oxalate groups forms 2-D host H-bonded single layer in 1, double layer in 2 and 3, and undulated layer in 4 depending on the nature of the guest protonated N-heterocycles. Unlike cis-Hoxine⁺ or Hphen⁺ that employs lattice water molecules H-bonded to them to interconnect the host layers, trans-H₂bpy²⁺ or H₂TTD²⁺ acts a linker between the neighboring host layers to form 3-D supramolecular frameworks with channeled structures wherein the guest protonated cations are located.     

高浓度二氧化碳和臭氧对蒙古栎叶片活性氧代谢的影响

利用开顶箱熏蒸法,研究了高浓度O₃(≈80 nmol·mol^-1)和高浓度CO₂(≈700 μmol·mol^-1)及其复合处理对蒙古栎叶片活性氧代谢的影响.结果表明：高浓度O₃显著增加了蒙古栎叶片超氧阴离子(O₂^•)产生速率、过氧化氢(H₂O₂)和丙二醛(MDA)含量和电解质外渗率(P<0.05),显著降低了超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)活性和抗坏血酸(AsA)含量(P<0.05).高浓度CO₂对蒙古栎叶片活性氧代谢影响不显著.高浓度O₃和CO₂复合处理的叶片O₂^•产生速率、H₂O₂和MDA含量和电解质外渗率上升不明显,说明高浓度CO₂缓解了高浓度O₃对蒙古栎叶片的氧化胁迫.复合处理的叶片SOD、CAT、APX活性以及AsA和总酚含量显著高于O₃处理的叶片(P<0.05),说明高浓度CO₂缓解了高浓度O₃对叶片抗氧化系统的消极影响.     

New chelate complexes of trivalent Y and lanthanides (Eu, Ho, Yb) with a triazene N-oxide: Synthesis, structural characterization and luminescence properties

Deprotonated 3-(4-nitrophenyl)-1-phenyltriazene N-oxide reacts with YCl₃·6H₂O and LnCl₃·6H₂O (Ln = Eu, Ho, Yb) to give the monoclinic chelate complexes [Y{O₂N(C₆H₄)NNN(O)Ph}₄](Et₃NH)·H₂O (1) (Ph = C₆H₅; Et = C₂H₅) and [Ln^III{O₂N(C₆H₄)NNN(O)Ph}₄](Et₃NH)·H₂O·{CH₃OH∗} {Ln^III = Eu (2), Ho (3), Yb∗ (4), in which the metal centers present a square antiprismatic configuration. As already observed for hydrated ammonium complexes of triazene-oxides ligands with (C₆H₄)−NO₂ groups, multiple, effective O···H and N···H interactions hold the species in supramolecular 3D assemblies. The optical and the luminescent properties of the triazene-oxide europium complex 2 are also presented and fully discussed.