2-Benzoxazolinone (BOA) induced oxidative stress, lipid peroxidation and changes in some antioxidant enzyme activities in mung bean (Phaseolus aureus)

2-Benzoxazolinone (BOA), a well-known allelochemical with strong phytotoxicity, is a potential herbicidal candidate. The aim of the present study was to determine whether phytotoxicity of BOA is due to induction of oxidative stress caused by generation of reactive oxygen species (ROS) and the changes in levels of antioxidant enzymes induced in response to BOA. Effect of BOA was studied on electrolyte leakage, lipid peroxidation (LP), hydrogen peroxide (H(2)O(2)) generation, proline (PRO) accumulation, and activities of antioxidant enzymes-superoxide dismutase (SOD, 1.15.1.1), ascorbate peroxidase (APX, 1.11.1.11), guaiacol peroxidase (GPX, 1.11.1.7), catalase (CAT, 1.11.1.6) and glutathione reductase (GR, 1.6.4.2) in Phaseolus aureus (mung bean). BOA significantly enhanced malondialdehyde (MDA) content, a product of LP, in both leaves and roots of mung bean. The amount of H(2)O(2), a product of oxidative stress, and endogenous PRO increased many-fold in response to BOA. Accumulation of PRO, MDA and H(2)O(2) indicates the cellular damage in the target tissue caused by ROS generated by BOA. In response to BOA, there was a significant increase in the activities of scavenging enzymes SOD, APX, GPX, CAT, and GR in root and leaf tissue of mung bean. At 5 mM BOA, GR activity in roots showed a nearly 22-fold increase over that in control. The present study concludes that BOA induces oxidative stress in mung bean through generation of ROS and upregulation of activities of various scavenging enzymes.     

Comparative antioxidant enzyme and lipid peroxidation study in erythrocytes and liver of some freshwater fish

1. Superoxide dismutase (SOD), catalase (C), peroxidase (P) and glutathione peroxidase (GSH-Px) were estimated in the erythrocytes and liver of the carp, the tench and the crucian carp during a two-years period, 1983-1984 (autumn). 2. The lipid peroxidation (LP) of the erythrocytes and liver homogenates was also compared. 3. The activities of the enzymes examined showed significant interspecies variations. 4. Significant differences were observed between enzyme activities (except for SOD in the liver) and lipid peroxidation in erythrocytes and liver of investigated fish species. 5. The very high values of peroxide enzyme activities in fish erythrocytes and SOD in fish liver suggest the predominant role of these enzymes in protection of polyunsaturated acids against uncontrolled oxidative processes.     

Abscisic acid-regulated responses of aba2-1 under osmotic stress: the abscisic acid-inducible antioxidant defence system and reactive oxygen species production

We investigated the interaction among abscisic acid (ABA), reactive oxygen species (ROS) and antioxidant defence system in the transduction of osmotic stress signalling using Arabidopsis thaliana WT (Columbia ecotype, WT) and an ABA-deficient mutant (aba2-1). For this, 50 μm ABA and osmotic stress, induced with 40% (w/v) polyethylene glycol (PEG8000; -0.7 MPa), were applied to WT and aba2-1 for 6, 12 or 24 h. Time course analysis was undertaken for determination of total/isoenzyme activity of the antioxidant enzymes, superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11), NADPH oxidase (NOX; EC 1.6.3.1) activity; scavenging activity of the hydroxyl radical (OH˙), hydrogen peroxide (H(2) O(2) ); endogenous ABA and malondialdehyde (MDA). The highest H(2) O(2) and MDA content was found in PEG-treated groups of both genotypes, but with more in aba2-1. ABA treatment under stress reduced the accumulation of H(2) O(2) and MDA, while it promoted activity of SOD, CAT and APX. APX activity was higher than CAT activity in ABA-treated WT and aba2-1, indicating a protective role of APX rather than CAT during osmotic stress-induced oxidative damage. Treatment with ABA also significantly induced increased NOX activity. Oxidative damage was lower in ABA-treated seedlings of both genotypes, which was associated with greater activity of SOD (Mn-SOD1 and 2 and Fe-SOD isoenzymes), CAT and APX in these seedlings after 24 h of stress. These results suggest that osmotic stress effects were overcome by ABA treatment because of increased SOD, CAT, APX and NOX.     

Antioxidant enzymes suppress nitric oxide production through the inhibition of NF-kappa B activation: role of H(2)O(2) and nitric oxide in inducible nitric oxide synthase expression in macrophages.

Reactive molecules O(-)(2), H(2)O(2), and nitrogen monoxide (NO) are produced from macrophages following exposure to lipopolysaccharide (LPS) and involved in cellular signaling for gene expression. Experiments were carried out to determine whether these molecules regulate inducible nitric oxide synthase (iNOS) gene expression in RAW264.7 macrophages exposed to LPS. NO production was inhibited by the antioxidative enzymes catalase, horseradish peroxidase, and myeloperoxidase but not by superoxide dismutase (SOD). In contrast, the NO-producing activity of LPS-stimulated RAW264.7 cells was enhanced by the NO scavengers hemoglobin (Hb) and myoglobin. The antioxidant enzymes decreased levels of iNOS mRNA and protein in LPS-stimulated RAW264.7 cells, whereas the NOS inhibitor N(G)-monomethyl-L-arginine as well as Hb increased the level of iNOS protein but not mRNA, indicating that NO inhibits iNOS protein expression. NF-kappa B was activated in LPS-stimulated RAW264.7 cells and the activation was significantly inhibited by antioxidant enzymes, but not by Hb. Similar results were obtained using LPS-stimulated rodent peritoneal macrophages. Extracellular O(-)(2) generation by LPS-stimulated macrophages was suppressed by SOD, but not by antioxidative enzymes, while accumulation of intracellular reactive oxygen species was inhibited by antioxidative enzymes, but not by SOD. Exogenous H(2)O(2) induced NF-kappa B activation in macrophages, which was inhibited by catalase and pyrroline dithiocarbamate (PDTC). H(2)O(2) enhanced iNOS expression and NO production in peritoneal macrophages when added with interferon-gamma, and the effect of H(2)O(2) was inhibited by catalase and PDTC. These findings suggest that H(2)O(2) production from LPS-stimulated macrophages participates in the upregulation of iNOS expression via NF-kappa B activation and that NO is a negative feedback inhibitor of iNOS protein expression.     

A novel 65-mer peptide imitates the synergism of superoxide dismutase and glutathione peroxidase

Reactive oxygen species (ROS) are involved in cell growth, differentiation, and death. Excessive amounts of ROS (e.g., O(2)(-), H(2)O(2), and HO) play a role in aging as well as in many human diseases. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) are critical antioxidant enzymes in living organisms. SOD catalyzes the dismutation of O(2)(-) to H(2)O(2), and GPx catalyzes the reduction of H(2)O(2) and other harmful peroxides by glutathione (GSH). They not only function in catalytic processes but also protect each other, resulting in more efficient removal of ROS, protection of cells against injury, and maintenance of the normal metabolism of ROS. To imitate the synergism of SOD and GPx, a 65-mer peptide (65P), containing sequences that form the domains of the active center of SOD and the catalytic triad of GPx upon the incorporation of some metals, was designed on the basis of native enzyme structural models; 65P was expressed in the cysteine auxotrophic expression system to obtain Se-65P. Se-65P was converted into Se-CuZn-65P by incorporating Cu(2+) and Zn(2+). Se-CuZn-65P exhibited high SOD and GPx activities because it has a delicate dual-activity center. The synergism of the enzyme mimic was evaluated by using an in vitro model and a xanthine/xanthine oxidase/Fe(2+)-induced mitochondrial damage model system. We anticipate that the peptide enzyme mimic with synergism is promising for the treatment of human diseases and has potential applications in medicine as a potent antioxidant.     

Correlative Interrelations between the Oxygen Consumption Rate, Body Temperature and Activities of the Key Antioxidant Enzymes of Liver of Mus musculus

Using one-, two-, and three-dimensional statistical methods, there were analyzed peculiarities of distribution and the degree of the correlative-regressional dependence between the parameters characterizing the oxygen consumption rate (V _O2), body temperature (BT), activities of three key enzymes of the antioxidant system - superoxide dismutase (SOD), catalase (CL), and glutathion peroxidase (GP) in 15 females of the laboratory population of Mus musculus. The performed studies have shown that the three-dimensional non-linear models better correspond to the actual data and clearly demonstrate specificity of the antioxidant enzymes, as regulatory targets. Changes of the SOD and CL activities depend mainly on V _O2, whereas GP can be the target equally accessible for the regulatory factors of oxidative processes and thermoregulation.     

Lethality of disrupted intestinal lamina propia cells for Trichinella spiralis in vitro.

The possible direct role of inflammatory cells in resistance to Trichinella spiralis was studied by observing the effects of lamina propria cells from the small intestine (LP cells) of immunized rats on various stages of the parasite. Effects produced by physically disrupted cells were compared to those produced by intact cells on worms exposed to phytohemagglutinin or immune serum. LP cells were isolated from the rat intestine by collagenase digestion of everted gut segments that were previously denuded of epithelium by treatment with hyaluronidase. Disrupted cells, but not intact ones, selectively killed T. spiralis juvenile and adult worms in vitro, whereas larvae were unaffected by similar treatment. Attempts to identify the lethal component of disrupted cells led to an evaluation of the enzyme, peroxidase. Mucosal peroxidase is localized in LP cells and its activity increases several-fold during intestinal trichinosis. It is presumed to be myeloperoxidase, a particulate-bound enzyme of myeloid-derived leukocytes that functions as part of a potent antimicrobial system in combination with H2O2 and a halide. Results indicated that the vermicidal component of LP cells was associated with the pellet fraction of disrupted centrifuged LP cells, but was not linked to a peroxidase-H2O2-halide system.     

Effect of reduced oxygen tension on reactive oxygen species production and activity of antioxidant enzymes in swine granulosa cells

During follicle growth swine granulosa cells are physiologically exposed to a progressive oxygen shortage. It has already been shown that hypoxia stimulates angiogenesis through an increase of VEGF production, however, despite considerable progress in the understanding of the final events induced by cellular hypoxia, the signal transduction pathway remains elusive. Recent evidence suggest a role for Reactive Oxygen Species (ROS) as hypoxia signal transducer. Granulosa cells were isolated from pig follicles (> 5 mm) and cultured for 18 h in normoxic (19% O2), hypoxic (5% O2) or anoxic (1% O2) conditions. Following the incubation ROS (O2- and H2O2) production and the activity of scavenging enzymes (SOD, catalase and peroxidase) were determined. It was apparent from our data that ROS generation was reduced by hypoxia. On the contrary, SOD and peroxidase, but not catalase, increased their activity. Further studies are needed to verify whether ROS are involved in signalling hypoxia.     

The pro-oxidative activity of SOD and nitroxide SOD mimics.

Native Cu,Zn-SOD and synthetic SOD mimics sometimes demonstrate an apparently anomalous bell-shaped dose-response relationship when protecting various biological systems from oxidative stress. Several mechanisms have been proposed to account for such an effect, including: overproduction of H(2)O(2), peroxidative activity of SOD, and opposing roles played by O(2)(*-) in both initiation and termination of radical chain reactions. In the present study, ferrocyanide and thiols, which are susceptible to one-electron and two-electron oxidation, respectively, were subjected to a flux of superoxide in the presence and absence of SOD or SOD mimics. The results show that 1) either O(2)(*-)/HO(2)(*) or H(2)O(2) alone partially inactivates papain, whereas when combined they act synergistically; 2) nitroxide SOD mimics, but not SOD, exhibit a bell-shaped dose-response relationship in protecting papain from inactivation; 3) SOD, which at low dose inhibits superoxide-induced oxidation of ferrocyanide, loses its antioxidative effect as its concentration increases. These findings offer an additional explanation for the pro-oxidative activity of SOD and SOD mimics without invoking any dual activity of O(2)(*-) or a combined effect of SOD and H(2)O(2). The most significant outcome of an increase in SOD level is a decrease of [O(2)(*-)](steady state), rather than any notable elevation of [H(2)O(2)](steady state). As a result, the reaction kinetics of the high oxidation state of each catalyst is altered. In the presence of ultra-low [O(2)(*-)](steady state), the oxidized form of SOD [Cu(II),Zn-SOD] or SOD mimic (oxo-ammonium cation) does not react with O(2)(*-) but rather oxidizes the target molecule that it was supposed to have protected. Consequently, these catalysts exert an anti- or pro-oxidative effect depending on their concentration.     

Water stress-induced abscisic acid accumulation triggers the increased generation of reactive oxygen species and up-regulates the activities of antioxidant enzymes in maize leaves

The interrelationship among water-stress-induced abscisic acid (ABA) accumulation, the generation of reactive oxygen species (ROS), and the activities of several antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) was investigated in leaves of detached maize (Zea mays L.) plants exposed to -0.7 MPa water stress induced by polyethylene glycol (PEG 6000). Time-course analyses of ABA content, the production of ROS, and the activities of antioxidant enzymes in water-stressed leaves showed that a significant increase in the content of ABA preceded that of ROS, which was followed by a marked increase in the activities of these antioxidant enzymes. Pretreatment with an ABA biosynthesis inhibitor, tungstate, significantly suppressed the accumulation of ABA, and also reduced the increased generation of ROS and the up-regulation of these antioxidant enzymes in water-stressed leaves. A mild oxidative stress induced by paraquat, which generates O(2)(-) and then H(2)O(2), resulted in a significant enhancement in the activities of antioxidant enzymes in non-water-stressed leaves. Pretreatment with some ROS scavengers, such as Tiron and dimethylthiourea (DMTU), and an inhibitor of NAD(P)H oxidase, diphenyleneiodonium (DPI), almost completely arrested the increase in ROS and the activities of these antioxidant enzymes induced by water stress or ABA treatment. These data suggest that water stress-induced ABA accumulation triggers the increased generation of ROS, which, in turn, leads to the up-regulation of the antioxidant defence system.     

Susceptibility of Eimeria bovis and Toxoplasma gondii to oxygen intermediates and a new mathematical model for parasite killing

Eimeria bovis and Toxoplasma gondii differ in their susceptibility to macrophages activated by lymphokines. Interferon-gamma can activate macrophages to totally inhibit E. bovis sporozoite development, whereas growth of T. gondii tachyzoites in macrophages is not totally affected. The susceptibility of these parasites to oxygen intermediates and their ability to evade the oxidative burst by macrophages were investigated in cell-free systems. Using a logistic model to assess growth inhibition, T. gondii growth was impaired by 50% at 10(-4.25) M (56 microM) H2O2, with 30 min as the optimum time for measuring inhibition. Preliminary results indicate that T. gondii follows mode-one and mode-two killing with relation to time after exposure to H2O2, implying a role for OH. and the induction of a DNA repair mechanism. The same model was used to assess inhibition of E. bovis growth that was more susceptible, being inhibited to 50% by 10(-5) M (10 microM) H2O2. Both parasites were susceptible to the effects of xanthine-xanthine oxidase that releases a full complement of oxygen intermediates (H2O2, OH., (1)O2, and O2-). Adding quenchers or scavengers to the system confirmed that T. gondii was susceptible to products of the interaction of O2- and H2O2 (OH. and (1)O2), and that E. bovis sporozoites were at least partially susceptible to H2O2 and O2-, but extremely susceptible to OH.. These data were supported by studies on scavenging enzymes present in the parasites. Toxoplasma gondii was rich in superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPO), and E. bovis had less catalase and SOD.(ABSTRACT TRUNCATED AT 250 WORDS)     

Source of superoxide anion radical in aerobic mixtures consisting of NAD[P]H, 5-methylphenazinium methyl sulfate and nitroblue tetrazolium chloride

The source of superoxide anion radical (O2-.) in aerobic mixtures consisting of NAD[P]H, 5-methylphenazinium methyl sulfate (or its 1-methoxy derivative) and tetrazolium salt was investigated using superoxide dismutase (SOD), Mn(II), ferricytochrome-C, and epinephrine as probes. NAD[P]H + phenazine + O2 was found to reduce nitroblue tetrazolium, iodonitrotetrazolium, and thiazolyl blue in a manner sensitive to agents that dismutase O2-., viz., SOD and Mn(II). It also mediated the reduction of ferricytochrome-C, and augmented the autooxidation of epinephrine to the adrenochrome, without a tetrazolium salt present in the medium. The autooxidation of epinephrine, but not the reduction of ferricytochrome-C, was found to be sensitive to SOD. Nitroblue tetrazolium, either singly or in combination with SOD, did not stimulate the reduction of ferricytochrome-C. The oxidation of NADH, mediated by a catalytically low concentration of phenazine(+O2), was augmented two-fold by SOD. These observations are consistent with, and lend support to, a scheme of redox events (Scheme-3) wherein it is proposed that the source of O2-. in the NAD[P]H + phenazine + tetrazolium(+O2) system is the reduced phenazine, that the tetrazoinyl radical (a one-electron reduction product of tetrazolium) may not reduce O2 to O2-., that the redox reaction between semiquinone radicals of phenazine and O2 is reversible, and that the disproportionation of semiquinone radicals constitutes an important rate-limiting reaction in the expression of phenazine redox couple.     

Response of antioxidative enzymes to plum pox virus in two apricot cultivars

Recent evidence has indicated that activated oxygen species (AOS) may function as molecular signals in the induction of defence genes. In the present work, the response of antioxidative enzymes to the plum pox virus (PPV) was examined in two apricot (Prunus armeniaca L.) cultivars, which behaved differently against PPV infection. In the inoculated resistant cultivar (Goldrich), a decrease in catalase (CAT) as well as an increase in total superoxide dismutase (SOD) and dehydroascorbate reductase (DHAR) activities were observed. Ascorbate peroxidase (APX), glutathione reductase (GR) and monodehydroascorbate reductase (MDHAR) did not change significantly in relation to non-inoculated (control) plants. In the susceptible cultivar (Real Fino), inoculation with PPV brought about a decrease in CAT, SOD and GR, whereas a rise in APX, MDHAR and DHAR activities was found in comparison to non-inoculated (control) plants. Apricot leaves contain only CuZn-SOD isozymes, which responded differently to PPV depending on the cultivar. Goldrich leaves contained 6 SODs and both SOD 1 and SOD 2 increased in the inoculated plants. In leaves from Real Fino, 5 SODs were detected and only SOD 5 was increased in inoculated plants. The different behaviour of SODs (H2O2-generating enzymes) and APX (an H2O2-remover enzyme) in both cultivars suggests an important role for H2O2 in the response to PPV of the resistant cultivar, in which no change in APX activity was observed. This result also points to further studies in order to determine if an alternative H2O2-scavenging mechanism takes place in the resistant apricot cultivar exposed to PPV. On the other hand, the ability of the inoculated resistant cultivar to induce SOD 1 and SOD 2 as well as the important increase of DHAR seems to suggest a relationship between these activities and resistance to PPV. This is the first report about the effect of PPV infection on the antioxidative enzymes of apricot plants. It opens the way for the further studies, which are necessary for a better understanding of the role of antioxidative processes in viral infection by PPV in apricot plants.     

On the mechanism of the Mn3(+)-induced neurotoxicity of dopamine:prevention of quinone-derived oxygen toxicity by DT diaphorase and superoxide dismutase

Dopamine (DA) is rapidly oxidized by Mn3(+)-pyrophosphate to its cyclized o-quinone (cDAoQ), a reaction which can be prevented by NADH, reduced glutathione (GSH) or ascorbic acid. The oxidation of DA by Mn3+, which appears to be irreversible, results in a decrease in the level of DA, but not in a formation of reactive oxygen species, since oxygen is neither consumed nor required in this reaction. The formation of cDAoQ can initiate the generation of superoxide radicals (O2-.) by reduction-oxidation cycling, i.e. one-electron reduction of the quinone by various NADH- or NADPH-dependent flavoproteins to the semiquinone (QH.), which is readily reoxidized by O2 with the concomitant formation of O2-.. This mechanism is believed to underly the cytotoxicity of many quinones. Two-electron reduction of cDAoQ to the hydroquinone can be catalyzed by the flavoprotein DT diaphorase (NAD(P)H:quinone oxidoreductase). This enzyme efficiently maintains DA quinone in its fully reduced state, although some reoxidation of the hydroquinone (QH2) is observed (QH2 + O2----QH. + O2-. + H+; QH. + O2----Q + O2-.). In the presence of Mn3+, generated from Mn2+ by O2-. (Mn2+ + 2H+ + O2-.----Mn3+ + H2O2) formed during the autoxidation of DA hydroquinone, the rate of autoxidation is increased dramatically as is the formation of H2O2. Furthermore, cDAoQ is no longer fully reduced and the steady-state ratio between the hydroquinone and the quinone is dependent on the amount of DT diaphorase present. The generation of Mn3+ is inhibited by superoxide dismutase (SOD), which catalyzes the disproportionation of O2-. to H2O2 and O2. It is noteworthy that addition of SOD does not only result in a decrease in the amount of H2O2 formed during the regeneration of Mn3+, but, in fact, prevents H2O2 formation. Furthermore, in the presence of this enzyme the consumption of O2 is low, as is the oxidation of NADH, due to autoxidation of the hydroquinone, and the cyclized DA o-quinone is found to be fully reduced. These observations can be explained by the newly-discovered role of SOD as a superoxide:semiquinone (QH.) oxidoreductase catalyzing the following reaction: O2-. + QH. + 2H+----QH2 + O2. Thus, the combination of DT diaphorase and SOD is an efficient system for maintaining cDAoQ in its fully reduced state, a prerequisite for detoxication of the quinone by conjugation with sulfate or glucuronic acid. In addition, only minute amounts of reactive oxygen species will be formed, i.e. by the generation of O2-., which through disproportionation to H2O2 and further reduction by ferrous ions can be converted to the hydroxyl radical (OH.). Absence or low levels of these enzymes may create an oxidative stress on the cell and thereby initiate events leading to cell death.     

Role of zinc on lipid peroxidation and antioxidative enzymes in intestines of ethanol-fed rats

This study was undertaken to investigate the effects of zinc on lipid peroxidation and various antioxidative enzymes in the intestines of male Wistar rats fed on ethanol. It was observed that NADPH-dependent lipid peroxidation (LP) was significantly increased upon ethanol treatment for 4 and 8 wk. The concentraton of glutathione as well as the activities of catalase, superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR) were also found to be significantly increased upon ethanol feeding at all of the treatment intervals. The glutathione levels were found to be further elevated upon combined zinc and ethanol treatments. Interestingly, the administration of zinc to ethanol-fed rats was able to bring down the elevated levels of LP, catalase, SOD, and GPx, thus indicating the antiperoxidative potential of zinc under such conditions.     

Accumulation of Superoxide Radical in Corn Leaves During Waterlogging

The changes in superoxide (O2-) production, hydrogen peroxide (H2O2) content and active oxygen scavenging system in corn (Zea mays L. ) leaves under waterlogging stress were investigated to explore the relationship between O2- accumulation and waterlogging injury. Corn plants were grown in pots in a controlled environment. The results showed that prolonged waterlogging treatment conducted at 4-leaf stage caused a significant increase in the production of O2- and H2O2, while the extent of O2- change was more than that of H2O2. Malondialdehyde (MDA) accumulation, chlorophyll loss and electrolye leakage were positively correlated with O2- production in corn waterlogged leaves. Foliage spraying with 0. 1 mmol/L paraquat (02- producer) at the start of waterlogging treatment led to a significant increase in 02-, H202 and MDA levels. The addition of DDTC (SOD activity inhibitor) aggravated 02- formation in waterlogged leaves. Waterlogging apperantly reduced the activities of SOD. catalase (CAT), ascorbate peroxidase (AP) and the concentrations of ascorbic acid (ASA) and glutathione (GSH). It was noted that the decline in SOD activity proceeded the diminishment of H2O2 scavengers in chloroplasts (i. e. AP, AsA and GSH). The present findings suggest that O2- is involved in waterlogging damage, and excessive accumulation of 02- is due to the reduced SOD activity.     

Renal antioxidant enzymes and glutathione redox status in leptin-induced hypertension

Previously, we have demonstrated that leptin increases blood pressure (BP) in the rats through two oxidative stress-dependent mechanisms: stimulation of extracellular signal-regulated kinases (ERK) by H(2)O(2) and scavenging of nitric oxide (NO) by superoxide (O(2-.)). Herein, we examined if renal glutathione system and antioxidant enzymes determine the mechanism of prohypertensive effect of leptin. Leptin administered at 0.5 mg/kg/day for 4 or 8 days increased BP and renal Na(+),K(+)-ATPase activity and reduced fractional sodium excretion; these effects were prevented by NADPH oxidase inhibitor, apocynin. Superoxide scavenger, tempol, abolished the effect of leptin on BP and renal Na(+) pump in rats receiving leptin for 8 days, whereas ERK inhibitor, PD98059, was effective in animals treated with leptin for 4 days. Leptin administered for 4 days decreased glutathione (GSH) and increased glutathione disulfide (GSSG) in the kidney. In animals receiving leptin for 8 days GSH returned to normal level, which was accompanied by up-regulation of gamma-glutamylcysteine synthetase (gamma-GCS), a rate-limiting enzyme of the GSH biosynthetic pathway. In addition, superoxide dismutase (SOD) activity was decreased, whereas glutathione peroxidase (GPx) was increased in rats receiving leptin for 8 days. Cotreatment with gamma-GCS inhibitor, buthionine sulfoximine (BSO), accelerated, whereas GSH precursor, N-acetylcysteine (NAC), attenuated leptin-induced changes in gamma-GCS, SOD, and GPx. In addition, coadministration of BSO changed the mechanism of BP elevation from H(2)O(2)-ERK to (O(2-.))-NO dependent in animals receiving leptin for 4 days, whereas NAC had the opposite effect in rats treated with leptin for 8 days. These results suggest that initial change in GSH redox status induces decrease in SOD/GPx ratio, which results in greater amount of (O)2-.)) versus H(2)O(2) in later phase of leptin treatment, thus shifting the mechanism of BP elevation from H(2)O(2)-ERK to (O(2-.))-NO dependent.     

大豆萌发过程的活性氧代谢

本文研究了大豆萌发过程中活性氧的产生与清除,并探讨了光因子在活性氧代谢中的作用。大豆呼吸强度、O产生速率及H2O2水平都在吸水后第四天达到高峰,然后下降,三者的变化趋势同步。SOD、POD及APX的活性随萌发过程而逐渐增强,最后趋于平稳。SOD同工酶谱中分别于萌发的第二、第三天各出现一条新的酶带。CAT在萌发的初期猛增50倍左右,之后趋于稳定。在三种清除H2O2的酶（CAT、POD、APX）中,CAT清除H2O2的能力远远高于POD与APX,CAT可能是大豆萌发过程中最主要的H2O2清除酶。光萌发时呼吸强度低于暗中萌发,但O产生速率与H2O2水平高于暗萌发,光萌发时O的产生占总耗氧量的1．1—2．7％,而暗中萌发为0．9—1．3％。光条件下SOD、APX活性明显高于暗中萌发,而POD与CAT则在光和暗条件下相差不大。     

Characterization of lactosporin, a novel antimicrobial protein produced by Bacillus coagulans ATCC 7050

Aims:  To characterize the antimicrobial protein produced by Bacillus coagulans used in the probiotic dietary supplement (Lactospore^® Probiotic, Sabinsa Corp., Piscataway, NJ, USA).
Methods and Results:  Bacillus coagulans ATCC 7050 was grown at 37°C for 18 h. The cell free supernatant was concentrated 10-fold (lactosporin preparation, LP). The antimicrobial activity of LP was confirmed against Micrococcus luteus ATCC 10420 in a well diffusion assay. The proteinaceous nature of LP was determined following exposure to different enzymes. The activity of LP was pH-dependent but stable to heat. The isoelectric point of LP was determined to be 3·5–4·0. PCR analyses showed no similarity between lactosporin and known antimicrobial proteins produced by the Bacillus spp.
Conclusions:  Lactosporin is a novel antimicrobial protein. Initial characterization indicates that it may fall outside of the conventional classification of class I and II bacteriocins. Loss of activity after exposure to a number of proteolytic enzymes and lipase suggest that lactosporin may posses a lipid moiety which contributes to its inhibitory activity.
Significance and Impact of the Study:  The unique characteristics of lactosporin, including its antimicrobial activity against pathogenic micro-organisms, indicate that it may have potential for application in foods and personal care products.     

Modulation of oxidant lung injury by using liposome-entrapped superoxide dismutase and catalase

Increased cellular generation of partially reduced species of oxygen mediates the toxicity of hyperoxia to cultured endothelial cells and rats exposed to 95-100% oxygen. Liposomal entrapment and intracellular delivery of superoxide dismutase (SOD) to cultured porcine aortic endothelial cells increased the specific activity of cellular SOD up to 15-fold. The liposome-mediated augmentation of SOD activity persisted in cell monolayers and rendered these cells resistant to oxygen-induced injury in a cell SOD activity-dependent manner. Addition of free SOD to culture medium had no effect on cell SOD activity or resistance to oxygen toxicity. SOD and catalase-containing liposomes injected i.v. into rats increased lung-associated enzyme specific activities two- to fourfold. Liposome entrapment of both SOD and catalase significantly increased the circulating half-lives of these enzymes and was critical for prevention of in vivo oxygen toxicity. Free SOD and catalase injected i.v. in the absence or presence of control liposomes did not increase corresponding lung enzyme activities or survival time in 100% oxygen. These studies show that O2- and H2O2 are important mediators of oxygen toxicity and that intracellular delivery of oxygen protective enzymes can reduce tissue injury owing to overproduction of partially reduced oxygen species.