Chitosan-chelated carbon dots-based nanozyme of extreme stability with super peroxidase activity and antibacterial ability for wound healing

Bacterial infection often leads to failed wound healing, causing one-third of death cases globally. However, antibacterial nanomaterials and natural enzymes face limitations including low antibacterial efficiency, lack of catalytic performance, low safety, and instability. Therefore, a new Fe/N-doped chitosan-chelated carbon dot-based nanozyme CS@Fe-N CDs was developed, which showed multiple advantages such as highly efficient antibacterial activity, excellent peroxidase-like activity, high stability, and high biocompatibility, shortening the wound healing time. The ultra-small (6.14 ± 3.38 nm) CS@Fe-N CDs nanozyme accelerated the H2O2 to ·OH conversion, exhibiting excellent antibacterial performance against Staphylococcus aureus. The antibacterial activity was increased by over 2000-fold after catalysis. The CS@Fe-N CDs nanozyme also displayed outstanding peroxidase activity (Vmax/Km = 1.77 × 10-6/s), 8.8-fold higher than horseradish peroxidase. Additionally, the CS@Fe-N CDs nanozyme exhibited high stability at broad pH values (pH 1-12) and temperature ranges (20-90 °C). In vitro evaluation of cell toxicity proved that the CS@Fe-N CDs nanozyme had negligible cytotoxicity. In vivo, wound healing experiments demonstrated that the CS@Fe-N CDs could shorten the healing time of rat wounds by at least 4 days, and even had a better curative effect than penicillin. In conclusion, this therapeutic platform provides an effective antibacterial and biologically safe healing strategy for skin wounds.

Effects of exogenous zinc on the physiological characteristics and enzyme activities of Passiflora edulis Sims f. edulis seedlings

Passionflower (Passiflora edulis Sims) is widely distributed in tropical and subtropical areas for edible, medicinal and skin care product processing, and the market demand is large. Zinc (Zn) is a necessary trace element for plant growth and development. In many countries, the content of Zn in soil is low and/or bioavailability is low. The exogenous application of Zn has become a common agronomic measure in agriculture. However, the effect of Zn on the physiological characteristics and enzyme activity of passionflower seedlings is not clear. In this study, pot experiments were conducted to analyse the effects of different concentrations of Zn (0, 200, 400, 800 mg kg-1) on the plant growth, photosynthetic pigments, osmotic regulators, membrane system and antioxidant enzyme system of purple passionflower (Passiflora edulis Sims f. edulis) seedlings, and Pearson correlation and principal component analyses were performed. The results showed that (1) the 200 mg kg-1 Zn treatment increased the contents of chlorophyll a (37.65%), chlorophyll b (41.22%), chlorophyll a+b (38.59%) and carotenoids (29.74%). The value of chlorophyll a/b changed little and had no effect on leaf growth. (2) The contents of proline (Pro) and malondialdehyde (MDA) in P. edulis Sims f. edulis seedlings treated with 400 mg kg-1 Zn increased significantly by 116.84% and 42.69%, respectively. The activities of catalase (CAT) and peroxidase (POD) increased by 16.82% and 18.70%, respectively. Superoxide dismutase (SOD), leaf area (LA), leaf perimeter (LP) and leaf width (LW) decreased significantly by 47.20%, 19.75%, 8.32% and 11.97%, respectively. (3) 800 mg kg-1 Zn significantly increased the contents of Pro (202.56%) and MDA (26.7%) and the activities of CAT (16.00%) and POD (67.00%), while the soluble sugar (SS), SOD, LA, LP and LW decreased significantly by 36.67%, 32.86%, 23.36%, 8.32% and 11.18%, respectively. (4) There was a significant positive correlation between Pro and photosynthetic pigments and between SOD and leaf growth and a significant negative correlation between POD and SS and between SOD and MDA. (5) A low concentration (200 mg kg-1) of Zn promoted the growth of P. edulis Sims f. edulis seedlings and allowed stress caused by high Zn concentrations to be tolerated. The results of this study can provide a reference for the application of Zn fertilizer to P. edulis Sims f. edulis.

GYY4137, a hydrogen sulfide donor, protects against endothelial dysfunction in porcine coronary arteries exposed to myeloperoxidase and hypochlorous acid

BACKGROUND AND AIMS

Myeloperoxidase (MPO) and its principal reaction product hypochlorous acid (HOCl) are part of the innate immune response but are also associated with endothelial dysfunction, thought to involve a reduction in nitric oxide (NO) bioavailability. We aimed to investigate the effect of MPO and HOCl on vasorelaxation of coronary arteries and to assess directly the involvement of NO. In addition, we hypothesised that the slow release hydrogen sulfide (H2S) donor GYY4137 would salvage coronary artery endothelial function in the presence of MPO and HOCl.

METHODS AND RESULTS

Contractility of porcine coronary artery segments was measured using isometric tension recording. Incubation with MPO (50 ng/ml) plus hydrogen peroxide (H2O2) (30 μM; substrate for MPO) impaired endothelium-dependent vasorelaxation to bradykinin in coronary arteries. HOCl (10-500 μM) also impaired endothelium-dependent relaxations. There was no effect of MPO plus H2O2, or HOCl, on endothelium-independent relaxations to 5'-N-ethylcarboxamidoadenosine and sodium nitroprusside. L-NAME (300 μM), a NO synthase inhibitor, attenuated bradykinin relaxations, leaving L-NAME-resistant relaxations to bradykinin mediated by endothelium-dependent hyperpolarization. In the presence of L-NAME, MPO plus H2O2 largely failed to impair endothelium-dependent relaxations to bradykinin. Similarly, HOCl failed to inhibit endothelium-dependent relaxations to bradykinin in the presence of L-NAME. GYY4137 (1-100 μM) protected endothelium-dependent relaxations to bradykinin from dysfunction caused by MPO plus H2O2, and HOCl, with no effect alone on bradykinin relaxation responses. The specific MPO inhibitor aminobenzoic acid hydrazide (ABAH) (1 and 10 μM) also protected against MPO plus H2O2-induced endothelial dysfunction (at 10 μM ABAH), but was less potent than GYY4137.

CONCLUSIONS

MPO plus H2O2, and HOCl, impair coronary artery endothelium-dependent vasorelaxation via inhibition of NO. GYY4137 protects against endothelial dysfunction in arteries exposed to MPO plus H2O2, and HOCl. H2S donors such as GYY4137 are possible therapeutic options to control excessive MPO activity in cardiovascular diseases.

Physiological responses of typical subtropical landscape shrubs to artificial light at night

Artificial light at night is rapidly spreading and has become an important component of global change. Although numerous studies have focused on its potential ecological impacts, the physiological response mechanisms of landscape plants to artificial light at night have rarely been quantified. With common landscape shrubs in subtropical regions of China, Hydrangea paniculata, Photinia fraseri and Ligustrum japonicum, as test materials, we exa-mined the responses of antioxidant enzyme system and biomass in the light environment at night under different light quality (yellow light, white light) with different light intensities (20, 40, 60 lx) . The results showed that artificial light at night significantly increased the membrane peroxidation, stimulated plant antioxidant protection systems and raised the antioxidant enzyme activities of the three species. The effects of light quality on plant antioxidant enzymes varied across dspecies. The peroxidase (POD) and catalase (CAT) activities of H. paniculata under white light were 1.5 and 1.3 times as that under yellow light, respectively. Both enzyme activities of P. fraseri were 1.1 times as that under white light than under yellow light. The activities of two enzymes in L. japonicum under white light were 88.6% and 99.5% of those under yellow light, respectively. The antioxidant enzyme activities of the three species increased with increasing light intensity at night, whereas the contents of malondialdehyde increased rapidly and the antioxidant enzyme activities decreased when beyond a certain light intensity threshold (at 120 d, the threshold was about 40 lx). The protective enzymes that played the major role under nighttime light stress were different among the three species. For H. paniculata, POD and CAT complemented each other to resist stress-induced oxidative damage, while the main enzyme of L. japonicum was POD. The biomass of the three species increased significantly under artificial light at night. H. paniculata was the most sensitive to nighttime light stress, while L. japonicum had the strongest resistance to the stress. The deciduous shrub H. paniculata could tolerate the white night light lower than 40 lx, while the evergreen shrubs P. fraseri and L. japonicum could tolerate the yellow night light lower than 40 lx.

Rationale and design of ENDEAVOR: A sequential phase 2b-3 randomized clinical trial to evaluate the effect of myeloperoxidase inhibition on symptoms and exercise capacity in heart failure with preserved or mildly reduced ejection fraction

AIMS

Mitiperstat (formerly AZD4831) is a novel selective myeloperoxidase inhibitor. Currently, no effective therapies target comorbidity-induced systemic inflammation, which may be a key mechanism underlying heart failure with preserved or mildly reduced ejection fraction (HFpEF/HFmrEF). Circulating neutrophils secrete myeloperoxidase, causing oxidative stress, microvascular endothelial dysfunction, interstitial fibrosis, cardiomyocyte remodelling and diastolic dysfunction. Mitiperstat may therefore improve function of the heart and other organs, and ameliorate heart failure symptoms and exercise intolerance. ENDEAVOR is a combined, seamless phase 2b-3 study of the efficacy and safety of mitiperstat in patients with HFpEF/HFmrEF.

METHODS

In phase 2b, approximately 660 patients with heart failure and ejection fraction >40% are being randomized 1:1:1 to mitiperstat 2.5 mg, 5 mg or placebo for 48 weeks. Eligible patients have baseline 6-min walk distance (6MWD) of 30-400 m with a <50 m difference between screening and randomization and Kansas City Cardiomyopathy Questionnaire total symptom score (KCCQ-TSS) ≤90 points at screening and randomization. The dual primary endpoints are change from baseline to week 16 in 6MWD and KCCQ-TSS. The sample size provides 85% power to detect placebo-adjusted improvements of 21 m in 6MWD and 6.0 points in KCCQ-TSS at overall two-sided alpha of 0.05. Safety is monitored throughout treatment, with a focus on maculopapular rash. In phase 3 of ENDEAVOR, approximately 820 patients will be randomized 1:1 to mitiperstat or placebo.

CONCLUSION

ENDEAVOR is the first phase 2b-3 study to evaluate whether myeloperoxidase inhibition can improve symptoms and exercise capacity in patients with HFpEF/HFmrEF.

Effect of Exogenous Plant Growth Regulators and Rejuvenation Measures on the Endogenous Hormone and Enzyme Activity Responses of Acer mono Maxim in Cuttage Rooting

The cuttage rooting method for Acer species is difficult to achieve a good efficacy as trees maintain good characteristics at the rejuvenation stage, thus improving the rooting of Acer species. The addition of exogenous hormones and rejuvenation can improve the rooting effect of cuttings; however, the specific regulatory mechanism is still unclear. Here, Acer mono Maxim rejuvenation and non-rejuvenation cuttings were used as test subjects, to investigate the effects of exogenous hormones on the activities of endogenous hormones and antioxidant enzymes in the rooting process of young cuttings. The results showed that exogenous growth-regulating substances significantly improved the rooting rate of A. mono. Exogenous hormones naphthylacetic acid (NAA) + indolebutyric acid (IBA) increased the initial levels of the endogenous hormones, indoleacetic acid (IAA) and abscisic acid (ABA), and the enzyme activities of peroxidase (POD) and polyphenol oxidase (PPO). Rejuvenation treatment prolonged the time of increase in ABA content and indoleacetic acid oxidase (IAAO) activity at the root primordium induction stage, while increasing trans-zeatin riboside (ZR) content and decreasing POD enzyme activity in cuttings. These results demonstrate that A. mono cuttings can achieve the purpose of improving the rooting rate by adding the exogenous hormone (NAA + IBA), which is closely related to the changes of endogenous hormone content and enzyme activity, and these changes of A. mono rejuvenation cuttings are different from non-rejuvenation cuttings.

Cerebrolysin Amelioration of Spinal Cord Ischemia/ Reperfusion Injury in Rabbit Model

AIM

To investigate the effects of cerebrolysin on inflammation, oxidative stress, apoptosis, and neurologic recovery in the setting of an experimental rabbit model of spinal cord ischemia/reperfusion injury (SCIRI).

MATERIAL AND METHODS

Rabbits were randomly divided into five groups: control, ischemia, vehicle, methylprednisolone (30 mg/kg), and cerebrolysin (5 ml/kg) group. The rabbits in the control group underwent only laparotomy; the other groups underwent spinal cord ischemia and reperfusion injury for 20 minutes. Neurologic examination after 24 hours was based on the Modified Tarlov scale. Myeloperoxidase activities, catalase and malondialdehyde levels, and caspase-3 concentrations were determined in serum and tissue samples. Serum xanthine oxidase levels were studied and histopathological and ultrastructural changes were examined.

RESULTS

After SCIRI, serum and tissue myeloperoxidase activities, malondialdehyde levels, caspase-3 concentrations, and serum xanthine oxidase activities were increased (p < 0.01?0.001). Catalase levels were significantly diminished (p < 0.001). Cerebrolysin treatment correlated with reduced myeloperoxidase and xanthine oxidase activities, malondialdehyde levels and caspase-3 concentrations; and with increased catalase levels (p < 0.001, for all). The cerebrolysin group showed improved histopathological, ultrastructural, and neurological outcomes.

CONCLUSION

For the first time in the literature, the current study reports anti-inflammatory, antioxidant, antiapoptotic, and neuroprotective effects of cerebrolysin in a SCIRI rabbit model.

Effects of inorganic arsenic species on the antioxidant enzyme system of the Amazon Sword Plant (Echinodorus amazonicus Rataj)

This study aims to examine the effects of Arsenite (As⁺³) and Arsenate (As⁺⁵) on the aquatic macrophyte Amazon Sword Plant (Echinodorus amazonicus Rataj). To this aim, different concentrations of As⁺³ and As⁺⁵ (0, 6, 18 and 54 μM) were analyzed. At the end of the trail, photosynthetic pigment contents, total protein amounts, the enzymatic antioxidants superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) activities and the amount of malondialdehyde (MDA) in the leaf samples of E. amazonicus were investigated. The antioxidant enzyme activities increased at low concentrations (32.13% for SOD, 185% for CAT and 201.5% for POX in the groups of 6 μM As⁺⁵), but decreased at high concentrations (64.98% for SOD, 21.64% for CAT and 21.29% for POX in the groups of 54 μM As⁺³). MDA increased in all the treatment groups. The highest MDA contents were observed as 96% for 54 μM As⁺³ and 71.50% for 54 μM As⁺⁵. Photosynthetic pigment contents and the amount of protein were decreased with higher concentrations. The most significant decreases in protein content were 65% for 54 μM As⁺³ and 34.9% for 54 μM As⁺⁵. As a result, the toxicity of As⁺³ was higher and the toxic effect increased at higher concentrations.

Ulexite modulates the neurotoxicological outcomes of acetylferrocene-exposed rainbow trout

In this study, the neuroprotective action potential by ulexite (UX) (18.75 mg/L) against acetylferrocene (AFC) (3.82 mg/L) induced neurotoxicity was aimed to investigate in brain tissues of Oncorhynchus mykiss. For this purpose, the effects on neurotoxicity markers, proinflammatory cytokines, antioxidant immune system, DNA, and apoptosis mechanisms were assessed on brain tissues in the 48-96  h of the 96- trial period. In this research, it was determined that brain-derived nerve cell growth factor (BDNF) level and acetylcholinesterase (AChE) activity were inhibited in the brain tissue compared to the control group by AFC. In addition, inhibition in glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) values (which are antioxidant system biomarkers), and inductions in malondialdehyde (MDA) and myeloperoxidase (MPO) amounts (which are indicators of lipid peroxidation) were determined (p < 0.05) after exposure to AFC. And, while tumor necrosis factor-α (TNF-α) and IL-6 levels were increased in the AFC-exposed group, Nrf-2 levels were found to be remarkably decreased. Upregulation was also detected in 8-hydroxydeoxyguanosine (8-OHdG) and caspase-3 levels, which are related to DNA damage and apoptosis mechanism. On the contrary, UX (single/with AFC) suppressed the AChE and BDNF inhibition by AFC. Moreover, UX mitigated AFC-induced oxidative, inflammatory, and DNA damage and attenuated AFC-mediated neurotoxicity via activating Nrf2 signaling in fish. Collectively, our findings revealed that UX supplementation might exert beneficial effects and may be considered as a natural and promising neuroprotective agent against AFC-induced toxicity.

Superoxide Radical-Mediated Self-Synthesized Au/MoO3-x Hybrids with Enhanced Peroxidase-like Activity and Photothermal Effect for Anti-MRSA Therapy

A rapid increase in methicillin-resistant Staphylococcus aureus (MRSA) induced infection has been noticed in recent years and the biofilm formed by MRSA further delays wound healing, causing a high mortality rate. Hence, a safe and effective superoxide radical (O₂^•-) mediated self-synthesis strategy is developed to prepare Au-doped MoO_3-x (Au/MoO_3-x) plasmonic-semiconductor hybrid for the elimination of MRSA mediated wound infection. The synthesis mechanism of Au NPs is systematically investigated, proving that O₂^•- plays a key role in reduction of HAuCl₄ into Au NPs in the presence of H₂O and O₂. Au-doped MoO_3-x exhibits the improved photothermal conversion efficiency (∼52.40%) compared with MoO_3-x (∼41.11%). Moreover, the peroxidase (POD)-like activity of Au/MoO_3-x hybrid is higher than that of MoO_3-x NPs, resulting in increased yield of highly toxic ·OH. In combination with the enhanced photothermal and POD-like properties, Au/MoO_3-x hybrid achieves efficient elimination of MRSA bacteria with eradication ratio of ∼99.76%. Additionally, the as-prepared Au/MoO_3-x NPs exhibit excellent biosafety, which is verified via in vitro and in vivo experiments. This study provides the basis for exploring MoO_3-x-based hybrids via a green O₂^•--mediated self-synthesis approach.

Strategies in a metallophyte species to cope with manganese excess

The effect of exposure to high Mn concentration was studied in a metallophyte species, Erica andevalensis, using hydroponic cultures with a range of Mn concentrations (0.06, 100, 300, 500, and 700 mg L^-1). At harvest, biomass production, element uptake, and biochemical indicators of metal stress (leaf pigments, organic acids, amino acids, phenols, and activities of catalase, peroxidase, superoxide dismutase) were determined in leaves and roots. Increasing Mn concentrations led to a decrease in biomass accumulation, and tip leaves chlorosis was the only toxicity symptom detected. In a similar way, photosynthetic pigments (chlorophylls a and b, and carotenoids) were affected by high Mn levels. Among organic acids, malate and oxalate contents in roots showed a significant increase at the highest Mn concentration, while in leaves, Mn led to an increasing trend in citrate and malate contents. An increase of Mn also induced an increase in superoxide dismutase activity in roots and catalase activity in leaves. As well, significant changes in free amino acids were induced by Mn concentrations higher than 300 mg L^-1, especially in roots. No significant changes in phenolic compounds were observed in the leaves, but root phenolics were significantly increased by increasing Mn concentrations in treatments. When Fe supply was increased 10 and 20 times (7-14 mg Fe L^-1 as Fe-EDDHA) in the nutrient solutions at the highest Mn concentration (700 mg Mn L^-1), it led to significant increases in photosynthetic pigments and biomass accumulation. Manganese was mostly accumulated in the roots, and the species was essentially a Mn excluder. However, considering the high leaf Mn concentration recorded without toxicity symptoms, E. andevalensis might be rated as a Mn-tolerant species.

Iodine-doped carbon dots with inherent peroxidase catalytic activity for photocatalytic antibacterial and wound disinfection

A new type of nitrogen-iodine co-doped carbon dot (N/I-CD) was synthesized by a one-step hydrothermal method with a fluorescence quantum yield of 37%. The prepared N/I-CDs exhibit peroxidase-like activity, can catalyze bio-safety levels of H2O2 to generate hydroxyl radicals (•OH) under visible light and enhance the level of reactive oxygen species (ROS) in bacteria cells. All in vitro experiments showed that the designed system has strong photocatalytic antibacterial activity against both E. coli and S. aureus bacteria. The light-induced antibacterial function of N/I-CDs was evaluated under the conditions of changing other experimental parameters. When the visible light irradiation time was extended to 60 min, the antibacterial efficiency of N/I-CDs (0.21 mg·mL-1) against S. aureus and E. coli reached 100% in the presence of exogenous H2O2 (0.07 mM). More importantly, wound disinfection in vivo demonstrates the high antibacterial efficiency, low toxicity and application potential of good biocompatibility due to the nanozyme activity of N/I-CDs.

A two-step gas/liquid strategy for the production of N-doped defect-rich transition metal dichalcogenide nanosheets and their antibacterial applications

Herein, we developed a general two-step gas expansion and exfoliation strategy based on a urea-assisted hydrothermal process combined with sonication exfoliation for the production of nitrogen (N)-doped plus defect-rich transition metal dichalcogenide (TMD) nanosheets (NSs) such as N-MoS₂ and N-WS₂ NSs. The interlayers of bulk MoS₂ (or WS₂) were expanded with urea molecules dissolved in distilled water, which were decomposed to NH₃ during the hydrothermal process. Simultaneously, sulfur atoms were partly replaced by N atoms to achieve N doping. Subsequently, sonication exfoliation of the urea-treated bulk MoS₂ (or WS₂) promoted the production of defect-rich NSs. Importantly, the defect-rich N-MoS₂ and N-WS₂ NSs exhibit enhanced peroxidase-like catalytic activity after being captured by bacteria, and can catalyze hydrogen peroxide (H₂O₂) to produce more toxic hydroxyl radicals (˙OH) than non-N-doped MoS₂ or WS₂ NSs. As a result, the N-MoS₂ or N-WS₂ NSs were capable of effectively killing Gram-negative ampicillin resistant Escherichia coli (Amp^rE. coli) and Gram-positive endospore-forming Bacillus subtilis (B. subtilis) and promoting bacteria-infected wound healing. This work not only provides a simple, universal exfoliation strategy for producing defect-rich N-doped TMD NSs but also provides a promising catalytic antibacterial option and has potential for many other catalytic applications.

Virus-Like Fe3O4@Bi2S3 Nanozymes with Resistance-Free Apoptotic Hyperthermia-Augmented Nanozymitic Activity for Enhanced Synergetic Cancer Therapy

Nanomaterials with intrinsic peroxidase-like activities are able to catalyze the oxidation of the substrate with the peroxide, which have been widely considered as artificial enzymatic agents in cancer therapy. However, current peroxidase catalytic oxidation treatments generating reactive oxygen species rely highly on hydrogen peroxide and pH, which limit greatly their therapeutic efficiency in the tumor microenvironment. Here, we report a strategy to construct the complex virus-like Fe₃O₄@Bi₂S₃ nanocatalysts (F-BS NCs) by connecting typical peroxidase Fe₃O₄ (MNPs) with a narrow band gap semiconductor Bi₂S₃ (BS) to enhance the enzymatic activity resorting to the limited intratumoral peroxide and efficient external photothermal stimuli. In this formulation, the integrated F-BS NCs induce cancer-cell death through mild photothermal treatment and sequential photothermal-stimulative catalysis of H₂O₂ into highly toxic ^•OH under 808 nm laser, which successfully realize a remarkable synergistic anticancer achievement.

Enzyme-Like Metal-Organic Frameworks in Polymeric Membranes for Efficient Removal of Aflatoxin B1

Biodegradation is a mild and efficient way to protect humans and animals from mycotoxins. However, microbes and enzymes are susceptible to environmental change, lack of stability, and reusability. In this work, three peroxidase-like metal-organic frameworks (MOFs), as artificial substitutes of natural peroxidase, are used for aflatoxin B₁ (AFB₁) removal, demonstrating the strong removal ability for AFB₁ and anti-interference ability toward other substances. There are distinct adsorption and catalytic properties among these MOFs that are mainly because of the differences in structure and Fe ion active sites. Then, we immobilized these MOFs into ultrafiltration membranes to form a multifunctional membrane (i.e., filtration, adsorption, and catalysis) for AFB₁ removal with good reusability that can be operated in simultaneous adsorption/catalysis or adsorption followed by catalysis/regeneration modes. Physicochemical analysis and animal experiments showed that the degradation products are probably several low-carbon substances whose toxic groups are cleaved.

MPO (Myeloperoxidase) Reduces Endothelial Glycocalyx Thickness Dependent on Its Cationic Charge

Objective- The leukocyte heme-enzyme MPO (myeloperoxidase) exerts proinflammatory effects on the vascular system primarily linked to its catalytic properties. Recent studies have shown that MPO, depending on its cationic charge, mediates neutrophil recruitment and activation. Here, we further investigated MPO's extracatalytic properties and its effect on endothelial glycocalyx (EG) integrity. Approach and Results- In vivo staining of murine cremaster muscle vessels with Alcian Blue 8GX provided evidence of an MPO-dependent decrease in anionic charge of the EG. MPO binding to the glycocalyx was further characterized using Chinese hamster ovary cells and its glycosaminoglycan mutants-pgsA-745 (mutant Chinese hamster ovary cells lacking heparan sulfate and chondroitin sulfate glycosaminoglycan) and pgsD-677 (mutant Chinese hamster ovary cells lacking heparan sulfate glycosaminoglycan), which revealed heparan sulfate as the main mediator of MPO binding. Further, EG integrity was assessed in terms of thickness using intravital microscopy of murine cremaster muscle. A significant reduction in EG thickness was observed on infusion of catalytically active MPO, as well as mutant inactive MPO and cationic polymer polylysine. Similar effects were also observed in wild-type mice after a local inflammatory stimulus but not in MPO-knockout mice. The reduction in EG thickness was reversed after removal of vessel-bound MPO, suggesting a possible physical collapse of the EG. Last, experiments with in vivo neutrophil depletion revealed that MPO also induced neutrophil-mediated shedding of the EG core protein, Sdc1 (syndecan-1). Conclusions- These findings provide evidence that MPO, via ionic interaction with heparan sulfate side chains, can cause neutrophil-dependent Sdc1 shedding and collapse of the EG structure.

Unraveling the Enzymatic Activity of Oxygenated Carbon Nanotubes and Their Application in the Treatment of Bacterial Infections

Carbon nanotubes (CNTs) and their derivatives have emerged as a series of efficient biocatalysts to mimic the function of natural enzymes in recent years. However, the unsatisfiable enzymatic efficiency usually limits their practical usage ranging from materials science to biotechnology. Here, for the first time, we present the synthesis of several oxygenated-group-enriched carbon nanotubes (o-CNTs) via a facile but green approach, as well as their usage as high-performance peroxidase mimics for biocatalytic reaction. Exhaustive characterizations of the enzymatic activity of o-CNTs have been provided by exploring the accurate effect of various oxygenated groups on their surface including carbonyl, carboxyl, and hydroxyl groups. Because of the "competitive inhibition" effect among all of these oxygenated groups, the catalytic efficiency of o-CNTs is significantly enhanced by weakening the presence of noncatalytic sites. Furthermore, the admirable enzymatic activity of these o-CNTs has been successfully applied in the treatment of bacterial infections, and the results of both in vitro and in vivo nanozyme-mediated bacterial clearance clearly demonstrate the feasibility of o-CNTs as robust peroxidase mimics to effectively decrease the bacterial viability under physiological conditions. We believe that the present study will not only facilitate the construction of novel efficient nanozymes by rationally adjusting the degree of the "competitive inhibition" effect, but also broaden the biological usage of o-CNT-based nanomaterials via their satisfactory enzymatic activity.

Peroxidasin contributes to lung host defense by direct binding and killing of gram-negative bacteria

Innate immune recognition is classically mediated by the interaction of host pattern-recognition receptors and pathogen-associated molecular patterns; this triggers a series of downstream signaling events that facilitate killing and elimination of invading pathogens. In this report, we provide the first evidence that peroxidasin (PXDN; also known as vascular peroxidase-1) directly binds to gram-negative bacteria and mediates bactericidal activity, thus, contributing to lung host defense. PXDN contains five leucine-rich repeats and four immunoglobulin domains, which allows for its interaction with lipopolysaccharide, a membrane component of gram-negative bacteria. Bactericidal activity of PXDN is mediated via its capacity to generate hypohalous acids. Deficiency of PXDN results in a failure to eradicate Pseudomonas aeruginosa and increased mortality in a murine model of Pseudomonas lung infection. These observations indicate that PXDN mediates previously unrecognized host defense functions against gram-negative bacterial pathogens.

Nanocatalysts promote Streptococcus mutans biofilm matrix degradation and enhance bacterial killing to suppress dental caries in vivo

Dental biofilms (known as plaque) are notoriously difficult to remove or treat because the bacteria can be enmeshed in a protective extracellular matrix. It can also create highly acidic microenvironments that cause acid-dissolution of enamel-apatite on teeth, leading to the onset of dental caries. Current antimicrobial agents are incapable of disrupting the matrix and thereby fail to efficiently kill the microbes within plaque-biofilms. Here, we report a novel strategy to control plaque-biofilms using catalytic nanoparticles (CAT-NP) with peroxidase-like activity that trigger extracellular matrix degradation and cause bacterial death within acidic niches of caries-causing biofilm. CAT-NP containing biocompatible Fe3O4 were developed to catalyze H2O2 to generate free-radicals in situ that simultaneously degrade the biofilm matrix and rapidly kill the embedded bacteria with exceptional efficacy (>5-log reduction of cell-viability). Moreover, it displays an additional property of reducing apatite demineralization in acidic conditions. Using 1-min topical daily treatments akin to a clinical situation, we demonstrate that CAT-NP in combination with H2O2 effectively suppress the onset and severity of dental caries while sparing normal tissues in vivo. Our results reveal the potential to exploit nanocatalysts with enzyme-like activity as a potent alternative approach for treatment of a prevalent biofilm-associated oral disease.

Cationic peptides neutralize Ox-LDL, prevent its uptake by macrophages, and attenuate inflammatory response

OBJECTIVE

Apolipoprotein A1 (ApoA1) and apolipoprotein E (ApoE) mimetic peptides have attracted attention due to their ability to reduce atherosclerosis and exhibit antioxidant, anti-inflammatory, and hypolipidemic properties. In this study, we tested whether three distinct and unrelated cationic peptides would inhibit the oxidation of lipoproteins and whether they would counteract and neutralize the negatively charged modified lipoproteins, inhibit their uptake and inflammation by macrophages.

METHODS AND RESULTS

5F-mimetic peptide of ApoA1, LL27 derived from the anti-microbial peptide hCAP, and a human glycodelin derived peptide were commercially synthesized. We noted that these three distinct cationic lysine-rich peptides, two of which were unrelated to any known apolipoproteins, inhibited copper-mediated oxidation of lipoproteins and reduced lipid peroxides in a lysine dependent manner. The peptides also retarded the electrophoretic mobility of previously oxidized LDL and acetylated LDL by virtue of their net positive charge. Pre-incubation of peptides with modified lipoproteins reduced the uptake of the latter by macrophages, thus preventing the formation of foam cells. The cationic peptides inhibited oxidized LDL (Ox-LDL)-induced inflammatory response both in vitro and in vivo.

CONCLUSION

Based on these results, we suggest that in addition to the well known mimetic peptides, other suitable cationic peptides may be of use for controlling Ox-LDL mediated inflammation and atherosclerotic progression.

Peroxidasin-like protein: a novel peroxidase homologue in the human heart

AIMS

Peroxidases serve diverse biological functions including well-characterized activities in host defence and hormone biosynthesis. More recently, peroxidasin (PXDN) was found to be involved in collagen IV cross-linking in the extracellular matrix (ECM). The aim of this study was to characterize the expression and function of peroxidasin-like protein (PXDNL), a previously unknown peroxidase homologue.

METHODS AND RESULTS

We cloned the PXDNL cDNA from the human heart and identified its expression pattern by northern blot, in situ hybridization, and immunohistochemistry. PXDNL is expressed exclusively in the heart and it has evolved to lose its peroxidase activity. The protein is produced by cardiomyocytes and localizes to cell-cell junctions. We also demonstrate that PXDNL can form a complex with PXDN and antagonizes its peroxidase activity. Furthermore, we show an increased expression of PXDNL in the failing myocardium.

CONCLUSION

PXDNL is a unique component of the heart with a recently evolved inactivation of peroxidase function. The elevation of PXDNL levels in the failing heart may contribute to ECM dysregulation due to its antagonism of PXDN function.

Myeloperoxidase induces the priming of platelets

The release of myeloperoxidase (MPO) from polymorphonuclear neutrophils is a hallmark of vascular inflammation and contributes to the pathogenesis of vascular inflammatory processes. However, the effects of MPO on platelets as a contributory mechanism in vascular inflammatory diseases remain unknown. Thus, MPO interaction with platelets and its effects on platelet function were examined. First, dose-dependent binding of MPO (between 1.7 and 13.8nM) to both human and mouse platelets was observed. This was in direct contrast to the absence of MPO in megakaryocytes. MPO was localized both on the surface of and inside platelets. Cytoskeleton inhibition did not prevent MPO localization inside the three-dimensional platelet structure. MPO peroxidase activity was preserved upon the MPO binding to platelets. MPO sequestered in platelets catabolized NO, documented by the decreased production of NO (on average, an approximately 2-fold decrease). MPO treatment did not affect the viability of platelets during short incubations; however, it decreased platelet viability after long-term storage for 7 days (an approximately 2-fold decrease). The activation of platelets by MPO was documented by an MPO-mediated increase in the expression of surface platelet receptors P-selectin and PECAM-1 (of about 5 to 20%) and the increased formation of reactive oxygen species (of about 15 to 200%). However, the activation was only partial, as MPO did not induce the aggregation of platelets nor potentiate platelet response to classical activators. Nor did MPO induce a significant release of the content of granules. The activation of platelets by MPO was connected with increased MPO-treated platelet interaction with polymorphonuclear leukocytes (an approximately 1.2-fold increase) in vitro. In conclusion, it can be suggested that MPO can interact with and activate platelets, which can induce priming of platelets, rather than the classical robust activation of platelets. This can contribute to the development of chronic inflammatory processes in vessels.

The effect of nitrobenzene on antioxidative enzyme activity and DNA damage in tobacco seedling leaf cells

Nitrobenzene, although widely used in industry, is a highly toxic environmental pollutant. To evaluate the toxicity of nitrobenzene to tobacco seedlings, seedlings were exposed to varying concentrations of nitrobenzene (0-100 mg/L) for 24 h. The contents of reactive oxygen species (hydrogen peroxide [H(2)O(2)] and superoxide anion [O2(-)]) and the activities of antioxidative enzymes (superoxide dismutase [SOD], guaiacol peroxidase [POD], and catalase [CAT]) were measured in leaf cells. Damage to DNA was assessed by single-cell gel electrophoresis (comet assay). Compared with the control, the contents of H(2) O(2) increased significantly with nitrobenzene concentrations ranging from 5 to 100 mg/L. Activity of SOD was induced by 50 to 100 mg/L of nitrobenzene but not by 10 to 25 mg/L. Activity of POD was stimulated by nitrobenzene at 10 to 50 mg/L but inhibited at 100 mg/L. Activity of CAT was increased significantly only by 100 mg/L. Lipid peroxidation increased with 50 to 100 mg/L, which indicated that nitrobenzene induced oxidative stress in tobacco leaf cells. Comet assay of the leaf cells showed a significant enhancement of the head DNA (H-DNA), tail DNA (T-DNA), and olive tail moment (OTM) with increasing doses of nitrobenzene. The values of H-DNA, T-DNA, and OTM exhibited significant differences from the control when stress concentrations were higher than 10 mg/L. The results indicated that nitrobenzene caused oxidative stress, which may be one of the mechanisms through which nitrobenzene induces DNA damage.

Exposure of endothelial cells to physiological levels of myeloperoxidase-modified LDL delays pericellular fibrinolysis

BACKGROUND

Blood fluidity is maintained by a delicate balance between coagulation and fibrinolysis. The endothelial cell surface is a key player in this equilibrium and cell surface disruptions can upset the balance. We investigated the role of pericellular myeloperoxidase oxidized LDLs (Mox-LDLs) in this balance.

METHODS AND RESULTS

We designed a technical device that enabled us to monitor fibrinolysis in real-time at the surface of an endothelial cell line (EA.hy926), and showed that Mox-LDL decreased pericellular fibrinolysis. There were no changes in fibrinolysis when EA.hy926 endothelial cells were exposed to native LDL (24 hours) at doses of 10, 50, 100 and up to 1250 µg/ml. However, treatment of EA.hy926 endothelial cells with 10 and 50 µg/ml of Mox-LDL (physiological serum concentrations) increased the lysis time by 15 and 13%, respectively (p<0.001), although this effect was not present at higher concentrations of 100 µg/ml. This effect was not correlated with any changes in PAI-1 or t-PA or PA Receptor (PAR) expression. No effect was observed at the surface of smooth muscle cells used as controls.

CONCLUSION

Our data link the current favorite hypothesis that modified LDL has a causal role in atheroma plaque formation with an old suggestion that fibrin may also play a causal role. Our data help complete the paradigm of atherosclerosis: Modified LDL locally enhances fibrin deposition (present work); fibrin deposits enhance endothelial permeability; this effect allows subendothelial accumulation of lipid and foam cells.

[Bactericidal effect of soybean peroxidase-hydrogen peroxide-potassium iodide system]

OBJECTIVE

To study the bactericidal effect and the possible mechanisms of the three components system [soybean peroxidases (SBP)-hydrogen peroxide (H2O2)-potassium iodide (KI), SBP-H2O2-KI].

METHODS

The inhibition and bactericidal effect of SBP-H2O2-KI system to bacteria was detected by OD600 and the number of live bacteria (CFU). The sensitivity was tested by comparing the minimum inhibitory concentration (MIC) of bacterial cultures before and after cultured under sub-lethal dose of SBP-H2O2-KI system. Oxidizing activity groups were detected with physical and chemical methods in order to explain the bactericidal mechanisms of SBP-H2O2-KI system.

RESULTS

SBP-H2O2-KI ternary system had rapid and high efficient bactericidal effect to a variety of bacterial strains in just several minutes. The MICs had no significant changes when bacterial cultures continuously cultured in sub-lethal dose of SBP-H2O2-KI system, and no resistance/tolerance mutant strains could be isolated from them. Both physical and chemical test results showed that no hydroxyl radical produced in SBP- H2O2-KI reaction system, chemical test results showed that no superoxide anion but a singlet oxygen and iodine produced in SBP-H2O2-KI reaction system.

CONCLUSION

These results suggested that singlet oxygen and iodine or the iodine intermediate state may possible be the main sterilization factors for SBP-H2O2-KI system, and hydroxyl radical and superoxide anion not. In addition, the both characteristics of SBP-H2O2-KI system: rapid and high efficient bactericidal effect, and bacteria difficultly resisting to it, indicated it would have a good potential application in medical and plant protection area.

In vitro antibacterial activity of E-101 Solution, a novel myeloperoxidase-mediated antimicrobial, against Gram-positive and Gram-negative pathogens

OBJECTIVES

E-101 Solution (E-101) is a novel myeloperoxidase-mediated antimicrobial. It is composed of porcine myeloperoxidase (pMPO), glucose oxidase, glucose as the substrate and specific amino acids in an aqueous vehicle. E-101 is being developed for topical application directly into surgical wounds to prevent surgical site infections (SSIs). The in vitro activity of E-101 was investigated.

METHODS

MIC, MBC, time-kill and antimicrobial combination experiments were performed according to CLSI guidelines with modifications. Resistance selection studies were performed using a serial passage method.

RESULTS

E-101 showed MIC(90) values of 0.03, 0.5 and 0.5 mg pMPO/L for staphylococci (n = 140), streptococci (n = 95) and enterococci (n = 55), respectively. MIC(90) values ranged between 0.03-0.5 and ≤ 0.004-0.12 mg pMPO/L for Enterobacteriaceae (n = 148) and Gram-negative non-Enterobacteriaceae (n = 92) strains, respectively. There was no antimicrobial tolerance to E-101 for Staphylococcus aureus, Streptococcus agalactiae or Streptococcus pyogenes. Time-kill studies demonstrated a rapid (<30 min) bactericidal effect against S. aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa in a concentration-dependent and time-dependent manner. There was no evidence of stable resistance to E-101 among staphylococci, enterococci, E. coli or P. aeruginosa strains and no evidence of E-101 interaction with antibiotics commonly used in clinical medicine. Conclusions E-101 shows potent and broad-spectrum in vitro activity against bacteria that are the causative pathogens of SSIs, thereby providing the impetus to test its clinical utility in the prevention of SSIs.

Anti-inflammatory evaluation of Coronopus didymus in the pleurisy and paw oedema models in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Mastrunço (Coronopus didymus--CD) is currently considered as a medicinal specie often used in Brazil, especially in southeast region, for the treatment of several diseases in which pain and inflammation are common. Treatment with the plant can be done by infusion, decoction, or through food. The aim of this study was: to investigate the anti-inflammatory effect of hydroalcoholic extract obtained from the leaves of CD following the traditional procedure.

MATERIALS AND METHODS

The anti-inflammatory activity was determined using mouse of pleurisy and paw oedema models, both process being induced by different flogistic agents such as: carrageenan (Cg), bradykinin (BK), histamine (HIS), substance P (SP), dextran (DEX) or prostaglandin E(2) (PGE(2)). We evaluated the effect of CD (200-600 mg/kg) administered by oral route (p.o.) upon leukocytes migration, myeloperoxidase (MPO), and adenosine-deaminase (ADA) activities and nitric oxide (NO) levels.

RESULTS

CD (200-600 mg/kg) inhibited the leukocytes by 60.0+/-1.42%, neutrophils by 82.75+/-1.29%, MPO by 42.30+/-4.23%, and ADA activities by 57.89+/-1.94%, as well as NO levels by 64.28+/-2.15% in Cg induced pleurisy. CD also inhibited total and differential leukocytes in the pleurisy induced by BK (1.30+/-0.11/0.29+/-0.02), HIS (1.20+/-0.09/0.42+/-0.05) and SP (0.74+/-0.06/0.14+/-0.01). In addition, CD was effective in reducing paw oedema induced by Cg by 72.79+/-1.13%, SP by 68.26.+/-0.78%, BK by 66.66.+/-0.77%, PGE(2) by 53.346.+/-1.18 and DEX by 65.14+/-2.35%.

CONCLUSION

Several mechanisms, including the inhibition of enzymes (MPO and ADA) and mediators (BK, HIS, SP, NO and PGE(2)) release and/or action, appear to account for the anti-inflammatory effect of Coronopus didymus.

The main components of St John's Wort inhibit low-density lipoprotein atherogenic modification: A beneficial “side effect” of an OTC antidepressant drug?

Hypericin and pseudohypericin are polycyclic-phenolic structurally related compounds found in Hypericum perforatum L. (St John's wort). As hypericin has been found to bind to LDL one may assume that it can act as antioxidant of LDL lipid oxidation, a property which is of prophylactic/therapeutic interest regarding atherogenesis as LDL oxidation may play a pivotal role in the onset of atherosclerosis. Therefore, in the present paper hypericin, pseudohypericin and hyperforin, an other structurally unrelated constituent in St John's wort were tested in their ability to inhibit LDL oxidation. LDL was isolated by ultracentrifugation and oxidation was initiated either by transition metal ions (copper), tyrosyl radical (myeloperoxidase/hydrogen peroxide/tyrosine) or by endothelial cells (HUVEC). LDL modification was monitored by conjugated diene and malondialdehyde formation. The data show that all compounds (hypericin, pseudohypericin and hyperforin) at doses as low as 2.5 micromol/l are potent antioxidants in the LDL oxidation systems used. The results indicate that the derivatives found in Hypericum perforatum have possible antiatherogenic potential.

The effect of sulfasalazine and its active components on human polymorphonuclear leukocyte function in relation to ulcerative colitis

Sulfasalazine and its active components, 5-aminosalicylic acid (5-ASA) and sulfapyridine (SP), are potent modulators of inflammatory reactions but with somewhat different modes of action. Investigating the effect of these compounds on normal human polymorphonuclear leukocytes in vitro, we show inhibition of different stages in the phagocytic process, such as migration (sulfasalazine and SP), superoxide production (sulfasalazine and SP), myeloperoxidase-mediated iodination and cytotoxicity (5-ASA and SP). It is thus suggested that sulfasalazine is not just a vehicle for delivering its active components in the colon, but that its therapeutic effect is ulcerative colitis and other inflammatory reactions is a result of the concurrent action of the three compounds.

The beneficial effect of Rheum tanguticum polysaccharide on protecting against diarrhea, colonic inflammation and ulceration in rats with TNBS-induced colitis: the role of macrophage mannose receptor in inflammation and immune response

Rhubarb has been used as a folk remedy for gastrointestinal disease in China for over two thousand years. In the present study, we evaluated the effect of Rheum tanguticum polysaccharide (RTP), a water soluble fraction extracted from rhubarb, on protection from inflammation and colonic damage in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats. RTP protected against diarrhea, colon weight increase, and ulceration induced by TNBS. It was at least as effective as dexamethasone (DEX). RTP significantly decreased myeloperoxidase (MPO) activity in the colonic mucosa. Oral administration of RTP was as effective as intraperitoneal (i.p.) injection on toxicity protection and MPO activity. To further investigate the possible underlying mechanism, we studied the role of mannose receptor (MR) in cytokine secretion, ligand binding and endocytosis of macrophages. The secretion of IFN-gamma was dramatically increased while IL-4 decreased in colitis compared to the control (normal rats), and RTP restored the condition similar to the control in vivo. The secretion of IFN-gamma by macrophages was induced by RTP and lipoarabinomannan (LAM) but not mannose in vitro. Mannose completely inhibited the effect of RTP, while RTP and LAM affected each other on IFN-gamma secretion. The MR-mediated ligand binding and endocytosis of macrophages were markedly decreased in colitis and RTP restored their function to near normal condition. The results indicated that RTP targeted MR and down-regulation of Th1-polarized immune response may be the possible mechanism for its attenuation of intestinal inflammation and damage. RTP may be useful for treatment of patients with inflammatory bowel disease.

Lifespan of etoposide-treated human neutrophils is affected by antioxidant ability of quercetin

Neutropenia is the primary dose-limiting effect of etoposide toxicity resulting in a decreased efficiency of cancer treatment. Hence, the protection of neutrophils has important clinical implications. We investigated whether quercetin, due to its antioxidant properties, is able to modulate the damaging activity of etoposide. DNA damage, evaluated by the comet assay, and apoptosis, determined by FACScan flow cytometry using Annexin/PI, increased with etoposide doses. The intracellular level of reactive oxygen species (ROS) was enhanced in resting neutrophils incubated with etoposide at concentrations up to 25 microM; above this concentration etoposide revealed antioxidant properties. Only in latex-activated neutrophils, i.e. with latex-stimulated respiratory burst was the ROS production inhibited, as assessed by the luminol amplified chemiluminescence. The characteristic electron spin resonance (ESR) signal of etoposide phenoxyl radical, which occurs in the presence of myeloperoxidase, H2O2 and etoposide, was quenched by quercetin in a dose-dependent manner (0.1-0.5 microM). Quercetin also inhibited DNA damage induced by etoposide and enhanced the inhibitory action of etoposide on the ROS formation in neutrophils. However, quercetin (1 microM) lowered early and late apoptosis/necrosis only when apoptosis was induced by 25 microM etoposide; at higher etoposide concentration apoptosis was enhanced. Summing up, antioxidant adjuvant therapy using quercetin can be beneficial in prolonging neutrophils' lifespan in peripheral blood only when etoposide plasma concentration is low.

Neurokinin-1 receptor antagonist treatment protects mice against lung injury in polymicrobial sepsis

Earlier work from our laboratory has suggested a role for the neuropeptide substance P (SP) in inducing lung injury in sepsis. In that study, mice lacking the preprotachykinin-A gene, which encodes for SP, were protected against lung injury in sepsis. To further substantiate the role of SP in sepsis and to study its mechanism, we have evaluated the effect of SR140333, a SP receptor antagonist, on lung injury in sepsis, which was induced in male Swiss mice by cecal ligation and puncture (CLP). Sham-operated animals received the same surgical procedure, except CLP. Vehicle or SR140333 (1 mg/kg, s.c.) was administered to CLP mice 30 min before or 1 h after the CLP. Eight hours after surgery, lung tissue was collected and analyzed for myeloperoxidase (MPO) activity, chemokines, cytokines, and adhesion molecules. The CLP procedure alone caused a significant increase in the lung levels of MIP-2, MCP-1, IL-1beta, IL-6, ICAM-1, E- and P-selectin, and MPO activity when compared with sham-operated mice. SR140333 injected 30 min before or 1 h after CLP significantly attenuated the increased lung MPO activity and levels of MIP-2, MCP-1, IL-1beta, IL-6, ICAM-1, and E- and P-selectin compared with CLP-operated mice injected with the vehicle. Histological evaluation of the lung sections further supported the beneficial effect of SR140333 on lung inflammation. Therefore, SP receptor antagonism can be a potential therapeutic target in polymicrobial sepsis, and this effect is brought about via reduction in leukocyte recruitment.

Betanin inhibits the myeloperoxidase/nitrite-induced oxidation of human low-density lipoproteins

Production of nitrogen dioxide by the activity of myeloperoxidase (MPO) in the presence of nitrite is now considered a key step in the pathophysiology of low-density lipoprotein (LDL) oxidation. This study shows that betanin, a phytochemical of the betalain class, inhibits the production of lipid hydroperoxides in human LDL submitted to a MPO/nitrite-induced oxidation. Kinetic measurements including time-course of particle oxidation and betanin consumption, either in the presence or in the absence of nitrite, suggest that the antioxidant effect is possibly the result of various actions. Betanin scavenges the initiator radical nitrogen dioxide and can also act as a lipoperoxyl radical-scavenger. In addition, unidentified oxidation product(s) of betanin by MPO/nitrite inhibit(s) the MPO/nitrite-induced LDL oxidation as effectively as the parent compound. In the light of betanin bioavailability and post-absorbtion distribution in humans, present findings may suggest favourable in vivo activity of this phytochemical.

Intramolecular Electron Transfer between Tyrosyl Radical and Cysteine Residue Inhibits Tyrosine Nitration and Induces Thiyl Radical Formation in Model Peptides Treated with Myeloperoxidase, H2O2, and NO2-

We investigated the effects of a cysteine residue on tyrosine nitration in several model peptides treated with myeloperoxidase (MPO), H(2)O(2), and nitrite anion (NO(2)(-)) and with horseradish peroxidase and H(2)O(2). Sequences of model peptides were acetyl-Tyr-Cys-amide (YC), acetyl-Tyr-Ala-Cys-amide (YAC), acetyl-Tyr-Ala-Ala-Cys-amide (YAAC), and acetyl-Tyr-Ala-Ala-Ala-Ala-Cys-amide (YAAAAC). Results indicate that nitration and oxidation products of tyrosyl residue in YC and other model peptides were barely detectable. A major product detected was the corresponding disulfide (e.g. YCysCysY). Spin trapping experiments with 5,5'-dimethyl-1-pyrroline N-oxide (DMPO) revealed thiyl adduct (e.g. DMPO-SCys-Tyr) formation from peptides (e.g. YC) treated with MPO/H(2)O(2) and MPO/H(2)O(2)/NO(2)(-). The steady-state concentrations of DMPO-thiyl adducts decreased with increasing chain length of model peptides. Blocking the sulfydryl group in YC with methylmethanethiosulfonate (that formed YCSSCH(3)) totally inhibited thiyl radical formation as did substitution of Tyr with Phe (i.e. FC) in the presence of MPO/H(2)O(2)/NO(2)(-). However, increased tyrosine nitration, tyrosine dimerization, and tyrosyl radical formation were detected in the MPO/H(2)O(2)/NO(2)(-)/YCSSCH(3) system. Increased formation of S-nitrosated YC (YCysNO) was detected in the MPO/H(2)O(2)/(*)NO system. We conclude that a rapid intramolecular electron transfer reaction between the tyrosyl radical and the Cys residue impedes tyrosine nitration and induces corresponding thiyl radical and nitrosocysteine product. Implications of this novel intramolecular electron transfer mechanism in protein nitration and nitrosation are discussed.

Inducible nitric oxide synthase expression is inhibited by myeloperoxidase

Nitric oxide (NO) plays key roles in vasodilation and host defense, yet the overproduction of NO by inducible nitric oxide synthase (iNOS) at inflammatory sites can also be pathogenic. Here, we investigate the role of MPO in modulating the induction of iNOS by IFNgamma/LPS (IL). In monocyte-macrophages (Mvarphi) treated with IL, MPO gene expression was found to be downregulated as iNOS was upregulated. In Mvarphi from MPO-knockout (KO) mice, the induction of iNOS by IL was earlier and higher than in MPO-positive cells, suggesting MPO is inhibitory. Consistent with that interpretation, the addition of purified MPO enzyme to cultured macrophages inhibited iNOS induction by IL. In addition, an inhibitor of MPO enzyme, 4-aminobenzohydrazide, enhanced iNOS induction in MPO-positive cells, but not in MPO-KO cells. Similarly, taurine, a scavenger of MPO-generated HOCl, enhanced iNOS induction in MPO-positive cells, but not in MPO-KO cells. MPO affects an early event, suppressing iNOS induction when added within 2h of IL, but not when added several hours after IL. The suppression by MPO was alleviated by NO donor, sodium nitroprusside, suggesting the suppression results from scavenging of NO by MPO. This interpretation is consistent with earlier reports that MPO consumes NO, and that low levels of NO donor augment induction of iNOS by IFNgamma/LPS. The implication of these findings is that MPO acts as gatekeeper, suppressing the deleterious induction of iNOS at inflammatory sites by illegitimate signals. The combined signaling of IFNgamma/LPS overrides the gatekeeper function by suppressing MPO gene expression.

Expression of Human Myeloperoxidase by Macrophages Promotes Atherosclerosis in Mice

Background— Myeloperoxidase (MPO) colocalizes with macrophages in the human artery wall, and its characteristic oxidation products have been detected in atherosclerotic lesions. Thus, oxidants produced by the enzyme might promote atherosclerosis. However, macrophages in mouse atherosclerotic tissue do not express MPO. Therefore, mice are an inappropriate model for testing the role of MPO in vascular disease. To overcome this problem, we generated and studied transgenic (Tg) mice that contained the human MPO gene.

Methods and Results— We produced human MPO -Tg mice with use of a Visna virus promoter. To confine MPO expression to macrophages, we lethally irradiated LDL receptor–deficient mice and repopulated their bone marrow with cells from wild-type mice or MPO -Tg mice. Despite having similarly high levels of cholesterol after maintenance on a high-fat, high-cholesterol diet, the MPO -Tg animals developed a 2-fold greater atherosclerotic area in the aorta than did mice transplanted with wild-type bone marrow ( P =0.00003).

Conclusions— Our observations indicate that expression of human MPO in macrophages promotes atherosclerosis in hypercholesterolemic mice, raising the possibility that the enzyme might be a potential therapeutic target for preventing cardiovascular disease in humans.

[Antimutagenic activity of Armoracia rusticana, Zea mays and Ficus carica plant extracts and their mixture]

Antimutagenic action of plant extracts of Armoracia rusticana, Ficus carica, Zea mays and their mixture on environmental xenobiotics has been investigated. The plant extracts and their mixture decreased the level of mutations induced by N-metil-N'-nitro-N-nitrozoguanidin (MNNG) in Vicia faba cells, chlorophyll mutations in Arabidopsis thaliana and NaF induced mutability in rat marrow cells. The studied plant extracts and their mixture demonstrate the ability to decrease the genotoxicity of environmental mutagens.

Topoisomerase II inhibition by myeloperoxidase-activated hydroquinone: A potential mechanism underlying the genotoxic and carcinogenic effects of benzene

Benzene is an established human and animal carcinogen. While many of the key mechanisms underlying its carcinogenic effects remain unknown, there is increasing evidence that chromosomal alterations play an important role in the development of the induced leukemias. Inhibition of enzymes involved in DNA replication and maintenance such as topoisomerases by benzene metabolites represents a potential mechanism by which benzene may induce its chromosome-altering effects. Previous work from our laboratory and others has demonstrated that bioactivated benzene metabolites are capable of inhibiting topoisomerase II (topo II) in isolated enzyme and cell systems as well as in mice administered benzene in vivo. The current studies were designed to build upon this hypothesis, and show that in the presence of human myeloperoxidase and H2O2, hydroquinone can be activated to a potent topo II inhibitor. In the absence of dithiothreitol, partial inhibition can be seen at hydroquinone concentrations as low as 50 nM. The potential role of topo II inhibition in the development of benzene-induced leukemia is also discussed in the context of other known leukemia-inducing agents. Current evidence indicates that multiple mechanisms are likely to contribute to benzene-induced leukemias, and that inhibition of topo II could represent an important step in the development of certain leukemia subtypes.

Oxazolone-induced murine model of ulcerative colitis

OBJECTIVE

Animal models are useful for studying disease, but there is a shortage of suitable models of ulcerative colitis. The aim of the present study was to set up an oxazolone-induced murine colitis model and use it to research the pathogenesis of inflammatory bowel disease.

METHODS

BALB/c mice were presensitized by painting the skin with 0.2 mL 3% oxazolone in 100% ethanol on days 0 and 1 followed by intrarectal administration of 0.15 mL 1% oxazolone in 50% ethanol on day 7. The disease activity index (DAI), histological changes of the colon, myeloperoxidase (MPO) activity and production of cytokines (TNF-alpha, IL-4, IFN-gamma) by the mucosa were evaluated.

RESULTS

There were obvious changes in the DAI, histology and MPO activity, and the production of interleukin-4 was markedly increased compared with the concentrations of TNF-alpha and IFN-gamma, which remained normal, in the lesions.

CONCLUSION

Oxazolone colitis is Th2-mediated and has similar histologic features and distribution of inflammation to ulcerative colitis (UC), which has important implications for the use of this model in the study of the pathogenesis and treatment of UC.

Preventative effects of lactulose in the trinitrobenzenesulphonic acid model of rat colitis

AIMS

Lactulose is a drug used as a laxative that has been shown to promote the growth of lactobacilli and bifidobacteria, acting as a prebiotic and with a potential beneficial effect in inflammatory bowel disease. The present study describes the preventive antiinflammatory activity of lactulose in the trinitrobenzenesulphonic acid (TNBS) model of rat colitis.

METHODS

Rats were rendered colitic by a colonic instillation of 10 mg of TNBS dissolved in 0.25 mL of 50% ethanol. One group of colitic rats received lactulose, which was incorporated in the drinking water (2.5% wt/vol) for 2 weeks before TNBS instillation, and colonic damage was evaluated 1 week after colitis induction. Different biochemical markers of colonic inflammation were assayed: myeloperoxidase activity, glutathione content, tumor necrosis factor alpha, leukotriene B4 levels, and colonic inducible nitric oxide synthase expression. In addition, bacterial counts (for lactobacilli and bifidobacteria) were performed in colonic contents from colitic rats.

RESULTS

The results show that lactulose exerted a preventive antiinflammatory effect in this model of rat colitis, as evidenced by a significant reduction of myeloperoxidase activity and by a decrease of both colonic tumor necrosis factor alpha and leukotriene B4 production. This effect was also characterized by an inhibition of colonic inducible nitric oxide synthase expression, which is unregulated as a consequence of the inflammatory status. This beneficial effect was associated with increased levels of lactobacilli and bifidobacteria species in colonic contents in comparison with untreated colitic rats.

CONCLUSION

In conclusion, the intestinal antiinflammatory effect of lactulose could be related to its prebiotic properties, supporting its potential use in human inflammatory bowel disease.

Leukocyte-derived myeloperoxidase amplifies high-glucose--induced endothelial dysfunction through interaction with high-glucose--stimulated, vascular non--leukocyte-derived reactive oxygen species

Vascular non-leukocyte-derived reactive oxygen species (ROS), such as superoxide and hydrogen peroxide (H(2)O(2)), have emerged as important molecules in diabetic endothelial dysfunction. In addition, leukocyte-derived myeloperoxidase (MPO) has been implicated in vascular injury, and its injury response is H(2)O(2) dependent. It is well known that MPO can use leukocyte-derived H(2)O(2); however, it is unknown whether the vascular-bound MPO can use high-glucose-stimulated, vascular non-leukocyte-derived H(2)O(2) to induce diabetic endothelial dysfunction. In the present study, we demonstrated that MPO activity is increased in vessels from diabetic rats. In high-glucose-incubated rat aortas and in carotid arteries from rats with acute hyperglycemia, vascular-bound MPO utilized high-glucose-stimulated H(2)O(2) to amplify the ROS-induced impairment of endothelium-dependent relaxation via reduction of nitric oxide bioavailability. Hypochlorous acid (HOCL)-modified LDL, a specific biomarker for the MPO/HOCL/chlorinating species pathway, was detected in LDL- and MPO-bound vessels with high-glucose-stimulated H(2)O(2). The results suggest that vascular-bound MPO could use high-glucose-stimulated H(2)O(2) to amplify high-glucose-induced injury in the vascular wall. MPO/H(2)O(2)/HOCL/chlorinating species may represent an important pathway in diabetes complications and a new mechanism in phagocyte- and systemic infection-induced exacerbation of diabetic vascular diseases.

Peroxidase-catalyzed coupling of phenol in the presence of model inorganic and organic solid phases

Peroxidase-catalyzed oxidative coupling reactions of phenol in aqueous systems variously containing silica sand, cellulose, lignin, and polymethylstyrene were investigated. These four solid phase materials represent a broad spectrum of different natural geosorbent types in terms of their physicochemical characteristics. Each solid was found to influence peroxidase-catalyzed phenol coupling, either by mitigation of enzyme inactivation, by participation in cross-coupling, or by a combination of these two activities. Mitigation of enzyme inactivation was observed for those three of the four model solids found to adsorb the enzyme effectively; i.e., cellulose, silica sand, and lignin. Two solids, polymethylstyrene and lignin, were found to participate significantly in cross-coupling reactions. It is postulated that relatively hydrophilic solids can mitigate peroxidase inactivation by forming enzyme-solid associations. Aromatic structures or unsaturated C-C bonds were found to be features of the solid-phase materials that allowed them to participate in cross-coupling. The results have important implications for process feasibility assessment and the engineering design of soil/sediment remediation systems employing enzymatic coupling schemes.

Saliva--a pivotal player in the pathogenesis of oropharyngeal cancer

Oropharyngeal (OP) cancer, which is usually squamous cell carcinoma, is the most common head and neck malignancy and accounts for 2–4% of all new cancers. It is primarily induced by exposure to tobacco. The paradigm of cigarette smoke (CS)-induced OP cancer's pathogenesis is based on the assumption that a constant direct attack of various CS carcinogens causes widespread accumulating cellular and DNA aberrations in the OP mucosal cells, in turn eventually resulting in malignant transformation. However, there is never a direct contact between CS and the OP mucosa. Saliva, bathing the mucosa from the oral cavity to the larynx, always intervenes, and CS must first interact with saliva before it reaches the mucosa. The current study investigated the role of saliva in the pathogenesis of OP cancer. A synergistic effect of CS and saliva on oral cancer cells was demonstrated. This synergism is based on the reaction between redox active metals in saliva and low reactive free radicals in CS, which results in the production of highly active hydroxyl free radicals. Thus, when exposed to CS, salivary behavior is reversed and the saliva loses its antioxidant capacity and becomes a potent prooxidant milieu. The devastating role of CS-borne aldehydes was demonstrated as well. Based on these results and on our recent reports demonstrating that CS destroys various salivary components, including protective ones such as peroxidase, the most important salivary antioxidant enzyme, a comprehensive view of the pivotal role of saliva in the pathogenesis of CS-induced OP cancer is suggested.

Responses of antioxidative enzymes to accumulation of copper in a copper hyperaccumulator of Commoelina communis

Discovery of a copper hyperaccumulator is very important for phytoremediation of copper-contaminated soil. In the present study a link was established between the copper accumulation in hyperaccumulator and that in nonaccumulator species of Commelina communis and its responses of antioxidative enzymes, including superoxide dismutase, guaiacol peroxidase, and ascorbate peroxidase. It was verified that copper exerted little physiological damage to copper hyperaccumulator species of Commelina communis at copper accumulation of >1,000 microg/g in dry leaf tissue. However, in nonaccumulator species of Commelina communis superoxide dismutase, guaiacol peroxidase, and ascorbate peroxidase were activated, and malondialdehyde content was increased, which were symptoms of physiological damage by copper intoxication. Therefore, antioxidative enzymes can be used as an indicator of copper toxicity before the visible symptoms can be observed.

Spread of oxidative damage and antioxidative response through cell layers of tobacco callus after UV-C treatment

Tobacco (Nicotiana tabacum L. cv. Petit Havana) callus cultures were exposed to UV-C high dose pulse-treatment (254 nm, 50 kJ m(-2), 1 h-treatment). After 6, 24 and 48 h from the end of the treatment, calli were cut transversally in two layers and oxidative damage (malondialdehyde [MDA] and hydrogen peroxide), non-enzymatic (radical scavenging antioxidants [RSA] and polyamines) and enzymatic antioxidants (ascorbate peroxidase [APX, EC 1.11.1.11], glutathione reductase [GR, EC 1.6.4.2], catalase [CAT, EC 1.11.1.6] and guaiacol peroxidase [GPX, EC 1.11.1.7]) were evaluated. At each time-point data referred to UV-C treated calli were compared to data of untreated ones (control). Despite of a strong increase of H2O2 content, a slight cellular damage was observed in both upper and lower layers 24 and 48 h after UV-C treatment. An activation first of non-enzymatic antioxidants and then of enzymatic antioxidants was detected in UV-C treated calli. In particular, RSA and putrescine (PUT) accumulated 6 h after UV-C treatment while APX, GR and GPX enzyme activities increased 24 h after UV-C irradiation. Catalase activity did not change. UV-C-induced oxidative stress and antioxidative response were observed also in cell layers not directly exposed to UV irradiation, indicating that a stress signal was transmitted to the whole mass of callus.

Isoperoxidases show differing sensitivity to salicylic acid

The effects of salicylic acid (SA) on the activity of total peroxidase and the patterns of isoperoxidases of cultured tobacco cells were investigated. The total peroxidase activity of tobacco cells was inhibited by 70% when the cells were treated with 5 mM SA for one week. The peroxidase activity of tobacco cells is declined by 90% in the presence of 30 mM SA. Moreover, the activity of isoperoxidases C3, A1, and A3 decreased dramatically with increasing SA concentration, while, one of the anodic isoperoxidases, A2, was somewhat resistant to SA treatment. When isoperoxidase C3 was isolated, SA inhibited the activity of purified C3 in a concentration-dependent manner. The IC50 of isoperoxidase C3 was approximately 0.45 mM. However, the inhibition of isoperoxidase C3 activity was removed by the addition of Fe2+ ion. The possible mechanism of inhibition of peroxidase by SA is discussed.

INCORPORATION OF AN OXYGEN FROM WATER INTO TROGLITAZONE QUINONE BY CYTOCHROME P450 AND MYELOPEROXIDASE

Troglitazone (TGZ) was the first glitazone used for the treatment of type II diabetes mellitus. TGZ undergoes an oxidative chroman ring-opening reaction to form a quinone product. Recently, cytochrome P450 (P450) was shown to be able to catalyze the formation of TGZ quinone. TGZ quinone was the major metabolite formed by dexamethasone-induced rat liver microsomes or myeloperoxidase (MPO) incubated with TGZ. The ultimate source for the quinone carbonyl oxygen atom of TGZ quinone was investigated using (18)O water in both enzyme reaction systems followed by liquid chromatography/tandem mass spectometry analysis of the TGZ quinone product. The resultant TGZ quinone formed by either liver microsomes or MPO contained a single atom of (18)O. The (18)O atom was determined to be the quinone carbonyl oxygen by collision-induced dissociation fragmentation of the (18)O-labeled TGZ quinone. The formation of TGZ quinone was inhibited approximately 90% by coincubation with ascorbic acid or cysteine in the MPO reaction system but only 10 to 20% in liver microsomes, which might reflect the difference in the mechanism by which TGZ quinone is formed by P450 and peroxidase. These results suggest that P450 catalyze an atypical reaction to form TGZ quinone, involving the incorporation of an oxygen from water into the quinone carbonyl position.

[Antimutagenic activity of plant extracts from Armoracia rusticana, Ficus carica and Zea mays and peroxidase in eukaryotic cells]

Antimutagene activity and high efficiency of antimutagene action of plant extracts from horseradish roots (Armoracia rusticana), fig brunches (Ficus carica) and mays seedlings (Zea mays) and their ability to decrease the frequency of spontaneous and induced by gamma-rays chromosome aberrations in meristematic cells of Vicia faba and marrow cells of mice have been shown. Comparative assessment of genoprotective properties of peroxidase and the studied extracts has revealed higher efficiency of antimutagene action of peroxidase.