Hypochlorite-induced oxidation of fibrinogen: Effects on its thermal denaturation and fibrin structure

BACKGROUND

Human fibrinogen, which plays a key role in plasma haemostasis, is a highly vulnerable target for oxidants. Fibrinogen undergoes posttranslational modifications that can potentially disrupt protein structure and function.

METHODS

For the first time, by differential scanning calorimetry, dynamic and elastic light scattering and confocal laser scanning microscopy, the consequences of HOCl/^-OCl-induced oxidation of fibrinogen on its thermal denaturation, molecular size distribution and fibrin clot network have been explored.

RESULTS

Within a wide range of HOCl/^-OCl concentrations (50-300 μM), the molecular size distribution remained unimodal; however, the average size of the hydrated molecules decreased. HOCl/^-OCl-induced oxidation of fibrinogen resulted in the diminished thermal stability of regions D and E. As evidenced by elastic light scattering and confocal laser scanning microscopy, HOCl/^-OCl caused the formation of abnormal fibrin with a decreased diameter of individual fibres.

CONCLUSIONS

The current results along with data from previous studies enable one to conclude that the effect of HOCl/^-OCl-mediated oxidation on the thermal stability of region D is influenced directly by oxidative damage to the D region structure. Since the E region is not subjected to oxidative modification, its structural damage is likely to be mediated by the oxidation of other protein structures, in particular α-helical coiled-coils.

GENERAL SIGNIFICANCE

The experimental findings acquired in the current study could help to elucidate the consequences of oxidative stress in vivo on damage to the structure of fibrinogen/fibrin under the action of different ROS species.

Comparison of the SARS-CoV-2-inactivating activities of the differently manufactured hypochlorous acid water products with various pH

The use of effective disinfectants is a key method of controlling the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Hypochlorous acid water (HAW) has a broad spectrum of virucidal activities. We previously reported that acidic electrolyzed water, one of the HAW products, had potent SARS-CoV-2-inactivating activity and showed promise as a disinfectant. However, different manufacturing methods have produced several HAW products with various pH values. Here, we compared the SARS-CoV-2-inactivating activities of various HAW products. At sufficiently high volume and residual chlorine concentration (RCC), the HAW products inactivated SARS-CoV-2 efficiently regardless of pH or manufacturing method. However, although HAW products at pH 5.0-6.4 maintained high RCC and sustained virucidal activity for 21 days, the RCC rapidly decreased in HAW products at pH ≤ 3.0. Our results may guide in choosing appropriate HAW products for different usage situations.

Hypochlorous acid selectively promotes toxicity and the expression of danger signals in human abdominal cancer cells

Tumors of the abdominal cavity, such as colorectal, pancreatic and ovarian cancer, frequently metastasize into the peritoneum. Large numbers of metastatic nodules hinder curative surgical resection, necessitating lavage with hyperthermic intraperitoneal chemotherapy (HIPEC). However, HIPEC not only causes severe side effects but also has limited therapeutic efficacy in various instances. At the same time, the age of immunotherapies such as biological agents, checkpoint‑ inhibitors or immune‑cell therapies, increasingly emphasizes the critical role of anticancer immunity in targeting malignancies. The present study investigated the ability of three types of long‑lived reactive species (oxidants) to inactivate cancer cells and potentially complement current HIPEC regimens, as well as to increase tumor cell expression of danger signals that stimulate innate immunity. The human abdominal cancer cell lines HT‑29, Panc‑01 and SK‑OV‑3 were exposed to different concentrations of hydrogen peroxide (H2O2), hypochlorous acid (HOCl) and peroxynitrite (ONOO‑). Metabolic activity was measured, as well as determination of cell death and danger signal expression levels via flow cytometry and detection of intracellular oxidation via high‑content microscopy. Oxidation of tumor decreased intracellular levels of the antioxidant glutathione and induced oxidation in mitochondria, accompanied by a decrease in metabolic activity and an increase in regulated cell death. At similar concentrations, HOCl showed the most potent effects. Non‑malignant HaCaT keratinocytes were less affected, suggesting the approach to be selective to some extent. Pro‑immunogenic danger molecules were investigated by assessing the expression levels of calreticulin (CRT), and heat‑shock protein (HSP)70 and HSP90. CRT expression was greatest following HOCl and ONOO‑ treatment, whereas HOCl and H2O2 resulted in the greatest increase in HSP70 and HSP90 expression levels. These results suggested that HOCl may be a promising agent to complement current HIPEC regimens targeting peritoneal carcinomatosis.

Induction of the reactive chlorine-responsive transcription factor RclR in Escherichia coli following ingestion by neutrophils

Neutrophils generate hypochlorous acid (HOCl) and related reactive chlorine species as part of their defence against invading microorganisms. In isolation, bacteria respond to reactive chlorine species by upregulating responses that provide defence against oxidative challenge. Key questions are whether these responses are induced when bacteria are phagocytosed by neutrophils, and whether this provides them with a survival advantage. We investigated RclR, a transcriptional activator of the rclABC operon in Escherichia coli that has been shown to be specifically activated by reactive chlorine species. We first measured induction by individual reactive chlorine species, and showed that HOCl itself activates the response, as do chloramines (products of HOCl reacting with amines) provided they are cell permeable. Strong RclR activation was seen in E. coli following phagocytosis by neutrophils, beginning within 5 min and persisting for 40 min. RclR activation was suppressed by inhibitors of NOX2 and myeloperoxidase, providing strong evidence that it was due to HOCl production in the phagosome. RclR activation demonstrates that HOCl, or a derived chloramine, enters phagocytosed bacteria in sufficient amount to induce this response. Although RclR was induced in wild-type bacteria following phagocytosis, we detected no greater sensitivity to neutrophil killing of mutants lacking genes in the rclABC operon.

Activation of regulator ArcA in the presence of hypochlorite in Salmonella enterica serovar Typhimurium

Oxidative stress is the main mechanism behind efficient disinfectants, causing damage in bacterial macromolecules. Importantly, bacteria activate resistance mechanisms in response to damage generated by oxidative stress. Strategies allowing pathogens to survive oxidative stress are highly conserved among microorganisms. Many of these strategies entail genomic responses triggered by signals transduced through Two Component Systems (TCS). Recently, we demonstrated that the TCS ArcAB (specifically ArcA) participates in bacterial responses to hypochlorite, regulating the uptake of this toxic compound and being involved in resistance and survival inside neutrophils, where hypochlorous acid abounds. Here, we demonstrated that ArcA is required in the response to oxidative stress generated by hypochlorite, independent of its cognate sensor ArcB or the Asp54 of ArcA, the only phosphorylable residue in ArcA, which is required to function as a gene regulator. Our results suggest that ArcA could have additional functions to respond to oxidative stress, independent of its regulatory activity, which might require interaction with other unknown relevant proteins.

HClO-Activated Fluorescence and Photosensitization from an AIE Nanoprobe for Image-Guided Bacterial Ablation in Phagocytes

Bacteria hiding in host phagocytes are difficult to kill, which can cause phagocyte disorders resulting in local and systemic tissue damage. Effective accumulation of activatable photosensitizers (PSs) in phagocytes to realize selective imaging and on-demand photodynamic ablation of bacteria is of great scientific and practical interests for precise bacteria diagnosis and treatment. Herein, HClO-activatable theranostic nanoprobes, DTF-FFP NPs, for image-guided bacterial ablation in phagocytes are introduced. DTF-FFP NPs are prepared by nanoprecipitation of an HClO-responsive near-infrared molecule FFP and an efficient PS DTF with aggregation-induced emission characteristic using an amphiphilic polymer Pluronic F127 as the encapsulation matrix. As an energy acceptor, FFP can quench both fluorescence and production of reactive oxygen species (ROS) of DTF, thus eliminating the phototoxicity of DTF-FFP NPs in normal cells and tissues. Once delivered to the infection sites, DTF-FFP NPs light up with red fluorescence and efficiently generate ROS owing to the degradation of FFP by the stimulated release of HClO in phagocytes. The selective activation of fluorescence and photosensitization is successfully confirmed by both in vitro and in vivo results, demonstrating the effectiveness and theranostic potential of DTF-FFP NPs in precise bacterial therapy.

Role of thiocyanate in the modulation of myeloperoxidase-derived oxidant induced damage to macrophages

Myeloperoxidase (MPO) is a vital component of the innate immune system, which produces the potent oxidant hypochlorous acid (HOCl) to kill invading pathogens. However, an overproduction of HOCl during chronic inflammatory conditions causes damage to host cells, which promotes disease, including atherosclerosis. As such, there is increasing interest in the use of thiocyanate (SCN^-) therapeutically to decrease inflammatory disease, as SCN^- is the favoured substrate for MPO, and a potent competitive inhibitor of HOCl formation. Use of SCN^- by MPO forms hypothiocyanous acid (HOSCN), which can be less damaging to mammalian cells. In this study, we examined the ability of SCN^- to modulate damage to macrophages induced by HOCl, which is relevant to lesion formation in atherosclerosis. Addition of SCN^- prevented HOCl-mediated cell death, altered the extent and nature of thiol oxidation and the phosphorylation of mitogen activated protein kinases. These changes were dependent on the concentration of SCN^- and were observed in some cases, at a sub-stoichiometric ratio of SCN^-: HOCl. Co-treatment with SCN^- also modulated HOCl-induced perturbations in the expression of various antioxidant and inflammatory genes. In general, the data reflect the conversion of HOCl to HOSCN, which can induce reversible modifications that are repairable by cells. However, our data also highlight the ability of HOSCN to increase pro-inflammatory gene expression and cytokine/chemokine release, which may be relevant to the use of SCN^- therapeutically in atherosclerosis. Overall, this study provides further insight into the cellular pathways by which SCN^- could exert protective effects on supplementation to decrease the development of chronic inflammatory diseases, such as atherosclerosis.

A multimodel regime for evaluating effectiveness of antimicrobial wound care products in microbial biofilms

Microbial biofilms have become increasingly recognized as a cause of wound chronicity. There are several topical antimicrobial wound care products available for use; however, their effectiveness has routinely been demonstrated with planktonic microorganisms. There is no target reference value for antimicrobial effectiveness of wound care products in biofilm models. In addition, data on antimicrobial activity of products in biofilm models are scattered across many test methods in a variety of studies. The aim of this work is to directly compare commercial products containing the commonly used topical antimicrobial agents iodine, silver, polyhexamethylene biguanide, octenidine, hypochlorous acid, benzalkonium chloride, and a surfactant-based topical containing poloxamer 188. Five different in vitro biofilm models of varied complexity were used, incorporating several bacterial pathogens such as Staphylococcus, Enterococcus, Streptococcus, Pseudomonas, Acinetobacter, Klebsiella, and Enterobacter. The fungal pathogens Candida albicans and Candida auris were also evaluated. A multispecies bacterial biofilm model was also used to evaluate the products. Additionally, C. albicans was used in combination with S. aureus and P. aeruginosa in a multikingdom version of the polymicrobial biofilm model. Statistically significant differences in antimicrobial performance were observed between treatments in each model and changing microbial growth conditions or combinations of organisms resulted in significant performance differences for some treatments. The iodine and benzalkonium chloride-containing products were overall the most effective in vitro and were then selected for in vivo evaluation in an infected immunocompromised murine model. Unexpectedly, the iodine product was statistically (P > .05) no different than the untreated control, while the benzalkonium chloride containing product significantly (P < .05) reduced the biofilm compared to untreated control. This body of work demonstrates the importance of not only evaluating antimicrobial wound care products in biofilm models but also the importance of using several different models to gain a comprehensive understanding of products' effectiveness.

Efficacy of sodium hypochlorite in the degradation antineoplastic drugs by NMR spectroscopy

Antineoplastic drugs are used to treat cancer, having their therapeutic effect by inhibiting the cell division process. Although cancer cells, due to their rapid growth, are more sensitive to the toxic effects of chemotherapeutic agents, healthy cells and tissues may also be damaged. Many studies show acute and chronic toxicity both in patients treated with chemotherapy and in exposed workers. In fact, exposure to these substances can also be linked to the formation of different types of secondary tumors. The International Agency on Research on Cancer (IARC) included some antineplastic drugs in Group 1 (carcinogenic to humans), in Group 2A (probable carcinogens for In recent years, many studies have evidenced the presence of antineoplastic drug contamination on work surfaces, materials and floors and based on these observations, international and national guidelines have been published to limit occupational exposure, with particular attention to procedures post-preparation of chemotherapy to limit as much as possible the accumulation of contaminated residues. The aim of the following study is to determine the effectiveness of the degradation of four antineoplastic drugs: 5-fluorouracil, azacitidine, cytarabine and irinotecan using a low concentration of sodium hypochlorite solution (0.115%). The analytical platform used to monitor the degradation course of the substances under examination was hydrogen nuclear magnetic spectroscopy (1H NMR). In the same experimental conditions the effectiveness of the degradation of the same antineoplastic drugs with a 99.9% ethanol solution was also evaluated. The study showed that the best degradation efficiency (> 90% ) is obtained with the hypochlorite solution after 15 minutes.

Effect of physio-chemical seed treatments on opium poppy downy mildews caused by Peronospora meconopsidis and P. somniferi

Downy mildew of opium poppy is the single biggest disease constraint afflicting the Australian poppy industry. Within the pathosystem, the transmission of infections via infested seed is of major concern. Both downy mildew pathogens of poppy; Peronospora meconopsidis and P. somniferi, are known contaminants of commercial seed stocks. Using seed naturally infested with these pathogens, the effect of physio-chemical seed treatments on seedling health and disease transmission were evaluated. Individual seed treatments were tested to determine optimal treatment parameters for each; including incubation time, temperature and treatment concentration. Optimised physiochemical treatments were then compared. The most effective treatment methods were seed washes in acidified electrolytic water (400 ppm hypochlorous acid for 5 min) and hypochlorite solution (2% NaOCI for 5 min). In seed to seedling transmission assays, these two treatments reduced transmission of P. somniferi by 88.8% and 74.61%, and P. meconopsidis by 93.3% and 100%, respectively. These methods are recommended for seed treatment of commercial opium poppy seed to assist in the control of the downy mildew diseases.

Identification of oxidant susceptible proteins in Salmonella Typhimurium

The human gut pathogen, Salmonella Typhimurium (S. Typhimurium) not only survives but also replicates inside the phagocytic cells. Bacterial proteins are the primary targets of phagocyte generated oxidants. Because of the different amino acid composition, some proteins are more prone to oxidation than others. Many oxidant induced modifications to amino acids have been described. Introduction of carbonyl group is one of such modifications, which takes place quite early following exposure of proteins to oxidants and is quite stable. Therefore, carbonyl groups can be exploited to identify oxidant susceptible proteins. Hypochlorous acid (HOCl) is one of the most potent oxidants produced by phagocytes. Incubation of S. Typhimurium with 3 mM HOCl resulted in more than 150 folds loss of bacterial viability. Proteins extracted from HOCl exposed S. Typhimurium cells showed about 60 folds (p < 0.001) more carbonyl levels as compared to unexposed cells. Similarly, 2, 4-Dinitrophenylhydrazine (2, 4-DNPH) derivatized proteins of HOCl treated S. Typhimurium cultures reacted strongly with anti-DNP antibodies as compared to buffer treated counterpart. Next, we have derivatized carbonyl groups on the proteins with biotin hydrazide. The derivatized proteins were then isolated by avidin affinity chromatography. Mass spectrometry based analysis revealed the presence of 204 proteins.

Structural Study on Hypochlorous Acid-Mediated Chlorination of Betanin and Its Decarboxylated Derivatives from an Anti-Inflammatory Beta vulgaris L. Extract

Hypochlorous acid (HOCl) produced by neutrophils is a part of the natural innate immune response system in the human body, but excessive levels of HOCl can ultimately be detrimental to health. Recent reports suggest that betacyanin plant pigments can act as potent scavengers of inflammatory factors and are notably effective against HOCl. In this contribution, chlorination mechanism and position of the electrophilic substitution in betacyanins was studied by high-resolution mass spectrometry and further structural analyses by NMR techniques, which completed the identification of the chlorinated betacyanins. For the study on the influence of the position of decarboxylation on the chlorination mechanism, a comparison of the chlorination position between betanin as well as 17-, and 2,17-decarboxylated betanins was performed. The structural study confirmed that the chlorination position in betanin occurs within the dihydropyridinic moiety at carbon C-18. Therefore, out of the aqueous free chlorine equilibrium species: HOCl, OCl-, Cl2, and Cl2O, the most potent chlorinating agents are HOCl and Cl2O postulated previously and the attack of the Cl⁺ ion on the carbon C-18 with a cyclic intermediate version is considered.

Evaluating the effectiveness of HOCl application on odor reduction and earthworm population growth during vermicomposting of food waste employing Eisenia fetida

Vermicomposting has been recommended as an eco-friendly method to transform organic waste into nutrient resources with minimum energy input. However, odor and pest issues associated with this method limit the use of vermicomposting, especially in indoor conditions. This study evaluated the effectiveness of applying hypochlorous acid (HOCl) to deodorize the vermicomposting process and improve the breeding environment for earthworms (Eisenia fetida). The deodorization performance of HOCl was compared by measuring the amount of ammonia (NH₃) and amine (R-NH₂) released from the decaying process of two types of food waste: HOCl-treated (HTW) waste and non-treated waste (NTW). The total and individual weights of earthworms in the waste treated with HOCl was measured to evaluate the impact on earthworm reproduction after applying HOCl. The results showed that HOCl application could reduce NH₃ by 40% and R-NH₂ by 80%, and increase the earthworm population size and total weight by up to 29% and 92%, respectively, compared to the control group. These results suggest that HOCl application is potentially an efficient method to control the odor and to boost earthworm reproduction and thus facilitate vermicomposting for improved food waste treatment and environmental quality.

Hypotonic, Acidic Oxidizing Solution Containing Hypochlorous Acid (HClO) as a Potential Treatment of Hailey-Hailey Disease

Hailey–Hailey disease (HHD) is a rare, chronic and recurrent blistering disorder, characterized by erosions occurring primarily in intertriginous regions and histologically by suprabasal acantholysis. Mutation of the Golgi Ca²⁺-ATPase ATP2C1 has been identified as having a causative role in Hailey–Hailey disease. HHD-derived keratinocytes have increased oxidative-stress that is associated with impaired proliferation and differentiation. Additionally, HHD is characterized by skin lesions that do not heal and by recurrent skin infections, indicating that HHD keratinocytes might not respond well to challenges such as wounding or infection. Hypochlorous acid has been demonstrated in vitro and in vivo to possess properties that rescue both oxidative stress and altered wound repair process. Thus, we investigated the potential effects of a stabilized form of hypochlorous acid (APR-TD012) in an in vitro model of HHD. We found that treatment of ATP2C1-defective keratinocytes with APR-TD012 contributed to upregulation of Nrf2 (nuclear factor (erythroid-derived 2)-like 2). Additionally, APR TD012-treatment restored the defective proliferative capability of siATP2C1-treated keratinocytes. We also found that the APR-TD012 treatment might support wound healing process, due to its ability to modulate the expression of wound healing associated cytokines. These observations suggested that the APR-TD012 might be a potential therapeutic agent for HHD-lesions.

The myeloperoxidase product, hypochlorous acid, reduces thrombus formation under flow and attenuates clot retraction and fibrinolysis in human blood

Hypochlorite (HOCl), a strong oxidant and antimicrobial agent, has been proposed to be associated with hemostatic abnormalities during inflammatory response. However, its complex impact on hemostasis is not completely understood. In this report we studied the effect of clinically relevant (micromolar) HOCl concentrations on thrombus formation under flow, kinetics of platelet-fibrin clot formation, its architecture, retraction, and lysis. We found that HOCl (up to 500 µM) did not affect kinetics of coagulation measured in whole blood. HOCl (500-1000 µM) markedly diminished thrombus formation under flow. Clot retraction rate was reduced by HOCl dose-dependently (50-500 µM). HOCl (125-500 µM) inhibited fibrinolysis in whole blood and in platelet-depleted plasma, dose-dependently. Activity of plasmin was reduced by HOCl at concentrations started from 500 µM. HOCl (up to 500 µM) did not reduce plasminogen binding to fibrin under flow. HOCl (125-500 µM) modulated architecture of fibrin- and platelet-fibrin clots towards structures made of thin and densely packed fibers. Exposure of pure fibrinogen to HOCl (10-1000 µM) resulted in formation of dityrosine and was associated with altered fibrin structure derived from such modified fibrinogen. HOCl-altered fibrin net structure was not related with modulation of platelet procoagulant response, thrombin generation, and factor XIII activity. We conclude that, in human blood, clinically relevant HOCl concentrations may inhibit thrombus formation under flow, clot retraction and fibrinolysis. Fibrinolysis and clot retraction seem to be the most sensitive to HOCl-evoked inhibition. HOCl-modified fibrinogen and altered clot structure associated with it are likely to be primary sources of attenuated fibrinolysis.

Artificial Super Neutrophils for Inflammation Targeting and HClO Generation against Tumors and Infections

Neutrophils are powerful effector leukocytes that play an important role in innate immune systems for opposing tumor progression and ameliorating pathogen infections. Inspired by their distinct functions against tumors and infections, the artificial "super neutrophils" are proposed with excellent inflammation targeting and hypochlorous acid (HClO) generation characteristics for targeting and eliminating malignant tumor cells and pathogens. The "super neutrophils" are fabricated by embedding glucose oxidase (GOx) and chloroperoxidase (CPO) into zeolitic imidazolate framework-8 (ZIF-8) for HClO generation via enzymatic cascades, and then encapsulating them with the neutrophil membrane (NM) for inflammation targeting. In vitro and in vivo results indicate that these artificial "super neutrophils" can generate seven times higher reactive HClO than the natural neutrophils for eradicating tumors and infections. The "super neutrophils" demonstrated here with easy fabrication and good neutrophil-mimicking property exhibit great potential for biomedical applications.

Hypochlorous acid-modified extracellular matrix contributes to the behavioral switching of human coronary artery smooth muscle cells

The extracellular matrix (ECM) influences the structure and function of the arterial wall and modulates the behavior of vascular cells through ECM-cell interactions. Alterations to the ECM have been implicated in multiple pathological processes, including atherosclerosis which is characterized by low-grade chronic inflammation and the infiltration and proliferation of smooth muscle cells during disease development. Considerable evidence has been presented for a role for inflammation-derived oxidation in atherogenesis, with enzymatically-active myeloperoxidase (MPO), elevated levels of 3-chlorotyrosine (a biomarker of MPO-catalyzed damage) and oxidized ECM materials detected in advanced human atherosclerotic lesions. Whether oxidant-modified ECM contributes to the altered behavior of smooth muscle cells is however unclear. This study therefore investigated the effects of hypochlorous acid (HOCl), a major MPO-derived oxidant, on the structure of the native ECM synthesized by human coronary artery smooth muscle cells (HCAMSCs) and whether modified ECM proteins affected HCASMC adhesion, proliferation and gene expression. Exposure of native HCASMC-derived ECM to reagent HOCl or a MPO-Cl^--H₂O₂ system resulted in extensive ECM modifications as evidenced by the loss of antibody recognition of epitopes on type IV collagen, laminin, versican and fibronectin. Oxidation of HCASMC ECM markedly reduced HCASMC adhesion to matrix components, but facilitated subsequent proliferation in vitro. Multiple genes were upregulated in HCASMCs in response to HOCl-modified HCASMC-ECM including interleukin-6 (IL-6), fibronectin (FN1) and matrix-metalloproteinases (MMPs). These data reveal a mechanism through which inflammation-induced ECM-modification may contribute to the behavioral switching of HCASMCs, a key process in plaque formation during the development of atherosclerosis.

Role of hypochlorous acid (HOCl) and other inflammatory mediators in the induction of macrophage extracellular trap formation

The infiltration of activated leukocytes, including macrophages, at sites of inflammation and the formation and presence of hypochlorous acid (HOCl) are interlinked hallmarks of many debilitating disease processes, including atherosclerosis, arthritis, neurological and renal disease, diabetes and obesity. The production of extracellular traps by activated leukocytes in response to a range of inflammatory stimuli is increasingly recognised as an important process within a range of disease settings. We show that exposure of human monocyte-derived macrophages to pathophysiological levels of HOCl results in the dose-dependent extrusion of DNA and histones into the cellular supernatant, consistent with extracellular trap formation. Concurrent with, but independent of these findings, macrophage exposure to HOCl also resulted in an immediate and sustained cytosolic accumulation of Ca²⁺, culminating in the increased production of cytokines and chemokines. Polarisation of the macrophages prior to HOCl exposure revealed a greater propensity for inflammatory M1 macrophages to produce extracellular traps, whereas alternatively-activated M2 macrophages were less susceptible to HOCl insult. M1 macrophages also produced extracellular traps on exposure to phorbol myristate acetate (PMA), interleukin-8 (IL-8) and tumour necrosis factor α (TNFα). Taken together, these data indicate a potential role for macrophages in mediating extracellular trap formation, which may be relevant in pathological conditions characterised by chronic inflammation or excessive HOCl formation.

Impact of antimicrobial wipes compared with hypochlorite solution on environmental surface contamination in a health care setting: A double-crossover study

OBJECTIVE

Antimicrobial wipes are increasingly used in health care settings. This study evaluates, in a clinical setting, the efficacy of sporicidal wipes versus a cloth soaked in a 1,000 ppm chlorine solution.

INTERVENTION

A double-crossover study was performed on 2 different surgical and cardiovascular wards in a 1,000-bed teaching hospital over 29 weeks. The intervention period that consisted of surface decontamination with the preimpregnated wipe or cloth soaked in chlorine followed a 5-week baseline assessment of microbial bioburden on surfaces. Environmental samples from 11 surfaces were analyzed weekly for their microbial content.

RESULTS

A total of 1,566 environmental samples and 1,591 ATP swabs were analyzed during the trial. Overall, there were significant differences in the recovery of total aerobic bacteria (P < .001), total anaerobic bacteria (P < .001), and ATP measurement (P < .001) between wards and between the different parts of the crossover study. Generally, the use of wipes produced the largest reduction in the total aerobic and anaerobic counts when compared with the baseline data or the use of 1,000 ppm chlorine. Collectively, the introduction of training plus daily wipe disinfection significantly reduced multidrug-resistant organisms recovered from surfaces. Reversion to using 1,000 ppm chlorine resulted in the number of sites positive for multidrug-resistant organisms rising again.

CONCLUSIONS

This double-crossover study is the first controlled field trial comparison of using preimpregnated wipes versus cotton cloth dipped into a bucket of hypochlorite to decrease surface microbial bioburden. The results demonstrate the superiority of the preimpregnated wipes in significantly decreasing microbial bioburden from high-touch surfaces.

VPO1 Modulates Vascular Smooth Muscle Cell Phenotypic Switch by Activating Extracellular Signal-regulated Kinase 1/2 (ERK 1/2) in Abdominal Aortic Aneurysms

Background Hydrogen peroxide (H2O2) is a critical molecular signal in the development of abdominal aortic aneurysm ( AAA ) formation. Vascular peroxidase 1 ( VPO 1) catalyzes the production of hypochlorous acid ( HOC l) from H2O2 and significantly enhances oxidative stress. The switch from a contractile phenotype to a synthetic one in vascular smooth muscle cells ( VSMC s) is driven by reactive oxygen species and is recognized as an early and important event in AAA formation. This study aims to determine if VPO 1 plays a critical role in the development of AAA by regulating VSMC phenotypic switch. Methods and Results VPO 1 is upregulated in human and elastase-induced mouse aneurysmal tissues compared with healthy control tissues. Additionally, KLF 4, a nuclear transcriptional factor, is upregulated in aneurysmatic tissues along with a concomitant downregulation of differentiated smooth muscle cell markers and an increase of synthetic phenotypic markers, indicating VSMC phenotypic switch in these diseased tissues. In cultured VSMC s from rat abdominal aorta, H2O2 treatment significantly increases VPO 1 expression and HOC l levels as well as VSMC phenotypic switch. In support of these findings, depletion of VPO 1 significantly attenuates the effects of H2O2 and HOC l treatment. Furthermore, HOC l treatment promotes VSMC phenotypic switch and ERK 1/2 phosphorylation. Pretreatment with U0126 (a specific inhibitor of ERK 1/2) significantly attenuates HOC l-induced VSMC phenotypic switch. Conclusions Our results demonstrate that VPO 1 modulates VSMC phenotypic switch through the H2O2/ VPO 1/ HOC l/ ERK 1/2 signaling pathway and plays a key role in the development of AAA . Our findings also implicate VPO 1 as a novel signaling node that mediates VSMC phenotypic switch and plays a key role in the development of AAA . Clinical Trial Registration URL : www.chictr.org.cn . Unique identifier: Chi CTR 1800016922.

Neutrophil granule proteins generate bactericidal ammonia chloramine on reaction with hydrogen peroxide

The neutrophil enzyme, myeloperoxidase, by converting hydrogen peroxide (H₂O₂) and chloride to hypochlorous acid (HOCl), provides important defense against ingested micro-organisms. However, there is debate about how efficiently HOCl is produced within the phagosome and whether its reactions with phagosomal constituents influence the killing mechanism. The phagosome is a small space surrounding the ingested organism, into which superoxide, H₂O₂ and high concentrations of proteins from cytoplasmic granules are released. Previous studies imply that HOCl is produced in the phagosome, but a large proportion should react with proteins before reaching the microbe. To mimic these conditions, we subjected neutrophil granule extract to sequential doses of H₂O₂. Myeloperoxidase in the extract converted all the H₂O₂ to HOCl, which reacted with the granule proteins. 3-Chlorotyrosine, protein carbonyls and large amounts of chloramines were produced. At higher doses of H₂O₂, the extract developed potent bactericidal activity against Staphylococcus aureus. This activity was due to ammonia monochloramine, formed as a secondary product from protein chloramines and dichloramines. Isolated myeloperoxidase and elastase also became bactericidal when modified with HOCl and antibacterial activity was seen with a range of species. Comparison of levels of protein modification in the extract and in phagosomes implies that a relatively low proportion of phagosomal H₂O₂ would be converted to HOCl, but there should be sufficient for substantial protein chloramine formation and some breakdown to ammonia monochloramine. It is possible that HOCl could kill ingested bacteria by an indirect mechanism involving protein oxidation and monochloramine formation.

Morphometric characteristics of neutrophils stimulated by adhesion and hypochlorite

The aim of this work was to compare cell form, size and volume as well as the locomotor activity of polymorphonuclear leukocytes (PMNLs) stimulated by adhesion to glass and exposed to hypochlorous acid at non-toxic dose. After 20min of adhesion to a glass surface, volume, cell surface area and projection area of PMNLs were equaled to 143.1±21.4μm³, 288.8±28.8μm² and 248.3±32.3μm², respectively. Projection area of PMNLs exposed to NaOCl was noticeably enlarged as compared with control samples. The cell volume of 20min adherent cells exposed to NaOCl was enlarged in comparison with both control cells and 5min adhered exposed to NaOCl cells. NaOCl exposure induced a degranulation of PMNLs as measured by lysozyme release. Granules could be found both above the cell surface and on the substratum near the cell. The S/V ratio for PMNLs increased (from 1.52 to 2.02μm^-1) with the increasing of cell activation time. But at NaOCl addition the reverse tendency was observed (from 2.10 to 1.87μm^-1). In cells exposed to NaOCl the redistribution and decrease of concentration of F-actin took place. This observation supports the hypothesis that the priming of PMNLs with hypochlorous acid modifies cell motility and morphology and reflects also on other functions.

Hypochlorous Acid and Taurine-N-Monochloramine in Periodontal Diseases

Chronic periodontitis is a multi-factorial disease involving anaerobic bacteria and the generation of an inflammatory response, including the production of metalloproteinases, pro-inflammatory cytokines, and eicosanoids. Hypochlorous acid (HOCl) and taurine-N-monochloramine (TauCl) are the end-products of the neutrophilic polymorphonuclear leukocyte (PMN) respiratory burst. They act synergistically to modulate the inflammatory response. In the extracellular environment, HOCl and TauCl may directly neutralize interleukin 6 (IL-6) and several metalloproteinases, while HOCl increases the capacity of α2-macroglobulin to bind Tumor Necrosis Factor-alpha, IL-2, and IL-6, and facilitates the release of various growth factors. TauCl inhibits the production of inflammatory mediators, prostaglandins, and nitric oxide. HOCl activates tyrosine kinase signaling cascades, generating an increase in the production of extracellular matrix components, growth factors, and inflammatory mediators. Thus, HOCl and TauCl appear to play a crucial role in the periodontal inflammatory process. Taken together, these findings may offer opportunities for the development of novel host-modulating therapies for the treatment of periodontitis.

Effectiveness of Hypochlorous Acid to Reduce the Biofilms on Titanium Alloy Surfaces in Vitro

Chemotherapeutic agents have been used as an adjunct to mechanical debridement for peri-implantitis treatment. The present in vitro study evaluated and compared the effectiveness of hypochlorous acid (HOCl), sodium hypochlorite (NaOCl), and chlorhexidine (CHX) at eliminating Gram-negative (E. coli and P. gingivalis) and Gram-positive (E. faecalis and S. sanguinis) bacteria. The effect of irrigating volume and exposure time on the antimicrobial efficacy of HOCl was evaluated, and a durability analysis was completed. Live/dead staining, morphology observation, alamarBlue assay, and lipopolysaccharide (LPS) detection were examined on grit-blasted and biofilm-contaminated titanium alloy discs after treatment with the three chemotherapeutic agents. The results indicated that HOCl exhibited better antibacterial efficacy with increasing irrigating volumes. HOCl achieved greater antibacterial efficacy as treatment time was increased. A decrease in antimicrobial effectiveness was observed when HOCl was unsealed and left in contact with the air. All the irrigants showed antibacterial activity and killed the majority of bacteria on the titanium alloy surfaces of biofilm-contaminated implants. Moreover, HOCl significantly lowered the LPS concentration of P. gingivalis when compared with NaOCl and CHX. Thus, a HOCl antiseptic may be effective for cleaning biofilm-contaminated implant surfaces.

Site-specific Effects of DUOX1-Related Peroxidase on Intercellular Apoptosis Signaling

Intercellular apoptosis-inducing HOCl signaling is known as an interplay between superoxide anions/H₂O₂ of transformed target cells and dual oxidase 1 (DUOX1)-related peroxidase that is released from neighboring non-transformed or transformed effector cells. Effector cells are dispensable when the release of the peroxidase domain of DUOX1 from target cells is prevented through inhibition of matrix metalloproteinase (MMP) activity. Membrane-associated peroxidase is then co-localized to NADPH oxidase 1 (NOX1) and establishes HOCl signaling specifically in transformed cells, using the same biochemical pathways as classical intercellular HOCl signaling. Membrane-associated peroxidase protects against exogenous HOCl through reversal of the peroxidase reaction. In addition, membrane-associated peroxidase protects against NO/peroxynitrite signaling as it oxidates NO and decomposes peroxynitrite. The protective function of membrane-associated peroxidase (in the absence of MMP) is analogous to that of catalase, whereas the destructive effect of the enzyme, i.e. the synthesis of HOCl, is independent of its localization and of MMP activity.