Myeloperoxidase-catalyzed inactivation of alpha 1-protease inhibitor by human neutrophils

Clinical impact of ceruloplasmin levels at ANCA-associated vasculitis diagnosis

OBJECTIVES

Ceruloplasmin is an inhibitor of myeloperoxidase (MPO) activity that plays an important role in the pathophysiology of anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV). This study aimed to evaluate the prognostic impact of serum level of ceruloplasmin at diagnosis in patients with anti-MPO antibody-positive AAV.

METHODS

This retrospective monocentric study in Caen University Hospital involved all consecutive adult anti-MPO antibody-positive patients with microscopic polyangiitis or granulomatosis with polyangiitis, diagnosed between January 2010 and January 2022 with available serum sample at inclusion. Patients outcomes were analyzed from two subgroups constituted according to the median serum level of ceruloplasmin. The same analyses were then performed in anti-proteinase 3 (PR3) antibody-positive patients.

RESULTS

Within the 92 patients analyzed, 50 patients had anti-MPO antibodies with a median ceruloplasmin level of 0.44 [quartiles 1-3, 0.40-0.49] g/L and a median Birmingham Vasculitis Activity Score of 19 [14-22]. After a median follow-up period of 40 [22-86] months, 13 (26%) patients had died: 10 (40%) in the low ceruloplasmin group and 3 (12%) in the high ceruloplasmin group (p = 0.03), with a significantly worse survival rate in the low ceruloplasmin group (p = 0.021). No significant differences in relapse rate or renal failure was observed between the two groups. The same analyses performed in the group of AAV patients with anti-PR3 antibody did not show any differences.

CONCLUSION

In anti-MPO AAV patients, serum level of ceruloplasmin at diagnosis seems to be associated with a significant impact on survival.

Role of myeloperoxidase and oxidant formation in the extracellular environment in inflammation-induced tissue damage

The heme peroxidase family generates a battery of oxidants both for synthetic purposes, and in the innate immune defence against pathogens. Myeloperoxidase (MPO) is the most promiscuous family member, generating powerful oxidizing species including hypochlorous acid (HOCl). Whilst HOCl formation is important in pathogen removal, this species is also implicated in host tissue damage and multiple inflammatory diseases. Significant oxidant formation and damage occurs extracellularly as a result of MPO release via phagolysosomal leakage, cell lysis, extracellular trap formation, and inappropriate trafficking. MPO binds strongly to extracellular biomolecules including polyanionic glycosaminoglycans, proteoglycans, proteins, and DNA. This localizes MPO and subsequent damage, at least partly, to specific sites and species, including extracellular matrix (ECM) components and plasma proteins/lipoproteins. Biopolymer-bound MPO retains, or has enhanced, catalytic activity, though evidence is also available for non-catalytic effects. These interactions, particularly at cell surfaces and with the ECM/glycocalyx induce cellular dysfunction and altered gene expression. MPO binds with higher affinity to some damaged ECM components, rationalizing its accumulation at sites of inflammation. MPO-damaged biomolecules and fragments act as chemo-attractants and cell activators, and can modulate gene and protein expression in naïve cells, consistent with an increasing cycle of MPO adhesion, activity, damage, and altered cell function at sites of leukocyte infiltration and activation, with subsequent tissue damage and dysfunction. MPO levels are used clinically both diagnostically and prognostically, and there is increasing interest in strategies to prevent MPO-mediated damage; therapeutic aspects are not discussed as these have been reviewed elsewhere.

M. jannaschii FtsZ, a key protein in bacterial cell division, is inactivated by peroxyl radical-mediated methionine oxidation

Oxidation and inactivation of FtsZ is of interest due to the key role of this protein in bacterial cell division. In the present work, we studied peroxyl radical (from AAPH, 2,2'-azobis(2-methylpropionamidine)dihydrochloride) mediated oxidation of the highly stable FtsZ protein (MjFtsZ) from M. jannaschii, a thermophilic microorganism. MjFtsZ contains eleven Met, and single Tyr and Trp residues which would be expected to be susceptible to oxidation. We hypothesized that exposure of MjFtsZ to AAPH-derived radicals would induce Met oxidation, and cross-linking (via di-Tyr and di-Trp formation), with concomitant loss of its functional polymerization and depolymerization (GTPase) activities. Solutions containing MjFtsZ and AAPH (10 or 100 mM) were incubated at 37 °C for 3 h. Polymerization/depolymerization were assessed by light scattering, while changes in mass were analyzed by SDS-PAGE. Amino acid consumption was quantified by HPLC with fluorescence detection, or direct fluorescence (Trp). Oxidation products and modifications at individual Met residues were quantified by UPLC with mass detection. Oxidation inhibited polymerization-depolymerization activity, and yielded low levels of irreversible protein dimers. With 10 mM AAPH only Trp and Met were consumed giving di-alcohols, kynurenine and di-Trp (from Trp) and the sulfoxide (from Met). With 100 mM AAPH low levels of Tyr oxidation (but not di-Tyr formation) were also observed. Correlation with the functional analyses indicates that Met oxidation, and particularly Met164 is the key driver of MjFtsZ inactivation, probably as a result of the position of this residue at the protein-protein interface of longitudinal interactions and in close proximity to the GTP binding site.

Dual Transport of Active Substances with a Layer-by-Layer-Based Drug Delivery System to Terminate Inflammatory Processes

Conventional therapies for chronic inflammation with high dose application of active agents are often accompanied with severe side effects so that other therapeutical strategies shall be developed to be less physically demanding but still highly efficient. Locally applied Layer-by-Layer (LbL) microcarriers transporting a low, but efficient dosage of active agents directly into the inflamed tissue offer a gentle therapy option. Here, the inhibition of highly degradative enzyme human neutrophile elastase (HNE) is adressed, which is produced and secreted by neutrophile granulocytes (PMNs) in the progress of inflammation. The protected transport and release of its natural inhibitor α1-antitrypsin (AT) as a constituent of the microcarrier's biopolymer multilayer allows for an efficient inhibition of extra- and intracellular elastase. The HOCl scavenger molecule cefoperazone, which preserves AT activity, as an additional multilayer constituent induces a much higher efficacy of the inhibitor. The successful assembly of both agents in different layers of the multilayer and the subsequent HNE inhibition in PMNs is investigated. The parallel application of cefoperazone leads to an enhanced inhibitory effect even with reduced AT amount and reduced carrier:cell ratio. It is demonstrated that the modular assembly strategy of LbL carriers allows for efficient synergistic effect of active agents in inflammatory process.

Hypochlorous acid-mediated modification of proteins and its consequences

Myeloperoxidase (MPO) is a mammalian heme peroxidase released by activated immune cells, which forms chemical oxidants, including hypochlorous acid (HOCl), to kill bacteria and other invading pathogens. In addition to this important role in the innate immune system, there is significant evidence from numerous chronic inflammatory pathologies for the elevated production of HOCl and associated oxidative modification of proteins and damage to host tissue. Proteins are major targets for HOCl in biological systems, owing to their abundance and the high reactivity of several amino acid side-chains with this oxidant. As such, there is significant interest in understanding the molecular mechanisms involved in HOCl-mediated protein damage and defining the consequences of these reactions. Exposure of proteins to HOCl results in a wide range of oxidative modifications and the formation of chlorinated products, which alter protein structure and enzyme activity, and impact the function of biological systems. This review describes the reactivity of HOCl with proteins, including the specific pathways involved in side-chain modification, backbone fragmentation and aggregation, and outlines examples of some of the biological consequences of these reactions, particularly in relation to the development of chronic inflammatory disease.

Neutrophil elastase inhibitory effects of pentacyclic triterpenoids from Eriobotrya japonica (loquat leaves)

ETHNOPHARMACOLOGICAL RELEVANCE

Eriobotrya japonica, a traditional herbal medicine in China and Japan, has long been used to treat chronic bronchitis and coughs.

AIM OF THE STUDY

Pentacyclic triterpenoids (PTs), especially ursolic acid (UA), have been found as reversibly and competitively human neutrophil elastase (HNE) inhibitors. However, the limited solubility and poor bioavailability of PTs hinder their clinical use. Crude plant extracts may have a greater activity than isolated constituents of the equivalent dosage. In this study, an Eriobotrya japonica (loquat leaves) extract (triterpenoid composition of loquat leaves, TCLL) with enriched PTs such as UA was prepared. The study aims to compare the HNE inhibitory (HNEI) effect in vitro and the therapeutic effect on acute lung injury (ALI) in vivo between TCLL and UA.

MATERIALS AND METHODS

An HNEI activity bioassay was performed with Sivelestat sodium hydrate as a positive control. A lipopolysaccharide (LPS)-induced lung inflammatory model was established to evaluate TCLL's therapeutic effect on ALI in vivo. The absorption of UA in TCLL and in UA alone was determined using a Caco-2 cell uptake model and LC-MS.

RESULTS

The IC₅₀ values of TCLL and UA for the HNEI effect were 3.26 ± 0.56 μg/mL and 8.49 ± 0.42 μg/mL (P < 0.01), respectively. TCLL significantly improved the inflammatory cells and inflammatory cytokine production in mice compared with the LPS group (P < 0.05). Additionally, it performed better than the UA alone group (P < 0.05). Moreover, the uptake by Caco-2 cells of UA in TCLL was higher than that in UA alone (P < 0.05).

CONCLUSION

TCLL has a significant HNEI effect in vitro and a therapeutic effect on LPS-induced inflammation in a mouse model. Both the effects are more efficient than UA. Improved absorption of PTs in TCLL may be one explanation for these results.

An oxidation-resistant, recombinant alpha-1 antitrypsin produced in Nicotiana benthamiana

Proteases and reactive oxygen species (ROS) have long been implicated in playing key roles in host tissue injury at sites of inflammation dominated by macrophage activations and/or neutrophil infiltrations. Imbalances between proteases/antiproteases and ROS/antioxidants are recognized to contribute to amplification of inflammatory-based host tissue injury. This has been especially well-documented in such respiratory tract diseases as chronic obstructive pulmonary disease, cystic fibrosis, and acute respiratory distress syndrome. Inflammation-related protease/ROS disequilibria are further confounded by recognition that proteases can increase ROS by several different mechanisms and that ROS can inactivate proteases. The major human antiprotease, alpha-1 antitrypsin (AAT), is dramatically inactivated by ROS. AAT deficiency is the most prevalent genetic predisposing factor leading to emphysema, a condition treated by replacement infusions of plasma-derived AAT (hAAT) at a cost of up to $200,000 per year per patient. An updated method for production of a plant-made recombinant AAT (prAAT) engineered for enhanced oxidation resistance compared to hAAT is presented. Plant-made recombinant AAT shows comparable antiprotease activity to hAAT, and retains full activity under oxidative conditions that would deactivate hAAT. Additionally, we show that prAAT has similar effectiveness in preventing neutrophil elastase-induced cell death in an in vitro human bronchial epithelial cell culture model. We conclude that prAAT is potentially a "biobetter" AAT product that could be made available to individuals with a wide spectrum of inflammatory disorders characterized by overly aggressive neutrophilic infiltrations.

The other myeloperoxidase: Emerging functions

Myeloperoxidase (MPO) is a member of the mammalian peroxidase family. It is mainly expressed in neutrophils, monocytes and macrophages. As a catalyzer of reactive oxidative species and radical species formation, it contributes to neutrophil bactericidal activity. Nevertheless MPO invalidation does not seem to have major health consequences in affected individuals. This suggests that MPO might have alternative functions supporting its conservation during evolution. We will review the available data supporting these non-canonical functions in terms of tissue specific expression, function and enzymatic activity. Thus, we discuss its cell type specific expression. We review in between others its roles in angiogenesis, endothelial (dys-) function, immune reaction, and inflammation. We summarize its pathological actions in clinical conditions such as cardiovascular disease and cancer.

Myeloperoxidase in human neutrophil host defence

Human neutrophils represent the predominant leucocyte in circulation and the first responder to infection. Concurrent with ingestion of microorganisms, neutrophils activate and assemble the NADPH oxidase at the phagosome, thereby generating superoxide anion and hydrogen peroxide. Concomitantly, granules release their contents into the phagosome, where the antimicrobial proteins and enzymes synergize with oxidants to create an environment toxic to the captured microbe. The most rapid and complete antimicrobial action by human neutrophils against many organisms relies on the combined efforts of the azurophilic granule protein myeloperoxidase and hydrogen peroxide from the NADPH oxidase to oxidize chloride, thereby generating hypochlorous acid and a host of downstream reaction products. Although individual components of the neutrophil antimicrobial response exhibit specific activities in isolation, the situation in the environment of the phagosome is far more complicated, a consequence of multiple and complex interactions among oxidants, proteins and their by-products. In most cases, the cooperative interactions among the phagosomal contents, both from the host and the microbe, culminate in loss of viability of the ingested organism.

Maintenance of α(1)-antitrypsin activity by means of co-application of hypochlorous acid-scavengers in vitro and in the supernatant of polymorphonuclear leukocytes: as a basis for a new drug delivery approach

Tissue destruction, pain and loss of function in chronically inflamed tissues can result from noxious agents released from myeloperoxidase (MPO) and its highly reactive product hypochlorous acid (HOCl) or proteases such as neutrophil elastase (NE). Currently there exists a high demand for medications that provide gentle treatments, free from side effects inherent in those prescribed today. One method to circumvent side effects is through the use of locally applied drug delivery. In contrast to systemic therapy, the main advantages of transport systems are the low dosages of drug with a time-controlled delivery. The aim of this study was to ascertain interactions of NE and its inhibitor α(1)-antitrypsin (AT), the influence of hypochlorous acid (HOCl), as well as its scavengers, in order to define an effective mixture of drugs acting in a synergistic way which can be applied by means of drug delivery systems. These investigations determine the effective amounts of AT/HOCl-scavengers that drug mixtures need for delivery under inflammatory conditions in order to prevent tissue damage. AT was shown to inhibit NE in a dose-dependent manner, whereas a physiological concentration of 1.14 µM AT caused a significant NE inhibition (78%, pH 7.5). The concomitant existence of MPO/HOCl inactivated AT in a dose-dependent manner as well. To regain AT efficacy, HOCl-scavengers, such as L-methionine, α-aminosalicylic acid and cefoperazone were additionally applied. Finally, AT was assembled as surface layer onto layer-by-layer biopolymer-coated microcarriers and carrier phagocytosis by polymorphonuclear leukocytes could be shown.

Inhibition of human neutrophil elastase by pentacyclic triterpenes

SCOPE

Inhibiting human neutrophil elastase (HNE) is a promising strategy for treating inflammatory lung diseases, such as H1N1 and SARS virus infections. The use of sivelestat, the only clinically registered synthesized HNE inhibitor, is largely limited by its risk of organ toxicity because it irreversibly inhibits HNE. Therefore, potent reversible HNE inhibitors are promising alternatives to sivelestat.

METHODS AND RESULTS

An in vitro HNE inhibition assay was employed to screen a series of triterpenes. Six pentacyclic triterpenes, but not tetracyclic triterpenes, significantly inhibited HNE. Of these pentacyclic triterpenes, ursolic acid exhibited the highest inhibitory potency (IC50 = 5.51 µM). The HNE inhibitory activity of ursolic acid was further verified using a mouse model of acute smoke-induced lung inflammation. The results of nuclear magnetic resonance and HNE inhibition kinetic analysis showed that the pentacyclic triterpenes competitively and reversibly inhibited HNE. Molecular docking experiments indicated that the molecular scaffold, 28-COOH, and a double bond at an appropriate location in the pentacyclic triterpenes are important for their inhibitory activity.

CONCLUSION

Our results provide insights into the effects of pentacyclic triterpenes on lung inflammatory actions through reversible inhibition of HNE activity.

Biofilm-dependent airway infections: a role for ambroxol?

Biofilms are a key factor in the development of both acute and chronic airway infections. Their relevance is well established in ventilator associated pneumonia, one of the most severe complications in critically ill patients, and in cystic fibrosis, the most common lethal genetic disease in Caucasians. Accumulating evidence suggests that biofilms could have also a role in chronic obstructive pulmonary disease and their involvement in bronchiectasis has been proposed as well. When they grow in biofilms, microorganisms become multidrug-resistant. Therefore the treatment of biofilm-dependent airway infections is problematic. Indeed, it still largely based on measures aiming to prevent the formation of biofilms or remove them once that they are formed. Here we review recent evidence suggesting that the mucokinetic drug ambroxol has specific anti-biofilm properties. We also discuss how additional pharmacological properties of this drug could be beneficial in biofilm-dependent airway infections. Specifically, we review the evidence showing that: 1-ambroxol exerts anti-inflammatory effects by inhibiting at multiple levels the activity of neutrophils, and 2-it improves mucociliary clearance by interfering with the activity of airway epithelium ion channels and transporters including sodium/bicarbonate and sodium/potassium/chloride cotransporters, cystic fibrosis transmembrane conductance regulator and aquaporins. As a whole, the data that we review here suggest that ambroxol could be helpful in biofilm-dependent airway infections. However, considering the limited clinical evidence available up to date, further clinical studies are required to support the use of ambroxol in these diseases.

Influence of secretory leukocyte protease inhibitor-based peptides on elastase activity and their incorporation in hyaluronic acid hydrogels for chronic wound therapy

Chronic nonhealing skin wounds, such as leg ulcers and pressure sores, represent a major clinical problem and a financial burden for the health care systems. Chronic wounds are characterized by prolonged inflammatory phase that results in high levels of elastase, reactive oxygen species (ROS), and diminished growth factor activity. Under normal physiological conditions, elastase is a powerful host defence and its activity is regulated by endogenous inhibitors. The unrestrained elastase activity in chronic wounds may be tuned by exogenous active materials that inhibit elastase. Secretory leucocyte protease inhibitor, SLPI, is a potent endogenous inhibitor of elastase. Peptide fragments, KRCCPDTCGIKCL (Pep4) and KRMMPDTMGIKML (Pep4M), selected from SLPI primary structure were studied as potential elastase inhibitors. Kinetic studies performed for human neutrophil elastase (HNE) and porcine pancreatic elastase (PPE) in presence of these peptides revealed that both behave as uncompetitive and noncompetitive inhibitors of HNE and PPE, respectively. The influence of ROS and albumin on Pep4 and Pep4M inhibitory activity toward elastase reveals that this mixture increases the inhibitory activity of both peptides. These peptides were incorporated in hyaluronic acid hydrogels to evaluate the possibility of being used as active compounds in a drug delivery system. Assessment of HNE and PPE activity in the presence of these hydrogels formulations revealed a considerable decrease in enzyme activity. Although, only moderated elastase inhibition was observed, these peptides represent potential candidates for chronic wound applications, as there is no need for complete elastase inhibition in the normal wound healing process.

Direct interaction of ONO-5046 with human neutrophil elastase through ¹H NMR and molecular docking

Human neutrophil elastase (HNE) has been implicated as a major contributor in the pathogenesis of diseases, such as pulmonary emphysema, acute lung injury (ALI), acute respiratory distress syndrome (ARDS), and other inflammatory diseases. Therefore, searching for appropriate and potential human neutrophil elastase inhibitors (HNEI) that would restore the balance between the free enzyme and the endogenous inhibitors would be of therapeutic interest. ONO-5046 is the first specific HNEI to improve respiratory function and protect lung tissues against various lung injuries. However, the mechanism of ONO-5046 to HNE is still unclear. In this study, the binding properties of ONO-5046 were investigated through (1)H NMR, molecular docking, and bioassay methods to understand the effect of ONO-5046 to HNE. The proton spin-lattice relaxation rate and molecular rotational correlation time results indicated that ONO-5046 has higher affinity with HNE. The molecular docking study showed that ONO-5046 is perfectly matched for the primary enzyme specificity pocket (S1 pocket), and is tightly bound to this pocket of HNE through hydrophobic and hydrogen bonding interactions. The results of both methods were validated through analysis of the HNE inhibitory activity bioassay of ONO-5046 with an IC(50) value of 87.05 nM. Our data suggested that ONO-5046 could bind to HNE through direct interaction, and that molecular docking and NMR methods are valid approaches to survey new HNEI.

Mechanistic overview of reactive species-induced degradation of the endothelial glycocalyx during hepatic ischemia/reperfusion injury

Endothelial cells are covered by a delicate meshwork of glycoproteins known as the glycocalyx. Under normophysiological conditions the glycocalyx plays an active role in maintaining vascular homeostasis by deterring primary and secondary hemostasis and leukocyte adhesion and by regulating vascular permeability and tone. During (micro)vascular oxidative and nitrosative stress, which prevails in numerous metabolic (diabetes), vascular (atherosclerosis, hypertension), and surgical (ischemia/reperfusion injury, trauma) disease states, the glycocalyx is oxidatively and nitrosatively modified and degraded, which culminates in an exacerbation of the underlying pathology. Consequently, glycocalyx degradation due to oxidative/nitrosative stress has far-reaching clinical implications. In this review the molecular mechanisms of reactive oxygen and nitrogen species-induced destruction of the endothelial glycocalyx are addressed in the context of hepatic ischemia/reperfusion injury as a model disease state. Specifically, the review focuses on (i) the mechanisms of glycocalyx degradation during hepatic ischemia/reperfusion, (ii) the molecular and cellular players involved in the degradation process, and (iii) its implications for hepatic pathophysiology. These topics are projected against a background of liver anatomy, glycocalyx function and structure, and the biology/biochemistry and the sources/targets of reactive oxygen and nitrogen species. The majority of the glycocalyx-related mechanisms elucidated for hepatic ischemia/reperfusion are extrapolatable to the other aforementioned disease states.

Towards a four-dimensional view of neutrophils

Neutrophils are constitutively produced throughout adult life and are essential for host responses to many types of pathogen. Neutropenia has long been associated with poor prognosis in the clinic, yet we have an incomplete understanding of their life cycle, not only during homeostasis but also during infection and chronic inflammation. Here, we review recent advances that provide insight into the genetic and biochemical regulators of neutrophil production, function, and survival.

Elastase-induced pulmonary emphysema: insights from experimental models

Several distinct stimuli can be used to reproduce histological and functional features of human emphysema, a leading cause of disability and death. Since cigarette smoke is the main cause of emphysema in humans, experimental researches have attempted to reproduce this situation. However, this is an expensive and cumbersome method of emphysema induction, and simpler, more efficacious alternatives have been sought. Among these approaches, elastolytic enzymes have been widely used to reproduce some characteristics of human cigarette smoke-induced disease, such as: augmentation of airspaces, inflammatory cell influx into the lungs, and systemic inflammation. Nevertheless, the use of elastase-induced emphysema models is still controversial, since the disease pathways involved in elastase induction may differ from those occurring in smoke-induced emphysema. This indicates that the choice of an emphysema model may impact the results of new therapies or drugs being tested. The aim of this review is to compare the mechanisms of disease induction in smoke and elastase emphysema models, to describe the differences among various elastase models, and to establish the advantages and disadvantages of elastase-induced emphysema models. More studies are required to shed light on the mechanisms of elastase-induced emphysema.

Dual functionality of myeloperoxidase in rotenone-exposed brain-resident immune cells

Rotenone exposure has emerged as an environmental risk factor for inflammation-associated neurodegenerative diseases. However, the underlying mechanisms responsible for the harmful effects of rotenone in the brain remain poorly understood. Herein, we report that myeloperoxidase (MPO) may have a potential regulatory role in rotenone-exposed brain-resident immune cells. We show that microglia, unlike neurons, do not undergo death; instead, they exhibit distinctive activated properties under rotenone-exposed conditions. Once activated by rotenone, microglia show increased production of reactive oxygen species, particularly HOCl. Notably, MPO, an HOCl-producing enzyme that is undetectable under normal conditions, is significantly increased after exposure to rotenone. MPO-exposed glial cells also display characteristics of activated cells, producing proinflammatory cytokines and increasing their phagocytic activity. Interestingly, our studies with MPO inhibitors and MPO-knockout mice reveal that MPO deficiency potentiates, rather than inhibits, the rotenone-induced activated state of glia and promotes glial cell death. Furthermore, rotenone-triggered neuronal injury was more apparent in co-cultures with glial cells from Mpo(-/-) mice than in those from wild-type mice. Collectively, our data provide evidence that MPO has dual functionality under rotenone-exposed conditions, playing a critical regulatory role in modulating pathological and protective events in the brain.

Differences in lung glutathione metabolism may account for rodent susceptibility in elastase-induced emphysema development

Syrian Golden hamsters develop more severe emphysema than Sprague-Dawley rats after intratracheal instillation of the same dose of elastase/body weight. Although species variations in antielastase defenses may largely explain these results, other variables, such as differences in lung antioxidants, cannot be overlooked since oxidative stress modulates antiprotease activity. We propose that elastase instillation might affect lung glutathione (GSH) metabolism differently in these species. Our aim was to study in hamsters and rats, lung glutathione metabolism at different times, from the stage of diffuse alveolar damage to advanced emphysema. We measured total and oxidized glutathione content as well as activity and expression of enzymes related to GSH synthesis and redox cycling: γ-glutamylcysteine synthetase, glutathione peroxidase, and glutathione reductase. Whereas rats showed no significant changes in these measurements, hamsters showed significant derangement in GSH metabolism early after elastase instillation: 25% fall in total GSH ( P < 0.05) with no increase in oxidized glutathione associated with reduced enzyme activities 24 h after elastase [60% for γ-glutamylcysteine synthetase ( P < 0.01), 30% for glutathione peroxidase ( P < 0.01), and 75% for glutathione reductase ( P < 0.001)]. GSH homeostasis was restored at the end of the first week, involving transient increased expression of these enzymes. We conclude that elastase induces significant alterations in GSH metabolism of hamster lungs and no overall change in rat lungs. Although differences in disease severity may account for our findings, the hamster becomes vulnerable to functional inhibition of α1-antitrypsin by oxidants and thus, even more susceptible to injury than it would be, considering only its low α1-antitrypsin level.

Preparation and characterization of antioxidant nanospheres from multiple alpha-lipoic acid-containing compounds

The purpose of this study was to prepare and characterize antioxidant nanospheres composed of multiple alpha-lipoic acid-containing compounds (mALAs). It was found that the nanospheres were remarkably stable under physiologic conditions, maintained the antioxidant property of alpha-lipoic acid, and could be destabilized oxidatively and enzymatically. The preparations were simple and highly reproducible providing a new strategy for the development of nanometer-sized antioxidant biomaterials. The nanospheres may find applications as antioxidant therapeutics and oxidation-responsive antioxidant nanocontainers in drug delivery for pathological conditions characterized by oxidative stress including cancer and neurodegenerative diseases.

How human neutrophils kill and degrade microbes: an integrated view

Neutrophils constitute the dominant cell in the circulation that mediates the earliest innate immune human responses to infection. The morbidity and mortality from infection rise dramatically in patients with quantitative or qualitative neutrophil defects, providing clinical confirmation of the important role of normal neutrophils for human health. Neutrophil-dependent anti-microbial activity against ingested microbes represents the collaboration of multiple agents, including those prefabricated during granulocyte development in the bone marrow and those generated de novo following neutrophil activation. Furthermore, neutrophils cooperate with extracellular agents as well as other immune cells to optimally kill and degrade invading microbes. This brief review focuses attention on two examples of the integrated nature of neutrophil-mediated anti-microbial action within the phagosome. The importance and complexity of myeloperoxidase-mediated events illustrate a collaboration of anti-microbial responses that are endogenous to the neutrophil, whereas the synergy between the phagocyte NADPH (nicotinamide adenine dinucleotide phosphate) oxidase and plasma-derived group IIA phospholipase A(2) exemplifies the collective effects of the neutrophil with an exogenous factor to achieve degradation of ingested staphylococci.

Differential effects of flavonols on inactivation of α1-antitrypsin induced by hypohalous acids and the myeloperoxidase–hydrogen peroxide–halide system

Alpha1-antitrypsin is well known for its ability to inhibit human neutrophil elastase. Pretreatment of alpha1-antitrypsin with hypohalous acids HOCl and HOBr as well as with the myeloperoxidase-hydrogen peroxide-chloride (or bromide) system inactivated this proteinase. The flavonols rutin, quercetin, myricetin, and kaempferol inhibited the inactivation of alpha1-antitrypsin by HOCl and HOBr with rutin having the most pronounced effect. In contrast, these flavonols did not remove the proteinase inactivation by the myeloperoxidase-hydrogen peroxide-halide system. Taurine did not protect against the inactivation of alpha1-antitrypsin by HOCl, HOBr, or the myeloperoxidase-hydrogen peroxide-halide system, while methionine was efficient in all systems. A close association between myeloperoxidase and alpha1-antitrypsin was revealed by native gel electrophoresis and in-gel peroxidase staining. In addition, alpha1-antitrypsin binds to the myeloperoxidase components transferred after SDS-PAGE on a blotting membrane. With this complex formation, myeloperoxidase overcomes the natural antioxidative protective system of plasma and prevents the inactivation of alpha1-antitrypsin.

Azithromycin reduces spontaneous and induced inflammation in DeltaF508 cystic fibrosis mice

Background

Inflammation plays a critical role in lung disease development and progression in cystic fibrosis. Azithromycin is used for the treatment of cystic fibrosis lung disease, although its mechanisms of action are poorly understood. We tested the hypothesis that azithromycin modulates lung inflammation in cystic fibrosis mice.

Methods

We monitored cellular and molecular inflammatory markers in lungs of cystic fibrosis mutant mice homozygous for the ΔF508 mutation and their littermate controls, either in baseline conditions or after induction of acute inflammation by intratracheal instillation of lipopolysaccharide from Pseudomonas aeruginosa, which would be independent of interactions of bacteria with epithelial cells. The effect of azithromycin pretreatment (10 mg/kg/day) given by oral administration for 4 weeks was evaluated.

Results

In naive cystic fibrosis mice, a spontaneous lung inflammation was observed, characterized by macrophage and neutrophil infiltration, and increased intra-luminal content of the pro-inflammatory cytokine macrophage inflammatory protein-2. After induced inflammation, cystic fibrosis mice combined exaggerated cellular infiltration and lower anti-inflammatory interleukin-10 production. In cystic fibrosis mice, azithromycin attenuated cellular infiltration in both baseline and induced inflammatory condition, and inhibited cytokine (tumor necrosis factor-α and macrophage inflammatory protein-2) release in lipopolysaccharide-induced inflammation.

Conclusion

Our findings further support the concept that inflammatory responses are upregulated in cystic fibrosis. Azithromycin reduces some lung inflammation outcome measures in cystic fibrosis mice. We postulate that some of the benefits of azithromycin treatment in cystic fibrosis patients are due to modulation of lung inflammation.

Myeloperoxidase plays critical roles in killing Klebsiella pneumoniae and inactivating neutrophil elastase: effects on host defense

Activated neutrophils use myeloperoxidase (MPO) to generate an array of potent toxic oxidants. In the current studies we used genetically altered mice deficient in MPO to investigate the role of the enzyme in host defense against the Gram-negative bacterium Klebsiella pneumoniae, an important human pathogen. For comparison, we used mice deficient in the antimicrobial molecule, neutrophil elastase (NE). When challenged i.p., mice deficient in either MPO or NE were markedly more susceptible to bacterial infection and death. In vitro studies suggested that MPO impairs the morphology of bacteria in a distinctive way. Of importance, our in vitro studies found that MPO mediated oxidative inactivation of NE, an enzyme that has been widely implicated in the pathogenesis of various tissue-destructive diseases. This pathway of oxidative inactivation may be physiologically relevant, because activated neutrophils isolated from MPO-deficient mice exhibited increased elastase activity. Our observations provide strong evidence that MPO, like NE, is a key player in the killing of K. pneumoniae bacteria. They also suggest that MPO may modulate NE to protect the host from the tissue-degrading activity of this proteinase.

In vitro inhibition of human neutrophil histotoxicity by ambroxol: evidence for a multistep mechanism

Neutrophils are major culprits for the protease/antiprotease imbalance during various lung diseases, that is, chronic obstructive pulmonary disease, cystic fibrosis, idiopathic pulmonary fibrosis and adult respiratory distress syndrome. Thus, these cells are presently considered an ideal target for the pharmacologic control of tissue injury during these diseases. This study was planned in order to investigate if ambroxol and its precursor bromhexine are actually capable of preventing alpha-1-antitrypsin (A1AT) inactivation by stimulated neutrophils and possibly to look into the mechanisms underlying this event. Ambroxol inhibited the production of superoxide anion by activated neutrophils, whereas bromhexine had no inhibitory effect. Ambroxol decreased the production of hypochlorous acid (HOCl) from activated neutrophils with high efficiency, whereas bromhexine had a modest activity. Ambroxol and bromhexine were capable of limiting the chlorination of monochlorodimedon by HOCl, displaying the capacity of directly scavenging the oxidant. Ambroxol decreased the release of elastase and myeloperoxidase from activated neutrophils, whereas bromhexine was ineffective. Ambroxol prevented the A1AT inactivation by neutrophils, whereas bromhexine was completely ineffective. Among drugs currently available for in vivo use in humans, ambroxol is unique by virtue of its ability to prevent neutrophil-mediated A1AT inactivation via inhibition of HOCl production as well as HOCl scavenging. Also taking into account its capacity for curbing elastase release, the drug displays the potential to lessen the burden of oxidants/proteases and to increase the antiprotease shield at the site of inflammation. Thus, ambroxol appears to be a good candidate for raising attempts to develop new therapeutic histoprotective approaches to inflammatory bronchopulmonary diseases.

Oxidative and nitrosative events in asthma

Asthma affects over 15 million individuals in the United States, with over 1.5 million emergency room visits, 500,000 hospitalizations, and 5500 deaths each year, many of which are children. Airway inflammation is the proximate cause of the recurrent episodes of airflow limitation in asthma. Research applying molecular biology, chemistry, and cell biology to human asthma and model systems of asthma over the last decade has revealed that numerous biologically active proinflammatory mediators lead to increased production of reactive oxygen species (ROS) and the gaseous molecule nitric oxide (NO). Persistently increased ROS and NO in asthma lead to reactive nitrogen species (RNS) formation and subsequent oxidation and nitration of proteins, which may cause alterations in protein function that are biologically relevant to airway injury/inflammation. Eosinophil peroxidase and myeloperoxidase, leukocyte-derived enzymes, amplify oxidative events and are another enzymatic source of NO-derived oxidants and nitrotyrosine formation in asthma. Concomitant with increased generation of oxidative and nitrosative molecules in asthma, loss of protective antioxidant defense, specifically superoxide dismutase (SOD), contributes to the overall toxic environment of the asthmatic airway. This review discusses the rapidly accruing data linking oxidative and nitrosative events as critical participants in the acute and chronic inflammation of asthmatic airways.

New functions of neutrophils in the arthus reaction: expression of tissue factor, the clotting initiator, and fibrinolysis by elastase

The products of the blood clotting reaction, eg, thrombin and fibrinopeptides, have various proinflammatory activities and are suggested to modulate inflammation. The macrophage expression of tissue factor (TF), the clotting initiator, has been shown to cause clotting in the site of the delayed-type hypersensitivity reaction, a cellular immune response. However, the mechanism of the clotting induction in humoral immune response has been insufficiently studied. Therefore, the Arthus reaction, a model of immune-complex diseases, was produced in monkey skin that was examined for TF expression and fibrin deposition. TF antigen was positive on most of polymorphonuclear leukocytes, which were the main leukocytes in the lesions and were identified as neutrophils with an anti-neutrophil-elastase mAb. TF mRNA was detected in neutrophils by in situ hybridization using TF RNA probes, indicating de novo TF synthesis by the leukocytes. Specific binding of activated factor VII onto TF-positive neutrophils suggested the activity of neutrophil TF to trigger the cascade reaction of clotting. The number of TF-positive neutrophils were correlated in time with the intensity and extent of fibrin deposition that was visualized with an mAb specific for fibrin and peaked in 24 hours. Interestingly, the fibrin deposit was partially positive for an mAb specific for neutrophil elastase-digested fibrin. These results show in vivo evidence of a close relationship between neutrophils and both clotting and fibrinolysis in the Arthus reaction and may suggest that these neutrophil functions contribute to the pathogenesis of this hypersensitivity inflammation.

Effects of recombinant human DNase and hypertonic saline on airway inflammation in children with cystic fibrosis

Recombinant human DNase (rhDNase) is an established treatment in cystic fibrosis (CF), but it may liberate cationic mediators bound to DNA in the airways. An alternative mucolytic therapy is hypertonic saline (HS); however, HS may potentiate neutrophilic inflammation. We compared the effect of rhDNase and HS on cationic proinflammatory mediators in CF sputum. In a randomized, crossover trial, 48 children with CF were allocated consecutively to 12 weeks of once-daily 2.5 mg rhDNase, alternate-day 2.5 mg rhDNase, and twice-daily 7% HS. Sputum levels of total interleukin-8 (IL-8), free IL-8, myeloperoxidase, eosinophil cationic protein, and neutrophil elastase (NE) activity were measured before and after each treatment. The change in mediator levels from baseline with daily rhDNase and HS was not significant; however, with alternate-day rhDNase, there was an increase in free IL-8. When changes in mediator levels with daily rhDNase were compared with alternate-day rhDNase and HS, no significant differences were detected. Only changes in NE activity were associated with changes in lung function. In summary, we were unable to show that rhDNase or HS promote airway inflammation in CF.

Contributions of myeloperoxidase to proinflammatory events: more than an antimicrobial system

Optimal oxygen-dependent antimicrobial activity of circulating polymorphonuclear leukocytes reflects the synergistic effects of the myeloperoxidase (MPO)-hydrogen peroxide-halide system. Delivered from its storage compartment to the phagolysosome during fusion of the azurophilic granules, MPO catalyzes the oxidation of chloride in the presence of H2O2, chemistry unique to MPO, and thereby generates an array of highly reactive oxidants. Recent investigations of a wide range of inflammatory disorders have identified biochemical markers of MPO-dependent reactions, thus indirectly implicating MPO in their pathogenesis, progression, or perpetuation. The implied involvement of MPO-dependent events in diseases such as atherosclerosis forces reexamination of several fundamental tenets about MPO that are derived from studies of myeloid cells, most notably factors important in the regulated expression of MPO gene transcription. The evidence supporting a role for MPO in the pathogenesis of atherosclerosis, demyelinating diseases of the central nervous system, and specific cancers is reviewed and some of the new questions raised by these studies are discussed. Lastly, an appreciation for the existence of a broad family of proteins structurally related to MPO and the functional diversity implied by the corresponding structures may provide insights into novel ways in which MPO can function as more than an important antimicrobial component.

Uric acid mediates photodynamic inactivation of caprine alpha-2-macroglobulin

Uric acid (2,6,8 trioxopurine), the end product of purine metabolism in mammalian systems, has shown a wide range of antioxidant properties including scavenging of hydroxyl radical and singlet oxygen. In this study we show that in the presence of visible light, uric acid disrupted caprine alpha-2-macroglobulin (alpha(2) M) structure and antiproteolytic function in vitro. Proteinase cleaves the bait region of caprine inhibitor inducing major conformational changes and entrapping the enzyme within its molecular cage. In contrast to native alpha(2) M, modified antiproteinase lost half of its antiproteolytic potential within 4 hours of uric acid exposure. The changes in uv-absorption spectra of the treated protein suggested possible spatial rearrangement of subunits or conformational change. Analysis of the mechanism by which alpha(2) M was inactivated revealed that the process was dependent on generation of superoxide anion and hydrogen peroxide. Our findings suggest that antiproteolytic activity of caprine alpha(2) M could be compromised via oxidative modification mediated by uric acid. Moreover, low concentrations of alpha(2) M were found to stimulate superoxide production by some unknown mechanism.

Hypochlorite-induced oxidation of thiols: formation of thiyl radicals and the role of sulfenyl chlorides as intermediates

Activated phagocytic cells generate hypochlorite (HOCl) via release of hydrogen peroxide and the enzyme myeloperoxidase. HOCl plays an important role in bacterial cell killing, but excessive or misplaced production of HOCI is also known to cause tissue damage. Studies have shown that low-molecular-weight thiols such as reduced glutathione (GSH), and sulfur-containing amino acids in proteins, are major targets for HOCl. Radicals have not generally been implicated as intermediates in thiol oxidation by HOCl, though there is considerable literature evidence for the involvement of radicals in the metal ion-, thermal- or UV light-catalysed decomposition of sulfenyl or sulfonyl chlorides which are postulated intermediates in thiol oxidation. In this study we show that thiyl radicals are generated on reaction of a number of low-molecular-weight thiols with HOCl. With sub-stoichiometric amounts of HOCl, relative to the thiol, thiyl radicals are the major species detected by EPR spin trapping. When the HOCl is present in excess over the thiol, additional radicals are detected with compounds which contain amine functions; these additional radicals are assigned to nitrogen-centered species. Evidence is presented for the involvement of sulfenyl chlorides (RSCl) in the formation of these radicals, and studies with an authentic sulfenyl chloride have demonstrated that this compound readily decomposes in thermal-, metal-ion- or light-catalysed reactions to give thiyl radicals. The formation of thiyl radicals on oxidation of thiols with HOCl appears to compete with non-radical reactions. The circumstances under which radical formation may be important are discussed.

Phagocytes and oxidative stress

Neutrophils and other phagocytes manufacture O(2)(-) (superoxide) by the one-electron reduction of oxygen at the expense of NADPH. Most of the O(2)(-) reacts with itself to form H(2)O(2) (hydrogen peroxide). From these agents a large number of highly reactive microbicidal oxidants are formed, including HOCl (hypochlorous acid), which is produced by the myeloperoxidase-catalyzed oxidation of Cl(-) by H(2)O(2); OH(*) (hydroxyl radical), produced by the reduction of H(2)O(2) by Fe(++) or Cu(+); ONOO(-) (peroxynitrite), formed by the reaction between O(2)(-) and NO(*); and many others. These reactive oxidants are manufactured for the purpose of killing invading microorganisms, but they also inflict damage on nearby tissues, and are thought to be of pathogenic significance in a large number of diseases. Included among these are emphysema, acute respiratory distress syndrome, atherosclerosis, reperfusion injury, malignancy and rheumatoid arthritis.

The importance of data presentation regarding gingival crevicular fluid myeloperoxidase and elastase-like activity in periodontal disease and health status

BACKGROUND

The enzymatic profile of gingival crevicular fluid (GCF) is being analyzed with increasing interest, but related studies lack a general consensus on most methodological points, including the appropriate mode of data presentation.

METHODS

GCF myeloperoxidase (MPO) and elastase-like activity (ELA) levels were spectrophotometrically determined on a total of 60 subjects who were divided into three equal subgroups as early-onset periodontitis (EOP), adult periodontitis (AP), and healthy. GCF enzyme levels were calculated and evaluated both as total enzyme activity and enzyme concentration. The correlations between these GCF enzymes and clinical periodontal status were also analyzed.

RESULTS

With both modes of data presentation, the results regarding MPO activity were consistent. When presented either as total MPO activity or MPO concentration, the periodontally healthy group showed significantly lower MPO activity than the two patient groups (P<0.05). However, two modes of data presentation did not match when GCF ELA was concerned. When data were reported as total ELA, the healthy group exhibited lower enzyme activity (0.02 +/- 0.001 U) than EOP (0.04 +/- 0.01 U) and AP (0.06 +/- 0.02 U) groups; but when reported as concentration, the highest ELA levels were seen in the healthy group (221 +/- 31.53 nmol/min/ml), followed by AP (98.63 +/- 23.03 nmol/min/ml) and EOP (70.49 +/- 12.02 nmol/min/ml) (P<0.05). A strong-positive and significant correlation existed between GCF MPO and ELA. Correlations with clinical parameters were mostly observed with total activities.

CONCLUSIONS

The findings of the present study confirm the relationship between GCF ELA and MPO activity and periodontal disease and also support the functional relativity between the two enzymes. Furthermore, based on these findings, it can be suggested that data presentation by use of total activity seems to be more sensitive in both the reflection of the actual enzymatic profile of GCF and also the existing clinical periodontal status. For each GCF component, the validity of different modes of data presentation should be considered.

Cefoperazone prevents the inactivation of alpha(1)-antitrypsin by activated neutrophils

At sites of neutrophilic inflammation, tissue injury by neutrophil elastase is favored by phagocyte-induced hypochlorous acid-dependent inactivation of the natural elastase inhibitor alpha(1)-antitrypsin. In the present study, cefoperazone prevented alpha(1)-antitrypsin inactivation by neutrophils and reduced the recovery of hypochlorous acid from these cells. Moreover, the antibiotic reduced the free elastase activity in a neutrophil suspension supplemented with alpha(1)-antitrypsin without affecting the cells' ability to release elastase. These data suggest that the drug inactivates hypochlorous acid before its reaction with alpha(1)-antitrypsin, thereby permitting the antiprotease-mediated blockade of released elastase. In conclusion, cefoperazone appears to have the potential for limiting elastase-antielastase imbalances, attenuating the related tissue injury at sites of inflammation.

Proteinase 3, a potent secretagogue in airways, is present in cystic fibrosis sputum

We evaluated the roles of proteinase 3 (PR3) and human neutrophil elastase (HNE), two neutrophil serine proteinases in the mechanisms leading to airway inflammation and hypersecretion in cystic fibrosis (CF). Using specific enzyme-linked immunosorbent assay (ELISA), we found higher levels of PR3 than HNE in sputum from CF patients. Using two inhibitors, ICI (Imperial Chemical Industries) 200,355 (which inhibits both HNE and PR3) and secretory leukoproteinase inhibitor (SLPI) (which inhibits only HNE), we showed that PR3 was enzymatically active in sputum, and its activity, as assessed by SLPI-resistant serine proteinase activity, correlated highly with its antigenic concentration measured by ELISA. Interestingly, sputum pellet-associated serine proteinase activity was mostly due to HNE. PR3 purified from neutrophil azurophil granules triggered airway gland secretion, as measured by the release of radiolabeled molecules from cultured bovine tracheal serous cells pulse-labeled with Na235SO4. This secretory activity was inhibited by ICI 200,355. PR3 concentration in CF sputum was highly correlated with taurine concentration, a reliable marker of airway inflammation and respiratory scores (e.g., FEV1%), whereas no significant correlation was observed with HNE. We verified that Pseudomonas aeruginosa proteinases did not interfere with the assessment of PR3 and HNE. Indeed, the PR3/HNE ratio was greatest in patients chronically infected by P. aeruginosa. We suggest that PR3 may play a role in the hypersecretory process that is characteristic of CF.

ONO-5046 is a potent inhibitor of neutrophil elastase in human pleural effusion after lobectomy

The imbalance of neutrophil elastase and alpha1-antitrypsin in pleural effusion after lobectomy and the effects of the neutrophil elastase inhibitors, sodium N-[2-[4-(2,2-Dimethylpropionyloxy)phenyl-sulfonylamino]benzo yl]aminoacetic acid (ONO-5046) and purified alpha1-antitrypsin, on neutrophil elastase activity were determined. The amount of neutrophil elastase complexed to alpha1-antitrypsin, measured by an enzyme-linked immunosorbent assay, was 170 times higher in pleural effusion than in blood 3 h after lobectomy. The alpha1-antitrypsin levels measured by laser nephelometry did not increase in either blood or pleural effusion. Although neutrophil elastase activity, measured by the hydrolysis of succinyl-(Ala)3-p-nitroanilide, was not detected in blood, it was increased in pleural effusion 3 h and 24 h after lobectomy. ONO-5046, but not alpha1-antitrypsin, reduced the neutrophil elastase activity in pleural effusion. There is an imbalance of neutrophil elastase and alpha1-antitrypsin in pleural effusion after lobectomy. ONO-5046 is a potent inhibitor of neutrophil elastase activity in human pleural effusion.

Inactivation of urate oxidase by a system composed of lactoperoxidase, hydrogen peroxide and bromide

Urate oxidase from Candida utilis, an enzyme containing an essential thiol, was examined for its sensitivity to lactoperoxidase, an oxidant present in breast milk. Upon exposure to a system composed of lactoperoxidase, hydrogen peroxide and bromide at moderately alkaline pH, the urate oxidase exhibited comparable activity to the untreated enzyme; but upon exposure at moderately acidic pH, it lost its activity completely. Thus the lactoperoxidase-H2O2-bromide system significantly inactivated urate oxidase only at moderately acidic pH. This inactivation was prevented by the presence of N-acetylmethionine, a methionine analogue, or glutathione, which is a thiol compound analogous to an amino acid, indicating that it was probably due to the oxidation and damage of the methionine residue and/or the thiol group in the urate oxidase by the lactoperoxidase system, that loss of catalytic activity of the urate oxidase occurred.

Regional variability of lung inflammation in cystic fibrosis

Chest radiography in patients with cystic fibrosis (CF) frequently shows more severe changes in the upper lobes. We performed bronchoalveolar lavage (BAL) on 12 clinically stable, young adult patients with CF to determine whether inflammation varies significantly among geographically distinct areas of the lung. We found that absolute numbers of neutrophils were generally greater in BAL fluid from the upper lobe (25.7 +/- 7.9 x 10(5) neutrophils/ml [mean +/- SEM]) of the right lung than that obtained from the right lower lobe (6.8 +/- 2.8 x 10(5) neutrophils/ml; p < 0.01). The mean value of unopposed neutrophil elastase activity in upper-lobe BAL fluid (227 +/- 91 nmol peptide hydrolyzed/ml/min) was also significantly greater than that in lower-lobe BAL fluid (84 +/- 43 nmol/peptide hydrolyzed/ml/ min; p < 0.01), and similar differences were found for myeloperoxidase activity and DNA content. Neutrophil influx and unopposed neutrophil elastase for a given region correlated inversely with lung function or percentage of ideal body weight, and upper-versus lower-lobe differences were more pronounced in subjects with better preservation of lung function. Our findings suggest that regional variation in inflammation must be considered when utilizing BAL to study lower respiratory tract inflammation in CF or to monitor responses to therapeutic interventions that can potentially diminish lung inflammation. Our findings may also have implications for the study of the natural history of lung inflammation and infection in neonates, infants, and young children with CF.

Proteinase-free myeloperoxidase increases airway epithelial permeability in a whole trachea model

In cystic fibrosis the bronchiectatic conducting airways have large numbers of neutrophils in their walls and in their luminal contents. The neutrophil's primary granule enzyme activities of elastase and peroxidase are increased in the sputum of these patients. It has been postulated that these enzymes--together or individually--act to damage the airway epithelium. However, only peroxidase activity has consistently correlated with the degree of structural and functional airway disease in these patients with leakage of plasma protein into the airway lumen (Regelmann et al., Pediatr Pulmonol, 1995; 19:1-9). The present study was designed to test whether human neutrophil-derived myeloperoxidase can independently produce bronchial epithelial damage without the presence of proteases, as measured by increased permeability of the airway epithelium. Human peripheral blood neutrophils were purified, their primary granules isolated, and their peroxidase purified using affinity and ion exchange column chromatography. Activity of the proteinase-free peroxidase was measured using a chromogenic substrate. The effect of this peroxidase on the permeability of excised rat tracheas was measured using radioactive and fluorescent-labeled non-ionic molecules of varying molecular weight. Rat tracheas exposed to 15 minute treatments with either 130 U of peroxidase or hydrogen peroxide (10(-5) M) did not show a significant increase in the permeability of the epithelium to [3H]inulin, [14C]sucrose, and fluorescein isothiocyanate dextran 20 compared with control tracheas. However, those tracheas exposed to 130 U peroxidase followed by 10(-5) M hydrogen peroxide showed an increased permeability to each of the three test solutes. We conclude that proteinase-free myeloperoxidase, in the presence of non-toxic concentrations of its substrates, hydrogen peroxide and halide, produced increases in permeability to non-ionic molecules in the rat trachea within 15 minutes.

Scavenging of hypochlorous acid by carvedilol and ebselen in vitro

1. The antihypertensive drug carvedilol and the antiinflammatory selenoorganic compound ebselen were tested for their ability to react with the reactive oxygen species hypochlorous acid (HOCl) in vitro. 2. Carvedilol scavenges HOCl at a rate sufficient to protect a model molecule catalase against inactivation by HOCl. 3. Ebselen was resistant to HOCl when its glutathione-peroxidase mimetic property was compared with that of glutathione peroxidase.