Eosinophil cationic protein alters pulmonary surfactant structure and function in asthma

Stratification of asthma by lipidomic profiling of induced sputum supernatant

BACKGROUND

Asthma is a chronic respiratory disease with significant heterogeneity in its clinical presentation and pathobiology. There is need for improved understanding of respiratory lipid metabolism in asthma patients and its relation to observable clinical features.

OBJECTIVE

We performed a comprehensive, prospective, cross-sectional analysis of the lipid composition of induced sputum supernatant obtained from asthma patients with a range of disease severities, as well as from healthy controls.

METHODS

Induced sputum supernatant was collected from 211 adults with asthma and 41 healthy individuals enrolled onto the U-BIOPRED (Unbiased Biomarkers for the Prediction of Respiratory Disease Outcomes) study. Sputum lipidomes were characterized by semiquantitative shotgun mass spectrometry and clustered using topologic data analysis to identify lipid phenotypes.

RESULTS

Shotgun lipidomics of induced sputum supernatant revealed a spectrum of 9 molecular phenotypes, highlighting not just significant differences between the sputum lipidomes of asthma patients and healthy controls, but also within the asthma patient population. Matching clinical, pathobiologic, proteomic, and transcriptomic data helped inform the underlying disease processes. Sputum lipid phenotypes with higher levels of nonendogenous, cell-derived lipids were associated with significantly worse asthma severity, worse lung function, and elevated granulocyte counts.

CONCLUSION

We propose a novel mechanism of increased lipid loading in the epithelial lining fluid of asthma patients resulting from the secretion of extracellular vesicles by granulocytic inflammatory cells, which could reduce the ability of pulmonary surfactant to lower surface tension in asthmatic small airways, as well as compromise its role as an immune regulator.

Airway allergy causes alveolar macrophage death, profound alveolar disorganization and surfactant dysfunction

Respiratory disorders caused by allergy have been associated to bronchiolar inflammation leading to life-threatening airway narrowing. However, whether airway allergy causes alveolar dysfunction contributing to the pathology of allergic asthma remains unaddressed. To explore whether airway allergy causes alveolar dysfunction that might contribute to the pathology of allergic asthma, alveolar structural and functional alterations were analyzed during house dust mite (HDM)-induced airway allergy in mice, by flow cytometry, light and electron microscopy, monocyte transfer experiments, assessment of intra-alveolarly-located cells, analysis of alveolar macrophage regeneration in Cx3cr1 ^cre:R26-yfp chimeras, analysis of surfactant-associated proteins, and study of lung surfactant biophysical properties by captive bubble surfactometry. Our results demonstrate that HDM-induced airway allergic reactions caused severe alveolar dysfunction, leading to alveolar macrophage death, pneumocyte hypertrophy and surfactant dysfunction. SP-B/C proteins were reduced in allergic lung surfactant, that displayed a reduced efficiency to form surface-active films, increasing the risk of atelectasis. Original alveolar macrophages were replaced by monocyte-derived alveolar macrophages, that persisted at least two months after the resolution of allergy. Monocyte to alveolar macrophage transition occurred through an intermediate stage of pre-alveolar macrophage and was paralleled with translocation into the alveolar space, Siglec-F upregulation, and downregulation of CX3CR1. These data support that the severe respiratory disorders caused by asthmatic reactions not only result from bronchiolar inflammation, but additionally from alveolar dysfunction compromising an efficient gas exchange.

Dupilumab (Dupixent®) tends to be an effective therapy for uncontrolled severe chronic rhinosinusitis with nasal polyps: real data of a single-centered, retrospective single-arm longitudinal study from a university hospital in Germany

INTRODUCTION

Chronic rhinosinusitis with nasal polyps (CRSwNP) is an inflammatory disease, which is usually type 2-mediated in the western hemisphere, associated with severe therapeutic and socioeconomic challenges. The first targeted systemic treatment option for severe uncontrolled CRSwNP is a human monoclonal antibody against the interleukin-4 receptor α (IL-4Rα) subunit called dupilumab, which was approved for subcutaneous administration in Germany in October 2019. The purpose of this study is to investigate the efficacy of dupilumab in real life in patients treated with dupilumab in label according to license in our department in 2019-2021.

MATERIALS AND METHODS

Since October 2019, we have investigated 40 patients (18 men, 22 women) treated with dupilumab in a single-center, retrospective single-arm longitudinal study. The following parameters were collected before treatment (baseline), at 1 month, 4 months, 7 months, 10 months, and 13 months: the Sino-Nasal Outcome Test-22 (SNOT-22), the forced expiratory pressure in 1 s (FEV-1), the olfactometry using Sniffin' Sticks-12 identification test (SSIT), a visual analog scale of the total complaints, the Nasal Polyp Score (NPS), histologic findings as well as total serum IgE, eosinophilic cationic protein in serum and blood eosinophils.

RESULTS

The average age was 52.7 years (± 15.3). The follow-up period was 13 months. The SNOT-22 average was 60 points (± 22.2) at the first visit, 28.2 points (± 17.1) after 4 months and 20.8 points (± 17.7) after 13 months. The NPS was 4.3 points (± 1.5), after 4 months 2.1 points (± 1.3) and after 13 months 1.4 points (± 1.1). Olfactometry showed 3.2 points (± 3.7) at the baseline, 7.0 points (± 4.0) after 4 months and 7.8 points (± 3.5) after 13 months. The other parameters also improved. Most parameters showed linear dependence in the slopes under therapy (p < 0.001). Adverse side effects were mostly only mild, and no rescue therapy was needed.

CONCLUSION

There is a clear improvement in the medical condition and symptoms in all categories mentioned under therapy with dupilumab, as well as a reduction in the need for systemic glucocorticoids and revision surgery as rescue treatment. Our results show that dupilumab tends to be an effective therapy alternative for severe CRSwNP.

Fat mass index and airway hyperresponsiveness in Korean adults

OBJECTIVE

Airway hyperresponsiveness (AHR) is associated with asthma and obesity, which is defined as a high body mass index. Body mass mainly comprises fat mass (FM) and muscle mass (MM), which are independent of each other. We investigated the effect of changes in FM over time on the development of asymptomatic AHR in adults.

METHODS

This long-term longitudinal study included adults who were underwent health checkups at the Seoul National University Hospital Gangnam Center. The participants underwent two methacholine bronchial provocation tests with a follow-up period (between the first and second tests) of more than 3 years and bioelectrical impedance analysis (BIA) at all visits. FM index (FMI; FM normalized for height) and MM index (MMI; MM normalized for height) were calculated using BIA.

RESULTS

The study included 328 adult participants (61 women and 267 men). The mean number of BIA measurements was 6.96 and the follow-up duration was 6.69 years. In total, 13 participants showed a positive conversion of AHR. Multivariate analysis indicated that a high rate of change in FMI ([g/m²]/year), not MMI, was significantly associated with the risk of AHR development (P = 0.037) after adjustment for age, sex, smoking status, and FEV1 predicted.

CONCLUSION

A rapid gain of FM over time may be a risk factor for developing AHR in adults. Prospective studies are needed to confirm our results and evaluate the role of FM reduction in preventing AHR development in obese adults.

Bronchoprotective effect of deep inspirations in cough variant asthma: A distinguishing feature in the spectrum of airway disease?

PURPOSE

To assess the effect of deep inspirations (DIs) on airway behaviour in individuals with classic asthma (CA), cough variant asthma (CVA), and methacholine (MCh)-induced cough but normal airway sensitivity (COUGH) during bronchoprovocation.

METHODS

Twenty-five adults (18 female; 44.8 ± 12.3 years (Mean ± SD); n = 9 CA, n = 9 CVA, and n = 7 COUGH) completed two single-dose MCh challenges, with and without DIs. Bronchoprotection was assessed by comparing changes in bronchoconstriction (FEV₁, FVC, FEV₁/FVC, FEF₅₀, FEF_25-75), gas trapping (RV, RV/TLC) and impulse oscillometry (IOS) measurements.

RESULTS

The% changes in FEV₁ with and without DIs were not significantly different within any group. Decreases in FEF₅₀ and FEF_25-75 were greater in CA (p = 0.041 and p = 0.029), decreases in FVC (% predicted) and FEV₁/FVC(%) were less in CVA (p = 0.048 and p = 0.010), and increases in RV (L) and RV/TLC (% predicted) were less in COUGH (p = 0.007 and p = 0.028), respectively. No differences in IOS measurements were noted.

CONCLUSIONS

DIs triggered bronchoconstriction in CA, bronchoprotection in CVA, and prevented gas trapping in COUGH.

Bronchodilating effect of deep inspirations in asthma and chronic cough

The pathophysiologic processes distinguishing classic asthma (CA), cough-variant asthma (CVA), and methacholine (MCh)-induced cough but normal airway sensitivity (COUGH) are inadequately understood and may be a result of differences in the ability to bronchodilate following a deep inspiration (DI). The purpose of this study was to compare the bronchodilating effect of DIs in individuals with CA, CVA, and COUGH using high-dose MCh. Individuals aged 18-65 yr with CA or suspected CVA completed high-dose MCh testing to a maximum change in forced expiratory volume in 1 s (FEV1) of 50% from baseline (MAX). Impulse oscillometry (IOS) measurements and partial and maximal-flow volume curves (used to calculate a DI index) were recorded at baseline and at each dose of MCh. Body plethysmography was performed at baseline and MAX. Twenty-eight subjects [25 women, 39.8 ± 11.9 yr (means ± SD)] were studied (n = 11 CA, n = 10 CVA, and n = 7 COUGH). At MAX, the percent change in FEV1 was greater in subjects with CA compared with those with CVA (P < 0.001) and COUGH (P < 0.001), and the percent change in forced vital capacity was greater in those with CA than with COUGH (P = 0.017). Subjects with CA and CVA developed dynamic hyperinflation and gas trapping. In subjects with CA and CVA, all IOS parameters were significantly increased from baseline to MAX, except for central respiratory resistance (R20). In individuals with COUGH, total respiratory resistance, R20, and resonant frequency were significantly increased from baseline. At MAX, the DI index was positive in all groups, suggesting preserved bronchodilation (CA, 0.67 ± 0.97; CVA, 0.51 ± 0.73; COUGH, 0.01 ± 0.36; P = 0.211). We conclude that the bronchodilating effect of DIs is preserved in individuals with CA, CVA, and borderline with COUGH; however, hyperinflation and gas trapping are avoided in subjects with COUGH alone.

Mechanisms of airway hyper-responsiveness in asthma: the past, present and yet to come

Airway hyper-responsiveness (AHR) has long been considered a cardinal feature of asthma. The development of the measurement of AHR 40 years ago initiated many important contributions to our understanding of asthma and other airway diseases. However, our understanding of AHR in asthma remains complicated by the multitude of potential underlying mechanisms which in reality are likely to have different contributions amongst individual patients. Therefore, the present review will discuss the current state of understanding of the major mechanisms proposed to contribute to AHR and highlight the way in which AHR testing is beginning to highlight distinct abnormalities associated with clinically relevant patient populations. In doing so we aim to provide a foundation by which future research can begin to ascribe certain mechanisms to specific patterns of bronchoconstriction and subsequently match phenotypes of bronchoconstriction with clinical phenotypes. We believe that this approach is not only within our grasp but will lead to improved mechanistic understanding of asthma phenotypes and we hoped to better inform the development of phenotype-targeted therapy.

A biologically inspired lung-on-a-chip device for the study of protein-induced lung inflammation

This study reports a biomimetic microsystem that reconstitutes the lung microenvironment for monitoring the role of eosinophil cationic protein (ECP) in lung inflammation. ECP induces the airway epithelial cell expression of CXCL-12, which in turn stimulates the migration of fibrocytes towards the epithelium. This two-layered microfluidic system provides a feasible platform for perfusion culture, and was used in this study to reveal that the CXCL12-CXCR4 axis mediates ECP induced fibrocyte extravasation in lung inflammation. This 'lung-on-a-chip' microdevice serves as a dynamic transwell system by introducing a flow that can reconstitute the blood vessel-tissue interface for in vitro assays, enhancing pre-clinical studies. We made an attempt to develop a new microfluidic model which could not only simulate the transwell for studying cell migration, but could also study the migration in the presence of a flow mimicking the physiological conditions in the body. As blood vessels are the integral part of our body, this model gives an opportunity to study more realistic in vitro models of organs where the blood vessel i.e. flow based migration is involved.

Genetic factors explain half of all variance in serum eosinophil cationic protein

BACKGROUND

Eosinophil cationic protein (ECP) is one of four basic proteins of the secretory granules of eosinophils. It has a variety of functions associated with inflammatory responses. Little is known about the causes for variation in serum ECP levels.

AIM

To identify factors associated with variation in serum ECP and to determine the relative proportion of the variation in ECP due to genetic and non-genetic factors, in an adult twin sample.

METHODS

A sample of 575 twins, selected through a proband with self-reported asthma, had serum ECP, lung function, airway responsiveness to methacholine, exhaled nitric oxide, and skin test reactivity, measured. Linear regression analysis and variance component models were used to study factors associated with variation in ECP and the relative genetic influence on ECP levels.

RESULTS

Sex (regression coefficient = -0.107, P < 0.001), body mass index (BMI) (0.007, P = 0.028), and airway responsiveness to methacholine (0.074, P = 0.001) were significantly associated with ECP. Adjusted for these factors, ECP correlated 0.53 (P < 0.001) and 0.27 (P = 0.001) in monozygotic and dizygotic twins, respectively (P-value for difference = 0.05). According to the most parsimonious variance component model, genetic factors accounted for 57% (CI: 42-72%, P < 0.001) of the variance in ECP levels, whereas the remainder (43%) was ascribable to non-shared environmental factors. The genetic correlation between ECP and airway responsiveness to methacholine was statistically non-significant (r = -0.11, P = 0.50).

CONCLUSION

Around half of all variance in serum ECP is explained by genetic factors. Serum ECP is influenced by sex, BMI, and airway responsiveness. Serum ECP and airway responsiveness seem not to share genetic variance.

Surface tension in human pathophysiology and its application as a medical diagnostic tool

Introduction: Pathological features of disease appear to be quite different. Despite this diversity, the common feature of various disorders underlies physicochemical and biochemical factors such as surface tension. Human biological fluids comprise various proteins and phospholipids which are capable of adsorption at fluid interfaces and play a vital role in the physiological function of human organs. Surface tension of body fluids correlates directly to the development of pathological states.

Methods: In this review, the variety of human diseases mediated by the surface tension changes of biological phenomena and the failure of biological fluids to remain in their native state are discussed.

Results: Dynamic surface tension measurements of human biological fluids depend on various parameters such as sex, age and changes during pregnancy or certain disease. It is expected that studies of surface tension behavior of human biological fluids will provide additional information and might become useful in medical practice. Theoretical background on surface tension measurement and surface tension values of reference fluids obtained from healthy and sick patients are depicted.

Conclusion: It is well accepted that no single biomarker will be effective in clinical diagnosis. The surface tension measurement combined with routine lab tests may be a novel non-invasive method which can not only facilitate the discovery of diagnostic models for various diseases and its severity, but also be a useful tool for monitoring treatment efficacy. We therefore expect that studies of surface tension behavior of human biological fluids will provide additional useful information in medical practice.

Pulmonary surfactant in the airway physiology: a direct relaxing effect on the smooth muscle

Beside alveoli, surface active material plays an important role in the airway physiology. In the upper airways it primarily serves in local defense. Lower airway surfactant stabilizes peripheral airways, provides the transport and defense, has barrier and anti-edematous functions, and possesses direct relaxant effect on the smooth muscle. We tested in vitro the effect of two surfactant preparations Curosurf® and Alveofact® on the precontracted smooth muscle of intra- and extra-pulmonary airways. Relaxation was more pronounced for lung tissue strip containing bronchial smooth muscle as the primary site of surfactant effect. The study does not confirm the participation of ATP-dependent potassium channels and cAMP-regulated epithelial chloride channels known as CFTR chloride channels, or nitric oxide involvement in contractile response of smooth muscle to surfactant.By controlling wall thickness and airway diameter, pulmonary surfactant is an important component of airway physiology. Thus, surfactant dysfunction may be included in pathophysiology of asthma, COPD, or other diseases with bronchial obstruction.

Eosinophil-associated lung diseases. A cry for surfactant proteins A and D help?

Surfactant proteins (SP)-A and SP-D (SP-A/-D) play important roles in numerous eosinophil-dominated diseases, including asthma, allergic bronchopulmonary aspergillosis, and allergic rhinitis. In these settings, SP-A/-D have been shown to modulate eosinophil chemotaxis, inhibit eosinophil mediator release, and mediate macrophage clearance of apoptotic eosinophils. Dysregulation of SP-A/-D function in eosinophil-dominated diseases is also not uncommon. Alterations in serum SP-A/-D levels are associated with disease severity in allergic rhinitis and chronic obstructive pulmonary disease. Furthermore, oligimerization of SP-A/-D, necessary for their proper function, can be perturbed by reactive nitrogen species, which are increased in eosinophilic disease. In this review, we highlight the associations of eosinophilic lung diseases with SP-A and SP-D levels and functions.

Influence of distinct asthma phenotypes on lung function following weight loss in the obese

BACKGROUND AND OBJECTIVE

There appears to be two distinct clinical phenotypes of obese patients with asthma-those with early-onset asthma and high serum IgE (TH2-high), and those with late-onset asthma and low serum IgE (TH2-low). The aim of the present study was to determine in the two phenotypes of obese asthma the effect of weight loss on small airway function.

METHODS

TH2-low (n = 8) and TH2-high (n = 5) obese asthmatics underwent methacholine challenge before and 12 months following bariatric surgery. Dose-response slopes as measures of sensitivity to airway closure and narrowing were measured as maximum % fall forced vital capacity (FVC) and forced expiratory volume in 1 s/FVC, respectively, divided by dose. Resting airway mechanics were measured by forced oscillation technique.

RESULTS

Weight loss reduced sensitivity to airway closure in TH 2-low but not TH2-high obese asthmatics (pre-post mean change ± 95% confidence interval: 1.8 ± 0.8 doubling doses vs -0.3 ± 1.7 doubling doses, P = 0.04). However, there was no effect of weight loss on the sensitivity to airway narrowing in either group (P = 0.8, TH2-low: 0.8 ± 1.0 doubling doses, TH2-high: -1.1 ± 2.5 doubling doses). In contrast, respiratory resistance (20 Hz) improved in TH2-high but not in TH2-low obese asthmatics (pre-post change median interquartile range: 1.5 (1.3-2.8) cmH₂O/L/s vs 0.6 (-1.8-0.8) cmH₂O/L/s, P = 0.03).

CONCLUSIONS

TH2-low obese asthmatics appear to be characterized by increased small airway responsiveness and abnormalities in resting airway function that may persist following weight loss. However, this was not the case for TH2-high obese asthmatics, highlighting the complex interplay between IgE status and asthma pathophysiology in obesity.

Nitric oxide enhances Th9 cell differentiation and airway inflammation

Th9 cells protect hosts against helminthic infection but also mediate allergic disease. Here we show that nitric oxide (NO) promotes Th9 cell polarization of murine and human CD4⁺ T cells. NO de-represses the tumor suppressor gene p53 via nitrosylation of Mdm2. NO also increases p53-mediated IL-2 production, STAT5 phosphorylation and IRF4 expression, all essential for Th9 polarization. NO also increases the expression of TGFβR and IL-4R, pivotal to Th9 polarization. OVA-sensitized mice treated with an NO donor developed more severe airway inflammation. Transferred Th9 cells induced airway inflammation, which was exacerbated by NO and blocked by anti-IL-9 antibody. Nos2^−/− mice had less Th9 cells and developed attenuated eosinophilia during OVA-induced airway inflammation compared to wild-type mice. Our data demonstrate that NO is an important endogenous inducer of Th9 cells and provide a hitherto unrecognized mechanism for NO-mediated airway inflammation via the expansion of Th9 cells.

Eosinophil peroxidase induces expression of cholinergic genes via cell surface neural interactions

Eosinophils localize to and release their granule proteins in close association with nerves in patients with asthma and rhinitis. These conditions are associated with increased neural function. In this study the effect of the individual granule proteins on cholinergic neurotransmitter expression was investigated. Eosinophil peroxidase (EPO) upregulated choline acetyltransferase (ChAT) and vesicular acetylcholine transporter (VAChT) gene expression. Fluorescently labeled EPO was seen to bind to the IMR-32 cell surface. Both Poly-L-Glutamate (PLG) and Heparinase-1 reversed the up-regulatory effect of EPO on ChAT and VAChT expression and prevented EPO adhesion to the cell surface. Poly-L-arginine (PLA) had no effect on expression of either gene, suggesting that charge is necessary but insufficient to alter gene expression. EPO induced its effects via the activation of NF-κB. MEK inhibition led to reversal of all up-regulatory effects of EPO. These data indicate a preferential role of EPO signaling via a specific surface receptor that leads to neural plasticity.

Quantification of pulmonary inflammation after segmental allergen challenge using turbo-inversion recovery-magnitude magnetic resonance imaging

RATIONALE

There is a need to develop novel noninvasive imaging biomarkers that help to evaluate antiinflammatory asthma treatments.

OBJECTIVES

To investigate whether the extent of the segmental lung edema measured noninvasively using turbo-inversion recovery-magnitude magnetic resonance imaging (TIRM MRI) corresponds to the severity of the regional allergic reaction determined by the percentage of eosinophils in bronchoalveolar lavage fluid (BAL) 24 hours after segmental allergen challenge in patients with asthma compared with normal control subjects.

METHODS

Eleven volunteers with allergic asthma and five healthy volunteers underwent segmental challenges with different allergen doses by two bronchoscopies 24 hours apart. They had lung MRI at baseline and 6 and 24 hours after segmental challenge. MRI TIRM scores were correlated with the eosinophilic response at 24 hours.

MEASUREMENTS AND MAIN RESULTS

In patients with asthma, there were significant differences of eosinophil percentages in BAL at 24 hours from segments given standard-dose, low-dose, or no allergen (saline) (P < 0.001). Correspondingly significant differences between the TIRM score in allergen standard-dose, low-dose, and saline-treated segments were observed at 24 hours post-challenge (P < 0.001). With increasing TIRM score at 24 hours the percent eosinophils per segment 24 hours post-challenge also increased accordingly (P < 0.001). There was interobserver agreement for TIRM score grading (kappa = 0.72 for 24-h time point).

CONCLUSIONS

The MRI-based noninvasive TIRM score is a promising biomarker for the noninvasive detection of the inflammatory response after segmental allergen challenge in patients with asthma and may serve to monitor the therapeutic effectiveness of novel antiinflammatory drugs in future human trials.

Deep inspiration volume and the impaired reversal of bronchoconstriction in asthma

It is unclear whether the failure to reverse bronchoconstriction with deep inspiration (DI) in asthma is due to reduced maximal dilatation of the DI. We compared the effect of different DI volumes on maximal dilatation and reversal of bronchoconstriction in nine asthmatics and ten non-asthmatics. During bronchoconstriction, subjects took DI to 40%, 70% and 100% inspiratory capacity, on separate days. Maximal dilatation was measured as respiratory system resistance (Rrs) at end-inspiration and residual dilatation as Rrs at end-expiration, both expressed as percent of Rrs at end-tidal expiration prior to DI. DI volume was positively associated with maximal dilatation in non-asthmatics (ANOVA p=0.055) and asthmatics (p=0.023). DI volume was positively associated with residual dilatation in non-asthmatics (p=0.004) but not in asthmatics (p=0.53). The degree of maximal dilatation independently predicted residual dilatation in non-asthmatics but not asthmatics. These findings suggest that the failure to reverse bronchoconstriction with DI in asthma is not due to reduced maximal dilatation, but rather due to increased airway narrowing during expiration.

Insights into the glycosaminoglycan-mediated cytotoxic mechanism of eosinophil cationic protein revealed by NMR

Protein-glycosaminoglycan interactions are essential in many biological processes and human diseases, yet how their recognition occurs is poorly understood. Eosinophil cationic protein (ECP) is a cytotoxic ribonuclease that interacts with glycosaminoglycans at the cell surface; this promotes the destabilization of the cellular membrane and triggers ECP's toxic activity. To understand this membrane destabilization event and the differences in the toxicity of ECP and its homologues, the high resolution solution structure of the complex between full length folded ECP and a heparin-derived trisaccharide (O-iPr-α-D-GlcNS6S-α(1-4)-L-IdoA2S-α(1-4)-D-GlcNS6S) has been solved by NMR methods and molecular dynamics simulations. The bound protein retains the tertiary structure of the free protein. The (2)S(0) conformation of the IdoA ring is preferably recognized by the protein. We have identified the precise location of the heparin binding site, dissected the specific interactions responsible for molecular recognition, and defined the structural requirements for this interaction. The structure reveals the contribution of Arg7, Gln14, and His15 in helix α1, Gln40 in strand β1, His64 in loop 4, and His128 in strand β6 in the recognition event and corroborates the previously reported participation of residues Arg34-Asn39. The participation of the catalytic triad (His15, Lys38, His128) in recognizing the heparin mimetic reveals, at atomic resolution, the mechanism of heparin's inhibition of ECP's ribonucleolytic activity. We have integrated all the available data to propose a molecular model for the membrane interaction process. The solved NMR complex provides the structural model necessary to design inhibitors to block ECP's toxicity implicated in eosinophil pathologies.

Impaired response to deep inspiration in obesity

Deep inspirations modulate airway caliber and airway closure and their effects are impaired in asthma. The association between asthma and obesity raises the question whether the deep inspiration (DI) effect is also impaired in the latter condition. We assessed the DI effects in obese and nonobese nonasthmatics. Thirty-six subjects (17 obese, 19 nonobese) underwent routine methacholine (Mch) challenge and 30 of them also had a modified bronchoprovocation in the absence of DIs. Lung function was monitored with spirometry and forced oscillation (FO) [resistance (R) at 5 Hz (R5), at 20 Hz (R20), R5-R20 and the integrated area of low-frequency reactance (AX)]. The response to Mch, assessed with area under the dose-response curves (AUC), was consistently greater in the routine challenge in the obese (mean ± SE, obese vs. nonobese AUC: R5: 15.7 ± 2.3 vs. 2.4 ± 2.0, P < 0.0005; R20: 5.6 ± 1.4 vs. 1.4 ± 1.2, P = 0.027; R5-R20: 10.2 ± 1.6 vs. 0.9 ± 0.1.4, P < 0.0005; AX: 115.6 ± 22.0 vs. 1.5 ± 18.9, P < 0.0005), but differences between groups in the modified challenge were smaller, indicating reduced DI effects in obesity. Given that DI has bronchodilatory and bronchoprotective effects, we further assessed these components separately. In the obese subjects, DI prior to Mch enhanced Mch-induced bronchoconstriction, but DI after Mch resulted in bronchodilation that was of similar magnitude as in the nonobese. We conclude that obesity is characterized by increased Mch responsiveness, predominantly of the small airways, due to a DI effect that renders the airways more sensitive to the stimulus.

The dynamic face of respiratory research: understanding the effect of airway disease on a lung in constant motion

The lungs are in a constant state of motion. The dynamic nature of tidal breathing, whereby cycles of pressure changes across the lungs cause the chest wall, lung tissue and airways to repeatedly expand and contract, ventilates the lung tissue and allows respiration to occur. However, these regular cycles of tidal inspirations and expirations are punctuated by breaths of differing volumes, most particularly periodic deep inspirations. In normal, healthy subjects, these deep inspirations have a dual effect in reducing airway responsiveness. Firstly, deep inspirations taken under baseline conditions protect the airways against subsequent bronchoconstriction, termed DI bronchoprotection. Secondly, deep inspirations are able to dramatically reverse bronchoconstriction. The ability for deep inspirations to reverse bronchoconstriction appears to be due to both the ability to dilate the airways with a full inspiration to total lung capacity (TLC) and the rate at which the airways re-narrow once tidal breathing is resumed. Deep inspiration reversal is reduced in subjects with asthma and is due both to a reduced ability to dilate the airways as well as an increase in the rate of re-narrowing. On the other hand, DI bronchoprotection is completely absent in asthma. Although the mechanisms behind these abnormalities remain unclear, the inability for deep inspirations to both protect against and fully reverse bronchoconstriction in patients with asthma appears critical in the development of airway hyperresponsiveness. As such, determining the pathophysiology responsible for the malfunction of deep inspirations in asthma remains critical to understanding the disease and is likely to pave the way for novel therapeutic targets.

Analysing the eosinophil cationic protein--a clue to the function of the eosinophil granulocyte

Eosinophil granulocytes reside in respiratory mucosa including lungs, in the gastro-intestinal tract, and in lymphocyte associated organs, the thymus, lymph nodes and the spleen. In parasitic infections, atopic diseases such as atopic dermatitis and asthma, the numbers of the circulating eosinophils are frequently elevated. In conditions such as Hypereosinophilic Syndrome (HES) circulating eosinophil levels are even further raised. Although, eosinophils were identified more than hundred years ago, their roles in homeostasis and in disease still remain unclear. The most prominent feature of the eosinophils are their large secondary granules, each containing four basic proteins, the best known being the eosinophil cationic protein (ECP). This protein has been developed as a marker for eosinophilic disease and quantified in biological fluids including serum, bronchoalveolar lavage and nasal secretions. Elevated ECP levels are found in T helper lymphocyte type 2 (atopic) diseases such as allergic asthma and allergic rhinitis but also occasionally in other diseases such as bacterial sinusitis. ECP is a ribonuclease which has been attributed with cytotoxic, neurotoxic, fibrosis promoting and immune-regulatory functions. ECP regulates mucosal and immune cells and may directly act against helminth, bacterial and viral infections. The levels of ECP measured in disease in combination with the catalogue of known functions of the protein and its polymorphisms presented here will build a foundation for further speculations of the role of ECP, and ultimately the role of the eosinophil.

Sputum dipalmitoylphosphatidylcholine level as a novel airway inflammatory marker in asthmatic children

INTRODUCTION

Pulmonary surfactant is a unique mixture of lipids and surfactant-specific proteins. Phosphatidylcholine comprises almost 80% of the total surfactant lipids, about half of which is dipalmitoylphosphatidylcholine (DPPC). Alteration of surfactant composition and function is documented with various airway or lung parenchyma disorders.

OBJECTIVE

To assess sputum concentration of DPPC as a major component of airways surfactant in asthmatic children compared to conventional airway inflammatory markers.

METHODS

This case control study included 68 well-known asthmatic children of different grades of severity and 20 age- and sex-matched normal children as controls. All children were subjected to thorough clinical examination, pulmonary function tests, sputum induction and processing for cytology, DPPC level and eosinophil cationic protein (ECP) level assessment.

RESULTS

Elevated DPPC levels were evident in all sputum samples of asthmatic children (mean value 626.6 +/- 189.7 mcg/mL) compared to controls (mean value 49.3 +/- 20.1 mcg/mL). Significant negative correlations (r = -0.83, -0.752 and -0.384) were found between asthmatics sputum DPPC levels and pulmonary function test parameters [% of forced expiratory volume in first second, % of forced vital capacity (FVC) and forced expiratory flow rate over 25%-75% part of FVC], respectively. Meanwhile, significant positive correlations were evident between asthmatics sputum DPPC levels and the sputum inflammatory cells and their sputum ECP levels.

CONCLUSION

Elevated DPPC levels are evident in induced sputum of all asthmatic children and they are significantly related to sputum ECP levels and pulmonary function test parameters. Nevertheless, the value of DPPC estimation in the clinical management of children with asthma remains to be determined.

Deep inspirations protect against airway closure in nonasthmatic subjects

The mechanism by which deep inspirations protect against increased airway responsiveness in nonasthmatic subjects is not known. The aim was to investigate the role of airway closure and airway narrowing in deep inspiration bronchoprotection. Twelve nonasthmatic and nine asthmatic subjects avoided deep inspirations (DI) for 20 min, then took five DI expired to functional residual capaciy (DI-FRC) or, on a separate day, no DI (no DI) before inhaling a single dose of methacholine. On another day, eight nonasthmatic subjects took five DI expired to residual volume (DI-RV). Peripheral airway function was measured by respiratory system reactance (Xrs), using the forced oscillation technique, and by forced vital capacity (FVC) as an index of airway closure. Respiratory system resistance (Rrs) and forced expiratory volume in 1 s (FEV1)/FVC were measured as indexes of airway narrowing. In nonasthmatic subjects, DI-FRC reduced the response measured by FEV1 (P=0.019), Xrs (P=0.02), and FVC (P=0.0005) but not by Rrs (P=0.15) or FEV1/FVC (P=0.52) compared with no DI. DI-RV had a less protective effect than DI-FRC on response measured by FEV1 (P=0.04) and FVC (P=0.016). There was no difference between all protocols when the response was measured by Xrs (P=0.20), Rrs (P=0.88), or FEV1/FVC (P=0.88). DI had no effect on methacholine response in asthmatic subjects. DI protect against airway responsiveness through an effect on peripheral airways involving reduced airway closure. The protective effect of DI on FEV1 and FVC was abolished by expiration to residual volume. We speculate that the reduced airway closure is due to reduced baseline ventilation heterogeneity and/or reduced airway surface tension.

Role of lung surfactant in respiratory disease: current knowledge in large animal medicine

Lung surfactant is produced by type II alveolar cells as a mixture of phospholipids, surfactant proteins, and neutral lipids. Surfactant lowers alveolar surface tension and is crucial for the prevention of alveolar collapse. In addition, surfactant contributes to smaller airway patency and improves mucociliary clearance. Surfactant-specific proteins are part of the innate immune defense mechanisms of the lung. Lung surfactant alterations have been described in a number of respiratory diseases. Surfactant deficiency (quantitative deficit of surfactant) in premature animals causes neonatal respiratory distress syndrome. Surfactant dysfunction (qualitative changes in surfactant) has been implicated in the pathophysiology of acute respiratory distress syndrome and asthma. Analysis of surfactant from amniotic fluid allows assessment of fetal lung maturity (FLM) in the human fetus and exogenous surfactant replacement therapy is part of the standard care in premature human infants. In contrast to human medicine, use and success of FLM testing or surfactant replacement therapy remain limited in veterinary medicine. Lung surfactant has been studied in large animal models of human disease. However, only a few reports exist on lung surfactant alterations in naturally occurring respiratory disease in large animals. This article gives a general review on the role of lung surfactant in respiratory disease followed by an overview of our current knowledge on surfactant in large animal veterinary medicine.

Eosinophil cationic protein high-affinity binding to bacteria-wall lipopolysaccharides and peptidoglycans

The eosinophil cationic protein (ECP) is an eosinophil-secreted RNase involved in the immune host defense, with a cytotoxic activity against a wide range of pathogens. The protein displays antimicrobial activity against both Gram-negative and Gram-positive strains. The protein can destabilize lipid bilayers, although the action at the membrane level can only partially account for its bactericidal activity. We have now shown that ECP can bind with high affinity to the bacteria-wall components. We have analyzed its specific association to lipopolysaccharides (LPSs), its lipid A component, and peptidoglycans (PGNs). ECP high-affinity binding capacity to LPSs and lipid A has been analyzed by a fluorescent displacement assay, and the corresponding dissociation constants were calculated using the protein labeled with a fluorophor. The protein also binds in vivo to bacteria cells. Ultrastructural analysis of cell bacteria wall and morphology have been visualized by scanning and transmission electron microscopy in both Escherichia coli and Staphylococcus aureus strains. The protein damages the bacteria surface and induces the cell population aggregation on E. coli cultures. Although both bacteria strain cells retain their shape and no cell lysis is patent, the protein can induce in E. coli the outer membrane detachment. ECP also activates the cytoplasmic membrane depolarization in both strains. Moreover, the depolarization activity on E. coli does not require any pretreatment to overcome the outer membrane barrier. The protein binding to the bacteria-wall surface would represent a first encounter step key in its antimicrobial mechanism of action.

Association between exhaled nitric oxide and systemic inflammatory markers

BACKGROUND

Asthma is an inflammatory condition of the airways, and there is some evidence to suggest that it is associated with a systemic inflammatory response, as measured by C-reactive protein (CRP) and fibrinogen. Exhaled nitric oxide is a noninvasive measure of asthmatic airway inflammation.

OBJECTIVE

To determine if there is an association between exhaled nitric oxide and these systemic inflammatory markers.

METHODS

The Dunedin Multidisciplinary Health and Development Study is a birth cohort of approximately 1,000 individuals born between April 1, 1972, and March 31, 1973. At the age of 32 years, study members were assessed for diagnosis of asthma, atopy by skin prick testing, smoking, body mass index, exhaled nitric oxide, high-sensitivity serum CRP, and plasma fibrinogen level.

RESULTS

There was no significant association between exhaled nitric oxide and CRP (P = .99). There was a trend to an inverse association between exhaled nitric oxide and fibrinogen (P = .049), but this was not significant after adjusting for smoking and use of corticosteroids or after further adjustment for body mass index and atopy (P = .71).

CONCLUSION

In this population-based sample of young adults, there was no association between airway inflammation, as measured by exhaled nitric oxide, and systemic inflammation, as measured by either CRP or fibrinogen.

Association between exhaled nitric oxide and systemic inflammatory markers

BACKGROUND

Asthma is an inflammatory condition of the airways, and there is some evidence to suggest that it is associated with a systemic inflammatory response, as measured by C-reactive protein (CRP) and fibrinogen. Exhaled nitric oxide is a noninvasive measure of asthmatic airway inflammation.

OBJECTIVE

To determine if there is an association between exhaled nitric oxide and these systemic inflammatory markers.

METHODS

The Dunedin Multidisciplinary Health and Development Study is a birth cohort of approximately 1,000 individuals born between April 1, 1972, and March 31, 1973. At the age of 32 years, study members were assessed for diagnosis of asthma, atopy by skin prick testing, smoking, body mass index, exhaled nitric oxide, high-sensitivity serum CRP, and plasma fibrinogen level.

RESULTS

There was no significant association between exhaled nitric oxide and CRP (P = .99). There was a trend to an inverse association between exhaled nitric oxide and fibrinogen (P = .049), but this was not significant after adjusting for smoking and use of corticosteroids or after further adjustment for body mass index and atopy (P = .71).

CONCLUSION

In this population-based sample of young adults, there was no association between airway inflammation, as measured by exhaled nitric oxide, and systemic inflammation, as measured by either CRP or fibrinogen.

Eosinophil cationic protein (ECP) polymorphisms and association with asthma, s-ECP levels and related phenotypes

BACKGROUND

Eosinophil cationic protein (ECP) is a potent cytotoxic secretory protein with bactericidal and antiviral properties. ECP is released by activated eosinophils and regarded as a marker of eosinophilic inflammation. High levels of ECP have been reported in cases of active asthma and other allergic diseases. This study aimed to assess whether three single-nucleotide polymorphisms (SNPs) in the ECP gene (RNASE3) on chromosome 14 q24-q31 or their haplotypes are associated with asthma, allergy, or related phenotypes.

METHODS

The three SNPs -38CA, +371CG and +499CG in RNASE3 and their haplotypes were analyzed for associations with asthma, serum-ECP (s-ECP) levels, allergic sensitization (positive skin-prick test to common allergens), bronchial hyperresponsiveness (BHR) assessed by methacholine inhalation, and serum-IgE (s-IgE) levels in 177 families from Norway and the Netherlands identified through siblings with asthma.

RESULTS

Transmission disequilibrium test (TDT) demonstrated significant associations between the A-G-G haplotype and asthma as well as the specific phenotypes allergic asthma (but not non-allergic asthma), high s-ECP, high s-IgE and BHR, while the C-G-G haplotype was associated with reduced occurrence of these traits. In addition, the -38A allele was associated with high s-ECP levels and allergic asthma.

CONCLUSION

The present study suggests that the A-G-G haplotype in the RNASE3 gene influences the development of asthma, in particular, an allergic form of asthma. Furthermore, as the -38CA SNP lies in close vicinity of known intron-regulatory sites, results of SNP analysis suggest that the detected association is possibly linked to a genetic transcriptional control of s-ECP levels.

Serum eosinophil-derived neurotoxin (EDN) in diagnosis and evaluation of severity and bronchial hyperresponsiveness in childhood asthma

This study sought to evaluate the use of serum eosinophil-derived neurotoxin (EDN), which has been proposed as a marker of airway inflammation in asthma in the diagnosis and evaluation of the severity and bronchial hyperresponsiveness in childhood asthma. We studied 72 children with atopic asthma, 36 children with nonatopic asthma, and 43 healthy controls. Skin prick tests, pulmonary function tests, and methacholine challenge tests were performed, in addition to total eosinophil count, serum ECP, and EDN being measured in all subjects. EDN levels were significantly higher in the atopic asthma group than those in the nonatopic asthma group or control group (p < 0.001), as were ECP levels (p < 0.001). EDN levels differed more significantly among groups divided by asthma severity (p < 0.001) than did ECP levels for these groups (p < 0.05). For the groups divided according to bronchial hyperresponsiveness, both EDN and ECP levels were significantly different (p < 0.005 and p < 0.01, respectively). Significant correlations were found between EDN and PC(20) (gamma = -0.281; p < 0.001), between ECP and PC(20) (gamma = -0.274; p < 0.005), and between EDN and ECP (gamma = 0.443; p < 0.001). In conclusion, serum EDN, as another marker of eosinophilic inflammation together with ECP, may aid in the diagnosis of asthma, especially atopic asthma, and in the evaluation of the severity and bronchial hyperresponsiveness in childhood asthma.

Mammalian antimicrobial proteins and peptides: overview on the RNase A superfamily members involved in innate host defence

The review starts with a general outlook of the main mechanisms of action of antimicrobial proteins and peptides, with the final aim of understanding the biological function of antimicrobial RNases, and identifying the key events that account for their selective properties. Although most antibacterial proteins and peptides do display a wide-range spectrum of action, with a cytotoxic activity against bacteria, fungi, eukaryotic parasites and viruses, we have only focused on their bactericidal activity. We start with a detailed description of the main distinctive structural features of the bacteria target and on the polypeptides, which act as selective host defence weapons.Following, we include an overview of all the current available information on the mammalian RNases which display an antimicrobial activity. There is a wealth of information on the structural, catalytic mechanism and evolutionary relationships of the RNase A superfamily. The bovine pancreatic RNase A (RNase A), the reference member of the mammalian RNase family, has been the main research object of several Nobel laureates in the 60s, 70s and 80s. A potential antimicrobial function was only recently suggested for several members of this family. In fact, the recent evolutionary studies indicate that this protein family may have started off with a host defence function. Antimicrobial RNases constitute an interesting example of proteins involved in the mammalian innate immune defence system. Besides, there is wealth of available information on the mechanism of action of short antimicrobial peptides, but little is known on larger polypeptides, that is, on proteins. Therefore, the identification of the mechanisms of action of antimicrobial RNases would contribute to the understanding of the proteins involved in the innate immunity.

Combined activities of secretory phospholipases and eosinophil lysophospholipases induce pulmonary surfactant dysfunction by phospholipid hydrolysis

BACKGROUND

Surfactant dysfunction is implicated in small airway closure in asthma. Increased activity of secretory phospholipase A(2) (sPLA(2)) in the airways is associated with asthma exacerbations. Phosphatidylcholine, the principal component of pulmonary surfactant that maintains small airway patency, is hydrolyzed by sPLA(2). The lysophosphatidylcholine product is the substrate for eosinophil lysophospholipases.

OBJECTIVE

To determine whether surfactant phospholipid hydrolysis by the combined activities of sPLA(2)s and eosinophil lysophospholipases induces surfactant dysfunction.

METHODS

The effect of these enzymes on surfactant function was determined by capillary surfactometry. Thin layer chromatography was used to correlate enzyme-induced changes in surfactant phospholipid composition and function. Phosphatidylcholine and its hydrolytic products were measured by using mass spectrometry.

RESULTS

Eosinophils express a 25-kd lysophospholipase and group IIA sPLA(2). Phospholipase A(2) alone induced only a small decrease in surfactant function, and 25-kd lysophospholipase alone degraded lysophosphatidylcholine but had no effect on surfactant function. The combined actions of sPLA(2) and lysophospholipase produced dose-dependent and time-dependent losses of surfactant function, concomitant with hydrolysis of phosphatidylcholine and lysophosphatidylcholine. Lysates of AML14.3D10 eosinophils induced surfactant dysfunction, indicating these cells express all the necessary lipolytic activities. In contrast, lysates of blood eosinophils required exogenous phospholipase A(2) to induce maximal surfactant dysfunction.

CONCLUSION

The combined activities of sPLA(2)s and eosinophil lysophospholipases are necessary to degrade surfactant phospholipids sufficiently to induce functional losses in surfactant activity as reported in asthma.

CLINICAL IMPLICATIONS

The phospholipases and lysophospholipases expressed by eosinophils or other airway cells may represent novel therapeutic targets for blocking surfactant degradation, dysfunction, and peripheral airway closure in asthma.

Surfactant protein D inhibits early airway response in Aspergillus fumigatus-sensitized mice

BACKGROUND

The surfactant protein SP-D has been reported to reduce bronchial hyper-responsiveness, blood eosinophilia, and T-helper type 2 cytokines in models of allergic asthma. However, little is known about the functional effect of SP-D on the early airway response upon allergen inhalation, which is an important feature of this disease.

OBJECTIVE

We investigated whether SP-D is able to reduce the immediate allergen-induced mediator release and the early bronchial obstruction in addition to its effects on airway inflammation and bronchial hyperresponsiveness in an Aspergillus fumigatus mouse asthma model.

METHODS

A. fumigatus-sensitized mice were treated with a recombinant fragment of human SP-D or placebo. Lung functions were measured in orotracheally intubated, spontaneously breathing animals using body plethysmography. In addition, passively sensitized precision-cut lung slices (PCLS) were used to determine the effect of SP-D on allergen-induced histamine release.

RESULTS

SP-D inhibited the allergen-induced early airway response and reduced airway hyperresponsiveness compared with placebo. Eosinophilia in bronchoalveolar lavage and lung tissue was reduced after SP-D treatment, possibly by reducing eotaxin levels in the lung. Furthermore, SP-D treatment reduced the allergen-induced histamine release from PCLS.

CONCLUSION

These data suggest that SP-D not only reduces allergen-induced eosinophilic inflammation and airway hyperresponsiveness but also provides protection against early airway obstruction by inhibition of early mediator release.

In vitro anti-allergic activities of a newly concocted traditional Chinese medicine--the wheeze-relief formula

Asthma is one of the most common chronic diseases worldwide. Western medications such as glucocorticoids are effective therapeutic agents but may be associated with side effects. Traditional Chinese medicine (TCM) has been used for treating allergic diseases with observable clinical benefits. The present study investigated whether a novel TCM concoction, the wheeze-relief formula (WRF), possesses in vitro anti-allergic activities. We measured the effects of WRF on the release of eosinophil cationic protein (ECP) by human eosinophils using fluorescence enzyme immunoassay, expression of chemokine receptor CCR3 and adhesion molecule CD49d on eosinophils using immunophenotyping, cytokine induction from peripheral blood mononuclear cells (PBMC) using cytometric bead array (CBA), and the gene expression of cytokines and cytokine receptors using cDNA expression array. Results demonstrated that WRF dose-dependently and significantly: (1) suppressed ECP release from eosinophils activated with granulocyte macrophage-colony stimulating factor (GM-CSF) and platelet activating factor (PAF); (2) inhibited the expression of CCR3 and CD49d on PAF-activated eosinophils; and (3) attenuated the production of tumor necrosis factor alpha and gene expression of IL-2 receptor chain alpha (CD25) on house dust mite (Der p 1) activated PBMC. The above results suggest a possible anti-allergic role of WRF and provide a biochemical basis for further clinical trial on human subjects.

Surfactant as an airway smooth muscle relaxant

A variety of clinical and experimental evidence indicates that surfactant may be important in the pathogenesis and treatment of asthma. The purpose of this study was to determine the pharmacologic effect of pulmonary surfactant and its major lipid and protein constituents on bronchial smooth muscle. First-generation bronchi from male Sprague-Dawley rats were contracted with methacholine and exposed to two kinds of surfactant: whole rat surfactant and two bovine surfactant extracts in clinical use. The latter lack the hydrophilic surfactant-associated proteins (SP)-A and SP-D. All the surfactants relaxed the rat bronchi in a concentration-dependent manner; however, whole rat surfactant was more potent than the bovine extracts. Both surfactant lipids and SP-A contributed to the bronchial relaxation. The relaxation response produced by the highest concentration (0.5 mg/ml) of whole rat surfactant was equivalent to that caused by substance P (5 microM) and approximately half of that caused by 1 microM isoproterenol. The relaxation response was epithelium-dependent and blocked by indomethacin but not by N-omega-nitro-L-arginine methyl ester. We conclude that surfactant can relax airway smooth muscle directly via a prostanoid-mediated, epithelium-dependent process that does not involve nitric oxide synthase.

Surface-exposed amino acids of eosinophil cationic protein play a critical role in the inhibition of mammalian cell proliferation

Eosinophil cationic protein (ECP) is a ribonuclease secreted from activated eosinophils that may cause tissue injure as a result of eosinophilic inflammation. ECP possesses bactericidal, antiviral and helminthotoxic activity and inhibits mammalian cell growth. The mechanism by which ECP exerts its toxicity is not known but it has been related to the ability of the protein to destabilise lipid bilayers. We have assessed the involvement of some cationic and aromatic surface exposed residues of ECP in the inhibition of proliferation of mammalian cell lines. We have constructed ECP mutants for the selected residues and assessed their ability to prevent cell growth. Trp10 and Trp35 together with the adjacent stacking residue are critical for the damaging effect of ECP on mammalian cell lines. These residues are also crucial for the membrane disruption activity of ECP. Other exposed aromatic residues packed against arginines (Arg75-Phe76 and Arg121-Tyr122) and specific cationic amino acids (Arg101 and Arg104) of ECP play a secondary role in the cell growth inhibition. This may be related to the ability of the protein to bind carbohydrates such as those found on the surface of mammalian cells.