Nitric oxide and protein nitration are eosinophil dependent in allergen-challenged mice

In silico studies of bioactive compounds from selected African plants with inhibitory activity against nitric oxide synthase and arginase implicated in asthma

Background

It is a known fact that arginine is a common substrate for arginase and nitric oxide synthase (NOS). However, an imbalance between both enzymes could lead to a change in airway responses. Reports suggest that increased activities of both enzymes could lead to airway hyper-responsiveness. Thus, the requests for NOS inhibitors that can also inhibit arginase as the elevated activities of both enzymes have detrimental consequence on airways in asthma. Bioactive compounds from Azadirachta indica, Crinum glaucum, and Mangifera indica are documented for anti-inflammatory, immunomodulatory, anti-histaminic, smooth-muscle relaxants, and anti-allergic potentials. However, the mechanisms of action of these bioactive compounds in conferring the aforementioned protections are not well characterized. The objective of this present study is to assess in silico inhibitory potentials of these bioactive compounds against NOS and arginase via binding at their active sites. The crystal structures of NOS and arginase were retrieved from the protein database, while the bioactive compounds were retrieved from PubChem. Drug-likeness of the selected bioactive compounds was assessed using DruLiTo software. The successful compounds were docked with active sites of enzymes using AutoDock Vina docking software, and the docked complexes were analyzed using LigPlot and protein-ligand profiler web server.

Results

The findings of the study revealed that the bioactive compounds from A. indica, C. glaucum, and M. indica were able to interact with the active sites of NOS and arginase with the exception of gallic acid (from M. indica) and nimbandiol (from A. indica); these compounds showed differential binding energies (kcal/mol) and a number of them had higher binding energies than l-arginine when docked with NOS.

Conclusion

Conclusively, the in silico analysis proposes that these compounds could prove to be probable anti-asthmatic drugs.

The Effect of Curcuma longa on Inflammatory Mediators and Immunological, Oxidant, and Antioxidant Biomarkers in Asthmatic Rats

The effects of Curcuma longa (C. longa) on total and differential WBC, inflammatory and immunologic mediators, and oxidant and antioxidant biomarkers in bronchoalveolar lavage fluid (BALF) of rats model of asthma were assessed. Animals were divided to 5 groups including control (C), asthma (sensitized to ovalbumin), and asthmatic groups treated with 0.75, 1.50, and 3.00 mg/ml C. longa (CL) and 1.25 μg/ml dexamethasone (D) (8 rats in each group). Total and differential WBC count, concentrations of phospholipase A₂ (PLA₂), total protein (TP), interferon-gamma (IFN-γ), interleukin-4 (IL-4), immunoglobulin E (IgE), NO₂, NO₃, malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and thiol in BALF were assessed. Total and most differential WBC counts and BALF levels of PLA₂, TP, IgE, IL-4, and oxidants in asthma group were higher but antioxidants and IFN-γ levels as well as IFN-γ/IL-4 ratio were lower than control group (p < 0.001 for all cases). Total WBC and levels of PLA₂, IgE, NO₂, and NO₃ were significantly reduced following treatment with C. longa, compared to asthma group (p < 0.001 for all cases). In groups treated with dexamethasone and two higher concentrations of C. longa, neutrophil and eosinophil counts as well as TP, IL-4, and MDA levels were significantly decreased but IFN-γ, IFN-γ/IL-4 ratio, and antioxidants were increased (except IFN-γ/IL-4 ratio), compared to asthma group (p < 0.05 to p < 0.001). Compared to dexamethasone, C. longa exerted more pronounced effects on lung inflammation, oxidative stress, and immune system in asthmatic rats.

Beneficial effects of naringenin and morin on interleukin-5 and reactive oxygen species production in BALB/c mice with ovalbumin-induced asthma

We investigated the effects of naringenin and morin on IL-5 and ROS production in PMA+ionomycin-treated EL-4 cells with the corroboration of their antioxidant and anti-inflammatory properties using an asthma-induced mouse model. The EL-4 cell line was used to study the outcomes of naringenin or morin, followed by cell viability studies. Western blot analysis and ELISA test were used to determine Th2 mediated cytokines. In vivo studies were carried out on BALB/c mice to induce allergic asthma using ovalbumin administered intraperitoneally. Intracellular ROS was determined using 2’,7’-dichlorodihydrofluorescein diacetate, followed by serum enzymatic (AST and ALT) estimations and inflammatory cell count in the bronchoalveolar lavage fluid (BALF) and lung tissues. Histopathological studies were conducted to examine lung tissue-stained architecture. Our findings suggested that naringenin and morin significantly suppressed IL-5 and ROS production via various pathways. Interestingly, by reducing NFAT activity, naringenin and morin stimulated HO-1 expression, thereby suppressing IL-5 secretion due to regulating the transcription factor Nrf2 via P13/Akt or ERK/JNK signalling pathways in EL-4 cells, demonstrating the involvement of HO-1 expression in inhibiting asthmatic inflammation. The increased inflammatory cells in the BALF were substantially decreased by both naringenin and morin, followed by inhibition in the elevated Th-2 cytokines levels. The TNF-α protein levels in an allergic asthma mouse model were significantly reduced by suppressing Akt phosphorylation and eosinophil formation. Recent findings confirmed that naringenin and morin possess the potential to control asthma-related immune responses through antioxidant and anti-inflammatory properties, indicating potential therapeutic agents or functional foods.

Citrus flavonoids suppress IL-5 and ROS through distinct pathways in PMA/ionomycin-induced EL-4 cells

Interleukin-5 (IL-5) strongly initiates the asthmatic inflammatory response, which affects 300 million patients with asthma annually worldwide, through oxidative stress generation. Citrus flavonoids have beneficial properties, such as anti-inflammatory and antioxidant properties, but the precise molecular mechanism of the inhibition of the asthmatic inflammatory response is still unclear. This study aimed to investigate the underlying mechanisms of ROS and IL-5 reduction with citrus flavonoid treatment in PMA/ionomycin-induced EL-4 cells. Our results showed that hesperetin and gardenin A dramatically suppressed ROS and IL-5 production through distinct pathways. Interestingly, hesperidin induced HO-1 expression through the transcription factor Nrf2 coupled with the PI3K/AKT or ERK/JNK signaling pathway, consequently downregulating NFAT activity and IL-5 secretion. Likewise, gardenin A induced HO-1 expression and subsequently suppressed IL-5 production by reducing NFAT activity and upregulating PPARγ in EL-4 cells, suggesting that inducing HO-1 expression may inhibit asthmatic inflammation. Altogether, hesperidin and gardenin A have great potential for regulating the asthma-associated immune responses through antioxidant properties.

Airway inflammation and lung function recovery after lobectomy in patients with primary lung cancer

OBJECTIVE

Fractional exhaled nitric oxide (FeNO), which represents airway inflammation, is an indicator of postoperative complication after lung surgery. However, its effects in the late postoperative period are unknown. The aim of this prospective study was to clarify the impact of FeNO on postoperative lung function in patients with lung cancer.

METHODS

We measured preoperative FeNO using NIOX VERO® in patients with primary lung cancer. Patients were divided into two groups according to their potential airway inflammatory status: preoperative FeNO levels below 25 ppb (N group) and above 25 ppb (H group). They were evaluated by spirometry at 3 and 6 months after surgery during follow-up. The relationship between postoperative lung function and preoperative FeNO was evaluated.

RESULTS

Between September 2017 and March 2019, 61 participants were enrolled. All of them underwent lobectomy as a curative surgery. There were no significant background variables between the two groups. Postoperative vital capacity (VC) and forced expiratory volume in 1 s (FEV1) in the H group achieved less predictive values than those in the N group, which were not significant. The postoperative VC and FEV1 from 3 to 6 months in the H group were significantly increased as compared to those in the N group (p < 0.001).

CONCLUSIONS

Preoperative FeNO is a predictor of delayed lung function recovery 3 months after lobectomy in lung cancer patients. The impact had extended to VC and FEV1. Although this impact is temporary, early postoperative intervention is expected to reduce the adverse effect.

Association between biomarkers and house dust mite sublingual immunotherapy in allergic asthma

BACKGROUND

House dust mite (HDM) sublingual immunotherapy (SLIT) has demonstrated efficacy in clinical trials of patients with asthma. Airway inflammation is a characteristic of respiratory allergy, but its relationship to SLIT remains unclear.

OBJECTIVE

We evaluate the association between clinical outcomes with pulmonary function and biomarkers in before and after HDM SLIT (UMIN Number 000022390).

METHODS

One hundred twelve patients with asthma sensitized to HDM were randomized to add-on 6 standardized quality (SQ)-HDM SLIT to pharmacotherapy or pharmacotherapy alone for 48 weeks. At baseline and end of study, biomarkers, blood eosinophils, serum IgE, serum periostin, fractional exhaled nitric oxide (FeNO), and spirometry and clinical symptoms were measured. Association between biomarkers and an increase in FEV₁ of 120 mL or greater were analysed.

RESULTS

Sublingual immunotherapy (SLIT) demonstrated a significant reduction of serum periostin (P < .001), FeNO (P < .01), and increase in HDM-specific IgE (P < .05), FEV₁ (P < .001) and improvement of clinical symptom scores, when compared to pharmacotherapy. The change in FEV₁ correlated with the changes in serum periostin (r = .696, P < .001) and the changes in FeNO (r = .682, P < .001). The independent predictor of improvement in airflow limitation was changed in serum periostin (r²  = .753, P = .013) and FeNO (P = .038). Based on cut-off values derived by receiver operating characteristic analysis (periostin 30.9 ng/mL, FeNO 28.0 ppb), patients were distinguished responders from non-responders, but with no predictive value for blood eosinophils or total IgE. The proportion of patients with both high periostin and FeNO levels was significantly higher in responder than in non-responder (P = .026).

CONCLUSIONS AND CLINICAL RELEVANCE

Adding HDM SLIT to pharmacotherapy resulted in reduced serum periostin and FeNO, and improved pulmonary function. Serum periostin and FeNO may be useful biomarkers for prediction of SLIT.

Impact of fractional exhaled nitric oxide on the outcomes of lung resection surgery: a prospective study

Background

Fractional exhaled nitric oxide (FeNO), which is representative of airway inflammation, is an indicator of chronic lung disease. However, its effect on the outcome of lung resection is unknown. The aim of this prospective study was to evaluate FeNO in patients who underwent lung resection, to analyze the perioperative dynamics, and clarify the impact on postoperative complications.

Methods

We measured FeNO using NIOX VERO^® once before and on days 1, 3, 5–7 after surgery in participants who were candidates for lung cancer surgery. The primary endpoint was the relationship between postoperative morbidity and preoperative FeNO. The secondary endpoint was the relationship between postoperative FeNO and additional treatment, including readmission.

Results

We enrolled 105 patients between September 2017 and March 2019. Anatomical lung resection was the predominant treatment (87%) for primary lung cancer. Postoperative pulmonary complications developed in 16 patients. Multivariate analysis revealed that preoperative FeNO was a significant predictor of postoperative pulmonary complications (P=0.002, OR: 1.004, 95% CI: 1.016–1.074). FeNO levels increased significantly after surgery (P=0.011). Postoperative FeNO was a significant predictor of the need for additional medical treatment within 30 days of surgery (P=0.001, OR: 1.068, 95% CI: 1.028–1.110).

Conclusions

Perioperative FeNO was a significant predictor of surgical outcome among patients who underwent lung resection. The measurement of FeNO is expected to be a simple and useful method for preventing subsequent deterioration in these patients.

Epigallocatechin-3-gallate protects against the exacerbation of allergic eosinophilic inflammation associated with obesity in mice

Obesity is linked to worse asthma symptoms. Epigallocatechin-3-gallate (EGCG) reduces airway inflammation, but no study investigated the effects of EGCG on obesity-associated asthma. We aimed here to evaluate the effects of EGCG on allergen-induced airway inflammation in high-fat diet-fed mice. Male C57Bl/6 mice maintained on either standard-chow or high-fat diet for 12 weeks were treated or not with EGCG (10 mg/kg/day, gavage, two weeks). Animals were intranasally challenged with ovalbumin (OVA). In lung tissue and bronchoalveolar lavage fluid (BALF), cell counting and markers of inflammation and oxidative stress were evaluated. High-fat diet-fed mice exhibited significantly higher body weight and epididymal fat mass compared with lean group. EGCG treatment reduced by 20% the epididymal fat mass in obese mice (P < 0.05). The OVA-induced increases of total cells and eosinophils in lung tissue of obese mice were significantly reduced EGCG treatment. The increased levels of TNF-α, IL-4, IL-5 and eotaxin in BALF of obese mice were normalized by EGCG. Likewise, the enhanced expression of inducible nitric oxide synthase (iNOS) and nitric oxide metabolite (NOx) levels in obese mice were normalized by EGCG. Reactive‑oxygen species (ROS) and superoxide dismutase (SOD) levels were elevated and reduced, respectively, in lung tissue of obese mice, both of which were restored by EGCG. In lean mice, EGCG had no significant effect in evaluated parameter (body measures, and inflammatory and oxidative markers). EGCG turns to normal the levels of inflammatory and oxidative stress markers in lungs of obese mice, suggesting it could be an option to attenuate obesity-related asthma.

Comparison of Pulmonary and Systemic NO- and PGI2-Dependent Endothelial Function in Diabetic Mice

Diabetes increases the risk of pulmonary hypertension and is associated with alterations in pulmonary vascular function. Still, it is not clear whether alterations in the phenotype of pulmonary endothelium induced by diabetes are distinct, as compared to peripheral endothelium. In the present work, we characterized differences between diabetic complications in the lung and aorta in db/db mice with advanced diabetes. Male, 20-week-old db/db mice displayed increased HbA1c and glucose concentration compatible with advanced diabetes. Diabetic lungs had signs of mild fibrosis, and pulmonary endothelium displayed significantly ultrastructural changes. In the isolated, perfused lung from db/db mice, filtration coefficient (K_f,c) and contractile response to TXA₂ analogue were enhanced, while endothelial NO-dependent modulation of pulmonary response to hypoxic ventilation and cumulative production of NO₂⁻ were impaired, with no changes in immunostaining for eNOS expression. In turn, 6-keto-PGF_1α release from the isolated lung from db/db mice was increased, as well as immunostaining of thrombomodulin (CD141). In contrast to the lung, NO-dependent, acetylcholine-induced vasodilation, ionophore-stimulated NO₂⁻ generation, and production of 6-keto-PGF_1α were all impaired in aortic rings from db/db mice. Although eNOS immunostaining was not changed, that of CD141 was clearly lowered. Interestingly, diabetes-induced nitration of proteins in aorta was higher than that in the lungs. In summary, diabetes induced marked ultrastructural changes in pulmonary endothelium that were associated with the increased permeability of pulmonary microcirculation, impaired NO-dependent vascular function, with compensatory increase in PGI₂ production, and increased CD141 expression. In contrast, endothelial dysfunction in the aorta was featured by impaired NO-, PGI₂-dependent function and diminished CD141 expression.

Nitric Oxide and Collagen Expression in Allergic Upper-Airway Disease

Background

The presence of nitric oxide (NO) in high concentrations has been described in the nasal mucosa of patients with untreated allergic rhinitis. We sought to examine the role of exogenous, as well as endogenous, NO in the production of collagen type I and type III by human nasal fibroblasts.

Methods

Primary cultured fibroblasts derived from eosinophilic nasal polyps were exposed to NO donors (500 μM of S-nitroso-N-acetyl-d,l-penicillamine (SNAP) 1000 μM of 3,3-bis(aminoethyl)-1-hydroxy-2-oxo-1-triazene (DETA-NONOate)) and various other compounds over a 24-hour incubation period. Collagen production was evaluated qualitatively by immunocytochemistry and quantitatively by Western blot analysis.

Results

Maximally stimulated fibroblasts established a 2.2-fold increase in the production of type III collagen relative type I, as compared with baseline. Oxyhemoglobin, an NO scavenger, abolished this effect. SNAP (500 μM) caused a 15.68 ± 0.68% increase in collagen type I synthesis as compared with unstimulated controls (p < 0.05). In contrast, incubation with SNAP caused an increase in collagen type III production by a factor of 34.68 ± 0.32% (p < 0.05).

Conclusion

NO stimulates collagen expression in human nasal polyp-derived fibroblasts. This stimulation appeared to favor the up-regulation of collagen type III, leading to a shift in the ratio of collagen type I to type III production.

Understanding the Unfolded Protein Response in the Pathogenesis of Asthma

Asthma is a heterogeneous, chronic inflammatory disease of the airways. It is a complex disease with different clinical phenotypes and results in a substantial socioeconomic burden globally. Poor understanding of pathogenic mechanisms of the disease hinders the investigation into novel therapeutics. Emerging evidence of the unfolded protein response (UPR) in the endoplasmic reticulum (ER) has demonstrated previously unknown functions of this response in asthma development. A worsening of asthmatic condition can be brought on by stimuli such as oxidative stress, pathogenic infections, and allergen exposure. All of which can induce ER stress and activate UPR leading to activation of different inflammatory responses and dysregulate the innate immune functions in the airways. The UPR as a central regulator of asthma pathogenesis may explain several unknown mechanism of the disease onset, which leads us in new directions for future asthma treatments. In this review, we summarize and discuss the causes and impact of ER–UPR in driving the pathogenesis of asthma and highlight its importance in clinical implications.

Eosinophils promote inducible NOS-mediated lung allograft acceptance

Lungs allografts have worse long-term survival compared with other organ transplants. This is most likely due to their unique immunoregulation that may not respond to traditional immunosuppression. For example, local NO generation by inducible NOS (iNOS) is critical for lung allograft acceptance but associates with rejection of other solid organs. The source of NO in accepting lung allografts remains unknown. Here, we report that, unlike the case for other pulmonary processes in which myeloid cells control NO generation, recipient-derived eosinophils play a critical and nonredundant role in iNOS-mediated lung allograft acceptance. Depletion of eosinophils reduces NO levels to that of recipients with global deletion of iNOS and leads to a costimulatory blockade-resistant form of rejection. Furthermore, NO production by eosinophils depends on Th1 polarization by inflammatory mediators, such as IFN-γ and TNF-α. Neutralization of such mediators abrogates eosinophil suppressive capacity. Our data point to what we believe to be a unique and previously unrecognized role of eosinophil polarization in mediating allograft tolerance and put into perspective the use of high-dose eosinophil-ablating corticosteroids after lung transplantation.

The -786 T/C polymorphism of NOS3 gene is a susceptibility marker of COPD among Tunisians that correlates with nitric oxide levels and airflow obstruction

OBJECTIVE

The goal of this study was to examine the role of G894T (rs1799983), -786T/C (rs3918161) and a 27 bp variable number of tandem repeats (VNTR) 4B/4A of NOS3 gene on the risk and severity of COPD.

METHODS

The study included 194 controls and 138 COPD patients. NOS3 G894T, -786T/C and 4B/4A variants were determined by PCR analysis based on the banding pattern on gel electrophoresis. Pulmonary function was evaluated using body plethysmography. The levels of nitric oxide, peroxynitrite and lipid peroxides (T-BARS) were determined using spectrophotometric methods. Levels of serum IL-6, TNF-α and TGFβ were determined by ELISA.

RESULTS

In case-control studies, both G894T and -786T/C variants were associated with COPD risk. A significantly increased risk of COPD was found with the NOS3894T and -786C alleles (OR:1.93, P=0.001; OR:2.05, P=0.001, respectively). No significant impact of the G894T and 4B/4A SNPs was found on COPD severity, while a significant correlation was retrieved between the NOS3 -786T/C variation and advanced stages (OR: 1.89, P=0.009). In addition, COPD patients with the -786CC genotype exhibited lower FEV1% values in comparison to -786TT carriers (48±3.28 vs. 58.06±2.3, P=0.01, respectively). Patients having the -786CC genotype presented lower plasma levels of nitric oxide and higher T-BARS in comparison to -786TT individuals (173.22±13.4 vs. 228.93±16.8, P=0.01; 1.8±0.15 vs. 1.22±0.15, P=0.01, respectively).

CONCLUSION

This study provides the first evidence for the association of G894T, -786T/C variants with COPD risk among Tunisians. The -786T/C variation correlates with enhanced airflow limitation. This finding could be related to altered levels of nitric oxide and enhanced lipid peroxides among patients carrying the -786CC genotype.

Diagnostic utility of fractional exhaled nitric oxide in prolonged and chronic cough according to atopic status

BACKGROUND

Cough-variant asthma (CVA) and cough-predominant asthma (CPA) are the major causes of persistent cough in Japan. The utility of fractional exhaled nitric oxide (FeNO) measurement in the differential diagnosis of persistent cough has been reported, but the influence of atopic status, which is associated with higher FeNO levels, on the diagnostic utility of FeNO has been unknown.

METHODS

We retrospectively analyzed 105 non-smoking patients with prolonged and chronic cough that were not treated with corticosteroids and anti-leukotrienes.

RESULTS

CPA was diagnosed in 37 patients, CVA in 40, and non-asthmatic cough (NAC) in 28. FeNO levels were significantly higher in the CPA [35.8 (7.0-317.9) ppb] and CVA [24.9 (3.1-156.0) ppb] groups than in the NAC group [18.2 (6.9-49.0) ppb] (p < 0.01 by Kruskal-Wallis test). The optimal cut-off for distinguishing asthmatic cough (AC; CPA and CVA) from NAC was 29.2 ppb [area under the curve (AUC) 0.74, p < 0.01]. Ninety-one percent of subjects with FeNO levels ≥29.2 ppb had AC. Meanwhile, 40% of AC patients had FeNO levels <29.2 ppb. Stratified cut-off levels were 31.1 ppb (AUC 0.83) in atopic subjects vs. 19.9 ppb (AUC 0.65) in non-atopic subjects (p = 0.03 for AUC).

CONCLUSIONS

Although high FeNO levels suggested the existence of AC, lower FeNO levels had limited diagnostic significance. Atopic status affects the utility of FeNO levels in the differential diagnosis of prolonged and chronic cough.

Antiallergic effect of piperine on ovalbumin-induced allergic rhinitis in mice

CONTEXT

Allergic rhinitis (AR) is a global health problem that affects a large number of population. Piperine (PIP) has been reported to exhibit anti-inflammatory, anti-histaminic, and immunomodulatory activities; however, its antiallergic profile has not been studied.

OBJECTIVE

The objective of the study was to investigate the antiallergic potential of PIP in ova-albumin (OVA)-induced AR, mast cell degranulation (MSD), and OVA-induced paw edema.

MATERIALS AND METHODS

Mice were sensitized with OVA alternately on 1, 3, 5, 7, 9, 11, and 13th day. They were treated with either vehicle, PIP (10, 20, and 40 mg/kg, p.o.), or montelukast (10 mg/kg, p.o.) from the 14th to 20th day. On the 21st day, intranasal (OVA: 5% µl) challenge was done. Animals were evaluated for physiological parameters, biochemical parameters, spleen weight, expression of interleukins (IL-6 and IL-1β), and immunoglobin-E (IgE). Histopathology of nasal mucosa, lungs, and spleen was carried out. MSD and paw edema studies were made to understand the mechanism of action.

RESULTS

PIP (10, 20, and 40 mg/kg, p.o.) showed a significant dose-dependent protection with respect to nasal rubbing, redness of nose, and sneezing (p < 0.001) following nasal challenge. PIP dose dependently reduced histamine, NO concentration (p < 0.001), as well as reduced expression of IL-6, IL-1β, and IgE (p < 0.001) as compared with the control group. Histopathology showed inhibition of infiltration of eosinophils and hyperplasia. It dose dependently reduced MSD and paw edema (p < 0.001).

DISCUSSION AND CONCLUSION

PIP acts by mast cell-stabilizing activity, exhibits immunomodulatory and anti-inflammatory activity, thereby providing an effective treatment for AR.

A common variant in RAB27A gene is associated with fractional exhaled nitric oxide levels in adults

BACKGROUND

Exhaled nitric oxide (FeNO) is a biomarker for eosinophilic inflammation in the airways and for responsiveness to corticosteroids in asthmatics.

OBJECTIVE

We sought to identify in adults the genetic determinants of fractional exhaled nitric oxide (FeNO) levels and to assess whether environmental and disease-related factors influence these associations.

METHODS

We performed a genome-wide association study of FeNO through meta-analysis of two independent discovery samples of European ancestry: the outbred EGEA study (French Epidemiological study on the Genetics and Environment of Asthma, N = 610 adults) and the Hutterites (N = 601 adults), a founder population living on communal farms. Replication of main findings was assessed in adults from an isolated village in Sardinia (Talana study, N = 450). We then investigated the influence of asthma, atopy and tobacco smoke exposure on these genetic associations, and whether they were also associated with FeNO values in children of the EAGLE (EArly Genetics & Lifecourse Epidemiology, N = 8858) consortium.

RESULTS

We detected a common variant in RAB27A (rs2444043) associated with FeNO that reached the genome-wide significant level (P = 1.6 × 10(-7) ) in the combined discovery and replication adult data sets. This SNP belongs to member of RAS oncogene family (RAB27A) and was associated with an expression quantitative trait locus for RAB27A in lymphoblastoid cell lines from asthmatics. A second suggestive locus (rs2194437, P = 8.9 × 10(-7) ) located nearby the sodium/calcium exchanger 1 (SLC8A1) was mainly detected in atopic subjects and influenced by inhaled corticosteroid use. These two loci were not associated with childhood FeNO values.

CONCLUSIONS AND CLINICAL RELEVANCE

This study identified a common variant located in RAB27A gene influencing FeNO levels specifically in adults and with a biological relevance to the regulation of FeNO levels. This study provides new insight into the biological mechanisms underlying FeNO levels in adults.

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.

Acute glutathione depletion leads to enhancement of airway reactivity and inflammation via p38MAPK-iNOS pathway in allergic mice

Glutathione (GSH) plays a major role in allergic airway responses through a variety of mechanism which include direct scavenging of oxidative species, being a reducing equivalent and regulation of cellular signaling through redox sensitive mechanisms. Therefore, the aim of the present study was to evaluate the role of acute GSH depletion on airway reactivity, inflammation and NO signaling in a mouse model of allergic asthma. Buthionine sulfoximine (BSO), an inhibitor of gamma-glutamylcysteine synthetase was used for depletion of GSH levels. Acute depletion of GSH with BSO worsened allergen induced airway reactivity and inflammation through increase in nitrosative stress as reflected by increased inducible NO synthase (iNOS) expression, total nitrates and nitrites (NOx), nitrotyrosine, protein carbonyls, and decreased total antioxidant capacity. Treatment with p38 mitogen-activated protein kinase (MAPK) and iNOS inhibitors attenuated the effects of GSH depletion on airway reactivity and inflammation through attenuation of nitrosative stress as evidenced by a decrease in NOx, nitrotyrosine, protein carbonyls and increase in total antioxidant capacity (TAC). In conclusion, these data suggest that acute depletion of glutathione is associated with alteration of airway responses through an increase in nitrosative stress in allergic airways of mice.

Nitration of protein without allergenic potential triggers modulation of antioxidant response in type II pneumocytes

Inhalation of nitrogen and reactive oxygen species (ROS) is known to induce lung inflammation, which is prevented by enzymatic and nonenzymatic antioxidant systems. These agents form nitrated allergens that were shown to enhance allergenicity. The aim of this study was to examine the influence of nitrated proteins on inflammation and antioxidant status of the lung. Ovalbumin (OVA) in nitrated form (nOVA) was intraperitoneally (ip) injected in mice for sensitization and in nitrated or unmodified form for challenge to induce allergic bronchial inflammation. To study the allergen potential of unrelated protein and verify cross-reactivity, nitrated and unmodified keyhole limpet hemocyanin (nKLH, KLH) was used for challenge. Challenge with OVA or nOVA reduced lung function and increased eosinophilia and protein content in bronchoalveolar lavage fluid (BALF). Challenge with nitrated or native OVA or KLH elevated glutathione (GSH) ratio in type II pneumocytes. Reduced mRNA expression of glutathione peroxidase (GPX) 3, glutathione reductase (GR), superoxide dismutase (SOD) 2, and catalase (CAT) was most prominent after challenge with nitrated OVA and nitrated KLH, respectively. Challenge with nOVA enhanced SOD1 mRNA reduction. Immunostaining of GPX 3 and SOD2 increased after challenge with OVA or nOVA, while reactivity of GR and reactivity of SOD2 were reduced after challenge with KLH or nKLH. SOD1 immunostaining was diminished after challenge with nonnitrated OVA or KLH. CAT immunoreaction was similar in all groups. Nitrated proteins without allergenic potential triggered mRNA reduction of antioxidants in type II cells after sensitization with a nitrated allergen but did not induce bronchial inflammation.

EC-18, a synthetic monoacetyldiglyceride (1-palmitoyl-2-linoleoyl-3-acetylglycerol), attenuates the asthmatic response in an aluminum hydroxide/ovalbumin-induced model of asthma

EC-18 is a synthetic monoacetyldiaglyceride that is a major constituent in antlers of Sika deer (Cervus nippon Temmenick). In this study, we evaluated the protective effects of EC-18 on Th2-type cytokines, eosinophil infiltration, and other factors in an aluminum hydroxide/ovalbumin (OVA)-induced murine asthma model. Mice were sensitized on days 0 and 14 by intraperitoneal injection of OVA with aluminum hydroxide. On days 21, 22 and 23 after the initial sensitization, the mice received an airway challenge with OVA for 1h using an ultrasonic nebulizer. EC-18 was administered to mice by oral gavage at doses of 30mg/kg and 60mg/kg once daily from day 18 to 23. Methacholine responsiveness was measured 24h after the final OVA challenge, and the bronchoalveolar lavage fluid (BALF) was collected 48h after the final OVA challenge. EC-18 significantly reduced methacholine responsiveness, T helper type 2 (Th2) cytokines, eotaxin-1, immunoglobulin (Ig) E, IgG, and the number of inflammatory cells. In addition, EC-18-treated mice exhibited the reduction in the expression of inducible nitric oxide synthase (iNOS) in lung tissue. In the histological analysis using hematoxylin-eosin stain and periodic acid-Schiff stain, EC-18 attenuated the infiltration of inflammatory cells into the airway and reduced the level of mucus production. Our results showed that EC-18 effectively suppressed the asthmatic response induced by OVA challenge. These effects were considered to be associated with iNOS suppression. In conclusion, this study suggests that EC-18 may be a therapeutic agent for allergic asthma.

Techniques for assessing small airways function: Possible applications in asthma and COPD

In recent years special interest has been expressed for the contribution of small airways in the pathophysiology, clinical manifestations and treatment of asthma and COPD. Small airways contribute little to the total respiratory resistance so that extensive damage of small airways may occur before the appearance of any symptoms, and this is the reason why they are characterized as the "silent zone" of airways. Furthermore, the peripheral localization of the small airways and their small diameter constitutes difficult their direct assessment. Thus, they are usually studied indirectly, taking advantage of the effects of their obstruction, such as premature closure, air trapping, heterogeneity of ventilation, and lung volume dependence of airflow limitation. Today, several heterogeneous methods for the assessment of small airways are available. These can be either functional (spirometry, plethysmography, resistance measurements, nitrogen washout, alveolar nitric oxide, frequency dependence of compliance, flow-volume curves breathing mixture of helium-oxygen) or imaging (mainly through high resolution computed tomography). The above-mentioned methods are summarized in Table 1. However, no method is currently considered as the "gold standard" and it seems that combinations of tests are needed. Furthermore, it is not clear whether the small airways are affected in all patients with asthma or COPD and their clinical significance remains under investigation. Well-designed future studies with large numbers of patients are expected to reveal which of the methods for assessing the small airways is the most accurate, reliable and reproducible, for which patients, and which can be used for the evaluation of the effects of treatment.

Eosinophilic inflammation in allergic asthma

Eosinophils are circulating granulocytes involved in pathogenesis of asthma. A cascade of processes directed by Th2 cytokine producing T-cells influence the recruitment of eosinophils into the lungs. Furthermore, multiple elements including interleukin (IL)-5, IL-13, chemoattractants such as eotaxin, Clara cells, and CC chemokine receptor (CCR)3 are already directly involved in recruiting eosinophils to the lung during allergic inflammation. Once recruited, eosinophils participate in the modulation of immune response, induction of airway hyperresponsiveness and remodeling, characteristic features of asthma. Various types of promising treatments for reducing asthmatic response are related to reduction in eosinophil counts both in human and experimental models of pulmonary allergic inflammation, showing that the recruitment of these cells really plays an important role in the pathophysiology of allergic diseases such asthma.

The effect of heparin on antigen-induced mucus hypersecretion in the nasal epithelium of sensitized rats

BACKGROUND

Heparin is a potential anti-inflammatory drug for allergic airway inflammation. To elucidate the effects of heparin on allergic inflammation, we examined the in vivo effects of heparin on antigen-induced mucus hypersecretion and infiltration of eosinophils and neutrophils in the nasal epithelium of sensitized rats.

METHODS

We induced hypertrophic and metaplastic changes of goblet cells in the nasal epithelium of ovalbumin (OVA)-sensitized rats by intranasal challenge with OVA. The effects of intranasal instillation with low molecular weight heparin (LMWH; 1-1000IU/0.1ml) on mucus production and eosinophil/neutrophil infiltration were examined.

RESULTS

Intranasal instillation with low-dose LMWH (1-10IU/0.1ml) at 30 minutes before OVA instillation stimulated OVA-induced mucus production in the nasal epithelium of sensitized rats, whereas treatment with 100IU/0.1ml LMWH showed no effect. Intranasal instillation with high-dose LMWH (1000IU/0.1ml) significantly inhibited OVA-induced mucus production. Intranasal instillation with LMWH (1-1000IU/0.1ml) dose-dependently inhibited eosinophil and neutrophil infiltration into the rat nasal mucosa.

CONCLUSIONS

These results indicate that heparin inhibits mucus hypersecretion and infiltration of eosinophils and neutrophils in allergic inflammation, though the inhibitory effect against mucus production is obtained in high-dose heparin. Intranasal instillation with high-dose heparin may provide a new therapeutic strategy for the treatment of nasal allergic inflammation.

Associations between nitric oxide synthase genes and exhaled NO-related phenotypes according to asthma status

Background

The nitric oxide (NO) pathway is involved in asthma, and eosinophils participate in the regulation of the NO pool in pulmonary tissues. We investigated associations between single nucleotide polymorphisms (SNPs) of NO synthase genes (NOS) and biological NO-related phenotypes measured in two compartments (exhaled breath condensate and plasma) and blood eosinophil counts.

Methodology

SNPs (N = 121) belonging to NOS1, NOS2 and NOS3 genes were genotyped in 1277 adults from the French Epidemiological study on the Genetics and Environment of Asthma (EGEA). Association analyses were conducted on four quantitative phenotypes: the exhaled fraction of NO (Fe_NO), plasma and exhaled breath condensate (EBC) nitrite-nitrate levels (NO2–NO3) and blood eosinophils in asthmatics and non-asthmatics separately. Genetic heterogeneity of these phenotypes between asthmatics and non-asthmatics was also investigated.

Principal Findings

In non-asthmatics, after correction for multiple comparisons, we found significant associations of Fe_NO levels with three SNPs in NOS3 and NOS2 (P≤0.002), and of EBC NO2–NO3 level with NOS2 (P = 0.002). In asthmatics, a single significant association was detected between Fe_NO levels and one SNP in NOS3 (P = 0.004). Moreover, there was significant heterogeneity of NOS3 SNP effect on Fe_NO between asthmatics and non-asthmatics (P = 0.0002 to 0.005). No significant association was found between any SNP and NO2–NO3 plasma levels or blood eosinophil counts.

Conclusions

Variants in NO synthase genes influence Fe_NO and EBC NO2–NO3 levels in adults. These genetic determinants differ according to asthma status. Significant associations were only detected for exhaled phenotypes, highlighting the critical relevance to have access to specific phenotypes measured in relevant biological fluid.

Oxidative stress in asthma

Asthma is a chronic inflammatory lung disease that results in airflow limitation, hyperreactivity, and airway remodeling. There is strong evidence that an imbalance between the reducing and oxidizing systems favoring a more oxidative state is present in asthma. Endogenous and exogenous reactive oxygen species, such as superoxide anion, hydroxyl radical, hypohalite radical, and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide, peroxynitrite, and nitrite, play a major role in the airway inflammation and are determinants of asthma severity. Asthma is also associated with decreased antioxidant defenses, such as superoxide dismutase, catalase, and glutathione. In this review, we will summarize the current knowledge and discuss the current and future strategies for the modulation of oxidative stress in asthma.

[Physiology and physiopathology of the distal airways in asthma]

The small airways are those with an internal diameter of less than 2 mm. The contribution of these airways to total airflow resistance is small in healthy individuals but can represent 50-90 % of total airflow resistance in asthmatics. Suspicion of small airways disease has been based on reduction of midexpiratory and instantaneous flows, although wide variability in their values and the absence of a sufficiently validated cut-off point has limited their clinical application. Static pulmonary volumes can provide indirect evidence of the state of the most distal airways, revealing two effects of their alteration: air trapping and dynamic hyperinflation. While determination of airway resistance by plethysmography and of respiratory system resistance measured by flow interruption are highly non-specific, the forced oscillation technique allows obstruction of the small airways to be distinguished from that of medium-caliber airways. The characteristic pattern of peripheral obstruction includes a decrease in frequency-dependent resistance, reduced reactivity and an increase in resonance frequency. Single-or multiple-breath nitrogen washout can also provide specific information on the small airways, although the apparatus required is less frequently available. Analysis through bicompartmental models of exhaled nitric oxide allows alveolar nitric oxide concentrations to be determined, which seems to provide information on inflammatory activity in the small airways.

Utility of two-compartment models of exhaled nitric oxide in patients with asthma

Two-compartment models provide more precise information about the contribution of the different portions of the airways to exhaled nitric oxide (NO). Airway wall concentration of NO (Caw,NO) and maximum flux of NO in the airways (J'aw,NO) reflect the tissue production rate of NO and they can be modified by corticosteroids. The airway wall diffusing capacity of NO (Daw,NO) depends on diverse physical and anatomical determinants of the airways, such as gas exchange surface area. Daw,NO can be modified by structural and physiological changes that are characteristic of airway remodeling, which take place over the long term. The alveolar concentration of NO (Calv,NO) represents the degree of small airway inflammation. The persistence of high Calv,NO in patients treated with inhaled corticosteroids could reflect the incapacity of these drugs to reach distal locations due to the heterogeneity of the acinar ventilation. In this review, we evaluate the parameters provided by the compartmentalized analysis of exhaled NO that could be useful in characterizing asthma patients.

Nitric oxide metabolism in asthma pathophysiology

BACKGROUND

Asthma, a chronic inflammatory disease is typically characterized by bronchoconstriction and airway hyper-reactivity.

SCOPE OF REVIEW

A wealth of studies applying chemistry, molecular and cell biology to animal model systems and human asthma over the last decade has revealed that asthma is associated with increased synthesis of the gaseous molecule nitric oxide (NO).

MAJOR CONCLUSION

The high NO levels in the oxidative environment of the asthmatic airway lead to greater formation of reactive nitrogen species (RNS) and subsequent oxidation and nitration of proteins, which adversely affect protein functions that are biologically relevant to chronic inflammation. In contrast to the high levels of NO and nitrated products, there are lower levels of beneficial S-nitrosothiols (RSNO), which mediate bronchodilation, due to greater enzymatic catabolism of RSNO in the asthmatic airways.

GENERAL SIGNIFICANCE

This review discusses the rapidly accruing data linking metabolic products of NO as critical determinants in the chronic inflammation and airway reactivity of asthma. This article is part of a Special Issue entitled Biochemistry of Asthma.

Nitric oxide in asthma physiopathology

Asthma is a chronic inflammatory airway disease characterized by allergen-induced airway hyperresponsiveness, airway inflammation, and remodeling. Nitric oxide (NO) derived from constitutive and inducible enzymes affects many aspects of asthma physiopathology. Animal in vivo studies have indicated that inhibition of iNOS may play a central role in the modulation of these features, particularly extracellular matrix remodeling. Additionally, increases in iNOS-derived NO, observed in asthmatic patients, may lead to an increase in peroxynitrite and an imbalance of oxidant and antioxidant pathways. In addition, endogenous nitric oxide produced by constitutive enzymes may protect against the remodeling of the lung. Therefore, nitric oxide donors and/or iNOS inhibitors may have therapeutic potential in asthma treatment and can also be used with corticosteroids to counteract airway remodeling. This paper focuses on the pathophysiological role of nitric oxide, mainly derived from inducible isoforms, in the various pathologic mechanisms of allergic asthma and the importance of nitric oxide and/or arginase inhibitors in asthma treatment.

Role of the Mac-1 and VLA-4 integrins, and concomitant Th2-cytokine production, in nitric oxide modulated eosinophil migration from bone marrow to lungs in allergic mice

Although numerous studies demonstrate the participation of nitric oxide (NO) in various inflammatory diseases, the precise function of NO in allergic asthma remains unclear. We investigated whether iNOS inhibition could interfere with the kinetics of VLA-4 and Mac-1 expression and adhesion properties of bone marrow and peripheral blood eosinophils of sensitized mice after antigen exposure. Treatment of allergic mice with 1400 W (iNOS inhibitor) increased the adhesion of bone marrow eosinophils to ICAM-1, but not blood eosinophils, at 24h and 48 h after OVA-challenge. Conversely, adhesion of blood eosinophils from 1400 W-treated mice to VCAM-1 diminished at 24h and was almost completely blocked at 48 h. 1400 W did not induce any change in the adhesion of bone marrow eosinophils to VCAM-1, at 24h, but cells collected 48 h after challenge showed significantly lower adherence. Flow cytometry demonstrated that 1400 W resulted in a significantly increased Mac-1 expression on bone marrow eosinophils at 24h, as compared to control mice. However, at 24h, 1400 W significantly decreased Mac-1 and VLA-4 expressions on blood eosinophils. At 48 h, the expressions of both Mac-1 and VLA-4 returned to previous levels. Results show a temporal effect of iNOS upon Mac-1 expression and function, the chief adhesion molecule involved in the eosinophil efflux from the bone marrow at 24h. In contrast, Mac-1 and VLA-4 were involved in eosinophil mobilization from blood to lungs at 48 h after antigen challenge. Data suggest an important role of the Mac-1 and VLA-4 in the iNOS-modulated migration of eosinophils to the lungs of allergic mice.

Concomitant administration of nitric oxide and glucocorticoids improves protection against bronchoconstriction in a murine model of asthma

Glucocorticoids (GC) remain the first choice of treatment in asthma, but GC therapy is not always effective and is associated with side effects. In a porcine study in our laboratory, simultaneous administration of GC and nitric oxide (NO) attenuated the endotoxin-induced inflammatory response and made GC treatment more effective than inhaled NO or steroids alone. In the present study, we aimed to further investigate the interactions between NO and GC treatment in two murine models of asthma. Inflammation was induced by endotoxin, ovalbumin, or a combination of both. With an animal ventilator and a forced oscillation method (FlexiVent), lung mechanics and airway reactivity to methacholine in response to various treatments were assessed. We also describe histology and glucocorticoid receptor (GR) protein expression in response to inhaled NO treatment [40 ppm NO gas or NO donors sodium nitroprusside (SNP) or diethylamine NONOate (DEA/NO)]. SNP and GC provided protection against bronchoconstriction to a similar degree in the model of severe asthma. When GC-treated mice were given SNP, maximum airway reactivity was further reduced. Similar effects were seen after DEA/NO delivery to GC-treated animals. Using 1-H-[1,2,4]-oxadiazolo-[4,3-a]-quinoxalin-1-one (ODQ), a soluble guanylate cyclase inhibitor, we found this effect of NO donors to be mediated through a cGMP-independent mechanism. In the severe model, prolonged NO treatment restored or even increased the nuclear levels of GR. In conclusion, in our murine model of severe asthma GC treatment provided protection to only a limited degree against bronchoconstriction, while concomitant treatment with a NO donor was markedly more potent than the use of either NO or GC alone.

Redox control of asthma: molecular mechanisms and therapeutic opportunities

An imbalance in reducing and oxidizing (redox) systems favoring a more oxidative environment is present in asthma and linked to the pathophysiology of the defining symptoms and signs including airflow limitation, hyper-reactivity, and airway remodeling. High levels of hydrogen peroxide, nitric oxide ((*)NO), and 15-F(2t)-isoprostane in exhaled breath, and excessive oxidative protein products in lung epithelial lining fluid, peripheral blood, and urine provide abundant evidence for pathologic oxidizing processes in asthma. Parallel studies document loss of reducing potential by nonenzymatic and enzymatic antioxidants. The essential first line antioxidant enzymes superoxide dismutases (SOD) and catalase are reduced in asthma as compared to healthy individuals, with lowest levels in those patients with the most severe asthma. Loss of SOD and catalase activity is related to oxidative modifications of the enzymes, while other antioxidant gene polymorphisms are linked to susceptibility to develop asthma. Monitoring of exhaled (*)NO has entered clinical practice because it is useful to optimize asthma care, and a wide array of other biochemical oxidative and nitrative biomarkers are currently being evaluated for asthma monitoring and phenotyping. Novel therapeutic strategies that target correction of redox abnormalities show promise for the treatment of asthma.

[Lung function testing and assessment of distal airways in asthma]

INTRODUCTION

Small airways are defined (in humans) as those<2mm in diameter.

BACKGROUND

They were originally described as the "quiet zone" of the lungs contributing less than 10% of the total resistance to airflow. Pulmonary function tests remain the most used method to assess distal airway flow limitation.

VIEWPOINTS

However, these tests are limited in adults and also in children because MEF25-75% and FEF50% are highly variable spirometric indices and they depend on vital capacity, which increases with expiratory time in obstructed subjects. There is a need for promising non invasive new tools like the forced oscillation technique to measure resistance. The increased availability of the exhaled fraction of nitric oxide (FeNO) measurement means that this method is accessible and attractive.

CONCLUSION

The production of nitric oxide (NO) can be assessed by measuring the fraction of NO during a prolonged expiration (FENO) or by estimating other parameters of NO exchange including the alveolar NO concentration (CalvNO) and may provide information about small airway inflammation and assist the optimal control of the disease.

Induced nitric oxide synthase as a major player in the oncogenic transformation of inflamed tissue

Nitric oxide (NO) is a free radical that is involved in the inflammatory process and carcinogenesis. There are four nitric oxide synthase enzymes involved in NO production: induced nitric oxide synthase (iNOS), endothelial NO synthase (eNOS), neural NO synthase (nNOS), and mitochondrial NOS. iNOS is an inducible and key enzyme in the inflamed tissue. Recent literatures indicate that NO as well as iNOS and eNOS can modulate cancer-related events including nitro-oxidative stress, apoptosis, cell cycle, angio-genesis, invasion, and metastasis. This chapter focuses on linking NO/iNOS/eNOS to inflammation and carcinogenesis from experimental evidence to potential targets on cancer prevention and treatment.

Both allergic and nonallergic asthma are associated with increased FE(NO) levels, but only in never-smokers

BACKGROUND

Allergic asthma is consistently associated with increased FE(NO) levels whereas divergence exists regarding the use of exhaled nitric oxide (NO) as marker of inflammation in nonallergic asthma and in asthmatic smokers. The aim of this study is to analyze the effect of having allergic or nonallergic asthma on exhaled nitric oxide levels, with special regard to smoking history.

METHODS

Exhaled NO measurements were performed in 695 subjects from Turin (Italy), Gothenburg and Uppsala (both Sweden). Current asthma was defined as self-reported physician-diagnosed asthma with at least one asthma symptom or attack recorded during the last year. Allergic status was defined by using measurements of specific immunoglobulin E (IgE). Smoking history was questionnaire-assessed.

RESULTS

Allergic asthma was associated with 91 (60, 128) % [mean (95% CI)] increase of FE(NO) while no significant association was found for nonallergic asthma [6 (-17, 35) %] in univariate analysis, when compared to nonatopic healthy subjects. In a multivariate analysis for never-smokers, subjects with allergic asthma had 77 (27, 145) % higher FE(NO) levels than atopic healthy subjects while subjects with nonallergic asthma had 97 (46, 166) % higher FE(NO) levels than nonatopic healthy subjects. No significant asthma-related FE(NO) increases were noted for ex- and current smokers in multivariate analysis.

CONCLUSIONS

Both allergic and nonallergic asthma are related to increased FE(NO) levels, but only in never-smoking subjects. The limited value of FE(NO) to detect subjects with asthma among ex- and current smokers suggests the predominance of a noneosinophilic inflammatory phenotype of asthma among ever-smokers.

Human eosinophil adhesion and degranulation stimulated with eotaxin and RANTES in vitro: lack of interaction with nitric oxide

Background

Airway eosinophilia is considered a central event in the pathogenesis of asthma. The toxic components of eosinophils are thought to be important in inducing bronchial mucosal injury and dysfunction. Previous studies have suggested an interaction between nitric oxide (NO) and chemokines in modulating eosinophil functions, but this is still conflicting. In the present study, we have carried out functional assays (adhesion and degranulation) and flow cytometry analysis of adhesion molecules (VLA-4 and Mac-1 expression) to evaluate the interactions between NO and CC-chemokines (eotaxin and RANTES) in human eosinophils.

Methods

Eosinophils were purified using a percoll gradient followed by immunomagnetic cell separator. Cell adhesion and degranulation were evaluated by measuring eosinophil peroxidase (EPO) activity, whereas expression of Mac-1 and VLA-4 was detected using flow cytometry.

Results

At 4 h incubation, both eotaxin (100 ng/ml) and RANTES (1000 ng/ml) increased by 133% and 131% eosinophil adhesion, respectively. L-NAME alone (but not D-NAME) also increased the eosinophil adhesion, but the co-incubation of L-NAME with eotaxin or RANTES did not further affect the increased adhesion seen with chemokines alone. In addition, L-NAME alone (but not D-NAME) caused a significant cell degranulation, but it did not affect the CC-chemokine-induced cell degranulation. Incubation of eosinophils with eotaxin or RANTES, in absence or presence of L-NAME, did not affect the expression of VLA-4 and Mac-1 on eosinophil surface. Eotaxin and RANTES (100 ng/ml each) also failed to elevate the cyclic GMP levels above baseline in human eosinophils.

Conclusion

Eotaxin and RANTES increase the eosinophil adhesion to fibronectin-coated plates and promote cell degranulation by NO-independent mechanisms. The failure of CC-chemokines to affect VLA-4 and Mac-1 expression suggests that changes in integrin function (avidity or affinity) are rather involved in the enhanced adhesion.

Effects of L-arginine and phosphodiesterase-5 inhibitor, sildenafil, on inflammation and airway responsiveness of sensitized BP2 mice

Nitric oxide (NO) levels are elevated in the exhaled breath of asthmatic patients and NO is considered as a biomarker of airway inflammation. However, the functions of NO in the airways are not completely understood. L-arginine, as the substrate of NO synthases, is the precursor of NO which stimulates guanylate cyclase and leads to the formation of cyclic GMP (cGMP). Sildenafil, a phosphodiestérase-5 (PDE-5) inhibitor, prevents the degradation of cGMP. In this study the effects of L-arginine and sildenafil treatment, alone or in combination, were evaluated in ovalbumin-sensitized BP2 mice. These effects concerning the airway responsiveness to inhaled methacholine (MCh) were evaluated by whole-body plethysmography (WBP), the inflammatory response evaluated by bronchoalveolar lavage fluid (BALF) analyses and lung tissue biopsies (eosinophilic inflammation associated with lung remodelling), and NO metabolite measurements (by Griess reaction) in BALF. Ovalbumin sensitization induced: (a) an inflammatory reaction with eosinophil and neutrophil influx in BALF and lung; and (b) an increased bronchial responsiveness to MCh. L-arginine treatment [50 mg/kg intraperitoneally (i.p.), for 7 days] increased the relative amount of eosinophils and neutrophils in BALF, had a tendency to increase the airway responsiveness to inhaled MCh and increased the NO metabolite level in BAL. Sildenafil treatment (20 mg/kg i.p. for 7 days) did not affect the airway responsiveness to MCh and had a lower effect compared with L-arginine on inflammatory reactions. The combination of the two treatments resulted in a dramatic enhancement of the airway responsiveness to inhaled MCh. The relative amount of eosinophils was increased and lung histology showed obvious worsened tissular lesions such as epithelial shedding and hypertrophy, hyperplasia of smooth muscle cells, and fibrosis. These findings are consistent with the notion that NO production plays a role in the development of airway inflammation and hyperresponsiveness of sensitized mice and highlighted the potential risk of the L-arginine dietary complement or PDE5 treatment in asthmatic patients.

High serum levels of tumour necrosis factor-alpha and interleukin-8 in severe asthma: markers of systemic inflammation?

BACKGROUND

Severe asthma is characterized by elevated levels of pro-inflammatory cytokines and neutrophilic inflammation in the airways. Blood cytokines, markers of 'systemic' inflammation, may be a feature of amplified inflammation in severe asthma.

OBJECTIVE

To detect differences in IL-8, TNF-alpha, IL-16 and IL-13 levels in the serum(s) of stable severe and mild-moderate asthmatics related to blood leucocytes proportion, airway calibre and exhaled nitric oxide (NO) levels.

METHODS

We assessed cytokine serum levels by ELISA and blood leucocyte counts by an alkaline peroxidase method in 20 healthy controls, 22 mild-moderate [forced expiratory volume in 1 s (FEV1)(%pred): 89+/-3] and 14 severe asthmatics [FEV1(%pred): 49+/-2].

RESULTS

IL-8 and TNF-alpha levels were higher in severe asthmatics than in mild-moderate asthmatics or in controls (P<0.05). No differences in IL-16 and IL-13 levels were detected. Severe asthmatics showed higher circulating neutrophil and eosinophil number than controls (P<0.05). In severe asthmatics, exhaled NO levels were superior than in controls (P<0.05), but inferior than in mild-moderate asthmatics (P<0.05). We found positive correlation between TNF-alpha levels and exhaled NO (r=0.67; P=0.01) or circulating neutrophil counts (r=0.57; P=0.03) in severe asthmatics.

CONCLUSION

sTNF-alpha and sIL-8 are markers of 'systemic' inflammation in severe asthmatics, in conjunction with augmented circulating neutrophils, suggesting the involvement of neutrophil-derived cytokine pattern in severe asthma.

Endothelial nitric oxide synthase (NOS3) knockout decreases NOS2 induction, limiting hyperoxygenation and conferring protection in the postischemic heart

Although it has been shown that endothelial nitric oxide synthase (eNOS)-derived nitric oxide downregulates mitochondrial oxygen consumption during early reperfusion, its effects on inducible NOS (iNOS) induction and myocardial injury during late reperfusion are unknown. Wild-type (WT) and eNOS(-/-) mice were subjected to 30 min of coronary ligation followed by reperfusion. Expression of iNOS mRNA and protein levels and peroxynitrite production were lower in postischemic myocardium of eNOS(-/-) mice than levels in WT mice 48 h postreperfusion. Significantly improved hemodynamics (+/-dP/dt, left ventricular systolic pressure, mean arterial pressure), increased rate pressure product, and reduced myocardial infarct size (18 +/- 2.5% vs. 31 +/- 4.6%) were found 48 h after reperfusion in eNOS(-/-) mice compared with WT mice. Myocardial infarct size was also significantly decreased in WT mice treated with the specific iNOS inhibitor 1400W (20.5 +/- 3.4%) compared with WT mice treated with PBS (33.9 +/- 5.3%). A marked reperfusion-induced hyperoxygenation state was observed by electron paramagnetic resonance oximetry in postischemic myocardium, but Po(2) values were significantly lower from 1 to 72 h in eNOS(-/-) than in WT mice. Cytochrome c-oxidase activity and NADH dehydrogenase activity were significantly decreased in postischemic myocardium in WT and eNOS(-/-) mice compared with baseline control, respectively, and NADH dehydrogenase activity was significantly higher in eNOS(-/-) than in WT mice. Thus deficiency of eNOS exerted a sustained beneficial effect on postischemic myocardium 48 h after reperfusion with preserved mitochondrial function, which appears to be due to decreased iNOS induction and decreased iNOS-derived peroxynitrite in postischemic myocardium.

Mechanism of nitrite oxidation by eosinophil peroxidase: implications for oxidant production and nitration by eosinophils

Eosinophil peroxidase is a haem enzyme of eosinophils that is implicated in oxidative tissue injury in asthma. It uses hydrogen peroxide to oxidize thiocyanate and bromide to their respective hypohalous acids. Nitrite is also a substrate for eosinophil peroxidase. We have investigated the mechanisms by which the enzyme oxidizes nitrite. Nitrite was very effective at inhibiting hypothiocyanous acid ('cyanosulphenic acid') and hypobromous acid production. Spectral studies showed that nitrite reduced the enzyme to its compound II form, which is a redox intermediate containing Fe(IV) in the haem active site. Compound II does not oxidize thiocyanate or bromide. These results demonstrate that nitrite is readily oxidized by compound I, which contains Fe(V) at the active site. However, it reacts more slowly with compound II. The observed rate constant for reduction of compound II by nitrite was determined to be 5.6x10(3) M(-1) x s(-1). Eosinophils were at least 4-fold more effective at promoting nitration of a heptapeptide than neutrophils. This result is explained by our finding that nitrite reacts 10-fold faster with compound II of eosinophil peroxidase than with the analogous redox intermediate of myeloperoxidase. Nitration by eosinophils was increased 3-fold by superoxide dismutase, which indicates that superoxide interferes with nitration. We propose that at sites of eosinophilic inflammation, low concentrations of nitrite will retard oxidant production by eosinophil peroxidase, whereas at higher concentrations nitrogen dioxide will be a major oxidant formed by these cells. The efficiency of protein nitration will be decreased by the diffusion-controlled reaction of superoxide with nitrogen dioxide.

Lipopolysaccharide exposure makes allergic airway inflammation and hyper-responsiveness less responsive to dexamethasone and inhibition of iNOS

Allergic airway disease can be refractory to anti-inflammatory treatment, whose cause is unclarified. Therefore, in the present experiment, we have tested the hypothesis that co-exposure to lipopolysacharide (Lps) and allergen results in glucocorticoid-resistant eosinophil airway inflammation and hyper-responsiveness (AHR). Ovalbumin (Ova)-sensitized BALB/c mice were primed with 10 microg intranasal Lps 24 h before the start of Ova challenges (20 min on 3 consecutive days). Dexamethasone (5 mg/kg/day) was given on the last 2 days of Ova challenges. AHR, cellular build-up, cytokine and nitrite concentrations of bronchoalveolar lavage fluid (BALF) and lung histology were examined. To assess the role of iNOS-derived NO in airway responsiveness, mice were treated with a selective inhibitor of this enzyme (1400W) 2 h before AHR measurements. More severe eosinophil inflammation and higher nitrite formation were found in Lps-primed than in non-primed allergized mice. After Lps priming, AHR and concentrations of T-helper type 2 cytokines in BALF were decreased, but still remained significantly higher than in controls. Eosinophil inflammation was partially, while nitrite production and AHR were observed to be largely dexamethasone resistant in Lps-primed allergized animals. 1400W effectively and rapidly diminished the AHR in Ova-sensitized and challenged mice, but failed to affect it after Lps priming plus allergization. In conclusion, Lps inhalation may exaggerate eosinophil inflammation and reduce responsiveness to anti-inflammatory treatment in allergic airway disease.

Nitrotyrosine proteome survey in asthma identifies oxidative mechanism of catalase inactivation

Reactive oxygen species and reactive nitrogen species produced by epithelial and inflammatory cells are key mediators of the chronic airway inflammation of asthma. Detection of 3-nitrotyrosine in the asthmatic lung confirms the presence of increased reactive oxygen and nitrogen species, but the lack of identification of modified proteins has hindered an understanding of the potential mechanistic contributions of nitration/oxidation to airway inflammation. In this study, we applied a proteomic approach, using nitrotyrosine as a marker, to evaluate the oxidation of proteins in the allergen-induced murine model of asthma. Over 30 different proteins were targets of nitration following allergen challenge, including the antioxidant enzyme catalase. Oxidative modification and loss of catalase enzyme function were seen in this model. Subsequent investigation of human bronchoalveolar lavage fluid revealed that catalase activity was reduced in asthma by up to 50% relative to healthy controls. Analysis of catalase isolated from asthmatic airway epithelial cells revealed increased amounts of several protein oxidation markers, including chloro- and nitrotyrosine, linking oxidative modification to the reduced activity in vivo. Parallel in vitro studies using reactive chlorinating species revealed that catalase inactivation is accompanied by the oxidation of a specific cysteine (Cys(377)). Taken together, these studies provide evidence of multiple ongoing and profound oxidative reactions in asthmatic airways, with one early downstream consequence being catalase inactivation. Loss of catalase activity likely amplifies oxidative stress, contributing to the chronic inflammatory state of the asthmatic airway.

Effects of nitric oxide synthases in chronic allergic airway inflammation and remodeling

The precise role of each nitric oxide (NO) synthase (NOS) isoform in the pathobiology of asthma is not well established. Our objective was to investigate the contribution of constitutive NO synthase (cNOS) and inducible NOS (iNOS) isoforms to lung mechanics and inflammatory and remodeling responses in an experimental model of chronic allergic pulmonary inflammation. Guinea pigs were submitted to seven ovalbumin exposures with increasing doses (1 approximately 5 mg/ml) for 4 wk. The animals received either chronic L-NAME (N-nitro-L-arginine methyl ester, in drinking water) or 1,400 W (iNOS-specific inhibitor, intraperitoneal) treatments. At 72 h after the seventh inhalation of ovalbumin solution, animals were anesthetized, mechanically ventilated, exhaled NO was collected, and lung mechanical responses were evaluated before and after antigen challenge. Both L-NAME and 1,400 W treatments increased baseline resistance and decreased elastance of the respiratory system in nonsensitized animals. After challenge, L-NAME increased resistance of the respiratory system and collagen deposition on airways, and decreased peribronchial edema and mononuclear cell recruitment. Administration of 1,400 W reduced resistance of the respiratory system response, eosinophilic and mononuclear cell recruitment, and collagen and elastic fibers content in airways. L-NAME treatment reduced both iNOS- and neuronal NOS-positive eosinophils, and 1,400 W diminished only the number of eosinophils expressing iNOS. In this experimental model, inhibition of NOS-derived NO by L-NAME treatment amplifies bronchoconstriction and increases collagen deposition. However, blockage of only iNOS attenuates bronchoconstriction and inflammatory and remodeling processes.

Effects of acute and chronic nitric oxide inhibition in an experimental model of chronic pulmonary allergic inflammation in guinea pigs

Endogenously produced nitric oxide is a recognized regulator of physiological lung events, such as a neurotransmitter and a proinflammatory mediator. We tested the differences between chronic and acute nitric oxide inhibition by Nω-nitro-l-arginine methyl ester (l-NAME) treatment in lung mechanics, inflammation, and airway remodeling in an experimental asthma model in guinea pigs. Both acute and chronic l-NAME treatment reduced exhaled nitric oxide in sensitized animals ( P < 0.001). Chronic l-NAME treatment increased baseline and maximal responses after antigen challenge of respiratory system resistance and reduced peribronchial edema and mononuclear cells airway infiltration ( P < 0.05). Acute administration of l-NAME increased maximal values of respiratory system elastance and reduced mononuclear cells and eosinophils in airway wall ( P < 0.05). Chronic ovalbumin exposure resulted in airway wall thickening due to an increase in collagen content ( P < 0.005). Chronic nitric oxide inhibition increased collagen deposition in airway wall in sensitized animals ( P < 0.05). These data support the hypothesis that in this model nitric oxide acts as a bronchodilator, mainly in proximal airways. Furthermore, chronic nitric oxide inhibition was effective in reducing edema and mononuclear cells in airway wall. However, airway eosinophilic inflammation was unaltered by chronic l-NAME treatment. In addition, nitric oxide inhibition upregulates collagen deposition in airway walls.

NOS 1 is required for allergen-induced expression of NOS 2 in mice

BACKGROUND

Although increased nitric oxide (NO) production in asthma is mediated largely by upregulation of the inducible form of nitric oxide synthase (iNOS, or NOS 2), some studies have suggested an important role for the usually constitutive neural NOS isoform (nNOS, or NOS 1).

AIM

To investigate how NOS 1 may influence allergic inflammation, we used NOS 1 knockout mice and their wild-type (WT) controls.

METHODS

Mice were sensitized and challenged with ovalbumin (OVA) using a protocol known to upregulate NOS 2 in the airways.

RESULTS

In addition to expected increases in NOS 2 activity, OVA challenge led to increases in calcium-dependent NOS activity, which was accounted for by increased expression of NOS 1 at both mRNA (n = 5, p < 0.001) and protein levels (n = 5, p < 0.01). In NOS-1-deficient mice, OVA challenge induced less eosinophilia (n = 7, p < 0.05) and much less NO production (n = 10, p < 0.01) than in WT controls, reflecting not only the expected absence of NOS 1, but also lack of upregulation of NOS 2. This interaction appeared to be stimulus specific as NOS-1-deficient mice did upregulate NOS 2 following exposure to lipopolysaccharide (n = 5, p < 0.001).

CONCLUSIONS

These findings underscore the importance of NOS 1 in allergic airway inflammation and suggest a mechanism by which NOS 1 may influence overall NO production in the airways.

Repeated inhalation challenge with diphenylmethane-4,4'-diisocyanate in brown Norway rats leads to a time-related increase of neutrophils in bronchoalveolar lavage after topical induction

Diphenylmethane-4,4'-diisocyanate (MDI) is a low-molecular-weight chemical known to cause occupational asthma. The objective of this study was to evaluate the topical and inhalation routes of sensitization on the elicitation response of MDI in the Brown Norway (BN) rat model following repeated challenge exposures. BN rats were either induced topically (150 microl MDI on the flanks, booster administration to the skin of the dorsum of both ears using 75 microl/dorsum of each ear) or by inhalation (5x3 h/d, 28.3+/-3.0 mg MDI/m3 [+/-SD]). Inhalation challenge exposures with MDI (15.7+/-1.4 mg/m3, duration 30 min) were made on d 21, 35, 50, and 64. One day after each challenge, rats were rechallenged with methacholine (MCh) aerosol. Respiratory changes were monitored during challenges. One day after the MCh challenge, selected endpoints in bronchoalveolar lavage (BAL), the weights of lungs, and auricular and lung-associated lymph nodes were determined. After the first and last challenge, lymph nodes and lungs were examined by histopathology. Repeated challenge with MDI or MCh did not elicit marked changes in respiratory patterns at any time point. Mild but consistent time-related increased BAL neutrophils and slightly increased lung and lymph-node weights occurred in topically sensitized rats as compared to the remaining groups. In topically sensitized rats, in the lung histopathology revealed activated lymphatic tissue and an increased recruitment of airway eosinophils. Immunoglobulin (Ig) E determinations (serum and BAL) did not show any differences amongst the groups. Thus, high-dose topical induction with MDI was associated with a neutrophilic and eosinophilic inflammatory response in the lung after repeated inhalation challenge with MDI, with magnitude of effect dependent on the specific methodology used.

Protein nitration in chronic sinusitis and nasal polyposis: role of eosinophils

OBJECTIVES

To investigate the possible role of eosinophil peroxidase (EPO) in 3-nitrotyrosine (3NT) formation.

STUDY DESIGN AND SETTING

Observational study employing immunocytochemistry to assess the presence of 3NT, inducible nitric oxide synthase (iNOS), eosinophils, mast cells, neutrophils, and lymphocytes in ethmoid sinus mucosal biopsies from normal controls and subjects with allergic and nonallergic chronic sinusitis and nasal polyposis.

RESULTS

3NT was more evident in biopsies from sinusitis patients (2.67 +/- 0.14, n = 21) than in healthy mucosa (0.43 +/- 0.2, n = 7, P < 0.01), but scores in atopic and nonatopic subjects were similar. Colocalization studies confirmed that 3NT was largely confined to eosinophils. No relationship was found between 3NT and other immune cells. 3NT detection was not correlated with the amount of immunostaining for iNOS.

SIGNIFICANCE

Chronic sinusitis is accompanied by 3NT formation, which is largely restricted to the eosinophils, and likely driven by the action of eosinophil peroxidase, rather than by nitric oxide levels.

EBM RATING

B-2.