Inducible nitric oxide synthase after sensitization and allergen challenge of Brown Norway rat lung

A new approach for activation of the kiwifruit cysteine protease for usage in in-vitro testing

Actinidin (Act d 1), a highly abundant cysteine protease from kiwifruit, is one of the major contributors to the development of kiwifruit allergy. Many studies have focused on the optimization of Act d 1 purification and its role in the development of food allergies. Testing on cell culture monolayers is a common step in the elucidation of food allergen sensitization. In the case of cysteine proteases, an additional activation step with L-cysteine is required before the testing. Hence, we aimed to evaluate whether L-cysteine already present in commonly used cell culture media would suffice for Act d 1 activation. Successfully activated Act d 1 (98.1% of proteolytic activity, as compared to L-cysteine activated Act d 1) was further tested in two commonly used 2D model systems (Caco-2 and HEK293 cells) to evaluate its role on the mRNA expression of cytokines involved in the innate immunity (IL-1β, IL-6, TNFα, TSLP). Furthermore, the contribution of Act d 1 in the promotion of inflammation through regulation of inducible nitric oxide synthase (iNOS) mRNA expression was also examined. These results demonstrate that activation of cysteine proteases can be achieved without previous enzyme incubation in L-cysteine -containing solution. Act d 1 incubated in cell culture medium was able to modulate gene expression of pro-inflammatory cytokines when tested on two model systems of the epithelial barrier.

Suppression of Hepatic Cyp1a2 by Total Ginsenosides in Lipopolysaccharide-Treated Mice and Primary Mouse Hepatocytes

The roots of Panax ginseng (ginseng) have been extensively used in traditional Chinese medicine. However, herb-drug interactions between ginseng and other co-administered drugs are not fully understood concerning the effect of ginseng on drug metabolism and clearance. The current study aimed to elucidate the effect of total ginsenosides, a typical ginseng extract, on the regulation of Cyp1a2, a key enzyme to regulate drug metabolism under the normal and inflammatory conditions in mice. Female C57BL/6J mice treated with vehicle and lipopolysaccharide (LPS) were intragastrically administered ginseng extract for 7 days before hepatic P450 expression was analyzed. Primary mouse hepatocytes were also employed to further explore the effects of total ginsenosides on Cyp1a2 expression. The results showed that total ginsenosides in P. ginseng extract exhibited a concentration-dependent suppression on Cyp1a2 mRNA and protein level in both mice and primary mouse hepatocytes. Notably, the inhibitory effects of total ginsenosides on Cyp1a2 mRNA and protein expression were further enhanced following LPS treatment. Therefore, future research is warranted to investigate the role of ginsenosides in the regulation of hepatic CYP450s. Moreover, consumption of ginseng as food or supplement should be monitored for patients on combinational therapy, especially those with inflammatory diseases.

Comparative evaluation of anti-inflammatory properties of thymoquinone and curcumin using an asthmatic murine model

This study was designed to compare the inhibitory effects of thymoquinone (TQ) and curcumin (CMN) on the biological changes associating asthma. TQ appeared to exhibit greater inhibitory effects on the aggregation of inflammatory cells in bronchoalveolar lavage (BAL) fluid and in lung tissues. We also measured the effects of the two agents on serum IgE and the changes in the mRNA levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α) and transforming growth factor-β1 (TGF-β1). Serum IgE was significantly decreased by TQ and CMN with TQ being more potent. Also, TQ showed superior inhibitory effects on iNOS and TGF-β1. Meanwhile, CMN was more potent in inhibiting mRNA expression of TNF-α. These results suggest that TQ is more potent in inhibiting the inflammatory changes associating asthma. On the other hand, CMN was a less potent inhibitor of all measured parameters, despite its superior inhibitory effect on TNF-α mRNA levels.

Involvement of nitric oxide (NO) in cough reflex sensitivity between non-sensitized and OVA-sensitized guinea pigs

Background

Exhaled nitric oxide (ENO) is elevated in bronchial asthma patients, and inhaled corticosteroid therapy lowers the elevated ENO levels in such patients. ENO appears to be an inflammatory marker, but its role in the pathophysiology of cough remains unclear. This study aimed to elucidate the relationship between NO and increased cough reflex sensitivity induced by allergic airway reactions.

Methods

Cough reflex sensitivity to inhaled capsaicin was observed under NO depletion caused by NO synthase (NOS) inhibitors in non-sensitized and ovalbumin (OVA)-sensitized guinea pigs. The bronchoalveolar lavage fluid (BALF) was analyzed in an NO depletion setting using the inducible NOS (iNOS) inhibitor ONO1714 in OVA-sensitized guinea pigs.

Results

NO depletion by the non-selective NOS inhibitor L-NAME suppressed cough reflex sensitivity in non-sensitized guinea pigs and OVA-induced increase in cough reflex sensitivity in sensitized guinea pigs; however, iNOS inhibition caused by ONO1714 partially suppressed the OVA-induced increase in cough reflex sensitivity, but not the normal cough response in non-sensitized guinea pigs. ONO1714 did not change BAL cell components in OVA-sensitized guinea pigs.

Conclusions

The results suggest that NO may be involved not only in the normal cough reflex circuit, but also in the OVA-induced increase in cough reflex sensitivity, possibly via a different mechanism of action. Further studies are needed to clarify the precise mechanism.

Antigen challenge influences various transcription factors of rat bronchus: protein/DNA array study

Although the transcription factors are required for expression of the proinflammatory cytokines and immune proteins which are involved in airway hyperresponsiveness and inflammation of bronchial asthma, the antigen-induced alterations of the transcription factors in bronchi have not yet been revealed. Therefore, in order to profile the alteration pattern of the transcription factors after antigen challenge in bronchi, we used protein/DNA arrays. Rats were sensitized and repeatedly challenged with 2,4-dinitrophenylated Ascaris suum antigen. Half, 1, 2 and 4 h after the last antigen challenge, protein/DNA array was performed with nuclear extract of bronchial tissue. Twenty-one the transcription factors exhibited an activation after the last antigen challenge in rat bronchial tissue. Among them, upstream transcription factor-1 (USF-1) and CAAT box general (CBF) were markedly activated after the last antigen challenge. Conversely, 4 transcription factors were inactivated after the last challenge. In development of bronchial asthma, some of the transcription factors may have an ability to modulate the transcription of inflammatory proteins such as cytokines, inflammatory enzymes, etc. Furthermore, the transcription factors, such as USF-1 and CBF, which have not been taken notice so far are also presumed to play an important role in the development of bronchial asthma.

Differential expression of nuclear factor-kappaB mediates increased pulmonary expression of tumor necrosis factor-alpha and virus-induced asthma

Infections with respiratory pathogens such as respiratory syncytial virus and rhinovirus have been associated with the development of long-term chronic airway disease. To better understand the events responsible for this clinical outcome, a rodent model of virus-induced chronic airway disease has been characterized. Upon infection with Sendai virus (parainfluenza virus type-1), Brown Norway (BN) rats develop an asthma-like clinical syndrome, while Fischer 344 (F344) rats fully recover. Our previous studies demonstrated that after infection, tumor necrosis factor-alpha (TNF-alpha) expression is substantially higher in BN rats compared to F344 rats, and this may at least partially mediate the virus-induced airway abnormalities. To investigate the underlying mechanism(s) for the increased TNF-alpha expression, the role of nuclear factor-kappaB (NF-kappaB), an important regulator of TNF-alpha gene transcription, was examined. Supershift electrophoretic mobility shift assays (EMSAs) indicate that normal F344 rats predominantly express the p65 subunit of NF-kappaB in the lungs, and virus infection temporarily increases expression of the p50 subunit. In contrast, normal BN rats have higher expression of the p50 subunit in the pulmonary tract. Upon infection, p50-subunit expression in BN rats increases to levels higher than those observed in virus-infected F344 rats. Interestingly, treatment of infected BN rats with dexamethasone at doses known to prevent virus-induced airway abnormalities increases pulmonary expression of the p65 subunit, and decreases TNF-alpha mRNA levels in the lungs. Furthermore, direct inhibition of TNF-alpha also increases pulmonary expression of p65 in virus-infected BN, but not F344, rats. Taken together, these results suggest that differential expression of NF-kappaB subunits may play an important role in the development of post-viral chronic airway abnormalities.

Novel dry powder formulation of ovalbumin for development of COPD-like animal model: Physicochemical characterization and biomarker profiling in rats

This study was directed toward the development of novel ovalbumin dry powder inhalation system (OVA-DPI) for preparing experimental animal models of chronic obstructive pulmonary disease, with the aim of aiding the drug discovery. OVA-DPI, prepared with jet mill, showed high dispersion and emission from capsule as evaluated by cascade impactor. Based on the results from long term stability studies employing scanning electron microscopy, UPLC/ESI-MS analysis, powder X-ray diffraction and TG/DTA analyses, the OVA-DPI, stored at room temperature, was found to be stable for more than 3 years as evidenced by no significant degradation and crystal polymorphism. Intratracheal administration of OVA-DPI in OVA-sensitized rats resulted in 11-fold increase of infiltrated granulocytes, especially neutrophil, which would be characteristics of severe asthma/COPD symptoms. Of all plasma biomarkers monitored, myeloperoxidase activity and lactate dehydrogenase leakage into blood seemed to be sensitive indicators of lung injury in this model. In addition, biphasic increase of LDH was observed with peak responses at 3 and 24h after antigen challenge, suggesting that OVA-DPI could cause both acute and delayed inflammatory reactions. Upon these findings, OVA-DPI can be useful and reproducible research tool for the development of experimental asthma/COPD model.

Elevated asymmetric dimethylarginine alters lung function and induces collagen deposition in mice

Increasing evidence suggests that lung mechanics and structure are maintained in part by an intimate balance between the L-arginine-metabolizing enzymes nitric oxide synthase (NOS) and arginase. Asymmetric dimethylarginine (ADMA) is a competitive endogenous inhibitor of NOS. The role of ADMA in the regulation of NOS and arginase in the airways has not yet been explored. Our objective was to investigate the role of ADMA in lung physiology. A murine model of continuous subcutaneous ADMA infusion via osmotic minipump was used for assessment of elevated ADMA in vivo, and primary lung fibroblasts were used for in vitro assessments. Two weeks after minipump placement, animals were anesthetized and mechanically ventilated, and lung mechanical responses were evaluated. Lungs were assessed histologically and biochemically for collagen content, arginase activity, and arginase protein levels. Lung lavage fluid was assessed for cellularity, nitrite, urea, and cytokine concentrations. ADMA infusion resulted in significantly enhanced lung resistance and decreased dynamic compliance in response to methacholine. These physiologic changes were associated with significantly increased lung collagen content in the absence of inflammation. Significant decreases in lung fluid nitrite were accompanied by elevated lung fluid urea and arginase activity in lung homogenates. These changes were reversed in mice 4 weeks after completion of ADMA administration. In addition, treatment of primary mouse lung fibroblasts with ADMA stimulated arginase activity and collagen formation in vitro. These data support the idea that ADMA may play a role in airway diseases, including asthma and pulmonary fibrosis, through NOS inhibition and enhancement of arginase activity.

Peripheral blood mononuclear cell NF-kappaB p105 mRNA decreases during asthmatic attacks

BACKGROUND

NF-kappaB is a transcription factor involved in expression of many inflammatory cytokines, chemical transmitters, and adhesion molecules. It has been reported to play a major role in the pathogenesis of asthma. NF-kappaB p50, which is the actual subunit that results from the cleavage of p105, is required for the induction of eosinophilia via IL-5 and chemokines.

METHODS

The subjects were 10 patients with a mean age of 59.3 years (14-82 years). NF-kappaB p105 mRNA in peripheral blood mononuclear cells during the presence or absence of asthmatic attacks was investigated. Total RNA was extracted from peripheral blood mononuclear cells. After cDNA was synthesized using random primers, NF-kappaB p105 mRNA level was measured by real-time polymerase chain reaction.

RESULTS

The NF-kappaB p105 mRNA level in peripheral blood mononuclear cells was lower during asthmatic attacks than in the absence of attacks, showing a significant difference (Wilcoxon's signed rank test: p<0.01).

CONCLUSIONS

A drop in NF-kappaB p105 during an asthma attack could result in increased NF-kappaB activity. There is a possibility that a change in the NF-kappaB p105 mRNA level might indicate some pathogenetic state in bronchial asthma attacks.

Asymmetric dimethylarginine induces oxidative and nitrosative stress in murine lung epithelial cells

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) produced by epithelial and inflammatory cells are key mediators of the chronic airway inflammation of asthma. Low L-arginine levels can result in the uncoupling of nitric oxide synthase (NOS) leading to production of both ROS and RNS. Asymmetric dimethylarginine (ADMA) is a competitive endogenous inhibitor of all NOS isoforms and has been demonstrated to inhibit NO formation and increase oxidative stress in vascular endothelial and smooth muscle cells. The effect of ADMA on inducible NOS (iNOS) activity in epithelial cells has not been explored. In this study, we investigated whether addition of exogenous ADMA alters the generation of NO and superoxide anion (O2-), leading to peroxynitrite (ONOO-) formation in a mouse epithelial cell line. In stimulated LA-4 cells, ADMA dose-dependently inhibited nitrite accumulation after 24 h of treatment. In addition, ADMA concentrations as low as 10 microM induced rapid increases in O2- production as measured by dihydroethidium oxidation. Furthermore, using dihydrorhodamine to monitor ONOO- formation, ADMA caused a dose-dependent increase in ONOO- after treatment for 24 h. Similar effects of ADMA were seen using purified iNOS protein in a cell-free system. Together, these data indicate that elevated ADMA may contribute to the production of ROS and RNS in airway inflammation.

Modulation of nitric oxide pathways: therapeutic potential in asthma and chronic obstructive pulmonary disease

Nitric oxide (NO) is present in the exhaled breath of humans and other mammalian species. It is generated in the lower airways by enzymes of the nitric oxide synthase (NOS) family, although nonenzymatic synthesis and consumptive processes may also influence levels of NO in exhaled breath. The biological properties of NO in the airways are multiple, complex, and bidirectional. Under physiological conditions, NO appears to play a homeostatic bronchoprotective role. However, its proinflammatory properties could also potentially cause tissue injury and contribute to airway dysfunction in disease states such as asthma and chronic obstructive pulmonary disease (COPD). This article will review the physiological and pathophysiological roles of NO in the airways, discuss the rationale for the use of drugs that modulate NO pathways--nitric oxide synthase inhibitors and NO donors--to treat inflammatory airway diseases, and attempt to predict the likely therapeutic benefit of such agents.

Exposure of Brown Norway Rats to Diesel Exhaust Particles Prior to Ovalbumin (OVA) Sensitization Elicits IgE Adjuvant Activity but Attenuates OVA-Induced Airway Inflammation

Exposure to diesel exhaust particles (DEP) during the sensitization process has been shown to increase antigen-specific IgE production and aggravate allergic airway inflammation in human and animal models. In this study, we evaluated the effect of short-term DEP exposure on ovalbumin (OVA)-mediated responses using a post-sensitization model. Brown Norway rats were first exposed to filtered air or DEP (20.6 +/- 2.7 mg/m3) for 4 h/day for five consecutive days. One day after the final air or DEP exposure (day 1), rats were sensitized with aerosolized OVA (40.5 +/- 6.3 mg/m3), and then again on days 8 and 15, challenged with OVA on day 29, and sacrificed on days 9 or 30, 24 h after the second OVA exposure or the final OVA challenge, respectively. Control animals received aerosolized saline instead of OVA. DEP were shown to elicit an adjuvant effect on the production of antigen-specific IgE and IgG on day 30. At both time points, no significant airway inflammatory responses and lung injury were found for DEP exposure alone. However, the OVA-induced inflammatory cell infiltration, acellular lactate dehydrogenase activity and albumin content in bronchoalveolar lavage (BAL) fluid, and numbers of T cells and their CD4+ and CD8+ subsets in lung-draining lymph nodes were markedly reduced by DEP on day 30 compared with the air-plus-OVA exposure group. The OVA-induced nitric oxide (NO) in the BAL fluid and production of NO, interleukin (IL)-10, and IL-12 by alveolar macrophages (AM) were also significantly lowered by DEP on day 30 as well as day 9. DEP or OVA alone decreased intracellular glutathione (GSH) in AM and lymphocytes on days 9 and 30. The combined DEP and OVA exposure resulted in further depletion of GSH in both cell types. These results show that short-term DEP exposure prior to sensitization had a delayed effect on enhancement of the sensitization in terms of allergen-specific IgE and IgG production, but caused an attenuation of the allergen-induced airway inflammatory responses.

Effect of diesel exhaust particles on allergic reactions and airway responsiveness in ovalbumin-sensitized brown Norway rats

We have previously demonstrated that exposure to diesel exhaust particles (DEP) prior to ovalbumin (OVA) sensitization in rats reduced OVA-induced airway inflammation. In the present study, Brown Norway rats were first sensitized to OVA (42.3 +/- 5.7 mg/m3) for 30 min on days 1, 8, and 15, then exposed to filtered air or DEP (22.7 +/- 2.5 mg/m3) for 4 h/day on days 24-28, and challenged with OVA on day 29. Airway responsiveness was examined on day 30, and animals were sacrificed on day 31. Ovalbumin sensitization and challenge resulted in a significant infiltration of neutrophils, lymphocytes, and eosinophils into the lung, elevated presence of CD4+ and CD8+ T lymphocytes in lung draining lymph nodes, and increased production of serum OVA-specific immunoglobulin (Ig)E and IgG. Diesel exhaust particles pre-exposure augmented OVA-induced production of allergen-specific IgE and IgG and pulmonary inflammation characterized by marked increases in T lymphocytes and infiltration of eosinophils after OVA challenge, whereas DEP alone did not have these effects. Although OVA-sensitized rats showed modest response to methacholine challenge, it was the combined DEP and OVA exposure that produced significant airway hyperresponsiveness in this animal model. The effect of DEP pre-exposure on OVA-induced immune responses correlated with an interactive effect of DEP with OVA on increased production of reactive oxygen species (ROS) and nitric oxide (NO) by alveolar macrophages (AM) and alveolar type II (ATII) cells, NO levels in bronchoalveolar lavage fluid, the induction of inducible NO synthase expression in AM and ATII cells, and a depletion of total intracellular glutathione (GSH) in AM and lymphocytes. These results show that DEP pre-exposure exacerbates the allergic responses to the subsequent challenge with OVA in OVA-sensitized rats. This DEP effect may be, at least partially, attributed to the elevated generation of ROS in AM and ATII cells, a depletion of GSH in AM and lymphocytes, and an increase in AM and ATII cell production of NO.

The effect of N-acetylcysteine on Clara cells and Clara cell 16 kDa protein in a murine model of allergen-induced airway inflammation

OBJECTIVE

The aim of this study was to investigate the number of Clara cells and the production and secretion of Clara cell 16 kDa protein (CC16) in a murine model of allergen-induced airway inflammation, as well as the effects of N-acetylcysteine (NAC) on CC16 and Clara cell numbers, in order to determine the mechanism of the anti-inflammatory effect of NAC.

METHODOLOGY

BALB/c mice were divided into control, ovalbumin (OVA) and NAC groups. An allergen-induced airway inflammation model (OVA group) was established by sensitizing and challenging mice with OVA. NAC was administered as an oral treatment. The number of Clara cells and the production of CC16 were determined by immunohistochemistry. The CC16 levels in bronchoalveolar lavage fluid (BALF) were determined by Western blotting.

RESULTS

The proportion of Clara cells in terminal and respiratory bronchioles significantly decreased in the OVA group compared to the control group (P < 0.01). NAC treatment did not change the proportion of Clara cells in the OVA group (P > 0.05). CC16 production by Clara cells in the OVA groups was significantly lower than that of the control group (P < 0.01), but was elevated following NAC treatment (P < 0.05). The CC16 level in BALF of the OVA group was lower than that of the control group (P < 0.01), but was elevated by NAC treatment (P < 0.05). NAC reduced the total number of white cells and the percentage of eosinophils in BALF. Moreover, it inhibited airway inflammation.

CONCLUSIONS

The number of Clara cells and the production and secretion of CC16 were reduced in a murine model of allergen-induced airway inflammation. Antioxidants can enhance the expression of CC16, which might be a mechanism by which they suppress airway inflammation.

Enhanced nitric oxide production associated with airway hyporesponsiveness in the absence of IL-10

Interleukin (IL)-10 is an anti-inflammatory cytokine implicated in the regulation of airway inflammation in asthma. Among other activities, IL-10 suppresses production of nitric oxide (NO); consequently, its absence may permit increased NO production, which can affect airway smooth muscle contractility. Therefore, we investigated airway reactivity (AR) in response to methacholine (MCh) in IL-10 knockout (-/-) mice compared with wild-type C57BL/6 (C57) mice, in which airway NO production was measured as exhaled NO (E(NO)), and NO production was altered with administration of either NO synthase (NOS)-specific inhibitors or recombinant murine (rm)IL-10. AR, measured as enhanced pause in vivo, and tracheal ring tension in vitro were lower in IL-10(-/-) mice by 25-50%, which was associated with elevated E(NO) levels (13 vs. 7 ppb). Administration of NOS inhibitors N(G)-nitro-L-arginine methyl ester (8 mg/kg ip) or L-N(6)-(1-iminoethyl)-lysine (3 mg/kg ip) to IL-10(-/-) mice decreased E(NO) by an average of 50%, which was associated with increased AR, to levels similar to C57 mice. E(NO) in IL-10(-/-) mice decreased in a dose-dependent fashion in response to administered rmIL-10, to levels similar to C57 mice (7 ppb), which was associated with a 30% increment in AR. Thus increased NO production in the absence of IL-10, decreased AR, which was reversed with inhibition of NO, either by inhibition of NOS, or with reconstitution of IL-10. These findings suggest that airway NO production can modulate airway smooth muscle contractility, resulting in airway hyporesponsiveness when IL-10 is absent.

Nuclear factor kappa B activation in human cord blood mononuclear cells

The immunologic signals participating in immune responses early in life have not been completely elucidated. Regarding the characterization of neonatal cells, little is known concerning the activity of transcription factor nuclear factor kappa B (NF-kappaB), which regulates inflammatory genes and cytokine production. The aim of this study was to characterize NF-kappaB activation in cord blood mononuclear cells (CBMC). We analyzed the potential association of NF-kappaB activity with lymphocyte proliferation and influences on cytokine secretion in the early immune system. To determine the contribution of a disease whereby inheritance may impact neonatal immunity, we assessed the influence of maternal allergic disease on NF-kappaB regulation and cytokine secretion. CBMC from healthy newborns were isolated and stimulated with mitogen (n = 28). Nuclear extracts were analyzed by electrophoretic mobility shift assay, cytokine secretion by ELISA. FISH analysis excluded relevant maternal contamination of CBMC. All samples showed a positive lymphoproliferative response, and NF-kappaB activity was both increased and decreased after mitogen stimulation. Increased NF-kappaB activation was significantly associated with decreased TNF-alpha secretion (median 6.1 versus 50.3 pg/mL) in unstimulated CBMC. Mitogen stimulation resulted in increased NF-kappaB activity with a trend to increased IL-13 production. Maternal allergic disease was associated with higher TNF-alpha (median 982 versus 173 pg/mL) and IL-13 secretion (median 1328 versus 1120 pg/mL) after mitogen stimulation. Together, NF-kappaB activity is differentially activated in cord blood and associated with a distinct cytokine pattern. Whether differential NF-kappaB activity in cord blood is related to the subsequent development of immune diseases requires further investigation.

Nitric oxide synthase inhibition: therapeutic potential in asthma

Nitric oxide (NO) is synthesized from L-arginine in the human respiratory tract by enzymes of the NO synthase (NOS) family. Levels of NO in exhaled air are increased in asthma, and measurement of exhaled NO has been advocated as a noninvasive tool to monitor the underlying inflammatory process. However, the relation of NO to disease pathophysiology is uncertain, and in particular the fundamental question of whether it should be viewed primarily as beneficial or harmful remains unanswered. Exogenously administered NO has both bronchodilator and bronchoprotective properties. Although it is unlikely that NO is an important regulator of basal airway tone, there is good evidence that endogenous NO release exerts a protective effect against various bronchoconstrictor stimuli. This response is thought to involve one or both of the constitutive NOS isoforms, endothelial NOS (eNOS) and neuronal NOS (nNOS). Therefore, inhibition of these enzymes is unlikely to be therapeutically useful in asthma and indeed may worsen disease control. On the other hand, the high concentrations of NO in asthma, which are believed to reflect upregulation of inducible NOS (iNOS) by proinflammatory cytokines, may produce various deleterious effects. These include increased vascular permeability, damage to the airway epithelium, and promotion of inflammatory cell infiltration. However, the possible effects of iNOS inhibition on allergic inflammation in asthma have not yet been described and studies in animal models have yielded inconsistent findings. Thus, the evidence to suggest that inhibition of iNOS would be a useful therapeutic strategy in asthma is limited at present. More definitive information will require studies combining agents that potently and specifically target individual NOS isoforms with direct measurement of inflammatory markers.

Subfertility, Uterine Hypoplasia, and Partial Progesterone Resistance in Mice Lacking the Krüppel-like Factor 9/Basic Transcription Element-binding Protein-1 (Bteb1) Gene

Progesterone receptor (PR), a ligand-activated transcription factor, is a key regulator of cellular proliferation and differentiation in reproductive tissues. The transcriptional activity of PR is influenced by co-regulatory proteins typically expressed in a tissue- and cell-specific fashion. We previously demonstrated that basic transcription element-binding protein-1 (BTEB1), a member of the Sp/Krüppel-like family of transcription factors, functionally interacts with the two PR isoforms, PR-A and PR-B, to mediate progestin sensitivity of target genes in endometrial epithelial cells in vitro. Here we report that ablation of the Bteb1 gene in female mice results in uterine hypoplasia, reduced litter size, and increased incidence of neonatal deaths in offspring. The reduced litter size is solely a maternal genotype effect and results from fewer numbers of implantation sites, rather than defects in ovulation. In the early pregnant uterus, Bteb1 expression in stromal cells temporally coincides with PR-A isoform-dependent decidual formation at the time of implantation. Expression of two implantation-specific genes, Hoxa10 and cyclin D3, was decreased in uteri of early pregnant Bteb1-null mutants, whereas that of Bteb3, a related family member, was increased, the latter possibly compensating for the loss of Bteb1. Progesterone responsiveness of several uterine genes was altered with Bteb1-null mutation. These results identify Bteb1 as a functionally relevant PR-interacting protein and suggest its selective modulation of cellular processes that are regulated by PR-A in the uterine stroma.

Effect of an inhibitor of Jun N-terminal protein kinase, SP600125, in single allergen challenge in sensitized rats

Jun N-terminal kinase (JNK) has been implicated in the pathogenesis of inflammatory diseases including asthma. We examined the effect of SP600125 (anthra [1,9-cd] pyrazol-6 (2H)-one), a novel inhibitor of JNK in a model of asthma. Brown-Norway rats were sensitized to ovalbumin and treated with SP600125 intraperitoneally (90 mg/kg in total). SP600125 inhibited allergen-induced, increased activity of phosphorylated c-jun but not of phosphorylated-MAPKAPK2, indicative of activation of p38 MAPK, in the lung. SP600125 inhibited macrophage (P < 0.04), lymphocyte (P < 0.05), eosinophil (P < 0.04) and neutrophil (P < 0.005) numbers in bronchoalveolar lavage. Eosinophil and T-cell accumulation in the airways, mRNA expression for interleukin-1beta, tumour necrosis factor-beta, interleukin-3, interleukin-4 and interleukin-5, serum levels of allergen-specific immunoglobulin E and bronchial hyperresponsiveness were not affected by SP600125. Selective inhibition of JNK reduced inflammatory cell egress into the airway lumen after single allergen exposure. The role of JNK mitogen-activated protein kinase activation may be limited in the pathogenesis of bronchial hyperresponsiveness after single allergen exposure.

Changes in the expression of NO synthase isoforms after ozone: the effects of allergen exposure

Background

The functional role of nitric oxide (NO) and various nitric oxide synthase (NOS) isoforms in asthma remains unclear.

Objective

This study investigated the effects of ozone and ovalbumin (OVA) exposure on NOS isoforms.

Methods

The expression of inducible NOS (iNOS), neuronal NOS (nNOS), and endothelial NOS (eNOS) in lung tissue was measured. Enhanced pause (P_enh) was measured as a marker of airway obstruction. Nitrate and nitrite in bronchoalveolar lavage (BAL) fluid were measured using a modified Griess reaction.

Results

The nitrate concentration in BAL fluid from the OVA-sensitized/ozone-exposed/OVA-challenged group was greater than that of the OVA-sensitized/saline-challenged group. Methacholine-induced P_enh was increased in the OVA-sensitized/ozone-exposed/OVA-challenged group, with a shift in the dose-response curve to the left, compared with the OVA-sensitized/saline-challenged group. The levels of nNOS and eNOS were increased significantly in the OVA-sensitized/ozone-exposed/OVA-challenged group and the iNOS levels were reduced compared with the OVA-sensitized/saline-challenged group.

Conclusion

In mice, ozone is associated with increases in lung eNOS and nNOS, and decreases in iNOS. None of these enzymes are further affected by allergens, suggesting that the NOS isoforms play different roles in airway inflammation after ozone exposure.

Nuclear factor-kappaB: its role in health and disease

Nuclear factor-kappaB (NF-kappaB) is a major transcription factor that plays an essential role in several aspects of human health including the development of innate and adaptive immunity. The dysregulation of NF-kappaB is associated with many disease states such as AIDS, atherosclerosis, asthma, arthritis, cancer, diabetes, inflammatory bowel disease, muscular dystrophy, stroke, and viral infections. Recent evidence also suggests that the dysfunction of NF-kappaB is a major mediator of some human genetic disorders. Appropriate regulation and control of NF-kappaB activity, which can be achieved by gene modification or pharmacological strategies, would provide a potential approach for the management of NF-kappaB related human diseases. This review summarizes the current knowledge of the physiological and pathophysiological functions of NF-kappaB and its possible role as a target of therapeutic intervention

Selective interactions of Kruppel-like factor 9/basic transcription element-binding protein with progesterone receptor isoforms A and B determine transcriptional activity of progesterone-responsive genes in endometrial epithelial cells

The Sp/KLF transcription factor basic transcription element-binding protein (BTEB1) regulates gene transcription by binding to GC-rich sequence motifs present in the promoters of numerous tissue-specific as well as housekeeping genes. Similar to other members of this family, BTEB1 can act as a transactivator or transrepressor depending on cell and promoter context, although the molecular mechanism underlying these distinct activities remains unclear. Here we report that BTEB1 can mediate signaling pathways involving the nuclear receptor for the steroid hormone progesterone in endometrial epithelial cells by its selective interaction with the progesterone receptor (PR) isoforms, PR-A and PR-B. Functional interaction with ligand-activated PR-B resulted in superactivation of PR-B transactivity, facilitated the recruitment of the transcriptional integrator CREB-binding protein within the PR-dimer, and was dependent on the structure of the ligand bound by PR-B. By contrast, BTEB1 did not influence agonist-bound PR-A transactivity, although it augmented PR-A inhibition of PR-B-mediated transactivation as well as potentiated ligand-independent PR-A transcriptional activity in the presence of CREB-binding protein. We also demonstrate similar positive modulatory actions of BTEB1-related family members Krüppel-like family (KLF) 13/FKLF2/BTEB3 and Sp1 on PR-B transactivity. Further, we provide support for the potential significance of the selective functional interactions of PR isoforms with BTEB1 in the peri-implantation uterus using mouse and pig models and in the breast cancer cell lines MCF-7 and T47D. Our results suggest a novel mechanism for the divergent physiological consequences of PR-A and PR-B on progesterone-dependent gene transcription in the uterus involving select KLF members.

Pharmacological assessment of the nitric-oxide synthase isoform involved in eosinophilic inflammation in a rat model of sephadex-induced airway inflammation

Excessive local production of nitric oxide (NO) has been suggested to play a role in rodent models of airway inflammation and in pulmonary diseases such as asthma. However, even given the plethora of data available including gene expression data, pharmacological data, and gene deletion studies in animal models, it is still not clear which nitric-oxide synthase (NOS) isoform is involved in eosinophilic airway inflammation. In this rat study, the nonselective NOS inhibitor L-NAME (N(G)-nitro-L-arginine methyl ester), but not a selective inducible NOS (iNOS) inhibitor 1400W (N-3-(aminomethyl)benzyl)acetamidine), impacted on Sephadex-induced inflammation by significantly inhibiting lung edema, eosinophil infiltration, tumor necrosis factor alpha, interleukin-13, and eotaxin levels in the lung tissue. Furthermore, iNOS gene expression was not induced following Sephadex administration, which confirms that iNOS does not play a role in this model. To demonstrate that this phenomenon was not restricted to this model of asthma, L-NAME, but not 1400W, was shown to reduce eosinophilia in an antigen-induced model. However, in contrast to the Sephadex model, there was an induction of iNOS gene expression after antigen challenge. In a model of aerosolized lipopolysaccharide-induced inflammation, where iNOS gene expression is increased, 1400W inhibited the increased neutrophilia. These data suggest that the compound has been administered using an appropriate dosing regimen for iNOS inhibition in the rat lung. In conclusion, it appears that constitutive, not inducible, NOS isoforms are important in NO production in models of allergic inflammation, which questions whether there is a role for iNOS inhibitors as therapy for the treatment of asthma.

Nuclear factor-kappaB inhibitors abolish hypoxic vasoconstriction in sheep-isolated pulmonary arteries

The aim of this study was to determine the role of nuclear factor-kappaB (NF-kappaB) in hypoxic constriction of isolated pulmonary arteries. Rings were suspended in an organ bath filled with Krebs-Henseleit solution and isometric contractions were recorded continuously. Hypoxia (%95 N(2)-%5 CO(2)) had no marked effect on resting force in artery rings. However, hypoxia caused further contractions in serotonin-precontracted arteries. Hypoxia-induced vasoconstrictions were abolished by preincubation with NF-kappaB inhibitors, pyrrolidine dithiocarbamate (100 microM) or pyrithione (10 microM). These results suggest that reactive oxygen species and/or NF-kappaB activation may be involved in the hypoxia-induced vasoconstriction in sheep-isolated pulmonary arteries.

Role of nitric oxide in allergic inflammation and bronchial hyperresponsiveness

The role of nitric oxide (NO) in allergic inflammation and bronchial hyperresponsiveness is unclear. We studied a selective prodrug nitric oxide synthase (NOS)-2 inhibitor, L-N(6)-(1-iminoethyl)lysine 5-tetrazole amide (SC-51). In ovalbumin-sensitized and challenged rats, exhaled NO levels increased by 3 h following challenge (3.73 +/- 0.74 ppb; P < 0.05), peaking at 9 h (11.0 +/- 2.75; P < 0.01) compared to saline controls (1.87 +/- 0.26; P < 0.05 and 2.81 +/- 0.18; P < 0.01). Immunoreactive lung NOS2 expression was increased in ovalbumin-challenged rats compared with ovalbumin-sensitized, saline-challenged rats at 8 h post-challenge. SC-51 (10 mg/kg; p.o.) inhibited allergen-induced increase in exhaled NO levels to 1.3 +/- 0.17 ppb. SC-51 inhibited bronchial hyperresponsiveness in ovalbumin-sensitized and challenged rats (P < 0.05). In sensitized non-exposed rats, SC-51 increased bronchial responsiveness (P < 0.05). SC-51 reduced the allergen-induced increase in bronchoalveolar lavage neutrophils, but caused a nonsignificant reduction in bronchial mucosal eosinophil numbers. NO generated through NOS2 contributes to allergen-induced bronchial hyperresponsiveness but not to bronchial eosinophilia, indicating that these are independently expressed.

Effectiveness of oral N -acetylcysteine in a rat experimental model of asthma

Oxidative stress appears to be relevant to asthma pathogenesis. Therefore, the effectiveness of the antioxidant N -acetylcysteine was examined on antigen-induced pulmonary responses in sensitized Brown-Norway rats. N -acetylcysteine (oral, 1 mmol kg(-1)per day for 7 days before challenge) did not reduce the immediate bronchospasm that followed aerosol antigen exposure but prevented airway hyperreactivity to 5-hydroxytryptamine at 24 h after antigen challenge, and reduced the eosinophils (from 0.178 +/- 0.038 in the absence to 0.064 +/- 0.020 x10(6)cells ml(-1)in the presence of N -acetylcysteine;P< 0.05), and Evans blue dye extravasation in bronchoalveolar lavage fluid. Taurine levels in bronchoalveolar lavage fluid from antigen-challenged rats were higher than control values but treatment with N -acetylcysteine failed to further increase these augmented levels. In conclusion, oral N -acetylcysteine showed beneficial effects in an in vivo model of experimental asthma, which confirm and extend the previous positive findings obtained in other models of lung injury.

Increased pulmonary activation of nuclear factor-kappaB (NF-kappaB) in foals inoculated with Rhodococcus equi is associated with increased expression of inflammatory cytokines

Previous studies revealed that foals inoculated with virulent Rhodococcus equi had significantly higher pulmonary levels of interleukin-1beta, interleukin-12 p40, interferon-gamma, and tumor necrosis factor-alpha mRNA compared to foals inoculated with an avirulent plasmid-cured derivative. The purpose of this study was to determine if the increases in cytokine expression were associated with increased pulmonary activation of nuclear factor-kappaB (NF-kappaB). Electrophoretic mobility shift assays were performed on pulmonary nuclear protein extracted from foals treated with phosphate-buffered saline, or inoculated with either virulent or avirulent R. equi. NF-kappaB activation was increased in the nuclear extracts from foals inoculated with virulent R. equi at 14 days after inoculation when increased cytokine expression was also observed. Southwestern histochemistry revealed activated NF-kappaB in multinucleated giant cells that often contained bacteria. These results indicate that the cytokine response to R. equi is at least partially mediated by NF-kappaB activation.

Effects of taurine on pulmonary responses to antigen in sensitized Brown-Norway rats

Oxidative stress appears relevant to asthma. Therefore, the effects of the antioxidant taurine (oral, 1 and 3 mmol x kg(-1) x day(-1) for 7 days before challenge) were examined on antigen-induced responses in sensitized Brown-Norway rats. Taurine did not reduce the bronchospasm produced by aerosol antigen but prevented airway hyperreactivity to 5-hydroxytryptamine (5-HT) at 24 h after antigen exposure, and reduced the eosinophils (from 0.178+/-0.038x10(6) to 0.044+/-0.014x10(6)* and 0.048+/-0.013x10(6)* cells ml(-1) in antigen and antigen+taurine 1 or 3 mmol x kg(-1), respectively; *P<0.05 vs. antigen), lipid hydroperoxides, and Evans blue dye extravasation in bronchoalveolar lavage fluid. Taurine levels in bronchoalveolar lavage fluid from antigen-challenged rats were higher than control values but treatment with taurine failed to further increase these levels. In conclusion, oral taurine showed beneficial effects in an in vivo model of experimental asthma, which confirm and extend the previous positive findings obtained in other models of lung injury.

Reactive nitrogen and oxygen species in airway inflammation

The free radical nitric oxide (NO) is an important mediator of many biological processes. Interestingly, the molecule appears to be a two-edged sword. Apart from NO having a function as a paracrine messenger, NO-derived oxidants are important weapons against invading pathogens. The role of NO in the airways is similarly ambiguous. Besides the task as a bronchodilator, NO and its derivatives play a role in the pathophysiology of asthma via their putative damaging effects on the airways. This deleterious effect can be increased by a nitrosative response to respiratory tract infections, since both the infectious agent and the host may suffer from the consequent nitrosative stress. Interestingly, respiratory infections can also compromise the beneficial (bronchodilator) effects of NO. This paper gives an overview on NO and its derivatives in the pathophysiology of airway inflammation.

Decreased pulmonary and tracheal smooth muscle expression and activity of type 1 nitric oxide synthase (nNOS) after ovalbumin immunization and multiple aerosol challenge in guinea pigs

Pharmacological evidence supports a role of a transient decreased endogenous nitric oxide (NO) synthesis in ovalbumin (OVA)-induced early airway hyperresponsiveness in guinea pigs. However, no data are available regarding the expression and activity of the constitutive NO synthases (cNOS; NOS1 and NOS3, nNOS and eNOS, respectively) in this model. Therefore, we evaluated cNOS activity (conversion of L-[3H]arginine to L-[3H]citrulline in the presence of Ca2+ and calmodulin), nitrate and nitrite (NOx) concentration (modified Griess method), and NOS1 and NOS3 protein expression (Western blot) in lung homogenates and in the tracheal smooth muscle from OVA-immunized and multiple aerosol-challenged guinea pigs (six challenges, once daily). The expression and activity of the inducible NOS isoform (NOS2), the levels of exhaled NO, and the in vivo airway reactivity were also determined. Constitutive NOS activity and NO(x) concentration were significantly lower 6 h after the last OVA challenge as compared with saline exposure, being similar at 24 h. Expression of NOS1 paralleled cNOS activity, which was reduced 6, but not 24 h after OVA challenge. The decrease in NOS1 expression was accompanied by a significant decrease in the amounts of exhaled NO and by a maximal airway hyperresponsiveness to histamine. The levels of NOS3 were not modified at the two time points evaluated, and no NOS2 expression and activity were found at any time point. Similar modifications were observed in the tracheal smooth muscle. We conclude that OVA stimulation in immunized guinea pigs induced a transient reduction in NOS1 protein expression and activity in the respiratory system, which probably participates in airway hyperresponsiveness.

Allergic airway hyperresponsiveness and eosinophil infiltration is reduced by a selective iNOS inhibitor, 1400W, in mice

Nitric oxide (NO) hyperproduction has been reported in asthmatic airways and may contribute to airway inflammatory responses. The purpose of this study was to examine the role of NO via inducible NO synthase (iNOS) in allergic airway inflammation using a selective iNOS inhibitor, N-[3-(aminomethyl)benzyl] acetamidine (1400W), in ovalbumin (OVA)-sensitized Balb/c mice. Sensitized animals were challenged with aerosolized 0.5% OVA for 1 h on two occasions 4 h apart. 1400W or the vehicle was administered by osmotic mini-pump from 2 h before to 24 h after OVA challenge. Twenty-four hours after OVA challenge, the vehicle-treated mice showed a significant airway hyperresponsiveness to intravenous methacholine (P<0.05) as well as an influx of eosinophils into the airways (P<0.05). iNOS immunoreactivity was obvious in the epithelial and, to a lesser extent, the infiltrated inflammatory cells. iNOS protein in the airway assessed by Western blotting also increased. Pretreatment with 1400W almost completely abolished the OVA-induced airway hyperresponsiveness and to a lesser extent eosinophil accumulation into the airways. These results suggest that NO synthesized by iNOS may participate in airway hyperresponsiveness and eosinophil infiltration into the airways after allergic reaction.

Exhaled nitric oxide: a novel biomarker of adverse respiratory health effects in epidemiological studies

The sampling of exhaled breath is a noninvasive procedure that can be performed easily in adults, children, and patients with respiratory disease. Several studies have demonstrated increased exhaled nitric oxide in patients with pulmonary disease, including asthma. In addition, exhaled nitric oxide may be an elegant tool for monitoring of environmental health effects of air pollution and the prevalence of atopy in epidemiological surveys. Recent literature about exhaled nitric oxide is presented in this article. Technical, physiological, and behavioral confounding factors of exhaled nitric oxide measurement are outlined.

The role of nuclear factor-kappa B in pulmonary diseases

Nuclear factor-kappa B (NF-kappaB) is a family of DNA-binding protein factors that are required for transcription of most proinflammatory molecules, including adhesion molecules, enzymes, cytokines, and chemokines. NF-kappaB activation seems to be a key early event in a variety of cell and animal model systems developed to elucidate the pathobiology of lung diseases. The purpose of this short review is to describe what is known about the molecular biology of NF-kappaB and to review information that implicates NF-kappaB in the pathogenesis of lung disease, including ARDS, systemic inflammatory response syndrome, asthma, respiratory viral infections, occupational and environmental lung disease, and cystic fibrosis.

NF-κB/Rel Transcription Factors: c-Rel Promotes Airway Hyperresponsiveness and Allergic Pulmonary Inflammation

The NF-κB/Rel family of transcription factors induces many genes involved in immune and inflammatory responses. Mice with germline deletions of individual NF-κB/Rel subunits have different phenotypes, suggesting that the NF-κB/Rel transcription factors have different functions. We tested whether c-Rel promotes allergic asthma using a murine model of allergen-induced pulmonary inflammation and airway hyperresponsiveness. Our investigation focused on c-Rel, which is expressed in lymphoid cells and is important for lymphocyte activation. In response to allergen sensitization and challenge, c-Rel-deficient mice did not develop increases in pulmonary inflammation, bronchoalveolar lavage fluid eosinophilia, or total serum IgE. c-Rel deficiency also prevented the induction of airway hyperresponsiveness. Allergen-treated wild-type mice had increased DNA binding to an NF-κB consensus site. Chemokine expression was altered in allergen-treated c-Rel-deficient mice. Monocyte chemoattractant protein-1, which is regulated by NF-κB, was decreased in allergen-treated c-Rel-deficient mice relative to wild-type controls. The increase in NF-κB/Rel transcription factors after allergen challenge in wild-type mice and the decrease in allergen reactivity found in c-Rel-deficient mice indicate that c-Rel promotes allergic inflammation. Alteration of pulmonary chemokine expression in c-Rel-deficient mice may inhibit allergen-induced pulmonary inflammation and airway hyperresponsiveness.

Activators and target genes of Rel/NF-kappaB transcription factors

The vertebrate transcription factor NF-kappaB is induced by over 150 different stimuli. Active NF-kappaB, in turn, participates in the control of transcription of over 150 target genes. Because a large variety of bacteria and viruses activate NF-kappaB and because the transcription factor regulates the expression of inflammatory cytokines, chemokines, immunoreceptors, and cell adhesion molecules, NF-kappaB has often been termed a 'central mediator of the human immune response'. This article contains a complete listing of all NF-kappaB inducers and target genes described to date. The collected data argue that NF-kappaB functions more generally as a central regulator of stress responses. In addition, NF-kappaB activation blocks apoptosis in several cell types. Coupling stress responsiveness and anti-apoptotic pathways through the use of a common transcription factor may result in increased cell survival following stress insults.

Ovalbumin sensitization changes the inflammatory response to subsequent parainfluenza infection. Eosinophils mediate airway hyperresponsiveness, m(2) muscarinic receptor dysfunction, and antiviral effects

Asthma exacerbations, many of which are virus induced, are associated with airway eosinophilia. This may reflect altered inflammatory response to viruses in atopic individuals. Inhibitory M(2) muscarinic receptors (M(2)Rs) on the airway parasympathetic nerves limit acetylcholine release. Both viral infection and inhalational antigen challenge cause M(2)R dysfunction, leading to airway hyperresponsiveness. In antigen-challenged, but not virus-infected guinea pigs, M(2)R dysfunction is due to blockade of the receptors by the endogenous antagonist eosinophil major basic protein (MBP). We hypothesized that sensitization to a nonviral antigen before viral infection alters the inflammatory response to viral infection, so that M(2)R dysfunction and hyperreactivity are eosinophil mediated. Guinea pigs were sensitized to ovalbumin intraperitoneally, and 3 wk later were infected with parainfluenza. In sensitized, but not in nonsensitized animals, virus-induced hyperresponsiveness and M(2)R dysfunction were blocked by depletion of eosinophils with antibody to interleukin (IL)-5 or treatment with antibody to MBP. An additional and unexpected finding was that sensitization to ovalbumin caused a marked (80%) reduction in the viral content of the lungs. This was reversed by the antibody to IL-5, implicating a role for eosinophils in viral immunity.

Contribution of nitric oxide synthases 1, 2, and 3 to airway hyperresponsiveness and inflammation in a murine model of asthma

Asthma is a chronic disease characterized by increased airway responsiveness and airway inflammation. The functional role of nitric oxide (NO) and the various nitric oxide synthase (NOS) isoforms in human asthma is controversial. To investigate the role of NO in an established model of allergic asthma, mice with targeted deletions of the three known isoforms of NOS (NOS1, 2, and 3) were studied. Although the inducible (NOS2) isoform was significantly upregulated in the lungs of ovalbumin (OVA)-sensitized and -challenged (OVA/OVA) wild-type (WT) mice and was undetectable in similarly treated NOS2-deficient mice, airway responsiveness was not significantly different between these groups. OVA/OVA endothelial (NOS3)-deficient mice were significantly more responsive to methacholine challenge compared with similarly treated NOS1 and NOS1&3-deficient mice. Airway responsiveness in OVA/OVA neuronal (NOS1)-deficient and neuronal/endothelial (NOS1&3) double-deficient mice was significantly less than that observed in similarly treated NOS2 and WT groups. These findings demonstrate an important function for the nNOS isoform in controlling the inducibility of airway hyperresponsiveness in this model of allergic asthma.

Allergen-induced early and late asthmatic responses are not affected by inhibition of endogenous nitric oxide

Endogenous exhaled nitric oxide (NO) is increased during the late response to inhaled allergen in patients with asthma and may be bronchoprotective in asthma or have a deleterious effect when generated in excess under inflammatory conditions. To investigate this, we evaluated the effect of inhibiting endogenous NO production with nebulized NG-nitro-L-arginine methyl ester (L-NAME), a nonselective NO synthase (NOS) inhibitor, on early and late asthmatic responses to inhaled allergen in patients with mild allergic asthma. After a screening allergen challenge (AC), 22 male patients attended two visits conducted in a double-blind, randomized, placebo-controlled, crossover manner. Twelve patients demonstrating an early asthmatic response only (single responders) inhaled either L-NAME 170 mg or 0.9% saline 20 min before AC, with exhaled NO and FEV1 measured for 3 h. Ten patients demonstrating both early and late asthmatic responses (dual responders) were studied in a similar fashion but inhaled two further doses of L-NAME or placebo 3.5 and 7 h after the initial dose, with exhaled NO and FEV1 measured for 10 h. L-NAME reduced exhaled NO levels by 77 +/- 5% (p < 0.01) and 71 +/- 7% (p < 0.01) in single and dual responders, respectively, but had no significant effect on early or late asthmatic responses. Following AC in single responders, the mean (+/- SEM) maximum fall in FEV1 after L-NAME and saline was 21.2 +/- 2.9% and 23.8 +/- 3.0%, respectively, and in dual responders, 31.2 +/- 4.5% and 31.8 +/- 5. 8% during the early asthmatic responses, and 27.4 +/- 3.9% and 30.6 +/- 4.5% during the late asthmatic responses, respectively. Area under the curve (AUC) did not significantly differ. AUC0-2 h in single responders after L-NAME and saline was 20.2 +/- 3.9 and 24.9 +/- 4.4 Delta% FEV1/h, and in dual responders, 37.6 +/- 8.4 and 36.7 +/- 8.4 Delta% FEV1/h, respectively, and 106.2 +/- 18.9 and 117.1 +/- 22.4 Delta% FEV1/h, respectively, for the AUC4-10 h. This study suggests that in mild allergic asthma, endogenous NO neither protects against nor contributes to the processes underlying airway responses to inhaled allergen.

Role of endogenous nitric oxide in allergen-induced airway responses in guinea-pigs

1. Endogenous nitric oxide (NO) can be detected in exhaled air and accumulates in inflamed airways. However its physiological role has not been fully elucidated. In this study, we investigated a role for endogenous NO in allergen-induced airway responses. Sensitised guinea-pigs were treated with NG-nitro-L-arginine methyl ester L-NAME (2.0 mM) or aminoguanidine (AG) (2.0 mM) 30 min before the allergen challenge, and 3 and 4 h after the challenge. Alternatively, L-arginine (2.4 mM) treatment was performed 30 min before, and 2 and 3 h after the challenge. In all groups, ovalbumin (OVA) challenge (2 mg ml(-1) for 2 min) was performed, and airway responses, NO production, infiltration of inflammatory cells, plasma exudation and histological details were examined. 2. Allergen-challenged animals showed an immediate airway response (IAR) and a late airway response (LAR), which synchronised with an increase in exhaled NO. Treatment with L-NAME and AG did not affect IAR while they significantly blocked LAR (72% and 80% inhibition compared to vehicle) and production of NO (35% and 40% inhibition). On the other hand, treatment with L-arginine did not affect IAR but potentiated LAR (74% augmentation). 3. In bronchoalveolar lavage (BAL) fluid, allergen-induced increases in eosinophils were reduced by 48% for L-NAME treatment compared to vehicle, and increased by 56% for L-arginine treatment. 4. Treatment with L-NAME significantly decreased airway microvascular permeability to both Monastral blue (MB) and Evans blue (EB) dye (50.6% and 44% inhibition). 5. We conclude that allergen-induced LAR is closely associated with NO production, and that NO plays a critical role in inflammatory cell infiltration and plasma exudation in the allergic condition.