Role of nitric oxide and superoxide anions in interleukin-1 beta-induced airway hyperresponsiveness to bradykinin

Design, synthesis and evaluation of phenylfuroxan nitric oxide-donor phenols as potential anti-diabetic agents

Both nitric oxide (NO) dysfunction and oxidative stress have been regarded as the important factors in the development and progression of diabetes and its complications. Multifunctional compounds with hypoglycemic, NO supplementation and anti-oxidation will be the promising agents for treatment of diabetes. In this study, six phenylfuroxan nitric oxide (NO) donor phenols were synthesized, which were designed via a combination approach with phenylfuroxan NO-donor and natural phenols. These novel synthetic compounds were screened in vitro for α-glucosidase inhibition, NO releasing, anti-oxidation, anti-glycation and anti-platelet aggregation activity as well as vasodilatation effects. The results exhibited that compound T5 displayed more excellent activity than other compounds. Moreover, T5 demonstrated significant hypoglycemic activity in diabetic mice and oral glucose tolerance test (OGTT) mice. T5 also showed NO releasing and anti-oxidation in diabetic mice. Based on these results, compound T5 deserves further study as potential new multifunctional anti-diabetic agent with antioxidant, NO releasing, anti-platelet aggregation and vasodilatation properties.

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.

Effect of 10 pharmacologic probes on mRNA levels of inducible nitric oxide synthetase and selected inflammatory cytokines in a rat model of acute otitis media

Ten drugs were screened for their ability to decrease inflammatory mediator (IL-6, inducible nitric oxide synthetase [iNOS], IL-1beta and monocyte chemotactic protein [MCP-1]) expression in a rat model of acute otitis media caused by Streptococcus pneumoniae. Six adult rats were randomly assigned to each of 12 groups corresponding to uninfected controls and treatments with saline, aminoguanidine, anisomycin, dexamethasone, ketorolac, L-N(G)-nitroarginine methylester, methylprednisolone, mycophenolic acid, pentoxiphylline, tacrolimus or WEB2086. Forty-eight h after the start of treatment, the ears of the animals in the 11 treatment groups were challenged with S. pneumoniae. Forty-eight h later, all animals were killed and middle ear mucosa was harvested and assayed for RNA message. Messages for IL-6, iNOS and MCP-1 were significantly increased as a result of infection. Most treatments decreased MCP-1 and four decreased IL-6 and iNOS. Tacrolimus and dexamethasone decreased IL-6, iNOS and MCP-1. These results show that pharmacological agents can modify the expression of inflammatory mediators in this model and may have clinically relevant effects.

Interleukin-1beta and tumour necrosis factor-alpha increase microvascular leakage in the guinea pig trachea

OBJECTIVE

Airway microvascular leakage is considered to be an important component of airway inflammation in asthma. In the present study we examined the effect of interleukin-1beta (IL-1beta) and tumour necrosis factor-alpha (TNFalpha) on airway microvascular leakage in vivo.

METHODOLOGY

Tracheal Evans blue extravasation was examined in an isolated tracheal segment, in anaesthetized mechanically ventilated guinea pigs. Baseline tracheal microvascular leakage was measured in five animals. As a control group for aerosol challenge, the isolated tracheal segment (n = 5) underwent saline aerosol challenge. To test whether a combination of IL-1beta (10 ng/mL) and TNFalpha (100 ng/mL) induced Evans blue extravasation, the trachea was exposed to an aerosol of these cytokines (n = 5). As a positive control the tracheal segment was challenged with histamine aerosol (5 x 10(-2) mol) (n = 3). All aerosol challenges were for 1 min.

RESULTS

TNFalpha and IL-1beta aerosol challenge significantly increased Evans blue extravasation (28.9 +/- 1.6 microg/g wet tissue, mean +/- SE) compared to saline challenge (13.8 +/- 3.0 microg/g; P < 0.05). Tracheal dye extravasation without aerosol challenge, was not significantly different from saline-challenged animals (17.5 +/- 2.9 and 13.8 +/- 3.0 microg/g, respectively). Histamine significantly increased Evans blue extravasation (50.1 +/- 4.8 microg/g; P < 0.05) compared to saline challenge.

CONCLUSION

Pro-inflammatory cytokines, TNFalpha and IL-1beta are able to induce significant microvascular leakage in the guinea pig trachea.

Reactive oxygen species as mediators in asthma

This review describes production and effects of reactive oxygen species (ROS) on airway function. ROS are important in many physiological processes but can also have detrimental effects on airway cells and tissues when produced in high quantities or during the absence of sufficient amounts of anti-oxidants. Therefore, these mediators play a prominent role in the pathogenesis of various inflammatory airway disorders, including asthma. Effects of ROS on airway function in asthma have been studied with isolated airway cells and tissues and with animal models and patients. With the use of inhibitors, transgenic animals and measurements of the release of ROS within the airways, it became clear that oxidative stress contributes to the initiation and worsening of inflammatory respiratory disorders.

Modulation of calcium homeostasis as a mechanism for altering smooth muscle responsiveness in asthma

Airway hyperresponsiveness remains a defining characteristic of asthma. Traditional views assert that airway smooth muscle is an important structural effector cell in the bronchi that modulates bronchomotor tone induced by contractile agonists. New evidence, however, suggests that abnormalities in airway smooth muscle functions, induced by variety of extracellular stimuli, may play an important role in the development of airway hyperresponsiveness. Studies using isolated bronchial preparations or cultured cells show that inflammatory mediators and cytokines may alter calcium homeostasis in airway smooth muscle and render the cells nonspecifically hyperreactive to agonists.

Contribution of bradykinin B(1) and B(2) receptors in allergen-induced bronchial hyperresponsiveness

Bradykinin (BK) is a peptide mediator generated at sites of inflammation and its effects are mediated through constitutively expressed B(2) receptor or through induction of B(1) receptors. We examined the role of these receptors in bronchial hyperresponsiveness (BHR). Brown-Norway rats sensitized with ovalbumin (OA) and Al(OH)(3) intraperitoneally, were exposed 3 wk later to either saline or OA aerosol. B(1) receptor antagonist desArg(10)[Hoe140] (200 nmol/kg or 1 micromol/kg, intraperitoneally) or B(2) receptor antagonist Hoe140 (200 nmol/kg, intraperitoneally) was administered 30 min before allergen exposure. Hoe140 had no effect on OA-induced BHR to acetylcholine (ACh) and bronchoalveolar lavage fluid (BALF) cellular profiles, but inhibited bronchoconstriction to BK (p < 0.04). At both doses, desArg(10)[Hoe140] dose-dependently inhibited allergen-induced BHR to ACh (p < 0.01), but had no effect on bronchoconstriction to BK or baseline ACh responsiveness. The inflammatory cells in BALF were not affected apart from reduced lymphocyte numbers at the highest dose. B(1) receptor mRNA expression measured by Northern analysis was increased after allergen exposure in sensitized lungs, with a peak at 2 to 6 h after exposure, whereas B(2) receptor mRNA expression remained unchanged. Newly induced BK B(1) receptors may be involved in allergen-induced BHR to ACh, whereas constitutive B(2) receptors mediate BK-induced bronchoconstriction.

Hyperresponsiveness in the human nasal airway: new targets for the treatment of allergic airway disease

Allergic rhinitis is a condition which affects over 15% of the population in the United Kingdom. The pathological process involves two stages: nasal inflammation, and the development of nasal airway hyperresponsiveness (AHR) to allergen and a number of other stimuli. This results in the amplification of any subsequent allergic reaction, contributing to the chronic allergic state. A number of different hypotheses have been proposed to explain the underlying mechanism of AHR, including a role for eosinophil-derived proteins, free radicals and neuropeptides. While there may be a number of independent pathways which can result in AHR, evidence obtained from both animal models and in vivo experiments in humans indicate that some mediators may interact with one another, resulting in AHR. Further research into these interactions may open new avenues for the pharmacological treatment of chronic allergic rhinitis, and possibly other allergic airway diseases.

Involvement of superoxide and nitric oxide on airway inflammation and hyperresponsiveness induced by diesel exhaust particles in mice

We previously demonstrated that chronic intratracheal instillation of diesel exhaust particles (DEP) induces airway inflammation and hyperresponsiveness in the mouse, and that these effects were partially reversed by the administration of superoxide dismutase (SOD). In the present study, we have investigated the involvement of superoxide in DEP-induced airway response by analyzing the localization and activity of two enzymes: (1) a superoxide producer, NADPH cytochrome P-450 reductase (P-450 reductase), and (2) a superoxide scavenger, SOD, in the lungs of the exposed mice and controls. P-450 reductase was detected mainly in ciliated cells and clara cells: its activity was increased by the repeated intratracheal instillation of DEP. While CuZn-SOD and Mn-SOD were also present in the airway epithelium, their activity was significantly decreased following DEP instillation. Exposure to DEP doubled the level of nitric oxide (NO) in the exhaled air. DEP exposure also increased the level of constitutive NO synthase (cNOS) in the airway epithelium and inducible NO synthase (iNOS) in the macrophages. Pretreatment with N-G-monomethyl L-arginine, a nonspecific inhibitor of NO synthase, significantly reduced the airway hyperresponsiveness induced by DEP. These results indicate that superoxide and NO may each contribute to the airway inflammation and hyperresponsiveness induced by the repeated intratracheal instillation of DEP in mice.

Lack of effect of nitric oxide inhibition on bronchial tone and methacholine-induced bronchoconstriction in man

The role of nitric oxide (NO) as a bronchodilator has been studied in humans with controversial results. The aim of the present study was to investigate the role of endogenous NO on bronchial tone by studying whether nitric oxide synthase (NOS) inhibition with NGnitro-L-arginine-methyl-ester (L-NAME) influences basal bronchial tone, or potentiates methacholine-induced bronchoconstriction. In a preliminary experiment in five subjects, a significant reduction in exhaled NO was found after delivering L-NAME (15 mg in saline) (from 3.9 +/- 1.2 to 2.4 +/- 1.1 nmol min-1, P < 0.05). In nine healthy non-smokers, specific airway conductance (SGAW), as a measure of airway calibre, was recorded after delivering, in a double-blind, controlled vs. placebo fashion, both nebulized L-NAME and saline, at baseline and after methacholine-induced bronchoconstriction. There was no significant difference between the baseline SGAW values before and after delivering L-NAME (0.264 +/- 0.04 and 0.267 +/- 0.05 cm H2O-1 s-1, respectively). After pre-treatment with L-NAME, SGAW values during methacholine-induced bronchoconstriction were not different in comparison to values obtained after saline inhalation. It is concluded that decreased endogenous NO does not influence bronchial tone in healthy people, nor does it modify methacholine-induced bronchoconstriction.

Mechanisms of impaired beta-adrenoceptor-induced airway relaxation by interleukin-1beta in vivo in the rat

We studied the in vivo mechanism of beta-adrenergic receptor (beta-AR) hyporesponsiveness induced by intratracheal instillation of interleukin-1beta (IL-1beta, 500 U) in Brown-Norway rats. Tracheal and bronchial smooth muscle responses were measured under isometric conditions ex vivo. Contractile responses to electrical field stimulation and to carbachol were not altered, but maximal relaxation induced by isoproterenol (10(-6)-10(-5) M) was significantly reduced 24 h after IL-1beta treatment in tracheal tissues and to a lesser extent, in the main bronchi. Radioligand binding using [125I]iodocyanopindolol revealed a 32+/-7% reduction in beta-ARs in lung tissues from IL-1beta-treated rats, without any significant changes in beta2-AR mRNA level measured by Northern blot analysis. Autoradiographic studies also showed significant reduction in beta2-AR in the airways. Isoproterenol-stimulated cyclic AMP accumulation was reduced by IL-1beta at 24 h in trachea and lung tissues. Pertussis toxin reversed this hyporesponsiveness to isoproterenol but not to forskolin in lung tissues. Western blot analysis revealed an IL-1beta-induced increase in Gi(alpha) protein expression. Thus, IL-1beta induces an attenuation of beta-AR-induced airway relaxation through mechanisms involving a reduction in beta-ARs, an increase in Gi(alpha) subunit, and a defect in adenylyl cyclase activity.