Hyperresponsiveness In Rats Research Articles

Eucalyptol reduces airway hyperresponsiveness in rats following cigarette smoke-exposed

BackgroundCigarette smoke is the major cause of airway inflammatory disease, including airway hyperresponsiveness. Eucalyptol (EUC), also named 1.8-cineole, is a monoterpenoid found in essential oil of medicinal plants, showing several biological effects. Hypothesis/purposeBased in the eucalyptol protective activity in respiratory diseases as asthma, our hypothesis is that eucalyptol is able to reduce the airway hyperresponsiveness and the respiratory mechanic parameters in rats exposed to cigarette smoke. Study designWistar rats were divided into control and cigarettes smoke (CS) groups. CS group was daily subjected to cigarette smoke and treated by inhalation for 15 min/day with EUC (1 mg/mL) or vehicle during 30 days. After treatment, bronchoalveolar lavage (BAL) was collected to analyze the inflammatory profile, and tracheal rings were isolated for evaluation of the airway smooth muscle hyperresponsiveness. Lung function was analyzed in vivo. MethodsThe inflammatory profile was evaluated by optical microscopy performing total (Neubauer chamber) and differential leukocyte count (smear slides stained in H&E). The hyperresponsiveness was evaluated in tracheal rings contracted with potassium chloride (KCl) carbamoylcholine (CCh), or Barium chloride (BaCl2) in presence or absence of nifedipine. The lung function (Newtonian resistance-RN) was evaluated by bronco stimulation with methacholine (MCh). ResultsBAL from CS group increased the influx of leukocyte, mainly neutrophils and macrophages compared to control group. EUC reduced by 71% this influx. The tracheal contractions induced by KCl, CCh or BaCl2 were reduced by EUC in 59%, 42% and 26%, respectively. The last one was not different of nifedipine activity. Newtonian resistance (RN) was also reduced in 37% by EUC compared to CS group. ConclusionEUC reduces the hyperresponsiveness and the airway inflammatory profile, recovering the lung function.

Pituitary Adenylate Cyclase Activating Peptide (1-38) and its analog (Acetyl-[Ala15, Ala20] PACAP 38-polyamide) reverse methacholine airway hyperresponsiveness in rats

The aim of this study was to investigate both functionally and structurally bronchodilator effects of Pituitary adenylate cyclase activating peptide (PACAP38) and acetyl-[Ala15, Ala20] PACAP38-polyamide, a potent PACAP38 analog, in rats challenged by methacholine (MeCh). Male Wistar rats were divided randomly into five groups. Groups 1 and 2 inhaled respectively aerosols of saline or increasing doses of MeCh (0.5, 1, 2.12, 4.25, 8.5, 17, 34 and 68mg/L). The other groups received terbutaline (Terb) (250 µg/rat) (10-6 M), PACAP38 (50 µg/rat) (0.1 mM) or PACAP38 analog (50 µg/rat) associated to MeCh from the dose of 4.25 mg/L. Total lung resistances (RL) were recorded before and 2 min after MeCh administration by pneumomultitest equipment. MeCh administration induced a significant and a dose-dependent increase (p<0.05) of RL compared to control rats. Terb, PACAP38 and PACAP38 analog reversed significantly the MeCh-induced bronchial constriction, smooth muscle (SM) layer thickness and bronchial lumen mucus abundance. PACAP38 analog prevents effectively bronchial smooth muscle layer thickness, mucus hypersecretion and lumen decrease. Therefore, it may constitute a potent therapeutic bronchodilator.

Pituitary Adenylate Cyclase-Activating Polypeptide Reverses Ammonium Metavanadate-Induced Airway Hyperresponsiveness in Rats.

The rate of atmospheric vanadium is constantly increasing due to fossil fuel combustion. This environmental pollution favours vanadium exposure in particular to its vanadate form, causing occupational bronchial asthma and bronchitis. Based on the well admitted bronchodilator properties of the pituitary adenylate cyclase-activating polypeptide (PACAP), we investigated the ability of this neuropeptide to reverse the vanadate-induced airway hyperresponsiveness in rats. Exposure to ammonium metavanadate aerosols (5 mg/m3/h) for 15 minutes induced 4 hours later an array of pathophysiological events, including increase of bronchial resistance and histological alterations, activation of proinflammatory alveolar macrophages, and increased oxidative stress status. Powerfully, PACAP inhalation (0.1 mM) for 10 minutes alleviated many of these deleterious effects as demonstrated by a decrease of bronchial resistance and histological restoration. PACAP reduced the level of expression of mRNA encoding inflammatory chemokines (MIP-1α, MIP-2, and KC) and cytokines (IL-1α and TNF-α) in alveolar macrophages and improved the antioxidant status. PACAP reverses the vanadate-induced airway hyperresponsiveness not only through its bronchodilator activity but also by counteracting the proinflammatory and prooxidative effects of the metal. Then, the development of stable analogs of PACAP could represent a promising therapeutic alternative for the treatment of inflammatory respiratory disorders.

Phytochemical study guided by the myorelaxant activity of the crude extract, fractions and constituent from stem bark of Hymenaea courbaril L.

Ethnopharmacological relevanceHymenaea courbaril L. (Caesalpinoideae) is used in Brazilian folk medicine to treat anemia, kidney problems, sore throat and other dysfunctions of the respiratory system, such as bronchitis and asthma, although such properties are yet to be scientifically validated. Aim of the studyIn order to give a scientific basis to support the traditional use of Hymenaea courbaril, this study was designed to evaluate antioxidant, myorelaxant and anti-inflammatory properties of the ethanol extract from stem bark and its fractions. The myorelaxant effect of astilbin, a flavonoid isolated from the bioactive ethyl acetate fraction (EAF), has also been evaluated. Material and methodsIn the present study ethanol extract from stem bark (EEHC) and fractions were analyzed using bioassay-guided fractionation. The following activities were investigated: antioxidant by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, myorelaxant on rat tracheal smooth muscle, and anti-inflammatory using ovalbumin-induced leukocytosis and airway hyperresponsiveness in rats. ResultsThe results of the present investigation show that the whole extract of Hymenaea courbaril and some of its fractions strongly scavenged DPPH radical. The extract showed myorelaxant activity on rat trachea, being EAF its highest efficient fraction. Bio-guided study allowed the isolation of astilbin, a well-known flavonoid. The activity induced by this compound indicates that it may be partly responsible for the myorelaxant effect of EAF. EAF reduced contractions that depended on divalent cation inflow through voltage-operated Ca2+ channels (VOCCs) or receptor-operated Ca2+ channels (ROCCs), but it was more potent to inhibit VOCC- than ROCC-dependent contraction induced by Ca2+ addition in ACh-enriched Ca2+-free medium. Oral pretreatment of antigen-challenged animals with EAF prevented airway hyperresponsiveness on KCl-induced contraction and reduced the number of total white cells, particularly eosinophils and neutrophils in bronchoalveolar lavage. ConclusionsThis study provided scientific basis that Hymenaea courbaril presents potential antioxidant, myorelaxant and anti-inflammatory actions, which support its use in folk medicine to treat inflammatory airway diseases.

Single-wall carbon nanotube-induced airway hyperresponsiveness in rats and a postulated mechanism of action

Inflammatory responses, oxidative stress, as well as fibrosis in lungs induced by a type of nano-sized carbon nanotubes (single-walled carbon nanotubes (SWCNTs)) have been investigated. However, studies examining the effects of SWCNTs on airway hyperresponsiveness (AHR) are not so numerous. We examined the effects of pulmonary exposure to SWCNTs on AHR and sought the underlying molecular mechanisms. Wistar rats were divided into four experimental groups and repeatedly administered vehicle or 0.02, 0.20 and 2.00 mg kg−1 body weight SWCNTs through the intratracheal route. We found that 0.20 and 2.00 mg kg−1 body weight SWCNTs in rats caused significant exacerbation of AHR. SWCNTs also amplified the lung protein levels of T helper 2 cytokines, immunoglobulin production in serum, profiles of immune cells in lungs, and levels of oxidative stress-related biomarkers in the airways, and exhibited airway remodelling. These results suggest that SWCNTs can exacerbate AHR in rats by enhancing airway inflammation and pulmonary oxidative stress.

Phosphodiesterases inhibition by Bacilli Calmette-Guérin contributes to decrease asthma in allergic rats.

Phosphodiesterases (PDE) hydrolyse intracellular cAMP and cGMP to inactive 5' monophosphates. Decreased level of cAMP is involved in the pathogenesis of asthma. We and others have shown that phosphodiesterases were upregulated in the lung of allergic rats, and Bacilli Calmette-Guérin (BCG) induced the production of cAMP in vitro. However, it is unclear how BCG's effect asthma and whether it is related to PDEs.In this study, BCG was intraperitoneally injected into male Sprague-Dawley rats sensitized and later the rats were challenged with ovabumin/pertusis. The inflammation in lungs was measured. Airway hyperresponsiveness was determined using MedLab software after intravenous methacholine challenge. Furthermore, cAMP level and adenylate cyclase activity in lungs were analyzed by ELISA, phosphodiesterases activities were analyzed by HPLC, while PDEs mRNA levels in lungs was analyzed by reverse transcription-polymerase chain reaction. Administration of BCG significantly attenuated allergen-induced lung inflammatory response and hyper responsiveness as compared with vehicle treatment. Furthermore, the levels of cAMP in lungs were significantly increased in BCG-treated allergic rats. Interestingly, administration of BCG decreased the activity of cAMP-PDE, but not adenylyl cyclase (AC), activity in lungs of animals. Furthermore, pretreatment with BCG significantly decreased the mRNA levels of PDE4A, 4C, 5 and 8, which were induced in lungs of allergic rats. BCG administration attenuated airway inflammatory response and bronchial hyper responsiveness in rats, which are the most important symptoms in asthma. The decreased PDEs mRNA and inhibited cAMP-PDE activities by BCG contribute, at least in part, prevention of allergen-induced airway inflammation and asthma in rats.

Phosphodiesterases inhibition by Bacilli Calmette-Guérin contributes to decrease asthma in allergic rats.

Phosphodiesterases (PDE) hydrolyse intracellular cAMP and cGMP to inactive 5' monophosphates. Decreased level of cAMP is involved in the pathogenesis of asthma. We and others have shown that phosphodiesterases were upregulated in the lung of allergic rats, and Bacilli Calmette-Guérin (BCG) induced the production of cAMP in vitro. However, it is unclear how BCG's effect asthma and whether it is related to PDEs.In this study, BCG was intraperitoneally injected into male Sprague-Dawley rats sensitized and later the rats were challenged with ovabumin/pertusis. The inflammation in lungs was measured. Airway hyperresponsiveness was determined using MedLab software after intravenous methacholine challenge. Furthermore, cAMP level and adenylate cyclase activity in lungs were analyzed by ELISA, phosphodiesterases activities were analyzed by HPLC, while PDEs mRNA levels in lungs was analyzed by reverse transcription-polymerase chain reaction. Administration of BCG significantly attenuated allergen-induced lung inflammatory response and hyper responsiveness as compared with vehicle treatment. Furthermore, the levels of cAMP in lungs were significantly increased in BCG-treated allergic rats. Interestingly, administration of BCG decreased the activity of cAMP-PDE, but not adenylyl cyclase (AC), activity in lungs of animals. Furthermore, pretreatment with BCG significantly decreased the mRNA levels of PDE4A, 4C, 5 and 8, which were induced in lungs of allergic rats. BCG administration attenuated airway inflammatory response and bronchial hyper responsiveness in rats, which are the most important symptoms in asthma. The decreased PDEs mRNA and inhibited cAMP-PDE activities by BCG contribute, at least in part, prevention of allergen-induced airway inflammation and asthma in rats.

Anti-asthmatic potential of chrysin on ovalbumin-induced bronchoalveolar hyperresponsiveness in rats

Context: Chrysin, a flavonoid obtained from various natural sources, has been reported to act as an anti-inflammatory and antioxidant agent. However, its anti-allergic action is not fully understood.Objective: In this study, we investigated the in vivo anti-asthmatic activity of chrysin.Materials and methods: The effects of chrysin were evaluated using ovalbumin (OVA) (two subcutaneous 1 mL injections of 20 μg) to induce bronchoalveolar hyperresponsiveness in rats. Chrysin, when administered at 3, 10, and 30 mg/kg, p.o., respectively, before OVA challenge, reduced inflammatory cell (total and differential cell count) infiltration into the lungs measured from bronchoalveolar lavage fluid as supported by lung histology.Results: The total lung injury score was reduced in a dose-dependent manner, evaluated in six different categories (infiltration of leucocytes, type of inflammatory exudates, status of bronchi, perivascular status of lung blood vessels, integrity of alveoli and activation of alveolar macrophages). Various cellular injury parameters such as alkaline phosphatase, lactate dehydrogenase, and total protein were estimated and found to be reduced by chrysin pretreatment. Further, chrysin was found to reduce nitrite concentration (NO) and lipid peroxidation, suggesting its antioxidant activity.Discussion and conclusion: Chrysin showed anti-asthmatic potential, probably due to the alteration of Th1/Th2 polarization via the suppression of inducible nitric oxide synthase, nuclear factor-κB, and activation protein.

Different effects of smoke from heavy and light cigarettes on the induction of bronchial smooth muscle hyperresponsiveness in rats

Cigarette smoking is one of the main risk factors in the development of chronic obstructive pulmonary disease (COPD). It has been suggested that an augmented agonist-induced, RhoA mediated Ca²⁺ sensitization is responsible for the enhanced bronchial smooth muscle contraction induced by cigarette smoking. In the present study, to determine whether or not these phenomena are dependent on the degree of exposure to the components of cigarette smoke, we examined the effects of exposure to mainstream smoke derived from either light or heavy cigarettes on both the contractile responsiveness and the expression of RhoA in bronchial smooth muscle. Male Wistar rats were exposed to mainstream cigarette smoke for 2 hr/day for 2 weeks. Twenty-four hr after the last cigarette smoke exposure, we measured isometrical contractions of the bronchial smooth muscle. The concentration-response curve to ACh was significantly shifted upward after heavy cigarette smoke (HCS) exposure, whereas no significant difference was observed in the case of light cigarette smoke (LCS) exposure compared with control rats. No significant difference in K⁺ responsiveness was observed between the groups. The expression of RhoA protein in bronchial preparations from rats repeatedly exposed to HCS, but not to LCS, was significantly increased as compared with that of the control animals. On the other hand, inhalation of nicotine had no effect on either the ACh- and high K⁺ depolarization-induced contractions or the expression of RhoA protein. The increased expression of RhoA seems to have an important role in the augmented contractile responses of the airways in rats, a characteristic feature of early COPD.

Angiotensin II induces hyperresponsiveness of bronchial smooth muscle via an activation of p42/44 ERK in rats

Angiotensin II (Ang II) might be an important mediator in the pathogenesis of bronchial asthma, although the mechanisms of airway hyperresponsiveness caused by Ang II are not yet clear. Whether p42/44 ERK contributes to the Ang II-elicited bronchial smooth muscle (BSM) hyperresponsiveness in rats was presently examined. The RT-PCR analyses revealed that Ang II AT(1A), AT(1B), and AT(2) receptors, angiotensinogen, angiotensin-converting enzyme, but not renin, were expressed in the lungs, trachea, and main bronchi of rats. Only a small and transient contraction was induced by the application of Ang II in the main bronchial smooth muscle; the contraction was inhibited by losartan, an AT(1) receptor antagonist. The contractions induced by carbachol (CCh), high K(+) depolarization, and sodium fluoride (NaF; a G protein activator) were augmented by pretreatment with Ang II. The BSM hyperresponsiveness induced by Ang II was abolished by losartan. Furthermore, the Ang II-induced BSM hyperresponsiveness to CCh was attenuated by pretreatment with U-0126, a p42/44 ERK kinase (MEK-1/2) inhibitor. In conclusion, Ang II-induced BSM hyperresponsiveness through the activation of p42/44 ERK may play an important role in the pathophysiology of bronchial asthma, although Ang II itself caused a small force development in the bronchial smooth muscle.

Connective tissue mast cells are the target of formaldehyde to induce tracheal hyperresponsiveness in rats: Putative role of leukotriene B 4 and nitric oxide

Formaldehyde (FA) exposure induces upper airways irritation and respiratory abnormalities, but its mechanisms are not understood. Since mast cells are widely distributed in the airways, we hypothesized that FA might modify the airways reactivity by mechanism involving their activation. Tracheal rings of rats were incubated with Dulbecco's modified medium culture containing FA (0.1 ppm) in 96-well plastic microplates in a humid atmosphere. After 30 min, 6 h, and 24–72 h, the rings were suspended in an organ bath and dose–response curve to methacholine (MCh) were determined. Incubation with FA caused a transient tracheal hyperresponsiveness to MCh that was independent from tracheal epithelium integrity. Connective tissue mast cell depletion caused by compound 48/80 or mast cell activation by the allergic reaction, before exposure of tracheal rings to FA prevented the increased responsiveness to MCh. LTB 4 concentrations were increased in the culture medium of tracheas incubated with FA for 48 h, whereas the LTB 4-receptor antagonist MK886 (1 μM) added before FA exposure rendered the tracheal rings normoreactive to MCh. In addition, FA exposure did not cause hyperresponsiveness in tracheal segments incubated with l-arginine (1 μM). We suggest that airway connective tissue mast cells constitute the target and may provide the increased LTB 4 generation as well as an elevated consumption of NO leading to tracheal hyperresponsiveness to MCh.

Oral administration of allergen extracts from Dermatophagoides farinae desensitizes specific allergen-induced inflammation and airway hyperresponsiveness in rats

Clinically sublingual immunotherapy (SLIT) by using allergen extracts effectively alleviates the symptoms of allergic rhinitis and asthma. Supposed that oral administration of high-dose of allergen extracts imitates SLIT and may prevent IgE-related responses in allergic diseases, we investigated the effects of oral administration of allergen extracts from Dermatophagoides farinae (Derf) on allergen-induced inflammation and airway hyperresponsiveness (AHR) in a model of asthmatic rat. After administration to the specific Derf-sensitized rats with Derfdrop solution containing Derf1 and Derf2 extracts derived from Derf, the effects of Derfdrop on AHR, inflammatory cell accumulation, cytokine production in the bronchoalveolar lavage fluid and lung tissue, as well as serum IgE and IgG levels were investigated. Results indicated that Derfdrop not only dose-dependently prevented the AHR in response to methacholine, but also significantly reduced the serum total and allergen-specific IgE levels, all the maximal effects were achieved at dose of 5 mg/kg/d, and were as comparable as those of dexamethasone at dose of 1.0 mg/kg/d. Furthermore, oral administration of Derfdrop not only dose-dependently elevated allergen-specific serum IgG levels and reduced total and allergen-specific IgE levels, but also normalized the imbalance between the Th1 cytokine, IFN-γ and Th2 cytokine, IL-4. Finally, oral administration of Derfdrop significantly reduced Goblet cell hyperplasia and eosinophilia in the Derf-sensitized allergic rat model. These data suggest that Derfdrop effectively improves specific allergen-induced inflammation and AHR in Derf-sensitized and -challenged rats and provide with the rationale for clinical SLIT by using Derfdrop in a specific allergen-induced asthma.

Sensitizing effects of chronic exposure and acute inhalation of ovalbumin aerosol on pulmonary C fibers in rats

The effect of ovalbumin (Ova) sensitization on pulmonary C-fiber sensitivity was investigated. Brown-Norway rats were sensitized by intraperitoneal injection of Ova followed by aerosolized Ova three times per week for 3 wk. Control rats received the vehicle. At the end of the third week, single-unit fiber activities (FA) of pulmonary C fibers were recorded in anesthetized, artificially ventilated rats. Our results showed the following: 1) Ova sensitization induced airway inflammation (infiltration of eosinophils and neutrophils) and airway hyperresponsiveness in rats; 2) baseline FA in sensitized rats was significantly higher than that in control ones; 3) similarly, the pulmonary C-fiber response to right atrial injection of capsaicin was markedly higher in sensitized rats, which were significantly amplified after the acute Ova inhalation challenge; and 4) similar patterns, but smaller magnitudes of the differences in C-fiber responses to adenosine and lung inflation, were also found between sensitized and control rats. In conclusion, Ova sensitization elevated the baseline FA and excitability of pulmonary C fibers, and the hypersensitivity was further potentiated after the acute Ova inhalation challenge in sensitized rats. Chronic allergic inflammatory reactions in the airway probably contributed to the sensitizing effect on these lung afferents.

Effects of respiratory syncytial virus infection on the airway neuronal plasticity and its relationship to the bronchial hyperresponsiveness in rats

Effects of respiratory syncytial virus infection on the airway neuronal plasticity and its relationship to the bronchial hyperresponsiveness in rats

Possible involvement of G i3 protein in augmented contraction of bronchial smooth muscle from antigen-induced airway hyperresponsive rats

To investigate a possible involvement of pertussis toxin (PTX)-sensitive heterotrimeric G proteins in the pathogenesis of airway hyperresponsiveness, the effect of PTX treatment on the augmented contractile response to acetylcholine (ACh) in bronchial smooth muscle of antigen-induced airway hyperresponsive rats was determined. In bronchial smooth muscle of airway hyperresponsive rats that were actively sensitized and repeatedly challenged with 2,4-dinitrophenylated Ascaris suum antigen, ACh-induced contractions were markedly augmented. The augmented contractile responses in the airway hyperresponsive group were significantly inhibited after treatment with PTX (1 μg/mL for 6 hr, 37°), whereas only a slight attenuation was observed in the normal control group. The level of Gα i3 (measured by immunoblotting), but not other α-subunits of G i/o family proteins, in bronchial smooth muscle of the airway hyperresponsive rats was significantly increased as compared with that of control animals. It is concluded that PTX-sensitive muscarinic contractile responses of bronchial smooth muscle might be augmented upon antigen-induced airway hyperresponsiveness in rats, probably due to an up-regulation of Gα i3 protein of bronchial smooth muscle.

Role of Mast Cells in Antigen-Induced Airway Inflammation and Bronchial Hyperresponsiveness in Rats

The participation of mast cells in the induction of antigen-induced airway inflammation and bronchial hyperresponsiveness (BHR) to acetylcholine (ACh) was investigated using pharmacological agents and mast cell-deficient rats (Ws/Ws). A significant increase in the number of leukocytes in bronchoalveolar lavage fluid (BALF) and bronchial responsiveness to ACh were observed 24 h after antigen (ovalbumin) challenge in sensitized Brown-Norway (BN) rats. Disodium cromoglycate and terfenadine did not inhibit antigen-induced airway inflammation and BHR in sensitized BN rats. In contrast, cyclosporin A (CyA), FK-506 and prednisolone significantly inhibited antigen-induced airway inflammation and BHR in sensitized BN rats. In addition, disodium cromoglycate, terfenadine and prednisolone, but not CyA and FK-506, inhibited homologous passive cutaneous anaphylaxis in rats. Furthermore, a significant increase in the number of leukocytes in BALF and BHR was also observed in Ws/Ws rats 24 h after inhalation of antigen; however, the magnitude of BHR in Ws/Ws rats was lower than that in the congenic rats. These findings suggest that mast cells play a partial role in the development of antigen-induced BHR in rats and that the induction of BHR is barely suppressed by mast cell stabilizing agents.

Involvement of haemoxygenase-1 in ozone-induced airway inflammation and hyperresponsiveness

Haemoxygenase catalyses the degradation of haem to bilirubin, and the inducible form of haemoxygenase, haemoxygenase-1, is highly induced in response to oxidative stress in vitro. The effect of haemoxygenase-1 in oxidant stress in vivo is not known. We determined the effect of exposure to ozone on haemoxygenase-1 expression, and the modulation of haemoxygenase-1 expression on ozone-induced lung neutrophilia and bronchial hyperresponsiveness in rats. Ozone caused a significant induction of lung haemoxygenase-1. Pretreatment of rats with haemoglobin, a potent inducer of haemoxygenase-1, resulted in a large induction of haemoxygenase-1 expression, and inhibited ozone-induced neutrophilia and bronchial hyperresponsiveness. Tin protoporphyrin, a competitive inhibitor of haemoxygenase, reduced the expression of haemoxygenase-1 induced by haemoglobin. It enhanced ozone-induced neutrophilia, but not the bronchial hyperresponsiveness, and reduced the protective effect of haemoglobin. Overall, there was an association between bronchial hyperresponsiveness and the neutrophilic response. These data indicate that haemoxygenase-1 plays an important role in modulating the effects of an oxidant, such as ozone in the lungs.

Gq protein level increases concurrently with antigen-induced airway hyperresponsiveness in rats

In the present study, bronchial Gq protein level of the airway hyperresponsive rats was determined by using immunoblot analysis. In the airway hyperresponsive rats that were sensitized and repeatedly antigen challenged, the in vitro bronchial responsiveness to acetylcholine was significantly enhanced as compared with that in the sensitized control group. Moreover, the bronchial contraction induced by 10 μM AlF 4 − (generated by 10 μM AlCl 3 plus 10 mM NaF) was significantly elevated after repeated antigen challenge (0.44±0.13 and1.09±0.09 g tension in the control and airway hyperresponsive groups, respectively; P<0.01). In both groups, immunoblotting with the antibody against Gαq gave a single 42 kD band. The Gαq protein levels in the airway hyperresponsive group (0.58±0.12) estimated by Gαq/β-actin ratio was significantly greater than those in the control group (0.30±0.10; P<0.05). These findings suggest that the increase in Gαq protein level may be involved in the pathogenesis of antigen-induced airway hyperresponsiveness in rats.

Inhibition of ozone-induced lung neutrophilia and nuclear factor-κB binding activity by vitamin A in rat

Vitamin A binds to retinoic acid receptors, which in turn may interact with other transcription factors. We determined its effect (2500 and 5000 IU/kg) on nuclear factor-κB binding activity in the lung, airway inflammation and bronchial hyperresponsiveness in rats exposed to ozone. Ozone (3 ppm, 3 h) caused neutrophil influx into bronchoalveolar lavage fluid (16.2±0.8×10 5 cells/ml, p<0.01) and bronchial hyperresponsiveness (−logPC 200ACh=2.54±0.19, p<0.05, compared to control animals, respectively). Vitamin A inhibited this neutrophilia dose-dependently together with the increased DNA-binding activity of nuclear factor-κB in lung extracts. Vitamin A did not affect bronchial hyperresponsiveness at both doses. Vitamin A inhibits ozone-induced neutrophilic inflammation through a reduction in nuclear factor-κB DNA binding activity.

A possible involvement of thromboxane A2and peptide leukotrienes in hyperresponsiveness of Sephadex-treated rat lung parenchyma

An augmented contraction and elevated thromboxane (TX) B2release were observed, when the isolated parenchyma from Sephadex-treated rats was stimulated by 5-hydroxytryptamine (5-HT). Release of peptide leukotrienes (pLTs) was also increased by the stimuli. In the Sephadex-induced hyperresponsiveness model, DP-1904, a novel TX synthetase inhibitor, at the concentrations of 3 × 10-7~3 × 10-6 M, reduced the augmented contraction. Also, indomethacin (3 × 10-6 M), a histamine H1antagonist and AA-2414 (10-6 M, a TXA2antagonist, significantly attenuated the hyperresponsiveness to 5-HT. ICI-198,615 (10-7 M), a leukotriene receptor antagonist, partially but significantly reduced the augmented contraction. In an ex vivo study, oral DP-1904 significantly inhibited both the augmented contraction and elevated TXB2release from Sephadex-treated rat parenchyma, but did not affect the blood eosinophilia induced by Sephadex-treatment.These results suggested that the ability to synthesize newly generated lipid mediators such as TXA2and pLTs to exogenous 5-HT was altered upward by Sephadex injection, and so could lead to augmented contraction of established hyperresponsiveness in rats.