1,428 research outputs found
Rna Interference Prevents Lipopolysaccharide-Induced Preprotachykinin Gene Expression
No full textWe showed previously that lipopolysaccharide (LPS) induces noncholinergic airway hyperreactivity to capsaicin via an upregulation of tachykinin synthesis. This study was designed to test whether double-stranded preprotachykinin ( ds PPT) RNA, RNA interference (RNAi), prevents the LPS- induced alterations. First, cultured primary nodose ganglial cells of newborn Brown-Norway rats were divided into four groups: control; LPS; LPS +RNAi; and LPS+RNAi+liposome. Second, young Brown-Norway rats for the in vivo study were divided into three groups (control; LPS; and LPS+RNAi), and ds PPT RNA was microinjected bilaterally into the nodose ganglia in the LPS+RNAi group. Then, ganglial cells were collected from the culture whereas the nodose ganglia and lungs were sampled from the animals, and PPT mRNA and substance P (SP) levels were analyzed. Also, airway reactivity to capsaicin was performed in vivo. LPS induced significant increases in PPT mRNA and SP levels in vitro and in vivo and an increase in airway reactivity to capsaicin in vivo. However, ds PPT RNA, but not scrambled RNA, prevented all LPS-induced alterations. The effect of ds PPT RNA was not enhanced by liposome in vitro. Therefore, we demonstrated that the local application of RNAi prevents effectively the activation of the noncholinergic system modulating the lungs/airways
Airway Hyperresponsiveness and Remodeling in Antigen-Challenged Guinea Pigs
No full textAirway hyperresponsiveness (AHR) is the main feature of allergic subjects /animals, and its underlying mechanism is not clear. We explored whether antigen-induced AHR is associated with cytokine generation, inflammatory cell infiltration, and/or remodeling of airway smooth muscle. Guinea pigs were divided into three groups: control-1, control-2, and ovalbumin (OA). Animals in the control-1 group were not sensitized, while those in the control-2 and the OA group were sensitized with OA. Forty to forty-two days after the initial sensitization or equivalent time, animals in the control-2 group inhaled saline aerosol and those in the OA group inhaled OA aerosol for 30 min. Twenty- four h after OA challenge or equivalent time, animals in each group were further divided into two subgroups: methacholine and hyperventilation. Functional tests were carried out before and after the methacholine or hyperventilation treatment. Immediately after the functional study, bronchoalveolar lavage fluid was collected for determination of inflammatory cells and tumor necrosis factor-alpha (TNF-alpha). The trachea was then removed to determine smooth muscle mass. In both the methacholine and hyperventilation subgroups, significantly more severe airway constriction was found in the OA group, indicating OA- induced AHR. Eosinophil accumulation increased in the control-2 group and this increase was further augmented in the OA group. In addition, TNF-alpha level and smooth muscle mass significantly increased in the OA group. These results suggest that OA challenge-induced AHR is associated with increases in TNF-alpha level, cellular infiltration, and airway smooth muscle mass
Airway Resistance Due to Alveolar Gas Compression Measured by Barometric Plethysmography in Mice
No full textWe developed a method for measuring airway resistance (Raw) in mice that does not require a measurement of airway flow. An analysis of Raw induced by alveolar gas compression showed the following relationship for an animal breathing spontaneously in a closed box: Raw = AbtVb/[Vt (Ve + 0.5 Vt)] . Here Abt is the area under the box pressure-time curve during inspiration or expiration, Vb is box volume, Vt is tidal volume, and Ve is functional residual capacity (FRC). In anesthetized and conscious unrestrained mice, from experiments with both room temperature box air and body temperature humidified box air, the contributions of gas compression to the box pressure amplitude were 15 and 31% of those due to the temperature-humidity difference between box and alveolar gas. We corrected the measured Abt and Vt for temperature-humidity and gas compression effects, respectively, using a sinusoidal analysis. In anesthetized mice, Raw averaged 4.3 cmH2O·ml–1·s, fourfold greater than pulmonary resistance measured by conventional methods. In conscious mice with an assumed FRC equal to that measured in the anesthetized mice, the corrected Raw at room temperature averaged 1.9 cmH2O·ml–1·s. In both conscious mice and anesthetized mice, exposure to aerosolized methacholine with room temperature box air significantly increased Raw by around eightfold. Here we assumed that in the conscious mice both Vt and FRC remained constant. In both conscious and anesthetized mice, body temperature humidified box air reduced the methacholine-induced increase in Raw observed at room temperature. The method using the increase in Abt with bronchoconstriction provides a conservative estimate for the increase in Raw in conscious mic
Chronic Hypoxia- and Monocrotaline-Induced Elevation of Hypoxia-Inducible Factor-1 Alpha Levels and Pulmonary Hypertension
No full textA close relationship exists between hypoxia-inducible factor (HIF)-1alpha and pulmonary hypertension. The present study was carried out to explore if there are temporal alterations in HIF-1alpha levels during prolonged hypoxia and after monocrotaline (MCT) treatment. First, young Wistar rats were divided into 5 groups: control, hypoxia-1, hypoxia-2, hypoxia-3 and hypoxia-4. Hypoxic rats were placed in a closed hypobaric chamber (380 mm Hg) for a 1-week (hypoxia-1 ), 2-week (hypoxia-2), 3-week (hypoxia-3) or 5 -week (hypoxia -4) period. Second, other young Wistar rats were divided into 4 groups: control, MCT-1, MCT-2 and MCT-3. MCT-treated rats were injected subcutaneously once with MCT (60 mg/kg) for a 1-week (MCT-1), 2- week (MCT-2) or 3-week (MCT-3) period. Subsequently, pulmonary arterial pressure (Ppa) and the weight ratio of the right ventricle to the left ventricle plus the septum [RV/(LV + S)] were measured, and lungs were obtained for the determination of HIF-1alpha via Western blot analysis. Both hypoxia and MCT induced temporal increases in the Ppa, the ratio RV/( LV + S) and HIF-1alpha levels. A close relationship between the Ppa and HIF-1alpha level was found in both hypoxia-and MCT-treated animals. In addition, the PaO2 level significantly decreased in rats 1-3 weeks after MCT treatment. These results, along with previous data in the literature, suggest that both chronic hypoxia- and MCT-induced lung hypoxia activate an increase in the production of HIF-1alpha, and result in vascular remodeling and pulmonary hypertension. Copyright (C) 2004 National Science Council, ROC and S. Karger AG, Basel
Lipopolysaccharide-Induced Preprotachykinin Gene Expression and Bronchial Hyperreactivity
No full textReactive Oxygen Species in Sustained Airway Constriction Induced by Citric Acid Aerosol Inhalation
No full textOxygen Radicals in Bronchoconstriction of Guinea Pigs Elicited by Isocapnic Hyperpnea
No full textThe role of oxygen radicals in isocapnic hyperpnea-induced bronchoconstriction (HIB) of guinea pigs was investigated using scavengers of the radicals. In series 1, 50 young guinea pigs were randomly divided into seven groups: control 1, control 2, chlorisondamine, tetrodotoxin(TTX ), acute dimethylthiourea (DMTU), tachykinin depletion, and 5% CO2 in air. Animals of the control 2 group received vehicle ( saline) infusion while those of the control 1 group did not. Chlorisondamine was used to block ganglionic transmission, TTX to interrupt nerve conduction, DMTU to scavenge hydroxyl radicals, and chronic capsaicin pretreatment to deplete tachykinins. The animals in the last group were ventilated with dry 5% CO2 in air during hyperpnea. In series 2, 13 additional animals were used to test the effects of intratracheal administration of superoxide dismutase and catalase (SOD + CAT) on HIB. Each animal was anesthetized with pentobarbital sodium, cannulated with a tracheal cannula and venous catheter, paralyzed with gallamine triethiodide, and mechanically ventilated. During the baseline period, each animal was ventilated normally with humidified air. Then it was hyperventilated 15 min with a dry gas mixture of 95% O2-5% CO2, except animals in the last group of series 1. Subsequently, all animals returned to normal ventilation with humidified air for 45 min (recovery period). The maximal expiratory flow and dynamic compliance were obtained periodically during the recovery period. The isocapnic hyperpnea using 95% O2-5% CO2, but not 5% CO2 in air , caused bronchoconstriction that was significantly blocked by acute DMTU, acute SOD + CAT, and tachykinin depletion. In an additional group of six animals, acute DMTU did not significantly alter acetylcholine-induced airway constriction.(ABSTRACT TRUNCATED AT 250 WORDS)#A089308
Mast Cells in Citric Acid-Induced Cough of Guinea Pigs
No full textIt was demonstrated previously that mast cells play an important role in citric acid (CA)-induced airway constriction. To investigate the role of mast cells in CA- induced cough, three experiments were carried out in this study. In the first experiment, 59 guinea pigs were employed and we used compound 48/80 to deplete mast cells, cromolyn sodium to stabilize mast cells, MK-886 to inhibit leukotriene synthesis, pyrilamine to antagonize histamine H1 receptor, methysergide to antagonize serotonin receptor, and indomethacin to inhibit cyclooxygenase. In the second experiment, 56 compound 48/80-pretreated animals were divided into two parts; the first one was used to test the role of exogenous leukotriene ( LT) C4, while the second one to test the role of exogenous histamine in CA -induced cough. Each animal with one of the above pretreatments was exposed sequentially to saline (baseline) and CA (0.6 M) aerosol, each for 3 min. Then, cough was recorded for 12 min using a barometric body plethysmograph. In the third experiment, the activation of mast cells upon CA inhalation was investigated by determining arterial plasma histamine concentration in 17 animals. Exposure to CA induced a marked increase in cough number. Compound 48/80, cromolyn sodium, MK-886 and pyrilamine, but not indomethacin or methysergide, significantly attenuated CA-induced cough. Injection of LTC 4 or histamine caused a significant increase in CA -induced cough in compound 48/80-pretreated animals. In addition, CA inhalation caused significant increase in plasma histamine concentration, which was blocked by compound 48/80 pretreatment. These results suggest that mast cells play an important role in CA aerosol inhalation-induced cough via perhaps mediators LTs and histamine
Amiodarone-Induced Pulmonary Fibrosis in Fischer 344 Rats
No full text Amiodarone is a potent antiarrhythmic agent with a number of side- effects, the most serious being the development of pulmonary toxicity. The purpose of the study was to determine if a single intratracheal instillation of amiodarone would induce pulmonary fibrosis and associated functional changes in rats. Female Fischer 344 rats were given a single intratracheal instilllation of 200 μl containing 1.25 mg amiodarone (n=9) while the control group received an equivalent volume of sterile water (n =8). After 6 weeks, pulmonary function tests, lung hydroxyproline measurements and lung histology were performed. The amiodarone-treated animals showed a significant reduction in the coefficient of diffusion ( kCO) and a significant increase in lung hydoxyproline levels as compared to the control group. The treated group had abnormal histology including areas of septal thickening with cellular infiltration of the interstitial and alveolar spaces, whereas the control group had normal histology. These observations suggest that the intratracheal instillation route of amiodarone treatment produces a fibrotic response in rats that can be measured physiologically, biochemically and histologically. This model may aid in the elucidation of the mechanism of amiodarone-induced pulmonary toxicity ( AIPT)./ABS
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