Tracheal Responses Research Articles

Efecto de la fluticasona inhalada sobre la inflamación pulmonar administrada durante y después de la sensibilización de cobayas

Objective The effect of an inhaled corticosteroid, fluticasone propionate (FP) lung inflammation of sensitized guinea pig was examined. Material and methods Four groups of guinea pigs (n=8) were sensitized (S) with ovalbumin (OA). Control group was given similar solutions without OA. One S group was treated with inhaled 250 μg inhaled FP twice/day during, other group after sensitization for 18 days and two groups were treated with placebo, one during, and the other after sensitization. One day after the last treatment, tracheal responses of all animal groups to methacholine and OA were examined. Total and differential white blood cell (WBC) counts of lung lavage and lung pathology were also examined. Results Tracheal responsiveness to both methacholine and OA and WBC of both placebo groups were significantly higher than those of control group ( P<0.001 for all cases). The lungs of placebo groups showed variable pathological changes (non significant to P<0.001) compared to control group. Tracheal responsiveness in two treated groups with FP to both methacholine and OA were significantly decreased compared to placebo groups ( P<0.01 to P<0.001). Treatment with FP leads to improvement in total ( P<0.001) and differential WBC counts (non significant to P<0.001) as well as mucosal detachment ( P<0.001), but not other pathological changes. Conclusions These results showed a protective effect of FP on tracheal responsiveness and lung inflammation. In addition, this study showed that treatment with inhaled fluticasone propionate, during sensitization (development of inflammation and pathological changes) was more effective than after sensitization (establishment of inflammation and pathological changes).

Perinatal Nicotine Exposure‐Induced Upper Airway and Lung Parenchymal Structural and Functional Changes are Blocked by Concomitant PPARγ Agonist Administration

Recently, we have demonstrated the down‐regulation of the homeostatic alveolar mesenchymal PPARγ signaling and the up‐regulation of Wnt signaling in offspring lung following perinatal exposure to nicotine (NC). However, the molecular and functional alterations in upper airways in this setting are not known. Our objectives were to determine the effects of a PPARγ agonist on perinatal nicotine exposure‐induced alterations in 1) mesenchymal markers of tracheal constriction, and 2) acetylcholine‐induced tracheal constriction responses. Pair‐fed pregnant Sprague Dawley rat dams received diluent, NC (1 mg/kg, sc), and NC (1 mg/kg, sc) + a PPARγ agonist, Rosiglitazone (RGZ) (3 mg/kg, i.p), once daily from e6 until the pups were 21‐days old, when the pups were sacrificed and tracheas collected for mRNA/protein expression and tracheal tension studies. Compared to control, with perinatal NC exposure, mRNA and protein expression of α‐smooth muscle actin, calponin, collagen 1 and 3 were significantly increased. Similarly, compared to controls, tracheal constriction responses were also significantly increased. Concomitant treatment with RGZ blocked the NC‐induced alterations in both tracheal constriction marker expression and constriction responses. Alterations in upper airway function in a rodent model of perinatal NC exposure were blocked by concomitant administration of RGZ. We speculate that perinatal smoke exposure‐induced asthma in offspring can be effectively prevented by PPARγ agonists. Disclosure: Supported by grants from the NIH (HL75405, HD51857, HD058948) and the TRDRP (14RT‐0073, 15IT‐0250, 17RT‐0170).

Role of meconium in the reaction of airways smooth musculature in the newborn with meconium aspiration syndrome (MAS).

The role of meconium in the respiratory system was studied in newborns, who died from various causes (250 up to 3000 g of weight). We monitored tracheal rings response to dopamine, serotonin and ethanol in different concentrations (dopamine: 0,05 mg/ml, 0,5 mg/ml, 5 mg/ml; serotonin (5-HT): 10-4, 10-3, 10-2, 10-1 mol/dm3; ethanol: 0,02 ml, 0,5 ml, 1,0 ml; 96%). Tracheal smooth musculature tonus (TSM) was examined in 48 tracheal preparations taken after the newborn exitus due to different reasons. Based on functional researche of isolated preparations of tracheas, it may be concluded that: aspiration of meconium has not changed the response of TSM to dopamine, serotonin and ethanol (p>0,1) in comparison with the control group, which have died due to different lung inflammatory processes (e.g. pneumonia, bronchopneumonia, atelectasis, cerebral hemorrhage). The results suggest that meconium does not potentiate the constricting action of dopamine, serotonin and ethanol in tracheobronchial system. Meconium causes mild relaxation of the TSM through a mechanism that is not intermediated by the products of cyclooxygenases (prostaglandins, prostacyclins) from the tracheal epithelium or proteins. Also, as it seems, the direct activity of many tested acids in the smooth musculature has no significant impact on increase of the airways tonus in MAS syndrome.

The Effect of Thymoquinone, the Main Constituent ofNigella sativaon Tracheal Responsiveness and White Blood Cell Count in Lung Lavage of Sensitized Guinea Pigs

In previous studies, the relaxant, anticholinergic (functional antagonism) and antihistaminic, effects of Nigella sativa have been demonstrated on guinea pig tracheal chains. In the present study, the prophylactic effect of thymoquinone (one of the constituents of Nigella sativa) on tracheal responsiveness and white blood cell (WBC) count in lung lavage of sensitized guinea pigs was examined. Four groups of sensitized guinea pigs to ovalbumin (OA) were given drinking water alone (group S), drinking water containing low or high concentrations of thymoquinone (S + LTQ and S + HTQ groups) or inhaled fluticasone propionate (FP 250 microg) twice a day (positive control group) (n = 7, for all groups). Tracheal responses of control and four groups of sensitized animals to methacholine at an effective concentration causing 50 % of maximum response (EC(50) M) were measured. Tracheal responses to 0.1 % OA, relative to contraction induced by 10 microM methacholine were also examined. Total WBC and its differential count in lung lavage were also measured. The tracheal responsiveness to methacholine, OA and WBC of S guinea pigs was significantly higher than those of controls (p < 0.001 for all cases). Tracheal responsiveness in S + LTQ, S + HTQ, and FP groups to both methacholine (p < 0.05 to p < 0.001) and OA (p < 0.001 for all cases) was significantly decreased compared to that of the S group. Total WBC was also decreased in all experimental groups compared to that of the S group (p < 0.001 for all groups). There was an increase in eosinophils and a decrease in neutrophils, lymphocytes and monocytes in the S animals compared to the controls (p < 0.001 for all cases). Treatment with both concentrations of thymoquinone and FP variably improved differential WBC count changes compared to the S animals (nonsignificant to p < 0.001). The improvement in tracheal responsiveness, total WBC, eosinophils and lymphocytes changes in the S animals treated with both concentrations of TQ were significantly greater than those of FP (p < 0.05 to p < 0.001). These results showed a preventive effect of thymoquinone, one constituent of N. sativa, on tracheal responsiveness and inflammatory cells of lung lavage of sensitized guinea pigs which was comparable or even greater than that of the inhaled steroid.

Regulation of Drosophila embryonic tracheogenesis by dVHL and hypoxia

The tracheal system of Drosophila melanogaster is an interconnected network of gas-filled epithelial tubes that develops during embryogenesis and functions as the main gas-exchange organ in the larva. Larval tracheal cells respond to hypoxia by activating a program of branching and growth driven by HIF-1α/ sima-dependent expression of the breathless ( btl) FGF receptor. By contrast, the ability of the developing embryonic tracheal system to respond to hypoxia and integrate hard-wired branching programs with sima-driven tracheal remodeling is not well understood. Here we show that embryonic tracheal cells utilize the conserved ubiquitin ligase dVHL to control the HIF-1 α/ sima hypoxia response pathway, and identify two distinct phases of tracheal development with differing hypoxia sensitivities and outcomes: a relatively hypoxia-resistant ‘early’ phase during which sima activity conflicts with normal branching and stunts migration, and a relatively hypoxia-sensitive ‘late’ phase during which the tracheal system uses the dVHL/sima/btl pathway to drive increased branching and growth. Mutations in the archipelago ( ago) gene, which antagonizes btl transcription, re-sensitize early embryos to hypoxia, indicating that their relative resistance can be reversed by elevating activity of the btl promoter. These findings reveal a second type of tracheal hypoxic response in which Sima activation conflicts with developmental tracheogenesis, and identify the dVHL and ago ubiquitin ligases as key determinants of hypoxia sensitivity in tracheal cells. The identification of an early stage of tracheal development that is vulnerable to hypoxia is an important addition to models of the invertebrate hypoxic response.

Tracheal inflammatory response to bacterial cellulose dressing after surgical scarification in rabbits

SummaryExuberant scarring tissue formation is among the failure causes of tracheal stenosis surgery. Dressings that could avoid such reaction could be very helpful in these cases. Bacterial cellulose, produced by acetobacter xylinun can be useful in these cases. There are no studies in the laryngotracheal region.Aimto assess subglottic tissue response in rabbits after scarification and placement of cellulose dressing, and comparing it to a control group.Study designexperimental.Materials and Methods26 rabbits underwent laryngotracheal scarification, received the dressing and were compared to the control group. We established four follow up periods. Laryngotracheal specimens underwent histological exam and the results were statistically assessed.Resultsthe study group had statistically similar results when compared to the control group in the following parameters: vascular congestion, purulent oozing, acute inflammation, epithelial integrity, fibrous proliferation and granulous proliferation.Conclusionwe did not observe differences between the study and control groups as far as inflammation and scarring are concerned. There were no inflammatory signs associated with the use of the cellulose membrane that did no occur because of surgery.

In vivo optical coherence tomography detection of differences in regional large airway smoke inhalation induced injury in a rabbit model

Smoke inhalation injury causes acute airway injury that may result in airway compromise with significant morbidity and mortality. We investigate the ability of high resolution endobronchial optical coherence tomography (OCT) to obtain real-time images for quantitatively assessing regional differences between upper tracheal versus lower tracheal and bronchial airway injury responses to smoke inhalation in vivo using a prototype spectral domain (SLD)-OCT system we constructed, and flexible fiber optic probes. 33 New Zealand White rabbits are intubated and mechanically ventilated. The treatment groups are exposed to inhaled smoke. The OCT probe is introduced through the endotracheal tube and maintained in place for 5 to 6 h. Images of airway mucosa and submucosa are obtained at baseline and at specified intervals postexposure. Starting within less than 15 min after smoke inhalation, there is significant airway thickening in the smoke-exposed animals. This is maintained over 5 h of imaging studies. The lower tracheal airway changes, correlating closely with carboxyhemoglobin levels, are much greater than upper tracheal changes. Significant differences are seen in lower trachea and bronchi after acute smoke inhalation compared to upper trachea as measured in vivo by minimally invasive OCT. OCT is capable of quantitatively detecting regional changes in airway swelling following inhalation injury.

Differential corticosterone responses to stress in the lung in two strains of Flinders rats

Acute stress affects a variety of organs and cellular systems. These include the hypothalamic-pituitary-adrenal (HPA) axis, corticotropin-releasing factor (CRF), mast cells and nerves. Flinders-sensitive (FSL) rat strains have hypercholinergic responses and are more sensitive than Flinders-resistant rats (FRL) to anaphylaxis. To investigate the effects of acute water avoidance stress (1 h) on FSL and FRL tracheal epithelial tissue. We measured short circuit current (I(sc)) as a measure of tracheal response, and the effect of substance P (SP) on tracheal epithelium in Ussing chambers. Electron microscopy was performed to assess mast cell activation. Both strains showed increased I(sc) responses to stress, inhibited by prior injection of the CRF receptor 1 and 2 antagonist, alpha-helical CRF-(9-41). No increases in conductance were seen. Stress responses were accompanied by electron microscopic morphologic evidence for mast cell degranulation, which was not completely inhibited by alpha-helical CRF-(9-41) pre-treatment. Stress primed the epithelium for an enhanced response to SP in FSL, but this again was not inhibited by alpha-helical CRF-(9-41). FRL had 2.5 times the corticosterone response of FSL. Acute stress affects the tracheal epithelium, not accompanied by changes in ion permeability, but associated with mast cell degranulation. Because blunted HPA axis responses are associated with vulnerability to inflammation, this may partially explain the findings. These stress effects on the lung have a genetic basis associated with relative corticosterone responses, are complex and only in part mediated by CRF.

The Preoperative Use of Gabapentin, Dexamethasone, and Their Combination in Varicocele Surgery: A Randomized Controlled Trial

We investigated the effects of gabapentin and dexamethasone given together or separately 1 h before the start of surgery on laryngoscopy, tracheal intubation, intraoperative hemodynamics, opioid consumption, and postoperative pain in patients undergoing varicocele operations. Patients were randomly divided into four double-blind groups: group C (control, n = 20) received placebo, group G (gabapentin, n = 20) received 800 mg gabapentin, group D (dexamethasone, n = 20) received 8 mg dexamethasone, group GD (gabapentin plus dexamethasone) received both 800 mg gabapentin and 8 mg dexamethasone IV 1 h before the start of surgery. Standard induction and maintenance of anesthesia were accomplished and continued by propofol and remifentanil infusion. Heart rate and arterial blood pressure were recorded before induction and after intubation. Intraoperative total remifentanil consumption was recorded. Hemodynamic variables and visual analog scale were recorded for 24 h. Side effects were noted. Hemodynamics at 1, 3, 5, and 10 min after tracheal intubation, total remifentanil consumption during surgery, postoperative visual analog scale scores at 30 min, 1, 2, 4, 6, and 12 h, and postoperative nausea and vomiting were found to be significantly lower in group GD than in group G and group D (P < 0.05 for both), and substantially lower when compared with group C (P < 0.001). All values in group C were also higher than in groups G and D (P < 0.05). Gabapentin and dexamethasone administered together an hour before varicocele surgery results in less laryngeal and tracheal intubation response, improves postoperative analgesia, and prevents postoperative nausea and vomiting better than individual administration of each drug.

A Modified in vitro Method for Studying Tracheal Smooth Muscle Response to Drugs

Background: Vascular or nasal mucosal strips have been successfully used to study smooth muscle contractility in vitro. Using the trachea of the rat, we developed a simple and rapid in vitro technique for testing the effects of drugs that induce tracheal constriction or relaxation. Methods: We used our preparation to test the effectiveness of acetylcholine and methacholine as tracheal contraction drugs and the effectiveness of verapamil as a tracheal relaxing drug. A 5 mm long portion of rat trachea was submersed in 30 ml Kreb's solution in a muscle bath at room temperature. Changes in tracheal contractility in response to the application of parasympathetic mimetic agents were measured using a transducer connected to a Pentium Ⅲ computer equipped with polygraphy software. Results: Addition of parasympathetic mimetics to the incubation medium caused the tracheal to contract in a dose-dependent manner. Addition of verapamil, a relaxation agent, induced a relaxation response only when the preparation had been pretreated with a tracheal constricting agent such as methacholine. Responses to verapamil were dose-dependent. Conclusion: The degree of drug-induced tracheal contraction or relaxation is dosedependent. This method could prove useful for studying the effects of drugs on tracheal smooth muscle activity.

The Effects of Lidocaine, Fentanyl, Nicardipine, and Esmolol on Hemodynamic and Bispectral Index Responses during Induction with Thiopental Sodium

Background: The laryngoscopy and tracheal intubation may accompany with undesirable side effects such as hypertension, tachycardia, arrhythmia, and awareness. The aim of this study was to investigate whether the correlation between the hemodynamics and bispectral index (BIS) changes after tracheal intubation following the administration of various adjuvants to attenuate tracheal response exists or not. Methods: The patients were randomly assigned to one of five groups (control, lidocaine, fentanyl, nicardipine, or esmolol) and the drugs were administered at preselected time before tracheal intubation. The heart rate (HR), blood pressure, rate-pressure product (RPP), BIS and the episode of BIS more than 65 (BIS ≥ 65) were measured. Results: There were significant differences in the mean arterial pressure and RPP between control group and other groups. The HR was the most attenuated in esmolol group. The HR and RPP was the most increased in nicardipine group except control group. There was no significant difference in the maximal BIS among the five groups. The BIS ≥ 65 were 50% in control group and 0.3% in nicardipine group. Conclusions: All the adjuvant drugs in the study attenuated with a various degree of the tracheal responses. However, there was no correlation between the changes of hemodynamics and BIS after the administration of various adjuvants following tracheal intubation. (Korean J Anesthesiol 2007; 53: S 7～13)

REAL-TIME HIGH-RESOLUTION COMPARISON OF TRACHEAL AND BRONCHIAL INJURY CHANGES DURING SMOKE INHALATION IN RABBITS USING OPTICAL COHERENCE TOMOGRAPHY.

Background Smoke inhalation injury causes acute airway swelling that results in significant morbidity and mortality. There are currently no available modalities for early detection of this edema. We performed high-resolution endobronchial optical coherence tomography (OCT) using a prototype SLD-OCT system and flexible fiberoptic probes we constructed to obtain novel real-time images of inhalation at near histologic levels showing differences between tracheal and bronchial responses to smoke in vivo. Method Nineteen New Zealand rabbits (four controls, seven tracheal, and eight bronchial) were intubated and mechanically ventilated. The experimental group was exposed to inhaled smoke. The OCT probe was introduced through the endotracheal tube. Images of airway mucosa and submucosa were obtained at baseline and at set time intervals. The mucosal and submucosal thickness was measured and compared between the three groups. The images were also compared to histologic sections of the trachea. Results Starting at 30 minutes after smoke inhalation, there was significant bronchial airway thickening. This was maintained through 360 minutes. No significant tracheal thickening was detected. Conclusions OCT is capable of detecting changes in airway swelling following inhalation injury and may be very useful for inhalation injury assessment. Significant differences were seen between bronchial and tracheal effects of acute smoking inhalation. Further studies will be needed to determine the causes for these differences.

Demonstration of antihistamine properties with AST-1: a bioactive extract from garden slugs (Diplosolenodes occidentalis)

Parched and ground whole garden slugs are claimed in rural Jamaican folklore practices to have useful effects in the treatment of bronchial asthma. Since this claim may be associated with respiratory dysfunction due to histamine from allergic sensitization, the authors investigated the effects of a semi-pure alcoholic extract (AST-1) on histamine-induced contraction of the guinea pig in vitro tracheal muscle preparation and cutaneous allergic responses in ovalbumin sensitized guinea pigs. Chemical analysis of AST-1 by column chromatography and thin layer chromatography indicated two compounds in the composition, but the molecular structures were not determined Pharmacological evaluation of AST-1 produced a concentration-dependent inhibition of histamine-induced contraction of the guinea pig tracheal muscle preparation. AST-1 also inhibited contraction of the tracheal muscle produced by selective H1 receptor stimulation with HTMT dimaleate. H2 receptors were not involved, as indicated by the absence of contraction with dimaprit hydrochloride, a selective H2 agonist. Also, in ovalbumin sensitized guinea pigs, AST-1 and diphenhydramine, a selective H1 antagonist, inhibited the cutaneous responses due to intradermal injection of histamine and ovalbumin. These results suggest that AST-1 has H1 anti-histamine properties which can inhibit histamine-induced tracheobronchial muscle contraction and cutaneous responses due to allergy.

Tracheal responsiveness to both isoprenaline and beta2‐adrenoreceptor blockade by propranolol in cigarette smoke exposed and sensitized guinea pigs

Airway hyperresponsiveness is the main feature of asthma and also exists in cigarette smokers. In previous studies we have shown increased airway responsiveness to isoprenaline in asthmatic patients and smokers. In this study, tracheal responsiveness to isoprenaline and beta-adrenergic receptor blockade was investigated in animals exposed to cigarette smoke (AECS) with or without sensitization by ovalbumin (OA). Guinea pigs were exposed to cigarette smoke over a 3-month period with or without sensitization by injection and inhalation of OA. Tracheal responses in AECS, AECS + sensitized and control animals (n = 7 for each group) to isoprenaline in the absence and presence of 20 nmol/L propranolol were measured and EC(50) was established. The propranolol blockade (concentration ratio minus one (CR-1)) was calculated (post-propranolol EC(50)/EC(50)) - 1. The tracheal response of AECS and AECS + sensitized guinea pigs to isoprenaline was significantly higher than that of control animals (EC(50): 4.24 +/- 0.54, 3.66 +/- 0.53 and 7.71 +/- 0.68.79 micromol for AECS, AECS + sensitized and control animals, respectively) (P < 0.001). There was no significant difference in EC(50) between AECS and AECS + sensitized. CR-1 was also significantly higher in the trachea of AECS and AECS + sensitized compared with controls (13.39 +/- 2.22 and 15.35 +/- 2.95 vs. 3.10 +/- 0.6, P < 0.05 in both cases). There was no significant difference in CR-1 between AECS and AECS + sensitized. There was a significant correlation between the tracheal response to isoprenaline (EC(50)) and CR-1 (r =-0.731, P < 0.001). There was no significant difference in tracheal maximum response to isoprenaline between the three groups of animals. The results of this study indicate an increased tracheal response to a beta(2)-adrenergic stimulating drug and enhanced beta(2)-adrenergic blockade by propranolol in both AECS and AECS + sensitized. These results suggest similar increase in airway responsiveness to beta(2)-adrenergic agonists and beta(2)-receptor blockade in AECS and AECS + sensitized guinea pigs.

Influence of epithelium on beta-adrenoceptor desensitization of guinea pig tracheal smooth muscle

The effect of tissue incubation with a beta2-agonist of denuded and intact epithelium trachea on the responsiveness to isoprenaline and beta-receptor blocked by propranolol (CR-1) was examined in this study. We examined the effect of epithelium removal on the beta-adrenoceptor desensitization resulting from incubation of guinea pig trachea in the beta-adrenergic agonist isoprenaline (10 microM). Desensitization was measured as the change in EC50, the concentration of beta-agonist that produced 50% relaxation of tracheal rings contracted with methacholine. As a second measure of desensitization, we measured the shift in EC50 resulting from incubation of tracheal rings with the beta-adrenoceptor antagonist propranolol (20 nM), expressed as CR-1 ([post-propranolol EC50/baseline EC50]-1). Initially, we measured desensitization immediately after incubation in isoprenaline; subsequently, we repeated the protocol and allowed a 30 min rest between the end of incubation and the measurement. The sensitivity of denuded epithelium trachea to isoprenaline and (CR-1) was significantly higher than that of intact epithelium only in non-incubated preparations (p<0.05 to p<0.001). Incubation to isoprenaline caused a significant reduction in the tracheal response to isoprenaline in both the denuded groups (p<0.005 for both cases) and intact epithelium groups (p<0.05 for both cases). Incubation to isoprenaline also caused a significant reduction in (CR-1) value in both the denuded groups (p<0.005 for group 2 and p<0.001 for group 4) and intact epithelium only in group 1 (p<0.05). However, the changes in EC50 due to tissue incubation with isoprenaline were significantly greater in denuded than intact epithelium trachea (p<0.05 for all cases) and for CR-1 value only in groups 1 and 2 (p<0.05). These results indicate decrease in both tracheal response to beta-agonist (tolerance) and CR-1 (due to incubation of tissues with isoprenaline), which were greater in denuded epithelium groups.

In vitro tracheal hyperresponsiveness to muscarinic receptor stimulation by carbachol in a rat model of bleomycin‐induced pulmonary fibrosis

1 Bleomycin-induced lung injury is widely used as an experimental model to investigate the pathophysiology of pulmonary fibrosis but the alterations in the pharmacological responsiveness of airways isolated from bleomycin-exposed animals has been scarcely investigated. The aim of this study was to examine the in vitro tracheal responses to muscarinic receptor stimulation with carbachol in a rat bleomycin model. 2 Concentration-response curves to carbachol (10 nm to 0.1 mm) were obtained in tracheal rings isolated from Sprague-Dawley rats 14 days after endotracheal bleomycin or saline. The intracellular calcium signal in response to carbachol (10 microm) was measured by epifluorescence microscopy using fura-2 in primary cultures of tracheal smooth muscle cells from bleomycin- and saline-exposed rats. Circulating plasma tumour necrosis factor (TNF)-alpha/interleukin (IL)-1beta levels were measured by enzyme-linked immunosorbent assay. 3 Maximal contraction in response to carbachol was significantly greater in tracheal rings from bleomycin-exposed rats compared with controls (15.8 +/- 1.3 mN vs. 11.8 +/- 1.4 mN; n = 19, P < 0.05). 4 Carbachol (10 microm) elicited a transient increase of intracellular calcium with greater increment in tracheal smooth muscle cells from bleomycin-exposed rats compared with controls (372 +/- 42 nmvs. 176 +/- 20 nm; n = 7, P < 0.01). 5 Circulating plasma levels of TNF-alpha/IL-1beta were augmented in bleomycin-exposed rats compared with controls. Tissue incubation with TNF-alpha (100 ng ml(-1))/IL-1beta (10 ng ml(-1)) increased in vitro tracheal responsiveness to carbachol. 6 In conclusion, tracheal contraction in response to muscarinic receptor stimulation with carbachol was increased in bleomycin-exposed rats. This in vitro cholinergic hyperresponsiveness may be related to the augmented levels of inflammatory cytokines in bleomycin-exposed rats.

Reduced airway hyperresponsiveness and tracheal responses during allergic asthma in mice lacking tyrosine kinase inducible T-cell kinase

Patients with allergic asthma have symptoms of a predominant T(H)2 response, including airway eosinophilic inflammation and increased mucous production in the lungs. This accompanies increased airways responsiveness, which can be life threatening. Because T(H)2 cells and cytokines have been implicated in contributing to these symptoms, pathways that control the development of these cells or that regulate their cytokine production represent good targets for controlling this disease. We have previously shown that mice lacking the tyrosine kinase inducible T-cell kinase (ITK) have drastically reduced airway inflammation in a model of allergic asthma. However, it was not clear whether this translated into reduced airways hyperresponsiveness. We have analyzed tracheal responsiveness and airways hyperresponsiveness of wild-type (WT) and ITK null mice during induction of experimental allergic asthma. Experimental allergic asthma was induced in WT and ITK knockout mice. Tracheal responses to carbachol, acetylcholine, and potassium chloride were analyzed. Airways hyperresponsiveness to methacholine challenge was also analyzed in allergen-challenged mice, along with lung and bronchoalveolar lavage fluid T(H)2 cytokine message and protein. ITK null mice have reduced tracheal responses to cholinergic challenge in vitro before as well as after allergen challenge. These mice also have reduced airways hyperresponsiveness in response to allergen challenge, which could be rescued by transferring WT splenocytes or purified WT CD4+ T cells. This reduced airways response was preferentially accompanied by reduced expression of T(H)2 cytokines in the lungs. Our results indicate that the tyrosine kinase ITK and its function in T cells represent an attractive target for antiasthmatic drugs. Modulating the expression or activity of ITK may be a novel strategy to block allergic airway inflammation.

Influence of Epithelium and Isoprenaline Incubation on Responsiveness of Guinea-Pig Trachea to Methacholine

There are reports regarding harmful effect of long-term use of β₂-agonist drugs on asthma severity and airway responsiveness. In the present study, the responses of guinea pig trachea with intact and denuded epithelium (groups 1 and 2, n = 10) to methacholine as EC₅₀ were measured in tissues nonincubated or incubated with 10 µmol/l isoprenaline during the resting period. The same protocol was performed in groups 3 and 4 (n = 5 for each group) with an additional 30 min rest time after isoprenaline incubation. The response of trachea with denuded epithelium (groups 2 and 4) to methacholine was significantly higher than that with intact epithelium both in incubated and nonincubated conditions (groups 1 and 3, p < 0.05 to p < 0.001). Incubation with isoprenaline caused a significant reduction in the tracheal response to methacholine in both the denuded groups (p < 0.005 and p < 0.001) and intact epithelium groups (p < 0.005 for both cases). The reduction in tracheal responsiveness to methacholine due to incubation in epithelium denuded trachea (groups 2 and 4) was nonsignificantly greater than that of intact epithelium tissues. There was no difference between groups 3 and 4 with those of groups 1 and 2 in both incubated and non incubated conditions. The maximum contractility response to methacholine was not different between tracheal chains with denuded and intact epithelium and did not change due to incubation with isoprenaline. The results of this study indicate reduction of tracheal response to methacholine due to incubation of tissues with isoprenaline, which was relatively more pronounced in epithelium denuded trachea.

Modulation of the contractile responses of guinea pig isolated tracheal rings after chronic intermittent hypobaric hypoxia with and without cold exposure

Previous studies have documented that repetitive exposure to intermittent hypoxia, such as that encountered in preparation to high-altitude ascent, influences breathing. However, the impact of intermittent hypoxia on airway smooth muscle has not been explored. Ascents to high altitude, in addition to hypoxia, expose individuals to cold air. The objective of the present study is to examine the effect of chronic intermittent hypobaric hypoxia (CIH) and CIH combined with cold exposure (CIHC) on tracheal smooth muscle responses to various contractile and relaxant agonists. Experiments were performed on tracheal rings harvested from adult guinea pigs exposed either to CIH or CIHC [14 days (6 h/day) at barometric pressure of 350 mmHg with and without cold exposure of 5 degrees C] or to room air (normoxia). CIH and CIHC attenuated maximum contractile responses to ACh compared with normoxia. The maximum contractile response to histamine decreased with CIH, whereas CIHC restored the response back to normoxia. Both CIH and CIHC attenuated maximum contractile responses to 5-HT. Altered contractile responses after CIH and CIHC were independent of epithelium. Isoproterenol-induced relaxation was not altered by CIH, whereas it was enhanced after CIHC, and these responses were independent of the epithelium. The data demonstrate that intermittent exposure to hypoxia profoundly influences contractile response of tracheal smooth muscle, and cold exposure can further modulate the response, implying the importance of cold at high altitude.

Rat tracheal epithelial responses to water avoidance stress

Psychologic stress has major effects on many organs and cellular systems. The hypothalamic-pituitary-adrenal axis, corticotropin-releasing factor (CRF), mast cells, and nerves have all been shown to be involved in intestinal epithelial responses to stress. There has been little information in the literature on stress and the lung. To investigate Wistar rat tracheal epithelial responses to acute water avoidance stress (1 hour). Tracheal tissue was examined in Ussing chambers. Increases in short-circuit current, but not in conductance, occurred after stress and were inhibited by previous injection of the CRF 1 and 2 receptor antagonist, alpha-helical CRF-(9-41). Electron microscopic morphologic evidence for tracheal mast cell activation and degranulation was found after stress. Stress and CRF injection both enhanced responses to substance P, but these effects were not inhibited by alpha-helical CRF. The data suggest that acute stress affects tracheal epithelium and sensitizes it to enhanced responses to substance P, partly through mast cell activation. Many but not all of these effects are mediated by CRF. These results offer the possibility that stress may be involved in inflammatory diseases of the lung such as asthma.