RESUMEN
After parainfluenza type 1 (Sendai) virus infection as weanlings, Brown Norway (BN), unlike Fischer 344 (F344), rats develop an asthma-like phenotype. Reduced postinfection interferon (IFN)-gamma levels in bronchoalveolar lavage fluid from BN weanlings and the prevention of chronic airway sequelae in BN rats by IFN-gamma treatment led to the hypothesis that cells from BN weanlings have a reduced ability to secrete IFN-gamma. After stimulation with Sendai virus or interleukin (IL)-12, splenocytes from uninfected BN weanlings secreted significantly less IFN-gamma than did splenocytes from F344 weanlings (P < 0.005), as determined by enzyme-linked immunosorbent assay. Because levels of potential IFN-gamma-secreting cells in the spleen differed between the strains, natural killer (NK) cells, an important IFN-gamma source during early antiviral responses, were purified from spleens of uninfected weanlings. When stimulated with IL-12, BN NK cells secreted significantly less IFN-gamma than did F344 NK cells (P < 0.001). Incubation of NK cells from either strain with IL-12 and IL-18 resulted in synergistic increases in IFN-gamma production, but BN cells still secreted significantly less IFN-gamma than did F344 cells (P < 0.05). Similarly, after incubation with either IFN-alpha or IFN-alpha plus IL-18, BN NK cells secreted significantly less IFN-gamma than did F344 NK cells (P < 0.05). Therefore, reduced IFN-gamma secretion by NK cells in BN weanlings may play a role in the development of postviral chronic airway dysfunction.
Asunto(s)
Interferón gamma/metabolismo , Células Asesinas Naturales/inmunología , Células Asesinas Naturales/metabolismo , Enfermedades Pulmonares Obstructivas/inmunología , Proteínas Proto-Oncogénicas , Infecciones por Respirovirus/inmunología , Animales , Líquido del Lavado Bronquioalveolar/química , Células Cultivadas , Proteínas de Unión al ADN/biosíntesis , Susceptibilidad a Enfermedades/inmunología , Susceptibilidad a Enfermedades/metabolismo , Interferón-alfa/farmacología , Interferón gamma/análisis , Interleucina-12/análisis , Interleucina-12/metabolismo , Interleucina-12/farmacología , Interleucina-18/farmacología , Janus Quinasa 2 , Células Asesinas Naturales/citología , Recuento de Leucocitos , Enfermedades Pulmonares Obstructivas/virología , Masculino , Fosforilación , Biosíntesis de Proteínas , Isoformas de Proteínas/biosíntesis , Proteínas Tirosina Quinasas/biosíntesis , Ratas , Ratas Endogámicas BN , Ratas Endogámicas F344 , Receptores de Interleucina/biosíntesis , Receptores de Interleucina-12 , Respirovirus/inmunología , Factor de Transcripción STAT4 , Organismos Libres de Patógenos Específicos , Bazo/citología , Bazo/inmunología , Bazo/metabolismo , Bazo/virología , Linfocitos T/citología , TYK2 Quinasa , Transactivadores/biosíntesisRESUMEN
Viral respiratory infections cause acute bronchiolitis and physiologic dysfunction in human infants and in animals. It is possible that the pulmonary dysfunction is a consequence of the inflammatory cells that are recruited during viral illness. We hypothesized that blockade of intercellular adhesion molecule-1 (ICAM-1), a major cell adhesion molecule, would impede the ingress of leukocytes during viral infection and attenuate virus-induced pulmonary dysfunction. Adult male rats were inoculated with parainfluenza type 1 (Sendai) virus or sterile vehicle, and treated with blocking or nonblocking MAb specific for rat ICAM-1. Respiratory system resistance, oxygenation (PaO2), methacholine responsiveness, and bronchoalveolar lavage (BAL) leukocyte counts were measured in anesthetized, paralyzed, ventilated rats. Treatment with the blocking ICAM-1 antibody reduced virus-induced increases in BAL neutrophils and lymphocytes by 70% (p < 0.001), but did not affect BAL monocytes/macrophages. Peripheral blood leukocyte counts were elevated in anti-ICAM-1 blocking antibody-treated rats (p = 0.0003). Although virus-induced increases in resistance and decreases in PaO2 were not affected by anti-ICAM-1 treatment, there was a small but significant attenuation of virus-induced methacholine hyperresponsiveness (p = 0.02). We conclude that ICAM-1 has an important role in neutrophil and lymphocyte infiltration during respiratory viral illness, and that virus-induced changes in pulmonary physiology are not related directly to the numbers of neutrophils and lymphocytes that migrate to the air spaces during infection.
Asunto(s)
Anticuerpos Monoclonales/inmunología , Bronquiolitis Viral/fisiopatología , Molécula 1 de Adhesión Intercelular/inmunología , Infecciones por Respirovirus/fisiopatología , Respirovirus/aislamiento & purificación , Enfermedad Aguda , Animales , Bronquiolitis Viral/inmunología , Bronquiolitis Viral/virología , Líquido del Lavado Bronquioalveolar , Masculino , Ratas , Ratas Sprague-Dawley , Infecciones por Respirovirus/inmunología , Infecciones por Respirovirus/virologíaRESUMEN
Bronchoalveolar lavage (BAL) is a well-characterized technique for analysis of cellular constituents of the airways and air spaces, but whole lung lavage requires that the animal be euthanized. We describe a technique of segmental BAL in rats that allows serial measurements of inflammation. A tracheal tube was placed, under direct visualization, in lightly anesthetized animals, and a catheter was passed through the tracheal tube and advanced to a wedge position. Five 0.1-ml volumes of buffer solution were instilled and then withdrawn with gentle suction. In normal rats, the percentages of neutrophils, eosinophils, and mononuclear cells had a high level of agreement in the segmental samples compared with those obtained subsequently by whole lung lavage. In rats with acute pulmonary inflammation, the differential leukocyte counts from segmental samples exhibited patterns of change that differed from those of whole lung lavage; however, most segmental samples were obtained from the left lung base so that regional variability could be minimized in serial studies. Lung mechanics and airway inflammation were not affected by repeated segmental BALs done 2 wk apart.
Asunto(s)
Lavado Broncoalveolar/métodos , Envejecimiento/fisiología , Animales , Líquido del Lavado Bronquioalveolar/citología , Recuento de Células , Interpretación Estadística de Datos , Eosinófilos , Recuento de Leucocitos , Pulmón/citología , Pulmón/crecimiento & desarrollo , Pulmón/fisiología , Masculino , Monocitos , Neutrófilos , Ratas , Ratas Endogámicas BNRESUMEN
After viral bronchiolitis at an early age, Brown Norway (BN) rats develop chronic airway dysfunction consisting of inflammation, remodeling, episodic reversible obstruction, and hyperresponsiveness. We hypothesized that supplementation of interferon gamma (IFN-gamma) during viral illness would alter the inflammatory response and attenuate the postviral sequelae. Weanling rats were treated daily with aerosolized interferon gamma (IFN-gamma), from 2 d prior through 7 d after inoculation, and compared with saline-treated infected rats and with noninfected control rats. The IFN-gamma treatment had no significant effect on viral titers, growth retardation, or total bronchoalveolar leukocytes, but there was a slight decrease in lung interleukin-4 (IL-4) mRNA (p = 0.015) during the first week. Despite having minimal effects on the acute illness, the IFN-gamma had marked effects on postviral sequelae, the IFN-gamma group having less bronchiolar inflammation (p = 0.025) and fibrosis (p = 0.01), and lacking abnormalities in pulmonary resistance (p = 0.028) and dynamic compliance (p = 0.006) compared with the untreated postviral group. We conclude that IFN-gamma modulated the inflammatory response to viral illness, such that acute airway injury did not evolve into chronic airway dysfunction. If similar processes contribute to the development of human asthma, it may be possible to interrupt the progression of airway dysfunction with an early immunomodulatory intervention.
Asunto(s)
Asma/patología , Bronquiolitis Viral/patología , Interferón gamma/farmacología , Enfermedades Pulmonares Obstructivas/patología , Infecciones por Respirovirus/patología , Respirovirus , Resistencia de las Vías Respiratorias/efectos de los fármacos , Animales , Hiperreactividad Bronquial/patología , Humanos , Interferón gamma/metabolismo , Interleucina-4/metabolismo , Pulmón/efectos de los fármacos , Pulmón/patología , Rendimiento Pulmonar/efectos de los fármacos , Masculino , Ratas , Ratas Endogámicas BNAsunto(s)
Asma/fisiopatología , Hiperreactividad Bronquial/virología , Infecciones del Sistema Respiratorio/fisiopatología , Virosis/fisiopatología , Asma/patología , Asma/virología , Bronquios/inervación , Bronquios/fisiopatología , Endotelio/fisiopatología , Epitelio/fisiopatología , Humanos , Macrófagos/fisiología , Infecciones del Sistema Respiratorio/complicaciones , Virosis/complicacionesRESUMEN
Viral respiratory infections cause acute airway abnormalities consisting of inflammation and physiological dysfunction in both animals and humans. It is likely that inflammatory cell products, such as cytokines, contribute substantially to viral-induced airway dysfunction. We hypothesized that imiquimod, an immune response enhancing agent that induces interferon-alpha, would attenuate the development of airway dysfunction during acute viral illness in rats. Adult Brown Norway rats were inoculated with parainfluenza type 1 (Sendai) virus or sterile vehicle, and treated with either imiquimod or water. Respiratory system resistance (Rrs), arterial oxygen tension (Pa,O2), lung viral titres and bronchoalveolar lavage (BAL) leucocyte counts were measured in anaesthetized, paralysed, ventilated rats. Virus-infected, water-treated rats had a significant decrease in Pa,O2 and had significant increases in leucocyte count and Rrs when compared to both the virus-infected, imiquimod-treated, (Pa,O2, p = 0.03; leucocyte count, p = 0.02; and Rrs, p = 0.009) and noninfected, water-treated rats (Pa,O2, p = 0.007; leucocyte count, p = 0.001; and Rrs, p = 0.01). In addition, imiquimod suppressed BAL eosinophils in both virus-infected (p = 0.02) and noninfected (p = 0.001) groups, and lowered overall virus titres (p = 0.03). Thus, both virus-induced airway inflammation and physiological dysfunction were attenuated significantly by imiquimod treatment in this animal model. By further delineating mechanisms by which infections induce airway dysfunction in animal models, more specific pharmacological interventions can be developed for the treatment of virus-induced asthma.
Asunto(s)
Adyuvantes Inmunológicos/uso terapéutico , Aminoquinolinas/uso terapéutico , Enfermedades Respiratorias/virología , Infecciones por Respirovirus/complicaciones , Infecciones por Respirovirus/tratamiento farmacológico , Animales , Peso Corporal/efectos de los fármacos , Líquido del Lavado Bronquioalveolar/citología , Imiquimod , Inflamación/patología , Inflamación/virología , Interferones/sangre , Masculino , Ratas , Enfermedades Respiratorias/patología , Respirovirus/aislamiento & purificación , Infecciones por Respirovirus/virologíaRESUMEN
Respiratory viral infections have been associated with airway obstruction and hyperresponsiveness, and exacerbations of asthma. Although virus-induced asthma is thought to be precipitated by airway inflammation, the clinical efficacy and rationale for using antiinflammatory treatment during such exacerbations remains controversial. The purpose of this study was to use a well characterized animal model of respiratory viral illness to test the hypothesis that the inflammatory response to viral infection is responsible for the development of airway dysfunction. Adult rats were inoculated with either Sendai virus or sterile vehicle and treated with daily injections of dexamethasone or saline. At postinoculation d 4, 5, or 6, rats were evaluated for airway obstruction, hyperresponsivenes, inflammation, and lung viral titers. Saline-treated infected rats had significant airway obstruction (increased resistance, decreased dynamic compliance), hyperresponsiveness (i.v. methacholine), and inflammation (increased bronchoalveolar lavage leukocytes) compared with noninfected controls. In contrast, dexamethasone-treated infected rats had no increase in bronchoalveolar lavage leukocytes and significantly smaller changes in airway physiology, but had increased lung viral titers compared with saline-treated infected rats. We conclude that glucocorticoid suppression of the inflammatory response to respiratory viral infection largely prevents virus-associated airway dysfunction.
Asunto(s)
Dexametasona/farmacología , Infecciones del Sistema Respiratorio/fisiopatología , Infecciones por Respirovirus/fisiopatología , Animales , Líquido del Lavado Bronquioalveolar/citología , Inflamación , Leucocitos/patología , Pulmón/virología , Masculino , Ratas , Ratas Sprague-Dawley , Infecciones del Sistema Respiratorio/tratamiento farmacológico , Infecciones del Sistema Respiratorio/virología , Respirovirus/aislamiento & purificación , Infecciones por Respirovirus/tratamiento farmacológico , Factores de TiempoRESUMEN
Viral bronchiolitis in human infants has been associated with persistent airway abnormalities, but not proven as a cause. Previously we observed some adult rats had airway obstruction and hyperresponsiveness following bronchiolitis at an early age. The purpose of this study was to determine, via serial measurements of lung mechanics, whether the postbronchiolitis airway obstruction was episodic or continuous, and to determine the magnitude and duration of glucocorticoid effects. Rats were either virus- (n = 14) or sham-inoculated (n = 8) at 3 wks of age. Lung mechanics were measured 6 times in each rat at postinoculation Weeks 11-18. Half the rats in each group were treated with dexamethasone for 3 d at Week 15. The virus group had higher lung resistance (p = 0.03) and lower dynamic compliance (p = 0.005) than control rats, with airway obstruction occurring in an episodic pattern. Dexamethasone treatment had a transient effect in postbronchiolitis rats; lung resistance normalized in Week 15 (p = 0.006), then returned to pretreatment levels by Weeks 16-18. We conclude that viral bronchiolitis in rats can result in a chronic syndrome of intermittent, reversible airway obstruction which has multiple parallels with human asthma over a prolonged time period.
Asunto(s)
Resistencia de las Vías Respiratorias , Bronquiolitis Viral/fisiopatología , Resistencia de las Vías Respiratorias/efectos de los fármacos , Animales , Bronquiolitis Viral/tratamiento farmacológico , Dexametasona/uso terapéutico , Glucocorticoides/uso terapéutico , Rendimiento Pulmonar/efectos de los fármacos , Masculino , Ratas , Ratas Endogámicas BNRESUMEN
Parainfluenza type 1 (Sendai) virus infection in young rats induces airway growth abnormalities associated with persistent pulmonary dysfunction and hyperresponsiveness. The objectives of this study were to compare virus-susceptible brown Norway (BN) rats and virus-resistant F344 rats and to determine which of several virus-induced structural abnormalities, including bronchiolar hypoplasia, alveolar dysplasia, bronchiolar mural fibrosis, and increases in bronchiolar mast cells, were associated with virus-induced increases in pulmonary resistance and hyperresponsiveness to methacholine. We also determined whether bronchiolar mural thickening and fibrosis may be caused by increased bronchiolar expression of cytokines such as TGF-beta 1 into airways. BN rats infected with virus developed increases in respiratory resistance and hyperresponsiveness that persisted for 28 to 65 d after inoculation. Functional abnormalities were most strongly associated with bronchiolar mural thickening and fibrosis as well as with recruitment of inflammatory cells, including macrophages, mast cells, lymphocytes, and eosinophils, into the bronchiolar wall. F344 rats were resistant to significant virus-induced alterations in bronchiolar airway wall thickness and mast cell increases as well as to pulmonary function abnormalities. BN rats had increase pulmonary mRNA levels of TGF-beta 1 at 10 and 14 d after viral inoculation as compared with F344 rats. BN rats also had greater numbers of bronchiolar macrophages expressing TGF-beta 1 protein that were localized in bronchiolar walls at 10, 14, and 30 d after inoculation. We conclude that recruitment and persistence of airway inflammatory cells and airway wall fibrosis may be important alterations induced by viral lower respiratory disease during early life that can lead to long-term airway dysfunction and hyperresponsiveness. Virus-induced airway fibrosis may be mediated in part by increased TGF-beta 1 gene expression by bronchiolar macrophages in genetically susceptible individuals.
Asunto(s)
Bronquios/patología , Virus de la Parainfluenza 1 Humana , Mecánica Respiratoria , Infecciones del Sistema Respiratorio/metabolismo , Infecciones del Sistema Respiratorio/patología , Infecciones por Respirovirus/metabolismo , Infecciones por Respirovirus/patología , Factor de Crecimiento Transformador beta/metabolismo , Resistencia de las Vías Respiratorias , Animales , Animales Recién Nacidos , Hiperreactividad Bronquial/etiología , Pruebas de Provocación Bronquial , Susceptibilidad a Enfermedades , Fibrosis , Inmunohistoquímica , Hibridación in Situ , Inflamación/patología , Pulmón/metabolismo , Pulmón/patología , Rendimiento Pulmonar , Macrófagos/metabolismo , Mastocitos/patología , Cloruro de Metacolina , Ratas , Ratas Endogámicas BN , Ratas Endogámicas F344 , Infecciones del Sistema Respiratorio/fisiopatología , Infecciones por Respirovirus/fisiopatologíaRESUMEN
Respiratory viral infections have been associated with exacerbations of asthma in humans, and are known to produce airway obstruction and hyperresponsiveness in rats. Virus-induced airway dysfunction may result in part from inflammatory cells and their products, and agents that target these mechanisms might therefore attenuate viral airway injury. The 21-aminosteroid class of drugs has been reported to attenuate tissue injury in a variety of models, and we hypothesized that U-83836E, an orally-active aminosteroid, would prevent the development of airway dysfunction during acute viral illness. Adult rats were inoculated with either parainfluenza type 1 (Sendai) virus or sterile vehicle, treated with either U-83836E 20 mg/kg or water by oral gavage twice daily, and studied on postinoculation day 5, 6 or 7. Anesthetized, paralysed, mechanically ventilated rats were placed in a body plethysmograph for measurements of airway obstruction (resistance, dynamic compliance, eucapneic PaO2), and responsiveness to i.v. methacholine; lungs were lavaged to obtain inflammatory cells. The water-treated virus group was significantly different from the non-infected controls for all variables. Virus-induced hyperresponsiveness was attenuated (P = 0.027) by aminosteroid treatment, although airway obstruction and inflammation were not improved by the treatment. We conclude that 21-aminosteroids may protect airways from virus-induced hyperresponsiveness.
Asunto(s)
Hiperreactividad Bronquial/tratamiento farmacológico , Cromanos/uso terapéutico , Depuradores de Radicales Libres/uso terapéutico , Piperazinas/uso terapéutico , Infecciones por Respirovirus/tratamiento farmacológico , Respirovirus , Enfermedad Aguda , Obstrucción de las Vías Aéreas/tratamiento farmacológico , Animales , Líquido del Lavado Bronquioalveolar/citología , Evaluación Preclínica de Medicamentos , Masculino , RatasRESUMEN
Studies with isolated cells are important to the understanding of mechanisms by which eosinophils participate in allergic inflammation. Due to species variability, isolation techniques and cell biology need to be defined for each source. We developed methods to obtain rat eosinophils with purity and viability exceeding 90%, characterized the superoxide anion production of these cells in response to standard activators, and compared these results with those previously obtained in our laboratories with the use of human eosinophils. Rat eosinophils responded vigorously to phorbol myristate acetate and poorly to platelet-activating factor and to N-formyl-methionyl-leucyl-phenylalanine, parallel to the responses of human eosinophils. In contrast, rat eosinophils responded unlike human eosinophils to other activators, having a larger response to calcium ionophore A23187, a smaller response to serum-treated or serum-opsonized zymosan, and a negative rather than positive modulatory effect of cytochalasin B. We conclude that rat eosinophils can be obtained in high purity and with intact responsiveness to a number of different activators.
Asunto(s)
Eosinófilos/fisiología , Superóxidos/sangre , Animales , Calcimicina/farmacología , Separación Celular/métodos , Citocalasina B/farmacología , Eosinófilos/citología , Eosinófilos/efectos de los fármacos , Humanos , Técnicas In Vitro , Cinética , Masculino , N-Formilmetionina Leucil-Fenilalanina/farmacología , Factor de Activación Plaquetaria/farmacología , Ratas , Acetato de Tetradecanoilforbol/farmacología , Zimosan/farmacologíaRESUMEN
To test the hypothesis that parasympathetic airway tone may affect airway responsiveness, we measured bronchoconstrictor responses to intravenous bethanechol (BCh) in anesthetized vagotomized rats with and without background vagal nerve stimulation and developed a predictive model based on pharmacological additivity between endogenous and intravenous agonists. A high degree of agreement (r2 = 0.93) between the measured and predicted responses indicated that intravenous BCh and parasympathetic tone had bronchoconstrictor effects that were pharmacologically additive. An expansion of the additive model was used to determine that the percentage of decrease in respiratory system conductance (Grs) would be a measure of airway response independent of background parasympathetic tone. As predicted, the percentage of decrease in Grs after intravenous BCh was minimally affected by background vagal stimulation. However, the percentage of decrease in Grs was augmented by vagal stimulation for intravenous 5-hydroxytryptamine hydrochloride, a known parasympathetic neuromodulator, and for methacholine, an agonist with nicotinic as well as muscarinic activity (P < 0.02 for each agonist). We conclude that airway parasympathetic tone can be a source of variability for airway responsiveness when substances having neuromodulatory activity are involved in the provocative challenge.
Asunto(s)
Broncoconstrictores/farmacología , Sistema Nervioso Parasimpático/fisiología , Sistema Respiratorio/efectos de los fármacos , Sistema Respiratorio/inervación , Animales , Betanecol/farmacología , Estimulación Eléctrica , Inyecciones Intravenosas , Masculino , Modelos Biológicos , Ratas , Ratas Endogámicas , Vagotomía , Nervio Vago/fisiologíaRESUMEN
Viral respiratory infections in humans have been associated with exacerbations of late allergic responses and asthma, as well as with airway abnormalities that persist after resolution of the acute infection. We hypothesized that augmented parasympathetic contractile mechanisms may contribute to postviral airway dysfunction. We studied airway physiology in anesthetized rats at 1 to 8 wk after inoculation with Parainfluenza 1 virus or vehicle. The virus groups had airway obstruction (abnormal lung mechanics, gas exchange and residual volume), and increased sensitivity to intravenous methacholine at 1 to 4 wk, although methacholine hypersensitivity was minimal in vagotomized rats; these abnormalities were absent at 7 to 8 wk after inoculation. Airway responses to vagal parasympathetic nerve stimulation were enhanced markedly at 1 to 4 wk, and significantly at 7 to 8 wk, after viral inoculation. Dysfunction of M2 muscarinic autoreceptors during acute viral infection was indicated by a significant attenuation of gallamine-induced augmentation of airway parasympathetic responses; in contrast, gallamine-augmentation of parasympathetic responses at 2 to 8 wk after viral inoculation was not different from noninfected control animals. We conclude that respiratory virus infection in rats produces airway dysfunction that remains for weeks after resolution of the acute infection, and that is caused in part by parasympathetic hyperresponsiveness, associated both with M2 autoreceptor malfunction and with M2-independent mechanism(s).
Asunto(s)
Asma/fisiopatología , Hiperreactividad Bronquial/fisiopatología , Infecciones por Paramyxoviridae/complicaciones , Sistema Nervioso Parasimpático/fisiopatología , Infecciones del Sistema Respiratorio/complicaciones , Animales , Asma/complicaciones , Pruebas de Provocación Bronquial , Estimulación Eléctrica , Trietyoduro de Galamina/farmacología , Masculino , Cloruro de Metacolina , Antagonistas Muscarínicos , Virus de la Parainfluenza 1 Humana , Ratas , Ratas Sprague-Dawley , Receptores Muscarínicos/fisiología , Mecánica Respiratoria , Nervio Vago/fisiologíaRESUMEN
We found a branch of the carotid sinus nerve in 44 of 48 dogs. We propose that this branch be referred to as the "circumsinus" branch of the carotid sinus nerve. Both chemoreceptor and baroreceptor activity were detected in this branch during electrophysiological recording efforts utilizing classic nerve recording techniques. Its convenient location permits whole nerve or single unit recording without having to transect, dissect, or even expose the carotid sinus nerve. Carotid baroreceptor and chemoreceptor activity can be monitored with most of the carotid bifurcation's neural pathways intact.
Asunto(s)
Seno Carotídeo/fisiología , Células Quimiorreceptoras/fisiología , Presorreceptores/fisiología , Animales , Seno Carotídeo/anatomía & histología , Seno Carotídeo/inervación , Perros , Electrofisiología , Femenino , Masculino , Terminología como AsuntoRESUMEN
Viral bronchiolitis is a common disease that may result in persistent airway abnormalities. Previous studies of neonatal bronchiolitis in rats revealed chronic sequelae, including airway obstruction, airway hyperresponsiveness, increased production of airway eicosanoids, and increased numbers of bronchiolar mast cells. To address the hypothesis that postbronchiolitis airway obstruction is caused in part by reversible processes, we tested whether obstruction could be reversed by a brief course of high-dose corticosteroids. Neonatal Brown Norway rats (5 days of age) were inoculated with parainfluenza type 1 virus or sterile vehicle. At 8 wk of age, rats were treated with dexamethasone (1.4 mg.kg-1 x day-1 sc) or saline for 3 days and were evaluated for lung mechanics, gas exchange, and lung inflammatory cells 1 day after the last injection. Dexamethasone normalized the chronic virus-induced airway obstruction and reduced the numbers of bronchiolar mast cells and other inflammatory cells. Resistance and dynamic compliance correlated significantly with bronchiolar mast cells but not with other airway inflammatory cell infiltrates. We conclude that the airway abnormalities that persist in rats after recovery from neonatal bronchiolitis are associated with increased numbers of bronchiolar mast cells and are largely due to corticosteroid-sensitive mechanisms.
Asunto(s)
Bronquiolitis Viral/tratamiento farmacológico , Dexametasona/uso terapéutico , Resistencia de las Vías Respiratorias/fisiología , Animales , Animales Recién Nacidos , Bronquiolitis Viral/patología , Bronquiolitis Viral/fisiopatología , Femenino , Histamina/sangre , Pulmón/patología , Masculino , Mastocitos/fisiología , Oxígeno/sangre , Virus de la Parainfluenza 1 Humana , Infecciones por Paramyxoviridae/patología , Embarazo , Intercambio Gaseoso Pulmonar/fisiología , Ratas , Ratas Endogámicas BNRESUMEN
To evaluate the association of various leukocytes with pulmonary resistance and methacholine responsiveness, we induced pulmonary eosinophil-rich inflammation in IgE-sensitized (ovalbumin) Sprague Dawley rats. Sensitized rats were challenged with either relevant (OA) or irrelevant antigen by tracheal insufflation a) with no other treatment, b) in conjunction with intravenous Sephadex beads pretreatment, or c) with antigen coupled covalently to Sepharose beads. About 24 h after antigen challenge, respiratory system resistance (Rrs), response to aerosolized methacholine, and pulmonary histopathology were evaluated. Challenge with OA, insufflation with Sepharose, and treatment with i.v. Sephadex all independently increased inflammatory cell infiltrates, but the combination of OA with the other agents did not significantly enhance the inflammatory response over OA alone. Interactive stepwise regression techniques were utilized to identify correlates for Rrs and methacholine responsiveness. Mononuclear cell score was a significant predictor (p < .01) for Rrs, and insufflation of Sepharose had a significant independent effect on Rrs (p = .01) above that predicted by mononuclear cell infiltrates. Conversely, eosinophil score and neutrophil score were not significant predictors for Rrs, and challenges with antigen or Sephadex had no significant independent effect on Rrs beyond that predicted from mononuclear cell infiltrates. Eosinophil score was the only significant histological predictor for methacholine responsiveness (p < .0001). Challenges with Sephadex, antigen and Sepharose did not significantly change methacholine responsiveness independently of the changes associated with eosinophil infiltrates. These findings suggest that mononuclear cells and eosinophils contribute to increases in airway resistance and responsiveness, respectively, following the induction of pulmonary inflammation by both allergic and non-allergic stimuli.
Asunto(s)
Resistencia de las Vías Respiratorias , Eosinófilos/fisiología , Leucocitos Mononucleares/fisiología , Neumonía/etiología , Resistencia de las Vías Respiratorias/efectos de los fármacos , Animales , Dextranos , Masculino , Cloruro de Metacolina/farmacología , Neumonía/fisiopatología , Ratas , Ratas Sprague-DawleyRESUMEN
Subsequent to observations that pulmonary responses to antigen challenge are of different magnitudes in sensitized rats that are anesthetized with different drugs, we conducted studies to test whether the alterations in responses were due to changes in airway responsiveness to cholinergic or serotonergic challenge, opioid-receptor mediated events, or changes in mast cell mediator release. Immunoglobulin E-sensitized rats anesthetized with ketamine/urethan had larger changes in lung resistance and plasma histamine after pulmonary antigen challenge compared with rats anesthetized with fentanyl-droperidol. Blockade of opioid receptors with naloxone did not affect the responses. In unsensitized rats, airway responses to aerosolized methacholine were similar for the two anesthetics, indicating unchanged smooth muscle responsiveness; however, airway responses to intravenous serotonin were enhanced by ketamine and ablated by droperidol. We conclude that ketamine- and droperidol-induced alterations of pulmonary allergic responses are due to changes in sensitivity to serotonin and in mast cell mediator release. We speculate that mast cell mediator release may be modulated by a serotonin receptor-linked mechanism.
Asunto(s)
Anestésicos/farmacología , Hipersensibilidad/fisiopatología , Pulmón/efectos de los fármacos , Resistencia de las Vías Respiratorias/efectos de los fármacos , Animales , Antígenos/administración & dosificación , Histamina/sangre , Pulmón/inmunología , Pulmón/fisiopatología , Masculino , Mastocitos/efectos de los fármacos , Cloruro de Metacolina/farmacología , Ratas , Ratas Endogámicas , Serotonina/farmacologíaRESUMEN
Viral bronchiolitis in human infants has been associated with permanent changes in small airways and gas exchange and an increased incidence of hyperresponsive airways later in life. Respiratory infection by Sendai virus in neonatal rats also has been reported to cause permanent changes in lung morphology and increased numbers of bronchiolar mast cells and eosinophils. We evaluated pulmonary mechanics, gas exchange, and airway responsiveness in rats at 7 and 13-16 wk after neonatal Sendai virus infection. Rats from the virus group had lower arterial PO2 and increased total lung resistance compared with controls. There were no significant differences between groups for arterial PCO2, dynamic lung compliance, quasi-static respiratory system compliance, or vital capacity. Rats from the infected group were significantly more sensitive to aerosolized methacholine than were controls, although both virus and control groups became less sensitive with age. We conclude that neonatal Sendai virus infection in rats results in persistent alterations in lung function and airway responsiveness. This phenomenon may be valuable for the study of the relationships among airway inflammation, lung morphology, and airway hyperresponsiveness, and it may be relevant to human airway disease.
Asunto(s)
Bronquiolitis Viral/fisiopatología , Infecciones por Paramyxoviridae/fisiopatología , Mecánica Respiratoria/fisiología , Resistencia de las Vías Respiratorias/efectos de los fármacos , Resistencia de las Vías Respiratorias/fisiología , Animales , Animales Recién Nacidos , Asma/etiología , Bronquiolitis Viral/complicaciones , Cloruro de Metacolina/farmacología , Virus de la Parainfluenza 1 Humana , Infecciones por Paramyxoviridae/complicaciones , Intercambio Gaseoso Pulmonar/efectos de los fármacos , Intercambio Gaseoso Pulmonar/fisiología , Ratas , Ratas Endogámicas , Mecánica Respiratoria/efectos de los fármacosRESUMEN
The objectives of this study were to determine the kinetics of Sendai virus-induced increases in bronchiolar mast cells and to determine whether virus-induced increases in bronchiolar mast cells were associated with increased airway responsiveness to methacholine and with altered allergic inflammatory responses to antigen stimulation. Mast cell density in intrapulmonary airways was measured in outbred CD (Crl:CDBR) rats by use of morphometric techniques at 7, 15, 30, 60, and 90 days after viral or sham inoculation. Density of bronchiolar mast cells was higher in virus-inoculated rats than in control rats at 30, 60, and 90 days after inoculation (P less than 0.01), but not at 7 or 15 days after inoculation. Total pulmonary mast cell numbers were increased in virus-inoculated rats at 30 days after inoculation. Rats at 42 days after viral inoculation had over a threefold increase in sensitivity to the concentration of nebulized metbacholine that would stimulate a 50% increase in respiratory resistance. Virus-inoculated rats sensitized to ovalbumin had over a 10-fold increase (P less than 0.02) in pulmonary neutrophils that were recovered by bronchoalveolar lavage at 4 hours after ovalbumin aerosol challenge. Virus-inoculated rats at this time also had higher densities of neutrophils in bronchiolar walls than allergen-exposed control rats. The results indicate that Sendai virus induces increases in numbers of bronchiolar mast cells at times from 30 to 90 days after inoculation, and that mast cell increases are associated with airway hyperresponsiveness to methacholine and heightened allergic airway inflammatory reactions.
Asunto(s)
Bronquiolitis/fisiopatología , Mastocitos/fisiología , Virus de la Parainfluenza 1 Humana , Infecciones por Paramyxoviridae/fisiopatología , Sistema Respiratorio/fisiopatología , Animales , Líquido del Lavado Bronquioalveolar/citología , Recuento de Células , Modelos Animales de Enfermedad , Eosinófilos/ultraestructura , Inmunización , Mastocitos/inmunología , Mastocitos/ultraestructura , Cloruro de Metacolina , Microscopía Electrónica , Neutrófilos/ultraestructura , Ovalbúmina , Ratas , Sistema Respiratorio/inmunología , Sistema Respiratorio/patología , Coloración y EtiquetadoRESUMEN
Previous studies suggested that although rats that were passively sensitized [monoclonal murine immunoglobulin E (IgE)] would respond to pulmonary antigen challenge with an immediate increase in resistance, they exhibited no late increases in resistance, unlike late changes in rats actively sensitized to preferentially produce IgE antibody. We hypothesized that passively sensitized rats also would not develop antigen-induced pulmonary inflammation. In a blinded protocol we compared immediate responses and pulmonary resistance and inflammation at 8, 19 and 24 h after challenge with placebo antigen, with dinitrophenol-bovine serum albumin (DNP-BSA) to elicit a passively sensitized response, or with ovalbumin (OA) to elicit an actively sensitized response. Despite similar immediate responses to OA and DNP-BSA, only the rats challenged with OA had marked inflammatory changes and a significant incidence of late elevations in resistance. Inflammation scores and lung resistance were significantly correlated only in the OA group. We also observed that anesthesia with fentanyl/droperidol significantly attenuated the immediate but not the late responses to antigen challenge, compared with rats anesthetized with ketamine. We conclude that IgE-mediated immediate responses to pulmonary antigen challenge are insufficient, and may be unnecessary, to initiate antigen-induced late inflammatory changes.