Aerosolized polymerized type I collagen reduces airway inflammation and remodelling in a guinea pig model of allergic asthma.

Collagen-polyvinylpyrrolidone (Collagen-PVP) has been demonstrated to elicit immunomodulatory properties in different chronic inflammatory diseases. Nevertheless, its effects on asthma are still unknown. We have evaluated whether collagen-PVP could modulate airway inflammation and remodelling in a guinea pig model of allergic asthma. Sensitized guinea pigs were challenged with the allergen (ovalbumin) six times (at 10-day intervals). From the third challenge on, animals were treated every 5 days with saline aerosols containing 0.16, 0.33, or 0.66 mg/ml of collagen-PVP (n = 5, respectively). Some guinea pigs, sensitized and challenged with saline as well as treated with 0 or 0.66 mg/ml collagen-PVP, were included in the study as control (n = 7) and sham groups (n = 5), respectively. From the first challenge on, ovalbumin induced a transient airway obstruction, measured by barometric plethysmography, which was not modified by collagen-PVP treatments. After the last allergen challenge, guinea pigs were anesthetized to obtain bronchoalveolar lavage (BAL) and the left lung caudal lobe. As expected, BAL cell count from allergen-challenged guinea pigs showed abundant neutrophils and eosinophils, as well as numerous tumor necrosis factor (TNF)-alpha-expressing granulocytes and macrophages in airway wall (determined by immunohistochemical assay). Neutrophilia and TNF-alpha-expressing leukocytes, from collagen-PVP treated animals, diminished from 0.16 mg/ml, and eosinophilia from 0.66 mg/ml of collagen-PVP doses. Histological changes induced by allergen challenges include thickening of connective tissue below airway epithelium and vascular wall widening of airway adjacent vessels; these changes were reduced by collagen-PVP treatment. Collagen-PVP seems to have anti-inflammatory and antifibrotic properties in this guinea pig asthma model.

Capacitative Ca2+ entry during Ca2+ undershoot in bovine airway smooth muscle.

In numerous cells, Ca2+ undershoot is commonly observed after withdrawing stimulus that release Ca2+ from intracellular stores. In airway smooth muscle (ASM), the fast intracellular Ca2+ concentration ([Ca2+]i) drop during undershoot is produced by sarcoplasmic reticulum (SR) reloading, but the mechanisms involved in the long lasting basal [Ca2+]i recovery are unknown. We investigated the post-caffeine Ca2+ undershoot recovery in ASM isolated cells from bovine trachea. [Ca2+]i determination was done by a ratiometric method by incubating cells with Fura-2/AM. After inducing a transient response, caffeine withdrawn generated a Ca2+ undershoot. SR-Ca2+ content during maximum undershoot drop was approximately 40% of SR caffeine-releasable Ca2+ (SR-Ca2+ load). Undershoot recovery rate increased in presence of cyclopiazonic acid (CPA, a SR-Ca2+ ATPase inhibitor), but SR-Ca2+ load was reduced. Genistein (a tyrosine kinase inhibitor) slowed down the Ca2+ undershoot drop and the SR-Ca2+ load but did not affect the undershoot recovery rate. Ni2+ (a capacitative Ca2+ inhibitor), but neither SKF-96365 (a passive Ca2+ entry inhibitor) nor econazole (a capacitative Ca2+ inhibitor in non-excitable cells), inhibited Ca2+ undershoot recovery and SR-Ca2+ load. Our data suggest that capacitative Ca2+ entry is involved in bovine ASM Ca2+ undershoot recovery, and that changes in Ca2+ undershoot have an impact on SR-Ca2+ loading which might affect in turn ASM excitability.

Spontaneous changes in guinea-pig respiratory pattern during barometric plethysmography: role of catecholamines and nitric oxide.

Barometric plethysmography for unrestrained animals is a non-invasive method that allows repetitive measurements of pulmonary function, but habituation of the conscious animal to this technique has not been explored. Respiratory frequency (f(R)) and 'enhanced pause' (P(enh)) were measured by barometric plethysmography for a period of 8 h in guinea-pigs. Compared with basal values, during the first hour of recording a progressive increase in P(enh) (up to 25-50%) and a corresponding decrease in f(R) were recorded, followed by a relative plateau in each for up to 8 h. These changes were avoided by a 30-min pretreatment with propranolol and l-NAME (nitric oxide synthase inhibitor), with P(enh) values as high as this plateau phase since the beginning of recording. Atropine, salbutamol or budesonide did not modify the progressive increment in P(enh). We concluded that catecholamines and nitric oxide are released when guinea-pigs are introduced into the plethysmographic chamber, leading to initial low P(enh) values. These mediators probably diminish owing to habituation of the animal to the new environment, with an apparent progressive increment in P(enh). These spontaneous changes in P(enh) and f(R) must be taken into account during barometric plethysmography in order to avoid misinterpretation of the results.