Kinetics of in vitro bronchoconstriction in an elastolytic mouse model of emphysema

Abstract

Thin-slice videomicroscopy was used to examine the kinetics of constriction in small airways in situ.Balb/C mice inhaled elastase (0-20 IU), and were then left to recover for 14 days before euthanisation and lung removal. Cholinergic responsiveness was assessed in thin lung slices. Magnitude and velocity of narrowing in response to 10 -5 M acetylcholine (ACh), as well as the full concentration-response relationship for ACh (10 -8 -10 -5 M) were assessed.In vivo exposure to elastase was accompanied by statistically significantly decreased magnitudes and velocities of contraction, but no change in the ACh concentration-response relationship. Conversely, overnight, in vitro exposure of slices from control animals to elastase (2.5 mg?mL -1 ) resulted in increased magnitudes and velocities of airway narrowing, with impaired relaxation, as well as marked tearing of the airways from the surrounding parenchyma. These changes are characteristic of decreased tethering forces on the airway wall.Thus, the lung slice technique coupled with videomicroscopic analysis of airway contraction velocities provides a powerful tool to study airway-parenchymal interactions. The elastolytic model of emphysema, which manifests with airspace enlargement and loss of parenchymal attachments, is accompanied by decreased airway contraction kinetics. The mechanism(s) underlying this loss of function remain to be elucidated.

Effects of allergen on airway narrowing dynamics as assessed by lung-slice technique

“…Several technical aspects of the lung-slice technique used herein have been validated: extent of inflation; concentration of agarose; and wide range of airway sizes [15]. In order to evaluate the optimal rate of data acquisition for estimating contraction velocities, a single recording at 10 frames per second (fps) was performed and divided into several other videos with lower frame rates by selecting appropriate frames (e.g.…”

“…Acetylcholine was used at 1 mM to assess responsiveness, this concentration has been shown to be essentially maximally effective [11,15,16] and, as figure 1 did not indicate there to be a change in sensitivity, a full concentration-response relationship was unnecessary.…”

Videomicrometry of lung slices: a glimpse of the dynamic airway parenchyma interaction in emphysematous lungs

“…As reported by KHAN et al [11], overnight incubation of thin slices of mouse lung with elastase produced visible tissue destruction, as evidenced by patchy parenchyma and epithelial degeneration. As expected, airways in the elastase-treated slices narrowed at a greater rate and to a greater extent compared with normal controls.…”

“…BERGNER and SANDERSON [10] pioneered the technique of videomicrometry with sufficient temporal and spatial resolution to describe the time courses of calcium transients and airway smooth muscle contraction in lung slices. KHAN et al [11] have extended the technique to characterise the kinetics of bronchoconstriction in a mouse model of elastase-induced emphysema. Creative uses of this innovative technique are likely to lead to fruitful research involving analysis of complex mechanical interactions among tissue components.…”

A Fungal Protease Allergen Provokes Airway Hyperresponsiveness in Asthma

“…Serine protease (elastase)-mediated airway destruction contributes to cigarette smokeinduced airway obstruction 31 . Treatment of lung slices from naïve mice with a serine protease (human neutrophil elastase) led to significantly increased airway contraction 32 . In a separate study, intratracheal administration of elastase to guinea pigs augmented bronchoconstriction in response to inhaled acetylcholine through an unknown mechanism 33 .…”