Repeated Allergen Inhalation Induces Cytoskeletal Remodeling in Smooth Muscle from Rat Bronchioles

Airway hyperresponsiveness (AHR) is associated with airway wall structural remodeling and alterations in airway smooth muscle (ASM) function. Previously, in bronchioles from Brown Norway rats challenged by repeated ovalbumin (OVA) inhalation, we have reported increased force generation and depletion of smooth muscle contractile proteins. Here, we investigated if cytoskeletal changes in smooth muscle could account for this paradox. Sensitized rats (n = 5/group) were repeatedly challenged with OVA or saline, and the lungs were removed 24 h after the last challenge. Levels of globular (G) and filamentous (F) actin in bronchioles were determined by DNase I inhibition and contraction assessed in intact small bronchioles using a myograph. DNase I inhibition assays showed that G-actin monomers were more abundant (∼ 1F:2G) in extracts from resting small bronchioles from OVA- or saline-challenged animals. However, while contractile protein levels in bronchioles were reduced by OVA (P < 0.05), the proportion of F:G...