Role of c‐Src tyrosine kinase in airway smooth muscle contraction

Abstract

One component of asthma is airway hyperactivity whereby the airway smooth muscle (ASM) cells abnormally constrict (to a greater degree) in the presence of an excitatory stimulus. It is not known whether serotonin (5‐HT) and acetylcholine (ACh) differentially impact ASM contraction via c‐Src phosphorylation (activation).This study investigated the contractile responses to ACh and 5‐HT in the presence of a non‐selective tyrosine kinase inhibitor (genistein) and Src‐family kinase inhibitors (PP1 and PP2). We also examined whether these contractile agonists influenced c‐Src phosphorylation. Bovine tracheal ASM segments (0.5cm × 3cm) were dissected, mounted vertically in an organ bath and the isometric changes in tension were measured. Segments were flash frozen and subjected to western blotting. PP1 and PP2 significantly reduced the contractile response of 5‐HT by 73% and 70% respectively, but did not change the response to ACh. Genistein completely abolished responses to 5‐HT but did not affect responses to ACh. Western blotting data suggests increased c‐Src phosphorylation in response to both 5‐HT and ACh.These data suggest c‐Src tyrosine kinase activation is uniquely sensitive to 5‐HT (relative to ACh) and might be a key molecular player in ASM contraction when ASM cells are stimulated by the 5‐HT G‐protein coupled receptor.Research Support: CIHR