The Pivotal Role of Airway Smooth Muscle in Asthma Pathophysiology

Figure 2

Mechanisms underlying mast cell myositis in asthma. In asthma, the mechanisms leading to an infiltration of airway smooth muscle (ASM) layer by mast cells, termed mast cell myositis, involve (1) mast cell chemotaxis towards the ASM bundle, (2) direct mast cell-ASM cell adhesion, and (3) mast cell-extracellular matrix- (ECM-) ASM cell adherence. Upon mast cell activation, mast cells release mediators which activate ASM cells, such as tryptase and TNF-α (TNFSF2). As a consequence, ASM cells produce and secrete chemotactic factors for mast cells, leading to an autoactivation loop. Under stimulation by Th1, Th2, and/or proinflammatory cytokines, produced by various inflammatory cells, ASM cells also secrete a wide range of mast cell chemotactic factors.