Exploring mechanisms of airway hyperresponsiveness in human airway smooth muscle cells
Creators: name: Woo, Joanna
Publisher: name: No Publisher Supplied
Year: 2024

description: Asthma is a chronic airway disease characterized by airflow obstruction through airway narrowing and marked by inflammation, remodeling, and reactivity of the airway wall, influenced by environmental stimuli and genetic factors. Airway hyperresponsiveness (AHR), a key hallmark of asthma, evokes bronchospasm through airway contraction. Airway smooth muscle (ASM) cells are the central effector driving AHR, which regulate airway lumen diameter by regulating muscle tone. In patients with asthma, ASM cells are hypercontractile, raising questions about the mechanisms behind ASM dysfunction. Effective therapeutic approaches to mitigate AHR require insight into the modulatory role ASM play in asthma development and severity. The purpose of this dissertation is to uncover targets for AHR in response to cytokines present in the airways in asthma pathogenesis by investigating drivers of ASM contraction. To pinpoint mediators of AHR, we first explored the role of environmental triggers on ASM contraction. Factors contributing to AHR such as exposure to toxicants, underlying metabolic diseases, or infection can induce structural changes in the airway lumen and stimulate airway contraction through increased cytokine secretion and expression. However, ASM are particularly prone to contraction after cytokine exposure, as inflammatory cytokines can either directly stimulate ASM contraction, act as sensitizers to contractile stimuli, or trigger the secretion of contractile mediators from surrounding cells. ASM cells shorten primarily through excitation-contraction (E-C) coupling, driven by three mechanisms: calcium signaling, calcium sensitization, and actin polymerization, all enhanced by contractile agonists and cytokine stimulation. We identified the volume-regulated anion channel (VRAC) as a potential mediator of ASM contraction, present ubiquitously throughout different tissues as a regulator of cell physiology and signaling. However, little is known about the role of VRAC in the signaling and mechanics in airway diseases. To further investigate the modulatory role of VRAC in airway physiology, we posited that VRAC affects E-C coupling and ASM contraction. We determined the effects of VRAC inhibition on E-C coupling mediators, ASM stiffening, and bronchoconstriction using human ASM cells and human precision-cut lung slices. Inhibition of VRAC attenuated phosphorylation of various proteins within E-C coupling pathways, primarily inactivating mediators of calcium sensitization and actin polymerization. ASM stiffening and bronchoconstriction were also reduced with pharmacological inhibition of VRAC. Here, we identify a mechanism of ASM contraction through modulation of highly expressed VRAC in human ASM cells. By identifying potential contractile signaling mediators, our research provides further insights into the role of membrane channels like VRAC in GPCR-mediated signaling and ASM shortening. This dissertation research highlights the investigation of potential contractile signaling mediators, providing further insight into mechanisms of ASM contraction and AHR required to identify targets for asthma therapy.