Wang, Shengyu

Mechanical forces on the airway can contribute to altered contractility and remodeling in airway diseases, but the mechanisms are not clearly understood. Using human airway smooth muscle cells exposed to cyclic forces with static stretch to mimic breathing and static pressure, we found that the effects of stretch are mediated through STIM1, resulting in the activation of multiple pathways, including Piezo channels and the inflammasome, with potential downstream influences on contractility and remodeling.

Introduction Asthma is acutely aggravated and chronically worsened by cigarette smoke (CS), as well as secondhand smoke exposure. In this regard, studies show significant differences between women vs. men in their response to the detrimental effects of CS, suggesting that female sex steroids (particularly estrogen) may be involved. Airway smooth muscle (ASM) cell proliferation and airway remodeling is a key feature of asthma and COPD. Surprisingly, there is little information regarding sex steroid effects on cigarette smoke‐induced changes of airway structure and function. In the current study, we hypothesize that estrogen interferes with CSE exposure‐induced proliferation, thereby contributing to airway smooth muscle remodeling. Methods and Results Human ASM tissues (epithelium‐denuded) and isolated ASM cells were from lung samples of patients with known smoking histories undergoing thoracic surgery for non‐infectious, focal pathology. Exposure of human ASM to cigarette smoke extract (CSE, Kentucky research cigarette 1RF4) 1%CSE or 2%CSE for 24h significantly increased ASM proliferation (proliferation assay: Cell Titer Aueous One, and Cyquant). Exposure of physiological concentrations of 17‐β‐estradiol (E 2, 1nM) did not alter ASM proliferation at baseline. Interestingly, E 2 pre‐treatment (1 h prior to CSE exposure) significantly reduced CSE‐induced human ASM proliferation. This was further confirmed by Western blot analysis for proliferative markers PCNA and Cyclin E. In addition, to explore the mechanistic bases of differential effects of E 2 on ASM proliferation under basal and CSE‐exposed conditions, the estrogen receptor profile in ASM tissue was screened in parallel for patients with and without smoking histories. Human ASM tissue from smokers samples showed substantial increased ERα and β expression compared to non‐smokers. Inhibition of ERα and β prevented the effects of estrogen on CSE‐induced increases in proliferation. Conclusions Collectively, estrogen exposure decreased human ASM proliferation induced by CSE. ER expression and signaling is enhanced in CSE induced inflamed ASM, with a potential beneficial role in reducing remodeling with CS exposure. These results will lay the foundation for examining the role of estrogen signaling in pathogenesis of cigarette smoke‐induced airway remodeling and possible sex based therapeutic targets in smoking‐related diseases. Support or Funding Information Supported by Flight Attendants Medical Research Institute (VS) and NIH R01 grant HL123494 (VS)

Airway remodeling in asthma driven by inflammation involves proliferation of epithelial cells and airway smooth muscle (ASM), as well as enhanced extracellular matrix (ECM) generation and deposition, i.e., fibrosis. Accordingly, understanding profibrotic mechanisms is important for developing novel therapeutic strategies in asthma. Recent studies, including our own, have suggested a role for locally produced growth factors such as brain-derived neurotrophic factor (BDNF) in mediating and modulating inflammation effects. In this study, we explored the profibrotic influence of BDNF in the context of asthma by examining expression, activity, and deposition of ECM proteins in primary ASM cells isolated from asthmatic vs. nonasthmatic patients. Basal BDNF expression and secretion, and levels of the high-affinity BDNF receptor TrkB, were higher in asthmatic ASM. Exogenous BDNF significantly increased ECM production and deposition, especially of collagen-1 and collagen-3 (less so fibronectin) and the activity of matrix metalloproteinases (MMP-2, MMP-9). Exposure to the proinflammatory cytokine TNFα significantly increased BDNF secretion, particularly in asthmatic ASM, whereas no significant changes were observed with IL-13. Chelation of BDNF using TrkB-Fc reversed TNFα-induced increase in ECM deposition. Conditioned media from asthmatic ASM enhanced ECM generation in nonasthmatic ASM, which was blunted by BDNF chelation. Inflammation-induced changes in MMP-2, MMP-9, and tissue inhibitor metalloproteinases (TIMP-1, TIMP-2) were reversed in the presence of TrkB-Fc. These novel data suggest ASM as an inflammation-sensitive source of BDNF within human airways, with autocrine effects on fibrosis relevant to asthma.