Bronchial epithelial cells release inflammatory markers linked to airway inflammation and remodeling in response to TLR5 ligand flagellin

Purevsuren Losol; Mi-Hong Ji; Jin Hee Kim; Jun-Pyo Choi; Jeong-Eun Yun; Jang-Ho Seo; Byung-Keun Kim; Yoon-Seok Chang; Sae-Hoon Kim

doi:10.1016/j.waojou.2023.100786

Bronchial epithelial cells release inflammatory markers linked to airway inflammation and remodeling in response to TLR5 ligand flagellin

World Allergy Organ J. 2023 Jun 10;16(6):100786. doi: 10.1016/j.waojou.2023.100786. eCollection 2023 Jun.

Authors

Purevsuren Losol^{1

2

3}, Mi-Hong Ji¹, Jin Hee Kim¹, Jun-Pyo Choi¹, Jeong-Eun Yun^{1

2}, Jang-Ho Seo², Byung-Keun Kim⁴, Yoon-Seok Chang^{1

2

3}, Sae-Hoon Kim^{1

2}

Affiliations

¹ Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, South Korea.
² Department of Internal Medicine, Seoul National University College of Medicine, Seoul, South Korea.
³ Medical Research Center, Seoul National University, Seoul, South Korea.
⁴ Department of Internal Medicine, Korea University Medical Center Anam Hospital, Seoul, South Korea.

Abstract

Background/aims: Flagellin, which is abundant in gram-negative bacteria, including Pseudomonas, is reported to influence on inflammatory responses in various lung diseases. However, its effect on airway epithelial cells in contribution to asthma pathogenesis is not elucidated yet. We aimed to investigate the effect of TLR5 ligand flagellin on the transcriptomic profile of primary human epithelial cells and to determine the markers of airway inflammation.

Methods: Normal human bronchial epithelial (NHBE) cells were grown and differentiated in air-liquid interface (ALI) culture for 14-16 days. The cells were treated with flagellin in vitro at 10 and 100 ng/ml for 3 and 24 h. The conditioned media and cells were harvested to validate inflammatory markers involved in airway inflammation using ELISA, Western blot, and quantitative PCR methods. RNA-sequencing was performed to investigate the transcriptional response to flagellin in ALI-NHBE cells.

Results: Altered transcriptional responses to flagellin in differentiated bronchial epithelial cells were determined, including genes encoding chemokines, matrix metalloproteinases, and antimicrobial biomolecules. Pathway analysis of the transcriptionally responsive genes revealed enrichment of signaling pathways. Flagellin induced the mRNA expressions of proinflammatory cytokines and chemokines, and secretion of GM-CSF, CXCL5, CCL5 and CXCL10. Flagellin enhanced the protein expression of MMP-13 in TGF-β1 and TGF-β2 pretreated cell lysates and Wnt/β-catenin signaling.

Conclusions: These findings suggest that flagellin could be a potent inducer of inflammatory markers that may contribute to airway inflammation and remodeling.

Keywords: Airway; Epithelial cell; Flagellin; Inflammation; TLR5.