Cigarette smoke extract enhances neutrophil elastase-induced IL-8 production via proteinase-activated receptor-2 upregulation in human bronchial epithelial cells

• Published in: Experimental & molecular medicine 2018-07, Vol.50 (7), p.1-9
• Main Authors: Lee, Kyoung-Hee, Lee, Jinwoo, Jeong, Jiyeong, Woo, Jisu, Lee, Chang-Hoon, Yoo, Chul-Gyu
• Format: Article
• Language: English
• Subjects: 631/80/304; 631/80/86; 96; 96/95; AKT protein; Animals; Biomedical and Life Sciences; Biomedicine; Bronchi - cytology; Bronchi - drug effects; Bronchi - metabolism; Cells, Cultured; Chronic obstructive pulmonary disease; Cigarette smoke; Elastase; Epithelial cells; Extracellular signal-regulated kinase; Female; Gene expression; Humans; Inflammation; Interleukin 8; Interleukin-8 - genetics; Interleukin-8 - metabolism; Kinases; Lung diseases; MAP kinase; Medical Biochemistry; MEK inhibitors; Membrane proteins; Mice; Mice, Inbred C57BL; Molecular Medicine; mRNA; Neutrophils; Neutrophils - metabolism; Obstructive lung disease; Oxidative stress; p38 Mitogen-Activated Protein Kinases - metabolism; Pancreatic Elastase - metabolism; Proteinase; Proteinase-activated receptor 2; Receptor, PAR-2 - genetics; Receptor, PAR-2 - metabolism; Respiratory Mucosa - drug effects; Respiratory Mucosa - metabolism; siRNA; Stem Cells; Tobacco Smoke Pollution - adverse effects; Up-Regulation
• ISSN: 1226-3613; 2092-6413
• DOI: 10.1038/s12276-018-0114-1

Although inflammation, oxidative stress, and protease-antiprotease imbalance have been referred to as a pathogenic triad in chronic obstructive pulmonary disease (COPD), little is known about how they interact. The objectives of this study were to elucidate the effect of cigarette smoke extract (CSE) on the neutrophil elastase (NE)-induced inflammatory response and its molecular mechanism in bronchial epithelial cells. We observed that NE activated extracellular signal-regulated kinase (ERK) and induced IL-8 production. Blocking ERK activation using a MEK inhibitor (U0126) suppressed NE-induced IL-8 secretion and knockdown of proteinase-activated receptor 2 (PAR2) using siRNAs inhibited both NE-induced ERK activation and subsequent IL-8 release, suggesting that NE-induced IL-8 production is dependent on PAR2-mediated ERK activation. Interestingly, pre-exposure to CSE markedly enhanced NE-induced IL-8 production. As PAR2 acts as a receptor for NE, we next investigated the effect of CSE on PAR2 expression as a molecular mechanism for the increased IL-8 production induced by NE in CSE exposed cells. CSE, but not NE, increased the expression of PAR2 mRNA and surface membrane protein. Inhibition of p38 MAPK reduced PAR2 expression induced by CSE while inhibition of the ERK and Akt pathway had no effect. Consequently, p38 inhibition significantly abrogated CSE-induced enhancement of IL-8 production in NE-treated cells. Of note, we observed increased PAR2 levels in lung homogenates and lung epithelial cells from CSE-treated mice and from both smokers and patients with COPD. Taken together, these results suggest that CSE upregulates PAR2 in normal human bronchial epithelial cells, thereby enhancing the inflammatory response to NE. Lung disease: How cigarette smoking enhances lung inflammation A study of the effect of cigarette smoke extract (CSE) on lung lining cells clarifies the interaction between CSE and an enzyme implicated in causing chronic obstructive pulmonary disease (COPD). The enzyme elastase is released by neutrophils and is known to induce inflammation, which causes lung irritation in COPD. Chul-Gyu Yoo and colleagues at Seoul National University in South Korea exposed cultured human lung cells to CSE. This exposure activated specific molecular signaling processes by which the elastase enzyme-induced inflammation was enhanced. Of particular note was an increase in the levels of a cell surface receptor protein in CSE-treated cells. This protein was in