Role of hyaluronan and reactive oxygen species in tissue kallikrein-mediated epidermal growth factor receptor activation in human airways.
In human airways, oxidative stress-induced submucosal gland cell hypertrophy and hyperplasia, histological features of chronic bronchitis, have been linked to epidermal growth factor receptor (EGFR) activation. To explore mechanisms of oxidative stress-induced EGFR activation and signaling, primary cultures of human tracheal submucosal gland (SMG) cells were used to assess EGFR ligand release, EGFR phosphorylation, p44/42 MAPK phosphorylation, and mucin 5AC synthesis in response to reactive oxygen species generated by xanthine/xanthine oxidase (X/XO). Exposure to X/XO increased release of epidermal growth factor (EGF) from these cells, thereby activating EGFR, phosphorylating MAPK, and increasing mucin 5AC production. The importance of EGF was confirmed by transfection of small interfering RNA inhibiting pro-EGF production, which resulted in inhibition of EGFR and MAPK phosphorylation despite X/XO exposure. Blocking signaling by using specific protease inhibitors showed that tissue kallikrein (TK) processed pro-EGF in response to X/XO. Airway TK is bound and inactivated by luminal hyaluronan (HA), and treatment of submucosal gland cells with X/XO induced HA depolymerization and TK activation. These events were blocked by reactive oxygen species scavengers and addition of exogenous excess HA and TK inhibitors. Thus, HA plays a crucial role in regulating airway TK activity and thereby TK-mediated release of active EGF from human SMG cells. Sustained HA depolymerization is expected to cause TK activation, EGF release, and EGFR signaling and to lead to SMG cell hypertrophy and hyperplasia as well as mucus hypersecretion with subsequent airflow obstruction.
Division of Pulmonary and Critical Care Medicine, University of Miami School of Medicine, 1600 NW 10th Avenue, Miami, FL 33136, USA.
Susana M
SM
Casalino-Matsuda
Maria Elena
ME
Monzon
Gregory E
GE
Conner
Matthias
M
Salathe
Rosanna M
RM
Forteza
D001980:Bronchi / Q000502:physiology*; D066246:ErbB Receptors / Q000235:genetics / Q000502:physiology*; D006801:Humans; D006820:Hyaluronic Acid / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020840:Tissue Kallikreins / Q000502:physiology*; D014132:Trachea / Q000502:physiology*
D017382:Reactive Oxygen Species; D006820:Hyaluronic Acid; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020840:Tissue Kallikreins