FSTL1 aggravates cigarette smoke-induced airway inflammation and airway remodeling by regulating autophagy

BACKGROUND: Cigarette smoke (CS) is a major risk factor for Chronic Obstructive Pulmonary Disease (COPD). Follistatin-like protein 1 (FSTL1), a critical factor during embryogenesis particularly in respiratory lung development, is a novel mediator related to inflammation and tissue remodeling. We tried to investigate the role of FSTL1 in CS-induced autophagy dysregulation, airway inflammation and remodeling. METHODS: Serum and lung specimens were obtained from COPD patients and controls. Adult female wild-type (WT) mice, FSTL1(±) mice and FSTL1(flox/+) mice were exposed to room air or chronic CS. Additionally, 3-methyladenine (3-MA), an inhibitor of autophagy, was applied in CS-exposed WT mice. The lung tissues and serum from patients and murine models were tested for FSTL1 and autophagy-associated protein expression by ELISA, western blotting and immunohistochemical. Autophagosome were observed using electron microscope technology. LTB4, IL-8 and TNF-α in bronchoalveolar lavage fluid of mice were examined using ELISA. Airway remodeling and lung function were also assessed. RESULTS: Both FSTL1 and autophagy biomarkers increased in COPD patients and CS-exposed WT mice. Autophagy activation was upregulated in CS-exposed mice accompanied by airway remodeling and airway inflammation. FSTL1(±) mice showed a lower level of CS-induced autophagy compared with the control mice. FSTL1(±) mice can also resist CS-induced inflammatory response, airway remodeling and impaired lung function. CS-exposed WT mice with 3-MA pretreatment have a similar manifestation with CS-exposed FSTL1(±) mice. CONCLUSIONS: FSTL1 promotes CS-induced COPD by modulating autophagy, therefore targeting FSTL1 and autophagy may shed light on treating cigarette smoke-induced COPD.