Role And Mechanism Of MTOR In Regulating MMP12 In COPD

Background: Chronic obstructive pulmonary disease(COPD)is characterized by incompletely irreversible and progressive airflow limitation,chronic airway inflammation,systemic effects and complications.The primary risk factor for COPD is prolonged cigarette smoking.Mechanistic target of rapamycin(mTOR)is a highly conserved serine/threonine protein kinase that can form complexes of m TOC1 or mTORC2 with other proteins.mTOR is able to regulate cell proliferation and metabolism after being activated.Previous study had shown that stress-induced protein Rtp801 can contribute to cigarette smoke-induced emphysema by inhibiting the activity of mTOR.Protease-antiprotease imbalance is a key feature of COPD,in which matrix metalloproteinase 12(MMP12)plays an important role in the pathogenesis of COPD.MMP12 is produced by macrophages which can degrade elastin.MMP12 knockout mice resistant to develop emphysema after long-term cigarette smoke exposure.However,studies concerning how MMP12 induced by cigarette smoke is barely known.Objective: To investigate function and mechanism of mTOR in regulating the expression of MMP12 in COPD.Methods: The expression of mTOR in cigarette smoke extract(CSE)treated peritoneal macrophage and bone marrow-derived macrophage was examined by western blot(WB).WB and quantitative real-time PCR were used to detect the MMP12 expression in mTOR inhibitors(rapamycin and torin 1)pre-treated or genetic knockdown cells.The expression of MMP12 induced by CSE in mTOR knockdown cells was detected after treating with the NF-?B inhibitor BAY 11-7082.In vivo,WB and flow cytometry were used to detect the activity of mTOR in macrophages after cigarette smoke exposure.Macrophage mTOR deficiency mice were used to identify the role of mTOR in regulation the cigarette smoke induced MMP12,inflammation and emphysema.Results: 1)In vitro,CSE can decrease the expression of mTOR,and lead to amplified MMP12 expression.2)mTOR can inhibit the expression of MMP12 through inhibition of NF-?B pathway.3)In vivo,mTOR activity increased after cigarette smoke exposure in macrophages,and mTOR can inhibit the expression of MMP12,the occurrence of airway inflammation and the development emphysema.Conclusion: Cigarette smoke can modulate the activity of mTOR in macrophages,which can suppress the expression of MMP12 through NF-?B signaling pathway.mTOR is able to inhibit cigarette smoke induced airway inflammation and the development of emphysema in mouse model.