Objective:Metalloproteinases 9(MMP－9)of alveolar macrophages(AM)has been shown to play an important role in the formation of chronic obstructive pulmonary disease(COPD) and emphysema. However,its effect on expression and regulation mechanism is still not clear. This study is aimed to investigate the potential role of sirtuin1(Sirt1)in the expression and regulation mechanism of matrix metalloproteinases 9(MMP－9)in alveolar macrophages(AM). Methods:The AMs were cultured in rats,the simulation model was established using cigarette smoking extract(CSE). To observe change of expression of MM9 in cells. The interference model was established using siRNA to observe expression of MMP－9 after the inhibition of Sirt1. Results:MMP－9 expression increased significantly(P < 0.05)due to 1% CSE stimulation. However,this effect can be antagonized by the Sirt1 agonist resveratrol in a concentration dependent manner. MMP－9 expression in AM cells increased significantly after siRNA interference(P < 0.05). Conclusion:Sirt1 is involved in the expression of MMP9 in AM,and may play a protective role in COPD.