Cigarette smoke exposure increases their recruitment and activation in the respiratory tract, leading to the production of various proinflammatory mediators, including cytokines/chemokines (TNF‐α, IL‐6 and CCL2), ROS (superoxide and NO), and proteases (MMP9 and 12) (Stampfli & Anderson, 2009) that drives the development of emphysema (Barnes, 2016). Here, MMP9 is linked to pulmonary emphysema.