In vitro SIRT1 protein levels have been reported to decrease in lung epithelia (Yao et al., 2012), endothelial cells (Arunachalam et al., 2010), and macrophages after exposure to CSE; this finding was also noticed in the lungs of smokers and patients with COPD (Rajendrasozhan et al., 2008). This evidence concerns the gene SIRT1 and chronic obstructive pulmonary disease.