Fig. 2.

Cigarette smoke promotes p16 promoter-driven luciferase activity and senescence. a Luciferase imaging of p16^−/− lungs from mice exposed to RA or CS for 4 months. b Average radiance measuring luciferase activity in p16^−/− lungs (*p = 0.0114). c Luciferase staining in RA- and CS-treated lungs; images were taken of alveolar space in p16^−/− mice. Arrowheads indicate luciferase-positive AECII cells and arrows indicate macrophages (scale bar = 40 µm). d Quantitative real-time PCR of p16 RNA (*p = 0.0307, **p = 0.0003) and e SA β-Gal activity measured in whole lung homogenates after 4 months of RA or CS (*p = 0.0005). N, p16^+/+ RA = 4–8, p16^+/+ CS = 10–14, p16^−/− RA = 4–7, and p16^−/− CS = 12–14 mice