Sirt1 overexpression inhibits PM_2.5-induced TM down-regulation and fibrin formation. WT C57BL/6 mice were given 5 μg of pAdTrack-CMV (control) or pAdTrack-Sirt1 (Sirt1) by tail vein injection as described in “In vivo gene delivery.” Forty-eight hours later, lungs were collected. (A) Lung cryosections were incubated with nonimmune IgG (NIgG) or Sirt1 antibody (Sirt1) for immunofluorescence study. (B) Lung homogenates were subjected to immunoblotting to examine Sirt1 expression (n = 4 mice/group). Forty-eight hours after Sirt1 gene delivery, mice were exposed to PBS or PM_2.5 (100 μg) by intranasal instillation. Twenty-four hours later, lungs were collected. Lung homogenates prepared were subjected to immunoblotting. Blots and normalized bar graphs show TM expression (C) and fibrin production (D) in the lungs of Sirt1^+/+ and Sirt1^−/− littermates. Data are presented as mean + SEM (n ≥ 6 mice/group; *P < .05).