Sirt1 regulates KLF2 expression in the lung after PM_2.5 exposure. (A) Sirt1^+/+ and Sirt1^−/− littermates were exposed to PBS or PM_2.5 (100 μg) by intranasal instillation. Twenty-four hours later, lungs were collected. Nuclear proteins were extracted from the lung samples and subjected to immunoblotting to examine lung KLF2 expression. Data are presented as mean + SEM (n ≥ 7 mice/group). (B) WT C57BL/6 mice were given 5 μg of pAdTrack-CMV (control) or pAdTrack-Sirt1 (Sirt1) by tail vein injection as described “In vivo gene delivery.” 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. Nuclear proteins were extracted from the lung samples and subjected to immunoblotting to examine lung KLF2 expression. The blots and normalized bar graphs show KLF2 expression. Data are presented as mean + SEM (n ≥ 7 mice/group; *P < .05).