Next, it was observed that upon HDAC1 overexpression or PP2A silencing in the PU treated ALI mice, the alveolar septum was significantly thickened and the lung tissues were severely damaged, a large number of inflammatory cells were infiltrated, and the total cell number, neutrophil number in BALF were increased (Fig. 5C, D). Here, HDAC1 is linked to acute respiratory distress syndrome.