Similar to this viewpoint, PEBP4 deficiency significantly increased lung MPO activity (Fig. 2G), an indicator of neutrophil infiltration [12], and promoted the secretion of serum TNF-α, IL-1β, and IL-6 (Fig. 2H-J), as well as notablely up-regulated the protein expression of lung COX-2 (Fig. 2K), an inflammatory enzyme [12], in ALI mice. Here, MPO is linked to acute respiratory distress syndrome.