CCL2 and acute respiratory distress syndrome: It is reported that nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways play crucial roles in the inflammatory progression of ALI, and the activation of these pathways promotes the excessive release of cytokines and chemokines including interleukin (IL)-6, tumor necrosis factor (TNF)-alpha and monocyte chemoattractant protein (MCP)-1 [3,4].