TLR4 and acute respiratory distress syndrome: We focused on a novel WNT1 inducible secreted protein (WISP1 or CCN4; also referred to as WNT1 inducible signaling protein-1)–integrin β5 pathway of TLR4-mediated pulmonary inflammation and injury in this two-hit model as we previously noted key roles for WISP1 and beta integrins in VILI [21] and CLP [22, 23] mediated ALI.