CXCL8 and acute respiratory distress syndrome: In ARDS patients, the IL-6 serum levels showed significant positive correlations with the serum levels of endothelial injury indicators such as IL-8, MCP-1, and PAI-1 (r = 0.9372, P < 0.0001; r = 0.5074, P = 0.02574; and r = 0.6587, P = 0.0022, respectively; Fig. 2B).