PECAM1 and acute respiratory distress syndrome: CD31+ NLRP3+ and CD31+ caspase-1+ cells were markedly reduced in lung tissues of ALI mice after treatment with metformin, and treatment with NAM reversed the inhibitory effect of metformin on NLRP3 and caspase-1 activation in the pulmonary endothelial cells of mice exposed to LPS administration (Figures 6E–H).