Other studies using acute animal models of lung injury such as after cardiopulmonary bypass [21] and after infusion of Escherichia coli lipopolysaccharide [25] also demonstrated that blocking of proteases, primarily MMP-9 and neutrophil elastase with a modified tetracycline (COL-3) prevented lung injury and ultimately the development of ARDS. This evidence concerns the gene MMP9 and acute respiratory distress syndrome.