Levels of histone deacetylase 1 (HDAC1) and sirtuin 1 (SIRT1), which are reported to participate in the mechanisms for experimental pulmonary emphysema, were significantly diminished in the lungs of the triple n/i/eNOSs−/− mice (Supplementary Fig. S5). This evidence concerns the gene HDAC1 and pulmonary emphysema.