MMP9 and hypersensitivity pneumonitis: Gao et al. investigate the antifibrotic effects of DBT on bleomycin-induced pulmonary fibrosis in rats and found that DBT administration attenuated the degree of alveolitis and lung fibrosis and markedly reduced the mRNA levels of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) [27].