Previously, Pullamsetti et al. (24) have reported that the expression of dimethylarginine dimethylaminohydrolase (DDAH), a cytoplasmic enzyme that is closely associated with inducible nitric oxide synthase (iNOS) to promote inflammatory and fibrotic phenotypes, is pathologically upregulated in the lungs of pulmonary fibrosis patients, and our biochemical and immunohistochemical studies (20, 21, 25) show that PPIs inhibit DDAH to reduce soluble and total collagen levels. The gene discussed is NOS2; the disease is pulmonary fibrosis.