AGTR1 and pulmonary fibrosis: In this study, by using aliskiren to directly inhibit renin enzymatic activity, we demonstrated that renin activity is required for the development of lung fibrosis in this model; by using hydralazine to normalize blood pressure in RenTgMK mice, which does not interfere with the RAS, we showed that the development of lung fibrosis is independent of high blood pressure; and by blocking the AT1 receptor signaling with losartan, we proved that lung fibrosis is at least in part induced by the activation of the AT1 receptor signaling pathway.