ALDH7A1 and pulmonary fibrosis: First, the PAN-PDE has significant inhibitory activity against multiple PDE isoforms, including PDE1, PDE3, PDE4, PDE5, PDE7, and PDE8, which are involved in airway remodeling and the development of pulmonary fibrosis (Wright et al., 1998; Fuhrmann et al., 1999).