The involvement of NO-cyclic GMP-phosphodiesterase type 5 (PDE5) pathway was demonstrated previously by a group of researchers where PDE5 inhibition provided an anti-inflammatory response by influencing activated T cells to reduce cytokine (IL-6) release and subsequently diminished pulmonary fibrosis with improvement in oxygenation and stimulation of vascular repair. Here, PDE5A is linked to pulmonary fibrosis.