These inhibitors are categorized based on the PDE subtype they target: PDE5 inhibitors are employed to alleviate erectile dysfunction and pulmonary hypertension by promoting smooth muscle relaxation and enhancing blood circulation; PDE4 inhibitors elevate cAMP levels and are effective for pulmonary diseases such as asthma and COPD by targeting the airways, skin, immune system, and brain. Here, ALDH7A1 is linked to pulmonary arterial hypertension.