ALDH7A1 and pulmonary arterial hypertension: Inhibitors of PDE (the most famous of this group being Viagra) can prolong or enhance the effects of physiological responses mediated by cAMP and cGMP by inhibition of their degradation by PDE and are considered potential therapeutics for pulmonary arterial hypertension, coronary heart disease, dementia, depression, and schizophrenia [37].