Tetrahydrobiopterin: pleiotropic roles in cardiovascular pathophysiology.

Tetrahydrobiopterin (BH4) functions as a cofactor in several important enzyme systems. Substantial evidence implicates BH4 as a key regulator of endothelial nitric oxide synthase (eNOS) in the setting of endothelial dysfunction and atherosclerosis. Investigators have now taken early steps in addressing the potential of BH4 as a therapeutic strategy. However, it has become more apparent that the role of BH4 in other enzymatic pathways, including other NOS isoforms and the aromatic amino acid hydroxylases, may have a bearing on important aspects of cardiovascular homeostasis. Together with eNOS, these enzymes may play key roles in diverse cardiovascular disease states such as ischaemia-reperfusion injury, cardiac hypertrophy, cardiac autonomic function and pulmonary hypertension. This review provides an overview of the role of BH4 in cardiovascular pathophysiology.