Summary
The cofactor tetrahydrobiopterin (BH4) is required for nitric oxide (NO) production
by all nitric oxide synthase (NOS) enzymes and is a key regulator of cellular redox
signalling. When BH4 levels become limiting NOS enzymes become ‘uncoupled’ and produce
superoxide rather than NO. Endothelial cell BH4 is required for the maintenance of
vascular function through NO production, and reduced BH4 levels are associated with
vascular dysfunction. Evidence increasingly points to important roles for BH4 and
NOS enzymes in other vascular cell types. Leukocytes have a fundamental role in atherosclerosis,
and new evidence points to a role in the control of hypertension. Leukocytes are a
major site of iNOS expression, and the regulation of this isoform is another mechanism
by which BH4 availability may modulate disease. This review provides an overview of
BH4 control of NOS function in both endothelial cells and leukocytes in the context
of vascular disease and current therapeutic evaluations.
Keywords
Tetrahydrobiopterin - BH4 - vascular disease - reactive oxygen species (ROS) - nitric
oxide