NAD (P) H oxidases are the major sources of intracellular ROS production in Hcy-induced endothelial cells and NAD (P) H oxidases consist of multiple subunits, containing membrane-associated Nox1–4 and p22phox subunits, with Nox4 playing the key role in vasculopathies [36, 37]. Here, NOX4 is linked to vascular disorder.