Differential expression of NOX isoforms dependent on the vessel bed have also been described, with veins expressing more NOX-2 and p22phox, and arteries expressing more NOX-4 [103] Importantly, a strong correlation between O2•– production with p22phox and NOX-4; NOX activity and endothelial dysfunction was observed [103]. This evidence concerns the gene NOX4 and endothelial dysfunction.