NOS3 and endothelial dysfunction: To this end, treatment of EA.hy926 cells with 100 μM of MG for 8 h did not modify total eNOS but significantly decreased phosphorylation of eNOS (Ser-1177), an effect that was significantly blunted by BH4 (100 μM), sepiapterin (20 μM) or ONOO- suppression but not by the BH4 control NH4 (100 μM) or L-NAME (50 μM) suggesting that both eNOS phosphorylation (Ser-1177) and eNOS uncoupling are closely linked to MG-triggered endothelial dysfunction (Figure 5A and5B).