Their results revealed a new mechanism by which the natural alkaloids in motherwort effectively reversed homocysteine-induced endothelial dysfunction and prevented endothelial nitric oxide synthase (eNOS) uncoupling by increasing the expression of enzyme GTP–cyclohydrolase I (GTPCH1) and dihydrofolate reductase (DHFR) [75]. Here, NOS3 is linked to endothelial dysfunction.