Aim: 

Asymmetric dimethylarginine (ADMA), a competitive inhibitor of nitric oxide synthase, acts as a modulator of the vascular response. ADMA levels depend on the dimethylarginine-dimethylaminohydrolase (DDAH) activity, its main catabolic pathway. We study the interactions of oxidized LDL (oxLDL), with DDAH/ADMA/NO pathway and the potential role of estradiol on human umbilical artery endothelial cells (HUAEC).

Methods: 

Primary HUAEC were subjected to desired treatments for 24 hours. ADMA was measured in culture supernatants by HPLC. DDAH activity was evaluated by a colorimetric method. Protein expression was analysed by immunoblotting.

Results: 

oxLDL (100mg/mL) significantly increases ADMA levels, whereas estradiol (1nM) only decreases ADMA levels in the presence of oxLDL. Protein methyltransferase-1 (PRMT-1) and DDAH-I protein expression remain unchanged after all treatments. oxLDL treatment, with or without estradiol, increases DDAH-II and reduces eNOS protein expression.

Conclusion: 

The raise of ADMA levels induced by oxLDL increases DDAH-II expression. This enzyme seems to be active only in the presence of estradiol. The eNOS decreased expression caused by oxLDL is not reverted by estradiol.

Supported by Ministerio de Ciencia e Innovación, ISCIII (FIS 06/0589, FIS 08/0634, RED HERACLES RD06/0009); Consellería de Sanidad, GV (AP 09/2007, AP 121/08). PJO holds a post-doc position, and AS is a FPI fellow (BFPI 06/145), both from Consellería de Educación, Generalitat Valenciana, Spain.