Gene transfer of dimethylarginine dimethylaminohydrolase-2 improves the impairments of DDAH/ADMA/NOS/NO pathway in endothelial cells induced by lysophosphatidylcholine

Dimethylarginine dimethylaminohydrolase (DDAH) is a key enzyme responsible for the metabolism of nitric oxide (NO) synthase (NOS) inhibitor asymmetric dimethylarginine (ADMA), and DDAH2 is the predominant isoform in vascular endothelium. Lysophosphatidylcholine (LPC) and ADMA are implicated in endothelial dysfunction of atherosclerosis. This study was to examine changes in DDAH/ADMA/NOS/NO pathway in endothelial cells after exposure to LPC and investigate whether DDAH2 gene transfer could reverse LPC-induced changes. Human endothelial cell line ECV304 cells were transfected with recombinant pcDNA3.1-hDDAH2 plasmid and incubated with 3 μmol/L LPC for 48 h. Cells were harvested for assays of DDAH transcription, DDAH and NOS activities. The culture medium was collected for measurements of ADMA and nitrite/nitrate concentrations. LPC treatment suppressed DDAH2 transcription and DDAH activity in parallel with increased ADMA concentration, inhibited NOS activity and decreased NO metabolites content. DDAH2 gene transfer not only prevented the suppression of DDAH activity and the elevation of endogenous ADMA, but also attenuated the inhibition of NOS activity and the reduction of NO level induced by LPC in endothelial cells. These results suggest that LPC induces impairments of DDAH/ADMA/NOS/NO pathway, and DDAH2 gene transfer could improve the LPC-elicited impairments in endothelial cells.