Background: Elevated endogenous asymmetric dimethylarginine (ADMA) is an independent risk factor for atherosclerosis, and dimethylarginine dimethylaminohydrolase (DDAH) is the key enzyme responsible for the metabolism of ADMA. This study was to determine whether reduced vascular DDAH activity was implicated in endothelial dysfunction of atherosclerosis and whether ex vivo gene transferring of DDAH2 could upregulate vascular DDAH activity and improve endothelial dysfunction associated with atherosclerosis.
Methods: Recombinant adenovirus encoding human DDAH2 gene driven by a cytomegalovirus (CMV) promoter was constructed and used to infect thoracic aortic rings from hyperlipidemic rabbits. Vascular hDDAH2 transcription, DDAH activity and endothelium-dependent relaxation were measured in thoracic aortas of hyperlipidemic and control rabbits.
Results: Vascular DDAH activity was distinctly reduced (0.048±0.002 vs 0.095 ± 0.007U/g protein, n=5, P<0.01) in atherosclerotic aortas in accompany with impaired endothelium-dependent relaxation, whereas serum ADMA levels were markedly elevated in hyperlipidemic rabbits (2.24 ± 0.12 vs 1.22 ± 0.12µmol/L, n=5, P<0.01) compared to control rabbits. Ex vivo gene transferring of hDDAH2 to atherosclerotic aortas not only increased the functional expression of hDDAH2 as shown by presenting hDDAH2 mRNA and enhancing DDAH activity (0.112 ± 0.008 U/g protein, n=5) but also markedly improved the impaired endothelium-dependent relaxation in atherosclerotic arteries.
Conclusions: Reduced vascular DDAH activity contributes to endothelial dysfunction in hyperlipidemic rabbits. Ex vivo gene transferring of hDDAH2 can improve the endothelial dysfunction and inhibited DDAH activity, indicating that targeted modulation of DDAH2 gene in vascular endothelium may be a novel approach for treatment of endothelial dysfunction in atherosclerosis.
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