Abstract 1670: Overexpression of Dimethylarginine Dimethylaminohydrolase-2 Reverses Endothelial Dysfunction in Diabetic Rat Aortas
Elevated asymmetric dimethylarginine (ADMA) is an independent risk factor for endothelial dysfunction. Dimethylarginine dimethylaminohydrolase (DDAH) is the key enzyme responsible for the metabolism of ADMA, and DDAH2 is the predominant isoform in endothelium. This study was to determine whether suppression of DDAH2 expression was involved in endothelial dysfunction of diabetic rats and whether adenovirus-mediated DDAH2 gene transfer could improve the endothelial dysfunction. Diabetic model was induced by intraperitoneal injection of streptozotocin to male Sprague-Dawley rats. Human DDAH2 gene was transferred to isolated rat aortas by infection with Ad5CMVhDDAH2. Changes in DDHA/ADMA/NO pathway of diabetic and control rats were examined. Results showed that endothelium-dependent relaxation response to cumulative acetylcholine (Ach, 0.003 ~ 3 μmol/L) was impaired in aortic rings from diabetic rats as shown by the lower Emax and the higher EC50 value compared to control rats (P < 0.01). This impairment was accompanied with an elevation of serum ADMA concentrations (2.18 ± 0.23 vs 1.14 ± 0.12 μmol/L, n = 5, P < 0.01), decrease of vascular DDAH activity (0.052 ± 0.003 vs 0.098 ± 0.010 U/g protein, n = 5, P < 0.01), and suppression of DDAH2 transcription in aortas of diabetic rats compared to control rats, whereas DDAH1 transcription was not different between the two groups. Ex vivo transferring DDAH2 gene to aortas of diabetic rats not only enhanced vascular DDAH activity (0.220 ± 0.020 vs 0.057 ± 0.006 U/g protein, n = 5, P < 0.01), but also improved the impaired endothelium-dependent relaxation of diabetic aortas compared to untransferred diabetic aortas. Transferring DDAH2 gene to normal aortas from control rats only lowered the EC50 rather than affected the Emax of aortic rings response to Ach compared to untransferred control rings. Suppression of vascular DDAH2 expression and DDAH activity contributes to endothelial dysfunction in diabetic rats. DDAH2 gene transfer can normalize these changes, indicating that targeted transferring DDAH2 to blood vessel by gene or protein engineering may be a novel approach for the treatment of endothelial dysfunction in diabetes mellitus.