Abstract 17603: Transgenic Overexpression of Alanine-glyoxylate Aminotransferase 2 in Mice Lowers Asymmetric Dimethylarginine and Improves Vasomotor Function

Abstract

Background: ADMA (asymmetric dimethylarginine), an inhibitor of nitric oxide synthase, has been shown to be associated with the risk of cardiovascular diseases. There are two known pathways for ADMA catabolism: hydrolysis to citrulline by dimethylarginine dimethylaminohydrolases (DDAH) and transamination by alanine-glyoxylate aminotransferase 2 (AGXT2) with formation of asymmetric dimethylguanidino valeric acid (ADGV). In contrast to the first pathway, the second one is poorly characterized. The goal of our study was to test the hypothesis that transgenic overexpression of AGXT2 would lead to lowering of systemic levels of ADMA and improvement of vasomotor function. Results: We generated transgenic mice (TG) with ubiquitous overexpression of AGXT2 under control of the chicken beta actin (CAG) promoter. qPCR and Western Blot were used to confirm the ubiquitous expression of the transgene. We did not observe and developmental or phenotypic abnormalities in the TG animals. Biochemical data were generated using HPLC-MS/MS. AGXT2 TG mice had ADMA plasma levels decreased by 15% (p<0.05), whereas ADGV plasma levels were 6 times higher in comparison with wild-types (p<0.001). Lung and heart of TG animals exhibited 2 times lower tissue ADMA content in comparison with controls (p<0.05). Isolated aortic rings were used to estimate endothelium-dependent and -independent relaxation in response to acetylcholine (Ach) and sodium nitroprusside (SNP), respectively. Aortas from AGXT2 TG mice demonstrated an increase in maximal response to ACh (p<0.05). There was a similar relaxation in response to SNP in both groups. We did not observe any differences in mean arterial blood pressure measured by telemetry between the wild type and AGXT2 TG mice. Conclusion: In the current study we were able to demonstrate that upregulation of AGXT2 leads to lowering of ADMA levels and improvement in endothelial-dependent relaxation in vivo. AGXT2 thereby may be a potential drug target for long-term reduction of systemic ADMA levels in cardiovascular pathologies. This is especially important, because all the efforts to develop ADMA-lowering interventions by means of upregulation of DDAH have not been successful so far.