Abstract 5223: Dimethylarginine Dimethylaminohydrolase 1Modulates Endothelial Cell Growth and Injury Repair Through No and Akt

Abstract

Dimethylarginine dimethylaminohydrolase-1 (DDAH1) modulates endothelial nitric oxide (NO) production by degrading asymmetric methylarginines that act as endogenous NO synthase (NOS) inhibitors. Since we recently found DDAH1 strongly expressed in vascular endothelial cells, this study examined effects of DDAH1 on endothelial function. Here, by using selective gene silencing of DDAH1 with small interfering RNA (siRNA) and overexpression of DDAH1 in HUVEC, we demonstrate that DDAH1 acts to promote endothelial cell proliferation, migration and tube formation both by the traditional role of degrading asymmetric methylarginines and a novel molecular pathway of increasing Akt activity. Specifically, overexpression of DDAH1 Abstracts From Scientific Sessions 2009 S1073 dose-dependently increased p-Akt Ser473 , Akt activity and p-eNOS Ser1177 , while selective gene silencing of DDAH1 with siRNA decreased endothelial p-Akt Ser473 and p-eNOS Ser1177 . Importantly, incubation of HUVEC with the NOS inhibitors L-NAME or ADMA, the soluble guanylyl cyclase inhibitor ODQ, or the membrane permeable cGMP analog 8-pCPT-cGMP had no effect on p-Akt Ser473 , indicating that the increase of p-Akt Ser473 produced by DDAH1 was NO and cGMP independent. Overexpression of constitutively active Akt rescued HUVEC from DDAH1 knockdown, while the increases of HUVEC tube formation, proliferation and migration after DDAH1 overexpression were abolished by the Akt inhibitor ly294002. Moreover, using endothelial specific DDAH1 gene deficient mice generated in our laboratory, we demonstrated that endothelial spouting from cultured aortic rings and in vivo vascular endothelial repair after wire injury were impaired compared to wild type mice. DDAH1 KO also attenuated vascular p-Akt Ser473 but not total Akt. Together, the data demonstrate that DDAH1 plays an important role in vascular endothelial cell growth and injury repair by regulating both NO production and Akt activity. This research has received full or partial funding support from the American Heart Association, National Center.