Dimethylarginine Dimethylaminohydrolase 1 Modulates Endothelial Cell Growth Through Nitric Oxide and Akt
Objective—Dimethylarginine dimethylaminohydrolase 1 (DDAH1) modulates NO production by degrading the endogenous nitric oxide (NO) synthase (NOS) inhibitors asymmetrical dimethylarginine (ADMA) and l-NMMA. This study examined whether, in addition to degrading ADMA, DDAH1 exerts ADMA-independent effects that influence endothelial function.
Methods and Results—Using selective gene silencing of DDAH1 with small interfering RNA and overexpression of DDAH1 in human umbilical artery endothelial cells, we found that DDAH1 acts to promote endothelial cell proliferation, migration, and tube formation by Akt phosphorylation, as well as through the traditional role of degrading ADMA. Incubation of human umbilical artery endothelial cells with the NOS inhibitors l-NAME or ADMA, the soluble guanylyl cyclase inhibitor 1H-(1,2,4)oxadiazolo-(4,3–2)quinoxalin-1-one, or the cGMP analog 8-pCPT-cGMP had no effect on phosphorylated (p)-AktSer473, indicating that the increase in p-AktSer473 produced by DDAH1 was independent of the NO-cGMP signaling pathway. DDAH1 formed a protein complex with Ras, and DDAH1 overexpression increased Ras activity. The Ras inhibitor manumycin-A or dominant-negative Ras significantly attenuated the DDAH1-induced increase in p-AktSer473. Furthermore, DDAH1 knockout impaired endothelial sprouting from cultured aortic rings, and overexpression of constitutively active Akt or DDAH1 rescued endothelial sprouting in the aortic rings from these mice.
Conclusion—DDAH1 exerts a unique role in activating Akt that affects endothelial function independently of degrading endogenous NOS inhibitors.
- Received March 4, 2010.
- Accepted December 21, 2010.
- © 2011 American Heart Association, Inc.