Endothelial DDAH1 is an Important Regulator of Angiogenesis but Does Not Regulate Vascular Reactivity or Hemodynamic Homeostasis
Background—Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthesis and a risk factor for cardiovascular disease. Dimethylarginine dimethylaminohydrolase (DDAH) enzymes are responsible for ADMA breakdown. It has been reported that endothelial DDAH1 accounts for the majority of ADMA metabolism. However, we and others have shown strong DDAH1 expression in a range of non-endothelial cell types suggesting the endothelium is not the only site of metabolism. We have developed a new endothelial specific DDAH1 knockout mouse (DDAH1En-/-) to investigate the significance of the endothelial ADMA in cardiovascular homeostasis.
Methods and Results—DDAH1 deletion in the DDAH1En-/- mouse was mediated by Tie-2 driven Cre expression. DDAH1 deletion was confirmed through immunocytochemistry; while western blotting showed DDAH1 remained in the kidney and liver confirming expression in non-endothelial cells. Plasma ADMA was unchanged in DDAH1En-/- mice and cultured aortas released similar amounts of ADMA to controls. Consistent with these observations, vasoreactivity ex vivo and hemodynamics in vivo were unaltered in DDAH1En-/- mice. In contrast, we observed significantly impaired angiogenic responses both ex vivo and in vivo.
Conclusions—We demonstrate that endothelial DDAH1 is not a critical determinant of plasma ADMA, vascular reactivity or hemodynamic homeostasis. DDAH1 is widely expressed in a range of vascular and non-vascular cell-types; therefore the additive effect of DDAH1 expression in multiple organ systems determines plasma ADMA concentrations. Endothelial deletion of DDAH1 profoundly impairs the angiogenic capacity of endothelial cells indicating that intracellular ADMA is a critical determinant of endothelial cell response.
- Assymetric Dimethylarginine
- Dimethylarginine dimethylaminohydrolase
- nitric oxide
- Received December 23, 2014.
- Revision received April 7, 2015.
- Accepted April 10, 2015.
Circulation is published on behalf of the American Heart Association, Inc., by Wolters Kluwer. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial License (http://creative commons.org/licenses/by-nc/3.0/), which permits use, distribution, and reproduction in any medium, provided that the original work is properly cited and is not used for commercial purposes.