Adenoviral-mediated overexpression of DDAH improves vascular tone regulation

Abstract

Nitric oxide (NO) is a key physiological mediator in the cardiovascular, neuronal and immune systems. Numerous reports have detailed the effects of reduced NO production on signaling in these systems and reduced NO generation has been associated with many pathological conditions. 1 In the cardiovascular system, genetic or pharmacological inhibition of NO production leads to attenuation of vascular relaxation, increased vascular resistance and increased blood pressure. Therefore, endogenous mechanisms that regulate NO production are of considerable interest. 2In the cardiovascular system, NO is synthesized by the endothelial isoform of nitric oxide synthase (eNOS) and the activity of this enzyme has been reported to be regulated at many levels including transcription, translation, post-translational modification and co-factor availability.2 In addition to these mechanisms, eNOS activity can be regulated by the level of endogenously produced asymmetrically methylated arginines which are competitive enzyme inhibitors.3 In humans, two endogenously produced asymmetric methylarginines are present; asymmetric dimethylarginine (ADMA) and N-monomethylarginine (l-NMMA). However, ADMA is found at approximately 10-fold the concentration of l-NMMA and is therefore thought to be the most functionally significant asymmetric methylarginine.3 Methylarginines are generated by the post-translational methylation of certain arginine residues in proteins catalyzed by a family of protein arginine methyltransferases (PRMTs). Adenoviral-mediated overexpression of DDAH improves vascular tone regulationBelen Torondel, Manasi Nandi*, Peter Kelly*, Beata Wojciak-Stothard, Ingrid Fleming and James Leiper Abstract Dimethylarginine dimethylaminohydrolase (DDAH) degrades asymmetric dimethylarginine (ADMA), an endogenously produced nitric oxide (NO) synthase inhibitor. In mammals, two isoforms of DDAH, DDAH1 and DDAH2, are expressed in the cardiovascular system, suggesting that ADMA concentrations are actively regulated in blood vessels, raising the possibility that cardiovascular metabolism of ADMA constitutes a novel mechanism for the regulation of NO production. The purpose of this study was to determine the role of DDAH-catalyzed asymmetric methylarginine metabolism in the regulation of vascular function. We developed adenoviral vectors for the expression of human DDAH1 and 2. Overexpression of DDAH1 or 2 in human umbilical vein endothelial cells (HUVEC) increases DDAH activity, reduces ADMA concentrations and increases NO production. Similarly, overexpression of DDAH1 or 2 in DDAH1 +/-mice carotid vessels increases NO production and attenuates the response to phenylephrine (PE), enhances acetylcholine (ACh) relaxation and attenuates the effect of exogenously applied ADMA. Finally, overexpression of either DDAH1 or 2 completely reversed the vascular dysfunction seen in DDAH1 +/-mice. These data indicate that basal concentrations of ADMA in blood vessels are sufficient to regulate NO production, that increases in the level of either DDAH1...

Nitric oxide synthase derangements and hypertension in kidney disease

“…This agrees with Pope and colleagues, who suggest that DDAH2 regulates endothelial NO production by non-ADMA mechanisms [27]. However, DDAH2 global overexpression does lower plasma ADMA and prevents vascular response to infused ADMA [28] and overexpression of DDAH 2 in cultured endothelial cells reduces ADMA and increases NO production [29]. Further, several DDAH1 and 2 polymorphisms have been described in man [22] including a strong association between DDAH2 polymorphisms and plasma ADMA in type 2 diabetics [30].…”

Effect of rosiglitazone on asymmetric dimethylarginine metabolism in thioacetamide-induced acute liver injury

“…Contrary to ADMA, SDMA, does not inhibit NOS, and is excreted via kidneys [6]. High DDAH activity in transgenic mice decreases plasma ADMA concentrations and increases NOS activity [7]. Both production and degradation of ADMA, as well as ADMA-mediated inhibition of NOS occur intracellularly.…”

Genetic variation in the dimethylarginine dimethylaminohydrolase 1 gene (DDAH1) is related to asymmetric dimethylarginine (ADMA) levels, but not to endothelium-dependent vasodilation

“…Similarly, overexpression of DDAH1 or DDAH2 in DDAH1 knock-out mice carotid vessels increased NO production and enhanced acetylcholine (ACh) relaxation. 27 Overexpression of human DDAH-1 in transgenic mice markedly reduced ADMA levels and increased acetylcholine-mediated vasodilation. The attenuation of acetylcholine-mediated vasodilation by exogenous ADMA was not seen in these transgenic mice when compared to wild-type mice.…”