Abstract 11293: Increased Circulating Asymmetric Dimethylarginine in Chronic Kidney Disease Mice Induces Endothelial Dysfunction by Inhibiting Ca/Calmodulin-Dependent Protein Kinase II-eNOS Signaling
Background — Patients with chronic kidney disease (CKD) have impaired endothelial function. The serum asymmetric dimethylarginine (ADMA) level is elevated in CKD. ADMA is known to be an endogenous inhibitor of endothelial nitric oxide synthase (eNOS) through substrate competitive inhibition. Therefore, we assessed whether an increased ADMA level is a cause of endothelial dysfunction using a CKD mouse model and investigated the possible underlying mechanism.
Methods and Results — We created a CKD model by performing a 5/6 nephrectomy (Nx) in wild-type (WT) mice and transgenic (Tg) mice overexpressing dimethylarginine dimethylaminohydrolase (DDAH)-1, the enzyme that metabolizes ADMA. The baseline serum BUN levels were similar in WT and Tg mice. Nx increased BUN by 2-fold in WT and Tg mice. In WT mice, Nx increased serum ADMA by 20%. In Tg mice, serum ADMA was reduced to 50% compared with WT mice and was not increased by Nx. An isometric tension study using aortic rings showed that Nx deteriorated endothelium-dependent relaxation in WT mice, but not in Tg mice. Furthermore, exogenous ADMA abolished endothelium-dependent relaxation in the aorta of WT mice. Western blotting analyses revealed that Nx reduced eNOS phosphorylation in the aorta of WT mice without changing the eNOS expression levels. In cultured human umbilical vein endothelial cells, ADMA treatment at a concentration corresponding to the serum level in Nx mice did not affect the basal phosphorylation of eNOS and calcium/calmodulin-dependent protein kinase II (CaMKII), one of the upstream kinases for eNOS activation, but reduced the agonist-stimulated phosphorylation of eNOS and CaMKII.
Conclusions — Nx induced endothelial dysfunction in WT mice, but not in DDHA-1-Tg mice, suggesting that increased circulating ADMA may impair endothelial function in CKD. This effect occurs via a novel mechanism whereby ADMA reduces arterial eNOS phosphorylation by inhibiting CaMKII-mediated signaling.
- © 2010 by American Heart Association, Inc.