Abstract 15505: Aortic Stiffening in L-NAME Treated C57bl6 Mice Precedes Peripheral Hypertension and Cardiac Hypertrophy: Early Endothelial Dysfunction Shifts to Late-term Vascular Smooth Muscle Cell Disease

Introduction: Endothelial dysfunction (ED) acts as a common player in most cardiovascular (CV) risk factors (e.g. hypertension, smoking) underlining its importance in CV ageing. Therefore, this study aims to characterize ex vivo aortic function changes in Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) treated mice. Methods: C57Bl6 mice (male, n=10) received 0.5 mg/mL L-NAME through the drinking water for 1, 2, 4, 8, and 16 weeks, followed by in-depth ex vivo thoracic aorta isometric reactivity studies and arterial stiffness (Peterson modulus, Ep) measurements in the Rodent Oscillatory Tension set-up for Arterial Compliance (ROTSAC). In addition, peripheral blood pressure (BP, Coda), aortic pulse wave velocity (aPWV, Vevo2100), and echocardiography (Vevo2100) were measured in vivo . (Data are represented as mean±SEM) Results: L-NAME treated mice display fast-onset aortic stiffening after 1-week L-NAME (Fig. A, B), followed by the development of peripheral hypertension (Fig. C) and cardiac disease (Fig. D-F) after 4-weeks L-NAME. Ex vivo aorta studies reveal different stages of disease. Early on (1-4 weeks), mice show elevated phenylephrine (PE) contractions (Fig. G) and impaired acetylcholine (ACh) relaxations (Fig. H), consistent with L-NAME related ED. After 8 weeks, endothelial function and PE contractions normalize. Relaxations to exogenous NO remain unaltered (Fig. I). In contrast to the recovery of ACh relaxations, stiffness analysis in the ROTSAC reveals constantly reduced basal NO levels (Fig. J), and a late-term shift (16 weeks) towards vascular smooth muscle cell (VSMC) disease. This involves basal cytoplasmic calcium loading (Fig. K) and a sharply increasing contribution of voltage-gated calcium channels (Fig. L). Conclusions: NOS inhibition by L-NAME treatment causes a distinct time-dependent aortic disease phenotype, underlying fast-onset arterial stiffening which precedes peripheral hypertension and cardiac disease.