Abstract 192: Depletion of Inflammatory Monocytes Reduces Endothelial Nitric Oxide Synthase Uncoupling and iNOS Derived Nitrosative Stress in Angiotensin II-induced Vascular Dysfunction

Abstract

Background Endothelial nitric oxide synthase (eNOS) uncoupling occurs in disease states of vascular dysfunction and amplifies vascular oxidative stress and loss of NO bioactivity. Inflammatory myelomonocytic cells as a major source of superoxide are critical for angiotensin-II induced vascular dysfunction; however their role in mediating eNOS uncopuling has not been defined yet. Methods and results Angiotensin II (1mg/kg/d, 7d) increased the number of CD11b + Gr-1 low iNOS + monocytes and macrophages in mouse aorta (verified by flow cytometry) in paralell to increasing nox4 and heme oxygenase 1 expression (assessed by Western blot analysis) and inducing eNOS uncoupling, measured by differential NOS dependent superoxide formation in the endothelial layer and glutathionylation of eNOS. Toxin mediated ablation of macrophages in LysM iDTR transgenic mice restored all of these parameters. Conversely, ablation of LysM + cells reduced iNOS expression and normalized vascular levels of tetrahydrobiopterin (measured by high-performance liquid chromatography) and expression of the GTP cyclohydrolase-1, essential for tetrahydrobiopterin synthesis, all of which were increased by angiotensin II in control mice. Conclusion Depletion of LysM + monocytes reduces angiotensin II induced eNOS uncopuling in vascular dysfunction, and simultaneously protects from iNOS mediated nitrosative stress: These findings highlight the role of vascular inflammatory cells in disturbed NO-bioactivity and vascular function