Atherosclerosis is associated with alterations in nitric oxide (NO)͞ cGMP signaling. In early stages of the disease, inflammatory and possibly other cells produce reactive oxygen species that scavenge vasoprotective NO. In addition to the oxidative stress, expression and activity of enzymes downstream to NO formation may also be affected. Here, we show in the aortas of chronically hypercholesterolemic rabbits (a model of late-stage atherosclerosis), both subunits and specific activity of the NO receptor soluble guanylyl cyclase (sGC) were significantly reduced, whereas overall NO synthase activity was unaffected. These changes were most prominent in the neointimal layer, wherein cGMP-dependent protein kinase I (cGK) levels also were reduced. Additionally, a protein (p38 nt ) that was constitutively tyrosine-nitrated was detected, and its expression was significantly reduced in atherosclerotic aorta. Phosphorylation of the cGK substrate vasodilator-stimulated phosphoprotein (VASP) at Ser-239, an established biochemical endpoint of NO͞cGMP signaling, also was reduced. Thus, late-stage atherosclerosis is associated not only with enhanced NO breakdown but also with altered NO reception and cGMP signaling. Preferential downregulation in neointima suggests a direct connection of these changes to neointimal proliferation and vascular dysfunction and provides a rationale for future pharmacotherapy using classical and novel sGC activators.hypercholesterolemia ͉ soluble guanylyl cyclase ͉ vasodilator-stimulated phosphoprotein ͉ cGMP-dependent protein kinase A therosclerosis is major risk factor to cardiovascular diseases such as coronary heart disease and stroke. The pathophysiology of atherosclerosis is highly complex, multifactorial, and yet to be fully understood (1). A common feature observed is malperfusion of tissues as a result of luminally obstructive atherosclerotic plaques, augmented vascular tone, and reduced sensitivity to endothelium-dependent vasodilators in atherosclerotic arteries from humans (2) and cholesterol-fed animals (3).Nitric oxide (NO) is an important antiatherosclerotic autocoid, which exerts antiproliferative and vasodilatory effect on vasculature and antiaggregatory effect on platelets. Vascular dysfunction in atherosclerosis is partly attributed to reduced tetrahydrobiopterin-dependent (4-7) production or bioavailability of endothelium-derived NO (8), which is supported by the observation of reduced activity and expression of endothelial NO synthase III (NOS-III) (9) in atherosclerotic vessels (10, 11). Additionally, the tissue half-life of NO is further reduced by reactive oxygen species (superoxide, O 2 Ϫ ) that scavenge NO and thereby impair its vasoprotective activity (12). Therefore, formation of O 2 Ϫ , by NADPH oxidase (13, 14) or xanthine oxidase (15) or uncoupled endothelial NOS (16) and͞or its decomposition, by superoxide dismutase (SOD) (17)(18)(19), are thought to play important roles in the pathogenesis of atherosclerosis.Endothelium-derived NO stimulates the production of the se...