Reduced cGMP signaling associated with neointimal proliferation and vascular dysfunction in late-stage atherosclerosis

Abstract

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...

The impact of genome‐wide association studies on the pathophysiology and therapy of cardiovascular disease

“…Studies investigating the effect of sGC on plaque formation in mouse models are eagerly awaited. A protective role of sGC is thereby strongly suggested by studies showing that cGMP formation is reduced in neointimal lesions (Melichar et al , 2004) and that cGMP leads to down‐regulation of the expression of adhesion molecules for the recruitment of leucocytes into atherosclerotic plaques (Ahluwalia et al , 2004). The common variant associated with CAD (rs7692387) is located in an intron however, and the exact mechanism from genotype to phenotype at this locus thus far remains elusive.…”

NOX1, 2, 4, 5: counting out oxidative stress

“…The NO receptor soluble guanylate cyclase (sGC) (see Figure 1) generates cyclic GMP (cGMP) when NO binds to it. A biomarker of the NO‐sGC signalling cascade is the phosphorylation of the cGMP‐dependent protein kinase (cGK) substrate vasodilator‐stimulated phosphoprotein (VASP) (Melichar et al ., 2004). P‐VASP can therefore be used as a marker for NO bioavailability.…”

Distinct molecular requirements for activation or stabilization of soluble guanylyl cyclase upon haem oxidation‐induced degradation

“…Its oxidation or loss renders the enzyme insensitive to NO. Oxidative stress, a hallmark of many cardiovascular diseases, impairs the NO‐cGMP signalling (Melichar et al. , 2004).…”