Acute simvastatin increases endothelial nitric oxide synthase phosphorylation via AMP-activated protein kinase and reduces contractility of isolated rat mesenteric resistance arteries

Abstract

Statins can have beneficial cholesterol-independent effects on vascular contractility, which may involve increases in the bioavailability of NO (nitric oxide) as a result of phosphorylation of eNOS (endothelial NO synthase). Although this has been attributed to phosphorylation of Akt (also known as protein kinase B), studies in cultured cells have shown that statins can phosphorylate AMPK (AMP-activated protein kinase); it is unknown whether this has functional effects in intact arteries. Thus we investigated the acute effects of simvastatin on resistance arterial contractile function, evaluating the involvement of NO, Akt and AMPK. Isolated rat mesenteric resistance arteries were mounted on a wire myograph. The effects of incubation (1 and 2 h) with simvastatin (0.1 or 1 μM) on contractile responses were examined in the presence and absence of L-NNA (N-nitro-L-arginine; 10 μM) or mevalonate (1 mM). Effects on eNOS, phospho-eNOS (Ser1177), and total and phospho-Akt and -AMPK protein expression were investigated using Western blotting. The effect of AMPK inhibition (compound C, 10 μM) on eNOS phosphorylation and contractile responses were also studied. Simvastatin (1 μM, 2 h) significantly reduced constriction to U46619 and phenylephrine and enhanced dilations to ACh (acetylcholine) in depolarized, but not in U46619-pre-constricted arteries. These effects were completely and partially prevented by L-NNA and mevalonate respectively. Simvastatin increased eNOS and AMPKα phosphorylation, but had no effect on Akt protein expression and phosphorylation after 2 h incubation. Compound C prevented the effects of simvastatin on eNOS phosphorylation and contractility. Thus simvastain can acutely modulate resistance arterial contractile function via mechanisms that involve the AMPK/phospho-eNOS (Ser1177)/NO-dependent pathway.

AMP-Activated Protein Kinase Inhibits Arterial Smooth Muscle Cell Proliferation in Vasodilator-Stimulated Phosphoprotein-Dependent Manner

“…These anti-migratory and anti-proliferative effects of AMPK are consistent with the findings of others in human and rodent ASM [25,26]. Moreover, complementing its growth inhibitory actions AMPK has been shown to elicit vascular relaxation [6,27] and to maintain vascular barrier function during hypoxia [28], thus making it an attractive candidate for further study in the vasculature.…”

Role of Micro-RNAs 221/222 on Statin Induced Nitric Oxide Release in Human Endothelial Cells

“…For example, Aoki et al reported that, besides the NOS3 mRNA up-regulation, fluvastatin also modified the phosphorylation pattern of endothelial cells 12 . A similar posttranslational modification was observed in isolated rat arteries treated with simvastatin 13 , which also caused an enhanced phosphorylation of eNOS at the Ser 1177 through regulation of the PKB/Akt, a process that leads to a higher enzyme activity and increased NO release 14 .…”

Statins as Regulators of Redox State in the Vascular Endothelium: Beyond Lipid Lowering

“…Atorvastatin has also been shown in ECs to increase eNOS phosphorylation at Ser-633 in an adenosine monophosphate activated protein kinase (AMPK)-mediated way (79). Moreover, ex vivo incubation of rat mesenteric resistance arteries with simvastatin induces rapid AMPKmediated eNOS phosphorylation at Ser-1177 (93). This leads to improved endothelium-dependent vasorelaxation in myograph chamber vasomotor studies, an effect reversed both by inhibition of eNOS by N-nitro-l-arginine methyl ester (LNAME) and by co-incubation with mevalonate.…”