Improvement of age-related endothelial dysfunction by simvastatin: effect on NO and COX pathways

Abstract

The effects of oral administration of the HMG-CoA reductase inhibitor, simvastatin (SV), on age-related endothelial dysfunction were investigated in the aorta of male Wistar rats. Adult (12-14 weeks) and old (60-80 weeks) rats were treated daily for 12 weeks with either vehicle or SV (1 mg kg(-1)). In old rats, SV treatment did not significantly affect systolic blood pressure and LDL-cholesterol, but it reduced plasma cholesterol, triglycerides and oxidised LDL though it did not affect total antioxidant status. SV improved endothelium-dependent relaxation to acetylcholine and A-23187 in vessels from aged, but not adult, rats. This effect was linked to a greater NO vasodilatation via an increased expression of endothelial NO-synthase. A mechanism sensitive to superoxide dismutase and catalase also accounts for enhanced endothelial vasodilatation. Finally, SV did not affect the release of prostacyclin, but it inhibited the generation of thromboxane (TX) A2 from COX-2 isoform. The effect of the latter was sensitive to the Tp receptor antagonist, ICI-192,605. The present study provides evidence that oral administration of SV improves endothelial dysfunction in the aorta from aged rats by mechanisms associated with enhanced NO vasodilatation, reduced release of TXA2 from cyclo-oxygenase, and increased antioxidant properties of the vessel wall. These data underscore a new therapeutic perspective for SV in age-related endothelial dysfunction.

Figure 1

SV improves the endothelial function of aorta from aged (a–c, n=7), but not in those from adult (d–f, n=6), rats after 12 weeks of treatment. Concentration–response curves to ACh (a and d), A-23187 (b and e) and SNP (c and f) in aortic rings from placebo- and SV-treated rats ^***P<0.001 placebo versus SV-treated rats. ^###P<0.001 aged versus adult rats.

Figure 2

Concentration–response curves to ACh in aortic rings from placebo- (a) and SV-treated (b) rats in the absence and presence of L-NAME (3 × 10⁻⁴ mol l⁻¹). ^**P<0.01; ^***P<0.001 control versus curve in the presence of L-NAME. NO-mediated vasodilation expressed as difference between areas under the curve in the absence and presence of L-NAME (c). Data represented are mean±s.e.m. of n=7. ^**P<0.01 placebo versus SV. Representative Western blot of aortic eNOS and bars showing optic densitometry of n=4 blots of eNOS. (d) ^*P<0.05 placebo- versus SV-treated rats.

Figure 3

Concentration–response curves to ACh of aortic rings from placebo- (a) and SV-treated (b) rats in the absence and presence of indomethacin (10⁻⁵ mol l⁻¹), NS-398 (10⁻⁶ mol l⁻¹) or indomethacin (10⁻⁵ mol l⁻¹) plus L-NAME (3 × 10⁻⁴ mol l⁻¹). Data represented are mean±s.e.m. of n=7. ^*P<0.05; ^**P<0.01; ^***P<0.001 control versus curve in the presence of inhibitor. Representative Western blot and bars showing optic densitometry of n=4 blots of aortic COX-1 (c) and COX-2 (d). ^**P<0.01 placebo versus SV.

Figure 4

Concentration–response curves to ACh in aortic rings from placebo- (a) and SV-treated (b) rats in the absence and presence of the Tp receptor antagonist ICI-192,605 (10⁻⁶ mol l⁻¹). ^***P<0.001 control versus curve in the presence of inhibitor. TXB₂ (c) and PGF_1α (d) released by aortic rings from placebo- (open bar) and SV-treated (closed bar). Data represented are mean±s.e.m. of n=7. ^*P<0.05 placebo versus SV-treated rats. Concentration–response curves to the TX receptor agonist U46619 in endothelium-intact aortic rings from adult (open triangle) and old rats treated with either placebo (open circle) or SV (filled circle) (e). Data represented are mean±s.e.m. of n=6.

Figure 5

Concentration–response curves to ACh in aortic rings from placebo- (a) and SV-treated (b) rats in the absence and presence of ROS scavengers SOD (150 UI ml⁻¹) plus catalase (1000 UI ml⁻¹). Data represented are mean±s.e.m. of n=7. ^*P<0.05; ^**P<0.01 control versus curve in the presence of inhibitor.