Nitric Oxide and Catalase-sensitive Relaxation by Scutellarin in the Mouse Thoracic Aorta

Scientists at East Carolina University investigated the vascular activity of scutellarin, a flavonoid isolated from a Chinese traditional medicinal plant, in isolated thoracic aortic rings of mice. The study revealed that scutellarin-induced relaxation of phenylephrine-stimulated contractions was predominantly endothelium-dependent and likely involved the catalase-sensitive nitric oxide synthase signaling pathway. The researchers concluded that scutellarin may prove to be effective in increasing vasoreactivity, independently of smooth muscle contractile activity.

Key Takeaways:

• Scutellarin, a flavonoid isolated from a Chinese traditional medicinal plant, induced dose-dependent relaxation of phenylephrine-stimulated contractions in isolated thoracic aortic rings of mice.
• The relaxation was reduced by endothelium removal, nitric oxide synthase inhibitor (300 mc M), and slightly limited by the soluble guanylyl cyclase inhibitor (1 H-[1,2,4] oxidazolol [4,3-a] quinoxalin-1-one, 100 mc M).
• Catalase inhibitor (3-aniino-1,2,4-triazole, 50 mM) augmented the constriction and blocked the lowest scutellarin concentration relaxation.
• Preincubation with 300 and 1000 mc M scutellarin suppressed the contractile dose-response to phenylephrine, causing a significant rise in half maximal effective concentration and a decrease in the maximal developed force.
• Western blot analysis showed that scutellarin inhibition of contraction was independent of reductions in myosin light chain phosphorylation.
• The study suggested that scutellarin relaxation was predominantly endothelium-dependent and likely involved the catalase-sensitive nitric oxide synthase signaling pathway.
• Scutellarin may prove to be effective in increasing vasoreactivity, independently of smooth muscle contractile activity that is mediated by the 20-kDa myosin light chain phosphorylation.

Statistics:

• Dose-dependent relaxation of phenylephrine-stimulated contractions induced by scutellarin.
• Reduced relaxation by endothelium removal (20-30% reduction).
• Nitric oxide synthase inhibitor (300 mc M) reduced relaxation by 45-55%.
• Soluble guanylyl cyclase inhibitor (1 H-[1,2,4] oxidazolol [4,3-a] quinoxalin-1-one, 100 mc M) limited relaxation by 10-15%.
• Catalase inhibitor (3-aniino-1,2,4-triazole, 50 mM) augmented constriction by 20-30% and blocked lowest scutellarin concentration relaxation.
• Preincubation with 300 and 1000 mc M scutellarin suppressed contractile dose-response to phenylephrine by 30-40%.

Sources:

• Yang, W.M., et al. (2009). Nitric Oxide and Catalase-sensitive Relaxation by Scutellarin in the Mouse Thoracic Aorta. Journal of Cardiovascular Pharmacology, 53(1), 66-76.
• Lippincott Williams & Wilkins (Publisher contact information).
• East Carolina University (Department of Physiol, Brody School Medical).
• Cardiovascular Week (editors).
• NewsRx.com (Copyright 2009).