# Vasodilatory Effect of n-Butanol Extract from Sanguisorba officinalis L. and Its Mechanism

## TL;DR

This study shows that a butanol extract from Sanguisorba officinalis induces blood vessel relaxation through specific biochemical pathways involving nitric oxide and calcium regulation.

## Contribution

The study identifies the molecular mechanisms by which the butanol extract of Sanguisorba officinalis induces vasorelaxation.

## Key findings

- BSO increases nitric oxide production and activates the PI3K-Akt-eNOS-NO pathway in endothelial cells.
- BSO-induced vasorelaxation is mediated through NO-sGC-cGMP-K⁺ channels in vascular smooth muscle cells.
- BSO reduces blood pressure and heart rate in rats in a concentration-dependent manner.

## Abstract

The dried root of Sanguisorba officinalis L. (commonly known as Diyu) has been studied for its various pharmacological effects, including its antibacterial, antitumor, antioxidant, and anti-inflammatory activities. In the present study, primary cultured vascular endothelial cells (HUVECs) and isolated phenylephrine-precontracted rat thoracic aortic rings were examined to investigate the possible mechanism of a butanol extract of Diyu (BSO) in its vascular relaxant effect. HUVECs treated with BSO produced a significantly higher amount of nitric oxide (NO) compared to the control. However, its production was inhibited by pretreatment with NG-nitro-L-arginine methylester (L-NAME) or wortmannin. BSO also increased the phosphorylation levels of endothelial nitric oxide synthase (eNOS) and Akt. In the aortic ring, BSO relaxed PE-precontracted rat thoracic aortic rings in a concentration-dependent manner. The absence of the vascular endothelium significantly attenuated BSO-induced vasorelaxation. The non-selective NOS inhibitor, L-NAME, and the selective inhibitor of soluble guanylyl cyclase (sGC), 1H-[1,2,4]-oxadiazolo-[4,3-α]-quinoxalin-1-one (ODQ), dramatically inhibited the BSO-induced relaxation effect of the endothelium-intact aortic ring. Ca2+-free buffer and intracellular Ca2+ homeostasis regulators (TG, Gd3+, and 2–APB) inhibited BSO-induced vasorelaxation. In Ca2+-free Krebs solution, BSO markedly reduced PE-induced contraction. Vasodilation induced by BSO was significantly inhibited by wortmannin, an inhibitor of Akt. Pretreatment with the non-selective inhibitor of Ca2+-activated K+ channels (KCa), tetraethylammonium (TEA), significantly attenuated the BSO-induced vasorelaxant effect. Furthermore, BSO decreased the systolic blood pressure and heart rate in a concentration-dependent manner in rats. In conclusion, BSO induces vasorelaxation via endothelium-dependent signaling, primarily through the activation of the PI3K-Akt-eNOS-NO signaling pathway in endothelial cells, and the activation of the NO-sGC-cGMP-K⁺ channels pathway in vascular smooth muscle cells. Additionally, store-operated Ca2+ entry (SOCE)-eNOS pathways and the inhibition of Ca2⁺ mobilization from intracellular stores contribute to BSO-induced vasorelaxation.