Piceatannol-3'-O-β-D-glucopyranoside as an active component of rhubarb activates endothelial nitric oxide synthase through inhibition of arginase activity

Ainieng Woo,Byungsun Min,Sungwoo Ryoo

doi:10.3858/emm.2010.42.7.053

Abstract

Arginase competitively inhibits nitric oxide synthase (NOS) via use of the common substrate L-arginine. Arginase II has recently reported as a novel therapeutic target for the treatment of cardiovascular diseases such as atherosclerosis. Here, we demonstrate that piceatannol-3'-O-beta-D-glucopyranoside (PG), a potent component of stilbenes, inhibits the activity of arginase I and II prepared from mouse liver and kidney lysates, respectively, in a dose-dependent manner. In human umbilical vein endothelial cells, incubation of PG markedly blocked arginase activity and increased NOx production, as measured by Griess assay. The PG effect was associated with increase of eNOS dimer ratio, although the protein levels of arginase II or eNOS were not changed. Furthermore, isolated mice aortic rings treated with PG showed inhibited arginase activity that resulted in increased nitric oxide (NO) production upto 78%, as measured using 4-amino-5-methylamino-2',7'-difluorescein (DAF-FM) and a decreased superoxide anions up to 63%, as measured using dihydroethidine (DHE) in the intact endothelium. PG showed IC((50)) value of 11.22 microM and 11.06 microM against arginase I and II, respectively. PG as an arginase inhibitor, therefore, represents a novel molecule for the therapy of cardiovascular diseases derived from endothelial dysfunction and may be used for the design of pharmaceutical compounds.

Highlights

The endothelium plays a central role in overall vascular homeostasis by regulating vasoreactivity, platelet activation, leukocyte adhesion, and smooth muscle cell proliferation and migration
Were 75 ± 6, 74 ± 5, and 53 ± 8%, respectively (Figure 2C). These data indicated that PG has a strong and specific inhibitory effect on both arginase I and II even if PG has no selectivity for a specific arginase isoform
With the idea that arginase modulates nitrite and nitrate (NOx) production by nitric oxide synthase (NOS) through limiting L-arginine substrate is emerging as a general mechanism for NOS regulation and appear to contribute to the pathobiology of a number of disease processes in which nitric oxide (NO) is dysregulated, we here demonstrate for the first time that PG, as an active component of Rhubarb, inhibits arginase activity and reciprocally increases NOx production

Summary

Introduction

The endothelium plays a central role in overall vascular homeostasis by regulating vasoreactivity, platelet activation, leukocyte adhesion, and smooth muscle cell proliferation and migration. The expression and function of arginase I in macrophages, hepatocytes, and vascular smooth muscle cells, is stimulated by lipopolysaccharide (LPS), IL-13, altered oxygen tension, and balloon dilatation of coronary arteries (Modolell et al, 1995; Louis et al, 1998; Que et al 1998; Klasen et al, 2001; Chicoine et al, 2004; Morris et al, 2004; Ryoo et al, 2006; Nelin et al, 2007). Arginase inhibition actively augments NO production and reportedly has beneficial effects on normal cardiac function and on vascular dysfunction typical of atherogenesis, aging, and erectile dysfunction, and sickle cell disease (Bivalacqua et al, 2001; Berkowitz et al, 2003; Morris et al, 2004; Steppan et al, 2006; White et al, 2006; Bivalacqua et al, 2007; Hsu et al, 2007; Xu et al, 2007)

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