Baicalein is a flavonoid extracted from the root of Scutellaria baicalensis Georgi, a medicinal plant traditionally used in Oriental medicine. Among its biological activities, baicalein has been reported to exhibit antioxidant effects. Endothelin-1 (ET-1) is a potent vasopressor synthesized by endothelial cells both in culture and in vivo. The aims of this study were to test the hypothesis that baicalein may alter strain-induced ET-1 secretion and to identify the putative underlying signaling pathways in endothelial cells. We show that baicalein inhibited strain-induced ET-1 secretion. Baicalein also inhibited strain-increased reactive oxygen species (ROS) formation and the extracellular signal-regulated kinases (ERK) phosphorylation. Using a reporter gene assay, baicalein and the antioxidant Trolox also attenuated the strain-stimulated activator protein-1 (AP-1) reporter activity. We conclude that baicalein inhibits strain-induced ET-1 gene expression, partially by interfering with the ERK pathway via attenuation of ROS formation. These results highlight the molecular pathways that may contribute to the beneficial effects of baicalein in the vascular system such as stroke prevention.
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