Endothelial dysfunction and oxidative stress likely play roles in PM2.5-induced harmful effects. Epigallocatechin-3-gallate (EGCG), the major polyphenolic constituent of green tea, is a potent antioxidant that exerts protective effects on cardiovascular diseases (CVDs) in part by scavenging free radicals. The exposure to ambient fine particulate matter (PM2.5) is responsible for certain CVDs. The aim of the present study was to investigate whether EGCG could also inhibit PM2.5-induced oxidative stress by activating the nuclear factor E2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway in human umbilical vein endothelial cells (HUVECs). PM2.5 (200 μg/mL) increased both cell death and intracellular ROS levels significantly, whereas EGCG (50–400 μM) inhibited these effects in a concentration-dependent manner. Western blotting and PCR demonstrated that EGCG increased Nrf2 and HO-1 expression in HUVECs that had been exposed to PM2.5. PD98059 (a selective inhibitor of extracellular signal regulated kinase [ERK]-1/2) and SB203580 (a selective inhibitor of p38 MAPK), but not SP600125 (a selective inhibitor of c-jun N-terminal kinase [JNK]), attenuated the EGCG-induced Nrf2 and HO-1 expression. In addition, silencing Nrf2 abolished EGCG-induced Nrf2 and HO-1 upregulation and enhancement of cell viability. The present study suggests that EGCG protects HUVECs from PM2.5-induced oxidative stress injury by upregulating Nrf2/HO-1 via activation of the p38 MAPK and the ERK1/2 signaling pathways.

Farrerol, isolated from Rhododendron dauricum L., has been proven to be an important multifunctional physiologically active component, but its vasoactive mechanism is not clear. The present study was performed to observe the vasoactive effects of farrerol on rat aorta and to investigate the possible underlying mechanisms. Isolated aortic rings of rat were mounted in an organ bath system and the myogenic effects stimulated by farrerol were studied. Intracellular Ca2+ ([Ca2+]in) was measured by molecular probe fluo-4-AM and the activities of L-type voltage-gated Ca2+ channels (LVGC) were studied with whole-cell patch clamp in cultured vascular smooth muscle cells (VSMCs). The results showed that farrerol significantly induced dose-dependent relaxation on aortic rings, while this vasorelaxation was not affected by NG-nitro-l-arginine methylester ester or endothelium denudation. In endothelium-denuded aortas, farrerol also reduced Ca2+-induced contraction on the basis of the stable contraction induced by KCl or phenylephrine (PE) in Ca2+-free solution. Moreover, after incubation with verapamil, farrerol can induce relaxation in endothelium-denuded aortas precontracted by PE, and this effect can be enhanced by ruthenium red, but not by heparin. With laser scanning confocal microscopy method, the farrerol-induced decline of [Ca2+]in in cultured VSMCs was observed. Furthermore, we found that farrerol could suppress Ca2+ influx via LVGC by patch clamp technology. These findings suggested that farrerol can regulate the vascular tension and could be developed as a practicable vasorelaxation drug.

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Farrerol, a typical natural flavanone and major active component in var., has been shown to possess vasoactive ability . The aim of this study was to investigate its effect on aorta gene expression in spontaneously hypertensive rats. Twelve-week-old male normotensive Wistar Kyoto rats and spontaneously hypertensive rats were treated with orally administered farrerol (50 mg/kg body weight) for 8 wk before they were sacrificed. We found that aorta samples showed 444 upregulated genes in control spontaneously hypertensive rats compared with the control Wistar Kyoto rats. Administration of farrerol in spontaneously hypertensive rats increased the expression of 2329 genes in the aorta compared with the control spontaneously hypertensive rats. Gene expression profiles performed on the aorta revealed that farrerol induced changes in vascular smooth muscle contraction, mitogen-activated protein kinase signaling pathway, regulation of actin cytoskeleton, vascular endothelial growth factor signaling pathway, calcium signaling pathway, and renin angiotensin system. Furthermore, 10 genes involved in the pathway of vascular smooth muscle contraction were verified using real-time polymerase chain reaction technique, and several novel potential target genes for the farrerol treatment of hypertension were identified. The findings of this study lend support to the potential use of farrerol as a novel therapeutic and antihypertensive candidate drug to prevent the development of hypertension.

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To detect the structure‑activity associations of farrerol derivatives, the relaxation activity of farrerol derivatives was observed in isolated aortic rings pre‑contracted using phenylephrine in Sprague‑Dawley rats. All compounds tested in the present study produced a relaxation effect, which was significantly affected by the molecular structure. Using a collagen gel contraction assay, the present study further evaluated the inhibitiory effect of farrerol derivatives in a decreased collagen gel area, induced by Angiotensin II. The results indicated that farrerol derivatives could inhibit collagen contraction, and that the inhibitory effect was associated with the molecular structure of the compounds. Furthermore, the inhibitory strength of the different compounds was consistent with the results of vascular tension detection. The activity of the farrerol derivatives was closely associated with the molecular structure. The analysis indicated that an electron‑withdrawing substituent in the ortho position of the phenyl group (ring B) was crucial in order to observe improved vasorelaxation activity, whereas a hydroxyl or methoxy group was unfavorable. A para electron‑donating group was oberved to increase compound activity. In addition, when the B ring was heterocycle rather than a phenyl ring, the vasorelaxation ability was weakened.

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