BACKGROUND AND PURPOSE
Transient receptor potential vanilloid 4 (TRPV4) is a Ca
2+-permeable channel with multiple modes of activation. Apigenin is a plant-derived flavone, which has potential preventive effects on the development of cardiovascular disease. We set out to explore the effects of apigenin on TRPV4 channel activity and its role in vasodilatation.
EXPERIMENTAL APPROACHThe effects of apigenin (0.01-30 mM) on TPRV4 channels were investigated in HEK293 cells over-expressing TRPV4, rat primary cultured mesenteric artery endothelial cells (MAECs) and isolated small mesenteric arterial segments using whole-cell patch clamp, fluorescent Ca 2+ imaging, intracellular recording and pressure myography.
KEY RESULTSWhole-cell patch clamp and fluorescent Ca 2+ imaging in HEK cells over-expressing TRPV4 showed that apigenin concentration-dependently stimulated the TRPV4-mediated cation current and Ca 2+ influx. In MAECs, apigenin stimulated Ca 2+ influx in a concentration-dependent manner. These increases in cation current and Ca 2+ influx were markedly inhibited by TRPV4-specific blockers and siRNAs. Furthermore, pressure myography and intracellular recording in small third-order mesenteric arteries showed that apigenin dose-dependently evoked smooth muscle cell membrane hyperpolarization and subsequent vascular dilatation, which were significantly inhibited by TRPV4-specific blockers. TRPV4 blocker or charybdotoxin (200 nM) plus apamin (100 nM) diminished the apigenin-induced dilatation.
CONCLUSION AND IMPLICATIONSThis is the first study to demonstrate the selective stimulation of TRPV4 by apigenin. Apigenin was found to activate TRPV4 channels in a dose-dependent manner in HEK cells over-expressing TRPV4 and in native endothelial cells. In rat small mesenteric arteries, apigenin acts on TRPV4 in endothelial cells to induce EDHF-mediated vascular dilatation. [Ca 2+ ]i, intracellular calcium concentration; ChTx, charybdotoxin; EDHF, endothelium-derived hyperpolarizing factor; GFP, green fluorescence protein; Indo, indomethacin; L-NAME, N w -nitro-L-arginine methyl ester; MAECs, primary cultured rat mesenteric arterial endothelial cells; siRNA, small interfering RNA; TRPV4, transient receptor potential vanilloid 4
Abbreviations
Luteolin attenuates myocardial ischemia/reperfusion (I/R) injury in diabetes through activating nuclear factor erythroid 2-related factor 2 (Nrf2)-related antioxidative response. Though sestrin2, a highly conserved stress-inducible protein, is regarded as a...
Alcohol has a vasodilating effect on rat artery depending on the resting tension. Both extracellular and intracellular Ca(2+) mobilization of vascular smooth muscle cells are involved in the vascular effect of alcohol.
Luteolin is an antioxidative, antitumor and anti-inflammatory flavone. It has been shown to reduce endothelial dysfunction, but the mechanism is not clear. We set out to explore the effects of luteolin on apoptosis and its mechanism of action in endothelial cells. The effect of luteolin on pyrogallol-induced superoxide stress and the subsequent apoptosis was studied in the mouse heart capillary endothelial cell line H5V and human umbilical vein endothelial cells, by the use of flow cytometry, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide, Hoechst staining, and western blot. Pyrogallol (0-400 lM) dose-dependently induced reactive oxygen species production, cytotoxicity, an annexin V-fluorescein isothiocyanate increase, mitochondrial transmembrane depolarization and DNA condensation in both H5V and human umbilical vein endothelial cells; these actions were reversed by luteolin (0.78-50 lM) in a concentration-dependent manner. Luteolin suppressed the poly (ADP-ribose) polymerase activation, caspase-8 cleavage and p38 mitogen-activated protein kinase activation triggered by pyrogallol, and stimulated the extracellular signal-regulated kinase signaling pathway to counteract the pyrogallol-induced apoptotic signals. Luteolin is an effective agent for the protection of endothelial cells from superoxide stress-induced apoptosis via the extracellular signal-regulated kinase signaling pathway.
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