Gentiopicroside Produces Endothelium-Independent Vasodilation by Deactivating the PI3K/Akt/Rho-Kinase Pathway in Isolated Rat Thoracic Aorta

Abstract

Gentiopicroside (GPS), a main active secoiridoid glucoside derived from the roots of perennial herbs in the Gentianaceae family, has antispasmodic and relaxant effects. However, the vasorelaxant effects of GPS on aortic rings and the molecular mechanisms involved in these effects are not yet clear. Therefore, we investigated whether GPS inhibits phenylephrine- (PE-) or KCl-induced contractions in isolated rat thoracic aortic rings. The present study found that GPS produced a dose-dependent relaxation in aortic rings precontracted with PE or KCl and significantly reduced CaCl2-, narciclasine- (Rho-kinase activator-), and phorbol-12,13-diacetate- (PKC activator-) induced vasocontractions. Pretreatment with NG-Nitroarginine methyl ester hydrochloride (L-NAME, NOS inhibitor), methylene blue (sGC inhibitor), indomethacin (COX inhibitor), 4-aminopyridine (KV channel inhibitor), and glibenclamide (KATP channel inhibitor) had no influence on the vasorelaxant effect of GPS, while BaCl2 (Kir channel inhibitor), tetraethylammonium chloride (KCa channel inhibitor), ruthenium red (RYR inhibitor), and heparin (IP3R inhibitor) significantly reduced GPS-induced vasorelaxation. Moreover, GPS pretreatment remarkably inhibited the influx of Ca2+ in vascular smooth muscle cells stimulated using KCl or PE-containing CaCl2 solution. Western blot analysis confirmed that GPS treatment inhibited PE-induced increases in the protein levels of p-Akt, p-myosin light chain (MLC), and p-myosin-binding subunit of myosin phosphatase 1 (MYPT1) in the aortic rings. Additionally, the vasorelaxation activity of GPS was attenuated upon pretreatment with LY294002 (PI3K/Akt inhibitor), Y27632 (Rho-kinase inhibitor), and verapamil (L-type Ca2+ channel inhibitor). These findings demonstrate that GPS exhibits endothelium-independent vasorelaxant effects through inhibition of voltage-dependent, receptor-operated, and inositol triphosphate receptor (IP3R)/ryanodine receptor- (RYR-) mediated Ca2+ channels as well as the PI3K/Akt/Rho-kinase signaling pathway.

Cardiovascular Effects of Nigella Sativa on Isolated Rabbit Heart and its Impact on Cardiac Remodeling

“…The effects of NS on heart rate and contractility of isolated heart in the presence of calcium free Krebs solution have been observed in the past. 17 The isolated perfused hearts of Nigella treated rats showed the physiological cardiac hypertrophy in rats induced by long term NS supplementation, baseline peak tension and the maximum rate of tension development. 18 The bradycardia at low dose and tachycardia at high dose are related with the calcium channel blocking effects of NS as confirmed by various other studies.…”

Levosimendan Relaxes Thoracic Aortic Smooth Muscle in Mice by Inhibiting PKC and Activating Inwardly Rectifying Potassium Channels

“…Angiotensin, endothelin, NE, and other vasoconstrictors inhibit K ATP and K ir channels by activating Ca 2+independent or Ca 2+ -dependent PKC. [20][21][22][23][24]27 It is important to note that the K ATP channel is a Ca 2+ -independent potassium channel activated by PKC kinase. In this study, we observed that levosimendan induces vasorelaxation through inhibition of extracellular calcium influx.…”

“…However, it remains unknown whether the activity of the inwardly rectifying potassium channel is regulated by levosimendan in the thoracic aorta. Studies have also shown that PKC kinases participate in vasodilation, and the activity of PKC is closely related to K ir , 20,21 K ATP channels, [22][23][24] and intracellular Ca 2+ levels. [20][21][22][23][24] Therefore, this study investigated the functional role of PKC-dependent K ir channels and the involvement of intracellular Ca 2+ in levosimendan-mediated relaxation in the vascular smooth muscle of the thoracic aortas of mice.…”