Inhibition of intracellular Ca2+ mobilization and potassium channels activation are involved in the vasorelaxation induced by 7-hydroxycoumarin.

Coumarins exhibit a wide variety of biological effects, including activities in the cardiovascular system and the aim of this study was to evaluate the vascular therapeutic potential of 7-Hydroxicoumarin (7-HC). The vascular effects induced by 7-HC (0.001 µM-300 µM), were investigated by in vitro approaches using isometric tension measurements in rat superior mesenteric arteries and by in silico assays using Ligand-based analysis. Our results suggest that the vasorelaxant effect of 7-HC seems to rely on potassium channels, notably through large conductance Ca2+-activated K+ (BKCa) channels activation. In fact, 7-HC (300 µM) significantly reduced CaCl2-induced contraction as well as the reduction of intracellular calcium mobilization. However, the relaxation induced by 7-HC was independent of store-operated calcium entry (SOCE). Moreover, in silico analysis suggests that potassium channels have a common binding pocket, where 7-HC may bind and hint that its binding profile is more similar to quinine's than verapamil's. These results are compatible with the inhibition of Ca2+ release from intracellular stores, which is prompted by phenylephrine and caffeine. Taken together, these results demonstrate a therapeutic potential of 7-HC on the cardiovascular system, making it a promising lead compound for the development of drugs useful in the treatment of cardiovascular diseases.

Itaconimides derivatives induce relaxation in mesenteric artery and negative inotropism by inhibition of CA2+ influx.

BACKGROUND: The aim of this study was to evaluate the cardiovascular effects of N-phenyl-itaconimide (Imide-1), N-4-methyl-phenyl-itaconimide (Imide-2), N-4-methoxy-phenyl-itaconimide (Imide-3) and N-4-chloro-phenyl-itaconimide (Imide-4), and investigate the mechanisms of action involved in the observed responses. METHODS: The relaxant effect was investigated in rat superior mesenteric arteries by using isometric tension measurements. Additionally, in isolated atria were evaluated the heart rate and force of cardiac contraction and in vivo experiments was evaluated blood pressure and heart rate. RESULTS: Cumulative administration of itaconimides (3 × 10-8 to 3 × 10-4 M) in pre-contracted mesenteric artery rings with phenylephrine, 1 µM, induced endothelium-independent vasorelaxation. The itaconimides showed similar maximum efficacies. Additionally, Imide-3 induced vasorelaxation in rings exposed to a depolarizing-tyrode solution containing 60 mM KCl or 20 mM KCl similar to the control, suggesting the non-participation of K+ channels. Imide-3 attenuated Ca2+ influx in a concentration-dependent manner. As well, imide-3 reduced CaCl2-induced contraction in nominally calcium-free medium, in the presence of cyclopiazonic acid (20 µM), phenylephrine (1 µM) and nifedipine (1 µM), indicating a reduction of Ca2+ influx by receptor-operated channels (ROC) and store-operated channels (SOC). The presence of SKF 96365 (10-5 M), SOC blocker, did not significantly alter the vasorelaxant effect induced by imide-3. Moreover, imide-3 induced a negative inotropic effect. In vivo studies, in non-anesthetized normotensive rats, imide-3 lowered blood pressure and induced bradycardia. CONCLUSIONS: These results suggest that itaconimides have concentration-dependent vascular effects and the vasorelaxation seems to be endothelium-independent. The vasodilatory effect induced by imide-3 may be due to a possible influence on the CaV and ROC. In addition, imide-3 is able to reduce force of cardiac contraction, blood pressure and promote bradycardia.

Participation of the TRP channel in the cardiovascular effects induced by carvacrol in normotensive rat.

Carvacrol has been described as an agonist/antagonist of different transient receptor potential (TRP) channels and voltage-dependent calcium channels (Cavs). The aim of this study was to evaluate the role of Cav and TRP channels following carvacrol stimulation. Initially, in mesenteric artery rings carvacrol relaxed phenylephrine-induced contractions. Furthermore, carvacrol inhibited contraction elicited by CaCl2 in depolarizing nominally without Ca2+ medium and antagonized the contractions induced by S(-)-Bay K 8644 and inhibited Ca2+ currents indicating the inhibition of Ca2+ influx through L-type Cav. Additionally, carvacrol antagonized the contractions induced by CaCl2 in the presence of nifedipine/Cyclopiazonic acid/phenylephrine or nifedipine/Cyclopiazonic acid/KCl 60, suggesting a possible inhibition of calcium influx by store operated channels (SOCs), receptor operated channels (ROCs) and/or TRP channels. Interestingly, among the TRP channel blockers used, the effect induced by carvacrol was attenuated by Mg2+ and potentiated by La3+ and Gd3+, suggesting that TRP channels are involved in relaxation induced by carvacrol. Monoterpene also induced hypotension and bradycardia in non-anesthetized normotensive rats and negative inotropic and chronotropic effects. In conclusion, these results suggest that the hypotensive effect of carvacrol is probably due to bradycardia and a peripheral vasodilatation that involves, at least, the inhibition of the Ca2+ influx through Cav and TRP channels.