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Perivascular adipose tissue (PVAT) is a specialized type of adipose tissue that surrounds most mammalian blood vessels. PVAT is a metabolically active, endocrine organ capable of regulating blood vessel tone, endothelium function, vascular smooth muscle cell growth and proliferation, and contributing critically to cardiovascular disease onset and progression. In the context of vascular tone regulation, under physiological conditions, PVAT exerts a potent anticontractile effect by releasing a plethora of vasoactive substances, including NO, H2S, H2O2, prostacyclin, palmitic acid methyl ester, angiotensin 1-7, adiponectin, leptin, and omentin. However, under certain pathophysiological conditions, PVAT exerts pro-contractile effects by decreasing the production of anticontractile and increasing that of pro-contractile factors, including superoxide anion, angiotensin II, catecholamines, prostaglandins, chemerin, resistin, and visfatin. The present review discusses the regulatory effect of PVAT on vascular tone and the factors involved. In this scenario, dissecting the precise role of PVAT is a prerequisite to the development of PVAT-targeted therapies. [ABSTRACT FROM AUTHOR]

This study was designed to unveil effects of 5-nm sized, polyvinylpyrrolidone-coated gold nanoparticles (AuNPs) on vascular Ca V 1.2 and Ca V 3.1 channels. Ba 2+ currents through both channels (I Ba1.2 and I Ba3.1 ) were recorded in single myocytes isolated from the rat tail main artery by means of the whole-cell patch-clamp method. AuNPs increased I Ba1.2 and I Ba3.1 amplitude in a concentration- and V h -dependent manner. Neither the voltage dependence of inactivation and activation curves nor inactivation and activation kinetics were affected by AuNPs. In conclusion, these findings warrant further investigation to clarify whether different types of NPs possess the same stimulatory activity and may represent a toxic hazard to humans. [ABSTRACT FROM AUTHOR]

Papaverine is an opium alkaloid, primarily used as an antispasmodic drug and as a cerebral and coronary vasodilator. Its phosphodiesterase inhibitory activity promotes increase of cAMP levels mainly in the cytosol. As cAMP is known to modulate L-type Ca 2+ channel activity, here we tested the proposition that papaverine could affect vascular channel function. An in-depth analysis of the effect of papaverine on Ba 2+ or Ca 2+ current through L-type Ca 2+ channel [I Ba(L) or I Ca(L) ], performed in rat tail artery myocytes using either the whole-cell or the perforated patch-clamp method, was accompanied by a functional study on rat aorta rings. Papaverine increased current amplitude under both the perforated or whole-cell configuration. Stimulation of the current by papaverine was concentration-, V h -, frequency-, and charge carrier-dependent, and fully reverted by drug washout. The PKA inhibitor H89, but not the PKG inhibitor Rp-8-Br-cGMPS, antagonised papaverine- as well as IBMX- (another phosphodiesterase inhibitor) induced I Ba(L) stimulation. In cells pre-treated with IBMX, application of papaverine failed to increase current amplitude. Papaverine sped up the inactivation kinetics of I Ba(L) , though only at concentrations ≥ 30 μM, and shifted the voltage dependence of the inactivation curve to more negative potentials. In rings, the vasorelaxing activity of papaverine was enhanced by previous treatment with nifedipine. In conclusion, papaverine stimulates vascular L-type Ca 2+ channel via a PKA-dependent mechanism, thus antagonising its main vasodilating activity. [ABSTRACT FROM AUTHOR]

Abstract: In skeletal muscle sarcoplasmic reticulum vesicles, 3,5-di-t-butyl catechol (DTCAT) promotes the release of Ca2+ through the activation of ryanodine receptor Ca2+ channels. DTCAT mechanical and electrophysiological effects have now been investigated in rat aorta rings and single tail artery myocytes. Rat aorta rings incubated with either 30 μM ryanodine or 100 μM DTCAT developed tension, which averaged 36% and 7%, respectively, of that induced by phenylephrine. DTCAT reduced concentration-dependently both aorta ring contractions to high K+ (IC50 =13.5 μM) and L-type Ba2+ current (IC50 =22.0 μM) in isolated myocytes. Tetraethylammonium did not reverse the antispasmodic effect of DTCAT in rings stimulated with either 25 or 60 mM K+. DTCAT relaxed concentration-dependently phenylephrine-pre-contracted rings with intact endothelium (IC50 =10.9 μM). This effect was markedly reduced by pre-incubation of rings with 100 μM Nω-nitro-l-arginine methyl ester. DTCAT antagonised phenylephrine-induced contractions in endothelium-deprived rings, either in the presence or in the absence of ryanodine (IC50 =18.7 μM and 39.8 μM, respectively). Furthermore, both DTCAT (IC50 =53.3 μM) and ryanodine reduced significantly the response to phenylephrine in the absence of extracellular Ca2+. Phenylephrine-stimulated influx of extracellular Ca2+ was markedly inhibited when tissues were pre-treated with DTCAT (IC50 =19.0 μM) as well as nifedipine. DTCAT (>100 μM) was also able to antagonise the contractions induced by phorbol 12-myristate, 13-acetate. In conclusion, this is the first demonstration that DTCAT inhibits vascular smooth muscle voltage-operated Ca2+ channels and promotes the release of endothelial nitric oxide. Ryanodine receptor Ca2+ channels activation or the impairment of the contractile apparatus by DTCAT seem to play a secondary role in its vascular activity. [Copyright &y& Elsevier]

1: The aim of this study was to investigate the effects of 3,5-diacetyl- (DP1-DP5) and 3,5-dibenzoyl-1,4-dihydropyridines (DP6-DP11) on vascular functions in vitro, by comparing their mechanical and electrophysiological actions in rat aorta rings and single rat tail artery myocytes, respectively, and to quantify their multidrug resistance (MDR)-reversing activity in L5178 Y mouse T-lymphoma cells transfected with MDR1 gene. 2: In rat aorta, the 11 compounds tested, but 3,5-dibenzoyl-4-(3-phenoxyphenyl)-1,4-dihydro-2,6-dimethylpyridine (DP7), 3,5-dibenzoyl-4-(3-chlorophenyl)-1,4-dihydro-2,6-dimethylpyridine (DP9), 3,5-dibenzoyl-4-(4-chlorophenyl)-1,4-dihydro-2,6-dimethylpyridine (DP10) and 3,5-dibenzoyl-4-phenyl-1,4-dihydro-2,6-dimethylpyridine (DP11), antagonized 60?mM K+ (K60)-induced contraction in a concentration-dependent manner, with IC50 (M) values ranging between 5.65 × 10-7 and 2.23 × 10-5. 3: The 11 dihydropyridines tested, but DP7, inhibited L-type Ca2+ current recorded in artery myocytes in a concentration-dependent manner, with IC50 (M) values ranging between 1.12 × 10-6 and 6.90 × 10-5. 4: The K+-channel opener cromakalim inhibited the Ca2+-induced contraction in K30 but not that evoked in K60. On the contrary, DP7 was ineffective in both experimental conditions. 5: When the rings were preincubated with 1?mM Ni2+ plus 1?µM nifedipine, the response to phenylephrine was significantly reduced by 2,5-di-t-butyl-1,4-benzohydroquinone (BHQ), a well-known endoplasmic reticulum Ca2+-ATPase inhibitor. DP7 had no effects on this model system. 6: In L5178 MDR cell line, the 11 dihydropyridines tested, but 3,5-diacetyl-4-(2-nitrophenyl)-1,4-dihydro-2,6-dimethylpyridine (DP1), 3,5-diacetyl-4-(3-phenoxyphenyl)-1,4-dihydro-2,6-dimethylpyridine (DP2) and 3,5-diacetyl-4-(3-chlorophenyl)-1,4-dihydro-2,6-dimethylpyridine (DP4), exhibited an MDR-reversing activity, with IC50 values ranging between 3.02 × 10-7 and 4.27 × 10-5, DP7 being the most potent. 7: In conclusion, DP7 may represent a lead compound for the development of potent dihydropyridine MDR chemosensitizers devoid of vascular effects.British Journal of Pharmacology (2004) 141, 415-422. doi:10.1038/sj.bjp.0705635 [ABSTRACT FROM AUTHOR]

The effects of myricetin (3,3’,4’,5,5’,7-hesahydroxyflavone), a natural flavonoid found in edible plants, were studied on vascular smooth muscle L-type Ca2+ channels by comparing its mechanical, radioligand binding, and electrophysiological properties to those of the Ca2+ channel agonist (S)-(-)-Bay K 8644. In rat aorta rings, both myricetin and (S)-(-)-Bay K 8644 induced contractile responses, which were dependent upon prior exposure to K+. At 15 mM K+ (K15) the pEC50 values for myricetin and (S)-(-)-Bay K 8644 were 4.43±0.03 and 7.92±0.13, respectively. Furthermore, the maximum tension response to myricetin was not significantly different from that elicited by either (S)-(-)-Bay K 8644 or K60. The Ca2+ channel blockers nifedipine, verapamil and diltiazem antagonised and fully reverted myricetin-, (S)-(-)-Bay K 8644- as well as K60-induced contractions. Both myricetin and (S)-(-)-Bay K 8644 potentiated rat aorta ring responses to K+, shifting the K+ concentration-response curve to the left. (S)-(-)-Bay K 8644, but not myricetin, inhibited in a concentration-dependent manner (+)-[3H]PN200–110 binding in porcine aortic membranes. Electrophysiological recordings from single rat tail artery myocytes, under amphotericin B-perforated as well as conventional methods, showed that both myricetin and (S)-(-)-Bay K 8644 increased L-type Ba2+ current (IBa(L)) and shifted the maximum of the current-voltage relationship by 10 mV in the hyperpolarising direction, without, however, modifying the threshold potential. Furthermore, (S)-(-)-Bay K 8644 accelerated both activation and inactivation kinetics of IBa(L) while myricetin slowed down the activation kinetics. Finally, both (S)-(-)-Bay K 8644 and myricetin slowed down deactivation kinetics of IBa(L). These results suggest that myricetin induces vasoconstriction by activating L-type Ca2+ channel with similar efficacy but a site of action different to that of (S)-(-)-Bay K 8644. [ABSTRACT FROM AUTHOR]

Summary. Background: Several studies have indicated that quercetin promotes relaxation of vascular smooth muscle both in vivo and in vitro. However, Saponara et al. [(2002) Br J Pharmacol 135: 1819–1827] have demonstrated that quercetin is an activator of vascular L-type Ca[sup 2+] channels. Aim of the study :We investigated the mechanical and electrophysiological properties of quercetin and its rutoside, rutin, in an attempt to clarify how Ca[sup 2+] channel activation might be related to the myorelaxing activity. Methods: Aorta ring preparations and single tail artery myocytes were employed for functional and patch-clamp experiments, respectively. Results: Rutin was found to relax intact rat aorta rings, which had been precontracted with phenylephrine (pIC[sub 50] = 5.65 ± 0.31) but in contrast had no effect on depolarised (60 mM K[sup +] ) preparations or on those from which the endothelium had been removed. Furthermore, rutin did not affect L-type Ca[sup 2+] current recorded in rat tail artery myocytes. The quercetin-induced relaxation of intact rings precontracted with phenylephrine exhibited two components characterised by 6.23 ± 0.38 and 4.66 ± 0.09 pIC[sub 50] , respectively. Removal of the endothelium abolished the first component, leaving the second unaltered. Moreover, quercetin was found to relax 60 mM K[sup +] depolarised rings with a pIC[sub 50] of 4.59 ± 0.03. The application of quercetin in isolated smooth muscle cells brought about a marked increase of L-type Ca[sup 2+] current (pEC[sub 50] = 5.09 ± 0.05). Unlike quercetin, Bay K 8644 contracted aorta rings preincubated with 10, 20 or 30 mM K[sup +] . The myotonic effect of Bay K 8644 was observed both in the absence or presence of 30 μM quercetin. The application of Bay K 8644 (10–100 nM) caused a further significant increase in L-type Ca[sup 2+] current in rat tail artery myocytes stimulated with 30 μM quercetin. Conclusions: Quercetin is a... [ABSTRACT FROM AUTHOR]

In the search for novel, bi-functional compounds acting as Ca V 1.2 channel blockers and K+ channel stimulators, which represent an effective therapy for hypertension, 3,3′- O -dimethylquercetin was isolated for the first time from Brazilian Caatinga green propolis. Its effects were investigated through electrophysiological, functional, and computational approaches. In rat tail artery myocytes, 3,3′- O -dimethylquercetin blocked Ba2+ currents through Ca V 1.2 channels (I Ba1.2) in a concentration-dependent manner, with the inhibition being reversed upon washout. The compound also shifted the voltage dependence of the steady-state inactivation curve to more negative potentials without affecting the slope of the inactivation and activation curves. Furthermore, the flavonoid stimulated K Ca 1.1 channel currents (I KCa1.1). In silico simulations provided additional evidence for the binding of 3,3′- O -dimethylquercetin to K Ca 1.1 and Ca V 1.2 channels and elucidated its mechanism of action. In depolarized rat tail artery rings, the flavonoid induced a concentration-dependent relaxation. Moreover, in rat aorta rings its antispasmodic effect was inversely related to the transmembrane K+ gradient. In conclusion, 3,3′- O -dimethylquercetin demonstrates effective in vitro vasodilatory properties, encouraging the exploration of its scaffold to develop novel derivatives for potential use in the treatment of hypertension. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The functional interaction between two L-type Ca2+ channel activators, quercetin and (S)-(−)-methyl-1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)pyridine-5-carboxylate (Bay K 8644), has been investigated in vascular smooth muscle cells. L-type Ca2+ currents [I Ca(L)] were recorded in freshly isolated rat tail main artery myocytes using the whole-cell patch-clamp method. Bay K 8644 increased I Ca(L) in a concentration-dependent manner with a pEC50 value of 8.25. Pre-incubation of myocytes with concentrations of quercetin per se ineffective as an L-type Ca2+ channel activator (0.1 and 0.3 μM) inhibited significantly the maximal response evoked by Bay K 8644, but left unaltered its potency. Quercetin (0.1 μM) prevented the hyperpolarizing shift of the steady-state inactivation curve induced by 0.1 μM Bay K 8644 and its stimulation of I Ca(L) tail current intensity without modifying Bay K 8644-induced effects on I Ca(L) activation, inactivation, deactivation kinetics as well as on use-dependence and recovery from inactivation. Quercetin at nutritionally meaningful concentrations, limited the responsiveness of vascular L-type Ca2+ channels to the pharmacological stimulation operated by Bay K 8644. These data contribute to a better understanding of quercetin effects on experimental in vivo cardioprotection. [Copyright &y& Elsevier]

The conjugation of doxorubicin (DOX) with nitric oxide (NO)-releasing groups gave rise to novel anthracyclines, such as nitrooxy-DOX (NitDOX), capable to overcome multidrug resistance. The widely described anthracycline cardiovascular toxicity, however, might limit their clinical use. This study aimed to investigate NitDOX-induced effects, as potential hazard, on vascular smooth muscle A7r5 and endothelial EA.hy926 cell viability, on the mechanical activity of freshly and cultured rat aorta rings, as well as on Ca v 1.2 channels of A7r5 cells. DOX was used as a reference compound. Although an increase in intracellular radicals and a reduction in mitochondrial potential occurred upon treatment with both drugs, A7r5 and EA.hy926 cells proved to be more sensitive to DOX than to NitDOX. Both compounds promoted comparable effects in A7r5 cells, whereas NitDOX was less active than DOX in inducing DNA damage and in eliciting apoptotic-mediated cell death revealed as an increase in sub-diploid-, DAPI- and annexin V-positive- EA.hy926 cell percentage. Moreover, in EA.hy926 cells, NitDOX doubled basal NO content, while preincubation with the NO-scavenger PTIO increased NitDOX-induced cytotoxicity. DOX exhibited a negligible contracturing effect in endothelium-intact rings, while NitDOX induced a significant ODQ-sensible, vasodilation in endothelium-denuded rings. In arteries cultured with both drugs for 7 days, NitDOX prevented either phenylephrine- or KCl-induced contraction at a concentration 10-fold higher than that of DOX. These results demonstrate that NitDOX displays a more favourable vascular toxicity profile than DOX. Taking into account its greater efficacy against drug-resistant cells, NitDOX is worth of further investigations in preclinical and clinical settings. • NitDOX is a NO-releasing doxorubicin (DOX) capable to overcome multidrug resistance. • NitDOX was less cytotoxic than DOX, particularly in EA.hy926 cells, where it released NO. • NitDOX induced a significant ODQ-sensible, vasodilation in endothelium-denuded rings. • NitDOX displayed lower long-term vascular effects as compared to DOX. [ABSTRACT FROM AUTHOR]

[Display omitted] Mdivi-1 is widely used as a pharmacological tool to inhibit dynamin-related protein-1-mediated mitochondrial fission. Whether this compound may interact directly or indirectly with ion channels or cellular pathways fundamental for the regulation of vascular smooth muscle tone remains unknown. The present study aimed to assess the effect of mdivi-1 on Ca V 1.2 and K Ca 1.1 channels, both in vitro and in silico as well as on the mechanical activity of rat aorta rings. Mdivi-1 was an effective Ca V 1.2 channel blocker, docking in a Ca V 1.2 channel antagonist binding region, stimulated K Ca 1.1 channel current, binding to a sensing region common to other stimulators, and possibly inhibited the Rho-kinase pathway. These effects contributed to its vasorelaxant activity observed in rings stimulated with high KCl, phenylephrine, or NaF. Neither structurally different dynamin inhibitors nor a stimulator affected the Ca2+ antagonistic and vasorelaxant activities of the compound. However, mito-tempol reduced its vasorelaxant potency towards phenylephrine. Finally, mdivi-1 antagonized mitochondrial fission triggered by phenylephrine. In conclusion, mdivi-1 is an effective in vitro vasorelaxant agent at concentrations routinely employed to block dynamin-related protein-1. Ion channels and pathways key to the maintenance of vessel active tone are involved in this mechanism. These yet undiscovered off-target effects raise caution for the interpretation of mitochondrial fission signalling. [ABSTRACT FROM AUTHOR]

Sdox is a synthetic H 2 S-releasing doxorubicin (Dox) less cardiotoxic and more effective than Dox in pre-clinical, Dox-resistant tumour models. The well-known anthracycline vascular toxicity, however, might limit Sdox clinical use. This study aimed at evaluating Sdox vascular toxicity in vitro, using Dox as reference compound. Both vascular smooth muscle A7r5 and endothelial EA.hy926 cells were more sensitive to Dox than Sdox, although both drugs equally increased intracellular free radical levels. Sdox released H 2 S in both cell lines. The H 2 S scavenger hydroxocobalamin partially reverted Sdox-induced cytotoxicity in A7r5, but not in EA.hy926 cells, suggesting a role for H 2 S in smooth muscle cell death. Markers of Sdox-induced apoptosis were significantly lower than, in A7r5 cells, and comparable to those of Dox in EA.hy926 cells. In A7r5 cells, Dox increased the activity of caspase 3, 8, and 9, Sdox affecting only that of caspase 3. Moreover, both drugs induced comparable DNA damage in A7r5 cells, while Sdox was less toxic than Dox in Ea.hy926 cells. In fresh aorta rings, only Dox weakly increased phenylephrine-induced contraction when endothelium was present. In rings cultured with both drugs for 7 days, Sdox blunted phenylephrine- and high K+-induced contractions though at a concentration 10-fold higher than that of Dox. In conclusion, Sdox may represent the prototype of an innovative anthracycline, effective against Dox-resistant tumours, displaying a more favourable vascular toxicity profile compared to the parent compound. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] Ca V 1.2 channels play a fundamental role in the regulation of vascular smooth muscle tone. The aim of the present study was to synthesize morin derivatives bearing the nitrophenyl moiety of dihydropyridine Ca2+ antagonists to increase the flavonoid vasorelaxant activity. The effects of morin and its derivatives were assessed on Ca V 1.2 and K Ca 1.1 channels, both in vitro and in silico , as well as on the contractile responses of rat aorta rings. All compounds were effective Ca V 1.2 channel blockers, positioning in the α 1C subunit region where standard blockers bind. Among the four newly synthesized morin derivatives, the penta-acetylated morin-1 was the most efficacious Ca2+ antagonist, presenting a vasorelaxant profile superior to that of the parent compound and, contrary to morin, antagonized also the release of Ca2+ from the sarcoplasmic reticulum; surprisingly, it also stimulated K Ca 1.1 channel current. Computational analysis demonstrated that morin-1 bound close to the K Ca 1.1 channel S6 segment. In conclusion, these findings open a new avenue for the synthesis of valuable multi-functional, vasorelaxant morin derivatives capable to target several pathways underpinning the pathogenesis of hypertension. [ABSTRACT FROM AUTHOR]