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Norbormide (NRB) is a Rattus-selective toxicant, which was serendipitously discovered in 1964 and formerly marketed as an eco-friendly rodenticide that was deemed harmless to non-Rattus species. However, due to inconsistent efficacy and the emergence of second-generation anticoagulants, its usage declined, with registration lapsing in 2003. NRBs' lethal action in rats entails irreversible vasoconstriction of peripheral arteries, likely inducing cardiac damage: however, the precise chain of events leading to fatality and the target organs involved remain elusive. This unique contractile effect is exclusive to rat arteries and is induced solely by the endo isomers of NRB, hinting at a specific receptor involvement. Understanding NRB's mechanism of action is crucial for developing species-selective toxicants as alternatives to the broad-spectrum ones currently in use. Recent research efforts have focused on elucidating its cellular mechanisms and sites of action using novel NRB derivatives. The key findings are as follows: NRB selectively opens the rat mitochondrial permeability transition pore, which may be a factor that contributes to its lethal effect; it inhibits rat vascular KATP channels, which potentially controls its Rattus-selective vasoconstricting activity; and it possesses intracellular binding sites in both sensitive and insensitive cells, as revealed by fluorescent derivatives. These studies have led to the development of a prodrug with enhanced pharmacokinetic and toxicological profiles, which is currently undergoing registration as a novel efficacious eco-sustainable Rattus-selective toxicant. The NRB-fluorescent derivatives also show promise as non-toxic probes for intracellular organelle labelling. This review documents in more detail these developments and their implications. [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]

To characterize the role of cAMP-dependent protein kinase (PKA) in regulating vascular Ca 2+ current through Ca v 1.2 channels [I Ca1.2 ], we have documented a marked capacity of the isoquinoline H-89, widely used as a PKA inhibitor, to reduce current amplitude. We hypothesized that the I Ca1.2 inhibitory activity of H-89 was mediated by mechanisms unrelated to PKA inhibition. To support this, an in-depth analysis of H-89 vascular effects on both I Ca1.2 and contractility was undertaken by performing whole-cell patch-clamp recordings and functional experiments in rat tail main artery single myocytes and rings, respectively. H-89 inhibited I Ca1.2 with a pIC 50 (M) value of about 5.5, even under conditions where PKA activity was either abolished by both the PKA antagonists KT5720 and protein kinase inhibitor fragment 6–22 amide or enhanced by the PKA stimulators 6-Bnz-cAMP and 8-Br-cAMP. Inhibition of I Ca1.2 by H-89 appeared almost irreversible upon washout, was charge carrier- and voltage-dependent, and antagonised by the Ca v 1.2 channel agonist (S)-(-)-Bay K 8644. H-89 did not alter both potency and efficacy of verapamil, did not affect current kinetics or voltage-dependent activation, while shifting to the left the 50% voltage of inactivation in a concentration-dependent manner. H-89 docked at the α 1C subunit in a pocket region close to that of (S)-(-)-Bay K 8644 docking, forming a hydrogen bond with the same, key amino acid residue Tyr-1489. Finally, both high K + - and (S)-(-)-Bay K 8644-induced contractions of rings were fully reverted by H-89. In conclusion, these results indicate that H-89 inhibited vascular I Ca1.2 and, consequently, the contractile function through a PKA-independent mechanism. Therefore, caution is recommended when interpreting experiments where H-89 is used to inhibit vascular smooth muscle PKA. [ABSTRACT FROM AUTHOR]

The P-glicoprotein (P-gp) inhibitor MC18 has been recently proposed as a valuable PET tracer to measure P-gp expression in vivo. The aim of this study was to evaluate the toxic hazard towards the vasculature of MC18 along with the structurally related and more potent P-gp inhibitor MC70. Their effects on A7r5 and EA.hy926 cells viability, on the mechanical activity of fresh and cultured rat aorta rings as well as on Cav1.2 channel current ( ICa1.2) of A7r5 cells were studied. At concentrations >10 μM, MC18 and MC70 decreased cell viability causing evident morphological changes. In fresh rat aorta rings, both compounds (0.1-100 μM) antagonized phenylephrine-induced contraction in a concentration-dependent manner, with IC50 values in the range of 1.67-14.49 μM, whereas only MC18 caused a concentration-dependent decrease of the 60 mM K+ (K60)-induced responses. In rings cultured for 7 days with both compounds (1-10 μM), 10 μM MC70 significantly reduced, while 10 μM MC18 completely prevented the contractile response to both phenylephrine and K60. MC18 and MC70 (0.1-100 μM) inhibited ICa1.2 in a concentration-dependent manner with IC50 values of 16.81 and 32.13 μM, respectively. These findings demonstrate that MC18-induced vascular effects took place at concentrations that are at least three orders of magnitude higher than those (≤10 nM) allowing in vivo measurement of P-gp expression. Thus, MC18, and possibly MC70, can be considered promising PET tools for in vivo P-gp quantification. [ABSTRACT FROM AUTHOR]

Ion channels underlie a wide variety of physiological processes that involve rapid changes in cell dynamics, such as cardiac and vascular smooth muscle contraction. Overexpression or dysfunction of these membrane proteins are the basis of many cardiovascular diseases that represent the leading cause of morbidity and mortality for human beings. In the last few years, flavonoids, widely distributed in the plant kingdom, have attracted the interest of many laboratories as an emerging class of fine ion, in particular Ca v , channels modulators. Pieces of in vitro evidence for direct as well as indirect effects exerted by various flavonoids on ion channel currents are now accumulating in the scientific literature. This activity may be responsible, at least in part, for the beneficial and protective effects of dietary flavonoids toward cardiovascular diseases highlighted in several epidemiological studies. Here we examine numerous studies aimed at analysing this feature of flavonoids, focusing on the mechanisms that promote their sometimes controversial activities at cardiovascular Ca v channels. New methodological approaches, such as molecular modelling and docking to Ca v 1.2 channel α 1c subunit, used to elucidate flavonoids intrinsic mechanism of action, are introduced. Moreover, flavonoid-membrane interaction, bioavailability, and antioxidant activity are taken into account and discussed. [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]

Several studies demonstrate the beneficial effects of dietary flavonoids on the cardiovascular system. Since perivascular adipose tissue (PVAT) plays an active role in the regulation of vascular tone in both health and diseases, the present study aimed to assess the functional interaction between PVAT and flavonoids in vitro on rat aorta rings. Several flavonoids proved to display both antispasmodic and spasmolytic activities towards noradrenaline-induced contraction of rings deprived of PVAT (-PVAT). However, on PVAT-intact (+PVAT) rings, both actions of some flavonoids were lost and/or much decreased. In rings-PVAT, the superoxide donor pyrogallol mimicked the effect of PVAT, while in rings+PVAT the antioxidant mito-tempol restored both activities of the two most representative flavonoids, namely apigenin and chrysin. The Rho-kinase inhibitor fasudil, or apigenin and chrysin concentration-dependently relaxed the vessel active tone induced by the Rho-kinase activator NaF; the presence of PVAT counteracted apigenin spasmolytic activity, though only in the absence of mito-tempol. Similar results were obtained in rings pre-contracted by phenylephrine. Finally, when β 3 receptors were blocked by SR59230A, vasorelaxation caused by both flavonoids was unaffected by PVAT. These data are consistent with the hypothesis that both noradrenaline and apigenin activated adipocyte β 3 receptors with the ensuing release of mitochondrial superoxide anion, which once diffused toward myocytes, counteracted flavonoid vasorelaxant activity. This phenomenon might limit the beneficial health effects of dietary flavonoids in patients affected by either obesity and/or other pathological conditions characterized by sympathetic nerve overactivity. [Display omitted] [ABSTRACT FROM AUTHOR]

The effect of freeze-dried red wine (FDRW) on cardiac function and electrocardiogram (ECG) in Langendorff-isolated rat hearts was investigated. FDRW significantly decreased left ventricular pressure and coronary perfusion pressure, the latter being dependent on the activation of both phosphatidylinositol 3-kinase and eNOS. FDRW did not affect the QRS and QT interval in the ECG, although at 56 μg of gallic acid equivalents/mL, it prolonged PQ interval and induced a second-degree atrioventricular block in 3 out of 6 hearts. This is the first study demonstrating that at concentrations resembling a moderate consumption of red wine, FDRW exhibited negative inotropic and coronary vasodilating activity leaving unaltered ECG, whereas at very high concentrations, it induced arrhythmogenic effects. [ABSTRACT FROM AUTHOR]

Abstract: The neuroprotective agent riluzole [2-amino-6-(trifluoromethoxy)benzothiazole] has been shown to antagonize neuronal high-voltage activated Ca2+ currents. In the search for novel scaffolds leading to potential antihypertensive agents, a series of 2-aryl- and 2-amido-benzothiazoles (HUP) were assessed for their vasorelaxing property on rat aorta rings and for their L-type Ba2+ currents [I Ba(L)] blocking activity on single myocytes isolated from the rat tail artery. HUP5 and HUP30, the most potent of the series, inhibited phenylephrine-induced contraction with IC50 values in the range 3–6µM. The presence of endothelium did not modify their spasmolytic activity. Both HUP5 and HUP30 increased tissue levels of cGMP and shifted to the left the concentration–response curve to sodium nitroprusside. In rings precontracted by phenylephrine, tetraethylammonium or 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ) shifted to the right the concentration–relaxation curves of HUP5 and HUP30. The antispasmodic effect of HUP5 and HUP30 was more marked on rings stimulated with 25/30mM than with 60mM K+. HUP5 and HUP30 antagonized both extracellular Ca2+ influx and Ca2+ mobilization from intracellular stores in response to phenylephrine: this effect was not modified by the presence of ODQ. I Ba(L) was partly inhibited by HUP5 and blocked by HUP30 in a concentration-dependent as well as ODQ-independent manner. In conclusion, HUP5 and HUP30 are vasorelaxing agents that stimulate soluble guanylyl cyclase, activate K+ channels, and block extracellular Ca2+ influx. The present benzothiazole derivatives form a novel class of multifunctional vasodilators which may give rise to effective antihypertensive agents. [Copyright &y& Elsevier]

Abstract: Regulation of smooth muscle contraction is driven by a number of protein kinases: the evidence for this often originates from studies that investigate the effects of extracellularly added specific protein kinase inhibitors. Six compounds, thought to be selective inhibitors of various kinases, were analysed for their effects on vascular L-type Ca2+ channels because this potential subsidiary activity could strongly influence our understanding of the pathways involved in smooth muscle contraction. Whole-cell L-type Ba2+ currents [I Ba(L)] were recorded in single myocytes, and contractile responses were measured from endothelium-denuded rings taken from the rat tail artery. Although ML-7, ML-9, and wortmannin (MLCK inhibitors), HA-1077 and Y-27632 (Rho-associated kinase inhibitors), and GF-109203X (PKC inhibitor) relaxed rings pre-contracted with high KCl in a concentration-dependent manner, their effect on I Ba(L) intensity was surprisingly variable. Wortmannin showed negligible effects while HA-1077 and Y-27632 were ineffective. I Ba(L) was partly inhibited by GF-109203X and blocked by ML-7 and ML-9 in a concentration-dependent manner, with the blockade by ML-7 being voltage-dependent. Whilst ML-7, ML-9, and GF-109203X sped up the inactivation kinetics of I Ba(L), GF-109203X did not modify ML-7- or ML-9-induced effects, with both intensity and kinetics of the current remaining unchanged. In contrast, application of Bay K 8644 on myocytes pre-treated with ML-7 or ML-9 raised I Ba(L) beyond control values. In conclusion, ML-7 and ML-9 inhibit L-type Ca2+ channels via a mechanism independent of MLCK, PKC or Rho kinase activities, and as such caution should be used in employing these agents to elucidate the role of kinases in smooth muscle contraction. [Copyright &y& Elsevier]

Abstract: Osthole is a coumarin extracted from Cnidium monnieri (L.) Cusson. The medicinal plant is widely used in Vietnamese as well as Chinese traditional medicine as a vasodilating and antihypertensive agent. Here we have tested the proposition that the block of Cav1.2 channels is mainly responsible for its vascular activity. An in-depth analysis of the effect of osthole on Cav1.2 current (ICa1.2) was performed in rat tail artery myocytes using the whole-cell patch-clamp method. Osthole decreased ICa1.2 in a concentration- and voltage-dependent manner. At holding potentials of −50 and −80mV, the pIC50 values were 4.78±0.07 and 4.36±0.08, respectively; the latter corresponded to the drug apparent dissociation constant for resting channels, K R , of 47.8μM. Osthole speeded up the inactivation kinetics of ICa1.2 and shifted the voltage dependence of the inactivation curve to more negative potentials in a concentration-dependent manner, with an apparent dissociation constant for inactivated channels (K I ) of 6.88μM. Block of ICa1.2 was frequency-dependent and the rate of recovery from inactivation was slowed down. In conclusion, osthole is a vascular Cav1.2 channel antagonist stabilizing the channel in its inactivated state. This mechanism may account for the systolic blood pressure reduction induced by the drug in animal models of hypertension and points to osthole as a lead for the development of novel antihypertensive agents. [Copyright &y& Elsevier]

The aim of this study was to investigate the effects of two novel multidrug-resistance reverting agents, ALIS 409 [1,3-dimethyl-1,3- p-fluorophenyl-1,3(3-morfolinopropyl)-1,3-disiloxan dihydrochloride] and ALIS 421 {1,3-dimethyl-1,3-(4-fluorophenyl)-1,3[3(4-buthyl)-(1-piperazinyl)-propyl]-1,3-disiloxan tetrahydrochloride}, on vascular functions in vitro. A comparison of their mechanical and electrophysiological actions in rat aorta rings and single rat tail artery myocytes, respectively, was performed. In endothelium-denuded rat aorta rings, ALIS 409 and ALIS 421 antagonized 60 mM K+-induced contraction in a concentration-dependent manner with IC50 values of 52.2 and 15.5 μM, respectively. ALIS 409 and ALIS 421 inhibited L-type Ca2+ current recorded in artery myocytes in a concentration-dependent manner with IC50 values of 6.4 and 5.6 μM, respectively. In rat aorta, ALIS 409 and ALIS 421 antagonized the sustained tonic contraction induced by phenylephrine with IC50 values of 58.0 and 13.7 μM (endothelium-denuded rings) and of 73.9 and 31.9 μM (endothelium-intact rings), respectively. In endothelium-denuded rings, ryanodine reduced significantly the response to phenylephrine in the absence of extracellular Ca2+ whereas nifedipine, ALIS 409 or ALIS 421 did not affect it. Phenylephrine-stimulated influx of extracellular Ca2+ was markedly reduced when tissues were pretreated with ALIS 409, ALIS 421 or nifedipine, and stimulated when they were pretreated with ryanodine. Application of ALIS 409 (up to 100 μM) to intact rat aorta rings failed to induce mechanical responses. Our results provide functional evidence that the myorelaxing effect elicited either by ALIS 409 or by ALIS 421 involved mainly the direct blockade of extracellular Ca2+ influx. This effect, however, took place at concentrations much higher than those effective as modifiers of multidrug resistance in cancer cells. [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]

Abstract: In the present study, the effects of 3,5-di-t-butylcatechol (DTCAT) on ryanodine receptor Ca2+ channel (RyRC) of skeletal muscle sarcoplasmic reticulum (SR) vesicles were investigated, both by monitoring extravesicular Ca2+ concentration directly with the Ca2+ indicator dye arsenazo III and by studying the high-affinity [3H]ryanodine binding. DTCAT stimulated Ca2+ release from junctional (terminal cisternae) vesicles in a concentration-dependent manner, with a threshold activating concentration of 30μM and a pEC50 value of 3.43±0.03M. The release of Ca2+ induced by DTCAT was antagonized in a concentration-dependent manner by ruthenium red, thus indicating that RyRC is involved in the mechanism of stimulation. A structure–activity relationship analysis carried out on a limited number of compounds suggested that both hydroxy and t-butyl groups in DTCAT were important for the activation of RyRC. DTCAT inhibited [3H]ryanodine binding to SR vesicles with a K i of 232.5μM, thus indicating that it acted directly at the skeletal muscle ryanodine receptor binding site to stimulate Ca2+ release. In conclusion, the ability of DTCAT to release Ca2+ from TC vesicles of skeletal muscle is noteworthy in view of its possible use as an alternative compound to either caffeine or halothane for performing the “In vitro contracture test” to diagnose the susceptibility of some patients to develop malignant hyperthermia under particular pharmacological treatments. [Copyright &y& Elsevier]

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]

The cardiac action potential is regulated by several ion channels. Drugs capable to block these channels, in particular the human ether-à-go-go -related gene (hERG) channel, also known as K V 11.1 channel, may lead to a potentially lethal ventricular tachyarrhythmia called " Torsades de Pointes ". Thus, evaluation of the hERG channel off-target activity of novel chemical entities is nowadays required to safeguard patients as well as to avoid attrition in drug development. Flavonoids, a large class of natural compounds abundantly present in food, beverages, herbal medicines, and dietary food supplements, generally escape this assessment, though consumed in consistent amounts. Continuously growing evidence indicates that these compounds may interact with the hERG channel and block it. The present review, by examining numerous studies, summarizes the state-of-the-art in this field, describing the most significant examples of direct and indirect inhibition of the hERG channel current operated by flavonoids. A description of the molecular interactions between a few of these natural molecules and the Rattus norvegicus channel protein, achieved by an in silico approach, is also presented. [ABSTRACT FROM AUTHOR]

[Display omitted] • Application of a research platform for food geographical authentication. • Multivariate investigation for Allium ampeloprasum L. from Valdichiana (Tuscany). • A. ampeloprasum L. showed a different chemical composition compared to A. sativum. • Glutathione was identified as a potential marker of authentication. • A. ampeloprasum L. extracts displayed interesting vasoactive properties. A research platform for food authentication was set up by combining stable isotope ratio analysis, metabolomics by gas and liquid mass-spectrometry and NMR investigations, chemometric analyses for food excellences. This multi-analytical approach was tested on samples of elephant garlic (Allium ampeloprasum L.), a species belonging to the same genus of common garlic (Allium ampeloprasum L.), mainly produced in southern Tuscany-(Allium ampeloprasum). The isotopic composition allowed the product to be geographically characterized. Flavonoids, like (+)-catechin, cinnamic acids, quercetin glycosides were identified. The samples showed also a significant amount of dipeptides, sulphur-containing metabolites and glutathione, the latter of which could be considered a molecular marker of the analyzed elephant garlic. For nutraceutical profiling to reach quality labels, extracts were investigated in specific biological assays, displaying interesting vasorelaxant properties in rat aorta by mediating nitric oxide release from the endothelium and exhibited positive inotropic and negative chronotropic effects in rat perfused heart. [ABSTRACT FROM AUTHOR]

Bio‐based products are nowadays useful tools able to affect the productivity and quality of conventionally cultivated crops. Several bio‐based products are currently on the market; one of the newest and most promising is the wood distillate (WD) derived from the pyrolysis process of waste biomass after timber. Its foliar application has been widely investigated and shown to promote the antioxidant profile of cultivated crops. WD was used here as additive for the cultivation of tomato (Solanum lycopersicum L.) plants. The application improved quality (chemical) parameters, minerals, polyphenols, and lycopene contents of tomato fruits. The extracts of WD‐treated and untreated tomatoes have been chemically and biologically characterized. The 1H‐NMR and ESI‐mass spectrometry analyses of the extracts revealed the presence of different fatty acids, amino acids and sugars. In particular, the WD‐treated tomatoes showed the presence of pyroglutamic acid and phloridzin derivatives, but also dihydrokaempferol, naringenin glucoside, cinnamic acid, and kaempferol‐3‐O‐glucoside. When tested in cells, the extracts showed a promising anti‐inflammatory profile in lipopolysaccharide (LPS)‐stimulated RAW 264.7 macrophages. Furthermore, the extracts displayed a slight vasorelaxant activity on rat aorta rings (either endothelium‐denuded or endothelium‐intact) pre‐contracted with phenylephrine or potassium chloride. Practical Application: Wood distillate has been used for tomato plant growth. Tomatoes showed improved nutritional parameters, and their extracts displayed antioxidant and anti‐inflammatory activities. [ABSTRACT FROM AUTHOR]

The P-glicoprotein (P-gp) inhibitor tariquidar is used to detect functional alterations of blood brain barrier pumps in PET imaging. The doses required, however, up to 4-fold higher than those already used in clinical trials to reverse multidrug resistance, cause syncopal episode and hypotension. Therefore, the effects of these doses toward the vasculature were investigated and an in-depth analysis of tariquidar-mediated effects on A7r5 and EA.hy926 cells viability, on the mechanical activity of freshly and cultured rat aorta rings and on L-type Ca 2+ current [I Ca(L) ] of A7r5 cells has been performed. In both A7r5 and EA.hy926 cells, tariquidar was not cytotoxic up to 1 μM concentration. On the contrary, at 10 μM, it caused apoptosis already after 24 h treatment. In fresh aorta rings, 10 μM tariquidar partially relaxed phenylephrine-, but not 60 mM K + (K60)-induced contraction. In rings treated with 10 μM tariquidar for 7 days, the contractile response to both phenylephrine and K60 remained unchanged. Finally, tariquidar did not modify I Ca1.2 intensity and kinetics. In conclusion, Tariquidar might exert both cytotoxic and acute, weak vascular effects at concentrations comparable to those employed in PET imaging. This implies that caution should be exercised when using it as diagnostic tool. [ABSTRACT FROM AUTHOR]

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]

The abnormal activation of Src family kinases (SFKs) due to deregulation of the B-cell receptor (BCR) signalling pathway provides a promising target for development of new pharmacological strategy to overcome the ibrutinib resistance in diffuse large B-cell lymphoma (DLBCL). In this work, we demonstrated that Si409, a pyrazolo[3,4-d]pyrimidine-based compound, has the ability to inhibit key members of SFKs and to reduce the proliferation of several B-cell tumor cell lines. Preclinical cytotoxicity profile, in vivo pharmacokinetic (PK) properties, and therapeutic efficacy in subcutaneous murine DLBCL model have been evaluated. Results obtained through these preliminary analyses revealed a promising role of Si409 and suggested its further development for the treatment of DLBCL. [ABSTRACT FROM AUTHOR]

Hypertension is a risk factor for cardiovascular diseases, which are the main cause of morbidity and mortality in the world. In the search for new molecules capable of targeting KCa1.1 and CaV1.2 channels, the expression of which is altered in hypertension, the in vitro vascular effects of a series of flavonoids extracted from the heartwoods, roots, and leaves of Dalbergia tonkinensis Prain, widely used in traditional medicine, were assessed. Rat aorta rings, tail artery myocytes, and docking and molecular dynamics simulations were used to analyse their effect on these channels. Formononetin, orobol, pinocembrin, and biochanin A showed a marked myorelaxant activity, particularly in rings stimulated by moderate rather than high KCl concentrations. Ba2+ currents through CaV1.2 channels (IBa1.2) were blocked in a concentration-dependent manner by sativanone, 3′-O-methylviolanone, pinocembrin, and biochanin A, while it was stimulated by ambocin. Sativanone, dalsissooside, and eriodictyol inhibited, while tectorigenin 7-O-[β-D-apiofuranosyl-(1→6)-β-D-glucopyranoside], ambocin, butin, and biochanin A increased IKCa1.1. In silico analyses showed that biochanin A, sativanone, and pinocembrin bound with high affinity in target-sensing regions of both channels, providing insight into their potential mechanism of action. In conclusion, Dalbergia tonkinensis is a valuable source of mono- and bifunctional, vasoactive scaffolds for the development of novel antihypertensive drugs. [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]

[Display omitted] Flavonoids, ubiquitously distributed in the plant world, are regularly ingested with diets rich in fruit, vegetables, wine, and tea. During digestion, they are partially absorbed in the stomach. The present work aimed to assess the in vitro effects of quercetin and ten structurally related flavonoids on the rat gastric fundus smooth muscle, focussing on ATP-dependent K+ (K ir 6.1) channels, which play a central role in the regulation of resting membrane potential, membrane excitability and, consequently, of gastric motility. Whole-cell currents through K ir 6.1 channels (I Kir6.1) were recorded with the patch-clamp technique and the mechanical activity of gastric fundus smooth muscle strips was studied under isometric conditions. Galangin ≈ tamarixetin > quercetin > kaempferol > isorhamnetin ≈ luteolin ≈ fisetin > (±)-taxifolin inhibited pinacidil-evoked, glibenclamide-sensitive I Kir6.1 in a concentration-dependent manner. Morin, rutin, and myricetin were ineffective. The steric hindrance of the molecule and the number and position of hydroxyl groups on the B ring played an important role in the activity of the molecule. Molecular docking simulations revealed a possible binding site for flavonoids in the C-terminal domain of the K ir 6.1 channel subunit SUR2B, in a flexible loop formed by residues 251 to 254 of chains C and D. Galangin and tamarixetin, but not rutin relaxed both high K+- and carbachol-induced contraction of fundus strips in a concentration-dependent manner. Furthermore, both flavonoids shifted to the right the concentration-relaxation curves to either pinacidil or L-cysteine constructed in strips pre-contracted by high K+, rutin being ineffective. In conclusion, I Kir6.1 inhibition exerted by dietary flavonoids might counterbalance their myorelaxant activity, affect gastric accommodation or, at least, some stages of digestion. [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]

1 The aim of this study was to investigate the effects of quereetin, a natural polyphenolic flavonoid, on voltage-dependent Ca[sup2+] channels of smooth muscle cells freshly isolated from the rat tail artery, using either the conventional or the amphotericin B-perforated whole-cell patch-clamp method. 2 Quercetin increased L-type Ca[sup2] current[I[sub Ca(L)] in a concentration- (pEC[sub50]= 5.09±0.05) and voltage-dependent manner and shifted the maximum of the current-voltage relationship by 10 mV in the hyperpolarizing direction, without, however, modifying the threshold and the equilibrium potential for Ca[sup2+], Quercetin-indueed I[subCa(L)] stimulation was reversible upon wash-out. T-type Ca[sup2] current was not affected by quercetin. 3 Quercetin shifted the voltage dependence of the steady-state inactivation and activation curves to more negative potentials by about 5.5 and 7.5 mV respectively, in the mid-potential of the curves as well as increasing the slope of activation. Quercetin slowed both the activation and the deactivation kinetics of the I[subCa(L)]. The inactivation time course was also slowed but only at voltages higher than 10 mV. Moreover quercetin slowed the rate of recovery from inactivation. 4 These results prove quercetin to be a naturally-occurring L-type Ca[sup2] channel activator. [ABSTRACT FROM AUTHOR]

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]

Several epidemiological studies demonstrate that moderate (red) wine consumption may afford protection against cardiovascular diseases. Protection is ascribed to the biological activity of wine components, many of which, however, are discarded during winemaking. In vitro rat thoracic aorta rings contracted with phenylephrine or KCl were used to assess the vasorelaxant activity of extracts from wine pomaces (seeds and skins) of the Calabrian autochthonous grape variety Magliocco dolce (Arvino). NMR spectroscopy was used to ascertain their chemical composition. Data demonstrate that seed and skin, but not must, extracts are capable of relaxing vascular preparations in an endothelium-dependent manner, similarly to the red wine extract, due to the presence of comparable amounts of bioactive constituents. In rings pre-contracted with 20–30 mM KCl, only seed extracts showed a moderate relaxation. The most efficacious vasodilating extract (wine) showed a good antioxidant profile in both [(2,2-diphenyl-1-picrylhydrazyl)acid] radical (DPPH) and [2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid)] radical (ABTS) assays. In conclusion, winemaking from Magliocco dolce grape can provide potentially health-promoting by-products useful in cardiovascular disease management. [ABSTRACT FROM AUTHOR]

In pre-hypertension, moderate control of blood pressure (BP) can be obtained by a nutritional approach. The effects of a diet enriched with defatted larvae of the mealworm Tenebrio molitor (Coleoptera: Tenebrionidae) (TM) endowed with ACE inhibitory activity was studied in both spontaneously hypertensive rats (SHR) and in the age-matched normotensive Wistar Kyoto strain. These were fed for 4 weeks with standard laboratory rodent chow supplemented with or without TM or captopril. In SHR, the TM diet caused a significant reduction in BP, heart rate and coronary perfusion pressure, as well as an increase in red blood cell glutathione/glutathione disulphide ratio. Rat brain slices of SHR were more resistant to oxidative stress and contained lower levels of inflammatory cytokines, while vascular and liver enzyme-activities were not affected. These results suggest that TM can be considered a new functional food that can lower BP in vivo and thus control cardiovascular-associated risk factors such as hypertension. [ABSTRACT FROM AUTHOR]

A role for mitochondrial fission in vascular contraction has been proposed based on the vasorelaxant activity of the dynamin (and mitochondrial fission) inhibitors mdivi-1 and dynasore. However, mdivi-1 is capable to inhibit Ba2+ currents through Ca V 1.2 channels (I Ba1.2), stimulate K Ca 1.1 channel currents (I KCa1.1), and modulate pathways key to the maintenance of vessel active tone in a dynamin-independent manner. Using a multidisciplinary approach, the present study demonstrates that dynasore, like mdivi-1, is a bi-functional vasodilator, blocking I Ba1.2 and stimulating I KCa1.1 in rat tail artery myocytes, as well as promoting relaxation of rat aorta rings pre-contracted by either high K+ or phenylephrine. Conversely, its analogue dyngo-4a, though inhibiting mitochondrial fission triggered by phenylephrine and stimulating I KCa1.1 , did not affect I Ba1.2 but potentiated both high K+- and phenylephrine-induced contractions. Docking and molecular dynamics simulations identified the molecular basis supporting the different activity of dynasore and dyngo-4a at Ca V 1.2 and K Ca 1.1 channels. Mito-tempol only partially counteracted the effects of dynasore and dyngo-4a on phenylephrine-induced tone. In conclusion, the present data, along with previous observations (Ahmed et al., 2022) rise caution for the use of dynasore, mdivi-1, and dyngo-4a as tools to investigate the role of mitochondrial fission in vascular contraction: to this end, a selective dynamin inhibitor and/or a different experimental approach are needed. [ABSTRACT FROM AUTHOR]

Therapies addressing multiple stages of Plasmodium falciparum life cycle are highly desirable for implementing malaria elimination strategies. MMV019918 ( 1 , 1-[5-(4-bromo-2-chlorophenyl)furan-2-yl]- N -[(piperidin-4-yl)methyl]methanamine) was selected from the MMV Malaria Box for its dual activity against both asexual stages and gametocytes. In-depth structure-activity relationship studies and cytotoxicity evaluation led to the selection of 25 for further biological investigation. The potential transmission blocking activity of 25 versus P. falciparum was confirmed through the standard membrane-feeding assay. Both 1 and 25 significantly prolonged atrioventricular conduction time in Langendorff-isolated rat hearts, and showed inhibitory activity of Ba 2+ current through Ca v 1.2 channels. An in silico target-fishing study suggested the enzyme phosphoethanolamine methyltransferase ( Pf PMT) as a potential target. However, compound activity against Pf PMT did not track with the antiplasmodial activity, suggesting the latter activity relies on a different molecular target. Nevertheless, 25 showed interesting activity against Pf PMT, which could be an important starting point for the identification of more potent inhibitors active against both sexual and asexual stages of the parasite. [ABSTRACT FROM AUTHOR]

[Display omitted] • Artificial intelligence accelerates the drug discovery. • O -substituted morin derivatives show interesting vasorelaxant activity. • Ca V 1.2 channels seem to be the main targets involved in the vasorelaxant activity. • The pentamethyl derivative 5a reveals a multi-target activity. Morin is a vasorelaxant flavonoid, whose activity is ascribable to Ca V 1.2 channel blockade that, however, is weak as compared to that of clinically used therapeutic agents. A conventional strategy to circumvent this drawback is to synthesize new derivatives differently decorated and, in this context, morin-derivatives able to interact with Ca V 1.2 channels were found by employing the potential of PLATO in target fishing and reverse screening. Three different derivatives (5a - c) were selected as promising tools, synthesized, and investigated in in vitro functional studies using rat aorta rings and rat tail artery myocytes. 5a - c were found more effective vasorelaxant agents than the naturally occurring parent compound and antagonized both electro- and pharmaco-mechanical coupling in an endothelium-independent manner. 5a , the series' most potent, reduced also Ca2+ mobilization from intracellular store sites. Furthermore, 5a ≈ 5c > 5b inhibited Ba2+ current through Ca V 1.2 channels. However, compound 5a caused also a concentration-dependent inhibition of K Ca 1.1 channel currents. [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]

We present a series of oxadiazolothiazinones, selective inotropic agents on isolated cardiac tissues, devoid of chronotropy and vasorelaxant activity. Functional and binding data for the precursor of the series (compound 1) let us hypothesize LTCC blocking activity and the existence of a recognition site specific for this scaffold. We synthesized and tested 22 new derivatives: introducing a para-methoxyphenyl at C-8 led to compound 12 (EC50 = 0.022 μM), twice as potent as its para-bromo analogue (1). For 10 analogues, we extended the characterization of the biological properties by including the assessment of metabolic stability in human liver microsomes and cytochrome P450 inhibition potential. We observed that the methoxy group led to active compounds with low metabolic stability and high CYP inhibition, whereas the protective effect of bromine resulted in enhanced metabolic stability and reduced CYP inhibition. Thus, we identified two para-bromo benzothiazino-analogues as candidates for further studies. [ABSTRACT FROM AUTHOR]

As a result of the ring-into-ring conversion of nitrosoimidazole derivatives, we obtained a molecular scaffold that, when properly decorated, is able to decrease inotropy by blocking L-type calcium channels. Previously, we used this scaffold to develop a quantitative structure-activity relationship (QSAR) model, and we used the most potent oxadiazolothiazinone as a template for ligand-based virtual screening. Here, we enlarge the diversity of chemical decorations, present the synthesis and in vitro data for 11 new derivatives, and develop a new 3D-QSAR model with recent in silico techniques. We observed a key role played by the oxadiazolone moiety: given the presence of positively charged calcium ions in the transmembrane channel protein, we hypothesize the formation of a ternary complex between the oxadiazolothiazinone, the Ca2+ ion and the protein. We have supported this hypothesis by means of pharmacophore generation and through the docking of the pharmacophore into a homology model of the protein. We also studied with docking experiments the interaction with a homology model of P-glycoprotein, which is inhibited by this series of molecules, and provided further evidence toward the relevance of this scaffold in biological interactions. [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]

Quercetin, a flavonoid abundantly present in the Mediterranean diet, is considered a vasodilator despite its recognized capability to stimulate vascular Ca V 1.2 channel current (I Ca1.2). The present study was undertaken to assess its possible vasocontractile activity. Functional and electrophysiology experiments were performed in vitro on rat aorta rings and tail artery myocytes along with an in-depth molecular modelling analysis. The Ca V 1.2 channel stimulator (S)-(−)-methyl-1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl) pyridine-5-carboxylate (Bay K 8644) was used as reference compound. Quercetin and Bay K 8644 caused a significant leftward shift of KCl concentration-response curve. Neither agent affected basal muscle tone, though in rings pre-treated with thapsigargin or 15 mM KCl they caused a strong, concentration-dependent contraction. Both quercetin and Bay K 8644 potentiated the response to Ca2+ in weakly depolarised rings. At high KCl concentrations, however, quercetin caused vasorelaxation. While Bay K 8644 stimulated I Ca1.2 , this effect being sustained with time, quercetin-induced stimulation was transient, although the molecule in solution underwent only marginal oxidation. Quercetin transient stimulation was not affected by pre-treatment with isoprenaline, sodium nitroprusside, or dephostatin; however, it converted to a sustained one in myocytes pre-incubated with Gö6976. Classical molecular dynamics simulations revealed that quercetin and Bay K 8644 formed hydrogen bonds with target sensing residues of Ca V 1.2 channel favouring the inactivated conformation. In conclusion, quercetin-induced stimulation of I Ca1.2 promoted vasocontraction when Ca2+ buffering function of sarcoplasmic reticulum was impaired and/or smooth muscle cell membrane was moderately depolarised, as it may occur under certain pathological conditions. [ABSTRACT FROM AUTHOR]

Abstract: 3,5-Di-t-butyl catechol (DTCAT) releases Ca2+ from rat skeletal muscle sarcoplasmic reticulum (SR) vesicles. Hence, it is a candidate for use as a substitute for halothane or caffeine in the in vitro contracture test for the diagnosis of susceptibility to malignant hyperthermia (MH). To characterize the effect of DTCAT at cell level, Ca2+ release experiments were performed on cultured, human skeletal muscle myotubes using the fluorescent Ca2+ indicator fura2-AM. DTCAT was also assayed in the in vitro contracture test on human skeletal muscle bundles obtained from individuals diagnosed susceptible (MHS), normal (MHN) or equivocal for halothane (MHEH) and compared to the standard test substances caffeine and halothane. DTCAT increased, in a concentration-dependent manner and with a higher efficacy as compared to caffeine, the free, intracellular Ca2+ levels of cultured MHN and MHS skeletal muscle myotubes. This effect was similar in both types of myotubes and involved the release of Ca2+ from SR stores as well as Ca2+-influx from the extracellular space. Inhibition of ryanodine receptors either with ryanodine or with ruthenium red markedly reduced DTCAT-induced increase in intracellular Ca2+ concentration while abolishing that induced by caffeine. In MHN skeletal muscle bundles, DTCAT induced contractures with an EC50 value of 160±91μM. However, the sensitivity of MHS or MHEH muscles to DTCAT was similar to that of MHN muscles. In conclusion, DTCAT is not suitable for the diagnosis of MH susceptibility due to its failure to discriminate between MHN and MHS muscles. [Copyright &y& Elsevier]

The aim of this study was to investigate the effects of the four isomers (3a, 3b, 3c and 3d) of a novel multidrug resistance-reverting agent - 3,4,5-trimethoxybenzoic acid 4-(methyl-{4-[3-(3,4,5-trimethoxyphenyl)acryloyloxy]cyclohexyl}amino)cyclohexyl ester - on vascular functions in vitro. A comparison of their mechanical and electrophysiological actions in rat aorta rings and single rat tail artery myocytes, respectively, was performed. In rat aorta rings, 3a-d antagonized both 60 mmol/l K+- and phenylephrine-induced contraction in a concentration-dependent manner, with maximal relaxation values averaging 50% of controls, 3d being the most effective of the series. The vasorelaxing effect was similar either in presence or absence of intact endothelium. In rat tail artery myocytes, out of the four isomers, only 3a consistently inhibited Ba2+ current through Cav1.2 channels. Our results provide functional evidence that 3a-d are weak vasorelaxing agents, although at concentrations much higher than those effective for multidrug resistance reversion in cancer cells. Copyright © 2011 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Quercetin and ferulic acid are two phytochemicals extensively represented in the plant kingdom and daily consumed in considerable amounts through diets. Due to a common phenolic structure, these two molecules share several pharmacological properties, e.g., antioxidant and free radical scavenging, anti-cancer, anti-inflammatory, anti-arrhythmic, and vasorelaxant. The aim of the present work was the combination of the two molecules in a single chemical entity, conceivably endowed with more efficacious vasorelaxant activity. Preliminary in silico studies herein described suggested that the new hybrid compound bound spontaneously and with high affinity on the KCa1.1 channel. Thus, the synthesis of the 3′-ferulic ester derivative of quercetin was achieved and its structure confirmed by 1H- and 13C-NMR spectra, HSQC and HMBC experiments, mass spectrometry, and elementary analysis. The effect of the new hybrid compound on vascular KCa1.1 and CaV1.2 channels revealed a partial loss of the stimulatory activity that characterizes the parent compound quercetin. Therefore, further studies are necessary to identify a better strategy to improve the vascular properties of this flavonoid. [ABSTRACT FROM AUTHOR]

Abstract: Cardiac effects of 3,5-dibenzoyl-4-(3-phenoxyphenyl)-1,4-dihydro-2,6-dimethylpyridine (DP7), a novel multidrug resistance (MDR) inhibitor, in Langendorff-perfused rat heart have been investigated and compared to that of nifedipine. Nifedipine decreased concentration-dependently (IC50 =8.89±1.09×10−8 M) left ventricular pressure leaving unaltered coronary perfusion pressure, whereas DP7 did not affect both parameters. Nifedipine did not modify both QRS and QT intervals of electrocardiogram (ECG). Second-degree atrioventricular block or ventricular rhythm occurred in presence of nifedipine, however, in 4 out of 6 hearts. DP7, up to 30 μM, failed to alter ECG parameters. In conclusion, DP7, may represent a lead compound for the development of potent dihydropyridine MDR chemosensitizers devoid of cardiac effects. [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]

We have investigated the effects of the rat-specific vasoconstrictor agent norbormide on the mechanical and electrophysiological properties of rat non-vascular smooth muscles. Norbormide (50 μM) did not affect the resting tone of urinary bladder, tracheal, and duodenal rings. In all tissues, KCl-induced concentration–response curves were shifted downward by norbormide (5 and 50 μM). In urinary bladder and tracheal rings, norbormide inhibited contractile responses to carbachol only at the higher concentration (50 μM). In single gastric fundus myocytes, 50 μM norbormide inhibited L-type Ca2+ current (ICa(L)) by about 60%, neither affecting both activation and inactivation rates of the current nor the current–voltage curve along the voltage axis. Our results indicate that rat non-vascular smooth muscles are relaxed by norbormide with a mechanism likely involving a reduction of Ca2+ entry through L-type Ca2+ channels. [Copyright &y& Elsevier]

[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]