Homologous or heterologous administration of mRNA or adenovirus-vectored vaccines show comparable immunogenicity and effectiveness against the SARS-CoV-2 Omicron variant.

BACKGROUND: Heterologous prime-boost schedules have been employed in SARS-CoV-2 vaccination, yet additional data on immunogenicity and effectiveness are still needed. RESEARCH DESIGN AND METHODS: Here, we measured the immunogenicity and effectiveness in the real-world setting of the mRNA booster dose in 181 subjects who had completed primary vaccination with ChAdOx1, BNT162b2, or mRNA1273 vaccines (IMMUNO_COV study; protocol code 18,869). The spike-specific antibody and B cell responses were analyzed up to 6 months after boosting. RESULTS: After an initial slower antibody response, the heterologous ChAdOx1/mRNA prime-boost formulation elicited spike-specific IgG titers comparable to homologous approaches, while spike-specific B cells showed a higher percentage of CD21-CD27- atypical cells compared to homologous mRNA vaccination. Mixed combinations of BNT162b2 and mRNA-1273 elicited an immune response comparable with homologous strategies. Non-significant differences in the Relative Risk of infection, calculated over a period of 18 months after boosting, were reported among homologous or heterologous vaccination groups, indicating a comparable relative vaccine effectiveness. CONCLUSIONS: Our data endorse the heterologous booster vaccination with mRNA as a valuable alternative to homologous schedules. This approach can serve as a solution in instances of formulation shortages and contribute to enhancing vaccine strategies for potential epidemics or pandemics.

B cell response after SARS-CoV-2 mRNA vaccination in people living with HIV.

BACKGROUND: Limited longitudinal data are available on immune response to mRNA SARS-CoV-2 vaccination in people living with HIV (PLWHIV); therefore, new evidence on induction and persistence of spike-specific antibodies and B cells is needed. METHODS: In this pilot study we investigated the spike-specific humoral and B cell responses up to six months after vaccination with two doses of mRNA vaccines in 84 PLWHIV under antiretroviral therapy compared to 79 healthy controls (HCs). RESULTS: Spike-specific IgG persisted six months in PLWHIV with no significant differences compared to HCs, even though a significantly lower IgG response was observed in patients with CD4+ T cells < 350/mmc. The frequency of subjects with antibodies capable of inhibiting ACE2/RBD binding was comparable between PLWHIV and HCs a month after the second vaccine dose, then a higher drop was observed in PLWHIV. A comparable percentage of spike-specific memory B cells was observed at month six in PLWHIV and HCs. However, PLWHIV showed a higher frequency of spike-specific IgD- CD27- double-negative memory B cells and a significantly lower rate of IgD- CD27+ Ig-switched memory B cells compared to HCs, suggesting a reduced functionality of the antigen-specific memory B population. CONCLUSIONS: The mRNA vaccination against SARS-CoV-2 elicits humoral and B cell responses quantitatively similar between PLWHIV and HCs, but there are important differences in terms of antibody functionality and phenotypes of memory B cells, reinforcing the notion that tailored vaccination policies should be considered for these patients.

SARS-CoV-2 vaccination has been demonstrated to protect people from severe COVID-19 and death. This is achieved through the induction of a specific immune response that recognizes and responds to the virus. Limited data are available on the immune response to SARS-CoV-2 vaccination in people living with HIV (PLWHIV). In this study, we evaluated the immune response up to six months after vaccination with two doses of vaccines in PLWHIV being treated with the standard antiretroviral therapy. We show that the immune response observed in PLWHIV is broadly similar to that in healthy subjects but that there are some differences in the cells induced as part of the immune response. We therefore suggest that specific vaccination policies should be considered for these PLWHIV.

Sdox, a H2S releasing anthracycline, with a safer profile than doxorubicin toward vasculature.

Sdox is a synthetic H2S-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 H2S in both cell lines. The H2S scavenger hydroxocobalamin partially reverted Sdox-induced cytotoxicity in A7r5, but not in EA.hy926 cells, suggesting a role for H2S 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.

Evidence of SARS-CoV-2-Specific Memory B Cells Six Months After Vaccination With the BNT162b2 mRNA Vaccine.

SARS-CoV-2 mRNA vaccines have demonstrated high efficacy and immunogenicity, but limited information is currently available on memory B cell generation and long-term persistence. Here, we investigated spike-specific memory B cells and humoral responses in 145 subjects, up to 6 months after the BNT162b2 vaccine (Comirnaty) administration. Spike-specific antibodies peaked 7 days after the second dose and significant antibody titers and ACE2/RBD binding inhibiting activity were still observed after 6 months, despite a progressive decline over time. Concomitant to antibody reduction, spike-specific memory B cells, mostly IgG class-switched, increased in the blood of vaccinees and persisted 6 months after vaccination. Following the in vitro restimulation, circulating memory B cells reactivated and produced spike-specific antibodies. A high frequency of spike-specific IgG+ plasmablasts, identified by computational analysis 7 days after boost, positively correlated with the generation of IgG+ memory B cells at 6 months. These data demonstrate that mRNA BNT162b2 vaccine elicits strong B cell immunity with spike-specific memory B cells that still persist 6 months after vaccination, playing a crucial role for a rapid response to SARS-CoV-2 virus encounter.

Efficacy and durability of two- vs. three-drug integrase inhibitor-based regimens in virologically suppressed HIV-infected patients: Data from real-life ODOACRE cohort.

OBJECTIVES: The aim of the present study was to compare the efficacy and durability of treatment switch to two-drug (2DR) vs. three-drug (3DR) integrase inhibitor (InSTI)-based regimens in a real-life setting. METHODS: Within the ODOACRE cohort, we selected adult patients with HIV RNA < 50 copies/mL switching to an InSTI-based 2DR or 3DR. Survival analyses were performed to estimate the probability of virological failure (VF, defined as one HIV RNA > 1000 copies/mL or two consecutive HIV RNA > 50 copies/mL) and treatment discontinuation (TD, defined as any modification, intensification or interruption of the regimen), and to evaluate their predictors. RESULTS: Overall, 1666 patients were included, of whom 1334 (80%) were treated with a 3DR (19.9%, 25.0% and 55.1% elvitegravir-, raltegravir- and dolutegravir-based, respectively) and 332 (20%) with a 2DR (79.2% dolutegravir + lamivudine and 20.8% dolutegravir + rilpivirine). Over a median (interquartile range) follow-up of 100 (52-150) weeks, 52 (3.1%) patients experienced VF with an incidence of 1.5/100 person-year of follow-up (PYFU). The estimated 96-week probability of VF was similar for the 2DR and 3DR groups (2.3% vs. 2.8%, P = 0.53), but it was higher for elvitegravir (4.9%) and raltegravir (5.0%) than for dolutegravir (1.5%) (P = 0.04). Four hundred (24%) patients discontinued their InSTI-based regimen, with an incidence of 11.3/100 PYFU. At 96 weeks, 3DRs showed a higher probability of TD for any reason (20.6% vs. 11.2%, P < 0.001) and TD for toxicity (9.0% vs. 6.6%, P = 0.02) when compared with 2DRs. A higher risk of TD for central nervous system toxicity was observed for dolutegravir than for elvitegravir and raltegravir (4.0% vs. 2.5% vs. 0.6%, P = 0.005). CONCLUSIONS: In virologically suppressed HIV-infected patients, 2DRs showed an efficacy similar to 3DRs but with better tolerability.

In vitro vascular toxicity assessment of NitDOX, a novel NO-releasing doxorubicin.

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 Cav1.2 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.

Vasorelaxing Activity of Stilbenoid and Phenanthrene Derivatives from Brasiliorchis porphyrostele: Involvement of Smooth Muscle CaV1.2 Channels.

Five compounds, 3,4'-dihydroxy-3',5,5'-trimethoxydihydrostilbene, 1: ; 3,4'-ihydroxy-3',5'-dimethoxydihydrostilbene, 2: ; 3,4'-dihydroxy-5,5'-dimethoxydihydrostilbene, 3: ; 9,10-dihydro-2,7-dihydroxy-4,6-dimethoxyphenanthrene, 4: ; and the previously unreported 1,2,6,7-tetrahydroxy-4-methoxyphenanthrene, 5: were isolated from the South American orchid, Brasiliorchis porphyrostele. An in-depth analysis of their vascular effects was performed on in vitro rat aorta rings and tail main artery myocytes. Compounds 1:  - 4: were shown to possess vasorelaxant activity on rings pre-contracted by the α 1 receptor agonist phenylephrine, the CaV1.2 stimulator (S)-(-)-Bay K 8644, or depolarized with high K+ concentrations. However, compound 5: was active solely on rings stimulated by 25 mM but not 60 mM K+. The spasmolytic activity of compounds 1: and 4: was significantly affected by the presence of an intact endothelium. The KATP channel blocker glibenclamide and the KV channel blocker 4-aminopyridine significantly antagonized the vasorelaxant activity of compounds 4: and 1: , respectively. In patch-clamp experiments, compounds 1:  - 4: inhibited Ba2+ current through CaV1.2 channels in a concentration-dependent manner, whereas neither compound 4: nor compound 1: affected K+ currents through KATP and KV channels, respectively. The present in vitro, comprehensive study demonstrates that Brasiliorchis porphyrostele may represent a source of vasoactive agents potentially useful for the development of novel antihypertensive agents that has now to be validated in vivo in animal models of hypertension.

Apoptotic-Induced Effects of Acacia Catechu Willd. Extract in Human Colon Cancer Cells.

The research for innovative treatments against colon adenocarcinomas is still a great challenge. Acacia catechu Willd. heartwood extract (AC) has health-promoting qualities, especially at the gastrointestinal level. This study characterized AC for its catechins content and investigated the apoptosis-enhancing effect in human colorectal adenocarcinoma HT-29 cells, along with its ability to spare healthy tissue. MTT assay was used to describe the time course, concentration dependence and reversibility of AC-mediated cytotoxicity. Cell cycle analysis and AV-PI and DAPI-staining were performed to evaluate apoptosis, together with ROS formation, mitochondrial membrane potential (MMP) changes and caspase activities. Rat ileum and colon rings were tested for their viability and functionality to explore AC effects on healthy tissue. Quantitative analysis highlighted that AC was rich in (±)-catechin (31.5 ± 0.82 mg/g) and (-)-epicatechin (12.5 ± 0.42 mg/g). AC irreversibly decreased cell viability in a concentration-dependent, but not time-dependent fashion. Cytotoxicity was accompanied by increases in apoptotic cells and ROS, a reduction in MMP and increases in caspase-9 and 3 activities. AC did not affect rat ileum and colon rings' viability and functionality, suggesting a safe profile toward healthy tissue. The present findings outline the potential of AC for colon cancer treatment.

4-Imidazo[2,1-b]thiazole-1,4-DHPs and neuroprotection: preliminary study in hits searching.

In the present work we describe the synthesis, characterization and evaluation of neuroprotective effects of a focused library of 4-imidazo[2,1-b]thiazole-1,4-dihydropyridines. Furthermore, the new dihydropyridines were subjected to functional in vitro assays in cardiac tissues and vascular smooth muscle to determine their possible selectivity in counteracting the effects of neurodegeneration. In particular the strategy adopted for designing the compounds involves the imidazo[2,1-b]thiazole nucleus. The observed properties show that substituents at C2 and C6 of the bicyclic scaffold are able to influence the cardiovascular parameters and the neuroprotective activity. In comparison to nifedipine, a set of derivatives such as compound 6, showed a neuroprotective profile of particular interest.

MC225, a Novel Probe for P-glycoprotein PET Imaging at the Blood-brain Barrier: In Vitro Cardiovascular Safety Evaluation.

The P-glycoprotein (P-gp) substrate MC225, at concentrations ≤10 nM, is a valuable radiotracer for positron emission tomography imaging of P-gp function in rats and mice. The aim of this study was to evaluate its potential toxic hazard toward the cardiovascular system through an in-depth analysis of its effects on rat aorta rings, on CaV1.2 channel current (ICa1.2) of A7r5 cells and on Langendorff-perfused rat heart. In aortic rings, MC225 relaxed phenylephrine-induced contraction in a concentration-dependent and endothelium-independent manner, with an IC50 value of about 1 µM. At concentrations ≥3 µM, it antagonized the response to cumulative concentrations of K. MC225, 1 and 10 µM, inhibited ICa1.2 by 15% and 31%, respectively, without affecting either current activation or inactivation kinetics. In Langendorff-perfused rat hearts, only 10 µM MC225 significantly decreased left ventricular pressure and increased coronary perfusion pressure while reducing heart rate and prolonging the cardiac cycle length as well as the atrioventricular conduction time (PQ interval) on the electrocardiogram. Lower concentrations of the drug were ineffective. These findings demonstrate that MC225-induced cardiovascular effects took place at concentrations that are at least 2 orders of magnitude higher than those allowing in vivo measurement of P-gp function. Therefore, MC225 represents a promising positron emission tomography tool for in vivo straightforward P-gp quantification.

In vitro vascular toxicity of tariquidar, a potential tool for in vivo PET studies.

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 Ca2+ current [ICa(L)] of A7r5 cells has been performed. In both A7r5 and EA.hy926 cells, tariquidar was not cytotoxic up to 1µM concentration. On the contrary, at 10µM, it caused apoptosis already after 24h treatment. In fresh aorta rings, 10µM tariquidar partially relaxed phenylephrine-, but not 60mM K+ (K60)-induced contraction. In rings treated with 10µM tariquidar for 7days, the contractile response to both phenylephrine and K60 remained unchanged. Finally, tariquidar did not modify ICa1.2 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.

Vascular Toxicity Risk Assessment of MC18 and MC70, Novel Potential Diagnostic Tools for In Vivo PET Studies.

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 Cav 1.2 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.

The vasodilator papaverine stimulates L-type Ca(2+) current in rat tail artery myocytes via a PKA-dependent mechanism.

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 [IBa(L) or ICa(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-, Vh-, 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 IBa(L) stimulation. In cells pre-treated with IBMX, application of papaverine failed to increase current amplitude. Papaverine sped up the inactivation kinetics of IBa(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.

In vitro vasoactivity of zerumbone from Zingiber zerumbet.

The sesquiterpene zerumbone, isolated from the rhizome of Zingiber zerumbet Sm., besides its widespread use as a food flavouring and appetiser, is also recommended in traditional medicine for the treatment of several ailments. It has attracted great attention recently for its effective chemopreventive and therapeutic effects observed in various models of cancer. To assess the zerumbone safety profile, a pharmacology study designed to flag any potential adverse effect on vasculature was performed. Zerumbone was tested for vasorelaxing activity on rat aorta rings and for L-type Ba(2+) current blocking activity on single myocytes isolated from the rat-tail artery. The spasmolytic effect of zerumbone was more marked on rings stimulated with 60 mM than with 30 mM K(+) (IC50 values of 16 µM and 102 µM, respectively). In the presence of 60 mM K(+), zerumbone concentration-dependently inhibited the contraction induced by the cumulative additions of Ca(2+), this inhibition being inversely related to the Ca(2+) concentration. Phenylephrine-induced contraction was inhibited by the drug, though less efficiently and independently of the presence of an intact endothelium, without affecting Ca(2+) release from the intracellular stores. Zerumbone inhibited the L-type Ba(2+) current (estimated IC50 value of 458.7 µM) and accelerated the kinetics of current decay. In conclusion, zerumbone showed an overall weak in vitro vasodilating activity, partly attributable to the blocking of the L-type Ca(2+) channel, which does not seem to represent, however, a serious threat to its widespread use.

Vascular L-type Ca²âº channel blocking activity of sulfur-containing indole alkaloids from Glycosmis petelotii.

In the search for novel natural compounds endowed with potential antihypertensive activity, a new sulfur-containing indole alkaloid, N-demethylglypetelotine (2), and its known analogue glypetelotine (1), were isolated from the leaves of Glycosmis petelotii. Their structures were established on the basis of spectroscopic evidence. The two alkaloids were assessed for vasorelaxing activity on rat aorta rings and for L-type Ba(2+) current [I(Ba(L))] blocking activity on single myocytes isolated from rat tail artery. Both glypetelotine and N-demethylglypetelotine inhibited phenylephrine-induced contraction with IC50 values of 20 and 50 µM, respectively. The presence of endothelium did not modify their spasmolytic effect. Neither glypetelotine nor N-demethylglypetelotine affected Ca(2+) release from the sarcoplasmic reticulum induced by phenylephrine. The spasmolytic effect of glypetelotine increased with membrane depolarization. In the presence of 60 mM K(+), both compounds inhibited, in a concentration-dependent manner, the contraction induced by cumulative addition of Ca(2+), this inhibition being inversely related to Ca(2+) concentration. Glypetelotine and, less efficiently N-demethylglypetelotine, inhibited I(Ba(L)), the former compound also affecting I(Ba(L)) kinetics. In conclusion, glypetelotine is a novel vasorelaxing agent which antagonizes L-type Ca(2+) channels.

Vasorelaxing activity of two coumarins from Murraya paniculata leaves.

In the search for novel chemical scaffolds leading to potential antihypertensive agents, the methanol extract of Murraya paniculata leaves was assessed for its effects on isolated rat aorta rings. The vasorelaxing effect of the chloroform fraction of the methanol plant extract was the most potent for its vasorelaxing activity on rat aorta rings contracted by 60 mM K(+) (K60). Two coumarins were isolated from the chloroform fraction: the novel kimcuongin (1) and the known murracarpin (2). Their structures were determined from spectroscopic evidences including (1)H- and (13)C-NMR, correlation spectroscopy (COSY), nuclear Overhauser effect spectroscopy (NOESY), heteronuclear multiple bond correlation (HMBC), heteronuclear single quantum correlation (HSQC), and high resolution mass spectrometry (HR-MS). Kimcuongin and, to a lesser extent, murracarpin, showed vasorelaxing activity with IC50 values of 37.7 µM and 139.3 µM, respectively. The coumarins kimcuongin and murracarpin may thus represent a novel class of vasodilators of natural source.

2-Aryl- and 2-amido-benzothiazoles as multifunctional vasodilators on rat artery preparations.

The neuroprotective agent riluzole [2-amino-6-(trifluoromethoxy)benzothiazole] has been shown to antagonize neuronal high-voltage activated Ca(2+) 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 Ba(2+) 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 3-6 µM. 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 25/30 mM than with 60 mM K(+). HUP5 and HUP30 antagonized both extracellular Ca(2+) influx and Ca(2+) 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 Ca(2+) influx. The present benzothiazole derivatives form a novel class of multifunctional vasodilators which may give rise to effective antihypertensive agents.

Quercetin mitochondriotropic derivatives antagonize nitrate tolerance and endothelial dysfunction of isolated rat aorta rings.

Chronic use of glyceryl trinitrate is limited by serious side effects, inter alia tolerance and endothelial dysfunction of coronary and resistance arteries. The natural flavonoid quercetin has been shown to counteract the development of glyceryl trinitrate tolerance in vitro. Two mitochondriotropic, 4-O-triphenylphosphoniumbutyl derivatives of quercetin (QTA-3BTPI and Q-3BTPI) were compared to quercetin for protection against glyceryl trinitrate-induced tolerance and endothelial dysfunction of isolated rat aorta rings. Both QTA-3BTPI and Q-3BTPI significantly counteracted the reduced vascular responsiveness to both glyceryl trinitrate and acetylcholine caused by prolonged exposure of the vessel to glyceryl trinitrate itself, their potency being much greater than that of quercetin. QTA-3BTPI, however, turned out to cause endothelial dysfunction per se. Since Q-3BTPI antagonized in vitro nitrate tolerance and endothelial dysfunction of vessels, this encourages assessing whether this effect is displayed also in vivo during long-term glyceryl trinitrate treatment.