Long-lasting Hypotensive Effect in Renal Hypertensive Rats Induced by Nitric Oxide Released From a Ruthenium Complex:

NONO2P, a novel nitric oxide donor, causes vasorelaxation through NO/sGC/PKG pathway, K+ channels opening and SERCA activation

BACKGROUND & AIMS

The treatment of cardiovascular diseases (CVD) could greatly benefit from using nitric oxide (NO) donors. This study aimed to investigate the mechanisms of action of NONO2P that contribute to the observed responses in the mesenteric artery. The hypothesis was that NONO2P would have similar pharmacological actions to sodium nitroprusside (SNP) and NO.

METHODS

Male Wistar rats were euthanized to isolate the superior mesenteric artery for isometric tension recordings. NO levels were measured using the DAF-FM/DA dye, and cyclic guanosine monophosphate (cGMP) levels were determined using a cGMP-ELISA Kit.

RESULTS

NONO2P presented a similar maximum efficacy to SNP. The free radical of NO (NO•) scavengers (PTIO; 100 μM and hydroxocobalamin; 30 μM) and nitroxyl anion (NO-) scavenger (L-cysteine; 3 mM) decreased relaxations promoted by NONO2P. The presence of the specific soluble guanylyl cyclase (sGC) inhibitor (ODQ; 10 μM) nearly abolished the vasorelaxation. The cGMP-dependent protein kinase (PKG) inhibition (KT5823; 1 μM) attenuated the NONO2P relaxant effect. The vasorelaxant response was significantly attenuated by blocking inward rectifying K+ channels (Kir), voltage-operated K+ channels (KV), and large conductance Ca2+-activated K+ channels (BKCa). NONO2P-induced relaxation was attenuated by cyclopiazonic acid (10 μM), indicating that sarcoplasmic reticulum Ca2+-ATPase (SERCA) activation is involved in this relaxation. Moreover, NONO2P increased NO levels in endothelial cells and cGMP production.

CONCLUSIONS

NONO2P induces vasorelaxation with the same magnitude as SNP, releasing NO• and NO-. Its vasorelaxant effect involves sGC, PKG, K+ channels opening, and SERCA activation, suggesting its potential as a therapeutic option for CVD.

Long-term effects of photobiomodulation therapy on blood pressure in obese rats induced by a high-fat diet

The main cardiovascular disease risk associated with obesity is hypertension. The therapeutic use of photobiomodulation therapy (PBM) is suggested for the treatment of wound healing, osteoarthritis, and arterial diseases. However, few studies have measured how red laser (at 660 nm) acts over hypertension, and any of those studies used experimental obesity model. The aim of the study was an attempt to evaluate the long-term effect of PBM on systolic blood pressure in an animal model of obesity, induced by a high-fat diet (HFD). Our results indicate that PBM carried out 3 days a week was able to prevent the increase in blood pressure (133.75 ± 4.82 mmHg, n = 8) induced by a high-fat diet (150.00 ± 4.57 mmHg, n = 8; p < 0.05), restore nitric oxide levels (control: 31.7 ± 5.5 μM, n = 8; HFD + PBM: 29.9 ± 3.7 μM, n = 8 > HFD: 22.2 ± 2.9 μM, n = 8, p < 0.05), decrease lipoperoxidation (control: 1.65 ± 0.25 nM, n = 8; HFD + PBM: 2.05 ± 0.55 nM, n = 8 < HFD: 3.20 ± 0.47 nM, n = 8; p < 0.05), and improve endothelial function (pD2 control: 7.39 ± 0.08, n = 8 > pD2 HFD + PBM: 7.15 ± 0.07, n = 8 > HFD: 6.94 ± 0.07, n = 8; p < 0.05). Our results indicate that PBM prevents the elevation of blood pressure in an obese animal model by a mechanism that involves improvement of endothelial function through an antioxidant effect.

The role of nitric oxide in renovascular hypertension: from the pathophysiology to the treatment

Renovascular hypertension is one of the most relevant causes of secondary hypertension, mostly caused by atherosclerotic renovascular stenosis or fibromuscular dysplasia. The increase in angiotensin II production, oxidative stress, and formation of peroxynitrite promotes the decrease in nitric oxide (NO) availability and the development of hypertension, renal and endothelial dysfunction, and cardiac and vascular remodeling. The NO produced by nitric oxide synthases (NOS) acts as a vasodilator; however, endothelial NOS uncoupling (eNOS) also contributes to NO reduced availability in renovascular hypertension. NO donors and NO-derived metabolites have been investigated in experimental renovascular hypertension and have shown promissory effects in attenuating blood pressure and organ damage in this condition. Therefore, understanding the role of decreased NO in the pathophysiology of renovascular hypertension promotes the study and development of NO donors and molecules that can be converted into NO (such as nitrate and nitrite), contributing for the treatment of this condition in the future.

Synthesis and potential vasorelaxant effect of a novel ruthenium-based nitro complex

This study aimed to investigate the synthesis and potential vasodilator effect of a novel ruthenium complex, cis-[Ru(bpy)₂(2-MIM)(NO₂)]PF₆ (bpy = 2,2'-bipyridine and 2-MIM = 2-methylimidazole) (FOR711A), containing an imidazole derivative via an in silico molecular docking model using β1 H-NOX (Heme-nitric oxide/oxygen binding) domain proteins of reduced and oxidized soluble guanylate cyclase (sGC). In addition, pharmacokinetic properties in the human organism were predicted through computational simulations and the potential for acute irritation of FOR711A was also investigated in vitro using the hen's egg chorioallantoic membrane (HET-CAM). FOR711A interacted with sites of the β1 H-NOX domain of reduced and oxidized sGC, demonstrating shorter bond distances to several residues and negative values of total energy. The predictive study revealed molar refractivity (RM): 127.65; Log Po/w = 1.29; topological polar surface area (TPSA): 86.26 Å²; molar mass (MM) = 541.55 g/mol; low solubility, high unsaturation index, high gastrointestinal absorption; toxicity class 4; failure to cross the blood-brain barrier and to react with cytochrome P450 (CYP) enzymes CYP1A2, CYP2C19, CYP2C9, CYP2D6 and CYP3A4. After the HET-CAM assay, the FOR711A complex was classified as non-irritant (N.I.) and its vasodilator effect was confirmed through greater evidence of blood vessels after the administration and ending of the observation period of 5 min. These results suggest that FOR711A presented a potential stimulator/activator effect of sGC via NO/sGC/cGMP. However, results indicate it needs a vehicle for oral administration.

Nitric Oxide as a Central Molecule in Hypertension: Focus on the Vasorelaxant Activity of New Nitric Oxide Donors

Cardiovascular diseases include all types of disorders related to the heart or blood vessels. High blood pressure is an important risk factor for cardiac complications and pathological disorders. An increase in circulating angiotensin-II is a potent stimulus for the expression of reactive oxygen species and pro-inflammatory cytokines that activate oxidative stress, perpetuating a deleterious effect in hypertension. Studies demonstrate the capacity of NO to prevent platelet or leukocyte activation and adhesion and inhibition of proliferation, as well as to modulate inflammatory or anti-inflammatory reactions and migration of vascular smooth muscle cells. However, in conditions of low availability of NO, such as during hypertension, these processes are impaired. Currently, there is great interest in the development of compounds capable of releasing NO in a modulated and stable way. Accordingly, compounds containing metal ions coupled to NO are being investigated and are widely recognized as having great relevance in the treatment of different diseases. Therefore, the exogenous administration of NO is an attractive and pharmacological alternative in the study and treatment of hypertension. The present review summarizes the role of nitric oxide in hypertension, focusing on the role of new NO donors, particularly the metal-based drugs and their protagonist activity in vascular function.

Nitric Oxide Donors as Potential Drugs for the Treatment of Vascular Diseases Due to Endothelium Dysfunction

Endothelial dysfunction and consequent vasoconstriction are a common condition in patients with hypertension and other cardiovascular diseases. Endothelial cells produce and release vasodilator substances that play a pivotal role in normal vascular tone. The mechanisms underlying endothelial dysfunction are multifactorial. However, enhanced reactive oxygen species (ROS) production and consequent vasoconstriction instead of endothelium-derived relaxant generation and consequent vasodilatation contribute to this dysfunction considerably. The main targets of the drugs that are currently used to treat vascular diseases concerning enzyme activities and protein functions that are impaired by endothelial nitric oxide synthase (eNOS) uncoupling and ROS production. Nitric oxide (NO) bioavailability can decrease due to deficient NO production by eNOS and/or NO release to vascular smooth muscle cells, which impairs endothelial function. Considering the NO cellular mechanisms, tackling the issue of eNOS uncoupling could avoid endothelial dysfunction: provision of the enzyme cofactor tetrahydrobiopterin (BH4) should elicit NO release from NO donors, to activate soluble guanylyl cyclase. This should increase cyclic guanosine-monophosphate (cGMP) generation and inhibit phosphodiesterases (especially PDE5) that selectively degrade cGMP. Consequently, protein kinase-G should be activated, and K+ channels should be phosphorylated and activated, which is crucial for cell membrane hyperpolarization and vasodilation and/or inhibition of ROS production. The present review summarizes the current concepts about the vascular cellular mechanisms that underlie endothelial dysfunction and which could be the target of drugs for the treatment of patients with cardiovascular disease.

Antihypertensive potential of cis-[Ru(bpy)2(ImN)(NO)]3+, a ruthenium-based nitric oxide donor

The aim of this study was to investigate the antihypertensive properties of cis-[Ru(bpy)₂ImN(NO)]³⁺ (FOR0811) in normotensive and in N^ω-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats. Vasorelaxant effects were analyzed by performing concentration response curve to FOR0811 in rat aortic rings in the absence or presence of 1H-[1,2,4]-oxadiazolo-[4,3,-a]quinoxalin-1-one (ODQ), L-cysteine or hydroxocobalamin. Normotensive and L-NAME-hypertensive rats were treated with FOR0811 and the effects in blood pressure and heart rate variability in the frequency domain (HRV) were followed. FOR0811 induced relaxation in rat aortic rings. Neither endothelium removal nor L-cysteine altered the FOR0811 effects. However, the incubation with ODQ and hydroxocobalamin completely blunted FOR0811 effects. FOR0811 administered intravenously by bolus infusion (0.01-1 mg/bolus) or chronically by using subcutaneous implanted osmotic pumps significantly reduced the mean arterial blood pressure. The effect was long lasting and did not induce reflex tachycardia. FOR0811 prevented both LF and VLF increases in L-NAME hypertensive rats and has antihypertensive properties. This new ruthenium complex compound might be a promising nitric oxide donor to treat cardiovascular diseases.

Energy-dependent effect trial of photobiomodulation on blood pressure in hypertensive rats

The main purpose of this work was to construct an energy-dependent response curve of photobiomodulation on arterial pressure in hypertension animal model. To reach this objective, we have used a two-kidney one clip (2K-1C) rat model. Animals received acute laser light irradiation (660 nm) on abdominal region using different energy (0.6, 1.8, 3.6, 7.2, 13.8, 28.2, 55.8, and 111.6 J), the direct arterial pressure was measured by femoral cannulation, and systolic arterial pressure (SAP), diastolic arterial pressure (DAP), heart rate (HR), and time of effect were obtained. Our results indicated that 660 nm laser light presents an energy-dependent hypotensive effect, and 28.2 J energy irradiation reached the maximum hypotensive effect, inducing a decreased SAP, DAP, and HR (decrease in SAP: - 19.23 ± 1.82 mmHg, n = 11; DAP: - 9.57 ± 2.23 mmHg, n = 11; HR: - 39.15 ± 5.10 bpm, n = 11; and time of hypotensive effect: 3068.00 ± 719.00 s, n = 11). The higher energy irradiation evaluated (111.6 J) did not induce a hypotensive effect and induced an increase in HR (21.69 ± 7.89 bpm, n = 7). Taken together, our results indicate that red laser energy irradiation from 7.2 to 55.8 J is the effective therapeutic window to reduce SAP, DAP, MAP, and HR and induce a long-lasting hypotensive effect in rats, with effect loss at higher energy irradiation (111.6 J).

Photobiomodulation induces hypotensive effect in spontaneously hypertensive rats

To evaluate whether acute photobiomodulation can elicit a hypotensive effect in spontaneously hypertensive rats (SHR). Male SHR were submitted to the implantation of a polyethylene cannula into the femoral artery. After 24 h, baseline measurements of the hemodynamic parameters: systolic, diastolic, and mean arterial pressure, and heart rate were accomplished for 1 h. Afterwards, laser application was simulated, and the hemodynamic parameters were recorded for 1 h. In the same animal, the laser was applied at six different positions of the rat's abdomen, and the hemodynamic parameters were also recorded until the end of the hypotensive effect. The irradiation parameters were red wavelength (660 nm); average optical power of 100 mW; 56 s per point (six points); spot area of 0.0586 cm²; and irradiance of 1.71 W/cm² yielding to a fluency of 96 J/cm² per point. For measuring plasma NO levels, blood was collected before the recording, as well as immediately after the end of the mediated hypotensive effect. Photobiomodulation therapy was able to reduce the systolic arterial pressure in 69% of the SHR submitted to the application, displaying a decrease in systolic, diastolic, and mean arterial pressure. No change in heart rate was observed. Nevertheless, there was an increase in serum nitric oxide levels in the SHR responsive to photobiomodulation. Our results suggest that acute irradiation with a red laser at 660 nm can elicit a hypotensive effect in SHR, probably by a mechanism involving the release of NO, without changing the heart rate.

Endothelial Dysfunction and Inflammation Precedes Elevations in Blood Pressure Induced by a High-Fat Diet

Background

Obesity leads to a chronic inflammatory state, endothelial dysfunction and hypertension.

Objective

To establish the time-course of events regarding inflammatory markers, endothelial dysfunction, systolic blood pressure (SBP) in obesity in only one experimental model.

Methods

We fed male Wistar rats (eight-week age) with a standard diet (Control - CT, n = 35), or palatable high-fat diet (HFD, n = 35) for 24 weeks. Every six weeks, 7 animals from each group were randomly selected for euthanasia. SBP and serum levels of interleukin-6, tumor necrosis factor-α, C-reactive protein, adiponectin and nitric oxide were determined. Endothelial and vascular smooth muscle functions were determined in dissected aorta and lipid peroxidation was measured. Statistical significance was set at p < 0.05.

Results

Levels of pro-inflammatory cytokines began to increase after six weeks of a high-fat diet, while those of the anti-inflammatory cytokine adiponectin decreased. Interestingly, the endothelial function and serum nitric oxide began to decrease after six weeks in HFD group. The SBP and lipid peroxidation began to increase at 12 weeks in HFD group. In addition, we showed that total visceral fat mass was negatively correlated with endothelial function and positively correlated with SBP.

Conclusion

Our results show the time-course of deleterious effects and their correlation with obesity.

Nitric oxide donor [Ru(terpy)(bdq)NO]3+ induces uncoupling and phosphorylation of endothelial nitric oxide synthase promoting oxidant production

[Ru(terpy)(bdq)NO]3+ (TERPY) is a nitric oxide (NO) donor that promotes relaxation of the mesenteric artery and aorta in rats. We sought to investigate whether it acts as both an NO donor and endothelial NO synthase (eNOS) activator, as shown previously for nitroglycerin. Human umbilical vein endothelial cells (HUVECs) and human embryonic kidney 293 cells transfected with empty vector (HEK) or eNOS cDNA (HEK-eNOS) were treated with TERPY (1µM) for different lengths of time. eNOS expression, dimerization, and Ser1177 phosphorylation, caveolin-1 (Cav-1) oligomerization, Cav-1 Tyr14 phosphorylation were evaluated by Western blotting. Studies also assessed the production of reactive oxygen/nitrogen species (ROS/RNS) in HUVECs and HEK-eNOS cells. In HEK cells devoid of eNOS, TERPY released NO without additional stimulus indicating that is an NO donor. Moreover, in HEK-eNOS cells, TERPY-induced NO production that was blocked by L-NAME. In addition, TERPY increased ROS and ONOO- production which were blocked by more than 80% by BH4 (essential eNOS co-factor) and eNOS siRNA. These results suggest that TERPY-induced ROS and ONOO- production were originated from eNOS. HUVECs stimulated with TERPY showed increased eNOS Ser1177 and Cav-1 Tyr14 phosphorylation, and decreased eNOS dimerization, Cav-1 oligomerization, and Cav-1/eNOS interaction after 20min. It suggests that TERPY induces eNOS hyperactivation and uncoupling by disrupting Cav-1/eNOS interaction and depleting BH4. Endothelium-dependent vasodilation in response to NO donor TERPY is associated with eNOS activation and uncoupling, and thereby appears to be mediated, at least in part, via eNOS-dependent ROS/RNS production.

Resveratrol Treatment Normalizes the Endothelial Function and Blood Pressure in Ovariectomized Rats

Background:

Despite knowing that resveratrol has effects on blood vessels, blood pressure and that phytostrogens can also improve the endothelium-dependent relaxation/vasodilation, there are no reports of reveratrol's direct effect on the endothelial function and blood pressure of animals with estrogen deficit (mimicking post-menopausal increased blood pressure).

Objective:

To verify the effect of two different periods of preventive treatment with resveratrol on blood pressure and endothelial function in ovariectomized young adult rats.

Methods:

3-month old female Wistar rats were used and distributed in 6 groups: intact groups with 60 or 90 days, ovariectomized groups with 60 or 90 days, and ovariectomized treated with resveratrol (10 mg/kg of body weight per day) for 60 or 90 days. The number of days in each group corresponds to the duration of the experimental period. Vascular reactivity study was performed in abdominal aortic rings, systolic blood pressure was measured and serum nitric oxide (NO) concentration was quantified.

Results:

Ovariectomy induced blood pressure increase 60 and 90 days after surgery, whereas the endothelial function decreased only 90 days after surgery, with no difference in NO concentration among the groups. Only longer treatment (90 days) with resveratrol was able to improve the endothelial function and normalize blood pressure.

Conclusion:

Our results suggest that 90 days of treatment with resveratrol is able to improve the endothelial function and decrease blood pressure in ovariectomized rats.

Fundamentos:

Apesar de se saber que o resveratrol apresenta efeitos sobre a pressão arterial e os vasos sanguíneos, e que os fitoestrógenos podem melhorar o relaxamento/vasodilatação dependente do endotélio, não há relatos do efeito direto do resveratrol sobre a pressão arterial e a função endotelial em animais com deficiência de estrógeno (mimetizando a pressão arterial aumentada pós-menopausa).

Objetivo:

Verificar o efeito de dois diferentes períodos de tratamento preventivo com resveratrol sobre a pressão arterial e a função endotelial em ratas adultas jovens ovariectomizadas.

Métodos:

Foram utilizadas ratas Wistar com 3 meses de idade, distribuídas em 6 grupos: grupos intactas com 60 ou 90 dias, grupos ovariectomizadas com 60 ou 90 dias, grupos ovariectomizadas e tratadas com resveratrol na dose de 10mg/kg de massa corporal por dia, durante 60 ou 90 dias, sendo o número de dias em cada grupo relativo à duração do período experimental. Foi realizado um estudo de reatividade vascular em anéis da aorta abdominal, mensurada a pressão arterial sistólica e quantificada a concentração sérica de óxido nítrico (NO).

Resultados:

A ovariectomia induziu aumento da pressão arterial 60 e 90 dias após a cirurgia, enquanto a função endotelial decaiu apenas após 90 dias, e não houve diferença na concentração de NO entre os grupos. Apenas o tratamento prolongado com resveratrol (90 dias) foi capaz de melhorar a função endotelial e normalizar a pressão arterial.

Conclusão:

Nossos resultados sugerem que o tratamento por 90 dias com resveratrol é capaz de melhorar a função endotelial e diminuir a pressão sanguínea em ratas ovariectomizadas.

Ruthenium Complex Improves the Endothelial Function in Aortic Rings From Hypertensive Rats

BACKGROUND:

The endothelium is a monolayer of cells that extends on the vascular inner surface, responsible for the modulation of vascular tone. By means of the release of nitric oxide (NO), the endothelium has an important protective function against cardiovascular diseases.

OBJECTIVE:

Verify if cis- [Ru(bpy)2(NO2)(NO)](PF6)2 (BPY) improves endothelial function and the sensibility of conductance (aorta) and resistance (coronary) to vascular relaxation induced by BPY.

METHODS:

Normotensive (2K) and hypertensive (2K-1C) Wistar rats were used. For vascular reactivity study, thoracic aortas were isolated, rings with intact endothelium were incubated with: BPY(0.01 to10 µM) and concentration effect curves to acetylcholine were performed. In addition, cumulative concentration curves were performed to BPY (1.0 nM to 0.1 µM) in aortic and coronary rings, with intact and denuded endothelium.

RESULTS:

In aorta from 2K-1C animals, the treatment with BPY 0.1µM increased the potency of acetylcholine-induced relaxation and it was able to revert the endothelial dysfunction. The presence of the endothelium did not modify the effect of BPY in inducing the relaxation in aortas from 2K and 2K-1C rats. In coronary, the endothelium potentiated the vasodilator effect of BPY in vessels from 2K and 2K-1C rats.

CONCLUSION:

Our results suggest that 0.1 µM of BPY is able to normalize the relaxation endothelium dependent in hypertensive rats, and the compound BPY induces relaxation in aortic from normotensive and hypertensive rats with the same potency. The endothelium potentiate the relaxation effect induced by BPY in coronary from normotensive and hypertensive rats, with lower effect on coronary from hypertensive rats.

FUNDAMENTO:

O endotélio é uma monocamada de células que se estende sobre a superfície interna vascular, responsável pela modulação do tônus vascular. Por meio da liberação de óxido nítrico (NO), o endotélio tem uma função protetora importante contra doenças cardiovasculares.

OBJETIVO:

Verificar se o cis- [Ru (BPY)2 (NO2) (NO)] (PF6) 2 (BPY) melhora a função endotelial e a sensibilidade da condutância (aorta) e da resistência (coronária) ao relaxamento vascular induzido por BPY.

MÉTODOS:

Foram utilizados ratos Wistar normotensos (2K) e hipertensos (2K-1C). Para o estudo de reatividade vascular, as aortas torácicas foram isoladas, os anéis com endotélio intacto foram incubados com: BPY (0,01 a 10 µM) e se realizaram curvas de efeito de concentração para acetilcolina. Adicionalmente, foram feitas curvas de concentração cumulativas para BPY (1,0 nM a 0,1 µM) nos anéis aórticos e coronários, com endotélio intacto e nu.

RESULTADOS:

Na aorta de animais 2K-1C, o tratamento com BPY 0,1 µM aumentou a potência do relaxamento induzido pela acetilcolina e foi capaz de reverter a disfunção endotelial. A presença do endotélio não modificou o efeito da BPY na indução do relaxamento em aortas de ratos 2K e 2K-1C. Na coronária, o endotélio potencializou o efeito vasodilatador do BPY em vasos de ratos 2K e 2K-1C.

CONCLUSÃO:

Nossos resultados sugerem que 0,1 µM de BPY é capaz de normalizar o relaxamento dependente do endotélio em ratos hipertensos, e o composto BPY induz relaxamento na aorta de ratos normotensos e hipertensos com a mesma potência. O endotélio potencializa o efeito de relaxamento induzido pela BPY em coronárias de ratos normotensos e hipertensos, com menor efeito em coronárias de ratos hipertensos.

In vitro Treatment with cis-[Ru(H-dcbpy-)2(Cl)(NO)] Improves the Endothelial Function in Aortic Rings with Endothelial Dysfunction

PURPOSE

The ruthenium complex cis-[Ru(H-dcbpy-)2(Cl)(NO)] (DCBPY) is a nitric oxide (NO) donor and studies suggested that the ruthenium compounds can inactivate O2-. The aim of this study is to test if DCBPY can revert and/or prevent the endothelial dysfunction.

METHODS

Normotensive (2K) and hypertensive (2K-1C) wistar rats were used. To vascular reactivity study, thoracic aortas were isolated, rings with intact endothelium were incubated with: DCBPY: 0.1; 1 and 10μM, DCBPY plus hydroxocobalin (NO scavenger) or tempol during 30 minutes, and concentration effect curves to acetylcholine were performed. The potency values (pD2) and maximum effect (ME) were analyzed. The O2- was generated using hypoxantine xantine oxidase and the reduction of cytochrome c, NO consumption by O2- and the effect in avoid NO consumption was measured.

RESULTS

In 2K-1C DCBPY at 0.1; 1 or 10μM improved the relaxation endothelium dependent induced by acetylcholine in aortic rings compared to control 2K-1C, and also improved ME. In rings from 2K incubation with DCBPY (0.1; 1.0 and 10 μM) did not change pD2 or ME. Incubation with 0.1 μM of DCBPY plus hydroxocobalamin did not modify the potency and ME in 2K-1C compared to DCBPY (0.1 μM). DCBPY and SOD inhibits the reduction of cytochrome c and inhibited the NO consumption by O2-, showing that O2- has been removed from the solution.

CONCLUSION

Our results suggest that DCBPY at a lower concentration (0.1 µM) is not an NO generator, but can inactivate superoxide and improves the endothelial function.

Pharmacological characterization of the vasodilating effect induced by the ruthenium complex cis-[Ru(NO)(NO2)(bpy)2].(PF6)2

Nitric oxide (NO) can be found in different species and is a potent vasodilator. The ruthenium compound cis-[Ru(NO)(NO2)(bpy)2].(PF6)2 (BPY) can generate NO. This study aimed to investigate the BPY stability at physiological pH, the cellular mechanisms involved in BPY effect, NO species originating from BPY, and to verify how BPY affects blood pressure. Our results has shown that at pH 7.4 and 9.4, the NO coordinated to ruthenium (Ru-NO) is converted to nitrite (Ru-NO2) and remains stable. In aortic rings, the stable configuration of BPY (Ru-NO2) induces vascular relaxation in a concentration-dependent manner. Thus, further experiments were made with stable configuration of BPY (Ru-NO2). The relaxation induced by BPY was abolished in the presence of guanylyl cyclase inhibitor and decreased in the presence of potassium channel blocker. By using radicalar (NO) and nitroxyl (NO) scavenger, our results suggest that the BPY mainly release the radicalar species. By using fluorescence probes to detect intracellular NO concentration ([NO]i) and cytosolic Ca concentration ([Ca]c), we verified that in smooth muscle cells, BPY induces an increase in [NO]i and a decrease in [Ca]c. The intravenous bolus injection of 1.25, 2.5, and 5.0 mg/kg from stable configuration of BPY results in a decrease on basal blood pressure values. Taken together, our results indicated that the stable configuration of the compound BPY induces vascular relaxation in aorta because of NO release and decrease of [Ca]c in vascular smooth muscle cells. Also, the stable configuration is able to reduce the blood pressure in a dose-dependent manner.

Ruthenium-based nitric oxide-donating and carbon monoxide-donating molecules

Objectives

Over the past few years, the use of metallocomplexes for medical purposes has considerably grown. Because of its favourable characteristics, ruthenium has taken a significant place in this expanding field of research. Several ruthenium-containing metal compounds have been developed as delivery agents of physiological important molecules such as nitric oxide (NO) and carbon monoxide (CO).

Key findings

This review focuses on the (vaso)relaxant capacity of ruthenium-based NO-donating and CO-donating molecules in view of their potential usefulness in the treatment of cardiovascular diseases and erectile dysfunction.

Summary

Ruthenium seems to be a valuable candidate for the design of NO-donating and CO-donating molecules. To date, ruthenium remains of interest in drug research as the search for new alternatives is still necessary.

Ruthenium complexes as NO donors for vascular relaxation induction

Nitric oxide (NO) donors are substances that can release NO. Vascular relaxation induction is among the several functions of NO, and the administration of NO donors is a pharmacological alternative to treat hypertension. This review will focus on the physicochemical description of ruthenium-derived NO donor complexes that release NO via reduction and light stimulation. In particular, we will discuss the complexes synthesized by our research group over the last ten years, and we will focus on the vasodilation and arterial pressure control elicited by these complexes. Soluble guanylyl cyclase (sGC) and potassium channels are the main targets of the NO species released from the inorganic compounds. We will consider the importance of the chemical structure of the ruthenium complexes and their vascular effects.

Enhancing vascular relaxing effects of nitric oxide-donor ruthenium complexes

Ruthenium-derived complexes have emerged as new nitric oxide (NO) donors that may help circumvent the NO deficiency that impairs vasodilation. NO in vessels can be produced by the endothelial cells and/or released by NO donors. NO interacts with soluble guanylyl-cyclase to produce cGMP to activate the kinase-G pathway. As a result, conductance arteries, veins and resistance arteries dilate, whereas the cytosolic Ca2+ levels in the smooth muscle cells decrease. NO also reacts with oxygen or the superoxide anion, to generate reactive oxygen species that modulate NO-induced vasodilation. In this article, we focus on NO production by NO synthase and discuss the vascular changes taking place during hypertension originating from endothelial dysfunction. We will describe how the NO released from ruthenium-derived complexes enhances the vascular effects arising from failed NO generation or lack of NO bioavailability. In addition, how ruthenium-derived NO donors induce the hypotensive effect by vasodilation is also discussed.