Vasodilator effects of organotransition-metal nitrosyl complexes, novel nitric oxide donors

β-Cyclodextrin and cucurbit[7]uril as protective encapsulation agents of the CO-releasing molecule [CpMo(CO)3Me]

The CO releasing ability of the complex [CpMo(CO)3Me] (1) (Cp = η5-C5H5) has been assessed using a deoxymyoglobin-carbonmonoxymyoglobin assay. In the dark, CO release was shown to be promoted by the reducing agent sodium dithionite in a concentration-dependent manner. At lower dithionite concentrations, where dithionite-induced CO release was minimised, irradiation at 365 nm with a low-power UV lamp resulted in a strongly enhanced release of CO (half-life (t1/2) = 6.3 min), thus establishing complex 1 as a photochemically activated CO-releasing molecule. To modify the CO release behaviour of the tricarbonyl complex, the possibility of obtaining inclusion complexes between 1 and β-cyclodextrin (βCD) or cucurbit[7]uril (CB7) by liquid-liquid interfacial precipitation (1@βCD(IP)), liquid antisolvent precipitation (1@CB7), and mechanochemical ball-milling (1@βCD(BM)) was evaluated. All these methods led to the isolation of a true inclusion compound (albeit mixed with nonincluded 1 for 1@βCD(BM)), as evidenced by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), FT-IR and FT-Raman spectroscopies, and 13C{1H} magic angle spinning (MAS) NMR. PXRD showed that 1@βCD(IP) was microcrystalline with a channel-type crystal packing structure. High resolution mass spectrometry studies revealed the formation of aqueous phase 1 : 1 complexes between 1 and CB7. For 1@βCD(IP) and 1@CB7, the protective effects of the hosts led to a decrease in the CO release rates with respect to nonincluded 1. βCD had the strongest effect, with a ca. 10-fold increase in t1/4 for dithionite-induced CO release, and a ca. 2-fold increase in t1/2 for photoinduced CO release.

C1q/TNF-related protein-9 ameliorates hypoxia-induced pulmonary hypertension by regulating secretion of endothelin-1 and nitric oxide mediated by AMPK in rats

Injury/dysfunction of the endothelium of pulmonary arteries contributes to hypoxia-induced pulmonary hypertension (HPH). We investigated whether C1q/tumor necrosis factor-related protein-9 (CTRP9), a newly identified cardiovascular agent, has protective roles in the development of HPH. HPH was induced in adult male rats by chronic hypobaric hypoxia. CTRP9 overexpression by adeno-associated virus (AAV)-CTRP9 transfection attenuated the increases in right ventricular systolic pressure, right ventricular hypertrophy index, and pulmonary arterial remodeling of rats under hypoxia. Importantly, CTRP9 overexpression improved endothelium-dependent vasodilation in pulmonary arterioles in HPH rats. CTRP9 overexpression enhanced expression of phosphorylated 5′-adenosine monophosphate-activated protein kinase (p-AMPK) and phosphorylated endothelial nitric oxide synthase (p-eNOS), and reduced phosphorylated extracellular signal-regulated protein kinase (p-ERK1/2) expression in pulmonary microvascular endothelial cells (PMVECs) of HPH rats. In cultured PMVECs, CTRP9 not only preserved the decrease of AMPK and eNOS phosphorylation level and nitric oxide (NO) production induced by hypoxia, but also blocked the increase in hypoxia-induced ERK1/2 phosphorylation level and endothelin (ET)-1 production. Furthermore, the effects of CTRP9 were interrupted by inhibitors or knockdown of AMPK. CTRP9 enhances NO production and reduces ET-1 production by regulating AMPK activation. CTRP9 could be a target for HPH.

Metal-based drugs

Metals have been considered for millennia to have medicinal values. With the advent of modern medicine, many metal-based drugs have proven to be highly effective in the clinic. Many different metal ions have shown activity against a range of diseases. The unique electronic structure of transition metals offers great versatility, not always seen in organic drugs, in terms of the ability to tune the properties of a given molecule. This review gives a brief overview of the most established therapeutic metals, and their more common applications, such as platinum-based anticancer drugs. New developments within the field of metallodrugs and novel strategies being employed to improve methods of delivery, are also discussed.

Hydrogen saline is protective for acute lung ischaemia/reperfusion injuries in rats

BACKGROUND

Protective effects of saturated hydrogen (H(2)) saline on cardiac ischaemia-reperfusion (I/R) injury have been demonstrated previously. This study was designed to show that hydrogen-rich saline is protective in preventing lung I/R injury in rats.

METHODS

Adult male Sprague-Dawley rats underwent 45 min occlusion of the right lung roots and 120 min reperfusion. Rats were divided randomly into three groups: sham-operated control group, I/R plus saline treatment, and I/R plus hydrogen-rich saline treatment (0.6 mmol/L, 0.5 ml/kg/d). Three days of intraperitoneal injection of hydrogen-rich saline before the reperfusion combined with immediate administration of hydrogen-rich saline after the reperfusion were performed. Following reperfusion, the lung tissue and the pulmonary artery was immediately obtained and the W/D ratio, pulmonary artery contraction and relaxation ability, H-E staining, TUNEL staining, caspase-3, MDA, 8-OHdG content and measurement of such biomarkers as WBC, CRP were measured or carried out.

RESULTS

Hydrogen saline significantly protected vasoactivity of the pulmonary artery, reduced pulmonary oedema, decreased lung malondialdehyde (MDA), 8-OHdG concentration, alleviated lung epithelial cell apoptosis and lowered the level of such biomarkers as WBC, CRP, ALT and TBiL.

CONCLUSIONS

It is concluded that hydrogen-rich saline is a novel, simple, safe and effective method to attenuate pulmonary I/R injury.

A new nitrosyl ruthenium complex nitric oxide donor presents higher efficacy than sodium nitroprusside on relaxation of airway smooth muscle

Nitric oxide (NO) has been demonstrated to be the primary agent in relaxing airways in humans and animals. We investigated the mechanisms involved in the relaxation induced by NO-donors, ruthenium complex [Ru(terpy)(bdq)NO(+)](3+) (TERPY) and sodium nitroprusside (SNP) in isolated trachea of rats contracted with carbachol in an isolated organs chamber. For instance, we verified the contribution of K(+) channels, the importance of sGC/cGMP pathway, the influence of the extra and intracellular Ca(2+) sources and the contribution of the epithelium on the relaxing response. Additionally, we have used confocal microscopy in order to analyze the action of the NO-donors on cytosolic Ca(2+) concentration. The results demonstrated that both compounds led to the relaxation of trachea in a dependent-concentration way. However, the maximum effect (E(max)) of TERPY is higher than the SNP. The relaxation induced by SNP (but not TERPY) was significantly reduced by pretreatment with ODQ (sGC inhibitor). Only TERPY-induced relaxation was reduced by tetraethylammonium (K(+) channels blocker) and by pre-contraction with 75mM KCl (membrane depolarization). The response to both NO-donors was not altered by the presence of thapsigargin (sarcoplasmic reticulum Ca(2+)-ATPase inhibitor). The epithelium removal has reduced the relaxation only to SNP, and it has no effect on TERPY. The both NO-donors reduced the contraction evoked by Ca(2+) influx, while TERPY have shown a higher inhibitory effect on contraction. Moreover, the TERPY was more effective than SNP in reducing the cytosolic Ca(2+) concentration measured by confocal microscopy. In conclusion, these results show that TERPY induces airway smooth muscle relaxation by cGMP-independent mechanisms, it involves the fluxes of Ca(2+) and K(+) across the membrane, it is more effective in reducing cytosolic Ca(2+) concentration and inducing relaxation in the rat trachea than the standard drug, SNP.

New nitric oxide donors based on ruthenium complexes

Nitric oxide (NO) donors produce NO-related activity when applied to biological systems. Among its diverse functions, NO has been implicated in vascular smooth muscle relaxation. Despite the great importance of NO in biological systems, its pharmacological and physiological studies have been limited due to its high reactivity and short half-life. In this review we will focus on our recent investigations of nitrosyl ruthenium complexes as NO-delivery agents and their effects on vascular smooth muscle cell relaxation. The high affinity of ruthenium for NO is a marked feature of its chemistry. The main signaling pathway responsible for the vascular relaxation induced by NO involves the activation of soluble guanylyl-cyclase, with subsequent accumulation of cGMP and activation of cGMP-dependent protein kinase. This in turn can activate several proteins such as K+ channels as well as induce vasodilatation by a decrease in cytosolic Ca2+. Oxidative stress and associated oxidative damage are mediators of vascular damage in several cardiovascular diseases, including hypertension. The increased production of the superoxide anion (O2-) by the vascular wall has been observed in different animal models of hypertension. Vascular relaxation to the endogenous NO-related response or to NO released from NO deliverers is impaired in vessels from renal hypertensive (2K-1C) rats. A growing amount of evidence supports the possibility that increased NO inactivation by excess O2- may account for the decreased NO bioavailability and vascular dysfunction in hypertension.

Nitric oxide releasing metal-diazeniumdiolate complexes strongly induce vasorelaxation and endothelial cell proliferation

The preparation, characterization, and NO-releasing properties of metal complexes derived from N-aminoethylpiperazine-N-diazeniumdiolate (HPipNONO), [Cu(PipNONO)Cl] and [Ni(PipNONO)Cl], and the Ni(II) complex derived from the Schiff base between HPipNONO and salicylaldehyde, [Ni(SalPipNONO)], are described. Compounds [Cu(PipNONO)Cl] and [Ni(SalPipNONO)] release NO at a much slower rate than HPipNONO in aqueous buffer in the pH range between 6.8 and 8.0. The kinetics of NO release by [Ni(SalPipNONO)] is complex, with an apparent stepwise release of NO molecules. Both [Cu(PipNONO)Cl] and [Ni(SalPipNONO)] are effective vasorelaxant agents of precontracted rabbit aorta rings, and are active in the nM concentration range. In addition, these complexes promote the proliferation of endothelial cells. Both vascular activities were inhibited by a specific inhibitor of guanylate cyclase, suggesting the involvement of the cGMP pathway. In all biological assays, the reference agent sodium nitroprusside was shown to be 10-1000-fold less potent than the two metal-NONOates.

Mechanisms Involved in the Hypotensive Effect of a κ-Opioid Receptor Agonist in Hypertensive Rats

BACKGROUND

It remains unclear whether the activation of kappa-opioid receptors has strong hypotensive effects under hypertensive condition, and the underlying mechanisms have not yet been investigated. Therefore, the present study is designed to use spontaneously hypertensive rats (SHR) to investigate the effects of a kappa-opioid receptor agonist on the regulation of urinary formation in hypertensive conditions and to identify its underlying mechanism.

METHODS

The hemodynamics, urine flow rate, vasodilatation of isolated renal artery, and plasma hormones were determined by physiological in vivo experimental technique, isolated artery perfusion technique and radioimmunoassay.

RESULTS

Intravenous administration of U50, 448H significantly decreased mean arterial blood pressure in both Wistar-Kyoto (WKY) rats and SHR. However, the blood pressure vasodepressor effect of U50, 448H was much more profound in SHR than in WKY rats. Administration of U50, 448H in SHR not only caused significantly greater effects in increasing urine volume and decreasing plasma anti-diuretic hormone than in WKY rats, but also caused significant reduction in plasma angiotensin. Moreover, vasodilatory effect of U50, 488H was significantly exhibited in the renal artery segments isolated from SHR. All effects described above were abolished by nor-binaltorphimine.

CONCLUSIONS

These data indicate that the depressor effect of U50, 488H in SHR is significantly stronger than that in WKY rats, and the effect is mediated or modulated by a kappa-opioid receptor sensitive mechanism. The sensitized hypotensive effect of U50, 488H in SHR may be attributed, in part, to its vasodilatory effect, enhanced beneficial effect on plasma humoral factors, and stronger diuretic effect in these hypertensive animals.

Nitric oxide homeostasis as a target for drug additives to cardioplegia

The vascular endothelium of the coronary arteries has been identified as the important organ that locally regulates coronary perfusion and cardiac function by paracrine secretion of nitric oxide (NO) and vasoactive peptides. NO is constitutively produced in endothelial cells by endothelial nitric oxide synthase (eNOS). NO derived from this enzyme exerts important biological functions including vasodilatation, scavenging of superoxide and inhibition of platelet aggregation. Routine cardiac surgery or cardiologic interventions lead to a serious temporary or persistent disturbance in NO homeostasis. The clinical consequences are "endothelial dysfunction", leading to "myocardial dysfunction": no- or low-reflow phenomenon and temporary reduction of myocardial pump function. Uncoupling of eNOS (one electron transfer to molecular oxygen, the second substrate of eNOS) during ischemia-reperfusion due to diminished availability of L-arginine and/or tetrahydrobiopterin is even discussed as one major source of superoxide formation. Therefore maintenance of normal NO homeostasis seems to be an important factor protecting from ischemia/reperfusion (I/R) injury. Both, the clinical situations of cardioplegic arrest as well as hypothermic cardioplegic storage are followed by reperfusion. However, the presently used cardioplegic solutions to arrest and/or store the heart, thereby reducing myocardial oxygen consumption and metabolism, are designed to preserve myocytes mainly and not endothelial cells. This review will focus on possible drug additives to cardioplegia, which may help to maintain normal NO homeostasis after I/R.

Vasorelaxation induced by the new nitric oxide donor cis-[Ru(Cl)(bpy)(2)(NO)](PF(6)) is due to activation of K(Ca) by a cGMP-dependent pathway

We investigated the effects of selective K(+) channel blockers and guanylyl cyclase inhibitor on the rat aorta relaxation induced by the new NO donor cis-[Ru(Cl)(bpy)(2)(NO)](PF(6)) (RUNOCL), following endothelium removal. NO release from RUNOCL was obtained by photo-induction using a visible light system lambda > 380 nm. RUNOCL induced relaxation of phenylephrine contracted aortic rings under light with the maximum effect (ME) of 101.2+/-3.7% and pD(2): 6.62+/-0.16 (n=7), but not in the absence of light. Relaxation stimulated with RUNOCL was also studied on 60 mM of KCl-contracted arteries or after incubation with the non-selective K(+) channel blocker (1 mM TEA) or the selective K(+) channel blockers (3 microM glibenclamide (K(ATP)), 1 mM 4-aminopyridine (K(V), 4-AP), 1 microM apamin (SK(Ca)-APA) or 0.1 microM iberiotoxin (BK(Ca) IBTX). Relaxation induced by RUNOCL was lower in KCl-contracted aortic rings with ME of 68.6+/-10.0% and pD(2): 3.92+/-0.60 (n=4). As compared to Phe-contracted arteries the potency of RUNOCL in inducing rat aorta relaxation was reduced by K(+) channel blockers as demonstrated by the pD(2) values from 6.62+/-0.16 (n=7) (control) to (TEA: 5.32+/-0.108, n=5; IBTX: 5.63+/-0.02 (n=5), APA: 5.73+/-0.13 (n=5)). But the ME was reduced only by IBTX (60.7+/-3.4%). 4-AP and glibenclamide had no effect on the relaxation induced by RUNOCL. The aortic tissue cGMP content increased with RUNOCL under light irradiation from 63.13+/-0.45 fmol/microg to 70.56+/-4.64 fmol/microg of protein (n=4) and the inhibition of guanylyl cyclase with ODQ reduced the ME: 30.1+/-1.6% and pD(2): 6.35+/-0.05 (n=4). Our results suggest that the NO released by photo-induction from RUNOCL induces rat aorta relaxation by activation of K(Ca) by a cGMP-dependent pathway.

Comparison of the mechanisms underlying the relaxation induced by two nitric oxide donors: sodium nitroprusside and a new ruthenium complex

We studied the mechanisms involved in the relaxation induced by nitric oxide (NO) donors, ruthenium complex ([Ru(terpy)(bdq)NO(+)](3+)-TERPY) and sodium nitroprusside (SNP) in denuded rat aorta. Both NO donors induced vascular relaxation independent of the agonist used in the pre-contraction. [Ru(terpy)(bdq)NO(+)](3+) and SNP activated guanylyl cyclase (GC) and K(+) channels. The production of cGMP induced by [Ru(terpy)(bdq)NO(+)](3+) - was higher than that obtained with SNP. The combination of GC inhibitor with K(+)channels blocker almost abolished the relaxation induced by the NO donors. The extracellular NO scavenger oxyhemoglobin reduced the potency without changing the maximum effect (Emax) of both NO donors. By using specific NO species scavengers, hydroxocobalamin and l-cysteine, we have identified the contribution of free radical NO (NO()) and nytroxil anion (NO(-)), respectively, to the rat aorta relaxation induced by both NO donors. The selective scavengers for NO() and NO(-) reduced the potency but not the Emax of [Ru(terpy)(bdq)NO(+)](3+). However, the NO(-) scavenger had no effect on the relaxation induced by SNP and NO() scavenger reduced only the potency to SNP. The inhibition of sarcoplasmic reticulum Ca(2+)-ATPase reduced only the potency of SNP without effect on the relaxation induced by [Ru(terpy)(bdq)NO(+)](3+). Our results demonstrate that both NO donors induce relaxation by activating the GC and K(+) channels. The NO() is the unique NO specie involved in the SNP-relaxation. On the other hand, the relaxant effect of [Ru(terpy)(bdq)NO(+)](3+) involves both NO() and NO(-), that produce higher concentration of cGMP. The inhibition of sarcoplasmic reticulum Ca(2+)-ATPase reduces the relaxation induced by SNP but it did not alter the relaxation induced by [Ru(terpy)(bdq)NO(+)](3+).

Vasorelaxing effect of U50,488H in pulmonary artery and underlying mechanism in rats

AIM

To investigate the relaxation effect and underlying mechanism of U50,488H (a selective kappa-opioid receptor agonist) in pulmonary artery in the rat.

METHODS

Isolated pulmonary artery ring was perfused and the tension of the vessel was measured.

RESULTS

U50,488H relaxed the pulmonary artery ring in a dose-dependent manner and the effect was abolished by nor-binaltorphimine, a selective kappa-opioid receptor antagonist. The relaxation effect of U50,488H in pulmonary artery was partially endothelium-dependent and was significantly attenuated in the presence of L-NAME. The relaxation effect of U50,488H was significantly attenuated by K(V) channel blocker 4-AP (4-aminopyridine), but not by glibenclamide (ATP-sensitive K+ channel blocker) nor TEA (tetraethylamonium, Ca2+-activated K+ channel blocker). Further study also showed that endothelium denudation and 4-AP have an additive inhibitory effect on pulmonary artery relaxation caused by U50,488H.

CONCLUSION

Kappa-opioid receptor activation by U50,488H relaxes pulmonary artery via two separate pathways: one is endothelium-derived nitric oxide, the other is K(V) channel in pulmonary artery smooth muscle.

A macrocyclic nitrosyl ruthenium complex is a NO donor that induces rat aorta relaxation

The vasorelaxation induced by a nitrosyl macrocyclic ruthenium complex, proposed as a new nitric oxide (NO) carrier, was studied in rat isolated aorta. The compound trans-[RuCl([15]aneN4)NO]2+ was characterized by elemental analysis, UV-visible spectrum, and infrared spectrum. Based on the electrochemical process, the reduction of the compound was followed by NO release, which was also observed using norepinephrine as a reducing agent and NO released was analyzed by a sensor. Vasorelaxation induced by this NO donor was studied and compared to those obtained with sodium nitroprusside (SNP). The relaxation induced by the compound was concentration-dependent in denuded rat aortas and occurred only in pre-contracted arteries with norepinephrine. The macrocyclic compound induced relaxation with a similar efficacy as SNP, although the potency of SNP was slightly greater. The time to reach maximum relaxation (595 s) was longer than that of SNP (195 s). Relaxation was completely abolished by oxyhemoglobin, a known NO scavenger.

In vivo effects of the controlled NO donor/scavenger ruthenium cyclam complexes on blood pressure

Ruthenium(II/III) complexes able to bind and release NO* were tested in vivo, in conscious Wistar rats instrumented for continuous blood pressure (BP) measurement and administration of in bolus injections (5 to 100 nmol/Kg i.v.) of trans-[Ru(II)Cl(NO+)(cyclam)](PF6)2 (cyclam-NO) or sodium nitroprusside (SNP). For normotensive rats, cyclam-NO produced a sustained 10% BP reduction of basal MAP during 7 +/- 0.4 to 11 +/- 0.3 min. In acute hypertensive rats, cyclam-NO produced BP reduction 3-fold larger than in normotensive rats and similar to that of SNP (maximal effect: 41 +/- 1.3 vs. 45 +/- 2.2 mmHg, respectively). However, the duration of the effect of cyclam-NO was 13 to 21-fold longer than that of SNP. The hypotensive effect of cyclam-NO was fully blocked in presence of continuous infusion of a NO* scavenger, carboxy-PTIO (6 mmol/Kg/min), or of the inhibitor of cGMP activation, methylene blue (83 nmol/Kg/min), or of the cyclam-NO precursor, trans-[RuCl(tfins)(cyclam)](tfms) (cyclam-tfms) (500 mmol/Kg/min). The long lasting BP reduction of cyclam-NO can be interpreted in terms of a slower rate of NO* release (k-NO = 2.2 x 10(-3) S(-1) at 35 degrees C) following chemical reduction (E(0') = 0.10 V vs NHE). In summary, cyclam-NO showed an hypotensive effect around 20 times longer than SNP in either normotensive or hypertensive rats, which was completely inhibited by methylene blue or carboxy-PTIO. Continuous infusion of cyclam-tfms completely blocked the hypotensive effect of cyclam-NO by scavenging the NO* released by the reduced cyclam-NO.

Venodilator action of an organotransition-metal nitrosyl complex

Nitrovasodilators, such as nitroglycerin, cause endothelium-independent dilatation of arterial and capacitance vessels via the release of nitric oxide (NO). This study examined the venodilator effect of CpCr(NO)(2)Cl (organotransition-metal nitrosyl complex) relative to that of nitroglycerin in conscious, unrestrained rats. Organotransition-metal nitrosyl complexes have releasable NO directly attached to metal centres. The dose-response effects of CpCr(NO)(2)Cl and nitroglycerin on the mean arterial pressure and the mean circulatory filling pressure (index of the body venous tone) were obtained in rats continuously infused with either normal saline or noradrenaline. The results show that both CpCr(NO)(2)Cl and nitroglycerin reduced the mean arterial pressure in rats with normal or elevated vasomotor tone. However, maximum depressor response of CpCr(NO)(2)Cl was greater than that of nitroglycerin. In vehicle-treated rats, both compounds increased the mean circulatory filling pressure. In rats with elevated vasomotor tone through the infusion of noradrenaline, both agents reduced the mean circulatory filling pressure. These results show that CpCr(NO)(2)Cl is an efficacious depressor and venodilator agent.