NO donors induce vascular relaxation by different cellular mechanisms in hypertensive and normotensive rats.

PURPOSE: This study investigated the intracellular mechanisms involved in the vasodilatation induced by the classic NO donor SNP and the non-classic NO donor cis-[Ru(bpy)2(py)(NO2)](PF6) (or RuBPY) in mesenteric resistance arteries obtained from renal hypertensive (2K-1C) and normotensive (2K) rats. METHODS: On the basis of fluorimetric assays in cultured vascular smooth muscle cells (VSMCs) isolated from 2K-1C and 2K rats, we measured NO release from SNP and RuBPY, cytosolic Ca2+ concentration ([Ca2+]c), and reactive oxygen species (ROS) with the selective probes DAF-2DA, Fluo-3AM and the more selective probe for peroxynitrite (7-CBA), respectively. We determined isometric tension in mesenteric arteries to assess SNP- and RuBPY-induced relaxation. RESULTS: SNP and RuBPY released NO in comparable amounts in cultured aortic VSMCs from hypertensive 2K-1C and normotensive 2K rats. The NO0 scavenger hydroxocobalamin blunted NO release. Sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) inhibition with thapsigargin reduced [Ca2+]c in normotensive 2K rat VSMCs only. ROS amounts were greater in hypertensive 2K-1C than in normotensive 2K rat VSMCs, but neither SNP nor RuBPY altered ROS concentrations in any of the groups. SNP and RuBPY induced similar relaxation in hypertensive 2K-1C and normotensive 2K rat mesenteric resistance arteries. The SNP and RuBPY-induced relaxation involves sGC and PKG activation. On the other hand, SNP but not RuBPY activates K+ channels. Interestingly, SERCA inhibition reduces SNP induced relaxation only in normotensive 2K rat mesenteric arteries whereas RuBPY-induced relaxation does not involve SERCA activation in both normotensive and hypertensive arteries. CONCLUSION: Our results indicate that SNP and RuBPY-induced mesenteric resistance artery relaxation involves NO/sGC/cGMP/PKG pathway activation. K+ channels and SERCA activation is required to SNP but not for RuBPY-induced relaxation. Moreover, SERCA seems to be impaired in hypertensive 2K-1C rat mesenteric resistance arteries although it does not impact SNP- or RuBPY-induced relaxation.

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.

The new NO donor Terpy induces similar relaxation in mesenteric resistance arteries of renal hypertensive and normotensive rats.

The present work aimed to investigate the cellular mechanisms involved on the vasorelaxation induced by the new nitric oxide donor [Ru(terpy)(bdq)NO](3+) (Terpy) in isolated mesenteric resistance artery and to compare the vascular responses in isolated vessels from 2K and 2K-1C hypertensive rats. We have used this artery because it is important to the control of vascular resistance and consequently to the blood pressure control. The NO donor Terpy induced relaxation in a concentration-dependent way in mesenteric resistance arteries. There were no differences between renal hypertensive (2K-1C) and normotensive (2K) in Terpy-induced relaxation neither in NO released. The relaxation induced by Terpy was inhibited by the soluble guanylyl-cyclase (sGC) inhibitor ODQ both in 2K and in 2K-1C with similar amplitude. In agreement with these data, the protein expression of the subunits α1 and ß1 of the enzyme sGC was not different between 2K-1C and 2K mesenteric bed. The relaxation induced by Terpy was inhibited by the cGMP-dependent protein kinase (G kinase) inhibitor or by the non-selective K(+) channel blocker tetraethylamonium (TEA), but with no difference between 2K-1C and 2K arteries. The relaxation induced by Terpy was also inhibited by the SERCA inhibitor thapsigargin in both groups. Taken together, these results show that the vascular relaxation induced by the NO donor [Ru(terpy)(bdq)NO](3+) involves the activation of NO/sGC/cGMP/GK pathway, activation of K(+) channels sensitive to TEA and SERCA in normotensive and renal hypertensive rat mesenteric resistance arteries. Surprisingly, Terpy-induced vasorelaxation is similar in mesenteric resistance arteries of renal hypertensive and normotensive rats.

Hypotensive and vasorelaxing effects of the new NO-donor [Ru(terpy)(bdq)NO(+)](3+) in spontaneously hypertensive rats.

Drugs that release nitric oxide (NO) usually have limitations due to their harmful effects. Sodium nitroprusside (SNP) induces a rapid hypotension that leads to reflex tachycardia, which could be an undesirable effect in patients with heart disease, a common feature of hypertension. The nitrosyl ruthenium complex [Ru(terpy)(bdq)NO(+)](3+) (TERPY) is a NO donor that is less potent than SNP in denuded aortic rings. This study evaluated the hypotension and vasorelaxation induced by this NO donor in Wistar (W) and spontaneously hypertensive rats (SHR) and compared to the results obtained with SNP. Differently from the hypotension induced by SNP, the action of TERPY was slow, long lasting and it did not lead to reflex tachycardia in both groups. The hypotension induced by the NO-donors was more potent in SHR than in W. TERPY induced relaxation with similar efficacy to SNP, although its potency is lower in both strains. The relaxation induced by TERPY is similar in W and SHR, but SNP is more potent and efficient in SHR. The relaxation induced by TERPY is partially dependent on guanylate cyclase in SHR aorta. The NO released from the NO donors measured with DAF-2 DA by confocal microscopy shows that TERPY releases similar amounts of NO in W and SHR, while SNP releases more NO in SHR aortic rings.

Long-lasting hypotensive effect in renal hypertensive rats induced by nitric oxide released from a ruthenium complex.

In this study, we investigated the effect of the ruthenium complex [Ru(terpy)(bdq)NO] (TERPY) on the arterial pressure from renal hypertensive 2 kidney-1 clip (2K-1C) rats, which was compared with sodium nitroprusside (SNP). The most interesting finding was that the intravenous bolus injection of TERPY (2.5, 5.0, 7 mg/kg) had a dose-dependent hypotensive effect only in 2K-1C rats. On the other hand, SNP (35 and 70 µg/kg) presented a similar hypotensive effect in both normotensive (2K) and 2K-1C although the effect of 70 µg/kg was >35 µg/kg. The injection of the nonselective NO-synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) increased the arterial pressure in 2K and 2K-1C rats with a similar magnitude. After infusion of L-NAME, the hypotensive effect induced by TERPY and SNP was potentiated in both 2K and in 2K-1C rats. The administration of the superoxide scavenger 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl increased the hypotensive effect induced by TERPY or SNP in both 2K and 2K-1C rats. The hypotensive effect induced by TERPY was longer than that produced by SNP. Taken together, our results show that the TERPY has a long-lasting hypotensive effect, which has a dose dependence and higher magnitude in 2K-1C compared with in 2K rats. In comparison with SNP, TERPY is less potent in inducing arterial pressure fall, but it presents a much longer hypotensive effect.

Probiotics for dementia: a systematic review and meta-analysis of randomized controlled trials.

CONTEXT: Dementia is the fifth leading cause of death in the world. Animal studies indicate that in addition to the aging process, intestinal microbiota may play an important role in the neurodegeneration process through the modulation of the gut-brain axis. OBJECTIVE: A systematic review and meta-analysis was conducted to determine the effectiveness of probiotic and synbiotic supplementation on the cognitive function of individuals with dementia. DATA SOURCES: MEDLINE, BVS, SciELO, CENTRAL, Embase, and grey literature were searched from their inception to January 2019. STUDY SELECTION: We included data from randomized clinical trials (RCTs) that addressed dementias and assessed the following outcomes: cognitive function; inflammatory, oxidative stress, and metabolic markers; nutritional status; and intestinal microbiota composition. DATA EXTRACTION: Data searches, article selection, data extraction, and risk-of-bias assessments were performed according to the Cochrane guidelines. Data were pooled by inverse-variance random-effects meta-analyses. GRADE (Grading of Recommendations Assessment, Development, and Evaluations) was used to assess the quality of evidence. RESULTS: Data from 3 RCTs involving 161 individuals with Alzheimer's disease receiving Lactobacillus and Bifidobacterium strains showed no beneficial effect of probiotic supplementation on cognitive function (standardized mean difference, 0.56; 95%CI: -0.06 to 1.18), with very low certainty of evidence. However, probiotic supplementation improved plasma triglycerides, very-low-density lipoprotein cholesterol, insulin resistance, and plasma malondialdehyde. No RCTs included synbiotic supplementation or assessed microbiota composition. CONCLUSION: Current evidence regarding the use of probiotics and synbiotics for individuals with dementia is insufficient to support their clinical application. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration no: CRD42018116148.

Nitric oxide generated by the compound RuBPY promotes the vascular smooth cell membrane hyperpolarization.

The cis-[Ru(bpy)(2)(py)NO(2)](PF(6)) specie (RuBPY) has been used as nitric oxide (NO) delivery agent. It is an NO reservoir and it is thermodynamically stable in aqueous solution. This study aimed to evaluate the NO specie generated by RuBPY as compared to NO released from sodium nitroprusside (SNP) and to study the cellular mechanisms specially focusing the activation of soluble guanylyl-cyclase (sGC), K(+) channels and the cell membrane hyperpolarization, which are the main targets for NO-inducing vascular relaxation. NO generated by RuBPY and the vascular smooth muscle cell (VSMC) membrane potential were measured by confocal microscopy. The cellular mechanisms of aorta relaxation were investigated using K(+) channel blockers and sGC inhibitor. NO released from RuBPY was higher than NO released from SNP. RuBPY released only radicalar NO(0) and SNP released both NO(-) and NO(0). The concentration-effect curves for RuBPY-induced relaxation was shifted to the right by inhibition of sGC with ODQ and by the non-selective blockade of K(+) channels with TEA. The simultaneous combination of ODQ and TEA abolished the vasorelaxation induced by RuBPY. The membrane potential measured by the sensitive dye 4-Di-ANNEPS demonstrated that RuBPY induces cell membrane hyperpolarization. Taken together, our results indicate that the large amount of NO(0) specie generated by RuBPY induces vasorelaxation due to activation of sGC, K(+) channels sensitive to TEA, and cell membrane hyperpolarization. These results indicate that NO(0) generated from RuBPY can also directly activate the K(+) channels in an independent way of sGC.