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

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. 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. 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. 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.

Araújo AV ，Andrade FA ，Paulo M ，de Paula TD ，Potje SR ，Pereira AC ，Bendhack LM ... -  《-》

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 β1 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.

Araújo AV ，Pereira AC ，Grando MD ，da Silva RS ，Bendhack LM ... -  《-》

NO donors-relaxation is impaired in aorta from hypertensive rats due to a reduced involvement of K(+) channels and sarcoplasmic reticulum Ca(2+)-ATPase.

To examine the vasodilatation induce by the NO donors, [Ru(terpy)(bdq)NO](3+) (TERPY) and sodium nitroprusside (SNP), and to compare their effects in aortic rings from hypertensive 2K-1C and normotensive 2K rats. Vascular reactivity was performed in aortic rings pre-contracted with phenylephrine (Phe 100nM). We have analyzed the maximal relaxation (Emax) and potency (pD(2)) of NO donors. Potency of SNP was greater than TERPY in both arterial groups. The vasodilatation induced by TERPY was greater in 2K than in 2K-1C, and it was inhibited by sGC inhibitor ODQ in 2K and in 2K-1C aortic rings. ODQ did not alter the efficacy to SNP, but it reduced its potency in 2K and 2K-1C. The blockade of K(+) channels reduced the potency of TERPY only in aortic rings of 2K. On the other hand, the potency of SNP was reduced in both 2K and 2K-1C. The combination of ODQ and TEA reduced the relaxation induced by TERPY and SNP in 2K and reduced the efficacy to SNP in 2K-1C aortic rings but it had no additional effect on the TERPY relaxation in 2K-1C aortas. The production of cGMP induced by TERPY was greater than that produced by SNP, which was similarly increased in 2K and 2K-1C. Sarcoplasmic reticulum Ca-ATPase inhibition only impaired the relaxation induced by SNP in 2K aortic rings. Taken together, our results provide evidences that in this model of hypertension, impaired K(+) channels activation by TERPY and SERCA activation by SNP may contribute to decreased vasodilatation.

Bonaventura D ，de Lima RG ，da Silva RS ，Bendhack LM ... -  《-》

Hypotensive effect and vascular relaxation in different arteries induced by the nitric oxide donor RuBPY.

NO donors are compounds that release NO that can be used when the endogenous NO bioavailability is impaired. The compound cis-[Ru(bpy)2(py)(NO2)](PF6) (RuBPY) is a nitrite-ruthenium, since it has a NO2 in its molecule. The aim of the present study was to evaluate the effect of RuBPY on arterial pressure, as well as on the vascular relaxation of different vascular arteries in renal hypertensive (2K-1C) and normotensive (2K) rats. We have evaluated the arterial pressure and heart rate changes as well as the RuBPY and SNP-induced relaxation (thoracic aorta, mesenteric resistance, coronary and basilar arteries). The administration of RuBPY in awake rats evoked a smaller but long lasting hypotensive effect when compared to SNP, with no increase in heart rate. The relaxation induced by RuBPY was similar between 2K-1C and 2K rats in thoracic aorta, mesenteric resistance and coronary arteries. However, the relaxation induced by RuBPY was smaller in basilar arteries from 2K-1C than in 2K. Taken together, our results show that RuBPY presents several advantages over SNP, since it does not induce hypotensive effect in normotensive animals, the hypotensive effect is slower, with no reflex tachycardia, and it is long lasting. In addition, RuBPY induces coronary artery relaxation (useful for angina) and presented only a small effect on basilar artery (may not induce headache).

Pereira AC ，Araújo AV ，Paulo M ，Andrade FA ，Silva BR ，Vercesi JA ，da Silva RS ，Bendhack LM ... -  《-》

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

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. 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. 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. 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.

Moraes RA ，Brito DS ，Araujo FA ，Jesus RLC ，Silva LB ，Sá DS ，Silva da Silva CD ，Pernomian L ，Wenceslau CF ，Priviero F ，Webb RC ，Silva DF ... -  《-》