NONO2P, nitric oxide donor, induces vasorelaxation via NO/sGC/K+ channels pathway

Moraes, R. A.^1,2,4 , Araújo, F. A.^1,2 , Jesus, R. L. C.¹ , Silva, L.B.¹ , Brito, D.S.¹ , Sá, D. S.³ , Silva, C. D. S.³ , Priviero F.⁴ , Webb, R.C.⁴ , Silva, D. F.^1,2

¹Laboratory of Cardiovascular Physiology and Pharmacology, Bioregulation Department, Federal University of Bahia (UFBA), Salvador, Bahia, Brazil ²Gonçalo Moniz Institute, FIOCRUZ, Salvador, BA, Brazil ³Federal Institute of Bahia, IFBA, Salvador, BA, Brazil ⁴University of South Carolina, Columbia, SC, USA

Introduction: Decreased bioavailability of nitric oxide (NO) is linked with several cardiovascular diseases. In this way, NO donors have been developed to replace the deficiency in endogenous NO. However, the clinically used NO donors, nitroglycerin and sodium nitroprusside (SNP), have some limitations such as tolerance and toxicity, respectively. The aim of this study was to investigate the vascular activity of NONO2P.

Methods: Male Wistar rats were euthanized, and the superior mesenteric artery was isolated for recordings of isometric force, and in vivo experiments were performed to evaluate blood pressure in non-anesthetized normotensive rats.

Results: Cumulative administration of the NONO2P (10-13 to 3x10-6M) induced endothelium-independent relaxation (Emax:111.51 ± 2.31%; pD2: 8.51 ± 0.08) in arterial rings pre-contracted with phenylephrine (Phe,1μM). Interestingly, the free radical (NO• ) scavenger (hydroxocobalamin 30μM) and nitroxyl anions (NO− ) scavenger (L-cysteine; 3mM) decreased relaxations promoted by NONO2P. The presence of the specific soluble guanylyl cyclase (sGC) inhibitor, ODQ (10µM), abolished the vasorelaxant effect (Emax: 15.38 ± 11.85%). The relaxation was reduced in pre-contracted rings with Phe exposed to Tyrode's solution containing 20 mM of K+ (Emax: 102.83 ± 2.10%; pD2: 7.73 ± 0.04), suggesting the participation of K+ channels in the relaxation. Pre-incubation with cyclopiazonic acid (10µM), inhibitor of sarcoendoplasmic reticulum calcium ATPase (SERCA), shifted the relaxation concentration-response to the right (pD2: 7.69 ± 0.04). Moreover, NONO2P presented similar maximum efficacy to SNP (Emax: 114.24 ± 3.47%). Besides, NONO2P lowered blood pressure in normotensive rats. Conclusion: The endothelium-independent vasorelaxant effect induced by NONO2P involves sGC, SERCA and K+ channel activation. NONO2P is able to promote vasorelaxation with the same magnitude as SNP. In addition, NONO2P reduces blood pressure, becoming a promising molecule as a novel therapeutic alternative for the treatment of cardiovascular diseases.

Financial support: CAPES, FAPESB and NIH.