The nitric oxide donor RuBPY does not induce in vitro cross-tolerance with acetylcholine

NONO2P, a nitric oxide donor, induces relaxation in coronary artery, negative inotropism and hypotensive effect in rats

Reduced NO synthesis and/or bioavailability is related with many cardiovascular diseases, such as coronary artery disease and hypertension. This study aimed to evaluate the effects of cis-[Ru(NO)(NO2)(phen)2](PF6)2-(NONO2P) on blood pressure in normotensive and hypertensive rats. Specifically, we wanted to investigate its action on the atrial contractility, mesenteric and coronary arteries function. Male Wistar and spontaneously hypertensive rats (SHR) (13-18 weeks old) were used to assess the NONO2P effects on blood pressure and heart rate. Superior mesenteric and coronary arteries, and atria were isolated for recording to analyze force changes. Cultured endothelial cells were used to measure intracellular reactive oxygen species (ROS) generation using fluorescent dye (dihydroethidium, DHE). Acute administration of NONO2P induced hypotension in non-anesthetized normotensive and hypertensive rats. Moreover, NONO2P caused a negative inotropic effect without altering cardiac rhythmicity. Further, NONO2P displays a vasorelaxant effect on different blood vessels (mesenteric and coronary arteries). For comparison purposes, we observed that NONO2P and NTG presented with a similar potency and maximum response values in inducing relaxation in coronary arteries. On the other hand, mesenteric arteries were more sensitive to both donors, NONO2P and NTG, than the coronary artery. In addition, exposure to NONO2P induced tolerance and increased ROS levels. This is the first evidence that NONO2P induces hypotension, negative cardiac inotropism and coronary artery relaxation. In addition, pre-exposure to NONO2P induces vascular tolerance. Overall, these results may shed light on the potential therapeutic use of NONO2P, particularly in treating angina and hypertensive crises.

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.