Why Methylene Blue Have to Be Always Present in the Stocking of Emergency Antidotes.

Evidence-based review of the existing literature ultimately recommends stocking of Methylene Blue (MB) as an emergency antidote in the United States. The same is reported around the world in Japan, Greece, Italy and Canada. The observation that MB is always present as the main antidote required in emergency and critical care units calls for a revisit on its effects on the NO/cGMP system to reemphasize its multisystem actions. Therefore, the present review aimed to display the role of MB in emergency units, concerning: 1) Polytrauma and circulatory shock; 2) Neuroprotection, 3) Anaphylaxis and, 4) Overdose and poisoning.

The effect of extracellular pH changes on intracellular pH and nitric oxide concentration in endothelial and smooth muscle cells from rat aorta.

AIMS: It has been known for more than a century that pH changes can alter vascular tone. However, there is no consensus about the effects of pH changes on vascular response. In this study, we investigated the effects of extracellular pH (pHo) changes on intracellular pH (pHi) and intracellular nitric oxide concentration ([NO]i) in freshly isolated endothelial cells and cross sections from rat aorta. MAIN METHODS: The HCl was used to reduce the pHo from 7.4 to 7.0 and from 7.4 to 6.5; the NaOH was used to increase the pHo from 7.4 to 8.0 and from 7.4 to 8.5. The fluorescent dyes 5-(and-6)-carboxy SNARF-1, acetoxymethyl ester, acetate (SNARF-1) and diaminofluorescein-FM diacetate (DAF-FM DA) were employed to measure the pHi and [NO]i, respectively. The fluorescence intensity was measured in freshly isolated endothelial cells by flow cytometry and in freshly obtained aorta cross sections by confocal microscopy. KEY FINDINGS: The endothelial and vascular smooth muscle pHi was increased at pHo 8.5. The extracellular acidification did not change the endothelial pHi, but the smooth muscle pHi was reduced at pHo 7.0. At pHo 8.5 and pHo 6.5, the endothelial [NO]i was increased. Both extracellular alkalinization and acidification increased the vascular smooth muscle [NO]i. SIGNIFICANCE: Not all changes in pHo did result in pHi changes, but disruption of acid-base balance in both directions induced NO synthesis in the endothelium and/or vascular smooth muscle.

Cardiovascular therapeutics targets on the NO-sGC-cGMP signaling pathway: a critical overview.

In a brief overview, in NO-sGC-cGMP signaling in a blood vessel, l-arginine is converted in the endothelium monolayer by the endothelial nitric oxide synthase (eNOS) to NO which diffuses into both the vessel lumen and the vessel wall, thereby activating soluble guanylate cyclase (sGC). Heme-dependent sGC stimulators and hem-independent sGC activators increase the cellular cGMP concentration via the direct activation of sGC, which results in both vasorelaxation and inhibition of platelet aggregation. Studies of the 90's definitively established the role of endothelium in all cardiovascular diseases, which were associated with endothelial dysfunction by impaired release of endothelium-derived relaxing factors with consequent risk of spasm and thrombosis. The rationale of this review is based on the fact that the discovery of NO changed the concepts of cardiovascular disease mechanisms. However, considering the jargon "from the bench to clinical practice" we concluded that a potential therapeutic revolution did not follow the pathophysiological revolution. The review is focused on general aspects without regard for advanced research aspects, and designed in two main groups: the NO/cGMP positive stimulators and blockers as "future and encouraging" new therapeutic drugs. The potential vasodilators include 1) NOS uncoupling; 2) NOS enhancers (AVE compounds); 3) NO donors (nitrovasodilators); 4) NO-independent activators (BAY compounds), and; 5) PDE5 inhibitors. The potential vasoconstrictors include 1) NOS-blockers (L-NAME, L-NMMA); 2) sGC-blockers (methylene blue), and; 3) PDEs. Few texts, selected by excellence and relevance, were crucial and considerably facilitated the elaboration of this text, in addition to our own experimental and clinical experience working on vasoplegic endothelium dysfunction.

The protective effect of cilostazol on isolated rabbit femoral arteries under conditions of ischemia and reperfusion: the role of the nitric oxide pathway.

OBJECTIVES: The clinical significance of ischemia/reperfusion of the lower extremities demands further investigation to enable the development of more effective therapeutic alternatives. This study investigated the changes in the vascular reactivity of the rabbit femoral artery and nitric oxide metabolites under partial ischemia/ reperfusion conditions following cilostazol administration. METHODS: Ischemia was induced using infrarenal aortic clamping. The animals were randomly divided into seven groups: Control 90 minutes, Ischemia/Reperfusion 90/60 minutes, Control 120 minutes, Ischemia/Reperfusion 120/90 minutes, Cilostazol, Cilostazol before Ischemia/Reperfusion 120/90 minutes, and Ischemia 120 minutes/Cilostazol/ Reperfusion 90 minutes. Dose-response curves for sodium nitroprusside, acetylcholine, and the calcium ionophore A23187 were obtained in isolated femoral arteries. The levels of nitrites and nitrates in the plasma and skeletal muscle were determined using chemiluminescence. RESULTS: Acetylcholine-and A23187-induced relaxation was reduced in the Ischemia/Reperfusion 120/90 group, and treatment with cilostazol partially prevented this ischemia/reperfusion-induced endothelium impairment. Only cilostazol treatment increased plasma levels of nitrites and nitrates. An elevation in the levels of nitrites and nitrates was observed in muscle tissues in the Ischemia/Reperfusion 120/90, Cilostazol/Ischemia/Reperfusion, and Ischemia/ Cilostazol/Reperfusion groups. CONCLUSION: Hind limb ischemia/reperfusion yielded an impaired endothelium-dependent relaxation of the femoral artery. Furthermore, cilostazol administration prior to ischemia exerted a protective effect on endothelium-dependent vascular reactivity under ischemia/reperfusion conditions.

The protective effect of cilostazol on isolated rabbit femoral arteries under conditions of ischemia and reperfusion: the role of the nitric oxide pathway

OBJECTIVES: The clinical significance of ischemia/reperfusion of the lower extremities demands further investigation to enable the development of more effective therapeutic alternatives. This study investigated the changes in the vascular reactivity of the rabbit femoral artery and nitric oxide metabolites under partial ischemia/ reperfusion conditions following cilostazol administration. METHODS: Ischemia was induced using infrarenal aortic clamping. The animals were randomly divided into seven groups: Control 90 minutes, Ischemia/Reperfusion 90/60 minutes, Control 120 minutes, Ischemia/Reperfusion 120/90 minutes, Cilostazol, Cilostazol before Ischemia/Reperfusion 120/90 minutes, and Ischemia 120 minutes/Cilostazol/ Reperfusion 90 minutes. Dose-response curves for sodium nitroprusside, acetylcholine, and the calcium ionophore A23187 were obtained in isolated femoral arteries. The levels of nitrites and nitrates in the plasma and skeletal muscle were determined using chemiluminescence. RESULTS: Acetylcholine-and A23187-induced relaxation was reduced in the Ischemia/Reperfusion 120/90 group, and treatment with cilostazol partially prevented this ischemia/reperfusion-induced endothelium impairment. Only cilostazol treatment increased plasma levels of nitrites and nitrates. An elevation in the levels of nitrites and nitrates was observed in muscle tissues in the Ischemia/Reperfusion 120/90, Cilostazol/Ischemia/Reperfusion, and Ischemia/ Cilostazol/Reperfusion groups. CONCLUSION: Hind limb ischemia/reperfusion yielded an impaired endothelium-dependent relaxation of the femoral artery. Furthermore, cilostazol administration prior to ischemia exerted a protective effect on endotheliumdependent vascular reactivity under ischemia/reperfusion conditions.

Acidosis induces relaxation mediated by nitric oxide and potassium channels in rat thoracic aorta.

We investigated the mechanism by which extracellular acidification promotes relaxation in rat thoracic aorta. The relaxation response to HCl-induced extracellular acidification (7.4 to 6.5) was measured in aortic rings pre-contracted with phenylephrine (Phe, 10(-6) M) or KCl (45mM). The vascular reactivity experiments were performed in endothelium-intact and denuded rings, in the presence or absence of indomethacin (10(-5) M), L-NAME (10(-4) M), apamin (10(-6) M), and glibenclamide (10(-5) M). The effect of extracellular acidosis (pH 7.0 and 6.5) on nitric oxide (NO) production was evaluated in isolated endothelial cells loaded with diaminofluorescein-FM diacetate (DAF-FM DA, 5µM). The extracellular acidosis failed to induce any changes in the vascular tone of aortic rings pre-contracted with KCl, however, it caused endothelium-dependent and independent relaxation in rings pre-contracted with Phe. This acidosis induced-relaxation was inhibited by L-NAME, apamin, and glibenclamide, but not by indomethacin. The acidosis (pH 7.0 and 6.5) also promoted a time-dependent increase in the NO production by the isolated endothelial cells. These results suggest that extracellular acidosis promotes vasodilation mediated by NO, K(ATP) and SK(Ca), and maybe other K(+) channels in isolated rat thoracic aorta.

Vascular relaxation of canine visceral arteries after ischemia by means of supraceliac aortic cross-clamping followed by reperfusion.

BACKGROUND: The supraceliac aortic cross-clamping can be an option to save patients with hipovolemic shock due to abdominal trauma. However, this maneuver is associated with ischemia/reperfusion (I/R) injury strongly related to oxidative stress and reduction of nitric oxide bioavailability. Moreover, several studies demonstrated impairment in relaxation after I/R, but the time course of I/R necessary to induce vascular dysfunction is still controversial. We investigated whether 60 minutes of ischemia followed by 30 minutes of reperfusion do not change the relaxation of visceral arteries nor the plasma and renal levels of malondialdehyde (MDA) and nitrite plus nitrate (NOx). METHODS: Male mongrel dogs (n = 27) were randomly allocated in one of the three groups: sham (no clamping, n = 9), ischemia (supraceliac aortic cross-clamping for 60 minutes, n = 9), and I/R (60 minutes of ischemia followed by reperfusion for 30 minutes, n = 9). Relaxation of visceral arteries (celiac trunk, renal and superior mesenteric arteries) was studied in organ chambers. MDA and NOx concentrations were determined using a commercially available kit and an ozone-based chemiluminescence assay, respectively. RESULTS: Both acetylcholine and calcium ionophore caused relaxation in endothelium-intact rings and no statistical differences were observed among the three groups. Sodium nitroprusside promoted relaxation in endothelium-denuded rings, and there were no inter-group statistical differences. Both plasma and renal concentrations of MDA and NOx showed no significant difference among the groups. CONCLUSION: Supraceliac aortic cross-clamping for 60 minutes alone and followed by 30 minutes of reperfusion did not impair relaxation of canine visceral arteries nor evoke biochemical alterations in plasma or renal tissue.

Chronic alcoholism associated with diabetes impairs erectile function in rats.

OBJECTIVE: To investigate the effects of chronic ethanol consumption and diabetes on nitric oxide (NO)-mediated relaxation of cavernosal smooth muscle (CSM). MATERIAL AND METHODS: Male Wistar rats were divided into four groups: control, isocaloric, diabetic and ethanol-diabetic. The CSMs were mounted in organ chambers for measurement of isometric tension. Contraction of the strips was induced by electrical field stimulation (EFS, 1-32 Hz) and phenylephrine. We also evaluated the effect of ethanol consumption on the relaxation induced by acetylcholine (ACh; 0.01-1000 micromol/L), sodium nitroprusside (SNP, 0.01-1000 micromol/L) or EFS (1-32 Hz) in strips pre-contracted with phenylephrine (10 micromol/L). Immunoexpression of endothelial NO synthase (eNOS) and inducible NOS (iNOS) was also accessed. RESULTS: The endothelium-dependent relaxation induced by ACh was decreased in CSM from ethanol-diabetic rats when compared with the controls, with a mean (sem) of 21 (4) vs 37 (2)%. Similarly, the potency and maximal responses induced by SNP were reduced in the ethanol-diabetic [3.97 (0.38) and 85 (1)%, respectively] and diabetic groups [3.78 (0.56) and 81 (2)%, respectively] when compared with the controls [5.3 (0.22) and 90 (3)%, respectively] and isocaloric [5.3 (0.19) and 92 (1)%, respectively] groups. Noradrenergic nerve-mediated contractions of CSM in response to EFS were increased in rats from ethanol-diabetic and diabetic groups when compared with the control and isocaloric groups. Conversely, there were no differences in EFS-induced relaxation among the groups. The immunostaining assays showed overexpression of eNOS and iNOS in the CSM from diabetic and ethanol-diabetic rats when compared with the control and isocaloric rats. CONCLUSION: There was an impairment of relaxation of CSM from ethanol-diabetic and diabetic rats that involved a decrease in the NO-cyclic guanosine monophosphate signalling pathway by endothelium-dependent mechanisms accompanied by a change in the CSM contractile sensitivity.

Diabetes and vascular disease: basic concepts of nitric oxide physiology, endothelial dysfunction, oxidative stress and therapeutic possibilities.

The vascular manifestations associated with diabetes mellitus (DM) result from the dysfunction of several vascular physiology components mainly involving the endothelium, vascular smooth muscle and platelets. It is also known that hyperglycemia-induced oxidative stress plays a role in the development of this dysfunction. This review considers the basic physiology of the endothelium, especially related to the synthesis and function of nitric oxide. We also discuss the pathophysiology of vascular disease associated with DM. This includes the role of hyperglycemia in the induction of oxidative stress and the role of advanced glycation end-products. We also consider therapeutic strategies.

Comparisons of the release of vasodilator substances from left and right cardiac chambers of the isolated perfused rabbit heart: implications for intraventricular thrombus formation.

Prostacyclin (PgI(2)) and endothelium-derived nitric oxide (EDNO) are produced by the arterial and venous endothelium. In addition to their vasodilator action on vascular smooth muscle, both act together to inhibit platelet aggregation and promote platelet disaggregation. EDNO also inhibits platelet adhesion to the endothelium. EDNO and PgI(2) have been shown to be released from the cultured endocardial cells. In this study, we examined the release of vasoactive substances from the intact endocardium by using isolated rabbit hearts perfused with physiological salt solution (95% O(2)/5% CO(2), T=37 degrees C). The right and left cardiac chambers were perfused through separate constant-flow perfusion loops (physiological salt solution, 8 ml min(-1)). Effluent from left and right cardiac, separately, was bioassayed on canine coronary artery smooth muscle, which had been contracted with prostaglandin F(2alpha_)(2 x 10(-6)M) and no change in tension was exhibit. However, addition of calcium ionophore A23187 (10(-6)M) to the cardiac chambers' perfusion line induced vasodilation of the bioassay coronary ring, 61.4+/-7.4% versus 70.49+/-6.1% of initial prostaglandin F(2alpha) contraction for the left and right cardiac chambers perfusate, respectively (mean+/-SEM, n=10, p>0.05). Production of vasodilator was blocked totally in the left heart but, only partially blocked in the right heart by adding indomethacin (10(-5)M) to the perfusate, respectively, 95.2+/-2.2% versus 41.5+/-4.8% (mean+/-SEM, n=10, p<0.05). 6-Keto prostaglandin F(1alpha), measured in the endocardial superfusion effluent was also higher for the left cardiac chambers than for the right at the time of stimulation with the A23187, respectively, 25385.88+/-5495 pg/ml (n=8) versus 13,132.45+/-1839.82 pg/ml (n=8), (p<0.05). These results showed that cyclooxygenase pathway plays major role in generating vasoactive substances for the left cardiac chamber endocardium; while it is not the main pathway for the right ventricular endocardium at which EDNO and PgI(2) could act together and potentiate their antithrombogenic activities in isolated perfused rabbit heart. This may be an explanation for the intraventricular thrombus mostly seen in left ventricle rather than in right ventricle as a complication of myocardial infarction.