Nicorandil as a hybrid between nitrates and potassium channel activators

Nitric oxide dilates rat retinal blood vessels by cyclooxygenase-dependent mechanisms

It has been suggested that nitric oxide (NO) stimulates the cyclooxygenase (COX)-dependent mechanisms in the ocular vasculature; however, the importance of the pathway in regulating retinal circulation in vivo remains to be elucidated. Therefore, we investigated the role of COX-dependent mechanisms in NO-induced vasodilation of retinal blood vessels in thiobutabarbital-anesthetized rats with and without neuronal blockade (tetrodotoxin treatment). Fundus images were captured with a digital camera that was equipped with a special objective lens. The retinal vascular response was assessed by measuring changes in diameter of the retinal blood vessel. The localization of COX and soluble guanylyl cyclase in rat retina was examined using immunohistochemistry. The NO donors (sodium nitroprusside and NOR3) increased the diameter of the retinal blood vessels but decreased systemic blood pressure in a dose-dependent manner. Treatment of rats with indomethacin, a nonselective COX inhibitor, or SC-560, a selective COX-1 inhibitor, markedly attenuated the vasodilation of retinal arterioles, but not the depressor response, to the NO donors. However, both the vascular responses to NO donors were unaffected by the selective COX-2 inhibitors NS-398 and nimesulide. Indomethacin did not change the retinal vascular and depressor responses to hydralazine, 8-(4-chlorophenylthio)-guanosine-3′, 5′-cyclic monophosphate (a membrane-permeable cGMP analog) and 8-(4-chlorophenylthio)-adenosine-3′, 5′-cyclic monophosphate (a membrane-permeable cAMP analog). Treatment with SQ 22536, an adenylyl cyclase inhibitor, but not ODQ, a soluble guanylyl cyclase inhibitor, significantly attenuated the NOR3-induced vasodilation of retinal arterioles. The COX-1 immunoreactivity was found in retinal blood vessels. The retinal blood vessel was faintly stained for soluble guanylyl cyclase, although the apparent immunoreactivities on mesenteric and choroidal blood vessels were observed. These results suggest that NO exerts a substantial part of its dilatory effect via a mechanism that involves COX-1-dependent pathway in rat retinal vasculature.

Effects of chronic treatment with a low dose of nicorandil on the function of the rat aorta during ageing

1. It is known that ATP-sensitive potassium (K(ATP)) channels regulate the membrane potential of smooth muscle cells and vascular tone. Because their activity is altered during ageing, many pharmacological treatments aimed at improving K(ATP) channel and cardiovascular functions have been evaluated. Nicorandil, a K(ATP) channel opener, nitric oxide (NO) donor and anti-oxidant, induces vasodilation, decreases blood pressure and exhibits cardioprotection in ageing, as well as after ischaemia-reperfusion. 2. In the present study, using tension myography and biochemical and histological techniques, we investigated the effects of chronic (2 months) low-dose nicorandil (0.1 mg/kg per day) treatment on the function of rat aorta during ageing (in 4-, 12- and 24-month old rats). 3. The results showed that chronic nicorandil treatment significantly improves mechanical relaxation and noradrenaline-induced vasoconstriction in aged rats. At all ages, the nicorandil-induced vasodilation was primarily mediated by its NO donor group. Nicorandil treatment resulted in an additional 0.5-1 elastic lamella in the aorta and decreased total protein, collagen and elastin content in the aortic wall at all ages. However, in 4-month-old rats, nicorandil significantly increased the elastin : total protein ratio by 19%. 4. In contrast with results of previous studies that used high doses of nicorandil (i.e. 60 mg/kg per day), low-dose nicorandil treatment in the present study did not lead to a progressive desensitization to nicorandil and may be beneficial in improving arterial function in ageing or cardiovascular diseases.

Nicorandil protects ATP-sensitive potassium channels against oxidation-induced dysfunction in cardiomyocytes of aging rats

ATP-sensitive potassium channels (K(ATP) channels) regulate vascular tone and cardiac contraction through their action on the membrane potential of smooth muscle cells and cardiomyocytes. Because aging and diseases alter K(ATP) channel activity, many pharmacological treatments aimed at improving their function, therefore cardiovascular function, have been evaluated. Nicorandil, a K(ATP) channel opener, nitric oxide donor and antioxidant, is used as a treatment of angina pectoris and induces vasodilation, blood pressure decrease and cardioprotection in aging as well as after ischemia-reperfusion. Here, using the patch-clamp technique, we have studied the effect a chronic low dose of nicorandil (0.1 mg/kg per day for 2 months), on the activity of cardiomyocyte K(ATP) channels as a function of age, in newborn, 4-, 12- and 24-month old rats. Nicorandil exerted an anti-oxidant and protective action on cardiomyocyte K(ATP) channels, especially in aged animals, leading to restoration of a normal channel activity. These findings could justify further therapeutical applications.

Sildenafil-mediated neovascularization and protection against myocardial ischaemia reperfusion injury in rats: role of VEGF/angiopoietin-1

Sildenafil citrate (SC), a drug for erectile dysfunction, is now emerging as a cardiopulmonary drug. Our study aimed to determine a novel role of sildenafil on cardioprotection through stimulating angiogenesis during ischaemia (I) reperfusion (R) at both capillary and arteriolar levels and to examine the role of vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang-1) in this mechanistic effect. Rats were divided into: control sham (CS), sildenafil sham (SS), control + IR (CIR) and sildenafil + IR (SIR). Rats were given 0.7 mg/kg, (i.v) of SC or saline 30 min. before occlusion of left anterior descending artery followed by reperfusion (R). Sildenafil treatment increased capillary and arteriolar density followed by increased blood flow (2-fold) compared to control. Treatment with sildenafil demonstrated increased VEGF and Ang-1 mRNA after early reperfusion. PCR data were validated by Western blot analysis. Significant reduction in infarct size, cardiomyocyte and endothelial apoptosis were observed in SC-treated rats. Increased phosphorylation of Akt, eNOS and expression of anti-apoptotic protein Bcl-2, and thioredoxin, hemeoxygenase-1 were observed in SC-treated rats. Echocardiography demonstrated increased fractional shortening and ejection fraction following 45 days of reperfusion in the treatment group. Stress testing with dobutamine infusion and echocardiogram revealed increased contractile reserve in the treatment group. Our study demonstrated for the first time a strong additional therapeutic potential of sildenafil by up-regulating VEGF and Ang-1 system, probably by stimulating a cascade of events leading to neovascularization and conferring myocardial protection in in vivo I/R rat model.

Nicorandil suppressed myocardial injury after percutaneous coronary intervention

BACKGROUND

Nicorandil exerts beneficial effects as an adjunctive therapy for patients with ischemic heart disease. This study was designed to assess the effects of nicorandil on the myocardial protective benefits of elective percutaneous coronary intervention (PCI).

METHODS

We randomly divided 49 patients scheduled to undergo elective PCI into two groups, nicorandil and control. Before PCI, the former received an intravenous bolus injection of nicorandil (4 mg), followed by continuous infusion at 6 mg/h for 24 h after intervention. Oral administration of nicorandil was continued until follow-up coronary angiography (CAG). Serial venous blood samples, for measurement of creatine kinase (CK), creatine kinase MB isoform (CK-MB), troponin I (TnI) and myoglobin, were obtained before PCI, and at 0 h, 4 h, 24 h and 48 h after PCI. Left ventricular function and left ventricular wall motion were evaluated by means of contrast ventriculography before PCI and follow-up CAG.

RESULTS

At 24 h after PCI, elevations of cardiac enzymes were significantly suppressed in the nicorandil as compared to the control group; CK (78.1+/-34.9 versus 117.4+/-137.9 U/l, P=0.0141), CK-MB (1.57+/-1.90 versus 2.67+/-4.50 U/l, P=0.0485) and TnI (0.37+/-0.55 versus 0.86+/-1.65 ng/ml, P=0.0101). Regional left ventricular wall motion was significantly improved at follow-up in the nicorandil as compared to the control group.

CONCLUSIONS

Nicorandil suppressed elevations of cardiac enzymes after elective PCI and left ventricular wall motion was also significantly improved at follow-up, suggesting that nicorandil enhances the myocardial protective effect of PCI against angioplasty-related myocardial injury.

Myocardial protection in man--from research concept to clinical practice

Myocardial protection aims at preventing myocardial tissue loss: (a) In the acute stage, i.e., during primary angioplasty in acute myocardial infarction. In this setup, the attenuation of reperfusion injury is the main target. As a "mechanical" means, post-conditioning has already been tried in man with encouraging results. Pharmacologic interventions that could be of promise are statins, insulin, peptide hormones, including erythropoietin, fibroblast growth factor, and many others. (b) The patient with chronic coronary artery disease offers another paradigm, with the target of avoidance of further myocyte loss through apoptosis and inflammation. Various pharmacologic agents may prove useful in this context, together with exercise and "mechanical" improvement of cardiac function with attenuation of myocardial stretch, which by itself is a noxious influence. A continuous effort toward acute and chronically preserving myocardial integrity is a concept concerning both the researcher and the clinician.

Prevention of no-reflow/slow-flow phenomenon during rotational atherectomy--a prospective randomized study comparing intracoronary continuous infusion of verapamil and nicorandil

BACKGROUND

The potential exists for microcirculatory impairment during rotational coronary atherectomy (RA) due to embolization of plaque debris, platelet aggregation, or vasospasm. This prospective randomized pilot study aimed to confirm favorable effects of nicorandil during RA compared with verapamil.

METHODS

We randomly assigned 200 patients with 219 coronary lesions planned to undergo RA with intracoronary infusion of nicorandil cocktail (100 patients, 109 lesions), which contained nicorandil 24 mg, nitroglycerin 5 mg, and heparin 10,000 U in 1000 mL saline, or verapamil cocktail (100 patients, 110 lesions), which contained verapamil 10 mg instead of nicorandil. Drug cocktails were infused through a 4F Teflon sheath of the rotablator system during RA. The primary end point was incidence of no-reflow/slow-flow phenomenon; secondary end points were those of continuous ST elevation, Q-wave myocardial infarction (MI), and non-Q-wave MI.

RESULTS

Group baseline and coronary angiographic characteristics were similar. Rotational atherectomy was performed successfully, and no patients died or required emergency coronary artery bypass grafting. Incidence of no-reflow/slow-flow phenomenon was significantly lower in the nicorandil group (nicorandil 5/109 lesions, verapamil 13/110 lesions, P < .005). Incidences of persistent ST-segment elevation and non-Q-wave MI were significantly lower in the nicorandil group (ST-segment elevation: nicorandil 3/100 patients, verapamil 10/100 patients, P < .05; non-Q-wave MI: nicorandil 2/100, verapamil 9/100 patients, P < .05). One patient each in the 2 groups experienced Q-wave MI.

CONCLUSION

Our findings suggest that continuous intracoronary infusion of nicorandil during RA prevents acute periprocedural complications. Nicorandil should be used as adjunctive treatment during RA.

Efficacy of intracoronary nicardipine in the treatment of no-reflow during percutaneous coronary intervention

OBJECTIVES

The goal of this study was to evaluate the safety and efficacy of nicardipine in reversing no-reflow during percutaneous coronary intervention (PCI).

BACKGROUND

No-reflow is a common complication of PCI in patients with acute coronary syndromes or venous bypass graft disease. Although nicardipine has an attractive pharmacological profile and has been used clinically to treat no-reflow, there is a paucity of published data regarding its effectiveness in this setting.

METHODS

We conducted a retrospective analysis of 72 consecutive patients who received intracoronary nicardipine to reverse no-reflow during coronary intervention. Qualitative TIMI flow grade and quantitative TIMI frame count methods were used to assess the efficacy of nicardipine.

RESULTS

A mean of 460 +/- 360 mcg of intracoronary nicardipine was used. No-reflow was successfully reversed with complete restoration of TIMI 3 flow in 71 of 72 patients (98.6%). TIMI flow grade improved from 1.65 +/- 0.53 prior to nicardipine to 2.97 +/- 0.24 after treatment (P < 0.001). TIMI frame count decreased from 57 +/- 40 at the time of no-reflow to 15 +/- 12 after nicardipine administration (P < 0.001). Nicardipine therapy was well tolerated without adverse hemodynamic or chronotropic effects.

CONCLUSIONS

In this largest series to date, intracoronary nicardipine was demonstrated to be a safe and highly effective pharmacological agent to reverse no-reflow during PCI.

Vasodilator effect of nicorandil on retinal blood vessels in rats

We examined the effect of nicorandil on retinal blood vessels in rats in vivo. Male Wistar rats (8 to 10 weeks old) were anaesthetised with thiobutabarbital (120 mg/kg, intraperitoneal). Fundus images were captured with a digital camera that was equipped with a special objective lens. Diameters of retinal blood vessels were measured with a personal computer. Nicorandil (1-300 microg kg(-1) min(-1), intravenous [i.v.]) increased diameters of retinal blood vessels and decreased systemic blood pressure in a dose-dependent manner. Both responses to nicorandil were attenuated by glibenclamide (20 mg/kg, i.v.), an adenosine triphosphate (ATP)-dependent K(+) (K(ATP)) channel blocker. On the other hand, indomethacin (5 mg/kg, i.v.), a cyclooxygenase inhibitor, attenuated the vasodilation of retinal blood vessels, but not depressor response, to nicorandil and sodium nitroprusside. Pinacidil (1-300 microg kg(-1) min(-1), i.v.), a K(ATP) channel opener, also dilated retinal blood vessels and decreased systemic blood pressure. The responses to pinacidil were prevented by glibenclamide, but not by indomethacin. The vasodilation of retinal arteriole, but not depressor response, to sodium nitroprusside (1-30 microg kg(-1) min(-1), i.v.), a nitric oxide donor, was attenuated by indomethacin. These results suggest that nicorandil dilates retinal blood vessels through opening of K(ATP) channels and production of prostaglandins that are probably generated by nitric oxide.

Effect of intravenous nicorandil and preexisting angina pectoris on short- and long-term outcomes in patients with a first ST-segment elevation acute myocardial infarction

Published reports have indicated that prodromal angina before acute myocardial infarction (AMI) is associated with better outcomes and that nicorandil has cardioprotective effects on ischemic hearts. We compared cardioprotective effects of intravenous nicorandil with preconditioning effects by prodromal angina in patients with AMI who underwent percutaneous coronary intervention (PCI). In total, 368 patients with first ST-elevation AMI who underwent PCI were randomly assigned to receive nicorandil 12 mg or a placebo intravenously just before PCI. Subjects were assigned to 1 of 4 groups: 52 patients with prodromal angina were given placebo, 129 patients without prodromal angina were given nicorandil, 56 patients with prodromal angina were given nicorandil, and 131 patients without prodromal angina were given placebo. Coronary microvascular impairment after PCI was prevented at similar frequencies in groups with prodromal angina and groups on nicorandil. Five-year rates for freedom from major cardiac events were similar across groups with prodromal angina given placebo, without prodromal angina given nicorandil, and with prodromal angina given nicorandil (92.3%, 93.8%, and 92.9%, respectively) but were significantly lower in the group without prodromal angina given placebo (80.2%, p = 0.0019, 0.044, and 0.042, respectively). In conclusion, intravenous administration of nicorandil before PCI exerts pharmacologic cardioprotective effects similar to ischemic preconditioning in patients with AMI.

Nicorandil reduces myocardial no-reflow by protection of endothelial function via the activation of KATP channel

INTRODUCTION

It has been found that nicorandil can attenuate myocardial no-reflow. However, the exact cause of this beneficial effect has remained unclear. We investigated whether the beneficial effect of nicorandil on myocardial no-reflow could be partly due to its protection against endothelial dysfunction.

METHODS

Ligation area and area of no-reflow were determined echocardiographically and pathologically in sixty-two animals randomized into 7 study groups: 9 controls, 9 nicorandil-treated, 8 glibenclamide (K(ATP) channel blocker)-treated, 10 N(G)-monomethyl-L-arginine (L-NMMA, nonselective nitric oxide synthase antagonist)-treated, 10 nicorandil and glibenclamide-treated, 8 nicorandil and L-NMMA-treated and 8 sham-operated. The acute myocardial infarction and reperfusion model was created with one 3-h occlusion of the left anterior descending coronary artery followed by 2 h of reperfusion. Constitutive nitric oxide synthase (cNOS) activity and inducible nitric oxide synthase (iNOS) activity were also quantified.

RESULTS

Compared with the control group, nicorandil significantly improved ventricular function, increased coronary blood flow volume (P<0.01), decreased area of no-reflow and reduced necrosis area. Nicorandil also increased the cNOS activity and decreased iNOS activity (P<0.05). L-NMMA and glibenclamide abrogated the effects of nicorandil on ventricular function, coronary blood flow volume, area of no-reflow, necrosis area and cNOS activity, but not iNOS activity.

CONCLUSIONS

The beneficial effect of nicorandil on myocardial no-reflow could be due to its protection of endothelial function via the activation of K(ATP) channel.

New Insights in the Treatment Strategy for Pulmonary Arterial Hypertension

INTRODUCTION

Recent advances in our understanding of the pathophysiological and molecular mechanisms involved in pulmonary arterial hypertension have led to the development of novel and rational pharmacological therapies. In addition to conventional therapy (i.e., supplemental oxygen and calcium channel blockers), prostacyclin or endothelin receptor antagonists have been recommended as a first-line therapy for pulmonary arterial hypertension. However, these treatments have potential limitations with regard to their long-term efficacy and improvement in survival. Furthermore, intravenous prostacyclin (epoprostenol) therapy, which is recommended by most experts for patients with New York Heart Association (NYHA) functional class IV, is complicated, uncomfortable for patients, and expensive because of the cumbersome administration system. Considering these circumstances, it is necessary to develop additional novel therapeutic approaches that target the various components of this multifactorial disease.

CASE REPORT

In this short review, we present an overview of the current treatment options for pulmonary arterial hypertension and describe a case report with primary pulmonary hypertension. A male patient with NYHA functional class IV and showing no response to calcium channel blockers and prostacyclin exhibited significantly improved exercise tolerance and hemodynamics and long-term survival for more than 2.5 years after receiving an oral combination therapy of a phosphodiesterase type 5 inhibitor (sildenafil), phosphodiesterase type 3 inhibitor (pimobendan), and nicorandil.

FUTURE PERSPECTIVE

We also discuss the background and plausible potential mechanisms involved in this case, as well as future perspectives in the treatment of pulmonary arterial hypertension.

Comparison of the effects of nicorandil versus verapamil on the incidence of slow flow/no reflow during rotational atherectomy

In rotational atherectomy, the slow-flow/no-reflow phenomenon is a common complication, which usually results in myocardial injury. We prospectively randomized 111 patients with successful rotational atherectomy into a verapamil group (group V, n = 56) and a nicorandil group (group N, n = 55). We compared final burr size, total ablation time, maximum decrease in revolutions per minute, incidence of slow flow/no reflow, creatine kinase-MB increase, and cardiac troponin T increase between the 2 groups. Patient and procedural characteristics were not significantly different between groups. The incidence of no reflow/slow flow was significantly lower in group N than in group V (3.6% vs 17.9%, respectively, p <0.05). The incidence of a minor increase in cardiac markers was also significantly lower in group N than in group V (creatine kinase-MB 3.6% vs 16.1%, p <0.05; cardiac troponin T 5.5% vs 21.4%, p <0.05). In conclusion, our results showed that nicorandil decreases the incidence of slow flow/no reflow during rotational atherectomy.

Nicorandil opens mitochondrial K(ATP) channels not only directly but also through a NO-PKG-dependent pathway

Nicorandil, a hybrid of nitrate generator and potassium channel opener, protects ischemic myocardium by opening mitochondrial ATP sensitive potassium (mitoK(ATP)) channels. We recently found that nitric oxide (NO) opened K(ATP) channels in rabbit hearts by a protein kinase G (PKG) mechanism. This study examined whether the NO-donor property of nicorandil also contributes to opening of mitoK(ATP) channels through PKG. MitoK(ATP) channel opening was monitored in adult rabbit cardiomyocytes by measuring reactive oxygen species (ROS) production, an established marker of channel opening. Nicorandil increased ROS production in a dose-dependent manner. The selective mitoK(ATP) channel inhibitor 5-hydroxydecanoate (200 microM) completely blocked ROS production by nicorandil at all doses. The PKG inhibitor 8-bromoguanosine-3',5'-cyclic monophosphorothioate, Rpisomer (Rp-8-Br-cGMPs, 50 microM) shifted the dose-ROS production curve to the right with an increase of the EC(50) from 2.4 x 10(-5) M to 6.9 x 10(-5) M. Rp- 8-Br-cGMPs did not affect the increase in ROS production by the selective mitoK(ATP) channel opener diazoxide while it completely blocked increased ROS production from the NO donor S-nitroso-N-acetylpenicillamine (1 microM). Furthermore ODQ, an antagonist of soluble guanylyl cyclase, blocked nicorandil's ability to increase ROS generation. These results indicate that nicorandil, in addition to its direct effect on the channels, opens mitoK(ATP) channels indirectly via a NO-PKG signaling pathway.

QT dispersion and left ventricular function after stent placement in acute myocardial infarction

BACKGROUND

QT dispersion is increased in acute myocardial infarction (AMI), but the relation of QT dispersion to left ventricular (LV) function has not yet been fully elucidated. The purpose of this study was to evaluate the relationship between QT dispersion and LV function in patients with successful coronary stenting in AMI.

METHODS

Seventy five patients with AMI who underwent percutaneous transluminal coronary angioplasty (PTCA) were enrolled in this study. Corrected QT dispersion was measured before, immediately after, 24 h after, 48 h after, and 6 months after PTCA. Left ventricular ejection fraction (LVEF) was evaluated by left ventriculography at 6 months after PTCA.

RESULTS

Corrected QT dispersion at 24 h after and 48 h after PTCA were significantly related to LVEF by univariate analysis (r=-0.282, p<0.05 and r=-0.326, p<0.01, respectively). In multiple regression model, corrected QT dispersion at 24 h after and 48 h after PTCA revealed significant associations with LVEF (R(2)=0.441, coefficient=-0.283, p=0.006 and R(2)=0.411, coefficient=-0.225, p=0.039, respectively), but corrected QT dispersion before, immediately after, and 6 months after PTCA were not associated with LVEF.

CONCLUSIONS

Corrected QT dispersion at 24 h after and 48 h after PTCA in AMI correlate with LVEF at 6 months after PTCA.

Nicorandil administration shows cardioprotective effects in patients with poor TIMI and collateral flow as well as good flow after AMI

BACKGROUND

Nicorandil (NCR) has been reported to have cardioprotective effects in patients with AMI. And collateral flow and TIMI flow are also important determinants of final salvaged myocardium in patients with AMI. There is no evidence as to whether TIMI or collateral flow modifies the cardioprotective effects of NCR in patients with AMI.

METHODS AND RESULTS

We studied 68 initial AMI patients without restenosis which was defined as 50% diameter reduction of the intervention site in the chronic period. On initial CAG, 41 patients with poor flow (collateral: Rentrop 0 or 1 and TIMI 0 or 1) were NCR/Non-NCR = 20/21. Twenty-seven patients with good flow (collateral: Rentrop 2 or 3 or TIMI 2 or 3) were NCR/Non-NCR = 13/14. NCR was administered intravenously (4 mg) via intracoronary injection (2 mg) or continuously (4 mg/h). 99mTc-tetrofosmin (TF) and 123I-BMIPP SPECT were performed in the subacute and chronic (6 Mo) periods. In 20 SPECT segments, summed defect scores (TDS) and regional wall motion (WMS: -1=dyskinesis -4 = normal) of AMI segments using TF-QGS were estimated. In poor flow patients, the following values for NCR patients were higher (p < 0.05) than for Non-NCR patients in the improvement degree of TDS (BMIPP) (NCR: 6.5 +/- 3.9 vs. Non-NCR: 4.0 +/- 3.4), the improvement degree of TDS (TF) (NCR: 5.7 +/- 4.6 vs. Non-NCR: 2.2 +/- 4.6), and delta WMS (NCR: 1.4 +/- 1.1 vs. Non-NCR: 0.9 +/- 1.0). In good flow patients, the following values for NCR patients were better (p < 0.05) than for Non-NCR patients in TDS (BMIPP) (subacute) (NCR: 9.9 +/- 5.2 vs. Non-NCR: 16.5 +/- 10.4) and (chronic) (NCR: 5.1 +/- 5.2 vs. Non-NCR: 12.4 +/- 8.5), WMS (subacute) (NCR: 1.7 +/- 1.3 vs. Non-NCR: 1.0 +/- 1.0), and WMS (chronic) (NCR: 3.0 +/- 1.5 vs. Non-NCR: 2.1 +/- 1.3).

CONCLUSION

We conclude that the cardioprotective effects of nicorandil administration are observable in both AMI patients with poor collateral and TIMI flow and good flow before reperfusion therapy.

Nicorandil but not ISDN Upregulates Endothelial Nitric Oxide Synthase Expression, Preventing Left Ventricular Remodeling and Degradation of Cardiac Function in Dahl Salt-sensitive Hypertensive Rats With Congestive Heart Failure

Cardiac endothelial nitric oxide synthase (ecNOS) was suppressed and inducible NOS (iNOS) enhanced at the decompensated heart failure stage in 18-week-old Dahl salt-sensitive (DS) hypertensive rats to which a high-salt diet had been administered from the age of 6 weeks. Nicorandil (NIC) enhanced ecNOS by activating Adenosine triphosphate-sensitive potassium channels (K-ATP channels) in the normal rat left ventricle. In this study, left ventricular hypertrophy, remodeling, function, cardiac ecNOS, and iNOS were compared between NIC and isosorbide dinitrate (ISDN) treatments in DS hypertensive rats with congestive heart failure. We examined DS hypertensive rats of 18 weeks of age to which 8% NaCl had been administered from the age of 6 weeks, and to which subdepressor doses of NIC (6 mg/kg/d), ISDN (6 mg/kg/d), and vehicle (CON) were administered from the age of 11 weeks. Contractility (Ees), stiffness (Eed), left ventricular end-diastolic volume, and left ventricular end-systolic volume were measured by conductance catheter and micromanometer on the basis of the pressure-volume relationship, and mRNA and protein levels of ecNOS and iNOS in the left ventricle were measured by reverse transcription-polymerase chain reaction and Western blot analysis at 18 weeks. LV mass index and LV dimensions were smaller in the NIC and ISDN groups than in the CON group (P < 0.01), and the first parameter was lower in the NIC than in the ISDN group (P < 0.01). Ees was also better maintained in the NIC and ISDN groups than in the CON group (NIC: 3349 +/- 649; ISDN: 2950 +/- 577, P < 0.05 vs. NIC; CON: 1424 +/- 375 mL/mmHg, P < 0.01 vs. treatments). Eed was exacerbated only in the ISDN group. NIC enhanced whereas ISDN suppressed ecNOS mRNA and protein levels (NIC 2.0-fold and 1.8-fold, ISDN 0.70-fold and 0.8-fold vs. CON; P < 0.01, respectively). However, no intragroup differences in iNOS mRNA or protein levels were observed for the 3 groups. More significant improvements in cardiac function and LV hypertrophy regression were observed in an NIC group than in an ISDN group of DS hypertensive rats. Activation of the K-ATP channel seems to induce this beneficial effect, which may be mediated in part by enhanced ecNOS expression in the heart in DS hypertensive congestive heart failure rat model.

Continuous Administration of Nicorandil Decreases QT Dispersion During the Chronic Phase of Acute Myocardial Infarction

We previously reported that continuous intravenous (IV) administration of nicorandil (NIC) inhibits QT dispersion (QTd). However, no prior study has evaluated the efficacy of NIC when administered orally to acute myocardial infarction (AMI) patients following continuous IV administration. Thirty patients with anteroseptal infarction in whom revascularization was performed successfully within 6 hours of AMI onset were included in the study and assigned to one of 3 groups: group A (continuous IV administration of NIC), group B (continuous IV and oral administration of NIC), and group C (no treatment with NIC). After 24 hours, QTd in groups A and B was significantly decreased compared to QTd in group C (P < 0.01) (group A, 58.1; group B, 58.2; and group C, 81.3). The QTd obtained 3 months later was significantly shorter in group B subjects who were orally administered NIC, and QTd before percutaneous coronary intervention (PCI) was restored in group A, in which no NIC had been administered orally [group A, 66.7; group B, 54.1; and group C, 73.9; P < 0.05 (group A versus group B) and P < 0.01 (group B versus group C)]. The effects were evaluated by comparing different routes of administration. Continuous IV and subsequent oral administration of NIC inhibited prolongation of QTd, suggesting that these effects may prevent the occurrence of cardiac events during both the acute and chronic phases of AMI.

Impact of Nicorandil to Prevent Reperfusion Injury in Patients With Acute Myocardial Infarction Sigmart Multicenter Angioplasty Revascularization Trial (SMART)

BACKGROUND

Nicorandil in conjunction with percutaneous coronary intervention (PCI) has been reported to reduce reperfusion injury events and improve cardiac function in patients with acute myocardial infarction (AMI). This multicenter study was undertaken to determine the effectiveness and optimal administration of nicorandil in AMI patients.

METHODS AND RESULTS

Ninety-two patients with first AMI were randomly assigned to 1 of 3 groups: intracoronary administration of nicorandil (Group A), combined intravenous and intracoronary administration of nicorandil (Group B), and no nicorandil administration (Group C). The primary endpoint was a composite of the incidence of reperfusion-induced arrhythmia, chest pain, and no-reflow/slow-reflow. The secondary endpoint was the combined rate of improvement in the Thrombolysis in Myocardial Infarction frame count (cTFC) and ST resolution (STR). A significant difference was observed in the primary endpoint for Group B as compared with Group C (p<0.05). In the meantime, a significant improvement was shown in the secondary endpoint for Group B compared with Group C (p=0.04 and 0.006 for cTFC and STR, respectively).

CONCLUSIONS

Combined intravenous and intracoronary administration of nicorandil reduces reperfusion injury during PCI and improves the cTFC and STR in AMI, and appears to be preferable to intracoronary administration alone.

Nicorandil Promotes Myocardial Capillary and Arteriolar Growth in the Failing Heart of Dahl Salt-Sensitive Hypertensive Rats

Long-term administration of vasodilators increases shear stress, which is thought to be important for vascular growth in the heart. Nicorandil, an activator of ATP-sensitive potassium channels with a nitrate-like action, is a potent vasodilator. We have now investigated the effects of nicorandil on vascular growth and gene expression in the failing heart of Dahl salt-sensitive (DS) hypertensive rats. DS rats fed a high-salt diet from 6 weeks of age develop concentric cardiac hypertrophy secondary to hypertension at 11 weeks, followed by heart failure at 18 weeks. DS rats on such a diet were treated with a nonantihypertensive oral dose of nicorandil (6 mg/kg per day) or vehicle from 11 to 18 weeks of age. Treatment of DS rats with nicorandil improved cardiac function and attenuated the development of heart failure. Myocardial capillary and arteriolar densities did not differ between vehicle-treated DS rats and age-matched controls. The abundance of mRNAs for endothelial NO synthase (eNOS), vascular endothelial growth factor (VEGF), the VEGF receptor Flt-1, and basic fibroblast growth factor (bFGF) in the myocardium was markedly reduced in vehicle-treated DS rats compared with controls. Treatment of DS rats with nicorandil greatly increased capillary and arteriolar densities and inhibited the downregulation of eNOS, VEGF, fms-like tyrosin kinase-1, and bFGF gene expression. This, nicorandil stimulates coronary capillary and arteriolar growth and thereby likely suppresses the development of heart failure in DS rats. Nicorandil may prove beneficial for the treatment of hypertensive heart failure as well as of ischemic heart disease.

Effects of Nicorandil on Monocrotaline-Induced Pulmonary Arterial Hypertension in Rats

We investigated whether nicorandil might prevent and reverse monocrotaline (MCT)-induced pulmonary arterial hypertension. Rats were injected with 50 mg/kg of MCT subcutaneously and randomized to either 7.5 mg/kg/d of nicorandil in drinking water or placebo for 3 weeks. Animals that were treated with MCT and survived for 3 weeks were assigned to either nicorandil or placebo. Nicorandil markedly attenuated pulmonary arterial hypertension with severe structural remodeling of the pulmonary vessels. The survival rate at 3 weeks after treatment was significantly increased in the nicorandil group compared with the placebo group (73% versus 39%, P<0.05). In the placebo group, endothelial nitric oxide synthase (eNOS) protein was significantly decreased, the numbers of the CD45-positive cells and those of the proliferating cell nuclear antigen-positive cells were increased in the lung tissue, and P-selectin was intensely expressed on the endothelium of the pulmonary arteries. These features were prevented by nicorandil. Late treatment with nicorandil did not palliate established pulmonary arterial hypertension nor improved survival. Thus, nicorandil inhibited development of MCT-induced pulmonary arterial hypertension but failed to reverse it. These effects were associated with marked up-regulation of diminished lung eNOS protein along with improvement of pulmonary vascular endothelial activation and anti-inflammatory and anti-proliferative effects in the lung tissue.

Gestational change of K+ channel opener effect is correlated with the expression of uterine KATP channel subunits

OBJECTIVE

We analyzed the gestational changes of pharmacological activity and molecular levels of KATP channels in rat myometrium.

STUDY DESIGN

Using rat myometrium, the effects of K+ channel openers (KCOs) were examined in an isometric tension study of oxytocin-induced contraction. We also examined the effects of KCOs on the intracellular Ca2+ levels of cultured myometrial cells. The expression of myometrial KATP channels was assessed by RT-PCR and Northern blot analysis.

RESULTS

The effect of KCOs were altered during pregnancy, with a significant increase of their potency at day 18 of pregnancy followed by a decline towards the non-pregnant level at the day of delivery. KCOs suppressed the Ca2+ influx across the cell membrane. The mRNAs encoding each component of myometrial KATP channels, Kir6.1 and SUR2B, exhibited gestational stage-dependent alterations similar to those of the effects of KCOs.

CONCLUSION

These findings suggest that KCOs inhibit uterine myometrial contraction more effectively during pregnancy than in the non-pregnant state due to gestation-enhanced expression of KATP channels, implying that KCOs might be useful for preventing premature delivery.

Comparative effects of nicorandil with isosorbide mononitrate on cardiac sympathetic nerve activity and left ventricular function in patients with ischemic cardiomyopathy

BACKGROUND

Nicorandil, an adenosine triphosphate-sensitive potassium channel opener, improves left ventricular (LV) remodeling after myocardial infarction in rat models. However, the effects of chronic nicorandil therapy on cardiac sympathetic nerve activity in patients with ischemic cardiomyopathy have not been determined.

METHODS

Thirty-six patients with ischemic cardiomyopathy (LV ejection fraction [LVEF] < 40%) who underwent successful revascularization procedure before 6 months were treated by standard conventional therapy. Eighteen patients were randomized to additionally receive nicorandil (15 mg/d), whereas the other 18 patients received isosorbide mononitrate (40 mg/d). The delayed heart-to-mediastinum count ratio (H/M ratio), delayed total defect score (TDS), and washout rate (WR) were determined from (123)I-meta-iodobenzylguanidine (MIBG) scintigraphy before and 6 months after treatment. Left ventricular end-diastolic volume (LVEDV) and LVEF were determined by echocardiography.

RESULTS

Total defect score, H/M ratio, WR, LVEDV, and LVEF at baseline were similar for both groups. After treatment, in patients receiving nicorandil, TDS decreased from 50 +/- 6 to 40 +/- 11 (P < .005), H/M ratio increased from 1.68 +/- 0.23 to 1.79 +/- 0.26 (P = .005), and WR decreased from 46% +/- 9% to 40% +/- 12% (P < .005). In addition, LVEDV decreased from 178 +/- 31 to 157 +/- 30 mL (P < .0005), and LVEF increased from 33% +/- 6% to 39% +/- 7% (P < .05). In patients receiving isosorbide mononitrate, no significant changes were observed in these parameters. Moreover, there was a significant correlation between the percent change of LVEF and that of TDS from baseline to 6 months in the patients receiving nicorandil (r = -0.569, P < .05).

CONCLUSIONS

The present study demonstrates improvements in cardiac (123)I-MIBG scintigraphic and echocardiographic parameters with nicorandil treatment. These findings indicate that nicorandil can improve cardiac sympathetic nerve activity and LV function in patients with ischemic cardiomyopathy.

Impact of a single intravenous administration of nicorandil before reperfusion in patients with ST-segment-elevation myocardial infarction

BACKGROUND

Intravenous nicorandil, a hybrid compound of ATP-sensitive potassium channel opener and nitric oxide donor, has been reported to ameliorate early functional and clinical problems in patients with acute myocardial infarction. However, its effects on the late phase remain unclear.

METHODS AND RESULTS

This follow-up study to 5 years of a randomized, double-blinded trial was conducted among 368 patients with first ST-segment-elevation myocardial infarction undergoing percutaneous coronary intervention (PCI). They were randomly assigned to receive 12 mg of nicorandil or a placebo intravenously just before reperfusion. We analyzed incidence of cardiovascular death or rehospitalization for congestive heart failure after PCI as well as various aspects of epicardial flow and microvascular function. Mean follow-up was 2.4 years (SD, 1.4). A total of 12 (6.5%) patients receiving nicorandil and 30 (16.4%) receiving placebo had cardiovascular death or hospital admission for congestive heart failure (hazard ratio, 0.39; 95% CI, 0.20 to 0.76; P=0.0058). Postprocedural TIMI 3 flow was obtained in 89.7% of the nicorandil group and in 81.4% of the placebo (hazard ratio, 1.99; 95% CI, 1.09 to 3.65; P=0.025). Corrected TIMI frame count was furthermore lower in the nicorandil group (21.0+/-9.1 versus 25.1+/-14.1; P=0.0009). ST-segment resolution >50% was observed in 79.5% and 61.2% of the nicorandil and placebo groups, respectively (hazard ratio, 2.45; 95% CI, 1.54 to 3.90; P=0.0002).

CONCLUSIONS

The addition of intravenous nicorandil to PCI leads to beneficial clinical outcomes and prevents cardiovascular events of long duration and death in patients with ST-segment-elevation myocardial infarction.

Is the sarcolemmal or mitochondrial K(ATP) channel activation important in the antiarrhythmic and cardioprotective effects during acute ischemia/reperfusion in the intact anesthetized rabbit model?

The relative contributions of cardiomyocyte sarcolemmal ATP-sensitive K(+) (K(ATP)) and mitochondrial K(ATP) channels in the cardioprotection and antiarrhythmic activity induced by K(ATP) channel openers remain obscure, though the mitochondrial K(ATP) channels have been proposed to be involved as a subcellular mediator in cardioprotection afforded by ischemic preconditioning. In the present study, we sought to investigate the effects of administration of ATP-sensitive K(+) channel (K(ATP)) openers (nicorandil and minoxidil), a specific mitochondrial K(ATP) channel blocker (5-hydroxydecanoate (5-HD)) and a specific sarcolemmal K(ATP) channel blocker (HMR 1883; (1-[5-[2-(5-chloro-o-anisamido)ethyl]-2-methoxyphenyl]sulfonyl-3-methylthiourea) prior to coronary occlusion as well as prior to post-ischemic reperfusion on survival rate, ischemia-induced and reperfusion-induced arrhythmias and myocardial infarct size in anesthetized albino rabbits. The thorax was opened in the left 4th intercostal space and after pericardiotomy the heart was exposed. In Group I (n=88), occlusion of the left main coronary artery and hence, myocardial ischemia-induced arrhythmias was achieved by tightening a previously placed loose silk ligature for 30 min. In Group II (n=206), arrhythmias were induced by reperfusion following a 20-min ligation of the left main coronary artery. Both in Group I and Group II, intravenous (i.v.) administration of nicorandil (0.47 mg/kg), minoxidil (0.5 mg/kg), HMR 1883 (3 mg/kg)/nicorandil and HMR 1883 (3 mg/kg)/minoxidil before coronary artery occlusion increased survival rate (86%, 75%, 75% and 86% vs. 55% in the control subgroup in Group I; 75%, 67%, 67% and 75% vs. 46% in the control subgroup in Group II), significantly decreased the incidence and severity of life-threatening arrhythmias. In Group II, i.v. administration of nicorandil and minoxidil before coronary artery occlusion significantly decreased myocardial infarct size. However, i.v. administration of nicorandil or minoxidil before reperfusion did neither increase survival rate nor confer any antiarrhythmic or cardioprotective effects. The antiarrhythmic and cardioprotective effects of both nicorandil and minoxidil were abolished by pretreating the rabbits with 5-HD (5 mg/kg, i.v. bolus), a selective mitochondrial K(ATP) channel blocker but not by HMR 1883 (3 mg/kg). In the present study, higher levels of malondialdehyde (MDA) and lower levels of reduced glutathione (GSH) and superoxide dismutase (SOD) in necrotic zone of myocardium in all the 16 subgroups in Group II suggest little anti-free radical property of nicorandil and minoxidil. We conclude that intervention by intravenous administration of nicorandil and minoxidil (through the selective activation of mitochondrial K(ATP) channels) increased survival rate and exhibited antiarrhythmic and cardioprotective effects during coronary occlusion and reperfusion in anesthetized rabbits when administered prior to coronary occlusion. The cardiomyocyte mitochondrial K(ATP) channel may be a pharmacologically modulable target of cardioprotection and antiarrhythmic activity.

Therapeutic potential of nitric oxide donors in the prevention and treatment of atherosclerosis

Well-known risk factors for atherosclerosis include hypercholesterolaemia, hypertension, diabetes, and smoking. These conditions are associated with endothelial dysfunction, which itself is associated with reduced endothelial generation of nitric oxide (NO). This is an overview of the implications of NO generation in atherosclerosis and of the potential therapeutic benefit of drugs which donate NO, such as organic nitrates, nicorandil, and sydnonimines, or those which increase the availability of endogenous NO, such as statins, angiotensin-converting enzyme inhibitors, L-arginine, and tetrahydrobiopterin.

Cardiac Preconditioning during Percutaneous Coronary Interventions

Ischemic preconditioning (PC) is a polygenic defensive cellular adaptive phenomenon of the heart to ischemic stress, whereby the heart changes its phenotype to become more resistant to subsequent ischemia. Early and late of PC represent two chronologically and pathophysiologically distinct phases of this phenomenon, which can be recruited pharmacologically. We represent a post hoc analysis examining the late PC-mimetic effects of nitroglycerin (NTG) on peri-procedural myocardial necrosis during percutaneous coronary intervention (PCI). A group of 66 patients presenting with angina were randomized, 24 h prior to a scheduled PCI for single obstructive CAD, to a 4 h pretreatment with intravenous NTG or saline. Measurements of electrocardiographic ST-segment shifts, echocardiographic regional wall motion and angina scores demonstrated that NTG pre-treatment preconditioned the heart by rendering it resistant to ischemia during balloon inflations. NTG-pretreated patients exhibited trends towards lower average peak CK (131.1 vs. 188.6 U/L, P = 0.38) and CK-MB levels (7.1 vs. 12.6 ng/ml, P = 0.40). NTG, however, had no significant impact on the incidence of post-procedural MI or any cardiac enzyme elevation. The exploitation of ischemic and pharmacological PC may prove a useful strategy to confer cardioprotection during high-risk PCI and is worth exploring.

The Nicorandil-Induced Vasodilation in Humans Is Inhibited by Miconazole

Nicorandil, N-(2-hydroxyethyl)-nicotinamide nitrate, exerts its vasodilatory effects by opening ATP-sensitive potassium (K-ATP) channels and by acting as the exogenous nitric oxide (NO). It is not clear, however, whether the actions of other endothelium-dependent vasodilators, such as NO, endothelium-derived hyperpolarizing factor (EDHF), and prostaglandins, contribute to nicorandil-induced vasodilation in the vasculature in humans. We evaluated forearm blood flow (FBF) response to intraarterial infusion of nicorandil alone and in the presence of glibenclamide, a K-ATP channel inhibitor, N(G)-monomethyl-L-arginine, an NO synthase inhibitor, indomethacin, a cyclooxygenase inhibitor, or miconazol, a cytochrome P-450 inhibitor, in 24 healthy male subjects. FBF was measured using strain-gauge plethysmography. Infusion of nicorandil significantly increased the FBF response in a dose-dependent manner. Intraarterial infusion of glibenclamide attenuated nicorandil-induced vasodilation (160.9 +/- 21.2% versus 90.2 +/- 19.4%, P < 0.01), and miconazole also attenuated the FBF response to nicorandil (160.9 +/- 21.2% versus 66.1 +/- 9.2%, P < 0.001). N-monomethyl-L-arginine or indomethacin did not alter the FBF response to nicorandil. These findings suggest that nicorandil causes vasodilation in forearm circulation in humans, at least in part through a pathway that is dependent on K-ATP channels and cytochrome P-450, but not on endogenous NO and prostaglandins. EDHF may contribute to nicorandil-induced vasodilation in humans.

Intravenous nicorandil can reduce QT dispersion and prevent bradyarrhythmia during percutaneous transluminal coronary angioplasty of the right coronary artery

BACKGROUND

Nicorandil, a potassium channel opener, is used for the treatment of angina pectoris and has a pharmacologic preconditioning effect. This study evaluated whether intravenous nicorandil reduces QT dispersion and prevents bradyarrhythmia during percutaneous transluminal coronary angioplasty (PTCA) of the right coronary artery.

METHODS

A historical cohort study on the effect of nicorandil on QT dispersion and bradyarrhythmia was conducted. Fifty patients who underwent PTCA of the right coronary artery were enrolled. The patients were divided into a nicorandil (n = 25) group and control group (n = 25). Nicorandil was injected at 4 mg/h continuously 1 hour before PTCA in the nicorandil group. QT dispersion was measured at 1 hour before PTCA (baseline), immediately before PTCA, and 1 minute after the initiation of the first balloon inflation.

RESULTS

QT dispersion at 1 minute after the initiation of the first balloon inflation in the control group increased significantly (QT dispersion: 37.1 +/- 17.8 msec and 21.7 +/- 12.2 msec, respectively, P < .001 vs baseline in the control group), and this was larger than at 1 minute after the initiation of the first balloon inflation in the nicorandil group (QT dispersion: 37.1 +/- 17.8 msec and 20.8 +/- 9.4 msec, respectively, P < .001). By two-way repeated measures analysis of variance, there were significant interactions between the time factor and the grouping factor in QT dispersion (P < .001). Bradyarrhythmia was observed in 6 patients in the control group, but none was observed in the nicorandil group.

CONCLUSIONS

Intravenous nicorandil reduces QT dispersion and prevents bradyarrhythmia during PTCA of the right coronary artery.

Impact of nicorandil in angina: subgroup analyses

AIMS

IONA (impact of nicorandil in angina) is a randomised, double blind, placebo controlled trial of nicorandil, with a target dose of 20 mg twice daily. The consistency of benefits seen in subgroups is reported.

METHODS

The primary composite end point of the study was coronary heart disease death, non-fatal myocardial infarction, or unplanned hospitalisation for cardiac chest pain. Subgroups were defined using baseline characteristics including, age, sex, histories of smoking, diabetes, hypertension, myocardial infarction, revascularisation, anginal status, anti-anginal treatment, other cardiovascular drugs, and an overall assessment of risk.

RESULTS

A total of 5126 patients were randomised to receive nicorandil or identical placebo in addition to standard anti-anginal treatment. Overall, nicorandil reduced the incidence of the primary end point from 15.5% to 13.1% (hazard ratio (HR) 0.83, 95% confidence interval (CI) 0.72 to 0.97; p = 0.014). There was no evidence of significant heterogeneity of benefit across all subgroups studied. The absolute risk reduction was greatest and the numbers needed to treat to prevent one event was lowest in subjects at greatest risk.

CONCLUSIONS

The IONA study demonstrates a significant improvement in outcome by nicorandil treatment across a broad range of patients with stable angina.

Effects of nicorandil on cardiac sympathetic nerve activity after reperfusion therapy in patients with first anterior acute myocardial infarction

PURPOSE

Ischaemic preconditioning (PC) is a cardioprotective phenomenon in which short periods of myocardial ischaemia result in resistance to decreased contractile dysfunction during a subsequent period of sustained ischaemia. Nicorandil, an ATP-sensitive potassium channel opener, can induce PC effects on sympathetic nerves during myocardial ischaemia. However, its effects on cardiac sympathetic nerve activity (CSNA) and left ventricular remodelling have not been determined. In this study, we sought to determine whether nicorandil administration improves CSNA in patients with acute myocardial infarction (AMI).

METHODS

We studied 58 patients with first anterior AMI, who were randomly assigned to receive nicorandil (group A) or isosorbide dinitrate (group B) after primary coronary angioplasty. The nicorandil or isosorbide dinitrate was continuously infused for >48 h. The extent score (ES) was determined from 99mTc-pyrophosphate scintigraphy, and the total defect score (TDS) was determined from 201Tl scintigraphy 3-5 days after primary angioplasty. The left ventricular end-diastolic volume (LVEDV) and left ventricular ejection fraction (LVEF) were determined by left ventriculography 2 weeks later. The delayed heart/mediastinum count (H/M) ratio, delayed TDS and washout rate (WR) were determined from 123I-meta-iodobenzylguanidine (MIBG) images 3 weeks later. The left ventriculography results were re-examined 6 months after treatment.

RESULTS

Fifty patients originally enrolled in the trial completed the entire protocol. After treatment, no significant differences were observed in ES or left ventricular parameters between the two groups. However, in group A (n=25), the TDSs determined from 201Tl and 123I-MIBG were significantly lower (26+/-6 vs 30+/-5, P<0.01, and 32+/-8 vs 40+/-6, P<0.0001, respectively), the H/M ratio significantly higher (1.99+/-0.16 vs 1.77+/-0.30, P<0.005) and the WR significantly lower (36%+/-8% vs 44%+/-12%, P<0.005) than in group B (n=25). Moreover, 6 months after treatment, LVEDV and LVEF were better in group A than in group B.

CONCLUSION

These findings indicate that nicorandil can have beneficial effects on CSNA and left ventricular remodelling in patients with first anterior AMI.

NO donor-activated PKC-delta plays a pivotal role in ischemic myocardial protection through accelerated opening of mitochondrial K-ATP channels

Nitric oxide (NO) can activate protein kinase C (PKC) and the activation of mitochondrial ATP-sensitive potassium (K-ATP) channels is cardioprotective. However, interactions among NO, PKC, and mitochondrial K-ATP channels remain vague. To clarify the cardioprotective mechanism induced by nicorandil, we compared its ability to activate PKC isoforms with that of the mitochondrial K-ATP channel opener, diazoxide. We induced myocardial infarction in rats by 30 minutes of ischemia followed by reperfusion, then assessed the infarct size 3 weeks later. We also examined the translocation of PKC isoforms in the isolated perfused rat heart. Nicorandil and diazoxide reduced infarct size, and the effect of nicorandil, but not of diazoxide attenuated by the PKC inhibitor, chelerythrine, or by the NO quencher, carboxy PTIO. Immunoblotting revealed that nicorandil translocated PKC-delta to the mitochondria, and that this was inhibited by carboxy PTIO. The protective effect of nicorandil against myocardial infarction partly depended on the translocation of PKC-delta to the mitochondria, which we attributed to the NO donor effect of nicorandil. The PKC-delta- dependent activation of mitochondrial K-ATP channel opening might be synergistic with its direct effect, making nicorandil an efficient opener of such channels.

Nicorandil prevents oxidative stress-induced apoptosis in neurons by activating mitochondrial ATP-sensitive potassium channels

Nicorandil, a clinically useful drug for the treatment of ischemic heart disease, has an anti-apoptotic effect in cardiomyocytes, and activation of mitochondrial ATP-sensitive potassium (mitoKATP) channels underlies this effect. Recently, several studies showed that nicorandil reduced brain injury in animal models of brain ischemia. Based on these facts, we hypothesized that nicorandil may have anti-apoptotic effects in neurons mediated by mitoKATP channels. We investigated the effect of nicorandil on apoptosis induced by oxidative stress using cultured cerebellar granule neurons. Nicorandil (100 micromol/l) significantly suppressed the number of cells with TUNEL-positive nuclei and the increase in caspase-3 activity induced by 20 micromol/l H2O2. An indicator dye for mitochondrial inner membrane potential (DeltaPsim) revealed that nicorandil prevented the loss of DeltaPsim induced by H2O2 in a concentration-dependent manner. These effects were abolished by 5-hydroxydecanoate (5HD; 500 micromol/l), a mitoKATP channel blocker. The present results showed that nicorandil has anti-apoptotic effects in neurons, at least in part, by preserving DeltaPsim.

Comparison Between Nicorandil and Magnesium as an Adjunct Cardioprotective Agent to Percutaneous Coronary Intervention in Acute Anterior Myocardial Infarction

BACKGROUND

It has been reported that both nicorandil and magnesium have a cardioprotective effect in experimental ischemia - reperfusion models. In the present study, the cardioprotective effects of nicorandil and magnesium as an adjunct to reperfusion therapy in patients with acute myocardial infarction (AMI) were compared.

METHODS AND RESULTS

Forty consecutive patients with AMI caused by occlusion of anterior descending coronary artery were randomized into 3 groups: (1) Group N: nicorandil was given as 4 mg iv and 4 mg ic before reperfusion, followed by continuous infusion at 4 mg/h for 24 h; (2) Group M: magnesium was administered at 10 mmol iv before reperfusion, followed by continuous infusion at 0.4 mmol/h for 24 h; and (3) Group C: neither nicorandil nor magnesium was given. Left ventriculography was performed immediately after reperfusion and 3 months later. There was no significant change in regional wall motion (RWM) in either Group C or M, whereas that of group N improved significantly. The change in RWM in Group N was significantly greater than in Group C (Group N: 0.92+/-0.92, Group M: 0.44+/-0.80, Group C: -0.01+/-0.65, p<0.05).

CONCLUSIONS

The early administration of nicorandil as an adjunct to reperfusion is useful for cardioprotection in AMI, but magnesium is not.

Myocardial perfusion during transient slow-flow in the patient with old vein graft intervention: Assessment by serial measurement of pressure-derived fractional flow reserve and thermodilution-derived coronary flow reserve

A patient with distal slow-flow after stenting in the old vein graft intervention was reported. This case is a first in whom guidewire-based serial measurement of pressure-derived fractional flow reserve (FFR(myo)) and thermodilution-based coronary flow reserve (CFR(thermo)) clearly demonstrated the serial change of microvascular circulation. During slow-flow, CFR(thermo) remained in low value despite significant improvement of FFR(myo) from 0.61 to 0.90. After thrombus aspiration and nicorandil injection, coronary flow reestablished immediately. CFR(thermo) improved significantly from 1.3 during slow-flow to 3.6 after restoration of flow.

Synergistic effect of nicorandil and amlodipine on lysosomal hydrolases during experimental myocardial infarction in rats

The synergistic effect of nicorandil (K(ATP) channel opener) and amlodipine (calcium channel blocker) on lysosomal hydrolases in serum and heart was examined by determining the activity of beta-glucuronidase, beta-N-acetyl glucosaminidase, beta-galactosidase, cathepsin-D and acid phosphatase on isoproterenol-induced myocardial infarction in rats. The rats given isoproterenol (150 mg kg(-1) daily, i.p.) for 2 d showed significant increase in serum and heart lysosomal hydrolases activity. Isoproterenol administration to rats resulted in decreased stability of the membranes, which was reflected by the lowered activity of cathepsin-D and beta-glucuronidase in mitochondrial, nuclear, lysosomal and microsomal fractions. Pretreatment with nicorandil (2.5 mg kg(-1) daily, p.o.) and amlodipine (5.0 mg kg(-1) daily, p.o.) for 3 d significantly prevented these alterations and restored the enzyme activity to near normal. These findings demonstrate that the pretreatment with nicorandil and amlodipine could preserve lysosomal integrity and hence establish the cardioprotective effect of the combination.

Ischaemic preconditioning and outcomes after angioplasty: effects of drug therapy

Ischaemic preconditioning is one of the mechanisms by which human myocardium and human life are protected from ischaemic insults. One of the clinical situations in which we can discuss preconditioning is repetitive coronary occlusions by balloon inflation during elective percutaneous transluminal coronary angioplasty (PTCA) for stable angina pectoris. The severity of myocardial ischaemia assessed by ST-segment elevation or chest pain is less during the second balloon inflation compared with the first, if the duration of the first coronary occlusion is sufficient to precondition the myocardium. Many drugs have been identified that produce a reduction or induction in indices of preconditioning during PTCA. Preconditioning-mimetic drugs include adenosine, bradykinin, nitroglycerin and nicorandil. It is of paramount importance that we investigate and develop preconditioning-mimetic drugs which may enable an increased tolerance to effort angina, limit infarction size in susceptible patients, and decrease the incidence of sudden cardiac death as a result of ventricular tachyarrhythmias.

Modulation of slow waves by hyperpolarization with potassium channel openers in antral smooth muscle of the guinea-pig stomach

Modulation of spontaneous electrical activities (slow waves, pacemaker potentials and follower potentials) in response to hyperpolarization produced by the ATP-sensitive K+ channel openers (KCOs) pinacidil or nicorandil was investigated in smooth muscle tissues of the guinea-pig stomach antrum. With hyperpolarization, the amplitude of slow waves and follower potentials was reduced and that of pacemaker potentials was increased, with a minor modulation of their frequency. The attenuation of slow waves was associated with an inhibition of the 1st component and abolition of the 2nd component. All these actions of KCOs were antagonized by glibenclamide. An increase in the extracellular K+ concentration prevented the KCO-induced hyperpolarization with partial restoration of slow waves, suggesting that the inhibition was produced mainly by a decrease in membrane resistance. Exposure of tissues to KCOs for a long period of time (> 20 min) resulted in the reappearance of slow waves displaying both 1st and 2nd components. The 2nd component of the slow wave, which displayed a slower recovery, was inhibited again by 5-hydroxydecanoic acid, an inhibitor of mitochondrial ATP-sensitive K+ channels. Noradrenaline hyperpolarized the membrane by activating apamin-sensitive K+ channels and increased the amplitude and frequency of slow waves through activation of alpha 1-adrenoceptors, actions different from those of KCOs. Thus, inhibition of slow waves by KCOs may be primarily related to the decrease in amplitude of a passive electrotonic component, possibly due to a reduction of the input resistance. The hyperpolarization shifted the threshold potential for generation of the 2nd component of slow waves to negative levels, presumably due to modulation of mitochondrial functions.

The effects of vasodilators on the relaxation of guinea-pig aorta during acute recoil

BACKGROUND

We have investigated the effects of various vasodilators on smooth muscle relaxation during acute recoil with guinea-pig aorta to find effective therapies to prevent acute recoil at percutaneous transluminal coronary angioplasty (PTCA).

METHODS

Muscle strips from guinea-pig aorta without endothelium were placed in a bath filled with modified Krebs solution. The strip was isotonically stretched with a tension of 9 mN for 1 min, and then isometric tension was measured until the tension reached a steady state. Various vasodilators were applied during isometric tension measurement.

RESULTS

When no drug was applied (control), isometric tension reached a steady state within 20 min. The steady state was approximately 10% lower (more relaxed) than the stretched level. When isosorbide dinitrate (ISDN, 1 mM) was applied during isometric measurement, 18.7+/-5.3% greater relaxation occurred than in control relaxation (P<0.05, n=5). When nicorandil (1 mM) was applied, the following relaxation was 18.6+/-5.7% greater than control (P<0.05, n=8). The simultaneous application of glibenclamide (1 mM) completely inhibited such additional relaxation by nicorandil. Application of nifedipine (10 microM) caused a 12.9+/-2.5% greater relaxation than control (P=0.066, n=4). The first metabolite of sarpogrelate (BP984, 10 microM) caused much greater relaxation than control (23.7+/-7.9%, P<0.05, n=6). Amlodipine (10 microM), phentolamine (10 microM), and sarpogrelate (10 microM) had no influence on the relaxation of the strip.

CONCLUSIONS

ISDN, nicorandil and BP984 significantly increase relaxation of the muscle strips after stretching compared to the control. These vasodilators may reduce acute recoil of the smooth muscle after PTCA.

Effect of intracoronary nicorandil administration on preventing no-reflow/slow flow phenomenon during rotational atherectomy

A major limitation of the rotational atherectomy (RA) procedure is the occurrence of the no-reflow/slow flow phenomenon and the optimal strategy is still evolving. Recent clinical studies have demonstrated the beneficial effects of nicorandil, an adenosine triphosphate (ATP)-sensitive potassium channel opener, on no-reflow in patients with acute myocardial infarction. The purpose of this study was to evaluate the effect of nicorandil on no-reflow/slow flow phenomenon during RA procedures. Sixty-one patients who underwent RA of complex coronary lesions were randomly divided into 2 groups: (i) nicorandil cocktail (n=24 patients, 37 lesions) and (ii) verapamil cocktail (n=37 patients, 63 lesions). In each group, the drug cocktail mixed with pressurized saline was infused through the 4Fr Teflon sheath of the rotablator system during the RA procedure. In the nicorandil group, the drug cocktail consisted of 24 mg of nicorandil, 5 mg of nitroglycerin, and 10,000 U of heparin. In the verapamil group, the drug cocktail consisted of 10 mg of verapamil, 5 mg of nitroglycerin, and 10,000 U of heparin. Baseline and procedure characteristics did not differ between the 2 groups. RA was performed successfully, and death, Q-wave myocardial infarction, or emergency coronary artery bypass surgery did not occur in any patients. The no-reflow/slow flow phenomenon was observed in 11/63 (17.4%) lesions of the verapamil group, but in only 1/37 (2.7%) lesions of the nicorandil group (p=0.03). No untoward complications were observed during nicorandil infusion. These data indicate that the intracoronary continuous infusion of nicorandil during RA procedures is easy and safe, and prevents no-reflow/slow flow phenomenon more effectively than infusion of verapamil.

Adenosine production and its interaction with protection of ischemic and reperfusion injury of the myocardium

Adenosine exerts cardioprotective effects on the ischemic myocardium. A flexibly mounted microdialysis probe was used to measure the concentration of interstitial adenosine and to assess the activity of ecto-5'-nucleotidase (a key enzyme responsible for adenosine production) in in vivo rat hearts. The level of adenosine during perfusion of adenosine 5'-adenosine monophosphate (AMP) was given as an index of the activity of ecto-5'-nucleotidase in the tissue. Endogenous norepinephrine (NE) activates both alpha(1)-adrenoceptors and protein kinase C (PKC), which, in turn, activates ecto-5'-nucleotidase via phosphorylation thereby enhancing the production of interstitial adenosine. Histamine-release NE activates PKC, which increased ecto-5'-nucleotidase activity and augmented release of adenosine. Opening of cardiac ATP sensitive K(+) (K(ATP)) channels may cause hydroxyl radical (.OH) generation through NE release. Lysophosphatidylcholine (LPC), an endogenous amphiphiphilic lipid metabolite, also increases the concentration of interstitial adenosine in rat hearts, through the PKC-mediated activation of endogenous ecto-5'-nucleotidase. Nitric oxide (NO) facilitates the production of interstitial adenosine, via guanosine 3',5'-cyclic monophosphate (cGMP)-mediated activation of ecto-5'-nucleotidase as another pathway. These mechanisms play an important role in high sensitivity of the cardiac adenosine system. Adenosine plays an important role as a modulator of ischemic reperfusion injury, and that the production and mechanism of action of adenosine are linked with NE release.