Anti-free-radical and neutrophil-modulating properties of the nitrovasodilator, nicorandil

Nicorandil/ morphine crosstalk accounts for antinociception and hepatoprotection in hepatic fibrosis in rats: Distinct roles of opioid/cGMP and NO/KATP pathways

Previous report indicated that nicorandil potentiated morphine antinociception and attenuated hepatic injury in liver fibrotic rats. Herein, the underlying mechanisms of nicorandil/morphine interaction were investigated using pharmacological, biochemical, histopathological, and molecular docking studies. Male Wistar rats were injected intraperitoneally (i.p.) with carbon tetrachloride (CCl4, 40%, 2 ml/kg) twice weekly for 5 weeks to induce hepatic fibrosis. Nicorandil (15 mg/kg/day) was administered per os (p.o.) for 14 days in presence of the blockers; glibenclamide (KATP channel blocker, 5 mg/kg, p.o.), L-NG-nitro-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor, 15 mg/kg, p.o.), methylene blue (MB, guanylyl cyclase inhibitor, 2 mg/kg, i.p.) and naltrexone (opioid antagonist, 20 mg/kg, i.p.). At the end of the 5th week, analgesia was evaluated using tail flick and formalin tests along with biochemical determinations of liver function tests, oxidative stress markers and histopathological examination of liver tissues. Naltrexone and MB inhibited the antinociceptive activity of the combination. Furthermore, combined nicorandil/morphine regimen attenuated the release of endogenous peptides. Docking studies revealed a possible interaction of nicorandil on µ, κ and δ opioid receptors. Nicorandil/morphine combination protected against liver damage as evident by decreased liver enzymes, liver index, hyaluronic acid, lipid peroxidation, fibrotic insults, and increased superoxide dismutase activity. Nicorandil/morphine hepatoprotection and antioxidant activity were inhibited by glibenclamide and L-NAME but not by naltrexone or MB. These findings implicate opioid activation/cGMP versus NO/KATP channels in the augmented antinociception, and hepatoprotection, respectively, of the combined therapy and implicate provoked cross talk by nicorandil and morphine on opioid receptors and cGMP signaling pathway. That said, nicorandil/morphine combination provides a potential multitargeted therapy to alleviate pain and preserve liver function.

Nicorandil reduces morphine withdrawal symptoms, potentiates morphine antinociception, and ameliorates liver fibrosis in rats

AIMS

Chronic liver disease (CLD) is a serious medical condition affecting patients globally and pain management poses a unique challenge. ATP-sensitive potassium channels (K_ATP) are expressed in nociceptive neurons and hepatic cells. We tested the hypothesis whether morphine and nicorandil, K_ATP channel opener, alone and in combination possess hepatoprotective, antinociceptive effect and alter morphine physical dependence.

MAIN METHODS

Intraperitoneal injection (i.p.) of carbon tetrachloride (CCl₄) induced liver fibrosis in male Wistar rats. Nicorandil (15 mg/kg/day) was administered per os for two weeks. Morphine (3.8, 5, 10 mg/kg, i.p.) was administered prior to antinociception testing in tail flick and formalin tests. Morphine physical dependence following naloxone injection, fibrotic, oxidative stress markers, and liver histopathology were assessed.

KEY FINDINGS

Morphine alone, produced insignificant changes of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), hyaluronic acid (HA), hepatic hydroxyproline (Hyp), malondialdehyde (MDA), and superoxide dismutase (SOD) levels and exerted significant antinociception in the pain models. Nicorandil alone protected against liver damage (decreased serum ALT, AST, HA, hepatic Hyp, MDA, increased SOD levels, improved fibrosis scores). Nicorandil/morphine combination produced remarkable hepatoprotection and persistent analgesia compared to morphine alone as evidenced by reduced (EC50) of morphine. Nicorandil augmented morphine analgesia and markedly decreased withdrawal signs in morphine-dependent rats.

SIGNIFICANCE

The data showed for the first time, the hepatoprotection and augmented antinociception mediated by nicorandil/morphine combination in liver fibrosis via antioxidant and antifibrotic mechanisms. Nicorandil ameliorated withdrawal signs in morphine dependence in CLD. Thus, combining nicorandil/morphine provides a novel treatment strategy to ameliorate hepatic injury, potentiate antinociception and overcome morphine-induced physical dependence in liver fibrosis.

Nicorandil mitigates amiodarone-induced pulmonary toxicity and fibrosis in association with the inhibition of lung TGF-β1/PI3K/Akt1-p/mTOR axis in rats

The long-term side effect of the antiarrhythmic drug, amiodarone (AMIO), such as lung toxicity, remains a critical clinical issue. The previous knowledge denotes diverse antioxidant, anti-inflammatory, and antifibrotic properties of the anti-anginal drug, nicorandil (NI). Therefore, we aimed to investigate the possible protective effect of NI on pulmonary tissue remodelling following AMIO-induced lung toxicity. The included rats were assigned into four equal groups (n = 8): (1) control, (2) control group that received NI 10 mg kg^-1  day^-1 , (3) model group that received AMIO in a dose of 60 mg kg^-1  day^-1 , and (4) treated group (AMIO-NI) that were treated with AMIO plus NI as shown above. Drug administration continued for 10 weeks. AMIO resulted in deteriorated (p < 0.001) pulmonary functions accompanied by respiratory acidosis. AMIO showed an obvious histological injury score with intense collagen deposition, disturbed nitric oxide synthase enzymes (NOS/iNOS), and increased alpha smooth muscle actin expression. Furthermore, AMIO upregulated the transforming growth factor (TGF-β1)/phosphoinositide-3 kinase (PI3K)-Akt1-p/mammalian target of rapamycin (mTOR) axis, which determined the possible mechanism of AMIO on pulmonary remodelling. NI treatment significantly (p < 0.001) prevented the AMIO-induced lung toxicity, as well as inhibited the TGF-β1/PI3K/Akt1-p/mTOR axis in the lung tissue of rats. The results were confirmed by an in-vitro study. CONCLUSION: The current results revealed that NI was effective in preserving the lung structure and functions. Amelioration of the oxidative stress and modulation of TGF-β1/PI3K/Akt1-p/mTOR have been achieved. This study suggests NI administration as a preventive therapy from the serious pulmonary fibrosis side effect of AMIO.

Hypothesis: The potential therapeutic role of nicorandil in COVID-19

At present, there is yet no specific antiviral treatment or immunization against the newly identified human severe acute respiratory syndrome virus (SARS-CoV2) that results in a rapidly progressive pandemic coronavirus disease 2019 (COVID-19). We believe in a crucial need for a clinical strategy to counteract this viral pandemic based on the known pathogenesis throughout the disease course. Evidence suggests that exaggerated patient's inflammatory response and oxidative stress are likely to aggravate the disease pathology. The resulting endothelial dysfunction further induces fibrosis and coagulopathy. These disturbances can generate severe acute respiratory distress syndrome (ARDS) that can progress into respiratory and circulatory failure. Nicorandil is an anti-anginal vasodilator drug acts by increasing nitric oxide bioavailability and opening of the KATP channel. Recently, nicorandil has been recognized to possess multiple protective effects against tissue injury. Here, we address a possible modulatory role of nicorandil against COVID-19 pathogenesis. We hypothesise nicorandil would be an effective form of adjuvant therapy against COVID-19.

Nicorandil for Periprocedural Myocardial Injury in Elective Percutaneous Coronary Intervention: A Meta-Analysis of 10 Randomized Controlled Trials

The clinical outcomes of nicorandil in percutaneous coronary intervention (PCI) are conflicting. We sought to evaluate the effects of nicorandil on periprocedural myocardial injury (PMI) in elective PCI. Eligible studies that reported the effect of nicorandil on PMI in elective PCI were obtained from PubMed, Web of Science, and Cochrane Library (up to October 28, 2019). The outcomes were PMI and major adverse cardiovascular and cerebrovascular events (MACCEs). Ten randomized controlled trials with 1304 patients undergoing elective PCI were evaluated. Nicorandil significantly reduced the incidence of PMI (odds ratio [OR] = 0.48; P = .0003); however, there was no significant difference in MACCEs (OR = 0.80; P = .45) between the 2 groups. Subgroup analyses showed that nicorandil significantly lowered the PMI risk when only patients with stable coronary artery disease (OR = 0.41; P = .0008) were considered and when nicorandil was administered intravenously (OR = 0.41; P = .0007) or orally (OR = 0.33; P = .0001). This meta-analysis suggests that nicorandil could reduce the incidence of PMI without increasing the occurrence of MACCEs in elective PCI. The effect of nicorandil in lowering the PMI risk is associated with the diagnosis of the patients and the route of nicorandil administration.

Doxorubicin-induced oxidative stress: The protective effect of nicorandil on HL-1 cardiomyocytes

The primary cardiotoxic action of doxorubicin when used as antitumor drug is attributed to the generation of reactive oxygen species (ROS) therefore effective cardioprotection therapies are needed. In this sense, the antianginal drug nicorandil has been shown to be effective in cardioprotection from ischemic conditions but the underlying molecular mechanism to cope with doxorubicin-induced ROS is unclear. Our in vitro study using the HL-1 cardiomyocyte cell line derived from mouse atria reveals that the endogenous nitric oxide (NO) production was stimulated by nicorandil and arrested by NO synthase inhibition. Moreover, while the NO synthase activity was inhibited by doxorubicin-induced ROS, the NO synthase inhibition did not affect doxorubicin-induced ROS. The inhibition of NO synthase activity by doxorubicin was totally prevented by preincubation with nicorandil. Nicorandil also concentration-dependently (10 to 100 μM) decreased doxorubicin-induced ROS and the effect was antagonized by 5-hydroxydecanoate. The inhibition profile of doxorubicin-induced ROS by nicorandil was unaltered when an L-arginine derivative or a protein kinase G inhibitor was present. Preincubation with pinacidil mimicked the effect of nicorandil and the protection was eliminated by glibenclamide. Quantitative colocalization of fluorescence indicated that the mitochondrion was the target organelle of nicorandil and the observed response was a decrease in the mitochondrial inner membrane potential. Interference with H⁺ movement across the mitochondrial inner membrane, leading to depolarization, also protected from doxorubicin-induced ROS. The data indicate that activation of the mitochondrial ATP-sensitive K⁺ channel by nicorandil causing mitochondrial depolarization, without participation of the NO donor activity, was responsible for inhibition of the mitochondrial NADPH oxidase that is the main contributor to ROS production in cardiomyocytes. Impairment of the cytosolic Ca²⁺ signal induced by caffeine and the increase in lipid peroxidation, both of which are indicators of doxorubicin-induced oxidative stress, were also prevented by nicorandil.

Effect of Potassium-Channel Opener Therapy on Reperfused Infarction in Hypertrophied Hearts: Demonstration of Preconditioning by Using Functional and Contrast-Enhanced Magnetic Resonance Imaging

Effects of therapy with the potassium-channel opener and vasodilator nicorandil were studied in reperfused infarction of hypertrophied hearts by using magnetic resonance imaging (MRI), hemodynamic measurements, and histochemical staining. Aortic banding was performed on 22 Sprague-Dawley rats to induce left ventricular (LV) hypertrophy; 11 were the controls. Eight weeks later, the left coronary artery was occluded for 25 minutes in all 33 animals, followed by 3 hours of reperfusion. During occlusion, 11 rats with LV hypertrophy received nicorandil (0.1 mg/kg bolus and 1.5 mg/kg/h for 3 hours). The new necrosis-specific contrast agent Gadophrin-3 was administered to all animals to delineate infarction on multislice T1-weighted spin-echo MRI. Nicorandil increased ischemic tolerance of LV hypertrophy as shown by the reduction of infarction size from 19.3% ± 1.3% to 10.0% ± 2.5% LV ( P= .005). Infarction size in treated animals was identical to control (9.3% ± 1.6%). Close correlation was found between MRI and postmortem findings. Functional MRI revealed an improvement in ejection fraction in nicorandil-treated hearts (48.5% ± 3.4% vs 38.1% ± 3.2%, P = .04). LV end-diastolic volume and pressure, aortic pressure, and peripheral vascular resistance were highest in untreated hypertrophied hearts. Brief ischemia caused severe injury in hypertrophied hearts. Infusing nicorandil increased the tolerance of hypertrophied hearts to ischemia. MRI is a suitable technique for the evaluation of new therapies in LV hypertrophy.

Nicorandil Attenuates Reperfusion Injury after Long Cardioplegic Arrest

The cardioprotective efficacy of nicorandil in cardiac surgery was determined using a surgically relevant 4-hr cardioplegic arrest model. Each isolated rabbit heart was parabiotically blood-perfused using a modified Langendorff column. The magnitude of left ventricular developed pressure and rate of change of developed pressure over time were measured before (baseline) and after ischemia. Nicorandil was administered either pre-ischemia, post-ischemia, pre/post-ischemia, or continuously (before, during, and after ischemia). The endothelium of the coronary artery was observed by scanning electron microscopy. Serum myeloperoxidase activities were also measured. Although pretreatment with nicorandil did not affect recovery of developed pressure, administration of nicorandil after ischemia, or before and after ischemia, enhanced the recovery of developed pressure. Serum myeloperoxidase activity was decreased in the pre/post-ischemia and continuous groups. Endothelial reperfusion injury decreased in all nicorandil-treated groups. Administration of nicorandil attenuated ischemia-reperfusion injury of the myocardium and coronary endothelium while ameliorating leukocyte activation. In the event of unexpected prolonged cardioplegic arrest, administration of nicorandil, even just after declamping, may improve cardiac function. However, pre-ischemia administration alone was not helpful in the heart subjected to prolonged cardioplegic arrest.

Nicorandil in patients with acute myocardial infarction undergoing primary percutaneous coronary intervention: a systematic review and meta-analysis

Background

Nicorandil, as an adjunctive therapy with primary percutaneous coronary intervention (PCI), had controversial benefits in cardioprotection in patients with acute myocardial infarction (AMI).

Methods and Results

We performed a systematic review of randomized controlled trials (RCTs) comparing treatment with nicorandil prior to reperfusion therapy with control (placebo or no nicorandil) in patients who suffered from AMI and performed primary PCI. PubMed, EMBASE and CENTRAL databases and other sources were searched without language and publication restriction. 14 trials involving 1680 patients were included into this meta-analysis. Nicorandil significantly reduced the incidence of thrombolysis in myocardial infarction (TIMI) flow grade ≤2 (risk ratio [RR], 0.57; 95% confidence interval [CI]: 0.42 to 0.79), the Timi frame count (TFC) (mean difference [MD], -5.19; 95% CI: -7.13 to -3.26), increased left ventricular ejection fraction (LVEF) (%) (MD, 3.08; 95% CI: 0.79 to 5.36), and reduced the incidence of ventricular arrhythmia (RR, 0.53; 95% CI: 0.37 to 0.76) and congestive heart failure (CHF) (RR, 0.41; 95% CI: 0.22 to 0.75). No difference in the pear creatine kinase (CK) value (MD, -290.19; 95% CI: -793.75 to 213.36) or cardiac death (RR, 0.39; 95% CI: 0.09 to 1.67) was observed.

Conclusions

Nicorandil prior to reperfusion is associated with improvement of coronary reflow as well as suppression of ventricular arrhythmia, and further improves left ventricular function in patients who suffered from AMI and underwent primary PCI. But the definite clinical benefits of nicorandil were not found, which may be due to the small sample size of the selected studies.

Effect of nicorandil and amlodipine on bio-chemical parameters during isoproterenol induced myocardial necrosis in rats

OBJECTIVE

To investigate the protective effect of nicorandil and amlodipine in isoproterenol induced myocardial necrosis in rats.

METHODS

The effect of nicorandil and amlodipine on bio-chemical parameters during isoproterenol induced myocardial necrosis in rats was examined by determining the activity of creatine phosphokinase (CK), lactate dehydrogenase (LDH), and transaminases (AST, ALT) in the serum of the animals.

RESULTS

Isoproterenol (150mg/kg/day) administered rats showed statistically significant rise in activities of LDH(1.02±0.19 to 1.85±0.05), CK(4.3±0.19 to 7.37±.27), AST(0.38±.03 to 0.78±.05) and ALT(0.19±.017 to 0.346±.027) in the serum. Pre-co-treatment of rats with nicorandil and amlodipine significantly lowered the raised levels of these enzymes and thereby restoring the enzyme activity to near normal as was clear from the chart i.e. LDH was 1.10±0.04, CK was 4.37±0.19, AST and ALT were 0.39±0.028 and 0.199±0.04 respectively.

CONCLUSION

It is demonstrated that pre-co-treatment with nicorandil and amlodipine either alone or in combination help in providing protective effect on isoproterenol induced myocardial necrosis.

Protective mechanism of nicorandil on rat myocardial ischemia-reperfusion

OBJECTIVES

To study the protective mechanism of nicorandil on myocardial ischemia-reperfusion injury.

METHODS

Fifty rats were randomly divided into five groups, four of which were operated on to produce myocardial ischemia-reperfusion. Nicorandil (5 mg/kg) was administrated by intravenous injection to three of the groups. The myocardial ultrastructure was observed by electron microscope. The expression levels of the antiapoptotic protein Bcl-2 and the pro-apoptotic protein Bax were detected by immunohistochemical staining with rhodamine 123. The mitochondrial membrane potential was detected by spectrophotometry.

RESULTS

The activity of lactate dehydrogenase (LDH) and malondialdehyde (MDA) content was decreased and the activity of superoxide dismutase (SOD) was increased in the three nicorandil groups, compared with those in the group without nicorandil (P < 0.01, P < 0.05). The positive staining level of the expressed Bcl-2 was increased and the expressed Bax was decreased (P < 0.01) in the three nicorandil groups, compared with those in the group without nicorandil. The mitochondrial inner membrane potential was increased in the three nicorandil groups compared with that in the group without nicorandil (P < 0.05).

CONCLUSION

A suitable level of nicorandil has a protective effect on rats' myocardial ischemia-reperfusion injury, and is mainly based on the opening of the mitochondrial KATP channel and the lowing of Ca overload.

High index of microcirculatory resistance level after successful primary percutaneous coronary intervention can be improved by intracoronary administration of nicorandil

BACKGROUND

Although microvascular dysfunction following percutaneous coronary intervention (PCI) can be evaluated with the index of microcirculatory resistance (IMR), no method of treatment has been established. We hypothesized that intracoronary administration of nicorandil can improve IMR after successful primary PCI in patients with ST-segment elevation myocardial infarction (STEMI).

METHODS AND RESULTS

In 40 patients with first STEMI after successful primary PCI, IMR was measured using PressureWire(TM) Certus (St. Jude Medical, MN, USA). In 20 of the patients (Group N), IMR was measured at baseline and after intracoronary nicorandil (2 mg/10 ml). In the other 20 patients (Control), IMR was measured at baseline, after intracoronary saline (10 ml) and after intracoronary nicorandil (2 mg/10 ml). In Group N, IMR significantly decreased after intracoronary nicorandil (median IMR, 27.7-18.7 U, P<0.0001). In the Control group, IMR did not change after saline administration (median IMR, 24.3-23.8 U, P=0.8193), but was significantly decreased after intracoronary nicorandil (median IMR, 23.8-14.9 U, P<0.0001). Next, all 40 patients were divided into subgroups by tertile of baseline IMR. In those with intermediate to high IMR (baseline IMR > or =21), intracoronary nicorandil significantly decreased IMR, although it did not change IMR in those with low IMR (baseline IMR <21).

CONCLUSIONS

High IMR levels in patients with STEMI after successful primary PCI can be improved by intracoronary administration of nicorandil.

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.

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.

Effects of perhexiline and nitroglycerin on vascular, neutrophil and platelet function in patients with stable angina pectoris

Perhexiline, a "metabolic" anti-anginal agent currently under investigation in management of congestive heart failure and acute coronary syndromes improves platelet nitric oxide responsiveness in patients with impaired responsiveness. The current study investigated possible interactions between perhexiline and the nitric oxide donor nitroglycerin on arterial stiffness, neutrophil superoxide release and on platelet nitric oxide responsiveness. Patients (n=39) with stable angina pectoris, awaiting cardiac catheterization were randomized to additional perhexiline or unchanged drug therapy; all patients received nitroglycerin infusion for 2 h. Vasomotor responses to perhexiline and combined perhexiline/nitroglycerin were examined using changes in augmentation index, measured via applanation tonometry. Neutrophil superoxide release was measured ex vivo utilizing lucigenin mediated chemiluminescence and effect of perhexiline on inhibition of platelet aggregation by sodium nitroprusside was also measured. Perhexiline alone did not affect augmentation index, neutrophil superoxide release, or ex vivo platelet sodium nitroprusside response. Nitroglycerin decreased augmentation index (P<0.01) and superoxide release (P<0.05). Magnitude of inhibition of superoxide release was significantly enhanced by perhexiline pre-treatment (P<0.05); however perhexiline had no effect on magnitude of vasomotor response to nitroglycerin. In conclusion, perhexiline exerts no effects on arterial stiffness and does not potentiate nitroglycerin induced dilatation. In patients with normal platelet function perhexiline does not affect platelet nitric oxide responsiveness. In vivo low dose nitroglycerin inhibits neutrophil superoxide release; this effect is potentiated by pre-treatment with perhexiline. These "anti-inflammatory" effects of nitroglycerin may contribute to utility in acute coronary syndromes and congestive heart failure.

Investigation of the Mechanisms Underlying the Gastroprotective Effect of Nicorandil

AIM

This study investigated possible mechanisms underlying the gastroprotective effect of nicorandil on experimentally-induced gastric lesions in rats.

METHODS

Rats were randomly assigned to vehicle-, nicorandil (10 mg/kg)-, glibenclamide (6 mg/kg)-, nicorandil + glibenclamide- and cimetidine-pretreated groups, in addition to non-stressed control group, to demonstrate whether the K(ATP )channel opening contributed to nicorandil's gastroprotection. Lesions were induced by water immersion-restraint stress (WIRS) and ulcer indices were determined. Gastric juice parameters (pH, acid output, pepsin and mucin concentrations) were determined. Another set of rats was divided into control, saline-pretreated and nicorandil (10 mg/kg)-pretreated groups. Rats underwent WIRS and their stomachs were used for determination of gastric mucosal lipid peroxides, histamine, PGE(2), and total nitrites levels.

RESULTS

Nicorandil displayed significant protection against gastric lesions formation, abolished by concomitant administration of glibenclamide. Nicorandil significantly reduced gastric acid and pepsin secretion, but upon coadministration with glibenclamide, these effects were blocked. Additionally, nicorandil significantly reduced gastric mucosal lipid peroxides and total nitrites, but did not affect PGE(2) and histamine levels.

CONCLUSION

Results confirm a gastroprotective effect for nicorandil, the mechanism of which comprises K(ATP) channel opening, free radical scavenging, decrease of pepsin and acid secretion and prevention of the detrimental rise in nitric oxide during WIRS.

LPS from Escherichia coli protects against indomethacin-induced gastropathy in rats--role of ATP-sensitive potassium channels

The effect of lipopolysaccharide (LPS) in gastric protection has not been elucidated, but ATP-sensitive potassium (K(ATP)) channels are known to be involved in gastric defense. We evaluated the effect of LPS administration on indomethacin-induced gastropathy, and the role of K(ATP) channels in this event. Rats received intravenous (i.v.) LPS administration. After 1/2, 6, 24 or 48 h, indomethacin was injected. 3H later, gastric damage and myeloperoxidase activity were determined. Another group received LPS and 5 h later, glibenclamide, diazoxide or glibenclamide plus diazoxide. After 1 h, the rats received indomethacin and 3 h later, gastric damage and myeloperoxidase activity were evaluated. LPS reduced dose dependently gastric damage and myeloperoxidase activity induced by indomethacin. Glibenclamide reversed this LPS effect on indomethacin-induced gastropathy. Glibenclamide plus diazoxide administration did not change this LPS effect. Thus LPS has a protective effect against indomethacin-induced gastropathy, probably through activation of K(ATP) channels.

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 attenuates NF-kappaB activation, adhesion molecule expression, and cytokine production in patients with coronary artery bypass surgery

Nicorandil (NCR), a KATP channel opener, has been reported to preserve microvascular integrity in patients with reperfused myocardial infarction. We tested the hypothesis that NCR suppresses myocardial ischemia and reperfusion injury via the attenuation of cytokine production. Forty patients who underwent coronary artery bypass graft surgery were studied. The patients were randomly divided into two groups, i.e., the patients with NCR (4-6 mg/h; N group, n = 20) or without NCR (C group, n = 20). Cardiac surgery was performed under anesthesia using fentanyl and propofol. Blood were sampled at the time of induction of anesthesia, pre-cardiopulmonary bypass, 60 min after aortic occlusion, and 60, 120, and 180 min after declamping the aorta. The activation of NF-kappaB, expression of adhesion molecules, and cytokine production were evaluated in blood samples from the control volunteers by flow cytometric analysis with or without lipopolysaccharide (LPS) stimulation in vitro. Serum IL-6 and IL-8 levels in both groups increased 60 min after declamping the aorta compared with the preoperative value (P < 0.001); the increases of these parameters in N group were lower than those in C group (P < 0.05). Serum creatine kinase with muscle and brain subunits and troponin-T levels increased 60 min after declamping the aorta in two groups (P < 0,001), but the increases of both parameters in N group were lower than those in C group (P < 0.05). NF-kappaB activation, CD11b/CD18 expression, and the production of TNF-alpha, IL-8, and IL-6 in monocytes and granulocytes were inhibited by NCR in vitro. NCR suppressed the increase of inflammatory cytokines such as IL-6 and IL-8 levels, and reduced myocardial reperfusion injury. The inhibition on NF-kappaB activation, adhesion molecule expression, and cytokine production may be one of the important mechanisms of myocardial protection of NCR.

Long-Term Oral Treatment with Nicorandil Prevents the Progression of Left Ventricular Hypertrophy and Preserves Viability

Left ventricular (LV) hypertrophy and myocardial infarction play important roles in the progressive LV dysfunction. We hypothesized that the potassium-channel opener and nitrate-like vasodilator nicorandil prevents the development of LV hypertrophy and preserves myocardial viability. Twenty-four rats were subjected to aortic stenosis for 8 weeks to produce LV hypertrophy and assigned to non-treated and nicorandil-treated (3 mg/kg/d) groups. A third group (n = 12) without stenosis or treatment served as control. All 36 animals were subjected to reperfused infarction by 25-minute occlusion of the left coronary artery followed by 3 hours of reperfusion. Spin-echo magnetic resonance (MR) images were acquired to measure infarction size, LV mass, volumes, ejection fraction, and wall thickness. A necrosis-specific contrast agent, Gadophrin-3, was used to delineate necrotic myocardium. Aortic and LV pressures were measured invasively. At postmortem, LV mass and infarction size were determined and compared with MR findings. Nicorandil prevented the development of LV hypertrophy. Infarction size of nicorandil-treated animals was similar to control animals. Non-treated animals with aortic banding had higher LV mass (P < 0.001), lower ejection fraction (P = 0.006), and larger infarction size (P < 0.001) than treated and control animals. MR and postmortem data showed close agreement. Nicorandil therapy prevented the development of cardiac hypertrophy and protected myocardium against ischemia.

Effect of nicorandil, a K+ATP -channel opener, on coronary capillary architecture and volume after early myocardial ischemia-reperfusion--a 3-dimensional confocal laser microscopic study--

BACKGROUND

Previous experimental and clinical studies have reported that nicorandil, an adenosine triphosphate (ATP)-sensitive K+ channel opener, exerts a beneficial effect on microvascular function and clinical outcome after myocardial ischemia. The present study assessed whether intravenous administration of nicorandil affects the 3-dimensional (3-D) architectural characteristics of capillaries and their volume after early myocardial reperfusion.

METHODS AND RESULTS

Using the hearts of open-chest anesthetized rats, the left anterior descending artery was occluded for 7 min followed by reperfusion. Nicorandil or saline was infused intravenously during occlusion and reperfusion. The entire coronary microvasculature was filled with contrast medium after the hearts were arrested. Capillaries were observed 3-dimensionally by confocal laser scanning microscopy in both the control area and reperfused area of all samples. The capillary volume fraction was computed from the 3-D images. The reperfused area in both the nicorandil and saline groups showed characteristic architectural changes of the capillaries. Capillary volume fraction in the reperfused area was significantly reduced in saline group, compared with nicorandil group [12.7+/-7.2% vs 18.1 +/-5.3% (p<0.01)].

CONCLUSIONS

Intravenous nicorandil administration has a beneficial effect on capillary damage after reperfusion.

Nicorandil improves cardiac function and clinical outcome in patients with acute myocardial infarction undergoing primary percutaneous coronary intervention: role of inhibitory effect on reactive oxygen species formation

BACKGROUND

Early reperfusion therapy improves the clinical outcomes of patients with acute myocardial infarction (AMI), but benefits are limited by reperfusion injury in some patients. We examined the effect of nicorandil, a hybrid of K(ATP) channel opener and nicotinamide nitrate, on reactive oxygen species (ROS) formation and clinical outcomes after primary percutaneous coronary intervention (PCI) for AMI.

METHODS

Fifty-eight patients with AMI were randomized into control (n = 25) and nicorandil pretreatment groups (n = 33). In the nicorandil group, nicorandil (4 mg as a bolus injection followed by constant infusion at 8 mg/hour for 24 hours) was administered just after admission. ROS formation was assessed by measuring urinary excretion of 8-epi-prostaglandin F2alpha (PGF2alpha) and compared between the 2 groups. Cardiac function and the incidence of reperfusion injury and cardiac events were also compared.

RESULTS

Urinary 8-epi-PGF2alpha excretion was increased 2-fold at 60 to 90 minutes after PCI in the control group, whereas it was unchanged after PCI in the nicorandil group (P <.0001 between the 2 groups). The incidence of no-reflow phenomenon was lower in the nicorandil group than in the control group. Left ventricular ejection fraction and cardiac index at 6 months were greater in the nicorandil group than in controls. Plasma brain natriuretic peptide level at 6 months was lower in the nicorandil group. Incidences of inhospital cardiac events and rehospitalization were lower in the nicorandil group than in controls.

CONCLUSIONS

Nicorandil improves cardiac function and clinical outcomes in patients with AMI. Suppression of ROS formation may be involved in the mechanism.

Plasmolemmal potassium gradient does not affect lung protection by an ATP-regulated potassium channel opener

BACKGROUND

We have previously shown that metabolic arrest induced with ATP-regulated potassium channel openers (PCOs) can improve lung preservation by adding Aprikalim (a PCO, Rhone-Poulene Roher) to modified Euro-Collins solution for pulmonary artery flush. Because the membrane hyperpolarizing effects of a PCO potentially competes with the depolarizing effects of a hyperkalemic solution, this study evaluated the effects of the potassium gradient on PCO-mediated lung protection.

STUDY DESIGN

Twenty rabbits underwent lung protection in four groups. Group 1 underwent harvest and reperfusion as a "no ischemia" control. Groups 2, 3, and 4 underwent harvest followed by 18 hours of cold ischemic storage before reperfusion. Groups 1 and 4 received Euro Collins as the pulmonary flush at induction of ischemia. Group 2 received Euro Collins plus Aprikalim (100 microM); and group 3 received lactated Ringer's plus Aprikalim. After ischemic storage, the lungs were reperfused with autologous blood for 2 hours. Every 30 minutes, the lungs were given a 10-minute 100% fractional inspired oxygen (F(i)O(2)) challenge to measure maximal gas exchange as an indication of graft function.

RESULTS

Repeated measures ANOVA showed Aprikalim improved graft function after 18 hours of cold ischemia (p < 0.0001). No significant differences were found when Aprikalim was used in either Euro-Collins (group 2) or lactated Ringer's (group 3) solution.

CONCLUSIONS

The ability of the PCO Aprikalim to preserve gas exchange in a model of hypothermic pulmonary ischemia-reperfusion injury was not affected by the plasmolemmal potassium gradient. This is consistent with recent findings in myocardial protection studies that the protective effects of PCOs may be intracellular.

Nicorandil versus isosorbide dinitrate as adjunctive treatment to direct balloon angioplasty in acute myocardial infarction

OBJECTIVE

To compare the effects of nicorandil (a hybrid ATP sensitive potassium channel (K+(ATP) channel) opener/nitric oxide donor) with those of isosorbide dinitrate (ISDN) on myocardial microcirculation and cardiac function in patients with acute myocardial infarction (AMI) who had undergone reperfusion treatment by direct balloon angioplasty.

DESIGN

Double blind randomised study.

PATIENTS

60 patients with AMI in Killip class I.

INTERVENTIONS

Patients were assigned into two treatment groups: a nicorandil group (n = 30) and an ISDN group (n = 30). Each drug was infused intravenously at 6 mg/h for 72 hours starting at admission and was administered directly to the treated coronary artery immediately after angioplasty.

RESULTS

Compared with ISDN, nicorandil more frequently caused recovery of ST segment elevation just after reperfusion (15 of 27 (55.5%) in the nicorandil group v 5 of 26 (19.2%) in the ISDN group, p = 0.006). The nicorandil group had higher values of averaged peak velocity 40 minutes after reperfusion (mean (SD) 24.8 (13.3) cm/s v 16.0 (11.1) cm/s, p = 0.045) and higher values of regional wall motion of the infarcted area three weeks after onset of AMI (-1.78 (1.11) v -2.50 (1.04) SD/chord, p = 0.046).

CONCLUSIONS

A combination of nicorandil drip infusion starting before reperfusion and intracoronary injection immediately after reperfusion is more effective than a similarly performed infusion of ISDN in preserving myocardial microcirculation in the reperfused AMI area. The nicorandil regimen resulted in better left ventricular regional wall motion.

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.

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.

Warm ischemia lung protection with pinacidil: an ATP regulated potassium channel opener

BACKGROUND

Ischemia/reperfusion injury remains a limiting factor in lung transplantation. Traditional hyperkalemic preservation solutions are associated with a host of metabolic derangements. ATP-regulated potassium channel openers (PCOs) may provide an attractive alternative to traditional solutions by utilizing inherent mechanisms of ischemic preconditioning. The purpose of this study was to assess warm ischemia graft protection with pinacidil, a nonspecific PCO.

METHODS

An isolated recirculating blood perfused ventilated rabbit lung model was used (n = 15). No ischemia control lungs underwent immediate reperfusion (n = 5). Warm ischemia control lungs were flushed with lactated Ringers (LR), stored at 37 degrees C for 2.5 hours and then reperfused for 2 hours (n = 5). PCO protected lungs were flushed with LR + 100 micromol/L pinacidil, stored, and then reperfused (n = 5). Intermittent blood gases were taken from the pulmonary artery and left atria. Every 30 minutes, graft function was assessed with a 10-minute 100% fractional inspired oxygen concentration challenge to measure maximal gas exchange. Lung samples were graded for histologic injury and assayed for myeloperoxidase activity.

RESULTS

A mixed-models repeated measures ANOVA demonstrated a significant difference between groups. Tukey's honestly significant difference multiple comparison test demonstrated significantly improved graft function and reduced histologic injury with pinacidil protection compared with the warm ischemia controls. There was no significant difference in graft function or pathology grade between the pinacidil protected lungs and the no ischemia controls. A similar trend, although not significant, was seen in myeloperoxdiase activity.

CONCLUSIONS

Potassium channel openers with pinacidil can provide pulmonary protection against warm ischemia reperfusion injury.

Myocardial protection of immature rabbits: polarizing versus depolarizing

BACKGROUND

This study was designed to identify the potassium-channel opener pinacidil as a cardioplegic agent vs hyperkalemic cardioplegia in terms of its efficacy in immature cardioprotection.

METHODS

By a Langendorff model, 21 hearts of 21- to 28-day-old New Zealand rabbits underwent 90 min of global hypothermic (15 degrees C) ischemia protected with a different single dose of hypothermic (4 degrees C) cardioplegia (pinacidil [50 micromol/l], St. Thomas' solution combined with pinacidil [50 micromol/l], and St. Thomas' solution). The percent recovery of the cardiac function, creatine kinase release, and cellular ultrastructure were compared.

RESULTS

Pinacidil (50 micromol/l) provided significantly the best postreperfused percentage recovery of the function than the other groups; pinacidil cardioplegia showed a significant reduction of creatine kinase release in the coronary flow compared with the other groups; St. Thomas' solution combined with pinacidil showed the highest release. Percentage recovery of the coronary flow, water contents, and ultrastructural changes were similar between the groups.

CONCLUSIONS

Pinacidil provided better protection during ischemia-reperfusion in the immature rabbit heart than St. Thomas' solution, whereas pinacidil combined with St. Thomas' solution showed the worst protective effects in immature hearts.

Targeting nucleotide-requiring enzymes: implications for diazoxide-induced cardioprotection

Modulation of mitochondrial respiratory chain, dehydrogenase, and nucleotide-metabolizing enzyme activities is fundamental to cellular protection. Here, we demonstrate that the potassium channel opener diazoxide, within its cardioprotective concentration range, modulated the activity of flavin adenine dinucleotide-dependent succinate dehydrogenase with an IC50 of 32 microM and reduced the rate of succinate-supported generation of reactive oxygen species (ROS) in heart mitochondria. 5-Hydroxydecanoic fatty acid circumvented diazoxide-inhibited succinate dehydrogenase-driven electron flow, indicating a metabolism-dependent supply of redox equivalents to the respiratory chain. In perfused rat hearts, diazoxide diminished the generation of malondialdehyde, a marker of oxidative stress, which, however, increased on diazoxide washout. This effect of diazoxide mimicked ischemic preconditioning and was associated with reduced oxidative damage on ischemia-reperfusion. Diazoxide reduced cellular and mitochondrial ATPase activities, along with nucleotide degradation, contributing to preservation of myocardial ATP levels during ischemia. Thus, by targeting nucleotide-requiring enzymes, particularly mitochondrial succinate dehydrogenase and cellular ATPases, diazoxide reduces ROS generation and nucleotide degradation, resulting in preservation of myocardial energetics under stress.

Synergistic effect of Nicorandil and Amlodipine on tissue defense system during experimental myocardial infarction in rats

The synergistic protective effect of Nicorandil (K(ATP) channel opener) and Amlodipine (calcium channel blocker) on heart tissue antioxidant defense system and lipid profile were examined on isoproterenol induced myocardial infarction in rats. The rats given isoproterenol (150 mg kg(-1) daily, i.p.) for 2 days showed significant changes in antioxidant defense system and lipid profile levels. Pretreatment with Nicorandil (2.5 mg kg(-1) daily, p.o.) and Amlodipine (5.0 mg kg(-1) daily, p.o.) for 3 days significantly prevented these alterations and restored the enzyme activities to near normal. These findings indicate the synergistic protective effect of Nicorandil and Amlodipine on tissue defense system and lipid metabolism during isoproterenol induced cardiac damage.

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.

Nicorandil and leukocyte activation

Nicorandil, a hybrid compound of an ATP-sensitive potassium (KATP ) channel opener and a nitric oxide donor, has been reported to preserve microvascular integrity in patients with reperfused myocardial infarction. The aim of the current study was to test the hypothesis that nicorandil suppresses activation of polymorphonuclear leukocytes (PMNLs), resulting in reduction of PMNL migration into tissue upon ischemia/reperfusion. Nicorandil, along with the mitochondrial KATP channel opener diazoxide and the nitric oxide donors nitroglycerin and isosorbide dinitrate, suppressed pseudopod projection in human PMNLs treated with 10(-9)-formyl-methionyl-leucyl-phenylalanine (FMLP) and subjected to shear stress (5 dyn/cm(2)) with a cone-and-plate shear device. Suppression by nicorandil and diazoxide was reversed by KATP channel blockers, 5 hydroxydecanoate and glibenclamide. FMLP-induced increase of [Ca2+] in PMNLs was suppressed by nicorandil and diazoxide, and 5 hydroxy-decanoate and glibenclamide reversed this suppression. Results of reverse transcription polymerase chain reaction with rat PMNL mRNA indicated the presence of mRNAs of Kir6.2 and Kir6.1 but not mRNAs of sulfonylurea receptor 1 or 2. Isosorbide dinitrate, diazoxide, and nicorandil reduced leukocyte migration and microvascular obstruction in reperfused ischemic tissue of rat mesenteric microcirculation. In conclusion, nicorandil attenuates ischemia/reperfusion-induced PMNL activation via donation of nitric oxide and K channel-related cascade.

Nicorandil ameliorates posttransplant dysfunction in cardiac allografts harvested from non-heart-beating donors

OBJECTIVE

Warm ischemia is a major cause of cardiac allograft dysfunction in non-heart-beating donors (NHBDs). We evaluated the cardioprotective effects of nicorandil, an adenosine triphosphate-sensitive potassium channel opener, on the early posttransplant left ventricular (LV) function of hearts harvested from asphyxiated canine NHBDs.

METHODS

Hypoxic cardiac arrest was induced in 12 donor dogs. In 6, nicorandil was administered intravenously at 100 micrograms/kg + 25 micrograms/kg/min after respiratory arrest and hearts were preserved with nicorandil-supplemented cardioplegic solution (nicorandil group). The remaining 6 did not receive nicorandil at any time during the experiment (control group). Hearts were orthotopically transplanted after a mean myocardial ischemic time of 4 hours.

RESULTS

All 12 recipients were weaned from cardiopulmonary bypass without inotropic support. In the control group, posttransplant cardiac indices and left ventricular end-systolic pressure (LVESP) decreased significantly, while LV max-dP/dt and Tau increased over pretransplant values. No differences were seen in parameters between pretransplant and posttransplant values in the nicorandil group. Posttransplant cardiac indices, LVESP, and LV max + dP/dt were higher in the nicorandil group than in controls, while posttransplant LV max-dP/dt in the nicorandil group was lower.

CONCLUSIONS

Our results indicate that pretreatment with nicorandil during hypoxic perfusion before cardiac arrest and subsequent preservation with nicorandil-supplemented cardioplegia ameliorates early posttransplant LV dysfunction of hearts harvested from asphyxiated NHBDs.

Left ventricular remodeling after infarction: sequential MR imaging with oral nicorandil therapy in rat model

PURPOSE

To use magnetic resonance (MR) imaging in quantification of the short- and long-term effects of therapy with orally administered nicorandil on left ventricular (LV) geometry and function independent of infarction size.

MATERIALS AND METHODS

Forty-six rats were subjected to reperfused infarction and randomly divided into two groups. Group 1 rats (n = 21) were treated with nicorandil (3 mg/kg/day in drinking water) for 4 days before infarction and 8 weeks after infarction (hereafter, the nicorandil group). Group 2 rats (n = 25) received tap water for the same period and served as the control group. Mesoporphyrin- (as a necrosis-specific agent) enhanced MR imaging was used to define necrotic myocardium on day 2 after infarction in all 46 animals. Contrast material-enhanced MR images showed large but identical infarction size in 11 control and 11 nicorandil rats. Only these 22 rats underwent repeat MR imaging at 8 weeks after infarction. The following variables were measured: LV volumes, ejection fraction, mass, wall thickness, and infarction size. Student t test and analysis of variance for repeated measurements were used for statistical analysis.

RESULTS

The size of the necrotic region on mesoporphyrin-enhanced MR images was 39% +/- 3 of the size of the left ventricle in the control group and 41% +/- 2 in the nicorandil group (difference not significant, unpaired Student t test). Pretreatment with nicorandil for 6 days before imaging did not reduce LV dilation or improve function compared with those in control animals with identical infarction size. Eight weeks after infarction, control animals showed deterioration in LV function, wall thinning, and gradient in regional dysfunction (analysis of variance test). Nicorandil produced significant salutary effects on LV ejection fraction (37% +/- 3 in the nicorandil group vs 24% +/- 3 in the control group), end-diastolic volume (0.53 mL +/- 0.03 vs 0.65 mL +/- 0.04), end-systolic volume (0.36 mL +/- 0.03 vs 0.49 mL +/- 0.05), LV wall thickening in remote noninfarcted myocardium (28% +/- 2 vs 19% +/- 1), and a rim of infarction (16% +/- 2 vs 8% +/- 1) (P <.05 for all parameters). The increase in LV mass was reduced in the nicorandil group (0.73 g +/- 0.03) compared with that in the control group (0.89 g +/- 0.04) (P <.05).

CONCLUSION

In animals studied longitudinally, MR imaging demonstrated the deleterious changes in LV geometry and function in the period after infarction and the salutary effects of medical therapy.

Sheng-Mai-San is protective against post-ischemic myocardial dysfunction in rats through its opening of the mitochondrial KATP channels

The present study used isolated rat hearts to investigate whether (1) Sheng-Mei-San (SMS), a traditional Chinese formulation comprising Radix Ginseng, Radix Ophiopogonis and Fructus Schisandrae, is protective against post-ischemic myocardial dysfunction, and (2) whether the cardioprotective effect of SMS is related to scavenging of hydroxyl radicals and opening the mitochondrial KATP channels. The excised hearts of male Sprague-Dawley rats were perfused on a Langendorff apparatus with Krebs-Henseleit solution with a gas mixture of 95% O2 and 5% CO2. Left ventricular end-diastolic pressure (LVEDP, mmHg), left ventricular developed pressure (LVDP, mmHg), +/-dP/dt (mmHg/s) and coronary flow (ml/min) were continuously monitored. All hearts were perfused for a total of 120 min consisting of a 30-min pre-ischemic period followed by a 30-min global ischemia and 60-min reperfusion. Lactate, lactate dehydrogenase (LDH) and 2,5-dihydroxybenzoic acid (2,5-DHBA) concentrations in the effluent were measured during reperfusion. Three days' treatment with SMS (1.67 ml/kg per day) inhibited the rise in LVEDP and improved the post-ischemic LVDP and +/-dP/dt significantly better than in the untreated control hearts during reperfusion. SMS increased the coronary flow at baseline, and during reperfusion. Pretreatment with 5-hydroxydecanoic acid (5-HD), a mitochondrial KATP channel blocker, abolished the inhibition of the rise in LVEDP, the increase in coronary flow and the improvement in LVDP and +/-dP/dt induced by SMS. SMS significantly attenuated the concentrations of lactate, LDH and 2,5-DHBA during reperfusion, but the pretreatment with 5-HD restored them; 5-HD alone did not affect the concentrations. SMS improved the post-ischemic myocardial dysfunction through opening the mitochondrial KATP channels.

Highly protective effects of chronic oral administration of nicorandil on the heart of ageing rats

1. We have tested the effects of 2 month oral treatment with the KATP opener, nitric oxide (NO) donor and anti-oxidant molecule nicorandil (0.1 mg/kg per day) on major physiological parameters and heart function of 4-, 12- and 24-month-old rats. 2. Several methods were used: (i) measurement of blood pressure using a non-invasive tail-cuff method; (ii) perfusion of isolated heart; (iii) lactate dehydrogenase (LDH) dosage; and (iv) measurement of monophasic action potential of rat isolated hearts. 3. Blood pressure and ventricular action potential duration regularly increase with age in control animals, whereas nicorandil restores these parameters in aged animals to levels present in young adult animals. Moreover, following ischaemia, nicorandil treatment improved isolated heart survival rate (100 vs. 50% for nicorandil-treated rats and controls, respectively), heart work and left ventricular developed pressure, whereas it decreased cardiac cell damage (LDH release) and perfusion pressure. 4. This condition of chronic oral nicorandil treatment presents a strong potential in the improvement of cardiac function in normal and pathological ageing.

Blood pool contrast-enhanced MRI detects suppression of microvascular permeability in early postinfarction reperfusion after nicorandil therapy

Nicorandil is an adenosine triphosphate-sensitive potassium channel opener with a nitrate-like effect. It is approved for clinical use in Europe and Japan as an antianginal drug. The purpose of this investigation was to assess the acute effects of nicorandil therapy on microvascular injury using the blood pool MR contrast medium, NC100150 injection (Clariscan). Microvascular injury was produced in 24 rats using 45 min of coronary occlusion / 3 hr reperfusion. Nicorandil was infused at 15 min of occlusion and during reperfusion. Control animals received a saline solution. MR imaging was used to characterize microvascular permeability, quantify the extent of microvascular injury, LV volume, and wall thickness. Hyperenhancement at 30 min after administration of 0.05 mmol/kg Clariscan mapped the extent of ischemia-induced loss of microvascular integrity. The accumulation of Clariscan in the injured region was significantly suppressed in nicorandil compared to control rats. Nicorandil reduced the extent of microvascular injury from 44 +/- 2% to 18 +/- 2% (P < 0.01) and true infarction size from 29 +/- 2% to 12 +/- 1%. The extent of the hyperenhanced region correlated with the true size of area at risk at autopsy. On spin-echo MRI during end-diastole, nicorandil reduced LV end-diastolic volume and preserved wall thickness in remote myocardium; both parameters are markers of LV dilatation caused by acute infarction (remodeling). In conclusion, blood pool contrast-enhanced MRI has the potential to depict and quantify the extent of microvascular permeability and injury. Nicorandil suppressed microvascular permeability, reduced infarction size, and improved LV function in early postinfarction reperfusion.

Potassium channel openers protect cardiac mitochondria by attenuating oxidant stress at reoxygenation

K(+) channel openers have been recently recognized for their ability to protect mitochondria from anoxic injury. Yet the mechanism responsible for mitochondrial preservation under oxidative stress is not fully understood. Here, mitochondria were isolated from rat hearts and subjected to 20-min anoxia, followed by reoxygenation. At reoxygenation, increased generation of reactive oxygen species (ROS) was associated with reduced ADP-stimulated oxygen consumption, blunted ATP production, and disrupted mitochondrial structural integrity coupled with cytochrome c release. The prototype K(+) channel opener diazoxide markedly reduced mitochondrial ROS production at reoxygenation with a half-maximal effect of 29 microM. Diazoxide also preserved oxidative phosphorylation and mitochondrial membrane integrity, as indicated by electron microscopy and reduced cytochrome c release. The protective effect of diazoxide was reproduced by the structurally distinct K(+) channel opener nicorandil and antagonized by 5-hydroxydecanoic acid, a short-chain fatty acid derivative and presumed blocker of mitochondrial ATP-sensitive K(+) channels. Opener-mediated mitochondrial protection was simulated by the free radical scavenger system composed of superoxide dismutase and catalase. However, the effect of openers on ROS production was maintained in nominally K(+)-free medium in the presence or absence of the K(+) ionophore valinomycin and was mimicked by malonate, a modulator of the mitochondrial redox state. This suggests the existence of a K(+) conductance-independent pathway for mitochondrial protection targeted by K(+) channel openers. Thus the cardioprotecive mechanism of K(+) channel openers includes direct attenuation of mitochondrial oxidant stress at reoxygenation.

Effects of nicorandil on myocardial function and metabolism in the post-ischaemic reperfused heart with or without inhalation anaesthetics

BACKGROUND

Nicorandil, which is an ATP-sensitive K channel opener, has been reported to protect the ischaemic myocardium. However, its interaction with inhalation anaesthetics on the ischaemic myocardium has not been well elucidated. So, we have investigated whether isoflurane or sevoflurane modify the effects of nicorandil on cardiac function and metabolism in the rat heart-lung preparation.

METHODS

Animals were allocated to 4 groups as follows: Control group, no drug; Nic group, nicorandil; Nic+Iso group, nicorandil and isoflurane; Nic+Sev group, nicorandil and sevoflurane. Seven minutes after the start of perfusion, nicorandil was administered and 10 min after the start of perfusion, the heart was rendered globally ischaemic for 10 min, and then the heart was reperfused for 10 min.

RESULTS

LVdP/dt max in the Nic group was higher than those in the other groups. Right atrial pressure in the Nic+Iso and Nic+Sev groups was significantly higher than in the Control and Nic groups. Myocardial ATP in the Nic group was higher than in the other groups. DHBA levels in the perfusate in the Nic and Nic+Iso groups were lower than those in the Control and Nic+Sev groups, but those in the Nic+Sev group were higher than those in the other groups.

CONCLUSIONS

Nicorandil improved post-ischaemic cardiac function and preserved high-energy phosphates. However, these beneficial effects of nicorandil were abolished by the combination with isoflurane or sevoflurane. In addition, sevoflurane increased hydroxyl radical formation in the post-ischaemic reperfused heart.

Role of mitochondrial and sarcolemmal K(ATP) channels in ischemic preconditioning of the canine heart

We tested whether mitochondrial or sarcolemmal ATP-sensitive K(+) (K(ATP)) channels play a key role in ischemic preconditioning (IP) in canine hearts. In open-chest beagle dogs, the left anterior descending artery was occluded four times for 5 min each with 5-min intervals of reperfusion (IP), occluded for 90 min, and reperfused for 6 h. IP as well as cromakalim and nicorandil (nonspecific K(ATP) channel openers) markedly limited infarct size (6.3 +/- 1.2, 8.9 +/- 1.9, and 7.2 +/- 1.6%, respectively) compared with the control group (40.9 +/- 4.1%). A selective mitochondrial K(ATP) channel blocker, 5-hydroxydecanoate, partially blunted the limitation of infarct size in the animals subjected to IP and those treated with cromakalim and nicorandil (21.6 +/- 3.8, 25.1 +/- 4.6, and 19.8 +/- 5.2%, respectively). A nonspecific K(ATP) channel blocker, glibenclamide, completely abolished the effect of IP (38.5 +/- 6.2%). Intracoronary or intravenous administration of a mitochondria-selective K(ATP) channel opener, diazoxide, at >100 micromol/l could only partially decrease infarct size (19.5 +/- 4.3 and 20.1 +/- 4.4%, respectively). In conclusion, mitochondrial and sarcolemmal K(ATP) channels independently play an important role in the limitation of infarct size by IP in the canine heart.