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

Modulating the Bioactivity of Nitric Oxide as a Therapeutic Strategy in Cardiac Surgery

Cardiac surgery, including cardioplegic arrest and extracorporeal circulation, causes endothelial dysfunction, which can lead to no-reflow phenomenon and reduction of myocardial pump function. Nitric oxide (NO) deficiency is involved in this pathologic process, thereby providing a fundamental basis for the use of NO replacement therapy. Presently used drugs and additives to cardioplegic and heart preservation solutions are not able to reliably protect endothelial cells and cardiomyocytes from ischemia-reperfusion injury. This review discusses promising NO-releasing compounds of various chemical classes for cardioplegia and reperfusion, which effectively maintain NO homeostasis under experimental conditions, and presents the mechanisms of their action on the cardiovascular system. Incomplete preclinical studies and a lack of toxicity assessment, however, hinder translation of these drug candidates into the clinic. Perspectives for modulation of endothelial function using NO-mediated mechanisms are discussed. They are based on the cardioprotective potential of targeting vascular gap junctions and endothelial ion channels, intracoronary administration of progenitor cells, and endothelial-specific microRNAs. Some of these strategies may provide important therapeutic benefits for human cardiovascular interventions.

Nicorandil, a KATP Channel Opener, Attenuates Ischemia-Reperfusion Injury in Isolated Rat Lungs

PURPOSE

Nicorandil is a hybrid between nitrates and K_ATP channel opener activators. The aim of this study was to evaluate the nicorandil's effects on ischemia-reperfusion (IR) lung injury and examine the mechanism of its effects.

METHODS

Isolated rat lungs were divided into 6 groups. In the sham group, the lungs were perfused and ventilated for 150 min. In the IR group, after perfusion and ventilation for 30 min, they were interrupted (ischemia) for 60 min, and then resumed for 60 min. In the nicorandil (N) + IR group, nicorandil 6 mg was added before ischemia (nicorandil concentration was 75 µg ml^-1). In the glibenclamide + N + IR group, the L-NAME (N_ω-Nitro-L-arginine methyl ester) + N + IR group and ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one) + N + IR group, glibenclamide 3 µM, L-NAME 100 µM, and ODQ 30 µM were added 5 min before nicorandil administration, respectively. We measured the coefficient of filtration (Kfc) of the lungs, total pulmonary vascular resistance, and the wet-to-dry lung weight ratio (WW/DW ratio).

RESULTS

Kfc was significantly increased after 60 min reperfusion compared with baseline in the IR group, but no change in the sham group. An increase in Kfc was inhibited in the N + IR group compared with the IR group (0.92 ± 0.28 vs. 2.82 ± 0.68 ml min^-1 mmHg^-1 100 g^-1; P < 0.01). Also, nicorandil attenuated WW/DW ratio was compared with IR group (8.3 ± 0.41 vs. 10.9 ± 2.5; P < 0.05). Nicorandil's inhibitory effect was blocked by glibenclamide and ODQ (P < 0.01), but not by L-NAME.

CONCLUSIONS

Nicorandil attenuated IR injury in isolated rat lungs. This protective effect appears to involve its activation as K_ATP channel opener as well as that of the sGC-cGMP pathway.

Nicorandil decreases cardiac events during and after noncardiac surgery

STUDY OBJECTIVE

To assess whether nicorandil reduces the likelihood of cardiac events during and after intermediate risk surgery.

DESIGN

Multicenter study.

SETTING

13 hospitals in Japan.

PATIENTS

Intermediate-risk patients were identified by the presence of risk factors such as angina, a history of myocardial infarction, heart failure, diabetes mellitus, and abnormal electrocardiography (ECG).

INTERVENTIONS

Nicorandil was given to these patients during the operation.

MEASUREMENTS AND MAIN RESULTS

Cardiac events during the operation and the following 5 days were monitored. The frequency of cardiac events in nicorandil-treated patients was compared with those in nontreated patients. Eighty-four patients received nicorandil during surgery and 237 patients received standard care. Cardiac events in the nicorandil-treated group occurred less frequently both during the operation (odds ratio, 0.15; 95% confidence interval, 0.03-0.76; P=0.02) and after it (odds ratio, 0.24; 95% confidence interval, 0.06-0.90; P=0.04).

CONCLUSIONS

Nicorandil reduces the frequency of cardiac events in patients undergoing noncardiac surgery, both during and after the operation.

Nicorandil: a review of its use in the management of stable angina pectoris, including high-risk patients

Nicorandil (Adancor, Angicor, Dancor, Nikoril [Europe], Ikorel [Europe and Oceania], Sigmart [Japan, Korea and Taiwan]) is an adenosine triphosphate (ATP)-sensitive potassium (KATP) channel agonist with nitrate-like properties used in the management of stable angina pectoris. With well established monotherapeutic antianginal activity and a beneficial effect (when added to optimal antianginal therapy) on clinical outcomes in high-risk patients with stable angina, twice-daily oral nicorandil is a useful alternative or addition to other antianginal therapy.

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.