Nicorandil-Pretreated Mesenchymal Stem Cell-Derived Exosomes Facilitate Cardiac Repair After Myocardial Infarction via Promoting Macrophage M2 Polarization by Targeting miR-125a-5p/TRAF6/IRF5 Signaling Pathway

Background

Exosomes derived from bone marrow mesenchymal stem cells (MSC-exo) have been considered as a promising cell-free therapeutic strategy for ischemic heart disease. Cardioprotective drug pretreatment could be an effective approach to improve the efficacy of MSC-exo. Nicorandil has long been used in clinical practice for cardioprotection. This study aimed to investigate whether the effects of exosomes derived from nicorandil pretreated MSC (MSCNIC-exo) could be enhanced in facilitating cardiac repair after acute myocardial infarction (AMI).

Methods

MSCNIC-exo and MSC-exo were collected and injected into the border zone of infarcted hearts 30 minutes after coronary ligation in rats. Macrophage polarization was detected 3 days post-infarction, cardiac function as well as histological pathology were measured on the 28th day after AMI. Macrophages were separated from the bone marrow of rats for in vitro model. Exosomal miRNA sequencing was conducted to identify differentially expressed miRNAs between MSCNIC-exo and MSC-exo. MiRNA mimics and inhibitors were transfected to MSCs or macrophages to explore the specific mechanism.

Results

Compared to MSC-exo, MSCNIC-exo showed superior therapeutic effects on cardiac functional and structural recovery after AMI and markedly elevated the ratio of CD68+ CD206+/ CD68+cells in infarcted hearts 3 days post-infarction. The notable ability of MSCNIC-exo to promote macrophage M2 polarization was also confirmed in vitro. Exosomal miRNA sequencing and both in vivo and in vitro experiments identified and verified that miR-125a-5p was an effector of the roles of MSCNIC-exo in vivo and in vitro. Furthermore, we found miR-125a-5p promoted macrophage M2 polarization by inhibiting TRAF6/IRF5 signaling pathway.

Conclusion

This study suggested that MSCNIC-exo could markedly facilitate cardiac repair post-infarction by promoting macrophage M2 polarization by upregulating miR-125a-5p targeting TRAF6/IRF5 signaling pathway, which has great potential for clinical translation.

Nicorandil alleviates cardiac microvascular ferroptosis in diabetic cardiomyopathy: Role of the mitochondria-localized AMPK-Parkin-ACSL4 signaling pathway

Mitochondria-associated ferroptosis exacerbates cardiac microvascular dysfunction in diabetic cardiomyopathy (DCM). Nicorandil, an ATP-sensitive K+ channel opener, protects against endothelial dysfunction, mitochondrial dysfunction, and DCM; however, its effects on ferroptosis and mitophagy remain unexplored. The present study aimed to assess the beneficial effects of nicorandil against endothelial ferroptosis in DCM and the underlying mechanisms. Cardiac microvascular perfusion was assessed using a lectin perfusion assay, while mitophagy was assessed via mt-Keima transfection and transmission electron microscopy. Ferroptosis was examined using mRNA sequencing, fluorescence staining, and western blotting. The mitochondrial localization of Parkin, ACSL4, and AMPK was determined via immunofluorescence staining. Following long-term diabetes, nicorandil treatment improved cardiac function and remodeling by alleviating cardiac microvascular injuries, as evidenced by the improved microvascular perfusion and structural integrity. mRNA-sequencing and biochemical analyses showed that ferroptosis occurred and Pink1/Parkin-dependent mitophagy was suppressed in cardiac microvascular endothelial cells after diabetes. Nicorandil treatment suppressed mitochondria-associated ferroptosis by promoting the Pink1/Parkin-dependent mitophagy. Moreover, nicorandil treatment increased the phosphorylation level of AMPKα1 and promoted its mitochondrial translocation, which further inhibited the mitochondrial translocation of ACSL4 via mitophagy and ultimately suppressed mitochondria-associated ferroptosis. Importantly, overexpression of mitochondria-localized AMPKα1 (mitoAα1) shared similar benefits with nicorandil on mitophagy, ferroptosis and cardiovascular protection against diabetic injury. In conclusion, the present study demonstrated the therapeutic effects of nicorandil against cardiac microvascular ferroptosis in DCM and revealed that the mitochondria-localized AMPK-Parkin-ACSL4 signaling pathway mediates mitochondria-associated ferroptosis and the development of cardiac microvascular dysfunction.

Nicorandil attenuates cognitive impairment after traumatic brain injury via inhibiting oxidative stress and inflammation: Involvement of BDNF and NGF

BACKGROUND AND PURPOSE

Cognitive impairment is a prevalent adverse consequence of traumatic brain injury (TBI). The neuroprotective effects of nicorandil (N-(2-hydroxyethyl)-nicotinamide nitrate) has been previously documented, yet its protective effects against cognitive dysfunction post-TBI remain unclear. Hence, the present study was aimed to evaluate whether nicorandil attenuates cognitive dysfunction in TBI rats and the underlying mechanism behind this process.

METHODS

The TBI model was established with a controlled cortical impact (CCI). The effects of nicorandil on cognitive dysfunction of rats with TBI were examined through Novel object recognition (NOR) test, Y-maze test, and Morris water maze (MWM) task. After behavioral tests, hippocampal tissue was collected for Quantitative real-time PCR, Western blot analysis, and Enzyme-linked immunosorbent assay (ELISA) assay.

RESULTS

We observed that nicorandil administration effectively ameliorates learning and memory impairment in TBI rats. Alongside, nicorandil treatment attenuated oxidative stress in the hippocampus of TBI rats, characterized by the decreased reactive oxygen species generation, malondialdehyde, and protein carbonyls levels, and concurrent promotion of antioxidant-related factors (including superoxide dismutase, glutathione peroxidase, and catalase) activities. Additionally, nicorandil treatment attenuated the inflammatory response in the hippocampus of TBI rat, as evidenced by the upregulated levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α), as well as the downregulated level of IL-10. Mechanistically, nicorandil treatment significantly enhanced the mRNA and protein levels of neurotrophic factors, brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the hippocampus of TBI rats.

CONCLUSION

These findings suggest that nicorandil mitigates cognitive impairment after TBI by suppressing oxidative stress and inflammation, potentially through enhancing BDNF and NGF levels.

Hepatoprotective effect of nicorandil against acetaminophen-induced oxidative stress and hepatotoxicity in mice via modulating NO synthesis

Acetaminophen (APAP) overdose can produce hepatotoxicity and consequently liver damage. This study investigated the hepatoprotective impacts of nicorandil on hepatic damage induced by APAP. Nicorandil was administered orally (100 mg/kg) for seven days before APAP challenge (500 mg/kg, ip). Pretreatment with nicorandil reduced serum levels of aminotransferases, bilirubin, GGT and LDH, and increased serum level of albumin. Moreover, nicorandil inhibited the increase in liver MDA levels and reversed the decline in GSH content and SOD activity. Besides, it notably alleviated APAP-induced necrosis observed in histopathological findings. Additionally, nicorandil alleviated APAP-induced NO overproduction and iNOS expression; however, the protein expression of eNOS was significantly increased. Moreover, nicorandil markedly reduced hepatic TNF-α and NF-κB levels, in addition to decreasing the protein expression of MPO in hepatic tissues. Furthermore, flow cytometry (annexin V-FITC/PI) displayed a significant decline in late apoptotic and necrotic cells, and an increase in viable cells in nicorandil group. Also, nicorandil caused a significant boost in hepatic antiapoptotic marker bcl-2 level. The presented data proposed that the protective effect of nicorandil might be attributed to its antioxidant, its impact on NO homeostasis, and its anti-inflammatory properties. Therefore, nicorandil may be a promising candidate for protection from liver injury induced by APAP.

Formulation of an HPMC Gel Drug Reservoir System with Ethanol-Water as a Solvent System and Limonene as a Penetration Enhancer for Enhancing in vitro Transdermal Delivery of Nicorandil

The objective of the present study was to formulate a hydroxypropyl methylcellulose (HPMC) gel drug reservoir system with ethanol-water as a solvent system and limonene as a penetration enhancer for enhancing the transdermal delivery of nicorandil so as to develop and fabricate a membrane-moderated transdermal therapeutic system (TTS). The in vitro permeation of nicorandil was determined across rat abdominal skin from a solvent system consisting of ethanol or various proportions of ethanol and water. The ethanol-water (70:30 v/v) solvent system that provided an optimal transdermal permeation was used in formulating an HPMC gel drug reservoir system with selected concentrations (0% w/w, 4% w/w, 6% w/w, 8% w/w or 10% w/w) of limonene as a penetration enhancer for further enhancement of transdermal permeation of nicorandil. The amount of nicorandil permeated in 24 h was found increased with an increase in the concentration of limonene in the drug reservoir system up to a concentration of 6% w/w, but beyond this concentration there was no further increase in the amount of drug permeated. The flux of nicorandil was 370.9 +/- 4.2 microg/cm2 x h from the drug reservoir system with 6% w/w of limonene, which is about 2.6 times the required flux to be obtained across rat abdominal skin for producing the desired plasma concentration for the predetermined period in humans. The results of a Fourier Transform Infrared study indicated that limonene enhanced the percutaneous permeation of nicorandil by partially extracting the stratum corneum lipids. It is concluded that the HPMC gel drug reservoir system prepared with a 70:30 v/v ethanol-water solvent system containing 6% w/w of limonene is useful in designing and fabricating a membrane-moderated TTS of nicorandil.

Dual mechanism of action of nicorandil on rabbit corpus cavernosal smooth muscle tone

The potential of ATP-sensitive potassium channel openers (KCOs) for the treatment of male erectile dysfunction has recently been suggested based on positive clinical outcomes following intra-cavernosal administration of pinacidil. Agents that increase the levels of cGMP via elevation of nitric oxide (NO) nitroglycerin, for example, are also effective in improving erectile function preclinically and clinically. The aim of the present study was to determine the effects and mechanism of the action of nicorandil on rabbit corpus cavernosum. The in vitro regulation of smooth muscle tone was assessed in isolated cavernosal tissues pre-contracted with phenylephrine. Nicorandil, but not its major metabolite, relaxed phenylephrine-precontracted cavernosum smooth muscle with an EC(50) of 15 microM. The effects of nicorandil were only partially reversed by the K(ATP) channel blocker glyburide (10 microM) or by a soluble guanylate cyclase (sGC) inhibitor 1H-[1,2,4] oxadiazole [4,3-a] quinoxalin-1-one (ODQ, 3 microM). However, a combination of ODQ and glyburide completely blocked the relaxant effects of nicorandil. The results of the present study indicate that nicorandil can relax rabbit cavernosal tissue in vitro via a mechanism that involves activation of K(ATP) channels and stimulation of soluble guanylate cyclase.

Inhibitory effects of nicorandil on rat mesangial cell proliferation via the protein kinase G pathway

We investigated the effects of nicorandil, which is a hybrid between a nitrate and an ATP-sensitive potassium channel (K(ATP)) opener, on cultured rat mesangial cell proliferation. Nicorandil (1 microM to 1 mM inhibited [(3)H]thymidine incorporation into rat mesangial cells in a concentration-dependent manner. Nicorandil (1 microM to 1 mM) also inhibited the number of cells. Nicorandil increased cyclic guanosine 3',5'-cyclic monophosphate accumulation in mesangial cells. A protein kinase G inhibitor, KT5823, partially eliminated the inhibition of mesangial cell proliferation by nicorandil. Methylene blue, a guanylate cyclase inhibitor, blocked the inhibitory effect of nicorandil on mesangial cell proliferation. We also examined the effects of K(ATP) mediators. Cromakalim, a K(ATP) activator, and glibenclamide, a K(ATP) inhibitor, had little effect on the proliferation of mesangial cells. These results suggest that the inhibitory effects of nicorandil on mesangial cell proliferation are mediated via the protein kinase G pathway.

New windows on the mechanism of action of K(ATP) channel openers

K(ATP) channel openers are a diverse group of drugs with a wide range of potential therapeutic uses. Their molecular targets, the K(ATP) channels, exhibit tissue-specific responses because they possess different types of regulatory sulfonylurea receptor subunits. It is well recognized that complex interactions occur between K(ATP) channel openers and nucleotides, but the cloning of the K(ATP) channel has introduced a new dimension to the study of these events and has furthered our understanding of the molecular basis of the action of K(ATP) channel openers.

Nicorandil. An updated review of its use in ischaemic heart disease with emphasis on its cardioprotective effects

Nicorandil is a drug with both nitrate-like and ATP-sensitive potassium-channel (K+ ATP) activating properties. By virtue of this dual mechanism of action, the drug acts as a balanced coronary and peripheral vasodilator and reduces both preload and afterload. The K+ ATP channel has been shown to be involved in the phenomenon of myocardial preconditioning, and studies in animal models of ischaemia-reperfusion-induced myocardial stunning or infarction indicate that nicorandil has cardio-protective effects. Studies in patients undergoing percutaneous transluminal coronary angioplasty (PTCA) have shown that the administration of nicorandil reduces ST-segment elevation during ischaemia. Nicorandil significantly improved the results of exercise tolerance tests versus baseline in patients with stable effort angina pectoris in early noncomparative trials. The drug also improved the results of exercise tolerance tests relative to placebo in early randomised, double-blind, placebo-controlled trials. In randomised, double-blind comparative studies in patients with angina pectoris, nicorandil has demonstrated equivalent efficacy, as measured by exercise tolerance testing, to isosorbide di- and mononitrate, metoprolol, propranolol, atenolol, diltiazem, amlodipine and nifedipine. The effects of nicorandil on various aspects of myocardial recovery from ischaemic damage caused by acute myocardial infarction have been investigated in the short term. Regional left ventricular (LV) wall motion, a marker of myocardial function, was significantly improved in nicorandil recipients relative to control. The main adverse event associated with nicorandil as treatment for angina pectoris is headache. This can be minimised by commencing nicorandil at a low dose in patients prone to headache. There have been infrequent case reports of mouth ulcers in patients receiving nicorandil; causality has not been conclusively established, but product prescribing information indicates that an alternative treatment should be considered if persistent aphthous or severe mouth ulceration occurs. Thus, nicorandil remains a useful background therapy for patients with angina pectoris. The drug has also demonstrated potential cardioprotective effects when used as part of an intervention strategy directly after acute myocardial infarction in high-risk patients. Further large scale longer term studies of nicorandil in this latter indication are awaited with interest.

Nicorandil metabolism in rat myocardial mitochondria

The in vitro study using rats was carried out to clarify the hypothesis that nicorandil is denitrated and then may produce nitric oxide (NO) in myocardial mitochondria. In the presence of a NADPH-generating system, [14C]nicorandil, which was incubated in mitochondrial and microsomal fractions of the lung, heart, or liver, was converted to its main denitrated metabolite, SG-86 and other metabolites. Apparent Km and Vmax for nicorandil in mitochondrial and microsomal fractions of the heart were considerably similar to those of the lung, but completely different from those of the liver. It seems that glutathione-S-transferases (GSTs) are not primarily involved in the conversion of nicorandil to SG-86, because a known GST inhibitor, indomethacin, did not affect the nicorandil degradation in the mitochondrial fraction. Nitrite, the stable metabolite of NO, was measured by the Griess reaction. In the presence of an NADPH-generating system, nicorandil significantly increased nitrite production in myocardial mitochondria, but SG-86 did not. These data strongly indicate that nicorandil is metabolized to SG-86 in myocardial mitochondria, then releasing NO, and that GSTs are not primarily responsible for the conversion of nicorandil to SG-86.

Myocardial distribution and biotransformation in vitro and in vivo of nicorandil in rats, with special reference to mitochondria

This study reports subcellular localization of nicorandil in the myocardium and metabolism in mitochondria after oral dosing of 3 mg/kg nicorandil to rats. In the in vitro experiments, nicorandil, which was incubated with tissue homogenates (liver, kidney, heart, and small intestine), was metabolized to its denitrated compound, SG-86, and unknown substances. In the absence of a NADPH-generating system in the heart, the metabolic activity existed only in the mitochondrial fraction, but not in cytosolic and microsomal fractions. In the presence of the system, the activity in the mitochondrial fraction became much higher. To examine subcellular distribution of nicorandil in the myocardium, [14C]nicorandil was orally given to rats. Fifteen minutes after oral dosing of 3 mg/kg [14C]nicorandil, of which myocardial concentration reached a peak, nicorandil and SG-86 were found in mitochondrial fractions as well as in cytosolic and microsomal ones of the heart. Electron-microscopic autoradiograms, 15 min after oral dosing of 3 mg/kg [3H]nicorandil to rats, also showed the existence of the silver grains (showing radioactivity) in mitochondria of the heart. We conclude that nicorandil given orally is distributed in mitochondria of the heart, being partly transformed into SG-86, and that the myocardial mitochondria may be a potential site of action of nicorandil, an opener of KATP channels, which have been demonstrated to be present in this subcellular particle.