Qiang Ma

Mff‐Dependent Mitochondrial Fission Contributes to the Pathogenesis of Cardiac Microvasculature Ischemia/Reperfusion Injury via Induction of mROS‐Mediated Cardiolipin Oxidation and HK2/VDAC1 Disassociation‐Involved mPTP Opening

Background The cardiac microvascular system ischemia/reperfusion injury following percutaneous coronary intervention is a clinical thorny problem. This study explores the mechanisms by which ischemia/reperfusion injury induces cardiac microcirculation collapse. Methods and Results In wild‐type mice, mitochondrial fission factor (Mff) expression increased in response to acute microvascular ischemia/reperfusion injury. Compared with wild‐type mice, homozygous Mff‐deficient (Mffgt) mice exhibited a smaller infarcted area, restored cardiac function, improved blood flow, and reduced microcirculation perfusion defects. Histopathology analysis demonstrated that cardiac microcirculation endothelial cells (CMECs) in Mffgt mice had an intact endothelial barrier, recovered phospho‐endothelial nitric oxide synthase production, opened lumen, undivided mitochondrial structures, and less CMEC death. In vitro, Mff‐deficient CMECs (derived from Mffgt mice or Mff small interfering RNA–treated) demonstrated less mitochondrial fission and mitochondrial‐dependent apoptosis compared with cells derived from wild‐type mice. The loss of Mff inhibited mitochondrial permeability transition pore opening via blocking the oligomerization of voltage‐dependent anion channel 1 and subsequent hexokinase 2 separation from mitochondria. Moreover, Mff deficiency reduced the cyt‐c leakage into the cytoplasm by alleviating cardiolipin oxidation resulting from damage to the electron transport chain complexes and mitochondrial reactive oxygen species overproduction. Conclusions This evidence clearly illustrates that microcirculatory ischemia/reperfusion injury can be attributed to Mff‐dependent mitochondrial fission via voltage‐dependent anion channel 1/hexokinase 2–mediated mitochondrial permeability transition pore opening and mitochondrial reactive oxygen species/cardiolipin involved cyt‐c release.

Melatonin protects cardiac microvasculature against ischemia/reperfusion injury via suppression of mitochondrial fission-VDAC1-HK2-mPTP-mitophagy axis

The cardiac microvascular system, which is primarily composed of monolayer endothelial cells, is the site of blood supply and nutrient exchange to cardiomyocytes. However, microvascular ischemia/reperfusion injury (IRI) following percutaneous coronary intervention is a woefully neglected topic, and few strategies are available to reverse such pathologies. Here, we studied the effects of melatonin on microcirculation IRI and elucidated the underlying mechanism. Melatonin markedly reduced infarcted area, improved cardiac function, restored blood flow, and lower microcirculation perfusion defects. Histological analysis showed that cardiac microcirculation endothelial cells (CMEC) in melatonin‐treated mice had an unbroken endothelial barrier, increased endothelial nitric oxide synthase expression, unobstructed lumen, reduced inflammatory cell infiltration, and less endothelial damage. In contrast, AMP‐activated protein kinase α (AMPKα) deficiency abolished the beneficial effects of melatonin on microvasculature. In vitro, IRI activated dynamin‐related protein 1 (Drp1)‐dependent mitochondrial fission, which subsequently induced voltage‐dependent anion channel 1 (VDAC1) oligomerization, hexokinase 2 (HK2) liberation, mitochondrial permeability transition pore (mPTP) opening, PINK1/Parkin upregulation, and ultimately mitophagy‐mediated CMEC death. However, melatonin strengthened CMEC survival via activation of AMPKα, followed by p‐Drp1S616 downregulation and p‐Drp1S37 upregulation, which blunted Drp1‐dependent mitochondrial fission. Suppression of mitochondrial fission by melatonin recovered VDAC1‐HK2 interaction that prevented mPTP opening and PINK1/Parkin activation, eventually blocking mitophagy‐mediated cellular death. In summary, this study confirmed that melatonin protects cardiac microvasculature against IRI. The underlying mechanism may be attributed to the inhibitory effects of melatonin on mitochondrial fission‐VDAC1‐HK2‐mPTP‐mitophagy axis via activation of AMPKα.

Liraglutide protects cardiac microvascular endothelial cells against hypoxia/reoxygenation injury through the suppression of the SR-Ca2+–XO–ROS axis via activation of the GLP-1R/PI3K/Akt/survivin pathways

Microvascular endothelial cells (CMECs) oxidative damage resulting from hypoxia/reoxygenation (H/R) injury is responsible for microcirculation perfusion disturbances and the progression of cardiac dysfunction. However, few strategies are available to reverse such pathologies. Here, we studied the effects and mechanisms of liraglutide on CEMCs oxidative damage, focusing in particular on calcium overload-triggered free radical injury signals and the GLP-1R/PI3K/Akt/survivin survival pathways. The results indicate that H/R increased IP3R expression but reduced SERCA2a expression, which rapidly raised intracellular Ca(2+) levels, subsequently leading to Ca(2+)-dependent xanthine oxidase (XO) activation, reactive oxygen species (ROS) production and the cellular apoptosis of CMECs. However, liraglutide pretreatment abrogated Ca(2+)-mediated oxidative apoptosis. Furthermore, liraglutide regulated the rate of IP3R/SERCA2a gene transcription and conserved SERCA2a-ATPase activity via the maintenance of ATP production under H/R, which drove excessive Ca(2+) reflux to the sarcoplasmic reticulum (SR) and inhibited Ca(2+) release from the SR, ultimately restoring Ca(2+) homeostasis. Furthermore, the regulatory role of liraglutide on Ca(2+) balance in conjunction with its up-regulation of superoxide dismutase, glutathione and glutathione peroxidase collectively scavenged the excess ROS under H/R. Moreover, we showed that liraglutide strengthened Akt phosphorylation and subsequently survivin expression. In addition, both the blockade of the GLP-1R/PI3K/Akt pathways and the siRNA-mediated knockdown of survivin abolished the protective effects of liraglutide on SR-Ca(2+) function and CMECs oxidative apoptosis. In summary, this study confirmed that H/R induced CMECs oxidative damage through the SR-Ca(2+)-XO-ROS injury signals and that liraglutide pretreatment may suppress such CMECs damage through the PI3K/Akt/survivin pathways.

Protective role of melatonin in cardiac ischemia-reperfusion injury: From pathogenesis to targeted therapy

Acute myocardial infarction (MI) is a major cause of mortality and disability worldwide. In patients with MI, the treatment option for reducing acute myocardial ischemic injury and limiting MI size is timely and effective myocardial reperfusion using either thombolytic therapy or primary percutaneous coronary intervention (PCI). However, the procedure of reperfusion itself induces cardiomyocyte death, known as myocardial reperfusion injury, for which there is still no effective therapy. Recent evidence has depicted a promising role of melatonin, which possesses powerful antioxidative and anti‐inflammatory properties, in the prevention of ischemia‐reperfusion (IR) injury and the protection against cardiomyocyte death. A number of reports explored the mechanism of action behind melatonin‐induced beneficial effects against myocardial IR injury. In this review, we summarize the research progress related to IR injury and discuss the unique actions of melatonin as a protective agent. Furthermore, the possible mechanisms responsible for the myocardial benefits of melatonin against reperfusion injury are listed with the prospect of the use of melatonin in clinical application.

Melatonin protected cardiac microvascular endothelial cells against oxidative stress injury via suppression of IP3R-[Ca 2+ ]c/VDAC-[Ca 2+ ]m axis by activation of MAPK/ERK signaling pathway

The cardiac microvascular reperfusion injury is characterized by the microvascular endothelial cells (CMECs) oxidative damage which is responsible for the progression of cardiac dysfunction. However, few strategies are available to reverse such pathologies. This study aimed to explore the mechanism by which oxidative stress induced CMECs death and the beneficial actions of melatonin on CMECs survival, with a special focused on IP3R-[Ca2+]c/VDAC-[Ca2+]m damage axis and the MAPK/ERK survival signaling. We found that oxidative stress induced by H2O2 significantly activated cAMP response element binding protein (CREB) that enhanced IP3R and VDAC transcription and expression, leading to [Ca2+]c and [Ca2+]m overload. High concentration of [Ca2+]m suppressed ΔΨm, opened mPTP, and released cyt-c into cytoplasm where it activated mitochondria-dependent death pathway. However, melatonin could protect CMECs against oxidative stress injury via stimulation of MAPK/ERK that inactivated CREB and therefore blocked IP3R/VDAC upregulation and [Ca2+]c/[Ca2+]m overload, sustaining mitochondrial structural and function integrity and ultimately blockading mitochondrial-mediated cellular death. In summary, these findings confirmed the mechanisms by which oxidative injury induced CMECs mitochondrial-involved death and provided an attractive and effective way to enhance CMECs survival.

Melatonin therapy for diabetic cardiomyopathy: A mechanism involving Syk-mitochondrial complex I-SERCA pathway

Melatonin and its metabolites have been demonstrated to modulate the glucose, dyslipidemia and other metabolic disorders. This study aimed to explore a novel mechanism responsible for diabetic cardiomyopathy development, and also validated whether melatonin played a protective role in repairing damaged heart in the diabetes setting. Our data demonstrated that spleen tyrosine kinase (Syk) was activated by chronic high-glucose stimulus and contributed to the development of diabetic cardiomyopathy. However, genetic ablation of Syk or supplementation of melatonin to inhibit Syk activation improved diabetic myocardial function, reduced cardiac fibrosis and preserved cardiomyocytes viability. Mechanistically, activated Syk repressed the expression and activity of mitochondrial complex I (COX-1), unfortunately evoking mitochondrial and/or cellular ROS overproduction. Subsequently, excessive superoxide facilitated SERCA peroxidation which failed to re-uptake the cytoplasmic calcium back into endoplasmic reticulum (ER), leading to cellular calcium overload. Finally, activated oxidative stress and calcium overload collectively promoted the high-glucose-induced cardiomyocytes death via caspase-9-related mitochondrial apoptosis and caspase-12-involved ER apoptosis, respectively. Interestingly, inhibition of Syk via Syk genetic ablation or melatonin administration blocked Syk/COX-1/SERCA signalling pathways, and thus abolished mitochondrial- and ER-mediated cardiomyocyte death in the setting of diabetes. Based on these results, we suggest a novel pathway by which high-glucose stimulus induces diabetic cardiomyopathy is possibly through an activation of Syk/COX-1/SERCA axis which could be abrogated by melatonin treatment.

Inhibitory effect of melatonin on necroptosis via repressing the Ripk3-PGAM5-CypD-mPTP pathway attenuates cardiac microvascular ischemia-reperfusion injury

The molecular features of necroptosis in cardiac ischemia–reperfusion (IR) injury have been extensively explored. However, there have been no studies investigating the physiological regulatory mechanisms of melatonin acting on necroptosis in cardiac IR injury. This study was designed to determine the role of necroptosis in microvascular IR injury, and investigate the contribution of melatonin in repressing necroptosis and preventing IR‐mediated endothelial system collapse. Our results demonstrated that Ripk3 was primarily activated by IR injury and consequently aggravated endothelial necroptosis, microvessel barrier dysfunction, capillary hyperpermeability, the inflammation response, microcirculatory vasospasms, and microvascular perfusion defects. However, administration of melatonin prevented Ripk3 activation and provided a pro‐survival advantage for the endothelial system in the context of cardiac IR injury, similar to the results obtained via genetic ablation of Ripk3. Functional investigations clearly illustrated that activated Ripk3 upregulated PGAM5 expression, and the latter increased CypD phosphorylation, which obligated endothelial cells to undergo necroptosis via augmenting mPTP (mitochondrial permeability transition pore) opening. Interestingly, melatonin supplementation suppressed mPTP opening and interrupted endothelial necroptosis via blocking the Ripk3‐PGAM5‐CypD signal pathways. Taken together, our studies identified the Ripk3‐PGAM5‐CypD‐mPTP axis as a new pathway responsible for reperfusion‐mediated microvascular damage via initiating endothelial necroptosis. In contrast, melatonin treatment inhibited the Ripk3‐PGAM5‐CypD‐mPTP cascade and thus reduced cellular necroptosis, conferring a protective advantage to the endothelial system in IR stress. These findings establish a new paradigm in microvascular IR injury and update the concept for cell death management handled by melatonin under the burden of reperfusion attack.

Nicorandil attenuates carotid intimal hyperplasia after balloon catheter injury in diabetic rats

BackgroundDiabetic patients suffer from undesired intimal hyperplasia after angioplasty. Nicorandil has a trend to reduce the rate of target lesion revascularization. However, whether nicorandil inhibits intimal hyperplasia and the possible mechanisms underlying it remain to be determined. We aimed at assessing the effect of nicorandil on intimal hyperplasia in diabetic rats.MethodsAfter intraperitoneal injection of streptozotocin (STZ, 50xa0mg/kg), balloon injury model was established in carotid arteries of diabetic rats. Rats were randomized to vehicle, nicorandil (15xa0mg/kg/day) or 5-hydroxydecanoate (5-HD, 10xa0mg/kg/day), a mitochondrial ATP-sensitive potassium channel (mitoKATP channel)-selective antagonist. Perivascular delivery of εPKC siRNA was conducted to determine the role of εPKC pathway in intimal hyperplasia. In hyperglycemia environment (25xa0mM glucose), primary culture of vascular smooth muscle cells (VSMCs) were treated with nicorandil or 5-HD. Cell proliferation and cell migration were analyzed.ResultsIntimal hyperplasia significantly increased 14xa0days after balloon injury in diabetic rats (pxa0<xa00.01). Nicorandil inhibited intima development, reduced inflammation and prevented cell proliferation in balloon-injured arteries (pxa0<xa00.01). The protective effects of nicorandil were reversed by 5-HD (pxa0<xa00.05). εPKC was activated in balloon-injured arteries (pxa0<xa00.01). Nicorandil inhibited εPKC activation by opening mitoKATP channel. Perivascular delivery of εPKC siRNA inhibited intimal hyperplasia, inflammation and cell proliferation (pxa0<xa00.01). High glucose-induced VSMCs proliferation and migration were inhibited by nicorandil. εPKC activation induced by high glucose was also inhibited by nicorandil and that is partially reversed by 5-HD. εPKC knockdown prevented VSMCs proliferation and migration (pxa0<xa00.01).ConclusionsOur study demonstrates that nicorandil inhibits intimal hyperplasia in balloon-injured arteries in diabetic rats. Nicorandil also prevents VSMCs proliferation and migration induced by high glucose. The beneficial effect of nicorandil is conducted via opening mitoKATP channel and inhibiting εPKC activation.

Trend in young coronary artery disease in China from 2010 to 2014: a retrospective study of young patients ≤ 45

BackgroundThe incidence of young coronary heart disease (CHD, ≤45xa0years) in China is increasing. Secondary prevention to counter this trend is an important contemporary public health issure.MethodsA total of 5288 patients (≤45xa0years) diagnosed with CHD and hospitalized at the Chinese PLA General Hospital and Anzhen Hospital, both in Beijing, were enrolled after satisfying the inclusion criteria.ResultsYoung CHD patients increased in number from 2010 to 2014, especially men. Among the studied patients, there was no significant change over those years in blood pressure, but heart rate increased significantly (Pu2009<u20090.05) and body mass index showed a rising trend (Pu2009>u20090.05). The incidence of hypertension increased from 40.7 to 47.5%, diabetes from 20.3 to 26.1%, and hyperlipidemia from 27.3 to 35.7% (Pu2009<u20090.05). However, the incidences of smoking and drinking both trended downward (Pu2009<u20090.05). The levels of total cholesterol and triglycerides also showed a downward trend (Pu2009<u20090.05), as did levels of low-density lipoprotein, but not to the point of statistical significance (Pu2009>u20090.05). Mortality during hospitalization decreased significantly from 2010 to 2014 (Pu2009<u20090.05), but there was no significant improvement in the incidences of cardiac death and major adverse cardiovascular events (MACE) after 1-year follow-up (Pu2009>u20090.05).ConclusionsOver the 5xa0years studied, the overall incidence of cardiac death and MACE for young CHD patients (≤45xa0years) has shown little improvement. Secondary prevention of young CHD, and its risk factors, as well as appropriate courses of medical treatment must be further elucidated.

Delayed reendothelialization with rapamycin is rescued by the addition of nicorandil in balloon-injured rat carotid arteries

Rapamycin is an immunosuppressive agent that is added to drug eluting stents. It prevents restenosis, but it also impairs reendothelialization. Nicorandil is a hybrid agent with adenosine triphosphated (ATP)-sensitive K+ (KATP) channel opener and nitrate properties. It prevents oxidative stress and cell apoptosis induced by rapamycin in endothelial cells in vitro. However, whether nicorandil promotes reendothelialization after angioplasty delayed by rapamycin remains to be determined. Balloon injury model was established in SD rats. Nicorandil increased reendothelialization impaired by rapamycin, and it decreased xanthine oxidase (XO)-generated reactive oxygen species (ROS) induced by rapamycin. In addition, eNOS expression inhibited by rapamycin was increased by nicorandil in vivo. In vitro, rapamycin-impeded cardiac microvascular endothelial cells (CMECs) migration, proliferation and rapamycin-induced ROS production were reversed by nicorandil. Knockdown of XO partially inhibited rapamycin-induced ROS production and cell apoptosis in CMECs, and it promoted CMECs migration and proliferation suppressed by rapamycin. Knockdown of Akt partially prevents eNOS upregulation promoted by nicorandil. The beneficial effect of nicorandil is exhibited by inhibiting XO and up-regulating Akt pathway. Nicorandil combined with rapamycin in effect rescue the deficiencies of rapamycin alone in arterial healing after angioplasty.