Qinhua Jin

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.

DUSP1 alleviates cardiac ischemia/reperfusion injury by suppressing the Mff-required mitochondrial fission and Bnip3-related mitophagy via the JNK pathways

Mitochondrial fission and selective mitochondrial autophagy (mitophagy) form an essential axis of mitochondrial quality control that plays a critical role in the development of cardiac ischemia-reperfusion (IR) injury. However, the precise upstream molecular mechanism of fission/mitophagy remains unclear. Dual-specificity protein phosphatase1 (DUSP1) regulates cardiac metabolism, but its physiological contribution in the reperfused heart, particularly its influence on mitochondrial homeostasis, is unknown. Here, we demonstrated that cardiac DUSP1 was downregulated following acute cardiac IR injury. In vivo, compared to wild-type mice, DUSP1 transgenic mice (DUSP1TG mice) demonstrated a smaller infarcted area and the improved myocardial function. In vitro, the IR-induced DUSP1 deficiency promoted the activation of JNK which upregulated the expression of the mitochondrial fission factor (Mff). A higher expression level of Mff was associated with elevated mitochondrial fission and mitochondrial apoptosis. Additionally, the loss of DUSP1 also amplified the Bnip3 phosphorylated activation via JNK, leading to the activation of mitophagy. Increased mitophagy overtly consumed mitochondrial mass resulting into the mitochondrial metabolism disorder. However, the reintroduction of DUSP1 blunted Mff/Bnip3 activation and therefore alleviated the fatal mitochondrial fission/mitophagy by inactivating the JNK pathway, providing a survival advantage to myocardial tissue following IR stress. The results of our study suggest that DUSP1 and its downstream JNK pathway are therapeutic targets for conferring protection against IR injury by repressing Mff-mediated mitochondrial fission and Bnip3-required mitophagy.

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.

Ripk3 promotes ER stress-induced necroptosis in cardiac IR injury: A mechanism involving calcium overload/XO/ROS/mPTP pathway

Receptor-interacting protein 3 (Ripk3)-mediated necroptosis contributes to cardiac ischaemia-reperfusion (IR) injury through poorly defined mechanisms. Our results demonstrated that Ripk3 was strongly upregulated in murine hearts subjected to IR injury and cardiomyocytes treated with LPS and H2O2. The higher level of Ripk3 was positively correlated to the infarction area expansion, cardiac dysfunction and augmented cardiomyocytes necroptosis. Function study further illustrated that upregulated Ripk3 evoked the endoplasmic reticulum (ER) stress, which was accompanied with an increase in intracellular Ca2+ level ([Ca2+]c) and xanthine oxidase (XO) expression. Activated XO raised cellular reactive oxygen species (ROS) that mediated the mitochondrial permeability transition pore (mPTP) opening and cardiomyocytes necroptosis. By comparison, genetic ablation of Ripk3 abrogated the ER stress and thus blocked the [Ca2+]c overload-XO-ROS-mPTP pathways, favouring a pro-survival state that ultimately resulted in the inhibition of cardiomyocytes necroptosis in the setting of cardiac IR injury. In summary, the present study helps to elucidate how necroptosis is mediated by ER stress, via the calcium overload /XO/ROS/mPTP opening axis.

Combination therapy reduces the incidence of no-reflow after primary per-cutaneous coronary intervention in patients with ST-segment elevation acute myocardial infarction.

Background No-reflow is associated with an adverse outcome and higher mortality in patients with ST-segment elevation acute myocardial infarction (STEMI) who undergo percutaneous coronary intervention (PCI) and is considered a dynamic process characterized by multiple pathogenetic components. The aim of this study was to investigate the effectiveness of a combination therapy for the prevention of no-reflow in patient with acute myocardial infarction (AMI) undergoing primary PCI. Methods A total of 621 patients with STEMI who underwent emergency primary PCI were enrolled in this study. Patients with high risk of no-reflow (no-flow score ≥ 10, by using a no-flow risk prediction model, n = 216) were randomly divided into a controlled group (n = 108) and a combination therapy group (n = 108). Patients in the controlled group received conventional treatment, while patients in combination therapy group received high-dose (80 mg) atorvastatin pre-treatment, intracoronary administration of adenosine (140 µg/min per kilogram) during PCI procedure, platelet membrane glycoprotein IIb/IIIa receptor antagonist (tirofiban, 10µg/kg bolus followed by 0.15 µg/kg per minute) and thrombus aspiration. Myocardial contrast echocardiography was performed to assess the myocardial perfusion 72 h after PCI. Major adverse cardiac events (MACE) were followed up for six months. Results Incidence of no-reflow in combination therapy group was 2.8%, which was similar to that in low risk group 2.7% and was significantly lower than that in control group (35.2%, P < 0.01). The myocardial perfusion (A × β) values were higher in combination therapy group than that in control group 72 h after PCI. After 6 months, there were six (6.3%) MACE events (one death, two non-fatal MIs and three revascularizations) in combination therapy group and 12 (13.2%) (four deaths, three non-fatal MIs and five revascularizations, P < 0.05) in control group. Conclusions Combination of thrombus aspiration, high-dose statin pre-treatment, intracoronary administration of adenosine during PCI procedure and platelet membrane glycoprotein IIb/IIIa receptor antagonist reduce the incidence of no-reflow after primary PCI in patients with acute myocardial infarction who are at high risk of no-reflow.

Assessment of Characteristics of Neointimal Hyperplasia after Drug-Eluting Stent Implantation in Patients with Diabetes Mellitus: An Optical Coherence Tomography Analysis

Objective: This study aims to assess the characteristics of neointimal hyperplasia after drug-eluting stent (DES) implantation in patients with diabetes mellitus (DM) by optical coherence tomography (OCT). Methods: OCT was performed in 109 patients (45 with DM and 64 without DM) 1 year after DES implantation. Neointimal coverage and thickness on the luminal side were measured. The characteristics of neointimal hyperplasia were classified into three patterns, namely, high signal pattern, low signal pattern and layered signal pattern, according to the neointimal signal intensity. The development of in-stent neoatherosclerosis was also examined. In the DM group, glycated hemoglobin (HbA1c) levels were analyzed in order to assess their contribution to neointimal characteristics. Results: OCT results indicated that neointimal thickness was thicker in the DM group than in the non-DM group (177.19 ± 165.36 vs. 166.76 ± 132.38 μm, p < 0.001). Lower incidence of high signal pattern (58.33 vs. 75.34%, p = 0.037) and higher incidence of in-stent neoatherosclerosis (18.33 vs. 5.48%, p = 0.027) were observed in the DM group. In the DM subgroup with HbA1c >7%, significantly higher incidence of low signal pattern (37.50 vs. 21.43%, p = 0.001) and layered signal pattern (18.75 vs. 3.57%, p = 0.001) and lower incidence of high signal pattern were observed (43.75 vs. 75.0%, p < 0.001). In-stent neoatherosclerosis was also frequently detected in the high HbA1c group compared with the low HbA1c group (28.13 vs. 7.14%, p = 0.048). Conclusion: Neointimal characteristics differed between DM and non-DM patients. HbA1c levels in DM patients contributed to the development of neointimal hyperplasia and in-stent neoatherosclerosis.

Incidence, Predictors, and Clinical Impact of Tissue Prolapse after Coronary Intervention: An Intravascular Optical Coherence Tomography Study

Objectives: To evaluate the predictors of tissue prolapse after stenting and whether this phenomenon can affect the clinical outcome. Methods: All consecutive patients who underwent optical coherence tomography (OCT) examination after stent implantation were included. Qualitative and quantitative assessment of tissue prolapse after stent implantation was performed. The lesions were classified into 4 groups according to the severity of tissue prolapse. We analyzed the clinical, procedural, and image-based predictors of severe tissue prolapse and evaluated the clinical impact of tissue prolapse. Results: Tissue prolapse within the stented segment was visible in 102/104 (98.08%) cases. The frequency and severity of tissue prolapse was similar in acute coronary syndrome (ACS) and non-ACS lesions. The OCT-defined thin cap fibroatheroma (TCFA) was related with severe tissue prolapse (≧grade III) (r = 17.722, p < 0.001). No difference in events was observed among different tissue prolapse groups during the hospitalization period and 1-year follow-up. Conclusions: The incidence of tissue prolapse after stent implantation was relatively high, irrespective of the clinical presentation. OCT-defined TCFA lesions were more likely with severe tissue prolapse (≧grade III). Tissue prolapse was not associated with clinical events during the hospitalization period and 1-year clinical follow-up.

MiR-138 protects cardiac cells against hypoxia through modulation of glucose metabolism by targetting pyruvate dehydrogenase kinase 1

Dysfunction of cardiac cells under hypoxia has been identified as an essential event leading to myocytes functional failure. MiRNAs are importantly regulatory small-noncoding RNAs that negatively regulate gene expression through the direct binding of 3′-UTR region of their target mRNAs. Recent studies have demonstrated that miRNAs are aberrantly expressed in the cardiovascular system under pathological conditions.Pyruvate dehydrogenase kinase 1 (PDK1) is a kinase which phosphorylates pyruvate dehydrogenase to inactivate it, leading to elevated anaerobic glycolysis and decreased cellular respiration. In the present study, we report that miR-138 expressions were significantly suppressed under long exposure to hypoxia. In addition, overexpression of miR-138 protects human cardiac cells against hypoxia. We observed miR-138 inhibits glycolysis but promotes mitochondrial respiration through directly targetting PDK1. Moreover, we demonstrate that hypoxia induces cardiac cell death through increased glycolysis and decreased mitochondrial respiration. Inhibition of glycolysis by either glycolysis inhibitor or knockdown glycolysis enzymes, Glucose transportor 1 (Glut1) or PDK1 contributes to cardiac cells’ survival. The cell sentivity to hypoxia was recovered when the PDK1 level was restored in miR-138 overexpressing cardiac cells. The present study leads to the intervention of novel therapeutic strategies against cardiac cells dysfunction during surgery or ischemia.

Deep Learning-Based Detection and Segmentation for BVS Struts in IVOCT Images

Bioresorbable Vascular Scaffold (BVS) is the latest stent type for the treatment of coronary artery disease. A major challenge of BVS is that once it is malapposed during implantation, it may potentially increase the risks of late stent thrombosis. Therefore it is important to analyze struts malapposition during implantation. This paper presents an automatic method for BVS malapposition analysis in intravascular optical coherence tomography images. Struts are firstly detected by a detector trained through deep learning. Then, struts boundaries are segmented using dynamic programming. Based on the segmentation, apposed and malapposed struts are discriminated automatically. Experimental results show that the proposed method successfully detected 97.7% of 4029 BVS struts with 2.41% false positives. The average Dice coefficient between the segmented struts and ground truth was 0.809. It concludes that the proposed method is accurate and efficient for BVS struts detection and segmentation, and enables automatic malapposition analysis.