Yinli Xu

Melatonin ameliorates myocardial ischemia/reperfusion injury in type 1 diabetic rats by preserving mitochondrial function: role of AMPK-PGC-1α-SIRT3 signaling

Enhancing mitochondrial biogenesis and reducing mitochondrial oxidative stress have emerged as crucial therapeutic strategies to ameliorate diabetic myocardial ischemia/reperfusion (MI/R) injury. Melatonin has been reported to be a safe and potent cardioprotective agent. However, its role on mitochondrial biogenesis or reactive oxygen species (ROS) production in type 1 diabetic myocardium and the underlying mechanisms remain unknown. We hypothesize that melatonin ameliorates MI/R injury in type 1 diabetic rats by preserving mitochondrial function via AMPK-PGC-1α-SIRT3 signaling pathway. Both our in vivo and in vitro data showed that melatonin reduced MI/R injury by improving cardiac function, enhancing mitochondrial SOD activity, ATP production and oxidative phosphorylation complex (II, III and IV), reducing myocardial apoptosis and mitochondrial MDA, H2O2 generation. Importantly, melatonin also activated AMPK-PGC-1α-SIRT3 signaling and increased SOD2, NRF1 and TFAM expressions. However, these effects were abolished by Compound C (a specific AMPK signaling blocker) administration. Additionally, our cellular experiment showed that SIRT3 siRNA inhibited the cytoprotective effect of melatonin without affecting p-AMPK/AMPK ratio and PGC-1α expression. Taken together, we concluded that melatonin preserves mitochondrial function by reducing mitochondrial oxidative stress and enhancing its biogenesis, thus ameliorating MI/R injury in type 1 diabetic state. AMPK-PGC1α-SIRT3 axis plays an essential role in this process.

Melatonin rescues cardiac thioredoxin system during ischemia-reperfusion injury in acute hyperglycemic state by restoring Notch1/Hes1/Akt signaling in a membrane receptor-dependent manner.

Stress hyperglycemia is commonly observed in patients suffering from ischemic heart disease. It not only worsens cardiovascular prognosis but also attenuates the efficacies of various cardioprotective agents. This study aimed to investigate the protective effect of melatonin against myocardial ischemia‐reperfusion (MI/R) injury in acute hyperglycemic state with a focus on Notch1/Hes1/Akt signaling and intracellular thioredoxin (Trx) system. Sprague Dawley rats were subjected to MI/R surgery and high‐glucose (HG, 500 g/L) infusion (4 mL/kg/h) to induce temporary hyperglycemia. Rats were treated with or without melatonin (10 mg/kg/d) during the operation. Furthermore, HG (33 mmol/L)‐incubated H9c2 cardiomyoblasts were treated in the presence or absence of luzindole (a competitive melatonin receptor antagonist), DAPT (a γ‐secretase inhibitor), LY294002 (a PI3‐kinase/Akt inhibitor), or thioredoxin‐interacting protein (Txnip) adenoviral vectors. We found that acute hyperglycemia aggravated MI/R injury by suppressing Notch1/Hes1/Akt signaling and intracellular Trx activity. Melatonin treatment effectively ameliorated MI/R injury by reducing infarct size, myocardial apoptosis, and oxidative stress. Moreover, melatonin also markedly enhanced Notch1/Hes1/Akt signaling and rescued intracellular Trx system by upregulating Notch1, N1ICD, Hes1, and p‐Akt expressions, increasing Trx activity, and downregulating Txnip expression. However, these effects were blunted by luzindole, DAPT, or LY294002. Additionally, Txnip overexpression not only decreased Trx activity, but also attenuated the cytoprotective effect of melatonin. We conclude that impaired Notch1 signaling aggravates MI/R injury in acute hyperglycemic state. Melatonin rescues Trx system by reducing Txnip expression via Notch1/Hes1/Akt signaling in a membrane receptor‐dependent manner. Its role as a prophylactic/therapeutic drug deserves further clinical study.

Melatonin protects diabetic heart against ischemia-reperfusion injury, role of membrane receptor-dependent cGMP-PKG activation

It has been demonstrated that the anti-oxidative and cardioprotective effects of melatonin are, at least in part, mediated by its membrane receptors. However, the direct downstream signaling remains unknown. We previously found that melatonin ameliorated myocardial ischemia-reperfusion (MI/R) injury in diabetic animals, although the underlying mechanisms are also incompletely understood. This study was designed to determine the role of melatonin membrane receptors in melatonins cardioprotective actions against diabetic MI/R injury with a focus on cGMP and its downstream effector PKG. Streptozotocin-induced diabetic Sprague-Dawley rats and high-glucose medium-incubated H9c2 cardiomyoblasts were utilized to determine the effects of melatonin against MI/R injury. Melatonin treatment preserved cardiac function and reduced oxidative damage and apoptosis. Additionally, melatonin increased intracellular cGMP level, PKGIα expression, p-VASP/VASP ratio and further modulated myocardial Nrf-2-HO-1 and MAPK signaling. However, these effects were blunted by KT5823 (a selective inhibitor of PKG) or PKGIα siRNA except that intracellular cGMP level did not changed significantly. Additionally, our in vitro study showed that luzindole (a nonselective melatonin membrane receptor antagonist) or 4P-PDOT (a selective MT2 receptor antagonist) not only blocked the cytoprotective effect of melatonin, but also attenuated the stimulatory effect of melatonin on cGMP-PKGIα signaling and its modulatory effect on Nrf-2-HO-1 and MAPK signaling. This study showed that melatonin ameliorated diabetic MI/R injury by modulating Nrf-2-HO-1 and MAPK signaling, thus reducing myocardial apoptosis and oxidative stress and preserving cardiac function. Importantly, melatonin membrane receptors (especially MT2 receptor)-dependent cGMP-PKGIα signaling played a critical role in this process.

The transcriptome responses of cardiomyocyte exposed to hypothermia.

Hypothermia has positive and negative consequences on the body. Hypothermia depresses myocardial contraction, conduction, and metabolic rate in the heart. However, little is known about the underlying molecular mechanisms. Herein, we compared the gene expression of human adult ventricular cardiomyocytes (AC16) under hypothermia to find differences between different temperatures, and elucidate the candidate genes that may play important roles in the response to hypothermia. A total of 2413 differentially expressed genes (DEGs) were identified by microarray hybridization, which provided abundant data for further analysis. Gene Ontology (GO) enrichment analysis revealed that genes related to transcription, and protein and lipid metabolism were significantly enriched. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEGs were significantly enriched in TGF-β pathway and cytokine-cytokine receptor interaction, which may play important roles in changes affected by hypothermia. A set of transcription factors (TFs) (CPBP, Churchill, NF-AT1, GKLF, SRY, ZNF333, ING4, myogenin, DRI1 and CRX) was recognized to be the functional layer of key nodes, which mapped the signal of hypothermia to transcriptome. The identified DEGs, pathways and predicted TFs could facilitate further investigations of the detailed molecular mechanisms.

Plasma Circular RNAs, Hsa_circRNA_025016, Predict Postoperative Atrial Fibrillation After Isolated Off‐Pump Coronary Artery Bypass Grafting

Background Circular RNAs (circRNAs) are pervasively expressed in highly divergent eukaryotes and are stable in body fluids. However, the link between circRNAs and onset of atrial fibrillation (AF) has not previously been investigated. We aimed to identify plasma circRNAs that are able predict AF after cardiac surgery. Methods and Results Plasma circRNA expression profiles were investigated in a total of 769 patients with or without AF after isolated off‐pump coronary artery bypass grafting. First, a circRNA microarray was used to screen 13 617 human circRNAs in plasma samples from patients in the discovery cohort (n=30). A quantitative polymerase chain reaction assay was then applied to evaluate the expression of 9 selected circRNAs in the training cohort (n=365). This approach revealed that hsa_circRNA_025016 was upregulated in patients with new‐onset AF with a high diagnostic accuracy as assessed by the area under the receiver operating characteristic curve (=0.802). Additionally, a satisfactory diagnostic performance of hsa_circRNA_025016 was found in the validation cohort (n=284). Furthermore, Kyoto Encyclopedia of Genes and Genomes biological pathway analysis indicated that hsa_circ_025016 participated in melanogenesis, insulin secretion, and the thyroid hormone signaling pathway. A positive correlation between hsa_circ_025016 and fasting blood glucose was also identified in both cohorts. Conclusions Hsa_circ_025016 is a potential biomarker for predicting new‐onset AF after isolated off‐pump coronary artery bypass grafting.

Long noncoding RNA upregulated in hypothermia treated cardiomyocytes protects against myocardial infarction through improving mitochondrial function

BACKGROUND Myocardial infarction (MI) is one of the most common causes of cardiac morbidity and mortality. Many evidences suggest that hypothermia have a more pronounced impact as an adjunctive therapy for MI to reduce infarct size. However, the function of long non-coding RNAs (lncRNA) in therapeutic hypothermia for MI remains poorly understood. METHODS In this study, we investigated the expression of lncRNA-UIHTC (upregulated in hypothermia treated cardiomyocytes, NONHSAT094064) in ischemic heart tissues. To investigate its function, overexpression of UIHTC was performed by adeno-associated virus vectors after MI model in rat. RESULTS lncRNA-UIHTC was upregulated in ischemic or injury cardiomyocytes. Overexpression of lncRNA-UIHTC in peri-infarction attenuated cardiac dysfunction in vivo. Mechanistically, lncRNA-UIHTC enhanced the mitochondrial function via upregulation of PGC1α. Moreover, when we knocked down PGC1α, the mitochondrial maximal oxygen consumption and ATP levels enhanced by overexpression of UIHTC were nearly completely restored. CONCLUSIONS Altogether we have provided a new mechanism whereby hypothermia protected heart against ischemic via lncRNA-UIHTC. The UIHTC provided a new potential therapeutic target for MI but prevented the complications of hypothermia.

Data on long noncoding RNA upregulated in hypothermia treated cardiomyocytes protects against myocardial infarction through improving mitochondrial function

This article elaborates on cardioprotective action of hypothermia related long noncoding RNA against myocardial infarction through improving mitochondrial function, which preset by J Zhang. Herein, we provide the materials and methods used in that study. And provided the detail of dysregulation of lncRNAs under the treatment of hypothermia. Furthermore, we found that lnc-UIHTC (lncRNA upregulated in hypothermia treated cardiomyocyte, NONHSAT094064) attenuated cardiomyocytes apoptosis in vitro.

Kaiso protects human umbilical vein endothelial cells against apoptosis by differentially regulating the expression of B-cell CLL/lymphoma 2 family members

Endothelial cell injury can promote the development of various cardiovascular diseases, thus, fully understanding the mechanisms underlying the maintenance of vascular endothelial cell homoeostasis may help prevent and treat cardiovascular disease. Kaiso, a zinc finger and BTB domain containing transcription factor, is key to embryonic development and cancer, but how Kaiso interacts with vascular endothelium is not fully understood. We report that Kaiso has an anti-apoptotic function in human umbilical vein endothelial cells (HUVECs) and human microvascular endothelial cells (HMEC-1s). Overexpression of Kaiso significantly increased cell viability and inhibited hydrogen peroxide-induced apoptosis. Furthermore, Kaiso increased expression of B-cell CLL/lymphoma 2 (BCL2) and reduced expression of BCL2-associated X protein (BAX) and BCL2-interacting killer (BIK) by differentially regulating gene promoter activity. Methylated DNA and specific Kaiso binding site (KBS) contributed to gene regulatory activity of Kaiso. In addition, p120ctn functioned cooperatively in Kaiso-mediated transcriptional regulation.

Relationship between Angiotensin Converting Enzyme, Apelin, and New-Onset Atrial Fibrillation after Off-Pump Coronary Artery Bypass Grafting

It has been shown that inflammation and oxidative stress are important factors in postoperative atrial fibrillation (POAF). Angiotensin converting enzyme (ACE) and apelin have a close relationship with inflammation and oxidative stress. The effect of ACE and apelin on POAF after off-pump coronary artery bypass grafting (OPCABG) remains a question. The concentrations of serum ACE, angiotensin II (Ang II), apelin, bradykinin (BK), malondialdehyde (MDA), and C reactive protein (CRP) were measured in the perioperative period of OPCABG. The levels of serum ACE in the POAF group were higher than in the no POAF group both preoperatively and postoperatively. Apelin in the POAF group was lower than in the no POAF group. There was a correlation between serum ACE and apelin. Postoperatively, CRP and MDA in the POAF group were higher than in the no POAF group; however, there was no difference before the operation. Preoperative ACE and apelin were both significant and independent risk factors for POAF. In conclusion, the high ACE and low apelin preoperatively led to CRP and MDA being increased postoperatively, which was probably associated with POAF after OPCABG. Apelin may be a new predictor for POAF.