Huishan Wang

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.

Diallyl trisulfide ameliorates myocardial ischemia–reperfusion injury by reducing oxidative stress and endoplasmic reticulum stress-mediated apoptosis in type 1 diabetic rats: role of SIRT1 activation

Diallyl trisulfide (DATS) protects against apoptosis during myocardial ischemia-reperfusion (MI/R) injury in diabetic state, although the underlying mechanisms remain poorly defined. Previously, we and others demonstrated that silent information regulator 1 (SIRT1) activation inhibited oxidative stress and endoplasmic reticulum (ER) stress during MI/R injury. We hypothesize that DATS reduces diabetic MI/R injury by activating SIRT1 signaling. Streptozotocin (STZ)-induced type 1 diabetic rats were subjected to MI/R surgery with or without perioperative administration of DATS (40xa0mg/kg). We found that DATS treatment markedly improved left ventricular systolic pressure and the first derivative of left ventricular pressure, reduced myocardial infarct size as well as serum creatine kinase and lactate dehydrogenase activities. Furthermore, the myocardial apoptosis was also suppressed by DATS as evidenced by reduced apoptotic index and cleaved caspase-3 expression. However, these effects were abolished by EX527 (the inhibitor of SIRT1 signaling, 5xa0mg/kg). We further found that DATS effectively upregulated SIRT1 expression and its nuclear distribution. Additionally, PERK/eIF2α/ATF4/CHOP-mediated ER stress-induced apoptosis was suppressed by DATS treatment. Moreover, DATS significantly activated Nrf-2/HO-1 antioxidant signaling pathway, thus reducing Nox-2/4 expressions. However, the ameliorative effects of DATS on oxidative stress and ER stress-mediated myocardial apoptosis were inhibited by EX527 administration. Taken together, these data suggest that perioperative DATS treatment effectively ameliorates MI/R injury in type 1 diabetic setting by enhancing cardiac SIRT1 signaling. SIRT1 activation not only upregulated Nrf-2/HO-1-mediated antioxidant signaling pathway but also suppressed PERK/eIF2α/ATF4/CHOP-mediated ER stress level, thus reducing myocardial apoptosis and eventually preserving cardiac function.

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.

Gender differences in fibrosis remodeling in patients with long-standing persistent atrial fibrillation

The success rate of catheter ablation in atrial fibrillation (AF) is known to be lower in females than in males. However, while the exact mechanism for this phenomenon remains to be elucidated, tissue fibrosis may play an important role in this regard. It has been shown that fibrosis promotes AF and its recurrence, thereby substantially reducing the efficacy of catheter ablation in AF patients. Thus, we hypothesized that fibrosis may contribute to gender differences in the outcomes of AF catheter ablation. Here we systematically assessed pulmonary vein sleeves obtained from 166 patients with and without long-standing persistent-AF (LSP-AF) in order to identify gender-specific mechanistic differences in fibrosis remodeling of AF patients. Histological analysis revealed that the female LSP-AF group, rather than its male counterpart, had a higher degree of fibrosis when compared to the NON-AF group. Further analysis using microarray, immunohistochemistry and Western Blot displayed that gender differences in fibrosis remodeling of LSP-AF were mainly due to the inherent differential expression of fibrosis-related genes (n=32) and proteins (n=6). Especially, those related to the TGFβ/Smad3 pathway appeared to be up-regulated in the female LSP-AF group thus promoting an aggravation of fibrosis remodeling. In summary, our data suggest that the aggravation of fibrosis remodeling in women may be an important reason for the low success rate of AF catheter ablation when compared to men. Therefore, inhibiting the TGFβ/Smad3 pathway-mediated fibrosis could represent an interesting target for future therapeutic concepts to improve the success rate of AF catheter ablation in women.The success rate of catheter ablation in atrial fibrillation (AF) is known to be lower in females than in males. However, while the exact mechanism for this phenomenon remains to be elucidated, tissue fibrosis may play an important role in this regard. It has been shown that fibrosis promotes AF and its recurrence, thereby substantially reducing the efficacy of catheter ablation in AF patients. Thus, we hypothesized that fibrosis may contribute to gender differences in the outcomes of AF catheter ablation.Here we systematically assessed pulmonary vein sleeves obtained from 166 patients with and without long-standing persistent-AF (LSP-AF) in order to identify gender-specific mechanistic differences in fibrosis remodeling of AF patients.Histological analysis revealed that the female LSP-AF group, rather than its male counterpart, had a higher degree of fibrosis when compared to the NON-AF group. Further analysis using microarray, immunohistochemistry and Western Blot displayed that gender differences in fibrosis remodeling of LSP-AF were mainly due to the inherent differential expression of fibrosis-related genes (n=32) and proteins (n=6). Especially, those related to the TGFβ/Smad3 pathway appeared to be up-regulated in the female LSP-AF group thus promoting an aggravation of fibrosis remodeling. In summary, our data suggest that the aggravation of fibrosis remodeling in women may be an important reason for the low success rate of AF catheter ablation when compared to men. Therefore, inhibiting the TGFβ/Smad3 pathway-mediated fibrosis could represent an interesting target for future therapeutic concepts to improve the success rate of AF catheter ablation in women.

Relation of Mitochondrial DNA Copy Number in Peripheral Blood to Postoperative Atrial Fibrillation After Isolated Off-Pump Coronary Artery Bypass Grafting

Oxidative stress has been considered to be an important factor contributing to postoperative atrial fibrillation (PoAF). Mitochondrial DNA (mtDNA) copy number in peripheral blood has been found to be associated with a patients oxidative stress. Therefore, we sought to determine whether there was association between mtDNA copy number and the onset of atrial fibrillation. mtDNA copy numbers were measured using the quantitative real-time polymerase chain reaction in peripheral blood from 485 consecutive patients with sinus rhythm undergoing coronary artery bypass grafting. The blood was collected before surgery. In the cohort, the incidence of PoAF was 20.8% (101/485). The mean mtDNA copy number was significantly higher in patents with PoAF than in those with sinus rhythm (36.43 vs 16.63, p <0.001). The receiver operating characteristic analysis proved that the mtDNA copy number could predict PoAF with good sensitivity and specificity (area under the curvexa0= 0.814, cutoffxa0=xa020.91, sensitivityxa0= 70.3%, specificityxa0= 80.2%, p <0.001). On multivariate logistic and Cox regression analysis, mtDNA copy number was shown to be a significant independent risk factor for PoAF (odds ratioxa0= 10.01, p <0.001 and hazard ratioxa0= 7.011, pxa0= 0.004). There was a strong positive correlation between mtDNA copy number and malondialdehyde in patients with PoAF (rxa0= 0.449, pxa0= 0.01). In conclusion, we showed that elevated mtDNA copy number in peripheral blood is associated with PoAF. Further investigation is needed to validate mtDNA copy number as a predictive biomarker for PoAF and to explore its potential role in arrhythmogenesis.

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.

Research progress on combat trauma treatment in cold regions.

Cold regions are a special combat environment in which low temperatures have a great impact on human metabolism and other vital functions, including the nervous, motion, cardiovascular, circulatory, respiratory, and urinary systems; consequently, low temperatures often aggravate existing trauma, leading to high mortality rates if rapid and appropriate treatment is not provided. Hypothermia is an independent risk factor of fatality following combat trauma; therefore, proactive preventative measures are needed to reduce the rate of mortality. After summarizing the basic research on battlefield environments and progress in the prevention and treatment of trauma, this article concludes that current treatment and prevention measures for combat trauma in cold regions are inadequate. Future molecular biology studies are needed to elucidate the mechanisms and relevant cell factors underlying bodily injury caused by cold environment, a research goal will also allow further exploration of corresponding treatments.

Diallyl trisulfide exerts cardioprotection against myocardial ischemia-reperfusion injury in diabetic state, role of AMPK-mediated AKT/GSK-3β/HIF-1α activation

Diallyl trisulfide (DATS), the major active ingredient in garlic, has been reported to confer cardioprotective effects. However, its effect on myocardial ischemia-reperfusion (MI/R) injury in diabetic state and the underlying mechanism are still unknown. We hypothesize that DATS reduces MI/R injury in diabetic state via AMPK-mediated AKT/GSK-3β/HIF-1α activation. Streptozotocin-induced diabetic rats received MI/R surgery with or without DATS (20mg/kg) treatment in the presence or absence of Compound C (Com.C, an AMPK inhibitor, 0.25mg/kg) or LY294002 (a PI3K inhibitor, 5mg/kg). We found that DATS significantly improved heart function and reduced myocardial apoptosis. Additionally, in cultured H9c2 cells, DATS (10μM) also attenuated simulated ischemia-reperfusion injury. We found that AMPK and AKT/GSK-3β/HIF-1α signaling were down-regulated under diabetic condition, while DATS markedly increased the phosphorylation of AMPK, ACC, AKT and GSK-3β as well as HIF-1α expression in MI/R-injured myocardium. However, these protective actions were all blunted by Com.C administration. Additionally, LY294002 abolished the stimulatory effect of DATS on AKT/GSK-3β/HIF-1α signaling without affecting AMPK signaling. While 2-methoxyestradiol (a HIF-1α inhibitor) reduced HIF-1α expression without affecting AKT/GSK-3β signaling. Taken together, these data showed that DATS protected against MI/R injury in diabetic state by attenuating cellular apoptosis via AMPK-mediated AKT/GSK-3β/HIF-1α signaling. Its cardioprotective effect deserves further study.

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.