Remote ischemic preconditioning in patients undergoing cardiac surgery with six ischemic cycles

BACKGROUND

We have previously shown that remote ischemic preconditioning (RIP), which utilizes in part the extracellular RNA (eRNA)/RNase1 pathway, can induce ischemic tolerance in humans. Because RIP has thus far been tested only with four cycles of extremity ischemia/reperfusion, we investigated the influence of six cycles of ischemia on the eRNA/RNase1 pathway in cardiac patients.

METHODS

Six cycles of RIP were carried out in 14 patients undergoing cardiac surgery. Blood samples were taken at 13 timepoints during surgery and at three timepoints after surgery for determining serum levels of RNase1, eRNA, and TNF-α. Trans-cardiac gradients between the myocardial blood inflow and outflow were calculated.

RESULTS

Between the fourth and the sixth RIP cycles, a noticeable increase in the levels of eRNA (fourth: 151.6 (SD: 44.2) ng/ml vs sixth: 181.8 (SD: 87.5) ng/ml, p = .071), and a significant increase in RNase1 (fourth: 151.1 (SD: 42.6) U/ml vs sixth: 175.3 (SD: 41.2) U/ml, p = .001), were noted. The trans-cardiac gradients of RNase1 and eRNA before and after ischemia were not significantly different (p = .158 and p = .221; p = .397 and p = .683, respectively). Likewise, the trans-cardiac gradient of TNF-α was similar before and after ischemia. During the first 48 h after the surgery, RNase1 activity rose significantly and exceeded baseline values (135.7 (SD: 40.6) U/ml before and 279.2 (SD: 85.6) U/ml after surgery, p = .001) as did eRNA levels (148,6 (SD: 35.4) ng/ml before and 396.5 (SD: 154.5) ng/ml after surgery, p = .005), whereas TNF-α levels decreased significantly (91.7 (SD: 47.7) pg/ml before and 35.7 (SD: 36.9) pg/ml after surgery, p = .001).

CONCLUSION

Six RIP cycles increased the RNase1 levels significantly above those observed with four cycles. More clinical data are required to show whether this translates into a benefit for patients.

Inactivation of nuclear histone deacetylases by EP300 disrupts the MiCEE complex in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and highly lethal lung disease with unknown etiology and poor prognosis. IPF patients die within 2 years after diagnosis mostly due to respiratory failure. Current treatments against IPF aim to ameliorate patient symptoms and to delay disease progression. Unfortunately, therapies targeting the causes of or reverting IPF have not yet been developed. Here we show that reduced levels of miRNA lethal 7d (MIRLET7D) in IPF compromise epigenetic gene silencing mediated by the ribonucleoprotein complex MiCEE. In addition, we find that hyperactive EP300 reduces nuclear HDAC activity and interferes with MiCEE function in IPF. Remarkably, EP300 inhibition reduces fibrotic hallmarks of in vitro (patient-derived primary fibroblast), in vivo (bleomycin mouse model), and ex vivo (precision-cut lung slices, PCLS) IPF models. Our work provides the molecular basis for therapies against IPF using EP300 inhibition.

Idiopathic pulmonary fibrosis (IPF) is a lethal disease with insufficient treatment strategies. Here the authors show that reduction of the microRNA MIRLET7D and hyperactivation of EP300 contribute to impaired epigenetic silencing by the MiCEE complex in pulmonary fibroblasts of IPF patients, and demonstrate the benefit of inhibiting EP300 for the treatment of IPF.

The Role of Redox Dysregulation in the Inflammatory Response to Acute Myocardial Ischaemia-reperfusion Injury - Adding Fuel to the Fire

BACKGROUND

The inflammatory response to acute myocardial ischaemia/ reperfusion injury (IRI) plays a critical role in determining myocardial infarct (MI) size, and subsequent post-MI left ventricular (LV) remodelling, making it a potential therapeutic target for improving clinical outcomes in patients presenting with an acute myocardial infarction (AMI). Recent experimental studies using advanced imaging and molecular techniques, have yielded new insights into the mechanisms through which reactive oxygen species (ROS) contribute to the inflammatory response induced by acute myocardial IRI - "adding fuel to the fire". The infiltration of inflammatory cells into the MI zone, leads to elevated myocardial concentrations of ROS, cytokine release, and activation of apoptotic and necrotic death pathways. Anti-oxidant and anti-inflammatory therapies have failed to protect the heart against acute myocardial IRI. This may be, in part, due to a lack of understanding of the time course, nature and mechanisms of the inflammation and redox dysregulation, which occur in the setting of acute myocardial IRI.

CONCLUSION

In this article, we examine the inflammatory response and redox dysregulation induced by acute myocardial IRI, and highlight potential therapeutic options for targeting redox dysregulation, in order to attenuate the detrimental effects of the inflammatory response following an AMI, so as to reduce MI size and prevent heart failure.

MiD49 and MiD51: New mediators of mitochondrial fission and novel targets for cardioprotection

Acute myocardial infarction (AMI) and the heart failure (HF) that often follows are among the leading causes of death and disability worldwide. As such novel therapies are needed to reduce myocardial infarct (MI) size, and preserve left ventricular (LV) systolic function in order to reduce the propensity for HF following AMI. Mitochondria are dynamic organelles that can undergo morphological changes by two opposing processes, mitochondrial fusion and fission. Changes in mitochondrial morphology and turnover are a vital part of maintaining mitochondrial health, DNA stability, energy production, calcium homeostasis, cellular division, and differentiation, and disturbances in the balance of fusion and fission can predispose to mitochondrial dysfunction and cell death. Changes in mitochondrial morphology are governed by mitochondrial fusion proteins (Mfn1, Mfn2 and OPA1) and mitochondrial fission proteins (Drp1, hFis1, and Mff). Recent experimental data suggest that mitochondria undergo fission during acute ischemia/reperfusion injury (IRI), generating fragmented dysfunctional mitochondrial and predisposing to cell death. We and others have shown that genetic and pharmacological inhibition of the mitochondrial fission protein Drp1 can protect cardiomyocytes from acute IRI and reduce MI size. Novel components of the mitochondrial fission machinery, mitochondrial dynamics proteins of 49 kDa (MiD49) and mitochondrial dynamics proteins of 51 kDa (MiD51), have been recently described, which have been shown to mediating mitochondrial fission by targeting Drp1 to the mitochondrial surface. In this review article, we provide an overview of MiD49 and MiD51, and highlight their potential as novel therapeutic targets for treating cardiovascular diseases such as AMI, anthracycline cardiomyopathy, and pulmonary arterial hypertension.

Thrombin selectively induces transcription of genes in human monocytes involved in inflammation and wound healing

Thrombin is essential for blood coagulation but functions also as a mediator of cellular signalling. Gene expression microarray experiments in human monocytes revealed thrombin-induced upregulation of a limited subset of genes, which are almost exclusively involved in inflammation and wound healing. Among these, the expression of F3 gene encoding for tissue factor (TF) was enhanced indicating that this physiological initiator of coagulation cascade may create a feed-forward loop to enhance blood coagulation. Activation of protease-activated receptor type 1 (PAR1) was shown to play a main role in promoting TF expression. Moreover, thrombin induced phosphorylation of ERK1/2, an event that is required for expression of thrombin-regulated genes. Thrombin also increased the expression of TF at the protein level in monocytes as evidenced by Western blot and immunostaining. Furthermore, FXa generation induced by thrombin-stimulated monocytes was abolished by a TF blocking antibody and therefore it is entirely attributable to the expression of tissue factor. This cellular activity of thrombin provides a new molecular link between coagulation, inflammation and wound healing.

Mortality and cancer after 12 versus 30 months dual antiplatelet therapy

The optimal duration and cancer risks of antiplatelet therapy following percutaneous coronary intervention (PCI) are unclear. We compared cancer and all-cause mortality after dual antiplatelet therapy (DAPT) for the combination of clopidogrel and aspirin (ASA) versus ASA alone over 18 months follow-up in event-free patients at 12 months DAPT from the Health Insurance Review and Assessment (HIRA) dataset via the Korean Outcomes Registry Evaluating Antithrombotics (KOREA). We selected PCI patients who were event free for 12 months and maintained a consistent antiplatelet regimen for 18 more months. The primary endpoints were any cancer and all-cause mortality at 30 months follow-up after PCI. From 320,351 screened post-PCI patient HIRA records, we excluded 294,413 and qualified 25,938, constituting DAPT (n=10,992) and ASA (n=14,946) groups. The Propensity Score Matching (PSM), and Inverse Probability of Treatment Weighting (IPTW) revealed no significant differences in background demographics and clinical characteristics for DAPT versus ASA patients. At 30-months post-PCI, after massive (>91 %) exclusions, cancer risk was higher for continuous DAPT [455 (4.15 %) vs 606 (4.04 %); HR=1.221; 95 %CI: 1.061–1.405; p=0.005], which remained significant by PSM (p=0.006) or IPTW (p=0.007), while all-cause mortality was similar [136 (1.24 %) vs 192 (1.28 %) HR=0.999; 95 %CI: 0.736–1.135; p=0.993]. This analysis suggests a potential mild excess cancer risk, but no mortality benefit in Korean post-PCI patients treated with DAPT for an additional 18 months beyond conventional 12 months DAPT. These data are not supporting continuing DAPT for more than one year in East Asians. Analysing cancer types and assessing potential cancer association with bleeding are warranted.

Mechanism and consequences of the shift in cardiac arginine metabolism following ischaemia and reperfusion in rats

Cardiac ischaemia and reperfusion leads to irreversible injury and subsequent tissue remodelling. Initial reperfusion seems to shift arginine metabolism from nitric oxide (NO) to polyamine formation. This may limit functional recovery at reperfusion. The hypothesis was tested whether ischaemia/reperfusion translates such a shift in arginine metabolism in a tumour necrosis factor (TNF)-α-dependent way and renin-angiotensin system (RAS)-dependent way into a sustained effect. Both, the early post-ischaemic recovery and molecular adaptation to ischaemia/reperfusion were analysed in saline perfused rat hearts undergoing global no-flow ischaemia and reperfusion. Local TNF-α activation was blocked by inhibition of TNF-α sheddase ADAM17. To interfere with RAS captopril was administered. Arginase was inhibited by administration of Nor-NOHA. Long-term effects of ischemia/reperfusion on arginine metabolism were analysed in vivo in rats receiving an established ischaemia/reperfusion protocol in the closed chest mode. mRNA expression analysis indicated a shift in the arginine metabolism from NO formation to polyamine metabolism starting within 2 hours (h) of reperfusion and translated into protein expression within 24 h. Inhibition of the TNF-α pathway and captopril attenuated these delayed effects on post-ischaemic recovery. This shift in arginine metabolism was associated with functional impairment of hearts within 24 h. Inhibition of arginase but not that of TNF-α and RAS pathways improved functional recovery immediately. However, no benefit was observed after four months. In conclusion, this study identified TNF-α and RAS to be responsible for depressed cardiac function that occurred a few hours after reperfusion.

Assessing the effects of mitofusin 2 deficiency in the adult heart using 3D electron tomography

The effects of mitofusin 2 (MFN2) deficiency, on mitochondrial morphology and the mitochondria-junctional sarcoplasmic reticulum (jSR) complex in the adult heart, have been previously investigated using 2D electron microscopy, an approach which is unable to provide a 3D spatial assessment of these imaging parameters. Here, we use 3D electron tomography to show that MFN2-deficient mitochondria are larger in volume, more elongated, and less rounded; have fewer mitochondria-jSR contacts, and an increase in the distance between mitochondria and jSR, when compared to WT mitochondria. In comparison to 2D electron microscopy, 3D electron tomography can provide further insights into mitochondrial morphology and the mitochondria-jSR complex in the adult heart.

Targeting of Extracellular RNA Reduces Edema Formation and Infarct Size and Improves Survival After Myocardial Infarction in Mice

BACKGROUND

Following myocardial infarction (MI), peri-infarct myocardial edema formation further impairs cardiac function. Extracellular RNA (eRNA) released from injured cells strongly increases vascular permeability. This study aimed to assess the role of eRNA in MI-induced cardiac edema formation, infarct size, cardiac function, and survival after acute MI and to evaluate the therapeutic potential of ribonuclease 1 (RNase-1) treatment as an eRNA-degrading intervention.

METHODS AND RESULTS

C57BL/6J mice were subjected to MI by permanent ligation of the left anterior descending coronary artery. Plasma eRNA levels were significantly increased compared with those in controls starting from 30 minutes after ligation. Systemic application of RNase-1, but not DNase, significantly reduced myocardial edema formation 24 hours after ligation compared with controls. Consequently, eRNA degradation by RNase-1 significantly improved the perfusion of collateral arteries in the border zone of the infarcted myocardium 24 hours after ligation of the left anterior descending coronary artery, as detected by micro-computed tomography imaging. Although there was no significant difference in the area at risk, the area of vital myocardium was markedly larger in mice treated with RNase-1 compared with controls, as detected by Evans blue and 2,3,5-triphenyltetrazolium chloride staining. The increase in viable myocardium was associated with significantly preserved left ventricular function, as assessed by echocardiography. Moreover, RNase-1 significantly improved 8-week survival following MI.

CONCLUSIONS

eRNA is an unrecognized permeability factor in vivo, associated with myocardial edema formation after acute MI. RNase-1 counteracts eRNA-induced edema formation and preserves perfusion of the infarction border zone, reducing infarct size and protecting cardiac function after MI.

Unique morphological characteristics of mitochondrial subtypes in the heart: the effect of ischemia and ischemic preconditioning

RATIONALE

Three subsets of mitochondria have been described in adult cardiomyocytes - intermyofibrillar (IMF), subsarcolemmal (SSM), and perinuclear (PN). They have been shown to differ in physiology, but whether they also vary in morphological characteristics is unknown. Ischemic preconditioning (IPC) is known to prevent mitochondrial dysfunction induced by acute myocardial ischemia/reperfusion injury (IRI), but whether IPC can also modulate mitochondrial morphology is not known.

AIMS

Morphological characteristics of three different subsets of adult cardiac mitochondria along with the effect of ischemia and IPC on mitochondrial morphology will be investigated.

METHODS

Mouse hearts were subjected to the following treatments (N=6 for each group): stabilization only, IPC (3x5 min cycles of global ischemia and reperfusion), ischemia only (20 min global ischemia); and IPC and ischemia. Hearts were then processed for electron microscopy and mitochondrial morphology was assessed subsequently.

RESULTS

In adult cardiomyocytes, IMF mitochondria were found to be more elongated and less spherical than PN and SSM mitochondria. PN mitochondria were smaller in size when compared to the other two subsets. SSM mitochondria had similar area to IMF mitochondria but their sphericity measures were similar to PN mitochondria. Ischemia was shown to increase the sphericity parameters of all 3 subsets of mitochondria; reduce the length of IMF mitochondria, and increase the size of PN mitochondria. IPC had no effect on mitochondrial morphology either at baseline or after ischemia.

CONCLUSION

The three subsets of mitochondria in the adult heart are morphologically different. IPC does not appear to modulate mitochondrial morphology in adult cardiomyocytes.

MicroRNA-142 is a multifaceted regulator in organogenesis, homeostasis, and disease

Over the past decade, microRNA-142 (miR-142) is emerging as a major regulator of cell fate decision in the hematopoietic system. However, miR-142 is expressed in many other tissues, and recent evidence suggests that it may play a more pleiotropic role during embryonic development. In addition, miR-142 has been shown to play important functions in disease. miR-142 displays a functional role in cancer, virus infection, inflammation, and immune tolerance. Both a guide strand (miR-142-3p) and passenger strand (miR-142-5p) are generated from the miR-142 hairpin. miR-142-3p and -5p display overlapping but also independent target genes. Loss of function mouse models (genetrap, global knock out [KO], and conditional KO) have been reported and support the important role of miR-142 in different biological processes. This review will summarize the abundant literature already available for miR-142 and will lay the foundation for future works on this important microRNA. Developmental Dynamics 246:285-290, 2017. © 2016 Wiley Periodicals, Inc.