miR-223-3p Prevents Necroptotic Macrophage Death by Targeting Ripk3 in a Negative Feedback Loop and Consequently Ameliorates Advanced Atherosclerosis.

BACKGROUND: The formation of large necrotic cores results in vulnerable atherosclerotic plaques, which can lead to severe cardiovascular diseases. However, the specific regulatory mechanisms underlying the development of necrotic cores remain unclear. METHODS: To evaluate how the modes of lesional cell death are reprogrammed during the development of atherosclerosis, the expression levels of key proteins that are involved in the necroptotic, apoptotic, and pyroptotic pathways were compared between different stages of plaques in humans and mice. Luciferase assays and loss-of-function studies were performed to identify the microRNA-mediated regulatory mechanism that protects foamy macrophages from necroptotic cell death. The role of this mechanism in atherosclerosis was determined by using a knockout mouse model with perivascular drug administration and tail vein injection of microRNA inhibitors in Apoe-/- mice. RESULTS: Here, we demonstrate that the necroptotic, rather than the apoptotic or pyroptotic, pathway is more activated in advanced unstable plaques compared with stable plaques in both humans and mice, which closely correlates with necrotic core formation. The upregulated expression of Ripk3 (receptor-interacting protein kinase 3) promotes the C/EBPß (CCAAT/enhancer binding protein beta)-dependent transcription of the microRNA miR-223-3p, which conversely inhibits Ripk3 expression and forms a negative feedback loop to regulate the necroptosis of foamy macrophages. The knockout of the Mir223 gene in bone marrow cells accelerates atherosclerosis in Apoe-/- mice, but this effect can be rescued by Ripk3 deficiency or treatment with the necroptosis inhibitors necrostatin-1 and GSK-872. Like the Mir223 knockout, treating Apoe-/- mice with miR-223-3p inhibitors increases atherosclerosis. CONCLUSIONS: Our study suggests that miR-223-3p expression in macrophages protects against atherosclerotic plaque rupture by limiting the formation of necrotic cores, thus providing a potential microRNA therapeutic candidate for atherosclerosis.

A streamlined pathway for transcatheter aortic valve implantation: the BENCHMARK study.

BACKGROUND AND AIMS: There is significant potential to streamline the clinical pathway for patients undergoing transcatheter aortic valve implantation (TAVI). The purpose of this study was to evaluate the effect of implementing BENCHMARK best practices on the efficiency and safety of TAVI in 28 sites in 7 European countries. METHODS: This was a study of patients with severe symptomatic aortic stenosis (AS) undergoing TAVI with balloon-expandable valves before and after implementation of BENCHMARK best practices. Principal objectives were to reduce hospital length of stay (LoS) and duration of intensive care stay. Secondary objective was to document patient safety. RESULTS: Between January 2020 and March 2023, 897 patients were documented prior to and 1491 patients after the implementation of BENCHMARK practices. Patient characteristics were consistent with a known older TAVI population and only minor differences. Mean LoS was reduced from 7.7 ± 7.0 to 5.8 ± 5.6 days (median 6 vs. 4 days; P < .001). Duration of intensive care was reduced from 1.8 to 1.3 days (median 1.1 vs. 0.9 days; P < .001). Adoption of peri-procedure best practices led to increased use of local anaesthesia (96.1% vs. 84.3%; P < .001) and decreased procedure (median 47 vs. 60 min; P < .001) and intervention times (85 vs. 95 min; P < .001). Thirty-day patient safety did not appear to be compromised with no differences in all-cause mortality (0.6% in both groups combined), stroke/transient ischaemic attack (1.4%), life-threatening bleeding (1.3%), stage 2/3 acute kidney injury (0.7%), and valve-related readmission (1.2%). CONCLUSIONS: Broad implementation of BENCHMARK practices contributes to improving efficiency of TAVI pathway reducing LoS and costs without compromising patient safety.

Endothelial ENPP2 (Ectonucleotide Pyrophosphatase/Phosphodiesterase 2) Increases Atherosclerosis in Female and Male Mice.

BACKGROUND: Maladapted endothelial cells (ECs) secrete ENPP2 (ectonucleotide pyrophosphatase/phosphodiesterase 2; autotaxin)-a lysophospholipase D that generates lysophosphatidic acids (LPAs). ENPP2 derived from the arterial wall promotes atherogenic monocyte adhesion induced by generating LPAs, such as arachidonoyl-LPA (LPA20:4), from oxidized lipoproteins. Here, we aimed to determine the role of endothelial ENPP2 in the production of LPAs and atherosclerosis. METHODS: We quantified atherosclerosis in mice harboring loxP-flanked Enpp2 alleles crossed with Apoe-/- mice expressing tamoxifen-inducible Cre recombinase under the control of the EC-specific bone marrow X kinase promoter after 12 weeks of high-fat diet feeding. RESULTS: A tamoxifen-induced EC-specific Enpp2 knockout decreased atherosclerosis, accumulation of lesional macrophages, monocyte adhesion, and expression of endothelial CXCL (C-X-C motif chemokine ligand) 1 in male and female Apoe-/- mice. In vitro, ENPP2 mediated the mildly oxidized LDL (low-density lipoprotein)-induced expression of CXCL1 in aortic ECs by generating LPA20:4, palmitoyl-LPA (LPA16:0), and oleoyl-LPA (LPA18:1). ENPP2 and its activity were detected on the endothelial surface by confocal imaging. The expression of endothelial Enpp2 established a strong correlation between the plasma levels of LPA16:0, stearoyl-LPA (LPA18:0), and LPA18:1 and plaque size and a strong negative correlation between the LPA levels and ENPP2 activity in the plasma. Moreover, endothelial Enpp2 knockout increased the weight of high-fat diet-fed male Apoe-/- mice. CONCLUSIONS: We demonstrated that the expression of ENPP2 in ECs promotes atherosclerosis and endothelial inflammation in a sex-independent manner. This might be due to the generation of LPA20:4, LPA16:0, and LPA18:1 from mildly oxidized lipoproteins on the endothelial surface.

MicroRNA-21 Controls Circadian Regulation of Apoptosis in Atherosclerotic Lesions.

BACKGROUND: The necrotic core partly formed by ineffective efferocytosis increases the risk of an atherosclerotic plaque rupture. Microribonucleic acids contribute to necrotic core formation by regulating efferocytosis and macrophage apoptosis. Atherosclerotic plaque rupture occurs at increased frequency in the early morning, indicating diurnal changes in plaque vulnerability. Although circadian rhythms play a role in atherosclerosis, the molecular clock output pathways that control plaque composition and rupture susceptibility are unclear. METHODS: Circadian gene expression, necrotic core size, apoptosis, and efferocytosis in aortic lesions were investigated at different times of the day in Apoe-/-Mir21+/+ mice and Apoe-/-Mir21-/- mice after consumption of a high-fat diet for 12 weeks. Genome-wide gene expression and lesion formation were analyzed in bone marrow-transplanted mice. Diurnal changes in apoptosis and clock gene expression were determined in human atherosclerotic lesions. RESULTS: The expression of molecular clock genes, lesional apoptosis, and necrotic core size were diurnally regulated in Apoe-/- mice. Efferocytosis did not match the diurnal increase in apoptosis at the beginning of the active phase. However, in parallel with apoptosis, expression levels of oscillating Mir21 strands decreased in the mouse atherosclerotic aorta. Mir21 knockout abolished circadian regulation of apoptosis and reduced necrotic core size but did not affect core clock gene expression. Further, Mir21 knockout upregulated expression of proapoptotic Xaf1 (XIAP-associated factor 1) in the atherosclerotic aorta, which abolished circadian expression of Xaf1. The antiapoptotic effect of Mir21 was mediated by noncanonical targeting of Xaf1 through both Mir21 strands. Mir21 knockout in bone marrow cells also reduced atherosclerosis and necrotic core size. Circadian regulation of clock gene expression was confirmed in human atherosclerotic lesions. Apoptosis oscillated diurnally in phase with XAF1 expression, demonstrating an early morning peak antiphase to that of the Mir21 strands. CONCLUSIONS: Our findings suggest that the molecular clock in atherosclerotic lesions induces a diurnal rhythm of apoptosis regulated by circadian Mir21 expression in macrophages that is not matched by efferocytosis, thus increasing the size of the necrotic core.

Regulatory Non-coding RNAs in Atherosclerosis.

Regulatory RNAs like microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) control vascular and immune cells' phenotype and thus play a crucial role in atherosclerosis. Moreover, the mutual interactions between miRNAs and lncRNAs link both types of regulatory RNAs in a functional network that affects lesion formation. In this review, we deduce novel concepts of atherosclerosis from the analysis of the current data on regulatory RNAs' role in endothelial cells (ECs) and macrophages. In contrast to arterial ECs, which adopt a stable phenotype by adaptation to high shear stress, macrophages are highly plastic and quickly change their activation status. At predilection sites of atherosclerosis, such as arterial bifurcations, ECs are exposed to disturbed laminar flow, which generates a dysadaptive stress response mediated by miRNAs. Whereas the highly abundant miR-126-5p promotes regenerative proliferation of dysadapted ECs, miR-103-3p stimulates inflammatory activation and impairs endothelial regeneration by aberrant proliferation and micronuclei formation. In macrophages, miRNAs are essential in regulating energy and lipid metabolism, which affects inflammatory activation and foam cell formation.Moreover, lipopolysaccharide-induced miR-155 and miR-146 shape inflammatory macrophage activation through their oppositional effects on NF-kB. Most lncRNAs are not conserved between species, except a small group of very long lncRNAs, such as MALAT1, which blocks numerous miRNAs by providing non-functional binding sites. In summary, regulatory RNAs' roles are highly context-dependent, and therapeutic approaches that target specific functional interactions of miRNAs appear promising against cardiovascular diseases.

Secondary prevention implantable cardioverter-defibrillator (ICD) therapy: value in octogenarians.

BACKGROUND: Implantable cardioverter-defibrillator (ICD) therapy is well established for secondary prevention, but studies on the efficacy and safety in elderly patients are still lacking. This retrospective study compared the outcome after ICD implantation between octogenarians and other age groups. METHODS: Data were obtained from a local ICD registry. Patients who received ICD implantation for secondary prevention at our department were included. All-cause mortality, appropriate ICD therapy and acute adverse events requiring surgical intervention were compared between different age groups. RESULTS: 519 patients were enrolled, 34 of whom were aged ≥ 80 years. During the median follow-up of 35 months after ICD implantation 129 patients (annual mortality rate 5.0%) had died, including 16 patients aged ≥ 80 years (annual mortality rate 9.4%). The mortality rate of patients aged ≥ 80 years was significantly higher than that of patients aged ≤ 69 years (p < 0.001), but similar to that of patients aged 70-79 years. Age at the time of ICD implantation was an independent predictor of all-cause mortality (p < 0.001). 29.7% of patients had appropriate ICD therapy with no difference between age groups. Acute adverse events leading to surgical intervention were low (n = 13) and not age-related. CONCLUSION: Age is an independent predictor of mortality after ICD implantation for secondary prevention. Mortality rates did not differ significantly between octogenarians and other elderly aged 70-79 years. Appropriate ICD therapy and acute adverse events leading to surgical intervention were not age-related. Implantable cardioverter-defibrillator therapy for secondary prevention seems to be an effective and safe treatment modality in octogenarians.

HIF-1α (Hypoxia-Inducible Factor-1α) Promotes Macrophage Necroptosis by Regulating miR-210 and miR-383.

OBJECTIVE: Inflammatory activation changes the mitochondrial function of macrophages from oxidative phosphorylation to reactive oxygen species production, which may promote necrotic core formation in atherosclerotic lesions. In hypoxic and cancer cells, HIF-1α (hypoxia-inducible factor) promotes oxygen-independent energy production by microRNAs. Therefore, we studied the role of HIF-1α in the regulation of macrophage energy metabolism in the context of atherosclerosis. Approach and Results: Myeloid cell-specific deletion of Hif1a reduced atherosclerosis and necrotic core formation by limiting macrophage necroptosis in apolipoprotein E-deficient mice. In inflammatory bone marrow-derived macrophages, deletion of Hif1a increased oxidative phosphorylation, ATP levels, and the expression of genes encoding mitochondrial proteins and reduced reactive oxygen species production and necroptosis. microRNA expression profiling showed that HIF-1α upregulates miR-210 and downregulates miR-383 levels in lesional macrophages and inflammatory bone marrow-derived macrophages. In contrast to miR-210, which inhibited oxidative phosphorylation and enhanced mitochondrial reactive oxygen species production, miR-383 increased ATP levels and inhibited necroptosis. The effect of miR-210 was due to targeting 2,4-dienoyl-CoA reductase, which is essential in the ß oxidation of unsaturated fatty acids. miR-383 affected the DNA damage repair pathway in bone marrow-derived macrophages by targeting poly(ADP-ribose)-glycohydrolase (Parg), which reduced energy consumption and increased cell survival. Blocking the targeting of Parg by miR-383 prevented the protective effect of Hif1a deletion in macrophages on atherosclerosis and necrotic core formation in mice. CONCLUSIONS: Our findings unveil a new mechanism by which activation of HIF-1α in inflammatory macrophages increases necroptosis through microRNA-mediated ATP depletion, thus increasing atherosclerosis by necrotic core formation.

Novel Implantable Cardioverter Defibrillator Programming With High Rate Cut-Off, Long Detection Intervals and Multiple Anti-Tachycardia Pacing Reduces Mortality.

BACKGROUND: Implantable cardioverter defibrillator (ICD) therapies, even when appropriate, are associated with increased risk. Therapy-reducing strategies have been shown to reduce the mortality rate.Methods and Results:In total, 895 patients with ICD and cardiac resynchronization therapy with defibrillation function (CRT-D) were included in the study; of these, 506 (57%) patients undergoing secondary prevention were included. Devices implanted before May 2014 were programmed according to conventional programming (CP), the others according to our novel programming (NP) with high rate cut-off, longer detection intervals and 4-6 anti-tachycardia pacing (ATP) trains in the ventricular tachycardia (VT) zone. Time-to-first-event for mortality, appropriate and inappropriate therapies were analyzed. Follow-up time was 24.0 months (IQR 13.0-24.0 months). There was a significant reduction in mortality rate (11.4% vs. 25.4%, P<0.001) and in the rate of appropriate (18.8% vs. 42.2%, P<0.001) and inappropriate therapies (5.2% vs. 18.0%, P<0.001) with NP according to Kaplan-Meier analyses. In multivariate analysis, NP (hazard ratio [HR]=0.35; P<0.001), chronic kidney disease (HR=1.55), reduced ejection fraction (EF) (HR=1.35), secondary ICD indication (HR=2.35) and age at implantation (HR=1.02) were associated with mortality reduction. NP was also associated with significant reduction in the rate of appropriate and inappropriate therapies. These results were consistent after stratification for primary and secondary prevention. CONCLUSIONS: Novel ICD programming reduced mortality and morbidity due to appropriate or inappropriate ICD therapies in secondary as well as in primary ICD indication.

Heart failure with recovered ejection fraction (HFrecEF): A new entity with improved cardiac outcome.

BACKGROUND: Aim of the study was a better characterization of heart failure (HF) with recovered ejection fraction (HFrecEF) and undulating EF (HFuEF) with regard to re-hospitalization due to congestive HF (CHF), adequate electric therapies (AETs) and mortality compared to HF with reduced EF (HFrEF), mid-range EF (HFmrEF) and preserved EF (pEF). METHODS: Retrospective study of 342 participants with an implantable cardioverter defibrillator (ICD) for primary or secondary prevention. Type of HF was classified according to left ventricular EF with 4.7 ± 3.1 investigations for each patient. RESULTS: Re-hospitalization due to CHF was similar in HFrecEF (7 (9.5%)), HFmrEF (2(9.0%)) and pEF (8(12.9%); p = n.s.) and significantly higher in HFrEF (62(38.0%)) and HFuEF (6(28.6%); p < .001 compared to HFrecEF and HFrEF). AETs were significantly lower in HFrecEF (13(17.6%)) compared to HFrEF (57(35.0%)), HFmrEF (7(31.8%)), pEF (18(29.0%)) and HFuEF (6(28.6%); each p < .01 compared to HFrecEF). Mortality was similar in HFrecEF (6(8.1%)) compared to HFuEF (0(0%)), pEF (4(6.5%)) and HFmrEF (2(9.0%), p = n.s.) and significantly lower compared to HFrEF (52(31.9%), p < .001). HFrEF was the strongest predictor for mortality besides age and chronic renal insufficiency according to Cox Regression (each p < .05) opposite to arterial hypertension, diabetes, type of cardiomyopathy and secondary prevention ICD indication (each p = n.s.). CONCLUSIONS: HFrecEF indicates as a new entity of HF with similar prognosis as pEF and HFmrEF with regard to re-hospitalization due to CHF and mortality and even better prognosis with regard to AETs. HFuEF showed similar rates of re-hospitalization due to CHF and AETs compared to HFrEF, but lower rates of mortality.

miR155 Deficiency Reduces Myofibroblast Density but Fails to Improve Cardiac Function after Myocardial Infarction in Dyslipidemic Mouse Model.

Myocardial infarction remains the most common cause of heart failure with adverse remodeling. MicroRNA (miR)155 is upregulated following myocardial infarction and represents a relevant regulatory factor for cardiac remodeling by engagement in cardiac inflammation, fibrosis and cardiomyocyte hypertrophy. Here, we investigated the role of miR155 in cardiac remodeling and dysfunction following myocardial infarction in a dyslipidemic mouse model. Myocardial infarction was induced in dyslipidemic apolipoprotein E-deficient (ApoE-/-) mice with and without additional miR155 knockout by ligation of the LAD. Four weeks later, echocardiography was performed to assess left ventricular (LV) dimensions and function, and mice were subsequently sacrificed for histological analysis. Echocardiography revealed no difference in LV ejection fractions, LV mass and LV volumes between ApoE-/- and ApoE-/-/miR155-/- mice. Histology confirmed comparable infarction size and unaltered neoangiogenesis in the myocardial scar. Notably, myofibroblast density was significantly decreased in ApoE-/-/miR155-/- mice compared to the control, but no difference was observed for total collagen deposition. Our findings reveal that genetic depletion of miR155 in a dyslipidemic mouse model of myocardial infarction does not reduce infarction size and consecutive heart failure but does decrease myofibroblast density in the post-ischemic scar.

Dicer in Macrophages Prevents Atherosclerosis by Promoting Mitochondrial Oxidative Metabolism.

BACKGROUND: Alternative macrophage activation, which relies on mitochondrial oxidative metabolism, plays a central role in the resolution of inflammation and prevents atherosclerosis. Moreover, macrophages handle large amounts of cholesterol and triglycerides derived from the engulfed modified lipoproteins during atherosclerosis. Although several microRNAs regulate macrophage polarization, the role of the microRNA-generating enzyme Dicer in macrophage activation during atherosclerosis is unknown. METHODS: To evaluate the role of Dicer in atherosclerosis, Apoe-/- mice with or without macrophage-specific Dicer deletion were fed a high-fat diet for 12 weeks. Anti-argonaute 2 RNA immunoprecipitation chip and RNA deep sequencing combined with microRNA functional screening were performed in the Dicer wild-type and knockout bone marrow-derived macrophages to identify the individual microRNAs and the mRNA targets mediating the phenotypic effects of Dicer. The role of the identified individual microRNA and its target in atherosclerosis was determined by tail vein injection of the target site blockers in atherosclerotic Apoe-/- mice. RESULTS: We show that Dicer deletion in macrophages accelerated atherosclerosis in mice, along with enhanced inflammatory response and increased lipid accumulation in lesional macrophages. In vitro, alternative activation was limited whereas lipid-filled foam cell formation was exacerbated in Dicer-deficient macrophages as a result of impaired mitochondrial fatty acid oxidative metabolism. Rescue of microRNA (miR)-10a, let-7b, and miR-195a expression restored the oxidative metabolism in alternatively activated Dicer-deficient macrophages. Suppression of ligand-dependent nuclear receptor corepressor by miR-10a promoted fatty acid oxidation, which mediated the lipolytic and anti-inflammatory effect of Dicer. miR-10a expression was negatively correlated to the progression of atherosclerosis in humans. Blocking the interaction between ligand-dependent nuclear receptor corepressor and miR-10a by target site blockers aggravated atherosclerosis development in mice. CONCLUSIONS: Dicer plays an atheroprotective role by coordinately regulating the inflammatory response and lipid metabolism in macrophages through enhancing fatty acid-fueled mitochondrial respiration, suggesting that promoting Dicer/miR-10a-dependent metabolic reprogramming in macrophages has potential therapeutic implications to prevent atherosclerosis.

Paradoxical Suppression of Atherosclerosis in the Absence of microRNA-146a.

RATIONALE: Inflammation is a key contributor to atherosclerosis. MicroRNA-146a (miR-146a) has been identified as a critical brake on proinflammatory nuclear factor κ light chain enhancer of activated B cells signaling in several cell types, including endothelial cells and bone marrow (BM)-derived cells. Importantly, miR-146a expression is elevated in human atherosclerotic plaques, and polymorphisms in the miR-146a precursor have been associated with risk of coronary artery disease. OBJECTIVE: To define the role of endogenous miR-146a during atherogenesis. METHODS AND RESULTS: Paradoxically, Ldlr-/- (low-density lipoprotein receptor null) mice deficient in miR-146a develop less atherosclerosis, despite having highly elevated levels of circulating proinflammatory cytokines. In contrast, cytokine levels are normalized in Ldlr-/-;miR-146a-/- mice receiving wild-type BM transplantation, and these mice have enhanced endothelial cell activation and elevated atherosclerotic plaque burden compared with Ldlr-/- mice receiving wild-type BM, demonstrating the atheroprotective role of miR-146a in the endothelium. We find that deficiency of miR-146a in BM-derived cells precipitates defects in hematopoietic stem cell function, contributing to extramedullary hematopoiesis, splenomegaly, BM failure, and decreased levels of circulating proatherogenic cells in mice fed an atherogenic diet. These hematopoietic phenotypes seem to be driven by unrestrained inflammatory signaling that leads to the expansion and eventual exhaustion of hematopoietic cells, and this occurs in the face of lower levels of circulating low-density lipoprotein cholesterol in mice lacking miR-146a in BM-derived cells. Furthermore, we identify sortilin-1(Sort1), a known regulator of circulating low-density lipoprotein levels in humans, as a novel target of miR-146a. CONCLUSIONS: Our study reveals that miR-146a regulates cholesterol metabolism and tempers chronic inflammatory responses to atherogenic diet by restraining proinflammatory signaling in endothelial cells and BM-derived cells.

Initial end-tidal carbon dioxide as a predictive factor for return of spontaneous circulation in nonshockable out-of-hospital cardiac arrest patients: A retrospective observational study.

BACKGROUND: Early outcome prediction in out-of-hospital cardiac arrest is still a challenge. End-tidal carbon dioxide (ETCO2) has been shown to be a reliable parameter to reflect the quality of cardiopulmonary resuscitation and the chance of return of spontaneous circulation (ROSC). OBJECTIVES: This study assessed the validity of early capnography as a predictive factor for ROSC and survival in out-of-hospital cardiac arrest victims with an underlying nonshockable rhythm. DESIGN: Retrospective observational study. SETTING/PATIENTS: During a 2-year observational period, data from 2223 out-of-hospital cardiac arrest victims within the city of Vienna were analysed. The focus was on the following patients: age more than 18 years, an underlying nonshockable rhythm, and advanced airway management within the first 15 min of advanced life support with subsequent capnography. INTERVENTION: No specific intervention was set in this observational study. MAIN OUTCOME MEASURES: The first measured ETCO2, assessed immediately after placement of an advanced airway, was used for further analysis. The primary outcome was defined as sustained ROSC, and the secondary outcome was 30-day survival. RESULTS: A total of 526 patients met the inclusion criteria. These were stratified into three groups according to initial ETCO2 values (<20, 20 to 45, >45 mmHg). Baseline data and resuscitation factors were similar among all groups. The odds of sustained ROSC and survival were significantly higher for patients presenting with higher values of initial ETCO2 (>45 mmHg): 3.59 [95% CI, 2.19 to 5.85] P = 0.001 and 5.02 [95% CI, 2.25 to 11.23] P = 0.001, respectively. On the contrary ETCO2 levels less than 20 mmHg were associated with significantly poorer outcomes. CONCLUSION: Patients with a nonshockable out-of-hospital cardiac arrest who presented with higher values of initial ETCO2 had an increased chance of sustained ROSC and survival. This finding could help decision making as regards continuation of resuscitation efforts.

Age-dependent effect of targeted temperature management on outcome after cardiac arrest.

BACKGROUND: In elder patients after out-of-hospital cardiac arrest, diminished neurologic function as well as reduced neuronal plasticity may cause a low response to targeted temperature management (TTM). Therefore, we investigated the association between TTM (32-34°C) and neurologic outcome in cardiac arrest survivors with respect to age. MATERIAL AND METHODS: This retrospective cohort study included patients 18 years of age or older suffering a witnessed out-of-hospital cardiac arrest with presumed cardiac cause, which remained comatose after return of spontaneous circulation. Patients were a priori split by age into four groups (<50 years (n = 496); 50-64 years (n = 714); 65-74 years (n = 395); >75 years (n = 280)). Subsequently, within these groups, patients receiving TTM were compared to those not treated with TTM. RESULTS: Out of 1885 patients, 921 received TTM for 24 hours. TTM was significantly associated with good neurologic outcome in patients <65 years of age whereas showing no effect in elders (65-74 years: OR: 1.49 (95% CI: 0.90-2.47); > 75 years: OR 1.44 (95% CI 0.79-2.34)). CONCLUSION: In our cohort, it seems that TTM might not be able to achieve the same benefit for neurologic outcome in all age groups. Although the results of this study should be interpreted with caution, TTM was associated with improved neurologic outcome only in younger individuals, patients with 65 years of age or older did not benefit from this treatment.

Mechanical Activation of Hypoxia-Inducible Factor 1α Drives Endothelial Dysfunction at Atheroprone Sites.

OBJECTIVE: Atherosclerosis develops near branches and bends of arteries that are exposed to low shear stress (mechanical drag). These sites are characterized by excessive endothelial cell (EC) proliferation and inflammation that promote lesion initiation. The transcription factor HIF1α (hypoxia-inducible factor 1α) is canonically activated by hypoxia and has a role in plaque neovascularization. We studied the influence of shear stress on HIF1α activation and the contribution of this noncanonical pathway to lesion initiation. APPROACH AND RESULTS: Quantitative polymerase chain reaction and en face staining revealed that HIF1α was expressed preferentially at low shear stress regions of porcine and murine arteries. Low shear stress induced HIF1α in cultured EC in the presence of atmospheric oxygen. The mechanism involves the transcription factor nuclear factor-κB that induced HIF1α transcripts and induction of the deubiquitinating enzyme Cezanne that stabilized HIF1α protein. Gene silencing revealed that HIF1α enhanced proliferation and inflammatory activation in EC exposed to low shear stress via induction of glycolysis enzymes. We validated this observation by imposing low shear stress in murine carotid arteries (partial ligation) that upregulated the expression of HIF1α, glycolysis enzymes, and inflammatory genes and enhanced EC proliferation. EC-specific genetic deletion of HIF1α in hypercholesterolemic apolipoprotein E-defecient mice reduced inflammation and endothelial proliferation in partially ligated arteries, indicating that HIF1α drives inflammation and vascular dysfunction at low shear stress regions. CONCLUSIONS: Mechanical low shear stress activates HIF1α at atheroprone regions of arteries via nuclear factor-κB and Cezanne. HIF1α promotes atherosclerosis initiation at these sites by inducing excessive EC proliferation and inflammation via the induction of glycolysis enzymes.

Dicer generates a regulatory microRNA network in smooth muscle cells that limits neointima formation during vascular repair.

MicroRNAs (miRNAs) coordinate vascular repair by regulating injury-induced gene expression in vascular smooth muscle cells (SMCs) and promote the transition of SMCs from a contractile to a proliferating phenotype. However, the effect of miRNA expression in SMCs on neointima formation is unclear. Therefore, we studied the role of miRNA biogenesis by Dicer in SMCs in vascular repair. Following wire-induced injury to carotid arteries of Apolipoprotein E knockout (Apoe -/-) mice, miRNA microarray analysis revealed that the most significantly regulated miRNAs, such as miR-222 and miR-21-3p, were upregulated. Conditional deletion of Dicer in SMCs increased neointima formation by reducing SMC proliferation in Apoe -/- mice, and decreased mainly the expression of miRNAs, such as miR-147 and miR-100, which were not upregulated following vascular injury. SMC-specific deletion of Dicer promoted growth factor and inflammatory signaling and regulated a miRNA-target interaction network in injured arteries that was enriched in anti-proliferative miRNAs. The most connected miRNA in this network was miR-27a-3p [e.g., with Rho guanine nucleotide exchange factor 26 (ARHGEF26)], which was expressed in medial and neointimal SMCs in a Dicer-dependent manner. In vitro, miR-27a-3p suppresses ARHGEF26 expression and inhibits SMC proliferation by interacting with a conserved binding site in the 3' untranslated region of ARHGEF26 mRNA. We propose that Dicer expression in SMCs plays an essential role in vascular repair by generating anti-proliferative miRNAs, such as miR-27a-3p, to prevent vessel stenosis due to exaggerated neointima formation.

Macrophage MicroRNAs as Therapeutic Targets for Atherosclerosis, Metabolic Syndrome, and Cancer.

Macrophages play a crucial role in the innate immune system and contribute to a broad spectrum of pathologies in chronic inflammatory diseases. MicroRNAs (miRNAs) have been demonstrated to play important roles in macrophage functions by regulating macrophage polarization, lipid metabolism and so on. Thus, miRNAs represent promising diagnostic and therapeutic targets in immune disorders. In this review, we will summarize the role of miRNAs in atherosclerosis, metabolic syndrome, and cancer by modulating macrophage phenotypes, which has been supported by in vivo evidence.

MicroRNA-Based Therapy of GATA2-Deficient Vascular Disease.

BACKGROUND: The transcription factor GATA2 orchestrates the expression of many endothelial-specific genes, illustrating its crucial importance for endothelial cell function. The capacity of this transcription factor in orchestrating endothelial-important microRNAs (miRNAs/miR) is unknown. METHODS: Endothelial GATA2 was functionally analyzed in human endothelial cells in vitro. Endogenous short interfering RNA-mediated knockdown and lentiviral-based overexpression were applied to decipher the capacity of GATA2 in regulating cell viability and capillary formation. Next, the GATA2-dependent miR transcriptome was identified by using a profiling approach on the basis of quantitative real-time polymerase chain reaction. Transcriptional control of miR promoters was assessed via chromatin immunoprecipitation, luciferase promoter assays, and bisulfite sequencing analysis of sites in proximity. Selected miRs were modulated in combination with GATA2 to identify signaling pathways at the angiogenic cytokine level via proteome profiler and enzyme-linked immunosorbent assays. Downstream miR targets were identified via bioinformatic target prediction and luciferase reporter gene assays. In vitro findings were translated to a mouse model of carotid injury in an endothelial GATA2 knockout background. Nanoparticle-mediated delivery of proangiogenic miR-126 was tested in the reendothelialization model. RESULTS: GATA2 gain- and loss-of-function experiments in human umbilical vein endothelial cells identified a key role of GATA2 as master regulator of multiple endothelial functions via miRNA-dependent mechanisms. Global miRNAnome-screening identified several GATA2-regulated miRNAs including miR-126 and miR-221. Specifically, proangiogenic miR-126 was regulated by GATA2 transcriptionally and targeted antiangiogenic SPRED1 and FOXO3a contributing to GATA2-mediated formation of normal vascular structures, whereas GATA2 deficiency led to vascular abnormalities. In contrast to GATA2 deficiency, supplementation with miR-126 normalized vascular function and expression profiles of cytokines contributing to proangiogenic paracrine effects. GATA2 silencing resulted in endothelial DNA hypomethylation leading to induced expression of antiangiogenic miR-221 by GATA2-dependent demethylation of a putative CpG island in the miR-221 promoter. Mechanistically, a reverted GATA2 phenotype by endogenous suppression of miR-221 was mediated through direct proangiogenic miR-221 target genes ICAM1 and ETS1. In a mouse model of carotid injury, GATA2 was reduced, and systemic supplementation of miR-126-coupled nanoparticles enhanced miR-126 availability in the carotid artery and improved reendothelialization of injured carotid arteries in vivo. CONCLUSIONS: GATA2-mediated regulation of miR-126 and miR-221 has an important impact on endothelial biology. Hence, modulation of GATA2 and its targets miR-126 and miR-221 is a promising therapeutic strategy for treatment of many vascular diseases.

Endothelial cells suppress monocyte activation through secretion of extracellular vesicles containing antiinflammatory microRNAs.

The blood contains high concentrations of circulating extracellular vesicles (EVs), and their levels and contents are altered in several disease states, including cardiovascular disease. However, the function of circulating EVs, especially the microRNAs (miRNAs) that they contain, are poorly understood. We sought to determine the effect of secreted vesicles produced by quiescent endothelial cells (ECs) on monocyte inflammatory responses and to assess whether transfer of microRNAs occurs between these cells. We observed that monocytic cells cocultured (but not in contact) with ECs were refractory to inflammatory activation. Further characterization revealed that endothelium-derived EVs (EC-EVs) suppressed monocyte activation by enhancing immunomodulatory responses and diminishing proinflammatory responses. EVs isolated from mouse plasma also suppressed monocyte activation. Importantly, injection of EC-EVs in vivo repressed monocyte/macrophage activation, confirming our in vitro findings. We found that several antiinflammatory microRNAs were elevated in EC-EV-treated monocytes. In particular, miR-10a was transferred to monocytic cells from EC-EVs and could repress inflammatory signaling through the targeting of several components of the NF-κB pathway, including IRAK4. Our findings reveal that ECs secrete EVs that can modulate monocyte activation and suggest that altered EV secretion and/or microRNA content may affect vascular inflammation in the setting of cardiovascular disease.