Virginija Jazbutyte

MicroRNA-24 Regulates Vascularity After Myocardial Infarction

Background— Myocardial infarction leads to cardiac remodeling and development of heart failure. Insufficient myocardial capillary density after myocardial infarction has been identified as a critical event in this process, although the underlying mechanisms of cardiac angiogenesis are mechanistically not well understood. Methods and Results— Here, we show that the small noncoding RNA microRNA-24 (miR-24) is enriched in cardiac endothelial cells and considerably upregulated after cardiac ischemia. MiR-24 induces endothelial cell apoptosis, abolishes endothelial capillary network formation on Matrigel, and inhibits cell sprouting from endothelial spheroids. These effects are mediated through targeting of the endothelium-enriched transcription factor GATA2 and the p21-activated kinase PAK4, which were identified by bioinformatic predictions and validated by luciferase gene reporter assays. Respective downstream signaling cascades involving phosphorylated BAD (Bcl-XL/Bcl-2–associated death promoter) and Sirtuin1 were identified by transcriptome, protein arrays, and chromatin immunoprecipitation analyses. Overexpression of miR-24 or silencing of its targets significantly impaired angiogenesis in zebrafish embryos. Blocking of endothelial miR-24 limited myocardial infarct size of mice via prevention of endothelial apoptosis and enhancement of vascularity, which led to preserved cardiac function and survival. Conclusions— Our findings indicate that miR-24 acts as a critical regulator of endothelial cell apoptosis and angiogenesis and is suitable for therapeutic intervention in the setting of ischemic heart disease.

Transforming Growth Factor-β–Induced Endothelial-to-Mesenchymal Transition Is Partly Mediated by MicroRNA-21

Objective—MicroRNAs are a class of small ribonucleotides regulating gene/protein targets by transcript degradation or translational inhibition. Transforming growth factor-&bgr; (TGF-&bgr;) is involved in cardiac fibrosis partly by stimulation of endothelial-to-mesenchymal transition (EndMT). Here, we investigated whether microRNA (miR)-21, a microRNA enriched in fibroblasts and involved in general fibrosis, has a role in cardiac EndMT. Methods and Results—TGF-&bgr; treatment of endothelial cells significantly increased miR-21 expression and induced EndMT characterized by suppression of endothelial and increase of fibroblast markers. Overexpression of miR-21 alone also stimulated EndMT. Importantly, miR-21 blockade by transfection of specific microRNA inhibitors partly prevented TGF-&bgr;-induced EndMT. Mechanistically, miR-21 silenced phosphatase and tensin homolog in endothelial cells, resulting in activation of the Akt-pathway. Akt inhibition partly restored TGF-&bgr;-mediated loss of endothelial markers during EndMT. In vivo, pressure overload of the left ventricle led to increased expression of miR-21 in sorted cardiac endothelial cells, which displayed molecular and phenotypic signs of EndMT. This was attenuated by treatment of mice subjected to left ventricular pressure overload with an antagomir against miR-21. Conclusion—TGF-&bgr;-mediated EndMT is regulated at least in part by miR-21 via the phosphatase and tensin homolog/Akt pathway. In vivo, antifibrotic effects of miR-21 antagonism are partly mediated by blocking EndMT under stress conditions.

Short Communication: Asymmetric Dimethylarginine Impairs Angiogenic Progenitor Cell Function in Patients With Coronary Artery Disease Through a MicroRNA-21–Dependent Mechanism

Rationale: The endogenous nitric oxide synthase inhibitor asymmetrical dimethylarginine (ADMA) is increased in patients with coronary artery disease and may regulate function of circulating angiogenic progenitor cells (APCs) by small regulatory RNAs. Objectives: To study the role of microRNAs in ADMA-mediated impairment of APCs. Methods and Results: By using microarray analyses, we established microRNA expression profiles of human APCs. We used ADMA to induce APC dysfunction and found 16 deregulated microRNAs. We focused on miR-21, which was 3-fold upregulated by ADMA treatment. Overexpression of miR-21 in human APCs impaired migratory capacity. To identify regulated miR-21 targets, we used proteome analysis, using difference in-gel electrophoresis followed by mass spectrometric analysis of regulated proteins. We found that transfection of miR-21 precursors significantly repressed superoxide dismutase 2 in APCs, which resulted in increased intracellular reactive oxygen species concentration and impaired nitric oxide bioavailability. MiR-21 further repressed sprouty-2, leading to Erk Map kinase–dependent reactive oxygen species formation and APC migratory defects. Small interference RNA–mediated superoxide dismutase 2 or sprouty-2 reduction also increased reactive oxygen species formation and impaired APC migratory capacity. ADMA-mediated reactive oxygen species formation and APC dysfunction was rescued by miR-21 blockade. APCs from patients with coronary artery disease and high ADMA plasma levels displayed >4-fold elevated miR-21 levels, low superoxide dismutase 2 expression, and impaired migratory capacity, which could be normalized by miR-21 antagonism. Conclusions: We identified a novel miR-21–dependent mechanism of ADMA-mediated APC dysfunction. MiR-21 antagonism therefore emerges as an interesting strategy to improve dysfunctional APCs in patients with coronary artery disease.

Improvement of Endothelial Dysfunction by Selective Estrogen Receptor-α Stimulation in Ovariectomized SHR

Abstract—Both known estrogen receptors, ER&agr; and ER&bgr;, are expressed in blood vessels. To gain further insight into the role of ER&agr; in a functional setting, we investigated the effect of the novel highly selective ER&agr; agonist Cpd1471 on vascular reactivity in ovariectomized spontaneously hypertensive rats (SHR). After ovariectomy or sham operation, 12-week-old female SHR received either 17&bgr;-estradiol (E2, 2 &mgr;g/kg body wt per day), the selective ER&agr; agonist Cpd1471 (30 &mgr;g/kg body wt per day), or placebo. Acetylcholine-induced endothelium-dependent vasorelaxation was significantly blunted in aortas from ovariectomized rats (Rmax, 53%±3% versus sham, 79%±2%; P <0.001). Treatment with E2 or Cpd1471 significantly augmented acetylcholine-induced relaxation in ovariectomized rats (Rmax, 70%±2%; resp, 73%±2%). Endothelium-independent relaxation induced by sodium nitroprusside was not different among the four groups. The contractile response induced by the nitric oxide (NO) synthase inhibitor N&ohgr;-nitro-l-arginine, an index of basal NO formation, was significantly lower in ovariectomized rats compared with sham-operated animals (53±2% versus 77%±5%; P <0.01) and was normalized by both E2 (70%±2%) and Cpd1471 (70%±3%). Aortic endothelial NO synthase (eNOS) expression and phosphorylation of the vasodilator-stimulated phosphoprotein, an index of NO/cGMP-signaling, was reduced in ovariectomized SHR and normalized by E2 and Cpd1471. In SHR after ovariectomy, endothelium-dependent NO-mediated vasorelaxation and eNOS expression are attenuated. The novel selective ER&agr; agonist Cpd1471 prevented these pathophysiological changes to a similar extent as E2. Thus, the pharmacological principle of selective ER&agr; activation mediates positive vascular effects.

Activation of mitochondrial large-conductance calcium-activated K+ channels via protein kinase A mediates desflurane-induced preconditioning.

BACKGROUND:ATP-regulated K+ channels are involved in anesthetic-induced preconditioning (APC). The role of other K+ channels in APC is unclear. We tested the hypothesis that APC is mediated by large-conductance calcium-activated K+ channels (KCa). METHODS:Pentobarbital-anesthetized male C57BL/6 mice were subjected to 45 min of coronary artery occlusion and 3 h reperfusion. Thirty minutes before coronary artery occlusion, 1.0 MAC desflurane was administered for 15 min alone or in combination with the large-conductance KCa channel activator NS1619 (1 &mgr;g/g i.p.), its respective vehicle dimethylsulfoxide (10 &mgr;L/g i.p.), the large-conductance KCa channel blocker iberiotoxin (0.05 &mgr;g/g i.p.), or the protein kinase A (PKA) inhibitor H-89 (0.5 &mgr;g/g intraventricular). Infarct size was determined with triphenyltetrazolium chloride and area at risk with Evans blue. Mitochondrial and sarcolemmal localization of large-conductance KCa channels in cardiac myocytes was investigated with immunocytochemical staining of isolated cardiac myocytes. RESULTS:Desflurane significantly reduced infarct size compared with control animals (7.4% ± 0.8% vs 51.3% ± 6.1%; P < 0.05). Activation of large-conductance KCa channels by NS1619 (7.5% ± 1.8%; P < 0.05) mimicked and blockade of large-conductance KCa channels by iberiotoxin (49.1% ± 7.5%) abrogated desflurane-induced preconditioning. PKA blockade by H-89 abolished desflurane-induced (45.1% ± 4.0%) but not NS1619-induced (9.0% ± 2.4%, P < 0.05) preconditioning. Immunocytochemical staining revealed that large-conductance KCa channels were localized in the mitochondria but not in the sarcolemma of cardiac myocytes. CONCLUSION:These data suggest that desflurane-induced APC is mediated in part by activation of mitochondrial large-conductance KCa channels, and that activation of these channels by desflurane is mediated by PKA.

Impact of Ischemia and Reperfusion Times on Myocardial Infarct Size in Mice In Vivo

The murine in vivo model of acute myocardial infarction is increasingly used to study signal transduction pathways. However, methodological details of this model are rarely published, and durations of ischemia and reperfusion (REP) time vary considerably among different laboratories. In this study, we tested the hypothesis that infarct size (IS) is dependent on both duration of ischemia and REP time. Pentobarbital-anesthetized male C57BL/6 mice were intubated, mechanically ventilated, and instrumented for continuous monitoring of mean arterial blood pressure and heart rate. After left fourth thoracotomy, the left anterior descending coronary artery was ligated. Mice were randomly assigned to receive 30, 45, or 60 mins of coronary artery occlusion (CAO) and 120, 180, or 240 mins of REP, respectively. IS was determined with triphenyltetrazolium chloride and area at risk (AAR) with Evans blue, respectively. Arterial blood gas analysis and hemodynamics were not different among groups. Prolongation of CAO from 30 to 60 mins significantly (* P < 0.05) increased IS from 18% ± 5% to 69% ± 3%*, from 20% ± 2% to 69% ± 6%* and from 42% ± 10% to 75% ± 2%* after 120, 180, and 240 mins REP, respectively. Moreover, IS was increased from 18% ± 5% to 42% ± 10%* (30 mins CAO) and from 40% ± 3% to 72% ± 6%* (45 mins CAO) when REP time was prolonged from 120 to 240 mins. IS was not increased when REP was prolonged from 120 to 240 mins at 60 mins CAO (69% ± 3% vs. 75% ± 2%). In the present study, we describe important methodological aspects of the murine in vivo model of acute myocardial infarction and provide evidence that, in this model, IS depends both on duration of ischemia and on REP time.

Impairment of endothelial progenitor cell function and vascularization capacity by aldosterone in mice and humans

AIMS Hyperaldosteronism is associated with vascular injury and increased cardiovascular events. Bone marrow-derived endothelial progenitor cells (EPCs) play an important role in endothelial repair and vascular homeostasis. We hypothesized that hyperaldosteronism impairs EPC function and vascularization capacity in mice and humans. METHODS AND RESULTS We characterized the effects of aldosterone and mineralocorticoid receptor (MR) blockade on EPC number and function as well as vascularization capacity and endothelial function. Treatment of human EPC with aldosterone induced translocation of the MR and impaired multiple cellular functions of EPC, such as differentiation, migration, and proliferation in vitro. Impaired EPC function was rescued by pharmacological blockade or genetic ablation of the MR. Aldosterone protein kinase A (PKA) dependently increased reactive oxygen species formation in EPC. Aldosterone infusion in mice impaired EPC function, EPC homing to vascular structures and vascularization capacity in a MR-dependent but blood pressure-independent manner. Endothelial progenitor cells from patients with primary hyperaldosteronism compared with controls of similar age displayed reduced migratory potential. Impaired EPC function was associated with endothelial dysfunction. MR blockade in patients with hyperaldosteronism improved EPC function and arterial stiffness. CONCLUSION Endothelial progenitor cells express a MR that mediates functional impairment by PKA-dependent increase of reactive oxygen species. Normalization of EPC function may represent a novel mechanism contributing to the beneficial effects of MR blockade in cardiovascular disease prevention and treatment.

Aging Reduces the Efficacy of Estrogen Substitution to Attenuate Cardiac Hypertrophy in Female Spontaneously Hypertensive Rats

Clinical trials failed to show a beneficial effect of postmenopausal hormone replacement therapy, whereas experimental studies in young animals reported a protective function of estrogen replacement in cardiovascular disease. Because these diverging results could in part be explained by aging effects, we compared the efficacy of estrogen substitution to modulate cardiac hypertrophy and cardiac gene expression among young (age 3 months) and senescent (age 24 months) spontaneously hypertensive rats (SHRs), which were sham operated or ovariectomized and injected with placebo or identical doses of 17&bgr;-estradiol (E2; 2 &mgr;g/kg body weight per day) for 6 weeks (n=10/group). Blood pressure was comparable among sham-operated senescent and young SHRs and not altered by ovariectomy or E2 treatment among young or among senescent rats. Estrogen substitution inhibited uterus atrophy and gain of body weight in young and senescent ovariectomized SHRs, but cardiac hypertrophy was attenuated only in young rats. Cardiac estrogen receptor-&agr; expression was lower in intact and in ovariectomized senescent compared with young SHRs and increased with estradiol substitution in aged rats. Plasma estradiol and estrone levels were lower not only in sham-operated but surprisingly also in E2-substituted senescent SHRs and associated with a reduction of hepatic 17&bgr;-hydroxysteroid dehydrogenase type 1 enzyme activity, which converts weak (ie, estrone) into potent estrogens, such as E2. Aging attenuates the antihypertrophic effect of estradiol in female SHRs and is associated with profound alterations in cardiac estrogen receptor-&agr; expression and estradiol metabolism. These observations contribute to explain the lower efficiency of estrogen substitution in senescent SHRs.

Estrogen receptor alpha interacts with 17beta-hydroxysteroid dehydrogenase type 10 in mitochondria.

Estrogen receptor alpha (ERalpha) is present in the nucleus, the cytosol and in mitochondria. The rat ERalpha ligand binding domain was employed as bait in a bacterial two-hybrid screening of a human heart cDNA library to detect novel protein-protein interaction partners of ERalpha in the heart. 17beta-Hydroxysteroid dehydrogenase type 10 (17beta-HSD10), which converts potent (17beta-estradiol) to less potent estrogens (estrone), co-localized with 17beta-HSD10 in the mitochondria of rat cardiac myocytes. GST pull-down experiments confirmed the interaction of ERalpha and 17beta-HSD10. These findings suggest that the ERalpha estrogen receptor might be involved in regulating intracellular estrogen levels by modulating 17beta-HSD10 activity.

Medroxyprogesterone acetate but not drospirenone ablates the protective function of 17 beta-estradiol in aldosterone salt-treated rats.

Controversial results obtained from human and animal studies on the prevention of heart disease by estrogens and progestins warrant a better understanding of nuclear hormone receptor function and interaction. To address this issue and taking into account that effects of synthetic progestins are not only referable to action through the progesterone receptor but may also be mediated by other steroid receptors, we characterized cardiovascular function and inflammatory gene expression in aldosterone salt-treated rats on long-term administration of 17β-estradiol, medroxyprogesterone acetate, and drospirenone, a new progestogen exhibiting antimineralocorticoid activity. The complex pattern of cardiovascular injury in ovariectomized Wistar rats induced by chronic aldosterone infusion plus a high-salt diet was significantly attenuated in sham-ovariectomized rats and by coadministration of 17β-estradiol in ovariectomized animals after 8 weeks of continuous treatment. The beneficial role of 17β-estradiol on blood pressure, cardiac hypertrophy, vascular osteopontin expression, perivascular fibrosis, and impaired NO-dependent relaxation of isolated aortic rings was completely abrogated by coadministration of medroxyprogesterone acetate. In contrast, drospirenone was either neutral or additive to 17β-estradiol in protecting against aldosterone salt-induced cardiovascular injury and inflammation. The current results support the hypothesis of complex interactions among estrogen, progesterone, glucocorticoid, androgen, and mineralocorticoid receptor signaling in cardiovascular injury and inflammation. Novel progestins, such as drospirenone, confer superior effects compared with medroxyprogesterone acetate in a model of aldosterone-induced heart disease because of its antimineralocorticoid properties.