scholarly journals Telomerase reverse transcriptase protects against angiotensin II-induced microvascular endothelial dysfunction

2018 ◽  
Vol 314 (5) ◽  
pp. H1053-H1060 ◽  
Author(s):  
Karima Ait-Aissa ◽  
Andrew O. Kadlec ◽  
Joseph Hockenberry ◽  
David D. Gutterman ◽  
Andreas M. Beyer
Keyword(s):  
Cardiovascular Disease ◽  
Angiotensin Ii ◽  
Reverse Transcriptase ◽  
Microvascular Dysfunction ◽  
Telomerase Reverse Transcriptase ◽  
Telomerase Rna ◽  
Ang Ii ◽  
Resistance Arteries ◽  
Novel Target

A rise in reactive oxygen species (ROS) may contribute to cardiovascular disease by reducing nitric oxide (NO) levels, leading to loss of NO’s vasodilator and anti-inflammatory effects. Although primarily studied in larger conduit arteries, excess ROS release and a corresponding loss of NO also occur in smaller resistance arteries of the microcirculation, but the underlying mechanisms and therapeutic targets have not been fully characterized. We examined whether either of the two subunits of telomerase, telomerase reverse transcriptase (TERT) or telomerase RNA component (TERC), affect microvascular ROS production and peak vasodilation at baseline and in response to in vivo administration to angiotensin II (ANG II). We report that genetic loss of TERT [maximal dilation: 52.0 ± 6.1% with vehicle, 60.4 ± 12.9% with Nω-nitro-l-arginine methyl ester (l-NAME), and 32.2 ± 12.2% with polyethylene glycol-catalase (PEG-Cat) ( P < 0.05), means ± SD, n = 9–19] but not TERC [maximal dilation: 79 ± 5% with vehicle, 10.7 ± 9.8% with l-NAME ( P < 0.05), and 86.4 ± 8.4% with PEG-Cat, n = 4–7] promotes flow-induced ROS formation. Moreover, TERT knockout exacerbates the microvascular dysfunction resulting from in vivo ANG II treatment, whereas TERT overexpression is protective [maximal dilation: 88.22 ± 4.6% with vehicle vs. 74.0 ± 7.3% with ANG II (1,000 ng·kg−1·min−1) ( P = not significant), n = 4]. Therefore, loss of TERT but not TERC may be a key contributor to the elevated microvascular ROS levels and reduced peak dilation observed in several cardiovascular disease pathologies. NEW & NOTEWORTHY This study identifies telomerase reverse transcriptase (TERT) but not telomerase RNA component as a key factor regulating endothelium-dependent dilation in the microcirculation. Loss of TERT activity leads to microvascular dysfunction but not conduit vessel dysfunction in first-generation mice. In contrast, TERT is protective in the microcirculation in the presence of prolonged vascular stress. Understanding the mechanism of how TERT protects against vascular stress represents a novel target for the treatment of vascular disorders.

scholarly journals Expression of Telomerase RNA Template, but Not Telomerase Reverse Transcriptase, Is Limiting for Telomere Length Maintenance In Vivo

2004 ◽  
Vol 24 (16) ◽  
pp. 7024-7031 ◽  
Author(s):  
Y. Jeffrey Chiang ◽  
Michael T. Hemann ◽  
Karen S. Hathcock ◽  
Lino Tessarollo ◽  
Lionel Feigenbaum ◽  
...  
Keyword(s):  
Reverse Transcriptase ◽  
Telomere Length ◽  
Telomerase Activity ◽  
Telomere Maintenance ◽  
Gene Copy ◽  
Telomerase Reverse Transcriptase ◽  
Telomerase Rna ◽  
Wild Type ◽  
Telomere Elongation

ABSTRACT Telomerase consists of two essential components, the telomerase RNA template (TR) and telomerase reverse transcriptase (TERT). The haplo-insufficiency of TR was recently shown to cause one form of human dyskeratosis congenita, an inherited disease marked by abnormal telomere shortening. Consistent with this finding, we recently reported that mice heterozygous for inactivation of mouse TR exhibit a similar haplo-insufficiency and are deficient in the ability to elongate telomeres in vivo. To further assess the genetic regulation of telomerase activity, we have compared the abilities of TR-deficient and TERT-deficient mice to maintain or elongate telomeres in interspecies crosses. Homozygous TERT knockout mice had no telomerase activity and failed to maintain telomere length. In contrast, TERT+/− heterozygotes had no detectable defect in telomere elongation compared to wild-type controls, whereas TR+/− heterozygotes were deficient in telomere elongation. Levels of TERT mRNA in heterozygous mice were one-third to one-half the levels expressed in wild-type mice, similar to the reductions in telomerase RNA observed in TR heterozygotes. These findings indicate that both TR and TERT are essential for telomere maintenance and elongation but that gene copy number and transcriptional regulation of TR, but not TERT, are limiting for telomerase activity under the in vivo conditions analyzed.

scholarly journals A 4-Base-Pair Core-Enclosing Helix in Telomerase RNA Is Essential for Activity and for Binding to the Telomerase Reverse Transcriptase Catalytic Protein Subunit

2020 ◽  
Vol 40 (24) ◽  
Author(s):  
Melissa A. Mefford ◽  
Evan P. Hass ◽  
David C. Zappulla
Keyword(s):  
Reverse Transcriptase ◽  
Rna Binding ◽  
Telomerase Reverse Transcriptase ◽  
Genome Replication ◽  
Telomerase Rna ◽  
Protein Subunit ◽  
Binding Interaction ◽  
Catalytic Core

ABSTRACT The telomerase ribonucleoprotein (RNP) counters the chromosome end replication problem, completing genome replication to prevent cellular senescence in yeast, humans, and most other eukaryotes. The telomerase RNP core enzyme is composed of a dedicated RNA subunit and a reverse transcriptase (telomerase reverse transcriptase [TERT]). Although the majority of the 1,157-nucleotide (nt) Saccharomyces cerevisiae telomerase RNA, TLC1, is rapidly evolving, the central catalytic core is largely conserved, containing the template, template-boundary helix, pseudoknot, and core-enclosing helix (CEH). Here, we show that 4 bp of core-enclosing helix is required for telomerase to be active in vitro and to maintain yeast telomeres in vivo, whereas the ΔCEH and 1- and 2-bp alleles do not support telomerase function. Using the CRISPR/nuclease-deactivated Cas9 (dCas9)-based CARRY (CRISPR-assisted RNA–RNA-binding protein [RBP] yeast) two-hybrid assay to assess binding of our CEH mutant RNAs to TERT, we find that the 4-bp CEH RNA binds to TERT but the shorter-CEH constructs do not, consistent with the telomerase activity and in vivo complementation results. Thus, the CEH is essential in yeast telomerase RNA because it is needed to bind TERT to form the core RNP enzyme. Although the 8 nt that form this 4-bp stem at the base of the CEH are nearly invariant among Saccharomyces species, our results with sequence-randomized and truncated-CEH helices suggest that this binding interaction with TERT is dictated more by secondary than by primary structure. In summary, we have mapped an essential binding site in telomerase RNA for TERT that is crucial to form the catalytic core of this biomedically important RNP enzyme.

scholarly journals Functional Multimerization of the Human Telomerase Reverse Transcriptase

2001 ◽  
Vol 21 (18) ◽  
pp. 6151-6160 ◽  
Author(s):  
Tara L. Beattie ◽  
Wen Zhou ◽  
Murray O. Robinson ◽  
Lea Harrington
Keyword(s):  
Reverse Transcriptase ◽  
Telomerase Activity ◽  
Telomerase Reverse Transcriptase ◽  
Telomerase Rna ◽  
Human Telomerase Reverse Transcriptase ◽  
Catalytic Core ◽  
Cell Extracts ◽  
Human Telomerase

ABSTRACT The telomerase enzyme exists as a large complex (∼1,000 kDa) in mammals and at minimum is composed of the telomerase RNA and the catalytic subunit telomerase reverse transcriptase (TERT). In Saccharomyces cerevisiae, telomerase appears to function as an interdependent dimer or multimer in vivo (J. Prescott and E. H. Blackburn, Genes Dev. 11:2790–2800, 1997). However, the requirements for multimerization are not known, and it remained unclear whether telomerase exists as a multimer in other organisms. We show here that human TERT (hTERT) forms a functional multimer in a rabbit reticulocyte lysate reconstitution assay and in human cell extracts. Two separate, catalytically inactive TERT proteins can complement each other in trans to reconstitute catalytic activity. This complementation requires the amino terminus of one hTERT and the reverse transcriptase and C-terminal domains of the second hTERT. The telomerase RNA must associate with only the latter hTERT for reconstitution of telomerase activity to occur. Multimerization of telomerase also facilitates the recognition and elongation of substrates in vitro and in vivo. These data suggest that the catalytic core of human telomerase may exist as a functionally cooperative dimer or multimer in vivo.

Angiotensin II modulates frizzled-2 receptor expression in rat vascular smooth muscle cells

2005 ◽  
Vol 108 (6) ◽  
pp. 523-530 ◽  
Author(s):  
Giovanna CASTOLDI ◽  
Serena REDAELLI ◽  
Willy M. M. van de GREEF ◽  
Cira R. T. di GIOIA ◽  
Giuseppe BUSCA ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Angiotensin Ii ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Vascular Smooth Muscle Cells ◽  
Muscle Cells ◽  
Ang Ii ◽  
Aortic Smooth Muscle

Ang II (angiotensin II) has multiple effects on vascular smooth muscle cells through the modulation of different classes of genes. Using the mRNA differential-display method to investigate gene expression in rat aortic smooth muscle cells in culture in response to 3 h of Ang II stimulation, we observed that Ang II down-regulated the expression of a member of the family of transmembrane receptors for Wnt proteins that was identified as Fzd2 [Fzd (frizzled)-2 receptor]. Fzds are a class of highly conserved genes playing a fundamental role in the developmental processes. In vitro, time course experiments demonstrated that Ang II induced a significant increase (P<0.05) in Fzd2 expression after 30 min, whereas it caused a significant decrease (P<0.05) in Fzd2 expression at 3 h. A similar rapid up-regulation after Ang II stimulation for 30 min was evident for TGFβ1 (transforming growth factor β1; P<0.05). To investigate whether Ang II also modulated Fzd2 expression in vivo, exogenous Ang II was administered to Sprague–Dawley rats (200 ng·kg−1 of body weight·min−1; subcutaneously) for 1 and 4 weeks. Control rats received normal saline. After treatment, systolic blood pressure was significantly higher (P<0.01), whereas plasma renin activity was suppressed (P<0.01) in Ang II- compared with the saline-treated rats. Ang II administration for 1 week did not modify Fzd2 expression in aorta of Ang II-treated rats, whereas Ang II administration for 4 weeks increased Fzd2 mRNA expression (P<0.05) in the tunica media of the aorta, resulting in a positive immunostaining for fibronectin at this time point. In conclusion, our data demonstrate that Ang II modulates Fzd2 expression in aortic smooth muscle cells both in vitro and in vivo.

Abstract MP03: ROCK2 Specific Inhibition Attenuates Angiotensin II-induced Hypertension In Mice

Hypertension ◽  
2021 ◽  
Vol 78 (Suppl_1) ◽  
Author(s):  
Daniel J Fehrenbach ◽  
Meena S Madhur
Keyword(s):  
Blood Pressure ◽  
T Cell ◽  
Angiotensin Ii ◽  
Repeated Measures ◽  
Flow Cytometric Analysis ◽  
Coiled Coil ◽  
Ang Ii ◽  
Induced Hypertension

Hypertension, or an elevated blood pressure, is the primary modifiable risk factor for cardiovascular disease, the number one cause of mortality worldwide. We previously demonstrated that Th17 activation and interleukin 17A (IL-17A)/IL-21 production is integral for the full development of a hypertensive phenotype as well as the renal and vascular damage associated with hypertension. Rho-associated coiled-coil containing protein Kinase 2 (ROCK2) serves as a molecular switch upregulating Th17 and inhibiting regulatory T cell (Treg) differentiation. We hypothesize that hypertension is characterized by excessive T cell ROCK2 activation leading to increased Th17/Treg ratios and ultimately end-organ damage. We first showed in vitro that KD025, an experimental orally bioavailable ROCK2 inhibitor inhibits Th17 cell proliferation and IL-17A/IL-21 production. To determine if hypertensive stimuli such as endothelial stretch increases T cell ROCK2 expression, we cultured human aortic endothelial cells exposed to 5% (normotensive) or 10% (hypertensive) stretch with circulating human T cells and HLA-DR+ antigen presenting cells. Hypertensive stretch increased T cell ROCK2 expression 2-fold. We then tested the effect of ROCK2 inhibition with KD025 (50mg/kg i.p. daily) in vivo on angiotensin II (Ang II)-induced hypertension. Treatment with KD025 significantly attenuated the hypertensive response within 1 week of Ang II treatment (systolic blood pressure: 139± 8 vs 108±7mmHg) and this persisted for the duration of the 4 week study reaching blood pressures 20 mmHg lower (135±13mmHg) than vehicle treated mice (158±4mmHg p<0.05 effect of treatment 2-way Repeated Measures ANOVA). Flow cytometric analysis of tissue infiltrating leukocytes revealed that KD025 treatment increased Treg/Th17 ratios in the kidney (0.61±0.03 vs 0.79±0.08, p<0.05 student’s t-test). Thus, T cell ROCK2 may be a novel therapeutic target for the treatment of hypertension.

Enhanced resistance artery sensitivity to agonists under isobaric compared with isometric conditions

1994 ◽  
Vol 266 (1) ◽  
pp. H147-H155 ◽  
Author(s):  
W. R. Dunn ◽  
G. C. Wellman ◽  
J. A. Bevan
Keyword(s):  
Membrane Potential ◽  
Angiotensin Ii ◽  
Myogenic Tone ◽  
Isometric Contractions ◽  
Fundamental Interaction ◽  
Resistance Artery ◽  
Resistance Arteries ◽  
Enhanced Resistance ◽  
Increased Sensitivity

We have compared the responsiveness of rabbit mesenteric resistance arteries with agonists under isometric and isobaric conditions. When pressurized (60 mmHg), arteries spontaneously reduced their diameter by 18.1%. An equivalent isometric stress did not generate force in a “wire” myograph. Subsequently, much higher concentrations of norepinephrine (NE) and histamine were required to cause isometric contractions than were needed to reduce vascular diameter of pressurized vessels, whereas angiotensin II produced a maintained response only in pressurized arteries. Reducing transmural pressure to 20 mmHg abolished pressure-induced myogenic tone and decreased arterial sensitivity to NE. Under isometric conditions, partial depolarization with KCl increased sensitivity to NE and histamine to within the concentration range effective in pressurized vessels and also "revealed" responses to angiotensin II. The membrane potential of the vascular smooth muscle cells under partially depolarized conditions was similar to that found in vivo and in vessels studied isobarically. These observations demonstrate a fundamental interaction between pressure-induced myogenic tone and the sensitivity of resistance arteries to vasoactive stimuli. This influence was mimicked in isometrically mounted vessels by partial depolarization, indicating a possible pivotal role for membrane potential in determining the reactivity of the resistance vasculature.

scholarly journals Angiotensin II, Hypercholesterolemia, and Vascular Smooth Muscle Cells: A Perfect Trio for Vascular Pathology

2020 ◽  
Vol 21 (12) ◽  
pp. 4525
Author(s):  
Amanda St. Paul ◽  
Cali B. Corbett ◽  
Rachael Okune ◽  
Michael V. Autieri
Keyword(s):  
Blood Pressure ◽  
Cardiovascular Disease ◽  
Smooth Muscle ◽  
Angiotensin Ii ◽  
Vascular Smooth Muscle ◽  
Vascular Diseases ◽  
Reduce Blood Pressure ◽  
Vascular Pathology ◽  
Lipid Lowering ◽  
Ang Ii

Cardiovascular disease is the leading cause of morbidity and mortality in the Western and developing world, and the incidence of cardiovascular disease is increasing with the longer lifespan afforded by our modern lifestyle. Vascular diseases including coronary heart disease, high blood pressure, and stroke comprise the majority of cardiovascular diseases, and therefore represent a significant medical and socioeconomic burden on our society. It may not be surprising that these conditions overlap and potentiate each other when we consider the many cellular and molecular similarities between them. These intersecting points are manifested in clinical studies in which lipid lowering therapies reduce blood pressure, and anti-hypertensive medications reduce atherosclerotic plaque. At the molecular level, the vascular smooth muscle cell (VSMC) is the target, integrator, and effector cell of both atherogenic and the major effector protein of the hypertensive signal Angiotensin II (Ang II). Together, these signals can potentiate each other and prime the artery and exacerbate hypertension and atherosclerosis. Therefore, VSMCs are the fulcrum in progression of these diseases and, therefore, understanding the effects of atherogenic stimuli and Ang II on the VSMC is key to understanding and treating atherosclerosis and hypertension. In this review, we will examine studies in which hypertension and atherosclerosis intersect on the VSMC, and illustrate common pathways between these two diseases and vascular aging.

scholarly journals Telomerase Activity Reconstitutedin Vitrowith Purified Human Telomerase Reverse Transcriptase and Human Telomerase RNA Component

2000 ◽  
Vol 275 (29) ◽  
pp. 22568-22573 ◽  
Author(s):  
Kenkichi Masutomi ◽  
Shuichi Kaneko ◽  
Naoyuki Hayashi ◽  
Tatsuya Yamashita ◽  
Yukihiro Shirota ◽  
...  
Keyword(s):  
Reverse Transcriptase ◽  
Telomerase Activity ◽  
Telomerase Reverse Transcriptase ◽  
Telomerase Rna ◽  
Human Telomerase Reverse Transcriptase ◽  
Human Telomerase

scholarly journals Telomerase biogenesis requires a novel Mex67 function and a cytoplasmic association with the Sm7 complex

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Yulia Vasianovich ◽  
Emmanuel Bajon ◽  
Raymund J Wellinger
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Life Cycle ◽  
Reverse Transcriptase ◽  
Nuclear Export ◽  
Complex Life Cycle ◽  
Telomerase Reverse Transcriptase ◽  
Telomerase Rna ◽  
The Core ◽  
Nuclear Stability

The templating RNA is the core of the telomerase reverse transcriptase. In Saccharomyces cerevisiae, the complex life cycle and maturation of telomerase includes a cytoplasmic stage. However, timing and reason for this cytoplasmic passage are poorly understood. Here, we use inducible RNA tagging experiments to show that immediately after transcription, newly synthesized telomerase RNAs undergo one round of nucleo-cytoplasmic shuttling. Their export depends entirely on Crm1/Xpo1, whereas re-import is mediated by Kap122 plus redundant, kinetically less efficient import pathways. Strikingly, Mex67 is essential to stabilize newly transcribed RNA before Xpo1-mediated nuclear export. The results further show that the Sm7 complex associates with and stabilizes the telomerase RNA in the cytoplasm and promotes its nuclear re-import. Remarkably, after this cytoplasmic passage, the nuclear stability of telomerase RNA no longer depends on Mex67. These results underscore the utility of inducible RNA tagging and challenge current models of telomerase maturation.

Angiotensin II is associated with activation of NF-κB-mediated genes and downregulation of PPARs

2002 ◽  
Vol 11 (1) ◽  
pp. 21-30 ◽  
Author(s):  
Doris M. Tham ◽  
Baby Martin-McNulty ◽  
Yi-xin Wang ◽  
Dennis W. Wilson ◽  
Ronald Vergona ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Adhesion Molecule ◽  
Vascular Inflammation ◽  
Aortic Aneurysms ◽  
Intercellular Adhesion Molecule ◽  
Ang Ii ◽  
Inflammatory Genes ◽  
Apoe Ko Mice ◽  
Apoe Ko

Angiotensin II (ANG II) promotes vascular inflammation through nuclear factor-κB (NF-κB)-mediated induction of pro-inflammatory genes. The role of peroxisome proliferator-activated receptors (PPARs) in modulating vascular inflammation and atherosclerosis in vivo is unclear. The aim of the present study was to examine the effects of ANG II on PPARs and NF-κB-dependent pro-inflammatory genes in the vascular wall in an in vivo model of atherosclerosis and aneurysm formation. Six-month-old male apolipoprotein E-deficient (apoE-KO) mice were treated with ANG II (1.44 mg/kg per day for 30 days). ANG II enhanced vascular inflammation, accelerated atherosclerosis, and induced formation of abdominal aortic aneurysms. These effects of ANG II in the aorta were associated with downregulation of both PPAR-α and PPAR-γ mRNA and protein and an increase in transcription of monocyte chemotactic protein-1 (MCP-1), macrophage-colony stimulating factor (M-CSF), endothelial-selectin (E-selectin), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) throughout the entire aorta. ANG II also activated NF-κB with increases in both p52 and p65 NF-κB subunits. In summary, these in vivo results indicate that ANG II, through activation of NF-κB-mediated pro-inflammatory genes, promotes vascular inflammation, leading to acceleration of atherosclerosis and induction of aneurysm in apoE-KO mice. Downregulation of PPAR-α and -γ by ANG II may diminish the anti-inflammatory potential of PPARs, thus contributing to enhanced vascular inflammation.

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