Telomere Length Shortening in Microglia: Implication for Accelerated Senescence and Neurocognitive Deficits in HIV

The widespread use of combination antiretroviral therapy (cART) has led to the accelerated aging of the HIV-infected population, and these patients continue to have a range of mild to moderate HIV-associated neurocognitive disorders (HAND). Infection results in altered mitochondrial function. The HIV-1 viral protein Tat significantly alters mtDNA content and enhances oxidative stress in immune cells. Microglia are the immune cells of the central nervous system (CNS) that exhibit a significant mitotic potential and are thus susceptible to telomere shortening. HIV disrupts the normal interplay between microglia and neurons, thereby inducing neurodegeneration. HIV cART contributes to the inhibition of telomerase activity and premature telomere shortening in activated peripheral blood mononuclear cells (PBMC). However, limited information is available on the effect of cART on telomere length (TL) in microglia. Although it is well established that telomere shortening induces cell senescence and contributes to the development of age-related neuro-pathologies, the effect of HIV-Tat on telomere length in human microglial cells and its potential contribution to HAND are not well understood. It is speculated that in HAND intrinsic molecular mechanisms that control energy production underlie microglia-mediated neuronal injury. TL, telomerase and mtDNA expression were quantified in microglial cells using real time PCR. Cellular energetics were measured using the Seahorse assay. The changes in mitochondrial function were examined by Raman Spectroscopy. We have also examined TL in the PBMC obtained from HIV-1 infected rapid progressors (RP) on cART and those who were cART naïve, and observed a significant decrease in telomere length in RP on cART as compared to RP’s who were cART naïve. We observed a significant decrease in telomerase activity, telomere length and mitochondrial function, and an increase in oxidative stress in human microglial cells treated with HIV Tat. Neurocognitive impairment in HIV disease may in part be due to accelerated neuro-pathogenesis in microglial cells, which is attributable to increased oxidative stress and mitochondrial dysfunction.

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Accelerated telomere attrition in children and teenagers with α1-antitrypsin deficiency

European Respiratory Journal ◽

10.1183/13993003.00176-2016 ◽

2016 ◽

Vol 48 (2) ◽

pp. 350-358 ◽

Cited By ~ 11

Author(s):

Amparo Escribano ◽

Sara Pastor ◽

Ana Reula ◽

Silvia Castillo ◽

Silvia Vicente ◽

...

Keyword(s):

Oxidative Stress ◽

High Risk ◽

Telomere Length ◽

Telomerase Activity ◽

Multiple Hypothesis Testing ◽

Intermediate Risk ◽

Telomere Shortening ◽

Telomere Attrition ◽

Antitrypsin Deficiency ◽

Risk Patients

Numerous studies have shown that oxidative stress accelerates telomere shortening in several lung pathologies. Since oxidative stress is involved in the pathophysiology of α1-antitrypsin deficiency (AATD), we hypothesised that telomere shortening would be accelerated in AATD patients. This study aimed to assess telomere length in AATD patients and to study its association with α1-antitrypsin phenotypes.Telomere length, telomerase activity, telomerase reverse transcriptase (hTERT) expression and biomarkers of oxidative stress were measured in 62 children and teenagers (aged 2–18 years) diagnosed with AATD and 18 controls (aged 3–16 years).Our results show that intermediate-risk (MZ; SZ) and high-risk (ZZ) AATD patients have significantly shorter telomeres and increased oxidative stress than controls. Correlation studies indicate that telomere length was related to oxidative stress markers in AATD patients. Multiple hypothesis testing revealed an association between telomere length, telomerase activity, hTERT expression and AATD phenotypes; high-risk patients showed shorter telomeres, lower hTERT expression and decreased telomerase activity than intermediate-risk and low-risk patients.AATD patients show evidence of increased oxidative stress leading to telomere attrition. An association between telomere and α1-antitrypsin phenotypes is observed suggesting that telomere length could be a promising biomarker for AATD disease progression.

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Telomere Shortening and Psychiatric Disorders: A Systematic Review

Cells ◽

10.3390/cells10061423 ◽

2021 ◽

Vol 10 (6) ◽

pp. 1423

Author(s):

Pedro A. Pousa ◽

Raquel M. Souza ◽

Paulo Henrique M. Melo ◽

Bernardo H. M. Correa ◽

Tamires S. C. Mendonça ◽

...

Keyword(s):

Oxidative Stress ◽

Psychological Distress ◽

Mental Disorders ◽

Psychiatric Disorders ◽

Telomere Length ◽

Traumatic Stress ◽

Molecular Mechanisms ◽

Cochrane Library ◽

Telomere Shortening ◽

Anxiety Depression

Telomeres are aging biomarkers, as they shorten while cells undergo mitosis. The aim of this study was to evaluate whether psychiatric disorders marked by psychological distress lead to alterations to telomere length (TL), corroborating the hypothesis that mental disorders might have a deeper impact on our physiology and aging than it was previously thought. A systematic search of the literature using MeSH descriptors of psychological distress (“Traumatic Stress Disorder” or “Anxiety Disorder” or “depression”) and telomere length (“cellular senescence”, “oxidative stress” and “telomere”) was conducted on PubMed, Cochrane Library and ScienceDirect databases. A total of 56 studies (113,699 patients) measured the TL from individuals diagnosed with anxiety, depression and posttraumatic disorders and compared them with those from healthy subjects. Overall, TL negatively associates with distress-related mental disorders. The possible underlying molecular mechanisms that underly psychiatric diseases to telomere shortening include oxidative stress, inflammation and mitochondrial dysfunction linking. It is still unclear whether psychological distress is either a cause or a consequence of telomere shortening.

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Oxidative Stress, Telomere Shortening, and Apoptosis Associated to Sarcopenia and Frailty in Patients with Multimorbidity

Journal of Clinical Medicine ◽

10.3390/jcm9082669 ◽

2020 ◽

Vol 9 (8) ◽

pp. 2669 ◽

Cited By ~ 2

Author(s):

Máximo Bernabeu-Wittel ◽

Raquel Gómez-Díaz ◽

Álvaro González-Molina ◽

Sofía Vidal-Serrano ◽

Jesús Díez-Manglano ◽

...

Keyword(s):

Oxidative Stress ◽

Telomere Length ◽

Prospective Observational Study ◽

Oxygen Species ◽

Oxidative Stress Markers ◽

Blood Leukocytes ◽

Telomere Shortening ◽

Blood Samples ◽

Stress Markers ◽

Total Antioxidant

Background: The presence of oxidative stress, telomere shortening, and apoptosis in polypathological patients (PP) with sarcopenia and frailty remains unknown. Methods: Multicentric prospective observational study in order to assess oxidative stress markers (catalase, glutathione reductase (GR), total antioxidant capacity to reactive oxygen species (TAC-ROS), and superoxide dismutase (SOD)), absolute telomere length (aTL), and apoptosis (DNA fragmentation) in peripheral blood samples of a hospital-based population of PP. Associations of these biomarkers to sarcopenia, frailty, functional status, and 12-month mortality were analyzed. Results: Of the 444 recruited patients, 97 (21.8%), 278 (62.6%), and 80 (18%) were sarcopenic, frail, or both, respectively. Oxidative stress markers (lower TAC-ROS and higher SOD) were significantly enhanced and aTL significantly shortened in patients with sarcopenia, frailty or both syndromes. No evidence of apoptosis was detected in blood leukocytes of any of the patients. Both oxidative stress markers (GR, p = 0.04) and telomere shortening (p = 0.001) were associated to death risk and to less survival days. Conclusions: Oxidative stress markers and telomere length were enhanced and shortened, respectively, in blood samples of polypathological patients with sarcopenia and/or frailty. Both were associated to decreased survival. They could be useful in the clinical practice to assess vulnerable populations with multimorbidity and of potential interest as therapeutic targets.

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Extensive Chromosome Instability in Acute Myeloid Leukemia Is Associated with Critical Telomere Shortening.

Blood ◽

10.1182/blood.v104.11.3376.3376 ◽

2004 ◽

Vol 104 (11) ◽

pp. 3376-3376

Author(s):

Susan J.J. Swiggers ◽

Marianne A. Kuijpers ◽

Maartje J. de Cort ◽

Berna Beverloo ◽

J. Mark J.M. Zijlmans

Keyword(s):

Telomere Length ◽

Reciprocal Translocation ◽

Genetic Instability ◽

Myeloid Leukemia ◽

Chromosomal Abnormalities ◽

Chromosome Instability ◽

Telomerase Activity ◽

In Vitro Models ◽

Telomere Shortening

Abstract Telomeres, the ends of linear chromosomes, have a critical role in protection against chromosome end-to-end fusion. Telomeres shorten in every cell division due to the end replication problem. Telomerase is a reverse transcriptase that adds telomeric DNA repeats to the ultimate chromosome end. In vitro models of long-term fibroblast cultures have identified two sequential mortality stages, senescence (M1) and crisis (M2). Senescence can be bypassed by loss of p53 or Rb function, whereas escape from crisis can only be achieved by activating a telomere maintenance mechanism, mostly telomerase reactivation. Cells that bypass senescence (M1) did not reactivate telomerase, resulting in further telomere shortening to a critical telomere length upon reaching crisis (M2). In these models, critical telomere shortening induces extensive chromosome instability, most likely via chromosome end-to-end fusions. Dicentric chromosomes lead to anaphase breakage-fusion-bridges resulting in multiple chromosomal aberrations. To investigate whether similar mechanisms may be involved in the development of genetic instability in human cancer, we studied telomere length and expression of critical telomeric proteins (TRF2 and POT1) in acute myeloid leukemia (AML) patients. AML is a good model for these studies since distinct subgroups of AML are characterized by either exchanges along chromosome arms (translocation or inversion), or by a complex karyotype with multiple chromosome aberrations. Groups were age-matched. Telomere length was studied in metaphase arrested leukemic cells using quantitative fluorescence in situ hybridization (Q-FISH) using a telomere-specific probe. Subsequently, metaphase spreads were hybridized with a leukemia-specific probe to confirm leukemic origin of each metaphase. Telomeres were significantly shorter in AML samples with multiple chromosomal abnormalities in comparison to AML samples with a reciprocal translocation/inversion or no abnormalities (mean±SEM=16±1.7 AFU, n=12 versus 29±4.3 AFU, n=18; p=0.015). Interestingly, telomerase activity level is significantly higher in AML samples with multiple chromosomal abnormalities, compared to AML samples with a reciprocal translocation or inversion (mean±SEM=330±95, n=11 versus 70±21, n=13; p=0.02). Expression levels of telomeric proteins TRF2 and POT1 were similar in these AML groups. Our observations suggest that, consistent with previous in vitro models in fibroblasts, critical telomere shortening may have a role in the development of genetic instability in human AML. Critically short telomeres in association with high levels of telomerase activity suggest that AML cells with multiple chromosomal abnormalities have bypassed crisis (M2). The longer telomeres and low levels of telomerase activity in AML cells with a reciprocal translocation or inversion suggest that they originate from an earlier stage, preceding crisis. Consequently, telomere length modulation may have a role in cancer prevention.

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Telomerase Activity and Telomere Length of CD4+CD25+ Regulatory T-Cells under Conditions of In Vitro and In Vivo Expansion.

Blood ◽

10.1182/blood.v104.11.3857.3857 ◽

2004 ◽

Vol 104 (11) ◽

pp. 3857-3857

Author(s):

Dominik G.F. Wolf ◽

Anna M. Wolf ◽

Christian Koppelstaetter ◽

Holger F. Rumpold ◽

Gert Mayer ◽

...

Keyword(s):

T Cells ◽

Regulatory T Cells ◽

Telomere Length ◽

Cancer Patients ◽

Telomerase Activity ◽

Telomere Maintenance ◽

Healthy Human ◽

Telomere Shortening

Abstract The expandability of CD4+CD25+ regulatory T-cells (Treg) has been shown in vitro and in vivo. Activation of telomerase activity is a prerequisite for clonal expansion and telomere maintenance in T-cells. There is currently no data available on the expression and function of telomerase in proliferating Treg. Analyses of telomere length by flow-FISH, real-time PCR and Southern blotting revealed that Treg isolated from healthy human volunteers have significantly shortened telomeres when compared to CD4+CD25− T-cells. However, telomere length is not further shortened in Treg isolated from the peripheral blood of cancer patients, despite the observation that the regulatory T-cell pool of these patients was significantly enlarged. To gain further insight into maintenance of telomere length of Treg, we induced in vitro proliferation of Treg by stimulation with anti-CD3 and IL-2. This led to a rapid increase of telomerase activity, as determined by PCR-ELISA. However, when we focused on the proliferating fraction of Treg using a sorting strategy based on the dilution of CFSE, we could show a significant telomere shortening in Treg with high proliferative and immmuno-suppressive capacity. Of note, proliferating CFSElow Treg are characterized by high telomerase activity, which however seems to be insufficient to avoid further telomere shortening under conditions of strong in vitro stimulation. In contrast, under conditions of in vivo expansion of Treg in cancer patients, the induction of telomerase activity is likely to compensate for further telomere erosion. These data might be of importance when considering the application of in vitro expanded Treg for the treatment of GvHD or autoimmune diseases, as telomere shortening might be associated with genomic instability.

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Maintenance of Telomere Length in Peripheral Blood CD4+CD25+ Regulatory T-Cells of Cancer Patients Despite Active Proliferation.

Blood ◽

10.1182/blood.v106.11.3309.3309 ◽

2005 ◽

Vol 106 (11) ◽

pp. 3309-3309

Author(s):

Dominik Wolf ◽

Holger Rumpold ◽

Christian Koppelstaetter ◽

Guenther Gastl ◽

Eberhard Gunsilius ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Regulatory T Cells ◽

Telomere Length ◽

Cancer Patients ◽

Peripheral Blood ◽

Telomerase Activity ◽

Telomere Shortening ◽

Active Proliferation

Abstract CD4+CD25+ regulatory T-cells (Treg) are increased in the peripheral blood of cancer patients. It remains unclear whether this is due to redistribution or active proliferation. The latter would require the up-regulation of telomerase activity, whose regulation also remains unknown for Treg. We therefore isolated Treg and the respective CD4+CD25− control T-cell population from peripheral blood of cancer patients (n=23) and healthy age-matched controls (n=17). Analysis of their content of T-cell receptor excision circles (TREC) revealed that the observed increase of Treg frequencies in peripheral blood is due to active cycling rather than to redistribution from other compartments (i.e. secondary lymphoid organs or bone-marrow), as Treg from cancer patients are characterized by a significant decrease of TREC content when compared to TREC content of Treg isolated from healthy age-matched controls. Surprisingly, despite their proven in vivo proliferation, telomere length is not further shortened in Treg from peripheral blood of cancer patients as shown by Flow-Fish, Real-Time PCR and Southern Blotting. Accodingly, telomerase activity of Treg was readily inducible in vitro by OKT3 together with IL-2. Notably, sorting of in vitro proliferating Treg using dilution of CFSE revealed a significant telomere shortening in Treg with high proliferative capacity (i.e. CFSElow fraction) under conditions of strong in vitro stimulatory growth conditions despite a high telomerase activity. Thus, under conditions of strong in vitro stimulation induction of telomerase seems to be insufficient to avoid progressive telomere shortening. In contrast, in actively proliferating peripheral blood Treg from patients with epithelial malignancies induction of telomerase activity is likely to compensate for further telomere erosion.

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Functional p53 Is Required for Effective Telomerase Inhibition in BCRABL- Positive CML Cells in Vitro

Blood ◽

10.1182/blood.v112.11.572.572 ◽

2008 ◽

Vol 112 (11) ◽

pp. 572-572

Author(s):

Ute Brassat ◽

Stefan Balabanov ◽

Melanie Braig ◽

Daniel Bali ◽

Kerstin Borgmann ◽

...

Keyword(s):

Telomere Length ◽

Growth Kinetics ◽

Blast Crisis ◽

Telomerase Activity ◽

Gfp Expression ◽

Telomere Shortening ◽

Telomerase Inhibition ◽

Group A ◽

Group B

Abstract Telomeres consist of repeat structures such as (TTAGGG)n in vertebrates and are localized at the end of chromosomes. Replication-dependent telomere shortening due to the end-replication problem can be counteracted by upregulation of an endogenous reverse transcriptase called telomerase. Increasing evidence suggests that critical telomere shortening results in genetic instability which may promote tumour evolution and telomerase activation during which critically short telomeres are stabilised and ongoing tumour growth is facilitated. In Chronic myeloid leukemia (CML) the high turnover of the malignant clone is driven by the oncogene BCR-ABL and leads to accelerated telomere shortening in chronic phase (CP) compared to telomere length in healthy individuals. Telomere shortening has been demonstrated to be correlated with disease stage, duration, prognosis and response to molecular targeted treatment. Despite of the accelerated telomere shortening observed, telomerase activity is increased in CP CML and further upregulated with progression of the disease to accelerated phase or blast crisis (AP/BC). To investigate the effect of telomerase inhibition on BCR-ABL-positive cells, we expressed a dominant-negative mutant of hTERT (vector pOS DNhTERT-IRES-GFP) in K562 cells. The cells were single sorted and clones in addition to bulk cultures were long term expanded in vitro. The expression of the transgene DNhTERT was monitored by the expression of GFP and function of DNhTERT was analyzed by measurement of telomere length (by flow-FISH) and telomerase activity (TRAP assay). Evaluation of these parameters showed the following patterns of growth kinetics and telomere biology in individual clones: Two clones lost telomere repeats and were transiently delayed in growth kinetics but eventually escaped from crisis without loss of GFP expression (indicated by a re-increase in telomere length and growth rate, group A) Three other clones lost GFP expression after initial and significant telomere reduction indicating loss of the transgene (group B). Finally, telomere length and growth kinetics of two remaining clones and of the bulk culture cells remained unaffected by expression of DN-hTERT (group C). Of note, none of the clones analyzed either died or entered cell cycle arrest. Further analyses of one clone of group A revealed impaired DNA damage response indicated by two fold increase in number of γH2AX foci in comparison to control cells. Moreover, the expression pattern of genes involved in DNA repair was significantly altered (Dual chip®). Network analysis of the altered genes using MetaCore® software confirmed p53 as a key regulator in signaling of DNA damage in these cells. CML blast crisis cell lines such as K562 are typically negative for functional p53 and p16INK4. Therefore, we went on and investigate if the presence of functional p53 is required for the induction of telomere-mediated apoptosis or senescence in BCR-ABL-positive cells. For this purpose, we restored p53 in telomerase-negative clones by using an inducible system (vector pBABE p53ERtam) in two clones from group A and group B. Induction of p53 in cells with critically short telomeres (telomere length 4–5 kb) lead to immediate induction of apoptosis while vector control cells continued to escape from crisis. These results suggest that the success of strategies aimed at telomerase inhibition in CML is dependent on the presence of functional p53 in BCR-ABL-positive cells which argues in favour of applying these strategies preferentially in CP as opposed to BC.

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Gene pathways associated with mitochondrial function, oxidative stress and telomere length are differentially expressed in the liver of rats fed lifelong on virgin olive, sunflower or fish oils

The Journal of Nutritional Biochemistry ◽

10.1016/j.jnutbio.2017.09.007 ◽

2018 ◽

Vol 52 ◽

pp. 36-44 ◽

Cited By ~ 14

Author(s):

Alfonso Varela-Lopez ◽

María Patricia Pérez-López ◽

César Luis Ramirez-Tortosa ◽

Maurizio Battino ◽

Sergio Granados-Principal ◽

...

Keyword(s):

Oxidative Stress ◽

Telomere Length ◽

Mitochondrial Function ◽

Differentially Expressed ◽

Fish Oils

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Functional Diversification of Replication Protein A Paralogs and Telomere Length Maintenance in Arabidopsis

Genetics ◽

10.1534/genetics.120.303222 ◽

2020 ◽

Vol 215 (4) ◽

pp. 989-1002

Author(s):

Behailu B. Aklilu ◽

François Peurois ◽

Carole Saintomé ◽

Kevin M. Culligan ◽

Daniela Kobbe ◽

...

Keyword(s):

Homologous Recombination ◽

Telomere Length ◽

Protein A ◽

Replication Protein A ◽

Telomerase Activity ◽

Replication Protein ◽

Telomeric Dna ◽

Telomere Shortening ◽

Replication Group

Replication protein A (RPA) is essential for many facets of DNA metabolism. The RPA gene family expanded in Arabidopsis thaliana with five phylogenetically distinct RPA1 subunits (RPA1A-E), two RPA2 (RPA2A and B), and two RPA3 (RPA3A and B). RPA1 paralogs exhibit partial redundancy and functional specialization in DNA replication (RPA1B and RPA1D), repair (RPA1C and RPA1E), and meiotic recombination (RPA1A and RPA1C). Here, we show that RPA subunits also differentially impact telomere length set point. Loss of RPA1 resets bulk telomeres at a shorter length, with a functional hierarchy for replication group over repair and meiosis group RPA1 subunits. Plants lacking RPA2A, but not RPA2B, harbor short telomeres similar to the replication group. Telomere shortening does not correlate with decreased telomerase activity or deprotection of chromosome ends in rpa mutants. However, in vitro assays show that RPA1B2A3B unfolds telomeric G-quadruplexes known to inhibit replications fork progression. We also found that ATR deficiency can partially rescue short telomeres in rpa2a mutants, although plants exhibit defects in growth and development. Unexpectedly, the telomere shortening phenotype of rpa2a mutants is completely abolished in plants lacking the RTEL1 helicase. RTEL1 has been implicated in a variety of nucleic acid transactions, including suppression of homologous recombination. Thus, the lack of telomere shortening in rpa2a mutants upon RTEL1 deletion suggests that telomere replication defects incurred by loss of RPA may be bypassed by homologous recombination. Taken together, these findings provide new insight into how RPA cooperates with replication and recombination machinery to sustain telomeric DNA.

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