Different rates of telomere shortening and telomerase activity reduction in CD8 T and CD16 NK lymphocytes with ageing

Telomeres are specialised structures located at the end of eukaryotic chromosomes, that get short during progressive cell divisions. Therefore, telomere may be an indicator of the mitotic history of a cell and it is also a determining factor for the residual cell life span. One mechanism, compensating for the telomere erosion, involves the induction of telomerase, a ribonucleoprotein-enzyme able to synthesize telomeric DNA repeats. In this study, old subjects of two consecutive decades were compared with a group of young controls to investigate whether ageing-related modifications differently affects telomere length and telomerase activity of human peripheral blood CD8 T and CD16 NK lymphocytes. Telomeres in individual cells were measured by flow-FISH and telomerase activity was determined using the TeloTAGGG telomerase PCR ELISA(PLUS) kit. Both CD8 T and NK lymphocytes showed an age-associated loss of telomeres at rates that were different between the subsets together with an age-associated reduction of telomerase activity that was progressive in CD8 and late in NK lymphocytes. We can assume that preserved innate immune response in the elderly is due to the negligible telomere shortening and the maintained telomerase expression that could allow NK cells of octogenarians to delay replicative senescence.     

Abnormal telomerase activity and telomere length in T and B cells from patients with systemic lupus erythematosus

OBJECTIVE: To evaluate the clinical significance of telomerase activity and telomere length in T and B lymphocytes from patients with systemic lupus erythematosus (SLE). METHODS: CD3+ (T cell) and CD19+ (B cell) lymphocytes were isolated from the peripheral blood of SLE patients and healthy controls by means of magnetic bead-coupled antibodies. SLE patients were classified as active or inactive cases according to the SLE Disease Activity Index (SLEDAI). Telomere activity of lymphocytes was measured by telomeric-repeat amplification protocol. Telomere length was measured by flow cytometry-fluorescence in situ hybridization. RESULTS: T cell telomerase activity was significantly higher in patients with both active and inactive SLE than in controls, but was lower than B cell telomerase activity in patients with active SLE, and was not correlated with SLEDAI results. B cell telomerase activity was only significantly higher than in controls in patients with active SLE, and was strongly correlated with SLEDAI. Four laboratory results, anti-dsDNA antibody titer, IgG level, C3 level, and CH50 level, were correlated with B cell telomerase activity. Telomere length in T cells was significantly shorter than in controls. In contrast, the telomere length in B cells did not differ significantly from controls. CONCLUSION: In patients with SLE, many T cells divide continuously. Their telomerase activity was higher than that in control T cells, but not so high as to prevent telomere shortening. In contrast, B cells do not divide abnormally in the inactive phase of SLE, but divide rapidly in the active phase.     

Developmental and tissue-specific regulation of mouse telomerase and telomere length.

Telomere shortening and telomerase activation in human somatic cells have been implicated in cell immortalization and cellular senescence. To further study the role of telomerase in immortalization, we assayed telomere length and telomerase activity in primary mouse fibroblasts, in spontaneously immortalized cell clones, and in mouse tissues. In the primary cell cultures, telomere length decreased with increased cell doublings and telomerase activity was not detected. In contrast, in spontaneously immortalized clones, telomeres were maintained at a stable length and telomerase activity was present. To determine if telomere shortening occurs in vivo, we assayed for telomerase and telomere length in tissues from mice of different ages. Telomere length was similar among different tissues within a newborn mouse, whereas telomere length differed between tissues in an adult mouse. These findings suggest that there is tissue-specific regulation of mouse telomerase during development and aging in vivo. In contrast to human tissues, most mouse tissues had active telomerase. The presence of telomerase in these tissues may reflect the ease of immortalization of primary mouse cells relative to human cells in culture.     

Vascular smooth muscle cells undergo telomere-based senescence in human atherosclerosis: effects of telomerase and oxidative stress

Although human atherosclerosis is associated with aging, direct evidence of cellular senescence and the mechanism of senescence in vascular smooth muscle cells (VSMCs) in atherosclerotic plaques is lacking. We examined normal vessels and plaques by histochemistry, Southern blotting, and fluorescence in situ hybridization for telomere signals. VSMCs in fibrous caps expressed markers of senescence (senescence-associated beta-galactosidase [SAbetaG] and the cyclin-dependent kinase inhibitors [cdkis] p16 and p21) not seen in normal vessels. In matched samples from the same individual, plaques demonstrated markedly shorter telomeres than normal vessels. Fibrous cap VSMCs exhibited markedly shorter telomeres compared with normal medial VSMCs. Telomere shortening was closely associated with increasing severity of atherosclerosis. In vitro, plaque VSMCs demonstrated morphological features of senescence, increased SAbetaG expression, reduced proliferation, and premature senescence. VSMC senescence was mediated by changes in cyclins D/E, p16, p21, and pRB, and plaque VSMCs could reenter the cell cycle by hyperphosphorylating pRB. Both plaque and normal VSMCs expressed low levels of telomerase. However, telomerase expression alone rescued plaque VSMC senescence despite short telomeres, normalizing the cdki/pRB changes. In vivo, plaque VSMCs exhibited oxidative DNA damage, suggesting that telomere damage may be induced by oxidant stress. Furthermore, oxidants induced premature senescence in vitro, with accelerated telomere shortening and reduced telomerase activity. We conclude that human atherosclerosis is characterized by senescence of VSMCs, accelerated by oxidative stress-induced DNA damage, inhibition of telomerase and marked telomere shortening. Prevention of cellular senescence may be a novel therapeutic target in atherosclerosis.     

雌激素对外周血白细胞端粒长度的影响

端粒随着每个细胞分裂而缩短,白细胞端粒长度(LTL)和端粒酶在多种疾病中被广泛研究,如心血管疾病及其相关代谢危险因素、神经系统疾病、恶性肿瘤等.端粒长度的变化可能由多种因素决定,包括遗传和环境因素等.出生时,男性和女性的端粒长度差异不明确,而成年女性的端粒普遍比男性长,这种性别差异可能与内源性雌激素暴露或激素替代治疗(...     

L’entérite : une manifestation peu fréquente et corticosensible du lupus érythémateux systémique

Introduction

. Lupus enteritis is a rare manifestation of systemic lupus erythematosus. The clinical manifestations are variable including abdominal pain, diarrhea, nausea and vomiting. Lupus enteritis is thought to be related to vasculitis.

Case reports

. We report here three new cases. All three patients aged of 45, 24 and 43 years (two females and one male) were admitted for abdominal pain, vomiting and diarrhea, and fulfilled the ACR criteria of systemic lupus erythematosus. The diagnosis of lupus enteritis was retained on the CT scan findings and the favorable outcome on corticosteroids after infectious etiologies were excluded.

Conclusion

. Lupus enteritis is thought to be one of the most common causes of acute abdominal pain in systemic lupus erythematosus. The diagnosis is based on clinical, radiological and biological findings. A good response to corticosteroids is usually reported.     

Association between oxidative DNA damage and telomere shortening in circulating endothelial progenitor cells obtained from metabolic syndrome patients with coronary artery disease

Metabolic syndrome (MS) induces an increase in oxidative stress and may be an important contributory factor for coronary artery disease (CAD). Telomere shortening of endothelial progenitor cells (EPCs) may be the key factor in endothelial cell senescence. The rate of telomere shortening is highly dependent on cellular oxidative damage. This study analyzed the relationship between telomere shortening and oxidative DNA damage in EPCs obtained from CAD patients with MS and without MS. We analyzed circulating EPCs in peripheral blood obtained from 57 patients with CAD (acute myocardial infarction [AMI], n=26; stable angina pectoris [AP], n=31) and 21 age-matched healthy subjects (control). Telomere length and telomerase activity were significantly lower in CAD patients than in controls, and were lower in AMI patients than in AP patients. Oxidative DNA damage was higher in CAD patients compared with controls, and oxidative DNA damage in AMI patients was also higher than in AP patients. There was a negative correlation between telomere length and oxidative DNA damage. Telomere length and telomerase activity were lower in CAD patients with MS than in those without MS. Oxidative DNA damage in CAD patients with MS was higher than in those without MS. In our in vitro study, oxidative treatments induced telomere shortening and decrease in telomerase activity of EPCs. These results suggest that EPC telomere shortening via increased oxidative DNA damage may play an important role in the pathogenesis of CAD. In addition, MS may be related to increased oxidative DNA damage and EPC telomere shortening.     

Neurolupus (2 partie). Description des outils diagnostiques et thérapeutiques devant une manifestation psychiatrique ou neurologique centrale au cours du lupus érythémateux systémique

Neurological and psychiatric manifestations of systemic lupus erythematosus are a heterogenous set of clinical manifestations grouped under the term of “neuropsychiatric systemic lupus erythematosus”. The classification of these manifestations published in 1999 has harmonized the definitions cases used in the studies but did not help the clinician to positively identify a specific manifestation of lupus or a neurological or psychiatric event occurred independently of the disease. Published cases series help us to identify neurological or psychiatric manifestations of lupus but modern diagnosis tools contribution have to be evaluated in order to optimize diagnosis management of such manifestations and to distinguish specific events related to lupus and independent manifestations. In this second part of our literature review about neuropsychiatric lupus, we propose to identify arguments, which could be in favor of lupus responsibility in front of a neurological or psychiatric event, and immunosuppressive treatments which are recommended.     

Telomere dynamics in arteries and mononuclear cells of diabetic patients: effect of diabetes and of glycemic control

Telomeres serve as a mitotic clock and biological marker of senescence. Diabetes mellitus (DM) is associated with damage to target organs and premature aging. We assessed the effect of glycemic control on telomere dynamics in arterial cells of 58 patients undergoing coronary artery bypass and in mononuclear blood cells of other diabetic (32 type I and 47 type II) patients comparing well controlled to uncontrolled patients. All were compared to age-dependent curve of healthy controls. Telomeres were significantly shorter in the arteries of diabetic versus non-diabetic patients (p=0.049) and in mononuclear cells of both type I and type II diabetes. In all study groups good glycemic control attenuated shortening of the telomeres. In arterial cells good glycemic control attenuated, but not abolished, the telomere shortening. In type II DM the mononuclear telomere attrition was completely prevented by adequate glycemic control. Telomere shortening in mononuclear cells of type I diabetic patients was attenuated but not prevented by good glycemic control. Results of this study suggest that diabetes is associated with premature cellular senescence which can be prevented by good glycemic control in type II DM and reduced in type I DM.     

Narcolepsie révélant un lupus érythémateux systémique

Many neurologic and psychiatric manifestations have been associated with systemic lupus erythematosus. Narcolepsy, currently hypothesized as related to an autoimmune process, has been rarely associated with systemic lupus erythematosus. We report a 36-year-old woman who presented with narcolepsy and who subsequently developed systemic lupus erythematosus. Excessive daytime sleepiness resolved after the administration of four intravenous bolus of cyclophosphamide and methylprednisolone followed by maintenance therapy with hydroxychloroquine, aspirine and prednisone. Narcolepsy should be included in the neuropsychiatric manifestations of systemic lupus erythematosus and it may have a parallel clinical course to the activity of the lupus.     

Telomere shortening and ageing

Telomeres form the ends of human chromosomes. Telomeres shorten with each round of cell division and this mechanism limits proliferation of human cells to a finite number of cell divisions by inducing replicative senescence, differentiation, or apoptosis. Telomere shortening can act as a tumor suppressor. However, as a downside, there is growing evidence indicating that telomere shortening also limits stem cell function, regeneration, and organ maintenance during ageing. Moreover, telomere shortening during ageing and disease is associated with increasing cancer risk. In this review we summarize our current knowledge on the role of telomere shortening in human ageing, chronic diseases, and cancer.     

Telomere length in cardiovascular disease: new challenges in measuring this marker of cardiovascular aging

Atherosclerosis is an age-related systemic disease characterized by systemic oxidative stress and low grade chronic inflammation. Various types of leukocytes play an important role within this process. Telomeres, the ends of chromosomes, shorten during each and every cell division and have therefore been regarded as a cellular clock. Telomere dysfunction has been implicated in aging and senescence, and shorter leukocyte telomere length (LTL) has been demonstrated to predict cardiovascular disease and mortality. However, although LTL can predict cardiovascular events in population studies, a number of factors have prevented its broad use as a surrogate end point, such as serum levels of LDL cholesterol. In this article we will provide an overview of telomere biology and telomere dynamics of different leukocyte populations, and we will also discuss pitfalls in the methodology of LTL quantification, in context with landmark studies, which measured LTL in cardiovascular disease. Finally, we will attempt to critically assess and explain the shortcomings of LTL as a biomarker and identify further research avenues that require further investigation before telomere length can be implemented as an individual biomarker for cardiovascular aging. From this it becomes evident that LTL can be susceptible to methodological errors affecting longitudinal reproducibility. LTL is generally confounded at least by genetic factors, population variation and leukocyte composition.     

Telomere dysfunction in peripheral blood mononuclear cells from patients with primary biliary cirrhosis

BackgroundChromosomal instability in peripheral blood mononuclear cells has a role in the onset of primary biliary cirrhosis. We hypothesized that patients with primary biliary cirrhosis may harbour telomere dysfunction, with consequent chromosomal instability and cellular senescence.AimTo evaluate the clinical significance of telomerase activity and telomere length in peripheral blood mononuclear cells from patients with primary biliary cirrhosis.Study designIn this population-based case control study, 48 women with primary biliary cirrhosis (25 with cirrhosis), 12 with chronic hepatitis C matched by age and severity of disease, and 55 age-matched healthy women were identified. Mononuclear cells from the peripheral blood of patients and controls were isolated. Telomere length and telomerase activity were measured.ResultsTelomere length and telomerase activity did not differ between cases (5.9 ± 1.5 kb) and controls (6.2 ± 1.4 kb, p_c = 0.164). Telomere shortening and advanced-stage disease strongly correlated with telomerase activity. Patients with advanced disease retained significantly less telomerase activity than those with early-stage disease (0.6 ± 0.9 OD vs. 1.5 ± 3.7 OD, p = 0.03). Telomere loss correlated with age, suggesting premature cellular ageing in patients with primary biliary cirrhosis.ConclusionOur data strongly support the telomere hypothesis of human cirrhosis, indicating that telomere shortening and telomerase activity represent a molecular mechanism in the evolution of human cirrhosis in a selected population of patients.     

Telomerase activity in normal leukocytes and in hematologic malignancies

Telomeres are essential for function and stability of eukaryotic chromosomes. In the absence of telomerase, the enzyme that synthesizes telomeric DNA, telomeres shorten with cell division, a process thought to contribute to cell senescence and the proliferative crisis of transformed cells. We reported telomere stabilization concomitant with detection of telomerase activity in cells immortalized in vitro and in ovarian carcinoma cells, and suggested that telomerase is essential for unlimited cell proliferation. We have now examined the temporal pattern of telomerase expression in selected hematologic malignancies. We found that, unlike other somatic tissues, peripheral, cord blood, and bone marrow leukocytes from normal donors expressed low levels of telomerase activity. In leukocytes from chronic lymphocytic leukemia (CLL) patients, activity was lower than in controls in early disease, and comparable with controls in late disease. Relative to bone marrow, telomerase activity was enhanced in myelodysplastic syndrome (MDS) and more significantly so in acute myeloid leukemia (AML). Regardless of telomerase levels, telomeres shortened with progression of the diseases. Our results suggest that early CLL and MDS cells lack an efficient mechanism of telomere maintenance and that telomerase is activated late in the progression of these cancers, presumably when critical telomere loss generates selective pressure for cell immortality.     

Telomeres, immune aging and autoimmunity

Telomere length is important in constraining the replicative potential of cells; cellular systems that are dependent on cell replenishment for renewal or on cell proliferation for functionality are highly sensitive to telomeric erosion. Cell replication invariably leads to telomere loss, which, in some cellular systems, is partially compensated for by telomerase activity. In addition to this typical telomere loss, several mechanisms of sporadic telomere loss exist. Heterogeneity in age-dependent telomere loss can be a consequence of increased cellular turnover during a lifetime, accelerated telomeric DNA damage, or defects in telomere repair. The immune system is a prime example of a highly dynamic cellular system, for which telomere maintenance is pivotal. Immune competence is strictly dependent on rapid expansions of clonal T- and B-cell populations, and telomere loss may contribute to defective immune responses in the elderly. Equally interestingly, accelerated T-cell aging combined with telomeric shortening may predispose for autoimmune responses and thereby explain the increased susceptibility for chronic inflammatory diseases in the elderly.     

Telomerase is required to slow telomere shortening and extend replicative lifespan of HSCs during serial transplantation

Telomere shortening ultimately limits the replicative life span of cultured human somatic cells. Telomeres also shorten during replicative aging in vivo in hematopoietic cells, including early hematopoietic progenitors and hematopoietic stem cells (HSCs), from humans and mice, despite readily detectable levels of telomerase in these cells. To assess the relevance of telomerase to the long-term replicative capacity of HSCs in vivo, we serially transplanted HSCs from wild-type and telomerase-deficient mice until exhaustion and monitored telomere length in HSCs during this process. Telomerase-deficient HSCs could be serially transplanted for only 2 rounds, whereas wild-type HSCs could be serially transplanted for at least 4 rounds. Furthermore, the rate of telomere shortening was increased approximately 2-fold during serial transplantation of telomerase-deficient HSCs. These findings suggest that one role for telomerase in the HSC is to partially counter the rate of telomere shortening during division of HSCs, thereby preventing premature loss of telomere function and providing added replicative capacity.     

Anticytokine therapy in systemic lupus erythematosus

Systemic lupus erythematosus is a prototype of heterogeneous autoimmune disease. There have been few newly approved therapeutic agents in lupus treatment for many reasons. Several animal studies and human data have shown that many potential cytokines are related to the pathogenesis and disease activity of systemic lupus erythematosus. Cytokines are produced by many immune cell types and have variable functions in the immune system. Following the success of biological agents in the treatment of inflammatory arthritis, inflammatory bowel disease, and psoriasis, biological targeting to specific cytokines or receptor molecules is now promising in the treatment of systemic lupus erythematosus. In addition to B-cell deleting modalities, clinical trials targeting potential cytokines associated with disease pathogenesis are underway at various clinical stages. Among potential cytokines, targeting agents against B-cell activating factor and interferon-alpha are in the most advanced stage, and belimumab (anti-B-cell activating factor antibody) could be the first biological agent approved in the treatment of systemic lupus erythematosus. Anti-tumor necrosis factor was tried with some success, but with a potential risk of infection in a small number of patients. In this review, we discuss the rationale for anticytokine therapies and review agents currently in clinical trials, and those that could be developed in the near future for systemic lupus erythematosus. We present the results mostly from published trials and data from http://clinicaltrials.gov/ct2/     

Telomeres, stem cells, and hematology

Telomeres are highly dynamic structures that adjust the cellular response to stress and growth stimulation based on previous cell divisions. This critical function is accomplished by progressive telomere shortening and DNA damage responses activated by chromosome ends without sufficient telomere repeats. Repair of critically short telomeres by telomerase or recombination is limited in most somatic cells, and apoptosis or cellular senescence is triggered when too many uncapped telomeres accumulate. The chance of the latter increases as the average telomere length decreases. The average telomere length is set and maintained in cells of the germ line that typically express high levels of telomerase. In somatic cells, the telomere length typically declines with age, posing a barrier to tumor growth but also contributing to loss of cells with age. Loss of (stem) cells via telomere attrition provides strong selection for abnormal cells in which malignant progression is facilitated by genome instability resulting from uncapped telomeres. The critical role of telomeres in cell proliferation and aging is illustrated in patients with 50% of normal telomerase levels resulting from a mutation in one of the telomerase genes. Here, the role of telomeres and telomerase in human biology is reviewed from a personal historical perspective.