[show abstract][hide abstract] ABSTRACT: BACKGROUND: Shorter telomere length and poor sleep are more prevalent at older ages, but their relationship is uncertain. This study explored associations between sleep duration and telomere length in a sample of healthy middle and early old age people. METHODS: Participants were 434 men and women aged 63.3 years on average drawn from the Whitehall II cohort study. Sleep duration was measured by self-report. RESULTS: There was a linear association between sleep duration and leukocyte telomere length in men but not in women (P = 0.035). Men reporting shorter sleep duration had shorter telomeres, independently of age, body mass index, smoking, educational attainment, current employment, cynical hostility scores and depressive symptoms. Telomeres were on average 6% shorter in men sleeping 5 hours or fewer compared with those sleeping more than 7 hours per night. CONCLUSION: This study adds to the growing literature relating sleep duration with biomarkers of aging, and suggests that shortening of telomeres might reflect mechanisms through which short sleep contributes to pathological conditions in older men.
PLoS ONE 01/2012; 7(10):e47292. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Hostility is associated with a significantly increased risk of age-related disease and mortality, yet the pathophysiological mechanisms involved remain unclear. Here we investigated the hypothesis that hostility might impact health by promoting cellular aging.
We tested the relationship between cynical hostility and two known markers of cellular aging, leukocyte telomere length (TL) and leukocyte telomerase activity (TA), in 434 men and women from the Whitehall II cohort.
High-hostile men had significantly shorter leukocyte TL than their low-hostile counterparts. They also had elevated leukocyte TA, with a significantly increased likelihood of having both short TL and high TA, compared with low-hostile individuals.
Because telomerase is known to counteract telomere shortening by synthesizing telomeric DNA repeats, particularly in the context of shortened telomeres, heightened TA might represent a compensatory response in high-hostile individuals. The relationship between hostility and disease is stronger in men than in women, and men generally have a shorter life expectancy than women. Our findings suggest that telomere attrition might represent a novel mechanism mediating the detrimental effects of hostility on men's health.
[show abstract][hide abstract] ABSTRACT: Low socioeconomic status (SES) may be associated with accelerated biological aging, but findings relating SES with telomere length have been inconsistent. We tested the hypotheses that shorter telomere length and telomerase activity would be related more robustly to education, an early life indicator of socioeconomic position, than to current indicators of socioeconomic circumstances. Healthy men and women aged 53-76 years from the Whitehall II epidemiological cohort provided blood samples from which telomere length was assessed in 448 and telomerase activity in 416. Educational attainment was classified into four levels, while household income and grade of employment were measured as indicators of current socioeconomic circumstances. Age, gender, blood pressure, glycated hemoglobin, high density lipoprotein cholesterol, smoking, body mass index and physical activity were included as covariates. We found that lower educational attainment was associated with shorter telomere length after controlling statistically for biological and behavioral covariates. Neither household income nor employment grade was related to telomere length. The association between telomere length and education remained significant after adjusting for current socioeconomic circumstances. In men, highest levels of telomerase activity were found in the lowest education group. We conclude that low SES defined in terms of education but not current socioeconomic circumstances is associated with shortened telomeres. Low educational attainment may be an indicator of long-term SES trajectories, and be associated with accumulated allostatic load resulting in telomere shortening. Education may also promote problem-solving skills leading to reduced biological stress responsivity, with favorable consequences for biological aging.
Brain Behavior and Immunity 04/2011; 25(7):1292-8. · 5.61 Impact Factor
[show abstract][hide abstract] ABSTRACT: Honey is a broad spectrum antimicrobial agent which can enhance wound healing. A beneficial effect in cancer has been shown in cell cultures and in animal studies and a number of further nutritional and physiological effects of relevance to health and function have been shown for honey. A representative sub-sample of 665 men within the Caerphilly Cohort kept a weighed dietary record for seven days. Risk factors for vascular and other diseases in 41 men who recorded eating honey suggest that these men were on the whole healthier than the 624 men who had not recorded honey consumption. All-cause mortality during 25 years of follow-up was considerably lower in the men who had consumed honey, the hazard ratio, adjusted for a number of possible confounding factors, being 0.44 (95% confidence limits 0.23, 0.86; P<0.017). Because of the small number of subjects and of deaths in this study, further data from other large cohorts will be required before any effect upon mortality and other health effects of honey consumption can be adequately evaluated.
[show abstract][hide abstract] ABSTRACT: Most mitotically competent mammalian cell types can react to stress by undergoing a phenotypically distinctive and permanent form of growth arrest called "cellular senescence." This response has been extensively characterized in cell culture and more recently it has been found to occur also in vivo in a number of tissues. In this review I will present the case for the occurrence of senescence in the vascular endothelium. I will also discuss the mechanisms and factors that modulate endothelial cell replicative capacity and the onset of senescence. Finally, I will examine the senescent phenotype and its possible consequences for the development and progression of vascular diseases.
Journal of Applied Physiology 12/2008; 106(1):326-32. · 3.48 Impact Factor
[show abstract][hide abstract] ABSTRACT: When endothelial cells from different vascular beds are grown in culture they show a limited capacity to divide, eventually entering into a permanent and phenotypically distinctive non-dividing state referred to as 'replicative senescence'. Replicative senescence is thought to result from progressive shortening of telomeric DNA and consequent telomere dysfunction. More recently, it has been realised that senescence can also be induced by a variety of insults, including those causing intracellular oxidative stress. In this report, we review evidence for the occurrence of endothelial cell senescence in vivo. We will also examine the causes, mechanisms and regulation of this process as they emerge from our studies in cell culture, focusing in particular on the roles of oxidative stress, telomerase, growth factors and nitric oxide.
[show abstract][hide abstract] ABSTRACT: Nitric oxide (NO) has been known for many years to bind to cytochrome C oxidase, the terminal acceptor in the mitochondrial electron transport chain, in competition with oxygen. This interaction may be significant in vivo and explain some of the biological actions of NO. In this article we review the evidence showing that binding of NO to cytochrome C oxidase elicits intracellular signaling events, including the diversion of oxygen to nonrespiratory substrates and the generation of reactive oxygen species. We discuss findings indicating that these NO-elicited events act as triggers by which mitochondria modulate signal transduction cascades involved in the induction of cellular defense mechanisms and adaptive responses. We also discuss instances in which the effects of NO on the electron transport chain might lead to mitochondrial dysfunction and pathology.
[show abstract][hide abstract] ABSTRACT: Telomerase, a reverse transcriptase involved in the maintenance of telomere function and cellular replicative capacity, is thought to be regulated by nitric oxide (NO). Here, we have used pharmacological tools and RNA interference to re-assess the role of NO in the regulation of telomerase and senescence of human umbilical vein endothelial cells. Acute or chronic treatment of these cells with the NO donors diethylenetriamine/NO (DETA-NO) or S-nitroso-N-acetylpenicillamine (SNAP) at concentrations which generated NO in the 1-300 nM range did not modulate telomerase activity. Similarly these agents did not affect cellular replicative capacity during long-term sub-cultivation. The NO synthase (NOS) inhibitor N(G)-monomethyl-L-arginine (1 mM) reduced basal levels of c-GMP by 50% but had no effect on telomerase activity or replicative capacity. Withdrawal of ascorbic acid increased the intracellular pro-oxidant capacity, reduced telomerase activity and increased the accumulation of senescent cells upon serial passage in culture. However, this shift to a more oxidative redox state did not unmask the putative capacity of NO to modulate telomerase or senescence. Infection of cells with a lentiviral vector expressing a small hairpin RNA targeted against endothelial NOS inhibited endogenous NO production completely but failed to affect the decrease of telomerase activity or the accumulation of senescent cells observed with passage in culture. Our findings suggest that physiological concentrations of NO do not modulate telomerase levels or replicative capacity of endothelial cells, regardless of their cellular oxidative status.
[show abstract][hide abstract] ABSTRACT: Tea drinking appears to protect against the development of coronary heart disease (CHD), but the mediating pathways are uncertain. We studied the effects of 6 weeks of black tea or placebo on platelet activation, C-reactive protein (CRP), total antioxidant status, and soluble (s) P-Selectin in a randomized double-blind trial.
Healthy non-smoking men aged 18-55 years were randomized to black tea (N=37) or placebo (N=38) following a 4-week washout period during which they drank no tea, coffee or caffeinated beverages, but consumed caffeinated placebo tea. Bloods were drawn after 6 weeks of treatment. Platelet activation was assessed by measuring leukocyte-platelet aggregates using whole blood flow cytometry.
Following treatment, the tea group had fewer monocyte-platelet aggregates (means 5.84 versus 6.60%, P=0.027), neutrophil-platelet aggregates (P=0.017), total leukocyte-platelet aggregates (P=0.027), and lower plasma C-reactive protein (means 0.76 versus 0.97 mg/L, P=0.05) than the placebo group. There were no differences in total antioxidant status or soluble P-Selectin.
Chronic tea consumption reduces platelet activation and plasma C-reactive protein in healthy men. Effects cannot be attributed to observer bias or lifestyle confounders. These effects of tea may contribute to sustained cardiovascular health.
[show abstract][hide abstract] ABSTRACT: Tea has anecdotally been associated with stress relief, but this has seldom been tested scientifically.
To investigate the effects of 6 weeks of black tea consumption, compared with matched placebo, on subjective, cardiovascular, cortisol and platelet responses to acute stress, in a parallel group double-blind randomised design.
Seventy-five healthy nonsmoking men were withdrawn from tea, coffee and caffeinated beverages for a 4-week wash-out phase during which they drank four cups per day of a caffeinated placebo. A pretreatment laboratory test session was carried out, followed by either placebo (n = 38) or active tea treatment (n = 37) for 6 weeks, then, a final test session. Cardiovascular measures were obtained before, during and after two challenging behavioural tasks, while cortisol, platelet and subjective measures were assessed before and after tasks.
The tasks induced substantial increases in blood pressure, heart rate and subjective stress ratings, but responses did not differ between tea and placebo treatments. Platelet activation (assessed using flow cytometry) was lower following tea than placebo treatment in both baseline and post-stress samples (P < 0.005). The active tea group also showed lower post-task cortisol levels compared with placebo (P = 0.032), and a relative increase in subjective relaxation during the post-task recovery period (P = 0.036).
Compared with placebo, 6 weeks of tea consumption leads to lower post-stress cortisol and greater subjective relaxation, together with reduced platelet activation. Black tea may have health benefits in part by aiding stress recovery.
[show abstract][hide abstract] ABSTRACT: Previous studies have demonstrated shortened bleeding times in patients with acute coronary syndromes, especially in myocardial infarction (MI). In this study we have investigated platelet hyper-function using the PFA-100 with collagen/adenosine diphosphate and collagen/epinephrine cartridges in 78 patients presenting with acute chest pain. Patients were classified into MI, unstable angina (UA) and non-specific chest pain. All patients received 300 mg aspirin (ASA) more than 2 h before blood samples were collected. Twenty healthy normal subjects were also tested before and 2 h after 300 mg ASA (n = 10). The collagen/adenosine diphosphate closure time was significantly shorter in MI patients (median, 71 s; P = 0.0237) but not in UA patients (median, 81 s; P > 0.05) compared with normal subjects (median, 92.5 s). The collagen/epinephrine closure times were significantly longer in UA patients (median, 233 s) than in untreated controls (median, 125 s; P < 0.0001), as expected, but there was no difference in MI patients (median, 149.24 s; P > 0.05), suggesting that the MI patients were not all responding to ASA. Analysis of a subset of the apparent ASA non-responders (n = 5) by platelet aggregation demonstrated that this was not related to failure of ASA to block cyclo-oxygenase activity. Von Willebrand factor levels were significantly elevated in both UA and MI patients compared with normal subjects (mean, 175.5 and 248.9 versus 89.1 s; P < 0.0001 and P < 0.0001, respectively) and were also significantly higher in the MI group compared with the UA group (P < 0.05). There is evidence for platelet hyper-function and elevated von Willebrand factor levels in the MI group that could explain their decreased responsiveness to ASA on the collagen/epinephrine cartridge.
Blood Coagulation and Fibrinolysis 11/2005; 16(8):557-62. · 1.25 Impact Factor
[show abstract][hide abstract] ABSTRACT: The platelet-lowering drug anagrelide inhibits bone marrow megakaryocytopoiesis by an unknown mechanism. Recently, it was found that anagrelide is bio-transformed in humans into two major metabolites (6,7-dichloro-3-hydroxy-1,5 dihydro-imidazo[2,1-b]quinazolin-2-one (BCH24426) and 2-amino-5,6-dichloro-3,4,-dihydroquinazoline (RL603). Whether these metabolites have biological activities that may underlie the mode of action of the parent drug is presently unclear. To clarify this question here we have compared the activities of anagrelide, BCH24426 and RL603 on the growth and differentiation of CD34(+) haematopoietic progenitor cells in liquid culture and on the migration of differentiated megakaryocytes. Incubation with either anagrelide, BCH24426 or RL603 did not affect the early expansion of CD34(+) cells stimulated by thrombopoietin. In contrast, both anagrelide and BCH24426 potently inhibited the development of megakaryocytes (IC(50) +/- s.e.m. = 26 +/- 4 and 44 +/- 6 nM, respectively), whereas RL603 showed no significant effect. Anagrelide and BCH24426 did not affect erythroid or myelomonocytic differentiation stimulated by erythropoietin or granulocyte-macrophage colony-stimulating factor, demonstrating the selectivity of these compounds against the megakaryocytic lineage. Neither anagrelide nor its metabolites showed a significant effect on the migratory response of megakaryocytes towards stromal cell-derived factor-1alpha. Although BCH24426 was shown to be considerably more potent than anagrelide as an inhibitor of phosphodiesterase type III (PDEIII) (IC(50) = 0.9 vs 36 nM) this activity did not correlate with the potency of inhibition of megakaryocyte development. Furthermore, other PDEIII inhibitors of widely differing potency were shown to have negligible effects on megakaryocytopoiesis. Taken together our results demonstrate that anagrelide and BCH24426 target a cellular event involved specifically in the megakaryocyte differentiation programme, which is independent of PDEIII inhibition.
British Journal of Pharmacology 11/2005; 146(3):324-32. · 5.07 Impact Factor
[show abstract][hide abstract] ABSTRACT: In most somatic mammalian cell types extensive replication and various types of cellular insults induce a permanent form of growth arrest called senescence. Senescence has been comprehensively characterised in cell culture, but its occurrence in vivo has only recently started to become appreciated. In this mini-review, we examine the evidence for the occurrence of senescence in vivo, with particular emphasis on the cardiovascular system. We also describe the senescent phenotype and discuss its pathophysiological implications. We examine findings in animal models of ageing and human genetic disorders that argue for and against a role of senescence in age-related pathologies in general and vascular disease in particular.
[show abstract][hide abstract] ABSTRACT: In cultured human umbilical vein endothelial cells (HUVECs), fibroblast growth factor-2 (FGF-2), but not vascular endothelial growth factor-A (VEGF-A), upregulates telomerase activity. Here, we examined the functional significance of this differential regulation on the replicative life span of HUVECs. HUVECs were serially passaged until senescence under four different conditions: (1) EGM-2, a medium containing both VEGF-A and FGF-2; (2) basal medium (BM), consisting of EGM-2 devoid of FGF-2 and VEGF-A; (3) BM supplemented with FGF-2; and (4) BM supplemented with VEGF-A. Cells cultured in BM demonstrated decreased growth rate and ceased to proliferate at approximately 15 population doublings (PDs), whereas those cultured with VEGF-A alone initially proliferated vigorously but arrested growth abruptly at a PD level comparable with cultures grown in BM. In contrast, cells maintained in EGM-2 or in BM/FGF-2 attained a normal replicative life span (approximately 40 PDs). These differences in replicative behavior were reflected by the early appearance of a senescent phenotype in cultures grown in BM or BM/VEGF-A. HUVECs grown in the presence of VEGF-A alone have a decreased life span compared with cultures maintained with FGF-2. This suggests that the upregulation of telomerase activity by FGF-2, an effect not achieved with VEGF-A, plays a functional role in preventing the early onset of senescence.
Annals of the New York Academy of Sciences 07/2004; 1019:111-5. · 4.38 Impact Factor
[show abstract][hide abstract] ABSTRACT: Replicative senescence and oxidative stress have been implicated in ageing, endothelial dysfunction and atherosclerosis. Replicative senescence is determined primarily by telomere integrity. In endothelial cells the glutathione redox-cycle plays a predominant role in the detoxification of peroxides. The aim of this study was to elucidate the role of the glutathione-dependent antioxidant system on the replicative capacity and telomere dynamics of cultured endothelial cells. Human umbilical vein endothelial cells were serially passaged while exposed to regular treatment with 0.1 microM tert-butyl hydroperoxide, a substrate of glutathione peroxidase, or 10 microM L-buthionine-[S,R]-sulphoximine, an inhibitor of glutathione synthesis. Both treatments induced intracellular oxidative stress but had no cytotoxic or cytostatic effects. Nonetheless, treated cultures entered senescence prematurely (30 versus 46 population doublings), as determined by senescence-associated beta-galactosidase staining and a sharp decrease in cell density at confluence. In cultures subjected to oxidative stress terminal restriction fragment (TRF) analysis demonstrated faster telomere shortening (110 versus 55 bp/population doubling) and the appearance of distinct, long TRFs after more than 15-20 population doublings. Fluorescence in situ hybridisation analysis of metaphase spreads confirmed the presence of increased telomere length heterogeneity, and ruled out telomeric end-to-end fusions as the source of the long TRFs. The latter was also confirmed by Bal31 digestion of genomic DNA. Similarly, upregulation of telomerase could not account for the appearance of long TRFs, as oxidative stress induced a rapid and sustained decrease in this activity. These findings demonstrate a key role for glutathione-dependent redox homeostasis in the preservation of telomere function in endothelial cells and suggest that loss of telomere integrity is a major trigger for the onset of premature senescence under mild chronic oxidative stress.
[show abstract][hide abstract] ABSTRACT: We studied atheromatous lesion formation in an animal model of accelerated ageing. The senescence-accelerated prone mouse (SAM-P) has a reduced life-span and exhibits clinical features characteristic of human ageing. Our aim was to establish whether these mice are more susceptible to atherosclerosis than a related strain, senescence-accelerated resistant mice (SAM-R), which age normally. We fed a Western-type diet to 14 SAM-P/8 and 14 SAM-R/1 mice for 17 weeks, starting at 28 weeks of age, measuring their serum lipid profiles before and after this diet. We stained aortic root cryostat cross-sections with Oil red O, and assessed lipid deposition morphometrically. We used immunohistochemistry to detect macrophages in the aortic roots. We found that despite showing similar alterations in lipid profile, SAM-P/8 mice developed more prevalent and extensive fatty lesions than SAM-R/1 mice. Furthermore, the lipid lesions in SAM-P/8 mice showed a greater frequency of invasion by macrophages. We conclude that mice, which age at an accelerated rate, are more prone to early atherogenesis than mice which age normally. We suggest that this increased susceptibility may result from abnormalities in the oxidative status and cellular replicative capacity of these mice.
[show abstract][hide abstract] ABSTRACT: Mature megakaryocytes (MKs) are large cells, having an approximate diameter in humans of 20–40 μm. They develop from CD34+ multipotent hematopoietic progenitors through a complex differentiation process driven primarily by the hormone thrombopoietin
(TPO) (reviewed in refs.
1,2). The cellular hierarchy of the megakaryocytic lineage comprises three types of cells (3,4): MK progenitors, immature MKs or promegakaryoblasts, and mature MKs (Fig. 1). MK progenitors (HPP-CFU, BFU and CFU in Fig. 1; see caption for definitions) are a functionally heterogeneous group of cells, endowed with varying degrees of proliferative capacity,
all of which express the surface antigen CD34. Promegakaryoblasts are transitional cells, intermediate between the proliferating
progenitor cells and the mature, differentiated MKs (5). They are also a heterogeneous group of cells, which undergo polyploidization during development and increase their size
and cytoplasmic complexity. Mature MKs are polyploid cells that no longer proliferate but have the unique ability to shed
their cytoplasm (6), and as a result, produce in the order of 2000–3000 platelets/cell. In addition to TPO, other pleiotropic growth factors
and cytokines (see
Fig. 1) can act synergistically on hematopoietic progenitors to promote the growth and maturation of MK (7–9).
Fig. 1.Overview of megakaryocyte development and expression of differentiation markers. Broken lines indicate low levels of antigen
expression. Abbreviations: TPO, thrombopoietin; IL, interleukin; GM-CSF, granulocytemacrophage colony-stimulating factor;
SCF, stem cell factor; EPO, erythropoietin; FL, flt ligand; LIF, leukemia inhibitory factor; Onc M, oncostatin M; SDF-1, stromal
cell derived factor 1; HPP CFU, high-proliferative potential colony-forming unit; BFU, burst-forming unit; CFU, colony-forming
unit; vWF, von Willebrand factor; PF4, platelet factor 4; TSP, thrombospondin; GP, glycoprotein.
[show abstract][hide abstract] ABSTRACT: A common variant in intron 5 of the thrombopoietin (TPO) gene (4830C>A) has been associated with risk of myocardial infarction (MI). To explore the molecular mechanism of this association, the ability of the intron to act as a transcription enhancer and to influence mRNA splicing was tested.
In HepG2 cells the presence of intron 5 upstream of the TPO promoter decreased promoter activity to between 60% and 30%. This effect was orientation dependent; in the reverse orientation, intron 5 caused a twofold greater decrease in promoter activity compared to the forward orientation. However, the effects were similar with either the C or the 4830A allele. An in vitro exon trapping system was used to study the effect of the polymorphism on splicing events in exon 6. The full-length (TPO-1) and three previously reported splice variants (TPO-2, TPO-3, and TPO-5) were identified. The 4830A allele resulted in a small but statistically significant increase in production of the TPO-3 splice variant relative to the full-length transcript (10.6%+/-0.6%) compared to the 4830C allele (8.3%+/-0.6%) (p=0.02). Generation of TPO-5 was also slightly increased, but this did not reach significance.
The identification of a potential "silencer" sequence in intron 5 of the TPO gene demonstrates the complexity of control of expression of the gene. Although the precise role of the different splice variants is not known, the finding that the 4830C>A sequence change alters their relative amounts, suggests a possible molecular mechanism whereby TPO genotype may influence the risk of MI.