Telomere Biology and Cardiovascular Disease

Abstract

Abstract-Accumulation of cellular damage with advancing age leads to atherothrombosis and associated cardiovascular disease. Ageing is also characterized by shortening of the DNA component of telomeres, the specialized genetic segments located at the end of eukaryotic chromosomes that protect them from end-to-end fusions. By inducing genomic instability, replicative senescence and apoptosis, shortening of the telomeric DNA is thought to contribute to organismal ageing. In this Review, we discuss experimental and human studies that have linked telomeres and associated proteins to several factors which influence cardiovascular risk (eg, estrogens, oxidative stress, hypertension, diabetes, and psychological stress), as well as to neovascularization and the pathogenesis of atherosclerosis and heart disease. Two chief questions that remain unanswered are whether telomere shortening is cause or consequence of cardiovascular disease, and whether therapies targeting the telomere may find application in treating these disorders (eg, cell "telomerization" to engineer blood vessels of clinical value for bypass surgery, and to facilitate cell-based myocardial regeneration strategies). Given that most research to date has focused on the role of telomerase, it is also of up most importance to investigate whether alterations in additional telomere-associated proteins may contribute to the pathogenesis of cardiovascular disease. Key Words: telomeres Ⅲ telomerase Ⅲ atherosclerosis Ⅲ heart disease Ⅲ oxidative stress Ⅲ hypertension Ⅲ diabetes Ⅲ estrogens T elomeres are special chromatin structures located at the ends of eukaryotic chromosomes that prevent the recognition of chromosomal ends as double-stranded DNA breaks, thereby protecting these regions from recombination and degradation and avoiding a DNA damage cellular response. The telomeric DNA is composed of noncoding doublestranded repeats of G-rich tandem DNA sequences (TTAGGG in vertebrates) that are extended several thousand base pairs (10 to 15 kb in humans and 25 to 40 kb in mice) and end in a 150 to 200 nucleotide 3Ј single-stranded overhang (G-strand overhang) (Figure 1). 1,2 Several specific proteins are associated to telomeric DNA, including telomerase and the telomeric repeat binding factors 1 and 2 (TRF1, TRF2) which directly bind to the TTAGGG repeat and interact with other factors forming large protein complexes that regulate telomere length and structure. Mammalian telomerase consists of a RNA component (telomerase RNA component [TERC]) that serves as a template for the synthesis of new telomeric TTAGGG repeats by the telomerase reverse transcriptase component (TERT). Telomere components and structure has been comprehensively discussed elsewhere. 2

Rap1 induces cytokine production in pro-inflammatory macrophages through NFκB signaling and is highly expressed in human atherosclerotic lesions

“…Telomere attrition is accelerated as the cell ages or faces stress. [42][43][44] Indeed, in senescent PAECs, the amount of Rap1 in the cytosol is elevated compared with young PAECs. 37 Thus, it is tempting to speculate that as telomere length is reduced, the ratio between telomere-bound and "free" Rap1 (available for the cytoplasmic activation of the NFkB pathway) is affected.…”

Depression gets old fast: do stress and depression accelerate cell aging?

“…[149] Preliminary data suggest that telomere shortening is a function of the duration of the lifetime exposure to depression (Wolkowitz et al, unpublished) and may not be present in individuals with short lifetime exposures to depression. In nondepressed populations, shortening of leukocyte telomeres is associated with atherosclerosis and CV disease, [151][152][153] osteoporosis [154] and cognitive impairment, [155] and with increased medical morbidity and earlier mortality from a number of causes, including CV and infectious disease, and dementia. [156] For example, shortened telomeres are associated with a greater than three-fold increase in the risk of myocardial infarction and stroke, and with a greater than eightfold increase in the risk of death from infectious disease.…”

Expanding the clinical phenotype of autosomal dominant dyskeratosis congenita caused by TERT mutations

“…9 The frequency of cardiac fibrosis in patients with DC caused by TERT mutations has still to be determined in a larger cohort of patients.…”