Endothelial dysfunction and aging: an update

Cyclin-dependent kinase 5-mediated hyperphosphorylation of sirtuin-1 contributes to the development of endothelial senescence and atherosclerosis

BACKGROUND

Endothelial senescence represents one of the major characteristics of vascular aging and promotes the development of atherosclerosis. Sirtuin-1 (SIRT1) is an NAD-dependent deacetylase possessing antiaging activities. During the occurrence of endothelial senescence, both the expression and activity of SIRT1 are downregulated. The present study was designed to investigate the molecular mechanisms contributing to the loss-of-SIRT1 function in senescent endothelial cells.

METHODS AND RESULTS

After repetitive passages, primary cultures of porcine aortic endothelial cells exhibited a severe senescence phenotype. Western blotting revealed that phosphorylation of SIRT1 at serine 47 (S47) was significantly enhanced in senescent endothelial cells. S47 phosphorylation was stimulated by agents promoting senescence and attenuated by drugs with antisenescence properties. Mutation of S47 to nonphosphorable alanine (S47A) enhanced whereas replacing S47 with phospho-mimicking aspartic acid (S47D) abolished the antisenescent, growth-promoting, and LKB1-downregulating actions of SIRT1. Phosphorylation at S47 was critically involved in the nuclear retention of SIRT1 but abolished its association with the telomeric repeat-binding factor 2-interacting protein 1. Cyclin-dependent kinase 5 (CDK5) was identified as an SIRT1 kinase modulating S47 phosphorylation. Knockdown or inhibition of CDK5 reduced the number of senescent endothelial cells, promoted nuclear exportation of SIRT1, and attenuated the expression of inflammatory genes in porcine aortic endothelial cells. The truncated regulatory subunit of CDK5, P25, accumulated in senescent porcine aortic endothelial cells and atherosclerotic aortas. Long-term treatment with roscovitine, a CDK5 inhibitor, blocked the development of cellular senescence and atherosclerosis in aortas of hypercholesterolemic apolipoprotein E-deficient mice.

CONCLUSION

CDK5-mediated hyperphosphorylation of SIRT1 facilitates the development of endothelial senescence and atherosclerosis.

Differential modulation of nitric oxide synthases in aging: therapeutic opportunities

Vascular aging is the term that describes the structural and functional disturbances of the vasculature with advancing aging. The molecular mechanisms of aging-associated endothelial dysfunction are complex, but reduced nitric oxide (NO) bioavailability and altered vascular expression and activity of NO synthase (NOS) enzymes have been implicated as major players. Impaired vascular relaxation in aging has been attributed to reduced endothelial NOS (eNOS)-derived NO, while increased inducible NOS (iNOS) expression seems to account for nitrosative stress and disrupted vascular homeostasis. Although eNOS is considered the main source of NO in the vascular endothelium, neuronal NOS (nNOS) also contributes to endothelial cells-derived NO, a mechanism that is reduced in aging. Pharmacological modulation of NO generation and expression/activity of NOS isoforms may represent a therapeutic alternative to prevent the progression of cardiovascular diseases. Accordingly, this review will focus on drugs that modulate NO bioavailability, such as nitrite anions and NO-releasing non-steroidal anti-inflammatory drugs, hormones (dehydroepiandrosterone and estrogen), statins, resveratrol, and folic acid, since they may be useful to treat/to prevent aging-associated vascular dysfunction. The impact of these therapies on life quality in elderly and longevity will be discussed.

Microparticles induce cell cycle arrest through redox-sensitive processes in endothelial cells: implications in vascular senescence

BACKGROUND

Chronic disease accelerates endothelial dysfunction in aging, a process associated with cell senescence. However, the mechanisms underlying this process are unclear. We examined whether endothelial cell (EC)-derived microparticles (MPs) facilitate EC senescence and questioned the role of reactive oxygen species in this process.

METHODS AND RESULTS

Senescence was induced by sequential passaging of primary mouse ECs. Cells retained phenotypic characteristics of ECs from passage 4 through passage 21. Passage 21 ECs exhibited features of senescence, including increased staining of senescence-associated β-galactosidase (SA-βgal), a greater percentage of cells in G(1)/G(0) phase of the cell cycle, and increased phosphorylation of p66(Shc) (P<0.05). Microparticle formation from passage 21 ECs was increased versus passage 4 ECs (∼2.2-fold increase versus passage 4, P<0.05), and the Rho kinase inhibitor fasudil blocked this increase. Exposure of passage 4 ECs to MPs shifted cells from a proliferating to a nonproliferating phenotype, as indicated by cell cycle analysis and increased senescence-associated β-galactosidase staining. MPs increased EC generation of O(2) (•-) (∼2.7-fold) and H(2)O(2) (∼2.6-fold), effects blocked by apocynin (nicotinamide adenine dinucleotide phosphate oxidase inhibitor) and rotenone (mitochondrial oxidase inhibitor) but not by allopurinol (xanthine oxidase inhibitor). MPs increased expression of cell cycle proteins p 21 cip1 and p16ink4a and stimulated phosphorylation of p66(Shc) in ECs (P<0.05 versus untreated ECs). Pretreatment with the reactive oxygen species scavenger sodium 4,5-dihydroxybenzene-1,3-disulfonate (tiron) abrogated the prosenescent effects of MPs.

CONCLUSIONS

MPs promote EC senescence through nicotinamide adenine dinucleotide phosphate oxidase- and mitochondrial-derived reactive oxygen species. Such redox-sensitive processes may be important in vascular dysfunction in aging. (J Am Heart Assoc. 2012;1:e001842 doi: 10.1161/JAHA.112.001842.).

Vascular Aging in Women: is Estrogen the Fountain of Youth?

Aging is associated with structural and functional changes in the vasculature, including endothelial dysfunction, arterial stiffening and remodeling, impaired angiogenesis, and defective vascular repair, and with increased prevalence of atherosclerosis. Cardiovascular risk is similar for older men and women, but lower in women during their fertile years. This age- and sex-related difference points to estrogen as a protective factor because menopause is marked by the loss of endogenous estrogen production. Experimental and some clinical studies have attributed most of the protective effects of estrogen to its modulatory action on vascular endothelium. Estrogen promotes endothelial-derived NO production through increased expression and activity of endothelial nitric oxide synthase, and modulates prostacyclin and thromboxane A(2) release. The thromboxane A(2) pathway is key to regulating vascular tone in females. Despite all the experimental evidence, some clinical trials have reported no cardiovascular benefit from estrogen replacement therapy in older postmenopausal women. The "Timing Hypothesis," which states that estrogen-mediated vascular benefits occur only before the detrimental effects of aging are established in the vasculature, offers a possible explanation for these discrepancies. Nevertheless, a gap remains in current knowledge of cardiovascular aging mechanisms in women. This review comprises clinical and experimental data on the effects of aging, estrogens, and hormone replacement therapy on vascular function of females. We aim to clarify how menopause and aging contribute jointly to vascular aging and how estrogen modulates vascular response at different ages.

Thymoquinone improves aging-related endothelial dysfunction in the rat mesenteric artery

Aging-related endothelial dysfunction is characterized by blunted nitric oxide (NO)- and endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxations in arteries, which may be due, at least in part, to increased oxidative stress. Endothelial dysfunction will promote the initiation and development of major cardiovascular diseases such as atherosclerosis and hypertension. Thymoquinone (TQ) is the most active constituent of the volatile oil of Nigella sativa seeds with well-documented antioxidative properties and vasodilator effects. This study determined whether TQ improves the endothelial function in middle-aged rats. Control young rats (16 weeks) received solvent (ethanol, 3% v/v), and middle-aged rats (46 weeks) either solvent or TQ (10 mg/kg/day) in the drinking water. Mesenteric artery reactivity was determined in organ chambers, vascular oxidative stress by dihydroethidine and MitoSOX staining, and expression of target proteins by immunohistochemical staining. Aging-related blunted NO- and EDHF-mediated responses were associated with downregulation of endothelial NO synthase (eNOS) and calcium-activated potassium channels (SK(Ca) and IK(Ca)) expression. Endothelial dysfunction was also associated with oxidative stress and an upregulation of angiotensin II and AT1 receptor expressions. Intake of TQ for 14 days restored NO- and EDHF-mediated relaxations, normalized oxidative stress, the expression level of eNOS, SK(Ca), IK(Ca), and the components of the angiotensin system in the mesenteric artery of middle-aged rats. Thus, TQ improves endothelial function in aging, at least in part, through inhibition of oxidative stress and normalization of the angiotensin system. TQ may represent a novel therapeutic approach for aging-associated vascular diseases.

Vascular aging and hemodynamic stability in the intraoperative period

The proportion of elderly people in the population is steadily increasing, and the inevitable consequence is that this subpopulation is more frequently represented in common medical procedures and surgeries. Understanding the circulatory changes that accompany the aging process is therefore becoming increasingly timely and relevant. In this short review, we discuss aspects of vascular control in aging that are particularly relevant in the maintenance of intraoperative hemodynamic stability. We subsequently review the effects of certain notable anesthetic agents with respect to the aging vasculature.

Aging-shifted prostaglandin profile in endothelium as a factor in cardiovascular disorders

Age-associated endothelium dysfunction is a major risk factor for the development of cardiovascular diseases. Endothelium-synthesized prostaglandins and thromboxane are local hormones, which mediate vasodilation and vasoconstriction and critically maintain vascular homeostasis. Accumulating evidence indicates that the age-related changes in endothelial eicosanoids contribute to decline in endothelium function and are associated with pathological dysfunction. In this review we summarize currently available information on aging-shifted prostaglandin profiles in endothelium and how these shifts are associated with cardiovascular disorders, providing one molecular mechanism of age-associated endothelium dysfunction and cardiovascular diseases.

Perspectives of Targeting mTORC1-S6K1 in Cardiovascular Aging

The global population aging is accelerating and age-associated diseases including cardiovascular diseases become more challenging. The underlying mechanisms of aging and age-associated cardiovascular dysfunction remain elusive. There are substantial evidences demonstrating a pivotal role of the mammalian target of rapamycin complex 1 (mTORC1) and its down-stream effector S6K1 signaling in mammalian lifespan regulation and age-related diseases such as type II diabetes mellitus and cancer. The role of mTORC1–S6K1 in age-related cardiovascular diseases is, however, largely unknown and the available experimental results are controversial. This review article primarily summarizes the most recent advances toward understanding the role of mTORC1–S6K1 in cardiovascular aging and discusses the future perspectives of targeting mTORC1–S6K1 signaling as a healthy lifespan extension modality in anti-aging and anti-cardiovascular aging.

Expression of proinflammatory, proatherogenic genes is reduced by the Mediterranean diet in elderly people

Ageing is an important determinant of atherosclerosis development rate, mainly by the creation of a chronic low-grade inflammation. Diet, and particularly its fat content, modulates the inflammatory response in the fasting and postprandial states. Our aim was to study the effects of dietary fat on the expression of genes related to inflammation (NF-κB, monocyte chemoattractant protein 1 (MCP-1), TNF-α and IL-6) and plaque stability (matrix metalloproteinase 9, MMP-9) during the postprandial state of twenty healthy, elderly people who followed three diets for 3 weeks each: (1) Mediterranean diet (Med Diet) enriched in MUFA with virgin olive oil; (2) SFA-rich diet; and (3) low-fat, high-carbohydrate diet enriched in n-3 PUFA (CHO-PUFA diet) by a randomised crossover design. At the end of each period, after a 12-h fast, the subjects received a breakfast with a composition similar to the one when the dietary period ended. In the fasting state, the Med Diet consumption induced a lower gene expression of the p65 subunit of NF-κB compared with the SFA-rich diet (P = 0·019). The ingestion of the Med Diet induced a lower gene postprandial expression of p65 (P = 0·033), MCP-1 (P = 0·0229) and MMP-9 (P = 0·041) compared with the SFA-rich diet, and a lower gene postprandial expression of p65 (P = 0·027) and TNF-α (P = 0·047) compared with the CHO-PUFA diet. Direct plasma quantification mostly reproduced the findings. Our data suggest that consumption of a Med Diet reduces the postprandial inflammatory response in mononuclear cells compared with the SFA-rich and CHO-PUFA diets in elderly people. These findings may be partly responsible for the lower CVD risk found in populations with a high adherence to the Med Diet.

Endothelial cell apoptosis in brown adipose tissue of rats induced by hyperinsulinaemia: the possible role of TNF-α

The aim of the present study was to investigate whether hyperinsulinaemia, which frequently precedes insulin resistance syndrome (obesity, diabetes), induces apoptosis of endothelial cells (ECs) in brown adipose tissue (BAT) and causes BAT atrophy and also, to investigate the possible mechanisms underlying ECs death. In order to induce hyperinsuli-naemia, adult male rats of Wistar strain were treated with high dose of insulin (4 U/kg, intraperitonely) for one or three days. Examinations at ultrastructural level showed apoptotic changes of ECs, allowing us to point out that changes mainly but not exclusively, occur in nuclei. Besides different stages of condensation and alterations of the chromatin, nuclear fragmentation was also observed. Higher number of ECs apoptotic nuclei in the BAT of hyperinsulinaemic rats was also confirmed by propidium iodide staining. Immunohistochemical localization of tumor necrosis factor-alpha (TNF-α) revealed increased expression in ECs of BAT of hyperinsulinaemic animals, indicating its possible role in insulin-induced apoptotic changes. These results suggest that BAT atrophy in hyperinsulinaemia is a result of endothelial and adipocyte apoptosis combined, rather than any of functional components alone.

Biochemical and molecular aspects of vascular adrenergic regulation of blood pressure in the elderly

Hypertension, orthostatic hypotension, arterial insufficiency, and atherosclerosis are common disorders in the elderly that lead to significant morbidity and mortality. One common factor to these conditions is an age-related decline in vascular beta-adrenergic receptor-mediated function and subsequent cAMP generation. Presently, there is no single cellular factor that can explain this age-related decline, and thus, the primary cause of this homeostatic imbalance is yet to be identified. However, the etiology is clearly associated with an age-related change in the ability of beta-adrenergic receptor to respond to agonist at the cellular level in the vasculature. This paper will review what is presently understood regarding the molecular and biochemical basis of age-impaired beta-adrenergic receptor-mediated signaling. A fundamental understanding of why β-AR-mediated vasorelaxation is impaired with age will provide new insights and innovative strategies for the management of multiple clinical disorders.

Pharmacological effects and clinical applications of propionyl-L-carnitine

Propionyl-L-carnitine (PLC) is a naturally occurring derivative of carnitine that plays an important role in the metabolism of both carbohydrates and lipids, leading to an increase of ATP generation. PLC, however, is not only a metabolic drug; it is also a potent antiradical agent and thus may protect tissues from oxidative damage. PLC has been demonstrated to exert a protective effect in different models of both cardiac and endothelial dysfunction, to prevent the progression of atherosclerosis, and, more recently, to improve some of the cardiometabolic alterations that frequently accompany insulin resistance. As a result, most of the clinical trials conducted in humans highlight PLC as a potential treatment option in cardiovascular diseases such as peripheral arterial disease, chronic heart failure, or stable angina, especially when type 2 diabetes mellitus or hyperglycemia (i.e., patients on hemodialysis) are also present. The aim of this review is to summarize the pharmacological effects and possible therapeutic applications of PLC, including the most recent findings to date.

Vital signs in older patients: age-related changes

Vital signs are objective measures of physiological function that are used to monitor acute and chronic disease and thus serve as a basic communication tool about patient status. The purpose of this analysis was to review age-related changes of traditional vital signs (blood pressure, pulse, respiratory rate, and temperature) with a focus on age-related molecular changes, organ system changes, systemic changes, and altered compensation to stressors. The review found that numerous physiological and pathological changes may occur with age and alter vital signs. These changes tend to reduce the ability of organ systems to adapt to physiological stressors, particularly in frail older patients. Because of the diversity of age-related physiological changes and comorbidities in an individual, single-point measurements of vital signs have less sensitivity in detecting disease processes. However, serial vital sign assessments may have increased sensitivity, especially when viewed in the context of individualized reference ranges. Vital sign change with age may be subtle because of reduced physiological ranges. However, change from an individual reference range may indicate important warning signs and thus may require additional evaluation to understand potential underlying pathological processes. As a result, individualized reference ranges may provide improved sensitivity in frail, older patients.

Molecular inflammation as an underlying mechanism of the aging process and age-related diseases

Aging is a biological process characterized by time-dependent functional declines that are influenced by changes in redox status and by oxidative stress-induced inflammatory reactions. An organism's pro-inflammatory status may underlie the aging process and age-related diseases. In this review, we explore the molecular basis of low-grade, unresolved, subclinical inflammation as a major risk factor for exacerbating the aging process and age-related diseases. We focus on the redox-sensitive transcription factors, NF-κB and FOXO, which play essential roles in the expression of pro-inflammatory mediators and anti-oxidant enzymes, respectively. Major players in molecular inflammation are discussed with respect to the age-related up-regulation of pro-inflammatory cytokines and adhesion molecules, cyclo-oxygenase-2, lipoxygenase, and inducible nitric oxide synthase. The molecular inflammation hypothesis proposed by our laboratory is briefly described to give further molecular insights into the intricate interplay among redox balance, pro-inflammatory gene activation, and chronic age-related inflammatory diseases. The final section discusses calorie restriction as an aging-retarding intervention that also exhibits extraordinarily effective anti-inflammatory activity by modulating GSH redox, NF-κB, SIRT1, PPARs, and FOXOs.

Low-dose irradiation causes rapid alterations to the proteome of the human endothelial cell line EA.hy926

High doses of ionising radiation damage the heart by an as yet unknown mechanism. A concern for radiological protection is the recent epidemiological data indicating that doses as low as 100-500 mGy may induce cardiac damage. The aim of this study was to identify potential molecular targets and/or mechanisms involved in the pathogenesis of low-dose radiation-induced cardiovascular disease. The vascular endothelium plays a pivotal role in the regulation of cardiac function and is therefore a potential target tissue. We report here that low-dose radiation induced rapid and time-dependent changes in the cytoplasmic proteome of the human endothelial cell line EA.hy926. The proteomes were investigated at 4 and 24 h after irradiation at two different dose rates (Co-60 gamma ray total dose 200 mGy; 20 mGy/min and 190 mGy/min) using 2D-DIGE technology. Differentially expressed proteins were identified, after in-gel trypsin digestion, by MALDI-TOF/TOF tandem mass spectrometry, and peptide mass fingerprint analyses. We identified 15 significantly differentially expressed proteins, of which 10 were up-regulated and 5 down-regulated, with more than ±1.5-fold difference compared with unexposed cells. Pathways influenced by the low-dose exposures included the Ran and RhoA pathways, fatty acid metabolism and stress response.

Novel Nox homologues in the vasculature: focusing on Nox4 and Nox5

The Noxes (NADPH oxidases) are a family of ROS (reactive oxygen species)-generating enzymes. Of the seven family members, four have been identified as important sources of ROS in the vasculature: Nox1, Nox2, Nox4 and Nox5. Although Nox isoforms can be influenced by the same stimulus and co-localize in cellular compartments, their tissue distribution, subcellular regulation, requirement for cofactors and NADPH oxidase subunits and ability to generate specific ROS differ, which may help to understand the multiplicity of biological functions of these oxidases. Nox4 and Nox5 are the newest isoforms identified in the vasculature. Nox4 is the major isoform expressed in renal cells and appear to produce primarily H2O2. The Nox5 isoform produces ROS in response to increased levels of intracellular Ca2+ and does not require the other NADPH oxidase subunits for its activation. The present review focuses on these unique Noxes, Nox4 and Nox5, and provides novel concepts related to the regulation and interaction in the vasculature, and discusses new potential roles for these isoforms in vascular biology.

The aging heart, myocardial fibrosis, and its relationship to circulating C-type natriuretic Peptide

Myocardial aging is characterized by left ventricular (LV) fibrosis leading to diastolic and systolic dysfunction. Studies have established the potent antifibrotic and antiproliferative properties of C-type natriuretic peptide (CNP); however, the relationship between circulating CNP, LV fibrosis, and associated changes in LV function with natural aging are undefined. Accordingly, we characterized the relationship of plasma CNP with LV fibrosis and function in 2-, 11-, and 20-month-old male Fischer rats. Further in vitro, we established the antiproliferative actions of CNP and the participation of the clearance receptor using adult human cardiac fibroblasts. Here we establish for the first time that a progressive decline in circulating CNP characterizes natural aging and is strongly associated with a reciprocal increase in LV fibrosis that precedes impairment of diastolic and systolic function. Additionally, we demonstrate in cultured adult human cardiac fibroblasts that the direct antiproliferative actions of high-dose CNP may involve a non-cGMP pathway via the clearance receptor. Together, these studies provide new insights into myocardial aging and the relationship to the antifibrotic and antiproliferative peptide CNP.

Cyclooxygenase-2 inhibition restored endothelium-mediated relaxation in old obese zucker rat mesenteric arteries

Metabolic syndrome is associated with reduced endothelial vasodilator function. It is also associated with the induction of cyclooxygenase-2 (COX2), which produces vasoactive prostanoids. The frequency of metabolic syndrome increases with age and aging per se is a risk factor associated with reduced endothelium-mediated relaxation. Nevertheless, the combined effect of aging and metabolic syndrome on the endothelium is less known. We hypothesized that COX2 derived prostanoids may affect endothelium function in metabolic syndrome associated with aging. We used obese Zucker rats, a model of metabolic syndrome. First order mesenteric arteries were isolated from 4- and 12-month-old rats and acetylcholine (endothelium)-dependent relaxation determined using wire-myography. Endothelium-mediated relaxation, impaired in young Zucker rats (89 versus 77% maximal relaxation; lean versus Zucker), was further reduced in old Zucker rats (72 versus 51%, lean versus Zucker). The effect of the nitric oxide-synthesis inhibitor L-NAME on the relaxation was reduced in both young and old Zucker rats without change in eNOS expression level. COX inhibition (indomethacin) improved acetylcholine-mediated relaxation in old obese rats only, suggesting involvement of vasoconstrictor prostanoids. In addition, COX2 inhibition (NS398) and TxA2/PGH2 receptor blockade (SQ29548) both improved relaxation in old Zucker rat arteries. Old Zucker rats had the highest TxB2 (TxA2 metabolite) blood level associated with increased COX2 immunostaining. Chronic COX2 blockade (Celecoxib, 3 weeks) restored endothelium-dependent relaxation in old Zucker rats to the level observed in old lean rats. Thus the combination of aging and metabolic syndrome further impairs endothelium-dependent relaxation by inducing an excessive production of COX2-derived vasoconstrictor(s); possibly TxA2.

Inhibition of iNOS protects endothelial-dependent vasodilation in aged rats

AIM

To examine whether iNOS contributes to endothelial dysfunction in aged rats.

METHODS

Male Sprague Dawley rats were divided into three groups: young rats, aged rats treated with vehicle and aged rats treated with N-[3-(Aminomethyl) benzyl] acetamidine (1400W, 1 mg/kg, ip). Vasorelaxation was measured in isolated thoracic aorta. iNOS expression of thoracic aortic arteries was detected using immunohistochemistry and Western blot. Nitrotyrosine (a marker for peroxynitrite formation) content and expression in thoracic aortic tissue were determined using enzyme linked immunosorbent assay and immunohistochemistry.

RESULTS

Maximal relaxation induced by acetylcholine (10⁻⁹ to 10⁻⁵ mol/L) in the aged rats treated with vehicle was significantly decreased (70%±15%, P<0.01), as compared with the young rats (95%±8%). However, the maximal relaxation induced by acidified NaNO2 (an endothelium-independent vasodilator) had no significant difference between the two groups. Moreover, iNOS and nitrotyrosine expression increased in the vessels of the aged rats. In the aged rats treated with 1400W (a highly selective iNOS inhibitor) nitrotyrosine expression was reduced and acetylcholine-induced vasorelaxation was markedly improved (maximal relaxation was increased to 87%±8%, P<0.05), but the acidified NaNO₂-induced vasorelaxation had no significant change.

CONCLUSION

Our study demonstrated that inhibition of iNOS by 1400W increased endothelium-dependent vasodilation in aged rats. The mechanism was related with attenuation of peroxynitrite formation.

Mitochondrial dysfunction in some oxidative stress-related genetic diseases: Ataxia-Telangiectasia, Down Syndrome, Fanconi Anaemia and Werner Syndrome

Oxidative stress is a phenotypic hallmark in several genetic disorders characterized by cancer predisposition and/or propensity to premature ageing. Here we review the published evidence for the involvement of oxidative stress in the phenotypes of Ataxia-Telangiectasia (A-T), Down Syndrome (DS), Fanconi Anaemia (FA), and Werner Syndrome (WS), from the viewpoint of mitochondrial dysfunction. Mitochondria are recognized as both the cell compartment where energetic metabolism occurs and as the first and most susceptible target of reactive oxygen species (ROS) formation. Thus, a critical evaluation of the basic mechanisms leading to an in vivo pro-oxidant state relies on elucidating the features of mitochondrial impairment in each disorder. The evidence for different mitochondrial dysfunctions reported in A-T, DS, and FA is reviewed. In the case of WS, clear-cut evidence linking human WS phenotype to mitochondrial abnormalities is lacking so far in the literature. Nevertheless, evidence relating mitochondrial dysfunctions to normal ageing suggests that WS, as a progeroid syndrome, is likely to feature mitochondrial abnormalities. Hence, ad hoc research focused on elucidating the nature of mitochondrial dysfunction in WS pathogenesis is required. Based on the recognized, or reasonably suspected, role of mitochondrial abnormalities in the pathogenesis of these disorders, studies of chemoprevention with mitochondria-targeted supplements are warranted.