Age-related Vascular Diseases Research Articles

Signaling mechanisms of angiotensin II in regulating vascular senescence

Angiotensin (Ang) II, the major effector of the rennin–angiotensin–aldosterone system (RAAS), has multiple functions in regulating cardiovascular hemodynamics and structure. Recent evidence strongly supports that Ang II promotes the onset and progression of vascular senescence, which is associated with vascular functional and structural changes, contributing to age-related vascular diseases. The vast majority of the cardiovascular actions of Ang II, including vascular senescence, are mediated by the Ang II type-1 (AT 1) receptor. Similar to its growth-promoting process, the signaling mechanisms of AT 1 receptor-mediated vascular senescence-promoting effects involve activation of small G-protein Ras such as Ki-ras2A, mitogen-activated protein kinases (MAPK) such as extracellular signal-regulated kinase 1/2, and transcription factors including nuclear factor (NF)-κB and activator protein (AP)-1, and increased generation of reactive oxygen species. Moreover, AT 1 receptor stimulation has been suggested to inactivate cyclin-dependent kinase complexes by up-regulation of cell cycle regulators such as p53 and p21, resulting in cellular senescence. Furthermore, the interaction between Ang II and aldosterone (Aldo) in their contribution to cardiovascular pathophysiology has been highlighted. Aldo can interact with Ang II signaling via a genomic mechanism mediated by the mineralocorticoid receptor (MR). Aldo via MR couples with the AT 1 receptor to elicit the Ras/NF-κB, AP-1/p53/p21 pathway involving oxidative stress, leading to synergistic promotion of vascular senescence. Although the precise mechanisms controlling cellular senescence are currently poorly understood, this article reviews recent findings on the signaling mechanisms elicited by RAAS from the perspective of AT 1 receptor blockers and/or MR blockers in the treatment of age-related vascular diseases.

Vascular Disease and Future Risk of Depressive Symptomatology in Older Adults: Findings from the Health, Aging, and Body Composition Study

The vascular depression hypothesis suggests that age-related vascular diseases and risk factors contribute to late-life depression. Although neuroimaging studies provide evidence for an association between depression and severity of vascular lesions in the brain, studies of depression and indicators of vascular risk have been less consistent. We examined 1796 elders ages 70-79 from the Health, Aging and Body Composition study without depression at baseline and examined the association between prevalent vascular disease and related conditions at baseline and 2-year incidence of elevated depressive symptoms, defined as a score > 8 on the 10-item Center for Epidemiologic Studies Depression (CES-D) scale. After adjustment for demographic data and physical and cognitive functioning, several vascular conditions remained associated with increased risk of depressive symptomatology including metabolic syndrome and its components (low high-density lipoprotein cholesterol and high fasting glucose), coronary heart disease, a positive Rose questionnaire for angina, and high hemoglobin a1c. Cumulative vascular risk based upon a composite of 10 vascular diseases and risk factors was independently associated with incident elevated depression at 2-year follow-up after controlling for demographic data, physical and cognitive functioning, and selected comorbid medical conditions. These results provide support for the vascular depression hypothesis in demonstrating an association between vascular conditions and risk factors and subsequent risk of depressive symptomatology. Older adults with vascular conditions and risk factors require close monitoring of depressive symptoms.

Searching for aging‐related proteins in human dermal microvascular endothelial cells treated with anti‐aging agents

Endothelial cells constitute an interface between blood and tissue and act as a medium for active interaction between plasma and the intracellular environment for homeostasis. Aging of endothelial cells plays a significant role in the pathophysiology of age-related vascular diseases; however, precise mechanisms for senescence have not been elucidated. Proteomics allows identification of protein structures, functions, and characteristics, and can be applied to the study of aging processes. Using cultured human dermal microvascular endothelial cells and two-dimensional proteomic mapping, we studied the effects of kinetin, epigallocatechin-3-gallate, all-trans-retinoic acid, and selenium on their senescence and searched for the aging-related proteins. The treatments resulted in 68 qualitative changes and 172 quantitative changes, and we were able to identify 46 spots among them. All of the agents indicated above induced changes in the expression of moesin, rho guanosine-5'-diphosphate-dissociation inhibitor, and actin, confirmed by immunoblotting and confocal laser microscopy. As these proteins were associated with cell cycle and cytoskeleton, immunoblotting of the proteins related to cell cycle was performed. Although practical significance remains to be confirmed by in vivo research, this fundamental discovery may provide a basis for understanding the mechanism of aging and age-related diseases.

老化因子制御による血管治療の開発

Vascular cells have a finite lifespan when cultured in vitro and eventually enter an irreversible growth arrest state called "cellular senescence." It has been reported that many of the changes in senescent vascular cell behavior are consistent with the changes seen in age-related vascular diseases. Recently, senescent vascular cells have been demonstrated in human atherosclerotic lesions but not non-atherosclerotic lesions. Moreover, these cells express increased levels of proinflammatory molecules and decreased levels of endothelial nitric oxide synthase, suggesting that cellular senescence in vivo contributes to the pathogenesis of human atherosclerosis. One widely discussed hypothesis of senescence is the telomere hypothesis. An increasing body of evidence has established the critical role of the telomere in vascular cell senescence. More recent evidence suggests that telomere-independent mechanisms are implicated in vascular cell senescence. Activation of Ras, an important signaling molecule involved in atherogenic stimuli, induces vascular cell senescence and thereby promotes vascular inflammation in vitro and in vivo. Constitutive activation of Akt also induces vascular cell senescence. This novel role of Akt in regulating the cellular lifespan may contribute to various human diseases including atherosclerosis and diabetes mellitus. Although a causal link between vascular aging and vascular cell senescence remains elusive, a large body of data is consistent with cellular senescence contributing to age-associated vascular disorders. This review considers the clinical relevance of vascular cell senescence in vivo and discusses the potential of antisenescence therapy for human atherosclerosis.

T-kininogen induces endothelial cell proliferation

Basal proliferation of endothelial cells increases with age, and this might play a role in the etiology of age-related vascular diseases, as well as angiogenesis. Serum kininogen levels increase during aging in rats and humans, and T-kininogen (T-KG) can affect proliferative homeostasis in several cell models. Both kinins and kininogens have been shown previously to be angiogenic through activation of endothelial cell proliferation, and here we show that exposure of endothelial cells to T-KG results in vigorous cell proliferation, accompanied by ERK/AKT activation. In our experiments, the proliferative response requires B1 and B2 kinin receptors, even though kinins are not released from the precursor. We hypothesize that the age-related increase in T-KG could play a significant role in the age-related dysregulation of vascular physiology and function.

Add Alzheimer’s disease to the list of autoimmune diseases

A sole pathological event leading to Alzheimer's disease (AD) remains undiscovered in spite of decades of costly research. In fact, it is more probable that the causes of AD are the result of a myriad of intertwining pathologies. However, hope remains that a single awry event could lead to the many pathological events observed in AD brain tissues thereby creating the presentation of simultaneous pathologies. Age-related vascular diseases, which include an impaired blood-brain barrier (BBB), are a common denominator associated with various degrees of dementia, including AD. Recently, a key finding not only demonstrated the anomalous presence of immunoglobulin (Ig) detection in the brain parenchyma of AD tissues but, most importantly, specific neurons that showed degenerative, apoptotic features contained these vascular-derived antibodies. In addition, subsequent studies detected classical complement components, C1q and C5b-9, in these Ig-positive neurons, which also were spatially more associated with reactive microglia over the Ig-negative neurons. Thus, it is possible that the mere presence of anti-neuronal autoantibodies in the serum, whose importance had been previously dismissed, may be without pathological consequence until there is a BBB dysfunction to allow the deleterious effects of these autoantibodies access on their targets. Hence, these observations suggest autoimmunity-induced cell death in AD.

Vascular cell senescence in human atherosclerosis

Vascular cells have a finite lifespan when cultured in vitro and eventually enter an irreversible growth arrest called cellular senescence. Many of the changes in senescent vascular cell behavior are consistent with the changes seen in age-related vascular diseases. We have demonstrated the presence of senescent vascular cells in human atherosclerotic lesions, but not non-atherosclerotic lesions. Moreover, these cells express increased levels of proinflammatory molecules and decreased levels of endothelial nitric oxide synthase, suggesting that cellular senescence in vivo contributes to the pathogenesis of human atherosclerosis. One widely discussed hypothesis of senescence is the teleomere hypothesis. An increasing body of evidence has established the critical role of the telomere in vascular cell senescence. Another line of evidence suggests that telomere-independent mechanisms are also involved in vascular cell senescence. Activation of Ras, an important signaling molecule involved in atherogenic stimuli, induces vascular cell senescence and thereby promotes vascular inflammation in vitro and in vivo, while Akt negatively controls the lifespan of human vascular cells, both of which have been known to promote aging in organisms such as yeast and worms. These data suggest that the signaling pathways of longevity are conserved in human vascular cells. Further understanding of the mechanism underlying cellular senescence will provide insights into the potential of antisenescence therapy for vascular aging.

The role of vascular cell senescence in atherosclerosis: antisenescence as a novel therapeutic strategy for vascular aging.

Vascular cells have a finite lifespan when cultured in vitro and eventually enter an irreversible growth arrest called "cellular senescence." It has been reported that many of the changes in senescent vascular cell behavior are consistent with the changes seen in age-related vascular diseases. Recently, senescent vascular cells have been demonstrated in human atherosclerotic lesions but not in non-atherosclerotic lesions. Moreover, these cells express increased levels of proinflammatory molecules and decreased levels of endothelial nitric oxide synthase, suggesting that cellular senescence in vivo contributes to the pathogenesis of human atherosclerosis. One widely discussed hypothesis of senescence is the telomere hypothesis. An increasing body of evidence has established the critical role of the telomere in vascular cell senescence. Introduction of telomere malfunction has been shown to lead to vascular dysfunction that promotes atherogenesis, whereas telomere lengthening extends cell lifespan and protects against vascular dysfunction associated with senescence. Indeed, recent studies have demonstrated that telomere attrition occurs in the blood vessels and is associated with human atherosclerosis. More recent evidence suggests that telomere-independent mechanisms are implicated in vascular cell senescence. Activation of Ras, an important signaling molecule involved in atherogenic stimuli, induces vascular cell senescence and thereby, promotes vascular inflammation in vitro and in vivo. Although a causal link between vascular aging and vascular cell senescence remains elusive, a large body of data is consistent with cellular senescence contributing to age-associated vascular disorders. This review considers the clinical relevance of vascular cell senescence in vivo and discusses the potential of antisenescence therapy for human atherosclerosis.

Role of telomere in endothelial dysfunction in atherosclerosis.

Telomeres consist of repeats of G-rich sequence at the end of chromosomes. These DNA repeats are synthesized by enzymatic activity associated with an RNA protein complex called telomerase. In most somatic cells, telomerase activity is insufficient, and telomere length decreases with increasing cell division, resulting in an irreversible cell growth arrest, termed cellular senescence. Cellular senescence is associated with an array of phenotypic changes suggestive of aging. Until recently, cellular senescence has largely been studied as an in-vitro phenomenon; however, there is accumulating evidence that indicates a critical role of telomere function in the pathogenesis of human atherosclerosis. This review attempts to summarize recent work in vascular biology that supports the "telomere hypothesis". We discuss the possible relevance of telomere function to vascular aging and the therapeutic potential of telomere manipulation. It has been reported that many of the changes in senescent vascular cell behavior are consistent with known changes seen in age-related vascular diseases. Introduction of telomere malfunction has been shown to lead to endothelial dysfunction that promotes atherogenesis, whereas telomere lengthening extends cell lifespan and protects against endothelial dysfunction associated with senescence. Indeed, recent studies have demonstrated that telomere attrition and cellular senescence occur in the blood vessels and are associated with human atherosclerosis. Recent findings suggest that vascular cell senescence induced by telomere shortening may contribute to atherogenesis and may provide insights into a novel treatment of antisenescence to prevent atherosclerosis.

Role of homocysteine in age-related vascular and non-vascular diseases.

Homocysteine (Hcy) may represent a metabolic link in the pathogenesis of atherosclerotic vascular diseases and old-age dementias. Hyperhomocysteinemia is an independent risk factor for coronary artery disease and peripheral vascular disease, and is also associated with cerebrovascular disease; specifically, the risk of extracranial carotid atherosclerosis significantly increases in relation to Hcy levels. Hcy is a reliable marker of vitamin B12 deficiency, a common condition in the elderly which is known to induce neurological deficits including cognitive impairment; a high prevalence of folate deficiency has been reported in psychogeriatric patients suffering from depression and dementia. Both these vitamins occupy a key position in the remethylation and synthesis of S-adenosylmethionine (SAMe), a major methyl donor in CNS; therefore, deficiencies in either of these vitamins lead to a decrease in SAMe and increase in Hcy, which can be critical in the aging brain. Another pathogenetic mechanism linking high Hcy levels to reduced cognitive performances in the elderly might be represented by excitotoxicity, since hyperhomocysteinemia may lead to an excessive production of homocysteic acid and cysteine sulphinic acid, which act as endogenous agonists of NMDA receptors. Considering the reasonably high prevalence in the general population of a genetic predisposition to a thermolabile form of the enzyme 5,10-methylenetetrahydrofolate reductase (MTHFR), hyperhomocysteinemia can be seen as the result of multiple genetic and environmental factors leading to vascular and/or neurodegenerative disorders where age-related involutive phenomena represent a common pathogenetic ground. Systematic studies in different psychogeriatric conditions monitoring Hcy levels and clinical features before and after vitamin supplementation are therefore highly recommended.

Elevated promotion of prostacyclin production by synthetic lipid A analogs in aged human endothelial cells in culture

We examined the effects of E. coli lipopolysaccharide (LPS) and synthetic analogs of lipid A, a bioactive moiety of LPS, on the prostacyclin (PGI 2) production by young and old human endothelial cells in vitro. PGI 2 production by endothelial cells has been shown to decrease during in vitro cellular senescence as well as in vivo. LPS and all the analogs tested in this study did not stimulate PGI 2 production by young endothelial cells more than twofold. However, LPS and the majority of the lipid A analogs examined stimulated the PGI 2 production by old cells more than twofold (∼ two- to sixfold). These results indicate that the responses to certain stimuli sometimes differ markedly between young and old cells, and this should be carefully considered when evaluating the biological effects of various compounds. Furthermore, these results suggest that certain synthetic lipid A analogs can be used as drugs to prevent some age-related vascular diseases.

Vascular calcium overload. Physiological and pharmacological consequences.

Pronounced vascular calcium overload, especially of compliance arteries, is an important aspect of aging, and of various age-related vascular diseases such as hypertension and atherosclerosis. The development of new drugs specifically aimed at attenuating the evolution and/or pathological consequences of vascular calcium overload is hindered by the paucity of animal models available. Although several laboratory animals exhibit vascular calcium overload, this evolves slowly and is far less marked than in man. Nevertheless, Fleckenstein and associates (1989) suggested a suitable animal model involving the treatment of young rats with vitamin D3 and nicotine; such treatment produces pronounced vascular calcium overload within a few weeks. This paper describes the cardiovascular effects of such treatment, and our preliminary attempts to pharmacologically modify vascular calcium overload and its cardiovascular consequences.