| ObjectionIn 1999, China has entered an aged society. Epidemiological studies have showed that our population is aging, the aged population in China will increase by 3 percent per year and will reach 400 million in 2037. Structural and functional changes of blood vessel with advancing age are namely vascular aging. Clinical study indicated with advancing age, the incidence of many cardiovascular diseases such as hypertension, coronary heart disease, heart dysfunction and stroke increased rapidly. Some studies also indicated that the increased risk of cardiovascular diseases in aged population is the result of age-disease interactions. The Baltimore longitudinal aging study found the age-related structural and functional changes in blood vessel were closely correlated with age-depended cardiovascular diseases. Many biochemical processes and physiologic functions are impaired with normal aging and thereby result in a number of detrimental health consequences in the elderly population, which leads to losses of independence for tasks of daily living. Aging is the single largest risk factor for cardiovascular disease. It is thought that the impact of age on the risk of the occurrence, severity, and prognosis of cardiovascular disease is due, in part, to age-associated changes in cardiovascular structure and/or function, however, this hypothesis has not been well studied. Therefore, the researches on vascular aging have been the impelling social requirement with aged society coming rapidly. The study of vascular aging mechanism is the footstone for prevention and treatment of vascular remodeling and the related diseases. Vascular aging is the independent risk factor for cardiovascular diseases and the aging related structural and functional changes in blood vessel may be the latent target for prevention and treatment of cardiovascular diseases.Cell apoptosis theory about aging is widely accepted. Cell senescence is an aging-associated or a vascular disease-associated phenomenon. Senescent endothelial cells are more prone to proapoptotic stimuli. Passaging of endothelial cells per se renders them susceptible to apoptosis. Litter doubt that endothelial cell apoptosis can occur in vivo. Various stimuli, such as inflammatory cytokines, Ang II, oxidized lipids and turbulent blood flow seem to promote this process.Normal aging is characterized by changes in the activity or responsiveness of a number of hormonal systems. Among these is the angiotensin II (Ang II), which may be involved in the development of the aging process itself. It is assumed that Ang II promotes vascular aging, thereby contributing to the pathogenesis of human atherosclerosis. In addition, Ang II type 1 receptor blocker (ARB) whether started early or late, retard the progression of aging, which may decrease markers of senescence by reducing the expression of p21, p27, p53 and Rb expression in aging animal model.Occurrence of aging has been considered to be the outcome of gene products that promote either cell death or cell survival. It is a complex cellular process regulated through several genes; nevertheless, many of these pathways are only partly identified. Recent study showed that Bcl-2 family is the best characterized and believed to be critical in regulating apoptosis with aging. With increasing age, Bcl-2 and Bax genes have emerged as critical components for mediating numerous cellular responses including control of cell growth, differentiation, adaptation, aging and apoptosis. Bcl-2 is an anti-senescent factor. Bcl-2 has been shown to its ability to inhibit senescence as well as apoptosis. When Bcl-2 is down-regulated, the cells become more sensitive to death and display a shorter life span. Several studies demonstrated a protective, antiapoptotic, anti-senescent effect of Bcl-2 protein in various cells both in vitro and in vivo. Bcl-2 and Bax proteins form homo- and heterodimers (Bcl-2-Bcl-2, Bcl-2-Bax, Bax-Bax). Prevalence of homodimers Bcl-2 was found to determine survival while prevalence of Bax homodimers was typical for cells aimed to die.Based on above results, the following hypothesis is formed that with aging, the expression of Bcl-2 is down-regulated, while the expressions of Bax and Caspase-3 are up-regulated, so Valsartan ameliorates aging by regulating Bcl-2 and Bax gene expressions. These are the first data to demonstrate protective effects of Valsartan in vascular aging by increasing Bcl-2 level while decreasing Bax expression.Methods1. Cell experiment1.1 The cultured HUVECs in vitro were divided into 3 groups,the control group, Ang II group(stimulated with 10-6mol/l Ang II for 48h),Valsartan group(valsartan was added to cells 1h before 10-6mol/l Ang II).1.2β-gal stain, cell cycle analysis were used to identify cell aging status.1.3 Annexin V/PI staining was used to detect cell apoptosis ratio.1.4 Fluorescent microscope and transmission electric microscopy were used to evaluate the structure of HUVECs.1.5 Immunohistochemistry was used to analyze the expression of apoptosis-regulation genes Bcl-2 and Bax.1.6RT-PCR and Western-Blot were used to analyze the expression of apoptosis-regulation genes Bcl-2,Bax and Caspase-3.2. Animal experiment2.1 Wistar rats were divided into three groups, the young group (3-4 month old), the old control group (22-24 month old), Valsartan group (treated with valsartan 30mg·kg-1·d-1 for 4 months from 18-20 month of age).2.2 Aorta artery structure and function were analysed.2.3 MDA and SOD level in plasma were detected.2.4 Measurement of the flexibility of rat aorta artery segment by constant liquid injection was investigated. 2.5Immunohistochemistry was used to analyze the expression of apoptosis-regulation genes Bcl-2 and Bax.2.6RT-PCR and Western-Blot were used to analyze the expression of apoptosis-regulation genes Bcl-2,Bax and Caspase-3.Results1. Cell experiment1.1 Ang II stimulation enhanced the positive cell number ofβ-gal stained HUVEC, depressed cell proliferation.1.2 The apoptotic cells significantly increased under fluorescent microscope and transmission electric microscopy in Ang II group.1.3 Valsartan treatment alleviated aging associated changes, mRNA and protein expression of Bcl-2 increased, but the expression of Bax and Caspase-3 decreased compared to those of Ang II group.2. Animal experiment2.1 With advancing age, aorta artery structure and function changed.2.2 MDA concentration in Valsartan group evidently declined, but SOD markedly ascended.2.3 The aorta artery flexibility increased, especially flexibility areas were significantly different.2.4 In Valsartan group, mRNA and protein expression of Bcl-2 increased, but the expression of Bax and Caspase-3 decreased compared to those of the aging group.Conclusion1. Cell apoptosis is possibly an important factor for endothelial cells senescence. One of its molecular mechanisms might be associated with decreasing the expression level of Bcl-2 and increasing that of Bax and Caspase-3, which regulate the unbalance between mRNA and protein expression of Bcl-2 and Bax.2. Valsartan contributes some protective effects to the endothelial cells senescence.3. Age related vascular remodeling changes came forth in rats belonging to age group.4. In aging aortic tissues, mRNA and protein expression of Bcl-2 decreased, but the expression of Bax and Caspase-3 increased.5. Valsartan treatment upregulated mRNA and protein expression of Bcl-2 in aging aorta arteries, alleviated aorta structural and functional changes. |
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