Background-Angiotensin II (Ang II) has been reported to contribute to the pathogenesis of various human diseases including atherosclerosis, and inhibition of Ang II activity has been shown to reduce the morbidity and mortality of cardiovascular diseases. We have previously demonstrated that vascular cell senescence contributes to the pathogenesis of atherosclerosis; however, the effects of Ang II on vascular cell senescence have not been examined. Methods and Results-Ang

Several clinical studies have shown that insulin resistance is prevalent among patients with heart failure, but the underlying mechanisms have not been fully elucidated. Here, we report a mechanism of insulin resistance associated with heart failure that involves upregulation of p53 in adipose tissue. We found that pressure overload markedly upregulated p53 expression in adipose tissue along with an increase of adipose tissue inflammation. Chronic pressure overload accelerated lipolysis in adipose tissue. In the presence of pressure overload, inhibition of lipolysis by sympathetic denervation significantly downregulated adipose p53 expression and inflammation, thereby improving insulin resistance. Likewise, disruption of p53 activation in adipose tissue attenuated inflammation and improved insulin resistance but also ameliorated cardiac dysfunction induced by chronic pressure overload. These results indicate that chronic pressure overload upregulates adipose tissue p53 by promoting lipolysis via the sympathetic nervous system, leading to an inflammatory response of adipose tissue and insulin resistance.

Abstract-Circadian rhythms are regulated by a set of clock genes that form transcriptional feedback loops and generate circadian oscillation with a 24-hour cycle. Aging alters a broad spectrum of physiological, endocrine, and behavioral rhythms. Although recent evidence suggests that cellular aging contributes to various age-associated diseases, its effects on the circadian rhythms have not been examined. We report here that cellular senescence impairs circadian rhythmicity both in vitro and in vivo. Circadian expression of clock genes in serum-stimulated senescent cells was significantly weaker compared with that in young cells. Introduction of telomerase completely prevented this reduction of clock gene expression associated with senescence. Stimulation by serum activated the cAMP response element-binding protein, but the activation of this signaling pathway was significantly weaker in senescent cells. Treatment with activators of this pathway effectively restored the impaired clock gene expression of senescent cells. When young cells were implanted into young mice or old mice, the implanted cells were effectively entrained by the circadian rhythm of the recipients. In contrast, the entrainment of implanted senescent cells was markedly impaired. These results suggest that senescence decreases the ability of cells to transmit circadian signals to their clocks and that regulation of clock gene expression may be a novel strategy for the treatment of age-associated impairment of circadian rhythmicity. (Circ Res. 2006;98:532-539.)Key Words: senescence Ⅲ clock gene Ⅲ aging Ⅲ CREB Ⅲ ERK C ellular senescence is a limited ability of primary human cells to divide when cultured in vitro and is accompanied by a specific set of phenotypic changes in morphology and gene expression and function. These phenotypic changes have been suggested to play a role in human aging and age-associated diseases. 1 This hypothesis of cellular aging was established by Hayflick 2 and is supported by the evidence that the replicative potential of primary cultured human cells is dependent on donor age and that the growth potential of cultured cells is correlated well with the mean maximum lifespan of the species of origin. 2 We have previously reported that senescent vascular cells are predominately localized in the plaque of human atherosclerosis but not in normal lesions and that vascular cell senescence results in vascular dysfunction. 3 Recently, we also demonstrated that atherogenic stimulation induces vascular cell senescence and vascular inflammation, thereby contributing to the development of atheroma. 4 There is also evidence indicating that progressive telomere shortening, a biomarker of cellular aging, occurs in human blood vessels, which may be related to age-associated vascular diseases. 5-10 Thus, vascular cell senescence in vivo may contribute to the pathogenesis of vascular aging. 11Aging is associated with a variety of alterations of circadian rhythms. 12,13 These include impairment of the rhythms for blood pressure, locomoto...

Abstract-Impairment of circadian rhythmicity in the elderly has been suggested to cause age-associated diseases such as atherosclerosis and hypertension. Endothelium-derived nitric oxide (NO) is a critical regulator of cardiovascular homeostasis, but its production declines with aging, thereby inducing vascular dysfunction. We show here that impaired circadian rhythmicity is related to a decrease of NO production with aging. Treatment with an NO donor significantly upregulated the promoter activity of the clock gene Period via the cAMP response element-dependent and the E-box enhancer element-dependent pathways. Both phosphorylation and S-nitrosylation by NO are involved in this upregulation. In aged animals, endothelial NO synthase activity was markedly decreased during the daytime, along with impairment of clock gene expression and the circadian variation in blood pressure. Treatment of aged animals with an NO donor significantly improved the impairments. Inhibition of NO synthase activity also led to impairment of clock gene expression and blood pressure rhythm. These results suggest that NO is a key regulator of the circadian clock in the cardiovascular system and may be a novel target for the treatment of age-associated alteration of circadian rhythms.