Reduction of amyloid beta-peptide accumulation in Tg2576 transgenic mice by oral vaccination.

Alzheimer's disease (AD) is pathologically characterized by the presence of extracellular senile plaques and intracellular neurofibrillary tangles. Amyloid beta-peptide (Abeta) is the main component of senile plaques, and the pathological load of Abeta in the brain has been shown to be a marker of the severity of AD. Abeta is produced from the amyloid precursor protein by membrane proteases and is known to aggregate. Recently, immune-mediated cerebral clearance of Abeta has been studied extensively as potential therapeutic strategy. In previous studies that used a purified Abeta challenge in a mouse model of AD, symptomatic improvement was reported. However, a clinical Alzheimer's vaccine trial in the United States was stopped because of severe side effects. Immunization with the strong adjuvant used in these trials might have activated an inflammatory Th1 response. In this study, to establish a novel, safer, lower-cost therapy for AD, we tested an oral vaccination in a wild-type and a transgenic mouse model of AD administered via green pepper leaves expressing GFP-Abeta. Anti-Abeta antibodies were effectively induced after oral immunization. We examined the immunological effects in detail and identified no inflammatory reactions. Furthermore, we demonstrated a reduction of Abeta in the immunized AD-model mice. These results suggest this edible vehicle for Abeta vaccination has a potential clinical application in the treatment of AD.

Reduced nitric oxide causes age-associated impairment of circadian rhythmicity.

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.

Cellular senescence impairs circadian expression of clock genes in vitro and in vivo.

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.

Angiotensin II induces premature senescence of vascular smooth muscle cells and accelerates the development of atherosclerosis via a p21-dependent pathway.

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 II significantly induced premature senescence of human vascular smooth muscle cells (VSMCs) via the p53/p21-dependent pathway in vitro. Inhibition of this pathway effectively suppressed induction of proinflammatory cytokines and premature senescence of VSMCs by Ang II. Ang II also significantly increased the number of senescent VSMCs and induced the expression of proinflammatory molecules and of p21 in a mouse model of atherosclerosis. Loss of p21 markedly ameliorated the induction of proinflammatory molecules by Ang II, thereby preventing the development of atherosclerosis. Replacement of p21-deficient bone marrow cells with wild-type cells had little influence on the protective effect of p21 deficiency against the progression of atherogenesis induced by Ang II. CONCLUSIONS: We demonstrated that Ang II promotes vascular inflammation by inducing premature senescence of VSMCs both in vitro and in vivo. Our results suggest a critical role of p21-dependent premature senescence of VSMCs in the pathogenesis of atherosclerosis.

Adipose tissue inflammation in diabetes and heart failure.

Adipose tissue inflammation induces systemic insulin resistance in persons with obesity and heart failure, and has a crucial role in the progression of these diseases. Chronic inflammatory processes share a common mechanism in which increased production of reactive oxygen species activates p53 and NF-κB signaling, leading to up-regulation of pro-inflammatory cytokine expression and impairment of glucose metabolism. Since inhibition of these processes could slow the progression of various diseases, targeting adipose inflammation has the potential to become a new therapeutic approach for diabetes and heart failure.

p53-induced adipose tissue inflammation is critically involved in the development of insulin resistance in heart failure.

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.