Ageing induced vascular smooth muscle cell senescence in atherosclerosis

Interaction between mTOR pathway inhibition and autophagy induction attenuates adriamycin-induced vascular smooth muscle cell senescence through decreased expressions of p53/p21/p16

Cellular senescence is related to aging and extremely stable proliferative arrest with active metabolism. Senescent cells can activate mammalian target of rapamycin (mTOR) pathway, which plays a crucial role in the regulation of cell metabolism, cellular growth, and autophagy in senescence-associated cardiovascular diseases. Therefore, we examined whether mTOR pathway could induce cellular senescence by inhibition of autophagy in vascular smooth muscle cells (VSMCs). We found that adriamycin-induced VSMC senescence is accompanied by increased activity of mTOR, a major controller of cell growth and a negative regulator of autophagy. VSMC senescence induced by activation of mTOR pathway led to reduced levels of signal-associated autophagy proteins, and inhibition of mTOR pathway resulted in a drastic decrease in the number of senescence-associated β-galactosidase (SA-β-gal)-stained cells and increased levels of signal-associated autophagy proteins. Autophagic inhibition potentiated adriamycin-induced mTOR pathway activation as well as increase in the number of SA-β-gal-stained VSMCs. Results of further experiments showed that mTOR pathway inhibition regulates adriamycin-induced expression of senescence markers (p53/p21/p16), which plays an important role in different aspects of cellular aging. Taken together, these results support the idea that intervention to modulate the interaction between mTOR pathway and autophagy could be a potential strategy for longevity.

Rejuvenation of Cardiac Tissue Developed from Reprogrammed Aged Somatic Cells

Induced pluripotent stem cells (iPSCs) derived via somatic cell reprogramming have been reported to reset aged somatic cells to a more youthful state, characterized by elongated telomeres, a rearranged mitochondrial network, reduced oxidative stress, and restored pluripotency. However, it is still unclear whether the reprogrammed aged somatic cells can function normally as embryonic stem cells (ESCs) during development and be rejuvenated. In the current study, we applied the aggregation technique to investigate whether iPSCs derived from aged somatic cells could develop normally and be rejuvenated. iPSCs derived from bone marrow myeloid cells of 2-month-old (2 M) and 18-month-old (18 M) C57BL/6-Tg (CAG-EGFP)1Osb/J mice were aggregated with embryos derived from wild-type ICR mice to produce chimeras (referred to as 2 M CA and 18 M CA, respectively). Our observations focused on comparing the ability of the iPSCs derived from 18 M and 2 M bone marrow cells to develop rejuvenated cardiac tissue (the heart is the most vital organ during aging). The results showed an absence of p16 and p53 upregulation, telomere length shortening, and mitochondrial gene expression and deletion in 18 M CA, whereas slight changes in mitochondrial ultrastructure, cytochrome C oxidase activity, ATP production, and reactive oxygen species production were observed in CA cardiac tissues. The data implied that all of the aging characteristics observed in the newborn cardiac tissue of 18 M CA were comparable with those of 2 M CA newborn cardiac tissue. This study provides the first direct evidence of the aging-related characteristics of cardiac tissue developed from aged iPSCs, and our observations demonstrate that partial rejuvenation can be achieved by reprogramming aged somatic cells to a pluripotent state.

Aged garlic extract exerts endothelium-dependent vasorelaxant effect on rat aorta by increasing nitric oxide production

BACKGROUND

Clinical trials have shown that aged garlic extract (AGE) is effective in reducing blood pressure of hypertensive patients. However, the mechanisms involved remain to be elucidated.

PURPOSE

The aim of the present study was to investigate the vasorelaxant effect of AGE on the aorta and its mechanism of action in order to clarify the blood pressure-lowering action of AGE.

METHODS

The vasorelaxant effect was evaluated in isolated rat aortic rings. After aortic rings were contracted by 3 × 10^-6M norepinephrine (NE) for 30min, AGE and other test drugs were added to the aortic rings. All results were expressed as percentages of the maximal NE-induced contraction.

RESULTS

AGE induced the concentration-dependent vasorelaxation of isolated rat aortic rings that had been precontracted with norepinephrine. The effect of AGE was severely impaired in aortic rings lacking endothelium. In addition, the effect of AGE was inhibited by a nitric oxide synthase (NOS) inhibitor and a nitric oxide (NO) scavenger. Moreover, AGE treatment of aorta significantly increased the NO production. When various constituents of AGE were tested, the vasorelaxation of aorta was observed only in the presence of L-arginine, a substrate of NOS.

CONCLUSION

AGE causes endothelium-dependent vasorelaxation of aorta via stimulation of NO production and that L-arginine in AGE serves as a key agent for NOS-mediated NO production.

Aortic dissection is associated with reduced polycystin-1 expression, an abnormality that leads to increased ERK phosphorylation in vascular smooth muscle cells

The vascular smooth muscle cell (VSMC) phenotypic switch is a key pathophysiological change in various cardiovascular diseases, such as aortic dissection (AD), with a high morbidity. Polycystin-1 (PC1) is significantly downregulated in the VSMCs of AD patients. PC1 is an integral membrane glycoprotein and kinase that regulates different biological processes, including cell proliferation, apoptosis, and cell polarity. However, the role of PC1 in intracellular signaling pathways remains poorly understood. In this study, PC1 downregulation in VSMCs promoted the expression of SM22α, ACTA2 and calponin 1 (CNN1) proteins. Furthermore, PC1 downregulation in VSMCs upregulated phospho-MEK, phospho-ERK and myc, but did not change phospho-JNK and phospho-p38. These findings suggest that the MEK/ERK/myc signaling pathway is involved in PC1-mediated human VSMC phenotypic switch. Opposite results were observed when an ERK inhibitor was used in VSMCs downregulated by PC1. When the C-terminal domain of PC1 (PC1 C-tail) was overexpressed in VSMCs, the expression levels of phosphor-ERK, myc, SM22α, ACTA2 and CNN1 proteins were downregulated. The group with the overexpressed mutant protein (S4166A) in the PC1 C-tail showed similar results to the group with the downregulated PC1 in VSMCs. These results suggest that the Ser at the 4166 site in PC1 is crucial in the PC1 mediated MEK/ERK/myc signaling pathway, which might be the key pathophysiological cause of AD.

Senescent endothelial cells: Potential modulators of immunosenescence and ageing

Recent studies have demonstrated that the accumulation of senescent endothelial cells may be the primary cause of cardiovascular diseases. Because of their multifunctional properties, endothelial cells actively take part in stimulating the immune system and inflammation. In addition, ageing is characterized by the progressive deterioration of immune cells and a decline in the activation of the immune response. This results in a loss of the primary function of the immune system, which is eliminating damaged/senescent cells and neutralizing potential sources of harmful inflammatory reactions. In this review, we discuss cellular senescence and the senescence-associated secretory phenotype (SASP) of endothelial cells and summarize the link between endothelial cells and immunosenescence. We describe the possibility that age-related changes in Toll-like receptors (TLRs) and microRNAs can affect the phenotypes of senescent endothelial cells and immune cells via a negative feedback loop aimed at restraining the excessive pro-inflammatory response. This review also addresses the following questions: how do senescent endothelial cells influence ageing or age-related changes in the inflammatory burden; what is the connection between ECs and immunosenescence, and what are the crucial hypothetical pathways linking endothelial cells and the immune system during ageing.