Protective effect of curcumin (Curcuma longa) against d-galactose-induced senescence in mice

Brain senescence plays an important role in cognitive dysfunction and neurodegenerative disorders. Curcumin was reported to have beneficial effect against several neurodegenerative disorders including Alzheimer's disease. Therefore, the present study was conducted in order to explore the possible role of curcumin against d-galactose-induced cognitive dysfunction, oxidative damage, and mitochondrial dysfunction in mice. Chronic administration of d-galactose for 6 weeks significantly impaired cognitive function (both in Morris water maze and elevated plus maze), locomotor activity, oxidative defense (raised lipid peroxidation, nitrite concentration, depletion of reduced glutathione and catalase activity), and mitochondrial enzyme complex activities (I, II, and III) as compared to vehicle treated group. Curcumin (15 and 30 mg/kg) and galantamine (5 mg/kg) treatment for 6 weeks significantly improved cognitive tasks, locomotor activity, oxidative defense, and restored mitochondrial enzyme complex activity as compared to control (d-galactose). Chronic d-galactose treatment also significantly increased acetylcholine esterase activity that was attenuated by curcumin (15 and 30 mg/kg) and galantamine (5 mg/kg) treatment. In conclusion, the present study highlights the therapeutic potential of curcumin against d-galactose induced senescence in mice.     

CYP3A4 overexpression enhances the cytotoxicity of the antitumor triazoloacridinone derivative C-1305 in CHO cells

Aim:

To examine how the higher expression level of CYP3A4 isoenzyme influenced the cytotoxicity of the antitumor triazoloacridinone derivative C-1305 in Chinese hamster ovary (CHO) cells.

Methods:

Three CHO cell lines were examined: wild-type CHO cells; CHO-HR cells with overexpression of human cytochrome P450 reductase (CPR); and CHO-HR-3A4 cells with coexpression of human CYP3A4 and CPR. Cellular responses caused by C-1305 were monitored using DAPI staining, cell cycle analysis, phosphatydilserine externalization analysis and SA-β-galactosidase expression analysis. Cell viability was assessed with simultaneous FDA and PI staining.

Results:

Treatment with C-1305 for 72 h exhibited different levels of cytotoxicity in the 3 cell lines, and the values of IC80 in CHO, CHO-HR and CHO-HR-3A4 cells were 0.087±0.005, 0.032±0.0001, and 0.064±0.0095 μmol/L, respectively. The cell cycle analysis revealed that both CHO and CHO-HR cells underwent transient G₂/M arrest, whereas CHO-HR-3A4 cells did not accumulate in this phase. Prolonged exposure up to 120 h caused time-dependent increase in the sub-G₁ fraction in all the 3 cell lines. Treatment with C-1305 caused cell death through apoptosis and necrosis. However, these processes were more pronounced in the transfected CHO cells than in the wild-type cells. The cells surviving after C-1305 exposure underwent senescence.

Conclusion:

CYP3A4 overexpression potently enhances the cellular responses (apoptosis, necrosis and senescence) caused by C-1305 in CHO cells.     

Induction of senescence in cancer cells by the G-quadruplex stabilizer, BMVC4, is independent of its telomerase inhibitory activity

BACKGROUND AND PURPOSE Telomerase is the enzyme responsible for extending G-strand telomeric DNA and represents a promising target for treatment of neoplasia. Inhibition of telomerase can be achieved by stabilization of G-quadruplex DNA structures. Here, we characterize the cellular effects of a novel G-quadruplex stabilizing compound, 3,6-bis(4-methyl-2-vinylpyrazinium iodine) carbazole (BMVC4). EXPERIMENTAL APPROACH The cellular effects of BMVC4 were characterized in both telomerase-positive and alternative lengthening of telomeres (ALT) cancer cells. The molecular mechanism of how BMVC4 induced senescence is also addressed. KEY RESULTS BMVC4-treated cancer cells showed typical senescence phenotypes. BMVC4 induced senescence in both ALT and telomerase-overexpressing cells, suggesting that telomere shortening through telomerase inhibition might not be the cause for senescence. A large fraction of DNA damage foci was not localized to telomeres in BMVC4-treated cells and BMVC4 suppressed c-myc expression through stabilizing the G-quadruplex structure located at its promoter. These results indicated that the cellular targets of BMVC4 were not limited to telomeres. Further analyses showed that BMVC4 induced DNA breaks and activation of ataxia telangiectasia-mutated mediated DNA damage response pathway. CONCLUSIONS AND IMPLICATIONS BMVC4, a G-quadruplex stabilizer, induced senescence by activation of pathways of response to DNA damage that was independent of its telomerase inhibitory activity. Thus, BMVC4 has the potential to be developed as a chemotherapeutic agent against both telomerase positive and ALT cancer cells.     

HDAC4 stabilizes SIRT1 via sumoylation SIRT1 to delay cellular senescence

The nicotinamide adenine dinucleotide‐dependent protein deacetylase silent information regulator 2 (Sir2) regulates cellular lifespan in several organisms. Histone deacetylase 4 (HDAC4) belongs to the class IIa group of HDACs; this class of HDACs is composed of proteins that are important regulators of gene expression that control pleiotropic cellular functions. However, the role of HDAC4 in cellular senescence is still unknown. This study shows that the expression patterns of HDAC4 and Sirtuin 1 (SIRT1; the mammalian homolog of Sir2) are positively correlated during cellular senescence. Moreover, the overexpression of HDAC4 delays senescence, whereas the knockdown of HDAC4 leads to premature senescence in human fibroblasts. Furthermore, it is demonstrated that HDAC4 increases endogenous SIRT1 expression by enhancing its sumoylation modification levels, thereby stabilizing its protein levels. This study, therefore, provides a new molecular mechanism for the regulation of cellular senescence.     

快速老化小鼠SAMP8模型粪便代谢物和肠道菌群改变的研究

目的研究快速老化小鼠SAMP8模型老化过程中粪便代谢物和肠道菌群的变化。方法采用1H-NMR代谢组学和宏基因组学技术,探索衰老相关的代谢标志物和肠道菌群,并对代谢物与肠道菌群进行Pearson关联分析。结果 SAMP8小鼠粪便中指认出31种内源性代谢物,与SAMR1小鼠相比,13种代谢物发生显著改变。差异代谢物主要富集在4条代谢途径:苯丙氨酸、酪氨酸和色氨酸的生物合成,缬氨酸、亮氨酸和异亮氨酸的生物合成,苯丙氨酸代谢,组氨酸代谢。肠道菌群分析发现10月龄快速老化小鼠SAMP8肠道菌群多样性明显改变,10种菌群的相对丰度显著改变。相关性分析结果表明,Christensenellaceae菌科与苯丙氨酸、组氨酸、缬氨酸、异亮氨酸和尿苷酸均呈正相关;Dehalobacterium菌属与酪氨酸,Planococcaceae动球菌科与缬氨酸均呈负相关。结论通过研究快速老化小鼠SAMP8模型粪便代谢物和菌群的变化规律,为衰老机制及抗衰老药物研究提供实验依据。     

线粒体功能对细胞衰老的影响及中医药与艾灸延缓衰老的研究进展

自古以来,延缓衰老、健康长寿是人们的普遍愿望.如今中国将人民健康放在优先发展的战略地位.如何维持健康的生命,减缓人体的衰老是值得关注的问题.人体衰老从微观层面上可表现为细胞衰老,细胞增殖与分化能力和生理功能逐渐发生衰退的变化过程即细胞衰老,细胞衰老是一种正常的生理功能,负责清除受损细胞,是组织损伤或急性应激后的再生和恢...     

六味地黄汤对快速老化模型小鼠下丘脑-垂体-卵巢轴的调节作用及机理研究

目的 研究快速老化模型小鼠(senescence accelerated mice,SAM)增龄过程中下丘脑一垂体一卵巢(HPO)轴功能的变化及六味地黄汤(LW)的调节作用。方法采用阴道涂片法确定动物的动情周期;放射免疫分析法检测血清雌二醇(E2)水平及下丘脑β-内啡肽(β-EP)和P物质(SP)含量;蛋白免疫印迹法(westemb lotting法)检测垂体促黄体生成素(LH)、垂体及卵巢雌激素受体a(ERa)水平。结果在增龄过程中SAM快速老化亚系SAM-prone／8(SAMP8)的动情周期和动情间期均较同龄抗快速老化系SAM-resis-tance／1(SAMRl)明显延长,血清E2水平显著降低、垂体LH水平显著升高,下丘脑β-EP含量随增龄逐渐下降,SP含量一过性升高后又下降,卵巢ERa表达量明显低下。LW能显著缩短SAMP8动情间期,增加卵巢重量,升高血清E2水平,明显降低垂体LH水平;并能升高下丘脑β-EP含量,提高卵巢ERa的表达量,但却明显降低下丘脑SP含量。口服雌激素能显著提高SAMP8血清E2水平,降低垂体LH水平,升高下丘脑β-EP及SP含量,并增加垂体ERa表达量,但明显降低卵巢重量及ERa水平。结论SAMP8在衰老过程中所表现的进行性HPO轴功能紊乱与下丘脑肽类神经递质含量及卵巢ERa水平的变化具有密切关系。LW对SAMP8 HPO轴功能紊乱具有改善或调节作用。     

EWS/FLI1 suppresses retinoblastoma protein function and senescence in Ewing's sarcoma cells

Ewing's Family Tumors (EFTs) most commonly harbor a specific t(11;22) translocation that generates the EWS/FLI1 fusion protein responsible for malignant transformation. Many potential downstream targets of EWS/FLI1 have been identified but a detailed mechanism by which the fusion protein brings about transformation remains unknown. In this report, we show that depletion of EWS/FLI1 in Ewing's cell lines results in a senescence phenotype, a marked increase in expression of the G1/S regulatory proteins p27^kip1 and p57^kip2, and a significant decrease in cyclin D1 and CDK2. We also demonstrate for the first time, to our knowledge, that knockdown of EWS/FLI1 leads to hypophosphorylation and functional activation of the retinoblastoma (pRb) family of proteins. Consistent with activation of the pRb proteins, E2F‐responsive genes such as cyclin A are repressed in EWS/FLI1‐depleted cells. Together, these results support the role of EWS/LI1 as an inhibitor of cellular senescence and implicate the retinoblastoma family of proteins as key mediators of this inhibition. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:886–893, 2008     

Increased electrotonic coupling in aged rat hippocampus: a possible mechanism for cellular excitability changes

The effects of aging on the intercellular transfer of the low molecular weight fluorescent dye 5,6-carboxyfluorescein was studied in subfields fascia dentata, CA1, and CA3 of rat hippocampal slices maintained in vitro. All three areas exhibited a statistically significant increase in dye coupling with age. The increased dye coupling was accompanied by an apparent increase in postsynaptic excitability as assessed by the ratio of the population spike to EPSP components of the extracellulary recorded field potential. The possibility that artifactual dye coupling due to cell fusion contributed significantly to these results was ruled out by the demonstrations that a high molecular weight, dextran-coupled fluorescein compound did not produce multiple fills and that dye coupling with carboxyfluorescein could be prevented by prior intracellular loading with Ca++, a procedure that decouples gap junctions in other tissue. The increase in extent of electrical coupling suggested by these data may largely account for the apparent increase in cellular excitability of this tissue with age and may reflect the mechanism by which the senescent hippocampus compensates for the loss of afferent input during the course of normal aging. The additional possibility is raised that increased electrical coupling may reflect a mechanism for permanent associative storage of information in this system.