胚肾发育过程中诱骗受体2表达与细胞衰老的关系

目的通过研究诱骗受体2(DcR2)在小鼠胚肾发育过程中的定位和表达,探讨DcR2在胚肾发育中与细胞衰老的关系。 方法分别选取胚龄为12.5 d、16.5 d、20.5 d和出生后8w小鼠的肾脏组织,使用过碘酸雪夫(PAS)染色观察肾组织形态,定量RT-PCR检测肾组织DcR2 mRNA表达水平,免疫组织化学染色观察DcR2的表达分布,免疫荧光共染检测DcR2与近端肾小管标志绒毛蛋白villin、远端肾小管标志水通道蛋白2(AQP-2)、衰老标志P16、胞核形态标志物核纤层蛋白B1(LaminB1)、增殖标志Ki-67和增殖细胞核抗原(PCNA)的共表达关系。 结果随着胚肾的发育,胚肾组织中DcR2 mRNA及蛋白表达逐渐增多,且明显高于成年肾脏;DcR2特异性表达于肾小管,且与villin共表达,但不与AQP-2共表达;DcR2阳性细胞高表达P16,却低表达LaminB1、Ki-67和PCNA。 结论DcR2特异性表达于胚肾近端肾小管细胞,且表达水平随胚龄增长而增多。此外,DcR2阳性细胞具有衰老相关表型,提示DcR2可能在胚肾发育过程中通过调控细胞衰老而具有重要作用。     

Dose rectification of an imbalance between DPP4 and GLP‐1 ameliorates chronic stress‐related vascular aging and atherosclerosis?

Exposure to psychosocial stress is a risk factor for cardiovascular disease, including vascular aging and regeneration. Dipeptidyl peptidase‐4 (DPP‐4) exerts many physiological and pharmacological functions by regulating its extremely abundant substrates [eg., glucagon‐like peptide‐1 (GLP‐1), stromal cell‐derived factor‐1α/C‐X‐C chemokine receptor type‐4, etc.]. Over the past decade, emerging data has revealed unexpected roles for DPP‐4 and GLP‐1 in intracellular signaling, oxidative stress production, lipid metabolism, cell apoptosis, immune activation, insulin resistance, and inflammation. This mini review focuses on recent findings in this field, highlighting an imbalance between DPP4 and GLP‐1 as a potential therapeutic target in the management of vascular aging and atherosclerosis in animals under experimental stress conditions.     

MicroRNA-34a通过上调Cdc42和Rac1促进人晶状体上皮细胞衰老和凋亡

目的:观察MicroRNA-34a对人晶状体上皮细胞系SRA01/04衰老和凋亡的影响及作用机制。方法:qRT-PCR检测年龄相关性白内障(ARC)晶状体和透明晶状体上皮细胞中MicroRNA-34a表达水平,采用脂质体转染试剂盒将MicroRNA-34a mimics(过表达组)、MicroRNA-34a inhibitors(抑制组)和空脂质体(对照组)转染至SRA01/04细胞,qRT-PCR检测MicroRNA-34a的表达量;采用β-半乳糖苷酸(SA-β-gal)染色检测转染后细胞的衰老情况。Annexin V-FITC/PI双染色流式细胞仪检测MicroRNA-34a对人晶状体细胞系SRA01/04细胞凋亡的影响;蛋白免疫印迹检测Cdc42、Rac1蛋白的表达。结果:透明晶状体前囊膜组织中MicroRNA-34a的表达量显著低于ARC晶状体前囊膜组织(P<0.05);MicroRNA-34a过表达组、对照组、MicroRNA-34a抑制组SA-β-gal阳性率分别为(87.56±2.34)%、(12.22±2.74)%、(3.45±0.45)%。MicroRNA-34a过表达组明显高于对照组,而MicroRNA-34a抑制组SA-β-gal阳性率明显低于对照组(P<0.05);MicroRNA-34a抑制组、对照组和MicroRNA-34a过表达组的细胞凋亡率分别为(5.87±1.22)%、(12.26±2.14)%、(29.45±3.12)%,MicroRNA-34a抑制组细胞凋亡率明显低于对照组,而MicroRNA-34a过表达组细胞凋亡率明显高于对照组(P<0.05);MicroRNA-34a过表达组中Cdc42和Rac1的表达明显高于对照组(P<0.05),MicroRNA-34a抑制组中Cdc42和Rac1的表达明显低于对照组(P<0.05)。结论:MicroRNA-34a可能通过上调Cdc42和Rac1促进人晶状体上皮细胞衰老和凋亡。     

Accelerated premature stress-induced senescence of young annulus fibrosus cells of rats by high glucose-induced oxidative stress

Purposes

Diabetes mellitus (DM) is thought to be an important aetiological factor in intervertebral disc degeneration. A glucose-mediated increase of oxidative stress is a major causative factor in development of diseases associated with DM. The aim of this study was to investigate the effect of high glucose on mitochondrial damage, oxidative stress and senescence of young annulus fibrosus (AF) cells.

Methods

AF cells were isolated from four-week-old young rats, cultured, and placed in either 10 % FBS (normal control) or 10 % FBS plus two different high glucose concentrations (0.1 M and 0.2 M) (experimental conditions) for one and three days. We identified and quantified the mitochondrial damage and reactive oxygen species (ROS) (oxidative stress). We also identified and quantified the occurrence of senescence and telomerase activity. Finally, the expressions of proteins were determined related to replicative senescence (p53-p21-pRB) and stress-induced senescence (p16-pRB).

Results

Two high glucoses enhanced the mitochondrial damage in young rat AF cells, which resulted in an excessive generation of ROS in a dose- and time-dependent manner for one and three days compared to normal control. Two high glucose concentrations increased the occurrence of senescence of young AF cells in a dose- and time-dependent manner. Telomerase activity declined in a dose- and time-dependent manner. Both high glucose treatments increased the expressions of p16 and pRB proteins in young rat AF cells for one and three days. However, compared to normal control, the expressions of p53 and p21 proteins were decreased in young rat AF cells treated with both high glucoses for one and three days.

Conclusions

The present study demonstrated that high glucose-induced oxidative stress accelerates premature stress-induced senescence in young rat AF cells in a dose- and time-dependent manner rather than replicative senescence. These results suggest that prevention of excessive generation of oxidative stress by strict blood glucose control could be important to prevent or to delay premature intervertebral disc degeneration in young patients with DM.     

Aging as a consequence of selection to reduce the environmental risk of dying

Each animal in the Darwinian theater is exposed to a number of abiotic and biotic risk factors causing mortality. Several of these risk factors are intimately associated with the act of energy acquisition as such and with the amount of reserve the organism has available from this acquisition for overcoming temporary distress. Because a considerable fraction of an individual’s lifetime energy acquisition is spent on somatic maintenance, there is a close link between energy expenditure on somatic maintenance and mortality risk. Here, we show, by simple life-history theory reasoning backed up by empirical cohort survivorship data, how reduction of mortality risk might be achieved by restraining allocation to somatic maintenance, which enhances lifetime fitness but results in aging. Our results predict the ubiquitous presence of senescent individuals in a highly diverse group of natural animal populations, which may display constant, increasing, or decreasing mortality with age. This suggests that allocation to somatic maintenance is primarily tuned to expected life span by stabilizing selection and is not necessarily traded against reproductive effort or other traits. Due to this ubiquitous strategy of modulating the somatic maintenance budget so as to increase fitness under natural conditions, it follows that individuals kept in protected environments with very low environmental mortality risk will have their expected life span primarily defined by somatic damage accumulation mechanisms laid down by natural selection in the wild.

There is substantial empirical support for the notion that animals on average live far longer in a properly designed protected environment than in their natural environment (1–4). This implies that ecological risk factors are major determinants of life expectancy in the wild (5, 6), irrespective of variation in mortality risk with age (7) and of variation in the degree of senescence in wild animals (8–12). Regardless of intraspecies genetic and phenotypic variation and the huge interspecies variability in the repertoires of abiotic and biotic risk factors causing mortality in the wild, all individuals are faced with the destiny that one day, they will draw the fatal ticket in the Darwinian lottery. This raises the question of whether there exists a ubiquitous life-history strategy response to this ominous fact that is favored by natural selection.The hypothesis we will examine is that there exists such a life-history strategy, independent of temporal mortality risk profiles, which is materialized through a universal physiological principle of tuning the allocation to somatic maintenance to expected life span so that lifetime fitness is enhanced. The rationale for this is that an intimate link exists between the energy acquisition needs of an individual and mortality risk. Because somatic maintenance accounts for a substantial part of the lifetime need of acquired energy (13), restraining allocation to somatic maintenance from early on might reduce mortality risk because it allows either reduced energy acquisition activity or alternative use of the freed energy. Restraining the allocation to somatic maintenance incurs costs in terms of increasing somatic damage. However, as long as the accrued somatic damage is controlled in such a way that the costs do not materialize until rather late in life, when an individual would most probably already be dead, the penalty in terms of fitness may be more than compensated for by increased earlier survival (14). A life-history analysis assessing the evolutionary relevance of this hypothesis by elucidating the link between energy acquisition, risk reduction, and somatic maintenance, which is also firmly linked to empirical data, has apparently not yet been articulated.Our assessment of the above hypothesis is based on a simple life-history model illustrated using cohort survivorship data from the same species, obtained both in a natural ecological setting and also in a properly designed protective environment. This allows comparison of different somatic maintenance strategies with regard to female lifetime reproductive success and the intrinsic rate of natural increase, without invoking complex and specific population dynamics models that would narrow the empirical reach of predictions in terms of range of life-history regimes. The life-history model predicts that natural selection will, independent of temporal mortality risk profiles, favor restrained allocation to maintenance, despite causing accumulation of somatic damage in later life.After we present our model and results illustrating its relevance for three real-life case studies, we will examine its implications and relationships with the main current theories of evolution of aging (mutation accumulation, antagonistic pleiotropy, and disposable soma theory) (14). Our hypothesis is conceptually closest to the disposable soma theory. In essence, the disposable soma theory proposes that natural selection should favor allocation to somatic maintenance only as much as is necessary to keep the organism in good functional condition for as long as it has a reasonable chance still to be alive, subject to the prevailing level of risk. Within this viewpoint, it is commonly suggested to be optimal to allocate surplus resources in other activities that enhance fitness, thereby predicting trade-offs between, for example, longevity and reproduction. In our model, however, the emphasis is specifically on how restraining the allocation to maintenance increases fitness in early and middle life by lessening the mortality risk as such, without being traded against any other trait before late in life. If the predicted intimate link between risk reduction and somatic maintenance can be established through further theoretical and experimental work, we anticipate that it will advance our understanding of the evolutionary basis of aging and of the nature of any trade-offs that might arise. We also expect that enhanced understanding of why aging occurs may contribute fresh insights to guide research on physiological causes of and possible interventions to improve the aging process, a matter of high biomedical importance.     

Normal development is an integral part of tumorigenesis in T cell-specific PTEN-deficient mice

PTEN is a tumor suppressor gene but whether cancer can develop in all PTEN-deficient cells is not known. In T cell-specific PTEN-deficient (tPTEN^−/−) mice, which suffer from mature T cell lymphomas, we found that premalignancy, as defined by elevated AKT and senescence pathways, starts in immature T cell precursors and surprisingly not in mature T cells. Premalignancy only starts in 6-week-old mice and becomes much stronger in 9-week-old mice although PTEN is lost since birth. tPTEN^−/− immature T cells do not become tumors, and senescence has no role in this model because these cells exist in a novel cell cycle state, expressing proliferating proteins but not proliferating to any significant degree. Instead, the levels of p27^kip1, which is lower in tPTEN^−/− immature T cells and almost nonexistent in tPTEN^−/− mature T cells, correlate with the proliferation capability of these cells. Interestingly, transient reduction of these cancer precursor cells in adult tPTEN^−/− mice within a crucial time window significantly delayed lymphomas and mouse lethality. Thus, loss of PTEN alone is not sufficient for cells to become cancerous, therefore other developmental events are necessary for tumor formation.     

Social disadvantage,genetic sensitivity,and children’s telomere length

Disadvantaged social environments are associated with adverse health outcomes. This has been attributed, in part, to chronic stress. Telomere length (TL) has been used as a biomarker of chronic stress: TL is shorter in adults in a variety of contexts, including disadvantaged social standing and depression. We use data from 40, 9-y-old boys participating in the Fragile Families and Child Wellbeing Study to extend this observation to African American children. We report that exposure to disadvantaged environments is associated with reduced TL by age 9 y. We document significant associations between low income, low maternal education, unstable family structure, and harsh parenting and TL. These effects were moderated by genetic variants in serotonergic and dopaminergic pathways. Consistent with the differential susceptibility hypothesis, subjects with the highest genetic sensitivity scores had the shortest TL when exposed to disadvantaged social environments and the longest TL when exposed to advantaged environments.A large body of research has documented a positive association between exposure to disadvantaged social environments and morbidity and mortality (1, 2). A key mechanism for explaining this association is chronic stress, which is believed to degrade physiological functioning (3–6), thus “weathering” the individual and making him or her less resistant to disease (7, 8). We examined (i) whether the association between exposure to a disadvantaged environment and stress biomarkers was evident in childhood and (ii) whether the association was more pronounced for children carrying specific genetic variants. To measure the effect of stress on children’s physiological state, we used telomere length (TL) as a biomarker. A recent line of research suggests that accelerated shortening of the telomere, the (TTAGGG)_n sequence repeat at the end of each chromosome, is a good biomarker of exposure to lifetime stress (3, 6, 8–11). To measure the social environment, we used an index based on four dimensions: economic conditions, parenting quality, family structure/stability, and maternal depression.Our analysis extends the existing literature on social environments and TL in several ways. First, we focus on children, whereas prior research has focused primarily on adults, with few exceptions (12). Second, we examine a sample of African American boys whereas prior research has used mostly samples of whites. Third, we examine for the first time, to our knowledge, whether the association between the social environment and TL is moderated by variations in selected genes. Although recent research suggests that some people are genetically more sensitive than others to their social environments (13–15), research on TL has not taken account of this potential moderating factor. Finally, we use a saliva DNA source of TL, which we show to be highly correlated with blood leukocyte TL (see Figs. S2 and S3). Our study validates other work showing that multiple tissues, including saliva, can be used to measure TL (16, 17).     

作物秸秆对黄瓜衰老中根系活力和叶片氮代谢的影响

以‘津优4号’黄瓜为试验材料,研究施用不同作物秸秆对衰老过程中黄瓜根系活力和叶片氮代谢关键酶、叶片氮素含量及可溶性蛋白含量等影响。结果表明,与对照相比,作物秸秆还田不仅显著提高了黄瓜的根系活力、叶绿素含量和叶片氮代谢关键酶硝酸还原酶、谷氨酰胺合成酶、谷氨酸合成酶的活性,降低了谷氨酸脱氢酶活性,而且还降低了叶片铵态氮的含量(15.6 μg·g^-1),提高了叶片硝态氮、可溶性蛋白及游离氨基酸的含量,有效地保持较高的氮代谢水平,延缓了黄瓜的衰老。其中施用玉米秸秆效果最好,黄瓜的根系活力、硝酸还原酶活性、可溶性蛋白含量分别比对照提高了23.4%、33.3%、18.7%,其次为花生秸秆,硝酸还原酶活性比对照提高了10.8%,施用稻壳效果不明显。