Regulation of lifespan by sensory perception in Caenorhabditis elegans

Caenorhabditis elegans senses environmental signals through ciliated sensory neurons located primarily in sensory organs in the head and tail. Cilia function as sensory receptors, and mutants with defective sensory cilia have impaired sensory perception. Cilia are membrane-bound microtubule-based structures and in C. elegans are only found at the dendritic endings of sensory neurons. Here we show that mutations that cause defects in sensory cilia or their support cells, or in sensory signal transduction, extend lifespan. Our findings imply that sensory perception regulates the lifespan of this animal, and suggest that in nature, its lifespan may be regulated by environmental cues.     

Food and metabolic signalling defects in a Caenorhabditis elegans serotonin-synthesis mutant

The functions of serotonin have been assigned through serotonin-receptor-specific drugs and mutants; however, because a constellation of receptors remains when a single receptor subtype is inhibited, the coordinate responses to modulation of serotonin levels may be missed. Here we report the analysis of behavioural and neuroendocrine defects caused by a complete lack of serotonin signalling. Analysis of the C. elegans genome sequence showed that there is a single tryptophan hydroxylase gene (tph-1)-the key enzyme for serotonin biosynthesis. Animals bearing a tph-1 deletion mutation do not synthesize serotonin but are fully viable. The tph-1 mutant shows abnormalities in behaviour and metabolism that are normally coupled with the sensation and ingestion of food: rates of feeding and egg laying are decreased; large amounts of fat are stored; reproductive lifespan is increased; and some animals arrest at the metabolically inactive dauer stage. This metabolic dysregulation is, in part, due to downregulation of transforming growth factor-beta and insulin-like neuroendocrine signals. The action of the C. elegans serotonergic system in metabolic control is similar to mammalian serotonergic input to metabolism and obesity.     

A cytosolic catalase is needed to extend adult lifespan in C. elegans daf-C and clk-1 mutants.

The dauer larva is an alternative larval stage in Caenorhabditis elegans which allows animals to survive through periods of low food availability. Well-fed worms live for about three weeks, but dauer larvae can live for at least two months without affecting post-dauer lifespan. Mutations in daf-2 and age-1, which produce a dauer constitutive (Daf-C) phenotype, and in clk-1, which are believed to slow metabolism, markedly increase adult lifespan. Here we show that a ctl-1 mutation reduces adult lifespan in otherwise wild-type animals and eliminates the daf-c and clk-1-mediated extension of adult lifespan. ctl-1 encodes an unusual cytosolic catalase; a second gene, ctl-2, encodes a peroxisomal catalase. ctl-1 messenger RNA is increased in dauer larvae and adults with the daf-c mutations. We suggest that the ctl-1 catalase is needed during periods of starvation, as in the dauer larva, and that its misexpression in daf-c and clk-1 adults extends lifespan. Cytosolic catalase may have evolved to protect nematodes from oxidative damage produced during prolonged dormancy before reproductive maturity, or it may represent a general mechanism for permitting organisms to cope with the metabolic changes that accompany starvation.     

Stochastic and genetic factors influence tissue-specific decline in ageing C. elegans

The nematode Caenorhabditis elegans is an important model for studying the genetics of ageing, with over 50 life-extension mutations known so far. However, little is known about the pathobiology of ageing in this species, limiting attempts to connect genotype with senescent phenotype. Using ultrastructural analysis and visualization of specific cell types with green fluorescent protein, we examined cell integrity in different tissues as the animal ages. We report remarkable preservation of the nervous system, even in advanced old age, in contrast to a gradual, progressive deterioration of muscle, resembling human sarcopenia. The age-1(hx546) mutation, which extends lifespan by 60-100%, delayed some, but not all, cellular biomarkers of ageing. Strikingly, we found strong evidence that stochastic as well as genetic factors are significant in C. elegans ageing, with extensive variability both among same-age animals and between cells of the same type within individuals.     

Production of sperm reduces nematode lifespan.

Sex and death are two fundamental but poorly understood aspects of life. They are often thought to be linked because reproduction requires the diversion of limited resources from somatic growth and maintenance. This diversion of resources in mated animals, often called a cost of reproduction, is usually expressed as a reduction of lifespan in mated animals, although some debate exists on the best way to measure this cost. I report here that in the soil nematode, Caenorhabditis elegans, sex significantly decreases male lifespan without reducing hermaphrodite lifespan. The reduction of mated male lifespan seems to be caused by additional sperm production and not by the physical activity of mating. This conclusion is supported by observations that a mutation reducing sperm production increased mean lifespan by about 65% in both mated males and hermaphrodites. This suggests that spermatogenesis, rather than oogenesis or the physical act of mating, is a major factor reducing lifespan in C. elegans. This contradicts the traditional biological assumption that large oocytes are much costlier to produce than small sperm.     

PFOS暴露对秀丽线虫寿长的影响及其与IIS相关基因的关联

以秀丽隐杆线虫(C.elegans)为模型,本文研究了全氟辛烷磺酸(PFOS)对机体寿长的影响及初步机理.结果显示0.2~200μmol/L的PFOS暴露50 h导致野生型秀丽线虫寿长呈剂量依赖性缩短.在4类转基因线虫上,观察到Insulin/IGF-l.1信号通路(IIS)相关的daf-16、daf-2和age-1基因突变或敲除能影响线虫的寿长.进一步观察PFOS暴露导致4类转基因线虫的寿长变化率,并与野生型线虫比较.在CF1139和CF1580突变种上daf-16或daf-2的突变均未改变PFOS的缩短寿长效应.而在CF1295和TJ1052转基因型上发现daf-16b的基因敲除或age-1基因突变阻断PFOS的减寿效应.结果表明PFOS慢性暴露能加速动物衰老,缩短寿长.PFOS作用与IIS信号通路关系密切,daf-16b和age-1基因在其中起重要作用.     

DhHP-6延长秀丽线虫寿命的作用机制

考察次血红素六肽(DhHP-6)对秀丽线虫寿命的影响及其与DAF-16(abnormal dauer -formation-16)的关系. [JP2]实验结果表明: DhHP-6给药可提高野生秀丽线虫的平均寿命约20%, 未影响DAF-16表达缺失型秀丽线虫的平均寿命; DhHP-6可促进DAF-16入核, 启动下游基因表达; DhHP-6给药可增强DAF-16的转录活性, 提高sod-3表达量, 降低线虫体内的自由基含量.     

Absence of effects of Sir2 overexpression on lifespan in C. elegans and Drosophila

Overexpression of sirtuins (NAD(+)-dependent protein deacetylases) has been reported to increase lifespan in budding yeast (Saccharomyces cerevisiae), Caenorhabditis elegans and Drosophila melanogaster. Studies of the effects of genes on ageing are vulnerable to confounding effects of genetic background. Here we re-examined the reported effects of sirtuin overexpression on ageing and found that standardization of genetic background and the use of appropriate controls abolished the apparent effects in both C. elegans and Drosophila. In C. elegans, outcrossing of a line with high-level sir-2.1 overexpression abrogated the longevity increase, but did not abrogate sir-2.1 overexpression. Instead, longevity co-segregated with a second-site mutation affecting sensory neurons. Outcrossing of a line with low-copy-number sir-2.1 overexpression also abrogated longevity. A Drosophila strain with ubiquitous overexpression of dSir2 using the UAS-GAL4 system was long-lived relative to wild-type controls, as previously reported, but was not long-lived relative to the appropriate transgenic controls, and nor was a new line with stronger overexpression of dSir2. These findings underscore the importance of controlling for genetic background and for the mutagenic effects of transgene insertions in studies of genetic effects on lifespan. The life-extending effect of dietary restriction on ageing in Drosophila has also been reported to be dSir2 dependent. We found that dietary restriction increased fly lifespan independently of dSir2. Our findings do not rule out a role for sirtuins in determination of metazoan lifespan, but they do cast doubt on the robustness of the previously reported effects of sirtuins on lifespan in C. elegans and Drosophila.     

水溶性人参皂苷对秀丽隐杆线虫生物学功能的影响

 以秀丽隐杆线虫作模式生物, 研究水溶性人参皂苷成分对线虫的寿命、 产卵和运动等生命活动的影响. 结果表明: 质量浓度为200 μg/mL的人参皂苷可使线虫寿命延长, 减缓衰老; 质量浓度为500 μg/mL的人参皂苷则对线虫具有一定的毒性作用.     

Sirtuin activators mimic caloric restriction and delay ageing in metazoans

Caloric restriction extends lifespan in numerous species. In the budding yeast Saccharomyces cerevisiae this effect requires Sir2 (ref. 1), a member of the sirtuin family of NAD+-dependent deacetylases. Sirtuin activating compounds (STACs) can promote the survival of human cells and extend the replicative lifespan of yeast. Here we show that resveratrol and other STACs activate sirtuins from Caenorhabditis elegans and Drosophila melanogaster, and extend the lifespan of these animals without reducing fecundity. Lifespan extension is dependent on functional Sir2, and is not observed when nutrients are restricted. Together these data indicate that STACs slow metazoan ageing by mechanisms that may be related to caloric restriction.     

Engulfment genes cooperate with ced-3 to promote cell death in Caenorhabditis elegans.

Genetic studies have identified over a dozen genes that function in programmed cell death (apoptosis) in the nematode Caenorhabditis elegans. Although the ultimate effects on cell survival or engulfment of mutations in each cell death gene have been extensively described, much less is known about how these mutations affect the kinetics of death and engulfment, or the interactions between these two processes. We have used four-dimensional-Nomarski time-lapse video microscopy to follow in detail how cell death genes regulate the extent and kinetics of apoptotic cell death and removal in the early C. elegans embryo. Here we show that blocking engulfment enhances cell survival when cells are subjected to weak pro-apoptotic signals. Thus, genes that mediate corpse removal can also function to actively kill cells.     

松花粉的抗氧化作用

先对松花粉进行脱油、水提、冻干,获得水提物冻干品,再与缺陷型大肠杆菌菌液进行混合,稀释至终质量浓度为0.5,1.0,2.0mg/mL,喂食模式生物秀丽隐杆线虫(线虫).通过测定线虫的寿命、产卵、吞咽及运动能力,确定松花粉水提物对线虫无明显毒性作用;通过10mmol/L过氧化氢体外氧化压力诱导线虫,确定0.5,1.0,2.0mg/mL松花粉水提物对线虫体外氧化压力有显著保护作用.     

MOD-1 is a serotonin-gated chloride channel that modulates locomotory behaviour in C. elegans

The neurotransmitter and neuromodulator serotonin (5-HT) functions by binding either to metabotropic G-protein-coupled receptors (for example, 5-HT1, 5-HT2, 5-HT4 to 5-HT7), which mediate 'slow' modulatory responses through numerous second messenger pathways, or to the ionotropic 5-HT3 receptor, a non-selective cation channel that mediates 'fast' membrane depolarizations. Here we report that the gene mod-1 (for modulation of locomotion defective) from the nematode Caenorhabditis elegans encodes a new type of ionotropic 5-HT receptor, a 5-HT-gated chloride channel. The predicted MOD-1 protein is similar to members of the nicotinic acetylcholine receptor family of ligand-gated ion channels, in particular to GABA (gamma-aminobutyric acid)- and glycine-gated chloride channels. The MOD-1 channel has distinctive ion selectivity and pharmacological properties. The reversal potential of the MOD-1 channel is dependent on the concentration of chloride ions but not of cations. The MOD-1 channel is not blocked by calcium ions or 5-HT3a-specific antagonists but is inhibited by the metabotropic 5-HT receptor antagonists mianserin and methiothepin. mod-1 mutant animals are defective in a 5-HT-mediated experience-dependent behaviour and are resistant to exogenous 5-HT, confirming that MOD-1 functions as a 5-HT receptor in vivo.     

以秀丽隐杆线虫为模型的玛咖功效评价

先对玛咖进行脱油、水提、冻干,再将所得水提物冻干品与Escherichia coli OP50菌液进行混合,稀释至终质量浓度为1,2mg/mL.以秀丽隐杆线虫(简称线虫)为模型,考察玛咖水提物对线虫的抗氧化作用:经寿命、产卵、吞咽、运动能力实验表明,玛咖水提物对线虫无明显毒性作用,且1,2mg/mL玛咖水提物均能显著延长线虫寿命;由玛咖水提物对线虫热激氧化压力诱导表明,玛咖水提物对线虫体外热激氧化压力有保护作用;通过油红O对脂肪染色表明,玛咖水提物具有一定降脂功效.     

A conserved siRNA-degrading RNase negatively regulates RNA interference in C. elegans

In many organisms, introducing double-stranded RNA (dsRNA) causes the degradation of messenger RNA that is homologous to the trigger dsRNA--a process known as RNA interference. The dsRNA is cleaved into short interfering RNAs (siRNAs), which hybridize to homologous mRNAs and induce their degradation. dsRNAs vary in their ability to trigger RNA interference: many mRNA-targeting dsRNAs show weak phenotypes, and nearly all mRNAs of the Caenorhabditis elegans nervous system are refractory to RNA interference. C. elegans eri-1 was identified in a genetic screen for mutants with enhanced sensitivity to dsRNAs. Here we show that eri-1 encodes an evolutionarily conserved protein with domains homologous to nucleic-acid-binding and exonuclease proteins. After exposure to dsRNA or siRNAs, animals with eri-1 mutations accumulate more siRNAs than do wild-type animals. C. elegans ERI-1 and its human orthologue degrade siRNAs in vitro. In the nematode worm, ERI-1 is predominantly cytoplasmic and is expressed most highly in the gonad and a subset of neurons, suggesting that ERI-1 siRNase activity suppresses RNA interference more intensely in these tissues. Thus, ERI-1 is a negative regulator that may normally function to limit the duration, cell-type specificity or endogenous functions of RNA interference.     

葡萄籽粗多糖的体内外抗氧化作用

为了研究葡萄籽粗多糖(crude polysaccharides from grape seeds,GSCPs)体外抗氧化作用及对秀丽隐杆线虫的体内抗氧化作用,采用水提醇沉法提取GSCPs,检测GSCPs对1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基和羟自由基的清除作用及对DNA氧化损伤的抑制作用;建立RAW 264.7巨噬细胞氧化损伤模型,在细胞水平探讨GSCPs的抗氧化能力;同时利用秀丽隐杆线虫研究GSCPs的体内抗氧化功能。体外实验结果表明:GSCPs可有效清除自由基,抑制DNA的氧化损伤,质量浓度为0.4mg/mL的GSCPs对DPPH自由基的清除率达84%,对羟自由基清除率为89%;GSCPs可以下调H₂O₂诱导的RAW 264.7巨噬细胞活性氧(reactive oxygen species,ROS)水平,正向调节细胞内超氧化物歧化酶(superoxide dismutase,SOD)和谷胱甘肽过氧化物酶(glutathione peroxidase,GSH-Px)活性,质量浓度为0.2mg/mL的GSCPs处理组可使细胞内SOD活性从H₂O₂处理组的81.1%升至96.3%,GSH-Px活性从H₂O₂处理组的92.1%升至99.6%。此外,GSCPs可延长秀丽隐杆线虫寿命,提高其对抗急性氧化应激的能力,有效清除秀丽隐杆线虫体内的ROS。质量浓度为0.8mg/mL GSCPs处理组秀丽隐杆线虫的平均寿命较对照组延长27.67%,将急性氧化应激的秀丽隐杆线虫平均存活时间延长33.58%,秀丽隐杆线虫体内ROS生成量较对照组可降低56.33%。因此,葡萄籽粗多糖在体内外均表现出良好的抗氧化性,可用于抗氧化功能产品的开发。     

Glycogenolysis induced by serotonin in brain: identification of a new class of receptor

Serotonin-containing neurones in brain have been proposed to have a role in the control of physiological mechanisms such as sleep, thermoregulation, pain perception and endocrine secretions as well as in the physiopathology of migraine or depressive illness. One difficulty in testing these possibilities lies in the scarcity of pharmacological agents able to interact selectively with the probably multiple classes of serotonin receptors in the central nervous system. Development of such agents would be facilitated by simple in vitro models in which biological responses to serotonin in mammalian brain could be quantified. Thus a serotonin-sensitive adenylate cyclase has been characterized in rat brain, but the response to serotonin is weak in newborn and practically absent in adult animals. In addition, two pharmacologically distinct classes of serotoninergic binding site have been identified using 3H-serotonin and 3H-spiperone as ligands, but their identification as receptors remains to be established. More recently, serotonin has been shown to stimulate phosphorylation of a neuronal protein in slices from the facial motor nucleus, although the receptors mediating this action were not characterized. We now report that serotonin stimulates glycogen hydrolysis in slices of cerebral cortex, that this action is mediated by a novel class of receptors and that tricyclic antidepressants are among the best competitive antagonists of the indolamine.