Pharmacogenetic analysis of lithium-induced delayed aging in Caenorhabditis elegans

A randomized, phase 2 clinical trial of lithium carbonate in Machado-Joseph disease

BACKGROUND

Because lithium exerts neuroprotective effects in preclinical models of polyglutamine disorders, our objective was to assess the safety and efficacy of lithium carbonate (0.5-0.8 milliequivalents per liter) in patients with Machado-Joseph disease (spinocerebellar ataxia type 3 [MJD/SCA3]).

METHODS

For this phase 2, single-center, double-blind, parallel, placebo-controlled trial (ClinicalTrials.gov identifier NCT01096082), 62 patients who had MJD/SCA3 with a disease duration ≤10 years and an independent gait were randomly assigned (1:1) to receive either lithium or placebo.

RESULTS

After 24 weeks, 169 adverse events were reported, including 50.3% in the lithium group (P = 1.00; primary safety outcome). Sixty patients (31 in the placebo group and 29 in the lithium group) were analyzed for efficacy (intention-to-treat analysis). Mean progression between groups did not differ according to scores on the Neurological Examination Score for the Assessment of Spinocerebellar Ataxia (NESSCA) after 48 weeks (-0.35; 95% confidence interval, -1.7 to 1.0; primary efficacy outcome). The lithium group exhibited minor progression on the PATA speech-rate (P = 0.002), the nondominant Click Test (P = 0.023), the Spinocerebellar Ataxia Functional Index (P = 0.003), and the Composite Cerebellar Functional Score (P = 0.029).

CONCLUSIONS

Lithium was safe and well tolerated, but it had no effect on progression when measured using the NESSCA in patients with MJD/SCA3. This slowdown in secondary outcomes deserves further clarification.

Chromatin structure and transposable elements in organismal aging

Epigenetic regulatory mechanisms are increasingly appreciated as central to a diverse array of biological processes, including aging. An association between heterochromatic silencing and longevity has long been recognized in yeast, and in more recent years evidence has accumulated of age-related chromatin changes in Caenorhabditis elegans, Drosophila, and mouse model systems, as well as in the tissue culture-based replicative senescence model of cell aging. In addition, a number of studies have linked expression of transposable elements (TEs), as well as changes in the RNAi pathways that cells use to combat TEs, to the aging process. This review summarizes the recent evidence linking chromatin structure and function to aging, with a particular focus on the relationship of heterochromatin structure to organismal aging.

Small-molecule mechanism of action studies in Caenorhabditis elegans

A general protocol for exogenous small-molecule pull-down experiments with Caenorhabditis elegans is described; it provides a link between small-molecule screens in worms and existing mutant and RNAi technologies, thereby enabling organismal mechanism of action studies for the natural product clovanemagnolol. Forward chemical genetic screens followed by mechanism of action studies with C. elegans, when coupled with genetic validation of identified targets to reproduce the small molecule's phenotypic effects, provide a unique platform for discovering the biological targets of compounds that affect multicellular processes. First, the use of an immobilized FK506 derivative and soluble competition experiments with optimally prepared soluble C. elegans proteome successfully identified interactions with FK506 binding proteins 1 to 6. This approach was used to determine an unknown mechanism of action for clovanemagnolol, a small molecule that promotes axonal branching in both primary neuronal cultures and in vivo in C. elegans. Following the synthesis of an appropriately functionalized solid-phase reagent bearing a clovanemagnolol analogue pull-down experiments employing soluble competition identified kinesin light chain-1 (KLC-1), a protein involved in axonal cargo transport, as a putative target. This was corroborated through the use of mutant worms lacking klc-1 and possessing GFP neuronal labeling, reproducing the axonal branching phenotype induced by the small molecule clovanemagnolol.

Lipid-lowering fibrates extend C. elegans lifespan in a NHR-49/PPARalpha-dependent manner

Compounds that delay aging in model organisms may be of significant interest to anti-aging medicine, since these substances potentially provide pharmaceutical approaches to promote healthy lifespan in humans. We here aimed to test whether pharmaceutical concentrations of three fibrates, pharmacologically established serum lipid-lowering drugs and ligands of the nuclear receptor PPARalpha in mammals, are capable of extending lifespan in a nematodal model organism for aging processes, the roundworm Caenorhabditis elegans. Adult C. elegans (wild-type N2 as well as two nhr-49-deficient strains, RB1716 and VC870) were maintained on agar plates and were fed E. coli strain OP50 bacteria. Bezafibrate, clofibrate, and fenofibrate were applied to the agar, respectively, to test whether they may promote longevity by quantifying survival in the presence and absence of the respective compounds. All three fibrates extended C. elegans N2 lifespan when applied at a concentration of 10 micromolar. Bezafibrate additionally extended C. elegans N2 lifespan at concentrations of 1 micromolar and 0.1 micromolar. In strains deficient for nhr-49, a functional orthologue of the mammalian peroxisome proliferator-activated receptor alpha (PPARalpha), all three compounds were incapable of extending lifespan. Taken together, fibrates promote C. elegans longevity in an NHR-49-dependent manner possibly by promoting mitohormesis and suggesting that these compounds may promote lifespan also in mammals.

Knockdown of the C. elegans kinome identifies kinases required for normal protein homeostasis, mitochondrial network structure, and sarcomere structure in muscle

BACKGROUND

Kinases are important signalling molecules for modulating cellular processes and major targets of drug discovery programs. However, functional information for roughly half the human kinome is lacking. We conducted three kinome wide, >90%, RNAi screens and epistasis testing of some identified kinases against known intramuscular signalling systems to increase the functional annotation of the C. elegans kinome and expand our understanding of kinome influence upon muscle protein degradation.

RESULTS

96 kinases were identified as required for normal protein homeostasis, 74 for normal mitochondrial networks and 50 for normal sarcomere structure. Knockdown of kinases required only for normal protein homeostasis and/or mitochondrial structure was significantly less likely to produce a developmental or behavioural phenotype than knockdown of kinases required for normal sarcomere structure and/or other sub-cellular processes. Lastly, assessment of kinases for which knockdown produced muscle protein degradation against the known regulatory pathways in C. elegans muscle revealed that close to half of kinase knockdowns activated autophagy in a MAPK dependent fashion.

CONCLUSIONS

Roughly 40% of kinases studied, 159 of 397, are important in establishing or maintaining muscle cell health, with most required for both. For kinases where decreased expression triggers protein degradation, autophagy is most commonly activated. These results increase the annotation of the C. elegans kinome to roughly 75% and enable future kinome research. As 33% of kinases identified have orthologues expressed in human muscle, our results also enable testing of whether identified kinases function similarly in maintaining human muscle homeostasis.

Drug absorption efficiency in Caenorhbditis elegans delivered by different methods

BACKGROUND

Caenorhbditis elegans has being vigorously used as a model organism in many research fields and often accompanied by administrating with various drugs. The methods of delivering drugs to worms are varied from one study to another, which make difficult in comparing results between studies.

METHODOLOGY/PRINCIPAL FINDINGS

We evaluated the drug absorption efficiency in C. elegans using five frequently used methods with resveratrol with low aqueous solubility and water-soluble 5-Fluoro-2'-deoxyuridine (FUDR) as positive compounds. The drugs were either applied to the LB medium with bacteria OP50, before spreading onto Nematode Growth Medium (NGM) plates (LB medium method), or to the NGM with live (NGM live method) or dead bacteria (NGM dead method), or spotting the drug solution to the surface of plates directly (spot dead method), or growing the worms in liquid medium (liquid growing method). The concentration of resveratrol and FUDR increased gradually within C. elegans and reached the highest during 12 hours to one day and then decreased slowly. At the same time point, the higher the drug concentration, the higher the metabolism rate. The drug concentrations in worms fed with dead bacteria were higher than with live bacteria at the same time point. Consistently, the drug concentration in medium with live bacteria decreased much faster than in medium with dead bacteria, reach to about half of the original concentration within 12 hours.

CONCLUSION

Resveratrol with low aqueous solubility and water-soluble FUDR have the same absorption and metabolism pattern. The drug metabolism rate in worms was both dosage and time dependent. NGM dead method and liquid growing method achieved the best absorption efficiency in worms. The drug concentration within worms was comparable with that in mice, providing a bridge for dose translation from worms to mammals.

Curcumin and neurodegenerative diseases

Over the last 10 years curcumin has been reported to be effective against a wide variety of diseases and is characterized as having anticarcinogenic, hepatoprotective, thrombosuppressive, cardioprotective, antiarthritic, and anti-infectious properties. Recent studies performed in both vertebrate and invertebrate models have been conducted to determine whether curcumin was also neuroprotective. The efficacy of curcumin in several preclinical trials for neurodegenerative diseases has created considerable excitement mainly because of its lack of toxicity and low cost. This suggests that curcumin could be a worthy candidate for nutraceutical intervention. As aging is a common risk factor for neurodegenerative diseases, it is possible that some compounds that target aging mechanisms could also prevent these kinds of diseases. One potential mechanism to explain several of the general health benefits associated with curcumin is that it may prevent aging-associated changes in cellular proteins that lead to protein insolubility and aggregation. This loss in protein homeostasis is associated with several age-related diseases. Recently, curcumin has been found to help maintain protein homeostasis and extend lifespan in the model invertebrate Caenorhabditis elegans. Here, we review the evidence from several animal models that curcumin improves healthspan by preventing or delaying the onset of various neurodegenerative diseases.

Pharmacological lifespan extension of invertebrates

There is considerable interest in identifying small, drug-like compounds that slow aging in multiple species, particularly in mammals. Such compounds may prove to be useful in treating and retarding age-related disease in humans. Just as invertebrate models have been essential in helping us understand the genetic pathways that control aging, these model organisms are also proving valuable in discovering chemical compounds that influence longevity. The nematode Caenorhabditis elegans has numerous advantages for such studies including its short lifespan and has been exploited by a number of investigators to find compounds that impact aging. Here, we summarize the progress being made in identifying compounds that extend the lifespan of invertebrates, and introduce the challenges we face in translating this research into human therapies.

An aging program at the systems level?

Many genes and pathways are known to modulate lifespan in various organisms, but it remains unclear whether there exists a common aging program, and how individual variations of lifespan can occur in an isogenic population. Recent studies on aging regulation at the systems and epigenetic levels point to the possibility of regulating and potentially reversing the aging epigenome and transcriptome, resulting in differential aging status and aging rate in different individuals. Here, the author summarize some of these findings and discuss the possibility of integrating multiple layers of aging regulation at the systems level, to identify an aging program that can explain lifespan variations introduced by environmental and developmental history.

The great unravelling: chromatin as a modulator of the aging process

During embryogenesis, the establishment of chromatin states permits the implementation of genetic programs that allow the faithful development of the organism. However, these states are not fixed and there is much evidence that stochastic or chronic deterioration of chromatin organization, as correlated by transcriptional alterations and the accumulation of DNA damage in cells, occurs during the lifespan of the individual. Whether causal or simply a byproduct of macromolecular decay, these changes in chromatin states have emerged as potentially central conduits of mammalian aging. This review explores the current state of our understanding of the links between chromatin organization and aging.

UNC-4 antagonizes Wnt signaling to regulate synaptic choice in the C. elegans motor circuit

Coordinated movement depends on the creation of synapses between specific neurons in the motor circuit. In C. elegans, this important decision is regulated by the UNC-4 homeodomain protein. unc-4 mutants are unable to execute backward locomotion because VA motor neurons are mis-wired with inputs normally reserved for their VB sisters. We have proposed that UNC-4 functions in VAs to block expression of VB genes. This model is substantiated by the finding that ectopic expression of the VB gene ceh-12 (encoding a homolog of the homeodomain protein HB9) in unc-4 mutants results in the mis-wiring of posterior VA motor neurons with VB-like connections. Here, we show that VA expression of CEH-12 depends on a nearby source of the Wnt protein EGL-20. Our results indicate that UNC-4 prevents VAs from responding to a local EGL-20 cue by disabling a canonical Wnt signaling cascade involving the Frizzled receptors MIG-1 and MOM-5. CEH-12 expression in VA motor neurons is also opposed by a separate pathway that includes the Wnt ligand LIN-44. This work has revealed a transcriptional mechanism for modulating the sensitivity of specific neurons to diffusible Wnt ligands and thereby defines distinct patterns of synaptic connectivity. The existence of comparable Wnt gradients in the vertebrate spinal cord could reflect similar roles for Wnt signaling in vertebrate motor circuit assembly.

Aging epigenetics: causes and consequences

Growth and development of higher organisms are regulated by the orchestrated change of epigenetic marks over time. In addition, there is also an epigenetic variation without any apparent role in development that is thought to be the result of the stochastic accumulation of epigenetic errors. The process depends on genetic and environmental factors and, when it takes place in adult stem cells, it could play an important role in aging, although the underlying molecular mechanisms are still largely unknown.

A multi-tissue analysis identifies HLA complex group 9 gene methylation differences in bipolar disorder

Epigenetic studies of DNA and histone modifications represent a new and important activity in molecular investigations of human disease. Our previous epigenome-wide scan identified numerous DNA methylation differences in post-mortem brain samples from individuals affected with major psychosis. In this article, we present the results of fine mapping DNA methylation differences at the human leukocyte antigen (HLA) complex group 9 gene (HCG9) in bipolar disorder (BPD). Sodium bisulfite conversion coupled with pyrosequencing was used to interrogate 28 CpGs spanning ∼700 bp region of HCG9 in 1402 DNA samples from post-mortem brains, peripheral blood cells and germline (sperm) of bipolar disease patients and controls. The analysis of nearly 40 000 CpGs revealed complex relationships between DNA methylation and age, medication as well as DNA sequence variation (rs1128306). Two brain tissue cohorts exhibited lower DNA methylation in bipolar disease patients compared with controls at an extended HCG9 region (P=0.026). Logistic regression modeling of BPD as a function of rs1128306 genotype, age and DNA methylation uncovered an independent effect of DNA methylation in white blood cells (odds ratio (OR)=1.08, P=0.0077) and the overall sample (OR=1.24, P=0.0011). Receiver operating characteristic curve A prime statistics estimated a 69-72% probability of correct BPD prediction from a case vs control pool. Finally, sperm DNA demonstrated a significant association (P=0.018) with BPD at one of the regions demonstrating epigenetic changes in the post-mortem brain and peripheral blood samples. The consistent multi-tissue epigenetic differences at HCG9 argue for a causal association with BPD.

Aluminium exposure disrupts elemental homeostasis in Caenorhabditis elegans

Aluminium (Al) is highly abundant in the environment and can elicit a variety of toxic responses in biological systems. Here we characterize the effects of Al on Caenorhabditis elegans by identifying phenotypic abnormalities and disruption in whole-body metal homeostasis (metallostasis) following Al exposure in food. Widespread changes to the elemental content of adult nematodes were observed when chronically exposed to Al from the first larval stage (L1). Specifically, we saw increased barium, chromium, copper and iron content, and a reduction in calcium levels. Lifespan was decreased in worms exposed to low levels of Al, but unexpectedly increased when the Al concentration reached higher levels (4.8 mM). This bi-phasic phenotype was only observed when Al exposure occurred during development, as lifespan was unaffected by Al exposure during adulthood. Lower levels of Al slowed C. elegans developmental progression, and reduced hermaphrodite self-fertility and adult body size. Significant developmental delay was observed even when Al exposure was restricted to embryogenesis. Similar changes in Al have been noted in association with Al toxicity in humans and other mammals, suggesting that C. elegans may be of use as a model for understanding the mechanisms of Al toxicity in mammalian systems.

Histone methylation: a dynamic mark in health, disease and inheritance

Organisms require an appropriate balance of stability and reversibility in gene expression programmes to maintain cell identity or to enable responses to stimuli; epigenetic regulation is integral to this dynamic control. Post-translational modification of histones by methylation is an important and widespread type of chromatin modification that is known to influence biological processes in the context of development and cellular responses. To evaluate how histone methylation contributes to stable or reversible control, we provide a broad overview of how histone methylation is regulated and leads to biological outcomes. The importance of appropriately maintaining or reprogramming histone methylation is illustrated by its links to disease and ageing and possibly to transmission of traits across generations.

Pharmacological maintenance of protein homeostasis could postpone age-related disease

Over the last 10 years, various screens of small molecules have been conducted to find long sought interventions in aging. Most of these studies were performed in invertebrates but the demonstration of pharmacological lifespan extension in the mouse has created considerable excitement. Since aging is a common risk factor for several chronic diseases, there is a reasonable expectation that some compounds capable of extending lifespan will be useful for preventing a range of age-related diseases. One of the potential targets is protein aggregation which is associated with several age-related diseases. Genetic studies have long indicated that protein homeostasis is a critical component of longevity but recently a series of chemicals have been identified in the nematode Caenorhabditis elegans that lead to the maintenance of the homeostatic network and extend lifespan. Herein we review these interventions in C. elegans and consider the potential of improving health by enhancing protein homeostasis.

A predictable worm: application of Caenorhabditis elegans for mechanistic investigation of movement disorders

Ongoing investigations into causes and cures for human movement disorders are important toward the elucidation of diseases such as Parkinson's disease (PD) and dystonia. The use of animal model systems can provide links to susceptibility factors, as well as therapeutic interventions. In this regard, the nematode roundworm, Caenorhabditis elegans, is ideal for examining age-dependent neurodegenerative disease studies. It is genetically tractable, has a short lifespan, and a well-defined nervous system. Green fluorescent protein is readily visualized in C. elegans because it is a transparent organism, thus the nervous system and factors that alter the viability of neurons can be directly examined in vivo. Through expression of the human PD-associated protein (α-synuclein in the worm dopamine neurons), neurodegeneration is observed in an age-dependent manner. Furthermore, expression of the early-onset dystonia-related protein torsinA increases vulnerability to endoplasmic reticulum (ER) stress in C. elegans, because torsinA is located in the ER. Here we provide an overview of collaborative studies we have conducted that collectively demonstrate the usefulness of the nematode model to discern functional effectors of dopaminergic neurodegeneration and ER stress that translate to mammalian data in the fields of PD and dystonia. Taken together, the application of C. elegans toward the evaluation of genetic modifiers for movement disorders research has predictive value and serves to accelerate the path forward for therapeutic interventions.

Histone methylation makes its mark on longevity

How long organisms live is not entirely written in their genes. Recent findings reveal that epigenetic factors that regulate histone methylation, a type of chromatin modification, can affect lifespan. The reversible nature of chromatin modifications suggests that therapeutic targeting of chromatin regulators could be used to extend lifespan and healthspan. This review describes the epigenetic regulation of lifespan in diverse model organisms, focusing on the role and mode of action of chromatin regulators that affect two epigenetic marks, trimethylated lysine 4 of histone H3 (H3K4me3) and trimethylated lysine 27 of histone H3 (H3K27me3), in longevity.

The H3K27 demethylase UTX-1 regulates C. elegans lifespan in a germline-independent, insulin-dependent manner

Aging is accompanied by alterations in epigenetic marks that control chromatin states, including histone acetylation and methylation. Enzymes that reversibly affect histone marks associated with active chromatin have recently been found to regulate aging in Caenorhabditis elegans. However, relatively little is known about the importance for aging of histone marks associated with repressed chromatin. Here, we use a targeted RNAi screen in C. elegans to identify four histone demethylases that significantly regulate worm lifespan, UTX-1, RBR-2, LSD-1, and T26A5.5. Interestingly, UTX-1 belongs to a conserved family of histone demethylases specific for lysine 27 of histone H3 (H3K27me3), a mark associated with repressed chromatin. Both utx-1 knockdown and heterozygous mutation of utx-1 extend lifespan and increase the global levels of the H3K27me3 mark in worms. The H3K27me3 mark significantly drops in somatic cells during the normal aging process. UTX-1 regulates lifespan independently of the presence of the germline, but in a manner that depends on the insulin-FoxO signaling pathway. These findings identify the H3K27me3 histone demethylase UTX-1 as a novel regulator of worm lifespan in somatic cells.

Transgenerational epigenetic inheritance of longevity in Caenorhabditis elegans

Chromatin modifiers regulate lifespan in several organisms, raising the question of whether changes in chromatin states in the parental generation could be incompletely reprogrammed in the next generation and thereby affect the lifespan of descendents. The histone H3 lysine 4 trimethylation (H3K4me3) complex composed of ASH-2, WDR-5, and the histone methyltransferase SET-2 regulates C. elegans lifespan. Here we show that deficiencies in the H3K4me3 chromatin modifiers ASH-2, WDR-5, or SET-2 in the parental generation extend the lifespan of descendents up until the third generation. The transgenerational inheritance of lifespan extension by members of the ASH-2 complex is dependent on the H3K4me3 demethylase RBR-2, and requires the presence of a functioning germline in the descendents. Transgenerational inheritance of lifespan is specific for the H3K4me3 methylation complex and is associated with epigenetic changes in gene expression. Thus, manipulation of specific chromatin modifiers only in parents can induce an epigenetic memory of longevity in descendents.

Metformin as a geroprotector

Abstract Geroprotectors are drugs that decrease the rate of aging and therefore extend life span. Metformin has been described as a geroprotector, and several studies have shown that metformin can slow down the rate of aging. The mechanisms behind the geroprotective effect of metformin are less established. The goal of this review is to investigate the evidence for the geroprotective effect of metformin and to describe the possible mechanisms behind it.

Epigenetics in C. elegans: facts and challenges

Epigenetics is defined as the study of heritable changes in gene expression that are not accompanied by changes in the DNA sequence. Epigenetic mechanisms include histone post-translational modifications, histone variant incorporation, non-coding RNAs, and nucleosome remodeling and exchange. In addition, the functional compartmentalization of the nucleus also contributes to epigenetic regulation of gene expression. Studies on the molecular mechanisms underlying epigenetic phenomena and their biological function have relied on various model systems, including yeast, plants, flies, and cultured mammalian cells. Here we will expose the reader to the current understanding of epigenetic regulation in the roundworm C. elegans. We will review recent models of nuclear organization and its impact on gene expression, the biological role of enzymes modifying core histones, and the function of chromatin-associated factors, with special emphasis on Polycomb (PcG) and Trithorax (Trx-G) group proteins. We will discuss how the C. elegans model has provided novel insight into mechanisms of epigenetic regulation as well as suggest directions for future research.

Clozapine and lithium require Caenorhabditis elegans β-arrestin and serum- and glucocorticoid-inducible kinase to affect Daf-16 (FOXO) localization

Numerous studies have implicated low levels of signaling in the Akt network with psychotic illnesses, and a growing body of literature has shown that all classes of antipsychotic drugs increase Akt signaling. The most clinically effective antipsychotic drug is clozapine. With Caenorhabditis elegans as a model system, this study demonstrates that clozapine is unique among antipsychotic drugs because it requires β-arrestin and serum and glucocorticoid-inducible kinase (SGK) in addition to Akt to suppress the nuclear localization of DAF-16 (Forkhead box O [FOXO]). Lithium, a mood stabilizer often used to treat psychosis, also requires β-arrestin and SGK to suppress the nuclear localization of DAF-16.

Lithium, an anti-psychotic drug, greatly enhances the generation of induced pluripotent stem cells

Somatic cells can be reprogrammed into induced pluripotent stem cells (iPSCs) by defined factors. The low efficiency of reprogramming and genomic integration of oncogenes and viral vectors limited the potential application of iPSCs. Here we report that Lithium (Li), a drug used to treat mood disorders, greatly enhances iPSC generation from both mouse embryonic fibroblast and human umbilical vein endothelial cells. Li facilitates iPSC generation with one (Oct4) or two factors (OS or OK). The effect of Li on promoting reprogramming only partially depends on its major target GSK3β. Unlike other GSK3β inhibitors, Li not only increases the expression of Nanog, but also enhances the transcriptional activity of Nanog. We also found that Li exerts its effect by promoting epigenetic modifications via downregulation of LSD1, a H3K4-specific histone demethylase. Knocking down LSD1 partially mimics Li's effect in enhancing reprogramming. Our results not only provide a straightforward method to improve the iPSC generation efficiency, but also identified a histone demethylase as a critical modulator for somatic cell reprogramming.

Lithium protects against oxidative stress-mediated cell death in α-synuclein-overexpressing in vitro and in vivo models of Parkinson's disease

Lithium has recently been suggested to have neuroprotective properties in relation to several neurodegenerative diseases. In this study, we examined the potential cytoprotective effect of lithium in preventing oxidative stress-induced protein accumulation and neuronal cell death in the presence of increased α-synuclein levels in vitro and in vivo. Specifically, lithium administration was found to protect against cell death in a hydrogen peroxide-treated, stable α-synuclein-enhanced green fluorescent protein (EGFP)-overexpressing dopaminergic N27 cell line. Lithium feeding (0.255% lithium chloride) of 9-month-old pan-neuronal α-synuclein transgenic mice over a 3-month period was also sufficient to prevent accumulation of oxidized/nitrated α-synuclein as a consequence of chronic paraquat/maneb administration in multiple brain regions, including the glomerular layer, mitral cells, and the granule cell layer of the olfactory bulb (OB), striatum, substantia nigra pars compacta (SNpc) and Purkinje cells of the cerebellum. Lithium not only prevented α-synuclein-mediated protein accumulation/aggregation in these brain regions but also protected neuronal cells including mitral cells and dopaminergic SNpc neurons against oxidative stress-induced neurodegeneration. These results suggest that lithium can prevent both α-synuclein accumulation and neurodegeneration in an animal model of PD, suggesting that this drug, already FDA-approved for use in bipolar disorder, may constitute a novel therapy for another human disease.

Amyloid-binding compounds maintain protein homeostasis during ageing and extend lifespan

Genetic studies indicate that protein homeostasis is a major contributor to metazoan longevity. Collapse of protein homeostasis results in protein misfolding cascades and the accumulation of insoluble protein fibrils and aggregates, such as amyloids. A group of small molecules, traditionally used in histopathology to stain amyloid in tissues, bind protein fibrils and slow aggregation in vitro and in cell culture. We proposed that treating animals with such compounds would promote protein homeostasis in vivo and increase longevity. Here we show that exposure of adult Caenorhabditis elegans to the amyloid-binding dye Thioflavin T (ThT) resulted in a profoundly extended lifespan and slowed ageing. ThT also suppressed pathological features of mutant metastable proteins and human β-amyloid-associated toxicity. These beneficial effects of ThT depend on the protein homeostasis network regulator heat shock factor 1 (HSF-1), the stress resistance and longevity transcription factor SKN-1, molecular chaperones, autophagy and proteosomal functions. Our results demonstrate that pharmacological maintenance of the protein homeostatic network has a profound impact on ageing rates, prompting the development of novel therapeutic interventions against ageing and age-related diseases.

Measuring Caenorhabditis elegans life span in 96 well microtiter plates

Lifespan is a biological process regulated by several genetic pathways. One strategy to investigate the biology of aging is to study animals that harbor mutations in components of age-regulatory pathways. If these mutations perturb the function of the age-regulatory pathway and therefore alter the lifespan of the entire organism, they provide important mechanistic insights^1-3.

Another strategy to investigate the regulation of lifespan is to use small molecules to perturb age-regulatory pathways. To date, a number of molecules are known to extend lifespan in various model organisms and are used as tools to study the biology of aging^4-16. The number of molecules identified thus far is small compared to the genetic "toolset" that is available to study the biology of aging.

Caenorhabditis elegans is one of the principle models used to study aging because of its excellent genetics and short lifespan of three weeks. More recently, C.elegans has emerged as a model organism for phenotype based drug screens^5,7,16-20 because of its small size and its ability to grow in microtiter plates.

Here we present an assay to measure C.elegans lifespan in 96 well microtiter plates. The assay was developed and successfully used to screen large libraries for molecules that extend C.elegans lifespan⁷. The reliability of the assay was evaluated in multiple tests: first, by measuring the lifespan of wild type animals grown at different temperatures; second, by measuring the lifespan of mutants with altered lifespans; third, by measuring changes in lifespan in response to different concentrations of the antidepressant Mirtazepine. Mirtazepine has previously been shown to extend lifespan in C.elegans⁷. The results of these tests show that the assay is able to replicate previous findings from other assays and is quantitative. The microtiter format also makes this lifespan assay compatible with automated liquid handling systems and allows integration into automated platforms.

Interaction networks of lithium and valproate molecular targets reveal a striking enrichment of apoptosis functional clusters and neurotrophin signaling

The overall neurobiological mechanisms by which lithium and valproate stabilize mood in bipolar disorder patients have yet to be fully defined. The therapeutic efficacy and dissimilar chemical structures of these medications suggest that they perturb both shared and disparate cellular processes. To investigate key pathways and functional clusters involved in the global action of lithium and valproate, we generated interaction networks formed by well-supported drug targets. Striking functional similarities emerged. Intersecting nodes in lithium and valproate networks highlighted a strong enrichment of apoptosis clusters and neurotrophin signaling. Other enriched pathways included MAPK, ErbB, insulin, VEGF, Wnt and long-term potentiation indicating a widespread effect of both drugs on diverse signaling systems. MAPK1/3 and AKT1/2 were the most preponderant nodes across pathways suggesting a central role in mediating pathway interactions. The convergence of biological responses unveils a functional signature for lithium and valproate that could be key modulators of their therapeutic efficacy.

Biology of the Mi-2/NuRD Complex in SLAC (Stemness, Longevity/Ageing, and Cancer)

The dynamic chromatin activities of Mi-2/Nucleosome Remodeling and Histone deacetylation (Mi-2/NuRD) complexes in mammals are at the basis of current research on stemness, longevity/ageing, and cancer (4-2-1/SLAC), and have been widely studied over the past decade in mammals and the elegant model organism, Caenorhabditis elegans. Interestingly, a common emergent theme from these studies is that of distinct coregulator-recruited Mi-2/NuRD complexes largely orchestrating the 4-2-1/SLAC within a unique paradigm by maintaining genome stability via DNA repair and controlling three types of transcriptional programs in concert in a number of cellular, tissue, and organism contexts. Thus, the core Mi-2/NuRD complex plays a central role in 4-2-1/SLAC. The plasticity and robustness of 4-2-1/SLAC can be interpreted as modulation of specific coregulator(s) within cell-specific, tissue-specific, stage-specific, or organism-specific niches during stress induction, ie, a functional module and its networking, thereby conferring differential responses to different environmental cues. According to “Occam’s razor”, a simple theory is preferable to a complex one, so this simplified notion might be useful for exploring 4-2-1/SLAC with a holistic view. This thought could also be valuable in forming strategies for future research, and could open up avenues for cancer prevention and antiageing strategies.

Low-dose lithium uptake promotes longevity in humans and metazoans

Purpose

Lithium is a nutritionally essential trace element predominantly contained in vegetables, plant-derived foods, and drinking water. Environmental lithium exposure and concurrent nutritional intake vary considerably in different regions. We here have analyzed the possibility that low-dose lithium exposure may affect mortality in both metazoans and mammals.

Methods

Based on a large Japanese observational cohort, we have used weighted regression analysis to identify putative effects of tap water-derived lithium uptake on overall mortality. Independently, we have exposed Caenorhabditis elegans, a small roundworm commonly used for anti-aging studies, to comparable concentrations of lithium, and have quantified mortality during this intervention.

Results

In humans, we find here an inverse correlation between drinking water lithium concentrations and all-cause mortality in 18 neighboring Japanese municipalities with a total of 1,206,174 individuals (β = −0.661, p = 0.003). Consistently, we find that exposure to a comparably low concentration of lithium chloride extends life span of C. elegans (p = 0.047).

Conclusions

Taken together, these findings indicate that long-term low-dose exposure to lithium may exert anti-aging capabilities and unambiguously decreases mortality in evolutionary distinct species.

The garlic constituent diallyl trisulfide increases the lifespan of C. elegans via skn-1 activation

Medicinal benefits of Allium vegetables, such as garlic, have been noted throughout recorded history, including protection against cancer and cardiovascular disease. We now demonstrate that garlic constituent diallyl trisulfide (DATS) increases longevity of Caenorhabditis elegans by affecting the skn-1 pathway. Treatment of worms with 5-10 μM DATS increased worm mean lifespan even when treatment is started during young adulthood. To explore the mechanisms involved in the DATS-mediated increase in longevity, we treated daf-2, daf-16, and eat-2 mutants and found that DATS increased the lifespan of daf-2 and daf-16 mutants, but not the eat-2 mutants. Microarray experiments demonstrated that a number of genes regulated by oxidative stress and the skn-1 transcription factor were also changed by DATS treatment. Consistently, DATS treatment leads to the induction of the skn-1 target gene gst-4, and this induction was dependent on skn-1. We also found that the effects of DATS on worm lifespan depend on skn-1 activity in both in the intestine and ASI neurons. Together our data suggest that DATS is able to increase worm lifespan by enhancing the function of the pro-longevity transcription factor skn-1.

Understanding bipolar disorder: the epigenetic perspective

Bipolar disease (BPD) is a complex major psychiatric disorder that affects between 1% and 2% of the population and exhibits ?85% heritability. This has made BPD an appealing target for genetic studies yet, despite numerous attempts, the genetic basis of this disease remains elusive. Recently, it has come to light that epigenetic factors may also influence the development of BPD. These factors act via stable but reversible modifications of DNA and chromatin structure. In this chapter, we revisit the epidemiological, clinical, and molecular findings in BPD and reanalyze them from the perspective of inherited and acquired epigenetic misregulation. Epigenetic research has great potential to enhance our understanding of the molecular basis of BPD.

Chemical genetic screen identifies lithocholic acid as an anti-aging compound that extends yeast chronological life span in a TOR-independent manner, by modulating housekeeping longevity assurance processes

In chronologically aging yeast, longevity can be extended by administering a caloric restriction (CR) diet or some small molecules. These life-extending interventions target the adaptable target of rapamycin (TOR) and cAMP/protein kinase A (cAMP/PKA) signaling pathways that are under the stringent control of calorie availability. We designed a chemical genetic screen for small molecules that increase the chronological life span of yeast under CR by targeting lipid metabolism and modulating housekeeping longevity pathways that regulate longevity irrespective of the number of available calories. Our screen identifies lithocholic acid (LCA) as one of such molecules. We reveal two mechanisms underlying the life-extending effect of LCA in chronologically aging yeast. One mechanism operates in a calorie availability-independent fashion and involves the LCA-governed modulation of housekeeping longevity assurance pathways that do not overlap with the adaptable TOR and cAMP/PKA pathways. The other mechanism extends yeast longevity under non-CR conditions and consists in LCA-driven unmasking of the previously unknown anti-aging potential of PKA. We provide evidence that LCA modulates housekeeping longevity assurance pathways by suppressing lipid-induced necrosis, attenuating mitochondrial fragmentation, altering oxidation-reduction processes in mitochondria, enhancing resistance to oxidative and thermal stresses, suppressing mitochondria-controlled apoptosis, and enhancing stability of nuclear and mitochondrial DNA.

A deuterohemin peptide extends lifespan and increases stress resistance in Caenorhabditis elegans

This group has invented a novel deuterohemin containing peptide deuterohemin-AlaHisThrValGluLys (DhHP-6), which has various biological activities including protection of murine ischemia reperfusion injury, improving cell survival and preventing apoptosis. It was hypothesized that DhHP-6 is beneficial on the lifespan of Caenorhabditis elegans (C. elegans) and increases their resistance to heat and oxidative stress. C. elegans were treated with different concentrations of DhHP-6. Survival time and sensitivity to heat and paraquat were investigated. The data demonstrated that the mean survival time of C. elegans was significantly increased (p < 0.05) in the DhHP-6 treated group compared with the control group. The maximum lifespan was not affected by DhHP-6 treatment. DhHP-6 improved the survival rate of C. elegans in the acute heat stress (35 degrees C) and rescued the C. elegans' sensitivity to paraquat in acute oxidative stress. Superoxide dismutase 3 (SOD-3) protein was up-regulated by DhHP-6 treatment. It was further demonstrated that stress resistance genes such as hsp-16.1, hsp-16.49 and sir-2.1 were regulated by DhHP-6. DAF-16 and SIR-2.1 genes are essential for the beneficial effect of DhHP-6. Therefore, the investigation into the beneficial effect of DhHP-6 on C. elegans' lifespan has the potential to develop novel drugs to prevent ageing.

Elevated histone expression promotes life span extension

Changes to the chromatin structure accompany aging, but the molecular mechanisms underlying aging and the accompanying changes to the chromatin are unclear. Here, we report a mechanism whereby altering chromatin structure regulates life span. We show that normal aging is accompanied by a profound loss of histone proteins from the genome. Indeed, yeast lacking the histone chaperone Asf1 or acetylation of histone H3 on lysine 56 are short lived, and this appears to be at least partly due to their having decreased histone levels. Conversely, increasing the histone supply by inactivation of the histone information regulator (Hir) complex or overexpression of histones dramatically extends life span via a pathway that is distinct from previously known pathways of life span extension. This study indicates that maintenance of the fundamental chromatin structure is critical for slowing down the aging process and reveals that increasing the histone supply extends life span.

Insulin-like signaling determines survival during stress via posttranscriptional mechanisms in C. elegans

The insulin-like signaling (ILS) pathway regulates metabolism and is known to modulate adult life span in C. elegans. Altered stress responses and resistance to a wide range of stressors are also associated with changes in ILS and contribute to enhanced longevity. The transcription factors DAF-16 and HSF-1 are key effectors of the longevity phenotype. We demonstrate that increased intrinsic thermotolerance, due to lower ILS, is not dependent on stress-induced transcriptional responses but instead requires active protein translation. Translation profiling experiments reveal genes that are posttranscriptionally regulated in response to altered ILS during heat shock in a DAF-16-dependent manner. Furthermore, several novel proteins are specifically required for ILS effects on thermotolerance. We propose that lowered ILS results in metabolic and physiological changes. These DAF-16-induced changes precondition a translational response under acute stress to modulate survival.

Trehalose extends longevity in the nematode Caenorhabditis elegans

Trehalose is a disaccharide of glucose found in diverse organisms and is suggested to act as a stress protectant against heat, cold, desiccation, anoxia, and oxidation. Here, we demonstrate that treatment of Caenorhabditis elegans with trehalose starting from the young-adult stage extended the mean life span by over 30% without any side effects. Surprisingly, trehalose treatment starting even from the old-adult stage shortly thereafter retarded the age-associated decline in survivorship and extended the remaining life span by 60%. Demographic analyses of age-specific mortality rates revealed that trehalose extended the life span by lowering age-independent vulnerability. Moreover, trehalose increased the reproductive span and retarded the age-associated decrease in pharyngeal-pumping rate and the accumulation of lipofuscin autofluorescence. Trehalose also enhanced thermotolerance and reduced polyglutamine aggregation. These results suggest that trehalose suppressed aging by counteracting internal or external stresses that disrupt protein homeostasis. On the other hand, the life span-extending effect of trehalose was abolished in long-lived insulin/IGF-1-like receptor (daf-2) mutants. RNA interference-mediated inactivation of the trehalose-biosynthesis genes trehalose-6-phosphate synthase-1 (tps-1) and tps-2, which are known to be up-regulated in daf-2 mutants, decreased the daf-2 life span. These findings indicate that a reduction in insulin/IGF-1-like signaling extends life span, at least in part, through the aging-suppressor function of trehalose. Trehalose may be a lead compound for potential nutraceutical intervention of the aging process.

Members of the H3K4 trimethylation complex regulate lifespan in a germline-dependent manner in C. elegans

The plasticity of aging suggests that longevity may be controlled epigenetically by specific alterations in chromatin state. The link between chromatin and aging has mostly focused on histone deacetylation by the Sir2 family1,2, but less is known about the role of other histone modifications in longevity. Histone methylation plays a crucial role during development and in maintaining stem cell pluripotency in mammals3. Regulators of histone methylation have been associated with aging in worms4,5,6,7 and flies8, but characterization of their role and mechanism of action has been limited. Here we identify the ASH-2 trithorax complex9, which trimethylates histone H3 at lysine 4 (H3K4), as a regulator of lifespan in C. elegans in a directed RNAi screen in fertile worms. Deficiencies in members of the ASH-2 complex–ASH-2 itself, WDR-5, and the H3K4 methyltransferase SET-2 extend worm lifespan. Conversely, the H3K4 demethylase RBR-2 is required for normal lifespan, consistent with the idea that an excess of H3K4 trimethylation–a mark associated with active chromatin–is detrimental for longevity. Lifespan extension induced by ASH-2 complex deficiency requires the presence of an intact adult germline and the continuous production of mature eggs. ASH-2 and RBR-2 act in the germline, at least in part, to regulate lifespan and to control a set of genes involved in lifespan determination. These results suggest that the longevity of the soma is regulated by an H3K4 methyltransferase/demethylase complex acting in the C. elegans germline.

Mixed lineage leukemia: histone H3 lysine 4 methyltransferases from yeast to human

The fourth lysine of histone H3 is post-translationally modified by a methyl group via the action of histone methyltransferase, and such a covalent modification is associated with transcriptionally active and/or repressed chromatin states. Thus, histone H3 lysine 4 methylation has a crucial role in maintaining normal cellular functions. In fact, misregulation of this covalent modification has been implicated in various types of cancer and other diseases. Therefore, a large number of studies over recent years have been directed towards histone H3 lysine 4 methylation and the enzymes involved in this covalent modification in eukaryotes ranging from yeast to human. These studies revealed a set of histone H3 lysine 4 methyltransferases with important cellular functions in different eukaryotes, as discussed here.

Potential mechanisms involved in the prevention of neurodegenerative diseases by lithium

Lithium is a monovalent cation that was introduced in 1949 by John Cade for the treatment of bipolar disorder. Clinical reports and subsequent studies confirmed this application and the beneficial effects of this compound. However, over the last 15 years, various authors have also demonstrated the neuroprotective effects of lithium against several neurotoxic paradigms. Thus, experimental studies in neuronal cell cultures and animal models of Alzheimer disease and others pathologies have provided strong evidence for the potential benefits of lithium. The main mechanism underlying its neuroprotective effects is thought to be inhibition of glycogen synthase kinase-3 (GSK-3), although other biochemical pathways in the brain could also be affected. In this review, the main mechanisms of lithium action are summarized, including the modulation of glutamate receptors, effects on arachidonic acid metabolism, its role with respect to AKT, and other potential mechanisms. In addition, its effects on neuroprotective proteins such as Bcl-2 and p53 are also discussed. Although the cellular and molecular biological effects of lithium may constitute an effective therapeutic strategy for Alzheimer disease, further clinical and experimental studies with this drug and specific GSK-3 inhibitors are necessary to confirm the use of lithium in therapeutic approaches to neurodegenerative diseases.

Polycomb Repressive Complex 2 and Trithorax modulate Drosophila longevity and stress resistance

Polycomb Group (PcG) and Trithorax Group (TrxG) proteins are key epigenetic regulators of global transcription programs. Their antagonistic chromatin-modifying activities modulate the expression of many genes and affect many biological processes. Here we report that heterozygous mutations in two core subunits of Polycomb Repressive Complex 2 (PRC2), the histone H3 lysine 27 (H3K27)-specific methyltransferase E(Z) and its partner, the H3 binding protein ESC, increase longevity and reduce adult levels of trimethylated H3K27 (H3K27me3). Mutations in trithorax (trx), a well known antagonist of Polycomb silencing, elevate the H3K27me3 level of E(z) mutants and suppress their increased longevity. Like many long-lived mutants, E(z) and esc mutants exhibit increased resistance to oxidative stress and starvation, and these phenotypes are also suppressed by trx mutations. This suppression strongly suggests that both the longevity and stress resistance phenotypes of PRC2 mutants are specifically due to their reduced levels of H3K27me3 and the consequent perturbation of Polycomb silencing. Consistent with this, long-lived E(z) mutants exhibit derepression of Abd-B, a well-characterized direct target of Polycomb silencing, and Odc1, a putative direct target implicated in stress resistance. These findings establish a role for PRC2 and TRX in the modulation of organismal longevity and stress resistance and indicate that moderate perturbation of Polycomb silencing can increase longevity.

Quantitative measurement of aging using image texture entropy

MOTIVATION

A key element in understanding the aging of Caenorhabditis elegans is objective quantification of the morphological differences between younger and older animals. Here we propose to use the image texture entropy as an objective measurement that reflects the structural deterioration of the C. elegans muscle tissues during aging.

RESULTS

The texture entropy and directionality of the muscle microscopy images were measured using 50 animals on Days 0, 2, 4, 6, 8, 10 and 12 of adulthood. Results show that the entropy of the C. elegans pharynx tissues increases as the animal ages, but a sharper increase was measured between Days 2 and 4, and between Days 8 and 10. These results are in agreement with gene expression findings, and support the contention that the process of C. elegans aging has several distinct stages. This can indicate that C. elegans aging is driven by developmental pathways, rather than stochastic accumulation of damage.

AVAILABILITY

The image data are freely available on the Internet at http://ome.grc.nia.nih.gov/iicbu2008/celegans, and the Haralick and Tamura texture analysis source code can be downloaded at http://ome.grc.nia.nih.gov/wnd-charm.

Multiple mild heat-shocks decrease the Gompertz component of mortality in Caenorhabditis elegans

Exposure to mild heat-stress (heat-shock) can significantly increase the life expectancy of the nematode Caenorhabditis elegans. A single heat-shock early in life extends longevity by 20% or more and affects life-long mortality by decreasing initial mortality only; the rate of increase in subsequent mortality (Gompertz component) is unchanged. Repeated mild heat-shocks throughout life have a larger effect on life span than does a single heat-shock early in life. Here, we ask how multiple heat-shocks affect the mortality trajectory in nematodes and find increases of life expectancy of close to 50% and of maximum longevity as well. We examined mortality using large numbers of animals and found that multiple heat-shocks not only decrease initial mortality, but also slow the Gompertz rate of increase in mortality. Thus, multiple heat-shocks have anti-aging hormetic effects and represent an effective approach for modulating aging.

Long-term functional side-effects of stimulants and sedatives in Drosophila melanogaster

BACKGROUND

Small invertebrate animals, such as nematodes and fruit flies, are increasingly being used to test candidate drugs both for specific therapeutic purposes and for long-term health effects. Some of the protocols used in these experiments feature such experimental design features as lifelong virginity and very low densities. By contrast, the ability of both fruit flies and nematodes to resist stress is frequently correlated with their longevity and other functional measures, suggesting that low-stress assays are not necessarily the only useful protocol for testing the long-term effects of drugs.

METHODOLOGY/PRINCIPAL FINDINGS

Here we report an alternative protocol for fruit fly drug-testing that maximizes reproductive opportunities and other types of interaction, with moderately high population densities. We validate this protocol using two types of experimental tests: 1. We show that this protocol detects previously well-established genetic differences between outbred fruit fly populations. 2. We show that this protocol is able to distinguish among the long-term effects of similar types of drugs within two broad categories, stimulants and tranquilizers.

CONCLUSIONS

Large-scale fly drug testing can be conducted using mixed-sex high-density cage assays. We find that the commonly-used stimulants caffeine and theobromine differ dramatically in their chronic functional effects, theobromine being more benign. Likewise, we find that two generic pharmaceutical tranquilizers, lithium carbonate and valproic acid, differ dramatically in their chronic effects, lithium being more benign. However, these findings do not necessarily apply to human subjects, and we thus do not recommend the use of any one substance over any other.

Lithium and neuropsychiatric therapeutics: neuroplasticity via glycogen synthase kinase-3beta, beta-catenin, and neurotrophin cascades

Mood disorders are not merely attributed to the functional defect of neurotransmission, but also are due to the structural impairment of neuroplasticity. Chronic stress decreases neurotrophin levels, precipitating or exacerbating depression; conversely, antidepressants increase expression of various neurotrophins (e.g., brain-derived neurotrophic factor and vascular endothelial growth factor), thereby blocking or reversing structural and functional pathologies via promoting neurogenesis. Since the worldwide approval of lithium therapy in 1970, lithium has been used for its anti-manic, antidepressant, and anti-suicidal effects, yet the therapeutic mechanisms at the cellular level remain not-fully defined. During the last five years, multiple lines of evidence have shown that the mood stabilization and neurogenesis by lithium are due to the lithium-induced inhibition of glycogen synthase kinase-3beta (GSK-3beta), allowing accumulation of beta-catenin and beta-catenin-dependent gene transcriptional events. Altered levels of GSK-3beta and beta-catenin are associated with various neuropsychiatric and neurodegenerative diseases, while various classical neuropsychiatric drugs inhibit GSK-3beta and up-regulate beta-catenin expression. In addition, evidence has emerged that insulin-like growth factor-I enhances antidepression, anti-anxiety, memory, neurogenesis, and angiogenesis; antidepressants up-regulate expression of insulin-like growth factor-I, while insulin-like growth factor-I up-regulates brain-derived neurotrophic factor expression and its receptor TrkB level, as well as brain-derived neurotrophic factor-induced synaptic protein levels. More importantly, physical exercise and healthy diet raise transport of peripheral circulating insulin-like growth factor I into the brain, reinforcing the expression of neurotrophins (e.g., brain-derived neurotrophic factor) and the strength of cell survival signalings (e.g., phosphoinositide 3-kinase / Akt / GSK-3beta pathway). This review will focus on the rapidly advancing new trends in the last five years about lithium, GSK-3beta/beta-catenin, and neurotrophin cascades.

Enhanced endothelial cell senescence by lithium-induced matrix metalloproteinase-1 expression

Endothelial cell (EC) senescence and dysfunction occurring after chronic injury and inflammation are highly associated with the development and progression of cardiovascular diseases. However, the factors involved in the establishment of EC senescence remain poorly understood. We have previously shown that lithium, an inhibitor of glycogen synthase kinase (GSK)-3beta and activator of the Wnt/beta-catenin signaling pathway, induces an EC senescent-like phenotype. Herein, we show that lithium induces a rapid and pronounced up-regulation of the matrix metalloproteinase (MMP)-1, an inflammation and senescent cell marker, at the mRNA and protein levels, whereas the induction of two other senescent cell markers is either weak (interleukin-8) or delayed (plasminogen activator inhibitor-1). Lithium effect on MMP-1 expression is also specific among other MMPs and not mediated by GSK3beta inhibition. Lithium affects MMP-1 expression mainly at the transcriptional level but neither the AP1/Ets regulatory sites nor the redox sensitive (-1607/2G) site in MMP-1 promoter are involved in lithium-dependent MMP-1 regulation. However, down-regulation of p53, a target of lithium in EC, dampens both basal and lithium-induced MMP-1 expression, which further links MMP-1 up-regulation with the establishment of cell senescence. Although increased MMP-1 levels are usually associated with angiogenesis in enabled proliferative EC, the exogenous addition of activated MMP-1 on lithium- arrested EC increases the number of EC positive for the senescent-associated-beta-galactosidase marker. Conversely, down-regulation of MMP-1 expression by small interfering RNAs blunts the lithium-dependent increase in senescent-associated-beta-galactosidase positive cells. Altogether our data indicate that lithium-induced MMP-1 may participate in the reinforcement of EC senescence and reveal a novel mechanism for lithium-induced tissue remodeling.

Activation of Akt by lithium: pro-survival pathways in aging

The effects of lithium on senescence were investigated using the senescence-accelerated mouse prone 8 (SAMP8) mice and cultures of aging cerebellar granule cells. Our in vitro findings, using cerebellar granule neurons, demonstrate that lithium (1-10mM) exerts neuroprotective effects in young cultures (7-8 days) against LY294002-induced Akt inhibition. Furthermore, lithium (10mM) inhibits GSK-3beta activity by upregulating p-GSK-3beta (ser-9) and increases p-FOXO1 (Ser256) suggesting an effective anti-apoptotic effect. Our data also showed that lithium in aged cultures exerts anti-apoptotic effects via Akt activation and consequent inhibition of downstream targets regulated by this enzyme. Finally, the administration of lithium to senescence-accelerated mice (SAMP8) and senescence-accelerated resistant mice (SAMR1) at 3 months of age also caused increased Akt activity and p-FoxO-1. These results demonstrate the effectiveness of lithium in preventing age-related neural loss and the potential therapeutic applications of lithium in treatment/prevention of neurological disease.

The anticonvulsant ethosuximide disrupts sensory function to extend C. elegans lifespan

Ethosuximide is a medication used to treat seizure disorders in humans, and we previously demonstrated that ethosuximide can delay age-related changes and extend the lifespan of the nematode Caenorhabditis elegans. The mechanism of action of ethosuximide in lifespan extension is unknown, and elucidating how ethosuximide functions is important for defining endogenous processes that influence lifespan and for exploring the potential of ethosuximide as a therapeutic for age-related diseases. To identify genes that mediate the activity of ethosuximide, we conducted a genetic screen and identified mutations in two genes, che-3 and osm-3, that cause resistance to ethosuximide-mediated toxicity. Mutations in che-3 and osm-3 cause defects in overlapping sets of chemosensory neurons, resulting in defective chemosensation and an extended lifespan. These findings suggest that ethosuximide extends lifespan by inhibiting the function of specific chemosensory neurons. This model is supported by the observation that ethosuximide-treated animals displayed numerous phenotypic similarities with mutants that have chemosensory defects, indicating that ethosuximide inhibits chemosensory function. Furthermore, ethosuximide extends lifespan by inhibiting chemosensation, since the long-lived osm-3 mutants were resistant to the lifespan extension caused by ethosuximide. These studies demonstrate a novel mechanism of action for a lifespan-extending drug and indicate that sensory perception has a critical role in controlling lifespan. Sensory perception also influences the lifespan of Drosophila, suggesting that sensory perception has an evolutionarily conserved role in lifespan control. These studies highlight the potential of ethosuximide and related drugs that modulate sensory perception to extend lifespan in diverse animals.

Aging is a major factor that contributes to disease and disability in humans, but no medicines have been demonstrated to delay human aging. We previously conducted a screen for FDA-approved drugs that can extend the lifespan of the nematode worm C. elegans, resulting in the identification of ethosuximide, a medicine used to treat epilepsy. To elucidate the mechanism of action of ethosuximide in lifespan extension, we conducted a genetic screen for C. elegans mutations that cause resistance to ethosuximide. Here, we describe the identification of genes that are critical for ethosuximide sensitivity. These genes are necessary for the function of neurons that mediate sensory perception. Furthermore, ethosuximide treatment caused defects in sensory perception. These results indicate that ethosuximide affects lifespan by inhibiting neurons that function in the perception of sensory cues. These studies highlight the importance of sensory neurons in lifespan determination and demonstrate that a drug can act on specific cells within the nervous system to extend lifespan. Sensory perception also modulates Drosophila lifespan, suggesting this is an evolutionarily conserved relationship. Our results indicate that sensory perception may be a promising target for pharmacological extension of lifespan in a variety of animals.

Compounds that confer thermal stress resistance and extended lifespan

The observation that long-lived and relatively healthy animals can be obtained by simple genetic manipulation prompts the search for chemical compounds that have similar effects. Since aging is the most important risk factor for many socially and economically important diseases, the discovery of a wide range of chemical modulators of aging in model organisms could prompt new strategies for attacking age-related disease such as diabetes, cancer and neurodegenerative disorders [Collins, J.J., Evason, K., Kornfeld, K., 2006. Pharmacology of delayed aging and extended lifespan of Caenorhabditis elegans. Exp. Gerontol.; Floyd, R.A., 2006. Nitrones as therapeutics in age-related diseases. Aging Cell 5, 51-57; Gill, M.S., 2006. Endocrine targets for pharmacological intervention in aging in Caenorhabditis elegans. Aging Cell 5, 23-30; Hefti, F.F., Bales, R., 2006. Regulatory issues in aging pharmacology. Aging Cell 5, 3-8]. Resistance to multiple types of stress is a common trait in long-lived genetic variants of a number of species; therefore, we have tested compounds that act as stress response mimetics. We have focused on compounds with antioxidant properties and identified those that confer thermal stress resistance in the nematode Caenorhabditis elegans. Some of these compounds (lipoic acid, propyl gallate, trolox and taxifolin) also extend the normal lifespan of this simple invertebrate, consistent with the general model that enhanced stress resistance slows aging.