Genetic variation in glia-neuron signalling modulates ageing rate

RSU-1 regulates the integrity of dense bodies in muscle cells of aging Caenorhabditis elegans

Muscle contraction is vital for animal survival, and the sarcomere is the fundamental unit for this process. However, the functions of many conserved sarcomere proteins remain unknown, as their mutants do not exhibit obvious defects. To address this, Caenorhabditis elegans was utilized as a model organism to investigate RSU-1 function in the body wall muscle. RSU-1 is found to colocalize with UNC-97 at the dense body and M-line, and it is particularly crucial for regulating locomotion in aging worms, rather than in young worms. This suggests that RSU-1 has a specific function in maintaining muscle function during aging. Furthermore, the interaction between RSU-1 and UNC-97/PINCH is essential for RSU-1 to modulate locomotion, preserve filament structure, and sustain the M-line and dense body throughout aging. Overall, these findings highlight the significant contribution of RSU-1, through its interaction with UNC-97, in maintaining proper muscle cell function in aging worms.

Phasic/tonic glial GABA differentially transduce for olfactory adaptation and neuronal aging

Phasic (fast) and tonic (sustained) inhibition of γ-aminobutyric acid (GABA) are fundamental for regulating day-to-day activities, neuronal excitability, and plasticity. However, the mechanisms and physiological functions of glial GABA transductions remain poorly understood. Here, we report that the AMsh glia in Caenorhabditis elegans exhibit both phasic and tonic GABAergic signaling, which distinctively regulate olfactory adaptation and neuronal aging. Through genetic screening, we find that GABA permeates through bestrophin-9/-13/-14 anion channels from AMsh glia, which primarily activate the metabolic GABAB receptor GBB-1 in the neighboring ASH sensory neurons. This tonic action of glial GABA regulates the age-associated changes of ASH neurons and olfactory responses via a conserved signaling pathway, inducing neuroprotection. In addition, the calcium-evoked, vesicular glial GABA release acts upon the ionotropic GABAA receptor LGC-38 in ASH neurons to regulate olfactory adaptation. These findings underscore the fundamental significance of glial GABA in maintaining healthy aging and neuronal stability.

Identification and Targeted Quantification of Endogenous Neuropeptides in the Nematode Caenorhabditis elegans Using Mass Spectrometry

The nematode Caenorhabditis elegans lends itself as an excellent model organism for peptidomics studies. Its ease of cultivation and quick generation time make it suitable for high-throughput studies. The nervous system, with its 302 neurons, is probably the best-known and studied endocrine tissue. Moreover, its neuropeptidergic signaling pathways display numerous similarities with those observed in other metazoans. Here, we describe two label-free approaches for neuropeptidomics in C. elegans: one for discovery purposes, and another for targeted quantification and comparisons of neuropeptide levels between different samples. Starting from a detailed peptide extraction procedure, we here outline the liquid chromatography tandem mass spectrometry (LC-MS/MS) setup and describe subsequent data analysis approaches.

System-wide mapping of peptide-GPCR interactions in C. elegans

Neuropeptides and peptide hormones are ancient, widespread signaling molecules that underpin almost all brain functions. They constitute a broad ligand-receptor network, mainly by binding to G protein-coupled receptors (GPCRs). However, the organization of the peptidergic network and roles of many peptides remain elusive, as our insight into peptide-receptor interactions is limited and many peptide GPCRs are still orphan receptors. Here we report a genome-wide peptide-GPCR interaction map in Caenorhabditis elegans. By reverse pharmacology screening of over 55,384 possible interactions, we identify 461 cognate peptide-GPCR couples that uncover a broad signaling network with specific and complex combinatorial interactions encoded across and within single peptidergic genes. These interactions provide insights into peptide functions and evolution. Combining our dataset with phylogenetic analysis supports peptide-receptor co-evolution and conservation of at least 14 bilaterian peptidergic systems in C. elegans. This resource lays a foundation for system-wide analysis of the peptidergic network.

Ethyl acetate extract of Gastrodia elata protects Caenorhabditis elegans from oxidative stress and amyloid β peptide toxicity

Gastrodia elata Blume is a traditional Chinese medicine with a long history, which has numerous pharmacological activities, such as anti-inflammation, anti-oxidation and protection of nerves. The present study investigated the regulatory effect of ethyl acetate extract of Gastrodia elata (EEGE) on the β-amyloid (Aβ) toxicity of Caenorhabditis elegans (C. elegans). First, the main components of EEGE were analyzed using high-performance liquid chromatography, and the total phenols, total flavonoids and total antioxidant capacity of EEGE were determined. Next, the regulation effect of EEGE on Aβ-induced toxicity of C. elegans was evaluated through experiments on nematode paralysis, lifespan, oxidative and heat stress, locomotor ability, reproductive ability, reactive oxygen species (ROS) level, Aβ aggregation test, malondialdehyde (MDA) level, catalase (CAT) activity and superoxide dismutase (SOD) activity. Finally, the mechanism of EEGE was elucidated using RNA sequencing (RNA-Seq) and the expression levels of related genes were verified using quantitative PCR. The present study revealed that the main components of EEGE included phosphorylated (p)-hydroxybenzyl alcohol, p-hydroxybenzaldehyde and 4,4'-dihydroxydiphenylmethane, possessing strong in vitro free radical scavenging and reducing abilities. In addition, after the intervention of EEGE, the paralysis of nematodes could be delayed, the survival time of the nematodes was prolonged, the survival rate of the nematodes under stress (high temperature and oxidation) conditions was improved, the activity capacity and reproductive capacity of the nematodes were improved, the activities of SOD and CAT were improved and the levels of ROS and MDA were reduced. Notably, EEGE directly inhibited Aβ plaque aggregation in nematodes. RNA-Seq analysis showed that EEGE regulated metabolism and longevity-related genes, and these genes were regulated by the insulin/IGF-1 signaling (IIS) pathway. Therefore, the present study hypothesized that the regulatory mechanism of EEGE was significantly related to the IIS pathway. The present research results demonstrated that the protective effect of EEGE on transgenic C. elegans was to reduce Aβ protein aggregation, improve the in vivo antioxidant level, effectively remove free radicals and to regulate the expression of genes related to IIS pathway, thereby reducing Aβ-induced toxicity and delaying nematode paralysis.

Glia of C. elegans coordinate a protective organismal heat shock response independent of the neuronal thermosensory circuit

Aging organisms lose the ability to induce stress responses, becoming vulnerable to protein toxicity and tissue damage. Neurons can signal to peripheral tissues to induce protective organelle-specific stress responses. Recent work shows that glia can independently induce such responses. Here, we show that overexpression of heat shock factor 1 (hsf-1) in the four astrocyte-like cephalic sheath cells of Caenorhabditis elegans induces a non-cell-autonomous cytosolic unfolded protein response, also known as the heat shock response (HSR). These animals have increased lifespan and heat stress resistance and decreased protein aggregation. Glial HSR regulation is independent of canonical thermosensory circuitry and known neurotransmitters but requires the small clear vesicle release protein UNC-13. HSF-1 and the FOXO transcription factor DAF-16 are partially required in peripheral tissues for non-cell-autonomous HSR, longevity, and thermotolerance. Cephalic sheath glial hsf-1 overexpression also leads to pathogen resistance, suggesting a role for this signaling pathway in immune function.

Mechanisms Underlying Brain Aging Under Normal and Pathological Conditions

Aging is a major risk factor for many human diseases, including cognitive impairment, which affects a large population of the elderly. In the past few decades, our understanding of the molecular and cellular mechanisms underlying the changes associated with aging and age-related diseases has expanded greatly, shedding light on the potential role of these changes in cognitive impairment. In this article, we review recent advances in understanding of the mechanisms underlying brain aging under normal and pathological conditions, compare their similarities and differences, discuss the causative and adaptive mechanisms of brain aging, and finally attempt to find some rules to guide us on how to promote healthy aging and prevent age-related diseases.

V-ATPase/TORC1-mediated ATFS-1 translation directs mitochondrial UPR activation in C. elegans

To adapt mitochondrial function to the ever-changing intra- and extracellular environment, multiple mitochondrial stress response (MSR) pathways, including the mitochondrial unfolded protein response (UPRmt), have evolved. However, how the mitochondrial stress signal is sensed and relayed to UPRmt transcription factors, such as ATFS-1 in Caenorhabditis elegans, remains largely unknown. Here, we show that a panel of vacuolar H+-ATPase (v-ATPase) subunits and the target of rapamycin complex 1 (TORC1) activity are essential for the cytosolic relay of mitochondrial stress to ATFS-1 and for the induction of the UPRmt. Mechanistically, mitochondrial stress stimulates v-ATPase/Rheb-dependent TORC1 activation, subsequently promoting ATFS-1 translation. Increased translation of ATFS-1 upon mitochondrial stress furthermore relies on a set of ribosomal components but is independent of GCN-2/PEK-1 signaling. Finally, the v-ATPase and ribosomal subunits are required for mitochondrial surveillance and mitochondrial stress-induced longevity. These results reveal a v-ATPase-TORC1-ATFS-1 signaling pathway that links mitochondrial stress to the UPRmt through intimate crosstalks between multiple organelles.

Betulinic acid increases lifespan and stress resistance via insulin/IGF-1 signaling pathway in Caenorhabditis elegans

Numerous studies reported that betulinic acid (BA), a natural product extracted from birch bark, exhibited various beneficial effects in vitro. However, its pharmacological activities in aging are rarely understood. In this study, Caenorhabditis elegans was deployed as a whole animal model to investigate the impacts of BA on lifespan and stress resistance. Wild-type C. elegans were fed in the presence or absence of BA and tested for a series of phenotypes, including longevity, mobility, reproductive capacity, pharyngeal pumping, heat stress, and oxidative stress. BA at the optimal dose (50 μg/mL) extended the lifespan, improved the healthspan, and significantly evoked the increased oxidative stress resistance in C. elegans. Incorporating the genetic analysis with different types of longevity mutants, DAF-16, the downstream effector of the Insulin/IGF-1 receptor signaling, was revealed to mediate the protective effects of BA on lifespan and antioxidant activity. Together, these data showcased the potential of BA in promoting healthy aging, which shall facilitate its further development in the food and pharmaceutical industries.

Anti-aging effects of chlorpropamide depend on mitochondrial complex-II and the production of mitochondrial reactive oxygen species

Sulfonylureas are widely used oral anti-diabetic drugs. However, its long-term usage effects on patients’ lifespan remain controversial, with no reports of influence on animal longevity. Hence, the anti-aging effects of chlorpropamide along with glimepiride, glibenclamide, and tolbutamide were studied with special emphasis on the interaction of chlorpropamide with mitochondrial ATP-sensitive K⁺ (mitoK-ATP) channels and mitochondrial complex II. Chlorpropamide delayed aging in Caenorhabditis elegans, human lung fibroblast MRC-5 cells and reduced doxorubicin-induced senescence in both MRC-5 cells and mice. In addition, the mitochondrial membrane potential and ATP levels were significantly increased in chlorpropamide-treated worms, which is consistent with the function of its reported targets, mitoK-ATP channels. Increased levels of mitochondrial reactive oxygen species (mtROS) were observed in chlorpropamide-treated worms. Moreover, the lifespan extension by chlorpropamide required complex II and increased mtROS levels, indicating that chlorpropamide acts on complex II directly or indirectly via mitoK-ATP to increase the production of mtROS as a pro-longevity signal. This study provides mechanistic insight into the anti-aging effects of sulfonylureas in C. elegans.

In silico analyses of neuropeptide-like protein (NLP) profiles in parasitic nematodes

Nematode parasite infections cause disease in humans and animals and threaten global food security by reducing productivity in livestock and crop farming. The escalation of anthelmintic resistance in economically important nematode parasites underscores the need for the identification of novel drug targets in these worms. Nematode neuropeptide signalling is an attractive system for chemotherapeutic exploitation, with neuropeptide G-protein coupled receptors (NP-GPCRs) representing the lead targets. In order to successfully validate NP-GPCRs for parasite control it is necessary to characterise their function and importance to nematode biology. This can be aided through identification of receptor activating ligand(s) via deorphanisation. Such efforts require the identification of all neuropeptide ligands within parasites. Here we mined the genomes of nine therapeutically relevant pathogenic nematodes to characterise the neuropeptide-like protein complements and demonstrate that: (i) parasitic nematodes possess a reduced complement of neuropeptide-like protein-encoding genes relative to Caenorhabditis elegans; (ii) parasite neuropeptide-like protein profiles are broadly conserved between nematode clades; (iii) five Ce-nlps are completely conserved across the nematode species examined; (iv) the extent and position of neuropeptide-like protein-motif conservation is variable; (v) novel RPamide-encoding genes are present in parasitic nematodes; (vi) novel Allatostatin-C-like peptide encoding genes are present in both C. elegans and parasitic nematodes; (vii) novel neuropeptide-like protein families are absent in C. elegans; and (viii) highly conserved nematode neuropeptide-like proteins are bioactive. These data highlight the complexity of nematode neuropeptide-like proteins and reveal the need for nomenclature revision in this diverse neuropeptide family. The identification of neuropeptide-like protein ligands, and characterisation of those with functional relevance, advance our understanding of neuropeptide signalling to support exploitation of the neuropeptidergic system as an anthelmintic target.

Neuropeptides and Behaviors: How Small Peptides Regulate Nervous System Function and Behavioral Outputs

One of the reasons that most multicellular animals survive and thrive is because of the adaptable and plastic nature of their nervous systems. For an organism to survive, it is essential for the animal to respond and adapt to environmental changes. This is achieved by sensing external cues and translating them into behaviors through changes in synaptic activity. The nervous system plays a crucial role in constantly evaluating environmental cues and allowing for behavioral plasticity in the organism. Multiple neurotransmitters and neuropeptides have been implicated as key players for integrating sensory information to produce the desired output. Because of its simple nervous system and well-established neuronal connectome, C. elegans acts as an excellent model to understand the mechanisms underlying behavioral plasticity. Here, we critically review how neuropeptides modulate a wide range of behaviors by allowing for changes in neuronal and synaptic signaling. This review will have a specific focus on feeding, mating, sleep, addiction, learning and locomotory behaviors in C. elegans. With a view to understand evolutionary relationships, we explore the functions and associated pathophysiology of C. elegans neuropeptides that are conserved across different phyla. Further, we discuss the mechanisms of neuropeptidergic signaling and how these signals are regulated in different behaviors. Finally, we attempt to provide insight into developing potential therapeutics for neuropeptide-related disorders.

Antiaging Effects of Vicatia thibetica de Boiss Root Extract on Caenorhabditis elegans and Doxorubicin-Induced Premature Aging in Adult Mice

The roots of Vicatia thibetica de Boiss are a kind of Chinese herb with homology of medicine and food. This is the first report showing the property of the extract of Vicatia thibetica de Boiss roots (HLB01) to extend the lifespan as well as promote the healthy parameters in Caenorhabditis elegans (C. elegans). For doxorubicin- (Doxo-) induced premature aging in adult mice, HLB01 counteracted the senescence-associated biomarkers, including P21 and γH2AX. Interestingly, HLB01 promoted the expression of collagen in C. elegans and mammalian cell systemically, which might be one of the essential factors to exert the antiaging effects. In addition, HLB01 was also found as a scavenger of free radicals, thereby performing the antioxidant ability. Lifespan extension by HLB01 was also dependent on DAF-16 and HSF-1 via oxidative stress resistance and heat stress resistance. Taken together, overall data suggested that HLB01 could extend the lifespan and healthspan of C. elegans and resist Doxo-induced senescence in mice via promoting the expression of collagen, antioxidant potential, and stress resistance.

A perspective on C. elegans neurodevelopment: from early visionaries to a booming neuroscience research

The formation of the nervous system and its striking complexity is a remarkable feat of development. C. elegans served as a unique model to dissect the molecular events in neurodevelopment, from its early visionaries to the current booming neuroscience community. Soon after being introduced as a model, C. elegans was mapped at the level of genes, cells, and synapses, providing the first metazoan with a complete cell lineage, sequenced genome, and connectome. Here, I summarize mechanisms underlying C. elegans neurodevelopment, from the generation and diversification of neural components to their navigation and connectivity. I point out recent noteworthy findings in the fields of glia biology, sex dimorphism and plasticity in neurodevelopment, highlighting how current research connects back to the pioneering studies by Brenner, Sulston and colleagues. Multifaceted investigations in model organisms, connecting genes to cell function and behavior, expand our mechanistic understanding of neurodevelopment while allowing us to formulate emerging questions for future discoveries.

Defective Autophagy and Mitophagy in Alzheimer's Disease: Mechanisms and Translational Implications

The main histopathology of Alzheimer's disease (AD) is featured by the extracellular accumulation of amyloid-β (Aβ) plaques and intracellular tau neurofibrillary tangles (NFT) in the brain, which is likely to result from co-pathogenic interactions among multiple factors, e.g., aging or genes. The link between defective autophagy/mitophagy and AD pathologies is still under investigation and not fully established. In this review, we consider how AD is associated with impaired autophagy and mitophagy, and how these impact pathological hallmarks as well as the potential mechanisms. This complicated interplay between autophagy or mitophagy and histopathology in AD suggests that targeting autophagy or mitophagy probably is a promising anti-AD drug candidate. Finally, we review the implications of some new insights for induction of autophagy or mitophagy as the new therapeutic way that targets processes upstream of both NFT and Aβ plaques, and hence stops the neurodegenerative course in AD.

Neuroprotective Effects of Physical Activity via the Adaptation of Astrocytes

The multifold benefits of regular physical exercise have been largely demonstrated in human and animal models. Several studies have reported the beneficial effects of physical activity, both in peripheral tissues and in the central nervous system (CNS). Regular exercise improves cognition, brain plasticity, neurogenesis and reduces the symptoms of neurodegenerative diseases, making timeless the principle of “mens sana in corpore sano” (i.e., a healthy mind in a healthy body). Physical exercise promotes morphological and functional changes in the brain, acting not only in neurons but also in astrocytes, which represent the most numerous glial cells in the brain. The multiple effects of exercise on astrocytes comprise the increased number of new astrocytes, the maintenance of basal levels of catecholamine, the increase in glutamate uptake, the major release of trophic factors and better astrocytic coverage of cerebral blood vessels. The purpose of this review is to highlight the effects of exercise on brain function, emphasize the role of astrocytes in the healthy CNS, and provide an update for a better understanding of the effects of physical exercise in the modulation of astrocyte function.

Male pheromones modulate synaptic transmission at the C. elegans neuromuscular junction in a sexually dimorphic manner

The development of functional synapses in the nervous system is important for animal physiology and behaviors, and its disturbance has been linked with many neurodevelopmental disorders. The synaptic transmission efficacy can be modulated by the environment to accommodate external changes, which is crucial for animal reproduction and survival. However, the underlying plasticity of synaptic transmission remains poorly understood. Here we show that in Caenorhabditis elegans, the male environment increases the hermaphrodite cholinergic transmission at the neuromuscular junction (NMJ), which alters hermaphrodites' locomotion velocity and mating efficiency. We identify that the male-specific pheromones mediate this synaptic transmission modulation effect in a developmental stage-dependent manner. Dissection of the sensory circuits reveals that the AWB chemosensory neurons sense those male pheromones and further transduce the information to NMJ using cGMP signaling. Exposure of hermaphrodites to the male pheromones specifically increases the accumulation of presynaptic CaV2 calcium channels and clustering of postsynaptic acetylcholine receptors at cholinergic synapses of NMJ, which potentiates cholinergic synaptic transmission. Thus, our study demonstrates a circuit mechanism for synaptic modulation and behavioral flexibility by sexual dimorphic pheromones.

Hedgehog Signaling Modulates Glial Proteostasis and Lifespan

The conserved Hedgehog signaling pathway has well-established roles in development. However, its function during adulthood remains largely unknown. Here, we investigated whether the Hedgehog signaling pathway is active during adult life in Drosophila melanogaster, and we uncovered a protective function for Hedgehog signaling in coordinating correct proteostasis in glial cells. Adult-specific depletion of Hedgehog reduces lifespan, locomotor activity, and dopaminergic neuron integrity. Conversely, increased expression of Hedgehog extends lifespan and improves fitness. Moreover, Hedgehog pathway activation in glia rescues the lifespan and age-associated defects of hedgehog mutants. The Hedgehog pathway regulates downstream chaperones, whose overexpression in glial cells was sufficient to rescue the shortened lifespan and proteostasis defects of hedgehog mutants. Finally, we demonstrate the protective ability of Hedgehog signaling in a Drosophila Alzheimer's disease model expressing human amyloid beta in the glia. Overall, we propose that Hedgehog signaling is requisite for lifespan determination and correct proteostasis in glial cells.

BiT age: A transcriptome-based aging clock near the theoretical limit of accuracy

Aging clocks dissociate biological from chronological age. The estimation of biological age is important for identifying gerontogenes and assessing environmental, nutritional, or therapeutic impacts on the aging process. Recently, methylation markers were shown to allow estimation of biological age based on age‐dependent somatic epigenetic alterations. However, DNA methylation is absent in some species such as Caenorhabditis elegans and it remains unclear whether and how the epigenetic clocks affect gene expression. Aging clocks based on transcriptomes have suffered from considerable variation in the data and relatively low accuracy. Here, we devised an approach that uses temporal scaling and binarization of C. elegans transcriptomes to define a gene set that predicts biological age with an accuracy that is close to the theoretical limit. Our model accurately predicts the longevity effects of diverse strains, treatments, and conditions. The involved genes support a role of specific transcription factors as well as innate immunity and neuronal signaling in the regulation of the aging process. We show that this binarized transcriptomic aging (BiT age) clock can also be applied to human age prediction with high accuracy. The BiT age clock could therefore find wide application in genetic, nutritional, environmental, and therapeutic interventions in the aging process.

Maintenance of protein homeostasis in glia extends lifespan in C. elegans

Mounting evidence support that glia play a key role in organismal ageing. However, the mechanisms by which glia impact ageing are not understood. One of the processes that has significant impact on the rate of ageing is the unfolded protein response. The more robust the UPR, the more the organism can counteract the effect of environmental and genetic stressors. However, how decline of cellular UPR translates into organismal ageing and eventual death is not fully understood. Here we discuss recent findings highlighting that neuropeptides released by glia act long distance to regulate ageing in C. elegans. Taking advantage of the short lifespan and the genetic amenability of this organism, the endoplasmic reticulum unfolded protein responses (UPR^ER) can be activated in C. elegans glia. This leads to cell-nonautonomous activation of the UPR^ER in the intestine. Activation of intestinal UPR^ER requires the function of genes involved in neuropeptide processing and release, suggesting that neuropeptides signal from glia to the intestine to regulate ER stress response. Importantly, the cell-nonautonomous activation of UPR^ER leads to extension of lifespan. Taken together, these data suggest that environmental and genetic factors that impact the response of glia to stress have the potential to influence organismal ageing. Further research on the specific neuropeptides involved should cast new light on the mechanism of ageing and may suggest novel anti-ageing therapies.

The transcriptional coactivator CBP/p300 is an evolutionarily conserved node that promotes longevity in response to mitochondrial stress

Organisms respond to mitochondrial stress by activating multiple defense pathways including the mitochondrial unfolded protein response (UPR^mt). However, how UPR^mt regulators are orchestrated to transcriptionally activate stress responses remains largely unknown. Here we identified CBP-1, the worm ortholog of the mammalian acetyltransferases CBP/p300, as an essential regulator of the UPR^mt, as well as mitochondrial stress-induced immune response, reduction of amyloid-β aggregation and lifespan extension in Caenorhabditis elegans. Mechanistically, CBP-1 acts downstream of histone demethylases, JMJD-1.2/JMJD-3.1, and upstream of UPR^mt transcription factors including ATFS-1, to systematically induce a broad spectrum of UPR^mt genes and execute multiple beneficial functions. In mouse and human populations, transcript levels of CBP/p300 positively correlate with UPR^mt transcripts and longevity. Furthermore, CBP/p300 inhibition disrupts, while forced expression of p300 is sufficient to activate, the UPR^mt in mammalian cells. These results highlight an evolutionarily conserved mechanism that determines mitochondrial stress response, and promotes health and longevity through CBP/p300.

Effects of aging on gene expression in blood of captive Tibetan macaques ( Macaca thibetana) and comparisons with expression in humans

Changes in gene expression occur as animals, including primates, age. Macaques have long been used as a model species for primate evolution and biomedical studies. Here, to study gene expression in Tibetan macaques (Macaca thibetana, TMs) and its differences to humans, we applied RNA-Seq to obtain the blood transcriptomes of 24 TMs. In total, 2 523 age-associated differentially expressed genes (DEGs) were identified. Several pathways and processes that regulate aging, including the FoxO signaling pathway, autophagy, and platelet activation, were significantly enriched in the up-regulated DEGs. Two significantly age-related modules were identified by weighted gene co-expression network analysis (WGCNA). The TMs and humans shared 279 common DEGs, including 111 up-regulated and 141 down-regulated genes with advancing age in the same expression direction. However, 27 age-related DEGs presented the opposite expression direction in TMs as that in humans. For example, INPPL1, with inhibitory effects on the B cell receptor signaling pathway, was up-regulated in humans but down-regulated in TMs. In general, our study suggests that aging is a critical factor affecting gene expression in the captive TM population. The similarities and differences in gene expression patterns between TMs and humans could provide new insights into primate evolution and benefit TM model development.

Sirtuin 6: A potential therapeutic target for cardiovascular diseases

Cardiovascular diseases (CVDs) are serious diseases endangering human health due to high morbidity and mortality worldwide, and numerous signal molecules are involved in this pathological process. As a member of the Sirtuin family NAD ⁺-dependent deacetylases, indeed, Sirtuin 6 (SIRT6) plays an important role in regulating biological homeostasis, longevity, and various diseases. More importantly, SIRT6 performs as an indispensable role in glucose and lipid metabolism, inflammation and genomic stability for the occurrence and development of various CVDs. Recent advances: among sirtuins, SIRT6 was frequently unveiled thanks for its protective roles against heart failure, cardiovascular remodeling and atherosclerosis, and identified as an essential intervention target of CVDs, bringing SIRT6 into the focus of clinical interest. Herein, we provide an overview of the current molecular mechanism through which SIRT6 regulates CVDs, and we highlight a potential therapeutic target for CVDs.

Sensory Glia Detect Repulsive Odorants and Drive Olfactory Adaptation

Glia are typically considered as supporting cells for neural development and synaptic transmission. Here, we report an active role of a glia in olfactory transduction. As a polymodal sensory neuron in C. elegans, the ASH neuron is previously known to detect multiple aversive odorants. We reveal that the AMsh glia, a sheath for multiple sensory neurons including ASH, cell-autonomously respond to aversive odorants via G-protein-coupled receptors (GPCRs) distinct from those in ASH. Upon activation, the AMsh glia suppress aversive odorant-triggered avoidance and promote olfactory adaptation by inhibiting the ASH neuron via GABA signaling. Thus, we propose a novel two-receptor model where the glia and sensory neuron jointly mediate adaptive olfaction. Our study reveals a non-canonical function of glial cells in olfactory transduction, which may provide new insights into the glia-like supporting cells in mammalian sensory procession.

Cell-type-specific promoters for C. elegans glia

Glia shape the development and function of the C. elegans nervous system, especially its sense organs and central neuropil (nerve ring). Cell-type-specific promoters allow investigators to label or manipulate individual glial cell types, and therefore provide a key tool for deciphering glial function. In this technical resource, we compare the specificity, brightness, and consistency of cell-type-specific promoters for C. elegans glia. We identify a set of promoters for the study of seven glial cell types (F16F9.3, amphid and phasmid sheath glia; F11C7.2, amphid sheath glia only; grl-2, amphid and phasmid socket glia; hlh-17, cephalic (CEP) sheath glia; and grl-18, inner labial (IL) socket glia) as well as a pan-glial promoter (mir-228). We compare these promoters to promoters that are expressed more variably in combinations of glial cell types (delm-1 and itx-1). We note that the expression of some promoters depends on external conditions or the internal state of the organism, such as developmental stage, suggesting glial plasticity. Finally, we demonstrate an approach for prospectively identifying cell-type-specific glial promoters using existing single-cell sequencing data, and we use this approach to identify two novel promoters specific to IL socket glia (col-53 and col-177).

Verapamil extends lifespan in Caenorhabditis elegans by inhibiting calcineurin activity and promoting autophagy

Previous evidence has revealed that increase in intracellular levels of calcium promotes cellular senescence. However, whether calcium channel blockers (CCBs) can slow aging and extend lifespan is still unknown. In this study, we showed that verapamil, an L-type calcium channel blocker, extended the Caenorhabditis elegans (C. elegans) lifespan and delayed senescence in human lung fibroblasts. Verapamil treatment also improved healthspan in C. elegans as reflected by several age-related physiological parameters, including locomotion, thrashing, age-associated vulval integrity, and osmotic stress resistance. We also found that verapamil acted on the α1 subunit of an L-type calcium channel in C. elegans. Moreover, verapamil extended worm lifespan by inhibiting calcineurin activity. Furthermore, verapamil significantly promoted autophagy as reflected by the expression levels of LGG-1/LC3 and the mRNA levels of autophagy-related genes. In addition, verapamil could not further induce autophagy when tax-6, calcineurin gene, was knocked down, indicating that verapamil-induced lifespan extension is mediated via promoting autophagy processes downstream of calcineurin. In summary, our study provided mechanistic insights into the anti-aging effect of verapamil in C. elegans.

Two conserved epigenetic regulators prevent healthy ageing

It has long been assumed that lifespan and healthspan correlate strongly, yet the two can be clearly dissociated^1-6. Although there has been a global increase in human life expectancy, increasing longevity is rarely accompanied by an extended healthspan^4,7. Thus, understanding the origin of healthy behaviours in old people remains an important and challenging task. Here we report a conserved epigenetic mechanism underlying healthy ageing. Through genome-wide RNA-interference-based screening of genes that regulate behavioural deterioration in ageing Caenorhabditis elegans, we identify 59 genes as potential modulators of the rate of age-related behavioural deterioration. Among these modulators, we found that a neuronal epigenetic reader, BAZ-2, and a neuronal histone 3 lysine 9 methyltransferase, SET-6, accelerate behavioural deterioration in C. elegans by reducing mitochondrial function, repressing the expression of nuclear-encoded mitochondrial proteins. This mechanism is conserved in cultured mouse neurons and human cells. Examination of human databases^8,9 shows that expression of the human orthologues of these C. elegans regulators, BAZ2B and EHMT1, in the frontal cortex increases with age and correlates positively with the progression of Alzheimer's disease. Furthermore, ablation of Baz2b, the mouse orthologue of BAZ-2, attenuates age-dependent body-weight gain and prevents cognitive decline in ageing mice. Thus our genome-wide RNA-interference screen in C. elegans has unravelled conserved epigenetic negative regulators of ageing, suggesting possible ways to achieve healthy ageing.

The Role of Ca2+ Signaling in Aging and Neurodegeneration: Insights from Caenorhabditis elegans Models

Ca²⁺ is a ubiquitous second messenger that plays an essential role in physiological processes such as muscle contraction, neuronal secretion, and cell proliferation or differentiation. There is ample evidence that the dysregulation of Ca²⁺ signaling is one of the key events in the development of neurodegenerative processes, an idea called the "calcium hypothesis" of neurodegeneration. Caenorhabditis elegans (C. elegans) is a very good model for the study of aging and neurodegeneration. In fact, many of the signaling pathways involved in longevity were first discovered in this nematode, and many models of neurodegenerative diseases have also been developed therein, either through mutations in the worm genome or by expressing human proteins involved in neurodegeneration (β-amyloid, α-synuclein, polyglutamine, or others) in defined worm tissues. The worm is completely transparent throughout its whole life, which makes it possible to carry out Ca²⁺ dynamics studies in vivo at any time, by expressing Ca²⁺ fluorescent probes in defined worm tissues, and even in specific organelles such as mitochondria. This review will summarize the evidence obtained using this model organism to understand the role of Ca²⁺ signaling in aging and neurodegeneration.

Natural Variation in a Dendritic Scaffold Protein Remodels Experience-Dependent Plasticity by Altering Neuropeptide Expression

The extent to which behavior is shaped by experience varies between individuals. Genetic differences contribute to this variation, but the neural mechanisms are not understood. Here, we dissect natural variation in the behavioral flexibility of two Caenorhabditis elegans wild strains. In one strain, a memory of exposure to 21% O₂ suppresses CO₂-evoked locomotory arousal; in the other, CO₂ evokes arousal regardless of previous O₂ experience. We map that variation to a polymorphic dendritic scaffold protein, ARCP-1, expressed in sensory neurons. ARCP-1 binds the Ca²⁺-dependent phosphodiesterase PDE-1 and co-localizes PDE-1 with molecular sensors for CO₂ at dendritic ends. Reducing ARCP-1 or PDE-1 activity promotes CO₂ escape by altering neuropeptide expression in the BAG CO₂ sensors. Variation in ARCP-1 alters behavioral plasticity in multiple paradigms. Our findings are reminiscent of genetic accommodation, an evolutionary process by which phenotypic flexibility in response to environmental variation is reset by genetic change.

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Behavioral flexibility varies across Caenorhabditis and C. elegans wild isolates

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A natural polymorphism in ARCP-1 underpins inter-individual variation in plasticity

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ARCP-1 is a dendritic scaffold protein localizing cGMP signaling machinery to cilia

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Disrupting ARCP-1 alters behavioral plasticity by changing neuropeptide expression

Glia-Neuron Interactions in Caenorhabditis elegans

Glia are abundant components of animal nervous systems. Recognized 170 years ago, concerted attempts to understand these cells began only recently. From these investigations glia, once considered passive filler material in the brain, have emerged as active players in neuron development and activity. Glia are essential for nervous system function, and their disruption leads to disease. The nematode Caenorhabditis elegans possesses glial types similar to vertebrate glia, based on molecular, morphological, and functional criteria, and has become a powerful model in which to study glia and their neuronal interactions. Facile genetic and transgenic methods in this animal allow the discovery of genes required for glial functions, and effects of glia at single synapses can be monitored by tracking neuron shape, physiology, or animal behavior. Here, we review recent progress in understanding glia-neuron interactions in C. elegans. We highlight similarities with glia in other animals, and suggest conserved emerging principles of glial function.

Postoperative cognitive dysfunction in the aged: the collision of neuroinflammaging with perioperative neuroinflammation

The aging population is burgeoning globally and this trend presents great challenges to the current healthcare system as the growing number of aged individuals receives procedures of surgery and anesthesia. Postoperative cognitive dysfunction (POCD) is a severe postoperative neurological sequela. Advanced age is considered as an independent risk factor of POCD. Mounting evidence have shown that neuroinflammation plays an essential role in POCD. However, it remains debatable why this complication occurs highly in the aged individuals. As known, aging itself is the major common high-risk factor for age-associated disorders including diabetes, cardiovascular disease, cancer, and neurodegenerative diseases. Chronic low-grade neuroinflammation (dubbed neuroinflammaging in the present paper) is a hallmark alternation and contributes to age-related cognitive decline in the normal aging. Interestingly, several lines of findings show that the neuroinflammatory pathogenesis of POCD is age-dependent. It suggests that age-related changes, especially the neuroinflammaging, are possibly associated with the postoperative cognitive impairment. Understanding the role of neuroinflammaging in POCD is crucial to elucidate the mechanism of POCD and develop strategies to prevent or treat POCD. Here the focus of this review is on the potential role of neuroinflammaging in the mechanism of POCD. Lastly, we briefly review promising interventions for this neurological sequela.

Healthy aging: A bibliometric analysis of the literature

Due to dramatic growth of the aging population worldwide, there has been an urgent call for a public health strategy to manage healthy aging, with the ultimate goal being advancement of aging research. Considerable progress has been made in uncovering the mystery of aging process using multidisciplinary methods. There is a growing consensus in the field that aging traits which were originally thought to be disparate are likely to be interconnected. Thus, emerging research is needed to incorporate current findings of aging by building multiscale network models. This study reported the network of healthy aging research using bibliometric approaches. Based on the results, aging of the brain and muscle is a primary research focus which is a critical part of the multiscale network regulating the aging process. Among aging-associated diseases, Alzheimer's disease and frailty are among the main research focuses, and emerging work has focused on developing diagnostic tools for these diseases. For research on anti-aging interventions, calorie restriction, physical activity, and anti-aging pharmacology are the main interventions, of which the underlying mechanisms have been comprehensively studied in animal models.

Analysis of Epistasis in Natural Traits Using Model Organisms

The ability to detect and understand epistasis in natural populations is important for understanding how biological traits are influenced by genetic variation. However, identification and characterization of epistasis in natural populations remains difficult due to statistical issues that arise as a result of multiple comparisons, and the fact that most genetic variants segregate at low allele frequencies. In this review, we discuss how model organisms may be used to manipulate genotypic combinations to power the detection of epistasis as well as test interactions between specific genes. Findings from a number of species indicate that statistical epistasis is pervasive between natural genetic variants. However, the properties of experimental systems that enable analysis of epistasis also constrain extrapolation of these results back into natural populations.

AKT inhibition-mediated dephosphorylation of TFE3 promotes overactive autophagy independent of MTORC1 in cadmium-exposed bone mesenchymal stem cells

Cadmium (Cd) is a toxic metal that is widely found in numerous environmental matrices and induces serious adverse effects in various organs and tissues. Bone tissue seems to be a crucial target of Cd contamination. Macroautophagy/autophagy has been proposed to play a pivotal role in Cd-mediated bone toxicity. However, the mechanisms that underlie Cd-induced autophagy are not yet completely understood. We demonstrated that Cd treatment increased autophagic flux and inhibition of the autophagic process using Atg7 gene silencing blocked the Cd-induced mesenchymal stem cell death. Mechanistically, Cd activated nuclear translocation of TFE3 but not that of TFEB or MITF, which contributed to the expression of autophagy-related genes and lysosomal biogenesis. Specifically, Cd decreased expression of phospho-AKT (Ser473). The reduction in AKT activity led to dephosphorylation of cytosolic TFE3 at Ser565 and promoted TFE3 nuclear translocation independently of MTORC1. Notably, Cd treatment increased the activity of PPP3/calcineurin, and pharmacological inhibition of PPP3/calcineurin with FK506 suppressed AKT dephosphorylation and TFE3 activity. These results suggest that PPP3/calcineurin negatively regulates AKT phosphorylation and is involved in Cd-induced TFE3-dependent autophagy. Modulation of the PPP3/calcineurin-AKT-TFE3 autophagic-lysosomal machinery may offer novel therapeutic approaches for the treatment of Cd-induced bone damage. Abbreviations: ACTB: actin: beta; AKT: thymoma viral proto-oncogene; AMPK: AMP-activated protein kinase; ATG: autophagy related; Baf A1: bafilomycin A₁; Cd: cadmium; FOXO3: forkhead box O3; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MITF: melanogenesis associated transcription factor; MSC: mesenchymal stem sell; MTORC1: mechanistic target of rapamycin kinase complex 1; RPS6KB1: ribosomal protein S6 kinase: polypeptide 1; SGK1: serum/glucocorticoid regulated kinase 1; SQSTM1/p62: sequestosome 1;TFE3: transcription factor E3; TFEB: transcription factor EB; TFEC: transcription factor EC.

Differentiation of Glial Cells From hiPSCs: Potential Applications in Neurological Diseases and Cell Replacement Therapy

Glial cells are the most abundant cell type in the central nervous system (CNS) and play essential roles in maintaining brain homeostasis, forming myelin, and providing support and protection for neurons, etc. Over the past decade, significant progress has been made in the reprogramming field. Given the limited accessibility of human glial cells, in vitro differentiation of human induced pluripotent stem cells (hiPSCs) into glia may provide not only a valuable research tool for a better understanding of the functions of glia in the CNS but also a potential cellular source for clinical therapeutic purposes. In this review, we will summarize up-to-date novel strategies for the committed differentiation into the three major glial cell types, i.e., astrocyte, oligodendrocyte, and microglia, from hiPSCs, focusing on the non-neuronal cell effects on the pathology of some representative neurological diseases. Furthermore, the application of hiPSC-derived glial cells in neurological disease modeling will be discussed, so as to gain further insights into the development of new therapeutic targets for treatment of neurological disorders.

Emerging Roles of Astrocytes in Neuro-Vascular Unit and the Tripartite Synapse With Emphasis on Reactive Gliosis in the Context of Alzheimer's Disease

Astrocytes, which are five-fold more numerous than neurons in the central nervous system (CNS), are traditionally viewed to provide simple structural and nutritional supports for neurons and to participate in the composition of the blood brain barrier (BBB). In recent years, the active roles of astrocytes in regulating cerebral blood flow (CBF) and in maintaining the homeostasis of the tripartite synapse have attracted increasing attention. More importantly, astrocytes have been associated with the pathogenesis of Alzheimer's disease (AD), a major cause of dementia in the elderly. Although microglia-induced inflammation is considered important in the development and progression of AD, inflammation attributable to astrogliosis may also play crucial roles. A1 reactive astrocytes induced by inflammatory stimuli might be harmful by up-regulating several classical complement cascade genes thereby leading to chronic inflammation, while A2 induced by ischemia might be protective by up-regulating several neurotrophic factors. Here we provide a concise review of the emerging roles of astrocytes in the homeostasis maintenance of the neuro-vascular unit (NVU) and the tripartite synapse with emphasis on reactive astrogliosis in the context of AD, so as to pave the way for further research in this area, and to search for potential therapeutic targets of AD.

Papers of note in Nature 551 (7679)

This week’s articles highlight interactions between astrocytes and neurons that influence both cell types’ form and function; a genetic basis for individual variation in aging; and the mechanism by which an E3 ubiquitin ligase adaptor affects synaptic transmission.