Regulation of lifespan by neural excitation and REST

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.

Neuroinflammation induces synaptic scaling through IL-1β-mediated activation of the transcriptional repressor REST/NRSF

Neuroinflammation is associated with synapse dysfunction and cognitive decline in patients and animal models. One candidate for translating the inflammatory stress into structural and functional changes in neural networks is the transcriptional repressor RE1-silencing transcription factor (REST) that regulates the expression of a wide cluster of neuron-specific genes during neurogenesis and in mature neurons. To study the cellular and molecular pathways activated under inflammatory conditions mimicking the experimental autoimmune encephalomyelitis (EAE) environment, we analyzed REST activity in neuroblastoma cells and mouse cortical neurons treated with activated T cell or microglia supernatant and distinct pro-inflammatory cytokines. We found that REST is activated by a variety of neuroinflammatory stimuli in both neuroblastoma cells and primary neurons, indicating that a vast transcriptional change is triggered during neuroinflammation. While a dual activation of REST and its dominant-negative splicing isoform REST4 was observed in N2a neuroblastoma cells, primary neurons responded with a pure full-length REST upregulation in the absence of changes in REST4 expression. In both cases, REST upregulation was associated with activation of Wnt signaling and increased nuclear translocation of β-catenin, a well-known intracellular transduction pathway in neuroinflammation. Among single cytokines, IL-1β caused a potent and prompt increase in REST transcription and translation in neurons, which promoted a delayed and strong synaptic downscaling specific for excitatory synapses, with decreased frequency and amplitude of spontaneous synaptic currents, decreased density of excitatory synaptic connections, and decreased frequency of action potential-evoked Ca2+ transients. Most important, the IL-1β effects on excitatory transmission were strictly REST dependent, as conditional deletion of REST completely occluded the effects of IL-1β activation on synaptic transmission and network excitability. Our results demonstrate that REST upregulation represents a new pathogenic mechanism for the synaptic dysfunctions observed under neuroinflammatory conditions and identify the REST pathway as therapeutic target for EAE and, potentially, for multiple sclerosis.

A neuronal blood marker is associated with mortality in old age

Neurofilament light chain (NfL) has emerged as a promising blood biomarker for the progression of various neurological diseases. NfL is a structural protein of nerve cells, and elevated NfL levels in blood are thought to mirror damage to the nervous system. We find that plasma NfL levels increase in humans with age (n = 122; 21-107 years of age) and correlate with changes in other plasma proteins linked to neural pathways. In centenarians (n = 135), plasma NfL levels are associated with mortality equally or better than previously described multi-item scales of cognitive or physical functioning, and this observation was replicated in an independent cohort of nonagenarians (n = 180). Plasma NfL levels also increase in aging mice (n = 114; 2-30 months of age), and dietary restriction, a paradigm that extends lifespan in mice, attenuates the age-related increase in plasma NfL levels. These observations suggest a contribution of nervous system functional deterioration to late-life mortality.

Space Medicine: Why Do Recently Published Papers about Telomere Length Alterations Increase our Uncertainty Rather than Reduce it?

There is a growing interest in examining alterations in telomere length as a reliable biomarker of general health, as well as a marker for predicting later morbidity and mortality. Substantial evidence shows that telomere length is associated with aging; telomere shortening acts as a "counting mechanism" that drives replicative senescence by limiting the mitotic potential of normal (but not malignant) cells. In this Correspondence, we attempt to answer the question of why recently published papers about telomere length alterations increase our uncertainty rather than reduce it. This discussion includes three major research areas regarding telomere length: environmental stressors, aging, and life span. Our review suggests that activation of telomerase activity due to stressors in space might be a double-edged sword with both favorable and unfavorable consequences. The selection of an effect's consequence must clearly elucidate the experimental conditions as well as associated stressors. In this Correspondence, we attempt to answer the question of why recently published papers about telomere length alterations increase our uncertainty rather than reduce it. The selection of an effect's consequence must clearly elucidate the experimental conditions as well as associated stressors. Both positive and negative consequences must be clearly addressed in order to bolster the conclusions, as well as identify future research directions.

Review of How Genetic Research on Segmental Progeroid Syndromes Has Documented Genomic Instability as a Hallmark of Aging But Let Us Now Pursue Antigeroid Syndromes!

The purpose of this early contribution to the new Fellows Forum of this pioneering journal for what is now called Geroscience is to provide an example of how the author's interest in using the emerging tools of human genetics has led to strong support for one of the hallmarks of aging-Genomic Instability. We shall also briefly review our emerging interests in the genetic analysis of what we have called Antigeroid Syndromes. While there has been significant progress in that direction via genetic studies of centenarians, the search for genetic pathways that make individuals unusually resistant or resilient to the ravages of specific geriatric disorders has been comparatively neglected. We refer to these disorders as Unimodal Antigeroid Syndromes. It is our hope that our young colleagues will consider research efforts in that direction.

Impact of supervised beego, a traditional Chinese water-only fasting, on thrombosis and haemostasis

Beego is a traditional Chinese complete water-only fasting practice initially developed for spiritual purposes, later extending to physical fitness purposes. Beego notably includes a psychological induction component that includes meditation and abdominal breathing, light body exercise and ends with a specific gradual refeeding program before returning to a normal diet. Beego has regained its popularity in recent decades in China as a strategy for helping people in subhealthy conditions or with metabolic syndrome, but we are unaware of any studies examining the biological effects of this practice. To address this, we here performed a longitudinal study of beego comprising fasting (7 and 14 day cohorts) and a 7-day programmed refeeding phase. In addition to detecting improvements in cardiovascular physiology and selective reduction of blood pressure in hypertensive subjects, we observed that beego decreased blood triacylglycerol (TG) selectively in TG-high subjects and increased cholesterol in all subjects during fasting; however, the cholesterol levels were normalised after completion of the refeeding program. Strikingly, beego reduced platelet formation, activation, aggregation and degranulation, resulting in an alleviated thrombosis risk, yet maintained haemostasis by sustaining levels of coagulation factors and other haemostatic proteins. Mechanistically, we speculate that downregulation of G6B and MYL9 may influence the observed beego-mediated reduction in platelets. Fundamentally, our study supports that supervised beego reduces thrombosis risk without compromising haemostasis capacity. Moreover, our results support that beego under medical supervision can be implemented as non-invasive intervention for reducing thrombosis risk, and suggest several lines of intriguing inquiry for future studies about this fasting practice (http://www.chictr.org.cn/index.aspx, number, ChiCTR1900027451).

Differential transcript usage unravels gene expression alterations in Alzheimer's disease human brains

Alzheimer's disease (AD) is the leading cause of dementia in aging individuals. Yet, the pathophysiological processes involved in AD onset and progression are still poorly understood. Among numerous strategies, a comprehensive overview of gene expression alterations in the diseased brain could contribute for a better understanding of the AD pathology. In this work, we probed the differential expression of genes in different brain regions of healthy and AD adult subjects using data from three large transcriptomic studies: Mayo Clinic, Mount Sinai Brain Bank (MSBB), and ROSMAP. Using a combination of differential expression of gene and isoform switch analyses, we provide a detailed landscape of gene expression alterations in the temporal and frontal lobes, harboring brain areas affected at early and late stages of the AD pathology, respectively. Next, we took advantage of an indirect approach to assign the complex gene expression changes revealed in bulk RNAseq to individual cell types/subtypes of the adult brain. This strategy allowed us to identify previously overlooked gene expression changes in the brain of AD patients. Among these alterations, we show isoform switches in the AD causal gene amyloid-beta precursor protein (APP) and the risk gene bridging integrator 1 (BIN1), which could have important functional consequences in neuronal cells. Altogether, our work proposes a novel integrative strategy to analyze RNAseq data in AD and other neurodegenerative diseases based on both gene/transcript expression and regional/cell-type specificities.

Aging Effects on the Neuroplastic Attributes of Multisensory Cortical Networks as Triggered by a Computerized Music Reading Training Intervention

The constant increase in the graying population is the result of a great expansion of life expectancy. A smaller expansion of healthy cognitive and brain functioning diminishes the gains achieved by longevity. Music training, as a special case of multisensory learning, may induce restorative neuroplasticity in older ages. The current study aimed to explore aging effects on the cortical network supporting multisensory cognition and to define aging effects on the network's neuroplastic attributes. A computer-based music reading protocol was developed and evaluated via electroencephalography measurements pre- and post-training on young and older adults. Results revealed that multisensory integration is performed via diverse strategies in the two groups: Older adults employ higher-order supramodal areas to a greater extent than lower level perceptual regions, in contrast to younger adults, indicating an age-related shift in the weight of each processing strategy. Restorative neuroplasticity was revealed in the left inferior frontal gyrus and right medial temporal gyrus, as a result of the training, while task-related reorganization of cortical connectivity was obstructed in the group of older adults, probably due to systemic maturation mechanisms. On the contrary, younger adults significantly increased functional connectivity among the regions supporting multisensory integration.

Theanine, Antistress Amino Acid in Tea Leaves, Causes Hippocampal Metabolic Changes and Antidepressant Effects in Stress-Loaded Mice

By comprehensively measuring changes in metabolites in the hippocampus of stress-loaded mice, we investigated the reasons for stress vulnerability and the effect of theanine, i.e., an abundant amino acid in tea leaves, on the metabolism. Stress sensitivity was higher in senescence-accelerated mouse prone 10 (SAMP10) mice than in normal ddY mice when these mice were loaded with stress on the basis of territorial consciousness in males. Group housing was used as the low-stress condition reference. Among the statistically altered metabolites, depression-related kynurenine and excitability-related histamine were significantly higher in SAMP10 mice than in ddY mice. In contrast, carnosine, which has antidepressant-like activity, and ornithine, which has antistress effects, were significantly lower in SAMP10 mice than in ddY mice. The ingestion of theanine, an excellent antistress amino acid, modulated the levels of kynurenine, histamine, and carnosine only in the stress-loaded SAMP10 mice and not in the group-housing mice. Depression-like behavior was suppressed in mice that had ingested theanine only under stress loading. Taken together, changes in these metabolites, such as kynurenine, histamine, carnosine, and ornithine, were suggested to be associated with the stress vulnerability and depression-like behavior of stressed SAMP10 mice. It was also shown that theanine action appears in the metabolism of mice only under stress loading.

Hallmarks of Health

Health is usually defined as the absence of pathology. Here, we endeavor to define health as a compendium of organizational and dynamic features that maintain physiology. The biological causes or hallmarks of health include features of spatial compartmentalization (integrity of barriers and containment of local perturbations), maintenance of homeostasis over time (recycling and turnover, integration of circuitries, and rhythmic oscillations), and an array of adequate responses to stress (homeostatic resilience, hormetic regulation, and repair and regeneration). Disruption of any of these interlocked features is broadly pathogenic, causing an acute or progressive derailment of the system coupled to the loss of numerous stigmata of health.

Cell non-autonomous regulation of health and longevity

As the demographics of the modern world skew older, understanding and mitigating the effects of aging is increasingly important within biomedical research. Recent studies in model organisms demonstrate that the aging process is frequently modified by an organism’s ability to perceive and respond to changes in its environment. Many well-studied pathways that influence aging involve sensory cells, frequently neurons, that signal to peripheral tissues and promote survival during the presence of stress. Importantly, this activation of stress response pathways is often sufficient to improve health and longevity even in the absence of stress. Here, we review the current landscape of research highlighting the importance of cell non-autonomous signaling in modulating aging from C. elegans to mammals. We also discuss emerging concepts including retrograde signaling, approaches to mapping these networks, and development of potential therapeutics.

LSD1 is an environmental stress-sensitive negative modulator of the glutamatergic synapse

Along with neuronal mechanisms devoted to memory consolidation –including long term potentiation of synaptic strength as prominent electrophysiological correlate, and inherent dendritic spines stabilization as structural counterpart– negative control of memory formation and synaptic plasticity has been described at the molecular and behavioral level. Within this work, we report a role for the epigenetic corepressor Lysine Specific Demethylase 1 (LSD1) as a negative neuroplastic factor whose stress-enhanced activity may participate in coping with adverse experiences. Constitutively increasing LSD1 activity via knocking out its dominant negative splicing isoform neuroLSD1 (neuroLSD1^KO mice), we observed extensive structural, functional and behavioral signs of excitatory decay, including disrupted memory consolidation. A similar LSD1 increase, obtained with acute antisense oligonucleotide-mediated neuroLSD1 splicing knock down in primary neuronal cultures, dampens spontaneous glutamatergic transmission, reducing mEPSCs. Remarkably, LSD1 physiological increase occurs in response to psychosocial stress-induced glutamatergic signaling. Since this mechanism entails neuroLSD1 splicing downregulation, we conclude that LSD1/neuroLSD1 ratio modulation in the hippocampus is instrumental to a negative homeostatic feedback, restraining glutamatergic neuroplasticity in response to glutamate. The active process of forgetting provides memories with salience. With our work, we propose that softening memory traces of adversities could further represent a stress-coping process in which LSD1/neuroLSD1 ratio modulation may help preserving healthy emotional references.

Advances in transcriptome analysis of human brain aging

Aging is associated with gradual deterioration of physiological and biochemical functions, including cognitive decline. Transcriptome profiling of brain samples from individuals of varying ages has identified the whole-transcriptome changes that underlie age-associated cognitive declines. In this review, we discuss transcriptome-based research on human brain aging performed by using microarray and RNA sequencing analyses. Overall, decreased synaptic function and increased immune function are prevalent in most regions of the aged brain. Age-associated gene expression changes are also cell dependent and region dependent and are affected by genotype. In addition, the transcriptome changes that occur during brain aging include different splicing events, intersample heterogeneity, and altered levels of various types of noncoding RNAs. Establishing transcriptome-based hallmarks of human brain aging will improve the understanding of cognitive aging and neurodegenerative diseases and eventually lead to interventions that delay or prevent brain aging.

High neural activity accelerates the decline of cognitive plasticity with age in Caenorhabditis elegans

The ability to learn progressively declines with age. Neural hyperactivity has been implicated in impairing cognitive plasticity with age, but the molecular mechanisms remain elusive. Here, we show that chronic excitation of the Caenorhabditis elegans O₂-sensing neurons during ageing causes a rapid decline of experience-dependent plasticity in response to environmental O₂ concentration, whereas sustaining lower activity of O₂-sensing neurons retains plasticity with age. We demonstrate that neural activity alters the ageing trajectory in the transcriptome of O₂-sensing neurons, and our data suggest that high-activity neurons redirect resources from maintaining plasticity to sustaining continuous firing. Sustaining plasticity with age requires the K⁺-dependent Na⁺/Ca²⁺ (NCKX) exchanger, whereas the decline of plasticity with age in high-activity neurons acts through calmodulin and the scaffold protein Kidins220. Our findings demonstrate directly that the activity of neurons alters neuronal homeostasis to govern the age-related decline of neural plasticity and throw light on the mechanisms involved.

A randomized control trial of meditation compared to music listening to improve cognitive function for breast cancer survivors: Feasibility and acceptability

BACKGROUND

and Purpose: Many breast cancer survivors (BCS) experience persistent cognitive and psychological changes associated with their cancer and/or treatment and that have limited treatment options. Therefore, the purpose of this study was to explore the feasibility and effects of a Kirtan Kriya meditation (KK) intervention on cognitive and psychological symptoms compared to an attention control condition, classical music listening (ML), in BCS.

MATERIALS AND METHODS

A randomized control trial design was used. Participants completed eight-week interventions. Cognitive function and psychological symptoms were measured at baseline and post-intervention. Mixed analysis of variance models were examined for all cognitive and psychological outcomes.

RESULTS

27 BCS completed the study. Intervention adherence was 88%. Both groups improved in perceived cognitive impairments, cognition related quality of life, verbal memory, and verbal fluency (p's < 0.01). There were no significant group by time effects for cognitive and psychological outcomes, except stress. The ML group reported lower stress at time 2 (p < 0.05).

CONCLUSION

KK and ML are feasible, acceptable, and cost-effective interventions that may be beneficial for survivors' cognition and psychological symptoms. Both interventions were easy to learn, low cost, and required just 12 min/day. Meditation or music listening could offer providers evidence-based suggestions to BCS experiencing cognitive symptoms.

CLINICAL TRIALS REGISTRATION NUMBER

NCT03696056.

Modeling neurodegeneration in Caenorhabditis elegans

The global burden of neurodegenerative diseases underscores the urgent need for innovative strategies to define new drug targets and disease-modifying factors. The nematode Caenorhabditis elegans has served as the experimental subject for multiple transformative discoveries that have redefined our understanding of biology for ∼60 years. More recently, the considerable attributes of C. elegans have been applied to neurodegenerative diseases, including amyotrophic lateral sclerosis, Alzheimer's disease, Parkinson's disease and Huntington's disease. Transgenic nematodes with genes encoding normal and disease variants of proteins at the single- or multi-copy level under neuronal-specific promoters limits expression to select neuronal subtypes. The anatomical transparency of C. elegans affords the use of co-expressed fluorescent proteins to follow the progression of neurodegeneration as the animals age. Significantly, a completely defined connectome facilitates detailed understanding of the impact of neurodegeneration on organismal health and offers a unique capacity to accurately link cell death with behavioral dysfunction or phenotypic variation in vivo. Moreover, chemical treatments, as well as forward and reverse genetic screening, hasten the identification of modifiers that alter neurodegeneration. When combined, these chemical-genetic analyses establish critical threshold states to enhance or reduce cellular stress for dissecting associated pathways. Furthermore, C. elegans can rapidly reveal whether lifespan or healthspan factor into neurodegenerative processes. Here, we outline the methodologies employed to investigate neurodegeneration in C. elegans and highlight numerous studies that exemplify its utility as a pre-clinical intermediary to expedite and inform mammalian translational research.

Summary: While unsurpassed as an experimental system for fundamental biology, Caenorhabditis elegans remains undervalued for its translational potential. Here, we highlight significant outcomes from, and resources available for, C. elegans-based research into neurodegenerative disorders.

Soticlestat, a novel cholesterol 24-hydroxylase inhibitor shows a therapeutic potential for neural hyperexcitation in mice

Cholesterol 24-hydroxylase (CH24H) is a brain-specific enzyme that converts cholesterol into 24S-hydroxycholesterol, the primary mechanism of cholesterol catabolism in the brain. The therapeutic potential of CH24H activation has been extensively investigated, whereas the effects of CH24H inhibition remain poorly characterized. In this study, the therapeutic potential of CH24H inhibition was investigated using a newly identified small molecule, soticlestat (TAK-935/OV935). The biodistribution and target engagement of soticlestat was assessed in mice. CH24H-knockout mice showed a substantially lower level of soticlestat distribution in the brain than wild-type controls. Furthermore, brain-slice autoradiography studies demonstrated the absence of [³H]soticlestat staining in CH24H-knockout mice compared with wild-type mice, indicating a specificity of soticlestat binding to CH24H. The pharmacodynamic effects of soticlestat were characterized in a transgenic mouse model carrying mutated human amyloid precursor protein and presenilin 1 (APP/PS1-Tg). These mice, with excitatory/inhibitory imbalance and short life-span, yielded a remarkable survival benefit when bred with CH24H-knockout animals. Soticlestat lowered brain 24S-hydroxycholesterol in a dose-dependent manner and substantially reduced premature deaths of APP/PS1-Tg mice at a dose lowering brain 24S-hydroxycholesterol by approximately 50%. Furthermore, microdialysis experiments showed that soticlestat can suppress potassium-evoked extracellular glutamate elevations in the hippocampus. Taken together, these data suggest that soticlestat-mediated inhibition of CH24H may have therapeutic potential for diseases associated with neural hyperexcitation.

Interactions among IGF-1, AKT2, FOXO1, and FOXO3 variations and between genes and physical activities on physical performance in community-dwelling elders

This study assessed the interactions among IGF-1, AKT2, FOXO1, and FOXO3 variations and the interactions of gene and physical activity on handgrip strength, arm muscle mass-adjusted handgrip (armGrip), gait speed (GS), timed up and go (TUG), and leg press strength (LPS). Nine single nucleotide polymorphisms (SNPs) containing three IGF-1 SNPs (rs6214, rs5742692, and rs35767), two AKT2 SNPs (rs892119 and rs35817154), two FOXO1 SNPs (rs17446593 and rs10507486), and two FOXO3 SNPs (rs9480865 and rs2153960) were genotyped in 472 unrelated elders with a mean age of 73.8 years. We observed significant interactions of IGF-1 SNP rs6214 and rs35767 with regular physical activity on TUG and GS; and AKT2 SNP rs892119 and FOXO3 SNP rs9480865 with regular physical activity on armGrip. Genotype GG of IGF-1 rs6214 and rs35767 in individuals without regular physical activity had poor performance in TUG and GS, as well as GG of AKT2 rs892119 decreased armGrip in individuals without regular physical activity. After FDR adjustment, no significant gene-gene interactions were found. A sedentary lifestyle may increase the risk of impairing physical performance and regular physical activity is a remedy for sarcopenia, even a little regular physical activity can overcome carrying some risk alleles in this pathway.

Reactive Oxygen Species Modulate Activity-Dependent AMPA Receptor Transport in C. elegans

The AMPA subtype of synaptic glutamate receptors (AMPARs) plays an essential role in cognition. Their function, numbers, and change at synapses during synaptic plasticity are tightly regulated by neuronal activity. Although we know that long-distance transport of AMPARs is essential for this regulation, we do not understand the associated regulatory mechanisms of it. Neuronal transmission is a metabolically demanding process in which ATP consumption and production are tightly coupled and regulated. Aerobic ATP synthesis unavoidably produces reactive oxygen species (ROS), such as hydrogen peroxide, which are known modulators of calcium signaling. Although a role for calcium signaling in AMPAR transport has been described, there is little understanding of the mechanisms involved and no known link to physiological ROS signaling. Here, using real-time in vivo imaging of AMPAR transport in the intact C. elegans nervous system, we demonstrate that long-distance synaptic AMPAR transport is bidirectionally regulated by calcium influx and activation of calcium/calmodulin-dependent protein kinase II. Quantification of in vivo calcium dynamics revealed that modest, physiological increases in ROS decrease calcium transients in C. elegans glutamatergic neurons. By combining genetic and pharmacological manipulation of ROS levels and calcium influx, we reveal a mechanism in which physiological increases in ROS cause a decrease in synaptic AMPAR transport and delivery by modulating activity-dependent calcium signaling. Together, our results identify a novel role for oxidant signaling in the regulation of synaptic AMPAR transport and delivery, which in turn could be critical for coupling the metabolic demands of neuronal activity with excitatory neurotransmission.SIGNIFICANCE STATEMENT Synaptic AMPARs are critical for excitatory synaptic transmission. The disruption of their synaptic localization and numbers is associated with numerous psychiatric, neurologic, and neurodegenerative conditions. However, very little is known about the regulatory mechanisms controlling transport and delivery of AMPAR to synapses. Here, we describe a novel physiological signaling mechanism in which ROS, such as hydrogen peroxide, modulate AMPAR transport by modifying activity-dependent calcium signaling. Our findings provide the first evidence in support of a mechanistic link between physiological ROS signaling, AMPAR transport, localization, and excitatory transmission. This is of fundamental and clinical significance since dysregulation of intracellular calcium and ROS signaling is implicated in aging and the pathogenesis of several neurodegenerative disorders, including Alzheimer's and Parkinson's disease.

Synergy between amyloid-β and tau in Alzheimer's disease

Patients with Alzheimer's disease (AD) present with both extracellular amyloid-β (Aβ) plaques and intracellular tau-containing neurofibrillary tangles in the brain. For many years, the prevailing view of AD pathogenesis has been that changes in Aβ precipitate the disease process and initiate a deleterious cascade involving tau pathology and neurodegeneration. Beyond this 'triggering' function, it has been typically presumed that Aβ and tau act independently and in the absence of specific interaction. However, accumulating evidence now suggests otherwise and contends that both pathologies have synergistic effects. This could not only help explain negative results from anti-Aβ clinical trials but also suggest that trials directed solely at tau may need to be reconsidered. Here, drawing from extensive human and disease model data, we highlight the latest evidence base pertaining to the complex Aβ-tau interaction and underscore its crucial importance to elucidating disease pathogenesis and the design of next-generation AD therapeutic trials.

Schizophrenia and Epigenetic Aging Biomarkers: Increased Mortality, Reduced Cancer Risk, and Unique Clozapine Effects

BACKGROUND

Schizophrenia (SZ) is associated with increased all-cause mortality, smoking, and age-associated proteins, yet multiple previous studies found no association between SZ and biological age using Horvath's epigenetic clock, a well-established aging biomarker based on DNA methylation. However, numerous epigenetic clocks that may capture distinct aspects of aging have been developed. This study tested the hypothesis that altered aging in SZ manifests in these other clocks.

METHODS

We performed a comprehensive analysis of 14 epigenetic clocks categorized according to what they were trained to predict: chronological age, mortality, mitotic divisions, or telomere length. To understand the etiology of biological age differences, we also examined DNA methylation predictors of smoking, alcohol, body mass index, serum proteins, and cell proportions. We independently analyzed 3 publicly available multiethnic DNA methylation data sets from whole blood, a total of 567 SZ cases and 594 nonpsychiatric controls.

RESULTS

All data sets showed accelerations in SZ for the 3 mortality clocks up to 5 years, driven by smoking and elevated levels of 6 age-associated proteins. The 2 mitotic clocks were decelerated in SZ related to antitumor natural killer and CD8T cells, which may help explain conflicting reports about low cancer rates in epidemiological studies of SZ. One cohort with available medication data showed that clozapine is associated with male-specific decelerations up to 7 years in multiple chronological age clocks.

CONCLUSIONS

Our study demonstrates the utility of studying the various epigenetic clocks in tandem and highlights potential mechanisms by which mental illness influences long-term outcomes, including cancer and early mortality.

Lifespan regulation in α/β posterior neurons of the fly mushroom bodies by Rab27

Brain function has been implicated to control the aging process and modulate lifespan. However, continuous efforts remain for the identification of the minimal sufficient brain region and the underlying mechanism for neuronal regulation of longevity. Here, we show that the Drosophila lifespan is modulated by rab27 functioning in a small subset of neurons of the mushroom bodies (MB), a brain structure that shares analogous functions with mammalian hippocampus and hypothalamus. Depleting rab27 in the α/βp neurons of the MB is sufficient to extend lifespan, enhance systemic stress responses, and alter energy homeostasis, all without trade‐offs in major life functions. Within the α/βp neurons, rab27KO causes the mislocalization of phosphorylated S6K thus attenuates TOR signaling, resulting in decreased protein synthesis and reduced neuronal activity. Consistently, expression of dominant‐negative S6K in the α/βp neurons increases lifespan. Furthermore, the expression of phospho‐mimetic S6 in α/βp neurons of rab27KO rescued local protein synthesis and reversed lifespan extension. These findings demonstrate that inhibiting TOR‐mediated protein synthesis in α/βp neurons is sufficient to promote longevity.

Endosomal-lysosomal dysfunction in metabolic diseases and Alzheimer's disease

The endosomal-lysosomal pathways and related autophagic processes are responsible for proteostasis, involving complexes between lysosomes and autophagosomes. Lysosomes are a key component of homeostasis, involved in cell signaling, metabolism, and quality control, and they experience functional compromise in metabolic diseases, aging, and neurodegenerative diseases. Many genetic mutations and risk factor genes associated with proteinopathies, as well as with metabolic diseases like diabetes, negatively influence endocytic trafficking and autophagic clearance. In contrast, health-improving exercise induces autophagy-lysosomal degradation, perhaps promoting efficient digestion of injured organelles so that undamaged organelles ensure cellular healthiness. Reductions in lysosomal hydrolases are implicated in Alzheimer's, Parkinson's, and lysosomal storage diseases, as well as obesity-related pathology, and members of the cathepsin enzyme family are involved in clearing both Aβ42 and α-synuclein. Upregulation of cathepsin hydrolases improves synaptic and memory functions in models of dementia and in exercising humans, thus identifying lysosomal-related systems as vital for healthy cognitive aging.

Intergenerational toxicity of nonylphenol ethoxylate (NP-9) in Caenorhabditis elegans

The ethoxylated isomers of nonylphenol (NPEs, NP-9) are one of the main active ingredients present in nonionic surfactants employed as herbicides, cosmetics, paints, plastics, disinfectants and detergents. These chemicals and their metabolites are commonly found in environmental matrices. The aim of this work was to evaluate the intergenerational toxicity of NP-9 in Caenorhabditis elegans. The lethality, length, width, locomotion and lifespan were investigated in the larval stage L4 of the wild strain N2. Transgenic green fluorescent protein (GFP) strains were employed to estimate changes in relative gene expression. RT-qPCR was utilized to measure mRNA expression for neurotoxicity-related genes (unc-30, unc-25, dop-3, dat-1, mgl-1, and eat-4). Data were obtained from parent worms (P0) and the first generation (F1). Lethality of the nematode was concentration-dependent, with 48 h-LC₅₀ values of 3215 and 1983 μM in P0 and F1, respectively. Non-lethal concentrations of NP-9 reduced locomotion. Lifespan was also decreased by the xenobiotic, but the negative effect was greater in P0 than in F1. Non-monotonic concentration-response curves were observed for body length and width in both generations. The gene expression profile in P0 was different from that registered in F1, although the expression of sod-4, hsp-70, gpx-6 and mtl-2 increased with the surfactant concentration in both generations. None of the tested genes followed a classical concentration-neurotoxicity relationship. In P0, dopamine presented an inverted-U curve, while GABA and glutamate displayed a bimodal type. However, in F1, inverted U-shaped curves were revealed for these genes. In summary, NP-9 induced intergenerational responses in C. elegans through mechanisms involving ROS, and alterations of the GABA, glutamate, and dopamine pathways.

Neuronal regulation of bone marrow stem cell niches

The bone marrow (BM) is the primary site of postnatal hematopoiesis and hematopoietic stem cell (HSC) maintenance. The BM HSC niche is an essential microenvironment which evolves and responds to the physiological demands of HSCs. It is responsible for orchestrating the fate of HSCs and tightly regulates the processes that occur in the BM, including self-renewal, quiescence, engraftment, and lineage differentiation. However, the BM HSC niche is disturbed following hematological stress such as hematological malignancies, ionizing radiation, and chemotherapy, causing the cellular composition to alter and remodeling to occur. Consequently, hematopoietic recovery has been the focus of many recent studies and elucidating these mechanisms has great biological and clinical relevance, namely to exploit these mechanisms as a therapeutic treatment for hematopoietic malignancies and improve regeneration following BM injury. The sympathetic nervous system innervates the BM niche and regulates the migration of HSCs in and out of the BM under steady state. However, recent studies have investigated how sympathetic innervation and signaling are dysregulated under stress and the subsequent effect they have on hematopoiesis. Here, we provide an overview of distinct BM niches and how they contribute to HSC regulatory processes with a particular focus on neuronal regulation of HSCs under steady state and stress hematopoiesis.

Termination of acute stress response by the endocannabinoid system is regulated through lysine-specific demethylase 1-mediated transcriptional repression of 2-AG hydrolases ABHD6 and MAGL

Acute environmental stress rarely implies long-lasting neurophysiological and behavioral alterations. On the contrary, chronic stress exerts a potent toxic effect at the glutamatergic synapse whose altered physiology has been recognized as a core trait of neuropsychiatric disorders. The endocannabinoid system (ECS) plays an important role in the homeostatic response to acute stress. In particular, stress induces synthesis of endocannabinoid (eCB) 2-arachidonyl glycerol (2-AG). 2-AG stimulates presynaptic cannabinoid 1 (CB1) receptor contributing to stress response termination through inhibition of glutamate release, restraining thereafter anxiety arousal. We employ mouse models of stress response coupled to gene expression analyses, unravelling that in response to acute psychosocial stress in the mouse hippocampus, ECS-mediated synaptic modulation is enhanced via transcriptional repression of two enzymes involved in 2-AG degradation: α/β-hydrolase domain containing 6 (ABHD6) and monoacylglycerol lipase (MAGL). Such a process is orchestrated by the epigenetic corepressor LSD1 who directly interacts with promoter regulatory regions of Abhd6 and Magl. Remarkably, negative transcriptional control of Abhd6 and Magl is lost in the hippocampus upon chronic psychosocial stress, possibly contributing to trauma-induced drift of synapse physiology toward uncontrolled glutamate transmission. We previously showed that in mice lysine-specific demethylase 1 (LSD1) increases its hippocampal expression in response to psychosocial stress preventing excessive consolidation of anxiety-related plasticity. In this work, we unravel a nodal epigenetic modulation of eCB turn over, shedding new light on the molecular substrate of converging stress-terminating effects displayed by ECS and LSD1.

Mild Inactivation of RE-1 Silencing Transcription Factor (REST) Reduces Susceptibility to Kainic Acid-Induced Seizures

RE-1 Silencing Transcription factor (REST) controls several steps in neural development by modulating the expression of a wide range of neural genes. Alterations in REST expression have been associated with the onset of epilepsy; however, whether such alterations are deleterious or represent a protective homeostatic response remains elusive. To study the impact of REST modulation on seizure propensity, we developed a tool for its negative modulation in vivo. The tool is composed of the paired-amphipathic helix 1 (PAH1) domain, a competitive inhibitor of REST activation by mSin3, fused to the light-oxygen-voltage sensing 2 (LOV2) domain of Avena sativa phototropin 1, a molecular switch to alternatively hide or expose the PAH1 inhibitor. We employed the C450A and I539E light-independent AsLOV2 variants to mimic the closed (inactive) and open (active) states of LOV2-PAH1, respectively. Recombinant AAV1/2 viral particles (rAAVs) allowed LOV2-PAH1 expression in HEK293T cells and primary neurons, and efficiently transduced hippocampal neurons in vivo. mRNA expression analysis revealed an increased expression of several neuronal genes in the hippocampi of mice expressing the open probe. AAV-transduced mice received a single dose of kainic acid (KA), a treatment known to induce a transient increase of REST levels in the hippocampus. Remarkably, mice expressing the active variant displayed a reduced number of KA-induced seizures, which were less severe compared to mice carrying the inactive probe. These data support the validity of our tool to modulate REST activity in vivo and the potential impact of REST modulation on epileptogenesis.

Theanine, the Main Amino Acid in Tea, Prevents Stress-Induced Brain Atrophy by Modifying Early Stress Responses

Chronic stress can impair the health of human brains. An important strategy that may prevent the accumulation of stress may be the consumption of functional foods. When senescence-accelerated mice prone 10 (SAMP10), a stress-sensitive strain, were loaded with stress using imposed male mouse territoriality, brain volume decreased. However, in mice that ingested theanine (6 mg/kg), the main amino acid in tea leaves, brain atrophy was suppressed, even under stress. On the other hand, brain atrophy was not clearly observed in a mouse strain that aged normally (Slc:ddY). The expression level of the transcription factor Npas4 (neuronal PAS domain protein 4), which regulates the formation and maintenance of inhibitory synapses in response to excitatory synaptic activity, decreased in the hippocampus and prefrontal cortex of stressed SAMP10 mice, but increased in mice that ingested theanine. Lipocalin 2 (Lcn2), the expression of which increased in response to stress, was significantly high in the hippocampus and prefrontal cortex of stressed SAMP10 mice, but not in mice that ingested theanine. These data suggest that Npas4 and Lcn2 are involved in the brain atrophy and stress vulnerability of SAMP10 mice, which are prevented by the consumption of theanine, causing changes in the expression of these genes.

Increased REST to Optimize Life Span?

Reduced levels of neural activity are associated with a longer life span in the nematode Caenorhabditis elegans and in mice. Augmented neural activity is associated with a shorter life span. Recent studies show that levels of repressor element 1-silencing transcription factor (REST) increase with normal aging in mice and humans, and reduce neuronal excitation. In C. elegans, increased expression of spr-4, a functional REST homologue, increased the worm life span and is required for classical life span increase mediated by reduced DAF-2/insulin-IGF-1 and increased DAF-16. Preliminary evidence shows that REST and FOXO1, a DAF-16, homologue increase during mammalian aging, and that REST activity is needed for the age-related FOXO1 increase. On the contrary, REST is activated in epilepsy and plays a role in the pathogenesis of Huntington's disease. A simple unifying hypothesis suggests that REST is a "goldilocks-effect factor": too little REST promotes excitotoxic activity, which in turn leads to neurodegenerative diseases such as Alzheimer's. Appropriate increased levels of REST maintain the excitation/inhibition (E-I) balance by reducing potential excitotoxic activity. Increased levels of REST beyond this are toxic as neurons become dysfunctional due to loss of a neuronal phenotype.