Drosophila Nrf2/Keap1 Mediated Redox Signaling Supports Synaptic Function and Longevity and Impacts on Circadian Activity

The implications of exercise in Drosophila melanogaster: insights into Akt/p38 MAPK/Nrf2 pathway associated with Hsp70 regulation in redox balance maintenance

This study investigated the potential effects of exercise on the responses of energy metabolism, redox balance maintenance, and apoptosis regulation in Drosophila melanogaster to shed more light on the mechanisms underlying the increased performance that this emerging exercise model provides. Three groups were evaluated for seven days: the control (no exercise or locomotor limitations), movement-limited flies (MLF) (no exercise, with locomotor limitations), and EXE (with exercise, no locomotor limitations). The EXE flies demonstrated greater endurance-like tolerance in the swimming test, associated with increased citrate synthase activity, lactate dehydrogenase activity and lactate levels, and metabolic markers in exercise. Notably, the EXE protocol regulated the Akt/p38 MAPK/Nrf2 pathway, which was associated with decreased Hsp70 activation, culminating in glutathione turnover regulation. Moreover, reducing the locomotion environment in the MLF group decreased endurance-like tolerance and did not alter citrate synthase activity, lactate dehydrogenase activity, or lactate levels. The MLF treatment promoted a pro-oxidant effect, altering the Akt/p38 MAPK/Nrf2 pathway and increasing Hsp70 levels, leading to a poorly-regulated glutathione system. Lastly, we demonstrated that exercise could modulate major metabolic responses in Drosophila melanogaster aerobic and anaerobic metabolism, associated with apoptosis and cellular redox balance maintenance in an emergent exercise model.

Activation of the Cap'n'collar C pathway (Nrf2 pathway in vertebrates) signaling in insulin pathway compromised Drosophila melanogaster flies ameliorates the diabetic state upon pro-oxidant conditions

The insulin pathway is a crucial central system for metabolism and growth. The Nrf2 signaling pathway functions to counteract oxidative stress. Here we sought to study the consequences of an oxidative stress challenge to insulin compromised and control adult flies of different ages, varying the activation state of the Nrf2 pathway in flies, the Cap'n'collar C pathway. For this, we employed two different pro-oxidative conditions: 3 % hydrogen peroxide or 20 mM paraquat laced in the food. In both cases, wild type (control) flies die within a few days, yet there are significant differences between males and females, and also within flies of different ages (seven versus thirty days old flies). We repeated the same conditions with young (seven days old) flies that were heterozygous for a loss-of-function mutation in Keap1. There were no significant differences. We then tested two hypomorphic viable conditions of the insulin pathway (heteroallelic combination for the insulin receptor and the S6 Kinase), challenged in the same way: Whereas they also die in the pro-oxidant conditions, they fare significantly better when heterozygous for Keap1, in contrast to controls. We also monitored locomotion in all of these conditions, and, in general, found significant differences between flies without and with a mutant allele (heterozygous) for Keap1. Our results point to altered oxidative stress conditions in diabetic flies. These findings suggest that modest activation of the Cap'n'collar C pathway may be a treatment for diabetic symptoms.

Transcutaneous Electrical Acupoint Stimulation Improves Postoperative Sleep Quality in Patients Undergoing Laparoscopic Gastrointestinal Tumor Surgery: A Prospective, Randomized Controlled Trial

INTRODUCTION

This study was conducted to observe the effect of transcutaneous electrical acupoint stimulation (TEAS) on the postoperative sleep quality of patients undergoing gastrointestinal tumor surgery and to verify the possible mechanism.

METHODS

Eighty-three patients were allocated to the TEAS or Sham group. Patients in the TEAS group received TEAS treatment (disperse-dense waves; frequency, 2/100 Hz) on bilateral Shenmen (HT7), Neiguan (PC6) and Zusanli (ST36) points for 30 min each time, total three times in the perioperative period. In the Sham group, electrodes were placed; however, no current was given. Sleep quality was assessed on the day before surgery (P1) and the first and third days after surgery (D1 and D3) using the Pittsburgh Sleep Quality Index (PSQI) and Athens Insomnia Scale (AIS). Postoperative pain was assessed using visual analog scale (VAS) 72 h postoperatively. The incidences of abdominal distension, dizziness, postoperative nausea and vomiting (PONV) and pulmonary complications were recorded. Serum levels of inflammatory cytokines and the expression of key factors of oxidative stress and key molecules of the nuclear factor erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE) signal pathway were measured.

RESULTS

TEAS ameliorated sleep quality at D1 and D3 (PSQI P < 0.05, AIS P < 0.05) and decreased postoperative pain as demonstrated by lower VAS scores compared to the Sham group (P < 0.05). The incidences of abdominal distension and PONV were also lower in the TEAS group. Markers of oxidative stress were increased (P < 0.05), and the serum concentration of interleukin-6 (IL-6) was significantly lower in the TEAS group. The key mediators of the Nrf2/ARE pathway were enhanced after TEAS.

CONCLUSION

Perioperative TEAS improved postoperative sleep quality, reduced postoperative pain and alleviated postoperative adverse effects in patients undergoing laparoscopic gastrointestinal tumor surgery resection. This may be associated with activating Nrf2/ARE signal pathway and decreasing its inflammatory actions.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ( http://www.chictr.org.cn/index.aspx ), ChiCTR2100054971.

Triose-phosphate isomerase deficiency is associated with a dysregulation of synaptic vesicle recycling in Drosophila melanogaster

Introduction

Numerous neurodegenerative diseases are associated with neuronal dysfunction caused by increased redox stress, often linked to aberrant production of redox-active molecules such as nitric oxide (NO) or oxygen free radicals. One such protein affected by redox-mediated changes is the glycolytic enzyme triose-phosphate isomerase (TPI), which has been shown to undergo 3-nitrotyrosination (a NO-mediated post-translational modification) rendering it inactive. The resulting neuronal changes caused by this modification are not well understood. However, associated glycation-induced cytotoxicity has been reported, thus potentially causing neuronal and synaptic dysfunction via compromising synaptic vesicle recycling.

Methods

This work uses Drosophila melanogaster to identify the impacts of altered TPI activity on neuronal physiology, linking aberrant TPI function and redox stress to neuronal defects. We used Drosophila mutants expressing a missense allele of the TPI protein, M81T, identified in a previous screen and resulting in an inactive mutant of the TPI protein (TPI^M81T , wstd¹). We assessed synaptic physiology at the glutamatergic Drosophila neuromuscular junction (NMJ), synapse morphology and behavioural phenotypes, as well as impacts on longevity.

Results

Electrophysiological recordings of evoked and spontaneous excitatory junctional currents, alongside high frequency train stimulations and recovery protocols, were applied to investigate synaptic depletion and subsequent recovery. Single synaptic currents were unaltered in the presence of the wstd¹ mutation, but frequencies of spontaneous events were reduced. Wstd¹ larvae also showed enhanced vesicle depletion rates at higher frequency stimulation, and subsequent recovery times for evoked synaptic responses were prolonged. A computational model showed that TPI mutant larvae exhibited a significant decline in activity-dependent vesicle recycling, which manifests itself as increased recovery times for the readily-releasable vesicle pool. Confocal images of NMJs showed no morphological or developmental differences between wild-type and wstd¹ but TPI mutants exhibited learning impairments as assessed by olfactory associative learning assays.

Discussion

Our data suggests that the wstd¹ phenotype is partially due to altered vesicle dynamics, involving a reduced vesicle pool replenishment, and altered endo/exocytosis processes. This may result in learning and memory impairments and neuronal dysfunction potentially also presenting a contributing factor to other reported neuronal phenotypes.

Psychostimulants influence oxidative stress and redox signatures: the role of DNA methylation

Objective: Psychostimulant use induces oxidative stress and alters redox imbalance, influencing epigenetic signatures in the central nervous system (CNS). Among the various epigenetic changes, DNA methylation is directly linked to oxidative stress metabolism via critical redox intermediates such as NAD+, S-adenosylmethionine (SAM), and 2-oxoglutarate. Fluctuations in these intermediates directly influence epigenetic signatures, which leads to detectable alterations in gene expression and protein modification. This review focuses on recent advances in the impact of psychostimulant use on redox-imbalance-induced DNA methylation to develop novel epigenetics-based early interventions. Methods: This review is based on collective research data obtained from the PubMed, Science Direct, and Medline databases. The keywords used in the electronic search in these databases were redox, substance use disorder, psychostimulants, DNA methylation, and neurological diseases. Results: Instability in DNA methylation levels and redox expression effects are reported in various behavioral models stimulated by psychostimulants and opioids, indicating the widespread involvement of epigenetic changes in DNA methylation signatures in neurological disorders. Discussion: This review summarizes the need for more studies and experimental evaluations of DNA-methylation-based strategies that may help to understand the association between psychostimulant use and oxidative stress or redox-linked metabolic recalibration influencing neuronal impairments.

Dual Oxidase, a Hydrogen-Peroxide-Producing Enzyme, Regulates Neuronal Oxidative Damage and Animal Lifespan in Drosophila melanogaster

Reducing the oxidative stress in neurons extends lifespan in Drosophila melanogaster, highlighting the crucial role of neuronal oxidative damage in lifespan determination. However, the source of the reactive oxygen species (ROS) that provoke oxidative stress in neurons is not clearly defined. Here, we identify dual oxidase (duox), a calcium-activated ROS-producing enzyme, as a lifespan determinant. Due to the lethality of duox homozygous mutants, we employed a duox heterozygote that exhibited normal appearance and movement. We found that duox heterozygous male flies, which were isogenized with control flies, demonstrated extended lifespan. Neuronal knockdown experiments further suggested that duox is crucial to oxidative stress in neurons. Our findings suggest duox to be a source of neuronal oxidative stress associated with animal lifespan.

Evolutionarily conserved transcription factors as regulators of longevity and targets for geroprotection

Aging is the single largest risk factor for many debilitating conditions, including heart diseases, stroke, cancer, diabetes, and neurodegenerative disorders. While far from understood in its full complexity, it is scientifically well-established that aging is influenced by genetic and environmental factors, and can be modulated by various interventions. One of aging's early hallmarks are aberrations in transcriptional networks, controlling for example metabolic homeostasis or the response to stress. Evidence in different model organisms abounds that a number of evolutionarily conserved transcription factors, which control such networks, can affect lifespan and healthspan across species. These transcription factors thus potentially represent conserved regulators of longevity and are emerging as important targets in the challenging quest to develop treatments to mitigate age-related diseases, and possibly even to slow aging itself. This review provides an overview of evolutionarily conserved transcription factors that impact longevity or age-related diseases in at least one multicellular model organism (nematodes, flies, or mice), and/or are tentatively linked to human aging. Discussed is the general evidence for transcriptional regulation of aging and disease, followed by a more detailed look at selected transcription factor families, the common metabolic pathways involved, and the targeting of transcription factors as a strategy for geroprotective interventions.

Non-additive gene interactions underpin molecular and phenotypic responses in honey bee larvae exposed to imidacloprid and thymol

Understanding the cumulative risk of chemical mixtures at environmentally realistic concentrations is a key challenge in honey bee ecotoxicology. Ecotoxicogenomics, including transcriptomics, measures responses in individual organisms at the molecular level which can provide insights into the mechanisms underlying phenotypic responses induced by one or more stressors and link impacts on individuals to populations. Here, fifth instar honey bee larvae were sampled from a previously reported field experiment exploring the phenotypic impacts of environmentally realistic chronic exposures of the pesticide imidacloprid (5 μg.kg^-1 for six weeks) and the acaricide thymol (250 g.kg^-1 applied via Apiguard gel in-hive for four weeks), both separately and in combination. RNA-seq was used to discover individual and interactive chemical effects on larval gene expression and to uncover molecular mechanisms linked to reported adult and colony phenotypes. The separate and combined treatments had distinct gene expression profiles which represented differentially affected signaling and metabolic pathways. The molecular signature of the mixture was characterised by additive interactions in canonical stress responses associated with oxidative stress and detoxification, and non-additive interactions in secondary responses including developmental, neurological, and immune pathways. Novel emergent impacts on eye development genes correlated with long-term defects in visual learning performance as adults. This is consistent with these chemicals working through independent modes of action that combine to impact common downstream pathways, and highlights the importance of establishing mechanistic links between molecular and phenotypic responses when predicting effects of chemical mixtures on ecologically relevant population outcomes.

Honeysuckle extract (Lonicera pallasii L.) exerts antioxidant properties and extends the lifespan and healthspan of Drosophila melanogaster

Honeysuckle Lonicera pallasii (Lonicera caerulea L.) is an excellent source of anthocyanins which have a number of health-promoting properties mainly associated with antioxidant and anti-inflammatory activities. Cyanidin-3-O-glucoside (C3G) is one of the most common anthocyanins naturally found in honeysuckle. The goal of the present study was to investigate antioxidant and anti-aging properties of Lonicera pallasii (Lonicera caerulea L.) extract (LE) and C3G using red blood cells (RBC) and Drosophila melanogaster models. LE and C3G treatment at a concentration of 100 μM induced enhancement of median and maximum lifespan up to 8%. LE and C3G supplementation at a concentration of 100 μM increased stress resistance up to 10%. The locomotor activity decreased during LE and C3G treatment in 4 and 6 weeks up to 52% in females. The integrity of the intestinal barrier was increased by 4% after LE treatment. These effects were accompanied by increased expression of Hif1 (pro-longevity gene) in response to C3G treatment and decreased expression of Keap1 (anti-longevity gene) after C3G and LE supplementation. RNA interference-mediated knockdown of Sirt6 completely abolished the positive effect obtained of LE and C3G supplementation in males which indicates that lifespan-extending effect is associated with Sirt6 activation. The experiments on the various in-vitro models (including radical scavenging activity and oxidative hemolysis of RBC demonstrated antioxidant and membrane-protective activities of LE and C3G. The present study indicates that Lonicera extract can prolong the lifespan and improve the healthspan of Drosophila model through biological and antioxidant activities.

Understanding the Emerging Link Between Circadian Rhythm, Nrf2 Pathway, and Breast Cancer to Overcome Drug Resistance

The levels of different molecules in the cell are rhythmically cycled by the molecular clock present at the cellular level. The circadian rhythm is closely linked to the metabolic processes in the cells by an underlying mechanism whose intricacies need to be thoroughly investigated. Nevertheless, Nrf2 has been identified as an essential bridge between the circadian clock and cellular metabolism and is activated by the by-product of cellular metabolism like hydrogen peroxide. Once activated it binds to the specific DNA segments and increases the transcription of several genes that play a crucial role in the normal functioning of the cell. The central clock located in the suprachiasmatic nucleus of the anterior hypothalamus synchronizes the timekeeping in the peripheral tissues by integrating the light-dark input from the environment. Several studies have demonstrated the role of circadian rhythm as an effective tumor suppressor. Tumor development is triggered by the stimulation or disruption of signaling pathways at the cellular level as a result of the interaction between cells and environmental stimuli. Oxidative stress is one such external stimulus that disturbs the prooxidant/antioxidant equilibrium due to the loss of control over signaling pathways which destroy the bio-molecules. Altered Nrf2 expression and impaired redox balance are associated with various cancers suggesting that Nrf2 targeting may be used as a novel therapeutic approach for treating cancers. On the other hand, Nrf2 has also been shown to enhance the resistance of cancer cells to chemotherapeutic agents. We believe that maximum efficacy with minimum side effects for any particular therapy can be achieved if the treatment strategy regulates the circadian rhythm. In this review, we discuss the various molecular mechanisms interlinking the circadian rhythm with the Nrf2 pathway and contributing to breast cancer pathogenesis, we also talk about how these two pathways work in close association with the cell cycle which is another oscillatory system, and whether this interplay can be exploited to overcome drug resistance during chemotherapy.

The KEAP1-NRF2 System in Healthy Aging and Longevity

Aging is inevitable, but the inherently and genetically programmed aging process is markedly influenced by environmental factors. All organisms are constantly exposed to various stresses, either exogenous or endogenous, throughout their lives, and the quality and quantity of the stresses generate diverse impacts on the organismal aging process. In the current oxygenic atmosphere on earth, oxidative stress caused by reactive oxygen species is one of the most common and critical environmental factors for life. The Kelch-like ECH-associated protein 1-NFE2-related factor 2 (KEAP1-NRF2) system is a critical defense mechanism of cells and organisms in response to redox perturbations. In the presence of oxidative and electrophilic insults, the thiol moieties of cysteine in KEAP1 are modified, and consequently NRF2 activates its target genes for detoxification and cytoprotection. A number of studies have clarified the contributions of the KEAP1-NRF2 system to the prevention and attenuation of physiological aging and aging-related diseases. Accumulating knowledge to control stress-induced damage may provide a clue for extending healthspan and treating aging-related diseases. In this review, we focus on the relationships between oxidative stress and aging-related alterations in the sensory, glandular, muscular, and central nervous systems and the roles of the KEAP1-NRF2 system in aging processes.

A Crosstalk between the Biorhythms and Gatekeepers of Longevity: Dual Role of Glycogen Synthase Kinase-3

This review discusses genetic and molecular pathways that link circadian timing with metabolism, resulting in the emergence of positive and negative regulatory feedback loops. The Nrf2 pathway is believed to be a component of the anti-aging program responsible for the healthspan and longevity. Nrf2 enables stress adaptation by activating cell antioxidant defense and other metabolic processes via control of expression of over 200 target genes in response to various types of stress. The GSK3 system represents a “regulating valve” that controls fine oscillations in the Nrf2 level, unlike Keap1, which prevents significant changes in the Nrf2 content in the absence of oxidative stress and which is inactivated by the oxidative stress. Furthermore, GSK3 modifies core circadian clock proteins (Bmal1, Clock, Per, Cry, and Rev-erbα). Phosphorylation by GSK3 leads to the inactivation and degradation of circadian rhythm-activating proteins (Bmal1 and Clock) and vice versa to the activation and nuclear translocation of proteins suppressing circadian rhythms (Per and Rev-erbα) with the exception of Cry protein, which is likely to be implicated in the fine tuning of biological clock. Functionally, GSK3 appears to be one of the hubs in the cross-regulation of circadian rhythms and antioxidant defense. Here, we present the data on the crosstalk between the most powerful cell antioxidant mechanism, the Nrf2 system, and the biorhythm-regulating system in mammals, including the impact of GSK3 overexpression and knockout on the Nrf2 signaling. Understanding the interactions between the regulatory cascades linking homeostasis maintenance and cell response to oxidative stress will help in elucidating molecular mechanisms that underlie aging and longevity.

Multidrug Resistance Like Protein 1 Activity in Malpighian Tubules Regulates Lipid Homeostasis in Drosophila

Simple Summary

Multidrug resistance proteins (MRPs) are important for ion transport, toxin/xenobiotic secretion, and signal transduction. Although studies have been undertaken to understand their physiological function, it is not fully known how MRPs may regulate metabolism. We knocked down the expression of Drosophila multidrug-resistance like protein 1 (MRP) in several tissues central to metabolic regulation. Reducing MRP in Malpighian tubules, the functional equivalent to the human kidney, was sufficient to disrupt metabolic homeostasis, owing to abnormal lipid accumulation, as well as changes in feeding behavior. It also increased oxidative stress resistance in adult flies, possibly due to reduced levels of reactive oxygen species.

Abstract

Multidrug resistance proteins (MRPs), members of the ATP-binding cassette transporter (ABC transporter) family, are pivotal for transporting endo- and xenobiotics, which confer resistance to anticancer agents and contribute to the clearance of oxidative products. However, their function in many biological processes is still unclear. We investigated the role of an evolutionarily conserved MRP in metabolic homeostasis by knocking down the expression of Drosophila multidrug-resistance like protein 1 (MRP) in several tissues involved in regulating metabolism, including the gut, fat body, and Malpighian tubules. Interestingly, only suppression of MRP in the Malpighian tubules, the functional equivalent to the human kidney, was sufficient to cause abnormal lipid accumulation and disrupt feeding behavior. Furthermore, reduced Malpighian tubule MRP expression resulted in increased Hr96 (homolog of human pregnane X receptor) expression. Hr96 is known to play a role in detoxification and lipid metabolism processes. Reduced expression of MRP in the Malpighian tubules also conveyed resistance to oxidative stress, as well as reduced normal levels of reactive oxygen species in adult flies. This study reveals that an evolutionarily conserved MRP is required in Drosophila Malpighian tubules for proper metabolic homeostasis.

Sesamin Activates Nrf2/Cnc-Dependent Transcription in the Absence of Oxidative Stress in Drosophila Adult Brains

Sesamin, a major lignin in sesame seeds, possesses health-promoting properties. Sesamin feeding suppresses several aging-related phenotypes such as age-dependent accumulation of damaged proteins in the muscles and neuronal loss in the brains of Drosophila adults with high levels of reactive oxygen species. Sesamin promotes the transcription of several genes that are responsible for oxidative stress, although the underlying mechanism remains unclear. Here, we aimed to demonstrate that sesamin mediates its action through activation of a transcription factor, Nrf2 (Cnc in Drosophila), essential for anti-aging oxidative stress response. Nrf2/Cnc activation was determined using the antioxidant response element, Green Fluorescence Protein reporter, that can monitor Nrf2/Cnc-dependent transcription. We observed strong fluorescence in the entire bodies, particularly in the abdomens and brains, of adult flies fed sesamin. Interestingly, Nrf2/Cnc was strongly activated in neuronal cells, especially in several neuron types, including glutamatergic and cholinergic, and some dopaminergic and/or serotonergic neurons but not in GABAergic neurons or the mushroom bodies of flies fed sesamin. These results indicate that the anti-aging effects of sesamin are exerted via activation of Nrf2/Cnc-dependent transcription to circumvent oxidative stress accumulation in several types of neurons of adult brains. Sesamin could be explored as a potential dietary supplement for preventing neurodegeneration associated with accumulation of oxidative stress.

Minocycline inhibits sleep deprivation-induced aberrant microglial activation and Keap1-Nrf2 expression in mouse hippocampus

Sleep deprivation (SD) is a hallmark of modern society and associated with many neuropsychiatric disorders, including depression and anxiety. However, the cellular and molecular mechanisms underlying SD-associated depression and anxiety remain elusive. Does the neuroinflammation play a role in mediating the effects of SD? In this study, we investigated SD-induced cellular and molecular alterations in the hippocampus and asked whether treatment with an anti-inflammatory drug, minocycline, could attenuate these alterations. We found that SD animals exhibit activated microglia and decreased levels of Keap1 and Nrf2 (antioxidant and anti-inflammatory factors) in the hippocampus. In vivo local field potential recordings show decreased theta and beta oscillations, but increased high gamma oscillations, as a result of SD. Behavioral analysis revealed increased immobility time in the forced swim and tail suspension tests, and decreased sucrose intake in SD mice, all indicative of depressive-like behavior. Moreover, open field test and elevated plus maze test results indicated that SD increases anxiety-like behavior. Interestingly, treatment with the microglial modulator minocycline prevented SD-induced microglial activation, restored Keap1 and Nrf2 levels, normalized neuronal oscillations, and alleviated depressive-like and anxiety-like behavior. The present study reveals that microglial activation and Keap1-Nrf2 signaling play a crucial role in SD-induced behavioral alteration, and that minocycline treatment has a protective effect on these alterations.

The Vhl E3 ubiquitin ligase complex regulates melanisation via sima, cnc and the copper import protein Ctr1A

VHL encodes a tumour suppressor, which possesses E3 ubiquitin ligase activity in complex with EloC and Cul2. In tumour cells or in response to hypoxia, VHL activity is lost, causing accumulation of the transcription factor HIF-1alpha. In this study, we demonstrated that in Drosophila, Rpn9, a regulatory component of the 26 s proteasome, participates in the Vhl-induced proteasomal degradation of sima, the Drosophila orthologue of HIF-1alpha. Knockdown of Vhl induces increased melanisation in the adult fly thorax and concurrent decrease in pigmentation in the abdomen. Both these defects are rescued by knockdown of sima and partially by knockdown of cnc, which encodes the fly orthologue of the transcription factor Nrf2, the master regulator of oxidative stress response. We further show that sima overexpression and Rpn9 knockdown both result in post-translational down-regulation of the copper uptake transporter Ctr1A in the fly eye and that Ctr1A expression exacerbates Vhl knockdown defects in the thorax and rescues these defects in the abdomen. We conclude that Vhl negatively regulates both sima and cnc and that in the absence of Vhl, these transcription factors interact to regulate Ctr1A, copper uptake and consequently melanin formation. We propose a model whereby the co-regulatory relationship between sima and cnc flips between thorax and abdomen: in the thorax, sima is favoured leading to upregulation of Ctr1A; in the abdomen, cnc dominates, resulting in the post-translational downregulation of Ctr1A.

Preserving transcriptional stress responses as an anti-aging strategy

The progressively increasing frailty, morbidity and mortality of aging organisms coincides with, and may be causally related to, their waning ability to adapt to environmental perturbations. Transcriptional responses to challenges, such as oxidative stress or pathogens, diminish with age. This effect is manifest in the declining function of the stress responsive transcription factor Nrf2. Protective gene expression programs that are controlled by the Drosophila Nrf2 homolog, CncC, support homeostasis and longevity. Age‐associated chromatin changes make these genes inaccessible to CncC binding and render them inert to signal‐dependent transcriptional activation in old animals. In a previous paper, we have reported that overexpression of the CncC dimerization partner Maf‐S counteracts this degenerative effect and preserves organism fitness. Building on this work, we show here that Maf‐S overexpression prevents loss of chromatin accessibility and maintains gene responsiveness. Moreover, the same outcome, along with an extension of lifespan, can be achieved by inducing CncC target gene expression pharmacologically throughout adult life. Thus, pharmacological or dietary interventions that can preserve stress responsive gene expression may be feasible anti‐aging strategies.

Tissue-specific Nrf2 signaling protects against methylmercury toxicity in Drosophila neuromuscular development

Methylmercury (MeHg) can elicit cognitive and motor deficits due to its developmental neuro- and myotoxic properties. While previous work has demonstrated that Nrf2 antioxidant signaling protects from MeHg toxicity, in vivo tissue-specific studies are lacking. In Drosophila, MeHg exposure shows greatest developmental toxicity in the pupal stage resulting in failed eclosion (emergence of adults) and an accompanying 'myosphere' phenotype in indirect flight muscles (IFMs). To delineate tissue-specific contributions to MeHg-induced motor deficits, we investigated the potential of Nrf2 signaling in either muscles or neurons to moderate MeHg toxicity. Larva were exposed to various concentrations of MeHg (0-20 µM in food) in combination with genetic modulation of the Nrf2 homolog cap-n-collar C (CncC), or its negative regulator Keap1. Eclosion behavior was evaluated in parallel with the morphology of two muscle groups, the thoracic IFMs and the abdominal dorsal internal oblique muscles (DIOMs). CncC signaling activity was reported with an antioxidant response element construct (ARE-GFP). We observed that DIOMs are distinguished by elevated endogenous ARE-GFP expression, which is only transiently seen in the IFMs. Dose-dependent MeHg reductions in eclosion behavior parallel formation of myospheres in the DIOMs and IFMs, while also increasing ARE-GFP expression in the DIOMs. Modulating CncC signaling via muscle-specific Keap1 knockdown and upregulation gives a rescue and exacerbation, respectively, of MeHg effects on eclosion and myospheres. Interestingly, muscle-specific CncC upregulation and knockdown both induce lethality. In contrast, neuron-specific upregulation of CncC, as well as Keap1 knockdown, rescued MeHg effects on eclosion and myospheres. Our findings indicate that enhanced CncC signaling localized to either muscles or neurons is sufficient to rescue muscle development and neuromuscular function from a MeHg insult. Additionally, there may be distinct roles for CncC signaling in myo-morphogenesis.

Modulated Expression of the Protein Kinase GSK3 in Motor and Dopaminergic Neurons Increases Female Lifespan in Drosophila melanogaster

Most eukaryotic genes express multiple transcripts and proteins, and a sophisticated gene expression strategy plays a crucial role in ensuring the cell-specificity of genetic information and the correctness of phenotypes. The Drosophila melanogaster gene shaggy encodes several isoforms of the conserved glycogen synthase kinase 3 (GSK3), which is vitally important for multiple biological processes. To characterize the phenotypic effects of differential shaggy expression, we explored how the multidirectional modulation of the expression of the main GSK3 isoform, Shaggy-PB, in different tissues and cells affects lifespan. To this end, we used lines with transgenic constructs that encode mutant variants of the protein. The effect of shaggy misexpression on lifespan depended on the direction of the presumed change in GSK3 activity and the type of tissue/cell. The modulation of GSK3 activity in motor and dopaminergic neurons improved female lifespan but caused seemingly negative changes in the structural (mitochondrial depletion; neuronal loss) and functional (perturbed locomotion) properties of the nervous system, indicating the importance of analyzing the relationship between lifespan and healthspan in invertebrate models. Our findings provide new insights into the molecular and cellular bases of lifespan extension, demonstrating that the fine-tuning of transcript-specific shaggy expression in individual groups of neurons is sufficient to provide a sex-specific increase in survival and slow aging.

Mutations in genes cnc or dKeap1 modulate stress resistance and metabolic processes in Drosophila melanogaster

The transcription factor Nrf2 and its negative regulator Keap1 play important roles in the maintenance of redox homeostasis in animal cells. Nrf2 activates defenses against oxidative stress and xenobiotics. Homologs of Nrf2 and Keap1 are present in Drosophila melanogaster (CncC and dKeap1, respectively). The aim of this study was to explore effects of CncC deficiency (due to mutation in the cnc gene) or enhanced activity (due to mutation in the dKeap1 gene) on redox status and energy metabolism of young adult flies in relation to behavioral traits and resistance to a number of stressors. Deficiency in either CncC or dKeap1 delayed pupation and increased climbing activity and heat stress resistance in 2-day-old adult flies. Males and females of the ∆keap1 line shared some similarities such as elevated antioxidant defense as well as lower triacylglyceride and higher glucose levels. Males of the ∆keap1 line also had a higher activity of hexokinase, whereas ∆keap1 females showed higher glycogen levels and lower values of respiratory control and ATP production than flies of the control line. Mutation of cnc gene in allele cnc^EY08884 caused by insertion of P{EPgy2} transposon in cnc promotor did not affect significantly the levels of metabolites and redox parameters, and even activated some components of antioxidant defense. These data suggest that the mutation can be hypomorphic as well as CncC protein can be dispensable for adult fruit flies under physiological conditions. In females, CncC mutation led to lower mitochondrial respiration, higher hexokinase activity and higher fecundity as compared with the control line. Either CncC activation or its deficiency affected stress resistance of flies.

Evolutionary Conservation of Transcription Factors Affecting Longevity

The increasing number of older people is resulting in an increased prevalence of age-related diseases. Research has shown that the ageing process itself is a potential point of intervention. Indeed, gene expression can be optimised for health in older ages through manipulation of transcription factor (TF) activity. This review is focused on the ever-growing number of TFs whose effects on ageing are evolutionarily conserved. These regulate a plethora of functions, including stress resistance, metabolism, and growth. They are engaged in complex interactions within and between different cell types, impacting the physiology of the entire organism. Since ageing is not programmed, the conservation of their effects on lifespan is most likely a reflection of the conservation of their functions in youth.

CRISPR-Generated Nrf2a Loss- and Gain-of-Function Mutants Facilitate Mechanistic Analysis of Chemical Oxidative Stress-Mediated Toxicity in Zebrafish

The transcription factor Nrf2a induces a cellular antioxidant response and provides protection against chemical-induced oxidative stress, as well as playing a critical role in development and disease. Zebrafish are a powerful model to study the role of Nrf2a in these processes but have been limited by reliance on transient gene knockdown techniques or mutants with only partial functional alteration. We developed several lines of zebrafish carrying different null (loss of function, LOF) or hyperactive (gain of function, GOF) mutations to facilitate our understanding of the Nrf2a pathway in protecting against oxidative stress. The mutants confirmed Nrf2a dependence for induction of the antioxidant genes gclc, gstp, prdx1, and gpx1a and identified a role for Nrf2a in the baseline expression of these genes, as well as for sod1. Specifically, the 4-fold induction of gstp by tert-butyl hydroperoxide (tBHP) in wild type fish was abolished in LOF mutants. In addition, baseline gstp expression in GOF mutants increased by 12.6-fold and in LOF mutants was 0.8-fold relative to wild type. Nrf2a LOF mutants showed increased sensitivity to the acute toxicity of cumene hydroperoxide (CHP) and tBHP throughout the first 4 days of development. Conversely, GOF mutants were less sensitive to CHP toxicity during the first 4 days of development and were protected against the toxicity of both hydroperoxides after 4 dpf. Neither gain nor loss of Nrf2a modulated the toxicity of R-(-)-carvone (CAR), despite the ability of this compound to potently induce Nrf2a-dependent antioxidant genes. Similar to other species, GOF zebrafish mutants exhibited significant growth and survival defects. In summary, these new genetic tools can be used to facilitate the identification of downstream gene targets of Nrf2a, better define the role of Nrf2a in the toxicity of environmental chemicals, and further the study of diseases involving altered Nrf2a function.