Keap1/Nrf2 signaling regulates oxidative stress tolerance and lifespan in Drosophila

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.

Modulation of muscle redox and protein aggregation rescues lethality caused by mutant lamins

Mutations in the human LMNA gene cause a collection of diseases called laminopathies, which includes muscular dystrophy and dilated cardiomyopathy. The LMNA gene encodes lamins, filamentous proteins that form a meshwork on the inner side of the nuclear envelope. How mutant lamins cause muscle disease is not well understood, and treatment options are currently limited. To understand the pathological functions of mutant lamins so that therapies can be developed, we generated new Drosophila models and human iPS cell-derived cardiomyocytes. In the Drosophila models, muscle-specific expression of the mutant lamins caused nuclear envelope defects, cytoplasmic protein aggregation, activation of the Nrf2/Keap1 redox pathway, and reductive stress. These defects reduced larval motility and caused death at the pupal stage. Patient-derived cardiomyocytes expressing mutant lamins showed nuclear envelope deformations. The Drosophila models allowed for genetic and pharmacological manipulations at the organismal level. Genetic interventions to increase autophagy, decrease Nrf2/Keap1 signaling, or lower reducing equivalents partially suppressed the lethality caused by mutant lamins. Moreover, treatment of flies with pamoic acid, a compound that inhibits the NADPH-producing malic enzyme, partially suppressed lethality. Taken together, these studies have identified multiple new factors as potential therapeutic targets for LMNA-associated muscular dystrophy.

Honey bee sHSP are responsive to diverse proteostatic stresses and potentially promising biomarkers of honey bee stress

The pollination services provided by the honey bee are critical in both natural and agricultural ecosystems. Honey bee colonies in the United States have suffered from an increased rate of die-off in recent years, stemming from a complex set of interacting stresses that remain poorly described. Defining specific common cellular processes and cellular stress responses impacted by multiple stressors represent a key step in understanding these synergies. Proteotoxic stresses negatively impact protein synthesis, folding, and degradation. Diverse proteotoxic stresses induce expression of genes encoding small heat shock proteins (sHSP) of the expanded lethal (2) essential for life (l(2)efl) gene family. In addition to upregulation by the Integrated Stress Response (ISR), the Heat Shock Response (HSR), and the Oxidative Stress Response (OSR), our data provide first evidence that sHSP genes are upregulated by the Unfolded Protein Response (UPR). As these genes appear to be part of a core stress response that could serve as a useful biomarker for cellular stress in honey bees, we designed and tested an RT-LAMP assay to detect increased l(2)efl gene expression in response to heat-stress. While this assay provides a powerful proof of principle, further work will be necessary to link changes in sHSP gene expression to colony-level outcomes, to adapt our preliminary assay into a Point of Care Testing (POCT) assay appropriate for use as a diagnostic tool for use in the field, and to couple assay results to management recommendations.

Carbon dots up-regulate heme oxygenase-1 expression towards acute lung injury therapy

Pneumonia is a kind of inflammation, which can cause high morbidity and mortality, and the treatment of pneumonia has received widespread attention. Heme oxygenase-1 (HMOX1) is a cell protective enzyme and can generate an anti-inflammatory response. Here, we demonstrate that degradable carbon dots (from L-ascorbic acid, CDs-1) can up-regulate the expression of HMOX1 in animal cells and tissues, which has a therapeutic effect on LPS-induced acute lung injury in mice. It was confirmed from in vitro experiments that CDs-1 could significantly up-regulate the expression of mRNA and the protein of HMOX1, which can increase the expression of HMOX1 by 5 times in a short time, decreasing the reactive oxygen species level in a cellular inflammation model induced by LPS. Furthermore, a series of in vivo comparative experiments show that CDs-1 could effectively treat acute lung injury and improve the survival rate of mice to 80%. Our work provides a practical way for the treatment of acute inflammation and the promising application of CDs in anti-inflammation.

Lifespan Extension in Long-Lived Vertebrates Rooted in Ecological Adaptation

Contemporary studies on aging and longevity have largely overlooked the role that adaptation plays in lifespan variation across species. Emerging evidence indicates that the genetic signals of extended lifespan may be maintained by natural selection, suggesting that longevity could be a product of organismal adaptation. The mechanisms of adaptation in long-lived animals are believed to account for the modification of physiological function. Here, we first review recent progress in comparative biology of long-lived animals, together with the emergence of adaptive genetic factors that control longevity and disease resistance. We then propose that hitchhiking of adaptive genetic changes is the basis for lifespan changes and suggest ways to test this evolutionary model. As individual adaptive or adaptation-linked mutations/substitutions generate specific forms of longevity effects, the cumulative beneficial effect is largely nonrandom and is indirectly favored by natural selection. We consider this concept in light of other proposed theories of aging and integrate these disparate ideas into an adaptive evolutionary model, highlighting strategies in decoding genetic factors of lifespan control.

Downregulation of Perilipin1 by the Immune Deficiency Pathway Leads to Lipid Droplet Reconfiguration and Adaptation to Bacterial Infection in Drosophila

Lipid droplets (LDs), the highly dynamic intracellular organelles, are critical for lipid metabolism. Dynamic alterations in the configurations and functions of LDs during innate immune responses to bacterial infections and the underlying mechanisms, however, remain largely unknown. In this study, we trace the time-course morphology of LDs in fat bodies of Drosophila after transient bacterial infection. Detailed analysis shows that perilipin1 (plin1), a core gene involved in the regulation of LDs, is suppressed by the immune deficiency signaling, one major innate immune pathway in Drosophila During immune activation, downregulated plin1 promotes the enlargement of LDs, which in turn alleviates immune reaction-associated reactive oxygen species stress. Thus, the growth of LDs is likely an active adaptation to maintain redox homeostasis in response to immune deficiency activation. Therefore, our study provides evidence that plin1 serves as a modulator on LDs' reconfiguration in regulating infection-induced pathogenesis, and plin1 might be a potential therapeutic target for coordinating inflammation resolution and lipid metabolism.

A cis-regulatory element promoting increased transcription at low temperature in cultured ectothermic Drosophila cells

Background

Temperature change affects the myriad of concurrent cellular processes in a non-uniform, disruptive manner. While endothermic organisms minimize the challenge of ambient temperature variation by keeping the core body temperature constant, cells of many ectothermic species maintain homeostatic function within a considerable temperature range. The cellular mechanisms enabling temperature acclimation in ectotherms are still poorly understood. At the transcriptional level, the heat shock response has been analyzed extensively. The opposite, the response to sub-optimal temperature, has received lesser attention in particular in animal species. The tissue specificity of transcriptional responses to cool temperature has not been addressed and it is not clear whether a prominent general response occurs. Cis-regulatory elements (CREs), which mediate increased transcription at cool temperature, and responsible transcription factors are largely unknown.

Results

The ectotherm Drosophila melanogaster with a presumed temperature optimum around 25 °C was used for transcriptomic analyses of effects of temperatures at the lower end of the readily tolerated range (14–29 °C). Comparative analyses with adult flies and cell culture lines indicated a striking degree of cell-type specificity in the transcriptional response to cool. To identify potential cis-regulatory elements (CREs) for transcriptional upregulation at cool temperature, we analyzed temperature effects on DNA accessibility in chromatin of S2R+ cells. Candidate cis-regulatory elements (CREs) were evaluated with a novel reporter assay for accurate assessment of their temperature-dependency. Robust transcriptional upregulation at low temperature could be demonstrated for a fragment from the pastrel gene, which expresses more transcript and protein at reduced temperatures. This CRE is controlled by the JAK/STAT signaling pathway and antagonizing activities of the transcription factors Pointed and Ets97D.

Conclusion

Beyond a rich data resource for future analyses of transcriptional control within the readily tolerated range of an ectothermic animal, a novel reporter assay permitting quantitative characterization of CRE temperature dependence was developed. Our identification and functional dissection of the pst_E1 enhancer demonstrate the utility of resources and assay. The functional characterization of this CoolUp enhancer provides initial mechanistic insights into transcriptional upregulation induced by a shift to temperatures at the lower end of the readily tolerated range.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08057-4.

Antioxidant activities of sulfated Codonopsis polysaccharides in acute oxidative stress

This study aimed to explore the protective effect of sulfated Codonopsis polysaccharides (SCP) on acute oxidative stress. SCP was modified by chlorosulfonic acid-pyridine method from Codonopsis polysaccharides (CP), which had 34.48% of sulfate content determined by ultrasonic-acidic barium chromate spectrophotometry. The analysis of Fourier transform-infrared spectroscopy (FT-IR) appeared an absorption peak of SCP at 811.91 cm^-1 , which related to C-O-SO₃ . In vitro test, the antioxidant activities of CP and SCP was induced by H₂ O₂ in RAW264.7 cells, results indicated that SCP and CP could significantly enhance the activity of superoxide dismutase (SOD), glutathione peroxidase (GDH-Px) and catalase (CAT), and nitric oxide (NO) and decrease the level of malondialdehyde (MDA), reactive oxygen species (ROS), and inducible nitric oxide synthase (iNOS) secreted by RAW264.7 cells compared with modeling group (p < .05). The flow cytometry results also revealed that SCP and CP could markedly inhibit the apoptosis of macrophage induced by acute oxidative stress. In vivo test, 50% ethanol was used to induce mice acute oxidative stress, results indicated that the blood biochemical parameters in mice were restored to normal levels following administration of SCP and CP, andalanineamino transferase (ALT), aspartate transaminase (AST), total protein (TP), albumin (ALB), glucose (GLU), and creatinine (UREA) had significant differences compared with modeling group (p < .05). Quantitative real-time PCR analysis revealed that SCP and CP could promote the expression of Keap1 and Nrf2. In summary, both SCP and CP had protective effects against acute oxidative stress. PRACTICAL APPLICATIONS: Oxidative stress is a kind of stress injury, which can cause a variety of diseases and accelerate physical aging. Codonopsis has many active components, among which Codonopsis polysaccharide has antioxidant effect. Recent studies have found that Codonopsis polysaccharides could be modified by sulfate molecules to obtain higher antioxidant activity. The modified Codonopsis polysaccharides could significantly promote the production of antioxidant enzymes (SOD, CAT, GDH-Px) and reduce the content of oxidative stress marks (ROS, MDA). Moreover, its antioxidant mechanism may be related to the Keap1 /Nrf2 signaling pathway. Therefore, SCP was an effective antioxidant, and could be used as a potential health food with antioxidant and anti-aging effects.

The transcription factor Xrp1 is required for PERK-mediated antioxidant gene induction in Drosophila

PERK is an endoplasmic reticulum (ER) transmembrane sensor that phosphorylates eIF2α to initiate the Unfolded Protein Response (UPR). eIF2α phosphorylation promotes stress-responsive gene expression most notably through the transcription factor ATF4 that contains a regulatory 5’ leader. Possible PERK effectors other than ATF4 remain poorly understood. Here, we report that the bZIP transcription factor Xrp1 is required for ATF4-independent PERK signaling. Cell-type-specific gene expression profiling in Drosophila indicated that delta-family glutathione-S-transferases (gstD) are prominently induced by the UPR-activating transgene Rh1^G69D. Perk was necessary and sufficient for such gstD induction, but ATF4 was not required. Instead, Perk and other regulators of eIF2α phosphorylation regulated Xrp1 protein levels to induce gstDs. The Xrp1 5’ leader has a conserved upstream Open Reading Frame (uORF) analogous to those that regulate ATF4 translation. The gstD-GFP reporter induction required putative Xrp1 binding sites. These results indicate that antioxidant genes are highly induced by a previously unrecognized UPR signaling axis consisting of PERK and Xrp1.

Mifepristone Increases Life Span of Virgin Female Drosophila on Regular and High-fat Diet Without Reducing Food Intake

Background: The synthetic steroid mifepristone is reported to have anti-obesity and anti-diabetic effects in mammals on normal and high-fat diets (HFD). We previously reported that mifepristone blocks the negative effect on life span caused by mating in female Drosophila melanogaster. Methods: Here we asked if mifepristone could protect virgin females from the life span-shortening effect of HFD. Mifepristone was assayed for effects on life span in virgin females, in repeated assays, on regular media and on media supplemented with coconut oil (HFD). The excrement quantification (EX-Q) assay was used to measure food intake of the flies after 12 days mifepristone treatment. In addition, experiments were conducted to compare the effects of mifepristone in virgin and mated females, and to identify candidate mifepristone targets and mechanisms. Results: Mifepristone increased life span of virgin females on regular media, as well as on media supplemented with either 2.5 or 5% coconut oil. Food intake was not reduced in any assay, and was significantly increased by mifepristone in half of the assays. To ask if mifepristone might rescue virgin females from all life span-shortening stresses, the oxidative stressor paraquat was tested, and mifepristone produced little to no rescue. Analysis of extant metabolomics and transcriptomics data suggested similarities between effects of mifepristone in virgin and mated females, including reduced tryptophan breakdown and similarities to dietary restriction. Bioinformatics analysis identified candidate mifepristone targets, including transcription factors Paired and Extra-extra. In addition to shortening life span, mating also causes midgut hypertrophy and activation of the lipid metabolism regulatory factor SREBP. Mifepristone blocked the increase in midgut size caused by mating, but did not detectably affect midgut size in virgins. Finally, mating increased activity of a SREBP reporter in abdominal tissues, as expected, but reporter activity was not detectably reduced by mifepristone in either mated or virgin females. Conclusion: Mifepristone increases life span of virgin females on regular and HFD without reducing food intake. Metabolomics and transcriptomics analyses suggest some similar effects of mifepristone between virgin and mated females, however reduced midgut size was observed only in mated females. The results are discussed regarding possible mifepristone mechanisms and targets.

Derlin-1 and TER94/VCP/p97 are required for intestinal homeostasis

Adult stem cells are critical for the maintenance of residential tissue homeostasis and functions. However, the roles of cellular protein homeostasis maintenance in stem cell proliferation and tissue homeostasis are not fully understood. Here, we find that Derlin-1 and TER94/VCP/p97, components of the ER-associated degradation (ERAD) pathway, restrain intestinal stem cell proliferation to maintain intestinal homeostasis in adult Drosophila. Depleting any of them results in increased stem cell proliferation and midgut homeostasis disruption. Derlin-1 is specifically expressed in the ER of progenitors and its C-terminus is required for its function. Interestingly, we find that increased stem cell proliferation is resulted from elevated ROS levels and activated JNK signaling in Derlin-1- or TER94-deficient progenitors. Further removal of ROS or inhibition of JNK signaling almost completely suppressed increased stem cell proliferation. Together, these data demonstrate that the ERAD pathway is critical for stem cell proliferation and tissue homeostasis. Thus we provide insights into our understanding of the mechanisms underlying cellular protein homeostasis maintenance (ER protein quality control) in tissue homeostasis and tumor development.

A Role of Stress Sensor Nrf2 in Stimulating Thermogenesis and Energy Expenditure

During chronic cold stress, thermogenic adipocytes generate heat through uncoupling of mitochondrial respiration from ATP synthesis. Recent discovery of various dietary phytochemicals, endogenous metabolites, synthetic compounds, and their molecular targets for stimulating thermogenesis has provided promising strategies to treat or prevent obesity and its associated metabolic diseases. Nuclear factor E2 p45-related factor 2 (Nrf2) is a stress response protein that plays an important role in obesity and metabolisms. However, both Nrf2 activation and Nrf2 inhibition can suppress obesity and metabolic diseases. Here, we summarized and discussed conflicting findings of Nrf2 activities accounting for part of the variance in thermogenesis and energy metabolism. We also discussed the utility of Nrf2-activating mechanisms for their potential applications in stimulating energy expenditure to prevent obesity and improve metabolic deficits.

Single and mixed exposure to cadmium and mercury in Drosophila melanogaster: Molecular responses and impact on post-embryonic development

Heavy metals, like many other chemical elements, are naturally present in the environment; however, the concentrations of these metals in various environmental matrices have increased through their intensive use in many human activities (such as industry, mining and agriculture). Among the heavy metals, cadmium (Cd) and mercury (Hg) induce a wide variety of defects in animals. While the effects of these heavy metals have been widely documented, a single exposure paradigm is typically used. Few studies have focused on evaluating combined exposure to these metals. However, in the environment, animals are confronted with a plethora of substances simultaneously; thus, the presence and origin of such substances must be determined to reduce the sources of contamination. Using the model of the fruit fly Drosophila melanogaster, for which many tools are readily available, we investigated how different concentrations of Cd and Hg in single and combined exposures impact post-embryonic development. In parallel, we evaluated the extended expression pattern of 38 molecular targets used as potential biomarkers of exposure through qPCR. Our results showed that both metals caused developmental delays and mortality in dose-dependent responses. Both metals were able to deregulate genes involved in hormonal control, general stress, and oxidative stress. Importantly, we confirmed synergistic interactions between Cd and Hg. Our results indicate the importance of assessing several biomarkers and their kinetics in mixtures. Drosophila represents a useful model for monitoring the toxicity of substances in polluted environments.

NRF2 and Hypoxia-Inducible Factors: Key Players in the Redox Control of Systemic Iron Homeostasis

Significance: Oxygen metabolism and iron homeostasis are closely linked. Iron facilitates the oxygen-carrying capacity of blood, and its deficiency causes anemia. Conversely, excess free iron is detrimental for stimulating the formation of reactive oxygen species, causing tissue damage. The amount and distribution of iron thus need to be tightly regulated by the liver-expressed hormone hepcidin. This review analyzes the roles of key oxygen-sensing pathways in cellular and systemic regulation of iron homeostasis; specifically, the prolyl hydroxylase domain (PHD)/hypoxia-inducible factor (HIF) and the Kelch-like ECH-associated protein 1/NF-E2 p45-related factor 2 (KEAP1/NRF2) pathways, which mediate tissue adaptation to low and high oxygen, respectively. Recent Advances: In macrophages, NRF2 regulates genes involved in hemoglobin catabolism, iron storage, and iron export. NRF2 was recently identified as the molecular sensor of iron-induced oxidative stress and is responsible for BMP6 expression by liver sinusoidal endothelial cells, which in turn activates hepcidin synthesis by hepatocytes to restore systemic iron levels. Moreover, NRF2 orchestrates the activation of antioxidant defenses that are crucial to protect against iron toxicity. On the contrary, low iron/hypoxia stabilizes renal HIF2a via inactivation of iron-dependent PHD dioxygenases, causing an erythropoietic stimulus that represses hepcidin via an inhibitory effect of erythroferrone on bone morphogenetic proteins. Intestinal HIF2a is also stabilized, increasing the expression of genes involved in dietary iron absorption. Critical Issues: An intimate crosstalk between oxygen-sensing pathways and iron regulatory mechanisms ensures that fluctuations in systemic iron levels are promptly detected and restored. Future Directions: The realization that redox-sensitive transcription factors regulate systemic iron levels suggests novel therapeutic approaches. Antioxid. Redox Signal. 35, 433-452.

The Nrf2-Keap1 pathway is activated by steroid hormone signaling to govern neuronal remodeling

The evolutionarily conserved Nrf2-Keap1 pathway is a key antioxidant response pathway that protects cells/organisms against detrimental effects of oxidative stress. Impaired Nrf2 function is associated with cancer and neurodegenerative diseases in humans. However, the function of the Nrf2-Keap1 pathway in the developing nervous systems has not been established. Here we demonstrate a cell-autonomous role of the Nrf2-Keap1 pathway, composed of CncC/Nrf2, Keap1, and MafS, in governing neuronal remodeling during Drosophila metamorphosis. Nrf2-Keap1 signaling is activated downstream of the steroid hormone ecdysone. Mechanistically, the Nrf2-Keap1 pathway is activated via cytoplasmic-to-nuclear translocation of CncC in an importin- and ecdysone-signaling-dependent manner. Moreover, Nrf2-Keap1 signaling regulates dendrite pruning independent of its canonical antioxidant response pathway, acting instead through proteasomal degradation. This study reveals an epistatic link between the Nrf2-Keap1 pathway and steroid hormone signaling and demonstrates an antioxidant-independent but proteasome-dependent role of the Nrf2-Keap1 pathway in neuronal remodeling.

Ubx-Collier signaling cascade maintains blood progenitors in the posterior lobes of the Drosophila larval lymph gland

Drosophila larval hematopoiesis occurs in a specialized multi-lobed organ called the lymph gland. Extensive characterization of the organ has provided mechanistic insights into events related to developmental hematopoiesis. Spanning from the thoracic to the abdominal segment of the larvae, this organ comprises a pair of primary, secondary, and tertiary lobes. Much of our understanding arises from the studies on the primary lobe, while the secondary and tertiary lobes have remained mostly unexplored. Previous studies have inferred that these lobes are composed of progenitors that differentiate during pupation; however, the mechanistic basis of this extended progenitor state remains unclear. This study shows that posterior lobe progenitors are maintained by a local signaling center defined by Ubx and Collier in the tertiary lobe. This Ubx zone in the tertiary lobe shares several markers with the niche of the primary lobe. Ubx domain regulates the homeostasis of the posterior lobe progenitors in normal development and an immune-challenged scenario. Our study establishes the lymph gland as a model to tease out how the progenitors interface with the dual niches within an organ during development and disorders.

Gastrodin extends the lifespan and protects against neurodegeneration in the Drosophila PINK1 model of Parkinson's disease

Gastrodin is the main bioactive ingredient of a famous Chinese herb Rhizoma Gastrodiae. Many studies have reported that gastrodin has antioxidative and neuroprotective effects, although its effect on longevity and the mechanism of neuroprotection have not been well studied. Here, we use Drosophila melanogaster as a model to investigate the longevity and neuroprotective effects of gastrodin. Gastrodin significantly extended the lifespan, increased the climbing ability, enhanced the resistance to oxidative stress, increased the enzyme activities of superoxide dismutase (SOD) and catalase (CAT), and promoted the expression of anti-oxidative genes in old flies. The food intake, reproduction and starvation resistance were not affected in flies treated with gastrodin. Moreover, gastrodin delayed the onset of Parkinson-like phenotypes in Pink1^B9 mutant flies, including the prolongation of the lifespan, rescue of the climbing ability, rescue of the progressive loss of a cluster of dopaminergic neurons in the protocerebral posterial lateral 1 region, and increase of the dopamine content in the brain. Gastrodin did not ameliorate the tau-induced neurobehavioral deficits in the fly AD model of taupathy. Together, these results indicate that gastrodin could prolong the lifespan by regulating the antioxidant ability, and protect against neurodegeneration in the Pink1^B9 model of PD. This suggests that gastrodin can be considered as an ideal therapeutic candidate for drug development towards anti-aging.

Proteostasis failure and mitochondrial dysfunction leads to aneuploidy-induced senescence

Aneuploidy, an unbalanced number of chromosomes, is highly deleterious at the cellular level and leads to senescence, a stress-induced response characterized by permanent cell-cycle arrest and a well-defined associated secretory phenotype. Here, we use a Drosophila epithelial model to delineate the pathway that leads to the induction of senescence as a consequence of the acquisition of an aneuploid karyotype. Whereas aneuploidy induces, as a result of gene dosage imbalance, proteotoxic stress and activation of the major protein quality control mechanisms, near-saturation functioning of autophagy leads to compromised mitophagy, accumulation of dysfunctional mitochondria, and the production of radical oxygen species (ROS). We uncovered a role of c-Jun N-terminal kinase (JNK) in driving senescence as a consequence of dysfunctional mitochondria and ROS. We show that activation of the major protein quality control mechanisms and mitophagy dampens the deleterious effects of aneuploidy, and we identify a role of senescence in proteostasis and compensatory proliferation for tissue repair.

Cardamonin Inhibited IL-1β Induced Injury by Inhibition of NLRP3 Inflammasome via Activating Nrf2/NQO-1 Signaling Pathway in Chondrocyte

In this study we investigated the role and mechanism of cardamonin on IL-1β induced injury in OA. CHON-001 cells were treated with cardamonin and IL-1β and transfected with silencing nuclear factor erythroid 2-related factor 2 (siNrf2). Cell viability was detected by Cell Counting Kit-8 assay and flow cytometer assay was utilized for cell apoptosis assessment. IL-6, IL-8, TNF-α and Nrf2 mRNA expression was tested by qRT-PCR. Western blot was employed to evaluate MMP-3, MMP-13, Collagen II, Nrf2, NQO-1, NLRP3, Caspase 1 and apoptosis-associated speck-like protein containing a caspase-1 recruitment domain (ASC) protein levels. In CHON-001 cells, IL-1β suppressed cell viability and Collagen II level while promoting cell apoptosis and expression of pro-inflammatory cytokines (IL-6, IL-8, TNF-α), MMPs (MMP-3, MMP-13), NQO-1, and NLRP3 inflammasome (NLRP3, Caspase 1 and ASC), with no significant influence on Nrf2. Cardamonin reversed the effect of IL-1β on cell viability, cell apoptosis, pro-inflammatory cytokines, MMPs, Collagen II, and NLRP3 inflammasome levels. In addition, cardamonin advanced Nrf2 and NQO-1 expression of CHON-001 cells. SiNrf2 reversed the function of cardamonin on IL-1β-induced cell apoptosis and expression of pro-inflammatory cytokines, Nrf2, NQO-1, and NLRP3 inflammasome in chondrocytes. Taken together Cardamonin inhibited IL-1β induced injury by inhibition of NLRP3 inflammasome via activating Nrf2/NQO1 signaling pathway in chondrocyte.

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.

Enhanced NRF2 expression mitigates the decline in neural stem cell function during aging

Although it is known that aging affects neural stem progenitor cell (NSPC) biology in fundamental ways, the underlying dynamics of this process are not fully understood. Our previous work identified a specific critical period (CP) of decline in NSPC activity and function during middle age (13–15 months), and revealed the reduced expression of the redox‐sensitive transcription factor, NRF2, as a key mediator of this process. Here, we investigated whether augmenting NRF2 expression could potentially mitigate the NSPC decline across the identified CP. NRF2 expression in subventricular zone (SVZ) NSPCs was upregulated via GFP tagged recombinant adeno‐associated viral vectors (AAV‐NRF2‐eGFP), and its cellular and behavioral effects compared to animals that received control vectors (AAV‐eGFP). The vectors were administered into the SVZs of aging rats, at time points either before or after the CP. Results indicate that animals that had received AAV‐NRF2‐eGFP, prior to the CP (11 months of age), exhibited substantially improved behavioral function (fine olfactory discrimination and motor tasks) in comparison to those receiving control viruses. Further analysis revealed that NSPC proliferation, self‐renewal, neurogenesis, and migration to the olfactory bulb had significantly increased upon NRF2 upregulation. On the other hand, increasing NRF2 after the CP (at 20 months of age) produced no notable changes in NSPC activity at either cellular or behavioral levels. These results, for the first time, indicate NRF2 pathway modulation as a means to support NSPC function with age and highlight a critical time‐dependency for activating NRF2 to enhance NSPC function.

Nrf2/HO-1 Signaling Activator Acetyl-11-keto-beta Boswellic Acid (AKBA)-Mediated Neuroprotection in Methyl Mercury-Induced Experimental Model of ALS

Methylmercury (MeHg) is a potent neurotoxin that causes neurotoxicity and neuronal cell death. MeHg exposure also leads to oligodendrocyte destruction, glial cell overactivation, and demyelination of motor neurons in the motor cortex and spinal cord. As a result, MeHg plays an important role in the progression of amyotrophic lateral sclerosis (ALS)-like neurocomplications. ALS is a fatal neurodegenerative disorder in which neuroinflammation is the leading cause of further CNS demyelination. Nuclear factor erythroid-2-related factor-2 (Nrf2)/Heme oxygenase-1 (HO-1) signaling pathway was thought to be a potential target for neuroprotection in ALS. Acetyl-11-keto-beta-boswellic acid (AKBA) is a multi-component pentacyclic triterpenoid mixture derived from Boswellia serrata with anti-inflammatory and antioxidant properties. The research aimed to investigate whether AKBA, as a Nrf2 / HO-1 activator, can provide protection against ALS. Thus, we explored the role of AKBA on the Nrf2/HO-1 signaling pathway in a MeHg-induced experimental ALS model. In this study, ALS was induced in Wistar rats by oral gavage of MeHg 5 mg/kg for 21 days. An open field test, force swim test, and grip strength were performed to observe experimental rats' motor coordination behaviors. In contrast, a morris water maze was performed for learning and memory. Administration of AKBA 50 mg/kg and AKBA 100 mg/kg continued from day 22 to 42. Neurochemical parameters were evaluated in the rat's brain homogenate. In the meantime, post-treatment with AKBA significantly improved behavioral, neurochemical, and gross pathological characteristics in the brain of rats by increasing the amount of Nrf2/HO-1 in brain tissue. Collectively, our findings indicated that AKBA could potentially avoid demyelination and encourage remyelination.

Loss of Fis1 impairs proteostasis during skeletal muscle aging in Drosophila

Increased levels of dysfunctional mitochondria within skeletal muscle are correlated with numerous age‐related physiopathological conditions. Improving our understanding of the links between mitochondrial function and muscle proteostasis, and the role played by individual genes and regulatory networks, is essential to develop treatments for these conditions. One potential player is the mitochondrial outer membrane protein Fis1, a crucial fission factor heavily involved in mitochondrial dynamics in yeast but with an unknown role in higher‐order organisms. By using Drosophila melanogaster as a model, we explored the effect of Fis1 mutations generated by transposon Minos‐mediated integration. Mutants exhibited a higher ratio of damaged mitochondria with age as well as elevated reactive oxygen species levels compared with controls. This caused an increase in oxidative stress, resulting in large accumulations of ubiquitinated proteins, accelerated muscle function decline, and mitochondrial myopathies in young mutant flies. Ectopic expression of Fis1 isoforms was sufficient to suppress this phenotype. Loss of Fis1 led to unbalanced mitochondrial proteostasis within fly muscle, decreasing both flight capabilities and lifespan. Fis1 thus clearly plays a role in fly mitochondrial dynamics. Further investigations into the detailed function of Fis1 are necessary for exploring how mitochondrial function correlates with muscle health during aging.

Antioxidant Activity of Hemp (Cannabis sativa L.) Seed Oil in Drosophila melanogaster Larvae under Non-Stress and H2O2-Induced Oxidative Stress Conditions

The oil extracted from hemp seeds has significant nutritional and biological properties due to the unique composition of polyunsaturated fatty acids and various antioxidant compounds. The potential of this oil for the prevention of oxidative stress and for the treatment of oxidative-stress-induced ailments is of increasing interest. Most studies of hemp seed oil were conducted in-vitro, meaning we lack information about effects and activity in vivo. In the present study, we evaluated the hypothesis that hemp seed oil at different concentrations improves the oxidative state of D. melanogaster, under non-stress as well as hydrogen-peroxide-induced stress. We analyzed the effects of hemp seed oil on oxidative stress markers and on the life cycle of D.melanogaster under non-stress and hydrogen-peroxide-induced stress conditions. D.melanogaster larvae were exposed to hemp seed oil concentrations ranging from 12.5 to 125 μL/mL. The results revealed that under non-stress conditions, oil concentrations up to 62.5 µL/mL did not induce negative effects on the life cycle of D. melanogaster and maintained the redox status of the larval cells at similar levels to the control level. Under oxidative stress conditions, biochemical parameters were significantly affected and only two oil concentrations, 18.7 and 31.2 µL/mL, provided protection against hydrogen peroxide stress effects. A higher oil concentration (125 μL/mL) exerted negative effects on the oxidative status and increased larval mortality. The tested oil was characterized chemically by NMR, transesterification, and silylation, followed by GC-MS analyses, and was shown to contain polyunsaturated fatty acid triglycerides and low levels of tocopherols. The high levels of linoleic and linolenic acids in the oil are suggested to be responsible for the observed in vivo antioxidant effects. Taken together, the results show that hemp seed oil is effective for reducing oxidative stress at the cellular level, thus supporting the hypothesis. The obtained results point to the potential of hemp seed oil for the prevention and treatment of conditions caused by the action of reactive oxygen species.

Disentangling the aging gene expression network of termite queens

Background

Most insects are relatively short-lived, with a maximum lifespan of a few weeks, like the aging model organism, the fruit-fly Drosophila melanogaster. By contrast, the queens of many social insects (termites, ants and some bees) can live from a few years to decades. This makes social insects promising models in aging research providing insights into how a long reproductive life can be achieved. Yet, aging studies on social insect reproductives are hampered by a lack of quantitative data on age-dependent survival and time series analyses that cover the whole lifespan of such long-lived individuals. We studied aging in queens of the drywood termite Cryptotermes secundus by determining survival probabilities over a period of 15 years and performed transcriptome analyses for queens of known age that covered their whole lifespan.

Results

The maximum lifespan of C. secundus queens was 13 years, with a median maximum longevity of 11.0 years. Time course and co-expression network analyses of gene expression patterns over time indicated a non-gradual aging pattern. It was characterized by networks of genes that became differentially expressed only late in life, namely after ten years, which associates well with the median maximum lifespan for queens. These old-age gene networks reflect processes of physiological upheaval. We detected strong signs of stress, decline, defense and repair at the transcriptional level of epigenetic control as well as at the post-transcriptional level with changes in transposable element activity and the proteostasis network. The latter depicts an upregulation of protein degradation, together with protein synthesis and protein folding, processes which are often down-regulated in old animals. The simultaneous upregulation of protein synthesis and autophagy is indicative of a stress-response mediated by the transcription factor cnc, a homolog of human nrf genes.

Conclusions

Our results show non-linear senescence with a rather sudden physiological upheaval at old-age. Most importantly, they point to a re-wiring in the proteostasis network and stress as part of the aging process of social insect queens, shortly before queens die.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07649-4.

Metabolically active and polyploid renal tissues rely on graded cytoprotection to drive developmental and homeostatic stress resilience

Body tissues are frequently exposed to stress, from toxic byproducts generated during cellular metabolism through to infection or wounding. Although it is well-established that tissues respond to exogenous injury by rapidly upregulating cytoprotective machinery, how energetically demanding tissues - vulnerable to persistent endogenous insult - withstand stress is poorly understood. Here, we show that the cytoprotective factors Nrf2 and Gadd45 act within a specific renal cell subtype, the energetically and biosynthetically active 'principal' cells, to drive stress resilience during Drosophila renal development and homeostasis. Renal tubules lacking Gadd45 exhibit striking morphogenetic defects (with cell death, inflammatory infiltration and reduced ploidy) and accumulate significant DNA damage in post-embryonic life. In parallel, the transcription factor Nrf2 is active during periods of intense renal physiological activity, where it protects metabolically active renal cells from oxidative damage. Despite its constitutive nature, renal cytoprotective activity must be precisely balanced and sustained at modest sub-injury levels; indeed, further experimental elevation dramatically perturbs renal development and function. We suggest that tissues requiring long-term protection must employ restrained cytoprotective activity, whereas higher levels might only be beneficial if activated transiently pre-emptive to exogenous insult.

Reactive Oxygen Species in intestinal stem cell metabolism, fate and function

Long dismissed as merely harmful respiratory by-products, Reactive Oxygen Species (ROS) have emerged as critical intracellular messengers during cell growth and differentiation. ROS's signaling roles are particularly prominent within the intestine, whose high regenerative capacity is maintained by Intestinal Stem Cells (ISCs). In this review, we outline roles for ROS in ISCs as revealed by studies using Drosophila and mouse model systems. We focus particularly on recent studies highlighting how ROS ties to metabolic adaptations, which ensure energy supply matches demand during ISC activation and differentiation. We describe how declines in these adaptive mechanisms, through aging or pathology, promote reciprocal changes in ISC metabolism and ROS signaling. These changes ultimately contribute to aberrant ISC function, a loss of tissue homeostasis, and a shortened lifespan.

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.

Drosophila as an emerging model organism for studies of food-derived antioxidants

Dietary supplementation with antioxidants provides health benefits by preventing diseases caused by oxidative stress and damage. Consequently, there has been growing interest in the study of antioxidative foods and their active ingredients. Oxidative stress and antioxidative responses are mechanistically conserved from Drosophila to mammals. Therefore, as a well-established model organism with a short life cycle and advantages of genetic manipulation, the fruit fly has been increasingly employed to assess functions of antioxidants in vivo. In this review, the antioxidative defense mechanisms, methods used and assays developed in Drosophila to evaluate antioxidant supplementation, are highlighted. The main manifestations of antioxidation include reduction of reactive species, up-regulation of endogenous antioxidants, inhibition on oxidative damage to biomacromolecules, enhanced resistance against oxidative stress and extension of lifespan, which are related to the activations of nuclear factor erythroid 2-related factor 2-antioxidant response element pathway and other adaptive responses. Moreover, the key considerations and future perspectives for the application of Drosophila models in the studies of food-derived antioxidants are discussed.

Glial Hedgehog signalling and lipid metabolism regulate neural stem cell proliferation in Drosophila

The final size and function of the adult central nervous system (CNS) are determined by neuronal lineages generated by neural stem cells (NSCs) in the developing brain. In Drosophila, NSCs called neuroblasts (NBs) reside within a specialised microenvironment called the glial niche. Here, we explore non-autonomous glial regulation of NB proliferation. We show that lipid droplets (LDs) which reside within the glial niche are closely associated with the signalling molecule Hedgehog (Hh). Under physiological conditions, cortex glial Hh is autonomously required to sustain niche chamber formation. Upon FGF-mediated cortex glial overgrowth, glial Hh non-autonomously activates Hh signalling in the NBs, which in turn disrupts NB cell cycle progression and its ability to produce neurons. Glial Hh's ability to signal to NB is further modulated by lipid storage regulator lipid storage droplet-2 (Lsd-2) and de novo lipogenesis gene fatty acid synthase 1 (Fasn1). Together, our data suggest that glial-derived Hh modified by lipid metabolism mechanisms can affect the neighbouring NB's ability to proliferate and produce neurons.

Transcriptomic profiling of long- and short-lived mutant mice implicates mitochondrial metabolism in ageing and shows signatures of normal ageing in progeroid mice

Genetically modified mouse models of ageing are the living proof that lifespan and healthspan can be lengthened or shortened, and provide a powerful context in which to unravel the molecular mechanisms at work. In this study, we analysed and compared gene expression data from 10 long-lived and 8 short-lived mouse models of ageing. Transcriptome-wide correlation analysis revealed that mutations with equivalent effects on lifespan induce more similar transcriptomic changes, especially if they target the same pathway. Using functional enrichment analysis, we identified 58 gene sets with consistent changes in long- and short-lived mice, 55 of which were up-regulated in long-lived mice and down-regulated in short-lived mice. Half of these sets represented genes involved in energy and lipid metabolism, among which Ppargc1a, Mif, Aldh5a1 and Idh1 were frequently observed. Based on the gene sets with consistent changes, and also the whole transcriptome, the gene expression changes during normal ageing resembled the transcriptome of short-lived models, suggesting that accelerated ageing models reproduce partially the molecular changes of ageing. Finally, we identified new genetic interventions that may ameliorate ageing, by comparing the transcriptomes of 51 mouse mutants not previously associated with ageing to expression signatures of long- and short-lived mice and ageing-related changes.

Proteotoxic stress is a driver of the loser status and cell competition

Cell competition allows winner cells to eliminate less fit loser cells in tissues. In Minute cell competition, cells with a heterozygous mutation in ribosome genes, such as RpS3+/- cells, are eliminated by wild-type cells. How cells are primed as losers is partially understood and it has been proposed that reduced translation underpins the loser status of ribosome mutant, or Minute, cells. Here, using Drosophila, we show that reduced translation does not cause cell competition. Instead, we identify proteotoxic stress as the underlying cause of the loser status for Minute competition and competition induced by mahjong, an unrelated loser gene. RpS3+/- cells exhibit reduced autophagic and proteasomal flux, accumulate protein aggregates and can be rescued from competition by improving their proteostasis. Conversely, inducing proteotoxic stress is sufficient to turn otherwise wild-type cells into losers. Thus, we propose that tissues may preserve their health through a proteostasis-based mechanism of cell competition and cell selection.

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.

Docosahexanoic acid signals through the Nrf2-Nqo1 pathway to maintain redox balance and promote neurite outgrowth

Evidence suggests that n-3 polyunsaturated fatty acids may act as activators of the Nrf2 antioxidant pathway. The antioxidant response, in turn, promotes neuronal differentiation and neurite outgrowth. Nrf2 has recently been suggested to be a cell intrinsic mediator of docosohexanoic acid (DHA) signaling. In the current study, we assessed whether DHA-mediated axodendritic development was dependent on activation of the Nrf2 pathway and whether Nrf2 protected from agrochemical-induced neuritic retraction. Expression profiling of the DHA-enriched Fat-1 mouse brain relative to wild type showed a significant enrichment of genes associated with neuronal development and neuronal projection and genes associated with the Nrf2-transcriptional pathway. Moreover, we found that primary cortical neurons treated with DHA showed a dose-dependent increase in Nrf2 transcriptional activity and Nrf2-target gene expression. DHA-mediated activation of Nrf2 promoted neurite outgrowth and inhibited oxidative stress-induced neuritic retraction evoked by exposure to agrochemicals. Finally, we provide evidence that this effect is largely dependent on induction of the Nrf2-target gene NAD(P)H: (quinone acceptor) oxidoreductase 1 (NQO1), and that silencing of either Nrf2 or Nqo1 blocks the effects of DHA on the axodendritic compartment. Collectively, these data support a role for the Nrf2-NQO1 pathway in DHA-mediated axodendritic development and protection from agrochemical exposure.

An NRF2 Perspective on Stem Cells and Ageing

Redox and metabolic mechanisms lie at the heart of stem cell survival and regenerative activity. NRF2 is a major transcriptional controller of cellular redox and metabolic homeostasis, which has also been implicated in ageing and lifespan regulation. However, NRF2's role in stem cells and their functioning with age is only just emerging. Here, focusing mainly on neural stem cells, which are core to adult brain plasticity and function, we review recent findings that identify NRF2 as a fundamental player in stem cell biology and ageing. We also discuss NRF2-based molecular programs that may govern stem cell state and function with age, and implications of this for age-related pathologies.

Glial Nrf2 signaling mediates the neuroprotection exerted by Gastrodia elata Blume in Lrrk2-G2019S Parkinson's disease

The most frequent missense mutations in familial Parkinson's disease (PD) occur in the highly conserved LRRK2/PARK8 gene with G2019S mutation. We previously established a fly model of PD carrying the LRRK2-G2019S mutation that exhibited the parkinsonism-like phenotypes. An herbal medicine, Gastrodia elata Blume (GE), has been reported to have neuroprotective effects in toxin-induced PD models. However, the underpinning molecular mechanisms of GE beneficiary to G2019S-induced PD remain unclear. Here, we show that these G2019S flies treated with water extracts of GE (WGE) and its bioactive compounds, gastrodin and 4-HBA, displayed locomotion improvement and dopaminergic neuron protection. WGE suppressed the accumulation and hyperactivation of G2019S proteins in dopaminergic neurons and activated the antioxidation and detoxification factor Nrf2 mostly in the astrocyte-like and ensheathing glia. Glial activation of Nrf2 antagonizes G2019S-induced Mad/Smad signaling. Moreover, we treated LRRK2-G2019S transgenic mice with WGE and found that the locomotion declines, the loss of dopaminergic neurons, and the number of hyperactive microglia were restored. WGE also suppressed the hyperactivation of G2019S proteins and regulated the Smad2/3 pathways in the mice brains. We conclude that WGE prevents locomotion defects and the neuronal loss induced by G2019S mutation via glial Nrf2/Mad signaling, unveiling a potential therapeutic avenue for PD.

Context-dependent responses of Drosophila intestinal stem cells to intracellular reactive oxygen species

Reactive oxygen species (ROS) contribute to cellular redox environment and serve as signaling molecules. Excessive ROS can lead to oxidative stress that are involved in a broad spectrum of physiological and pathological conditions. Stem cells have unique ROS regulation while cancer cells frequently show a constitutive oxidative stress that is associated with the invasive phenotype. Antioxidants have been proposed to forestall tumor progression while targeted oxidants have been used to destroy tumor cells. However, the delicate beneficial range of ROS levels for stem cells and tumor cells under distinct contexts remains elusive. Here, we used Drosophila midgut intestinal stem cell (ISCs) as an in vivo model system to tackle this question. The ROS levels of ISCs remained low in comparison to that of differentiated cells and increased with ageing, which was accompanied by elevated proliferation of ISCs in aged Drosophila. Neither upregulation nor downregulation of ROS levels significantly affected ISCs, implicating an intrinsic homeostatic range of ROS in ISCs. Interestingly, we observed similar moderately elevated ROS levels in both tumor-like ISCs induced by Notch (N) depletion and extracellular matrix (ECM)-deprived ISCs induced by β-integrin (mys) depletion. Elevated ROS levels further promoted the proliferation of tumor-like ISCs while reduced ROS levels suppressed the hyperproliferation phenotype; on the other hand, further increased ROS facilitated the survival of ECM-deprived ISCs while reduced ROS exacerbated the loss of ECM-deprived ISCs. However, N- and mys-depleted ISCs, which resembled metastatic tumor cells, harbored even higher ROS levels and were subjected to more severe cell loss, which could be partially prevented by ectopic supply of antioxidant enzymes, implicating a delicate pro-surviving and proliferating range of ROS levels for ISCs. Taken together, our results revealed stem cells can differentially respond to distinct ROS levels under various conditions and suggested that the antioxidant-based intervention of stem cells and tumors should be formulated with caution according to the specific situations.

The Two Cysteines of Tau Protein Are Functionally Distinct and Contribute Differentially to Its Pathogenicity in Vivo

Although Tau accumulation is clearly linked to pathogenesis in Alzheimer's disease and other Tauopathies, the mechanism that initiates the aggregation of this highly soluble protein in vivo remains largely unanswered. Interestingly, in vitro Tau can be induced to form fibrillar filaments by oxidation of its two cysteine residues, generating an intermolecular disulfide bond that promotes dimerization and fibrillization. The recently solved structures of Tau filaments revealed that the two cysteine residues are not structurally equivalent since Cys-322 is incorporated into the core of the fibril, whereas Cys-291 projects away from the core to form the fuzzy coat. Here, we examined whether mutation of these cysteines to alanine affects differentially Tau mediated toxicity and dysfunction in the well-established Drosophila Tauopathy model. Experiments were conducted with both sexes, or with either sex. Each cysteine residue contributes differentially to Tau stability, phosphorylation status, aggregation propensity, resistance to stress, learning, and memory. Importantly, our work uncovers a critical role of Cys-322 in determining Tau toxicity and dysfunction.SIGNIFICANCE STATEMENT Cysteine-291 and Cysteine-322, the only two cysteine residues of Tau present in only 4-Repeat or all isoforms, respectively, have competing functions: as the key residues in the catalytic center, they enable Tau auto-acetylation; and as residues within the microtubule-binding repeat region are important not only for Tau function but also instrumental in the initiation of Tau aggregation. In this study, we present the first in vivo evidence that their substitution leads to differential consequences on Tau's physiological and pathophysiological functions. These differences raise the possibility that cysteine residues play a potential role in determining the functional diversity between isoforms.

Downregulation of the tyrosine degradation pathway extends Drosophila lifespan

Aging is characterized by extensive metabolic reprogramming. To identify metabolic pathways associated with aging, we analyzed age-dependent changes in the metabolomes of long-lived Drosophila melanogaster. Among the metabolites that changed, levels of tyrosine were increased with age in long-lived flies. We demonstrate that the levels of enzymes in the tyrosine degradation pathway increase with age in wild-type flies. Whole-body and neuronal-specific downregulation of enzymes in the tyrosine degradation pathway significantly extends Drosophila lifespan, causes alterations of metabolites associated with increased lifespan, and upregulates the levels of tyrosine-derived neuromediators. Moreover, feeding wild-type flies with tyrosine increased their lifespan. Mechanistically, we show that suppression of ETC complex I drives the upregulation of enzymes in the tyrosine degradation pathway, an effect that can be rescued by tigecycline, an FDA-approved drug that specifically suppresses mitochondrial translation. In addition, tyrosine supplementation partially rescued lifespan of flies with ETC complex I suppression. Altogether, our study highlights the tyrosine degradation pathway as a regulator of longevity.

Stressful development: integrating endoderm development, stress, and longevity

In addition to performing digestion and nutrient absorption, the intestine serves as one of the first barriers to the external environment, crucial for protecting the host from environmental toxins, pathogenic invaders, and other stress inducers. The gene regulatory network (GRN) governing embryonic development of the endoderm and subsequent differentiation and maintenance of the intestine has been well-documented in C. elegans. A key regulatory input that initiates activation of the embryonic GRN for endoderm and mesoderm in this animal is the maternally provided SKN-1 transcription factor, an ortholog of the vertebrate Nrf1 and 2, which, like C. elegans SKN-1, perform conserved regulatory roles in mediating a variety of stress responses across metazoan phylogeny. Other key regulatory factors in early gut development also participate in stress response as well as in innate immunity and aging and longevity. In this review, we discuss the intersection between genetic nodes that mediate endoderm/intestine differentiation and regulation of stress and homeostasis. We also consider how direct signaling from the intestine to the germline, in some cases involving SKN-1, facilitates heritable epigenetic changes, allowing transmission of adaptive stress responses across multiple generations. These connections between regulation of endoderm/intestine development and stress response mechanisms suggest that varying selective pressure exerted on the stress response pathways may influence the architecture of the endoderm GRN, thereby leading to genetic and epigenetic variation in early embryonic GRN regulatory events.

The proteasome beta 5 subunit is essential for sexually divergent adaptive homeostatic responses to oxidative stress in D. melanogaster

Our studies center on the physiological phenomenon of adaptive homeostasis in which very low, signaling levels of an oxidant can induce transient expansion of the baseline homeostatic range of protective mechanisms, resulting in transient stress protection. The 20S proteasome is a major element of such inducible defense enzymes against oxidative stress but the relative importance of each of its three proteolytic subunits, β1, β2, and β5, is only poorly understood. We focused the present studies on determining the role of the β5 subunit in adaptation, survival, and lifespan. Decreased expression of the 20S proteasome β5 subunit (with RNAi) blocked the adaptive increase in the catalytic activities of the 20S proteasome response to signaling levels of H₂O₂ in female flies. Similarly, female-specific adaptive increases in survival following H₂O₂ pretreatment and subsequent toxic challenge was blocked. In contrast, direct overexpression of the 20S proteasome β5 subunit enabled an increased 20S proteasome proteolytic response, but prevented further adaptive homeostatic increases through H₂O₂ signaling, indicating there is a maximum 'ceiling' to the adaptive response. Males showed no adaptive change in proteasomal levels or activity whatsoever with H₂O₂ pretreatment and exhibited no significant impact upon the other 2 proteolytic subunits of the proteasome. However, chronic loss of the β5 subunit led to shortened lifespan in both sexes. Our exploration of the importance of the 20S proteasome β5 subunit in adaptive homeostasis highlights the interconnection between signal transduction pathways and regulated gene expression in sexually divergent responses to oxidative stimulation.

Potential Anti-Aging Substances Derived from Seaweeds

Aging is a major risk factor for many chronic diseases, such as cancer, cardiovascular disease, and diabetes. The exact mechanisms underlying the aging process are not fully elucidated. However, a growing body of evidence suggests that several pathways, such as sirtuin, AMP-activated protein kinase, insulin-like growth factor, autophagy, and nuclear factor erythroid 2-related factor 2 play critical roles in regulating aging. Furthermore, genetic or dietary interventions of these pathways can extend lifespan by delaying the aging process. Seaweeds are a food source rich in many nutrients, including fibers, polyunsaturated fatty acids, vitamins, minerals, and other bioactive compounds. The health benefits of seaweeds include, but are not limited to, antioxidant, anti-inflammatory, and anti-obese activities. Interestingly, a body of studies shows that some seaweed-derived extracts or isolated compounds, can modulate these aging-regulating pathways or even extend lifespans of various animal models. However, few such studies have been conducted on higher animals or even humans. In this review, we focused on potential anti-aging bioactive substances in seaweeds that have been studied in cells and animals mainly based on their anti-aging cellular and molecular mechanisms.

Patent Review (2017-2020) of the Keap1/Nrf2 Pathway Using PatSeer Pro: Focus on Autoimmune Diseases

Research on the antioxidant pathway comprising the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and its cytoplasmic inhibitor Kelch-like ECH-associated protein 1 (Keap1) is ever increasing. As modulators of this pathway have started to be used in clinical trials and clinical practice, Nrf2 has become the subject of several patents. To assess the patent landscape of the last three years on Nrf2 and evaluate the main fields they refer to, we used the web-based tool PatSeer Pro to identify patents mentioning the Nrf2 pathway between January 2017 and May 2020. This search resulted in 509 unique patents that focus on topics such as autoimmune, neurodegenerative, liver, kidney, and lung diseases and refer to modulators (mainly activators) of the Nrf2 pathway as potential treatments. Autoimmunity emerged as the main theme among the topics of Nrf2 patents, including a broad range of diseases, such as systemic sclerosis, systemic lupus erythematosus, multiple sclerosis, inflammatory bowel diseases, Hashimoto's thyroiditis, etc.; however, there was a dearth of experimental support for the respective patents' claims. Given that chronic inflammation is the main element of the pathophysiology of most autoimmune diseases, the majority of patents referring to activation of Nrf2 as a method to treat autoimmune diseases base their claims on the well-established anti-inflammatory role of Nrf2. In conclusion, there is strong interest in securing intellectual property rights relating to the potential use of Nrf2 pathway activators in a variety of diseases, and this trend parallels the rise in related research publications. However, in the case of autoimmunity, more research is warranted to support the potential beneficial effects of Nrf2 modulation in each disease.

Xenobiotic transcription factors CncC and maf regulate expression of CYP321A16 and CYP332A1 that mediate chlorpyrifos resistance in Spodoptera exigua

Insect cytochrome P450 s (P450 s) are associated with the metabolic detoxification of toxic xenobiotics and their constitutive upregulation is often associated with resistance to natural and synthetic toxicants. The P450 s CYP321A16 and CYP332A1 are constitutively overexpressed in an insecticide-resistant strain of beet armyworm, Spodoptera exigua. However, the function and upstream regulation of these two P450 s remain unknown. Here, we investigated the function of CYP321A16 and CYP332A1 in resistance to the organophosphate insecticide, chlorpyrifos and their regulation by the transcription factors CncC and Maf. Transgenic strains of Drosophila melanogaster expressing CYP321A16 or CYP332A1 showed higher levels of tolerance to chlorpyrifos than the control flies with the same genetic background. Furthermore, recombinant CYP321A16 and CYP332A1 proteins metabolized chlorpyrifos. Analysis of the putative promoter sequences of the genes coding for CYP321A16 and CYP332A1 revealed conserved CncC/Maf binding sites. Transfection of luciferase reporter plasmids containing the promoter of CYP450 gene together with CncC and Maf expression plasmids significantly enhanced the activity of the reporter. Promoter truncation identified a site in the promoter of CYP321A16 that is critical for the CncC/Maf binding. These data demonstrate that resistance to chlorpyrifos in S. exigua is conferred by the combined action of CYP321A16 and CYP332A1 and uncovered their regulation by the transcription factors CncC and Maf.

Adipokinetic hormone regulates cytochrome P450-mediated imidacloprid resistance in the brown planthopper, Nilaparvata lugens

Insect resistance to chemical insecticide is a global problem that presents an ongoing threat to sustainable agriculture. Although the increased production of detoxification enzymes has been frequently implicated in resistance development, the mechanisms employed by insecticide-resistant insects for overexpression of these genes remain elusive. Here we report that neuropeptide adipokinetic hormone (AKH) negatively regulates the expression of CYP6ER1 and CYP6AY1, two important cytochrome P450 monooxygenases (P450s) that confer resistance to neonicotinoid imidacloprid in the brown planthopper (BPH). Imidacloprid exposure suppresses AKH synthesis in the susceptible BPH, and AKH is inhibited in the imidacloprid-resistant strain. RNA interference (RNAi) and AKH peptide injection revealed that imidacloprid exposure inhibits the AKH signaling cascade and then provokes reactive oxygen species (ROS) burst. These in turn activate the transcription factors cap 'n' collar isoform-C (CncC) and muscle aponeurosis fibromatosis (MafK). RNAi and ROS scavenger assays showed that ROS induces CYP6ER1 expression by activating CncC and MafK, while ROS mediates induction of CYP6AY1 through another unidentified pathway in the resistant BPH. Collectively, these results provide new insights into the regulation of insecticide resistance and implicate both the neuropeptide AKH-mediated ROS burst and transcription factors are involved in the overexpression of P450 detoxification genes in insecticide-resistant insects.

Transiently "Undead" Enterocytes Mediate Homeostatic Tissue Turnover in the Adult Drosophila Midgut

We reveal surprising similarities between homeostatic cell turnover in adult Drosophila midguts and "undead" apoptosis-induced compensatory proliferation (AiP) in imaginal discs. During undead AiP, immortalized cells signal for AiP, allowing its analysis. Critical for undead AiP is the Myo1D-dependent localization of the initiator caspase Dronc to the plasma membrane. Here, we show that Myo1D functions in mature enterocytes (ECs) to control mitotic activity of intestinal stem cells (ISCs). In Myo1D mutant midguts, many signaling events involved in AiP (ROS generation, hemocyte recruitment, and JNK signaling) are affected. Importantly, similar to AiP, Myo1D is required for membrane localization of Dronc in ECs. We propose that ECs destined to die transiently enter an undead-like state through Myo1D-dependent membrane localization of Dronc, which enables them to generate signals for ISC activity and their replacement. The concept of transiently "undead" cells may be relevant for other stem cell models in flies and mammals.

Effects of selected insecticidal substances on mRNA transcriptome in larvae of Apis mellifera

For the last decade, scientists have reported a loss of honeybee colonies. Multiple factors like parasites, pathogens and pesticides are dealt as possible drivers of honeybee losses. In particular, insecticides are considered as a major factor of pollinator poisoning. We applied sublethal concentrations of four insecticidal substances to honeybee larval food and analyzed the effects on transcriptome. The aim was to identify candidate genes indicating early negative impacts after application of insecticidal substances. Honeybee larvae were kept in-vitro under hive conditions (34-35 °C) and fed with dimethoate, fenoxycarb, chlorantraniliprole and flupyradifurone in sublethal concentrations between day 3-6 after grafting. Larvae at day 4, 6 and 8 were sampled and their transcriptome analyzed. By use of a RT-qPCR array differences in gene expression of selected gene families (immune system, development detoxification) were measured. Targets mainly involved in development, energy metabolism and the immune system were significantly affected by the insecticidal substances tested, selectively inducing genes of the detoxification system, immune response and nutritional stress.

Hydroxylated sphingolipid biosynthesis regulates photoreceptor apical domain morphogenesis

Apical domains of epithelial cells often undergo dramatic changes during morphogenesis to form specialized structures, such as microvilli. Here, we addressed the role of lipids during morphogenesis of the rhabdomere, the microvilli-based photosensitive organelle of Drosophila photoreceptor cells. Shotgun lipidomics analysis performed on mutant alleles of the polarity regulator crumbs, exhibiting varying rhabdomeric growth defects, revealed a correlation between increased abundance of hydroxylated sphingolipids and abnormal rhabdomeric growth. This could be attributed to an up-regulation of fatty acid hydroxylase transcription. Indeed, direct genetic perturbation of the hydroxylated sphingolipid metabolism modulated rhabdomere growth in a crumbs mutant background. One of the pathways targeted by sphingolipid metabolism turned out to be the secretory route of newly synthesized Rhodopsin, a major rhabdomeric protein. In particular, altered biosynthesis of hydroxylated sphingolipids impaired apical trafficking via Rab11, and thus apical membrane growth. The intersection of lipid metabolic pathways with apical domain growth provides a new facet to our understanding of apical growth during morphogenesis.

Low doses of the neonicotinoid insecticide imidacloprid induce ROS triggering neurological and metabolic impairments in Drosophila

Declining insect population sizes are provoking grave concern around the world as insects play essential roles in food production and ecosystems. Environmental contamination by intense insecticide usage is consistently proposed as a significant contributor, among other threats. Many studies have demonstrated impacts of low doses of insecticides on insect behavior, but have not elucidated links to insecticidal activity at the molecular and cellular levels. Here, the histological, physiological, and behavioral impacts of imidacloprid are investigated in Drosophila melanogaster, an experimental organism exposed to insecticides in the field. We show that oxidative stress is a key factor in the mode of action of this insecticide at low doses. Imidacloprid produces an enduring flux of Ca2+ into neurons and a rapid increase in levels of reactive oxygen species (ROS) in the larval brain. It affects mitochondrial function, energy levels, the lipid environment, and transcriptomic profiles. Use of RNAi to induce ROS production in the brain recapitulates insecticide-induced phenotypes in the metabolic tissues, indicating that a signal from neurons is responsible. Chronic low level exposures in adults lead to mitochondrial dysfunction, severe damage to glial cells, and impaired vision. The potent antioxidant, N-acetylcysteine amide (NACA), reduces the severity of a number of the imidacloprid-induced phenotypes, indicating a causal role for oxidative stress. Given that other insecticides are known to generate oxidative stress, this research has wider implications. The systemic impairment of several key biological functions, including vision, reported here would reduce the resilience of insects facing other environmental challenges.