Dysregulation of DAF-16/FOXO3A-mediated stress responses accelerates oxidative DNA damage induced aging

Neuronal IL-17 controls Caenorhabditis elegans developmental diapause through CEP-1/p53

During metazoan development, how cell division and metabolic programs are coordinated with nutrient availability remains unclear. Here, we show that nutrient availability signaled by the neuronal cytokine, ILC-17.1, switches Caenorhabditis elegans development between reproductive growth and dormancy by controlling the activity of the tumor suppressor p53 ortholog, CEP-1. Specifically, upon food availability, ILC-17.1 signaling by amphid neurons promotes glucose utilization and suppresses CEP-1/p53 to allow growth. In the absence of ILC-17.1, CEP-1/p53 is activated, up-regulates cell-cycle inhibitors, decreases phosphofructokinase and cytochrome C expression, and causes larvae to arrest as stress-resistant, quiescent dauers. We propose a model whereby ILC-17.1 signaling links nutrient availability and energy metabolism to cell cycle progression through CEP-1/p53. These studies describe ancestral functions of IL-17 s and the p53 family of proteins and are relevant to our understanding of neuroimmune mechanisms in cancer. They also reveal a DNA damage-independent function of CEP-1/p53 in invertebrate development and support the existence of a previously undescribed C. elegans dauer pathway.

Cisplatin-induced DNA crosslinks trigger neurotoxicity in C. elegans

The anticancer drug cisplatin (CisPt) injures post-mitotic neuronal cells, leading to neuropathy. Furthermore, CisPt triggers cell death in replicating cells. Here, we aim to unravel the relevance of different types of CisPt-induced DNA lesions for evoking neurotoxicity. To this end, we comparatively analyzed wild-type and loss of function mutants of C. elegans lacking key players of specific DNA repair pathways. Deficiency in ercc-1, which is essential for nucleotide excision repair (NER) and interstrand crosslink (ICL) repair, revealed the most pronounced enhancement in CisPt-induced neurotoxicity with respect to the functionality of post-mitotic chemosensory AWA neurons, without inducing neuronal cell death. Potentiation of CisPt-triggered neurotoxicity in ercc-1 mutants was accompanied by complex alterations in both basal and CisPt-stimulated mRNA expression of genes involved in the regulation of neurotransmission, including cat-4, tph-1, mod-1, glr-1, unc-30 and eat-18. Moreover, xpf-1, csb-1, csb-1;xpc-1 and msh-6 mutants were significantly more sensitive to CisPt-induced neurotoxicity than the wild-type, whereas xpc-1, msh-2, brc-1 and dog-1 mutants did not distinguish from the wild-type. The majority of DNA repair mutants also revealed increased basal germline apoptosis, which was analyzed for control. Yet, only xpc-1, xpc-1;csb-1 and dog-1 mutants showed elevated apoptosis in the germline following CisPt treatment. To conclude, we provide evidence that neurotoxicity, including sensory neurotoxicity, is triggered by CisPt-induced DNA intra- and interstrand crosslinks that are subject of repair by NER and ICL repair. We hypothesize that especially ERCC1/XPF, CSB and MSH6-related DNA repair protects from chemotherapy-induced neuropathy in the context of CisPt-based anticancer therapy.

Failure to repair endogenous DNA damage in β-cells causes adult-onset diabetes in mice

Age is the greatest risk factor for the development of type 2 diabetes mellitus (T2DM). Age-related decline in organ function is attributed to the accumulation of stochastic damage, including damage to the nuclear genome. Islets of T2DM patients display increased levels of DNA damage. However, whether this is a cause or consequence of the disease has not been elucidated. Here, we asked if spontaneous, endogenous DNA damage in β-cells can drive β-cell dysfunction and diabetes, via deletion of Ercc1, a key DNA repair gene, in β-cells. Mice harboring Ercc1-deficient β-cells developed adult-onset diabetes as demonstrated by increased random and fasted blood glucose levels, impaired glucose tolerance, and reduced insulin secretion. The inability to repair endogenous DNA damage led to an increase in oxidative DNA damage and apoptosis in β-cells and a significant loss of β-cell mass. Using electron microscopy, we identified β-cells in clear distress that showed an increased cell size, enlarged nuclear size, reduced number of mature insulin granules, and decreased number of mitochondria. Some β-cells were more affected than others consistent with the stochastic nature of spontaneous DNA damage. Ercc1-deficiency in β-cells also resulted in loss of β-cell function as glucose-stimulated insulin secretion and mitochondrial function were impaired in islets isolated from mice harboring Ercc1-deficient β-cells. These data reveal that unrepaired endogenous DNA damage is sufficient to drive β-cell dysfunction and provide a mechanism by which age increases the risk of T2DM.

Iron oxide/silver hybrid nanoparticles impair the cholinergic system and cause reprotoxicity in Caenorhabditis elegans

Iron oxide nanoparticles present superparamagnetic properties that enable their application in various areas, including drug delivery at specific locations in the organism. Silver nanoparticles have potent antimicrobial effects. Although the combination of Fe3O4-NPs and Ag-NPs in one hybrid nanostructure (Fe3O4@Ag-NPs) demonstrated promising targeted biomedical applications, their toxicological effects are unknown and need to be assessed. Caenorhabditis elegans is a promising model for nanotoxicological analysis, as it allows an initial screening of new substances. After exposure to Fe3O4-NPs, Ag-NPs and Fe3O4@Ag-NPs, we observed that hybrid NPs reduced the C. elegans survival and reproduction. Higher concentrations of Fe3O4@Ag-NPs caused an increase in cell apoptosis in the germline and a decrease in egg laying, which was associated with a decrease in worm swimming movements and abnormalities in the cholinergic neurons. Fe3O4@Ag-NPs caused an increase in reactive oxygen species, along with activation of DAF-16 transcription factor. A higher expression of the target genes GST-4::GFP and SOD-3::GFP were evidenced, which suggests the activation of the antioxidant system. Our results indicate the reprotoxicity caused by high levels of Fe3O4@Ag-NPs, as well as cholinergic neurotoxicity and activation of the antioxidant system in C. elegans, suggesting that high concentrations of these nanomaterials can be harmful to living organisms.

Proteomic basis of mortality resilience mediated by FOXO3 longevity genotype

FOXO3 is a ubiquitous transcription factor expressed in response to cellular stress caused by nutrient deprivation, inflammatory cytokines, reactive oxygen species, radiation, hypoxia, and other factors. We showed previously that the association of inherited FOXO3 variants with longevity was the result of partial protection against mortality risk posed by aging-related life-long stressors, particularly cardiometabolic disease. We then referred to the longevity-associated genotypes as conferring "mortality resilience." Serum proteins whose levels change with aging and are associated with mortality risk may be considered as "stress proteins." They may serve as indirect measures of life-long stress. Our aims were to (1) identify stress proteins that increase with aging and are associated with an increased risk of mortality, and (2) to determine if FOXO3 longevity/resilience genotype dampens the expected increase in mortality risk they pose. A total of 4500 serum protein aptamers were quantified using the Somalogic SomaScan proteomics platform in the current study of 975 men aged 71-83 years. Stress proteins associated with mortality were identified. We then used age-adjusted multivariable Cox models to investigate the interaction of stress protein with FOXO3 longevity-associated rs12212067 genotypes. For all the analyses, the p values were corrected for multiple comparisons by false discovery rate. This led to the identification of 44 stress proteins influencing the association of FOXO3 genotype with reduced mortality. Biological pathways were identified for these proteins. Our results suggest that the FOXO3 resilience genotype functions by reducing mortality in pathways related to innate immunity, bone morphogenetic protein signaling, leukocyte migration, and growth factor response.

Protective effects of pumpkin polysaccharide hydrolysates on oxidative stress injury and its potential mechanism - Antioxidant mechanism of pumpkin polysaccharide hydrolysates

Pumpkin polysaccharides (PPe) exhibit multiple bioactive properties, including the ability to reduce blood sugar and lipids. Our prior investigation discovered that hydrolysates (PPe-s) derived from PPe demonstrated stronger antioxidant capabilities than PPe. The objective of the current study was to explore the potential mechanism of PPe-s, utilizing Caenorhabditis elegans and MIN6 cells as models. The results of this investigation revealed that PPe-s exhibited strong scavenging ability towards ABTS⁺ and OH·in vitro. Additionally, PPe-s extended the lifespan of C. elegans under hydrogen peroxide stress (p < 0.05) by upregulating the mRNA expression of daf-16, sod-1, sod-3, and skn-1 (all >1.43-fold, p < 0.05). Furthermore, PPe-s enhanced the proliferation activity of MIN6 cells, induced by alloxan, increased insulin secretion and cAMP levels, and excreted intracellular excessive Ca²⁺ in a concentration-dependent manner. Our study demonstrated that PPe-s upregulated the expression levels of antioxidative-related genes and augmented the antioxidant defense system.

Cellular mechanisms in brain aging: Focus on physiological and pathological aging

Aging is a natural phenomenon characterized by accumulation of cellular damage and debris. Oxidative stress, cellular senescence, sustained inflammation, and DNA damage are the main cellular processes characteristic of aging associated with morphological and functional decline. These effects tend to be more pronounced in tissues with high metabolic rates such as the brain, mainly in regions such as the prefrontal cortex, hippocampus, and amygdala. These regions are highly related to cognitive behavior, and therefore their atrophy usually leads to decline in processes such as memory and learning. These cognitive declines can occur in physiological aging and are exacerbated in pathological aging. In this article, we review the cellular processes that underlie the triggers of aging and how they relate to one another, causing the atrophy of nerve tissue that is typical of aging. The main topic of this review to determine the central factor that triggers all the cellular processes that lead to cellular aging and discriminate between normal and pathological aging. Finally, we review how the use of supplements with antioxidant and anti-inflammatory properties reduces the cognitive decline typical of aging, which reinforces the hypothesis of oxidative stress and cellular damage as contributors of physiological atrophy of aging. Moreover, cumulative evidence suggests their possible use as therapies, which improve the aging population's quality of life.

In Vivo Anti-Alzheimer and Antioxidant Properties of Avocado (Persea americana Mill.) Honey from Southern Spain

There is growing evidence that Alzheimer's disease (AD) can be prevented by reducing risk factors involved in its pathophysiology. Food-derived bioactive molecules can help in the prevention and reduction of the progression of AD. Honey, a good source of antioxidants and bioactive molecules, has been tied to many health benefits, including those from neurological origin. Monofloral avocado honey (AH) has recently been characterized but its biomedical properties are still unknown. The aim of this study is to further its characterization, focusing on the phenolic profile. Moreover, its antioxidant capacity was assayed both in vitro and in vivo. Finally, a deep analysis on the pathophysiological features of AD such as oxidative stress, amyloid-β aggregation, and protein-tau-induced neurotoxicity were evaluated by using the experimental model C. elegans. AH exerted a high antioxidant capacity in vitro and in vivo. No toxicity was found in C. elegans at the dosages used. AH prevented ROS accumulation under AAPH-induced oxidative stress. Additionally, AH exerted a great anti-amyloidogenic capacity, which is relevant from the point of view of AD prevention. AH exacerbated the locomotive impairment in a C. elegans model of tauopathy, although the real contribution of AH remains unclear. The mechanisms under the observed effects might be attributed to an upregulation of daf-16 as well as to a strong ROS scavenging activity. These results increase the interest to study the biomedical applications of AH; however, more research is needed to deepen the mechanisms under the observed effects.

Elucidation of the nematicidal mode of action of grammicin on Caenorhabditis elegans

Grammicin (Gra) is derived from the endophytic fungus Xylaria grammica EL000614 and shows nematicidal activity against the devastating root-knot nematode Meloidogyne incognita in-vitro, in planta, and in-field experiments. However, the mechanism of the nematicidal action of Gra remains unclear. In this study, Gra exposure to the model genetic organism Caenorhabditis elegans affected its L1, L2/3, L4, and young adult stages. In addition, Gra treatment increased the intracellular reactive oxygen species (ROS) levels of C. elegans and M. incognita. Molecular docking interaction analysis indicated that Gra could bind and interact with GCS-1, GST-4, and DAF-16a in order of low binding energy, followed by SOD-3, SKN-1, and DAF-16b. This implies that the anthelmintic action of Gra is related to the oxidative stress response. To validate this mechanism, we examined the expression of the genes involved in the oxidative stress responses following treatment with Gra using transgenic C. elegans strains such as the TJ356 strain zIs356 [daf-16p::daf-16a/b::GFP + rol-6 (su1006)], LD1 ldIs7 [skn-1p::skn-1b/c::GFP + rol-6 (su1006)], LD1171 ldIs3 [gcs-1p::GFP + rol-6 (su1006)], CL2166 dvIs19 [(pAF15) gst-4p::GFP::NLS], and CF1553 strain muIs84 [(pAD76) sod-3p::GFP + rol-6 (su1006)]. Gra treatment caused nuclear translocation of DAF-16/FoxO and enhanced gst-4::GFP expression, but it had no change in sod-3::GFP expression. These results indicate that Gra induces oxidative stress response via phase II detoxification without reduced cellular redox machinery. Gra treatment also inhibited the nuclear localization of SKN-1::GFP in the intestine, which may lead to a condition in which oxidative stress tolerance is insufficient to protect C. elegans by the inactivation of SKN-1, thus inducing nematode lethality. Furthermore, Gra caused the mortality of two mutant strains of C. elegans, CB113 and DA1316, which are resistant to aldicarb and ivermectin, respectively. This indicates that the mode of action of Gra is different from the traditional nematicides currently in use, suggesting that it could help develop novel approaches to control plant-parasitic nematodes.

Cyanidin-3-O-glucoside promotes stress tolerance and lifespan extension of Caenorhabditis elegans exposed to polystyrene via DAF-16 pathway

Microplastic pollution has attracted growing attention due to its prevalent and persistent exposure to general population through the food chain, but few reports have focused on the toxicological prevention of polystyrene (PS). Using the wild-type and mutant strains, this study explored the impacts of PS and cyanidin-3-O-glucoside (C3G) on stress tolerance and lifespan of Caenorhabditis elegans (C. elegans). In N2 nematodes, PS exposure initiated the oxidative stress and subsequent lifespan reduction, while these adverse impacts could be positively improved by C3G treatment. Considering the pivotal role of DAF-16 pathway in stress tolerance and lifespan regulation, the expression of the daf-16 gene and its downstream antioxidant genes (clt-2, hsp-16.1, sod-3, sod-5) were examined, and found to be significantly enhanced by C3G. Since the sod-3 gene was up-regulated the most fold by C3G, the activity of SOD enzyme that encoded by the sod-3 was examined, and could be obviously enhanced upon C3G treatment. This explained the improved oxidative stress and delayed oxidation-associated aging after C3G intervention. Nevertheless, these positive effects of C3G were weakened in daf-16(-) mutant strain (with deleted DAF-16 gene), for which the beneficial effects of C3G in promoting stress resistance and lifespan extension were inhibited. These findings suggested that the DAF-16 gene and its downstream antioxidant genes, have participated in C3G's regulations on redox balance and lifespan that impacted by nano-polystyrene particles. This study highlighted the link between dietary components and environmentally driven disturbance.

Integrated -omics approach reveals persistent DNA damage rewires lipid metabolism and histone hyperacetylation via MYS-1/Tip60

Although DNA damage is intricately linked to metabolism, the metabolic alterations that occur in response to DNA damage are not well understood. We use a DNA repair-deficient model of ERCC1-XPF in Caenorhabditis elegans to gain insights on how genotoxic stress drives aging. Using multi-omic approach, we discover that nuclear DNA damage promotes mitochondrial β-oxidation and drives a global loss of fat depots. This metabolic shift to β-oxidation generates acetyl-coenzyme A to promote histone hyperacetylation and an associated change in expression of immune-effector and cytochrome genes. We identify the histone acetyltransferase MYS-1, as a critical regulator of this metabolic-epigenetic axis. We show that in response to DNA damage, polyunsaturated fatty acids, especially arachidonic acid (AA) and AA-related lipid mediators, are elevated and this is dependent on mys-1. Together, these findings reveal that DNA damage alters the metabolic-epigenetic axis to drive an immune-like response that can promote age-associated decline.

Toxic effects of thallium acetate by acute exposure to the nematode C. elegans

BACKGROUND

Thallium (Tl) is a toxic metalloid and an emerging pollutant due to electronic devices and dispersal nearby base-metal mining. Therefore, Tl poses a threat to human health and especially the long-term impact on younger individuals exposed is still unknown. This study aimed to evaluate the toxic effects of thallium acetate in C. elegans in early larval stages, considering physiological and behavioral endpoints, as well as the Tl absorption and bioaccumulation.

METHODS

Caenorhabditis elegans (C. elegans) was exposed to Thallium acetate (50, 100, 150, 200, 250, 500, and 1000 μM) in the L1 larval stage, with the purpose to observe the toxic effects invoked until adulthood. Transgenic worms strains were transported GFP, reporters to DAF-16 and were used to verify the antioxidant response. ICP-MS quantified total Tl⁺ concentration to evidence Tl uptake and bioaccumulation.

RESULTS

Thallium acetate caused a significant reduction in the number of living worms (p < 0.0001 in 100-1000 μM), a delay in larval development (p < 0.01; p < 0.001 and p < 0.0001 in 100-1000 μM) through the larval stages, and egg production in the worm's uterus was reduced. Thallium acetate also induced behavioral changes. Additionally, thallium acetate activated antioxidant pathway responses in C. elegans by translocating the DAF-16 transcription factor and activation of SOD-3::GFP expression. The Tl⁺ quantification in worms showed its absorption in the L1 larval stage and bioaccumulation in the body after development.

CONCLUSIONS

Thallium acetate reduced survival, delayed development, caused behavioral changes, induced responses inherent to oxidative stress, and serious damage to the worm's reproduction. In addition, C. elegans absorbed and bioaccumulated Tl⁺. Together, our results highlight the impacts of Tl⁺ exposure in the early stages of life, even for a short period.

FOXR1 regulates stress response pathways and is necessary for proper brain development

The forkhead box (Fox) family of transcription factors are highly conserved and play essential roles in a wide range of cellular and developmental processes. We report an individual with severe neurological symptoms including postnatal microcephaly, progressive brain atrophy and global developmental delay associated with a de novo missense variant (M280L) in the FOXR1 gene. At the protein level, M280L impaired FOXR1 expression and induced a nuclear aggregate phenotype due to protein misfolding and proteolysis. RNAseq and pathway analysis showed that FOXR1 acts as a transcriptional activator and repressor with central roles in heat shock response, chaperone cofactor-dependent protein refolding and cellular response to stress pathways. Indeed, FOXR1 expression is increased in response to cellular stress, a process in which it directly controls HSPA6, HSPA1A and DHRS2 transcripts. The M280L mutant compromises FOXR1's ability to respond to stress, in part due to impaired regulation of downstream target genes that are involved in the stress response pathway. Quantitative PCR of mouse embryo tissues show Foxr1 expression in the embryonic brain. Using CRISPR/Cas9 gene editing, we found that deletion of mouse Foxr1 leads to a severe survival deficit while surviving newborn Foxr1 knockout mice have reduced body weight. Further examination of newborn Foxr1 knockout brains revealed a decrease in cortical thickness and enlarged ventricles compared to littermate wild-type mice, suggesting that loss of Foxr1 leads to atypical brain development. Combined, these results suggest FOXR1 plays a role in cellular stress response pathways and is necessary for normal brain development.

Analysis of representative mutants for key DNA repair pathways on healthspan in Caenorhabditis elegans

Although the link between DNA damage and aging is well accepted, the role of different DNA repair proteins on functional/physiological aging is not well-defined. Here, using Caenorhabditis elegans, we systematically examined the effect of three DNA repair genes involved in key genome stability pathways. We assayed multiple health proxies including molecular, functional and resilience measures to define healthspan. Loss of XPF-1/ERCC-1, a protein involved in nucleotide excision repair (NER), homologous recombination (HR) and interstrand crosslink (ICL) repair, showed the highest impairment of functional and stress resilience measures along with a shortened lifespan. brc-1 mutants, with a well-defined role in HR and ICL are short-lived and highly sensitive to acute stressors, specifically oxidative stress. In contrast, ICL mutant, fcd-2 did not impact lifespan or most healthspan measures. Our efforts also uncover that DNA repair mutants show high sensitivity to oxidative stress with age, suggesting that this measure could act as a primary proxy for healthspan. Together, these data suggest that impairment of multiple DNA repair genes can drive functional/physiological aging. Further studies to examine specific DNA repair genes in a tissue specific manner will help dissect the importance and mechanistic role of these repair systems in biological aging.

Combinatorial Approach Using Caenorhabditis elegans and Mammalian Systems for Aging Research

Aging is associated with functional and structural declines in organisms over time. Organisms as diverse as the nematode Caenorhabditis elegans and mammals share signaling pathways that regulate aging and lifespan. In this review, we discuss recent combinatorial approach to aging research employing C. elegans and mammalian systems that have contributed to our understanding of evolutionarily conserved aging-regulating pathways. The topics covered here include insulin/IGF-1, mechanistic target of rapamycin (mTOR), and sirtuin signaling pathways; dietary restriction; autophagy; mitochondria; and the nervous system. A combinatorial approach employing high-throughput, rapid C. elegans systems, and human model mammalian systems is likely to continue providing mechanistic insights into aging biology and will help develop therapeutics against age-associated disorders.

Zoledronate extends healthspan and survival via the mevalonate pathway in a FOXO-dependent manner

Over recent decades, increased longevity has not been paralleled by extended healthspan, resulting in more years spent with multiple diseases in older age. As such, interventions to improve healthspan are urgently required. Zoledronate is a nitrogen containing bisphosphonate, which inhibits the farnesyl pyrophosphate synthase (FPPS) enzyme, central to the mevalonate pathway. It is already used clinically to prevent fractures in osteoporotic patients, who have been reported to derive unexpected and unexplained survival benefits. Using Drosophila as a model we determined the effects of Zoledronate on lifespan, parameters of healthspan (climbing ability and intestinal dysplasia) and the ability to confer resistance to oxidative stress using a combination of genetically manipulated Drosophila strains and Western blotting. Our study shows that Zoledronate extended lifespan, improved climbing activity and reduced intestinal epithelial dysplasia and permeability with age. Mechanistic studies showed that Zoledronate conferred resistance to oxidative stress and reduced accumulation of X-ray-induced DNA damage via inhibition of FPPS. Moreover, Zoledronate was associated with inhibition of pAKT in the mTOR pathway downstream of the mevalonate pathway and required dFOXO for its action, both molecules associated with increased longevity. Taken together, our work indicates that Zoledronate, a drug already widely used to prevent osteoporosis and dosed only once a year, modulates important mechanisms of ageing. Its repurposing holds great promise as a treatment to improve healthspan.

The aqueous extract of Fridericia chica grown in northern Colombia ameliorates toxicity induced by Tergitol on Caenorhabditis elegans

The aqueous extract of fallen leaves from Fridericia chica (Bonpl.) L.G. Lohmann is utilized as a remedy in communities at northern Colombia. Traditional uses include wound healing, gastrointestinal inflammation, leukemia and psoriasis, among others. The aims of this research were to evaluate the potential of the aqueous extract of fallen leaves of F. chica (AEFchica) to inhibit ethoxylated nonylphenol (Tergitol)-induced toxicity in Caenorhabditis elegans; and to identify its main components. The pharmacological properties of AEFchica was evaluated using a Tergitol-induced toxicity model in Caenorhabditis elegans. Lethality, locomotion, reproduction, and DAF-16 nuclear translocation were quantified. The chemical composition of AEFchica was carried out using ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry. AEFchica induced very little lethality on C. elegans (5.6%) even at high concentrations (10,000 μg/mL). The extract had no effect on locomotion impairing induced by ethoxylated nonylphenol. However, AEFchica (1000 μg/mL) abrogated Tergitol-induced mortality, recovering up to 53.3% of the nematodes from lethality induced by 10 mM Tergitol. Similarly, it also blocked Tergitol-dependent reproduction inhibition (82.1% recovery), as well as DAF-16 nuclear translocation (>95%), suggesting a prominent role on oxidative stress control. The chemical analysis indicated the presence of a great variety of molecules with known antioxidant, metabolic and immune modulator properties, such as hydroxylated methoxy flavones, N-methyl-1-deoxynojirimycin, and rehmaionoside A. In short, the aqueous extract of F. chica protects C. elegans from the deleterious effects of Tergitol on lethality, reproduction and oxidative stress involving DAF-16-mediated pathway. This extract is a promising source of bioactive phytochemicals for multi-target pharmacological purposes.

Age-related expression of prominent regulatory elements in mouse brain: catastrophic decline of FOXO3a

Aging is associated with changes in regulation, particularly among diverse regulators in the brain. We assayed prominent regulatory elements in mouse brain to explore their relationship to one another, stress, and aging. Notably, unphosphorylated (activated) forkhead transcription factor 3a (uFOXO3a) expressed exponential decline congruent with increasing age-related mortality. Decline in uFOXO3a would impact homeostasis, aging rate, stress resistance, and mortality. We also examined other regulators associated with aging and FOXO3a: protein kinase B (PKB), the mechanistic target of rapamycin (mTOR), 70 kDa ribosomal S6 kinase (P70S6K), and 5' AMP-activated protein kinase (AMPK). It would require powerful regulatory distortion, conflicting tradeoffs and/or significant damage to inflict exponential decline of a transcription factor as crucial as FOXO3a. No other regulator examined expressed an exponential pattern congruent with aging. PKB was strongly associated with decreases in uFOXO3a, but the aging pattern of PKB did not support a causal linkage. Although mTOR expressed a trend for age-related increase, this was not significant. We considered that the mTOR downstream element, P70S6K, might suppress FOXO3a, but remarkably, it expressed a strong positive association. The age-related pattern of AMPK was also incompatible. Literature suggested the immunological regulator NFĸB (nuclear factor kappa-light-chain-enhancer of activated B cells) increases with age and suppresses FOXO3a. This would inhibit apoptosis, autophagy, mitophagy, proteostasis, detoxification, antioxidants, chaperones, and DNA repair, thus exacerbating aging. We conclude that a key aspect of aging involves distortion of key regulators in the brain.

Tissue-Specific DNA Repair Activity of ERCC-1/XPF-1

Hereditary DNA repair defects affect tissues differently, suggesting that in vivo cells respond differently to DNA damage. Knowledge of the DNA damage response, however, is largely based on in vitro and cell culture studies, and it is currently unclear whether DNA repair changes depending on the cell type. Here, we use in vivo imaging of the nucleotide excision repair (NER) endonuclease ERCC-1/XPF-1 in C. elegans to demonstrate tissue-specific NER activity. In oocytes, XPF-1 functions as part of global genome NER (GG-NER) to ensure extremely rapid removal of DNA-helix-distorting lesions throughout the genome. In contrast, in post-mitotic neurons and muscles, XPF-1 participates in NER of transcribed genes only. Strikingly, muscle cells appear more resistant to the effects of DNA damage than neurons. These results suggest a tissue-specific organization of the DNA damage response and may help to better understand pleiotropic and tissue-specific consequences of accumulating DNA damage.

Comparative Transcriptomics Identifies Neuronal and Metabolic Adaptations to Hypergravity and Microgravity in Caenorhabditis elegans

Deep space exploration is firmly within reach, but health decline during extended spaceflight remains a key challenge. In this study, we performed comparative transcriptomic analysis of Caenorhabditis elegans responses to varying degrees of hypergravity and to two spaceflight experiments (ICE-FIRST and CERISE). We found that progressive hypergravitational load concomitantly increases the extent of differential gene regulation and that subtle changes in ∼1,000 genes are reproducibly observed during spaceflight-induced microgravity. Consequently, we deduce those genes that are concordantly regulated by altered gravity per se or that display inverted expression profiles during hypergravity versus microgravity. Through doing so, we identify several candidate targets with terrestrial roles in neuronal function and/or cellular metabolism, which are linked to regulation by daf-16/FOXO signaling. These data offer a strong foundation from which to expedite mechanistic understanding of spaceflight-induced maladaptation in higher organisms and, ultimately, promote future targeted therapeutic development.

•

Comparative transcriptomics in C. elegans exposed to hypergravity and spaceflight

•

Bioinformatics identifies novel putative regulators of altered gravitational load

•

Candidate molecules infer a close gravity > daf-16/FOXO > neuronal link

FOXO3 longevity genotype mitigates the increased mortality risk in men with a cardiometabolic disease

FOXO3 is a prominent longevity gene. To date, no-one has examined whether longevity-associated FOXO3 genetic variants protect against mortality in all individuals, or only in those with aging-related diseases. We therefore tested longevity-associated FOXO3 single nucleotide polymorphisms in a haplotype block for association with mortality in 3,584 elderly American men of Japanese ancestry, 2,512 with and 1,072 without a cardiometabolic disease (CMD). At baseline (1991–1993), 1,010 CMD subjects had diabetes, 1,919 had hypertension, and 738 had coronary heart disease (CHD). Follow-up until Dec 31, 2019 found that in CMD-affected individuals, longevity-associated alleles of FOXO3 were associated with significantly longer lifespan: haplotype hazard ratio 0.81 (95% CI 0.72-0.91; diabetes 0.77, hypertension 0.82, CHD 0.83). Overall, men with a CMD had higher mortality than men without a CMD (P=6x10^-7). However, those men with a CMD who had the FOXO3 longevity genotype had similar survival as men without a CMD. In men without a CMD there was no association of longevity-associated alleles of FOXO3 with lifespan. Our study provides novel insights into the basis for the long-established role of FOXO3 as a longevity gene. We suggest that the FOXO3 longevity genotype increases lifespan only in at-risk individuals by protection against cardiometabolic stress.

Fight to the bitter end: DNA repair and aging

DNA carries the genetic information that directs complex biological processes; thus, maintaining a stable genome is critical for individual growth and development and for human health. DNA repair is a fundamental and conserved mechanism responsible for mending damaged DNA and restoring genomic stability, while its deficiency is closely related to multiple human disorders. In recent years, remarkable progress has been made in the field of DNA repair and aging. Here, we will extensively discuss the relationship among DNA damage, DNA repair, aging and aging-associated diseases based on the latest research. In addition, the possible role of DNA repair in several potential rejuvenation strategies will be discussed. Finally, we will also review the emerging methods that may facilitate future research on DNA repair.

Downregulated FOXO3a Associates With Poor Prognosis and Promotes Cell Invasion and Migration via WNT/β-catenin Signaling in Cervical Carcinoma

Background: Emerging studies have demonstrated that the Forkhead transcription factor FOXO3a is closely correlated with the progression of multiple tumors. Nevertheless, the biological role and prognostic value of FOXO3a have yet to be fully elucidated in cervical carcinoma. This study was designed to determine the molecular mechanism and prognosis of FOXO3a in cervical carcinoma.

Methods: The protein levels of FOXO3a were detected using immunohistochemistry and Western blotting. The relationships between FOXO3a expression and clinicopathological variables were analyzed. The biological mechanism of FOXO3a in cervical carcinoma cells (HeLa and CaSki) was investigated. We also explored the effect of FOXO3a on WNT/β-catenin signaling with respect to its expression and function.

Results: The results demonstrated that decreased FOXO3a expression was related to increased tumor stage and grade, positive lymph node metastasis, and poor survival outcome in cervical carcinoma. Survival analysis revealed that the FOXO3a level is an independent prognostic factor for cervical carcinoma patients. Furthermore, the data indicated that the downregulation of FOXO3a expression promotes cell invasion and migration, while FOXO3a overexpression exhibited the opposite effects on cervical carcinoma. In addition, FOXO3a acted as a negative regulator of the canonical WNT/ β-catenin pathway in cervical carcinoma. Moreover, overexpression of FOXO3a also inhibited the expression of MMP2 and MMP9.

Conclusion: These results reveal that FOXO3a, serving as a tumor suppressor gene, could suppress cell invasion and migration via the WNT/β-catenin signaling pathway and indicates a good prognosis in cervical carcinoma.

DAF-16 and SMK-1 Contribute to Innate Immunity During Adulthood in Caenorhabditis elegans

Aging is accompanied by a progressive decline in immune function termed "immunosenescence". Deficient surveillance coupled with the impaired function of immune cells compromises host defense in older animals. The dynamic activity of regulatory modules that control immunity appears to underlie age-dependent modifications to the immune system. In the roundworm Caenorhabditis elegans levels of PMK-1 p38 MAP kinase diminish over time, reducing the expression of immune effectors that clear bacterial pathogens. Along with the PMK-1 pathway, innate immunity in C. elegans is regulated by the insulin signaling pathway. Here we asked whether DAF-16, a Forkhead box (FOXO) transcription factor whose activity is inhibited by insulin signaling, plays a role in host defense later in life. While in younger C. elegans DAF-16 is inactive unless stimulated by environmental insults, we found that even in the absence of acute stress the transcriptional activity of DAF-16 increases in an age-dependent manner. Beginning in the reproductive phase of adulthood, DAF-16 upregulates a subset of its transcriptional targets, including genes required to kill ingested microbes. Accordingly, DAF-16 has little to no role in larval immunity, but functions specifically during adulthood to confer resistance to bacterial pathogens. We found that DAF-16-mediated immunity in adults requires SMK-1, a regulatory subunit of the PP4 protein phosphatase complex. Our data suggest that as the function of one branch of the innate immune system of C. elegans (PMK-1) declines over time, DAF-16-mediated immunity ramps up to become the predominant means of protecting adults from infection, thus reconfiguring immunity later in life.

Toxicity of nonylphenol and nonylphenol ethoxylate on Caenorhabditis elegans

Among the most used chemicals in the world are nonionic surfactants. One of these environmental pollutants is nonylphenol ethoxylate (NP-9), also known as Tergitol, and its degradation product, nonylphenol (NP). The objective of this work was to determine the toxicity of NP and NP-9 in Caenorhabditis elegans. Wild-type L4 larvae were exposed to different concentrations of the surfactants to measure functional endpoints. Mutant strains were employed to promote the activation of toxicity signaling pathways related to mtl-2, gst-1, gpx-4, gpx-6, sod-4, hsp-70 and hsp-4. Additionally, stress response was also assessed using a daf-16::GFP transgenic strain. The lethality was concentration dependent, with 24-h LC₅₀ of 122 μM and 3215 μM for NP and NP-9, respectively. Both compounds inhibited nematode growth, although NP was more potent; and at non-lethal concentrations, nematode locomotion was reduced. The increase in the expression of tested genes was significant at 10 μM for NP-9 and 0.001 μM for NP, implying a likely role for the activation of oxidative and cellular stress, as well as metabolism pathways. With the exception of glutathione peroxidase, which has a bimodal concentration-response curve for NP, typical of endocrine disruption, the other curves for this xenobiotic in the strains evaluated were almost flat for most concentrations, until reaching 50-100 μM, where the effect peaked. NP and NP-9 induced the activation and nuclear translocation of DAF-16, suggesting that transcription of stress-response genes may be mediated by the insulin/IGF-1 signaling pathway. In contrast, NP-9 induced a concentration-dependent response for the sod-4 and hsp-4 mutants, with greater fluorescence induction than NP at similar levels. In short, NP and NP-9 affect the physiology of C. elegans and modulate gene expression related to ROS production, cellular stress and metabolism of xenobiotics.

FoxO3a depletion accelerates cutaneous wound healing by regulating epithelial‑mesenchymal transition through β‑catenin activation

The hysteresis of keratinocyte (KC) re-epithelialization is an important factor resulting in chronic wounds; however, the molecular mechanisms involved in this cellular response remain yet to be completely elucidated. The present study demonstrated the function of transcription factor Forkhead box O3a (FoxO3a) in KC growth and migration functional effects, resulting in restrained KC re-epithelialization during wound healing. In chronic wound tissue samples, the expression of FoxO3a was significantly increased when compared with the acute wound healing group (P<0.01). Overexpressing FoxO3a significantly inhibited, whereas silencing endogenous FoxO3a enhanced, the growth and migration of HaCaT cells in vitro. Further investigation revealed that FoxO3a negatively regulated matrix metalloproteinases 1 and 9, and increased the expression of tissue inhibitor of metalloproteinase 1. In addition, the upregulation of FoxO3a retarded, whereas the downregulation of FoxO3a accelerated, transforming growth factor-β1-induced epithelial-mesenchymal transition in HaCaT cells. Mechanistically, the overexpression of FoxO3a inactivated β-catenin signaling and markedly reduced the levels of nuclear β-catenin. These results reveal a novel mechanism of FoxO3a in regulating KC re-epithelialization, and provide novel targets for the prevention and treatment of chronic wounds.

FOXO3a from the Nucleus to the Mitochondria: A Round Trip in Cellular Stress Response

Cellular stress response is a universal mechanism that ensures the survival or negative selection of cells in challenging conditions. The transcription factor Forkhead box protein O3 (FOXO3a) is a core regulator of cellular homeostasis, stress response, and longevity since it can modulate a variety of stress responses upon nutrient shortage, oxidative stress, hypoxia, heat shock, and DNA damage. FOXO3a activity is regulated by post-translational modifications that drive its shuttling between different cellular compartments, thereby determining its inactivation (cytoplasm) or activation (nucleus and mitochondria). Depending on the stress stimulus and subcellular context, activated FOXO3a can induce specific sets of nuclear genes, including cell cycle inhibitors, pro-apoptotic genes, reactive oxygen species (ROS) scavengers, autophagy effectors, gluconeogenic enzymes, and others. On the other hand, upon glucose restriction, 5′-AMP-activated protein kinase (AMPK) and mitogen activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) -dependent FOXO3a mitochondrial translocation allows the transcription of oxidative phosphorylation (OXPHOS) genes, restoring cellular ATP levels, while in cancer cells, mitochondrial FOXO3a mediates survival upon genotoxic stress induced by chemotherapy. Interestingly, these target genes and their related pathways are diverse and sometimes antagonistic, suggesting that FOXO3a is an adaptable player in the dynamic homeostasis of normal and stressed cells. In this review, we describe the multiple roles of FOXO3a in cellular stress response, with a focus on both its nuclear and mitochondrial functions.

Recent advances in understanding the mechanisms determining longevity

The field of aging research has progressed significantly over the past decades. Exogenously and endogenously inflicted molecular damage ranging from genotoxic to organellar damage drives the aging process. Repair mechanisms and compensatory responses counteract the detrimental consequences of the various damage types. Here, we discuss recent progress in understanding cellular mechanisms and interconnections between signaling pathways that control longevity. We summarize cell-autonomous and non-cell-autonomous mechanisms that impact the cellular and organismal aging process

Serum cholesterol positively associated with oxidative DNA damage: a propensity score-matched analysis

Oxidative DNA damage pathogenically links to some major diseases. This study aimed to comprehensively assess the association between serum total cholesterol (TC) and oxidative DNA damage based on propensity score matching (PSM) method. A total of 407 participants chronically exposed to arsenic via drinking water from China were enrolled. Oxidative DNA damage was determined with urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG). Serum TC was classified into favourable TC (FTC, TC <5.18 mmol/L) and unfavourable TC (NFTC, TC ≥5.18 mmol/L) categories. Multivariable generalised linear regression model was applied to examine the association. Of 407 participants, 125 pairs with FTC and NFTC subjects were matched using PSM. Urinary 8-OHdG/creatinine levels in NFTC were significantly higher than those in FTC category (p = .002). As compared to the counterparts, additional adjusted log-transformed 8-OHdG/creatinine increase was observed in NFTC for unmatched (β = 0.12, p = .052) and matched (β = 0.17, p < .001) participants, respectively. We also detected obviously increased log-transformed urinary 8-OHdG/creatinine with per interquartile range raise of serum TC either in unmatched (β = 0.10, p = .007) or matched (β = 0.16, p = .003) subjects. In conclusion, serum TC was independently associated with oxidative DNA damage. Our findings provided new insights on the health promotion of lipids relevant to the early warning of diseases due to oxidative DNA damage.