Cytochrome b5 protects photoreceptors from light stress-induced lipid peroxidation and retinal degeneration

Differences between long- and short-wavelength light-induced retinal damage and the role of PARP-1 in retinal injury induced by blue light

Photobiomodulation (PBM) therapy uses light of different wavelengths to treat various retinal degeneration diseases, but the potential damage to the retina caused by long-term light irradiation is still unclear. This study were designed to detect the difference between long- and short-wavelength light (650-nm red light and 450-nm blue light, 2.55 mW/cm2, reference intensity in PBM)-induced injury. In addition, a comparative study was conducted to investigate the differences in retinal light damage induced by different irradiation protocols (short periods of repeated irradiation and a long period of constant irradiation). Furthermore, the protective role of PARP-1 inhibition on the molecular mechanism of blue light-induced injury was confirmed by a gene knockdown technique or a specific inhibitor through in vitro and in vivo experiments. The results showed that the susceptibility to retinal damage caused by irradiation with long- and short-wavelength light is different. Shorter wavelength lights, such as blue light, induce more severe retinal damage, while the retina exhibits better resistance to longer wavelength lights, such as red light. In addition, repeated irradiation for short periods induces less retinal damage than constant exposure over a long period. PARP-1 plays a critical role in the molecular mechanism of blue light-induced damage in photoreceptors and retina, and inhibiting PARP-1 can significantly protect the retina against blue light damage. This study lays an experimental foundation for assessing the safety of phototherapy products and for developing target drugs to protect the retina from light damage.

Dendrobium nobile Polysaccharide Attenuates Blue Light-Induced Injury in Retinal Cells and In Vivo in Drosophila

Blue light is the higher-energy region of the visible spectrum. Excessive exposure to blue light is known to induce oxidative stress and is harmful to the eyes. The stems of Dendrobium nobile Lindl. (Orchidaceae), named Jinchaishihu, have long been used in traditional Chinese medicine (TCM) for nourishing yin, clearing heat, and brightening the eyes. The polysaccharide is one of the major components in D. nobile. However, the effect on ocular cells remains unclear. This study aimed to investigate whether the polysaccharide from D. nobile can protect the eyes from blue light-induced injury. A crude (DN-P) and a partially purified polysaccharide (DN-PP) from D. nobile were evaluated for their protective effects on blue light-induced damage in ARPE-19 and 661W cells. The in vivo study investigated the electroretinographic response and the expression of phototransduction-related genes in the retinas of a Drosophila model. The results showed that DN-P and DN-PP could improve blue light-induced damage in ARPE-19 and 661W cells, including cell viability, antioxidant activity, reactive oxygen species (ROS)/superoxide production, and reverse opsin 3 protein expression in a concentration-dependent manner. The in vivo study indicated that DN-P could alleviate eye damage and reverse the expression of phototransduction-related genes, including ninaE, norpA, Gαq, Gβ76C, Gγ30A, TRP, and TRPL, in a dose-dependent manner in blue light-exposed Drosophila. In conclusion, this is the first report demonstrating that D. nobile polysaccharide pretreatment can protect retinal cells and retinal photoreceptors from blue light-induced damage. These results provide supporting evidence for the beneficial potential of D. nobile in preventing blue light-induced eye damage and improving eyesight.

Light exposure and its applications in human health

Light exposure has been proven to have a significant impact on human health. As a result, researchers are increasingly exploring its potential benefits and drawbacks. With advancements in understanding light and the manufacturing of light sources, modern health lighting has become widely utilized in daily life and plays a critical role in the prevention and treatment of various illnesses. The use of light in healthcare is a global trend, with many countries actively promoting the development and application of relevant scientific research and medical technology. This field has gained worldwide attention and support from scientists and doctors alike. In this review, we examine the application of lighting in human health and recent breakthroughs in light exposure related to pathology, therapeutic strategies, molecular changes, and more. Finally, we also discuss potential future developments and areas of application.

Blue Light Exposure Caused Large-Scale Transcriptional Changes in the Abdomen and Reduced the Reproductive Fitness of the Fall Armyworm Spodoptera frugiperda

In the present study, we found that blue light stress negatively affected the development periods, body weight, survival and reproduction of Spodoptera frugiperda, and it showed a dose-dependent reaction, as longer irradiation caused severer effects. Further transcriptome analysis found blue light stress induced fast and large-scale transcriptional changes in the head, thorax and, particularly, the abdomen of female S. frugiperda adults. A functional enrichment analysis indicated that shorter durations of blue light irradiation induced the upregulation of more stress response- and defense-related genes or pathways, such as abiotic stimuli detection and response, oxidative stress, ion channels and protein-kinase-based signal pathways. In the abdomen, however, different durations of blue-light-exposure treatments all induced the downregulation of a large number genes and pathways related to cellular processes, metabolism, catalysis and reproduction, which may be a trade-off between antistress defense and other processes or a strategy to escape stressful conditions. These results indicate irradiation duration- and tissue-specific blue light stress responses and consequences, as well as suggest that the stress that results in transcriptional alterations is associated with the stress that causes a fitness reduction in S. frugiperda females.

Systematic assessment of transcriptomic and metabolic reprogramming by blue light exposure coupled with aging

The prevalent use of light-emitting diodes (LEDs) has caused revolutionary changes in modern life, but the potential hazards to health of blue light are poorly understood. N6-methyladenosine (m6A) is the most prevalent posttranscriptional modification in eukaryotes and can modulate diverse physiological processes by regulating mRNA fate. Here, to understand the effects and molecular mechanisms of daily low-intensity blue light exposure (BLE) and ascertain whether m6A methylation plays a role in BLE-induced phenotypes, we constructed a series of Drosophila models under different durations of daily low-intensity BLE and obtained multiomics profiles. Our results revealed that BLE could induce transcriptomic, m6A epitranscriptomic, and metabolomic reprogramming in Drosophila along with aging process. Importantly, the m6A methylation sites enriched in the 5' untranslated regions (UTRs) of Drosophila transcripts showed strong age specificity and could be altered by BLE. We experimentally validated that aging-related gene Tor and circadian rhythm-related gene per were regulated by 5' UTR-enriched m6A methylation. Overall, our study provides a systematic assessment of m6A RNA methylome reprogramming by BLE and aging in Drosophila model.

Proteome-wide quantitative analysis of redox cysteine availability in the Drosophila melanogaster eye reveals oxidation of phototransduction machinery during blue light exposure and age

The retina is one of the highest oxygen-consuming tissues because visual transduction and light signaling processes require large amounts of ATP. Thus, because of the high energy demand, oxygen-rich environment, and tissue transparency, the eye is susceptible to excess production of reactive oxygen species (ROS) resulting in oxidative stress. Oxidative stress in the eye is associated with the development and progression of ocular diseases including cataracts, glaucoma, age-related macular degeneration, and diabetic retinopathy. ROS can modify and damage cellular proteins, but can also be involved in redox signaling. In particular, the thiol groups of cysteines can undergo reversible or irreversible oxidative post-translational modifications (PTMs). Identifying the redox-sensitive cysteines on a proteome-wide scale provides insight into those proteins that act as redox sensors or become irreversibly damaged upon exposure to oxidative stress. In this study, we profiled the redox proteome of the Drosophila eye under prolonged, high intensity blue light exposure and age using iodoacetamide isobaric label sixplex reagents (iodo-TMT) to identify changes in cysteine availability. Although redox metabolite analysis of the major antioxidant, glutathione, revealed similar ratios of its oxidized and reduced form in aged or light-stressed eyes, we observed different changes in the redox proteome under these conditions. Both conditions resulted in significant oxidation of proteins involved in phototransduction and photoreceptor maintenance but affected distinct targets and cysteine residues. Moreover, redox changes induced by blue light exposure were accompanied by a large reduction in light sensitivity that did not arise from a reduction in the photopigment level, suggesting that the redox-sensitive cysteines we identified in the phototransduction machinery might contribute to light adaptation. Our data provide a comprehensive description of the redox proteome of Drosophila eye tissue under light stress and aging and suggest how redox signaling might contribute to light adaptation in response to acute light stress.

Retinopathy of prematurity: A review of pathophysiology and signaling pathways

Retinopathy of prematurity (ROP) is a vasoproliferative disorder of the retina and a leading cause of visual impairment and childhood blindness worldwide. The disease is characterized by an early stage of retinal microvascular degeneration, followed by neovascularization that can lead to subsequent retinal detachment and permanent visual loss. Several factors play a key role during the different pathological stages of the disease. Oxidative and nitrosative stress and inflammatory processes are important contributors to the early stage of ROP. Nitric oxide synthase and arginase play important roles in ischemia/reperfusion-induced neurovascular degeneration. Destructive neovascularization is driven by mediators of the hypoxia-inducible factor pathway, such as vascular endothelial growth factor and metabolic factors (succinate). The extracellular matrix is involved in hypoxia-induced retinal neovascularization. Vasorepulsive molecules (semaphorin 3A) intervene preventing the revascularization of the avascular zone. This review focuses on current concepts about signaling pathways and their mediators, involved in the pathogenesis of ROP, highlighting new potentially preventive and therapeutic modalities. A better understanding of the intricate molecular mechanisms underlying the pathogenesis of ROP should allow the development of more effective and targeted therapeutic agents to reduce aberrant vasoproliferation and facilitate physiological retinal vascular development.

Modulating the Kynurenine pathway or sequestering toxic 3-hydroxykynurenine protects the retina from light-induced damage in Drosophila

Tissue health is regulated by a myriad of exogenous or endogenous factors. Here we investigated the role of the conserved Kynurenine pathway (KP) in maintaining retinal homeostasis in the context of light stress in Drosophila melanogaster. cinnabar, cardinal and scarlet are fly genes that encode different steps in the KP. Along with white, these genes are known regulators of brown pigment (ommochrome) biosynthesis. Using white as a sensitized genetic background, we show that mutations in cinnabar, cardinal and scarlet differentially modulate light-induced retinal damage. Mass Spectrometric measurements of KP metabolites in flies with different genetic combinations support the notion that increased levels of 3-hydroxykynurenine (3OH-K) and Xanthurenic acid (XA) enhance retinal damage, whereas Kynurenic Acid (KYNA) and Kynurenine (K) are neuro-protective. This conclusion was corroborated by showing that feeding 3OH-K results in enhanced retinal damage, whereas feeding KYNA protects the retina in sensitized genetic backgrounds. Interestingly, the harmful effects of free 3OH-K are diminished by its sub-cellular compartmentalization. Sequestering of 3OH-K enables the quenching of its toxicity through conversion to brown pigment or conjugation to proteins. This work enabled us to decouple the role of these KP genes in ommochrome formation from their role in retinal homeostasis. Additionally, it puts forward new hypotheses on the importance of the balance of KP metabolites and their compartmentalization in disease alleviation.

Light modulates Drosophila lifespan via perceptual systems independent of circadian rhythms

Across taxa, sensory perception modulates aging in response to important ecological cues, including food, sex, and danger. The range of sensory cues involved, and their mechanism of action, are largely unknown. We therefore sought to better understand how one potential cue, that of light, impacts aging in Drosophila melanogaster. In accordance with recently published data, we found that flies lived significantly longer in constant darkness. Extended lifespan was not accompanied by behavioral changes that might indirectly slow aging such as activity, feeding, or fecundity, nor were circadian rhythms necessary for the effect. The lifespans of flies lacking eyes or photoreceptor neurons were unaffected by light kept at normal housing conditions, and transgenic activation of these same neurons was sufficient to phenocopy the effects of environmental light on lifespan. The relationship between light and lifespan was not correlated with its intensity, duration, nor the frequency of light-dark transitions. Furthermore, high-intensity light reduced lifespan in eyeless flies, indicating that the effects we observed were largely independent of the known, non-specific damaging effects associated with light. Our results suggest that much like other environmental cues, light may act as a sensory stimulus to modulate aging.

Age-dependent effects of blue light exposure on lifespan, neurodegeneration, and mitochondria physiology in Drosophila melanogaster

Blue light is a predominant component of light emitting devices (LEDs), which are increasingly present in our environment. There is already accumulating evidence that blue light exposure causes damage to retinal cells in vitro and in vivo; however, much less is known about potential effects of blue light on non-retinal cells. That blue light may be detrimental at the organismal level independent from retinal effect was recently shown by findings that it reduces lifespan in worms and also in flies with genetically ablated retinas. Here, we investigated the effects of blue light exposure across the fly lifespan and found that susceptibility to blue light stress is strongly age-dependent. The blue light of the same intensity and duration reduced survival and increased neurodegeneration more significantly in old flies than in young flies. These differences appear to be caused, at least in part, by impairments of mitochondrial respiratory function. We report that blue light significantly reduces the activity of Complex II in the electron transport system and decrease the biochemical activity of succinate dehydrogenase in both young and old flies. In addition, complex I and complex IV activities are reduced by age, as are ATP levels. We therefore propose that older flies are more sensitive to blue light because the light-induced mitochondrial damage potentiates the age-related impairments in energy metabolism that occurs even in darkness. Taken together, our results show that damaging effects of blue light at the organismal level are strongly age dependent and are associated with reduced activity of specific components of energy producing pathways in mitochondria.

Oral Macrocystis pyrifera Fucoidan Administration Exhibits Anti-Inflammatory and Antioxidant Properties and Improves DSS-Induced Colitis in C57BL/6J Mice

Inflammatory bowel disease (IBD) is a complex and multifactorial disorder characterised by relapsing and remitting inflammation of the intestinal tract. Oxidative stress (OS) is the result of an imbalance between production and accumulation of reactive oxygen species (ROS), which has been associated with inflammatory responses and implicated in the exacerbation of IBD. Fucoidan, a sulfated polysaccharide from brown seaweed, is a well-known anti-inflammatory agent and emerging evidence indicates that fucoidan extracts from Macrocystis pyrifera (MPF and DP-MPF) may also modulate oxidative stress. This study investigated the impact of fucoidan extracts, MPF and DP-MPF in a dextran sodium sulphate (DSS)-induced mouse model of acute colitis. 3% DSS was administered in C57BL/6J male mice over a period of 7 days, and MPF and DP-MPF were co-administered orally at a dose of 400 mg/kg body weight. Our results indicated that MPF and DP-MPF significantly prevented body weight loss, improved the disease activity index (DAI), restored colon lengths, reduced the wet colon weight, reduced spleen enlargement, and improved the overall histopathological score. Consistent with the reported anti-inflammatory functions, fucoidan extracts, MPF and DP-MPF significantly reduced the colonic levels of myeloperoxidase (MPO), nitric oxide (NO), malondialdehyde (MDA) and increased the levels of antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT). In addition, MPF and DP-MPF significantly inhibited levels of pro-inflammatory cytokines in colon-derived tissues. Collectively, our results indicate that MPF and DP-MPF exhibited anti-inflammatory and antioxidant effects representing a promising therapeutic strategy for the cure of IBD.

Systemic glucose levels are modulated by specific wavelengths in the solar light spectrum that shift mitochondrial metabolism

Systemic glucose levels can be modulated with specific solar wavelengths that influence mitochondrial metabolism. Mitochondrial respiration can be modulated using light that shifts ATP production with exceptional conservation of effect across species, from insects to humans. Known wavelengths have opposing effects of photobiomodulation, with longer wavelengths (660–900 nm red/infrared) increasing ATP production, and 420 nm (blue) light suppressing metabolism. Increasing mitochondrial respiration should result in a greater demand for glucose, and a decrease should result in a reduced demand for glucose. Here we have tested the hypothesis that these wavelengths alter circulating glucose concentration. We first established an oral glucose tolerance test curve in a bumblebee model, which showed sustained increase in systemic glucose beyond that seen in mammals, with a gradual normalisation over eight hours. This extended period of increased systemic glucose provided a stable model for glucose manipulation. Bees were starved overnight and given a glucose load in the morning. In the first group glucose levels were examined at hourly intervals. In the second group, bees were additionally exposed to either 670 nm or 420 nm light and their blood glucose examined. Increasing mitochondrial activity with 670 nm light at the peak of circulating glucose, resulted in a significant 50% reduction in concentration measured. Exposure to 420nm light that retards mitochondrial respiration elevated systemic glucose levels by over 50%. The impact of 670 nm and 420 nm on mitochondria is highly conserved. Hence, different wavelengths of visible light may be used to modulate systemic metabolism bidirectionally and may prove an effective agent in mammals.

FtbZIP12 Positively Regulates Responses to Osmotic Stress in Tartary Buckwheat

ABFs play a key role in regulating plant osmotic stress. However, in Tartary buckwheat, data on the role of ABF genes in osmotic stress remain limited and its associated mechanism in osmoregulation remain nebulous. Herein, a novel ABF family in Tartary buckwheat, FtbZIP12, was cloned and characterized. FtbZIP12 is a transcriptional activator located in the nucleus; its expression is induced by NaCl, mannitol, and abscisic acid (ABA). Atopic expression of FtbZIP12 in Arabidopsis promoted seed germination, reduced damage to primary roots, and improved the tolerance of seedlings to osmotic stress. The quantitative realtime polymerase chain reaction (RT-qPCR) results showed that the expressions of the typical genes related to stress, the SOS pathway, and the proline synthesis pathway in Arabidopsis were significantly (p < 0.05) upregulated under osmotic stress. FtbZIP12 improved the osmotic pressure resistance by reducing the damage caused by reactive oxygen species to plants and maintained plant homeostasis by upregulating the expression of genes related to stress, osmotic regulation, and ion homeostasis. This study identified a key candidate gene for understanding the mechanism underlying osmotic-stress-regulated function in Tartary buckwheat, thereby providing a theoretical basis for improving its yield and quality.

Chronic Cadmium Exposure Induces Impaired Olfactory Learning and Altered Brain Gene Expression in Honey Bees (Apis mellifera)

The honey bee (Apis mellifera) plays vital ecological roles in the pollination of crops and the maintenance of ecological balance, and adult honey bees may be exposed to exogenous chemicals including heavy metals during their foraging activities. Cadmium (Cd) is regarded as a nonessential toxic metal and is readily accumulated in plants; honey bees can therefore acquire Cd through the collection of contaminated nectar. In the present study, honey bees were chronically exposed to Cd to investigate the effects of sublethal cadmium doses on the olfactory learning and brain gene expression profiles of honey bees. The results showed that Cd-treated bees exhibited significantly impaired olfactory learning performances in comparison with control bees. Moreover, the head weight was significantly lower in Cd-treated bees than in control bees after chronic exposure to Cd. Gene expression profiles between the Cd treatment and the control revealed that 79 genes were significantly differentially expressed. Genes encoding chemoreceptors and olfactory proteins were downregulated, whereas genes involved in response to oxidative stress were upregulated in Cd-treated bees. The results suggest that Cd exposure exerts oxidative stress in the brain of honey bees, and the dysregulated expression of genes encoding chemoreceptors, olfactory proteins, and cytochrome P450 enzymes is probably associated with impaired olfactory learning in honey bees.

Chronic blue light leads to accelerated aging in Drosophila by impairing energy metabolism and neurotransmitter levels

Blue light (BL) is becoming increasingly prevalent in artificial illumination, raising concerns about its potential health hazard to humans. In fact, there is evidence suggesting that acute BL exposure may lead to oxidative stress and death of retinal cells specialized for photoreception. On the other hand, recent studies in Drosophila melanogaster demonstrated that chronic BL exposure across lifespan leads to accelerated aging manifested in reduced lifespan and brain neurodegeneration even in flies with genetically ablated eyes, suggesting that BL can damage cells and tissues not specialized for light perception. At the physiological level, BL exposure impairs mitochondria function in flies, but the metabolic underpinnings of these effects have not been studied. Here, we investigated effects of chronic BL on metabolic pathways in heads of eyes absent (eya²) mutant flies in order to focus on extra-retinal tissues. We compared metabolomic profiles in flies kept for 10 or 14 days in constant BL or constant darkness, using LC-MS and GC-MS. Data analysis revealed significant alterations in the levels of several metabolites suggesting that critical cellular pathways are impacted in BL-exposed flies. In particular, dramatic metabolic rearrangements are observed in heads of flies kept in BL for 14 days, including highly elevated levels of succinate but reduced levels of pyruvate and citrate, suggesting impairments in energy production. These flies also show onset of neurodegeneration and our analysis detected significantly reduced levels of several neurotransmitters including glutamate and Gamma-aminobutyric acid (GABA), suggesting that BL disrupts brain homeostasis. Taken together, these data provide novel insights into the mechanisms by which BL interferes with vital metabolic pathways that are conserved between fly and human cells.

Regulating Effect of Cytochrome b5 Overexpression on Human Breast Cancer Cells

Imbalance in the cellular redox system is thought to be associated with the induction and progression of breast cancers, and heme proteins may regulate the redox balance. Cytochrome b₅ (Cyt b₅) is a small mitochondrial heme protein. Its function and regulating mechanism in breast cancer remain unknown. In this study, we elucidated the level of endogenous oxidative stress in breast cancer cells, MCF-7 cells (hormone receptor-positive cells) and MDA-MB-231 cells (triple-negative cells), and investigated the difference in Cyt b₅ content. Based on the low content of Cyt b₅ in MDA-MB-231 cells, the overexpression of Cyt b₅ was found to regulate the oxidative stress and apoptosis cascades, including ERK1/2 and Akt signaling pathways. The overexpressed Cyt b₅ MDA-MB-231 cells were shown to exhibit decreased oxidative stress, less phosphorylation of ERK1/2 and Akt, and less cleavage of caspases 3 and 9 upon treatment with H₂O₂, as compared to those of normal MDA-MB-231 cells. Moreover, the overexpressed Cyt b₅ most likely functioned by interacting with its protein partner, Cyt c, as suggested by co-immunoprecipitation studies. These results indicated that Cyt b₅ has different effects on breast cancer cells of different phenotypes, which provides useful information for understanding the multiple roles of Cyt b₅ and provides clues for clinical treatment.

Aging and Light Stress Result in Overlapping and Unique Gene Expression Changes in Photoreceptors

Advanced age is one of the leading risk factors for vision loss and eye disease. Photoreceptors are the primary sensory neurons of the eye. The extended photoreceptor cell lifespan, in addition to its high metabolic needs due to phototransduction, makes it critical for these neurons to continually respond to the stresses associated with aging by mounting an appropriate gene expression response. Here, we sought to untangle the more general neuronal age-dependent transcriptional signature of photoreceptors with that induced by light stress. To do this, we aged flies or exposed them to various durations of blue light, followed by photoreceptor nuclei-specific transcriptome profiling. Using this approach, we identified genes that are both common and uniquely regulated by aging and light induced stress. Whereas both age and blue light induce expression of DNA repair genes and a neuronal-specific signature of death, both conditions result in downregulation of phototransduction. Interestingly, blue light uniquely induced genes that directly counteract the overactivation of the phototransduction signaling cascade. Lastly, unique gene expression changes in aging photoreceptors included the downregulation of genes involved in membrane potential homeostasis and mitochondrial function, as well as the upregulation of immune response genes. We propose that light stress contributes to the aging transcriptome of photoreceptors, but that there are also other environmental or intrinsic factors involved in age-associated photoreceptor gene expression signatures.

The Clock:Cycle complex is a major transcriptional regulator of Drosophila photoreceptors that protects the eye from retinal degeneration and oxidative stress

The aging eye experiences physiological changes that include decreased visual function and increased risk of retinal degeneration. Although there are transcriptomic signatures in the aging retina that correlate with these physiological changes, the gene regulatory mechanisms that contribute to cellular homeostasis during aging remain to be determined. Here, we integrated ATAC-seq and RNA-seq data to identify 57 transcription factors that showed differential activity in aging Drosophila photoreceptors. These 57 age-regulated transcription factors include two circadian regulators, Clock and Cycle, that showed sustained increased activity during aging. When we disrupted the Clock:Cycle complex by expressing a dominant negative version of Clock (Clk^DN) in adult photoreceptors, we observed changes in expression of 15–20% of genes including key components of the phototransduction machinery and many eye-specific transcription factors. Using ATAC-seq, we showed that expression of Clk^DN in photoreceptors leads to changes in activity of 37 transcription factors and causes a progressive decrease in global levels of chromatin accessibility in photoreceptors. Supporting a key role for Clock-dependent transcription in the eye, expression of Clk^DN in photoreceptors also induced light-dependent retinal degeneration and increased oxidative stress, independent of light exposure. Together, our data suggests that the circadian regulators Clock and Cycle act as neuroprotective factors in the aging eye by directing gene regulatory networks that maintain expression of the phototransduction machinery and counteract oxidative stress.

Age-associated changes to the retinal transcriptome often correlate with physiological changes, such as loss of visual function and increase in cell death. However, the mechanisms that contribute to these transcriptomic changes are poorly understood. Here, we used a genomics/bioinformatics approach to identify transcription factor binding sites with differential activity in aging Drosophila retina outer photoreceptors. Amongst these age-regulated transcription factors, we identify the circadian regulators Clock and Cycle. Using a genetics approach, we find that photoreceptor-specific disruption of the Clock:Cycle complex makes the Drosophila eye susceptible to light-dependent retinal degeneration, and light-independent increase of oxidative stress, showing that a functional circadian clock contributes to visual health and function in Drosophila. Because disruption of circadian rhythms has been associated with the onset of several age-related eye diseases, our data shows that the Drosophila retina serves as a useful model to study how disruption of the circadian clock contributes to neurodegeneration in the retina.

Quantitative Proteomic and Metabolomic Profiling Reveals Altered Mitochondrial Metabolism and Folate Biosynthesis Pathways in the Aging Drosophila Eye

Aging is associated with increased risk of ocular disease, suggesting that age-associated molecular changes in the eye increase its vulnerability to damage. Although there are common pathways involved in aging at an organismal level, different tissues and cell types exhibit specific changes in gene expression with advanced age. Drosophila melanogaster is an established model system for studying aging and neurodegenerative disease that also provides a valuable model for studying age-associated ocular disease. Flies, like humans, exhibit decreased visual function and increased risk of retinal degeneration with age. Here, we profiled the aging proteome and metabolome of the Drosophila eye and compared these data with age-associated transcriptomic changes from both eyes and photoreceptors to identify alterations in pathways that could lead to age-related phenotypes in the eye. Of note, the proteomic and metabolomic changes observed in the aging eye are distinct from those observed in the head or whole fly, suggesting that tissue-specific changes in protein abundance and metabolism occur in the aging fly. Our integration of the proteomic, metabolomic, and transcriptomic data reveals that changes in metabolism, potentially due to decreases in availability of B vitamins, together with chronic activation of the immune response, may underpin many of the events observed in the aging Drosophila eye. We propose that targeting these pathways in the genetically tractable Drosophila system may help to identify potential neuroprotective approaches for neurodegenerative and age-related ocular diseases. Data are available via ProteomeXchange with identifier PXD027090.

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Tissue-specific changes in protein abundance occur in the aging Drosophila eye.

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Increase in mitochondrial metabolism enzyme abundance in the aging eye.

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Decrease in corneal lens protein abundance and calcium buffering in the aging eye.

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Dysregulated metabolism impacts vitamin B and methionine metabolism in the aging eye.

Green light extends Drosophila longevity

The role of visible light on longevity is incompletely understood. Here we show the effect of visible light in Drosophila melanogaster is wavelength specific. Life span was significantly extended by green light, whereas blue light reduced longevity dramatically, and minor impact was observed with red light. While oxidative stress, heat stress, or caloric restriction does not contribute to the beneficial effect of green light, our study found that the life span extension effect of green light might be mediated by microbiota or photosensitive micronutrients in food medium. In conclusion, we report that green light can extend longevity and present the potential of light as a noninvasive therapy for aging-related diseases.

Age-Related Macular Degeneration Revisited: From Pathology and Cellular Stress to Potential Therapies

Age-related macular degeneration (AMD) is a neurodegenerative disease of the aging retina, in which patients experience severe vision loss. Therapies available to patients are limited and are only effective in a sub-population of patients. Future comprehensive clinical care depends on identifying new therapeutic targets and adopting a multi-therapeutic approach. With this goal in mind, this review examines the fundamental concepts underlying the development and progression of AMD and re-evaluates the pathogenic pathways associated with the disease, focusing on the impact of injury at the cellular level, with the understanding that critical assessment of the literature may help pave the way to identifying disease-relevant targets. During this process, we elaborate on responses of AMD vulnerable cells, including photoreceptors, retinal pigment epithelial cells, microglia, and choroidal endothelial cells, based on in vitro and in vivo studies, to select stressful agents, and discuss current therapeutic developments in the field, targeting different aspects of AMD pathobiology.

Mutations in the splicing regulator Prp31 lead to retinal degeneration in Drosophila

Retinitis pigmentosa (RP) is a clinically heterogeneous disease affecting 1.6 million people worldwide. The second-largest group of genes causing autosomal dominant RP in human encodes regulators of the splicing machinery. Yet, how defects in splicing factor genes are linked to the aetiology of the disease remains largely elusive. To explore possible mechanisms underlying retinal degeneration caused by mutations in regulators of the splicing machinery, we induced mutations in Drosophila Prp31, the orthologue of human PRPF31, mutations in which are associated with RP11. Flies heterozygous mutant for Prp31 are viable and develop normal eyes and retina. However, photoreceptors degenerate under light stress, thus resembling the human disease phenotype. Degeneration is associated with increased accumulation of the visual pigment rhodopsin 1 and increased mRNA levels of twinfilin, a gene associated with rhodopsin trafficking. Reducing rhodopsin levels by raising animals in a carotenoid-free medium not only attenuates rhodopsin accumulation, but also retinal degeneration. Given a similar importance of proper rhodopsin trafficking for photoreceptor homeostasis in human, results obtained in flies presented here will also contribute to further unravel molecular mechanisms underlying the human disease.

This paper has an associated First Person interview with the co-first authors of the article.

Summary: Retinitis pigmentosa (RP) is a human disease resulting in blindness, which affects 1 in 4.000 people worldwide. So far >90 genes have been identified that are causally related to RP. Mutations in the splicing factor PRPF31 are linked to RP11. We induced mutations in the Drosophila orthologue Prp31 and show that flies heterozygous for Prp31 undergo light-dependent retinal degeneration. Degeneration is associated with increased accumulation of the light-sensitive molecule, rhodopsin 1. In fact, reducing rhodopsin levels by dietary intervention modifies the extent of retinal degeneration. This model will further contribute to better understand the aetiology of the human disease.

ADAM17-triggered TNF signalling protects the ageing Drosophila retina from lipid droplet-mediated degeneration

Animals have evolved multiple mechanisms to protect themselves from the cumulative effects of age‐related cellular damage. Here, we reveal an unexpected link between the TNF (tumour necrosis factor) inflammatory pathway, triggered by the metalloprotease ADAM17/TACE, and a lipid droplet (LD)‐mediated mechanism of protecting retinal cells from age‐related degeneration. Loss of ADAM17, TNF and the TNF receptor Grindelwald in pigmented glial cells of the Drosophila retina leads to age‐related degeneration of both glia and neurons, preceded by an abnormal accumulation of glial LDs. We show that the glial LDs initially buffer the cells against damage caused by glial and neuronally generated reactive oxygen species (ROS), but that in later life the LDs dissipate, leading to the release of toxic peroxidated lipids. Finally, we demonstrate the existence of a conserved pathway in human iPS‐derived microglia‐like cells, which are central players in neurodegeneration. Overall, we have discovered a pathway mediated by TNF signalling acting not as a trigger of inflammation, but as a cytoprotective factor in the retina.

ScPNP-A, a plant natriuretic peptide from Stellera chamaejasme, confers multiple stress tolerances in Arabidopsis

As a class of peptide hormone, plant natriuretic peptides (PNPs) play an important role in maintaining water and salt balance in plants, as well as in the physiological processes of biotic stress and pathogen resistance. However, in plants, except for some PNPs, such as the Arabidopsis thaliana PNP-A (AtPNP-A), of which the function has not yet been thoroughly revealed, few PNPs in other plants have been reported. In this study, a PNP-A (ScPNP-A) has been identified and characterized in Stellera chamaejasme for the first time. ScPNP-A is a double-psi beta-barrel (DPBB) fold containing protein and is localized in the extracellular (secreted) space. In S. chamaejasme, the expression of ScPNP-A was significantly up-regulated by salt, drought and cold stress. Changes at the physiological and biochemical levels and the expression of resistance-related genes indicated that overexpression of ScPNP-A can significantly improve salt, drought and freezing tolerance in Arabidopsis. ScPNP-A could stimulate the opening, not the closing of stomata, and its expression was not enhanced by external application of ABA. Furthermore, overexpression of ScPNP-A resulted in the elevated expression of genes in the ABA biosynthesis and reception pathway. These suggested that there may be some cross-talk between ScPNP-A and the ABA-dependent signaling pathways to regulate water related stress, however further experimentation is required to understand this relationship. In addition, overexpression of ScPNP-A can enhance the resistance to pathogens by enhancing SAR in Arabidopsis. These results indicate that ScPNP-A could function as a positive regulator in plant response to biotic stress and abiotic stress.

Daily blue-light exposure shortens lifespan and causes brain neurodegeneration in Drosophila

Light is necessary for life, but prolonged exposure to artificial light is a matter of increasing health concern. Humans are exposed to increased amounts of light in the blue spectrum produced by light-emitting diodes (LEDs), which can interfere with normal sleep cycles. The LED technologies are relatively new; therefore, the long-term effects of exposure to blue light across the lifespan are not understood. We investigated the effects of light in the model organism, Drosophila melanogaster, and determined that flies maintained in daily cycles of 12-h blue LED and 12-h darkness had significantly reduced longevity compared with flies maintained in constant darkness or in white light with blue wavelengths blocked. Exposure of adult flies to 12 h of blue light per day accelerated aging phenotypes causing damage to retinal cells, brain neurodegeneration, and impaired locomotion. We report that brain damage and locomotor impairments do not depend on the degeneration in the retina, as these phenotypes were evident under blue light in flies with genetically ablated eyes. Blue light induces expression of stress-responsive genes in old flies but not in young, suggesting that cumulative light exposure acts as a stressor during aging. We also determined that several known blue-light-sensitive proteins are not acting in pathways mediating detrimental light effects. Our study reveals the unexpected effects of blue light on fly brain and establishes Drosophila as a model in which to investigate long-term effects of blue light at the cellular and organismal level.

Effects of light on aging and longevity

Increasing evidence suggests an important role for light in regulation of aging and longevity. UV radiation is a mutagen that can promote aging and decrease longevity. In contrast, NIR light has shown protective effects in animal disease models. In invertebrates, visible light can shorten or extend lifespan, depending on the intensity and wavelength composition. Visible light also impacts human health, including retina function, sleep, cancer and psychiatric disorders. Possible mechanisms of visible light include: controlling circadian rhythms, inducing oxidative stress, and acting through the retina to affect neuronal circuits and systems. Changes in artificial lighting (e.g., LEDs) may have implications for human health. It will be important to further explore the mechanisms of how light affects aging and longevity, and how light affects human health.

Lipid peroxidation in neurodegeneration

Neurodegenerative diseases have great social and economic impact and cause millions of deaths every year. The potential molecular mechanisms in these pathologies have been widely studied and implicate lipid peroxidation as an important factor in the development of neurodegenerative disorders such as Alzheimer's, Parkinson's and Huntington's diseases. Data indicates that pathologic mechanisms specifically involve ferroptosis and mitochondrial dysfunction. Here we review the molecular mechanisms related to the lipid peroxidation that involve the development of neurodegeneration, as well as the utility of some biomarkers in diagnosis, prognosis and evaluation of new therapies for neurodegenerative diseases.

Perturbed Biochemical Pathways and Associated Oxidative Stress Lead to Vascular Dysfunctions in Diabetic Retinopathy

Diabetic retinopathy (DR) is a vascular insult that accompanies the hyperglycemic state. Retinal vasculature holds a pivotal role in maintaining the integrity of the retina, and any alteration to retinal vasculature affects retinal functions. The blood retinal barrier, a prerequisite to vision acuity, is most susceptible to damage during the progression of DR. This is a consequence of impaired biochemical pathways such as the polyol, advanced end glycation products (AGE), hexosamine, protein kinase C (PKC), and tissue renin-angiotensin system (RAS) pathways. Moreover, the role of histone modification and altered miRNA expression is also emerging as a major contributor. Epigenetic changes create a link between altered protein function and redox status of retinal cells, creating a state of metabolic memory. Although various biochemical pathways underlie the etiology of DR, the major insult to the retina is due to oxidative stress, a unifying factor of altered biochemical pathways. This review primarily focuses on the critical biochemical pathways altered in DR leading to vascular dysfunctions and discusses antioxidants as plausible treatment strategies.

The Resveratrol Alleviates the Hepatic Toxicity of CuSO4 in the Rat

Cu is toxic to humans and other animals. Oxidative stress is an important mechanism involved in Cu toxicity. Resveratrol (RSV) is an antioxidative compound, so could counteract Cu toxicity. The aim of this study was to determine whether RSV protects the liver from the effects of CuSO₄. Forty male Sprague-Dawley rats (5 weeks old, 110-120 g) were divided into four groups (n = 10 per group), a control group and groups treated with CuSO₄ at a dose of 200 mg/kg body weight (BW), RSV at a dose of 15 mg/kg BW, and CuSO₄ at a dose of 200 mg/kg BW and RSV at a dose of 15 mg/kg BW. The treatments were orally administered for 30 days. The livers were removed from the rats at the end of the study, and the cytochrome P450, cytochrome b5, Cu, Fe, Zn, glutathione peroxidase, superoxide dismutase, reactive oxygen species, aspartate aminotransferase, and alanine aminotransferase concentrations in the livers were determined. CuSO₄ decreased the BW, liver weight, and cytochrome P450, cytochrome b5, Fe, Zn, glutathione peroxidase, and superoxide dismutase concentrations but increased the Cu, aspartate aminotransferase, alanine aminotransferase, and reactive oxygen species concentrations relative to the control group. RSV alleviated the toxic effects of CuSO₄ on the liver, indicating that RSV attenuates CuSO₄-induced liver injury by decreasing the liver transaminase concentration and oxidative stress, promoting antioxidative activity and cytochrome P450 enzymes, and maintaining balance in the trace element concentrations. The results indicate that RSV could be used to treat CuSO₄ toxicity.

Proper splicing contributes to visual function in the aging Drosophila eye

Changes in splicing patterns are a characteristic of the aging transcriptome; however, it is unclear whether these age-related changes in splicing facilitate the progressive functional decline that defines aging. In Drosophila, visual behavior declines with age and correlates with altered gene expression in photoreceptors, including downregulation of genes encoding splicing factors. Here, we characterized the significance of these age-regulated splicing-associated genes in both splicing and visual function. To do this, we identified differential splicing events in either the entire eye or photoreceptors of young and old flies. Intriguingly, aging photoreceptors show differential splicing of a large number of visual function genes. In addition, as shown previously for aging photoreceptors, aging eyes showed increased accumulation of circular RNAs, which result from noncanonical splicing events. To test whether proper splicing was necessary for visual behavior, we knocked down age-regulated splicing factors in photoreceptors in young flies and examined phototaxis. Notably, many of the age-regulated splicing factors tested were necessary for proper visual behavior. In addition, knockdown of individual splicing factors resulted in changes in both alternative splicing at age-spliced genes and increased accumulation of circular RNAs. Together, these data suggest that cumulative decreases in splicing factor expression could contribute to the differential splicing, circular RNA accumulation, and defective visual behavior observed in aging photoreceptors.

Blue light induces a neuroprotective gene expression program in Drosophila photoreceptors

BACKGROUND

Light exposure induces oxidative stress, which contributes to ocular diseases of aging. Blue light provides a model for light-induced oxidative stress, lipid peroxidation and retinal degeneration in Drosophila melanogaster. In contrast to mature adults, which undergo retinal degeneration when exposed to prolonged blue light, newly-eclosed flies are resistant to blue light-induced retinal degeneration. Here, we sought to characterize the gene expression programs induced by blue light in flies of different ages to identify neuroprotective pathways utilized by photoreceptors to cope with light-induced oxidative stress.

RESULTS

To identify gene expression changes induced by blue light exposure, we profiled the nuclear transcriptome of Drosophila photoreceptors from one- and six-day-old flies exposed to blue light and compared these with dark controls. Flies were exposed to 3 h blue light, which increases levels of reactive oxygen species but does not cause retinal degeneration. We identified substantial gene expression changes in response to blue light only in six-day-old flies. In six-day-old flies, blue light induced a neuroprotective gene expression program that included upregulation of stress response pathways and downregulation of genes involved in light response, calcium influx and ion transport. An intact phototransduction pathway and calcium influx were required for upregulation, but not downregulation, of genes in response to blue light, suggesting that distinct pathways mediate the blue light-associated transcriptional response.

CONCLUSION

Our data demonstrate that under phototoxic conditions, Drosophila photoreceptors upregulate stress response pathways and simultaneously, downregulate expression of phototransduction components, ion transporters, and calcium channels. Together, this gene expression program both counteracts the calcium influx resulting from prolonged light exposure, and ameliorates the oxidative stress resulting from this calcium influx. Thus, six-day-old flies can withstand up to 3 h blue light exposure without undergoing retinal degeneration. Developmental transitions during the first week of adult Drosophila life lead to an altered gene expression program in photoreceptors that includes reduced expression of genes that maintain redox and calcium homeostasis, reducing the capacity of six-day-old flies to cope with longer periods (8 h) of light exposure. Together, these data provide insight into the neuroprotective gene regulatory mechanisms that enable photoreceptors to withstand light-induced oxidative stress.

Oxidative Stress and Effect of Treatment on the Oxidation Product Decomposition Processes in IBD

Oxidative stress plays an important role in IBD because chronic intestinal inflammation is associated with the overproduction of reactive oxygen species (ROS) leading to oxidative stress, which has been implicated in IBD. Many lines of evidence suggest that IBD is associated with an imbalance between ROS and antioxidant activity which generates oxidative stress as the result of either ROS overproduction or a decrease in antioxidant activity. Our study was to evaluate the influence of oxidative stress and antioxidants on the course of the disease and treatment of IBD patients. Our results show that an increase of LOOH levels positively correlates with an increase in MDA levels; therefore, MDA may be a marker indicating lipid peroxidation. Also, being the decomposition product of oxidation processes, MDA may be applied as a useful biomarker for identifying the effect of endogenous oxidative stress in Crohn's disease patients. The anti-inflammatory efficacy of AZA drugs may be the result of a reduction of the amount of lipid peroxides in the intestinal mucosa cells in CD patients and facilitate mucosal healing.