Neuroprotective role of plumbagin on eye damage induced by high-sucrose diet in adult fruit fly Drosophila melanogaster

Impaired insulin signaling and diet-induced type 3 diabetes pathophysiology increase amyloid β expression in the Drosophila model of Alzheimer's disease

Compelling evidence has strongly linked unregulated sugar levels to developing Alzheimer's disease, suggesting Alzheimer's to be 'diabetes of the brain or 'type 3 diabetes. Insulin resistance contributes to the pathogenesis of Alzheimer's disease due to uncontrolled and unchecked blood glucose, though the interrelatedness between Alzheimer's disease and type 2 diabetes is debatable. Here we describe the consequences of inducing type 3 diabetes by feeding Drosophila on a high sucrose diet, which effectively mimics the pathophysiology of diabetes. A high sucrose diet increases glycogen and lipid accumulation. Inducing type 3 diabetes worsened neurodegeneration and accelerated disease progression in Drosophila expressing the Alzheimer's Familial Arctic mutation. High sucrose milieu also negatively affected locomotor ability and reduced the lifespan in the Alzheimer's disease model of Drosophila. The results showed that creating diabetic conditions by using insulin receptor (InR) knockdown in the eyes of Drosophila led to a degenerative phenotype, indicating a genetic interaction between the insulin signaling pathway and Alzheimer's disease. The expression of PERK reflects disruption in the endoplasmic reticulum homeostasis due to amyloid-β (Aβ) under a high sucrose diet. These observations demonstrated an association between type 3 diabetes and Alzheimer's disease, and that a high sucrose environment has a degenerating effect on Alzheimer's disease condition.

Oral administration of plumbagin is beneficial in in vivo models of Duchenne muscular dystrophy through control of redox signaling

Duchenne muscular dystrophy (DMD) is a progressive muscle-wasting disease. Recently approved molecular/gene treatments do not solve the downstream inflammation-linked pathophysiological issues such that supportive therapies are required to improve therapeutic efficacy and patients' quality of life. Over the years, a plethora of bioactive natural compounds have been used for human healthcare. Among them, plumbagin, a plant-derived analog of vitamin K3, has shown interesting potential to counteract chronic inflammation with potential therapeutic significance. In this work we evaluated the effects of plumbagin on DMD by delivering it as an oral supplement within food to dystrophic mutant of the fruit fly Drosophila melanogaster and mdx mice. In both DMD models, plumbagin show no relevant adverse effect. In terms of efficacy plumbagin improved the climbing ability of the dystrophic flies and their muscle morphology also reducing oxidative stress in muscles. In mdx mice, plumbagin enhanced the running performance on the treadmill and the muscle strength along with muscle morphology. The molecular mechanism underpinning these actions was found to be the activation of nuclear factor erythroid 2-related factor 2 pathway, the re-establishment of redox homeostasis and the reduction of inflammation thus generating a more favorable environment for skeletal muscles regeneration after damage. Our data provide evidence that food supplementation with plumbagin modulates the main, evolutionary conserved, mechanistic pathophysiological hallmarks of dystrophy, thus improving muscle function in vivo; the use of plumbagin as a therapeutic in humans should thus be explored further.

Pathological Defects in a Drosophila Model of Alzheimer's Disease and Beneficial Effects of the Natural Product Lisosan G

Alzheimer's disease (AD) brains are histologically marked by the presence of intracellular and extracellular amyloid deposits, which characterize the onset of the disease pathogenesis. Increasing evidence suggests that certain nutrients exert a direct or indirect effect on amyloid β (Aβ)-peptide production and accumulation and, consequently, on AD pathogenesis. We exploited the fruit fly Drosophila melanogaster model of AD to evaluate in vivo the beneficial properties of Lisosan G, a fermented powder obtained from organic whole grains, on the intracellular Aβ-42 peptide accumulation and related pathological phenotypes of AD. Our data showed that the Lisosan G-enriched diet attenuates the production of neurotoxic Aβ peptides in fly brains and reduces neuronal apoptosis. Notably, Lisosan G exerted anti-oxidant effects, lowering brain levels of reactive oxygen species and enhancing mitochondrial activity. These aspects paralleled the increase in autophagy turnover and the inhibition of nucleolar stress. Our results give support to the use of the Drosophila model not only to investigate the molecular genetic bases of neurodegenerative disease but also to rapidly and reliably test the efficiency of potential therapeutic agents and diet regimens.

Targeting autophagy with natural products as a potential therapeutic approach for diabetic microangiopathy

As the quality of life improves, the incidence of diabetes mellitus and its microvascular complications (DMC) continues to increase, posing a threat to people's health and wellbeing. Given the limitations of existing treatment, there is an urgent need for novel approaches to prevent and treat DMC. Autophagy, a pivotal mechanism governing metabolic regulation in organisms, facilitates the removal of dysfunctional proteins and organelles, thereby sustaining cellular homeostasis and energy generation. Anomalous states in pancreatic β-cells, podocytes, Müller cells, cardiomyocytes, and Schwann cells in DMC are closely linked to autophagic dysregulation. Natural products have the property of being multi-targeted and can affect autophagy and hence DMC progression in terms of nutrient perception, oxidative stress, endoplasmic reticulum stress, inflammation, and apoptosis. This review consolidates recent advancements in understanding DMC pathogenesis via autophagy and proposes novel perspectives on treating DMC by either stimulating or inhibiting autophagy using natural products.

Plumbagin inhibits fungal growth, HMGB1/LOX-1 pathway and inflammatory factors in A. fumigatus keratitis

To investigate the anti-inflammatory and antifungal effects of plumbagin (PL) in Aspergillus fumigatus (A. fumigatus) keratitis, the minimum inhibitory concentration (MIC), time-killing curve, spore adhesion, crystal violet staining, calcium fluoride white staining, and Propidium Iodide (PI) staining were employed to assess the antifungal activity of PL in vitro against A. fumigatus. The cytotoxicity of PL was assessed using the Cell Counting Kit-8 (CCK8). The impact of PL on the expression of HMGB1, LOX-1, TNF-α, IL-1β, IL-6, IL-10 and ROS in A. fumigatus keratitis was investigated using RT-PCR, ELISA, Western blot, and Reactive oxygen species (ROS) assay. The therapeutic efficacy of PL against A. fumigatus keratitis was assessed through clinical scoring, plate counting, Immunofluorescence and Hematoxylin-Eosin (HE) staining. Finally, we found that PL inhibited the growth, spore adhesion, and biofilm formation of A. fumigatus and disrupted the integrity of its cell membrane and cell wall. PL decreased IL-6, TNF-α, and IL-1β levels while increasing IL-10 expression in fungi-infected mice corneas and peritoneal macrophages. Additionally, PL significantly attenuated the HMGB1/LOX-1 pathway while reversing the promoting effect of Boxb (an HMGB1 agonist) on HMGB1/LOX-1. Moreover, PL decreased the level of ROS. In vivo, clinical scores, neutrophil recruitment, and fungal burden were all significantly reduced in infected corneas treated with PL. In summary, the inflammatory process can be inhibited by PL through the regulation of the HMGB-1/LOX-1 pathway. Simultaneously, PL can exert antifungal effects by limiting fungal spore adhesion and biofilm formation, as well as causing destruction of cell membranes and walls.

Exposure to the Natural Compound Climacostol Induces Cell Damage and Oxidative Stress in the Fruit Fly Drosophila melanogaster

The ciliate Climacostomum virens produces the metabolite climacostol that displays antimicrobial activity and cytotoxicity on human and rodent tumor cells. Given its potential as a backbone in pharmacological studies, we used the fruit fly Drosophila melanogaster to evaluate how the xenobiotic climacostol affects biological systems in vivo at the organismal level. Food administration with climacostol demonstrated its harmful role during larvae developmental stages but not pupation. The midgut of eclosed larvae showed apoptosis and increased generation of reactive oxygen species (ROS), thus demonstrating gastrointestinal toxicity. Climacostol did not affect enteroendocrine cell proliferation, suggesting moderate damage that does not initiate the repairing program. The fact that climacostol increased brain ROS and inhibited the proliferation of neural cells revealed a systemic (neurotoxic) role of this harmful substance. In this line, we found lower expression of relevant antioxidant enzymes in the larvae and impaired mitochondrial activity. Adult offsprings presented no major alterations in survival and mobility, as well the absence of abnormal phenotypes. However, mitochondrial activity and oviposition behavior was somewhat affected, indicating the chronic toxicity of climacostol, which continues moderately until adult stages. These results revealed for the first time the detrimental role of ingested climacostol in a non-target multicellular organism.

Targeting Mitochondrial Dysfunction and Oxidative Stress to Prevent the Neurodegeneration of Retinal Ganglion Cells

The imbalance of redox homeostasis contributes to neurodegeneration, including that related to the visual system. Mitochondria, essential in providing energy and responsible for several cell functions, are a significant source of reactive oxygen and/or nitrogen species, and they are, in turn, sensitive to free radical imbalance. Dysfunctional mitochondria are implicated in the development and progression of retinal pathologies and are directly involved in retinal neuronal degeneration. Retinal ganglion cells (RGCs) are higher energy consumers susceptible to mitochondrial dysfunctions that ultimately cause RGC loss. Proper redox balance and mitochondrial homeostasis are essential for maintaining healthy retinal conditions and inducing neuroprotection. In this respect, the antioxidant treatment approach is effective against neuronal oxidative damage and represents a challenge for retinal diseases. Here, we highlighted the latest findings about mitochondrial dysfunction in retinal pathologies linked to RGC degeneration and discussed redox-related strategies with potential neuroprotective properties.