Flavonoids ameliorate aluminum chloride-induced learning and memory impairments via suppression of apoptosis and oxidative stress in rats

Post-exposure self-recovery reverses oxidative stress, ameliorates pathology and neurotransmitters imbalance and rescues spatial memory after time-dependent aluminum exposure in rat brain

Aluminum is a potent neurotoxin, responsible for memory impairment and cognitive dysfunction. The neurotoxic effect of aluminum on cognitive impairment is well documented, however, exposure to aluminum in a time-dependent manner and post-exposure self-recovery still needs to be elaborated. This research aimed to (1) study the time-dependent effect of aluminum exposure by administering a total dose of 5850 mg/kg of Al over two different time periods: 30 and 45 days (130 and 195 mg/kg of AlCl3 respectively), and (2) study 20 days post-exposure self-recovery effect in both aluminum-exposed groups by giving distilled water. Cognitive abilities were investigated through Morris water maze test and hole board test and compared in both exposure and recovery groups. Oxidative stress markers and neurotransmitter levels were measured for both exposure and recovery groups. To understand the mechanism of aluminum exposure and recovery, immunohistochemical analysis of synaptophysin (Syp) and glial fibrillary acidic protein (GFAP) was performed. Results showed cognitive dysfunction, oxidative stress-induced damage, reduced neurotransmitter levels, decreased immunoreactivity of Syp, and increased GFAP. However, these parameters showed a larger improvement in the recovery group where rats were given aluminum for 30 days period in comparison to recovery group followed by 45 days of aluminum exposure. These results suggest that restoration of cognitive ability is affected by the duration of aluminum exposure. The study findings provide us with insight into the adverse effects of aluminum exposure and can be utilized to guide future preventive and therapeutic strategies against aluminum neurotoxicity.

Synthesis, characterization and biological evaluation of aurones as potential neuroprotective agents

Aim: To synthesize aurone (Ar) derivatives and to demonstrate their effects against diabetes mellitus (DM) and neurodegeneration. Materials & methods: Five Ar (A-E) derivatives were synthesized, characterized by proton NMR and screened for antioxidant, anti-diabetic and anti-cholinesterase activities. They were further evaluated for neuroprotective effects in streptozotocin (STZ)-induced neurodegenerative model. Results: Among the aurone derivatives ArE demonstrated significant reversal of cognitive impairment, oxidative stress and neuroinflammation. Biochemical analysis revealed anti-diabetic and neuroprotective effects, possibly through downregulation of inflammatory markers and upregulation of antioxidant enzymes. Conclusion: Synthesized Ar (A-E) exhibits promising therapeutic potential against STZ-induced neurodegeneration and DM by modulating inflammatory and oxidative pathways, suggesting a novel avenue for disease management.

Protective effect of flavonoids on oxidative stress injury in Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease, which is mainly caused by the damage of the structure and function of the central nervous system. At present, there are many adverse reactions in market-available drugs, which can't significantly inhibit the occurrence of AD. Therefore, the current focus of research is to find safe and effective therapeutic drugs to improve the clinical treatment of AD. Oxidative stress bridges different mechanism hypotheses of AD and plays a key role in AD. Numerous studies have shown that natural flavonoids have good antioxidant effects. They can directly or indirectly resist -oxidative stress, inhibit Aβ aggregation and Tau protein hyperphosphorylation by activating Nrf2 and other oxidation-antioxidation-related signals, regulating synaptic function-related pathways, promoting mitochondrial autophagy, etc., and play a neuroprotective role in AD. In this review, we summarised the mechanism of flavonoids inhibiting oxidative stress injury in AD in recent years. Moreover, because of the shortcomings of poor biofilm permeability and low bioavailability of flavonoids, the advantages and recent research progress of nano-drug delivery systems such as liposomes and solid lipid nanoparticles were highlighted. We hope this review provides a useful way to explore safe and effective AD treatments.

METTL3-mediated m6A RNA methylation was involved in aluminum-induced neurotoxicity

Aluminum (Al) exposure has been linked to the development of a variety of neurodegenerative diseases. However, whether m6A RNA methylation participated in Al-induced neurotoxicity remain to be defined. In this study, mice were administrated with aluminum-lactate at dose of 220 mg/kg. bw by gavage for 3 months. Meanwhile, the primary hippocampal neurons were isolated and treated with 0, 50, 100, 150 μM aluminum-lactate, respectively for 7 days. Al exposure caused neuronal shrinkage, decreased Nissl bodies, and increased apoptosis. In accordance, in vitro studies also showed that Al exposure led to neuronal apoptosis in a dose-dependent manner, together with the decline in m6A RNA methylation levels. Moreover, the mRNA expression of Mettl3, Mettl14, Fto, and Ythdf2 were decreased upon Al exposure. Notably, the protein expression of METTL3 was dramatically down-regulated by 42% and 35% in Al-treated mice and neurons, suggesting METTL3 might exert a crucial role in Al-induced neurotoxicity. We next established a mouse model with hippocampus-specific overexpressing of Mettl3 gene to confirm the regulatory role of RNA methylation and found that METTL3 overexpression relieved the neurological injury induced by Al. The integrated MeRIP-seq and RNA-seq analysis elucidated that 631 genes were differentially expressed at both m6A RNA methylation and mRNA expression. Notably, EGFR tyrosine kinase inhibitor resistance, Rap1 signaling pathway, protein digestion and absorption might be involved in Al-induced neurotoxicity. Moreover, VEGFA, Thbs1, and PDGFB might be the central molecules. Collectively, our findings provide the novel sight into the role of m6A RNA methylation in neurodegenerative disease induced by Al.

Aluminum exposure induces central nervous system impairment via activating NLRP3-medicated pyroptosis pathway

PURPOSE

Aluminum is an environmental toxicant whose long-term exposure is closely associated with nervous system impairment. This study mainly investigated neurological impairment induced by subchronic aluminum exposure via activating NLRP3-medicated pyroptosis pathway.

METHODS

In vivo, Kunming mice were exposed to AlCl3 (30.3 mg/kg, 101 mg/kg and 303 mg/kg) via drinking water for 3 months, and administered with Rsv (100 mg/kg) by gavage for 1 month. Cognitive impairment was assessed by Morris water maze test, and pathological injury was detected via H&E staining. BBB integrity, pyroptosis and neuroinflammation were evaluated through western blotting and immunofluorescence methods. In vitro, BV2 microglia was treated with AlCl3 (0.5 mM, 1 mM and 2 mM) to sensitize pyroptosis pathway. The protein interaction was verified by co-immunoprecipitation, and neuronal damage was estimated via a conditioned medium co-culture system with BV2 and TH22 cells.

RESULTS

Our results showed that AlCl3 induced mice memory disorder, BBB destruction, and pathological injury. Besides, aluminum caused glial activation, sensitized DDX3X-NLRP3 pyroptosis pathway, released cytokines IL-1β and IL-18, initiating neuroinflammation. BV2 microglia treated with AlCl3 emerged hyperactivation and pyroptotic death, and Ddx3x knockdown inhibited pyroptosis signaling pathway. DDX3X acted as a live-or-die checkpoint in stressed cells by regulating NLRP3 inflammasome and G3BP1 stress granules. Furthermore, aluminum-activated microglia had an adverse effect on co-cultured neurons and destroyed nervous system homeostasis.

CONCLUSION

Aluminum exposure could induce pyroptosis and neurotoxicity. DDX3X determined live or die via selectively regulating pro-survival stress granules or pro-death NLRP3 inflammasome. Excessive activation of microglia might damage neurons and aggravate nerve injury.

Puerarin alleviates sleep disorders in aged mice related to repairing intestinal mucosal barrier

More and more evidence suggests that puerarin, a potential remedy for gut inflammation, may have an ameliorative effect on sleep disturbances. However, the relationship between puerarin and sleep disruption has not been extensively researched. This study aims to explore the role and mechanisms of puerarin in improving sleep disorders. We established a light-induced sleep disorder model in mice and assessed the effects of puerarin on cognitive behavior using open field and water maze tests. Pathological detection demonstrated that sleep disturbances resulted in observable damage to the liver, lung, and kidney. Puerarin reversed multi-organ damage and inflammation. Further, puerarin activated paneth cells, resulting in increased lysozyme and TGF-β production, and stimulating intestinal stem cell proliferation. Puerarin also effectively inhibited the expression of F4/80, iNOS, TNF-α, and IL-1β in the small intestine, while it increased Chil3, CD206, and Arg-1 levels. Moreover, puerarin treatment significantly decreased P-P65, TLR4, Bcl-xl, and cleaved caspase-3 protein levels while increasing barrier protein levels, including ZO-1, Occludin, Claudin 1 and E-cadherin suggesting a reduction in inflammation and apoptosis in the gut. Overall, puerarin diminished systemic inflammation, particularly intestinal inflammation, and enhanced intestinal barrier integrity in mice with sleep disorders. Our findings suggest a potential new therapeutic pathway for sleep disorders.

Effects of aerobic exercise and dietary flavonoids on cognition: a systematic review and meta-analysis

Introduction: Studies have shown that exercise increases angiogenesis and perfusion in the hippocampus, activates neurogenesis in the dentate gyrus and increases synaptic plasticity, as well as increases the complexity and number of dendritic spines, all of which promote memory function and protect against cognitive decline. Flavonoids are gaining attention as antioxidants in health promotion due to their rich phenolic content, particularly for their modulating role in the treatment of neurodegenerative diseases. Despite this, there has been no comprehensive review of cognitive improvement supplemented with flavonoid and prescribed with exercise or a combination of the two interventions has been conducted. The purpose of this review is to determine whether a combined intervention produces better results when given together than when given separately. Methods: Relevant articles assessing the effect of physical exercise, flavonoid or in combination on cognitive related biomarkers and neurobehavioral assessments within the timeline of January 2011 until June 2023 were searched using three databases; PubMed, PROQUEST and SCOPUS. Results: A total of 705 articles were retrieved and screened, resulting in 108 studies which are in line with the objective of the current study were included in the analysis. Discussion: The selected studies have shown significant desired effect on the chosen biomarkers and neurobehavioral assessments. Systematic Review Registration: identifier: [CRD42021271001].

Recent insights into autophagy and metals/nanoparticles exposure

Some anthropogenic pollutants, such as heavy metals and nanoparticles (NPs), are widely distributed and a major threat to environmental safety and public health. In particular, lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and mercury (Hg) have systemic toxicity even at extremely low concentrations, so they are listed as priority metals in relation to their significant public health burden. Aluminum (Al) is also toxic to multiple organs and is linked to Alzheimer's disease. As the utilization of many metal nanoparticles (MNPs) gradually gain traction in industrial and medical applications, they are increasingly being investigated to address potential toxicity by impairing certain biological barriers. The dominant toxic mechanism of these metals and MNPs is the induction of oxidative stress, which subsequently triggers lipid peroxidation, protein modification, and DNA damage. Notably, a growing body of research has revealed the linkage between dysregulated autophagy and some diseases, including neurodegenerative diseases and cancers. Among them, some metals or metal mixtures can act as environmental stimuli and disturb basal autophagic activity, which has an underlying adverse health effect. Some studies also revealed that specific autophagy inhibitors or activators could modify the abnormal autophagic flux attributed to continuous exposure to metals. In this review, we have gathered recent data about the contribution of the autophagy/mitophagy mediated toxic effects and focused on the involvement of some key regulatory factors of autophagic signaling during exposure to selected metals, metal mixtures, as well as MNPs in the real world. Besides this, we summarized the potential significance of interactions between autophagy and excessive reactive oxygen species (ROS)-mediated oxidative damage in the regulation of cell survival response to metals/NPs. A critical view is given on the application of autophagy activators/inhibitors to modulate the systematic toxicity of various metals/MNPs.

Puerarin: a potential natural neuroprotective agent for neurological disorders

Puerarin is an isoflavone compound derived from Pueraria lobata in traditional Chinese medicine. Accumulating evidence has indicated that puerarin demonstrates multiple pharmacological effects and exhibits treatment potential for various neurological disorders. Based on the latest research progress on puerarin as a neuroprotective agent, its pharmacological activity, molecular mechanism, and therapeutic application were systematically reviewed with emphasis on pre-clinical studies. The related information was extracted and compiled from major scientific databases, including PubMed, ScienceDirect, SpringerLink, and Chinese National Knowledge Infrastructure, using 'Puerarin', 'Neuroprotection', 'Apoptosis', 'Autophagy', 'Antioxidant', 'Mitochondria', 'Anti-inflammation' as keywords. This review complied with The Preferred Reporting Items for Systematic Reviews criteria. Forty-three articles met established inclusion and exclusion criteria. Puerarin has shown neuroprotective effects against a variety of neurological disorders, including ischemic cerebrovascular disease, subarachnoid hemorrhage, epilepsy, cognitive disorders, traumatic brain injury, Parkinson's disease, Alzheimer's disease, anxiety, depression, diabetic neuropathy, and neuroblastoma/glioblastoma. Puerarin demonstrates anti-apoptosis, proinflammatory mediator inhibitory, autophagy regulatory, anti-oxidative stress, mitochondria protection, Ca²⁺ influx inhibitory, and anti-neurodegenerative activities. Puerarin exerts noticeable neuroprotective effects on various models of neurological disorders in vivo (animal). This review will contribute to the development of puerarin as a novel clinical drug candidate for the treatment of neurological disorders. However, well-designed, high-quality, large-scale, multicenter randomized clinical studies are needed to determine the safety and clinical utility of puerarin in patients with neurological disorders.

Lnc001209 Participates in aluminium-induced apoptosis of PC12 cells by regulating PI3K-AKT-mTOR signalling pathway

Aluminium (Al) is a common environmental neurotoxin, but the molecular mechanism underlying its toxic effects remains unclear. Many studies have shown that aluminium exposure leads to increased neuronal apoptosis. This study aimed to investigate the mechanisms and signalling pathways involved in aluminium exposure-induced neuronal apoptosis. The results showed a decrease in the number of PC12 cells and changes in cell morphology in the aluminium maltol exposure group. The viability of PC12 cells decreased gradually with increasing of exposure doses, and the apoptosis rate increased. The expression of Lnc001209 decreased gradually with an increase in the aluminium exposure dose. After transfection of Lnc001209 siRNA in aluminium-exposed PC12 cells, the protein expression levels of p-Akt Ser473, p-Akt Thr308, p-P85 Tyr467, p-mTOR Ser2448 and CD36 were increased. RNA pull-down MS showed that Lnc001209 interacts with the CD36 protein. Expression of the CD36 protein was increased in PC12 cells exposed to aluminium. The results of the CD36 intervention experiment showed that the protein expression levels of p-Akt Ser473, p-Akt Thr308, p-P85 Tyr467, and p-mTOR Ser2448 likely increased after CD36 overexpression. In addition, the phosphorylation level of AKT had the most significant increase. The enhancement of p-Akt activity promotes neuronal apoptosis.

Hesperidin protects against aluminum-induced renal injury in rats via modulating MMP-9 and apoptosis: biochemical, histological, and ultrastructural study

Aluminum, one of the most abundant metallic elements, is known to be toxic to multiple organs including the kidneys. This study aimed to investigate the pleiotropic nephroprotective effects of Hesperidin in aluminum chloride (ALCL3)-induced renal injury, highlighting the potential molecular mechanisms underlying. Twenty-four male albino rats were divided into four groups: control, Hesperidin (80 mg/kg BW, orally), ALCL3 (10 mg/kg BW, IP), and ALCL3 + Hesperidin groups. By the end of the study, blood samples were collected, and tissue samples were harvested at sacrifice. ALCL3 rats showed dramatically declined renal function, enhanced intrarenal oxidative stress, inflammation, apoptosis, and extravagant renal histopathological damage with interstitial fibrosis as shown by a higher Endothelial, Glomerular, Tubular, and Interstitial (EGTI) score. Hesperidin significantly reversed all the aforementioned detrimental effects in ALCL3-treated rats. The study verified the nephroprotective effects of Hesperidin on ALCL3-induced renal damage and confirmed the critical role of extracellular matrix (ECM) remodeling and apoptosis inhibition.

Evaluation of Taraxacum mongolicum flavonoids in diets for Channa argus based on growth performance, immune responses, apoptosis and antioxidant defense system under lipopolysaccharide stress

To ascertain the effects of Taraxacum mongolicum flavonoids (TMF) on the growth performance, digestive enzyme activity, immune indices, inflammatory response and antioxidant capacity of Channa argus, 400 C. argus with an average body weight of (8.08 ± 0.21) g were selected and divided randomly into four groups. They were fed with four experimental diets supplemented with TMF of 0 (control), 25, 50 and 100 mg/kg for 56 d, and then challenged with lipopolysaccharide (LPS) for 96 h, afterwards indices were detected. The results manifested that the addition of TMF above 50 mg/kg in the dietary could significantly improve the final body weight, WGR, SGR and PER of C. argus, while decreased FCR (P < 0.05). Similarly, the 50 mg/kg group had the highest activity of digestive enzymes (protease, lipase, amylase) in intestine and hepatopancreas, which were notably higher than those in the control group (P < 0.05). Nevertheless, 100 mg/kg group could effectively inhibit the liver and gut injury caused by LPS and reduce the contents of ALT and AST, LPS and LBP in serum. In the immune (LY, AKP, ACP, IgM, C3) and antioxidant (T-AOC, SOD, CAT, GSH-PX, GR, ASA, MDA) systems, 100 mg/kg groups were the optimal group, which were remarkably higher than those of the control group (P < 0.05). Additionally, the expression of genes revealed that 100 mg/kg group could noteworthy restrain the expression of pro-inflammatory factors (tnf-α, il-1β, il-8) and pro-apoptosis (cas-3,8,9, p53, bax, bcl-2) related genes, up-regulate the expression of anti-inflammatory (il-10, tgf-β) factors, antioxidant-related (nrf2, gpx, gst, cat) genes and heat shock proteins (hsp70, hsp90). Simultaneously, the survival rate of C. argus in the 100 mg/kg TMF-supplemented group was the highest after LPS challenge. Our results elucidate that dietary supplementation TMF protects C. argus from LPS-induced inflammatory injury, to ameliorate digestion, immune response, antioxidant status and apoptosis, implying that TMF could be regarded as an anti-inflammatory and antioxidant agent adding to aquatic animal feed.

Involvement of Mitophagy in Primary Cultured Rat Neurons Treated with Nanoalumina

The aim of this study was to explore the influence of the neurotoxicity of nanoalumina on primarily cultured neurons. Normal control, particle size control, aluminum, micron-alumina, and nanoalumina at 50-nm and 13-nm particle sizes were included as subjects to evaluate the level of apoptosis, necrosis, and autophagy in primarily cultured neurons and further explore the mitophagy induced by nanoalumina. The results demonstrated that nanoalumina could induce neuronal cell apoptosis, necrosis, and autophagy, among which autophagy was the most notable. When the autophagy inhibitor was added to the nanoalumina-treated group, it significantly downregulated the protein expression levels of Beclin-1 and LC3II/LC3. Observation under a transmission electron microscope and a fluorescence microscope revealed mitophagy characteristics induced by nanoalumina. Additionally, the neurotoxicological effects induced by nanoalumina were more significant than those induced by aluminum and in a particle size-dependent manner.

The effect of Luteolin on DNA damage mediated by a copper catalyzed Fenton reaction

Luteolin has been reviewed as a flavonoid possessing potential cardioprotective, anti-inflammatory, anti-cancer activities. Having multiple biological effects, luteolin may act as either an antioxidant or a pro-oxidant. In this work, the protective role of copper(II)-chelation by luteolin on DNA damage via the Cu-Fenton reaction was studied. EPR and UV-vis spectroscopic data demonstrated that the luteolin, lacking 3-OH group, chelates to Cu(II) via the 5-OH and 4-CO groups, respectively. EPR spin trapping experiments using DMPO spin trap confirmed that the coordination of luteolin to Cu(II) significantly suppressed formation of hydroxyl and superoxide radicals (by 80%) in a Cu-Fenton system. Absorption titrations showed that the chelation of Cu(II) by luteolin slightly increased the mild intercalation strength of its interaction with DNA, as compared with free luteolin. Comparison with kaempferol and quercetin revealed, that the strength of the interaction between the free flavonoids/Cu-flavonoid complexes with DNA is only mildly affected by the presence/absence of 3-OH group. Due to the differences in the sensitivities of absorption titrations and viscometry, the latter confirmed weaker DNA intercalating efficiency of Cu-luteolin complex than does free luteolin. A dose dependent protective effect of luteolin against ROS-induced DNA damage was observed using gel electrophoresis. This effect was more pronounced compared to quercetin and kaempferol. In conclusion, the administration of luteolin to patients suffering from oxidative stress-related diseases with disturbed Cu-metabolism such as Alzheimer's diseases (antioxidant effect) and certain cancers (prooxidant effect) may have several health benefits.