Multifunctional Selenium Nanoparticles with Different Surface Modifications Ameliorate Neuroinflammation through the Gut Microbiota-NLRP3 Inflammasome-Brain Axis in APP/PS1 Mice

Silicon dioxide nanoparticles induce anxiety-like behavior in a size-specific manner via the microbiota-gut-brain axis

The impacts of silicon dioxide nanoparticles (SiO2-NPs) on human health have attracted increasing interest due to their widespread utilization in medicine and food additives. However, the size-dependent effects of SiO2-NPs on brain health remain sparse. Herein we investigated alterations in behavioral patterns, the gut microbiota, inflammation and oxidative stress of mice after a 12-week exposure to SiO2-NPs with either small size (NP-S) or large size (NP-L). A more pronounced deleterious effect of NP-S was found on anxiety-like behavior in mice relative to NP-L. We also found that SiO2-NPs exposure induced inflammation and oxidative stress in the colon, hippocampus and cortex of mice in a size-specific manner. Correlation network analysis revealed potential links between anxiety-like behavior and SiO2-NPs-induced shifts in the gut microbiota including Parvibacter, Faecalibaculum, Gordonibacter and Ileibacterium. Furthermore, anxiety-like behavior caused by SiO2-NPs exposure exhibited correlations with decreased levels of hippocampal IL-10 and cortex Nqo1 as well as increased levels of intestinal Acox1 and hippocampal TNF-α. Therefore, our findings suggest that exposure to SiO2-NPs promoted anxiety-like behavior through the mediation of interplay between the gut and the brain, and SiO2-NPs of smaller size may generate a more adverse effect on brain health.

The Role of Gut Microbiota in the Neuroprotective Effects of Selenium in Alzheimer's Disease

The objective of the present review was to provide a timely update on the molecular mechanisms underlying the beneficial role of Se in Alzheimer's disease pathogenesis, and discuss the potential role of gut microbiota modulation in this neuroprotective effect. The existing data demonstrate that selenoproteins P, M, S, R, as well as glutathione peroxidases and thioredoxin reductases are involved in regulation of Aβ formation and aggregation, tau phosphorylation and neurofibrillary tangles formation, as well as mitigate the neurotoxic effects of Aβ and phospho-tau. Correspondingly, supplementation with various forms of Se in cellular and animal models of AD was shown to reduce Aβ formation, tau phosphorylation, reverse the decline in brain antioxidant levels, inhibit neuronal oxidative stress and proinflammatory cytokine production, improve synaptic plasticity and neurogenesis, altogether resulting in improved cognitive functions. In addition, most recent findings demonstrate that these neuroprotective effects are associated with Se-induced modulation of gut microbiota. In animal models of AD, Se supplementation was shown to improve gut microbiota biodiversity with a trend to increased relative abundance of Lactobacillus, Bifidobacterium, and Desulfivibrio, while reducing that of Lachnospiracea_NK4A136, Rikenella, and Helicobacter. Moreover, the relative abundance of Se-affected taxa was significantly associated with Aβ accumulation, tau phosphorylation, neuronal oxidative stress, and neuroinflammation, indicative of the potential role of gut microbiota to mediate the neuroprotective effects of Se in AD. Hypothetically, modulation of gut microbiota along with Se supplementation may improve the efficiency of the latter in AD, although further detailed laboratory and clinical studies are required.

Effect of Selenium nanoparticles on Paraquat-induced-neuroinflammation and oligodendocyte modulation: Implication of the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway

BACKGROUND

Paraquat (PQ), is an extensively used herbicide and is a well-established powerful neurotoxin. However, the mechanism underlying its neurotoxicity still needs further investigation.

AIM OF WORK

The study investigated the pathogenesis of PQ-induced neuroinflammation of the substantia nigra pars compacta (SNPC) and cerebellum and evaluated the potential effect of selenium nanoparticles (SeN) against such neurotoxicity.

METHODS

Thirty-six mice were randomly divided into three groups; Control group, PQ group: mice received PQ 10 mg/kg (i.p), and PQ + SeN group; mice received PQ in addition to oral SeN 0.1 mg/kg. All regimens were administered for 14 days. The mice's brains were processed for biochemical, molecular, histological, and immune-histochemical assessment.

RESULTS

SeN increased the SNPC and cerebellum antioxidants (reduced glutathione, glutathione peroxidase, and superoxide dismutase 1) while decreasing malondialdehyde concentration. Also, SeN increased the anti-inflammatory interleukin (IL)-10 and decreased the pro-inflammatory IL-1β and -6 along with improving the angiogenic nitric oxide and reducing caspase-1. Further, western blots of phosphorylated Janus kinase (JAK2)/signal transducer and activator of transcription3 (STAT3) proteins showed a significant decline. Those improving effects of SeN on SNPC, and cerebellum were supported by the significantly preserved dopaminergic and Purkinje neurons, the enhanced myelin fibers on Luxol fast blue staining, and the marked increase in Olig-2, Platelet-derived growth factor-alpha, and tyrosine hydroxylase immunoreactivity.

CONCLUSION

SeN could mitigate PQ-induced neurotoxicity via its antioxidant, anti-inflammatory, and antiapoptotic properties.

A Comprehensive Analytical Review of Polyphenols: Evaluating Neuroprotection in Alzheimer's Disease

Alzheimer's Disease (AD), a prevalent neurodegenerative disorder, is the primary cause of dementia. Despite significant advancements in neuroscience, a definitive cure or treatment for this debilitating disease remains elusive. A notable characteristic of AD is oxidative stress, which has been identified as a potential therapeutic target. Polyphenols, secondary metabolites of plant origin, have attracted attention due to their potent antioxidant properties. Epidemiological studies suggest a correlation between the consumption of polyphenol-rich foods and the prevention of chronic diseases, including neurodegenerative disorders, which underscores the potential of polyphenols as a therapeutic strategy in AD management. Hence, this comprehensive review focuses on the diverse roles of polyphenols in AD, with a particular emphasis on neuroprotective potential. Scopus, ScienceDirect, and Google Scholar were used as leading databases for study selection, from 2018 to late March 2024. Analytical chemistry serves as a crucial tool for characterizing polyphenols, with a nuanced exploration of their extraction methods from various sources, often employing chemometric techniques for a holistic interpretation of the advances in this field. Moreover, this review examines current in vitro and in vivo research, aiming to enhance the understanding of polyphenols' role in AD, and providing valuable insights for forthcoming approaches in this context.

Hormetic Nutrition and Redox Regulation in Gut-Brain Axis Disorders

The antioxidant and anti-inflammatory effects of hormetic nutrition for enhancing stress resilience and overall human health have received much attention. Recently, the gut-brain axis has attracted prominent interest for preventing and therapeutically impacting neuropathologies and gastrointestinal diseases. Polyphenols and polyphenol-combined nanoparticles in synergy with probiotics have shown to improve gut bioavailability and blood-brain barrier (BBB) permeability, thus inhibiting the oxidative stress, metabolic dysfunction and inflammation linked to gut dysbiosis and ultimately the onset and progression of central nervous system (CNS) disorders. In accordance with hormesis, polyphenols display biphasic dose-response effects by activating at a low dose the Nrf2 pathway resulting in the upregulation of antioxidant vitagenes, as in the case of heme oxygenase-1 upregulated by hidrox® or curcumin and sirtuin-1 activated by resveratrol to inhibit reactive oxygen species (ROS) overproduction, microbiota dysfunction and neurotoxic damage. Importantly, modulation of the composition and function of the gut microbiota through polyphenols and/or probiotics enhances the abundance of beneficial bacteria and can prevent and treat Alzheimer's disease and other neurological disorders. Interestingly, dysregulation of the Nrf2 pathway in the gut and the brain can exacerbate selective susceptibility under neuroinflammatory conditions to CNS disorders due to the high vulnerability of vagal sensory neurons to oxidative stress. Herein, we aimed to discuss hormetic nutrients, including polyphenols and/or probiotics, targeting the Nrf2 pathway and vitagenes for the development of promising neuroprotective and therapeutic strategies to suppress oxidative stress, inflammation and microbiota deregulation, and consequently improve cognitive performance and brain health. In this review, we also explore interactions of the gut-brain axis based on sophisticated and cutting-edge technologies for novel anti-neuroinflammatory approaches and personalized nutritional therapies.

Transthyretin-Penetratin: A Potent Fusion Protein Inhibitor against Alzheimer's Amyloid-β Fibrillogenesis with High Blood Brain Barrier Crossing Capability

The design of a potent amyloid-β protein (Aβ) inhibitor plays a pivotal role in the prevention and treatment of Alzheimer's disease (AD). Despite endogenous transthyretin (TTR) being recognized as an Aβ inhibitor, the weak inhibitory and blood brain barrier (BBB) crossing capabilities hinder it for Aβ aggregation inhibition and transport. Therefore, we have herein designed a recombinant TTR by conjugating a cationic cell penetrating peptide (penetratin, Pen), which not only enabled the fusion protein, TTR-Pen (TP), to present high BBB penetration but also greatly enhanced the potency of Aβ inhibition. Namely, the protein fusion made TP positively charged, leading to a potent suppression of Aβ40 fibrillization at a low concentration (1.5 μM), while a TTR concentration as high as 12.5 μM was required to gain a similar function. Moreover, TP could mitigate Aβ-induced neuronal death, increase cultured cell viability from 72% to 92% at 2.5 μM, and extend the lifespan of AD nematodes from 14 to 18 d. Thermodynamic studies revealed that TP, enriched in positive charges, presented extensive electrostatic interactions with Aβ40. Importantly, TP showed excellent BBB penetration performance, with a 10 times higher BBB permeability than TTR, which would allow TP to enter the brain of AD patients and participate in the transport of Aβ species out of the brain. Thus, it is expected that the fusion protein has great potential for drug development in AD treatment.

Unravelling the in vitro and in vivo potential of selenium nanoparticles in Alzheimer's disease: A bioanalytical review

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by progressive cognitive decline and the accumulation of beta-amyloid plaques and tau tangles in the brain. Current therapies have limited efficacy, prompting the search for novel treatments. Selenium nanoparticles (SeNPs) have emerged as promising candidates for AD therapy due to their unique physicochemical properties and potential therapeutic effects. This review provides an overview of SeNPs and their potential application in AD treatment, as well as the main bioanalytical techniques applied in this field. SeNPs possess antioxidant and anti-inflammatory properties, making them potential candidates to combat the oxidative stress and neuroinflammation associated with AD. Moreover, SeNPs have shown the ability to cross the blood-brain barrier (BBB), allowing them to target brain regions affected by AD pathology. Various methods for synthesizing SeNPs are explored, including chemical, physical and biological synthesis approaches. Based on the employment of algae, yeast, fungi, and plants, green methods offer a promising and biocompatible alternative for SeNPs production. In vitro studies have demonstrated the potential of SeNPs in reducing beta-amyloid aggregation and inhibiting tau hyperphosphorylation, providing evidence of their neuroprotective effects on neuronal cells. In vivo studies using transgenic mouse models and AD-induced symptoms have shown promising results, with SeNPs treatment leading to cognitive improvements and reduced amyloid plaque burden in the hippocampus. Looking ahead, future trends in SeNPs research involve developing innovative brain delivery strategies to enhance their therapeutic potential, exploring alternative animal models to complement traditional mouse studies, and investigating multi-targeted SeNPs formulations to address multiple aspects of AD pathology. Overall, SeNPs represent a promising avenue for AD treatment, and further research in this field may pave the way for effective and much-needed therapeutic interventions for individuals affected by this debilitating disease.

Long-Term Krill Oil Administration Alleviated Early Mild Cognitive Impairment in APP/PS1 Mice

SCOPE

Alzheimer's disease is an age-dependent neurodegenerative disorder. Mounting studies focus on the improvement of advanced cognitive impairment by dietary nutrients. Krill oil (KO), a rich source of DHA/EPA and astaxanthin, is effective in improving cognitive function. The study mainly investigates the protective effects of long-term KO administration on early cognitive impairment.

METHODS AND RESULTS

Results show that 2 months KO administration (50 and 100 mg kg-1 BW) can dramatically promote learning and memory abilities. Mechanism studies demonstrate that KO reduces amyloid β concentration by regulating the amyloidogenic pathway, inhibits neuro-inflammation via regulating TLR4-NLRP3 signaling pathway, and prevents neuron injure. KO supplementation also enhances gut barrier integrity, reduces serum lipopolysaccharide leakage, and alters the gut microbiota by reducing Helicobacteraceae, Lactobacillaceae proportion, increasing Dubosiella and Akkermansia relative abundance. Particularly, a significant increase of isovaleric acid, propionic acid, and acetic acid levels is observed after KO supplementation. Correlation analysis shows that short-chain fatty acids (SCFAs), gut microbiota, and cognitive function are strongly correlated.

CONCLUSIONS

The results reveal that KO relieves early mild cognitive impairment possibly for its role in mediating the gut microbiome-SCFAs-brain axis. Thus, KO may provide potential intervention strategies to prevent cognitive impairment in the early stages through the microbiota-gut-brain axis.

Comparison of Neuroprotection and Regulating Properties on Gut Microbiota between Selenopeptide Val-Pro-Arg-Lys-Leu-SeMet and Its Native Peptide Val-Pro-Arg-Lys-Leu-Met In Vitro and In Vivo

Selenopeptides are promising candidates for intervening in neuroinflammation; however, the key role of selenium (Se) in selenopeptides remains poorly understood. To address this gap, we compared the neuroprotective effects of selenopeptide Val-Pro-Arg-Lys-Leu-SeMet (namely, Se-P1) and its native peptide Val-Pro-Arg-Lys-Leu-Met (namely, P1). Our results demonstrate that Se-P1 treatment exhibits superior antioxidant and antineuroinflammatory effects in PC12 cells and lipopolysaccharide (LPS)-injured mice compared to P1. Moreover, the administration of Se-P1 and P1 resulted in a shift in the gut microbiota composition. Notably, during LPS-induced injury, Se-P1 treatment demonstrated greater stability in maintaining gut microbiota composition compared to P1 treatment. Specifically, Se-P1 may have a positive impact on gut microbiota dysbiosis by modulating inflammatory-related bacteria such as enhancing Lactobacillus abundance while reducing that of Lachnospiraceae_NK4A136_group. Furthermore, the alteration of metabolites induced by Se-P1 treatment exhibited a significant correlation with gut microbiota, subsequently modulating the inflammatory-related metabolic pathways including histidine metabolism, lysine degradation, and purine metabolism. These findings suggest that organic Se contributes to the bioactivities of Se-P1 in mitigating neuroinflammation in LPS-injured mice compared to P1. These findings hold significant value for the development of potential preventive or therapeutic strategies against neurodegenerative diseases and introduce novel concepts in selenopeptide nutrition and supplementation recommendations.

The Developments of Surface-Functionalized Selenium Nanoparticles and Their Applications in Brain Diseases Therapy

Selenium (Se) and its organic and inorganic compounds in dietary supplements have been found to possess excellent pharmacodynamics and biological responses. However, Se in bulk form generally exhibits low bioavailability and high toxicity. To address these concerns, nanoscale selenium (SeNPs) with different forms, such as nanowires, nanorods, and nanotubes, have been synthesized, which have become increasingly popular in biomedical applications owing to their high bioavailability and bioactivity, and are widely used in oxidative stress-induced cancers, diabetes, and other diseases. However, pure SeNPs still encounter problems when applied in disease therapy because of their poor stability. The surface functionalization strategy has become increasingly popular as it sheds light to overcome these limitations in biomedical applications and further improve the biological activity of SeNPs. This review summarizes synthesis methods and surface functionalization strategies employed for the preparation of SeNPs and highlights their applications in treating brain diseases.

Microbiota-gut-brain axis and related therapeutics in Alzheimer's disease: prospects for multitherapy and inflammation control

Alzheimer's disease (AD) is the most common type of dementia in the elderly and causes neurodegeneration, leading to memory loss, behavioral disorder, and psychiatric impairment. One potential mechanism contributing to the pathogenesis of AD may be the imbalance in gut microbiota, local and systemic inflammation, and dysregulation of the microbiota-gut-brain axis (MGBA). Most of the AD drugs approved for clinical use today are symptomatic treatments that do not improve AD pathologic changes. As a result, researchers are exploring novel therapeutic modalities. Treatments involving the MGBA include antibiotics, probiotics, transplantation of fecal microbiota, botanical products, and others. However, single-treatment modalities are not as effective as expected, and a combination therapy is gaining momentum. The purpose of this review is to summarize recent advances in MGBA-related pathological mechanisms and treatment modalities in AD and to propose a new concept of combination therapy. "MGBA-based multitherapy" is an emerging view of treatment in which classic symptomatic treatments and MGBA-based therapeutic modalities are used in combination. Donepezil and memantine are two commonly used drugs in AD treatment. On the basis of the single/combined use of these two drugs, two/more additional drugs and treatment modalities that target the MGBA are chosen based on the characteristics of the patient's condition as an adjuvant treatment, as well as the maintenance of good lifestyle habits. "MGBA-based multitherapy" offers new insights for the treatment of cognitive impairment in AD patients and is expected to show good therapeutic results.

Latent Potential of Multifunctional Selenium Nanoparticles in Neurological Diseases and Altered Gut Microbiota

Neurological diseases remain a major concern due to the high world mortality rate and the absence of appropriate therapies to cross the blood-brain barrier (BBB). Therefore, the major focus is on the development of such strategies that not only enhance the efficacy of drugs but also increase their permeability in the BBB. Currently, nano-scale materials seem to be an appropriate approach to treating neurological diseases based on their drug-loading capacity, reduced toxicity, targeted delivery, and enhanced therapeutic effect. Selenium (Se) is an essential micronutrient and has been of remarkable interest owing to its essential role in the physiological activity of the nervous system, i.e., signal transmission, memory, coordination, and locomotor activity. A deficiency of Se leads to various neurological diseases such as Parkinson's disease, epilepsy, and Alzheimer's disease. Therefore, owing to the neuroprotective role of Se (selenium) nanoparticles (SeNPs) are of particular interest to treat neurological diseases. To date, many studies investigate the role of altered microbiota with neurological diseases; thus, the current review focused not only on the recent advancement in the field of nanotechnology, considering SeNPs to cure neurological diseases, but also on investigating the potential role of SeNPs in altered microbiota.

The potential of the gut microbiome for identifying Alzheimer's disease diagnostic biomarkers and future therapies

Being isolated from the peripheral system by the blood-brain barrier, the brain has long been considered a completely impervious tissue. However, recent findings show that the gut microbiome (GM) influences gastrointestinal and brain disorders such as Alzheimer's disease (AD). Despite several hypotheses, such as neuroinflammation, tau hyperphosphorylation, amyloid plaques, neurofibrillary tangles, and oxidative stress, being proposed to explain the origin and progression of AD, the pathogenesis remains incompletely understood. Epigenetic, molecular, and pathological studies suggest that GM influences AD development and have endeavored to find predictive, sensitive, non-invasive, and accurate biomarkers for early disease diagnosis and monitoring of progression. Given the growing interest in the involvement of GM in AD, current research endeavors to identify prospective gut biomarkers for both preclinical and clinical diagnoses, as well as targeted therapy techniques. Here, we discuss the most recent findings on gut changes in AD, microbiome-based biomarkers, prospective clinical diagnostic uses, and targeted therapy approaches. Furthermore, we addressed herbal components, which could provide a new venue for AD diagnostic and therapy research.

Getting drugs to the brain: advances and prospects of organic nanoparticle delivery systems for assisting drugs to cross the blood-brain barrier

The blood-brain barrier (BBB) plays an irreplaceable role in protecting the central nervous system (CNS) from bloodborne pathogens. However, the BBB complicates the treatment of CNS diseases because it prevents almost all therapeutic drugs from getting into the CNS. With the growing understanding of the physiological characteristics of the BBB and the development of nanotechnology, nanomaterial-based drug delivery systems have become promising tools for delivering drugs across the BBB to the CNS. Herein, we systematically summarize the recent progress in organic-nanoparticle delivery systems for treating CNS diseases and evaluate their mechanisms in overcoming the BBB with the aim to provide a comprehensive understanding of the advantages, disadvantages, and challenges of organic nanoparticles in delivering drugs across the BBB. This review may inspire new research ideas and directions for applying nanotechnology to treat CNS diseases.

Chaihu-shugan-san alleviates depression-like behavior in mice exposed to chronic unpredictable stress by altering the gut microbiota and levels of the bile acids hyocholic acid and 7-ketoDCA

Chaihu-Shugan-San (CSS) is a traditional botanical drug formula often prescribed to treat depression in oriental countries, but its pharmacotherapeutic mechanism remains unknown. It was recently reported that CSS alters the composition of intestinal microflora and related metabolites such as bile acids (BAs). Since the intestinal microflora affects physiological functions of the brain through the gut-microbiota-brain axis, herein we investigated whether CSS altered BA levels, gut microflora, and depression-like symptoms in chronic unpredictable mild stress (CUMS) mice, a well-established mouse model of depression. Furthermore, we determined whether BA manipulation and fecal microbiota transplantation altered CSS antidepressant actions. We found that the BA chelator cholestyramine impaired the antidepressant effects of CSS, which was partially rescued by dietary cholic acid. CSS increased the relative abundance of Parabacteroides distasonis in the colon of CUMS mice, and increased serum levels of various BAs including hyocholic acid (HCA) and 7-ketodeoxycholic acid (7-ketoDCA). Furthermore, gut bacteria transplantation from CSS-treated mice into untreated or cholestyramine-treated CUMS mice restored serum levels of HCA and 7-ketoDCA, alleviating depression-like symptoms. In the hippocampus, CSS-treated mice had decreased expression of genes associated with BA transport (Bsep and Fxr) and increased expression of brain-derived neurotrophic factor and its receptor, TrkB. Overall, CSS increases intestinal P. distasonis abundance, leading to elevated levels of secondary BAs in the circulation and altered expression of hippocampal genes implicated in BA transport and neurotrophic signaling. Our data strongly suggest that the gut microbiota-brain axis contributes to the potent antidepressant action of CSS by modulating BA metabolism.

Comparative Metagenomics and Metabolomes Reveals Abnormal Metabolism Activity Is Associated with Gut Microbiota in Alzheimer's Disease Mice

A common symptom in Alzheimer's disease (AD) is cognitive decline, of which the potential pathogenesis remains unclear. In order to understand the mechanism of gut microbiota in AD, it is necessary to clarify the relationship between gut microbiota and metabolites. Behavioral tests, pathological examination, metagenomics, and metabolomics were applied to analyze the difference of gut microbiota and metabolome between APP^swe/PS1^ΔE9 (PAP) mice with cognitive decline and age-matched controls, and their possible correlations. Our results showed that PAP mice and health mice had different structures of the bacterial communities in the gut. The abundances and diversities of the bacterial communities in health mice were higher than in PAP mice by metagenomics analysis. The abundances of Libanicoccus massiliensis, Paraprevotella clara, and Lactobacillus amylovorus were significantly increased in PAP mice, while the abundances of Turicibacter sanguinis, Dubosiella newyorkensis, and Prevotella oris were greatly reduced. Furthermore, PAP mice possessed peculiar metabolic phenotypes in stool, serum, and hippocampus relative to WT mice, as is demonstrated by alterations in neurotransmitters metabolism, lipid metabolism, aromatic amino acids metabolism, energy metabolism, vitamin digestion and absorption, and bile metabolism. Microbiota-host metabolic correlation analysis suggests that abnormal metabolism in stool, serum, and hippocampus of PAP mice may be modulated by the gut microbiota, especially T. sanguinis, D. newyorkensis, and P. oris. Therefore, abnormal metabolism activity is associated with gut microbiota in Alzheimer's disease mice. Our results imply that modifying host metabolism through targeting gut microbiota may be a novel and viable strategy for the prevention and treatment of AD in the future.