Amyloid peptides with antimicrobial and/or microbial agglutination activity

Interplay between Antimicrobial Peptides and Amyloid Proteins in Host Defense and Disease Modulation

The biological properties of antimicrobial peptides (AMPs) and amyloid proteins and their cross-talks have gained increasing attention due to their potential implications in both host defense mechanisms and amyloid-related diseases. However, complex interactions, molecular mechanisms, and physiological applications are not fully understood. The interplay between antimicrobial peptides and amyloid proteins is crucial for uncovering new insights into immune defense and disease mechanisms, bridging critical gaps in understanding infectious and neurodegenerative diseases. This review provides an overview of the cross-talk between AMPs and amyloids, highlighting their intricate interplay, mechanisms of action, and potential therapeutic implications. The dual roles of AMPs, which not only serve as key components of the innate immune system, combating microbial infections, but also exhibit modulatory effects on amyloid formation and toxicity, are discussed. The diverse mechanisms employed by AMPs to modulate amyloid aggregation, fibril formation, and toxicity are also discussed. Additionally, we explore emerging evidence suggesting that amyloid proteins may possess antimicrobial properties, adding a new dimension to the intricate relationship between AMPs and amyloids. This review underscores the importance of understanding the cross-talk between AMPs and amyloids to better understand the molecular processes underlying infectious diseases and amyloid-related disorders and to aid in the development of therapeutic avenues to treat them.

The antibacterial defence role of β-defensin in the seahorse testis

Seahorses represent the only known group of animals with male pregnancy. Seahorses have small testis that produce a limited quantity of sperm. To date, the response of this immune-privileged organ to pathogenic infections has not been reported. β-defensin (BD) is an important innate immune defence factor against pathogens in vertebrate testis. To elucidate its immunoprotection in seahorse testis, we identified the Hippocampus erectus β-defensin (HeBD) sequence in its genome via phylogenetic tree and protein-sequence structure analysis. Gene-expression analysis showed that HeBD was highly expressed in the seahorse testis and was significantly upregulated after bacterial infection, indicating that HeBD expression was related to testicular immune responses. Furthermore, antibacterial activity testing demonstrated that the mature HeBD peptide exhibited broad-spectrum aggregation activity but only moderate antibacterial activity. We found that the mature HeBD mature significantly neutralised bacterial endotoxin activity. In conclusion, our results imply that HeBD serves an immunoprotective role in seahorse testis.

Multiplex antimicrobial activities of the self-assembled amphiphilic polypeptide β nanofiber KF-5 against vaginal pathogens

BACKGROUND

Vaginal infections caused by multidrug-resistant pathogens such as Candida albicans and Gardnerella spp. represent a significant health challenge. Current treatments often fail because of resistance and toxicity. This study aimed to synthesize and characterize a novel amphiphilic polypeptide, KF-5, and evaluate its antibacterial and antifungal activities, biocompatibility, and potential mechanisms of action.

RESULTS

The KF-5 peptide was synthesized via solid-phase peptide synthesis and self-assembled into nanostructures with filamentous and hydrogel-like configurations. Characterization by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) confirmed the unique nanostructural properties of KF-5. KF-5 (125, 250, or 500 µg/ml) demonstrated potent antibacterial and antifungal activities, with significant inhibitory effects on drug-resistant Candida albicans and Gardnerella spp. (P < 0.05). In vitro assays revealed that 500 µg/ml KF-5 disrupted microbial cell membranes, increased membrane permeability, and induced lipid oxidation, leading to cell death (P < 0.05). Cytotoxicity tests revealed minimal toxicity in human vaginal epithelial cells, keratinocytes, and macrophages, with over 95% viability at high concentrations. Molecular dynamics simulations indicated that KF-5 interacts with phospholipid bilayers through electrostatic interactions, causing membrane disruption. In vivo studies using a mouse model of vaginal infection revealed that 0.5, 1, and 2 mg/ml KF-5 significantly reduced fungal burden and inflammation, and histological analysis confirmed the restoration of vaginal mucosal integrity (P < 0.01). Compared with conventional antifungal treatments such as miconazole, KF-5 exhibited superior efficacy (P < 0.01).

CONCLUSIONS

KF-5 demonstrates significant potential as a safe and effective antimicrobial agent for treating vaginal infections. Its ability to disrupt microbial membranes while maintaining biocompatibility with human cells highlights its potential for clinical application. These findings provide a foundation for further development of KF-5 as a therapeutic option for combating drug-resistant infections.

MAD-microbial (origin of) Alzheimer's disease hypothesis: from infection and the antimicrobial response to disruption of key copper-based systems

Microbes have been suspected to cause Alzheimer's disease since at least 1908, but this has generally remained unpopular in comparison to the amyloid hypothesis and the dominance of Aβ and Tau. However, evidence has been accumulating to suggest that these earlier theories are but a manifestation of a common cause that can trigger and interact with all the major molecular players recognized in AD. Aβ, Tau and ApoE, in particular appear to be molecules with normal homeostatic functions but also with alternative antimicrobial functions. Their alternative functions confer the non-immune specialized neuron with some innate intracellular defenses that appear to be re-appropriated from their normal functions in times of need. Indeed, signs of infection of the neurons by biofilm-forming microbial colonies, in synergy with herpes viruses, are evident from the clinical and preclinical studies we discuss. Furthermore, we attempt to provide a mechanistic understanding of the AD landscape by discussing the antimicrobial effect of Aβ, Tau and ApoE and Lactoferrin in AD, and a possible mechanistic link with deficiency of vital copper-based systems. In particular, we focus on mitochondrial oxidative respiration via complex 4 and ceruloplasmin for iron homeostasis, and how this is similar and possibly central to neurodegenerative diseases in general. In the case of AD, we provide evidence for the microbial Alzheimer's disease (MAD) theory, namely that AD could in fact be caused by a long-term microbial exposure or even long-term infection of the neurons themselves that results in a costly prolonged antimicrobial response that disrupts copper-based systems that govern neurotransmission, iron homeostasis and respiration. Finally, we discuss potential treatment modalities based on this holistic understanding of AD that incorporates the many separate and seemingly conflicting theories. If the MAD theory is correct, then the reduction of microbial exposure through use of broad antimicrobial and anti-inflammatory treatments could potentially alleviate AD although this requires further clinical investigation.

Exploring pathological link between antimicrobial and amyloid peptides

Amyloid peptides (AMYs) and antimicrobial peptides (AMPs) are considered as the two distinct families of peptides, characterized by their unique sequences, structures, biological functions, and specific pathological targets. However, accumulating evidence has revealed intriguing pathological connections between these peptide families in the context of microbial infection and neurodegenerative diseases. Some AMYs and AMPs share certain structural and functional characteristics, including the ability to self-assemble, the presence of β-sheet-rich structures, and membrane-disrupting mechanisms. These shared features enable AMYs to possess antimicrobial activity and AMPs to acquire amyloidogenic properties. Despite limited studies on AMYs-AMPs systems, the cross-seeding phenomenon between AMYs and AMPs has emerged as a crucial factor in the bidirectional communication between the pathogenesis of neurodegenerative diseases and host defense against microbial infections. In this review, we examine recent developments in the potential interplay between AMYs and AMPs, as well as their pathological implications for both infectious and neurodegenerative diseases. By discussing the current progress and challenges in this emerging field, this account aims to inspire further research and investments to enhance our understanding of the intricate molecular crosstalk between AMYs and AMPs. This knowledge holds great promise for the development of innovative therapies to combat both microbial infections and neurodegenerative disorders.

m5C RNA methylation: a potential mechanism for infectious Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder caused by a variety of factors, including age, genetic susceptibility, cardiovascular disease, traumatic brain injury, and environmental factors. The pathogenesis of AD is largely associated with the overproduction and accumulation of amyloid-β peptides and the hyperphosphorylation of tau protein in the brain. Recent studies have identified the presence of diverse pathogens, including viruses, bacteria, and parasites, in the tissues of AD patients, underscoring the critical role of central nervous system infections in inducing pathological changes associated with AD. Nevertheless, it remains unestablished about the specific mechanism by which infections lead to the occurrence of AD. As an important post-transcriptional RNA modification, RNA 5-methylcytosine (m5C) methylation regulates a wide range of biological processes, including RNA splicing, nuclear export, stability, and translation, therefore affecting cellular function. Moreover, it has been recently demonstrated that multiple pathogenic microbial infections are associated with the m5C methylation of the host. However, the role of m5C methylation in infectious AD is still uncertain. Therefore, this review discusses the mechanisms of pathogen-induced AD and summarizes research on the molecular mechanisms of m5C methylation in infectious AD, thereby providing new insight into exploring the mechanism underlying infectious AD.

Amyloid peptide - synthetic polymer blends with enhanced mechanical and biological properties

Interest in utilizing amyloids to develop biomaterials is increasing due to their potential for biocompatibility, unique assembling morphology, mechanical stability, and biophysical properties. However, challenges include the complexity of peptide chemistry and the practical techniques required for processing amyloids into bulk materials. In this work, two decapeptides with fibrillar and globular morphologies were selected, blended with poly(ethylene oxide), and fabricated into composite mats via electrospinning. Notable enhancements in mechanical properties were observed, attributed to the uniform distribution of the decapeptide assemblies within the PEO matrix. Morphological differences, such as the production of thinner nanofibers, are attributed to the increased conductivity from the zwitterionic nature of the decapeptides. Blend rheology and post-processing analysis revealed how processing might affect the amyloid aggregation and secondary structure of the peptides. Both decapeptides demonstrated good biocompatibility and strong antioxidant activity, indicating their potential for safe and effective use as biomaterials. By evaluating these interdependencies, this research lays the foundation for understanding the structure-property-processing relationships of peptide-polymer blends and highlights the strong potential for developing applications in biotechnology.

Regional Differences in Microbial Infiltration of Brain Tissue from Alzheimer's Disease Patients and Control Individuals

Alzheimer's disease (AD) is characterized by cognitive decline and neuropathology including amyloid beta (Aβ) plaques and neurofibrillary tangles (tau). Factors initiating or driving these pathologies remain unclear, though microbes have been increasingly implicated. Our data and others' findings indicate that microbes may be common constituents of the brain. It is notable that Aβ and tau have antimicrobial properties, suggesting a response to microbes in the brain. We used 16S rRNA sequencing to compare major bacterial phyla in post-mortem tissues from individuals exhibiting a range of neuropathology and cognitive status in two brain regions variably affected in AD. Our data indicate that strong regional differences exist, driven in part by the varied presence of Proteobacteria and Firmicutes. We confirmed our data using ELISA of bacterial lipopolysaccharide (LPS) and lipoteichoic acid in the same brain tissue. We identified a potential association between the composition of phyla and the presence of neuropathology but not cognitive status. Declining cognition and increasing pathology correlated closely with serum LPS, but not brain levels of LPS, although brain LPS showed a strong negative correlation with cerebral amyloid angiopathy. Collectively, our data suggest a region-specific heterogeneity of microbial populations in brain tissue potentially associated with neurodegenerative pathology.

Optimizing Antimicrobial Peptide Design: Integration of Cell-Penetrating Peptides, Amyloidogenic Fragments, and Amino Acid Residue Modifications

The escalating threat of multidrug-resistant pathogens necessitates innovative approaches to combat infectious diseases. In this study, we examined peptides R23FS*, V31KS*, and R44KS*, which were engineered to include an amyloidogenic fragment sourced from the S1 protein of S. aureus, along with one or two cell-penetrating peptide (CPP) components. We assessed the antimicrobial efficacy of these peptides in a liquid medium against various strains of both Gram-positive bacteria, including S. aureus (209P and 129B strains), MRSA (SA 180 and ATCC 43300 strains), and B. cereus (strain IP 5832), and Gram-negative bacteria such as P. aeruginosa (ATCC 28753 and 2943 strains) and E. coli (MG1655 and K12 strains). Peptides R23FS*, V31KS*, and R44KS* exhibited antimicrobial activity comparable to gentamicin and meropenem against all tested bacteria at concentrations ranging from 24 to 48 μM. The peptides showed a stronger antimicrobial effect against B. cereus. Notably, peptide R44KS* displayed high efficacy compared to peptides R23FS* and V31KS*, particularly evident at lower concentrations, resulting in significant inhibition of bacterial growth. Furthermore, modified peptides V31KS* and R44KS* demonstrated enhanced inhibitory effects on bacterial growth across different strains compared to their unmodified counterparts V31KS and R44KS. These results highlight the potential of integrating cell-penetrating peptides, amyloidogenic fragments, and amino acid residue modifications to advance the innovation in the field of antimicrobial peptides, thereby increasing their effectiveness against a broad spectrum of pathogens.

Human in vivo evidence of associations between herpes simplex virus and cerebral amyloid-beta load in normal aging

BACKGROUND

Mounting data suggests that herpes simplex virus type 1 (HSV-1) is involved in the pathogenesis of AD, possibly instigating amyloid-beta (Aβ) accumulation decades before the onset of clinical symptoms. However, human in vivo evidence linking HSV-1 infection to AD pathology is lacking in normal aging, which may contribute to the elucidation of the role of HSV-1 infection as a potential AD risk factor.

METHODS

To shed light into this question, serum anti-HSV IgG levels were correlated with 18F-Florbetaben-PET binding to Aβ deposits and blood markers of neurodegeneration (pTau181 and neurofilament light chain) in cognitively normal older adults. Additionally, we investigated whether associations between anti-HSV IgG and AD markers were more evident in APOE4 carriers.

RESULTS

We showed that increased anti-HSV IgG levels are associated with higher Aβ load in fronto-temporal regions of cognitively normal older adults. Remarkably, these cortical regions exhibited abnormal patterns of resting state-functional connectivity (rs-FC) only in those individuals showing the highest levels of anti-HSV IgG. We further found that positive relationships between anti-HSV IgG levels and Aβ load, particularly in the anterior cingulate cortex, are moderated by the APOE4 genotype, the strongest genetic risk factor for AD. Importantly, anti-HSV IgG levels were unrelated to either subclinical cognitive deficits or to blood markers of neurodegeneration.

CONCLUSIONS

All together, these results suggest that HSV infection is selectively related to cortical Aβ deposition in normal aging, supporting the inclusion of cognitively normal older adults in prospective trials of antimicrobial therapy aimed at decreasing the AD risk in the aging population.

Viral Infections, Are They a Trigger and Risk Factor of Alzheimer's Disease?

Alzheimer's Disease (AD), a progressive and debilitating condition, is reported to be the most common type of dementia, with at least 55 million people believed to be currently affected. Many causation hypotheses of AD exist, yet the intriguing link between viral infection and its possible contribution to the known etiology of AD has become an attractive focal point of research for the field and a challenging study task. In this review, we will explore the historical perspective and milestones that led the field to investigate the viral connection to AD. Specifically, several viruses such as Herpes Simplex Virus 1 (HSV-1), Zika virus (ZIKV), and severe cute respiratory syndrome coronavirus 2 (SARS-CoV-2), along with several others mentioned, include the various viruses presently considered within the field. We delve into the strong evidence implicating these viruses in the development of AD such as the lytic replication and axonal transport of HSV-1, the various mechanisms of ZIKV neurotropism through the human protein Musashi-1 (MSI1), and the spread of SARS-CoV-2 through the transfer of the virus through the BBB endothelial cells to glial cells and then to neurons via transsynaptic transfer. We will also explore beyond these mere associations by carefully analyzing the potential mechanisms by which these viruses may contribute to AD pathology. This includes but is not limited to direct neuronal infections, the dysregulation of immune responses, and the impact on protein processing (Aβ42 and hyperphosphorylated tau). Controversies and challenges of the virus-AD relationship emerge as we tease out these potential mechanisms. Looking forward, we emphasize future directions, such as distinct questions and proposed experimentations to explore, that the field should take to tackle the remaining unanswered questions and the glaring research gaps that persist. Overall, this review aims to provide a comprehensive survey of the past, present, and future of the potential link between viral infections and their association with AD development while encouraging further discussion.

How do Antimicrobial Peptides Interact with the Outer Membrane of Gram-Negative Bacteria? Role of Lipopolysaccharides in Peptide Binding, Anchoring, and Penetration

Gram-negative bacteria possess a complex structural cell envelope that constitutes a barrier for antimicrobial peptides that neutralize the microbes by disrupting their cell membranes. Computational and experimental approaches were used to study a model outer membrane interaction with an antimicrobial peptide, melittin. The investigated membrane included di[3-deoxy-d-manno-octulosonyl]-lipid A (KLA) in the outer leaflet and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) in the inner leaflet. Molecular dynamics simulations revealed that the positively charged helical C-terminus of melittin anchors rapidly into the hydrophilic headgroup region of KLA, while the flexible N-terminus makes contacts with the phosphate groups of KLA, supporting melittin penetration into the boundary between the hydrophilic and hydrophobic regions of the lipids. Electrochemical techniques confirmed the binding of melittin to the model membrane. To probe the peptide conformation and orientation during interaction with the membrane, polarization modulation infrared reflection absorption spectroscopy was used. The measurements revealed conformational changes in the peptide, accompanied by reorientation and translocation of the peptide at the membrane surface. The study suggests that melittin insertion into the outer membrane affects its permeability and capacitance but does not disturb the membrane's bilayer structure, indicating a distinct mechanism of the peptide action on the outer membrane of Gram-negative bacteria.

The Gut-Brain Axis in Alzheimer's and Parkinson's Diseases: The Catalytic Role of Mitochondria

Accumulating evidence suggests that gut inflammation is implicated in neuroinflammation in Alzheimer's and Parkinson's diseases. Despite the numerous connections it remains unclear how the gut and the brain communicate and whether gut dysbiosis is the cause or consequence of these pathologies. Importantly, several reports highlight the importance of mitochondria in the gut-brain axis, as well as in mechanisms like gut epithelium self-renewal, differentiation, and homeostasis. Herein we comprehensively address the important role of mitochondria as a cellular hub in infection and inflammation and as a link between inflammation and neurodegeneration in the gut-brain axis. The role of mitochondria in gut homeostasis and as well the crosstalk between mitochondria and gut microbiota is discussed. Significantly, we also review studies highlighting how gut microbiota can ultimately affect the central nervous system. Overall, this review summarizes novel findings regarding this cross-talk where the mitochondria has a main role in the pathophysiology of both Alzheimer's and Parkinson's disease strengthen by cellular, animal and clinical studies.

Enhancing the Antimicrobial Properties of Peptides through Cell-Penetrating Peptide Conjugation: A Comprehensive Assessment

Combining antimicrobial peptides (AMPs) with cell-penetrating peptides (CPPs) has shown promise in boosting antimicrobial potency, especially against Gram-negative bacteria. We examined the CPP-AMP interaction with distinct bacterial types based on cell wall differences. Our investigation focused on AMPs incorporating penetratin CPP and dihybrid peptides containing both cell-penetrating TAT protein fragments from the human immunodeficiency virus and Antennapedia peptide (Antp). Assessment of the peptides TAT-AMP, AMP-Antp, and TAT-AMP-Antp revealed their potential against Gram-positive strains (Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus (MRSA), and Bacillus cereus). Peptides TAT-AMP and AMP-Antp using an amyloidogenic AMP from S1 ribosomal protein Thermus thermophilus, at concentrations ranging from 3 to 12 μM, exhibited enhanced antimicrobial activity against B. cereus. TAT-AMP and TAT-AMP-Antp, using an amyloidogenic AMP from the S1 ribosomal protein Pseudomonas aeruginosa, at a concentration of 12 µM, demonstrated potent antimicrobial activity against S. aureus and MRSA. Notably, the TAT-AMP, at a concentration of 12 µM, effectively inhibited Escherichia coli (E. coli) growth and displayed antimicrobial effects similar to gentamicin after 15 h of incubation. Peptide characteristics determined antimicrobial activity against diverse strains. The study highlights the intricate relationship between peptide properties and antimicrobial potential. Mechanisms of AMP action are closely tied to bacterial cell wall attributes. Peptides with the TAT fragment exhibited enhanced antimicrobial activity against S. aureus, MRSA, and P. aeruginosa. Peptides containing only the Antp fragment displayed lower activity. None of the investigated peptides demonstrated cytotoxic or cytostatic effects on either BT-474 cells or human skin fibroblasts. In conclusion, CPP-AMPs offer promise against various bacterial strains, offering insights for targeted antimicrobial development.

Amyloid hexapeptide prevent dental caries by antibiofilm formation

OBJECTIVES

Biofilm formed by cariogenic microbes is the direct cause of dental caries, therefore, prevention of dental caries should be anti-biofilm-based. Previously, we found the amyloid hexapeptides efficiently inhibited biofilm formation by aggregating into amyloid fibrils agglutinating microbes. This study aimed to select the most stable amyloid hexapeptide GIDLKI (GI6) and study its anti-caries effect.

METHODS

Biofilms of multi-species bacteria, derived from mixed saliva, were cultured to evaluate the anti-biofilm formation effect of GI6. And then, the primary cariogenic bacterium Streptococcus mutans (S.mutans) was cultured in BHI with various pH, gradient concentrations of sucrose, glucose, and calcium ions to evaluate the anti-biofilm formation effects of GI6. Then models of human enamel block caries and twenty male SPF-SD rat caries induced by S. mutans biofilm were constructed, and confocal laser scanning microscopy, scanning electron microscopy, and micro-computed tomography were applied to investigate the anti-biofilm formation, anti-caries effects and use safety of GI6.

RESULTS

GI6 could inhibit the multi-species bacteria biofilm formation and remained effective in anti-biofilm activity against S. mutans in environments closely related to caries. GI6 suppressed S. mutans biofilm formation and thus prevented or alleviated the development of caries in human tooth blocks and rat teeth. GI6 did not affect the intestinal flora, serum biochemical parameters, and the pathological changes of various organs.

CONCLUSIONS

Amyloid hexapeptides, including but not limited to GI6, are novel effective anti-caries agents that can be used to prevent dental caries safely.

CLINICAL SIGNIFICANCE

This study explored the anti-biofilm formation and anti-caries effect of GI6 in vitro, highlighting the anti-biofilm formation therapy for dental caries and setting a foundation for the practical application of GI6 for the treatment of dental caries.

Viruses - a major cause of amyloid deposition in the brain

INTRODUCTION

Clinically, Alzheimer's disease (AD) is a syndrome with a spectrum of various cognitive disorders. There is a complete dissociation between the pathology and the clinical presentation. Therefore, we need a disruptive new approach to be able to prevent and treat AD.

AREAS COVERED

In this review, the authors extensively discuss the evidence why the amyloid beta is not the pathological cause of AD which makes therefore the amyloid hypothesis not sustainable anymore. They review the experimental evidence underlying the role of microbes, especially that of viruses, as a trigger/cause for the production of amyloid beta leading to the establishment of a chronic neuroinflammation as the mediator manifesting decades later by AD as a clinical spectrum. In this context, the emergence and consequences of the infection/antimicrobial protection hypothesis are described. The epidemiological and clinical data supporting this hypothesis are also analyzed.

EXPERT OPINION

For decades, we have known that viruses are involved in the pathogenesis of AD. This discovery was ignored and discarded for a long time. Now we should accept this fact, which is not a hypothesis anymore, and stimulate the research community to come up with new ideas, new treatments, and new concepts.

The C-terminal 32-mer fragment of hemoglobin alpha is an amyloidogenic peptide with antimicrobial properties

Antimicrobial peptides (AMPs) are major components of the innate immune defense. Accumulating evidence suggests that the antibacterial activity of many AMPs is dependent on the formation of amyloid-like fibrils. To identify novel fibril forming AMPs, we generated a spleen-derived peptide library and screened it for the presence of amyloidogenic peptides. This approach led to the identification of a C-terminal 32-mer fragment of alpha-hemoglobin, termed HBA(111-142). The non-fibrillar peptide has membranolytic activity against various bacterial species, while the HBA(111-142) fibrils aggregated bacteria to promote their phagocytotic clearance. Further, HBA(111-142) fibrils selectively inhibited measles and herpes viruses (HSV-1, HSV-2, HCMV), but not SARS-CoV-2, ZIKV and IAV. HBA(111-142) is released from its precursor by ubiquitous aspartic proteases under acidic conditions characteristic at sites of infection and inflammation. Thus, HBA(111-142) is an amyloidogenic AMP that may specifically be generated from a highly abundant precursor during bacterial or viral infection and may play an important role in innate antimicrobial immune responses.

Dementia, infections and vaccines: 30 years of controversy

This paper reports the proceedings of a virtual meeting convened by the European Interdisciplinary Council on Ageing (EICA), to discuss the involvement of infectious disorders in the pathogenesis of dementia and neurological disorders leading to dementia. We recap how our view of the infectious etiology of dementia has changed over the last 30 years in light of emerging evidence, and we present evidence in support of the implication of infection in dementia, notably Alzheimer's disease (AD). The bacteria and viruses thought to be responsible for neuroinflammation and neurological damage are reviewed. We then review the genetic basis for neuroinflammation and dementia, highlighting the genes that are currently the focus of investigation as potential targets for therapy. Next, we describe the antimicrobial hypothesis of dementia, notably the intriguing possibility that amyloid beta may itself possess antimicrobial properties. We further describe the clinical relevance of the gut-brain axis in dementia, the mechanisms by which infection can move from the intestine to the brain, and recent findings regarding dysbiosis patterns in patients with AD. We review the involvement of specific pathogens in neurological disorders, i.e. SARS-CoV-2, human immunodeficiency virus (HIV), herpes simplex virus type 1 (HSV1), and influenza. Finally, we look at the role of vaccination to prevent dementia. In conclusion, there is a large body of evidence supporting the involvement of various infectious pathogens in the pathogenesis of dementia, but large-scale studies with long-term follow-up are needed to elucidate the role that infection may play, especially before subclinical or clinical disease is present.

Computer-Aided Screening and Revealing Action Mechanism of Green Tea Polyphenols Intervention in Alzheimer's Disease

The accumulation of cross-β-sheet amyloid fibrils is a hallmark of the neurodegenerative process of Alzheimer's disease (AD). Although it has been reported that green tea substances such as epicatechin (EC), epicatechin-3-gallate (ECG), epigallocatechin (EGC) and epigallocatechin-3-gallate (EGCG) could alleviate the symptoms of AD and other neurodegenerative diseases, the pharmacological mechanism remains largely unexplored. This study aimed to reveal the underlying mechanism of EC, ECG, EGC and EGCG in AD using a computer-aided screening strategy. Our results showed that the four tea polyphenols interfered with the signaling pathways of AD via calcium signaling channels, neurodegeneration-multiple disease signal pathways and others. We also identified the key residues of the interaction between VEGFA and the four active components, which included Glu64 and Phe36. Overall, we have provided valuable insights into the molecular mechanism of tea polyphenols, which could be used as a reference to improve therapeutic strategies against AD.