The hypothesis that Helicobacter pylori predisposes to Alzheimer's disease is biologically plausible

Fecal Microbiota Transplantation from Methionine-Restricted Diet Mouse Donors Improves Alzheimer's Learning and Memory Abilities Through Short-Chain Fatty Acids

Alzheimer's disease (AD) is marked by impaired cognitive functions, particularly in learning and memory, owing to complex and diverse mechanisms. Methionine restriction (MR) has been found to exert a mitigating effect on brain oxidative stress to improve AD. However, the bidirectional crosstalk between the gut and brain through which MR enhances learning and memory in AD, as well as the effects of fecal microbiota transplantation (FMT) from MR mice on AD mice, remains underexplored. In this study, APP/PS1 double transgenic AD mice were used and an FMT experiment was conducted. 16S rRNA gene sequencing, targeted metabolomics, and microbial metabolite short-chain fatty acids (SCFAs) of feces samples were analyzed. The results showed that MR reversed the reduction in SCFAs induced by AD, and further activated the free fatty acid receptors, FFAR2 and FFAR3, as well as the transport protein MCT1, thereby signaling to the brain to mitigate inflammation and enhance the learning and memory capabilities. Furthermore, the FMT experiment from methionine-restricted diet mouse donors showed that mice receiving FMT ameliorated Alzheimer's learning and memory ability through SCFAs. This study offers novel non-pharmaceutical intervention strategies for AD prevention.

Helicobacter pylori outer membrane vesicles directly promote Aβ aggregation and enhance Aβ toxicity in APP/PS1 mice

Helicobacter pylori (H. pylori) infection has been found associated with Alzheimer's disease (AD) with unclear mechanisms. Outer Membrane Vesicles (OMVs) are spherical particles secreted by Gram-negative bacteria. Here we explore the effect of H. pylori OMVs on Aβ aggregation and toxicity. We show intraperitoneally-injected H. pylori OMVs enter the brain and co-localize with Aβ plaques in APP/PS1 mice, accompanied by aggravated Aβ pathology, exacerbated cognitive deficits and synaptic impairment, indicating that H. pylori OMVs promote β-amyloidosis and AD development. The in vitro results further identify that H. pylori OMVs significantly accelerate Aβ aggregation and increase Aβ-induced neurotoxicity. Through lipidomic analysis, we reveal that lipid components, particularly LPC 18:0 in H. pylori OMVs accelerate Aβ aggregation and enhance Aβ neurotoxicity. Moreover, H. pylori OMVs-enhanced Aβ neurotoxicity is mediated by Ca2+. These findings reveal a mechanism of H. pylori OMVs in accelerating AD development in which the bacterial OMVs-originated lipid components play a key role in promoting Aβ aggregation and neurotoxicity.

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.

Baicalein ameliorates cognitive impairment of vascular dementia rats via suppressing neuroinflammation and regulating intestinal microbiota

Neuroinflammation induced by chronic cerebral hypoperfusion (CCH) plays a crucial role in the pathophysiologic mechanisms of vascular dementia (VD). A growing body of research has found that intestinal microbiota is associated with a variety of central nervous system disorders and that there is a relationship between intestinal microbiota dysbiosis and cognitive dysfunction and inflammatory responses. Baicalein belongs to the class of flavonoids and has a variety of biological functions, including anti-inflammatory, antioxidant and anti-apoptotic. Baicalein has a significant improvement in memory and learning, and can be used as a potential drug for the protection and treatment of central nervous system disorders. Whether baicalein has an ameliorative effect on cognitive impairment in VD, and whether its mechanism is related to the inhibition of inflammatory response and regulation of intestinal microbiota has not been reported. We used bilateral common carotid artery occlusion (BCCAO) to establish a VD rat model. Morris water maze (MWM) test showed that baicalein improved cognitive dysfunction in VD rats. We applied HE staining, immunofluorescence and ELISA to observe that baicalein treatment significantly improved CCH-induced neuronal damage in the CA1 region of the hippocampus, and reduced glial cell activation and release of pro-inflammatory factors. Western blot showed that baicalein inhibited the activation of the TLR4/MyD88/NF-κB signaling pathway in VD rats. We applied 16 S rDNA sequencing to analyze the composition of the intestinal microbiota. The results showed that baicalein modulated the diversity and composition of the intestinal microbiota, and suppressed the relative abundance of inflammation-associated microbiota in VD rats. In conclusion, this study found that baicalein ameliorated cognitive impairment, attenuated hippocampal inflammatory responses, inhibited the TLR4/MyD88/NF-κB signaling pathway, and modulated intestinal microbiota in VD rats.

Helicobacter pylori infection contributes to the expression of Alzheimer's disease-associated risk factors and neuroinflammation

Over time, mounting evidence has demonstrated extra-gastric manifestations of Helicobacter pylori infection. As such, a number of studies demonstrated the potential contribution of H. pylori infection to the incidence and progression of Alzheimer's disease (AD). Considering unanswered questions regarding the effect of H. pylori infection on brain activity, we sought to investigate the impact of H. pylori infection on the expression of AD-associated risk factors. We used two H. pylori clinical strains obtained from two patients with peptic ulcer and evaluated their influence on the expression level of AD-associated genes (APP, ApoE2, ApoE4, ABCA7, BIN1, Clu, CD33) and genes for inflammatory markers (TLR-4, IL-8, TNF-α) by RT-qPCR in human glioblastoma (U87MG) and astrocyte (1321N1) cell lines. The expression of inflammatory cytokines was further assessed by ELISA assay. The exposure of U97MG and 1321N1 cells to H. pylori strains resulted in a significant enhancement in the expression level of the risk allele ApoE4, while reducing the expression of the protective allele ApoE2. H. pylori infection remarkably increased the expression level of main AD-associated risk genes, and also pro-inflammatory cytokines. Furthermore, we noticed a substantial elevation in the mRNA expression level of transmembrane receptor TLR-4 following H. pylori infection. Our findings presented the potential for H. pylori to stimulate the expression of AD-associated risk genes and trigger neuroinflammation in the brain tissue. This, in principle, leads to the recommendation that AD patients should perhaps test for H. pylori infection and receive treatments upon positive detection.

Helicobacter pylori outer membrane vesicles induce astrocyte reactivity through nuclear factor-κappa B activation and cause neuronal damage in vivo in a murine model

BACKGROUND

Helicobacter pylori (Hp) infects the stomach of 50% of the world's population. Importantly, chronic infection by this bacterium correlates with the appearance of several extra-gastric pathologies, including neurodegenerative diseases. In such conditions, brain astrocytes become reactive and neurotoxic. However, it is still unclear whether this highly prevalent bacterium or the nanosized outer membrane vesicles (OMVs) they produce, can reach the brain, thus affecting neurons/astrocytes. Here, we evaluated the effects of Hp OMVs on astrocytes and neurons in vivo and in vitro.

METHODS

Purified OMVs were characterized by mass spectrometry (MS/MS). Labeled OMVs were administered orally or injected into the mouse tail vein to study OMV-brain distribution. By immunofluorescence of tissue samples, we evaluated: GFAP (astrocytes), βIII tubulin (neurons), and urease (OMVs). The in vitro effect of OMVs in astrocytes was assessed by monitoring NF-κB activation, expression of reactivity markers, cytokines in astrocyte-conditioned medium (ACM), and neuronal cell viability.

RESULTS

Urease and GroEL were prominent proteins in OMVs. Urease (OMVs) was present in the mouse brain and its detection coincided with astrocyte reactivity and neuronal damage. In vitro, OMVs induced astrocyte reactivity by increasing the intermediate filament proteins GFAP and vimentin, the plasma membrane α_Vβ₃ integrin, and the hemichannel connexin 43. OMVs also produced neurotoxic factors and promoted the release of IFNγ in a manner dependent on the activation of the transcription factor NF-κB. Surface antigens on reactive astrocytes, as well as secreted factors in response to OMVs, were shown to inhibit neurite outgrowth and damage neurons.

CONCLUSIONS

OMVs administered orally or injected into the mouse bloodstream reach the brain, altering astrocyte function and promoting neuronal damage in vivo. The effects of OMVs on astrocytes were confirmed in vitro and shown to be NF-κB-dependent. These findings suggest that Hp could trigger systemic effects by releasing nanosized vesicles that cross epithelial barriers and access the CNS, thus altering brain cells.

Baicalein-corrected gut microbiota may underlie the amelioration of memory and cognitive deficits in APP/PS1 mice

Background: Baicalein is an active ingredient extracted from the root of S. baicalensis Georgi, which exhibits cardiovascular protection, anti-inflammatory, and anti-microbial properties. Our previous study showed that chronic treatment of Baicalein ameliorated cognitive dysfunction in a mouse model of Alzheimer's disease (AD). However, it remains unknown whether Baicalein ameliorates cognitive deficits in AD mouse models by altering gut microbiota and its metabolites. Methods: Behavioral tests, metagenomic and untargeted metabolomics analyses were used to evaluate the effects of Baicalein on the APP/PS1 mice. Results: Our research showed that treatment of Baicalein for 2 weeks ameliorated cognition and memory in a dose-dependent manner, as indicated by the significant increases in the Discrimination index and Number of crossings and decrease in latency to the previous platform location in 8-month of age APP/PS1 mice in novel object recognition and water maze tests. The metagenomic analysis showed the abundance of the dominant phyla in all groups, including Bacteroidetes (14.59%-67.02%) and Firmicutes (20.19%-61.39%). LEfSe analysis of metagenomics identified three species such as s__Roseburia_sp_1XD42_69, s__Muribaculaceae_bacterium_Isolate_104_HZI, s__Muribaculaceae_bacterium_Isolate_110_HZI as Baicalein-treated potential biomarkers. Metabolite analysis revealed the increment of metabolites, including glutamate, thymine and hexanoyl-CoA. Conclusion: The effects of Baicalein on memory and cognition may relate to the metabolism of nucleotides, lipids and glucose.

Jiedu-Yizhi Formula Alleviates Neuroinflammation in AD Rats by Modulating the Gut Microbiota

Background

The Jiedu-Yizhi formula (JDYZF) is a Chinese herbal prescription used to treat Alzheimer's disease (AD). It was previously confirmed that JDYZF can inhibit the expression of pyroptosis-related proteins in the hippocampus of AD rats and inhibit gut inflammation in AD rats. Therefore, it is hypothesized that JDYZF has a regulatory effect on the gut microbiota.

Methods

In this study, an AD rat model was prepared by bilateral hippocampal injection of Aβ_25-35 and AD rats received high, medium, and low doses of JDYZF orally for 8 weeks. The body weights of the AD rats were observed to assess the effect of JDYZF. The 16S rRNA sequencing technique was used to study the regulation of the gut microbiota by JDYZF in AD rats. Immunohistochemical staining was used to observe the expression levels of Caspase-1 and Caspase-11 in the hippocampus.

Results

JDYZF reduced body weight in AD rats, and this effect may be related to JDYZF regulating body-weight-related gut microbes. The 16S rRNA analysis showed that JDYZF increased the diversity of the gut microbiota in AD rats. At the phylum level, JDYZF increased the abundances of Bacteroidota and Actinobacteriota and decreased the abundances of Firmicutes, Campilobacterota, and Desulfobacterota. At the genus level, the abundances of Lactobacillus, Prevotella, Bacteroides, Christensenellaceae_R-7_group, Rikenellaceae_RC9_gut_group, and Blautia were increased and the abundances of Lachnospiraceae-NK4A136-group, Anaerobiospirillum, Turicibacter, Oscillibacter, Desulfovibrio, Helicobacter, and Intestinimonas were decreased. At the species level, the abundances of Lactobacillus johnsonii, Lactobacillus reuteri, and Lactobacillus faecis were increased and the abundances of Helicobacter rodentium and Ruminococcus_sp_N15.MGS-57 were decreased. Immunohistochemistry showed that JDYZF reduced the levels of Caspase-1- and Caspase-11-positive staining.

Conclusion

JDYZF has a regulatory effect on the gut microbiota of AD rats, which may represent the basis for the anti-inflammatory effect of JDYZF.

Neuroinflammation in neurodegeneration via microbial infections

Recent epidemiological studies show a noticeable correlation between chronic microbial infections and neurological disorders. However, the underlying mechanisms are still not clear due to the biological complexity of multicellular and multiorgan interactions upon microbial infections. In this review, we show the infection leading to neurodegeneration mediated by multiorgan interconnections and neuroinflammation. Firstly, we highlight three inter-organ communications as possible routes from infection sites to the brain: nose-brain axis, lung-brain axis, and gut-brain axis. Next, we described the biological crosstalk between microglia and astrocytes upon pathogenic infection. Finally, our study indicates how neuroinflammation is a critical player in pathogen-mediated neurodegeneration. Taken together, we envision that antibiotics targeting neuro-pathogens could be a potential therapeutic strategy for neurodegeneration.

Gastrointestinal Changes and Alzheimer's Disease

BACKGROUND

There is a well-described mechanism of communication between the brain and gastrointestinal system in which both organs influence the function of the other. This bi-directional communication suggests that disease in either organ may affect function in the other.

OBJECTIVE

To assess whether the evidence supports gastrointestinal system inflammatory or degenerative pathophysiology as a characteristic of Alzheimer's disease (AD).

METHODS

A review of both rodent and human studies implicating gastrointestinal changes in AD was performed.

RESULTS

Numerous studies indicate that AD changes are not unique to the brain but also occur at various levels of the gastrointestinal tract involving both immune and neuronal changes. In addition, it appears that numerous conditions and diseases affecting regions of the tract may communicate to the brain to influence disease.

CONCLUSION

Gastrointestinal changes represent an overlooked aspect of AD, representing a more system influence of this disease.

Inhibition of Rho Kinase by Fasudil Ameliorates Cognition Impairment in APP/PS1 Transgenic Mice via Modulation of Gut Microbiota and Metabolites

Background: Fasudil, a Rho kinase inhibitor, exerts therapeutic effects in a mouse model of Alzheimer's disease (AD), a chronic neurodegenerative disease with progressive loss of memory. However, the mechanisms remain unclear. In addition, the gut microbiota and its metabolites have been implicated in AD.

Methods: We examined the effect of fasudil on learning and memory using the Morris water-maze (MWM) test in APPswe/PSEN1dE9 transgenic (APP/PS1) mice (8 months old) treated (i.p.) with fasudil (25 mg/kg/day; ADF) or saline (ADNS) and in age- and gender-matched wild-type (WT) mice. Fecal metagenomics and metabolites were performed to identify novel biomarkers of AD and elucidate the mechanisms of fasudil induced beneficial effects in AD mice.

Results: The MWM test showed significant improvement of spatial memory in APP/PS1 mice treated with fasudil as compared to ADNS. The metagenomic analysis revealed the abundance of the dominant phyla in all the three groups, including Bacteroidetes (23.7–44%) and Firmicutes (6.4–26.6%), and the increased relative abundance ratio of Firmicutes/Bacteroidetes in ADNS (59.1%) compared to WT (31.7%). In contrast, the Firmicutes/Bacteroidetes ratio was decreased to the WT level in ADF (32.8%). Lefse analysis of metagenomics identified s_Prevotella_sp_CAG873 as an ADF potential biomarker, while s_Helicobacter_typhlonius and s_Helicobacter_sp_MIT_03-1616 as ADNS potential biomarkers. Metabolite analysis revealed the increment of various metabolites, including glutamate, hypoxanthine, thymine, hexanoyl-CoA, and leukotriene, which were relative to ADNS or ADF microbiota potential biomarkers and mainly involved in the metabolism of nucleotide, lipids and sugars, and the inflammatory pathway.

Conclusions: Memory deficit in APP/PS1 mice was correlated with the gut microbiome and metabolite status. Fasudil reversed the abnormal gut microbiota and subsequently regulated the related metabolisms to normal in the AD mice. It is believed that fasudil can be a novel strategy for the treatment of AD via remodeling of the gut microbiota and metabolites. The novel results also provide valuable references for the use of gut microbiota and metabolites as diagnostic biomarkers and/or therapeutic targets in clinical studies of AD.

Helicobacter pylori infection and risk for developing dementia: an evidence-based meta-analysis of case-control and cohort studies

BACKGROUND

Infection with multiple pathogens may play a key role in the pathogenesis of dementia. Whether Helicobacter pylori (H. pylori) infection is associated causally with dementia is controversial.

OBJECTIVE

We conduct a meta-analysis of case-control and cohort studies on the association between H. pylori infection and the risk for all-cause and Alzheimer's disease (AD) dementia.

METHODS

Two independent reviewers searched the PubMed, Cochrane Library, and Embase databases with English language restrictions from the date of conception to September 18, 2020. The primary analysis was as follows: the exposure variable was H. pylori infection, and the outcome was incident all-cause and AD dementia. Pooled odds ratios (OR), relative risk (RR), and corresponding 95% confidence intervals (CI) were obtained using the fixed-or random-effect model. Forest plots were generated to summarize the results.

RESULTS

Ten studies involving 96,561 participants were included in the meta-analysis: 5 case-control studies and 5 cohort studies. The overall pooled cohort studies showed a significant positive association between H. pylori infection and all-cause dementia with pooled RR of 1.36 (95% CI, 1.11-1.67). There was no association between H. pylori infection and risk for developing AD: RR of 1.33 (95% CI, 0.86-2.05) in cohort studies, and OR of 1.72 (95% CI, 0.97-3.04) in case-control studies. Significant heterogeneity was showed in each comparison group.

CONCLUSION

This meta-analysis supports a positive association between H. pylori infection and the risk of all-cause dementia, but not AD dementia. Due to the interference of confounding factors, randomized controlled trials are needed to prove their causality.

The Role of Formyl Peptide Receptors in Permanent and Low-Grade Inflammation: Helicobacter pylori Infection as a Model

Formyl peptide receptors (FPRs) are cell surface pattern recognition receptors (PRRs), belonging to the chemoattractant G protein-coupled receptors (GPCRs) family. They play a key role in the innate immune system, regulating both the initiation and the resolution of the inflammatory response. FPRs were originally identified as receptors with high binding affinity for bacteria or mitochondria N-formylated peptides. However, they can also bind a variety of structurally different ligands. Among FPRs, formyl peptide receptor-like 1 (FPRL1) is the most versatile, recognizing N-formyl peptides, non-formylated peptides, and synthetic molecules. In addition, according to the ligand nature, FPRL1 can mediate either pro- or anti-inflammatory responses. Hp(2-20), a Helicobacter pylori-derived, non-formylated peptide, is a potent FPRL1 agonist, participating in Helicobacter pylori-induced gastric inflammation, thus contributing to the related site or not-site specific diseases. The aim of this review is to provide insights into the role of FPRs in H. pylori-associated chronic inflammation, which suggests this receptor as potential target to mitigate both microbial and sterile inflammatory diseases.

Complex Interaction between Resident Microbiota and Misfolded Proteins: Role in Neuroinflammation and Neurodegeneration

Neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD) and Creutzfeldt-Jakob disease (CJD) are brain conditions affecting millions of people worldwide. These diseases are associated with the presence of amyloid-β (Aβ), alpha synuclein (α-Syn) and prion protein (PrP) depositions in the brain, respectively, which lead to synaptic disconnection and subsequent progressive neuronal death. Although considerable progress has been made in elucidating the pathogenesis of these diseases, the specific mechanisms of their origins remain largely unknown. A body of research suggests a potential association between host microbiota, neuroinflammation and dementia, either directly due to bacterial brain invasion because of barrier leakage and production of toxins and inflammation, or indirectly by modulating the immune response. In the present review, we focus on the emerging topics of neuroinflammation and the association between components of the human microbiota and the deposition of Aβ, α-Syn and PrP in the brain. Special focus is given to gut and oral bacteria and biofilms and to the potential mechanisms associating microbiome dysbiosis and toxin production with neurodegeneration. The roles of neuroinflammation, protein misfolding and cellular mediators in membrane damage and increased permeability are also discussed.

An In Vitro Model to Investigate the Role of Helicobacter pylori in Type 2 Diabetes, Obesity, Alzheimer's Disease and Cardiometabolic Disease

Helicobacter pylori (Hp) is a Gram-negative bacterium colonizing the human stomach. Nuclear Magnetic Resonance (NMR) analysis of intracellular human gastric carcinoma cells (MKN-28) incubated with the Hp cell filtrate (Hpcf) displays high levels of amino acids, including the branched chain amino acids (BCAA) isoleucine, leucine, and valine. Polymerase chain reaction (PCR) Array Technology shows upregulation of mammalian Target Of Rapamycin Complex 1 (mTORC1), inflammation, and mitochondrial dysfunction. The review of literature indicates that these traits are common to type 2 diabetes, obesity, Alzheimer’s diseases, and cardiometabolic disease. Here, we demonstrate how Hp may modulate these traits. Hp induces high levels of amino acids, which, in turn, activate mTORC1, which is the complex regulating the metabolism of the host. A high level of BCAA and upregulation of mTORC1 are, thus, directly regulated by Hp. Furthermore, Hp modulates inflammation, which is functional to the persistence of chronic infection and the asymptomatic state of the host. Finally, in order to induce autophagy and sustain bacterial colonization of gastric mucosa, the Hp toxin VacA localizes within mitochondria, causing fragmentation of these organelles, depletion of ATP, and oxidative stress. In conclusion, our in vitro disease model replicates the main traits common to the above four diseases and shows how Hp may potentially manipulate them.

Alzheimer's Disease: Protective Effects of Mycobacterium vaccae, a Soil-Derived Mycobacterium with Anti-Inflammatory and Anti-Tubercular Properties, on the Proteomic Profiles of Plasma and Cerebrospinal Fluid in Rats

BACKGROUND

Alzheimer's disease (AD) is an inflammatory neurodegenerative disease that may be associated with prior bacterial infections. Microbial "old friends" can suppress exaggerated inflammation in response to disease-causing infections or increase clearance of pathogens such as Mycobacterium tuberculosis, which causes tuberculosis (TB). One such "old friend" is Mycobacterium vaccae NCTC 11659, a soil-derived bacterium that has been proposed either as a vaccine for prevention of TB, or as immunotherapy for the treatment of TB when used alongside first line anti-TB drug treatment.

OBJECTIVE

The goal of this study was to use a hypothesis generating approach to explore the effects of M. vaccae on physiological changes in the plasma and cerebrospinal fluid (CSF).

METHODS

Liquid chromatography-tandem mass spectrometry-based proteomics were performed in plasma and CSF of adult male rats after immunization with a heat-killed preparation of M. vaccae NCTC 11659 or borate-buffered saline vehicle. Gene enrichment analysis and analysis of protein-protein interactions were performed to integrate physiological network changes in plasma and CSF. We used RT-qPCR to assess immune and metabolic gene expression changes in the hippocampus.

RESULTS

In both plasma and CSF, immunization with M. vaccae increased proteins associated with immune activation and downregulated proteins corresponding to lipid (including phospholipid and cholesterol) metabolism. Immunization with M. vaccae also increased hippocampal expression of interleukin-4 (IL-4) mRNA, implicating anti-inflammatory effects in the central nervous system.

CONCLUSION

M. vaccae alters host immune activity and lipid metabolism. These data are consistent with the hypothesis that microbe-host interactions may protect against possible infection-induced, inflammation-related cognitive impairments.

Interaction between MyD88, TIRAP and IL1RL1 against Helicobacter pylori infection

The Toll-interleukin 1 receptor superfamily includes the genes interleukin 1 receptor-like 1 (IL1RL1), Toll like receptors (TLRs), myeloid differentiation primary-response 88 (MyD88), and MyD88 adaptor-like (TIRAP). This study describes the interaction between MyD88, TIRAP and IL1RL1 against Helicobacter pylori infection. Cases and controls were genotyped at the polymorphic sites MyD88 rs6853, TIRAP rs8177374 and IL1RL1 rs11123923. The results show that specific combinations of IL1RL1-TIRAP (AA-CT; P: 2,8 × 10^–17) and MyD88-TIRAP-IL1RL1 (AA-CT-AA; P: 1,4 × 10^–8) – but not MyD88 alone—act synergistically against Helicobacter pylori. Nuclear magnetic resonance (NMR) clearly discriminates cases from controls by highlighting significantly different expression levels of several metabolites (tyrosine, tryptophan, phenylalanine, branched-chain amino acids, short chain fatty acids, glucose, sucrose, urea, etc.). NMR also identifies the following dysregulated metabolic pathways associated to Helicobacter pylori infection: phenylalanine and tyrosine metabolism, pterine biosynthesis, starch and sucrose metabolism, and galactose metabolism. Furthermore, NMR discriminates between the cases heterozygous at the IL1RL1 locus from those homozygous at the same locus. Heterozygous patients are characterized by high levels of lactate, and IL1RL1—both associated with anti-inflammatory activity—and low levels of the pro-inflammatory molecules IL-1β, TNF-α, COX-2, and IL-6.

Double hit viral parasitism, polymicrobial CNS residency and perturbed proteostasis in Alzheimer's disease: A data driven, in silico analysis of gene expression data

The aim of this study was to determine the interaction of peripheral immunity vs. the CNS in the setting of AD pathogenesis at the transcriptomic level in a data driven manner. For this purpose, publicly available gene expression data from the GEO Datasets repository. We performed differential gene expression and functional enrichment analyses were performed on the five retrieved studies: (a) three hippocampal cortex (HC) studies (b) one study of peripheral blood mononuclear cells (PBMC) and (c) one involving neurofibrillary tangle - containing neurons of the entorhinal cortex (NFT EC). Subsequently, BLAST was used to determine protein conservation between human proteins vs. microbial, whereas putative protein / oligopeptide antigenicity were determined via RANKPep. Gene ontology and pathway analyses revealed significantly enriched viral parasitism pathways in both PBMC and NFT - EC datasets, mediated by ribosomal protein families and epigenetic regulators. Among these, a salient viral pathway referred to Influenza A infection. NFT - EC annotations included leukocyte chemotaxis and immune response pathways. All datasets were significantly enriched for infectious pathways, as well as pathways involved in impaired proteostasis and non - phagocytic cell phagosomal cascades. In conclusion, our in silico analysis outlined an ad hoc model of AD pathophysiology in which double hit (PBMC and NFT-EC) viral parasitism is mediated by eukaryotic translational hijacking, and may be further implicated by impaired immune responses. Overall, our results overlap with the antimicrobial protection hypothesis of AD pathogenesis and support the notion of a pathogen - driven etiology.

An Innovative Approach to Control H. pylori-Induced Persistent Inflammation and Colonization

Helicobacter pylori (H. pylori) is a Gram-negative bacterium which colonizes the human stomach. The ability of H. pylori to evade the host defense system and the emergence of antibiotic resistant strains result in bacteria persistence and chronic inflammation, which leads to both severe gastric and extra-gastric diseases. Consequently, innovative approaches able to overcome H. pylori clinical outcomes are needed. In this work, we develop a novel non-toxic therapy based on the synergistic action of H. pylori phage and lactoferrin adsorbed on hydroxyapatite nanoparticles, which effectively impairs bacteria colonization and minimizes the damage of the host pro-inflammatory response.

Role of Helicobacter pylori infection in the manifestation of old age-related diseases

Helicobacter pylori is one of the most prevalent infection worldwide. It affects individuals of different age groups. Elderly people tend to resist eradication treatment and worsening of infection can lead to several gastric and non-gastric pathologies. Aging-associated cellular and molecular alteration can increase the risk of other pathologies such as osteoporosis, Alzheimer's disease, Parkinson's disease, respiratory and renal dysfunction, and cancer in geriatric patients, more than other age groups. This review article highlights some of the most common old age diseases and the role of H. pylori infection as a risk factor to worsen the conditions, presented by the molecular evidences of these associations. These studies can help clinicians to understand the underlying pathogenesis of the disease and identify high-risk patients, aiding clearer diagnosis and treatment.

Association between Alzheimer's Disease and Oral and Gut Microbiota: Are Pore Forming Proteins the Missing Link?

Alzheimer's disease (AD) is a neurodegenerative condition affecting millions of people worldwide. It is associated with cerebral amyloid-β (Aβ) plaque deposition in the brain, synaptic disconnection, and subsequent progressive neuronal death. Although considerable progress has been made to elucidate the pathogenesis of AD, the specific causes of the disease remain highly unknown. Recent research has suggested a potential association between certain infectious diseases and dementia, either directly due to bacterial brain invasion and toxin production, or indirectly by modulating the immune response. Therefore, in the present review we focus on the emerging issues of bacterial infection and AD, including the existence of antimicrobial peptides having pore-forming properties that act in a similar way to pores formed by Aβ in a variety of cell membranes. Special focus is placed on oral bacteria and biofilms, and on the potential mechanisms associating bacterial infection and toxin production in AD. The role of bacterial outer membrane vesicles on the transport and delivery of toxins as well as porins to the brain is also discussed. Aβ has shown to possess antimicrobial activity against several bacteria, and therefore could be upregulated as a response to bacteria and bacterial toxins in the brain. Although further research is needed, we believe that the control of biofilm-mediated diseases could be an important potential prevention mechanism for AD development.

Review: Impact of Helicobacter pylori on Alzheimer's disease: What do we know so far?

BACKGROUND

Helicobacter pylori has changed radically gastroenterologic world, offering a new concept in patients' management. Over time, more medical data gave rise to diverse distant, extragastric manifestations and interactions of the "new" discovered bacterium. Special interest appeared within the field of neurodegenerative diseases and particularly Alzheimer's disease, as the latter and Helicobacter pylori infection are associated with a large public health burden and Alzheimer's disease ranks as the leading cause of disability. However, the relationship between Helicobacter pylori infection and Alzheimer's disease remains uncertain.

METHODS

We performed a narrative review regarding a possible connection between Helicobacter pylori and Alzheimer's disease. All accessible relevant (pre)clinical studies written in English were included. Both affected pathologies were briefly analyzed, and relevant studies are discussed, trying to focus on the possible pathogenetic role of this bacterium in Alzheimer's disease.

RESULTS

Data stemming from both epidemiologic studies and animal experiments seem to be rather encouraging, tending to confirm the hypothesis that Helicobacter pylori infection might influence the course of Alzheimer's disease pleiotropically. Possible main mechanisms may include the bacterium's access to the brain via the oral-nasal-olfactory pathway or by circulating monocytes (infected with Helicobacter pylori due to defective autophagy) through disrupted blood-brain barrier, thereby possibly triggering neurodegeneration.

CONCLUSIONS

Current data suggest that Helicobacter pylori infection might influence the pathophysiology of Alzheimer's disease. However, further large-scale randomized controlled trials are mandatory to clarify a possible favorable effect of Helicobacter pylori eradication on Alzheimer's disease pathophysiology, before the recommendation of short-term and cost-effective therapeutic regimens against Helicobacter pylori-related Alzheimer's disease.