Porphyromonas gingivalis lipopolysaccharide induces cognitive dysfunction, mediated by neuronal inflammation via activation of the TLR4 signaling pathway in C57BL/6 mice

Unraveling brain aging through the lens of oral microbiota

The oral cavity is a complex physiological community encompassing a wide range of microorganisms. Dysbiosis of oral microbiota can lead to various oral infectious diseases, such as periodontitis and tooth decay, and even affect systemic health, including brain aging and neurodegenerative diseases. Recent studies have highlighted how oral microbes might be involved in brain aging and neurodegeneration, indicating potential avenues for intervention strategies. In this review, we summarize clinical evidence demonstrating a link between oral microbes/oral infectious diseases and brain aging/neurodegenerative diseases, and dissect potential mechanisms by which oral microbes contribute to brain aging and neurodegeneration. We also highlight advances in therapeutic development grounded in the realm of oral microbes, with the goal of advancing brain health and promoting healthy aging.

Porphyromonas gingivalis Induces Disturbance of Kynurenine Metabolism Through the Gut-Brain Axis: Implications for Alzheimer's Disease

Porphyromonas gingivalis is one of the major pathogens of chronic periodontitis. P. gingivalis can cause systemic inflammation, amyloid β protein deposition, and hyperphosphorylation of tau protein, leading to Alzheimer's disease (AD)-like lesions. P. gingivalis oral infection causes gut microbiota alteration, gut barrier dysfunction, and intestinal immune response and inflammation. The microbiota-gut-brain axis has a potential role in the pathogenesis of AD. Whether P. gingivalis affects AD-like lesions via the gut-brain axis needs more study. In this study, orally administered P. gingivalis induced alveolar resorption, intestinal barrier impairment, and AD-like lesions. Oral infection with P. gingivalis induced oral and gut microflora dysbiosis, imbalance of the tryptophan metabolism pathway of gut microbiota, and elevated levels of 3-hydroxykynurenine in the sera and hippocampi. The key metabolite, 3-hydroxykynurenine, suppressed Bcl2 gene expression, leading to neuronal apoptosis and promoting AD-like lesions in vivo and in vitro. These findings suggest that P. gingivalis can induce AD pathogenesis through the gut-brain axis, providing new ideas for the prevention and treatment of AD.

Infections, genetics, and Alzheimer's disease: Exploring the pathogenic factors for innovative therapies

Alzheimer's disease (AD) is a progressive neurodegenerative condition that creates a significant global health challenge and profoundly affects patients and their families. Recent research has highlighted the critical role of microorganisms, particularly viral infections, in the pathogenesis of AD. The involvement of viral infections in AD pathogenesis is predominantly attributed to their ability to induce neuroinflammation and amyloid beta (Aβ) deposition in the brain. The extant research exploring the relationship between viruses and AD has focused largely on Herpesviridae family. Traces of Herpesviruses, such as Herpes Simplex Virus-1 and Epstein Barr Virus, have been found in the brains of patients with AD. These viruses are thought to contribute to the disease progression by triggering chronic inflammatory responses in the brain. They can remain dormant in the brain, and become reactivated due to stress, a secondary viral infection, or immune-senescence in older adults. This review focuses on the association between Herpesviridae and bacterial infections with AD. We explore the genetic factors that might regulate viral illness and discuss clinical trials investigating antiviral and anti-inflammatory agents as possible therapeutic strategies to mitigate cognitive decline in patients with AD. In summary, understanding the interplay between infections, genetic factors, and AD pathogenesis may pave the way for novel therapeutic approaches, facilitating better management and possibly even prevent this debilitating disease.

[Prevotella nigrescens exacerbates periodontal inflammation and impairs cognitive function in mice]

OBJECTIVES

To investigate the effects of periodontitis induced by Prevotella nigrescens (Pn) combined with ligation on cognitive functions in mice.

METHODS

Twenty-four C57BL/6J mice were randomly divided into control group, ligation group, and ligation + Pn treatment (P+Pn) group. Experimental periodontitis was induced by silk ligation of the first molars followed by topical application of Pn for 6 weeks. After modeling, alveolar bone resorption was assessed using micro-CT and histological analysis. Learning and memory abilities of the mice were evaluated using open field test (OFT), novel object recognition test (NORT), and Morris water maze test (MWM). Seven weeks after the start of modeling, the mice were sacrificed for examining histopathological changes in the hippocampus using HE and Nissl staining.

RESULTS

After 6 weeks of molar ligation, micro-CT revealed horizontal alveolar bone resorption and furcation exposure in the mice, and histological analysis showed apical migration of the junctional epithelium, epithelial ridge hyperplasia, and lymphocyte infiltration, and these changes were obviously worsened in P+Pn group. Alveolar bone height decreased significantly in both ligation groups compared to the control group. Cognitive tests showed that the mice in both of the ligation groups traveled shorter distances in OFT, showed reduced novel object preference in NORT, and exhibited longer escape latencies in MWM, and the mice in P+Pn group had significantly poorer performances in the tests. Histologically, obvious neuronal cytoplasmic degeneration, necrosis, nuclear pyknosis, vacuolation, and reduced Nissl bodies and viable neurons were observed in the hippocampal regions of the mice in the two ligation groups.

CONCLUSIONS

Pn infection aggravates alveolar bone destruction, accelerates necrosis and causes morphological abnormalities of neuronal cells in the hippocampus to reduce cognitive functions of mice with periodontitis.

Porphyromonas gingivalis outer membrane vesicles alter cortical neurons and Tau phosphorylation in the embryonic mouse brain

Porphyromonas gingivalis (Pg) is an oral bacterial pathogen that has been associated with systemic inflammation and adverse pregnancy outcomes such as low birth weight and pre-term birth. Pg drives these sequelae through virulence factors decorating the outer membrane that are present on non-replicative outer membrane vesicles (OMV) that are suspected to be transmitted systemically. Given that Pg abundance can increase during pregnancy, it is not well known whether Pg-OMV can have deleterious effects on the brain of the developing fetus. We tested this possibility by treating pregnant C57/Bl6 mice with PBS (control) and OMV from ATCC 33277 by tail vein injection every other day from gestational age 3 to 17. At gestational age 18.5, we measured dam and pup weights and collected pup brains to quantify changes in inflammation, cortical neuron density, and Tau phosphorylated at Thr231. Dam and pup weights were not altered by Pg-OMV exposure, but pup brain weight was significantly decreased in the Pg-OMV treatment group. We found a significant increase of Iba-1, indicative of microglia activation, although the overall levels of IL-1β, IL-6, TNFα, IL-4, IL-10, and TGFβ mRNA transcripts were not different between the treatment groups. Differences in IL-1β, IL-6, and TNFα concentrations by ELISA showed IL-6 was significantly lower in Pg-OMV brains. Cortical neuron density was modified by treatment with Pg-OMV as immunofluorescence showed significant decreases in Cux1 and SatB2. Overall p-Tau Thr231 was increased in the brains of pups whose mothers were exposed to Pg-OMV. Together these results demonstrate that Pg-OMV can significantly modify the embryonic brain and suggests that Pg may impact offspring development via multiple mechanisms.

Plant and animal-derived fusion nanovesicles rescue inflammation-compromised osteogenic potential of periodontal ligament stem cells

Periodontitis is a chronic inflammatory disease affecting the supporting tissues of the teeth and has emerged as a global public health issue. Current therapies primarily address pathogenic factors and alleviate symptoms, with limited options available for complete restoration and reconstruction of already absorbed periodontal bone tissue. In this study, we developed a nanotherapeutic strategy utilizing fusion nanovesicles (FVs) to modulate the inflammatory microenvironment and create a regenerative niche for periodontal ligament stem cells (PDLSCs), which play a crucial role in periodontal tissue repair. The FVs are composed of Scutellaria baicalensis nanovesicles (SBNVs) with anti-Porphyromonas gingivalis (P. gingivalis) and anti-inflammatory properties, combined with PDLSC membrane-derived nanovesicles genetically engineered to express TNFR1. These FVs preserved the biological activity of SBNVs and the immunomodulatory function of PDLSCs. Additionally, FVs effectively captured and cleared TNF-α from the microenvironment through TNFR1. Moreover, FVs alleviated the inflammatory response of PDLSCs induced by P. gingivalis-LPS (Pg-LPS) and TNF-α, restoring their proliferation, migration, and osteogenic differentiation capabilities. Hence, this nanotherapeutic strategy holds great potential for treating periodontitis.

Precision delivery of pretreated macrophage-membrane-coated Pt nanoclusters for improving Alzheimer's disease-like cognitive dysfunction induced by Porphyromonas gingivalis

Oral infection with Porphyromonas gingivalis (P. gingivalis), a kind of pathogenic bacteria causing periodontitis, can increase the risk of Alzheimer's disease (AD) and cause cognitive decline. Therefore, precise intracerebral antimicrobial therapy to reduce the load of P. gingivalis in brain may serve as a potential therapeutic approach to improve AD-like cognitive impairment. A kind of nano-delivery system precisely targets bacteria in the brain through coating P. gingivalis stimulated macrophage membrane onto the surface of platinum nanoclusters (Pg-M-PtNCs). Approximate 50 nm spherical Pg-M-PtNCs demonstrate good biocompatibility and the pretreated macrophage membranes can inhibit macrophages phagocytosis and increase the adherence to bacteria. Pg-M-PtNCs can significantly inhibit the growth of P.gingivalis in vitro, and are effectively delivered and remain at the infection site in the mice brain to reduce the bacterial load and neuronal damage, and then improve the AD-like cognitive dysfunction in the chronic periodontitis mice. Platinum nanoclusters coated with P. gingivalis pretreated macrophage membrane play an important role in targeting bacteria in the brain, and effectively improve AD-like cognitive function disorder caused by P. gingivalis infection in the brain.

Porphyromonas gingivalis: a potential trigger of neurodegenerative disease

Porphyromonas gingivalis (P. gingivalis) is a gram-negative bacterium and the main causative agent of periodontitis, a disease closely associated with the development of periodontal disease. The progression of periodontitis, a chronic infectious disease, is intricately linked to the inflammatory immune response. Inflammatory cytokines act on periodontal tissues via immunomodulation, resulting in the destruction of the periodontal tissue. Recent studies have established connections between periodontitis and various systemic diseases, including cardiovascular diseases, tumors, and neurodegenerative diseases. Neurodegenerative diseases are neurological disorders caused by immune system dysfunction, including Alzheimer's and Parkinson's diseases. One of the main characteristics of neurodegenerative diseases is an impaired inflammatory response, which mediates neuroinflammation through microglial activation. Some studies have shown an association between periodontitis and neurodegenerative diseases, with P. gingivalis as the primary culprit. P. gingivalis can cross the blood-brain barrier (BBB) or mediate neuroinflammation and injury through a variety of pathways, including the gut-brain axis, thereby affecting neuronal growth and survival and participating in the onset and progression of neurodegenerative diseases. However, comprehensive and systematic summaries of studies on the infectious origin of neurodegenerative diseases are lacking. This article reviews and summarizes the relationship between P. gingivalis and neurodegenerative diseases and its possible regulatory mechanisms. This review offers new perspectives into the understanding of neurodegenerative disease development and highlights innovative approaches for investigating and developing tailored medications for treating neurodegenerative conditions, particularly from the viewpoint of their association with P. gingivalis.

Periodontitis increases the risk of gastrointestinal dysfunction: an update on the plausible pathogenic molecular mechanisms

Periodontitis is an immuno-inflammatory disease of the soft tissues surrounding the teeth. Periodontitis is linked to many communicable and non-communicable diseases such as diabetes, cardiovascular disease, rheumatoid arthritis, and cancers. The oral-systemic link between periodontal disease and systemic diseases is attributed to the spread of inflammation, microbial products and microbes to distant organ systems. Oral bacteria reach the gut via swallowed saliva, whereby they induce gut dysbiosis and gastrointestinal dysfunctions. Some periodontal pathogens like Porphyromonas. gingivalis, Klebsiella, Helicobacter. Pylori, Streptococcus, Veillonella, Parvimonas micra, Fusobacterium nucleatum, Peptostreptococcus, Haemophilus, Aggregatibacter actinomycetomcommitans and Streptococcus mutans can withstand the unfavorable acidic, survive in the gut and result in gut dysbiosis. Gut dysbiosis increases gut inflammation, and induce dysplastic changes that lead to gut dysfunction. Various studies have linked oral bacteria, and oral-gut axis to various GIT disorders like inflammatory bowel disease, liver diseases, hepatocellular and pancreatic ductal carcinoma, ulcerative colitis, and Crohn's disease. Although the correlation between periodontitis and GIT disorders is well established, the intricate molecular mechanisms by which oral microflora induce these changes have not been discussed extensively. This review comprehensively discusses the intricate and unique molecular and immunological mechanisms by which periodontal pathogens can induce gut dysbiosis and dysfunction.

Porphyromonas gingivalis and Its Outer Membrane Vesicles Induce Neuroinflammation in Mice Through Distinct Mechanisms

BACKGROUND

Alzheimer's disease (AD) is the most common chronic neurodegenerative disorder, with neuroinflammation playing an important role in its progression to become a major research focus. The role of Porphyromonas gingivalis (Pg) and its outer membrane vesicles (Pg OMVs) in AD development is uncertain, particularly regarding their effects on neuroinflammation.

METHODS

The cognition of mice injected with Pg, Pg OMVs, or PBS via the tail vein was assessed by the Morris water maze test. Pathological changes in the mouse brain were analyzed via immunohistochemistry, immunofluorescence and hematoxylin‒eosin (H&E) staining, and the ultrastructure of the hippocampus was observed via transmission electron microscopy (TEM). Plasma levels of inflammatory factors were assessed by enzyme-linked immunosorbent assay (ELISA). Protein levels of brain inflammatory factor, occludin, and NLRP3 inflammasome-related proteins were assessed by western blotting.

RESULTS

Memory impairment; notable neuroinflammation, including astrocyte and microglial activation; and elevated protein levels of IL-1β, TNF-α, and IL-6 in the hippocampus were detected in the Pg and Pg OMV groups. However, Pg induced weight loss and systemic inflammation, such as splenomegaly and increased IL-1β and TNF-α levels in plasma, whereas Pg OMVs had minimal impact. In addition, Pg induced more pronounced activation of the NLRP3 inflammasome compared to Pg OMVs. In contrast, only the Pg OMV group exhibited blood-brain barrier (BBB) disruption characterized by reduced integrity of tight junctions and lower levels of occludin protein.

CONCLUSIONS

Pg is associated with a significant immune response and systemic inflammation, which in turn exacerbates neuroinflammation via activating NLRP3 inflammasome. However, Pg OMVs might elude the systemic immune response and disrupt tight junctions, thereby entering the brain and directly triggering neuroinflammation.

Limosilactobacillus reuteri RE225 alleviates gout by modulating the TLR4/MyD88/NF-κB inflammatory pathway and the Nrf2/HO-1 oxidative stress pathway, and by regulating gut microbiota

BACKGROUND

Gout poses a significant health threat. The use of Lactobacillus from the gut microbiota is one potential remedy. However, the intricate molecular mechanisms governing the impact of Lactobacillus on gout remain largely uncharted. In this study, a strain of Limosilactobacillus reuteri RE225 was separated from the gut of mice and colitis was treated with polypeptide intervention.

RESULTS

Limosilactobacillus reuteri RE225 reduced foot tumefaction markedly in mice with gout and extended the pain threshold time in their feet. It also improved the health of gut microbiota. Intervention with L. reuteri RE225 also suppressed the TLR4/MyD88/NF-κB and nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathways in the mice, reduced the levels of pro-inflammatory cytokines - interleukin 1β (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor-α (TNF-α) - and increased the level of the anti-inflammatory cytokine interleukin 10 (IL-10), thereby mitigating inflammation.

CONCLUSION

This study provides a theoretical basis for the comprehensive development of Limosilactobacillus reuteri and new ideas for the non-pharmacological treatment of gout. © 2024 Society of Chemical Industry.

Exploring the Link Between Periodontitis and Alzheimer's Disease-Could a Nanoparticulate Vaccine Break It?

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder, as approximately 55 million people worldwide are affected, with a significant tendency to increase. It reveals three main pathological features: amyloid plaques, neurofibrillary tangles, and neuroinflammation, responsible for the neurodegenerative changes that slowly lead to deterioration of personality and cognitive control. Over a century after the first case report, effective treatments remain elusive, likely due to an incomplete understanding of the precise mechanisms driving its pathogenesis. Recent studies provide growing evidence of an infectious aetiology for AD, a hypothesis reinforced by findings that amyloid beta functions as an antimicrobial peptide. Among the microorganisms already associated with AD, Porphyromonas gingivalis (Pg), the keystone pathogen of periodontitis (PeD), has received particular attention as a possible aetiological agent for AD development. Herein, we review the epidemiological and genetic evidence linking PeD and Pg to AD, highlighting the identification of periodontal bacteria in post mortem analysis of AD patients' brains and identifying putative mechanistic links relevant to the biological plausibility of the association. With the focus on AD research shifting from cure to prevention, the proposed mechanisms linking PeD to AD open the door for unravelling new prophylactic approaches able to reduce the global burden of AD. As hypothesised in this review, these could include a bionanotechnological approach involving the development of an oral nanoparticulate vaccine based on Pg-specific antigens. Such a vaccine could prevent Pg antigens from progressing to the brain and triggering AD pathology, representing a promising step toward innovative and effective AD prevention.

Alzheimer's Disease and Porphyromonas gingivalis: Exploring the Links

Recent research highlights compelling links between oral health, particularly periodontitis, and systemic diseases, including Alzheimer's disease (AD). Although the biological mechanisms underlying these associations remain unclear, the role of periodontal pathogens, particularly Porphyromonas gingivalis, has garnered significant attention. P. gingivalis, a major driver of periodontitis, is recognized for its potential systemic effects and its putative role in AD pathogenesis. This review examines evidence connecting P. gingivalis to hallmark AD features, such as amyloid β accumulation, tau hyperphosphorylation, neuroinflammation, and other neuropathological features consistent with AD. Virulence factors, such as gingipains and lipopolysaccharides, were shown to be implicated in blood-brain barrier disruption, neuroinflammation, and neuronal damage. P. gingivalis-derived outer membrane vesicles may serve to disseminate virulence factors to brain tissues. Indirect mechanisms, including systemic inflammation triggered by chronic periodontal infections, are also supposed to exacerbate neurodegenerative processes. While the exact pathways remain uncertain, studies detecting P. gingivalis virulence factors and its other components in AD-affected brains support their possible role in disease pathogenesis. This review underscores the need for further investigation into P. gingivalis-mediated mechanisms and their interplay with host responses. Understanding these interactions could provide critical insights into novel strategies for reducing AD risk through periodontal disease management.

Identifying Alzheimer's disease genes in apolipoprotein E-/- mice brains with confirmed Porphyromonas gingivalis entry

Background

The apolipoprotein E allele ε4 is the most well-known predisposing genetic risk factor for Alzheimer's disease (AD).

Objective

To identify AD genes in apolipoprotein E-/- (ApoE-/-) mice brains with confirmed entry of Porphyromonas gingivalis.

Methods

TaqMan™ Mouse AD arrays were performed on orally infected ApoE-/- mice with confirmed P. gingivalis entry and compared with sham infected mice brains (N = 4) at 12- and 24-weeks post infection.

Results

Gene expression by qPCR demonstrated that in the P. gingivalis 12-weeks post oral infection, two genes were statistically significantly changed in their expression. These were cyclin dependent kinase 5 regulatory subunit 1 (Cdk5r1, 0.15 logfold change, p = 0.05) and Interleukin 1 alpha, (IL1a, -0.10 log fold change, p = 0.012). In the P. gingivalis 24-weeks post oral infection, three genes were statistically significantly changed in their expression. These were cholinergic receptor nicotinic alpha 7 subunit or Chrna7 (0.10 log fold change, p = 0.02), mitogen-activated protein kinase 1 or Mapk1 (0.10 log fold change, p = 0.05) and visinin like 1 or Vnsl1 (0.01 log fold change, p = 0.04). 87 out of 92 AD target genes demonstrated no difference between infected and sham mice brains.

Conclusions

Five genes, from a recognized AD panel had statistically significantly altered expression in the ApoE-/- mouse AD model following P. gingivalis entry into the brain. This suggests the ApoE-/- genetic variation may control the biological activity of specific genes relevant to inflammation and neuronal plasticity following P. gingivalis infection.

Alzheimer's disease-like pathology induced by Porphyromonas gingivalis in middle-aged mice is mediated by NLRP3 inflammasome via the microbiota-gut-brain axis

BACKGROUND

Porphyromonas gingivalis (P. gingivalis) has been found to enter the brain and induce inflammation, contributing to Alzheimer's disease (AD). P. gingivalis is also closely linked to gut dysbiosis. However, does P. gingivalis induce AD-like pathology through the microbiota-gut-brain axis? There is limited literature on this topic.

OBJECTIVE

To determine the precise causal link among P. gingivalis, intestinal inflammation, and AD-related pathology.

METHODS

12- to 13-month-old female C57BL/6J mice were subjected to ligature placement and oral administration of P. gingivalis over a 24-week period. Then, cognitive performance was evaluated with behavioral tests, while AD neuropathological changes, neuroinflammation, and intestinal inflammation were assessed through qPCR, immunofluorescence, and western blot, and gut microbiota was analyzed by 16S rRNA.

RESULTS

Mice exposed to P. gingivalis showed impaired behavior in open field test, novel object recognition, and Y-maze tests. The bacterium infiltrated their brains, increasing Aβ42, AβPP, and Aβ fragments, promoting tau phosphorylation and microglial activation, and reducing levels of ZO-1, PSD95, SYP, and NeuN proteins. Inflammatory factors like NLRP3, caspase-1, IL-1β, IL-6, and TNF-α were elevated in both brains and intestine, while ZO-1 and occludin levels decreased in intestine. P. gingivalis also altered gut microbial compositions.

CONCLUSIONS

P. gingivalis induced gut dysbiosis and activated the NLRP3 inflammasome in the intestine and brains of mice. This led to impairment of both the intestinal and brain-blood barriers, triggering neuroinflammation and promoting the progression of AD. These findings highlight the critical role of NLRP3 inflammasome activation in the microbiota-gut-brain axis in the AD-like pathology induced by P. gingivalis.

Oral microbiome and nitric oxide biomarkers in older people with mild cognitive impairment and APOE4 genotype

Apolipoprotein E4 (APOE4) genotype and nitric oxide (NO) deficiency are risk factors for age-associated cognitive decline. The oral microbiome plays a critical role in maintaining NO bioavailability during aging. The aim of this study was to assess interactions between the oral microbiome, NO biomarkers, and cognitive function in 60 participants with mild cognitive impairment (MCI) and 60 healthy controls using weighted gene co-occurrence network analysis and to compare the oral microbiomes between APOE4 carriers and noncarriers in a subgroup of 35 MCI participants. Within the MCI group, a high relative abundance of Neisseria was associated with better indices of cognition relating to executive function (Switching Stroop, rs = 0.33, P = 0.03) and visual attention (Trail Making, rs = -0.30, P = 0.05), and in the healthy group, Neisseria correlated with working memory (Digit Span, rs = 0.26, P = 0.04). High abundances of Haemophilus (rs = 0.38, P = 0.01) and Haemophilus parainfluenzae (rs = 0.32, P = 0.03), that co-occurred with Neisseria correlated with better scores on executive function (Switching Stroop) in the MCI group. There were no differences in oral nitrate (P = 0.48) or nitrite concentrations (P = 0.84) between the MCI and healthy groups. Linear discriminant analysis Effect Size identified Porphyromonas as a predictor for MCI and Prevotella intermedia as a predictor of APOE4-carrier status. The principal findings of this study were that a greater prevalence of oral P. intermedia is linked to elevated genetic risk for dementia (APOE4 genotype) in individuals with MCI prior to dementia diagnosis and that interventions that promote the oral Neisseria-Haemophilus and suppress Prevotella-dominated modules have potential for delaying cognitive decline.

Neuroinflammation in Alzheimer disease

Increasing evidence points to a pivotal role of immune processes in the pathogenesis of Alzheimer disease, which is the most prevalent neurodegenerative and dementia-causing disease of our time. Multiple lines of information provided by experimental, epidemiological, neuropathological and genetic studies suggest a pathological role for innate and adaptive immune activation in this disease. Here, we review the cell types and pathological mechanisms involved in disease development as well as the influence of genetics and lifestyle factors. Given the decade-long preclinical stage of Alzheimer disease, these mechanisms and their interactions are driving forces behind the spread and progression of the disease. The identification of treatment opportunities will require a precise understanding of the cells and mechanisms involved as well as a clear definition of their temporal and topographical nature. We will also discuss new therapeutic strategies for targeting neuroinflammation, which are now entering the clinic and showing promise for patients.

Current perspectives on microglia-neuron communication in the central nervous system: Direct and indirect modes of interaction

BACKGROUND

The incessant communication that takes place between microglia and neurons is essential the development, maintenance, and pathogenesis of the central nervous system (CNS). As mobile phagocytic cells, microglia serve a critical role in surveilling and scavenging the neuronal milieu to uphold homeostasis.

AIM OF REVIEW

This review aims to discuss the various mechanisms that govern the interaction between microglia and neurons, from the molecular to the organ system level, and to highlight the importance of these interactions in the development, maintenance, and pathogenesis of the CNS.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Recent research has revealed that microglia-neuron interaction is vital for regulating fundamental neuronal functions, such as synaptic pruning, axonal remodeling, and neurogenesis. The review will elucidate the intricate signaling pathways involved in these interactions, both direct and indirect, to provide a better understanding of the fundamental mechanisms of brain function. Furthermore, gaining insights into these signals could lead to the development of innovative therapies for neural disorders.

Microglial DBP Signaling Mediates Behavioral Abnormality Induced by Chronic Periodontitis in Mice

Several lines of evidence implicate that chronic periodontitis (CP) increases the risk of mental illnesses, such as anxiety and depression, yet, the associated molecular mechanism for this remains poorly defined. Here, it is reported that mice subjected to CP exhibited depression-like behaviors and hippocampal memory deficits, accompanied by synapse loss and neurogenesis impairment in the hippocampus. RNA microarray analysis disclosed that albumin D-site-binding protein (DBP) is identified as the most prominently upregulated target gene following CP, and in vivo and in vitro immunofluorescence methods showed that DBP is preferentially expressed in microglia but not neurons or astrocytes in the hippocampus. Interestingly, it is found that the expression of DBP is significantly increased in microglia after CP, and knockdown of microglial DBP ameliorated the behavioral abnormality, as well as reversed the synapse loss and hippocampal neurogenesis damage induced by CP. Furthermore, DBP knockdown improved the CP-induced hippocampal inflammation and microglial polarization. Collectively, these results indicate a critical role of DBP in orchestrating chronic periodontitis-related behavioral abnormality, hippocampal synapse loss and neurogenesis deficits, in which the microglial activation may be indispensably involved.

The PB2 I714S mutation influenced mammalian adaptation of the H3N2 canine influenza virus by interfering with nuclear import efficiency and RNP complex assembly

Avian influenza viruses (AIVs) are the origin of multiple mammal influenza viruses. The genetic determinants of AIVs adapted to humans have been widely elucidated, however, the molecular mechanism of cross-species transmission and adaptation of AIVs to canines are still poorly understood. In this study, two H3N2 influenza viruses isolated from a live poultry market (A/environment/Guangxi/13431/2018, GX13431) and a swab sample from a canine (A/canine/Guangdong/0601/2019, GD0601) were used to investigate the possible molecular basis that determined H3N2 AIV adapting to canine. We found that GD0601 exhibited more robust polymerase activity in cells and higher pathogenicity in mice compared with its evolution ancestor H3N2 AIV GX13431. A series of reassortments of the ribonucleoprotein (RNP) complex showed that the PB2 subunit was the crucial factor that conferred high polymerase activity of GD0601, and the substitution of I714S in the PB2 subunit of GD0601 attenuated the replication and pathogenicity in mammal cells and the mouse model. Mechanistically, the reverse mutation of I714S in the PB2 polymerase subunit which was identified in AIV GX13431 reduced the nuclear import efficiency of PB2 protein and interfered with the interactions of PB2-PA/NP that affected the assembly of the viral RNP complex. Our study reveals amino acid mutation at the position of 714 in the nuclear localization signal (NLS) area in PB2 plays an important role in overcoming the barrier from poultry to mammals of the H3N2 canine influenza virus and provides clues for further study of mammalian adaptation mechanism of AIVs.

Additive effect of clove essential oil combined with hydrogen inhalation improves psychological harm caused by lipopolysaccharide in mice

BACKGROUND

Psychological anxiety and depression, as well as memory impairment, are frequently linked to inflammation. Clove essential oil (CEO) administration and hydrogen (H2) inhalation have been proven to have anti-inflammatory and alleviating effects on related psychological disorders in the past. The current study investigated the potential to improve anxiety-like behaviors and cognitive function by a combination of CEO and H2 treatment.

METHODS

The mice were administered lipopolysaccharide (LPS) to induce inflammation and oxidative stress response and cause psychological disorders. Using this animal model, we conducted experiments to test whether essential oil and H2 inhalation could improve the psychological damage in behavior caused by LPS. Subsequently, elevated plus maze (EPM), forced swimming test (FST), and passive avoidance (PA) test were performed for evaluation of mice anxiety, depression, and response to electric shock, respectively. Furthermore, the biochemical analysis was used to examine the expression levels of inflammatory and oxidative stress markers.

RESULTS

Our results showed that CEO administration and H2 inhalation alone or in combination positively improved inflammation-induced anxiety, depression, and cognitive memory deficits in the mice. In the single treatment groups, CEO demonstrated better results than H2 inhalation in the elevated plus maze, forced swimming, and passive avoidance tests, while combined treatment with both provided a further improved enhancement effect. Biochemical analysis of the cerebral cortex revealed that CEO and H2 therapy reversed the LPS-induced inflammation and oxidative stress response.

CONCLUSIONS

Our results suggest that a combination of CEO and H2 has the potential to treat psychological disorders or neuropsychiatric disorders.

Oral administration of Porphyromonas gingivalis to mice with diet-induced obesity impairs cognitive function associated with microglial activation in the brain

Objective

Both periodontal disease and obesity are risk factors for dementia, but their links to 1brain function remain unclear. In this study, we examined the effects of oral infection with a periodontal pathogen on cognitive function in a mouse model of obesity, focusing on the roles of microglia.

Methods

To create a mouse model of diet-induced obesity and periodontitis, male C57BL/6 J mice were first fed a high-fat diet containing 60% lipid calories for 18 weeks, beginning at 12 weeks of age, to achieve diet-induced obesity. Then, Porphyromonas gingivalis administration in the oral cavity twice weekly for 6 weeks was performed to induce periodontitis in obese mice.

Results

Obese mice orally exposed to P. gingivalis showed cognitive impairment in the novel object recognition test. Increased expression levels of inflammatory cytokines (e.g. interleukin-1β and tumor necrosis factor-α) were observed in the hippocampus of P. gingivalis-treated obese mice. Immunohistochemical analysis revealed that microglia cell body size was increased in the hippocampus and prefrontal cortex of P. gingivalis-treated obese mice, indicating microglial activation. Furthermore, depletion of microglia by PLX3397, a colony-stimulating factor 1 receptor inhibitor, ameliorated cognitive dysfunction.

Conclusion

These results suggest that microglia mediate periodontal infection-induced cognitive dysfunction in obesity.

Protective effects of a lactobacilli mixture against Alzheimer's disease-like pathology triggered by Porphyromonas gingivalis

Porphyromonas gingivalis (P. gingivalis) is one of the pathogens involved in gingival inflammation, which may trigger neuroinflammatory diseases such as Alzheimer's disease (AD). This study aimed to investigate the protective (preventive and treatment) effects of a lactobacilli mixture combining Lactobacillus reuteri PTCC1655, Lactobacillus brevis CD0817, Lacticaseibacillus rhamnosus PTCC1637, and Lactobacillus plantarum PTCC1058 against P. gingivalis-induced gingival inflammation and AD-like pathology in rats. These probiotic strains exhibited cognitive enhancement effects, but this study proposed to assess their activity in a mixture. To propose a probable mechanism for P. gingivalis cognitive impairments, the TEs balance were analyzed in hippocampus and cortex tissues. Animals were divided into five groups: the control, lactobacilli, P. gingivalis, lactobacilli + P. gingivalis (prevention), and P. gingivalis + lactobacilli group (treatment) groups. The behavioral and histopathological changes were compared among them. Finally, The Trace elements (TEs) levels in the hippocampus and cortex tissues were analyzed. The palatal tissue sections of the P. gingivalis infected rats showed moderate inflammation with dense infiltration of inflammatory cells, a limited area of tissue edema, and vascular congestion. Additionally, passive avoidance learning and spatial memory were impaired. Histopathological tests revealed the presence of Aβ-positive cells in the P. gingivalis group. While the Aβ-positive cells decreased in the treatment group, their formation was inhibited in the preventive group. Administration of a mixture of lactobacilli (orally) effectively mitigated the gingival inflammation, Aβ production, and improved learning and memory functions. Moreover, Zn, Cu, and Mn levels in the hippocampus were dramatically elevated by P. gingivalis infection, whereas lactobacilli mixture mitigated these disruptive effects. The lactobacilli mixture significantly prevented the disruptive effects of P. gingivalis on gingival and brain tissues in rats. Therefore, new formulated combination of lactobacilli may be a good candidate for inhibiting the P. gingivalis infection and its subsequent cognitive effects. The current study aimed to evaluate the effects of a lactobacilli mixture to manage the disruptive effects of P. gingivalis infection on memory.

SorCS2 is involved in promoting periodontitis-induced depression-like behaviour in mice

BACKGROUND

Emerging evidence supports the association between periodontitis and depression, although the mechanisms are unclear. This study investigated the role of SorCS2 in the pathogenesis of periodontitis-induced depression.

MATERIALS AND METHODS

An experimental periodontitis model was established using SorCS2 knockout mice and their wild-type littermates, and depression-like behaviour was evaluated. The expression of proBDNF signalling, neuronal activity, and glutamate-associated signalling pathways were further measured by western blotting and immunofluorescence. In addition, neuroinflammatory status, astrocytic and microglial markers, and the expression of corticosterone-related factors were measured by immunofluorescence, western blotting, and enzyme-linked immunosorbent assays.

RESULTS

SorCS2 deficiency alleviated periodontitis-induced depression-like behaviour in mice. Further results suggested that SorCS2 deficiency downregulated the expression of pro-BDNF and glutamate signalling and restored neuronal activities in mice with periodontitis. Neuroinflammation in the mouse hippocampus was triggered by experimental periodontitis but was not affected by SorCS2 deficiency. The levels of corticosterone and the expression of glucocorticoid receptors were also not altered.

CONCLUSION

Our study, for the first time, reveals the critical role of SorCS2 in the pathogenesis of periodontitis-induced depression. The underlying mechanism involves proBDNF and glutamate signalling in the hippocampus, providing a novel therapeutic target for periodontitis-associated depression.

Oral Pathobiont-Derived Outer Membrane Vesicles in the Oral-Gut Axis

Oral pathobionts are essential in instigating local inflammation within the oral cavity and contribute to the pathogenesis of diseases in the gastrointestinal tract and other distant organs. Among the Gram-negative pathobionts, Porphyromonas gingivalis and Fusobacterium nucleatum emerge as critical drivers of periodontitis, exerting their influence not only locally but also as inducers of gut dysbiosis, intestinal disturbances, and systemic ailments. This dual impact is facilitated by their ectopic colonization of the intestinal mucosa and the subsequent mediation of distal systemic effects by releasing outer membrane vesicles (OMVs) into circulation. This review elucidates the principal components of oral pathobiont-derived OMVs implicated in disease pathogenesis within the oral-gut axis, detailing virulence factors that OMVs carry and their interactions with host epithelial and immune cells, both in vitro and in vivo. Additionally, we shed light on the less acknowledged interplay between oral pathobionts and the gut commensal Akkermansia muciniphila, which can directly impede oral pathobionts' growth and modulate bacterial gene expression. Notably, OMVs derived from A. muciniphila emerge as promoters of anti-inflammatory effects within the gastrointestinal and distant tissues. Consequently, we explore the potential of A. muciniphila-derived OMVs to interact with oral pathobionts and prevent disease in the oral-gut axis.

Proteomic analysis of P. gingivalis-Lipopolysaccharide induced neuroinflammation in SH-SY5Y and HMC3 cells

Chronic periodontitis and its keystone pathogen, Porphyromonas gingivalis, have increasingly been linked with Alzheimer's disease (AD). However, P.gingivalis-lipopolysaccharide (LPS) mediated release of neuroinflammatory proteins contributes to AD remains underexplored. In this study, we utilized data-independent acquisition mass spectrometry to characterize P.gingivalis-LPS induced profile of differentially expressed proteins associated with the neuroinflammatory response in human neuroblastoma (SH-SY5Y) and human microglial (HMC3) cells. We reported a set of 124 proteins in SH-SY5Y cells and 96 proteins in HMC3 cells whose levels were significantly upregulated or downregulated by exposure to P. gingivalis-LPS. Our findings demonstrate that P. gingivalis-LPS contributed to the elevated expressions of dementia biomarkers and pro-inflammatory cytokines that include APP, Aβ1-42, Aβ1-40, T-Tau, p-Tau, VEGF, TGF-β, IL-1β, IL-6 and TNF-α through 2 distinct pathways of extracellular sensing by cell surface receptors and intracellular cytosolic receptors. Interestingly, intracellular signaling proteins activated with P. gingivalis-LPS transfection using Lipofectamine™ 2000 had significantly higher fold change protein expression compared to the extracellular signaling with P. gingivalis-LPS treatment. Additionally, we also explored P. gingivalis-LPS mediated activation of caspase-4 dependent non canonical inflammasome pathway in both SH-SY5Y and HMC3 cells. In summary, P. gingivalis-LPS induced neuroinflammatory protein expression in SH-SY5Y and HMC3 cells, provided insights into the specific inflammatory pathways underlying the potential link between P. gingivalis-LPS infection and the pathogenesis of Alzheimer's disease and related dementias.

Associations between immune-inflammatory markers, age, and periodontal status: a cross-sectional study

Since periodontal disease is associated with many systemic diseases, it is important to evaluate its effects on host responses in elderly individuals. To this end, this study investigated salivary interleukin (IL)-17, IL-18, toll-like receptor (TLR) 2, TLR4, and tumor necrosis factor-alpha (TNF-α) levels in patient groups with different periodontal health statuses and immunologically evaluated the relationship between age and periodontal health status. A total of 60 individuals aged 18-40 years (young individuals) and 60 individuals aged 65 years or older (elderly individuals) were included in this study. According to periodontal disease status, the patients were divided into periodontally healthy, gingivitis, and periodontitis subgroups. Clinical periodontal parameters, including probing depth (PD), clinical attachment level (CAL), plaque index (PI), and gingival index (GI), were recorded. Saliva samples were collected and analyzed using ELISA to determine the levels of IL-17, IL-18, TLR2, TLR4, and TNF-α. Higher clinical periodontal parameter (PD, CAL, PI, and GI) and inflammatory marker (IL-17, IL-18, TNF-α, TLR2, and TLR4) levels were found in patients with periodontitis than those in periodontally healthy individuals and patients with gingivitis (P < 0.05). Salivary inflammatory marker levels were significantly higher in elderly individuals than those in young individuals in all subgroups (P < 0.05). A positive correlation was found between inflammatory marker levels and clinical periodontal parameters, but there was no correlation between TLR2 and PI or GI. This study suggests a significant increase in host response to periodontal disease as the disease progresses, with the levels of cytokines and TLR expression exhibiting an increasing trend with age. Increased IL-17, IL-18, TLR2, TLR4, and TNF-α levels in elderly individuals in all periodontal health subgroups might suggest the role of these cytokines and TLR pathway in the pathogenesis of periodontal diseases.

Microbiota-immune-brain interactions: A new vision in the understanding of periodontal health and disease

This review highlights the significance of interactions between the microbiota, immune system, nervous and hormonal systems, and the brain on periodontal health and disease. Microorganisms in the microbiota, immune cells, and neurons communicate via homeostatic nervous and hormonal systems, regulating vital body functions. By modulating pro-inflammatory and anti-inflammatory adaptive immune responses, these systems control the composition and number of microorganisms in the microbiota. The strength of these brain-controlled responses is genetically determined but is sensitive to early childhood stressors, which can permanently alter their responsiveness via epigenetic mechanisms, and to adult stressors, causing temporary changes. Clinical evidence and research with humans and animal models indicate that factors linked to severe periodontitis enhance the responsiveness of these homeostatic systems, leading to persistent hyperactivation. This weakens the immune defense against invasive symbiotic microorganisms (pathobionts) while strengthening the defense against non-invasive symbionts at the gingival margin. The result is an increased gingival tissue load of pathobionts, including Gram-negative bacteria, followed by an excessive innate immune response, which prevents infection but simultaneously destroys gingival and periodontal tissues. Thus, the balance between pro-inflammatory and anti-inflammatory adaptive immunity is crucial in controlling the microbiota, and the responsiveness of brain-controlled homeostatic systems determines periodontal health.

Peri-implantitis with a potential axis to brain inflammation: an inferential review

Peri-implantitis (PI) is a chronic, inflammatory, and infectious disease which affects dental implants and has certain similarities to periodontitis (PD). Evidence has shown that PD may be related to several types of systemic disorders, such as diabetes and insulin resistance, cardiovascular diseases, respiratory tract infections, adverse pregnancy outcomes, and neurological disorders. Furthermore, some types of bacteria in PD can also be found in PI, leading to certain similarities in the immunoinflammatory responses in the host. This review aims to discuss the possible connection between PI and neuroinflammation, using information based on studies about periodontal disorders, a topic whose connection with systemic alterations has been gaining the interest of the scientific community. Literature concerning PI, PD, and systemic disorders, such as neuroinflammation, brain inflammation, and neurological disorder, was searched in the PubMed database using different keyword combinations. All studies found were included in this narrative review. No filters were used. Eligible studies were analyzed and reviewed carefully. This study found similarities between PI and PD development, maintenance, and in the bacterial agents located around the teeth (periodontitis) or dental implants (peri-implantitis). Through the cardiovascular system, these pathologies may also affect blood-brain barrier permeability. Furthermore, scientific evidence has suggested that microorganisms from PI (as in PD) can be recognized by trigeminal fiber endings and start inflammatory responses into the trigeminal ganglion. In addition, bacteria can traverse from the mouth to the brain through the lymphatic system. Consequently, the immune system increases inflammatory mediators in the brain, affecting the homeostasis of the nervous tissue and vice-versa. Based on the interrelation of microbiological, inflammatory, and immunological findings between PD and PI, it is possible to infer that immunoinflammatory changes observed in PD can imply systemic changes in PI. This, as discussed, could lead to the development or intensification of neuroinflammatory changes, contributing to neurodegenerative diseases.

Neuroprotective Properties of Rutin Hydrate against Scopolamine-Induced Deficits in BDNF/TrkB/ERK/CREB/Bcl2 Pathways

Background/Objectives: Alzheimer's disease (AD) is an age-related degenerative brain disorder characterized by a progressive decline in cognitive function and memory. This study aimed to evaluate whether rutin hydrate (RH) has neuroprotective effects in an AD-like learning and memory impairment rat model induced by scopolamine (SCO). Methods: The rats were administered with RH (100 mg/kg) and SCO (1.5 mg/kg) and underwent behavioral tests, including the Morris water maze test, Y-maze test, and passive avoidance test, to evaluate their learning and memory abilities. Additionally, long-term potentiation (LTP) was induced to observe changes in the field excitatory postsynaptic potential (fEPSP) activity. Results: RH treatment attenuated the SCO-induced shortening of step-through latency in the passive avoidance (PA) test, increased the percentage of alternation in the Y-maze, and increased the time spent in the target zone in the Morris water maze (MWM). Moreover, RH increased the total activity of fEPSP following theta burst stimulation and attenuated the SCO-induced blockade of fEPSP. RH also ameliorated the SCO-induced decrease in the expression levels of the BDNF, TrkB, ERK, CREB, and Bcl-2 proteins and the increase in the Bax protein level in the rat hippocampus. This demonstrates that RH has beneficial neuroprotective effects in the brain, improving learning, memory, and synaptic plasticity in rats. Conclusions: Our results highlight the molecular and cellular mechanisms through which RH exerts its neuroprotective effects in the prevention and treatment of learning and memory deficit disorders. RH could potentially be used as a therapeutic strategy for the restoration of learning and memory function and the prevention of the progression of AD.

Porphyromonas gingivalis virulence factors induce toxic effects in SH-SY5Y neuroblastoma cells: GRK5 modulation as a protective strategy

Periodontitis (PDS) is a chronic inflammatory disease initiated by a dysbiosis of oral pathogenic bacterial species, such as Porphyromonas gingivalis (Pg). These bacteria can penetrate the bloodstream, releasing various endo and exotoxins that fuel the infection, and stimulate toxic inflammation in different compartments, including the brain. However, the specific mechanisms by which PDS/Pg contribute to brain disorders, such as Alzheimer's disease (AD), remain unclear. This study assessed the effects of Pg's virulence factors - lipopolysaccharide (LPS-Pg) and gingipains (gps) K (Kgp) and Rgp - on SH-SY5Y cells. Our results demonstrated that LPS-Pg activated signaling through the Toll-like receptor (TLR)-2/4 induced a significant downregulation of G protein-coupled receptor kinase 5 (GRK5). Additionally, LPS-Pg stimulation resulted in a robust increase in Tau phosphorylation (pTau) and p53 levels, while causing a marked reduction in Bcl2 and increased cell death compared to unstimulated cells (Ns). LPS-Pg also elevated inducible nitric oxide synthase (iNOS) expression, leading to oxidative damage. In cells overexpressing GRK5 via Adenovirus, LPS-Pg failed to increase iNOS and pTau levels compared to GFP control cells. High GRK5 levels also prevented the nuclear accumulation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB). Furthermore, the overexpression of a GRK5 mutant form lacking the nuclear localization signal (ΔNLS) nearly abolished LPS-Pg induced p53 and iNOS upregulation. Finally, we tested whether Kgp and Rgp mediated similar effects and our data showed that both gps caused a marked downregulation of GRK5 leading to increased p53 and pTau levels. In conclusion, this study provides further insight into the toxic effects elicited by Pg in cells and suggests that preventing GRK5 deficiency may be a valid strategy to mitigate Pg-induced toxic effects (i.e. cell death, oxidative damage, and Tau hyperphosphorylation) in SH-SY5Y cells, which are typical molecular hallmarks of neurodegenerative disorders.

PDTC improves cognitive impairment in LPS-induced ARDS by regulating miR-181c/NF-κB axis-mediated neuroinflammation

BACKGROUND

Cognitive impairment is a severe complication of acute respiratory distress syndrome (ARDS). Emerging studies have revealed the effects of pyrrolidine dithiocarbamate (PDTC) on improving surgery-induced cognitive impairment. The major aim of the study was to investigate whether PDTC protected against ARDS-induced cognitive dysfunction and to identify the underlying mechanisms involved.

METHODS

The rat model of ARDS was established by intratracheal instillation of lipopolysaccharide (LPS), followed by treatment with PDTC. The cognitive function of rats was analyzed by the Morris Water Maze, and pro-inflammatory cytokines were assessed by quantitative real-time PCR, enzyme-linked immunosorbent assay, and western blot assays. A dual-luciferase reporter gene assay was performed to identify the relationship between miR-181c and its target gene, TAK1 binding protein 2 (TAB2).

RESULTS

The results showed that PDTC improved cognitive impairment and alleviated neuroinflammation in the hippocampus in LPS-induced ARDS model. Furthermore, we demonstrated that miR-181c expression was downregulated in the hippocampus of the ARDS rats, which was restored by PDTC treatment. In vitro studies showed that miR-181c alleviated LPS-induced pro-inflammatory response by inhibiting TAB2, a critical molecule in the nuclear factor (NF)-κB signaling pathway.

CONCLUSION

PDTC improves cognitive impairment in LPS-induced ARDS by regulating miR-181c/NF-κB axis-mediated neuroinflammation, providing a potential opportunity for the treatment of this disease.

Oral Microbiome Dysbiosis as a Risk Factor for Stroke: A Comprehensive Review

Stroke represents a significant global health burden, with a substantial impact on mortality, morbidity, and long-term disability. The examination of stroke biomarkers, particularly the oral microbiome, offers a promising avenue for advancing our understanding of the factors that contribute to stroke risk and for developing strategies to mitigate that risk. This review highlights the significant correlations between oral diseases, such as periodontitis and caries, and the onset of stroke. Periodontal pathogens within the oral microbiome have been identified as a contributing factor in the exacerbation of risk factors for stroke, including obesity, dyslipidemia, atherosclerosis, hypertension, and endothelial dysfunction. The alteration of the oral microbiome may contribute to these conditions, emphasizing the vital role of oral health in the prevention of cardiovascular disease. The integration of dental and medical health practices represents a promising avenue for enhancing stroke prevention efforts and improving patient outcomes.

Porphyromonas gingivalis promote microglia M1 polarization through the NF-кB signaling pathway

Background

Porphyromonas gingivalis (P.gingivalis) is associated with the onset of Alzheimer's disease (AD), but the underlying molecular mechanism is unclear. Neuroinflammation in the brain from the microglial immune response induces the pathological progression of AD. In this study, the roles and molecular mechanism of P.gingivalis in microglial inflammation in vitro were investigated.

Methods

In this study, a P.gingivalis oral administration mouse model was generated, and microglia were stimulated with P.gingivalis in vitro. The viability of the microglia after P.gingivalis treatment was evaluated through CCK-8 and live/dead cell staining. Inflammation in brain tissue after P.gingivalis treatment and the immune response of microglia in vitro were detected by RT‒PCR, Western blotting and IF. Moreover, the RNA sequence was used, and the role of the NF-κB signalling pathway in microglial activation was analysed after P.gingivalis stimulation.

Results

The mRNA and protein levels of IL-6 and IL-17 were increased, and the expression of IL-10 was decreased in brain tissue after P.gingivalis oral administration. The viability of the HMC3 cells significantly decreased with 5% P.gingivalis after stimulation. The results of live/dead cell staining also showed the inhibitory effect of 5% P.gingivalis supplementation on cell viability. Moreover, 5% P.gingivalis supplementation increased the mRNA and protein levels of IL-6 and IL-17 and decreased IL-10 expression in HMC3 cells. P.gingivalis supplementation increased the mRNA and protein levels of iNOS and CD86 and decreased CD206 expression in HMC3 cells. RNA sequencing revealed that the NF-κB signalling pathway was involved in this process. Furthermore, p-P65 was upregulated and p-IKBα was downregulated in brain tissue and HMC3 cells after P.gingivalis stimulation, and an NF-κB signalling pathway inhibitor (QNZ) reversed the viability, M1 polarization and inflammatory factors of microglia in HMC3 cells in vitro.

Conclusions

In conclusion, P.gingivalis induced neuroinflammation in the brain, possibly through promotion of M1 polarization of microglia via activation of the NF-κB signalling pathway during the progression of AD.

Gibberellic acid targeting ZBTB16 reduces NF-κB dependent inflammatory stress in sepsis-induced neuroinflammation

OBJECTIVE

Sepsis is frequently complicated by neuroinflammation. Gibberellic acid (GA3) is recognized for its anti-inflammatory properties. In this study, our objective was to investigate whether GA3 could alleviate Nuclear factor-kappa B (NF-κB) -dependent inflammatory stress in sepsis-induced neuroinflammation.

METHODS

C57BL/6 J mice were administered 10 mg/kg lipopolysaccharide (LPS) to induce sepsis. BV2 cells were pre-incubated with GA3 and subjected lipopolysaccharide stimulation to replicate the inflammatory microglia during sepsis. Subsequently, we assessed the release of IL-6, TNF-α, and IL-1β, along with the expression of Zbtb16, NF-κB, and IκB. To investigate whether any observed anti-inflammatory effects of GA3 were mediated through a Zbtb16-dependent mechanism, Zbtb16 was silenced using siRNA.

RESULTS

GA3 improved the survival of sepsis mice and alleviated post-sepsis cognitive impairment. Additionally, GA3 attenuated microglial M1 activation (pro-inflammatory phenotype), inflammation, and neuronal damage in the brain. Moreover, GA3 inhibited the release of TNF-α, IL-6, and IL-1β in microglia stimulated with LPS. The NF-κB signaling pathway emerged as one of the key molecular pathways associated with the impact of GA3 on LPS-stimulated microglia. Lastly, GA3 upregulated Zbtb16 expression in microglia that had been downregulated by LPS. The inhibitory effects of GA3 on microglial M1 activation were partially reversed through siRNA knockdown of Zbtb16.

CONCLUSIONS

Pre-incubation of microglia with GA3 led to the upregulation of the NF-κB regulator, Zbtb16. This process counteracted LPS-induced microglial M1 activation, resulting in an anti-inflammatory effect upon subsequent LPS stimulation.

Distinctive subgingival microbial signatures in older adults with different levels of cognitive function

AIM

To examine association between subgingival microbial signatures and levels of cognitive impairment in older adults.

MATERIALS AND METHODS

We analysed subgingival plaque samples and 16S ribosomal RNA sequences for microbiota among 165 participants (normal controls [NCs]: 40, subjective cognitive decline [SCD]: 40, mild cognitive impairment [MCI]: 49 and dementia: 36).

RESULTS

The bacterial richness was lower among individuals with worse cognitive function, and subgingival microbial communities differed significantly among the four groups. Declining cognitive function was associated with decreasing relative abundance of genera Capnocytophaga, Saccharibacteria_genera_incertae_sedis, Lautropia and Granulicatella, and increasing abundance of genus Porphyromonas. Moreover, there were differentially abundant genera among the groups. Random forest model based on subgingival microbiota could distinguish between cognitive impairment and NC (AUC = 0.933, 95% confidence interval 0.873-0.992). Significant correlations were observed between oral microbiota and sex, Montreal Cognitive Assessment (MoCA) score and Mini-Mental State Examination score. Partial correlation analysis showed that Leptotrichia and Burkholderia were closely negatively associated with the MoCA score after adjusting for multiple covariates. Gene function was not significantly different between SCD and NC groups, whereas three homozygous genes were altered in MCI patients and two in dementia patients.

CONCLUSIONS

This is the first study to demonstrate an association between the composition, function and metabolic pathways of subgingival microbiota and different levels of cognitive function among older individuals. Future cohort studies should assess its diagnostic usefulness for cognitive impairment.

Gingipains may be one of the key virulence factors of Porphyromonas gingivalis to impair cognition and enhance blood-brain barrier permeability: An animal study

AIM

Blood-brain barrier (BBB) disorder is one of the early findings in cognitive impairments. We have recently found that Porphyromonas gingivalis bacteraemia can cause cognitive impairment and increased BBB permeability. This study aimed to find out the possible key virulence factors of P. gingivalis contributing to the pathological process.

MATERIALS AND METHODS

C57/BL6 mice were infected with P. gingivalis or gingipains or P. gingivalis lipopolysaccharide (P. gingivalis LPS group) by tail vein injection for 8 weeks. The cognitive behaviour changes in mice, the histopathological changes in the hippocampus and cerebral cortex, the alternations of BBB permeability, and the changes in Mfsd2a and Cav-1 levels were measured. The mechanisms of Ddx3x-induced regulation on Mfsd2a by arginine-specific gingipain A (RgpA) in BMECs were explored.

RESULTS

P. gingivalis and gingipains significantly promoted mice cognitive impairment, pathological changes in the hippocampus and cerebral cortex, increased BBB permeability, inhibited Mfsd2a expression and up-regulated Cav-1 expression. After RgpA stimulation, the permeability of the BBB model in vitro increased, and the Ddx3x/Mfsd2a/Cav-1 regulatory axis was activated.

CONCLUSIONS

Gingipains may be one of the key virulence factors of P. gingivalis to impair cognition and enhance BBB permeability by the Ddx3x/Mfsd2a/Cav-1 axis.

The mechanisms of Porphyromonas gingivalis-derived outer membrane vesicles-induced neurotoxicity and microglia activation

Background/purpose

Periodontitis is associated with various systemic diseases, potentially facilitated by the passage of Porphyromonas gingivalis outer membrane vesicles (Pg-OMVs). Several recent studies have suggested a connection between Pg-OMVs and neuroinflammation and neurodegeneration, but the precise causal relationship remains unclear. This study aimed to investigate the mechanisms underlying these associations using in vitro models.

Materials and methods

Isolated Pg-OMVs were characterized by morphology, size, and gingipain activity. We exposed SH-SY5Y neuroblastoma cells and BV-2 microglial cells to various concentrations of Pg-OMVs. Cell morphology, a 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, an enzyme-linked immunosorbent assay, and Western blot analysis were used to evaluate the cellular mechanism underlying Pg-OMV-induced neurotoxicity in neuronal cells and inflammatory responses in microglial cells.

Results

Exposure to Pg-OMVs induced neurotoxicity in SH-SY5Y cells, as evidenced by cellular shrinkage, reduced viability, activation of apoptotic pathways, and diminished neuronal differentiation markers. Gingipain inhibition mitigated these effects, suggesting that gingipain mediates Pg-OMVs-induced neurotoxicity in SH-SY5Y cells. Our research on neuroinflammation suggests that upon endocytosis of Pg-OMVs by BV-2 cells, lipopolysaccharide (LPS) can modulate the production of inducible nitric oxide synthase and tumor necrosis factor-alpha by activating pathways that involve phosphorylated AKT and the phosphorylated JNK pathway.

Conclusion

Our study demonstrated that following the endocytosis of Pg-OMVs, gingipain can induce neurotoxicity in SH-SY5Y cells. Furthermore, the Pg-OMVs-associated LPS can trigger neuroinflammation via AKT and JNK signaling pathways in BV-2 cells.

Lipopolysaccharides derived from Porphyromonas gingivalis and Escherichia coli: Differential and interactive effects on novelty-induced hyperlocomotion, blood cytokine levels and TLR4-related processes

Lipopolysaccharide (LPS), a component of the Gram-negative bacterial cell wall, activates Toll-like receptors (TLRs). Porphyromonas gingivalis (Pg) may be involved in the progression of periodontal disease. Mice exposed to a novel environment show hyperlocomotion that is inhibited by systemic administration of LPS derived from Escherichia coli (Ec-LPS). However, whether Pg-LPS influences novelty-induced locomotion is unknown. Accordingly, we carried out an open field test to analyse the effects of Pg-LPS. For comparison, effects of Ec-LPS were also studied. We additionally investigated the influence of systemic administration of Pg-LPS or Ec-LPS on IL-6, TNF-alpha, and IL-10 levels in blood, as they could be involved in the changes in locomotion. The TLR4 receptor antagonist TAK-242 was used to study the involvement of TLR4. Since Pg-LPS may block TLR4 in vitro, we analysed the effects of Pg-LPS on Ec-LPS-induced changes in behavioural and biochemical parameters. Male ddY mice were used. Pg- or Ec-LPS and TAK-242 were administered intraperitoneally. Ec-LPS (840 μg/kg), but not Pg-LPS (100, 500 and 840 μg/kg), inhibited novelty-induced locomotion, which was antagonized by TAK-242 (3.0 mg/kg). Ec-LPS (840 μg/kg) increased blood levels of IL-6 and IL-10, which were antagonized by TAK-242 (3.0 mg/kg). However, TAK-242 did not inhibit Ec-LPS-induced increases in TNF-alpha levels in blood. Pg-LPS (100, 500, and 840 μg/kg) did not alter blood IL-6, TNF-alpha, or IL-10 levels. The Ec-LPS-induced increase in blood IL-10, but not IL-6 and TNF-alpha, levels was inhibited by Pg-LPS (500 μg/kg). These results suggest that TLR4 stimulation mediates the inhibition of novel environment-induced locomotion in mice following systemic administration of Ec-LPS, while also increasing blood IL-6 and IL-10 levels. In contrast, Pg-LPS did not exhibit these effects. The present study also provides in vivo evidence that Pg-LPS can inhibit TLR4-mediated increases in blood levels of IL-10, a cytokine thought to prevent the development of periodontal disease.

A TNF-α inhibitor abolishes sepsis-induced cognitive impairment in mice by modulating acetylcholine and nitric oxide homeostasis, BDNF release, and neuroinflammation

Neurodegenerative disorders have a pathophysiology that heavily involves neuroinflammation. In this study, we used lipopolysaccharide (LPS) to create a model of cognitive impairment by inducing systemic and neuroinflammation in experimental animals. LPS was injected intraperitoneally at a dose of 0.5 mg/kg during the last seven days of the study. Adalimumab (ADA), a TNF-α inhibitor, was injected at a dose of 10 mg/kg a total of 3 times throughout the study. On the last two days of the experiment, 50 mg/kg of curcumin was administered orally as a positive control group. Open field (OF) and elevated plus maze tests (EPM) were used to measure anxiety-like behaviors. The tail suspension test (TST) was used to measure depression-like behaviors, while the novel object recognition test (NOR) was used to measure learning and memory activities. Blood and hippocampal TNF α and nitric oxide (NO) levels, hippocampal BDNF, CREB, and ACh levels, and AChE activity were measured by ELISA. LPS increased anxiety and depression-like behaviors while decreasing the activity of the learning-memory system. LPS exerted this effect by causing systemic and neuroinflammation, cholinergic dysfunction, and impaired BDNF release. ADA controlled LPS-induced behavioral changes and improved biochemical markers. ADA prevented cognitive impairment induced by LPS by inhibiting inflammation and regulating the release of BDNF and the cholinergic pathway.

P. gingivalis in oral-prostate axis exacerbates benign prostatic hyperplasia via IL-6/IL-6R pathway

BACKGROUND

Benign prostatic hyperplasia (BPH) is the most common disease in elderly men. There is increasing evidence that periodontitis increases the risk of BPH, but the specific mechanism remains unclear. This study aimed to explore the role and mechanism of the key periodontal pathogen Porphyromonas gingivalis (P. gingivalis) in the development of BPH.

METHODS

The subgingival plaque (Sp) and prostatic fluid (Pf) of patients with BPH concurrent periodontitis were extracted and cultured for 16S rDNA sequencing. Ligature-induced periodontitis, testosterone-induced BPH and the composite models in rats were established. The P. gingivalis and its toxic factor P. gingivalis lipopolysaccharide (P.g-LPS) were injected into the ventral lobe of prostate in rats to simulate its colonization of prostate. P.g-LPS was used to construct the prostate cell infection model for mechanism exploration.

RESULTS

P. gingivalis, Streptococcus oralis, Capnocytophaga ochracea and other oral pathogens were simultaneously detected in the Pf and Sp of patients with BPH concurrent periodontitis, and the average relative abundance of P. gingivalis was found to be the highest. P. gingivalis was detected in both Pf and Sp in 62.5% of patients. Simultaneous periodontitis and BPH synergistically aggravated prostate histological changes. P. gingivalis and P.g-LPS infection could induce obvious hyperplasia of the prostate epithelium and stroma (epithelial thickness was 2.97- and 3.08-fold that of control group, respectively), and increase of collagen fibrosis (3.81- and 5.02-fold that of control group, respectively). P. gingivalis infection promoted prostate cell proliferation, inhibited apoptosis, and upregulated the expression of inflammatory cytokines interleukin-6 (IL-6; 4.47-fold), interleukin-6 receptor-α (IL-6Rα; 5.74-fold) and glycoprotein 130 (gp130; 4.47-fold) in prostatic tissue. P.g-LPS could significantly inhibit cell apoptosis, promote mitosis and proliferation of cells. P.g-LPS activates the Akt pathway through IL-6/IL-6Rα/gp130 complex, which destroys the imbalance between proliferation and apoptosis of prostate cells, induces BPH.

CONCLUSION

P. gingivalis was abundant in the Pf of patients with BPH concurrent periodontitis. P. gingivalis infection can promote BPH, which may affect the progression of BPH via inflammation and the Akt signaling pathway.

Chondroitin sulphate modified MoS2 nanoenzyme with multifunctional activities for treatment of Alzheimer's disease

Nano-MoS2 exhibit oxidoreductase-like activities, and has been shown to effectively eliminate excessive intracellular ROS and inhibit Aβ aggregation, thus demonstrating promising potential for anti-Alzheimer's disease (anti-AD) intervention. However, the low water dispersibility and high toxicity of nano-MoS2 limits its further application. In this study, we developed a chondroitin sulphate (CS)-modified MoS2 nanoenzyme (CS@MoS2) by harnessing the excellent biocompatibility of CS and the exceptional activities of nano-MoS2 to explore its potential in anti-AD research. Promisingly, CS@MoS2 significantly inhibited Aβ1-40 aggregation and prevented toxic injury in SH-SY5Y cells caused by Aβ1-40. In addition, CS@MoS2 protected these cells from oxidative stress damage by regulating ROS production, as well as promoting the activities of SOD and GSH-Px. CS@MoS2 also modulated the intracellular Ca2+ imbalance and downregulated Tau hyperphosphorylation by activating GSK-3β. CS@MoS2 suppressed p-NF-κB (p65) translocation to the nucleus by inhibiting MAPK phosphorylation, and modulated the expression of downstream anti- and proinflammatory cytokines. Owing to its multifunctional activities, CS@MoS2 effectively improved spatial learning, memory, and anxiety in D-gal/AlCl3-induced AD mice. Taken together, these results indicate that CS@MoS2 has significant potential for improving the therapeutic efficacy of the prevention and treatment of AD, while also presenting a novel framework for the application of nanoenzymes.

The changing of α5-GABAA receptors expression and distribution participate in sevoflurane-induced learning and memory impairment in young mice

BACKGROUND

Sevoflurane is a superior agent for maintaining anesthesia during surgical procedures. However, the neurotoxic mechanisms of clinical concentration remain poorly understood. Sevoflurane can interfere with the normal function of neurons and synapses and impair cognitive function by acting on α5-GABAAR.

METHODS

Using MWM test, we evaluated cognitive abilities in mice following 1 h of anesthesia with 2.7%-3% sevoflurane. Based on hippocampal transcriptome analysis, we analyzed the differential genes and IL-6 24 h post-anesthesia. Western blot and RT-PCR were performed to measure the levels of α5-GABAAR, Radixin, P-ERM, P-Radixin, Gephyrin, IL-6, and ROCK. The spatial distribution and expression of α5-GABAAR on neuronal somata were analyzed using histological and three-dimensional imaging techniques.

RESULTS

MWM test indicated that partial long-term learning and memory impairment. Combining molecular biology and histological analysis, our studies have demonstrated that sevoflurane induces immunosuppression, characterized by reduced IL-6 expression levels, and that enhanced Radixin dephosphorylation undermines the microstructural stability of α5-GABAAR, leading to its dissociation from synaptic exterior and resulting in a disordered distribution in α5-GABAAR expression within neuronal cell bodies. On the synaptic cleft, the expression level of α5-GABAAR remained unchanged, the spatial distribution became more compact, with an increased fluorescence intensity per voxel. On the extra-synaptic space, the expression level of α5-GABAAR decreased within unchanged spatial distribution, accompanied by an increased fluorescence intensity per voxel.

CONCLUSION

Dysregulated α5-GABAAR expression and distribution contributes to sevoflurane-induced partial long-term learning and memory impairment, which lays the foundation for elucidating the underlying mechanisms in future studies.

The role of Toll-like receptors in neuropsychiatric disorders: Immunopathology, treatment, and management

Neuropsychiatric disorders denote a broad range of illnesses involving neurology and psychiatry. These disorders include depressive disorders, anxiety, schizophrenia, bipolar disorder, attention deficit hyperactivity disorder, autism spectrum disorders, headaches, and epilepsy. In addition to their main neuropathology that lies in the central nervous system (CNS), lately, studies have highlighted the role of immunity and neuroinflammation in neuropsychiatric disorders. Toll-like receptors (TLRs) are innate receptors that act as a bridge between the innate and adaptive immune systems via adaptor proteins (e.g., MYD88) and downstream elements; TLRs are classified into 13 families that are involved in normal function and illnesses of the CNS. TLRs expression affects the course of neuropsychiatric disorders, and is influenced during their pharmacotherapy; For example, the expression of multiple TLRs is normalized during the major depressive disorder pharmacotherapy. Here, the role of TLRs in neuroimmunology, treatment, and management of neuropsychiatric disorders is discussed. We recommend longitudinal studies to comparatively assess the cell-type-specific expression of TLRs during treatment, illness progression, and remission. Also, further research should explore molecular insights into TLRs regulation and related pathways.

Mitochondrial dysfunction precedes hippocampal IL-1β transcription and cognitive impairments after low-dose lipopolysaccharide injection in aged mice

Acute cognitive impairments termed delirium often occur after inflammatory insults in elderly patients. While previous preclinical studies suggest mitochondria as a target for reducing neuroinflammation and cognitive impairments after LPS injection, fewer studies have evaluated the effects of a low-grade systemic inflammation in the aged brain. Thus, to identify the significance of mitochondrial dysfunction after a clinically relevant systemic inflammatory stimulus, we injected old-aged mice (18-20 months) with low-dose lipopolysaccharide (LPS, 0.04 mg/kg). LPS injection reduced mitochondrial respiration in the hippocampus 24 h after injection (respiratory control ratio [RCR], state3u/state4o; control = 2.82 ± 0.19, LPS = 2.57 ± 0.08). However, gene expression of the pro-inflammatory cytokine IL-1β was increased (RT-PCR, control = 1.00 ± 0.30; LPS = 2.01 ± 0.67) at a more delayed time point, 48 h after LPS injection. Such changes were associated with cognitive impairments in the Barnes maze and fear chamber tests. Notably, young mice were unaffected by low-dose LPS, suggesting that mitochondrial dysfunction precedes neuroinflammation and cognitive decline in elderly patients following a low-grade systemic insult. Our findings highlight mitochondria as a potential therapeutic target for reducing delirium in elderly patients.

Transcriptome analysis on pulmonary inflammation between periodontitis and COPD

Objective

The aim of this study is to investigate the correlation between periodontal disease and chronic obstructive pulmonary disease (COPD) from the perspective of gene regulation, as well as the inflammatory pathways involved.

Methods

Forty C57BL/6 mice were randomly divided into four groups: control group, chronic periodontitis (CP) group, COPD group, and CP&COPD group. Lung tissue samples were selected for messenger ribonucleic acid (mRNA) sequencing analysis, and differential genes were screened out. Gene enrichment analysis was carried out, and then crosstalk gene enrichment analysis was conducted to explore the pathogenesis related to periodontal disease and COPD.

Results

Results of enrichment analysis showed that the differentially expressed genes (DEGs) in the CP group were concentrated in response to bacterial origin molecules. The DEGs in the COPD group gene were enriched in positive regulation of B cell activation. The DEGs in the CP&COPD group were concentrated in neutrophil extravasation and neutrophil migration. The mice in the three experimental groups had 19 crosstalk genes, five of which were key genes.

Conclusions

Lcn2, S100a8, S100a9, Irg1, Clec4d are potential crossover genes of periodontal disease and COPD. Lcn2, S100a8, S100a9 are correlated with neutrophils in both diseases. Irg1 and Clec4d may bind to receptors on the surface of lymphocytes to produce cytokines and activate inflammatory pathways, this requires further research.

Association between oral microbiome and breast cancer in the east Asian population: A Mendelian randomization and case-control study

BACKGROUND

The causal relationship between breast cancer (BC) and the oral microbiome remains unclear. In this case-control study, using two-sample Mendelian randomization (MR), we thoroughly explored the relationship between the oral microbiome and BC in the East Asian population.

METHODS

Genetic summary data related to oral microbiota and BC were collected from genome-wide association studies involving participants of East Asian descent. MR estimates were generated by conducting various analyses. Sequencing data from a case-control study were used to verify the validity of these findings.

RESULTS

MR analysis revealed that 30 tongue and 37 salivary bacterial species were significantly associated with BC. Interestingly, in both tongue and salivary microbiomes, we observed the causal effect of six genera, namely, Aggregatibacter, Streptococcus, Prevotella, Haemophilus, Lachnospiraceae, Oribacterium, and Solobacterium, on BC. Our case-control study findings suggest differences in specific bacteria between patients with BC and healthy controls. Moreover, sequencing data confirmed the MR analysis results, demonstrating that compared with the healthy control group, the BC group had a higher relative abundance of Pasteurellaceae and Streptococcaceae but a lower relative abundance of Bacteroidaceae.

CONCLUSIONS

Our MR analysis suggests that the oral microbiome exerts a causative effect on BC risk, supported by the sequencing data of a case-control study. In the future, studies should be undertaken to comprehensively understand the complex interaction mechanisms between the oral microbiota and BC.

Abnormal amyloid precursor protein processing in periodontal tissue in a murine model of periodontitis induced by Porphyromonas gingivalis

OBJECTIVE

The study aimed to investigate the change of amyloid precursor protein (APP) processing and amyloid β (Aβ) metabolites in linking periodontitis to Alzheimer's disease (AD).

BACKGROUND

Aβ is one of the main pathological features of AD, and few studies have discussed changes in its expression in peripheral tissues or analyzed the relationship between the peripheral imbalance of Aβ production and clearance.

METHODS

A murine model of periodontitis was established by oral infection with Porphyromonas gingivalis (P. gingivalis). Micro-computed tomography (Micro-CT) was used to observe the destruction of the alveolar bone. Nested quantitative polymerase chain reaction (qPCR) was used to measure small quantities of P.gingivalis DNA in different tissues. Behavioral experiments were performed to measure cognitive function in the mice. The mRNA levels of TNF-α, IL-6, IL-8, RANKL, OPG, APP695, APP751, APP770, and BACE1 in the gingival tissues or cortex were detected by RT-PCR. The levels of Aβ1-40 and Aβ1-42 in gingival crevicular fluid (GCF) and plasma were tested by ELISA.

RESULTS

P. gingivalis oral infection was found to cause alveolar bone resorption and impaired learning and memory. P.gingivalis DNA was detected in the gingiva, blood and cortex of the P.gingivalis group by nested qPCR (p < .05). The mRNA expression of TNF-α, IL-6, IL-8, RANKL/OPG, and BACE1 in the gingival tissue was significantly higher than that in the control group (p < .05). Similarly, upregulated mRNA levels of APP695 and APP770 were observed in the gingival tissuses and cortex of the P. gingivalis group (p < .05). The levels of Aβ1-40 and Aβ1-42 in the GCF and plasma of the P. gingivalis group were significantly higher than those in the control group (p < .05).

CONCLUSION

P. gingivalis can directly invade the brain via hematogenous infection. The invasion of P. gingivalis could trigger an immune response and lead to an imbalance between Aβ production and clearance in peripheral tissues, which may trigger an abnormal Aβ metabolite in the brain, resulting in the occurrence and development of AD.

The Critical Role of Pyroptosis in Peri-Implantitis

Background

Peri-implantitis (PI) is a prevalent complication of implant treatment. Pyroptosis, a distinctive inflammatory programmed cell death, is crucial to the pathophysiology of PI. Despite its importance, the pyroptosis-related genes (PRGs) influencing PI's progression remain largely unexplored.

Methods

This study conducted histological staining and transcriptome analyze from three datasets. The intersection of differentially expressed genes (DEGs) and PRGs was identified as pyroptosis-related differentially expressed genes (PRDEGs). Functional enrichment analyses were conducted to shed light on potential underlying mechanisms. Weighted Gene Co-expression Network Analysis (WGCNA) and a pyroptotic macrophage model were utilized to identify and validate hub PRDEGs. Immune cell infiltration in PI and its relationship with hub PRDEGs were also examined. Furthermore, consensus clustering was performed to identify new PI subtypes. Protein-protein interaction (PPI) network, competing endogenous RNA (ceRNA) network, mRNA-mRNA binding protein regulatory (RBP) network, and mRNA-drugs regulatory network of hub PRDEGs were also analyzed.

Results

Eight hub PRDEGs were identified: PGF, DPEP1, IL36B, IFIH1, TCEA3, RIPK3, NET7, and TLR3, which are instrumental in the PI's progression. Two PI subtypes were distinguished, with Cluster 1 exhibiting higher immune cell activation. The exploration of regulatory networks provided novel mechanisms and therapeutic targets in PI.

Conclusion

Our research highlights the critical role of pyroptosis and identifies eight hub PRDEGs in PI's progression, offering insights into novel immunotherapy targets and laying the foundation for advanced diagnostic and treatment strategies. This contributes to our understanding of PI and underscores the potential for personalized clinical management.