Background Periodontitis is one of the most common oral diseases and is a potential risk factor for systemic diseases. In this study, we aimed to investigate the association between periodontitis and learning and memory impairment. Methods We established a periodontitis model by topical application of Porphyromonas gingivalis lipopolysaccharide ( P. gingivalis -LPS) into the palatal gingival sulcus of the maxillary first molars of 10-week-old male rats for a 10-week period. We assessed alveolar bone resorption using micro–computed tomography analysis and learning and memory ability using the Morris water maze test. We determined the levels of cytokines [interleukin (IL)-1β, IL-6, IL-8, and IL-21] and LPS in the peripheral blood and cortex, as well as toll-like receptor 4 (TLR4)/NF-κB signaling pathway activation, using reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and western blot. We determined activation of microglia and astrocytes, expression of Aβ1-42, APP and Tau by immunohistochemistry. Finally, we measured the expression of amyloid precursor protein (APP) and its key secretases, as well as the Aβ1-40/1-42 ratio, by RT-PCR, western blot, and ELISA. Results We found that periodontitis induced learning and memory impairment in the rats. Further, we observed that it induced significant alveolar bone resorption. There was an increase in the levels of inflammatory cytokines and LPS. Moreover, we confirmed TLR4/NF-κB signaling pathway activation. We also observed activated microglia and astrocytes with enlarged cell bodies and irregular protrusions. Finally, we observed the promotion of β- and γ-secretases APP processing. Conclusion Our findings indicated that periodontitis was associated with learning and memory impairment, probably induced by neuroinflammation via activating the TLR4/NF-κB signaling pathway. Furthermore, abnormal APP processing could be involved in this progress.

Periodontitis is one of the most common oral diseases worldwide, and it is associated with various systemic diseases, including cognitive diseases. STAT3 regulates the inflammatory cascade and influences adaptive immunity by modulating Th17/Treg cell differentiation. In this study, we aimed to explore the effect of adaptive immunity inside and outside the brain on the association between periodontitis and cognitive impairment and understand the role of the STAT3 signaling pathway. We established Porphyromonas gingivalis LPS‐induced periodontitis mice models by injecting P. gingivalis LPS into the gingival sulcus of mice. Behavioral tests showed that learning and memory abilities were impaired. The flow cytometry data showed an imbalance in the Th17/Treg ratio in the blood and brain samples of the mice. The expression of Th17‐related cytokines (IL‐1β, IL‐17A, IL‐21, and IL‐22) increased, whereas that of Treg‐related cytokines (IL‐2 and IL‐10) decreased in both the blood and the brain. The level of LPS increased and the STAT3 signaling pathway was activated during this process. These effects were reversed by C188‐9, a STAT3 inhibitor. In conclusion, P. gingivalis LPS‐induced periodontitis may promote the occurrence and progression of cognitive impairment by modulating the Th17/Treg balance inside and outside the brain. The STAT3 signaling pathway may have immunoregulatory effects on the mouth‐to‐brain axis.

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Background Increasing evidence suggests a causal link between periodontitis and cognitive disorders. Systemic inflammation initiated by periodontitis may mediate the development of cognitive impairment. Our study aims to investigate the effect of ligature-induced periodontitis on cognitive function and the role of signal transducers and activators of transcription 3 (STAT3) in this process. Materials and methods Ligature-induced periodontitis was established, and the rats were treated intraperitoneally with/without the pSTAT3 inhibitor cryptotanshinone (CTS). Alveolar bone resorption and periodontal inflammation were detected by micro-computed tomography analysis and histopathological evaluation. Locomotor activity and cognitive function were evaluated by the open field test and the Morris water maze test, respectively. The activation of microglia and astrocytes in the hippocampus and cortex was assessed by immunohistochemistry (IHC). The expression of interleukins (IL-1β, IL-6, IL-8, IL-21) in both the periphery and cortex was evaluated by RT-PCR and ELISA. The expression of TLR/NF-κB and ROS cascades was evaluated by RT-PCR. The expression of pSTAT3 and the activation of the STAT3 signaling pathway (JAK2, STAT3, and pSTAT3) in the periodontal tissue and cortex were assessed by IHC and Western blot. The expression of amyloid precursor protein (APP) and its key secretases was evaluated by RT-PCR. The level of amyloid β-protein (Aβ) and the ratio of Aβ1-40/1-42 were measured via ELISA in the plasma and cortex while IHC was used to detect the level of Aβ1-42 in the brain. Results In periodontal ligature rats, significant alveolar bone resorption and local inflammatory cell infiltration were present. Apparent increases in inflammatory cytokines (IL-1β, IL-6, IL-8, and IL-21) were detected in peripherial blood and brain. Additionally, spatial learning and memory ability was impaired, while locomotor activity was not affected. Activated microglia and astrocytes were found in the cortex and hippocampus, presenting as enlarged cell bodies and irregular protrusions. Levels of TLR/NF-kB, PPAR and ROS were altered. The STAT3 signaling pathway was activated in both the periodontal tissue and cortex, and the processing of APP by β- and γ-secretases was promoted. The changes mentioned above could be relieved by the pSTAT3 inhibitor CTS. Conclusions Ligature-induced periodontitis in rats resulted in systemic inflammation and further abnormal APP processing, leading to cognitive impairments. In this progress, the activation of the STAT3 signaling pathway may play an important role by increasing inflammatory load and promoting neuroinflammation.

Alzheimer’s disease (AD) is a degenerative disease of the central nervous system with unclear etiology and pathogenesis. In recent years, as the infectious theory and endotoxin hypothesis of AD has gained substantial attention, several studies have proposed that Porphyromonas gingivalis (P. gingivalis), one of the main pathogenic bacteria of chronic periodontitis, and the lipopolysaccharide (LPS) of P. gingivalis may lead to AD-like pathological changes and cognition impairment. However, research on the relationship between P. gingivalis-LPS and neuroinflammation is still lacking. Our study aimed to investigate the effects of P. gingivalis-LPS preparation on immuno-inflammation in microglial cells and further compared the differential inflammatory response induced by P. gingivalis-LPS and Escherichia coli (E. coli) LPS preparations. The results showed that P. gingivalis-LPS could upregulate the gene expression and release of pro-inflammatory factors in BV-2 microglial cells, including IL-1β, IL-6, TNF-α, IL-17, and IL-23. We also observed an increase in the level of Toll-like receptor 2/4 (TLR2/4) and NF-κB/STAT3 signaling. Moreover, the changes mentioned above were more significant in the E. coli-LPS group and the effects of both kinds of LPS could be differentially reversed by the administration of the TLR2 inhibitor C29 and TLR4 inhibitor TAK-242. The molecular simulation showed that the binding affinity of P. gingivalis-lipid A to TLR4-MD-2 was weaker than E. coli-lipid A, which was probably due to the presence of fewer acyl chains and phosphate groups of P. gingivalis-lipid A than E. coli-lipid A. We conclude that P. gingivalis-LPS could activate TLR2/4-mediated NF-κB/STAT3 signaling pathways, which ultimately resulted in an immune-inflammatory response in BV-2 microglia. In contrast to E. coli-LPS, P. gingivalis-LPS is a weaker TLR2/4 agonist and NF-κB/STAT3 signaling activator. Furthermore, the different fatty acid chains and phosphate groups between P. gingivalis-lipid A and E. coli-lipid A may be the reason for the weaker activating properties of P. gingivalis-LPS.

Although epidemiological studies suggest that periodontitis is tightly associated with ischemic stroke, its impact on ischemic stroke and the underlysing mechanisms are poorly understood. Recent studies have shown that alteration in gut microbiota composition influences the outcomes of ischemic stroke. In the state of periodontitis, many oral pathogenic bacteria in the saliva are swallowed and transmitted to the gut. However, the role of periodontitis microbiota in the pathogenesis and progression of ischemic stroke is unclear. Therefore, we hypothesized that the periodontitis salivary microbiota influences the gut immune system and aggravates ischemic stroke. Mice receiving gavage of periodontitis salivary microbiota showed significantly worse stroke outcomes. And these mice also manifested more severe neuroinflammation, with higher infiltration of inflammatory cells and expression of inflammatory cytokines in the ischemic brain. More accumulation of Th17 cells and IL-17+ γδ T cells were observed in the ileum. And in Kaede transgenic mice after photoconversion. Migration of CD4+ T cells and γδ T cells from the ileum to the brain was observed after ischemic stroke in photoconverted Kaede transgenic mice. Furthermore, the worse stroke outcome was abolished in the IL-17A knockout mice. These findings suggest that periodontitis salivary microbiota increased IL-17A-producing immune cells in the gut, likely promoted the migration of these cells from the gut to the brain, and subsequently provoked neuroinflammation after ischemic stroke. These findings have revealed the role of periodontitis in ischemic stroke through the gut and provided new insights into the worse outcome of ischemic stroke coexisting with periodontitis in clinical trials.

Background: Increasing evidence suggests a causal link between periodontitis and cognitive disorders. Systemic inflammation initiated by periodontitis may mediate the development of cognitive impairment. Our study aims to investigate the effect of ligature-induced periodontitis on cognitive function and the role of Signal transducers and activators of transcription 3 (STAT3) in this process.Materials and Methods: Ligature-induced periodontitis was established, and the rats were treated intraperitoneally with/without the pSTAT3 inhibitor cryptotanshinone (CTS). Alveolar bone resorption and periodontal inflammation were detected by micro-computed tomography (micro-CT) analysis and histopathological evaluation. Locomotor activity and cognitive function were evaluated by the Open field test (OFT) and the Morris water maze test (MWM), respectively. The activation of microglia and astrocytes in hippocampus and cortex was assessed by immunohistochemistry (IHC). The expression of interleukins (IL-1β, IL-6, IL-8, IL-21) in both periphery and cortex was evaluated by RT-PCR and ELISA. The expression of pSTAT3 and the activation of the STAT3 signaling pathway (JAK2, STAT3, and pSTAT3) in both oral cavity and cortex was assessed by IHC and Western blotting. The expression of amyloid precursor protein (APP) and its key secretase enzymes were evaluated by RT-PCR. The level of amyloid β-protein (Aβ) and the ratio of Aβ1-40/1-42 were measured via ELISA in plasma and cortex while IHC was used to detect the level of Aβ1-42 in brain.Results: In periodontal ligature rats, significant alveolar bone resorption and local inflammatory cell infiltration were present. Apparent increases in inflammatory cytokines (IL-1β, IL-6, IL-8 and IL-21) were detected. in both periphery and brain. Additionally, spatial learning and memory ability was impaired, while locomotor activity was not affected. Activated microglia and astrocytes were found in the cortex and hippocampus, presenting as enlarged cell bodies and irregular protrusions. The STAT3 signaling pathway was activated in both oral cavity and cortex and the processing of APP by β- and γ-secretases was promoted. Change mentioned above could be relieved by the pSTAT3 inhibitor CTS. Conclusions: Ligature-induced periodontitis in rats resulted in systemic inflammation and further abnormal APP processing, leading to cognitive impairments. In this progress, the activation of the STAT3 signaling pathway may play an important role by increasing inflammatory load and promoting neuroinflammation.

Background Mucosal neuroma (MN) is a benign neural tumor of peripheral nerves histologically characterized by irregular tortuous bundles of nerve cells with prominent perineurium that lie scattered throughout the submucosa. The tumor is usually associated with the multiple endocrine neoplasia type 2B (MEN 2B) but rarely occurs without the other components of MEN 2B. We present a case of solitary MN without MEN 2B that occurs in the maxillary incisor gingival papilla that has not been reported yet and review the literature. Case presentation: A 29-year-old woman presented to our outpatient department with an upper anterior teeth gingiva painless mass for 2-year. Intraoral examination revealed a small, tough, basal wide, well-defined mass in the labial gingival papilla between maxillary central incisor. Excisional biopsy showed that it was characterized by nerve bundles in various sizes surrounded by normal connective tissue in the submucosa under HE staining; Immunohistochemically, the mass showed strongly positive staining of S-100 protein, NSE,NF and weakly positive of EMA. The Laboratory examination and ultrasonography showed no signs of MEN 2B. In the first 6 months of follow-up, there was no evidence of recurrence and other components of MEN 2B. The patient was asymptomatic and she is still being followed up every 6 months. Based on these features, the lesion was finally diagnosed as a solitary gingival MN. Conclusions This study showed a rare solitary MN in the gingiva papilla without MEN 2B that has not been reported yet. The histopathological evaluation can be helpful in the differential diagnosis of MN. It is hoped that a greater understanding of solitary MN without MEN 2B in the oral cavity will avoid potential misdiagnosis, and contribute to determining the correct management, which appears to be complete surgical excision with close follow-up for recurrence and other components of MEN 2B surveillance.