Periodontitis as a Risk Factor for Alzheimer's Disease: The Experimental Journey So Far, with Hope of Therapy

Alantolactone improves cognitive impairment in rats with Porphyromonas gingivalis infection by inhibiting neuroinflammation, oxidative stress, and reducing Aβ levels

Neuroinflammation caused by the chronic periodontal pathogen Porphyromonas gingivalis is growing regarded as as a key factor in the pathogenesis of Alzheimer's disease (AD). Alantolactone (AL), a sesquiterpene lactone isolated from the root of Inula racemosa Hook. f, has been proven to provide various neuroprotective effects. However, whether AL can improve cognitive impairment caused by P. gingivalis infection remains unclear. In this research, a rat model of P. gingivalis infection was used to examine the neuroprotective benefits of AL. The results revealed that 6 weeks of AL treatment (50 and 100 mg/kg) shortened escape latency and increased the number of crossings over the platform location and time spent in the target quadrant of P. gingivalis-infected rats in the Morris water maze experiment. By activating the Nrf2/HO-1 pathway, AL suppressed malondialdehyde (MDA) levels and simultaneously increased the activity of total superoxide dismutase (T-SOD). Furthermore, AL lowered the presence of IL-6, IL-1β, and TNFα in the hippocampal and cortical tissues of P. gingivalis-infected rats by inhibiting astrocyte and microglial activation and NF-κB phosphorylation. AL also significantly reduced Aβ levels in the cortical and hippocampus tissues of rats infected with P. gingivalis. In conclusion, AL improved cognitive impairment in P. gingivalis-infected rats by inhibiting neuroinflammation, reducing Aβ1-42 level, and exerting antioxidative stress effects.

Screening for Systemic Diseases Associated with Dental Self-Care in Japanese Adolescents

Background: Toothbrushing is important for maintaining oral health and preventing periodontal disease. However, the association between toothbrushing and systemic diseases remains unclear in adolescence. In this study, the association between dental self-care (frequency and duration of toothbrushing) and systemic diseases/disorders in adolescents was examined. Methods: We conducted a retrospective review of mandatory medical questionnaires administered during legally mandated freshman medical checkups between 2017 and 2019 at the University of Tokyo, Japan. Out of 9376 total responses, 9098 cases involving individuals under the age of 20 were included in the analysis. Respondents were classified into three groups based on their daily toothbrushing frequency: "1 time or less", "twice", and "3 times or more". For the duration of each toothbrushing session, they were classified into three groups: "1 min or less", "2-3 min", and "4 min or more". A statistical analysis was performed by Pearson's χ2 test and multinomial logistic regression analysis. Results: Regarding frequency of daily toothbrushing: The χ2 test showed no significant relationship between frequency of toothbrushing and 17 systemic diseases/disorders. A multivariate analysis found that gingival bleeding and sex were independent factors. The risk of gingival bleeding decreased dramatically with increased frequency of toothbrushing (odds ratio (OR): 0.428; 95% confidence interval (CI), 0.366-0.501; p < 0.001). Regarding the amount of time spent on toothbrushing: The χ2 test showed atopic dermatitis and arrhythmia were significantly associated with the duration of toothbrushing (p = 0.032 and p = 0.016, respectively). In the multivariate analysis, atopic dermatitis, gingival bleeding, and sex were independent factors regarding the duration of toothbrushing; longer brushing time was associated with a lower risk of atopic dermatitis (OR: 0.731, 95% CI: 0.578-0.924, p = 0.009) and a lower risk of gingival bleeding (OR: 0.643, 95% CI: 0.567-0.729, p < 0.001). Conclusions: Dental self-care was most strongly associated with gingival bleeding, while the risk of atopic dermatitis was found to increase with shorter toothbrushing times. The results suggest that dental self-care during adolescence is important not only for oral health but also for general health.

Periodontitis: A Plausible Modifiable Risk Factor for Neurodegenerative Diseases? A Comprehensive Review

The aim of this comprehensive review is to summarize recent literature on associations between periodontitis and neurodegenerative diseases, explore the bidirectionality and provide insights into the plausible pathogenesis. For this purpose, systematic reviews and meta-analyses from PubMed, Medline and EMBASE were considered. Out of 33 retrieved papers, 6 articles complying with the inclusion criteria were selected and discussed. Additional relevant papers for bidirectionality and pathogenesis were included. Results show an association between periodontitis and Alzheimer's disease, with odds ratios of 3 to 5. A bidirectional relationship is suspected. For Parkinson's disease (PD), current evidence for an association appears to be weak, although poor oral health and PD seem to be correlated. A huge knowledge gap was identified. The plausible mechanistic link for the association between periodontitis and neurodegenerative diseases is the interplay between periodontal inflammation and neuroinflammation. Three pathways are hypothesized in the literature, i.e., humoral, neuronal and cellular, with a clear role of periodontal pathogens, such as Porphyromonas gingivalis. Age, gender, race, smoking, alcohol intake, nutrition, physical activity, socioeconomic status, stress, medical comorbidities and genetics were identified as common risk factors for periodontitis and neurodegenerative diseases. Future research with main emphasis on the collaboration between neurologists and dentists is encouraged.

Implications of gut and oral microbiota in neuroinflammatory responses in Alzheimer's disease

A diverse and stable microbiota promotes a healthy state, nevertheless, an imbalance in gut or oral bacterial composition, called dysbiosis, can cause gastrointestinal disorders, systemic inflammatory states and oxidative stress, among others. Recently, gut and oral dysbiosis has been linked to Alzheimer's disease (AD), which is considered the most common form of dementia and a public health priority due to its high prevalence and incidence. The aim of this review is to highlight the implications of gut and oral microbiota in the neuroinflammation characteristic of AD pathology and the subsequent cognitive impairment. It is a systematic review of the current literature obtained by searching the PubMed, Web of Science and Scopus databases. The characteristic intestinal dysbiosis in AD patients leads to increased permeability of the intestinal barrier and activates immune cells in the central nervous system due to translocation of microbiota-derived metabolites and/or bacteria into the circulation leading to increased neuroinflammation and neuronal loss, thus generating the cognitive impairment characteristic of AD. The presence in the central nervous system of Porphyromonas gingivalis can cause an increased neuroinflammation and beta-amyloid peptide accumulation.

The Antimicrobial Properties of Cannabis and Cannabis-Derived Compounds and Relevance to CB2-Targeted Neurodegenerative Therapeutics

Cannabinoid receptor 2 (CB2) is of interest as a much-needed target for the treatment or prevention of several neurogenerative diseases. However, CB2 agonists, particularly phytocannabinoids, have been ascribed antimicrobial properties and are associated with the induction of microbiome compositional fluxes. When developing novel CB2 therapeutics, CB2 engagement and antimicrobial functions should both be considered. This review summarizes those cannabinoids and cannabis-informed molecules and preparations (CIMPs) that show promise as microbicidal agents, with a particular focus on the most recent developments. CIMP-microbe interactions and anti-microbial mechanisms are discussed, while the major knowledge gaps and barriers to translation are presented. Further research into CIMPs may proffer novel direct or adjunctive strategies to augment the currently available antimicrobial armory. The clinical promise of CIMPs as antimicrobials, however, remains unrealized. Nevertheless, the microbicidal effects ascribed to several CB2 receptor-agonists should be considered when designing therapeutic approaches for neurocognitive and other disorders, particularly in cases where such regimens are to be long-term. To this end, the potential development of CB2 agonists lacking antimicrobial properties is also discussed.

Oral Health in Japan: State-of-the-Art and Perspectives

In the near future, Japan is entering a super-aging society that will be called the age of 100 years of life [...].