Periodontal Pathogens and Their Links to Neuroinflammation and Neurodegeneration

Abstract

Pathogens that play a role in the development and progression of periodontitis have gained significant attention due to their implications in the onset of various systemic diseases. Periodontitis is characterized as an inflammatory disease of the gingival tissue that is mainly caused by bacterial pathogens. Among them, Porphyromonas gingivalis, Treponema denticola, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, and Tannerella forsythia are regarded as the main periodontal pathogens. These pathogens elicit the release of cytokines, which in combination with their virulence factors induce chronic systemic inflammation and subsequently impact neural function while also altering the permeability of the blood–brain barrier. The primary objective of this review is to summarize the existing information regarding periodontal pathogens, their virulence factors, and their potential association with neuroinflammation and neurodegenerative diseases. We systematically reviewed longitudinal studies that investigated the association between periodontal disease and the onset of neurodegenerative disorders. Out of the 24 studies examined, 20 showed some degree of positive correlation between periodontal disease and neurodegenerative disorders, with studies focusing on cognitive function demonstrating the most robust effects. Therefore, periodontal pathogens might represent an exciting new approach to develop novel preventive treatments for neurodegenerative diseases.

Importance of Metalloproteinase 8 (MMP-8) in the Diagnosis of Periodontitis

“…Insufficient oral hygiene, understood as improper or irregular tooth brushing, failure to clean interdental spaces, and avoidance of follow-up dental visits, leads to plaque accumulation [ 44 , 45 ]. Dental plaque is a structurally and functionally organized biofilm containing microorganisms that is deposited on the tooth surface [ 46 ]. The presence of certain batteries in bacterial plaque is associated with an increased susceptibility, initiation, and progression of periodontitis.…”

“…This group includes bacteria such as Porphyromonas gingivalis , Treponema denticola , and Tannerella forsythia . Other bacteria, from beyond the red complex, that are important in the pathogenesis of periodontal disease include, among others, Fusobacterium nucleatum , Campylobacter rectus , and Peptostreptococcus micros [ 46 , 47 ].…”

Investigating the Connection between Chronic Periodontitis and Parkinson’s Disease: Findings from a Korean National Cohort Study

“…CP incidence rises with age, predominantly affecting males, often associated with lower education levels, income, and rural residence [4]. Influenced by factors such as dental plaque accumulation, specific periodontopathic microbes, and host immune response [5,6], CP can extend beyond oral infection [6], potentially impacting systemic health [7,8], including associations with cardiovascular disease [9,10], diabetes [11], kidney disorders [12], and neurodegenerative diseases [13].…”

“…PD patients commonly experience oral symptoms [15], contributing to oral health issues alongside compromised motor and cognitive control [16,17]. Studies consistently report poor oral health in PD patients, with a high prevalence of CP [17][18][19], suggesting a potential link between PD and CP due to chronic inflammation and dysbiosis [10,13,20]. Given the widespread occurrence of both CP and PD in Korea [3,21], concerns regarding their comorbidity, especially among elderly individuals with CP, have emerged.…”

“…CP affects 85.5% of individuals aged 60-69 [3], while PD affects approximately 0.4% of those aged 50 and older [21]. Clarifying the potential link between CP and PD holds significant clinical importance [13,22,23], particularly in the absence of preventive measures for PD and considering CP's global prevalence [2].…”