Extracellular neutrophil traps in periodontitis

Abstract

Trapping the crevicular bacteria prevents their adhesion to and invasion of the gingiva. The combination of neutrophil extracellular traps and crevicular exudate outflow appears to be a 'novel' defense mechanism for the clearance of crevicular bacteria in chronic periodontitis.

Characterization of Filifactor alocis and its immune evasion strategies employed against human neutrophils.

“…In vivo observation of neutrophils revealed their presence in the dental plaque and that NET formation is detected in the oral biofilm, the saliva, and also the crevicular exudate (155,197,(380)(381)(382). Due to the large quantity of bacteria present dispersed throughout the gingival crevice, phagocytosis is an ineffective means for bacterial control, therefore NETs could serve as a more effective strategy for neutrophils to respond to infection (197).…”

“…On the other hand, ineffective NET production could be a contributing factor in periodontal disease development (149). NETs have previously been observed to be present in both purulent exudates from the gingiva as well as in gingival crevicular fluid from patients suffering from chronic periodontitis (149,197). Using immunofluorescent imaging, NETs have been visualized in gingival connective tissues at inflammatory sites of infection, however, in healthy patients, less NET formation is detected (149).…”

“…This process can occur in viable or dying neutrophils and is effective in trapping bacteria due to its electrostatic charge interactions and in killing due to its ability to produce a localized high concentration of antimicrobial peptides in the presence of a wide variety of stimuli (154,157,168,363,364). Depending on the stimuli used to activate neutrophils, activation of the NADPH oxidase and production of intracellular ROS may or may not be required for NET formation (157,197,(364)(365)(366).…”

“…NETs have been discovered in the gingival epithelium and can be attributed to a first response to periodontal bacteria presence by the host (197,367). In the context of periodontal disease, both excessive and ineffective NET production have been associated with development of the disease (149).…”

“…In the context of periodontal disease, both excessive and ineffective NET production have been associated with development of the disease (149). Many oral bacteria can produce DNase, which serves to degrade DNA, and may provide a means to escape trapping and killing by NETs (151,197,(368)(369)(370)(371)(372). However, crevicular exudate outflow may inhibit optimal functioning of the bacterial DNases, and work in concert with NETs to clear pathogens from the oral cavity and prevent development of periodontitis (197).…”