Peripheral blood neutrophil extracellular trap production and degradation in chronic periodontitis

Aims: To investigate ex vivo peripheral neutrophil extracellular trap (NET) production and their subsequent degradation by plasma in chronic periodontitis patients, and periodontally and systemically healthy-matched controls.

Materials and methods: Chronic periodontitis patient and control (n=40 pairs) peripheral blood neutrophils were stimulated for NET quantification. A subset of patients received nonsurgical periodontal therapy (n=19) and NETs were quantified 3-months later alongside controls. Blood plasma was collected from patients and controls to quantify plasma-induced NET degradation (n=19 pairs). Subsequent experiments quantified plasma concentrations of DNase-1, immunoglobulin G (IgG), free light chains (FLCs) and cystatin C.

Results: No differences were observed in NET production between patients and controls. However, NET production decreased significantly in patient’s post-treatment. Plasma NET degradation was significantly lower in patients than controls, which may be due to significantly reduced DNase-1 levels as demonstrated, or potentially due to elevated IgG/FLC concentrations in patients. NET degradation post-periodontal treatment was comparable between patients and controls.

Conclusions: NET production was comparable between patients and controls; however, nonsurgical therapy causes attenuated NETs. NET degradation by plasma is impaired in untreated chronic periodontitis, potentially increasing the chronic NET burden, which may enhance antimicrobial function, or conversely, increase the risk of autoimmune/inflammatory responses.