Filifactor alocis manipulates human neutrophils affecting their ability to release neutrophil extracellular traps induced by PMA

Abstract

Neutrophils operate at the site of injury or inflammation in the periodontal pocket to ensure periodontal health and clearance of bacterial pathogens. Filifactor alocis is recently identified as a potential periodontal pathogen, and in this study, we assessed the formation of neutrophil extracellular traps (NETs), in response to the presence of the organism . NET formation by human neutrophils was not induced when challenged with F. alocis, independent of opsonization, viability, time, or bacterial dose. F. alocis also failed to induce NETs from TNF-α-primed neutrophils and did not induce the release of extracellular neutrophil elastase. However, significant NET induction was observed when neutrophils were challenged with Streptococcus gordonii or Peptoanaerobacter stomatis, In addition, co-infection studies revealed that the presence of F. alocis with S. gordonii or P. stomatis does not enhance or reduce NETs. Additionally, F. alocis failed to impact pre-formed NETs induced by either S. gordonii or P. stomatis. Pretreatment with F. alocis prior to stimulation with phorbol 12-myristate 13-acetate (PMA), S. gordonii, or P. stomatis revealed that the bacterium is capable of reducing only PMA but not S. gordonii or P. stomatis NET formation. These results indicate that F. alocis manipulates neutrophils, inhibiting the triggering of NET induction.

A specific low-density neutrophil population correlates with hypercoagulation and disease severity in hospitalized COVID-19 patients

“…NET assay. NET formation was tested using confocal microscopy as previously described (79). Sorted CD16 Int (0.5 × 10 6 cells/well) were resuspended in NET media (colorless RPMI + 0.5% BSA +10 mM HEPES) and seeded onto sterile acid-washed coverslip coated with (1 mg/mL) poly-l-lysine.…”

Periodontal Pathogens’ strategies disarm neutrophils to promote dysregulated inflammation

“…Resisted (Maekawa et al, 2014;Makkawi et al, 2017;Stobernack et al, 2018) Minimally induced (Hirschfeld et al, 2017) MMP9 (Ding et al, 1997) No effect (Hirschfeld et al, 2017) Not killed (Odell & Wu, 1992) Ingested (Jayaprakash et al, 2015;Lenzo, O'Brien-Simpson, Cecil, Holden, & Reynolds, 2016) Induced (Bryzek et al, 2019) Killed (Jayaprakash et al, 2015) F. alocis Ingested (Edmisson et al, 2018) Minimally induced (Edmisson et al, 2018) Secretory vesicles, Gelatinase & Specific granules (Armstrong et al, 2018;Edmisson et al, 2018) No effect & inhibits PMA-induced (Armstrong et al, 2018) Not killed (Edmisson et al, 2018) P. stomatis Resisted (Jimenez Flores et al, 2017) Robust induction (Jimenez Flores et al, 2017) Robust, all 4 granule subtypes (Jimenez Flores et al, 2017) Induced (Armst...…”

“…Adding to the pro‐inflammatory phenotype is the fact that when F. alocis and P. stomatis are recognized by TLR2/6 heterodimers, they promote the release of neutrophil‐derived cytokines and chemokines, although P. stomatis induces a substantially larger amount of cytokines and chemokines compared to both F. alocis and P. gingivalis (Vashishta et al., 2019). Another notable difference between these two Gram‐positive periodontal pathogens is that P. stomatis elicits significant NET release, while F. alocis does not induce NET formation at any bacterial dose or time tested, and pre‐treatment of neutrophils with F. alocis significantly inhibits PMA‐induced NETs (Armstrong et al., 2018). Although it is unknown what effect P. stomatis has on neutrophil apoptosis, there is some data that indicate that F. alocis prolongs neutrophil lifespan (Miralda et al., 2020).…”

Interactions Between Neutrophils and Periodontal Pathogens in Late-Onset Periodontitis

“…F. alocis is also capable of reducing NETs. However, it only reduces NETs formation induced by phorbol 12-myristate 13-acetate (PMA), but not pre-formed NETs (Armstrong et al, 2018). This finding suggests that extracellular DNase expression is not the mechanism of F. alocis to reduce NETs; however, the exact mechanism has not been explained.…”