The frequent severe COVID-19 course in patients with periodontitis suggests a link of the
aetiopathogenesis of both diseases. The formation of intravascular neutrophil extracellular
traps (NETs) is crucial to the pathogenesis of severe COVID-19. Periodontitis is
characterised by an increased level of circulating NETs, a propensity for increased NET
formation, delayed NET clearance and low-grade endotoxemia (LGE). The latter has an
enormous impact on innate immunity and susceptibility to infection with SARS-CoV-2.
LPS binds the SARS-CoV-2 spike protein and this complex, which is more active than
unbound LPS, precipitates massive NET formation. Thus, circulating NET formation is the
common denominator in both COVID-19 and periodontitis and other diseases with low grade endotoxemia like diabetes, obesity and cardiovascular diseases (CVD) also
increase the risk to develop severe COVID-19. Here we discuss the role of propensity
for increased NET formation, DNase I deficiency and low-grade endotoxaemia in
periodontitis as aggravating factors for the severe course of COVID-19 and possible
strategies for the diminution of increased levels of circulating periodontitis-derived NETs in
COVID-19 with periodontitis comorbidity
