Peripheral blood neutrophil cytokine hyper-reactivity in chronic periodontitis

Pro-inflammatory cytokine release (IL-8, IL-6, TNF-α, IL-1β) by peripheral blood neutrophils, isolated from periodontitis patients (before/after therapy) and matched controls, was determined after 18 h culture in the presence/absence of Escherichia coli LPS, opsonised Staphylococcus aureus, heat-killed Fusobacterium nucleatum and Porphyromonas gingivalis. All cultures demonstrated differences in the amounts of each cytokine detected (P < 0.0001), with a clear release pattern (IL-8 > IL-6 > TNF-α = IL-1β). Median cytokine release from unstimulated patient neutrophils was consistently, but non-significantly, higher than from control cells. Stimulated cytokine release from untreated patient neutrophils was also consistently higher than from control cells. This hyper-reactivity was significant for all tested cytokines when data for all stimuli were combined (P < 0.016). In terms of individual stimuli, significant hyper-reactivity was detected with LPS (IL-8), F. nucleatum (IL-8, TNF-α), opsonised S. aureus (IL-8, TNF-α, IL-1β) and P. gingivalis (IL-8, IL-1β). Cytokine production by patient neutrophils did not reduce following successful non-surgical periodontal therapy and, except for responses to F. nucleatum, the cytokine hyper-reactivity detected pre-therapy was retained. These data demonstrate that chronic periodontitis is characterised by neutrophils that constitutively exhibit cytokine hyper-reactivity, the effects of which could modulate local and systemic inflammatory-immune responses and influence the risk and severity of periodontitis-associated systemic inflammatory diseases.