Method: PBNs from chronic periodontitis patients and age/gender matched controls (n=20 pairs) were assayed for extracellular superoxide production using Lucigenin chemiluminescence, with and without exogenous stimulation (including Porphyromonas gingivalis, Fusobacterium nucleatum, opsonised Staphyloccus aureus, Escherichia coli lipopolysaccharide [LPS] and phorbol myristate acetate [PMA]). NET production by patients and control neutrophils were also fluorometrically quantified (Palmer et al2012) with and without stimulation (PMA and hypochlorous acid [HOCl]). Periodontitis patients received non-surgical treatment and their PBN responses were re-assessed 3-months later (n=20 pairs).
Result: Pre-treatment patient PBNs demonstrated higher superoxide release in all assays with and without exogenous stimulation than their healthy age and gender matched counterparts, consistent with our previous reports. However, subsequent NET quantification revealed no significant difference in the production of NETs between periodontitis patients and controls at baseline (p=0.32) and in response to stimulation (PMA p=0.27, HOCl p=0.42).
Conclusion: These findings confirm that periodontitis patient peripheral blood neutrophils exhibit hyperactivity and hyper-reactivity, in terms of superoxide production, but this does not translate to elevated NET release from circulating PBNs. This may be due to recently reported self-protective mechanisms within glutathione deficient periodontitis neutrophils, involving re-siting of the NADPH-oxidase to membrane lipid rafts to direct ROS extracellularly (Dias et al 2013).