Delayed neutrophil apoptosis in chronic periodontitis patients

Abstract

Background, aims: Neutrophil cells constitute the first defense barrier against the oral bacterial challenge in the periodontium. Reduction of neutrophils could impair this response against periopathogenic bacteria such as Porphyromonas gingivalis. Our previous work implicates the apoptosis of neutrophils in the pathogenesis of periodontitis. We now demonstrate that granulocyte monocyte-colony stimulating factor (GM-CSF) present in the gingival crevicular fluid (GCF) and secreted during the immune response reduces the apoptosis of neutrophils. Method: In this study, the presence of GM-CSF and tumor necrosis factor-alpha (TNF-α) in GCF was determined in samples obtained from adult patients with periodontitis and from control subjects with clinically healthy gingiva. GCF was collected for 30 s using Periopaper® strips, and cytokines were quantified by ELISA. We used ex vivo culture of gingival tissue biopsies for 2 and 4 days in the presence of GM-CSF. Apoptosis was determined using the terminal TdT-mediated dUTP-biotin nick end labeling (TUNEL) technique, and expression of Bax by immunohistochemistry. Results: The presence of GM-CSF and TNF-α was detected in the majority of sites from periodontal patients (83.3% and 63.3%, respectively), presenting a total amount of 27.65 and 42.38pg, respectively. GM-CSF reduces the neutrophil apoptosis determined by double staining with TUNEL and myeloperoxidase and by a reduction of Bax expression. Conclusions: These findings suggest a novel mechanism by which neutrophils specifically accumulate in adult patients with periodontitis.