Modulation of Phagocytosis, Chemotaxis, and Adhesion of Neutrophils by Areca Nut Extracts

Background: A higher prevalence of periodontal diseases among areca chewers than non‐areca chewers has been demonstrated. Neutrophils, representing the first line of the host defense mechanism against microbial infection, play important roles in maintaining periodontal health. This study determined the possible effects of areca nut on phagocytosis, chemotaxis, and adhesion of human neutrophils. Methods: Aqueous extracts of ripe areca nut without husk (rANE) and fresh and tender areca nut with husk (tANE) were examined for their effects on neutrophil phagocytosis using flow cytometry and confocal laser scanning microscopy. The effects of rANE and tANE on chemotaxis and adhesion of neutrophils to human aortic endothelial cells were examined using fluorescence‐labeled neutrophils. Results: Both rANE and tANE inhibited the phagocytic activity of neutrophils in a dose‐dependent manner. The levels of internalized fluorescent bacteria in neutrophils decreased after ANE treatment. However, exposure of neutrophils to rANE and tANE stimulated the chemotaxis activity of neutrophils to N‐formyl‐Met‐Leu‐Phe (fMLP) and enhanced adhesion of neutrophils to human aortic endothelial cells in a dose‐dependent manner. Moreover, treatment of neutrophils with rANE was more effective than incubation with tANE. Conclusions: Components of areca nut inhibited phagocytosis activity of neutrophils but enhanced chemotaxis and adhesion of neutrophils. Alterations in functions of neutrophils may lead to signs of clinical diseases associated with areca chewing. The components in ANEs that are responsible for these observations remain to be elucidated.