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.

Inhibitory effects of areca nut extracts on phagocytosis of Actinobacillus actinomycetemcomitans ATCC 33384 by neutrophils.

BACKGROUND: Areca quid chewers have a higher prevalence of periodontal disease than non-chewers. Little is known about the influence of areca quid on the immune system. This study was to determine the possible effects of the areca nut on phagocytic activity of human neutrophils. METHODS: Aqueous extracts of ripe areca nut without husk (rANE), fresh and tender areca nut with husk (tANE), a major alkaloid (arecoline), and a phenolic component ([+]-catechin) of areca nut were examined for their effects on cellular viability using trypan blue exclusion assay. The possible effects on the phagocytic activity of neutrophils against a periodontal pathogen, Actinobacillus actinomycetemcomitans ATCC 33384, were determined using flow cytometry and confocal laser scanning microscopy. RESULTS: At the concentrations tested, rANE, tANE, arecoline, and (+)-catechin did not significantly affect viability of neutrophils. However, rANE, tANE, arecoline, and (+)-catechin inhibited the phagocytic activity of neutrophils in a dose-dependent manner. Approximately 50% of the relative phagocytic activity of neutrophils was affected when 50 microg/ml of rANE, 400 microg/ml of tANE, 20,000 microg/ml of arecoline, or 2,500 microg/ml of (+)- catechin was used. Decreased levels of internalized fluorescent bacteria were also demonstrated. However, arecoline or (+)-catechin alone could not be used to explain the inhibitory effects observed for rANE and tANE. CONCLUSIONS: Components of areca nut reduced the uptake of A. actinomycetemcomitans ATCC 33384 by human neutrophils. The inhibition of areca nut on phagocytosis of neutrophils may be one possible mechanism by which the areca nut compromises the periodontal health of areca quid chewers.