Areca nut extracts reduce the intracellular reactive oxygen species and release of myeloperoxidase by human polymorphonuclear leukocytes

Abstract

Polymorphonuclear leukocytes (PMN) represent the first line of host defense. Areca nut extract inhibits the bactericidal activity of, and the release of superoxide anion (O2- ) by, PMN. This study investigated the effects of areca nut extract on the intracellular production of reactive oxygen species (ROS) and on the extracellular release of lysosomal enzyme, myeloperoxidase (MPO), by PMN. The effects of arecoline, a principal component of areca nut, were also examined. Human PMN were treated with various concentrations of areca nut extract or arecoline followed by treatment with Hanks' balanced salt solution, with or without cytochalasin B and fMet-Leu-Phe (CB/fMLP). The viability of PMN was determined using propidium iodide staining and flow cytometry. The presence of intracellular ROS was determined using 2',7'-dichlorofluorescin diacetate and fluorometry. MPO release was determined using a substrate assay. Areca nut extract (25 and 50 microg/ml) significantly decreased the viability of PMN. The intracellular levels of ROS and the extracellular release of MPO were induced in PMN by CB/fMLP. Exposure of PMN to areca nut extract (up to 25 microg/ml) or to arecoline (up to 2 mg/ml) did not directly affect the levels of ROS and MPO activity. However, under conditions that did not affect the viability of PMN, the ability of CB/fMLP to trigger production of intracellular ROS and release of MPO in human PMN was significantly suppressed by areca nut extract and arecoline. Areca nut impaired the activation of PMN by CB/fMLP that might decrease the effectiveness of PMN in the host defense. Alternatively, exposure of PMN to areca nut extract could decrease the capacity of PMN to damage tissues.