title: NADPH oxidase-derived reactive oxygen species-mediated activation of ERK1/2 is required for apoptosis of human neutrophils induced by Entamoeba histolytica.
abstract: The extracellular tissue penetrating protozoan parasite Entamoeba histolytica has been known to induce host cell apoptosis. However, the intracellular signaling mechanism used by the parasite to trigger apoptosis is poorly understood. In this study, we investigated the roles of reactive oxygen species (ROS), and of MAPKs in the Entamoeba-induced apoptosis of human neutrophils. The neutrophils incubated with live trophozoites of E. histolytica revealed a marked increase of receptor shedding of CD16 as well as phosphatidylserine (PS) externalization on the cell surface. The Entamoeba-induced apoptosis was effectively blocked by pretreatment of cells with diphenyleneiodonium chloride (DPI), a flavoprotein inhibitor of NADPH oxidase. A large amount of intracellular ROS was detected after exposure to viable trophozoites, and the treatment with DPI strongly inhibited the Entamoeba-induced ROS generation. However, a mitochondrial inhibitor rotenone did not attenuate the Entamoeba-induced ROS generation and apoptosis. Although E. histolytica strongly induced activation of ERK1/2 and p38 MAPK in neutrophils, the activation of ERK1/2 was closely associated with ROS-mediated apoptosis. Pretreatment of neutrophils with MEK1 inhibitor PD98059, but not p38 MAPK inhibitor SB202190, prevented Entamoeba-induced apoptosis. Moreover, DPI almost completely inhibited Entamoeba-induced phosphorylation of ERK1/2, but not phosphorylation of p38 MAPK. These results strongly suggest that NADPH oxidase-derived ROS-mediated activation of ERK1/2 is required for the Entamoeba-induced neutrophil apoptosis.
authors.affiliation: Department of Parasitology, Institute of Tropical Medicine, and Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Seobo
authors.initials: S
authors.lastname: Sim
authors.forename: Tai-Soon
authors.initials: TS
authors.lastname: Yong
authors.forename: Soon-Jung
authors.initials: SJ
authors.lastname: Park
authors.forename: Kyung-Il
authors.initials: KI
authors.lastname: Im
authors.forename: Yoon
authors.initials: Y
authors.lastname: Kong
authors.forename: Jae-Sook
authors.initials: JS
authors.lastname: Ryu
authors.forename: Duk-Young
authors.initials: DY
authors.lastname: Min
authors.forename: Myeong Heon
authors.initials: MH
authors.lastname: Shin
mesh_terms: D000818:Animals; D017209:Apoptosis; D004748:Entamoeba histolytica / Q000472:pathogenicity*; D004749:Entamoebiasis; D004789:Enzyme Activation; D006801:Humans; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D019255:NADPH Oxidases / Q000378:metabolism*; D009504:Neutrophils / Q000469:parasitology* / Q000473:pathology; D010766:Phosphorylation; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D017382:Reactive Oxygen Species; D019255:NADPH Oxidases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3