Gen Kano1, Maha Almanan, Bruce S Bochner, Nives Zimmermann. 1. Division of Allergy and Immunology, Cincinnati Children's Hospital, and the Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA.
Abstract
BACKGROUND: Sialic acid-binding immunoglobulin-like lectin (Siglec)-8 is expressed on human eosinophils, where its ligation induces cell death. Paradoxically, Siglec-8-mediated cell death is markedly enhanced by the presence of the activation and survival factor IL-5 and becomes independent of caspase activity. OBJECTIVE: In this report we investigate the mechanism of Siglec-8-mediated cell death in activated eosinophils. METHODS: Human peripheral blood eosinophils were treated with agonistic anti-Siglec-8 antibody and IL-5, and cell death was determined by using flow cytometry and morphology. Phosphorylation of mitogen-activated protein kinase (MAPK) was determined by using phosphoLuminex, flow cytometry, and Western blotting. Reactive oxygen species (ROS) accumulation was determined by using dihydrorhodamine fluorescence. RESULTS: Costimulation with anti-Siglec-8 and IL-5 significantly increased the rate and proportion of cell death by means of necrosis accompanied by granule release compared with that seen after stimulation with anti-Siglec-8 alone, in which apoptosis predominated. Together with the caspase-independent mode of cell death in costimulated cells, these findings suggest the activation of a specific and distinct biochemical pathway of cell death during anti-Siglec-8/IL-5 costimulation. Phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and MAPK-ERK kinase (MEK) 1 was significantly enhanced and sustained in costimulated cells compared with that seen in cells stimulated with IL-5 alone; anti-Siglec-8 alone did not cause ERK1/2 phosphorylation. MEK1 inhibitors blocked anti-Siglec-8/IL-5-induced cell death. ROS accumulation was induced by Siglec-8 ligation in a MEK-independent manner. In contrast, an ROS inhibitor prevented the anti-Siglec-8/IL-5-induced enhancement of ERK phosphorylation and cell death. Exogenous ROS mimicked stimulation by anti-Siglec-8 and was sufficient to induce enhanced cell death in IL-5-treated cells. Collectively, these data suggest that the enhancement of ERK phosphorylation is downstream of ROS generation. CONCLUSIONS: In activated eosinophils ligation of Siglec-8 leads to ROS-dependent enhancement of IL-5-induced ERK phosphorylation, which results in a novel mode of biochemically regulated eosinophil cell death.
BACKGROUND:Sialic acid-binding immunoglobulin-like lectin (Siglec)-8 is expressed on human eosinophils, where its ligation induces cell death. Paradoxically, Siglec-8-mediated cell death is markedly enhanced by the presence of the activation and survival factor IL-5 and becomes independent of caspase activity. OBJECTIVE: In this report we investigate the mechanism of Siglec-8-mediated cell death in activated eosinophils. METHODS:Human peripheral blood eosinophils were treated with agonistic anti-Siglec-8 antibody and IL-5, and cell death was determined by using flow cytometry and morphology. Phosphorylation of mitogen-activated protein kinase (MAPK) was determined by using phosphoLuminex, flow cytometry, and Western blotting. Reactive oxygen species (ROS) accumulation was determined by using dihydrorhodamine fluorescence. RESULTS: Costimulation with anti-Siglec-8 and IL-5 significantly increased the rate and proportion of cell death by means of necrosis accompanied by granule release compared with that seen after stimulation with anti-Siglec-8 alone, in which apoptosis predominated. Together with the caspase-independent mode of cell death in costimulated cells, these findings suggest the activation of a specific and distinct biochemical pathway of cell death during anti-Siglec-8/IL-5 costimulation. Phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and MAPK-ERK kinase (MEK) 1 was significantly enhanced and sustained in costimulated cells compared with that seen in cells stimulated with IL-5 alone; anti-Siglec-8 alone did not cause ERK1/2 phosphorylation. MEK1 inhibitors blocked anti-Siglec-8/IL-5-induced cell death. ROS accumulation was induced by Siglec-8 ligation in a MEK-independent manner. In contrast, an ROS inhibitor prevented the anti-Siglec-8/IL-5-induced enhancement of ERK phosphorylation and cell death. Exogenous ROS mimicked stimulation by anti-Siglec-8 and was sufficient to induce enhanced cell death in IL-5-treated cells. Collectively, these data suggest that the enhancement of ERK phosphorylation is downstream of ROS generation. CONCLUSIONS: In activated eosinophils ligation of Siglec-8 leads to ROS-dependent enhancement of IL-5-induced ERK phosphorylation, which results in a novel mode of biochemically regulated eosinophil cell death.
Authors: Josiane S Neves; Sandra A C Perez; Lisa A Spencer; Rossana C N Melo; Lauren Reynolds; Ionita Ghiran; Salahaddin Mahmudi-Azer; Solomon O Odemuyiwa; Ann M Dvorak; Redwan Moqbel; Peter F Weller Journal: Proc Natl Acad Sci U S A Date: 2008-11-18 Impact factor: 11.205
Authors: Cheryl Protheroe; Samantha A Woodruff; Giovanni de Petris; Vince Mukkada; Sergei I Ochkur; Sailajah Janarthanan; John C Lewis; Shabana Pasha; Tisha Lunsford; Lucinda Harris; Virender K Sharma; Michael P McGarry; Nancy A Lee; Glenn T Furuta; James J Lee Journal: Clin Gastroenterol Hepatol Date: 2009-04-01 Impact factor: 11.382
Authors: Young Sik Cho; Sreerupa Challa; David Moquin; Ryan Genga; Tathagat Dutta Ray; Melissa Guildford; Francis Ka-Ming Chan Journal: Cell Date: 2009-06-12 Impact factor: 41.582
Authors: Johannes M Pröpster; Fan Yang; Said Rabbani; Beat Ernst; Frédéric H-T Allain; Mario Schubert Journal: Proc Natl Acad Sci U S A Date: 2016-06-29 Impact factor: 11.205