title: Mechanism of Siglec-8-induced human eosinophil apoptosis: role of caspases and mitochondrial injury.
abstract: Sialic acid binding immunoglobulin like lectin (Siglec)-8 crosslinking with specific antibodies causes human eosinophil apoptosis. Mechanisms by which Siglec-8 crosslinking induces apoptosis are not known. Peripheral blood eosinophils were examined for caspase, mitochondria and reactive oxygen species (ROS) involvement after incubating the cells with anti-Siglec-8 crosslinking Abs or control Abs, in the presence or absence of selective inhibitors. Siglec-8 crosslinking induced rapid cleavage of caspase-3, caspase-8, and caspase-9 in eosinophils. Selective caspase-8 and/or caspase-9 inhibitors inhibited this apoptosis. Siglec-8 crosslinking on eosinophils increased dissipation of mitochondrial membrane potential upstream of caspase activation. Rotenone and antimycin, inhibitors of mitochondrial respiratory chain components, completely inhibited apoptosis. Additional experiments with an inhibitor of ROS, diphenyleneiodonium, demonstrated that ROS was also essential for Siglec-8-mediated apoptosis and preceded Siglec-8-mediated mitochondrial dissipation. These experiments show that Siglec-8-induced apoptosis occurs through the sequential production of ROS, followed by induction of mitochondrial injury and caspase cleavage.
authors.affiliation: Department of Medicine, Division of Allergy and Clinical Immunology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Esra
authors.initials: E
authors.lastname: Nutku
authors.forename: Sherry A
authors.initials: SA
authors.lastname: Hudson
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Bochner
mesh_terms: D015703:Antigens, CD / Q000378:metabolism*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000378:metabolism*; D017209:Apoptosis; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000502:physiology*; D004579:Electron Transport; D004804:Eosinophils / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D037102:Lectins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008564:Membrane Potentials; D008928:Mitochondria / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D061945:Caspase Inhibitors; D037102:Lectins; D017382:Reactive Oxygen Species; C403967:SIGLEC8 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases