title: Multinucleated giant cell formation exhibits features of phagocytosis with participation of the endoplasmic reticulum.
abstract: Macrophage fusion leading to formation of multinucleated giant cells during chronic inflammation is poorly understood in mechanism and physiological significance. To address this, we developed a system of human macrophage fusion that utilizes IL-4, IL-13, or alpha-tocopherol to generate large foreign body-type giant cells (FBGC). Extending our previously demonstrated requirements for F-actin and mannose receptor (MR) activity, we find that macrophage fusion exhibits further features of a phagocytic process. Pharmacological inhibition of IL-4-induced FBGC formation indicates critical roles for vacuolar-type ATPase, microtubules, the endoplasmic reticulum (ER), and calcium-independent phospholipase A(2) (iPLA(2)), but not calcium-dependent PLA(2) (cPLA(2)), secretory PLA(2) (sPLA(2)), cyclooxygenase, or lipoxygenase. Immunocytochemistry confirms iPLA(2) expression and absence of cPLA(2) or sPLA(2) expression in macrophages/FBGC. As markers of ER-mediated phagocytosis, calnexin and calregulin are detectable on non-permeabilized fusing macrophages and also concentrated at fusion interfaces where they co-localize with actin in permeabilized macrophages/FBGC. Furthermore, ER markers co-localize with concanavalin A reactivity on non-permeabilized fusing macrophages, suggesting that the ER may present MR ligand during fusion events. These data demonstrate for the first time that the mechanism of macrophage fusion leading to formation of multinucleated giant cells exhibits multiple features of phagocytosis with potential participation of the ER.
authors.affiliation: Institute of Pathology, Case Western Reserve University, 2085 Adelbert Road, Cleveland, OH 44106, USA.
authors.forename: Amy K
authors.initials: AK
authors.lastname: McNally
authors.forename: James M
authors.initials: JM
authors.lastname: Anderson
mesh_terms: D000251:Adenosine Triphosphatases / Q000187:drug effects / Q000378:metabolism; D002459:Cell Fusion / Q000379:methods*; D002478:Cells, Cultured; D003208:Concanavalin A / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015726:Giant Cells / Q000502:physiology* / Q000648:ultrastructure; D054522:Group VI Phospholipases A2; D006801:Humans; D007150:Immunohistochemistry; D018793:Interleukin-13 / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism; D037181:Lectins, C-Type / Q000378:metabolism; D008084:Lipoxygenase / Q000187:drug effects / Q000378:metabolism; D008264:Macrophages / Q000502:physiology / Q000648:ultrastructure; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000378:metabolism; D018613:Microscopy, Confocal; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology*; D010741:Phospholipases A / Q000378:metabolism; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D018793:Interleukin-13; D037181:Lectins, C-Type; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D011956:Receptors, Cell Surface; D003208:Concanavalin A; D015847:Interleukin-4; D008084:Lipoxygenase; D011451:Prostaglandin-Endoperoxide Synthases; D010741:Phospholipases A; D054522:Group VI Phospholipases A2; C516475:PLA2G6 protein, human; D000251:Adenosine Triphosphatases