title: Efferocytosis impairs pulmonary macrophage and lung antibacterial function via PGE2/EP2 signaling.
abstract: The ingestion of apoptotic cells (ACs; termed "efferocytosis") by phagocytes has been shown to trigger the release of molecules such as transforming growth factor beta, interleukin-10 (IL-10), nitric oxide, and prostaglandin E(2) (PGE(2)). Although the antiinflammatory actions of these mediators may contribute to the restoration of homeostasis after tissue injury, their potential impact on antibacterial defense is unknown. The lung is highly susceptible to diverse forms of injury, and secondary bacterial infections after injury are of enormous clinical importance. We show that ACs suppress in vitro phagocytosis and bacterial killing by alveolar macrophages and that this is mediated by a cyclooxygenase-PGE(2)-E prostanoid receptor 2 (EP2)-adenylyl cyclase-cyclic AMP pathway. Moreover, intrapulmonary administration of ACs demonstrated that PGE(2) generated during efferocytosis and acting via EP2 accounts for subsequent impairment of lung recruitment of polymorphonuclear leukocytes and clearance of Streptococcus pneumoniae, as well as enhanced generation of IL-10 in vivo. These results suggest that in addition to their beneficial homeostatic influence, antiinflammatory programs activated by efferocytosis in the lung have the undesirable potential to dampen innate antimicrobial responses. They also identify an opportunity to reduce the incidence and severity of pneumonia in the setting of lung injury by pharmacologically targeting synthesis of PGE(2) or ligation of EP2.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Health Systems, Ann Arbor, MI 48109, USA.
authors.forename: Alexandra I
authors.initials: AI
authors.lastname: Medeiros
authors.forename: Carlos H
authors.initials: CH
authors.lastname: Serezani
authors.forename: Sang Pyo
authors.initials: SP
authors.lastname: Lee
authors.forename: Marc
authors.initials: M
authors.lastname: Peters-Golden
mesh_terms: D000067956:Adenylyl Cyclase Inhibitors; D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D017077:Culture Media, Conditioned / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D016753:Interleukin-10 / Q000378:metabolism; D019169:Jurkat Cells; D008168:Lung / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D016676:Macrophages, Alveolar / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D010587:Phagocytosis / Q000187:drug effects / Q000276:immunology*; D011018:Pneumonia, Pneumococcal / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D011448:Prostaglandin Antagonists / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018078:Receptors, Prostaglandin E / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D058307:Receptors, Prostaglandin E, EP2 Subtype; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D013296:Streptococcus pneumoniae / Q000187:drug effects; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D017077:Culture Media, Conditioned; D016861:Cyclooxygenase Inhibitors; C545644:PTGER2 protein, human; D011448:Prostaglandin Antagonists; C545645:Ptger2 protein, mouse; D018078:Receptors, Prostaglandin E; D058307:Receptors, Prostaglandin E, EP2 Subtype; D016753:Interleukin-10; D000242:Cyclic AMP; D015232:Dinoprostone