title: Pore-Forming Toxins Induce Macrophage Necroptosis during Acute Bacterial Pneumonia.
abstract: Necroptosis is a highly pro-inflammatory mode of cell death regulated by RIP (or RIPK)1 and RIP3 kinases and mediated by the effector MLKL. We report that diverse bacterial pathogens that produce a pore-forming toxin (PFT) induce necroptosis of macrophages and this can be blocked for protection against Serratia marcescens hemorrhagic pneumonia. Following challenge with S. marcescens, Staphylococcus aureus, Streptococcus pneumoniae, Listeria monocytogenes, uropathogenic Escherichia coli (UPEC), and purified recombinant pneumolysin, macrophages pretreated with inhibitors of RIP1, RIP3, and MLKL were protected against death. Alveolar macrophages in MLKL KO mice were also protected during S. marcescens pneumonia. Inhibition of caspases had no impact on macrophage death and caspase-1 and -3/7 were determined to be inactive following challenge despite the detection of IL-1β in supernatants. Bone marrow-derived macrophages from RIP3 KO, but not caspase-1/11 KO or caspase-3 KO mice, were resistant to PFT-induced death. We explored the mechanisms for PFT-induced necroptosis and determined that loss of ion homeostasis at the plasma membrane, mitochondrial damage, ATP depletion, and the generation of reactive oxygen species were together responsible. Treatment of mice with necrostatin-5, an inhibitor of RIP1; GW806742X, an inhibitor of MLKL; and necrostatin-5 along with co-enzyme Q10 (N5/C10), which enhances ATP production; reduced the severity of S. marcescens pneumonia in a mouse intratracheal challenge model. N5/C10 protected alveolar macrophages, reduced bacterial burden, and lessened hemorrhage in the lungs. We conclude that necroptosis is the major cell death pathway evoked by PFTs in macrophages and the necroptosis pathway can be targeted for disease intervention.
authors.affiliation: Department of Microbiology, The University of Alabama at Birmingham, Birmingham, Alabama, United States of America.|Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.
authors.forename: Norberto
authors.initials: N
authors.lastname: González-Juarbe
authors.affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.
authors.forename: Ryan Paul
authors.initials: RP
authors.lastname: Gilley
authors.affiliation: Department of Microbiology, The University of Alabama at Birmingham, Birmingham, Alabama, United States of America.|Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.
authors.forename: Cecilia Anahí
authors.initials: CA
authors.lastname: Hinojosa
authors.affiliation: Department of Microbiology, The University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
authors.forename: Kelley Margaret
authors.initials: KM
authors.lastname: Bradley
authors.affiliation: Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee, United States of America.
authors.forename: Akinobu
authors.initials: A
authors.lastname: Kamei
authors.affiliation: Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee, United States of America.
authors.forename: Geli
authors.initials: G
authors.lastname: Gao
authors.affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.
authors.forename: Peter Herman
authors.initials: PH
authors.lastname: Dube
authors.affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.
authors.forename: Molly Ann
authors.initials: MA
authors.lastname: Bergman
authors.affiliation: Department of Microbiology, The University of Alabama at Birmingham, Birmingham, Alabama, United States of America.|Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.
authors.forename: Carlos Javier
authors.initials: CJ
authors.lastname: Orihuela
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001427:Bacterial Toxins / Q000633:toxicity*; D015153:Blotting, Western; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D016676:Macrophages, Alveolar / Q000382:microbiology*; D051379:Mice; D018345:Mice, Knockout; D009336:Necrosis; D018410:Pneumonia, Bacterial / Q000378:metabolism* / Q000473:pathology*; D052899:Pore Forming Cytotoxic Proteins / Q000633:toxicity*; D011494:Protein Kinases / Q000378:metabolism; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species
chemical_list: D001427:Bacterial Toxins; D052899:Pore Forming Cytotoxic Proteins; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C570694:MLKL protein, mouse; D011494:Protein Kinases