MyD88-dependent inflammasome activation and autophagy inhibition contributes to Ehrlichia-induced liver injury and toxic shock
| Autor: | Melanie J. Scott, Mounia Alaoui-El-Azher, Donna B. Stolz, Alan Wells, George K. Michalopoulos, Nahed Ismail, Jakob Z. Wells, Muhamuda Kader, Jennie Vorhauer, Bhushan B Kode |
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| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
0301 basic medicine
Lipopolysaccharide Inflammasomes Rickettsiales Fluorescent Antibody Technique Pathology and Laboratory Medicine Biochemistry chemistry.chemical_compound White Blood Cells Mice Animal Cells Mitophagy Medicine and Health Sciences Image Processing Computer-Assisted lcsh:QH301-705.5 Energy-Producing Organelles Liver injury Mice Knockout Immune System Proteins Microscopy Confocal biology Cell Death Ehrlichia T Cells Inflammasome Flow Cytometry Shock Septic 3. Good health Cell biology Bacterial Pathogens Mitochondria Intracellular Pathogens Medical Microbiology Cell Processes Female medicine.symptom Pathogens Cellular Types Cellular Structures and Organelles medicine.drug Research Article lcsh:Immunologic diseases. Allergy Autophagic Cell Death Immune Cells Immunology Immunoblotting Blotting Western Molecular Probe Techniques Inflammation Enzyme-Linked Immunosorbent Assay Bioenergetics Research and Analysis Methods Real-Time Polymerase Chain Reaction Microbiology 03 medical and health sciences AIM2 Microscopy Electron Transmission Virology Genetics medicine Autophagy In Situ Nick-End Labeling Animals Molecular Biology Techniques Microbial Pathogens Molecular Biology Blood Cells Bacteria Macrophages Organisms Ehrlichiosis Biology and Life Sciences Proteins Cell Biology Liver Failure Acute medicine.disease biology.organism_classification Mice Inbred C57BL Disease Models Animal 030104 developmental biology chemistry lcsh:Biology (General) Myeloid Differentiation Factor 88 Parasitology lcsh:RC581-607 |
| Zdroj: | PLoS Pathogens PLoS Pathogens, Vol 13, Iss 10, p e1006644 (2017) |
| ISSN: | 1553-7374 1553-7366 |
| Popis: | Severe hepatic inflammation is a common cause of acute liver injury following systemic infection with Ehrlichia, obligate Gram-negative intracellular bacteria that lack lipopolysaccharide (LPS). We have previously shown that type I IFN (IFN-I) and inflammasome activation are key host-pathogenic mediators that promote excessive inflammation and liver damage following fatal Ehrlichia infection. However, the underlying signals and mechanisms that regulate protective immunity and immunopathology during Ehrlichia infection are not well understood. To address this issue, we compared susceptibility to lethal Ixodes ovatus Ehrlichia (IOE) infection between wild type (WT) and MyD88-deficient (MyD88-/-) mice. We show here that MyD88-/- mice exhibited decreased inflammasome activation, attenuated liver injury, and were more resistant to lethal infection than WT mice, despite suppressed protective immunity and increased bacterial burden in the liver. MyD88-dependent inflammasome activation was also dependent on activation of the metabolic checkpoint kinase mammalian target of rapamycin complex 1 (mTORC1), inhibition of autophagic flux, and defective mitophagy in macrophages. Blocking mTORC1 signaling in infected WT mice and primary macrophages enhanced bacterial replication and attenuated inflammasome activation, suggesting autophagy promotes bacterial replication while inhibiting inflammasome activation. Finally, our data suggest TLR9 and IFN-I are upstream signaling mechanisms triggering MyD88-mediated mTORC1 and inflammasome activation in macrophages following Ehrlichia infection. This study reveals that Ehrlichia-induced liver injury and toxic shock are mediated by MyD88-dependent inflammasome activation and autophagy inhibition. Author summary Human monocytic ehrlichiosis (HME) is the most prevalent emerging infectious disease in the United States. Ehrlichia chaffeensis, etiologic agent of HME, is a Gram negative obligate intracellular bacterium transmitted by infected tick bites and can infect different cell type. Although Ehrlichia lack lipopolysaccharide (LPS), they induce potentially life threatening HME that mimic sepsis or toxic shock associated with multi-organ failure. The clinical diagnosis of HME is difficult, and definitive diagnosis is most often retrospective. Late antibiotic treatment is frequently ineffective in preventing disease progression to fatal multi-organ failure. Liver failure is one of the most serious complications and the most frequent cause of death in patients with HME, however we only have a limited understanding of how this liver failure is caused during fatal Ehrlichia infection. The objective of this study is to determine how LPS-negative Ehrlichia activates inflammatory responses in macrophages during Ehrlichia infection to promote liver damage. We show here that MyD88-signaling causes detrimental derangement of the immune system and subsequent liver damage by regulating two key innate immune events in macrophages: autophagy and inflammasome activation. Targeting host-pathogenic pathways in ehrlichiosis can be incorporated into future design of novel therapeutic approaches for HME. |
| Databáze: | OpenAIRE |
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