title: Remodeling of lipid bodies by docosahexaenoic acid in activated microglial cells.
abstract: Organelle remodeling processes are evolutionarily conserved and involved in cell functions during development, aging, and cell death. Some endogenous and exogenous molecules can modulate these processes. Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid, has mainly been considered as a modulator of plasma membrane fluidity in brain development and aging, while DHA's role in organelle remodeling in specific neural cell types at the ultrastructural level remains largely unexplored. DHA is notably incorporated into dynamic organelles named lipid bodies (LBs). We hypothesized that DHA could attenuate the inflammatory response in lipopolysaccharide (LPS)-activated microglia by remodeling LBs and altering their functional interplay with mitochondria and other associated organelles.
  
  
  
  We used electron microscopy to analyze at high spatial resolution organelle changes in N9 microglial cells exposed to the proinflammogen LPS, with or without DHA supplementation. Our results revealed that DHA reverses several effects of LPS in organelles. In particular, a large number of very small and grouped LBs was exclusively found in microglial cells exposed to DHA. In contrast, LBs in LPS-stimulated cells in the absence of DHA were sparse and large. LBs formed in the presence of DHA were generally electron-dense, suggesting DHA incorporation into these organelles. The accumulation of LBs in microglial cells from mouse and human was confirmed in situ. In addition, DHA induced numerous contacts between LBs and mitochondria and reversed the frequent disruption of mitochondrial integrity observed upon LPS stimulation. Dilation of the endoplasmic reticulum lumen was also infrequent following DHA treatment, suggesting that DHA reduces oxidative stress and protein misfolding. Lipidomic analysis in N9 microglial cells treated with DHA revealed an increase in phosphatidylserine, indicating the role of this phospholipid in normalization and maintenance of physiological membrane functions. This finding was supported by a marked reduction of microglial filopodia and endosome number and significant reduction of LPS-induced phagocytosis.
  
  
  
  DHA attenuates the inflammatory response in LPS-stimulated microglial cells by remodeling LBs and altering their interplay with mitochondria and other associated organelles. Our findings point towards a mechanism by which omega-3 DHA participates in organelle reorganization and contributes to the maintenance of neural cell homeostasis.
authors.affiliation: Department of Molecular Medicine, Faculty of Medicine, Université Laval, Axe Neurosciences, Centre de recherche du CHU de Québec, Québec, QC, Canada. tremblay.marie-eve@crchudequebec.ulaval.ca.
authors.forename: Marie-Eve
authors.initials: ME
authors.lastname: Tremblay
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montréal, QC, Canada.
authors.forename: Issan
authors.initials: I
authors.lastname: Zhang
authors.affiliation: Department of Molecular Medicine, Faculty of Medicine, Université Laval, Axe Neurosciences, Centre de recherche du CHU de Québec, Québec, QC, Canada.
authors.forename: Kanchan
authors.initials: K
authors.lastname: Bisht
authors.affiliation: Department of Molecular Medicine, Faculty of Medicine, Université Laval, Axe Neurosciences, Centre de recherche du CHU de Québec, Québec, QC, Canada.
authors.forename: Julie C
authors.initials: JC
authors.lastname: Savage
authors.affiliation: Department of Molecular Medicine, Faculty of Medicine, Université Laval, Axe Neurosciences, Centre de recherche du CHU de Québec, Québec, QC, Canada.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Lecours
authors.affiliation: Department of Psychiatry and Neuroscience, Faculty of Medicine, Centre de recherche de l'Institut universitaire en santé mentale de Québec, Université Laval, Québec, QC, Canada.
authors.forename: Martin
authors.initials: M
authors.lastname: Parent
authors.affiliation: Department of Biology, Concordia University, Montréal, QC, Canada.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Titorenko
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montréal, QC, Canada. dusica.maysinger@mcgill.ca.
authors.forename: Dusica
authors.initials: D
authors.lastname: Maysinger
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D016207:Cytokines / Q000378:metabolism / Q000648:ultrastructure; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005227:Fatty Acids / Q000378:metabolism; D066292:Lipid Droplets / Q000187:drug effects* / Q000648:ultrastructure; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D017628:Microglia / Q000187:drug effects* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D015388:Organelles / Q000187:drug effects / Q000648:ultrastructure; D010587:Phagocytosis / Q000187:drug effects; D013997:Time Factors; D014280:Triglycerides / Q000378:metabolism
chemical_list: D016207:Cytokines; D005227:Fatty Acids; D008070:Lipopolysaccharides; D014280:Triglycerides; D004281:Docosahexaenoic Acids
keywords: Docosahexaenoic acid; Endoplasmic reticulum; Inflammation; Lipid bodies; Lipopolysaccharide; Microglia; Mitochondria; N9 microglial cells; Phagocytosis