title: Dynamics and regulation of lipid droplet formation in lipopolysaccharide (LPS)-stimulated microglia.
abstract: Lipid droplets (LDs) are neutral lipid-rich organelles involved in many cellular processes. A well-known example is their accumulation in leukocytes upon activation by pro-inflammatory stimuli such as lipopolysaccharides (LPS) derived from gram-negative bacteria. A role of LDs and LD-associated proteins during inflammation in the brain is unknown, however. We have now studied their dynamics and regulation in microglia, the resident immune cells in the brain. We find that LPS treatment of microglia leads to the accumulation in them of LDs, and enhancement of the size of LDs. This induction of LDs was abolished by triacsin C, an inhibitor of triglyceride biosynthesis. LPS strongly activated c-Jun N-terminal kinase (JNK) and p38 MAPK stress signaling pathways and increased the expression of LD-associated protein perilipin-2 (ADRP) in a time-dependent manner. Immunostaining showed that perilipin-2 in LPS-treated microglia predominantly colocalized with LDs. Inhibitors of p38 α/β (SB203580) and PI3K/Akt pathway (LY294002), but not that of JNK (SP600125), reduced LPS-induced LD accumulation and eliminated the activating effect of LPS on perilipin-2. In addition, cytosolic phospholipase A(2) (cPLA(2)-α), a key enzyme for arachidonic acid release, colocalized with LPS-induced LDs. These observations suggest that LDs may play an important role in eicosanoid synthesis in activated microglia; they provide a novel insight into the regulation of LDs in inflammatory cells of the brain and point to a potential role of p38 α/β in LPS-induced LD accumulation. Collectively, our findings imply that LD formation and perilipin-2 induction could be microglial biomarkers of inflammation in the central nervous system.
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, Canada H3G 1Y6.
authors.forename: Armen
authors.initials: A
authors.lastname: Khatchadourian
authors.forename: Simon D
authors.initials: SD
authors.lastname: Bourque
authors.forename: Vincent R
authors.initials: VR
authors.lastname: Richard
authors.forename: Vladimir I
authors.initials: VI
authors.lastname: Titorenko
authors.forename: Dusica
authors.initials: D
authors.lastname: Maysinger
mesh_terms: D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D015153:Blotting, Western; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D003594:Cytoplasmic Granules / Q000187:drug effects* / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D054513:Group IV Phospholipases A2 / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D007700:Kinetics; D008055:Lipids / Q000737:chemistry*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D017628:Microglia / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018613:Microscopy, Confocal; D008954:Models, Biological; D009025:Morpholines / Q000494:pharmacology; D019301:Oleic Acid / Q000494:pharmacology; D000070780:Perilipin-2; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011725:Pyridines / Q000494:pharmacology; D013997:Time Factors; D014280:Triglycerides / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000873:Anthracenes; D002867:Chromones; D004791:Enzyme Inhibitors; D054513:Group IV Phospholipases A2; D007093:Imidazoles; D048031:JNK Mitogen-Activated Protein Kinases; D008055:Lipids; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D009025:Morpholines; D019301:Oleic Acid; D000070780:Perilipin-2; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011725:Pyridines; D014280:Triglycerides; D048051:p38 Mitogen-Activated Protein Kinases; C000602983:Plin2 protein, mouse; C432165:pyrazolanthrone; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C093642:SB 203580