title: Attenuated free cholesterol loading-induced apoptosis but preserved phospholipid composition of peritoneal macrophages from mice that do not express group VIA phospholipase A2.
abstract: Mouse macrophages undergo ER stress and apoptosis upon free cholesterol loading (FCL). We recently generated iPLA(2)beta-null mice, and here we demonstrate that iPLA(2)beta-null macrophages have reduced sensitivity to FCL-induced apoptosis, although they and wild-type (WT) cells exhibit similar increases in the transcriptional regulator CHOP. iPLA(2)beta-null macrophages are also less sensitive to apoptosis induced by the sarcoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin and the scavenger receptor A ligand fucoidan, and restoring iPLA(2)betaexpression with recombinant adenovirus increases apoptosis toward WT levels. WT and iPLA(2)beta-null macrophages incorporate [(3)H]arachidonic acid ([(3)H]AA]) into glycerophosphocholine lipids equally rapidly and exhibit identical zymosan-induced, cPLA(2)alpha-catalyzed [(3)H]AA release. In contrast, although WT macrophages exhibit robust [(3)H]AA release upon FCL, this is attenuated in iPLA(2)beta-null macrophages and increases toward WT levels upon restoring iPLA(2)beta expression. Recent reports indicate that iPLA(2)beta modulates mitochondrial cytochrome c release, and we find that thapsigargin and fucoidan induce mitochondrial phospholipid loss and cytochrome c release into WT macrophage cytosol and that these events are blunted in iPLA(2)beta-null cells. Immunoblotting studies indicate that iPLA(2)beta associates with mitochondria in macrophages subjected to ER stress. AA incorporation into glycerophosphocholine lipids is unimpaired in iPLA(2)beta-null macrophages upon electrospray ionization-tandem mass spectrometry analyses, and their complex lipid composition is similar to WT cells. These findings suggest that iPLA(2)beta participates in ER stress-induced macrophage apoptosis caused by FCL or thapsigargin but that deletion of iPLA(2)beta does not impair macrophage arachidonate incorporation or phospholipid composition.
authors.affiliation: Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
authors.forename: Shunzhong
authors.initials: S
authors.lastname: Bao
authors.affiliation: Departments of Medicine and of Anatomy and Cell Biology, Columbia University, New York, New York 10032.
authors.forename: Yankun
authors.initials: Y
authors.lastname: Li
authors.affiliation: Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
authors.forename: Xiaoyong
authors.initials: X
authors.lastname: Lei
authors.affiliation: Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
authors.forename: Mary
authors.initials: M
authors.lastname: Wohltmann
authors.affiliation: Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
authors.forename: Wu
authors.initials: W
authors.lastname: Jin
authors.affiliation: Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
authors.forename: Alan
authors.initials: A
authors.lastname: Bohrer
authors.affiliation: Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
authors.forename: Clay F
authors.initials: CF
authors.lastname: Semenkovich
authors.affiliation: Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
authors.forename: Sasanka
authors.initials: S
authors.lastname: Ramanadham
authors.affiliation: Departments of Medicine and of Anatomy and Cell Biology, Columbia University, New York, New York 10032.
authors.forename: Ira
authors.initials: I
authors.lastname: Tabas
authors.affiliation: Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the. Electronic address: jturk@wustl.edu.
authors.forename: John
authors.initials: J
authors.lastname: Turk
mesh_terms: D000818:Animals; D017209:Apoptosis; D016718:Arachidonic Acid / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005260:Female; D054522:Group VI Phospholipases A2; D017737:Macrophages, Peritoneal / Q000737:chemistry / Q000166:cytology*; D013058:Mass Spectrometry; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000737:chemistry; D010741:Phospholipases A / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D054467:Phospholipases A2; D010743:Phospholipids / Q000032:analysis*; D011134:Polysaccharides / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D013107:Sphingolipids / Q000032:analysis; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D010743:Phospholipids; D011134:Polysaccharides; D012333:RNA, Messenger; D013107:Sphingolipids; D016718:Arachidonic Acid; D019284:Thapsigargin; D045304:Cytochromes c; C007789:fucoidan; D002784:Cholesterol; D010741:Phospholipases A; D054522:Group VI Phospholipases A2; D054467:Phospholipases A2; C516476:Pla2g6 protein, mouse