Attenuated free cholesterol loading-induced apoptosis but preserved phospholipid composition of peritoneal macrophages from mice that do not express group VIA phospholipase A2.
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.
Bao
Shunzhong
S
Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
Li
Yankun
Y
Departments of Medicine and of Anatomy and Cell Biology, Columbia University, New York, New York 10032.
Lei
Xiaoyong
X
Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
Wohltmann
Mary
M
Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
Jin
Wu
W
Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
Bohrer
Alan
A
Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
Semenkovich
Clay F
CF
Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
Ramanadham
Sasanka
S
Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the.
Tabas
Ira
I
Departments of Medicine and of Anatomy and Cell Biology, Columbia University, New York, New York 10032.
Turk
John
J
Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, Missouri 63110 and the. Electronic address: jturk@wustl.edu.
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
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