TY - JOUR
T1 - Attenuated free cholesterol loading-induced apoptosis but preserved phospholipid composition of peritoneal macrophages from mice that do not express group VIA phospholipase A2
AU - Bao, Shunzhong
AU - Li, Yankun
AU - Lei, Xiaoyong
AU - Wohltmann, Mary
AU - Jin, Wu
AU - Bohrer, Alan
AU - Semenkovich, Clay F.
AU - Ramanadham, Sasanka
AU - Tabas, Ira
AU - Turk, John
PY - 2007/9/14
Y1 - 2007/9/14
N2 - Mouse macrophages undergo ER stress and apoptosis upon free cholesterol loading (FCL). We recently generated iPLA2β-null mice, and here we demonstrate that iPLA2β-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 2β-null macrophages are also less sensitive to apoptosis induced by the sarcoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin and the scavenger receptor A ligand fucoidan, and restoring iPLA2β expression with recombinant adenovirus increases apoptosis toward WT levels. WT and iPLA2β-null macrophages incorporate [3H] arachidonic acid ([3H]AA]) into glycerophosphocholine lipids equally rapidly and exhibit identical zymosan-induced, cPLA2β-catalyzed [3H]AA release. In contrast, although WT macrophages exhibit robust [3H]AA release upon FCL, this is attenuated in iPLA 2β-null macrophages and increases toward WT levels upon restoring iPLA2β expression. Recent reports indicate that iPLA2β 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 iPLA2β-null cells. Immunoblotting studies indicate that iPLA2β associates with mitochondria in macrophages subjected to ER stress. AA incorporation into glycerophosphocholine lipids is unimpaired in iPLA2β-null macrophages upon electrospray ionization-tandem mass spectrometry analyses, and their complex lipid composition is similar to WT cells. These findings suggest that iPLA 2β participates in ER stress-induced macrophage apoptosis caused by FCL or thapsigargin but that deletion of iPLA2β does not impair macrophage arachidonate incorporation or phospholipid composition.
AB - Mouse macrophages undergo ER stress and apoptosis upon free cholesterol loading (FCL). We recently generated iPLA2β-null mice, and here we demonstrate that iPLA2β-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 2β-null macrophages are also less sensitive to apoptosis induced by the sarcoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin and the scavenger receptor A ligand fucoidan, and restoring iPLA2β expression with recombinant adenovirus increases apoptosis toward WT levels. WT and iPLA2β-null macrophages incorporate [3H] arachidonic acid ([3H]AA]) into glycerophosphocholine lipids equally rapidly and exhibit identical zymosan-induced, cPLA2β-catalyzed [3H]AA release. In contrast, although WT macrophages exhibit robust [3H]AA release upon FCL, this is attenuated in iPLA 2β-null macrophages and increases toward WT levels upon restoring iPLA2β expression. Recent reports indicate that iPLA2β 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 iPLA2β-null cells. Immunoblotting studies indicate that iPLA2β associates with mitochondria in macrophages subjected to ER stress. AA incorporation into glycerophosphocholine lipids is unimpaired in iPLA2β-null macrophages upon electrospray ionization-tandem mass spectrometry analyses, and their complex lipid composition is similar to WT cells. These findings suggest that iPLA 2β participates in ER stress-induced macrophage apoptosis caused by FCL or thapsigargin but that deletion of iPLA2β does not impair macrophage arachidonate incorporation or phospholipid composition.
UR - http://www.scopus.com/inward/record.url?scp=34848891265&partnerID=8YFLogxK
U2 - 10.1074/jbc.M701316200
DO - 10.1074/jbc.M701316200
M3 - Article
C2 - 17627946
AN - SCOPUS:34848891265
VL - 282
SP - 27100
EP - 27114
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 37
ER -