Phospholipase C-dependent hydrolysis of phosphatidylcholine hydroperoxides to diacylglycerol hydroperoxides and its reduction by phospholipid hydroperoxide glutathione peroxidase.
We have shown that 1,2-diacylglycerol hydroperoxides activate protein kinase C (PKC) as efficiently as does phorbol ester [Takekoshi S, Kambayashi Y, Nagata H, Takagi T, Yamamoto Y, Watanabe K. Activation of protein kinase C by oxidized diacylglycerol. Biochem Biophys Res Commun 1995; 217: 654-660]. 1,2-Diacylglycerol hydroperoxides also stimulate human neutrophils to release superoxide whereas their hydroxides do not [Yamamoto Y, Kambayashi Y, Ito T, Watanabe K, Nakano M. 1,2-Diacylglycerol hydroperoxides induce the generation and release of superoxide anion from human polymorphonuclear leukocytes. FEBS Lett 1997; 412: 461-464]. One of the proposed mechanisms for the formation of 1,2-diacylglycerol hydroperoxides is the hydrolysis of phosphatidylcholine hydroperoxides by phospholipase C (PLC). To confirm this hypothesis, we incubated 1-palmitoyl-2-linoleoyl-phosphatidylcholine (PLPC) liposomes containing PLPC hydroperoxides (PLPC-OOH) with Bacillus cereus PLC and found 1-palmitoyl-2-linoleoylglycerol (PLG) and its hydroperoxide (PLG-OOH) were produced. PLC hydrolyzed the two substrates without preference, as the yields of PLG and PLG-OOH were the same even though cholesterol was incorporated into liposomes to increase bilayer integrity. Phospholipid hydroperoxide glutathione peroxidase (PHGPX) reduced PLG-OOH to its hydroxide in the presence of glutathione while the conventional cytosolic glutathione peroxidase did not. These data suggest that PLC hydrolyzes oxidized biomembranes to give 1,2-diacylglycerol hydroperoxides for PKC stimulation but PHGPX may prevent neutrophil stimulation by reducing 1,2-diacylglycerol hydroperoxides to their hydroxides.
Kambayashi
Y
Y
Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan.
Takekoshi
S
S
Watanabe
K
K
Yamamoto
Y
Y
D000818:Animals; D001407:Bacillus / Q000378:metabolism; D002784:Cholesterol / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology; D004075:Diglycerides / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005979:Glutathione Peroxidase / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism* / Q000494:pharmacology*; D006868:Hydrolysis; D051379:Mice; D009504:Neutrophils / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism*; D013552:Swine; D013696:Temperature; D013997:Time Factors; D010738:Type C Phospholipases / Q000378:metabolism*
D004075:Diglycerides; D010713:Phosphatidylcholines; D002784:Cholesterol; D006861:Hydrogen Peroxide; D005979:Glutathione Peroxidase; D010738:Type C Phospholipases