title: Isolevuglandin-modified phosphatidylethanolamine is metabolized by NAPE-hydrolyzing phospholipase D.
abstract: Lipid aldehydes including isolevuglandins (IsoLGs) and 4-hydroxynonenal modify phosphatidylethanolamine (PE) to form proinflammatory and cytotoxic adducts. Therefore, cells may have evolved mechanisms to degrade and prevent accumulation of these potentially harmful compounds. To test if cells could degrade isolevuglandin-modified phosphatidylethanolamine (IsoLG-PE), we generated IsoLG-PE in human embryonic kidney 293 (HEK293) cells and human umbilical cord endothelial cells and measured its stability over time. We found that IsoLG-PE levels decreased more than 75% after 6 h, suggesting that IsoLG-PE was indeed degraded. Because N-acyl phosphatidylethanolamine-hydrolyzing phospholipase D (NAPE-PLD) has been described as a key enzyme in the hydrolysis of N-acyl phosphatidylethanoamine (NAPE) and both NAPE and IsoLG-PE have large aliphatic headgroups, we considered the possibility that this enzyme might also hydrolyze IsoLG-PE. We found that knockdown of NAPE-PLD expression using small interfering RNA (siRNA) significantly increased the persistence of IsoLG-PE in HEK293 cells. IsoLG-PE competed with NAPE for hydrolysis by recombinant mouse NAPE-PLD, with the catalytic efficiency (V(max)/K(m)) for hydrolysis of IsoLG-PE being 30% of that for hydrolysis of NAPE. LC-MS/MS analysis confirmed that recombinant NAPE-PLD hydrolyzed IsoLG-PE to IsoLG-ethanolamine. These results demonstrate that NAPE-PLD contributes to the degradation of IsoLG-PE and suggest that a major physiological role of NAPE-PLD may be to degrade aldehyde-modified PE, thereby preventing the accumulation of these harmful compounds.
authors.affiliation: Division of Clinical Pharmacology, and.
authors.forename: Lilu
authors.initials: L
authors.lastname: Guo
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Gragg
authors.forename: Zhongyi
authors.initials: Z
authors.lastname: Chen
authors.forename: Yongqin
authors.initials: Y
authors.lastname: Zhang
authors.forename: Venkataraman
authors.initials: V
authors.lastname: Amarnath
authors.forename: Sean S
authors.initials: SS
authors.lastname: Davies
mesh_terms: D000447:Aldehydes / Q000378:metabolism*; D000818:Animals; D020868:Gene Silencing; D057809:HEK293 Cells; D006801:Humans; D006868:Hydrolysis; D051379:Mice; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D010739:Phospholipase D / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: D000447:Aldehydes; D010714:Phosphatidylethanolamines; D010739:Phospholipase D; C483858:phosphatidylethanolamine; C506062:Napepld protein, mouse; C581518:NAPEPLD protein, human
keywords: N-acyl ethanolamine; N-acyl phosphatidylethanolamine; cytotoxicity; inflammation; isoketal; oxidative stress
references.citation: Anal Biochem. 2010 Oct 15;405(2):236-45
references.pmid: 20599652
references.citation: Circ Res. 2005 Dec 9;97(12):1262-9
references.pmid: 16284182
references.citation: Free Radic Biol Med. 2004 Nov 15;37(10):1604-11
references.pmid: 15477011
references.citation: Brain Pathol. 2011 Sep;21(5):544-57
references.pmid: 21251115
references.citation: Anal Biochem. 2004 Nov 1;334(1):155-63
references.pmid: 15464964
references.citation: J Neurosci. 2008 Jan 30;28(5):1058-63
references.pmid: 18234884
references.citation: Biochim Biophys Acta. 2009 Apr;1791(4):307-13
references.pmid: 19233311
references.citation: Biochim Biophys Acta. 1997 Jan 7;1344(1):1-5
references.pmid: 9022751
references.citation: Biochemistry. 2006 Apr 18;45(15):4720-6
references.pmid: 16605240
references.citation: Free Radic Biol Med. 2009 Dec 1;47(11):1539-52
references.pmid: 19751823
references.citation: J Lipid Res. 2010 May;51(5):999-1009
references.pmid: 19965577
references.citation: Adv Prostaglandin Thromboxane Leukot Res. 1985;15:323-6
references.pmid: 2936114
references.citation: Biochem J. 2005 Jul 1;389(Pt 1):241-7
references.pmid: 15760304
references.citation: J Biol Chem. 2004 Feb 13;279(7):5298-305
references.pmid: 14634025
references.citation: Free Radic Biol Med. 2012 Sep 15;53(6):1226-38
references.pmid: 22898174
references.citation: J Biol Chem. 2011 May 20;286(20):18170-80
references.pmid: 21454544
references.citation: Neurobiol Dis. 2009 Jan;33(1):57-71
references.pmid: 18930143
references.citation: FEBS Lett. 1999 Jul 16;455(1-2):41-4
references.pmid: 10428468
references.citation: J Biol Chem. 2006 May 5;281(18):12325-35
references.pmid: 16527816
references.citation: FASEB J. 2002 May;16(7):715-7
references.pmid: 11978738