Document Detail

Inhibition of carboxylesterase activity of THP1 monocytes/macrophages and recombinant human carboxylesterase 1 by oxysterols and fatty acids.
MedLine Citation:
PMID:  19761868     Owner:  NLM     Status:  MEDLINE    
Two major isoforms of human carboxylesterases (CEs) are found in metabolically active tissues, CES1 and CES2. These hydrolytic enzymes are involved in xenobiotic and endobiotic metabolism. CES1 is abundantly expressed in human liver and monocytes/macrophages, including the THP1 cell line; CES2 is expressed in liver but not in monocytes/macrophages. The cholesteryl ester hydrolysis activity in human macrophages has been attributed to CES1. Here, we report the direct inhibitory effects of several endogenous oxysterols and fatty acids on the CE activity of THP1 monocytes/macrophages and recombinant human CES1 and CES2. Using THP1 whole-cell lysates we found: (1) 27-hydroxycholesterol (27-HC) is a potent inhibitor of carboxylesterase activity (IC50=33 nM); (2) 24(S),25-epoxycholesterol had moderate inhibitory activity (IC(50)=8.1 microM); and (3) cholesterol, 7-ketocholesterol, 22(R)-hydroxycholesterol, 24(S)-hydroxycholesterol, and 25-hydroxycholesterol each had little inhibitory activity. 27-HC was a partially noncompetitive inhibitor of recombinant CES1 (K(iapp)=10 nM) and impaired intracellular CES1 activity following treatment of intact THP1 cells. In contrast, recombinant CES2 activity was not inhibited by 27-HC, suggesting isoform-selective inhibition by 27-HC. Furthermore, unsaturated fatty acids were better inhibitors of CES1 activity than saturated fatty acids, while CES2 activity was unaffected by any fatty acid. Arachidonic acid (AA) was the most potent fatty acid inhibitor of recombinant CES1 and acted by a noncompetitive mechanism (K(iapp)=1.7 microM); when not complexed to albumin, exogenous AA penetrated intact THP1 cells and inhibited CES1. Inhibition results are discussed in light of recent structural models for CES1 that describe ligand binding sites separate from the active site. In addition, oxysterol-mediated inhibition of CES1 activity was demonstrated by pretreatment of human liver homogenates or intact THP1 cells with exogenous 27-HC, which resulted in significantly reduced hydrolysis of the pyrethroid insecticide bioresmethrin, a CES1-specific xenobiotic substrate. Collectively, these findings suggest that CE activity of recombinant CES1, cell lysates, and intact cells can be impaired by naturally occurring lipids, which may compromise the ability of CES1 to both detoxify environmental pollutants and metabolize endogenous compounds in vivo.
J Allen Crow; Katye L Herring; Shuqi Xie; Abdolsamad Borazjani; Philip M Potter; Matthew K Ross
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2009-09-15
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1801     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  2010 Jan 
Date Detail:
Created Date:  2009-11-30     Completed Date:  2010-06-17     Revised Date:  2014-03-19    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  31-41     Citation Subset:  IM    
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MeSH Terms
Arachidonic Acid / pharmacology
Carboxylic Ester Hydrolases / antagonists & inhibitors*,  genetics,  metabolism
Fatty Acids / pharmacology*
Hydroxycholesterols / pharmacology*
Macrophages / cytology,  enzymology*,  metabolism
Monocytes / cytology,  enzymology*,  metabolism
Recombinant Proteins / antagonists & inhibitors,  genetics,  metabolism
Grant Support
Reg. No./Substance:
0/Fatty Acids; 0/Hydroxycholesterols; 0/Recombinant Proteins; 20380-11-4/27-hydroxycholesterol; 27YG812J1I/Arachidonic Acid; EC 3.1.1.-/Carboxylic Ester Hydrolases; EC protein, human

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