Abstract
Prostaglandin endoperoxide H synthases (PGHS)-1 and -2, also called cyclooxygenases, convert arachidonic acid (AA) to prostaglandin H2 (PGH2) in the committed step of prostaglandin biosynthesis. Both enzymes are homodimers, but the monomers often behave asymmetrically as conformational heterodimers during catalysis and inhibition. Here we report that aspirin maximally acetylates one monomer of human (hu) PGHS-2. The acetylated monomer of aspirin-treated huPGHS-2 forms 15-hydroperoxyeicosatetraenoic acid from AA, whereas the nonacetylated partner monomer forms mainly PGH2 but only at 15 to 20% of the rate of native huPGHS-2. These latter conclusions are based on the findings that the nonsteroidal anti-inflammatory drug diclofenac binds a single monomer of native huPGHS-2, having an unmodified Ser530 to inhibit the enzyme, and that diclofenac inhibits PGH2 but not 15-hydroperoxyeicosatraenoic acid formation by acetylated huPGHS-2. The 18R- and 17R-resolvins putatively involved in resolution of inflammation are reportedly formed via aspirin-acetylated PGHS-2 from eicosapentaenoic acid and docosahexaenoic acid, respectively, so we also characterized the oxygenation of these omega-3 fatty acids by aspirin-treated huPGHS-2. Our in vitro studies suggest that 18R- and 17R-resolvins could be formed only at low rates corresponding to less than 1 and 5%, respectively, of the rates of formation of PGH2 by native PGHS-2.
Footnotes
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The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.
These studies were supported by the National Institutes of Health National Institute of General Medical Sciences [Grant GM068848]; and the National Institutes of Health National Heart, Lung, and Blood Institute [Grant HL085149].
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.109.063115.
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ABBREVIATIONS:
- PGHS
- prostaglandin endoperoxide H synthase
- COX
- cyclooxygenase
- AA
- arachidonic acid
- hu
- human
- nsNSAID
- nonspecific nonsteroidal anti-inflammatory drug
- EPA
- eicosapentaenoic acid
- DHA
- docosahexaenoic acid
- TCA
- trichloroacetic acid
- 11-HETE
- 11-hydroxyeicosatetraenoic acid
- 15-HETE
- 15-hydroxyeicosatetraenoic acid
- 11-HEPE
- 11-hydroxyeicosapentaenoic acid
- 15-HEPE
- 15-hydroxyeicosapentaenoic acid
- 18-HEPE
- 18-hydroxyeicosapentaenoic acid
- 13-HDHA
- 13-hydroxydocosahexaenoic acid
- 17-HDHA
- 17-hydroxydocosahexaenoic acid
- RvE1
- Resolvin E1, 5S,12R,18R-trihydroxy-6Z,8E,10E,14Z,16E-eicosapentaenoic acid
- 17R-RvD1
- 17R-resolvin D1, 7S,8R,17R-trihydroxy-4Z,9E,13Z,15E,19Z-docosahexaenoic acid
- PGH2
- prostaglandin H2
- ASA
- acetylsalicylic acid
- HPLC
- high-performance liquid chromatography
- MS/MS
- tandem mass spectrometry
- LC-MS/MS
- liquid chromatography/tandem mass spectrometry
- 15R-HETE
- 15R-hydroxy-eicosatetraenoic acid.
- Received December 13, 2009.
- Accepted March 1, 2010.
- Copyright © 2010 The American Society for Pharmacology and Experimental Therapeutics
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