Prostaglandin endoperoxide H synthases-1 and -2 (PGHS-1 and -2), also known as cyclooxygenases-1 and -2 (COX-1 and COX-2), catalyze the conversion of arachidonic acid (AA) to prostaglandin H2 (PGH2) in the committed step of prostaglandin (PG) biosynthesis. PGHSs are the primary targets of COX inhibitors, which include nonspecific nonsteroidal anti-inflammatory drugs (nsNSAIDs) and COX-2 specific inhibitors called coxibs. COX inhibitors are the most widely used pharmaceutical agents in the U.S. However, the use of these inhibitors carries significant risks. About 20,000 deaths annually are attributable to adverse effects of these drugs, the molecular basis for which is unknown. Using purified human PGHSs, we have discovered that PGHS activities are modulated through an unusual allosteric mechanism by all common fatty acids (FAs) including those that are not PGHS substrates. FAs can stimulate or inhibit PGHS activity with the specific effect being dependent on the PGHS isoform and the FA. The effects occur at physiologic FA concentrations and are observed in cells as well as with purified enzymes. The biochemical basis for the regulation of PGHSs by FAs involves cross-talk between monomers comprising PGHS homodimers. Although the monomers have identical amino acid sequences, the conformations of the two monomers comprising a PGHS homodimer differ. One monomer binds FAs and behaves as an allosteric monomer while the other acts as the catalytic monomer. Finally and importantly, responses of purified human PGHSs to COX inhibitors are modulated by FAs, again depending on the FA, the inhibitor and the PGHS isoform. With different COX inhibitors, FAs can influence binding of an inhibitor to one or to both monomers. The goals of the proposed research are to determine how PGHSs and their responses to widely used COX inhibitors are affected by FAs at the molecular, cellular and whole animal levels. Our underlying hypothesis is that both in vivo PG production and responses to COX inhibitors are significantly modulated by the milieu of FAs in which the enzymes find themselves-the FA tone--and that this FA environment is importantly influenced by the FA composition of the diet. We presume that every individual establishes a FA tone as a consequence of dietary habits in the context of their genetic background. We speculate that certain FA tones predispose susceptible individuals to adverse consequences of COX inhibitors. We expect that our studies delineating FA/COX inhibitor interactions will be a first step leading to changes in the way COX inhibitors are prescribed to people on different diets and to dietary adjustments to provide for the safer use of COX inhibitors.

Public Health Relevance

This research is relevant to public health because it will provide a fundamental understanding of how different kinds of dietary fats can alter responses to common anti- inflammatory and analgesic drugs including aspirin, celecoxib, ibuprofen and naproxen. These drugs cause many adverse cardiovascular, renal and gastrointestinal side effects. Understanding how differences in the fat content of the diet can alter responses to these drugs will lead to changes in the way they are prescribed to people on different diets and will minimize the side effects.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM068848-12
Application #
8658102
Study Section
Integrative Nutrition and Metabolic Processes Study Section (INMP)
Program Officer
Barski, Oleg
Project Start
2003-09-01
Project End
2015-05-31
Budget Start
2014-06-01
Budget End
2015-05-31
Support Year
12
Fiscal Year
2014
Total Cost
$470,646
Indirect Cost
$150,130
Name
University of Michigan Ann Arbor
Department
Biochemistry
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Dame, Michael K; Attili, Durga; McClintock, Shannon D et al. (2018) Identification, isolation and characterization of human LGR5-positive colon adenoma cells. Development 145:
Dong, Liang; Zou, Hechang; Yuan, Chong et al. (2016) Interactions of 2-O-arachidonylglycerol ether and ibuprofen with the allosteric and catalytic subunits of human COX-2. J Lipid Res 57:1043-50
Dong, Liang; Yuan, Chong; Orlando, Benjamin J et al. (2016) Fatty Acid Binding to the Allosteric Subunit of Cyclooxygenase-2 Relieves a Tonic Inhibition of the Catalytic Subunit. J Biol Chem 291:25641-25655
Dong, Liang; Zou, Hechang; Yuan, Chong et al. (2016) Different Fatty Acids Compete with Arachidonic Acid for Binding to the Allosteric or Catalytic Subunits of Cyclooxygenases to Regulate Prostanoid Synthesis. J Biol Chem 291:4069-78
Yuan, Chong; Smith, William L (2015) A cyclooxygenase-2-dependent prostaglandin E2 biosynthetic system in the Golgi apparatus. J Biol Chem 290:5606-20
Jiang, Yan; Djuric, Zora; Sen, Ananda et al. (2014) Biomarkers for personalizing omega-3 fatty acid dosing. Cancer Prev Res (Phila) 7:1011-22
Dame, Michael K; Jiang, Yan; Appelman, Henry D et al. (2014) Human colonic crypts in culture: segregation of immunochemical markers in normal versus adenoma-derived. Lab Invest 94:222-34
Kuklev, Dmitry V; Hankin, Joseph A; Uhlson, Charis L et al. (2013) Major urinary metabolites of 6-keto-prostaglandin F2? in mice. J Lipid Res 54:1906-14
Dong, Liang; Sharma, Narayan P; Jurban, Brice J et al. (2013) Pre-existent asymmetry in the human cyclooxygenase-2 sequence homodimer. J Biol Chem 288:28641-55
Zou, Hechang; Yuan, Chong; Dong, Liang et al. (2012) Human cyclooxygenase-1 activity and its responses to COX inhibitors are allosterically regulated by nonsubstrate fatty acids. J Lipid Res 53:1336-47

Showing the most recent 10 out of 32 publications