Biomedical subjects

Gary D Snyder

Publications and source records attributed to Gary D Snyder.

4 recordsLinked to original sources

PubMed2005

14,15-Dihydroxyeicosatrienoic acid activates peroxisome proliferator-activated receptor-alpha.

Epoxyeicosatrienoic acids (EETs), lipid mediators synthesized from arachidonic acid by cytochrome P-450 epoxygenases, are converted by soluble epoxide hydrolase (SEH) to the corresponding dihydroxyeicosatrienoic acids (DHETs). Originally considered as inactive degradation products of EETs, DHETs have biological activity in some systems. Here we examined the capacity of EETs and DHETs to activate peroxisome proliferator-activated receptor-alpha (PPARalpha). We find that among the EET and DHET regioisomers, 14,15-DHET is the most potent PPARalpha activator in a COS-7 cell expression system. Incubation with 10 microM 14,15-DHET produced a 12-fold increase in PPARalpha-mediated luciferase activity, an increase similar to that produced by the PPARalpha agonist Wy-14643 (20 microM). Although 10 microM 14,15-EET produced a threefold increase in luciferase activity, this was abrogated by the SEH inhibitor dicyclohexylurea. 14-Hexyloxytetradec-5(Z)-enoic acid, a 14,15-EET analog that cannot be converted to a DHET, did not activate PPARalpha. However, PPARalpha was activated by 2-(14,15-epoxyeicosatrienoyl)glycerol, which was hydrolyzed and the released 14,15-EET converted to 14,15-DHET. COS-7 cells incorporated 14,15-[3H]DHET from the medium, and the cells also retained a small amount of the DHET formed during incubation with 14,15-[3H]EET. Binding studies indicated that 14,15-[3H]DHET binds to the ligand binding domain of PPARalpha with a Kd of 1.4 microM. Furthermore, 14,15-DHET increased the expression of carnitine palmitoyltransferase 1A, a PPARalpha-responsive gene, in transfected HepG2 cells. These findings suggest that 14,15-DHET, produced from 14,15-EET by the action of SEH, may function as an endogenous activator of PPARalpha.

8,11,14-Eicosatrienoic Acid↗

PubMed2005

Activation of peroxisome proliferator-activated receptor alpha by substituted urea-derived soluble epoxide hydrolase inhibitors.

Soluble epoxide hydrolase (sEH) plays a major role in regulating vascular epoxyeicosatrienoic acid metabolism and function, and substituted urea derivatives that inhibit sEH activity reduce blood pressure in hypertensive rats. We found that substituted urea derivatives containing a dodecanoic acid group, besides effectively inhibiting sEH, increased peroxisome proliferator-activated receptor (PPAR) alpha activity. In PPARalpha transfected COS-7 cells, treatment with 10 microM N-cyclohexyl-N'-dodecanoic acid urea (CUDA) or N-adamantanyl-N'-dodecanoic acid urea (AUDA) produced 6- and 3-fold increases, respectively, in PPARalpha activation. Neither CUDA nor AUDA activated PPARdelta or PPARgamma directly, indicating selectivity for PPARalpha. CUDA did not alter PPARalpha protein expression, and it competitively inhibited the binding of Wy-14643 (pirinixic acid) to the ligand binding domain of PPARalpha, suggesting that it functions as a PPARalpha ligand. CUDA and AUDA were metabolized to chain-shortened beta-oxidation products, a process that reduced their potency as sEH inhibitors and their ability to bind and activate PPARalpha. N,N'-Dicylclohexylurea and N-cyclohexyl-N'-dodecylurea, sEH inhibitors that do not contain a carboxylic acid group, did not activate PPARalpha. In HepG2 cells, CUDA increased the expression of the PPARalpha-responsive gene carnitine palmitoyltransferase 1A. We conclude that CUDA and AUDA, by virtue of their carboxylic acid substitution, activate PPARalpha in addition to potently inhibiting sEH. Further development of these compounds could lead to a class of agents with hypotensive and lipid-lowering properties that may be valuable for the prevention and treatment of cardiovascular disease.

8,11,14-Eicosatrienoic Acid↗

PubMed2004

Epoxyeicosatrienoic acids (EETs): metabolism and biochemical function.

Epoxyeicosatrienoic acids (EETs), which are synthesized from arachidonic acid by cytochrome P450 epoxygenases, function primarily as autocrine and paracrine effectors in the cardiovascular system and kidney. They modulate ion transport and gene expression, producing vasorelaxation as well as anti-inflammatory and pro-fibrinolytic effects. EETs are incorporated into the sn-2 position of phospholipids and are rapidly mobilized when a cell is treated with a Ca(2+) ionophore, suggesting that they may play a role in phospholipid-mediated signal transduction processes. Soluble epoxide hydrolase (sEH) converts EETs to dihydroxyeicosatrienoic acids (DHETs), and inhibition of sEH is a potential approach for enhancing the biological activity of EETs. EETs also undergo chain-elongation and beta-oxidation, and the accumulation of partial beta-oxidation products increases when sEH is inhibited. Some functional effects of EETs occur through activation of either the guanine nucleotide binding protein Galphas or the Src signal transduction pathways, suggesting that EETs act by binding to membrane receptors. However, other evidence indicates that the modulation of gene expression occurs through an intracellular action of EETs. Because of the diversity of biochemical and functional responses produced by EETs, it is doubtful that a single mechanism or signal transduction pathway can account for all of their actions.

8,11,14-Eicosatrienoic Acid↗

PubMed2002

Evidence for a membrane site of action for 14,15-EET on expression of aromatase in vascular smooth muscle.

Epoxyeicosatrienoic acids (EETs) are synthesized in the endothelial cells of vascular tissues. They are released from the endothelial cells and produce relaxation of the smooth muscle cells by hyperpolarization. The present findings demonstrate that EETs also regulate aromatase activity in vascular smooth muscle cells. Exposure of cultured rat aortic smooth muscle cells to either 1 microM 14,15-EET or 1 microM 11,12-EET inhibits dibutyryl cAMP-induced aromatase activity by 80-100%. 11,12-Dihydroxyeicosatrienoic acid, the hydration product of 11,12-EET, has no effect on dibutyryl cAMP-induced vascular smooth muscle aromatase activity. In contrast to 14,15-EET, the N-methylsulfanilamide derivative of 14,15-EET (14,15-EET-SA) was neither metabolized nor incorporated into cell lipids, but it retained the ability to inhibit cAMP-induced aromatase activity. Furthermore, the 14,15-EET-SA inhibition of cAMP-induced aromatase activity persisted when the sulfanilamide derivative of 14,15-EET was covalently tethered to silica beads (average diameter, 0.5 microm), which restricted 14,15-EET-SA from entering the cell. These data are consistent with the presence of a receptor for EETs in the plasma membrane and support the hypothesis that the inhibition of aromatase by EETs is initiated by the interaction of EET with the putative plasma membrane receptor.

8,11,14-Eicosatrienoic Acid↗