Revising the structure of a new eicosanoid from human platelets to 8,9-11,12-diepoxy-13-hydroxyeicosadienoic acid.

Eicosanoids are critical mediators of fever, pain, and inflammation generated by immune and tissue cells. We recently described a new bioactive eicosanoid generated by cyclooxygenase-1 (COX-1) turnover during platelet activation that can stimulate human neutrophil integrin expression. On the basis of mass spectrometry (MS/MS and MS3), stable isotope labeling, and GC-MS analysis, we previously proposed a structure of 8-hydroxy-9,11-dioxolane eicosatetraenoic acid (DXA3). Here, we achieved enzymatic synthesis and 1H NMR characterization of this compound with results in conflict with the previously proposed structural assignment. Accordingly, by using LC-MS, we screened autoxidation reactions of 11-hydroperoxy-eicosatetraenoic acid (11-HpETE) and thereby identified a candidate sharing the precise reverse-phase chromatographic and MS characteristics of the platelet product. We optimized these methods to increase yield, allowing full structural analysis by 1H NMR. The revised assignment is presented here as 8,9-11,12-diepoxy-13-hydroxyeicosadienoic acid, abbreviated to 8,9-11,12-DiEp-13-HEDE or DiEpHEDE, substituted for the previous name DXA3 We found that in platelets, the lipid likely forms via dioxolane ring opening with rearrangement to the diepoxy moieties followed by oxygen insertion at C13. We present its enzymatic biosynthetic pathway and MS/MS fragmentation pattern and, using the synthetic compound, demonstrate that it has bioactivity. For the platelet lipid, we estimate 16 isomers based on our current knowledge (and four isomers for the synthetic lipid). Determining the exact isomeric structure of the platelet lipid remains to be undertaken.

The hydrolysis of bimatoprost in corneal tissue generates a potent prostanoid FP receptor agonist.

Using human and bovine corneal tissue, we investigated the in vitro metabolism of bimatoprost (17-phenyl-18,19,20-trinor-prostaglandin F(2alpha) ethyl amide, Lumigan (Allergan, Inc, Irvine, CA). Enzymatic amidase activity, which converts bimatoprost to the corresponding prostaglandin carboxylic acid, was found to be present in corneal tissue from both species. Using HPLC and mass spectrometry for analyses, conversion of bimatoprost to 17-phenyl-18,19,20-trinor prostaglandin F(2alpha) continued for at least 24 hours after excision of the cornea, with a conversion rate of approximately 25 microg/24 hours. This hydrolysis product is identical to the free acid of latanoprost with the exception of a double, rather than a single, bond at the carbon 13-14 position. Assuming that this conversion also occurs in vivo at a similar rate, this hydrolysis product may account for the reduction of intraocular pressure occurring in patients treated with bimatoprost.

Synthesis of 15R-PGD2: a potential DP2 receptor agonist.

The first total synthesis of 15R-PGD(2)3 was accomplished. The approach used in this report is also an efficient method to produce 15R-PGE(2). 15R-PGD(2), a potential DP(2) receptor agonist, could be an important novel tool for defining the role of this receptor in inflammatory diseases.