Metabolomics and Systems Biology

A number of tissue bioactive lipids, including eicosanoids, are dramatically and instantly increased during tissue removal from the body and handling, thus altering quantification results for their basal levels. In addition to enzymatic synthesis, eicosanoid like isoprostanes are also produced upon oxidative stress. We, and others, have demonstrated that high energy focused microwave irradiation (MW) prevents a rapid, 30-fold increase in brain and 150-fold increase in kidney eicosanoid mass within seconds upon tissue extraction from the body. In addition, MW is also required to prevent postmortem alterations of another bioactive lipid group, endocannabinoid, including 2-arachydonoylglycerol (2-AG) and N-arachidonoylethanolamine. We validated stability of endogenous eicosanoids and endocannabinoids under tissue exposure to MW and the application of MW to measure true basal levels of prostaglandins, isoprostanes, and endocannabinoids. We also demonstrated that chiral chromatography is required to differentiate between eicosanoids and non-enzymatically produced isoprostanes. Our results indicate that MW combined with chiral LC-MS/MS is a safe and required technique to quantify tissue levels of a number of bioactive lipids including eicosanoids.