Edited by Benjamin F. Cravatt, The Scripps Research Institute, La Jolla, CA, and approved June 6, 2017 (received for review June 24, 2016)
The health benefits of ω-3 fatty acids are mediated, in part, through metabolic conversion to bioactive epoxides. Here we detail the discovery and initial characterization of naturally occurring ω-3–derived endocannabinoid epoxides that are formed via enzymatic oxidation of ω-3 endocannabinoids by cytochrome P450s. These dual functional ω-3 endocannabinoid epoxides are anti-inflammatory and vasodilatory and reciprocally modulate platelet aggregation. By virtue of their physiological properties, they are expected to play important roles in neuroinflammation and in cerebrovascular diseases such as stroke.
Clinical studies suggest that diets rich in ω-3 polyunsaturated fatty acids (PUFAs) provide beneficial anti-inflammatory effects, in part through their conversion to bioactive metabolites. Here we report on the endogenous production of a previously unknown class of ω-3 PUFA–derived lipid metabolites that originate from the crosstalk between endocannabinoid and cytochrome P450 (CYP) epoxygenase metabolic pathways. The ω-3 endocannabinoid epoxides are derived from docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) to form epoxyeicosatetraenoic acid-ethanolamide (EEQ-EA) and epoxydocosapentaenoic acid-ethanolamide (EDP-EA), respectively. Both EEQ-EAs and EDP-EAs are endogenously present in rat brain and peripheral organs as determined via targeted lipidomics methods. These metabolites were directly produced by direct epoxygenation of the ω-3 endocannabinoids, docosahexanoyl ethanolamide (DHEA) and eicosapentaenoyl ethanolamide (EPEA) by activated BV-2 microglial cells, and by human CYP2J2. Neuroinflammation studies revealed that the terminal epoxides 17,18-EEQ-EA and 19,20-EDP-EA dose-dependently abated proinflammatory IL-6 cytokines while increasing anti-inflammatory IL-10 cytokines, in part through cannabinoid receptor-2 activation. Furthermore the ω-3 endocannabinoid epoxides 17,18-EEQ-EA and 19,20-EDP-EA exerted antiangiogenic effects in human microvascular endothelial cells (HMVEC) and vasodilatory actions on bovine coronary arteries and reciprocally regulated platelet aggregation in washed human platelets. Taken together, the ω-3 endocannabinoid epoxides’ physiological effects are mediated through both endocannabinoid and epoxyeicosanoid signaling pathways. In summary, the ω-3 endocannabinoid epoxides are found at concentrations comparable to those of other endocannabinoids and are expected to play critical roles during inflammation in vivo; thus their identification may aid in the development of therapeutics for neuroinflammatory and cerebrovascular diseases.
Author contributions: D.R.M., J.E.W., A.A.A., R.A., M.P.C., R.W.J., K.A.K., M.H., and A.D. designed research; D.R.M., J.E.W., A.A.A., R.A., M.P.C., and J.E.K. performed research; D.R.M. and A.D. contributed new reagents/analytic tools; D.R.M., J.E.W., A.A.A., R.A., M.P.C., R.W.J., K.A.K., M.H., and A.D. analyzed data; and D.R.M., J.E.W., A.A.A., R.A., R.W.J., K.A.K., M.H., and A.D. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1610325114/-/DCSupplemental.
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