Characterization Of The Specialized Pro-Resolving Lipid Mediator Metabolome and Implications For Their Endogenous Formation

Vanderbilt University Medical Center, Nashville TN

Investigators

Abstract

PROJECT SUMMARY Out of control, or dysregulated, inflammation is a hallmark of numerous human diseases. Oxidized lipid mediators, oxylipins, are short-lived autacoids that play important roles in the etiology of inflammation. Quantification of urinary metabolites of prostaglandins and leukotrienes has been a key approach towards understanding of the role of these molecules – as well as the drugs used to inhibit them (ie. aspirin) – in human physiology and disease. Specialized pro-resolving lipid mediators (SPMs) are oxylipins typically generated from eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), that promote the resolution of inflammation. SPMs and their stable analogues are being developed as therapeutics to treat inflammatory-related diseases. But, while these molecules have been detected in certain biological settings, the extent to which SPMs are generated in vivo remains unclear. Importantly, there are distinct biological mechanisms – such as SPM metabolism and quantification of SPM metabolites – that have yet to be considered. Recently, our laboratory identified a novel route of SPM metabolism. We demonstrated that resolvin D5 (RvD5), one of the most abundant SPMs, is a substrate for uridine 5'-diphospho-glucuronosyltransferase (UGT) 1A9 and is rapidly metabolized via glucuronide conjugation. Limited studies on SPM metabolism exist; thus, we seek herein to gain a comprehensive understanding of SPM transformation. The central hypothesis of this proposal is that understanding the metabolism of SPMs is critical for the accurate and complete quantification of these bioactive lipids in human disease and homeostasis. We seek to address this hypothesis through three specific aims. In Specific Aim 1, we will identify and characterize routes pathways by which SPM are transformed using an in vitro model of human metabolism. We will study the metabolic inactivation of four structurally-distinct SPM – resolvin E4 (RvE4), resolvin D1 (RvD1), RvD5, and maresin 2 (MaR2). In Specific Aim 2, we will follow the metabolism of these SPMs in mouse models of human metabolism and inflammation. Additionally, we will utilize human plasma and urine samples previously collected as part of the Fatty Acid Desaturase Activity, Fish Oil, and Colorectal Cancer Prevention Study (FADAFO) to evaluate SPM metabolite formation in humans. Finally, in Specific Aim 3, we will address the concept that metabolism of SPM, particularly by UGTs, can be affected by commonly used medications, including non-steroidal anti-inflammatory drugs (NSAIDs). The effect of aspirin, ibuprofen, and other NSAIDs on the metabolism of SPMs will be explored in our proposed cellular and animal models. Together these aims present an innovative approach to detecting endogenous SPM formation. Identifying pathways that transform these molecules and establishing precise methods to ensure their accurate quantification will help to clarify mechanisms – and therapies – that regulate inflammation and outline a unique strategy to comprehensively evaluate SPM production for human clinical trials and epidemiological studies.