Mechanisms regulating the biosynthesis and signaling of oxylipins

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PROJECT SUMMARY Oxylipins are oxygenated bioactive lipids derived from polyunsaturated fatty acids that have diverse and integral functions in health and disease, including inflammation, cancer, and cardiovascular diseases. Oxylipins are short-lived, locally acting signaling molecules that are synthesized on demand by cyclooxygenases (COX), lipoxygenases (LOX), or cytochrome P450 monooxygenases. Advances in lipidomics have led to the detection of disease-specific changes in oxylipins. Although the identification of disease-specific changes in oxylipins has the power to be used for disease diagnosis, prognosis, or treatment, the translation of lipidomic studies into the clinic remains challenging due to a lack of biological understanding of oxylipins. To better understand the clinical relevance of disease-specific changes, we identified critical gaps in our knowledge that need to be addressed, including 1) what mechanisms regulate the coordinated synthesis of multiple oxylipins leading to cell-specific oxylipin patterns; and 2) how the signals elicited from individuals oxylipins are integrated into biological functions. To address these gaps in our knowledge, the long-term goal of our research program is to decipher the signaling mechanism responsible for the synthesis and function of individual oxylipins to understand the functional consequence of their alterations in diseases. Without further mechanistic insights into disease-specific changes in oxylipins, it is unlikely novel oxylipins will be effectively targeted for clinical purposes. Platelets are the ideal model system to study oxylipin biology because they produce nanomolar levels of approximately 15 oxylipins from COX and 12(S)-lipoxygenase (12-LOX) and offer a simplified model to study the biological consequences of oxylipin dysregulation. In this proposal, we will focus on the function of 12-LOX and its arachidonic acid (AA)-derived metabolite, 12-HETE, which have broad clinical and biological significance. However, due to the lack of consensus on the function of 12-HETE, the mechanism by which 12- LOX contributes to inflammation, cancer progression, and clotting is controversial and represents a substantial knowledge gap. This proposal will study 12-LOX and 12-HETE as a prototypical examples to address its role in disease, and develop tools to characterize the function of oxylipins by using gene-edited human megakaryocytes, which have been shown to faithfully recapitulate the donor-derived platelets. Our short-term goals are to 1) determine the intracellular mechanisms used to release and deliver substrate to 12-LOX and 2) identify the downstream signaling pathway(s) activated by 12-HETE in platelets. Our studies will provide valuable insight into the mechanistic understanding of oxylipin synthesis and function that could ultimately aid in developing new therapeutic approaches for a broad range of diseases.