Abstract 682: Pharmacological Inhibition of COX and LOX Pathways Leads to Substrate Rediversion: A Novel Plasma Lipidomics Assay to Screen Drugs in Human Blood

Abstract

Cardiovascular complications from cyclooxygenase (COX)-2-selective nonsteroidal anti-inflammatory drugs (NSAIDs) prompted interest in microsomal prostaglandin synthase 1 (mPGES-1), downstream of COX-2, as an alternative drug target. Unlike COX-2, global deletion of mPGES-1 in mice suppresses prostaglandin E2 (PGE2) and augments prostacyclin PGI2 through substrate rediversion, and does not predispose to thrombogenesis and hypertension. However, after cell-specific deletions of mPGES-1, the predominant substrate rediversion product amongst the prostaglandins varies by cell type. We hypothesized that inhibition of mPGES-1 leads to changes in bioactive lipids beyond the prostaglandin pathway, and that substrate rediversion associated with a more favorable cardiovascular profile after mPGES-1 vs COX-2 inhibition can be translated from mouse to human studies. In this project, we aimed 1) to develop a mass spectrometry-based, broad-spectrum lipidomics approach to measure arachidonate-derived products additional to prostanoids; and 2) to work out an in vitro human whole blood assay (hWBA) to study substrate rediversion upon mPGES-1 vs COX-2 inhibition. We have developed a novel, reproducible analytical method to scan the impact of drugs on the bioactive lipidome. Using an in vitro hWBA and HPLC-MS/MS lipidomics analysis, we observed substrate rediversion in both COX and LOX pathways after mPGES-1 inhibition, which was distinct from inhibiting COX-1/2. We further optimized this assay to screen combinations of inhibitors from COX and lipoxygenase (LOX) cascades. Overall, we have shown that a clear signature of inhibiting diverse targets - mPGES-1, COX and LOX enzymes - can be readily detected from experiments of small samples sizes, and discovered novel aspects of drug effect due to substrate rediversion. Our findings contribute to the comparative cardiovascular safety of inhibiting mPGES-1 vs COX-2 and demonstrate the impact of combining mPGES-1 with LOX inhibitions on the hemostatic system