Enzymatic Lipid Oxygenation and Ferroptosis Resistance: A Critical Evaluation of the Lipid Antioxidant Barrier Hypothesis

Lipid peroxidation has long been viewed primarily as a destructive process—a chaotic, free radical-driven cascade culminating in membrane damage and cell death—although its beneficial aspects have been increasingly recognized over the past decades. However, a growing body of evidence challenges this inflexible hypothesis, as exemplified by the recent demonstration that lipoxin A4, a product of directed enzymatic lipid oxygenation, actively suppresses ferroptosis. In this review, we synthesize the emerging paradigm of directed lipid oxygenation as a regulated, adaptive mechanism that may function as a physiologically regulated lipid antioxidant barrier. We contrast the stochastic chemistry of non-enzymatic lipid peroxidation with the stereospecific, enzymatically driven oxygenation catalyzed primarily by lipoxygenases (LOXs), cyclooxygenases (PTGSs), and cytochrome P450 enzymes, and hypothesize that these two modes compete for polyunsaturated fatty acid (PUFA) substrates, thereby determining cellular outcomes. We further examine how enzymatic lipid oxygenation generates bioactive oxylipins, including specialized pro-resolving mediators (SPMs), that activate cytoprotective transcriptional programs such as the NRF2 pathway. Central to this framework is the coupled operation of LOX-mediated oxygenation and GPX4-mediated hydroperoxide detoxification: the protective outcome depends on GPX4 as the gatekeeper that channels LOX products toward protective signaling rather than ferroptotic accumulation. The implications for ferroptosis are particularly profound: unchecked lipid peroxidation drives ferroptotic cell death, whereas directed enzymatic lipid oxygenation may oppose it. Whether this constitutes an endogenous barrier remains a hypothesis, and our model does not depend on depletion of the PUFA substrate pool. Finally, we outline therapeutic opportunities and outstanding questions for the field.