Resolving the Role of Lipoxygenases in the Initiation and Execution of Ferroptosis

TLDR

Lipoxygenases generate lipid hydroperoxides and have been implicated as central players in ferroptosis, a cell death modality driven by lipid peroxidation. The authors created HEK cell lines overexpressing disease‑associated LOX isoforms (5‑LOX, p12‑LOX, 15‑LOX‑1) that were sensitized to ferroptosis, and showed that radical‑trapping antioxidants could protect lipids from autoxidation, the chain reaction that produces these hydroperoxides. Rescue of the LOX‑overexpressing cells by a subset of LOX inhibitors and the equal potency of cytoprotective compounds across lines indicate that while LOX activity contributes to the lipid‑hydroperoxide pool initiating ferroptosis, lipid autoxidation is the primary driver of cell death.

Abstract

Lipoxygenases (LOXs) have been implicated as central players in ferroptosis, a recently characterized cell death modality associated with the accumulation of lipid hydroperoxides: the products of LOX catalysis. To provide insight on their role, human embryonic kidney cells were transfected to overexpress each of the human isoforms associated with disease, 5-LOX, p12-LOX, and 15-LOX-1, which yielded stable cell lines that were demonstrably sensitized to ferroptosis. Interestingly, the cells could be rescued by less than half of a diverse collection of known LOX inhibitors. Furthermore, the cytoprotective compounds were similarly potent in each of the cell lines even though some were clearly isoform-selective LOX inhibitors. The cytoprotective compounds were subsequently demonstrated to be effective radical-trapping antioxidants, which protect lipids from autoxidation, the autocatalytic radical chain reaction that produces lipid hydroperoxides. From these data (and others reported herein), a picture emerges wherein LOX activity may contribute to the cellular pool of lipid hydroperoxides that initiate ferroptosis, but lipid autoxidation drives the cell death process.