Ferroptosis is a non-apoptotic form of regulated cell death caused by the failure of the glutathione-dependent lipid-peroxide-scavenging network. FINO2 is an endoperoxide-containing 1,2-dioxolane that can initiate ferroptosis selectively in engineered cancer cells. We investigated the mechanism and structural features necessary for ferroptosis initiation by FINO2. We found that FINO2 requires both an endoperoxide moiety and a nearby hydroxyl head group to initiate ferroptosis. In contrast to previously described ferroptosis inducers, FINO2 does not inhibit system xc− or directly target GPX4, as do erastin and RSL3, respectively, or deplete GPX4 protein, as does FIN56. Instead, FINO2 causes both indirect loss of GPX4 enzymatic function and directly oxidizes iron, ultimately causing widespread lipid peroxidation. These findings suggest that endoperoxides such as FINO2 can initiate a multi-pronged mechanism of ferroptosis.

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The facile abstraction of bis-allylic hydrogens from polyunsaturated fatty acids (PUFAs) is the hallmark chemistry responsible for initiation and propagation of autoxidation reactions. The products of these autoxidation reactions can form cross-links to other membrane components, damage proteins and nucleic acid. We report that PUFAs deuterated at bis-allylic sites are much more resistant to autoxidation reactions, due to the isotope effect. This is shown using coenzyme Q-deficient Saccharomyces cerevisiae coq mutants with defects in biosynthesis of coenzyme Q (Q). Q functions in respiratory energy metabolism and also functions as a lipid-soluble antioxidant. Yeast coq mutants incubated in the presence of the PUFAs α-linolenic or linoleic acid exhibit 99% loss of colony formation after four hours, demonstrating a profound loss of viability. In contrast, coq mutants treated with monounsaturated oleic acid or with one of the deuterated PUFAs:11,11-D2-Linoleic or 11,11,14,14-D4-αLinolenic retain viability similar to wild-type yeast. Deuterated PUFAs also confer protection to wild-type yeast subjected to heat stress. These results indicate that isotope-reinforced PUFAs are stabilized compared to standard PUFAs, and they protect coq mutants and wild-type yeast cells against the toxic effects of lipid autoxidation products. These findings suggest new approaches to controlling ROS-inflicted cellular damage and oxidative stress.

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Autoxidation of polyunsaturated fatty acids (PUFAs) damages lipid membranes and generates numerous toxic by‐products implicated in neurodegeneration, aging, and other pathologies. Abstraction of bis‐allylic hydrogen atoms is the rate‐limiting step of PUFA autoxidation, which is inhibited by replacing bis‐allylic hydrogens with deuterium atoms (D‐PUFAs). In cells, the presence of a relatively small fraction of D‐PUFAs among natural PUFAs is sufficient to effectively inhibit lipid peroxidation (LPO). Here, we investigate the effect of various D‐PUFAs on the stability of liposomes under oxidative stress conditions. The permeability of vesicle membranes to fluorescent dyes was measured as a proxy for bilayer integrity, and the formation of conjugated dienes was monitored as a proxy for LPO. Remarkably, both approaches reveal a similar threshold for the protective effect of D‐PUFAs in liposomes. We show that protection rendered by D‐PUFAs depends on the structure of the deuterated fatty acid. Our findings suggest that protection of PUFAs against autoxidation depends on the total level of deuterated bi‐sallylic (CD2) groups present in the lipid bilayer. However, the phospholipid containing 6,6,9,9,12,12,15,15,18,18‐d10‐docosahexaenoic acid exerts a stronger protective effect than should be expected from its deuteration level. These findings further support the application of D‐PUFAs as preventive/therapeutic agents in numerous pathologies that involve LPO.