Discovering compounds and mechanisms for inhibiting ferroptosis, a form of regulated, nonapoptotic cell death, has been of great interest in recent years. In this study, we demonstrate the ability of XJB-5-131, JP4-039, and other nitroxide-based lipid peroxidation mitigators to prevent ferroptotic cell death in HT-1080, BJeLR, and panc-1 cells. Several analogues of the reactive oxygen species (ROS) scavengers XJB-5-131 and JP4-039 were synthesized to probe structure–activity relationships and the influence of subcellular localization on the potency of these novel ferroptosis suppressors. Their biological activity correlated well over several orders of magnitude with their structure, relative lipophilicity, and respective enrichment in mitochondria, revealing a critical role of intramitochondrial lipid peroxidation in ferroptosis. These results also suggest that preventing mitochondrial lipid oxidation might offer a viable therapeutic opportunity in ischemia/reperfusion-induced tissue injury, acute kidney injury, and other pathologies that involve ferroptotic cell death pathways.

Recent synthetic and biological studies of the viridin class of steroidal furans have revealed multiple opportunities for fundamental discoveries as well as advanced drug design. Wortmannin is a potent enzyme inhibitor that binds to the ATP site of important regulatory kinases such as PI-3 kinase and Polo-like kinase. The natural product shares a unique mechanism-based biological activation pathway with other viridins. Furthermore, while there have been several encouraging approaches toward the total synthesis of these compounds, there is still ample room for improvements in synthetic strategies and tactics, and the development of structurally simplified analogs that exert more specific biological effects and are devoid of toxicity issues that have thwarted the clinical development of the parent compounds.

Oxidative damage is a well‐established driver of aging. Evidence of oxidative stress exists in aged and degenerated discs, but it is unclear how it affects disc metabolism. In this study, we first determined whether oxidative stress negatively impacts disc matrix metabolism using disc organotypic and cell cultures. Mouse disc organotypic culture grown at atmospheric oxygen (20% O₂) exhibited perturbed disc matrix homeostasis, including reduced proteoglycan synthesis and enhanced expression of matrix metalloproteinases, compared to discs grown at low oxygen levels (5% O₂). Human disc cells grown at 20% O₂ showed increased levels of mitochondrial‐derived superoxide anions and perturbed matrix homeostasis. Treatment of disc cells with the mitochondria‐targeted reactive oxygen species (ROS) scavenger XJB‐5‐131 blunted the adverse effects caused by 20% O₂. Importantly, we demonstrated that treatment of accelerated aging Ercc1^−/Δ mice, previously established to be a useful in vivo model to study age‐related intervertebral disc degeneration (IDD), also resulted in improved disc total glycosaminoglycan content and proteoglycan synthesis. This demonstrates that mitochondrial‐derived ROS contributes to age‐associated IDD in Ercc1^−/Δ mice. Collectively, these data provide strong experimental evidence that mitochondrial‐derived ROS play a causal role in driving changes linked to aging‐related IDD and a potentially important role for radical scavengers in preventing IDD. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1150–1157, 2013