Sensitivity of primary mitochondrial disease fibroblasts to ferroptosis: The role of intracellular iron

Primary mitochondrial diseases (PMDs) are directly linked to oxidative phosphorylation (OXPHOS) dysfunction. Here, we investigated the selective sensitivity of PMD patient fibroblasts compared to healthy control primary human skin fibroblasts (PHSF) to ferroptosis, and the role of iron in this cell death mechanism. To address this, we investigated sensitivity to ferroptosis inducers, the effects of iron supplementation, and intracellular iron pools. The selectivity of PMD fibroblasts ferroptotic cell death was found to be more pronounced with class 1 ferroptosis inducers (FINs) that deplete GSH than upon direct GPX4 inhibitors. Notably, exogenous iron discriminatory triggered ferroptosis in patient fibroblasts and enhanced BSO-induced cell death in both patient and control cells. Further study revealed elevated basal levels of labile iron in patient fibroblasts, but mRNA analysis of iron-regulating genes did not reveal major expression differences. These findings suggest that increased labile iron predisposes PMD fibroblasts to ferroptosis. Complementation of defective OXPHOS restored ferroptosis sensitivity and LIP levels in a cell line with an NDUFS7 mutation, indicating a functional relationship caused by OXPHOS deficiency. Further understanding this interplay may provide insights into therapeutic strategies targeting iron homeostasis to mitigate ferroptotic cell death in PMDs.