Ferroptosis propagates to neighboring cells via cell-cell contacts

Ferroptosis is an iron-dependent form of regulated cell death characterized by accumulation of peroxidized lipids and plasma membrane disruption, whose molecular mechanism of execution remains poorly understood. Here, we developed a new optogenetic system, Opto-GPX4Deg, for light-induced degradation of the lipid reducing protein GPX4, which allows controlled ferroptosis induction with high precision in time and space. By using Opto-GPX4Deg to study cell death dynamics within the cellular population, we found that lipid peroxidation, followed by ferroptotic death, spread to neighboring cells in a distance-dependent manner. Remarkably, ferroptosis propagation showed a strong dependency on cell confluence and preferentially affected adjacent cells. Our findings establish cell death propagation as a feature of ferroptosis and provide new understanding of the mechanism involved.