Cell death and barrier disruption by clinically used iodine concentrations

Povidone-iodine (PVP-I) inactivates a broad range of pathogens. Despite its widespread use over decades, the safety of PVP-I remains controversial. Its extended use in the current SARS-CoV-2 virus pandemic urges the need to clarify safety features of PVP-I on a cellular level. Our investigation in epithelial, mesothelial, en-dothelial, and innate immune cells revealed that the toxicity of PVP-I is caused by diatomic iodine (I2), which is rapidly released from PVP-I to fuel organic halogenation with fast first-order kinetics. Eukaryotic toxicity manifests at below clinically used concentrations with a threshold of 0.1% PVP-I (wt/vol), equalling 1 mM of total available I2. Above this threshold, membrane disruption, loss of mitochondrial membrane potential, and abolition of oxidative phosphorylation induce a rapid form of cell death we propose to term iodoptosis. Furthermore, PVP-I attacks lipid rafts, leading to the failure of tight junctions and thereby compromising the barrier functions of surface-lining cells. Thus, the therapeutic window of PVP-I is considerably narrower than com-monly believed. Our findings urge the reappraisal of PVP-I in clinical practice to avert unwarranted toxicity whilst safeguarding its benefits.

Automated summary

The safety of Povidone-iodine (PVP-I) is controversial, and its toxicity is mainly caused by diatomic iodine (I2). The higher the concentration and duration of PVP-I, the greater the toxicity to cells. Additionally, PVP-I can disrupt cell membranes and lipid rafts, leading to cellular dysfunction. Therefore, a reevaluation of PVP-I in clinical practice is necessary to avoid unnecessary toxicity.