The study investigates the role of aquaporins in facilitating the diffusion of hydrogen peroxide (H₂O₂) across membranes. Aquaporins are membrane proteins that efficiently transport water, and their function in other polar or charged molecules is less well understood. The researchers screened 24 aquaporin isoforms from plants and mammals in five yeast strains with varying sensitivity to oxidative stress. They found that expression of human AQP8 and plant Arabidopsis TIP1;1 and TIP1;2 in yeast increased the sensitivity of the yeast to H₂O₂, leading to decreased growth and survival. Further experiments using a fluorescence assay with intact yeast cells confirmed that these aquaporins mediate H₂O₂ diffusion. Silver ions, which block aquaporin-mediated water diffusion, also reversed the aquaporin-dependent growth repression and H₂O₂-induced fluorescence. These findings provide the first molecular genetic evidence that specific aquaporins can facilitate the diffusion of H₂O₂ through the cell membrane.The study investigates the role of aquaporins in facilitating the diffusion of hydrogen peroxide (H₂O₂) across membranes. Aquaporins are membrane proteins that efficiently transport water, and their function in other polar or charged molecules is less well understood. The researchers screened 24 aquaporin isoforms from plants and mammals in five yeast strains with varying sensitivity to oxidative stress. They found that expression of human AQP8 and plant Arabidopsis TIP1;1 and TIP1;2 in yeast increased the sensitivity of the yeast to H₂O₂, leading to decreased growth and survival. Further experiments using a fluorescence assay with intact yeast cells confirmed that these aquaporins mediate H₂O₂ diffusion. Silver ions, which block aquaporin-mediated water diffusion, also reversed the aquaporin-dependent growth repression and H₂O₂-induced fluorescence. These findings provide the first molecular genetic evidence that specific aquaporins can facilitate the diffusion of H₂O₂ through the cell membrane.