Aquaporins, a family of membrane proteins, facilitate the diffusion of hydrogen peroxide (H₂O₂) across cell membranes. This study demonstrates that specific aquaporins, such as human AQP8 and plant Arabidopsis TIP1;1 and TIP1;2, enable the transport of H₂O₂. The research used yeast strains with varying sensitivities to oxidative stress to test the role of aquaporins in H₂O₂ transport. Expression of these aquaporins in yeast reduced growth and survival in the presence of H₂O₂. Further evidence was obtained using a fluorescence assay with an intracellular reactive oxygen species-sensitive dye, showing that H₂O₂-induced fluorescence was reversed by silver ions (Ag⁺), which block aquaporin-mediated water diffusion. These findings provide the first molecular genetic evidence that specific aquaporins facilitate H₂O₂ diffusion. H₂O₂ is a reactive oxygen species (ROS) that, despite its potential toxicity, plays a role in signaling. It is not charged, not a radical, and has an intermediate oxidation state, making it distinct from other ROS. While ROS are involved in various signal transduction pathways, their transport across membranes remains poorly understood. Recent studies suggest that H₂O₂ can act as an intercellular signaling molecule, requiring transport across at least two membranes. Aquaporins, which are efficient water channels, are likely candidates for facilitating H₂O₂ transport due to their structural similarity to water. The study used yeast as a model system to investigate aquaporin-mediated H₂O₂ transport. Yeast strains with different sensitivities to oxidative stress were transformed with various aquaporins, and their growth and survival were assessed in the presence of H₂O₂. The results showed that expression of certain aquaporins increased sensitivity to H₂O₂, indicating that these proteins facilitate its transport. Silver ions, which block aquaporin-mediated water diffusion, also reversed the effects of H₂O₂ on yeast growth and fluorescence, supporting the role of aquaporins in H₂O₂ transport. The study also examined the effect of H₂O₂ on yeast spheroplasts and found that aquaporin-expressing spheroplasts exhibited altered swelling kinetics. These findings suggest that aquaporins play a role in the transport of H₂O₂ across membranes. The results highlight the importance of aquaporins in the regulation of H₂O₂ transport and their potential role in cellular signaling and stress responses. The study provides new insights into the function of aquaporins in facilitating the diffusion of H₂O₂ across membranes.Aquaporins, a family of membrane proteins, facilitate the diffusion of hydrogen peroxide (H₂O₂) across cell membranes. This study demonstrates that specific aquaporins, such as human AQP8 and plant Arabidopsis TIP1;1 and TIP1;2, enable the transport of H₂O₂. The research used yeast strains with varying sensitivities to oxidative stress to test the role of aquaporins in H₂O₂ transport. Expression of these aquaporins in yeast reduced growth and survival in the presence of H₂O₂. Further evidence was obtained using a fluorescence assay with an intracellular reactive oxygen species-sensitive dye, showing that H₂O₂-induced fluorescence was reversed by silver ions (Ag⁺), which block aquaporin-mediated water diffusion. These findings provide the first molecular genetic evidence that specific aquaporins facilitate H₂O₂ diffusion. H₂O₂ is a reactive oxygen species (ROS) that, despite its potential toxicity, plays a role in signaling. It is not charged, not a radical, and has an intermediate oxidation state, making it distinct from other ROS. While ROS are involved in various signal transduction pathways, their transport across membranes remains poorly understood. Recent studies suggest that H₂O₂ can act as an intercellular signaling molecule, requiring transport across at least two membranes. Aquaporins, which are efficient water channels, are likely candidates for facilitating H₂O₂ transport due to their structural similarity to water. The study used yeast as a model system to investigate aquaporin-mediated H₂O₂ transport. Yeast strains with different sensitivities to oxidative stress were transformed with various aquaporins, and their growth and survival were assessed in the presence of H₂O₂. The results showed that expression of certain aquaporins increased sensitivity to H₂O₂, indicating that these proteins facilitate its transport. Silver ions, which block aquaporin-mediated water diffusion, also reversed the effects of H₂O₂ on yeast growth and fluorescence, supporting the role of aquaporins in H₂O₂ transport. The study also examined the effect of H₂O₂ on yeast spheroplasts and found that aquaporin-expressing spheroplasts exhibited altered swelling kinetics. These findings suggest that aquaporins play a role in the transport of H₂O₂ across membranes. The results highlight the importance of aquaporins in the regulation of H₂O₂ transport and their potential role in cellular signaling and stress responses. The study provides new insights into the function of aquaporins in facilitating the diffusion of H₂O₂ across membranes.