The permeability of human red blood cell membranes to hydrogen peroxide is independent of aquaporins.

ABSTRACT: Hydrogen peroxide (H₂O₂) not only is an oxidant but also is an important signaling molecule in vascular biology, mediating several physiological functions. Red blood cells (RBCs) have been proposed to be the primary sink of H₂O₂ in the vasculature because they are the main cellular component of blood with a robust antioxidant defense and a high membrane permeability. However, the exact permeability of human RBC to H₂O₂ is neither known nor is it known if the mechanism of permeation involves the lipid fraction or protein channels. To gain insight into the permeability process, we measured the partition constant of H₂O₂ between water and octanol or hexadecane using a novel double-partition method. Our results indicated that there is a large thermodynamic barrier to H₂O₂ permeation. The permeability coefficient of H₂O₂ through phospholipid membranes containing cholesterol with saturated or unsaturated acyl chains was determined to be 4 × 10^-4 and 5 × 10^-3 cm s^-1, respectively, at 37 °C. The permeability coefficient of human RBC membranes to H₂O₂ at 37 °C, on the other hand, was 1.6 × 10^-3 cm s^-1. Different aquaporin-1 and aquaporin-3 inhibitors proved to have no effect on the permeation of H₂O₂. Moreover, human RBCs devoid of either aquaporin-1 or aquaporin-3 were equally permeable to H₂O₂ as normal human RBCs. Therefore, these results indicate that H₂O₂ does not diffuse into RBCs through aquaporins but rather through the lipid fraction or a still unidentified membrane protein.

SUBMITTER: Orrico F 

PROVIDER: S-EPMC8753180 | biostudies-literature | 2021 Dec

REPOSITORIES: biostudies-literature