Size-selective permeation-enhancing modulation of the tight junction by receptor-binding domains of <i>Clostridium perfringens</i> enterotoxin and <i>Clostridium perfringens</i> iota-toxin

Modulation of claudin-based bicellular tight junction (TJ) and angulin-based tricellular TJ seals has been shown to enhance mucosal permeation of macromolecules, by using the receptor-binding fragments of <i>Clostridium perfringens</i> enterotoxin (C-CPE194, C-CPEmt, and C-CPEm19) and <i>Clostridium perfringens</i> iota-toxin (angubindin-1) as claudin modulators and an angulin modulator, respectively. Here, we compared the activity of these modulators on the TJ in human intestinal Caco-2 cells. All the claudin modulators loosened TJ integrity more potently compared to angubindin-1 with the order of potency being C-CPEm19 > C-CPE194 > C-CPEmt, and results for permeation enhancement were similar. Treatment with C-CPEmt and C-CPE194 at 100 µg/mL for 48 h enhanced the permeation of dextran sized 20 kDa and 70 kDa, respectively. Treatment with C-CPEm19 at 30 µg/mL for 48 h enhanced permeation of dextran with a molecular mass of up to 150 kDa. Furthermore, co-treatment of bicellular TJ modulators, such as C-CPEmt, C-CPE194, and C-CPEm19, and tricellular TJ modulators, such as angubindin-1, showed additive TJ-loosening and permeation-enhancing activities compared with individual treatments; specifically, C-CPEm19 and angubindin-1 co-treatment increased permeation of large molecules (70 kDa and 150 kDa). These findings indicate that TJ modulators may be used as size-selective permeation enhancers.