A Theory of Charge Selectivity Reversal in Cation- or Anion-Selective Tight Junctions between Epithelial Cells: A Nonlocal Electrostatic Approach

A theory was developed to explain how charge selectivity is reversed in tight junctions (TJs) between epithelial cells when the sign of the TJ fixed charge changes. An original method that allows for the ion cavity effect was used to calculate the changes in ion solvation energies that occur upon ion transfer in TJs. An equation was derived to describe the Na+ to Cl– permeability ratio of TJs as a function of the concentration and sign of TJ fixed charges and the correlation length of water. The theory agrees with published experimental data that Na+/Cl– selectivity is reversed in Madin–Darby canine kidney (MDCK) cells when claudin-15 protein molecules with a changed sign of amino acid residues are expressed in TJs.