Effect of Oxidative Stress on the Transport of P-Glycoprotein Substrate through the Cell Monolayer

P-glycoprotein (Pgp) is an ATP-dependent transmembrane protein that is involved in the efflux of lipophilic substances. The aim of this work was to evaluate the effect of oxidative stress (OS) on the transport of Pgp substrate through the monolayer of Caco-2 cells, which overexpress this transporter. OS was simulated by incubating cells with H2O2. Exposure to H2O2 at concentrations 10 and 50 mu M for 3 h caused a decrease in the activity (but not the amount) of Pgp with preservation of intercellular contacts and the integrity of the cell membrane. An increase in the concentration of H2O2 to 100 mu M decreased the amount of Pgp, disrupted the integrity of the cell monolayer, and increased the transcellular and paracellular transport of the Pgp substrate fexofenadine. Exposure to H2O2 at concentrations of 0.1-1 mu M for 24 h increased the amount of Pgp mediated by the transcription factor Nrf2, but the activity of the transporter protein remained unchanged. At a concentration of 10 M, H2O2 decreased the Pgp activity and increased the permeability of the cell membrane, while at 50-100 mu M the amount and activity of Pgp decreased and the para- and transcellular permeability of the cell monolayer for the Pgp substrate fexofenadine increased. Thus, H2O2 increases the transport of the fexofenadine through the cell monolayer by inhibiting the activity of the transporter protein, reducing its amount, as well as disrupting the integrity of the cell membrane and intercellular contacts. Cells can adapt to these influences by increasing the amount of Pgp.