Functioning of the P-glycoprotein Membrane Transport Protein under Conditions of the Inhibition of Glutathione Synthesis

The functioning and mechanism of P-glycoprotein (Pgp) regulation under conditions of inhibition of glutathione synthesis in human colon adenocarcinoma (Caco-2) cells, which are a model of xenobiotic absorption, were studied in vitro. Glutathione synthesis was inhibited by the action of D,L-buthionine sulfoximine (BSO, an inhibitor of gamma-glutamylcysteine synthetase). It was found that BSO at concentrations of 50-500 mu M and incubation for 3 h had no effect on the glutathione level and reduced Pgp activity. An increase in exposure time with BSO at concentrations of 10-100 mu M to 24 h led to the development of moderate oxidative stress and an increase in the amount of Pgp (the effect was realized via transcription factor Nrf2). At the same time, the Pgp activity increased upon exposure to BSO at a concentration of 10 mu M and decreased t concentrations of 100-500 mu M. The development of pronounced oxidative stress upon exposure to BSO at a concentration of 500 mu M for 72 h was accompanied by a decrease in the amount and activity of Pgp. Thus, BSO is a direct inhibitor of Pgp; however, a decrease in the level of SH groups caused by this substance can lead to an increase in the Nrf2 level, which, in turn, causes an increase in the amount and activity of this transport protein. The results can be used in clinical practice to optimize the dosing of transport protein substrates in the treatment of diseases accompanied by the development of oxidative stress in the intestine.

Automated summary

The functioning and mechanism of P-glycoprotein regulation were studied under conditions of inhibition of glutathione synthesis. It was found that BSO directly inhibits Pgp activity, but also increases the amount and activity of Pgp through activation of the Nrf2 pathway.