Multidrug resistance-associated protein 2 (MRP2) enhances 4-hydroxynonenal-induced toxicity in Madin-Darby canine kidney II cells

4-Hydroxy-trans-2,3-nonenal (HNE) is a toxic end product of lipid peroxidation. This multifunctional aldehyde reacts with proteins, phospholipids, and nucleic acids, consequently activating/inactivating enzymes, affecting signal transduction and gene expression. HNE is mainly detoxified by glutathione (GSH) conjugation. In our previous report, we showed that GSH conjugates of 4-hydroxynonenal (HNE-SG) are substrates of multidrug resistance-associated protein 2 (MRP2). MRP2 has been shown to export HNE-SG conjugates into the extracellular space. In the present study, the role of MRP2 in the detoxification of HNE was studied using Madin-Darby canine kidney II (MDCK II) cells expressing human MRP2. MRP2 reduced the intracellular accumulation of HNE-SG conjugate but unexpectedly increased the susceptibility of cells to HNE. The viability of cells was reduced to approximately 70% in the presence of 62.5 muM HNE in MDCK II cells expressing MRP2, whereas MDCK 11 cells remained unaffected. MRP2 accelerated the elimination of intracellular GSH via a conjugation reaction with HNE (half-life of GSH was 30.1 and 12.2 min for MDCK II cells and MDCK II cells expressing MRP2, respectively). Moreover, the consumption of GSH was unlimited in MDCK II cells expressing MRP2, finally resulting in necrosis. These results indicate that MRP2 has an adverse effect during the detoxification of HNE in MDCK II cells and suggest that expression of MRP2 may enhance the damage caused by oxidative stress.