Phospholipid flippase associates with cisplatin resistance in plasma membrane of lung adenocarcinoma A(549) cells

The fusion of the liposomes containing (N-(7-nitro-2, 1, 3-benzoxadiazol-4- yl)-1,2-hexadecanoyl-Sn-glycero-3-labeled phosphatidylethanolamine (NBD-PE) with A(549) and A(549)/DDP cells was performed, and the activity of the ph ospholipid flippase in the plasma membrane of the cells was measured by flu orescence intensity change of NBD-PE in the outer membrane. When A(549) or A(549)/DDP cells containing NBD-PE were incubated at 37 degreesC for 0, 30, 60 and 90 min, the fluorescence intensities in the outer membrane of the c ells were 0%, 1.4%, 2.9% and 7.8% for A(549) cells, and 0%, 10.5%, 15.5% an d 18.3% for A(549)/DDP cells respectively, demonstrating that the phospholi pid flippase was distributed in the plasma membrane of A(549) cells, but it s activity in the drug-resistant A(549)/DDP cells was much higher than that in the A(549) cells. When the A(549)/DDP cells were incubated with a multi drug resistance reverse agent, verapamil, for 60 min at 37 degreesC, the re sults showed that the NBD-PE in outer membrane decreased by 25.0% compared with the control's. Furthermore, when A(549)/DDP cells were incubated with 25 mu mol/L cisplatin, which is a specific anticancer drug, the flippase ac tivity decreased by 31.6%, and it further decreased with the increase of ci splatin concentration, suggesting that phospholipid flippase in the membran e might be related to the cisplatin-resistance of human lung adenocarcinoma cancer cells.